bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of vancomycin and related substances by liquid chromatography/ion trap mass spectrometry
Authors: Diana J. , Visky D. , Hoogmartens J. , Van Schepdael A. , Adams E.
Published: January 2006

Liquid chromatography (LC) methods compatible with mass spectrometry (MS) that are suitable for impurity profiling of vancomycin mixtures have not been described in the literature. The mobile phases of the existing methods contain non‐volatile additives and/or solvents that give problems in combination with MS. In this paper, a reversed‐phase LC/tandem mass spectrometry method is described for the investigation of vancomycin and related substances. The LC method uses a Zorbax Extend C18 column (250 × 4.6 mm i.d.), 5 µm, and a mobile phase consisting of methanol, water and ammonium acetate solution (pH 9.0). This method allows us to separate vancomycin and its impurities. Mass spectral data are acquired on an LCQ ion trap mass spectrometer equipped with an electrospray interface operated in the positive and negative ion modes. The LCQ is ideally suited for identification of impurities and related substances because it provides on‐line LC/MSn capability, which allows efficient identification without time‐consuming isolation and purification procedures. Using this method, the fragmentation of vancomycin and known derivatives was studied and the structures of six substances occurring in commercial samples were elucidated. Copyright © 2006 John Wiley & Sons, Ltd.
Combined Atomic Force Microscopy and Optical Microscopy Measurements as a Method To Investigate Particle Uptake by Cells
Authors: Muñoz Javier Almudena , Kreft Oliver , Piera Alberola Alicia , Kirchner Christian , Zebli Bernd , Susha Andrei S. , Horn Elias , Kempter Susanne , Skirtach Andre G. , Rogach Andrey L. , Rädler Joachim , Sukhorukov Gleb B. , Benoit Martin , Parak Wolfgang J.
Published: January 2006

We propose a combination of atomic force microscopy (AFM) and optical microscopy for the investigation of particle uptake by cells. Positively and negatively charged polymer microcapsules were chosen as model particles, because their interaction with cells had already been investigated in detail. AFM measurements allowed the recording of adhesion forces on a single‐molecule level. Due to the micrometer size of the capsules, the number of ingested capsules could be counted by optical microscopy. The combination of both methods allowed combined measurement of the adhesion forces and the uptake rate for the same model particle. As a demonstration of this system, the correlation between the adhesion of positively or negatively charged polymer microcapsules onto cell surfaces and the uptake of these microcapsules by cells has been investigated for several cell lines. As is to be expected, we find a correlation between both processes, which is in agreement with adsorption‐dependent uptake of the polymer microcapsules by cells.
Chemical Mapping of Individual Semiconductor Nanostructures
Authors: Ratto Fulvio , Locatelli Andrea , Fontana Stefano , Kharrazi Sharmin , Ashtaputre Shriwas , Kulkarni Sulabha K. , Heun Stefan , Rosei Federico
Published: January 2006

We demonstrate experimentally the power of a novel analytical tool for X‐ray spectromicroscopy. This provides a minimally intrusive elemental mapping of surfaces at the nanoscale and holds the promise of remarkable versatility. We have applied our procedure to the characterization of Ge(Si) islands on Si(111) substrates, with the aim of investigating the surface stoichiometry gradients and gaining insight into the intermixing dynamics. By identifying Si‐richer edges with respect to the centers, we are able to associate alloying in these islands to surface transport processes.
Cover Picture: Selective Loading of Kinesin‐Powered Molecular Shuttles with Protein Cargo and its Application to Biosensing (Small 3/2006)
Authors: Ramachandran Sujatha , Ernst Karl‐Heinz , Bachand George D. , Vogel Viola , Hess Henry
Published: January 2006

The cover picture illustrates a functionalized microtubule transported by surface‐adhered kinesin motor proteins. Through a streptavidin bridge, biotinylated antibodies are attached to the microtubule (outer diameter of 24 nm) and are able to capture antigens, such as the heart attack marker myoglobin. Successful capture is reported via the binding of fluorescently‐labeled antibodies, which complete the double‐antibody sandwich assay on the microtubule. The motor‐driven, active transport of this nanoscale bioassay will enable further separation and concentration, as well as sensitive detection. For more information please read the Communication "Selective Loading of Kinesin‐Powered Molecular Shuttles with Protein Cargo and its Application to Biosensing" by H. Hess and co‐workers on page 330 ff.
Hochtemperatur‐Festkörperchemie: Der Niederdruck‐Hochfrequenz‐Plasmabrenner: Synthese stabiler und metastabile Oxometallate der Lanthanoide
Authors: Müller‐Buschbaum Hanskarl
Published: January 2006

High Temperature Solid State Chemistry. The Low Pressure High Frequency‐Plasmaburner: Synthesis of Stable and Metastable Oxometalates of Rare Earth Oxides

Reactions between high temperature refractory oxides (Alkaline Earth oxides and Rare Earth oxides) always require exceptionally high temperatures for the synthesis of new compounds, especially for the preparation of single crystals. It will be shown, that conventional electrical heaters on the base of resistance heating don't achieve the melting points of refractory oxides. Other methods like solar radiation, electron beam heating ore hot flames (oxyhydrogen / oxyacetylene welding torch) are discussed. In the middle of the sixties of last century the open high pressure and the closed low pressure HF‐plasma burners had been developed. The following contribution gives once attention to the discovery and application of the closed low pressure plasma burner. In this paper the synthesis of stable and metastable (entropy stabilized) compounds (> 2000 °C) between Alkaline Earth and Rare Earth Oxides is shown. In detail the contribution makes clear how to prepare stable (CaFe2O4‐type) and metastable compounds of the composition AM2O4 (SrCr2O4, α‐CaCr2O4, BaCr2O4). These prototypes are the basis for micro space disordered compounds like SrCa2Ln6O12, SrCa2Ln10O18 and BaSrCaLn22O23. Using high temperature synthesis the thermodynamic stable compound SrNd2O4 altered to the metastable Sr3Nd4O7‐type. On the other hand the formation of BaLn2O4 does not occur for the heavy Rare Earth elements. Instead of the well‐known CaFe2O4‐type a complicated new stable structure type of the composition Ba3Ln4O9 is created.

The closed high frequency plasma burner makes possible to reinvestigate the “dissolution” of Alkaline Earth oxides in Rare Earth oxides aid of single crystals. A typical example is the formation of Ln2−xCaxO3−x. Starting with cubic Ho2O3 (C‐form) small values of x (x<0,2) stabilize the monoclinic form (B‐Form) of Rare Earth oxides (B‐Ho2−xCaxO3−x). For compositions 1.0 ≥ x ≥ 0.2 the monoclinic B‐form of Rare Earth oxides is left in favour of a new structure type Ca2Ho2O5. It may by regard as modified monoclinic B‐form with a statistically distributed deficiency of oxygen.

In the end the importance of atomic hydrogen, produced by high temperatures of plasma torches, is shown in case of the reduction of TiO2 and in case of the formation of Eu2+, stabilized by compounds of the composition Eu2+BeLn2O5.
Ein Licht emittierender Imidazol‐substituierter 2,2'‐Bipyridin‐Ruthenium(II)‐Komplex als Sensorfür die Reaktion von Protonen und Metallionen am peripheren Imidazolring
Authors: Schramm Frank , Görls Helmar , Walther Dirk
Published: January 2006

A Light Emitting Imidazole Substituted 2,2'‐Bipyridin Ruthenium(II) Complex as a Sensor for Reactions of Protons and Metal ions on the Peripheral Imidazole Ring

Ruthenium(II) complexes of the type [(tbbpy)2Ru(L‐L)](PF6)2 (tbbpy = bis‐4,4'‐di‐tert‐butyl‐2,2'‐bipyridine; 1: L‐L = 5‐(N‐ethoxymethyl‐1H‐imidazol‐2‐yl)‐[2,2']bipyridine; 2: L‐L = 1H‐imidazol‐2‐yl)‐[2,2']bipyridine) were prepared from [(tbbpy)2RuCl2] and the chelate ligands L‐L followed by treatment with NH4[PF6]. Characterization occurred by ESI‐MS, 1H‐ und 13C NMR spectroscopy. The molecular structure of 2, crystallized with five water molecules, was determined by an X‐ray diffraction analysis. The ruthenium(II) ion is surrounded distorted octahedral by the six N‐donor ligand atoms of the chelate ligands and two complex molecules are connected via the water molecules which form a hydrogen bonded network with the two nitrogen atoms of the peripheral imidazole ring.

The water‐free complex 2 in THF emits light at room temperature. Both, the deprotonation and the protonation of the peripheral imidazole ring results in systems which show extremely weak emission intensity only. Also, the interaction of 2 with water decreases the intensity of the emission. The coordination of metal ions at the imidazole ring of 2 or at the imidazolate ring of the deprotonated species 2a is indicated by an increase of the emission intensity and the change of the emission maxima.
Synthesis and Characterization of a New Three‐dimensional Organically Templated Nickel‐Zinc Phosphate
Authors: Lin Zhi‐En , Fan Wei , Chino Naotaka , Gao Feifei , Yokoi Toshiyuki , Okubo Tatsuya
Published: January 2006

A new organically templated nickel–zinc phosphate, [C2N2H10]·[Ni2.4Zn3.6(PO4)4(HPO4)]·H2O, has been synthesized from an aqueous solution containing NiCl2·6H2O, Zn(OAc)2·2H2O, H3PO4 and ethylenediamine as the structure‐directing agent. The compound crystallizes in the monoclinic system, space group C2/c (No. 15), a = 19.1563(5), b = 5.0316(2), c = 21.1724(5) Å, α = 103.201(3)°, V = 1986.81(11) Å3, Z = 4. It possesses a three‐dimensional framework constructed from MO4 (M = Ni, Zn), PO4, and HPO4 tetrahedra through their vertices. One‐dimensional 8‐ring channels are found in the structure, with the diprotonated organic templates residing in the tunnels and interacting with the inorganic framework by extensive hydrogen bonds. The framework is characterized by infinite helical chains of corner‐sharing MO4 (M = Ni, Zn) tetrahedra.
Structural and Spectroscopic Characterization of Ammonium Thiosaccharinate Monohydrate
Authors: Baran Enrique J. , Piro Oscar E. , Zinczuk Juan
Published: January 2006

The crystal structure of NH4[tsac]·H2O (tsac = anion of the thiosaccharin molecule) has been determined by single crystal X‐ray diffractometry. It crystallizes in the orthorhombic space group Pbca with Z = 8. The infrared spectrum of the compound was also recorded and its most important features discussed on the basis of its structural peculiarities.
A Novel Huge Diamond‐like Three‐fold Interpenetrated Network of CuI and Crown Ether
Authors: Heller Maik
Published: January 2006

The quest for mercury sensitive ion exchangers results in a diamondlike network $^{3}_{\infty}\rm [(CUI)_{2}(1,10DT18C6)]$ (1). This is in contrast to the similar well known 44 network $^{2}_{\infty}\rm [(CUI)(1,10DT18C6)]$ described by Röttgers and Sheldrick [1] a 3D strucutre. 1 is accessible by treatment of CuI with 1,10‐dithia‐18‐crown‐6 in acetonitrile solution in a sealed glass tube in the presence of HgI, but it doesn't contain mercury at all. It seems that either the presence of mercury salts or the excess of iodine ions plays a catalytic role, which is not clarified yet. The main building blocks of 1 are distorted cubes of CuI, which are linked with crown ether rods to give an adamantanlike structure. The space inside the diamondlike network is filled by interpenetration with in sum three similar networks. The longest distance between oppositely CuI cubes in the adamantanlike building block is with 44.796(9) Å three times the b axis.
Ion Pairing, H‐bonding, and π‐π Interactions in Cobalt(II) Compound Containing Guanidinium Counter Ion
Authors: Sheshmani Shabnam , Aghabozorg Hossein , Panah Fahimeh Mohammad , Alizadeh Robabeh , Kickelbick Guido , Nakhjavan Bahar , Moghimi Abolghasem , Ramezanipour Farshid , Aghabozorg Hamid Reza
Published: January 2006

A novel proton transfer compound, (GH)2(phendc), (1), was synthesized from the reaction of 1,10‐phenanthroline‐2,9‐dicarboxylic acid, phendcH2, and guanidine hydrochloride, (GH)(Cl), (G: guanidine). The characterization was performed using IR, 1H and 13C NMR spectroscopy. The cobalt(II) compounds were synthesized using proton transfer compounds containing guanidinium counter ion. These proton transfer compounds are (GH)2(phendc), and (GH)2(pydc) (pydcH2: 2,6‐pyridinedicarboxylic acid). The chemical formulae and space groups are (GH)2[Co(phendc)2]·4H2O, $P{\bar 1}$ (2), and (GH)2[Co(H2O)6][Co(pydc)2]2, P21/n (3). Non‐covalent interactions such as ionpairing, hydrogen bonding and π‐π stacking are discussed.
Comment on the Paper: “Synthesis and Electrochemical Study of Antifluorite‐type Phases in the Li‐M‐N‐O (M = Ti, V) Systems” [1]
Authors: Niewa Rainer , Zherebtsov Dmitry A.
Published: January 2006

Based on experimental data it is shown that samples in a solid solution series of the system Li7[VN4]–Li2O with partial Li–V order can be obtained.
Answer to the Comment submitted by R. Niewa and D. A. Zherebtsov on the Paper “Synthesis and Electrochemical Study of Antifluorite‐type Phases in the Li‐M‐N‐O (M = Ti, V) Systems” [1]
Authors: Palacín M. R.
Published: January 2006

In the reaction conditions leading to γ‐Li7VN4, no ordered solid solution γ‐Li7VN4–Li2O seems to exist but rather a mixture of two phases: γ‐Li7VN4 and a lithium vanadium oxynitride with the disordered anti‐fluorite structure. Even though the trend may be different in the case of β‐Li7VN4–Li2O, neutron diffraction experiments would be desirable to confirm/dismiss these assumptions, as they would allow to determine the number of phases and polymorphs present and the degree of Li/V or N/O order, if any.
Ein neues cis‐[Bi3I12]3−‐Anion in Tri(n‐butyl)methylammonium Dodecaiodotribismutat
Authors: Okrut A. , Feldmann C.
Published: January 2006

The Novel cis‐[Bi3I12]3−‐Anion in Tri(n‐butyl)methylammoniumdodecaiodo‐tribismutate

By reaction of equivalent amounts of BiI3, KI and I2 in [N(CH3) (n‐C4H9)3][N(SO2CF3)2] as Ionic Liquid, transparent reddish crystals with the composition [N(CH3)(n‐C4H9)3]3[Bi3I12] are formed. Concerning to X‐ray diffraction investigations based on single crystals as well as powders, [N(CH3)(n‐C4H9)3]3[Bi3I12] crystallizes monoclinic (P21/c; a = 2383.0(5); b = 1241.0(3); c = 2493.0(5) pm; β = 97.50(3)°; Z = 4). The anion consists of distorted (BiI6)‐octahedra, which are face‐shared via cis‐oriented octahedral faces. With the cis‐[Bi3I12]3−‐anion such a connectivity is firstly described.
Two Novel Three‐Dimensional Lead(II) Coordination Polymers Involving 16‐Membered Rings: [Pb2(Bs‐glu)2(bipy)2] and [Pb2(Bs‐glu)2(phen)2]
Authors: Ma Lu‐Fang , Wang Li‐Ya , Wang Jian‐Ge , Wang Yu‐Fang , Feng Xun
Published: January 2006

The reaction of Pb(CH3COO)2·3H2O with N‐benzesulfonyl‐L‐glutamic acid in the presence of 2, 2′‐bipyridine (bipy) or 1,10‐phenanthroline (phen) produced two novel complexes [Pb2(Bs‐glu)2(bipy)2] (1) and [Pb2(Bs‐glu)2(phen)2] (2) (Bs‐glu = N‐benzesulfonyl‐L‐glutamic acid dianion). In 1 chains bearing alternative 16‐membered rings and Pb2O3 nodes are constructed from the interactions of PbII ions with the carboxylates of Bs‐glu ligands. To the best of our knowledge, this is the first lead(II) complex of carboxylates with the formation of chains of Pb2O3. In 2 the 16‐membered ring units are connected by centrosymmetric Pb2O2 nodes to form chains. Complexes 1 and 2 construct the 3‐D supramolecular architectures through versatile hydrogen bonds and π‐π stacking interactions.
Crystal Structure of μ‐Oxo‐bis[9,22‐(bisbutyloxy)hemiporphyrazinato]iron(III)
Authors: Haberroth Klaus , Hanack Michael , Maichle‐Mössmer Cäcilia
Published: January 2006

The crystal structure of the title compound, C68H60N16O5Fe2, shows a dinuclear complex of two crystallographically independent, distorted hemiporphrazinato iron complexes with five‐coordinate iron and oxygen as bridging ligand. The Fe1‐O1‐Fe2 angle is 151.16°, the Fe‐O bond lengths are Fe1‐O1 [1.771(2) Å] and Fe2‐O1 [1.773(2) Å]. The dinuclear complexes have a staggered conformation with a dihedral angle of 26.2°, but coaxially to form tetrameric units is not observed. The molecule is characterized by short Fe‐N (isoindole) bonds [1.998(3) Å] and long Fe‐N (pyridine) bonds, values range from [2.175(3) Å] to [2.245(3) Å].
Crystal Structure and Spectroscopic Characterization of Lithium Saccharinate 11/6 Hydrate, a Hygroscopic and Potentially Physiologically Active Compound
Authors: Naumov Pancče , Jovanovski Gligor , Tancčeva Slavica , Ng Seik Weng
Published: January 2006

The structure of the only structurally yet uncharacterized alkali saccharinate, lithium saccharinate, is reported, together with the infrared spectra of its protonated and partially deuterated analogues. The compound crystallizes as strongly hygroscopic colorless triclinic crystal blocks of a 11/6 hydrate, LiC7H4NO3S·11/6H2O, space group $P{\bar 1}$, with unit cell dimensions a = 10.070(1), b = 15.755(2), c = 19.134(2) Å, α = 68.085(2), β = 76.940(2), γ = 84.169(2)°, V = 2743.0(5) Å3 and Z = 12 at T = 200(2) K.
Synthesis, Structure, and Magnetic Behavior of a 1‐D Coordination Polymer [Ni(NIT4py)2(ip)(H2O)]n
Authors: Wang Shu‐Ping , Gao Dong‐Zhao , Liao Dai‐Zheng , Jiang Zong‐Hui , Yan Shi‐Ping
Published: January 2006

A new coordination polymer of the formula [Ni(NIT4py)2(ip)(H2O)]n(NIT4py = 2‐(4′‐pyridinyl)‐4,4,5,5‐tetramethylimidazoline‐1‐oxyl‐3‐oxide and ip = isophthalate dianion) has been synthesized and characterized by elemental analyses, IR spectrum, and single‐crystal X‐ray diffraction. The coordination about each Ni2+ ion is a distorted octahedra. Each isophthalate dianion binds two Ni2+ ions in monodentate‐bidentate mode, leading to a 1‐D chain. Among the chains, the coordinated water molecules and carboxylato oxygen atoms form hydrogen bonds, generating an infinite 1‐D ladder structure of a double‐chain. The magnetic study shows that the decrease of χMT value in the low temperature for the complex is mainly ascribed to the zero‐field splitting of the distorted octahedral Ni2+ ions.
Externalities and labour market linkages in a dynamic two-sector model of tropical agriculture
Authors: SHIVELY GERALD E.
Published: January 2006

This paper examines environmental and labour market linkages between two agricultural systems-one upstream and another downstream. Using data from the Philippine province of Palawan as a point of departure, the paper develops a dynamic, two-sector model of an agricultural watershed to study the evolution and impact of an erosion externality. Attention focuses on the interplay between erosion generated by the extensive upstream sector and labour productivity in a labour-intensive downstream sector. A key feature of the model is that labour productivity and labour demand downstream are influenced by the externality generated upstream. Production of the externality, in turn, is influenced by wage employment opportunities downstream. Time paths of equilibrium wages are derived. A simulation is used to study the impact of environmental payments to upland households in exchange for allocating labour away from the externality-producing activity. The analysis shows how natural processes and economic interactions between two groups influence the benefits of agricultural intensification.
Food-for-work for poverty reduction and the promotion of sustainable land use: can it work?
Authors: HOLDEN STEIN , BARRETT CHRISTOPHER B. , HAGOS FITSUM
Published: January 2006

Food-for-work (FFW) programs are commonly used both for short-term relief and long-term development purposes. This paper assesses the potential of FFW programs to reduce poverty and promote sustainable land use in the longer run. There is a danger that such programs distort labor allocation or crowd out private investments and therefore have unintended negative effects. We explore this issue using survey evidence from northern Ethiopia that we use to motivate a simple theoretical model, a more detailed version of which we then implement through an applied bio-economic model calibrated to northern Ethiopia. The analysis explores how FFW project outcomes may depend on FFW project design, market conditions, and technology characteristics. We show that FFW programs may either crowd out or crowd in private investments and highlight factors that condition whether FFW promotes or undercuts sustainable land use.
A property model of pregnancy
Authors: Ford Mary
Published: January 2006

This paper elaborates what the author considers to be a promising alternative to the orthodox ‘conflict model’ of pregnancy: a model of adjudication based on an understanding of pregnancy as a property relationship. The conflict model, which purports to balance the rights and interests of the pregnant woman against those of the foetus, is now widely acknowledged to be unsatisfactory. This paper argues for the complete abandonment of the conflict model in all its guises, and the adoption of a new ‘property model’ of pregnancy. The property model, it is argued, has several distinct advantages over traditional or orthodox ways of debating and adjudicating pregnancy: it explains and justifies features which currently appear as inconsistencies or contradictions in the current law, and provides possible solutions to contested issues such as surrogacy, the ‘rights’ of fathers in decision-making about pregnancy, and the role of the state in setting limits on abortion.
Electron holes, ion waves, and anomalous resistivity in space plasmas
Authors: Dyrud Lars P. , Oppenheim Meers M.
Published: January 2006

Phase‐space electron holes are seen in simulations, laboratory plasmas, and many regions of the Earth's space environment. We present simulations of beam plasmas showing that the generation and decay of electron holes results in a reduction of electron current, implying a parallel resistivity. We show that resistivity occurs in simulations where a cold electron beam is coincident with a warmer background plasma and appears to be mediated by the generation of ion acoustic waves propagating obliquely to the magnetic field. Initially, electron holes scatter electrons in the beam direction, steepening the electron beam distribution, eventually launching ion acoustic waves that cause resistivity and strong ion heating perpendicular to . These effects occur in both strongly and weakly magnetized plasmas. Given that electron holes are observed in many space plasmas, these results have important implications for a number of magnetospheric and auroral ionospheric processes. For auroral plasmas, electron hole resistivity could support parallel electric fields on the order of several mV/m, accounting for parallel potential drops from tens to hundreds of eV. For the magnetopause, simulations show effective collision rates of 0.00015 ωpe, which could enhance dissipation and diffusion across the boundary.
Microstructure evolution of aqueous fluid‐bearing wehrlites: Implications for the fluid distribution in polymineralic rocks
Authors: Ohuchi Tomohiro , Nakamura Michihiko
Published: January 2006

The microstructure of aqueous fluid‐bearing wehrlites was experimentally studied in order to investigate the fluid distribution in polymineralic rocks. Wehrlites of various forsterite/diopside ratios were synthesized with 1.0–1.5 wt % water at 1200°C and 1.2 GPa for 1.5–668 hours. Conspicuous grain growth, drag, and coagulation of pore fluids were observed in the time series experiments. The pore fluids were classified into two types: those surrounded only by a single phase (G‐type) and those surrounded by both forsterite and diopside (I‐type). In the short time runs the relative volume fraction of I‐type pores in all the pores, FI, agrees well with the value calculated from an ideal pore distribution model in which all the grains are randomly distributed. The FI of wehrlites with various forsterite/diopside ratios increased with average grain size and reached a steady state value at 80–90% in about 160–163 hours. The increase of FI is explained by “interphase boundary trapping”: G‐type pore fluids move faster than I‐type, and the number of G‐type becoming I‐type by being trapped into the interphase boundary per unit time is larger than that of I‐type pores transforming to G‐type. The experimental results suggest that large fractions of pore fluids might be distributed at the grain junctions surrounded by more than two mineral phases in natural rocks as a result of grain growth. The connectivity of the fluid network in polymineralic rocks may be strongly influenced by modal composition of the rocks as well as by the dihedral angles among the fluid and two mineral phases.
Identification of periodic autoregressive moving average models and their application to the modeling of river flows
Authors: Tesfaye Yonas Gebeyehu , Meerschaert Mark M. , Anderson Paul L.
Published: January 2006

The generation of synthetic river flow samples that can reproduce the essential statistical features of historical river flows is useful for the planning, design, and operation of water resource systems. Most river flow series are periodically stationary; that is, their mean and covariance functions are periodic with respect to time. This article develops model identification and simulation techniques based on a periodic autoregressive moving average (PARMA) model to capture the seasonal variations in river flow statistics. The innovations algorithm is used to obtain parameter estimates. An application to monthly flow data for the Fraser River in British Columbia is included. A careful statistical analysis of the PARMA model residuals, including a truncated Pareto model for the extreme tails, produces a realistic simulation of these river flows.
Robust location of surface explosions by a network of acoustic arrays
Authors: Pinsky V. , Gitterman Y. , Hofstetter A. , Shapira A.
Published: January 2006

This study experimentally assesses a capability of a network, comprised of several small tripartite infrasound arrays, to locate accurately surface explosion sources at distances of several tens of kilometres. The location procedure, we developed, utilises first arrival phase delays and includes two main stages. Firstly a preliminary source location is obtained as intersection point of back‐azimuths estimated for each individual array. Then using jointly time delays from different arrays, a refined location is found via non‐linear grid‐search optimization technique. The procedure features are: independency from a source‐station travel time model, reduced influence of the outliers, optional adaptation to the varying multi‐channel noise. High location accuracy (a few hundred meters) was achieved for field experimental on‐surface explosions in Sayarim valley, Israel, recorded by special tripartite infrasound arrays.
Importance of dew in controlling the air‐surface exchange of HONO in rural forested environments
Authors: He Yi , Zhou Xianliang , Hou Jian , Gao Honglian , Bertman Steven B.
Published: January 2006

Mechanisms regarding formation and loss of nitrous acid (HONO) in the rural atmosphere are not well understood. Results of field observations and laboratory experiments implicate the importance of dew in controlling the surface‐atmosphere exchange of HONO. Dew water, abundantly available on ground surfaces, especially on canopy surfaces in forested regions, during summer and autumn nights, serves as a sink and a temporary reservoir of atmospheric HONO and as a source in the morning when the dew droplets evaporate.
Inertial Alfvén waves and acceleration of electrons in nonuniform magnetic fields
Authors: Watt C. E. J. , Rankin R. , Rae I. J. , Wright D. M.
Published: January 2006

We present results from self‐consistent simulations of the electron response to shear Alfvén pulses in the presence of non‐uniform magnetic fields and the associated mirror force. We discuss how energies of resonantly accelerated beam particles are affected by the local phase velocity of the pulse, and show that time‐of‐flight models are inadequate for describing electron acceleration since the acceleration can occur at more than one location along the field line as the pulse propagates toward the ionosphere. We also demonstrate that electron conics in low‐altitude satellite observations of electron acceleration can be explained in terms of field‐aligned inertial Alfvén wave pulses, without the requirement of a static potential drop or a standing Alfvén wave structure.
Ionospheric Alfvén resonator excitation due to nearby thunderstorms
Authors: Surkov V. V. , Hayakawa M. , Schekotov A. Y. , Fedorov E. N. , Molchanov O. A.
Published: January 2006

A theory of midlatitude Ionospheric Alfvén Resonator (IAR) excitation due to random cloud‐to‐ground lightning discharges is developed. Electromagnetic wave radiated from the lightning discharges penetrates into the ionosphere, thereby exciting the shear Alfvén and magnetosonic waves in the F region of ionosphere. The IAR arises due to wave reflection from the Alfvén velocity gradients in the topside ionosphere. Typically, the ionospheric resonance cavity accumulates the shear Alfvén wave energy with periods from 1 s to a few tenths of seconds. To proceed analytically, a suitably idealized plane‐stratified model of the medium was used that ignores the magnetic field line curvature and dip angle but includes plasma conductivity variations with altitude. The thunderstorm centers distributed around a ground‐recording station is assumed to be statistically independent sources of the lightning activity, which is a stochastic Poisson process. The lightning onset time and the current moment is supposed to be a random value, while the shape and duration of return strokes are deterministic. Model calculations of the IAR spectrum due to nearby thunderstorm activity were applied to interpret ULF observation made at Karimshino station (52.94°N, 158.25°E) in Kamchatka peninsula. It is shown that the sharp impulses which are in one‐to‐one correspondence with the appearance of the spectral resonance structure (SRS) in dynamic spectrograms can be the result from nearby lightning discharges followed by impulse IAR excitation. The correlation functions and power spectra of the IAR due to random lightning discharge process is studied both analytically and numerically. We found that the nearby thunderstorms in the range of 1000–2000 km make a main contribution to the SRS signature of the midlatitude IAR, whereas the remote/tropic thunderstorm activity is of minor importance. It is not inconceivable that there may exist other permanent mechanisms of the midlatitude IAR excitation, for example, the high‐altitude neutral wind in the E region might also be operative.
A model of secondary Farley‐Buneman waves in the auroral electrojet
Authors: Bahcivan H. , Hysell D. L.
Published: January 2006

We present a model of type II radar echoes associated with Farley‐Buneman instability in the auroral E region. The plasma waves responsible for broad‐type auroral radar echoes are described as secondary ion acoustic structures driven by the electric fields of the primary Farley‐Buneman waves. Numerical solutions of a one‐dimensional model of the secondary structures exhibit density irregularities advecting in the background electron flow direction while propagating and evolving in the transverse direction. The velocity of transverse propagation depends on amplitude, a circumstance that leads to nonlinear proper evolution in the form of compression or steepening. On the basis of symmetry, radar Doppler spectra should exhibit spectral shifts and widths proportional to the cosine and sine of the electron flow angle, respectively. This prediction is in line with a number of theoretical and experimental observations.
Locating and modeling regional earthquakes with two stations
Authors: Tan Ying , Zhu Lupei , Helmberger Donald V. , Saikia Chandan K.
Published: January 2006

We developed a new technique CAPloc to retrieve full source parameters of small seismic events from regional seismograms, which include origin time, epicenter location, depth, focal mechanism, and moment magnitude. Despite rather complicated propagation effects at short periods, a simple localized one‐dimensional model can well explain signals of periods 3–10 s if we break the three‐component records into different segments and allow differential time shifts among them. These differential time shifts, once established from a calibration process or a well‐determined tomographic map, can be used together with P wave travel times to refine an event's location. In this study, we tested whether our new method could produce satisfactory results with as few as two stations, so that we can improve source estimates of poorly monitored events with sparse waveform data. We conducted the test on 28 events in the Tibetan Plateau. The focal mechanisms and locations determined from only two stations agree well with those determined from a whole PASSCAL array. In particular, our new method produces better locations than International Seismological Centre, with the average mislocation error reduced from ∼16 to ∼5 km. We also tested whether an event's depth and mechanism can be determined separately from its epicenter relocation in a two‐step approach. We find that the two‐step approach does not always give the correct solution, but the reliability of a solution can be evaluated using a reduced chi‐square value.
Clouds and 7Be: Perusing connections between cosmic rays and climate
Authors: Hedfors J. , Aldahan A. , Kulan A. , Possnert G. , Karlsson K.‐G. , Vintersved I.
Published: January 2006

Time series data on 7Be, precipitation, temperature, and satellite imagery of cloud cover over Scandinavia, together with cosmic ray and sunspot activity, were used to elucidate the relationship between cosmic rays and clouds, and ultimately climate change. The results indicate a coherent negative correlation between total cloud cover and 7Be on intraseasonal, seasonal, and decadal scales. Although the reasons behind this correlation are unclear, a full‐scale implication of this feature is in the possible use of 7Be and 10Be records for proxy paleo‐reconstruction of total cloud cover. This is a strongly needed, but generally difficult to quantify parameter in climate models.
Evidence for the role of ion‐induced particle formation during an atmospheric nucleation event observed in Tropospheric Ozone Production about the Spring Equinox (TOPSE)
Authors: Kanawade Vijay , Tripathi S. N.
Published: January 2006

Various in situ measurements show evidence of new particle formation over a wide range of latitudes in the middle to upper troposphere and lower stratosphere. However, the exact mechanism of new particle formation is still uncertain. Using a combination of satellite‐derived brightness temperature, air parcel backward trajectory information, in situ measurements of aerosol and precursor gases and an aerosol microphysical model driven by parameterized ion‐induced nucleation, we investigate the mechanism responsible for, and factors leading to, new particle formation in the middle to upper troposphere during the Tropospheric Ozone Production about the Spring Equinox (TOPSE) experiment. The number concentrations of modeled ultrafine particles of diameters 3 to 4 nm (N3–4nm) and 3 to 8 nm (N3–8nm) are consistent with in situ measurements indicating that new particle formation likely occurred by ion‐induced nucleation a day prior to the time of measurement. A reduction in preexisting aerosol surface area in a region of cloud outflow probably triggered particle nucleation. These studies indicate that under typical middle to upper troposphere conditions, the ion mechanism is likely an important source of ultrafine particles, and these newly formed particles can grow to act as cloud condensation nuclei.
Derivation of unit hydrograph using a transfer function approach
Authors: Yang Z. , Han D.
Published: January 2006

The unit hydrograph (UH) concept and model have been widely used in the hydrological field over the past decades. However, the estimation of such a model in practice has always been a challenge for researchers and practitioners because such a model is usually ill formed in mathematical terms. The large number of parameters (or the number of ordinates) in a unit hydrograph model are correlated to a certain degree, and this could cause unstable results. So far, the research has been mainly focused on restricting the negative values and smoothing the oscillation by brute force methods, such as linear programming, and has achieved a certain degree of success. However, the number of parameters involved and the lack of stable model response are still a problem. In this study, a new model structure has been proposed that would inherently remove the negative UH ordinates and guarantee a smooth curve. This model is derived by the unit pulse response of a given discrete transfer function in the time domain by restricting its poles along the positive real axis in its Z domain (that is, there are no imaginary components and no negative real values). The model is termed the physically realizable transfer function. The strengths of its structure are that it is numerically stable, physically realizable, parsimonious in parameters, and easy to implement in real time for its state and parameter updating. Its shortcomings are that it has nonlinear pole positions and a more complicated parameter estimation process. A case study with two events in England has been used to demonstrate the application of such a model.
Pore‐scale modeling and continuous time random walk analysis of dispersion in porous media
Authors: Bijeljic Branko , Blunt Martin J.
Published: January 2006

We provide a physically based explanation for the complex macroscopic behavior of dispersion in porous media as a function of Peclet number, Pe, using a pore‐scale network model that accurately predicts the experimental dependence of the longitudinal dispersion coefficient, DL, on Pe. The asymptotic dispersion coefficient is only reached after the solute has traveled through a large number of pores at high Pe. This implies that preasymptotic dispersion is the norm, even in experiments in statistically homogeneous media. Interpreting transport as a continuous time random walk, we show that (1) the power law dispersion regime is controlled by the variation in average velocity between throats (the distribution of local Pe), giving DL ∼ Peδ with δ = 3 − β ≈ 1.2, where β is an exponent characterizing the distribution of transit times between pores, (2) the crossover to a linear regime DL ∼ Pe for Pe > Pecrit ≈ 400 is due to a transition from a diffusion‐controlled late time cutoff to transport governed by advective movement, and (3) the transverse dispersion coefficient DT ∼ Pe for all Pe ≫ 1.
Allosteric modulation, thermodynamics and binding to wild‐type and mutant (T277A) adenosine A1receptors of LUF5831, a novel nonadenosine‐like agonist
Authors: Heitman Laura H , Mulder‐Krieger Thea , Spanjersberg Ronald F , Von Frijtag Drabbe Künzel Jacobien K , Dalpiaz Alessandro , IJzerman Adriaan P
Published: January 2006

The interaction of a new nonribose ligand (LUF5831) with the human adenosine A1receptor was investigated in the present study.

Radioligand binding experiments were performed in the absence and presence of diverse allosteric modulators on both wild‐type (wt) and mutant (T277A) adenosine A1receptors. Thermodynamic data were obtained by performing these assays at different temperatures. In addition, cyclic adenosine monophosphate (cAMP) assays were performed.

The presence of allosteric modulators had diverse effects on the affinity of LUF5831,N6‐cyclopentyladenosine (CPA), a full agonist, and 8‐cyclopentyl‐1,3‐dipropylxanthine (DPCPX), an inverse agonist/antagonist, for the adenosine A1receptor. PD81,723, for example, increased the affinity of CPA, while the affinity of LUF5831 was decreased. However, the affinity of DPCPX was decreased even more. In addition, LUF5831 was shown to have an affinity for the mutant (T277A) adenosine A1receptor (Ki=122±22 nM), whereas CPA's affinity was negligible. The results of temperature‐dependent binding assays showed that the binding of LUF5831 was entropy driven, in between the behaviour of CPA binding to the high‐ and low‐affinity states of the receptor, respectively.

The inhibition of the forskolin‐induced production of cAMP through activation of the wt adenosine A1receptor showed that LUF5831 had a submaximal effect (37±1%) in comparison to CPA (66±5%). On the mutant receptor, however, neither CPA nor LUF5831 inhibited cAMP production.

This study indicates that the nonribose ligand, LUF5831, is a partial agonist for the adenosine A1receptor.

British Journal of Pharmacology(2006)147, 533–541. doi:10.1038/sj.bjp.0706655
Vanilloid VR1receptor is involved in rimonabant‐induced neuroprotection
Authors: Pegorini Simona , Zani Alessia , Braida Daniela , Guerini‐Rocco Chiara , Sala Mariaelvina
Published: January 2006

Recently, a potential neuroprotective effect of rimonabant, independent of the CB1receptor interaction, has been proposed. In the present study, the role of transient receptor potential channel vanilloid subfamily member 1, named VR1, on neuroprotective effect of rimonabant, on global cerebral ischemia in gerbils, was investigated.

Rimonabant (0.05–3 mg kg−1), given i.p. 5 min after recirculation, dose dependently antagonized the ischemia‐induced decrease in electroencephalographic (EEG) total spectral power and restored relative frequency band distribution 7 days after ischemia.

Rimonabant (0.125–0.5 mg kg−1) fully prevented ischemia‐induced hyperlocomotion 1 day after ischemia and memory impairment evaluated in a passive avoidance task, 3 days after ischemia.

At 7 days after ischemia, the survival of pyramidal cells, in the CA1subfield, was respectively 91 and 96%, in the animals given rimonabant 0.25 and 0.5 mg kg−1, compared to the vehicle group. Higher doses were not protective.

The protection induced by rimonabant followed a bell‐shaped curve, the maximal active doses being 0.25 and 0.5 mg kg−1.

Capsazepine (0.01 mg kg−1), a selective VR1vanilloid receptor antagonist, completely reversed rimonabant‐induced neuroprotective effects against EEG flattening, memory impairment and CA1hippocampal neuronal loss.

These findings suggest that VR1vanilloid receptors are involved in rimonabant's neuroprotection even if other mechanisms can contribute to this effect.

British Journal of Pharmacology(2006)147, 552–559. doi:10.1038/sj.bjp.0706656
Red wine alcohol promotes quercetin absorption and directs its metabolism towards isorhamnetin and tamarixetin in rat intestine in vitro
Authors: Dragoni Stefania , Gee Jennifer , Bennett Richard , Valoti Massimo , Sgaragli Giampietro
Published: January 2006

Moderate consumption of red wine has been associated with beneficial effects on human health, and this has been attributed to the flavonoid content. Factors that influence the bioavailability of this group of polyphenolic compounds are therefore important.

Using the rat cannulated everted jejunal sac technique, we have investigated the effect of alcohol on the intestinal absorption of quercetin and its 3‐O‐glucoside from red wine. Tissue preparations were incubated in whole or dealcoholised red wine, diluted 1 : 1 with Krebs buffer for 20 min at 37°C, after which the mucosa was removed and processed for HPLC analysis. Tissues exposed to red wine had significantly higher amounts of both quercetin (× −3; P<0.001) and quercetin‐3‐O‐glucoside (× −1.5; P<0.01) associated with them, compared with sacs incubated in the dealcoholised equivalent. In addition, both tamarixetin (T) and isorhamnetin (I), in the mucosal tissue from sacs exposed to the whole wine, were significantly elevated approximately two fold (P<0.05; P<0.01, respectively).

Similar results were obtained when sacs were incubated in Krebs buffer containing a mixture of pure quercetin and quercetin‐3‐O‐glucoside with or without alcohol, and, although effects on the apparent absorption of Q and Q‐3‐G were not so marked, concentrations of the metabolites quercetin‐3‐O‐glucuronide and I were significantly increased by the presence of alcohol (P<0.01 and P<0.001, respectively).

It is therefore plausible that the moderate alcohol content of red wine contributes to its beneficial health effects in humans by both increasing the absorption of quercetin and quercetin‐3‐O‐glucoside and by channelling their metabolism towards O‐methylation to yield compounds (T and I), which have potential protective effects against cancer and cardiovascular diseases.

British Journal of Pharmacology (2006) 147, 765–771. doi:10.1038/sj.bjp.0706662
Control of structure and photophysical properties by protonation and subsequent intramolecular hydrogen bonding
Authors: Sun Mengtao
Published: January 2006

Protonation and subsequent intramolecular hydrogen bonding as methods to control chain structure and tune luminescence in heteroatomic conjugated polymers were reported experimentally [A. P. Monkman et al., J. Am. Chem. Soc. 124, 6049 (2002)]. In this paper, the structure and photophysical properties of the model teraryl compound of phenylene-pyridylene copolymer before and after protonation are theoretically studied with quantum chemistry methods. From the optimized ground states, intramolecular hydrogen bonding to the adjacent oxygen atom in the alkoxy substituent planarizes the backbone of the molecules, and the optimized detailed results of compound 9 before and after protonation, such as the dihedral angles between the central benzene and the two pyridyl rings, the bond lengths, and the bond angles, are consistent with the experimental results. From the results of the calculated excited states, the protonation and subsequent intramolecular hydrogen bonding result in the redshifts of the absorption, the increase of the ionization energy, the increase of the electron affinity, the decrease of the energy difference of the highest occupied molecular orbital and lowest unoccupied molecular orbital, the decrease of the binding gap, and the delocalization of the electron-hole coherence. The photophysical properties of compound 9 before and after protonation are further studied with a three-dimensional real-space analysis method of transition and charge difference densities (study transition dipole moment and charge transfer in the absorption and fluorescence processes) and two-dimensional real-space analysis method of transition density matrices (study the electron-hole coherence and the excitation delocalization). The calculated results show theoretically an insight understanding on the influence of the protonation and subsequent intramolecular hydrogen bonding to chain structure and photophysical properties.
Nonlinear characteristics of the Fowler–Nordheim plot for field emission from In2O3 nanowires grown on InAs substrate
Authors: Li S. Q. , Liang Y. X. , Wang T. H.
Published: January 2006

Nonlinear characteristics of the Fowler–Nordheim (F–N) plot for field emission from In2O3 nanowires (NWs) is investigated. The field emission from the aligned and nonaligned In2O3 NWs are measured and a stable emission with fluctuations less than 10% was obtained for the aligned In2O3 NWs. It is found that the nonaligned In2O3 NWs with a longer length have higher turn-on and threshold electric fields. Their F–N plots, showing pronounced nonlinear characteristics, are divided into several regions based on physical origins. Field penetration competes with surface states in influencing the field emission of the In2O3 NWs with increasing the electric field, which is responsible for the nonlinear characteristics of the F–N plots.