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This is the first report of Fermi Gamma-ray Space Telescope observations of the quasar 3C 454.3, which has been undergoing pronounced long-term outbursts since 2000. The data from the Large Area Telescope (LAT), covering 2008 July 7-October 6, indicate strong, highly variable {gamma}-ray emission with an average flux of {approx} 3 x 10{sup -6} photons cm{sup -2} s{sup -1}, for energies > 100 MeV. The {gamma}-ray flux is variable, with strong, distinct, symmetrically-shaped flares for which the flux increases by a factor of several on a time scale of about three days. This variability indicates a compact emission region, and the requirement that the source is optically thin to pair-production implies relativistic beaming with Doppler factor {delta} > 8, consistent with the values inferred from VLBI observations of superluminal expansion ({delta} {approx} 25). The observed {gamma}-ray spectrum is not consistent with a simple power-law, but instead steepens strongly above {approx} 2 GeV, and is well described by a broken power-law with photon indices of {approx} 2.3 and {approx} 3.5 below and above the break, respectively. This is the first direct observation of a break in the spectrum of a high luminosity blazar above 100 MeV, and it is likely direct …

Mineralized tissues, such as bone and tooth dentin, serve as structural materials in the human body and, as such, have evolved to resist fracture. In assessing their quantitative fracture resistance or toughness, it is important to distinguish between intrinsic toughening mechanisms which function ahead of the crack tip, such as plasticity in metals, and extrinsic mechanisms which function primarily behind the tip, such as crack bridging in ceramics. Bone and dentin derive their resistance to fracture principally from extrinsic toughening mechanisms which have their origins in the hierarchical microstructure of these mineralized tissues. Experimentally, quantification of these toughening mechanisms requires a crack-growth resistance approach, which can be achieved by measuring the crack-driving force, e.g., the stress intensity, as a function of crack extension ("R-curve approach"). Here this methodology is used to study of the effect of aging on the fracture properties of human cortical bone and human dentin in order to discern the microstructural origins of toughness in these materials.

We report on the first simultaneous observations that cover the optical, X-ray, and high-energy gamma-ray bands of the BL Lac object PKS 2155-304. The gamma-ray bands were observed for 11 days, between 2008 August 25 and 2008 September 6 (MJD 54704-54715), jointly with the Fermi Gamma-ray Space Telescope and the HESS atmospheric Cherenkov array, providing the first simultaneous MeV-TeV spectral energy distribution (SED) with the new generation of {gamma}-ray telescopes. The ATOM telescope and the RXTE and Swift observatories provided optical and X-ray coverage of the low-energy component over the same time period. The object was close to the lowest archival X-ray and very high energy (VHE; >100 GeV) state, whereas the optical flux was much higher. The light curves show relatively little ({approx}30%) variability overall when compared to past flaring episodes, but we find a clear optical/VHE correlation and evidence for a correlation of the X-rays with the high-energy spectral index. Contrary to previous observations in the flaring state, we do not find any correlation between the X-ray and VHE components. Although synchrotron self-Compton models are often invoked to explain the SEDs of BL Lac objects, the most common versions of these models are at odds with the correlated …

The Antarctic Muon and Neutrino Detector Array (AMANDA) began collecting data with ten strings in 1997. Results from the first year of operation are presented. Neutrinos coming through the Earth from the Northern Hemisphere are identified by secondary muons moving upward through the array. Cosmic rays in the atmosphere generate a background of downward moving muons, which are about 10{sup 6} times more abundant than the upward moving muons. Over 130 days of exposure, we observed a total of about 300 neutrino events. In the same period, a background of 1.05 x 10{sup 9} cosmic ray muon events was recorded. The observed neutrino flux is consistent with atmospheric neutrino predictions. Monte Carlo simulations indicate that 90 percent of these events lie in the energy range 66 GeV to 3.4 TeV. The observation of atmospheric neutrinos consistent with expectations establishes AMANDA-B10 as a working neutrino telescope.

Present experiments on TMX-U and modeling of MFTF-B indicate that plasma-surface interactions can be controlled in MFTF-B. The MFTF-B configuration uses a hot electron population created by ECRH and a sloshing-ion population created by neutral beams in the thermal barrier region to create a potential that confines the central cell ions. Neutral beams and ICRH are used to heat the central cell ions. Plasma-surface interactions can be minimized at radial surfaces by control of the axial confinement of the edge plasma. The thermal barrier configuration is sensitive to the background neutral density, and requires low wall reflux and efficient shielding by the edge plasma. Glow discharge cleaning, titanium gettering, and control of the gas from neutral beams will be used to provide wall conditioning and to reduce the background gas pressure. The shielding efficiency of the plasma edge has been modeled in MFTF-B by comparing computer codes with current experimental measurements. In addition, it is very important to reduce high-energy neutral-beam-injected impurities; this is accomplished by using gettering or magnetic separation in the injector systems. Plasma-edge scrapers, diverter-like devices, and direct-conversion equipment will be located in the end region. Major disruptions are not anticipated. Finally, MFTF-B will also test some …

Two programming models for parallelizing the Angular Domain Decomposition (ADD) of the discrete ordinates (S{sub n}) approximation of the neutron transport equation are examined. These are the shared memory model based on the POSIX threads (Pthreads) standard, and the message passing model based on the Message Passing Interface (MPI) standard. These standard libraries are available on most multiprocessor platforms thus making the resulting parallel codes widely portable. The question is: on a fixed platform, and for a particular code solving a given test problem, which of the two programming models delivers better parallel performance? Such comparison is possible on Symmetric Multi-Processors (SMP) architectures in which several CPUs physically share a common memory, and in addition are capable of emulating message passing functionality. Implementation of the two-dimensional,(S{sub n}), Arbitrarily High Order Transport (AHOT) code for solving neutron transport problems using these two parallelization models is described. Measured parallel performance of each model on the COMPAQ AlphaServer 8400 and the SGI Origin 2000 platforms is described, and comparison of the observed speedup for the two programming models is reported. For the case presented in this paper it appears that the MPI implementation scales better than the Pthreads implementation on both platforms.

We have developed cermet membranes that nongalvanically separate hydrogen from gas mixtures. The highest measured hydrogen flux was 20.0 cm{sup 3} (STP)/min-cm{sup 2} for an ANL-3a membrane at 900 C. For ANL-3 membranes with thickness of 40-500 {micro}m, hydrogen permeation is limited by the bulk diffusion of hydrogen through the metal phase. The effect of hydrogen partial pressure on permeation rate confirmed this conclusion, suggesting that higher permeation rates may be obtained by decreasing the membrane thickness. Permeation rate in a syngas atmosphere for times up to 190 h showed no degradation in performance, which indicates that ANL-3 membranes may be suitable for long-term, practical hydrogen separation.

The multi-ampere currents required for high luminosity operation of an asymmetric B factory leads to extremely stressing requirements on a vacuum system suitable for maintaining long beam-gas lifetimes and acceptable background levels in the detector. We present the design for a Cu alloy vacuum chamber and its associated pumping system for the 9 GeV electron storage ring of the proposed B factory based on PEP. The excellent thermal and photo-desorption properties of Cu allows handling the high proton flux in a conventional, single chamber design with distributed ion pumps. The x-ray opacity of the Cu is sufficiently high that no additional lead shielding is necessary to protect the dipoles from the intense synchrotron radiation generated by the beam. The design allows chamber commissioning in <500 hr of operation. 5 refs., 3 figs., 2 tabs.

There are several goals for the neutron source strength monitor system for the International Thermonuclear Experimental Reactor (ITER). Desired is a stable, reliable, time-dependent neutron detection system which exhibits a wide dynamic range and broad energy response to incident neutrons while being insensitive to gamma rays and having low noise characteristics in a harsh reactor environment. This system should be able to absolutely calibrated in-situ using various neutron sources. An array of proportional counters of varying sensitivities is proposed along with the most promising possible locations. One proposed location is in the pre-shields of the neutron camera collimators which would allow an integrated design of neutron systems with good detector access. As part of an ongoing conceptual design for this system, the detector-specific issues of dynamic range, performance monitoring, and sensitivity will be presented. The location options of the array will be discussed and most importantly, the calibration issues associated with a heavily shielded vessel will be presented.

Bunch compressors, designed to increase the peak current, can lead to a microbunching instability with detrimental effects on the beam quality. This is a major concern for free electron lasers (FELs) where very bright electron beams are required, i.e. beams with low emittance and energy spread. In this paper, we apply our self-consistent, parallel solver to study the microbunching instability in the first bunch compressor system of FERMI{at}Elettra. Our basic model is a 2D Vlasov-Maxwell system. We treat the beam evolution through a bunch compressor using our Monte Carlo mean field approximation. We randomly generate N points from an initial phase space density. We then calculate the charge density using a smooth density estimation procedure, from statistics, based on Fourier series. The electric and magnetic fields are calculated from the smooth charge/current density using a novel field formula that avoids singularities by using the retarded time as a variable of integration. The points are then moved forward in small time steps using the beam frame equations of motion, with the fields frozen during a time step, and a new charge density is determined using our density estimation procedure. We try to choose N large enough so that the charge density …

The Law of Corresponding States has been demonstrated for a number of pure substances and binary mixtures, and provides evidence that the transport properties viscosity and diffusion can be determined from a molecular shape function, often taken to be a Lennard-Jones 12-6 potential, that requires two scaling parameters: a well depth {var_epsilon}{sub ij} and a collision diameter {sigma}{sub ij}, both of which depend on the interacting species i and j. We obtain estimates for {var_epsilon}{sub ij} and {sigma}{sub ij} of interacting species by finding the values that provide the best fit to viscosity data for binary mixtures, and compare these to calculated parameters using several 'combining rules' that have been suggested for determining parameter values for binary collisions from parameter values that describe collisions of like molecules. Different combining rules give different values for {sigma}{sub ij} and {var_epsilon}{sub ij} and for some mixtures the differences between these values and the best-fit parameter values are rather large. There is a curve in ({var_epsilon}{sub ij}, {sigma}{sub ij}) space such that parameter values on the curve generate a calculated viscosity in good agreement with measurements for a pure gas or a binary mixture. The various combining rules produce couples of parameters {var_epsilon}{sub ij}, …

Despite increasing attention paid to parallel I/O and the introduction of MPI-IO, there is limited, practical data to help guide a programmer in the choice of a good parallel write strategy in the absence of a parallel file system. In this study we experimentally evaluate several methods for implementing parallel computations that interleave a significant number of contiguous or strided writes to a local disk on Linux-based multiprocessor nodes. Using synthetic benchmark programs written with MPI and Pthreads, we have acquired detailed performance data for different application characteristics of programs running on dual processor nodes. In general, our results show that programs that perform a significant amount of I/O relative to pure computation benefit greatly from the use of threads, while programs that perform relatively little I/O obtain excellent results using only MPI. For a pure MPI approach, we have found that it is best to use two writing processes with mmap(). For Pthreads it is usually best to use write() for contiguous data and writev() for strided data. Codes that use mmap() tend to benefit from periodic syncs of the data of the data to the disk, while codes that use write() or writev() tend to have better performance …

We report the discovery of Very High Energy (VHE; &gt;100 GeV) gamma-ray emission from the source 1FGL J2001.1+4351, (RA 20 01 13.5, dec 43 53 02.8, J2000), which is positionally consistent with the location of the flat spectrum radio source MG4 J200112+4352 (RA 20 01 12.9, dec 43 52 52.8, J2000). The VHE detection is based on a 1.5 hour-long observation performed on July 16th in stereoscopic mode with the two 17m diameter imaging Cherenkov telescopes on La Palma, Canary Islands, Spain. The preliminary analysis of the MAGIC data using the standard cuts optimized for soft energy spectra sources yields a detection of 125 gamma-rays above 90 GeV, corresponding to a pre-trail statistical significance of 7.6 standard deviations. The observed flux is estimated to be {approx}20% of the Crab nebula flux above 100 GeV. Earlier MAGIC observations indicated a substantially lower flux; hence indicating that the source is variable on a few days timescale.

A software system, GRAVE (Geometry Rendering and Visual Editor), has been developed at the Oak Ridge National Laboratory (ORNL) to perform interactive visualization and development of models used as input to the TORT three-dimensional discrete ordinates radiation transport code. Three-dimensional and two-dimensional visualization displays are included. Display capabilities include image rotation, zoom, translation, wire-frame and translucent display, geometry cuts and slices, and display of individual component bodies and material zones. The geometry can be interactively edited and saved in TORT input file format. This system is an advancement over the current, non-interactive, two-dimensional display software. GRAVE is programmed in the Java programming language and can be implemented on a variety of computer platforms. Three- dimensional visualization is enabled through the Visualization Toolkit (VTK), a free-ware C++ software library developed for geometric and data visual display. Future plans include an extension of the system to read inputs using binary zone maps and combinatorial geometry models containing curved surfaces, such as those used for Monte Carlo code inputs. Also GRAVE will be extended to geometry visualization/editing for the DORT two-dimensional transport code and will be integrated into a single GUI-based system for all of the ORNL discrete ordinates transport codes.

In a solid-state heat capacity laser (SSHCL), waste heat is stored in the lasing slabs, minimizing temperature gradients and optical distortions. After the maximum number of pulses is reached, the slabs are cooled or rapidly exchanged with cool slabs. During the past several years, our laboratory at LLNL has built a number of SSHCLs, demonstrating powers beyond 10 kW. In this paper, we model target interactions produced by a 10 kW device (500 J/pulse and 20 Hz), operating at a wavelength of 1.053 {micro}m. The laser contains 9 Nd:glass slabs pumped by flashlamps.

Silica nanoparticles exhibiting hexagonal, cubic, and vesicular mesostructures have been prepared using aerosol assisted, self-assembled process. This process begins with homogennous aerosol droplets containing silica source, water, ethanol, and surfactant, in which surfactant concentration is far below the critical micelle concentration (cmc). Solvent evaporation enriches silica and surfactant inducing interfacial self-assembly confined to a spherical aerosol droplet and results in formation of completely solid, ordered spherical particles with stable hexagonal, cubic, or vesicular mesostructures.

A university laboratory experiment for the US Department of Energy magnetic fusion research program required a simulant for liquid lithium. The simulant choices were narrowed to liquid gallium and galinstan (Ga-In-Sn) alloy. Safety information on liquid gallium and galinstan were compiled, and the choice was made to use galinstan. A laboratory safety walkthrough was performed in the fall of 2002 to support the galinstan experiment. The experiment has been operating successfully since early 2002.

Using a streak camera, we measured the longitudinal profiles of a positron bunch in the Low Energy Ring (LER) of KEKB at various currents. The measured charge densities were used to construct a simple Q=1 broadband impedance model. The model, with three parameters, not only gave an excellent description of longitudinal dynamics for positive momentum compaction factor but also for the negative ones, including bunch shortening below a threshold and bursting modes above the threshold. Furthermore, our study indicated that the threshold of microwave instability was about 0.5 mA in bunch current in the LER. At the nominal operating current 1.0 mA, there was a 20% increase of the energy spread. The results of measurement, analysis, and simulations will be presented in this paper.

The newest workhorse of the National Energy Research Scientific Computing Center is a Cray XT4 with 9,736 dual core nodes. This paper summarizes Franklin user experiences from friendly early user period to production period. Selected successful user stories along with top issues affecting user experiences are presented.

Models with low-scale breaking of global symmetries in the neutrino sector provide an alternative to the seesaw mechanism for understanding why neutrinos are light. Such models can easily incorporate light sterile neutrinos required by the LSND experiment. Furthermore, the constraints on the sterile neutrino properties from nucleosynthesis and large scale structure can be removed due to the non-conventional cosmological evolution of neutrino masses and densities. We present explicit, fully realistic supersymmetric models, and discuss the characteristic signatures predicted in the angular distributions of the cosmic microwave background.

We describe the use of a flow-focusing microfluidic reactorto measure the kinetics of theCdSe-to-Ag2Se nanocrystal cation exchangereaction using micro-X-ray absorption spectroscopy (mu XAS). The smallmicroreactor dimensions facilitate the millisecond mixing of CdSenanocrystal and Ag+ reactant solutions, and the transposition of thereaction time onto spatial coordinates enables the in situ observation ofthe millisecond reaction with mu XAS. XAS spectra show the progression ofCdSe nanocrystals to Ag2Se over the course of 100 ms without the presenceof long-lived intermediates. These results, along with supporting stoppedflow absorption experiments, suggest that this nanocrystal cationexchange reaction is highly efficient and provide insight into how thereaction progresses in individual particles. This experiment illustratesthe value and potential of in situ microfluidic X-ray synchrotrontechniques for detailed studies of the millisecond structuraltransformations of nanoparticles and other solution-phase reactions inwhich diffusive mixing initiates changes in local bond structures oroxidation states.

The solution-mediated syntheses and single crystal structures of (N₂C₆H₁₄)&middot;Zn(HPO₄)₂&middot;H₂O (I), H₃N(CH₂)₃NH₃&middot;Zn₂(HPO₄)₃ (II), and (N₂C₆H₁₄)&middot;Zn₃(HPO₄)₄ (III) are described. These phases contain vertex-sharing Zn0₄ and HP0₄ tetrahedra, accompanied by doubly- protonated organic cations. Despite their formal chemical relationship, as members of the series of t&middot;Zn_n(HP0₄)_n+1 (t= template, n = 1-3), these phases adopt fimdamentally different crystal structures, as one-dimensional, two-dimensional, and three-dimensional Zn0₄/HP0₄ networks, for I, II, and III respectively. Similarities and differences to some other zinc phosphates are briefly discussed. Crystal data: (N₂C₆H₁₄)&middot;Zn(HP0₄)₂&middot;H₂0, M_r = 389.54, monoclinic, space group P2₁/n (No. 14), a = 9.864 (4) &Aring;, b = 8.679 (4) &Aring;, c = 15.780 (3) &Aring;, &beta; = 106.86 (2)&deg;, V= 1294.2 (8) &Aring;³, Z = 4, R(F) = 4.58%, R_W(F) = 5.28% [1055 reflections with I >3&sigma;(I)]. H₃N(CH₂)₃NH₃&middot;Zn₂(HP0₄)₃, M_r = 494.84, monoclinic, space group P2₁/c (No. 14), a= 8.593 (2)&Aring;, b= 9.602 (2)&Aring;, c= 17.001 (3)&Aring;, &beta;= 93.571 (8)&deg;, V = 1400.0 (5) &Aring;³, Z = 4, R(F) = 4.09%, R_W(F) = 4.81% [2794 reflections with I > 3&sigma; (I)]. (N₂C₆H₁₄)&middot;Zn₃(HP0₄)₄, M_r= 694.25, monoclinic, space group P2₁/n (No. 14), a = 9.535 (2) &Aring;, b = 23.246 (4)&Aring;, c= 9.587 (2)&Aring;, &beta;= 117.74 (2)&deg;, V= 1880.8 (8) &Aring;³, Z …

The solution-mediated syntheses and single crystal structures of (CH₃NH₃)₃&middot;Zn₄0(AsO₄)₃ and (CH₃NH₃)₃&middot;Zn₄O(P0₄)₃ are reported. These compounds are built up from vertex-sharing three-dimensional Zn0₄ + AsO₄/P0₄ tetrahedral frameworks encapsulating methylammonium cations in three-dimensional channel systems. These phases are closely related to the zeolite- like M₃Zn₄O(XO₄)₃&middot;nH₂O family of phases. Crystal data for (CH₃NH₃)₃&middot;Zn₄0(AsO₄)₃, M, = 790.47, monoclinic, space group P2₁ (No. 4), a = 7.814 (3)&Aring;, b = 15.498 (6)&Aring;, c = 7.815 (3) &Aring;, {beta} = 92.91 (2)0, V = 945.1 (9) &Aring;³, Z = 2, R(F) = 3.01%, R_W(F) = 3.98% (2301 reflections, 236 parameters). Crystal data for (CH₃NH₃)₃&middot;Zn₄0(P0₄)₃: M, = 658.63, monoclinic, space group P2₁ (No. 4), a = 7.6569 (5) &Aring;, b = 15.241 (1)&Aring;, c= 7.6589 (5) &Aring;, {beta} = 92.740 (1)0, V= 892.7 (5) &Aring;³, Z = 2, R(F)= 8.07%, R_W(F)= 9.60% (2694 reflections, 106 parameters).