Photoacoustic investigation of the optical absorption and thermal diffusivity in SixTe100−x glassesstar

The photoacoustic technique is used to determine the optical energy gap E0 of bulk SixTe100−x glasses in the glass-forming region 10 ≤ x ≤ 28. The thermal diffusivity α of these samples has also been measured. The variation of E0 and α with x is reported. It is found that E0 increases with x nearly linearly with a sharp decrease in the rate of increase beyond x = 20. The thermal diffusivity also increases with x up to x = 20 but decreases for compositions with higher values of x. The observed behaviour is explained on the basis of a chemical bond approach. It is accounted for in terms of the increase in the number of Te---Te bonds and formation of SiTe4 tetrahedra with an increase in the chalcogen content.

Direct numerical simulation of autoignition in a non-premixed, turbulent medium

In this paper, direct numerical simulation of autoignition in an initially non-premixed medium under isotropic, homogeneous, and decaying turbulence is presented. The pressure-based method developed herein is a spectral implementation of the sequential steps followed in the predictor-corrector type of algorithms; it includes the effects of density fluctuations caused by spatial inhomogeneities ill temperature and species. The velocity and pressure field are solved in the spectral space while the scalars and density field are solved in the physical space. The presented results reveal that the autoignition spots originate and evolve at locations where (1) the composition corresponds to a small range around a specific mixture fraction, and (2) the conditional scaler dissipation rate is low. A careful examination of the data obtained indicates that the autoignition spots originate in the vortex cores, and the hot gases travel outward as combustion progresses. Hence, the applicability of the transient laminar flamelet model for this problem is questioned. The dependence of autoignition characteristics on parameters such as (1) die initial eddy-turnover time and (2) the initial ratio of length scale of scalars to that of velocities are investigated. Certain implications of new results on the conditional moment closure modeling are discussed.

Thermal decomposition studies on copolyurethanes based on hydroxyl terminated polybutadiene and poly(12-hydroxy stearic acid-co-TMP) ester polyol

Thermal degradation of copolyurethanes based on hydroxyl terminated polybutadiene (HTPB) and poly(12-hydroxy stearic acid-co-TMP) ester polyol (PEP) with varying compositions has been studied by thermo-gravimetric and pyrolysis-GC techniques. The copolyurethanes were found to decompose in multiple stages and the kinetic parameters were found to be dependent on the method of their evaluation. The activation energy for the initial stage of decomposition was found to increase, and for the main stage decreases with the increase in PEP content. The pyrolysis-GC studies on the ammonium perchlorate filled copolyurethanes (solid propellants) showed that the major products during the pyrolysis were C-2, C-3 hydrocarbons and butadiene. The amount of C-2 fraction in the pyrolyslate increased with solid loading, as well as with the HTPB content in the copolyurethanes. A linear relationship apparently exists between the amount of C-2 fraction and the burn rates of the solid propellants. (C) 2000 Elsevier Science Ltd. All rights reserved.

Induction of allergen-specific IgE and IgG responses by anti-idiotypic antibodies

In order to explore idiotypic, anti-idiotypic, and anti-anti-idiotypic responses to allergens, BALB/c mice were immunized with affinity- purified human idiotypic antibodies directed against a highly purified shrimp allergen. This resulted in the production of anti-idiotypic antibodies which were quantitated by using rabbit idiotypic antibodies raised against the same purified allergen. The mouse anti-idiotypic antibodies recognized shrimp-specific human idiotypic antibodies of the IgE isotype from 18 of 20 individuals, and IgG antibodies from 14 of 20 shrimp-sensitive patients. Immunization of BALB/c mice with affinity- purified, allergen-specific anti-idiotypic antibodies induced anti- allergen IgE and IgG responses in the absence of the allergen. This paper thus presents evidence that anti-idiotypic antibodies raised against allergen-specific idiotypic antibodies may substitute for the original allergen in the induction of allergen-specific idiotypic antibodies. The demonstration of shared idiotopes on IgG and IgE antibodies in the sera of shrimp-sensitive patients supports the use of allergen-specific anti-idiotypic antibodies as surrogate allergens.

Three-Dimensional Unsteady Flow With Heat and Mass Transfer Over a Continuous Stretching Surface

A numerical solution of the unsteady boundary layer equations under similarity assumptions is obtained. The solution represents the three-dimensional unsteady fluid motion caused by the time-dependent stretching of a flat boundary. It has been shown that a self-similar solution exists when either the rate of stretching is decreasing with time or it is constant. Three different numerical techniques are applied and a comparison is made among them as well as with earlier results. Analysis is made for various situations like deceleration in stretching of the boundary, mass transfer at the surface, saddle and nodal point flows, and the effect of a magnetic field. Both the constant temperature and constant heat flux conditions at the wall have been studied.

Interaction between the Z-type DNA duplex and 1,3-propanediamine:crystal structure of d(CACGTG)(2) at 1.2 angstrom resolution

The crystal structure of a hexamer duplex d(CACGTG)(2) has been determined and refined to an R-factor of 18.3% using X-ray data up to 1.2 angstrom resolution. The sequence crystallizes as a left-handed Z-form double helix with Watson-Crick base pairing. There is one hexamer duplex, a spermine molecule, 71 water molecules, and an unexpected diamine (Z-5, 1,3-propanediamine, C3H10N2)) in the asymmetric unit. This is the high-resolution non-disordered structure of a Z-DNA hexamer containing two AT base pairs in the interior of a duplex with no modifications such as bromination or methylation on cytosine bases. This structure does not possess multivalent cations such as cobalt hexaammine that are known to stabilize Z-DNA. The overall duplex structure and its crystal interactions are similar to those of the pure-spermine form of the d(CGCGCG)(2) structure. The spine of hydration in the minor groove is intact except in the vicinity of the T5A8 base pair. The binding of the Z-5 molecule in the minor grove of the d(CACGTG)(2) duplex appears to have a profound effect in conferring stability to a Z-DNA conformation via electrostatic complementarity and hydrogen bonding interactions. The successive base stacking geometry in d(CACGTG)(2) is similar to the corresponding steps in d(CG)(3). These results suggest that specific polyamines such as Z-5 could serve as powerful inducers of Z-type conformation in unmodified DNA sequences with AT base pairs. This structure provides a molecular basis for stabilizing AT base pairs incorporated into an alternating d(CG) sequence.

Representation av kvinnor och män – Hur prioriterar riksdagsledamöter frågor i den finska riksdagen? En kvantitativ studie av motionerna i riksdagen 2007

Pro gradu uppsatsen diskuterar betydelsen av representation för grupper i samhället genom att diskutera kvinnors representation. Kvinnor är en grupp i samhället som länge varit underrepresenterad, men som under de senaste 100 åren fått en betydligt bättre position i den offentliga beslutfattningen. För att ge bakgrund till frågeställningen beskrivs kvinnors deltagande i den finska riksdagen. Begreppen deskriptiv, substantiell och symbolisk representation diskuteras. Undersökningar av kvinnors representation både deskriptivt och substantiellt på parlamentsnivå presenteras. Forskningsfrågan i uppsatsen består av fyra frågeställningar om hur motioner görs i riksdagen och hur kön kan identifieras i motionerna. Frågeställningarna bygger på den teoretiska diskussionen och meningen med frågeställningar är att styra analysen av motionerna. I teoriavsnittet behandlas kvinnors representation och den vetenskapliga diskussionen om sambandet mellan substantiell och deskriptiv representation. Diskussionen utgår från Hanna Pitkins olika kategorier av representation. I den teoretiska diskussionen behandlas även begreppen den kritiska massan, närvarons politik och kritiska aktörer. I stycket diskuteras även vilka frågeställningar, som är relevanta att undersöka när man diskuterar kvinnors representation i samhället. När representationen av kvinnor diskuteras är det viktigt att minnas att kvinnor inte utgör en homogen grupp och att även män kan representera kvinnor innehållsmässigt. Efter den teoretiska diskussionen presenteras metoden för undersökningen. Som metod används kvantitativa statistiska metoder för att kunna undersöka ett större material, som kan ge en bättre helhetsbild av hur kvinnor representeras i motionerna. Materialet för undersökningen är motioner som är gjorda i den finska riksdagen 2007. Resultaten i undersökningen visar att motionerna används av både opposition och regering och att det finns en möjlighet för samarbete över partigränser. Andra faktorer, som påverkade hur aktivt man gjorde motioner var bland annat riksdagsledamöternas ålder och den valregion ledamöterna var från. När man såg speciellt på motionärernas kön framkom det skillnader i kvinnors och mäns motionsbeteende. Överlag gör män mera motioner än kvinnor i den finska riksdagen. Kvinnor har än idag en större tendens att göra motioner om socialpolitik och speciellt familje- och barnpolitik än vad män har. Männen igen väljer att göra motioner, som traditionellt har setts som starkt manliga, så som trafik och allmänna utrymmen. Resultaten visade också att kvinnors intressen inte är vanligt som motivering för motioner. Man fann också att riksdagsledamöters koppling till kvinnoorganisationer hade en betydelse när det gällde sannolikheten att göra motioner som motiverades med kvinnors intressen i samhället. Uppsatsen diskuterar orsaker till resultaten och ser att det finns orsaker att fortsätta diskutera sambandet mellan deskriptiv och substantiell representation.

A Compact Model incorporating Quantum Effects for Ultra-Thin-Body Double-Gate MOSFETs

We propose a compact model which predicts the channel charge density and the drain current which match quite closely with the numerical solution obtained from the Full-Band structure approach. We show that, with this compact model, the channel charge density can be predicted by taking the capacitance based on the physical oxide thickness, as opposed to C-eff, which needs to be taken when using the classical solution.

Evolution of polyembryony: Consequences to the fitness of mother and offspring

Polyembryony, referring here to situations where a nucellar embryo is formed along with the zygotic embryo, has different consequences for the fitness of the maternal parent and offspring. We have developed genetic and inclusive fitness models to derive the conditions that permit the evolution of polyembryony under maternal and offspring control. We have also derived expressions for the optimal allocation (evolutionarily stable strategy, ESS) of resources between zygotic and nucellar embryos. It is seen that (i) Polyembryony can evolve more easily under maternal control than under that of either the offspring or the ‘selfish’ endosperm. Under maternal regulation, evolution of polyembryony can occur for any clutch size. Under offspring control polyembryony is more likely to evolve for high clutch sizes, and is unlikely for low clutch sizes (<3). This conflict between mother and offspring decreases with increase in clutch size and favours the evolution of polyembryony at high clutch sizes, (ii) Polyembryony can evolve for values of “x” (the power of the function relating fitness to seed resource) greater than 0.5758; the possibility of its occurrence increases with “x”, indicating that a more efficient conversion of resource into fitness favours polyembryony. (iii) Under both maternal parent and offspring control, the evolution of polyembryony becomes increasingly unlikely as the level of inbreeding increases, (iv) The proportion of resources allocated to the nucellar embryo at ESS is always higher than that which maximizes the rate of spread of the allele against a non-polyembryonic allele.Finally we argue that polyembryony is a maternal counter strategy to compensate for the loss in her fitness due to brood reduction caused by sibling rivalry. We support this assertion by two empirical evidences: (a) the extent of polyembryony is positively correlated with brood reduction inCitrus, and (b) species exhibiting polyembryony are more often those that frequently exhibit brood reduction.