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K Neuffer

Publications and source records attributed to K Neuffer.

9 recordsLinked to original sources
PubMed2001

Sliding drops in the diffuse interface model coupled to hydrodynamics.

Using a film thickness evolution equation derived recently combining long-wave approximation and diffuse interface theory [L. M. Pismen and Y. Pomeau, Phys. Rev. E 62, 2480 (2000)] we study one-dimensional surface profiles for a thin film on an inclined plane. We discuss stationary flat film and periodic solutions including their linear stability. Flat sliding drops are identified as universal profiles, whose main properties do not depend on mean film thickness. The flat drops are analyzed in detail, especially how their velocity, advancing and receding dynamic contact angles and plateau thicknesses depend on the inclination of the plane. A study of nonuniversal drops shows the existence of a dynamical wetting transition with hysteresis between droplike solutions and a flat film with small amplitude nonlinear waves.

Journal Article↗
PubMed2001

Film rupture in the diffuse interface model coupled to hydrodynamics.

The process of dewetting of a thin liquid film is usually described using a long-wave approximation yielding a single evolution equation for the film thickness. This equation incorporates an additional pressure term-the disjoining pressure-accounting for the molecular forces. Recently a disjoining pressure was derived coupling hydrodynamics to the diffuse interface model [L. M. Pismen and Y. Pomeau, Phys. Rev. E 62, 2480 (2000)]. Using the resulting evolution equation as a generic example for the evolution of unstable thin films, we examine the thickness ranges for linear instability and metastability for flat films, the families of stationary periodic and localized solutions, and their linear stability. The results are compared to simulations of the nonlinear time evolution. From this we conclude that, within the linearly unstable thickness range, there exists a well defined subrange where finite perturbations are crucial for the time evolution and the resulting structures. In the remainder of the linearly unstable thickness range the resulting structures are controlled by the fastest flat film mode assumed up to now for the entire linearly unstable thickness range. Finally, the implications for other forms of disjoining pressure in dewetting and for spinodal decomposition are discussed.

Journal Article↗
PubMed2001

Surface patterns of laterally extended thin liquid films in three dimensions.

We examine the fully nonlinear behavior of a thin liquid film in three spatial dimension for a large lateral extension. A partial differential equation is used for the spatiotemporal evolution of the height of the film. To take intermolecular forces in the liquid into account, we concentrate on a recently formulated model of Pismen and Pomeau, who derived an expression for the disjoining pressure only from the wetting properties of the fluid. Finally, the motion of a falling film on an inclined plane is studied within this model.

Journal Article↗
PubMed2001

Dewetting: film rupture by nucleation in the spinodal regime.

Unstable thin liquid films on solid substrates dewet by hole nucleation on defects or by a linear surface instability (spinodal dewetting). A system with destabilizing short-range and stabilizing long-range molecular interactions is investigated. We show that, for a subrange within the linearly unstable film thickness range, nucleation determines the final structure, whereas spinodal dewetting is of negligible influence. The results are also applicable to the spinodal decomposition of binary mixtures.

Journal Article↗
PubMed1977

[Studies of the tolerance and toxicity of Luzern-green-meal pellets after selenium fertilization].

In a feeding trial, rabbits allotted in 3 experimental groups were fed rations containing 2.09, 9.83 and 19.5 mg selenium/kg feed in the form of selenium-enriched alfalfa green meal pellets. The selenium enrichment was done by foliar application (spraying) of the 20--25 cm high plant stand with 2.5 kg SeO2 per hectare in watery solution. The control animals were given normal alfalfa green meal pellets of 0.16 ppm selenium content. Toxicity and lethality, tolerance limit and nutritive effect of the pellets were studied. Plant-assimilated selenium was found to be converted more efficiently by the animal organism than was selenium from inorganic compounds (higher retention rate, better gain in body weight and lower feed expenditure). Therefore, the selenium supply to farm animals should be improved by feeding crops that were given selenium dressings.

Animal Feed↗
PubMed1976

[LD50 values and selenium concentration in rabbit organs after parenteral administration of sodium selenite and determination of toxicity of urososelevit pro inj].

The LD50-values of sodium selenite after i/m injection to rabbits was determined by means of probit-regression straight line. Simultaneously a combination of vitamin E and sodium selenite was tested for toxicity in order to examine the effect of vitamin E on the selenium toxicity. The LD50/24h was 2.53 mg sodium selenite/kg body mass and in combination with vitamin E (30 IU vitamin E/5 mg NaSeO3) 2.73 mg/kg. Furthermore the selenium concentration was determined in blood, liver, kidney and muscles of animals which died or were killed after 24 h respectively. Not only chemical analysis but also relations of time-dose-efficiency and significantly increased LD50-values show a certain protective effect of vitamin E on selenium intoxication.

Animals↗
PubMed1976

[LD 50 and selenium concentration in the organs of rabbits following oral administration of sodium selenite and testing of the toxicity of Ursoselevit-Prämix].

LD50/24hr was established in the first of a series of experiments on 72 rabbits for orally applied sodium selenite. The dosage was 8.62 mg/kg live weight, the confidence interval being (1 - alpha = 0.95) +/- 0.13 mg/kg. The value was four times as high following intravenous application. Complete lethality was recorded from 15 mg Na2SeO3/kg live weight within 21 hours. Thirty-six animals were involved in the second experiment of the series. They had 50 or 100 per cent Ursoselevit-Prämix (30 ppm Se) in their rations. Body mass development of the test animals was superior to that recorded from the controls in the first 50 days, after which limit the former declined strongly in a few days. Their general condition worsened. Postmortem findings, following slaughter, included catarrhal enteritis, toxic liver dystrophy, scattered pulpous tumours in the spleen, and interstitial nephritis. In the third experiment (50 per cent Ursoselevit-Prämix with 60 ppm Se in the rations), the test animals developed better than the controls during the first two months, after which point they exhibited the same clinical symptoms as those observed in the second experiment, stopped to put on weight, and eventually turned cachectic. The pathomorphological findings were identical with those obtained from the second experiment. The selenium concentrations in the organs of the test animals all were much higher than those of the controls. Their amounts in excess to base values were up to eleven times in the blood, nine times in the liver, twelve times in the kidneys, and 13 times in the muscles.

Administration, Oral↗