Dynamics of a two-dimensional vapor bubble confined between superheated or subcooled parallel plates

The dynamics of a long, two-dimensional vapor bubble confined in the gap between two superheated or subcooled parallel plates is analyzed theoretically. The unsteady expansion and/or contraction of the bubble is driven by mass transfer between the liquid and the vapor. The analysis uses the approach developed by Wilson et al. J. Fluid Mech. 391, 1 1999 for a situation with 'large' gaps and 'small' superheating or subcooling to consider a situation with small gaps and large superheating or subcooling in which the mass transfer from or to the semicircular nose of the bubble is comparable to that from or to the thin liquid films on the plates. In order to permit a semi- analytical treatment the analysis is restricted to low Prandtl number liquids. When both plates are superheated the bubble always expands. In this case there are two possible constant-velocity continuous-film solutions for the expansion of the bubble, namely, an unstable fast mode and a stable slow mode. The evolution of the bubble is calculated numerically for a range of values of the parameters. In particular, these calculations show that eventually the bubble expands either with the constant velocity of the slow mode or exponentially. When both plates are subcooled the bubble always collapses to zero length in a finite time. When one plate is subcooled and the other plate is superheated the situation is rather more complicated. If the magnitude of the subcooling is less than that of the superheating then if the magnitude of the subcooling is greater than a critical value then a variety of complicated behaviors including the possibility of an unexpected 'waiting time' behavior in which the bubble remains almost stationary for a finite period oftime can occur before the bubble eventually collapses to a finite length in an infinite time, whereas if it is less than this critical value then the bubble always expands and eventually does so exponentially. If the magnitude of the subcooling is greater than that of the superheating then the bubble always collapses to zero length in a finite time

A new crystal form of penicillin acylase from Escherichia coli

A new crystal form of penicillin acylase (penicillin amidohydrolase, E.C. 3.5.1.11) from Escherichia coli W (ATCC 11105) is reported. The crystals were grown using a combination of hanging-drop and streak-seeding methods. The crystals are in the monoclinic space group P2(1) with cell dimensions a = 51.52, b = 131.95, c = 64.43 Angstrom, beta = 106.12 degrees. There is one heterodimer in the asymmetric unit (Vm = 2.45 Angstrom(3) Da(-1)) and the solvent content is 49%. Preliminary data have been collected to d(min) = 2.7 Angstrom using a MAR Research image plate and a rotating-anode X-ray source. Subsequent experiments show diffraction beyond 1.3 Angstrom at a synchrotron radiation source

Investigations on Nonlinear Polariton Dispersion in Ferroelectric Superlattice System

Superlattices have drawn considerableattention in the recent years. In this work, thebehaviour of polaritons in a quantum wellsuperlattice system is analysed both at thecentre and at the edge of the brillouin zoneusing LiNbO3/ LiTaO3 as an example. Thesignificance of the polariton modes areanalysed. New modes due to nonlinearity on thepolaritonic gap, where the propagation ofelectromagnetic wave is forbidden, are obtainedin the system as suggested by some recentliterature. The variation of frequency with thethickness is also studied

Investigations on Nonlinear Polariton Dispersion in Ferroelectric Superlattice System

Superlattices have drawn considerable attention in the recent years. In this work, the behaviour of polaritons in a quantum well superlattice system is analysed both at the centre and at the edge of the brillouin zone using LiNbO3/ LiTaO3 as an example. The significance of the polariton modes are analysed. New modes due to nonlinearity on the polaritonic gap, where the propagation of electromagnetic wave is forbidden, are obtained in the system as suggested by some recent literature. The variation of frequency with the thickness is also studied

Conservation of structure and mechanism in primary and secondary transporters exemplified by SiaP, a sialic acid binding virulence factor from Haemophilus influenzae

Extracytoplasmic solute receptors (ESRs) are important components of solute uptake systems in bacteria, having been studied extensively as parts of ATP binding cassette transporters. Herein we report the first crystal structure of an ESR protein from a functionally characterized electrochemical ion gradient-dependent secondary transporter. This protein, SiaP, forms part of a tripartite ATP-independent periplasmic transporter specific for sialic acid in Haemophilus influenzae. Surprisingly, the structure reveals an overall topology similar to ATP binding cassette ESR proteins, which is not apparent from the sequence, demonstrating that primary and secondary transporters can share a common structural component. The structure of SiaP in the presence of the sialic acid analogue 2,3-didehydro-2-deoxyN-acetylneuraminic acid reveals the ligand bound in a deep cavity with its carboxylate group forming a salt bridge with a highly conserved Arg residue. Sialic acid binding, which obeys simple bimolecular association kinetics as determined by stopped-flow fluorescence spectroscopy, is accompanied by domain closure about a hinge region and the kinking of an alpha-helix hinge component. The structure provides insight into the evolution, mechanism, and substrate specificity of ESR-dependent secondary transporters that are widespread in prokaryotes

Gene-flow between populations of cotton bollworm Helicoverpa armigera (Lepidoptera: Noctuidae) is highly variable between years

Both large and small scale migrations of Helicoverpa armigera Hübner in Australia were investigated using AMOVA analysis and genetic assignment tests. Five microsatellite loci were screened across 3142 individuals from 16 localities in eight major cotton and grain growing regions within Australia, over a 38-month period (November 1999 to January 2003). From November 1999 to March 2001 relatively low levels of migration were characterized between growing regions. Substantially higher than average gene-flow rates and limited differentiation between cropping regions characterized the period from April 2001 to March 2002. A reduced migration rate in the year from April 2002 to March 2003 resulted in significant genetic structuring between cropping regions. This differentiation was established within two or three generations. Genetic drift alone is unlikely to drive genetic differentiation over such a small number of generations, unless it is accompanied by extreme bottlenecks and/or selection. Helicoverpa armigera in Australia demonstrated isolation by distance, so immigration into cropping regions is more likely to come from nearby regions than from afar. This effect was most pronounced in years with limited migration. However, there is evidence of long distance dispersal events in periods of high migration (April 2001–March 2002). The implications of highly variable migration patterns for resistance management are considered.K.D. Scott, K.S. Wilkinson, N. Lawrence, C.L. Lange, L.J. Scott, M.A. Merritt, A.J. Lowe and G.C Graha

Three-dimensional structure of Serratia marcescens nuclease at 1.7 Å resolution and mechanism of its action

AbstractThe three-dimensional crystal structure of Serratia marcescens (Sm) nuclease has been refined at 1.7 Å resolution to the R-factor of 17.3% and R-free of 22.2%. The final model consists of 3678 non-hydrogen atoms and 443 water molecules. The analysis of the secondary and the tertiary structures of the Sm nuclease suggests a topology which reveals essential inner symmetry in all the three layers forming the monomer. We propose the plausible mechanism of its action based on a concerted participation of the catalytically important amino acid residues of the enzyme active site

UNDERSTANDING THE DETERMINANTS OF BLOCKCHAIN ADOPTION IN SUPPLY CHAINS: AN EMPIRICAL STUDY IN CHINA

This study adopts affordance approach to understand how supply chain managers interpret the possible benefits that can be performed within blockchain-enabled supply chain applications. With a focus on governance efficiency improvement, the impacts of traceability and transparency affordance on uncertainty reduction were examined from the perspective of transaction cost theory in supply chain industry. Partial least squares – structural equation modelling (PLS-SEM) was used to analyze the data collected from 364 experienced supply chain managers in China. The results revealed that traceability affordance exerted significant impacts on environmental and trading partner uncertainty rather than transparency affordance, which in turn affected the adoption intention. This study contributes to the extant literature by embedding transaction cost in blockchain affordances. The findings are useful in guiding practitioners to improve blockchain system design for reducing uncertainties in supply chain environment, leading to a higher adoption rate of blockchain technology

Role of inertia in two-dimensional deformation and breakup of a droplet

We investigate by Lattice Boltzmann methods the effect of inertia on the deformation and break-up of a two-dimensional fluid droplet surrounded by fluid of equal viscosity (in a confined geometry) whose shear rate is increased very slowly. We give evidence that in two dimensions inertia is {\em necessary} for break-up, so that at zero Reynolds number the droplet deforms indefinitely without breaking. We identify two different routes to breakup via two-lobed and three-lobed structures respectively, and give evidence for a sharp transition between these routes as parameters are varied.Comment: 4 pages, 4 figure