133 research outputs found
Finding unique PCR products on distributed databases
Thanks to the development of genetic engineering, various kinds of genomic information are being unveiled. Hence, now, it becomes feasible to study in molecular biology by analyzing the entire genomic information. On the other hand, the quantity of the genomic information stocked in database is increasing day after day. In order to process the whole information, we have to develop an effective method to deal with lots of data. It is indispensable not only to make an effective and rapid algorithm but also to use high-speed computer resource so as to analyze the biological information. For this purpose, as one of the most promised computing environments, the grid computing architecture has appeared recently. The European Data Grid (EDG) is one of the grid com-puting environments. In the first stage of designing hybridization probes and PCR primers, it is extremely important to find genuinely unique sequence on a target genome. We deployed a novel method to design PCR primers, which takes into account not only the specificity of the primer itself but also the uniqueness of the product length. In this paper, we improve our proposed method to find unique PCR products on distributed databases. We show also the sequences found by our method, which can not be uniquely observed by any probe sequence but by a pair of PCR primers on S. cerevisiae genome. 1
Orbitally Driven Spin Pairing in the 3D Non-Magnetic Mott Insulator BaVS3: Evidence from Single Crystal Studies
Static electrical and magnetic properties of single crystal BaVS_3 were
measured over the structural (T_S=240K), metal-insulator (T_MI=69K), and
suspected orbital ordering (T_X=30K) transitions. The resistivity is almost
isotropic both in the metallic and insulating states. An anomaly in the
magnetic anisotropy at T_X signals a phase transition to an ordered low-T
state. The results are interpreted in terms of orbital ordering and spin
pairing within the lowest crystal field quasi-doublet. The disordered insulator
at T_X<T<T_MI is described as a classical liquid of non-magnetic pairs.Comment: 4 pages, 5 figures, revtex, epsf, and multicol style. Problem with
figures fixed. To appear in Phys. Rev. B Rap. Com
Ab initio calculation of resonant X-ray scattering in Manganites
We study the origin of the resonant x-ray signal in manganites and generalize
the resonant cross-section to the band structure framework. With {\it ab
initio} LSDA and LSDA+U calculations we determine the resonant x-ray spectrum
of LaMnO. The calculated spectrum and azimuthal angle dependence at the Mn
-edge reproduce the measured data without adjustable parameters. The
intensity of this signal is directly related to the orthorhombicity of the
lattice. We also predict a resonant x-ray signal at the La -edge, caused by
the tilting of the MnO octahedra. This shows that the resonant x-ray signal
in the hard x-ray regime can be understood in terms of the band structure of a
material and is sensitive to the fine details of crystal structure.Comment: 4 pages, 4 figures, accepted for publication in Phys. Rev.
Magnon Heat Transport in (Sr,La)_14Cu_24O_41
We have measured the thermal heat conductivity kappa of the compounds
Sr_14Cu_24O_41 and Ca_9La_5Cu_24O_41 containing doped and undoped spin ladders,
respectively. We find a huge anisotropy of both, the size and the temperature
dependence of kappa which we interpret in terms of a very large heat
conductivity due to the magnetic excitations of the one-dimensional spin
ladders. This magnon heat conductivity decreases with increasing hole doping of
the ladders. The magnon heat transport is analyzed theoretically using a simple
kinetic model. From this analysis we determine the spin gap and the temperature
dependent mean free path of the magnons which ranges by several thousand
angstroms at low temperature. The relevance of several scattering channels for
the magnon transport is discussed.Comment: 6 pages, 5 figures, submitted to Phys. Rev.
Manganites at Quarter Filling: Role of Jahn-Teller Interactions
We have analyzed different correlation functions in a realistic spin-orbital
model for half-doped manganites. Using a finite-temperature diagonalization
technique the CE phase was found in the charge-ordered phase in the case of
small antiferromagnetic interactions between electrons. It is shown
that a key ingredient responsible for stabilization of the CE-type spin and
orbital-ordered state is the cooperative Jahn-Teller (JT) interaction between
next-nearest Mn neighbors mediated by the breathing mode distortion of
Mn octahedra and displacements of Mn ions. The topological phase
factor in the Mn-Mn hopping leading to gap formation in one-dimensional models
for the CE phase as well as the nearest neighbor JT coupling are not able to
produce the zigzag chains typical for the CE phase in our model.Comment: 16 pages with 16 figures, contains a more detailed parameter estimate
based on the structural data by Radaelli et al. (accepted for publication in
Phys. Rev. B
Phase Diagram of the Heisenberg Spin Ladder with Ring Exchange
We investigate the phase diagram of a generalized spin-1/2 quantum
antiferromagnet on a ladder with rung, leg, diagonal, and ring-exchange
interactions. We consider the exactly soluble models associated with the
problem, obtain the exact ground states which exist for certain parameter
regimes, and apply a variety of perturbative techniques in the regime of strong
ring-exchange coupling. By combining these approaches with considerations
related to the discrete Z_4 symmetry of the model, we present the complete
phase diagram.Comment: 17 pages, 10 figure
Primordial Black Hole Formation in a Double Inflation Model in Supergravity
It has been recently pointed out that the initial value problem in new
inflation models is naturally solved by supergravity effects if there exists a
pre-inflation before the new inflation. We study this double inflation model in
details and find that density fluctuations on small cosmological scales are
much larger than those on large scales due to peculiar property of the new
inflation. We show that this results in production of primordial black holes
which have masses in a certain parameter region of the
double inflation model. We stress that these black holes may be identified with
MACHOs observed in the halo of our galaxy.Comment: 19 pages (RevTeX file), KUNS-147
Quantum Phase Transition in the SU(4) Spin-Orbital Model on the Triangular Lattice
Motivated by the absence of cooperative Jahn-Teller effect in LiNiO2 and
BaVS3, two layered oxides with triangular planes, we study the SU(4) symmetric
spin-orbital model on the triangular lattice. Upon reducing the next-nearest
neighbour coupling, we show that the system undergoes a quantum phase
transition to a liquid phase. A variational approach to this liquid phase shows
that simple types of long-range correlations are suppressed, suggesting that it
is stable against lattice distortions.Comment: 5 pages, 5 figures, RevTex
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