bluuebunny/crossref_metadata_2025 huggingface dataset:
Ternary bulk metallic glasses formed by minor alloying of Cu8Zr5 icosahedron
Authors: Xia Junhai , Qiang Jianbing , Wang Yingmin , Wang Qing , Dong Chuang
Published: March 2006

Icosahedron Cu8Zr5, derived from the Cu8Zr3 phase structure, corresponds to the deepest eutectic Cu0.618Zr0.382. Near this composition is the best glass-forming Cu–Zr composition, Cu0.64Zr0.36. (Cu0.64Zr0.36)1−xMx and (Cu0.618Zr0.382)1−xMx were examined for glass formation, where M represents Nb, Sn, Mo, Si, V, Ag, or Ta. A series of Cu–Zr based bulk metallic glasses are discovered with minor Nb, Sn, Mo, Ag, and Ta additions (lower than 3at.%). The minor alloying mechanism was discussed in the light of atomic size and electron concentration factors.
Luminescent properties and reduced dimensional behavior of hydrothermally prepared Y2SiO5:Ce nanophosphors
Authors: Cooke D. W. , Lee J.-K. , Bennett B. L. , Groves J. R. , Jacobsohn L. G. , McKigney E. A. , Muenchausen R. E. , Nastasi M. , Sickafus K. E. , Tang M. , Valdez J. A. , Kim J.-Y. , Hong K. S.
Published: March 2006

Hydrothermally prepared nanophosphor Y2SiO5:Ce crystallizes in the P21∕c structure, rather than the B2∕b structure observed in bulk material. Relative to bulk powder, nanophosphors of particle size ∼25–100nm diameter exhibit redshifts of the photoluminescence excitation and emission spectra, reduced self absorption, enhanced light output, and medium-dependent radiative lifetime. Photoluminescence data are consistent with reduced symmetry of the P21∕c structure and are not necessarily related to reduced dimensionality of the nanophosphor. In contrast, medium-dependent lifetime and enhanced light output are attributed to nanoscale behavior. Perturbation of the Ce ion electric field is responsible for the variable lifetime.
Lasing in an intermediate twisted phase between cholesteric and smectic A phase
Authors: Chanishvili Andro , Chilaya Guram , Petriashvili Gia , Barberi Riccardo , De Santo Maria P. , Matranga Mario A. , Ciuchi Federica
Published: March 2006

This work describes the observation of lasing in an intermediate chiral phase of a dye-doped cholesteric liquid crystal mixture. This intermediate phase exists between cholesteric and smectic A phase and it presents anomalous selective reflection properties. The lasing was observed at the long-wavelength edge of the photonic band gap.
Selective growth of graphite micro-rods with SiO2 nanowire cores by chemical vapor deposition
Authors: Zhang Zhengjun , Xu Chunhua , Yue Yang
Published: March 2006

We report here the synthesis and highly substrate-site selective growth behavior of graphite microrods cored with silica nanowires by chemical vapor deposition. This technique allows us to deposit vertically aligned microrods preferentially on silicon regions of patterned SiO2∕Si substrates. One might also transform the microrods into other forms, for example, into microtubes of graphite and/or α-Fe2O3 nanoparticles by some chemical and/or physical routes. The structure and the growth mechanism of the graphite microrods were investigated and discussed.
e
∕
a
dependence of the lattice instability of cubic Heusler alloys from first principles
Authors: Zayak A. T. , Adeagbo W. A. , Entel P. , Rabe K. M.
Published: March 2006

First-principles calculations are used to investigate chemical trends in the structural instability of the high-symmetry cubic structure for a selected set of ferromagnetic Heusler compounds. The role of the valence-electron-to-atom ratio e∕a is investigated both by comparing compounds of different compositions, and by artificially changing the electron density in the first-principles calculations. Systematic trends in the interatomic force constant, previously found to be an indicator of the structural instability, are identified and discussed.
Temperature dependence of nanoholes free volume in polypropylene glycols
Authors: Consolati G.
Published: March 2006

Estimation of the free volume fraction in disordered systems can be obtained by combining specific volume measurements with positron annihilation lifetime data. Usually, nanoholes are supposed to expand isotropically under, e.g., temperature increase. This letter shows results for a homologous series of polypropylene glycols which are discussed in terms of anisotropic nanoholes expansion, ascribed to constraints on the molecular motions. A relationship between volume and unconstrained, average size of the cavity is obtained in the form of a power law with a noninteger exponent.
Investigation of an oxide layer by femtosecond-laser-assisted atom probe tomography
Authors: Gault B. , Menand A. , Geuser F. de , Deconihout B. , Danoix R.
Published: March 2006

In this letter, we report results obtained from the atom-probe tomography (APT) analysis of an oxide layer developed on a pure iron specimen under low pressure of oxygen. These specimens are generally fragile, and hard to analyze in APT. Here we show that by the use of femtosecond laser pulses, the oxide layer could be field evaporated atom by atom allowing its chemical identification at the atomic scale. The evidence of iron atomic planes through the whole oxide layer suggests that oxygen atoms diffuse though the oxide layer during the first stages of the oxidation process.
The Contested Strategies of Local Governance: Community Strategies, Development Plans, and Local Government Modernisation
Authors: Tewdwr-Jones Mark , Morphet Janice , Allmendinger Philip
Published: March 2006

The current round of local government modernisation in England, which commenced in 1997, has focused primarily on three main areas—new council constitutions, e-government, and performance. However, a fourth strand of initiatives relates to the power of well-being and the duty to prepare a community strategy, in partnership with a local strategic partnership. Academic commentators and planners, who have been focusing on the proposed UK planning reforms as contained within the Planning and Compulsory Purchase Act (passed in 2004), have largely ignored the development of this strand. In this paper we explore these aspects of the local government modernisation agenda for planners and pull out some of the key issues for comparison in the ownership, role, and development of the new plans: community strategies and development plans. Opportunities and difficulties of ensuring that new development plans become the spatial expression of community strategies is assessed through an illustration of the relationship between the London Borough of Camden's community strategy and its unitary development plan. Following a review of the content of both documents, wider assessments are drawn out and we conclude by debating the implications of and challenges for a future reformed planning system at the local level.
Green Urban Political Ecologies: Toward a Better Understanding of Inner-City Environmental Change
Authors: Heynen Nik
Published: March 2006

This research uses a Marxist urban political ecology framework to link processes of urban environmental metabolization explicitly to the consumption fund of the built environment. Instead of reinventing the wheel, I argue in this paper that Marxist notions of metabolism are ideal for investigating urban environmental change and the production of uneven urban environments. In so doing, I argue that despite the embeddedness of Harvey's circuits of capital within urban political economy, these connected notions still have a great deal to offer regarding better understanding relations between consumption and metabolization of urban environments. From this theoretical perspective, I investigate urban socionatural metabolization as a function of the broader socioeconomic processes related to urban restructuring within the USA between 1962 and 1993 in the Indianapolis inner-city urban forest. The research examines the relations between changes in household income and changes in urban forest canopy cover. The results of the research indicate that there was a significant decline over time in the Indianapolis urban forest canopy and that median household was related to these changes, thus demonstrating a concrete example of urban environmental metabolization.
The Sacred and the Profane: Biotechnology, Rationality, and Public Debate
Authors: Davies Gail
Published: March 2006

This paper explores the forms of argumentation employed by participants in a recent public engagement process in the United Kingdom around new technologies for organ transplantation, with specific reference to xenotransplantation and stem-cell research. Two forms of reasoning recur throughout participants' deliberations which challenge specialist framing of this issue. First, an often scatological humour and sense of the profane are evident in the ways in which participants discuss the bodily transformations that such technologies demand. Second, a sense of the sacred, in which new biotechnologies are viewed as against nature or in which commercial companies are ‘playing god’, is a repetitive and well-recognised concern. Such forms of reasoning are frequently dismissed by policymakers as ‘uninformed gut reactions’. Yet they also form a significant part of the repertoire of scientists themselves as they proclaim the hope of new medical breakthroughs, or seek to reconstruct ideas of the body to facilitate new biotechnological transformations. Through questioning of assumptions in Habermas's notion of discourse ethics, and exploring the importance of hybridity and corporeality as concepts in ethical thinking, the author suggests that, far from being ill-formed opinions, such reasonings perform an important function for thinking through the ontological significance of the corporealisation of these proposed new forms of human and animal bodies.
Lost in Translation? Exploring the Interface between Local Environmental Research and Policymaking
Authors: Evans James P
Published: March 2006

In this paper I interrogate the relationship between environmental science and local governance in the United Kingdom. Effectively linking science and policy is critical to sustainable planning, and within the rhetoric of evidence-based policy it is often assumed that science conducted in a locality will feed linearly into the governance of that locality. This assumption is unpacked through the detailed study of an end-user-oriented environmental research project. I argue that the reproduction of separate scientific and political spheres prevented the research from being relevant to the governance of that locality. Theoretical and practical approaches to the spatialities of the research–policy interface are considered in order to politically reconstruct the local as a meaningful field of environmental governance.
Testing the Importance of the Explanatory Variables in a Mixed Geographically Weighted Regression Model
Authors: Mei Chang-Lin , Wang Ning , Zhang Wen-Xiu
Published: March 2006

A mixed geographically weighted regression (MGWR) model is a kind of regression model in which some coefficients of the explanatory variables are constant, but others vary spatially. It is a useful statistical modelling tool in a number of areas of spatial data analysis. After an MGWR model is identified and calibrated, which has been well studied recently, one of the important inference problems is to evaluate the influence of the explanatory variables in the constant-coefficient part on the response of the model. This is useful in the selection of the variables and for the purpose of explanation. In this paper, a statistical inference framework for this issue is suggested and, besides the F-approximation, which has been frequently used in the literature of the geographically weighted regression technique, a bootstrap procedure for deriving the p-value of the test is also suggested. The performance of the test is investigated by extensive simulations. It is demonstrated that both the F-approximation and the bootstrap procedure work satisfactorily.
Material Connectivity, the Immaterial and the Aesthetic of Eating Practices: An Argument for How Genetically Modified Foodstuff Becomes Inedible
Authors: Roe Emma J
Published: March 2006

Concern about eating biotechnologically produced foodstuffs is embedded within the complex relationship between food, science, politics, and everyday eating practices. In this paper I consider how this concern is expressed less at the reflexive level of opinions and attitudes and more at the nonreflexive level of eating practices. Therefore, I draw upon literatures that talk of a practical everyday aesthetic and literatures that assert the significance of the material to geographical work, and go on to argue for the significance of a material connective aesthetic within eating practices. This argument is developed empirically and theoretically by considering to what extent consumers can discuss the edibility of different types of carrots in terms of superficial material qualities, integral material qualities, and the immaterial. Crucially, the process of edibility formation is thus understood as relationally embedded in the material environment. This provokes a realisation for an ethics and a politics of (im)material connectivities. This work contributes to geographical work in which an embodied affective ethic is employed, by arguing that the transversal qualities of the material are as significant as the transversal qualities of ‘affect’. It is relevant to those studying consumption, biogeographies, and nonreflexive practices.
Invited Review. Understanding and Controlling Radical Polymerization
Authors: Moad G , Solomon DH
Published: March 2006

The present state of our understanding of the mechanism of radical polymerization is summarized. The scope for control over the polymerization process so as to obtain predictable microstructure and reaction kinetics as well as optimal polymer properties is discussed and, where possible, illustrated by examples from current research.
Zinc(II)-Chloride Complexes in Acetonitrile-Water Mixtures
Authors: Clare BW , Hefter G , Singh P
Published: March 2006

Equilibrium constants for the formation of ZnCln2-n complexes have been measured in some acetonitrile ( MeCN )-water mixtures ranging from 0 to 100% MeCN at 25°C and I = 0.1 M (Et4NClO4), by potentiometric titration. The equilibria shift strongly in favour of the formation of the higher-order complexes (n = 3, 4) at high MeCN concentrations. This is shown to be due to differences in the magnitude of unfavourable solvation of the Zn2+, Cl - and ZnCln2-n ions in MeCN-H2O solutions. The Gibbs free energies of transfer of all of these ions from water to MeCN-H2O mixtures are strongly positive, but the net change in the transfer function for the formation of the higher-order complexes is favourable. Thus the formation of these complexes is predominant in MeCN -rich aqueous solutions. Approximate measurements in propiononitrile indicate that the ZnCln2-n complexes are even stronger than in acetonitrile.
Ligand Exchange and Redox Reactions of Chromium(V): Isolation of the Chromium(V) Oxalato Complexes From the Ligand Exchange Reaction of Bis[2-ethyl-2-hydroxybutanoato(2-)]oxochromate(V) With Oxalate in 50% Aqueous Acetic Acid
Authors: Bramley R , Farrell RP , Ji JY , Lay PA
Published: March 2006

The moderately stable
chromium(v) complex, trans-bis[2-ethyl-2-hydroxybutanoato(2-)] oxo -chromate(v), [Cr( ehba )2O]- (1), has been assessed for its suitability as a synthetic intermediate for the
preparation of other chromium(v) complexes. This complex undergoes a ligand exchange reaction with excess oxalic acid to form an equilibrium mixture of chromium(v) complexes which have been assigned the structures [Cr( ehba )2O]-, [Cr( ehba )(ox)O]- (2), [Cr(ox)2O]- (3) and cis -[Cr(ox)2(OH2)O]- (4). The products of the ligand exchange reaction were characterized by a combination of u.v ./visible spectroscopy, e.p.r . spectroscopy and electrochemistry. The equilibrium mixture of chromium(v) complexes decays to
form chromium(III) products by a redox reaction which is much slower than the initial ligand exchange reaction. The difference in the rates of ligand exchange and subsequent reduction allows the extraction of the chromium(v) ligand exchange products into dichloromethane. n.m.r. spectroscopy and electrochemical techniques were used to identify these products. Under appropriate conditions (high oxalic acid concentrations) the major species extracted are the bis [ oxalato (2-)] oxochromate (v) complexes which have been isolated as oily solids in relatively pure form (≥90% pure) for the first time. n.m.r. spectroscopic evidence indicates that the isolated solid was a mixture of (3) and (4) which explains the difficulty encountered in crystallizing the solid. These ligand exchange reactions may be of general utility in the synthesis of chromium(v) complexes.
The Preparation and Characterization of Substituted Pentaphenylcyclopentadienyl Ligands, Their Precursors, and Complexes of Iron
Authors: Field LD , Ho KM , Lindall CM , Masters AF , Webb AG
Published: March 2006

The synthesis and characterization by infrared, 1H and 13C n.m.r . and mass spectroscopy of the compounds C5Ph4(p-C6H4R)X (R = H, Me, Et, But; X = OH, Br, H), C5Ph4-n(p-C6H4Me)nO (n = 1, 2, 4), C5Ph5-n(p-C6H4Me)nX (n = 2, 3; X = OH, Br) and C5Ph4(p-C6H4R)Fe(CO)2Br (R = H, Me, Et, But) are described.
Potential Antimalarials. IX. Di-mannich Bases of 4-(7′-trifluoro-methylquinazolin-4′-ylamino)phenol and 4-(7′-Trifluoromethylquinolin-4′-ylamino)phenol
Authors: Barlin GB , Jiravinyu C
Published: March 2006

Syntheses are reported for a series of di-Mannich bases of 4-(7′-trifluoromethylquinazolin-4′-ylamino)phenol derived from 4-chloro-7-trifluoromethylquinazoline with the di-Mannich bases of 4-aminophenol. Some analogous quinolines were prepared similarly. When tested for antimalarial activity against Plasmodium falciparum in vitro, the quinazolines were rather less active than the corresponding quinolines.
The Total Synthesis of (±)-cis-trans-Trikentrin A
Authors: Macleod JK , Monahan LC
Published: March 2006

The synthesis of the title compounds, which are novel cyclopent [g] indoles isolated from a marine sponge Trikentrion flabelliforme, is described. An aryl radical cyclization and a 1,5-electrocyclic reaction of a nitrene are key steps in formation of the two five- membered rings.
Approaches to the Synthesis of 5-Benzylidene-2-imidazolin-4-ones
Authors: Prager RH , Tsopelas C
Published: March 2006

Aromatic aldehydes , but not ketones, can be condensed with glycocyamidine . The corresponding alkylbenzylideneglycocyamidines may be made from glycidic esters by reaction with guanidine, followed by cyclization with acetic anhydride. A number of mono- and di -acetylated derivatives of 6,7-dihydropyrrolo[2,3-c]azepine-4,8(1H,5H)- dione have been prepared, but failed to undergo the Darzens reaction. Bromo- and iodo-2-arylazoimidazoles, protected on nitrogen by the methoxyethoxymethyl group, failed to undergo clean lithiation.
The Chemistry of Pyrrolic Compounds. LXII. The Oxidative Cyclization of Bilenes-b: Identification of the Expelled Carbon Fragment
Authors: Atkinson EJ , Brophy JJ , Clezy PS
Published: March 2006

Oxidative cyclization of the 1,19-dibenzylbilene-b salt (12) with copper(II) acetate in acetic acid/methanol yielded the expected meso-phenylporphyrin (13). Careful examination of the by-products by g.l.c./m.s , revealed the presence of benzyl acetate, indicating the fragment excluded was lost at the alcohol oxidation level. When trifluoroacetic acid was present in the cyclization mixture benzyl trifluoroacetate was the only fragment identified. Heating the meso-phenylporphyrin (13) yielded the cyclic ketonic porphyrin derivative (14).
Crystal Structures of the Selenate Alums CsM[SeO4]2.12H2O (M = Al, Cr, Fe, Rh or In)
Authors: Armstrong RS , Beattie JK , Best SP , Braithwaite GP , Delfavero P , Skelton BW , White AH
Published: March 2006

Structure determinations ofthe alums CsM[SeO4]2.12H2O have been carried out for M =aluminium(III), chromium(III), iron(III), rhodium(III) and indium(III). Structures of the cubic crystals, space group Pa3, were determined at 295(1) K. For Al, Cr, Fe, Rh and In, respectively, crystals with a = 12.544(3), 12.575(3), 12.615(5), 12.532(7) and 12.694(6)Ǻ gave 568, 561, 556, 566 and 269 independent reflections which refined to R = 0.040, 0.041, 0.051, 0.031 and 0.027. The compounds belong to the α alum structural class, in contrast to the caesium sulfate alums of aluminium, chromium, iron and indium, which have the β alum structure. This difference between the α and β alum structures does not affect the MIII-O bond length.
The Rearrangement in the Molecular Ion of 2-(2′-Methoxyphenyl)benzoic Acid
Authors: Gillis RG , Porter QN
Published: March 2006

The molecular ion of 2-(2′-methoxyphenyl)benzoic acid, formed by electron impact at 70 eV , loses CH3O*, CH3OH and other small fragments presumably from the syn conformation. It also gives rearrangement ions at m/z 94, C6H6O, and at m/z 135, C8H7O2, in which part of a functional group in one ring has been transferred to the other ring. To identify the rings, the one that contained the methoxy group was labelled with bromine. The bromine atom was lost from many fragment ions in the 70-eV mass spectrum, but the 10-eV spectrum provided sufficient evidence to propose a mechanism for the rearrangement which occurs in the anti conformation of the molecular ion. Hydrogen-deuterium exchange between labelled functional groups appears to proceed normally.
A One- and Two-Dimensional 1H and 13C N.M.R. Study of Some Lichen Triterpenoids of the Pyxinol Group
Authors: Wilkins AL , Elix JA , Whitton AA
Published: March 2006

A complete assignment of the 13C and 1H n.m.r. resonances of the lichen triterpenoids, pyxinol, 3,25-di-O-acetylpyxinol and 3,12,25-tri-O-acetylpyxinol has been achieved by using a combination of one- and two-dimensional n.m.r. data and T1 values. Hydrogen bonding between the 12β- hydroxy group and the carbonyl oxygen of the 25-acetoxy group of 3,25- di-O-acetylpyxinol leads to the furan ring system adopting a� conformation different from that adopted by 25-hydroxy analogues, hence differing chemical shifts are observed for some of the carbons of rings C and D and the furan ring.
The Structure of the Lichen Depsidones Fulgidin and Isofulgidin
Authors: Birkbeck AA , Sargent MV , Elix JA
Published: March 2006

The depsidone isofulgidin (1) (2,4,7-trichloro-3-hydroxy-8-methoxy-1,6-dimethyl-11H-dibenzo-[ b,el [1,4]dioxepin-11-one), has been isolated from the lichen Rinodina dissa together with atranorin and diploicin (3). lsofulgidin (1) has also been detected in the lichens Hafellia parastata and Fulgensia canariensis. The structure of the isomeric lichen depsidone fulgidin has been established as 2,4,9-trichloro-3-hydroxy-8-methoxy-1,6-dimethyl-11H-dibenzo[ b,e ][1,4]dioxepin-11-one (4) by unambiguous synthesis.
The Synthesis of Cyclohexane-1,3-diones Bearing an Isoxazoline or a Dihydro-1,2-oxazine Ring at C2
Authors: Best WM , Brown RFC , Tiso PD , Watson KG
Published: March 2006

Dimedone (6) was C-acylated with 4-(1′-methylethylideneaminooxy) butanoic acid (7), and the product (8) was hydrolysed to give 2-(5′,6′-dihydro-4′H-1′,2′-oxazin-3′-yl)- 5,5-dimethylcyclohexane-1,3-dione (3). The 2-(4′,5′-dihydroisoxazol-3′-yl) 1,3-dione (4) was obtained in <2% yield from dimedone anion and 3-nitro-2-isoxazoline (11).
The Alkaloids of Picrasma javanica: Further Studies
Authors: Arbain D , Byrne LT , Sargent MV , Skelton BW , White AH
Published: March 2006

The structures of two β- carboline alkaloids previously isolated from Picrasma javanica Bl . ( Simarubaceae ) are revised to 1-ethenyl-4-methoxy-9H-pyrido[3,4-b]indol-8-ol (8-hydroxydehydrocrenatine) (5) and 1-ethyl-4-methoxy-9H-pyrido[3,4-b]indol-8-ol (8-hydroxycrenatine) (6), chiefly on the grounds of a single-crystal X-ray structural determination of the former compound.
The Alkaloids of Margaritaria indica (Euphorbiaceae). The Crystal Structure and Absolute Configuration of the Hydrobromide of (+)-15α-Methoxy-14,15-dihydrophyllochrysine
Authors: Arbain D , Byrne LT , Cannon JR , Engelhardt LM , White AH
Published: March 2006

(-)-Phyllochrysine (1), (-)-securinine (2) and a new alkaloid (+)-15α-methoxy-14,15-dihydrophyllochrysine (3) have been isolated from both the bark and roots of Margaritaria indica ( Dalz .) G. L. Webster. The structure and absolute configuration of (3) follow from its spectroscopic properties and its synthesis from (-)- phyllochrysine (1) as well as from the crystal structure of its hydrobromide, obtained by X-ray diffraction. Diffractometer data at 295 K were refined by least-squares techniques to a residual of 0.053 (991 'observed' reflections). Crystals of 15α-methoxy-14,15-dihydrophyllochrysine hydrobromide are orthorhombic, P212121, a 14.324(3), b 14.194(3), c 7.240(2)Ǻ, Z 4.
A Potentiometric Study on Proton-Transfer Equilibria and Cationic Conjugation in Pyridine N-Oxide Systems in Acetone and Methanol
Authors: Chmurzynski L , Kaczmarczyk E , Nesterowicz M , Wawrzyniak G , Warnke Z
Published: March 2006

The potentiometric titration method has been used to study the equilibria of cationic in sytems formed by substituted pyridine N-oxides in the polar, non-aqueous solvents acetone and methanol. For comparison, the systems with trimethylamine N-oxide as a representative of aliphatic amine N-oxides and pyridine representing parent heterocyclic amines were also studied. The cationic heteroconjugation constants, i.e. the equilibrium constants for conjugation reactions between free and protonated N-bases leading to the formation of unsymmetric BHB'+ cations, were determined in experimental systems with and without proton transfer. It was found that there were significant differences in the values of the cationic heteroconjugation constants determined in these two acid-base systems. The proton-transfer reactions limit and even preclude the determination of the cationic heteroconjugation constants. On this basis it was concluded that the heteroconjugation constants should be determined in systems without proton transfer. In such systems, in the amphiprotic solvent methanol, cationic heteroconjugation was ascertained in all substituted pyridine N-oxide systems, the values of heteroconjugation constants being relatively low (logarithms of their values of the order of 2-2.5), and only negligible in systems involving trimethylamine N-oxide. A more pronounced tendency towards cationic heteroconjugation of the [OHO]+ type was observed in the aprotic protophobic acetone, where heteroconjugation constants were determined for all amine N-oxide systems studied including those containing protonated trimethylamine N-oxide as a proton donor. However, the values of the cationic heteroconjugation constants were found to be, in methanol likewise, relatively low (log KBHB'+ of the order of 2-3). On the contrary, a greater extent of cationic heteroconjugation equilibria was observed in methanol than in acetone in the case of systems containing pyridine, i.e. [NHO]+ type bridges formed by amine N-oxides and heterocyclic amines. In methanol the heteroconjugation constants turned out to be determinable for all such systems studied (logarithms of the equilibrium constants being of the same order as for N-oxide systems), whereas in acetone the hetero constants were indeterminable for all systems.
The Molecular Structure of (Bicyclo[3.3.1]nona-2,6-diene)dichloropalladium(II)
Authors: Woolcock J , Niederhut M , Craven BM
Published: March 2006

The molecular structure of (C9H12)PdCl2 in solution has been studied by two-dimensional n.m.r. spectroscopy, and the crystal structure has been determined. The spectroscopic results support earlier conclusions that in solution the Pd-diene interactions involve non-equivalent carbon atoms at each of the equivalent ethenic centres. The crystals are disordered with respect to the atoms of the eight-membered ring. The molecule has point symmetry 2 and is chiral. However, in the crystal structure, the molecules are in the special position with symmetry m2m in the orthorhombic space group Cmcm. Thus right- and left-handed molecules randomly occupy the same site. Full-matrix least-squares refinement with all 485 reflections (dmin = 0.85 Ǻ, Mo Kα radiation) measured at ambient temperature gave R(F) = 0.047 and Rw(F) = 0.038 for 430 reflections with F2 > 2σ. The distance Pd-Cl is 2.300(3) Ǻ. The short Pd-C2 and Pd-C3 distances (2.223 and 2.245 Ǻ, respectively) differ by only 1.2σ. However, the ethenic carbon atoms are non equivalent since C2 is considerably closer to the PdCl2 plane than C 3 (0.43 v. 0.99 A). The shortest distance between disordered sites for superposed molecules is 0.61 Ǻ. The corresponding platinum(II) complex is isomorphous and is disordered in the same way.
The Structural Basis of the Fluorite-Related Rare Earth Higher Oxides
Authors: Kang ZC , Eyring L
Published: March 2006

In this paper phenomenological structural principles, and rules for their application are advanced for predicting the ideal structures of the higher oxides of the rare earths that (1) establish a generic formula incorporating all known phases, (2) guide the correct modeliing of the established structures of members, (3) demonstrate that structures previously proposed but proven incorrect do not follow the structural principles, (4) predict the structures not yet established for known phases, including polymorphs, (5) provide rationalization for phases fitting the generic formula that have not yet been found. The structural principles flow naturally from the fluorite substructure characteristic of all established phases.
The Rare Earth(III) Nitrate Dimethyl Sulfoxide Adducts [( dmso )nLn(O2NO)3]
Authors: Semenova LI , Skelton BW , White AH
Published: March 2006

Adducts [( dmso )nLn(O2NO)3], obtained by the crystallizatior , of lanthanoid (III) nitrate ( Ln (NO3)3.-xH2O) with excess dimethyl sulfoxide (' dmso ') in methanol or ethanol, have been the subject of a series of room-temperature single-crystal X-ray studies, defining more clearly the manner in which stoichiometry and structure systematically vary with change in metal ion radius. All complexes studied are mononuclear, the metal ion being complexed by three bidentate nitrate ligands and a number of dmso ligands , four for La-Sm and three beyond. The array La- Sm is monoclinic C2/c, a ≈ 14.9, b ≈ 15.5, c ≈ 15.5 Ǻ, β ≈ 108.4°, Z = 4 f.u .; the metal atom is disposed on a crystallographic 2 axis, which also passes through one of the nitrate groups. The series Eu -Tm (inclusive also of Y) is monoclinic, P21/n, a ≈ 11.5, b ≈ 12.7, c ≈ 13.6 Ǻ, β ≈ 100°, Z = 4 f.u ., while Yb and Lu are also monoclinic, P21/c, a ≈ 10.0, b ≈ 12.6, c ≈ 16 Ǻ, β ≈ 100.6°, Z = 4 f.u.
Double Non-Stoichiometry: The Lithium Vanadium Oxide Bronzes βLixV2O5-y
Authors: Galy J , Galy J , Savariault JM , Savariault JM , Roucau C , Roucau C
Published: March 2006

The β (or β') LixV2O5 phases lose oxygen at high temperature, the approximate formula LixV2O5-y, leading to the formation of phases LixV6O15 LixV9O22 and LixV12O29. A general formula is proposed to relate this series, LixV3(1+n)O8+7n, to the corresponding n values of 1, 2 and 3. In fact, n, as an integer, can be formally varied in the range 0 ≤ n → ∞. Their crystal structures are derived by a structural mechanism based on extended Wadsley defects, denoted 1/10[051](100), affecting the LixV6O15 structure. Numerous syntheses performed in the Li2O-V2O5-V2O4 ystem have revealed that no intergrowth structure occurs between the n values 1-2 and 2-3, while, for n > 3, a defect structure has been evidenced by high resolution electron microscopic investigations. The LixV12O29-є phase is depicted as an intergrowth of the structure of the n = 4 member, i.e. LixV15O36, in the sequence of the LixV12O29 crystal structure. In a general discussion, the structural relationships between these phases are particularly emphasized, extended defects crossing tunnel structures being rather unusual.
On the flushing of Port Phillip Bay: an application of HF ocean radar
Authors: Prytz A. , Heron M. L.
Published: March 2006

HF ocean radar can produce maps of surface current in coastal ocean and
estuarine waters by providing coverage in both the space and time dimensions.
The deployment of COSRAD in Port Phillip Bay for two successive five-day
periods provided hourly values of surface currents over the topographically
complex area at the south end of the bay. Analysis of the current data
provided tidal ellipses for the validation of numerical models, with resultant
residual currents of the order of 0·05 m
s–1. The repeated hourly maps were the basis for
producing Lagrangian tracks; most tracks resulted in trapped paths which
remained for long periods of time in the matrix of channels and sand-banks. A
‘tidal run’ technique was developed to calculate the length of
Lagrangian tracks over one phase (ebb or flood) of the main tidal component.
All tidal runs were about equal to, or shorter than, the length of the
relevant channel; this indicates that tidal forcing is not effective in
flushing the bay. In contrast, the observed residual currents can be an
effective flushing agent if they persist for three days or longer. It is
suggested that phenomena on the scale of meteorological to seasonal forcing
are the effective flushing agents for Port Phillip Bay.
Causes of observed temporal variability of nutrient fluxes from a southern Australian marine embayment
Authors: Nicholson Geoff J. , Longmore Andy R.
Published: March 2006

Benthic chambers were used to measure temporal differences of
sediment–water column flux of dissolved oxygen (DO), ammonium, nitrite
plus nitrate, phosphate, silicate and total carbon dioxide
(TCO2) in Port Phillip Bay. Three clear and three dark
benthic chambers were deployed between October 1994 and January 1996 at each
of three sites: near the outflow of a major sewage treatment plant, near the
mouth of a river and in the deep centre of the bay. Analysis of variance
indicated that chamber type did not significantly affect magnitude of flux for
the majority of deployments. Water temperature at the time of deployment had a
significant effect on the fluxes of DO, TCO2 ,
NH4 , and SiO4 at the central bay
site and for all fluxes at the other two sites. There was a relationship
between TCO2 flux in the sediment and C production in
the water column (r2 =
0.6552). The denitrification efficiency at the central bay site was usually
>80% at all times, and altered by ~30% seasonally at the
other two sites. It is likely that the effect of water temperature on a suite
of biological processes is the predominant source of temporal variation in
these benthic fluxes.
Heavy metals in waters and sediments of Port Phillip Bay, Australia
Authors: Fabris G. J. , Monahan C. A. , Batley G. E.
Published: March 2006

Despite significant inputs of heavy metals from rivers, creeks and drains and
a major sewage treatment plant to Port Phillip Bay, Victoria, Australia,
attenuation processes in the water column are such that metal concentrations
in the bay waters are comparable to uncontaminated estuaries elsewhere in the
world. Sedimentation appeared to be largely responsible for metal removal,
with strong correlations between particulate metals and iron in input waters
sampled over a storm event. Storm events contributed between 9 (Zn) and 21
(Cr) times the metal loads that enter the bay during low flow conditions.
Although metal accumulations in sediments are below guideline concentrations
in the major deposition zones, they are highest close to input sources. A
unique feature of bay waters was the high concentration of dissolved arsenic
(2.8 µg L–1). The source appears to be
natural sediment mineralogy, and sediment cores were found to be depleted in
arsenic near the sedimentŒwater interface. Overall, the findings
suggested that current heavy metal inputs do not represent a threat to the
health of the bay.
Nutrient fluxes measured by two types of benthic chamber
Authors: Nicholson G. J. , Longmore A. R. , Berelson W. M.
Published: March 2006

Comparisons were made between benthic nutrient fluxes in a shallow marine
embayment measured by a sophisticated automated benthic chamber device and a
much simpler design. Both devices have similar chamber dimensions. The
sophisticated design can be deployed by line from a vessel, incorporates an
sealed waterproof computer, uses one chamber and all operations are fully
programmable; dissolved oxygen concentrations are electronically monitored
every 6 min and stored by the computer. The simpler design incorporates three
opaque and three clear chambers per site to investigate small-scale sediment
differences and the effect of benthic photosynthetic production on fluxes;
dissolved oxygen concentrations are electronically monitored every 10 min.
within all chambers and stored in a data logger; the deployment and recovery
and sampling operations other than for DO require the use of divers. Except
where sediments differ greatly over a few metres, both chamber devices deliver
similar results and indicate the consistency of the technique regardless of
the design. The simpler design is limited by the need for diver deployment and
sampling. An automated chamber array is recommended as the best way of
measuring ‘patchy’ sediments
Assessment of the sources, transport and fate of sewage-derived organic matter in Port Phillip Bay, Australia, using the signature lipid coprostanol
Authors: Volkman John K. , O'Leary Teresa , Leeming Rhys , Nichols Peter D. , Volkman John K.
Published: March 2006

To evaluate the distribution of faecal material in Port Phillip Bay, surface
sediments from sites throughout the bay and inflowing water courses were
analysed for fatty acids and sterols. Water samples were also collected to
identify possible sources of faecal contamination. Bay sediments had total
fatty acid concentrations between 4 and 183 µg
g–1 (dry weight) and total sterol concentrations
between 0.6 and 39.2 µg g–1. Creek sediments
contained more sterols, ranging from 22.8–148 µg
g–1. These lipid distributions suggest that the
bulk of the labile organic matter derives from marine microalgae, primarily
diatoms. Coprostanol (5β-cholestan-3β-ol), a sterol often used as an
indicator of faecal contamination, was also present. Concentrations ranged
from <0.01–0.55 µg g–1 in surface
sediments, with values over 0.25 µg g–1 and
5β-/5α-C27 stanol ratios greater than 0.4,
indicative of sewage inputs. A clearer picture of distributions of
sewage-derived organic matter was obtained when coprostanol was normalized to
total organic matter rather than sediment dry weight. Areas showing higher
coprostanol concentrations included those adjacent to the main sewage
treatment plant and several low-volume drains and creeks, indicating localized
problems of sewage contamination.
Use of excess 210Pb and 228Th to estimate rates of sediment accumulation and bioturbation in Port Phillip Bay, Australia
Authors: Hancock G. J. , Hunter J. R.
Published: March 2006

Rates of sediment accumulation, sediment mixing and depositional particle
fluxes were estimated by use of excess 210Pb and
228Th. In central Port Phillip Bay, there was a rapidly
mixed surface layer and two layers of different mixing rates at 2–20 cm
and 21–45 cm depths. When the sediment profiles of excess
210Pb and 228Th were combined and
diffusive mixing was assumed, the sediment accumulation rate in the 2–20
cm layer was constrained to be <0.15 cm year–1.
The mixing coefficient in the 2–20 cm layer was 5.0 ± 0.1
cm2 year–1. Hence, mixing
rather than sedimentation governs the distribution of
210Pb and 228Th in the surficial
20 cm. Below 20 cm, the different mixing regime may be due to the dominance of
deposit-feeders at these depths. Evidence for bioturbation to a depth of 50 cm
was obtained from profiles of excess 210Pb and
228Ra deficiency. The mean residence time of particles
in the central bay water column was 10 ± 2 days (a normalized
depositional particle flux of 0.16 ± 0.02 g
cm–2 year–1). This
flux is three times the upper estimate of the sediment accumulation rate,
indicating that most of the suspended particulate matter in the water column
is resuspended bottom sediment.
Denitrification and denitrifying efficiencies in sediments of Port Phillip Bay: direct determinations of biogenic N2 and N-metabolite fluxes with implications for water quality
Authors: Heggie David T. , Skyring Graham W. , Orchardo Joseph , Longmore Andrew R. , Nicholson Geoffrey J. , Berelson William M.
Published: March 2006

High-precision measurements of N2 in benthic chamber
waters indicated that denitrification occurs within the major sedimentary
facies in Port Phillip Bay. The integrated fluxes of biogenic
N2 , ammonia, nitrate and nitrite showed that the
stoichiometric relationship between organic C and N in the muddy sediments,
occupying about 70% of the seafloor, was 5.7, this being similar to the
Redfield ratio of 6.6. High denitrifying efficiencies (75–85%;
denitrification rates ~1.3 mmol N2
m–2 day–1) at organic
carbon loadings of ~15–25 mmol m–2
day–1 indicate that most N processed through the
sediments was returned to the overlying waters as biologically (generally)
unavailable N2. At sites of high organic carbon loadings
to the sediments (>100 mmol m–2
day–1) denitrification rates and denitrifying
efficiencies were near zero and most N is returned to the Bay waters as
biologically available ammonium. In chambers ‘spiked’ with
15NO3 , denitrifyers used nitrate
produced in the sediments in situ, rather than the exogenous nitrate in
overlying waters. The sedimentary microbial processes of ammonification,
nitrification and denitrification are therefore tightly coupled.
Molecular diffusive fluxes of oxygen in sediments of Port Phillip Bay in south-eastern Australia
Authors: Burke Christopher M.
Published: March 2006

Port Phillip Bay is a large, shallow, semi-enclosed bay in south-eastern
Australia. Micro- electrodes were used to measure profiles of oxygen
concentration in sediment cores taken from nine sites in the bay in January
and February 1994. The effects of sediment surface topography, flow rate of
the overlying water and irradiance on the distribution of oxygen in the
sediments, and on the molecular diffusive fluxes of oxygen, were determined.
Oxygen typically penetrated ≤3 mm into the sediment. Deeper penetration
occurred when oxygen was photosynthetically produced
in situ. In most cores the sediments consumed oxygen.
Molecular diffusive fluxes of oxygen, determined from the gradient of oxygen
in the DBL, were compared with fluxes modelled from the sediment gradient of
oxygen. The modelled diffusive fluxes are considered to give better estimates
of the diffusive fluxes in situ. Modelled fluxes ranged
from 1.5 to 28.5 mmol O2 m–2
day–1, which was 43% (s.d. =
36%, n = 16) of the total flux at each
site. Cores from two sites demonstrated efflux of oxygen, up to 71 mmol
O2 m–2
day–1, as a result of photosynthesis
in situ. The high degree of variability in oxygen fluxes
within cores demonstrates the dynamism of oxygen cycling in these sediments.
Uptake of ammonium by four species of macroalgae in Port Phillip Bay, Victoria, Australia
Authors: Campbell Stuart J.
Published: March 2006

The uptake rates of ammonium were determined for three species of native
macroalgae and an exotic macroalga from Port Phillip Bay. All species
exhibited rate-saturated mechanisms of uptake described by
Michaelis–Menten uptake kinetics. At the highest concentration examined
(28.6 µmol NH4-N)
Hincksia sordida had a higher rate of uptake (435
µmol NH4 -N g dry wt–1
h–1) than Ulva sp. (108
µmol NH4-N g dry wt–1
h–1) or
Polysiphonia decipiens (53 µmol
NH4 -N g dry wt–1
h–1). Maximum surge uptake rate was highest for
H. sordida and lowest for
P. decipiens (802 and 57 µmol
NH4 -N g dry wt–1
h–1 respectively). The introduced phaeophyte
Undaria pinnatifida had an intermediate capacity for
ammonium uptake which was dependent on blade maturity. Differences in the
ratio of maximum uptake rate to half-saturation rate between surge and
assimilation uptake phases suggest a propensity for some species to take up
ammonium at low concentrations. The relationships between nutrient uptake and
growth among species would afford mature U. pinnatifida,
H. sordida and Ulva sp. a
competitive advantage for ammonium uptake in winter during high N
availability, whereas P. decipiens would be able to
exploit low N concentrations in spring and summer.
Effect of burrowing macrobenthos on the flux of dissolved substances across the water - sediment interface
Authors: Ford Phillip W. , Bird Fiona L. , Hancock Gary J.
Published: March 2006

The effect of burrowing activities of ghost shrimp
(Neocallichirus limosus and
Biffarius arenosus) and heart urchin
(Echinocardium cordatum) on the flux of dissolved
substances across the water–sediment interface was examined by comparing
the transport of the tracer deuterium oxide (D2O)
between sediments and overlying water in experimental laboratory tanks with
and without fauna. This experiment was complemented by measurements of the
diffusive flux of naturally occurring isotopes of radium
(224Ra and 223Ra) from the
sediments into the water column. Despite different burrowing habits, all three
species enhanced flux of D2O and the Ra isotopes by
similar amounts. In sandy sediments, both shrimps and urchins enhanced flux of
D2O across the water–sediment interface 2.5 fold.
In muddy sediments, however, results were inconclusive. There was little
difference in flux of 224Ra and
223Ra between muddy and sandy sediments; flux was
2.3–3.9 times higher in the presence of the burrowing species than in
their absence. These findings emphasize (i) the
important role of burrowing macrofauna in the transport of dissolved
substances between the sediment and water bodies and
(ii) the dependence of various biogeochemical processes,
including nutrient release, on the benthic macrofauna of Port Phillip Bay.
Long-term prediction of water quality for three types of catchment
Authors: Sokolov Serguei , Black Kerry P.
Published: March 2006

A simple dynamic model relating the temporal change of the total mass of
chemicals in a catchment to the chemical loading in the river provides
high-accuracy predictions of absolute and time- integrated chemical loads. The
developed model is able to reproduce effectively and simultaneously for all
considered time scales the observed hysteresis in the relationship between
chemical concentration in stream water and river discharge. Three types of
catchment have been examined for long-term modelling: a local urban
streamwater catchment, a transition urban–agricultural catchment and a
large catchment with varied land use (urban, agricultural and protected
forested areas). The long-period changes in model parameters and in
water-quality variables are determined for each catchment.
Coupled hydrodynamic and transport models of Port Phillip Bay, a semi-enclosed bay in south-eastern Australia
Authors: Walker S. J.
Published: March 2006

Coupled hydrodynamic and transport models of Port Phillip Bay were developed
as part of the Port Phillip Bay Environmental Study. Model coupling was
achieved via a particle tracking method, giving great flexibility in both
geometry and time step for the transport model. This technique allowed
ecological (water quality) modules to be included efficiently, so that
long-term management scenarios could be adequately addressed. Validation of
the hydrodynamic model was done primarily against observed sea-level and
current meter data. For the transport model, comparisons were made with data
on salinity in the bay observed over five years. Despite some disagreement
between the hydrodynamic model and observations of longer-term (non-tidal)
currents, the transport model provided good simulations of salinity throughout
the bay. Transport-model flushing time for the bay was about 270 days (similar
to estimates obtained from salinity and radionuclide measurements), varying
with model geometry and with position inside the bay. As well as providing
physical forcing for ecological simulations (described elsewhere in this
issue), the models identified a systematic bias in the known freshwater budget
for the bay.