Although less widespread than Al-toxic acid soils, Mntoxic acid soils do exist in Hawaii (Hue et al., 1998a), Manganese toxicity is a serious constraint to many crops grown Brazil (R.S. Yost, personal communication, 1999), and on acid soils in Hawaii. To develop management strategies to deal with the Mn problem, four experiments were conducted. First, to the Philippines (Hue, 1999). For example, a major porstudy soil pH effect, a pH gradient from 4.7 (unamended) to 6.0 was tion of agricultural land on Oahu, Hawaii, consists of established in a high-Mn Oxisol (Wahiawa series), using combinations soils with 10 to 40 g kg Ϫ1 total Mn concentration (Fujiof Ca(OH) 2 (lime) and CaSO 4 • 2H 2 O (gypsum); soybean [Glycine moto and Sherman, 1948). These soils, mostly Oxisols max (L.) Merr. cv. Kahala] was grown as a test crop. Second, effects of basaltic origin, are often located in areas of low to of Ca, and particularly SO 4 , on ameliorating Mn toxicity to soybean moderate elevations (70-250 m above sea level) and were subsequently evaluated. Third, soil Mn solubility by organic with moderate annual rainfall (50-150 cm) (Swindale molecules was studied in the laboratory as a function of chemical and Uehara, 1966). The total Mn contents of these structure, pH, and equilibration time. Fourth, soybean responses to Hawaii Oxisols are about 10 times greater than the green manure and biosolids applied at 5 and 10 g kg Ϫ1 to the Wahiawa average soil Mn content worldwide (Kabata-Pendias soil were compared with those of the unamended control and CaCO 3 treatments. Manganese concentration in the saturated paste extract and Adriano, 1995). However, total soil Mn only indiof the first experiment increased 100-fold for each pH unit decrease. cates the potential toxicity. Actual Mn toxicity is associ-A combination of gypsum and lime was more effective in correcting ated with forms that are either water soluble or easily Mn toxicity than either amendment alone. Soybean growth was better reducible. Adams (1984) suggested a reducible Mn correlated with leaf Ca/Mn ratio than with leaf Mn concentration. range of 50 to 100 mg kg Ϫ1 , above which Mn toxicity Increased SO 4 concentration alleviated Mn toxicity. Organic molewould occur. To avoid Mn toxicity, Hue et al. (1998b) cules or ions containing OH-OH in the ortho position or SH groups, proposed to keep Mn concentrations in the saturated such as catechol, tannic acid, and cysteine, were more effective in paste extract below 0.5 mg L Ϫ1. This value agrees well dissolving soil Mn than molecules or ions not containing these funcwith the critical toxic levels of 5 to 10 M Mn (0.27-0.55 tional groups. Application of green manure and biosolids generally mg L Ϫ1) in nutrient solutions that contained some Si increased Mn toxicity. (0.75-40 mg Si L Ϫ1) (Horst and Marschner, 1978). The same authors reported that Mn toxicity in bean (Phaseolus vulgaris L.) was observed at 0.5 M when the nutri

. Histopathological findings of tubular degeneration and inflammatory cell infiltration reinforced GM-induced nephrotoxicity. All these alterations were attenuated by previous oral treatment with GF. Animals from the GM؉GF groups showed amelioration in renal function parameters and reduced lipid peroxidation and nitrosative stress, in addition to an increment in the levels of glutathione (GSH) and superoxide dismutase (SOD) activity. Gingerols also promoted significant reductions in mRNA transcription for TNF-␣, IL-2, and IFN-␥. These effects were dose dependent. These results demonstrate that GF promotes a nephroprotective effect on GM-mediated nephropathy by oxidative stress, inflammatory processes, and renal dysfunction.

This study focuses in the mathematical modelling of the enzymic synthesis of amoxicillin by the reaction of p-hydroxyphenylglycine methyl ester and 6-aminopenicillanic acid (6APA), catalyzed by penicillin G acylase (PGA) immobilized on glutaraldehyde-chitosan, at 25°C and pH 6.5. Previous work on the kinetics and mechanism of reaction showed that the use of neural networks seems to be an interesting alternative to simulate experimental data of antibiotic production. Therefore, two feedforward neural networks, with one hidden layer, were trained and used to forecast the rates of amoxicillin and p-hydroxyphenylglycine (POHPG) net production. First of all, some parameters that affect the network performed were investigated, such as the number of nodes between the input and hidden layers and the number of interactions during the learning phase. Afterwards, hybrid models that coupled artificial neural networks to mass-balance equations were used to reproduce the performance of batch reactors for the production of amoxicillin. This approach provided accurate results, within the range of substrate concentration studied.

A surface‐sensitive technique based on the angular distributions of X‐ray photoelectron intensities has been used to study the adsorption pattern of Ca, Si and P on gibbsite surfaces. The profile distributions of ions extending from the average Al(OH)3 surface plane appear to be in the order: Ca closer to the surface than Si for CaSiO3 as adsorbate and Ca at nearly the same plane and above Si for CaCl2 + Si(OH)4 as adsorbates irrespective of adsorbate pH. The average positions, relative to the Al(OH)3 atoms are: Si and P appear above the surface level when adsorbed from their respective acid forms, as is the case for more complex adsorbates like Si(OH)4 + H3PO4 + CaCl2, where Ca appears at the surface level. An atomic rearrangement on the gibbsite surface seems to occur in the latter case. These experiments have demonstrated that it is possible to apply the XPS (X‐ray photoelectron spectroscopy) angular distribution technique for adsorption studies on powdered soil materials, a subject of relevant interest in earth sciences.

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