BUSCADOR RECOLECTA

This work broadens the study of lipid and protein oxidation marker compounds in foal meat, employing the technology of Attenuated Total Reflectance-Fourier Transform Mid-Infrared Spectroscopy (ATR-FT/MIR, shortened in the following as MIR). As a main objective, marker compounds from 23 foals were extracted and their absorbance spectra were measured to establish prediction models (calibration and validation) between them and classical quantification analysis of the compounds. Another objective was to ascertain whether a previous extraction of the marker compounds before executing their MIR analysis is preferable compared to direct MIR measurements on the raw meat samples. In this context, marker compound results (TBARS between 0.4387 and 2.1040, and carbonyls between 4.07 and 4.68) showed more consistent predictive models than the ones achieved using quantitative analysis of the spectra obtained from the raw meat. Lipid oxidation compounds predictive models obtained in this work offered an R-cv(2) of 63.18% and protein oxidation R-cv(2) obtained in this project showed a value of 54.24%. Thus, MIR technology arises as a promising tool to identify and quantify products derived from lipid and protein oxidation in fresh foal meat., This research was funded by INIA Instituto Nacional de Investigacion y Tecnologia Agraria y Alimentaria, grant number RTA 2012-00090-C03-01 and by the Spanish Ministerio de Ciencia, Innovacion y Universidades, Project RTI2018-094475-B-I00 (MCIU/AEI/FEDER,UE).

Bull’s eye antennas exhibit remarkable directivity
considering their low profile, albeit accompanied by high sidelobes.
This undesirable radiation characteristic is tackled here by reporting a complementary split ring feeding whereby the broadside
space-wave partially responsible for the high sidelobes is cancelled
while the leaky wave is excited effectively. This feeding results in an
asymmetric bull’s eye antenna with minimal profile (∼ 0.73λ0) and
no protrusions on the radiating interface. The fabricated 10-period
antenna operating in the Ka-band shows a directivity of 23.5 dBi, a
sidelobe level of −22.9 dB (>6 dB improvement compared to other
bull’s eye antennas) and a beamwidth of 3.7◦ and 6.7◦ in the E- and
H-plane, respectively., This work was supported in part by the Engineering
and Physical Sciences Research Council (EPSRC) under Grant EP/S018395/1;
and in part by the Spanish “Ministerio de Ciencia e Innovación (MCIN)”
and the Spanish “Agencia Estatal de Investigación (AEI)” under Grant
MCIN/AEI/10.13039/501100011033/FEDER “Una manera de hacer Europa”
through Project RTI2018-094475-B-I00. The work of M. Navarro-Cía was
supported by the Royal Society under Grant RSG/R1/180040, and in part by the
University of Birmingham [Birmingham Fellowship].

This article presents the design of a flat Luneburg
metalens antenna at V-band using gap waveguide (GW) technology. The metalens consists of a parallel plate waveguide (PPW)
loaded with metallic pins whose height is modulated to get an
effective refractive index that follows the Luneburg equation.
A Groove GW (GGW) H-plane horn is used to illuminate
the metalens, such that the rays are collimated and a planar
wavefront is generated in the direction of propagation. Since the
structure at hand is planar, it can be efficiently integrated on flat
surfaces. Moreover, the fully metallic structure is mechanically
robust and presents lower losses than lenses including dielectric
substrates. A prototype has been fabricated and tested, simulations and experimental results are in very good agreement. The
metalens yields an input reflection coefficient (S11) below −10 dB
from 45 to 70 GHz, whereas the −3 dB gain fractional bandwidth
is 26.2% with respect to a center frequency of 60 GHz, with a
peak of 22.5 dB at 61 GHz. These features make this design an
interesting solution for millimeter-wave (MMW) applications., This work was supported in part by MCIN/AEI/
10.13039/501100011033/FEDER “Una manera de hacer Europa” under
Project RTI2018-094475-B-I00 and in part by the Spanish State
Research Agency under Project PID2019-109984RBC43/AEI/10.13039/
501100011033.

Understanding meat quality attribute changes during ageing by using non-destructive techniques is an emergent pursuit in the agroindustry research field. Using beef certified samples from the protected geographical indication (PGI) “Ternera de Navarra”, the primary goal of this study was to use Fourier transform infrared spectroscopy on the middle infrared region (FTIR-MIR) as a tool for the examination of meat tenderness evolution throughout ageing. Samples of the longissimus dorsi muscle of twenty young bulls were aged for 4, 6, 11, or 18 days at 4 °C. Animal carcass classification and sample proximate analysis were performed to check sample homogeneity. Raw aged steaks were analyzed by FTIR-MIR spectroscopy (4000–400 cm−1) to record the vibrational spectrum. Texture profile analysis was performed using a multiple compression test (compression rates of 20%, 80%, and 100%). Compression values were found to decrease notably between the fourth and sixth day of ageing for the three compression rates studied. This tendency continued until the 18th day for C20. For C80 and C100, there was not a clear change in the 11th and 18th days of the study. Regarding FTIR-MIR as a prediction method, it achieved an R2 lower than 40%. Using principal component analysis (PCA) of the results, the whole spectrum fingerprint was used in the discrimination of the starting and final ageing days with correct maturing time classifications. Combining the PCA treatment together with the discriminant analysis of spectral data allowed us to differentiate the samples between the initial and the final ageing points, but it did not single out the intermediate points., This work was supported by the Spanish “Ministerio de Ciencia e Innovación (MCIN)” and the Spanish “Agencia Estatal de Investigación (AEI)” (MCIN/AEI/10.13039/501100011033/FEDER “Una manera de hacer Europa”) trough Project Number. RTI2018-094475-B-I00.

In this work, we propose, design, and evaluate three types of : three types of metasurfaces using tripod-shaped unit cells when working as thin-film sensing devices. The three meta-atoms of the proposed metasensors area simple solid tripod, a hollow tripod, and a hollow tripod structure with arms.The best design showed a mean numerical sensitivity of 1.42 × 10−4nm for extremely thin samples, meaning an improvement of 381% with respect to the initial designs. These results highlight the importance of using metastructures with complex geometries that enable high-intensity electric field distributions over the whole metasurface., This research was funded by Spanish Ministerio de Ciencia, Innovación y Universidades, 094475-B-I00 (MCIU/AEI/FEDER,UE).

In this paper, a flat lens antenna using Gap Waveguide (GW) technology working in the millimeter waves band was designed. The metamaterial lens is fed using a Groove Gap Waveguide (GGW) horn antenna in order to achieve a plane wavefront at broadside. Both devices, metalens and GGW antenna achieve excellent radiation results when combined together. Due to metallic composition, the structure presents more robustness, low loss, and adaptability to a flat surface, able to be used in millimeter wave application., This research was funded by Spanish Ministerio de Ciencia, Innovación y Universidades, Project RTI2018-094475-B-I00 (MCIU/AEI/FEDER,UE).

Conventional metasurfaces provide control over the electromagnetic waves in a single working frequency operating either in transmission or reflection. Full-Space Metasurfaces (FSM) are an extension that allows operation at two different frequencies with independent functionalities in transmission and reflection. This paper presents a gradient index FSM device based on a 3-layered unit cell where the phase modulation is implemented following the Pancharatman-Berry (PB) principle. The device is designed to operate at millimeter waves, with the lowest frequency operating in reflection and the highest one in transmission. To check the structure performance, a metasurface was designed to provide beam steering in reflection at 49.4 GHz and an amplitude image hologram in transmission at 104 GHz., This work was supported by MCIN/AEI/10.13039/
501100011033/FEDER “Una manera de hacer Europa” via
Project No. RTI2018-094475-B-I00

In this Letter, an all metallic sensor based on ε-near-zero (ENZ) metamaterials is studied both numerically and experimentally when working at microwave frequencies. To emulate an ENZ medium, a sensor is made by using a narrow hollow rectangular waveguide, working near the cutoff frequency of its fundamental TE 10 mode. The performance of the sensor is systematically evaluated by placing subwavelength dielectric analytes (with different sizes and relative permittivities) within the ENZ waveguide and moving them along the propagation and transversal axes. It is experimentally demonstrated how this ENZ sensor is able to detect deeply subwavelength dielectric bodies of sizes up to 0.04λ and height 5 × 10 −3 λ with high sensitivities (and the figure of merit) up to 0.05 1/RIU (∼0.6 1/GHz) and 0.6 1/RIU when considering the sensor working as a frequency- or amplitude-shift-based device, respectively., This work was supported by MCIN/AEI/10.13039/ 501100011033/FEDER ‘Una manera de hacer Europa’ via Project No. RTI2018-094475-B-I00. V.P.-P

This paper reports the numerical and experimental study of the strain sensing effect of bidimensional quasiperiodic structures made with dielectric cylinders. Structures of around 100 cylinders arranged following a Penrose quasiperiodic disposition were simulated, built and measured, in different states of deformation. The selected quasiperiodic structure contains a symmetric decagonal ring resonator that shows two states in its photonic band gap. The frequency of these states varies linearly in opposite directions as the structure is axially deformed, becoming an interesting sensing principle that can be exploited to build optical strain gauges. As a proof of concept, centimeter-scale glass cylinder (εr=4.5) structures were fabricated and their transmission spectra were measured in the microwave range. The same structures were simulated using finite integration time domain showing a good agreement with the measurements. The sensitivity of the prototype built was 12.4 kHz/µε, very linear in a wide range. Therefore, we conclude that the states in the gap of the resonator rings of 2D quasicrystals can find an interesting application in optical strain gauge construction., Ministerio de Ciencia, Innovación y Universidades (RTI2018-094475-B-I00)

Despite three decades of effort, predicting accurately
extraordinary transmission through subwavelength hole
arrays has proven challenging. The lack of quantitative design
and modeling capability to take into account the inherent
complexity of high frequency instrumentation has prevented the
development of practical high-performance components based on
this phenomenon. This paper resorts to the Method of Moments
to provide not only such missing quantitative prediction but
also a theoretical framework to understand and shed more
light on the far-field and near-field physics of the extraordinary
terahertz (THz) transmission through subwavelength hole
arrays under different illumination and detection conditions.
An excellent agreement between the numerical and experimental
results with various illumination and detection setups is obtained,
demonstrating the suitability of this computationally efficient
modeling tool to predict the response of extraordinary transmission
structures in practical situations., The work of M. Camacho was supported by
the Engineering and Physical Sciences Research Council (EPSRC), U.K.,
through the EPSRC Centre for Doctoral Training in Metamaterials under
Grant EP/L015331/1. The work of S. A. Kuznetsov was supported by the
Russian Foundation for Basic Research (RFBR) under Grant 18-29-20066.
The work of M. Beruete was supported by the Ministerio de Ciencia,
Innovación y Universidades under Grant RTI2018-094475-B-I00. The work of
M. Navarro-Cía was supported in part by the Royal Society under Grant
RSG/R1/180040 and in part by the University of Birmingham (Birmingham
Fellowship).

We propose a pillbox antenna in combination with a geodesic lens at 60 GHz. The antenna is implemented in a dual-layer parallel plate waveguide. The waves from a geodesic lens in a first layer, after being reflected by a parabolic mirror connecting the rims of the two layers, enter a second layer and illuminate the radiation aperture. Since the lens produces a virtual focus, the reflector works as if it is fed from that a further location, making the system more compact., Project RTI2018-094475-B-I00 funded by MCIN/ AEI /10.13039/501100011033/ FEDER “Una manera de
hacer Europa”. This article is based upon work from COST Action SyMat CA18223, supported by COST
(European Cooperation in Science and Technology)

Applying the Pancharatnam–Berry (PB) principle to half-wave plate (HWP) metasurfaces allows the manipulation of wavefronts along with the conversion of the handedness of circularly polarized incident waves by simply rotating the meta-atoms that compose the metasurface. PB metasurfaces (PBM) working in transmission mode with four or more layers have been demonstrated to reach levels of transmission effi- ciency near 100% but also have resulted in bulky structures. On the other hand, compact tri-layer ultrathin (k/8) designs have reached levels near 90% but are more challenging than single- or bi-layer structures from a manufacturing viewpoint. Here, we propose a compact ultrathin (<k/13) transmissive PBM with only two layers (which significantly simplifies the fabrication process) achieving a transmission efficiency level of around 90%, focusing the wavefront of a circularly polarized incident wave and converting its handedness. The metasurface is com- posed of identical bi-layered H-shaped unit cells (meta-atoms) whose transmission phases are chosen by introducing different rotation angles to each unit cell according to a lens spatial phase profile. The structure is analytically and numerically studied and experimentally measured, verifying an excellent behavior as an HWP PB metalens at 87 GHz., This research was funded by Spanish Ministerio de Ciencia,
Innovación y Universidades, Project RTI2018-094475-B-I00 (MCIU/AEI/FEDER,UE). Sergei Kuznetsov acknowledges
support from the Ministry of Science and Higher Education
of the Russian Federation, Project 075-15-2020-797.

Nowadays, the meat industry requires non-destructive, sustainable, and rapid methods
that can provide objective and accurate quality assessment with little human intervention. Therefore,
the present research aimed to create a model that can classify beef samples from longissimus thoracis
muscle according to their tenderness degree based on hyperspectral imaging (HSI). In order to
obtain different textures, two main strategies were used: (a) aging type (wet and dry aging with
or without starters) and (b) aging times (0, 7, 13, 21, and 27 days). Categorization into two groups
was carried out for further chemometric analysis, encompassing group 1 (ngroup1 = 30) with samples
with WBSF < 53 N whereas group 2 (ngroup2 = 28) comprised samples with WBSF values 53 N.
Then, classification models were created by applying the partial least squares discriminant analysis
(PLS-DA) method. The best results were achieved by combining the following pre-processing
algorithms: 1st derivative + mean center, reaching 70.83% of correctly classified (CC) samples and
67.14% for cross validation (CV) and prediction, respectively. In general, it can be concluded that HSI
technology combined with chemometrics has the potential to differentiate and classify meat samples
according to their textural characteristics., This research was funded by Fondo Europeo de Desarrollo Regional, program FEDER 2014-2020 of Navarra, and by the Government of Navarra (project 0011-1365-2019-000091). Open Access funding was provided by Universidad Pública de Navarra. This work was also supported by the Spanish Ministry MCIN/AEI/10.13039/501100011033/FEDER, via Project No. RTI2018-094475-B-I00.

This article reports on the development and evaluation of a reconfigurable millimeter-wave reflectarray (RA)
based on liquid-crystal (LC) substrate operating in the D-band
(105–125 GHz). The RA is composed of a high-impedance
surface (HIS) with a meta-array of 33 × 29 patches on a
2-mm-thick quartz substrate, separated from the ground plane
(GP) by a 40-µm-thick LC layer. A novel LC composition with
low dielectric losses (<0.003) and high dielectric anisotropy
(>1.3) has been developed for operation at millimeter waves.
The results demonstrate a reflection phase tunability of 210◦
and low insertion losses of 2.5 dB. Furthermore, the device
was demonstrated as a proof of concept for 1-D beam-steering
applications, exhibiting an operational bandwidth of 12 GHz., This work was supported by MCIN/AEI/10.13039/501100011033/FEDER 'Una manera de hacer Europa' under Project RTI2018-094475-B-I00. The work of Sergei A. Kuznetsov was supported by the Ministry of Science and Higher Education of the Russian Federation under Grant 075-15-2020-797 (13.1902.21.0024).