Sediment greenhouse gases (methane and carbon dioxide) in the Lobo-Broa Reservoir, São Paulo State, Brazil: Concentrations and diffuse emission fluxes for carbon budget considerations

Carbon gases (methane, CH₄, and carbon dioxide, CO₂) were measured for the first time in sediments of the Lobo‐Broa Reservoir, near São Carlos in São Paulo State, Brazil. It is believed these are the first measurements of this kind in any of the many reservoirs located in Brazil. Even though the Lobo‐Broa Reservoir is classified as oligotrophic, the sediment gas concentrations were exceedingly high, ranging from 0.4–3 mmol L^?1 for CH₄ and 1–9 mmol L^?1 for CO₂. Both gases exceeded their in situ gas saturation values at these shallow water depths (7 m in central basin; 11 m at dam), resulting in numerous sediment bubbles. Organic matter was highly concentrated in the reservoir sediments, averaging 25.5% loss on ignition (LOI) (dam) to 26.9% LOI (central basin) for the 0–12 cm depth interval, with values as high as 29–30% LOI (12% organic carbon) in the surface 0–5 mm layer. The theoretical flux of dissolved pore water carbon gases to the sediment–water interface (SWI) averaged 3.4 mmol L^?1 m^?2 day^?1 CH₄ and 7.3 mmol L^?1 m^?2 day^?1 CO₂ for the surface 0–10 mm. From gas emission measurements at the water surface, it was calculated that 90% of CH₄ is consumed either at the SWI or in the water column, resulting in a loss of 0.31 mmol L^?1 m^?2 day^?1 of CH₄ to the atmosphere. However, only 20% of the total CO₂ gas transported across the water–atmosphere interface (36.3 mmol L^?1 m^?2 day^?1, or 1600 mg CO₂ m^?2 day^?1) was produced in the sediments. The remaining 80% of CO₂ probably comes from other carbon sources. With CH₄ oxidation in the aerobic water column, close to 30% of the carbon gas flux to the atmosphere could be accounted for by gas production of CO₂ and CH₄ in the sediments and their diffuse transport to the water column.     

The state of Tin on Pt–Sn/Nb2O5 catalysts

The effect of tin addition on niobia supported catalysts was studied and compared to the properties of alumina supported bimetallic Pt–Sn catalysts. The catalyst surfaces were probed by methylcyclopentane conversion, showing that both the presence of Sn and the reduction of the support caused a decrease in hydrogenolysis activity, favoring the ring enlargement reaction. The thermodynamics of reduction of these systems, evaluated by following the reduction step (temperature programmed reduction — TPR) with a differential scanning calorimeter (DSC), and irreversible H₂ and CO uptakes, allowed to conclude that a Pt–Sn alloy is formed on niobia supported catalysts.     

Imidazolium salts as liquid coupling agents for the preparation of polypropylene‐silica composites

This article describes the application of ionic liquid 1‐decyl‐3‐methylimidazolium tetrafluoroborate in the preparation of polypropylene‐silica composites. The sol‐gel technology was used to prepare xerogel silica‐ionic liquid hybrid S1 , which was obtained as a free flowing powder of aggregated spherical particles. Ionic liquid free silica S2 was obtained by extraction and calcination of S1 . Melt blending of isotactic polypropylene with S1 and S2 afforded the composites C1 (with ionic liquid) and C2 (without ionic liquid), respectively. The presence of ionic liquid on the S1 silica surface promoted significantly improved silica dispersion in the polymer matrix and prevented compression of the silica particles. Furthermore, the crystallization temperature of composite C1 was significantly higher, which indicated that silica‐ionic liquid filler S1 acted as nucleating agent. The resistance to thermal decomposition of both composites was increased, but this was higher in the presence of ionic liquid. These results show that liquid salts can function as coupling agents and compatibalizers for the preparation of polymeric composites with differentiated properties. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

A candidate recombination modifier gene for Zea mays L

Maize meiotic mutant desynaptic (dy) was tested as a candidate recombination modifier gene because its effect is manifested in prophase I. Recombination rates for desynaptic (dy) and its wild type were compared in two ways: (1) segregation analysis using six linked molecular markers on chromosome 1L and (2) cytogenetic analysis using fluorescence in situ hybridization (FISH)-aided meiotic configurations observed in metaphase I. Chromosome 1L map lengths among the six linked markers were 45-63 cM for five F2 dy/dy plants, significantly lower than the wild-type F2 map distance of 72 cM. Chromosomes 2 and 6 were marked with rDNA FISH probes, and their map lengths were estimated from FISH-adorned meiotic configurations using the expectation-maximization algorithm. Chiasma frequencies for dy/dy plants were significantly reduced for both arms of chromosome 2, for chromosome arm 6L, and for eight unidentified chromosomes. There was a notable exception for the nucleolus-organizing region-bearing arm chromosome arm 6S, where dy increased chiasma frequency. Maize meiotic mutant desynaptic is a recombination modifier gene based on cytogenetic and segregation analyses.     

A brief note on thermoluminescence analysis of photosystem II and lipid peroxidation during the shelf life of ready-to-use rocket (Diplotaxis tenuifolia L.)

The quality of leafy vegetables has to be guaranteed for consumers over the whole postharvest period, usually limited to 5–7 days. The analyses to evaluate the quality of vegetables are very time- and resource consuming, so the use of qualitative markers can be much useful. The aim of this work was to evaluate the use of thermoluminescence (TL) parameters as qualitative markers of fresh-cut leafy vegetables during the shelf life. TL is a technique consisting of a cooling, followed by the progressive warming, of a preilluminated sample to reveal the different types of charge pairs as successive emission bands, which are resolved better than the corresponding decay phases recorded at constant temperature. Experiments were performed on rocket (Diplotaxis tenuifolia L.) stored at 2 °C for 7 days. During storage, several changes in TL glow curves were found. The position of the peaks showed a shift to higher temperature. The area of the peaks, relating to the photosystem II (20–65 °C), grew up lightly; whereas in the temperature range that detects lipidic peroxidation (65–140 °C), the TL emission became more than twice. These changes demonstrated that, during the shelf life, a progressive destabilization of PSII centres occurred and that lipid peroxidation products were accumulated in membranes. TL could be used to estimate the damages immediately after as well as during the storage period. This is the first time that TL was used to evaluate the quality of fresh-cut vegetables products during the shelf life.     

Non-invasive nasal ventilation in a a case of hypercapnic coma

Noninvasive positive pressure ventilation (NPPV) via nasal mask is well known to be effective in the treatment of acute respiratory failure (ARF) secondary to chronic obstructive pulmonary disease (COPD). A case of ARF with hypercapnic coma due to exacerbation of COPD is described. Six hours of conservative therapy with oxygen and medical treatment did not show any result. As endotracheal intubation (ET) was avoided on the basis of advanced age, poor life expectancy of the patient and family wish, NPPV was set up using a pressure triggered ventilator. After 61 hours of uninterrupted NPPV, the acid-base alteration and the lethargic status was fully reversed. The conclusions is drawn that NPPV may be useful also in the treatment of patients affected by severe decompensated hypercapnic respiratory failure in whom ET is not indicated.     

Purpura fulminans in the newborn. Report of two cases successfully treated with heparin and antithrombin III

Purpura fulminans is a rare form of disseminated intravascular coagulation characterized by rapidly progressive purpuric lesions, hypotension and, in some cases, fever. In neonates, purpura fulminans usually develops following deficiency of anticoagulant protein C or S, although acquired forms have been described. The management of disseminated intravascular coagulation is still controversial, with some studies finding a positive effect of anticoagulants and others showing no effect or even a detrimental one. Therefore, at present, management is limited to the treatment of underlying disease and replacement of clotting factors. Personal experience is reported on the efficacy of heparin in combination with antithrombin III in the treatment of purpura fulminans in two preterm neonates who did not have inherited deficiency of protein C or S and developed the disease possibly following prolonged labor (36 hours) in the first case, and maternal neoplasia, in the second. Both neonates presented with widespread cyanotic areas rapidly evolving in purpuric lesions and hemorrhagic bullae. Laboratory tests (prolonged prothrombin and partial thromboplastin time, fibrinogen and antithrombin III concentrations below normal ranges, d-dimer highly positive) were consistent with disseminated intravascular coagulation. In both cases anticoagulant treatment with heparin (50 UI/kg in bolus followed by 15 UI/kg/h) and antithrombin III was associated with resolution of disseminated intravascular coagulation and prompt amelioration of the purpuric lesions, without apparent side effects.     

Effect of roasting on the radical scavenging activity of cocoa beans

The free-radical scavenging activity of cocoa samples subjected to different roasting treatments has been determined. The samples (raw, pre-roasted and roasted) were separated into four molecular weight fractions per sample (>30, 30–10, 10–5, and <5 kDa). The free-radical scavenging activity was determined with the DPPH^• (1,1-dipheny-2-picrylhydrazyl), and ABTS^•+ [2,2’-azinobis (3-ethylbenzothiazoline-6-sulfonic acid)] free-radical scavenging assays for all samples. Both tests were compared in terms of sensitivity and measurement precision, at different reaction times. Comparing the results from each test, the free-radical scavenging activity trends were similar for each fraction but with notable differences in the sensitivity of the assays. Analysis of the concentration of reducing substances, such as water soluble phenolics, melanoidins, carbohydrates, etc, in these fractions by the photometric Folin–Ciocalteu assay, showed a similar pattern to the free-radical scavenging activity trend. Moreover, this comparison showed that there were significantly (P < 0.05) more reducing substances and free-radical scavenging activity in the 10–5 kDa roasted cocoa bean fraction.     

Contents of volume 49 (1991)

Contents of volume 49 (1991)