Unlocking Efficient Ultrafast Bound-Electron Optical Nonlinearities via Mirror Induced Quasi Bound States in the Continuum.

The operation of photonic devices often relies on modulation of their refractive index. While the sub-bandgap index change through bound-electron optical nonlinearity offers a faster response than utilizing free carriers with an overbandgap pump, optical switching often suffers from inefficiency. Here, we use a recently observed metasurface based on mirror-induced optical bound states in the continuum, to enable superior modulation characteristics. We achieve a pulsewidth-limited switching time of 100 fs, reflectance change of 22%, remarkably low energy consumption of 255 µJ/cm2, and an enhancement of modulation contrast by a factor of 440 compared to unpatterned silicon. Additionally, the narrow photonic resonance facilitates the detection of the dispersive nondegenerate two-photon nonlinearity, allowing tunable pump and probe excitation. These findings are explained by a two-band theoretical model for the dispersive nonlinear index. The demonstrated efficient and rapid switching holds immense potential for applications, including quantum photonics, sensing, and metrology.

Optical properties of plasmonic tunneling junctions.

Over the last century, quantum theories have revolutionized our understanding of material properties. One of the most striking quantum phenomena occurring in heterogeneous media is the quantum tunneling effect, where carriers can tunnel through potential barriers even if the barrier height exceeds the carrier energy. Interestingly, the tunneling process can be accompanied by the absorption or emission of light. In most tunneling junctions made of noble metal electrodes, these optical phenomena are governed by plasmonic modes, i.e., light-driven collective oscillations of surface electrons. In the emission process, plasmon excitation via inelastic tunneling electrons can improve the efficiency of photon generation, resulting in bright nanoscale optical sources. On the other hand, the incident light can affect the tunneling behavior of plasmonic junctions as well, leading to phenomena such as optical rectification and induced photocurrent. Thus, plasmonic tunneling junctions provide a rich platform for investigating light-matter interactions, paving the way for various applications, including nanoscale light sources, sensors, and chemical reactors. In this paper, we will introduce recent research progress and promising applications based on plasmonic tunneling junctions.

Optical Bound States in the Continuum Enabled by Magnetic Resonances Coupled to a Mirror.

Dielectric metasurfaces made of high refractive index and low optical loss materials have emerged as promising platforms to achieve high-quality factor modes enabling strong light-matter interaction. Bound states in the continuum have shown potential to demonstrate narrow spectral resonances but often require asymmetric geometry and typically feature strong polarization dependence, complicating fabrication and limiting practical applications. We introduce a novel approach for designing high-quality bound states in the continuum using magnetic dipole resonances coupled to a mirror. The resulting metasurface has simple geometric parameters requiring no broken symmetry. To demonstrate the unique features of our photonic platform we show a record-breaking third harmonic generation efficiency from the metasurface benefiting from the strongly enhanced electric field at high-quality resonances. Our approach mitigates the shortcomings of previous platforms with simple geometry enabling facile and large-area fabrication of metasurfaces paving the way for applications in optical sensing, detection, quantum photonics, and nonlinear devices.

Second Harmonic Generation from a Single Plasmonic Nanorod Strongly Coupled to a WSe2 Monolayer.

Monolayer transition metal dichalcogenides, coupled to metal plasmonic nanocavities, have recently emerged as new platforms for strong light-matter interactions. These systems are expected to have nonlinear-optical properties that will enable them to be used as entangled photon sources, compact wave-mixing devices, and other elements for classical and quantum photonic technologies. Here, we report the first experimental investigation of the nonlinear properties of these strongly coupled systems, by observing second harmonic generation from a WSe2 monolayer strongly coupled to a single gold nanorod. The pump-frequency dependence of the second-harmonic signal displays a pronounced splitting that can be explained by a coupled-oscillator model with second-order nonlinearities. Rigorous numerical simulations utilizing a nonperturbative nonlinear hydrodynamic model of conduction electrons support this interpretation and reproduce experimental results. Our study thus lays the groundwork for understanding the nonlinear properties of strongly coupled nanoscale systems.

The Involvement of Insulin-Like Growth Factor 1 and Nerve Growth Factor in Alzheimer's Disease-Like Pathology and Survival Role of the Mix of Embryonic Proteoglycans: Electrophysiological Fingerprint, Structural Changes and Regulatory Effects on Neurotrophins.

Alzheimer's disease (AD)-associated neurodegeneration is triggered by different fragments of amyloid beta (Aß). Among them, Aß (25-35) fragment plays a critical role in the development of neurodegeneration-it reduces synaptic integrity by disruption of excitatory/inhibitory ratio across networks and alters the growth factors synthesis. Thus, in this study, we aimed to identify the involvement of neurotrophic factors-the insulin-like growth factor 1 (IGF-1) and nerve growth factor (NGF)-of AD-like neurodegeneration induced by Aß (25-35). Taking into account our previous findings on the neuroprotective effects of the mix of proteoglycans of embryonic genesis (PEG), it was suggested to test its regulatory effect on IGF-1 and NGF levels. To evaluate the progress of neurodegeneration, in vivo electrophysiological investigation of synaptic activity disruption of the entorhinal cortex-hippocampus circuit at AD was performed and the potential recovery effects of PEG with relative structural changes were provided. To reveal the direct effects of PEG on brain functional activity, the electrophysiological pattern of the single cells from nucleus supraopticus, sensomotor cortex and hippocampus after acute injection of PEG was examined. Our results demonstrated that after i.c.v. injection of Aß (25-35), the level of NGF decreased in cerebral cortex and hypothalamus, and, in contrast, increased in hippocampus, prompting its multidirectional role in case of brain damage. The concentration of IGF-1 significantly increased in all investigated brain structures. The administration of PEG balanced the growth factor levels accompanied by substantial restoration of neural tissue architecture and synaptic activity. Acute injection of PEG activated the hypothalamic nucleus supraopticus and hippocampal neurons. IGF-1 and NGF levels were found to be elevated in animals receiving PEG in an absence of amyloid exposure. We suggest that IGF-1 and NGF play a critical role in the development of AD. At the same time, it becomes clear that the neuroprotective effects of PEG are likely mediated via the regulation of neurotrophins.

Tailoring the quality factors and nonlinear response in hybrid plasmonic-dielectric metasurfaces.

Plasmonic nanoantennas and metamaterials concentrate optical energy into nanometric volumes strongly enhancing the light-matter interaction. This makes them promising platforms for optical sensing, nonlinear effects and quantum optics. However, absorption losses and radiative damping result in broad, low quality factor (Q) resonances of plasmonic systems that significantly limit their performance. Here, we develop a hybrid plasmonic/dielectric metasurface that can simultaneously achieve high Q and large field enhancement values in the near infrared by forming a hybridized mode between the nanoantennas' plasmonic mode and the photonic waveguide mode of Si device layer. The tunability of the modes and quality factors of our platform allows us to study the effect of the geometric parameters on the optical properties of the metasurface. We demonstrate that the strongest near field enhancement and nonlinear signal generation can be achieved by balancing the high Q factors and in-coupling efficiency in hybrid resonators.

Effect of in vivo and in vitro exposure to electrostatic field on some hematological parameters in rats.

The aim of this study was to investigate the effect of the external electrostatic field (ESF) on some hematological parameters in rats. Both in vivo and in vitro experiments were carried out. In in vivo investigations, rats were exposed to ESF (200 kV/m) during short (1 h) and long periods (6 days, 6 h daily). For in vitro study, the blood of intact rats was exposed to ESF for 1 h. Blood hematology was measured using validated ABX Micros ESV 60 Veterinary Hematology Analyzer. DNA damage in blood leucocytes was detected by means of comet assay. ESF effect on blood cell count was mainly manifested in white blood cells (WBC) and platelets. Damage of WBC was shown both in vitro and in vivo despite alterations in the count. This means the observed increase in WBC count in some cases might be a result of WBC compensatory mobilization from the bone marrow. Red blood cell (RBC) count and related parameters were slightly affected by ESF. Nevertheless, alterations in the shape and size of RBC were manifested. All ESF effects were extinguished in 14 days after the end of exposure. Bioelectromagnetics. 37:513-526, 2016. © 2016 Wiley Periodicals, Inc.

Biological effects of the electrostatic field: red blood cell-related alterations of oxidative processes in blood.

UNLABELLED: The aim of this study was to determine activities of pro-/antioxidant enzymes, reactive oxygen species (ROS) content, and oxidative modification of proteins and lipids in red blood cells (RBCs) and blood plasma of rats exposed to electrostatic field (200 kV/m) during the short (1 h) and the long periods (6 day, 6 h daily). Short-term exposure was characterized by the increase of oxidatively damaged proteins in blood of rats. This was strongly expressed in RBC membranes. After long-term action, RBC content in peripheral blood was higher than in control (P < 0.01) and the attenuation of prooxidant processes was shown. HIGHLIGHTS: External electrostatic field (200 kV/m) alters the balance in pro-/antioxidant processes. We examine oxidative processes in plasma and RBC (hemolysate and membranes). Biological effects of static electric field depend on exposure time. Acute action of electrostatic field (ESF) characterized by activation of the prooxidant processes. Long-term exposure reflected with prevalence of antioxidant activities.

Non-thermal emission in gap-mode plasmon photoluminescence.

Photoluminescence from spatially inhomogeneous plasmonic nanostructures exhibits fascinating wavelength-dependent nonlinear behaviors due to the intraband recombination of hot electrons excited into the conduction band of the metal. The properties of the excited carrier distribution and the role of localized plasmonic modes are subjects of debate. In this work, we use plasmonic gap-mode resonators with precise nanometer-scale confinement to show that the nonlinear photoluminescence behavior can become dominated by non-thermal contributions produced by the excited carrier population that strongly deviates from the Fermi-Dirac distribution due to the confinement-induced large-momentum free carrier absorption beyond the dipole approximation. These findings open new pathways for controllable light conversion using nonequilibrium electron states at the nanoscale.

Clinical performance and application of novel serum collection "Ser-Col" device in the practice of laboratory diagnosis of infection diseases and several other immunochemical tests.

BACKGROUND: Dried blood collection devices might be beneficial for diagnosing infectious diseases in areas far from the medical facilities and in lockdown situations. There are several reports on the efficacy of such applications for qualitative tests. Here we demonstrated the feasibility of a novel Ser-Col blood collection device as a standardized approach for qualitative and quantitative detection of infectious markers and several over immunochemical tests. METHODS: In the current study, we included 395 adult participants, 191 men and 204 women, with a median age of 41 years, as well as 75 children with a median age of 3 years. Serological status was determined by testing serum samples for three groups of infection diseases: hepatitis A and C, SARS-CoV-2, and herpes family viruses, as well as for thyroid peroxidase (TPO), prolactin, vitamin B12, and folate. Blood collected on the Ser-Col device (Labonovum) was eluted using an automated system (SCAUT Ser-Col automation, Blok System Supply) and manually. Ser-Col results were compared with serum sampled via standard venipuncture considered as the reference. RESULTS: High correlation coefficients (r = 0.95-0.99) were observed between serum samples collected with Ser-Col and via standard venipuncture for the following tests: anti-HCV, anti-SARS-CoV-2 IgG, anti-HSV-2 IgG, and anti-CMV IgM. Correlation coefficients between Ser-Col and standard venipuncture serum for anti-HSV-1 IgG, anti-CMV IgG, and anti-EBV tests were relatively low (r = 0.73-0.77). Correlation coefficients for anti-TPO, prolactin, vitamin B12, and folate were also characterized with high values (r = 0.97-0.99). CONCLUSIONS: High accuracy and quantitative correlation were demonstrated between Ser-Col and samples collected by standard venipuncture. Hence, the Ser-Col blood collection device should be considered as a promising alternative for blood collection, storage, and transportation in both adult and pediatric populations.

Evaluation of the risk of developing hepatocellular carcinoma in chronic Hepatitis C patients receiving antiviral treatment.

INTRODUCTION: Chronic HC leads to the development of liver cirrhosis (LC) and hepatocellular carcinoma (HCC). The treatment of chronic HC with DAAs reduces mortality from LC and HCC. The study aimed to investigate the serological markers specific to HCC (PIVKA-II and AFP) in patients with chronic HC before and after DAA treatment. METHODOLOGY: The study involved 35 HCV patients (mean age: 56.23 ± 1.45) divided into two groups. Group 1 included 15 HCV + HCC patients and Group 2 included 20 HCV non-HCC patients. RESULTS: At the end of treatment all the patients were HCV RNA negative. Three months after the end of antiviral treatment, HCV RNA was undetectable in all patients, while a complete biochemical and virological response was observed in 66.7% of HCV + HCC patients and 85.0% of HCV non-HCC patients. PIVKA-II levels before the initiation of antiviral treatment were high in all patients. At the end of the treatment, in the HCV non-HCC group, normalization of PIVKA-II levels was observed only in 20.0% cases, and in 60.0% of cases 3 months after the treatment. Meanwhile, in patients with HCC and chronic HCV, PIVKA-II levels were within the normal range 3 months after treatment in only 13.3% of patients. CONCLUSIONS: It is necessary to monitor HCV patients with cirrhosis (F4) and severe fibrosis (F3) without HCC, who have high PIVKA-II and AFP levels and/or ALT activity despite obtaining sustained virologic response 3 months after treatment with DAAs.

Dynamics of self-hybridized exciton-polaritons in 2D halide perovskites.

Excitons, bound electron-hole pairs, in two-dimensional hybrid organic inorganic perovskites (2D HOIPs) are capable of forming hybrid light-matter states known as exciton-polaritons (E-Ps) when the excitonic medium is confined in an optical cavity. In the case of 2D HOIPs, they can self-hybridize into E-Ps at specific thicknesses of the HOIP crystals that form a resonant optical cavity with the excitons. However, the fundamental properties of these self-hybridized E-Ps in 2D HOIPs, including their role in ultrafast energy and/or charge transfer at interfaces, remain unclear. Here, we demonstrate that >0.5 µm thick 2D HOIP crystals on Au substrates are capable of supporting multiple-orders of self-hybridized E-P modes. These E-Ps have high Q factors (>100) and modulate the optical dispersion for the crystal to enhance sub-gap absorption and emission. Through varying excitation energy and ultrafast measurements, we also confirm energy transfer from higher energy E-Ps to lower energy E-Ps. Finally, we also demonstrate that E-Ps are capable of charge transport and transfer at interfaces. Our findings provide new insights into charge and energy transfer in E-Ps opening new opportunities towards their manipulation for polaritonic devices.

Coherent control of light scattering from nanostructured materials by second-harmonic generation.

We introduce an active, all-optical method for controlling the intensity and directionality of light scattering from single nanostructures. The method is based on the coherent interplay between linear light scattering and second-harmonic generation. The intensity and directionality of scattered light can be controlled by the phase delay and the relative angle between excitation beams. We discuss the principle of this coherent control technique and perform numerical model calculations.

Biological effects of static electric field: Plasma/serum proteome analysis of rats.

The external static electric field (SEF) of man-made origin brings to the substantially increased SEF background in a human environment the biological activity of which is a moot question. The paper reports on rats blood plasma/serum proteome modifications by means of 1D polyacrilamide gel electrophoresis and clotting process alterations after the short- and long-term SEF exposures of 200 kV/m. The results indicate decrease of fast α1 and α2 globular proteins in plasma coinciding with clotting acceleration after the short-term SEF, and attenuation of clotting-dependent proteome modifications reflected with incomplete coagulation after the long-term SEF exposure. Increased lysozyme activity in serum unlike plasma was observed after both SEF exposures. Applied model of the high-voltage SEF environment indicates dependence of biological systems functioning on the external SEF.

Optical Nonlinearity in Silicon Nanowires Enabled by Bound States in the Continuum.

Intense electromagnetic fields localized within resonant photonic nanostructures provide versatile opportunities for engineering nonlinear optical effects on a subwavelength scale. For dielectric structures, optical bound states in the continuum (BICs, resonant nonradiative modes that exist within the radiation continuum) are an emerging strategy to localize and intensify fields. Here, we report efficient second and third harmonic generation from Si nanowires (NWs) encoded with BIC and quasi-BIC resonances. In situ dopant modulation during vapor-liquid-solid NW growth was followed by wet-chemical etching to periodically modulate the diameter of the Si NWs and create cylindrically symmetric geometric superlattices (GSLs) with precisely defined axial and radial dimensions. By variation of the GSL structure, BIC and quasi-BIC resonant conditions were created to span visible and near-infrared optical frequencies. To probe the optical nonlinearity of these structures, we collected linear extinction spectra and nonlinear spectra from single-NW GSLs, demonstrating that quasi-BIC spectral positions at the fundamental frequency are directly correlated with enhanced harmonic generation at second and third harmonic frequencies. Interestingly, we find that deliberate geometric detuning from the BIC condition leads to a quasi-BIC resonance with maximal harmonic generation efficiency by providing a balance between the capacity to trap light and the capacity to couple to the external radiation continuum. Moreover, under focused illumination, as few as 30 geometric unit cells are required to achieve more than 90% of the approximate maximum theoretical efficiency of an infinite structure, indicating that nanostructures with projected areas smaller than ∼10 µm2 can support quasi-BICs for efficient harmonic generation. The results represent an important step toward the design of efficient harmonic generation at the nanoscale and further highlight the photonic utility of BICs at optical frequencies in ultracompact one-dimensional nanostructures.

Enhancing the nonlinear optical response using multifrequency gold-nanowire antennas.

We introduce and experimentally demonstrate the concept of multifrequency optical antennas that are designed for controlling the nonlinear response of materials. These antennas consist of two arms of different lengths, each resonant with one of the incoming frequencies. They are embedded in a nonlinear medium (indium tin oxide) that acts as a receiver. Because the two arms have different spectral resonances, tuning of the antenna gap size has minimal effect on the linear optical properties. However, it strongly affects the nonlinear response. Thus, by employing antenna elements with different spectral resonances, we provide a strategy to decouple the nonlinear response of nanomaterials from their linear optical properties.

The synergy of ß amyloid 1-42 and oxidative stress in the development of Alzheimer's disease-like neurodegeneration of hippocampal cells.

Alzheimer's disease (AD) is a type of dementia that affects memory, thinking and behavior. Symptoms eventually become severe enough to interfere with daily tasks. Understanding the etiology and pathogenesis of AD is necessary for the development of strategies for AD prevention and/or treatment, and modeling of this pathology is an important step in achieving this goal. ß-amyloid peptide (Aß) injection is a widely used approach for modeling AD. Nevertheless, it has been reported that the model constructed by injection of Aß in combination with a prooxidant cocktail (ferrous sulfate, Aß, and buthionine sulfoximine (BSO) (FAB)) best reflects the natural development of this disease. The relationship between oxidative stress and Aß deposition and their respective roles in Aß-induced pathology in different animal models of AD have been thoroughly investigated. In the current paper, we compared the effects of Aß 1-42 alone with that of Aß-associated oxidative stress induced by the FAB cocktail on the neurodegeneration of hippocampal cells in vitro. We constructed a FAB-induced AD model using rat primary hippocampal cells and analyzed the contribution of each compound. The study mainly focused on the prooxidant aspects of AD pathogenesis. Moreover, cellular bioenergetics was assessed and routine metabolic tests were performed to determine the usefulness of this model. The data clearly show that aggregated Aß1-42 alone is significantly less toxic to hippocampal cells. Aggregated Aß damages neurons, and glial cells proliferate to remove Aß from the hippocampus. External prooxidant agents (Fe2+) or inhibition of internal antioxidant defense by BSO has more toxic effects on hippocampal cells than aggregated Aß alone. Moreover, hippocampal cells fight against Aß-induced damage more effectively than against oxidative damage. However, the combination of Aß with external oxidative damage and inhibition of internal antioxidant defense is even more toxic, impairs cellular defense systems, and may mimic the late phase of AD-associated cell damage. Our findings strongly indicate a critical role for the combination of Aß and oxidative stress in the development of neurodegeneration in vitro.

Nonlinear dark-field microscopy.

Dark-field microscopy is a background-free imaging method that provides high sensitivity and a large signal-to-noise ratio. It finds application in nanoscale detection, biophysics and biosensing, particle tracking, single molecule spectroscopy, X-ray imaging, and failure analysis of materials. In dark-field microscopy, the unscattered light path is typically excluded from the angular range of signal detection. This restriction reduces the numerical aperture and affects the resolution. Here we introduce a nonlinear dark-field scheme that overcomes this restriction. Two laser beams of frequencies ω1 and ω2 are used to illuminate a sample surface and to generate a purely evanescent field at the four-wave mixing (4WM) frequency ω4wm = 2ω1 - ω2. The evanescent 4WM field scatters at sample features and generates radiation that is detected by standard far-field optics. This nonlinear dark-field scheme works with samples of any material and is compatible with applications ranging from biological imaging to failure analysis.

Novel Probable Glance at Inflammatory Scenario Development in Autistic Pathology.

Autism Spectrum Disorder (ASD) is characterized by persistent deficits in social communication and restricted-repetitive patterns of behavior, interests, or activities. ASD is generally associated with chronic inflammatory states, which are linked to immune system dysfunction and/or hyperactivation. The latter might be considered as one of the factors damaging neuronal cells. Several cell types trigger and sustain such neuroinflammation. In this study, we traced different markers of immune system activation on both cellular (immune cell phenotypes) and mediatory levels (production of cytokines) alongside adverse hematology and biochemistry screening in a group of autistic children. In addition, we analyzed the main metabolic pathways potentially involved in ASD development: energy (citric acid cycle components), porphyrin, and neurotransmitter metabolism. Several ASD etiological factors, like heavy metal intoxication, and risk factors-genetic polymorphisms of the relevant neurotransmitters and vitamin D receptors-were also analyzed. Finally, broad linear regression analysis allowed us to elucidate the possible scenario that led to the development of chronic inflammation in ASD patients. Obtained data showed elevated levels of urinary cis-aconitate, isocitrate, alfa-ketoglutarate, and HMG. There were no changes in levels of metabolites of monoamine neurotransmitters, however, the liver-specific tryptophan kinurenine pathway metabolites showed increased levels of quinolinate (QUIN) and picolinate, whereas the level of kynurenate remained unchanged. Abovementioned data demonstrate the infringement in energy metabolism. We found elevated levels of lead in red blood cells, as well as altered porphyrin metabolism, which support the etiological role of heavy metal intoxication in ASD. Lead intoxication, the effect of which is intensified by a mutation of the VDR-Taq and MAO-A, leads to quinolinic acid increase, resulting in energy metabolism depletion and mitochondrial dysfunction. Moreover, our data backing the CD4+CD3+ T-cell dependence of mitochondrial dysfunction development in ASD patients reported in our previous study leads us to the conclusion that redox-immune cross-talk is considered a main functional cell damaging factor in ASD patients.

Alpha2-Adrenoblockers Regulate Development of Oxidative Stress and Cognitive Behaviour of Rats under Chronic Acoustic Stress Conditions.

Noise is a wide-spread stress factor in modern life produced by urbanization, traffic, and an industrialized environment. Noise stress causes dysfunction and neurotransmission impairment in the central nervous system, as well as changes in hormone levels. In this study, we have examined the level of α-Tocopherol (α-T) and malondialdehyde (MDA) in plasma and the erythrocytes' membrane (EM), as well as the behavioral characteristics of a noise-induced stress model in rats. In addition, the modulating effect of α2-adrenoblockers, beditin, and mesedin on the aforementioned parameters has been investigated. For these purposes, albino male rats were divided into four groups: (1) untreated; (2) noise-exposed, (3) noise-exposed and beditin-treated (2 mg/kg, i.p.), and (4) noise-exposed and mesedin-treated (10 mg/kg, i.p.) animals. Noise-exposed groups were treated with 91dBA noise on 60 days with a daily duration of 8 h. Increased MDA and decreased α-T levels in plasma and EM were observed upon chronic high-level noise exposure. Locomotor and behavioral activity assessed with a Y-maze revealed disorientation and increased anxiety under chronic noise exposure. Prominently, α2-adrenoblockers alleviated both behavioral deficits and oxidative stress, providing evidence for the involvement of α2-adrenoceptor in the pathophysiology of noise-induced stress.