bluuebunny/crossref_metadata_2025 huggingface dataset:
One‐dimensional Cadmium(II) Coordination Polymers: Syntheses and Crystal Structures of [Cd(H2O)3(C5H6O4)]·2H2O, Cd(H2O)2(C6H8O4), and Cd(H2O)2(C8H12O4)
Authors: Sun Jie , Zheng Yue‐Qing
Published: May 2003

[Cd(H2O)3(C5H6O4)]·2H2O (1) and Cd(H2O)2(C6H8O4) (2) were prepared from reactions of fresh CdCO3 precipitate with aqueous solutions of glutaric acid and adipic acid, respectively, while Cd(H2O)2(C8H12O4) (3) crystallized in a filtrate obtained from the hydrothermal reaction of CdCl2·2.5H2O, suberic acid and H2O. Compound 1 consists of hydrogen bonded water molecules and linear {[Cd(H2O)3](C5H6O4)2/2} chains, which result from the pentagonal bipyramidally coordinated Cd atoms bridged by bis‐chelating glutarato ligands. In 2 and 3, the six‐coordinate Cd atoms are bridged by bis‐chelating adipato and suberato ligands into zigzag chains according to {[Cd(H2O)3](C5H6O4)2/2} and {[Cd(H2O)2](C8H12O4)2/2}, respectively. The hydrogen bonds between water and the carboxylate oxygen atoms are responsible for the supramolecular assemblies of the zigzag chains into 3D networks. Crystallographic data: (1) P1¯ (no. 2), a = 8.012(1), b = 8.160(1), c = 8.939(1) Å, α = 82.29(1)°, β = 76.69(1)°, γ = 81.68(1)°, U = 559.6(1) Å3, Z = 2; (2) C2/c (no. 15), a = 16.495(1), b = 5.578(1), c = 11.073(1) Å, β = 95.48(1)°, U = 1014.2(1) Å3, Z = 4; (3) P2/c (no. 13), a = 9.407(2), b = 5.491(1), c = 11.317(2) Å, β = 95.93(3)°, U = 581.4(2) Å3, Z = 2.
Synthesis, Crystal Structure, and Spectral Properties of a Cobalt(II) Complex with N‐Salicylidene‐p‐Toluidine
Authors: Cseh Liliana , Csunderlik Carol , Pantenburg Ingo , Meyer Gerd , Costisor Otilia
Published: May 2003

The complex Co(C14H13NO)2Cl2 with the protonated N‐salicylidene‐p‐toluidine ligand was synthesized from an ethanolic solution of CoCl2·6H2O and N‐salicylidene‐p‐toluidine. The crystal structure was determined from X‐ray single crystal data (monoclinic, space group Cc, a = 1496.2(3) pm, b = 1257.4(4) pm, c = 1544.6(3) pm, β = 115.01(1)°, Z = 4). Co2+ adopts a distorted tetrahedral geometry. The UV‐Vis and IR spectra of the complex are discussed.
ACu9X4 ‐ Neue Verbindungen mit der CeNi8, 5Si4, 5‐Struktur (A: Sr, Ba; X: Si, Ge)
Authors: Kranenberg C. , Mewis A.
Published: May 2003

Durch Erhitzen entsprechender Elementgemenge auf 1000° ‐ 1100 °C entstehen SrCu9Si4 (a = 8, 146(1), c = 11, 629(2)Å), BaCu9Si4 (a = 8, 198(2), c = 11, 735(2)Å), SrCu9Ge4 (a = 8, 273(2), c = 11, 909(5)Å) sowie BaCu9Ge4 (a = 8, 338(4), c = 12, 011(7)Å) in Form dunkelgrauer Pulver. Die Verbindungen sind isotyp (I4/mcm, Z = 4) und kristallisieren in einer geordneten Besetzungsvariante des kubischen NaZn13‐Typs, der auch von der binären Phase BaCu13 gebildet wird. Deren Cu2‐Positionen werden bei den ternären Verbindungen geordnet von Kupfer und Silicium bzw. Germanium besetzt. Dies führt zu einer Erniedrigung der Symmetrie und einer Verzerrung der Koordinationspolyeder. Messungen des elektrischen Widerstands an BaCu9Si4 weisen die Verbindungen als metallische Leiter aus.
[Mn4Br(CH=CMe2)3(μ3‐NPEt3)4] — ein 2‐Methyl‐prop‐1‐enyl‐Phosphaniminato‐Komplex von Mangan(II) mit Heterokubanstruktur
Authors: Rölle Ulrike , Harms Klaus , Dehnicke Kurt
Published: May 2003

[Mn4Br(CH=CMe2)3(μ3‐NPEt3)4] — a 2‐Methyl‐prop‐1‐enyl‐Phosphoraneiminato Complex of Manganese(II) with Heterocubane Structure

[Mn4Br(CH=CMe2)3(μ3‐NPEt3)4] (1) has been prepared from [MnBr(μ3‐NPEt3)]4 and BrMg(CH=CMe2) in thf solution and subsequent extraction of the solvent‐free residue with n‐hexane. 1 forms red single crystals from diethylether solution, which are characterized by a crystal structure determination. Space group P1¯, Z = 2, lattice dimensions at —80 °C: a = 1144.7(1), b = 1411.3(2), c = 1521.8(2) pm, α = 91.581(14), β = 90.163(14), γ = 91.947(14)°, R1 = 0.0448. 1 exhibits a Mn4N4 heterocubane core, a terminally coordinated bromine ligand and three Mn—CH=CMe2 groups with M—C bond lengths of 213.8 pm on average.
Synthese und Kristallstruktur von Te3O3(PO4)2, einer Verbindung mit fünffach koordiniertem Tellur(IV)
Authors: Mayer Helmut , Weil Matthias
Published: May 2003

Polykristallines Te3O3(PO4)2 bildet sich bei der Entwässerung von (Te2O3)(HPO4) über die Zwischenstufe (Te8O10)(PO4)4. Farblose Einkristalle der Titelverbindung können gezielt durch Tempern stöchiometrischer Mengen der binären Oxide P2O5 und TeO2 im geschlossenen Kieselglasrohr bei 590 °C für 8 Stunden erhalten werden. Die Kristallstruktur (P21/c, Z = 4, a = 12.375(2), b = 7.317(1), c = 9.834(1)Å, β = 98.04(1)°, 1939 Strukturfaktoren, 146 Parameter, R[F2 > 2σ(F2)] = 0.0187, wR2(F2 alle) = 0.0367) wurde aus Vierkreisdiffraktometerdaten bestimmt und besteht aus [TeO5]‐Polyedern und PO4‐Tetraedern als einfachste Baueinheiten. In der Netzwerkstruktur sind zwei Telluratome über sehr kurze Bindungen zu Oxidsauerstoffen zu [Te2O3]2+‐Zickzackketten verbunden, die sich entlang [001] erstrecken. Das dritte Te‐Atom ist mit einer kurzen Te‐O‐Bindung seitlich an dieser Kette verankert und mit den Ecken von PO4‐Tetraedern zu den anionischen [Te(PO4)2]2—‐Einheiten verknüpft. Dadurch bilden sich Schichten der Zusammensetzung [Te2O3][Te(PO4)2] parallel zur bc‐Ebene aus, die über schwache Te‐O‐Bindungen dreidimensional verknüpft werden.
MNE Nitrido Bridges with Transition Metal Nitrogen Multiple Bonds and E = Phosphorus, Sulfur, and Chlorine
Authors: Dehnicke Kurt
Published: May 2003

A compilation is given on new syntheses, properties, and structures of complexes with M≡N—E ↔ M=N=E nitrido bridges with transition metal nitrogen multiple bonds and participation of the main group elements E of phosporus, sulfur, and chlorine.

1. MNP: This atomic sequence is realized in phosphoraneiminato complexes with transition metals in high oxidation states and termal bond of the (NPR3—) ligand. A series of new complexes of this type is reported with M = zirconium, hafnium, molybdenum, tungsten, and rhenium, among these the homoleptic species [Hf(NPPh3)4] and [M(NPPh3)4]2+ with M = Mo and W. Therefrom the isolobal complexes [:N≡Mo(NPPh3)3], [:O≡W(NPPh3)3]+, [(O)2Mo(NPPh3)2], and [(O)3Re(NPPh3)] are derived.

2. MNS: Adding to compounds with this atomic sequence, new complexes were developed on the basis of the functional ligand groups thionitrosyl (a), dinitridosulphate(II) (b), dinitridosulphate(IV) (c), and cyclothiazeno (d) (cyclo‐3, 5‐dithia‐2, 4, 6‐triazino):

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3. MNCl: Novel N‐chloroimido complexes of tungsten are described. [F4W≡N—Cl]4, which is tetrameric according to the IR spectrum, was obtained by direct fluorination from [Cl4W≡N—Cl]2 or, surprisingly, from W(N)Cl3. With acetonitrile the monomeric molecular complex [CH3CN→WF4(≡N—Cl)] is formed. In an unexpected pathway K[F5W≡N—Cl] was obtained from a redox reaction of W(N)Cl3 with trimethylstannyl fluoride in the presence of potassium fluoride. The ionic compound forms double layers with short Cl···F contacts.
Recent Advances in the Synthesis of N‐Heteroatom Substituted Imido Complexes Containing a Nitrido Bridge [M=N—E] (M = Group 4, 5 and 6 Metal, E = B, Si, Ge, P, S)
Authors: Weber Klaus , Korn Klaus , Schorm Andrea , Kipke Jennifer , Lemke Martin , Khvorost Alexander , Harms Klaus , Sundermeyer Jörg
Published: May 2003

The focus of the current report lies on recent developments of synthetic methods applied to the synthesis of some high‐valent complexes containing the nitrido functionality [N]3— as a link between a group 4, 5 or 6 transition metal and a main group element E (E = B, Si, Ge, P, S). Emphasis is put on results, that have been obtained within the “Schwerpunktprogramm “Nitridobrücken” funded by the Deutsche Forschungsgemeinschaft. The synthetic methods include condensation reactions of reactive chloro and oxo complexes (M = V, Nb, Ta, Cr, Mo, W) with silylamines, sulfonylamides, with N‐silyl and N‐lithio iminophosphoranes, furthermore methatesis reactions of oxo complexes with N‐sulfonyl sulfinyl amides (M = V, Cr, Mo, W), the oxidative addition of element azides to d2 metal centers (M = V, W), and finally transamination reactions of N‐H iminophosphoranes with amido complexes (M = Ti, Sm).
Reactions of the Complexes ReNCl2(PMe2Ph)3, [ReNCl4]—, [OsO3N]—, and Cl3VNCl with Metal Halides
Authors: Strähle Joachim
Published: May 2003

The nitrido complexes ReNCl2(PMe2Ph)3 and [OsO3N]— have strong basic terminal nitrido ligands which can react with Lewis acidic metal halides to form nitrido bridges. The synthesis and structure of complexes with ReNCl2(PMe2Ph)3 and nitrido bridges Re≡N‐M (M = B, Ga, Sn, Ti, Zr, V, Nb, Ta, Mo, Re, Pd, Au, and Zn) as well as of complexes with [OsO3N]— and nitrido bridges Os≡N‐M (M = Pd and Pt) are reported. Strong Lewis acids can also remove phosphine or chloro ligands from ReNCl2(PMe2Ph)3. The resulting complex fragments subsequently combine to yield oligomeric complexes with nitrido bridges Re≡N‐Re. If the reaction with strong Lewis acids is carried out in a chlorinated solvent the solvent can be decomposed to form HCl which then protonates the nitrido ligand affording an imido complex. [ReNCl4]— is able to form nitrido bridges to electrophilic halides if a donor ligand is coordinated in trans position to the nitrido ligand to enhance its basicity sufficiently. The synthesis and structure of examples with nitrido bridges Re≡N‐M (M = Pd, Pt, Ta) are reported.

The chloro imido complex Cl3V≡N‐Cl can act as a nitride ion transfer reagent. Its reaction with MoCl5 yields Mo2NCl8 whereas with MoCl3 the nitride chlorides Mo3N2Cl11 and MoNCl3 are obtained. Cl3VNCl can also act as an reactive intermediate by the reaction of VN with a halide as was shown by the reaction of MoCl5 with VN yielding Mo2NCl7. The structures of these molybdenum nitride chlorides are discussed.
Reactions of Rhenium and Technetium Nitrido Complexes with ER3 Fragments (E = B, Ga, Al, C, P; R = H, Alkyl, Aryl)
Authors: Abram Ulrich , Schmidt‐Brücken Burkhard , Hagenbach Adelheid , Hecht Maren , Kirmse Reinhard , Voigt Andreas
Published: May 2003

Terminal ‘N3—’ ligands in rhenium and technetium nitrido complexes are sufficiently nucleophilic to react with Lewis acids under formation of nitrido‐bridged compounds. The reactivity of the nucleophilic centre and the nature of the formed compounds are strongly dependent on the Lewis acid and the composition of the metal complex used.

Air‐stable compounds with Re≡N‐ER3 bridges are formed when ER3 is BR3 (R = H, Cl, Br, Ethyl, Phenyl, C6F5), BCl2Ph, GaCl3, CPh3+, or PPh3. The six‐co‐ordinate rhenium(V) complexes [ReNX2(PMe2Ph)3] (X = Cl, Br), [ReN(X)(Et2dtc)(PMe2Ph)2] (Et2dtc— = diethyldithiocarbamate) and [ReN(Et2dtc)2(PMe2Ph)] have been proved to be excellent starting materials for this type of reactions, whereas the five‐co‐ordinate precursors [ReNCl2(PPh3)2], [ReN(Et2dtc)2], [ReN{Ph2P(S)NP(S)Ph2}2] or [ReNCl4]— only react with the most reactive Lewis bases of the examples mentioned above such as BCl2Ph or B(C6F5)3. The rhenium‐nitrido bond lengths remain almost unchanged by the adduct formation, whereas a significant decrease of the trans‐influence of the nitrido complexes has been observed as can be seen by a shortening of the corresponding bond lengths or dimerization of five‐co‐ordinate precursors.

Electrophilic attack of the Lewis acid to a donor atom of the equatorial co‐ordination sphere of the rhenium complex results in the formation of ‘underco‐ordinate’ metal centres which resemble to di‐, tri or tetrameric units with asymmetric nitrido bridges between each two rhenium atoms.

EPR spectroscopy is an excellent tool to reflect the formation of nitrido bridges at the paramagnetic (d1) [ReNX4]— core (X = F, Cl, Br, NCS). The spectral parameters derived for the products of reactions of [ReNCl4]— with various boron compounds indicate an increase of the covalency of the equatorial Re‐L bonds as a consequence of the formation of a nitrido bridge.

The tendency for the formation of nitrido bridges with Lewis acids is significantly lower for technetium compounds compared to their rhenium analogues. Only a few examples with BH3 and BPhCl2 have been established.
N‐Silylaminotitanium Chlorides — Synthesis, Structures, Multinuclear Magnetic Resonance, and some Applications
Authors: Wrackmeyer Bernd , Weidinger Jürgen , Pedall Andreas , Milius Wolfgang
Published: May 2003

N‐Silylaminotitanium trichlorides, Me3S(R)N‐TiCl3 (18) [R = tBu (a), SiMe3 (b), 9‐borabicyclo[3.3.1]nonyl (9‐BBN)(c)], and (CH2SiMe2)2N‐TiCl3 (18d) were obtained in high yield and high purity from the reaction of the respective bis(silylamino)plumbylene with an excess of titanium tetrachloride. The crystal structure of 18a was determined by X‐ray analysis. The reactions of the analogous stannylenes with an excess of TiCl4 did not lead to 18. N‐Lithio‐trimethylsilyl[9‐(9‐borabicyclo[3.3.1]nonyl)]amine (8) was prepared, structurally characterized and used for the synthesis of a new bis(amino)stannylene 10 and a plumbylene 11. The compounds 18a—d served as ideal starting materials for the synthesis of bis(silylamino)titanium dichlorides, where the silylamino groups can be identical (19) or different (20). This was achieved either by the reaction of 18 again with bis(amino)plumbylenes or with lithium N‐silylamides. In contrast to the direct synthesis starting from titanium tetrachloride and two equivalents of the respective lithium amide, which in general affords 19 with identical amino groups only in low yield, the procedure starting from 18 is much more versatile and gave the pure compounds 19 or 20 in almost quantitative yield. Further treatment of the dichlorides 19 or 20 with lithium amides led to tris(amino)titanium chlorides 21. The dichlorides 19 or 20 reacted with two equivalents of alkynyllithium reagents to give the first well characterized examples of di(alkyn‐1‐yl)bis(N‐silylamino)titanium compounds 22—27. These compounds reacted with trialkylboranes (triethyl or tripropylborane) by 1, 1‐organoboration. In some cases, the extremely reactive reaction products could be identified as novel 1, 1‐bis(silylamino)titana‐2, 4‐cyclopentadienes 28—31 bearing a dialkylboryl group in 3‐position. In solution, the proposed structures of all products were deduced from a consistent set of data derived from multinuclear magnetic resonance spectroscopy (1H, 11B, 13C, 14N, 15N, 29Si, 35Cl NMR).
From [M≡N] and [M—N—E] Complexes to Models for Metal Oxidoreductases
Authors: Sellmann Dieter , Sutter Jörg
Published: May 2003

The article reviews results of research that was initially aiming at complexes containing new and unusual [M—N—E] element combinations (M = transition metal, E = main group element), but soon turned into studies on model complexes for metal enzymes such as nitrogenases, hydrogenases or CO dehydrogenases, because several of the resulting [M—N—E] complexes exhibited reactions relevant to these enzymes. It could be shown that alkylation of transition metal thiolate nitride complexes gives alkylimido complexes when bulky and mild alkylation reagents, e.g. Ph3C+, are used. Hydride addition to [Ru(NO)(pybuS4)]+ yielded [Ru(HNO)(pybuS4)], which contains a bifurcated [M—N(X, Y)] bridge. The diazene complex [μ‐N2H2{Ru(PCy3)(S4)}2] undergoes H+/D+ and H+/D2 exchange reactions that enabled to rationalize the until then inexplicable ‘N2 dependent HD formation’ catalyzed by nitrogenases. Out of a larger number of [Ni(NE)(S3)] complexes, the compound [Ni(NHPPr3)(S3)] proved capable to model structure and reactivity features of [NiFe] hydrogenases. The [Ni(L)(S3)] complexes with L = N3— and N(SiMe3)2— exhibit extremely high reactivity towards CO, CO2 and SO2. The reactions lead to NCO—, CN— and NSO— complexes and bear potential relevance for carbon monoxide dehydrogenase reactions.
Control of Oxidation States of Transition Elements (Cr, Mn) in Nitridometalates and the Solid Solution Series Li6(Ca1‐xSrx)2[Mn2N6]
Authors: Hochrein Oliver , Höhn Peter , Kniep Rüdiger
Published: May 2003

The formation of ternary nitridometalates from the elements in the case of the systems Li—Cr, V, Mn—N leads to compounds which contain the transition metals in the highest (VV, CrVI) or a comparably high (MnV) oxidation state. In the corresponding calcium and strontium systems, the transition metals show a lower oxidation state (VIII, CrIII, MnIII). Transition metals with intermediate oxidation states (CrV, MnIV) are present in the quaternary (mixed cation) compounds Li4Sr2[CrN6], Li6Ca2[MnN6], and Li6Sr2[MnN6] (R3¯(#148), a = 585.9(3) pm, c = 1908.6(4) pm, Z = 3), as well as in the solid solution series Li6(Ca1—xSrx)2[MnN6].
Misfolded plant virus proteins: elicitors and targets of ubiquitylation
Authors: Jockusch Harald , Wiegand Christiane
Published: June 2003

Mutant tobacco mosaic virus (TMV) coat proteins (CPs) with known amino acid replacements provide well defined examples of destabilized tertiary structures. Here we show that misfolded TMV CPs, but not functional wild‐type CPs, induce massive ubiquitylation in tobacco cells and that denatured, insoluble CP subunits are the main substrates of ubiquitin conjugation. As TMV CPs can be easily manipulated they are unique tools to study the molecular basis of the plant cell's response to aberrant protein structures and the associated intracellular stress reactions.
Mutagenesis analysis of the yeast Nha1 Na+/H+ antiporter carboxy‐terminal tail reveals residues required for function in cell cycle
Authors: Simón Ernesto , Barceló Anna , Ariño Joaquı́n
Published: June 2003

The yeast Nha1 Na+,K+/H+ antiporter may play an important role in regulation of cell cycle, as high‐copy expression of the NHA1 gene is able to rescue the blockage at the G1/S transition of cells lacking Sit4 protein phosphatase and Hal3 activities. Interestingly, this function was independent of the role of the antiporter in improving tolerance to sodium cations, it required the integrity of a relatively large region (from residues 800 to 948) of its carboxy‐terminal moiety, and was not performed by the fission yeast homolog antiporter Sod2, which lacks a carboxy‐terminal tail. Here we show that a hybrid protein composed of the Sod2 antiporter fused to the carboxy‐terminal half of Nha1 strongly increased sodium tolerance, but did not allow growth at high potassium nor did rescue growth of the sit4 hal3 conditional mutant strain. Deletion of Nha1 residues from 800 to 849, 900 to 925 or 926 to 954 abolished the function of Nha1 in cell cycle without affecting sodium tolerance. A screening for loss‐of‐function mutations at the 775–980 carboxy‐terminal tail of Nha1 has revealed a number of residues required for function in cell cycle, most of them clustering in two regions, from residues 869 to 876 (cluster A) and 918 to 927 (cluster B). The later is rather conserved in other related antiporters, while the former is not.
Actin dependent CD95 internalization is specific for Type I cells
Authors: Algeciras-Schimnich Alicia , E. Peter Marcus
Published: June 2003

CD95 Type I and Type II cells differ in the requirement for mitochondrial contribution to the execution of apoptosis. Mitochondria are required to amplify the apoptosis signal only in Type II cells. Here we show that CD95 internalizes in an actin dependent manner only in Type I cells and that the two CD95 apoptosis cell types differ in their threshold of active caspase‐8 required to execute apoptosis. The data suggest that CD95 is linked to the cytoskeleton in different ways in the two cell types and that they have adapted to different levels of active caspase‐8 generated at the activated receptor.
New intracellular components of bone morphogenetic protein/Smad signaling cascades
Authors: Zwijsen An , Verschueren Kristin , Huylebroeck Danny
Published: June 2003

Bone morphogenetic proteins (BMPs) regulate many processes in the embryo, including cell type specification, patterning, apoptosis, and epithelial–mesenchymal interaction. They also act in soft and hard tissues in adult life. Their signals are transduced from the plasma membrane to the nucleus through a limited number of Smad proteins. The list of Smad‐interacting proteins is however growing and it is clear that these partners determine the outcome of the signal. We summarize the present status in BMP/Smad signaling, with emphasis on recently identified Smad partners and how these proteins may cooperate in the regulation of the expression of BMP target genes.
Adiponectin represents an independent cardiovascular risk factor predicting serum HDL‐cholesterol levels in type 2 diabetes
Authors: Zietz B , Herfarth H , Paul G , Ehling A , Müller-Ladner U , Schölmerich J , Schäffler A
Published: June 2003

Low levels of high‐density lipoprotein (HDL)‐cholesterol represent an independent cardiovascular risk factor and, besides reduced physical activity, mechanisms leading to decreased HDL‐cholesterol levels are not known. We aimed to test the hypothesis, that adiponectin provides a missing link between type 2 diabetes and low levels of HDL‐cholesterol, independent from common metabolic risk factors. 523 patients with type 2 diabetes were investigated for adiponectin serum levels and parameters of lipid metabolism. Even after correction for age, gender, BMI and fasting insulin concentration, serum levels of adiponectin were highly significant (P<0.0001) and positively (regression analysis: r=0.86) associated with HDL‐cholesterol levels in type 2 diabetes. Conclusion: adiponectin seems to predict HDL‐cholesterol levels in patients with diabetes mellitus type 2. Low levels of adiponectin are associated with low levels of HDL‐cholesterol independently from common metabolic risk factors and therefore represent an independent cardiovascular risk factor in type 2 diabetes. Thus, adiponectin is a potentially new drug target in the treatment of dyslipidaemia.
Caspase‐1‐induced calpastatin degradation in myoblast differentiation and fusion: cross‐talk between the caspase and calpain systems
Authors: Barnoy Sivia , Kosower Nechama S.
Published: June 2003

Previously, we found that calpastatin diminished transiently prior to myoblast fusion (rat L8 myoblasts), allowing calpain‐induced protein degradation, required for fusion. Here we show that the transient diminution in calpastatin is due to its degradation by caspase‐1. Inhibition of caspase‐1 prevents calpastatin diminution and prevents myoblast fusion. Caspase‐1 activity is transiently increased during myoblast differentiation. Both calpain and caspase appear to be responsible for the fusion‐associated membrane protein degradation. Caspase‐1 has been implicated in the activation of proinflammatory cytokines, and in cell apoptosis. The involvement of caspase‐1 in L8 myoblast fusion represents a novel function for this caspase in a non‐apoptotic differentiation process, and points to cross‐talk between the calpain and caspase systems in some differentiation processes.
The C‐terminal domain of focal adhesion kinase reduces the tumor cell invasiveness in chondrosarcoma cell lines
Authors: Lee Jin Woo , Kim Yun Hee , Park Hee Boong , Xu Li‐Hui , Cance William G. , Block Joel A. , Scully Sean P.
Published: May 2003

Human chondrosarcoma is a malignancy that has no effective systemic therapy, making the interruption of the metastatic cascade critical to enhance patient survival. The processes of local invasion and metastases share similar mechanisms at a cellular level. Focal adhesion kinase (FAK) has been implicated in local invasion of malignant tumor cells. In the current manuscript we examine the effect of FAK inhibition on cell attachment to extracellular matrix (ECM) and in vitro invasion. Bovine articular chondrocytes and two human chondrosarcoma cell lines were utilized to examine FAK activity in tumor cell invasiveness. Endogenous FAK activity was inhibited by adenoviral transfection with the C‐terminal domain of FAK. This inhibition resulted from decreased FAK phosphorylation, while FAK expression remained unchanged. Inhibition of FAK phosphorylation and hence its activity lead to decreased cell adhesion to Type II collagen and decreased cell invasiveness. These effects were not due to changes in integrin expression, indicating that the inhibition was the result of disruption of outside: in signaling. There are three important aspects to these results. The first is that interruption of transmembrane signaling can affect cell attachment. The second is that in chondrosarcoma, cell differentiation correlates with FAK expression and metastatic potential. Thirdly, that cell invasiveness correlates with FAK activity and implies a mechanistic role for this molecular complex in local invasion and metastasis. © 2003 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved.
Relationship of demethylation processes to veratric acid concentration and cell density in cultures of Rhodococcus erythropolis
Authors: Paździoch‐Czochra Marzanna , Malarczyk Elżbieta , Sielewiesiuk Jan
Published: June 2003

The aim of this study was to investigate the correlation between veratrate degradation, veratric acid concentration and cell density in Rhodococcus erythropolis cultures. The optimum culture conditions for veratrate demethylation proved to be a cell density of A
660=1 and a concentration of 0.02% veratrate. All the products of demethylation (i.e. vanillic and protocatechuic acids) were found to be present and correlated with the appearance of high levels of free radicals and formaldehyde after contact of the cells with veratrate. Demethylation was accompanied by oscillatory changes in the levels of endogenous oxygen uptake and phenolic products. Changes in veratrate concentration and cell density caused a disturbance in the demethylation process and also in the efficiency of phenolics, formaldehyde and reactive oxygen species.
Runx transcription factors and the developmental balance between cell proliferation and differentiation
Authors: Coffman James A.
Published: June 2003

The runt box (Runx) is a highly conserved DNA binding and protein—protein interaction domain that defines a family of heterodimeric transcription factors with essential roles in metazoan development. The first member of this family to be identified was the Drosophila regulatory gene runt, which was named by virtue of its function in establishing segmentation patterns during embryogenesis, and subsequently discovered to have additional functions in sex determination and neurogenesis. A second Drosophila Runx gene, lozenge, is required for cell patterning in the eye and for hematopoiesis. The genome project has revealed the existence of two additional Drosophila Runx genes, which to date have not been functionally characterized. Other invertebrate species with well‐characterized Runx transcription factors include the nematode Caenorhabditis elegans and the sea urchin Strongylocentrotus purpuratus, each of which apparently contains only a single Runx gene.

There are three Runx genes in mammals; Runx1 is required for definitive hematopoiesis and is a frequently mutated gene in human leukemia, Runx2 is required for osteogenesis and is associated with cleidocranial dysplasia, and Runx3 controls neurogenesis in the dorsal root ganglia and cell proliferation in the gastric epithelium, and is frequently deleted or silenced in human gastric cancer. Studies using mammalian systems and sea urchins indicate that Runx proteins have essential functions in both cell proliferation and differentiation, and in mammals they are both proto‐oncogenes and tumor suppressors. Thus, a central question concerning the cell biology of Runx proteins is how are the opposing functions of this class of transcription factors regulated during development? Here I review current knowledge of Runx protein structure, function and regulation, and outline directions for future research aimed at understanding how Runx protein function is modulated during the transition from cell proliferation to differentiation in animal development.
Barriers to Physical Activity Perceived by Adolescent Girls
Authors: Robbins Lorraine B. , Pender Nola J. , Kazanis Anamaria S.
Published: May 2003

Girls in the United States are at high risk for inactivity and resultant overweight or obesity. Perceived barriers to physical activity are critical factors for health care professionals to consider when intervening with this population to increase physical activity. This descriptive study identified barriers to physical activity reported by girls in middle school. Participants were recruited from two middle schools in the Midwest. Using a Likert‐type scale, a total of 77 ethnically diverse girls, ages 11 to 14, responded to 23 items representing barriers to physical activity participation. Mean scores and percentages were computed for each barrier statement. The top barriers to physical activity that emerged for the girls in this investigation were “I am self‐conscious about my looks when I exercise” and “I am not motivated to be active.” Strategies that health professionals can use to counsel girls of this age in overcoming barriers to physical activity are presented. This health‐related information can enhance anticipatory guidance to girls.
A Life in Medicine: A Literary Anthology
Authors: Van Hoover Cheri
Published: May 2003

Edited by Robert Coles, MD, and Randy Testa with Joseph O'Donnel, MD, Penny Armstrong, CNM, MSN, and M. Brownell Anderson. New York: The New Press, 2002. 329 pages. $27.95, hardcover. Reviewed by: Cheri Van Hoover, CNM, MS, Faculty OB/GYN Group, Assistant Clinical Professor, University of California at San Francisco.
Abnormal Uterine Bleeding in Adolescents
Authors: Quint Elisabeth H. , Smith Yolanda R.
Published: May 2003

Menarche is an important event during adolescence. For most girls, it marks completion of puberty and the onset of reproductive capability. Menarche usually occurs when both breast and pubic hair development are at Tanner stage 4. Menstrual problems are common during adolescence due to slow maturation of the hypothalamic‐pituitary‐ovarian axis and can last 2 to 5 years after menarche. Although most problems are explained by anovulation, other causes must be considered and excluded in a logical and cost‐effective manner. Frequently, the bleeding problems observed in adolescence require evaluation and intervention.
Social Outcomes of Early Childbearing: Important Considerations for the Provision of Clinical Care
Authors: Fessle Kathryn Bondy
Published: May 2003

Traditional understanding of adolescent childbearing includes a belief that the social and economic consequences for both mother and child are almost universally negative. Recent research, however, reveals that the outcomes resulting from the birth of children to young mothers are diverse and complex. Social circumstances contributing to adolescent pregnancy and parenting, such as poverty, poor educational opportunity, and violence, are also causes of less than optimal outcomes for young mothers and their children; thus, attributions of cause and effect are difficult to make. By reviewing outcomes research that approaches this question in a number of more creative ways, clinicians can gain a more complete understanding of this phenomenon. It is hoped that health care providers with access to new evidence about the social consequences of adolescent childbearing will have improved success and satisfaction in providing competent, compassionate care to pregnant and parenting adolescents.
Adolescent Sexual Risk Assessment
Authors: Martyn Kristy K. , Martin Rosiland
Published: May 2003

This article describes the use of a self‐administered event history calendar and interviews about sexual partners, sexual activity, and contraception within the broader context of the adolescent's life. Constant comparative analysis was used to analyze the event history calendar interview data. Detailed 5‐ to 9‐year sexual histories were obtained on the event history calendars, including patterns of sexual activity progression and triggers for unintended sexual intercourse. Discussions of protective and risky sexual decision making were stimulated by adolescents' self‐report of sexual risk behavior in their own words and reflective responses on the event history calendar. Both the adolescents and the interviewers thought the calendars encouraged recall and discussion of sexual risk behavior.
Improving Suicide Risk Assessment in a Managed-Care Environment
Authors: Brown G.S. , Jones Edward R. , Betts Ellen , Wu Jingyang
Published: May 2003

Summary: This article describes the quality improvement intervention of a managed behavioral healthcare company to improve the quality of suicide risk assessments by its panel of providers. At-risk cases are identified by the patient's self-reported high frequency of suicidal ideation on a standardized outcome measure. Clinicians also assess severity of suicidal ideation based on clinical interviews. The clinician's assessment is identified as probably erroneous if the patient report indicates a high frequency of suicidal ideation and the clinicians assessment of suicidal ideation is none. The article describes the methods used to encourage clinicians to utilize information from the patient self-report measure as part of the clinical assessment. Probable suicidal ideation assessment errors were subsequently reduced by 29% over a 1-year period of administration.
Effects of rain on Ku‐band backscatter from the ocean
Authors: Contreras Robert F. , Plant William J. , Keller William C. , Hayes Kenneth , Nystuen Jeffrey
Published: June 2003

During the Kwajalein Experiment (KWAJEX) in July and August 1999, measurements of the normalized radar cross section of the ocean, σo, were made at Ku‐band with HH and VV polarizations from the R/V Ronald H. Brown. Data were collected at a variety of incidence angles during periods of rainfall as well as during clear conditions. During the experiment the rainfall rate ranged from 0 to 80 mm hr−1. Coincident with the backscatter measurements, measurements of rain rate, wind speed, wind direction, and fluxes of heat and momentum were made. Since we were primarily interested in backscatter from the surface, we removed backscatter from the raindrops themselves for the σo measurements reported here. As a secondary result we show that the backscatter from the rain drops is a good indicator of rain rate. Most of the data were collected with the ship stationary and the bow held into the wind. Thus the azimuth angle between the antenna look direction and the direction from which the wind came was predominantly between 0° and 90°. Over this range, rain was found to increase σo at incidence angles of 30° to 75°, to have little effect near 20°, and to decrease σo very slightly between 14° and 16°. At all incidence angles, no discernible dependence of σo on wind speed was found during rainfall for wind speeds below 10 m s−1; within experimental error the level of σo depended only on rain rate. For the lower incidence angles, this dependence was very small while at the higher incidence angles, σo depended on rain rate to a power that varied between about 0.5 and 1.2, being somewhat higher at large incidence angles and higher for HH polarization. The implication of these results is that rain produces small‐scale surface displacements (wavelengths shorter than about 3 cm) that roughen the ocean surface much more than the wind for wind speeds below 10 m s−1. The results also imply that when rain fills the entire scatterometer footprint on the surface and the wind speeds are low to moderate, scatterometry at Ku band is impossible.
Validation through comparison: Measurement and calculation of the bistatic radar cross section of a stealth target
Authors: Gürel L. , Bağcı H. , Castelli J. C. , Cheraly A. , Tardivel F.
Published: June 2003

Bistatic radar cross section (BRCS) values of a stealth airborne target are predicted by performing both scaled‐model measurements and numerical simulations. In order to achieve the solution of large‐scale electromagnetic problems in the numerical simulation environment, the fast multipole method (FMM) is implemented and used. The FMM has produced remarkably accurate results, in addition to its efficiency. The efficiency of the FMM is due to its reduced computational complexity and memory requirement, which are both O(N1.5). Comparison of the measured and computed BRCS values has resulted in a striking agreement, which serves to validate both of the prediction techniques.
Atmospheric sulfur deposition alters pathways of gaseous carbon production in peatlands
Authors: Vile Melanie A. , Bridgham Scott D. , Wieder R. Kelman , Novák Martin
Published: June 2003

Peatlands represent large carbon (C) reservoirs that can act as a source or sink for greenhouse gases. The response of peatland gaseous C fluxes to global climate change and atmospheric sulfate deposition, however, remains uncertain. Methanogenesis is thought to be one of the most important anaerobic C mineralization pathways in peatlands, especially in regions where input of sulfate from acid deposition is low. However, sulfate reduction has been quantified rarely in freshwater wetlands. Here we report greater anaerobic C flow through sulfate reduction than through methanogenesis at all sites situated along a global atmospheric sulfur deposition gradient. Stoichiometric mass balance suggests that fermentation is a dominant anaerobic C mineralization pathway in unpolluted peatlands, while methanogenesis contributed minimally to total anaerobic carbon mineralization in these sites. Furthermore, global increases of atmospheric sulfur deposition minimize the impacts of climatic warming by simultaneously decreasing rates of methanogenesis while causing little change in rates of total anaerobic C mineralization in Sphagnum‐dominated peatlands.
Optimization of an inductively coupled plasma–optical emission spectrometry method for the rapid determination of high‐precision Mg/Ca and Sr/Ca in foraminiferal calcite
Authors: Green D. R. H. , Cooper M. J. , German C. R. , Wilson P. A.
Published: June 2003

The ability to measure Mg/Ca and Sr/Ca in foraminiferal calcite has increased in importance following their identification as palaeoceanographic tracers with significant potential to constrain past changes in ocean chemistry and temperature. However, in order to tackle palaeoceanographic problems, it is essential to develop methods for the determination of these ratios that have both rapid sample throughput and high analytical precision. Here, we demonstrate the importance of simultaneous measurement for high‐precision Mg/Ca and Sr/Ca analysis. Our method is readily applicable to automated analysis over a wide range of Ca concentrations and is not subject to significant matrix effects. Using a “dual view” inductively coupled plasma–optical emission spectrometer (ICP‐OES), supported by a dedicated autosampler, we have investigated three nebulizers and two spray chambers and determined optimum analytical parameters. We show that there are consistent relationships between signal‐to‐noise ratio and gas flow rates and that the working sample dilution range has an important effect on linear response. Further, for this instrument it is important to manually constrain the timing of measurements to obtain truly simultaneous readings. Using the method developed, precisions of better than 0.21% are obtained for Mg/Ca and Sr/Ca in solutions containing between 1 and 4 ppm Ca with no significant matrix effect, using a Glass Expansion “Conikal” nebulizer coupled with a “Tracey” spray chamber, in autosampler mode.
Simulated North Atlantic‐Nordic Seas water mass exchanges in an isopycnic coordinate OGCM
Authors: Nilsen J. E. Ø. , Gao Y. , Drange H. , Furevik T. , Bentsen M.
Published: June 2003

The variability in the volume exchanges between the North Atlantic and the Nordic Seas during the last 50 years is investigated using a synoptic forced, global version of the Miami Isopycnic Coordinate Ocean Model (MICOM). The simulated volume fluxes agree with the existing observations. The net volume flux across the Faroe‐Shetland Channel (FSC) is positively correlated with the net flux through the Denmark Strait (DS; R = 0.74 for 3 years low pass filtering), but negatively correlated with the net flux across the Iceland‐Faroe Ridge (IFR; R = −0.80). For the Atlantic inflow across the FSC and IFR, the correlation is R = −0.59. For the transports through the FSC and DS, the simulation suggests that an atmospheric pattern resembling the North Atlantic Oscillation is the main driving force for the variations, involving Ekman fluxes and barotropic adjustment. The model also shows a 0.7 Sv reduction of the Atlantic inflow to the Nordic Seas since the late 50's.
Transport of forest fire smoke above the tropopause by supercell convection
Authors: Fromm Michael D. , Servranckx René
Published: June 2003

A recent letter [Fromm et al., 2000] postulated a link between boreal forest fire smoke and observed stratospheric aerosol enhancements in 1998. Therein a case was made that severe convection played a role in the cross‐tropopause transport. A similar occurrence of stratospheric aerosol enhancements in the boreal summer of 2001 was the stimulus to investigate the causal mechanism more deeply. Herein, we show a detailed case illustrating the unambiguous creation of a widespread, dense smoke cloud in the upper troposphere and lower stratosphere (UT/LS) by a Canadian forest fire and explosive convection in May 2001. This event is the apparent common point for several downstream stratospheric mystery cloud observations. Implications of this finding and those pertaining to the boreal summer of 1998 are that convection and boreal biomass burning have an under‐resolved and under‐appreciated impact on the upper troposphere, lower stratosphere, radiative transfer, and atmospheric chemistry.
A theoretical study of the energetics and IR frequencies of hydroxyl defects in forsterite
Authors: Braithwaite J. Spencer , Wright Kate , Catlow C. Richard A.
Published: June 2003

Computer modeling techniques have been used to study the structure and energetics of H defects in Mg2SiO4 forsterite and their infrared stretching frequencies. The calculated defect binding energies indicate that OH groups will combine with cation vacancies to form neutral defect complexes. Such defect clusters are stabilized by strong hydrogen bonding. Calculated infrared stretching frequencies for OH in different environments have been determined for the first time and show two distinct groups of frequencies. The values of these frequencies, together with their directional components, are compared to experimental measurements. This comparison shows that in pure forsterite, H defects will be associated with both Si and Mg vacancies, but will not occur as isolated OH groups, in line with the results from consideration of defect energetics.
Variability of the shelf break jet in the Middle Atlantic Bight: Internally or externally forced?
Authors: Fratantoni P. S. , Pickart R. S.
Published: June 2003

Velocity records from two bottom‐mounted acoustic Doppler current profilers, deployed at the shelf break south of New England are used to characterize the mesoscale variability of the shelf break frontal jet in the Middle Atlantic Bight. While on average the jet is equatorward, energetic current fluctuations dominate the 18‐month record at a period near 13 days. The fluctuations are characterized by a deceleration in the equatorward flow over the full water column and are strong enough to reverse the jet near the bottom. The origin of the observed variability is explored with the help of local wind records, concurrent velocity measurements from three tall current meter moorings deployed over the continental slope, and Gulf Stream frontal position information. While we are unable to attribute definitively the observed variability to a single forcing mechanism, we are able to discount several of the traditional possibilities. These include local effects, such as wind driving and tidal rectification, as well as offshore forcing due to Gulf Stream rings, topographic Rossby waves, and the meandering of the Gulf Stream. It is most probable that the fluctuations are caused by baroclinic instability of the shelf break jet. However, we are not able to determine this unequivocally, as our records differ from historical observations of instabilities, and stability models tend to oversimplify the salient features of the jet.
On the formation of Subtropical Countercurrent to the west of the Hawaiian Islands
Authors: Liu Qinyu , Wang Shaoxia , Wang Qi , Wang Wei
Published: June 2003

Analysis of recent ocean model‐assimilation results suggest that the eastward countercurrent in the Northern Subtropical Pacific may be divided into two branches: one in the Northwestern Pacific (19°N ∼ 27°N to the west of 170°E) and the other to the west of the Hawaii Islands (to the west of the 158°W) along 19°N ∼ 20°N. Two mechanisms contribute to the formation of the eastward countercurrent to the west of Hawaii: First, the Hawaiian Islands blocks the easterly trade winds and generates a dipole of wind stress vorticity with positive wind curl to the north of the Islands (20°N ∼ 23°N) and with negative curl to the south (16°N ∼ 19°N). This dipole of wind stress vorticity acts to create an eastward current jet to the west of the Hawaii Island, through the Sverdrup relation. Second, the islands can directly block the westward North Equator Current (NEC) to generate an eastward current to the west of the islands. We use a numerical model to test these mechanisms for the generation of the eastward countercurrent to the west of the Hawaii Islands. The results show that while the dipole of the wind stress vorticity is helpful in the forming of the eastward countercurrent, and as the NEC impinges upon the Islands the westward traveling “vortex streets” formed in the ocean plays a key role in intensifying the eastward current to the west of the Hawaiian Islands.
Variability in tropical tropospheric ozone: Analysis with Global Ozone Monitoring Experiment observations and a global model
Authors: Valks P. J. M. , Koelemeijer R. B. A. , van Weele M. , van Velthoven P. , Fortuin J. P. F. , Kelder H.
Published: June 2003

Tropical tropospheric ozone columns (TTOCs) have been determined with a convective‐cloud‐differential (CCD) method, using ozone column and cloud measurements from the Global Ozone Monitoring Experiment (GOME) instrument. GOME cloud top pressures, derived with the Fast Retrieval Scheme for Clouds from the Oxygen A‐band (FRESCO) method, indicate that most convective cloud top levels are between 300 and 500 hPa and do not extend to the tropical tropopause. The new GOME‐CCD method takes this tropical transition layer below the tropopause into account and uses above‐cloud and clear‐sky ozone column measurements to derive a monthly mean TTOC below 200 hPa. Validation of the GOME‐TTOCs with seven Southern Hemisphere Additional Ozonesondes (SHADOZ) sites shows good agreement, with an RMS difference of about 5 Dobson units. In the northern tropics the GOME‐TTOC compares most of the time well with in situ measurements at Paramaribo (6°N, 55°W) and Abidjan (5°N, 4°W). Analysis of the GOME‐TTOCs for 2000 and 2001, with the aid of the chemistry‐transport model TM3, illustrates that the variability in the TTOC depends on a complex interaction of several processes, including biomass burning, lightning, and large‐scale transport. The much larger extent of the South Atlantic TTOC maximum in September–October 2001, compared to September–October 2000, can be attributed to differences in large‐scale transport. An exceptional situation in the northern tropics occurred during the biomass burning season December 2001 to January 2002, when there were almost no fires over northern Africa. This resulted in strongly reduced TTOCs over the Atlantic between the equator and 10°N.