Peracetic acid‐enhanced photocatalytic and sonophotocatalytic inactivation of E. coli in aqueous suspensions

BACKGROUND: Although chlorination is an effective and widely employed method of water disinfection, it suffers serious drawbacks such as the formation of toxic chlorinated by‐products. Therefore, other disinfection technologies have been researched and developed, including advanced oxidation. RESULTS: The efficacy of heterogeneous photocatalysis and sonophotocatalysis induced by UV‐A irradiation and low frequency (24–80 kHz) ultrasound irradiation in the presence of TiO₂ as the photocatalyst and peracetic acid (PAA) as an additional disinfectant to inactivate E. coli in sterile water was evaluated. PAA‐assisted UV‐A/TiO₂ photocatalysis generally leads to nearly complete E. coli inactivation in 10–20 min of contact time with the extent of inactivation depending on the photocatalyst type and loading (in the range 100–500 mg L^?1) and PAA concentration (in the range 0.5–2 mg L^?1). The simultaneous application of ultrasound and UV‐A irradiation in the presence of TiO₂ and PAA prompted further E. coli inactivation. CONCLUSIONS: The proposed advanced disinfection technology offers complete E. coli inactivation at short treatment times and low PAA doses. Copyright © 2010 Society of Chemical Industry     

标准与市场

“曾经，专业市场为中国纺织服装行业的发展出了大力气。但是现在．专业市场越来越多．重复建设、不正当竞争等问题却也屡见不鲜。专业市场的量上来了，质却还停滞不前。大多数专业市场的影响力只限于很小的一个地理范围，能在全国范围内产生影响的专业市场少之又少。如此的小打小闹．一方面无法支撑专业市场的发展，另方面使得业内外及消费者对专业市场的偏见越来越深。很多人认为，专业市场就是卖低档货的地方，其实不然。真正的专业市场，是为有实力的企业、包括品牌企业的流通和形象宣传服务的，为生产企业与商贸。DIL通企业的沟通和交易提供场所。所以．规范专业市场的问题就显得很迫切。”采访中．中国纺织品商业协会彭桂福会长的焦急之情溢于言表。     

Ultrafine 316 L stainless steel particles with frozen-in magnetic structures characterized by means of electron backscattered diffraction

Electron Backscatter Diffraction (EBSD) studies clearly revealed a different crystallographic structure of the smallest particle size fraction of gas-atomized AISI 316 L stainless steel powder (< 4 μm) compared with larger sized fractions of the same powder (< 45 μm). Despite similar chemical compositions, the predominating structure of the smallest particle size fraction was ferritic (i.e., has ferromagnetic properties) whereas the larger sized particle fractions and massive 316 L revealed an expected austenitic and non-magnetic structure. From these findings, it follows that direct magnetic separation can be applied to separate very fine sized particles. These structural differences explain previously observed dissimilarities from corrosion and metal release perspectives.     

Chemical composition, mineral content and antioxidant activity of Verbena officinalis L.

Aqueous and hydroalcoholic extracts from Verbena officinalis L. were obtained and characterised. The analysis by HPLC-DAD and LC-MS allowed the detection and identification of three iridoids, fifteen flavonoids and four phenolic acid derivatives. Four flavonoids, scutellarein 7-diglucuronide (9), scutellarein 7-glucuronide (13), pedalitin 6-galactoside (15) and scutellarein 7-glucoside (19) are reported for the first time from this plant. In addition, three new flavonoids have been isolated: scutellarein 7-O-(2-O-feruloyl)-diglucuronide (5), pedalitin 6-O-diglucuronide (6) and pedalitin 6-O-(2-O-feruloyl)-diglucuronide (13). To our knowledge, these flavonoids have not been reported as natural products. Both extracts showed significant antioxidant activity using three in vitro model systems and the results have been correlated with total phenolic and total flavonoid contents. The results have allowed establishing an important relation structure-activity and significant correlations have also been found between the mineral content and the flavonoids present in both extracts.     

An experimental investigation of the combustion of technical tetrachlorobenzene in a laboratory scale incinerator

An experimental study of the combustion of technical 1,2,3,4-tetrachlorobenzene has been carried out in conditions closely similar to those in incinerators of industrial hazardous wastes. A non-premixed flame fed by a fuel spray was stabilized in a reactor heated electrically. Measurements of axial and radial temperatures and species concentration profiles in well-defined conditions have been systematically repeated to specify the influence exerted by key parameters on the efficiency of the thermal degradation process. The reactor’s wall temperature was varied from 1223 to 1363 K. Air injection was distributed between axial and peripheral injectors to change the swirl intensity. Two fuel injectors have been compared to assess the influence of atomization efficiency. A methane-air pilot flame helped to anchor the flame and to decrease the overall Cl/H ratio. The latter was also decreased by addition of water vapor. Results show that conditions leading to a complete consumption of the fuel can be associated with very limited carbon conversion into CO₂ and chlorine conversion into HCl.     

Structural Test Approach for Embedded Analog Circuits Based on a Built-in Current Sensor

This paper presents a test method based on the analysis of the dynamic power supply current, both quiescent and transient, of the circuit under test. In an off-chip measurement, the global interconnect impedance associated with the chip package and the test equipment and, also, the chip input/output cells will complicate the extraction of the information provided by the current waveform of the circuit under test. Thus, the supply current is measured on-chip by a built-in current sensor integrated in the die itself. To avoid the effective reduction of the voltage supply, the measurement is performed in parallel by replicating the current that flows through selected branches of the analog circuit. With the aim of reducing the test equipment requirements, the built-in current sensor output generates digital level pulses whose width is related to the amplitude and duration of the circuit current transients. In this way the defective circuit is exposed by comparing the digital signature of the circuit under test with the expected one for the fault-free circuit. A fault evaluation has been carried out to check the efficiency of the proposed test method. It uses a fault model that considers catastrophic and parametric faults at transistor level. Two benchmark circuits have been fabricated to experimentally verify the defect detection by the built-in current sensor. One is an operational amplifier; the other is a structure of switched current cells that belongs to an analog-to-digital converter.     

Specific detection of viable Listeria monocytogenes in Spanish wastewater treatment plants by Fluorescent In Situ Hybridization and PCR

Listeria monocytogenes detection in wastewater can be difficult because of the large amount of background microbiota and the presence of viable but non-culturable forms in this environment. The aim of this study was to evaluate a Fluorescent In Situ Hybridization (FISH) assay combined with Direct Viable Count (DVC) method for detecting viable L. monocytogenes in wastewater samples, as an alternative to conventional culture methods. 16S rRNA sequence data were used to design a specific oligonucleotide probe. In order to assess the suitability of the method, the assays were performed on naturally (n = 87) and artificially (n = 14) contaminated samples and results were compared to those obtained with the isolation of cells on selective media and with a PCR method. The detection limit of FISH and PCR assays was 10⁴ cells/mL without enrichment and 10 cells/mL after enrichment. A total of 47 samples, including 3 samples from effluent sites, yielded FISH positive results for L. monocytogenes. Using DVC-FISH technique, the presence of viable L. monocytogenes cells was detected in 23 out of these 47 FISH positive wastewater samples. PCR and culture methods yielded 27 and 23 positive results, respectively. According to these results, FISH technique has the potential to be used as a sensitive method for the detection and enumeration of L. monocytogenes in environmental wastewater samples.     

Viability assessment of lactic acid bacteria in commercial dairy products stored at 4 °C using LIVE/DEAD® BacLightTM staining and conventional plate counts

The viability of lactic acid bacteria (LAB) from commercial fermented milks was studied during storage at 4 °C. The enumeration of total viable bacteria was assessed using fluorescence microscopy. Plate counting on selective media was used to enumerate LAB. Using LIVE/DEAD® BacLight^TM viability staining, it was observed that bacterial counts decreased gradually after expiry dates, the number of viable bacteria remaining above 10⁶ bacteria g^?1 for all of the products. Viable cell counts estimated by plating onto selective media were lower than those obtained by direct microscopic counting. The viability of LAB contained in acid products decreased during their storage period at 4 °C. All products contain viable LAB ranging from 10⁸ to 10⁹ bacteria g^?1 and could be considered as probiotic, given that the recommended minimum number of probiotic bacteria in such food products is approximately 10⁷ bacteria mL^?1 product. The number of bifidobacteria in commercial fermented milks declared to contain bifidobacteria varied from 10⁴ to 10⁷ bacteria mL^?1. This study confirms the usefulness of fluorescent techniques for a rapid and accurate evaluation of bacterial viability in probiotic products.     

Computational approach to the rational design of molecularly imprinted polymers for voltammetric sensing of homovanillic acid

A methodology based on density functional theory calculations for the design of molecularly imprinted polymers (MIPs) is described. The method allows the rational choice of the most suitable monomer and polymerization solvent among a set of chemicals traditionally used in MIP formulations for the molecular imprinting of a given template. It is based on the comparison of the stabilization energies of the prepolymerization adducts between the template and different functional monomers. The effect of the polymerization solvent is included using the polarizable continuum model. A voltammetric sensor for homovanillic acid was constructed using different MIPs as recognition element, confirming that the solvent (toluene) and functional monomer (methacrylic acid) selected according to the theoretical predictions lead to the most efficient molecular recognition sensing phase. With the voltammetric sensor prepared using the MIP designed according to the theoretical predictions, a linear response for concentrations of homovanillic acid between 5 x 10(-8) and 1 x 10(-5) M can be obtained. The limit of detection is 7 x 10(-9) M. The selectivity obtained for homovanillic acid over other structurally related compounds buttresses the validity of this strategy of design.     

Analysis of liquid-phase chemical detection using guided shear horizontal-surface acoustic wave sensors

Direct chemical sensing in liquid environments using polymer-guided shear horizontal surface acoustic wave sensor platforms on 36 degrees rotated Y-cut LiTaO3 is investigated. Design considerations for optimizing these devices for liquid-phase detection are systematically explored. Two different sensor geometries are experimentally and theoretically analyzed. Dual delay line devices are used with a reference line coated with poly (methyl methacrylate) (PMMA) and a sensing line coated with a chemically sensitive polymer, which acts as both a guiding layer and a sensing layer or with a PMMA waveguide and a chemically sensitive polymer. Results show the three-layer model provides higher sensitivity than the four-layer model. Contributions from mass loading and coating viscoelasticity changes to the sensor response are evaluated, taking into account the added mass, swelling, and plasticization. Chemically sensitive polymers are investigated in the detection of low concentrations (1-60 ppm) of toluene, ethylbenzene, and xylenes in water. A low-ppb level detection limit is estimated from the present experimental measurements. Sensor properties are investigated by varying the sensor geometries, coating thickness combinations, coating properties, and curing temperature for operation in liquid environments. Partition coefficients for polymer-aqueous analyte pairs are used to explain the observed trend in sensitivity for the polymers PMMA, poly(isobutylene), poly(epichlorohydrin), and poly(ethyl acrylate) used in this work.