(Table 1) Downhole variation of potassium, apparent K-Ar age, and inert gas abundances at DSDP Holes 69-504B, 70-504B and 83-504B

Ne, Ar, Kr, Xe, and K2O were measured in representative samples of holocrystalline basalt from DSDP Hole 504B. No hiatus in inert gas abundance is recognized at the base of the "oxic" alteration zone and the extent rather than the nature of alteration appears to determine these abundances. When the inert gas abundances are separately plotted against K2O, two distinct trends of loss emerge, one for alteration involving K-gain, the other for K-loss. Apparent whole-rock K-Ar ages are anomalous in the upper 50 m of basement, and below 300 m sub-basement. In the intervening zone of basement, celadonization adds sufficient potassium and eliminates enough "primary" 40Ar early in the history of the basalts for "excess" 40Ar to become subordinate to radiogenic 40Ar in basalts showing potassium enrichment greater than 0.2%. Stratigraphically correct K-Ar ages are obtained, therefore, from K-enriched basalts of the oxic alteration zone.

Chemistry of potassium halides and their role in corrosion in biomass and waste firing

Compared to the use of traditional fossil fuels (coal, oil, natural gas), combustion of biomass and waste fuels has several environmental and economic advantages for heat and power generation. However, biomass and waste fuels might contain halogens (Cl, Br, F), alkali metals (Na, K) and heavy metals (Zn, Pb), which may cause harmful emissions and corrosion problems. Hightemperature corrosion occurs typically on furnace waterwalls and superheaters. The corrosion of the boiler tube materials limits the increase of thermal efficiency of steam boilers and leads to costly shutdowns and repairs. In recent years, some concerns have been raised about halogen (Cl, Br, and F)-related hightemperature corrosion in biomass- and waste-fired boilers. Chlorine-related high-temperature corrosion has been studied extensively. The presence of alkali chlorides in the deposits is believed to play a major role in the corrosion observed in biomass and waste fired boilers. However, there is much less information found in literature on the corrosion effect of bromine and fluorine. According to the literature, bromine is only assumed to play a role similar to chlorine; the role of fluorine is even less understood. In this work, a series of bubbling fluidized bed (BFB) bench-scale tests were carried out to characterize the formation and sulfation behaviors of KCl and KBr in BFB combustion conditions. Furthermore, a series of laboratory tests were carried out to investigate the hightemperature corrosion behaviors of three different superheater steels (10CrMo9-10, AISI 347 and Sanicro 28) exposed to potassium halides in ambient air and wet air (containing 30% H2O). The influence of H2O and O2 on the high-temperature corrosion of steels both with and without a salt (KCl) in three gas atmospheres (2% H2O-30% O2-N2, 2% H2O-2% O2-N2 and 30% H2O-2% O2-N2) was also studied. From the bench-scale BFB combustion tests, it was found that HBr has a clearly higher affinity for the available K forming KBr than HCl forming KCl. The tests also indicated that KCl has a higher tendency for sulfation than KBr. From the laboratory corrosion tests in ambient air (also called “dry air” in Paper III and Paper IV), it was found that at relatively low temperatures (≤ 550 °C) the corrosivity of KBr and KF are similar to KCl. At 600 °C, KF showed much stronger corrosivity than KBr and KCl, especially for 10CrMo9-10 and AISI 347. When exposed to KBr or KF, 10CrMo9-10 was durable at least up to 450 °C, while AISI 347 and Sanicro 28 were durable at least up to 550 °C. From the laboratory corrosion tests in wet air (30% H2O), no obvious effect of water vapor was detected at 450 °C. At 550 °C, the influence of water vapor became significant in some cases, but the trend was not consistent. At 550 °C, after exposure with KBr, 10CrMo9-10 suffered from extreme corrosion; after exposure with KF and KCl, the corrosion was less severe, but still high. At 550 °C, local deep pitting corrosion occurred on AISI 347 and Sanicro 28 after exposure with KF. Some formation of K2CrO4 was observed in the oxide layer. At 550 °C, AISI 347 and Sanicro 28 suffered from low corrosion (oxide layer thickness of < 10 μm) after exposure with KBr and KCl. No formation of K2CrO4 was observed. Internal oxidation occurred in the cases of AISI 347 with KBr and KCl. From the laboratory corrosion tests in three different gas atmospheres (2% H2O-30% O2-N2, 2% H2O-2% O2-N2 and 30% H2O-2% O2-N2), it was found that in tests with no salt, no corrosion occurred on AISI 347 and Sanicro 28 up to 600 °C in both the “O2-rich” (2% H2O-30% O2-N2) and “H2O-rich” (30% H2O-2% O2-N2) gas atmospheres; only 10CrMo9-10 showed increased corrosion with increasing temperature. For 10CrMo9-10 in the “O2-rich” atmosphere, the presence of KCl significantly increased the corrosion compared to the “no salt” cases. For 10CrMo9-10 in the “H2O-rich” atmosphere, the presence or absence of KCl did not show any big influence on corrosion. The formation of K2CrO4 was observed only in the case with the “O2-rich” atmosphere. Considering both the results from the BFB tests and the laboratory corrosion tests, if fuels containing Br were to be combusted, the corrosion damage of superheaters would be expected to be higher than if the fuels contain only Cl. Information generated from these studies can be used to help the boiler manufacturers in selecting materials for the most demanding combustion systems.

Determination of potassium and sodium in an ash sample by gamma-ray spectroscopy

Neutron activation analysis and gamma-ray spectroscopy were used to determine the quantity of potassium and sodium in an ash sample of Tabebuia sp bombarded with thermal neutrons. These techniques, widely applied in nuclear physics, can be used in the context of wood science as an alternative for the usual physical chemistry methods applied in this area. The quantity of K and Na in an 8.60 +/- 0.10 mg of ash was determined as being 1.3 +/- 0.3 mg and 11.0 +/- 1.8 mu g, respectively. The ratio of Tabebuia sp converted into ash was also determined as 0.758 +/- 0.004%.

Impact of potassium and phosphorus in biomass on the properties of fast Pyrolysis bio-oil

This study investigates fast pyrolysis bio-oils produced from alkali-metal-impregnated biomass (beech wood). The impregnation aim is to study the catalytic cracking of the pyrolysis vapors as a result of potassium or phosphorus. It is recognized that potassium and phosphorus in biomass can have a major impact on the thermal conversion processes. When biomass is pyrolyzed in the presence of alkali metal cations, catalytic cracking of the pyrolysis liquids occurs in the vapor phase, reducing the organic liquids produced and increasing yields of water, char, and gas, resulting in a bio-oil that has a lower calorific value and an increased chance of phase separation. Beech wood was impregnated with potassium or phosphorus (K impregnation and P impregnation, respectively) in the range of 0.10-2.00 wt %. Analytical pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) was used to examine the pyrolysis products during thermal degradation, and thermogravimetric analysis (TGA) was used to examine the distribution of char and volatiles. Both potassium and phosphorus are seen to catalyze the pyrolytic decomposition of biomass and modify the yields of products. 3-Furaldehyde and levoglucosenone become more dominant products upon P impregnation, pointing to rearrangement and dehydration routes during the pyrolysis process. Potassium has a significant influence on cellulose and hemicellulose decomposition, not just on the formation of levoglucosan but also other species, such as 2(5H)-furanone or hydroxymethyl-cyclopentene derivatives. Fast pyrolysis processing has also been undertaken using a laboratory-scale continuously fed bubbling fluidized-bed reactor with a nominal capacity of 1 kg h-1 at the reaction temperature of 525 °C. An increase in the viscosity of the bio-oil during the stability assessment tests was observed with an increasing percentage of impregnation for both additives. This is because bio-oil undergoes polymerization while placed in storage as a result of the inorganic content. The majority of inorganics are concentrated in the char, but small amounts are entrained in the pyrolysis vapors and, therefore, end up in the bio-oil.

Qualidade do café natural e despolpado em diferentes condições de secagem e tempos de armazenamento

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Estudo dos fatores envolvidos na qualidade fisiológica de sementes de Brachiaria brizantha

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Alterações na composição química e sensorial de café (Coffea arabica L.) nos processos pós-colheita

An interdisciplinary study was conducted to evaluate the effects of drying and storage time on changes in the quality of natural and fully washed coffees beans dried out in the yard and mechanically dried at a temperature of 60/40°C in air dryer machine. The coffee beans (Coffea arabica L.) harvested in cherries were processed by dry and wet methods, being subjected to pre-drying yard, followed by drying yard in the sun with air heated of 60/40°C until it reached the water content of 11% (wb). After reached the thermal equilibrium with the environment, the beans were packed in jute bag with a capacity of five kilograms and stored in uncontrolled environment during the period of one year, and removing material from each treatment every three months. To characterize the effect of drying and storage time on the coffee quality different methodologies was evaluated. It was observed less drying time for the fully washed coffee 60/40°C, and thus less energy consumed in the drying process until the point of storage, for the natural coffee there was significant effect of time on the chemical quality, biochemical and sensory; fully washed coffee proved to be more tolerant to drying than natural coffee, regardless of drying method, showing a better drink quality and less variation in chemical composition and biochemistry.

Potassium and Argon data for dating the core, and radiochemical data of a series of measurements made on layers inside various manganese nodules from the Pacific Ocean

Although various models have been proposed to explain the origin of manganese nodules (see Goldberg and Arrhenius), two major hypotheses have received extensive attention. One concept suggests that manganese nodules form as the result of interaction between submarine volcanic products and sea water. The common association of manganese nodules with volcanic materials constitutes the main evidence for this theory. The second theory involves a direct inorganic precipitation of manganese from sea water. Goldberg and Arrhenius view this process as the oxidation of divalent manganese to tetravalent manganese by oxygen under the catalytic action of particulate iron hydroxides. Manganese accumulation by the Goldberg and Arrhenius theory would be a relatively slow and comparatively steady process, whereas Bonatti and Nayudu believe manganese nodule formation takes place subsequent to the eruption of submarine volcanoes by the acidic leaching of lava.

Solution structure and proposed binding mechanism of a novel potassium channel toxin kappa-conotoxin PVIIA

Background: kappa-PVIIA is a 27-residue polypeptide isolated from the venom of Conus purpurascens and is the first member of a new class of conotoxins that block potassium channels. By comparison to other ion channels of eukaryotic cell membranes, voltage-sensitive potassium channels are relatively simple and methodology has been developed for mapping their interactions with small-peptide toxins, PVIIA, therefore, is a valuable new probe of potassium channel structure. This study of the solution structure and mode of channel binding of PVIIA forms the basis for mapping the interacting residues at the conotoxin-ion channel interface. Results: The three-dimensional structure of PVIIA resembles the triple-stranded beta sheet/cystine-knot motif formed by a number of toxic and inhibitory peptides. Subtle structural differences, predominantly in loops 2 and 4, are observed between PVIIA and other conotoxins with similar structural frameworks, however. Electrophysiological binding data suggest that PVIIA blocks channel currents by binding in a voltage-sensitive manner to the external vestibule and occluding the pore, Comparison of the electrostatic surface of PVIIA with that of the well-characterised potassium channel blocker charybdotoxin suggests a likely binding orientation for PVIIA, Conclusions: Although the structure of PVIIA is considerably different to that of the alpha K scorpion toxins, it has a similar mechanism of channel blockade. On the basis of a comparison of the structures of PVIIA and charybdotoxin, we suggest that Lys19 of PVIIA is the residue which is responsible for physically occluding the pore of the potassium channel.

Eag1 potassium channel immunohistochemistry in the CNS of adult rat and selected regions of human brain

Eag1 (K(v)10.1) is the founding member of an evolutionarily conserved superfamily of voltage-gated K+ channels. In rats and humans Eag1 is preferentially expressed in adult brain but its regional distribution has only been studied at mRNA level and only in the rat at high resolution. The main aim of the present study is to describe the distribution of Eag1 protein in adult rat brain in comparison to selected regions of the human adult brain. The distribution of Eag1 protein was assessed using alkaline-phosphatase based immunohistochemistry. Eag1 immunoreactivity was widespread, although selective, throughout rat brain, especially noticeable in the perinuclear space of cells and proximal regions of the extensions, both in rat and human brain. To relate the results to the relative abundance of Eag1 transcripts in different regions of rat brain a reverse-transcription coupled to quantitative polymerase chain reaction (real time PCR) was performed. This real time PCR analysis showed high Eag1 expression in the olfactory bulb, cerebral cortex, hippocampus, hypothalamus, and cerebellum. The results indicate that Eag1 protein expression greatly overlaps with mRNA distribution in rats and humans. The physiological relevance of potassium channels in the different regions expressing Eag1 protein is discussed. (C) 2008 IBRO. Published by Elsevier Ltd. All rights reserved.

Denitrification, leaching and immobilisation of N-15-labelled nitrate in winter under windrowed harvesting residues in hoop pine plantations of 1-3 years old in subtropical Australia

A field study was carried out to investigate the impacts of windrowed harvesting residues on denitrification, immobilisation and leaching of N-15-labelled nitrate applied at 20 kg N ha(-1) to microplots in second-rotation hoop pine (Araucaria cunninghamii) plantations of 1-3 years old in southeast Queensland, Australia. The PVC microplots were 235 mm in diameter and 150 mm. long, and driven into the 100 mm soil. There were three replications of such microplots for each of the six treatments which were areas just under and between 1-, 2- and 3-year-old windrows of harvesting residues. Based on gaseous N losses estimated by the difference between the recoveries of bromide (Br) applied at 100 kg Br ha(-1) and N-15-labelled nitrate, denitrification was highest (23% based on N-15 loss) in the areas just under the 1-year-old windrows 25 days after a simulated 75 mm rainfall and following several natural rainfall events. There was no significant difference in N-15 losses (14-17%) among the other treatments. The N-15 immobilisation rate was highest for microplots in the areas between the 1-year-old windrows and generally higher for microplots in the areas just under the windrows (30-39%) than that (26-30%) between the windrows. Direct measurement of N-15 gas emissions (N-15(2) + (N2O)-N-15) confirmed that the highest denitrification rate occurred in the microplots under the 1-year-old windrows although the gaseous N-15 loss calculated by gas emission was only about one-quarter that estimated by the N-15 mass balance method. A significant, positive linear relationship (P < 0.05) existed between the gaseous N-15 losses measured by the two methods used. The research indicates that considerable mineral N could be lost via denitrification during the critical inter-rotation period and early phase of the second rotation. However, the impacts of windrowed harvesting residues on N losses via denitrification might only last for a period of about 2 years. Published by Elsevier Science B.V.

The surface chemistry of leaching coal fly ash

The utilization of coal fly ash in the construction and non-construction areas has seen a rapid growth in the last decade. As production outweighs the utilization of fly ash, its disposal as a dilute or dense slurry is still practiced in coal fired power stations. In this review the surface chemistry of leaching coal fly ash is presented to highlight the role of mass transfer in providing resistance and consequently delayed leaching of elements, when fly ash is disposed or used for value addition. (C) 2002 Elsevier Science B.V. All rights reserved.

The production of vermicompost from dairy sludge and its value as a plant growth medium

Dairy sludge generated at Glanbia Ingredients Ltd., Kilkenny has up until now been landspread. This study investigated the feasibility of using earthworms to vermicompost the sludge as an alternative method of treatment. It was found that high levels of ammonia in the sludge led to earthworm fatality but that by manually aerating the sludge the ammonia could be volatilised or by adding zeolite the ammonia could be absorbed, thus solving the problem. In a medium scale trial, the earthworm species Dendrobaena veneta and Eisenia fetida dominated the polyculture. Earthworms grew and generated cocoons during vermicomposting. During vermicomposting no leachate was generated. Nutrient changes took place during vermicomposting. There were high levels of nitrate, increased calcium and sulphate in the vermicomposted dairy sludge. The amount of magnesium, potassium and chloride did not change, while phosphate was undetectable after vermicomposting. The levels of nitrate and phosphate were good indicators of the extent of vermicomposting. The vermicomposted dairy sludge provided improved growth and yields of radishes and barley compared to the dairy sludge and control. Compared to the vermicompost, the dairy sludge provided heavier ryegrass yields and more marigolds with larger flower diameters. Generally, it is the amount of phosphate in dairy sludge that dictates how much can be applied as a fertiliser on land. Vermicomposting reduced the amount of phosphate to an undetectable level but on the other hand created a problem of high nitrate levels. In a pot trial with grass grown in vermicompost the nitrate leached from the vermicompost. In field conditions the leaching of nitrate might occur and could cause an increased risk of contamination of groundwater and watercourses.

Potassium restores vasorelaxation of resistance arterioles in non-hypertensive DOCA/salt fed mice.

BACKGROUND: Potassium-enriched diets exert renal and cardiovascular protective effects, but the underlying mechanisms are largely unknown. METHODS: Using the dorsal skinfold chamber model for intravital microscopy, we examined endothelium-dependent vasorelaxation of precapillary resistance arterioles in response to acetylcholine or the NO donor SNAP in awake mice. Experiments were performed in uni-nephrectomized one renin gene (Ren-1c) C57BL/6 mice (control group) and in mice having received a continuous administration of deoxycorticosterone acetate and a dietary supplementation of 1% sodium chloride for 8weeks (DOCA/salt group). An additional group of DOCA/salt treated animals received a dietary supplement of 0.4% KCl for 3weeks prior to the experiments (DOCA/salt + potassium group). RESULTS: DOCA/salt treatment for 8weeks resulted in hypokalemia, but blood pressure remained unchanged. In DOCA/salt mice, relaxation of resistance arterioles was blunted in response to acetylcholine, and to a lesser extent to SNAP, suggesting endothelial dysfunction. Endothelium-dependent vasorelaxation was restored by the potassium-enriched diet. CONCLUSION: This study is the first to demonstrate a protective effect of potassium on endothelium-dependent vasorelaxation in the absence of confounding anti-hypertensive effects, as observed in most animal models and the clinical situation. We propose that the known cardio- and nephro-protective effects of potassium might - at least in part - be mediated by the salutary effects on endothelium-dependent arteriolar relaxation.

Haemodynamic consequences of changing potassium concentrations in haemodialysis fluids.

BACKGROUND: A rapid decrease of serum potassium concentrations during haemodialysis produces a significant increase in blood pressure parameters at the end of the session, even if effects on intra-dialysis pressure are not seen. Paradoxically, in animal models potassium is a vasodilator and decreases myocardial contractility. The purpose of this trial is to study the precise haemodynamic consequences induced by acute changes in potassium concentration during haemodialysis. METHODS: In 24 patients, 288 dialysis sessions, using a randomised single blind crossover design, we compared six dialysate sequences with different potassium profiles. The dialysis sessions were divided into 3 tertiles, casually modulating potassium concentration in the dialysate between the value normally used K and the two cut-off points K+1 and K-1 mmol/l. Haemodynamics were evaluated in a non-invasive manner using a finger beat-to-beat monitor. RESULTS: Comparing K-1 and K+1, differences were found within the tertiles regarding systolic (+5.3, +6.6, +2.3 mmHg, p < 0.05, < 0.05, ns) and mean blood pressure (+4.3, +6.4, -0.5 mmHg, p < 0.01, < 0.01, ns), as well as peripheral resistance (+212, +253, -4 dyne.sec.cm-5, p < 0.05, < 0.05, ns). The stroke volume showed a non-statistically-significant inverse trend (-3.1, -5.2, -0.2 ml). 18 hypotension episodes were recorded during the course of the study. 72% with K-1, 11% with K and 17% with K+1 (p < 0.01 for comparison K-1 vs. K and K-1 vs. K+1). CONCLUSIONS: A rapid decrease in the concentration of serum potassium during the initial stage of the dialysis-obtained by reducing the concentration of potassium in the dialysate-translated into a decrease of systolic and mean blood pressure mediated by a decrease in peripheral resistance. The risk of intra-dialysis hypotension inversely correlates to the potassium concentration in the dialysate. TRIAL REGISTRATION NUMBER: NCT01224314.