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Search Results: 1 - 10 of 6106 matches for " Matthias "
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Combined Hemostasis and Adhesion Prevention with the Novel Agent 4DryField® PH—Initial Observations  [PDF]
Matthias Korell
Surgical Science (SS) , 2014, DOI: 10.4236/ss.2014.512081
Abstract: Large size peritoneal trauma from extended surgery for high-grade expansive uterus pathology or endometriosis might result in severe diffuse bleeding and peritoneal adhesion formation with objectionable sequelae. This paper introduces 4DryField® PH polysaccharide powder certified for two indications: 1) given as powder 4DryField® PH provides hemostasis; 2) transformed into gel, 4DryField® PH forms an adhesion prevention barrier. Twenty-one women with expanded uterus pathology and/or deep infiltrating endometriosis had surgery including repair of intestine lesions (n = 8), ureterolysis/repair of bladder, including retrograde ureteric stents (n = 5). Subjective impression of hemostatic effect, drain loss and infection parameters were recorded. Six women had scheduled second look laparoscopy. 4DryField® PH applied as powder showed an immediate significant hemostatic effect in all instances, especially in profound diffuse bleeding. Mean drain loss was 497 ± 339 mL, moderate considering the extent of disease. Dripped with saline solution, 4DryField® PH immediately formed a viscous gel acting as a barrier for adhesion prevention. Second look laparoscopy revealed only one patient with significant adhesions. No adverse events were observed; discharge was at Day 6.2 ± 1.4. In this cohort with extended gynecological laparoscopic surgery 4DryField®
The Influence of LOS Components on the Statistical Properties of the Capacity of Amplify-and-Forward Channels  [PDF]
Gulzaib RAFIQ, Matthias PATZOLD
Wireless Sensor Network (WSN) , 2009, DOI: 10.4236/wsn.2009.11002
Abstract: Amplify-and-forward channels in cooperative networks provide a promising improvement in the network coverage and system throughput. Under line-of-sight (LOS) propagation conditions in such cooperative networks, the overall fading channel can be modeled by a double Rice process. In this article, we have stud-ied the statistical properties of the capacity of double Rice fading channels. We have derived the analytical expressions for the probability density function (PDF), cumulative distribution function (CDF), level- crossing rate (LCR), and average duration of fades (ADF) of the channel capacity. The obtained results are studied for different values of the amplitudes of the LOS components in the two links of double Rice fading channels. It has been observed that the statistics of the capacity of double Rice fading channels are quite dif-ferent from those of double Rayleigh and classical Rice fading channels. Moreover, the presence of an LOS component in any of the two links increases the mean channel capacity and the LCR of the channel capacity. The validity of the theoretical results is confirmed by simulations. The results presented in this article can be very useful for communication system designers to optimize the performance of cooperative networks in wireless communication systems.
Parameter Optimization for Amplify-and-Forward Relaying Systems with Pilot Symbol Assisted Modulation Scheme  [PDF]
Yi WU, Matthias PATZOLD
Wireless Sensor Network (WSN) , 2009, DOI: 10.4236/wsn.2009.11003
Abstract: Cooperative diversity is a promising technology for future wireless networks. In this paper, we consider a cooperative communication system operating in an amplify-and-forward (AF) mode with a pilot symbol as-sisted modulation (PSAM) scheme. It is assumed that a linear minimum mean square estimator (LMMSE) is used for the channel estimation at the receiver. A simple and easy-to-evaluate asymptotical upper bound (AUB) of the symbol-error-rate (SER) is derived for uncoded AF cooperative communication systems with quadrature amplitude modulation (QAM) constellations. Based on the AUB, we propose a criterion for the parameter optimization in the PSAM scheme. We discuss how the pilot spacing and the length of the Wiener ?lter should be chosen under the constraint of a tradeoff between pilot overhead, estimation accuracy, and receiver complexity. We also formulate an power allocation problem for the considered system. It is shown that the power allocation problem can optimally be solved by means of a gradient search method. Numerical simulations are presented to verify the correctness of the theoretical results and to demonstrate the benefits of the parameter optimization.
Towards a More Business-Oriented Definition of Corporate Social Responsibility: Discussing the Core Controversies of a Well-Established Concept  [PDF]
Matthias S. Fifka
Journal of Service Science and Management (JSSM) , 2009, DOI: 10.4236/jssm.2009.24037
Abstract: The concept of Corporate Social Responsibility (CSR) has been controversially discussed for over 50 years. Consequently, a wide variety of definitions and understandings of CSR have been developed throughout the decades. That has made it increasingly hard, or not to say impossible, to agree on a common perception of CSR. Concerning the various notions of CSR, four core controversies can be identified which revolve around certain elements of CSR: First of all, there is the underlying question if CSR is the business of business or if it is none of its business as Friedman has fa-mously argued. Second, should CSR contain legal obligations or is it a purely voluntary concept and, thus, ethical in nature? Strongly connected to that is the third controversy on whether CSR should be self-serving or if it has to be purely altruistic. Finally, there is widespread disagreement on the scope of CSR. Does it have a local, community-oriented focus or should it address concerns of a wider geographical scope? These controversies are analyzed and discussed here with the aim of developing a definition of CSR that does not remain confined to the academic world.
Leading Multicultural Teams in the PR China  [PDF]
Reinhard Meckl, Matthias Johanning
American Journal of Industrial and Business Management (AJIBM) , 2013, DOI: 10.4236/ajibm.2013.31007
Abstract:

This paper examines the effect of transformational, transactional and passive leadership on the performance of multicultural teams in the People’s Republic (PR) of China. 42 multicultural teams with a total of 158 team members employed at German companies in the PR China completed a questionnaire which has been analyzed to show the extent to which these three leadership styles moderate the relationship between cultural diversity and social integration, satisfaction, communication effectiveness and conflict. To evince an explanation for discrepancies it has also been examined whether all three leadership styles justified mediating effects. The relationship between cultural diversity and several team variables has been explained through the resource-oriented theory, the information processing theory, the similarity-attraction theory and the social identity and social categorization theory. The effect of transformational, transactional and passive leadership is based on the theory of charismatic leadership from Bass and its related “Full Range of Leadership”. Results suggest transformational, transactional and passive leadership moderate the relationship between cultural diversity and conflict. In addition, it has been shown that transactional leadership mediates all four group variables. This study identifies practical implications and proposes an agenda for future research.

Green’s Function Approach to the Bose-Hubbard Model  [PDF]
Matthias Ohliger, Axel Pelster
World Journal of Condensed Matter Physics (WJCMP) , 2013, DOI: 10.4236/wjcmp.2013.32020
Abstract:

We use a diagrammatic hopping expansion to calculate finite-temperature Green functions of the Bose-Hubbard model which describes bosons in an optical lattice. This technique allows for a summation of subsets of diagrams, so the divergence of the Green function leads to non-perturbative results for the boundary between the superfluid and the Mott phase for finite temperatures. Whereas the first-order calculation reproduces the seminal mean-field result, the second order goes beyond and shifts the phase boundary in the immediate vicinity of the critical parameters determined by high-precision Monte-Carlo simulations of the Bose-Hubbard model. In addition, our Greens function approach allows for calculating the excitation spectrum both for zero and finite temperature and for determining the effective masses of particles and holes.

A Comparison of X-ray and Strong Lensing Properties of Simulated X-ray Clusters
Matthias Bartelmann,Matthias Steinmetz
Physics , 1996, DOI: 10.1093/mnras/283.2.431
Abstract: We use gas-dynamical simulations of galaxy clusters to compare their X-ray and strong lensing properties. Special emphasis is laid on mass estimates. The cluster masses range between 6 x 10^14 solar masses and 4 x 10^15 solar masses, and they are examined at redshifts between 1 and 0. We compute the X-ray emission of the intracluster gas by thermal bremsstrahlung, add background contamination, and mimic imaging and spectral observations with current X-ray telescopes. Although the beta model routinely provides excellent fits to the X-ray emission profiles, the derived masses are typically biased low because of the restricted range of radii within which the fit can be done. For beta values of ~ 2/3, which is the average in our numerically simulated sample, the mass is typically underestimated by ~ 40 per cent. The masses of clusters which exhibit pronounced substructure are often substantially underestimated. We suggest that the ratio between peak temperature and emission-weighted average cluster temperature may provide a good indicator for ongoing merging and, therefore, for unreliable mass estimates. X-ray mass estimates are substantially improved if we fit a King density profile rather than the beta model to the X-ray emission, thereby dropping the degree of freedom associated with beta. Clusters selected for their strong lensing properties are typically dynamically more active than typical clusters. Bulk flows in the intracluster gas contain a larger than average fraction of the internal energy of the gas in such objects, hence the measured gas temperatures are biased low. The bulk of the optical depth for arc formation is contributed by clusters with intermediate rather than high X-ray luminosity. Arcs occur predominantly in clusters which exhibit substructure and are not in an equilibrium state. Finally we explain why the
On the spin parameter of dark-matter haloes
Matthias Steinmetz,Matthias Bartelmann
Physics , 1994, DOI: 10.1093/mnras/272.3.570
Abstract: The study by White (1984) on the growth of angular momentum in dark haloes is extended towards a more detailed investigation of the spin parameter $\lambda\equiv L\sqrt{E}/{G M^{2.5}}$. Starting from the Zel'dovich approximation to structure formation, a dark halo is approximated by a homogeneous ellipsoid with the inertial tensor of the (highly irregular) Lagrangian region $\Upsilon$ from which the dark halo forms. Within this approximation, an expression for the spin parameter can be derived, which depends on the geometry of $\Upsilon$, the cosmological density parameter $\Omega_0$, the overdensity of the dark halo, and the tidal torque exerted on it. For Gaussian random fields, this expression can be evaluated statistically. As a result, we derive a probability distribution of the spin parameter which gives $\lambda\simeq0.07^{+0.04}_{-0.05}$, consistent with numerical investigations. This probability distribution steeply rises with increasing spin parameter, reaching its maximum at $\lambda\simeq0.025$. The 10 (50,90) percentile values are $\lambda=0.02$ (0.05,0.11, respectively). There is a weak anticorrelation of the spin parameter with the peak height $\nu$ of the density fluctuation field $\lambda\propto \nu^{-0.29}$. The dependence on $\Omega_0$ and the variance $\sigma$ of the density-contrast field is very weak; there is only a marginal tendency for the spin parameter to be slightly larger for late-forming objects in an open universe. Due to the weak dependence on $\sigma$, our results should be quite generally applicable and independent on
Flow curves of dense colloidal dispersions: schematic model analysis of the shear-dependent viscosity near the colloidal glass transition
Matthias Fuchs,Matthias Ballauff
Physics , 2005, DOI: 10.1063/1.1859285
Abstract: A recently proposed schematic model for the non--linear rheology of dense colloidal dispersions is compared to flow curves measured in suspensions that consist of thermosensitive particles. The volume fraction of this purely repulsive model system can be adjusted by changing temperature. Hence, high volume fractions ($\phi \leq 0.63$) can be achieved in a reproducible manner. The quantitative analysis of the flow curves suggests that the theoretical approach captures the increase of the low shear viscosity with increasing density, the shear thinning for increasing shear rate, and the yielding of a soft glassy solid. Variations of the high shear viscosity can be traced back to hydrodynamic interactions which are not contained in the present approach but can be incorporated into the data analysis by an appropriate rescaling.
Nonlinear rheology of dense colloidal dispersions: a phenomenological model and its connection to mode coupling theory
Matthias Fuchs,Matthias Ballauff
Physics , 2005,
Abstract: Rheological properties, especially 'shear-thinning', of dense colloidal dispersions are discussed on three different levels. A generalized phenomonological Maxwell model gives a broad framework connecting glassy dynamics to the linear and non-linear rheology of dense amorphous particle solutions. First principles mode coupling theory calculations for the time or frequency dependent shear modulus give quantitative results for dispersions of hard colloidal spheres in the linear regime. Schematic models extending mode coupling theory to the non-linear regime recover the phenomenology of the generalized Maxwell model, and predict universal features of flow curves, stress versus shear-rate.
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