用~(12)C离子模拟质子引起的单粒子效应

在理论分析的基础上 ,提出了一种利用兰州重离子加速器提供的高能 12 C离子模拟质子引起单粒子效应的途径 .在保证核反应机制是引起单粒子效应主要机制的前提下 ,用高能 12 C离子可以模拟质子在功率金属 -氧化物 -半导体场效应晶体管中引起的单粒子烧毁以及单粒子栅极击穿 ,获得质子单粒子效应的饱和截面 ,定性研究质子单粒子效应的角度效应 ,还可以作为高能质子单粒子效应实验前的预备实验 .该方法拓展了兰州重离子加速器加速的轻的重离子在单粒子效应实验研究方面的应用 ,对现阶段国内开展质子单粒子效应实验研究具有重要意义

Effect of 80.55 MeV/u(12)C(6+) ions on radiosensitivity and cell cycle of human hepatoma cell lines

In this paper, the relationship between radiosensitivity, cell cycle alteration and the change of apoptosis in different human hepatoma cell lines irradiated by heavy ions were studied with the aim of building up the base data for clinical therapy. Exponentially growing hepatoma cell lines were irradiated by 80.55 MeV/u(12)C(6+) ions at a dose of 0 Gy, 0.5 Gy, 1 Gy, 2 Gy, 4 Gy and 8 Gy. The radiosensitivity was assessed by means of the colony-forming assay. The DNA content, the percentage of each cell-cycle phase and the apoptosis rate were obtained with flow cytometry methods. After the irradiation, the SF2 (survival fraction at 2 gray) of SMMC-7721 cells were evidently lower than that of HepG2 cells. The S phase arrest, G2/M phase arrest delay and the apoptosis in the two hepatoma cell lines varied with the increase of the dose and repair time. The heavy ions could obviously kill the human hepatoma cell lines. Compared to HepG2 cells, SMMC-7721 cells were more radiosensitive to C-12(6+) ions.

alpha-Spectroscopic factor of (16)O(gs) from the (12)C((16)O,(12)C)(16)O reaction

Elastic scattering angular distributions of (16)O + (12)C in the center of mass energy range from 8.55 MeV to 56.57 MeV have been analyzed considering the effect of the exchange of an alpha particle between projectile and target leading to the same nuclei of the entrance channel (elastic-transfer). An alpha particle spectroscopic factor for the ground state of the (16)O was determined. (C) 2011 Elsevier B.V. All rights reserved.

Acanthoscurrin Fragment 101-132: Total Synthesis at 60 degrees C of a Novel Difficult Sequence

Glycine-rich proteins (GRP), serve a variety of biological functions. Acanthoscurrin is an antimicrobial GRP isolated front hemocytes-of the Brazilian spider Acanthoscurria gomesiana. Aiming to contribute to the knowledge of the secondary structure and stepwise solid-phase synthesis of GRPs` glycine-rich domains, we attempted to prepare G(101)GGLGGGRGGGYG(113) GGGGYGGGYG(123)GGy(126)GGGKYK(132)-NH(2), acanthoscurrin C-terminal amidated fragment. Although a theoretical prediction did not indicate high aggregation potential for this peptide, repetitive incomplete aminoacylations were observed after incorporating Tyr(126) to the growing peptide-MBHA resin (Boc chemistry) at 60 degrees C. The problem was not solved by varying the coupling reagents or solvents, adding chaotropic salts to the reaction media or changing the resin/chemistry (Rink amide resin/Fmoc chemistry). Some improvement was mode when CLEAR amide resin (Fmoc chemistry) was 32 used, as it allowed for obtaining fragment (G(113)-K(132) NIR-FT-Raman spectra collected for samples of the growing peptide-MBHA, -Rink amide resin and -CLEAR amide resin revealed the presence of beta-sheet structures. Only the combination of CLEAR-amide resin, 60 degrees C, Fmoc-(Fmoc-Hmb)Gly-OH and LiCl (the last two used alternately) was able to inhibit the phenomenon, as proven by NIR-FT-Raman analysis of the growing peptide-resin, allowing the total synthesis of desired 132 fragment Gly(101)-K(132). In summary, this work describes a new difficult sequence, contributes to understanding stepwise solid-phase synthesis of this type of peptide and shows that, at least while protected and linked to a resin, this GRPs glycine-rich motif presents all early tendency to assume beta-sheet structures. (c) 2008 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 92: 65-75, 2009.

Expanding the Peptide beta-Turn in alpha gamma Hybrid Sequences: 12 Atom Hydrogen Bonded Helical and Hairpin Turns

Hybrid peptide segments containing contiguous alpha and gamma amino acid residues can form C-12 hydrogen bonded turns which may be considered as backbone expanded analogues of C-10 beta-turns) found in alpha alpha segments. Exploration of the regular hydrogen bonded conformations accessible for hybrid alpha gamma sequences is facilitated by the use of a stereochemically constrained gamma amino acid residue gabapentin (1-aminomethylcyclohexaneacetic acid, Gpn), in which the two torsion angles about C-gamma-C-beta (theta(1)) and C-beta-C-alpha (theta(2)) are predominantly restricted to gauche conformations. The crystal structures of the octapeptides Boc-Gpn-Aib-Gpn-Aib-Gpn-Aib-Gpn-Aib-OMe (1) and Boc-Leu-Phe-Val-Aib-Gpn-Leu-Phe-Val-OMe (2) reveal two distinct conformations for the Aib-Gpn segment. Peptide 1 forms a continuous helix over the Aib(2)-Aib(6) segment, while the peptide 2 forms beta-hairpin structure stabilized by four cross-strand hydrogen bonds with the Aib-Gpn segment forming a nonhelical C-12 turn. The robustness of the helix in peptide 1 in solution is demonstrated by NMR methods. Peptide 2 is conformationally fragile in solution with evidence of beta-hairpin conformations being obtained in methanol. Theoretical calculations permit delineation of the various C-12 hydrogen bonded structures which are energetically feasible in alpha gamma and gamma alpha sequences.

Crystal structure and conformation study of N-methyl-t-3-methyl-r-2, c-6-diphenylpiperidin-4-one thiosemicarbazone

Thiosemicarbazones are having the ability to bind with metal and inhibit the enzyme ribonucleoside diphosphate reductase(RDR),an enzyme which is involved in the synthesis of DNA precursors in the mammalian cells.The title compound N-methyl-t-3-methyl-r-2, c-6-diphenylpiperidin-4-one thiosemicarbazone (NMMDPT), CCDC 218052, was prepared using Mannich reaction and characterized by X-ray diffraction methods.The crystal data are:C20H24N4S; M.W= 352.49, triclinic,space group P (1) over bar, a = 8.467(2)angstrom, b = 10.228(2)angstrom, c = 12.249(2)angstrom; lpha=92.595(3)degrees, beta=104.173(3)degrees, gamma=13.628(3)degrees; V=930.0(3)angstrom(3), Z=2, D-cal=1.259Mgm(-3),mu=0.184mm(-1),lambda (MoKalpha)=0.71073 angstrom, final R1 and wR2 are 0.0470 and 0.1052, respectively. The piperidine rings adopt chair conformation. The planar phenyl rings are oriented equatorially at 2,6-positions of the piperidine ring. The molecular packing can be viewed as dimers held together by two N-H...S types of intermolecular hydrogen bonds. Weak C-H...pi interactions also support the stability of the molecules in the crystal in addition to van der Waals forces. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Evaluation of live-attenuated Salmonella vaccines expressing Campylobacter antigens for control of C. jejuni in poultry

Campylobacter jejuni is a zoonotic bacterial pathogen of worldwide importance. It is estimated that 460,000 human infections occur in the United Kingdom per annum and these involve acute enteritis and may be complicated by severe systemic sequelae. Such infections are frequently associated with the consumption of contaminated poultry meat and strategies to control C. jejuni in poultry are expected to limit pathogen entry into the food chain and the incidence of human disease. Toward this aim, a total of 840 Light Sussex chickens were used to evaluate a Salmonella enterica serovar Typhimurium ΔaroA vaccine expressing the C. jejuni amino acid binding protein CjaA as a plasmid-borne fusion to the C-terminus of fragment C of tetanus toxin. Chickens were given the vaccine at 1-day-old and two weeks later by oral gavage, then challenged after a further two weeks with C. jejuni. Across six biological replicates, statistically significant reductions in caecal C. jejuni of c. 1.4 log10 colony-forming units/g were observed at three and four weeks post-challenge relative to age-matched unvaccinated birds. Protection was associated with the induction of CjaA-specific serum IgY and biliary IgA. Protection was not observed using a vaccine strain containing the empty plasmid. Vaccination with recombinant CjaA subcutaneously at the same intervals significantly reduced the caecal load of C. jejuni at three and four weeks post-challenge. Taken together these data imply that responses directed against CjaA, rather than competitive or cross-protective effects mediated by the carrier, confer protection. The impact of varying parameters on the efficacy of the S. Typhimurium ΔaroA vaccine expressing TetC-CjaA was also tested. Delaying the age at primary vaccination had little impact on protection or humoral responses to CjaA. The use of the parent strain as carrier or changing the attenuating mutation of the carrier to ΔspaS or ΔssaU enhanced the protective effect, consistent with increased invasion and persistence of the vaccine strains relative to the ΔaroA mutant. Expression in the ΔaroA strain of a TetC fusion to Peb1A, but not TetC fusions to GlnH or ChuA, elicited protection against intestinal colonisation by C. jejuni that was comparable to that observed with the TetC-CjaA fusion. Our data are rendered highly relevant by use of the target host in large numbers and support the potential of CjaA- and Peb1A-based vaccines for control of C. jejuni in poultry. © 2009 Elsevier Ltd. All rights reserved.

Enhanced biological effect induced by a radioactive C-9-ion beam at the depths around its Bragg peak

To explore the potential of double irradiation source, radioactive C-9-ion beam, in tumor therapy, a comparative study oil the surviving effect of human salivary gland cells at different penetration depths between C-9 and C-12-ion beams has been carried out. The 9C-ion C beam, especially at the distal side of the beam came out more efficient in cell killing at the depths around its Bragg peak than the 12 Bragg peak. Compared to the C-12 beam, an increase in RBE by a factor of up to 2.13 has been observed at the depths distal to the Bragg peak of the 9C beam. The 9C beam showed an enhanced biological effect at the penetration depths around its Bragg peak, corresponding to the stopping region of the incident C-9-ions and where the delayed low-energy particles were emitted. Further analysis revealed that cell lethality by the emitted particles from the stopping C-9-ions is responsible for the excessive biological effect at the penetration depths around the Bragg peak of the C-9 beam.

Power law behavior of the isotope yield distributions in the multifragmentation regime of heavy ion reactions

Isotope yield distributions in the multifragmentation regime were studied with high-quality isotope identification, focusing on the intermediate mass fragments (IMFs) produced in semiviolent collisions. The yields were analyzed within the framework of a modified Fisher model. Using the ratio of the mass-dependent symmetry energy coefficient relative to the temperature, a(sym)/T, extracted in previous work and that of the pairing term, a(p)/T, extracted from this work, and assuming that both reflect secondary decay processes, the experimentally observed isotope yields were corrected for these effects. For a given I = N - Z value, the corrected yields of isotopes relative to the yield of C-12 show a power law distribution Y (N, Z)/Y(C-12) similar to A(-tau) in the mass range 1 <= A <= 30, and the distributions are almost identical for the different reactions studied. The observed power law distributions change systematically when I of the isotopes changes and the extracted tau value decreases from 3.9 to 1.0 as I increases from -1 to 3. These observations are well reproduced by a simple deexcitation model, with which the power law distribution of the primary isotopes is determined to be tau(prim) = 2.4 +/- 0.2, suggesting that the disassembling system at the time of the fragment formation is indeed at, or very near, the critical point.

The Main Path to C, N, O Elements in Big Bang Nucleosynthesis

The production of C, N, O elements in a standard big bang nucleosynthesis scenario is investigated. Using the up-to-date data of nuclear reactions in BBN, in particular the Li-8 (n, gamma) Li-9 which has been measured in China Institute of Atomic Energy, a full nucleosynthesis network calculation of BBN is carried out. Our calculation results show that the abundance of C-12 is increased for an order of magnitude after addition of the reaction chain Li-8(n, gamma) Li-9(alpha, n) B-12(beta) C-12, which was neglected in previous studies. We find that this sequence provides the main channel to convert the light elements into C, N, O in standard BBN.

MEASUREMENT OF TWO-PROTON CORRELATION FROM THE BREAK-UP OF Al-23

Experiments of Al-23 and Mg-22 radioactive beams bombarding a C-12 target at an energy of 60 similar to 70 A MeV have been performed at the projectile fragment separator beamline (RIPS) in the RIKEN Ring Cyclotron Facility to study the two-proton emission from Al-23 and Mg-22 excited states, respectively. The trajectorie of the decay products, namely Na-21 + p + p from Al-23 and Ne-20 + p + p from Mg-22, are clean identified. The relative momentum and opening angle between two protons in the rest frame of three body decay channels are obtained by relativistic-kinematics reconstruction. The results demonstrate that there are some di-proton emission components from He-2 cluster for the excited Al-23 and Mg-22.

MEASUREMENT OF THE PROTON-PROTON CORRELATION FUNCTION FROM THE BREAK-UP OF Mg-22 AND Ne-20

An experiment of Mg-22 and Ne-20 beams bombarding on a C-12 target at an energy of 60 similar to 70 A MeV has been performed at the RIKEN projectile fragment separator (RIPS)in the RIKEN Ring Cyclotron Facility to study the two-proton correlated emission from Mg-22 and Ne-20 excited states. The two-protons momentum correlation functions have been obtained for Mg-22 and Ne-20, respectively. The trajectories of the Mg-22 decayed products (Ne-20 + p + p) were also measured to get the angular correlations between the two protons in Center of Mass of decaying system by relativistic-kinematics reconstruction. The results exhibit that Mg-22 has the features of He-2 cluster decay mechanism.

Characterization of the 5' upstream regulatory region of the human myostatin gene: regulation of myostatin gene transcription by dexamethasone in vitro

We cloned and characterized a 3.3-kb fragment containing the 5'-regulatory region of the human myostatin gene. The promoter sequence contains putative muscle growth response elements for glucocorticoid, androgen, thyroid hormone, myogenic differentiation factor 1, myocyte enhancer factor 2, peroxisome proliferator-activated receptor, and nuclear factor-kappaB. To identify sites important for myostatin's gene transcription and regulation, eight deletion constructs were placed in C(2)C(12) and L6 skeletal muscle cells. Transcriptional activity of the constructs was found to be significantly higher in myotubes compared with that of myoblasts. To investigate whether glucocorticoids regulate myostatin gene expression, we incubated both cell lines with dexamethasone. On both occasions, dexamethasone dose dependently increased both the promoter's transcriptional activity and the endogenous myostatin expression. The effects of dexamethasone were blocked when the cells were coincubated with the glucocorticoid receptor antagonist RU-486. These findings suggest that glucocorticoids upregulate myostatin expression by inducing gene transcription, possibly through a glucocorticoid receptor-mediated pathway. We speculate that glucocorticoid-associated muscle atrophy might be due in part to the upregulation of myostatin expression.

Plasmid pRTL1 controlling 1-chloroalkane degradation by Rhodococcus rhodochrous NCIMB 13064

Rhodococcus rhodochrous NCIMB13064 can dehalogenate and use a wide range of 1-haloalkanes as sole carbon and energy source. The 1-chloroalkane degradation phenotype may be lost by cells spontaneously or after treatment with Mitomycin C. Two laboratory derivatives of the original strain exhibited differing degrees of stability of the chloroalkane degradation marker. Plasmids of approximately 100 kbp (pRTL1) and 80 kbp (pRTL2) have been found in R. rhodochrous NCIMB13064. pRTL1 was shown to be carrying at least some genes for the dehalogenation of 1-chloroalkanes with short chain lengths (C-3 to C-9). However, no connection was found between the utilization of 1-chloroalkanes with longer chain lengths (C-12 to C-18) and the presence of pRTL1. Three separate events were observed to lead to the inability of NCIMB13064 to dehalogenate the short-chain 1-chloroalkanes; the complete loss of pRTL1, the integration of pRTL1 into the chromosome, or the deletion of a 20-kbp fragment in pRTL1. High-frequency transfer of the 1-chloroalkane degradation marker associated with pRTL1 has been demonstrated in bacterial crosses between different derivatives of R. rhodochrous NCIMB13064, (C) 1995 Academic Press, Inc.

12" x 9" envelope from the Department of Interior to H. M. Spencer

This envelope is addressed to H. M. Spencer from the patent office of the Department of Interior. The stamp is dated March 28th of 1911. H.M. Spencer's address is written as R. F. D. No. 1, Cheraw, South Carolina, and the envelope has been written on mathematically with pencil.