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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 1493-1499 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a novel approach for including the effects of realistic silicon band structure in the simulation of electron transport with a Monte Carlo method. This will be achieved by an electron effective-mass and energy–over–wave-vector relation, which are derived directly from the density of states. Consistent with this model, the scattering rates as well as the equations of motion are determined by the density of states. With our approach the computation tables in three-dimensional momentum space can be replaced by one-dimensional tables in energy space. The necessary amount of memory size and table lookup time is therefore significantly reduced. The number of free parameters in our model is not higher than in the full band-structure model. We show by comparison with full band-structure Monte Carlo and experimental results that there is no loss in physical meaning by the use of the new method.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 3092-3096 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We calculate the charge pumping current of a metal-oxide-semiconductor transistor in the time domain utilizing a transient two-dimensional device simulation. The dynamics of the interface states are included in the solution of the time-dependent problem with full self-consistency. The calculated charge pumping curve is in good agreement with the experiment, especially the rise and fall patterns of the signal, which are very sensitive to the source/drain profiles in small devices. The extraction of the density of states shows the range of validity of the analytical models and their restrictions. The influence of hot-carrier stress on the charge pumping signal, which relates to inhomogeneous spatial distribution of interface states and fixed oxide charges, is also discussed in experiment and simulation.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 650-656 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Decreasing device dimensions will cause an increasing internal field strength in a semiconductor device. The average carrier energy is different from the thermal equilibrium value 3/2 kT. Modification of current transport is considered on different levels of approximation. In a local approximation we derive a field-dependent carrier mobility and temperature from a more general self-consistent formulation. Numerical estimation of hot-electron effects are given for a realistic n-channel metal-oxide-semiconductor field-effect transistor of various channel lengths. It is shown that both high-field and field-gradient effects will contribute.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 3592-3595 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We compare the high-energy distribution function of the lucky electron model, the Maxwellian distribution, and the asymptotic solution of Boltzmann's equation with Monte Carlo calculations in the effective-mass approximation. We show that the Monte Carlo calculations are in good agreement with the asymptotic solution of Boltzmann's equation for constant and for space-dependent electric fields while the other distributions do not agree with the Monte Carlo results.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 1435-1438 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We derive an analytical expression for the distribution function for high energetic carriers in an arbitrary two- or three-dimensional electric field utilizing Boltzmann's equation. This distribution function is of Maxwell–Boltzmann type if the system attains thermal equilibrium. We apply this new model to calculate the substrate and gate currents in a metal-oxide-semiconductor field-effect transistor and compare it with measurements from various devices.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Surgical endoscopy and other interventional techniques 13 (1999), S. 980-984 
    ISSN: 1432-2218
    Keywords: Key words: Rectal cancer — Preoperative staging — Endorectal ultrasound — Preoperative radiochemotherapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Objectives: Factors limiting the accuracy of endorectal ultrasound in staging, locally advanced primary rectal cancer after preoperative neoadjuvant radiochemotherapy (RCT) were evaluated. Methods: Patients (n= 84) with initial locally advanced rectal cancer (uT3/uT4) undergoing R0 resection were investigated after preoperative treatment that combined radiotherapy up to 45 Gy with two cycles of chemotherapy (5-FU and leucovorin on d 1–5 and 22–28). At 4 to 6 weeks after completion of RCT and before tumor resection, preoperative endoluminal ultrasound was performed. Results: The accuracy to predict the depth of tumor infiltration (T-category) was found to correlate with downstaging. The T-category was correctly staged before surgery in 15 of the 51 responders (29%) and in 27 of 33 nonresponders (82%), whereas misinterpretation occurred in 36 of the responders (71%) and in 6 of the nonresponders (18%) (p 〈 0.001). Neither tumor distance from anal verge nor tumor location correlated with the staging accuracy. Lymph node involvement was correctly assessed in 48 patients (57%). Wall invasion was correctly ascertained in 42 patients (50%), with under estimation in 11 patients (13%) and overestimation in 31 patients (37%). Conclusions: After radiochemotherapy, endosonography does not provide a satisfactory accuracy for preoperative staging of rectal cancer. New interpretation and diagnostic criteria are needed for the prediction of treatment response.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Zeitschrift für angewandte Mathematik und Physik 40 (1989), S. 440-455 
    ISSN: 1420-9039
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Description / Table of Contents: Zusammenfassung Ein kürzlich hergeleitetes Modell für stationären Energie- und Ladungsträgerfluß in Halbleitern—bestehend aus einem gekoppelten System von nichtlinearen elliptischen Gleichungen—wird mit Methoden der singulären Störungstheorie analysiert. Daraus ergeben sich Aussagen über die Lösungsstruktur und eine Rechtfertigung einer modifizierten Version der klassischen Konvektions-Diffusions-Approximation für den Ladungsträgerfluß.
    Notes: Abstract A recently derived model for stationary flow of energy and charge carriers in semiconductors—consisting of a coupled system of nonlinear elliptic equations—is analysed by the methods of singular perturbation theory. This analysis reveals the solution structure and justifies a modified version of the standard drift-diffusion approximation for charge carrier flow.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Langenbeck's archives of surgery 380 (1995), S. 359-364 
    ISSN: 1435-2451
    Keywords: β-hCG ; Gastric carcinoma Prognostic factors ; Immunohistochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Einleitung: Nach neueren Untersuchungen ist davon auszugehen, daß bei des Hälfte von Patienten mit einem Magenkarzinom β-hCG-positive Zellen im Tumor immunhistochemisch gefunden werden können. Ziel war daher, systematisch zu untersuchen, inwieweit β-hCG-immunreaktive Magenkarzinome von einem Anstieg des Serum-β-hCG begleitet werden and dieses damit als Verlaufsparameter zur Verfügung steht. Methode: Bei 54 Patienten mit einem Magenkarzinom wurde zur immunhistochemischen Darstellung ein gegen β-hCG gerichteter monoklonaler Antikörper (Fa. Sigma, 1:100) im APAAP-System verwendet. Die Auswertung wurde nach positiver and negatives Reaktion graduiert. Parallel wurde im Serum des Patienten β-hCG präoperativ mit einem Enzymimmunoassay (MEIA, Fa. Abbot) bestimmt. Tumor-stadium, Grading and Tumor-lokalisation werden in die Auswertung mit einbezogen. Ergebnisse: Es wird bestätigt, daß 41% (22 von 54) des Karzinome, unabhängig von ihrer Lokalisation im Magen, eine positive immunhistochemische Reaktion gegen β-hCG auslösen. Es zeigte sich in Abhängigkeit vom Tumorstadium eine positive β-hCG-Immunreaktivität in 27% (6 von 22) des Tumoren ohne Lymphknoten- and Fernmetastasierung (T1–4 N0 M0), in 54% (7 von 13) des Tumoren mit Lymphknotenaber ohne Fernmetastasen (T1–4 N≥1 M0) und in 47% (9 von 35) des Tumoren mit Fernmetastasierung. Schlecht differenzierte Tumoren (G3–4) waren zu 42% (15 von 36) und gut differenzierte Tumoren (G1–2) nur zu 39% (7 von 18) positiv. Aber lediglich bei einer Patientin war der β-hCG-Spiegel im Serum erhöht. Zusammenfassung: Immunhistochemisch β-hCG-positive Magenkarzinome werden vermehrt bei fortgeschrittenem Tumorstadium und Schlecht differenzierten Karzinomen gefunden. Diese Kar zinome scheinen aber nicht in ausreichender Menge β-hCG ins Serum abzugeben, was zu serologisch meßbar erhöh-ten Werten führt. β-hCG im Serum kann daher nicht als Prognosefaktor bzw. zur Verlaufskontrolle herangezogen werden. Abzuwarten bleibt, inwieweit die β-hCG-Expression von Tumorzellen u. U. Einfluß auf die Propose der Patienten besitzt.
    Notes: Abstract Introduction: Recent investigations indicate that in 50% of patients with gastric cancer, β-hCG-posiitive cells can be found in the tumour by immunohistochemical investigations. The objective of this study was to investigate how often β-hCG-immunoreactive gastric carcinomas were accompanied by an elevation in serum β-hCG, that could have been used as a course control variable. Methods: In 54 patients with gastric carcinoma a monoclonal antibody directed against β-hCG was used for immunohistochemical marking in the APAAP system. The evaluation was graded positive or negative. In parallel, serum β-hCG was determined preoperatively using an enzyme immunoassay (MEIA). Tumour stage, grading and tumour locallization were determinants in the evaluation. Results: We found that 41% (22 of 54) of the carcinomas induced a :positive immunohistochemical response to β-hCG, regardless of their location in the stomach. In relation to tumour stage, a positive β-hCG immunoreactivity was apparent in 27% (6/22) of tumours without lymph node or distant metastases (TI -4N0M0), in 54% (7/13) of tumours with lymph node and without distant metastases (T1−4N≥1 M0) and in 47% (9/35) of tumours with distant metastases. Poorly differentiated tumours (G3–4) were positive in 42% (15/36) and well-differentiated tumors (G1–2) in 39% (7/18) of cases. In only 1 patient was the β-hCG, level in serum elevated, however. Conclusions: β-hCG-Positive gastric carcinomas are found more frequently in advanced tumour stages and poorly differentiated carcinomas. These carcinomas, however, seem not to excrete β-hCG in sufficient amounts to produce measurable serum values. Therefore, β-hCG cannot be used a prognostic factor or for course control. The relevance of β-hCG expression of tumour cells to the patients' prognosis remains obscure.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Diseases of the colon & rectum 39 (1996), S. 1373-1378 
    ISSN: 1530-0358
    Keywords: Threedimensional endosonography ; Transrectal biopsy ; Recurrence ; Rectal cancer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract PURPOSE: The value of endorectal ultrasonography for postoperative follow-up of rectal cancer is limited by the inability to distinguish recurrent malignancy from benign lesions,e.g., fibrotic tissue. This study was conducted to investigate the role of three-dimensional (3D) endosonography for evaluation and biopsy of recurrent rectal cancer. METHODS: Endorectal ultrasonography was performed in routine follow-up program after resection of rectal cancer. 3D volume scans were recorded using a bifocal multiplane 3D transducer (7.5/10 MHz) with a 100
    Type of Medium: Electronic Resource
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