Spectral Properties of the Cauchy Operator and Its Product with Bergman's Projection on a Bounded Domain

In this paper exact asymptotic formulae are found for singularvalues of the Cauchy operator and the logarithmic potentialtype operator (on a bounded domain), as well as their productswith Bergman's projection. It is shown that these spectral characteristicsdetect geometric properties of a domain (area and the lengthof the boundary). The hypothesis "can we hear the shape of adrum", from a paper by J.M. Anderson, D. Khavinson, and V. Lomonosov[‘Spectral properties of some integral operators arisingin potential theory’, Quart. J. Math. Oxford (2) 43 (1992)387-407], is correct in the above sense. 1991 Mathematics SubjectClassification: 47B10.     

Absolute Intensities of the 10-µm Bands of (16)O(3)

Two hundred ninety experimental absolute intensities of nu(1) and nu(3) transitions of ozone have been measured, with good accuracy (<2%). They are used to derive the transition-moment parameters for these bands. The agreement between our observed and calculated line intensities is satisfactory. This work shows that the intensities of these two bands are on average 4% smaller than those used in the literature. In addition, 20 intensities of the nu(2) + nu(3) - nu(2) band confirm this value. Also, 42 line intensities of the 2nu(1)-nu(3) band are reported. Copyright 2001 Academic Press.     

Semileptonic (Λ b → Λcev) decay in a field theoretic quark model

The semileptonic decay width of heavy baryons such as (Λ _b → Λcev) has been estimated in the framework of a nonrelativistic field theoretic quark model where four component quark field operators along with a harmonic oscillator wave function are used to describe translationally invariant hadronic states. The present estimation does not make an explicit use of heavy quark symmetry and has a reasonable agreement with the experimentally measured decay width, polarisation ratio and form factors with the harmonic oscillator radii and quark momentum distribution inside the hadron as free parameters.     

Investigation of Interfacial Charge Separation at PbS QDs/(001) TiO2 Nanosheets Heterojunction Solar Cell

In the recent years, the heterojunction solar cells based on quantum dots (QDs) have attracted attention due to strong light absorbing characteristics and the size effect on the bandgap tuning. This paper reports on the kinetics of interfacial charge separation of PbS QDs/(001) TiO₂ nanosheets heterojunction solar cells. PbS QDs are deposited using a bifunctional linker molecule on two different TiO₂ films, i.e., TiO₂ nanosheets (with 001 dominant exposed facet) and TiO₂ nanoparticles (with 101 dominant exposed facet). Upon bandgap excitation, electrons are transferred from the PbS QDs conduction band to the lower lying conduction band of TiO₂. Based on the ultrafast pump‐probe laser spectroscopy technique, the kinetics of charge separation is scrutinized at the PbS/TiO₂ interface. The interfacial charge separation at PbS/TiO₂ nanosheets films made of (001) dominant exposed facets is five times faster than that on (101) dominant exposed facets TiO₂ nanoparticles. The quantum yields for charge injection are higher for the (001) TiO₂ nanosheets than the (101) TiO₂ nanoparticles due to enhanced interfacial interaction with (001) surface compared to the (101) nanoparticles. The superior interfacial charge separation at PbS/(001) nanosheets respect to PbS/(101) nanoparticles is consistent with the higher photocurrent and enhanced power conversion efficiency in the PbS QDs/(001) TiO₂ heterojunction solar cell. The use of (001) TiO₂ nanosheets can be a better alternative to conventional mesoporous TiO₂ films in QD heterojunction solar cells and perovskites‐based heterojunction solar cells.     

Far downstream analysis for the Blasius boundary-layer stability problem

In this paper, we examine the large Reynolds number (Re) asymptoticstructure of the wave number in the Orr–Sommerfeld regionfor the Blasius boundary layer on a semi-infinite flat plategiven by Goldstein (1983, J. Fluid Mech., 127, 59–81).We show that the inclusion of the term which contains the leading-ordernon-parallel effects, at O(Re^{– 1/2}), leads to a non-uniformexpansion. By considering the far downstream form of each termin the asymptotic expansion, we derive a length scale at whichthe non-uniformity appears, and compare this position with theposition seen in plots of the wave number.     

Further investigations on the influence of scale-up of a high shear granulator on the granule properties

This study focuses on the characterisation of strength, density, and size of granules produced in various scales of a high shear granulator. Calcium carbonate （Durca165） was used as the feed powder and aqueous polyethylene glycol （PEG 4000） as the binder. The dried granules were analysed for their strength, density, size distribution, and wall make-up. Granules were produced in granulators with four scales, 1, 5, 50, and 250 L under three scale-up rules of constant tip speed, constant shear stress, and constant Froude number. The results show that regardless of equipment scale, increasing the impeller speed has a great effect on crushing strength and stress. The underlying cause is an increase in granule density due to more consolidation at higher impeller speeds. Wall make-up is significantly reduced to less than 5% as the scale is increased from 1 to 250 L. The results of this study corroborate our previous findings that the constant tip speed rule is the best criterion for scale-up of high shear granulators.     

Wrap-around partitioning for block bidiagonal linear systems

A stable vector algorithm for the solution of block diagonallinear systems is obtained by a permutation of the unknownscalled wrap-around partitioning combined with standard QR factorization.Wrap-around partitioning uses blocking and selects the unknownsin the blocks in turns. After a suitable orthogonal eliminationstep one ends up with a reduced system which is again blockbidiagonal and so wrap-around partitioning can be applied again.Using a simple model for vectorization overhead it is shownthat small block sizes give best performance. The minimal blocksize 2, which corresponds to cyclic reduction, is suboptimaldue to memory bank conflicts.     

Functional and mechanistic analyses of biomimetic aminoacyl transfer reactions in de novo designed coiled coil peptides via rational active site engineering

Ribosomes and nonribosomal peptide synthetases (NRPSs) carry out instructed peptide synthesis through a series of directed intermodular aminoacyl transfer reactions. We recently reported the design of coiled-coil assemblies that could functionally mimic the elementary aminoacyl loading and intermodular aminoacyl transfer steps of NRPSs. These peptides were designed initially to accelerate aminoacyl transfer mainly through catalysis by approximation by closely juxtaposing four active site moieties, two each from adjacent noncovalently associated helical modules. In our designs peptide self-assembly positions a cysteine residue that is used to covalently capture substrates from solution via transthiolesterification (substrate loading step to generate the aminoacyl donor site) adjacent to an aminoacyl acceptor site provided by a covalently tethered amino acid or modeled by the epsilon-amine of an active site lysine. However, through systematic functional analyses of 48 rationally designed peptide sequences, we have now determined that the substrate loading and intermodular aminoacyl transfer steps can be significantly influenced (up to approximately 103-fold) by engineering changes in the active site microenvironment through amino acid substitutions and variations in the inter-residue distances and geometry. Mechanistic studies based on 15N NMR and kinetic analysis further indicate that certain active site constellations furnish an unexpectedly large pK(a) depression (1.5 pH units) of the aminoacyl-acceptor moiety, helping to explain the observed high rates of aminoacyl transfer in those constructs. Taken together, our studies demonstrate the feasibility of engineering efficient de novo peptide sequences possessing active sites and functions reminiscent of those in natural enzymes.