Interfacial structure and crystallographic studies of transformations in betat' and beta Cu---Zn alloys-II. martensitic formation of alpha1' plates in beta'

A TEM study of the interphase boundary structure of 9R orthorhombic alpha1' martensite formed in beta' Cu---Zn alloys shows that it consists of a single array of dislocations with Burgers vector parallel to left angle bracket110right-pointing angle beta and spaced about 3.5 nm apart. This Burgers vector lies out of the interface plane; hence the interface dislocations are glissile. Unexpectedly, though, the Burgers vectors of these dislocations are not parallel when referenced to the matrix and the martensite lattices. This finding is rationalized on published hard sphere models as a consequence of relaxation of a resultant of the Bain strain and lattice invariant shear displacements within the matrix phase.

Remaining time and opportunities at work: Relationships between age, work characteristics, and occupational future time perspective

The authors adapted the concept of future time perspective (FTP) to the work context and examined its relationships with age and work characteristics (job complexity and control). Structural equation modeling of data from 176 employees of various occupations showed that age is negatively related to 2 distinct dimensions of occupational FTP: remaining time and remaining opportunities. Work characteristics (job complexity and control) were positively related to remaining opportunities and moderated the relationship between age and remaining opportunities, such that the relationship became weaker with increasing levels of job complexity and control.

Defining Adequate Vitamin D Intake : Cross-sectional and Intervention Studies

D-vitamiini ylläpitää normaalia luun kasvua ja uudistumista koko elämän ajan. Suomessa, kuten monissa muissakin länsimaissa, väestön D-vitamiinitilanne on riittämätön – talvisin osalla jopa puutteellinen. Tässä väitöskirjassa on tutkittu, lisääkö D-vitamiini luumassan kertymistä kasvuiässä, ja ylläpitäkö D-vitamiini luuston tasapainoista aineenvaihduntaa aikuisiällä. Nämä vaikutukset saattavat ehkäisi osteoporoosin kehittymistä eri ikäkausina. Väitöskirjatyössä tutkittiin erisuuruisten D-vitamiinilisäysten vaikutuksia kolmessa eri ikäryhmässä, jotka olivat 11-12 -vuotiaat tytöt (N=228), 21-49 -vuotiaat miehet (N=54) ja 65-85 -vuotiaat naiset (N=52). Tutkittavat satunnaistettiin ryhmiin, jotka nauttivat joko lumevalmistetta tai 5-20 µg D3-vitamiinia vitamiinilisänä. Tutkimukset olivat kaksoissokkoutettuja. Tutkimuksen aikana tutkittavilta otettiin paastoveri- ja virtsanäytteitä. Lisäksi he täyttivät tutkimuslomakkeen taustatietojen kartoittamiseksi sekä frekvenssikyselylomakkeen kalsiumin ja D-vitamiinin saannin selvittämiseksi. Tyttöjen luunmineraalitiheys (BMD) mitattiin DXA–laitteella ja miesten volumetrinen luuntiheys pQCT-menetelmällä. Näytteistä määritettiin mm. seerumin 25-hydroksi-D-vitamiinin (=S-25-OHD), lisäkilpirauhashormonin (=S-PTH) ja luun aineenvaihduntaa kuvaavien merkkiaineiden pitoisuuksia. Murrosikäisten tyttöjen poikkileikkaustutkimuksessa S-25-OHD- ja luun muodostusmerkkiaineen pitoisuudet vaihtelivat kuukausien välillä; suurimmat pitoisuudet mitattiin syyskuussa ja pienimmät maaliskuussa, mikä kuvastaa vuodenaikaisvaihtelua. Vastaava vaihtelu havaittiin lannerangan ja reisiluun BMD:ssä. D-vitamiinilisäyksellä oli myönteinen vaikutus tyttöjen luumassan lisääntymiseen. Suurin D-vitamiinilisä (10 µg/vrk) lisäsi luumassaa 17.2% enemmän reisiluussa ja 12.5% enemmän lannerangassa verrattuna lumevalmistetta nauttivien tyttöjen vastaaviin tuloksiin, mutta tulos riippui hoitomyöntyvyydestä. D-vitamiinin vaikutus luustoon välittyi vähentyneen luun hajotuksen kautta. Tutkimustuloksiin perustuen riittävä D-vitamiinin saanti murrosikäisille tytöille on 15 µg/vrk. D-vitamiinilisän vaikutus 65-85 -vuotiaiden naisten S-25-OHD-pitoisuuteen vakioitui kuudessa viikossa annoksen ollessa 5-20 µg/vrk. Näillä D-vitamiiniannoksilla ei saavutettu tavoiteltavaa S-25-OHD-pitoisuutta, joka on 80 nmol/l. Arvioimme, että 60 nmol/l -pitoisuuden, jota esiintyy kesäisin tämän ikäryhmän suomalaisilla, tämän ikäryhmän naiset saavuttaisivat 24 µg:n päivittäisellä D-vitamiinin saannilla. Terveillä miehillä havaittiin vuodenaikaisvaihtelu S-25-OHD- ja S-PTH-pitoisuudessa sekä luun hajotusta kuvaavassa merkkiainepitoisuudessa. Toisaalta vaihtelua ei havaittu radiuksen volumetrisessä luuntiheydessä eikä luun muodostusmerkkiaineen pitoisuudessa. Vuodenaikaisvaihtelu estettiin 17 µg:n päivittäisellä D-vitamiinin saannilla, mutta tämän ei havaittu vaikuttavan radiuksen luuntiheyteen kuusi kuukautta kestävän tutkimuksen aikana. Yhteenvetona todetaan, että D-vitamiinin saanti on edelleenkin riittämätöntä tutkimusten kohderyhmillä. Tämä näkyy S-25-OHD- ja PTH-pitoisuuden sekä luunaineenvaihduntaa kuvaavien merkkiaineiden vuodenaikaisvaihteluna, mikä on haitallista luuston hyvinvoinnille. D-vitamiinin saantia tulisi lisätä, jotta vähintäänkin riittävä D-vitamiinitilanne (S-25-OHD>50 nmol/l) tai mahdollisesti jopa tavoiteltava D-vitaminitilanne (S-25-OHD≥80 nmol/l) saavutettaisiin. Jotta D-vitamiinin saannin lisääminen olisi kaikissa ikäryhmissä mahdollista, on suunniteltava nykyistä enemmän D-vitamiinilla täydennettyjä elintarvikkeita.

Fluorescent probe and NMR studies of the aggregation of bile salts in aqueous solution

The binding of the fluorescent probes 1-anilino-8-naphthalene sulfonate and dansyl cadaverine to the sodium salts of cholic, deoxycholic and dehydrocholic acids has been investigated. Enhanced probe solubilisation accompanies aggregation. Monitoring of fluorescence intensities as a function of bile salt concentration permits the detection of primary micelle formation, as well as secondary association. The transition concentrations obtained by fluorescence are in good agreement with values determined for the critical micelle concentrations, by other methods. Differences in the behaviour of cholate and deoxycholate have been noted. Fluorescence polarisation studies of 1,6-diphenyl-1,3,5-hexatriene solubilised in bile salt micelles suggest a higher microviscosity for the interior of the deoxycholate micelle as compared to cholate. 1H NMR studies of deoxycholate over the range 1–100 mg/ml suggest that micelle formation leads to a greater immobilisation of the C18 and C19 methyl groups as compared to the C21 methyl group. Well resolved 13C resonances are observed for all three steroids even at high concentration. Both fluorescence and NMR studies confirm that dehydrocholate does not aggregate.

Ultrafast Switching Time and Third Order Nonlinear Coefficients of Microwave Treated Single Walled Carbon Nanotube Suspensions

Microwave treated water soluble and amide functionalized single walled carbon nanotubes have been investigated using femtosecond degenerate pump-probe and nonlinear transmission experiments. The time resolved differential transmission using 75 femtosecond pulse with the central wavelength of 790 nm shows a bi-exponential ultrafast photo-bleaching with time constants of 160 fs (130 fs) and 920 fs (300 fs) for water soluble (amide functionalized) nanotubes. Open and closed aperture z-scans show saturation absorption and positive (negative) nonlinear refraction for water soluble (amide functionalized) nanotubes. Two photon absorption coefficient, beta(0) similar to 250 cm/GW (650 cm/GW) and nonlinear index, gamma similar to 15 cm(2)/pW (-30 cm(2)/pW) are obtained from the theoretical fit in the saturation limit to the data for two types of nanotubes.

Optimising initial population density, growth time and nitrogen nutrition for assessing resistance of wheat cultivars to root-lesion nematode (Pratylenchus thornei)

Pratylenchus thornei is a major pathogen of wheat in Australia. Two glasshouse experiments with four wheat cultivars that had different final populations (Pf) of P. thornei in the field were used to optimise conditions for assessing resistance. With different initial populations (Pi) ranging up to 5250 P. thornei/kg soil, Pf of P. thornei increased to 16 weeks after sowing, and then decreased at 20 weeks in some cultivar x Pi combinations. The population dynamics of P. thornei up to 16 weeks were best described by a modified exponential equation P f (t) = aP i e kt where P f (t) is the final population density at time t, P i is the initial population density, a is the proportion of P i that initiates population development, and k is the intrinsic rate of increase of the population. The cultivar GS50a had very low k values at Pi of 5250 and 1050 indicating its resistance, Suneca and Potam had high k values indicating susceptibility, whereas intolerant Gatcher had a low value at the higher Pi and a high value at the lower Pi. Nitrate fertiliser increased plant growth and Pf values of susceptible cultivars, but in unplanted soil it decreased Pf. Nematicide (aldicarb 5 mg/kg soil) killed P. thornei more effectively in planted than in unplanted soil and increased plant growth particularly in the presence of N fertiliser. In both experiments, the wheat cultivars Suneca and Potam were more susceptible than the cultivar GS50a reflecting field results. The method chosen to discriminate wheat cultivars was to assess Pf after growth for 16 weeks in soil with Pi ~1050–5250 P. thornei/kg soil and fertilised with 200 mg NO3–N/kg soil.

Chemical ordering in As-Se glasses: X-ray absorption edge and XPES studies

X-ray absorption edge and X-ray photoelectron spectroscopic studies of As-Se glasses seem to support a chemical ordering model.

Molecular vibrations and conformation of primary dithiocarbamate ester. Infrared and NMR studies on S-methyl dithiocarbamate

The i.r. spectra of a primary dithiocarbamate ester namely, S-methyl dithiocarbamate (SMDTC) and its N-dideuterated compound have been measured between 4000 and 30 cm−1. Spectra in solution and at liquid nitrogen temperature have also been obtained. Assignment of all the fundamentals has been proposed and supported from a full normal coordinate analysis. The band assignments for SMDTC have been compared with those of related molecules and the characteristic bands of primary thioamides are derived. Conformational flexibility of SMDTC has been examined by i.r. and proton NMR spectroscopy. The hindered rotation around the C---N bond has been studied by a complete line shape analysis. The magnitude of ---NH2 and ---CH3 torsional barriers is also estimated from vibrational frequencies and force constants.

Simple synthesis and spectroscopic studies on cobalt added ZnO nanocrystals

Cobalt doped zinc oxide nanoparticles were prepared through simple wet chemical method. X-ray diffraction studies confirm the prepared particles are in wurtzite structure. Scanning Electron Microscopy studies show the shape and morphology of the particles. To identify the presence of cobalt in ZnO, Energy Dispersive X-ray analysis was done. Optical absorption measurements show the presence of exciton peak at 375 nm. Photoluminescence studies were done with the excitation wavelength of 330 nm, which shows the emission because of exciton recombination and oxygen vacancy.

Clinical and immunological studies on persons exposed toParthenium hysterophorus L

Studies on 300 persons subjected by occupational hazard to the allergenic weed, Parthenium hysterophorus L. for periods ranging from 3 to 12 months revealed that 4% of them developed contact dermatitis of the exposed parts of the body, while 56% of them got sensitized to the weed without apparently exhibiting any dermatitis. None of them suffered from allergic manifestations like rhinitis or bronchial asthma during the period of study which extended for 2 years.

Structural and kinetic studies on the activators of succinate dehydrogenase

1. 1. Diverse classes of compounds such as dicarboxylates, pyrophosphates, quinols and nitrophenols are known to activate mitochondrial succinate dehydrogenase (EC 1.3.99.1). Examples in each class — malonate, pyrophosphate, ubiquinol and 2,4-dinitrophenol — are selected for comparative studies on the kinetic constants and structural relationship. 2. 2. The activated forms of the enzyme obtained on preincubating mitochondria with the effectors exhibited Michaelian kinetics and gave doublereciprocal plots which are nearly parallel to that of the basal form. On activation, Km for the substrate also increased along with V. The effectors activated the enzyme at low concentrations and inhibited, in a competitive fashion, at high concentrations. The binding constant for activation was lower than that for inhibition for each effector. 3. 3. These compounds possess ionizable twin oxygens separated by a distance of Image and having fractional charges in the range of −0.26 to −0.74 e. The common twin-oxygen feature of the substrate and the effectors suggested the presence of corresponding counter charges in the binding domain. The competitive nature of effectors with the substrate for inhibition further indicated the close structural resemblance of the activation and catalytic sites.

Structural and Functional Studies on Trimeric Autotransporters

Trimeric autotransporters are a family of secreted outer membrane proteins in Gram-negative bacteria. These obligate homotrimeric proteins share a conserved C-terminal region, termed the translocation unit. This domain consists of an integral membrane β-barrel anchor and associated α-helices which pass through the pore of the barrel. The α-helices link to the extracellular portion of the protein, the passenger domain. Autotransportation refers to the way in which the passenger domain is secreted into the extracellular space. It appears that the translocation unit mediates the transport of the passenger domain across the outer membrane, and no external factors, such as ATP, ion gradients nor other proteins, are required. The passenger domain of autotransporters contains the specific activities of each protein. These are usually related to virulence. In trimeric autotransporters, the main function of the proteins is to act as adhesins. One such protein is the Yersinia adhesin YadA, found in enteropathogenic species of Yersinia. The main activity of YadA from Y. enterocolitica is to bind collagen, and it also mediates adhesion to other molecules of the extracellular matrix. In addition, YadA is involved in serum resistance, phagocytosis resistance, binding to epithelial cells and autoagglutination. YadA is an essential virulence factor of Y. enterocolitica, and removal of this protein from the bacteria leads to avirulence. In this study, I investigated the YadA-collagen interaction by studying the binding of YadA to collagen-mimicking peptides by several biochemical and biophysical methods. YadA bound as tightly to the triple-helical model peptide (Pro-Hyp-Gly)10 as to native collagen type I. However, YadA failed to bind a similar peptide that does not form a collagenous triple helix. As (Pro-Hyp-Gly)10 does not contain a specific sequence, we concluded that a triple-helical conformation is necessary for YadA binding, but no specific sequence is required. To further investigate binding determinants for YadA in collagens, I examined the binding of YadA to a library of collagen-mimicking peptides that span the entire triple-helical sequences of human collagens type II and type III. YadA bound promiscuously to many but not all peptides, indicating that a triple-helical conformation alone is not sufficient for binding. The high-binding peptides did not share a clear binding motif, but these peptides were rich in hydroxyproline residues and contained a low number of charged residues. YadA thus binds collagens without sequence specificity. This strategy of promiscuous binding may be advantageous for pathogenic bacteria. The Eib proteins from Escherichia coli are immunoglobulin (Ig)-binding homologues of YadA. I showed conclusively that recombinant EibA, EibC, EibD and EibF bind to IgG Fc. I crystallised a fragment of the passenger domain of EibD, which binds IgA in addition to IgG. The structure has a YadA-like head domain and an extended coiled-coil stalk. The top half of the coiled-coil is right-handed with hendecad periodicity, whereas the lower half is a canonical left-handed coiled-coil. At the transition from right- to left-handedness, a small β-sheet protrudes from each monomer. I was able to map the binding regions for IgG and IgA using truncations and site-directed mutagenesis to the coiled-coil stalk and identified residues critical for Ig binding.

Structuring time and questioning to achieve tactical awareness in games lessons

Background: A paradigm shift in educational policy to create problem solvers and critical thinkers produced the games concept approach (GCA) in Singapore's Revised Syllabus for Physical Education (1999). A pilot study (2001) conducted on 11 primary school student teachers (STs) using this approach identified time management and questioning as two of the major challenges faced by novice teachers. Purpose: To examine the GCA from three perspectives: structure—lesson form in terms of teacher-time and pupil-time; product—how STs used those time fractions; and process—the nature of their questioning (type, timing, and target). Participants and setting: Forty-nine STs from three different PETE cohorts (two-year diploma, four-year degree, two-year post-graduate diploma) volunteered to participate in the study conducted during the penultimate week of their final practicum in public primary and secondary schools. Intervention: Based on the findings of the pilot study, PETE increased the emphasis on GCA content specific knowledge and pedagogical procedures. To further support STs learning to actualise the GCA, authentic micro-teaching experiences that were closely monitored by faculty were provided in schools nearby. Research design: This is a descriptive study of time-management and questioning strategies implemented by STs on practicum. Each lesson was segmented into a number of sub-categories of teacher-time (organisation, demonstration and closure) and pupil-time (practice time and game time). Questions were categorised as knowledge, technical, tactical or affective. Data collection: Each ST was video-taped teaching a GCA lesson towards the end of their final practicum. The STs individually determined the timing of the data collection and the lesson to be observed. Data analysis: Each lesson was segmented into a number of sub-categories of both teacher- and pupil-time. Duration recording using Noldus software (Observer 4.0) segmented the time management of different lesson components. Questioning was coded in terms of type, timing and target. Separate MANOVAs were used to measure the difference between programmes and levels (primary and secondary) in relation to time-management procedures and questioning strategies. Findings: No differences emerged between the programmes or levels in their time-management or questioning strategies. Using the GCA, STs generated more pupil time (53%) than teacher time (47%). STs at the primary level provided more technical practice, and those in secondary schools more small-sided game play. Most questions (58%) were asked during play or practice but were substantially low-order involving knowledge or recall (76%) and only 6.7% were open-ended or divergent and capable of developing tactical awareness. Conclusions: Although STs are delivering more pupil time (practice and game) than teacher-time, the lesson structure requires further fine-tuning to extend the practice task beyond technical drills. Many questions are being asked to generate knowledge about games but lack sufficient quality to enhance critical thinking and tactical awareness, as the GCA intends.