146 research outputs found
Ward Identities and High-energy Scattering Amplitudes in String Theory
High-energy limit of stringy Ward identities derived from the decoupling of
two types of zero-norm states in the old covariant first quantized (OCFQ)
spectrum of open bosonic string are used to check the consistency of saddle
point calculations of high energy scattering amplitudes of Gross and Mende and
Gross and Manes. Some inconsistencies of their saddle point calculations are
found even for the string-tree scattering amplitudes of the excited string
states. We discuss and calculate the missing terms of the calculation by those
authors to recover the stringy Ward identities. In addition, based on the
tree-level stringy Ward identities, we give the proof of a general formula,
which was proposed previously, of all high energy four-point string-tree
amplitudes of arbitrary particles in the string spectrum. In this formula all
such scattering amplitudes are expressed in terms of those of tachyons as
conjectured by Gross. The formula is extremely simple which manifestly
demonstrates the universal high energy behavior of the interactions among all
string states.Comment: 1 typo, to appear in Nucl. Phys.
Zero-norm states and stringy symmetries
We identify spacetime symmetry charges of 26D open bosonic string theory from
an infinite number of zero-norm states (ZNS) with arbitrary high spin in the
old covariant first quantized string spectrum. We give various evidences to
support this identification. These include massive sigma-model calculation,
Witten string field theory calculation, 2D string theory calculation and, most
importantly, three methods of high-energy stringy scattering amplitude
calculations. The last calculations explicitly prove Gross's conjectures in
1988 on high energy symmetry of string theory.Comment: 6 pages. Talks presented by Jen-Chi Lee at XXVIII Spanish Relativity
Meeting (ERE2005),"A Century of Relativity Physics",Oviedo,Spain,6-10 Sep
2005 and "4th Meeting on constrained Dynamics and Quantum Gravity",Cala
Gonone,Sardinia,Italy,12-16 Sep 2005. To appear in the Journal of Physics:
Conference Serie
High-energy zero-norm states and symmetries of string theory
High-energy limit of zero-norm states (HZNS) in the old covariant first
quantized (OCFQ) spectrum of the 26D open bosonic string, together with the
assumption of a smooth behavior of string theory in this limit, are used to
derive infinitely many linear relations among the leading high-energy, fixed
angle behavior of four point functions of different string states. As a result,
ratios among all high-energy scattering amplitudes of four arbitrary string
states can be calculated algebraically and the leading order amplitudes can be
expressed in terms of that of four tachyons as conjectured by Gross in 1988. A
dual calculation can also be performed and equivalent results are obtained by
taking the high-energy limit of Virasoro constraints. Finally, as a consistent
sample calculation, we compute all high-energy scattering amplitudes of three
tachyons and one massive state at the leading order by saddle-point
approximation to justify our results.Comment: 10 pages, no figure, modifications of text and reference
Optimisation- based time slot assignment and synchronisation for TDMA MAC in industrial wireless sensor network
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/166209/1/cmu2bf02232.pd
Scatterings of Massive String States from D-brane and Their Linear Relations at High Energies
We study scatterings of bosonic massive closed string states at arbitrary
mass levels from D-brane. We discover that all the scattering amplitudes can be
expressed in terms of the generalized hypergeometric function with special
arguments, which terminates to a finite sum and, as a result, the whole
scattering amplitudes consistently reduce to the usual beta function. For the
simple case of D-particle, we explicitly calculate high-energy limits of a
series of the above scattering amplitudes for arbitrary mass levels, and derive
infinite linear relations among them for each fixed mass level. The ratios of
these high-energy scattering amplitudes are found to be consistent with the
decoupling of high-energy zero-norm states of our previous works.Comment: 19 pages, no figure. v2:some minor corrections, refs added. v3:minor
changes and final in Nucl.Phys.
High-Energy Symmetry of Bosonic Open String Theory in the Light-like Linear Dilaton Background
High-energy limits of fixed-angle tree-level stringy scattering amplitudes in
the light-like linear dilaton background are calculated. Treating the time
component of the gradient of light-like dilaton field (V_0) as a moduli
parameter, we show that: (1) there exists a new fixed-point (V_0/E \to \infty)
in the moduli space of the bosonic open string theory, where a new high-energy
symmetry among scattering amplitudes can be identified, (2) this new symmetry
can be interpreted as a deformation of the flat-space high-energy symmetry, as
proposed by D. Gross. Hence, our results give a concrete illustration about the
relation between high-energy stringy symmetry and the background independent
formulation of string theory.Comment: 42pages, 3figures, 5tables, typos corrected, commments and reference
added
Functions of Some Capsular Polysaccharide Biosynthetic Genes in Klebsiella pneumoniae NTUH K-2044
The growing number of Klebsiella pneumoniae infections, commonly acquired in hospitals, has drawn great concern. It has been shown that the K1 and K2 capsular serotypes are the most detrimental strains, particularly to those with diabetes. The K1 cps (capsular polysaccharide) locus in the NTUH-2044 strain of the pyogenic liver abscess (PLA) K. pneumoniae has been identified recently, but little is known about the functions of the genes therein. Here we report characterization of a group of cps genes and their roles in the pathogenesis of K1 K. pneumoniae. By sequential gene deletion, the cps gene cluster was first re-delimited between genes galF and ugd, which serve as up- and down-stream ends, respectively. Eight gene products were characterized in vitro and in vivo to be involved in the syntheses of UDP-glucose, UDP-glucuronic acid and GDP-fucose building units. Twelve genes were identified as virulence factors based on the observation that their deletion mutants became avirulent or lost K1 antigenicity. Furthermore, deletion of kp3706, kp3709 or kp3712 (ΔwcaI, ΔwcaG or Δatf, respectively), which are all involved in fucose biosynthesis, led to a broad range of transcriptional suppression for 52 upstream genes. The genes suppressed include those coding for unknown regulatory membrane proteins and six multidrug efflux system proteins, as well as proteins required for the K1 CPS biosynthesis. In support of the suppression of multidrug efflux genes, we showed that these three mutants became more sensitive to antibiotics. Taken together, the results suggest that kp3706, kp3709 or kp3712 genes are strongly related to the pathogenesis of K. pneumoniae K1
Inhibition of cell motility by troglitazone in human ovarian carcinoma cell line
<p>Abstract</p> <p>Background</p> <p>Troglitazone (TGZ) is a potential anticancer agent. Little is known about the effect of this agent on cancer cell migration.</p> <p>Methods</p> <p>Human ovarian carcinoma cell line, ES-2 cells were treated with various concentrations of TGZ. Cell migration was evaluated by wound-healing and Boyden chamber transwell experiments. PPARγ expression was blocked by PPARγ small interfering RNA. The effects of TGZ on phosphorylation of FAK, PTEN, Akt were assessed by immunoblotting using phospho-specific antibodies. The cellular distribution of paxillin, vinculin, stress fiber and PTEN was assessed by immunocytochemistry.</p> <p>Results</p> <p>TGZ dose- and time-dependently impaired cell migration through a PPARγ independent manner. TGZ treatment impaired cell spreading, stress fiber formation, tyrosine phosphorylation of focal adhesion kinase (FAK), and focal adhesion assembly in cells grown on fibronectin substratum. TGZ also dose- and time-dependently suppressed FAK autophosphorylation and phosphorylation of the C-terminal of PTEN (a phosphatase). At concentration higher than 10 μM, TGZ caused accumulation of PTEN in plasma membrane, a sign of PTEN activation.</p> <p>Conclusion</p> <p>These results indicate that TGZ can suppress cultured ES-2 cells migration. Our data suggest that the anti-migration potential of TGZ involves in regulations of FAK and PTEN activity.</p
Genome-Wide Association Study of Young-Onset Hypertension in the Han Chinese Population of Taiwan
Young-onset hypertension has a stronger genetic component than late-onset counterpart; thus, the identification of genes related to its susceptibility is a critical issue for the prevention and management of this disease. We carried out a two-stage association scan to map young-onset hypertension susceptibility genes. The first-stage analysis, a genome-wide association study, analyzed 175 matched case-control pairs; the second-stage analysis, a confirmatory association study, verified the results at the first stage based on a total of 1,008 patients and 1,008 controls. Single-locus association tests, multilocus association tests and pair-wise gene-gene interaction tests were performed to identify young-onset hypertension susceptibility genes. After considering stringent adjustments of multiple testing, gene annotation and single-nucleotide polymorphism (SNP) quality, four SNPs from two SNP triplets with strong association signals (−log10(p)>7) and 13 SNPs from 8 interactive SNP pairs with strong interactive signals (−log10(p)>8) were carefully re-examined. The confirmatory study verified the association for a SNP quartet 219 kb and 495 kb downstream of LOC344371 (a hypothetical gene) and RASGRP3 on chromosome 2p22.3, respectively. The latter has been implicated in the abnormal vascular responsiveness to endothelin-1 and angiotensin II in diabetic-hypertensive rats. Intrinsic synergy involving IMPG1 on chromosome 6q14.2-q15 was also verified. IMPG1 encodes interphotoreceptor matrix proteoglycan 1 which has cation binding capacity. The genes are novel hypertension targets identified in this first genome-wide hypertension association study of the Han Chinese population
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