Electrically tunable metasurface in TN LC configuration with enhanced quality factor and metaatom-induced alignment.

Dynamic metasurface with subwavelength dimensions has emerged as a key optical technology in recent years. Although various active tuning mechanisms are being proposed, liquid crystal-based dynamic metasurface remains attractive due to its large index variation, electrical tunability, reliability, and mass fabricability. In this work, we report a dynamic metasurface for amplitude modulation in reflection, with twisted nematic liquid crystal configuration to reduce broadband reflection in the off state. The metasurface consists of coupled subwavelength grating fingers, which provide alignment for the liquid crystal without the need for an additional alignment material or process. The alignment of liquid crystal materials was examined between crossed polarizers, and the twist of nematic liquid crystal was confirmed. The coupled grating fingers exhibit a resonance quality factor of 27 at telecommunication wavelength and an amplitude modulation depth of 8 times of the minimum at 1630 nm. This work highlights the potential of liquid crystal-based tunable metasurface, combining polarization control via liquid crystal and spectrum control via metasurface. Furthermore, it also shows a way in which the interaction between liquid crystal and metasurface is used for an alignment layer-free cell assembly process.

Impact of sex and hypoxia on brain region-specific expression of membrane androgen receptor AR45 in rats.

Background: Sex differences in oxidative stress-associated cognitive decline are influenced by sex hormone levels. Notably, oxidative stress-associated neuronal cell death can be exacerbated through testosterone signaling via membrane androgen receptor AR45, which is complexed with G protein Gαq within plasma membrane-associated lipid rafts. The objective of this study was to elucidate the impact of sex on the expression of AR45 and Gαq in brain regions associated with cognitive function, specifically hippocampus subregions and entorhinal cortex. Additionally, we investigated whether chronic intermittent hypoxia (CIH), an oxidative stressor with sex-specific effects, would modulate AR45 and Gαq expression in these brain regions. Methods: Adult male and female Sprague-Dawley rats were exposed to CIH or normoxia (room air) during their sleep phase for 14 days. We quantified AR45 and Gαq protein expression in various cognition-associated brain regions [dorsal hippocampal CA1, CA3, dentate gyrus (DG), and entorhinal cortex (ETC)] via western blotting. For comparisons, AR45 and Gαq protein expression were also assessed in brain regions outside the hippocampal-ETC circuit [thalamus (TH) and striatum (STR)]. Results: The highest AR45 levels were expressed in the hippocampal CA1 and DG while the lowest expression was observed in the extrahippocampal STR. The highest Gαq levels were expressed in the hippocampal-associated ETC while the lowest expression was observed in the extrahippocampal TH. Females expressed higher levels of AR45 in the hippocampal DG compared to males, while no sex differences in Gαq expression were observed regardless of brain region assessed. Moreover, there was no effect of CIH on AR45 or Gαq expression in any of the brain regions examined. AR45 expression was positively correlated with Gαq expression in the CA1, DG, ETC, TH, and STR in a sex-dependent manner. Conclusion: Our findings reveal enrichment of AR45 and Gαq protein expression within the hippocampal-ETC circuit, which is vulnerable to oxidative stress and neurodegeneration during cognitive decline. Nonetheless, CIH does not modulate the expression of AR45 or Gαq. Importantly, there are sex differences in AR45 expression and its association with Gαq expression in various brain regions, which may underlie sex-specific differences in cognitive and motor function-associated declines with aging.

A rare case of Guillain-Barrè syndrome with unilateral facial palsy and asymmetrical ascending weakness: a case report.

Guillain-Barrè syndrome is a life threatening postinfectious disease causing acute paralytic neuropathy that rarely presents with asymmetrical limb weakness (1%) and unilateral facial nerve palsy (4.9%). Case Presentation: A 39-year-old male presented with pain and weakness in the right lower limb with right sided facial weakness. The cranial nerve examination revealed lower motor neuron type right facial palsy (Bell 's palsy). On rest neurological examination, he had decreased power in the right lower limb with an absent knee and ankle reflex on presentation. Later, the weakness was symmetrical in both lower limbs. Clinical Discussion: Cerebrospinal fluid analysis showed albuminocytologic dissociation with no cells and an elevated protein of 203.2 mg/dl. The nerve conduction study was abnormal in bilateral lower limbs suggesting severe demyelinating motor neuropathy. Intravenous Immunoglobulin was started with the dose of 25 gm (0.4 mg/kg) once daily for 5 days, that is, five doses. The patient started showing signs of recovery with the initial dose of immunoglobulin. Conclusion: The course of the disease usually recovers spontaneously and completely; however, plasma exchange and immunomodulatory therapy have shown improvement in patient with rapidly deteriorating symptoms.

Increasing steering angle of LCoS in a WSS system through integration with a metasurface.

Liquid crystal on silicon (LCoS) has been the dominant choice for wavelength selective switches (WSSs) in telecommunication industry due to its high spatial resolution and compatibility with software defined flexible grid feature. Current LCoS devices generally have a limited steering angle, which also limits the minimum footprint of the WSS system. The steering angle of LCoS devices is fundamentally determined by the pixel pitch, which is highly challenging to be optimized without resorting to other techniques. In this paper, we present an approach to increase the steering angle of LCoS devices through the integration with dielectric metasurfaces. Here a dielectric Huygens-type metasurface is integrated with an LCoS device to increase its steering angle by 10°. This approach can effectively minimize the overall size of the WSS system while maintaining a small form factor of the LCoS device.

Electrically tuned active metasurface towards metasurface-integrated liquid crystal on silicon (meta-LCoS) devices.

Active metasurfaces add a new dimension to static metasurfaces by introducing tunability, and this has received enormous attention from industry. Although various mechanisms have been proposed over the past few years in literature, solutions with good practicality are limited. Liquid crystal (LC)-based active metasurface is one of the most promising approaches due to the well-established LC industry. In this paper, an electrically tunable active metasurface was proposed and experimentally demonstrated using photoaligned nematic LC. The good quality of the LC photoalignment on the metasurface was demonstrated. Tunable transmission was obtained for telecommunication C band and the modulation depth in transmission amplitude of 94% was realized for 1530 nm. Sub-millisecond response time was achieved at operating a temperature of 60°C. The progress made here presents the potential of LC-based active metasurfaces for fast-switching photonic devices at optical communication wavelengths. More importantly, this work lays the foundations for the next-generation liquid crystal on silicon (LCoS) devices that are integrated with metasurfaces (meta-LCoS).

Monocarboxylate Transporters: Role and Regulation in Corneal Diabetes.

Diabetes mellitus (DM) is a group of metabolic diseases that is known to cause structural and functional ocular complications. In the human cornea, DM-related complications affect the epithelium, stroma, and nerves. Monocarboxylate transporters (MCTs) are a family of proton-linked plasma membrane transporters that carry monocarboxylates across plasma membranes. In the context of corneal health and disease, their role, presence, and function are largely undetermined and solely focused on the most common MCT isoforms, 1 through 4. In this study, we investigated the regulation of MCT1, 2, 4, 5, 8, and 10, in corneal DM, using established 3D self-assembled extracellular matrix (ECM) in vitro models. Primary stromal corneal fibroblasts were isolated from healthy (HCFs), type I (T1DMs), and type II (T2DMs) DM donors. Monoculture 3D constructs were created by stimulating stromal cells on transwells with stable vitamin C for two or four weeks. Coculture 3D constructs were created by adding SH-SY5Y neurons at two different densities, 12 k and 500 k, on top of the monocultures. Our data showed significant upregulation of MCT1 at 4 weeks for HCF, T1DM, and T2DM monocultures, as well as the 500 k nerve cocultures. MCT8 was significantly upregulated in HCF and T1DM monocultures and all of the 500 k nerve cocultures. Further, MCT10 was only expressed at 4 weeks for all cocultures and was limited to HCFs and T1DMs in monocultures. Immunofluorescence analysis showed cytoplasmic MCT expression for all cell types and significant downregulation of both MCT2 and MCT4 in HCFs, when compared to T1DMs and T2DMs. Herein, we reveal the existence and modulation of MCTs in the human diabetic cornea in vitro. Changes appeared dependent on neuronal density, suggesting that MCTs are very likely critical to the neuronal defects observed in diabetic keratopathy/neuropathy. Further studies are warranted in order to fully delineate the role of MCTs in corneal diabetes.

Orbital Tumors and Tumor like Lesions: A Hospital Based Study.

BACKGROUND: Orbital tumors have rare incidence, still they play a significant role in terms of morbidity and mortality. Orbital tumors may be primary, secondary or metastatic. These consist of benign and malignant lesions with extreme variations in pediatric and adult groups. These lesions can have acute or chronic onset, slow to rapid progression with or without bony destructions leading to vision loss, deformity and sometimes death. METHODS: This retrospective cross-sectional study was carried out in the Department of Ophthalmic Pathology and Laboratory Medicine in Biratnagar Eye Hospital. Fifty-one patients who underwent histopathological evaluation for their orbital lesions from June 2018 to December 2019 were included in the study. RESULTS: Orbital tumor and tumor like lesions comprised 27 cases (52.94%) in adults and 24 (47.06%) in paediatrics. Histopathologically, the most common pediatric benign tumor was dermoid cyst and malignant was secondary to orbital extension of retinoblastoma. Also, the most common adult benign orbital tumor was cavernous hemangioma and malignant was non Hodgkins lymphoma. The clinico-pathological accuracy for diagnosis was 68.63%. Association between age groups and nature of orbital lesions and between clinical and histopathological diagnosis was found to be statistically significant (p<0.05). CONCLUSIONS: Orbital tumors and tumor like lesions are uncommonly encountered. These masses showed significant variation in incidence in children versus adults. Combined efforts by different specialties help in early and prompt management of the orbital tumors.

Variety of Ordered Patterns in Donor-Acceptor Polymer Semiconductor Films Crystallized from Solution.

A huge challenge is to control the nucleation of crystallites/aggregates in the solution during polymer film formation to generate desired structures. In this work, we investigate crystallization of P(NDI2OD-T2), a donor-acceptor polymer semiconductor, with controlled solution flow along the contact line between the drying film and solution through a seesaw-like pivoting of samples during polymer drying. By controlling the pivoting frequency/amplitude, various types of line patterns can be observed: (I) an array of fishbone-like stripes oriented in the film-growth direction; (II) the pinning-depinning of contact line (PDCL)-mechanism-defined patterned wires along the contact line; and (III) periodic twined crystalline line pattern oriented in the direction of the contact line. The rich variety of pattern formation observed is attributed to the distinctiveness of the donor-acceptor conjugated polymer structure. The result measured from thin-film transistors made of the generated films/structures showed that the charge mobility of P(NDI2OD-T2) does not change much with the film morphology, which supports recent controversy over the charge-transportation mechanism of some donor-acceptor polymer semiconductors.

High-Resolution Electrochemical Transistors Defined by Mold-Guided Drying of PEDOT:PSS Liquid Suspension.

Ion-sensitive transistors with nanoscale or microscale dimensions are promising for high-resolution electrophysiological recording and sensing. Technology that can pattern polymer functional materials directly from a solution can effectively avoid any chemical damage induced by conventional lithography techniques. The application of a mold-guided drying technique to pattern PEDOT:PSS-based transistors with high resolution directly from the water-based suspension is presented in this paper. Gold electrodes with short channels were first defined by creating high-resolution polymer lines with mold-guided drying followed by pattern transfer through a lift-off process. Then, PEDOT:PSS lines were subsequently created through an identical mold-guided drying process on the predefined electrodes. Small-scale transistor devices with both shortened channel length and width exhibited a good high-frequency response because of the weak capacitive effect. This is particularly advantageous for electrochemical transistors since the use of conventional fabrication techniques is extremely challenging in this case. In addition, modified polymer chain alignment of the assembled PEDOT:PSS lines during the drying process was observed by optical and electrical measurement. The mold-guided drying technique has been proven to be a promising method to fabricate small-scale devices, especially for biological applications.

Density Modulation of Embedded Nanoparticles via Spatial, Temporal, and Chemical Control Elements.

Nanoparticle polymer composites have enabled material multifunctionalities that are difficult to obtain otherwise. A simple modification to a commercially available resin system enables a universal methodology to embed nanoparticles in resins via spatial, temporal, thermal, concentration, and chemical control parameters. Changes in nanoparticle density distribution are exploited to demonstrate dynamic optical and electronic properties that can be processed on-demand, without the need for expensive equipment or cleanroom facilities. This strategy provides access to the control of optical (cooperative plasmonic effects), electronic (insulator to a conductor), and chemical parameters (multimetal patterning). Using the same composite resin system, the followings are fabricated: i) diffraction gratings with tuneable diffraction efficiencies (10-78% diffraction efficiencies), ii) organic electrochemical transistors with a low drive voltage, and iii) embedded electrodes in confined spaces for potential diagnostic applications.

Accommodation-Free Head Mounted Display with Comfortable 3D Perception and an Enlarged Eye-box.

An accommodation-free displays, also known as Maxwellian displays, keep the displayed image sharp regardless of the viewer's focal distance. However, they typically suffer from a small eye-box and limited effective field of view (FOV) which requires careful alignment before a viewer can see the image. This paper presents a high-quality accommodation-free head mounted display (aHMD) based on pixel beam scanning for direct image forming on retina. It has an enlarged eye-box and FOV for easy viewing by replicating the viewing points with an array of beam splitters. A prototype aHMD is built using this concept, which shows high definition, low colour aberration 3D augmented reality (AR) images with an FOV of 36°. The advantage of the proposed design over other head mounted display (HMD) architectures is that, due to the narrow, collimated pixel beams, the high image quality is unaffected by changes in eye accommodation, and the approach to enlarge the eye-box is scalable. Most importantly, such an aHMD can deliver realistic three-dimensional (3D) viewing perception with no vergence-accommodation conflict (VAC). It is found that viewing the accommodation-free 3D images with the aHMD presented in this work is comfortable for viewers and does not cause the nausea or eyestrain side effects commonly associated with conventional stereoscopic 3D or HMD displays, even for all day use.

Broadband MoS2 Field-Effect Phototransistors: Ultrasensitive Visible-Light Photoresponse and Negative Infrared Photoresponse.

Inverse photoresponse is discovered from phototransistors based on molybdenum disulfide (MoS2 ). The devices are capable of detecting photons with energy below the bandgap of MoS2 . Under the illumination of near-infrared (NIR) light at 980 and 1550 nm, negative photoresponses with short response time (50 ms) are observed for the first time. Upon visible-light illumination, the phototransistors exhibit positive photoresponse with ultrahigh responsivity on the order of 104 -105 A W-1 owing to the photogating effect and charge trapping mechanism. Besides, the phototransistors can detect a weak visible-light signal with effective optical power as low as 17 picowatts (pW). A thermally induced photoresponse mechanism, the bolometric effect, is proposed as the cause of the negative photocurrent in the NIR regime. The thermal energy of the NIR radiation is transferred to the MoS2 crystal lattice, inducing lattice heating and resistance increase. This model is experimentally confirmed by low-temperature electrical measurements. The bolometric coefficient calculated from the measured transport current change with temperature is -33 nA K-1 . These findings offer a new approach to develop sub-bandgap photodetectors and other novel optoelectronic devices based on 2D layered materials.

High-resolution patterning of solution-processable materials via externally engineered pinning of capillary bridges.

Electronics based on solution-processable materials are promising for applications in many fields which stimulated enormous research interest in liquid-drying and pattern formation. However, assembling of structure with submicrometre/nanometre resolution through liquid process is very challenging. We show a simple method to rapidly generate polymer structures with deep-submicrometre-sized features over large areas. In this method, a solution film is dried on a substrate under a suspended flexible template with groove/ridge surface topography. Upon solvent evaporation, the solution splits in the grooves and forms capillary bridges between the template and substrate, which are firmly pinned by the edges of the template grooves. This groove pinning stabilizes the contact lines, thereby allowing the formation of fine patterned structures with high aspect ratios which were used to fabricate various functional materials and electronic devices. We also produced secondary self-assembled nano-stripe patterns with resolutions of about 50 nm on the primary lines.

Full resolution auto-stereoscopic mobile display based on large scale uniform switchable liquid crystal micro-lens array.

A full resolution auto-stereoscopic display for mobile phones is demonstrated. It is based on the sub-pixel level phase modulation of a switchable liquid crystal (LC) micro-lens array, which can be switched back to a conventional two-dimensional (2D) display. The full scale (4 inch) device aligns with the display panel perfectly at sub-pixel level and switches the entire display area uniformly with no distortion and no colour separation. The steering angle and crosstalk of the auto-stereoscopic display are evaluated by both simulation and experiment. The results show that satisfactory performance can be achieved by further reduction of the separation distance between the colour filter (CF) layer and the LC lens layer and close match it to the effective focal length of the LC lens.

Bilateral lateral rectus recession in exotropic Duane syndrome with downshoot.

OBJECTIVE: To report that maximum weakening of lateral rectus muscles can improve significant exotropia in primary position, abnormal head posture, retraction, narrowing of palpebral fissure and downshoot in exotropic duannes retraction syndrome. CASE: A 12-year-old boy with exotropic Duane syndrome presented with downshoot and globe retraction in attempted adduction. Squint surgery was undertaken to correct the alignment and treat the secondary aberrant movements doing maximum weakening of the lateral rectus muscles by hang- back method. At 6 months follow up visit, there was improvement in abnormal head posture, reduction of ocular deviation with downshoot and stereoacuity. CONCLUSION: Supramaximal recession of lateral rectus muscles can correct exotropia with down shoot in a patient with Duane retraction syndrome.