Theory and seaborne measurements are presented for the near infrared (NIR: 700-900 nm) water-leaving reflectance in turbid waters. According to theory, the shape of the NIR spectrum is determined largely by pure water absorption and is thus almost invariant. A ''similarity'' NIR reflectance spectrum is defined by normalization at 780 nm. This spectrum is calculated from seaborne reflectance measurements and is compared with that derived from laboratory water absorption measurements. Factors influencing the shape of the similarity spectrum are analyzed theoretically and by radiative transfer simulations. These simulations show that the similarity spectrum is valid for waters ranging from moderately turbid (e.g., water-leaving reflectance at 780 nm of order 10 Ϫ4 or total suspended matter concentration of order 0.3 g m Ϫ3 ) to extremely turbid (e.g., reflectance at 780 nm of order 10
Ϫ1or total suspended matter of order 200 g m
Ϫ3). Measurement uncertainties are analyzed, and the air-sea interface correction is shown to be critical for low reflectances. Applications of the NIR similarity spectrum to atmospheric correction of ocean color data and to the quality control of seaborne, airborne, and spaceborne reflectance measurements in turbid waters are outlined.Although ocean color remote sensing has focused primarily on visible wavelengths (400-700 nm) where photosynthetic pigments have detectable absorption features, there is a growing interest in water-leaving reflectances at near infrared (NIR) wavelengths, usually taken as the range 700-1,000 nm. There are essentially three reasons for this. First, although for atmospheric correction over clear waters the NIR water-leaving reflectance can usually be taken as zero (Gordon and Wang 1994), for turbid waters it is essential to model or estimate NIR water-leaving reflectance in order to 1 Corresponding author (K.Ruddick@mumm.ac.be). 2 Present address: Polytechnic of Namibia, P/Bag 13388, Windhoek, Namibia.
AcknowledgmentsThis study was funded by the Belgian Science Policy Office's STEREO program in the framework of the BELCOLOUR project SR/00/03, by the European Union under the REVAMP project EVG1-CT-2001-00049, and by PRODEX contract 15190/01. The captains, crews, and support staff of the research vessels Belgica and Zeeleeuw are thanked for their enthusiastic help with the seaborne measurements. Jean-Paul Huot and the scientists of the RE-VAMP project and the MERIS Validation Team are especially thanked for the many discussions that have helped to improve and control the quality of the seaborne measurements. Wolfgang Cordes of GKSS is acknowledged for the tests on polarization and droplet sensitivity of spectroradiometers. Rudiger Heuermann of TriOS and Jean-Pierre De Blauwe and André Pollentier of MUMM-Oostende are thanked for help with system design; Barbara Van Mol for help with figure preparation; Bouchra Nechad for discussions on the use of the near infrared (NIR) range for total suspended matter (TSM) retrieval; and Arnold Dekker for discussion of op...
In patients with rheumatoid arthritis, combination therapy with methotrexate, sulfasalazine, and hydroxychloroquine is more effective than either methotrexate alone or a combination of sulfasalazine, and hydroxychloroquine.
Objective. To compare the efficacy of combination therapy with methotrexate (MTX) and hydroxychloroquine (HCQ), MTX and sulfasalazine (SSZ), and MTX, HCQ, and SSZ in patients with rheumatoid arthritis (RA).Methods. RA patients (n ؍ 171) who had not previously been treated with combinations of the study medications were randomized to receive 1 of the 3 treatment combinations in this 2-year, double-blind, placebo-controlled protocol. HCQ was given at a dosage of 200 mg twice a day. The dosage of MTX was accelerated from 7.5 mg/week to 17.5 mg/week in all patients who were not in remission. Similarly, the dosage of SSZ was escalated from 500 mg twice a day to 1 gm twice a day in patients who were not in remission. The primary end point of the study was the percentage of patients who had a 20% response to therapy according to the American College of Rheumatology (ACR) criteria at 2 years.Results. Intent-to-treat analysis revealed that patients receiving the triple combination responded best, with 78% achieving an ACR 20% response at 2 years, compared with 60% of those treated with MTX and HCQ (P ؍ 0.05) and 49% of those treated with MTX and SSZ (P ؍ 0.002). Similar trends were seen for the ACR 50% response, with 55%, 40%, and 29% of patients in the 3 treatment groups, respectively, achieving these results at 2 years (P ؍ 0.005 for the triple combination group versus the MTX and SSZ group). All combination treatments were well-tolerated. Fourteen patients (evenly distributed among the 3 groups) withdrew from the protocol because of symptoms that were potentially related to the study medication.Conclusion. The triple combination of MTX, SSZ, and HCQ is well-tolerated, and its efficacy is superior to that of the double combination of MTX and SSZ and is marginally superior to that of the double combination of MTX and HCQ.
A semianalytical approach to the problem of determining inherent optical properties from satellite and in situ ocean color data is presented. The model uses empirically derived spectral slopes between neighboring wavebands in combination with radiative transfer modeling to determine the spectral absorption (alpha) and backscatter (b(b)); these values are then further decomposed into absorption due to phytoplankton, detrital, and colored dissolved organic matter components. When compared with over 400 in situ data points the model makes good retrievals of the total absorption and backscatter across the entire spectrum, with regression slopes close to unity, little or no bias, high percentage of variance explained, and low rms errors.
Abstract. Inter-comparison of data products from simultaneous measurements performed with independent systems and methods is a viable approach to assess the consistency of data and additionally to investigate uncertainties. Within such a context the inter-comparison called Assessment of In Situ Radiometric Capabilities for Coastal Water Remote Sensing Applications (ARC) was carried out at the Acqua Alta Oceanographic Tower in the northern Adriatic Sea to explore the accuracy of in situ data products from various in-and above-water optical systems and methods. Measurements were performed under almost ideal conditions, including a stable deployment platform, clear sky, relatively low sun zenith angles and moderately low sea state. Additionally, all optical sensors involved in the experiment were inter-calibrated through absolute radiometric calibration performed with the same standards and methods. Inter-compared data products include spectral waterleaving radiance L w (λ), above-water downward irradiance E d (0 + ,λ) and remote sensing reflectance R rs (λ). Data products from the various measurement systems/methods were directly compared to those from a single reference system/method. Results for R rs (λ) indicate spectrally averaged values of relative differences comprised between −1 and +6 %, while spectrally averaged values of absolute differences vary from approximately 6 % for the above-water systems/methods to 9 % for buoy-based systems/methods. The agreement between R rs (λ) spectral relative differences and estimates of combined uncertainties of the inter-compared systems/methods is noteworthy.
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