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MAXWELL STRESS INDUCED FLOW-DEFORMATION AND OPTICAL NONLINEARITIES IN LIQUID CRYSTALS (Invited Paper)
摘要： We present a critical account of intense pulsed-laser ?eld induced refractive index changes caused by ?ow, crystalline axis reorientation and distortion and other high order photonic processes in transparent liquid crystals. In particular, the optical nonlinearity associated with Maxwell Stress induced ?ow-reorientation in nematic liquid crystals is explicitly calculated, and their possibility for all-optical switching application is experimentally demonstrated. Similar ?ows processes have also been observed in Blue-Phase liquid crystals with nanosecond and picosecond pulsed-lasers.
关键词： all-optical switching,liquid crystals,optical nonlinearities,Blue-Phase liquid crystals,nematic liquid crystals,Maxwell Stress
更新于2025-09-04 15:30:14
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The Role of Endogenous Neuroprotective Mechanisms in the Prevention of Retinal Ganglion Cells Degeneration
摘要： Retinal neurons are not able to undergo spontaneous regeneration in response to damage. A variety of stressors, i.e., UV radiation, high temperature, ischemia, allergens, and others, induce reactive oxygen species production, resulting in consecutive alteration of stress-response gene expression and finally can lead to cell apoptosis. Neurons have developed their own endogenous cellular protective systems. Some of them are preventing cell death and others are allowing functional recovery after injury. The high efficiency of these mechanisms is crucial for cell survival. In this review we focus on the contribution of the most recently studied endogenous neuroprotective factors involved in retinal ganglion cell (RGC) survival, among which, neurotrophic factors and their signaling pathways, processes regulating the redox status, and different pathways regulating cell death are the most important. Additionally, we summarize currently ongoing clinical trials for therapies for RGC degeneration and optic neuropathies, including glaucoma. Knowledge of the endogenous cellular protective mechanisms may help in the development of effective therapies and potential novel therapeutic targets in order to achieve progress in the treatment of retinal and optic nerve diseases.
关键词： endogenous neuroprotection,optic neuropathy,retinal ganglion cells,cell survival,stress-response
更新于2025-09-04 15:30:14
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Physiological Response to Different Irradiation Regimes during Barley Seedlings Growth Followed by Drought Stress under Non-Photoinhibitory Light
摘要： Differences in physiological response of barley seedlings cultivated under low (LI, ~65 μmol m-2 s-1) and elevated irradiation (EI, ~450 μmol m-2 s-1) to upcoming drought were evaluated. After ten days of cultivation, drought stress was induced under LI by withholding water and was defined as: mild stress (MS), severe stress (SS), extreme stress (ES) and control (C, well watered). Decreased relative water content (RWC) in both LI and EI grown plants was associated with increased lipid peroxidation (TBARS) and electrolyte leakage (%EL) as well as with decreased total chlorophylls content at SS and ES. Antioxidative response to drought was, generally, indicated by higher accumulation of free proline, increased activities of catalase (CAT), guaiacol peroxidase (GPOD) and ascorbate peroxidase (APX). Even the majority of estimated physiological and biochemical parameters showed no differences between investigated light regimes before drought stress induction, the LI grown plants responded on drought by adjustment of the photosynthetic apparatus to prevent photoinhibitory oxidative damage. Photosynthesis downregulation in EI grown plants under ES was revealed due to reduced values of maximum quantum yield of photosystem II (Fv/Fm) and performance index (PIABS) showing that acclimatization to EI conditions lowered their tolerance to the following drought stress although it was applied under low irradiation (LI). Therefore, those plants had reduced capability to cope with the challenge of upcoming drought stress showing more pronounced cellular oxidative damage (SS and ES), less efficient and almost dysfunctional photosynthetic apparatus in extreme drought (ES).
关键词： antioxidative response,photosynthesis,Hordeum vulgare,light regime,drought stress,lipid peroxidation
更新于2025-09-04 15:30:14
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Knockdown of FOXO6 inhibits high glucose–induced oxidative stress and apoptosis in retinal pigment epithelial cells
摘要： Oxidative stress and apoptosis in retinal pigment epithelium cells are involved in the pathogenesis of diabetic retinopathy (DR). Forkhead box class O 6 (FOXO6) is a member of the FOXO family that can regulate diabetes‐induced oxidative stress. However, the role of FOXO6 in DR has not been clarified. The aim of the present study was to investigate the effects of FOXO6 on high glucose (HG)‐induced oxidative stress and apoptosis in ARPE‐19 cells. The results showed that FOXO6 was overexpressed in clinical vitreous samples from DR patients and in HG‐induced ARPE‐19 cells. Knockdown of FOXO6 by small interfeing RNA targeting FOXO6 (si‐FOXO6) mitigated the HG‐induced the production of reactive oxygen species and malondialdehyde, as well as the inhibition of superoxide dismutase activity. Knockdown of FOXO6 reduced the rate of cell apoptosis in HG‐induced ARPE‐19 cells. The increase in bax expression and decrease in bcl‐2 expression caused by HG stimulation were reversed by si‐FOXO6 transfection. Furthermore, knockdown of FOXO6 enhanced the activation of Akt/Nrf2 pathway in HG‐stimulated ARPE‐19 cells. Taken together, suppression of FOXO6 protects ARPE‐19 cells from HG‐induced oxidative stress and apoptosis, which is in part mediated by the activation of Akt/Nrf2 pathway.
关键词： Akt/Nrf2 pathway,oxidative stress,retinal pigment epithelium cells,forkhead box class O 6,diabetic retinopathy,apoptosis
更新于2025-09-04 15:30:14
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Assessing the Reliability of Thermal and Optical Imaging Techniques for Detecting Crop Water Status under Different Nitrogen Levels
摘要： Efficient management of irrigation water is fundamental in agriculture to reduce the environmental impacts and to increase the sustainability of crop production. The availability of adequate tools and methodologies to easily identify the crop water status in operating conditions is therefore crucial. This work aimed to assess the reliability of indices derived from imaging techniques—thermal indices (Ig (stomatal conductance index) and CWSI (Crop Water Stress Index)) and optical indices (NDVI (Normalized Difference Vegetation Index) and PRI (Photochemical Reflectance Index))—as operational tools to detect the crop water status, regardless the eventual presence of nitrogen stress. In particular, two separate experiments were carried out in a greenhouse, on two spinach varieties (Verdi F1 and SV2157VB), with different microclimatic conditions and under different levels of water and nitrogen application. Statistical analysis based on ANOVA test was carried out to assess the independence of thermal and optical indices from the crop nitrogen status. These imaging indices were successively compared through correlation analysis with reference destructive and non-destructive measurements of crop water status (stomatal conductance, chlorophyll a fluorescence, and leaf and soil water content), and linear regression models of thermal and optical indices versus reference measurements were calibrated. All models were significant (Fisher p-value lower than 0.05), and the highest R2 values (greater than 0.6) were found for the regression models between CWSI and the soil water content, NDVI and the leaf water content, and PRI and the stomatal conductance. Further analysis showed that imaging indices acquired by thermal cameras (especially CWSI) can be used as operational tools to detect the crop water status, since no dependence on plant nitrogen conditions was observed, even when the soil water depletion was very limited. Our results confirmed that imaging indices such as CWSI, NDVI and PRI can be used as operational tools to predict soil water status and to detect drought stress under different soil nitrogen conditions.
关键词： crop water status,crop water stress prediction,optical imaging sensor,thermal camera,spectral imaging index
更新于2025-09-04 15:30:14
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Response of Synechocystis sp. PCC 6803 to UV radiations by alteration of polyamines associated with thylakoid membrane proteins
摘要： The responses of Synechocystis sp. PCC 6803 exposed to UVA, UVB and UVC for at least 3 h were investigated with the emphasis on the changes of polyamines (PAs) levels in whole cells, thylakoid membrane fraction, and thylakoid membrane-associated proteins fraction. All UV radiations caused a slight decrease on cell growth but a drastic reduction of photosynthetic efficiency of Synechocystis cells. UV radiations, especially UVB and UVC, severely decreased the levels of PAs associated with thylakoid membrane proteins. The decreased PAs levels as affected by UV radiation correlated well with the decrease of photosynthetic efficiency, suggesting the role of PAs for the maintenance of photosynthetic activity of Synechocystis. PAs, especially spermidine (Spd) and putrescine (Put), were found abundantly in the thylakoid membrane fraction, and these PAs were associated mainly with the PSI trimer complex. Importantly, the exposure of Synechocystis cells to all UV radiations for 3 h resulted in the increase of Spd associated with the PSII monomer and dimer complex, suggesting its protective role against UV radiations despite the overall decrease of PAs.
关键词： Polyamine association,Thylakoid membrane protein complexes,Stress response,UV radiations,Synechocystis sp. PCC 6803
更新于2025-09-04 15:30:14
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Lipofuscin-mediated photodynamic stress induces adverse changes in nanomechanical properties of retinal pigment epithelium cells
摘要： Retinal pigment epithelium (RPE) is an important part of the blood-retina barrier (BRB) that separates the retina from the choroid. Although melanin granules contribute to the mechanical stability of the BRB complex, it is unknown if the age pigment lipofuscin affects mechanical properties of the tissue. To address this issue the effect of sub-lethal photic stress mediated by phagocytized lipofuscin granules, isolated from RPE of human donors, on morphology and mechanical properties of ARPE-19 cells was investigated. Nanomechanical analysis using atomic force spectroscopy revealed that irradiation of cells containing lipofuscin granules with blue light induced significant softening of the cells, which was accompanied by substantial reorganization of the cell cytoskeleton due to peroxidation of cellular proteins. Our results indicate that lipofuscin-mediated photic stress can cause significant modification of the RPE cells with the potential to disturb biological function of the BRB complex.
关键词： photic stress,lipofuscin,Retinal pigment epithelium,nanomechanical properties,blood-retina barrier
更新于2025-09-04 15:30:14
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[IEEE 48th European Solid-State Device Research Conference (ESSDERC 2018) - Dresden (2018.9.3-2018.9.6)] 2018 48th European Solid-State Device Research Conference (ESSDERC) - Novel IC Sub-Threshold IDDQ Signature And Its Relationship To Aging During High Voltage Stress
摘要： A sub-threshold quiescent current (IDDQ) signature is observed for the first time. 14 nm SOI Ring Oscillators (ROs) are used to study a characteristic knee/peak for different device types and threshold voltages undergoing different stress conditions. The relationship of the sub-threshold IDDQ characteristics to process variability and aging are explained with detailed circuit level simulations. This novel signature has potential applications for reliability analysis and aged/used chip detection.
关键词： sub-threshold current,IDDQ,circuit aging,aged/used chip detection,elevated voltage stress
更新于2025-09-04 15:30:14
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Piezophotonics: From fundamentals and materials to applications
摘要： The piezophotonic effect is the coupling between piezoelectric properties and photoexcitation, where strain-induced piezopotential modulates and controls the relevant optical process. Specifically, metal ions as activators are capable of responding to photoexcitation and subsequent emission of light, also called mechanoluminescence, in general, and piezoluminescence specifically for piezoelectrics. These phenomena are helpful for understanding the materials fundamentals and conceiving widespread device applications. In this article, we briefly introduce the physical mechanisms of piezophotonics, including piezoluminescence. Selected host materials and metal-ion activators are described for demonstrating the piezophotonic effect. We provide a unified profile and recent prototypical demonstrations of light emission triggered by mechanical stimuli. The devices based on these materials offer the advantages of remote detection, nondestructive analysis, and repeatability, hence they are promising candidates for applications in stress sensing, structural health diagnosis, three-dimensional handwriting, magnetic-optical sensing, energy harvesting, biomedicine, novel light sources, and displays.
关键词： energy harvesting,piezoluminescence,mechanoluminescence,piezophotonics,stress sensing
更新于2025-09-04 15:30:14
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The Neuroprotective Effect of Maltol against Oxidative Stress on Rat Retinal Neuronal Cells
摘要： Purpose: Maltol (3-hydroxy-2-methyl-4-pyrone), formed by the thermal degradation of starch, is found in coffee, caramelized foods, and Korean ginseng root. This study investigated whether maltol could rescue neuroretinal cells from oxidative injury in vitro. Methods: R28 cells, which are rat embryonic precursor neuroretinal cells, were exposed to hydrogen peroxide (H2O2, 0.0 to 1.5 mM) as an oxidative stress with or without maltol (0.0 to 1.0 mM). Cell viability was monitored with the lactate dehydrogenase assay and apoptosis was examined by the terminal deoxynucleotide transferase-mediated terminal uridine deoxynucleotidyl transferase nick end-labeling (TUNEL) method. To investigate the neuroprotective mechanism of maltol, the expression and phosphorylation of nuclear factor-kappa B (NF-κB), extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38 were evaluated by Western immunoblot analysis. Results: R28 cells exposed to H2O2 were found to have decreased viability in a dose- and time-dependent manner. However, H2O2-induced cytotoxicity was decreased with the addition of maltol. When R28 cells were exposed to 1.0 mM H2O2 for 24 hours, the cytotoxicity was 60.69 ± 5.71%. However, the cytotoxicity was reduced in the presence of 1.0 mM maltol. This H2O2-induced cytotoxicity caused apoptosis of R28 cells, characterized by DNA fragmentation. Apoptosis of oxidatively-stressed R28 cells with 1.0 mM H2O2 was decreased with 1.0 mM maltol, as determined by the TUNEL method. Western blot analysis showed that treatment with maltol reduced phosphorylation of NF-κB, ERK, and JNK, but not p38. The neuroprotective effects of maltol seemed to be related to attenuated expression of NF-κB, ERK, and JNK. Conclusions: Maltol not only increased cell viability but also attenuated DNA fragmentation. The results obtained here show that maltol has neuroprotective effects against hypoxia-induced neuroretinal cell damage in R28 cells, and its effects may act through the NF-κB and mitogen-activated protein kinase signaling pathways.
关键词： Oxidative stress,Neuroprotection,Maltol,Rat retinal neuronal cell
更新于2025-09-04 15:30:14