bluuebunny/crossref_metadata_2025_split huggingface dataset:
The reactivity of Samarium(II) in a Bis(indenyl) coordination environment
Authors: Evans William J. , Gummersheimer Tammy S. , Ziller Joseph W. 
Published: January 2005

AbstractThe reactivity of the organosamarium(II) indenyl complex (C9H7)2Sm(THF)x, 1, has been compared with that of (C5Me5)2Sm(THF)2, 2, and (C5Me5)2Sm, 3, by examination of characteristic organosamarium(II) reactions which form trivalent oxide, iodide, cyclo‐octatetraenyl and azobenzene complexes. Complex 1 reacts with excess N2O to form [(C9H7)2Sm(THF)]2(μ‐O), 4, and (C9H7)3Sm(THF), 5, as the major products. Two equivalents of 1 react with one equivalent of 1,2‐di‐iodoethane in THF to give (C9H7)SmI2(THF)2, 6, as well as 5. Complex 1 reacts with 1,3,5,7‐cyclo‐octatetraene in a 2:1 ratio in THF to form 5 and (C9H7)Sm(C8H8)(THF)x, 7, which has been fully characterized as the 2,2′‐bipyridine adduct (C9H7)Sm(C8H8)(C10H8N2), 7a. The reaction of 1 with azobenzene in a 2:1 ratio forms [(C9H7)Sm(N2Ph2)(THF)]x, 8, and 5. Complexes 4–6 and 7a have been definitively identified by X‐ray crystallography.Complex 4 crystallizes from THF in space group P1― [C; No. 2] with unit cell parameters at 163 K of a = 8.072(2) Å, b = 9.502(2) Å, c = 12.250(3) Å, α = 101.42(2)°, β = 90.71(2)°, γ = 102.50(2)°, V = 897.7(4) Å3 and Z = 1 for Dcalcd = 1.704 Mgm−3. Least‐squares refinement of the model based on 3924 reflections (|F0|)>3.0 σ (|F0|)) converged to a final RF=2.4%. The geometry around each Sm atom is a distorted tetrahedron and the Sm–O–Sm angle is 180°.Complex 5 crystallizes from THF/hexanes at −35°C in space group P63 [C; No. 173] with unit cell parameters at 163 K of a = 11.7370(14) Å, c = 10.1994(12) Å, V = 1216.8(3) Å3 and Z = 2 for Dcalcd = 1.550 Mg m−3. Least‐squares refinement of the model based on 976 reflections (|F0|> 3.0σ (|F0|) converged to a final RF = 2.3%. The three ring centroids and the THF oxygen atom define a distorted tetrahedron around samarium with a (ring centroid)–Sm–(ring centroid) angle of 116.0°.Complex 6 crystallizes from THF/hexanes as the trisolvate (C9H7)SmI2(THF)3, 6a, in space group P21/n [C; No. 14] with unit cell parameters at 163 K of a = 8.3969(12) Å, b = 17.165(5) Å, c = 33.592(7) Å, β = 96.468(15)°, V = 4811(2) Å3 and Z = 8 for Dcalcd = 2.031 Mg m−3. Least‐squares refinement of the model based on 5664 reflections (|F0|> 2.0 σ (|F0|)) converged to a final RF = 3.3%. The six ligands around Sm in 6a describe a distorted octahedron. The iodide ligands are trans to each other with a 153.8(1)° I–Sm–I angle.Adduct 7a crystallizes from hot THF/toluene in space group P1 [C; No. 2] with a unit cell parameters at 163 K of a = 7.886(7) Å, b = 16.72(2) Å, c = 17.48(2) Å, α = 62.96(7)°, β = 85.17(7)°, γ = 85.23(9)°, V = 2042(3) Å3 and Z = 4. The cyclooctateraenyl and indenyl ligands generate a bent metallocene structure for 7a which contains a chelating bipyridyl group in the plane bisecting the two rings.
Lanthanum isopropoxide catalyzed addition of activated nucleophiles to imines
Authors: Yamamoto Yoshinori , Fukui Hiroyuki , Honda Yoshihiro 
Published: January 2005

AbstractThe addition of certain activated nucleophiles to activated imines is catalyzed by lanthanum isopropoxide. As activated nucleophiles, methylmalononitrile and methyl 2‐cyanopropanoate can be utilized. Imines having an electronwithdrawing group either at the carbon or at the nitrogen atom of the C=N double bond can be used; for example N‐toluenesulfonylimines, N‐(4‐methoxycarbonylphenyl)imines and α‐imino esters.
Lanthanide silanolates: Development of new procedures for the modification of silicones with rare‐earth metals
Authors: Voskoboynikov Alexander Z. , Beletskaya Irina P. 
Published: January 2005

AbstractThe reactions of Lnl33 (Ln = La, Ce, Er, Yb) with sodium silanolate (NaOSiMe3) in THF at room temperature yield lanthanide silanolates Ln(OSiMe3)3 which seem to be oligomers with μ‐OSiMe3 ligands. Reaction of Cel3 with potassium siliconate, KO[Me1.96Ph0.04SiO]20.75K, yields a netted polymer [Me61.59Ph1.29Si31.44O39.02Ce]x. An analogous procedure which involves reaction of Lnl3 (Ln = Ln, Er) with KO[Me1.96Ph0.04SiO]50.00 K, and following treatment with NaOSiMe3, results in the formation of solublé product (Me3SiO)2LnO[Me1.96Ph0.04SiO]50.00 Ln(OSiMe3)2.
Maintaining rapid growth in moderate‐density Escherichia coli fermentations
Authors: Zawada James , Swartz James 
Published: January 2005

AbstractA novel feeding strategy that prolongs rapid growth rates for Escherichia coli fermentations to moderately high cell density is presented. High‐density fermentations are a common and successful means of producing biological products. However, acetate accumulation can be a substantial problem in these procedures. To avoid this problem, many feeding strategies and host modifications have been developed, but all result in relatively low growth rates. If a faster growth rate could be maintained, the growth phase of the process would be shortened, leading to increased productivity. It is also possible that the subsequent specific production rate could be enhanced by growing the early culture at a faster rate. We have developed a procedure to enable rapid growth to a cell density of 20 g/L and have used cell‐free protein synthesis to evaluate the relative potential of the resulting cells for producing recombinant proteins. The method uses glucose pulses and the duration of the dissolved oxygen response to calculate the appropriate glucose feed rate based on the glucose demand of the culture. Amino acids and vitamins were supplied in the medium to increase the growth rate. We were able to sustain a growth rate of 0.8/h up to 20 g/L dry cell weight without significant acetate accumulation. Analysis of amino acid consumption indicates that cell composition is an accurate predictor of amino acid demand for most amino acids. Cell‐free protein synthesis was used to compare the protein production potential of the high‐density cultures with that of cells grown in complex medium and harvested at low cell density and maximum growth rate. Protein production for the extract from the controlled, high‐density fermentations was 950 mg/L compared with 860 mg/L for the low‐density control. Therefore, the new control procedure has promising potential for developing rapid and productive industrial fermentations. ©2004 Wiley Periodicals, Inc.
Navigating public microarray databases
Authors: Penkett Christopher J. , Bähler Jürg 
Published: January 2005

AbstractWith the ever‐escalating amount of data being produced by genome‐wide microarray studies, it is of increasing importance that these data are captured in public databases so that researchers can use this information to complement and enhance their own studies. Many groups have set up databases of expression data, ranging from large repositories, which are designed to comprehensively capture all published data, through to more specialized databases. The public repositories, such as ArrayExpress at the European Bioinformatics Institute contain complete datasets in raw format in addition to processed data, whilst the specialist databases tend to provide downstream analysis of normalized data from more focused studies and data sources. Here we provide a guide to the use of these public microarray resources. Copyright © 2004 John Wiley & Sons, Ltd.
Ontologies for the description of mouse phenotypes
Authors: Gkoutos G. V. , Green E. C. J. , Mallon A.‐M. , Blake A. , Greenaway S. , Hancock J. M. , Davidson D. 
Published: January 2005

AbstractOntologies are becoming increasingly important for the efficient storage, retrieval and mining of biological data. The description of phenotypes using ontologies is a particularly complex problem. We outline a schema that can be used to describe phenotypes by combining orthologous axiomatic ontologies. We also describe tools for storing, browsing and searching such complex ontologies. Central to this approach is that assays (protocols for measuring phenotypic characters) describe what has been measured as well as how this was done, allowing assays to link individual organisms to ontologies describing phenotypes. We have evaluated this approach by automatically annotating data on 600 000 mutant mice phenotypes using the SHIRPA protocol. We believe this approach will enable the flexible, extensible and detailed description of phenotypes from any organism. Copyright © 2004 John Wiley & Sons, Ltd.
Screening for prostate carcinoma
Authors: D'Amico Anthony V. 
Published: January 2005

To date, the use of prostate‐specific antigen (PSA) screening in the U.S. has translated into lower PSA failure rates and, perhaps, to lower rates of disease‐specific mortality in men with prostate carcinoma. However, this later point remains a hypothesis and will be proven right or wrong in short order based on upcoming results from randomized screening studies.See also pages 943–51.
Single base pair change in the long‐range Sonic hedgehog limb‐specific enhancer is a genetic basis for preaxial polydactyly
Authors: Maas Sarah A. , Fallon John F. 
Published: January 2005

AbstractIn most instances of preaxial polydactyly (PPD), Sonic Hedgehog (Shh), an essential limb patterning signal, is ectopically expressed in an anterior region of the developing limb in addition to the normal posterior domain. It is thought that this anterior Shh expression leads directly to the development of the extra digits. Recent reports have identified a conserved limb‐specific Shh enhancer ∼1 megabase upstream of the Shh transcription initiation site, and individual base pair changes within this region are associated with PPD. We report here that a single base pair change within this enhancer is sufficient to drive β‐galactosidase expression in both anterior and posterior limb domains, similar to Shh expression in animal PPD models, whereas a wild‐type construct is expressed only in the posterior limb, similar to Shh expression in normal embryos. These findings provide the first direct evidence that a single base pair change within the limb‐specific Shh enhancer acts as a genetic basis for PPD. Developmental Dynamics 232:345–348, 2005. © 2005 Wiley‐Liss, Inc.
New simple tests for age‐at‐onset anticipation: Application to panic disorder
Authors: Tsai W.Y. , Heiman Gary A. , Hodge Susan E. 
Published: January 2005

AbstractRecently, testing for anticipation has received renewed interest. It is well known that standard statistical methods are inappropriate for this purpose due to problems of sampling bias. Few statistical tests have been proposed for comparing mean age of onset in affected parents with mean age of onset in affected children. All of them are difficult to compute and lack software to perform the tests. In this report, we formulate the problem in terms of symmetry tests. We propose a simple generalized paired t‐test and a Wilcoxon signed rank test to adjust for the bias caused by the right truncation of both the parent's and child's ages at onset. We also extend the generalized paired t‐test to a random effects model that enables analysis of correlated data from nuclear families, and could be further extended to larger family structures. We illustrate the approaches with an example of panic disorder. Genet. Epidemiol. © 2005 Wiley‐Liss, Inc.
Conformational analysis of proteins: Algorithms and data structures for array processing
Authors: Pottle C. , Pottle M. S. , Tuttle R. W. , Kinch R. J. , Scheraga H. A. 
Published: January 2005

AbstractCurrent efforts to determine the nature of the interactions that influence protein folding involve, among other things, minimization of an appropriate empirical conformational energy function (ECEPP, Emprical Conformational Energy Program for Peptides) to obtain the native structure. Because of the prohibitive cost of such a massive computational project, either on a conventional large‐scale machine at a self‐supporting installation or on a dedicated minicomputer, an alternative computer hardware system has been developed to aid in the conformational analysis of proteins. It consists of a Floating Point Systems AP‐120B array processor and a Prime 350 minicomputer host. A version of ECEPP has been adapted to run on the AP‐120B. The data structures and algorithms chosen for this version reflect the highly unusual parallel architecture of this machine. Benchmark comparisons with BPTI (Bovine Pancreatic Trypsin Inhibitor), a protein of 58 residues and a known structure, have been carried out on this system as well as on an IBM 370/168. They show a significant advantage in speed for the AP‐120B/Prime 350 system as well as a substantially lower cost. An energy minimization of BPTI with 154 variable dihedral angles is reported, an effort heretofore prohibited by the computer costs involved.
Hartree Fock instabilities of sulfur‐nitrogen ring systems: S2N2
Authors: Laidlaw W. G. , Bénard M. 
Published: January 2005

AbstractThe Hartree‐Fock instablities of S2N2 are reported and compared with those of S3N and S4N. These unsaturated sulfur nitrogen planar rings are π electron rich and although the symmetry adapted HF solutions are singlet stable at the experimental bond lengths they become unstable with only a very modest increase in bond length. The broken symmetry solutions for S2N3, S3N, and S4N are of planar C2v type with one of the nitrogens stripped of its π electrons, producing a π hole.
The photolysis of 3,3‐dimethylbutan‐2‐one (methyl t‐butyl ketone) and the decomposition of the acetyl radical
Authors: Frey H. M. , Vinall I. C. 
Published: January 2005

AbstractThe photolysis of 3,3‐dimethylbutan‐2‐one (MTBK) has been studied in the gas phase at 408 and 326 K, mainly with light of 313 nm wavelength. At the higher temperature, the major products were methane, ethane, isobutane, isobutene, neopentane, tetramethylbutane, and carbon monoxide. At 326 K, in addition to these products, appreciable quantities of acetaldehyde, acetone, and biacetyl were detected. Quantum yields were determined using acetone and pentan‐3‐one as actinometers. A conventional mechanism is able to explain most of the experimental data. At 326 K, the results may be interpreted to yield a value for the rate constant for decomposition of the acetyl radical. Some theoretical calculations are reported on the acetyl radical decomposition and some earlier experimental work on this radical reevaluated.
Liquid‐phase hydrogen abstraction from chlorinated ethanes by chlorine atoms
Authors: Martens G. J. , Franklin J. A. , Godfroid M. , Delvaux M. , Verbeyst J. 
Published: January 2005

AbstractThe hydrogen abstraction from the chlorinated ethanes by chlorine atoms has been investigated in the liquid phase. Rate constants relative to that for hydrogen abstraction from chloroform have been measured between 267° and 333°K using a competition technique. The results are compared with gas‐phase data.
Deactivation of vibrationally excited hydrogen fluoride (v=2 and v=1) by atomic fluorine
Authors: Blauer Jay A. , Solomon Wayne C. 
Published: January 2005

AbstractMeasurements have been made which provide information concerning the rate of energy transfer between vibrationally excited HF and atomic fluorine. It was found that HF (v = 1) deactivates about seven times slower than was determined in previous experiments. The deactivation rate constant for HF (v = 2) is about six times larger than for HF (v = 1).
Constant time interval method for analysis of reaction rate data
Authors: Shank Norman E. 
Published: January 2005

AbstractIn the study of chemical kinetics, many integrated reaction rate equations have the form In [f(A) + a] = bt + c, where a, b, and c are constants and f(A) is some function of the concentration of a reactant (or product) which can be calculated from the data. The left‐hand side of this equation cannot be graphed versus time if the constant a is unknown. However, it is shown that f(A2) varies linearly with f(A1) if A2 is the concentration of reactant measured at a constant time interval later than A1. The constants a and b can be determined from the linear graph. A number of specific examples are considered.
Explosion of acetylene–chlorine mixture at room temperatures initiated by small additions of oxygen: Kinetic study and mechanism
Authors: Shtern V. Ya. , Revsin A. F. , Sokolova E. I. 
Published: January 2005

AbstractOxygen added in amounts of 0.01‐0.1% was found to cause the explosion of an acetylene–chlorine mixture at temperatures as low as −78°C. Explosion occurrence and nature depend on the mode of mixing the reactants, the effect of oxygen being associated with concentration limits. The dependence of explosion‐inducing oxygen amounts on temperature, pressure, concentrations of reactants, reactor surface type and area, additions of inert gases, and reaction products were investigated. The effect of light on the C2H2 + Cl2 + O2 was studied. The composition of gaseous products resulting from acetylene–chlorine mixture explosion in the presence of minute amounts of oxygen, from a slow reaction inhibited and noninhibited by oxygen, and also from explosion at 400°C in the absence of oxygen, was determined. The results obtained point to the fact that any acetylene–chlorine mixture flash caused by small amounts of oxygen is a branched chain reaction involving activated particles, chain branching presumably being associated with the decomposition of radical CHCl=CHOO* → CH + HCl + CO2.
Thermal decomposition of 1,1,2,2‐tetramethylcyclopropane in a single‐pulse shock tube
Authors: Tsang Wing 
Published: January 2005

Abstract1,1,2,2‐Tetramethylcyclopropane (TTMC) has been decomposed in a single‐pulse shock tube. The main reaction process is magnified image Side reactions are unimportant. From comparative rate experiments (with cyclohexene decomposition as standard) the rate expression for these reactions are

These numbers are consistent with a «best» value for cyclohexene decomposition of
A measurement of the rate of the reaction N + H + M → NH + M
Authors: Brown Robert L. 
Published: January 2005

AbstractThe combination reaction between N and H atoms has been studied in a flow system by mixing H atoms produced by thermal dissociation of H2 with active nitrogen produced by a microwave discharge. Relative N atom concentrations were determined from the intensity of the yellow nitrogen afterglow. Absolute N and H atom concentrations were measured by EPR absorption spectroscopy. Absolute N atom concentrations were also determined by titration with NO. Upper and lower limits of 6.4 ± 1.5 × 10−32 and 3.1 ± 1.0 × 10−32 cm6 molecule−2 sec−1 were determined for the rate constant.
The temperature dependence and the mechanism of the SO2 (3B1) quenching reactions
Authors: Wampler Fred B. , Otsuka Kiyoshi , Calvert Jack G. , Damon Edward K. 
Published: January 2005

AbstractThe Arrhenius parameters have been determined for the SO2(3B1) quenching reaction (9), SO2(3B1) + M → (SO2  M), for 21 different molecules as quenching partner M. The rate constants were calculated from phosphorescence lifetime measurements made over a range of reactant pressures and temperatures. Excitation of the SO2 (3B1) molecules was accomplished by two very different methods: (1) a 3829 Å laser pulse generated the triplet directly through absorption within the “forbidden” SO2 (3B1) → SO2 (1A1) band; (2) a broadband Xe‐flash system generated SO2(3B1) molecules and triplets were formed subsequently by intersystem crossing, SO2(1B1) + M → SO2(3B1) + M. The measured rate constants were independent of the method of triplet formation employed. For the atmospheric gases, the activation energies (kcal/mole) were identical within the experimental error: N2, 2.9 ± 0.4; 02, 3.2 ± 0.5; Ar, 2.8 ± 0.6; CO2, 2.8 ± 0.4; CO, 2.7 ± 0.4; CH4, 2.5 ± 0.6. This energy corresponds to the first region of the SO2(3B1) → SO2(1A1) absorption spectra in which Brand and coworkers observe strong perturbations. It is suggested that the quenching in these cases results largely from the physical process involving potential energy surface crossing to another electronic state. Activation energies for SO2(3B1) quenching by the paraffinic hydrocarbons show a regular decrease in the series ethane, neopentane, propane, n‐butane, cyclohexane, and isobutane, which parallels closely the decrease in CH bond energies in these compounds. These and other data are most consistent with the dominance of chemical quenching in these cases. The rate constants for the olefinic and aromatic hydrocarbons and nitric oxide show only very small variations with temperature change, and they are near the kinetic collision number. These data support the hypothesis that quenching in these cases is associated with the formation of a charge‐transfer complex and subsequent chemical interactions between the SO2(3B1) molecule and the π‐system of these compounds.
Time‐resolved fluorescence studies on the formation and decomposition of the aromatic hydrocarbon‐aliphatic amine exciplex in solution
Authors: Nakashima Nobuaki , Mataga Noboru , Yamanaka Chiyoe 
Published: January 2005

AbstractFluorescence rise and decay processes were measured and rate parameters were determined for the pyrene‐tri‐n‐butylamine and pyrene‐N,N‐diethylaniline exciplex system in various solvents. An additional activation energy over that for the diffusional motion appears necessary for both exciplex formation and the deactivating quenching processes in the case of the pyrene‐tri‐n‐butylamine system. The rate‐determining step for these processes is electron transfer in the encounter collision leading to the nonrelaxed electron transfer state.
A comparison of the thermal and photochemical oxidation of 2‐propanol by two peroxoanions
Authors: Bida Gerald , Curci Ruggero , Edwards John O. 
Published: January 2005

AbstractThe chain length (i.e., relative quantum yield) for the oxidation of 2‐propanol by peroxodisulfate ion at 25°C has been studied. A number of initial experiments were carried out in order to clarify the influence of dissolved oxygen, light intensity, cupric ion, and acetone absorption. After these problems were understood, conditions satisfactory for evaluation of chain length were chosen. The chain length was found to be 500 (to within ±100). The difference between this value and the thermal oxidation chain length of 1800 at 60° is, in both direction and magnitude, as expected for a common mechanism and a low activation energy for the propagation steps. A remarkable difference is seen for comparable reactions of peroxodisulfate and peroxodiphosphate anions.
The collisional behaviour of the spin orbit states of the lead atom, Pb(63P1,2), studied by time‐resolved attenuation of atomic resonance radiation
Authors: Husain D. , Littler J. G. F. 
Published: January 2005

AbstractA kinetic study of lead atoms in the spin orbit states, Pb(63P1) and Pb Pb(63P2), 0.969 and 1.320 eV, respectively, above the 63P0 ground state, has been carried out by atomic absorption spectroscopy. The electronically excited lead atoms were generated by the pulsed irradiation of lead tetraethyl and monitored photoelectrically by time‐resolved attenuation of resonance radiation. The decay of the two atomic states has been studied in the presence of He, Ar, H2, D2, N2, O2, CO, NO, CO2, N2O, CH4, C2H4, C2H2 CF4, SF6, and PbEt4, and rate constants for the collisional quenching by these gases are reported. The resulting data are compared with those for the deactivation of other atomic spin orbit states of comparable energy. In general, the higher energy state, Pb(63P2), is found to be deactivated more rapidly. It would appear that the magnitude of the electronic energy to be transferred on collision governs the rates of quenching, at least where a weak interaction potential is involved, and that for most gases, deactivation of Pb(63P2) proceeds via Pb(63P1).