3,788 research outputs found
Onset of fluidization in vertically shaken granular material
When granular material is shaken vertically one observes convection, surface
fluidization, spontaneous heap formation and other effects. There is a
controversial discussion in literature whether there exists a threshold for the
Froude number below which these effects cannot be
observed anymore. By means of theoretical analysis and computer simulation we
find that there is no such single threshold. Instead we propose a modified
criterion which coincides with critical Froude number for small
driving frequency .Comment: 7 pages, 5 figure
CemOrange2 fusions facilitate multifluorophore subcellular imaging in C. elegans
Due to its ease of genetic manipulation and transparency, Caenorhabditis elegans (C. elegans) has become a preferred model system to study gene function by microscopy. The use of Aequorea victoria green fluorescent protein (GFP) fused to proteins or targeting sequences of interest, further expanded upon the utility of C. elegans by labeling subcellular structures, which enables following their disposition during development or in the presence of genetic mutations. Fluorescent proteins with excitation and emission spectra different from that of GFP accelerated the use of multifluorophore imaging in real time. We have expanded the repertoire of fluorescent proteins for use in C. elegans by developing a codon-optimized version of Orange2 (CemOrange2). Proteins or targeting motifs fused to CemOrange2 were distinguishable from the more common fluorophores used in the nematode; such as GFP, YFP, and mKate2. We generated a panel of CemOrange2 fusion constructs, and confirmed they were targeted to their correct subcellular addresses by colocalization with independent markers. To demonstrate the potential usefulness of this new panel of fluorescent protein markers, we showed that CemOrange2 fusion proteins could be used to: 1) monitor biological pathways, 2) multiplex with other fluorescent proteins to determine colocalization and 3) gain phenotypic knowledge of a human ABCA3 orthologue, ABT-4, trafficking variant in the C. elegans model organism
Status and overview of development of the Silicon Pixel Detector for the PHENIX experiment at the BNL RHIC
We have developed a silicon pixel detector to enhance the physics
capabilities of the PHENIX experiment. This detector, consisting of two layers
of sensors, will be installed around the beam pipe at the collision point and
covers a pseudo-rapidity of | \eta | < 1.2 and an azimuth angle of | \phi | ~
2{\pi}. The detector uses 200 um thick silicon sensors and readout chips
developed for the ALICE experiment. In order to meet the PHENIX DAQ readout
requirements, it is necessary to read out 4 readout chips in parallel. The
physics goals of PHENIX require that radiation thickness of the detector be
minimized. To meet these criteria, the detector has been designed and
developed. In this paper, we report the current status of the development,
especially the development of the low-mass readout bus and the front-end
readout electronics.Comment: 9 pages, 8 figures and 1 table in DOCX (Word 2007); PIXEL 2008
workshop proceedings, will be published in the Proceedings Section of
JINST(Journal of Instrumentation
Weyl symmetric structure of QCD vacuum
We consider Weyl symmetric structure of the classical vacuum in quantum
chromodynamics. In the framework of formalism of gauge invariant Abelian
projection we show that classical vacuums can be constructed in terms of
Killing vector fields on the group SU(3). Consequently, homotopic classes of
Killing vector fields determine the topological structure of the vacuum. In
particular, the second homotopy group \pi_2(SU(3)/U(1)\times U(1)) describes
all topologically non-equivalent vacuums which are classified by two
topological numbers. For each given Killing vector field one can construct six
vacuums forming Weyl sextet representation. An interesting feature of SU(3)
gauge theory is that it admits a Weyl symmetric vacuum represented by a linear
superposition of the six vacuums from the Weyl vacuum sextet. A non-trivial
manifestation of Weyl symmetry is demonstrated on monopole solutions. We
construct a family of finite energy monopole solutions in Yang-Mills-Higgs
theory which includes Weyl monopole sextet. From the analysis of the classical
vacuum structure and monopole solutions we conjecture that a similar Weyl
symmetric vacuum structure can be realized in quantum theory.Comment: 13 page
Fecal calprotectin and microbiota of the gut
Analysis of the literature and our research showed that an imbalance of the intestinal microbiota is associated with many diseases. We present some of the mechanisms of disease. Using non-invasive, simple, affordable method of determination of fecal calprotectin reveals the presence and progression of chronic non-specific inflammatory bowel disease, and can be widely used in clinical practic
Near-Infrared Molecular Hydrogen Emission from the Central Regions of Galaxies: Regulated Physical Conditions in the Interstellar Medium
The central regions of many interacting and early-type spiral galaxies are
actively forming stars. This process affects the physical and chemical
properties of the local interstellar medium as well as the evolution of the
galaxies. We observed near-infrared H2 emission lines: v=1-0 S(1), 3-2 S(3),
1-0 S(0), and 2-1 S(1) from the central ~1 kpc regions of the archetypical
starburst galaxies, M82 and NGC 253, and the less dramatic but still vigorously
star-forming galaxies, NGC 6946 and IC 342. Like the far-infrared continuum
luminosity, the near-infrared H2 emission luminosity can directly trace the
amount of star formation activity because the H2 emission lines arise from the
interaction between hot and young stars and nearby neutral clouds. The observed
H2 line ratios show that both thermal and non-thermal excitation are
responsible for the emission lines, but that the great majority of the
near-infrared H2 line emission in these galaxies arises from energy states
excited by ultraviolet fluorescence. The derived physical conditions, e.g.,
far-ultraviolet radiation field and gas density, from [C II] and [O I] lines
and far-infrared continuum observations when used as inputs to
photodissociation models, also explain the luminosity of the observed H2 v=1-0
S(1) line. The ratio of the H2 v=1-0 S(1) line to far-IR continuum luminosity
is remarkably constant over a broad range of galaxy luminosities; L_H2/L_FIR =
about 10^{-5}, in normal late-type galaxies (including the Galactic center), in
nearby starburst galaxies, and in luminous IR galaxies (LIRGs: L_FIR > 10^{11}
L_sun). Examining this constant ratio in the context of photodissociation
region models, we conclude that it implies that the strength of the incident UV
field on typical molecular clouds follows the gas density at the cloud surface.Comment: Accepted for ApJ, 24 pages, 17 figures, for complete PDF file, see
http://kao.re.kr/~soojong/mypaper/2004_pak_egh2.pd
Equation of state of asymmetric nuclear matter and collisions of neutron-rich nuclei
The ratio of pre-equilibrium neutrons to protons from collisions of
neutron-rich nuclei is studied as a function of their kinetic energies. This
ratio is found to be sensitive to the density dependence of the nuclear
symmetry energy, but is independent of the compressibility of symmetric nuclear
matter and the in-medium nucleon-nucleon cross sections. The experimental
measurement of this ratio thus provides a novel means for determining the
nuclear equation of state of asymmetric nuclear matter.Comment: 11 pages + 3 postscript figures, Phys. Rev. Lett. (1997) in pres
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