187 research outputs found
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X-Ray Scattering Applications Using Pulsed X-Ray Sources
Pulsed x-ray sources have been used in transient structural phenomena investigations for over fifty years; however, until the advent of synchrotrons sources and the development of table-top picosecond lasers, general access to ligh temporal resolution x-ray diffraction was relatively limited. Advances in diffraction techniques, sample excitation schemes, and detector systems, in addition to IncEased access to pulsed sources, have ld tO what is now a diverse and growing array of pulsed-source measurement applications. A survey of time-resolved investigations using pulsed x-ray sources is presented and research opportunities using both present and planned pulsed x-ray sources are discussed
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Vacancy and interstitial loops in irradiated copper
Significant advances have been made in diffuse scattering studies of irradiation induced dislocation loops in metals. Numerical calculational procedures have been developed that provide accurate diffuse scattering cross sections for vacancy and interstitial loops, and these cross sections have been used in conjunction with x-ray diffuse scattering studies of neutron and ion irradiated copper. Size distributions and concentrations have been obtained for both vacancy and interstitial loops and these results are compared with electron microscopy measurements. The size distributions obtained from diffuse scattering measurements show the vacancy loops to be smaller and more numerous than the interstitial loops, and indicate that equal numbers of vacancies and interstitials are in loops. The diffuse scattering and microscopy size distributions agree at the larger sizes, but the diffuse scattering method identifies more loops of the smaller sizes
The Abundance of New Kind of Dark Matter Structures
A new kind of dark matter structures, ultracompact minihalos (UCMHs) was
proposed recently. They would be formed during the radiation dominated epoch if
the large density perturbations are existent. Moreover, if the dark matter is
made up of weakly interacting massive particles, the UCMHs can have effect on
cosmological evolution because of the high density and dark matter annihilation
within them. In this paper, one new parameter is introduced to consider the
contributions of UCMHs due to the dark matter annihilation to the evolution of
cosmology, and we use the current and future CMB observations to obtain the
constraint on the new parameter and then the abundance of UCMHs. The final
results are applicable for a wider range of dark matter parametersComment: 4 pages, 1 tabl
Critical Exponents for Three-Dimensional Superfluid--Bose-Glass Phase Transition
The critical phenomenon of the zero temperature superfluid--Bose-glass phase
transition for hard-core bosons on a three-dimensional disordered lattice is
studied using a quantum real-space renormalization-group method. The
correlation-length exponent and the dynamic exponent z are computed. The
critical exponent z is found to be 2.5 for compressible states and 1.3 for
incompressible states. The exponent is shown to be insensitive to z as
that in the two-dimensional case, and has value roughly equal to 1.Comment: 11 pages, REVTE
Disordered Boson Systems: A Perturbative Study
A hard-core disordered boson system is mapped onto a quantum spin 1/2
XY-model with transverse random fields. It is then generalized to a system of
spins with an arbitrary magnitude S and studied through a 1/S expansion. The
first order 1/S expansion corresponds to a spin-wave theory. The effect of weak
disorder is studied perturbatively within such a first order 1/S scheme. We
compute the reduction of the speed of sound and the life time of the Bloch
phonons in the regime of weak disorder. Generalizations of the present study to
the strong disordered regime are discussed.Comment: 27 pages, revte
Tumor immunosurveillance in human cancers
Until now, the anatomic extent of tumor (TNM classification) has been by far the most important factor to predict the prognosis of colorectal cancer patients. However, in recent years, data collected from large cohorts of human cancers demonstrated that the immune contexture of the primary tumors is an essential prognostic factor for patients’ disease-free and overall survival. Tumoral and immunological markers predicted by systems biology methods are involved in the shaping of an efficient immune reaction and can serve as targets for novel therapeutic approaches. Global analysis of tumor microenvironment showed that the nature, the functional orientation, the density, and the location of adaptive immune cells within distinct tumor regions influence the risk of relapse events. The density and the immune cell location within the tumor have a prognostic value that is superior to the TNM classification, and tumor invasion is statistically dependent on the host-immune reaction. Thus, the strength of the immune reaction could advance our understanding of cancer evolution and have important consequences in clinical practice
Electroweak Supersymmetry around the Electroweak Scale
Inspired by the phenomenological constraints, LHC supersymmetry and Higgs
searches, dark matter search as well as string model building, we propose the
electroweak supersymmetry around the electroweak scale: the squarks and/or
gluinos are around a few TeV while the sleptons, sneutrinos, bino and winos are
within one TeV. The Higgsinos can be either heavy or light. We consider bino as
the dominant component of dark matter candidate, and the observed dark matter
relic density is achieved via the neutralino-stau coannihilations. Considering
the Generalized Minimal Supergravity (GmSUGRA), we show explicitly that the
electroweak supersymmetry can be realized, and the gauge coupling unification
can be preserved. With two Scenarios, we study the viable parameter spaces that
satisfy all the current phenomenological constraints, and we present the
concrete benchmark points. Furthermore, we comment on the fine-tuning problem
and LHC searches.Comment: RevTex4, 28 pages, 8 figures, 8 tables, version to appear in EPJ
The Similarity Hypothesis in General Relativity
Self-similar models are important in general relativity and other fundamental
theories. In this paper we shall discuss the ``similarity hypothesis'', which
asserts that under a variety of physical circumstances solutions of these
theories will naturally evolve to a self-similar form. We will find there is
good evidence for this in the context of both spatially homogenous and
inhomogeneous cosmological models, although in some cases the self-similar
model is only an intermediate attractor. There are also a wide variety of
situations, including critical pheneomena, in which spherically symmetric
models tend towards self-similarity. However, this does not happen in all cases
and it is it is important to understand the prerequisites for the conjecture.Comment: to be submitted to Gen. Rel. Gra
Testing population genetic structure using parametric bootstrapping and M IGRATE-N
We present a method for investigating genetic population structure using sequence data. Our hypothesis states that the parameters most responsible for the formation of genetic structure among different populations are the relative rates of mutation (μ) and migration (M). The evolution of genetic structure among different populations requires rates of M ≪ μ because this allows population-specific mutation to accumulate. Rates of μ ≪ M will result in populations that are effectively panmictic because genetic differentiation will not develop among demes. Our test is implemented by using a parametric bootstrap to create the null distribution of the likelihood of the data having been produced under an appropriate model of sequence evolution and a migration rate sufficient to approximate panmixia. We describe this test, then apply it to mtDNA data from 243 plethodontid salamanders. We are able to reject the null hypothesis of no population structure on all but smallest geographic scales, a result consistent with the apparent lack of migration in Plethodon idahoensis . This approach represents a new method of investigating population structure with haploid DNA, and as such may be particularly useful for preliminary investigation of non-model organisms in which multi-locus nuclear data are not available.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42796/1/10709_2004_Article_8358.pd
Genomic landscape of patients with FLT3-mutated acute myeloid leukemia (AML) treated within the CALGB 10603/RATIFY trial
The aim of this study was to characterize the mutational landscape of patients with FLT3-mutated acute myeloid leukemia (AML) treated within the randomized CALGB 10603/RATIFY trial evaluating intensive chemotherapy plus the multi-kinase inhibitor midostaurin versus placebo. We performed sequencing of 262 genes in 475 patients: mutations occurring concurrently with the FLT3-mutation were most frequent in NPM1 (61%), DNMT3A (39%), WT1 (21%), TET2 (12%), NRAS (11%), RUNX1 (11%), PTPN11 (10%), and ASXL1 (8%) genes. To assess effects of clinical and genetic features and their possible interactions, we fitted random survival forests and interpreted the resulting variable importance. Highest prognostic impact was found for WT1 and NPM1 mutations, followed by white blood cell count, FLT3 mutation type (internal tandem duplications vs. tyrosine kinase domain mutations), treatment (midostaurin vs. placebo), ASXL1 mutation, and ECOG performance status. When evaluating two-fold variable combinations the most striking effects were found for WT1:NPM1 (with NPM1 mutation abrogating the negative effect of WT1 mutation), and for WT1:treatment (with midostaurin exerting a beneficial effect in WT1-mutated AML). This targeted gene sequencing study provides important, novel insights into the genomic background of FLT3-mutated AML including the prognostic impact of co-mutations, specific gene-gene interactions, and possible treatment effects of midostaurin
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