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991.
Yong-Chul Jang Pradeep Jain Thabet Tolaymat Brajesh Dubey Shrawan Singh 《The Science of the total environment》2010,408(8):1878-1887
The chemical characterization of sediments accumulated in catch basins and stormwater ponds provides important information for assessing risks associated with management of these residuals upon removal of accumulated deposits in stormwater systems. In this study, over a period of 15 months, more than 150 residual samples were collected from 77 catch basin units and 22 stormwater ponds from 16 municipalities throughout the state of Florida. Concentrations (mg/kg) of metals and metalloids (arsenic, barium, cadmium, chromium, copper, lead, mercury, nickel, selenium, silver, and zinc) and trace organics (volatile organics, semi-volatile organics, herbicides, and pesticides) in the sediments were measured. In addition, the synthetic precipitation leaching procedure (SPLP) was utilized to evaluate pollutant leachability risk for a subset of the samples collected. Measured pollutant concentrations were compared to corresponding risk-based guidelines in Florida (i.e., Florida soil cleanup target levels) to assess potential human health risks of beneficial use of these residuals through land application. Leached concentrations were compared to risk-based water quality guidelines (i.e., Florida groundwater cleanup target levels) to examine the potential for groundwater contamination. Although several metals (arsenic, barium, chromium, copper, nickel, lead, and zinc) were routinely detected in the catch basin and stormwater pond sediments, their concentrations were generally lower than the Florida's risk-based cleanup target levels for soils. A small number of organochlorine compounds (e.g., 4,4′-DDE, 4,4′-DDT) were detected, but only in a limited number of the samples (less than 10%); leaching of trace organic pollutants above the Florida risk-based groundwater thresholds was rare. The results suggest that when land-applied or beneficially used, these residuals are not expected to pose a significant threat to human health or the environment and the results of this research will provide stormwater managers and environmental management authorities with a useful resource to examine proper disposal and beneficial use of catch basin and stormwater pond sediments. 相似文献
992.
The aim of this research was to exploit the chemical properties of natural products to control the incidence and extent of mould growth in houses. The screening of antimould activities of seven essential oil extracts showed that most of the extracts completely inhibited the growth of all three test mould at the concentration of 1% w/v on nutrient medium, whereas, different fractions of manuka oil showed varied activity. Subsequently, using both mycological and scanning electron microscopy, the testing of selected extracts on two different types of gypsum board finished with either paint or wall-paper, confirmed the antimould activity of eugenol, thymol and cinnamaldehyde against Penicillium corylophilum. This study identified certain essential oil extract as a potential mould inhibitor for panel products which is one of the most common mould habitats in the building environment. Mould growth in residential houses is a major concern and chemical fungicides commonly used to control the growth of mould are not often appropriate for indoor applications. Natural alternatives such as essential oils are desirable for this application. Knowledge gained through this research should lead to new niche panel product development to create healthier housing. 相似文献
993.
The inhibition effect of all the three Mannich bases against the corrosion of mild steel in 1 M HCl solution was studied by
weight loss, electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, and atomic force microscopy techniques.
Data obtained from EIS studies were analyzed to model the corrosion inhibition process through appropriate equivalent circuit
models. The adsorption of Mannich bases obeyed Langmuir adsorption isotherm. Both thermodynamic and activation parameters
were calculated and discussed. Polarization curves indicate that they are mixed type of inhibitors. All the Mannich bases
were adsorbed physically at lower concentration, whereas chemisorption was favored at higher concentration. The results obtained
from weight loss, EIS, and Potentiodynamic polarization are in good agreement. 相似文献
994.
Polyaniline salt was synthesized through the chemical oxidation of aniline with sodium persulfate as the oxidant and didecyl ester of 4‐sulfophthalic acid via three different polymerization pathways (aqueous, emulsion, and interfacial). In these polymerization processes, the ester acted as a novel plast dopant and as an emulsifier. The yield, conductivity, and number of ester units present in the polyaniline salts were determined. A polyaniline salt prepared by emulsion polymerization was soluble in chloroform and showed excellent solution‐processing properties. Polyaniline samples prepared by aqueous or interfacial polymerization were not soluble in chloroform. A soluble polyaniline salt was successfully synthesized through the washing of an organic layer containing the polyaniline salt with water in emulsion polymerization. X‐ray diffraction spectra of polyaniline salts prepared by the three different methods showed an ordered, layer‐type supramolecular structure. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
995.
Shivendra Singh Chauhan Jayanta Chakraborty Sanjeev Kumar 《Chemical engineering science》2010,65(13):3914-3927
New benchmarks are used to test two classes of discretization methods available in the literature to solve bivariate population balance equations (2-d PBEs), and the applicability of these mean-field equations to finite size systems. The new benchmarks, different from the extensions of their 1-d counterparts, relate to prediction of kinetics of mixing in particle phase under: (i) pure aggregation of particles, called aggregative mixing, and (ii) simultaneous breakup and coalescence of drops. The discretization methods for 2-d PBEs, derived from the widely used 1-d solution methods, are first classified into two classes. We choose one representative method from each class. The results show that the extensions based on minimum consistency of discretization perform quite well with respect to both the new and the old benchmarks, in comparison with the geometrical extensions of 1-d methods. We next revisit aggregative mixing using Monte-Carlo simulations. The simulations show that (i) the time variation of the extent of mixing in finite size systems has power law scaling with the system size, and (ii) the mean-field PBEs fail to capture the evolution of mixing for reduced population of particles at long times. The sum kernel limits the applicability of PBEs to substantially larger particle populations than that seen for the constant kernel. Interestingly, these populations are orders of magnitude larger than those at which the PBEs fail to capture the evolution of total particle population correctly. 相似文献
996.
Does plant diversity drive soil microbial diversity in temperate, upland grasslands? Plants influence microbial activity around their roots by release of carbon and pot studies have shown an impact of different grass species on soil microbial community structure. Therefore it is tempting to answer yes. However, evidence from field studies is more complex. This evidence is reviewed at three different scales. First, studies from the plant community scale are considered that have compared soil microbial community structure in pastures of different vegetation composition, as a consequence of pasture improvement. These show fungi dominating the biomass in unimproved pastures and bacteria when lime and fertilizers have been applied. Secondly, evidence for interactions between individual grass species and soil microbes is discussed at the level of the rhizosphere, by considering both pot experiments and field studies. These have produced contrasting and inconclusive results, often due to spatial heterogeneity of soil properties and microbial communities. In particular, increased soil pH and fertility in urine patches and other nutrient cycling processes interact to increase the spatially complexity of soil microbial communities. Finally three studies which have measured microbial community structure in the rhizoplane are considered. These show that bacterial diversity is not directly related to plant diversity, although fungal diversity is. In addition, the soil fungal community has been demonstrated to have an effect upon the composition of the bacterial community. We suggest that while current vegetation influences fungal communities (particularly mycorrhizae) and litter inputs fungal saprotrophs, bacterial community structure is influenced more by the quality or composition of soil organic matter, thereby reflecting carbon inputs to the soil over decades. 相似文献
997.
Vipin Kumar Soniya Juneja Sachin K. Sharma V. Singh T. P. Sharma 《Journal of Coatings Technology and Research》2010,7(3):399-402
In the present investigation, the polycrystalline films of Cd
X
Zn1–X
S were prepared using a sintering technique. We coated slurry consisting of CdS, ZnS in the desired proportion—CdCl2 (as adhesive) and ethylene glycol (as binder)—onto the glass substrates. The films were sintered at a range of temperatures
in air atmosphere for the optimization of sintering temperatures using reflection spectroscopy. It was noticed that below
500°C, CdS-dominated films were obtained, and above 500°C, ZnS-dominated films were obtained. The films of desired composition
giving appropriate results are obtained at 500°C. The reason is easily understood through reflection spectroscopic studies.
Thus, we found 500°C to be the optimum sintering temperature and 10 min was the proper sintering time. 相似文献
998.
Vimal Singh 《Analog Integrated Circuits and Signal Processing》2010,62(3):327-332
Most textbooks on analog circuits and signal processing describe the Barkhausen criterion pertaining to the determination
of sinusoidal oscillations in a closed-loop system. On the other hand, the Nyquist stability criterion is well known, as discussed
in most textbooks on control systems. Recently, some examples in which the Barkhausen criterion fails to produce the correct
condition for startup of oscillations have been reported. In the present paper, an explanation of oscillation startup based
on the Nyquist stability criterion is given and the close relationship between the Barkhausen and the Nyquist criteria highlighted.
It is shown that the Nyquist criterion (which is a rigorous technique) is a more robust approach than the Barkhausen criterion
concerning the determination of sinusoidal oscillations in a closed-loop system and that the Barkhausen criterion (whenever
it yields the correct result) is subsumed by the Nyquist criterion as a special case. The textbooks usually describe the Barkhausen
criterion as a separate topic, i.e., do not discuss the relationship of this criterion with the Nyquist criterion. It is,
therefore, felt that the present discussion will go a long way to put the subject in a broader perspective. 相似文献
999.
Busson P. Chawla N. Bach J. Le Tual S. Singh H. Gupta V. Urard P. 《Solid-State Circuits, IEEE Journal of》2010,45(1):84-94
A digital channel multiplexer for satellite outdoor unit running at 1 GHz clock frequency is implemented in 65 nm CMOS mixed oxide dual voltage technology. This multiplexer, based on a 1 GS/s digital signal processor (DSP) approach with 500 MHz input and output bandwidth, embeds two 8 bit 1 GS/s analog-digital converters (ADCs) and two 8 bit 1 GS/s digital-analog converter (DACs). It consumes less that 1022 mW at ambient temperature while achieving noise rejection up to 42.5 dB on a single tone, and > 37 dB on modulated satellite channels. 相似文献
1000.
Prashant Singh Pradeep Kumar Anju Katyal Rashmi Kalra Sujata K. Dass Satya Prakash Ramesh Chandra 《Catalysis Letters》2010,134(3-4):303-308
In this present work, we report that phosphotungstic acid provides a simple, efficient and environmentally benign route is a two-component one-pot domino Knoevenagel-type condensation/Michael reaction between 4-coumarin derivative and an aldehyde in water as a solvent in shorter duration with high yields. 相似文献