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Biomedical subjects

M Rauscher

Publications and source records attributed to M Rauscher.

At least 19 recordsLinked to original sources
PubMed2006

Slip vs. viscoelasticity in dewetting thin films.

Ultrathin polymer films on non-wettable substrates display dynamic features which have been attributed to either viscoelastic or slip effects. Here we show that in the weak- and strong-slip regime, effects of viscoelastic relaxation are either absent or essentially indistinguishable from slip effects. Strong slip modifies the fastest unstable mode in a rupturing thin film, which questions the standard approach to reconstruct the effective interface potential from dewetting experiments.

Journal Article↗
PubMed2005

A thin-film equation for viscoelastic liquids of Jeffreys type.

We derive a novel thin-film equation for linear viscoelastic media describable by generalized Maxwell or Jeffreys models. As a first application of this equation we discuss the shape of a liquid rim near a dewetting front. Although the dynamics of the liquid is equivalent to that of a phenomenological model recently proposed by Herminghaus et al. (S. Herminghaus, R. Seemann, K. Jacobs, Phys. Rev. Lett. 89, 056101 (2002)), the liquid rim profile in our model always shows oscillatory behaviour, contrary to that obtained in the former. This difference in behaviour is attributed to a different treatment of slip in both models.

Journal Article↗
PubMed2002

Fracture in mode I using a conserved phase-field model.

We present a continuum phase-field model of crack propagation. It includes a phase-field that is proportional to the mass density and a displacement field that is governed by linear elastic theory. Generic macroscopic crack growth laws emerge naturally from this model. In contrast to classical continuum fracture mechanics simulations, our model avoids numerical front tracking. The added phase-field smooths the sharp interface, enabling us to use equations of motion for the material (grounded in basic physical principles) rather than for the interface (which often are deduced from complicated theories or empirical observations). The interface dynamics thus emerges naturally. In this paper, we look at stationary solutions of the model, mode I fracture, and also discuss numerical issues. We find that the Griffith's threshold underestimates the critical value at which our system fractures due to long wavelength modes excited by the fracture process.

Journal Article↗
PubMed2001

Porous silicon formation and electropolishing.

Electrochemical etching of silicon in hydrofluoride containing electrolytes leads to pore formation for low and to electropolishing for high applied current. The transition between pore formation and polishing is accompanied by a change of the valence of the electrochemical dissolution reaction. The local etching rate at the interface between the semiconductor and the electrolyte is determined by the local current density. We model the transport of reactants and reaction products and thus the current density in both, the semiconductor and the electrolyte. Basic features of the chemical reaction at the interface are summarized in the law of mass-action-type boundary conditions for the transport equations at the interface. We investigate the linear stability of a planar and flat interface. Upon increasing the current density the stability flips either through a change of the valence of the dissolution reaction or by a nonlinear boundary condition at the interface.

Journal Article↗
PubMed1999

PR-1 protein inhibits the differentiation of rust infection hyphae in leaves of acquired resistant broad bean.

Treatment of broad bean leaves with salicylic acid (SA) or 2, 6-dichloro-isonicotinic acid (DCINA) induces resistance against the rust fungus Uromyces fabae resulting in reduced rust pustule density. Light-microscopy studies showed that in induced resistant plants the rust fungus is inhibited immediately after penetration through the stomatal pore. The differentiation of infection structures growing within the intercellular space of the leaf, i.e. infection hyphae and haustorial mother cells, is inhibited. Furthermore, low-temperature scanning electron microscopy studies of freeze fractures revealed protrusions at the tips of infection hyphae growing in induced resistant broad bean leaves. Treatment of in vitro-differentiating rust infection structures with intercellular fluids (IFs) from induced resistant plants confirmed that the fungus is sensitive towards an apoplastic anti-fungal activity only after having formed appressoria. Other legume rusts such as U. vignae and U. appendiculatus were likewise inhibited in the presence of IF from SA-treated broad bean leaves. Heterologous antibodies were used to study changes in the extracellular pathogenesis-related (PR) protein pattern after resistance induction. Western blots indicated that chitinases and beta-1,3-glucanases were present in both induced and control plants. In contrast, PR-1 proteins were newly synthesized in response to SA or DCINA application. The major induced PR-1 protein was purified and exhibited strong differentiation-inhibiting activity towards U. fabae infection structures. We conclude that the inhibition of rust infection hyphae in acquired resistant broad bean plants is mainly due to the anti-fungal activity of this induced basic PR-1 protein.

Antifungal Agents↗
PubMed1995

[Pulmonary arterial hypertension and primary biliary cirrhosis].

The authors report a case of the association of primary biliary cirrhosis and pulmonary hypertension presenting with syncopal complete atrioventricular block. The clinical, aetiopathological and therapeutic aspects of this pathology are reviewed with special emphasis on the value of early diagnosis of the pulmonary hypertension in cases of unusual dyspnoea in patients with primary biliary cirrhosis especially those of an age when they could benefit from liver-heart-lung transplantation.

Aged↗
PubMed1995

[Total permanent auricular paralysis. Review of the literature apropos of 109 cases].

Analysis of 109 well documented cases of permanent total atrial paralysis reported in the literature illustrated the features of this arrhythmia which is a well defined entity consisting of suppression of all electrical and mechanical activity of both atria lasting for more than 6 months. Standard electrocardiogram reveals junctional bradycardia of about 40 bpm without any visible P waves and narrow supraventricular QRS complexes in 80% of cases. This diagnosis can only be confirmed by meticulous bipolar endocavitary recordings exploring all atrial walls without recording an auriculogram and by right intra-atrial and coronary sinus stimulation which proves to be ineffective. This disease has a male predominance in two-thirds of cases and a familial nature in 18% of cases. Seventy one per cent of affected subjects are under the age of 50 years. In 33% of cases, it is associated with Emery-Dreifuss muscular dystrophy, in which it constitutes a specific sign allowing this dystrophy to be differentiated from all other forms, especially facio-scapulo-humeral myopathy, and in 30% of cases, it is associated with a degenerative disease such as diabetes, amyloidosis or primary cardiomyopathy. Idiopathic dilatation of the right atrium is revealed in 15% of cases. The arrhythmia is responsible for syncope or faintness in 31% of cases, cerebral vascular accidents in 21% of cases and heart failure in 35% of cases. Cardiac activation is dependent on a junctional escape rhythm. The mechanism of the lesion responsible is atrial fibrosis which may extend to the sinoatrial node. The treatment of choice consists of implantation of a VVI or VVIR mode cardiac pacemaker in combination with anticoagulant therapy.

Arrhythmias, Cardiac↗
PubMed1990

[Acute respiratory distress syndrome in the initial phase of myocardial infarction in adults].

Four patients developed an acute respiratory distress syndrome characterised by clinical and radiological signs of pulmonary oedema, a protein-rich oedema, severe hypoxemia refractory to oxygen therapy, contrasting with normal left ventricular filling pressures and indicating increased permeability of the alveolo-capillary membrane, 24 to 72 hours after the onset of acute myocardial infarction. After having excluded the usual causes of the acute respiratory distress syndrome, the authors suggest that acute myocardial infarction, especially when extensive, may cause a lesion of the alveolo-capillary membrane by an unknown mechanism. Treatment consisted in mechanical ventilation with positive expiratory pressures in 3 cases and with continuous positive pressure during spontaneous respiration in the third patient and in relay with controlled ventilation in the other two. These techniques of ventilation improved the hypoxemia and led to complete cure in all cases without evolution to pulmonary fibrosis. In addition to mechanical ventilation, all patients were given systematic antibiotic therapy because of the possibility of an infectious etiology while waiting for the results of microbiological and serological testing and because of the high risk of superinfection which plays an essential part in the outcome of the condition. The immediate response to treatment was favourable in all cases. One patient died suddenly of cardiogenic shock two weeks after this episode. The other patients are still alive 39, 38 and 20 months after infarction. The importance of the diagnosis of the acute respiratory distress syndrome in the acute phase of myocardial infarction resides in its therapeutic implications which are quite different to those of cardiogenic shock.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1990

[Annulo-aortic ectasia].

On the basis of a literature review and the study of 18 cases, the authors examine annuloaortic ectasia, which involves dilatation of the fibrous ring of the heart at the aortic orifice, marked by aortic regurgitation and dystrophic aneurysm of the ascending aorta. The authors noted a predominantly muscular disorder (14 males, 4 females) often detected from an assessment of aortic regurgitation without clinical, radiologic or specific electrical features. The value of echocardiography and Doppler echocardiography is clearly apparent from the diagnosis of the disease, monitoring of progress, selection of patients for invasive pre-operative explorations and post-operative surveillance. The developing gravity of this disease is stressed, rapid repercussions in the left ventricle intervening more than complications due to ectasia itself. This indicates the urgency of complete replacement of the whole ascending aorta and of the aortic valve with reimplantation of coronary arteries as in the Bentall or Bentall-Cabrol surgical intervention, seven cases of which have been reported with satisfactory results.

Adult↗
PubMed1976

[Evaluation of left ventricular function by external methods. Comparative study of systolic intervals and apexcardiography].

In a number of conditions characterised by major disturbance of myocardial contractility (15 cases of thyrotoxicosis, 18 of hypokinetic cardiomyopathy and 9 of hypertrophic cardiomyopathy), the authors have compared the results of measuring the systolic intervals as derived from the quotient PPE/TE with an analysis of the upstroke of the apex electrocardiogram derived from measurement of the t-da/dt interval and from the quotient da/dt/A. The quotient PPE/TE is markedly lowered in the hypokinetic cardiomyopathies. On the other hand this quotient does not differentiate between normal subjects and patients with thyrotoxicosis or hypertrophic cardiomyopathy. By contrast the measurements derived from the electrocardiogram, and especially the quotient da/dt/A, differentiate very clearly between the various pathological conditions.

Cardiomegaly↗
PubMed1976

[Carcinoid of the small intestines with right cardiac involvement. Clinical, phonomechanographical hemodynamic and anatomical study].

The authors report a case of carcinoid of the small intestine with liver metastases in whom the entire right side of the heart was affected, with severe tricuspid incompetence and pulmonary stenosis. The extent of the fibrosis, which affected all three layers of the heart on the right side has lead the authors to reconsider the various factors which cause the heart failure in carcinoid syndrome. This must now be included in the wider category of APUD. The severity of the tricuspid lesions compared with the derangement of the valvular and subvalvular structures makes an argument in favour of surgical correction.

Carcinoid Tumor↗