Search results for "break-up"

The utility of measuring tear film break-up time for prescribing contact lenses.

2017

Abstract Purpose To evaluate the clinical value of non-invasive keratograph tear film breakup time (NIKBUT) in the assessment of pre-corneal and pre-lens tear film quality for prescribing contact lenses (CLs). Methods Forty-six subjects aged 25.5 ± 4.3 (mean ± standard deviation) years were recruited. Visual acuity (VA), anterior eye health checks and NIKBUT were evaluated. On the following day, subjects were fitted with a daily Silicon Hydrogel (SiHy) CL in one eye and a Hydrogel (Hy) CL in the other. After four hours one material for both eyes was chosen based on a qualitative analysis which included VA, CL fitting and comfort. Information about the first and the mean NIKBUT was then cont…

Subduction‐Induced Back‐Arc Extension Versus Far‐Field Stretching: Contrasting Modes for Continental Marginal Break‐Up

2021

Modeling suggests that oblique extension facilitates rifting and continental break-up

2012

[1] In many cases the initial stage of continental break-up was and is associated with oblique rifting. That includes break-up in the Southern and Equatorial Atlantic, separation from eastern and western Gondwana as well as many recent rift systems, like Gulf of California, Ethiopia Rift and Dead Sea fault. Using a simple analytic mechanical model and advanced numerical, thermomechanical modeling techniques we investigate the influence of oblique extension on the required tectonic force in a three-dimensional setting. While magmatic processes have been already suggested to affect rift evolution, we show that additional mechanisms emerge due to the three-dimensionality of an extensional syst…

On the Role of Drop Break Up for Coalescence Processes and Morphology Development in Polymer Blends under Shear

2005

Drop sizes and drop-size distributions were determined as a function of time at constant shear rates, γ, by means of an optical shear cell in combination with an optical light microscope after preshearing the samples at high γ. The systems under investigation were PIB 3/PDMS 152 (PIB:  polyisobutylene, PDMS:  poly(dimethylsiloxane), numbers:  average molar masses in kg/mol) and COP 26*/PDMS 48 (COP:  poly(dimethyl-co-methylphenylsiloxane), asterisk:  apparent molar mass); all measurements refer to 25 °C. Systems and conditions were chosen such that shear rates in the vicinity of the intersection of the coalescence and the break up curves become experimentally accessible. Under these conditi…

Efficacy and safety study of an eyelid gel after repeated nocturnal application in healthy contact lens users and non-users

2020

Purpose: To evaluate skin biocompatibility of a nighttime hydrating eyelid gel and possible ocular surface effects in contact lens users (CLU) and non-contact lens users (NCLU). The formulation is registered as a medical device as Tridocosahexaenoine-AOX® (TDHA-AOX) (a concentrated DHA triglyceride), containing also hyaluronic acid (HA). Methods: A prospective, randomized, masked clinical trial was performed with 62 participants of both sexes, aged 20–70 years, split into: (1) CLU (n = 30) and (2) NCLU (n = 32). All participants were instructed to apply a single dose of the moisturizing gel (containing TDHA-AOX and HA) nightly to the upper and inner eyelids of their right eye (RE) only, and…

A wind tunnel study on the drop-to-particle conversion

1992

Abstract An experimental study was carried out to investigate the processes which occur during drop-to-particle conversion in atmospheric clouds whose drops are evaporating. The experiment was carried out in the Mainz vertical wind tunnel and in a 4-m high fall shaft. Drops consisting of aqueous solutions of NaCl, (NH 4 ) 2 SO 4 , and salts of artificial and natural ocean water, containing various kinds of solid, water-insoluble particles such as clays, were studied. The aerosol particles produced by the evaporation of drops had diameters in the range 0.1–1 μm, 5–20 μm, 40–80 μm and 100–300 μm. The shape and fall mode of these particles are discussed. It was found that the aerosol particles…

Growth Kinetics of Wetting Layers at Surfaces

1990

Monte Carlo simulation of lattice gas models for the wetting transitions in systems with short range forces are described. A nearest-neighbor simple cubic lattice with nonconserved “Glauber dynamics” is used, applying a slab geometry (LxL cross section). It is shown that the growth proceeds in two stages: for short times t, the thickness of the wetting layer at an initially nonwet wall increases proportional to the logarithm of the time; for t » L2(lnL)2 the thickness increases proportional to t1/2/L. Generalizations to other systems are briefly discussed. Also two-dimensional growth of a wetting film at surface steps is considered, considering “terraces” of an LxM geometry with M»L as subs…

Spherical microparticles production by supercritical antisolvent precipitation: Interpretation of results

2008

Abstract Supercritical antisolvent micronization has been the subject of many works aimed at the production of precipitates with controlled particle size and morphology. Several morphologies have been observed; but, the production of spherical micrometric particles has been the major objective of most of the studies performed. Therefore, in this work, literature data analysis on spherical and related morphologies has been performed. The ranges of process conditions at which spherical microparticles have been obtained have been listed and discussed. A possible formation mechanism is proposed that is based on the competition between jet break-up and liquid surface tension vanishing characteri…

Determination of the threshold of the break-up of invariant tori in a class of three frequency Hamiltonian systems

2001

We consider a class of Hamiltonians with three degrees of freedom that can be mapped into quasi-periodically driven pendulums. The purpose of this paper is to determine the threshold of the break-up of invariant tori with a specific frequency vector. We apply two techniques: the frequency map analysis and renormalization-group methods. The renormalization transformation acting on a Hamiltonian is a canonical change of coordinates which is a combination of a partial elimination of the irrelevant modes of the Hamiltonian and a rescaling of phase space around the considered torus. We give numerical evidence that the critical coupling at which the renormalization transformation starts to diverg…

Neutron momentum distributions from "core break-up" reactions of halo nuclei

1995

Neutron angular distributions from violent break-up reactions of Li-11 and Be-11 have been measured at 28 MeV/u and 280 MeV/u and at 41 MeV/u and 460 MeV/u, respectively. The derived neutron momentum distributions show a narrow component in transverse momentum that is within uncertainties independent of beam energy and target charge. This component is suggested to be simply related to the momentum distribution of the loosely bound halo neutron(s) in the projectiles.