653 research outputs found
A Note on String Field Theory in the Temporal Gauge
In this note, we review the recent developments in the string field theory in
the temporal gauge. (Based on a talk presented by N.I. in the workshop {\it
Quantum Field Theory, Integrable Models and Beyond}, Yukawa Institute for
Theoretical Physics, Kyoto University, 14-18 February 1994.)Comment: 20 pages, KEK-TH-411, LaTex fil
Stochastic Hamiltonian for Non-Critical String Field Theories from Double-Scaled Matrix Models
We present detailed discussions on the stochastic Hamiltonians for
non-critical string field theories on the basis of matrix models. Beginning
from the simplest case, we derive the explicit forms of the Hamiltonians
for the higher critical case (which corresponds to ) and for the
case , directly from the double-scaled matrix models. In particular, for
the two-matrix case, we do not put any restrictions on the spin configurations
of the string fields. The properties of the resulting infinite algebras of
Schwinger-Dyson operators associated with the Hamiltonians and the derivation
of the Virasoro and algebras therefrom are also investigated. Our results
suggest certain universal structure of the stochastic Hamiltonians, which might
be useful for an attempt towards a background independent string field theory.Comment: 70 pages, LaTeX, typographical errors are corrected, to be published
in Phys. Rev.
Loop Equations for + and - Loops in c = 1/2 Non-Critical String Theory
New loop equations for all genera in non-critical string
theory are constructed. Our loop equations include two types of loops, loops
with all Ising spins up (+ loops) and those with all spins down ( loops).
The loop equations generate an algebra which is a certain extension of
algebra and are equivalent to the constraints derived before in the
matrix-model formulation of 2d gravity. Application of these loop equations to
construction of Hamiltonian for string field theory is
considered.Comment: 21 pages, LaTex file, no figure
Age trajectories of glycaemic traits in non-diabetic South Asian and white individuals: the Whitehall II cohort study.
South Asian individuals have an increased prevalence of type 2 diabetes, but little is known about the development of glycaemic traits in this ethnic group. We compared age-related changes in glycaemic traits between non-diabetic South Asian and white participants
Linear-Time Algorithms for Computing Maximum-Density Sequence Segments with Bioinformatics Applications
We study an abstract optimization problem arising from biomolecular sequence
analysis. For a sequence A of pairs (a_i,w_i) for i = 1,..,n and w_i>0, a
segment A(i,j) is a consecutive subsequence of A starting with index i and
ending with index j. The width of A(i,j) is w(i,j) = sum_{i <= k <= j} w_k, and
the density is (sum_{i<= k <= j} a_k)/ w(i,j). The maximum-density segment
problem takes A and two values L and U as input and asks for a segment of A
with the largest possible density among those of width at least L and at most
U. When U is unbounded, we provide a relatively simple, O(n)-time algorithm,
improving upon the O(n \log L)-time algorithm by Lin, Jiang and Chao. When both
L and U are specified, there are no previous nontrivial results. We solve the
problem in O(n) time if w_i=1 for all i, and more generally in
O(n+n\log(U-L+1)) time when w_i>=1 for all i.Comment: 23 pages, 13 figures. A significant portion of these results appeared
under the title, "Fast Algorithms for Finding Maximum-Density Segments of a
Sequence with Applications to Bioinformatics," in Proceedings of the Second
Workshop on Algorithms in Bioinformatics (WABI), volume 2452 of Lecture Notes
in Computer Science (Springer-Verlag, Berlin), R. Guigo and D. Gusfield
editors, 2002, pp. 157--17
On the Quantum Geometry of Multi-critical CDT
We discuss extensions of a recently introduced model of multi-critical CDT to
higher multi-critical points. As in the case of pure CDT the continuum limit
can be taken on the level of the action and the resulting continuum surface
model is again described by a matrix model. The resolvent, a simple observable
of the quantum geometry which is accessible from the matrix model is calculated
for arbitrary multi-critical points. We go beyond the matrix model by
determining the propagator using the peeling procedure which is used to extract
the effective quantum Hamiltonian and the fractal dimension in agreement with
earlier results by Ambjorn et al. With this at hand a string field theory
formalism for multi-critical CDT is introduced and it is shown that the
Dyson-Schwinger equations match the loop equations of the matrix model. We
conclude by commenting on how to formally obtain the sum over topologies and a
relation to stochastic quantisation.Comment: 15 pages, 2 figures, improved discussion, some new results regarding
Hausdorff dimension, as publishe
Multiple episodes of ice loss from the Wilkes Subglacial Basin during the Last Interglacial
The Last Interglacial (LIG: 130,000-115,000 years ago) was a period of warmer global mean temperatures and higher and more variable sea levels than the Holocene (11,700-0 years ago). Therefore, a better understanding of Antarctic ice-sheet dynamics during this interval would provide valuable insights for projecting sea-level change in future warming scenarios. Here we present a high-resolution record constraining ice-sheet changes in the Wilkes Subglacial Basin (WSB) of East Antarctica during the LIG, based on analysis of sediment provenance and an ice melt proxy in a marine sediment core retrieved from the Wilkes Land margin. Our sedimentary records, together with existing ice-core records, reveal dynamic fluctuations of the ice sheet in the WSB, with thinning, melting, and potentially retreat leading to ice loss during both early and late stages of the LIG. We suggest that such changes along the East Antarctic Ice Sheet margin may have contributed to fluctuating global sea levels during the LIG
Molecular basis for sensitivity and acquired resistance to gefitinib in HER2-overexpressing human gastric cancer cell lines derived from liver metastasis
Gastric cancer metastasised to the liver was found to overexpress HER2 at a significantly higher incidence than primary gastric cancers. The purpose of the present study was to investigate the possibility of molecular therapy targeting HER2 overexpression in gastric cancer liver metastasis. We developed three new HER2-overexpressing gastric cancer cell lines (GLM-1, GLM-2, GLM-4) without epidermal growth factor receptor (EGFR) mutations derived from such liver metastasis, two of which had HER2 gene amplifications. All these GLM series of cell lines were highly sensitive to gefitinib in vitro, a specific inhibitor of EGFR tyrosine kinase (Iressa) rather than anti-HER2 antibody trastuzumab (Herceptin), whereas most of the HER2 low-expressing counterparts were not. In these HER2-overexpressing GLM series, protein kinase B (Akt), but not extracellular signal-regulated kinase 1/2 (ERK1/2), was constitutively phosphorylated, and gefitinib efficiently inhibited this Akt phosphorylation, induced strong apoptosis in vitro and exhibited antitumour activity in tumour xenografts in nude mice. This gefitinib-mediated antitumour effect in xenograft was significantly potentiated by trastuzumab treatment. On the other hand, gefitinib-resistant cells (GLM-1R) exhibited increased EGFR expression, followed by constitutive activation of mitogen-activated protein kinase (MAPK) pathway. These results suggest that the antitumour effect of gefitinib is due to the effective inhibition of HER2-driven constitutive activation of phosphatidylinositol-3-kinase (PI3K)/Akt pathway, and that the acquired resistance to gefitinib is due to the constitutive activation of Ras/MAPK pathway in compensation for PI3K/Akt pathway. Gastric cancer liver metastasis with HER2 overexpression would be a potential molecular target for gefitinib and trastuzumab
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