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This paper discusses the effects of vegetation on C- (4.75 GHz) and L- (1.6 GHz) band backscattering ( σ o ) measured throughout a growth cycle at incidence angles of 15, 35 and 55°. The utilized σ o data set was collected by a truck mounted scatterometer over a corn field and is supported by a comprehensive set of ground measurements, including soil moisture and vegetation biomass. Comparison of σ o measurement against simulations by the Integral Equation Method (IEM) surface scattering model (Fung et al., 1992) shows that the σ o measurements are dominated either by an attenuated soil return or by scattering from vegetation depending on the antenna configuration and growth stage. Further, the measured σ o is found to be sensitive to soil moisture even at peak biomass and large incidence angles, which is attributed to scattering along the soil-vegetation pathway. For the simulation of C-band σ o and the retrieval of soil moisture two methods have been applied, which are the semi-empirical water cloud model (Attema & Ulaby, 1978) and a novel method. This alternative method uses the empirical relationships between the vegetation water content ( W ) and the ratio of the bare soil and the measured σ o to correct for vegetation. It is found that this alternative method is superior in reproducing the measured σ o as well as retrieving soil moisture. The highest retrieval accuracies are obtained at a 35° incidence angle leading to RMSD's of 0.044 and 0.037 m 3 m − 3 for the HH and VV-polarization, respectively. In addition, the sensitivity of these soil moisture retrievals to W and surface roughness parameter uncertainties is investigated.

This paper reports on the retrieval of soil moisture from dual-polarized L-band (1.6 GHz) radar observations acquired at view angles of 15deg, 35deg, and 55deg, which were collected during a field campaign covering a corn growth cycle in 2002. The applied soil moisture retrieval algorithm includes a surface roughness and vegetation correction and could potentially be implemented as an operational global soil moisture retrieval algorithm. The surface roughness parameterization is obtained through inversion of the Integral Equation Method (IEM) from dual-polarized (HH and VV) radar observations acquired under nearly bare soil conditions. The vegetation correction is based on the relationship found between the ratio of modeled bare soil scattering contribution and observed backscatter coefficient (sigmasoil/sigmaobs) and vegetation water content (W). Validation of the retrieval algorithm against ground measurements shows that the top 5-cm soil moisture can be estimated with an accuracy between 0.033 and 0.064 cm3 ldr cm-3, depending on the view angle and polarization.

Controlled studies to investigate the interaction between crop growth, soil properties, hydrology, and management practices are common in agronomy. These sites (much as with real world farmland) often have complex management histories and topographic variability that must be considered. In 1993 an i

We present a method to calibrate and validate observational models that interrelate remotely sensed energy fluxes to geophysical variables of land and water surfaces. Coincident sets of remote sensing observation of visible and microwave radiations and geophysical data are assembled and subdivided into calibration (Cal) and validation (Val) data sets. Each Cal/Val pair is used to derive the coefficients (from the Cal set) and the accuracy (from the Val set) of the observation model. Combining the results from all Cal/Val pairs provides probability distributions of the model coefficients and model errors. The method is generic and demonstrated using comprehensive matchup sets from two very different disciplines: soil moisture and water quality. The results demonstrate that the method provides robust model coefficients and quantitative measure of the model uncertainty. This approach can be adopted for the calibration/validation of satellite products of land and water surfaces, and the resulting uncertainty can be used as input to data assimilation schemes.

L-band radiometry is recognized as a technique with a significant potential for providing spatial and temporal soil moisture variations [1, 2]. As a result, satellite missions dedicated to global soil moisture monitoring have been proposed. A 2D-interferometric L-band radiometer has recently been launched onboard the European SMOS (Soil moisture and Ocean Salinity) satellite, [3], and the NASA is in preparation of a similar suite of microwave instruments as a part of the Aquarius and SMAP (Soil Moisture Active/Passive missions, [4] which have anticipated launch dates in 2011 and 2014, respectively. The reliability of soil moisture products derived from these microwave observations will depend, at least in part, on the effectiveness of accounting for vegetation and surface roughness impacts.

Department of Chemistry. Wayne State University, Detroit, Michigan 48202, U.S.A. Manuscript received 31 May 1991 The equilibria in several Pfeiffer Effect systems. differing in concentrations and concentration ratios of complex to environment substance, were studied It was found that keeping the complex concentration constant while increasing the concentration of the environment substance, results in an increase in the conversion of one enantiomer of the complex to the other, which supports the proposed hydrogen-bonding mechanism for the equilibrium displacement.

Water-soluble derivatives of ara-cytidine (cytarabine, Cytosar) were prepared and tested for antitumor, immunosuppressive, and antiarthritic activities in animals after oral administration. The compounds tested included the 5'-palmitate, 5'-benzoate, and 5'-adamantoate esters of ara-cytidine, made water soluble by use of their hydrochloride salts of peptidyl derivatives, and two basic 5' esters (5'-nicotinoate and 5'-quinuclidinate) as their hydrochloride salts. Five of the compounds had antitumor activity superior to that found with ara-cytidine itself after oral administration in the L1210 leukemic mouse assay. One of these, 5'-adamantoyl-ara-cytidine hydrochloride, had antitumor activity after oral administration approaching that achieved with parenterally administered ara-cytidine.

This manuscript if one of a series of investigations into modifying the pharmacologic properties of the antitumor, antiviral, and immunosuppressive nucleoside ara-cytidine (cytarabine, Cytosar). The present paper summarizes our studies on depot ester derivatives of the nucleoside. We are able to predict with reasonable accuracy the biological activity as measured by increased life span in the L1210 leukemic mouse from a combination of two predictor variables: (1) the solubility of the ester in water and (2) its rate of hydrolysis by the mixed esterase system of animal plasma. We have tried unsuccessfully to correlate enzymatic hydrolysis rates with an alkaline hydrolysis model. Calculated Hansch partition (p) values had a correlation of r equal to 0.86 with water solubility. These p values had no additional predictive value. Based on our results, two esters were selected for clinical trial in cancer and rheumatoid arthritis.

Tobacco mosaic virus (TMV) protein (mol. wt. of subunit 18,270) was hydrolyzed with trypsin. The material soluble at pH 4.0 was fractionated by countercurrent distribution with the solvent system 2-butanol-0.1 M dichloroacetic acid. Preliminary investigations on these fractions have shown that nine apparently major tryptic hydrolysis products containing arginine and one containing lysine have been obtained from this fractionation. One arginine-containing peptide of large molecular weight was found in the portion of the digest insoluble at pH 4.0. One of these peptides has been found to contain arginine in both the N- and C-terminal positions. The nature and number of the N- and C-terminal residues produced as a result of the action of trypsin on TMV protein have been investigated. These results have revealed the presence of about one mole each of N-terminal glutamic acid, aspartic acid, serine, threonine, phenylalanine, tyrosine, and arginine and approximately two moles of glycine. Fractional amounts of N-terminal leucine and valine were also found. One mole each of C-terminal threonine and lysine and slightly more than nine moles of C-terminal arginine were determined.

Although cytarabine (cytosine arabinoside, ara -cytidine, Cytosar) is a potent immunosuppressant, antiviral and antitumor agent in animals and man, maximum inhibitory effects require the use of complex injection schedules. Previous reports have shown that good immunosuppressive and antitumor activities were attained with simple injection schedules using the 5′-adamantoate derivative. The current results show that a variety of 5′-acylates were equally as active as the 5′-adamantoate in suppressing immune responses in rodents (hemagglutinin formation in mice and hamsters, skin graft rejection in rats), and as antitumor agents in mice (L1210 leukemia). Similar results were attained in protecting mice from the lethal effects of intracranial herpes simplex infection, and in inhibiting DNA synthesis in phytohemagglutinin-stimulated human lymphocytes. The hypothesis for the enhanced potency of these newer derivatives was as follows: After injection of these insoluble derivatives, there is a finite time required for dispersion and solubilization. The freely circulating derivatives are resistant to deamination (and inactivation). After enzymatic hydrolysis to the free acid and cytarabine, the latter is then free to exert its inhibitory activities. The net effect is the maintenance of relatively low levels of cytarabine for long periods of time.

This manuscript if one of a series of investigations into modifying the pharmacologic properties of the antitumor, antiviral, and immunosuppressive nucleoside ara-cytidine (cytarabine, Cytosar). The present paper summarizes our studies on depot ester derivatives of the nucleoside. We are able to predict with reasonable accuracy the biological activity as measured by increased life span in the L1210 leukemic mouse from a combination of two predictor variables: (1) the solubility of the ester in water and (2) its rate of hydrolysis by the mixed esterase system of animal plasma. We have tried unsuccessfully to correlate enzymatic hydrolysis rates with an alkaline hydrolysis model. Calculated Hansch partition (p) values had a correlation of r equal to 0.86 with water solubility. These p values had no additional predictive value. Based on our results, two esters were selected for clinical trial in cancer and rheumatoid arthritis.

Water-soluble derivatives of ara-cytidine (cytarabine, Cytosar) were prepared and tested for antitumor, immunosuppressive, and antiarthritic activities in animals after oral administration. The compounds tested included the 5'-palmitate, 5'-benzoate, and 5'-adamantoate esters of ara-cytidine, made water soluble by use of their hydrochloride salts of peptidyl derivatives, and two basic 5' esters (5'-nicotinoate and 5'-quinuclidinate) as their hydrochloride salts. Five of the compounds had antitumor activity superior to that found with ara-cytidine itself after oral administration in the L1210 leukemic mouse assay. One of these, 5'-adamantoyl-ara-cytidine hydrochloride, had antitumor activity after oral administration approaching that achieved with parenterally administered ara-cytidine.