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11.
G Thumann UE Baum KU Bartz-Schmidt H Lanfermann P Landwehr P Esser W Konen 《Canadian Metallurgical Quarterly》1996,209(6):aA10-aA13
INTRODUCTION: Dural arteriovenous fistula of the Arteria carotis externa and the sinus cavernosus are rare vascular malformations. In the literature the prognosis and necessity of treatment is described very variable. PATIENTS AND METHODS: A 90 year old female presents in our outpatient clinic with acute exophthalmus, dilated episcleral veins, cerebral bruits and beginning orbital apex syndrome. After normal computerized axial tomography (CAT) without and with contrast medium, we were able to diagnose a dural AV-fistula by angiography. Shortly after dismission the patient had a spontaneous subarachnoidal haemorrhage with severe neurological symptoms. CONCLUSIONS: The suspect of an intracranial AV-malformation implies a detailed diagnostic search with precise localisation of the process. In any patient with intracerebral and intracranial fistula there has to be an individual check of possible and necessary treatment. It is impossible to classify dural AV-fistula as a benign disease with harmless clinical course. 相似文献
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The purpose of this review is to describe recent advances in non-invasive vascular imaging techniques and to discuss their current clinical applications for imaging of peripheral vessels. Principles for applying ultrasound, CT angiography (CTA), and magnetic resonance angiography (MRA) for non-invasive imaging of peripheral arteries and veins are presented. Clinical applications are reviewed for different vascular diseases, therapy planning, and follow-up studies. Conventional Doppler and color duplex sonography are the most cost-effective procedures to detect or rule out peripheral arterial occlusive disease (PAOD) and to provide specific recommendations for therapy. In the near future, contrast-enhanced MRA (CE MRA) with additional axial two-dimensional time-of-flight studies to search for non-anatomic runoff will replace diagnostic intra-arterial digital subtraction angiography (DSA) for planning of reconstructive surgery with acquisition slabs displaying projections similar to intra-arterial DSA. Color duplex sonography should also be the first non-invasive technique applied for the detection of peripheral aneurysms. Preoperative or preinterventional therapy planning of aneurysms may be performed by CTA or CE MRA. Compression ultrasound is the imaging procedure of choice in deep venous thrombosis (DVT). In the preoperative assessment of venous incompetence, color duplex sonography is the imaging technique which is sufficient in most cases. 相似文献
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A voltage controlled negative differential resistance (NDR) in n-channel MOSFETs of (100) orientation is investigated for lattice temperatures between 1.5 and 100 K in transverse magnetic fields up to 7 Tesla. By variation of the length of the pulses and by investigating samples of different geometry it is shown, that the NDR is not caused by lattice heating. Position and magnitude of the NDR depend substantially on the magnetic field. The observed effects can be explained by cooling of the hot carriers by the magnetic field. 相似文献
16.
Matthias Bussas Christoph Sawade Nicolas Kühn Tobias Scheffer Niels Landwehr 《Machine Learning》2017,106(9-10):1419-1440
We study prediction problems in which the conditional distribution of the output given the input varies as a function of task variables which, in our applications, represent space and time. In varying-coefficient models, the coefficients of this conditional are allowed to change smoothly in space and time; the strength of the correlations between neighboring points is determined by the data. This is achieved by placing a Gaussian process (GP) prior on the coefficients. Bayesian inference in varying-coefficient models is generally intractable. We show that with an isotropic GP prior, inference in varying-coefficient models resolves to standard inference for a GP that can be solved efficiently. MAP inference in this model resolves to multitask learning using task and instance kernels. We clarify the relationship between varying-coefficient models and the hierarchical Bayesian multitask model and show that inference for hierarchical Bayesian multitask models can be carried out efficiently using graph-Laplacian kernels. We explore the model empirically for the problems of predicting rent and real-estate prices, and predicting the ground motion during seismic events. We find that varying-coefficient models with GP priors excel at predicting rents and real-estate prices. The ground-motion model predicts seismic hazards in the State of California more accurately than the previous state of the art. 相似文献
17.
C. R. Becker V. Latussek M. Li A. Pfeuffer-Jeschke G. Landwehr 《Journal of Electronic Materials》1999,28(6):826-829
The valence band offset (Λ) between HgTe and CdTe has been determined by means of an optical investigation of (112)B oriented
HgTe/Hg1−xCdxTe superlattices. Based on the fact that the difference in energy between the first heavy hole and the first light hole subband
is to a good approximation due primarily to Λ, it has been shown that Λ=580±40 meV at 5K. In addition Λ has a significant
temperature dependence with a linear coefficient of −0.34±0.02 meV/K, i.e., Λ is 480±40 meV at room temperature. 相似文献
18.
S. V. Ivanov A. A. Toropov S. V. Sorokin T. V. Shubina I. V. Sedova P. S. Kop’ev Zh. I. Alferov A. Waag H. J. Lugauer G. Reuscher M. Keim F. F. Fischer G. Landwehr 《Semiconductors》1999,33(9):1016-1020
We report the results of an experimental study of molecular-beam epitaxy of ZnSe-based laser heterostructures with a new structure
of the active region, which contains a fractional-monolayer CdSe recombination region in an expanded ZnSe quantum well and
a waveguide based on a variably-strained, short-period superlattice are reported. Growth of a fractional-monolayer CdSe region
with a nominal thickness of 2–3 ML, i.e., less than the critical thickness, on a ZnSe surface (Δa/a∼7%) leads to the formation of self-organized, pseudomorphic, CdSe-enriched islands with lateral dimensions ∼10–30 nm and
density ∼2×1010 cm−2, which serve as efficient centers of carrier localization, giving rise to effective spatial separation of defective regions
and regions of radiative recombination and, as a result, a higher quantum efficiency. Laser structures for optical pumping
in the (Zn, Mg) (S, Se) system with a record-low threshold power density (less than 4 kW/cm2 at 300 K) and continuous-wave laser diodes in the system (Be, Mg, Zn) Se with a 2.5 to 2.8-ML-thick, fractional-monolayer
CdSe active region have been obtained. The laser structures and diodes have an improved degradation resistance.
Fiz. Tekh. Poluprovodn. 33, 1115–1119 (September 1999) 相似文献
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S. V. Ivanov A. A. Toropov S. V. Sorokin T. V. Shubina N. D. Il’inskaya A. V. Lebedev I. V. Sedova P. S. Kop’ev Zh. I. Alferov H. -J. Lugauer G. Reuscher M. Keim F. Fischer A. Waag G. Landwehr 《Semiconductors》1998,32(10):1137-1140
High-quality ZnSe-based heterostructures are grown by uninterrupted molecular beam epitaxy using the concept of strain compensation
and alternating-strain multilayers. To verify the advantages of this technique, optically pumped ZnSSe/ZnCdSe laser structures
containing short-period superlattices or multiple quantum wells have been grown and studied. A room-temperature injection
laser diode with a BeZnSe/ZnSe superlattice waveguide is described.
Fiz. Tekh. Poluprovodn. 32, 1272–1276 (October 1998) 相似文献