bluuebunny/crossref_metadata_2025 huggingface dataset:
Simple wavefunctions for dipositronium and the relationship between this species and the hydrogen molecule
Authors: Dunne Lawrence J. , Murrell John N.
Published: December 2003

Dipositronium (two electrons and two positrons) has a closer relationship to the hydrogen molecule than has often been assumed in past treatments. This article shows that appropriately modified mixtures of simple molecular orbital and Heitler–London wavefunctions are a good basis for the ground state of this species. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Long‐range interactions in embedded ionic cluster calculations
Authors: Quintanar Carlos , Caballero Reyna , Köster Andreas M.
Published: December 2003

The effect of long‐range Coulomb interactions on bulk properties is studied for the ionic solids NaBr and NaCl. The embedded cluster approach in the framework of density functional theory is employed. The Madelung potential is calculated with the Evjen cube summation method. To explore the effects of the long‐range interactions on the electron densities and the Madelung constant, the Evjen cube size is varied from 310 to 19650 point charges for 33 atom clusters. To study the size effect of the quantum region, all‐electron clusters with 33 to 87 atoms, embedded in Evjen cubes of 6859 point charges, are investigated. The results show that for the 81 and 87 atom clusters the Madelung potential is constant from the center up to the second neighbor shell. For the same atoms, in all clusters, the electron density at the nuclei has nearly the same value. The largest difference found for the positive ions was 0.54%, and for the negative ions, 0.14%. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Weyl representation of the permutation operators and exchange interaction
Authors: Luzanov A. V. , Prezhdo O. V.
Published: December 2003

Weyl phase–space representation is derived for the cyclic permutation operators that naturally occur in the quantum theory of exchange interaction. The classical‐like phase–space representation of exchange leads to a special type of coupling between the position and momentum variables. With Gaussian electronic structure basis sets in mind, it is shown that the position–momentum coupling seen in the Weyl representation of the exchange interaction is best described by diffuse Gaussians. A classical phase–space analog of exchange is derived for the Heisenberg–Dirac spin‐Hamiltonian. Novel one‐electron Wigner functions are introduced for description of the two‐electron spin correlations. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Inertial Sensed Ego‐motion for 3D Vision
Authors: Lobo Jorge , Dias Jorge
Published: December 2003

Inertial sensors attached to a camera can provide valuable data about camera pose and movement. In biological vision systems, inertial cues provided by the vestibular system are fused with vision at an early processing stage. In this article we set a framework for the combination of these two sensing modalities. Cameras can be seen as ray direction measuring devices, and in the case of stereo vision, depth along the ray can also be computed. The ego‐motion can be sensed by the inertial sensors, but there are limitations determined by the sensor noise level. Keeping track of the vertical direction is required, so that gravity acceleration can be compensated for, and provides a valuable spatial reference. Results are shown of stereo depth map alignment using the vertical reference. The depth map points are mapped to a vertically aligned world frame of reference. In order to detect the ground plane, a histogram is performed for the different heights. Taking the ground plane as a reference plane for the acquired maps, the fusion of multiple maps reduces to a 2D translation and rotation problem. The dynamic inertial cues can be used as a first approximation for this transformation, allowing a fast depth map registration method. They also provide an image independent location of the image focus of expansion and center of rotation useful during visual based navigation tasks. © 2004 Wiley Periodicals, Inc.
Principles of Fusion of Inertial Navigation and Dynamic Vision
Authors: Graovac Stevica
Published: December 2003

The possibility of fusion of navigation data obtained by two separate navigation
systems (strap‐down inertial one and dynamic vision based one)
is considered in this paper. The attention is primarily focused on principles
of validation of separate estimates before their use in a combined algorithm.
The inertial navigation system (INS) based on sensors of medium
level quality has been analyzed on one side, while a visual navigation method
is based on the analysis of a sequence of images of ground landmarks produced
by an on‐board TV camera. The accuracy of INS estimations is being
improved continuously by optimal estimation of a flying object's angular
orientation while the visual navigation system offers discrete corrections
during the intervals of presence of landmarks inside the camera's field
of view. The concept is illustrated by dynamic simulation of a realistic flight
scenario. © 2004 Wiley Periodicals, Inc.
Fusing Visual and Inertial Sensing to Recover Robot Ego‐motion
Authors: Alenyà Guillem , Martínez Elisa , Torras Carme
Published: December 2003

A method for estimating mobile robot ego‐motion is presented, which relies on tracking contours in real‐time images acquired with a calibrated monocular video system. After fitting an active contour to an object in the image, 3D motion is derived from the affine deformations suffered by the contour in an image sequence. More than one object can be tracked at the same time, yielding some different pose estimations. Then, improvements in pose determination are achieved by fusing all these different estimations. Inertial information is used to obtain better estimates, as it introduces in the tracking algorithm a measure of the real velocity. Inertial information is also used to eliminate some ambiguities arising from the use of a monocular image sequence. As the algorithms developed are intended to be used in real‐time control systems, considerations on computation costs are taken into account. © 2004 Wiley Periodicals, Inc.
Omnidirectional Vision and Inertial Clues for Robot Navigation
Authors: Stratmann Irem , Solda Erik
Published: December 2003

The structural features inherent in the visual motion field of a mobile robot contain useful clues about its navigation. The combination of these visual clues and additional inertial sensor information may allow reliable detection of the navigation direction for a mobile robot and also the independent motion that might be present in the 3D scene. The motion field, which is the 2D projection of the 3D scene variations induced by the camera‐robot system, is estimated through optical flow calculations. The singular points of the global optical flow field of omnidirectional image sequences indicate the translational direction of the robot as well as the deviation from its planned path. It is also possible to detect motion patterns of near obstacles or independently moving objects of the scene. In this paper, we introduce the analysis of the intrinsic features of the omnidirectional motion fields, in combination with gyroscopical information, and give some examples of this preliminary analysis. © 2004 Wiley Periodicals, Inc.
Electric fields of synaptic currents could influence diffusion of charged neurotransmitter molecules
Authors: Savtchenko Leonid P. , Kulahin Nikolaj , Korogod Sergey M. , Rusakov Dmitri A.
Published: December 2003

Rapid activation of synaptic receptor‐channels evokes an ion current that flows through the narrow synaptic cleft; this exerts a significant voltage drop and therefore strong electric field (104 V/m range) directed towards the current sinks in the cleft. To what extent this field affects fast diffusion of charged neurotransmitter molecules is not known. We draw a theoretical framework for this complex electrodiffusion phenomenon and establish the basic relationships between the synaptic current and the time course of neurotransmitter in the cleft. The analyses predict that excitatory currents could significantly accelerate the dispersion of negatively charged molecules from the cleft while attracting the positively charged molecules towards the current sinks. This previously unrecognized mechanism should affect the kinetics of synaptic receptor currents, thus contributing to fast synaptic signaling in the brain. Synapse 51:270–278, 2004. © 2003 Wiley‐Liss, Inc.
Changes in PKA activity and Gsα and Golfα levels after amphetamine‐ and cocaine‐induced behavioral sensitization
Authors: Crawford Cynthia A. , Choi Fiona Y. , Kohutek Jodi L. , Yoshida Shelly T. , Mcdougall Sanders A.
Published: December 2003

Neuroadaptations in the cAMP signal transduction system have been proposed to play a critical role in psychostimulant‐induced behavioral sensitization. Studies relevant to this hypothesis have provided conflicting evidence, however, because repeated cocaine and amphetamine treatment has been alternately reported to either increase or decrease protein kinase A (PKA) activity in the nucleus accumbens and dorsal striatum. In an attempt to reconcile these disparate findings, PKA activity and the stimulatory G‐protein subunits, Gsα and Golfα, were measured after rats had received a sensitization‐inducing regimen of amphetamine or cocaine. Results showed that seven consecutive daily injections of amphetamine or cocaine produced locomotor sensitization and caused a reduction in accumbal PKA activity. A challenge injection of amphetamine on the test day also reduced dorsal striatal PKA activity. Gsα levels were unaffected by psychostimulant exposure, while Golfα levels in the nucleus accumbens declined significantly after amphetamine or cocaine pretreatment. Because repeated amphetamine and cocaine treatment both induced behavioral sensitization and decreased accumbal PKA activity, it appears that psychostimulant‐induced increases in PKA activity are not necessary for the ultimate expression of behavioral sensitization. Synapse 51:241–248, 2004. © 2003 Wiley‐Liss, Inc.
Clozapine and dopamine D3 receptor antisense reduce cocaine‐ and amphetamine‐regulated transcript expression in the rat nucleus accumbens shell
Authors: Beaudry Geneviève , Zekki Hakima , Rouillard Claude , Lévesque Daniel
Published: December 2003

Cocaine‐ and amphetamine‐regulated transcript (CART) is a neuropeptide highly expressed in the hypothalamus and nucleus accumbens. Hypothalamic CART has been associated with food intake and body weight control, but in the nucleus accumbens the role of CART remains elusive. New generations of antipsychotic drugs show a good efficacy over psychotic symptoms but they induce an important weight gain. The mechanism underlying this unexpected side effect is still unknown. The present results show, for the first time, that acute and chronic treatment with the atypical neuroleptic clozapine, but not the conventional neuroleptic haloperidol, reduced the expression of CART mRNA in the shell of the nucleus accumbens. CART mRNA is colocalized with both dopamine D2 and D3 receptor transcripts in the nucleus accumbens shell. However, a dopamine D3 receptor, but not D2, antisense oligonucleotide administration reduced CART expression in this brain area. These results suggest that the dopamine D3 receptor, but not the D2, is involved in the control of CART expression in the nucleus accumbens and that it may participate in the modulation of CART mRNA levels by clozapine. The modulation of CART, an anorexigenic neuropeptide, in the dopamine mesolimbic pathway may potentially play a role in dysregulated food intake induced by some antipsychotic drugs. Synapse 51:233–240, 2004. © 2003 Wiley‐Liss, Inc.
Loss of nicotine‐induced behavioral sensitization in μ‐opioid receptor knockout mice
Authors: Yoo Ji‐Hoon , Lee Seok‐Yong , Loh Horace H. , Ho Ing K. , Jang Choon‐Gon
Published: December 2003

Repeated administration of nicotine produces behavioral sensitization. However, the possible mechanism of behavioral sensitization to nicotine remains unclear. The present study was undertaken in μ‐opioid receptor knockout mice, to examine the hypothesis that μ‐opioid receptors play a crucial role in behavioral sensitization to nicotine. All mice received saline or nicotine (0.05 mg/kg, s.c) twice a day for 7 consecutive days. The mice remained drug free for 3 days and on day 11 each group was challenged with saline or nicotine (0.05 mg/kg, s.c.). On day 1, it was observed that the single injection of nicotine (0.05 mg/kg, s.c.) did not influence locomotor activity in either μ‐opioid receptor knockout or in wildtype mice. On day 7 (24 h after mice had been treated twice daily for 6 consecutive days with an injection of 0.05 mg/kg of nicotine), the mice were challenged with a single injection of nicotine, which produced behavioral sensitization in the wildtype but not in μ‐opioid receptor knockout mice. On day 11, following 3 days of withdrawal after the second injection of nicotine on day 7, nicotine‐treated mice were challenged with a single injection of nicotine and showed the behavioral sensitization of wildtype. However, nicotine challenge did not induce behavioral sensitization in μ‐opioid receptor knockout mice. Our data indicate that a lack of μ‐opioid receptors can inhibit the effects of nicotine‐induced behavioral sensitization. This result strongly suggests that the μ‐opioid receptor plays an important role in behavioral sensitization to nicotine. Synapse 51:219–223, 2004. © 2003 Wiley‐Liss, Inc.
Lesion of subthalamic or motor thalamic nucleus in 6‐hydroxydopamine‐treated rats: Effects on striatal glutamate and apomorphine‐induced contralateral rotations
Authors: Touchon Justin C. , Moore Cynthia , Frederickson Julie , Meshul Charles K.
Published: December 2003

A unilateral lesion of the rat nigrostriatal pathway with 6‐hydroxydopamine (6‐OHDA) results in a decrease in the basal extracellular level of striatal glutamate, a nearly complete loss of tyrosine hydroxylase (TH) immunolabeling, an increase in the density of glutamate immunogold labeling within nerve terminals making an asymmetrical synaptic contact, and an increase in the number of apomorphine‐induced contralateral rotations. [Meshul et al. (1999) Neuroscience 88:1–16; Meshul and Allen (2000) Synapse 36:129–142]. In Parkinson's disease, a lesion of either the subthalamic nucleus (STN) or the motor thalamic nucleus relieves the patient of some of the motor difficulties associated with this disorder. In this rodent model, either the STN or motor thalamic nucleus was electrolytically destroyed 2 months following a unilateral 6‐OHDA lesions. Following a lesion of either the STN or motor thalamic nucleus in 6‐OHDA‐treated rats, there was a significant decrease (40–60%) in the number of apomorphine‐induced contralateral rotations compared to the 6‐OHDA group. There was a significant decrease (<30%) in the basal extracellular level of striatal glutamate in all of the experimental groups compared to the sham group. Following an STN and/or 6‐OHDA lesion, the decrease in striatal extracellular levels was inversely associated with an increase in the density of nerve terminal glutamate immunolabeling. There was no change in nerve terminal glutamate immunogold labeling in either the motor thalamic or motor thalamic plus 6‐OHDA lesion groups compared to the sham group. The decrease in the number of apomorphine‐induced rotations was not due to an increase in TH immunolabeling (i.e., sprouting) within the denervated striatum. This suggests that alterations in striatal glutamate appear not to be directly involved in the STN or motor thalamic lesion‐induced reduction in contralateral rotations. Synapse 51:287–298, 2004. Published 2003 Wiley‐Liss, Inc.
Gene expression profiling in the midbrain of striatal 6‐hydroxydopamine‐injected mice
Authors: Iwata Shin‐Ichi , Nomoto Masahiro , Morioka Hirofumi , Miyata Atsuro
Published: December 2003

In order to clarify mechanisms underlying dopaminergic neuronal death in Parkinson's disease (PD), a gene expression profiling study was performed in a rodent model of PD. In this model, mice are intrastriatally injected with 6‐hydroxydopamine (6‐OHDA) and dopaminergic neurons in the substantia nigra (SN) gradually die by retrograde degeneration. The SN were removed 2 h, 24 h, or 14 days after 6‐OHDA administration. Levels of mRNAs related to cell death or survival were quantified using adaptor‐tagged competitive PCR (ATAC‐PCR). The cyclin D1 gene showed an immediate increase in mRNA expression. After 24 h, when dopaminergic neurons were under intense degeneration, levels of caspase 8 mRNA and p53 apoptosis effecter related to pmp 22 (PERP) mRNA increased and, conversely, FAS mRNA decreased. After 14 days, when the degeneration was attenuated, levels of PERP mRNA and serum‐ and glucocorticoid‐regulated kinase (SGK) mRNA still increased. SGK has a similarity to AKT, which is an important molecule involved in nerve growth factor signal transduction. AKT mRNA levels are low in dopaminergic neurons. These results suggest that an increase in cyclin D1 mRNA triggers dopaminergic neurons to enter an abnormal cell cycle, which leads to neuronal degeneration and cell death, possibly induced by PERP and caspase 8. In addition to cell death‐related genes, several survival‐related genes are activated. SGK might function as a key enzyme for the survival of dopaminergic neurons. Synapse 51:279–286, 2004. © 2003 Wiley‐Liss, Inc.
Synthesis and Structure of the First Three‐legged Low‐dimensional Iron Phosphate, [H3N(CH2)3NH2(CH2)2NH2(CH2)3NH3][Fe3F6(HPO4)2(PO4)]·3H2O
Authors: Mandal Sukhendu , Pati Swapan K. , Green Mark A. , Wang Sue‐Lein , Natarajan Srinivasan
Published: December 2003

A hydrothermal reaction of iron acetylacetonate, phosphoric acid, HF, N, N′‐bis(3‐aminopropyl)ethylenediamine and water at 150 °C gave rise to a new iron phosphate, [H3N(CH2)3NH2(CH2)2NH2(CH2)3NH3][Fe3F6(HPO4)2(PO4)] · 3H2O (I). The structure consists of Fe(1)O4F2, Fe(2)O3F3 octahedral and P(1)O3(OH) and P(2)O4 tetrahedral building units connected through their vertices to form fragments of tancoite‐type units. The tancoite‐type units are linked through the phosphate tetrahedra forming an unusual iron phosphate with a hitherto unknown low‐dimensional structure with three‐iron center.Magnetic studies indicate a complex behavior at low temperature and the high‐temperature data (150 — 300 K) has a Curie‐Weiss behavior. The calculated room temperature magnetic moment is 6 μB per Fe atom, and the Neel temperature, TN = 46K. Crystal data: orthorhombic, space group = I212121 (no. 24), a = 9.9042(11), b = 12.8865(14), c = 19.783(2)Å, U = 2524.9(5), Z = 4.
Preparation of 1‐X‐2, 2‐Difluoroethenylxenon(II) Tetrafluoroborates [CF2=CXXe][BF4]
Authors: Frohn Hermann‐Josef , Bardin Vadim V.
Published: December 2003

The new type of alkenylxenon(II) salts [CF2=CXXe] [BF4] (X = H, Cl, CF3) was prepared by reacting the corresponding alkenyldifluoroboranes CF2=CXBF2 with XeF2 in 1, 1, 1, 3, 3‐pentafluoropropane (PFP) at —60 °C. The alkenylxenon(II) salts were characterised by multinuclear NMR spectroscopy. The influence of the substituent X at C‐1 on the stability of alkenylxenon(II) salts is discussed. Additionally the preparation of the potassium alkenyltrifluoroborate salts K [CF2=CXBF3] and their transformation into the boranes CF2=CXBF2 by fluoride abstraction in PFP is reported.
Metal‐Xenon Complexes
Authors: Seppelt Konrad
Published: December 2003

Long after the first isolation of a xenon compound in 1962 the first compounds with metal‐xenon bonds are prepared. The metal atoms are so far Au and Hg. The most stable metal xenon compounds decompose under loss of xenon slightly above room temperature. They can only exist if solvents and counter ions are weaker bases than atomic xenon. Solvents and counter ions used so far are HF, (SbF6)—, and (Sb2F11)—.
Two Mercury Chloro Thiocyanate Complexes: NH4[HgCl2(SCN)] and NH4[HgCl(SCN)2]
Authors: Gacemi Aissa , Benbertal Djamal , Bagieu‐Beucher Muriel , Lecchi Amélie , Mosset Alain
Published: December 2003

Single crystals of NH4[HgCl2(SCN)] (1) and NH4[HgCl(SCN)2] (2) are obtained by slow evaporation of ethanol solutions of HgCl2 and NH4SCN or Hg(SCN)2 and NH4Cl. 1 crystallizes in the monoclinic space group P21 (a = 9.297(1), b = 4.171(1), c = 9.198(1)Å, β = 92.827(5)°). The structure consists in HgCl2(SCN) linear chains, extending along the twofold axis, connected through the ammonium ions. 2 crystallizes in the monoclinic space group C2/c (a = 7.088(1), b = 19.986(2), c = 5.958(1)Å, β = 100.718(5)°). The structure consists of HgCl(SCN)2 molecules connected through the ammonium ions. The second order non linear optical properties of 1 are discussed.
Alkali‐Metal ortho‐Hydroxyphenolates: Syntheses and Crystal Structures from Powder X‐Ray Diffraction
Authors: Couhorn Uwe , Dronskowski Richard
Published: December 2003

Colorless and highly air‐ and moisture‐sensitive powders of M[o‐C6H4O(OH)] with M = K, Rb, or Cs have been synthesized from reaction mixtures of the appropriate alkali metal and catechol in thf. All compounds were structurally characterized by means of powder X‐ray diffraction using the Rietveld profile refinement technique including restraints for the C—C/C—O bond distances and the C—C—C angles. The atomic arrangements of M[o‐C6H4O(OH)] (K: monoclinic P21/c; Rb/Cs: orthorhombic Pbcm) are characterized by polymeric chains of [M1[4]O2[2]η6] units connected by hydrogen bonds, thereby making up layered structures similar to the one of catechol. The coordinatively unsaturated alkali metals are forming edge‐sharing MO4 pyramids and exhibit asymmetrical η6‐interactions with the phenylene rings. The symmetry of the unit cells increases with increasing size of the cation, and this results in a decrease of the monoclinic angle from 118.5° (catechol) to 93.7° (K compound), eventually leading to orthorhombic cells for the Rb and Cs compounds.
Die Kristallstrukturen von (NBu4)[(Ph3Sn)3(MoO4)2] und (NBu4)[(Ph3Sn)3(MoO4)2]·CH3CN: Organozinnmolybdate mit neuartigen 3D‐Netzwerken
Authors: Rosenland F. , Kondracka M. , Merzweiler K.
Published: December 2003

Die Umsetzung von (NBu4)2[Mo6O19] mit Ph3SnCl und (NBu4)OH in Acetonitril als Lösungsmittel führt zur Bildung von (NBu4)[(Ph3Sn)3(MoO4)2] (5). 5 und (NBu4)[(Ph3Sn)3(MoO4)2]·CH3CN (6) wurden durch Kristallstrukturanalysen charakterisiert. 5 kristallisiert monoklin in der Raumgruppe Cc mit den Gitterkonstanten (220 K): a = 1429, 5(4) pm, b = 2292, 2(3) pm, c = 2269, 7(5) pm, β = 107, 42(3)°. 6 kristallisiert orthorhombisch in der Raumgruppe P212121 mit den Gitterkonstanten (220 K): a = 1820, 5(1) pm, b = 1848, 6(2) pm and c = 2143, 9(1) pm. Die Kristallstrukturen von 5 und 6 bestehen aus isolierten (NBu4)+‐Kationen und anionischen 3D Netzwerken, die aus eckenverknüpften Ph3SnO2‐Bipyramiden und MoO4‐Tetraedern aufgebaut sind.
Platinum(II) Mixed Ligand Complexes with Thiourea Derivatives, Dimethyl Sulphoxide and Chloride: Syntheses, Molecular Structures, and ESCA Data
Authors: Hernández Wilfredo , Spodine Evgenia , Richter Rainer , Hallmeier Karl‐Heinz , Schröder Uwe , Beyer Lothar
Published: December 2003

The platinum(II) mixed ligand complexes [PtCl(L1‐6)(dmso)] with six differently substituted thiourea derivatives HL, R2NC(S)NHC(O)R′ (R = Et, R′ = p‐O2N‐Ph: HL1; R = Ph, R′ = p‐O2N‐Ph: HL2; R = R′ = Ph: HL3; R = Et, R′ = o‐Cl‐Ph: HL4; R2N = EtOC(O)N(CH2CH2)2N, R′ = Ph: HL5) and Et2NC(S)N=CNH‐1‐Naph (HL6), as well as the bis(benzoylthioureato‐κO, κS)‐platinum(II) complexes [Pt(L1, 2)2] have been synthesized and characterized by elemental analysis, IR, FAB(+)‐MS, 1H‐NMR, 13C‐NMR, as well as X‐ray structure analysis ([PtCl(L1)(dmso)] and [PtCl(L3, 4)(dmso)]) and ESCA ([PtCl(L1, 2)(dmso)] and [Pt(L1, 2)2]). The mixed ligand complexes [PtCl(L)(dmso)] have a nearly square‐planar coordination at the platinum atoms. After deprotonation, the thiourea derivatives coordinate bidentately via O and S, DMSO bonds monodentately to the PtII atom via S atom in a cis arrangement with respect to the thiocarbonyl sulphur atom. The Pt—S‐bonds to the DMSO are significant shorter than those to the thiocarbonyl‐S atom. In comparison with the unsubstituted case, electron withdrawing substituents at the phenyl group of the benzoyl moiety of the thioureate (p‐NO2, o‐Cl) cause a significant elongation of the Pt—S(dmso)‐bond trans arranged to the benzoyl‐O—Pt‐bond. The ESCA data confirm the found coordination and bonding conditions. The Pt 4f7/2 electron binding energies of the complexes [PtCl(L1, 2)(dmso)] are higher than those of the bis(benzoylthioureato)‐complexes [Pt(L1, 2)2]. This may indicate a withdrawal of electron density from platinum(II) caused by the DMSO ligands.
1:1 Adducts of Copper(I) and Silver(I) Halides with the Olefinic Phosphane Tri(1‐cyclohepta‐2, 4, 6‐trienyl)phosphane. Molecular Structures of CuX[P(C7H7)3] (X = Cl, Br), AgCl[P(C7H7)3] and {Cu(μ3‐I)[P(C7H7)3]}4
Authors: Herberhold Max , Akkus Nilgün , Milius Wolfgang
Published: December 2003

A suspension of CuX (X = Cl, Br) or AgCl in organic solvents (such as CH2Cl2) reacts with P(C7H7)3 (1) in a molar ratio 1:1 to give the mononuclear adducts CuX[P(C7H7)3] (X = Cl (2a), Br (2b)) and AgCl[P(C7H7)3] (3a) which crystallize as isotypic compounds in the orthorhombic space group Pnma (Z = 4). In the crystal, two (of the three) cyclohepta‐2, 4, 6‐trienyl substituents are present in the boat conformation, thus establishing a loose long‐distance interaction between the central double bond and the metal atom. A distorted pseudo‐tetrahedral coordination sphere is assumed to exist around the metal atom, with large P‐M‐X angles of 165.49(8)° (2a), 162.07(7)° (2b) and 168.54(3)° (3a), respectively. The tetrameric 1:1 adduct {Cu(μ3‐I)[P(C7H7)3]}4(2c) which was obtained from CuI and 1 in boiling ethanol, has also been characterized by X‐ray crystallography (monoclinic space group P2(1)/n, Z = 4); it contains all 12 cyclohepta‐2, 4, 6‐trienyl substituents in the chair conformation.

The NMR spectra (1H, 13C, 31P) of the new complexes 2a‐c and 3a indicate non‐rigid structures in solution. At room temperature, the 31P NMR signal of 3a appears as a doublet with an averaged coupling constant, 1J(Ag, P), of 700.1 Hz, whereas at —45 °C the two expected doublets are clearly discernible with coupling constants 1J(107Ag, 31P) = 671.0 Hz and 1J(109Ag, 31P) = 774.4 Hz, respectively.
Syntheses and Structures of two 1‐D Complexes, [Co(dmf)2(NCNCN)2] and [Cu(bipy)(NCNCN)]ClO4 with Bridging Dicyanamide Ligands
Authors: Dong Wen , Liang Mao , Sun Ya‐Qiu , Liu Zhan‐Quan
Published: December 2003

Two novel dicyanamide complexes [Co(dmf)2(NCNCN)2] (1) and [Cu(bipy)(NCNCN)]ClO4 (2) have been synthesized and structurally characterized. 1 crystallizes in the monoclinic space group C2 with a = 13.568(6)Å, b = 7.403(3)Å, c = 8.118(3)Å and Z = 2, whereas 2 crystallizes in the monoclinic system, Cc group, a = 14.270(7)Å, b = 9.143(5)Å, c = 12.371(1) Å, β = 118.612(7)°, and Z = 4. According to X‐ray crystallographic studies, in complex 1 each CoII ion is six‐coordinated with four nitrogen atoms from four μ1, 5‐dca (dca = dicyanamide) ligands and two oxygen atoms from two dmf ligands to form distorted octahedra. 1 forms a 1‐D network bridged via μ1, 5‐dca. 2 consists of a uniform Cu(NCNCN)Cu chain, each CuII ion is octahedrally coordinated with four nitrogen atoms from two μ1, 5‐dca ligands and one bipy ligand and two oxygen atoms from two ClO4— ions. The octahedral CuII ion shows a significant Jahn‐Teller distortion, with two axial oxygen atoms considerably farther from the copper than the four equatorial nitrogens.
Polysulfonylamine. CLXVI [1] Kristallstrukturen von Metall‐di(methansulfonyl)amiden. 15 [1] Die isotypen Kristallstrukturen von Ammonium‐ und Caesium‐dimesylamid: Kristallographische Kongruenz zwischen Wasserstoffbrücken N—H···O/N und Metall‐Ligand‐Bindungen Cs—O/N
Authors: Zerbe Eva‐Maria , Jones Peter G. , Moers Oliver , Blaschette Armand
Published: December 2003

Das Ammoniumsalz NH4[N(SO2CH3)2] ist isostrukturell zur früher beschriebenen Caesiumverbindung Cs[N(SO2CH3)2] (monoklin, Raumgruppe P21/n, Z = 4, V bei —140 °C: 0, 761 bzw. 0, 832 nm3). Das Caesiumion erreicht eine unregelmäßige (O6N)‐Heptakoordination durch Wechselwirkungen mit einem (O, N)‐ und einem (O, O)‐chelatisierenden sowie drei κ1O‐bindenden Anionen, während in der Struktur des Ammoniumsalzes jede der sieben (Cs—O/N)‐Bindungen perfekt von einer (N—H···O/N)‐Wasserstoffbrückenkomponente nachgeahmt wird. Zu diesem Zweck bilden drei N—H‐Donoren asymmetrische Dreizentrenbrücken, der vierte eine mittelstarke und annähernd lineare Zweizentrenbrücke. In den Kristallpackungen existieren zickzackförmige planare Kationreihen, die sich über Symmetriezentren fortpflanzen (Cs···Cs alternierend 422, 5 und 487, 5 pm, Cs···Cs···Cs 135, 7°; N···N alternierend 397, 4 und 474, 1 pm, N···N···N 136, 1°); die Kationreihen sind zwischen Anion‐Monoschichten in der Weise intercaliert, daß jede von vier translationsgenerierten Anionstapeln umgeben und gebunden wird und jeder Anionstapel zwei Kationreihen miteinander verknüpft. Im Endeffekt resultiert für die Caesiumverbindung ein dreidimensionales Netzwerk von Metall‐Ligand‐Bindungen, für das Ammoniumsalz ein damit kongruentes Netzwerk von Wasserstoffbrücken. Außerdem treten in beiden Strukturen schwache interanionische Wasserstoffbrücken des Typs C—H···O/N auf.
Surface Termination and Thermal Elimination Behaviour of Activated Hydrogenated Germanium
Authors: Schlecht Sabine , Himmel Hans‐Jörg
Published: December 2003

Activated hydrogenated germanium that shows a high chemical reactivity for insertion into various non‐metal/non‐metal bonds, was investigated by surface IR spectroscopy with respect to its surface properties and potential elimination reactions at the surface. Spectroscopic and kinetic data stongly suggest that the high reactivity is due to intrinsic defects and dangling bonds in the amorphous network and does not stem from an elimination step prior to the insertion of the activated germanium. Further investigations support our former description of activated germanium as a low‐valent germanium hydride with a minor content of chloride. In addition, small amounts of coordinated 1, 4‐dioxane can be found on the surface.
Synthesis and Crystal Structure of [Fe(Cp)2]3(Bi2Cl9)·thf
Authors: Savilov Serguei , Kloo Lars , Kuznetsov Alexei , Popovkin Boris , Fischer Andreas
Published: December 2003

Single crystals of [Fe(Cp)2]3(Bi2Cl9)·thf were obtained from a thf solution containing ferrocene and BiCl3. The structure shows disorder at room temperature which disappears upon cooling, coupled with a decrease in symmetry. The title compound crystallizes in the orthorhombic space group P212121 [a = 1698.64(2), b = 2318.69(3), c = 1085.66(2) pm] with three ferrocenium ions, one nonachlorodibismutate ion and one molecule of thf in the asymmetric unit.
Cyclooctatetraenyl Complexes of the Early Transition Metals and Lanthanides. 13. [1] The First Organolanthanide Complex of the Tripod Ligand [(C5H5)Co{P(O)(OEt)2}3]—
Authors: Reißmann Ulrike , Edelmann Frank T.
Published: December 2003

The reaction of [(η8‐C8H8)Sm(μ‐Cl)(THF)]2 (1) with Na[(C5H5)Co{P(O)(OEt)2}3] (2) in a molar ratio of 1:2 in THF solution affords orange, crystalline (η8‐C8H8)Sm[(C5H5)Co{P(O)(OEt)2}3] (3) as the first organolanthanide complex containing Kläui' tripod ligand. The compound has been fully characterized by elemental analysis and spectroscopic methods.
Anhydrous Mercurous Chlorate, Hg2(ClO3)2
Authors: Göbbels Dirk , Meyer Gerd
Published: December 2003

Colourless single crystals of the anhydrous mercurous chlorate were grown from a solution of mercuric oxide (HgO) in chloric acid (HClO3) in the presence of elemental mercury. The crystal structure (monoclinic, P21/n, Z = 4, a = 816.59(12), b = 641.02(5), c = 1290.3(2) pm, β = 97.506(12)°, R(all) = 0.0317) contains trans‐O2ClO‐Hg‐Hg‐OClO2 molecules with a Hg‐Hg distance of 251.03(4) pm, Hg‐O (bond) distances of 218 and 224 pm and Hg‐Hg‐O angles of 177 and 165°, respectively.
Synthesis and Crystal Structure of a new O, N Lithium Coordination Polymer
Authors: Ghassemzadeh Mitra , Heravi Majid M. , Hekmat‐Shoar Rahim , Neumüller Bernhard
Published: December 2003

The reaction of 4‐Amino‐6‐methyl‐1, 2, 4‐triazine‐3(2H)‐thione‐5‐one (HAMTTO) with n‐butyl lithium in dimethoxyethane (DME) gives the complex [Li(DME)(AMTTO)] (1). 1 was characterized by elemental analysis, IR‐ and mass‐spectrometry and an X‐ray structure analysis [space group P21/n, Z = 4, lattice dimensions at —80 °C: a = 867.6(1), b = 1721.5(2), c = 931.8(1) pm, β = 112.81(1)°, R1 = 0.0315. The complex is a coordination polymer along [001] with a zig‐zag arrangement.
Neue neutrale und kationische Mono‐Aziridin‐Komplexe des Typs [CpMn(CO)2Az], [CpCr(NO)2Az]+ und [(Ph3P)(CO)4ReAz]+ über CO‐, Hydrid‐ und Chlorid‐Abspaltungsreaktionen
Authors: Wilberger Roland , Piotrowski Holger , Warchhold Marcus , Lorenz Ingo‐Peter
Published: December 2003

Die Mono‐Aziridin‐Komplexe 1—5 werden nach drei unterschiedlich induzierten Substitutionsreaktionen hergestellt. Bei der photolytischen CO‐Abspaltung von [CpMn(CO)3] in Gegenwart von 2, 2‐Dimethylaziridin entsteht der neutrale Aziridin‐N‐Komplex [Cp(CO)2Mn{$\overline{N(H)CMe2C}$H2}] (1). Durch Hydrid‐Abspaltung von [(Ph3P)(CO)4ReH] mit CF3SO3H und nachfolgende Behandlung mit 2, 2‐Dimethylbzw. 2‐Ethyl‐aziridin lassen sich die salzartigen Aziridin‐Komplexe [(Ph3P)(CO)4Re{$\overline{N(H)CMe2C}$H2}](CF3SO3) (2) bzw. [(Ph3P)(CO)4Re{$\overline{N (H)CHEtC}$H2}](CF3SO3) (3) gewinnen. Die ebenfalls salzartigen Komplexe [Cp(NO)2Cr{$\overline{N(H)CMe2C}$H2}](BF4) (4) und [Cp(NO)2RCr{$\overline{N(H)CHEtC}$H2}](CF3SO3 (5) werden nach Chlorid‐Abstraktion aus [CpCr(NO)2Cl] mit AgX (X = BF4, CF3SO3) in Gegenwart von 2, 2‐Dimethyl‐ bzw. 2‐Ethylaziridin hergestellt. Den Röntgenstrukturanalysen zufolge sind die Metallatome trigonal pyramidal (1, 4, 5) bzw. oktaedrisch (cis‐Position, 2, 3) konfiguriert; die intakten Dreiringe sind über die verzerrt tetraedrisch konfigurierten N‐Atome gebunden. Verbindungen 1—5 sind hinsichtlich einer gezielten Alken‐Abspaltung unter Bildung von Nitren‐Komplexen stabil; ihre IR, 1H‐ und 13C{1H}‐NMR‐ und MS‐Spektren werden vorgestellt und diskutiert.
Darstellung, spektroskopische Charakterisierung und Normalkoordinatenanalyse der bindungsisomeren Tetrachloroiodoselenocyanatoosmate(IV). Kristallstruktur von trans‐(PPh4)2[OsCl4I(NCSe)]
Authors: Dallmann K. , Rehbehn S. , Preetz W.
Published: December 2003

Bei der Umsetzung einer Lösung von (n‐Bu4N)2[OsCl5I] in Dichlormethan mit darin suspendiertem Pb(SeCN)2 entstehen die Bindungsisomeren trans‐(n‐Bu4N)2[OsCl4I(NCSe)] (1) und trans‐(n‐Bu4N)2[OsCl4I(SeCN)] (2), die durch Ionenaustauschchromatographie an Diethylaminoethyl‐Cellulose getrennt werden. Die Röntgenstrukturanalyse an einem Einkristall von trans‐(PPh4)2[OsCl4I(NCSe)] (triklin, Raumgruppe P1¯, a = 10, 8950(13), b = 11, 076(2), c = 20, 980(2)Å, α = 96, 940(10), β = 98, 747(9), γ = 104, 419(11)°, Z = 2) zeigt, daß die annähernd lineare, zum Iodatom trans‐ständige Selenocyanatgruppe unter dem Os‐N‐C‐Winkel von 171, 1° koordiniert ist. Unter Verwendung der röntgenographisch bestimmten (1) und abgeschätzten (2) Molekülparameter lassen sich die IR‐ und Raman‐Spektren der beiden Bindungsisomeren durch Normalkoordinatenanalysen zuordnen. Die Valenzkraftkonstanten betragen fd(OsN) = 1, 70 und fd(OsSe) = 1, 15 mdyn/Å.
The causal ordering of mathematics anxiety and mathematics achievement: a longitudinal panel analysis
Authors: Ma X , Xu Jiangming
Published: December 2003

Using data from the Longitudinal Study of American Youth (LSAY), we aimed to determine the causal ordering between mathematics anxiety and mathematics achievement. Results of structural equation modelling showed that, across the entire junior and senior high school, prior low mathematics achievement significantly related to later high mathematics anxiety, but prior high mathematics anxiety hardly related to later low mathematics achievement. Mathematics achievement was more reliably stable from year to year than mathematics anxiety. There were statistically significant gender differences in the causal ordering between mathematics anxiety and mathematics achievement. Prior low mathematics achievement significantly related to later high mathematics anxiety for boys across the entire junior and senior high school but for girls at critical transition points only. Mathematics anxiety was more reliably stable from year to year among girls than among boys.
Increased leptin and white adipose tissue hypoplasia are sexually dimorphic in Lif null/Igf‐I haploinsufficient mice
Authors: Fernández-Moreno Carmen , Pichel Jose G , Chesnokova Vera , De Pablo Flora
Published: December 2003

We previously showed cooperation of leukemia inhibitory factor (LIF) and insulin‐like growth factor I (IGF‐I) during development. Mice doubly deficient in LIF and IGF‐I died at birth. We now analyze the possible combined influence of both factors on postnatal growth. The haploinsufficiency of the Igf‐I gene on a Lif null background caused a marked reduction in body mass index and white adipose tissue only in female mice. These animals had increased leptin, increased serum IGF‐I and apparent substitution of white adipose tissue by brown adipose tissue. The complex interrelationships between LIF and IGF‐I in regulating weight thus involve sexually dimorphic effects on adipose tissue differentiation and circulating leptin.
Radiative transfer equation inversion: Theory and shape factor models for retrieval of oceanic inherent optical properties
Authors: Hoge Frank E. , Lyon Paul E. , Mobley Curtis D. , Sundman Lydia K.
Published: December 2003

It is shown that the in‐water, shape factor formulation of the radiative transfer equation (RTE) (1) yields exact in‐air expressions for the remote sensing reflectance Rrs and the equivalent remotely sensed reflectance RSRa and (2) can be configured for inherent optical property (IOP) retrievals using standard linear matrix inversion methods. Inversion of the shape factor RTE is exact in the sense that no approximations are made to the RTE. Thus errors in retrieved IOPs are produced only by uncertainties in (1) the models for the shape factors and related quantities and (2) the IOP models required for inversion. Hydrolight radiative transfer calculations are used to derive analytical models for the necessary backscattering shape factor, radiance shape factor, fractional forward scattering coefficient, ratio of air‐to‐water mean cosines, and diffuse attenuation coefficient for in‐water upwelling radiance. These models predict the various shape factors with accuracies ranging typically from 2 to 20%. Using the modeled shape factors the in‐air remotely sensed reflectance RSRa can be predicted to within 20% of the correct (Hydrolight‐computed) values 96% of the time (or ±0.0005 sr−1 86% of the time) for the synthetic data used to determine the shape factor models. Inversion of this shape factor RTE using field data is a comprehensive study to be published in a later paper.
Comparison of thin ice thickness distributions derived from RADARSAT Geophysical Processor System and advanced very high resolution radiometer data sets
Authors: Yu Y. , Lindsay R. W.
Published: December 2003

Thin ice thickness distributions estimated from advanced very high resolution radiometer (AVHRR) and RADARSAT Geophysical Processor System (RGPS) data sets were compared over the Beaufort Sea and the Canada Basin for the period December 1996 to February 1997. The comparisons show a compelling agreement. High correlations were found in cases where thin ice grew in large, wide leads extending several hundred kilometers. At these large scales, estimates from AVHRR images and RGPS showed similar amounts of thin ice in leads. However, when major surface deformation occurred on small scales (100 m to 10 km), the finer spatial resolution (100 m) of RADARSAT images enabled the RGPS algorithm to derive more thin ice than that of AVHRR. Under such conditions the correlation between the two dropped, and a small negative bias (about 1%) was observed in the estimates from AVHRR. This bias, mostly concentrated at the very thin end of the thickness distribution, caused a further deficit in the AVHRR‐derived thin ice growth, roughly 0.2 cm/d. Although the AVHRR and RGPS algorithms treat snowfall differently in the ice thickness calculations, both snow assumptions appear reasonable. However, RGPS may underestimate the thin ice production because of the 3‐day sampling interval. With a better understanding of the sources of uncertainty and improved satellite estimates, a combination of these two satellite data could offer a wider coverage of thin ice thickness observations in the Arctic Basin.
Dense water cascading off the continental shelf
Authors: Shapiro G. I. , Huthnance J. M. , Ivanov V. V.
Published: December 2003

Cascading is a specific type of buoyancy‐driven current in which dense water formed by cooling, evaporation, or freezing in the surface layer over the continental shelf descends down the continental slope to a greater depth. We have identified, by world‐wide trawling and analysis of raw databases, several distinct mechanisms of preconditioning for cascades. We have validated, where possible, existing theories and developed simple models, which allow estimation of the parameters for preconditioning, initiating, and down‐slope fluxes as well as evolution of the temperature contrasts during cascading events. Compliance or noncompliance of observations with these simple and easy‐to‐use models has been related to the stage of cascade development and to local factors. Estimates of observed down‐slope transport rates in case studies accord with theory, which is thereby substantially validated. Typical values of cascading transport rates were in the range 0.5–1.6 m2s−1. We hazard a very approximate global estimate of order 105 km3yr−1 or average 3 Sv based on our findings and previous studies.
Modeling the densification of polar firn including heat diffusion: Application to close‐off characteristics and gas isotopic fractionation for Antarctica and Greenland sites
Authors: Goujon C. , Barnola J.‐M. , Ritz C.
Published: December 2003

Modeling the densification of polar firn is essential to estimate variations of close‐off characteristics (density, close‐off depth, delta age) in relation with past climate parameters (temperature and accumulation rates). Furthermore, the air composition in the firn is modified by gravitational and thermal fractionation, and stable isotope measurements of permanent gases like nitrogen or argon can provide information on the amplitude of these fractionations. In this work, we propose a new model coupling firn densification and heat diffusion. In addition to the determination of the firn thickness and gas‐ice age differences, the model allows a reconstruction of the time evolution of the temperature for different sites in Antarctica (Vostok) and Greenland (GISP2) and therefore the evolution of gravitational and thermal isotopic fractionations in firn. Under present‐day conditions, the modeled profiles are in good agreement with the available temperature measurements in firn. For sites with low accumulation rates such as Vostok, the results show the existence of temperature gradients in the firn column even when no rapid climatic changes occur. The comparison of the modeled δ15N results to measurements allows to better constrain the δ18O‐temperature relationship, used to infer the surface temperature history, and for GISP2, the model validates the long‐term borehole‐based temperature.
Geodynamic evolution of the Galápagos hot spot system (Central East Pacific) over the past 20 m.y.: Constraints from morphology, geochemistry, and magnetic anomalies
Authors: Werner R. , Hoernle K. , Barckhausen U. , Hauff F.
Published: December 2003

We report results of magnetic data from the Nazca Plate and of geochemical (major element and Sr‐Nd‐Pb‐isotope) analyses of rocks dredged from the Galápagos hot spot tracks (Cocos, Carnegie, Malpelo and Coiba Ridges and adjacent seamounts) in the Central East Pacific. Magnetic anomalies indicate that the Malpelo and Carnegie Ridges were once attached and that seafloor spreading separated the two ridges between 14.5 Ma and 9.5 Ma. The variations in Sr‐Nd‐Pb isotopic composition show that three of the mantle components currently observed at the Galápagos (Central, Southern, and Eastern) existed in the hot spot for at least 20 m.y., whereas the Northern Galápagos mantle component has been present for at least ∼15 Ma. Our data are consistent with the existence of a compositionally zoned/striped Galápagos plume since ∼20 Ma. Combined constraints from the morphology of the hot spot tracks, the magnetic record, and the isotope geochemistry of the rock samples provide new insights into the hot spot‐ridge geometry and interaction of the Galápagos hot spot with the Cocos‐Nazca spreading center (CNS) over the past 20 m.y. At 19.5 Ma a ridge jump moved the spreading axis to the northern edge of the hot spot. Between 19.5 and 14.5 Ma, the spreading axis was located above the center of the hot spot. At 14.5 Ma, a new ridge jump moved the spreading axis to the south, splitting the paleo‐Carnegie Ridge into the present Carnegie and Malpelo Ridges. The repeated ridge jumps reflect capture of the northwardly drifting spreading center by the Galápagos hot spot. At 11–12 Ma an offset of the spreading axis lay above the plume center. Spreading between the Carnegie and Malpelo Ridges continued until 9.5 Ma.
Cretaceous geomagnetic paleointensities: Thellier experiments on Pillow lavas and Submarine basaltic glass from the Ontong Java Plateau
Authors: Riisager Peter , Riisager Janna , Zhao Xixi , Coe Robert S.
Published: December 2003

We present new Thellier paleointensity results on pillow lavas and pillow‐rim submarine basaltic glass (SBG) from 120 Ma basalts erupted on the Ontong Java Plateau. All pillow lavas have suffered low‐temperature alteration and are unsuitable for Thellier paleointensity experiments. In contrast, pillow‐rim SBG is virtually impermeable to seawater and therefore has suffered little or no low‐temperature alteration. Out of 21 selected SBG samples with magnetic moment larger than 10−10 Am2, 18 samples (from 12 chilled SBG margins) yielded paleointensity estimates of good technical quality. Rock magnetic measurements show the primary carrier of remanence is low‐Ti titanomagnetite occurring in a continuous range of compositions starting from nearly pure magnetite. As suggested by a recent study, magnetic hysteresis parameters were monitored during the entire paleointensity experiment and a drastic change of parameters was observed above 400–440°C, which is in accordance with the partial thermoremanent magnetization checks failing significantly above the same temperature. We suggest that paleointensity estimates obtained below this critical temperature represent true determination of the paleomagnetic field strength. For several pillow margins two to three samples were measured, and in such cases the data agree well. Altogether we obtain reliable estimates from 12 SBG pillow‐rims, yielding a mean paleointensity of 27.1 ± 13.4 μT and a corresponding virtual axial dipole moment of 5.8 ± 2.8 · 1022 Am2. This value is slightly higher than whole rock data from similar aged subaerial lava flows. The paleosecular variation of the intensity estimates is slightly larger than previously reported for paleointensity determinations for the Cretaceous Normal Superchron.