Thermal analyses of Ohio bituminous coals

A suite of twenty-one bituminous coal samples from Ohio were analyzed by differential scanning calorimetry (DSC) and non-isothermal thermogravimetry (TG) techniques. Three regions of endothermic activity may be distinguished in the DSC scans in an inert atmosphere. The first peak (25–150°C) corresponds to loss of moisture from the coal, a second, very broad endotherm peaking in the range 400–500°C corresponds to devolatilization of the organic matter and a partially resolved endotherm at temperatures above 550°C probably corresponds to cracking and coking processes subsequent to the pyrolysis step. Evidence obtained from experiments with sealed pans suggest an autocatalytic effect exerted by the pyrolysis products. The use of the DSC technique to quantify the volatile matter content of coal seems less reliable than the proximate analyses obtained from non-isothermal TG in inert and O₂ atmospheres. Good agreement with ASTM values is observed by the latter method for a range of volatile matter and ash content.     

Thermal diffusivity of green river oil shale by the laser-flash technique

The thermal diffusivity of Green River oil shale has been measured by the laser-flash technique. Measurements were carried out in the temperature range 25–350°C and for various grades of shales ranging from 6 to 100 gal./ton. The thermal diffusivity (α) is seen to decrease with increasing temperature, especially for shales with low organic content. Richer shales, on the other hand, show very little sensitivity in their α values to temperature and grade. The α values measured for Green River oil shales fall in the range 0.1–0.9×10^?2 cm²/sec. Anisotropic effects were also observed for these α values; shales cored parallel to their bedding planes the diffusivities about 20–30% higher than those for the samples cored perpendicular to the stratigraphic planes. The presence of pore water in the shale is also shown to have a significant effect on α.     

UVB Shielding Role of FeCI3 and Certain Cyanobacterial Pigments

The shielding role of ferric iron (FeCl₃) and certain cyanobacterial pigments (a brown-colored pigment from Scytonema hofmanii culture filtrate and a pink extract from Nostoc spongiaeforme) against UVB-induced damage in the filamentous, nitrogen-fixing cyanobacterium Nostoc muscorum has been demonstrated. Addition of these colored compounds to agarose gels (1–3 mm thick) resulted in a considerable decrease in UVB transmittance through the gels. The lowest UVB transmittance (15%) occurred through a 3 mm gel containing 0.01% FeCl₃ followed by S. hofmanii culture filtrate (40%) and N. spongiaeforme extract (50%). These substances appear to act as very efficient UVB-absorbing screens. Percent survival and ¹⁴CO₂ uptake of N. muscorum increased significantly if UVB exposure was given on gels containing FeCl₃ or other UVB-shielding substances. The highest protection of N. muscorum was recorded with FeCl₃, followed by S. hofmanii culture filtrate and N. spongiaeforme extract. Such UV-shielding substances if present in required concentration range may enhance the survival of cyanobacteria exposed to high levels of UVB.     

Gluconic acid production in bioreactor with immobilized glucose oxidase plus catalase on polymer membrane adjacent to anion-exchange membrane

Gluconic acid was obtained in the permeate side of the bioreactor with glucose oxidase (GOD) immobilized onto anion-exchange membrane (AEM) of low-density polyethylene grafted with 4-vinylpiridine. The electric resistance of the anion-exchange membranes was increased after the enzyme immobilization on the membrane. The gluconic acid productions were relatively low with the GOD immobilized by any method on the AEM. To increase the enzyme reaction efficiency, GOD was immobilized on membrane of AN copolymer (PAN) adjacent to an anion-exchange membrane in bioreactor. Uses of anion-exchange membrane led to selective removal of the gluconic acid from the glucose solution and reduce the gluconic acid inhibition. The amount of gluconic acid obtained in the permeate side of the bioreactor with the GOD immobilized on the PAN membrane adjacent to the AEM under electrodialysis was about 30 times higher than that obtained with enzyme directly bound to the AEM. The optimal substrate concentration in the feed side was found to be about 1 g/l. Further experiments were carried out with the co-immobilized GOD plus Catalase (CAT) on the PAN membrane adjacent to the AEM to improve the efficiency of the immobilize system. The yield of this process was at least 95%. The storage stability of the co-immobilized GOD and CAT was studied (lost 20% of initial activity for 90 d). The results obtained clearly showed the higher potential of the dual membrane bioreactor with GOD plus CAT bound to ultrafiltration polymer membrane adjacent to the AEM. Storage stability of GOD activity in GOD plus CAT immobilized on PAN//AEM membranes and on AEM.     

Role of white light in reversing UV-B-mediated effects in the N2-fixing cyanobacterium Anabaena BT2

The effects of various irradiances of artificial UV-B (280-315 nm) in the presence or absence of visible light (photosynthetically active radiation) on growth, survival, 14CO2 uptake and ribulose 1,5-bisphosphate carboxylase (RuBISCO) activity were studied in the N2-fixing cyanobacterium Anabaena BT2. We tested the hypothesis whether or not visible radiation offers any protection against UV-B-induced deleterious effects on growth and photosynthesis in Anabaena BT2. Attempts were also made to determine the irradiances of UV-B where inhibitory effects could be mitigated by simultaneous irradiation with visible light. Exposure of cultures to 0.2 W m(-2) or higher irradiance of UV-B caused inhibition of growth and survival and growth ceased above 1.0 W m(-2). 14CO uptake and RuBISCO activity were found to be more sensitive to UV-B and around 60% reduction in 14CO2 uptake and RuBISCO activity occurred after exposure of cultures to 0.4 W m(-2) for 1 h. However, growth, 14CO2 uptake and RuBISCO activity were nearly normal when UV-B (0.4 W m(-2)) and visible light (14.4 W m(-2)) were given simultaneously. Blue radiation (450 nm) was found to be the most effective in photoreactivation against UV-B, better than UV-A or any other light wavelength band. Our results demonstrate that the studied cyanobacterium possesses active photoreactivation mechanism(s) against UV-B-mediated damage which in turn probably allow survival under natural conditions in spite of being continuously exposed to the UV-B component present in the solar radiation. Continued growth of many algae and cyanobacteria in the presence of intense solar UV-B radiation under natural conditions seems to be due to the active role of photoreactivation.     

Dinuclear ruthenium(II) polypyridyl complexes containing large, redox-active, aromatic bridging ligands: synthesis, characterization, and intramolecular quenching of MLCT excited states

Two new ruthenium(II) polypyridyl dimers containing the large planar aromatic bridging ligands 9,11,20,22-tetraazatetrapyrido[3,2-a:2'3'-c:3' ',2'-l:2',3'-n]pentacene (tatpp) and 9,11,20,22-tetraazatetrapyrido[3,2-a:2'3'-c:3',2' '-l:2',3'-n]pentacene-10,21-quinone (tatpq) have been synthesized and characterized by (1)H and (13)C NMR, MALDI mass spectrometry, and elemental analyses. The electronic properties (UV-vis, redox, photophysical) of these dimers are analyzed in the context of orbital calculations (PM3 level) on the bridging ligands. A localized orbital model is proposed in which low-lying acceptor orbitals on the center portion of the ligands effectively quench the Ru(II)-based MLCT emission via a mechanism that can be viewed as intramolecular electron transfer to specific subunits of the bridges.     

UV-B-induced synthesis of mycosporine-like amino acids in three strains of Nodularia (cyanobacteria)

Three filamentous and heterocystous cyanobacterial strains of Nodularia, Nodularia baltica, Nodularia harveyana and Nodularia spumigena, have been tested for the presence and induction of ultraviolet-absorbing/screening mycosporine-like amino acids (MAAs) by simulated solar radiation in combination with 395 (receiving photosynthetically active radiation (PAR) only), 320 (receiving PAR + UV-A) and 295 (receiving PAR + UV-A + UV-B) nm cut-off filters. Absorption spectroscopic analyses of the methanolic extracts of samples revealed a typical MAA peak at 334 nm in all three cyanobacteria. Specific contents of MAAs had a pronounced induction in the samples covered with 295 nm cut-off filters after 72 h of irradiation. In comparison, there was little induction of MAAs in the samples covered by 395 and 320 nm cut-off filters. High performance liquid chromatographic (HPLC) studies revealed the presence of two types of MAAs in all three cyanobacteria, which were identified as shinorine and porphyra-334, both absorbing maximally at 334 nm. The occurrence of porphyra-334 is rare in cyanobacteria. Specific content of both shinorine and porphyra-334 were induced remarkably only in the samples covered with 295 nm cut-off filters. The results indicate that in comparison to UV-A and PAR, UV-B is more effective in eliciting MAAs induction in the studied cyanobacteria.     

Electrical Conduction Mechanisms in Greeen River Oil Shale

The enthalpies of dissolution of anhydrous and hydrated uranyl formates, formic acid and hexahydrated uranyl nitrate in nitric acid at different concentrations have been measured and the following enthalpies of formation have been determined

     

Ag(I) catalyzed and uncatalyzed oxidation of dimethyl sulfoxide by ceric nitrate in nitric acid medium: A kinetic study

The uncatalyzed oxidation of dimethyl sulfoxide (DMSO) by Ce(IV) involves complex formation between them in nitric acid medium which yields final products. The orders in [Ce(IV)] and [DMSO] were one and fractional, respectively. With Ag(I) as catalyst, an Ag(I)-DMSO adduct is proposed. This adduct reacts with Ce(IV) bimolecularly to give a Ag(II)-DMSO adduct which finally yields the products. The rates exhibit fractional order in [Ag(I)] as well as [DMSO] and first order in [Ce(IV)].

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(DMSO) Ce(IV) , . [Ce(IV)] , [DMSO]—. Ag(I) , Ag(I)–DMSO. Ce(IV) , Ag(II)–DMSO, . [Ag(I)], [DMSO], [Ce(IV)].

     

An automated technique for thermoacoustimetry of solids

An automated technique for thermoacoustimetry of solids is described. The technique is illustrated by measurements on Green River and Kentucky oil shales.