4,830 research outputs found
Implication of EAS data for the study of primary cosmic rays above 10 to the 5th power GeV
Due to the strong decrease of the energetic cosmic ray flux its direct detection at the top of atmosphere with aircraft is limited at the present time to about 100,000 GeV. The intensity of all primary particles can be approximated in the range 100 to 100,000 GeV by power function with power index 2.65. There are predominantly protons and the rest is represented by several groups of nuclei. In the range of 100,000 to 10 to the 8th power GeV considerable disagreement is most probably connected with the uncertainity of the indirect derivation of the parameters of extensive air showers. Results for the primary spectrum in the range to the 8th power GeV, obtained by implication of extensive air showers (EAS) data from mountain altitudes are discussed
Thermal decomposition of a honeycomb-network sheet - A Molecular Dynamics simulation study
The thermal degradation of a graphene-like two-dimensional triangular
membrane with bonds undergoing temperature-induced scission is studied by means
of Molecular Dynamics simulation using Langevin thermostat. We demonstrate that
the probability distribution of breaking bonds is highly peaked at the rim of
the membrane sheet at lower temperature whereas at higher temperature bonds
break at random anywhere in the hexagonal flake. The mean breakage time
is found to decrease with the total number of network nodes by a power law
and reveals an Arrhenian dependence on temperature .
Scission times are themselves exponentially distributed. The fragmentation
kinetics of the average number of clusters can be described by first-order
chemical reactions between network nodes of different coordination. The
distribution of fragments sizes evolves with time elapsed from a
-function through a bimodal one into a single-peaked again at late
times. Our simulation results are complemented by a set of -order
kinetic differential equations for which can be solved exactly and
compared to data derived from the computer experiment, providing deeper insight
into the thermolysis mechanism.Comment: 21pages, 9 figures, LaTeX, revised versio
Subsquares Approach - Simple Scheme for Solving Overdetermined Interval Linear Systems
In this work we present a new simple but efficient scheme - Subsquares
approach - for development of algorithms for enclosing the solution set of
overdetermined interval linear systems. We are going to show two algorithms
based on this scheme and discuss their features. We start with a simple
algorithm as a motivation, then we continue with a sequential algorithm. Both
algorithms can be easily parallelized. The features of both algorithms will be
discussed and numerically tested.Comment: submitted to PPAM 201
Optical properties, electron-phonon coupling, and Raman scattering of vanadium ladder compounds
The electronic structure of two V-based ladder compounds, the quarter-filled
NaVO in the symmetric phase and the iso-structural half-filled
CaVO is investigated by ab initio calculations. Based on the
bandstructure we determine the dielectric tensor of these
systems in a wide energy range. The frequencies and eigenvectors of the fully
symmetric A phonon modes and the corresponding electron-phonon and
spin-phonon coupling parameters are also calculated from first-principles. We
determine the Raman scattering intensities of the A phonon modes as a
function of polarization and frequency of the exciting light.
All results, i.e. shape and magnitude of the dielectric function, phonon
frequencies and Raman intensities show very good agreement with available
experimental data.Comment: 11 pages, 10 figure
Inversionless light amplification and optical switching controlled by state-dependent alignment of molecules
We propose a method to achieve amplification without population inversion by
anisotropic molecules whose orientation by an external electric field is
state-dependent. It is based on decoupling of the lower-state molecules from
the resonant light while the excited ones remain emitting. The suitable class
of molecules is discussed, the equation for the gain factor is derived, and the
magnitude of the inversionless amplification is estimated for the typical
experimental conditions. Such switching of the sample from absorbing to
amplifying via transparent state is shown to be possible both with the aid of
dc and ac control electric fields.Comment: AMS-LaTeX v1.2, 4 pages with 4 figure
Infrared study of spin-Peierls compound alpha'-NaV2O5
Infrared reflectance of alpha'-NaV2O5 single crystals in the frequency range
from 50 cm-1 to 10000 cm-1 was studied for a, b and c-polarisations. In
addition to phonon modes identification, for the a-polarised spectrum a broad
continuum absorption in the range of 1D magnetic excitation energies was found.
The strong near-IR absorption band at 0.8 eV shows a strong anisotropy with
vanishing intensity in c-polarisation. Activation of new phonons due to the
lattice dimerisation were detected below 35K as well as pretransitional
structural fluctuations up to 65K.Comment: 3 pages, 2 figures, 1 table. Contributed paper for the SCES'98 (15-18
July 1998, Paris). To be published in Physica
A Drosophila Receptor Tyrosine Phosphatase Expressed in the Embryonic CNS and Larval Optic Lobes Is a Member of the Set of Proteins Bearing the "HRP" Carbohydrate Epitope
Recent studies have defined several cell surface glycoproteins expressed in the developing nervous system of insect embryos that may be involved in axon outgrowth and guidance processes. These glycoproteins include the fasciclins and a group of receptor-linked protein tyrosine phosphatases (R-PTPs). In embryos, the fasciclins are localized to axonal subsets, while the R-PTPs appear to be expressed on most or all CNS axons. To identify other neuronal cell surface glycoproteins in the Drosophila embryo, we have taken a biochemical approach. This is based on the observation that antisera against horseradish peroxidase (HRP) recognize a carbohydrate epitope that is selectively expressed in the insect nervous system. A large number of neuronal glycoproteins (denoted âHRP proteinsâ) apparently bear the HRP carbohydrate epitope. We have used polyclonal anti-HRP antibodies to purify these proteins from Drosophila embryos, and have obtained protein sequences from seven HRP protein bands. These data define three major HRP proteins as neurotactin, fasciclin I, and an R-PTP, DPTP69D. Western blotting data suggest that fasciclin II, neuroglian, DPTP10D, and DPTP99A are also HRP proteins. We show that DPTP69D, like the previously characterized R-PTPs, is localized to CNS axons in the embryo. In third instar larvae, DPTP69D expression is restricted to subsets of neuronal processes in the brain, ventral nerve cord, and eye disk. In the optic lobes, DPTP69D is localized to the neuropils of the lamina and medulla, and to an array of parallel thick bundles that may be the transmedullary fibers of the developing lobula complex
Ovalbumin sensitization and challenge increases the number of lung cells possessing a mesenchymal stromal cell phenotype
Abstract Background Recent studies have indicated the presence of multipotent mesenchymal stromal cells (MSCs) in human lung diseases. Excess airway smooth muscle, myofibroblasts and activated fibroblasts have each been noted in asthma, suggesting that mesenchymal progenitor cells play a role in asthma pathogenesis. We therefore sought to determine whether MSCs are present in the lungs of ovalbumin (OVA)-sensitized and challenged mice, a model of allergic airways disease. Methods Balb/c mice were sensitized and challenged with PBS or OVA over a 25 day period. Flow cytometry as well as colony forming and differentiation potential were used to analyze the emergence of MSCs along with gene expression studies using immunochemical analyses, quantitative polymerase chain reaction (qPCR), and gene expression beadchips. Results A CD45-negative subset of cells expressed Stro-1, Sca-1, CD73 and CD105. Selection for these markers and negative selection against CD45 yielded a population of cells capable of adipogenic, osteogenic and chondrogenic differentiation. Lungs from OVA-treated mice demonstrated a greater average colony forming unit-fibroblast (CFU-F) than control mice. Sorted cells differed from unsorted lung adherent cells, exhibiting a pattern of gene expression nearly identical to bone marrow-derived sorted cells. Finally, cells isolated from the bronchoalveolar lavage of a human asthma patient showed identical patterns of cell surface markers and differentiation potential. Conclusions In summary, allergen sensitization and challenge is accompanied by an increase of MSCs resident in the lungs that may regulate inflammatory and fibrotic responses.http://deepblue.lib.umich.edu/bitstream/2027.42/78265/1/1465-9921-11-127.xmlhttp://deepblue.lib.umich.edu/bitstream/2027.42/78265/2/1465-9921-11-127.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/78265/3/1465-9921-11-127-S1.DOCPeer Reviewe
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