Lead (Pb) free metal halide perovskites by atomistic design are of strong interest to photovoltaics and optoelectronics industries because of the pressing need to resolve Pb-related toxicity and ...instability challenges. In this study, structural, mechanical, electronic, and optical properties of Pb-free RbSnX3 (X = Cl, Br, I) perovskites have been evaluated by using ab initio density functional theory (DFT) calculations. The computed elastic constants suggest that the Rb-based halide perovskites are mechanically stable and highly ductile, making them suitable as flexible thin films in optoelectronic devices. Besides, the investigated electronic band structures reveal that the RbSnX3 compounds are direct bandgap semiconductors, suitable for photovoltaic and optoelectronic applications. Furthermore, several optical parameters such as dielectric functions, reflectivity, photon absorptions, refractive index, optical conductivity, and loss functions have been investigated and the results predict the excellent optoelectronic efficiency of RbSnX3. Also, the computed mechanical and optical properties of RbSnX3 (X = Cl, Br, I) have been compared with the previously studied CsBX3 (B = Ge, Sn, Pb; X = Cl, Br, I) phases, revealing that the Rb-based perovskites are extremely ductile and possess excellent light absorption and optical conductivity compared to the Cs-based perovskites. Importantly, RbSnI3 shows superior ductility, absorption coefficient, and optical conductivity compared to the CsBX3 (B = Ge, Sn, Pb; X = Cl, Br, I) perovskites. Superior absorption at the ultraviolet region of RbSnI3 holds great promise of this perovskite to be used in next-generation ultraviolet photodetectors.
Green turtles (Chelonia mydas) are endangered marine herbivores that break down food particles, primarily sea grasses, through microbial fermentation. However, the microbial community and its role in ...health and disease is still largely unexplored. In this study, we investigated and compared the fecal bacterial communities of eight wild-captured green turtles to four stranded turtles in the central Great Barrier Reef regions that include Bowen and Townsville. We used high-throughput sequencing analysis targeting the hypervariable V1-V3 regions of the bacterial 16S rRNA gene. At the phylum level, Firmicutes predominated among wild-captured green turtles, followed by Bacteroidetes and Proteobacteria. In contrast, Proteobacteria (Gammaproteobacteria) was the most significantly dominant phylum among all stranded turtles, followed by Bacteroidetes and Firmicutes. In addition, Fusobacteria was also significantly abundant in stranded turtles. No significant differences were found between the wild-captured turtles in Bowen and Townsville. At the family level, the core bacterial community consisted of 25 families that were identified in both the wild-captured and stranded green turtles, while two unique sets of 14 families each were only found in stranded or wild-captured turtles. The predominance of Bacteroides in all groups indicates the importance of these bacteria in turtle gut health. In terms of bacterial diversity and richness, wild-captured green turtles showed a higher bacterial diversity and richness compared with stranded turtles. The marked differences in the bacterial communities between wild-captured and stranded turtles suggest the possible dysbiosis in stranded turtles in addition to potential causal agents.
This study investigated Enterobacteriales and their antimicrobial resistance in green sea turtles captured adjacent to the central Great Barrier Reef (GBR) and proximate to urban development. Cloacal ...swabs were taken from 73 green turtles between 2015 and 2016. A total of 154 out of 341 Gram-negative bacterial isolates were identified as Enterobacteriales that represent 16 different species from 9 different genera. The dominant isolates were Citrobacter (30.52%), Edwardsiella (21.43%) and Escherichia (12.34%). The resistance against 12 antibiotics belonging to 6 different classes was determined. The isolates showed highest resistance to β-lactam antibiotics (78.57%) followed by quinolone (50%) and tetracycline classes (46.1%). Approximately one-third (37.7%) of the isolates identified exhibited multidrug-resistance. Isolates recovered from rehabilitated turtles were significantly multidrug resistant (p<0.009) compared to isolates from other study sites. These results provide baseline information on antimicrobial resistance while revealing gaps for further research to evaluate the level of pollution in the GBR.
•We reported evidence of microbial resistance to antibiotics in bacteria recovered from green turtles.•Enterobacteriales strains were resistant to commonly used therapeutic antibiotics.•37.7% of the Enterobacteriales isolates were identified as multi-drug resistant.•Multi-drug resistant isolates were more prevalent in stranded turtles in rehabilitation.
Stranded green turtles (Chelonia mydas) are often cared for in rehabilitation centers until they recover. Although the specific causal agents of diseases in stranded turtles are difficult to ...diagnose, we know that gut microbiota of green turtles play a vital role in health as well as a wide range of diseases. The objective of this study was to characterize and compare the gut bacterial communities between pre-hospitalization (PH) and post-rehabilitation (PR) stranded green turtles using high-throughput sequencing analysis targeting V1–V3 regions of the bacterial 16S rRNA gene. A total of eight cloacal swab samples were collected from four green turtles undergoing rehabilitation. Proteobacteria dominating in both PH and PR samples without any significant difference. Firmicutes was the second and Bacteroidetes was the third most abundant phylum in PH samples, while Bacteroidetes prevailed in PR samples, followed by Firmicutes. The predominance of the genus Bacteroides in both PH and PR samples indicates the importance of this genus in turtle gut health. At a class level, Epsilonproteobacteria was significantly (P<0.05) associated with PH samples and Deltaproteobacteria predominated (P<0.05) in PR samples. The significant abundance of Campylobacter fetus, Escherichia coli, Clostridium botulinum and Vibrio parahaemolyticus in PH samples indicate pathogenic associations with stranded green turtles with zoonotic potential. The presence of Salmonella enterica in only PR samples suggest possible acquisition of this bacteria during rehabilitation. In this study, all post-rehabilitation green turtles exhibited similar bacterial communities, irrespective of their microbial compositions at pre-hospitalization. The marked differences in the gut bacterial communities of PH and PR turtles indicate the outcome of dietary, management and environmental shift during rehabilitation. Therefore, it is important to address the process of restoring normal gut microbiota of recovered turtles prior to release back to their natural habitat.
Hollow core photonic crystal fiber is suggested and analyzed in this article for the identification of different blood components present in human blood. In order to visualize the fiber and ...investigate the performance of that sensor based on COMSOL simulation software, the suggested fiber is numerically analyze in terahertz frequency spectrum from 1.5 to 3 THz to obtain higher relative sensitivity (RS) and NA as well as lower absorption loss and confinement loss (CL) for better sensing applications. The reported hollow core fiber provides better interaction of light and the analytes, so that extremely high RS is achieved at a particular geometric condition. Furthermore, extremely low CL and effective material loss (EML) with high numerical aperture (NA) can be achieved from the suggested sensor which paves the way to apply the fiber in numerous biomedical applications.
A new kind of rectangular hollow core photonic crystal fiber (HC-PCF) has been proposed and analyzed in the terahertz regime to detect the chemical analytes. In this proposed HC-PCF a rectangular ...shaped air hole is used in the core and circular air holes are introduced in the cladding. Full vectorial finite element method (FEM) with perfectly matched layer (PML) boundary condition is used to investigate the guiding characteristics of the proposed HC-PCF. Our proposed PCF exhibits a high relative sensitivity and extremely low confinement loss for different chemical analytes. In addition, this proposed chemical sensor offers high birefringence, high numerical aperture and almost zero flattened dispersion over a wide frequency range. This proposed fiber can be used in chemical sensing as well as various polarization maintaining terahertz applications.
A petrol adulteration sensor based on a rectangular shaped hollow-core photonic crystal fiber is proposed and numerically analyzed in the terahertz regime. The performance of the proposed sensor was ...evaluated when it is employed to characterize different kerosene mixtures. In this research, the adulterated fuel sample is filled in the rectangular hollow channel and the electromagnetic signal of the terahertz band is also driven through the same channel. The received signal after the interaction of fuel with the terahertz signal will advise the refractive index of the fuel oil inside the core, which will also bear the information of how much extrinsic component is present in the fuel. The finite element method based simulation shows that the proposed sensor can reach a high relative sensitivity of 89% and presents low confinement losses at 2.8 THz. The reported sensing structure is easily realizable with the conventional manufacturing techniques. Consequently, this proposed fiber may be treated as an essential part of real-life applications of petrol adulteration measurements.
This study has reported an extremely high sensitive and nonlinear chemical sensor based on photonic crystal fiber is presented with numerical investigation. In order to reduce fabrication complexity, ...the proposed chemical detector is designed with circular air holes. To calculate the guiding characteristics, finite element method based Comsol software is used. Different types of commonly used materials are used as background material of that proposed sensor to ensure maximum relative sensitivity to the chemicals. The simulation results confirms that, very high relative sensitivity of 97.89%, 96.31%, 91.87% and 88.93% for benzene, chloroform, ethanol and water respectively at 1.55 µm of optical signal. Moreover the proposed chemical sensor offers negligible confinement loss of around 10
–10
dB/m for all sensing analytes. In addition, other important characteristics such as numerical aperture, nonlinearity are discussed in detail. The wavelength dependent light guiding characteristics for the solid materials and the sample under test is used in simulation to ensure better accuracy and to create real life environment.
A novel kind of porous core microstructure optical fiber is proposed in this paper. In order to create flexibility of the fiber only ring air hole is used for the cladding region. Finite Element ...Method (FEM) based Comsol v4.2 software is used to investigate the guiding characteristics of the proposed fiber. The optimum design parameter shows an ultrahigh birefringence of 0.051, low effective material loss of 0.07 cm−1 and low bending loss of 1.13 × 10−13 dB/cm at 1.2 THz. Moreover, the proposed fiber offers very low dispersion of 1.2 ± 0.32 ps/THz/cm over a wide range of frequency from 1.1 THz to 1.9 THz. Other important guiding characteristics such as confinement loss, effective area and single mode propagation are also discussed in detail. This structure may be a good choice in different remarkable terahertz applications.
Summary
Green turtles are endangered marine herbivorous hindgut fermenters that contribute to a variety of marine ecosystems. Debilitated turtles are often rehabilitated in turtle hospitals. Since ...accurate diagnosis of disease is difficult, broad‐spectrum antibiotics are routinely used as a general treatment, potentially causing collateral damage to the gut microbiome of the patient. Here, we evaluated the concept of the application of bacteriophage (phages) to eliminate targeted intestinal bacteria as an alternative to a broad‐spectrum antibiotic (enrofloxacin) in clinically healthy, captive green turtles. Additionally, the impact of a broad‐spectrum antibiotic (enrofloxacin) and phage therapy on the gut bacterial communities of green turtles was evaluated. Gut bacterial communities in faecal samples were analysed by sequencing the V1‐V3 regions of the bacterial 16S rRNA. Bacteria‐specific phage cocktails significantly (P < 0.05) reduced targeted Acinetobacter in phage‐treated turtles during the therapy. Compared to control, no significant difference was observed in the bacterial diversity and compositions in phage‐treated turtles. In contrast, bacterial diversity was significantly (P < 0.05) reduced in antibiotic‐treated turtles at day 15 and throughout the trial. The alteration in the bacterial microbiota of antibiotic‐treated turtles was largely due to an increase in abundance of Gram‐positive Firmicutes and a concurrent decrease in Gram‐negative Bacteroidetes, Proteobacteria and Verrucomicrobia. Additionally, we observed the relative abundance of several bacteria at lower taxonomic level was much less affected by phages than by antibiotics. These data offer the proof of concept of phage therapy to manipulate transient as well as indigenous bacterial flora in gut‐related dysbiosis of turtles.
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