Cold streams in early massive hot haloes as the main mode of galaxy formation.

Massive galaxies in the young Universe, ten billion years ago, formed stars at surprising intensities. Although this is commonly attributed to violent mergers, the properties of many of these galaxies are incompatible with such events, showing gas-rich, clumpy, extended rotating disks not dominated by spheroids. Cosmological simulations and clustering theory are used to explore how these galaxies acquired their gas. Here we report that they are 'stream-fed galaxies', formed from steady, narrow, cold gas streams that penetrate the shock-heated media of massive dark matter haloes. A comparison with the observed abundance of star-forming galaxies implies that most of the input gas must rapidly convert to stars. One-third of the stream mass is in gas clumps leading to mergers of mass ratio greater than 1:10, and the rest is in smoother flows. With a merger duty cycle of 0.1, three-quarters of the galaxies forming stars at a given rate are fed by smooth streams. The rarer, submillimetre galaxies that form stars even more intensely are largely merger-induced starbursts. Unlike destructive mergers, the streams are likely to keep the rotating disk configuration intact, although turbulent and broken into giant star-forming clumps that merge into a central spheroid. This stream-driven scenario for the formation of discs and spheroids is an alternative to the merger picture.

Interface imprinting by a rippled shock using an intense laser.

Perturbation imprinting at a flat interface by a rippled shock has been observed in a laser hydrodynamics experiment. A strong shock was driven through a three-layer target, with the first interface rippled, and the second flat. The chosen thickness of the second layer gave instability growth with opposite phases at the two interfaces, consistent with two-dimensional simulations and rippled shock theory.

[Modifications, due to nutrition, of methyl and methylene 1H NMR signals in human plasma and normal serum samples]. / Etude des modifications apportées par la nutrition sur les signaux de RMN 1H méthyliques et méthyléniques d'échantillons de plasmas et sérums humains normaux.

The line width test has been realised on twelve normal healthy persons (seven men and five women). Blood was collected at different time during one day. The results obtained when blood samples was taking after eating, showed an appreciable decrease in the average methylene and methyl line width. The same test realised on clear serum samples added up with increasing quantities of triglycerids rich lipoproteins leads to the same result.

Preliminary results of nuclear magnetic resonance studies of healthy human saliva.

Relaxation times T1 and T2 of water protons for stimulated and unstimulated parotid and submandibular saliva from healthy patients were measured in the conventional way using the Bruker PC 20 Minispec. Some measurements of dispersion were also carried out. An interpretation of the average values for T1 and T2 observed in the 20 MHz range is proposed for these types of saliva in relation to biochemical composition (total proteins, amylase activity, sialic acids and hexosamins) and viscosity. For parotid saliva T2(-1)-T1(-1) correlates significantly with amylase activity. In the submandibular saliva T2(-1)-T1(-1) correlates significantly with both mucins and alpha-amylase activity.

[In vitro differentiation of inflammatory and non-inflammatory states of the synovial fluid by magnetic protonic relaxation]. / Différenciation in vitro de l'état inflammatoire ou non inflammatoire du liquide synovial par relaxation magnétique protonique.

The differentiation between inflammatory and non inflammatory states has been performed using Nuclear Magnetic Resonance (NMR) in vitro by measuring relaxation times T1 and T2 in 84 synovials fluids obtained from various rheumatologic diseases. The results show that the T1/T2 ratio is more sensitive to distinguish these two situations rather than the isolated T1 or T2 values. In particular, high values of T1/T2 ratio are found in septic arthritis.

[Liquefaction of human sperm by a nuclear magnetic resonance technic. Effect of temperature]. / Etude de la liquéfaction du sperme humain par une technique de résonance magnétique nucléaire. Influence de la température.

An investigation of the liquefaction of human semen was performed using the technique of Nuclear Magnetic Resonance, by measuring the time of spin-spin proton relaxation. Measurements which were made at 24 degrees C and 37 degrees C over a 15-day period showed that significant degradation processes and protein transformations occurred during the first 3-5 days. Different phases of these processes were identified.

[Erythrocyte-plasma water exchange studied by nuclear magnetic resonance spin-spin (T2) relaxation. Relation between the time the water molecule stays in the erythrocyte and its volume]. / Etude des échanges d'eau hématie-plasma par relaxation magnétique nucléaire spin-spin (T2). Relation entre le temps de résidence de la molécule d'eau dans l'hématie et son volume.

A simple, precise and rapid pulse nuclear magnetic resonance technique for measuring the rate of water exchange across the erythrocyte membrane is presented. The effects of cell volume on cell water lifetime may be eliminated by the introduction of a cell water diffusion coefficient. This parameter is applied to the study of eleven blood samples.

Liquefaction of human semen by spin-spin proton relaxation technique.

An investigation of the liquefaction of human semen was performed using a technique of nuclear magnetic resonance, by measuring the time of spin-spin proton relaxation. Measurements made at 24 degrees C over a 15-day period showed that significant degradation processes and protein transformations occurred during the first 5 days. Different phases of these processes were identified.

[Simple method for preparation of rat liver DNA]. / Technique simple de préparation des acides désoxyribonucléiques de foie de rat.

The frozen tissue was sliced and then homogenized at 20 degree C in LiCl, 2 M; lauryl-trimethyl ammonium chloride (K & K No. 4484), 5%; pronase, B grade (calbiochem), 1 mg/ml and Tris-HCl 10 mM pH 7.5. The homogenate was left to stand 15 min at 20 degree C with occasional shaking. After centrifugation at 35 000 X g for 30 min at 0 degree C, the supernatant containing the crude DNA was purified by filtration on Ultrogel A 2 (LKB, Sweden). The Ultrogel A 2 column (2.5 X 45 cm) was equilibrated with a solution containing NaCl 2 M, EDTA 2.5 mM, Tris-HCl 10 mM pH 7.5. The flow rate was 3 ml cm-2 h-1. Five ml of the supernatant were placed on the column. The first peak contained highly polymerized (as demonstrated by ultracentrifugation) pure DNA (A260/A230 = 3.19; A260/A280 = 1.82). The yield was 2.26 mg of DNA/g of fresh liver.

[Isolation and characterization of beef thyroid giant RNA]. / Isolement et caractérisation des RNA géants de la glande thyroide de boeuf.

Total HMW-RNAs were prepared by three different methods (method with phenol, method with NaClO4, method without phenol using Ultrogel AcA 22 filtration). Giant RNAs were obtained in the void volume by filtration on Sepharose 2B. The giant RNAs/total HMW-RNA ratio is higher (6.77%) with the gel filtration method than with phenol or NaClO4 methods (1.41% and 1.00% respectively). The nucleotide composition of these RNAs is DNA-like and the sedimentation constants are approximately 70-100 S.