Search

Aluminum powder can increase the specific impulse and improve the combustion performance of a solid propellant; however, agglomeration can result in the loss of two-phase flow, a decrease in specific impulse of the propellant, and an increase in the thermal protection pressure of the motor structure. This study employs digital inline holography, which offers the advantage of non-contact three-dimensional measurements, to investigate the agglomeration particle size near the burning surface. This study aims to quantitatively analyze these particle size data to determine the effects of pressure, ammonium perchlorate particle size, coarse and fine ammonium perchlorate content ratio, and aluminum particle size on the agglomeration particle size distribution. The experimental results indicate that increasing the pressure from 0.1 MPa to 0.8 MPa reduces the average particle diameter of agglomeration by at least 9.6%, results in a more concentrated agglomeration particle size distribution, and decreases the volume and number proportion of agglomeration by approximately 7% and 17%, respectively. Furthermore, when the particle size of ammonium perchlorate decreases from 250 μm to 90 μm, the agglomeration particle size distribution becomes more concentrated, the average diameter of agglomeration decreases by at least 37.4%, and the number and volume proportion of agglomeration decrease by approximately 13% and 44%, respectively. The ratio of coarse and fine ammonium perchlorate content has a nonlinear effect on agglomeration. When this ratio is 0.6, the average agglomerate diameter decreases by at least 16%, the agglomeration particle size distribution is more concentrated than that the ratio is 0.39 and 1.29, and the agglomeration number and volume fraction decrease by more than 6% and 32%, respectively. Moreover, decreasing the initial aluminum particle size from 30 μm to 15 μm reduces the average agglomeration particle diameter by more than 21.6%, results in a more concentrated agglomeration particle size distribution, however, increases the number and volume proportion of agglomeration by approximately 17% and 8%, respectively. The conclusions of this study are expected to be significantly helpful in optimizing propellant formulation, reducing the particle size of aluminum agglomeration, and improving the combustion performance of propellants.

Currently, infections caused by drug-resistant bacteria have become a new challenge in anti-infective treatment, seriously endangering public health. In our continuous effort to develop new antimicrobials, a series of novel honokiol/magnolol amphiphiles were prepared by mimicking the chemical structures and antibacterial properties of cationic antimicrobial peptides. Among them, compound 5i showed excellent antibacterial activity against Gram-positive bacteria and clinical MRSA isolates (minimum inhibitory concentrations (MICs) = 0.5-2 μg/mL) with low hemolytic and cytotoxic activities and high membrane selectivity. Moreover, 5i exhibited rapid bactericidal properties, low resistance frequency, and good capabilities of disrupting bacterial biofilms. Mechanism studies revealed that 5i destroyed bacterial cell membranes, resulting in bacterial death. Additionally, 5i displayed high biosafety and potent in vivo anti-infective potency in a murine sepsis model. Our study indicates that these honokiol/magnolol amphiphiles shed light on developing novel antibacterial agents, and 5i is a potential antibacterial candidate for combating MRSA infections.

Nitrate ester plasticized polyether (NEPE) is a kind of high-energy solid propellant that has both good mechanical properties and high specific impulse. However, its unique composition makes its combustion mechanism different from both double-base propellants and composite propellants. In order to study the combustion mechanism of NEPE propellants, we improved the free radical cracking model of previous research to make it capable of predicting the burning rate of NEPE propellants. To study the combustion characteristics and provide data support for the model, an experimental system was built and four kinds of NEPE propellants with different compositions and grain size distributions were tested. The results show that our modified model can reflect the combustion characteristics of NEPE propellants with an acceptable accuracy. The difference between the model and the experimental data is mainly caused by uncertain environmental factors and the ignorance of interactions between components. Both the experimental data and the results predicted by the model show that increasing the backpressure helps to increase the burning rate of NEPE propellants. Furthermore, the grain size of the oxidizer inside the NEPE propellant has a more severe impact on the burning rate but a lighter impact on the burning rate pressure exponent in comparison with the grain size of aluminum. For aluminum-free NEPE propellants, the reaction in the gas phase is dominant in the combustion process while adding aluminum into the propellant makes the solid phase dominant in the final stage. The combustion of fine aluminum particles near the burning surface generates heat feedback to the burning surface which evidently influences the surface temperature. However, the agglomeration of coarse aluminum particles has little effect on the burning surface temperature.

Many phytopathogenic fungi cause severe damage to crop yields. In continuation of our research aimed at the discovery and development of natural products-based fungicides, a series of thirty-one sarisan attached 3-phenylisoxazolines were synthesized and evaluated for their antifungal activities against five phytopathogenic fungi ( B. cinerea , C. lagenarium , A. solani, F. solani , and F. graminearum ). Among all title sarisan derivatives, compounds IV2 , IV14 and IV23 showed potent antifungal activity against some phytopathogenic fungi. In particular, compound IV2 exhibited a broad-spectrum and more potent antifungal activity against A. solani , F. solani, and F. graminearum than the commercial fungicide Hymexazol. In addition, compounds IV2 , IV14 and IV23 also displayed relative low toxicity on normal NRK-52E cells. This work will give some insights into the development of sarisan derivatives as new fungicide candidates in plant protection.

While numerous studies have shown that fluoride or arsenic exposure may damage the reproductive system, there are few reports of co-exposure to fluoride and arsenic. In addition, the literature on autophagy and intestinal flora composition in reproductive toxicity studies of co-exposure to fluoride and arsenic is insufficient. In this study, we developed a rat model of fluoride and arsenic exposure via drinking water from pre-pregnancy to 90 days postnatal. Sprague-Dawley rats were randomly divided into sterile water control group, fluoride group (100 mg/L NaF), arsenic group (50 mg/L NaAsO2) and combined exposure group (100 mg/L NaF+50 mg/L NaAsO2). Our results showed that fluoride and arsenic exposure caused a reduction in testicular weight and significant pathological damage to tissue. We found that the levels of follicle-stimulating hormone, luteinizing hormone, and testosterone were reduced to varying degrees. Meanwhile experiments showed that fluoride and arsenic exposure can modulate autophagic flux, causing increased levels of Beclin1 and LC3 expression and decreased p62 expression. Analogously, by performing 16S sequencing of rat feces, we found 24 enterobacterial genera that differed significantly among the groups. Furthermore, the flora associated with testicular injury were identified by correlation analysis of hormonal indices and autophagy alterations with intestinal flora composition at the genus level, respectively. In summary, our study shows that fluoride and arsenic co-exposure alters autophagic flux in the testis, causes testicular injury, and reveals an association between altered intestinal flora composition and testicular injury.

In this study, a CO2 laser ignition experimental system was built to study the ignition process and characteristics of the Nitrate Ester Plasticized Polyether (NEPE) propellant. The effect of the energy density, ingredients, and the grain size distribution of the propellant on the ignition process was investigated using a CO2 laser igniter, a high-speed camera, and a tungsten-rhenium thermocouple. Four types of NEPE propellants were tested under different laser heat fluxes, and the ignition delay time, the ignition temperature, and the ignition energy were obtained. Experimental results show that the ignition process of the NEPE propellant can be divided into three stages, namely the first-gasification stage, the first-flame stage, and the ignition delay stage. When the energy density is lower than the ignition energy threshold, the ignition process cannot be achieved even under continuous energy loading. The increase of the energy density can lead to the decrease of the ignition delay time but has little effect on the ignition temperature. The ingredients and grain size distribution have great effects on both the ignition delay time and the ignition temperature. The grain size effect of aluminum is the largest compared with that of Ammonium Perchlorate (AP) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), while the grain size effect of AP is larger than that of HMX.

With the aim of revealing the detailed process of aluminum combustion in air, this paper reports an experimental study on the combustion of aluminum droplets. In this work, the aluminum wires were exposed and heated by a CO 2 laser to produce aluminum droplets, and then these droplets were ignited and burnt in air. The changing processes of aluminum wires, droplets and flames were directly recorded by a high-speed camera, which was equipped with a high magnification zoom lens. Meanwhile, the spectrum distribution of the flame was also registered by an optical spectrometer. Besides, burning residuals were collected and analyzed by the methods of Scanning Electron Microscopy (SEM) and Energy Dispersive Spectrometer (EDS). Experimental results show that, during combustion, the aluminum droplet is covered by a spherical vapor-phase flame, and the diameter of this flame is about 1.4 times of the droplet diameter, statistically. In the later stages of combustion, the molten aluminum and condensed oxide products can react to generate gaseous Al and Al 2 O spontaneously. Little holes are found on the surface of residuals, which are the transport channels of gaseous products, namely the gaseous Al and Al 2 O. The combustion residuals are consisted by lots of aluminum oxide particles with diameters less than 1 μm.

Fluorosis is a worldwide public health problem, and its adverse effects on the heart have been confirmed by many studies. Abnormal myocardial contractions are often associated with impairment of cardiac function as a cause or consequence. We designed two-part experiments to search for biomarkers and clarify the underlying molecular mechanism of fluoride on myocardial contraction. First, we used Pressure-volume Loop analysis to evaluate changes in myocardial function indexes with multiple fluoride exposure levels in mice (0, 30, 70, and 150 mg/L) exposed for 4 weeks. The results showed that fluoride exposure affects the heart pump function and reduces cardiac contractility. Then, we established a rat model of fluoride exposure (0, 30, 60, and 90 mg/L) for 6 months to carry out proteomic analysis of fluoride-induced myocardial contractile injury. Hematoxylin-eosin (H&E) staining was used to determine the severity of myocardial injury, and myocardial tissue samples were submitted for isobaric tags for relative and absolute quantitation (ITRAQ) analysis. A total of 1607 proteins were successfully identified with 294 differentially expressed proteins (DEPs) in fluoride treated groups. According to Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis, 12 DEPs were confirmed to be involved in pathways related to myocardial contraction. Furthermore, we constructed a protein-protein interaction (PPI) network for these 12 core DEPs to illustrate the role and location of each DEP in the myocardial contraction pathway. The results of this study are helpful for identify a potential mechanism and biomarkers of fluoride-induced myocardial contraction function damage, moreover, which can provide a new insight into the heart toxicity of fluoride in animals at the proteomics level.

Persimmon (Diospyros kaki L.) leaves are commonly used in Asia as tea infusion and as an agent in traditional medicine. The present study aims to explore the antitumor and immunomodulatory effects of total flavonoids extract from persimmon leaves (PLF) in H22 liver tumor-bearing mice. We found that the PLF showed significant inhibition on the liver tumor growth in mice with a tumor inhibition rate of up to 49.35%. In contrast to the severe side effects of cyclophosphamide (CTX), the PLF exhibited anti-cachexia effect and showed no alternation in the body weight and food intake in mice. Moreover, compared with the vehicle control and CTX group, the PLF significantly enhanced the thymus and spleen indices, level of serum interleukin-18 (IL-18), monocyte/macrophage phagocytosis, level of serum hemolysin, and activity of natural killer (NK) cells. This study demonstrated that the PLF could effectively inhibit liver tumor growth in vivo via enhancement of the immune function in mice, and it displayed the potential to be a safe and effective anticancer agent or functional immune-enhancing agent.

In the current study, a novel semi-dissolution/acidification/sol-gel transition (SD-A-SGT) method was explored for the preparation of polyelectrolyte complexing (PEC) composite hydrogels with natural polymers only. A chitosan (CS) powder was uniformly dispersed in a solution of poly(glutamic acid) (PGA) and alginate (SA) to form a semi-dissolved slurry mixture that was then exposed to an gaseous acidic atmosphere. CS was gradually dissolved and interacted with PGA and SA to form a CS/PGA/SA PEC composite hydrogel with a homogeneous structure. The SD-A-SGT procedure was able to overcome the shortcomings of direct mixing method via the PEC interaction. The effects of the hydrogel composition on its structure and properties were investigated by FTIR, XRD, rheology study, XPS, SEM, and swelling kinetics. The drug delivery performance of the CS/PGA/SA hydrogel was explored using piroxicam (PXC) as a model drug. PXC was in situ embedded in the hydrogel by the SD-A-SGT method. The hydrogel exhibited pH responsive drug release behaviors that were affected by the hydrogel composition. In all, the SD-A-SGT method for preparing PEC composite hydrogels has a great application potential in constructing the CS based hydrogels as medical materials.

The mixing and combustion process has an important impact on the engineering realization of the scramjet engine. The nonreacting and reacting flow fields in a transverse injection channel have been investigated numerically, and the predicted results have been compared with the available experimental data in the open literature, the wall pressure distributions, the separation length, as well as the penetration height. Further, the influences of the molecular weight of the fuel and the jet-to-crossflow pressure ratio on the wall pressure distribution have been studied. The obtained results show that the predicted results show reasonable agreement with the experimental data, and the variable trends of the penetration height and the separation distance are almost the same as those obtained in the experiment. The vapor pressure model is suitable to fit the relationship between the penetration height, the separation distance and the jet-to-crossflow pressure ratio. The combustion process mainly occurs upstream of the injection port, and it makes a great difference to the wall pressure distribution upstream of the injection port, especially when the jet-to-crossflow pressure ratio is large enough, namely 17.72 and 25.15 in the range considered in the current study. For hydrogen, the combustion downstream of the injection port occurs more intensively, and this may be induced by its smaller molecular weight.

In this study we investigated apoptosis and expression of the collagen I gene in newborn rat osteoblasts (OB) by the administration of varying concentrations of fluoride (F). Sodium fluoride (NaF) at concentrations of 0, 0.5, 5, 10, and 20mg/L was administered to cultured OB. The percentage of G(1)/G(0) (Gap 1/Gap 0), S (synthesis), G(2)/M (Gap 2/M, mitosis), and apoptosis rates in OB were analyzed with a Fluorescence-activated Cell Sorter (FACS) by propidium iodine (PI) staining after F treatment of 72 h. Effects of F treatment on COL1A1 and COL1A2 mRNA and collagen I protein levels were determined using quantitative real time RT-PCR (qRT-PCR) and immunofluorescence, respectively. This study demonstrates that there is a pronounced negative effect of long term NaF treatment on OB survival. These negative effects include an inhibition of the transformation from S phase into G(2)/M phase, increased apoptosis, and decreased COL1A1 mRNA, down-regulating the synthesis of COL I protein. The results suggest that COL I protein degradation in OB from F toxicity is due to a depletion of COL1A1 mRNA and not COL1A2.

Unbleached kraft pulp fibers were reacted with laccase in the presence of different phenolic compounds (isoeugenol, butyl p-hydroxybenzoate, p-coumaric acid, and ferulic acid) in order to confer them with new properties. After the enzymatic stage, antimicrobial tests demonstrated that the handsheets formed from the laccase/phenolic-treated pulp showed a greater efficacy against Gram-positive and Gram-negative bacteria compared to handsheet paper treated only with laccase and a control. Laccase in the presence of butyl p-hydroxybenzoate produced handsheets with the most significantly enhanced bactericidal effect. An analysis of scanning electron microscope images of the treated kraft pulps increased kappa numbers and surface features of the fibers. The reduction in the absolute value of the zeta potential of the pulps indicates that the phenolic compounds produce chemical cross-linking within the fiber surface. X-ray photoelectron spectroscopy shows that the lignin content of the pulp fiber surface increased after adding the laccase and phenolic compounds.