Analysis of Micro-scale Flame Structure of AP/HTPB Base Bleed Propellant Combustion

AbstractA complex multiple flame structure is formed during the combustion of AP/HTPB base bleed propellant. The AP monopropellant flame is concentrated in a thin zone above the burning surface of AP crystal to maintain self-sustained decomposition. Due to the low temperature near the burning surface, the diffusion between the decomposition products of AP and the pyrolysis products of HTPB occurs, and a partly pre-mixed diffusion flame structure-leading edge flame (LEF) is formed. The effects of pressure, chemical reaction rate and AP particle size on diffusion flame structure in the range from 20 atm to 100 atm are discussed. The Peclet number increases from 6.64 at 20 atm to 21.91 at 100 atm when AP particle size is 140 μm. The high temperature zone is blown away from the burning surface because the convective transport rate increases with the increase in Peclet number. The chemical reaction rate is enhanced and the diffusion mixing is inhibited as Damkohler number increases. The chemical heat release is more concentrated and the chemical reaction zone becomes narrow when Damkohler number changes from 330 at 20 atm to 4700 at 100 atm. When AP particle diameter is decreased to 60 μm, the diffusion time scale is reduced due to the reduced diffusion length scale. So the diffusion mixing is enhanced and a more pre-mixed flame is formed. The burning rate increases because the more pre-mixed heat release increases the heat feedback to the HTPB binder

Chloroquinone Inhibits Cell Proliferation and Induces Apoptosis in Nasopharyngeal Carcinoma Cell Lines

Purpose: To demonstrate the role of chloroquinone (CQ) in inducing apoptosis in HONE-1 and HNE-1, nasopharyngeal carcinoma (NPC) cell lines.Methods: Water-soluble tetrazolium salt (WST)-1 assay was used for the determination of cell proliferation while an inverted microscope was employed for the analysis of alterations in the morphology of the cells.Results: CQ treatment led to a significant reduction in the rate of cell proliferation in NPC cells after 48 h. In HONE-1 and HNE-1 cell lines viability was reduced to 89 and 82 %, respectively on treatment with 10 μΜ concentration of CQ without affecting normal human skin keratinocyte cell line, K38. The expression of Ki67, a marker for proliferation as well as proliferating cell nuclear antigen (PCNA), decreased in the CQ-treated NPC cells. Morphological examination of NPC cells revealed cell apoptosis on treatment with CQ after 48 h. Treatment of NPC cells with CQ induced activation of caspases and DNA was damaged which further confirmed CQ mediated induction of apoptosis. The level of apoptotic cells in CQ treated and untreated control HONE-1 cell cultures was 53.67 and 3.78 %, respectively (p < 0.05). In addition, CQ treatment decreased reactive oxygen species (ROS) generation in NPC cells.Conclusion: CQ inhibits cell proliferation of NPC cells by inducing apoptosis via DNA damage, and may be of therapeutic use for the treatment of NPC. However, this requires clinical investigation to ascertain its therapeutic potential.Keywords: Chloroquinone, Caspases, Apoptosis, Nuclear antigen, Nasopharyngeal carcinom

Stacking-Dependent Interlayer Phonons in 3R and 2H MoS2_{2}

We have investigated the interlayer shear and breathing phonon modes in MoS$_{2}$ with pure 3R and 2H stacking order by using polarization-dependent ultralow-frequency Raman spectroscopy. We observe up to three shear branches and four breathing branches in MoS$_{2}$ with thickness from 2 to 13 layers. The breathing modes show the same Raman activity behavior for both polytypes, but the 2H breathing frequencies are consistently several wavenumbers higher than the 3R breathing frequencies, signifying that 2H MoS$_{2}$ has slightly stronger interlayer lattice coupling than 3R MoS$_{2}$. In contrast, the shear-mode Raman spectra are strikingly different for 2H and 3R MoS$_{2}$. While the strongest shear mode corresponds to the highest-frequency branch in the 2H structure, it corresponds to the lowest-frequency branch in the 3R structure. Such distinct and complementary Raman spectra of the 3R and 2H polytypes allow us to survey a broad range of shear modes in MoS$_{2}$, from the highest to lowest branch. By combining the linear chain model, group theory, effective bond polarizability model and first-principles calculations, we can account for all the major observations in our experiment.Comment: 18 pages, 8 figures (supplemental material: 23 pages, 13 figures). 2D Materials, Accepted Manuscript online 24 January 201

Experimental Research on Internal Behaviors of Caved Rocks under the Uniaxial Confined Compression

As main composition of longwall gob, caved rocks’ behaviors and their impacts under compression crucially influence strata control, subsidence, associated resources extraction, and many other aspects. However, current researches are based on a whole sample, due to looseness of caved rocks and limitation of observation technology. In this paper, an experiment system was built to investigate internal behaviors of caved rocks’ sample, under the uniaxial confined compression, including movement and breakage behavior by the digital image processing technologies. The results show that the compression process of caved rocks could be divided into two stages by relative density. Boundary effect and changes of voids and contact pressure among caved rocks lead to different movement law in different position in sample’s interior. A stratification phenomenon of breakage was discovered, which presents breakage concentration in the middle of the sample. The nonlinear movement and shear dislocation induced by shifts among caved rocks are the reason of the breakage stratification phenomenon. This phenomenon would have an effect on the permeability and seepage research of similar medium

Prevalent Exon-Intron Structural Changes in the APETALA1/FRUITFULL, SEPALLATA, AGAMOUS-LIKE6, and FLOWERING LOCUS C MADS-Box Gene Subfamilies Provide New Insights into Their Evolution

AP1/FUL, SEP, AGL6, and FLC subfamily genes play important roles in flower development. The phylogenetic relationships among them, however, have been controversial, which impedes our understanding of the origin and functional divergence of these genes. One possible reason for the controversy may be the problems caused by changes in the exon-intron structure of genes, which, according to recent studies, may generate non-homologous sites and hamper the homology-based sequence alignment. In this study, we first performed exon-by-exon alignments of these and three outgroup subfamilies (SOC1, AG, and STK). Phylogenetic trees reconstructed based on these matrices show improved resolution and better congruence with species phylogeny. In the context of these phylogenies, we traced evolutionary changes of exon-intron structures in each subfamily. We found that structural changes have occurred frequently following gene duplication and speciation events. Notably, exons 7 and 8 (if present) suffered more structural changes than others. With the knowledge of exon-intron structural changes, we generated more reasonable alignments containing all the focal subfamilies. The resulting trees showed that the SEP subfamily is sister to the monophyletic group formed by AP1/FUL and FLC subfamily genes and that the AGL6 subfamily forms a sister group to the three abovementioned subfamilies. Based on this topology, we inferred the evolutionary history of exon-intron structural changes among different subfamilies. Particularly, we found that the eighth exon originated before the divergence of AP1/FUL, FLC, SEP, and AGL6 subfamilies and degenerated in the ancestral FLC-like gene. These results provide new insights into the origin and evolution of the AP1/FUL, FLC, SEP, and AGL6 subfamilies

Thymopentin (TP5), an immunomodulatory peptide, suppresses proliferation and induces differentiation in HL-60 cells

AbstractThymopentin (Arg–Lys–Asp–Val–Tyr, TP5) has shown immuno-regulatory activities in humans. In the present study, we investigated the effects of TP5 on the proliferation and differentiation of a human promyelocyte leukemia cell line, HL-60. It is noteworthy that TP5 displayed concentration-dependent inhibitory effects on the proliferation and colony formation of HL-60 cells. Furthermore, the decrease or even disappearance of AgNORs from nucleoli was observed in HL-60 cells after the treatment with TP5. The suppression induced by TP5 was accompanied by an accumulation of cell cycle in the G0/G1 phase. Moreover, TP5 significantly increased the NBT-reduction activity of HL-60 cells. Cytofluorometric and morphologic analysis indicated that TP5 had induced differentiation along the granulocytes lineage in HL-60 cells. d-tubocurarine (TUB) significantly antagonized the inhibitory effects induced by TP5, whereas atropine did not exhibit such effect. All the results indicated that TP5 was able to significantly inhibit proliferation and induce differentiation in HL-60 cells. Our observations also implied that TP5 not only acted as an immunomodulatory factor in cancer chemotherapy, but is also a potential chemotherapeutic agent in the human leukemia therapy

The effectiveness of artificial microbial community selection: a conceptual framework and a meta-analysis

The potential for artificial selection at the community level to improve ecosystem functions has received much attention in applied microbiology. However, we do not yet understand what conditions in general allow for successful artificial community selection. Here we propose six hypotheses about factors that determine the effectiveness of artificial microbial community selection, based on previous studies in this field and those on multilevel selection. In particular, we emphasize selection strategies that increase the variance among communities. We then report a meta-analysis of published artificial microbial community selection experiments. The reported responses to community selection were highly variable among experiments; and the overall effect size was not significantly different from zero. The effectiveness of artificial community selection was greater when there was no migration among communities, and when the number of replicated communities subjected to selection was larger. The meta-analysis also suggests that the success of artificial community selection may be contingent on multiple necessary conditions. We argue that artificial community selection can be a promising approach, and suggest some strategies for improving the performance of artificial community selection programs