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11.
We present evidence for a nonsingular origin of the Universe with intial conditions determined by quantum physics and relativistic
gravity. In particular, we establish that the present temperature of the microwave background and the present density of the
Universe agree well with our predictions from these intial conditions, after evolution to the present age using the Einstein-Friedmann
equation. Remarkably, the quantum origin for the Universe naturally allows its evolution at exactly the critical density.
We also discuss the consequences of these results to some fundamental aspects of quantum physics in the early Universe. 相似文献
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Reductions of 2-substituted quinoline--boranes by sodium bis-(2-methoxyethoxy)aluminum dihydride lead to 1,2,3,4-tetrahydroquinolines by hydride attack at C-4 and subsequent reduction of the resulting enamine. 相似文献
14.
Bhidayasiri R Bronstein JM Sinha S Krahl SE Ahn S Behnke EJ Cohen MS Frysinger R Shellock FG 《Magnetic resonance imaging》2005,23(4):549-555
Deep brain stimulation (DBS) is used increasingly in the field of movement disorders. The implanted electrodes create not only a prior risk to patient safety during MRI, but also a unique opportunity in the collection of functional MRI data conditioned by direct neural stimulation. We evaluated MRI-related heating for bilateral neurostimulation systems used for DBS with an emphasis on assessing clinically relevant imaging parameters. Magnetic resonance imaging was performed using transmit body radiofrequency (RF) coil and receive-only head RF coil at various specific absorption rates (SARs) of RF power. In vitro testing was performed using a gel-filled phantom with temperatures recorded at the electrode tips. Each DBS electrode was positioned with a single extension loop around each pulse generator and a single loop at the "head" end of the phantom. Various pulse sequences were used for MRI including fast spin-echo, echo-planar imaging, magnetization transfer contrast and gradient-echo techniques. The MRI sequences had calculated whole-body averaged SARs and local head SARs ranging from 0.1 to 1.6 W/kg and 0.1 to 3.2 W/kg, respectively. Temperature elevations of less than 1.0 degrees C were found with the fast spin-echo, magnetization transfer contrast, gradient-echo and echo-planar clinical imaging sequences. Using the highest SAR levels, whole-body averaged, 1.6 W/kg, local exposed-body, 3.2 W/kg, and local head, 2.9 W/kg, the temperature increase was 2.1 degrees C. These results showed that temperature elevations associated with clinical sequences were within an acceptable physiologically safe range for the MR conditions used in this evaluation, especially for the use of relatively low SAR levels. Notably, these findings are highly specific to the neurostimulation systems, device positioning technique, MR system and imaging conditions used in this investigation. 相似文献
15.
Ventura GT Hall GJ Nelson RK Frysinger GS Raghuraman B Pomerantz AE Mullins OC Reddy CM 《Journal of chromatography. A》2011,1218(18):2584-2592
The accurate establishment of oil similarity is a longstanding problem in petroleum geochemistry and a necessary component for resolving the architecture of an oil reservoir. Past limitations have included the excessive reliance on a relatively small number of biomarkers to characterize such complex fluids as crude oils. Here we use multiway principal components analysis (MPCA) on large numbers of specific chemical components resolved with comprehensive two-dimensional gas chromatography-flame ionization detection (GC×GC-FID) to determine the molecular relatedness of eight different maltene fractions of crude oils. MPCA works such that every compound eluting within the same first and second dimension retention time is quantitatively compared with what elutes at that same retention times within the other maltene fractions. Each maltene fraction and corresponding MPCA analysis contains upwards of 3500 quantified components. Reservoir analysis included crude oil sample pairs from around the world that were collected sequentially at depth within a single well, collected from multiple depths in the same well, and from different depths and different wells but thought to be intersected by the same permeable strata. Furthermore, three different regions of each GC×GC-FID chromatograms were analysed to evaluate the effectiveness of MPCA to resolve compositional changes related to the source of the oil generating sediments and its exposure to biological and/or physical weathering processes. Compositional and instrumental artefacts introduced during sampling and processing were also quantitatively evaluated. We demonstrate that MPCA can resolve multi-molecular differences between oil samples as well as provide insight into the overall molecular relatedness between various crude oils. 相似文献
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Comprehensive two-dimensional gas chromatography coupled with mass spectrometric detection (GC × GC/MS) is a three-dimensional analytical method. In its application to petroleum analysis, the high peak capacity of GC × GC produced chromatographic resolution of over 750 peaks from a marine diesel fuel. The MS detector provided a full-scan mass spectrum for each resolved peak. The integration of an MS detector with GC × GC provides increased capability to identify minor components, determine members of homologous series, and characterize ordered peak patterns of related components that are visible in the GC × GC chromatogram. 相似文献