Nuclear level densities and radiative strength functions (RSF) in {sup 56}Fe and {sup 57}Fe were measured using the {sup 57}Fe({sup 3}He,{alpha}{gamma}) and {sup 57}Fe({sup 3}He, {sup 3}He{prime}{gamma}) reactions, respectively, at Oslo Cyclotron Laboratory. A low-energy enhancement in the RSF below 4 MeV energy was observed. This finding cannot be explained by common theoretical models. In a second experiment, two-step cascade intensities with soft primary transitions from the {sup 56}Fe(n,2{gamma}) reaction were measured. The agreement between the two experiments confirms the low-energy enhancement in the RSF. In a third experiment, the neutron evaporation spectrum from the {sup 55}Mn(dn,N){sup 56}Fe reaction was measured at 7-MeV deuteron energy at John Edwards Accelerator Laboratory at Ohio University. Comparison of the level density of {sup 56}Fe obtained from the first and third experiments gives an overall good agreement. Furthermore, observed enhancement for soft {gamma} rays is supported by the last experiment.

Article discussing two different approaches, referred to as renewal and modulation, to generate time series with a nonexponential distribution of waiting times.

We report orientation-specific, surface-sensitive structural characterization of colloidal CdSe nanorods with extended X-ray absorption fine structure spectroscopy and ab-initio density functional theory calculations. Our measurements of crystallographically-aligned CdSe nanorods show that they have reconstructed Cd-rich surfaces. They exhibit orientation-dependent changes in interatomic distances which are qualitatively reproduced by our calculations. These calculations reveal that the measured interatomic distance anisotropy originates from the nanorod surface.

With the BABAR detector at the PEP-II asymmetric B Factory at SLAC, they present the first search for the decays B{sup 0} {yields} {ell}{sup +}{ell}{sup -}{gamma} ({ell} = e, {mu}). Using a data set of 292 fb{sup -1} collected at the {Upsilon}(4S) resonance, they find no significant signal and set the following branching fraction upper limits at 90% confidence level: {Beta}(B{sup 0} {yields} e{sup +}e{sup -}{gamma}) < 0.7 x 10{sup -7} and {Beta}(B{sup 0} {yields} {mu}{sup +}{mu}{sup -}{gamma}) < 3.4 x 10{sup -7}.

None

A unique electronics system has been built and tested for reading signals from the silicon-strip detectors of the Gamma-ray Large Area Space Telescope mission. The system amplifies and processes signals from 884,736 36-cm strips using only 160 W of power, and it achieves close to 100% detection efficiency with noise occupancy sufficiently low to allow it to self trigger. The design of the readout system is described, and results are presented from ground-based testing of the completed detector system.

Reflectivity measurements in the far infrared, performed on aluminum and copper samples, are presented and analyzed. Over a frequency range of interest for the LCLS bunch, the data is fit to the free-electron model, and to one including the anomalous skin effect. The models fit well, yielding parameters dc conductivity and relaxation times that are within 30-40% of expected values. We show that the induced energy in the LCLS undulator region is relatively insensitive to variations on this order, and thus we can have confidence that the wake effect will be close to what is expected.

We report high pressure dynamic compression experiments of liquid water along a quasi-adiabatic path leading to the formation of ice VII. We observe dynamic features resembling Van der Waals loops and find that liquid water is compacted to a metastable state close to the ice density before the onset of crystallization. By analyzing the characteristic kinetic time scale involved we estimate the nucleation barrier and conclude that liquid water has been compressed to a high pressure state close to its thermodynamic stability limit.

A search for nuclear resonance fluorescence excitations in {sup 235}U and {sup 239}Pu within the energy range of 1.0- to 2.5-MeV was performed using a 4-MeV continuous bremsstrahlung source at the High Voltage Research Laboratory at the Massachusetts Institute of Technology. Measurements utilizing high purity Ge detectors at backward angles identified 9 photopeaks in {sup 235}U and 12 photopeaks in {sup 239}Pu in this energy range. These resonances provide unique signatures that allow the materials to be non-intrusively detected in a variety of environments including fuel cells, waste drums, vehicles and containers. The presence and properties of these states may prove useful in understanding the mechanisms for mixing low-lying collective dipole excitations with other states at low excitations in heavy nuclei.

Standard jet finding techniques used in elementary particle collisions have not been successful in the high track density of heavy-ion collisions. This paper describes a modified cone-type jet finding algorithm developed for the complex environment of heavy-ion collisions. The primary modification to the algorithm is the evaluation and subtraction of the large background energy, arising from uncorrelated soft hadrons, in each collision. A detailed analysis of the background energy and its event-by-event fluctuations has been performed on simulated data, and a method developed to estimate the background energy inside the jet cone from the measured energy outside the cone on an event-by-event basis. The algorithm has been tested using Monte-Carlo simulations of Pb+Pb collisions at {radical}s = 5.5 TeV for the ALICE detector at the LHC. The algorithm can reconstruct jets with a transverse energy of 50 GeV and above with an energy resolution of {approx} 30%.

The GaAsP/GaAs strained superlattice photocathode structure has proven to be a significant advance for polarized electron sources operating with high peak currents per microbunch and relatively low duty factor. This is the characteristic type of operation for SLAC and is also planned for the ILC. This superlattice structure was studied at SLAC [1], and an optimum variation was chosen for the final stage of E-158, a high-energy parity violating experiment at SLAC. Following E-158, the polarized source was maintained on standby with the cathode being re-cesiated about once a week while a thermionic gun, which is installed in parallel with the polarized gun, supplied the linac electron beams. However, in the summer of 2005, while the thermionic gun was disabled, the polarized electron source was again used to provide electron beams for the linac. The performance of the photocathode 24 months after its only activation is described and factors making this possible are discussed.

The galaxy cluster 1E0657-56 (z = 0.296) is remarkably well-suited for addressing outstanding issues in both galaxy evolution and fundamental physics. We present a reconstruction of the mass distribution from both strong and weak gravitational lensing data. Multi-color, high-resolution HST ACS images allow detection of many more arc candidates than were previously known, especially around the subcluster. Using the known redshift of one of the multiply imaged systems, we determine the remaining source redshifts using the predictive power of the strong lens model. Combining this information with shape measurements of ''weakly'' lensed sources, we derive a high-resolution, absolutely-calibrated mass map, using no assumptions regarding the physical properties of the underlying cluster potential. This map provides the best available quantification of the total mass of the central part of the cluster. We also confirm the result from Clowe et al. (2004, 2006a) that the total mass does not trace the baryonic mass.

We describe an asymptotic analysis of the coupled nonlinear system of equations describing time-dependent three-dimensional monoenergetic neutron transport and isotopic depletion and radioactive decay. The classic asymptotic diffusion scaling of Larsen and Keller [1], along with a consistent small scaling of the terms describing the radioactive decay of isotopes, is applied to this coupled nonlinear system of equations in a medium of specified initial isotopic composition. The analysis demonstrates that to leading order the neutron transport equation limits to the standard time-dependent neutron diffusion equation with macroscopic cross sections whose number densities are determined by the standard system of ordinary differential equations, the so-called Bateman equations, describing the temporal evolution of the nuclide number densities.

Nanophase metallic materials show a maximum in strength as grain size decreases to the nano scale, indicating a break down of the Hall-Petch relation. Grain boundary sliding, as a possible accommodation mechanisms, is often the picture that explain computer simulations results and real experiments. In a recent paper, Bringa et al. Science 309, 1838 (2005), we report on the observation of an ultra-hard behavior in nanophase Cu under shock loading, explained in terms of a reduction of grain boundary sliding under the influence of the shock pressure. In this work we perform a detailed study of the effects of hydrostatic pressure on nanophase Cu plasticity and find that it can be understood in terms of pressure dependent grain boundary sliding controlled by a Mohr-Coulomb law.

In an effort to develop a magnetic resonance based diagnostic tool to be used for polymer production and surveillance, we have investigated the use of magnetic resonance imaging (MRI) and unilateral relaxometry. MRI provides a spatial map of the polymer, which can be correlated to the structure heterogeneity. Though highly detailed information can be obtained with MRI, the high equipment cost and expertise required to operate the system makes it a poor choice for a production setting. Unilateral relaxometry via the NMR MOUSE provides rapid, inexpensive polymer screening, useful in the development in new polymer parts or to identify potentially defective components. The NMR ProFiler (originally called the NMR MOUSE) was procured by Kansas City originally for production support of the W80 LEP with future applications as a surveillance diagnostic. A robotic autosampler has been designed allowing the detection of several components without the need for any human interaction. A summary of the qualification experiments and results to date from the ProFiler and the robotic unit will be presented.

The objective of this report is to determine the allowed inventory of chemicals stored in the same bay, building or magazine, i.e., in close proximity, with high explosives (HE) that would, in the event of an accident, result in acceptable risks to colocated workers and the public.

Niobium oxide was deposited reactively using a new type of high-density plasma sputter source. The plasma beam used for sputtering is generated remotely and its path to the target defined by the orthogonal locations of two electromagnets: one at the orifice of the plasma tube and the other just beneath the target plane. To accommodate very large batches of substrates, the trade-off between load capacity and deposition rates was evaluated. The effect on deposition rate was determined by moving the plasma source away from the target in one direction and by moving the target assembly away in an orthogonal direction. A simple methodology was used to reestablish the reactive deposition rate and oxide quality even when large changes were made to the chamber geometry. Deposition parameters were established to produce nonabsorbing niobium oxide films of about 100- and 350-nm thicknesses. The quality of the niobium oxide films was studied spectroscopically, ellipsometrically, and stoichiometrically.

None

We present new weak lensing observations of 1E0657-558 (z = 0.296), a unique cluster merger, that enable a direct detection of dark matter, independent of assumptions regarding the nature of the gravitational force law. Due to the collision of two clusters, the dissipationless stellar component and the fluid-like X-ray emitting plasma are spatially segregated. By using both wide-field ground based images and HST/ACS images of the cluster cores, we create gravitational lensing maps which show that the gravitational potential does not trace the plasma distribution, the dominant baryonic mass component, but rather approximately traces the distribution of galaxies. An 8{sigma} significance spatial offset of the center of the total mass from the center of the baryonic mass peaks cannot be explained with an alteration of the gravitational force law, and thus proves that the majority of the matter in the system is unseen.

Lawrence Livermore National Laboratory (LLNL) is recruiting Computer Scientists in the areas of: control systems, computer and information security, database applications development, scientific modeling and simulation, software engineering, and computer and network system administration.

A cement based waste form was evaluated to determine the rates at which various organics were released during heating caused by the cementitious heat-of-hydration reaction. Saltstone is a cement-based waste form for the disposal of low-level salt solution. Samples were prepared with either Isopar{reg_sign} L, a long straight chained hydrocarbon, or (Cs,K) tetraphenylborate, a solid that, upon heating, decomposes to benzene and other aromatic compounds. The saltstone samples were heated over a range of temperatures. Periodically, sample headspaces were purged and the organic constituents were captured on carbon beds and analyzed. Isopar{reg_sign} L was released from the saltstone in a direct relationship to temperature. An equation was developed to correlate the release rate of Isopar{reg_sign} L from the saltstone to the temperature at which the samples were cured. The release of benzene was more complex and relied on both the decomposition of the tetraphenylborate as well as the transport of the manufactured benzene through the curing saltstone. Additional testing with saltstone prepared with different surface area/volume also was performed.

Laser induced damage in potassium dihydrogen phosphate (KDP) has previously been shown to depend significantly on pulse duration for 351-nm Gaussian pulses. In this work we studied the properties of damage initiated by 1053-nm temporally Gaussian pulses with 10ns and 3ns FWHM durations. Our results indicate that the number of damage sites induced by 1053-nm light scales with pulse duration ({tau}) as ({tau}{sub 1}/{tau}{sub 2}){sup 0.17} in contrast to the previously reported results for 351-nm light as ({tau}{sub 1}/{tau}{sub 2}){sup 0.35}. This indicates that damage site formation is significantly less probable at longer wavelengths for a given fluence.

The goals of this study are: (1) to configure a thermal-hydrological, natural-ventilation model for simulating temperature, humidity, and condensate distributions in the coupled domains of in-drift airspace and near-field rockmass. Rokmass model: TOUGH2, in-drift model: MULTIFLUX (MF); (2) obtain meaningful results from the model for a practical application in which the beneficial effects of unheated drift sections are analyzed; and (3) study the sensitivity to the axial dispersion coefficient with the model.

Iron L-edge, iron K-edge, and sulfur K-edge X-ray absorption spectroscopy was performed on a series of compounds [Fe{sup III}H{sub 3}buea(X)]{sup n-} (X = S{sup 2-}, O{sup 2-}, OH{sup -}). The experimentally determined electronic structures were used to correlate to density functional theory calculations. Calculations supported by the data were then used to compare the metal-ligand bonding and to evaluate the effects of H-bonding in Fe{sup III}-O vs Fe{sup III-}S complexes. It was found that the Fe{sup III-}O bond, while less covalent, is stronger than the FeIII-S bond. This dominantly reflects the larger ionic contribution to the Fe{sup III-}O bond. The H-bonding energy (for three H-bonds) was estimated to be -25 kcal/mol for the oxo as compared to -12 kcal/mol for the sulfide ligand. This difference is attributed to the larger charge density on the oxo ligand resulting from the lower covalency of the Fe-O bond. These results were extended to consider an Fe{sup IV-}O complex with the same ligand environment. It was found that hydrogen bonding to Fe{sup IV-}O is less energetically favorable than that to Fe{sup III-}O, which reflects the highly covalent nature of the Fe{sup IV-}O bond.