The Possible Emergence of Life and Differentiation of a Shallow Biosphere on Irradiated Icy Worlds: The Example of Europa

Irradiated ice-covered ocean worlds with rocky mafic mantles may provide the conditions needed to drive the emergence and maintenance of life. Alkaline hydrothermal springs-relieving the geophysical, thermal, and chemical disequilibria between oceans and tidally stressed crusts-could generate inorganic barriers to the otherwise uncontrolled and kinetically disfavored oxidation of hydrothermal hydrogen and methane. Ionic gradients imposed across these inorganic barriers, comprising iron oxyhydroxides and sulfides, could drive the hydrogenation of carbon dioxide and the oxidation of methane through thermodynamically favorable metabolic pathways leading to early life-forms. In such chemostatic environments, fuels may eventually outweigh oxidants. Ice-covered oceans are primarily heated from below, creating convection that could transport putative microbial cells and cellular cooperatives upward to congregate beneath an ice shell, potentially giving rise to a highly focused shallow biosphere. It is here where electron acceptors, ultimately derived from the irradiated surface, could be delivered to such life-forms through exchange with the icy surface. Such zones would act as "electron disposal units" for the biosphere, and occupants might be transferred toward the surface by buoyant diapirs and even entrained into plumes. Key Words: Biofilms-Europa-Extraterrestrial life-Hydrothermal systems. Astrobiology 17, 1265-1273.

Photosynthetic membrane-less microbial fuel cells to enhance microalgal biomass concentration

The aim of this study was to quantitatively assess the net increase in microalgal biomass concentration induced by photosynthetic microbial fuel cells (PMFC). The experiment was conducted on six lab-scale PMFC constituted by an anodic chamber simulating an anaerobic digester connected to a cathodic chamber consisting of a mixed algae consortia culture. Three PMFC were operated at closed circuit (PMFC(+)) whereas three PMFC were left unconnected as control (PMFC(-)). PMFC(+) produced a higher amount of carbon dioxide as a product of the organic matter oxidation that resulted in 1.5-3 times higher biomass concentration at the cathode compartment when compared to PMFC(-).

An efficient and environment-friendly method of removing graphene oxide in wastewater and its degradation mechanisms

Graphene and graphene oxide (GO) have already existed in air, water and soil due to their popular application in functional materials. However, degradation of graphene and GO in wastewater has not been reported. Degradation of GO plays a key role in the elimination of graphene and GO in wastewater due to graphene being easily oxidized to GO. In this paper, GO was completely degraded to give CO2 by Photo-Fenton. The degradation intermediates were determined by UV-vis absorption spectra, elemental analysis (EA), fourier transform infrared (FT-IR) and liquid chromatography-mass spectrometry (LC-MS). Experimental results showed that graphene oxide was completely degraded to give CO2 after 28 days. Based on UV, FT-IR, LC-MS spectra and EA data of these degradation intermediates, the degradation mechanisms of GO were supposed. This paper suggests an efficient and environment-friendly method to degrade GO and graphene.

Synthesis of Diverse (11)C-Labeled PET Radiotracers via Direct Incorporation of [(11)C]CO2

Three new positron emission tomography (PET) radiotracers of interest to our functional neuroimaging and translational oncology programs have been prepared through new developments in [(11)C]CO2 fixation chemistry. [(11)C]QZ (glutaminyl cyclase) was prepared via a tandem trapping of [(11)C]CO2/intramolecular cyclization; [(11)C]tideglusib (glycogen synthase kinase-3) was synthesized through a tandem trapping of [(11)C]CO2 followed by an intermolecular cycloaddition between a [(11)C]isocyanate and an isothiocyanate to form the 1,2,4-thiadiazolidine-3,5-dione core; [(11)C]ibrutinib (Bruton's tyrosine kinase) was synthesized through a HATU peptide coupling of an amino precursor with [(11)C]acrylic acid (generated from [(11)C]CO2 fixation with vinylmagnesium bromide). All radiochemical syntheses are fully automated on commercial radiochemical synthesis modules and provide radiotracers in 1-5% radiochemical yield (noncorrected, based upon [(11)C]CO2). All three radiotracers have advanced to rodent imaging studies and preliminary PET imaging results are also reported.

Effect of Gold Particle Size on Steam Reforming of Methanol Over Au/CeO2-ZrO2 Catalysts

We examined the effect of the particle size of gold on steam reforming of methanol over Au/CeO2-ZrO2 catalysts. Gold was loaded onto CeO2-ZrO2 through deposition-precipitation. The average particle size (2-12 nm) of the gold was controlled by thermal reduction under H2 at various temperatures and by chemical reduction with various reducing agents. The catalytic activity decreased significantly with increasing particle size of the gold. The turnover frequency at the interface between gold and a support appeared to be independent of particle size in the range 2-5 nm, which implies that the perimeter of the particle may be the active site for this reaction. Methanol adsorption and conversion over these catalysts were also investigated with in-situ diffuse reflectance infrared Fourier transform spectroscopy. Analytical results for various adsorbed intermediate species during methanol conversion suggests that transformation of methoxy species is facilitated by use of smaller gold particles.

Co-gasification of wet sewage sludge and forestry waste in situ steam agent

The co-gasification of wet sewage sludge (80 wt.% moisture, WSS) and forestry waste (FW) blends was studied. The thermogravimetric analysis showed that weight loss and the maximum weight loss rate of the sample increased with the increase in FW content. The co-gasification process was performed in a lab-scale fixed bed gasifier to investigate the effects of WSS content and reactor temperature on product yields, gas composition and gasification performance. The results indicated that steam generated from the moisture content in WSS took part in the gasification with char. The gas yield decreased with the increasing WSS content. And the concentrations of H(2) and CO reached the maximum when the WSS content was 50%. The LHV of fuel gas ranged from 11.89 MJ/Nm(3) to 12.72 MJ/Nm(3) when the reactor temperature increased from 700 °C to 900 °C.

Chemical looping combustion in a rotating bed reactor--finding optimal process conditions for prototype reactor

A lab-scale rotating bed reactor for chemical looping combustion has been designed, constructed, and tested using a CuO/Al(2)O(3) oxygen carrier and methane as fuel. Process parameters such as bed rotating frequency, gas flows, and reactor temperature have been varied to find optimal performance of the prototype reactor. Around 90% CH(4) conversion and >90% CO(2) capture efficiency based on converted methane have been obtained. Stable operation has been accomplished over several hours, and also--stable operation can be regained after intentionally running into unstable conditions. Relatively high gas velocities are used to avoid fully reduced oxygen carrier in part of the bed. Potential CO(2) purity obtained is in the range 30 to 65%--mostly due to air slippage from the air sector--which seems to be the major drawback of the prototype reactor design. Considering the prototype nature of the first version of the rotating reactor setup, it is believed that significant improvements can be made to further avoid gas mixing in future modified and up-scaled reactor versions.

Stopped-flow spectrophotometric study of the kinetics and mechanism of CO₂ uptake by cis-[Cr(C₂O₄)(BaraNH₂)(OH₂)₂]+ cation and the acid-catalyzed decomposition of cis-[Cr(C₂O₄)(BaraNH₂)OCO₂]- anion in aqueous solution

The kinetics of CO₂ uptake by the cis-[Cr(C₂O₄)(BaraNH₂)(OH₂)₂]⁺ complex cation and the acid hydrolysis of the cis-[Cr(C₂O₄)(BaraNH₂)OCO₂]⁻ complex anion (where BaraNH₂ denotes methyl 3-amino-2,3-dideoxy-β-D-arabino-hexopyranoside) were studied using the stopped-flow technique. The reactions under study were investigated in aqueous solution in the 288–308 K temperature range. In the case of the reaction between CO₂ and cis-[Cr(C₂O₄)(BaraNH₂)(OH₂)₂]⁺ cation variable pH values (6.82–8.91) and the constant ionic strength of solution (H⁺, Na⁺, ClO₄⁻ = 1.0) were used. Carbon dioxide was generated by the reaction between sodium pyruvate and hydrogen peroxide. The acid hydrolysis of cis-[Cr(C₂O₄)(BaraNH₂)OCO₂]⁻ was investigated for varying concentrations of H⁺ ions (0.01–2.7 M). The obtained results enabled the determination of the number of steps of the studied reactions. Based on the kinetic equations, rate constants were determined for each step. Finally, mechanisms for both reactions were proposed and discussed. Based on the obtained results it was concluded that the carboxylation (CO₂ uptake) reactions of cis-[Cr(C₂O₄)(BaraNH₂)(OH₂)₂]⁺ and the decarboxylation (acid hydrolysis) of the cis-[Cr(C₂O₄)(BaraNH₂)OCO₂]⁻are the opposite of each other.

Kinetic and mechanistic investigations of mesotrione degradation in aqueous medium by Fenton process

In this work, chemical oxidation of mesotrione herbicide by Fenton process in acidic medium (pH 3.5) was investigated. Total disappearance of mesotrione and up to 95% removal of total organic carbon (TOC) were achieved by Fenton's reagent under optimized initial concentrations of hydrogen peroxide (H(2)O(2)) and ferrous iron (Fe(2+)) at pH 3.5. The time-dependent degradation profiles of mesotrione were satisfactorily fitted by first-order kinetics. Competition kinetic model was used to evaluate a rate constant of 8.8(± 0.2) × 10(9)M(-1) s(-1) for the reaction of mesotrione with hydroxyl radicals. Aromatic and aliphatic intermediates of mesotrione oxidation were identified and quantified by high performance liquid chromatography (HPLC). It seems that the degradation of mesotrione by Fenton process begins with the rupture of mesotrione molecule into two moieties: cyclohexane-1,3-dione derivative and 2-nitro-4-methylsulfonylbenzoic acid. Hydroxylation and release of sulfonyl and/or nitro groups from 2-nitro-4-methylsulfonylbenzoic acid lead to the formation of polyhydroxylated benzoic acid derivatives which undergo an oxidative opening of benzene ring into carboxylic acids that end to be transformed into carbon dioxide.

Low-temperature, mineral-catalyzed air oxidation: a possible new pathway for PAH stabilization in sediments and soils

Reactivity of polycyclic aromatic hydrocarbons (PAHs) in the subsurface is of importance to environmental assessment, as they constitute a highly toxic hazard. Understanding their reactivity in the long term in natural recovering systems is thus a key issue. This article describes an experimental investigation on the air oxidation of fluoranthene (a PAH abundant in natural systems polluted by industrial coal use) at 100°C on different mineral substrates commonly found in soils and sediments (quartz sand, limestone, and clay). Results demonstrate that fluoranthene is readily oxidized in the presence of limestone and clay, leading to the formation of high molecular weight compounds and a carbonaceous residue as end product especially for clay experiments. As demonstrated elsewhere, the experimental conditions used permitted the reproduction of the geochemical pathway of organic matter observed under natural conditions. It is therefore suggested that low-temperature, mineral-catalyzed air oxidation is a mechanism relevant to the stabilization of PAHs in sediments and soils.

Understanding the effect of cobalt particle size on Fischer-Tropsch synthesis: surface species and mechanistic studies by SSITKA and kinetic isotope effect

Co/γ-Al(2)O(3) catalysts with particle sizes in the range of 4-15 nm were investigated by isothermal hydrogenation (IH), temperature programmed hydrogenation (TPH), and steady-state isotopic transient kinetic analysis (SSITKA). Kinetic isotope effect experiments were used to probe possible mechanisms on Co/γ-Al(2)O(3) with different particle size. It was found that CO dissociated on Co/γ-Al(2)O(3) catalysts at 210 °C. The total amount of CO(2) formed following the dissociation depends on the cobalt crystal size. O-Co binding energy was found to be highly dependent on the Co metal particle size, whereas similar C-Co binding energy was found on catalysts with different Co particle size. Very strongly bonded carbon and oxygen surface species increased with decreasing particle size and acted as site blocking species in the methanation reaction. SSITKA experiments showed that the intrinsic activity (1/τ(CH(x))) remained constant as the particle size increased from 4 to 15 nm. The number of surface intermediates (N(CH(x))) increased with increasing particle size. The apparent activation energies were found similar for these catalysts, about 85 kJ/mol. D(2)-H(2) switches further confirmed that the particle size did not change the kinetically relevant steps in the reaction. The reactivity of the active sites on the 4 nm particles was the same as those on the 8, 11, and 15 nm particles, and only the number of total available surface active sites was less on the 4 nm particles than on the others.

Interaction and reaction of coadsorbed NO and CO on a Rh(100) single crystal surface

In order to assess the possibility to follow surface reactions in a quantitative way by vibrational spectroscopy, a combination of temperature programmed reaction spectroscopy (TPRS) and reflection absorption infrared spectroscopy (RAIRS) has been used to study the decomposition of NO and the reaction between NO and CO on Rh(100). NO adsorbs in two configurations: in an almost parallel position at coverages below 0.18 ML and, in addition, in an upright position, probably on a bridge site, at all coverages. Coadsorbing NO and CO has only a minor influence on NO binding, whereas CO shifts gradually from top toward the bridge site under the influence of NO. Combining TP-RAIRS with TPRS during the reaction between CO and NO enabled us to simultaneously study site occupation and obtain qualitative surface coverages and desorption rates. At low surface coverages, NO dissociation is observed at lower temperatures than CO(2) formation. Near saturation, NO dissociation becomes blocked and shifts up in temperature. NO dissociation occurs simultaneously with CO(2) formation. To decompose NO, free surface sites have to be generated through surface diffusion or desorption of some CO. During NO decomposition, the formed oxygen atoms react with CO to form CO(2), creating more empty sites. This may lead to an explosive surface reaction.

Reaction kinetics and polarization modulation infrared reflection absorption spectroscopy investigations of CO oxidation over planar Pt-group model catalysts

Microscopic and spectroscopic techniques at near-atmospheric pressures have been used in recent years to investigate CO oxidation over Pt-group metals. New insights have been obtained that allow broadening of the understanding of this reaction beyond the ultrahigh vacuum regime where it is well-understood. However, new issues also have arisen that need clarification. In this paper, we review recent work in our laboratory, using polarization modulation infrared reflection absorption spectroscopy (PM-IRAS) and reaction kinetics measurements from ultrahigh vacuum to near-atmospheric pressures. These studies reveal a continuity of this reaction with respect to pressure over Pt, Pd, and Rh; that is, Langmuir-Hinshelwood kinetics is exhibited over a wide pressure range with no apparent "pressure gap". The difference between Ru(0001) and other noble metals is well-understood with respect to higher oxygen binding energies and reduced CO inhibition. It is concluded that for all Pt-group metals the most active phase is one saturated with chemisorbed oxygen and with low CO coverages. The significance of oxide phases under most industrially relevant catalytic conditions suggested recently in the literature is not consistent with the experimental data.

Plasmon resonant enhancement of carbon monoxide catalysis

Irradiating gold nanoparticles at their plasmon resonance frequency creates immense plasmonic charge and high temperatures, which can be used to drive catalytic reactions. By integrating strongly plasmonic nanoparticles with strongly catalytic metal oxides, significant enhancements in the catalytic activity can be achieved. Here, we study the plasmonically driven catalytic conversion of CO to CO(2) by irradiating Au nanoparticle/Fe(2)O(3) composites. The reaction rate of this composite greatly exceeds that of the Au nanoparticles or Fe(2)O(3) alone, indicating that this reaction is not driven solely by the thermal (plasmonic) heating of the gold nanoparticles but relies intimately on the interaction of these two materials. A comparison of the plasmonically driven catalytic reaction rate with that obtained under uniform heating shows an enhancement of at least 2 orders of magnitude.

High Throughput Screening of Low Temperature CO Oxidation Catalysts Using IR Thermography

The catalytic oxidation of carbon monoxide to carbon dioxide is an important process used in several areas such as respiratory protection, industrial air purification, automotive emissions control, CO clean-up of flue gases and fuel cells. Research in this area has mainly focused on the improvement of catalytic activity at low temperatures. Numerous catalyst systems have been proposed, including those based on Pt, Pd, Rh, Ru, Au, Ag, and Cu, supported on refractory or reducible carriers or dispersed in perovskites. Well known commercial catalyst formulations for room temperature CO oxidation are based on CuMn2O4 (hopcalite) and CuCoAgMnOx mixed oxides. We have applied high-throughput and combinatorial methodologies to the discovery of more efficient catalysts for low temperature CO oxidation. The screening approach was based on a hierarchy of qualitative and semi-quantitative primary screens for the discovery of hits, and quantitative secondary screens for hit confirmation, lead optimization and scale-up. Parallel IR thermography was the primary screen, allowing one wafer-formatted library of 256 catalysts to be screened in approximately 1 hour. Multi-channel fixed bed reactors equipped with imaging reflection FTIR spectroscopy or GC were used for secondary screening. Novel RuCoCe compositions were discovered and optimized for CO oxidation and the effect of doping was investigated for supported and bulk mixed oxide catalysts. Another family of active hits that compare favorably with the Pt/Al2O3 benchmark is based on RuSn, where Sn can be used as a dopant (e.g. RuSn/SiO2) and/or as a high surface area carrier (e.g., SnO2 or Sn containing mixed metal oxides). Also, RuCu binary compositions were found to be active after a reduction pretreatment with hydrogen.

Heterogeneous conversion of calcite aerosol by nitric acid

The reaction of nitric acid with calcite aerosol at varying relative humidities has been studied under suspended particle conditions in an atmospheric reaction chamber using infrared absorption spectroscopy. The reactant concentration in the chamber, as well as the appearance of gas phase products and surface adsorbed species, was spectroscopically monitored before and after mixing with CaCO(3) (calcite) particles. The interaction with HNO(3) was found to lead to gas phase CO(2) evolution and increased water uptake due to heterogeneous conversion of the carbonate to particulate nitrate. The reaction was enhanced as the relative humidity of the system was increased, especially at relative humidities above the reported deliquescence point of particulate Ca(NO(3))(2). The measured reaction extent demonstrates that the total calcite particulate mass is available for reaction with HNO(3) and the conversion process is not limited to the particle surface. The spectroscopy of the surface formed nitrate suggests a highly concentrated solution environment with a significant degree of ion pairing. The implications of the HNO(3) loss and the formation of the particulate nitrate product for atmospheric chemistry are discussed.

Removal of p-xylene from an air stream in a hybrid biofilter

Biofiltration of an air stream containing p-xylene has been studied in a laboratory hybrid biofilter packed with a mixture of mature pig compost, forest soil and the packing material which was made of polyethylene (PE) and used in the moving bed biological reactor (MBBR) in wastewater treatment. Three flow rates, 9.17, 19.87 and 40.66 m(3)m(-2)h(-1), were investigated for p-xylene inlet concentration ranging from 0.1 to 3.3 g m(-3). A high elimination capacity of 80 g m(-3)h(-1) corresponding to removal efficiency of 96% was obtained at a flow rate of 9.17 m(3)m(-2)h(-1) (empty bed residence time of 132 s). At a flow rate of 40.66 m(3)m(-2)h(-1) (empty bed residence time of 30s), the maximum elimination capacity for p-xylene was 40 g m(-3)h(-1) and removal efficiencies were in the range of 47-100%. The production of carbon dioxide (P(CO(2))) is proportional to elimination capacity (EC) and the linear relation was formulated as P(CO(2))=1.65EC+15.58. Stable pH values ranging from 6.3 to 7.6 and low pressure drop values less than 0.2 cm H(2)O (19.6 Pa) of packing media in compost-based biofilter of hybrid biofilter were observed, which avoided acidification and compaction of packing media and sustained the activity of microorganism populations.

Effect of toluene as gaseous cosubstrate in bioremediation of hydrocarbon-polluted soil

The stimulation of the microbial population by a more bioavailable supplementary carbon source and by a surfactant pretreatment was studied in petroleum hydrocarbon-polluted soils bioremediation. Two types of soils were used, Soil A which had been recently polluted and the aged Soil B. They contained 52.4 and 50.4 g of total petroleum hydrocarbons per kg of dry soil, respectively. The effect of passing a continuous small stream of air containing a low concentration of gaseous toluene through packed 0.5 l (Ø=5.5 cm) columns was studied. For Soil A, after 62 days the THPs degradation was 28% higher in the toluene treated columns than in controls. In aged Soil B the effect of toluene was not significant, probably due to bioavailability limitations. With Soil B, the combined effect of toluene as cosubstrate and a surfactant pretreatment was studied and the hydrocarbons degradation was 29% higher in the toluene-amended columns than in the controls. Toluene removal was higher than 99% in all cases. Surfactant addition increased hydrocarbon degradation when toluene was also added suggesting that the biological reaction was the limiting process. The study shows the possibilities of using gaseous substrates, such as toluene, for the in situ or ex situ treatment of petroleum hydrocarbon-polluted soil in processes limited by the biological reaction. The main advantage of the treatment is that the compound can be easily and directly delivered to the polluted soil through the venting system.

Comparison of New Microemulsion Prepared “Pt-in-Ceria” Catalyst with Conventional “Pt-on-Ceria” Catalyst for Water−Gas Shift Reaction

New "Pt-in-CeO(2)" catalyst prepared by microemulsion method is shown to give higher activity for a water-gas shift reaction but with no formation of CH(4), the side product from hydrogenation of carbon oxides using a hydrogen-rich reformate as compared to conventional "Pt-on-CeO(2)" catalysts. Detailed characterization by DRIFT analysis and temperature programmed reduction presented in this work clearly suggest the ceria coverage on Pt inhibits the metal from forming a strong CO adsorption.

Photocatalytic Oxygenation of Pivalic Acid with Molecular Oxygen via Photoinduced Electron Transfer using 10-Methylacridinium Ions

Photoirradiation of the absorption band of the 10-methylacridinium ion (AcrH+) with visible light in deaerated CH3CN/H2O (1:1 v/v) containing pivalic acid (Bu(t)COOH) and less than 1 equiv of NaOH results in the selective formation of 9-tert-butyl-9,10-dihydro-10-methylacridine (AcrHBu(t)). The same product is obtained in O2-saturated CH3CN/H2O under visible light irradiation. Photoirradiation of the absorption band of AcrHBu(t) with UV light in deaerated CH3CN/H2O (1:1 v/v) results in the formation of tert-butyl hydroperoxide (Bu(t)OOH), accompanied by regeneration of AcrH+. This cycle can be repeated several times. When AcrH+ is replaced by the 9-phenyl derivative (AcrPh+), AcrPh+ acts as an effective photocatalyst for the one-pot photooxygenation of Bu(t)COOH in the presence of less than 1 equiv of NaOH relative to Bu(t)COOH with O2 to yield Bu(t)OOH and Bu(t)H. The photocatalytic oxygenation mechanism is discussed based on the detection of radical intermediates by laser flash photolysis and ESR measurements as well as quantum yield determination.

Quantum Molecular Dynamics Study of the Reaction of O2 with HOCO

The reaction of O2 with HOCO has been studied by using an ab initio direct dynamics method based on the UB3PW91 density functional theory. Results show that the reaction can occur via two mechanisms: direct hydrogen abstraction and an addition reaction through a short-lived HOC(O)O2 intermediate. The lifetime of the intermediate is predicted to be 660 +/- 30 fs. Although it is an activated reaction, the activation energy is only 0.71 kcal/mol. At room temperature, the obtained thermal rate coefficient is 2.1 x 10(-12) cm3 molecule(-1) s(-1), which is in good agreement with the experimental results.

Glucose reactions within the heating period and the effect of heating rate on the reactions in hot compressed water

Glucose reactions were conducted in hot compressed water (473-773 K, 4-40 MPa) by means of a batch-type reactor. The reactions in the heating period (about for 60s) were observed. More than 80% of the glucose was consumed in the heating period above 573 K. Gasification of glucose was promoted with increasing temperature. The effect of heating rate (from 4.2 to 15.8K/s) on glucose conversion was also examined, and gasification of glucose was enhanced with increasing the heating rate.

Recyclable Catalyst for Conversion of Carbon Dioxide into Formate Attributable to an Oxyanion on the Catalyst Ligand

The catalyst recycling in the conversion of CO2 into formate using the iridium complex with 4,7-dihydroxy-1,10-phenanthroline as a catalyst precursor is described. The catalyst precursor was dissolved in an aqueous KOH solution under CO2 pressure prior to the reaction, but was precipitated spontaneously at the end of the reaction. The acidification by the generation of formate caused the transformation from the water-soluble deprotonated form into the water-insoluble protonated form. When the reaction was carried out at 60 degrees C for 20 h using 0.1 M KOH solution under 6 MPa of H2:CO2 (1:1), the catalyst precursor was precipitated spontaneously and the added KOH was consumed completely. The catalyst was recovered by filtration, and the product was obtained by the evaporation of the filtrate. Iridium leaching into the filtrate was found to be 0.11 ppm (<2% of the loaded Ir). The recovered catalyst retained high catalytic activity for four cycles. Consequently, the CO2 conversion using the complex is an environmentally benign process, whose significant features are as follows: (i) catalyst recycling by self-precipitation/filtration, (ii) waste-free process, (iii) the easy isolation of the product, (iv) high efficiency under relatively mild conditions, and (v) aqueous catalysis without the use of organic materials. Furthermore, we have demonstrated the significant roles of the oxyanion generated from the acidic phenolic hydroxyl on the catalyst ligand, which are the catalyst recovery by acid-base equilibrium, as well as the water-solubility by its polarity and the catalyst activation by its electron-donating ability.

Effective protein release from PEG/PLA nano-particles produced by compressed gas anti-solvent precipitation techniques

Homogeneous PLA/insulin solutions containing different amounts of 350, 750 or 1900 Da PEG (0-75 wt.% PEG) were processed by semi-continuous compressed CO2 anti-solvent precipitation to fabricate protein-loaded polymeric nano-particles. Proper operative conditions (temperature, pressure, CO2 flow rate and washing time) yielded more than 70% product recovery. Scanning electron microscopy, transmission electron microscopy and light scattering demonstrated that spherical, smooth surfaced particles with size below 1 microm could be obtained. X-ray diffraction analysis showed that the gas anti-solvent process modifies the polylactide crystalline state. PEG concentration and molecular weight were found to affect both optimal operative conditions and morphological and biopharmaceutical properties of the final product. Insulin loading yield dropped from 95% to 65% by increasing the 1900 Da PEG content from 0 to 75 wt.% or the PEG molecular weight from 350 to 1900 Da. The release rate increased significantly as the PEG content in the formulation increases. After 3-month incubation the drug released raised from 10% to 100% by increasing the 1900 Da PEG content from 23 to 7 wt.%. Formulations containing the same 350, 750 or 1900 Da PEG amount (67 wt.% PEG) displayed similar release profiles. Insulin release was found to take place by diffusion mechanism, despite the observation of matrix degradation.

Photooxidation and its effects on the carboxyl content of dissolved organic matter in two coastal rivers in the southeastern United States

Photodecarboxylation (often stoichiometrically expressed as RCOOH + (1/2)O2 --> ROH + CO2) has long been postulated to be principally responsible for generating CO2 from photooxidation of dissolved organic matter (DOM). In this study, the quantitative relationships were investigated among O2 consumption, CO2 production, and variation of carboxyl content resulting from photooxidation of DOM in natural water samples obtained from the freshwater reaches of the Satilla River and Altamaha River in the southeastern United States. In terms of loss of dissolved organic carbon (DOC), loss of optical absorbance, and production of CO2, the rate of photooxidation of DOM was increased in the presence of Fe redox chemistry and with increasing O2 content. The ratio of photochemical O2 consumption to CO2 photoproduction ranged from approximately 0.8 to 2.5, depending on the O2 content, the extent of involvement of Fe, and probably the initial oxidation state of DOM as well. The absolute concentration of carboxyl groups ([-COOH]) on DOM only slightly decreased or increased over the course of irradiation, possibly depending on the stages of photooxidation, while the DOC-normalized carboxyl content substantially increased in the presence of Fe redox chemistry and sufficient O2. Both the initial [-COOH] and the apparent loss of this quantity over the course of irradiation was too small to account for the much larger production of CO2, suggesting that carboxyl groups were photochemically regenerated or that the major production pathway for CO2 did not involve photodecarboxylation. The results from this study can be chemically rationalized by a reaction scheme of (a) photodecarboxylation/ regeneration of carboxyl: CxHyOz(COOH)m + aO2 + (metals, hv) --> bCO2 + cH2O2 + Cx-bHy'Oz'(COOH)m-b(COOH)b or of (b) nondecarboxylation photooxidation: CxHyOz(COOH)m + aO2 + (metals, hv) --> bCO2 + cH2O2 + Cx-bHy'Oz'(COOH)m.

An improvement of 11C acetate synthesis--non-radioactive contaminants by irradiation-induced species emanating from the 11C carbon dioxide production target

An existing procedure for [11C]acetate synthesis, consisting of a reaction of methylmagnesium chloride and [11C]carbon dioxide in tetrahydrofuran, hydrolysis and ion-exchange purification on small columns, has been improved. The use of less Grignard reagent and application of commercial cartridges instead of home made ones led to an increase of the overall yield from 60-65% to over 80%. Malfunction in pure nitrogen targets for 11C production may lead to unexpected contaminants. It is recommended to incorporate in the target outlet line a trap for removal of nitrogen oxides.

Determination of dissolved CO2 concentration and CO2 production rate of mammalian cell suspension culture based on off-gas measurement

The determination of dissolved CO(2) and HCO(3)(-) concentrations as well as the carbon dioxide production rate in mammalian cell suspension culture is attracting more and more attention since the effects on major cell properties, such as cell growth rate, product quality/production rate, intracellular pH and apoptosis, have been revealed. But the determination of these parameters by gas analysis is complicated by the solution/dissolution of carbon dioxide in the culture medium. This means that the carbon dioxide transfer rate (CTR; which can easily be calculated from off-gas measurement) is not necessarily equal to carbon dioxide production rate (CPR). In this paper, a mathematical method to utilize off-gas measurement and culture pH for cell suspension culture is presented. The method takes pH changes, buffer and medium characteristics that effect CO(2) mass transfer into account. These calculations, based on a profound set of equations, allow the determination of the respiratory activity of the cells, as well as the determination of dissolved CO(2), HCO(3)(-) and total dissolved carbonate. The method is illustrated by application to experimental data. The calculated dissolved CO(2) concentrations are compared with measurements from an electrochemical CO(2) probe.

Purification of food-grade oligosaccharides using immobilised cells of Zymomonas mobilis

Immobilised cells of the bacterium Zymomonas mobilis were used to remove glucose, fructose, and sucrose from food-grade oligosaccharide mixtures. Unpurified fructo-, malto-, isomalto-, gentio-, and inulinoligosaccharides, containing total carbohydrate concentrations of 300 g l(-1), were added to immobilised cells, in 100 ml batch reactors. No pH control or nutrient additions were required. Contaminating glucose, fructose, and sucrose within the mixtures was completely fermented within 12 h. The fermentation end products were ethanol and carbon dioxide. A minor amount of sorbitol was also produced as a fermentation by-product in the inulin-oligosaccharide mixture. No degradation of the oligosaccharides in the mixtures was observed.

Spatial variability in herbicide degradation in the subsurface environment of a groundwater protection zone

The aim of this study was to investigate the spatial variability in degradation and mineralization of atrazine and isoproturon in subsurface samples taken from sandy loam soils overlying gravel terraces which form part of a groundwater protection zone. Percussion drilling was used to obtain samples from 11 boreholes (maximum depth 3 m). Unlabelled atrazine or isoproturon, and ring-14C-labelled atrazine or isoproturon were added to samples, incubated at 25 degrees C for up to 16 weeks, and analyzed for the residual herbicide or [14C]carbon dioxide. All samples showed the potential to degrade these herbicides, although the percentage degradation decreased by a factor of 2-3 from the surface soil to a depth of 3 m. This was associated with a decrease in organic matter content, but there was no change in the potential to mineralize acetate, indicating that specific changes in the catabolic ability of the microbial population occurred with depth. The capacity of samples to mineralize atrazine and isoproturon to carbon dioxide decreased markedly with depth, with no mineralization potential observed at a depth of 80 cm.

Simultaneous organic and nitrogen removal from municipal landfill leachate using an anaerobic-aerobic system

An anaerobic-aerobic system including simultaneous methanogenesis and denitrification was introduced to treat organic and nitrogen compounds in immature leachate from a landfill site. Denitrification and methanogenesis were successfully carried out in the anaerobic reactor while the organic removal and nitrification of NH4+,-N were carried out in the aerobic reactor when rich organic substrate was supplied with appropriate hydraulic retention time. The maximum organic removal rate was 15.2 kg COD/m3 d in the anaerobic reactor while the maximum NH4+-N removal rate and maximum nitrification rate were 0.84kg NH4+-N/m3/d and 0.50kg NO3--N/m3/d, respectively, in the aerobic reactor. The pH range for proper nitrification was 6-8.8 in the aerobic reactor. The organic compounds inhibited nitrification so that the organic removal in the anaerobic reactor could enhance the nitrification rate in the following aerobic reactor. The gas production rate was 0.33 m3/kg COD and the biogas compositions of CH4, CO2, and N2 were kept relatively constant, 66-75, 22-32, and 2-3%, respectively.

Acquisition and processing of data for isotope-ratio-monitoring mass spectrometry

Methods are described for continuous monitoring of signals required for precise analyses of 13C, 18O, and 15N in gas streams containing varying quantities of CO2 and N2. The quantitative resolution (i.e. maximum performance in the absence of random errors) of these methods is adequate for determination of isotope ratios with an uncertainty of one part in 10(5); the precision actually obtained is often better than one part in 10(4). This report describes data-processing operations including definition of beginning and ending points of chromatographic peaks and quantitation of background levels, allowance for effects of chromatographic separation of isotopically substituted species, integration of signals related to specific masses, correction for effects of mass discrimination, recognition of drifts in mass spectrometer performance, and calculation of isotopic delta values. Characteristics of a system allowing off-line revision of parameters used in data reduction are described and an algorithm for identification of background levels in complex chromatograms is outlined. Effects of imperfect chromatographic resolution are demonstrated and discussed and an approach to deconvolution of signals from coeluting substances described.

[Toxicological and hygienic evaluation of water obtained by the method of hydration of carbon dioxide]

The irritating, sensitizing, and toxic effect of water produced by the method of carbon dioxide hydration was examined in animal experiments and human observations. It was found that before and after decontamination this water did not cause skin irritation or organism sensitization, did not have a toxic effect on the CNS, liver, kidneys or blood morphology, and did not deteriorate adaptive capabilities of the animal or human body.

[Hygienic evaluation of water obtained by the method of hydration of carbon dioxide]

Water produced by the method of carbon dioxide hydration according to the Sabatier reaction was evaluated in hygienic terms. It was found that with respect to organoleptic and bacteriological parameters this water met the requirements for portable water, as described in the USSR Standards 2874-82. However, this water contained more nickel; therefore before drinking, it needed further purification, conditioning and testing.

Titan: some new results

New analyses of Voyager spectra of Titan have led to improvements in the determination of abundances of minor constituents as a function of latitude and altitude. Ground-based microwave observations have extended the Voyager results for HCN, and have demonstrated that CO is mysteriously deficient in the stratosphere. The origin of the CH4, CO, and N2 in Titan's atmosphere is still unresolved. Both primordial and evolutionary sources are compatible with the available evidence.

Preparation of [11C]carbon dioxide from [11C]cyanide

[11C]Carbon dioxide was prepared from [11C]cyanide. First, [11C]CH4 was produced by the (p, alpha) reaction on a N2/H2 mixture and was converted to [11C]CN- by reaction with ammonia over platinum at 1273 K. The [11C]CN- was adsorbed on a cobalt(II, III) oxide/ceramic furnace material at room temperature and was subsequently converted to [11C]CO2 by heating the cobalt(II, III) oxide to 948 K over a 10 min period and collecting the [11C]CO2 in a trap at 77 K. Specific activities as high as 600 mCi/mumol at end of bombardment (EOB) were obtained in a 15 microA irradiation for 10 min.

Radiation stability of organic matter in liquid and frozen H2O, NH3 and water-ammonia mixtures

The redox properties of irradiated liquid and frozen H2O, NH3 and H2O/NH3 mixtures at 298 K and 77 K, resp., towards some simple organic molecules have been checked by injecting carrierfree 11C atoms and analyzing their chemical state by means of radiochromatography. The reactions and the stability of organic products versus radiation dose (in this study by MeV protons) depend on temperature, phase state, mobility of radicals, their concentration and reactivity. Especially dangerous are the reactive OH and O2H radicals which oxidize organic material to inorganic CO2. Highest stability has been found at low temperatures (solid state, reduced mobility of radicals) and for systems containing H-donors (H2O/NH3 mixtures), which reduce the concentration of oxidizing radicals. The fact that many bodies in space consist of H2O-ice with NH3 and CH4 additives at temperatures between 10 and 150 K is promising in view of the survival of organic matter under high doses of radiation.

The atmosphere of the primitive earth and the prebiotic synthesis of organic compounds

The prebiotic synthesis of organic compounds using a spark discharge on various simulated prebiotic atmospheres at 25 degrees has been studied. Methane mixtures contained H2 + CH4 + H2O + N2 + NH3 with H2/CH4 molar ratios from 0 to 4 and pNH3 = 0.1 torr. A similar set of experiments without added NH3 was performed. The yields of amino acids (1.2 to 4.7% based on the carbon) are approximately independent of the H2/CH4 ratio and the presence of added NH3, and a wide variety of amino acids are obtained. Mixtures of H2 + CO + H2O + N2 and H2 + CO2 + H2O + N2, with and without added NH3, all give about 2% yields of amino acids at H2/CO and H2/CO2 ratios of 2 to 4. For the H2/CO and H2/CO2 ratios less than 1, the yields fall off drastically to as low as 10(-3)%. Glycine is almost the only amino acid produced from CO and CO2 atmospheres. These results show that the maximum yield is about the same for the three carbon sources at high H2/carbon ratios, but that CH4 is superior at low H2/carbon ratios. In addition, CH4 gives a much greater variety of amino acids than either CO or CO2. If it is assumed that amino acids more complex than glycine were required for the origin of life, then these results indicate the need for CH4 in the primitive atmosphere. The yields of cyanide and formaldehyde parallel the amino acid results, with yields of HCN and H2CO as high as 13% based on the carbon. Ammonia is also produced from N2 in experiments with no added NH3 in yields as high as 4.9%. These results show that large amounts of NH3 would have been synthesized on the primitive earth by electric discharges. The amount of ammonia formed by hydrolysis of HCN and various nitriles may have exceeded that formed directly in electric discharges.

Aerobic photodegradation of X(N) chelates of (ethylenedinitrilo)tetraacetic acid (EDTA): implications for natural waters

The behavior of several metal chelates [X(N)] of 1-14C-(ethylenedinitrilo) tetraacetic acid [EDTA] under irradiation from a wide spectrum Xenon arc lamp has been studied. In static tests at pH 4.5, chelates of Mn(II), Fe(II) and Co(II) photodegraded to give 14CO2 and CH2O. Chelates of Na(I), Mg(II), Ca(II), Ni(II), Cu(II), Zn(II), Cd(II), and Hg(II) did not exhibit any significant photodegradation as measured by 14CO2 evolution. It is concluded that the photodegradation of Fe(III)-EDTA by sunlight will prevent EDTA build up in natural waters.