Structure of Unsupported Small Palladium Nanoparticles

A tight binding molecular dynamics calculation has been conducted to study the size and coordination dependence of bond length and bond energy of Pd atomic clusters of 1.2–5.4 nm in diameter. It has been found that the bond contraction associated with bond energy increases in the outermost layer about 0.24 nm in a radial way, yet in the core interior the bond length and the bond energy remain their corresponding bulk values. This surface bond contraction is independent of the particle size

Size- and temperature-induced phase transformations of titanium nanoparticles

The size-temperature phase diagram of titanium nanoparticles has been obtained by calculating the corresponding Gibbs free energies of the FCC, BCC and HCP structures. It is found that these structures can transform from one into the other at specific sizes and temperature ranges, which is consistent with the available data reported in the literatures. Most importantly, we firstly predict that titanium particles with BCC structure can change to the FCC one in the size range 8.1–27.3 nm and in the temperature range 1156–1715 K

Gut microbiome variations in Rhinopithecus roxellanae caused by changes in the environment

Abstract Background The snub-nosed monkey (Rhinopithecus roxellanae) is an endangered animal species mainly distributed in China and needs to be protected. Gut microbiome is an important determinant of animal health and population survival as it affects the adaptation of the animals to different foods and environments under kinetic changes of intrinsic and extrinsic factors. Therefore, this study aimed to elucidate gut fecal microbiome profiles of snub-nosed monkeys affected by several extrinsic and intrinsic factors, including raising patterns (captive vs. wild), age, sex, and diarrheal status to provide a reference for making protection strategies. Results The 16S rRNA gene sequencing was firstly used to pre-check clustering of 38 fecal samples from the monkeys including 30 wild and 8 captive (5 healthy and 3 diarrheal) from three Regions of Shennongjia Nature Reserve, Hubei Province, China. Then the 24 samples with high-quality DNA from 18 wild and 6 captive (4 healthy and 2 diarrheal) monkeys were subjected to shotgun metagenomic sequencing to characterize bacterial gut microbial communities. We discovered that the raising pattern (captive and wild) rather than age and sex was the predominant factor attributed to gut microbiome structure and proportionality. Wild monkeys had significantly higher bacterial diversity and lower Bacteroidetes/Firmicutes ratios than captive animals. Moreover, the gut microbiomes in wild healthy monkeys were enriched for the genes involved in fatty acid production, while in captive animals, genes were enriched for vitamin biosynthesis and metabolism and amino acid biosynthesis from carbohydrate intermediates. Additionally, a total of 37 antibiotic resistant genes (ARG) types were detected. Unlike the microbiome diversity, the captive monkeys have a higher diversity of ARG than the wild animals. Conclusion Taken together, we highlight the importance of self-reprogramed metabolism in the snub-nosed monkey gut microbiome to help captive and wild monkeys adapt to different intrinsic and extrinsic environmental change

Synthesis of Cu₂O Nanotubes with Efficient Photocatalytic Activity by Electrochemical Corrosion Method

Metal oxide nanotubes have been synthesized with varied methods based on mechanisms such as the Kirkendall effect, dislocation-driven growth, and so on. However, most of these methods pose a challenge to these thermally unstable metal oxides. Herein, we first adopted the concept of electrochemical corrosion in the successful synthesis of scalable tubular Cu₂O nanoparticle (>10 μm in length, 20–500 nm in diameter) in aqueous solution at room temperature. By investigating different growth stages of the reaction process, a CuBr₂^– ion diffusion mechanism was rationally put forward associating with the literature, instead of the atom diffusion mechanism in the Kirkendall effect. The products exhibit outstanding specific surface area and photocatalytical activity. The present method provides a new route for synthesizing metal oxides with hollow structures

Identification of Atypical Enteropathogenic Escherichia coli O98 from Golden Snub-Nosed Monkeys with Diarrhea in China

Fecal samples (n = 76) were collected from 38 snub-nosed monkeys (Rhinopithecus roxellana) in Shennongjia National Nature Reserve (China) and examined for the presence of enteropathogenic Escherichia coli (EPEC). The 56 samples originated from 30 free-ranging monkeys on the reserve and 20 samples from 8 captive monkeys that were previously rescued and kept at the research center. Eight diarrhea samples were collected from four of the eight captive monkeys (two samples from each monkey), and two EPEC strains (2.6%) (95% confidence interval 0.3–9.2%) were isolated from two fecal samples from two diarrheic monkeys. Both strains belonged to serotype O98 and phylogenetic group D (TspE4C2+, ChuA+). The virulence gene detection identified these strains as an atypical EPEC (aEPEC) (bfpB–, stx1–, and stx2–) with the subtype eae+, escV+, and intiminβ+. These strains were highly sensitive to all the antibiotics tested. The lethal dose 50% of the two isolates in Kunming mice was 7.40 × 108 CFU/0.2 mL and 2.40 × 108 CFU/0.2 mL, respectively, indicating low virulence. Based on the report that this serotype had been isolated from some other non-human animals and humans with diarrhea, the first identification of aEPEC O98 strains and their drug resistance profile in R. roxellana is of ecological significance for disease control in this endangered species

Prevalence, Molecular Characteristics and Virulence Identification of Bovine Parainfluenza Virus Type 3 in China

Bovine parainfluenza virus type 3 (BPIV-3) is one of the major pathogens of the bovine respiratory disease complex (BRDC). BPIV-3 surveillance in China has been quite limited. In this study, we used PCR to test 302 cattle in China, and found that the positive rate was 4.64% and the herd-level positive rate was 13.16%. Six BPIV-3C strains were isolated and confirmed by electron microscopy, and their titers were determined. Three were sequenced by next-generation sequencing (NGS). Phylogenetic analyses showed that all isolates were most closely related to strain NX49 from Ningxia; the genetic diversity of genotype C strains was lower than strains of genotypes A and B; the HN, P, and N genes were more suitable for genotyping and evolutionary analyses of BPIV-3. Protein variation analyses showed that all isolates had mutations at amino acid sites in the proteins HN, M, F, and L. Genetic recombination analyses provided evidence for homologous recombination of BPIV-3 of bovine origin. The virulence experiment indicated that strain Hubei-03 had the highest pathogenicity and could be used as a vaccine candidate. These findings apply an important basis for the precise control of BPIV-3 in China

Unique Cu@CuPt Core–Shell Concave Octahedron with Enhanced Methanol Oxidation Activity

Although tremendous efforts have been devoted to the exploration of cost-effective, active, and stable electrochemical catalysts, only few significant breakthroughs have been achieved up to now. Therefore, exploring new catalysts and improving catalyst activity and stability are still major tasks at present. Controllable synthesis of Pt-based alloy nanocrystals with a uniform high-index surface and unique architecture has been regarded as an effective strategy to optimize their catalytic efficiency toward electrochemical reactions. Accordingly, here we present a one-pot facile solvothermal process to synthesize novel unique Cu@CuPt core–shell concave octahedron nanocrystals that exhibit both outstanding activity and long durability. By regulating temperatures during the synthesis process, we were able to control the reduction rate of Cu and Pt ions, which could subsequently lead to the sequential stacking of Cu and Pt atoms. Owing to the concave structure, the as-prepared core–shell nanoparticles hold a high-index surface of {312} and {413}. Such surfaces can provide a high density of atomic steps and terraces, which is suggested to be favorable for electrochemical catalysts. Specifically, the Cu@CuPt core–shell concave octahedron presents 8.6/13.1 times enhanced specific/mass activities toward the methanol oxidation reaction in comparison to those of a commercial Pt/C catalyst, respectively. Meanwhile, the as-prepared catalyst exhibits superior durability and antiaggregation properties under harsh electrochemical conditions. The facile method used here proposes a novel idea to the fabrication of nanocrystals with desired compositional distribution, and the as-prepared product offers exciting opportunities to be applied in direct methanol fuel cells