Decay Kinetics Research Articles

Photoluminescence optical and thermal quenching in heavily doped Gd3(Ga,Al)5O12:Ce, Mg single crystals: Dependence on the Ga3+, Ce3+, and Mg2+ concentration

Heavily doped single crystals of Gd3GaxAl5-xO12:Ce, Mg (x = 2.46–2.95) with different concentrations of Ce (0.016–0.188 at.%) and Mg (0–0.083 at.%) are investigated by the X-ray diffraction, photoluminescence, and thermoluminescence methods. Dependences of the luminescence characteristics, as well as crystal lattice parameters and distances between the Ce3+ and Mg2+ ions, on the Ga, Ce, and Mg concentration are studied. Mechanisms of the processes, resulting in the photoluminescence optical and thermal quenching and acceleration of decay kinetics, and the influence of the crystal composition on these processes are discussed. The role of close {Ce3+ - Mg2+Ga} pairs in these processes is considered. At T > 400 K, the luminescence thermal quenching is caused by the crossover process, while in the 200–350 K temperature range, by the electron transfer from the 5d1 excited state of Ce3+ to nearby defect levels (electron traps) located between the 5d1 level and the conduction band. The latter process results also in the appearance of thermally stimulated luminescence, and its efficiency depends on the Ga3+ content and concentration of intrinsic defects. The optimum concentrations of Ga3+ and Mg2+ ions in the investigated crystals are determined.

Review of thermal neutron scintillators: Evaluation metrics and future prospects for demanding applications

Neutron applications are progressing rapidly, requiring detectors to meet increasingly rigorous criteria. Specifications such as high neutron counting rates, fast timing resolution and low background have a significant impact on choice of scintillator and how scintillators are evaluated. This work considers detector requirements for neutron scattering instruments that are becoming more stringent as the sources and scattering technologies continue to improve. Meanwhile, both prominent scintillators used for neutron scattering detectors, ZnS:Ag/6LiF and GS-glass, remain stagnant. While these scintillators have been suitable for many years, they are becoming a limiting factor for neutron scattering instruments. ZnS:Ag is inhibiting count rate capability and GS-glass is too gamma sensitive so alternatives need to be found. A brief explanation of neutron scattering, its detector requirements and how those relate to scintillator properties will be discussed. Furthermore, this work explains how standard characterization methods and reporting of scintillation properties are not entirely suitable for high count rate, low background applications like neutron scattering. As a result, modifications to characterization of gamma discrimination, light output, and decay kinetics are suggested. Additional steps are suggested including neutron activation and a more appropriate assessment of count rate capability. A non-exhaustive set of 6Li containing neutron sensitive scintillators including ZnS:Ag/6LiF, GS20 glass, ZnO:Zn/6LiF, Cs6LiYCl:Ce, 6LiI:Eu, 6LiI:Ce, 6LiCaAlF:Eu, LiCaAlF:Ce, transparent rubber sheet (TRUST) 6LiCaAlF:Eu, TRUST 6LiCaAlF:Eu with added fluorophore and EJ-270 (6Li containing plastic) are reviewed and studied from this different perspective. Finally, new scintillator developments relevant to high count rate, low background applications are discussed.

Persistence of respiratory, enteric, and fecal indicator viruses in fecal sludge from on-site sanitation in Dakar, Senegal

ABSTRACT As wastewater-based epidemiology (WBE) broadens to include prevalent diseases with significant global health impact, existing surveillance systems concentrate on sewer-based infrastructure, which excludes the 2.7 billion people using non-sewered systems. To address this gap, our study explores the potential of fecal sludge treatment plants for WBE, emphasizing the stability of virus RNA targets within pooled fecal sludge. We screened fecal sludge from a centralized treatment facility in Dakar, Senegal for SARS-CoV-2, human norovirus, and microbial source trackers pepper mild mottle virus and tomato brown rugose fruit virus (ToBRFV). Decay kinetics of viral genomic RNA markers were examined at 4, 15, and 30 °C over 70 days. Results indicate the high persistence of viral targets in fecal sludge (T90 value of 3.3 months for exogenous SARS-CoV-2 N1 and N2 and 6.2 months for ToBRFV), with all targets detected throughout the 70-day experiment under various temperatures with limited decay (<90% reduction). This study addresses a crucial gap in understanding virus persistence in on-site sanitation systems by providing essential decay rate constants for effective target detection. Our results indicate that sampling at centralized facilities treating fecal sludge from on-site sanitation could facilitate localized pathogen surveillance in low-income settings.

Photoluminescence decay of mobile carriers influenced by imperfect quenching at particle surfaces with subdiffusive spread.

We recently presented a quantitative model to explain the particle-size dependence of photoluminescence (PL) quantum yields and revealed that exciton quenching is not diffusion controlled, but limited by surface reactions. However, the exciton decay kinetics has not been analyzed yet using our theoretical model. Here, we study kinetic aspects of the model and show that it should be extended to take into account subdiffusion rather than normal diffusion to maintain consistency with the observed complex decay kinetics; we also show that the PL decay kinetics is nonexponential even when the PL quenching is limited by surface reactions under subdiffusion. Our theoretical analysis of the PL quantum yield and the PL decay kinetics provides a comprehensive picture of mobile charge carriers, immobile polarons, and self-trapped excitons.

Heterogeneity of synaptic NMDA receptor responses within individual lamina I pain-processing neurons across sex in rats and humans.

Excitatory glutamatergic NMDA receptors (NMDARs) are key regulators of spinal pain processing, and yet the biophysical properties of NMDARs in dorsal horn nociceptive neurons remain poorly understood. Despite the clinical implications, it is unknown whether the molecular and functional properties of synaptic NMDAR responses are conserved between males and females or translate from rodents to humans. To address these translational gaps, we systematically compared individual and averaged excitatory synaptic responses from lamina I pain-processing neurons of adult Sprague-Dawley rats and human organ donors, including both sexes. By combining patch-clamp recordings of outward miniature excitatory postsynaptic currents with non-biased data analyses, we uncovered a wide range of decay constants of excitatory synaptic events within individual lamina I neurons. Decay constants of synaptic responses were distributed in a continuum from 1-20ms to greater than 1000ms, suggesting that individual lamina I neurons contain AMPA receptor (AMPAR)-only as well as GluN2A-, GluN2B- and GluN2D-NMDAR-dominated synaptic events. This intraneuronal heterogeneity in AMPAR- and NMDAR-mediated decay kinetics was observed across sex and species. However, we discovered an increased relative contribution of GluN2A-dominated NMDAR responses at human lamina I synapses compared with rodent synapses, suggesting a species difference relevant to NMDAR subunit-targeting therapeutic approaches. The conserved heterogeneity in decay rates of excitatory synaptic events within individual lamina I pain-processing neurons may enable synapse-specific forms of plasticity and sensory integration within dorsal horn nociceptive networks. KEY POINTS: Synaptic NMDA receptors (NMDARs) in spinal dorsal horn nociceptive neurons are key regulators of pain processing, but it is unknown whether their functional properties are conserved between males and females or translate from rodents to humans. In this study, we compared individual excitatory synaptic responses from lamina I pain-processing neurons of male and female adult Sprague-Dawley rats and human organ donors. Individual lamina I neurons from male and female rats and humans contain AMPA receptor-only as well as GluN2A, GluN2B- and GluN2D-NMDAR-dominated synaptic events. This may enable synapse-specific forms of plasticity and sensory integration within dorsal horn nociceptive networks. Human lamina I synapses have an increased relative contribution of GluN2A-dominated NMDAR responses compared with rodent synapses. These results uncover a species difference relevant to NMDAR subunit-targeting therapeutic approaches.

Blood Distribution of SARS-CoV-2 Lipid Nanoparticle mRNA Vaccine in Humans.

Lipid nanoparticle mRNA vaccines are an exciting but emerging technology used in humans. There is limited understanding of the factors that influence their biodistribution and immunogenicity. Antibodies to poly(ethylene glycol) (PEG), which is on the surface of the lipid nanoparticle, are detectable in humans and boosted by human mRNA vaccination. We hypothesized that PEG-specific antibodies could increase the clearance of mRNA vaccines. To test this, we developed methods to quantify both the vaccine mRNA and ionizable lipid in frequent serial blood samples from 19 subjects receiving Moderna SPIKEVAX mRNA booster immunization. Both the vaccine mRNA and ionizable lipid peaked in blood 1-2 days post vaccination (median peak level 0.19 and 3.22 ng mL-1, respectively). The vaccine mRNA was detectable and quantifiable up to 14-15 days postvaccination in 37% of subjects. We measured the proportion of vaccine mRNA that was relatively intact in blood over time and found that the decay kinetics of the intact mRNA and ionizable lipid were identical, suggesting the intact lipid nanoparticle recirculates in blood. However, the decay rates of mRNA and ionizable lipids did not correlate with baseline levels of PEG-specific antibodies. Interestingly, the magnitude of mRNA and ionizable lipid detected in blood did correlate with the boost in the level of PEG antibodies. Furthermore, the ability of a subject's monocytes to phagocytose lipid nanoparticles was inversely related to the rise in PEG antibodies. This suggests that the circulation of mRNA lipid nanoparticles into the blood and their clearance by phagocytes influence the PEG immunogenicity of the mRNA vaccines. Overall, this work defines the pharmacokinetics of lipid nanoparticle mRNA vaccine components in human blood after intramuscular injection and the factors that influence these processes. These insights should be valuable in improving the future safety and efficacy of lipid nanoparticle mRNA vaccines and therapeutics.

Variations in litterfall dynamics, root biomass, and sediment accretion in restored and recolonized mangroves in Leyte, Philippines

Litterfall production and decay, root biomass, and sediment accretion dynamics were investigated from restored ‘planted’ (R5, R8, R15, and R30 stands) and recolonized stands (C5, C12, and C20 stands) to investigate patterns in primary productivity, belowground biomass, and sediment accretion dynamics. Litterfall data was collected using litter traps over 12 months, while decay kinetics was investigated using a litterbag experiment. Root biomass and sediment accretion data were collected using makeshift acrylic corers. Litterfall production increased as stands aged, and tended to stabilize as it matured in restored (R8: 10.05 Mg/ha/yr; R30: 6.1 Mg/ha/yr) and recolonized stands (C5: 18.75 Mg/ha/yr; C20: 9.05 Mg/ha/yr). Leaf litter decay rates (K/d) showed no pattern with stand age, although the recolonized stands (range: 0.059–0.113 K/d) had lower decay rates compared to the restored (range: 0.073–0.123 K/d) and natural stands (range: 0.064–0.123 K/d). Root biomass declined with age in restored stands (R5: 67.16 Mg/ha, R30: 49.67 Mg/ha), but increased in recolonized stands (C5: 5.41 Mg/ha, C20: 19.50 Mg/ha). Very high rates of sediment accretion were found in younger restored (R5: 10.1 cm/yr) and recolonized stands (C5: 8.1 cm/yr) than mature stands (R30: 6.3 cm/yr; C20: 4.3 cm/yr). Our results showed disparities of patterns in mangrove vegetation growth in recolonized stands and huge potential contribution on mangrove productivity when these areas are effectively restored.

Operant alcohol self-administration targets GluA2-containing AMPAR expression and synaptic activity in the nucleus accumbens in a manner that drives the reinforcing properties of the drug.

The positive reinforcing effects of alcohol (ethanol) drive its repetitive use and contribute to alcohol use disorder (AUD). Ethanol alters the expression of glutamate AMPA receptor (AMPAR) subunits in reward-related brain regions, but the extent to which this molecular effect regulates ethanol's reinforcing properties is unclear. This study investigates whether ethanol self-administration changes AMPAR subunit expression and synaptic activity in the nucleus accumbens core (AcbC) to regulate ethanol's reinforcing effects in male C57BL/6J mice. Sucrose-sweetened ethanol self-administration (0.81±0.11 g/kg/day) increased AMPAR GluA2 protein expression in the AcbC, without effect on GluA1, compared to sucrose-only controls. Infusion of myristoylated Pep2m in the AcbC, which blocks GluA2 binding to N-ethylmaleimide-sensitive fusion protein (NSF) and reduces GluA2-containing AMPAR activity, reduced ethanol-reinforced responding without affecting sucrose-only self-administration or motor activity. Antagonizing GluA2-lacking AMPARs, through AcbC infusion of NASPM, had no effect on ethanol self-administration. AcbC neurons receiving projections from the basolateral amygdala (BLA) showed increased sEPSC frequency and GluA2-like decay kinetics in ethanol self-administering mice as compared to sucrose. Optogenetic activation of these neurons revealed an ethanol-enhanced AMPA/NMDA ratio and reduced paired-pulse ratio, indicating elevated AMPAR activity and glutamate release specifically at AcbC terminals of BLA projecting neurons. Ethanol use upregulates GluA2 protein expression in the AcbC and AMPAR synaptic activity in AcbC neurons receiving BLA projections. GluA2-containing AMPAR activity in the AcbC regulates the positive reinforcing effects of ethanol through an NSF-dependent mechanism. This highlights a potential target for therapeutic interventions in AUD.

Decay kinetics of human-associated pathogens in the marine microcosms reveals their new dynamics and potential indicators in the coastal waters of northern China

Pathogens in coastal waters cause infectious diseases and endanger public sanitation safety in humans and animals worldwide. To avoid these risks, timely detection of human-associated pathogens in waters is crucial. In this study, the decay kinetics of the molecular markers for human-associated pathogens, including enteric bacteria (Escherichia coli, Enterococcus, and Bacteroides), non-enteric bacteria (Staphylococcus aureus), crAssphage, and polyomavirus, were monitored over time at different temperatures and background microbes in seawater microcosms. The results indicated that temperature and native marine microbes were the main influential factors in attenuating bacterial pathogens. Remarkably, the effect of native microorganisms was more evidentially striking. Furthermore, Enterococcus was a more reliable and suitable fecal indicator bacterium than E. coli for the marine environment. The decay of crAssphage was like that of polyomavirus, indicating that it may be a good indicator of enterovirus in seawater. More importantly, the 16S amplicon sequencing data highlighted the decay kinetics of multiple bacterial pathogens in parallel with the dynamic changes of the whole bacterial communities. This study provides valuable information for public health risk management and a new approach to understanding the fate of bacteria in the coastal environment.

Energy transfer processes leading to strong NIR-to-red upconversion in the Yb-concentrated Sr3Yb0.98Er0.02(PO4)3 eulytite

The optical spectroscopy and the decay kinetics of samples with composition Sr3Yb(PO4)3, Sr3Y0.98Yb0.02(PO4)3, Sr3Y0.98Er0.02(PO4)3 and Sr3Yb0.98Er0.02(PO4)3 have been studied at room temperature. The presence of efficient energy transfer and migration processes has been clearly evidenced in the Sr3Yb(PO4)3 and Sr3Yb0.98Er0.02(PO4)3 materials, giving rise to strong visible upconversion upon excitation in the spectral region around 1 μm in the latter material. The strong anti-Stokes emission is connected to fast migration in the 2F5/2 level of Yb3+, due to the inefficient concentration quenching for this ion. In this class of materials, the upconversion processes could be optimized even in the presence of high concentrations of the Yb3+ sensitizer.

GluN3A and Excitatory Glycine Receptors in the Adult Hippocampus.

The GluN3A subunit of N-methyl-D-aspartate receptors (NMDARs) plays an established role in synapse development, but its contribution to neural circuits in the adult brain is less clear. Recent work has demonstrated that in select cell populations, GluN3A assembles with GluN1 to form GluN1/GluN3A receptors that are insensitive to glutamate and instead serve as functional excitatory glycine receptors (eGlyRs). Our understanding of these eGlyRs, and how they contribute to intrinsic excitability and synaptic communication within relevant networks of the developing and the mature brain, is only beginning to be uncovered. Here, using male and female mice, we demonstrate that GluN3A subunits are enriched in the adult ventral hippocampus (VH), where they localize to synaptic and extrasynaptic sites and can assemble as functional eGlyRs on CA1 pyramidal cells. GluN3A expression was barely detectable in the adult dorsal hippocampus (DH). We also observed a high GluN2B content in the adult VH, characterized by slow NMDAR current decay kinetics and a high sensitivity to the GluN2B-containing NMDAR antagonist ifenprodil. Interestingly, the GluN2B enrichment in the adult VH was dependent on GluN3A as GluN3A deletion accelerated NMDAR decay and reduced ifenprodil sensitivity in the VH, suggesting that GluN3A expression can regulate the balance of conventional NMDAR subunit composition at synaptic sites. Lastly, we found that GluN3A knock-out also enhanced both NMDAR-dependent calcium influx and NMDAR-dependent long-term potentiation in the VH. Together, these data reveal a novel role for GluN3A and eGlyRs in the control of ventral hippocampal circuits in the mature brain.

Persistence of two coronaviruses and efficacy of steam vapor disinfection on two types of carpet

BackgroundCoronaviruses, a group of highly transmissible and potentially pathogenic viruses, can be transmitted indirectly to humans via fomites. To date, no study has investigated their persistence on carpet fibers. Establishing persistence is essential before testing the efficacy of a disinfectant.MethodsThe persistence of BCoV and HCoV OC43 on polyethylene terephthalate (PET) and nylon carpet was first determined using infectivity and RT-qPCR assays. Then, the disinfectant efficacy of steam vapor was evaluated against both coronaviruses on nylon carpet.ResultsImmediately after inoculation of carpet coupons, 32.50% of BCoV and 3.87% of HCoV OC43 were recovered from PET carpet, compared to 34.86% of BCoV and 24.37% of HCoV OC43 recovered from nylon carpet. After incubation at room temperature for 1 h, BCoV and HCoV OC43 showed a 3.6 and > 2.8 log10 TCID50 reduction on PET carpet, and a 0.6 and 1.8 log10 TCID50 reduction on nylon carpet. Based on first-order decay kinetics, the whole gRNA of BCoV and HCoV OC43 were stable with k values of 1.19 and 0.67 h− 1 on PET carpet and 0.86 and 0.27 h− 1 on nylon carpet, respectively. A 15-s steam vapor treatment achieved a > 3.0 log10 TCID50 reduction of BCoV and > 3.2 log10 TCID50 reduction of HCoV OC43 on nylon carpet.ConclusionBCoV was more resistant to desiccation on both carpet types than HCoV OC43. Both viruses lost infectivity quicker on PET carpet than on nylon carpet. Steam vapor inactivated both coronaviruses on nylon carpet within 15 s.

Energy transfer mechanism in infrared-emitting NaYGeO4:Tm3+, Ho3+ phosphors

Two series of NaY0.85Tm0.15-xHoxGeO4 (x = 0.005–0.03) and NaY0.85-xTm0.15HoxGeO4 (x = 0.0–0.055) phosphors have been prepared by the citrate technique. According to XRPD study, all the germanates crystallize in olivine structure and have an orthorhombic lattice, space group Pnma, Z = 4. The diffuse reflectance spectra have been measured and the optical band gap has been estimated. Under 808 nm laser diode excitation, the NaYGeO4:Tm3+, Ho3+ samples exhibit luminescence in the range of 1640–2240 nm, which is caused by 3F4 → 3H6 transition in Tm3+ and 5I7 → 5I8 transition in Ho3+ ions. The highest intensity of holmium lines, while maintaining relatively high intensity of thulium lines, was observed for NaY0.82Tm0.15Ho0.03GeO4, NaY0.815Tm0.15Ho0.035GeO4 samples with the Tm3+/Ho3+ ratio close to 5/1. The luminescence decay kinetics has been studied and the rate of energy transfer from Tm3+ to Ho3+ ions has been calculated. The obtained results indicate an effective energy transfer accelerated by migration due to dipole-dipole interaction. The mechanism of excitation and infrared luminescence in NaYGeO4:Tm3+, Ho3+ phosphors has been proposed.

On the glow of cremated remains: long-lived green photo-luminescence of heat-treated human bones.

The long-lived green luminescence of human bone (that has been heated to 600°C for a short duration) is attributed to a carbon quantum dot material (derived from collagen) encapsulated and protected by an inorganic matrix (derived from bone apatite) and is more intense in dense rigid and crystalline parts of (healthy) human bones. The strong collagen-apatite interaction results (upon decomposition) in a protective inorganic environment of the luminescent centers allowing long-lived triplet-based emission of a carbon (quantum) dot-like material at room temperature, as well as resilience against oxidation between 550 and 650°C. The graphitic black phase (obtained upon heating around 400°C) is a precursor to the luminescent carbon-based material, that is strongly interacting with the crystalline inorganic matrix. Human bone samples that have been heated to 600°C were subjected to steady-state and time-resolved spectroscopy. Excitation-emission matrix (EEM) luminescence spectroscopy revealed a broad range of excitation and emission wavelengths, indicating a heterogeneous system with a broad density of emissive states. The effect of low temperature on the heat-treated bone was studied with Cryogenic Steady State Luminescence Spectroscopy. Cooling the bone to 80K leads to a slight increase in total emission intensity as well as an intensity increase towards to red part of the spectrum, incompatible with a defect state model displaying luminescent charge recombination in the inorganic matrix. Time-resolved spectroscopy with an Optical Multichannel Analyzer (OMA) and Time Correlated Single Photon Counting (TCSPC) of these samples showed that the decay could be fitted with a multi-exponential decay model as well as with second-order decay kinetics. Confocal Microscopy revealed distinct (plywood type) structures in the bone and high intensity-fast decay areas as well as a spatially heterogeneous distribution of green and (fewer) red emissive species. The use of the ATTO 565 dye aided in bone-structure visualization by chemical adsorption. Conceptually our data interpretation corresponds to previous reports from the material science field on luminescent powders.

D1-Tyr246 and D2-Tyr244 in photosystem II: Insights into bicarbonate binding and electron transfer from QA•− to QB

In photosystem II (PSII), D1-Tyr246 and D2-Tyr244 are symmetrically located at the binding site of the bicarbonate ligand of the non-heme Fe complex. Here, we investigated the role of the symmetrically arranged tyrosine pair, D1-Tyr246 and D2-Tyr244, in the function of PSII, by generating four chloroplast mutants of PSII from Chlamydomonas reinhardtii: D1-Y246F, D1-Y246T, D2-Y244F, and D2-Y244T. The mutants exhibited altered photoautotrophic growth, reduced PSII protein accumulation, and impaired O2-evolving activity. Flash-induced fluorescence yield decay kinetics indicated a significant slowdown in electron transfer from QA•− to QB in all mutants. Bicarbonate reconstitution resulted in enhanced O2-evolving activity, suggesting destabilization of bicarbonate binding in the mutants. Structural analyses based on a quantum mechanical/molecular mechanical approach identified the existence of a water channel that leads to incorporation of bulk water molecules and destabilization of the bicarbonate binding site. The water intake channels, crucial for bicarbonate stability, exhibited distinct paths in the mutants. These findings shed light on the essential role of the tyrosine pair in maintaining bicarbonate stability and facilitating efficient electron transfer in native PSII.

CoSe2 nanocrystals embedded in one-dimensional mesoporous carbon nanofibers as advanced anode for potassium-ion storage

High-performance potassium-ion batteries have received great attention for electrochemical energy storage owing to their low redox potential, abundant natural resources and excellent safety. As an advanced negative material, CoSe2 has been widely investigated for potassium-ion batteries. Unfortunately, the pure CoSe2 anode suffers from the fast capacity decay and sluggish kinetics, preventing its practical application. Herein, we introduce a novel strategy to fabricate the CoSe2 nanoparticles embedded in one-dimensional mesoporous carbon nanofibers (denoted as 1D-CoSe2@CNFs) with superior high-rate property and good cycle stability for the first time. In this designed material, the conductive carbon nanofibers are loaded with CoSe2 particles. The obtained 1D-CoSe2@CNFs anode shows a specific capacity of 706.3 mAh/g at 0.1 A/g and presents a high capacity retention ratio of around 96.3 % at 5 A/g over 400 cycles. Therefore, this fabricated 1D-CoSe2@CNFs nanocomposite can be employed as a novel negative electrode for potassium-ion storage.

Photobleaching Effect on the Sensitivity Calibration at 638 nm of a Phosphorus-Doped Single-Mode Optical Fiber Dosimeter.

We investigated the influence of the photobleaching (PB) effect on the dosimetry performances of a phosphosilicate single-mode optical fiber (core diameter of 6.6 µm) operated at 638 nm, within the framework of the LUMINA project. Different irradiation tests were performed under ~40 keV mean energy fluence X-rays at a 530 µ Gy(SiO2)/s dose rate to measure in situ the radiation-induced attenuation (RIA) growth and decay kinetics while injecting a 638 nm laser diode source with powers varying from 500 nW to 1 mW. For injected continuous power values under 1 µW, we did not measure any relevant influence of the photobleaching effect on the fiber radiation sensitivity coefficient of ~140 dB km-1 Gy-1 up to ~30 Gy. Above 1 µW, the fiber radiation sensitivity is significantly reduced due to the PB associated with the signal and can decrease to ~80 dB km-1 Gy-1 at 1 mW, strongly affecting the capability of this fiber to serve as a dosimeter-sensitive element. Higher power values up to 50 µW can still be used by properly choosing a pulsed regime with periodic injection cycles to reduce the PB efficiency and maintain the dosimetry properties. Basing on the acquired data, a simple model of the photobleaching effect on a coil of the investigated fiber is proposed in order to estimate its sensitivity coefficient evolution as a function of the cumulated dose and its fiber length when injecting a certain laser power. Additional studies need to investigate the influence of the temperature and the dose rate on the PB effects since these parameters were fixed during all the reported acquisitions.

Electrospun carbon nanofibers loaded with sulfur vacancy CoS2 as separator coating to accelerate sulfur conversion in Lithium-Sulfur batteries

Lithium–sulfur batteries (LSBs) have been sought after by researchers owing to their high energy density; however, the inevitable capacity decay and slow reaction kinetics have hindered their advancement. Here, we prepare a Prussian blue analog, Co3[Co(CN)6]2 and synthesize carbon nanofibers/S vacancy CoS2−x (CNFs/CoS2−x) as electrocatalysts for separator coating via electrospinning, carbonization, sulfurization, and hydrogen reduction. CNFs/CoS2−x exhibits excellent electrocatalytic activity, wherein S vacancies induce the partial oxidation of Co2+ to Co3+ in CoS2 and CNFs provide long-range electron transport pathways. Various electrochemical tests, such as Tafel, ion diffusion coefficient, Li2S precipitation, and Li2S6 symmetric cells, further confirm the enhanced electrocatalytic activity. The LSBs with CNFs/CoS2−x modified separator delivers an initial discharge capacity of 1056.7 mAh g−1 at 0.2C, maintaining 840.8 mAh g−1 after 100 cycles at 0.2C. When S loading is increased to 4.42 mg cm−2, the battery retains a discharge capacity of 687.9 mAh g−1 (3.04 mAh cm−2) after 70 cycles at 0.1C. Our work can provide a reference for synthesizing anion-vacancy materials and designing anion-vacancy electrocatalytic composites for LSBs.

Application of Steady-State and Time-Resolved Fluorescence Spectroscopy in Identification of Bee Products

In this study, steady-state and time-resolved fluorescence spectroscopy techniques have been applied to determine fluorescence characteristics and fluorescence decay kinetics parameters (fluorescence lifetimes and their amplitudes) of available on the Polish market bee products, including several nectar honeys, royal jelly, bee bread in honey and in liquid artificial honey. The fluorescence properties of the tested bee products arise from the presence of a unique composition of aromatic amino acids, vitamins, phenolic compounds and Maillard reaction products. In the 300–550 nm region of the emission spectra (excited at 280 nm), each of the tested bee products exhibited (showed) a specific and distinctive vibronic structure, which was not observed in the spectrum of artificial honey. Quantitative and qualitative composition as well as specific interactions between fluorescent constituents determine the specific fluorescence characteristics of a given bee product providing a unique fingerprint that can be used in the identification of bee products of different botanical origin. Combination of stationary and time-resolved fluorescence techniques seems to be a promising approach in the identification, authentication and quality control of bee products to verify their health-beneficial properties.

Three-Layered Composite Scintillator Based on the Epitaxial Structures of YAG and LuAG Garnets Doped with Ce3+ and Sc3+ Impurities.

In this study, we propose novel three-layer composite scintillators designed for the simultaneous detection of different ionizing radiation components. These scintillators are based on epitaxial structures of LuAG and YAG garnets, doped with Ce3+ and Sc3+ ions. Samples of these composite scintillators, containing YAG:Ce and LuAG:Ce single crystalline films with different thicknesses and LuAG:Sc single crystal substrates, were grown using the liquid phase epitaxy method from melt solutions based on PbO-B2O3 fluxes. The scintillation properties of the proposed composites, YAG:Ce film/LuAG:Sc film/LuAG:Ce crystal and YAG:Ce film/LuAG:Ce film/LuAG:Sc crystal, were investigated under excitation by radiation with α-particles from a 239Pu source, β-particles from 90Sr sources and γ-rays from a 137Cs source. Considering the properties of the mentioned composite scintillators, special attention was paid to the ability of simultaneous separation of the different components of mixed ionizing radiation containing the mentioned particles and quanta using scintillation decay kinetics. The differences in scintillation decay curves under α- and β-particle and γ-ray excitations were characterized using figure of merit (FOM) values at various scintillation decay intensity levels (1/e, 0.1, 0.05, 0.01).