Extension of TSVM to multi-class and hierarchical text classification problems With general losses

Transductive SVM (TSVM) is a well known semi-supervised large margin learning method for binary text classification. In this paper we extend this method to multi-class and hierarchical classification problems. We point out that the determination of labels of unlabeled examples with fixed classifier weights is a linear programming problem. We devise an efficient technique for solving it. The method is applicable to general loss functions. We demonstrate the value of the new method using large margin loss on a number of multi-class and hierarchical classification datasets. For maxent loss we show empirically that our method is better than expectation regularization/constraint and posterior regularization methods, and competitive with the version of entropy regularization method which uses label constraints.

High-resolution restoration of 3D structures from widefield images with extreme low signal-to-noise-ratio

Four-dimensional fluorescence microscopy-which records 3D image information as a function of time-provides an unbiased way of tracking dynamic behavior of subcellular components in living samples and capturing key events in complex macromolecular processes. Unfortunately, the combination of phototoxicity and photobleaching can severely limit the density or duration of sampling, thereby limiting the biological information that can be obtained. Although widefield microscopy provides a very light-efficient way of imaging, obtaining high-quality reconstructions requires deconvolution to remove optical aberrations. Unfortunately, most deconvolution methods perform very poorly at low signal-to-noise ratios, thereby requiring moderate photon doses to obtain acceptable resolution. We present a unique deconvolution method that combines an entropy-based regularization function with kernels that can exploit general spatial characteristics of the fluorescence image to push the required dose to extreme low levels, resulting in an enabling technology for high-resolution in vivo biological imaging.

Strong-coupling expansion for ultracold bosons in an optical lattice at finite temperatures in the presence of superfluidity

We develop a strong-coupling (t << U) expansion technique for calculating the density profile for bosonic atoms trapped in an optical lattice with an overall harmonic trap at finite temperature and finite on-site interaction in the presence of superfluid regions. Our results match well with quantum Monte Carlo simulations at finite temperature. We also show that the superfluid order parameter never vanishes in the trap due to the proximity effect. Our calculations for the scaled density in the vacuum-to-superfluid transition agree well with the experimental data for appropriate temperatures. We present calculations for the entropy per particle as a function of temperature which can be used to calibrate the temperature in experiments. We also discuss issues connected with the demonstration of universal quantum critical scaling in the experiments.

Gibbs free energy of formation of rhodium sulfides

Using a solid-state electrochemical technique, thermodynamic properties of three sulfide phases (RhS0.882, Rh3S4, Rh2S3) in the binary system (Rh + S) are measured as a function of temperature over the range from (925 to 1275) K. Single crystal CaF2 is used as the electrolyte. The auxiliary electrode consisting of (CaS + CaF2) is designed in such a way that the sulfur chemical potential converts into an equivalent fluorine potential at each electrode. The sulfur potentials at the measuring electrodes are established by the mixtures of (Rh + RhS0.882), (RhS0.882 + Rh3S4) and (Rh3S4 + Rh2S3) respectively. A gas mixture (H-2 + H2S + Ar) of known composition fixes the sulfur potential at the reference electrode. A novel cell design with physical separation of rhodium sulfides in the measuring electrode from CaS in the auxiliary electrode is used to prevent interaction between the two sulfide phases. They equilibrate only via the gas phase in a hermetically sealed reference enclosure. Standard Gibbs energy changes for the following reactions are calculated from the electromotive force of three cells: 2.2667Rh (s) + S-2 (g) -> 2.2667RhS(0.882) (s), Delta(r)G degrees +/- 2330/(J . mol(-1)) = -288690 + 146.18 (T/K), 4.44RhS(0.882) (s) + S-2 (g) -> 1.48Rh(3)S(4) (s), Delta(r)G degrees +/- 2245/(J . mol(-1)) = -245596 + 164.31 (T/K), 4Rh(3)S(4) (s) + S-2 (g) -> 6Rh(2)S(3) (s), Delta(r)G degrees +/- 2490/(J . mol(-1)) = -230957 + 160: 03 (T/K). Standard entropy and enthalpy of formation of rhodium sulfides from elements in their normal standard states at T = 298.15 K are evaluated. (C) 2013 Elsevier Ltd. All rights reserved.

Electrocaloric Effect in 0.85PMN-0.15PT Thin Films Deposited by Pulsed Laser Deposition

The electrocaloric effect (ECE) of 0.85PbMg(1/3)Nb(2/3)O(3-)0.15PbTiO(3) (0.85PMN-0.15PT) thin films deposited on (111) Pt/TiO2/SiO2/Si substrate by pulsed laser deposition (PLD) has been calculated. The reversible adiabatic temperature was calculated indirectly using the Maxwell's relation Delta T = -T/C rho integral(E2)(E1) (partial derivative P/partial derivative T)(sigma,E)dE. Permittivity and P-E measurements show an anomaly at 11 degrees C on heating only. This anomaly previously reported are claimed to arise due to the PNR depolarization upon heating. The absence of this anomaly during cooling suggests that no structural phase transition takes place. A negative electrocaloric effect is observed which is explained by the increase in the entropy term.

Thermodynamic Properties of LaCrO4, La2CrO6, and La2Cr3O12, and Subsolidus Phase Relations in the System Lanthanum-Chromium-Oxygen

In the system La-Cr-O, there are three ternary oxides (LaCrO4, La2Cr3O12, and La2CrO6) that contain Cr in higher valence states (V or VI). On heating, LaCrO4 decomposes to LaCrO3, La2Cr3O12 to a mixture of LaCrO4 and Cr2O3, and La2CrO6 to LaCrO3 and La2O3 with loss of oxygen. The oxygen potentials corresponding to these decomposition reactions are determined as a function of temperature using solid-state cells incorporating yttria-stabilized zirconia as the electrolyte. Measurements are made from 840K to the decomposition temperature of the ternary oxides in pure oxygen. The standard Gibbs energies of formation of the three ternary oxides are derived from the reversible electromotive force (EMF) of the three cells. The standard enthalpy of formation and standard entropy of the three ternary oxides at 298.15K are estimated. Subsolidus phase relations in the system La-Cr-O are computed from thermodynamic data and displayed as isothermal sections at several temperature intervals. The decomposition temperatures in air are 880 (+/- 3)K for La2Cr3O12, 936 (+/- 3)K for LaCrO4, and 1056 (+/- 4)K for La2CrO6.

Electrochemical Determination of Gibbs Energy of Formation of LaCrO3 Using a Composition-Graded Bielectrolyte

Presented are new measurements of the standard Gibbs free energy of formation of rhombohedral LaCrO3 from component oxides La2O3 and Cr2O3 in the temperature range from 875 to 1175K, using a bielectrolyte solid-state cell incorporating single crystal CaF2 and composition-graded solid electrolyte (LaF3)(y)(CaF2)(1-y) (y=0-0.32). The results can be represented analytically as Delta G(f(ox))(o) (+/- 2270)/Jmol(-1)=-72329+4.932 (T/K). The measurements were undertaken to resolve serious discrepancies in the data reported in the literature. A critical analysis of previous electrochemical measurements indicates several deficiencies that have been rectified in this study. The enthalpy of formation obtained in this study is consistent with calorimetric data. The standard enthalpy of formation of orthorhombic LaCrO3 from elements at 298.15K computed from the results of this study is Delta H-f(298.15)(o)/kJmol(-1)=-1536.2 (+/- 7). The standard entropy of orthorhombic LaCrO3 at 298.15K is estimated as 99.0 (+/- 4.5)J(molK)(-1).

Cooperativity and Structural Relaxations in PVDF/PMMA Blends in the Presence of MWNTs: An Assessment through SAXS and Dielectric Spectroscopy

Intermolecular cooperativity and structural relaxations in PVDF/PMMA blends were studied in this work with respect to different surface modified (amine, similar to NH2; carboxyl acid, similar to COOH and pristine) multiwalled nanotubes (MWNTs) at 1 wt % near blend's T-g and in the vicinity of demixing using dielectric spectroscopy, SAXS, DSC, and WAXD. Intermolecular cooperativity at T-g and configurational entropy was addressed in the framework of cooperative rearranging region (CRR) at T-g. Because of specific interactions between PVDF and NH2-MWNTs, the local composition fluctuates at its average value resulting in a broad T-g. The scale of cooperativity (xi(CRR)) and the number of segments in the cooperative volume (N-CRR) is comparatively smaller in the blends with NH2-MWNTs. This clearly suggests that the number of segments cooperatively relaxing is reduced in the blends due to specific interactions leading to more heterogeneity. The configurational entropy at T-g, as derived from Vogel-Fulcher and Adam-Gibbs analysis, was reduced in the blends in presence of MWNTs manifesting in entropic penalty of the chains. The crystallite size and the amorphous miscibility was evaluated using SAXS and was observed to be strongly contingent on the surface functional groups on MWNTs. Three distinct relaxations-alpha(c) due to relaxations in the crystalline phase of PVDF, alpha(m) indicating the amorphous miscibility in PVDF/PMMA blends, and alpha beta concerning the segmental dynamics of PMMA-were observed in the blends in the temperature range T-g < T < T-c. The dynamics as well as the nature of relaxations were observed to be dependent the surface functionality on the MWNTs. The dielectric permittivity was also enhanced in presence of MWNTs, especially with NH2-MWNTs, with minimal losses. The influence of the MWNTs on the spherulite size and crystalline morphology of the blends was also confirmed by POM and SEM.

Fermionic superfluid from a bilayer band insulator in an optical lattice

We propose a model to realize a fermionic superfluid state in an optical lattice circumventing the cooling problem. Our proposal exploits the idea of tuning the interaction in a characteristically low-entropy state, a band insulator in an optical bilayer system, to obtain a superfluid. By performing a detailed analysis of the model including fluctuations and augmented by a variational quantum Monte Carlo calculation of the ground state, we show that the superfluid state obtained has a high transition temperature of the order of the hopping energy. Our system is designed to suppress other competing orders such as a charge density wave. We suggest a laboratory realization of this model via an orthogonally shaken optical lattice bilayer.

Renyi entropies of free bosons on the torus and holography

We analytically evaluate the Renyi entropies for the two dimensional free boson CFT. The CFT is considered to be compactified on a circle and at finite temperature. The Renyi entropies S-n are evaluated for a single interval using the two point function of bosonic twist fields on a torus. For the case of the compact boson, the sum over the classical saddle points results in the Riemann-Siegel theta function associated with the A(n-1) lattice. We then study the Renyi entropies in the decompactification regime. We show that in the limit when the size of the interval becomes the size of the spatial circle, the entanglement entropy reduces to the thermal entropy of free bosons on a circle. We then set up a systematic high temperature expansion of the Renyi entropies and evaluate the finite size corrections for free bosons. Finally we compare these finite size corrections both for the free boson CFT and the free fermion CFT with the one-loop corrections obtained from bulk three dimensional handlebody spacetimes which have higher genus Riemann surfaces as its boundary. One-loop corrections in these geometries are entirely determined by quantum numbers of the excitations present in the bulk. This implies that the leading finite size corrections contributions from one-loop determinants of the Chern-Simons gauge field and the Dirac field in the dual geometry should reproduce that of the free boson and the free fermion CFT respectively. By evaluating these corrections both in the bulk and in the CFT explicitly we show that this expectation is indeed true.

Insight into instabilities in burning droplets

The complex multiscale physics of nano-particle laden functional droplets in a reacting environment is of fundamental and applied significance for a wide variety of applications ranging from thermal sprays to pharmaceutics to modern day combustors using new brands of bio-fuels. Formation of homogenous nucleated bubbles at the superheat limit inside vaporizing droplets (with or without nanoparticles) represents an unstable system. Here we show that self-induced boiling in burning functional pendant droplets can produce severe volumetric shape oscillations. Internal pressure build-up due to ebullition activity ejects bubbles from the droplet domain causing undulations on the droplet surface and oscillations in bulk. Through experiments, we establish that the degree of droplet deformation depends on the frequency and intensity of these bubble expulsion events. In a distinct regime of single isolated bubble residing in the droplet, however, pre-ejection transient time is identified by Darrieus-Landau evaporative instability, where bubble-droplet system behaves as a synchronized driver-driven system with bulk bubble-shape oscillations being imposed on the droplet. The agglomeration of nanophase additives modulates the flow structures within the droplet and also influences the bubble inception and growth leading to different levels of instabilities. (C) 2014 AIP Publishing LLC.

Constraining gravity using entanglement in AdS/CFT

We investigate constraints imposed by entanglement on gravity in the context of holography. First, by demanding that relative entropy is positive and using the Ryu-Takayanagi entropy functional, we find certain constraints at a nonlinear level for the dual gravity. Second, by considering Gauss-Bonnet gravity, we show that for a class of small perturbations around the vacuum state, the positivity of the two point function of the field theory stress tensor guarantees the positivity of the relative entropy. Further, if we impose that the entangling surface closes off smoothly in the bulk interior, we find restrictions on the coupling constant in Gauss-Bonnet gravity. We also give an example of an anisotropic excited state in an unstable phase with broken conformal invariance which leads to a negative relative entropy.

Non-equilibrium segmental dynamics driven by multiwall carbon nanotubes in PS/PVME blends

The present paper discusses the effect of multiwall carbon nanotubes (MWNTs) on the structural relaxation and the intermolecular cooperativity in dynamically asymmetric blends of PS/PVME (polystyrene/poly(vinyl methyl ether)). The temperature regime where chain connectivity effects dominate the thermodynamic concentration fluctuation (T/T-g > 0.75, T-g is the glass transition temperature of the blends) was studied using dielectric spectroscopy (DS). Interestingly, in the blends with MWNTs a bimodal distribution of relaxation was obtained in the loss modulus spectra. This plausibly is due to different environments experienced by the faster component (PVME) in the presence of MWNTs. The segmental dynamics of PVME was observed to be significantly slowed down in the presence of MWNTs and an Arrhenius-type behavior, weakly dependent on temperature, is observed at higher frequencies. This non-equilibrium dynamics of PVME is presumed to be originating from interphase regions near the surface of MWNTs. The length scale of the cooperative rearranging region (xi CRR) at T-g, assessed by calorimetric measurements, was observed to be higher in the case of blends with MWNTs. An enhanced molecular level miscibility driven by MWNTs in the blends corroborates with the larger xi CRR and comparatively more number of segments in CRR (in contrast to neat blends) around T-g. The configurational entropy and length scale of the cooperative volume was mapped as a function of temperature in the temperature regime, Tg < T < T-g + 60 K. The blends phase separated by spinodal decomposition which further led to an interconnected PVME network in PS. This further led to materials with very high electrical conductivity upon demixing.

INDUCTION OF FOLDED STRUCTURES IN DESIGNED PEPTIDES USING CONFORMATIONALLY CONSTRAINED RESIDUES

Folding into compact globular structures, with well-defined modules of secondary structure, appears to be a characteristic of long polypeptide chains, with a specific patterning of coded amino acid residues along the length of sequence. Cooperative hydrogen bond driven secondary structure formation and solvent forces, which contribute favorably to the entropy of folding, by promoting compaction of the polymeric chain, have long been discussed as major determinants of the folding process. First principles design approaches, which use non-coded amino acids, employ an alternative structure directing strategy, by using amino acid residues which exhibit a strong conformational bias for specific regions of the Ramachandran map. This overview of ongoing studies in the authors' laboratory, attempts to explore the use of conformationally restricted amino acid residues in the design of peptides with well-defined secondary structures. Short peptides composed of 20 genetically coded amino acids usually exist in solution as an ensemble of equilibrating conformations. Apolar peptide sequences, which are readily soluble in organic solvents like chloroform and methanol, facilitate formation of structures which are predominately driven by intramolecular hydrogen bond formation. The choice of sequences containing residues with a limited range of conformational choices strongly favors formation of local turn structures, stabilized by short range intramolecular hydrogen bonds. Two residue beta-turns can nucleate either helical or hairpin folding, depending on the precise conformation of the turn segment Restriction of the conformational space available to amino acid residues is easily achieved by introduction of an additional alkyl group at the C alpha carbon atom or by side chain backbone cyclization, as in proline. Studies of synthetic sequences incorporating two prototype residues alpha-aminoisobutyric acid (Aib) and D-proline (DPro) illustrate the utility of the strategy in construction of helices and hairpins. Extensions to the design of conformationally switchable sequences and structurally defined hybrid peptides containing backbone homologated residues are also surveyed.

Studies on a frustrated Heisenberg spin chain with alternating ferromagnetic and antiferromagnetic exchanges

We study Heisenberg spin-1/2 and spin-1 chains with alternating ferromagnetic (J(1)(F)) and antiferromagnetic (J(1)(A)) nearest-neighbor interactions and a ferromagnetic next-nearest-neighbor interaction (J(2)(F)). In this model frustration is present due to the non-zero J(2)(F). The model with site spin s behaves like a Haldane spin chain, with site spin 2s in the limit of vanishing J(2)(F) and large J(1)(F)/J(1)(A). We show that the exact ground state of the model can be found along a line in the parameter space. For fixed J(1)(F), the phase diagram in the space of J(1)(A)-J(2)(F) is determined using numerical techniques complemented by analytical calculations. A number of quantities, including the structure factor, energy gap, entanglement entropy and zero temperature magnetization, are studied to understand the complete phase diagram. An interesting and potentially important feature of this model is that it can exhibit a macroscopic magnetization jump in the presence of a magnetic field; we study this using an effective Hamiltonian.