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Investigating the Intelligibility of a Computer Vision System for Blind Users
Computer vision systems to help blind usersare becoming increasingly common yet often these systems are not intelligible. Our work investigates the intelligibility of a wearable computer vision system to help blind users locate and identify people in their vicinity. Providing a continuous stream of information, this system allows us to explore intelligibility through interaction and instructions, going beyond studies of intelligibility that focus on explaining a decision a computer vision system might make. In a study with 13 blind users, we explored whether varying instructions (either basic or enhanced) about how the system worked would change blind users’ experience of the system. We found offering a more detailed set of instructions did not affect how successful users were using the system nor their perceived workload. We did, however, find evidence of significant differences in what they knew about the system, and they employed different, and potentially more effective, use strategies. Our findings have important implications for researchers and designers of computer vision systemsfor blind users, as well more general implications for understanding what it means to make interactive computer vision systems intelligible
Hydrogen Bond Dynamics Near A Micellar Surface: Origin of the Universal Slow Relaxation at Complex Aqueous Interfaces
The dynamics of hydrogen bonds among water molecules themselves and with the
polar head groups (PHG) at a micellar surface have been investigated by long
molecular dynamics simulations. The lifetime of the hydrogen bond between a PHG
and a water molecule is found to be much longer than that between any two water
molecules, and is likely to be a general feature of hydrophilic surfaces of
organized assemblies. Analyses of individual water trajectories suggest that
water molecules can remain bound to the micellar surface for more than a
hundred picosecond. The activation energy for such a transition from the bound
to a free state for the water molecules is estimated to be about 3.5kcal/mole.Comment: 12 pages. Phys. Rev. Lett. (Accepted) (2002
Quantum geometry and gravitational entropy
Most quantum states have wavefunctions that are widely spread over the
accessible Hilbert space and hence do not have a good description in terms of a
single classical geometry. In order to understand when geometric descriptions
are possible, we exploit the AdS/CFT correspondence in the half-BPS sector of
asymptotically AdS_5 x S^5 universes. In this sector we devise a
"coarse-grained metric operator" whose eigenstates are well described by a
single spacetime topology and geometry. We show that such half-BPS universes
have a non-vanishing entropy if and only if the metric is singular, and that
the entropy arises from coarse-graining the geometry. Finally, we use our
entropy formula to find the most entropic spacetimes with fixed asymptotic
moments beyond the global charges.Comment: 29 pages, 2 figures; references adde
Fishery, growth, yield per recruit and stock assessment of Sphyraena obtusata Cuvier off Tuticorin, Gulf of Mannar
Annual average catch of 612.2 t of barracudas were landed at the catch rate of 17.1 kg/unit which constituted
3.9% in the total catch landed by trawlers during 1987 - '89 at Tuticorin. Higher effort input during
certain months did not coincide with better abundance of barracudas. Sphyraena obtusata Cuvier
constituted on an average 69.6% of the total catch of barracudas. Based on the length-frequency data,
the growth {^ameters have been estimated to be L 470.0 mm, K 1.0364/year and t^ -0.0098 ye. The
natural mortality coefficient (M) is 1.591, the average annual total mortality coefficient (Z) is 2.8317 and
the average exploitation rate (U) is 0.4123. The average standing stock is estimated to be 343.2 t and
average annual stock 1,032.71. Yield per recruit studies indicate that S. obtusata is not exposed to higher
fishing pressure as the average fishing mortality coefficient (F), 1.2407, for the prevailing age at first
capture, 0.4709 ye is lower than the respective F,^which can yield the Y,^ in both the M/K ratios 1.0
and 1.535. There is scope for increasing the effort of trawl net with a view to increase the catch of this
species at the prevailing conditions
Acute severe hyponatraemia following parathyroid surgery for primary hyperparathyroidism – A rare but life threatening complication
Massive-Scalar Absorption by Extremal p-branes
We study the absorption probability of minimally-coupled massive scalars by
extremal p-branes. In particular, we find that the massive scalar wave equation
under the self-dual string background has the same form as the massless scalar
wave equation under the dyonic string background. Thus it can be cast into the
form of a modified Mathieu equation and solved exactly. Another example that we
can solve exactly is that of the D=4 two-charge black hole with equal charges,
for which we obtain the closed-form absorption probability. We also obtain the
leading-order absorption probabilities for D3-, M2- and M5-branes.Comment: Latex, 11 pages, reference adde
Rare squid, Thysanoteuthis rhombus Troschel from the Gulf of Mannar, India
The occurrence of a rare oceanic squid, Thysanoteuthis rhbmbus, off Veerapandiaapetnam in Gulf of Mannar on the east coast of India is reported
Transformation of stimulus correlations by the retina
Redundancies and correlations in the responses of sensory neurons seem to
waste neural resources but can carry cues about structured stimuli and may help
the brain to correct for response errors. To assess how the retina negotiates
this tradeoff, we measured simultaneous responses from populations of ganglion
cells presented with natural and artificial stimuli that varied greatly in
correlation structure. We found that pairwise correlations in the retinal
output remained similar across stimuli with widely different spatio-temporal
correlations including white noise and natural movies. Meanwhile, purely
spatial correlations tended to increase correlations in the retinal response.
Responding to more correlated stimuli, ganglion cells had faster temporal
kernels and tended to have stronger surrounds. These properties of individual
cells, along with gain changes that opposed changes in effective contrast at
the ganglion cell input, largely explained the similarity of pairwise
correlations across stimuli where receptive field measurements were possible.Comment: author list corrected in metadat
Gravitational waves from inspiraling compact binaries: Validity of the stationary-phase approximation to the Fourier transform
We prove that the oft-used stationary-phase method gives a very accurate
expression for the Fourier transform of the gravitational-wave signal produced
by an inspiraling compact binary. We give three arguments. First, we
analytically calculate the next-order correction to the stationary-phase
approximation, and show that it is small. This calculation is essentially an
application of the steepest-descent method to evaluate integrals. Second, we
numerically compare the stationary-phase expression to the results obtained by
Fast Fourier Transform. We show that the differences can be fully attributed to
the windowing of the time series, and that they have nothing to do with an
intrinsic failure of the stationary-phase method. And third, we show that these
differences are negligible for the practical application of matched filtering.Comment: 8 pages, ReVTeX, 4 figure
Matched filtering of gravitational waves from inspiraling compact binaries: Computational cost and template placement
We estimate the number of templates, computational power, and storage
required for a one-step matched filtering search for gravitational waves from
inspiraling compact binaries. These estimates should serve as benchmarks for
the evaluation of more sophisticated strategies such as hierarchical searches.
We use waveform templates based on the second post-Newtonian approximation for
binaries composed of nonspinning compact bodies in circular orbits. We present
estimates for six noise curves: LIGO (three configurations), VIRGO, GEO600, and
TAMA. To search for binaries with components more massive than 0.2M_o while
losing no more than 10% of events due to coarseness of template spacing,
initial LIGO will require about 1*10^11 flops (floating point operations per
second) for data analysis to keep up with data acquisition. This is several
times higher than estimated in previous work by Owen, in part because of the
improved family of templates and in part because we use more realistic (higher)
sampling rates. Enhanced LIGO, GEO600, and TAMA will require computational
power similar to initial LIGO. Advanced LIGO will require 8*10^11 flops, and
VIRGO will require 5*10^12 flops. If the templates are stored rather than
generated as needed, storage requirements range from 1.5*10^11 real numbers for
TAMA to 6*10^14 for VIRGO. We also sketch and discuss an algorithm for placing
the templates in the parameter space.Comment: 15 pages, 4 figures, submitted to Phys. Rev.
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