System design methodology for power budgeting of 62.5 μmmultimode fiber systems

The authors present the data to support a recommendation of a new system loss budgeting rule applicable to high-component-count systems using 62.5 μm core diameter multimode fiber. The limited phase space or restricted launch characterization of fiber is demonstrated again to give the most accurate system loss prediction. However, for this fiber size, components such as connectors, switches, and couplers are shown to exhibit loss equivalent to the overfilled launch loss. Two mechanisms are found to explain why the overfilled launch component loss best characterizes their actual loss in common multimode fiber systems. Both are related to the large numerical aperture (NA) of the power distribution launched by the light-emitting diode (LED) system sources. It is important to note that these mechanisms only have been observed on components made with 62.5 μm multimode fiber. This behavior is likely to be different in other fiber sizes     

Numerical aperture of multimode fibers by several methods:resolving differences

An industrywide study among members of the Electronic Industries Association was conducted to document differences among three numerical aperture measurement methods. Results on 12 multimode graded index fibers indicate systematic differences exist among commonly used far-field and index profile techniques. Differences can be explained by a wavelength-dependent factor and choice of definitions. Conversion factors can be used to relate the various methods     

The role of coronary perfusion changes in cardiac dysfunction associated with brain death

The contribution of dopamine D1 receptor stimulation to the motor effects of dopaminergic drugs in patients with Parkinson's disease remains undetermined. The authors of this article studied the clinical efficacy, pharmacokinetics, and tolerability of the full D1 receptor agonist dihydrexidine, (+/-)-trans-10,11-dihydroxy-5,6,6a,7,8,12b-hexahydrobenzo[a] phenanthridine hydrochloride in a double-blind, placebo-controlled trial in four patients with Parkinson's disease. Single intravenous doses were carefully titrated according to a fixed schedule ranging from 2 mg to the highest tolerated dose (or a maximum of 70 mg) infused over either 15 or 120 minutes. The only patient to achieve a plasma drug concentration greater than 100 ng/ml had a brief but definite motor improvement accompanied by choreic dyskinesias similar to the response to levodopa. Dose-limiting adverse effects, including flushing, hypotension, and tachycardia, were observed in all cases, especially with rapid infusions. No nausea or emesis occurred. Pharmacokinetic studies yielded a plasma half-life < 5 minutes. These preliminary data suggest that dihydrexidine has a marginal therapeutic window for providing an antiparkinsonian effect, although it remains uncertain how much of this effect is attributable to pure D1 receptor stimulation.