Showing papers by "Tata Institute of Fundamental Research published in 2008"

The CMS experiment at the CERN LHC

Abstract: The Compact Muon Solenoid (CMS) detector is described. The detector operates at the Large Hadron Collider (LHC) at CERN. It was conceived to study proton-proton (and lead-lead) collisions at a centre-of-mass energy of 14 TeV (5.5 TeV nucleon-nucleon) and at luminosities up to 10(34)cm(-2)s(-1) (10(27)cm(-2)s(-1)). At the core of the CMS detector sits a high-magnetic-field and large-bore superconducting solenoid surrounding an all-silicon pixel and strip tracker, a lead-tungstate scintillating-crystals electromagnetic calorimeter, and a brass-scintillator sampling hadron calorimeter. The iron yoke of the flux-return is instrumented with four stations of muon detectors covering most of the 4 pi solid angle. Forward sampling calorimeters extend the pseudo-rapidity coverage to high values (vertical bar eta vertical bar <= 5) assuring very good hermeticity. The overall dimensions of the CMS detector are a length of 21.6 m, a diameter of 14.6 m and a total weight of 12500 t.

Nonlinear fluid dynamics from gravity

Abstract: Black branes in AdS5 appear in a four parameter family labeled by their velocity and temperature. Promoting these parameters to Goldstone modes or collective coordinate fields—arbitrary functions of the coordinates on the boundary of AdS5—we use Einstein's equations together with regularity requirements and boundary conditions to determine their dynamics. The resultant equations turn out to be those of boundary fluid dynamics, with specific values for fluid parameters. Our analysis is perturbative in the boundary derivative expansion but is valid for arbitrary amplitudes. Our work may be regarded as a derivation of the nonlinear equations of boundary fluid dynamics from gravity. As a concrete application we find an explicit expression for the expansion of this fluid stress tensor including terms up to second order in the derivative expansion.

QCD equation of state with almost physical quark masses

Abstract: We present results on the equation of state in QCD with two light quark flavors and a heavier strange quark. Calculations with improved staggered fermions have been performed on lattices with temporal extent ${N}_{\ensuremath{\tau}}=4$ and 6 on a line of constant physics with almost physical quark mass values; the pion mass is about 220 MeV, and the strange quark mass is adjusted to its physical value. High statistics results on large lattices are obtained for bulk thermodynamic observables, i.e. pressure, energy and entropy density, at vanishing quark chemical potential for a wide range of temperatures, $140\text{ }\text{ }\mathrm{MeV}\ensuremath{\le}T\ensuremath{\le}800\text{ }\text{ }\mathrm{MeV}$. We present a detailed discussion of finite cutoff effects which become particularly significant for temperatures larger than about twice the transition temperature. At these high temperatures we also performed calculations of the trace anomaly on lattices with temporal extent ${N}_{\ensuremath{\tau}}=8$. Furthermore, we have performed an extensive analysis of zero temperature observables including the light and strange quark condensates and the static quark potential at zero temperature. These are used to set the temperature scale for thermodynamic observables and to calculate renormalized observables that are sensitive to deconfinement and chiral symmetry restoration and become order parameters in the infinite and zero quark mass limits, respectively.

Observation of a Resonancelike Structure in the π +- ψ ' Mass Distribution in Exclusive B→Kπ +- ψ ' Decays

Abstract: Reference EPFL-ARTICLE-154575doi:10.1103/PhysRevLett.100.142001View record in Web of Science Record created on 2010-11-05, modified on 2017-12-10

Ultraviolet Survey of CO and H2 in Diffuse Molecular Clouds: The Reflection of Two Photochemistry Regimes in Abundance Relationships

Abstract: We carried out a comprehensive far-UV survey of 12CO and H2 column densities along diffuse molecular Galactic sight lines. This sample includes new measurements of CO from HST spectra along 62 sight lines and new measurements of H2 from FUSE data along 58 sight lines. In addition, high-resolution optical data were obtained at the McDonald and European Southern Observatories, yielding new abundances for CH, CH+, and CN along 42 sight lines to aid in interpreting the CO results. These new sight lines were selected according to detectable amounts of CO in their spectra and provide information on both lower density (≤100 cm−3) and higher density diffuse clouds. A plot of -->log N(CO) versus -->log N(H2) shows that two power-law relationships are needed for a good fit of the entire sample, with a break located at -->log N(CO , cm −2) = 14.1 and -->log N(H2) = 20.4, corresponding to a change in production route for CO in higher density gas. Similar logarithmic plots among all five diatomic molecules reveal additional examples of dual slopes in the cases of CO versus CH (break at -->log N = 14.1, 13.0), CH+ versus H2 (13.1, 20.3), and CH+ versus CO (13.2, 14.1). We employ both analytical and numerical chemical schemes in order to derive details of the molecular environments. In the denser gas, where C2 and CN molecules also reside, reactions involving C+ and OH are the dominant factor leading to CO formation via equilibrium chemistry. In the low-density gas, where equilibrium chemistry studies have failed to reproduce the abundance of CH+, our numerical analysis shows that nonequilibrium chemistry must be employed for correctly predicting the abundances of both CH+ and CO.

Conformal Nonlinear Fluid Dynamics from Gravity in Arbitrary Dimensions

Abstract: We generalize recent work to construct a map from the conformal Navier Stokes equations with holographically determined transport coefficients, in d spacetime dimensions, to the set of asymptotically locally AdSd+1 long wavelength solutions of Einstein's equations with a negative cosmological constant, for all 2$>d>2. We find simple explicit expressions for the stress tensor (slightly generalizing the recent result by Haack and Yarom (arXiv:0806.4602)), the full dual bulk metric and an entropy current of this strongly coupled conformal fluid, to second order in the derivative expansion, for arbitrary 2$>d>2. We also rewrite the well known exact solutions for rotating black holes in AdSd+1 space in a manifestly fluid dynamical form, generalizing earlier work in d = 4. To second order in the derivative expansion, this metric agrees with our general construction of the metric dual to fluid flows.

Lhx2 selector activity specifies cortical identity and suppresses hippocampal organizer fate

Abstract: The earliest step in creating the cerebral cortex is the specification of neuroepithelium to a cortical fate. Using mouse genetic mosaics and timed inactivations, we demonstrated that Lhx2 acts as a classic selector gene and essential intrinsic determinant of cortical identity. Lhx2 selector activity is restricted to an early critical period when stem cells comprise the cortical neuroepithelium, where it acts cell-autonomously to specify cortical identity and suppress alternative fates in a spatially dependent manner. Laterally, Lhx2 null cells adopt antihem identity, whereas medially they become cortical hem cells, which can induce and organize ectopic hippocampal fields. In addition to providing functional evidence for Lhx2 selector activity, these findings show that the cortical hem is a hippocampal organizer.

Ultraviolet Survey of CO and H_2 in Diffuse Molecular Clouds: The Reflection of Two Photochemistry Regimes in Abundance Relationships

Abstract: (Abridged) We carried out a comprehensive far-ultraviolet (UV) survey of ^12CO and H_2 column densities along diffuse molecular Galactic sight lines in order to explore in detail the relationship between CO and H_2. We measured new CO abundances from HST spectra, new H_2 abundances from FUSE data, and new CH, CH^+, and CN abundances from the McDonald and European Southern Observatories. A plot of log N(CO) versus log N(H_2) shows that two power-law relationships are needed for a good fit of the entire sample, with a break located at log N(CO, cm^-2) = 14.1 and log N(H_2) = 20.4, corresponding to a change in production route for CO in higher-density gas. Similar logarithmic plots among all five diatomic molecules allow us to probe their relationships, revealing additional examples of dual slopes in the cases of CO versus CH (break at log N = 14.1, 13.0), CH^+ versus H_2 (13.1, 20.3), and CH^+ versus CO (13.2, 14.1). These breaks are all in excellent agreement with each other, confirming the break in the CO versus H_2 relationship, as well as the one-to-one correspondence between CH and H_2 abundances. Our new sight lines were selected according to detectable amounts of CO in their spectra and they provide information on both lower-density (< 100 cm^-3) and higher-density diffuse clouds. The CO versus H_2 correlation and its intrinsic width are shown to be empirically related to the changing total gas density among the sight lines of the sample. We employ both analytical and numerical chemical schemes in order to derive details of the molecular environments. In the low-density gas, where equilibrium-chemistry studies have failed to reproduce the abundance of CH^+, our numerical analysis shows that nonequilibrium chemistry must be employed for correctly predicting the abundances of both CH^+ and CO.

Measurement of the inclusive jet cross section in pp̄ collisions at s=1.96TeV

Abstract: We report on a measurement of the inclusive jet cross section in p (p) over bar collisions at a center-of-mass energy root s = 1.96 TeV using data collected by the D0 experiment at the Fermilab Tevatron Collider corresponding to an integrated luminosity of 0: 70 fb(-1). The data cover jet transverse momenta from 50 to 600 GeV and jet rapidities in the range -2.4 to 2.4. Detailed studies of correlations between systematic uncertainties in transverse momentum and rapidity are presented, and the cross section measurements are found to be in good agreement with next-to-leading order QCD calculations.

Indices for Superconformal Field Theories in 3,5 and 6 Dimensions

Abstract: We present a trace formula for a Witten type Index for superconformal field theories in d=3,5 and 6 dimensions, generalizing a similar recent construction in d=4. We perform a detailed study of the decomposition of long representations into sums of short representations at the unitarity bound to demonstrate that our trace formula yields the most general index (i.e. quantity that is guaranteed to be protected by superconformal symmetry alone) for the corresponding superalgebras. Using the dual gravitational description, we compute our index for the theory on the world volume of N M2 and M5 branes in the large N limit. We also compute our index for recently constructed Chern Simons theories in three dimensions in the large N limit, and find that, in certain cases, this index undergoes a large N phase transition as a function of chemical potentials.

Indices for Superconformal Field Theories in 3,5 and 6 Dimensions

Abstract: We present a trace formula for a Witten type Index for superconformal field theories in d = 3, 5 and 6 dimensions, generalizing a similar recent construction in d = 4. We perform a detailed study of the decomposition of long representations into sums of short representations at the unitarity bound to demonstrate that our trace formula yields the most general index (i.e. quantity that is guaranteed to be protected by superconformal symmetry alone) for the corresponding superalgebras. Using the dual gravitational description, we compute our index for the theory on the world volume of N M2 and M5 branes in the large N limit. We also compute our index for recently constructed Chern Simons theories in three dimensions in the large N limit, and find that, in certain cases, this index undergoes a large N phase transition as a function of chemical potentials.

Local fluid dynamical entropy from gravity

Abstract: Spacetime geometries dual to arbitrary fluid flows in strongly coupled = 4 super Yang Mills theory have recently been constructed perturbatively in the long wavelength limit. We demonstrate that these geometries all have regular event horizons, and determine the location of the horizon order by order in a boundary derivative expansion. Intriguingly, the derivative expansion allows us to determine the location of the event horizon in the bulk as a local function of the fluid dynamical variables. We define a natural map from the boundary to the horizon using ingoing null geodesics. The area-form on spatial sections of the horizon can then be pulled back to the boundary to define a local entropy current for the dual field theory in the hydrodynamic limit. The area theorem of general relativity guarantees the positivity of the divergence of the entropy current thus constructed.

ARF1 is directly involved in dynamin-independent endocytosis

Abstract: Endocytosis of glycosylphosphatidyl inositol (GPI)-anchored proteins (GPI-APs) and the fluid phase takes place primarily through a dynamin- and clathrin-independent, Cdc42-regulated pinocytic mechanism. This mechanism is mediated by primary carriers called clathrin-independent carriers (CLICs), which fuse to form tubular early endocytic compartments called GPI-AP enriched endosomal compartments (GEECs). Here, we show that reduction in activity or levels of ARF1 specifically inhibits GPI-AP and fluid-phase endocytosis without affecting other clathrin-dependent or independent endocytic pathways. ARF1 is activated at distinct sites on the plasma membrane, and by the recruitment of RhoGAP domain-containing protein, ARHGAP10, to the plasma membrane, modulates cell-surface Cdc42 dynamics. This results in the coupling of ARF1 and Cdc42 activity to regulate endocytosis at the plasma membrane. These findings provide a molecular basis for a crosstalk of endocytosis with secretion by the sharing of a key regulator of secretory traffic, ARF1.

QCD at finite chemical potential with six time slices

Abstract: We investigate the Taylor expansion of the baryon number susceptibility, and hence, pressure, in a series in the baryon chemical potential (${\ensuremath{\mu}}_{B}$) through a lattice simulation with two flavors of light dynamical staggered quarks at a finer lattice cutoff $a=1/6T$. We determine the QCD cross over coupling at ${\ensuremath{\mu}}_{B}=0$. We find the radius of convergence of the series at various temperatures, and bound the location of the QCD critical point to be ${T}^{E}/{T}_{c}\ensuremath{\approx}0.94$ and ${\ensuremath{\mu}}_{B}^{E}/Tl1.8$. We also investigate the extrapolation of various susceptibilities and linkages to finite chemical potential.

Local Fluid Dynamical Entropy from Gravity

Abstract: Spacetime geometries dual to arbitrary fluid flows in strongly coupled N=4 super Yang Mills theory have recently been constructed perturbatively in the long wavelength limit. We demonstrate that these geometries all have regular event horizons, and determine the location of the horizon order by order in a boundary derivative expansion. Intriguingly, the derivative expansion allows us to determine the location of the event horizon in the bulk as a local function of the fluid dynamical variables. We define a natural map from the boundary to the horizon using ingoing null geodesics. The area-form on spatial sections of the horizon can then be pulled back to the boundary to define a local entropy current for the dual field theory in the hydrodynamic limit. The area theorem of general relativity guarantees the positivity of the divergence of the entropy current thus constructed.

M2-branes on M-folds

Abstract: We argue that the moduli space for the Bagger-Lambert A4 theory at level k is (8 × 8)/D2k, where D2k is the dihedral group of order 4k. We conjecture that the theory describes two M2-branes on a 2k ``M-fold'', in which a geometrical action of 2k is combined with an action on the branes. For k = 1, this arises as the strong coupling limit of two D2-branes on an O2− orientifold, whose worldvolume theory is the maximally supersymmetric SO(4) gauge theory. Finally, in an appropriate large-k limit we show that one recovers compactified M-theory and the M2-branes reduce to D2-branes.

Measurement of Bs0 Mixing Parameters from the Flavor-Tagged Decay Bs0→J/ψ

Abstract: From an analysis of the flavor-tagged decay B-s(0)-> J/psi phi we obtain the width difference between the B-s(0) light and heavy mass eigenstates, Delta Gamma(s)=0.19 +/- 0.07(stat)(-0.01)(+0.02)(syst) ps(-1), and the CP-violating phase, phi(s)=-0.57(-0.30)(+0.24)(stat)(-0.02)(+0.08)(syst). The allowed 90% CL intervals of Delta Gamma(s) and phi(s) are 0.06

Measurement of the forward-backward charge asymmetry in top-quark pair production

Abstract: We present the first measurement of the integrated forward-backward charge asymmetry in top-quark-top-antiquark pair (t (t) over bar) production in proton-antiproton (p (p) over bar) collisions in the lepton+jets final state. Using a b-jet tagging algorithm and kinematic reconstruction assuming t (t) over bar +X production and decay, a sample of 0.9 fb(-1) of data, collected by the D0 experiment at the Fermilab Tevatron Collider, is used to measure the asymmetry for different jet multiplicities. The result is also used to set upper limits on t (t) over bar +X production via a Z' resonance.

Forced Fluid Dynamics from Gravity

Abstract: We generalise the computations of arXiv:0712.2456 to generate long wavelength, asymptotically locally AdS_5 solutions to the Einstein-dilaton system with a slowly varying boundary dilaton field and a weakly curved boundary metric. Upon demanding regularity, our solutions are dual, under the AdS/CFT correspondence, to arbitrary fluid flows in the boundary theory formulated on a weakly curved manifold with a prescribed slowly varying coupling constant. These solutions turn out to be parametrised by four-velocity and temperature fields that are constrained to obey the boundary covariant Navier Stokes equations with a dilaton dependent forcing term. We explicitly evaluate the stress tensor and Lagrangian as a function of the velocity, temperature, coupling constant and curvature fields, to second order in the derivative expansion and demonstrate the Weyl covariance of these expressions. We also construct the event horizon of the dual solutions to second order in the derivative expansion, and use the area form on this event horizon to construct an entropy current for the dual fluid. As a check of our constructions we expand the exactly known solutions for rotating black holes in global AdS_5 in a boundary derivative expansion and find perfect agreement with all our results upto second order. We also find other simple solutions of the forced fluid mechanics equations and discuss their bulk interpretation. Our results may aid in determining a bulk dual to forced flows exhibiting steady state turbulence.

Large rotating AdS black holes from fluid mechanics

Abstract: We use the AdS/CFT correspondence to argue that large rotating black holes in global AdSD spaces are dual to stationary solutions of the relativistic Navier-Stokes equations on SD−2. Reading off the equation of state of this fluid from the thermodynamics of non-rotating black holes, we proceed to construct the nonlinear spinning solutions of fluid mechanics that are dual to rotating black holes. In all known examples, the thermodynamics and the local stress tensor of our solutions are in precise agreement with the thermodynamics and boundary stress tensor of the spinning black holes. Our fluid dynamical description applies to large non-extremal black holes as well as a class of large non-supersymmetric extremal black holes, but is never valid for supersymmetric black holes. Our results yield predictions for the thermodynamics of all large black holes in all theories of gravity on AdS spaces, for example, string theory on AdS5 × S5 and M theory on AdS4 × S7 and AdS7 × S4.

Shock acceleration as origin of the radio relic in A 521

Abstract: Aims. We present new high sensitivity observations of the radio relic in A521 carried out with the Giant Metrewave Radio Telescope at 327 MHz and with the Very Large Array at 4.9 and 8.5 GHz. Methods. We imaged the relic at these frequencies and carried out a detailed spectral analysis, based on the integrated radio spectrum between 235 MHz and 4.9 GHz, and on the spectral index image in the frequency range 327–610 MHz. To this aim we used the new GMRT observations and other proprietary as well as archival data. We also searched for a possible shock front co–located with the relic on a short archival Chandra X–ray observation of the cluster. Results. The integrated spectrum of the relic is consistent with a single power law; the spectral index image shows a clear trend of steepening going from the outer portion of the relic toward the cluster centre. We discuss the origin of the source in the light of the theoretical models for the formation of cluster radio relics. Our results on the spectral properties of the relic are consistent with acceleration of relativistic electrons by a shock in the intracluster medium. This scenario is further supported by our finding of an X–ray surface brightness edge coincident with the outer border of the radio relic. This edge is likely a shock front.

Production of new charmoniumlike states in e+e-→J/ψD(*) D̄(*) at s 10.6GeV

Abstract: We report a study of the processes e+e-→J/ψD(*)D(*). In J/ψD*D* we observe a significant enhancement in the D*D* invariant mass spectrum, which we interpret as a new charmoniumlike state and denote X(4160). The X(4160) parameters are M=(4156-20+25±15)MeV/c2 and Γ=(139-61+111±21)MeV. We also report a new measurement of the X(3940) mass and width: M=(3942-6+7±6) MeV/c2 and Γ=(37-15+26±8)MeV. The analysis is based on a 693fb-1 data sample recorded near the Υ(4S) resonance by the Belle detector at the KEKB asymmetric-energy collider. © 2008 The American Physical Society.

Superconducting properties and Hall effect of epitaxial NbN thin films

Abstract: We have measured the magnetotransport properties and Hall effect of a series of epitaxial NbN films grown on (100) oriented single crystalline MgO substrate under different conditions using reactive magnetron sputtering. Hall effect measurements reveal that the carrier density in NbN thin films is sensitive to the growth condition. The carrier density increases by a factor of 3 between the film with highest normal state resistivity $({\ensuremath{\rho}}_{n}\ensuremath{\sim}3.83\text{ }\ensuremath{\mu}\ensuremath{\Omega}\text{ }\text{m})$ and lowest transition temperature $({T}_{c}\ensuremath{\sim}9.99\text{ }\text{K})$ and the film with lowest normal state resistivity $({\ensuremath{\rho}}_{n}\ensuremath{\sim}0.94\text{ }\ensuremath{\mu}\ensuremath{\Omega}\text{ }\text{m})$ and highest transition temperature $({T}_{c}\ensuremath{\sim}16.11\text{ }\text{K})$, while the mobility of carriers does not change significantly. Our results show that ${T}_{c}$ of NbN is governed primarily by the carrier density rather than disorder scattering. By varying the carrier concentration during growth, we can vary the effective disorder $({k}_{F}l)$ from the moderately clean limit to the dirty limit, which makes this system ideal to study the interplay of carrier density and disorder on the superconducting properties of an $s$-wave superconductor.

The Local Group dwarf Leo T: H i on the brink of star formation

Abstract: We present Giant Meterwave Radio Telescope (GMRT) andWesterbork Synthesis Radio Telescope (WSRT) observations of the recently discovered Local Group dwarf galaxy, Leo T. The peak HI column density is measured to be 7 x 1020 cm(-2), and the total HI mass is 2.8 x 10(5) M-circle dot,, based on a distance of 420 kpc. Leo T has both cold (similar to 500 K) and warm (similar to 6000 K) HI at its core, with a global velocity dispersion of 6.9 km s(-1), from which we derive a dynamical mass within the HI radius of 3.3 x 10(6) M-circle dot, and a mass-to-light ratio of > 50. We calculate the Jeans mass from the radial profiles of the HI column density and velocity dispersion, and predict that the gas should be globally stable against star formation. This finding is inconsistent with the half light radius of Leo T, which extends to 170 pc, and indicates that local conditions must determine where star formation takes place. Leo T is not only the lowest luminosity galaxy with on-going star formation discovered to date, but it is also the most dark matter-dominated, gas-rich dwarf in the Local Group.

Collective three-flavor oscillations of supernova neutrinos

Abstract: Neutrinos and antineutrinos emitted from a core collapse supernova interact among themselves, giving rise to collective flavor conversion effects that are significant near the neutrinosphere. We develop a formalism to analyze these collective effects in the complete three-flavor framework. It naturally generalizes the spin-precession analogy to three flavors and is capable of analytically describing phenomena like vacuum/Mikheyev-Smirnov-Wolfenstein (MSW) oscillations, synchronized oscillations, bipolar oscillations, and spectral split. Using the formalism, we demonstrate that the flavor conversions may be ``factorized'' into two-flavor oscillations with hierarchical frequencies. We explicitly show how the three-flavor solution may be constructed by combining two-flavor solutions. For a typical supernova density profile, we identify an approximate separation of regions where distinctly different flavor conversion mechanisms operate, and demonstrate the interplay between collective and MSW effects. We pictorialize our results in terms of the ``${\mathbf{e}}_{3}\mathrm{\text{\ensuremath{-}}}{\mathbf{e}}_{8}$ triangle'' diagram, which is a tool that can be used to visualize three-neutrino flavor conversions in general, and offers insights into the analysis of the collective effects in particular.

Comments on the spectrum of CHL dyons

Abstract: We address a number of puzzles relating to the proposed formulae for the degeneracies of dyons in orbifold compactifications of the heterotic string to four dimensions with = 4 supersymmetry. The partition function for these dyons is given in terms of Siegel modular forms associated with genus-two Riemann surfaces. We point out a subtlety in demonstrating S-duality invariance of the resulting degeneracies and give a prescription that makes the invariance manifest. We show, using M-theory lift of string webs, that the genus-two contribution captures the degeneracy only if a specific irreducibility criterion is satisfied by the charges. Otherwise, in general there can be additional contributions from higher genus Riemann surfaces. We analyze the negative discriminant states predicted by the formula. We show that even though there are no big black holes in supergravity corresponding to these states, there are multi-centered particle-like configurations with subleading entropy in agreement with the microscopic prediction and our prescription for S-duality invariance. The existence of the states is moduli dependent and we exhibit the curves of marginal stability and comment on its relation to S-duality invariance.

Effect of cessation of tobacco use on the incidence of oral mucosal lesions in a 10-yr follow-up study of 12,212 users.

Abstract: OBJECTIVE: To study the effect of cessation of tobacco use on the incidence of lichen planus, leukoplakia and other oral mucosal lesions. DESIGN: A 10–yr cohort study in a rural population of Ernakulam district, Kerala, India. MATERIAL AND METHODS: Some 12 212 tobacco users were interviewed and examined in a basetine survey and re-examined annually for 10 years. At each examination they were exposed to health educational programs to encourage them to quit their tobacco use. The incidence rates were calculated using person-years method among those who stopped their tobacco use and all others. RESULTS: A total of 77 681 person-years of observation accrued among men and 32 544 among women. Among men 6.5% of these and among women 14.4% were in the stopped category. The incidence of oral lichen planus did not show any consistent association with cessation of tobacco habits (incidence ratio I.35) but for leukoplakia there was a substantial drop in the incidence after cessation (incidence ratio 0.3I). Several other tobacco-associated oral mucosal lesions such as oral lichen planus-like lesion, smoker's palate, preteukoplakia, central papillary atrophy of the tongue and leukoedema showed either zero, or very small incidence, after cessation. CONCLUSION: The reported association between tobacco use and lichen planus appears to be indirect but for all other lesions it is direct. The cessation of tobacco use led to a substantial fall in the incidence of leukoplakia and other lesions implying a reduced risk for oral cancer after cessation of tobacco use.

An on-line learning algorithm for energy efficient delay constrained scheduling over a fading channel

Abstract: In this paper, we consider the problem of energy efficient scheduling under average delay constraint for a single user fading channel. We propose a new approach for on-line implementation of the optimal packet scheduling algorithm. This approach is based on reformulating the value iteration equation by introducing a virtual state called post-decision state. The resultant value iteration equation becomes amenable to online implementation based on stochastic approximation. This approach has an advantage that an explicit knowledge of the probability distribution of the channel state as well as the arrivals is not required for the implementation. We prove that the on-line algorithm indeed converges to the optimal policy.