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1.
A new and general synthesis of 2,5-dioxopiperazine condensed with the thiazolidine ring is described. The synthesis involves the use of N-ethoxy carbonyl-2-ethoxy-1-2-dihydroquinoleine (EEDQ) as activating agent to form the 2,5-diketopiperazine (EEDQ) as activating agent to form the 2,5-diketopiperazine ring. By this method 9-carbobutoxy-7,7-dimethyl-2,5-dioxo-8-this-1,4-diazabicyclo[4.3.0] nonane (6) and 9-carboxy-8,8 dimethyl-2,5-dioxo-7-thia-1,4-diazabicy clo [4.3.0] nonane (8) were obtained, with near quantitative yield, from 4-carboxy-2-carbobutoxy-5,5 dimethylthiazolidine (4). The former was transformed into acid 7 by hydrolysis with barium bydroxyde and the latter was esterified with diazornethane thus producing a methylester 9. The use of the ethy lester of N-(2-cabobutoxy-4-carboxy-5,5-dimethyl-thiazolidine)glycine (10) for synthesis of 6 was also successful. The spectromethric data were interpreted and confirm the proposed structure of the new compounds. 相似文献
2.
The resolved structure of the lowest-energy oxo to osmium charge-transfer absorption band of trans-[OsO2(malonate)2]2- is analyzed on the basis of the exact molecular Ci symmetry determined from the structure of a crystal used for spectroscopy. The multiple progressions observed in the polarized spectra are rationalized in terms of the deviations from idealized D4h point group symmetry and compared to the spectra observed for complexes with D2h symmetry such as trans-[OsO2(oxalate)2]2- that show only a single dominant progression for this transition. 相似文献
3.
We apply a recent result of Borichev–Golinskii–Kupin on the Blaschke-type conditions for zeros of analytic functions on the complex plane with a cut along the positive semi-axis to the problem of the eigenvalues distribution of the Fredholm-type analytic operator-valued functions. 相似文献
4.
Philippe Pinel Bertrand Thirion Sébastien Meriaux Antoinette Jobert Julien Serres Denis Le Bihan Jean-Baptiste Poline Stanislas Dehaene 《BMC neuroscience》2007,8(1):91
Background
Although cognitive processes such as reading and calculation are associated with reproducible cerebral networks, inter-individual variability is considerable. Understanding the origins of this variability will require the elaboration of large multimodal databases compiling behavioral, anatomical, genetic and functional neuroimaging data over hundreds of subjects. With this goal in mind, we designed a simple and fast acquisition procedure based on a 5-minute functional magnetic resonance imaging (fMRI) sequence that can be run as easily and as systematically as an anatomical scan, and is therefore used in every subject undergoing fMRI in our laboratory. This protocol captures the cerebral bases of auditory and visual perception, motor actions, reading, language comprehension and mental calculation at an individual level. 相似文献5.
Microwave heating methods have been combined with the use of solid-supported catalysts to produce small solution-phase libraries of medicinally-relevant compounds. Palladium supported on charcoal (Pd/C) has been used to produce libraries of pyrazole compounds for screening in COX II studies via Suzuki cross coupling reactions, while the same catalyst has been used also to produce styryl-based nAChR compounds using analogous chemistry. Although the reaction substrates are very different (aryl vs. vinyl), this catalyst system provided consistently good and reliable results. The use of a polystyrene-supported Ru catalyst for ring-closing metathesis (RCM) reactions was also evaluated to prepare benzolactam structures for evaluation as factor Xa inhibitors. 相似文献
6.
Stanislas Vertu Jens Flügge Jean-Jacques Delaunay Olivier Haeberlé 《Central European Journal of Physics》2011,9(4):969-974
Tomographic Diffractive Microscopy is a technique, which permits to image transparent living specimens in three dimensions
without staining. It is commonly implemented in two configurations, by either rotating the sample illumination keeping the
specimen fixed, or by rotating the sample using a fixed illumination. Under the first-order Born approximation, the volume
of the frequency domain that can be mapped with the rotating illumination method has the shape of a “doughnut”, which exhibits
a so-called “missing cone” of non-captured frequencies, responsible for the strong resolution anisotropy characteristic of
transmission microscopes. When rotating the sample, the resolution is almost isotropic, but the set of captured frequencies
still exhibits a missing part, the shape of which resembles that of an apple core. Furthermore, its maximal extension is reduced
compared to tomography with rotating illumination. We propose various configurations for tomographic diffractive microscopy,
which combine both approaches, and aim at obtaining a high and isotropic resolution. We illustrate with simulations the expected imaging performances of these configurations. 相似文献
7.
In this work, we study the following nonlinear homogeneous Neumann boundary value problemβ (u) -diva (x, 7u) f in fΩ, a (x, u). η= 0 on Ω, where Ω is a smooth bounded open domain in RN, N ≥ 3 with smooth boundary Ωand ηthe outer unit normal vector on Ω . We prove the existence and uniqueness of an entropy solution for L1-data f. The functional setting involves Lebesgue and Sobolev spaces with variable exponent. 相似文献
8.
Abstract The dimerization by hetero Diels-Alder reaction of methyl 4,6-O-benzylidene-3-deoxy-3-C-methylene-α-D-erythro-hexopyranosid-2-ulose was found to be regio and stereospecific. The structure of the cycloadduct was assigned from NMR spectrographic and X-ray crystallographic results. These results indicated that this cycloaddition occurred by a concerted hetero Diels-Alder reaction with inverse electron demand. 相似文献
9.
The accuracy of tomographic particle image velocimetry for measurements of a turbulent boundary layer 总被引:1,自引:0,他引:1
Callum Atkinson Sebastien Coudert Jean-Marc Foucaut Michel Stanislas Julio Soria 《Experiments in fluids》2011,50(4):1031-1056
To investigate the accuracy of tomographic particle image velocimetry (Tomo-PIV) for turbulent boundary layer measurements,
a series of synthetic image-based simulations and practical experiments are performed on a high Reynolds number turbulent
boundary layer at Reθ = 7,800. Two different approaches to Tomo-PIV are examined using a full-volume slab measurement and a thin-volume “fat” light
sheet approach. Tomographic reconstruction is performed using both the standard MART technique and the more efficient MLOS-SMART
approach, showing a 10-time increase in processing speed. Random and bias errors are quantified under the influence of the
near-wall velocity gradient, reconstruction method, ghost particles, seeding density and volume thickness, using synthetic
images. Experimental Tomo-PIV results are compared with hot-wire measurements and errors are examined in terms of the measured
mean and fluctuating profiles, probability density functions of the fluctuations, distributions of fluctuating divergence
through the volume and velocity power spectra. Velocity gradients have a large effect on errors near the wall and also increase
the errors associated with ghost particles, which convect at mean velocities through the volume thickness. Tomo-PIV provides
accurate experimental measurements at low wave numbers; however, reconstruction introduces high noise levels that reduces
the effective spatial resolution. A thinner volume is shown to provide a higher measurement accuracy at the expense of the
measurement domain, albeit still at a lower effective spatial resolution than planar and Stereo-PIV. 相似文献
10.
We study a nonlinear elliptic problem with non-local boundary conditions and variable exponent. We prove an existence and uniqueness result of weak solution to this problem with general maximal monotone graphs. 相似文献