Strongly baryon-dominated disk galaxies at the peak of galaxy formation ten billion years ago.

In the cold dark matter cosmology, the baryonic components of galaxies-stars and gas-are thought to be mixed with and embedded in non-baryonic and non-relativistic dark matter, which dominates the total mass of the galaxy and its dark-matter halo. In the local (low-redshift) Universe, the mass of dark matter within a galactic disk increases with disk radius, becoming appreciable and then dominant in the outer, baryonic regions of the disks of star-forming galaxies. This results in rotation velocities of the visible matter within the disk that are constant or increasing with disk radius-a hallmark of the dark-matter model. Comparisons between the dynamical mass, inferred from these velocities in rotational equilibrium, and the sum of the stellar and cold-gas mass at the peak epoch of galaxy formation ten billion years ago, inferred from ancillary data, suggest high baryon fractions in the inner, star-forming regions of the disks. Although this implied baryon fraction may be larger than in the local Universe, the systematic uncertainties (owing to the chosen stellar initial-mass function and the calibration of gas masses) render such comparisons inconclusive in terms of the mass of dark matter. Here we report rotation curves (showing rotation velocity as a function of disk radius) for the outer disks of six massive star-forming galaxies, and find that the rotation velocities are not constant, but decrease with radius. We propose that this trend arises because of a combination of two main factors: first, a large fraction of the massive high-redshift galaxy population was strongly baryon-dominated, with dark matter playing a smaller part than in the local Universe; and second, the large velocity dispersion in high-redshift disks introduces a substantial pressure term that leads to a decrease in rotation velocity with increasing radius. The effect of both factors appears to increase with redshift. Qualitatively, the observations suggest that baryons in the early (high-redshift) Universe efficiently condensed at the centres of dark-matter haloes when gas fractions were high and dark matter was less concentrated.

Formaldehyde preparation methods for pressure and temperature dependent laser-induced fluorescence measurements.

Formaldehyde is an excellent tracer for the early phase of ignition of hydrocarbon fuels and can be used, e.g., for characterization of single droplet ignition. However, due to its fast thermal decomposition at elevated temperatures and pressures, the determination of concentration fields from laser-induced fluorescence (LIF) measurements is difficult. In this paper, we address LIF measurements of this important combustion intermediate using a calibration cell. Here, formaldehyde is created from evaporation of paraformaldehyde. We discuss three setups for preparation of formaldehyde/air mixtures with respect to their usability for well-defined heating of formaldehyde/air mixtures. The "basic setup" uses a resist heater around the measurement cell for investigation of formaldehyde near vacuum conditions or formaldehyde/air samples after sequential admixing of air. The second setup, described for the first time in detail here, takes advantage of a constant flow formaldehyde/air regime which uses preheated air to reduce the necessary time for gas heating. We used the constant flow system to measure new pressure dependent LIF excitation spectra in the 343 nm spectral region (41 (4) absorption band of formaldehyde). The third setup, based on a novel concept for fast gas heating via excitation of SF6 (chemically inert gas) using a TEA (transverse excitation at atmospheric pressure) CO2 laser, allows to further minimize both gas heating time and thermal decomposition. Here, an admixture of CO2 is served for real time temperature measurement based on Raman scattering. The applicability of the fast laser heating system has been demonstrated with gas mixtures of SF6 + air, SF6 + N2, as well as SF6 + N2 + CO2 at 1 bar total pressure.

Two-dimensional temperature measurements in particle loaded technical flames by filtered Rayleigh scattering.

Filtered Rayleigh scattering (FRS) is applied to determine two-dimensional temperature distributions in a hexamethyldisiloxane loaded propane/air flame intended for combustion chemical vapor deposition processes. An iodine cell as a molecular filter suppresses background scattering, e.g., by particles, while the wings of the spectrally broadened Rayleigh scattering can pass this filter. A frequency-doubled Nd:YAG laser is tuned to a strong absorption line of iodine. The gas temperature is deduced from the transmitted Rayleigh scattering signal. Since FRS also depends on molecule-specific scattering cross sections, the local gas composition of majority species is measured using the Raman scattering technique. Limits and restrictions are discussed.

A gas cloud on its way towards the supermassive black hole at the Galactic Centre.

Measurements of stellar orbits provide compelling evidence that the compact radio source Sagittarius A* at the Galactic Centre is a black hole four million times the mass of the Sun. With the exception of modest X-ray and infrared flares, Sgr A* is surprisingly faint, suggesting that the accretion rate and radiation efficiency near the event horizon are currently very low. Here we report the presence of a dense gas cloud approximately three times the mass of Earth that is falling into the accretion zone of Sgr A*. Our observations tightly constrain the cloud's orbit to be highly eccentric, with an innermost radius of approach of only ∼3,100 times the event horizon that will be reached in 2013. Over the past three years the cloud has begun to disrupt, probably mainly through tidal shearing arising from the black hole's gravitational force. The cloud's dynamic evolution and radiation in the next few years will probe the properties of the accretion flow and the feeding processes of the supermassive black hole. The kilo-electronvolt X-ray emission of Sgr A* may brighten significantly when the cloud reaches pericentre. There may also be a giant radiation flare several years from now if the cloud breaks up and its fragments feed gas into the central accretion zone.

Pulse stretcher with variable pulse length for excimer laser applications.

Excimer laser systems are often combined with pulse stretchers, e.g., in lithography and Raman spectroscopy to reduce pulse peak intensities. We developed a pulse stretcher which is suited especially for pulse length dependent applications, e.g., in material research. This pulse stretcher is based on imaging and provides identical beam profiles and divergences at different pulse lengths in combination with the possibility of switching between four pulse lengths. Therefore, beam splitters are mounted onto motorized translation stages. These features are important for the characterization and development of improved optical materials for deep-ultraviolet applications. Here, two 193 nm single tube excimer lasers (Lambda Physik: LPX 240i, Cymer: ELS 5600) were evaluated concerning their combinability with an attached pulse stretcher. The wave-front radii of the ELS 5600 are dependent on repetition rate or pulse energy and are changing during warming-up. Without adapted pulse shaping, this can cause destruction of stretcher optics due to moving foci. We found that the LPX 240i could be combined easily with a pulse stretcher using beam shaping with only one cylindrical lens. We could demonstrate that stretched 193 nm laser pulses retard aging of CaF(2) crystals.

High molecular gas fractions in normal massive star-forming galaxies in the young Universe.

Stars form from cold molecular interstellar gas. As this is relatively rare in the local Universe, galaxies like the Milky Way form only a few new stars per year. Typical massive galaxies in the distant Universe formed stars an order of magnitude more rapidly. Unless star formation was significantly more efficient, this difference suggests that young galaxies were much more molecular-gas rich. Molecular gas observations in the distant Universe have so far largely been restricted to very luminous, rare objects, including mergers and quasars, and accordingly we do not yet have a clear idea about the gas content of more normal (albeit massive) galaxies. Here we report the results of a survey of molecular gas in samples of typical massive-star-forming galaxies at mean redshifts of about 1.2 and 2.3, when the Universe was respectively 40% and 24% of its current age. Our measurements reveal that distant star forming galaxies were indeed gas rich, and that the star formation efficiency is not strongly dependent on cosmic epoch. The average fraction of cold gas relative to total galaxy baryonic mass at z = 2.3 and z = 1.2 is respectively about 44% and 34%, three to ten times higher than in today's massive spiral galaxies. The slow decrease between z approximately 2 and z approximately 1 probably requires a mechanism of semi-continuous replenishment of fresh gas to the young galaxies.

Increased arterial vascular tone during the night in patients with essential hypertension.

The time-dependent incidence of cardiovascular events points to an important role of chronobiology for arterial properties. To evaluate arterial properties in patients with essential hypertension, we assessed arterial vascular tone during sleep at night in patients with essential hypertension and normotensive control subjects. Vascular tone was continuously quantified by the reflective index obtained by non-invasive digital photoplethysmography and an algorithm for continuous, investigator-independent, automatic analysis of digital volume pulse. During the first half of the night, the reflective index was significantly higher in 31 patients with essential hypertension compared to 30 normotensive control subjects (30.0+/-0.2 vs 28.8+/-0.2; P=0.001). In patients with essential hypertension, the reflective index significantly increased from 30.0+/-0.2 in the first half (from 2301 to 0230) to 30.7+/-0.2 in the second half (from 0231 to 0600) of the night (n=31; P=0.027). In normotensive control subjects the reflective index also significantly increased from 28.8+/-0.2 in the first half of the night to 30.2+/-0.2 in the second half of the night (n=30; P=0.001). An increase of the reflective index tone indicated systemic vasoconstriction as confirmed by cold pressure tests and a significant correlation between arterial vascular tone and sympathetic nerve activity measured by microneurography from the peroneal nerve. Photoplethysmographic determination of arterial vascular tone demonstrated a significant increase of systemic arterial vascular tone in patients with essential hypertension during the first half of the night compared to normotensive control subjects.

Impaired renal allograft function is associated with increased arterial stiffness in renal transplant recipients.

It is important whether impairment of renal allograft function may deteriorate arterial stiffness in renal transplant recipients. In a cross-sectional study, arterial vascular characteristics were non-invasively determined in 48 patients with renal allograft using applanation tonometry and digital photoplethysmography. Mean age was 51 +/- 2 years (mean +/- SEM), and studies were performed 17 +/- 1 months after transplantation. The stage of chronic kidney disease was based on the glomerular filtration rate. We observed a significant association between the stage of chronic kidney disease and arterial stiffness of large arteries S1 and small arteries S2 in renal transplant recipients (each p < 0.05 by non-parametric Kruskal-Wallis test between groups). Multivariate linear regression analysis showed that male gender of patients with renal allograft (p < 0.01) reduced glomerular filtration rate (p = 0.01), and older age of kidney donor (p = 0.04) were independently associated with an increase of large artery stiffness S1. Furthermore, a significant association between the stage of chronic kidney disease and arterial vascular reactivity during reactive hyperemia was observed (p < 0.05 by non-parametric Kruskal-Wallis test between groups). It is concluded that impairment of renal allograft function is associated with an increased arterial stiffness in renal transplant recipients.

The addition of acarbose to insulin lispro reduces acute glycaemic responses in patients with type-2 diabetes.

This double-blind, placebo-controlled single-centre cross-over study assessed the efficacy of acarbose as adjunct to insulin lispro therapy in avoiding postprandial blood glucose rise. A total of 30 type 2 diabetic patients currently treated with insulin were included. On two consecutive days subjects received a standardised breakfast (covered by insulin lispro) and were randomly assigned study medication of either 100 mg acarbose or matching placebo. Basal and prandial insulin doses were maintained during the study period. A total of nine blood samples (for parameter assessment) were taken at 30-minute intervals. Primary efficacy variables were the difference in blood glucose rise from fasting to 90 min after breakfast between acarbose/lispro and lispro monotherapy and the difference in the postprandial glucose profile (area under the curve, 0 - 240 min). Secondary parameters consisted of differences in postprandial C-peptide, insulin and triglyceride time profiles between the two treatments. Acarbose treatment significantly reduced the rise in 90 min postprandial blood glucose (1.95 +/- 1.85 mmol/l) by more than half the increase observed under lispro monotherapy (4.37 +/- 2.13 mmol/l; p = 0.000). Postprandial blood glucose, C-peptide and serum insulin levels (AUC (0 - 240 min)) all significantly improved under acarbose treatment. Triglyceride levels were not affected by the combination therapy. Rapid-acting insulin lispro was efficiently complemented by the different mechanism of action of acarbose resulting in significant improvements of postprandial hyperglycaemia and the insulin profile.

The Structure and Evolution of Weakly Self-interacting Cold Dark Matter Halos.

The evolution of halos consisting of weakly self-interacting dark matter particles is investigated using a new numerical Monte Carlo N-body method. The halos initially contain kinematically cold, dense r-1 power-law cores. For interaction cross sections sigma*=sigmawsi&solm0;mp>/=10-100 cm2 g-1, weak self-interaction leads to the formation of isothermal, constant-density cores within a Hubble time as a result of heat transfer into the cold inner regions. This core structure is in good agreement with the observations of dark matter rotation curves in dwarf galaxies. The isothermal core radii and core densities are a function of the halo scale radii and scale masses which depend on the cosmological model. Adopting the currently popular LambdaCDM model, the predicted core radii and core densities are in good agreement with the observations. For large interaction cross sections, massive dark halos with scale radii rs>/=1.4x104 cm2 g-1 (sigma*)-1 kpc could experience core collapse during their lifetime, leading to cores with singular isothermal density profiles.

Recombinant human DNase (rhDNase) influences phospholipid composition, surface activity, rheology and consecutively clearance indices of cystic fibrosis sputum.

Cystic fibrosis (CF) is caused by mutation in the gene for the CF transmembrane conductance regulator which leads to massive, abnormally viscous, purulent sputum, chronic destructive endobronchitis and early death. Purified recombinant human (rh) DNase can digest extracellular DNA and its inhalation in these patients significantly improves lung function. To evaluate the poorly understood mechanisms, saliva protected sputum from patients treated with and without rhDNase were evaluated. Therapy with rhDNase resulted in a soluble sputum fraction that had a higher percentage of phosphatidylethanolamine, a phospholipid present mainly in cellular membranes, a much lower percentage of phosphatidylcholine, but a higher surface activity. The rigidity was significantly lower and the ratio of viscosity in proportion to elasticity increased. All these data are consistent with an increased clearability of the sputum by coughing, but not by mucociliary activity. Thus the interaction of inhaled rhDNase with the purulent mucus and the endobronchial inflammatory processes may induce changes that result in rheological properties favoring clearance of sputum by cough.

Uptake of l-Ascorbate by Intact Spinach Chloroplasts.

Uptake of l-[1-(14)C]ascorbate by intact ascorbate-free spinach (Spinacia oleracea L. cv Vital(r)) chloroplasts has been investigated using the technique of silicone oil filtering. Rates greater than 100 micromoles per milligram chlorophyll per hour (external concentration, 10 millimolar) of ascorbate transport were observed. Ascorbate uptake into the sorbitol-impermeable space (stroma) followed the Michaelis-Menten-type characteristic for substrate saturation. A K(m) of 18 to 40 millimolar was determined. Transport of ascorbate across the chloroplast envelope resulted in an equilibrium of the ascorbate concentrations between stroma and medium. A pH optimum of 7.0 to 7.5 and the lack of alkalization of the medium upon ascorbate uptake suggest that only the monovalent ascorbate anion is able to cross the chloroplast envelope. The activation energy of ascorbate uptake was determined to be 65.8 kilojoules (16 kilocalories) per mole (8 to 20 degrees C). Interference of ascorbate transport with substrates of the phosphate or dicarboxylate translocator could not be detected, but didehydroascorbate was a competitive inhibitor. Preloading of chloroplasts with didehydroascorbate resulted in an increase of V(max) but did not change the K(m) for ascorbate. Millimolar concentrations of the sulfhydryl reagent p-chloromercuriphenyl sulfonate inhibited ascorbate uptake. The data are interpreted in terms of ascorbate uptake into chloroplasts by the mechanism of facilitated diffusion mediated by a specific translocator.