月桂酸纤维素酯的均相法合成

在纤维素LiCl/N,N-二甲基乙酰胺(DMAc)均相溶液体系中,以对甲苯磺酰氯(TosCl)为共反应剂,原位活化月桂酸,合成了月桂酸纤维素酯。采用红外光谱、核磁共振、热重等分析手段对产品进行了表征。考察了反应物配比、温度、时间等酯化条件对产品取代度的影响。结果表明:酯化产品的取代度与反应物纤维素葡萄糖苷、月桂酸和对甲苯磺酰氯的配比、反应温度及反应时间有关。在最佳酯化条件下,所得产品的取代度(DS)为2.58。热重分析结果表明,酯化反应削弱了纤维素分子间及分子内的作用力,赋予了月桂酸纤维素酯较好的热加工性。月桂酸纤维素酯在有机溶剂中的溶解度随取代度的增加而提高。     

Water recovery from treated urban wastewater by ultrafiltration and reverse osmosis for landscape irrigation

Techno-economic feasibility of water recovery from secondary effluents of an urban wastewater treatment plant (WWTP) for landscape irrigation was investigated considering two distinctive strategies: ultrafiltration (UF)/chlorination and UF/reverse osmosis (RO). Experimental performance evaluations were conducted separately for UF membranes and for different RO trans-membrane pressures. The quality of the effluent recovered by the UF/RO system was in accordance with the national and international guidelines. The produced reuse water was first class quality according to the national guideline for all parameters except sodium adsorption ratio (SAR), which can be eliminated readily by direct addition of KCl into the recovered water. Estimated field-scale costs indicated that UF/RO yielded a total cost of US$12,500,000–13,600,000 with annual operating cost being US$482,000–533,000 at 5–20 bar. The economic estimations guaranteed reimbursement with US$7,600,000–7,400,000 net present value, 0.22–0.39 year payback time, US$0.44–0.49/m³ treatment cost, and a benefit/cost ratio of 0.57.     

Determination of Transglutaminase Activity Using Fluorescence Spectrophotometer

An improved fluorometric assay for determining the activity of the microbial transglutaminase (TGase) in the culture medium samples has been developed. The assay procedure measures the fluorescence enhancement due to the incorporation of monodansyl cadaverine (Substrate A) into pentafluorophenylester of CBZ-Gln-Gly (Substrate Q) at λ_exc. 260 nm and λ_em 538 nm. The effect of the competitive inhibitors in the culture medium samples on TGase activity was determined. The assay was combined with HPLC method for determining enzyme activity as an international unit (IU). Enzymatic reaction was monitored by HPLC and the rate of product formation was measured via amine substrate consumption rate. A conversion factor was obtained using HPLC and fluorescence spectrophotometer data together. This was formulated for quantification of TGase activity as IU using fluorometric assay reported in this study. The detection limit of the assay was determined as 0.0014 IU (0.5 mg). TGase activity remained linear upto the enzyme concentraion of 20 mg. This technique dramatically decreases the incubation time of enzyme to a few minutes of activity measurement.     

Counterion-coupled gemini (Cocogem) surfactants based on dodecylisopropylol amine and dicarboxylic acids: synthesis,characterization and evaluation as biocide against SRB

New cocogem surfactants were synthesized by interaction of dodecylisopropylol amine with dicarboxylic (oxalic, succinic, adipic, sebacic, tartaric, maleic, fumaric, isophthalic) acids. By tensiometric method, the surface activity of aqueous solutions of the synthesized cocogem surfactants at the border with air was studied and, by conductometric method, the specific electrical conductivity of these solutions was determined. The degree of counterion binding (β), critical micelle concentration (CMC), effectiveness of surface tension reduction (π_CMC), surface excess concentration (Γ_max), area per molecule at the interface (A_min), changes of Gibbs free energies of adsorption (ΔG_ad) and micellization (ΔG_mic) have been calculated. The character of change of the colloidal-chemical indices depending on spacer-group nature and length has been clarified. So, with an elongation of the spacer group and when passing from cis-form to trans-form, the value of CMC decreases. The obtained cocogem surfactants exhibit a considerable bactericidal effectiveness against sulfate-reducing bacteria. The bactericide properties of the cocogem surfactants containing in the spacer chain a saturated hydrocarbon fragment and benzene ring are stronger than for the others.     

Effect of various sludge digestion conditions on sulfonamide, macrolide, and tetracycline resistance genes and class I integrons

Wastewater treatment processes are of growing interest as a potential means to limit the dissemination of antibiotic resistance. This study examines the response of nine representative antibiotic resistance genes (ARGs) encoding resistance to sulfonamide (sulI, sulII), erythromycin (erm(B), erm(F)), and tetracycline (tet(O), tet(W), tet(C), tet(G), tet(X)) to various laboratory-scale sludge digestion processes. The class I integron gene (intI1) was also monitored as an indicator of horizontal gene transfer potential and multiple antibiotic resistance. Mesophilic anaerobic digestion at both 10 and 20 day solids retention times (SRTs) significantly reduced sulI, suII, tet(C), tet(G), and tet(X) with longer SRT exhibiting a greater extent of removal; however, tet(W), erm(B) and erm(F) genes increased relative to the feed. Thermophilic anaerobic digesters operating at 47 °C, 52 °C, and 59 °C performed similarly to each other and provided more effective reduction of erm(B), erm(F), tet(O), and tet(W) compared to mesophilic digestion. However, thermophilic digestion resulted in similar or poorer removal of all other ARGs and intI1. Thermal hydrolysis pretreatment drastically reduced all ARGs, but they generally rebounded during subsequent anaerobic and aerobic digestion treatments. To gain insight into potential mechanisms driving ARG behavior in the digesters, the dominant bacterial communities were compared by denaturing gradient gel electrophoresis. The overall results suggest that bacterial community composition of the sludge digestion process, as controlled by the physical operating characteristics, drives the distribution of ARGs present in the produced biosolids, more so than the influent ARG composition.     

Nitric Oxide (NO) and Lactic Acid Bacteria-Contributions to Health, Food Quality, and Safety

In this article, the effects of nitric oxide (NO) and nitric oxide producer bacteria on food quality, safety, and human health care high lighted. NO, which was previously recognized as a toxic gas, has attracted attention in the last two decades due to its vital role in many physiological processes of animals and plants. Particularly, it is important to note from the point of view of food quality and safety that lactic acid bacteria, which are used as starter cultures in foods, also have the capability of producing NO. There have been several studies on the color development of meat products that originated from NO production of lactic acid bacteria. For this reason, it is also important to emphasize the different aspects of interactions between food and NO.     

Generating test data from state‐based specifications

Although the majority of software testing in industry is conducted at the system level, most formal research has focused on the unit level. As a result, most system‐level testing techniques are only described informally. This paper presents formal testing criteria for system level testing that are based on formal specifications of the software. Software testing can only be formalized and quantified when a solid basis for test generation can be defined. Formal specifications represent a significant opportunity for testing because they precisely describe what functions the software is supposed to provide in a form that can be automatically manipulated. This paper presents general criteria for generating test inputs from state‐based specifications. The criteria include techniques for generating tests at several levels of abstraction for specifications (transition predicates, transitions, pairs of transitions and sequences of transitions). These techniques provide coverage criteria that are based on the specifications and are made up of several parts, including test prefixes that contain inputs necessary to put the software into the appropriate state for the test values. The test generation process includes several steps for transforming specifications to tests. These criteria have been applied to a case study to compare their ability to detect seeded faults. Copyright © 2003 John Wiley & Sons, Ltd.     

Calibration of a silver thin film gauge for short duration convective step heat load

Thin film gauges (TFGs) are a promising candidate for measuring transient heat fluxes in the applications involving very short duration of heating environment. They are basically resistance temperature detectors (RTDs) having the capability of responding in the range of few microseconds. In the present study, a silver thin film gauge (STFG) is fabricated and calibrated in-house with a view to assess the performance of STFGs in dynamic environment. Convective heat load is supplied by a hot-air gun where the heated air jet strikes the gauge and its response is obtained through voltage signal. Subsequently, the surface heat fluxes are estimated by using one dimensional heat conduction modeling. The similar experimental environment is studied to obtain the flow behavior of hot-air jet emanating into atmosphere by using numerical simulations. The self-similar velocities are plotted as well as the interference of outer domain into the experiment parameters has been studied. Ultimately, the surface heat fluxes obtained from various methods are compared to analyse the performance of this hand-made STFG. This study reveals the ability of STFGs to be used in practical short duration transient situations.     

The Effect of Ductile-Lithic Sand Grains,Overpressure and Secondary Dissolution on Porosity and Permeability and Their Relevance to Hydrocarbon Exploration in Aşkale Sub-Basin,East Anatolia,Turkey

Ductile lithic grain, secondary porosity, temperature, and overpressure control porosity and permeability in the Mio-Pliocene and Upper Oligocene sandstones of the A?kale sub-basin in East Anatolia. Ductile lithic grains account for between approximately 60–90% of the original sand grain population. There is a pronounced loss of porosity with increasing bruial depth in this sub-basin. At depths of less than 3000 m, this is due solely to ductile-lithic grain compaction where the rate of porosity loss of with depth increases with increasing ductile-lithic grain content. But at depths greater than 3000 m, the steep porosity increases with depth due to secondary solution activities and overpressure in the A?kale sub-basin in East Anatolia. Secondary porosity is a common diagenetic feature in the more deeply buried (> 3000 m) sediments in the A?kale sub-basin. The secondary porosity arises principally from dissolution of feldspar, to a lesser extent, of the quartz (approximately 10–30%). Overpressure is due to tectonic stress. Reservoir quality is thus controlled by secondary solution activities, overpressure, temperature (geothermal gradient) and depth of burial in the A?kale sub-basin in East Anatolia Basin.