515 research outputs found
The Behavior of Granular Materials under Cyclic Shear
The design and development of a parallel plate shear cell for the study of
large scale shear flows in granular materials is presented. The parallel plate
geometry allows for shear studies without the effects of curvature found in the
more common Couette experiments. A system of independently movable slats
creates a well with side walls that deform in response to the motions of grains
within the pack. This allows for true parallel plate shear with minimal
interference from the containing geometry. The motions of the side walls also
allow for a direct measurement of the velocity profile across the granular
pack. Results are presented for applying this system to the study of transients
in granular shear and for shear-induced crystallization. Initial shear profiles
are found to vary from packing to packing, ranging from a linear profile across
the entire system to an exponential decay with a width of approximately 6 bead
diameters. As the system is sheared, the velocity profile becomes much sharper,
resembling an exponential decay with a width of roughly 3 bead diameters.
Further shearing produces velocity profiles which can no longer be fit to an
exponential decay, but are better represented as a Gaussian decay or error
function profile. Cyclic shear is found to produce large scale ordering of the
granular pack, which has a profound impact on the shear profile. There exist
periods of time in which there is slipping between layers as well as periods of
time in which the layered particles lock together resulting in very little
relative motion.Comment: 10 pages including 12 figure
Role of a cdk5-associated protein, p35, in herpes simplex virus type 1 replication in vivo
Previous studies have shown that herpes simplex virus type 1 (HSV-1) replication is inhibited by the cyclin-dependent kinase (cdk) inhibitor roscovitine. One roscovitine-sensitive cdk that functions in neurons is cdk5, which is activated in part by its binding partner, p35. Because HSV establishes latent infections in sensory neurons, we sought to determine the role p35 plays in HSV-1 replication in vivo. For these studies, wild-type (wt) and p35-/- mice were infected with HSV-1 using the mouse ocular model of HSV latency and reactivation. The current results indicate that p35 is an important determinant of viral replication in vivo
Quasiperiodic Tip Splitting in Directional Solidification
We report experimental results on the tip splitting dynamics of seaweed
growth in directional solidification of succinonitrile alloys with
poly(ethylene oxide) or acetone as solutes. The seaweed or dense branching
morphology was selected by solidifying grains which are oriented close to the
{111} plane. Despite the random appearance of the growth, a quasiperiodic tip
splitting morphology was observed in which the tip alternately splits to the
left and to the right. The tip splitting frequency f was found to be related to
the growth velocity V as a power law f V^{1.5}. This finding
is consistent with the predictions of a tip splitting model that is also
presented. Small anisotropies are shown to lead to different kinds of seaweed
morphologies.Comment: 4 pages, 7 figures, submitted to Physical Review Letter
Vacuum polarization calculations for hydrogenlike and alkalilike ions
Complete vacuum polarization calculations incorporating finite nuclear size
are presented for hydrogenic ions with principal quantum numbers n=1-5.
Lithiumlike, sodiumlike, and copperlike ions are also treated starting with
Kohn-Sham potentials, and including first-order screening corrections. In both
cases dominant Uehling terms are calculated with high accuracy, and smaller
Wichmann- Kroll terms are obtained using numerical electron Green's functions.Comment: 23 pages, 1 figur
Campus Vol II N 3
Sayre, Nancy. The Long & Short of It . Prose. 2.
Wittich, Hugh. The Long & Short of It . Prose. 2.
Shaw, Jay. The Most Unforgettable Professor I\u27ve met . Prose. 4.
Utter, Wm. T. The Most Unforgettable Student I\u27ve Met . Prose. 4.
Mandamadiotis, Spiros. Traitors Are Innocent . Prose. 5.
Bammann, Glenn. Exposé . Prose. 6.
Robinson, Sam and Terry Thurn. How They Do It At Denison . Picture. 8.
Dekker, Olney. Quite a Record . Prose. 10.
Findeisen, Bob. New Courses . Prose. 11.
Findeisen, Bob. Budget Blues$ . Prose. 12.
Roudebush, Jane. Campus Wheel . Picture. 15.
Anonymous. Untitled. Poem. 15
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Youth Gambling: The health and wellbeing of New Zealand secondary school students in 2012
Gambling has become a widely available activity in today’s society (Hardoon & Derevensky, 2002; Turchi & Derevensky, 2006). In fact, many researchers “have noted that an entire generation has now grown up in an era when lottery and casino gambling is widely available and heavily advertised” (Volberg, Gupta, Griffiths, Ólason, & Delfabbro, 2010, p. 3). Evidence suggests that it has become a popular past-time not only for adults, but also for children and young people (Derevensky & Gupta, 2000; Gupta & Derevensky, 1998a; Hardoon & Derevensky, 2002; Jacobs, 2000; Splevins, Mireskandari, Clayton, & Blaszczynski, 2010; Turchi & Derevensky, 2006). Moreover, research indicates that gambling is one of the first risky activities that adolescents become involved with (i.e. they begin gambling prior to experimentation with alcohol, drugs, sexual behaviour) (Volberg, et al., 2010). Whilst for many youth involvement in gambling does not result in problematic behaviour, others go on to experience serious problems (Dickson, Derevensky, & Gupta, 2003).
A vast range of adolescent gambling prevalence studies that have been undertaken over the past 25 years, across different countries, and incorporating general populations as well as youth specifically. Rates of youth problem gambling have often been found to be higher than the rates identified for adults (Huang & Boyer, 2007; Shaffer & Hall, 1996; Welte, Barnes, Tidwell, & Hoffman, 2008; Williams, Page, Parke, & Rigbye, 2008), with some estimating them to be more than double those of adults (Gupta & Derevensky, 1998a; Jackson, Dowling, Thomas, Bond, & Patton, 2008; Lesieur, et al., 1991), or up to three times as high (Rigbye, 2010). However, it has also been recognised that there is far less research in this field compared to that which has explored other youth risk behaviours such as substance use (Blinn-Pike, Worthy, & Jonkman, 2010).
The gap in New Zealand-based information regarding prevalence of youth gambling has been identified previously (Bellringer, et al., 2003; Rossen, Tse, & Vaidya, 2009) and in 2003 it was recommended that research be undertaken to measure the involvement of New Zealand youth in gambling as well as associated factors and gambling-related problems (Bellringer, et al., 2003). A limited body of research has since employed various sources of data to consider youth gambling in New Zealand (e.g. Gray, 2010; Ministry of Health, 2008, 2009; Rossen, 2008; Rossen, Butler, & Denny, 2011).
An extremely valuable source of information on New Zealand youth is the University of Auckland’s (UoA) National youth health and wellbeing surveys. To date, the UoA’s Adolescent Health Research Group (AHRG) has completed three National youth health and wellbeing surveys.
The Youth2000 Survey Series aim to provide nationally representative information on the health and wellbeing of young people attending New Zealand secondary schools. The Survey Series includes a wide range of questions about issues that contribute to the health and wellbeing of young people (such as substance use, injuries and violence, home and family) and allow researchers to take an ecological approach to identifying overall risk and protective factors in young people’s lives. Youth’12, a survey of 8,500 secondary school students throughout New Zealand, is the most recent survey to be undertaken by the AHRG. The inclusion of gambling items in the Youth’12 survey provides a unique opportunity to examine the impacts of gambling and problem gambling on secondary school students throughout New Zealand within an ecological framework.
This report was commissioned by the Ministry of Health and begins with a comprehensive review of the local and international youth gambling literature, followed by an overview of the Youth2000 Survey Series and methodology for Youth’12. A thorough analysis of Youth’12 gambling items was undertaken with results being reported under the following eight categories (detailed results for each set of analyses are also provided in the appendices):
- Students and their own gambling (Section Five);
- Unhealthy gambling amongst students (Section Six);
- Attitudes and motivating factors towards gambling (Section Seven);
- The impacts of others’ gambling on students (Section Eight); and,
- Risk and protective factors for student gambling (Section Nine);
- Gambling and Māori taitamariki in Aotearoa (Section 10);
- Gambling and Pacific young people in New Zealand (Section 11); and,
- Gambling and Asian young people in New Zealand (Section 12).
Finally, a discussion chapter provides an overview of the findings and implications
Effect of low dose, short-term creatine supplementation on muscle power output in elite youth soccer players
Background: To determine the effects of a low dose, short-term Creatine monohydrate (Cr) supplementation (0.03 g.kg.d-1 during 14 d) on muscle power output in elite youth soccer players. Methods: Using a two-group matched, double blind, placebo-controlled design, nineteen male soccer players (mean age = 17.0 ± 0.5 years) were randomly assigned to either Cr (N = 9) or placebo (N = 10) group. Before and after supplementation, participants performed a 30s Wingate Anaerobic Test (WAnT) to assess peak power output (PPO), mean power output (MPO), fatigue index (FI), and total work. Results: There were significant increases in both PPO and MPO after the Cr supplementation period (P ≤ 0.05) but not the placebo period. There were also significant increases in total work, but not FI, after the Cr supplementation and placebo periods (P ≤ 0.05). Notably, there were differences in total work between the Cr and placebo groups after (P ≤ 0.05) but not before the 14 d supplementation period. Conclusion: There is substantial evidence to indicate that a low-dose, short-term oral Cr supplementation beneficially affected muscle power output in elite youth soccer players
Self-diffusion in dense granular shear flows
Diffusivity is a key quantity in describing velocity fluctuations in granular
materials. These fluctuations are the basis of many thermodynamic and
hydrodynamic models which aim to provide a statistical description of granular
systems. We present experimental results on diffusivity in dense, granular
shear in a 2D Couette geometry. We find that self-diffusivities are
proportional to the local shear rate with diffusivities along the mean flow
approximately twice as large as those in the perpendicular direction. The
magnitude of the diffusivity is D \approx \dot\gamma a^2 where a is the
particle radius. However, the gradient in shear rate, coupling to the mean
flow, and drag at the moving boundary lead to particle displacements that can
appear sub- or super-diffusive. In particular, diffusion appears superdiffusive
along the mean flow direction due to Taylor dispersion effects and subdiffusive
along the perpendicular direction due to the gradient in shear rate. The
anisotropic force network leads to an additional anisotropy in the diffusivity
that is a property of dense systems with no obvious analog in rapid flows.
Specifically, the diffusivity is supressed along the direction of the strong
force network. A simple random walk simulation reproduces the key features of
the data, such as the apparent superdiffusive and subdiffusive behavior arising
from the mean flow, confirming the underlying diffusive motion. The additional
anisotropy is not observed in the simulation since the strong force network is
not included. Examples of correlated motion, such as transient vortices, and
Levy flights are also observed. Although correlated motion creates velocity
fields qualitatively different from Brownian motion and can introduce
non-diffusive effects, on average the system appears simply diffusive.Comment: 13 pages, 20 figures (accepted to Phys. Rev. E
Neural correlates of enhanced visual short-term memory for angry faces: An fMRI study
Copyright: © 2008 Jackson et al.Background: Fluid and effective social communication requires that both face identity and emotional expression information are encoded and maintained in visual short-term memory (VSTM) to enable a coherent, ongoing picture of the world and its players. This appears to be of particular evolutionary importance when confronted with potentially threatening displays of emotion - previous research has shown better VSTM for angry versus happy or neutral face identities.Methodology/Principal Findings: Using functional magnetic resonance imaging, here we investigated the neural correlates of this angry face benefit in VSTM. Participants were shown between one and four to-be-remembered angry, happy, or neutral faces, and after a short retention delay they stated whether a single probe face had been present or not in the previous display. All faces in any one display expressed the same emotion, and the task required memory for face identity. We find enhanced VSTM for angry face identities and describe the right hemisphere brain network underpinning this effect, which involves the globus pallidus, superior temporal sulcus, and frontal lobe. Increased activity in the globus pallidus was significantly correlated with the angry benefit in VSTM. Areas modulated by emotion were distinct from those modulated by memory load.Conclusions/Significance: Our results provide evidence for a key role of the basal ganglia as an interface between emotion and cognition, supported by a frontal, temporal, and occipital network.The authors were supported by a Wellcome Trust grant (grant number 077185/Z/05/Z) and by BBSRC (UK) grant BBS/B/16178
Process evaluation of a community-based adolescent obesity prevention project in Tonga
<p>Abstract</p> <p>Background</p> <p>The rising burden of obesity in Tonga is alarming. The promotion of healthy behaviours and environments requires immediate urgent action and a multi-sectoral approach. A three-year community based study titled the Ma'alahi Youth Project (MYP) conducted in Tonga from 2005-2008 aimed to increase the capacity of the whole community (schools, churches, parents and adolescents) to promote healthy eating and regular physical activity and to reduce the prevalence of overweight and obesity amongst youth and their families. This paper reflects on the process evaluation for MYP, against a set of Best Practice Principles for community-based obesity prevention.</p> <p>Methods</p> <p>MYP was managed by the Fiji School of Medicine. A team of five staff in Tonga were committed to planning, implementation and evaluation of a strategic plan, the key planks of which were developed during a two day community workshop. Intervention activities were delivered in villages, churches and schools, on the main island of Tongatapu. Process evaluation data covering the resource utilisation associated with all intervention activities were collected, and analysed by dose, frequency and reach for specific strategies. The action plan included three standard objectives around capacity building, social marketing and evaluation; four nutrition; two physical activity objectives; and one around championing key people as role models.</p> <p>Results</p> <p>While the interventions included a wide mix of activities straddling across all of these objectives and in both school and village settings, there was a major focus on the social marketing and physical activity objectives. The intervention reach, frequency and dose varied widely across all activities, and showed no consistent patterns.</p> <p>Conclusions</p> <p>The adolescent obesity interventions implemented as part of the MYP program comprised a wide range of activities conducted in multiple settings, touched a broad spectrum of the population (wider than the target group), but the dose and frequency of activities were generally insufficient and not sustained. Also the project confirmed that, while the MYP resulted in increased community awareness of healthy behaviours, Tonga is still in its infancy in terms of conducting public health research and lacks research infrastructure and capacity.</p
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