Positioning graphical objects on computer screens: a three-phase model.

Objective: This experiment identifies and models phases during the positioning of graphical objects (called cursors in this article) on computer displays.

Background: The human computer-interaction community has traditionally used Fitts' law to model selection in graphical user interfaces, whereas human factors experiments have found the single-component Fitts' law inadequate to model positioning of real objects.

Method: Participants (N=145) repeatedly positioned variably sized square cursors within variably sized rectangular targets using computer mice.

Measuring evaporation rates of laser-trapped droplets by use of fluorescent morphology-dependent resonances.

Morphology-dependent resonances (MDRs) are used to measure accurately the evaporation rates of laser-trapped 1- to 2-mum droplets of ethylene glycol. Droplets containing 3 x 10(-5) M Rhodamine-590 laser dye are optically trapped in a 20-mum hollow fiber by two counterpropagating 150-mW, 800-nm laser beams. A weaker 532-nm laser excites the dye, and fluorescence emission is observed near 560 nm as the droplet evaporates.

Spectral Differentiation of Trace Concentrations of NO(2) from NO by Laser Photofragmentation with Fragment Ionization at 226 and 452 nm: Quantitative Analysis of NO-NO(2) Mixtures.

Laser-induced photofragmentation with fragment ionization is used to detect and spectrally differentiate trace concentrations of NO(2) from NO in NO-NO(2) mixtures. A laser operating near 226 or 452 nm ionizes the target molecules, and the resulting electrons are collected with miniature electrodes. NO is detected by (1 + 1) resonance-enhanced multiphoton ionization by means of its A (2)?(+) ? X (2)? (0, 0) transitions near 226 nm, whereas NO(2) is detected near 226 nm by laser photofragmentation with subsequent NO fragment ionization by means of both its A (2)?(+) ? X (2)? (0, 0) and (1, 1) transitions.

Clinical laboratories, the select agent program, and biological surety (biosurety).

The threat of bioterrorism has led to increased concerns over the availability of biological select agents and toxins (BSAT). Congress has implemented several public laws that have led to the development of federal regulations by the Centers for Disease Control and Prevention (CDC) and the US Department of Agriculture. The CDC regulation 42 CFR 73 has a direct impact on all clinical laboratories that may at some time identify BSAT in a clinical specimen.