流体润滑状态下磨粒尺寸对液压泵磨损的影响

本文研究了流体润滑状态下磨粒尺寸对液压泵磨损的影响。结果表明,在液压系统中,泵的磨损主要决定于磨粒与泵内关键运动副动态间隙之间的尺寸关系:尺寸小于动态间隙的磨粒影响很小;尺寸明显比动态间隙大的磨粒不会对泵产生磨损作用;尺寸与动态间隙很接近的磨粒能使泵发生严重磨损。作者还利用扫描电子显微镜对流体润滑状态下三体磨粒磨损中的磨屑形貌进行了观察与分析,并且提出了控制液压系统中磨粒损磨的可行施措。     

Composite materials based on zeolite 4A for adsorption heat pumps

Some additives and binders were chosen for the preparation of 4A-zeolite-based composites with high equivalent thermal conductivity for heat pumps application. Additives (SiC, Si₃N₄, graphite) and binders (PTFE, Al(OH)₃) were tested for their effectiveness in terms of equivalent thermal conductivity and maximum water adsorption capacity of the composites. The influence of the equivalent thermal conductivity of the composite adsorbents on the specific power of the heat pump was also calculated. Results show a significant improvement in the equivalent thermal conductivity of the composite samples which are prepared using aluminum hydroxide as binder, over that of zeolite pellet beds. Such composite materials could be used to build adsorption heat pumps with higher specific power and, consequently, with lower investment cost.     

Determination of bismuth and cadmium after solid-phase extraction with chromosorb-107 in a syringe

The determination of bismuth and cadmium by graphite furnace atomic absorption spectrometry (GFAAS) after solid-phase extraction (SPE) on Chromosorb-107 filled in a syringe was described. To retain the analytes, the sample solution treated with and without ammonium pyrolidine dithiocarbamate (APDC) was drawn into the syringe filled with Chromosorb-107 and discharged back manually. Bismuth and cadmium were quantitatively sorbed at pH ≥ 6 irrespective of whether the analyte was complexed with APDC prior to passing through the Chromosorb-107. Analyte elements sorbed on the resin were quantitatively eluted with 3.0 M of HNO₃ again drawing and discharging the eluent into the syringe and ejected it back. Optimum flow rates of sample or eluent for sorption and elution processes were 20 ml min⁻¹ for drawing and 20 ml min⁻¹ for discharging in all cases. Bismuth and cadmium were analyzed by graphite furnace atomic absorption spectrometry. The elements could be concentrated by drawing and discharging several portions of sample successively but eluting only one time. The validity of the proposed method was checked with standard reference materials (NIST SRM 1515 Apple-Leaves, CWW-TM-E Waste Water and CRM-SW Sea Water). The analyte elements were quantitatively (>95%) recovered from different matrices irrespective of treated samples with APDC. Detection limits (δ) were 0.8 and 1.2 μg l⁻¹ for Bi and Cd, respectively. The method can be characterized with fastness, simplicity, quantitative recovery and high reproducibility.     

水波泵研制的流体力学理论与设计计算

介绍了作者正在研制的水波泵目前所涉及到的流体力学理论。水波泵是一种巧妙地综合气波增压器和水锤泵功能的全新的水泵,它通过合理利用水波动力的特殊性质,将来流中的总体能量进行重新分配,使一部分来流水提高到所需的高压力,而其余部分水则降到较低的压力,即完成一个大多数能量向部分来流水转移的过程。该泵的研制对于充分开发和利用自然水力资源或工业与民用水循环系统的废弃能量,具有良好的经济价值及社会效益。文中在介绍水锤泵工作原理的基础上,分析了水击动力现象的产生和利用方法,再通过流体力学理论研究与计算,得出了水波泵一系列有用的设计参数,设计计算表明,水波泵的设计研究在流体动力学理论研究和运用具有突破性的意义,并达到预期的效果。     

Capillary isoelectric focusing coupled offline to matrix assisted laser desorption/ionization mass spectrometry

This work presents several critical details for making cIEF-MALDI-MS a robust technique which will allow for more routine application and aid in automation. This includes emphasis on the hardware necessary for syringe pump mobilization and proper protocol for preventing disruption from gas bubbles. Following these guidelines, excellent elution time reproducibility is demonstrated for six pI markers (RSD <5%). Additionally, the pI markers are used to calibrate the pH gradient and determine experimental pIs of proteins detected offline by mass spectrometry. This was demonstrated using a standard protein mixture of myoglobin and two forms of β-lactoglobulin. Experimental determination of protein pIs and molecular weights were found to be in agreement with literature values. The technical details discussed provide a sound foundation for applying the offline coupling of MALDI-MS with cIEF.     

Flow-through immunomagnetic separation system for waterborne pathogen isolation and detection: Application to Giardia and Cryptosporidium cell isolation

Simultaneous sample washing and concentration of two waterborne pathogen samples were demonstrated using a rotational magnetic system under continuous flow conditions. The rotation of periodically arranged small permanent magnets close to a fluidic channel carrying magnetic particle suspension allows the trapping and release of particles along the fluidic channel in a periodic manner. Each trapping and release event resembles one washing cycle.The performance of the magnetic separation system (MSS) was evaluated in order to test its functionality to isolate magnetic-labelled protozoan cells from filtered, concentrated tap water, secondary effluent water, and purified water. Experimental protocols described in US Environmental Protection Agency method 1623 which rely on the use of a magnetic particle concentrator, were applied to test and compare our continuous flow cell separation system to the standard magnetic bead-based isolation instruments. The recovery efficiencies for Giardia cysts using the magnetic tube holder and our magnetic separation system were 90.5% and 90.1%, respectively, from a tap water matrix and about 31% and 18.5%, respectively, from a spiked secondary effluent matrix. The recovery efficiencies for Cryptosporidium cells using the magnetic tube holder and our magnetic separation system were 90% and 83.3%, respectively, from a tap water matrix and about 38% and 36%, respectively, from a spiked secondary effluent matrix. Recoveries from all matrices with the continuous flow system were typically higher in glass tubing conduits than in molded plastic conduits.     

Energy Propagation Through a Protometabolism Leading to the Local Emergence of Singular Stationary Concentration Profiles

Living systems rely on chains of energy transfer from an energy source to maintain their metabolism. This task requires functionally identified components and organizations. However, propagation of a sustained energy flux through a cascade of reaction cycles has never been reproduced at a steady state in a simple chemical system. By using energy patterning and a diffusing hub reactant, we achieved the transfer of energy through an abiotic protometabolism. Patterned illumination was applied to a liquid solution of a reversible photoacid. It resulted in the local onset of a proton pump, which subsequently drove an extended reaction–diffusion cycle that involved pH‐sensitive reactants. Thus, light has been used for locally setting out of chemical equilibrium a reaction involving “blind” reactants. The spontaneous onset of an energy‐transfer chain notably drives the local generation of singular dissipative chemical structures; continuous matter fluxes are dynamically maintained at boundaries between spatially and chemically segregated zones, in the absence of any membrane or predetermined material structure.     

Theoretical analysis of bacterial efflux pumps inhibitors: Strategies in-search of competent molecules and develop next

Multi-drug resistance (MDR) bacteria pose a significant threat to our ability to effectively treat infections due to the development of several antibiotic resistant mechanisms. A major component in the development of the MDR phenotype in MDR bacteria is over expression of different-type of efflux pumps, which actively pump out antibacterial agents and biocides from the periplasm to the outside of the cell. Consequently, bacterial efflux pumps are an important target for developing novel antibacterial treatments. Potent efflux pump inhibitors (EPIs) could be used as adjunctive therapies that would increase the potency of existing antibiotics and decrease the emergence of MDR bacteria. Several potent inhibitors of efflux pumps have been reported which has been summarized here. All the natural and synthetic EPIs were optimized with Gaussian and Avogadro software. The optimized structures were docked with each class of efflux pumps and their bonding parameters were computed. The theoretical analyses were performed with density functional theory (DFT). Overall, computational study revealed a good trend of electrophilicity and ionization potential of the EPIs, the obtained average values are within in the range of 0.001414 AU ± 0.00032 and 0.208821 AU ± 0.015545, respectively. Interestingly, cathinone interacts with most of the efflux pumps among the tested inhibitors. The electrophilicity and ionization potential of cathinone are 0.00198 and 0.2388 AU, respectively. The study opens a new road for designing future-generation target-specific efflux pump inhibitors, as well as one molecule with multiple inhibition abilities.     

A Glycosylated Cationic Block Poly(β‐peptide) Reverses Intrinsic Antibiotic Resistance in All ESKAPE Gram‐Negative Bacteria

Carbapenem‐resistant Gram‐negative bacteria (GNB) are heading the list of pathogens for which antibiotics are the most critically needed. Many antibiotics are either unable to penetrate the outer‐membrane or are excluded by efflux mechanisms. Here, we report a cationic block β‐peptide (PAS8‐b‐PDM12) that reverses intrinsic antibiotic resistance in GNB by two distinct mechanisms of action. PAS8‐b‐PDM12 does not only compromise the integrity of the bacterial outer‐membrane, it also deactivates efflux pump systems by dissipating the transmembrane electrochemical potential. As a result, PAS8‐b‐PDM12 sensitizes carbapenem‐ and colistin‐resistant GNB to multiple antibiotics in vitro and in vivo. The β‐peptide allows the perfect alternation of cationic versus hydrophobic side chains, representing a significant improvement over previous antimicrobial α‐peptides sensitizing agents. Together, our results indicate that it is technically possible for a single adjuvant to reverse innate antibiotic resistance in all pathogenic GNB of the ESKAPE group, including those resistant to last resort antibiotics.