Dynamics of activationless reactions in solution

Recent picosecond and subpicosecond laser spectroscopy experiments have revealed several chemically and biologically important reactions in solution in which the reaction potential surface does not present a barrier to the motion along the reaction coordinate.The dynamics of these reactions display diverse and interesting behavior. They include the dependence of relaxation rate on the solvent viscosity, the solvent polarity, the temperature, and the wavelength of the exciting light. In this article we review the recent developments in the theoretical description of activationless processes in solution and compare them with the available experimental results

Allergenic Cross-Reactivity between Parthenium and Ragweed Pollen Allergens

Cross-reactivity of allergens from the pollen of the Compositae weeds, Parthenium hysterophorus (American feverfew) and Ambrosia (ragweed), in 2 groups of patients with different geographic distributions was studied. Parthenium-sensitive Indian patients, who were never exposed to ragweed, elicited positive skin reactions with ragweed pollen extracts. A significant correlation in the RAST scores of Parthenium and ragweed-specific IgE was observed with the sera of Parthenium and ragweed-sensitive Indian and US patients, respectively. RAST inhibition experiments demonstrated that the binding of IgE antibodies in the sera of ragweed-sensitive patients to short (Wl) and giant (W3) ragweed allergen discs could be inhibited by up to 94% by Parthenium pollen extracts. Similar inhibition (up to 82%) was obtained when the sera of Parthenium rhinitis patients were incubated with ragweed allergen extracts. A dose-dependent proliferation of lymphocytes from a Parthenium-sensitive rhinitis patient with elevated levels of both Parthenium and ragweed-specific IgE was observed when incubated with Parthenium and ragweed pollen extracts. A 1.6-fold higher proliferation, however, was observed with Parthenium pollen extract at a concentration of 100 µg/ml. These results suggest that shared epitopes present on Parthenium and ragweed pollen allergens are recognized by both Indian and US patients sensitized by exposure to Parthenium and ragweed pollen, respectively. The high degree of cross-reactivity between Parthenium and ragweed pollen allergens suggests that individuals sensitized to Parthenium may develop type-I hypersensitivity reactions to ragweed and vice versa when they travel to regions infested with the weed to which they had not been previously exposed.

Uncoupling Protein 2 and 3 Gene Polymorphisms and Their Association with Type 2 Diabetes in Asian Indians

Background: This study examined the association of -866G/A, Ala55Val, 45bpI/D, and -55C/T polymorphisms at the uncoupling protein (UCP) 3-2 loci with type 2 diabetes in Asian Indians. Methods: A case-control study was performed among 1,406 unrelated subjects (487 with type 2 diabetes and 919 normal glucose-tolerant NGT]), chosen from the Chennai Urban Rural Epidemiology Study, an ongoing population-based study in Southern India. The polymorphisms were genotyped using polymerase chain reaction-restriction fragment length polymorphism and direct sequencing. Haplotype frequencies were estimated using an expectation-maximization algorithm. Linkage disequilibrium was estimated from the estimates of haplotypic frequencies. Results: The genotype (P = 0.00006) and the allele (P = 0.00007) frequencies of Ala55Val of the UCP2 gene showed a significant protective effect against the development of type 2 diabetes. The odds ratios (adjusted for age, sex, and body mass index) for diabetes for individuals carrying Ala/Val was 0.72, and that for individuals carrying Val/Val was 0.37. Homeostasis insulin resistance model assessment and 2-h plasma glucose were significantly lower among Val-allele carriers compared to the Ala/Ala genotype within the NGT group. The genotype (P = 0.02) and the allele (P = 0.002) frequencies of -55C/T of the UCP3 gene showed a significant protective effect against the development of diabetes. The odds ratio for diabetes for individuals carrying CT was 0.79, and that for individuals carrying TT was 0.61. The haplotype analyses further confirmed the association of Ala55Val with diabetes, where the haplotypes carrying the Ala allele were significantly higher in the cases compared to controls. Conclusions: Ala55Val and -55C/T polymorphisms at the UCP3-2 loci are associated with a significantly reduced risk of developing type 2 diabetes in Asian Indians.

Desorptio/fotoionisaatio ilmanpaineessa takavarikoitujen huumausaineiden, steroidien ja räjähdysaineiden tutkimuksessa

Tutkimuksen tarkoituksena oli selvittää desorptio/fotoionisaatio ilmanpaineessa tekniikan (engl. desorption atmospheric pressure photoionization, DAPPI) soveltuvuutta rikosteknisen laboratorion näytteiden analysointiin. DAPPI on nopea massaspektrometrinen ionisaatiotekniikka, jolla voidaan tutkia yhdisteitä suoraan erilaisilta pinnoilta. DAPPI:ssa käytetään lämmitettyä mikrosirua, joka suihkuttaa höyrystynyttä liuotin- ja kaasuvirtausta kohti näytettä. Näytteen pinnan komponentit desorboituvat lämmön vaikutuksesta, jonka jälkeen ionisoituminen tapahtuu VUV-lampun emittoimien fotonien avulla.DAPPI:lla tutkittiin takavarikoituja huumausaineita, anabolisia steroideja ja räjähdysaineita sekä niiden jäämiä erilaisilta pinnoilta. Lisäksi kartoitettiin DAPPI:n mahdollisuuksia ja rajoituksia erilaisille näytematriiseille ilman näytteiden esikäsittelyä. Takavarikoitujen huumausaineiden tutkimuksessa analysoitiin erilaisia tabletteja, jauheita, kasvirouheita, huumekasveja (khat, oopium, kannabis) ja sieniä. Anabolisia steroideja tunnistettiin tableteista sekä ampulleista, jotka sisälsivät öljymäistä nestettä. Jauheet ripoteltiin kaksipuoliselle teipille ja analysoitiin siltä. Muut näytteet analysoitiin sellaisenaan ilman minkäänlaista esikäsittelyä, paitsi nestemäisten näytteiden kohdalla näyte pipetoitiin talouspaperille, joka analysoitiin DAPPI:lla. DAPPI osoittautui nopeaksi ja yksinkertaiseksi menetelmäksi takavarikoitujen huumausaineiden ja steroidien analysoimisessa. Se soveltui hyvin rikoslaboratorion erityyppisten näytteiden rutiiniseulontaan ja helpotti erityisesti huumekasvien ja öljymäisten steroidiliuosten tutkimusta. Massaspektrometrin likaantuminen pystyttiin ehkäisemään säätämällä näytteen etäisyyttä sen suuaukosta. Likaantumista ei havaittu huolimatta näytteiden korkeista konsentraatioista ja useita kuukausia jatkuneista mittauksista. Räjähdysaineiden tutkimuksessa keskityttiin seitsemän eri räjähdysaineen DAPPI-MS-menetelmän kehitykseen; trinitrotolueeni (TNT), nitroglykoli (NK), nitroglyseriini (NG), pentriitti (PETN), heksogeeni (RDX), oktogeeni (HMX) ja pikriinihappoä Nämä orgaaniset räjähteet ovat nitraattiyhdisteitä, jotka voidaan jakaa rakenteen puolesta nitroamiineihin (RDX ja HMX), nitroaromaatteihin (TNT ja pikriinihappo) sekä nitraattiestereihin (PETN, NG ja NK). Menetelmäkehityksessä räjähdysainelaimennokset pipetoitiin polymetyylimetakrylaatin (PMMA) päälle ja analysoitiin siitä. DAPPI:lla tutkittiin myäs autenttisia räjähdysainejäämiä erilaisista matriiseista. DAPPI:lla optimoitiin jokaiselle räjähdysaineelle sopiva menetelmä ja yhdisteet saatiin näkymään puhdasaineina. Räjähdysainejäämien analysoiminen erilaisista rikospaikkamateriaaleista osoittautui haastavammaksi tehtäväksi, koska matriisit aiheuttivat itsessään korkean taustan spektriin, josta räjähdysaineiden piikit eivät useimmiten erottuneet tarpeeksi. Muut desorptioionisaatiotekniikat saattavat soveltua paremmin haastavien räjähdysainejäämien havaitsemiseksi.

Bile-Acids in Asymmetric-Synthesis.2. Cholic-Acid Derived Novel Chiral Auxiliaries For Asymmetric Diels-Alder Reactions

Cholic acid-based chiral acrylate 5 yields a Diels-Alder adduct with cyclopent

Biorthogonal series method for Oseen type flows

A biorthogonal series method is developed to solve Oseen type flow problems. The theory leads to a new set of eigenfunctions for a specific class of linear non-selfadjoint operators containing the biharmonic one. These eigenfunctions differ from those given earlier in the literature for the biharmonic operator. The method is applied to the problem of thermocapillary flow in a cylindrical liquid bridge of finite length with axial through flow. Flow and temperature distributions are obtained at leading order of an expansion for small surface tension Reynolds number and Prandtl number. Another related problem considered is that of cylindrical cavity flow. Solutions for both cases are presented in terms of biorthogonal series. The effect of axial through flow on velocity and temperature fields is discussed by numerical evaluation of the truncated analytical series. The presence of axial through flow not only convectively shifts the vortices induced by surface forces in the direction of the through flow, but also moves their centers toward the outer cylindrical boundary. This process can lead to significantly asymmetric flow structures.

Diaphragm-type sputtered platinum thin film strain gauge pressure transducer

A diaphragm-type pressure transducer with a sputtered platinum film strain gauge (sensing film) has been designed and fabricated. The various steps followed to prepare thin film strain gauges on the diaphragm are described. M-bond 450 adhesive (Measurements Group, USA) has been employed as the insulating layer. A detailed procedure to cure this layer is given. A d.c. sputtering method is employed to prepare the platinum films. This paper also includes details of the strain gauge pattern and its location on the diaphragm. A description of the output characteristics and overall behaviour of the platinum thin film pressure transducer is reported.

Field-dependent changeover from current-to voltage-limiting characteristics by non-linear n-type BaTiO3 ceramics

Non-linear resistors having current-limiting capabilities at lower field strengths, and voltage-limiting characteristics (varistors) at higher field strengths, were prepared from sintered polycrystalline ceramics of (Ba0.6Sr0.4)(Ti0.97Zr0.03)O3+0.3 at % La, and reannealed after painting with low-melting mixtures of Bi2O3 + PbO +B2O3. These types of non-linear characteristics were found to depend upon the non-uniform diffusion of lead and the consequent distribution of Curie points (T c) in these perovskites, resulting in diffuse phase transitions. Tunnelling of electrons across the asymmetric barrier at tetragonak-cubic interfaces changes to tunnelling across the symmetric barrier as the cubic phase is fully stabilized through Joule heating at high field strengths. Therefore the current-limiting characteristics switch over to voltage-limiting behaviour because tunnelling to acceptor-type mid-bandgap states gives way to band-to-band tunnelling.

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 cast versus wrought microstructure on the processing map for hot working of stainless steel type AISI 304

Processing maps for hot working of as-cast and wrought stainless steels of type AISI 304 have been developed in the temperature range 600 to 1250°C and strain rate range 0.001 to 100 s−1. The domain of dynamic recrystallization (DRX) in as-cast material occurs at higher temperatures (1250°C) and lower strain rates (0.001 s−1) than in the wrought steel (1100°C and 0.01 s−1). The effect is explained in terms of enhanced nucleation rate of DRX due to the carbide, ferrite particles, stable oxides/nitrides and second-phase intermetallics in the as-cast microstructure. The DRX domain is wider in the wrought material although the peak efficiency is less (32%) than in the as-cast case (40%). The flow instability regime is not significantly affected by the initial microstructure

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.

Organometallic chemistry of diphosphazanes *1: VIII. Synthesis, spectroscopic studies and crystal structure of fac-[Mo(CO)3(MeCN)Ph2PN(iPr)P(Ph)(DMP)], and its reactions with tertiary phosphines

The reaction of fac-[Mo(CO)3(MeCN)3] with the unsymmetrical diphosphazane Ph2PN(iPr)P(Ph)(DMP) (L) gives the complex fac-[Mo(CO)3(MeCN)(L)] (2) in almost quantitative yield. The structure of the complex has been determined by an X-ray diffraction study. The compound reacts with PR3 (where R = Ph, OPh) to give fac-[Mo(CO)3(PR3)(L)] (3a, 4a), which undergoes an intramolecular isomerization to afford mer-[Mo(CO)3(PR3)(L)] (3b, 4b). Synthesis of cis-[Mo(CO)4(L)] (1) and fac-[MO(CO)3L] (2a) and their spectroscopic data are also reported.

Palladium(II) chloride complexes of bis(pyrazolyl)cyclotriphosphazenes

Reactions of the bis(3,5-dimethylpyrazolyl)cyclotriphosphazene derivatives gem-N3P3(MeNCH(2)CH(2)O)(2)(dmp)(2) (1) and nongeminal cis-N3P3(OPh)(4)(dmp)(2) (2) with PdCl2 afford complexes of the type [PdCl2.(L)] (L = 1 or 2). In these complexes, the phosphazenes act as bidentate NN-donor ligands with the two pyrazolyl pyridinic nitrogen atoms bonded to the metal, thus forming a six- and an eight-membered chelate ring, respectively. The structures of 2 and [PdCl2.(2)] (4) have been confirmed by single-crystal X-ray diffraction. Crystal data for 2: a = 16.759(2) Angstrom, b = 10.788(3) Angstrom, c = 19.635(9) Angstrom, beta = 101.61(3)degrees, P2(1/c), Z = 4, R = 0.038 for 4688 reflections with F > 5 sigma(F). Crystal data for 4: a = 9.701(3) Angstrom, b = 24.853(4) Angstrom, c = 15.794(4) Angstrom, beta = 101.46(2)degrees, P2(1/n), Z = 4, R = 0.030 for 5416 reflections with F > 5 sigma(F).

Processing map for hot working of stainless steel type AISI 316L

Processing and instability maps using a dynamic materials model have been developed for stainless steel type AISI 316L in the temperature range 600-1250-degrees-C and strain rate range 0.001-100 s-1 with a view to optimising its hot workability. Stainless steel type AISI 316L undergoes dynamic recrystallisation, with a peak efficiency of 35% at 1250-degrees-C and 0.05 s-1, which are the optimum parameters for hot working this material. The material undergoes dynamic recovery at 900-degrees-C and 0.001 s-1. The increase in the dynamic recrystallisation and dynamic recovery temperatures in comparison with stainless steel type AISI 304L is attributed to the presence of a backstress caused by the molybdenum additions. These results are in general agreement with those reported elsewhere on stainless steel type 316 deformed in hot extrusion and hot torsion. At temperatures < 850-degrees-C and strain rates > 10 s-1, the material exhibits flow localisation owing to adiabatic shear band formation, whereas at higher temperatures (> 850-degrees-C) and strain rates (> 10 s-1) mechanical twinning and wavy slip bands are observed. (C) 1993 The Institute of Materials.