1,258 research outputs found
Text Entry in Immersive Head-Mounted Display-Based Virtual Reality Using Standard Keyboards
We study the performance and user experience of two popular mainstream text
entry devices, desktop keyboards and touchscreen keyboards, for use in Virtual
Reality (VR) applications. We discuss the limitations arising from limited
visual feedback, and examine the efficiency of different strategies of use. We
analyze a total of 24 hours of typing data in VR from 24 participants and find
that novice users are able to retain about 60% of their typing speed on a
desktop keyboard and about 40-45\% of their typing speed on a touchscreen
keyboard. We also find no significant learning effects, indicating that users
can transfer their typing skills fast into VR. Besides investigating baseline
performances, we study the position in which keyboards and hands are rendered
in space. We find that this does not adversely affect performance for desktop
keyboard typing and results in a performance trade-off for touchscreen keyboard
typing
Dark matter within high surface brightness spiral galaxies
We present results from a detailed dynamical analysis of five high surface
brightness, late type spirals, studied with the aim to quantify the
luminous-to-dark matter ratio inside their optical radii. The galaxies' stellar
light distribution and gas kinematics have been observed and compared to
hydrodynamic gas simulations, which predict the 2D gas dynamics arising in
response to empirical gravitational potentials, which are combinations of
differing stellar disk and dark halo contributions. The gravitational potential
of the stellar disk was derived from near-infrared photometry, color-corrected
to constant (M/L); the dark halo was modelled by an isothermal sphere with a
core. Hydrodynamic gas simulations were performed for each galaxy for a
sequence of five different mass fractions of the stellar disk and for a wide
range of spiral pattern speeds. These two parameters mainly determine the
modelled gas distribution and kinematics. The agreement between the
non-axisymmetric part of the simulated and observed gas kinematics permitted us
to conclude that the galaxies with the highest rotation velocities tend to
possess near-maximal stellar disks. In less massive galaxies, with v_max<200
km/s, the mass of the dark halo at least equals the stellar mass within 2-3
R_disk. The simulated gas morphology provides a powerful tool to determine the
dominant spiral pattern speed. The corotation radius for all galaxies was found
to be constant at R_corotation ~ 3 R_disk and encloses the strong part of the
stellar spiral in all cases.Comment: 28 pages, 7 figures; to appear in the Astrophysical Journal, Vol.
586, March 200
Bodies, technologies and action possibilities: when is an affordance?
Borrowed from ecological psychology, the concept of affordances is often said to offer the social study of technology a means of re-framing the question of what is, and what is not, ‘social’ about technological artefacts. The concept, many argue, enables us to chart a safe course between the perils of technological determinism and social constructivism. This article questions the sociological adequacy of the concept as conventionally deployed. Drawing on ethnographic work on the ways technological artefacts engage, and are engaged by, disabled bodies, we propose that the ‘affordances’ of technological objects are not reducible to their material constitution but are inextricably bound up with specific, historically situated modes of engagement and ways of life
Compilation of extended recursion in call-by-value functional languages
This paper formalizes and proves correct a compilation scheme for
mutually-recursive definitions in call-by-value functional languages. This
scheme supports a wider range of recursive definitions than previous methods.
We formalize our technique as a translation scheme to a lambda-calculus
featuring in-place update of memory blocks, and prove the translation to be
correct.Comment: 62 pages, uses pi
Impact of measurement backaction on nuclear spin qubits in silicon
Phosphorus donor nuclear spins in silicon couple weakly to the environment
making them promising candidates for high-fidelity qubits. The state of a donor
nuclear spin qubit can be manipulated and read out using its hyperfine
interaction with the electron confined by the donor potential. Here we use a
master equation-based approach to investigate how the backaction from this
electron-mediated measurement affects the lifetimes of single and multi-donor
qubits. We analyze this process as a function of electric and magnetic fields,
and hyperfine interaction strength. Apart from single nuclear spin flips, we
identify an additional measurement-related mechanism, the nuclear spin
flip-flop, which is specific to multi-donor qubits. Although this flip-flop
mechanism reduces qubit lifetimes, we show that it can be effectively
suppressed by the hyperfine Stark shift. We show that using atomic precision
donor placement and engineered Stark shift, we can minimize the measurement
backaction in multi-donor qubits, achieving larger nuclear spin lifetimes than
single donor qubits
Inorganic carbon and pH dependency of Trichodesmium's photosynthetic rates.
We established the relationship between photosynthetic carbon fixation rates and pH, CO2 and HCO3- concentrations in the diazotroph Trichodesmium erythraeum IMS101. Inorganic 14C-assimilation was measured in TRIS-buffered ASW medium where the absolute and relative concentrations of CO2, pH and HCO3- were manipulated. First, we varied the total dissolved inorganic carbon concentration (TIC) (< 0 to ~ 5 mM) at constant pH, so ratios of CO2 and HCO3- remained relatively constant. Second, we varied pH (~ 8.54 to 7.52) at constant TIC, so CO2 increased whilst HCO3- declined. We found that 14C-assimilation could be described by the same function of CO2 for both approaches but showed different dependencies on HCO3- when pH was varied at constant TIC than when TIC was varied at constant pH. A numerical model of Trichodesmium's CCM showed carboxylation rates are modulated by HCO3- and pH. The decrease in Ci assimilation at low CO2, when TIC was varied, is due to HCO3- uptake limitation of the carboxylation rate. Conversely, when pH was varied, Ci assimilation declined due to a high-pH mediated increase in HCO3- and CO2 leakage rates, potentially coupled to other processes (uncharacterised within the CCM model) that restrict Ci assimilation rates under high-pH conditions
Quantum point contact on graphite surface
The conductance through a quantum point contact created by a sharp and hard
metal tip on the graphite surface has features which to our knowledge have not
been encountered so far in metal contacts or in nanowires. In this paper we
first investigate these features which emerge from the strongly directional
bonding and electronic structure of graphite, and provide a theoretical
understanding for the electronic conduction through quantum point contacts. Our
study involves the molecular-dynamics simulations to reveal the variation of
interlayer distances and atomic structure at the proximity of the contact that
evolves by the tip pressing toward the surface. The effects of the elastic
deformation on the electronic structure, state density at the Fermi level, and
crystal potential are analyzed by performing self-consistent-field
pseudopotential calculations within the local-density approximation. It is
found that the metallicity of graphite increases under the uniaxial compressive
strain perpendicular to the basal plane. The quantum point contact is modeled
by a constriction with a realistic potential. The conductance is calculated by
representing the current transporting states in Laue representation, and the
variation of conductance with the evolution of contact is explained by taking
the characteristic features of graphite into account. It is shown that the
sequential puncturing of the layers characterizes the conductance.Comment: LaTeX, 11 pages, 9 figures (included), to be published in Phys. Rev.
B, tentatively scheduled for 15 September 1998 (Volume 58, Number 12
Rupture by damage accumulation in rocks
The deformation of rocks is associated with microcracks nucleation and
propagation, i.e. damage. The accumulation of damage and its spatial
localization lead to the creation of a macroscale discontinuity, so-called
"fault" in geological terms, and to the failure of the material, i.e. a
dramatic decrease of the mechanical properties as strength and modulus. The
damage process can be studied both statically by direct observation of thin
sections and dynamically by recording acoustic waves emitted by crack
propagation (acoustic emission). Here we first review such observations
concerning geological objects over scales ranging from the laboratory sample
scale (dm) to seismically active faults (km), including cliffs and rock masses
(Dm, hm). These observations reveal complex patterns in both space (fractal
properties of damage structures as roughness and gouge), time (clustering,
particular trends when the failure approaches) and energy domains (power-law
distributions of energy release bursts). We use a numerical model based on
progressive damage within an elastic interaction framework which allows us to
simulate these observations. This study shows that the failure in rocks can be
the result of damage accumulation
TCR-engineered adoptive cell therapy effectively treats intracranial murine glioblastoma
BACKGROUND: Adoptive cellular therapies with chimeric antigen receptor T cells have revolutionized the treatment of some malignancies but have shown limited efficacy in solid tumors such as glioblastoma and face a scarcity of safe therapeutic targets. As an alternative, T cell receptor (TCR)-engineered cellular therapy against tumor-specific neoantigens has generated significant excitement, but there exist no preclinical systems to rigorously model this approach in glioblastoma.
METHODS: We employed single-cell PCR to isolate a TCR specific for the Imp3
RESULTS: We isolated and characterized the 3×1.1C TCR that displayed a high affinity for mImp3 but no wild-type cross-reactivity. To provide a source of mImp3-specific T cells, we generated the MISTIC mouse. In a model of adoptive cellular therapy, the infusion of activated MISTIC T cells resulted in rapid intratumoral infiltration and profound antitumor effects with long-term cures in a majority of GL261-bearing mice. The subset of mice that did not respond to the adoptive cell therapy showed evidence of retained neoantigen expression but intratumoral MISTIC T cell dysfunction. The efficacy of MISTIC T cell therapy was lost in mice bearing a tumor with heterogeneous mImp3 expression, showcasing the barriers to targeted therapy in polyclonal human tumors.
CONCLUSIONS: We generated and characterized the first TCR transgenic against an endogenous neoantigen within a preclinical glioma model and demonstrated the therapeutic potential of adoptively transferred neoantigen-specific T cells. The MISTIC mouse provides a powerful novel platform for basic and translational studies of antitumor T-cell responses in glioblastoma
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