Dictionary learning and sparse coding on Grassmann manifolds : an extrinsic solution

Recent advances in computer vision and machine learning suggest that a wide range of problems can be addressed more appropriately by considering non-Euclidean geometry. In this paper we explore sparse dictionary learning over the space of linear subspaces, which form Riemannian structures known as Grassmann manifolds. To this end, we propose to embed Grassmann manifolds into the space of symmetric matrices by an isometric mapping, which enables us to devise a closed-form solution for updating a Grassmann dictionary, atom by atom. Furthermore, to handle non-linearity in data, we propose a kernelised version of the dictionary learning algorithm. Experiments on several classification tasks (face recognition, action recognition, dynamic texture classification) show that the proposed approach achieves considerable improvements in discrimination accuracy, in comparison to state-of-the-art methods such as kernelised Affine Hull Method and graph-embedding Grassmann discriminant analysis.

A mass spectrometry study of XCO+, X = Si, Ge : Is SiCO+ a main group carbonyl? Comments on the bonding in ground state SiCO and the Si,C,O (+) potential energy surface

The cation\[Si,C,O](+) has been generated by 1) the electron ionisation (EI) of tetramethoxysilane and 2) chemical ionisation (CI) of a mixture of silane and carbon monoxide. Collisional activation (CA) experiments performed for mass-selected \[Si,C,O](+), generated by using both methods, indicate that the structure is not inserted OSiC+; however, a definitive structural assignment as Si+-CO, Si+-OC or some cyclic variant is impossible based on these results alone. Neutralisation-reionisation (+NR+) experiments for EI-generated \[Si,C,O](+) reveal a small peak corresponding to SiC+, but no detectable SiO+ signal, and thus establishes the existence of the Si+-CO isomer. CCSD(T)//B3LYP calculations employing a triple-zeta basis set have been used to explore the doublet and quartet potential-energy surfaces of the cation, as well as some important neutral states The results suggest that both Si+-CO and Si+ - OC isomers are feasible; however, the global minimum is (2)Pi SiCO+. Isomeric (2)Pi SiOC+ is 12.1 kcal mol(-1) less stable than (2)Pi SiCO+, and all quartet isomers are much higher in energy. The corresponding neutrals Si-CO and Si-OC are also feasible, but the lowest energy Si - OC isomer ((3)A") is bound by only 1.5 kcal mol(-1). We attribute most, if nor all, of the recovery signal in the +NR' experiment to SiCO+ survivor ions. The nature of the bonding in the lowest energy isomers of Si+ -(CO,OC) is interpreted with the aid of natural bond order analyses, and the ground stale bonding of SiCO+ is discussed in relation to classical analogues such as metal carbonyls and ketenes.

Analysis of albumin-associated peptides and proteins from ovarian cancer patients

Albumin binds low–molecular-weight molecules, including proteins and peptides, which then acquire its longer half-life, thereby protecting the bound species from kidney clearance. We developed an experimental method to isolate albumin in its native state and to then identify [mass spectrometry (MS) sequencing] the corresponding bound low–molecular-weight molecules. We used this method to analyze pooled sera from a human disease study set (high-risk persons without cancer, n= 40; stage I ovarian cancer, n = 30; stage III ovarian cancer, n = 40) to demonstrate the feasibility of this approach as a discovery method. Methods Albumin was isolated by solid-phase affinity capture under native binding and washing conditions. Captured albumin-associated proteins and peptides were separated by gel electrophoresis and subjected to iterative MS sequencing by microcapillary reversed-phase tandem MS. Selected albumin-bound protein fragments were confirmed in human sera by Western blotting and immunocompetition. Results In total, 1208 individual protein sequences were predicted from all 3 pools. The predicted sequences were largely fragments derived from proteins with diverse biological functions. More than one third of these fragments were identified by multiple peptide sequences, and more than one half of the identified species were in vivo cleavage products of parent proteins. An estimated 700 serum peptides or proteins were predicted that had not been reported in previous serum databases. Several proteolytic fragments of larger molecules that may be cancer-related were confirmed immunologically in blood by Western blotting and peptide immunocompetition. BRCA2, a 390-kDa low-abundance nuclear protein linked to cancer susceptibility, was represented in sera as a series of specific fragments bound to albumin. Conclusion Carrier-protein harvesting provides a rich source of candidate peptides and proteins with potential diverse tissue and cellular origins that may reflect important disease-related information.

Solution-processed dual-gate polymer field-effect transistors for display applications

We describe the advantages of dual-gate thin-film transistors (TFTs) for display applications. We show that in TFTs with active semiconductor layers composed of diketopyrrolopyrrole-naphthalene copolymer, the on-current is increased, the off-current is reduced, and the sub-threshold swing is improved compared to single-gate devices. Charge transport measurements in steady-state and under non-quasi-static conditions reveal the reasons for this improved performance. We show that in dual-gate devices, a much smaller fraction of charge carriers move in slow trap states. We also compare the activation energies for charge transport in the top-gate and bottom-gate configurations.

Solid-state assemblies and optical properties of conjugated oligomers combining fluorene and thiophene units

Two conjugated oligomers, representing elementary segments of fluorene-thiophene copolymers, are compared in terms of the microscopic morphology and the optical properties of thin deposits. The atomic force microscopy morphological data and the solid-state absorption and emission spectra are interpreted in terms of the assembly of the conjugated molecules. The compound with a terthiophene central unit and fluorene end-groups shows well-defined monolayer-by-monolayer assembly into micrometer-long stripe-like structures, with a crystalline herringbone-type organization within the monolayers. Polarized confocal microscopy indicates a strong orientation of the crystalline domains within the stripes. In contrast, the compound with a terfluorene central unit and thiophene end groups forms no textured aggregates and the optical spectra in the solid-state are very similar to those recorded in solution, suggesting that the molecules interact only weakly in the solid. The difference in behaviour between the two compounds most probably originates from their different capability to form densely-packed assemblies of interacting π-systems.

An observation about circular shortest paths: Dealing with additional constraints using branch and bound

Circular shortest paths represent a powerful methodology for image segmentation. The circularity condition ensures that the contour found by the algorithm is closed, a natural requirement for regular objects. Several implementations have been proposed in the past that either promise closure with high probability or ensure closure strictly, but with a mild computational efficiency handicap. Circularity can be viewed as a priori information that helps recover the correct object contour. Our "observation" is that circularity is only one among many possible constraints that can be imposed on shortest paths to guide them to a desirable solution. In this contribution, we illustrate this opportunity under a volume constraint but the concept is generally applicable. We also describe several adornments to the circular shortest path algorithm that proved useful in applications. © 2011 IEEE.

Self-Assembled Pd(II) Metallocycles Using an Ambidentate Donor and the Study of Square-Triangle Equilibria

The self-assembly reaction of a cis-blocked 90° square planar metal acceptor with a symmetrical linear flexible linker is expected to yield a [4 + 4] self-assembled square, a [3 + 3] assembled triangle, or a mixture of these.However, if the ligand is a nonsymmetrical ambidentate, it is expected to form a complex mixture comprising several linkage isomeric squares and triangles as a result of different connectivities of the ambidentate linker. We report instead that the reaction of a 90° acceptor cis-(dppf)Pd(OTf)2 [where dppf ) 1,1′-bis(diphenylphosphino)- ferrocene] with an equimolar amount of the ambidentate unsymmetrical ligand Na-isonicotinate unexpectedly yields a mixture of symmetrical triangles and squares in the solution. An analogous reaction using cis-(tmen)Pd(NO3)2 instead of cis-(dppf)Pd(OTf)2 also produced a mixture of symmetrical triangles and squares in the solution. In both cases the square was isolated as the sole product in the solid state, which was characterized by a single crystal structure analysis. The equilibrium between the triangle and the square in the solution is governed by the enthalpic and entropic contributions. The former parameter favors the formation of the square due to less strain in the structure whereas the latter one favors the formation of triangles due to the formation of more triangles from the same number of starting linkers. The effects of temperature and concentration on the equilibria have been studied by NMR techniques. This represents the first report on the study of square-triangle equilibria obtained using a nonsymmetric ambidentate linker. Detail NMR spectroscopy along with the ESI-mass spectrometry unambiguously identified the components in the mixture while the X-ray structure analysis determined the solid-state structure.

Analytical solution of unsteady three-dimensional MHD boundary layer flow and heat transfer due to impulsively stretched plane surface

The unsteady magnetohydrodynamic viscous flow and heat transfer of Newtonian fluids induced by an impulsively stretched plane surface in two lateral directions are studied by using an analytic technique, namely, the homotopy method. The analytic series solution presented here is highly accurate and uniformly valid for all time in the entire region. The effects of the stretching ratio and the magnetic field on the surface shear stresses and heat transfer are studied. The surface shear stresses in x- and y-directions and the surface heat transfer are enchanced by increasing stretching ratio for a fixed value of the magnetic parameter. For a fixed stretching ratio, the surface shear stresses increase with the magnetic parameter, but the heat transfer decreases. The Nusselt number takes longer time to reach the steady state than the skin friction coefficients. There is a smooth transition from the initial unsteady state to the steady state.

A technique for steady-state polarisation of stationary solid electrodes and its applications

A new technique has been devised to achieve a steady-state polarisation of a stationary electrode with a helical shaft rotating coaxial to it. A simplified theory for the convective hydrodynamics prevalent under these conditions has been formulated. Experimental data are presented to verify the steady-state character of the current-potential curves and the predicted dependence of the limiting current on the rotation speed of the rotor, the bulk concentration of the depolariser and the viscosity of the solution. Promising features of the multiple-segment electrodes concentric to a central disc electrode are pointed out.

Solid-State Acyl Migration In Salicylamides - An X-Ray Study Of The Ortho-Propionyl And Normal-Propionyl Derivatives

In recent years there has been an upsurge of interest in the study of organic reactions in the solid state. It is now realised that the crystalline matrix provides an extra-ordinary spatial control on the initiation and progress of these reactions. Electronic and dipolar effects which are important in solution are replaced by structural and geometric effects in solids. These 'spatial' or 'topochemical' aspects are important in understanding the mechanistic details of the reaction. In our laboratory, the thermally induced acyl migration in salicylamides from 0- to N- position in the solid state has been under study (Scheme 1). The structures of the acetyl and benzoyl derivatives (Ia,IIa, Ib and IIb) have been reported.

beta.-Turn conformation of N-acetyl-L-prolylglycyl-L-phenylalanine. Crystal structure and solution studies

Pro-Gly segments in peptides and proteins are prone to adopt the 0-turn conformation. This paper reports experimental data for the presence of this conformation in a linear tripeptide N-acetyl-L-prolylglycyl-L-phenylalanineb oth in the solid state and in solution. X-ray diffraction data on the tripeptide crystal show that it exists in the type I1 0-turn conformation. CD and proton NMR data show that this conformation persists in trifluoroethanol and methanol solutions in equilibrium with the nonhydrogen-bonded structures. Isomerization around the acetyl-prolyl bond is seen to take place in dimethyl sulfoxide solutions of the tripeptide.

Electrical transport in the perovskite solid solution LaNi1-xCoxO3

We have studied the resistivity and thermopower of the solid solution LaNi1-xCoxO3 in the temperature range 1.4K-300K. Effect of interaction and localization are seen in the low temperature transport data for x<0.55. A negative anomaly in the thermopower has been observed at low temperature for 0.1

Isomerization Dynamics In Solution In The Absence Of An Activation Barrier - Evaluation Of The Potential Parameters

We analyze recent experimental results of Sundström and Gillbro by using the theory of Bagchi, Fleming and Oxtoby. The experimental results are in good agreement with this theory, but not with the earlier theory of Förster and Hoffmann. By fitting the new experimental results to the theory, we obtain approximate estimates of the frequency of the excited surface (assumed harmonic) and the width of the sink function.

Oxides supported carbon air-electrodes for alkaline solution power devices

Porous carbon oxygen-reducing electrodes incorporated with perovskite oxide catalysts are reported. It has been possible to fabricate high-performance oxygen-reducing electrodes by introducing La0.5Sr0.5CoO3 and La0.99Sr0.01NiO3 with the activated coconut-shell charcoal; these electrodes could sustain load currents as high as 1 A cm−2 without serious degradation. A model to explain oxygen-reducing activity of these oxides has been proposed.

Sol → gel transition with rings in a finite polycondensing system in solution

We report a theoretical formulation for the mean cluster size distribution in a finite polycondensing system. Expressions for the mean number of n-mers with j bonds ( nj) are developed. Numerical calculations show that while the non-cyclic molecules make the dominant contribution to the small clusters, the large clusters are dominated by cyclic structures. The number of particles in ringless chains, n n,n-1, decays monotonically with n at all extents of reaction, but n n becomes bimodal near the gel point. We also find that the solvent plays an important role in the cluster size distribution.