767 research outputs found
Photon Frequency Entanglement Swapping
We propose a simple non-linear crystal based optical scheme for experimental
realization of the frequency entanglement swapping between the photons
belonging to two independent biphotons.Comment: 5 pages, 1 figure. Submitted to Phys.Lett.
Mice Lacking Dad1, the Defender against Apoptotic Death-1, Express Abnormal N-Linked Glycoproteins and Undergo Increased Embryonic Apoptosis
AbstractDad1 has been shown to play a role in preventing apoptotic cell death and in regulating levels of N-linked glycosylation in Saccharomyces cerevisiae and the BHK hamster cell line. To address the in vivo role of Dad1 in these processes during multicellular development, we have analyzed mice carrying a null allele for Dad1. Embryos homozygous for this mutation express abnormal N-glycosylated proteins and are developmentally delayed by embryonic day 7.5. Such mutants exhibit aberrant morphology, impaired mesodermal development, and increased levels of apoptosis in specific tissues. These defects culminate in homozygous embryos failing to turn the posterior axis and subsequent lethality by embryonic day 10.5. Thus, Dad1 is required for proper processing of N-linked glycoproteins and for certain cell survival in the mouse
Charmonium states in QCD-inspired quark potential model using Gaussian expansion method
We investigate the mass spectrum and electromagnetic processes of charmonium
system with the nonperturbative treatment for the spin-dependent potentials,
comparing the pure scalar and scalar-vector mixing linear confining potentials.
It is revealed that the scalar-vector mixing confinement would be important for
reproducing the mass spectrum and decay widths, and therein the vector
component is predicted to be around 22%. With the state wave functions obtained
via the full-potential Hamiltonian, the long-standing discrepancy in M1
radiative transitions of and are alleviated
spontaneously. This work also intends to provide an inspection and suggestion
for the possible among the copious higher charmonium-like states.
Particularly, the newly observed X(4160) and X(4350) are found in the
charmonium family mass spectrum as MeV and MeV, which strongly favor the assignments
respectively. The corresponding radiative transitions, leptonic and two-photon
decay widths have been also predicted theoretically for the further
experimental search.Comment: 16 pages,3 figure
Nonequilibrium transitions in complex networks: a model of social interaction
We analyze the non-equilibrium order-disorder transition of Axelrod's model
of social interaction in several complex networks. In a small world network, we
find a transition between an ordered homogeneous state and a disordered state.
The transition point is shifted by the degree of spatial disorder of the
underlying network, the network disorder favoring ordered configurations. In
random scale-free networks the transition is only observed for finite size
systems, showing system size scaling, while in the thermodynamic limit only
ordered configurations are always obtained. Thus in the thermodynamic limit the
transition disappears. However, in structured scale-free networks, the phase
transition between an ordered and a disordered phase is restored.Comment: 7 pages revtex4, 10 figures, related material at
http://www.imedea.uib.es/PhysDept/Nonlinear/research_topics/Social
Correspondence principle for a brane in Minkowski space and vector mesons
We consider a 3-brane of positive cosmological constant (de Sitter) in
D-dimensional Minkowski space. We show that the Poincare algebra in the bulk
yields a SO(4,2) algebra when restricted to the brane. In the limit of zero
cosmological constant (flat brane), this algebra turns into the conformal
algebra on the brane. We derive a correspondence principle for Minkowski space
analogous to the AdS/CFT correspondence. We discuss explicitly the cases of
scalar and gravitational fields. For a 3-brane of finite thickness in the
transverse directions, we obtain a spectrum for vector gravitational
perturbations which correspond to vector mesons. The spectrum agrees with the
one obtained in truncated AdS space by de Teramond and Brodsky provided D=10
and the bulk mass scale M is of order the geometric mean of the Planck mass
() on the brane and ( GeV).Comment: 8 pages in two-column ReVTeX
Vector lattice model for stresses in granular materials
A vector lattice model for stresses in granular materials is proposed. A two
dimensional pile built by pouring from a point is constructed numerically
according to this model. Remarkably, the pile violates the Mohr Coulomb
stability criterion for granular matter, probably because of the inherent
anisotropy of such poured piles. The numerical results are also compared to the
earlier continuum FPA model and the (scalar) lattice -model
Checkpoint kinase 2-mediated phosphorylation of BRCA1 regulates the fidelity of nonhomologous end-joining
The tumor suppressor gene BRCA1 maintains genomic integrity by protecting
cells from the deleterious effects of DNA double-strand breaks (DSBs).
Through its interactions with the checkpoint kinase 2 (Chk2) kinase and
Rad51, BRCA1 promotes homologous recombination, which is typically an
error-free repair process. In addition, accumulating evidence implicates
BRCA1 in the regulation of nonhomologous end-joining (NHEJ), which may
involve precise religation of the DSB ends if they are compatible (i.e.,
error-free repair) or sequence alteration upon rejoining (i.e.,
error-prone or mutagenic repair). However, the precise role of BRCA1 in
regulating these different subtypes of NHEJ is not clear. We provide here
the genetic and biochemical evidence to show that BRCA1 promotes
error-free rejoining of DSBs in human breast carcinoma cells while
suppressing microhomology-mediated error-prone end-joining and restricting
sequence deletion at the break junction during repair. The repair spectrum
in BRCA1-deficient cells was characterized by an increase in the formation
of >2 kb deletions and in the usage of long microhomologies distal to the
break site, compared with wild-type (WT) cells. This error-prone repair
phenotype could also be revealed by disruption of the Chk2 phosphorylation
site of BRCA1, or by expression of a dominant-negative kinase-dead Chk2
mutant in cells with WT BRCA1. We suggest that the differential control of
NHEJ subprocesses by BRCA1, in concert with Chk2, reduces the mutagenic
potential of NHEJ, thereby contributing to the prevention of familial
breast cancers
Comparative transcriptome analysis identified candidate genes for late leaf spot resistance and cause of defoliation in groundnut
Late leaf spot (LLS) caused by fungus Nothopassalora personata in groundnut is responsible for up to 50% yield loss. To dissect the complex nature of LLS resistance, comparative transcriptome analysis was performed using resistant (GPBD 4), susceptible (TAG 24) and a resistant introgression line (ICGV 13208) and identified a total of 12,164 and 9954 DEGs (differentially expressed genes) respectively in A- and B-subgenomes of tetraploid groundnut. There were 135 and 136 unique pathways triggered in A- and B-subgenomes, respectively, upon N. personata infection. Highly upregulated putative disease resistance genes, an RPP-13 like (Aradu.P20JR) and a NBS-LRR (Aradu.Z87JB) were identified on chromosome A02 and A03, respectively, for LLS resistance. Mildew resistance Locus (MLOs)-like proteins, heavy metal transport proteins, and ubiquitin protein ligase showed trend of upregulation in susceptible genotypes, while tetratricopeptide repeats (TPR), pentatricopeptide repeat (PPR), chitinases, glutathione S-transferases, purple acid phosphatases showed upregulation in resistant genotypes. However, the highly expressed ethylene responsive factor (ERF) and ethylene responsive nuclear protein (ERF2), and early responsive dehydration gene (ERD) might be related to the possible causes of defoliation in susceptible genotypes. The identified disease resistance genes can be deployed in genomics-assisted breeding for development of LLS resistant cultivars to reduce the yield loss in groundnut
Relativistic close coupling calculations for photoionization and recombination of Ne-like Fe XVII
Relativistic and channel coupling effects in photoionization and unified
electronic recombination of Fe XVII are demonstrated with an extensive 60-level
close coupling calculation using the Breit-Pauli R-matrix method.
Photoionization and (e + ion) recombination calculations are carried out for
the total and the level-specific cross sections, including the ground and
several hundred excited bound levels of Fe XVII (up to fine structure levels
with n = 10). The unified (e + ion) recombination calculations for (e + Fe
XVIII --> Fe XVII) include both the non-resonant and resonant recombination
(`radiative' and `dielectronic recombination' -- RR and DR). The low-energy and
the high energy cross sections are compared from: (i) a 3-level calculation
with 2s^2p^5 (^2P^o_{1/2,3/2}) and 2s2p^6 (^2S_{1/2}), and (ii) the first
60-level calculation with \Delta n > 0 coupled channels with spectroscopic
2s^2p^5, 2s2p^6, 2s^22p^4 3s, 3p, 3d, configurations, and a number of
correlation configurations. Strong channel coupling effects are demonstrated
throughout the energy ranges considered, in particular via giant
photoexcitation-of-core (PEC) resonances due to L-M shell dipole transition
arrays 2p^5 --> 2p^4 3s, 3d in Fe XIII that enhance effective cross sections by
orders of magnitude. Comparison is made with previous theoretical and
experimental works on photoionization and recombination that considered the
relatively small low-energy region (i), and the weaker \Delta n = 0 couplings.
While the 3-level results are inadequate, the present 60-level results should
provide reasonably complete and accurate datasets for both photoionization and
(e + ion) recombination of Fe~XVII in laboratory and astrophysical plasmas.Comment: 19 pages, 8 figures, Phys. Rev. A (submitted
A New Biology: A Modern Perspective on the Challenge of Closing the Gap between the Islands of Knowledge
This paper discusses the rebirth of the old quest for the principles of biology along the discourse line of machine-organism disanalogy and within the context of biocomputation from a modern perspective. It reviews some new attempts to revise the existing body of research and enhance it with new developments in some promising fields of mathematics and computation. The major challenge is that the latter are expected to also answer the need for a new framework, a new language and a new methodology capable of closing the existing gap between the different levels of complex system organization
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