new research topics in antenna

Tutorial and Research Trends in Antenna Technology

Antennas and antenna arrays serve as the “eyes and ears” for all wireless systems. 1-6 According to IEEE Standard (145-1983), 7 an antenna may be defined simply as “a means for transmitting and receiving radio waves.” The antenna serves as a transducer between the transmitter and the free space or between the medium and the receiver. In a broad sense, antennas may be classified into three categories, namely isotropic, omnidirectional and directional (see Figure 1 ). The isotropic antenna is a hypothetical concept of unity gain in all directions. 3 It serves as a benchmark by which to measure practical antenna elements. An omnidirectional antenna is the closest realization of an isotropic antenna with almost constant gain in one plane of reference (azimuth or elevation), 3 finding widespread use in broadcast applications. Directional antennas have higher directional gain and narrower radiation patterns (beams), desirable for applications like radio detection and ranging (radar) and point-to-point communications. 1-6

Michael Faraday, in 1830, introduced loop antenna as the part of his experiments studying the coupling of electric and magnetic fields. 8 Later Heinrich Hertz 8 discovered electromagnetic (EM) waves and designed a dipole antenna. In 1901, Guglielmo Marconi 8 sent information across Atlantic Ocean using multiple vertical wires connected to the ground. This was the first use of antenna arrays. 3 Maxwell 3, 8 wrote the first treatise on EM theory congregating principles postulated by Oersted, Faraday, Gauss and others, popularly known as Maxwell’s equations (see Figure 2 ). It is shown by Maxwell that any accelerated charge radiates, and hence, an antenna may be defined as an EM device that controls the flow of the time varying currents; thereby, producing EM radiation.

The antenna structure may be considered to have three sections, namely an EM generator, a guiding structure and a transition region (see Figure 3 ). Figure 3 is the result of a finite element method (FEM) simulation of a horn antenna showing the flow of rf energy in the respective sections. An EM generator inputs the EM wave into the guiding structure (the input of the flared horn), which directs it into the transition region. The transition region is a matching transformer, matching the impedance of guide with 377 ohms, the free space impedance. The EM wave escapes from the transition region into the free space, hence, causing the antenna to radiate.

Although the list of existing antenna types is too vast to summarize here, a few are selected and discussed, based on their commercial and military applications.

Antenna Basics

Antenna Qualifying Parameters (AQPs)

An antenna may be described quantitatively in terms of space and circuit parameters (see Figure 4 ). AQPs define the radiation and the impedance characteristics of an antenna, respectively, and are listed below: 3

1. Antenna Gain, G and directivity (directive gain), D

2. Antenna temperature, T

3. Radiation resistance, R

4. Half power beam width, BW 3dB

5. Pointing, look direction or scan angle

6. Sidelobe level (SLL) characteristics, such as peak SLL (PSLL), average SLL (ASLL).

7. Cross-polarization (x-pol) characteristics

8. Axial ratio (AR)

G measures directionality of an antenna pattern with reference to an isotropic antenna (G=1), thus, measurable in dBi (i for isotropic). It is different from D in the sense that it accounts for the various losses in conductors, space (radiation) and guides (dielectric or air), 3 not included in directive gain, D. Hence, G is always less than D. BW 3dB is the angular distance between the two – 3 dB points from the maximum, or peak, of the radiation pattern’s main beam. Look direction defines the direction in which the antenna pattern’s main beam is pointing while the array is scanning mechanically (using servo motors) or electronically (using digitally applied phase shifts to the elements of an array). 4 Figure 5 shows a typical radiation pattern for a directional antenna. Apart from the main lobe (ML), which is desired, there are other unwanted lobes of much smaller magnitude in comparison to the ML, called sidelobes and characterized by SLL.

Antenna Classification

Figure 7 shows a classification of various antenna geometries. It includes wire antennas, traveling wave antennas, reflector antennas, microstrip antennas, log-periodic antennas, aperture antennas and others such as near field communications (NFC) antennas and fractal antennas. An individual antenna element may have a gain from 0 dBi (monopole) to 10-12 dBi (e.g. tapered slot antenna and helical) depending upon the type.

Depending upon specifications such as power handling, G, SLL, size, weight and volume, a class may be chosen for certain applications. Astronomical radio telescope antennas, for example, require very high gain and high-power handling capabilities along with open installations in large areas exposed to different, and often severe, topological and environmental conditions. These requirements are typically fulfilled by reflector antenna arrays. 3 For platforms with limited real estate such as high altitude platforms (HAPS) 2 and fighter aircraft, microstrip antennas are useful, being light weight, low profile and conformable in nature. Traveling wave antennas and log-periodic antennas are very useful for ultra-wideband and high-power handling applications. Fractal antennas are useful for realization of embedded antenna structures inside mobile handsets. The planar inverted folded antenna (PIFA) is a good structure for body-wearable conformal antennas applications. Antenna arrays are useful for applications such as radar, requiring high gain for detection at longer ranges and directional beams for target tracking. 4

Antenna Arrays

Some applications require antennas with high gain, narrow BW 3dB and electronic beam steering. These are requirements that cannot be met easily with a single antenna. For these applications, antenna clusters known as antenna arrays must be used. 3 For a N-element array, G equals N times the single antenna gain, Go, i.e,

BW 3dB is inversely proportional to G, i.e.,

typically for equally fed array elements. 3

Antenna arrays can be classified into three main categories (see Figure 8 ):

• Linear antenna array (LAA), consisting of a one-dimensional cluster of antenna elements.
• Planar antenna array (PAA), consisting of a two-dimensional cluster of antenna elements.
• Conformal antenna array (CAA), consisting of a one- or two-dimensional cluster of antenna elements arranged conformally over a surface.

Generalized Expression for Directivity, D

D of an antenna array may be defined as 9

The directivity and gain of antenna are related by

The operational bandwidth (OBW) of an antenna may be defined as the range of the frequency points over which the antenna space and circuit parameters, measurable in terms of AQPs, are within desired limits defined by the user. The OBW may be classified in terms of radiation bandwidth and impedance bandwidth. 3

Research Trends in AntennaS AND Antenna Arrays

Several current research areas include, but are not limited to:

1. Microstrip reflect arrays

2. Reconfigurable microstrip antennas

3. Body-wearable antennas

4. Multiple input multiple output (MIMO) antennas

5. Ultra-wideband antennas (UWB)

6. Metamaterial antennas

7. Connected array antenna

8. Windscreen antenna

9. Fractal antennas

10. Smart antennas

11. Defected Ground Structure (DGS)/electromagnetic band gap (EBG) Antennas

12. Conformal Antenna Arrays

13. Shared Aperture Antennas

14. Radar antennas

Microstrip Reflect Arrays

The concept was introduced by Berry et al. 10 in 1963 using waveguide and was later realized using microstrip technology. 11-16 Reflector antennas and phased arrays form the working principle for reflect array antennas (see Figure 9 ). The variation in size and geometry of planar antenna elements leads to an equivalent phase shift imitating parabolic reflector behavior. The reflector intercepts the impinged wave from a radiator placed at its focal point and scatters back the energy, which collimates due to its designed geometry, and forms a radiated beam. It has associated space loss and spillover loss. A phased array, on the other hand, includes an RF network including phase shifters, attenuators, amplifiers and feed network to receive/transmit energy; thus, there is an associated RF loss. A reflect array antenna overcomes these issues. A reflect array is a phase transformation structure where most of the elements are near resonance; hence, it provides an alternative to a conventional parabolic reflector antenna.

Samaiyar et al. 14 discuss an application of reflect arrays for the realization of simultaneous transmit and receive operation at 5.8 GHz in the ISM band. Fukaya et al. 15 describe a Tx and an Rx reflect array satellite antenna comprising multiple horns and a single-layer flat reflect array that radiates scanning beams along different directions in azimuth by virtue of polarization and frequency. A reflect array designed using tightly coupled dipole arrays (TCDAs) operates from 3.4 to 10.6 GHz. 16 The microstrip reflect array antenna has been demonstrated to be a practical alternative to bulky reflector antennas and costly phased arrays.

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• Open access
• Published: 20 June 2022

A compact evolved antenna for 5G communications

• I. Marasco 1 , 2   na1 ,
• G. Niro 1 , 2   na1 ,
• V. M. Mastronardi 2 , 3 ,
• F. Rizzi 2 ,
• A. D’Orazio 1 ,
• M. De Vittorio 2 , 3   na1 &
• M. Grande 1   na1  

Scientific Reports volume  12 , Article number:  10327 ( 2022 ) Cite this article

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• Design, synthesis and processing
• Electrical and electronic engineering

Flexible and bendable electronics are gaining a lot of interest in these last years. In this scenario, compact antennas on flexible substrates represent a strategical technological step to pave the way to a new class of wearable systems. A crucial issue to overcome is represented by the poor radiation properties of compact antennas, especially in the case of flexible and thin substrates. In this paper, we propose an innovative design of a miniaturized evolved patch antenna whose radiation properties have been enhanced with a Split Ring Resonator (SRR) placed between the top and the ground plane. The antenna has been realized on a flexible and biocompatible substrate polyethylene naphthalate (PEN) of 250 μm by means of a new fabrication protocol that involves a three-layer 3D-inkjet printing and an alignment step. The antenna has been characterized in terms of the scattering parameter S 11 and the radiation pattern showing a good agreement between simulations and measurements.

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Introduction.

With the advent of 5G and new 6G network infrastructures, flexible and bendable IoT devices are becoming increasingly popular 1 , 2 . In this regard, the conception of wearable and bendable antennas is a crucial issue to overcome 3 , 4 . Scientific efforts concerned the design of miniature flexible antennas to cope with modern requirements such as wearability.

Due to the high demand coming from the market, rapid prototyping and cost-effective technologies for antenna fabrication are becoming crucial and, hence, multiple technologies have to be combined to achieve the very strict goals required by antenna design. From one side, the footprint of the antenna can be reduced increasing the operating frequency 5 . However, the higher is the transmission frequency the more probable is the insurgence of disturbing phenomena such as multipath fading and attenuation 6 . The second alternative is antenna miniaturization. This technique aims to decrease the resonance of antennas by increasing its electrical length, so with the same geometrical dimension antennas can radiate at a lower frequency. The main drawbacks of this strategy are the degrading of the radiation properties and bandwidth reduction. In addition to compact footprints, optimal radiation properties are needed. These requirements increase the difficulty of the design procedure since the geometry of the antenna must be efficiently optimized, typically and especially on very thin substrates.

In this context, artificial intelligence (AI) comes to aid. AI algorithms have been used for years to solve a huge variety of optimization problems, including antennas design. Among other methods, the genetic algorithm (GA) is one of the most used approaches regarding different electromagnetic problems such as photonics 7 and antennas 8 , 9 , 10 , 11 .

The genetic algorithm generates a set of trivial solutions, i.e. antenna geometries, which evolves step by step until the best solution is reached. Antennas generated according to this approach are said to be evolved 12 . Miitra 13 was one of the first authors to exploit this line of research. Reference 8 reports a tutorial about GA applied to this kind of applications while reference 9 details the design of antennas employing GA and the Method of Moments (MoM). In 10 , the GA is applied to miniaturize a patch antenna for cardiac pacemakers operating at 402–405 MHz. The coding scheme used to treat the problem consists of subdividing the patch into smaller sub-patches. Each sub-patch can be either metal or air. The same approach has also been used in 11 , where the genetic algorithm has been applied to a patch antenna shifting its resonance from 4.8 GHz to 2.16 GHz.

It has been demonstrated that the design of antennas by means of genetic algorithms is a good choice; however, only the miniaturization cannot be pushed far without suffering from low radiation efficiencies.

An approach used for improving this feature is the introduction of metamaterials. Each material in nature is composed of atoms and their properties and spatial orientations affect its electrical behavior. The idea behind the metamaterials is the logical expansion of this concept at a macroscopic scale. By creating an array of single cell having specific properties it is possible to generate tailored electrical and magnetic characteristics of the entire structure.

Metamaterials are applied to a huge variety of fields and one of the most promising regards the enhancement of radiation properties of small antennas.

Split Ring Resonators (SRRs) represent an optimal solution since their planar geometry and easy integration simplifies the fabrication process 14 . In particular, SRRs can be used to realized Artificial Magnetic Conductor (AMC) layers having effective permeability near to zero, i.e. Zero Index metamaterials (ZIMs). Recent studies employ ZIMs to improve the radiation properties of antennas by placing such supermaterials between the top layer of the antenna and the ground plane 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 . In this case, the ZIM acts as a very precise mirror that does not introduce phase variations in the reflected electromagnetic waves, improving the radiation characteristics of the ground plane on the bottom of the antenna. A problem arising from the use of metamaterials is that the inclusion of a superstrate adds a metallic layer to the stack composing the antenna, hence an alignment process must be performed.

A very attractive technological process for the fabrication of flexible antennas even of multilayers stacks 23 , 24 , is the ink-jet printing 25 , as it is the most economical, the fastest, and the cleanest solution. By this technique, the antennas are realized by depositing conductive inks through hundreds of nozzles which are mechanically controlled. Despite its optimal characteristics, this method does face some issues: the quality of the prints depends on the viscosity and the size of the droplet of the conductive ink 25 .

In addition, in the case of multilayers antennas fabricated on commercial substrates not direct printable, the alignment step becomes difficult. This happens because it is necessary to perform two different printing processes on both faces of the same dielectric. This last case can be the case of metamaterial antennas designed on stretchable substrates.

In 26 an example of a flexible antenna enhanced with a metamaterial has been reported. The antenna is composed of a polyimide substrate with a top radiating element placed on a second substrate with a 3 × 3 array of metamaterial structures and a ground plane at the bottom. However, in this case, a precise alignment is not strictly necessary since the superstate needs only the metallization of its bottom surface. Moreover, the two layers are not fully integrated but are just placed on each other.

As a consequence, even though in literature there exist a huge number of antennas realized using GA, metamaterials and inkjet printing, to the best of our knowledge, an antenna that exploits these three technologies jointly has not been reported yet.

The biggest issue to overcome is the lack of the rapid prototyping fabrication techniques on flexible substrates of a process characterized by multilayer printing with an optimal alignment between all the parts composing the antenna. In this work, we propose a flexible multilayer ink-jet printed evolved antenna. The stack is composed of five layers (three metallic and two dielectric). The radiative layer (i.e. top layer) is designed by using a genetic algorithm in order to miniaturize its footprint. The gain is enhanced by a split ring resonator which acts as a metamaterial and, at the bottom, the ground plane is placed to minimize the back radiation. The working frequency is in the sub-6 GHz band of the 5G spectrum, in particular, around 4 GHz.

The metallic layers are fabricated by means of a multi-material 3D printer which requires a precise alignment process on a 250 μm Polyethilene Naphtalate (PEN) substrate. The dielectric layers are attached to each other by a Polydimethylsiloxane (PDMS) adhesive interlayer of 40 μm.

Finally, the antenna has been characterized in terms of the S 11 parameter and 2D radiation patterns by means of VNA. The paper is organized as follows: in “ Genetic algorithm ” we described briefly the principal steps of the GA, in “ Antenna design and Split ring resonator ”, the antenna design is reported, in “Fabrication” the fabrication steps are described, in “Characterization” the characterization of the prototype is detailed and, finally, in “ Conclusion ” conclusions are presented.

Genetic algorithm

The Genetic Algorithm first formalized in 27 is a robust global optimization method based on Darwinian laws. The process starts from an initial random binary population (parents) that evolves iteratively towards the optimal solution under the selective influence of a cost function. The genetic algorithm works through eight main steps, as shown in Fig.  1 .

Flowchart of the Genetic Algorithm.

(1) Encoding the problem is schematized as a function of general parameters. A single parameter is treated as a gene. Generally, binary values are preferable to be used for the genes. Their arrangement (i.e. all the genes) forms the chromosome which describes the partial solution.

(2) Initialization the initial population is generated. The set of trivial solution is composed of random chromosomes.

(3) Evaluation of the population at this step, the fitness function is applied to all the elements of the population. At the end of this process, a direct correspondence between each chromosome and its relative fitness value is obtained, which quantifies the proximity of the trivial to the real solution of the problem.

(4) Chromosomes rank and selection process the chromosomes are grouped two by two. The selection can be performed randomly or by considering their fitness values.

(5) Crossover from each couple of chromosomes, the offsprings are generated. The descendants are created by mutual recombination of the genes of the initial chromosomes forming a new set of gene values starting from the parents.

(6) Mutation the set of trivial solutions is perturbated by the insertion of random variations which can speed up the convergence of the algorithm. Mutations can be applied to a single gene or multiple chromosomes and are strictly dependent on the nature of the problem. In general, the presence of mutations avoids stalling the solver in local minimum, however, a rate too high can degrade the performance.

(7) Reordering the fitness function is evaluated as in step 3, on the new offspring. The population is then rearranged by eliminating the chromosomes with the worst fitness values.

(8) Loop statement the best fitness value is compared to the threshold value and if the condition is matched the algorithm stops, while otherwise the entire process is repeated from step 3.

Antenna design

Figure  2 a reports the structure of the evolved antenna.

Sketches of the proposed antenna: ( a ) Exploded representation of the multilayer antenna, ( b ) top-view of the evolved patch antenna. Software used: Rhino 6, https://www.rhino3d.com/it/ .

The antenna is composed of 5 layers: from the top, the patch radiating element (level 1) which is on a dielectric substrate (level 2), then the metamaterial split ring resonator (level 3) placed on a second dielectric substrate (level 4) and the ground plane (level 5).

The dielectric substrates, made of PEN, have a thickness of 125 µm, a dielectric constant of 2.9 and a loss tangent equal to 0.005. PEN presents very good properties as a substrate for flexible electronics: it is a transparent and low-cost material. It is also characterized by a very high heat shrinkage coefficient and good resistance to acids and basis 28 , 29 .

Evolved patch antenna miniaturization

The miniaturization is carried out starting from a classical patch antenna operating at 6 GHz with a bandwidth of 50 MHz and a gain equal to 5.8 dBi. The classical patch antenna can be realized by using the algorithm detailed in Ref. 30 . However, it is not possible to control and engineer the bandwidth or the gain of the device but only the geometrical parameters. Conversely, our optimization problem can be treated using a binary coding scheme, hence, the genetic algorithm is the most straightforward to be implemented. The geometrical parameters of the antenna (Fig.  2 b) used in the simulation are listed in Table 1 .

The simulations have been performed considering the substrate as a loss-free dielectric layer having thickness equal to 125 µm.

The genetic algorithm implemented to miniaturize the antenna consists of the main steps described below.

(1) Encoding the encoding scheme used consists of subdividing the patch antenna into 32 pixels. A single pixel is treated as a gene and is encoded with a binary value, 1 if it is a metal pixel (yellow), 0 if it made of air (blue), as shown in Fig.  1 b. Each pixel has a square form and an edge length of 2 µm.

(2) Initialization the starting elements are generated randomly. The population size is strictly linked to the nature of the problem and its degrees of freedom. By considering a huge population, it could be possible to obtain better results but at the cost of higher computational times; on the contrary, by using a small size for the population the execution speeds up but the optimizer may get stacked in local minima. To minimize the convergence time avoiding the insurgence of partial solutions, the possible elements of the population can be restricted to delete pointless individuals. In this case, since the radiation efficiency is directly linked to the size of the radiating area, each element of the population must be made of metal in a percentage greater than 60%.

(3) Evaluation of the population the value of the cost function ( \(\mathrm{C}\left({f}_{R}\right)\) ) of each antenna is evaluated by calculating the resonance f R and the corresponding impedance value Z(f R ), by means of a finite difference time domain (FDTD) solver using the Eq. ( 1 ):

where f c is the objective frequency equal to 4 GHz, δ represents the tolerance to the resonant frequency and Z(f R ) is the value of the impedance assumed by the patch at its resonance. The exponential term assumes lower values when the resonance f R is near to the objective frequency. In addition, this function takes into account the impedance of the resonant peaks in order to discard antennas having a value of the real part of the impedance far from 50 Ω.

(4) Chromosomes rank and selection process the elements of the population are then grouped two by two using a roulette selection process. The probability associated with the selection of the single element π i follows a Boltzmann distribution, hence is evaluated by means of Eq. ( 2 ):

where c i is the value of the fitness function of the ith element of the population and β is a normalization factor equal to \(\upbeta =\frac{1}{\mathrm{N}}\sum_{\mathrm{i}=1}^{\mathrm{N}}{\mathrm{c}}_{\mathrm{i}}\) .

Elements characterized by a lower cost function, hence nearer to the final solution, result more attractive than the others; however, it is worth stressing that by using this selection process the probability of selecting the worse elements is not deprecated at all.

(5) Crossover two offsprings are then generated from each group by a single point cross-over.

(6) Mutation occasionally, a mutation event has occurred with a probability equal to 1%. The mutation corresponds to a variation of a single gene of an element of the population.

(7) Reordering the cost function is evaluated for each element of the new population. The elements are then reordered in an ascendent order with respect to their costs. The latest elements are discarded, and the best value is compared with the threshold value of the algorithm to decide on the convergence of the solution.

(8) Loop statement the process is repeated starting from step 3 until the condition on the threshold is reached.

In our implementation, the algorithm converged after 12 iterations giving as result an evolved patch antenna with a footprint of 16.88 × 13.76 mm 2 resonating at around 3.89 GHz with an S 11 dip of − 24.47 dB and a bandwidth of about 14 MHz.

The realized gain at the resonant frequency is equal to -0.647 dBi. The reduction of the dimensions of the antenna and, more important, of the ground plane always leads to worse radiation properties; to improve the antenna radiation pattern a mu-negative metamaterial composed of a square split ring resonator has been added between the top and the ground plane 31 .

Split ring resonator

The square split ring resonator is composed of two concentric etched split rings separated by a gap and having their apertures placed in the opposite direction (Fig.  3 a).

( a ) Geometry and ( b ) equivalent circuit, of the SRR.

The SRR behaves like an LC circuit as shown in Fig.  3 b 32 . The value of the inductance \({L}_{RING}\) of each ring can be expressed as in Eq. ( 3 ):

D represents the gap between two rings, W is the ring thickness, R2 and R1 are the outer and inner radius of the rings, respectively.

As regards the capacitance, \({C}_{RING}\) represents the capacitance of the single ring while \({C}_{GAP}\) the capacitance between the rings, respectively. \({C}_{RING}\) can be defined as in the following expression, Eq. ( 4 )

where t is the thickness of the ring and G the aperture of the ring.

Finally, \({C}_{GAP}\) can be expressed as in Eq. ( 5 ):

A is an equilibrium constant.

By considering the geometrical parameters of the SRR, the resonant frequency \({f}_{0}\) can be evaluated as in Eq. ( 6 ):

In this work, the geometry of the square split ring resonator has been properly designed to increase the gain at the working frequency of the antenna.

The geometrical dimensions of the square SRR are listed in Table 2 .

After this procedure, the entire structure is composed of 5 layers as shown in Fig.  2 a.

The results of the simulations are shown in Fig.  4 .

( a ) Simulated S 11 parameter of the multilayer antenna, ( b ) front perspective and ( c ) side perspective of 3D radiation patterns at 3.985 GHz; simulated polar plot for the plane ( d ) ϕ = 0° and ( e ) ϕ = 90°. Software used: figure a Matlab R2020a; ( b – d ) CST Microwave Studio 2021. https://it.mathworks.com/ , https://www.3ds.com/products-services/simulia/products/cst-studio-suite/ .

In Fig.  4 a the trend of S 11 parameter is shown; there is a dip of − 14.2 dB at 3.984 GHz with a bandwidth of about 15 MHz. The narrow-band could be increased by redesigning the cost-function of our algorithm or considering a circular patch 33 . In Fig.  4 b,c two different perspective of the 3D realized gain of the patch antenna at the resonant frequency are reported. The maximum value is equal to 1.89 dBi.

In Fig.  4 d,e the radiation pattern in the E-plane and H-plane are reported, respectively. In particular, for the E-plane ( \(\phi =0^\circ\) ) the main lobe magnitude is equal to 1.89 dBi and the main lobe direction is equal to 3.0° with an angular width (3 dB) equals to 93.2°. Whereas the H-plane ( \(\phi =90^\circ\) ) the main lobe magnitude is equal to 1.88 dBi and the main lobe direction is equal to 0° with an angular width (3 dB) equals to 92°.

It is worth stressing that with the insertion of the dielectric layer with an SRR, it is possible to observe an increase of the gain from –0.647 dBi to 1.89 dBi without modifying the footprint of the patch antenna. The directivity is equal to 6.48 dBi at the resonant frequency.

Table 3 shows a comparison between the 6 GHz starting patch antenna, the 4 GHz evolved one and the 4 GHz classical patch antenna.

The Genetic Algorithm allows to retain the starting patch antenna footprint (17 × 14 mm 2 ) at a lower working frequency of 3.96 GHz. In comparison with a classical patch antenna at the same frequency (whose physical dimension are 27 × 22 mm 2 ), we got a reduction in size of 60%. Besides, the evolved patch antenna presents a reduction in terms of gain and bandwidth, in line with the behaviour of miniaturized and electrically small antennas 34 .

Fabrication

The designed antenna has been fabricated by means of NanoDimesion’s DragonFly LDM™ 3D printer.

During the fabrication process, a material jetting of conductive ink through hundreds of nozzles has been performed. In particular, the metallic parts are made of AgCite, which is an Ag nanoparticles-based ink. All the process has been realized at a temperature of 140 °C necessary for the ink curing and sintering. The starting point of the print process is a complex 2D schematic of the device that is imported as a Gerber file and then converted into a layer-by-layer print instruction for multi-material 3D printer. Figure  5 exploits the fabrications steps.

( a ) Steps of the 3D printing process, ( b ) result of the alignment between patch and SRR and printed ground planes, ( c) representation of the multilayer antenna with the interlayer of PDMS, ( d ) flat and ( e ) bent fabricated prototype with SMA connector. Software used: Rhino 6.

More in detail, at the first stage the patch has been printed and then, a backside automated alignment follows for SRR printing on the bottom side. In parallel, the ground plane is printed near to the self-aligned SRR (Fig.  5 a). The radiating elements have a thickness equal to 35 µm; as a technological constraint, the metal thickness should be at least equal to 17 µm to guarantee perfect electrical conductivity. In Fig.  5 b, the alignment step realized on PEN substrate is reported. The two dielectric layers are cut by means of a laser cutter (Universal Laser System vls2.30) and then are joined with an adhesive interlayer of around 40 µm of Polydimethylsiloxane (PDMS), as reported in Fig.  5 c. It is worth pointing out that the choice of this elastomer guarantees the flexibility of the antenna. Finally, Fig.  5 d,e show the fabricated prototype.

Characterization

The antenna has been characterized in terms of the scattering parameter S 11 and the radiation pattern.

The return loss has been measured by means of a Vector Network Analyzer (VNA, Anritsu MS46122B).

Figure  6 a shows a comparison between the trends of the simulated (blue curve) and the measured (red curve) scattering parameter S 11 .

( a ) Simulated (blue curve) and measured (red curve) S 11 parameter of the multilayer antenna, measured ( b ) front perspective and ( c ) side perspective 3D radiation patterns; polar plot at ( d ) ϕ = 0° and ( e ) ϕ = 90° at 4 GHz; simulated (blue curve) and measured (red curve) ( f ) gain and ( g ) efficiency of the evolved patch antenna. Software used: proprietary software by Starlab from Satimo 18 GHz anechoic chamber, https://www.mvg-world.com/en/products/antenna-measurement/multi-probe-systems/starlab .

In particular, it is possible to see a dip of − 14.2 dB at 3.984 GHz and a dip of -13.41 dB at 3.962 GHz for the simulated and the measured evolved patch antenna, respectively. There is a shift of few tens of MHz due to the introduction of a SMA connector which introduces a static capacitance, therefore increasing the electrical length of the device 35 . Both curves present a dip around 4 GHz, the desired operating frequency, where the realized gain is equal to -0.8 dBi for the simulated antenna and -1.5 dBi for the fabricated one, when the losses are taken into account. Figure  6 b,c show the measured 3D radiation patterns that are in agreement with the simulated ones (Fig.  4 b,c). 2D polar plots and 3D radiation diagram were measured by means of the combination of an anechoic chamber (StarLab from Satimo) and a home-made setup. In Fig.  6 d,e the measured radiation patterns for E-plane and H-plane are reported. For the planes ϕ = 0° and ϕ = 90°, there is a very good agreement between simulations (Fig.  4 d,e) and measurements (Fig.  6 d,e). Figure  6 f shows the gain around the resonant frequency equal to 3.9 GHz: as it can be inferred by the plot, there is a good agreement between the numerical and experimental results. As regards the efficiency shown in Fig.  6 g, it is possible to note a higher value of the simulated one with respect to the measured one at the resonant frequency. It is worth stressing that this mismatch is due to multiple factors such as: the soldering of the connector, the presence of solvent mixed with the conductive part used in the 3D printing process and finally, the losses of the substrate at the resonant frequency that has been extrapolated from the lower frequencies value tabulated in the PEN datasheet (1 kHz-1 GHz) [Teonex Q51].

A multi-layer 3D-printed metamaterial-based evolved patch antenna has been presented. The genetic algorithm has proven to be a powerful method to optimize antenna miniaturization and the radiation properties have been improved with the insertion of the split-ring resonator. The fabrication protocol turns out to be very fast and capable of realizing antennas with a precise alignment step between the layers. The measurements of the S 11 parameter and the radiation patterns are in agreement with the simulations. The main resonance of the fabricated prototype is in the sub-6 GHz of 5G spectrum, showing a dip of S 11 parameter of − 27.41 dB at 3.962 GHz, with a bandwidth of 14.7 MHz. In case directivity and gain need to be enhanced, an array configuration of this patch can be implemented . We believe that the proposed approach could be a valid choice for the realization of compact, flexible and wearable IoT devices.

Data availability

All the data supporting the results of this study can be found within the article or upon request from the corresponding authors.

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These authors contributed equally: I. Marasco, G. Niro, M. De Vittorio, and M. Grande.

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I. Marasco, G. Niro, A. D’Orazio & M. Grande

Center for Biomolecular Nanotechnologies, Istituto Italiano di Tecnologia (IIT), Via E. Barsanti 14, 73010, Arnesano (LE), Italy

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I.M and G.N. performed the simulations, I.M., G.N. and V.M., fabricated the prototype, A.D., F.R., M.D.V. and M.G. supervised the work. I.M and G.N. drafted the manuscript. I.M., G.N., V.M., A.D., F.R., M.D.V. and M.G. contributed in preparation of the manuscript and revised the manuscript.

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Thin-film, high-frequency antenna array offers new flexibility for wireless communications

Princeton researchers have taken a step toward developing a type of antenna array that could coat an airplane's wings, function as a skin patch transmitting signals to medical implants, or cover a room as wallpaper that communicates with internet of things (IoT) devices.

The technology, which could enable many uses of emerging 5G and 6G wireless networks, is based on large-area electronics, a way of fabricating electronic circuits on thin, flexible materials. The researchers described its development in a paper published Oct. 7 in Nature Electronics .

The approach overcomes limitations of conventional silicon semiconductors, which can operate at the high radio frequencies needed for 5G applications, but can only be made up to a few centimeters wide, and are difficult to assemble into the large arrays required for enhanced communication with low-power devices.

"To achieve these large dimensions, people have tried discrete integration of hundreds of little microchips. But that's not practical -- it's not low-cost, it's not reliable, it's not scalable on a wireless systems level," said senior study author Naveen Verma, a professor of electrical and computer engineering and director of Princeton's Keller Center for Innovation in Engineering Education.

"What you want is a technology that can natively scale to these big dimensions. Well, we have a technology like that -- it's the one that we use for our displays" such as computer monitors and liquid-crystal display (LCD) televisions, said Verma. These use thin-film transistor technology, which Verma and colleagues adapted for use in wireless signaling.

The researchers used zinc-oxide thin-film transistors to create a 1-foot-long (30-centimeter) row of three antennas, in a setup known as a phased array. Phased antenna arrays can transmit narrow-beam signals that can be digitally programmed to achieve desired frequencies and directions. Each antenna in the array emits a signal with a specified time delay from its neighbors, and the constructive and destructive interference between these signals add up to a focused electromagnetic beam -- akin to the interference between ripples created by water droplets in a pond.

A single antenna broadcasts a fixed signal in all directions, "but a phased array can electrically scan the beam to different directions, so you can do point-to-point wireless communication," said lead study author Can Wu, a postdoctoral researcher at Stanford University who completed a Ph.D. in electrical and computer engineering at Princeton earlier this year.

Phased array antennas have been used for decades in long-distance communication systems such as radar systems, satellites, and cellular networks, but the technology developed by the Princeton team could bring new flexibility to phased arrays and enable them to operate at a different range of radio frequencies than previous systems.

"Large-area electronics is a thin film technology, so we can build circuits on a flexible substrate over a span of meters, and we can monolithically integrate all the components into a sheet that has the form factor of a piece of paper," said Wu.

In the study, the team fabricated the transistors and other components on a glass substrate, but a similar process could be used to create circuits on flexible plastic, said Wu.

This type of antenna system could be installed almost anywhere. When used like wallpaper in a room, it could enable quick, secure and energy-efficient communication with a distributed network of IoT devices such as temperature or motion sensors.

Having an antenna that's a flexible surface could also be beneficial for satellites, which are launched in a compact format and unfold as they reach orbit, and a large area could be advantageous for long-distance communication with aircraft.

"With an airplane, because its distance is so far, you lose a lot of the signal power, and you want to be able to communicate with high sensitivity. The wings are a fairly large area, so if you have a single point receiver on that wing it doesn't help too much, but if you can expand the amount of area that's capturing the signal by a factor of a hundred or a thousand, you can reduce your signal power and increase the sensitivity of your radio," said Verma.

In addition to Wu and Verma, the paper's coauthors, all from the Department of Electrical and Computer Engineering, were Ph.D. graduates Yoni Mehlman (2020) and Tiffany Moy (2017); graduate students Prakhar Kumar and Yue Ma; postdoctoral research associate Hongyang Jia; professor emeritus and senior scholar Sigurd Wagner; and James Sturm, the Stephen R. Forrest Professor in Electrical Engineering.

The work was supported in part by the Defense Advanced Research Projects Agency's Center for Brain-Inspired Computing and by Princeton's Program in Plasma Science and Technology. The research also utilized cleanroom facilities at the Princeton Institute for the Science and Technology of Materials.

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• Can Wu, Yoni Mehlman, Prakhar Kumar, Tiffany Moy, Hongyang Jia, Yue Ma, Sigurd Wagner, James C. Sturm, Naveen Verma. A phased array based on large-area electronics that operates at gigahertz frequency . Nature Electronics , 2021; 4 (10): 757 DOI: 10.1038/s41928-021-00648-z

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Taking RNAi from interesting science to impactful new treatments

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There are many hurdles to clear before a research discovery becomes a life-changing treatment for patients. That’s especially true when the treatments being developed represent an entirely new class of medicines. But overcoming those obstacles can revolutionize our ability to treat diseases.

Few companies exemplify that process better than Alnylam Pharmaceuticals. Alnylam was founded by a group of MIT-affiliated researchers who believed in the promise of a technology — RNA interference, or RNAi.

The researchers had done foundational work to understand how RNAi, which is a naturally occurring process, works to silence genes through the degradation of messenger RNA. But it was their decision to found Alnylam in 2002 that attracted the funding and expertise necessary to turn their discoveries into a new class of medicines. Since that decision, Alnylam has made remarkable progress taking RNAi from an interesting scientific discovery to an impactful new treatment pathway.

Today Alnylam has five medicines approved by the U.S. Food and Drug Administration (one Alnylam-discovered RNAi therapeutic is licensed to Novartis) and a rapidly expanding clinical pipeline. The company’s approved medicines are for debilitating, sometimes fatal conditions that many patients have grappled with for decades with few other options.

The company estimates its treatments helped more than 5,000 patients in 2023 alone. Behind that number are patient stories that illustrate how Alnylam has changed lives. A mother of three says Alnylam’s treatments helped her take back control of her life after being bed-ridden with attacks associated with the rare genetic disease acute intermittent porphyria (AIP). Another patient reported that one of the company’s treatments helped her attend her daughter’s wedding. A third patient, who had left college due to frequent AIP attacks, was able to return to school.

These days Alnylam is not the only company developing RNAi-based medicines. But it is still a pioneer in the field, and the company’s founders — MIT Institute Professor Phil Sharp, Professor David Bartel, Professor Emeritus Paul Schimmel, and former MIT postdocs Thomas Tuschl and Phillip Zamore — see Alnylam as a champion for the field more broadly.

“Alnylam has published more than 250 scientific papers over 20 years,” says Sharp, who currently serves as chair of Alnylam’s scientific advisory board. “Not only did we do the science, not only did we translate it to benefit patients, but we also described every step. We established this as a modality to treat patients, and I’m very proud of that record.”

Pioneering RNAi development

MIT’s involvement in RNAi dates back to its discovery. Before Andrew Fire PhD ’83 shared a Nobel Prize for the discovery of RNAi in 1998, he worked on understanding how DNA was transcribed into RNA, as a graduate student in Sharp’s lab.

After leaving MIT, Fire and collaborators showed that double-stranded RNA could be used to silence specific genes in worms. But the biochemical mechanisms that allowed double-stranded RNA to work were unknown until MIT professors Sharp, Bartel, and Ruth Lehmann, along with Zamore and Tuschl, published foundational papers explaining the process. The researchers developed a system for studying RNAi and showed how RNAi can be controlled using different genetic sequences. Soon after Tuschl left MIT, he showed that a similar process could also be used to silence specific genes in human cells, opening up a new frontier in studying genes and ultimately treating diseases.

“Tom showed you could synthesize these small RNAs, transfect them into cells, and get a very specific knockdown of the gene that corresponded to that the small RNAs,” Bartel explains. “That discovery transformed biological research. The ability to specifically knockdown a mammalian gene was huge. You could suddenly study the function of any gene you were interested in by knocking it down and seeing what happens. … The research community immediately started using that approach to study the function of their favorite genes in mammalian cells.”

Beyond illuminating gene function, another application came to mind.

“Because almost all diseases are related to genes, could we take these small RNAs and silence genes to treat patients?” Sharp remembers wondering.

To answer the question, the researchers founded Alnylam in 2002. (They recruited Schimmel, a biotech veteran, around the same time.) But there was a lot of work to be done before the technology could be tried in patients. The main challenge was getting RNAi into the cytoplasm of the patients’ cells.

“Through work in Dave Bartel and Phil Sharp's lab, among others, it became evident that to make RNAi into therapies, there were three problems to solve: delivery, delivery, and delivery,” says Alnylam Chief Scientific Officer Kevin Fitzgerald, who has been with the company since 2005.

Early on, Alnylam collaborated with MIT drug delivery expert and Institute Professor Bob Langer. Eventually, Alnylam developed the first lipid nanoparticles (LNPs) that could be used to encase RNA and deliver it into patient cells. LNPs were later used in the mRNA vaccines for Covid-19.

“Alnylam has invested over 20 years and more than $4 billion in RNAi to develop these new therapeutics,” Sharp says. “That is the means by which innovations can be translated to the benefit of society.”

From scientific breakthrough to patient bedside

Alnylam received its first FDA approval in 2018 for treatment of the polyneuropathy of hereditary transthyretin-mediated amyloidosis, a rare and fatal disease. It doubled as the first RNAi therapeutic to reach the market and the first drug approved to treat that condition in the United States.

“What I keep in mind is, at the end of the day for certain patients, two months is everything,” Fitzgerald says. “The diseases that we’re trying to treat progress month by month, day by day, and patients can get to a point where nothing is helping them. If you can move their disease by a stage, that’s huge.”

Since that first treatment, Alnylam has updated its RNAi delivery system — including by conjugating small interfering RNAs to molecules that help them gain entry to cells — and earned approvals to treat other rare genetic diseases along with high cholesterol (the treatment licensed to Novartis). All of those treatments primarily work by silencing genes that encode for the production of proteins in the liver, which has proven to be the easiest place to deliver RNAi molecules. But Alnylam’s team is confident they can deliver RNAi to other areas of the body, which would unlock a new world of treatment possibilities. The company has reported promising early results in the central nervous system and says a phase one study last year was the first RNAi therapeutic to demonstrate gene silencing in the human brain.

“There’s a lot of work being done at Alnylam and other companies to deliver these RNAis to other tissues: muscles, immune cells, lung cells, etc.,” Sharp says. “But to me the most interesting application is delivery to the brain. We think we have a therapeutic modality that can very specifically control the activity of certain genes in the nervous system. I think that’s extraordinarily important, for diseases from Alzheimer’s to schizophrenia and depression.”

The central nervous system work is particularly significant for Fitzgerald, who watched his father struggle with Parkinson’s.

“Our goal is to be in every organ in the human body, and then combinations of organs, and then combinations of targets within individual organs, and then combinations of targets within multi-organs,” Fitzgerald says. “We’re really at the very beginning of what this technology is going do for human health.”

It’s an exciting time for the RNAi scientific community, including many who continue to study it at MIT. Still, Alnylam will need to continue executing in its drug development efforts to deliver on that promise and help an expanding pool of patients.

“I think this is a real frontier,” Sharp says. “There’s major therapeutic need, and I think this technology could have a huge impact. But we have to prove it. That’s why Alnylam exists: to pursue new science that unlocks new possibilities and discover if they can be made to work. That, of course, also why MIT is here: to improve lives.”

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Research: What Companies Don’t Know About How Workers Use AI

• Jeremie Brecheisen

Three Gallup studies shed light on when and why AI is being used at work — and how employees and customers really feel about it.

Leaders who are exploring how AI might fit into their business operations must not only navigate a vast and ever-changing landscape of tools, but they must also facilitate a significant cultural shift within their organizations. But research shows that leaders do not fully understand their employees’ use of, and readiness for, AI. In addition, a significant number of Americans do not trust business’ use of AI. This article offers three recommendations for leaders to find the right balance of control and trust around AI, including measuring how their employees currently use AI, cultivating trust by empowering managers, and adopting a purpose-led AI strategy that is driven by the company’s purpose instead of a rules-heavy strategy that is driven by fear.

If you’re a leader who wants to shift your workforce toward using AI, you need to do more than manage the implementation of new technologies. You need to initiate a profound cultural shift. At the heart of this cultural shift is trust. Whether the use case for AI is brief and experimental or sweeping and significant, a level of trust must exist between leaders and employees for the initiative to have any hope of success.

• Jeremie Brecheisen is a partner and managing director of The Gallup CHRO Roundtable.

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This research topic focuses on antennas and arrays for electromagnetic imaging systems and their various applications. With the rapid rise of technological advancements in cost-effective and non-invasive imaging systems, particularly for medical applications, there is a demand for the development of a single antenna or an array of antennas that can be designed to enable maximum penetration of electromagnetic waves towards the targeted part of the human body. In addition, these antennas should be adequately shielded to avoid interference with wireless devices. Therefore, various materials, such as decoupling and matching materials, are needed to maximise signal penetration inside the targeted organ, while a proper absorber is required to cover the device. The selection of optimum physical properties of materials to serve the above-mentioned tasks depends on the frequency band in use, targeted organ, antenna design, cost, structure, weight, among other factors. Furthermore, the optimum material is usually not available in nature, and thus engineered materials are required to meet these requirements. Composite materials can be developed by adding filling materials, such as hollow glass microspheres, conductive particles or foaming agents to provide optimum properties. However, available solutions have significant drawbacks that limit their feasibility in medical devices. For instance, current broadband absorbers are thick, bulky, and fragile, making them unsuitable for use in portable devices. Designing proper couplers, decouplers and absorbers pose the main challenge, requiring the development of dielectric and magnetic materials with specific electromagnetic profiles, and their accurate characterisation. Substrate materials are also essential elements in designing couplers and absorbers, and their electromagnetic properties play a significant role in the overall performance of the electromagnetic device. Materials can be dielectric or magnetic, or a combination of both. As available dielectric and magnetic materials are dispersed over the used frequencies, while most electromagnetic medical devices operate at wide bands, emphasis is given to developing materials with a specific electric and magnetic properties profile. Designers have employed the available substrates to fabricate various microstrip components such as antennas, filters, dividers and phase-shifters. The designers were limited by the few discrete values of the permittivity and loss tangent. Engineered substrates, where the permittivity and loss tangent can be chosen by the designer will offer more freedom, and open the door to new designs. This Research Topic aims to provide an overview of the developments of electromagnetic technologies for biomedical and communication applications. Prospective authors are invited to submit original manuscripts, reviews, perspectives and mini reviews on topics including, but not limited to: 1. Antenna and array on engineered-materials substrate. 2. Metamaterial antennas and array. 3. wearable electromagnetic sensors. 4. flexible /on-body/implants antennas. 5. focused field antennas and arrays. 6. improve electromagnetic signal penetration into the human body. 7. Shielding and isolating array elements. 8. Metamaterials-based antennas and arrays. 9. Engineered-based substrate to improve the performance of electromagnetic imaging systems. 10. polymer-based dielectric substrate antenna array for medical electromagnetic imaging systems. 11.Microstrip components such as filters, dividers, phase shifters and resonators

Keywords : Engineered -material substrate, Metamaterials, Wearable Antennas, Shielding and isolating Antennas, and focusing the electromagnetic field.

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Research team develops an impact-based forecasting system for improved early flood warning

by Helmholtz Association of German Research Centres

Climate change increases the frequency of extreme events such as flooding. This reinforces the need to develop methods for more precise and faster flood forecasting in order to better protect the population in the future.

A research team from the Helmholtz Centre for Environmental Research (UFZ) and the German Research Centre for Geosciences (GFZ) has presented a flood forecasting system in Nature Communications that provides not only timely water levels but also dynamic high-resolution flood inundation maps. The researchers have been able to combine various forecasting models in such a way as to precisely forecast flood impacts on individual buildings.

Over the past years, great progress has been made in the spatiotemporal forecasting of flood events. It is thus now possible to predict maximum flood levels at locations of river gauges. Until now, however, estimates of the impacts of flooding on cities and municipalities were only rough or even completely inaccurate, especially for people at the lower river reaches away from gauge locations. However, this information is critical, as the affected population must be notified as quickly as possible in advance in order to initiate any necessary evacuation measures.

"What is needed is a state-of-the-art early flood warning system that provides high-resolution flood forecasts in a timely fashion and indicates the impacts of the flood on individual buildings," says senior author and UFZ modeler Prof. Luis Samaniego. This would be a key improvement for crisis management.

In a first step in developing the new flood forecasting system, the researchers from the two Helmholtz Centres combined the precipitation forecasts from the German Weather Service (NWP limited area ensemble prediction system) with the mesoscale hydrologic model (mHM) developed at the UFZ. This model not only provides information on water discharge, but also temporal soil moisture information—one of the critical factors for flood development.

Based on the available data from the catastrophic flood in the Ahr Valley in July 2021 and an ensemble prediction system with 20 members, they were able to predict hourly flood peak flows at gauge Altenahr in a hindcast mode. In this approach, they estimated the likelihood of exceedance of the 50-year or the 100-year flood levels.

Simulations revealed that 15% of the ensemble members would have forecast an exceedance of a 100-year flood with a lead time of 47 hours and thus nearly two days prior to the flood peak in the Ahr Valley. The closer the event came, the greater the probability that the 100-year level defined at that time would actually be exceeded: 75% of all ensemble members forecast the 100-year flood 17 hours before the flood peak, and finally 100% did so 7 hours in advance.

"If 75% of the forecasts in an ensemble predict a 100-year flood, there is a high probability that it will occur," says lead author and UFZ modeler Dr. Husain Najafi.

In the second step, the Helmholtz researchers combined the streamflow generated by mHM hydrologic model with the RIM2D hydrodynamic flood model developed by the GFZ Potsdam. RIM2D very rapidly simulates the inundation dynamics and the evolution of flood depths. This model, with a spatial resolution of 10 meters x 10 meters, first enables hourly forecasts inundation areas and depths and hence reveals which locations and to what extent specific buildings, streets, railway segments, hospitals or other critical infrastructure elements will be affected by a flooding event.

"The responsible authorities and the population therefore not only have information on a possible gauge water level 30 kilometers upstream, but also a high-resolution flood map showing the impacts of the flood. For example, they could know where people could be in danger or who have to be evacuated," says GFZ hydrologist Dr. Sergiy Vorogushyn.

The combined forecast model from the UFZ and GFZ has passed the first test in reconstructing the extreme flood event in the Ahr Valley. In a further test phase starting this summer, the automated model chain will be tested in real time as part of the second phase of the Helmholtz Climate Initiative in two additional catchments of Fils and Murr rivers in Baden-Württemberg.

If the model system also passes this phase, it can be applied for regions subject to high flood risk, especially due to flash floods. This could decisively strengthen the existing flood early warning systems and could extend the horizon of the forecasts to include flood impacts. This could significantly reduce affected populations and property damage in the future.

Journal information: Nature Communications

Provided by Helmholtz Association of German Research Centres

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Broad Public Support for Legal Abortion Persists 2 Years After Dobbs

By more than 2 to 1, americans say medication abortion should be legal, table of contents.

• Other abortion attitudes
• Overall attitudes about abortion
• Americans’ views on medication abortion in their states
• How statements about abortion resonate with Americans
• Acknowledgments
• The American Trends Panel survey methodology

Pew Research Center conducted this study to understand Americans’ views on the legality of abortion, as well as their perceptions of abortion access. For this analysis, we surveyed 8,709 adults from April 8 to 14, 2024. Everyone who took part in this survey is a member of the Center’s American Trends Panel (ATP), an online survey panel that is recruited through national, random sampling of residential addresses. This way nearly all U.S. adults have a chance of selection. The survey is weighted to be representative of the U.S. adult population by gender, race, ethnicity, partisan affiliation, education and other categories. Read more about the ATP’s methodology .

Here are the questions used for the report and its methodology .

Nearly two years after the Supreme Court overturned the 1973 Roe v. Wade decision guaranteeing a national right to abortion, a majority of Americans continue to express support for abortion access.

About six-in-ten (63%) say abortion should be legal in all or most cases. This share has grown 4 percentage points since 2021 – the year prior to the 2022 decision in Dobbs v. Jackson Women’s Health Organization that overturned Roe.

The new Pew Research Center survey, conducted April 8-14, 2024, among 8,709 adults, surfaces ongoing – and often partisan – divides over abortion attitudes:

• Democrats and Democratic-leaning independents (85%) overwhelmingly say abortion should be legal in all or most cases, with near unanimous support among liberal Democrats.
• By comparison, Republicans and Republican leaners (41%) are far less likely to say abortion should be legal in all or most cases. However, two-thirds of moderate and liberal Republicans still say it should be.

Since before Roe was overturned, both parties have seen a modest uptick in the share who say abortion should be legal.

As in the past, relatively few Americans (25%) say abortion should be legal in all cases, while even fewer (8%) say it should be illegal in all cases. About two-thirds of Americans do not take an absolutist view: 38% say it should be legal in most cases, and 28% say it should be illegal in most cases.

Related: Americans overwhelmingly say access to IVF is a good thing

Women’s abortion decisions

A narrow majority of Americans (54%) say the statement “the decision about whether to have an abortion should belong solely to the pregnant woman” describes their views extremely or very well. Another 19% say it describes their views somewhat well, and 26% say it does not describe their views well.

Views on an embryo’s rights

About a third of Americans (35%) say the statement “human life begins at conception, so an embryo is a person with rights” describes their views extremely or very well, while 45% say it does not describe their views well.

But many Americans are cross-pressured in their views: 32% of Americans say both statements about women’s decisions and embryos’ rights describe their views at least somewhat well.

Abortion access

About six-in-ten Americans in both parties say getting an abortion in the area where they live would be at least somewhat easy, compared with four-in-ten or fewer who say it would be difficult.

However, U.S. adults are divided over whether getting an abortion should be easier or harder:

• 31% say it should be easier for someone to get an abortion in their area, while 25% say it should be harder. Four-in-ten say the ease of access should be about what it is now.
• 48% of Democrats say that obtaining an abortion should be easier than it is now, while just 15% of Republicans say this. Instead, 40% of Republicans say it should be harder (just 11% of Democrats say this).

As was the case last year, views about abortion access vary widely between those who live in states where abortion is legal and those who live in states where it is not allowed.

For instance, 20% of adults in states where abortion is legal say it would be difficult to get an abortion where they live, but this share rises to 71% among adults in states where abortion is prohibited.

Medication abortion

Americans say medication abortion should be legal rather than illegal by a margin of more than two-to-one (54% vs. 20%). A quarter say they are not sure.

Like opinions on the legality of abortion overall, partisans differ greatly in their views of medication abortion:

• Republicans are closely split but are slightly more likely to say it should be legal (37%) than illegal (32%). Another 30% aren’t sure.
• Democrats (73%) overwhelmingly say medication abortion should be legal. Just 8% say it should be illegal, while 19% are not sure.

Across most other demographic groups, Americans are generally more supportive than not of medication abortion.

Across demographic groups, support for abortion access has changed little since this time last year.

Today, roughly six-in-ten (63%) say abortion should be legal in all (25%) or most (38%) cases. And 36% say it should be illegal in all (8%) or most (28%) cases.

While differences are only modest by gender, other groups vary more widely in their views.

Race and ethnicity

Support for legal abortion is higher among Black (73%) and Asian (76%) adults compared with White (60%) and Hispanic (59%) adults.

Compared with older Americans, adults under 30 are particularly likely to say abortion should be legal: 76% say this, versus about six-in-ten among other age groups.

Those with higher levels of formal education express greater support for legal abortion than those with lower levels of educational attainment.

About two-thirds of Americans with a bachelor’s degree or more education (68%) say abortion should be legal in all or most cases, compared with six-in-ten among those without a degree.

White evangelical Protestants are about three times as likely to say abortion should be illegal (73%) as they are to say it should be legal (25%).

By contrast, majorities of White nonevangelical Protestants (64%), Black Protestants (71%) and Catholics (59%) say abortion should be legal. And religiously unaffiliated Americans are especially likely to say abortion should be legal (86% say this).

Partisanship and ideology

Democrats (85%) are about twice as likely as Republicans (41%) to say abortion should be legal in all or most cases.

But while more conservative Republicans say abortion should be illegal (76%) than legal (27%), the reverse is true for moderate and liberal Republicans (67% say legal, 31% say illegal).

By comparison, a clear majority of conservative and moderate Democrats (76%) say abortion should be legal, with liberal Democrats (96%) overwhelmingly saying this.

Views of abortion access by state

About six-in-ten Americans (58%) say it would be easy for someone to get an abortion in the area where they live, while 39% say it would be difficult.

This marks a slight shift since last year, when 54% said obtaining an abortion would be easy. But Americans are still less likely than before the Dobbs decision to say obtaining an abortion would be easy.

Still, Americans’ views vary widely depending on whether they live in a state that has banned or restricted abortion.

In states that prohibit abortion, Americans are about three times as likely to say it would be difficult to obtain an abortion where they live as they are to say it would be easy (71% vs. 25%). The share saying it would be difficult has risen 19 points since 2019.

In states where abortion is restricted or subject to legal challenges, 51% say it would be difficult to get an abortion where they live. This is similar to the share who said so last year (55%), but higher than the share who said this before the Dobbs decision (38%).

By comparison, just 20% of adults in states where abortion is legal say it would be difficult to get one. This is little changed over the past five years.

Americans’ attitudes about whether it should be easier or harder to get an abortion in the area where they live also varies by geography.

Overall, a decreasing share of Americans say it should be harder to obtain an abortion: 33% said this in 2019, compared with 25% today.

This is particularly true of those in states where abortion is now prohibited or restricted.

In both types of states, the shares of Americans saying it should be easier to obtain an abortion have risen 12 points since before Roe was overturned, as the shares saying it should be harder have gradually declined.

By comparison, changes in views among those living in states where abortion is legal have been more modest.

While Americans overall are more supportive than not of medication abortion (54% say it should be legal, 20% say illegal), there are modest differences in support across groups:

• Younger Americans are somewhat more likely to say medication abortion should be legal than older Americans. While 59% of adults ages 18 to 49 say it should be legal, 48% of those 50 and older say the same.
• Asian adults (66%) are particularly likely to say medication abortion should be legal compared with White (55%), Black (51%) and Hispanic (47%) adults.
• White evangelical Protestants oppose medication abortion by about two-to-one (45% vs. 23%), with White nonevangelicals, Black Protestants, Catholics and religiously unaffiliated adults all being more likely than not to say medication abortion should be legal.
• Republicans are closely divided over medication abortion: 37% say it should be legal while 32% say it should be illegal. But similar to views on abortion access overall, conservative Republicans are more opposed (43% illegal, 27% legal), while moderate and liberals are more supportive (55% legal, 14% illegal).

Just over half of Americans (54%) say “the decision about whether to have an abortion should belong solely to the pregnant woman” describes their views extremely or very well, compared with 19% who say somewhat well and 26% who say not too or not at all well.

Democrats (76%) overwhelmingly say this statement describes their views extremely or very well, with just 8% saying it does not describe their views well.

Republicans are more divided: 44% say it does not describe their views well while 33% say it describes them extremely or very well. Another 22% say it describes them somewhat well.

Fewer Americans (35%) say the statement “human life begins at conception, so an embryo is a person with rights” describes their views extremely or very well. Another 19% say it describes their views somewhat well while 45% say it describes them not too or not at all well.

(The survey asks separately whether “a fetus is a person with rights.” The results are roughly similar: 37% say that statement describes their views extremely or very well.)

Republicans are about three times as likely as Democrats to say “an embryo is a person with rights” describes their views extremely or very well (53% vs. 18%). In turn, Democrats (66%) are far more likely than Republicans (25%) to say it describes their views not too or not at all well.

Some Americans are cross-pressured about abortion

When results on the two statements are combined, 41% of Americans say the statement about a pregnant woman’s right to choose describes their views at least somewhat well , but not the statement about an embryo being a person with rights. About two-in-ten (21%) say the reverse.

But for nearly a third of U.S. adults (32%), both statements describe their views at least somewhat well.

Just 4% of Americans say neither statement describes their views well.

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Public Opinion on Abortion

Americans overwhelmingly say access to ivf is a good thing, what the data says about abortion in the u.s., support for legal abortion is widespread in many countries, especially in europe, nearly a year after roe’s demise, americans’ views of abortion access increasingly vary by where they live, most popular, report materials.

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Epic science inside a cubic millimeter of brain.

Six layers of excitatory neurons color-coded by depth.

Credit: Google Research and Lichtman Lab

Anne J. Manning

Harvard Staff Writer

Researchers publish largest-ever dataset of neural connections

A cubic millimeter of brain tissue may not sound like much. But considering that that tiny square contains 57,000 cells, 230 millimeters of blood vessels, and 150 million synapses, all amounting to 1,400 terabytes of data, Harvard and Google researchers have just accomplished something stupendous.   

Led by Jeff Lichtman, the Jeremy R. Knowles Professor of Molecular and Cellular Biology and newly appointed dean of science , the Harvard team helped create the largest 3D brain reconstruction to date, showing in vivid detail each cell and its web of connections in a piece of temporal cortex about half the size of a rice grain.

Published in Science, the study is the latest development in a nearly 10-year collaboration with scientists at Google Research, combining Lichtman’s electron microscopy imaging with AI algorithms to color-code and reconstruct the extremely complex wiring of mammal brains. The paper’s three first co-authors are former Harvard postdoc Alexander Shapson-Coe, Michał Januszewski of Google Research, and Harvard postdoc Daniel Berger.

The ultimate goal, supported by the National Institutes of Health BRAIN Initiative , is to create a comprehensive, high-resolution map of a mouse’s neural wiring, which would entail about 1,000 times the amount of data the group just produced from the 1-cubic-millimeter fragment of human cortex.  

“The word ‘fragment’ is ironic,” Lichtman said. “A terabyte is, for most people, gigantic, yet a fragment of a human brain — just a minuscule, teeny-weeny little bit of human brain — is still thousands of terabytes.”  

Jeff Lichtman.

Kris Snibbe/Harvard Staff Photographer

The latest map contains never-before-seen details of brain structure, including a rare but powerful set of axons connected by up to 50 synapses. The team also noted oddities in the tissue, such as a small number of axons that formed extensive whorls. Because the sample was taken from a patient with epilepsy, the researchers don’t know whether such formations are pathological or simply rare.

Lichtman’s field is connectomics, which seeks to create comprehensive catalogs of brain structure, down to individual cells. Such completed maps would unlock insights into brain function and disease, about which scientists still know very little.

Google’s state-of-the-art AI algorithms allow for reconstruction and mapping of brain tissue in three dimensions. The team has also developed a suite of publicly available tools researchers can use to examine and annotate the connectome.

“Given the enormous investment put into this project, it was important to present the results in a way that anybody else can now go and benefit from them,” said Google collaborator Viren Jain.

Next the team will tackle the mouse hippocampal formation, which is important to neuroscience for its role in memory and neurological disease.

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