Crotalus catalinensis

Number of Pages: 4Integrative BiologyGeological Science

Distant pointing in desktop collaborative virtual environments

Deictic pointing—pointing at things during conversations—is natural and ubiquitous in human communication. Deictic pointing is important in the real world; it is also important in collaborative virtual environments (CVEs) because CVEs are 3D virtual environments that resemble the real world. CVEs connect people from different locations, allowing them to communicate and collaborate remotely. However, the interaction and communication capabilities of CVEs are not as good as those in the real world. In CVEs, people interact with each other using avatars (the visual representations of users). One problem of avatars is that they are not expressive enough when compare to what we can do in the real world. In particular, deictic pointing has many limitations and is not well supported. This dissertation focuses on improving the expressiveness of distant pointing—where referents are out of reach—in desktop CVEs. This is done by developing a framework that guides the design and development of pointing techniques; by identifying important aspects of distant pointing through observation of how people point at distant referents in the real world; by designing, implementing, and evaluating distant-pointing techniques; and by providing a set of guidelines for the design of distant pointing in desktop CVEs. The evaluations of distant-pointing techniques examine whether pointing without extra visual effects (natural pointing) has sufficient accuracy; whether people can control free arm movement (free pointing) along with other avatar actions; and whether free and natural pointing are useful and valuable in desktop CVEs. Overall, this research provides better support for deictic pointing in CVEs by improving the expressiveness of distant pointing. With better pointing support, gestural communication can be more effective and can ultimately enhance the primary function of CVEs—supporting distributed collaboration

Dilaton Contact Terms in the Bosonic and Heterotic Strings

Dilaton contact terms in the bosonic and heterotic strings are examined following the recent work of Distler and Nelson on the bosonic and semirigid strings. In the bosonic case dilaton two-point functions on the sphere are calculated as a stepping stone to constructing a `good' coordinate family for dilaton calculations on higher genus surfaces. It is found that dilaton-dilaton contact terms are improperly normalized, suggesting that the interpretation of the dilaton as the first variation of string coupling breaks down when other dilatons are present. It seems likely that this can be attributed to the tachyon divergence found in \TCCT. For the heterotic case, it is found that there is no tachyon divergence and that the dilaton contact terms are properly normalized. Thus, a dilaton equation analogous to the one in topological gravity is derived and the interpretation of the dilaton as the string coupling constant goes through.Comment: 44 pages, Figures now included. This replacement version includes the 7 figures as PostScript files appended to the end and the macros to insert them into the text. Also some typos in intermediate formulae were correcte

The role of magnetic anisotropy in spin filter junctions

We have fabricated oxide based spin filter junctions in which we demonstrate that magnetic anisotropy can be used to tune the transport behavior of spin filter junctions. Until recently, spin filters have been largely comprised of polycrystalline materials where the spin filter barrier layer and one of the electrodes are ferromagnetic. These spin filter junctions have relied on the weak magnetic coupling between one ferromagnetic electrode and a barrier layer or the insertion of a nonmagnetic insulating layer in between the spin filter barrier and electrode. We have demonstrated spin filtering behavior in La0.7Sr0.3MnO3/chromite/Fe3O4 junctions without nonmagnetic spacer layers where the interface anisotropy plays a significant role in determining transport behavior. Detailed studies of chemical and magnetic structure at the interfaces indicate that abrupt changes in magnetic anisotropy across the non-isostructural interface is the cause of the significant suppression of junction magnetoresistance in junctions with MnCr2O4 barrier layers.Comment: 7 pages, 7 figure

Property Value, User Cost, and Rent: An Investigation of the Residential Property Market in Hong Kong

We investigate the adjustment between the user cost of housing capital, rent, and property value using the impulse response analysis. We find that in the Hong Kong residential property market, rent responds to changes in the user cost relatively fast. But the direction of the responses varies. About one third displays incomplete response, another one third over-responds, and the rest displays a negative relationship. Further work is called for to clarify such results

World-Sheet Supersymmetry Without Contact Terms

Green and Seiberg showed that, in simple treatments of fermionic string theory, it is necessary to introduce contact interactions when vertex operators collide. Otherwise, certain superconformal Ward identities would be violated. In this note, we show how these contact terms arise naturally when proper account is taken of the superconformal geometry involved when punctures collide. More precisely, we show that there is no contact term at all! Rather, corrections arise to the ``na\"\i ve" formula when the boundary of moduli space is described correctly.Comment: 14pp., 2 figures (included

A murine model of variant late infantile ceroid lipofuscinosis recapitulates behavioral and pathological phenotypes of human disease.

Neuronal ceroid lipofuscinoses (NCLs; also known collectively as Batten Disease) are a family of autosomal recessive lysosomal storage disorders. Mutations in as many as 13 genes give rise to ∼10 variants of NCL, all with overlapping clinical symptomatology including visual impairment, motor and cognitive dysfunction, seizures, and premature death. Mutations in CLN6 result in both a variant late infantile onset neuronal ceroid lipofuscinosis (vLINCL) as well as an adult-onset form of the disease called Type A Kufs. CLN6 is a non-glycosylated membrane protein of unknown function localized to the endoplasmic reticulum (ER). In this study, we perform a detailed characterization of a naturally occurring Cln6 mutant (Cln6(nclf)) mouse line to validate its utility for translational research. We demonstrate that this Cln6(nclf) mutation leads to deficits in motor coordination, vision, memory, and learning. Pathologically, we demonstrate loss of neurons within specific subregions and lamina of the cortex that correlate to behavioral phenotypes. As in other NCL models, this model displays selective loss of GABAergic interneuron sub-populations in the cortex and the hippocampus with profound, early-onset glial activation. Finally, we demonstrate a novel deficit in memory and learning, including a dramatic reduction in dendritic spine density in the cerebral cortex, which suggests a reduction in synaptic strength following disruption in CLN6. Together, these findings highlight the behavioral and pathological similarities between the Cln6(nclf) mouse model and human NCL patients, validating this model as a reliable format for screening potential therapeutics

Repeatability of Clinical, Biomechanical, and Motor Control Profiles in People with and without Standing-Induced Low Back Pain

A major research focus is optimization of interventions for low back pain (LBP). Predisposing factors for LBP development have been previously identified. To differentiate changes in these factors with intervention, factor stability over time must be determined. Twenty-three volunteers without LBP participated in a LBP-inducing standing protocol on two separate days. Outcome measures included visual analog scale (VAS) for LBP and trunk/hip muscle coactivation patterns. Intraclass correlation coefficients (ICCs) were used to examine repeatability. Between-day repeatability of outcome measures was excellent (ICCs >0.80). Individuals were consistent in subjective LBP, with 83% reporting similar day-to-day VAS levels. Muscle co-activation patterns and LBP reports are stable measures over time for this LBP-inducing protocol. Changes in these measures following intervention can be considered to be treatment effects and are not due to natural variability. This provides support for use of this protocol in studying interventions for standing-induced LBP