Failure rate analysis using GLIMMIX

This paper illustrates use of a recently developed SAS macro, GLIMMIX, for implementing an analysis suggested by Wolfinger and O`Connell (1993) in modeling failure count data with random as well as fixed factor effects. Interest in this software tool arose from consideration of modernizing the Failure Rate Analysis Code (FRAC), developed at Los Alamos National Laboratory in the early 1980`s by Martz, Beckman and McInteer (1982). FRAC is a FORTRAN program developed to analyze Poisson distributed failure count data as a log-linear model, possibly with random as well as fixed effects. These statistical modeling assumptions are a special case of generalized linear mixed models, identified as GLMM in the current statistics literature. In the nearly 15 years since FRAC was developed, there have been considerable advances in computing capability, statistical methodology and available statistical software tools allowing worthwhile consideration of the tasks of modernizing FRAC. In this paper, the approaches to GLMM estimation implemented in GLIMMIX and in FRAC are described and a comparison of results for the two approaches is made with data on catastrophic time-dependent pump failures from a report by Martz and Whiteman (1984). Additionally, statistical and graphical model diagnostics are suggested and illustrated with the GLIMMIX analysis results

An unholy alliance: Christian identity extremists and ICTs

The rise of extremism has been a global concern, but white extremism, in particular, has been expanding rapidly within the United States (U.S.). Even more concerning is how white extremist groups have utilized Information and Communication Technologies (ICTs) to broaden their reach and spread their ideologies to larger audiences. This research examines the Christian Identity Movement (CIM) subset within the larger white extremist community. The CIM has utilized Christianity to justify extremist actions, a problem notably reflected in recent white extremist shooter manifestos. As extremist propaganda continues making its way through the digital landscape, this study aims to understand how the CIM has infiltrated the greater white extremist digital communities. This is particularly relevant as extremist groups are proliferating across numerous social media platforms. Due to the lack of scholarly literature currently discussing the nexus between white extremists, Christian Identity, technology, and social media, this research is necessary to understand the information flow between these groups online

Alkali Metal Trihalides: MX ̄ Ion Pair or MX-X Complex?

The alkali metal trihalides MX3 (M = Li, Na, K, Rb, and Cs; X = Cl, Br, and I) are systematically studied using coupled-cluster methods. Benchmarks using CCSD(T) against diatomic experimental results suggest satisfactory performance for the weighted core-valence basis sets (new basis sets for K, Rb, and Cs) selected for predicting reliable structures and harmonic vibrational frequencies. An isomer search using the B3LYP functional yields a planar, yet asymmetric T-shaped Cs structure as the global minimum for all MX3 species. Much higher level CCSD(T) computations show a moderate to strong distortion of the X3ˉ anion by the M+ cation in the respective equilibrium geometries. Most obviously, for LiCl3 the two Cl-Cl distances are separated by 0.786 Å. Even for CsI3, the structure least distorted from the M+X3ˉ model, the two I-I distances differ by 0.243 Å. It does not take much energy to distort the parent anions along an asymmetric stretch, so this is no surprise. The normal modes of vibration of the MX3 molecules are in better agreement with matrix isolation experiments than previous calculations. And these normal modes are revealing -- instead of the well-established antisymmetric and symmetric stretches of the “free” X3ˉ anions, relatively localized and mutually-perturbed X-X and M-X stretches are calculated. The suggestion emerges that the MX3 system may be alternatively described as an MX-X2 complex, rather than the M+X3ˉ ion pair. This perspective is supported by bonding analyses showing low electron densities at the bond critical points and natural bond orders between the MX and X2 moieties. The thermochemistry of fragmentations of MX3 to MX + X2 vs. M+ + X3ˉ also supports the alternative viewpoint of the bonding in this class of molecules

Constraints on Dark Matter Annihilation in Clusters of Galaxies with the Fermi Large Area Telescope

Nearby clusters and groups of galaxies are potentially bright sources of high-energy gamma-ray emission resulting from the pair-annihilation of dark matter particles. However, no significant gamma-ray emission has been detected so far from clusters in the first 11 months of observations with the Fermi Large Area Telescope. We interpret this non-detection in terms of constraints on dark matter particle properties. In particular for leptonic annihilation final states and particle masses greater than ~200 GeV, gamma-ray emission from inverse Compton scattering of CMB photons is expected to dominate the dark matter annihilation signal from clusters, and our gamma-ray limits exclude large regions of the parameter space that would give a good fit to the recent anomalous Pamela and Fermi-LAT electron-positron measurements. We also present constraints on the annihilation of more standard dark matter candidates, such as the lightest neutralino of supersymmetric models. The constraints are particularly strong when including the fact that clusters are known to contain substructure at least on galaxy scales, increasing the expected gamma-ray flux by a factor of ~5 over a smooth-halo assumption. We also explore the effect of uncertainties in cluster dark matter density profiles, finding a systematic uncertainty in the constraints of roughly a factor of two, but similar overall conclusions. In this work, we focus on deriving limits on dark matter models; a more general consideration of the Fermi-LAT data on clusters and clusters as gamma-ray sources is forthcoming.Comment: accepted to JCAP, Corresponding authors: T.E. Jeltema and S. Profumo, minor revisions to be consistent with accepted versio

Sealing of chromosomal DNA nicks during nucleotide excision repair requires XRCC1 and DNA ligase III alpha in a cell-cycle-specific manner

Impaired gap filling and sealing of chromosomal DNA in nucleotide excision repair (NER) leads to genome instability. XRCC1-DNA ligase IIIa (XRCC1-Lig3) plays a central role in the repair of DNA single-strand breaks but has never been implicated in NER. Here we show that XRCC1-Lig3 is indispensable for ligation of NER-induced breaks and repair of UV lesions in quiescent cells. Furthermore, our results demonstrate that two distinct complexes differentially carry out gap filling in NER. XRCC1-Lig3 and DNA polymerase d colocalize and interact with NER components in a UV- and incision-dependent manner throughout the cell cycle. In contrast, DNA ligase I and DNA polymerase are recruited to UV-damage sites only in proliferating cells. This study reveals an unexpected and key role for XRCC1-Lig3 in maintenance of genomic integrity by NER in both dividing and nondividing cells and provides evidence for cell-cycle regulation of NER-mediated repair synthesis in vivo

Azimuthal anisotropy and correlations in p+p, d+Au and Au+Au collisions at 200 GeV

We present the first measurement of directed flow ($v_1$) at RHIC. $v_1$ is found to be consistent with zero at pseudorapidities $\eta$ from -1.2 to 1.2, then rises to the level of a couple of percent over the range $2.4 < |\eta| < 4$. The latter observation is similar to data from NA49 if the SPS rapidities are shifted by the difference in beam rapidity between RHIC and SPS. Back-to-back jets emitted out-of-plane are found to be suppressed more if compared to those emitted in-plane, which is consistent with {\it jet quenching}. Using the scalar product method, we systematically compared azimuthal correlations from p+p, d+Au and Au+Au collisions. Flow and non-flow from these three different collision systems are discussed.Comment: Quark Matter 2004 proceeding, 4 pages, 3 figure

Azimuthal anisotropy: the higher harmonics

We report the first observations of the fourth harmonic (v_4) in the azimuthal distribution of particles at RHIC. The measurement was done taking advantage of the large elliptic flow generated at RHIC. The integrated v_4 is about a factor of 10 smaller than v_2. For the sixth (v_6) and eighth (v_8) harmonics upper limits on the magnitudes are reported.Comment: 4 pages, 6 figures, contribution to the Quark Matter 2004 proceeding

Plasma Wakefield Acceleration with a Modulated Proton Bunch

The plasma wakefield amplitudes which could be achieved via the modulation of a long proton bunch are investigated. We find that in the limit of long bunches compared to the plasma wavelength, the strength of the accelerating fields is directly proportional to the number of particles in the drive bunch and inversely proportional to the square of the transverse bunch size. The scaling laws were tested and verified in detailed simulations using parameters of existing proton accelerators, and large electric fields were achieved, reaching 1 GV/m for LHC bunches. Energy gains for test electrons beyond 6 TeV were found in this case.Comment: 9 pages, 7 figure