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S Franz

Publications and source records attributed to S Franz.

16 recordsLinked to original sources
PubMed2002

Dynamic phase transition for decoding algorithms.

The state-of-the-art error correcting codes are based on large random constructions (random graphs, random permutations, etc.) and are decoded by linear-time iterative algorithms. Because of these features, they are remarkable examples of diluted mean-field spin glasses, both from the static and dynamic points of view. We analyze the behavior of decoding algorithms by mapping them onto statistical-physics models. This allows us to understand the intrinsic (i.e., algorithm independent) features of this behavior.

Journal Article↗
PubMed2002

Kob-Andersen model: a nonstandard mechanism for the glassy transition.

We present results reflecting the analogies between the Kob-Andersen model and other glassy systems. Studying the stability of the blocked configurations above and below the transition we also give arguments that support their relevance for the glassy behavior of the model. However, we find, surprisingly, that the organization of the phase space of the system is different from the well known organization of other mean field spin glasses and structural glasses.

Journal Article↗
PubMed2002

A retrospective study of oesophageal endoscopy in cattle - oesophagoscopy for diagnosis of mucosal disease.

Oesophageal endoscopy in cattle has been rarely reported in the literature. It has, however, been used for many years as an aid to the diagnosis and treatment of illnesses of the upper gastrointestinal tract in small animals and horses. We have assessed the potential value of oesophagoscopy on 120 bovine patients presented at the 2nd Medical Clinic for Ruminants and Swine at the University of Veterinary Medicine, Vienna, over a period of three years. In the course of the study, cattle exhibiting symptoms such as salivation, regurgitation or swelling in the neck region were referred for endoscopic examination. The main indication was to confirm or exclude bovine virus diarrhoea virus infection in calves, in which typical erosions were visible endoscopically on the mucosa of the oesophagus in infected animals. In addition, endoscopy proved to be useful for the diagnosis of diverticula, ruptures and inflammation of the oesophagus. Oesophagoscopy can be considered to be a valuable supplementary aid to clinical examination and, in many cases, can facilitate diagnosis.

Animals↗
PubMed2001

Random heteropolymer dynamics.

We study the Langevin dynamics of the standard random heteropolymer model by mapping the problem to a supersymmetric field theory using the Martin-Siggia-Rose formalism. The resulting model is solved nonperturbatively employing a Gaussian variational approach. In constructing the solution, we assume that the chain is very long and impose the translational invariance which is expected to be present in the bulk of the globule by averaging over the center of mass coordinate. In this way we derive equations of motion for the correlation and response functions C(t,t') and R(t,t'). The order parameters are extracted from the asymptotic behavior of these functions. We find a dynamical phase diagram with frozen (glassy) and melted (ergodic) phases. In the glassy phase the system fails to reach equilibrium and exhibits aging of the type found in p-spin glasses. Within the approximations used in this study, the random heteropolymer model can be mapped to the problem of a manifold in a random potential with power law correlations.

Journal Article↗
PubMed2001

Exact solutions for diluted spin glasses and optimization problems.

We study the low temperature properties of p-spin glass models with finite connectivity and of some optimization problems. Using a one-step functional replica symmetry breaking ansatz we can solve exactly the saddle-point equations for graphs with uniform connectivity. The resulting ground state energy is in perfect agreement with numerical simulations. For fluctuating connectivity graphs, the same ansatz can be used in a variational way: For p-spin models (known as p-XOR-SAT in computer science) it provides the exact configurational entropy together with the dynamical and static critical connectivities (for p = 3, gamma(d) = 0.818, and gamma(s) = 0.918), whereas for hard optimization problems like 3-SAT or Bicoloring it provides new upper bounds for their critical thresholds ( gamma(var)(c) = 4.396 and gamma(var)(c) = 2.149).

Journal Article↗
PubMed2001

Ultrasonography of the teat canal in cows and sheep.

When the isolated teat of a cow was examined with an 8.5 MHz linear array transducer in a vertical plane, the teat canal appeared as a thin, white line, bordered on each side by parallel, thick, grey-black bands. In a horizontal plane a comparable image was obtained. In a sheep, images of comparable quality were obtained with a 12 MHz transducer. Histological studies of the tissues whose removal led to the disappearance of this characteristic ultrasonographic appearance showed that it was associated with the stratified keratinised squamous epithelium with distinct papillae. The content of keratin in the stratum corneum was apparently responsible for the bright zone; the stratum lucidum was not visible, and the surrounding dark, less echoic area was associated with the stratum granulosum. Doppler echography in live animals confirmed this designation. The outer layers of the teat wall were more echogenic.

Animals↗
PubMed2001

Spectral statistics of instantaneous normal modes in liquids and random matrices.

We study the statistical properties of eigenvalues of the Hessian matrix H (matrix of second derivatives of the potential energy) for a classical atomic liquid, and compare these properties with predictions for random matrix models. The eigenvalue spectra (the instantaneous normal mode or INM spectra) are evaluated numerically for configurations generated by molecular dynamics simulations. We find that distribution of spacings between nearest-neighbor eigenvalues, s, obeys quite well the Wigner prediction s exp(-s(2)), with the agreement being better for higher densities at fixed temperature. The deviations display a correlation with the number of localized eigenstates (normal modes) in the liquid; there are fewer localized states at higher densities that we quantify by calculating the participation ratios of the normal modes. We confirm this observation by calculating the spacing distribution for parts of the INM spectra with high participation ratios, obtaining greater conformity with the Wigner form. We also calculate the spectral rigidity and find a substantial dependence on the density of the liquid.

Journal Article↗
PubMed2001

Preactivated monocytes from hypertensive patients as a factor for atherosclerosis?

Recently, we reported our findings regarding the elevated secretion patterns of proinflammatory cytokines obtained from peripheral blood monocytes of hypertensive patients. To investigate the direct impact of these preactivated monocytes, the adhesion of monocytes from normal controls and hypertensive patients to vascular endothelial cell monolayers was determined spontaneously and after in vitro stimulation with either lipopolysaccharide (LPS) or angiotensin II (Ang II), with or without preincubation with the AT1 receptor antagonist eprosartan. Peripheral blood monocytes from 20 patients and 20 healthy individuals were isolated by density gradient centrifugation and plastic adherence; endothelial cells were obtained from human umbilical cords by collagenase digestion. The adhesion was determined by an assay with 51Cr-radiolabeled monocytes. Oxygen species release induced by phorbol myristate acetate (PMA) as a further activation marker was analyzed for monocytes and HUVEC by chemiluminescence (CL). Spontaneous adhesion of monocytes from patients and the adhesion after stimulation with Ang II were significantly increased compared with normal controls (P<0.05). Preincubation with eprosartan diminished the adhesion in both groups to comparable levels. In monocytes, peak levels of PMA and Ang II induced CL analysis were significantly higher in patients (P<0.005). These data indicate that preactivated monocytes from hypertensives may be of pathogenic importance in atherosclerosis.

Adult↗
PubMed2001

Medulloblastoma displays distinct regional matrix metalloprotease expression.

Matrix metalloproteases (MMPs) play an important role in tissue remodeling and neoangiogenesis during tumor progression. Little is known about the presence and regional distribution of MMPs in medulloblastomas. Based on immunohistochemical, immunocytochemical and zymographical analysis is the present study illustrates the differential pattern of MMP expression for the medulloblastoma compared to that of glioma and ependymoma. In 10 examined medulloblastoma tumors gelatinase-A was strongly expressed by clusters of tumor cells. Gelatinase-B was, similar to glioma and ependymoma, predominantly found around endothelial cells. The DAB signal for macrophage metalloelastase was seen around macrophages and matrilysin was expressed by single tumor cells. Stromelysin-1 protein was detected in medulloblastoma but not in glioma or ependymoma. From the presented data it follows that each tumor entity might display its own characteristic MMP expression pattern.

Astrocytoma↗
PubMed2000

Ultrametricity in three-dimensional edwards-anderson spin glasses

We perform an accurate test of ultrametricity in the aging dynamics of the three-dimensional Edwards-Anderson spin glass. Our method consists in considering the evolution in parallel of two identical systems constrained to have fixed overlap. This turns out to be a particularly efficient way to study the geometrical relations between configurations at distant large times. Our findings strongly hint towards dynamical ultrametricity in spin glasses, while this is absent in simpler aging systems with domain growth dynamics. A recently developed theory of linear response in glassy systems allows us to infer that dynamical ultrametricity implies the same property at the level of equilibrium states.

Journal Article↗
PubMed1998

[Changes in colitis surgery. I: Is there a standard in primary surgical treatment?].

In a 15 years period surgery of ulcerative colitis expanded from ileostomy (IS) via Kock's pouch (KP) and ileoanal pouch (IAP) to ileorectal anastomosis (IRA). Interactions between availability of methods and frequency of operations are investigated retrospectively in order to establish an optimal primary procedure. With an overall amount of 80 operations the yearly operative frequency raised in correlation to the introduction of continence reconstructive procedures. As a consequence of this fact history of disease was shortened to less than 8 year and global colitis-associated morbidity markedly decreased. For patients readiness to undergo operation Kock's pouch was only important at the beginning (n = 9/11.3%). Most decisive was IAP (n = 49/61.3%) which could be realized last even in an one-stage-procedure with better early results due to improved patients conditions and simplified technical modifications. IRA (n = 7/8.8%) played only a limited role in the last years for selected patients, whereas IS (n = 15/18.8%) kept reserved for contraindications to reconstructive surgery. For all procedures operative complications decreased from 46.1% (12/26) to 11.0% (6/54) and lethality to 0%. Late complications were related to proctectomy (nerve damage) and construction of IAP (pouchitis in 34.8% and defunctioning of the pouch in 10.4%), whereas IRA was free of specific morbidity so far. Surgery of ulcerative colitis is characterized today by restoration of anal continence. The advantage of the changed surgical concept lies within the ability to perform colectomy at an earlier stage of the disease. Safe construction of IAP is the most important technical progress. Early operation of colitis and late morbidity of pouch justify (preliminary) IRA. Thus, surgical standard in colitis-surgery is defined more individually.

Adolescent↗
PubMed1983

Role of insulin in lipoprotein secretion by cultured rat hepatocytes.

To study the effect of insulin on lipoprotein synthesis and secretion by the liver, apoprotein and lipid levels were measured in primary rat liver cell cultures grown on fibronectin-coated dishes. Triglycerides, phospholipids, apoprotein (apo) B, apo-E, and apo-C-III3 all accumulated in culture media linearly for periods up to 20 h. During incubations, cellular triglyceride contents increased slightly, while cellular apoprotein and phospholipid contents remained constant. In the absence of insulin, rates of accumulation in media of triglycerides, apo-B, apo-C-III3, and apo-E were 2.5 +/- 0.3 micrograms/mg and 33 +/- 5, 24 +/- 3, and 162 +/- 32 ng/mg cell protein per h, respectively. On gel permeation chromatography and density gradient ultracentrifugation, the majority of apoproteins in media were found to be associated with very low density lipoproteins (VLDL) and very little eluted or sedimented with albumin. Incubations in the presence of 50-800 microU/ml of insulin resulted in dose-dependent decreases of triglyceride, phospholipid, apo-B, and apo-E accumulation in the media, paralleled by increases in the cellular contents of these lipoprotein components. The inhibitory effects of insulin on secretion were reversible. Levels of apo-C-III3 and albumin were not affected by insulin. In addition to decreasing secretory rates, the proportion of apo-B, apo-E, and apo-C-III3 associated with VLDL also decreased after the addition of insulin. Concomitantly, the proportion of apo-B eluting with LDL and apo-C-III3, and apo-E eluting near albumin increased. Control experiments, in which exogenous 125I-VLDL or endogenously labeled [14C]VLDL were added to cultures, revealed that the insulin-induced differences in VLDL accumulation and the lipid association of media apoproteins were not due to differences in the processing of VLDL by cells cultured in the presence or absence of insulin. Therefore, it appears that insulin may inhibit the secretion of VLDL perhaps by reducing the intracellular association of lipids and apoproteins.

Animals↗
PubMedDate not supplied

[Sonography of the teat of cattle, sheep and goats in comparison with other methods of diagnostic imaging--a review].

Beside the clinical examination of udder/teat imaging methods e.g. sonography, radiography and endoscopy allow diagnosis. This publication will give a summary of currently used and potentially usable methods of diagnostic imaging applied to the teat. Advantages and disadvantages of the several methods were compared--as quoted in literature and completed by own experiences.

Animals↗