The potential for carbon dioxide removal by enhanced rock weathering in the tropics: An evaluation of Costa Rica.

Tropical environments show great potential to sequester CO2 by enhanced rock weathering (ERW) of powdered mafic rocks applied to agricultural fields. This study seeks to assess carbon dioxide reduction (CDR) potential in the humid tropics (1) by experimental weathering of mafic rock powders in conditions simulating humid tropical soils, and (2) from weathering rates determined from a Holocene tropical soil chronosequence where parent material is andesitic sediments. Experimentally determined weathering rates by leaching of basaltic andesites from Costa Rica (Arenal and Barva) for 50 t ha-1 applications indicate potential sequestration of 2.4 to 4.5 t CO2 ha-1 yr-1, whereas the USGS basalt standard BHVO-1 yields a rate of 11.9 t ha-1 yr-1 (influenced by more mafic composition and finer particle size). The chronosequence indicates a rate of 1.7 t CO2 ha-1 yr-1. The weathering experiment consisted of 0.6 mm of powdered rock applied atop 12 mm of Ultisol at 35 °C. To simulate a tropical soil solution, 100-mL aliquots of a dilute solution of oxalic acid in carbonated DI water were rained onto soils over a 14-day period to simulate soil moisture in the humid tropics. Solutions were collected and analyzed by ICPMS for concentrations of leached cations. A potential ERW scenario for Costa Rica was assessed assuming that one-half of lowland agricultural kaolinitic soils (mainly Ultisols, common crop and pasture soils, excluding protected areas) were to receive 50 t ha-1 of annual or biennial applications of powdered mafic rock. With an experimentally determined humid tropical CDR rate for basaltic andesite (3.5 t ha-1 yr-1) and allowances for carbon costs (e.g. emissions from processing and delivery) that reduce CDR to a net 3.2 t ha-1 yr-1, potential annual CDR of this tropical nation is ∼2-4 million tons, amounting to ∼25-50 % of annual CO2 emissions (mainly from transportation in Costa Rica).

Lack of correlation between fluvoxamine clearance and CYP1A2 activity as measured by systemic caffeine clearance.

OBJECTIVE: Evidence exists to suggest that fluvoxamine is metabolized by CYP1A2. The present study was undertaken in order to further elucidate the role of CYPIA2 in fluvoxamine disposition. METHODS: Twelve healthy non-smoking male volunteers participated in this cross-over study. Six subjects received first fluvoxamine 50 mg as a single oral dose and, some weeks later, caffeine 200 mg as a single oral dose. The other six subjects received the drugs in reverse order. Serum concentrations of fluvoxamine, caffeine and paraxanthine were measured and standard pharmacokinetic parameters were calculated. RESULTS: There were no significant correlations between caffeine clearance and fluvoxamine oral clearance (rs = -0.30; P = 0.43) or between the paraxanthine/caffeine ratio in serum 6 h after caffeine intake and fluvoxamine oral clearance (rs = -0.18; P = 0.58). CONCLUSION: CYP1A2 does not appear to be of major importance in the metabolism of fluvoxamine.

Adjudicating claims.

This chapter discusses the adjudication and case management processes and outlines sources of information and factors leading to denial of claim.

Non-linear fluvoxamine disposition.

AIMS: To study the pharmacokinetics of fluvoxamine when given in increasing doses to healthy volunteers. METHODS: Ten healthy, non-smoking men were given maintenance treatment with fluvoxamine for 4 weeks. Eight subjects were CYP2D6 extensive metabolisers (EMs) and two were CYP2D6 poor metabolisers (PMs). As a measure of the CYP1A2 phenotype, the paraxanthine/caffeine ratio in saliva after intake of caffeine was studied. The fluvoxamine doses given were 25 mg day(-1) the first week, 50 mg day(-1) the second week, 100 mg day(-1) the third week and 200 mg day(-1) the fourth week, divided in two daily doses. On the seventh day every week, serum concentrations of fluvoxamine were followed for a dose interval of 12 h. After discontinuation of treatment, fluvoxamine concentrations were followed for 1 week. RESULTS: For each of the three two-fold increases in given dose, the mean AUC increased 3.25-fold, 3.17-fold and 3.14-fold, respectively (P < 0.0001), indicating a decrease in oral clearance with increasing dose. The elimination half-life based upon the serum concentrations 12-48 h after discontinuation of fluvoxamine was 32.1 +/- 11.0 h whereas the half-life based upon the concentrations 3-7 days after discontinuation was significantly shorter, 15.8 +/- 4.2h (means +/- s.d.; P < 0.001). There were no significant correlations between the CYP1A2 phenotype and fluvoxamine AUCs at different doses (r = -0.56; P = 0.095 for the correlation between the paraxanthine/caffeine ratio in saliva and fluvoxamine AUC at a dose of 50 mg day[-1]). The two CYP2D6 PMs had AUC values in the same range as the EMs. CONCLUSIONS: The present study conclusively demonstrates that fluvoxamine exhibits non-linear kinetics within the therapeutic dose interval. The reason for non-linearity is not Michaelis-Menten saturation kinetics of a single metabolic pathway, but rather a complex involvement of multiple parallel pathways.

Effects of cyanide on the striatal dopamine receptor binding in the rat.

In previous studies we have shown that sodium cyanide decreases the striatal dopamine levels within 60 s compared with the controls. Treatment with sodium cyanide also increases the naturally occurring 3,4-dihydroxy-L-phenylalanine (L-DOPA) in the striatum, but not in any other region studied. An increase in the in vivo synthesis of dopamine in cyanide-treated rats has also been observed. In order to further elucidate the effects on the central dopaminergic pathways the effects of sodium cyanide on the striatal dopamine D1 and dopamine D2 receptor binding were studied in vitro and after administration of sodium cyanide. In the rats injected with sodium cyanide (2.0 mg/kg, i.p.) the Bmax of the striatal dopamine D1 receptor binding was significantly decreased 15 min and 1 h after the treatment. The striatal dopamine D2 receptor binding was decreased only at 1 h after the cyanide administration. Neither sodium cyanide nor its metabolite sodium thiocyanate did significantly change the striatal dopamine D1 and D2 receptor binding in vitro. Accordingly sodium cyanide and sodium thiocyanate do not have direct effects on the dopamine receptors studied. The effects of cyanide on dopamine D1 and D2 receptors are probably in part due to the effect of cyanide on the release of dopamine.

Randomized field experiments for program planning, development, and evaluation: an illustrative bibliography.

This bibliography lists references to over 300 field experiments undertaken in schools, hospitals, prisons, and other social settings, mainly in the U.S. The list is divided into 10 major categories corresponding to the type of program under examination. They include: criminal and civil justice programs, mental health, training and education, mass media, information collection, utilization, commerce and industry, welfare, health, and family planning. The main purpose of the bibliography is to provide evidence on feasibility and scope of randomized field tests, since despite their advantages, it is not always clear from managerial, political, and other constraints on research that they can be mounted. Dates of publications range from 1944 to 1978.