18,014 research outputs found
Towards a future singularity?
We discuss whether the future extrapolation of the present cosmological state
may lead to a singularity even in case of "conventional" (negative) pressure of
the dark energy field, namely . The discussion is based on an
often neglected aspect of scalar-tensor models of gravity: the fact that
different test particles may follow the geodesics of different metric frames,
and the need for a frame-independent regularization of curvature singularities.Comment: 8 pages. Essay written for the "2004 Awards for Essays on
Gravitation" (Gravity Research Foundation, Wellesley Hills, MA, USA), and
selected for "Honorable Mention
Plant canopy shape and the influences on UV exposures to the canopy
The solar spectra at selected sites over hemispherical, conical and pinnacle plant canopy models has been evaluated with a dosimetric technique. The irradiance at the sites varies by up to a factor of 0.31 compared to the irradiance on a horizontal plane. The biologically effective (UVBE) exposures evaluated with the dosimetric technique at sites over the plant canopy are up to 19% of that on a horizontal plane. Compared to a spectroradiometer, the technique provides a more practicable method of measuring the UVBE exposures at multiple sites over a plant canopy. Usage of a dosimeter at one site to provide the exposures at that site for different sun angles introduces an error of more than 50%. Knowledge of the spectra allowed the UV and UVBE exposures to be calculated at each site along with the exposures to the entire canopies. These were dependent on the sun angle and the canopy shape. For plant damage, the UVBE was a maximum of about 1.4 mJ cm-2/min. Compared to the hemispherical canopy, the UVBE exposure for generalised plant damage was 45% less for the pinnacle canopy and 23% less for the conical canopy. The canopy exposures could not be determined from measurements of the ambient exposure
A method for selecting an efficient diagnostic protocol for classification of perceptive and cognitive impairments in neurological patients
"Published in final edited form as: Conf Proc IEEE Eng Med Biol Soc. 2011 ; 2011: 1129â1132. doi:10.1109/IEMBS.2011.6090264."An important and unresolved problem in the assessment of perceptual and cognitive deficits in
neurological patients is how to choose from the many existing behavioral tests, a subset that is
sufficient for an appropriate diagnosis. This problem has to be dealt with in clinical trials, as well
as in rehabilitation settings and often even at bedside in acute care hospitals. The need for
efficient, cost effective and accurate diagnostic-evaluations, in the context of clinician time
constraints and concerns for patientsâ fatigue in long testing sessions, make it imperative to select
a set of tests that will provide the best classification of the patientâs deficits. However, the small
sample size of the patient population complicates the selection methodology and the potential
accuracy of the classifier. We propose a method that allows for ordering tests based on having
progressive increases in classification using cross-validation to assess the classification power of
the chosen test set. This method applies forward linear regression to find an ordering of the tests
with leave-one-out cross-validation to quantify, without biasing to the training set, the
classification power of the chosen tests.R01 NS064100 - NINDS NIH HHS; R01NS064100 - NINDS NIH HHSAccepted manuscrip
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