13,756 research outputs found
Obvious enhancement of the total reaction cross sections for P with Si target and the possible relavent mechanisms
The reaction cross sections of P and the corresponding isotones on
Si target were measured at intermediate energies. The measured reaction cross
sections of the N=12 and 13 isotones show an abrupt increase at . The
experimental results for the isotones with as well as P can
be well described by the modified Glauber theory of the optical limit approach.
The enhancement of the reaction cross section for P could be explained
in the modified Glauber theory with an enlarged core. Theoretical analysis with
the modified Glauber theory of the optical limit and few-body approaches
underpredicted the experimental data of P. Our theoretical analysis
shows that an enlarged core together with proton halo are probably the
mechanism responsible for the enhancement of the cross sections for the
reaction of P+Si.Comment: 16 pages, 5 figures, to be published in Phys.Rev.
Single N277A substitution in C2 of simian immunodeficiency virus envelope influences vaccine-elicited CD4i neutralizing and anti-V2 antibody responses
An effective HIV vaccine remains elusive, and immunogens capable of eliciting protective host humoral immunity have not yet been identified. Although HIV/SIV infections result in the abundant production of CD4-induced (CD4i) antibodies (Abs), these Abs are not protective due to steric restrictions following gp120 binding to CD4 on target cells. Here we report that both DNA- and vaccinia-based vaccines encoding SIVmac239 gp160 readily elicited high levels of CD4i Abs in experimental animals. We identified a highly conserved N-linked glycosylation site N277 in the C2 region which strongly affected the immunogenicity of the CD4i Ab domain. Moreover, a single N277A substitution significantly enhanced the immunogenicity of the V2 domain yielding higher titers and frequency of anti-V2 Ab responses as determined by ELISA and yeast antigen display mapping, respectively. Importantly, immune sera elicited by the N277A-mutated gp160 exhibited elevated antibody-dependent cellular cytotoxicity (ADCC) activity. ADCC activity correlated positively with the anti-V2 Ab titer yet, inversely with CD4i Ab titer. Thus, we identified a determinant of the CD4i domain that might affect vaccine-elicited anti-V2 Ab and ADCC responses to SIVmac239. Our findings may have implications for design of immunogens to direct B cell recognition in the development of an Ab-based HIV vaccine
Precise exogenous insertion and sequence replacements in poplar by simultaneous HDR overexpression and NHEJ suppression using CRISPR-Cas9
CRISPR-mediated genome editing has become a powerful tool for the genetic modification of biological traits. However, developing an efficient, site-specific, gene knock-in system based on homology-directed DNA repair (HDR) remains a significant challenge in plants, especially in woody species like poplar. Here, we show that simultaneous inhibition of non-homologous end joining (NHEJ) recombination cofactor XRCC4 and overexpression of HDR enhancer factors CtIP and MRE11 can improve HDR efficiency for gene knock-in. Using this approach, the BleoR gene was integrated onto the 3′ end of the MKK2 MAP kinase gene to generate a BleoR-MKK2 fusion protein. Based on fully edited nucleotides evaluated by TaqMan real-time PCR, the HDR-mediated knock-in efficiency was up to 48% when using XRCC4 silencing incorporated with a combination of CtIP and MRE11 overexpression compared with no HDR enhancement or NHEJ silencing. Furthermore, this combination of HDR enhancer overexpression and NHEJ repression also increased genome targeting efficiency and gave 7-fold fewer CRISPR-induced insertions and deletions (InDels), resulting in no functional effects on MKK2-based salt stress responses in poplar. Therefore, this approach may be useful not only in poplar and plants or crops but also in mammals for improving CRISPR-mediated gene knock-in efficiency
Reactor neutrino physics potentials of cryogenic pure-CsI crystal
The paper presents a world-leading scintillation light yield among inorganic
crystals measured from a 0.5 kg pure-CsI detector operated at 77 Kelvin.
Scintillation photons were detected by two 2-inch Hamamatsu SiPM arrays
equipped with cryogenic front end electronics. Benefiting the light yield
enhancement of pure-CsI at low temperatures and the high photon detection
efficiency of SiPM, a light yield of 52.1 photoelectrons per keV energy deposit
was obtained for X-rays and {\gamma}-rays with energies from 5.9 keV to 60 keV.
Instrumental and physical effects in the light yield measurement is carefully
analyzed. This is the first stable cryogenic operation of kg-scale pure-CsI
crystal readout by SiPM arrays at liquid nitrogen temperatures for several
days. The world-leading light yield opens a door for the usage of pure-CsI
crystal in several fields, particularly in detecting the coherent elastic
neutrino-nucleus scattering of reactor neutrinos. Potentials of using pure-CsI
crystals in neutrino physics are discussed in the paper.Comment: 10 pages, 16 figure
Measurement of the branching fractions of psi(2S) -> 3(pi+pi-) and J/psi -> 2(pi+pi-)
Using data samples collected at sqrt(s) = 3.686GeV and 3.650GeV by the BESII
detector at the BEPC, the branching fraction of psi(2S) -> 3(pi+pi-) is
measured to be [4.83 +- 0.38(stat) +- 0.69(syst)] x 10^-4, and the relative
branching fraction of J/psi -> 2(pi+pi-) to that of J/psi -> mu+mu- is measured
to be [5.86 +- 0.19(stat) +- 0.39(syst)]% via psi(2S) -> (pi+pi-)J/psi, J/psi
-> 2(pi+pi-). The electromagnetic form factor of 3(pi+pi-) is determined to be
0.21 +- 0.02 and 0.20 +- 0.01 at sqrt(s) = 3.686GeV and 3.650GeV, respectively.Comment: 17pages, 7 figures, submitted to Phys. Rev.
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