1^{1}H-NMR spin-echo measurements of the static and dynamic spin properties in λ\lambda-(BETS)2_{2}FeCl4_{4}

$^{1}$H-NMR spin-echo measurements of the spin-echo decay $M(2\tau)$ with a decay rate 1/$T_{2}$ and the frequency shift $\Delta\nu/\nu_{0}$ under applied magnetic field $\mathbf{B}$$_{0}$ = 9 T along the a-axis over a temperature range 2.0$-$180 K are reported for a single crystal of the organic conductor $\lambda$-(BETS)$_{2}$FeCl$_{4}$. It provides the spin dynamic and static properties in the paramagnetic metal (PM) and antiferromagnetic insulator (AFI) states as well as across the PM$-$AFI phase transition. A large slow beat structure in the spin-echo decay is observed with a typical beat frequency of $f$ $\sim$ 7 kHz and it varies across the spectrum. Its origin is attributed to the $^{1}$H$-$$^{1}$H dipole interactions rather than to the much larger dipolar field contribution from the Fe$^{3+}$ electrons (spin $S$ = 5/2). A simple phenomenological model provides an excellent fit to the data. The dominant $^{1}$H-NMR frequency shift comes from the dipolar field from the 3d Fe$^{3+}$ ions, and the Fe$^{3+}$ $-$ Fe$^{3+}$ exchange interactions ($J_{0}$) ($J_{0}$ includes the d$-$d exchange interactions through the $\pi-$electrons) have a substantial effect to the local field at the proton sites expecially at low temperatures. A good fit is obtained with $J_{0}$ = - 1.7 K. The data of the spin-echo decay rate 1/$T_{2}$ indicates that there is a significant change in the slow fluctuations of the local magnetic field at the $^{1}$H-sites on traversing the PM to AFI phase. This evidence supports earlier reports that the PM$-$AFI phase transition in $\lambda$-(BETS)$_{2}$FeCl$_{4}$ is driven magnetically and first order.Comment: 9 pages, 10 figures, resubmitted to Phys. Rev. B in response to comments of Editor and reviewers on March 23, 200

Investigation of the effects of inlet shapes on fan noise radiation

The effect of inlet shape on forward radiated fan tone noise directivities was investigated under experimentally simplified zero flow conditions. Simulated fan tone noise was radiated to the far field through various shaped zero flow inlets. Baseline data were collected for the simplest baffled and unbaffled straight pipe inlets. These data compared well with prediction. The more general inlet shapes tested were the conical, circular, and exponential surfaces of revolution and an asymmetric inlet achieved by cutting a straight pipe inlet at an acute angle. Approximate theories were developed for these general shapes and some comparisons with data are presented. The conical and exponential shapes produced directivities that differed considerably from the baseline data while the circular shape produced directivities similar to the baseline data. The asymmetric inlet produced asymmetric directivities with significant reductions over the straight pipe data for some angles

Quantitative multielement analysis using high energy particle bombardment

Charged particles ranging in energy from 0.8 to 4.0 MeV are used to induce resonant nuclear reactions, Coulomb excitation (gamma X-rays), and X-ray emission in both thick and thin targets. Quantitative analysis is possible for elements from Li to Pb in complex environmental samples, although the matrix can severely reduce the sensitivity. It is necessary to use a comparator technique for the gamma-rays, while for X-rays an internal standard can be used. A USGS standard rock is analyzed for a total of 28 elements. Water samples can be analyzed either by nebulizing the sample doped with Cs or Y onto a thin formvar film or by extracting the sample (with or without an internal standard) onto ion exchange resin which is pressed into a pellet

Infrared properties of dust grains derived from IRAS observations

The analysis of several diffuse interstellar clouds observed by the Infrared Astronomy Satellite (IRAS) is presented. The 60/100 micron flux ratios appear to be nearly constant in clouds with up to 1 sup m visual extinction at the center. Observations of a highly regular cloud in Chamaeleon show that the 12/100 micron ratio peaks at an intermediate radial distance and declines towards the center of the cloud. These observations indicate that nonequilibrium emission accounts only for the 12 and 25 micron bands; strong emission observed at the 60 micron band is probably due to equilibrium thermal radiation. The correlation of the 12 micron emission with a red excess observed for a high latitude cloud, L1780, is shown to be consistent with the assumption that both features are due to fluorescence by the same molecular species

Strain bursts in plastically deforming Molybdenum micro- and nanopillars

Plastic deformation of micron and sub-micron scale specimens is characterized by intermittent sequences of large strain bursts (dislocation avalanches) which are separated by regions of near-elastic loading. In the present investigation we perform a statistical characterization of strain bursts observed in stress-controlled compressive deformation of monocrystalline Molybdenum micropillars. We characterize the bursts in terms of the associated elongation increments and peak deformation rates, and demonstrate that these quantities follow power-law distributions that do not depend on specimen orientation or stress rate. We also investigate the statistics of stress increments in between the bursts, which are found to be Weibull distributed and exhibit a characteristic size effect. We discuss our findings in view of observations of deformation bursts in other materials, such as face-centered cubic and hexagonal metals.Comment: 14 pages, 8 figures, submitted to Phil Ma

Tuning grid storage resources for LHC data analysis

Grid Storage Resource Management (SRM) and local file-system solutions are facing significant challenges to support efficient analysis of the data now being produced at the Large Hadron Collider (LHC). We compare the performance of different storage technologies at UK grid sites examining the effects of tuning and recent improvements in the I/O patterns of experiment software. Results are presented for both live production systems and technologies not currently in widespread use. Performance is studied using tests, including real LHC data analysis, which can be used to aid sites in deploying or optimising their storage configuration

Proton NMR measurements of the local magnetic field in the paramagnetic metal and antiferromagnetic insulator phases of λ\lambda-(BETS)2_{2}FeCl4_{4}

Measurements of the $^{1}$H-NMR spectrum of a small ($\sim$ 4 $\mu$g) single crystal of the organic conductor $\lambda$-(BETS)$_{2}$FeCl$_{4}$ are reported with an applied magnetic field $\bf{B}$$_{0}$ = 9 T parallel to the a-axis in the $ac$-plane over a temperature $(T)$ range 2.0 $-$ 180 K. They provide the distribution of the static local magnetic field at the proton sites in the paramagnetic metal (PM) and antiferromagnetic insulator (AFI) phases, along with the changes that occur at the PM$-$AFI phase transition. The spectra have six main peaks that are significantly broadened and shifted at low $T$. The origin of these features is attributed to the large dipolar field from the 3d Fe$^{3+}$ ion moments (spin $S_{\rm{d}}$ = 5/2). Their amplitude and $T-$dependence are modeled using a modified Brillouin function that includes a mean field approximation for the total exchange interaction ($J_{0}$) between one Fe$^{3+}$ ion and its two nearest neighbors. A good fit is obtained using $J_{0}$ = $-$ 1.7 K. At temperatures below the PM$-$AFI transition temperature $T_{MI}$ = 3.5 K, an extra peak appears on the high frequency side of the spectrum and the details of the spectrum become smeared. Also, the rms linewidth and the frequency shift of the spectral distribution are discontinuous, consistent with the transition being first-order. These measurements verify that the dominant local magnetic field contribution is from the Fe$^{3+}$ ions and indicate that there is a significant change in the static local magnetic field distribution at the proton sites on traversing the PM to AFI phase transition.Comment: 11 pages, 7 figures. Revised version of cond-mat/0605044 resubmitted to Phys. Rev. B in response to comments of Editor and reviewer

Public or private religiosity: which Is protective for adolescent substance use and by what pathways?

While it is well understood that adolescent religiosity is associated with the use and abuse of licit and illicit substances, few studies have revealed the pathways through which religiosity buffers youth against involvement in such behavior. The aim of this study is to examine the complexity of the relationships between religiosity, sensation seeking, injunctive norms, and adolescent substance use. Using a national sample of adolescents (N = 18,614), negative binomial regression and path analysis were used to examine the various components of the relationship between religiosity and the use of cigarettes, alcohol, and marijuana. Results indicate that private religiosity moderates the relationship between key risk factors and substance use. Public and private religiosity were associated with tolerant injunctive substance use norms which, in turn, were associated with substance use. Implications for research and theory related to religiosity and adolescent substance use are discussed