Testing of a dual-mode microwave care regimen for hydrogel lenses

Purpose. To test the design of a patient care regimen for soft lenses that aims to provide the highest standards of disinfecting through use of domestic microwave cookers, while also providing storage equipment and solution that enable patients to follow a conventional cold disinfecting regimen when traveling. The cleaning efficacy of surfactant agents during microwave treatment was also considered. Methods. The microbiologic performance of the regimen and its disinfecting apparatus was tested according to the Food and Drug Administration (FDA) protocols for contact lens heat disinfectors. Subsequently, a prospective pilot clinical trial of the regimen involving 15 subjects was carried out to the protocols of the FDA and International Standards Organization 11,980:1997. Results. Lenses inoculated with 107 colony-forming units (cfu) of Enterococcus faecalis were disinfected to 0 cfu by a 12-s irradiation of a compact disinfecting case that held the lenses suspended in 12 ml saline. A proof of operation indicator performed correctly for all 10 cases tested. No adverse reactions were found in the pilot patient trial, using Renu multipurpose (Bausch & Lomb, Rochester, NY) as the test solution, and no statistically significant difference was found between test and control groups in respect of any sign. However, the greater incidence of edema, palpebral hyperemia, and lens front-surface deposition in the microwave test group may be clinically significant

Clinical trial of a patient-operated microwave care system for hydrogel contact lenses

The clinical effects of a patient-operated system of microwave disinfection for soft contact lenses were assessed in a prospective pilot trial involving 103 patients who were drawn from five optometric practices. Fifty-six subjects used the test system for 1 month, and 13 subjects continued use for a total of 3 months. Both test and control subjects were examined for clinical signs using slitlamp tests. After 1 month, the incidence of all signs reported in the microwave group was not significantly greater than in the control group (p = 0.267), and the same was true after 3 months (p = 0.214). There was a significantly greater incidence of edema in the 1-month test group and of staining in the control group. UV spectroscopic examination of worn lenses from test subjects exhibiting significant signs did not show a higher level of deposition than on lenses worn by control subjects (p = 0.397)

An empirical model for protostellar collapse

We propose a new analytic model for the initial conditions of protostellar collapse in relatively isolated regions of star formation. The model is non-magnetic, and is based on a Plummer-like radial density profile as its initial condition. It fits: the observed density profiles of pre-stellar cores and Class 0 protostars; recent observations in pre-stellar cores of roughly constant contraction velocities over a wide range of radii; and the lifetimes and accretion rates derived for Class 0 and Class I protostars. However, the model is very simple, having in effect only 2 free parameters, and so should provide a useful framework for interpreting observations of pre-stellar cores and protostars, and for calculations of radiation transport and time-dependent chemistry. As an example, we model the pre-stellar core L1544.Comment: To appear in Astrophysical Journal, Jan 20th, 2001. 18 pages incl. 3 fig

Magnetars: Time Evolution, Superfluid Properties, and Mechanism of Magnetic Field Decay

We calculate the coupled thermal evolution and magnetic field decay in relativistic model neutron stars threaded by superstrong magnetic fields (B > 10^{15} G). Our main goal is to evaluate how such ``magnetars'' evolve with time and how field decay modifies the transitions to core superfluidity and cooling dominated by surface X-ray emission. Observations of a thermal X-ray spectral component and fast timing noise place strong constraints on the presence of a superfluid core. We find that the transition to core superfluidity can be significantly delayed by field decay in the age range ~ 10^3-10^5 yrs. The mechanism of Hall drift is related to the stability of the core magnetic field, and to currents flowing outward through the crust. The heating effect is enhanced if it is continuous rather than spasmodic. Condensation of a heavy element layer at the surface is shown to cause only modest changes in the outward conduction of heat.Comment: Submitted to Ap.J. Letters 1 December 2003; revised 16 January 200

Searching for Globally Optimal Functional Forms for Inter-Atomic Potentials Using Parallel Tempering and Genetic Programming

We develop a Genetic Programming-based methodology that enables discovery of novel functional forms for classical inter-atomic force-fields, used in molecular dynamics simulations. Unlike previous efforts in the field, that fit only the parameters to the fixed functional forms, we instead use a novel algorithm to search the space of many possible functional forms. While a follow-on practical procedure will use experimental and {\it ab inito} data to find an optimal functional form for a forcefield, we first validate the approach using a manufactured solution. This validation has the advantage of a well-defined metric of success. We manufactured a training set of atomic coordinate data with an associated set of global energies using the well-known Lennard-Jones inter-atomic potential. We performed an automatic functional form fitting procedure starting with a population of random functions, using a genetic programming functional formulation, and a parallel tempering Metropolis-based optimization algorithm. Our massively-parallel method independently discovered the Lennard-Jones function after searching for several hours on 100 processors and covering a miniscule portion of the configuration space. We find that the method is suitable for unsupervised discovery of functional forms for inter-atomic potentials/force-fields. We also find that our parallel tempering Metropolis-based approach significantly improves the optimization convergence time, and takes good advantage of the parallel cluster architecture

Effects of microwave irradiation on the parameters of hydrogel contact lenses

Ten brands of hydrogel contact lenses were selected from five of the six British Approved Name lens classification groups to test in vitro the effects of repeated heat disinfection by means of microwave irradiation. Each lens type was tested over a number of cycles corresponding to its scheduled number of wearing days. The total diameter and back vertex power of all 80 test and 12 control lenses were measured at the end of their relevant cycling period. The back optic zone radius, center thickness, and water content were measured for 40 test and 8 control lenses. No clinically significant change was found in any of the 10 brands tested. Statistically significant changes were found in the back optic zone radius of the Frequency 55 group and water content of the Precision UV group. Some discoloration was noted in Ciba Visitint lenses

On air temperature fluctuations immediately above a glacier surface

Developing remote sensing techniques for measuring meteorological parameters in surface layers of snow field

Slip boundary conditions for shear flow of polymer melts past atomically flat surfaces

Molecular dynamics simulations are carried out to investigate the dynamic behavior of the slip length in thin polymer films confined between atomically smooth thermal surfaces. For weak wall-fluid interactions, the shear rate dependence of the slip length acquires a distinct local minimum followed by a rapid growth at higher shear rates. With increasing fluid density, the position of the local minimum is shifted to lower shear rates. We found that the ratio of the shear viscosity to the slip length, which defines the friction coefficient at the liquid/solid interface, undergoes a transition from a nearly constant value to the power law decay as a function of the slip velocity. In a wide range of shear rates and fluid densities, the friction coefficient is determined by the product of the value of surface induced peak in the structure factor and the contact density of the first fluid layer near the solid wall.Comment: 27 pages, 11 figure