The influence of age, gender and other information technology use on young people's computer use at school and home

Young people are exposed to a range of information technologies (IT) in different environments, including home and school, however the factors influencing IT use at home and school are poorly understood. The aim of this study was to investigate young people's computer exposure patterns at home and school, and related factors such as age, gender and the types of IT used. 1351 children in Years 1, 6, 9 and 11 from 10 schools in metropolitan Western Australia were surveyed. Most children had access to computers at home and school, with computer exposures comparable to TV, reading and writing. Total computer exposure was greater at home than school, and increased with age. Computer activities varied with age and gender and became more social with increased age, at the same time parental involvement reduced. Bedroom computer use was found to result in higher exposure patterns. High use of home and school computers were associated with each other. Associations varied depending on the type of IT exposure measure (frequency, mean weekly hours, usual and longest duration). The frequency and duration of children's computer exposure were associated with a complex interplay of the environment of use, the participant's age and gender and other IT activities

Garnet–monazite rare earth element relationships in sub-solidus metapelites: a case study from Bhutan

A key aim of modern metamorphic geochronology is to constrain precise and accurate rates and timescales of tectonic processes. One promising approach in amphibolite and granulite-facies rocks links the geochronological information recorded in zoned accessory phases such as monazite to the pressure–temperature information recorded in zoned major rock-forming minerals such as garnet. Both phases incorporate rare earth elements (REE) as they crystallize and their equilibrium partitioning behaviour potentially provides a useful way of linking time to temperature. We report REE data from sub-solidus amphibolite-facies metapelites from Bhutan, where overlapping ages, inclusion relationships and Gd/Lu ratios suggest that garnet and monazite co-crystallized. The garnet–monazite REE relationships in these samples show a steeper pattern across the heavy (H)REE than previously reported. The difference between our dataset and the previously reported data may be due to a temperature-dependence on the partition coefficients, disequilibrium in either dataset, differences in monazite chemistry or the presence or absence of a third phase that competed for the available REE during growth. We urge caution against using empirically-derived partition coefficients from natural samples as evidence for, or against, equilibrium of REE-bearing phases until monazite–garnet partitioning behaviour is better constrained

X-Ray Crystallographic Studies of Human Chorionic Gonadotropin

Human Chorionic Gonadotropin (hCG) is a glycoprotein hormone released by the trophoblast to stimulate progesterone production by the corpus luteum during the early stages of pregnancy. It exists as a heterodimer consisting of noncovalently bound alpha and beta-subunits. The alpha-subunit is common with the other members of this glycoprotein family, the pituitary hormones Luteinizing Hormone, Follicle Stimulating Hormone and Thyroid Stimulating Hormone. The alpha-subunit consists of 92 amino acid residues including ten cysteine residues which form five disulphide bridges. There are two N-linked oligosaccharide moieties bound to Asn 56 and Asn 82. The beta-subunit, which confers the specific biological role of each hormone, consists of 145 residues in hCG. There are twelve cysteine residues, conserved throughout the proteins, all involved in disulphide linkages. The beta-subunit is also heavily glycosylated with two long chain N-linked oligosaccharides at Asn 13 and Asn 30 and four O-linked oligosaccharides at Ser 121, Ser 127, Ser 132 and Ser 138. From circular dichroic work, hCG consists largely of aperiodic structure, 25-30% beta-sheet and 0-12% alpha-helix. There is a limited knowledge of the regions involved in the subunit interface and receptor binding areas, but many questions remain unanswered. This thesis describes my work in attempting to elucidate the three-dimensional structure of human Chorionic Gonadotropin by X-ray crystallography. HCG was partially deglycosylated by treatment with anhydrous Hydrogen Fluoride to produce the species HF-hCG. The tertiary structure was largely unaffected as HF-hCG was still capable of binding to receptor and had a similar secondary structure content as measured by Circular Dichroism (Keutmann et aL (1983a)). Crystals were grown of these HF-hCG species using the hanging drop method. Optimisation of the conditions led to crystals with sharp hexagonal bipyramidal morphology growing up to 0.4mm in each direction. The crystals were characterized and found to be of the space group P6i22 or enantiomer with cell dimensions a = b = 88.68A and c = 177.2A. The multiple isomorphous replacement method was employed for phase determination. Many potential heavy atom derivatives were screened using either visual comparison of precession photographs or by collection of a low resolution dataset on a Xentronics area detector and calculation of differences and difference Pattersons. Several derivatives were discovered, but unfortunately they shared one of the three major heavy atom binding sites. Data were collected on a Xentronics area detector, on film at station PX7.2 at the S.R.S., Daresbury and on the FAST at station PX9.6 at the S.R.S., Daresbury. Of the various datasets the film data were of the highest resolution, with diffraction observed to 2.5A but problems with radiation damage meant that more than one crystal was required to collect a full dataset. The best data collected were on the Xentronics area detector where a whole dataset could be collected with a single crystal. However, the maximum diffraction observed using the rotating anode source was 3.0A resolution. The data were processed using both the XENGEN and XDS packages, the latter giving far more accurate estimates of the intensities of the higher resolution data. The first derivative solved was K2Pt(CN)4 using a combination of difference Patterson maps and direct method techniques. S.I.R. phases calculated from this derivative were used to phase difference Fouriers for other derivatives. The anomolous data were used to determine the correct hand, and the true space group was found to be P6s22. MIR electron density maps were calculated and the solvent and protein regions were clear. However, it was not possible to distinguish the separate subunits. Phase refinement and phase extension methods were employed in an attempt to improve and extend the higher resolution phases. Solvent flattening, histogram matching and maximum entropy techniques all produced improved maps in which ?-sheet like density was apparent. Attempts were made to fit the sequence to the electron density, but this was made difficult both by the quality of the maps, and the extensive network of disulphide linkages. Also the unequivocal assignments of these linkages had not been made. Segments of poly alanine chain were fitted where possible and the partial structure used in phase combination in a "bootstrap" attempt to solve the structure

Excitation Functions of Stopping Power and Flow in Relativistic Heavy-Ion Collisions

Using a relativistic transport (ART) model, we study the stopping power, the formation of superdense hadronic matter as well as the strength of transverse and radial flow in central Au+Au collisions at beam momentum from 2 to 12 GeV/c per nucleon. We find that complete stopping is achieved in the whole beam momentum range. In particular, the proton rapidity distribution scaled by the beam rapidity is independent of the beam momentum, and this is in agreement with the experimental findings. Also, a large volume of superdense hadronic matter with a local energy density exceeding that expected for the transition of a hadronic matter to the quark-gluon plasma is formed in collisions at beam momenta greater than 8 GeV/c per nucleon. Furthermore, it is found that the transverse flow in these collisions is sensitive to the nuclear equation of state and decreases with increasing beam momentum. On the other hand, the radial flow is insensitive to the equation of state, and its strength increases with beam momentum.Comment: Talk given at NN97, Gatlinburg, Tennessee June 2-6,1997. To appear in the proc. in Nucl. Phys.

Depicted identities: Image and image-makers of post-1959 Tibet.

This thesis examines the role of images and image-makers in the period after 1959, when political control of Tibet was assumed by the People's Republic of China and thousands of Tibetans followed the Dalai Lama into exile. It is based on the work of image-makers in exile communities in India and in the Tibetan Autonomous Region of the People's Republic. The first section of the thesis establishes the importance of images in the exile community (with emphasis on the Tibetan capital-in-exile, Dharamsala) as religious objects and as definers of identity. Image-makers' responses to the conditions of exile and their engagement with new techniques of production and subject matter are discussed. Their works are analysed in the context of Tibetan debates about what constitutes appropriate imagery for exilic conditions. The thesis demonstrates that style is invented and negotiated in different ways, with significant differences emerging between image-makers in Dharamsala and those outside the capital-in-exile. The second section of the study examines the parallel history of image production in the Tibetan Autonomous Region. Here the impact of the colonial gaze is registered in a chapter on Chinese depictions of Tibet. The resulting entanglement of Chinese and Tibetan styles of image- making over the course of nearly five decades is outlined. Finally, the emergence of self-consciously Tibetan "modernist" images and image- makers is considered. A case study of one artist, who has worked in both the Tibetan Autonomous Region and the capital-in exile, draws the two sections into a problematised alignment. The contribution of this thesis rests in the analysis of Tibetan images during a period of dramatic political and social upheaval, a subject which has been largely ignored by art historians and is only beginning to be considered by anthropologists. It aims to enter into a debate about style in Tibetan painting from the perspective of post-1959 Tibetan image-makers

Photocurrent response from vertically aligned single-walled carbon nanotube arrays

Vertically-aligned arrays of single walled carbon nanotubes were created on an optically transparent electrode (FTO glass) these arrays were found to exhibit a prompt current and voltage when exposed to light. These cells were then investigated by electrochemical impedance spectroscopy and found to exhibit a dampening of the recombination reaction over the first 24 hours. Symmetrical cell modeling was successful in simulating the behavior of normal cell architecture

Structural characterisation of the N-glycan moiety of the barnacle settlement-inducing protein complex (SIPC)

Many barnacle species are gregarious and their cypris larvae display a remarkable ability to explore surfaces before committing to permanent attachment. The chemical cue to gregarious settlement behaviour – the settlement-inducing protein complex (SIPC) – is an α2-macroglobulin-like glycoprotein. This cuticular protein may also be involved in cyprid reversible adhesion if its presence is confirmed in footprints of adhesive deposited during exploratory behaviour, which increase the attractiveness of surfaces and signal other cyprids to settle. The full-length open-reading frame of the SIPC gene encodes a protein of 1547 amino acids with seven potential N-glycosylation sites. In this study on Balanus amphitrite, glycan profiling of the SIPC via hydrophilic interaction liquid chromatography with fluorescence detection (HILIC-fluorescence) provided evidence of predominantly high mannose glycans (M2–9), with the occurrence of monofucosylated oligomannose glycans (F(6)M2–4) in lower proportions. The high mannose glycosylation found supports previous observations of an interaction with mannose-binding lectins and exogenous mannose increasing settlement in B. amphitrite cypris larvae. Transmission electron microscopy of the deglycosylated SIPC revealed a multi-lobed globular protein with a diameter of ∼8 nm. Obtaining a complete structural characterisation of the SIPC remains a goal that has the potential to inspire solutions to the age-old problem of barnacle fouling.No Full Tex

Influence of Jail Incarceration and Homelessness Patterns on Engagement in HIV Care and HIV Viral Suppression among New York City Adults Living with HIV/AIDS

Objectives Both homelessness and incarceration are associated with housing instability, which in turn can disrupt continuity of HIV medical care. Yet, their impacts have not been systematically assessed among people living with HIV/AIDS (PLWHA). Methods We studied a retrospective cohort of 1,698 New York City PLWHA with both jail incarceration and homelessness during 2001–05 to evaluate whether frequent transitions between jail incarceration and homelessness were associated with a lower likelihood of continuity of HIV care during a subsequent one-year follow-up period. Using matched jail, single-adult homeless shelter, and HIV registry data, we performed sequence analysis to identify trajectories of these events and assessed their influence on engagement in HIV care and HIV viral suppression via marginal structural modeling. Results Sequence analysis identified four trajectories; 72% of the cohort had sporadic experiences of both brief incarceration and homelessness, whereas others experienced more consistent incarceration or homelessness during early or late months. Trajectories were not associated with differential engagement in HIV care during follow-up. However, compared with PLWHA experiencing early bouts of homelessness and later minimal incarceration/homelessness events, we observed a lower prevalence of viral suppression among PLWHA with two other trajectories: those with sporadic, brief occurrences of incarceration/homelessness (0.67, 95% CI = 0.50,0.90) and those with extensive incarceration experiences (0.62, 95% CI = 0.43,0.88). Conclusions Housing instability due to frequent jail incarceration and homelessness or extensive incarceration may exert negative influences on viral suppression. Policies and services that support housing stability should be strengthened among incarcerated and sheltered PLWHA to reduce risk of adverse health conditions