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1.
Methods to directly and indirectly identify the central sulcus are presented. In the axial plan, direct method is remarkable but obviously requires good visualization of the sulci in the central region. Sulci are readily visible in 90% of the cases on CT scans and in 50% of the cases on MRI. The method can also be applied when tumoral development erases the cerebral sulci by direct lecture of the controlateral rolandic region and right-left transfer. Within the precision limits of the method, it can be considered that the central sulci are symmetrical. The main signs are: the relative morphologies of the superior frontal sulcus and the precentral sulcus, the hook-shaped aspect of the middle part of the central sulcus, the internal end of the central sulcus projection anteriorly to the pars marginalis, the bifid nature of the internal end of the posterior central sulcus contouring the pars marginalis, and the lesser thickness of the posterior central gyrus compared with the precentral gyrus. The indirect method is less precise and is used when the direct method is unsuccessful. The central sulcus is identified on the sagittal images and, using the lateral view of the skull as a reference image, the topographic information is transferred to the axial images. 相似文献
2.
Chen S.F. Kingsbury B. Lidia Mangu Povey D. Saon G. Soltau H. Zweig G. 《IEEE transactions on audio, speech, and language processing》2006,14(5):1596-1608
This paper describes the technical and system building advances made in IBM's speech recognition technology over the course of the Defense Advanced Research Projects Agency (DARPA) Effective Affordable Reusable Speech-to-Text (EARS) program. At a technical level, these advances include the development of a new form of feature-based minimum phone error training (fMPE), the use of large-scale discriminatively trained full-covariance Gaussian models, the use of septaphone acoustic context in static decoding graphs, and improvements in basic decoding algorithms. At a system building level, the advances include a system architecture based on cross-adaptation and the incorporation of 2100 h of training data in every system component. We present results on English conversational telephony test data from the 2003 and 2004 NIST evaluations. The combination of technical advances and an order of magnitude more training data in 2004 reduced the error rate on the 2003 test set by approximately 21% relative-from 20.4% to 16.1%-over the most accurate system in the 2003 evaluation and produced the most accurate results on the 2004 test sets in every speed category. 相似文献
3.
A review of literature about the effect of oil pockets on improvement of sliding elements tribological performance as well as about the changes of surface topography during “zero-wear” process is shown. The paper presents also the results of experimental investigations done in the Department of Manufacturing Processes and Production Organisation of Rzeszow University of Technology, connected with the creation of oil pockets on sliding surfaces. In order to simulate a deterministic surface a program for the visualisation of pits was written. The procedures for assessment of the oil pocket size of specific shape and oil pockets coverage are presented. The tendencies of changes of surface topography and oil pockets dimensions during “zero-wear” process are also described. 相似文献
4.
Thin films, in the range of tens of micrometers thickness, have been prepared by casting onto glass plates the chloroform or N‐methylpyrrolidone solutions of polyimides or poly(imide‐amide)s containing silicon and phenylquinoxaline units in the main chain. The polymers have been synthesized by solution polycondensation reaction of aromatic diamines having preformed phenylquinoxaline rings with bis(3,4‐dicarboxyphenyl)dimethylsilane dianhydride or with a diacid chloride resulting from the reaction of this dianhydride with p‐aminobenzoic acid. The polymers were easily soluble in polar aprotic solvents and showed high thermal stability. The free‐standing films exhibited good mechanical properties with tensile strengths in the range of 48–86 MPa, tensile modulus in the range of 1.25–2.22 GPa and elongation at break in the range of 3–37%. Electrical insulating properties of some polymer films were evaluated on the basis of dielectric constant and dielectric loss and their variation with frequency and temperature. The values of the dielectric constant at 10 kHz were in the range of 2.94–3.08 for polyimides and 3.89–4.49 for poly(imide‐amide)s. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3062–3068, 2006 相似文献
5.
Marie-Laure Favier Pierre-Etienne Bost Christine Guittard Christian Demigné Christian Rémésy 《Lipids》1997,32(9):953-959
The effects of partially hydrolyzed, nonviscous, guar gum (PHGG) on cholesterol metabolism and digestive balance have been
compared with those of native guar gum (GUAR) in rats adapted to 0.4% cholesterol diets. Both types of guar gum elicited acidic
fermentations in the large intestine, but only GUAR effectively lowered plasma cholesterol (P<0.001), chiefly in the triglyceride-rich lipoprotein fraction. The biliary bile acid excretion was significantly enhanced
in rats fed GUAR (P<0.05), as well as the intestinal and cecal bile acid pool (P<0.001). In rats fed GUAR and to a lesser extent in those fed PHGG, the fecal excretion of bile acids and neutral sterol was
higher than in controls (P<0.01). The digestive balance (cholesterol intake-steroid excretion) was positive in control rats (+47 μmol/d), whereas it
was negative in rats fed GUAR (−20 μmol/d), which could involve a higher rate of endogenous cholesterol synthesis. In rats
fed PHGG, the steroid balance remained slightly positive. Liver 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase activity
was very low (22 pmol/min/mg protein), owing to cholesterol supplementation, in control rats or in rats fed PHGG, whereas
it was markedly higher (+463%) in rats fed GUAR. In conclusion, even if PHGG does alter some parameters of the enterohepatic
cycle of cholesterol and bile acids, its effects are not sufficient to elicit a significant cholesterol-lowering effect. The
intestinal (ileal or cecal) reabsorption of bile acids was not reduced, but rather increased, by GUAR; nevertheless the intestinal
capacities of reabsorption were overwhelmed by the enlargement of the digestive pool of bile acids. In the present model,
induction of HMG-CoA reductase probably takes place in the presence of elevated portal bile acid concentrations. 相似文献
6.
New organodilithium initiators were prepared in a hydrocarbon solvent in the absence of any polar additive. Although these initiators are insoluble when they are synthesized, they may be easily purified and reacted with dienes to give perfectly telechelic polydienes having unimodal distributions and low dispersity. A good agreement between experimental and theoretical molecular weights was observed. The polymer microstructures were similar to those of polymers initiated by butyllithium in the same solvent. Triblock thermoplastic elastomers were also prepared, the characteristics of which are given. The mechanical properties of a S.B.S. sample support also the claim of a good initiating ability and difunctionality of these initiators. 相似文献
7.
Owing to the low Tg of polystyrene, the mechanical properties of polystyrene-block-poly-butadiene-block-polystyrene (SBS) thermoplastic elastomers drop steeply above 60°C. To overcome this behavior, many research groups have considered the replacement of styrene (S) by α-methylstyrene (MS). We also attempted the synthesis of copolymers with a central polybutadiene (poly B) block and rigid blocks consisting of polystyrene (poly S) and poly(α-methylstyrene) (poly MS) blocks. Starting from a dilithium initiator, difunctional poly B's with low 1,2 content (10%) were prepared and toluene was added. After addition of a small amount of styrene, MS was added in the presence of a 15% (in vol) of THF at T ≤ ?40°C. The copolymers did not have the expected structure and poor mechanical properties resulted, which were, however, still measurable at 120°C. These results probably resulted from secondary reactions involving the MS carbanions. To identify these reactions and to control the polymer structure, the synthesis of multiblock copolymers was carried out with a monofunctional polybutadienyllithium to which were added successively S and MS (in a mixture of hexane and benzene as solvent). MS was added at low temperature in the presence of small amounts of THF or at room temperature after addition of TMEDA. These attempts were unsuccessful, the copolymer being always multimodal as a result of unwanted coupling reactions involving terminal double bonds. The synthesis of elastomers using a coupling reaction of poly MS–poly S–poly B was also considered but the yield in poly B was low since termination reactions involving the polar additive occurred. © 1994 John Wiley & Sons, Inc. 相似文献
8.
Silvana?Martini Constantin?Bertoli Maria?Lidia?Herrera Ian?Neeson Alejandro?MarangoniEmail author 《Journal of the American Oil Chemists' Society》2005,82(5):305-312
An ultrasonic technique was developed to study the crystallization process of edible fats on-line. A chirp wave was used instead
of the conventional pulser signal, thus achieving a higher signal-to-noise ratio. This enabled measurements to be made in
concentrated systems [≈20% solid fat content (SFC)] through a 8.11-cm thick sample without significant signal loss. Fat samples
were crystallized at 20, 25, and 30°C at a constant agitation rate of 400 rpm for 90 min. The crystallization process was
followed by ultrasonic spectroscopy and a low-resolution pulsed nuclear magnetic resonance spectrometer. Specific relationships
were found between ultrasonic parameters [integrated response, time of flight (TF), and full width half maximum] and SFC.
TF, which is an indirect measurement of the ultrasonic velocity (v), was highly correlated to SFC (r
2>0.9) in a linear fashion (v=2.601 SFC+1433.0). 相似文献
9.
C. G'sell V. Favier J. M. Hiver A. Dahoun M. J. Philippe G. R. Canova 《Polymer Engineering and Science》1997,37(10):1702-1711
The macroscopic stress-strain behavior of monoclinic polypropylene samples was investigated at 70°C under uniaxial tension and simple shear by means of a special videometric testing system that gives access to the constitutive equation of plastic behavior at constant strain rate up to large deformation. At several levels of plastic strain, the microstructural evolution of the material was characterized by means of X-ray scattering, densitometry and viscoelastic analysis. It appears that the strain hardening is high in tension, whereas it is nearly zero in shear. This behavior is associated with the development of a fiber texture in tension, which differs drastically from the planar crystalline texture developed in shear. Furthermore, it is shown that structural damage takes place as the plastic deformation proceeds in tension, while only little damage is recorded in shear. A viscoplastic model has been developed that specifically tales into account the various slip systems activated in the polypropylene crystallites and the elastic interactions of the lamellae through a self-consistent scheme. Simulations based on this model reproduce correctly the contrasting strain-hardening in tension and in shear and the different crystalline textures induced for these two loading paths. 相似文献
10.
Hamza El Marouazi Benoit van der Schueren Damien Favier Anaëlle Bolley Samuel Dagorne Thierry Dintzer Izabela Janowska 《应用聚合物科学杂志》2021,138(44):51300
Four series of polylactide (PLA) based composite films containing horizontally aligned few layer graphene (FLG) flakes of high aspect ratio and adsorbed albumin are prepared. The mechanical and thermal properties varies with percentage, dispersion degree and size of FLG flakes. Great improvement up to 290% and 360% of tensile modulus and strength respectively were obtained for the composite containing high lateral size of FLG at 0.17% wt, and up to 60% and 80% for the composite with very well dispersed 0.02% wt FLG. The composites of PLA and PEG-PLLA containing very well dispersed FLG flakes at 0.07% wt are ductile showing enhancement of elongation at break up to respectively 80% and 88%. Relatively high electrical conductivity, 5 × 10−3 S/cm, is measured for PLA film charged with 3% of FLG. 相似文献