bluuebunny/crossref_metadata_2025_split huggingface dataset:
Model reactions for abiotic mercury(II) methylation: Kinetics of methylation of mercury(II) by mono‐, di‐, and tri‐methyltin in seawater
Authors: Cerrati Gabriella , Bernhard Michael , Weber James H. 
Published: January 2005

AbstractThe usual presence of mercury(II) with monodi‐, and tri‐methyltin in water, sediments, and plants in estuarine environments suggests possible abiotic formation of methylmercury via methyl transfer from methyltin compounds. Kinetics studies of reactions between mercury(II) and methyltin compounds under pseudo‐first‐order conditions in seawater show that relative rate of methylmercury formation under the same conditions are: monomethyltin <trimethyltin> dimethyltin. This order is explainable mainly by the speciation and charge of methyltin compounds in seawater and by the existence of mercury(II) as a tetrachloro anion. A factorial experiment with the variables pH and salinity (seawater diluted with deionized water) showed that pH, but not salinity, is significant at the 95% confidence level; and that reaction rates increase as pH increases. These results suggest the possibility of abiotic methylation of mercury(II) in seawater. Additional experiments in seawater demonstrated an absence of methylation of mercury(II) (14 days) and mercury(0) (35 days) by methyl iodide.
Organometallic chemical vapor deposition using allyl precursors
Authors: Kirss Rein U 
Published: January 2005

AbstractHomoleptic allyl derivatives of many Main‐Group and transition metals, M(C3H5)n, are readily available through one‐pot syntheses using metal halides and allyl Grignard reagents or by alkylation of alkali‐metal salts. The relatively low molecular weight of a C3H5 ligand contributes to high vapor pressures whilst the stability of the allyl radical is predicted to reduce decomposition temperatures. These compounds represent a class of volatile precursors for organometallic chemical vapor deposition (OMCVD) of thin films. Film growth studies using iridium, molybdenum, palladium, platinum, rhodium, selenium, tellurium and tungsten compounds are reviewed and the relationships between pyrolysis pathways and film purity are discussed.
Organochromium precursors for low‐temperature OMCVD of chromium‐based coatings
Authors: Maury F 
Published: January 2005

AbstractMany organochromium compounds have been used as volatile chromium sources to prepare chromium‐based coatings by chemical vapor deposition. Chromium carbides, nitrides, oxides and alloys have been deposited on different substrates at low temperature (<500 °C). Organochromium precursors are reviewed and some of their draw‐backs are discussed. They are classified according to the nature of the chromium‐ligand bonds (carbonyls, amides, arenes or alkyls). Furthermore, experimental results obtained in the same apparatus for a series of representative precursors are reported to discuss, with literature data, how the ligand affects the composition and the structure of the films.
Complexes in polymers IV. FTIR microscopic characterization of thin organic polymer films containing embedded transition‐metal carbonyl complexes
Authors: Markwell Ross D , Butler Ian S , Gao Jian Ping , Shaver Alan 
Published: January 2005

AbstractThin films of polystyrene (PS), poly(methyl methacrylate) (PMMA) and polystyrene‐polyacrylonitrile copolymer (PS‐AN), containing various embedded transition‐metal complexes, have been studied by FTIR microscopy. The spatial distributions of the transition‐metal carbonyl complexes throughout the thin organic polymer films have been determined by a two‐dimensional IR mapping procedure. The spectral variations observed in the distribution of the metal carbonyls throughout the different polymer films are discussed. The IR data show that the technique used to prepare the organometallic‐embedded thin films (viz. freeze‐drying of solutions followed by hot mechanical pressing of the residues) does in general lead to homogeneous films which may eventually find industrial application, e.g. as membrane sensors for small molecules.
Novel nonionic siloxane surfactants
Authors: Wersig R , Sonnek G , Niemann C 
Published: January 2005

AbstractA new method for ethoxylation without application of pressure is described. Butynediololigo(oxyethylene) [H(OCH2CH2)nOCH2CCCH2O(CH2CH2O)nH with n=1–16] has been prepared in the presence of an electrophilic catalyst in a specially developed reciruculating apparatus. The products have been characterized by NMR and IR spectroscopy.New nonionic silicone surfactants have been synthesized by hydrosilylation of these butynediololigo(oxyethylenes) with defined siloxanes and polysiloxanes. Protection of the hydroxyl group before hydrosilylation was not necessary. Hydrosilylation was carried out in the presence of a solvent. It has been possible to obtain surfactants with a surface tension of about 21‐22 mN m−1 and an interfacial tension of 2 mN m−1.
In vitro antitumour activity of two isomeric cyclopalladiated compounds derived from benzoylbenzylidenimines
Authors: Navarro‐Ranninger C , LóPez‐Solera I , Pérez J M , Masaguer J R , Alonso C 
Published: January 2005

AbstractThe DNA thermal stabilizing effect and antitumour properties of two diastereoisomeric cyclopalladiated compounds, Pd2 [4‐CH3O–C6H4NC(COC6H5)C6H4]2(μ‐OAc)2 (I and II), derived from benzoylbenzylideneimines have been studied. The atropisomers containing two acetate‐bridged PdL2 units have a folded structure in boat form. The results show that both complexes interact with the DNA double helix but that compound II stabilizes the DNA more than compound I. It was also observed that the in vitro antiproliferative activity of compound II against colon (CX‐1) and lung (LX‐1) human tumour cells is higher than that of compound I. It is probable that the higher reactivity of compound II relative to compound I is due to the specific orientation of the benzoyl group with respect to the COCN chiral bond.
Antitumor effects of binuclear ferrocene derivatives
Authors: Popova L V , Babin V N , Belousov Yu A , Nekrasov Yu S , Snegireva A E , Borodina N P , Shaposhnikova G M , Bychenko O B , Raevskii P M , Morozova N B , Iiyina A I , Shitkov K G 
Published: January 2005

AbstractOn the basis of an earlier model of chemical carcinogenesis, the antitumor activity of the mono‐, bi‐ and poly‐nuclear ferrocene derivatives ferricenium tri‐iodide (1), ferricenium tetrachloroferrate (2), 1, 1′‐diethylferricenium triiodide: (3), N‐(ferrocenylmethyl)hexamethylenetetramine tetrafluoroborate (4), bis(ferrocenylmethyl)benzotriazolium tetrafluoroborate (5), bis(ferrocenyl‐α‐ethyl)benzotriazolium tetrafluoroborate (6) and bis(ferrocenylmethyl)‐2‐methylbenzimidazolium tetrafluoroborate (7), and the oligomer (—Fc—CH2—Fc+˙—CH2—)7–8− (PF6)7–8 (8) was studied in vivo (FcC10H8Fe). The tumor models studied included MCH‐11 (mouse sarcoma induced by methylcholantrene), P‐815 (mouse mastocytoma of DBA/2 origin) and virus‐induced Raucher leukemia (RLV). The cytotoxic effects of these preparations were examined against in vitro cultured normal murine cells (line L‐929). The binuclear ferrocene derivatives 5, 6 and 7 inhibited the development of experimental tumors in mice. Ferricenium tri‐iodide (1) was effective in Rauscher leukemia. Kinetic dependencies for most complexes had a two‐phase character: the region of inhibition of tumorogenesis was followed by a region in which the complexes accelerated the development of this process. The link between the structure of compounds 1–8 and their antitumor effects is discussed.
The analysis of organic mercury compounds using liquid chromatography with on‐line atomic fluorescence spectrometric detection
Authors: Hintelmann H , Wilken R‐D 
Published: January 2005

AbstractA new method for the analysis of organic mercury compounds is reported. The organomercurials are separated by high‐performance liquid chromatography (HPLC). The compounds are converted to mercury(0) in a continuous‐flow system by means of an oxidizing and a subsequent reducing solution. The elemental mercury generated is swept into the cell of an atomic fluorescence spectrometer (AFS) by a stream of argon. The compositions of the oxidizing solution, which contains peroxodisulphate and copper(II) in dilute sulphuric acid, and the reducing solution, which contains alkaline tin(II) chloride, were optimized, as were the gas–liquid separator (GLS), the condensing system and the geometry of the reaction coils. The method is applied to extracts of certified reference material (CRM) and to river sediments. High concentrations of methylmercury were found in the sediment samples. At one location, the presence of ethylmercury is derived from the sample chromatogram.
The effects of salinity and pH on the speciation of some triphenyltin compounds in estuarine sediments using Mössbauer spectroscopy
Authors: Whalen Deborah , Lucero Rosemarie , May Leopold , Eng George 
Published: January 2005

AbstractThe speciation of some triphenyltin compounds i.e. triphenyltin hydroxide, triphenyltin chloride, triphenyltin fluoride, under varying salinity and pH conditions, was studied by Mössbauer spectroscopy in both anoxic and oxic estuarine sediments. The results indicate that altering the pH or salinity of the sediment environment does not apparently affect the speciation of these compounds.
Hybrid organosilazane/organosilylamine telechelic oligomers—I. Two‐dimensional NMR spectroscopy characterization of dimethylsilylethylenediamine oligomers
Authors: Feng Ke , Abrahams Paul , Mariam Yitbarek H 
Published: January 2005

AbstractThe detailed characterization of multifunctional hybrid organosilazane/organosilylamine telechelic oligomers by IR and 1H, 13C and 29Si NMR spectroscopy in one and two dimenions has been undertaken. The specific multifunctional oligomers, comprising NH/NH2 or SiCl functionalities depending on the monomer feed‐ratio, were prepared from mono‐ and di‐functionally reacted dichlorodimethylsilane (DDS) and mono‐, di‐, tri‐ and tetra‐functionally reacted ethylenediamine (EDA). Varying the feed‐ratio afforded control of the microstructures of the oligomers and the preparation of oligomers with, in some cases, conterminously located silicon–chlorine (SiCl) groups. The combination of the NMR methods with the IR technique has enabled the detailed microstructural characterization of the oligomers and the identification of the functionalities therein. This approach and the knowledge gained from the DDS/EDA system has been applied to the microstructural characterization of other hybrid organosilazane/silylamine preceramic telechelic oligomers.
Fungicidal activity of tributyltin alkylsulfate esters
Authors: Roengsumran Sophon , Petsom Amorn , Thaniyavarn Suthep , Prachyakul Surat 
Published: January 2005

AbstractTributyltin alkyl sulfate esters, e.g. tributyltin dodecyl sulfate, tributyltin hexadecyl sulfate and tributyltin octadecyl sulfate, were synthesized from the reaction of bis(tributyltin) oxide and appropriate alkyl hydrogen sulfates. The resulting tributyltin alkyl sulfate esters were found to exhibit fungicidal activity on Penicillium, Aspergillus and Syncephalustrum species.
Alkylation of ionic mercury to methylmercury and dimethylmercury by methylcobalamin: Simultaneous determination by purge‐and‐trap GC in line with FTIR
Authors: Filippelli Marco , Baldi Franco 
Published: January 2005

AbstractA new approach was used to determine the reaction products of methylcobalamin and ionic mercury: purge‐and‐trap gas chromatography in line with Fourier transform infrared spectroscopy (PT GC/FTIR). This technique simultaneously and specifically determines the spectrum of dimethylmercury (DMeHg) and methylmercury produced by the reaction. No interference from other known organic mercury species could be detected. The method is different from others because it does not require solvent extraction of the organomercurials from aqueous solution, but relies on immediate volatilization from the reaction vessel by addition of 100 μl of 10 mM NaBH4. The sample was purged with nitrogen for 10 min. The volatile species of mercury were trapped in a column at −120°C, injected into the gas chromatograph and detected by FTIR. The efficiency of DMeHg and MeHg formation depended on different parameters: pH, temperature, reaction time, and the methylcobalamin/ionic mercury ratio. The initial reaction product was MeHg which was further transformed to DMeHg. The first methylation rate was two times faster than the second. MeHg formed first, reaching a maximum at higher temperatures (28°C and 37°C) and later decreasing as DMeHg formed. At lower temperatures (20°C) the rate of MeHg formation was slower, being similar to the formation rate of DMeHg. Different species of inorganic mercury such as HgSO4, Hg(NO3)2, Hg(SCN)2, HgCl2 and Hgl2 were used to study differences in methylation by methylcobalamin under standard conditions of acidity, temperature and cofactor Hg(II) ratio.
Synthesis and neurotropic activity of silyl‐substituted fufural thiosemicarbazones
Authors: Lukevics E , Demicheva L , Erchak N , Germane S 
Published: January 2005

Abstract5‐Silyl‐substituted‐2‐furaldehyde thiosemicarbazones were prepared by the condensation of the corresponding furfurals or furfural diethylace‐tals with thiosemicarbazide. The neurotropic activity of the synthesized thiosemicarbazones has been studied. The majority of the compounds examined possess high or medium neurotropic activity of the depressant type. They also show antihypoxic activity and decrease the duration of phenamine stereotype behaviour. Structure‐activity correlation has been found.
Crystal structure and fungitoxicity of aquatributyltin N‐phthaloylglycinate
Authors: Ng Seik Weng , Kuthubutheen A. J. , Kumar Das V. G. , Linden Anthony , Tiekink Edward R. T. 
Published: January 2005

AbstractThe [nBu3Sn(N‐phthaloylglycinate)(OH2)] compound has been prepared and characterized. The crystal structure reveals the tin atom, in each of the two molecules comprising the asymmetric unit, to exist in a distorted trigonal bipyramidal geometry in which the trigonal plane is defined by the three organic substituents and the axial sites are occupied by an oxygen atom derived from a monodentate carboxylate ligand and a coordinated water molecule. The [nBu3Sn(N‐phthaloylglycinate)(OH2)] compound and three other triorganotin derivatives of N‐phthaloyl‐protected amino acids display marked toxicity against several economically important plant pathogenic fungi.
How gallium arsenide wafers are made
Authors: Kitsunai Minoru , Yuki Takayoshi 
Published: January 2005

AbstractTen Japanese gallium arsenide wafer manufacturers voluntarily formed The Japan Manufacturers' Society of Compound Semiconductor Materials (JAMS‐CS) in 1983. This report summarizes the theories, the systems, and the operations of gallium arsenide production: the gradient freeze (GF) method, the liquidencapsulated Czochralski (LEC) method, the wafer processing, the vapor‐phase epitaxial (VPE) growth method, the liquid‐phase epitaxial (LPE) growth method, the metalorganic chemical vapor deposition (MO‐CVD) method and the molecular beam epitaxial (MBE) method.
Distribution and cycle of arsenic compounds in the ocean
Authors: Santosa Sri Juari , Wada Satoshi , Tanaka Shigeru 
Published: January 2005

AbstractIn order to understand the distribution and the cycle of arsenic compounds in the marine environment, the horizontal distributions of arsenic(V) [As(V)], arsenic(III) [As(III)], monomethylarsonic acid (MMAA) and dimethylarsinic acid (DMAA) in the Indian Pacific Oceanic surface waters have been investigated. This took place during cruises of the boat Shirase from Tokyo to the Syowa Station (15 November–19 December 1990), of the tanker Japan Violet from Sakai to Fujayrah (28 July–17 August 1991) and of the boat Hakuho‐maru from Tokyo to Auckland (19 September–27 October 1992). Vertical distributions of arsenic in the west Pacific Ocean have also been investigated.The concentration of As(V) was found to be relatively higher in the Antarctic than in the other areas. Its concentration varied from 340 ng dm−3 (China Sea) to 1045 ng dm−3 (Antarctic). On the other hand, the concentrations of the biologically produced species, MMAA and DMAA, were extremely low in the Antarctic and southwest Pacific waters. Their concentrations in Antarctic waters were 8 ng dm−3 and 22 ng dm−3 and those in the southwest Pacific were 12 ng dm−3 and 25 ng dm−3. In the other regions the concentration varied from 16 ng dm−3 (China Sea) to 36 ng dm−3 (north Indian Ocean) for MMAA and from 50 ng dm−3 (east Indian Ocean) to 172 ng dm−3 (north Indian Ocean) for DMAA. As a result, with the exception of Antarctic and southwest Pacific waters, the percentages of each arsenic species in the surface waters were very similar and varied from 52% (east Indian Ocean) to 63% (northwest Pacific Ocean) for As(V), from 22% (northwest Pacific Ocean) to 27% (east Indian Ocean) for As(III) and from 15% (northwest Pacific Ocean) to 21% (north and east Indian Oceans) for the methylated arsenics (MMAA+DMAA). These percentages in Antarctic waters were 97%, 0.2% and 2.8%, respectively, and those in the southwest Pacific Ocean were 97% for As(V)+As(III) and 3% for MMAA+DMAA. The very low concentrations of the biologically produced species in Antarctic waters and that of methylated arsenic in southwest Pacific waters indicated that the microorganism communities in these oceans was dominated by microorganisms having a low affinity towards arsenic. Furthermore, microorganism activity in the Antarctic was also limited due to the much lower temperature of the seawater there.The vertical profile of inorganic arsenic was 1350 ng dm−3 in surface waters, 1500 ng dm−3 in bottom waters with a maximum value of 1700 ng dm−3 at a depth of about 2000 m in west Pacific waters. This fact suggested the uptake of arsenic by microorganisms in the surface waters and the co‐precipitation of arsenic with hydrated heavy‐metal oxides in bottom waters. The suggested uptake of inorganic arsenic and subsequent methylation was also supported by the profile of DMAA, with a high concentration of about 26 ng dm−3 in surface water and a significant decrease to a value of 9 ng dm−3 at a depth of 1000 m.
Identification of extracellular arsenical metabolites in the growth medium of the microorganisms apiotrichum humicola and scopulariopsis brevicaulis
Authors: Cullen William R. , Li Hao , Hewitt Gary , Reimer Kenneth J. , Zalunardo Nadia 
Published: January 2005

AbstractThe separation and identification of some of the arsenic species produced in cells present in the growth medium when the microorganisms Apiotrichum humicola (previously known as Candida humicola) and Scopulariopsis brevicaulis were grown in the presence of arsenicals were achieved by using hydride generation–gas chromatography–atomic absorption spectrometry methodology (HG GC AA). Arsenite, monomethylarsonate, dimethylarsinate and trimethylarsine oxide were detected following incubation with arsenate. With arsenite as a substrate, the metabolites were monomethylarsonate, dimethylarsinate and trimethylarsine oxide; monomethylarsonate afforded dimethylarsinate and trimethylarsine oxide, and dimethylarsinate afforded trimethylarsine oxide. Trimethylarsine was not detected when the arsenic concentration was 1 ppm.
Methylation of arsenic by anaerobic microbial consortia isolated from lake sediment
Authors: Bright D. A. , Brock S. , Reimer K. J. , Cullen W. R. , Hewitt G. M. , Jafaar J. 
Published: January 2005

AbstractAnaerobic enrichment cultures, isolated from arsenic–contaminated lake sediment in the Canadian sub–arctic and grown in five selective media, methylated arsenate/arsenite to produce mono−, di− and tri–methyl arsenicals. The extent of methylation and methylarsenic species produced varied with the type of enrichment. Iron–reducing, manganese–reducing, sulfate–reducing and broad–spectrum anaerobic heterotrophic mixed cultures all produced methylarsenicals. Sulfate–reducing cultures produced higher concentrations of methylarsenicals (especially trimethyl species) than iron‐ or maganese–reducers. There is evidence that several of the methylarsenicals, which were hydride–reactive at pH 6, were methylarsenic(III) thiols. The organoarsenicals produced by enrichment cultures were the same as those detected in the porewater of the lake sediments used to initiate the enrichment cultures. Overall, this study demonstrates that microbes from anaerobic lake sediments can methylate (and demethylate) arsenic, a capability shared by manganese−, iron−, and sulfate–reducing microbial consortia.
Working Methods Paper: Critical considerations with respect to the identification of tin species in the environment
Authors: Quevauviller Philippe , Ritsema Rob , Morabito Roberto , Dirkx Wilfried M. R. , Chiavarini Salvatore , Bayona José M. , Donard Olivier F. X. 
Published: January 2005

AbstractBiogeochemical pathways of tin species in the environment are still controversial, e.g. with regard to methylation and transmethylation phenomena, owing to the fact that the identification of methylated tin‐compounds is often difficult. The previous tentative identification of a mixed methylbutyltin compound in sediment and biological samples by GC/AAS after hydride generation gave an illustration of this problem. This compound was previously identified in sediments by other authors and also suspected to occur in a contaminated sediment sample from the Boyardville Marina, France. The retention time obtained by GC/AAS corresponded to the actual retention time of a mixed methylbutyltin calibrant. However, additional checks demonstrated that the compound detected was actually monophenyltin. This evidence was produced by a thorough analysis of a selected sediment sample by alternative techniques such as GC/AAS and GC/AES after pentylation, GC/FPD and GC/MS. The results presented highlight the need for a full identification of compounds to avoid mis‐interpretation.
Quality control in the speciation analysis of butyltin compounds in marine biological samples by hydride generation–cold trapping and on‐line quartz furnace atomic absorption spectrometry
Authors: Pannier F. , Astruc A. , Astruc M. 
Published: January 2005

AbstractThe determination of tributyltin (TBT) in sea food (mussel, oyster, fish) by a hydride generation–cold trapping–quartz furnace atomic absorption spectrometry procedure has been studied with emphasis on quality control. Large amounts of spiked materials have been prepared and stored either frozen, or frozen after freeze‐drying. Extraction of TBT by 0.1 M hydrochloric acid in methanolic solution is efficient (88–96%) for wet samples or freeze‐dried samples. It is also efficient with freshly spiked materials. Consumption of sodium borohydride by the matrix makes it necessary to use quite large amounts of reagent to obtain optimal sensitivity. Analysis of a fish‐tissue Certified Reference Material seems to indicate a partial debutylation of TBT during transport and/or storage of this material.
Certified reference material (CRM 462) for the quality control of dibutyl‐ and tributyl‐tin determinations in coastal sediment
Authors: Quevauviller Ph. , Astruc M. , Ebdon L. , Desauziers V. , Sarradin P. M. , Astruc A. , Kramer G. N. , Griepink B. 
Published: January 2005

AbstractDeterminations of tributyltin (TBT) species, along with the degradation products mono‐ and dibutyltin (MBT and DBT), are routinely carried out by a number of laboratories to ascertain the level of organotin contamination of the marine enviroment, particularly in water, sediment and biota. In order to improve and control the quality of such analyses the EC Community Bureau of Reference, BCR (Measurements and Testing Programme), has organized two interlaboratory studies on TBT in water and TBT in a spiked sediment which were followed by a certification campaign for butyltins in a coastal sediment (CRM 462). This material was collected in the Arcachon Bay (France), then carefully prepared (controlled oven drying) and its homogeneity and long‐term stability were verified. This paper presents the certification work performed. The certified values for TBT and DBT are 70±14 ng g−1 (as TBT cation) and 128±16 ng g−1 (as DBT cation), respectively.