Optical properties of the South pole ice at depths between 0.8 and 1 kilometer.

The optical properties of the ice at the geographical South Pole have been investigated at depths between 0.8 and 1 kilometer. The absorption and scattering lengths of visible light ( approximately 515 nanometers) have been measured in situ with the use of the laser calibration setup of the Antarctic Muon and Neutrino Detector Array (AMANDA) neutrino detector. The ice is intrinsically extremely transparent. The measured absorption length is 59 +/- 3 meters, comparable with the quality of the ultrapure water used in the Irvine-Michigan-Brookhaven and Kamiokande proton-decay and neutrino experiments and more than twice as long as the best value reported for laboratory ice. Because of a residual density of air bubbles at these depths, the trajectories of photons in the medium are randomized. If the bubbles are assumed to be smooth and spherical, the average distance between collisions at a depth of 1 kilometer is about 25 centimeters. The measured inverse scattering length on bubbles decreases linearly with increasing depth in the volume of ice investigated.

The day the earth moved.

Diane Lowder wasn't sure how ready her hospital was for a catastrophe. But a unique disaster plan helped keep Northridge Hospital open after the '94 Los Angeles earthquake. Here's what Lowder saw at the epicenter.

Treatment options for rheumatoid arthritis: celecoxib, leflunomide, etanercept, and infliximab.

OBJECTIVE: To review new pharmacologic agents approved for use in the management of rheumatoid arthritis (RA). DATA SOURCES: A MEDLINE search (1966-January 2000) was conducted to identify English-language literature available on the pharmacotherapy of RA, focusing on celecoxib, leflunomide, etanercept, and infliximab. These articles, relevant abstracts, and data provided by the manufacturers were used to collect pertinent data. STUDY SELECTION: All controlled and uncontrolled trials were reviewed. DATA EXTRACTION: Agents were reviewed with regard to mechanism of action, efficacy, drug interactions, pharmacokinetics, dosing, precautions/contraindications, adverse effects, and cost. DATA SYNTHESIS: Traditional pharmacologic treatments for RA have been limited by toxicity, loss of efficacy, or both. Increasing discoveries into the mechanisms of inflammation in RA have led to the development of new agents in hopes of addressing these limitations. With the development of celecoxib, a selective cyclooxygenase-2 inhibitor, the potential exists to minimize the gastrotoxicity associated with nonsteroidal antiinflammatory drugs. Leflunomide has been shown to be equal to or less efficacious than methotrexate, and may be beneficial as a second-line disease-modifying antirheumatic drug (DMARD). The biologic response modifiers, etanercept and infliximab, are alternatives that have shown benefit alone or in combination with methotrexate. However, they should be reserved for patients who fail to respond to DMARD therapy. Further studies should be conducted to evaluate the long-term safety and efficacy of these agents as well as their role in combination therapy. CONCLUSIONS: Celecoxib, leflunomide, etanercept, and infliximab are the newest agents approved for RA. Clinical trials have shown that these agents are beneficial in the treatment of RA; however, long-term safety and efficacy data are lacking.

Optical properties of deep ice at the South Pole: absorption.

We discuss recent measurements of the wavelength-dependent absorption coefficients in deep South Pole ice. The method uses transit-time distributions of pulses from a variable-frequency laser sent between emitters and receivers embedded in the ice. At depths of 800-1000 m scattering is dominated by residual air bubbles, whereas absorption occurs both in ice itself and in insoluble impurities. The absorption coefficient increases approximately exponentially with wavelength in the measured interval 410-610 nm. At the shortest wavelength our value is approximately a factor 20 below previous values obtained for laboratory ice and lake ice; with increasing wavelength the discrepancy with previous measurements decreases. At ~415 to ~500 nm the experimental uncertainties are small enough for us to resolve an extrinsic contribution to absorption in ice: submicrometer dust particles contribute by an amount that increases with depth and corresponds well with the expected increase seen near the Last Glacial Maximum in Vostok and Dome C ice cores. The laser pulse method allows remote mapping of gross structure in dust concentration as a function of depth in glacial ice.