New Horizons in Near-Zero Refractive Index Photonics and Hyperbolic Metamaterials.

The engineering of the spatial and temporal properties of both the electric permittivity and the refractive index of materials is at the core of photonics. When vanishing to zero, those two variables provide efficient knobs to control light-matter interactions. This Perspective aims at providing an overview of the state of the art and the challenges in emerging research areas where the use of near-zero refractive index and hyperbolic metamaterials is pivotal, in particular, light and thermal emission, nonlinear optics, sensing applications, and time-varying photonics.

Magnetoplasmonic Nanoantennas for On-Chip Reconfigurable Optical Wireless Communications.

On-chip wireless communications require optical nanoantennas with dynamically tunable radiation patterns, which may allow for higher integration with multiple nanoantennas instead of two fixed nanoantennas in existing approaches. In this paper, we introduce a concept to enable active manipulation of radiated beam steering using applied magnetic fields. The proposed system consists of a highly directive Yagi-Uda-like arrangement of magnetoplasmonic nanoribs made of Co6Ag94 and immersed in SiO2. Numerical demonstration of the tilting of the radiated beam from the nanoantenna on its plane is provided with full-wave electromagnetic simulations using the finite element method. The tilt direction of the radiated beam can be changed by reversing the magnetization direction, while the conventional plasmonic nanoantenna pattern is recovered by demagnetizing the system. The geometry of the nanoantenna can be tailored to work at optical or infrared wavelengths, but a proof of concept for λ = 700 nm is conducted for taking advantage of the high magneto-optical activity of Co6Ag94. The design was based on experimental data for materials that can be fabricated via nanolithography, thus permitting magnetically on-chip reconfigurable optical wireless communications.

Magnetically Tunable Micro-Ring Resonators for Massive Magneto-Optical Modulation in Dense Wavelength Division Multiplexing Systems.

We demonstrate, numerically, a new concept for on-chip magneto-optical (MO) modulation in dense wavelength division multiplexing (DWDM) applications. Our idea uses materials and mechanisms that are compatible with current silicon-on-insulator fabrication and CMOS technologies for monolithic integration. The physics behind our idea stems in the exploitation of the enhanced MO activity of a micro-ring, made of cerium substituted yttrium iron garnet (Ce:YIG) material, to actively manipulate the resonance wavelengths of an adjacent micro-ring resonator (MRR) of silicon (Si). This active manipulation of the latter MO-MRR structure is used to modulate the optical signal traveling through a side-coupled Si bus waveguide. Moreover, by proper tailoring multiple MO-MRRs (side-coupled to the single Si bus waveguide) to match wavelength channels in DWDM across the entire C-band optical communications spectrum, we extend our proposal to massive and dynamic MO modulation in DWDM applications. Significantly, we noticed that the active MO shifting of the resonant wavelength (used for MO modulation here) can be used for improvements in the spectrum utilization efficiency in future elastic optical networks (EONs).

Design of Plasmonic Yagi-Uda Nanoantennas for Chip-Scale Optical Wireless Communications.

Optical wireless transmission has recently become a major cutting-edge alternative for on-chip/inter-chip communications with higher transmission speeds and improved power efficiency. Plasmonic nanoantennas, the building blocks of this new nanoscale communication paradigm, require precise design to have directional radiation and improved communication ranges. Particular interest has been paid to plasmonic Yagi-Uda, i.e., the optical analog of the conventional Radio Frequency (RF) Yagi-Uda design, which may allow directional radiation of plasmonic fields. However, in contrast to the RF model, an overall design strategy for the directional and optimized front-to-back ratio of the radiated far-field patterns is lacking. In this work, a guide for the optimized design of Yagi-Uda plasmonic nanoantennas is shown. In particular, five different design conditions are used to study the effects of sizes and spacing between the constituent parts (made of Au). Importantly, it is numerically demonstrated (using the scattered fields) that closely spaced nanoantenna elements are not appropriated for directional light-to-plasmon conversion/radiation. In contrast, if the elements of the nanoantenna are widely spaced, the structure behaves like a one-dimensional array of nanodipoles, producing a funnel-like radiation pattern (not suitable for on-chip wireless optical transmission). Therefore, based on the results here, it can be concluded that the constituent metallic rib lengths must be optimized to exhibit the resonance at the working wavelength, whilst their separations should follow the relation λeff/π, where λeff indicates the effective wavelength scaling for plasmonic nanostructures.

Optimization of Magnetoplasmonic ε-Near-Zero Nanostructures Using a Genetic Algorithm.

Magnetoplasmonic permittivity-near-zero (ε-near-zero) nanostructures hold promise for novel highly integrated (bio)sensing devices. These platforms merge the high-resolution sensing from the magnetoplasmonic approach with the ε-near-zero-based light-to-plasmon coupling (instead of conventional gratings or bulky prism couplers), providing a way for sensing devices with higher miniaturization levels. However, the applications are mostly hindered by tedious and time-consuming numerical analyses, due to the lack of an analytical relation for the phase-matching condition. There is, therefore, a need to develop mechanisms that enable the exploitation of magnetoplasmonic ε-near-zero nanostructures' capabilities. In this work, we developed a genetic algorithm (GA) for the rapid design (in a few minutes) of magnetoplasmonic nanostructures with optimized TMOKE (transverse magneto-optical Kerr effect) signals and magnetoplasmonic sensing. Importantly, to illustrate the power and simplicity of our approach, we designed a magnetoplasmonic ε-near-zero sensing platform with a sensitivity higher than 56∘/RIU and a figure of merit in the order of 102. These last results, higher than any previous magnetoplasmonic ε-near-zero sensing approach, were obtained by the GA intelligent program in times ranging from 2 to 5 min (using a simple inexpensive dual-core CPU computer).

Bulk Plasmon Polariton Modes in Hyperbolic Metamaterials for Giant Enhancement of the Transverse Magneto-Optical Kerr Effect.

We demonstrate a concept for the giant enhancement of the transverse magneto-optical Kerr effect (TMOKE) using bulk plasmon polariton (BPP) modes in non-magnetic multilayer hyperbolic metamaterials (HMMs). Since the BPP modes are excited through the attenuated total reflection (ATR) mechanism, using a Si-based prism-coupler, we considered a single dielectric magneto-optical (MO) spacer between the prism and the HMM. The working wavelength was estimated, using the effective medium approach for a semi-infinite dielectric-plasmonic multilayer, considering the region where the system exhibits type II HMM dispersion relations. Analytical results, by means of the scattering matrix method (SMM), were used to explain the physical principle behind our concept. Numerical results for giant TMOKE values (close to their maximum theoretical values, ±1) were obtained using the finite element method (FEM), applying the commercial software COMSOL Multiphysics. Our proposal comprises a simple and experimentally feasible structure that enables the study of MO phenomena in HMMs, which may find application in future nanostructured magnetoplasmonic metamaterials for active nanophotonic devices.

Design of Nanoarchitectures for Magnetoplasmonic Biosensing with Near-Zero-Transmittance Conditions.

Nanostructures exhibiting large transverse magneto-optical Kerr effect (TMOKE) are required for magnetoplasmonic biosensing if the aim is the minituarization and integration into microfluidic devices. In this work, we present a general strategy to design nanoarchitectures with enhanced TMOKE, which consist of an arrangement of gold ribs deposited on an magneto-optical (MO) dielectric slab of Bi:YIG (bismuth-substituted yttrium iron garnet) with a SiO2 substrate surrounded by water. Using the finite element method (FEM), we demonstrate numerically that the near-zero-transmittance condition is the most important requirement for high TMOKE values. This can be reached through geometric optimization of the nanoarchitecture by tuning the period, height, and width of the grating, thus leading to resonances at wavelengths where the MO dielectric slab has high MO activity. We also show that the TMOKE amplitude can be further increased if losses in metal ribs are reduced. For a magnetoplasmonic grating with optimized geometry, we demonstrated the potential detection of biologically relevant analytes with sensitivity in the order of 102 nm/RIU (refractive index unit). Since the nanoarchitecture proposed is experimentally feasible with, e.g., nanolithography techniques, one may expect that the design strategy may inspire the development of efficient magnetoplasmonic sensing platforms.

3D-Printed Quasi-Cylindrical Bragg Reflector to Boost the Gain and Directivity of cm- and mm-Wave Antennas.

We demonstrate a concept for a large enhancement of the directivity and gain of readily available cm- and mm-wave antennas, i.e., without altering any property of the antenna design. Our concept exploits the high reflectivity of a Bragg reflector composed of three bilayers made of transparent materials. The cavity has a triangular aperture in order to resemble the idea of a horn-like, highly directive antenna. Importantly, we report gain enhancements of more than 400% in relation to the gain of the antenna without the Bragg structure, accompanied by a highly directive radiation pattern. The proposed structure is cost-effective and easy to fabricate with 3D-printing. Our results are presented for frequencies within the conventional WiFi frequencies, based on IEEE 802.11 standards, thus, enabling easily implementation by non-experts and needing only to be placed around the antenna to improve the directivity and gain of the signal.

Chiral Dielectric Metasurfaces for Highly Integrated, Broadband Circularly Polarized Antenna.

We report on the design of a low-profile integrated millimeter-wave antenna for efficient and broadband circularly polarized electromagnetic radiation. The designed antenna comprises a chiral dielectric metasurface built with a 2×2 arrangement of dielectric cylinders with slanted-slots at the center. A broadbeam high-gain with wide axial ratio (AR)<3 dB bandwidth was reached by pairing the electric and magnetic resonances of the dielectric cylinders and the slanted slots when excited by an elliptically polarized driven-patch antenna. This electric-magnetic pairing can be tuned by varying the cylinders diameter and the tilting and rotation angles of the slanted slots. The simulation results indicate impedance-matching bandwidths up to 22.6% (25.3-31.6 GHz) with 3-dB AR bandwidths of 11.6% (26.9-30.2 GHz), which in terms of compactness (0.95λ0×0.95λ0) and performance are superior to previous antenna designs. Since the simulations were performed by assuming materials and geometries easily implementable experimentally, it is hoped that circularly polarized antennas based on chiral metasurfaces can be integrated into 5G and satellite communications.

Microfluidic Point-of-Care Devices: New Trends and Future Prospects for eHealth Diagnostics.

Point-of-care (PoC) diagnostics is promising for early detection of a number of diseases, including cancer, diabetes, and cardiovascular diseases, in addition to serving for monitoring health conditions. To be efficient and cost-effective, portable PoC devices are made with microfluidic technologies, with which laboratory analysis can be made with small-volume samples. Recent years have witnessed considerable progress in this area with "epidermal electronics", including miniaturized wearable diagnosis devices. These wearable devices allow for continuous real-time transmission of biological data to the Internet for further processing and transformation into clinical knowledge. Other approaches include bluetooth and WiFi technology for data transmission from portable (non-wearable) diagnosis devices to cellphones or computers, and then to the Internet for communication with centralized healthcare structures. There are, however, considerable challenges to be faced before PoC devices become routine in the clinical practice. For instance, the implementation of this technology requires integration of detection components with other fluid regulatory elements at the microscale, where fluid-flow properties become increasingly controlled by viscous forces rather than inertial forces. Another challenge is to develop new materials for environmentally friendly, cheap, and portable microfluidic devices. In this review paper, we first revisit the progress made in the last few years and discuss trends and strategies for the fabrication of microfluidic devices. Then, we discuss the challenges in lab-on-a-chip biosensing devices, including colorimetric sensors coupled to smartphones, plasmonic sensors, and electronic tongues. The latter ones use statistical and big data analysis for proper classification. The increasing use of big data and artificial intelligence methods is then commented upon in the context of wearable and handled biosensing platforms for the Internet of things and futuristic healthcare systems.

Designing Silver Nanoparticles for Detecting Levodopa (3,4-Dihydroxyphenylalanine, L-Dopa) Using Surface-Enhanced Raman Scattering (SERS).

Detection of the drug Levodopa (3,4-dihydroxyphenylalanine, L-Dopa) is essential for the medical treatment of several neural disorders, including Parkinson's disease. In this paper, we employed surface-enhanced Raman scattering (SERS) with three shapes of silver nanoparticles (nanostars, AgNS; nanospheres, AgNP; and nanoplates, AgNPL) to detect L-Dopa in the nanoparticle dispersions. The sensitivity of the L-Dopa SERS signal depended on both nanoparticle shape and L-Dopa concentration. The adsorption mechanisms of L-Dopa on the nanoparticles inferred from a detailed analysis of the Raman spectra allowed us to determine the chemical groups involved. For instance, at concentrations below/equivalent to the limit found in human plasma (between 10-7-10-8 mol/L), L-Dopa adsorbs on AgNP through its ring, while at 10-5-10-6 mol/L adsorption is driven by the amino group. At even higher concentrations, above 10-4 mol/L, L-Dopa polymerization predominates. Therefore, our results show that adsorption depends on both the type of Ag nanoparticles (shape and chemical groups surrounding the Ag surface) and the L-Dopa concentration. The overall strategy based on SERS is a step forward to the design of nanostructures to detect analytes of clinical interest with high specificity and at varied concentration ranges.

[Chronology and current status of the therapy in acute pancreatitis]. / Cronología y estado actual de las conductas terapéuticas en la pancreatitis aguda.

This article realize a retrospective analysis of the course of acute pancreatitis and evidence changes of concepts upon physiopathogenesis aspects, the natural history of the disease and the therapeutic management. The responsability of the biliary factor its accepted but the classic mechanism of the biliopancreatic reflux by common chanel its on discussion. Relativeness to natural history of the acute pancreatitis, however of to remain un known sone aspects to ellucidate on the future, today its accepted the biphasic course of the severe pancreatitis, with one initial period and other tardif, to second or their week, with septic complications or evolution to resolution of process. The concept of systemic inflammatory response syndrome and failure of organ systems (renal insufficiency, pulmonary insufficiency) its essential for interpretation of the ominous consequences of one inopportune surgical approach on the early period, associated with high mortality. One schematic personnel square present the different therapeutics procedures along the years, from the distant and dogmatic surgery for principle, until the actual moment where the conservative attitude its of unanimous acquiescence on critic period of disease. The surgery its indicated on second phase, with developing of septic complications, reactivation or persistence of systemic inflammatory response syndrome with increasing severity of pancreatitis.

Cronología y estado actual de las conductas terapéuticas en la pancreatitis aguda. / [Chronology and current status of the therapy in acute pancreatitis]

This article realize a retrospective analysis of the course of acute pancreatitis and evidence changes of concepts upon physiopathogenesis aspects, the natural history of the disease and the therapeutic management. The responsability of the biliary factor its accepted but the classic mechanism of the biliopancreatic reflux by common chanel its on discussion. Relativeness to natural history of the acute pancreatitis, however of to remain un known sone aspects to ellucidate on the future, today its accepted the biphasic course of the severe pancreatitis, with one initial period and other tardif, to second or their week, with septic complications or evolution to resolution of process. The concept of systemic inflammatory response syndrome and failure of organ systems (renal insufficiency, pulmonary insufficiency) its essential for interpretation of the ominous consequences of one inopportune surgical approach on the early period, associated with high mortality. One schematic personnel square present the different therapeutics procedures along the years, from the distant and dogmatic surgery for principle, until the actual moment where the conservative attitude its of unanimous acquiescence on critic period of disease. The surgery its indicated on second phase, with developing of septic complications, reactivation or persistence of systemic inflammatory response syndrome with increasing severity of pancreatitis.

Pancreatitis aguda: alteraciones y neurovasculares y microcirculatorias; estudio patogenico y terapéutico / Acute pancreatitis: neurovascular and microcirculatory changes; pathogenic and therapeutic study

Un total de 159 perros mestizos fueron distribuídos en 8 lotes de experiencia con el fin de investigar las alteraciones neurovasculares iniciales y la participación del sistema neurovegetativo en el curso evolutivo de las pancreatitis agudas. Los procedimientos utilizados y resultados obtenidos se detallan a continuación: 1. Se procedió a inducir pancreatitis agudas experimentales según dos métodos: a) inyección de bilis vesicular autóloga, en el conducto pancreático principal y b) confección de un asa ciega duodenal por exclusión a nivel del pilóro y del segmento duodenal inferior. En ambos procederes se observaron pancreatitis agudas severas com predominio de necrosis grasas en las obtenidas por inyección de bilis y con francas lesiones hemorrágicas en las producidas por oclusión duodenal. 2. El bloqueo anestésico del plexo celíaco al inibibir la conducción de estímulos a centros superiores suprimió el dolor y el shock conservando el buen estado general de los animales. No se mostró eficaz en cambio en el progreso de las alteraciones anatomopatológicos del páncreas. La resección del tronco de los esplácnicos seguida 72 horas después de la inducción de pancreatitis tuvo efectos semejantes. 3. La resección de los nervios esplácnicos seguida de un intervalo de tiempo suficiente (20 días) para la degeneración de las fibras nerviosas periféricas, antes de la provación de pancreatitis experimentales previno en forma absoluta del desnecadenamiento de las lesiones glandulares. 4. En el terreno somático, experiencias paralelas utilizando inyecciones intramusculares de esencia de trementina en miembros con o sin denervación previa, permite obtener conclusiones en todo semejantes a las anteriores, ratificando la participación directa del sistema neurovascular simpático en el proceso inflamatório en general...(AU)

Pancreatitis aguda: alteraciones y neurovasculares y microcirculatorias; estudio patogenico y terapéutico / Acute pancreatitis: neurovascular and microcirculatory changes; pathogenic and therapeutic study

Un total de 159 perros mestizos fueron distribuídos en 8 lotes de experiencia con el fin de investigar las alteraciones neurovasculares iniciales y la participación del sistema neurovegetativo en el curso evolutivo de las pancreatitis agudas. Los procedimientos utilizados y resultados obtenidos se detallan a continuación: 1. Se procedió a inducir pancreatitis agudas experimentales según dos métodos: a) inyección de bilis vesicular autóloga, en el conducto pancreático principal y b) confección de un asa ciega duodenal por exclusión a nivel del pilóro y del segmento duodenal inferior. En ambos procederes se observaron pancreatitis agudas severas com predominio de necrosis grasas en las obtenidas por inyección de bilis y con francas lesiones hemorrágicas en las producidas por oclusión duodenal. 2. El bloqueo anestésico del plexo celíaco al inibibir la conducción de estímulos a centros superiores suprimió el dolor y el shock conservando el buen estado general de los animales. No se mostró eficaz en cambio en el progreso de las alteraciones anatomopatológicos del páncreas. La resección del tronco de los esplácnicos seguida 72 horas después de la inducción de pancreatitis tuvo efectos semejantes. 3. La resección de los nervios esplácnicos seguida de un intervalo de tiempo suficiente (20 días) para la degeneración de las fibras nerviosas periféricas, antes de la provación de pancreatitis experimentales previno en forma absoluta del desnecadenamiento de las lesiones glandulares. 4. En el terreno somático, experiencias paralelas utilizando inyecciones intramusculares de esencia de trementina en miembros con o sin denervación previa, permite obtener conclusiones en todo semejantes a las anteriores, ratificando la participación directa del sistema neurovascular simpático en el proceso inflamatório en general...