Computer simulation of high-frequency combustion instability and its supression

Program for simulation of gas motion illustrates the effects of some of the variables on the combustion chambers of liquid propellant rocket engines. The program is based on numerically integrating the laws of inviscid fluid dynamics by two-step Lax-Wendroff technique

The physical nature of interplanetary dust as inferred by particles collected at 35 km

Particles were collected at an altitude of 35 km by two flights of a volume sampling micrometeorite collector. The collection scheme is very sensitive and is capable of collecting a significant number of particles. Many of the particles collected have chemical compositions similar to solar or to iron meteorites. Morphology of collected particles indicates that both true micrometeorites and ablation products were collected

Phylogenetic Analysis of Cell Types using Histone Modifications

In cell differentiation, a cell of a less specialized type becomes one of a more specialized type, even though all cells have the same genome. Transcription factors and epigenetic marks like histone modifications can play a significant role in the differentiation process. In this paper, we present a simple analysis of cell types and differentiation paths using phylogenetic inference based on ChIP-Seq histone modification data. We propose new data representation techniques and new distance measures for ChIP-Seq data and use these together with standard phylogenetic inference methods to build biologically meaningful trees that indicate how diverse types of cells are related. We demonstrate our approach on H3K4me3 and H3K27me3 data for 37 and 13 types of cells respectively, using the dataset to explore various issues surrounding replicate data, variability between cells of the same type, and robustness. The promising results we obtain point the way to a new approach to the study of cell differentiation.Comment: Peer-reviewed and presented as part of the 13th Workshop on Algorithms in Bioinformatics (WABI2013

Josephson Effect in Pb/I/NbSe2 Scanning Tunneling Microscope Junctions

We have developed a method for the reproducible fabrication of superconducting scanning tunneling microscope (STM) tips. We use these tips to form superconductor/insulator/superconductor tunnel junctions with the STM tip as one of the electrodes. We show that such junctions exhibit fluctuation dominated Josephson effects, and describe how the Josephson product IcRn can be inferred from the junctions' tunneling characteristics in this regime. This is first demonstrated for tunneling into Pb films, and then applied in studies of single crystals of NbSe2. We find that in NbSe2, IcRn is lower than expected, which could be attributed to the interplay between superconductivity and the coexisting charge density wave in this material.Comment: 3 pages, 2 figures. Presented at the New3SC-4 meeting, San Diego, Jan. 16-21 200

Totgeburt und plötzlicher Kindstod: Gemeinsamkeiten und Differenzen

Zusammenfassung: Die Totgeburtenrate hat in entwickelten Ländern in den letzten 30 Jahren im Gegensatz zur neonatalen Sterblichkeit und der Häufigkeit des plötzlichen Kindstodes kaum abgenommen. Dies ist verwunderlich, da heute weit weniger Totgeburten aufgrund einer Plazentainsuffizienz, eines maternalen Diabetes mellitus, einer Präeklampsie, oder durch Rhesusinkompatibilität und fetale Aneuploidien auftreten. Dagegen steigt die Rate an ätiologisch ungeklärten Fällen von Totgeburten an. Die eindrücklichen Erfolge in der Prävention des plötzlichen Kindstods zeigen, dass auch ätiologisch ungeklärte Erkrankungen wirkungsvoll verhindert werden können. Rauchen und Adipositas, sowie übermäßige Gewichtszunahme als Risikofaktoren für den intrauterinen Fruchttod sind vor Eintritt der Schwangerschaft modifizierbar. Die Erkennung und Therapie von Diabetes mellitus, Gestationsdiabetes und arterieller Hypertonie sind effektive Maßnahmen in der Schwangerschaft zur Verringerung von Totgeburten. Die Geburtseinleitung am Termin wäre ebenfalls eine effektive Methode zur Vermeidung von Totgeburten, wobei für eine vermiedene Totgeburt etwa 300 Geburtseinleitungen mit den damit verbundenen Nachteilen notwendig wäre

The Fixation of Nitrogen.

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Observation of Modulated Quadrupolar Structures in PrPb3

Neutron diffraction measurements have been performed on the cubic compound PrPb3 in a [001] magnetic field to examine the quadrupolar ordering. Antiferromagnetic components with q=(1/2+-d 1/2 0), (1/2 1/2+-d 0) (d~1/8) are observed below the transition temperature TQ (0.4 K at H=0) whose amplitudes vary linear with H and vanish at zero field, providing the first evidence for a modulated quadrupolar phase. For H<1 T, a non-square modulated state persists even below 100 mK suggesting quadrupole moments associated with a Gamma3 doublet ground state to be partially quenched by hybridization with conduction electrons.Comment: Physical Review Letters, in press. 4 pages, 4 figure