Search Results (871)

To address the micro-vibration isolation requirements of precision payloads in spacecraft, a Lorentz force-based magnetic levitation series vibration isolation platform is proposed. The Lorentz force actuator, overall coupling characteristics, and low-frequency vibration isolation performance of the platform are optimized, simulated, and experimentally validated. During the actuator design phase, an equivalent magnetic circuit model and an equivalent current model are established for the planar actuator. The theoretical relationship between magnetic flux density in the air gap and magnetization length is derived. Through finite element simulation, the optimal magnetization length is determined to be 7 mm. For the coupling analysis, a dynamic model of the platform is developed to quantify the coupling effects between translational and rotational motions. To evaluate the low-frequency vibration isolation performance, sinusoidal displacement at various frequencies is applied to emulate the space vibration environment and validate the isolation capability. The results show that the platform has low translational-rotational cross-coupling, and the vibration transmissibility of low-frequency micro-vibration is less than 35 dB. This system offers a high-precision, low-coupling solution for vibration isolation in precision optical instruments. Full article

A water-soluble high-molecular neutral polysaccharide (NP) was isolated from the eggs of the sea urchin Tripneustes gratilla. The formation of glucose only upon the treatment of NP by amyloglucosidase and the value of its optical rotation [α]_D +233.5 (c 0.2, water) confirmed its belonging to the family of α-d-glucans. According to the results of NMR spectroscopy and methylation analysis, the chains of NP are built up of non-reducing terminal, 4-linked and 4,6-disubstituted glucose residues at a ratio of 1:8:1. A branched structure with an average linear chain length of about five glucose residues was calculated from the spectrum of iodine complex. Contrary to the previously published structure of branched α-d-glucan from the sea urchin Strongylocentrotus nudus bearing single glucose units as branches, the polysaccharide NP contains oligosaccharide branches at position 6, which was confirmed by NMR data. Hence, NP has a glycogen-like structure with a rather high degree of branching, which markedly exceeds that of usual mammalian or fungal glycogens. Full article

Substantial improvements in the performance of optical interconnects based on multi-mode fibers are required to support emerging single-channel data transmission rates of 200 Gb/s and 400 Gb/s. Future optical components must combine very high modulation bandwidths—supporting signaling at 100 Gbaud and 200 Gbaud—with reduced spectral width to mitigate chromatic-dispersion-induced pulse broadening and increased brightness to further restrict flux-confining area in multi-mode fibers and thereby increase the effective modal bandwidth (EMB). A particularly promising route to improved performance within standard oxide-confined VCSEL technology is the introduction of multiple isolated or optically coupled oxide-confined apertures, which we refer to collectively as multi-aperture (MA) VCSEL arrays. We show that properly designed MA VCSELs exhibit narrow emission spectra, narrow far-field profiles and extended intrinsic modulation bandwidths, enabling longer-reach data transmission over both multi-mode (MMF) and single-mode fibers (SMF). One approach uses optically isolated apertures with lateral dimensions of approximately 2–3 µm arranged with a pitch of 10–12 µm or less. Such devices demonstrate relaxation oscillation frequencies of around 30 GHz in continuous-wave operation and intrinsic modulation bandwidths approaching 50 GHz. Compared with a conventional single-aperture VCSELs of equivalent oxide-confined area, MA designs can reduce the spectral width (root mean square values < 0.15 nm), lower series resistance (≈50 Ω) and limit junction overheating through more efficient multi-spot heat dissipation at the same total current. As each aperture lases in a single transverse mode, these devices exhibit narrow far-field patterns. In combination with well-defined spacing between emitting spots, they permit tailored restricted launch conditions in MMFs, enhancing effective modal bandwidth. In another MA approach, the apertures are optically coupled such that self-injection locking (SIL) leads to lasing in a single supermode. One may regard one of the supermodes as acting as a master mode controlling the other one. Streak-camera studies reveal post-pulse oscillations in the SIL regime at frequencies up to 100 GHz. MA VCSELs enable a favorable combination of wavelength chirp and chromatic dispersion, extending transmission distances over MMFs beyond those expected for zero-chirp sources and supporting transfer bandwidths up to 60 GHz over kilometer-length SMF links. Full article

In this work, bismuthate glasses with compositions of 64Bi₂O₃-(25-x)Pb₃(BO₃)₂-11Ga₂O₃-xPbO (where x = 2, 7, 12, 17) were prepared by the melt-quenching method, and their density, thermodynamic stability, Raman spectra, X-ray photoelectron spectra, Verdet constant, and nanosecond laser-induced damage threshold (LIDT) were characterized. As the content of PbO increases, the thermodynamic stability and laser-induced damage threshold of the glass gradually decrease, which corresponds to the increase in the glass’s optical basicity, the rise in non-bridging oxygen content, and the valence state transition of Bi ions observed in structural studies. A relatively large Verdet constant was obtained in the glass with the composition of 64Bi₂O₃-8Pb₃(BO₃)₂-11Ga₂O₃-17PbO, with a value of −0.191 min·G⁻¹·cm⁻¹ at a wavelength of 633 nm, which is much larger than that of commercially diamagnetic glasses. In addition, the variation in the Verdet constant at 1064 nm between 20 and 80 °C is less than 0.4 × 10⁻⁵ K⁻¹, which indicates that these bismuthate glasses are good candidates for magneto-optical devices under thermally unstable conditions. Full article

The organic/inorganic hybrid compound bis(2-amino-6-bromopyridinium) tetrachloridocuprate(II) (HABPy)₂[CuCl₄] was synthesized in crystalline form in a 77% yield from aqueous HCl solutions containing Cu(OAc)₂ and 2-amino-6-bromopyridine (ABPy). Single-crystal X-ray diffraction analysis revealed that the compound crystallizes in the monoclinic, centrosymmetric space group C2/c. The Cu atom shows a distorted tetrahedral coordination geometry with a τ₄ value of 0.69 (τ₄ = 1 for a perfect tetrahedron). The structure consists of organic (HABPy)⁺ cation layers at z = 0 and z = ½, alternating with inorganic [CuCl₄]²⁻ dianion layers at z = ¼ and z = ¾. These layers, parallel to the (001) plane, are interconnected by a plethora of supramolecular forces such as N–H···Cl hydrogen bonds, forming a three-dimensional network. Powder X-ray diffraction confirmed the purity of the synthesized bulk material. Fourier-transform infrared (FT-IR) spectroscopy and Raman spectroscopy support the protonation of the pyridine N atom. Hirshfeld surface analysis allowed us to further study the supramolecular forces in the crystal structure. The material shows purely paramagnetic behavior according to S = ½ with an effective magnetic moment µ_eff of 1.85 µB and a g factor of 2.14, in keeping with magnetically isolated [CuCl₄]²⁻ dianions. UV-vis diffuse reflectance spectroscopy of the orange-red material showed a tiny band at 314 nm and an intense band peaking at 622 nm. The optical gap was found to be 2.25 eV. The photoluminescence spectrum shows a partially structured band with maxima at 416 and 436 nm when irradiating at 370 nm, the wavelength of the maximum band found in the excitation spectrum. Full article

The gene SPG7 codes for the protein paraplegin, a subunit of the m-AAA protease in the inner mitochondrial membrane involved in protein quality control. SPG7 was initially identified as causing autosomal recessive hereditary spastic paraplegia (HSP), with a pure (insidiously progressive bilateral leg weakness and spasticity) and complex (with additional neurologic features including cerebellar signs and optic atrophy) forms. Now identified as one of the most common causes of HSP, SPG7-associated disease has been linked to additional neuro-ophthalmologic features, including isolated dominant optic atrophy, cerebellar eye signs (various forms of nystagmus, dysmetric saccades), progressive external ophthalmoplegia (PEO), and supranuclear vertical palsy. This review describes in detail the various neuro-ophthalmologic presentations of SPG7-associated disease, illustrating the role of mitochondrial dysfunction in the pathophysiology of these different entities. Knowledge of the different manifestations of SPG7-associated disease is crucial for both neurologists and ophthalmologists, and SPG7 should be considered in the work-up of patients presenting with entities such as optic atrophy, PEO, and cerebellar eye signs. Full article

The aim was to evaluate if purple yam starch esterification with octenyl succinic anhydride (PYS-OSA) enhances the properties of purple yam starch (PYS)-based films in a blend with tara gum (TG). PYS was isolated from purple yam tubers (PYTs) with distilled water; then, starch was dual-modified by ultrasound (as a pretreatment) and esterification (PYS-OSA). The films PYS:TG and PYS-OSA:TG were characterized through physicochemical and mechanical characterization. The thermal properties (T_o, T_c, T_p, and ΔH) of PYS-OSA decreased in the range of 3.4–7.6% compared to PYS. Fourier transform infrared spectroscopy (FTIR) confirmed esterification, revealing two new absorption bands at 1563.0 and 1726.5 cm⁻¹, and the degree of substitution (DS) was 0.023. The moisture content and solubility in water were 50.7 and 40.5% greater, respectively, for PYS-OSA:TG films compared to PYS:TG ones, but both films exhibited similar optical properties. The tensile strengths of PYS-OSA:TG films were higher than those of PYS:TG ones; however, the elongation at break was lower. PYS:TG and PYS-OSA:TG films were disintegrated by more than 70% after 13 days of being buried in soil. This work contributes to a better understanding of the starch isolated from purple yam tuber, with potential relevance for sustainable packaging applications. Full article

As sessile organisms, plants have developed strategies to cope with exposure to high radiation. The plant cuticle is located at the interface between the plant and the surrounding environment, thus acting as a first barrier that protects plants against environmental conditions, including solar radiation. The isolated cuticles displayed notable absorptance in the infrared spectral range which, according to Kirchhoff’s law of thermal radiation, equals the emission dissipation ability. Comparison among the different cuticles showed that a significant range of their reflectance, transmittance, and absorbance spectra match the spectral regions known as atmospheric windows, between 3–4 and 8–13 microns, located within the mid-infrared region (MIR). They allow energy to pass through into the outer space. These optical parameters varied between cuticles from different plant species and they were not a simple function of the cuticle’s thickness but the product of its specific composition in combination with its molecular arrangement. Full article

Linezolid, a synthetic antimicrobial agent, may induce oxidative damage in ocular tissues, particularly in the optic nerve. Adenosine triphosphate (ATP) is involved in the production of antioxidants that scavenge and neutralize reactive oxygen species. This study aims to evaluate the potential protective effect of exogenous ATP against linezolid-induced ocular damage in rats, in comparison with methylprednisolone. Wistar-type rats were divided into five groups as follows: healthy (HG), ATP-only (ATPG), linezolid-only (LZDG), ATP + linezolid (ATLDG), and methylprednisolone + linezolid groups (MPLDG). Oxidative stress markers, antioxidant biomarkers, and proinflammatory cytokines were analyzed in isolated ocular tissues. Optic nerve tissue was also evaluated histopathologically. Linezolid administration increased the oxidative stress marker MDA and the proinflammatory cytokine TNF-α, while decreasing antioxidant parameters such as tGSH, SOD and CAT in rat ocular tissues, compared to the healthy group. However, it did not significantly alter serum troponin I levels. Histopathological analysis revealed that linezolid induced oxidative damage and inflammation in optic nerve tissue, with marked glial alterations. ATP administration reduced linezolid-induced oxidative stress in ocular tissue, as indicated by decreased MDA levels. It also enhanced antioxidant defenses by increasing tGSH, SOD, and CAT levels. In addition, ATP lowered proinflammatory cytokine levels, thereby alleviating inflammation. These effects collectively contributed to the restoration of biochemical parameters toward normal levels. In addition, ATP mitigated linezolid-induced optic nerve damage and glial alterations. The critical role of ATP in reducing oxidative stress, restoring antioxidant balance, and suppressing inflammation may represent a promising therapeutic approach for linezolid-induced ocular toxicity. Full article

Virtual networks have emerged as a promising solution for enabling diverse users to efficiently share bandwidth resources over optical network infrastructures. Despite the invention of various schemes aimed at ensuring secure isolation among virtual networks, the security of data transfer in virtual networks remains a challenging problem. To address this challenge, the concept of evolving traditional optical networks into key programmable optical networks (KPONs) has been proposed. Inspired by this, this paper delves into the establishment of secure virtual networks over KPONs, in which the information-theoretically secure keys can be supplied for ensuring the information-theoretic security of data transfer within virtual networks. A layered architecture for secure virtual network provisioning over KPONs is proposed, which leverages software-defined networking to realize the programmable control of optical-layer resources. With this architecture, a heuristic algorithm, i.e., the key adaptation-based secure virtual network provisioning (KA-SVNP) algorithm, is designed to dynamically allocate key resources based on the adaption between the key supply and key demand. To evaluate the proposed solutions, an emulation testbed is established, achieving millisecond latencies for secure virtual network establishment and deletion. Moreover, numerical simulations indicate that the designed KA-SVNP algorithm performs superior to the benchmark algorithm in terms of the success probability of secure virtual network requests. Full article

Jefea lantanifolia (S. Schauer) Strother is traditionally used in Hidalgo, Mexico, to manage type 2 diabetes (T2D). The aerial parts are prepared as an infusion and consumed throughout the day. This study conducted a 2 h acute experiment under both fasting and postprandial conditions to evaluate the effects of the aqueous infusion (AE), the ethanol–water extract (EWE), and their isolated constituents in hyperglycemic rats. Structures were established using conventional spectroscopic methods. The absolute configuration was determined by optical rotation and calculated electronic circular dichroism (ECD) methods. Phytochemical analysis led to the isolation of six compounds: luteolin (1); 2β-hydroxy-dimerostemma brasiolide-1-O-(3-hydroxymethacrylate) (2); homoplantaginin (3); cynarin (4); luteolin-7-O-glucoside (5); and nepitrin (6). The extract was deemed safe at a dose of 2 g/kg b. w. in acute toxicity assays. In vivo experiments showed significant reductions in blood glucose levels during fasting, with compounds 2 and 3 achieving reductions of 42% and 40%, respectively, compared to 51% with glibenclamide. Postprandially, all treatments demonstrated effective glucose-lowering activity, particularly compound 3 and the EWE. These findings support the traditional use of J. lantanifolia and highlight its phytochemicals as promising candidates for further pharmacological investigation. Long-term studies and high-dose evaluations are warranted to validate therapeutic potential and establish safety profiles. Full article

This article presents a principled framework for selecting and tuning classical computer vision algorithms in the context of optical displacement sensing. By isolating key factors that affect algorithm behavior—such as feed window size and motion step size—the study seeks to move beyond intuition-based practices and provide rigorous, repeatable performance evaluations. Computer vision-based optical odometry sensors offer non-contact, high-precision measurement capabilities essential for modern metrology and robotics applications. This paper presents a systematic comparative analysis of three classical tracking algorithms—phase correlation, template matching, and optical flow—for 2D surface displacement measurement using synthetic image sequences with subpixel-accurate ground truth. A virtual camera system generates controlled test conditions using a multi-circle trajectory pattern, enabling systematic evaluation of tracking performance using 400 × 400 and 200 × 200 pixel feed windows. The systematic characterization enables informed algorithm selection based on specific application requirements rather than empirical trial-and-error approaches. Full article

Vision is a critical component of daily life, and its loss significantly hinders an individual’s ability to navigate, particularly when using public transportation systems. To address this challenge, this paper introduces a novel approach for accurately identifying bus route numbers and destinations, designed to assist visually impaired individuals in navigating urban transit networks. Our system integrates object detection, image enhancement, and Optical Character Recognition (OCR) technologies to achieve reliable and precise recognition of bus information. We employ a custom-trained You Only Look Once version 8 (YOLOv8) model to isolate the front portion of buses as the region of interest (ROI), effectively eliminating irrelevant text and advertisements that often lead to errors. To further enhance accuracy, we utilize the Enhanced Super-Resolution Generative Adversarial Network (ESRGAN) to improve image resolution, significantly boosting the confidence of the OCR process. Additionally, a post-processing step involving a pre-defined list of bus routes and the Levenshtein algorithm corrects potential errors in text recognition, ensuring reliable identification of bus numbers and destinations. Tested on a dataset of 120 images featuring diverse bus routes and challenging conditions such as poor lighting, reflections, and motion blur, our system achieved an accuracy rate of 95%. This performance surpasses existing methods and demonstrates the system’s potential for real-world application. By providing a robust and adaptable solution, our work aims to enhance public transit accessibility, empowering visually impaired individuals to navigate cities with greater independence and confidence. Full article

Four new compounds and three new natural products (1−7), including three novel cyclic tetrapeptides (penicopeptides B−D), along with three known spiroquinazoline analogs (8–10), were isolated from rice medium cultures of a sponge-associated Penicillium sp. SCSIO41035. The structural elucidations, including the determination of absolute configurations, were accomplished by comprehensive analyses utilizing NMR spectroscopy, HRESIMS, optical rotation data, X-ray crystallography experiments and electronic circular dichroism calculations. Differential NMR signals between symmetric units in cyclotetrapeptides 1 and 2 arise from the asymmetric solution conformations as investigated through conformational searching and theoretical calculations. The asymmetric conformations were primarily caused by the flexibility of the tyrosine residue’s phenyl side chain, with its substantial electron density significantly influencing the NMR signals of nearby groups. Bioactivity screening results displayed that isolated compounds demonstrated good neuraminidase inhibitory activity, with inhibition rates ranging from 43.16% to 85.40% at a concentration of 100 µg/mL. Full article

Farmland shelterbelts are vital ecological infrastructure for sustaining agriculture in arid regions, where high winds, soil erosion, and water scarcity severely constrain productivity. While their protective functions—reducing wind speed, controlling erosion, moderating microclimates, and enhancing yields—are well documented, previous studies have largely examined individual structural elements in isolation, leaving their interactive effects and trade-offs poorly understood. This review synthesizes current research on the structural optimization of shelterbelts, emphasizing the critical relationship between their physical and biological attributes and their protective functions. Key structural parameters—such as optical porosity, height, width, orientation, and species composition—are examined for their individual and interactive impacts on shelterbelt performance. Empirical and modeling studies indicate that moderate porosity maximizes wind reduction efficiency and extends the leeward protection zone, while multi-row, multi-species configurations effectively suppress soil erosion and improve microclimate conditions. Sheltered areas experience reduced evapotranspiration, increased humidity, and moderated temperatures, collectively enhancing crop water use efficiency and yielding significant improvements in crop production. Advanced methodologies, including field monitoring, wind tunnel testing, computational fluid dynamics, and remote sensing, are employed to quantify benefits and refine designs. A multi-objective optimization framework is essential to balance competing goals: maximizing wind reduction, minimizing water consumption, enhancing biodiversity, and ensuring economic viability. Future challenges involve adapting designs to climate change, integrating water-efficient and native species, leveraging artificial intelligence for predictive modeling, and addressing socio-economic barriers to implementation. Building on this evidence, we propose a multi-objective optimization framework to balance competing goals: maximizing wind protection, minimizing water use, enhancing biodiversity, and ensuring economic viability. We identify key research gaps including unresolved porosity thresholds, the climate resilience of alternative species compositions, and the limited application of optimization algorithms and outline future priorities such as region-specific design guidelines, AI-driven predictive models, and policy incentives. This review offers a novel, trade-off–aware synthesis to guide next-generation shelterbelt design in arid agriculture. Full article