Quantum SUSY signatures in low and high energy processes

In the search for phenomenological evidence of supersymmetry through the indirect method of quantum signatures, it is useful to seek correlations of the non-standard quantum effects in low and high energy proceses, such as those involving on one hand the properties of theB-mesons and on the other hand the physics of the top quark and of the Higgs bosons. There are regions of the MSSM parameter space where the potential quantum SUSY signatures in the two energy regimes are strongly interwoven and therefore the eventual detection of these correlated quantum effects would strongly point towards the existence of underlying supersymmetric dynamics.     

Electrical conductivity in vinyl chloride during polymerization

Vinyl chloride of good polymerization quality showed a measurable electrical conductivity. The ionic strength of redistilled VCM appeared to be independent of temperature in the range from 20 to 50°C, and to decrease at higher temperatures. Conductivity measurements during bulk polymerization of VCM showed that the conductivity decreased with conversion. Other results indicated that electrolytically active species, formed during the polymerization, were trapped in the polymer matrix.     

Training humans in non-native phoneme perception using a monkey psychoacoustic procedure

Humans were trained to categorize problem non-native phonemes using an animal psychoacoustic procedure that trains monkeys to greater than 90% correct in phoneme identification [Sinnott and Gilmore, Percept. Psychophys. 66, 1341-1350 (2004)]. This procedure uses a manual left versus right response on a lever, a continuously repeated stimulus on each trial, extensive feedback for errors in the form of a repeated correction procedure, and training until asymptotic levels of performance. Here, Japanese listeners categorized the English liquid contrast /r-l/, and English listeners categorized the Middle Eastern dental-retroflex contrast /d-D/. Consonant-vowel stimuli were constructed using four talkers and four vowels. Native listeners and phoneme contrasts familiar to all listeners were included as controls. Responses were analyzed using percent correct, response time, and vowel context effects as measures. All measures indicated nativelike Japanese perception of /r-l/ after 32 daily training sessions, but this was not the case for English perception of /d-D/. Results are related to the concept of "robust" (more easily recovered) versus "fragile" (more easily lost) phonetic contrasts [Burnham, Appl. Psycholing. 7, 207-240 (1986)].     

The educational needs and professional roles of Canadian physicians and nurses regarding genetic testing and adult onset hereditary disease

OBJECTIVE: To investigate the knowledge, professional involvement and confidence of Canadian nurses and physicians in providing genetic services for adult onset hereditary disease. METHODS: 1,425 physicians and 1,425 nurses received a mailed questionnaire with reminders. The response rates were 50% (n = 543) and 79% (n = 975), respectively. RESULTS: Forty-eight percent of physicians and 31% of nurses lacked formal education in genetics. Respondents reported being involved in caring for people at risk for adult onset hereditary disease. Their levels of confidence that they could perform tasks, such as counselling about predictive genetic tests, however, were lower than their levels of expectation that it would be important for them to provide these services. CONCLUSIONS: The expected roles and educational needs of Canadian nurses and physicians have broad areas of overlap suggesting the possibility of combined professional education programs and multiple ways of organizing teams to provide genetic services to people at risk for adult onset hereditary disease.     

The geometrical stability of non-linear normal modes in two degree of freedom systems

The geometrical stability of the non-linear normal mode vibrations of a class of two degree of freedom dynamical systems is studied by utilizing the definitions and analysis of Synge's “Geometry of Dynamics.”It is shown that instabilities can occur for small amplitudes of vibration only if (a) one of the associated linear normal modes possesses a frequency which is nearly a multiple of the frequency of the other linear normal mode, or (b) the frequency of one linear normal mode is nearly zero.     

Dynamics of two strongly coupled van der pol oscillators

A perturbation method is used to study the steady state behavior of two Van der Pol oscillators with strong linear diffusive coupling. It is shown that a bifurcation occurs which results in a transition from phase-locked periodic motions to quasi-periodic motions as the coupling is decreased or the detuning is increased. The analytical results are compared with a numerically generated solution.     

Dynamics of a system exhibiting the global bifurcation of a limit cycle at infinity

This paper concerns the dynamics of a class of non-linear oscillators of the form:

$\text{x″ + x ? ?x′(1?ax}{}^2\text{?bx′}{}^2\text{) = 0}$

. The non-linear term contains two parameters a and b which may be varied to give the Rayleigh and Van der Pol differential equations as special cases.The existence and approximation of limit cycles in this system are investigated using the Poincare-Bendixson theorem and the Lindstedt perturbation method. Analysis of the system at infinity is used to study the global bifurcation through which the limit cycle is created from four saddle-saddle connections between equilibrium points at infinity. Center manifold theory is used to determine the stability of the equilibrium points at infinity. Numerical integration is used to verify the analytical results.It is shown that an arbitrarily small perturbation to the damping term of the Rayleigh equation results in points close to the stable limit cycle escaping to infinity.     

Mathematical modelling and the learning trajectory: tools to support the teaching of linear algebra

In this article we present a didactic proposal for teaching linear algebra based on two compatible theoretical models: emergent models and mathematical modelling. This proposal begins with a problematic situation related to the creation and use of secure passwords, which leads students toward the construction of the concepts of spanning set and span. The objective is to evaluate this didactic proposal by determining the level of match between the hypothetical learning trajectory (HLT) designed in this study with the actual learning trajectory in the second experimental cycle of an investigation design-based research more extensive. The results show a high level of match between the trajectories in more than half of the conjectures, which gives evidence that the HLT has supported, in many cases, the achievement of the learning objective, and that additionally mathematical modelling contributes to the construction of these linear algebra concepts.     

On the existence and bifurcation of minimal normal modes

Minimal normal modes (MNMs) are defined as non-linear normal modes which give a true minimum to Jacobi's Principle of Least Action. It is shown that for a certain class of two degree of freedom non-linear conservative systems, MNMs generically occur in pairs. The nature of both generic and non-generic bifurcations of MNMs is derived and illustrative examples are given.     

Docking glycosaminoglycans to proteins: analysis of solvent inclusion

Glycosaminoglycans (GAGs) are anionic polysaccharides, which participate in key processes in the extracellular matrix by interactions with protein targets. Due to their charged nature, accurate consideration of electrostatic and water-mediated interactions is indispensable for understanding GAGs binding properties. However, solvent is often overlooked in molecular recognition studies. Here we analyze the abundance of solvent in GAG-protein interfaces and investigate the challenges of adding explicit solvent in GAG-protein docking experiments. We observe PDB GAG-protein interfaces being significantly more hydrated than protein–protein interfaces. Furthermore, by applying molecular dynamics approaches we estimate that about half of GAG-protein interactions are water-mediated. With a dataset of eleven GAG-protein complexes we analyze how solvent inclusion affects Autodock 3, eHiTs, MOE and FlexX docking. We develop an approach to de novo place explicit solvent into the binding site prior to docking, which uses the GRID program to predict positions of waters and to locate possible areas of solvent displacement upon ligand binding. To investigate how solvent placement affects docking performance, we compare these results with those obtained by taking into account information about the solvent position in the crystal structure. In general, we observe that inclusion of solvent improves the results obtained with these methods. Our data show that Autodock 3 performs best, though it experiences difficulties to quantitatively reproduce experimental data on specificity of heparin/heparan sulfate disaccharides binding to IL-8. Our work highlights the current challenges of introducing solvent in protein-GAGs recognition studies, which is crucial for exploiting the full potential of these molecules for rational engineering.