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231.
Ayyalasomayajula KK Dikshit V Yueh FY Singh JP Smith LT 《Analytical and bioanalytical chemistry》2011,400(10):3315-3322
Laser-induced breakdown spectroscopy (LIBS) has been employed for the analysis of slurry samples. Quantitative analysis of
slurry samples is crucial and challenging. The problems associated with slurry samples include splashing, surface turbulence,
and the difficulties of obtaining reproducible samples due to sedimentation. The LIBS analysis has achieved limited success
due to inherent disadvantages when applied to slurry samples. In order to achieve improved measurement precision and accuracy,
a spin-on-glass sampling method was evaluated. Five elements (Al, Ca, Fe, Ni, and Si) were examined in five slurry simulants
containing varying amounts of each ion. Three calibration models were developed by using univariate calibration, multiple
linear regression, and partial least square regression. LIBS analysis results obtained from the partial least square regression
model were determined to be the best fit to results obtained from inductively coupled plasma optical emission spectroscopy
analysis. 相似文献
232.
Mohana Krishna Reddy Mudiam Rajeev Jain Virendra K. Dua Amit Kumar Singh V. P. Sharma R. C. Murthy 《Analytical and bioanalytical chemistry》2011,401(5):1699-1705
A simple and rapid analytical method based on in-matrix ethyl chloroformate (ECF) derivatization has been developed for the
quantitative determination of bisphenol-A (BPA) in milk and water samples. The samples containing BPA were derivatised with
ECF in the presence of pyridine for 20 s at room temperature, and the non-polar derivative thus formed was extracted using
polydimethylsiloxane solid-phase microextraction (SPME) fibres with thicknesses of 100 μm followed by analysis using gas chromatography–mass
spectrometry. Three alkyl chloroformates (methyl, ethyl and isobutyl chloroformate) were tested for optimum derivatisation
yields, and ECF has been found to be optimum for the derivatisation of BPA. Several parameters such as amount of ECF, pyridine
and reaction time as well as SPME parameters were studied and optimised in the present work. The limit of detection for BPA
in milk and water samples was found to be 0.1 and 0.01 μg L−1, respectively, with a signal-to-noise ratio of 3:1. The limit of quantitation for BPA in milk and water was found to be 0.38
and 0.052 μg L−1, respectively, with a signal-to-noise ratio of 10:1. In conclusion, the method developed was found to be rapid, reliable
and cost-effective in comparison to silylation and highly suitable for the routine analysis of BPA by various food and environmental
laboratories. 相似文献
233.
For a given set M of positive integers, a problem of Motzkin asks for determining the maximal density μ(M) among sets of nonnegative integers in which no two elements differ by an element of M. The problem is completely settled when |M|?2, and some partial results are known for several families of M for |M|?3, including the case where the elements of M are in arithmetic progression. We consider some cases when M either contains an arithmetic progression or is contained in an arithmetic progression. 相似文献
234.
Bose SK Geetharani K Sahoo S Reddy KH Varghese B Jemmis ED Ghosh S 《Inorganic chemistry》2011,50(19):9414-9422
The reaction of [Cp*TaCl(4)], 1 (Cp* = η(5)-C(5)Me(5)), with [LiBH(4)·THF] at -78 °C, followed by thermolysis in the presence of excess [BH(3)·THF], results in the formation of the oxatantalaborane cluster [(Cp*Ta)(2)B(4)H(10)O], 2 in moderate yield. Compound 2 is a notable example of an oxatantalaborane cluster where oxygen is contiguously bound to both the metal and boron. Upon availability of 2, a room temperature reaction was performed with [Fe(2)(CO)(9)], which led to the isolation of [(Cp*Ta)(2)B(2)H(4)O{H(2)Fe(2)(CO)(6)BH}], 3. Compound 3 is an unusual heterometallic boride cluster in which the [Ta(2)Fe(2)] atoms define a butterfly framework with one boron atom lying in a semi-interstitial position. Likewise, the diselenamolybdaborane, [(Cp*Mo)(2)B(4)H(4)Se(2)], 4 was treated with an excess of [Fe(2)(CO)(9)] to afford the heterometallic boride cluster [(Cp*MoSe)(2)Fe(6)(CO)(13)B(2)(BH)(2)], 5. The cluster core of 5 consists of a cubane [Mo(2)Se(2)Fe(2)B(2)] and a tricapped trigonal prism [Fe(6)B(3)] fused together with four atoms held in common between the two subclusters. In the tricapped trigonal prism subunit, one of the boron atoms is completely encapsulated and bonded to six iron and two boron atoms. Compounds 2, 3, and 5 have been characterized by mass spectrometry, IR, (1)H, (11)B, (13)C NMR spectroscopy, and the geometric structures were unequivocally established by crystallographic analysis. The density functional theory calculations yielded geometries that are in close agreement with the observed structures. Furthermore, the calculated (11)B NMR chemical shifts also support the structural characterization of the compounds. Natural bond order analysis and Wiberg bond indices are used to gain insight into the bonding patterns of the observed geometries of 2, 3, and 5. 相似文献
235.
Rao TR Krishna ChR Reddy ChV Thampy US Reddy YP Rao PS Ravikumar RV 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,79(5):1116-1122
Optical and physical properties of Ni2+ doped 20ZnO+xLi2O+(30-x)Na2O+50B2O3 (5≤x≤25) glasses are carried out at room temperature. Powder XRD pattern of all the glass samples confirms the amorphous nature. Several physical parameters are evaluated for all the glasses with respect to the composition. The optical absorption spectra confirm the site symmetry of the Ni2+ doped glasses are near octahedral. Crystal field and inter-electronic repulsion parameters are also evaluated. It is interesting to observe that the optical band gap and Urbach energies exhibit the mixed alkali effect. The FT-IR spectral investigations of Ni2+ doped glasses exhibit characteristic vibrations of BO3 and BO4 units. 相似文献
236.
Kumar KS Kumar PM Kumar KA Sreenivasulu M Jafar AA Rambabu D Krishna GR Reddy CM Kapavarapu R Shivakumar K Priya KK Parsa KV Pal M 《Chemical communications (Cambridge, England)》2011,47(17):5010-5012
Concurrent construction of five and six membered fused N-heretocyclic ring was achieved via a conceptually new three-component reaction affording 6,6a-dihydroisoindolo[2,1-a]quinazoline-5,11-diones as novel inhibitors of TNF-αin vitro. This represents one of the few examples of direct TNF-α inhibition by small molecules. 相似文献
237.
Sharma K Singh RV Fahmi N 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,78(1):80-87
A series of Pd(II) and Pt(II) complexes with two N(∩)S donor ligands, 5-chloro-3-(indolin-2-one)benzothiazoline and 6-nitro-3-(indolin-2-one)benzothiazoline, have been synthesized by the reaction of metal chlorides (PdCl2 and PtCl2) with ligands in 1:2 molar ratios. All the synthesized compounds were characterized by elemental analyses, melting point determinations and a combination of electronic, IR, 1H NMR and 13C NMR spectroscopic techniques for structure elucidation. In order to evaluate the effect of metal ions upon chelation, both the ligands and their complexes have been screened for their antimicrobial activity against the various pathogenic bacterial and fungal strains. The metal complexes have shown to be more antimicrobial against the microbial species as compared to free ligands. One of the ligands, 5-chloro-3-(indolin-2-one)benzothiazoline and its corresponding palladium and platinum complexes have been tested for their antifertility activity in male albino rats. The marked reduction in sperm motility and density resulted in infertility by 62-90%. Significant alterations were found in biochemical parameters of reproductive organs in treated animals as compared to control group. It is concluded that all these effects may finally impair the fertility of male rats. 相似文献
238.
Kokatam S Pandey D Gupta R Krishna R Soni R 《Combinatorial chemistry & high throughput screening》2011,14(8):703-709
Angiogenesis is a promising area of research that targets key therapeutic areas like cancer; wound healing, inflammatory diseases, etc. There is an increasing demand for screening of potential angiogenic and anti-angiogenic agents using sensitive, robust cell-based assays. We have developed a reporter vector containing cis-acting elements that respond to growth factors/angiogenic ligands for use in a cell-based luciferase reporter assay. We performed transient transfection of our reporter gene vector in MCF-7 cells to establish its application for screening of potential pro/anti-angiogenic agents. Reporter gene transactivation studies with different concentrations of fetal bovine serum clearly indicated that the vector is functionally responsive to the angiogenic signals mediated by serum growth factors. We also used endostatin to inhibit transactivation and prove responsiveness to the anti-angiogenic agent. This vector is a promising tool for studying angiogenesis using cell-based reporter gene assays. 相似文献
239.
Porous materials such as metal-organic frameworks (MOFs) and zeolitic imidazolate frameworks (ZIFs) offer considerable potential for separating a variety of mixtures such as those relevant for CO(2) capture (CO(2)/H(2), CO(2)/CH(4), CO(2)/N(2)), CH(4)/H(2), alkanes/alkenes, and hydrocarbon isomers. There are basically two different separation technologies that can be employed: (1) a pressure swing adsorption (PSA) unit with a fixed bed of adsorbent particles, and (2) a membrane device, wherein the mixture is allowed to permeate through a micro-porous crystalline layer. In view of the vast number of MOFs, and ZIFs that have been synthesized there is a need for a systematic screening of potential candidates for any given separation task. Also of importance is to investigate how MOFs and ZIFs stack up against the more traditional zeolites such as NaX and NaY with regard to their separation characteristics. This perspective highlights the potency of molecular simulations in determining the choice of the best MOF or ZIF for a given separation task. A variety of metrics that quantify the separation performance, such as adsorption selectivity, working capacity, diffusion selectivity, and membrane permeability, are determined from a combination of Configurational-Bias Monte Carlo (CBMC) and Molecular Dynamics (MD) simulations. The practical utility of the suggested screening methodology is demonstrated by comparison with available experimental data. 相似文献
240.
Pathik Sahoo Dr. D. Krishna Kumar Dr. Srinivasa R. Raghavan Dr. Parthasarathi Dastidar 《化学:亚洲杂志》2011,6(4):1038-1047
Easy access to a class of chiral gelators has been achieved by exploiting primary ammonium monocarboxylate ( PAM ), a supramolecular synthon. A combinatorial library comprising of 16 salts, derived from 5 l ‐amino acid methyl esters and 4 cinnamic acid derivatives, has been prepared and scanned for gelation. Remarkably, 14 out of 16 salts prepared (87.5 % of the salts) show moderate to good gelation abilities with various solvents, including commercial fuels, such as petrol. Anti‐solvent induced instant gelation at room temperature has been achieved in all the gelator salts, indicating that the gelation process is indeed an aborted crystallization phenomenon. Rheology, optical and scanning electron microscopy, small angle neutron scattering, and X‐ray powder diffraction have been used to characterize the gels. A structure‐property correlation has been attempted, based on these data, in addition to the single‐crystal structures of 5 gelator salts. Analysis of the FT‐IR and 1H NMR spectroscopy data reveals that some of these salts can be used as supramolecular containers for the slow release of certain pest sex pheromones. The present study clearly demonstrates the merit of crystal engineering and the supramolecular synthon approach in designing new materials with multiple properties. 相似文献