59 research outputs found
Infrared Properties of Cataclysmic Variables from 2MASS: Results from the 2nd Incremental Data Release
Because accretion-generated luminosity dominates the radiated energy of most
cataclysmic variables, they have been ``traditionally'' observed primarily at
short wavelengths. Infrared observations of cataclysmic variables contribute to
the understanding of key system components that are expected to radiate at
these wavelengths, such as the cool outer disk, accretion stream, and secondary
star. We have compiled the J, H, and Ks photometry of all cataclysmic variables
located in the sky coverage of the 2 Micron All Sky Survey (2MASS) 2nd
Incremental Data Release. This data comprises 251 systems with reliably
identified near-IR counterparts and S/N > 10 photometry in one or more of the
three near-IR bands.Comment: 2 pages, including 1 figure. To appear in the proceedings of The
Physics of Cataclysmic Variables and Related Objects, Goettingen, Germany.
For our followup ApJ paper (in press), also see
http://www.ctio.noao.edu/~hoard/research/2mass/index.htm
Gravitational clustering of relic neutrinos and implications for their detection
We study the gravitational clustering of big bang relic neutrinos onto
existing cold dark matter (CDM) and baryonic structures within the flat
CDM model, using both numerical simulations and a semi-analytical
linear technique, with the aim of understanding the neutrinos' clustering
properties for direct detection purposes. In a comparative analysis, we find
that the linear technique systematically underestimates the amount of
clustering for a wide range of CDM halo and neutrino masses. This invalidates
earlier claims of the technique's applicability. We then compute the exact
phase space distribution of relic neutrinos in our neighbourhood at Earth, and
estimate the large scale neutrino density contrasts within the local
Greisen--Zatsepin--Kuzmin zone. With these findings, we discuss the
implications of gravitational neutrino clustering for scattering-based
detection methods, ranging from flux detection via Cavendish-type torsion
balances, to target detection using accelerator beams and cosmic rays. For
emission spectroscopy via resonant annihilation of extremely energetic cosmic
neutrinos on the relic neutrino background, we give new estimates for the
expected enhancement in the event rates in the direction of the Virgo cluster.Comment: 38 pages, 8 embedded figures, iopart.cls; v2: references added, minor
changes in text, to appear in JCA
Strong interface-induced spin-orbit coupling in graphene on WS2
Interfacial interactions allow the electronic properties of graphene to be
modified, as recently demonstrated by the appearance of satellite Dirac cones
in the band structure of graphene on hexagonal boron nitride (hBN) substrates.
Ongoing research strives to explore interfacial interactions in a broader class
of materials in order to engineer targeted electronic properties. Here we show
that at an interface with a tungsten disulfide (WS2) substrate, the strength of
the spin-orbit interaction (SOI) in graphene is very strongly enhanced. The
induced SOI leads to a pronounced low-temperature weak anti-localization (WAL)
effect, from which we determine the spin-relaxation time. We find that
spin-relaxation time in graphene is two-to-three orders of magnitude smaller on
WS2 than on SiO2 or hBN, and that it is comparable to the intervalley
scattering time. To interpret our findings we have performed first-principle
electronic structure calculations, which both confirm that carriers in
graphene-on-WS2 experience a strong SOI and allow us to extract a
spin-dependent low-energy effective Hamiltonian. Our analysis further shows
that the use of WS2 substrates opens a possible new route to access topological
states of matter in graphene-based systems.Comment: Originally submitted version in compliance with editorial guidelines.
Final version with expanded discussion of the relation between theory and
experiments to be published in Nature Communication
Alterations of E-cadherin and β-catenin in gastric cancer
BACKGROUND: The E-cadherin-catenin complex plays a crucial role in epithelial cell-cell adhesion and in the maintenance of tissue architecture. Perturbation in the expression or function of this complex results in loss of intercellular adhesion, with possible consequent cell transformation and tumour progression. METHODS: We studied the alterations of E-cadherin and β-catenin in a set of 50 primary gastric tumours by using loss of heterozygosity (LOH) analysis, gene mutation screening, detection of aberrant transcripts and immunohistochemistry (IHC). RESULTS: A high frequency (75%) of LOH was detected at 16q22.1 containing E-cadherin locus. Three cases (6%) showed the identical missense mutation, A592T. This mutation is not likely to contribute strongly to the carcinogenesis of gastric cancer, because a low frequency (1.6%) of this mutation was also found in 187 normal individuals. We also detected a low frequency (0.36%, 0%) of this mutation in 280 breast tumours and 444 other tumours, including colon and rectum, lung, endometrium, ovary, testis, kidney, thyroid carcinomas and sarcomas, respectively. We also analyzed the aberrant E-cadherin mRNAs in the gastric tumours and found that 7 tumours (18%) had aberrant mRNAs in addition to the normal mRNA. These aberrant mRNAs may produce abnormal E-cadherin molecules, resulting in weak cell-cell adhesion and invasive behaviour of carcinoma cells. Reduced expression of E-cadherin and β-catenin was identified at the frequency of 42% and 28%, respectively. Specially, 11 tumours (22%) exhibited positive cytoplasmic staining for β-catenin IHC. An association was found between reduced expression of E-cadherin and β-catenin. Moreover, an association was detected between reduced expression of E-cadherin and diffuse histotype. CONCLUSION: Our results support the hypothesis that alterations of E-cadherin and β-catenin play a role in the initiation and progression of gastric cancer
Immunisation with Recombinant PfEMP1 Domains Elicits Functional Rosette-Inhibiting and Phagocytosis-Inducing Antibodies to Plasmodium falciparum
BACKGROUND: Rosetting is a Plasmodium falciparum virulence factor implicated in the pathogenesis of life-threatening malaria. Rosetting occurs when parasite-derived P. falciparum Erythrocyte Membrane Protein One (PfEMP1) on the surface of infected erythrocytes binds to human receptors on uninfected erythrocytes. PfEMP1 is a possible target for a vaccine to induce antibodies to inhibit rosetting and prevent severe malaria. METHODOLOGY/FINDINGS: We examined the vaccine potential of the six extracellular domains of a rosette-mediating PfEMP1 variant (ITvar9/R29var1 from the R29 parasite strain) by immunizing rabbits with recombinant proteins expressed in E. coli. Antibodies raised to each domain were tested for surface fluorescence with live infected erythrocytes, rosette inhibition and phagocytosis-induction. Antibodies to all PfEMP1 domains recognized the surface of live infected erythrocytes down to low concentrations (0.02-1.56 µg/ml of total IgG). Antibodies to all PfEMP1 domains except for the second Duffy-Binding-Like region inhibited rosetting (50% inhibitory concentration 0.04-4 µg/ml) and were able to opsonize and induce phagocytosis of infected erythrocytes at low concentrations (1.56-6.25 µg/ml). Antibodies to the N-terminal region (NTS-DBL1α) were the most effective in all assays. All antibodies were specific for the R29 parasite strain, and showed no functional activity against five other rosetting strains. CONCLUSIONS/SIGNIFICANCE: These results are encouraging for vaccine development as they show that potent antibodies can be generated to recombinant PfEMP1 domains that will inhibit rosetting and induce phagocytosis of infected erythrocytes. However, further work is needed on rosetting mechanisms and cross-reactivity in field isolates to define a set of PfEMP1 variants that could induce functional antibodies against a broad range of P. falciparum rosetting parasites
A Gene-Phenotype Network for the Laboratory Mouse and Its Implications for Systematic Phenotyping
The laboratory mouse is the pre-eminent model organism for the dissection of human disease pathways. With the advent of a comprehensive panel of gene knockouts, projects to characterise the phenotypes of all knockout lines are being initiated. The range of genotype-phenotype associations can be represented using the Mammalian Phenotype ontology. Using publicly available data annotated with this ontology we have constructed gene and phenotype networks representing these associations. These networks show a scale-free, hierarchical and modular character and community structure. They also exhibit enrichment for gene coexpression, protein-protein interactions and Gene Ontology annotation similarity. Close association between gene communities and some high-level ontology terms suggests that systematic phenotyping can provide a direct insight into underlying pathways. However some phenotypes are distributed more diffusely across gene networks, likely reflecting the pleiotropic roles of many genes. Phenotype communities show a many-to-many relationship to human disease communities, but stronger overlap at more granular levels of description. This may suggest that systematic phenotyping projects should aim for high granularity annotations to maximise their relevance to human disease
Mouse anatomy ontologies:enhancements and tools for exploring and integrating biomedical data
Mouse anatomy ontologies provide standard nomenclature for describing normal and mutant mouse anatomy, and are essential for the description and integration of data directly related to anatomy such as gene expression patterns. Building on our previous work on anatomical ontologies for the embryonic and adult mouse, we have recently developed a new and substantially revised anatomical ontology covering all life stages of the mouse. Anatomical terms are organized in complex hierarchies enabling multiple relationships between terms. Tissue classification as well as partonomic, developmental, and other types of relationships can be represented. Hierarchies for specific developmental stages can also be derived. The ontology forms the core of the eMouse Atlas Project (EMAP) and is used extensively for annotating and integrating gene expression patterns and other data by the Gene Expression Database (GXD), the eMouse Atlas of Gene Expression (EMAGE) and other database resources. Here we illustrate the evolution of the developmental and adult mouse anatomical ontologies toward one combined system. We report on recent ontology enhancements, describe the current status, and discuss future plans for mouse anatomy ontology development and application in integrating data resources. Mamm Genome 2015 Oct; 26(9-10):422-3
Neutrino Masses, Mixing, and Oscillations
The Review summarizes much of particle physics and cosmology. Using data from previous editions, plus 2,873 new measurements from 758 papers, we list, evaluate, and average measured properties of gauge bosons and the recently discovered Higgs boson, leptons, quarks, mesons, and baryons. We summarize searches for hypothetical particles such as supersymmetric particles, heavy bosons, axions, dark photons, etc. Particle properties and search limits are listed in Summary Tables. We give numerous tables, figures, formulae, and reviews of topics such as Higgs Boson Physics, Supersymmetry, Grand Unified Theories, Neutrino Mixing, Dark Energy, Dark Matter, Cosmology, Particle Detectors, Colliders, Probability and Statistics. Among the 118 reviews are many that are new or heavily revised, including a new review on Neutrinos in Cosmology. Starting with this edition, the Review is divided into two volumes. Volume 1 includes the Summary Tables and all review articles. Volume 2 consists of the Particle Listings. Review articles that were previously part of the Listings are now included in volume 1. The complete Review (both volumes) is published online on the website of the Particle Data Group (http://pdg.lbl.gov) and in a journal. Volume 1 is available in print as the PDG Book. A Particle Physics Booklet with the Summary Tables and essential tables, figures, and equations from selected review articles is also available. The 2018 edition of the Review of Particle Physics should be cited as: M. Tanabashi (Particle Data Group), Phys. Rev. D 98, 030001 (2018)
Dark Energy from Mass Varying Neutrinos
We show that mass varying neutrinos (MaVaNs) can behave as a negative
pressure fluid which could be the origin of the cosmic acceleration. We derive
a model independent relation between the neutrino mass and the equation of
state parameter of the neutrino dark energy, which is applicable for general
theories of mass varying particles. The neutrino mass depends on the local
neutrino density and the observed neutrino mass can exceed the cosmological
bound on a constant neutrino mass. We discuss microscopic realizations of the
MaVaN acceleration scenario, which involve a sterile neutrino. We consider
naturalness constraints for mass varying particles, and find that both ev
cutoffs and ev mass particles are needed to avoid fine-tuning. These
considerations give a (current) mass of order an eV for the sterile neutrino in
microscopic realizations, which could be detectable at MiniBooNE. Because the
sterile neutrino was much heavier at earlier times, constraints from big bang
nucleosynthesis on additional states are not problematic. We consider regions
of high neutrino density and find that the most likely place today to find
neutrino masses which are significantly different from the neutrino masses in
our solar system is in a supernova. The possibility of different neutrino mass
in different regions of the galaxy and the local group could be significant for
Z-burst models of ultra-high energy cosmic rays. We also consider the cosmology
of and the constraints on the ``acceleron'', the scalar field which is
responsible for the varying neutrino mass, and briefly discuss neutrino density
dependent variations in other constants, such as the fine structure constant.Comment: 26 pages, 3 figures, refs added, typos corrected, comment added about
possible matter effect
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