Applications of a new theory extending continuum mechanics to the nanoscale

In this dissertation, we present the Slattery-Oh-Fu theory extending continuum mechanics to the nanoscale and its applications. We begin with an analysis of supercritical adsorption of argon, krypton, and methane on Graphon before we fully develop the theory. We compare our results both with existing experimental data and with prior molecular-based theories. Then, we present the general theory, which is based upon a long history of important developments beginning with Hamaker (1937). In the context of continuum mechanics, nanoscale problems always involve the immediate neighborhood of a phase interface or the immediate neighborhood of a three-phase line of contact or common line. We test this theory by using it to predict both the surface tensions of the n-alkanes and the static contact angles for the n-alkanes on PTFE and for several liquids on PDMS. For the contact angle predictions, the results are compatible with previously published experimental data. The results for the contact angle analysis also provide a successful test of a previously derived form of Young??s equation for the true, rather than apparent, common line. We also studied Mode I fracture at nanoscale. While we don??t have experimental data to compare, we get reasonable crack configuration and avoid stress singularity at the crack tip. Coalescence problems are revisited to explore the retardation effects in the computation of intermolecular forces. We get good agreement with experimental results. We conclude with a confidence that this theory can be used as a bridge between continuum mechanics and other molecular-based methods

Comparsion of bioleaching of copper sulphides by Acidithiobacillus ferrooxidans

Bioleaching of copper sulphides were investigated. The results show that the copper extraction from djurleite, bornite, covellite and chalcopyrite under the optimal conditions were 95.12, 84.5, 54.1, and 18.33%, respectively. A ranking for the bioleaching of copper sulfides was obtained: djurleite > bornite > covellite > chalcopyrite. A determination of the extent of adsorption of A. ferrooxidans on the surface of the minerals showed that the cell density of Acidithiobacillus ferrooxidans on djurleite was the highest. The order of adsorption on the copper sulphides was: djurleite > bornite > covellite > chalcopyrite. The results suggest a difference in affinity of bacteria for different copper sulphides. The higher the leaching rate of copper sulphides, the greater the density of bacteria absorbed on the surface of minerals.Keywords: Bioleaching, copper sulphides, Acidithiobacillus ferrooxidans, cell density, copper extractionAfrican Journal of Biotechnology, Vol. 13(5), pp. 664-672, 29 January, 201

Robust mode-locking in a hybrid ultrafast laser based on nonlinear multimodal interference

We experimentally demonstrate the realization of a half-polarization-maintaining (half-PM) fiber laser, in which mode-locking is provided by a reflective multimode-interference saturable absorber (SA). In the specially designed SA, linearly polarized light is coupled into a 15-cm-long graded-index multimode fiber (GIMF) through the PM fiber, and then reflected back to the PM structure through a mirror pigtailed with a single-mode fiber (SMF). The modulation depth and saturation peak power are measured to be 1.5% and 0.6 W, respectively. The proposed SA device is incorporated into a novel half-PM erbium-doped fiber oscillator, which generates soliton pulses with 409 fs temporal duration at a 33.3 MHz repetition rate. The proposed fiber laser is compared with a conventional non-PM fiber laser mode-locked by nonlinear polarization evolution (NPE) in terms of optical properties such as spectral bandwidth, pulse duration, and stability performance. Short- and long-time stability tests and superior noise performance corroborate robust mode-locking in this setup.Comment: to be published in Optics and Laser Technolog

Transcriptome sequencing reveals the effects of circRNA on testicular development and spermatogenesis in Qianbei Ma goats

Circular RNAs (circRNAs) play an important role in regulating the mammalian reproductive system, especially testicular development and spermatogenesis. However, their functions in testicular development and spermatogenesis in the Qianbei Ma goat, the Guizhou endemic breed are still unclear. In this study, tissue sectioning and circRNAs transcriptome analysis were conducted to compare the changes of morphology and circular RNAs gene expression profile at four different developmental stages (0Y, 0-month-old; 6Y, 6-month-old; 12Y, 12-month-old; 18Y, 18-month-old). The results showed that the circumferences and area of the seminiferous tubule gradually increased with age, and the lumen of the seminiferous tubule in the testis differentiated significantly. 12,784 circRNAs were detected from testicular tissues at four different developmental stages by RNA sequencing, and 8,140 DEcircRNAs (differentially expressed circRNAs) were found in 0Y vs. 6Y, 6Y vs. 12Y, 12Y vs. 18Y and 0Y vs. 18Y, 0Y vs. 12Y, 6Y vs. 18Y Functional enrichment analysis of the source genes showed that they were mainly enriched in testicular development and spermatogenesis. In addition, the miRNAs and mRNAs associated with DECircRNAs in 6 control groups were predicted by bioinformatics, and 81 highly expressed DECircRNAs and their associated miRNAs and mRNAs were selected to construct the ceRNA network. Through functional enrichment analysis of the target genes of circRNAs in the network, some candidate circRNAs related to testicular development and spermatogenesis were obtained. Such as circRNA_07172, circRNA_04859, circRNA_07832, circRNA_00032 and circRNA_07510. These results will help to reveal the mechanism of circRNAs in testicular development and spermatogenesis, and also provide some guidance for goat reproduction

Bioleaching of Al from Coarse-Grained Waste Printed Circuit Boards in a Stirred Tank Reactor

AbstractThe present work was aimed at studying the bioleachability of aluminium from coarse-grained waste printed circuit boards in a stirred tank reactor. Al recovery, variation of ORP and pH value, during the process of zero-valence Al bioleached by A. ferrooxidans, were discussed in detail. When WPCBs concentrations was 100 g/L, bacterial inoculation was 10% (v/v), temperature was 30°C, Al extraction rates of WPCBs was up to 82.13% after 30 days. Experimental results indicated that regeneration cyclic process of Fe2+ in bioleaching reactions can accelerate the extraction of Al. Zero-valence aluminium was mainly leached out chemically in the initial stage, and mainly leached out by Fe3+ and H+ in the late stage. The alkaline substance of WPCBs and the oxidation of Fe2+ consume H+, these result in the increasement of pH value in initial stage, whereafter, the decrease of pH value attributes to the hydrolysis of the ferric ion and jarosite precipitation formation

Stroke-Induced Immunosuppression And Poststroke Infection

Infections occur commonly after stroke and are strongly associated with an unfavourable functional outcome of these patients. Approaches for effective management of poststroke infection remain scarce, presenting an urgent need for preventive anti-infection strategies for patients who have suffered a stroke. Emerging evidence indicates that stroke impairs systemic immune responses and increases the susceptibility to infections, suggesting that the modification of impaired immune defence could be beneficial. In this review, we summarised previous attempts to prevent poststroke infections using prophylactic antibiotics and the current understanding of stroke-induced immunosuppression. Further elucidation of the immune mechanisms of stroke will pave the way to tailored design of new treatment to combat poststroke infection via modifying the immune system

Stirred-tank leaching of coarse-grained waste, printed circuit boards with Acidithiobacillus ferrooxidans

Stirred tank leaching of metals from coarse-grained waste, printed circuit boards (WPCB) used Acidithiobacillus ferrooxidans (A. ferrooxidans) at ambient temperature (20-35°C). The effect of the baffle size, WPCB concentration, and inoculation volume was tested. 95.92% of Cu, 93.53% of Al, 92.58% of Zn, 65.27% of Ni, and 95.33% of Sn in WPCBs were leached under the optimal conditions: no baffle, WPCB concentration of 5.0% (w/w), and inoculation volume of 5% (v/v). The alkaline substance and reactivity metal of WPCBs, and the oxidation of Fe2+, consume H+. Adding acid can maintain the pH value of the leaching solution, which is conducive to the growth and reproduction of the bacteria and improves the leaching efficiency of WPCBs. The second-order dynamics model can describe the acid consumption in the bioleaching process of coarse-grained WPCBs. Moreover, the Avrami equation can successfully explain the bioleaching kinetics of Cu, Al, Zn, Ni, and Sn from the coarse-grained WPCBs. The key factors controlling the bioleaching of coarse-grained WPCBs are metal reactivity and specific surface area. These results revealed that bioleaching metals from coarse-grained WPCBs using A.ferrooxidans is feasible, and has important significance to guiding its industrialization

Effects of N-Acetylcysteine on the Proliferation, Hormone Secretion Level, and Gene Expression Profiles of Goat Ovarian Granulosa Cells

The purpose of this paper was to investigate the effects of N-acetylcysteine (NAC) on the proliferation, hormone secretion, and mRNA expression profiles of ovarian granulosa cells (GCs) in vitro. A total of 12 ovaries from 6 follicular-stage goats were collected for granulosa cell extraction. The optimum concentration of NAC addition was determined to be 200 μM via the Cell Counting Kit 8 (CCK-8) method. Next, GCs were cultured in a medium supplemented with 200 μM NAC (200 μM NAC group) and 0 μ M NAC (control group) for 48 h. The effects of 200 μM NAC on the proliferation of granulosa cells and hormones were studied by 5-ethynyl-2′-deoxyuridine (EdU) assay and enzyme-linked immunosorbent assay (ELISA). mRNA expression was analyzed by transcriptome sequencing. The results indicate that 200 μM NAC significantly increased cell viability and the proportion of cells in the S phase but promoted hormone secretion to a lesser degree. Overall, 122 differentially expressed genes (DEGs) were identified. A total of 51 upregulated and 71 downregulated genes were included. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses indicated that the most DEGs were enriched in terms of cell growth regulation, cell growth, neuroactive ligand-receptor interaction, cytokine-cytokine receptor interaction, the cAMP-signaling pathway, and the Wnt-signaling pathway. Seven genes related to granulosa cell proliferation were screened, IGFBP4, HTRA4, SST, SSTR1, WISP1, DAAM2, and RSPO2. The above results provide molecular theoretical support for NAC as a feed additive to improve follicle development and improve reproductive performance in ewes