Investigating the Role of FlhF Identifies Novel Interactions With Genes Involved in Flagellar Synthesis in Campylobacter jejuni.

FlhF is a key protein required for complete flagellar synthesis, and its deletion results in the complete absence of a flagella and thus motility in Campylobacter jejuni. However, the specific mechanism still remains unknown. In this study, RNA-Seq, EMSAs, ChIP-qPCR and β-Galactosidase assays were performed to elucidate the novel interactions between FlhF and genes involved in flagellar synthesis. Results showed that FlhF has an overall influence on the transcription of flagellar genes with an flhF mutant displaying down-regulation of most flagellar related genes. FlhF can directly bind to the flgI promoter to regulate its expression, which has significant expression change in an flhF mutant. The possible binding site of FlhF to the flgI promoter was explored by continuously narrowing the flgI promoter region and performing further point mutations. Meanwhile, FlhF can directly bind to the promoters of rpoD, flgS, and fliA encoding early flagellin regulators, thereby directly or indirectly regulating the synthesis of class I, II, and III flagellar genes, respectively. Collectively, this study demonstrates that FlhF may directly regulate the transcription of flagellar genes by binding to their promoters as a transcriptional regulator, which will be helpful in understanding the mechanism of FlhF in flagellar biosynthetic and bacterial flagellation in general

A Hybrid Time-Scaling Transformation for Time-Delay Optimal Control Problems

In this paper, we consider a class of nonlinear time-delay optimal control problems with canonical equality and inequality constraints. We propose a new computational approach, which combines the control parameterization technique with a hybrid time-scaling strategy, for solving this class of optimal control problems. The proposed approach involves approximating the control variables by piecewise constant functions, whose heights and switching times are decision variables to be optimized. Then, the resulting problem with varying switching times is transformed, via a new hybrid time-scaling strategy, into an equivalent problem with fixed switching times, which is much preferred for numerical computation. Our new time-scaling strategy is hybrid in the sense that it is related to two coupled time-delay systems—one defined on the original time scale, in which the switching times are variable, the other defined on the new time scale, in which the switching times are fixed. This is different from the conventional time-scaling transformation widely used in the literature, which is not applicable to systems with time-delays. To demonstrate the effectiveness of the proposed approach, we solve four numerical examples. The results show that the costs obtained by our new approach are lower, when compared with those obtained by existing optimal control methods

THE ELECTRONIC EQUIPMENT MODAL ANALYSIS BASED ON THE SUB-STRUCTURE

Using the ANSYS finite element analysis software to analyze the modal of the case and its modules by the substructure method,the natural frequency and mode shape of the equipment are obtained. Synthesizing the results of the modal analysis,the comprehensive structure improvements recommendations are proposed. And the substructure method has important reference value for the large-scale electronic equipments

Enhanced flame retardant efficiency of in-situ polymerizing barium phenolic resin modified with carbon nanotubes

In order to study the flame retardant properties of hydroxylated multi-walled carbon nanotubes (MWCNTs-OH) modified barium phenolic resin (PR), MWCNTs-OH modified PR composites was prepared by in situ polymerization method. Thermal stability and flame retardancy of PR composites were studied by oxygen index (OI), thermo gravimetric(TG) analyzer, cone calorimeter and thermal field emission scanning electron microscope (FESEM). The results showed the OI increased by 3.6% when 0.2 wt% MWCNTs-OH was added, and the residual carbon increased by about 6.1%. The temperature at weight loss of 20% increased by nearly 5 °C and the apparent activation energy(AAE) increased by 11.052 kJ mol ^−1 with MWCNTs-OH of 0.2 wt% at high temperature stage. And pHRR of the sample decreased by 21.4%; time to ignition was delayed by 20 s. The proper amount of MWCNTs-OH could promote the formation of carbon layer during the pyrolysis of PR so to strengthen the ability to block heat transfer to improve the flame retardancy

Numerical study on the effects of opening form on the deflation for an air-supported membrane structure

Air-supported membrane structure has been widely applied to large-span space due to its advantages of light weight, low cost, reusability. The static load bearing capacity and the dynamic deployment simulation of air-supported membrane structure have received extensive attention. However, very few studies have been reported to investigate its deflation behavior. Although several dynamic finite element algorithms can be applied to the deflation simulation, their computational costs are large. The concept of critical pressure point was introduced in this paper, by which the deflation process was divided into two stages of decompression and collapse. A series of numerical simulations were performed to study the effects of opening area and position on the pressure change in decompression process for air-supported membrane structure. The study showed that the required time for the critical pressure point reached initially decreases sharply gradually evolving into a slight decrease as the opening area increases from 0.5 to 6 m2, which followed a power equation as a function of opening area. Moreover, for a fixed opening area, opening position at top exhibits a minimum value followed by middle position, while a maximum value is shown when the opening is at bottom position. It is obviously that the decompression phase is affected significantly by the opening area and position. The above results have a certain meaning for safety assessment of personal evacuation under emergency deflation of the air-supported membrane structure. Keywords: Air-supported membrane structure, Deflation, Opening form, Numerical simulation, Critical pressure poin

Experimental study on the effect of dry water materials on the fire extinguishing efficiency and suppression mechanism of wood crib fire

Micron-sized dry water particles assembled from gaseous silica and deionized water were prepared by physical dispersion method, and the effects of two chemical components on the microstructure and fire extinguishing efficiency of dry water materials were analyzed. Three different filling pressures were selected to study their effect on dry water extinguishing efficiency of wood crib fire. The effect of dry water on fire extinguishing efficiency of wood crib was studied by building wood crib of different sizes. The results show that the larger filling pressure inhibits the fire more obviously, but the dry water structure is easy to be damaged. Dry water can adhere to the inside of the wood crib structure and exert its role of cooling and isolating oxygen to inhibit its smoldering under a certain release pressure. With the increase of the size of wood crib, the suppression efficiency of dry water materials on wood crib fire gradually decreases with increasing extinguishing time. The fire extinguishing efficiency of dry water with sodium acetate is improved, but its structure is not stable. By comparing and analyzing the critical combustion rate and oxygen concentration of wood crib, it was found that continuous cooling to reduce the combustion rate and smoldering is the dominant mechanism of dry water on wood crib fire

Transcriptome analysis of sex-related genes in the blood clam Tegillarca granosa.

Blood clams (Tegillarca granosa) are one of the most commercial shellfish in China and South Asia with wide distribution in Indo-Pacific tropical to temperate estuaries. However, recent data indicate a decline in the germplasm of this species. Furthermore, the molecular mechanisms underpinning reproductive regulation remain unclear and information regarding genetic diversity is limited. Understanding the reproductive biology of shellfish is important in interpreting their embryology development, reproduction and population structure. Transcriptome sequencing (RNA-seq) rapidly obtains genetic sequence information from almost all transcripts of a particular tissue and currently represents the most prevalent and effective method for constructing genetic expression profiles.Non-reference RNA-seq, an Illumina HiSeq2500 Solexa system, and de novo assembly were used to construct a gonadal expression profile of the blood clam. A total of 63.75 Gb of clean data, with at least 89.46% of Quality30 (Q30), were generated which was then combined into 214,440 transcripts and 125,673 unigenes with a mean length of 1,122.63 and 781.30 base pairs (bp). In total, 27,325 genes were annotated by comparison with public databases. Of these, 2,140 and 2,070 differentially expressed genes (DEGs) were obtained (T05 T08 vs T01 T02 T04, T06 T07 vs T01 T02 T04; in which T01-T04 and T05-T08 represent biological replicates of individual female and male clams, respectively) and classified into two groups according to the evaluation of biological replicates. Then 35 DEGs and 5 sex-related unigenes, in other similar species, were investigated using qRT-PCR, the results of which were confirmed to data arising from RNA-seq. Among the DEGs, sex-related genes were identified, including forkhead box L2 (Foxl2), sex determining region Y-box (Sox), beta-catenin (β-catenin), chromobox homolog (CBX) and Sex-lethal (Sxl). In addition, 6,283 simple sequence repeats (SSRs) and 614,710 single nucleotide polymorphisms (SNPs) were identified from the RNA-seq results.This study provided the first complete gonadal transcriptome data for the blood clam and allowed us to search many aspects of gene sequence information, not limited to gender. This data will improve our understanding of the transcriptomics and reproductive biology of the blood clam. Furthermore, molecular markers such as SSRs and SNPs will be useful in the analysis of genetic evolution, bulked segregant analysis (BSA) and genome-wide association studies (GWAS). Our transcriptome data will therefore provide important genetic information for the breeding and conservation of germplasm

Experimental study on the influence of restricted distance on the discrete flame spread of different widths

In this paper, the effects of varying material widths on the propagation of discrete fires within diverse confined space conditions are investigated experimentally. The width-induced mechanisms influencing the flame spread of discrete solid surfaces in distinct confined spaces are comprehensively discussed, encompassing flame characteristics, pyrolysis front dynamics, flame spread rate, and mass loss rate. The findings reveal that the dimensionless flame height and width conform to a negative power relationship at varying restricted distances. Furthermore, a positive correlation between the width of the PMMA in confined spaces and both the flame spread rate and the mass loss rate is established. Notably, when the width is fixed, the confined space plays a dominant role in the propagation of flames. As the restricted distance decreases, the flames become more slender. Additionally, flame height, flame spread rate, and mass loss rate increase with the widening of the material. However, as the restricted distance becomes smaller, the effect of width becomes less pronounced. Under conditions of same restricted distance, an increased width results in a higher radiation factor, thereby enhancing the thermal feedback of the wall to the material, which in turn accelerates the spread rate of discrete flames. Moreover, due to the dominant role of radiant heat feedback provided by the confined walls to the discrete PMMA panels, the proportion of heat transferred by convection in the flames is minimal. Consequently, the influence of the convective coefficient's width variation on flame spread is relatively minor within confined spaces. Ultimately, an energy conservation model under confined spaces was established, which facilitated the analysis of the comprehensive mechanism of flame spread influenced by varying confined spaces and material widths