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121.
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A novel noble-gas compound, HXeOXeH, is identified using IR spectroscopy, and it seems to be the smallest known neutral molecule with two noble-gas atoms. HXeOXeH is prepared using, for example, UV photolysis of water in solid xenon and subsequent annealing at 40-45 K. The experimental observations are fully supported by extensive quantum chemical calculations. A large energy release of 8.3 eV is computationally predicted for the decomposition of HXeOXeH into the 2Xe + H2O global energy minimum. HXeOXeH may represent a first step toward the possible preparation of (Xe-O)n chains and it may be relevant to the terrestrial "missing xenon" problem.  相似文献   
123.
A rapid and accurate method for measuring low part-per-million levels of free and reversibly-bound sulfites in selected foods by using high-performance liquid chromatography (HPLC) with fluorometric detection was developed. Sulfites were extracted with sodium tetrachloromercurate solution and determined by HPLC-fluorescence spectrometry. During the HPLC analysis, the sample extract was reacted with sodium hydroxide to liberate the reversibly-bound sulfite and subsequently separated from other interferences by a size exclusion column. The effluent was then reacted with o-phthalaldehydelammonium chloride reagent to form a fluorescing 1-sulfonatoisoindole derivative and analyzed by a fluorescence detector. The method has been applied to a variety of foods and food products, with no significant interference encountered in matrixes such as soy products, cabbage, broccoli, brassica, ginger, fungus, mushroom, mandarin peel, potato chips, and biscuits. It was shown to have a broad linear range of 0.01 to 0.4 mg/L as SO2. The spike recoveries of sodium sulfite, sodium metabisulfite, and formaldehyde-sodium bisulfite adduct at the 5 to 10 mg/kg level in the tested food matrix were within 80-120%, and the limit of detection was 5 mg/kg. Laboratory of Government Chemist Reference Material LGC7111 (potato powder) was used to assess the accuracy of the method. The expanded measurement uncertainty of the method at 95% confidence level was estimated to be 17%.  相似文献   
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Colloidal silica gels are shown to stiffen with time, as demonstrated by both dynamic light scattering and bulk rheological measurements. Their elastic moduli increase as a power law with time, independent of particle volume fraction; however, static light scattering indicates that there are no large-scale structural changes. We propose that increases in local elasticity arising from bonding between neighboring colloidal particles can account for the strengthening of the network, while preserving network structure.  相似文献   
126.
We have calculated frequencies and intensities of fundamental and overtone vibrational transitions in water and water dimer with use of different vibrational methods. We have compared results obtained with correlation-corrected vibrational self-consistent-field theory and vibrational second-order perturbation theory both using normal modes and finally with a harmonically coupled anharmonic oscillator local mode model including OH-stretching and HOH-bending local modes. The coupled cluster with singles, doubles, and perturbative triples ab initio method with augmented correlation-consistent triple-zeta Dunning and atomic natural orbital basis sets has been used to obtain the necessary potential energy and dipole moment surfaces. We identify the strengths and weaknesses of these different vibrational approaches and compare our results to the available experimental results.  相似文献   
127.
Carbon‐based nanomaterials have garnered a lot of attention in the research of yesteryear. Here this study reports a composite based on fluorinated graphene oxide—a multifunctional subsidiary of graphene; and iron oxide nanoparticles as a contrast agent for magnetic resonance imaging (MRI). Extensive structural and functional characterization is carried out to understand composite behavior toward biotoxicity and its performance as a contrast agent. The electron withdrawing fluorine group decreases the charge transfer to iron oxide increasing the magnetic saturation of the composite thus enhancing the contrast. The interaction of paramagnetic and superparamagnetic systems yields a superior contrast agent for MRI and fluorescent imaging.  相似文献   
128.
Let G be a graph on n vertices in which every induced subgraph on vertices has an independent set of size at least . What is the largest so that every such G must contain an independent set of size at least q? This is one of the several related questions raised by Erd?s and Hajnal. We show that , investigate the more general problem obtained by changing the parameters s and t, and discuss the connection to a related Ramsey‐type problem. © 2007 Wiley Periodicals, Inc. J Graph Theory 56: 149–157, 2007  相似文献   
129.
This study covers a new method and related instrumentation for whole blood analysis for medical diagnostics. Two-μL whole blood samples were collected using “minimal invasive” diabetes lancet and placed on a thin glass rod mounted on a newly designed BloodProbe. The BloodProbe with the whole blood sample was inserted directly into a ChromatoProbe mounted on the GC inlet, and thus, no sample preparation was involved. The analysis was performed within 10 min using a GC-MS with Cold EI that is based on interfacing GC and MS with supersonic molecular beams (SMB) along with electron ionization of vibrationally cold sample compounds in the SMB (hence the name Cold EI). Our blood analysis revealed several observations: (1) Detailed mass chromatograms were generated with full range of all the nonpolar lipids in blood including fatty acids, cholesterol, cholesteryl esters, vitamin E, monoglycerides, diglycerides, and triglycerides. (2) The analysis of whole blood was found to be as informative as the conventional clinical analysis of blood serum. (3) Cholesteryl esters were more sensitive than free cholesterol alone to the effect of diet of obese people. (4) Major enhancement of several fatty acid methyl esters was found in the blood of a cancer patient with liver dysfunction. (5) Vitamin E as both α- and β-tocopherol was found with person-dependent ratio of these two compounds. (6) Elemental sulfur S8 was identified in blood. (7) Several drugs and other compounds were found and need further study of their correlation to medical issues.  相似文献   
130.
We present an efficient scheme to evaluate the [ 0 ](m) integrals that arise in many ab initio quantum chemical two-electron integral algorithms. The total number of floating-point operations (FLOPS ) required by the scheme has been carefully minimized, both for cases where multipole expansions of the integrals are admissable and for cases where this is not so. The algorithm is based on the use of a modified Chebyshev interpolation formula to compute the function exp(?T) and the integral Fm(T) = ∫01u2mexp(?Tu2) du very cheaply.  相似文献   
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