Application of arc-plasma discharges to coating of screw taps

The paper reports on results of technological research on the coating of standard screw taps with TiN layers deposited by means of arc-plasma discharges, which were carried out within a BULAT-type device equipped with three identical metal-plasma sources. Particular attention is paid to morphology of the coated surfaces. Some data about thickness and microhardness of the coating layers, as well as results of laboratory wear tests of the coated tools, are also presented.     

General Synthesis and Physicochemical Characterisation of a Series of Peptide‐Mimic Lysine‐Based Amino‐Functionalised Lipids

A series of novel malonic acid diamides (second generation) with two long hydrophobic alkyl chains and an alkaline polar head group was synthesised and characterised as a new class of amino‐functionalised lipids. These peptide‐mimic lipids are suitable for polynucleotide transfer. The lipids bear a novel backbone consisting of a lysine unit and a malonic acid unit. Six different head‐group structures, which vary in size and number of amino groups that can be protonated, were attached to the backbone structure. Furthermore, different alkyl chains were used to build the lipophilic part (namely tetradecyl, hexadecyl, and oleyl). Phase transitions of the new compounds in aqueous dispersions at pH 10 were analysed and discussed in terms of head group and alkyl chain variations. The shape and size of the formed aggregates of selected lipid dispersions were investigated by dynamic light scattering and transmission electron microscopy.     

The effect of cholesterol on the adsorption of phenyltin compounds onto phosphatidylcholine and sphingomyelin liposome membranes

Organometallic compounds are widely spread in the human environment sometimes, causing a substantial health risk. Their amphiphilic character enables them to intercalate and penetrate cell membranes, potentially affecting various vital cell functions. Compound adsorption onto the membrane depends on the compound properties, as well as on the membrane composition and state. When adsorbing onto the lipidic surface, phenyltins localize at areas where lipid bilayer organization is compatible with compound spatial requirements. The lipid bilayer is a dynamic and laterally nonuniform structure with complex local and global architecture correlated with a variety of cell functions. The selective binding of a toxic compound to selected membrane areas may, therefore, interfere with some types of cellular process. We present experimental results concerning phenyltin adsorption onto the lipid bilayer surface measured with the fluorescent probe fluorescein‐PE. Model lipid bilayers were formed from lipid mixtures mimicking various plasma membrane regions. The adsorption of Ph₃SnCl and P₂SnCl₂ onto the phosphatidylcholine–cholesterol bilayer was qualitatively different from sphingomyelin–cholesterol. The results presented indicate that phenyltins are likely to accumulate in areas containing phosphatidylcholine, outside of lipid rafts. Copyright © 2004 John Wiley & Sons, Ltd.     

Tropfenspektrum und Entrainment in beheizten Dampf-Flüssigkeits-Gemischen

Zusammenfassung Bei hohem Dampfgehalt separiert sich die Zweiphasenströmung in einem Flüssigkeitsfilm an der Wand und in einem Dampfstrom im Kern, der aber mit einer hohen Tropfenkonzentration beladen ist. Es wird die Verteilung der Flüssigkeit auf den Wandfilm und auf die durch Schubspannung und Impuls vom schneller fließenden Dampf herausgerissenen Tropfen einer theoretischen Betrachtung unterzogen. Messungen mit der Hochgeschwindigkeitskinematographie verdeutlichen die fluiddynamischen Vorgänge und liefern Vergleichsdaten für die Rechnung.

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Droplet-spectrum and entrainment in heated vapour-liquid flow

At high void fraction the two-phase flow is separated into a liquid film at the wall end and the vapour flow in the center of the channel. The vapour flow is highly loaded with droplets. Calculations were performed predicting the splitting of the total liquid flow in the film flow and in the vapour carried flow, which is produced by the momentum and the shear stress, due to the slip between vapour and liquid film. Measurements with the high-speed-cinematography illustrate the fluiddynamic behaviour and supply data for the comparison with the calculation.

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Formelzeichen A Fläche - c spezifische Wärmekapazität - d Durchmesser - E Entrainment auf Volumenanteil bezogen - g Erdbeschleunigung - h _FD spezifische Verdampfungswärme - M Massenstrom - m Massenstromdichte - p Druck - Q Wärmestrom - q Wärmestromdichte - R ₀ Gaskonstante - r Radius - s Geschwindigkeitsverhältnis zwischen Dampf und Tropfen - T Temperatur - U Umfang - w Geschwindigkeit - x Strömungsdampfgehalt auf Masse bezogen - z Längenkoordinate (Kanalachse) - örtlicher volumetrischer Dampfgehalt - Viskosität - Dichte - Schubspannung - Oberflächenspannung Indizes b beheizt - D Dampf - Ent Entrainment - Fl Flüssigkeit - i Filminnenseite - o Kanalwand, Rohrwand Herrn Prof. Dr.-Ing. U. Grigull zum 70. Geburtstag gewidmet     

The effect of lipid oxidation on the water permeability of phospholipids bilayers

The effect of lipid oxidation on water permeability of phosphatidylcholine membranes was investigated by means of both scattering stopped flow experiments and atomistic molecular dynamics simulations. Formation of water pores followed by a significant enhancement of water permeability was observed. The molecules of oxidized phospholipids facilitate pore formation and subsequently stabilize water in the membrane interior. A wide range of oxidation ratios, from 15 to 100 mol%, was considered. The degree of oxidation was found to strongly influence the time needed for the opening of a pore. In simulations, the oxidation ratio of 75 mol% was found to be a threshold for spontaneous pore formation in the tens of nanosecond timescale, whereas 15 mol% of oxidation led to significant water permeation in the timescale of seconds. Once a pore was formed, the water permeability was found to be virtually independent of the oxidation ratio.