Soot formation and burnout in flames

The amount of soot formed when burning a benzene/hexane mixture in a turbulent combustor was examined. Soot concentration profiles in the same combustor for kerosene fuel are given. The chemistry of the formation of soot precursors, the nucleation, growth and subsequent burnout of soot particles, and the effect of mixing on the previous steps were considered

Development of Muon Drift-Tube Detectors for High-Luminosity Upgrades of the Large Hadron Collider

The muon detectors of the experiments at the Large Hadron Collider (LHC) have to cope with unprecedentedly high neutron and gamma ray background rates. In the forward regions of the muon spectrometer of the ATLAS detector, for instance, counting rates of 1.7 kHz/square cm are reached at the LHC design luminosity. For high-luminosity upgrades of the LHC, up to 10 times higher background rates are expected which require replacement of the muon chambers in the critical detector regions. Tests at the CERN Gamma Irradiation Facility showed that drift-tube detectors with 15 mm diameter aluminum tubes operated with Ar:CO2 (93:7) gas at 3 bar and a maximum drift time of about 200 ns provide efficient and high-resolution muon tracking up to the highest expected rates. For 15 mm tube diameter, space charge effects deteriorating the spatial resolution at high rates are strongly suppressed. The sense wires have to be positioned in the chamber with an accuracy of better than 50 ?micons in order to achieve the desired spatial resolution of a chamber of 50 ?microns up to the highest rates. We report about the design, construction and test of prototype detectors which fulfill these requirements

Molecular Aspects of Secretory Granule Exocytosis by Neurons and Endocrine Cells

Neuronal communication and endocrine signaling are fundamental for integrating the function of tissues and cells in the body. Hormones released by endocrine cells are transported to the target cells through the circulation. By contrast, transmitter release from neurons occurs at specialized intercellular junctions, the synapses. Nevertheless, the mechanisms by which signal molecules are synthesized, stored, and eventually secreted by neurons and endocrine cells are very similar. Neurons and endocrine cells have in common two different types of secretory organelles, indicating the presence of two distinct secretory pathways. The synaptic vesicles of neurons contain excitatory or inhibitory neurotransmitters, whereas the secretory granules (also referred to as dense core vesicles, because of their electron dense content) are filled with neuropeptides and amines. In endocrine cells, peptide hormones and amines predominate in secretory granules. The function and content of vesicles, which share antigens with synaptic vesicles, are unknown for most endocrine cells. However, in B cells of the pancreatic islet, these vesicles contain GABA, which may be involved in intrainsular signaling.' Exocytosis of both synaptic vesicles and secretory granules is controlled by cytoplasmic calcium. However, the precise mechanisms of the subsequent steps, such as docking of vesicles and fusion of their membranes with the plasma membrane, are still incompletely understood. This contribution summarizes recent observations that elucidate components in neurons and endocrine cells involved in exocytosis. Emphasis is put on the intracellular aspects of the release of secretory granules that recently have been analyzed in detail

Experimental Test of a Two-dimensional Approximation for Dielectric Microcavities

Open dielectric resonators of different shapes are widely used for the manufacture of microlasers. A precise determination of their resonance frequencies and widths is crucial for their design. Most microlasers have a flat cylindrical geometry, and a two-dimensional approximation, the so-called method of the effective index of refraction, is commonly employed for numerical calculations. Our aim has been an experimental test of the precision and applicability of a model based on this approximation. We performed very thorough and accurate measurements of the resonance frequencies and widths of two passive circular dielectric microwave resonators and found significant deviations from the model predictions. From this we conclude that the model generally fails in the quantitative description of three-dimensional dielectric resonators.Comment: 10 pages, 13 figure

Correlation between Fermi surface transformations and superconductivity in the electron-doped high-TcT_c superconductor Nd2−x_{2-x}Cex_xCuO4_4

Two critical points have been revealed in the normal-state phase diagram of the electron-doped cuprate superconductor Nd$_{2-x}$Ce$_x$CuO$_4$ by exploring the Fermi surface properties of high quality single crystals by high-field magnetotransport. First, the quantitative analysis of the Shubnikov-de Haas effect shows that the weak superlattice potential responsible for the Fermi surface reconstruction in the overdoped regime extrapolates to zero at the doping level $x_c = 0.175$ corresponding to the onset of superconductivity. Second, the high-field Hall coefficient exhibits a sharp drop right below optimal doping $x_{\mathrm{opt}} = 0.145$ where the superconducting transition temperature is maximum. This drop is most likely caused by the onset of long-range antiferromagnetic ordering. Thus, the superconducting dome appears to be pinned by two critical points to the normal state phase diagram.Comment: 9 pages; 7 figures; 1 tabl

The Effect of Supplementing Mannan Oligosaccharide or Finely Ground Fiber, during the Summer on Body Temperature, Performance, and Blood Metabolites of Finishing Steers

Crossbred beef steers (12 pens, n=96) were used to determine the effect of adding Agrimos or 5% ground (1 in.) wheat straw compared to a control on body temperature, panting score and performance. Th ere were no differences in final BW, ADG, and DMI among treatments. Feed conversion was increased for cattle fed 5% additional ground straw when compared to control and Agrimos. Hot carcass weight, dressing %, LM area, and marbling score were not different among treatments. Cattle fed the control had greater 12th rib fat depth and USDA yield grade than cattle fed straw or Agrimos. Both average and maximum body temperatures were slightly greater for cattle fed Agrimos than for cattle fed control or added straw. Panting scores were decreased slightly for cattle fed the extra straw when compared to control and Agrimos. The addition of Agrimos or wheat straw to the diet had minimal effects on heat stress measures

Dynamics of tournaments: the soccer case

A random walk-like model is considered to discuss statistical aspects of tournaments. The model is applied to soccer leagues with emphasis on the scores. This competitive system was computationally simulated and the results are compared with empirical data from the English, the German and the Spanish leagues and showed a good agreement with them. The present approach enabled us to characterize a diffusion where the scores are not normally distributed, having a short and asymmetric tail extending towards more positive values. We argue that this non-Gaussian behavior is related with the difference between the teams and with the asymmetry of the scores system. In addition, we compared two tournament systems: the all-play-all and the elimination tournaments.Comment: To appear in EPJ

Fermi Surface of the Electron-doped Cuprate Superconductor Nd_{2-x}Ce_xCuO_{4} Probed by High-Field Magnetotransport

We report on the study of the Fermi surface of the electron-doped cuprate superconductor Nd$_{2-x}$Ce$_x$CuO$_{4}$ by measuring the interlayer magnetoresistance as a function of the strength and orientation of the applied magnetic field. We performed experiments in both steady and pulsed magnetic fields on high-quality single crystals with Ce concentrations of $x=0.13$ to 0.17. In the overdoped regime of $x > 0.15$ we found both semiclassical angle-dependent magnetoresistance oscillations (AMRO) and Shubnikov-de Haas (SdH) oscillations. The combined AMRO and SdH data clearly show that the appearance of fast SdH oscillations in strongly overdoped samples is caused by magnetic breakdown. This observation provides clear evidence for a reconstructed multiply-connected Fermi surface up to the very end of the overdoped regime at $x\simeq 0.17$. The strength of the superlattice potential responsible for the reconstructed Fermi surface is found to decrease with increasing doping level and likely vanishes at the same carrier concentration as superconductivity, suggesting a close relation between translational symmetry breaking and superconducting pairing. A detailed analysis of the high-resolution SdH data allowed us to determine the effective cyclotron mass and Dingle temperature, as well as to estimate the magnetic breakdown field in the overdoped regime.Comment: 23 pages, 8 figure