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Percent Deviation (percent + deviation)

Distribution by Scientific Domains

Chemistry	50%

Selected Abstracts

Solvent effects on kinetics of an aromatic nucleophilic substitution reaction in mixtures of an ionic liquid with molecular solvents and prediction using artificial neural networks

INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 3 2009
Aziz Habibi-Yangjeh
Kinetics of the reaction between 1-chloro-2,4-dinitrobenzene and aniline was studied in mixtures of 1-ethyl-3-methylimidazolium ethylsulfate ([EMIM][EtSO4]) with methanol, chloroform, and dimethylsulfoxide at 25°C. Single-parameter correlations of log kA versus normalized polarity parameter (ENT), hydrogen-bond acceptor basicity (,), hydrogen-bond donor acidity (,), and dipolarity/polarizability (,*) of media do not give acceptable results. Multiparameter linear regression (MLR) of log kA versus the solvatochromic parameters demonstrates that the reaction rate constant increases with ENT, ,*, and , and decreases with , parameter. To predict accurately solvent effects on the rate constant, optimized artificial neural network with three inputs (including ,, ,*, and , parameters) was applied for prediction of the log kA values in the prediction set. It was found that properly selected and trained neural network could fairly represent the dependence of the reaction rate constant on solvatochromic parameters. Mean percent deviation of 5.023 for the prediction set by the MLR model should be compared with the value of 0.343 by the artificial neural network model. These improvements are due to the fact that the reaction rate constant shows nonlinear correlations with the solvatochromic parameters. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 41: 153,159, 2009 [source]

Parametric studies for heating performance of an earth to air heat exchanger coupled with a greenhouse

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 11 2005
M. K. Ghosal
Abstract A thermal model has been developed to investigate the potential of using the stored thermal energy of the ground for greenhouse heating with the help of an earth to air heat exchanger (EAHE) system integrated with the greenhouse located in the premises of IIT, Delhi, India. Experiments were conducted extensively during the winter period from November 2002 to March 2003, but the model developed was validated against the clear and sunny days. Parametric studies performed for EAHE coupled with the greenhouse illustrate the effects of buried pipe length, pipe diameter, mass flow rate of air, depth of ground and soil types on greenhouse air temperatures. Temperatures of greenhouse air with the experimental parameters of EAHE were found to be on an average 7,8°C more in the winter than the same greenhouse without EAHE. Greenhouse air temperatures increase in the winter with increasing pipe length, decreasing pipe diameter, decreasing mass flow rate of flowing air inside buried pipe and increasing depth of ground up to 4 m. Predicted and measured values of greenhouse air temperature, which were verified in terms of root mean square of percent deviation and correlation coefficient, exhibited fair agreement. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Potentials of ion trap collisional spectrometry for liquid chromatography/electrospray ionization tandem mass spectrometry determination of buprenorphine and nor -buprenorphine in urine, blood and hair samples

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 8 2006
Donata Favretto
A liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) method has been developed for the analysis of buprenorphine (BUP) and nor -buprenorphine (NBUP) in biological fluids. Analytes are isolated from urine and blood, after addition of d4 -buprenorphine (d4 -BUP) as internal standard, by solid-phase extraction. Preparation of hair involves external decontamination, mechanical pulverization, overnight incubation in acidic medium, and neutralization prior to extraction. Enzymatic hydrolysis with , -glucuronidase may be performed to distinguish between free and total BUP. Chromatographic separation is accomplished by gradient elution on a cyanopropyl 2.1,×,150,mm column. Positive ion ESI and MS analyses are carried out in an ion trap mass spectrometer. The use of this mass analyzer allows effective collisional experiments to be performed on ESI-generated MH+ species. Abundant product ions are produced, which can be monitored together with precursor ions without losing sensitivity. Thus, assay selectivity is definitely increased with respect to LC/ESI-MS/MS methods in which only precursor ions are monitored. The method has good linearity (calibration curves were linear in the range 0.1,10,ng/mL in urine and blood, in the range 10,160,pg/mg in hair) and limits of detection of 0.05,ng/mL for both BUP and NBUP in blood and urine samples, of 4,pg/mg for both analytes in hair. Both intra- and inter-assay precision and accuracy were satisfactory at three concentrations studied: relative standard deviations were <13.7% in urine, <17.3% in blood, <17.8% in hair; percent deviation of the mean from the true value was always <10.5% in urine and blood, <16.1% in hair. The method can be used to determine both analytes in the urine and hair of drug addicts on replacement therapy, and in post-mortem blood specimens when there is suspicion of drug-related death. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Characterization of electrochemically active bacteria utilizing a high-throughput voltage-based screening assay

BIOTECHNOLOGY & BIOENGINEERING, Issue 2 2009
Justin Biffinger
Abstract Metal reduction assays are traditionally used to select and characterize electrochemically active bacteria (EAB) for use in microbial fuel cells (MFCs). However, correlating the ability of a microbe to generate current from an MFC to the reduction of metal oxides has not been definitively established in the literature. As these metal reduction assays may not be generally reliable, here we describe a four- to nine-well prototype high throughput voltage-based screening assay (VBSA) designed using MFC engineering principles and a universal cathode. Bacterial growth curves for Shewanella oneidensis strains DSP10 and MR-1 were generated directly from changes in open circuit voltage and current with five percent deviation calculated between each well. These growth curves exhibited a strong correlation with literature doubling times for Shewanella indicating that the VBSA can be used to monitor distinct fundamental properties of EAB life cycles. In addition, eight different organic electron donors (acetate, lactate, citrate, fructose, glucose, sucrose, soluble starch, and agar) were tested with S. oneidensis MR-1 in anode chambers exposed to air. Under oxygen exposure, we found that current was generated in direct response to additions of acetate, lactate, and glucose. Biotechnol. Bioeng. 2009;102: 436,444. © 2008 Wiley Periodicals, Inc. [source]