129 research outputs found
Nuclear liquid-gas phase transition studied with antisymmetrized molecular dynamics
The nuclear liquid-gas phase transition of the system in ideal thermal
equilibrium is studied with antisymmetrized molecular dynamics. The time
evolution of a many-nucleon system confined in a container is solved for a long
time to get a microcanonical ensemble of a given energy and volume. The
temperature and the pressure are extracted from this ensemble and the caloric
curves are constructed. The present work is the first time that a microscopic
dynamical model which describes nuclear multifragmentation reactions well is
directly applied to get the nuclear caloric curve. The obtained constant
pressure caloric curves clearly show the characteristic feature of the
liquid-gas phase transition, namely negative heat capacity (backbending), which
is expected for the phase transition in finite systems.Comment: 31 pages, 8 figures, added formalism details, several improvements
and new results, submitted to Phys. Rev.
Relevance of equilibrium in multifragmentation
The relevance of equilibrium in a multifragmentation reaction of very central
collisions at 35 MeV/nucleon is investigated by using
simulations of Antisymmetrized Molecular Dynamics (AMD). Two types of ensembles
are compared. One is the reaction ensemble of the states at each reaction time
in collision events simulated by AMD, and the other is the equilibrium
ensemble prepared by solving the AMD equation of motion for a many-nucleon
system confined in a container for a long time. The comparison of the ensembles
is performed for the fragment charge distribution and the excitation energies.
Our calculations show that there exists an equilibrium ensemble which well
reproduces the reaction ensemble at each reaction time for the investigated
period fm/. However, there are some other observables
which show discrepancies between the reaction and equilibrium ensembles. These
may be interpreted as dynamical effects in the reaction. The usual static
equilibrium at each instant is not realized since any equilibrium ensemble with
the same volume as that of the reaction system cannot reproduce the fragment
observables.Comment: 13 pages and 12figures; added a few sentences and corrected typos,
accepted in Phys. Rev.
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Approaches to the synthesis of penicillin
Several approaches to the synthesis of penicillin from 2-iminothioazolidine
50, from 2-thiothiazolidine 66 and by photocyclization of
77 and 78 were investigated. 2-Iminothiazolidine 50 was prepared
from dibromoester 45 by the action of benzylamine followed by treatment
of aziridine 46 with potassium or ammonium thiocyanate. Attempted
introduction of a two-carbon unit into 50 by decomposition of
ethyl diazoacetate afforded 51 and 52. Similarly, acetyl derivative
53 gave a carbon-hydrogen insertion product 54 upon pyrolysis. The
reaction of 53 with ethyl lithiodiazoacetate produced an unexpected
product 55.
The synthesis of 2-thiothiazolidines by their reaction of aziridine
56 with carbon disulfide or potassium thiocyanate yielded only
the undesired thiazolidines 57 and 60 respectively. However, the
reaction of 66 with diethyl bromomalonate gave a 2-substituted thiazolidine
7G Reduction of 70 with sodium borohydride produced 71.
Compounds 77 and 78 were synthesized by the coupling of 76
and 66 with phthalimidoacetyl chloride respectively. Attempted
p-lactam formation by photolysis of 77 or 78 yielded only Norrish
type II cleavage and no cyclization product.
Biogenetically patterned approaches to the synthesis of 6-aminopenicillanic
acid were also studied. Cysteine was protected at sulfur
and nitrogen by the acetamidomethyl and tert-Boc groups respectively
to give 86, which was condensed with aziridine 56 in the presence of
DCC yielding 88. Photolysis of 88 followed by deprotection of sulfur
gave the dimer 92. In another approach, a putative precursor of the
thioaldehyde 89 was synthesized by a sequence in which cystine 93
was converted to N, N' -di-tert-Boc cystine 96 by treatment of tertbutoxycarbonylazide,
the disulfide was cleaved by sodium metal in
liquid ammonia, and the resulting thiol was immediately condensed
with a-chloroacetophenone to give 97. Condensation of 97 with aziridine
56 in the presence of DCC produced 98 which upon photolysis
afforded polymer
Boundary conditions for star matter and other periodic fermionic systems
Bulk fermionic matter, as it can be notably found in supernova matter and
neutrons stars, is subject to correlations of infinite range due to the
antisymmetrisation of the N-body wave function, which cannot be explicitly
accounted for in a practical simulation. This problem is usually addressed in
condensed matter physics by means of the so-called Twist Averaged Boundary
Condition method. A different ansatz based on the localized Wannier
representation has been proposed in the context of antisymmetrized molecular
dynamics. In this paper we work out the formal relation between the two
approaches. We show that, while the two coincide when working with exact
eigenstates of the N-body Hamiltonian, differences appear in the case of
variational approaches, which are currently used for the description of stellar
matter. Some model applications with Fermionic Molecular Dynamics are shown
Biological basis and clinical study of glycogen synthase kinase-3b-targeted therapy by drug repositioning for glioblastoma
13301甲第4589号博士(医学)金沢大学博士論文要旨Abstract 以下に掲載:Oncotarget 8(14) pp.22811-22824 2017. Impactjournals. 共著者:古田 拓也, 淑瑠 ヘムラサビット, 董 宇, 宮下 勝吉, 木下 雅史, 内山 尚之, 林 康彦, 林 裕, 源 利成, 中田 光
Real-time analysis of the role of Ca2+ in flagellar movement and motility in single sea urchin sperm
Eggs of many marine and mammalian species attract sperm by releasing chemoattractants that modify the bending properties of flagella to redirect sperm paths toward the egg. This process, called chemotaxis, is dependent on extracellular Ca2+. We used stroboscopic fluorescence imaging to measure intracellular Ca2+ concentration ([Ca2+]i) in the flagella of swimming sea urchin sperm. Uncaging of cyclic GMP induced Ca2+ entry via at least two distinct pathways, and we identified a nimodipine-sensitive pathway, compartmentalized in the flagella, as a key regulator of flagellar bending and directed motility changes. We found that, contrary to current models, the degree of flagellar bending does not vary in proportion to the overall [Ca2+]i. Instead we propose a new model whereby flagella bending is increased by Ca2+ flux through the nimodipine-sensitive pathway, and is unaffected by [Ca2+]i increases through alternative pathways
Drug Repositioning for the Treatment of Glioma: Current State and Future Perspective
Gliomas are the most common primary brain tumors. Among them, glioblastoma (GBM) possesses the most malignant phenotype. Despite the current standard therapy using an alkylating anticancer agent, temozolomide, most patients with GBM die within 2 years. Novel chemotherapeutic agents are urgently needed to improve the prognosis of GBM. One of the solutions, drug repositioning, which broadens the indications of existing drugs, has gained attention. Herein, we categorize candidate agents, which are newly identified as therapeutic drugs for malignant glioma into 10 classifications based on these original identifications. Some drugs are in clinical trials with hope. Additionally, the obstacles, which should be overcome in order to accomplish drug repositioning as an application for GBM and the future perspectives, have been discussed
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