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A method to compute absolute free energies or enthalpies of fluids
Friederike Schmid,Tanja Schilling
Physics , 2010,
Abstract: We propose a new method to compute the free energy or enthalpy of fluids or disordered solids by computer simulation . The main idea is to construct a reference system by freezing one representative configuration, and then carry out a thermodynamic integration. We present a strategy and an algorithm which allows to sample the thermodynamic integration path even in the case of liquids, despite the fact that the particles can diffuse freely through the system. The method is described in detail and illustrated with applications to hard sphere fluids and solids with mobile defects.
Computing absolute free energies of disordered structures by molecular simulation
Tanja Schilling,Friederike Schmid
Physics , 2009, DOI: 10.1063/1.3274951
Abstract: We present a Monte Carlo simulation technique by which the free energy of disordered systems can be computed directly. It is based on thermodynamic integration. The central idea is to construct an analytically solvable reference system from a configuration which is representative for the state of interest. The method can be applied to lattice models (e.g., the Ising model) as well as off-lattice molecular models. We focus mainly on the more challenging off-lattice case. We propose a Monte Carlo algorithm, by which the thermodynamic integration path can be sampled efficiently. At the examples of the hard sphere liquid and a hard disk solid with a defect we discuss several properties of the approach.
Diagnosis and treatment of lumbosacral discospondylitis in a calf
Evelyne Muggli, Tanja Schmid, Regine Hagen, Barbara Schmid, Karl Nuss
BMC Veterinary Research , 2011, DOI: 10.1186/1746-6148-7-53
Abstract: A 5.5-month-old calf was presented with difficulty in rising, a stiff and slightly ataxic gait in the hind limbs and a shortened stride. The lumbosacral region was severely painful on palpation.Radiographic examination confirmed lumbosacral discospondylitis. Medical treatment with stall rest was instituted over six weeks. Radiographic and ultrasonographic follow-up examinations showed lysis of the endplates initially, then collapse of the intervertebral space at the lumbosacral junction and progressive sclerosis in the periphery of the lytic zones. Four weeks after institution of treatment, the calf could rise normally and the general condition gradually had returned to normal. The calf was discharged after 6 weeks and was sound at 3.5 months clinical and radiographic follow up examination. Thereafter, it was kept on alpine pastures without problems and was pregnant 1 year after the last examination.This report shows that recovery from lumbosacral discospondylitis is possible in heifers, provided that treatment is started before major neurologic deficits have developed and is continued for an extended period of time.Discospondylitis is defined as inflammation and infection of an intervertebral disk accompanied by osteomyelitis of the neighbouring vertebral bodies [1,2]. This disease has been reported in many domestic animals [3-7], but is generally rare. It is diagnosed more often in dogs and pigs than in cattle and horses [8,9].The most common cause of discospondylitis is haematogenous spread [1,10] of bacterial infection and less commonly fungal infection [1]. The disease is characterised by a chronic progressive course with clinical signs that include increased sensitivity in the area of the affected vertebrae, difficulty in rising and progressive neurological deficits, although signs may vary depending on the localisation and severity of the lesion. Other less specific signs may include pyrexia, anorexia and depression [1].Imaging techniques such as radiography
Duodenal ileus caused by a calf feeding nipple in a cow
Ueli Braun, Charlotte Schnetzler, Matteo Previtali, Christian Gerspach, Tanja Schmid
BMC Veterinary Research , 2011, DOI: 10.1186/1746-6148-7-2
Abstract: The clinical, biochemical and ultrasonographic findings in a five-year-old Swiss Braunvieh cow with duodenal ileus caused by a calf feeding nipple are described. The main clinical signs were anorexia, ruminal tympany, decreased faecal output and abomasal reflux syndrome. Ultrasonographic examination revealed reticular hyperactivity and a dilated duodenum. A diagnosis of duodenal ileus was made and the cow underwent right-flank laparotomy, which revealed a dilation of the cranial part of the duodenum because of obstruction by a pliable foreign body. This was identified via enterotomy as a calf feeding nipple. The cow was healthy at the time of discharge four days after surgery and went on to complete a successful lactation.To our knowledge, this is the first description of duodenal obstruction by a calf feeding nipple. This is an interesting case, which broadens the spectrum of the causes of duodenal ileus, which is usually caused by obstruction of the duodenum by a phytobezoar.Ileus of the duodenum results in abomasal reflux syndrome, which is characterised by rapid deterioration of the condition and demeanour in cattle [1]. Phytobezoars are the most common cause of obstruction of the duodenum. They are formed when fibrinous adhesions involving the reticulum impair the mechanism responsible for sorting the ingesta, which allows poorly digested feed to move into the abomasum, omasum and duodenum, where it may cause an obstruction of the duodenum [1,2]. In rare instances, coagulated blood may obstruct the duodenum [1,3-5], although this happens more commonly in the jejunum [5]. Trichobezoars may cause duodenal obstruction in calves [6]. Other causes in mature cattle are obstruction of the duodenum by gravel [7], mechanical compression of the duodenum by an abscess in the liver or omentum, or lymphosarcoma [3]. Functional stenosis of the duodenum refers to ileus in which a mechanical cause cannot be identified [8]. The duodenum may also be obstructed by pressure from t
The Wide and Complex Field of NAFLD Biomarker Research: Trends
Erika Wichro,Tanja Macheiner,Jasmin Schmid,Barbara Kavsek,Karine Sargsyan
ISRN Hepatology , 2014, DOI: 10.1155/2014/846923
Abstract: Background. Nonalcoholic fatty liver disease is now acknowledged as a complex public health issue linked to sedentary lifestyle, obesity, and related disorders like type 2 diabetes and metabolic syndrome. Aims. We aimed to retrieve its trends out of the huge amount of published data. Therefore, we conducted an extensive literature search to identify possible biomarker and/or biomarker combinations by retrospectively assessing and evaluating common and novel biomarkers to predict progression and prognosis of obesity related liver diseases. Methodology. We analyzed finally 62 articles accounting for 157 cohorts and 45,288 subjects. Results. Despite the various approaches, most cohorts were considerably small and rarely comparable. Also, we found that the same standard parameters were measured rather than novel biomarkers. Diagnostics approaches appeared incomparable. Conclusions. Further collaborative investigations on harmonizing ways of data acquisition and identifying such biomarkers for clinical use are necessary to yield sufficient significant results of potential biomarkers. 1. Introduction Nonalcoholic fatty liver disease (NAFLD) is acknowledged as a (public) health issue with an estimated prevalence of 30% in adults [1], of which approximately 25% progresses to nonalcoholic steatohepatitis (NASH) [2]. Sedentary lifestyle and high-fat and high-caloric dietary intake are strongly associated with NAFLD and nonalcoholic steatohepatitis (NASH). NAFLD and NASH occur not only in adults but also increasingly in childhood [3–5], accounting for a tremendous economic health burden [6]. The pathways of NAFLD/NASH and their alcohol-induced counterpart diseases are multifactorial, involving the liver metabolism key players: cytokines, adipokines, and apoptosis [7]. Alternative tools such as ultrasound or magnetic resonance imaging (MRI) [8] are becoming common in clinical routine; anyway in NAFLD/NASH diagnostics liver biopsy still remains the golden standard [9, 10]. In the context of personalized medicine, the research on biomarker to identify NAFLD and its development and progression is high priority for clinical routine. Our systematic data analysis of NAFLD research conducted in the last year, based on evaluation of extensive literature search, provided an overview of the most commonly published potential biomarkers for NAFLD. 2. Methodology We performed an extensive literature assessment to evaluate known and novel biomarkers for progression and prognosis of NASH/NAFLD. In this context, we extracted and evaluated cohorts and parameters and consolidated
Fluctuating Interfaces in Liquid Crystals
Friederike Schmid,Guido Germano,Stefan Wolfsheimer,Tanja Schilling
Physics , 2008, DOI: 10.1002/masy.200750611
Abstract: We review and compare recent work on the properties of fluctuating interfaces between nematic and isotropic liquid-crystalline phases. Molecular dynamics and Monte Carlo simulations have been carried out for systems of ellipsoids and hard rods with aspect ratio 15:1, and the fluctuation spectrum of interface positions (the capillary wave spectrum) has been analyzed. In addition, the capillary wave spectrum has been calculated analytically within the Landau-de Gennes theory. The theory predicts that the interfacial fluctuations can be described in terms of a wave vector dependent interfacial tension, which is anisotropic at small wavelengths (stiff director regime) and becomes isotropic at large wavelengths (flexible director regime). After determining the elastic constants in the nematic phase, theory and simulation can be compared quantitatively. We obtain good agreement for the stiff director regime. The crossover to the flexible director regime is expected at wavelengths of the order of several thousand particle diameters, which was not accessible to our simulations.
Suppression of superconductivity by V-doping and possible magnetic order in Sr2VO3FeAs
Marcus Tegel,Tanja Schmid,Tobias Stürzer,Masamitsu Egawa,Yixi Su,Anatoliy Senyshyn,Dirk Johrendt
Physics , 2010, DOI: 10.1103/PhysRevB.82.140507
Abstract: Superconductivity at 33 K in Sr2VO3FeAs is completely suppressed by small amounts of V-doping in Sr2VO3[Fe0.93(+/-0.01)V0.07(+/-0.01)]As. The crystal structures and exact stoichiometries are determined by combined neutron- and x-ray powder diffraction. Sr2VO3FeAs is shown to be very sensitive to Fe/V mixing, which interferes with or even suppresses superconductivity. This inhomogeneity may be intrinsic and explains scattered reports regarding Tc and reduced superconducting phase fractions in Sr2VO3FeAs. Neutron diffraction data collected at 4 K indicates incommensurate mag- netic ordering of the V-sublattice with a propagation vector q = (0,0,0.306). This suggests strongly correlated vanadium, which does not contribute significantly to the Fermi surface of Sr2VO3FeAs.
Teaching PCA through Letter Recognition  [PDF]
Tanja Van Hecke
Creative Education (CE) , 2011, DOI: 10.4236/ce.2011.23040
Abstract: This article presents the use of a real life problem to reach a deeper understanding among students of the benefits of principal components analysis. Pattern recognition applied on the 26 letters of the alphabet is a recognizable topic for the students. Moreover it is still verifiable with computer algebra software. By means of well defined exercises the student can be guided in an active way through the learning process.
Influence of Random Pinning on the Crystallization Process in Suspensions of Hard Spheres  [PDF]
Sven Dorosz, Tanja Schilling
Journal of Crystallization Process and Technology (JCPT) , 2014, DOI: 10.4236/jcpt.2014.42012
Abstract: We discuss crystal formation in supersaturated suspensions of monodisperse hard spheres with a concentration of hard spheres randomly pinned in space and time. The pinning procedure introduces an external length scale and an external time scale that restrict the accessible number of configureurations and ultimately the number of pathways leading to crystallization. We observe a significant drop in the nucleation rate density at a characteristic pinning concentration that can be directly related to the structure of the critical nucleus and the dynamics of its formation in the unpinned system.
Situs ambiguus in a Brown Swiss cow with polysplenia: case report
Alois Boos, Hans Geyer, Urs Müller, Jeanne Peter, Tanja Schmid, Christian Gerspach, Matteo Previtali, Maja Rütten, Titus Sydler, Colin C Schwarzwald, Elisabeth M Schraner, Ueli Braun
BMC Veterinary Research , 2013, DOI: 10.1186/1746-6148-9-34
Abstract: A 3.5-year-old Brown Swiss cow was referred to the Department of Farm Animals, Vetsuisse Faculty, University of Zurich, because of poor appetite and recurrent indigestion. A diagnosis of situs ambiguus was based on the results of physical examination, ultrasonography, exploratory laparotomy and post-mortem examination. The latter revealed that the rumen was on the right side and lacked compartmentalisation. There were two spleens, one on the left (26.5 x 12.0 cm) and one on the right (20.5 x 5.5 cm), and the omasum was located craniolateral to the ruminoreticulum on the left. The abomasum was located on the right, although it had initially been displaced to the left. The three-lobed liver occupied the left and central cranioventral aspect of the abdominal cavity (cavum abdominis). Only the right and left hepatic veins (vena hepatica dextra and sinistra) drained into the thoracic segment of the caudal vena cava (vena cava caudalis), and histological changes in the liver were indicative of impaired haemodynamics. The mesojejunum was not fused with the mesentery of the spiral loop (ansa spiralis) of the ascending colon (colon ascendens). The latter was folded and the transverse colon (colon transversum) ran caudal to the cranial mesenteric artery (arteria mesenteria cranialis). Fibrotic constrictions were seen in the lumen of the caecum and proximal loop (ansa proximalis) of the ascending colon. Both kidneys were positioned retroperitoneally in a lumbar position. The lumbar segment of the caudal vena cava did not descend to the liver and instead drained into the right azygous vein (vena azygos dextra).Recurrent digestive problems and poor production in this patient may have been caused by a lack of rumen compartmentalisation, abnormal abomasal motility, constrictions in the large intestine (intestinum crassum) and fibrosis of the liver. The abomasum had abnormal motility most likely because it was anchored inadequately and only at its cranial aspect to the liver by the
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