Marginally unstable Holmboe modes

Marginally unstable Holmboe modes for smooth density and velocity profiles are studied. For a large family of flows and stratification that exhibit Holmboe instability, we show that the modes with phase velocity equal to the maximum or the minimum velocity of the shear are marginally unstable. This allows us to determine the critical value of the control parameter R (expressing the ratio of the velocity variation length scale to the density variation length scale) that Holmboe instability appears R=2. We then examine systems for which the parameter R is very close to this critical value. For this case we derive an analytical expression for the dispersion relation of the complex phase speed c(k) in the unstable region. The growth rate and the width of the region of unstable wave numbers has a very strong (exponential) dependence on the deviation of R from the critical value. Two specific examples are examined and the implications of the results are discussed.Comment: Submitted to Physics of Fluid

Stratified shear flow instabilities at large Richardson numbers

Numerical simulations of stratified shear flow instabilities are performed in two dimensions in the Boussinesq limit. The density variation length scale is chosen to be four times smaller than the velocity variation length scale so that Holmboe or Kelvin-Helmholtz unstable modes are present depending on the choice of the global Richardson number Ri. Three different values of Ri were examined Ri =0.2, 2, 20. The flows for the three examined values are all unstable due to different modes namely: the Kelvin-Helmholtz mode for Ri=0.2, the first Holmboe mode for Ri=2, and the second Holmboe mode for Ri=20 that has been discovered recently and it is the first time that it is examined in the non-linear stage. It is found that the amplitude of the velocity perturbation of the second Holmboe mode at the non-linear stage is smaller but comparable to first Holmboe mode. The increase of the potential energy however due to the second Holmboe modes is greater than that of the first mode. The Kelvin-Helmholtz mode is larger by two orders of magnitude in kinetic energy than the Holmboe modes and about ten times larger in potential energy than the Holmboe modes. The results in this paper suggest that although mixing is suppressed at large Richardson numbers it is not negligible, and turbulent mixing processes in strongly stratified environments can not be excluded.Comment: Submitted to Physics of Fluid

Predictive modelling of topology and loop variations in dimeric DNA quadruplex structures.

We have used a combination of simulated annealing (SA), molecular dynamics (MD) and locally enhanced sampling (LES) methods in order to predict the favourable topologies and loop conformations of dimeric DNA quadruplexes with T2 or T3 loops. This follows on from our previous MD simulation studies on the influence of loop lengths on the topology of intramolecular quadruplex structures [P. Hazel et al. (2004) J. Am. Chem. Soc., 126, 16 405-16 415], which provided results consistent with biophysical data. The recent crystal structures of d(G4T3G4)2 and d(G4BrUT2G4) (P. Hazel et al. (2006) J. Am. Chem. Soc., in press) and the NMR-determined topology of d(TG4T2G4T)2 [A.T. Phan et al. (2004) J. Mol. Biol., 338, 93-102] have been used in the present study for comparison with simulation results. These together with MM-PBSA free-energy calculations indicate that lateral T3 loops are favoured over diagonal loops, in accordance with the experimental structures; however, distinct loop conformations have been predicted to be favoured compared to those found experimentally. Several lateral and diagonal loop conformations have been found to be similar in energy. The simulations suggest an explanation for the distinct patterns of observed dimer topology for sequences with T3 and T2 loops, which depend on the loop lengths, rather than only on G-quartet stability

The role of the family in resettlement

This practitioner’s guide unpicks different interpretations of ‘family’. It explores the family’s unique position to fulfil key characteristics that research has shown are associated with effective resettlement support. It highlights recommendations and considerations that can be adopted into the practices of those working with young people and their families. As well as outlining various ways that families can help with personal and structural support, the guide also provides tips for successfully engaging with family members and sets out ways of overcoming the challenges that exist to unlocking this important resource

Albumin concentrations are primarily determined by the body cell mass and the systemic inflammatory response in cancer patients with weight loss

The association between hypoalbuminemia and poor prognosis in patients with cancer is well recognized. However, the factors that contribute to the fall in albumin concentrations are not well understood. In the present study, we examined the relationship between circulating albumin concentrations, weight loss, the body cell mass (measured using total body potassium), and the presence of an inflammatory response (measured using C- reactive protein) in male patients (n=40) with advanced lung or gastrointestinal cancer. Albumin concentrations were significantly correlated with the percent ideal body weight (r=0.390, p lt 0.05), extent of reported weight loss (r=-0.492, p lt 0.01), percent predicted total body potassium (adjusted for age, height, and weight, r=0.686, p lt 0.001), and logo C-reactive protein concentrations (r=-0.545, p lt 0.001). On multiple regression analysis, the percent predicted total body potassium and log(10) C-reactive protein concentrations accounted for 63% of the variation in albumin concentrations (r(2) = 0.626, p lt 0.001). The interrelationship between albumin, body cell mass, and the inflammatory response is consistent with the concept that the presence of an ongoing inflammatory response contributes to the progressive loss of these vital protein components of the body and the subsequent death of patients with advanced cancer

Benefits of Artificially Generated Gravity Gradients for Interferometric Gravitational-Wave Detectors

We present an approach to experimentally evaluate gravity gradient noise, a potentially limiting noise source in advanced interferometric gravitational wave (GW) detectors. In addition, the method can be used to provide sub-percent calibration in phase and amplitude of modern interferometric GW detectors. Knowledge of calibration to such certainties shall enhance the scientific output of the instruments in case of an eventual detection of GWs. The method relies on a rotating symmetrical two-body mass, a Dynamic gravity Field Generator (DFG). The placement of the DFG in the proximity of one of the interferometer's suspended test masses generates a change in the local gravitational field detectable with current interferometric GW detectors.Comment: 16 pages, 4 figure

Animal Welfare Worldwide, the Opinion of Practicing Veterinarians

The objective of this study was to investigate the animal welfare issues considered the most important by companion animal veterinarians worldwide. For this purpose, a global survey of several potential animal welfare issues was distributed via SurveyMonkey® in multiple languages. The distribution of survey responses differed by region. The main animal welfare concern reported worldwide was obesity, although there were differences across regions, possibly due to cultural and socioeconomic factors. Anthropomorphism (attributing human qualities or characteristics to an animal) was an issue in western countries but less so in Asia, Africa, and Oceania. There were significant differences between Asia and Europe, Africa, and Oceania in the importance and prevalence of convenience euthanasia. There were also age and sex differences in participant responses, with older veterinarians reporting fewer welfare problems than younger veterinarians, and female veterinarians reporting more welfare issues than their male counterparts