A sufficient criterion for Kelvin–Helmholtz instability in the magnetopause boundary‐layer region

The Kelvin–Helmholtz instability has been investigated for the magnetopause boundary‐layer region by the linearized method. The plasma in magnetosheath and magnetopause is assumed to be semi‐infinitely extended homogeneous, nondissipative, and incompressible. It is observed that, if one relation of two plasma speeds on the two sides of the magnetopause, wave number, and boundary‐layer thickness exceeds a certain threshold, the instability sets in. This new analytically sufficient criterion for excitation of instability in the three‐layer plasma flow generalizes the corresponding Chandrasekhar’s instability criterion for two‐layer plasma flow. The known results have been recovered and modified, the new results have been discovered. It is proved that the velocity threshold for the onset of instability is low when the magnitude of the magnetosheath and boundary‐layer region magnetic field and the angle between them are small. Also the threshold depends on the direction of plasma flow. The following results are observed numerically. The growth of the instability is sensitive to the magnetic field direction in the magnetosheath. A slight variation in the magnetic field direction in the second region can substantially change the relative velocity threshold for instability. When the ratio of the density of the second and third layer (magnetosphere) increases or that of the first and third layer decreases, the threshold decreases. Apart from this a necessary criterion for instability is obtained for a particular case.

Compressible MHD boundary layer in the stagnation region of a sphere

The steady laminar compressible boundary layer flow of an electrically conducting fluid in the stagnation region of a sphere with an applied magnetic field has been studied. The effects of the induced magnetic field, mass transfer, and viscous dissipation have been taken into account. Both isothermal and adiabatic wall conditions have been considered. The governing equations have been solved numerically using a shooting method. The skin friction and heat transfer are found to be strongly affected by the magnetic field, mass transfer, wall temperature and Mach number. It is found that the magnetic field reduces the heat transfer. This is a significant result which can be used in controlling the heat transfer rate. The boundary layer solutions break down as the magnetic parameter tends to a certain critical value.

Coherent rainfall zones of the Indian region

We have delineated rainfall zones for the Indian region that are coherent with respect to the variations of the summer monsoon rainfall. Within each zone, the time series of the summer monsoon rainfall at every pair of stations are significantly positively correlated, and the mean interseries correlation for each zone is high. The interseries correlation data set is analysed in order to delineate the rainfall zones, using an objective method specifically developed for the purpose. Each of the zonal averages are shown to be representative of the zone as a whole. We suggest that this regionalization is appropriate for study of the variation of the summer monsoon rainfall over the Indian region on interannual and larger scales.

Effect of Zirconium on the Processing MAPS For Hot-Working of Alpha-Beta Brass

The effect of zirconium on the hot working characteristics of alpha and alpha-beta brass was studied in the temperature range of 500 to 850-degrees-C and the strain rate range of 0.001 to 100 s-1. On the basis of the flow stress data, processing maps showing the variation of the efficiency of power dissipation (given by [2m/(m+1)] where m is the strain rate sensitivity) with temperature and strain rate were obtained. The addition of zirconium to alpha brass decreased the maximum efficiency of power dissipation from 53 to 39%, increased the strain rate for dynamic recrystallization (DRX) from 0.001 to 0.1 s-1 and improved the hot workability. Alpha-beta brasses with and without zirconium exhibit a domain in the temperature range from 550 to 750-degrees-C and at strain rates lower than 1 s-1 with a maximum efficiency of power dissipation of nearly 50 % occurring in the temperature range of 700 to 750-degrees-C and a strain rate of 0.001 s-1. In the domain, the alpha phase undergoes DRX and controls the hot deformation of the alloy whereas the beta phase deforms superplastically. The addition of zirconium to alpha-beta brass has not affected the processing maps as it gets partitioned to the beta phase and does not alter the constitutive behavior of the alpha phase

Impact of physical processes on the chlorophyll distribution in the Bay of Bengal

Satellite-derived chlorophyll a concentration (chl a) maps show three regions with high chl a in the Bay of Bengal. First among these is close to the coast, particularly off river mouths, with high values coinciding with the season of peak discharge; second is in the southwestern bay during the northeast monsoon, which is forced by local Ekman pumping; and the third is to the east of Sri Lanka in response to the summer monsoon winds. Chlorophyll-rich water from the mouths of rivers flows either along the coast or in an offshore direction, up to several hundred kilometers, depending on the prevailing ocean current pattern. The Irrawady River plume flows toward offshore and then turns northwestward during October–December, but it flows along the coast into the Andaman Sea for the rest of the year. From the Ganga-Brahmaputra river mouth, chl a–rich water flows directly southward into the open bay during spring but along the Indian coast during summer and winter. Along the Indian coast, the flow of chl a–rich water is determined by the East India Coastal Current (EICC). Whenever the EICC meanders off the Indian coast, it leads to an offshore outbreak of chl a–rich water from the coastal region into open ocean. The EICC as well as open ocean circulation in the bay is made up of several eddies, and these eddies show relatively higher chl a. Eddies near the coast, however, can often have higher chl a because of advection from the coastal region rather than generation within the eddy itself. The bay experiences several cyclones in a year, most of them occurring during October–November. These cyclones cause a drop in the sea surface temperature, a dip in the sea level, and a local increase in chl a. The impact of a cyclone is weaker in the northern part of the bay because of stronger stratification compared to the southern parts.

Identification of tropomyosin as the major shrimp allergen and characterization of its IgE-binding epitopes

The major heat-stable shrimp allergen (designated as Sa-II), capable of provoking IgE-mediated immediate type hypersensitivity reactions after the ingestion of cooked shrimp, has been shown to be a 34-kDa heat- stable protein containing 300 amino acid residues. Here, we report that a comparison of amino acid sequences of different peptides generated by proteolysis of Sa-II revealed an 86% homology with tropomyosin from Drosophila melanogaster, suggesting that Sa-II could be the shrimp muscle protein tropomyosin. To establish that Sa-II is indeed tropomyosin, the latter was isolated from uncooked shrimp (Penaeus indicus) and its physicochemical and immunochemical properties were compared with those of Sa-II. Both tropomyosin and Sa-II had the same molecular mass and focused in the isoelectric pH range of 4.8 to 5.4. In the presence of 6 M urea, the mobility of both Sa-II and shrimp tropomyosin shifted to give an apparent molecular mass of 50 kDa, which is a characteristic property of tropomyosins. Shrimp tropomyosin bound to specific IgE antibodies in the sera of shrimp-sensitive patients as assessed by competitive ELISA inhibition and Western blot analysis. Tryptic maps of both Sa-II and tropomyosin as obtained by reverse phase HPLC were superimposable. Dot-blot and competitive ELISA inhibition using sera of shrimp-sensitive patients revealed that antigenic as well as allergenic activities were associated with two peptide fractions. These IgE-binding tryptic peptides were purified and sequenced. Mouse anti-anti-idiotypic antibodies raised against Sa-II specific human idiotypic antibodies recognized not only tropomyosin but also the two allergenic peptides, thus suggesting that these peptides represent the major IgE binding epitopes of tropomyosin. A comparison of the amino acid sequence of shrimp tropomyosin in the region of IgE binding epitopes (residues 50-66 and 153-161) with the corresponding regions of tropomyosins from different vertebrates confirmed lack of allergenic cross-reactivity between tropomyosins from phylogenetically distinct species.

Influence of state of stress on the processing map for hot working of stainless steel type AISI 304L: compression vs. torsion

Processing maps for hot working of stainless steel of type AISI 304L have been developed on the basis of the flow stress data generated by compression and torsion in the temperature range 600–1200 °C and strain rate range 0.1–100 s−1. The efficiency of power dissipation given by 2m/(m+1) where m is the strain rate sensitivity is plotted as a function of temperature and strain rate to obtain a processing map, which is interpreted on the basis of the Dynamic Materials Model. The maps obtained by compression as well as torsion exhibited a domain of dynamic recrystallization with its peak efficiency occurring at 1200 °C and 0.1 s−1. These are the optimum hot-working parameters which may be obtained by either of the test techniques. The peak efficiency for the dynamic recrystallization is apparently higher (64%) than that obtained in constant-true-strain-rate compression (41%) and the difference in explained on the basis of strain rate variations occurring across the section of solid torsion bar. A region of flow instability has occurred at lower temperatures (below 1000 °C) and higher strain rates (above 1 s−1) and is wider in torsion than in compression. To achieve complete microstructure control in a component, the state of stress will have to be considered.

Housing the skilled migrants in the Helsinki Metropolitan Area : International attractiveness of housing, neighbourhoods and the city region

The aim of this thesis is to examine the skilled migrants’ satisfaction with the Helsinki Metropolitan Area. The examination is executed on three scales: housing, neighbourhoods and the city region. Specific focus is on the built environment and how it meets the needs of the migrants. The empirical data is formed of 25 semi-structured interviews with skilled migrants and additionally 5 expert interviews. Skilled and educated workforce is an increasingly important resource in the new economy, and cities are competing globally for talented workers. With aging population and a need to develop its innovational structure, the Helsinki Metropolitan Area needs migrant workforce. It has been stated that quality of place is a central factor for skilled migrants when choosing where to settle, and from this perspective their satisfaction with the region is significant. In housing, the skilled migrants found the price-quality ratio and the general sizes of apartments inadequate. The housing market is difficult for the migrants to approach, since they often do not speak Finnish and there are prejudices towards foreigners. The general quality of housing was rated well. On the neighbourhood level, the skilled migrants had settled in residential areas which are also preferred by the Finnish skilled workers. While the migrants showed suburban orientation in their settlement patterns, they were not concentrated in the suburban areas which host large shares of traditional immigrant groups. Migrants were usually satisfied with their neighbourhoods; however, part of the suburban dwellers were unsatisfied with the services and social life in their neighbourhoods. Considering the level of the city region, the most challenging feature for the skilled migrants was the social life. The migrants felt that the social environment is homogeneous and difficult to approach. The physical environment was generally rated well, the most appreciated features being public transportation, human scale of the Metropolitan Helsinki, cleanliness, and the urban nature. Urban culture and services were seen good for the city region’s size, but lacking in international comparison.

Polarimetric Signatures in the Stratiform Region of a Mesoscale Convective System

Four polarimetric measurands were collected in the stratiform region of a mesoscale convective system. The four are the reflectivity factor, the differential reflectivity, the correlation coefficient between orthogonal copolar echoes, and the differential propagation constant. Most striking is a signature of large aggregates (about 10 mm in size) seen in the differential phase through the melting layer. Another significant feature is an abrupt notch in the correlation coefficient that occurs towards the bottom of the bright band. Aircraft observations and a one-dimensional cloud model are used to explain some polarimetric measurements and to infer the presence of aggregates, graupel, and supercooled cloud water in the stratiform region. These unique observations and model data provide inferences concerning the presence of graupel and the growth of large aggregates in the melting layer.

Processing maps for hot working of Cu-Ni-Zn alloys. Part I - Alpha-nickel silver

The constitutive behaviour of agr — nickel silver in the temperature range 700–950 °C and strain rate range 0.001–100 s–1 was characterized with the help of a processing map generated on the basis of the principles of the ldquodynamic materials modelrdquo of Prasadet al Using the flow stress data, processing maps showing the variation of the efficiency of power dissipation (given by 2m/(m+1) wherem is the strain-rate sensitivity) with temperature and strain rate were obtained, agr-nickel silver exhibits a single domain at temperatures greater than 750 °C and at strain rates lower than 1s–1, with a maximum efficiency of 38% occurring at about 950 °C and at a strain rate of 0.1 s–1. In the domain the material undergoes dynamic recrystallization (DRX). On the basis of a model, it is shown that the DRX is controlled by the rate of interface formation (nucleation) which depends on the diffusion-controlled process of thermal recovery by climb. At high strain rates (10 and 100s–1) the material undergoes microstructural instabilities, the manifestations of which are in the form of adiabatic shear bands and strain markings.

Processing maps for hot working of Cu-Ni-Zn alloys Part II Alpha-Beta nickel silver

The constitutive behaviour of agr-beta nickel silver in the temperature range 600�850 °C and strainrate range 0.001�100s�1 was characterized with the help of a processing map generated on the principles of the dynamic materials model. On the basis of the flow-stress data, processing maps showing the variation of the efficiency of power dissipation (given by [2m/(m+1)], wherem is the strain-rate sensitivity) with temperature and strain rate were obtained, agr-beta nickel silver exhibits a single domain at temperatures greater than 700 °C and at strain rates lower than 1 s�1 with a maximum efficiency of power dissipation of about 42% occurring at about 850 °C and at 0.1 s�1. In the domain, the agr phase undergoes dynamic recrystallization and controls the deformation of the alloy, while the beta phase deforms superplastically. Optimum conditions for the processing of agr-beta nickel silver are 850 °C and 0.1 s�1. The material undergoes unstable flow at strain rates of 10 and 100 s�1 and in the temperature range 600�750 °C, manifestated in the form of adiabatic shear bands.

Processing maps for hot-working of powder metallurgy 1100 Al-10 vol % SiC-particulate metal-matrix composite

The hot-working characteristics of the metal-matrix composite (MMC) Al-10 vol % SiC-particulate (SiCp) powder metallurgy compacts in as-sintered and in hot-extruded conditions were studied using hot compression testing. On the basis of the stress-strain data as a function of temperature and strain rate, processing maps depicting the variation in the efficiency of power dissipation, given by eegr = 2m/(m+1), where m is the strain rate sensitivity of flow stress, have been established and are interpreted on the basis of the dynamic materials model. The as-sintered MMC exhibited a domain of dynamic recrystallization (DRX) with a peak efficiency of about 30% at a temperature of about 500°C and a strain rate of 0.01 s�1. At temperatures below 350°C and in the strain rate range 0.001�0.01 s�1 the MMC exhibited dynamic recovery. The as-sintered MMC was extruded at 500°C using a ram speed of 3 mm s�1 and an extrusion ratio of 10ratio1. A processing map was established on the extruded product, and this map showed that the DRX domain had shifted to lower temperature (450°C) and higher strain rate (1 s�1). The optimum temperature and strain rate combination for powder metallurgy billet conditioning are 500°C and 0.01 s�1, and the secondary metal-working on the extruded product may be done at a higher strain rate of 1 s�1 and a lower temperature of 425°C.

Specific-heat measurements during cooling through the glass-transition region

In this paper we report the measurements of specific heats of five glass formers as they are cooled through the glass-transition region. The measurements are compared with other specific-heat measurements such as adiabatic-calorimetry and ac-calorimetry measurements. The data are then analyzed using a model of enthalpy relaxation and nonequilibrium cooling, which can track the nonequilibrium relaxation time tau(S). The relevant parameters that describe tau(S) are obtained, allowing us to compare the enthalpy-relaxation times obtained from this method with other methods. We display the clear connection of the unrelaxed enthalpy with the nonequilibrium relaxation time and also show the role played by the delayed heat release from the unrelaxed enthalpy in the glass-transition region. We have also made certain definite observations regarding the equilibrium configurational specific heat and the Vogel-Fulcher law, which describes tau(S).

Phage Displayed Short Peptides against Cells of Candida albicans Demonstrate Presence of Species, Morphology and Region Specific Carbohydrate Epitopes

Candida albicans is a commensal opportunistic pathogen, which can cause superficial infections as well as systemic infections in immuocompromised hosts. Among nosocomial fungal infections, infections by C. albicans are associated with highest mortality rates even though incidence of infections by other related species is on the rise world over. Since C. albicans and other Candida species differ in their susceptibility to antifungal drug treatment, it is crucial to accurately identify the species for effective drug treatment. Most diagnostic tests that differentiate between C. albicans and other Candida species are time consuming, as they necessarily involve laboratory culturing. Others, which employ highly sensitive PCR based technologies often, yield false positives which is equally dangerous since that leads to unnecessary antifungal treatment. This is the first report of phage display technology based identification of short peptide sequences that can distinguish C. albicans from other closely related species. The peptides also show high degree of specificity towards its different morphological forms. Using fluorescence microscopy, we show that the peptides bind on the surface of these cells and obtained clones that could even specifically bind to only specific regions of cells indicating restricted distribution of the epitopes. What was peculiar and interesting was that the epitopes were carbohydrate in nature. This gives insight into the complexity of the carbohydrate composition of fungal cell walls. In an ELISA format these peptides allow specific detection of relatively small numbers of C. albicans cells. Hence, if used in combination, such a test could help accurate diagnosis and allow physicians to initiate appropriate drug therapy on time.