Spatio-temporal measurement of ionization-induced modal index changes in gas-filled PCF by prism-assisted side-coupling.

We report the use of prism-assisted side-coupling to investigate the spatio-temporal dynamics of photoionization in an Ar-filled hollow-core photonic crystal fiber. By launching four different LP core modes we are able to probe temporal and spatial changes in the modal refractive index on timescales from a few hundred picoseconds to several hundred microseconds after the ionization event. We experimentally analyze the underlying gas density waves and find good agreement with quantitative and qualitative hydrodynamic predictions. Moreover, we observe periodic modulations in the MHz-range lasting for a few microseconds, indicating nanometer-scale vibrations of the fiber structure, driven by gas density waves.

Surgical management of patients on warfarin sodium.

PURPOSE: Management of anticoagulated patients has changed significantly over the past 10 years. The change occurred after the introduction of the international normalized ratio (INR) in 1983. This method of reporting prothrombin time for anticoagulated patients has resulted in a decrease in the level at which hematologists and cardiologists keep their patients anticoagulated. Currently, patients are anticoagulated less for the successful prevention of thromboemboli. Recent recommendations are to keep patients anticoagulated to an INR no greater than 3.5. It has been proposed that the extraction of teeth can be performed with INRs of 4 or less. Therefore, the current trend is to maintain patients on their anticoagulation regimens without altering their warfarin dosages. CONCLUSION: With proper local measures, teeth can be extracted safely and the development of thromboemboli in high-risk patients can still be prevented. However, with procedures having a high risk of bleeding, warfarin dosage may need to be modified.

Non-analytic problems in detecting arsenic and cadmium in children living near a cadmium refinery in Denver, Colorado.

The aim of the present study was to determine urinary arsenic (N = 322) and cadmium (N = 366) levels in children aged six months to six years who live near a working cadmium refinery and to compare their values with those of children from comparison neighborhoods. A questionnaire designed to identify exposure pathways was administered to the parents. There were unexpected problems in the study. Eighty-four percent of the arsenic samples were below the detection limit of 10 micrograms/l and summary statistics could not be calculated. Urinary arsenic and cadmium values could not be standardized for volume and concentration of urine because a large proportion of the samples had very low creatinine values. The original round of cadmium testing was afflicted with contamination problems, possibly due to the mishandling of pediatric urine bags by the parents during the collection procedure. A retest for cadmium levels under clinical conditions showed lower cadmium levels, all but two were below the detection limit. While biological monitoring of exposure to metals can be undertaken indirectly by measuring the concentration of the metals in urine, the analyses in this study were complicated by (1) not using more sensitive analytical tests for arsenic and cadmium determination, (2) not being able to standardize children's urinary values with creatinine, and (3) allowing in-home urine collection.