Comment on "Effect of growth interruptions on the light emission and indium clustering of InGaN/GaN multiple quantum wells" [Appl. Phys. Lett. 79, 2594 (2001)]

This entry is a comment on "Effect of growth interruptions on the light emission and indium clustering

Seeding without leading: making space for participant contribution in design elicitation techniques

As HCI embraces experience design, it will increasingly rely on new elicitation methods that are capable of drawing out the multi-faceted subjectivities of individuals without being overly prescriptive as to the final design or experience outcome. In this panel we wish to describe and discuss subtle elicitation techniques that allow the elicitation of participant ideas and interests with minimum prejudicing by the researcher. We argue that leaving space for meaning to be made by project nformants is a valuable approach to understanding both design requirements and use issues. We show work that has come from taking this approach and discuss why we have been concerned to keep a creative space open in our research and how we invite people into i

Targeted deep surveys of high Galactic latitude HI with the GBT

Over 800 sq. deg. of high Galactic latitude sky have been mapped at 21 cm with the Robert C. Byrd Green Bank Telescope (GBT). An improved knowledge of the telescope's beam characteristics has allowed us to reliably map not only regions of high column density, but also such regions as ELAIS N1, a targeted Spitzer field, which have very low HI column density. The additional fields we have observed cover a cross-section of dynamically and chemically interesting regions as indicated by the presence of intermediate/high velocity gas and/or anomalous far-IR (dust) colour.Comment: 7 pages, 5 figures. To appear in "The Dynamic ISM: A celebration of the Canadian Galactic Plane Survey" ASP Conference Serie

Leaky vessels as a potential source of stromal acidification in tumours

Malignant tumours are characterised by higher rates of acid production and a lower extracellular pH than normal tissues. Previous mathematical modelling has indicated that the tumour-derived production of acid leads to a gradient of low pH in the interior of the tumour extending to a normal pH in the peritumoural tissue. This paper uses mathematical modelling to examine the potential of leaky vessels as an additional source of stromal acidification in tumours. We explore whether and to what extent increasing vascular permeability in vessels can lead to the breakdown of the acid gradient from the core of the tumour to the normal tissue, and a progressive acidification of the peritumoural stroma. We compare our mathematical simulations to experimental results found in vivo with a tumour implanted in the mammary fat pad of a mouse in a window chamber construct. We find that leaky vasculature can cause a net acidification of the normal tissue away from the tumour boundary, though not a progressive acidification over time as seen in the experiments. Only through progressively increasing the leakiness can the model qualitatively reproduce the experimental results. Furthermore, the extent of the acidification predicted by the mathematical model is less than as seen in the window chamber, indicating that although vessel leakiness might be acting as a source of acid, it is not the only factor contributing to this phenomenon. Nevertheless, tumour destruction of vasculature could result in enhanced stromal acidification and invasion, hence current therapies aimed at buffering tumour pH should also examine the possibility of preventing vessel disruption

Nonlinear ac response of anisotropic composites

When a suspension consisting of dielectric particles having nonlinear characteristics is subjected to a sinusoidal (ac) field, the electrical response will in general consist of ac fields at frequencies of the higher-order harmonics. These ac responses will also be anisotropic. In this work, a self-consistent formalism has been employed to compute the induced dipole moment for suspensions in which the suspended particles have nonlinear characteristics, in an attempt to investigate the anisotropy in the ac response. The results showed that the harmonics of the induced dipole moment and the local electric field are both increased as the anisotropy increases for the longitudinal field case, while the harmonics are decreased as the anisotropy increases for the transverse field case. These results are qualitatively understood with the spectral representation. Thus, by measuring the ac responses both parallel and perpendicular to the uniaxial anisotropic axis of the field-induced structures, it is possible to perform a real-time monitoring of the field-induced aggregation process.Comment: 14 pages and 4 eps figure

Characterization of InGaN and InAlN epilayers by microdiffraction X-Ray reciprocal space mapping

We report a study of InGaN and InAlN epilayers grown on GaN/Sapphire substrates by microfocused three-dimensional X-ray Reciprocal Space Mapping (RSM). The analysis of the full volume of reciprocal space, while probing samples on the microscale with a focused X-ray beam, allows us to gain uniquely valuable information about the microstructure of III-N alloy epilayers. It is found that “seed” InGaN mosaic nanocrystallites are twisted with respect to the ensemble average and strain free. This indicates that the growth of InGaN epilayers follows the Volmer-Weber mechanism with nucleation of “seeds” on strain fields generated by the a-type dislocations which are responsible for the twist of underlying GaN mosaic blocks. In the case of InAlN epilayer formation of composition gradient was observed at the beginning of the epitaxial growth

Stau as the Lightest Supersymmetric Particle in R-Parity Violating SUSY Models: Discovery Potential with Early LHC Data

We investigate the discovery potential of the LHC experiments for R-parity violating supersymmetric models with a stau as the lightest supersymmetric particle (LSP) in the framework of minimal supergravity. We classify the final states according to their phenomenology for different R-parity violating decays of the LSP. We then develop event selection cuts for a specific benchmark scenario with promising signatures for the first beyond the Standard Model discoveries at the LHC. For the first time in this model, we perform a detailed signal over background analysis. We use fast detector simulations to estimate the discovery significance taking the most important Standard Model backgrounds into account. Assuming an integrated luminosity of 1 inverse femtobarn at a center-of-mass energy of 7 TeV, we perform scans in the parameter space around the benchmark scenario we consider. We then study the feasibility to estimate the mass of the stau-LSP. We briefly discuss difficulties, which arise in the identification of hadronic tau decays due to small tau momenta and large particle multiplicities in our scenarios.Comment: 26 pages, 18 figures, LaTeX; minor changes, final version published in PR

Fluctuations and correlations in population models with age structure

We study the population profile in a simple discrete time model of population dynamics. Our model, which is closely related to certain ``bit-string'' models of evolution, incorporates competition for resources via a population dependent death probability, as well as a variable reproduction probability for each individual as a function of age. We first solve for the steady-state of the model in mean field theory, before developing analytic techniques to compute Gaussian fluctuation corrections around the mean field fixed point. Our computations are found to be in good agreement with Monte-Carlo simulations. Finally we discuss how similar methods may be applied to fluctuations in continuous time population models.Comment: 4 page