74 research outputs found
A Simultaneous Solution to the ^6Li and ^7Li Big Bang Nucleosynthesis Problems from a Long-Lived Negatively-Charged Leptonic Particle
The Li abundance observed in metal poor halo stars exhibits a plateau
similar to that for Li suggesting a primordial origin. However, the
observed abundance of Li is a factor of larger and that of Li is
a factor of 3 lower than the abundances predicted in the standard big bang when
the baryon-to-photon ratio is fixed by WMAP. Here we show that both of these
abundance anomalies can be explained by the existence of a long-lived massive,
negatively-charged leptonic particle during nucleosynthesis. Such particles
would capture onto the synthesized nuclei thereby reducing the reaction Coulomb
barriers and opening new transfer reaction possibilities, and catalyzing a
second round of big bang nucleosynthesis. This novel solution to both of the Li
problems can be achieved with or without the additional effects of stellar
destruction.Comment: 6 pages, 2 figures, to be published in Physical Review
New Constraints on Radiative Decay of Long-Lived Particles in Big Bang Nucleosynthesis with New He Photodisintegration Data
A recent measurement of He photodisintegration reactions,
He(,)H and He(,)He with laser-Compton
photons shows smaller cross sections than those estimated by other previous
experiments at MeV. We study big-bang nucleosynthesis
with the radiative particle decay using the new photodisintegration cross
sections of He as well as previous data. The sensitivity of the yields of
all light elements D, T, He, He, Li, Li and Be to the cross
sections is investigated. The change of the cross sections has an influence on
the non-thermal yields of D, He and He. On the other hand, the
non-thermal Li production is not sensitive to the change of the cross
sections at this low energy, since the non-thermal secondary synthesis of
Li needs energetic photons of MeV. The non-thermal
nucleosynthesis triggered by the radiative particle decay is one of candidates
of the production mechanism of Li observed in metal-poor halo stars
(MPHSs). In the parameter region of the radiative particle lifetime and the
emitted photon energy which satisfies the Li production above the abundance
level observed in MPHSs, the change of the photodisintegration cross sections
at MeV as measured in the recent experiment leads to
% reduction of resulting He abundance, whereas the Li
abundance does not change for this change of the cross sections of
He(,)H and He(,)He. The Li abundance,
however, could show a sizable change and therefore the future precise
measurement of the cross sections at high energy 50 MeV is
highly required.Comment: 10 pages, 7 figures, conclusion not changed, to be published in PR
Big Bang Nucleosynthesis with long-lived strongly interacting relic particles
We study effects of relic long-lived strongly interacting massive particles
(X particles) on big bang nucleosynthesis (BBN). The X particle is assumed to
have existed during the BBN epoch, but decayed long before detected. The
interaction strength between an X and a nucleon is assumed to be similar to
that between nucleons. Rates of nuclear reactions and beta decay of X-nuclei
are calculated, and the BBN in the presence of neutral charged X^0 particles is
calculated taking account of captures of X^0 by nuclei. As a result, the X^0
particles form bound states with normal nuclei during a relatively early epoch
of BBN leading to the production of heavy elements. Constraints on the
abundance of X^0 are derived from observations of primordial light element
abundances. Particle models which predict long-lived colored particles with
lifetimes longer than about 200 s are rejected. This scenario prefers the
production of 9Be and 10B. There might, therefore, remain a signature of the X
particle on primordial abundances of those elements. Possible signatures left
on light element abundances expected in four different models are summarized.Comment: 6 pages, 2 figures, to appear in the Proceedings of IAU Symposium
268: Light elements in the Universe (C. Charbonnel, M. Tosi, F. Primas, C.
Chiappini, eds.; Cambridge Univ. Press
New results on catalyzed BBN with a long-lived negatively-charged massive particle
It has been proposed that the apparent discrepancies between the inferred
primordial abundances of 6Li and 7Li and the predictions of big bang
nucleosynthesis (BBN) can be resolved by the existence of a negatively-charged
massive unstable supersymmetric particle (X-) during the BBN epoch. Here, we
present new BBN calculations with an X- particle utilizing an improved nuclear
reaction network including captures of nuclei by the particle, nuclear
reactions and beta-decays of normal nuclei and nuclei bound to the X- particles
(X-nuclei), and new reaction rates derived from recent rigorous quantum
many-body dynamical calculations. We find that this is still a viable model to
explain the observed 6Li and 7Li abundances. However, contrary to previous
results, neutral X-nuclei cannot significantly affect the BBN light-element
abundances. We also show that with the new rates the production of heavier
nuclei is suppressed and there is no signature on abundances of nuclei heavier
than Be in the X--particle catalyzed BBN model as has been previously proposed.
We also consider the version of this model whereby the X- particle decays into
the present cold dark matter. We analyze the this paradigm in light of the
recent constraints on the dark-matter mass deduced from the possible detected
events in the CDMS-II experiment. We conclude that based upon the inferred
range for the dark-matter mass, only X- decay via the weak interaction can
achieve the desired 7Li destruction while also reproducing the observed 6Li
abundance.Comment: 6 pages, 2 figure
Effect of Long-lived Strongly Interacting Relic Particles on Big Bang Nucleosynthesis
It has been suggested that relic long-lived strongly interacting massive
particles (SIMPs, or particles) existed in the early universe. We study
effects of such long-lived unstable SIMPs on big bang nucleosynthesis (BBN)
assuming that such particles existed during the BBN epoch, but then decayed
long before they could be detected. The interaction strength between an
particle and a nucleon is assumed to be similar to that between nucleons. We
then calculate BBN in the presence of the unstable neutral charged
particles taking into account the capture of particles by nuclei to form
-nuclei. We also study the nuclear reactions and beta decays of -nuclei.
We find that SIMPs form bound states with normal nuclei during a relatively
early epoch of BBN. This leads to the production of heavy elements which remain
attached to them. Constraints on the abundance of particles during BBN
are derived from observationally inferred limits on the primordial light
element abundances. Particle models which predict long-lived colored particles
with lifetimes longer than 200 s are rejected based upon these
constraints.Comment: 19 pages, 4 figure
The X^- Solution to the ^6Li and ^7Li Big Bang Nucleosynthesis Problems
The Li abundance observed in metal poor halo stars appears to exhibit a
plateau as a function of metallicity similar to that for Li, suggesting a
big bang origin. However, the inferred primordial abundance of Li is
1000 times larger than that predicted by standard big bang
nucleosynthesis for the baryon-to-photon ratio inferred from the WMAP data.
Also, the inferred Li primordial abundance is 3 times smaller than the big
bang prediction. We here describe in detail a possible simultaneous solution to
both the problems of underproduction of Li and overproduction of Li in
big bang nucleosynthesis. This solution involves a hypothetical massive,
negatively-charged leptonic particle that would bind to the light nuclei
produced in big bang nucleosynthesis, but would decay long before it could be
detected. We consider only the -nuclear reactions and assume that the effect
of decay products is negligible, as would be the case if lifetime were large or
the mass difference between the charged particle and its daughter were small.
An interesting feature of this paradigm is that, because the particle remains
bound to the existing nuclei after the cessation of the usual big bang nuclear
reactions, a second longer epoch of nucleosynthesis can occur among -nuclei.
We confirm that reactions in which the hypothetical particle is transferred can
occur that greatly enhance the production of Li while depleting Li. We
also identify a new reaction that destroys large amounts of Be, and hence
reduces the ultimate Li abundance. Thus, big-bang nucleosynthesis in the
presence of these hypothetical particles, together with or without an event of
stellar processing, can simultaneously solve the two Li abundance problems.Comment: 18 pages, 7 figures, minor changes and references added, ApJ accepte
Multi-layered flyer accelerated by laser induced shock waves
Copyright 2000 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Physics of Plasmas, 7(2), 676-680, 2000 and may be found at http://dx.doi.org/10.1063/1.87385
Evaluation of the immunoregulatory capacities of feed microbial materials in porcine intestinal immune and epithelial cells.
The establishment of drug-free feeding systems has been required for secure and healthy lives- tock production. Although functional feed materials containing microorganisms as alternatives to enhance intestinal immunity are expected to be beneficial for reducing diarrhoea caused by pathogens in weaned piglets, the effects of such materials on porcine intestinal cells have not been investigated in detail. Therefore, this work evaluated the immunoregulatory functions of microbial feed materials in porcine intestinal immune and epithelial cells. Porcine immune cells isolated from Peyer?s patches and mesenteric lymph nodes were stimulated with six different feed materials containing microorganisms, and evaluated for lymphocyte mitogenicity and cytokine inductions. In addition, porcine intestinal epithelial cells were stimulated with the materials before treatment with heat-killed enterotoxigenic Escherichia coli (ETEC), and analyzed for the proinflammatory cytokine expressions. The material containing Bifidobacterium thermophilum significantly augmented lymphocytes? mitogenicity and also induced a high expression of IL-2, IL-6 and IFN-γ in immune cells, and inhibited ETEC-induced overexpression of IL-6 and IL-8 via regulation of Toll-like receptor signaling. These results suggest that this feed material stimulates intestinal epithelial and immune cells to exert immunoregulation, suggesting that this feed is expected to contribute to promoting the health of piglets without using antimicrobial feed materials.Fil: Kumagae, Naosuke. Tohoku University. Graduate School of Agricultural Science. Laboratory of Animal Products Chemistry. Food and Feed Immunology Group; Japón. Scientific Feed Laboratory Co. Ltd.; JapónFil: Villena, Julio Cesar. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Tucumán. Centro de Referencia para Lactobacilos (i); Argentina. Tohoku University. Graduate School of Agricultural Science. Laboratory of Animal Products Chemistry. Food and Feed Immunology Group; JapónFil: Tomosada, Yohsuke. Tohoku University. Graduate School of Agricultural Science. Laboratory of Animal Products Chemistry. Food and Feed Immunology Group; JapónFil: Kobayashi, Hisakazu . Tohoku University. Graduate School of Agricultural Science. Laboratory of Animal Products Chemistry. Food and Feed Immunology Group; JapónFil: Kanmani, Paulraj. Tohoku University. Graduate School of Agricultural Science. Laboratory of Animal Products Chemistry. Food and Feed Immunology Group; Japón. Japan Society for the Promotion of Science; JapónFil: Aso, Hisashi . Tohoku University. Graduate School of Agricultural Science. Cell Biology Laboratory; JapónFil: Sasaki, Takashi . Scientific Feed Laboratory Co. Ltd.; JapónFil: Yoshida, Motohiko . Scientific Feed Laboratory Co. Ltd.; JapónFil: Tanabe, Hiroshi. Scientific Feed Laboratory Co. Ltd.; JapónFil: Shibata, Isao. Scientific Feed Laboratory Co. Ltd.; JapónFil: Saito, Tadao . Tohoku University. Graduate School of Agricultural Science. Laboratory of Animal Products Chemistry. Food and Feed Immunology Group; JapónFil: Kitazawa, Haruki. Tohoku University. Graduate School of Agricultural Science. Laboratory of Animal Products Chemistry. Food and Feed Immunology Group; Japó
Oncolytic virus-mediated p53 overexpression promotes immunogenic cell death and efficacy of PD-1 blockade in pancreatic cancer
Immune checkpoint inhibitors, including anti-programmed cell death 1 (PD-1) antibody, provide improved clinical outcome in certain cancers. However, pancreatic ductal adeno-carcinoma (PDAC) is refractory to PD-1 blockade therapy due to poor immune response. Oncolytic virotherapy is a novel approach for inducing immunogenic cell death (ICD). We demonstrated the therapeutic potential of p53-expressing telo-merase-specific oncolytic adenovirus OBP-702 to induce ICD and anti-tumor immune responses in human PDAC cells with different p53 status (Capan-2, PK-59, PK-45H, Capan-1, MIA PaCa-2, BxPC-3) and murine PDAC cells (PAN02). OBP-702 significantly enhanced ICD with secretion of extracel-lular adenosine triphosphate and high-mobility group box pro-tein B1 by inducing p53-mediated apoptosis and autophagy. OBP-702 significantly promoted the tumor infiltration of CD8+ T cells and the anti-tumor efficacy of PD-1 blockade in a subcutaneous PAN02 syngeneic tumor model. Our results suggest that oncolytic adenovirus-mediated p53 overexpres-sion augments ICD and the efficacy of PD-1 blockade therapy against cold PDAC tumors. Further in vivo experiments would be warranted to evaluate the survival benefit of tumor-bearing mice in combination therapy with OBP-702 and PD-1 blockade
A case of primary renal angiosarcoma
A 78-year old man was diagnosed with a left bleeding renal cyst from CT scan results. Serial CT scans revealed the left kidney mass to be increasing in size and a new lesion in the liver. Renal cell carcinoma with liver metastasis was diagnosed and a radical nephrectomy performed. The initial pathological diagnosis was a benign chronic hematoma. However, the liver mass increased in size and multiplied, while another mass emerged in the twelfth thoracic vertebra with spinal paralysis and was immediately removed. Pathological findings for that specimen showed malignancy of stromal cell origin but low atypia. The renal specimen was re-evaluated using whole cross-section analysis and immunohistochemistry, and diagnosed as a primary renal angiosarcoma. Recombinant interleukin-2 therapy was started immediately; however, the patient died of metastatic disease 13 months after the initial operation. Although contrast imaging depicted the primary lesion as a non-specific hematoma with little focal pooling, and low-grade cytological atypia was shown pathologically, the angiosarcoma was extremely aggressive
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