A weight-function approach for determining watershed initial conditions for combustion waves

In many generic combustion models, one finds that a combustionwave will develop with a specific wave speed. However, thereare possible initial temperature profiles which do not evolveinto such waves, but rather die out to the ambient temperature.There can exist, in some models, a clear distinction betweenthose initial conditions that do evolve into combustion wavesand those that do not; this is sometimes referred to as thewatershed initial condition. When fuel consumption is consideredto be negligible, analytical methods can be used to obtain theexact watershed. In this paper, we consider the problem of determiningpseudo-watersheds and ascertaining the relationship betweenthese pseudo-watersheds and the exact watersheds. In the processa novel weight-function approach for infinite spatial domainsis developed.     

A low temperature study of antiferromagnetic YbVO4 by NMR thermally detected by nuclear orientation

NMR-TDNO results using an external ⁶⁰CoCo (hcp) nuclear orientation thermometer for non-irradiated, single crystal, antiferromagnetic YbVO₄ are compared with those obtained earlier with neutron activated samples using both internal and external γ-ray thermometers. Detailed comparisons are made for the ¹⁷¹Yb (I=1/2, 14.31% abundant) stable nucleus. This strongly asymmetric, largely homogeneous, resonance lineshape was retained and is readily power broadened. Extremely broad, field-dependent homogeneous thermometric responses are observed in the expected frequency range for the quadrupolar stable nucleus ¹⁷³Yb (I=5/2, 16.13% abundant) for both irradiated and non-irradiated samples. This revised version was published online in August 2006 with corrections to the Cover Date.     

Structural characterization of epitaxial Cr(x)Mo(1-x) alloy thin films

To develop a model system containing regularly spaced misfit dislocations for studies of the radiation resistance of nanoscale defects, epitaxial thin films of Cr, Mo, and Cr(x)Mo(1-x) alloys were deposited on MgO(001) by molecular beam epitaxy. Film compositions were chosen to vary the lattice mismatch with MgO. The film structure was investigated by x-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS) and scanning transmission electron microscopy (STEM). Epitaxial films with reasonably high crystalline quality and abrupt interfaces were achieved at a relatively low deposition temperature, as confirmed by STEM. However, it was found by XRD and RBS in the channeling geometry that increasing the Mo content of the CrMo alloy films degraded the crystalline quality, despite the improved lattice match with MgO. XRD rocking curve data indicated that regions of different crystalline order may be present within the films with higher Mo content. This is tentatively ascribed to spinodal decomposition into Cr-rich and Mo-rich regions, as predicted by the Cr(x)Mo(1-x) phase diagram.     

Indication of reactor ν(e) disappearance in the Double Chooz experiment

The Double Chooz experiment presents an indication of reactor electron antineutrino disappearance consistent with neutrino oscillations. An observed-to-predicted ratio of events of 0.944±0.016(stat)±0.040(syst) was obtained in 101 days of running at the Chooz nuclear power plant in France, with two 4.25 GW(th) reactors. The results were obtained from a single 10 m(3) fiducial volume detector located 1050 m from the two reactor cores. The reactor antineutrino flux prediction used the Bugey4 flux measurement after correction for differences in core composition. The deficit can be interpreted as an indication of a nonzero value of the still unmeasured neutrino mixing parameter sin(2)2θ(13). Analyzing both the rate of the prompt positrons and their energy spectrum, we find sin(2)2θ(13)=0.086±0.041(stat)±0.030(syst), or, at 90% C.L., 0.017相似文献   

Effects of the tumor promoter TPA on the induction of DNA synthesis in normal and RSV-transformed rat fibroblasts.

Induction of DNA synthesis by the tumor promoter tetradecanoyl phorbol acetate (TPA) was studied in a line of cultured rat fibroblasts (Rat-1) and their Rous sarcoma virus-transformed derivative (Rat-1 (RSV)). Following serum deprivation for 54 h to achieve quiescence, semiconservative DNA replication was measured by incubation of cells in BrdUrd and FdUrd after serum stimulation in the presence or absence of TPA. Optimal concentrations of TPA (0.1--0.5 microgram/ml) in serum-free medium induced a small increase (10--15%) in the amount of DNA made over a 30-h period in both Rat-1 and Rat-1 (RSV) cells. When Rat-1 cells were stimulated by a 4-h serum pulse, 30% of the DNA was replicated by 30 h. If the serum pulse was followed by TPA addition, 70% DNA replication was observed. If the serum pulse was preceded by TPA addition, the onset of DNA synthesis was delayed by several houses, but stimulation of DNA synthesis occurred. In contrast, the Rat-1 (RSV) cells did not show an increased in DNA synthesis induced by TPA in similar protocols, but the serum-induced onset of DNA synthesis was delayed by several hours in the presence of TPA. Therefore, TPA acts as a co-inducer of DNA synthesis in the Rat-1 but not in the Rat-1 (RSV) cells. The parent alcohol, phorbol, was inactive in Rat-1 cells, but delayed the onset of DNA synthesis in the Rat-1 (RSV) cells. We conclude that the co-inducing and delaying activities of TPA on DNA synthesis appear to be distinct and to act a different points in the G1 phase of the cell cycle.     

Suppression of matrix ions in ultraviolet laser desorption: Scanning electron microscopy and raman spectroscopy of the solid samples

Suppression of low-mass ion peaks in matrix-assisted ultraviolet laser desorption has been found to occur at low matrix-to-analyte molar ratios when using nicotinic acid as matrix, independent of the angle of illumination. Microscopic Raman scattering spectroscopy has been employed to investigate the matrix–analyte solid-state composition. The matrix-to-analyte molar ratios employed in preparing the solutions are reliable guides to the relative amounts of matrix and analyte molecules in the solid crystals, given the method of sample preparation employed involving drying under a stream of nitrogen. A qualitative model based on the proton supply-and-demand argument is tentatively proposed to explain the suppression phenomenon.     

Natural polyene α-pyrones. Synthesis of (±)-citreoviral

The total synthesis of (±)-citreoviral(2) and also of $\text{iso}$-citreoviral(21), using two conceptually distinct approaches starting from methyl tiglate, are described.     

Studies of Australian Ascidians. 5. Virenamides A-C, New Cytotoxic Linear Peptides from the Colonial Didemnid Ascidian Diplosoma virens

Three new linear cytotoxic tripeptides, virenamides A-C have been isolated from extracts of the Didemnid ascidian Diplosoma virens collected on the Great Barrier Reef, Australia. Their structures were deduced from 1D and 2D NMR spectral data and confirmed by HPLC analysis of the constituent amino acids after hydrolysis of the peptides and derivatization with 1-fluoro-2,4-dinitrophen-5-yl-L-alanine amide using Marfey's procedure.     

Some analytical results forABC,ABCD, andXBCD coupled spin 1/2 systems. II

In the preceding paper, it was shown that the calculation of the density matrix(t) for multiply connectedABC, etc., spin 1/2 spin systems can be greatly simplified by subdividing the Hamiltonian into , where is a suitable linear combination of the constants of the motion. In this paper, a framework for the determination of the time evolution of high-order multipolar quantum states is presented and discussed. It is shown that the necessary mathematical labour is reduced to a minimum by (i) exploiting the fact that is a good quantum number, and (ii) using the theory of partitioned matrices. For example, it is shown that for a generaln-coupled spin 1/2 system, the spin dynamics of the multipolar states, whereK _max is the maximum tensorial rank, can be determined without the need to diagonalize the full 2 ⁿ × 2 ⁿ Hamiltonian matrix, wheren is the number of spins. In fact, to describe the time evolution of the multipolar states it is only necessary to diagonalize twon ×n matrices at most. Finally, some cautionary remarks are made concerning the use of the weak-coupling approximation.