bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quantum Chemical Studies of Neutral and Ionized DyX, DyX2, and DyX3 Species (X = F, Cl, Br, I) and the Implications for the Mass Spectra of Gaseous DyX3
Authors: Saloni Julia , Roszak Szczepan , Hilpert Klaus , Miller Mirosław , Leszczynski Jerzy 
Published: March 2004

AbstractThe mass spectrum pattern of DyF3(g) and the appearance potentials for identified ions were measured and compared with the respective data obtained previously for DyCl3, DyBr3, and DyI3. The structural parameters, total energies, and vibrational frequencies of DyX3, DyX2, and DyX (X = F, Cl, Br, I) neutral and single ionized species were determined by quantum‐chemical studies. The theoretical appearance potentials of different ions, calculated from energies of gaseous species, are in the good agreement with the experimental data. Fragmentation energies of the DyXn+ ion, where n = 1, 2, 3, were computed and compared with the mass spectra patterns of the respective vapour species. A theoretical electron population analysis indicates the involvement of the s and f valence electrons of Dy in the bond formation as well as in the ionization processes. The σ‐back donation from halogen atoms to the dysprosium center partially compensates the electron density loss. The ionization strengthens the bonding in the DyX and DyX2 molecules. The ionization of DyX3 destroys the C3v symmetrical structure due to the Jahn−Teller effect. Contrary to the other studied systems, the open shell character of DyX3+ arises not only from unpaired electrons of dysprosium but also from electron density on halogen atoms. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
The Solid‐State Lanthanoid‐Assisted Hydrolysis of the Solvolytically “Inert” [AsF6]− Ion
Authors: Ponikvar Maja , Sedej Borka , Liebman Joel F. 
Published: March 2004

AbstractResults of elemental chemical analyses of the coordination compounds of the type LnFn(AsF6)3‐n (Ln = Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) indicated unexpectedly low stability of the generally highly hydrolytically stable [AsF6]− ion. Experiments conducted on model compounds of the type NdFn(AsF6)3‐n have shown that hydrolysis proceeded instantaneously during the reaction of the solid compound with water. The ligand substitution catalysis of the compounds is explained in terms of the distortion of the [AsF6]− octahedra earlier shown by vibrational spectroscopy. The study contrasts formally related reactions on the solid−solvent interface as opposed to those in homogeneous solution. A new look at some long studied and well‐known inorganic species is offered. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
The Construction of P−O/P−N Ligands on Platinum and Palladium
Authors: Bergamini Paola , Bertolasi Valerio , Milani Federico 
Published: March 2004

AbstractA variety of diphenyldiphosphinites have been prepared in a very stable form as PtII or PdII complexes by adding diols to a solution containing cis‐[MCl2(PPh2Cl)2] (M = Pt or Pd) preformed in situ from cis‐[MCl2(1,5‐COD)] (M = Pt; M = Pd) and PPh2Cl. This synthetic pathway can be used for diphosphinites derived from aliphatic 1,2 and 1,3 diols and also from the aromatic catechol. Besides the P−O bond, it is also shown here that the P−N bond can also be formed via nucleophilic attack of an amine group on coordinated PPh2Cl in the presence of a base resulting in some AMPP and BAMP complexes of PtII and PdII. The X‐ray crystal structures of the [cis‐1,2‐cyclohexanediyl bis(diphenylphosphinite)]platinum dichloride, of the AMPP palladium complex from (1R,2S)‐(−)‐norephedrine and of the BAMP palladium complex [P,P′‐diphenyl‐1,2‐cyclohexanediylbis(imino)bisphosphane]palladium dichloride have been determined. The chemical and optical stabilities of many complexes in solution have been monitored by 31P NMR spectroscopy. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Configuration of Octahedral Metal Compounds − Equilibrium, Crystal and Molecular Structure of Nickel(II) Complexes of Linear N2O4, N4S2 or N6 Donors Set Atoms Ligands
Authors: Mohamadou Aminou , Jubert Caroline , Gruber Nathalie , Barbier Jean‐Pierre 
Published: March 2004

AbstractTwo new nickel(II) complexes of symmetric hexadentate mixed‐ligand N,O [1,12‐bis(2‐pyridyl)‐5,8‐dioxa‐2,11‐diazadodecane (pydado)] and N,S [1,12‐bis(2‐pyridyl)‐5,8‐dithia‐2,11‐diazadodecane (pydadt)] donor atoms have been synthesised as perchlorate salts and characterised by X‐ray crystallography and ligand‐field spectroscopy. In both complexes the Ni2+ ion is hexacoordinate. The cation [Ni(pydado)]2+ is pseudo‐octahedral with the two pyridyl groups in trans position; all Ni−N and Ni−O bond lengths are practically equivalent. In [Ni(pydadt)]2+ complex, however, the size of the thioether sulfur atoms imposes a C2v symmetry; the pyridyl groups and the sulfur atoms are in trans positions and all Ni−N bond lengths are equivalent. The comparison of these structures with those of octahedral cobalt, copper and zinc complexes with the same ligands shows that their configurations depend not only on the nature of the two central donor atoms of the ligand, but also on the nature of the metallic ion. In aqueous solution, the stability constants of the NiII chelates with these two ligands, determined by potentiometry, show the formation of [Ni(LH)]3+ and [NiL]2+ species in all cases. The chelating power of the pydadt ligand is slightly greater than that of pydado. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Long Range Metal‐Metal Interactions Along Fe−NC−Ru−CN−Fe Chains
Authors: Sheng Tianlu , Vahrenkamp Heinrich 
Published: March 2004

AbstractTrinuclear complexes with linear FeII−NC−RuII−CN−FeII arrays were obtained by attachment of FeCp(dppe) units to the cyanoruthenium complexes trans‐[Ru(CN)2(Py)4] (Py = pyridine, 4‐methylpyridine, 4‐ethylpyridine) . From their cyclic voltammograms it can be concluded that there are long‐range metal−metal interactions between their external iron centers. Partial oxidation led to the isolation of the corresponding mixed‐valent FeII−NC−RuII−CN−FeIII complexes. For these the long range metal−metal interactions are evident from a broad MMCT band in the NIR spectra. The MMCT properties were quantified by an analysis using the Hush formalism. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
(μ‐Methylene)bis(methylzirconocene): Preparation, Molecular Structure, and Thermal Disproportionation
Authors: Hogenbirk Marijke , Schat Gerrit , Akkerman Otto S. , Bickelhaupt Friedrich , Schottek Jörg , Albrecht Markus , Fröhlich Roland , Kehr Gerald , Erker Gerhard , Kooijman Huub , Spek Anthony L. 
Published: March 2004

AbstractThe title compound [(μ‐CH2)(ZrCp2Me)2] (4) was prepared by the reaction of [Cp2Zr(Cl)Me] (6) with CH2(MgBr)2 (5) or (CH2Mg)n (7). It had been expected that the carbon atom bridging the two zirconium atoms of 4 might be a candidate for a planar tetracoordinate carbon atom, but the X‐ray crystal structures of two different modifications (crystals 1 and 2) showed it to be non‐planar; however, the widened Zr−C−Zr angle of 132.7(1) and 134.0(3)°, respectively, and an unsymmetrical coordination of the central μ‐CH2 group (average: Zr1−CH2 2.225 Å, Zr2−CH2 2.242 Å) indicates a tendency towards planarity. While 4 is relatively stable in THF solution, it disproportionates in toluene solution to give the 1,3‐dizirconacyclobutane (Cp2ZrCH2)2 (8) and [Cp2ZrMe2] (9), especially in the presence of magnesium salts; a tentative mechanism is presented. Reaction of 4 with B(C6F5)3 yielded the methyl‐bridged cationic complex 17, which, on treatment with trityl chloride, was transformed into the corresponding chloro complex 18; the latter was characterized by an X‐ray crystal structure determination. With THF and tetrahydrothiophene, 17 formed the unsymmetrical adducts 19a and 19b, respectively; NMR spectroscopic data revealed dynamic symmetrization due to methyl‐group exchange at 280 and 213 K, respectively. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Towards 3‐D Spherical Self‐Assembly by Ternary Surfactant Combinations: The Case of Magnetite Nanoparticles
Authors: Hou Yanglong , Gao Song , Ohta Toshiaki , Kondoh Hiroshi 
Published: March 2004

AbstractHere we report on a facile one‐step route to assemble magnetite nanoparticles into 3D‐spherical aggregates with an average diameter of 100 nm. The self‐assembly approach was achieved in a solvothermal reduction reaction with a ternary surfactant combination comprising trioctylphosphane oxide (TOPO), polyvinylpyrrolidone (PVP), and oleic acid as the “mortar”. Transmission electron microscopy (TEM) investigations indicated that the spherical aggregates were composed of magnetite nanoparticles. The mean size of the individual magnetite particles was estimated to be 6 nm, calculated by the Scherrer equation with the powder X‐ray diffraction (XRD) data. The formation mechanism of magnetite spheres can be attributed to the cooperation of the ternary surfactants described above. Magnetic measurements performed by a Quantum Design SQUID magnetometer on the nanoparticles exhibited superparamagnetic behavior above liquid‐nitrogen temperatures. Fourier‐transform infrared spectroscopy (FTIR), inductively coupled plasma‐atomic emission spectrometer (ICP‐AE) and X‐ray photoelectron spectroscopy (XPS) were also used in the characterization of the assembled magnetite spheres. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Supramolecular Host‐Guest Systems in Zeolites Prepared by Ship‐in‐a‐Bottle Synthesis
Authors: Corma Avelino , Garcia Hermenegildo 
Published: March 2004

AbstractZeolites have a microporous system defining large cavities interconnected by smaller windows. These cages can accommodate large molecules whose size, however, can be too big to cross the windows. The most important examples of these tridirectional zeolites are faujasites X and Y, but examples of other suitable zeolites are Beta, EMT and MCM‐22. The inclusion of large guests inside the cavities starts from smaller precursors that can diffuse through the zeolite pores and then react inside the cavities to form the target guest. This microreview discusses the special characterisation techniques necessary to study these systems, differentiating those that serve to assess the identity and purity of the guests from those that address the internal vs. external location of the guests with respect to the zeolite host. It is organized by grouping the examples of ship‐in‐a‐bottle synthesis according to the potential application of the system as catalysts, photocatalysts, sensors, in molecular machines, etc. Although proper credit is given to the pioneering reports on ship‐in‐a‐bottle synthesis, the emphasis is placed on the most recent examples of the literature covering up to mid 2003. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Cover Picture: Supramolecular Host‐Guest Systems in Zeolites Prepared by Ship‐in‐a‐Bottle Synthesis (Eur. J. Inorg. Chem. 6/2004)
Authors: Corma Avelino , Garcia Hermenegildo 
Published: March 2004

AbstractThe cover picture shows the results of modelling the diffusion of phthalodinitrile through the zeolite pores. Once inside, phthalodinitrile reacts to form a large phthalocyanine guest that remains entrapped inside the zeolite cavity. The resultingzeolite−guest chemistry resembles at molecular level a ship in a bottle that is a typical souvenir in many harbour cities. The zeolite‐encapsulated guest shows many promising applications as discussed in the Microreview by A. Corma and H. Garcia on p. 1143 ff.
Bioactive constituents, flavors and aromas of virgin oils obtained by processing olives with a natural enzyme extract
Authors: Ranalli Alfonso , Lucera Lucia , Contento Stefania , Simone Nicola , Del Re Paolo 
Published: March 2004

AbstractTo enhance both virgin olive oil quality and yields, a natural enzyme extract (Bioliva) was used during processing of four Italian olive cultivars (Leccino, Caroleo, Dritta and Coratina) carried out with a percolation‐centrifugation extraction system. This biological formulation is essentially made up of natural enzyme species capable of degrading the major constituents of the vegetal cell membrane, such as pectin and cellulose. The oils of the second extraction (centrifuged oils), considered in this work, were fully characterized. The enzyme effects resulted in an enhanced incorporation of minor components (phenols, tocopherols, volatiles, carotenes, xanthophylls and chlorophylls) into the oil phase with consequent significant improvement of the analytical parameters related to typicality, flavor and shelflife. No significant modifications concerning triacylglycerols, fatty acids, and non‐glycerol compounds mainly related to genuineness were observed. A significant improvement of the oil outputs and the features of by‐products was also achieved. Another important outcome to be highlighted is the lower values concerning the emulsified fat, suspended solids, dry matter and COD (chemical oxygen demand) characterising the liquid effluent (olive juice).
Influence of oil conditioning on the permeate flux and cake properties during microfiltration of lampante olive oil
Authors: Hafidi Abdellatif , Pioch Daniel , Teyssier Marie‐Laure , Ajana Hamid 
Published: March 2004

AbstractThis work studies the deacidification of lampante virgin olive oil (acidity ranging from 2.15–4.65%) by microfiltration through alumina membrane. The effects of (i) the amount of absorbed water during the neutralization of the free fatty acids with various NaOH concentrations, and (ii) the acid pre‐treatment with phosphoric acid on permeate fluxes during microfiltration were studied. Physical properties of the cake (specific resistance and compressibility) were also investigated. The soap molecules are known to self assemble and form multilamellar vesicles with hundreds of bilayers entrapping water molecules between the polar groups. Swelling and deformability of such structures must be influenced by the amount of solubilized water. Our results show for all tested oils that a dilute NaOH solution (20%) allows the highest flux through the membrane, i.e. about 3‐fold the flux resulting from 40%‐NaOH treatment. The improvement of the initial fluxes reached approximately 300% in comparison with those obtained with more concentrated NaOH solutions, whereas the use of a more diluted solution (10% NaOH) caused a loss of separation efficiency. The addition of 0.1% (wt/wt) of phosphoric acid prior to neutralization results in further flux improvement especially at the beginning of filtration. The initial fluxes doubled when passing from 0–0.05% H3PO4 and then, in case of 20% NaOH to 0.1%. The average cake‐specific resistance was the highest in the case of neutralization with 30% NaOH and the lowest when coupling 0.1% H3PO4 pre‐treatment with 20% NaOH neutralization. In the latter case the cake showed a highly compressible behavior.
Oil extraction from almond, apricot and rice bran by three‐phase partitioning after ultrasonication
Authors: Sharma Aparna , Gupta Munishwar Nath 
Published: March 2004

AbstractThree‐phase partitioning has been evaluated for extraction of oil from 3 different plant sources, namely almond, apricot and rice bran. After treatment of the slurries for 2, 4 and 6 min by ultrasonication followed by three‐phase partitioning, 87, 77 and 88% (wt/wt) oil was extracted within 1 h. The process required simultaneous addition of t‐butanol and ammonium sulphate to the slurries.
Effects of fish oil type, lipid antioxidants and presence of rapeseed oil on oxidative flavour stability of fish oil enriched milk
Authors: Let Mette B. , Jacobsen Charlotte , Meyer Anne S. 
Published: March 2004

AbstractAs a part of our ongoing experiments on optimization of the oxidative stability of fish oils in genuine food systems, this study investigated the oxidative deterioration of fish oil enriched milk emulsions during cold storage. The experimental data showed that addition of rapeseed oil to fish oil (1:1) prior to emulsification into milk significantly protected the emulsions against oxidative deterioration. Addition of propyl gallate and a citric acid ester to the fish oil prior to emulsification also protected the fish oil enriched milk during storage. Emulsions containing a rapeseed:fish oil mixture were oxidatively stable during 11 d at 2 °C. Thus, no additional inhibitory effect of the added antioxidants was observed. The peroxide value and concentrations of five selected volatiles derived from n‐3 PUFA degradation in rapeseed:fish oil mixture emulsions were not significantly different from the corresponding levels in neither the emulsion containing only rapeseed oil nor the milk. It is proposed that the tocopherols in rapeseed oil may be the protective factor. Three‐way chemometric exploratory data analysis was implemented in form of a parallel factor analysis (PARAFAC). The PARAFAC model provided an overview of the obtained data with significantly enhanced interpretability, and revealed information about groupings and correlations in our data.
Improving solvent‐free extraction of policosanol from rice bran by high‐intensity ultrasound treatment
Authors: Cravotto Giancarlo , Binello Arianna , Merizzi Gianfranco , Avogadro Milvio 
Published: March 2004

AbstractRice bran, a rich source of nutrients and pharmacologically active compounds, is currently discarded or used as livestock feed, only small amounts being earmarked for oil production. Oil extraction can be efficiently performed in 30 min under high‐intensity ultrasound either with hexane or without any organic solvent, using a basic aqueous solution instead. Under sonochemical conditions bran wax can also be hydrolyzed yielding policosanol (common name for a mixture of C24‐C34 linear saturated fatty alcohols). We suggest that wax, a waste of rice oil manufacture, should be exploited to recover its alcoholic moiety that is very rich in policosanol. Quantitative data on extraction and purification of policosanol are presented. Both the first bran fraction from rice polishing and the discarded wax from the manufacture of rice oil are convenient and profitable starting materials for the production of policosanol.
Determination of the oxidative stability of vegetable oils by Differential Scanning Calorimetry and Rancimat measurements
Authors: Kowalski Bolesław , Ratusz Katarzyna , Kowalska Dorota , Bekas Witold 
Published: March 2004

AbstractSamples of vegetable oils were oxidized at isothermal conditions in the cell of a Pressure Differential Scanning Calorimeter (PDSC) and in the Methrom Rancimat apparatus. The PDSC and Rancimat experiments were carried out at a temperature in the range of 90–160 °C. From resulting PDSC exotherms their times to reach the peak maximum (τPDSC) were determined and used for the assessment of the oxidative stability of the samples. Similarly the measured Rancimat induction times (τRancimat) were used. As PDSC and Rancimat results were obtained at different temperatures the equations for temperature extrapolations of the τPDSC and τRancimat values have been proposed. Using the Arrhenius type correlation between induction times and temperature and activated complex theory the reaction rate constants, activation energies, activation enthalpies and activation entropies for oils oxidation have been calculated.
The effect of bidirectional flow on tidal channel planforms
Authors: Fagherazzi Sergio , Gabet Emmanuel J. , Furbish David Jon 
Published: March 2004

AbstractSalt marsh tidal channels are highly sinuous. For this project, ﬁeld surveys and aerial photographs were used to characterize the planform of tidal channels at China Camp Marsh in the San Francisco Bay, California. To model the planform evolution, we assume that the topographic curvature of the channel centreline is a key element driving meander migration. Extraction of curvature data from a planimetric survey, however, presents certain problems because simple calculations based on equally distanced points on the channel axis produce numerical noise that pollutes the ﬁnal curvature data. We found that a spline interpolation and a polynomial ﬁt to the survey data provided us with a robust means of calculating channel curvature. The curvature calculations, combined with data from numerous cross‐sections along the tidal channel, were used to parameterize a computer model. With this model, based on recent theoretical work, the relationship between planform shape and meander migration as well as the consequences of bidirectional ﬂow on planform evolution have been investigated. Bank failure in vegetated salt marsh channels is characterized by slump blocks that persist in the channel for several years. It is therefore possible to identify reaches of active bank erosion and test model predictions. Our results suggest that the geometry and evolution of meanders at China Camp Marsh, California, reﬂect the ebb‐dominated regime. Copyright © 2004 John Wiley & Sons, Ltd.
Reconstructing the development of a gully in the Upper Kalaus basin, Stavropol region (southern Russia)
Authors: Belyaev V.R. , Wallbrink P.J. , Golosov V.N. , Murray A.S. , Sidorchuk A.Yu. 
Published: March 2004

AbstractThe Stavropol region of southern Russia is severely affected by human‐induced gully erosion. A lack of detailed information on the different stages of gully formation resulting from major agricultural expansion c. 100 years ago, is an obstacle for management and containment of these systems. In this study we combine measurements of particle‐bound radionuclides (137Cs, 210Pbex, 226Ra, 232Th and 40K) and classical geomorphology to investigate and reconstruct the different phases of development of a gully during the last c. 100 years. We believe the ﬁrst phase (1) involved an initial incision into the bottom of a small valley (catchment area c. 1 km2) about 100 years ago. A short period of rapid growth was followed by a longer stage of gully stabilization. Subsequent phases were: (2) the period 1954–1960 – re‐incision in the lower gully reach was initiated by a high‐magnitude rainfall event, and a substantial amount of sediment was delivered to the gully fan; (3) c. 1960–1986 – the knickpoint retreated slowly, sediment was redeposited nearby, and the fan surface became stable; (4) 1986–1987 – a dam was built in the gully mouth and breached shortly after construction following 2 days of high rainfall, and substantial sediment accumulated in the gully above the dam and below the spillway channel on the fan surface; (5) 1987–1993 – the knickpoint retreat continued and the lower fan surface was stable until 1993 when the last signiﬁcant runoff event overlayed it with c. 10 cm of fresh sediment. These detailed reconstructions of gully development stages allow the contribution of high‐magnitude events to gully growth and regional sediment delivery to be assessed. They further guide management actions to prevent such dam failures in the future. Copyright © 2004 John Wiley & Sons, Ltd.