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Biomedical subjects

P L Nash

Publications and source records attributed to P L Nash.

5 recordsLinked to original sources
PubMed2005

Efficient transition path sampling for systems with multiple reaction pathways.

A new algorithm is developed for sampling transition paths and computing reaction rates. To illustrate the use of this method, we study a two-dimensional system that has two reaction pathways: one pathway is straight with a relatively high barrier and the other is roundabout with a lower barrier. The transition rate and the ratio between the numbers of the straight and roundabout transition paths are computed for a wide range of temperatures. Our study shows that the harmonic approximation for fluctuations about the steepest-descent paths is not valid even at relatively low temperatures and, furthermore, that factors related to entropy have to be determined by the global geometry of the potential-energy surface (rather than just the local curvatures alone) for complex reaction systems. It is reasonable to expect that this algorithm is also applicable to higher dimensional systems.

Algorithms↗
PubMed2004

Path integral approach to Brownian motion driven with an ac force.

Brownian motion in a periodic potential driven by an ac (oscillatory) force is investigated for the full range of damping constant from the overdamped limit to the underdamped limit. The path (functional) integral approach is advanced to produce formulas for the probability distribution function and for the current of the Brownian particle in response to an ac driving force. The negative friction Langevin dynamics technique is employed to evaluate the dc current for various parameters without invoking the overdamped or the underdamped approximation. The dc current is found to have nonlinear dependence upon the damping constant, the potential parameter, and the ac force magnitude and frequency.

Journal Article↗
PubMed1998

CBC and differential in VLBW infants.

PURPOSE: This study tested the adequacy of established leukocyte indices in infants < or = 1,200 gm birth weight and < or = 32 weeks gestation. DESIGN: Charts of all admissions to the NICU from March 1991 through September 1994 were retrospectively reviewed. SAMPLE: All infants (n = 131) were outborn and admitted to the NICU within 24 hours after birth. MAIN OUTCOME VARIABLE: The leukocyte indices obtained during the first 72 hours after birth were plotted as a function of time in hours. RESULTS: Mode of delivery significantly affected total leukocyte count and absolute neutrophil count; sex and use of prenatal steroids did not. Ranges for total leukocyte count, absolute neutrophil count, and immature/total neutrophil (I:T) ratio demonstrate that normal values are variable and change over time. PRACTICE RECOMMENDATIONS: The wide distribution of values found, coupled with differences noted by mode of delivery, make normative data difficult to apply. The clinician must question the appropriateness of routinely obtaining a complete blood count and the clinical utility of the results.

Blood Cell Count↗
PubMed1990

Naloxone and its use in neonatal septic shock.

Current research suggests that the secretion of beta-endorphin from the pituitary gland may be associated with the refractory hypotension seen in patients with septic shock. Extensive animal research and a few clinical studies have demonstrated that naloxone, a narcotic antagonist, can increase MAP, cardiac output, and cardiac contractility and improve survival in victims of endotoxic shock. The ability of naloxone to improve MAP, however, appears to decrease with prolonged persistent hypotension (greater than eight hours). Studies also suggest that a synergistic effect exists between naloxone and the steroid methylprednisolone in improving the hemodynamics of these patients. In the future, naloxone may prove to be essential in the management of patients in the early stages of septic shock, but more complete clinical trials are warranted. It is imperative that nurses be involved in this type of clinical research.

Education, Nursing, Continuing↗