Experimental determination of turbulence in a GH2-GOX rocket combustion chamber

The intensity of turbulence and the Lagrangian correlation coefficient for a gaseous rocket combustion chamber have been determined from the experimental measurements of the tracer gas diffusion. A combination of Taylor's turbulent diffusion theory and Spalding's numerical method for solving the conservation equations of fluid mechanics was used to calculate these quantities. Taylor's theory was extended to consider the inhomogeneity of the turbulence field in the axial direction of the combustion chamber. An exponential function was used to represent the Lagrangian correlation coefficient. The results indicate that the maximum value of the intensity of turbulence is about 15% and the Lagrangian correlation coefficient drops to about 0.12 in one inch of the chamber length

Thiyl radicals are co-products of dinitrosyl iron complex (DNIC) formation.

Thiyl radicals are detected by EPR as co-products of dinitrosyl iron complex (DNIC) formation. In demonstrating that DNIC formation generates RS˙ in a NO rich environment, these results provide a novel route for S-nitroso thiol formation

Dynamics of Dinitrosyl Iron Complex (DNIC) Formation with Low Molecular Weight Thiols.

Dinitrosyl iron complexes (DNICs) are ubiquitous in mammalian cells and tissues producing nitric oxide (NO) and have been argued to play key physiological and pathological roles. Nonetheless, the mechanism and dynamics of DNIC formation in aqueous media remain only partially understood. Here, we report a stopped-flow kinetics and density functional theory (DFT) investigation of the reaction of NO with ferrous ions and the low molecular weight thiols glutathione (GSH) and cysteine (CysSH) as well as the peptides WCGPC and WCGPY to produce DNICs in pH 7.4 aqueous media. With each thiol, a two-stage reaction pattern is observed. The first stage involves several rapidly established pre-equilibria leading to a ferrous intermediate concluded to have the composition FeII(NO)(RS)2(H2O)x (C). In the second stage, C undergoes rate-limiting, unimolecular autoreduction to give thiyl radical (RS•) plus the mononitrosyl Fe(I) complex FeI(NO)(RS)(H2O)x following the reactivity order of CysSH > WCGPC > WCGPY > GSH. Time course simulations using the experimentally determined kinetics parameters demonstrate that, at a NO flux characteristic of inflammation, DNICs will be rapidly formed from intracellular levels of ferrous iron and thiols. Furthermore, the proposed mechanism offers a novel pathway for S-nitroso thiol (RSNO) formation in a biological environment

Enhancement of Superconducting Transition Temperature due to the strong Antiferromagnetic Spin Fluctuations in Non-centrosymmetric Heavy-fermion Superconductor CeIrSi3 :A 29Si-NMR Study under Pressure

We report a 29Si-NMR study on the pressure-induced superconductivity (SC) in an antiferromagnetic (AFM) heavy-fermion compound CeIrSi3 without inversion symmetry. In the SC state at P=2.7-2.8 GPa, the temperature dependence of the nuclear-spin lattice relaxation rate 1/T_1 below Tc exhibits a T^3 behavior without any coherence peak just below Tc, revealing the presence of line nodes in the SC gap. In the normal state, 1/T_1 follows a \sqrt{T}-like behavior, suggesting that the SC emerges under the non-Fermi liquid state dominated by AFM spin fluctuations enhanced around quantum critical point (QCP). The reason why the maximum Tc in CeIrSi3 is relatively high among the Ce-based heavy-fermion superconductors may be the existence of the strong AFM spin fluctuations. We discuss the comparison with the other Ce-based heavy-fermion superconductors.Comment: 4 pages, 5 figures, To be published in Phys. Rev. Let

Bridge over Olduvai Gorge: Capacity building and conservation of lithics and fossils

This paper explores decision-making processes involved in the conservation of lithics and fossils excavated at Olduvai Gorge, Tanzania. The site is renowned for discoveries of early humans from the Palaeolithic period, lithics and fossils that document the evolutionary history of humans, vertebrate fauna and their environment over the last two million years. Excavated specimens are treated in situ, at the field laboratory and at the UCL Institute of Archaeology in London. Factors such as accessibility, ease of transportation and preparation, disposal, Tg and toxicity of resins, and ease of re-treatability are considered to decide what can be used in treatments and how. Frequently used materials include Paraloid B-44 and cyclododecane for temporary consolidation and Paraloid B-44 for adhesion and gap-filling. We have found that, in such complex contexts, the more one engages with colleagues across the disciplines and local community groups, the smoother, stronger and more sustainable one’s efforts become

Crystallization of opals from polydisperse nanoparticles

We report the reversible formation of crystals of nanoparticles (opals) from solutions of polydisperse gold nanocrystals. The structures are identified by transmission electron microscopy, and are characterized by hexagonal domains of large particles at the center, surrounded radially by successively smaller particles. Simulated annealing Monte Carlo calculations are used to demonstrate that these configurations correspond to minimization of the mesoscopic van der Waals energy of polydisperse particles, and the driving force for ordering is the size dependence of dispersional attractions

Shift of the molecular bound state threshold in dense ultracold Fermi gases with Feshbach resonance

We consider a dense ultracold Fermi gas in the presence of a Feshbach resonance. We investigate how the treshold for bound state formation, which is just at the Feshbach resonance for a dilute gas, is modified due to the presence of the Fermi sea. We make use of a preceding framework of handling this many-body problem. We restrict ourselves to the simple case where the chemical potential $\mu$ is negative, which allows us to cover in particular the classical limit where the effect is seen to disappear. We show that, within a simple approach where basically only the effect of Pauli exclusion is included, the Fermi sea produces a large shift of the threshold, which is of order of the width of the Feshbach resonance. This is in agreement with very recent experimental findings.Comment: one reference adde