50,698 research outputs found
Sterile Neutrino Hot, Warm, and Cold Dark Matter
We calculate the incoherent resonant and non-resonant scattering production
of sterile neutrinos in the early universe. We find ranges of sterile neutrino
masses, vacuum mixing angles, and initial lepton numbers which allow these
species to constitute viable hot, warm, and cold dark matter (HDM, WDM, CDM)
candidates which meet observational constraints. The constraints considered
here include energy loss in core collapse supernovae, energy density limits at
big bang nucleosynthesis, and those stemming from sterile neutrino decay:
limits from observed cosmic microwave background anisotropies, diffuse
extragalactic background radiation, and Li-6/D overproduction. Our calculations
explicitly include matter effects, both effective mixing angle suppression and
enhancement (MSW resonance), as well as quantum damping. We for the first time
properly include all finite temperature effects, dilution resulting from the
annihilation or disappearance of relativistic degrees of freedom, and the
scattering-rate-enhancing effects of particle-antiparticle pairs (muons,
tauons, quarks) at high temperature in the early universe.Comment: 24 pages, including 8 figures. v3: to match version in PRD, added
references and numerous minor changes. High resolution color figures
available at http://superbeast.ucsd.edu/~kev/nucd
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Atmospheric modelling for NOMAD-UVIS on board the ExoMars Trace Gas Orbiter mission
The Ultraviolet and Visible Spectrometer (UVIS) instrument development process requires the construction of an atmospheric model to provide synthetic UV transmission spectra. We discuss the requirements of the model to enable observational limits to be found, and the potential for certain atmospheric parameters to be further constrained
Investigating microstructural variation in the human hippocampus using non-negative matrix factorization
In this work we use non-negative matrix factorization to identify patterns of microstructural variance in the human hippocampus. We utilize high-resolution structural and diffusion magnetic resonance imaging data from the Human Connectome Project to query hippocampus microstructure on a multivariate, voxelwise basis. Application of non-negative matrix factorization identifies spatial components (clusters of voxels sharing similar covariance patterns), as well as subject weightings (individual variance across hippocampus microstructure). By assessing the stability of spatial components as well as the accuracy of factorization, we identified 4 distinct microstructural components. Furthermore, we quantified the benefit of using multiple microstructural metrics by demonstrating that using three microstructural metrics (T1-weighted/T2-weighted signal, mean diffusivity and fractional anisotropy) produced more stable spatial components than when assessing metrics individually. Finally, we related individual subject weightings to demographic and behavioural measures using a partial least squares analysis. Through this approach we identified interpretable relationships between hippocampus microstructure and demographic and behavioural measures. Taken together, our work suggests non-negative matrix factorization as a spatially specific analytical approach for neuroimaging studies and advocates for the use of multiple metrics for data-driven component analyses
Experimental Investigation of Gully Formation Under Low Pressure and Low Temperature Conditions
International audienceIntroduction: A large morphological diversity of gullies is observed on Earth and on Mars. Debris flow – a non-newtonian flow comprising a sediment-water mix – is a common process attributed to gully formation on both planets [1, 2]. Many variables can influence the morphology of debris flows (grainsizes, discharge , slope, soil moisture, etc) and their respective influences are difficult to disentangle in the field. Furthermore effects specific to the martian environment have not yet been explored in detail. Some preliminary laboratory simulations have already been performed that isolate some of these variables. Cold room experiments [3] were already perfomed to test the effect of a melted surface layer on the formation of linear gullies over sand dunes. Low pressure experiments [4] were performed to test the effect of the atmospheric pressure on erosional capacity and runout distance of the flows. Our aim is to develop a new set of experiments both under Martian atmospheric pressure and terrestrial atmospheric pressure in order to reproduce the variability of the observed morphologies under well constrained experimental conditions
A NANOSCALE DENDRITIC MACROMOLECULES BASED ON ETHANE 1,2-DIAMINE AS POTENTIAL DRUG CARRIERS FOR NSAIDS: SYNTHESIS, CHARACTERIZATION AND APPLICATIONS
Objective: The present work deals with the objective of development and characterization of novel dendritic macromolecules as solubility enhancer and carrier for sustained release of Ketoprofen. Cytotoxicity and hemolytic assay of dendritic macromolecules were also estimated as an objective to evaluate its toxicity and biocompatibility.
Methods: Dendritic macromolecules were synthesized using divergent method. Synthesized macromolecules were characterized by spectral techniques such as FTIR, 1H-NMR, 13C-NMR electro-spray ionization mass spectrometry and elemental analysis. Enhanced aqueous solubility of ketoprofen was evaluated with respect to pH, generation number and concentration of dendrimer using Higuchi and Connors method. Sustained release of ketoprofen from ketoprofen loaded dendrimers was measured and compared with that of free ketoprofen. Hemolytic assay and cytotoxicity of G3 dendrimer on A-549 cell lines were studied to evaluate toxicity and biocompatibility of dendrimer. All dendritic macromolecules were fully characterized by spectral techniques.
Results: Solubility study revealed that aqueous solubility of ketoprofen by dendrimer increased with increase in pH, concentration and generation of dendrimer. Ketoprofen was released slowly from ketoprofen loaded dendrimer compared to that of free ketoprofen. Dendritic macromolecules were less cytotoxic and showed less hemolytic potential.
Conclusion: It can be concluded that dendrimer have high potential as carriers and solubility enhancers of hydrophobic drug.
Keywords: Triazine based dendrimer, Ketoprofen, Drug Carrier, Cytotoxicity, Hemolysis
Singularity Free Inhomogeneous Models with Heat Flow
We present a class of singularity free exact cosmological solutions of
Einstein's equations describing a perfect fluid with heat flow. It is obtained
as generalization of the Senovilla class [1] corresponding to incoherent
radiation field. The spacetime is cylindrically symmetric and globally regular.Comment: 6 pages, TeX, to appear in Class.Quant.Gra
Numerical Solution of 3rd order ODE Using FDM: On a Moving Surface in MHD Flow of Sisko Fluid
A Similarity group theoretical technique is used to transform the governing nonlinear partial differential equations of two dimensional MHD boundary layer flow of Sisko fluid into nonlinear ordinary differential equations. Then the resulting third order nonlinear ordinary differential equation with corresponding boundary conditions is linearised by Quasi linearization method. Numerical solution of the linearised third order ODE is obtained using Finite Difference method (FDM). Graphical presentation of the solution is given
Laminar Boundary Layer Flow of Sisko Fluid
The problem of steady two dimensional laminar boundary layer flow of non-Newtonian fluid is analyzed in the present paper. Sisko fluid model, one of the various fluid models of non- Newtonian fluid, is considered for stress-strain relationship. Similarity and numerical solutions obtained for the defined flow problem
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