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181.
A matter of debate is whether the use of a video-endoscope impairs visual orientation and manual precision in endonasal surgery. We investigated the influence of video-endoscopy compared to endoscopy on stereoacuity in a model of the nasal cavity. Twenty medical staff members were asked to touch defined points in a spatial model of the nasal cavity as quickly as possible and in correct order using 0 degree and 30 degrees endoscopes, looking directly through the endoscope or looking at a video monitor connected to a CCD camera on the endoscope. Time, number of omissions of points and faults in point sequence were recorded. Manipulations were significantly quicker when the "operative field" was seen directly through the endoscope compared to orientation from the monitor for both 0 degree endoscope 96 +/- 4.7 s. vs. 108 +/- 5.6 s. and 30 degrees endoscope 84 +/- 3.9 s. vs. 96 +/- 5.5 s. (+/- SEM). There was no difference in number of omissions and faults in sequence between "endoscope" and "video-endoscope." The fact that the use of a video-endoscope did not increase the number of faults in our experiment does not support the notion that performing endoscopic sinus surgery using a monitor is unsafe. In the hands of the participants who were experienced with the endoscope, however, the use of a video-endoscope slowed down manipulations to a significant degree. To which extent this may be due to the effect of training or to superiority of the endoscope per se will remain a matter of discussion until a group of experienced video-endoscopists will have repeated the study.  相似文献   
182.
183.
A unified model of one-dimensional ballistic and diffusive carrier transport in semiconductors, valid for arbitrary mean free path and arbitrary shape of the band edge profiles, is applied in a study of the effect of grain boundaries on the transport properties of photovoltaic materials. Adopting the trapping model to describe the grain boundaries, dark conductivities and photoconductivities are calculated as a function of donor density for samples consisting of chains of grains with length comparable to the mean free path. The results of the unified model are found to deviate substantially from those of the purely ballistic and purely diffusive limits.  相似文献   
184.
This review highlights some of the recently isolated and identified substances of higher Basidiomycetes mushrooms origin that express promising antitumor, immune modulating, cardiovascular and hypercholesterolemia, antiviral, antibacterial, and antiparasitic effects. Medicinal mushrooms have a long history of use in folk medicine. In particular, mushrooms useful against cancers of the stomach, esophagus, lungs, etc. are known in China, Russia, Japan, Korea, as well as the U.S.A. and Canada. There are about 200 species of mushrooms that have been found to markedly inhibit the growth of different kinds of tumors. Searching for new antitumor and other medicinal substances from mushrooms and to study the medicinal value of these mushrooms have become a matter of great significance. However, most of the mushroom origin antitumor substances have not been clearly defined. Several antitumor polysaccharides such as hetero-beta-glucans and their protein complexes (e.g., xyloglucans and acidic beta-glucan-containing uronic acid), as well as dietary fibers, lectins, and terpenoids have been isolated from medicinal mushrooms. In Japan, Russia, China, and the U.S.A. several different polysaccharide antitumor agents have been developed from the fruiting body, mycelia, and culture medium of various medicinal mushrooms (Lentinus edodes, Ganoderma lucidum, Schizophyllum commune, Trametes versicolor, Inonotus obliquus, and Flammulina velutipes). Both cellular components and secondary metabolites of a large number of mushrooms have been shown to effect the immune system of the host and therefore could be used to treat a variety of disease states.  相似文献   
185.
We designed laser-pumped cesium vapor magnetometers in the Mx configuration for the control and stabilization of magnetic field fluctuations and gradients in a new experiment searching for a permanent electric dipole moment of the neutron. The intrinsic sensitivity of the device was determined to be 30 fT in a measurement bandwidth of 1 Hz, limited by laser noise. In the shot noise limit the magnetometer can reach a sensitivity of 7 fT for 1 s integration time. Test measurements of the stability of a 2 µT magnetic field in a threefold magnetic shield have revealed fluctuations on the order of 200 fT to 300 fT with integration times in the range of 2 s to 100 s. Those fluctuations were traced back to the stability of the power supply used to generate the magnetic field. The laser-pumped magnetometer fulfills the requirements set by the planned neutron electric dipole moment experiment.  相似文献   
186.
In this research, impedance spectroscopy (IS) has been applied on top-contact pentacene organic field-effect transistors (OFETs) for characterization of the contact resistance and carrier transport properties. The various relaxation processes were analyzed based on the Maxwell–Wagner model, assuming pentacene as a dielectric material. The mobilities obtained from the IS analysis correspond well with that obtained from the current–voltage (I–V) analysis. This alternative method by IS provides an additional advantage of isolating the effect of carrier concentration when evaluating the mobility of OFETs.  相似文献   
187.
Several types of Decision Diagrams (DDs) have been proposed for the verification of Integrated Circuits. Recently, word-level DDs like BMDs, *BMDs, HDDs, K*BMDs and *PHDDs have been attracting more and more interest, e.g., by using *BMDs and *PHDDs it was for the first time possible to formally verify integer multipliers and floating point multipliers of significant bitlengths, respectively.On the other hand, it has been unknown, whether division, the operation inverse to multiplication, can be efficiently represented by some type of word-level DDs. In this paper we show that the representational power of any word-level DD is too weak to efficiently represent integer division. Thus, neither a clever choice of the variable ordering, the decomposition type or the edge weights, can lead to a polynomial DD size for division.For the proof we introduce Word-Level Linear Combination Diagrams (WLCDs), a DD, which may be viewed as a generic word-level DD. We derive an exponential lower bound on the WLCD representation size for integer dividers and show how this bound transfers to all other word-level DDs.  相似文献   
188.
The statistics of cell loss and misrouting due to transmission errors in asynchronous transfer mode (ATM) or cell-based systems, which result in unreliable data transmission and thus in a degradation of service quality, are developed. Results indicate that it is essential to use a decoding scheme for the virtual channel identifiers of a cell in order to satisfy the expectation of the subscriber with respect to transmission reliability and data security. The models of connections, exchanges, and transmission in the cell-based systems are presented  相似文献   
189.
Advances in integrated circuit fabrication technology over the past two decades have resulted in integrated circuits with smaller device dimensions and larger area and complexity.Due to this technology evolution, Electromigration became a major reliability concern in silicon VLSI circuits.Various Electromigration test structures are presented, to illustrate the interrelationship of current density, test structures geometry and material, and the Electromigration phenomena. Bayesian (non-classical) procedures have been applied to analyze the results of conventional Electromigration accelerating life tests.This enables to optimize the numerical results on the base of the results data.  相似文献   
190.
A laboratory exercise that allows the student to combine theory, numerical computation methods, and experimental observation to learn more about electromagnetic modes and modal patterns is presented. It provides students with the opportunity to derive the field equations and the characteristic equations from first principles, solve for the parameters of the modes and plot them, and visually compare the modes observed in the laboratory with those calculated  相似文献   
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