This work presents the important role of defects in achieving efficient luminescence and electrical conduction in pyrochlore materials. Undoped and Sm3+-doped La2Ce2O7 (LCO and LCOS) were stabilized ...in the defect fluorite structure. LCO depicted visible light emission under ultraviolet irradiation endowed by the defect states with a predominance of oxygen vacancies (VO). LCOS depicted color-tunable emission from blue to orange on Sm3+ doping and to white on changing the excitation wavelength from 413 to 254 nm. Raman spectroscopy shows an enhancement of the oxygen vacancy density on Sm3+ doping, which is seen in the increased electrical conduction of LCOS compared to that of LCO. Further, based on the DFT-calculated formation energy and cell volume, it was postulated that Sm3+ prefers Ce4+ sites over La3+ sites with the formation of VO as charge-compensating defects and the most favorable configurations are the SmCe–VO defect complexes. The higher luminescence lifetime of LCOS is because of the SmCe far away from the oxygen vacancies, while the lower lifetime, on the other hand, is attributed to the same with nearby oxygen vacancies. Positron annihilation lifetime spectroscopy (PALS) suggested the highest defect density in the case of the 7.5% Sm3+-doped LCOS sample. Thermoluminescence measurements on the other hand also show the highest density of deep traps associated with VO in the 7.5% Sm3+-doped LCOS sample. This was manifested in the enhanced conductance and lowest bulk resistance for this particular sample. Based on the results of this work, the high potential of LCOS for tunable light emission and as an afterglow phosphor and electrical conductor can be clearly seen and future work would further enrich knowledge on its multifunctionality.
Lithium iodides are very efficient single‐crystal scintillators for thermal neutron detection. Doping with silver, as activator ions, has shown to improve its limitation of discriminating gamma ...background by introducing pulse shape discrimination ability. To improve the scintillation performance, single crystals of LiI:Ag, codoped with different concentration of Sr ions, are grown and characterized in details. A systematic investigation of radioluminescence, thermoluminescence, and scintillation properties along with the decay kinetics provides better understanding about the role of defect structure in scintillation mechanism. The extra charge, provided by Sr2+ ions, is found to alter the defect structure with relative reduction of the contribution from the deeper trap centers in comparison with the shallow traps. Consequently, it leads to a significant improvement of light yield quenching under higher excitation density of charged particle irradiation. The 0.1% Sr codoped crystals provide a better discrimination ability of neutron and gamma radiations for simultaneous detection.
Lithium iodide (LiI) crystal scintillator doped with Eu is conventionally used for thermal neutron detection. “Ag”‐doped LiI provides the advantage of pulse shape discrimination ability to measure thermal neutrons in gamma background. “Sr” codoping in LiI:Ag crystals improves the scintillation performance characteristics further by tailoring the defect structure.
Using X-ray observations from the
NuSTAR
and
Swift
satellites, we present temporal and spectral properties of an intermediate polar (IP) IGR J16547-1916. A persistent X-ray period at ∼546 s ...confirming the optical spin period obtained from previous observations is detected. The detection of a strong X-ray spin pulse reinforces the classification of this system as an intermediate polar. The lack of orbital or side-band periodicities in the X-rays implies that the system is accreting predominantly via a disk. A variable covering absorber appears to be responsible for the spin pulsations in the low energy range. In the high energy band, the pulsations are likely due to the self occultation of tall shocks above the white dwarf surface. The observed double-humped X-ray spin pulse profile indicates two-pole accretion geometry with tall accretion regions in short rotating IP IGR J16547-1916. We present the variation of the spin pulse profile over an orbital phase to account for the effects of orbital motion on the spin pulsation. X-ray spectra obtained from the contemporaneous observations of
Swift
and
NuSTAR
in the 0.5–78.0 keV energy band are modeled with a maximum temperature of 31 keV and a blackbody temperature of 64 eV, along with a common column density of 1.8 × 10
23
cm
−2
and a power-law index of −0.22 for the covering fraction. An additional Gaussian component and a reflection component are needed to account for a fluorescent emission line at 6.4 keV and the occurrence of X-ray reflection in the system. We also present the spin phase-resolved spectral variations of IGR J16547-1916 in the 0.5–78.0 keV energy band and find dependencies in the X-ray spectral parameters during the rotation of the white dwarf.
Exploration of optical properties of organic crystalline semiconductors thin films is challenging due to submicron grain sizes and the presence of numerous structural defects, disorder and grain ...boundaries. Here we report on the results of combined linear dichroism (LD)/ polarization-resolved photoluminescence (PL) scanning microscopy experiments that simultaneously probe the excitonic radiative recombination and the molecular ordering in solution-processed metal-free phthalocyanine crystalline thin films with macroscopic grain sizes. LD/PL images reveal the relative orientation of the singlet exciton transition dipoles at the grain boundaries and the presence of a localized electronic state that acts like a barrier for exciton diffusion across the grain boundary. We also show how this energy barrier can be entirely eliminated through the optimization of deposition parameters that results in films with large grain sizes and small-angle boundaries. These studies open an avenue for exploring the influence of long-range order on exciton diffusion and carrier transport.
The present study was planned to detect the genes encoding carbapenemases, ESBLs and class 1 integron‐integrase among bacteria obtained from retail goat meat. Fermenting and non‐fermenting bacterial ...isolates (n = 57), recovered from 61 goat meat samples, were identified by 16S rRNA gene sequencing. Antimicrobial susceptibility of isolates was tested by the broth dilution method using ceftazidime, cefotaxime, meropenem and imipenem. Plasmids were isolated and tested for their physical characters. Plasmids were subjected to screening of carbapenemase, ESBL and intI1 gene. Conjugation assay was performed using blaNDM‐positive isolates as the donor, and Escherichia coli HB101 as the recipient. Isolates showed the high rates of resistance to ceftazidime (77·2%), cefotaxime (70·2%), meropenem (22·8%) and imipenem (17·5%). They showed variability in number and size (~1 to >20 kb) of plasmids. Among all, 1, 4, 13 and 31 isolates showed the blaKPC, blaNDM, blaSHV and blaTEM genes, respectively. The blaKPC‐2 gene was observed in one E. coli isolate. The blaNDM‐1 gene was detected in Stenotrophomonas maltophilia (n = 2), Acinetobacter baumannii (n = 1) and Ochrobactrum anthropi (n = 1) isolates. These isolates co‐harboured the blaTEM and blaSHV genes. The intI1 gene was detected in 22 (38·6%) isolates, and 16 of these isolates showed the carbapenemase and/or ESBL genes. The conjugative movement of blaNDM gene could not be proved after three repetitive mating experiments. The presence of genes encoding carbapenemases and ESBLs in bacteria from goat meat poses public health risks.
Significance and impact of the study: The emergence of carbapenemases and extended‐spectrum β‐lactamases (ESBLs) in bacteria has now become a global problem leading to failure of advanced antimicrobial therapy. We report for the first time the blaNDM‐1 gene in non‐fermenting Gram‐negative bacterial isolates, and the blaKPC‐2 gene in an Escherichia coli isolate from goat meat in India. The presence of carbapenemase genes in bacteria from goat meat develops serious concerns about public health and food safety. Analysis of genetic determinants of β‐lactam resistance in bacteria would be helpful to formulate a suitable control strategy.
The present study evaluated the antibacterial and antibiofilm activity of methanolic extract of Hemidesmus indicus root (MHIR) in combination with amoxicillin and clindamycin against biofilm‐forming ...methicillin‐resistant Staphylococcus aureus (MRSA) isolated from milk samples of mastitic cows. Microdilution susceptibility testing and microtitre plate assays were used to evaluate the in vitro efficacy of MHIR and antibiotic combinations against MRSA (n = 12). Furthermore, in vitro findings were validated in a murine model. Minimum inhibitory concentration and minimum biofilm inhibitory concentration of amoxicillin and clindamycin in combination with MHIR were significantly (P < 0·05) lower than when used alone against MRSA. In terms of antibacterial activity, MHIR showed additive interaction (fractional inhibitory concentrationindex >0·5–4) with amoxicillin and clindamycin against all the MRSA isolates, whereas MHIR synergizes (fractional biofilm inhibitory concentrationindex ≤0·5) the antibiofilm activity of amoxicillin and clindamycin against 58·33% and 83·33% of the MRSA isolates respectively. Amoxicillin/clindamycin in combination with MHIR significantly (P < 0·05) reduced disease activity score, and bacterial load and Gram‐positive spots in kidney and liver of MRSA‐infected mice. The combined efficacy of MHIR and amoxicillin/clindamycin was comparable to clindamycin alone but superior to amoxicillin alone. Hence, the combination of MHIR with amoxicillin/clindamycin is advocated in the treatment of MRSA‐associated infections.
Significance and Impact of the Study: The ability of methicillin‐resistant Staphylococcus aureus (MRSA) to form biofilms has become a challenge in the treatment of staphylococcal infections in both animals and humans. Antibiotics frequently fail to eradicate MRSA biofilm infections or, at best, only suppress the infection, potentially leading to disease recurrence. In the current study, methanolic extract of Hemidesmus indicus root (MHIR) was used as a natural and safer antibiofilm agent in combination with amoxicillin and clindamycin to treat MRSA infection. MHIR synergizes the antibacterial and antibiofilm activity of both antibiotics, resulting in the eradication of MRSA infection. In combination with MHIR, the effective dose of amoxicillin or clindamycin can also be reduced, avoiding an increased risk of in vivo toxicity.
Micronutrients, especially iron (Fe) and zinc (Zn), are deficient in the diets of people in underdeveloped countries. Biofortification of food crops is the best approach for alleviating the ...micronutrient deficiencies. Identification of germplasm with high grain Fe and Zn and understanding the genetic basis of their accumulation are the prerequisites for manipulation of these micronutrients. Some wild relatives of wheat were found to have higher grain Fe and Zn concentrations compared with the cultivated bread wheat germplasm. One accession of Triticum boeoticum (pau5088) that had relatively higher grain Fe and Zn was crossed with Triticum monococcum (pau14087), and a recombinant inbred line (RIL) population generated from this cross was grown at 2 locations over 2 years. The grains of the RIL population were evaluated for Fe and Zn concentration using atomic absorption spectrophotometer. The grain Fe and Zn concentrations in the RIL population ranged from 17.8 to 69.7 and 19.9 to 64.2 mg/kg, respectively. A linkage map available for the population was used for mapping quantitative trait loci (QTL) for grain Fe and Zn accumulation. The QTL analysis led to identification of 2 QTL for grain Fe on chromosomes 2A and 7A and 1 QTL for grain Zn on chromosome 7A. The grain Fe QTL were mapped in marker interval Xwmc382-Xbarc124 and Xgwm473-Xbarc29, respectively, each explaining 12.6% and 11.7% of the total phenotypic variation and were designated as QFe.pau-2A and QFe.pau-7A. The QTL for grain Zn, which mapped in marker interval Xcfd31-Xcfa2049, was designated as QZn.pau-7A and explained 18.8% of the total phenotypic variation.
Lithium borate (LBO) single crystals doped with Cu and Ag (0.25mol% each) (Li2B4O7:Cu,Ag) are grown by the Czochralski method. The thermoluminescence readout on Li2B4O7:Cu,Ag crystals showed three ...glow peaks at∼375, 441 and 516K for the heating rate of 1 K/s. The thermoluminescence sensitivity of the grown Li2B4O7:Cu,Ag single crystals is found to be 5 times TLD-100 and a linear dose response in the range 1mGy to 1kGy. The glow curve deconvolution reveals nearly first order kinetics for all the three peaks with trap depths 0.77, 1.25 and 1.34eV respectively and corresponding frequency factors 1.6×109, 1.3×1013 and 6.8×1011s−1. The continuous wave optically stimulated luminescence (CW-OSL) measurements were performed on the LBO:Cu,Ag single crystals using blue light stimulation. The traps responsible for the three thermoluminescence peaks in Li2B4O7:Cu,Ag are found to be OSL sensitive. The qualitative correlation between TL peaks and CW-OSL response is established. The photoluminescence studies show that in case of co-doping of Ag in LBO:Cu the emission at 370nm in Cu states dominates over the transitions in Ag states implying doping of Ag plays a role as sensitizer when co-doped with Cu and increases overall emission.
► Growth of crack free single crystals of Li2B4O7 :Cu and Ag. ► Study of TL and OSL parameters for Li2B4O7 :Cu and Ag. ► Correlation of OSL with TL peaks. ► Optimization of OSL readout time with respect to residual TL.
K2Ca2(SO4)3:Eu nanophosphor was synthesized by chemical coprecipitation method and annealed at different temperatures from 400 to 900 °C. The nanophosphor annealed at 600 °C showed cubic structure ...with crystallite size ~25 nm. TEM shows morphology of K2Ca2(SO4)3:Eu nanophosphor was in the form of nanorods having diameter ~20 nm and length of ~100–200 nm. These samples were irradiated with gamma radiation for the doses varying from 10 mGy to 10 kGy and their Thermoluminescence (TL) and continuous-wave optically stimulated luminescence (CW-OSL) have been studied. CW-OSL response was found to be maximal for the sample annealed at 600 °C. The TL glow curve of the nanophosphor apparently showed a major peak at around 160 °C accompanied by three low intensity peaks at ~75, 215 and 285 °C. The traps responsible for all the TL peaks in K2Ca2(SO4)3:Eu were also found to be OSL sensitive. The qualitative correlation between TL peaks and CW-OSL response suggested that the traps associated with low temperature peaks are responsible for fast decay and the traps associated with the higher temperature peaks are responsible for slow decay of the OSL signal. OSL response showed linear behavior up to 1 kGy and saturated with further increase in the gamma dose. The wide OSL response makes studied K2Ca2(SO4)3:Eu nanophosphor a good candidate for high dose measurement.
•K2Ca2(SO4)3:Eu nanophosphor was synthesized by chemical co-precipitation method.•TL and CW-OSL have been studied after annealing samples different temperatures.•TL glow curve is deconvoluted and trapping parameters are calculated.•The qualitative correlation between TL peaks and CW-OSL response have been investigated.•OSL response has linear behavior up to 1.0 kGy.
The present study was aimed to detect the carbapenemase, extended‐spectrum β‐lactamase (ESBL), and intI1 gene of class 1 integron among fermenting (n = 61) and nonfermenting (n = 10) bacterial ...isolates recovered from water samples (n = 128). Isolates were identified by 16S rRNA sequencing. These isolates showed reduced‐susceptibility to third‐generation cephalosporins and carbapenems. The isolates varied in number and size of plasmids (2 kb to >20 kb). Plasmid DNA screening showed 5·6, 7, 11·2 and 26·7% prevalence of blaKPC, blaNDM, blaSHV and blaTEM genes respectively. Diverse blaNDM (blaNDM‐1 and blaNDM‐4) and blaSHV subtypes (blaSHV‐2 and blaSHV‐11) were recorded, unlike the single allelic blaKPC (blaKPC‐2) and blaTEM (blaTEM‐1) gene. Of the total 27 bla‐gene‐producing bacterial isolates, seven isolates co‐harboured the carbapenemase genes (blaNDM or blaKPC or the both) along with the ESBL genes (blaSHV or blaTEM). The intI1 gene of class 1 integron was detected among 12 (44·4%) of ESBL‐ and/or carbapenemase‐harbouring isolates. Gene transferability was seen among four of the 10 Enterobacteriaceae donors. Carbapenemases and ESBLs with class 1 integron among aquatic environmental isolates raise the serious issue of the biosecurity and health of the ecosystem.
Significance and Impact of the Study
Anthropologically affected and polluted environment harbours the resistance threats, where a diverse bacterial species maintain, develop and exchange genetic determinants that constitute a risk to human and ecological health. The antimicrobial resistance (AMR) in Enterobacteriaceae and non‐Enterobacteriaceae bacteria caused the failure of the therapy of last resort (carbapenems) and thus lead to life‐threatening infections affecting public health. Surveillance and monitoring of AMR could be important for epidemiological, diagnostic testing and control of pathogens. This is a point‐prevalence study reporting the comparative occurrence and co‐occurrence of carbapenemase and extended‐spectrum β‐lactamase genes among fermenting and nonfermenting bacteria isolated from the aquatic environment in India.
Significance and Impact of the Study: Anthropologically affected and polluted environment harbours the resistance threats, where a diverse bacterial species maintain, develop and exchange genetic determinants that constitute a risk to human and ecological health. The antimicrobial resistance (AMR) in Enterobacteriaceae and non‐Enterobacteriaceae bacteria caused the failure of the therapy of last resort (carbapenems) and thus lead to life‐threatening infections affecting public health. Surveillance and monitoring of AMR could be important for epidemiological, diagnostic testing and control of pathogens. This is a point‐prevalence study reporting the comparative occurrence and co‐occurrence of carbapenemase and extended‐spectrum β‐lactamase genes among fermenting and nonfermenting bacteria isolated from the aquatic environment in India.
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