Nanoscale optical nonreciprocity with nonlinear metasurfaces.

Optical nonreciprocity is manifested as a difference in the transmission of light for the opposite directions of excitation. Nonreciprocal optics is traditionally realized with relatively bulky components such as optical isolators based on the Faraday rotation, hindering the miniaturization and integration of optical systems. Here we demonstrate free-space nonreciprocal transmission through a metasurface comprised of a two-dimensional array of nanoresonators made of silicon hybridized with vanadium dioxide (VO2). This effect arises from the magneto-electric coupling between Mie modes supported by the resonator. Nonreciprocal response of the nanoresonators occurs without the need for external bias; instead, reciprocity is broken by the incident light triggering the VO2 phase transition for only one direction of incidence. Nonreciprocal transmission is broadband covering over 100 nm in the telecommunication range in the vicinity of λ = 1.5 µm. Each nanoresonator unit cell occupies only ~0.1 λ3 in volume, with the metasurface thickness measuring about half-a-micron. Our self-biased nanoresonators exhibit nonreciprocity down to very low levels of intensity on the order of 150 W/cm2 or a µW per nanoresonator. We estimate picosecond-scale transmission fall times and sub-microsecond scale transmission rise. Our demonstration brings low-power, broadband and bias-free optical nonreciprocity to the nanoscale.

Skin Diseases in Patients With Primary Psychiatric Conditions in Northern India: A Cross-Sectional Study.

BACKGROUND: The relationship between skin diseases and psychiatric illnesses is bi-directional and is manifested as cause and effect. Psychiatric disorders such as stress, anxiety, and depression are seen to be instrumental in the development and progression of dermatological diseases on one hand, while on the other hand, cosmetic disfigurement caused by dermatological diseases is responsible for psychological distress in patients. The present study was conducted to investigate the spectrum of dermatological disorders in psychiatric patients to offer them holistic treatment and provide them with a better quality of life. METHODS: This cross-sectional, observational study was conducted at a tertiary medical care center. A total of 170 psychiatric patients referred to the dermatology department for different dermatological manifestations were enrolled in the study. A demographic profile of the patients was done, and an association between dermatological diseases and psychiatric illnesses was done. RESULTS:  Out of 170 study participants, 88 (51.8%) were females, and the rest (82, 48.2%) were males. A total of 13 major types of dermatological conditions were noted; among them, fungal infection (43, 25.3%) was the most common, followed by eczema (18, 10.6%), parasitic infestation (17, 10.0%), pigmentary disorder (13, 7.6%), acne (11, 6.5%), bacterial infection (11, 6.5%), pruritic disorder (11, 6.5%), hair disorder (9, 5.3%), drug reaction (9, 5.3%), papulosquamous disorder (7, 4.1%), and viral infection (6, 3.5%). Skin conditions other than the above-mentioned were present in 15 (8.8%) patients. The most common psychiatric illness in the present study was major depressive disorder (41, 24.1%), followed by generalized anxiety disorder (38, 22.4%) and psychosis not otherwise specified (34, 20.0%). Other psychiatric illnesses included in the study were bipolar affective disorder (22, 12.9%), schizophrenia (18, 10.6%), obsessive-compulsive disorder (12, 7.1%), and mixed anxiety depressive disorder (5, 2.9%). CONCLUSION: The findings of the present study depict that psychiatric patients with dermatological manifestations show a spectrum of dermatological conditions, primarily of infectious (fungal, parasitic, or viral) nature. This might be associated with a relatively poor hygienic status of psychiatric patients and thus their increased susceptibility to these disorders. Most of the time, the susceptibility to these skin conditions seemed to be opportunistic and unaffected by the type, duration, and level of control of psychiatric illness.

Generating OCT B-Scan DME images using optimized Generative Adversarial Networks (GANs).

Diabetic Macular Edema (DME) represents a significant visual impairment among individuals with diabetes, leading to a dramatic reduction in visual acuity and potentially resulting in irreversible vision loss. Optical Coherence Tomography (OCT), a technique that produces high-resolution retinal images, plays a vital role in the clinical assessment of this condition. Physicians typically rely on OCT B-Scan images to evaluate DME severity. However, manual interpretation of these images is susceptible to errors, which can lead to detrimental consequences, such as misdiagnosis and improper treatment strategies. Hence, there is a critical need for more reliable diagnostic methods. This study aims to address this gap by proposing an automated model based on Generative Adversarial Networks (GANs) to generate OCT B-Scan images of DME. The model synthesizes images from patients' baseline OCT B-Scan images, which could potentially enhance the robustness of DME detection systems. We employ five distinct GANs in this study: Deep Convolutional GAN, Conditional GAN, CycleGAN, StyleGAN2, and StyleGAN3, drawing comparisons across their performance. Subsequently, the hyperparameters of the best-performing GAN are fine-tuned using Particle Swarm Optimization (PSO) to produce more realistic OCT images. This comparative analysis not only serves to improve the detection of DME severity using OCT images but also provides insights into the appropriate choice of GANs for the effective generation of realistic OCT images from the baseline OCT datasets.

Fuzzy Logic-Based System for Identifying the Severity of Diabetic Macular Edema from OCT B-Scan Images Using DRIL, HRF, and Cystoids.

Diabetic Macular Edema (DME) is a severe ocular complication commonly found in patients with diabetes. The condition can precipitate a significant drop in VA and, in extreme cases, may result in irreversible vision loss. Optical Coherence Tomography (OCT), a technique that yields high-resolution retinal images, is often employed by clinicians to assess the extent of DME in patients. However, the manual interpretation of OCT B-scan images for DME identification and severity grading can be error-prone, with false negatives potentially resulting in serious repercussions. In this paper, we investigate an Artificial Intelligence (AI) driven system that offers an end-to-end automated model, designed to accurately determine DME severity using OCT B-Scan images. This model operates by extracting specific biomarkers such as Disorganization of Retinal Inner Layers (DRIL), Hyper Reflective Foci (HRF), and cystoids from the OCT image, which are then utilized to ascertain DME severity. The rules guiding the fuzzy logic engine are derived from contemporary research in the field of DME and its association with various biomarkers evident in the OCT image. The proposed model demonstrates high efficacy, identifying images with DRIL with 93.3% accuracy and successfully segmenting HRF and cystoids from OCT images with dice similarity coefficients of 91.30% and 95.07% respectively. This study presents a comprehensive system capable of accurately grading DME severity using OCT B-scan images, serving as a potentially invaluable tool in the clinical assessment and treatment of DME.

A Prospective Observational Study on Outcomes of Single Stage Posterior Decompression and Fixation for Dorsolumbar Spine Tuberculosis.

Objective To study the results of only posterior decompression and instrumentation in dorsal and dorsolumbar spine tuberculosis. Methods The patients ( n = 30) who were included in this study had dorsal or dorsolumbar spine tuberculosis, with or without neurological deficit, and with or without deformity. All 30 patients were managed by only posterior approach decompression and instrumentation. We studied cases for correction and maintenance of deformity at dorsal and dorsolumbar spine, functional outcome by the Oswestry disability index (ODI) and visual analogue scale (VAS) scores, as well as neurological outcome by the Frankel grade. Results In the current series, 30 patients were operated with single stage posterior decompression and instrumentation, and showed significant improvement in neurological status and functional outcomes, which were accessed by the ODI score, VAS score, and Frankel grade. Conclusion The posterior (extracavitary) approach provides optimum access to the lateral and anterior aspects of the spinal cord for good decompression. It facilitates early mobilization and avoids problems of prolonged recumbency, provides better functional outcome, and significantly better sagittal plane kyphosis correction.

High-harmonic generation from a subwavelength dielectric resonator.

Higher-order optical harmonics entered the realm of nanostructured solids being observed recently in optical gratings and metasurfaces with a subwavelength thickness. Structuring materials at the subwavelength scale allows us toresonantly enhance the efficiency of nonlinear processes and reduce the size of high-harmonic sources. We report the observation of up to a seventh harmonic generated from a single subwavelength resonator made of AlGaAs material. This process is enabled by careful engineering of the resonator geometry for supporting an optical mode associated with a quasi-bound state in the continuum in the mid-infrared spectral range at around λ = 3.7 µm pump wavelength. The resonator volume measures ~0.1 λ3. The resonant modes are excited with an azimuthally polarized tightly focused beam. We evaluate the contributions of perturbative and nonperturbative nonlinearities to the harmonic generation process. Our work proves the possibility to miniaturize solid-state sources of high harmonics to the subwavelength volumes.

A Prospective Observational Study on Outcomes of Single Stage Posterior Decompression and Fixation for Dorsolumbar Spine Tuberculosis / Estudo observacional prospectivo sobre os desfechos da descompressão posterior e fixação em estágio único na tuberculose da coluna dorsolombar

Abstract Objective To study the results of only posterior decompression and instrumentation in dorsal and dorsolumbar spine tuberculosis. Methods The patients (n = 30) who were included in this study had dorsal or dorsolumbar spine tuberculosis, with or without neurological deficit, and with or without deformity. All 30 patients were managed by only posterior approach decompression and instrumentation. We studied cases for correction and maintenance of deformity at dorsal and dorsolumbar spine, functional outcome by the Oswestry disability index (ODI) and visual analogue scale (VAS) scores, as well as neurological outcome by the Frankel grade. Results In the current series, 30 patients were operated with single stage posterior decompression and instrumentation, and showed significant improvement in neurological status and functional outcomes, which were accessed by the ODI score, VAS score, and Frankel grade. Conclusion The posterior (extracavitary) approach provides optimum access to the lateral and anterior aspects of the spinal cord for good decompression. It facilitates early mobilization and avoids problems of prolonged recumbency, provides better functional outcome, and significantly better sagittal plane kyphosis correction.

Resumo Objetivo Estudar os desfechos da descompressão posterior isolada e instrumentação na tuberculose da coluna dorsal e dorsolombar. Métodos Os pacientes (n = 30) incluídos neste estudo apresentavam tuberculose na coluna dorsal ou dorsolombar, acompanhada ou não por déficit neurológico e/ou deformidade. Todos os 30 pacientes foram tratados apenas por descompressão posterior e instrumentação. Estudamos a correção e manutenção da deformidade na coluna dorsal e dorsolombar, o desfecho funcional segundo o índice de deficiência de Oswestry (ODI) e a escala visual analógica (EVA); o desfecho neurológico foi estudado de acordo com a classificação de Frankel. Resultados Na atual série, 30 pacientes foram submetidos à descompressão posterior e instrumentação em estágio único e apresentaram melhora significativa no estado neurológico e desfecho funcional segundo os scores de ODI, EVA e classificação de Frankel. Conclusão A abordagem posterior (extracavitária) permite o acesso ideal aos aspectos laterais e anteriores da medula espinhal para uma boa descompressão. Facilita a mobilização precoce, evita problemas associados ao decúbito prolongado, proporciona melhor desfecho funcional e corrige a cifose no plano sagital de maneira significativamente melhor.

Metasurface-Controlled Photonic Rashba Effect for Upconversion Photoluminescence.

We demonstrate the effect of spin-momentum locking of upconversion photoluminescence emitted from rare-earth doped nanocrystals coupled to a phase-gradient dielectric metasurface. We observe different directionalities for left and right circular polarized light and associate this experimental observation with the photonic Rashba effect realized for upconverted photoluminescence that is manifested in the spin-dependent splitting of emitted light in the momentum space.

Enhanced Five-Photon Photoluminescence in Subwavelength AlGaAs Resonators.

Multiphoton processes of absorption photoluminescence have enabled a wide range of applications including three-dimensional microfabrication, data storage, and biological imaging. While the applications of two-photon and three-photon absorption and luminescence have matured considerably, higher-order photoluminescence processes remain more challenging to study due to their lower efficiency, particularly in subwavelength systems. Here, we report the observation of five-photon luminescence from a single subwavelength nanoantenna at room temperature enabled by the Mie resonances. We excite an AlGaAs resonator at around 3.6 µm and observe photoluminescence at around 740 nm. We show that the interplay of the Mie multipolar modes at the subwavelength scale can enhance the efficiency of the five-photon luminescence by at least 4 orders of magnitude, being limited only by sensitivity of our detector. Our work paves the way toward applications of higher-order multiphoton processes at the subwavelength scales enabled by the physics of Mie resonances.

Lasing Action from Anapole Metasurfaces.

We study active dielectric metasurfaces composed of two-dimensional arrays of split-nanodisk resonators fabricated in InGaAsP membranes with embedded quantum wells. Depending on the geometric parameters, such split-nanodisk resonators can operate in the optical anapole regime originating from an overlap of the electric dipole and toroidal dipole Mie-resonant optical modes, thus supporting strongly localized fields and high-Q resonances. We demonstrate room-temperature lasing from the anapole lattices of engineered active metasurfaces with low threshold and high coherence.

Room-temperature lasing from nanophotonic topological cavities.

The study of topological phases of light underpins a promising paradigm for engineering disorder-immune compact photonic devices with unusual properties. Combined with an optical gain, topological photonic structures provide a novel platform for micro- and nanoscale lasers, which could benefit from nontrivial band topology and spatially localized gap states. Here, we propose and demonstrate experimentally active nanophotonic topological cavities incorporating III-V semiconductor quantum wells as a gain medium in the structure. We observe room-temperature lasing with a narrow spectrum, high coherence, and threshold behaviour. The emitted beam hosts a singularity encoded by a triade cavity mode that resides in the bandgap of two interfaced valley-Hall periodic photonic lattices with opposite parity breaking. Our findings make a step towards topologically controlled ultrasmall light sources with nontrivial radiation characteristics.

Clinicobacteriological evaluation of leprosy patients with 1-5 skin lesions.

Background: Mycobacterium leprae is a noncultivable mycobacteria, and diagnosis of the disease is based on its clinical and histopathological characteristics and finding the bacteria in skin scrapings and in biopsies taken from the patients. The aim of this study was to shed light on the clinical classification (based on the number of skin lesions) used extensively in the field where patients classified as paucibacillary (PB) were positive on skin smears and histopathology leading to treatment failure and drug resistance. Methods: In this study, we enrolled untreated 62 leprosy patients with 1-5 skin lesions and did a detailed bacterio-histopathological analysis by slit-skin smears (SSSs) and histopathology. Results: Of 62 patients analyzed, 15 patients came out to be multibacillary (MB) and 47 were PB by SSS and histopathology. Conclusion: The findings of the present study showed that the WHO classification of leprosy based on the number of lesions seems to be inappropriate as it considers a number of MB lesions as PB only, thus misleading the treatment strategies. Hence, it is essential that a comprehensive clinicobacteriological assessment of leprosy cases should be done to ensure the appropriate bacillary status and guiding the appropriate treatment strategy.

A Comparative Study of Dexmedetomidine and Midazolam in Reducing Delirium Caused by Ketamine.

INTRODUCTION: Ketamine is a well known agent for sedation for short surgical procedures due to its very good analgesic action. But it has cardio stimulatory response and recovery from anaesthesia after Ketamine use is complicated by delirium and hallucination. In studies it is proved that these side effects can be reduced by premedication with benzodiazepines. The α2 adrenoceptor agonists are becoming popular for their properties like haemodynamic stability and reducing anaesthetic requirement. AIM: This study was planned to see the effects of Dexmedetomidine on emergent reaction of Ketamine, when used as premedication agent with Ketamine for conducting short surgeries in adult patients. MATERIALS AND METHODS: Study was conducted in 90 ASA class I and II male and female patients of age between 18-40 undergoing short procedures like laparoscopic ligation, skin grafting, dilatation and curettage, endoscopic procedures, excision of small swelling, etc. Patients were randomly divided into three groups of 30 each as follows: Group K: after premedication with inj. glycopyrrolate 0.01mg/kg, inj. Ketamine 2mg/kg, Group M: after premedication with inj. glycopyrrolate 0.01mg/kg and inj midazolam 0.05mg/kg, inj. Ketamine 2mg/kg, Group D: after premedication with inj glycopyrrolate 0.01 mg/kg and inj. Dexmedetomidine 0.5µg/kg, Ketamine 2mg/kg was given. Observations were made for cardiovascular response to invasive procedure, post anaesthetic anxiety and delirium with help of Memorial Delirium Assessment scale (MDAS). RESULTS: Midazolam reduced delirium to a greater level, but in comparison to control group and midazolam group, dexmedetomidine reduced delirium to a much greater level (p-value<0.001). Postoperative pain was less in Dexmedetomidine group (p-value< 0.001). CONCLUSION: Dexmedetomidine reduced delirium caused by Ketamine when used as a premedication agent. It produced more haemodynamic stable patients. Postoperative analgesia was also better.