Energy transfer kinetics of phycoerythrocyanins (PECs) from the cyanobacteriumAnabaena variabilis (I)

The exritation energy transfer processes in monomeric phycoerythrocyanins (PEC) have been studied in detail using steady-state and time-resolved fluorescence spectra techniques as well as the deconvolution tech-nique of spectra. The results indicate that the energy transfer processes should take place between α₈₄,-PVB and β₈₄- or β₁₅₅-PCB chromophores. the time constants of energy transfer are 34.7 and 130 ps individually; the component with lifetime of 1.57 ns originates from the fluorescence lifetime of the terminal emitter of β₈₄- and /or β₁₅₅ -PCB chro-mophores; and the component with lifetime of 515 ps might be assigned to the energy transfer between two PCB chro-mophores of β subunit. Project supported by the National Natural Science Foundation of China.     

Adsorption kinetics of various gases in carbon molecular sieves (CMS) produced from palm shell

Carbon molecular sieves (CMS) have been prepared from locally available palm shell of Tenera type by a thermal treatment technique involving carbonization followed by steam activation and benzene deposition technique. Carbonization of the dried palm shells was done at 900 °C for duration of 1 h followed by steam activation at 830 °C for 30–420 min to achieve activated carbons with different degree of burn-offs. The highest micropore volume of activated carbon obtained at 53.2% burn-off was found suitable to be used as a precursor for CMS production. Subsequent benzene deposition onto activated samples at temperature range from 600 to 900 °C for various benzene concentrations have resulted in a series of CMS with different kinetic selectivities. The molecular sieving behaviour of the CMS products was assessed by kinetic adsorption isotherms of O₂, N₂, CO₂ and CH₄ at room temperature.     

Pyrolysis/gas chromatography/mass spectrometry monitoring of fungal-biotreated distillery wastewater using Trametes sp. I-62 (CECT 20197)

Distillery wastewaters generated by ethanol production from fermentation of sugar-cane molasses, named vinasses, lead to important ecological impact due to their high content of soluble organic matter and their intense dark-brown color. Taking advantage of the well-known ability of white-rot fungi to degrade an extensive variety of organic pollutants, the capacity of Trametes sp. I-62 (CECT 20197) to detoxify this type of effluents was evaluated. In this work, pyrolysis/gas chromatography/mass spectrometry was applied to the chemical characterization of several fractions of Cuban distillery wastewater as well as to monitoring the changes which occurred after fungal treatment with this white-rot basidiomycete. Maximum effluent decolorization values and chemical oxygen demand reduction attained after seven days of fungal treatment were 73.3 and 61.7%, respectively, when 20% (v/v) of distillery vinasses was added to the culture medium. Under these conditions a 35-fold increase in laccase production by Trametes sp. I-62 was measured, but no manganese peroxidase activity could be detected. The pyrolysis/gas chromatography/mass spectrometry results showed a decrease in a number of pyrolysis products after seven days of fungal treatment, mainly furan derivatives. The decrease in the relative areas of these compounds could be related to the vinasse color-removal associated with melanoidin degradation. All these results indicated the potential use ofTrametes sp. I-62 in the detoxification of recalcitrant distillery vinasses.     

Development of saw palmetto (Serenoa repens) fruit and extract standard reference materials

As part of a collaboration with the National Institutes of Health’s Office of Dietary Supplements and the Food and Drug Administration’s Center for Drug Evaluation and Research, the National Institute of Standards and Technology has developed two standard reference materials (SRMs) representing different forms of saw palmetto (Serenoa repens), SRM 3250 Serenoa repens fruit and SRM 3251 Serenoa repens extract. Both of these SRMs have been characterized for their fatty acid and phytosterol content. The fatty acid concentration values are based on results from gas chromatography with flame ionization detection (GC-FID) and mass spectrometry (GC/MS) analysis while the sterol concentration values are based on results from GC-FID and liquid chromatography with mass spectrometry analysis. In addition, SRM 3250 has been characterized for lead content, and SRM 3251 has been characterized for the content of β-carotene and tocopherols. SRM 3250 (fruit) has certified concentration values for three phytosterols, 14 fatty acids as triglycerides, and lead along with reference concentration values for four fatty acids as triglycerides and 16 free fatty acids. SRM 3251 (extract) has certified concentration values for three phytosterols, 17 fatty acids as triglycerides, β-carotene, and γ-tocopherol along with reference concentration values for three fatty acids as triglycerides, 17 fatty acids as free fatty acids, β-carotene isomers, and δ-tocopherol and information values for two phytosterols. These SRMs will complement other reference materials currently available with concentrations for similar analytes and are part of a series of SRMs being developed for dietary supplements. Contribution of the US Government; not subject to copyright     

Pyrolysis of poly(vinyl chloride)

A pyrolysis–gas chromatography–mass spectrometric technique has been developed to study the thermal degradation of poly(vinyl chlorides) polymerized at different temperatures. Hydrogen chloride and benzene evolution during successive stages of pyrolysis have been quantitatively determined and correlated to the tacticity and molecular weight of the polymer. It was found that lowering the temperature of polymerization and molecular weight depresses benzene evolution and increases char weight but does not affect the HCl yield. It is suggested that the syndiotactic trans microstructure favored at low temperature of polymerization yields polyenes which cannot cyclize to form benzene. As the molecular weight decreases, the increase in number of vinyl chain ends facilitates pyrolytic crosslinking and char formation.     

Pyrolysis of poly(2-propylheptyl acrylate)

The thermal destruction processes of poly(2-propylheptyl acrylate) take place at the range of temperature 250–950 °C was investigated using pyrolysis–gas chromatography. Knowledge of the types and amounts of pyrolysis products will provide important information about the thermal degradation of homopolymer poly(2-propylheptyl acrylate) and the mechanisms involved. Unsaturated monomers 2-propylheptyl acrylate and 2-propylheptyl methacrylate, according to by-product alkyl alcohol 2-propylheptylalcohol, alkene 2-propylheptene-1, carbon dioxide, carbon monoxide, methane, and ethane were formed during thermal degradation of poly(2-propylheptyl acrylate).     

Fractional Pyrolysis of Algae and Model Compounds (cited: 1)

Pyrolysis of algae from Taihu Lake water blooms for bio-oil production was conducted from 473 K to 773 K by a fractional way in six steps. Palmitic acid, agarose and egg white were used as model compounds to study the origin of bio-oil ingredients and interaction of the intermediates from the algae components. In the first step at 473 K, the bio-oil obtained was composed of n-heptadecane and some small molecule acids. Quantities of carboxylic acids (mainly palmitic acid) and some amides, hydrocarbons, esters etc. were evolved in the second step at 523 K. For the third step at 573 K, except the carboxylic acids (still mainly palmitic acid), amides, nitriles, and phenols also accounted for a large proportion whereas respectable amount of indoles and alcohol ketones were attained. The main products in the later three steps were nitriles and phenols at 623 K, hydrocarbons and phenols at 673 K, and only phenols at 773 K, respectively. A higher heating value (HHV) of 36.0 MJ/kg of the bio-oil was obtained at 673 K. The hydrocarbons, palmitic acid and esters in the bio-oil were derived from lipids. The phenols, indoles, pyrroles, small molecular acids, amides like acetamide and some nitriles like phenyl-acetonitrile were generated from proteins. Amides and nitriles were also dated from the interaction of pyrolytic intermediates of lipids and proteins. Fewer products directly from the direct pyrolysis of saccharides were detected in the algae bio-oil due to the interaction of pyrolytic intermediates of saccharides and proteins in algae, and those interactions resulted in the formation of oligomers in the bio-oil at 473 and 523 K. Whereas very weak interaction was observed between lipids and saccharides. The process of fractional pyrolysis by varying temperature provided an advisable way for improving the selectivity of bio-oil from direct pyrolysis, and made the bio-oil much more applicable in down streaming utilization.     

Pyrolysis of kenaf (Hibiscus cannabinus L.) biomass: influence of ashless treatment on kinetics and thermal behavior

Journal of Thermal Analysis and Calorimetry - Recently, ashless pretreatment of lignocellulosic biomass prior to pyrolysis has been used for removing mineral matters to prevent slagging and...     

Pyrolysis of olive residue/low density polyethylene mixture: Part I Thermogravimetric kinetics

This paper demonstrates the thermal pyrolysis of olive residue, low density polyethylene (LDPE) and olive residue/LDPE mixture in an inert atmosphere of N2 using thermogravimetric analysis (TGA). Measurements were carried out in the temperature range 300K~973K at heating rates of 2K/min, 10K/min, 20K/min and 50K/min. Based on the results obtained, three temperature regimes were selected for studying the nonisothermal kinetics of olive residue/LDPE mixture. The first two were dominated by the olive residue pyrolysis, while the third was linked to the LDPE pyrolysis, which occurred at much higher temperatures. Discrepancies between the experimental and calculated TG/DTG profiles were considered as a measurement of the extent of interactions occurring on copyrolysis. The maximum degradation temperatures of each component in the mixture were higher than those the individual components; thus an increase in thermal stability was expected. The kinetic parameters associated with thermal degradation were determined using Friedman isoconversional method.     

Characterization of sugar palm (Arenga pinnata) fibres

The aim of this study was to characterize tensile and thermal properties of sugar palm (Arenga pinnata) fibres obtained from different heights (1, 3, 5, 7, 9, 11, 13, and 15?m) of sugar palm tree. This study has confirmed that in a mature sugar palm tree, degradation was occurred and altered the properties of its fibre. Fibres obtained at the area of live (green) palm frond were found to have a better tensile properties as a result of its optimum chemical composition especially cellulose, hemicelluloses and lignin. For the fibre obtained from the upper part of sugar palm tree, it shows slightly decreasing trend in tensile properties compared to mature fibres. It is due to the fibres are juvenile where their cell walls are progressively built up thus give slightly lower properties than matured fibres. For the fibre obtained from the area of dead palm frond, the fibres are considered to be degraded biologically. It is believed that polymeric chains in microfibrils were broken and their cellulose content was decreased which demonstrated inferior properties (tensile strength, modulus, elongation at break and toughness). The use of such fibre for application as reinforcing fibre in composite is not recommended since the strength of the fibre and composite will be reduced. There were four phases of decomposition of the fibres where the sequence of decomposition started with decomposition of moisture, followed by hemicelluloses, then cellulose and next is lignin while the ash was the last component left. The thermal degradation of these components were found in ranges of 45?C123, 210?C300, 300?C400, 160?C900 and 1723?°C, respectively. Thermogravimetric analysis and derivative thermogravimetric analysis curves showed that the fibre of 1?m showed higher thermal stability than the fibres of 3?C15?m. The different thermal stability for each fibre was due to different chemical compositions especially when the fibre containing high ash content which result in higher thermal stability.     

Pyrolysis of sweet orange (Citrus sinensis) dry peel

Three different products were obtained from the pyrolysis of dry peel sweet orange: bio-oil, char and non-condensable gases. The yield of each product was determined. The bio-oil was characterized by GC–MS to determine that can be used as a renewable source of valuable industrial chemicals or as a source of energy, high heating value was calculated by Channiwala and Parikh correlation based on Dulong's Formula.Thermogravimetric analysis at 1, 5, 10, 20, and 40 °C/min, shows three different overlapped steps resulting in an average mass loss of ∼80% within the temperature range of 114–569 °C. The bench scale pyrolysis experiments, produces average yields of 53.1, 21.1 and 25.8 wt.% for bio-oil, char and gases, respectively. Bio-oil characterization by GC–MS and FTIR identified limonene as its main component while other identified compounds included δ-limonene, alcohols, phenols, benzene, toluene, xylene and carboxylic acids.     

Pyrolysis of 8-diazo-7,9-diphenylcyclopent(A)acenaphthylene

Pyrolysis of the title compound in benzene is described.     

The adsorption behaviour of99Mo(VI),238U(VI),95Zr(IV) and95Nb(V) on alumina

The distribution of Mo(VI) and the interfering radiocontaminants U(VI), Zr(IV) and Nb(V) have been investigated between chromatographic alumina and aqueous hydrochloric acid solutions of concentrations ranging from 0.5M to 11M. At low acidities (less than 1M HCl) the distribution coefficients increase with the decrease of acid concentration, while in the region of 2–4M they increase with the increase of the acid concentration. Above 4M HCl, the increase inK _D continues with the acid concentration for both Zr(IV) and Nb(V), but constant values are reached for U(VI) and Mo(VI).     

Preparation of123I-α-(p-iodoanilino)phenylacetonitrile using HPLC

Synthesis of α-(p-iodoanilino)phenylacetonitrile (IAPAN), an amygdalin analog, labeled with I-123 (t1/2 13.3 hr) in a carrier-free state (i.e. no-carrier-added) was made possible by virtue of the high speed, sensitivity, and resolving power of HPLC. Aniline was iodinated by the action of no-carrier-added Na¹²³I in the presence of Cu(II), and the resulting iodaniline was reacted with benzaldehyde followed by the addition of HCN to yield the title compound. The radioactive IAPAN was separated from α-anilinophenylacetonitrile and other byproducts by reversed phase partition chromatography on an octadecylsilane column using 50% ethanol/H₂O as eluent. The product was correlated with authentic, classically characterized IAPAN, and with¹²³I IAPAN prepared by electrophilic exchange of IAPAN and ICl iodination of α-anilinophenylacetonitrile.     

Pyrolysis mechanism of trisbipyridineiron(II) chloride to iron nanoparticles

Pyrolysis of trisbipyridineiron(II) chloride under controlled thermal conditions and inert atmosphere of argon gas yields a residue of iron nanoparticles. Evolved gas analysis by GC?CMS and ¹H NMR revealed emission of bipyridine, 6-chlorobipyridine, 6,6??-dichlorbipyridine, bipyridine hydrochloride, and hydrochloric acid as decomposition products. CHN, XRPD, EDXRF, TEM, AFM, and ⁵⁷Fe M?ssbauer spectroscopy of the residue indicated formation of pure iron nanoparticles in the size range of 50?C72?nm. Based on these results a mechanism for thermal degradation of trisbipyridineiron(II) chloride has been worked out.     

Pyrolysis behaviour of titanium dioxide-poly(vinyl pyrrolidone) composite materials

Inorganic-organic hybrid materials are studied due to the unique properties they exhibit. As these materials become more widely applied, particularly as precursor materials for forming inorganic materials, it is essential that the pyrolysis behaviour is understood. Transparent yellow hybrid materials consisting of titanium dioxide and poly(vinyl pyrrolidone) were prepared using sol-gel processing techniques. The hybrids maintained their transparency up to the highest achieved inorganic loading of 57 wt.%. These materials were characterised using thermogravimetric analysis in which the organic component was pyrolysed. The resultant chars were then investigated using optical microscopy, x-ray diffraction, scanning electron microscopy, and atomic force microscopy. The inorganic loading had an effect on char formation, with higher loadings leading to the formation of pyrolysis intermediates which were less apparent in samples of lower inorganic content. The pyrolysis intermediates were found to be carbon-rich.     

Energy transfer kinetics of the np5(n + 1)p excited states of Ne and Kr

Energy transfer rate constants for Ne(2p(5)3p) and Kr(4p(5)5p) atoms colliding with ground state rare gas atoms (Rg) have been measured. In part, this study is motivated by the possibility of using excited rare gas atoms as the active species in optically pumped laser systems. Rg(np(5)(n + 1)s) metastable states may be produced using low-power electrical discharges. The potential then exits for optical pumping and laser action on the np(5)(n + 1)p ? np(5)(n + 1)s transitions. Knowledge of the rate constants for collisional energy transfer and deactivation of the np(5)(n + 1)p states is required to evaluate the laser potential for various Rg + buffer gas combinations. In the present study we have characterized energy transfer processes for Ne (2p(5)3p) + He for the six lowest energy states of the multiplet. Rate constants for state-to-state transfer have been determined. Deactivation of the lowest energy level of Kr (4p(5)5p) by He, Ne, and Kr has also been characterized. Initial results suggest that Kr (4p(5)5p) + Ne mixtures may be the best suited for optically pumped laser applications.