The Limits of Quintessence

We present evidence that the simplest particle-physics scalar-field models of dynamical dark energy can be separated into distinct behaviors based on the acceleration or deceleration of the field as it evolves down its potential towards a zero minimum. We show that these models occupy narrow regions in the phase-plane of w and w', the dark energy equation-of-state and its time-derivative in units of the Hubble time. Restricting an energy scale of the dark energy microphysics limits how closely a scalar field can resemble a cosmological constant. These results, indicating a desired measurement resolution of order \sigma(w')\approx (1+w), define firm targets for observational tests of the physics of dark energy.Comment: 4 pages, 2 figure

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: 1129–1132. 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 patients’ fatigue in long testing sessions, make it imperative to select a set of tests that will provide the best classification of the patient’s 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

Fermion masses in noncommutative geometry

Recent indications of neutrino oscillations raise the question of the possibility of incorporating massive neutrinos in the formulation of the Standard Model (SM) within noncommutative geometry (NCG). We find that the NCG requirement of Poincare duality constrains the numbers of massless quarks and neutrinos to be unequal unless new fermions are introduced. Possible scenarios in which this constraint is satisfied are discussed.Comment: 4 pages, REVTeX; typos are corrected in (19), "Possible Solutions" and "Conclusion" are modified; additional calculational details are included; references are update

Gear mesh compliance modeling

A computer model has been constructed to simulate the compliance and load sharing in a spur gear mesh. The model adds the effect of rim deflections to previously developed state-of-the-art gear tooth deflection models. The effects of deflections on mesh compliance and load sharing are examined. The model can treat gear meshes composed to two external gears or an external gear driving an internal gear. The model includes deflection contributions from the bending and shear in the teeth, the Hertzian contact deformations, and primary and secondary rotations of the gear rims. The model shows that rimmed gears increase mesh compliance and, in some cases, improve load sharing

Observations on sandfly fever in Malta and reference to its control by D.D.T.

1. Two Sandfly Fever epidemics are reviewed by a Naval Medical Officer whilst working ashore in a temporary barracks under wartime conditions.2. Sandfly Fever is not a dangerous disease, but under such con- ditions as occurred in Malta - in overcrowded dilapidated barracks - it may assume epidemic form which apart from purely medical and health considerations may cause a huge loss in man hours.. It can be most effectively controlled by Dichloro-Diphenyl-Trichlorethane. A method of using this is described. This insecticide used along with other prophylaxtic methods should prevent such epidemics occurring again.4. In comparing reports on Sandfly Fever one finds diversity of opinion on the aetiology of the disease, on its incubation period, on the period of infectivity in the blood, on the incidence amongst 'natives' and one the relative incidence of its clinical manifestations.6. Observations on 600 cases of Sandfly Fever in Yalta are given, from these and from other reports it appears that Sandfly Fever varies in different areas, this makes one wonder whether those differences are due to different types of viruses causing the disease, or to different vectors (is Phlebotcanus Fapatacii the only vector or not).6. An early or even immediate return to duty does not pre-capitate depression or mental distress, as is suggested in most of the relevant literature

The Role of Natural Gas and LNG in Supplying Our Energy Needs

The domestic natural gas industry experienced a spectacular growth during the two decades from 1950 to 1970. Demand for gas continues to rise and production has peaked at a time when the price for other energy sources is escalating. A price increase can stimulate production over the short term. Massive LNG imports can help the intermediate term supply. The long term natural gas situation is bleak and substitute natural gas sources must be employed. A conservation program and reordering of priorities for energy sources is essential for the United States as well as most industrial nations