High order Lagrangian velocity statistics in turbulence

We report measurements of the Lagrangian velocity structure functions of orders 1 through 10 in a high Reynolds number (Taylor microscale Reynolds numbers of up to R(lambda) = 815 ) turbulence experiment. Passive tracer particles are tracked optically in three dimensions and in time, and velocities are calculated from the particle tracks. The structure function anomalous scaling exponents are measured both directly and using extended self-similarity and are found to be more intermittent than their Eulerian counterparts. Classical Kolmogorov inertial range scaling is also found for all structure function orders at times that trend downward as the order increases. The temporal shift of this classical scaling behavior is observed to saturate as the structure function order increases at times shorter than the Kolmogorov time scale.     

Action of miscellaneous substances on the pregelification of aqueous solutions of copolymers

We have investigated the action on the gelification process of substances capable of H-bonding to the copolymers. These substances are urea, thiourea, a few amino acids (glycine, α- and β-alanine, diglycine, a-amino butyric acid), a few polyols (mannitol, erythrytol, polyvinyl alcohols, polyoxyethylene glycols), and a few glucides (glyceraldehyde, D-xylose, D-fructose, D-glucose, sucrose, and dextrans).

The action of these substances is followed as a function of time, at constant temperature and rate of shear, by means of the viscosity variations which occur spontaneously during a period before the solidification of the solutions. This period is called the “pregelification” period.

The results of this study show that substances, such as urea and thiourea, systematically lower the viscosity and its rate of change during the pregelification, whereas other substances have an action which is much more varied. The direction and intensity of the action are dependent on the state of copolymer ionization and on the spatial arrangement of atomic groups capable of hydrogen-bonding.     

Fractionation and proteomic analysis of the Walterinnesia aegyptia snake venom using OFFGEL and MALDI‐TOF‐MS techniques

Animal venoms are complex mixtures of more than 100 different compounds, including peptides, proteins, and nonprotein compounds such as lipids, carbohydrates, and metal ions. In addition, the existing compounds show a wide range of molecular weights and concentrations within these venoms, making separation and purification procedures quite tedious. Here, we analyzed for the first time by MS the advantages of using the OFFGEL technique in the separation of the venom components of the Egyptian Elapidae Walterinnesia aegyptia snake compared to two classical methods of separation, SEC and RP‐HPLC. We demonstrate that OFFGEL separates venom components over a larger scale of fractions, preserve respectable resolution with regard to the presence of a given compound in adjacent fractions and allows the identification of a greater number of ions by MS (102 over 134 total ions). We also conclude that applying several separating techniques (SEC and RP‐HPLC in addition to OFFGEL) provides complementary results in terms of ion detection (21 more for SEC and 22 more with RP‐HPLC). As a result, we provide a complete list of 134 ions present in the venom of W. aegyptia by using all these techniques combined.     

Investigating the role of c-Jun N-terminal kinases in the proliferation of Werner syndrome fibroblasts using diaminopyridine inhibitors

To develop more potent small molecules with enhanced free radical scavenger properties, a series of N-substituted isatin derivatives was synthesized, and the cytoprotective effect on the apoptosis of PC12 cells induced by H₂O₂ was screened. All these compounds were found to be active, and N-ethyl isatin was found with the most potent activity of 69.7% protective effect on PC12 cells. Structure-activity relationship analyses showed the bioactivity of N-alkyl isatins decline as the increasing of the chain of the alkyl group, furthermore odd-even effect was found in the activity, which is interesting for further investigation.     

Rotational intermittency and turbulence induced lift experienced by large particles in a turbulent flow

The motion of a large, neutrally buoyant, particle freely advected by a turbulent flow is determined experimentally. We demonstrate that both the translational and angular accelerations exhibit very wide probability distributions, a manifestation of intermittency. The orientation of the angular velocity with respect to the trajectory, as well as the translational acceleration conditioned on the spinning velocity, provides evidence of a lift force acting on the particle.     

Etude expérimentale IN VITRO du comportement rhéologique du sang en régime transitoire à faible vitesse de cisaillement

Résumé Des écoulements de type Couette en régime transitoire sont produits au moyen d'un microviscosimètre semi-automatique à cylindres coaxiaux muni d'un asservissement de la vitesse de rotation et d'un enregistreur à deux voies, et qui peut être associé à un générateur de fonction basse fréquence permettant de programmer la vitesse de rotation du cylindre extérieur du viscosimètre. Diverses sortes de rhéogramme ont été établies pour des échelons rectangulaires ou triangulaires de vitesse de cisaillement, ce dernier cas correspondant à l'enregistrement de courbes d'hystérèse. L'étude des changements de forme des rhéogrammes obtenus avec du sang humain en fonction de la loi de variation de la vitesse de cisaillement avec le temps a permis de déterminer un protocole expérimental optimal et de sélectionner quatre types d'hémorhéogramme qui font apparaître les principales propriétés rhéologiques du sang aux faibles valeurs de la vitesse de cisaillement. Ces hémorhéogrammes sont décrits en détail; des groupes de paramètres caractéristiques en sont déduits, qui permettent de comparer les divers sangs entre eux du point de vue rhéologique. Les valeurs de ces paramètres et leur précision sont données pour les sangs humains normaux.

---

Summary Couette type transient flows have been produced in a semi-automatic coaxial cylinder viscometer equipped with a two way recorder and a servo-motor which is possibly connected to a low frequency function generator programming the rotational speed of the outer cylinder of the viscometer. Several kinds of rheograms have been established for rectangular and triangular steps of shear rate, the latter case corresponding to the drawing of hysteresis curves. The study of the shape changes of the rheograms as a function of the time law of the shear rate variation has led to the establishment of an optimal experimental process for blood investigation, and to the selection of four types of hemorheograms showing the main rheological properties of blood at low shear rate. These hemorheograms have been described in detail, and groups of characteristic parameters have been deduced from them. These parameters enable the comparison of various bloods from rheological point of view. The values and the accuracy of these characteristic parameters are given for normal human bloods.

---

Zusammenfassung In einem Mikroviskosimeter mit zwei konzentrischen Zylindern werden nicht-stationäre Couette-Strömungen erzeugt: Das mit einer Nachlaufsteuerung versehene Viskosimeter ist an einen Niederfrequenz-Funktions-Generator angeschlossen, so daß die Umdrehungsgeschwindigkeit des äußeren Zylinders moduliert werden kann. EinX – Y-Schreiber erlaubt die zeichnerische Darstellung der Meßergebnisse. Es werden verschiedene Rheogramme für Rechteck- oder Dreiecksignale der Schergeschwindigkeit hergestellt. Im zweiten Falle erhält man Hysteresis-Kurven. Die Formänderung der Rheogramme für Humanblut in Abhängigkeit von der zeitlichen Veränderung der Schergeschwindigkeit erlaubt es, ein optimales Versuchsprotokoll zu ermitteln. Vier ausgewählte Haemorheogramm-Modelle stellen die wesentlichen rheologischen Eigenschaften des Blutes bei geringer Schergeschwindigkeit dar. Diese Hämorheogramme werden im einzelnen beschrieben; charakteristische Parametergruppen, die den Vergleich verschiedener Blutsorten bezüglich ihrer rheologischen Eigenschaften ermöglichen, werden abgeleitet. Es werden numerische Werte und Abweichungen dieser Parameter für normales Humanblut angegeben.

---

---

Avec 9 figures et 4 tableaux     

H-transfer rates in ion-neutral complexes versus those in intact aliphatic ions

The relative rates of H-transfer between partners in ion-neutral complexes were compared with those in intramolecular rearrangements using results of first differential photoionization mass spectrometry measurements. Complex-mediated H-transfers are inferred to have rates of the same order as those for intramolecular hydrogen rearrangements, suggesting a similar range of motion of the reactive sites in both types of reactions. It is also concluded that at their fastest H-transfers take place between the partners in ion-neutral complexes within at most the time of several rotations of the partners in the complexes. Copyright 1999 John Wiley & Sons, Ltd.     

Ueber die L?slichkeit einiger organischen S?uren in Aether und Alkohol

Ohne Zusammenfassung     

Effects of ultrasonic irradiation on the properties of coatings obtained by electroless plating and electro plating

This paper deals with the effects of ultrasonic irradiation on electroless copper coating i.e. metallic deposition on non-conductive substrates and on electroplating on metallic substrates. Ultrasonic irradiation was both applied during activation (surface preparation for the electroless coating) and during plating steps in both cases. Several parameters were monitored, such as plating rates, practical adhesion, hardness, internal stress versus varying acoustic powers and frequencies. Optimum conditions for irradiation time, frequency and power were determined for each step. It appears clearly that ultrasound use affects deposit properties. Then, changes in the coating mechanisms can be discussed, and several parameters will be explored in this paper, to explain enhancement of deposit properties: increase in catalyst specific area, stirring dependence, surface energy evolution, dihydrogen desorption, structure of coating.