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91.
The paper describes a new pocket size instrument called the ‘Cardiophone’ for the diagnosis of cardiac dysfunction. It is a continuous wave swept frequency ultrasonic echo-location system which produces dynamic auditory signals corresponding to the positional change of internal structures of the heart. The four valves are relatively easy to locate compared with conventional ECG machines. Preliminary clinical evaluation results are presented indicating the potential of the instrument for the general practitioner. 相似文献
92.
93.
Vapor-liquid equilibria have been measured in the binary systems hexamethyldisiloxane-toluene, hexamethyldisiloxane-ethanol and toluene-ethanol between 333.15 and 358.15 K and the results have been correlated using the Wilson equation. All three binary systems exhibit azeotropic behavior in the temperature range studied. 相似文献
94.
Bernard S. Kay 《Physics letters. [Part B]》1981,101(4):241-245
Classical gravity with higher derivatives, when coupled to the in-out matrix element of Tμν: (a) appears to be free from instabilities of the in-in theory; (b) may be considered as the “underlying classical theory” to Tomboulis' quantum gravity. I explain how these two facts may be adduced as evidence for the viability both of the former semi-classical approximation and of the latter approach to full quantum gravity. 相似文献
95.
Vanja Margetic Ticijana Ban Ota Samek Franz Leis Kay Niemax Roland Hergenröder 《Czechoslovak Journal of Physics》2004,54(4):423-429
Fluorescence measurements have been used to characterize the velocity of atoms in a femtosecond-laser-produced plasma. Nanogram
amounts of a copper sample were ablated by the focused radiation (λ=775 nm) of an all-solid-state laser. The laser was operated
at a pulse rate of 10 Hz with an energy of 200μJ per pulse. The microplasma expanded into a defined argon atmosphere of pressures between 0.02 and 850 mbar. Atomic fluorescence
was excited in the laser plume by a dye-laser pulse with the wavelength set to the line Cu I 282.4 nm. The narrowed beam of
the dye-laser was directed into the plasma at different heights above the sample surface. The fluorescence radiation was measured
with an échelle-spectrometer, equipped with an intensified-charge-coupled device as the detector. The velocity depends strongly
on the pressure of the ambient atmosphere and the distance from the sample surface. The highest velocity found at an argon
pressure of 0.02 mbar was 1.0×106 cm s−1. 相似文献
96.
Microcionamides A and B, bioactive peptides from the philippine sponge Clathria (Thalysias) abietina
Davis RA Mangalindan GC Bojo ZP Antemano RR Rodriguez NO Concepcion GP Samson SC de Guzman D Cruz LJ Tasdemir D Harper MK Feng X Carter GT Ireland CM 《The Journal of organic chemistry》2004,69(12):4170-4176
Microcionamides A (1) and B (2) have been isolated from the Philippine marine sponge Clathria (Thalysias) abietina. These new linear peptides are cyclized via a cystine moiety and have their C-terminus blocked by a 2-phenylethylenamine group. Their total structures, including absolute stereochemistry, were determined by a combination of spectral and chemical methods. Compound 1 was shown to slowly isomerize about the C-36/C-37 double bond when stored in DMSO. Microcionamides A (1) and B (2) exhibited significant cytotoxicity against the human breast tumor cells lines MCF-7 and SKBR-3 and displayed inhibitory activity against Mycobacterium tuberculosis H(37)Ra. 相似文献
97.
Saalwächter K 《The Journal of chemical physics》2004,120(1):454-464
We present an approach towards the analysis of the intensity decay in proton multiple-quantum experiments on polymeric networks in terms of slow fluctuations of the residual dipole-dipole coupling tensor. Solutions for individual spin pairs as well as the three-spin system of methyl groups are derived, and the influence of the cycle time of the multiple-quantum pulse sequence is evaluated. The multiple-quantum strategy discussed herein features the advantage that the magnitude of the fluctuating part of the residual dipole-dipole coupling constant and the correlation time of the slow process can be determined independently of the integral residual coupling constant as well as its distribution. The theory is applied to experiments on end-linked poly(dimethylsiloxane) model networks with mono- and bimodal chain length distributions, where it is found that, for all samples, correlation times of the slow processes average to about 1 ms, and that the magnitude of the fluctuating part of the dipole-dipole coupling is significantly smaller than the average dipole-dipole coupling constant. This observation is interpreted in terms of considerably restricted reorientations of topological constraints. 相似文献
98.
Kay L 《The Journal of the Acoustical Society of America》2001,109(2):803-808
The angular spatial resolution of a wide-angle air sonar using a continuous transmission frequency-modulated radiation, with the output coupled binaurally to the auditory system of a user, was measured under restrained controlled conditions. This was done to determine the effect of adding a narrow central field of view of 9 deg to a wide-angle sonar. The target objects were three equidistant vertical rods initially spaced apart by 10 deg. This was varied down to a spacing of 4 deg. Ten nonvisual subjects achieved an angular resolution of 6 deg. Four of these ten subjects continued learning to achieve an unexpected spatial resolution of 4 deg within the 9 deg central field. A mean error of approximately 1 deg in direction accuracy was achieved. It is inferred that the unique variations in the octave band ultrasonic echoes within the narrow field, and the invariance of the on-axis echo as one's head is turned, enables this angular resolution and accuracy to be achieved within the wide binaural field of view of 50 deg. This ability to resolve specula objects within a narrow angular resolution element of 9 deg is linked to the bat's ability to seemingly resolve object glints within a distal resolution element of less than 2 wavelengths. 相似文献
99.
Enantioselective Generation of Adjacent Stereocenters in a Copper‐Catalyzed Three‐Component Coupling of Imines,Allenes, and Diboranes 下载免费PDF全文
Kay Yeung Rebecca E. Ruscoe Dr. James Rae Dr. Alexander P. Pulis Prof. Dr. David J. Procter 《Angewandte Chemie (International ed. in English)》2016,55(39):11912-11916
A highly enantio‐ and diastereoselective copper‐catalyzed three‐component coupling affords the first general synthesis of homoallylic amines bearing adjacent stereocenters from achiral starting materials. The method utilizes a commercially available NHC ligand and copper source, operates at ambient temperature, couples readily available simple imines, allenes, and diboranes, and yields high‐value homoallylic amines that exhibit versatile amino, alkenyl, and boryl units. 相似文献
100.