13,176 research outputs found
Compressible flow structures interaction with a two-dimensional ejector: a cold-flow study
An experimental study has been conducted to examine the interaction of compressible ïŹow structures such as
shocks and vortices with a two-dimensional ejector geometry using a shock-tube facility. Three diaphragm pressure
ratios ofP4
=P1 = 4, 8, and 12 have been employed, whereP4
is the driver gas pressure andP1
is the pressure within
the driven compartment of the shock tube. These lead to incident shock Mach numbers of Ms = 1:34, 1.54, and 1.66,
respectively. The length of the driver section of the shock tube was 700 mm. Air was used for both the driver and
driven gases. High-speed shadowgraphy was employed to visualize the induced ïŹowïŹeld. Pressure measurements
were taken at different locations along the test section to study theïŹow quantitatively. The induced ïŹow is unsteady
and dependent on the degree of compressibility of the initial shock wave generated by the rupture of the diaphragm
Frank's constant in the hexatic phase
Using video-microscopy data of a two-dimensional colloidal system the
bond-order correlation function G6 is calculated and used to determine the
temperature-dependence of both the orientational correlation length xi6 in the
isotropic liquid phase and the Frank constant F_A in the hexatic phase. F_A
takes the value 72/pi at the hexatic to isotropic liquid phase transition and
diverges at the hexatic to crystal transition as predicted by the KTHNY-theory.
This is a quantitative test of the mechanism of breaking the orientational
symmetry by disclination unbinding
Electronic Instrumentation
Contains research objectives andNational Institutes of Health (Grant 5 505 FR-07047-03
Geodesics for Efficient Creation and Propagation of Order along Ising Spin Chains
Experiments in coherent nuclear and electron magnetic resonance, and optical
spectroscopy correspond to control of quantum mechanical ensembles, guiding
them from initial to final target states by unitary transformations. The
control inputs (pulse sequences) that accomplish these unitary transformations
should take as little time as possible so as to minimize the effects of
relaxation and decoherence and to optimize the sensitivity of the experiments.
Here we give efficient syntheses of various unitary transformations on Ising
spin chains of arbitrary length. The efficient realization of the unitary
transformations presented here is obtained by computing geodesics on a sphere
under a special metric. We show that contrary to the conventional belief, it is
possible to propagate a spin order along an Ising spin chain with coupling
strength J (in units of Hz), significantly faster than 1/(2J) per step. The
methods presented here are expected to be useful for immediate and future
applications involving control of spin dynamics in coherent spectroscopy and
quantum information processing
Electronic Instrumentation
Contains reports on status of research and three research projects.National Institutes of Health (Grant 1 505 FR07047-01)Electronic Instrumentation Group of the Research Laboratory of Electronics in research under NIH Grant 1 505 FR07047-0
Static and Dynamic Phases for Vortex Matter with Attractive Interactions
Exotic vortex states with long range attraction and short range repulsion
have recently been proposed to arise in superconducting hybrid structures and
multi-band superconductors. Using large scale simulations we examine the static
and dynamic properties of such vortex states interacting with random and
periodic pinning. In the absence of pinning this system does not form patterns
but instead completely phase separates. When pinning is present there is a
transition from inhomogeneous to homogeneous vortex configurations similar to a
wetting phenomenon. Under an applied drive, a dynamical dewetting process can
occur from a strongly pinned homogeneous state into pattern forming states. We
show that a signature of the exotic vortex interactions under transport
measurements is a robust double peak feature in the differential conductivity
curves.Comment: 5 pages, 4 postscript figure
Upper and lower bounds on the mean square radius and criteria for occurrence of quantum halo states
In the context of non-relativistic quantum mechanics, we obtain several upper
and lower limits on the mean square radius applicable to systems composed by
two-body bound by a central potential. A lower limit on the mean square radius
is used to obtain a simple criteria for the occurrence of S-wave quantum halo
sates.Comment: 12 pages, 2 figure
Gustatory responses in three prosimian and two simian primate species (Tupaia glis, Nycticebus coucang, Galago senegalensis, Callithrix jacchus jacchus and Saguinus midas niger) to six sweeteners and miraculin and their phylogenetic implications
The intake of six sweeteners was recorded together with their effects on the impulse activity of the chorda tympani proper nerve during their application to the tongue. The sweeteners were: acetosulfam, aspartame, D-tryptophan, glycine, xylitol and thaumatin. They were used at human equi-sweet concentrations. In all species, D-tryptophan was strongly preferred and gave a significant response, while aspartame and thaumatin gave neither a significant behavioral nor a significant neural response. Acetosulfam, glycine and xylitol elicited neural responses, but their behavioral effects differed from a rejection in some species to a preference in others. Miraculin, which has a sweetness inducing effect in man, showed this effect only in the platyrrhinean species and not in the prosimia
Peer mentorship and positive effects on student mentor and mentee retention and academic success
This study examined how the introduction of peer mentorship in an undergraduate health and social welfare programme at a large northern university affected student learning. Using an ethnographic case study approach, the study draws upon data collected from a small group of mentors and their mentees over a period of one academic year using interviews, reflective journals, assessment and course evaluation data.
Analysis of the data collected identified a number of key findings: peer mentorship improves assessment performance for both mentee and mentor; reduces stress and anxiety, enhances participation and engagement in the academic community, and adds value to student outcomes
Maximising transparency in a doctoral thesis: The complexities of writing about the use of QSR*NVIVO within a grounded theory study
This paper discusses the challenges of how to provide a transparent account of the use of the software programme QSR*NVIVO (QSR 2000) within a Grounded Theory framework (Glaser and Strauss 1967; Strauss and Corbin 1998). Psychology students are increasingly pursuing qualitative research projects such to the extent that the UK Economic and Social Research Council (ESRC) advise that students should have skill in the use of computer assisted qualitative data analysis software (CAQDAS) (Economic and Social Research Council 2001). Unlike quantitative studies, rigid formulae do not exist for writing-up qualitative projects for doctoral theses. Most authors, however, agree that transparency is essential when communicating the findings of qualitative research. Sparkes (2001) recommends that evaluative criteria for qualitative research should be commensurable with the aims, objectives, and epistemological assumptions of the research project. Likewise, the use of CAQDAS should vary according to the research methodology followed, and thus researchers should include a discussion of how CAQDAS was used. This paper describes how the evolving process of coding data, writing memos, categorising, and theorising were integrated into the written thesis. The structure of the written document is described including considerations about restructuring and the difficulties of writing about an iterative process within a linear document
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