326 research outputs found
Gas rich galaxies from the FIGGS survey
The FIGGS (Faint Irregular Galaxy GMRT Survey) is aimed at creating a
multi-wavelength observational data base for a volume limited sample of the
faintest gas rich galaxies. In this paper we discuss two very gas rich galaxies
that were observed as part of the FIGGS survey, viz. NGC 3741 and And IV. These
galaxies are unusual in that they have extremely extended gas disks and very
high ratios of dark to luminous matter. The very extended HI disks provide an
unique opportunity to trace the extended distribution of dark matter around
faint galaxies. We compare the baryon fraction of these galaxies with a sample
of galaxies with well measured rotation curves and discuss whether extremely
gas rich dwarf galaxies have abnormally small baryon fractions.Comment: 5 Pages, 4 Figures. To be published in the proceedings of "Galaxies
in the Local Volume", ed. B. Koribalski, H. Jerje
Decoherence and Programmable Quantum Computation
An examination of the concept of using classical degrees of freedom to drive
the evolution of quantum computers is given. Specifically, when externally
generated, coherent states of the electromagnetic field are used to drive
transitions within the qubit system, a decoherence results due to the back
reaction from the qubits onto the quantum field. We derive an expression for
the decoherence rate for two cases, that of the single-qubit Walsh-Hadamard
transform, and for an implementation of the controlled-NOT gate. We examine the
impact of this decoherence mechanism on Grover's search algorithm, and on the
proposals for use of error-correcting codes in quantum computation.Comment: submitted to Phys. Rev. A 35 double-spaced pages, 2 figures, in LaTe
The Diagnostic Potential of Transition Region Lines under-going Transient Ionization in Dynamic Events
We discuss the diagnostic potential of high cadence ultraviolet spectral data
when transient ionization is considered. For this we use high cadence UV
spectra taken during the impulsive phase of a solar flares (observed with
instruments on-board the Solar Maximum Mission) which showed excellent
correspondence with hard X-ray pulses. The ionization fraction of the
transition region ion O V and in particular the contribution function for the O
V 1371A line are computed within the Atomic Data and Analysis Structure, which
is a collection of fundamental and derived atomic data and codes which
manipulate them. Due to transient ionization, the O V 1371A line is enhanced in
the first fraction of a second with the peak in the line contribution function
occurring initially at a higher electron temperature than in ionization
equilibrium. The rise time and enhancement factor depend mostly on the electron
density. The fractional increase in the O V 1371A emissivity due to transient
ionization can reach a factor of 2--4 and can explain the fast response in the
line flux of transition regions ions during the impulsive phase of flares
solely as a result of transient ionization. This technique can be used to
diagnostic the electron temperature and density of solar flares observed with
the forth-coming Interface Region Imaging Spectrograph.Comment: 18 pages, 6 figure
On the crystal lattice parameters of graphite-like phases of the B-C system
The structure of graphite-like BCx phases (x = 1, 1.5, 3, 4, 32) has been
studied using conventional X-ray diffraction. The results have been obtained,
which unambiguously point to turbostratic (one- dimensionally disordered)
structure of all phases under study. The crystal lattice parameters, sizes of
coherent scattering domains, and microstrain values have been defined, which
have allowed us to find a correlation between the structure and stoichiometry
of the phases synthesized at the same temperature
Superhard Phases of Simple Substances and Binary Compounds of the B-C-N-O System: from Diamond to the Latest Results (a Review)
The basic known and hypothetic one- and two-element phases of the B-C-N-O
system (both superhard phases having diamond and boron structures and
precursors to synthesize them) are described. The attention has been given to
the structure, basic mechanical properties, and methods to identify and
characterize the materials. For some phases that have been recently described
in the literature the synthesis conditions at high pressures and temperatures
are indicated.Comment: Review on superhard B-C-N-O phase
Toward an internally consistent astronomical distance scale
Accurate astronomical distance determination is crucial for all fields in
astrophysics, from Galactic to cosmological scales. Despite, or perhaps because
of, significant efforts to determine accurate distances, using a wide range of
methods, tracers, and techniques, an internally consistent astronomical
distance framework has not yet been established. We review current efforts to
homogenize the Local Group's distance framework, with particular emphasis on
the potential of RR Lyrae stars as distance indicators, and attempt to extend
this in an internally consistent manner to cosmological distances. Calibration
based on Type Ia supernovae and distance determinations based on gravitational
lensing represent particularly promising approaches. We provide a positive
outlook to improvements to the status quo expected from future surveys,
missions, and facilities. Astronomical distance determination has clearly
reached maturity and near-consistency.Comment: Review article, 59 pages (4 figures); Space Science Reviews, in press
(chapter 8 of a special collection resulting from the May 2016 ISSI-BJ
workshop on Astronomical Distance Determination in the Space Age
Influence of Dietary Oil Content and Conjugated Linoleic Acid (CLA) on Lipid Metabolism Enzyme Activities and Gene Expression in Tissues of Atlantic Salmon (Salmo salar L.)
The overall objective is to test the hypothesis that conjugated linoleic acid (CLA) has beneficial effects in Atlantic salmon through affecting lipid and fatty acid metabolism. The specific aims of the present study were to determine the effects of CLA on some key pathways of fatty acid metabolism including fatty acid oxidation and highly unsaturated fatty acid (HUFA) synthesis. Salmon smolts were fed diets containing two levels of fish oil (low, ~18% and high, ~34%) containing three levels of CLA (a 1:1 mixture of 9-cis,trans-11 and trans-10,cis-12 at 0, 1 and 2% of diet) for 3 months. The effects of dietary CLA on HUFA synthesis and β-oxidation were measured and the expression of key genes in the fatty acid oxidation and HUFA synthesis pathways, and potentially important transcription factors, peroxisome proliferators activated receptors (PPARs), determined in selected tissues. Liver HUFA synthesis and desaturase gene expression was increased by dietary CLA and decreased by high dietary oil content. Carnitine palmitoyltransferase-I (CPT-I) activity and gene expression were generally increased by CLA in muscle tissues although dietary oil content had relatively little effect. In general CPT-I activity or gene expression was not correlated with β-oxidation. Dietary CLA tended to increase PPARα and β gene expression in both liver and muscle tissues, and PPARγ in liver. In summary, gene expression and activity of the fatty acid pathways were altered in response to dietary CLA and/or oil content, with data suggesting that PPARs are also regulated in response to CLA. Correlations were observed between dietary CLA, liver HUFA synthesis and desaturase gene expression, and liver PPARα expression, and also between dietary CLA, CPT-I expression and activity, and PPARα expression in muscle tissues. In conclusion, this study suggests that dietary CLA has effects on fatty acid metabolism in Atlantic salmon and on PPAR transcription factors. However, further work is required to assess the potential of CLA as a dietary supplement, and the role of PPARs in the regulation of lipid metabolism in fish
Consensus guidelines for the definition, detection and interpretation of immunogenic cell death.
Cells succumbing to stress via regulated cell death (RCD) can initiate an adaptive immune response associated with immunological memory, provided they display sufficient antigenicity and adjuvanticity. Moreover, multiple intracellular and microenvironmental features determine the propensity of RCD to drive adaptive immunity. Here, we provide an updated operational definition of immunogenic cell death (ICD), discuss the key factors that dictate the ability of dying cells to drive an adaptive immune response, summarize experimental assays that are currently available for the assessment of ICD in vitro and in vivo, and formulate guidelines for their interpretation
- …