Studying the statistical distribution of single-photon pulses from avalanche photodetectors

The statistical distributions of pulses from silicon avalanche photodetectors with p ⁺ n-v-n ⁺ and n ⁺ p-π-p ⁺ structures have been investigated in the photon-counting mode. Comparative analysis of the statistical distributions for these avalanche photodetectors is presented.     

Simultaneous measurement of quantum yield ratio and absorption ratio between acceptor and donor by linearly unmixing excitation–emission spectra

Quantum yield ratio (Q_A/Q_D) and absorption ratio (K_A/K_D) in all excitation wavelengths used between acceptor and donor are indispensable to quantitative fluorescence resonance energy transfer (FRET) measurement based on linearly unmixing excitation–emission spectra (ExEm‐spFRET). We here describe an approach to simultaneously measure Q_A/Q_D and K_A/K_D values by linearly unmixing the excitation–emission spectra of at least two different donor–acceptor tandem constructs with unknown FRET efficiency. To measure the Q_A/Q_D and K_A/K_D values of Venus (V) to Cerulean (C), we used a wide‐field fluorescence microscope to image living HepG2 cells separately expressing each of four different C–V tandem constructs at different emission wavelengths with 435 nm and 470 nm excitation respectively to obtain the corresponding excitation–emission spectrum (S_DA). Every S_DA was linearly unmixed into the contributions (weights) of three excitation–emission spectra of donor (W_D) and acceptor (W_A) as well as donor–acceptor sensitisation (W_S). Plot of W_S/W_D versus W_A/W_D for the four C–V plasmids from at least 40 cells indicated a linear relationship with 1.865 of absolute intercept (Q_A/Q_D) and 0.273 of the reciprocal of slope (K_A/K_D), which was validated by quantitative FRET measurements adopting 1.865 of Q_A/Q_D and 0.273 of K_A/K_D for C32V, C5V, CVC and VCV constructs respectively in living HepG2 cells.     

Indian medicinal plants are effective in the treatment and management of COVID-19

Indian medicinal plants are referred to as the “nectar of life” owing to their phytochemicals and bioactive complexes that are beneficial in treating diseases. Coronavirus disease 2019 (COVID-19) is a global health issue without any proper medication. The indigenous plants of India can be exploited to control the precise signs of SARS-CoV-2. The Ministry of AYUSH (Ayurveda, Yoga and Naturopathy, Unani, Siddha, and Homeopathy) has advised routine usage of medicinal plants for COVID-19. Medicinal plants like Zingiber officinalis, Azadirachta indica, Ocimum sanctum, Nigella sativa, Withania somnifera, Curcuma longa, Piper nigrum, Allium sativum, Tinospora cordifolia, etc. have immunity-boosting, antiviral, antibacterial, antioxidant and anti-inflammatory actions that can suppress and treat symptoms of COVID-19. In vitro, in vivo as well as in silico validation, these phytochemicals can help us to manage and treat COVID-19 disease. This integration of traditional knowledge in the prophylaxis of corona infection and current skills validating it for the development of precise and powerful therapeutic approaches will more efficiently resolve different clinical aspects of COVID-19. The review focuses on both traditional and emergent methods to prevent and treat COVID-19 with various Indian medicinal plants along with their phytochemicals.     

Resistance of silicon planar detectors to X-rays

We investigated the effect of X-rays with a dose of a few kilogrey on the characteristics of silicon planarp ⁺−n-detectors. The values of noise in terms of charge and the voltage-current and voltage-capacitance characteristics were analyzed. We determined the X-ray dose, for which the noise 1/f was generated. Charge accumulation in the protective oxide was responsible for this noise and affected the volt-ampere and volt-farad detector characteristics.     

Unexpected effect of the vehicle (grain ethanol) of homeopathic FSH on the in vitro survival and development of isolated ovine preantral follicles

The aims of this study were to investigate the effects of medium replacement system (experiment I) and of FSH presentations (homeopathic – FSH 6cH and allopathic FSH – rFSH; experiment II) on the in vitro development, hormone production and gene expression of isolated ovine preantral follicles cultured for 6 days. In experiment I, secondary follicles were cultured in the α‐MEM⁺ supplemented with FSH 6cH (0.05 fg/ml) or recombinant bovine FSH (100 ng/ml) without/with daily medium addition. The homeopathic FSH treatments with/without medium addition improved (p < .05) follicular development compared to rFSH100 treatment without addition. FSH 6cH with addition showed the highest (p < .05) estradiol production. To verify whether the effects of homeopathic FSH were not due to its vehicle, experiment II was performed. The α‐MEM⁺ was supplemented or not with alcohol (0.2% grain ethanol, v/v), FSH 6cH or rFSH100 with daily medium addition. Surprisingly, we found that all treatments improved follicular development compared to the α‐MEM⁺ (p < .05). Moreover, homeopathic FSH was similar to the other treatments including its vehicle. In conclusion, its vehicle (ethanol) causes the effect of homeopathic FSH on in vitro development of isolated ovine preantral follicles.     

Profiles of immune status and related pathways in sepsis: evidence based on GEO and bioinformatics

Sepsis, characterized as life-threatening sequential organ failure, is caused by a dysregulated host immune response to a pathogen. Conventional practice for sepsis is to control the inflammation source and administer highgrade antibiotics. However, the mortality rate of sepsis varies from 25–30% and can reach 50% if a septic shock occurs. In our current study, we used bioinformatics technology to detect immune status profiles in sepsis at the genomic level. We downloaded and analyzed gene expression profiles of GSE28750 from the Gene Expression Omnibus (GEO) database to determine differential gene expression and immune status between sepsis and normal samples. Next, we used the CIBERSORT method to quantify the proportions of immune cells in the sepsis samples. Then we explored the differentially expressed genes (DEGs) related to sepsis. Furthermore, gene ontology (GO) function and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis were used to present potential signaling pathways in sepsis. We found that in the sepsis samples, the CD8⁺ T cell fraction was consistently lower, based on the CIBERSORT method, whereas the neutrophil fraction was significantly higher in the sepsis samples. The GO function and KEGG pathway enrichment analysis identified 1573 DEGs that were significantly associated with neutrophil activation, neutrophil degranulation, neutrophil activation involved in the immune response, neutrophil-mediated immunity, and T cell activation in the biological processes group. In our study, we provided a first glance of associations between immune status and sepsis. Furthermore, our data regarding the reciprocal interaction between immune cells (neutrophils and CD8⁺ T cells) could improve our understanding of immune status profiles in sepsis. However, additional investigations should be performed to verify their clinical value.     

Effect of post-implantation annealing on the current-voltage characteristics of IR photodiodes based on <Emphasis Type="Italic">p</Emphasis>-HgCdTe

Current-voltage characteristics of IR photodiodes and distributions of charge carriers in n ⁺-n ⁻-p-structures based on vacancy p-doped Hg_{1 − x} Cd _x Te films with x = 0.22 are examined. Three-dimensional numerical modeling of the distribution of charge carriers and current-voltage characteristics during photodiode annealing is performed. The calculations predict that large tunnel currents in diodes after implantation can result from an elevated (more than 10¹⁵ cm⁻³) concentration of donors in the n ⁻-layer, which enhances tunneling by decreasing the thickness of the space charged region of the n-p-junction, and also from a small (less than 3 μm) depth of the p-n-junction.     

Electron and ion imaging of gland cells using the FIB/SEM system

The FIB/SEM system was satisfactorily used for scanning ion (SIM) and scanning electron microscopy (SEM) of gland epithelial cells of a terrestrial isopod Porcellio scaber (Isopoda, Crustacea). The interior of cells was exposed by site-specific in situ focused ion beam (FIB) milling. Scanning ion (SI) imaging was an adequate substitution for scanning electron (SE) imaging when charging rendered SE imaging impossible. No significant differences in resolution between the SI and SE images were observed. The contrast on both the SI and SE images is a topographic. The consequences of SI imaging are, among others, introduction of Ga⁺ ions on/into the samples and destruction of the imaged surface. These two characteristics of SI imaging can be used advantageously. Introduction of Ga⁺ ions onto the specimen neutralizes the charge effect in the subsequent SE imaging. In addition, the destructive nature of SI imaging can be used as a tool for the gradual removal of the exposed layer of the imaged surface, uncovering the structures lying beneath. Alternative SEM and SIM in combination with site-specific in situ FIB sample sectioning made it possible to image the submicrometre structures of gland epithelium cells with reproducibility, repeatability and in the same range of magnifications as in transmission electron microscopy (TEM). At the present state of technology, ultrastructural elements imaged by the FIB/SEM system cannot be directly identified by comparison with TEM images.     

单价银离子在 CaO-P2O5 系统玻璃中的发光特性

在弱还原气氛下制备了单价银离子(Ag⁺)掺杂的CaO-P₂O₅系统玻璃,测试了其在室温下的吸收光谱、激发光谱和发射光谱。Ag⁺-CaO-P₂O₅玻璃的吸收光谱表明两个吸收峰。高能峰位于220nm波长,由4d¹⁰→4d⁹5P¹跃迁引起,低能峰中心位于240nm波长,归因于4d¹⁰→4d⁹5s¹跃迁,该吸收与其发射特性有关。紫外波段的宽带吸收产生了可见波段强烈的荧光发射,发光峰位于440nm波长,半宽度为130nm.研究了掺质浓度与发光特性的关系,随着掺质浓度的增加(0.05～0.25mol%),发光峰向较长波段移动。在Ag₂O含量为0.5mol%时,出现了浓度猝灭现象。为了比较起见,同时还研制了Cu⁺-CaO-P₂O₅及Cu⁺-Ag⁺-CaO-P₂O₅玻璃。     

Immunophenotypic evaluation,and physiological and laboratory correlations of hematopoietic stem cells from umbilical cord blood

The use of umbilical cord blood stem cells is an efficient alternative for the transplantation of hematopoietic progenitor cells. A number of factors can influence the volume and amount of CD34⁺ cells, which are considered as immature and capable of proliferation. Quantification of CD34⁺ cells, evaluation of CD38 and c-kit molecules on these cells, as well as correlations of such factors as maternal age, gestational age, newborn sex and weight, umbilical cord length, placental weight with increased volume and concentration of immature cells, among others, were performed in 70 blood samples from term newborns. The mean volume of umbilical cord blood collected was 53.8±33.6 mL, where 30.96±18.9 CD34⁺/µL UCB cells were found, of which 16.66±8.32% were CD34⁺ CD38- cells, and 47.23±24.0% were CD34⁺ CD117^- cells. Newborn weight and placental weight were positively correlated with increased volume of collected UCB. The volume of collected blood was found to affect the absolute count of CD34⁺ cells and the relative value of these among total nucleated cells, as well as the percentage of CD34⁺CD117⁺ and CD34⁺CD117^- cells. CD34⁺ cells were positively correlated with leukocytes, and gestational age was negatively correlated with the number of CD34⁺ cells. Our results confirm the importance of the accurate quantification of CD34⁺ cells and their subsets, and that many factors may be related to the higher number of hematopoietic stem cells, which are crucial for successful transplantation.     

A comparative study of switching possibilities of silicon diodes with different axial distribution shapes of recombination centers

Three groups of silicon p ⁺-n-n ⁺ diodes with a small turn-off time ensured by charged particle irradiation were studied in the high-power (3 kA) and short (50 μs) current pulse switching modes. The diodes of the first group were irradiated by electrons with a 550-keV energy, those of the second group were irradiated by protons with a 2.5-MeV energy and then by electrons with a 6-MeV energy, and those of the third group were irradiated by electrons with a 6-MeV energy. The studied diodes have a 16-mm semiconductor element diameter and 3-kV maximum permissible disabled voltage. The radiation doses were selected in such a way as to obtain an approximately equal current carrier lifetime near the p ⁺-n junction (4 μs), measured by the Lacks method, when the forward current density is 1 A/cm². It was determined that, when diodes of the first group change to the OFF position, the peak power of energy losses is two and more times smaller than that of diodes of the second and third groups, when they are switched off. The diodes of the first group also feature a substantially smaller voltage, when the forward current is at maximum (by two times as compared with diodes of the second group and by seven times as compared with diodes of the third group) and significantly smaller (by several times) voltage spike at a sharp forward current increase instant.     

How does antiseptic mouthwashes against SARS-COV-2 affect the bond strength of universal adhesive to enamel?

This study compares the effect of different mouthwashes that have been recommended during the Coronavirus disease 2019 (COVID-19) pandemic on shear bond strength (SBS) of universal adhesive to enamel in regards to self-etch (SE) and etch-and-rinse (ER) modes. Flat enamel surfaces were obtained from 100 sound human maxillary central incisors. They were randomly allocated to five groups according to the different mouthwashes (no mouthwash/control [Ctrl], 0.2% chlorhexidine 1.5% hydrogen peroxide [H₂O₂], 0.2% povidone-iodine [PVP-I], Listerine [L]), and adhesive application modes (ER and SE) (n = 10). After the application of a universal adhesive (single bond universal), composite resin (Filtek Z250) was bonded by a cylinder-shaped mold (height: 2 mm, diameter: 2.4 mm). They were subjected to SBS test using a universal testing machine (AGS-X, Shimadzu Corp.) (crosshead speed: 1 mm/min). The resin–enamel interfaces were observed with a scanning electron microscope (SEM). The semiquantitative chemical microanalyses were performed with energy-dispersive spectroscopy (EDS). The data were statistically analyzed by two-way analysis of variance and Bonferroni test (p < .05). In SE mode, Group Ctrl revealed significantly higher SBS than all mouthwash groups (p < .05). In ER mode, Group Ctrl showed significantly higher SBS than H₂O₂ and PVP-I groups (p < .05). ER mode caused significantly higher SBS than SE mode in all mouthwash groups (p < .05). The SEM observations highlighted that Group Ctrl had a regular and intact hybrid layer with resin tag formation while the H₂O₂ and PVP-I groups exhibited a thin hybrid layer in both modes. EDS analysis indicated that in SE mode, all mouthwash groups presented increased O content compared to Group Ctrl. H₂O₂ and PVP-I that were suggested for preprocedural use during the COVID-19 pandemic, reduced the enamel bond strength of the universal adhesive in ER mode.     

Effect of Hardness Ratio on the Wear Performance and Subsurface Evolution of Ni3Al Matrix Composites

A favorable hardness ratio (H_disk/H_pin = H_d/H_p) could lead to a transition to mild wear during sliding contact. To determine a more appropriate H_d/H_p value for the sliding wear, the dry sliding pin-on-disk wear tests of Ni₃Al matrix composites (NMCs) with multilayer graphene (MLG) are undertaken at H_d/H_p values of 0.99, 0.83, 0.42, and 0.35 at sliding speeds of 0.1, 0.3, 0.5, and 0.7 m/s. It is found that the tribological properties of NMCs are strongly affected by the various hardness ratios. At 0.1 m/s, the friction coefficient decreases with a decrease in H_d/H_p value. The low friction coefficient is 0.14 and the wear rate is 0.9 × 10^?5 mm³ N^?1m^?1 under the ceramic counterpart with H_d/H_p of 0.35. At 0.7 m/s, the tribological properties show the opposite trend with a decrease in H_d/H_p. At an H_d/H_p of 0.35, the smooth compact layer on the worn surface could decrease the friction at 0.1 m/s, and the improved hardness in the subsurface by strain hardening would play an important role in the improvement of wear resistance. Under the metal counterpart with H_d/H_p of 0.99, plastic deformation only occurs on the contact surface and the MLG could suppress further shear deformation in the subsurface, leading to a low wear rate (2.4 × 10^?5 mm³ N^?1m^?1) and friction coefficient (0.15) at 0.7 m/s.     

Fluorescence relaxation in 3D from diffraction-limited sources of PAGFP or sinks of EGFP created by multiphoton photoconversion

The relaxation of fluorescence from diffraction‐limited sources of photoactivatable green fluorescent protein (PAGFP) or sinks of photobleached enhanced GFP (EGFP) created by multiphoton photo‐conversion was measured in solutions of varied viscosity (η), and in live, spherical Chinese hamster ovary (CHO) cells. Fluorescence relaxation was monitored with the probing laser fixed, or rapidly scanning along a line bisected by the photoconversion site. Novel solutions to several problems that hamper the study of PAGFP diffusion after multiphoton photoconversion are presented. A theoretical model of 3D diffusion in a sphere from a source in the shape of the measured multiphoton point‐spread function was applied to the fluorescence data to estimate the apparent diffusion coefficient, D_ap. The model incorporates two novel features that make it of broad utility. First, the model includes the no‐flux boundary condition imposed by cell plasma membranes, allowing assessment of potential impact of this boundary on estimates of D_ap. Second, the model uses an inhomogeneous source term that, for the first time, allows analysis of diffusion from sources produced by multiphoton photoconversion pulses of varying duration. For diffusion in aqueous solution, indistinguishable linear relationships between D_ap and η⁻¹ were obtained for the two proteins: for PAGFP, D_aq= 89 ± 2.4 μm² s⁻¹ (mean ± 95% confidence interval), and for EGFP D_aq= 91 ± 1.8 μm² s⁻¹. In CHO cells, the application of the model yielded D_ap= 20 ± 3 μm² s⁻¹ (PAGFP) and 19 ± 2 μm² s⁻¹ (EGFP). Furthermore, the model quantitatively predicted the decline in baseline fluorescence that accompanied repeated photobleaching cycles in CHO cells expressing EGFP, supporting the hypothesis of fluorophore depletion as an alternative to the oft invoked ‘bound fraction’ explanation of the deviation of the terminal fluorescence recovery from its pre‐bleach baseline level. Nonetheless for their identical diffusive properties, advantages of PAGFP over EGFP were found, including an intrinsically higher signal/noise ratio with 488‐nm excitation, and the requirement for ∼1/200th the cumulative light energy to produce data of comparable signal/noise.     

Cardioprotective effect of ivabradine via the AMPK/SIRT1/PGC-1α signaling pathway in myocardial ischemia/reperfusion injury induced in H9c2 cell

Post-resuscitation myocardial dysfunction (PRMD) is the most severe myocardial ischemia-reperfusion injury (MIRI) and is characterized by difficult treatment and poor prognosis. Research has shown the protective effects of the rational use of ivabradine (IVA) against PRMD; however, the molecular mechanisms of IVA remain unknown. In this study, an ischemia-reperfusion injury (IRI) model was established using hypoxic chambers. The results demonstrated that pretreatment with IVA reduced IRI-induced cytotoxicity and apoptosis. IVA attenuated mitochondrial damage, eliminated excess reactive oxygen species (ROS), suppressed IRI-induced ATP and NAD⁺ , and increased the AMP/ATP ratio. We further found that IVA increased the mRNA levels of sirtuin 1 (SIRT1) and peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α) and upregulated the expression levels of phosphorylated AMP-activated protein kinase (p-AMPK)/AMPK, SIRT1, and PGC-1α proteins. Interestingly, no change in AMPK mRNA levels was observed. Cardiomyocyte energy metabolism significantly changed after IRI. The aim of this study was to demonstrate the cardioprotective effect of Ivabradine via the AMPK/SIRT1/PGC-1α signaling pathway in myocardial ischemia/reperfusion injury-induced in H9c2 cell.     

Mechanical and Tribological Properties of Thin Remote Microwave Plasma CVD a-Si:N:C Films from a Single-Source Precursor

Silicon carbonitride (a-Si:N:C) films produced by remote plasma chemical vapor deposition (RP-CVD) were investigated. Tetramethyldisilazane as a single-source precursor and (H₂+N₂) upstream gas mixture for plasma generation were used. The influence of the upstream gas composition on the structure, density, mechanical and tribological properties of the films deposited on p-type Si (001) wafers (both heated—T _s =300°C and unheated—T _s =30°C) are reported. The H₂ RP-CVD process was found to result in the formation of outstanding low friction (0.04) and high hardness (H=27-31 GPa) a-Si:N:C films exhibiting promisingly high H/E values.     

Characteristics Evaluation of Plasma Sprayed Ceramic Coatings by Nano/Micro-Indentation Test

The most controversial topics in plasma sprayed ceramic coating systems recently are mechanical properties such as bond strength, cohesive strength and toughness. In our research, critical fracture load (P _c) and interface toughness (K _c) of four-coating materials were computed from the applied load, crack length and Young's modulus data that were measured by micro-Vickers and a nano-indentation test. It is reasonable to consider the P _c value as comparison data of bond strength, and the K _c value, considering a trace of indent in the interface, was computed by a modified (E/H)_I ^1/2ratio. Also, we knew that P _c decreased as the hardness of the coating increased. In the case of the high load (9.8 and 19.6N) in the Al₂O₃+13%TiO₂ coating, the critical point (P _co) was found at which the coating was broken. Used by a XRD phase analysis, we checked changes of the coating's properties and predicted a possible change of the phases in plasma-sprayed coating.     

Retaining ionic concentrations during in vitro storage of tissue for microanalytical studies

When human or animal tissue is to be investigated by X-ray microanalysis, it is sometimes necessary to store the tissue between removal from the organism and freezing. However, when excised tissue is stored in buffer, the elemental concentrations in the cell may change. In the present study, it was attempted to develop a storage buffer that would retain the cellular elemental concentrations close to their in situ values. To start, the NaCl component in Krebs–Ringer buffer was exchanged for K-gluconate and KCl for NaCl. This buffer was called a ‘100% high K⁺ solution’. Starting from this solution, part of the K-gluconate was replaced by an equivalent amount of NaCl. Incubation of excised rat liver (4 °C, 4 h) in 85% high K⁺ solution resulted in retention of cellular Na, K, Ca, S and Mg concentration most closely to the in situ state, whereas cellular Cl was retained best when the tissue was incubated in 75% high K⁺ solution. For rat submandibular gland, incubation in 80% high K⁺ solution resulted in optimal retention of cellular Na, K, Ca, P, S and Mg, while Cl was retained best in a 70% high K⁺ solution. Based on these results, an optimally modified Krebs–Ringer solution for the liver would consist of 119 mM K⁺, 26 mM Na⁺ and 45 mM Cl^?. An optimally modified Krebs–Ringer bicarbonate solution for the submandibular gland would be composed of 96 mM K⁺, 53 mM Na⁺ and 46 mM Cl^?. After incubation in the modified solutions (at 4 °C), cellular Na, Mg, S, Cl, K and Ca in both tissues were maintained close to the in situ state throughout a 6-h incubation. The cellular P concentration was reduced after incubation for 1 h; thereafter, in the liver cells it remained at this lower level for the rest of the incubation, whereas in the submandibular gland tissue it increased again after 4 h. The increase in cell volume (oedema) was less in tissue stored in the modified solutions, than in the 100% high K⁺ solutions. Incubation in high Na⁺ buffers (4 °C, 6 h) resulted in a progressive increase in the percentage of cells showing trypan blue uptake. A similar increase in trypan blue uptake was seen in the modified solution, but this increase levelled off after 4 h. After cholinergic stimulation in high Na⁺ solution (25 °C, 1 min), the expected decrease in cellular Cl concentration was seen in submandibular gland cells that had previously been preserved (4 °C, 4 h) in the modified solution, but not in those that had been preserved in the 100% high K⁺ solution.     

Immunohistochemical and ultrastructural evidence of functional organization along the Corydoras paleatus intestine

The Neotropical catfish, Corydoras paleatus (Callichthyidae) is a facultative air‐breathing teleost that makes use of the caudal portion of the intestine as an accessory air‐breathing organ. This portion is highly modified, being well vascularized with capillaries between epithelial cells, which makes it well suited for gas exchange. Instead, the cranial portion is a digestion and absorption site, as it has a typical intestinal epithelium with columnar cells arranged in a single row, villi and less vascularized tunica mucosa. Therefore, the intestine was studied by light and electron microscopy to assess differences between the cranial, middle and caudal portions. To characterize the potential for cell proliferation of this organ, we used anti‐proliferating cell nuclear antigen antibody and anti‐Na⁺K⁺‐ATPase monoclonal antibody to detect the presence of Na⁺/K⁺ pump. In C. paleatus it was observed that cell dynamics showed a decreasing gradient of proliferation in cranio‐caudal direction. Also, the intestine of this catfish is an important organ in ionoregulation: the basolateral Na⁺/K⁺ pump may have an active role, transporting Na⁺ out of the cell while helping to maintain the repose potential and to regulate cellular volume. Microsc. Res. Tech. 79:140–148, 2016. © 2016 Wiley Periodicals, Inc.