1,375 research outputs found
Neutrino Oscillations in Intermediate States.II -- Wave Packets
We analyze oscillations of intermediate neutrinos in terms of the scattering
of particles described by Gaussian wave packets. We study a scalar model as in
a previous paper (I) but in realistic situations, where the two particles of
the initial state and final state are wave packets and neutrinos are in the
intermediate state. The oscillation of the intermediate neutrino is found from
the time evolution of the total transition probability between the initial
state and final state. The effect of a finite lifetime and a finite relaxation
time are also studied. We find that the oscillation pattern depends on the
magnitude of wave packet sizes of particles in the initial state and final
state and the lifetime of the initial particle. For eV, the oscillation probability deviates from that of the standard
formula if the wave packet sizes are around m for 0.4 MeV neutrino.Comment: 29 pages, 11 figures. typos corrected, appendix adde
Dual-comb spectroscopy using free-running mechanical sharing dual-comb fiber lasers
We demonstrate balanced-detection dual-comb spectroscopy (DCS) using two
free-running mechanical sharing dual-comb fiber lasers assisted by an
all-computational digital phase correction algorithm. The mutual coherence
between the combs allows us perform mode-resolved spectroscopy of gaseous
hydrogen cyanide by digitally compensating residual timing and offset frequency
fluctuations of the dual-comb signal. Setting the repetition rate difference
between the combs to 500 Hz (1.5 kHz) yields more than 2000 resolved radio
frequency comb lines after phase correction in a 3-dB bandwidth centered at
1560 nm of wavelength. Through coadding the corrected interferograms (IGMs), we
obtain a single time-domain trace with a SNR of 6378 (13960) and 12.64 (13.77)
bits of dynamic range in 1 second of averaging. The spectral SNR of the coadded
trace reaches 529 (585), corresponding to a figure of merit of SNR of
1.310 (1.410). The measured absorption spectrum of
hydrogen cyanide agrees well with the HITRAN database.Comment: 12 pages, 5 figure
CD34 positive cells as endothelial progenitor cells in biology and medicine
CD34 is a cell surface antigen expressed in numerous stem/progenitor cells including hematopoietic stem cells (HSCs) and endothelial progenitor cells (EPCs), which are known to be rich sources of EPCs. Therefore, regenerative therapy using CD34+ cells has attracted interest for application in patients with various vascular, ischemic, and inflammatory diseases. CD34+ cells have recently been reported to improve therapeutic angiogenesis in a variety of diseases. Mechanistically, CD34+ cells are involved in both direct incorporation into the expanding vasculature and paracrine activity through angiogenesis, anti-inflammatory, immunomodulatory, and anti-apoptosis/fibrosis roles, which support the developing microvasculature. Preclinical, pilot, and clinical trials have well documented a track record of safety, practicality, and validity of CD34+ cell therapy in various diseases. However, the clinical application of CD34+ cell therapy has triggered scientific debates and controversies in last decade. This review covers all preexisting scientific literature and prepares an overview of the comprehensive biology of CD34+ cells as well as the preclinical/clinical details of CD34+ cell therapy for regenerative medicine
Design Study of CANGAROO-III, Stereoscopic Imaging Atmospheric Cherenkov Telescopes for sub-TeV Gamma-ray
CANGAROO-III is an Imaging Atmospheric Cherenkov Telescope (IACT) array of
four 10 m telescopes for very high energy (sub-TeV) gamma-ray astronomy. A
design study of the CANGAROO-III telescope system was carried out using the
Monte Carlo technique in order to optimize the pixel size and the telescope
spacing. Studies were also made of observations at low elevation angles.Comment: 17pages, 13 figures, elsart, to appear in Astro. Part. Phy
Search for TeV gamma-rays from SN 1987A in 2001
We searched for TeV gamma-rays from the remnant of SN 1987A around 5400 days
after the supernova. The observations were carried out in 2001, from November
16 to December 11, using the CANGAROO-II Imaging Atmospheric Cherenkov
Telescope. In total, 708 minutes of ON- and 1019 minutes of OFF-source data
were obtained under good conditions. The detection threshold was estimated to
be 1 TeV, due to the mean zenith angle of 39. The upper limits for the
gamma-ray flux were obtained and compared with the previous observations and
theoretical models. The observations indicate that the gamma-ray luminosity is
lower than erg s at TeV.Comment: 8 pages, 3 figures, submitted for publication, style file adde
Cilostazol Activates Function of Bone Marrow-Derived Endothelial Progenitor Cell for Re-endothelialization in a Carotid Balloon Injury Model
BACKGROUND: Cilostazol(CLZ) has been used as a vasodilating anti-platelet drug clinically and demonstrated to inhibit proliferation of smooth muscle cells and effect on endothelial cells. However, the effect of CLZ on re-endothelialization including bone marrow (BM)-derived endothelial progenitor cell (EPC) contribution is unclear. We have investigated the hypothesis that CLZ might accelerate re-endothelialization with EPCs. METHODOLOGY/PRINCIPAL FINDINGS: Balloon carotid denudation was performed in male Sprague-Dawley rats. CLZ group was given CLZ mixed feed from 2 weeks before carotid injury. Control group was fed normal diet. CLZ accelerated re-endothelialization at 2 weeks after surgery and resulted in a significant reduction of neointima formation 4 weeks after surgery compared with that in control group. CLZ also increased the number of circulating EPCs throughout the time course. We examined the contribution of BM-derived EPCs to re-endothelialization by BM transplantation from Tie2/lacZ mice to nude rats. The number of Tie2-regulated X-gal positive cells on injured arterial luminal surface was increased at 2 weeks after surgery in CLZ group compared with that in control group. In vitro, CLZ enhanced proliferation, adhesion and migration activity, and differentiation with mRNA upregulation of adhesion molecule integrin αvβ3, chemokine receptor CXCR4 and growth factor VEGF assessed by real-time RT-PCR in rat BM-derived cultured EPCs. In addition, CLZ markedly increased the expression of SDF-1α that is a ligand of CXCR4 receptor in EPCs, in the media following vascular injury. CONCLUSIONS/SIGNIFICANCE: CLZ promotes EPC mobilization from BM and EPC recruitment to sites of arterial injury, and thereby inhibited neointima formation with acceleration of re-endothelialization with EPCs as well as pre-existing endothelial cells in a rat carotid balloon injury model. CLZ could be not only an anti-platelet agent but also a promising tool for endothelial regeneration, which is a key event for preventing atherosclerosis or restenosis after vascular intervention
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