74,291 research outputs found
A covariant entropy bound conjecture on the dynamical horizon
As a compelling pattern for the holographic principle, our covariant entropy
bound conjecture is proposed for more general dynamical horizons. Then we apply
our conjecture to CDM cosmological models, where we find it imposes a
novel upper bound on the cosmological constant for our own universe
by taking into account the dominant entropy contribution from super-massive
black holes, which thus provides an alternative macroscopic perspective to
understand the longstanding cosmological constant problem. As an intriguing
implication of this conjecture, we also discuss the possible profound relation
between the present cosmological constant, the origin of mass, and the
anthropic principle.Comment: JHEP style, 9 pages, 1 figure, honorable mention award received from
Gravity Research Foundation for 2008 Essay Competitio
A Generalized Spatial Measure for Resilience of Microbial Systems
The emergent property of resilience is the ability of a system to return to an original state after a disturbance. Resilience may be used as an early warning system for significant or irreversible community transition; that is, a community with diminishing or low resilience may be close to catastrophic shift in function or an irreversible collapse. Typically, resilience is quantified using recovery time, which may be difficult or impossible to directly measure in microbial systems. A recent study in the literature showed that under certain conditions, a set of spatial-based metrics termed recovery length, can be correlated to recovery time, and thus may be a reasonable alternative measure of resilience. However, this spatial metric of resilience is limited to use for step-change perturbations. Building upon the concept of recovery length, we propose a more general form of the spatial metric of resilience that can be applied to any shape of perturbation profiles (for example, either sharp or smooth gradients). We termed this new spatial measure “perturbation-adjusted spatial metric of resilience” (PASMORE). We demonstrate the applicability of the proposed metric using a mathematical model of a microbial mat
3D Depthwise Convolution: Reducing Model Parameters in 3D Vision Tasks
Standard 3D convolution operations require much larger amounts of memory and
computation cost than 2D convolution operations. The fact has hindered the
development of deep neural nets in many 3D vision tasks. In this paper, we
investigate the possibility of applying depthwise separable convolutions in 3D
scenario and introduce the use of 3D depthwise convolution. A 3D depthwise
convolution splits a single standard 3D convolution into two separate steps,
which would drastically reduce the number of parameters in 3D convolutions with
more than one order of magnitude. We experiment with 3D depthwise convolution
on popular CNN architectures and also compare it with a similar structure
called pseudo-3D convolution. The results demonstrate that, with 3D depthwise
convolutions, 3D vision tasks like classification and reconstruction can be
carried out with more light-weighted neural networks while still delivering
comparable performances.Comment: Work in progres
Five-dimensional metric gravity and the accelerated universe
The metric theories of gravity are generalized to five-dimensional
spacetimes. By assuming a hypersurface-orthogonal Killing vector field
representing the compact fifth dimension, the five-dimensional theories are
reduced to their four-dimensional formalism. Then we study the cosmology of a
special class of models in a spatially flat FRW spacetime. It
is shown that the parameter can be constrained to a certain range by the
current observed deceleration parameter, and its lower bound corresponds to the
Kaluza-Klein theory. It turns out that both expansion and contraction of the
extra dimension may prescribe the smooth transition from the deceleration era
to the acceleration era in the recent past as well as an accelerated scenario
for the present universe. Hence five-dimensional gravity can naturally
account for the present accelerated expansion of the universe. Moreover, the
models predict a transition from acceleration to deceleration in the future,
followed by a cosmic recollapse within finite time. This differs from the
prediction of the five-dimensional Brans-Dicke theory but is in consistent with
a recent prediction based on loop quantum cosmology.Comment: 14 pages, 9 figures; Version published in PR
Dietary Nutrient Intake and Obesity Prevalence Among Native American Adolescents
The prevalence of obesity among adolescent minority populations has been long recognized, but little research has been done on Native Americans adolescents. Using anthropometric measurements and dietary assessments, the findings within each study have shown to obtain baseline measures to determine the prevalence of obesity within the Sherman Indian High School's Native American adolescent population. Data of each assessment appear to be of use for predicting obesity and creating effective future interventions. Compiling data using the Harvard School of Public Health Youth/Adolescent Questionnaire (HSPH YAQ), a semi-quantitative food frequency questionnaire allowed significant data to be found between normal and obese weight students. Utilizing each finding allows more effective ways of targeting and reversing the inclining rate of obesity among Native American adolescents. Results show that antioxidants being examined on such as vitamin E and lycopene are beneficial in lowering the obesity rate among Native American adolescents. Levels of fiber, thiamin and folate consumption was significantly lower among the obese population in Sherman Indian High School's Native American adolescents. Moreover, dietary mineral intake was shown to be lower among obese Native American adolescents comparing with the normal weight group. The results suggested that dietary consumption of these nutrients might correlate and predict obesity and lead to the development of effective interventions for Native Americans. This study also found the effects of total fiber and vitamin B in diets with lifestyle intervention in prediabetic adults, showing that total fiber intake among the normal weight students is significantly higher than obese students, indicating that fiber and vitamin profile could be important determinants of the effect of dietary intervention
Sea flavor content of octet baryons and intrinsic five-quark Fock states
Sea quark contents of the octet baryons are investigated by employing an
extended chiral constituent quark approach, which embodies higher Fock
five-quark components in the baryons wave-functions. The well-known flavor
asymmetry of the nucleon sea , is used as input to predict the
probabilities of , and in the nucleon, ,
and baryons, due to the intrinsic five-quark components in the
baryons wave functions.Comment: 22 page
Comment on a mechanism of dynamical breaking of supersymmetry
We re-examine the so-called Nambu-Jona-Lasinio mechanism suggested by Song,
Xu and Chin in breaking the supersymmetry in the Wess-Zumino model and show
that this mechanism cannot be justified without assuming special effects
between fermions. The fermion condensation suggested by them corresponds to an
unstable vacuum configuration. As a result, there is no fermion condensation
and no supersymmetry breaking in the model discussed by them.Comment: 10 pages, Plain Late
A covariant entropy conjecture on cosmological dynamical horizon
We here propose a covariant entropy conjecture on cosmological dynamical
horizon. After the formulation of our conjecture, we test its validity in
adiabatically expanding universes with open, flat and closed spatial geometry,
where our conjecture can also be viewed as a cosmological version of the
generalized second law of thermodynamics in some sense.Comment: JHEP style, 9 pages, 1 figure, typos corrected, accepted for
publication in JHE
Using handheld pocket computers in a wireless telemedicine system
Objectives: To see if senior emergency nurse practitioners can provide support to
inexperienced ones in a Minor Injuries Unit by using a wireless LAN system of
telemedicine transmitting images to a PDA when they were on duty. In addition,
whether such a system could be sufficiently accurate to make clinical diagnoses with
a high level of diagnostic confidence. This would permit an overall lower grade of
nurse to be employed to manage most of the cases as they arrive with a proportionate
lowering of costs.
Methods: The wireless LAN equipment could roam in the Minor Injuries Unit and
the experienced emergency Nurse practitioners could be at home, shopping or even
at a considerable distance from the centre.
Thirty pictorial images of patients who had been sent to the Review Clinic were
transmitted to a PDA various distances of one to sixteen miles from the centre. Two
senior emergency nurse practitioners viewed the images and opined on the diagnosis,
their degree of confidence in the diagnosis and their opinion of the quality of the
image.
Results: the images of patients were sharp, clear, and of diagnostic quality. The
image quality was only uncertain, as was the level of confidence of the diagnosis if
the patient was very dark skinned.
Conclusions: The wireless LAN system works with a remote PDA in this clinical
situation. However there are question marks over the availability of enough
experienced emergency nurse practitioners to staff a service that provides senior
cover for longer parts of the day and at weekends
Integrating Ecological and Engineering Concepts of Resilience in Microbial Communities
Many definitions of resilience have been proffered for natural and engineered ecosystems, but a conceptual consensus on resilience in microbial communities is still lacking. We argue that the disconnect largely results from the wide variance in microbial community complexity, which range from compositionally simple synthetic consortia to complex natural communities, and divergence between the typical practical outcomes emphasized by ecologists and engineers. Viewing microbial communities as elasto-plastic systems that undergo both recoverable and unrecoverable transitions, we argue that this gap between the engineering and ecological definitions of resilience stems from their respective emphases on elastic and plastic deformation, respectively. We propose that the two concepts may be fundamentally united around the resilience of function rather than state in microbial communities and the regularity in the relationship between environmental variation and a community\u27s functional response. Furthermore, we posit that functional resilience is an intrinsic property of microbial communities and suggest that state changes in response to environmental variation may be a key mechanism driving functional resilience in microbial communities
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