2,567,414 research outputs found
On Sound Relative Error Bounds for Floating-Point Arithmetic
State-of-the-art static analysis tools for verifying finite-precision code
compute worst-case absolute error bounds on numerical errors. These are,
however, often not a good estimate of accuracy as they do not take into account
the magnitude of the computed values. Relative errors, which compute errors
relative to the value's magnitude, are thus preferable. While today's tools do
report relative error bounds, these are merely computed via absolute errors and
thus not necessarily tight or more informative. Furthermore, whenever the
computed value is close to zero on part of the domain, the tools do not report
any relative error estimate at all. Surprisingly, the quality of relative error
bounds computed by today's tools has not been systematically studied or
reported to date. In this paper, we investigate how state-of-the-art static
techniques for computing sound absolute error bounds can be used, extended and
combined for the computation of relative errors. Our experiments on a standard
benchmark set show that computing relative errors directly, as opposed to via
absolute errors, is often beneficial and can provide error estimates up to six
orders of magnitude tighter, i.e. more accurate. We also show that interval
subdivision, another commonly used technique to reduce over-approximations, has
less benefit when computing relative errors directly, but it can help to
alleviate the effects of the inherent issue of relative error estimates close
to zero
Roll function in a flight simulator
Method introduces roll into the flying-spot scanner by modifying the scanning waveforms
Moduli spaces of noncommutative instantons: gauging away noncommutative parameters
Using the theory of noncommutative geometry in a braided monoidal category,
we improve upon a previous construction of noncommutative families of
instantons of arbitrary charge on the deformed sphere S^4_\theta. We formulate
a notion of noncommutative parameter spaces for families of instantons and we
explore what it means for such families to be gauge equivalent, as well as
showing how to remove gauge parameters using a noncommutative quotient
construction. Although the parameter spaces are a priori noncommutative, we
show that one may always recover a classical parameter space by making an
appropriate choice of gauge transformation.Comment: v2: 44 pages; minor changes. To appear in Quart. J. Mat
S100B is increased in Parkinson’s disease and ablation protects against MPTP-induced toxicity through the RAGE and TNF-α pathway
Peer reviewedPublisher PD
Parkinson's disease dementia: a neural networks perspective.
In the long-term, with progression of the illness, Parkinson's disease dementia affects up to 90% of patients with Parkinson's disease. With increasing life expectancy in western countries, Parkinson's disease dementia is set to become even more prevalent in the future. However, current treatments only give modest symptomatic benefit at best. New treatments are slow in development because unlike the pathological processes underlying the motor deficits of Parkinson's disease, the neural mechanisms underlying the dementing process and its associated cognitive deficits are still poorly understood. Recent insights from neuroscience research have begun to unravel the heterogeneous involvement of several distinct neural networks underlying the cognitive deficits in Parkinson's disease dementia, and their modulation by both dopaminergic and non-dopaminergic transmitter systems in the brain. In this review we collate emerging evidence regarding these distinct brain networks to give a novel perspective on the pathological mechanisms underlying Parkinson's disease dementia, and discuss how this may offer new therapeutic opportunities
A study of the means of increasing the dynamic range of visual simulation by means of a flying-spot scanner Final report
Increasing dynamic range of visual simulation for pilots using flying spot scanne
Financial Engineering and Rationality: Experimental Evidence Based on the Monty Hall Problem
Financial engineering often involves redefining existing financial assets to create new financial products. This paper investigates whether financial engineering can alter the environment so that irrational agents can quickly learn to be rational. The specific environment we investigate is based on the Monty Hall problem, a well-studied choice anomaly. Our results show that, by the end of the experiment, the majority of subjects understand the Monty Hall anomaly. Average valuation of the experimental asset is very close to the expected value based on the true probabilities.experiment, behavioral finance
The Gysin Sequence for Quantum Lens Spaces
We define quantum lens spaces as `direct sums of line bundles' and exhibit
them as `total spaces' of certain principal bundles over quantum projective
spaces. For each of these quantum lens spaces we construct an analogue of the
classical Gysin sequence in K-theory. We use the sequence to compute the
K-theory of the quantum lens spaces, in particular to give explicit geometric
representatives of their K-theory classes. These representatives are
interpreted as `line bundles' over quantum lens spaces and generically define
`torsion classes'. We work out explicit examples of these classes.Comment: 27 pages. v2: No changes in the scientific content and results.
Section 5 completely re-written and a final section added; suppressed two
appendices; added references; minor changes throughout the paper. To appear
in the JNc
Understanding the Escalation of Brain Drain in Nigeria From Poor Leadership Point of View
Migration of people from one place to another in countries of the world in search of better conditions of living predates history.
It ignited western societies’ contact with Africa and the rest of the world. Prior the contact, agriculture was the main stay of Africa’s
economy. Thus, the movement of farmers from one location to another in search of fertile grounds for cultivation was in vogue. After
independence in Nigeria, cattle rearers are known for relocating from the North to South during dry season in search of green grass to
sustain their cattle and occupation. In the present day Nigeria, the same scenario still abounds but in a new dimension. It now involves
movement of highly skilled manpower from the country to developed societies. Among other things, this paper finds out if there is a
relationship between poor leadership of the country and escalation of brain drain. Simple percentage and ranking method was used to
analyze the study’s data. Chi-square was used to test its hypothesis. Our result revealed a relationship between poor leadership of the
country and brain drain. It equally indicated that students are interested in travelling out of the country to developed societies after their
study. Also from the study, twelve causes of brain drain were indentified. Some of them are: mass unemployment, poor salaries and
conditions of service, mass poverty, crises-religious, communal, political, education etc. In respect of effects of brain drain on the nation’s
economy, eleven factors were identified by the respondents. Some of them are: loss of human capital assets to man various institutions in
the country, loss of tax of migrated manpower to foreign countries, loss of capital invested in education of migrated manpower assets etc.
Finally, eleven solutions were profiled to the lingering problem of brain drain. The most important ones are: Good leadership, salary and
conditions of service as well as rewarding system for diligent staff, mass employment etc
Regional Strategies of Multinational Pharmaceutical Firms
This paper examines the R&D and strategies of the world’s largest firms in the pharmaceuticals sector and finds a high degree of intra-regional sales. R&D and sales are more concentrated within North America and Europe than in Asia. In addition, the relative size of the U.S. market, compared to other parts of the triad, creates imbalances with respect to R&D, sales and international strategy.
- …