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Search Results: 1 - 10 of 405321 matches for " Nguyen-Tat M "
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Dünndarmpolypen bei Patienten mit Peutz-Jeghers-Syndrom: Empfehlungen zu Diagnostik und Therapie
Plum N,May A,Manner H,Nguyen-Tat M
Journal für Gastroenterologische und Hepatologische Erkrankungen , 2007,
Abstract: Das Peutz-Jeghers-Syndrom (PJS) ist charakterisiert durch eine Kombination von hamartomat sen gastrointestinalen Polypen und typischen Hautpigmentierungen. Die Polypen finden sich vorwiegend im Bereich des Dünndarms und k nnen zu intestinalen Obstruktionen, Invaginationen und Blutungen führen. Dünndarmdiagnostik: Die endoskopische Standarddiagnostik war bis vor wenigen Jahren auf GD, Push-Enteroskopie sowie Koloskopie mit Ileoskopie beschr nkt. Eine Darstellung der mittleren Dünndarmabschnitte erfolgte mittels Enteroklysma und/oder intraoperativer Endoskopie. Die Diagnostik der mittleren Dünndarmabschnitte wurde mit Einführung der Video-Kapselendoskopie (CE) 2001 revolution r ver ndert. Mit der CE gelang erstmals eine nicht invasive und komfortable Inspektion des kompletten Dünndarms. Des weiteren zeigen erste Studien zum MR-Enteroklysma gute Detektionsraten für Polypen mit einer Gr e 15 mm, bei kleineren Polypen ist die CE dem MR-Enteroklysma jedoch diagnostisch überlegen. Therapie von Dünndarmpolypen: Die endoskopische Resektion von Peutz-Jeghers-Polypen im Bereich von Magen, Duodenum, Kolon sowie Rektum geh rt in erfahrenen Zentren heute zur Therapie der ersten Wahl und hat die Chirurgie bereits auf den zweiten Platz verwiesen. Polypen im Bereich des mittleren Dünndarms wurden bisher prim r chirurgisch und/oder mittels intraoperativer Endoskopie therapiert. Mit Einführung der Doppelballonenteroskopie (DBE) ist neben einer verbesserten Diagnostik auch eine M glichkeit zur nicht-invasiven Therapie gegeben.
Admissibility of local systems for some classes of line arrangements
Nguyen Tat Thang
Mathematics , 2012,
Abstract: Let $\A$ be a line arrangement in the complex projective plane $\PP^2$. Denote by $M$ its complement and by $\M$ the set of points in $\A$ with multiplicity at least 3. A rank one local system $\mathcal{L}$ on $M$ is admissible if roughly speaking the dimension of the cohomology groups $H^m(M,\mathcal{L})$ can be computed directly from the cohomology algebra $H^{*}(M,\Bbb{C})$. In this work, we give a sufficient condition for the admissibility of all rank one local systems on $M$.
Bifurcation set, M-tameness, Asymptotic critical values and Newton polyhedrons
Nguyen Tat Thang
Mathematics , 2012,
Abstract: Let $F=(F_1, F_2, ..., F_m): \mathbb{C}^n \to \mathbb{C}^m$ be a polynomial dominant mapping with $n>m$. In this paper we give the relations between the bifurcation set of $F$ and the set of values where $F$ is not M-tame as well as the set of generalized critical values of $F$. We also construct explicitly a proper subset of $\mathbb{C}^m$ in terms of the Newton polyhedrons of $F_1, F_2, ..., F_m$ and show that it contains the bifurcation set of $F$. In the case $m= n-1$ we show that $F$ is a locally $C^{\infty}$-trivial fibration if and only if it is a locally $C^0$-trivial fibration.
Generalized Broughton polynomials and characteristic varieties
Nguyen Tat Thang
Mathematics , 2012,
Abstract: We introduce a family of generalized Broughton polynomials and compute the characteristic varieties of complement of a curve arrangement defined by fibers of some generalized Broughton polynomials
On the topology of rational functions in two complex variables
Nguyen Tat Thang
Mathematics , 2012,
Abstract: We give some characterizations for the critical values at infinity of a rational function in two complex variables in terms of the Euler characteristic, the Malgrange condition and the M-tameness
Magnitude of Annual Soil Loss from a Hilly Cultivated Slope in Northern Vietnam and Evaluation of Factors Controlling Water Erosion
Kiyoshi Kurosawa,Nguyen Hai Do,Tat Canh Nguyen,Kazuhiko Egashira
Applied and Environmental Soil Science , 2009, DOI: 10.1155/2009/464767
Abstract: A soil erosion experiment was conducted in northern Vietnam over three rainy seasons to clarify the magnitude of soil loss and factors controlling water erosion. The plot had a low (8%) or medium (14.5%) slope with land-cover of cassava or morning glory or being bare. Annual soil loss (177 to 2,361 g/m2) was a tolerable level in all low-slope plots but was not in some medium-slope plots. The effects of slope gradient and seasonal rainfall on the mean daily soil loss of the season were confirmed, but the effect of land-cover was not, owing to the small canopy cover ratio or leaf area index during the season. The very high annual soil loss (>2,200 g/m2) observed in the first year of some medium-slope plots was the site-specific effect from initial land preparation. Since the site-specific effect was large, the preparation must be done carefully on the slope.
Radiotherapy for marginally resected, unresectable or recurrent giant cell tumor of the bone: a rare cancer network study
Sumita Bhatia,Leszek Miszczyk,Martine Roelandts,Tat Dat Nguyen
Rare Tumors , 2011, DOI: 10.4081/rt.2011.e48
Abstract: The role of radiotherapy for local control of marginally resected, unresectable, and recurrent giant cell tumors of bone (GCToB) has not been well defined. The number of patients affected by this rare disease is low. We present a series of 58 patients with biopsy proven GCToB who were treated with radiation therapy. A retrospective review of the role of radiotherapy in the treatment of GCToB was conducted in participating institutions of the Rare Cancer Network. Eligibility criteria consisted of the use of radiotherapy for marginally resected, unresectable, and recurrent GCToB. Fifty-eight patients with biopsy proven GCToB were analyzed from 9 participating North American and European institutions. Forty-five patients had a primary tumor and 13 patients had a recurrent tumor. Median radiation dose was 50 Gy in a median of 25 fractions. Indication for radiation therapy was marginal resection in 33 patients, unresectable tumor in 13 patients, recurrence in 9 patients and palliation in 2 patients. Median tumor size was 7.0 cm. A significant proportion of the tumors involved critical structures. Median follow- up was 8.0 years. Five year local control was 85% . Of the 7 local failures, 3 were treated successfully with salvage surgery. All patients who received palliation achieved symptom relief. Five year overall survival was 94%. None of the patients experienced grade 3 or higher acute toxicity. This study reports a large published experience in the treatment of GCToB with radiotherapy. Radiotherapy can provide excellent local control for incompletely resected, unresectable or recurrent GCToB with acceptable morbidity.
Effect of Receive Spatial Diversity on the Degrees of Freedom Region in Multi-Cell Random Beamforming
Hieu Duy Nguyen,Rui Zhang,Hon Tat Hui
Mathematics , 2013,
Abstract: The random beamforming (RBF) scheme, jointly applied with multi-user diversity based scheduling, is able to achieve virtually interference-free downlink transmissions with only partial channel state information (CSI) available at the transmitter. However, the impact of receive spatial diversity on the rate performance of RBF is not fully characterized yet even in a single-cell setup. In this paper, we study a multi-cell multiple-input multiple-output (MIMO) broadcast system with RBF applied at each base station (BS) and either the minimum-mean-square-error (MMSE), matched filter (MF), or antenna selection (AS) based spatial receiver employed at each mobile terminal. We investigate the effect of different spatial diversity receivers on the achievable sum-rate of multi-cell RBF systems subject to both the intra- and inter-cell interferences. We first derive closed-form expressions for the distributions of the receiver signal-to-interference-plus-noise ratio (SINR) with different spatial diversity techniques, based on which we compare their rate performances at finite signal-to-noise ratios (SNRs). We then investigate the asymptotically high-SNR regime and for a tractable analysis assume that the number of users in each cell scales in a certain order with the per-cell SNR as SNR goes to infinity. Under this setup, we characterize the degrees of freedom (DoF) region for multi-cell RBF systems with different types of spatial receivers, which consists of all the achievable DoF tuples for the individual sum-rate of all the cells. The DoF region analysis provides a succinct characterization of the interplays among the receive spatial diversity, multiuser diversity, spatial multiplexing gain, inter-/intra-cell interferences, and BSs' collaborative transmission.
Multi-Cell Random Beamforming: Achievable Rate and Degrees of Freedom Region
Hieu Duy Nguyen,Rui Zhang,Hon Tat Hui
Mathematics , 2012,
Abstract: Random beamforming (RBF) is a practically favourable transmission scheme for multiuser multi-antenna downlink systems since it requires only partial channel state information (CSI) at the transmitter. Under the conventional single-cell setup, RBF is known to achieve the optimal sum-capacity scaling law as the number of users goes to infinity, thanks to the multiuser diversity enabled transmission scheduling that virtually eliminates the intra-cell interference. In this paper, we extend the study of RBF to a more practical multi-cell downlink system with single-antenna receivers subject to the additional inter-cell interference (ICI). First, we consider the case of finite signal-to-noise ratio (SNR) at each receiver. We derive a closed-form expression of the achievable sum-rate with the multi-cell RBF, based upon which we show an asymptotic sum-rate scaling law as the number of users goes to infinity. Next, we consider the high-SNR regime and for tractable analysis assume that the number of users in each cell scales in a certain order with the per-cell SNR. Under this setup, we characterize the achievable degrees of freedom (DoF) for the single-cell case with RBF. Then we extend the analysis to the multi-cell RBF case by characterizing the DoF region. It is shown that the DoF region characterization provides useful guideline on how to design a cooperative multi-cell RBF system to achieve optimal throughput tradeoffs among different cells. Furthermore, our results reveal that the multi-cell RBF scheme achieves the "interference-free DoF" region upper bound for the multi-cell system, provided that the per-cell number of users has a sufficiently large scaling order with the SNR. Our result thus confirms the optimality of multi-cell RBF in this regime even without the complete CSI at the transmitter, as compared to other full-CSI requiring transmission schemes such as interference alignment.
On linear deformations of Brieskorn singularities of two variables into generic maps
Kazumasa Inaba,Masaharu Ishikawa,Masayuki Kawashima,Tat Thang Nguyen
Mathematics , 2014,
Abstract: In this paper, we study deformations of Brieskorn polynomials of two variables obtained by adding linear terms consisting of the conjugates of complex variables and prove that the deformed polynomial maps have only indefinite fold and cusp singularities in general. We then estimate the number of cusps appearing in such a deformation. As a corollary, we show that a deformation of a complex Morse singularity with real linear terms has only indefinite folds and cusps in general and the number of cusps is 3.
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