Deformation twinning in pure aluminum has been considered to be a unique property of nanostructured aluminum. A lingering mystery is whether deformation twinning occurs in coarse-grained or ...single-crystal aluminum at scales beyond nanotwins. Here, we present the first experimental demonstration of macrodeformation twins in single-crystal aluminum formed under an ultrahigh strain rate (∼10^{6} s^{-1}) and large shear strain (200%) via dynamic equal channel angular pressing. Large-scale molecular dynamics simulations suggest that the frustration of subsonic dislocation motion leads to transonic deformation twinning. Deformation twinning is rooted in the rate dependences of dislocation motion and twinning, which are coupled, complementary processes during severe plastic deformation under ultrahigh strain rates.
γ-Aminobutyric acid (GABA), a major inhibitory neurotransmitter in the central nervous system, has several well-known physiological functions and has been applied to the production of many drugs and ...functional foods. The technology of GABA production via submerged fermentation by Streptococcus salivarius subsp. thermophilus Y2 was investigated in this paper. It indicated that the GABA production was related to the biochemical characteristics of glutamate decarboxylase (GAD) of S. salivarius subsp. thermophilus Y2. After 24 h of fermentation at 37 °C, which is the suitable culture conditions for GAD-production, then the culture condition were adjusted to the optimal temperature (40 °C) and pH (4.5) for the GAD reaction activity in biotransformation of cells and pyridoxal 5'-phosphate (0.02 mmol/l) were added to the broth at the 48 h, the GABA production was increased up to 1.76-fold, reaching 7984.75 ± 293.33 mg/l. The strain shows great potential use as a starter for GABA-containing yoghurt, cheese and other functional fermented food productions.
Lactic Acid Bacteria (LAB) regulate and maintain the stability of healthy microbial flora, inhibit the adhesion of pathogenic bacteria and promote the colonization of beneficial micro‐organisms. The ...drug resistance and pathogenicity of Salmonella enteritis SE47 isolated from retail eggs were investigated. Meanwhile, Enterococcus faecalis L76 and Lactobacillus salivarius LAB35 were isolated from intestine of chicken. With SE47 as indicator bacteria, the diameters of L76 and LAB35 inhibition zones were 12 mm and 8·5 mm, respectively, by agar inhibition circle method, which indicated that both of them had inhibitory effect on Salmonella, and L76 had better antibacterial effect; two chicken‐derived lactic acid bacteria isolates and Salmonella SE47 were incubated with Caco‐2. The adhesion index of L76 was 17·5%, which was much higher than that of LAB35 (10·21%) and SE47 (4·89%), this experiment shows that the higher the bacteriostatic effect of potential probiotics, the stronger the adhesion ability; then Caco‐2 cells were incubated with different bacteria, and the survival of Caco‐2 cells was observed by flow cytometry. Compared with Salmonella SE47, the results showed that lactic acid bacteria isolates could effectively protect Caco‐2 cells; finally, after different bacteria incubated Caco‐2 cells, according to the cytokine detection kit, the RNA of Caco‐2 cells was extracted and transcribed into cDNA, then detected by fluorescence quantitative PCR, the results showed that L76 could protect Caco‐2 cells from the invasion of Salmonella SE47, with less cell membrane rupture and lower expression of MIF and TNF genes. Therefore, the lactic acid bacteria isolates can effectively inhibit the adhesion of Salmonella and protect the integrity of intestinal barrier.
Significance and Impact of the Study: We evaluated the effect of Lactobacillus from chicken on Salmonella. The results showed that both Enterococcus faecalis L76 and Lactobacillus salivarius LAB35 could effectively inhibit Salmonella SE47, and the inhibitory effect of L76 was better than LAB35. Chicken derived lactic acid bacteria can effectively protect the integrity of cell membrane from Salmonella invasion by adhering to cells. Lactobacillus can effectively antagonize the immune regulation of Salmonella in vitro. It was found that L76 had better immunomodulatory effect than LAB35.
Propionibacterium acnes plays a major role in acne vulgaris. In the pre‐experiment, the growth of P. acnes was inhibited effectively using surfactin; however, the antibacterial mechanism has not been ...described. Therefore, the aim of this study was to evaluate antibacterial activity and analyse the mechanism of surfactin against P. acnes. Minimum inhibitory concentration, time‐killing kinetics and scanning electron microscopy were used to evaluate the activity of surfactin against P. acnes, which showed that 128 μg ml−1 effectively inhibited growth. Cell wall permeability was evaluated by detecting the extracellular alkaline phosphatase activity, which increased to 1·83‐ and 2·32‐fold after incubating with 128 and 256 μg ml−1 of surfactin for 10 h, respectively. Propidium iodide fluorescence, leakage of nucleic acid, protein, K+, and Ca2+, membrane potential and the leakage of calcein from small unilamellar vesicles all increased after incubation with surfactin, indicating that its strong biological activities act mainly by altering membrane integrity. In a mouse model of acne, surfactin significantly reduced P. acnes–induced epidermal swelling and erythema. These results indicate that surfactin effectively inhibited the growth of P. acnes by destroying the cell wall and membrane, and is a potential candidate for acne treatment.
Significance and Impact of the Study: Surfactin has a wide range of targets, thus drug resistance development is difficult. This study clarified the antibacterial mechanism of surfactin against Propionibacterium acnes, which would benefit the development of acne cosmetics and cosmeceuticals, and provide a potential method for producing acne‐treating natural ingredients.
We investigate dynamic fracture of three types of multiwalled carbon nanotube (MWCNT)/epoxy composites and neat epoxy under high strain-rate loading (105–106s−1). The composites include randomly ...dispersed, 1wt%, functionalized and pristine CNT/epoxy composites, as well as laminated, ∼50wt% CNT buckypaper/epoxy composites. The pristine and functionalized CNT composites demonstrate spall strength and fracture toughness slightly higher and lower than that of neat epoxy, respectively, and the spall strength of laminated CNT buckypaper/epoxy composites is considerably lower; both types of CNTs reduce the extent of damage. Pullout, sliding and immediate fracture modes are observed; the fracture mechanisms depend on the CNT–epoxy interface strength and fiber strength, and other microstructures such as the interface between CNT laminates. Compared to the functionalized CNT composites, weaker CNT–epoxy interface strength and higher fiber strength lead to a higher probability of sliding fracture and higher tensile strength in the pristine CNT composites at high strain rates. On the contrary, sliding fracture is more pronounced in the functionalized CNT composites under quasistatic loading, a manifestation of a loading-rate effect on fracture modes. Despite their helpful sliding fracture mode and large CNT content, the weak laminate–laminate interfaces play a detrimental role in fracture of the laminated CNT buckypaper/epoxy composites. Regardless of materials, increasing strain rates leads to pronounced rise in tensile strength and fracture toughness.
Aims: To optimize the transformation conditions and improve the transformation efficiency of Bacillus subtilis WB800 and DB104. Methods and Results: Trehalose, which could decrease the damage of ...electric shock to the cells, was added to the electroporation medium containing sorbitol and mannitol. The factors affecting the transformation efficiency, such as the growth phase of bacteria, cell concentration, electric field strength and plasmid variety, were examined and improved. The new method increased the transformation efficiency of B. subtilis by nearly 100‐fold compared with the conventional one. Conclusions: With the optimized method, the transformation efficiency came up to 3·64 × 105 transformants μg−1 DNA for WB800, and 2·10 × 105 transformants μg−1 DNA for DB104. Significance and Impact of the Study: This improvement in transformation efficiency will be largely attributed to the research of expression of exogenous genes in B. subtilis, gene library construction for directed evolution and transformation of wild‐type B. subtilis strains.
Salmonella
sp. specific gene fragment
3335471
was used to establish a PCR-based assay for rapid detection of
Salmonella
sp. To establish the PCR assay, internal amplification control (IAC) was ...constructed using the composite primer method; the optimal concentration was determined to be 365 copies/μL. Storage of freeze-dried PCR solutions at –20°C for 3 months had no effect on detection results. Tests of artificially contaminated milk showed that
Salmonella
choleraesuis
could be detected in 8 h when inoculated at 7 colony forming units (CFU)/10 mL. Next, a quantitative real-time PCR (RT-PCR) for detection of
Salmonella
sp. was developed. The assays showed high specificity for 13
Salmonella
strains and 16 non-
Salmonella
strains. The optimal concentration of the IAC was 425 copies/μL for RT-PCR. Using
S. choleraesuis
as the target strain, the detection sensitivity of genome was 1.23 fg/μL and the limit of detection was 1–4 CFU/10 mL in artificially contaminated milk with 6 h of non-selective enrichment. This study established highly efficient, sensitive PCR and RT-PCR systems, providing effective approaches for the rapid detection of
Salmonella
sp. in the food industry.
Lactic acid bacteria (LAB) are typical representatives of probiotics owing to their beneficial effects on the host. They have been widely used in the food industry, animal husbandry, health care, and ...other fields. In this study, 91 strains were isolated and purified from commercial yogurts. And their functional properties, such as bacteriostatic effects, drug resistances, growth performances, adhesion characteristics, surface hydrophobicity, self-aggregation, and copolymerization, were evaluated. The results showed that all indicators of LAB M3 are good, which was identified as
Lactobacillus casei
by 16S rDNA sequence analysis. Subsequently, the mice were gavaged with
Lactobacillus casei
M3, and a high-throughput sequencing technology was employed to detect their feces to evaluate the changes in microbial flora in mice. It found that
Lactobacillus casei
M3 can intervene in the intestines of mice, improve the abundance of beneficial microflora in reducing the incidence of colitis and preventing obesity, and improve the intestinal microflora. It would have a good application prospect in the field of food industry, health care or medicine.
To optimize a medium for nicotine degradation by Ochrobactrum intermedium DN2 in presence of yeast extract, glucose and Tween 80 using response surface methodology (RSM). In this study, the effects ...of yeast extract, glucose and Tween 80 on nicotine degradation were investigated in flasks using a novel nicotine-degrading bacterium, O. intermedium DN2. A full factorial central composite design was applied in the design of experiments and in the analysis of the experimental data. The results showed that the most significant variable influencing nicotine degradation was yeast extract, followed by glucose, and then Tween 80. Moreover these three factors interacted with each other and combined to produce positive effects on nicotine degradation. The experimental data also allowed the development of an empirical model (P < 0·0001) describing the inter-relationship between independent and dependent variables. By solving the regression equation, the optimal values of the variables were determined as: yeast extracts 0·094%, glucose 0·101% and Tween 80 0·080%. Using the medium obtained, about 1220 mg l⁻¹ of nicotine was degraded (95·55%) within 10 h at the specific biodegradation of 116·59 mg l⁻¹ h⁻¹ in 30-l bioreactor containing 25-l tobacco extract. An optimal medium of nicotine degradation by the strain DN2 was obtained. RSM proved to be reliable in developing the model, optimizing factors and analysing interaction effects. The results provide better understanding on the interactions between yeast extract, glucose and Tween 80 for nicotine biodegradation.
The bulk modulus of C60, Young's modulus of carbon nanotube, and the corresponding bond length are calculated by the tight binding method (M.J. Mehl and D.A. Papaconstantopoulos, Phys. Rev. B
54 ...(1996)
4519). The calculated bond lengths of C60 and the nanotube are in good agreement with experiments or first principle calculations. The calculated Young's modulus of the nanotube is found to be equal to 0.95
TPa, the bulk modulus of C60 is 0.86
TPa. These results also fall within the range of experimental data. In addition, the bulk modulus formula of C60 and Young's modulus of nanotubes are discussed further.
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