bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrostatic Calculation of the Substituent Effect: An Efficient Test on Isolated Molecules
Authors: Exner Otto , Böhm Stanislav 
Published: October 2003

AbstractThe energy of a disubstituted molecule has often been approximated by simple electrostatic formulas that represent the substituents as poles or dipoles. Herein, we test this approach on a new model system that is more direct and more efficient than testing on acid–base properties. The energies of 27 1,4‐derivatives of bicyclo[2.2.2]octane were calculated within the framework of the density functional theory at the B3LYP/6‐311+G(d,p) level; interaction of the two substituents was evaluated in terms of isodesmic homodesmotic reactions. This interaction energy, checked previously on some experimental gas‐phase acidities, was considered to be accurate and served as reference to test the electrostatic approximation. This approximation works well in the qualitative sense as far as the sign and the order of magnitude are concerned: beginning with the strongest interaction between two poles, a weaker interaction between pole and dipole, and the weakest between two dipoles. However, all the electrostatic calculations yield energies that are too small, particularly for weak interaction, and this fundamental defect is not remedied by some possible improvements. In particular, variation of the effective permittivity would require a physically impossible value less than unity. The explanation must lie in a more complex distribution of electron density than anticipated in the electrostatic model. It also follows that possible conclusions about the transmission of substituent effects “through space” have little validity.
Hydrogen Adsorption in Carbon Nanostructures: Comparison of Nanotubes, Fibers, and Coals
Authors: Schimmel H. Gijs , Kearley Gordon J. , Nijkamp Marije G. , Visser Cornelis T. , de Jong Krijn P. , Mulder Fokko M. 
Published: October 2003

AbstractSingle‐walled carbon nanotubes (SWNT) were reported to have record high hydrogen storage capacities at room temperature, indicating an interaction between hydrogen and carbon matrix that is stronger than known before. Here we present a study of the interaction of hydrogen with activated charcoal, carbon nanofibers, and SWNT that disproves these earlier reports. The hydrogen storage capacity of these materials correlates with the surface area of the material, the activated charcoal having the largest. The SWNT appear to have a relatively low accessible surface area due to bundling of the tubes; the hydrogen does not enter the voids between the tubes in the bundles. Pressure–temperature curves were used to estimate the interaction potential, which was found to be 580±60 K. Hydrogen gas was adsorbed in amounts up to 2 wt % only at low temperatures. Molecular rotations observed with neutron scattering indicate that molecular hydrogen is present, and no significant difference was found between the hydrogen molecules adsorbed in the different investigated materials. Results from density functional calculations show molecular hydrogen bonding to an aromatic CC bond that is present in the materials investigated. The claims of high storage capacities of SWNT related to their characteristic morphology are unjustified.
Computational Assessment of the Electronic Structure of 1‐Azacyclohexa‐2,3,5‐triene (3δ2‐1H‐Pyridine) and Its Benzo Derivative (3δ2‐1H‐Quinoline) as well as Generation and Interception of 1‐Methyl‐3δ2‐1H‐quinoline
Authors: Schöneboom Jan C. , Groetsch Stefan , Christl Manfred , Engels Bernd 
Published: October 2003

AbstractTreatment of a solution of 3‐bromo‐1‐methyl‐1,2‐dihydroquinoline (9) and [18]crown‐6 in furan or styrene with KOtBu followed by hydrolysis afforded a mixture of 1‐methyl‐1,2‐dihydroquinoline (10) and 1‐methyl‐2‐quinolone (11). If the reaction was performed in [D8]THF and the mixture was immediately analysed by NMR spectroscopy, 2‐tert‐butoxy‐1‐methyl‐1,2‐dihydroquinoline (17) was shown to be the precursor of 10 and 11. The structure of 17 is evidence for the title cycloallene 7, which arises from 9 by β elimination of hydrogen bromide and is trapped by KOtBu to give 17 so fast that cycloadditions of 7 with furan or styrene cannot compete. Since this reactivity is unusual compared to the large majority of the known six‐membered cyclic allenes, we performed quantum‐chemical calculations on 8, which is the parent compound of 7, and the corresponding isopyridine 6 to assess the electronic nature of these species. The ground state of 6 was no longer an allene (6 a) but the zwitterion 6 b. In the case of 8, the allene structure 8 a is more stable than the zwitterionic form 8 b by only ≈1 kcal mol−1. These results suggest a high reactivity of 6 and 8 towards nucleophiles and explains the behaviour of 7. In addition to the ground states, the low‐lying excited states of 6 and 8 were considered, which are represented by the diradicals 6 c and 8 c and, as singlets, lie above 6 b and 8 a by 19.1–24.8 and 14.4–17.7 kcal mol−1, respectively.
Unusual Iron(III) Ate Complexes Stabilized By Li–π Interactions
Authors: Mund Garry , Vidovic Dragoslav , Batchelor Raymond J. , Britten James F. , Sharma Rajendra D. , Jones Colin H. W. , Leznoff Daniel B. 
Published: October 2003

AbstractSeveral iron(III) complexes incorporating diamidoether ligands are described. The reaction between {Li2[RN(SiMe2)]2O} and FeX3 (X=Cl or Br; R=2,4,6‐Me3Ph or 2,6‐iPr2Ph) form unusual ate complexes, {FeX2Li[RN(SiMe2)]2O}2 (2, X=Cl, R=2,4,6‐Me3Ph; 3, X=Br, R=2,4,6‐Me3Ph; 4, X=Cl, R=2,6‐iPr2Ph) which are stabilized by Li–π interactions. These dimeric iron(III)–diamido complexes exhibit magnetic behaviour characteristic of uncoupled high spin (S= 5/2 ) iron(III) centres. They also undergo halide metathesis resulting in reduced iron(II) species. Thus, reaction of 2 with alkyllithium reagents leads to the formation of iron(II) dimer {Fe[Me3PhN(SiMe2)]2O}2 (6). Similarly, the previously reported iron(III)–diamido complex {FeCl[tBuN(SiMe2)]2O}2 (1) reacts with LiPPh2 to yield the iron(II) dimer {Fe[tBuN(SiMe2)]2O}2 but reaction with LiNPh2 gives the iron(II) product {Fe2(NPh2)2[tBuN(SiMe2)]2O} (5). Some redox chemistry is also observed as side reactions in the syntheses of 2–4, yielding THF adducts of FeX2: the one‐dimensional chain [FeBr2(THF)2]n (7) and the cluster [Fe4Cl8(THF)6]. The X‐ray crystal structures of 3, 5 and 7 are described.
Quality of service control in multimedia network clusters
Authors: Davoli Franco , Maryni Piergiulio 
Published: October 2003

AbstractWe introduce a control architecture in which several (independent) multimedia clusters share the same (local or metropolitan) networking resources in a controlled framework. In particular, a central entity (i.e., the Gatekeeper) harmonizes the transmission rates of the various clusters following a given sharing policy. Each cluster, in turn, adopts its own end‐to‐end rate control mechanism to meet the Gatekeeper's transmission rate indications. A testbed has been developed and the system has been evaluated with real experiments by using different types of transmission sources. A software architecture is also introduced and described, with particular reference to the middleware framework realized with the Jini system. Copyright © 2003 John Wiley & Sons, Ltd.
Modulation of the Communication between Redox Centers in a Tris(ferrocene)‐tren Ligand by Complexation of Lanthanide Ions
Authors: Heitzmann Marie , Moutet Jean‐Claude , Pécaut Jacques , Reynes Olivier , Royal Guy , Saint‐Aman Eric , Serratrice Guy 
Published: October 2003

AbstractThe tripodal ligand L built on the tren platform and bearing three chemically equivalent ferrocene units was prepared and characterized. Electrochemical investigations indicate that electrostatic communication occurs between the three ferrocene groups in L, which leads to the observation of two distinct voltammetric waves. The electrochemical communication between the three ferrocene moieties is disrupted in 1:1 (L:M3+) type complexes formed between L and Y3+ or Eu3+ metal cations and their electrochemical response tends towards that of a single three‐independent‐electrons oxidation wave. Modulation of the electrochemical properties of L in the presence of lanthanide ions might be exploited with a view to their electrochemical sensing in organic and aqueous media. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Syntheses, Structures, and Properties of Two‐Dimensional Honeycomb Networks from the Assembly of the Tripodal Ligand 2,4,6‐Tris[4‐(imidazol‐1‐ylmethyl)phenyl]‐1,3,5‐triazine with Metal Salts
Authors: Wan Shuang‐Yi , Li Yi‐Zhi , Okamura Taka‐aki , Fan Jian , Sun Wei‐Yin , Ueyama Norikazu 
Published: October 2003

AbstractTwo novel coordination networks, [Zn2(timpt)2(μ‐OH)](NO3)3 (1) and [Ni2(timpt)2(H2O)2(SO4)2]·0.5H2O (2) were obtained by assembly of 2,4,6‐tris[4‐(imidazol‐1‐ylmethyl)phenyl]‐1,3,5‐triazine (timpt) with the corresponding metal salts. The X‐ray single‐crystal diffraction analysis reveals that complex 1 possesses μ‐OH‐bridged dinuclear zinc(II) subunits (Zn2OH) and each timpt ligand connects three metal atoms to form a two‐dimensional (2D) honeycomb network structure, in which each independent sheet contains two sublayers. While in the case of complex 2, the nickel(II) atom is coordinated by N atoms of timpt, O atoms of sulfate anions and water molecules to give a 2D honeycomb network. The luminescence properties of timpt, 1 and 2 in the solid state were investigated at room temperature. The maximum emission wavelength of 1 is red‐shifted by 17 nm compared with that of timpt. While complex 2 showed an emission with remarkably reduced intensity under the same conditions. The results imply that the metal ions have great influence on the structure and properties of the complexes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Adolescent psychotherapy: An introduction
Authors: Rubenstein Alice K. 
Published: October 2003

AbstractAdolescent psychotherapy has only recently taken hold as distinct from either child or adult psychotherapy. This new recognition was born of necessity as practitioners saw that theories and techniques developed for treating children and adults were far less effective for treating adolescents. As necessity is often the mother of invention, new models for treating adolescents have emerged. While these models differ in many respects, they share three characteristics: the unique features of adolescents, psychotherapists requiring specialized knowledge and skills, and the need for adolescent psychotherapy to involve the broader systemic context of the adolescent's life. The articles in this issue ofIn Session: Journal of Clinical Psychologyinsist that practitioners recognize and challenge their assumptions about how psychotherapy with adolescents should be conducted. The articles highlight the need for specialized training, the scarcity of evidenced‐based research, and the ethical dilemmas that frequently occur when working with this population. © 2003 Wiley Periodicals, Inc. J Clin Psychol/In Session.
On treating adolescent girls: Focus on strengths and resiliency in psychotherapy
Authors: Johnson Norine G. 
Published: October 2003

AbstractThis strength‐based psychotherapy with adolescent girls and their families is derived from feminist psychology, positive psychology, and strength‐based interventions with teens. Research reviewed by the American Psychological Association's Presidential Task Force on Adolescent Girls formed the basis of specific interventions within this approach. Research findings that contributed are the effects on teen girls of positive parental relationships; utilizing strengths of their race, ethnicity, class, and gender; positive body images; being outspoken in relationships; problem‐solving skills that foster independence; and family support for independence. The strength‐based approach is illustrated by a case example of a 13‐year‐old European American girl with acting‐out behaviors, depression, and subclinical attention‐deficit/hyperactivity disorder. The case illustrates how to empower adolescent girls within therapy, when and how to include parents, how to change the focus to strengths, and how to help the parents assess and build upon their daughters' strengths. © 2003 Wiley Periodicals, Inc. J Clin Psychol/In Session.
Relational psychoanalytic treatment for young adult males
Authors: Pollack William S. 
Published: October 2003

AbstractThe clinical treatment of an adolescent young adult male is presented to both illustrate and operationalize the author's hypothesis that a new model of relational psychoanalytic treatment is likely to have beneficial effects, particularly among this population. The contention that males as young boys undergo a normative trauma of premature separation in our society, which is likely to give rise to underdiagnosed abandonment depressive syndromes in teenage boys, is argued. It is represented that psychotherapists attempting to diagnose and treat a wide rage of disorders in young males would do well to rethink their approach from this new perspective. © 2003 Wiley Periodicals, Inc. J Clin Psychol/In Session.
Control of endothelial cell proliferation by calcium influx and arachidonic acid metabolism: A pharmacological approach
Authors: Antoniotti Susanna , Fiorio Pla Alessandra , Pregnolato Sandra , Mottola Annalisa , Lovisolo Davide , Munaron Luca 
Published: October 2003

AbstractIn physiological conditions, endothelial cell proliferation is strictly controlled by several growth factors, among which bFGF and VEGF are the most effective. Both bind to specific tyrosine kinase receptors and trigger intracellular signal cascades. In particular, bFGF stimulates the release of arachidonic acid (AA) and its metabolites in many types of endothelial cells in culture. In bovine aortic endothelial cells, it has been suggested that AA is released by the recruitment of cytosolic phospholipase A2 (cPLA2). AA metabolites are involved in the control of both endothelial cell motility (mostly via the cyclooxygenase pathway) and proliferation (via the lipoxygenase (LOX) cascade). On the other hand, evidence has been provided for a proliferative role of AA‐induced calcium influx. By using a pharmacological approach, we have tried to elucidate the contribution to bovine aortic endothelial proliferation of the different pathways leading to production of AA and its metabolites. Two main informations were obtained by our experiments: first, AA release is not entirely due to cPLA2 involvement, but also to DAG lipase recruitment; second, cyclooxygenase derivatives play a role in the control of cell proliferation, and not only of motility. Moreover, by combining proliferation assays and single cell calcium measurements, we show that the blocking effect of carboxyamido‐triazole (CAI), an inhibitor of tumor growth and angiogenesis acting on calcium influx‐dependent pathways, including AA metabolism, is at least in part due to a direct effect on AA‐induced calcium influx. J. Cell. Physiol. 197: 370–378, 2003© 2003 Wiley‐Liss, Inc.
TNFα suppresses link protein and type II collagen expression in chondrocytes: Role of MEK1/2 and NF‐κB signaling pathways
Authors: Séguin Cheryle A. , Bernier Suzanne M. 
Published: October 2003

AbstractTumor necrosis factor α (TNFα) inhibits matrix synthesis by chondrocytes in rheumatoid arthritis and osteoarthritis; however, the underlying signaling pathways are poorly characterized. This study investigated the TNFα‐activated pathways regulating expression of two key components of the cartilage matrix—link protein and type II collagen. In rat articular chondrocytes, TNFα decreased link protein and type II collagen mRNA to undetectable levels within 48 h. Levels of link protein mRNA recovered more readily than type II collagen mRNA following removal of the cytokine. TNFα‐mediated reduction in mRNA of both matrix molecules occurred at the level of transcription and, for link protein, mRNA stability. Turnover of type II collagen and link protein mRNA was dependent on new protein synthesis. In both prechondrocytes and articular chondrocytes, TNFα induced concentration‐dependent activation of MEK1/2 and NF‐κB, but not p38 or JNK. Sustained activation of NF‐κB was observed for up to 72 h following continuous or transient exposure to TNFα. Using pharmacological and molecular approaches, the MEK1/2 and NF‐κB pathways were found to mediate inhibition of type II collagen and link protein gene expression by TNFα. Both prechondrocytes and articular chondrocytes are targets of TNFα. This study identifies pathways through which TNFα perturbs the synthesis and organization of articular cartilage matrix during inflammation. J. Cell. Physiol. 197: 357–369, 2003© 2003 Wiley‐Liss, Inc.
Role of nitric oxide, reactive oxygen species, and p38 MAP kinase in the regulation of human chondrocyte apoptosis
Authors: Kühn Klaus , Shikhman Alexander R. , Lotz Martin 
Published: October 2003

AbstractThis study addresses mechanisms by which interleukin‐1β (IL‐1β) regulates human chondrocyte apoptosis induced by a combination of the anti‐CD95 antibody CH‐11 and the proteasome inhibitor (PSI). The effect of IL‐1β on apoptosis varied among tissue samples. IL‐1β either enhanced (16/22 samples) or inhibited (6/22 samples) DNA fragmentation and caspase‐3 processing. The protective effect of IL‐1β was abrogated by the nitric oxide (NO) synthesis inhibitor N‐monomethyl‐l‐arginine (L‐NMMA) while apoptosis stimulation was not affected. The NO‐donors sodium nitroprusside (SNP) and S‐nitroso‐N‐acetyl penicillamine (SNAP) blocked DNA fragmentation, and this was associated with partial inhibition of caspase‐3 processing. Pyrrolidine dithiocarbamate (PDTC), a scavenger of reactive oxygen species (ROS) blocked apoptosis induction by CH‐11/PSI as well as the enhancement by IL‐1β. The pro‐apoptotic effects of IL‐1β were also abrogated by the p38 inhibitor SB 202190. In conclusion, IL‐1β augments CH‐11/PSI induced apoptosis in the majority of chondrocyte samples. The pro‐apoptotic effect of IL‐1β is not dependent on NO. In contrast, the anti‐apoptotic effect of IL‐1β observed in a minority of samples is partially NO‐dependent. J. Cell. Physiol. 197: 379–387, 2003© 2003 Wiley‐Liss, Inc.
Modulation of vascular smooth muscle cell growth by magnesium—role of mitogen—activated protein kinases
Authors: Touyz Rhian M. , Yao Guoying 
Published: October 2003

AbstractWe tested the hypothesis that Mg2+ influences growth of vascular smooth muscle cells (VSMCs) by modulating cell cycle activation through mitogen‐activated protein (MAP) kinase‐dependent pathways. Rat VSMCs were grown in culture medium containing normal Mg2+ (1.02 mmol/L, control) and increasing concentrations of Mg2+ (2–4 mmol/L) for 1–8 days. Effects of varying extracellular Mg2+ concentration ([Mg2+]e) on intracellular free Mg2+ concentration ([Mg2+]i) were assessed using mag‐fura. Growth actions of Mg2+ were evaluated by measuring cell cycle activation, DNA synthesis, and protein synthesis. Expression of cell cycle promoters, cyclin D1, cyclin E, Cdk2, and Cdk4 was assessed by immunoblotting. Phosphorylation of cell cycle inhibitors p21cip1 and p27kip1 and MAP kinases, ERK1/2, p38MAP kinase, and JNK was evaluated using phospho‐specific antibodies. [Mg2+]i increased in a dose‐dependent manner in response to increasing [Mg2+]e. These effects were evident within 2 days and maximal responses were obtained after 6 days. High [Mg2+]e induced cell cycle activation with a lower proportion of cells in G1 phase (75 ± 1.0%) and a higher fraction of cells in S phase (12 ± 0.7%) versus control (G1, 88.5 ± 1.4%; S, 6.8 ± 1.2%; P < 0.05). This was associated with increased protein content of cyclin D1 and Cdk4 and decreased activation of p21cip1 and p27kip1. In cells exposed to 2 mmol/L Mg2+, DNA and protein synthesis was increased ∼threefold. Phosphorylation of MEK1/2 and ERK1/2 was enhanced two to threefold in cells grown in 2 mmol/L Mg2+. These effects were rapid, occurring within 2 days. Phosphorylation of MEK3/6, p38 MAP kinase, and JNK was unaltered by increasing [Mg2]e. PD98059 (10−5 mol/L), specific MEK1/2 inhibitor, but not SB202190 (10−5 mol/L) (specific p38 MAP kinase inhibitor), attenuated Mg2+‐induced growth actions. These data demonstrate the novel findings that cell cycle activation and growth regulation by Mg2+ occurs via ERK1/2‐dependent, p38 MAP kinase‐independent pathways. J. Cell. Physiol. 197: 326–335, 2003© 2003 Wiley‐Liss, Inc.
Raman spectroscopy of some natural hydrotalcites with sulphate and carbonate in the interlayer
Authors: Frost Ray L. , Weier Matt L. , Kloprogge J. Theo 
Published: October 2003

AbstractThe structures of a series of nickel‐ and magnesium‐based hydrotalcites were explored using Raman microscopy. These natural hydrotalcites are based upon sulphate or carbonate being the counter anion in the interlayer. Variation in the position of the sulphate stretching vibrations occurs and is mineral dependent. Raman spectroscopy shows a reduction in the symmetry of both sulphate and carbonate, which leads to the conclusion that the anions are bonded to the brucite‐like hydroxyl surface and to the water in the interlayer. Water bending modes are identified in both the Raman and infrared spectra at positions greater than 1630 cm−1, indicating that the water is strongly hydrogen bonded to both the interlayer anions and the hydrotalcite surface. Copyright © 2003 John Wiley & Sons, Ltd.
Infrared and Raman spectral studies of L‐ornithine nitrate
Authors: Ramaswamy S. , Umadevi M. , Rajaram R. K. , Ramakrishnan V. 
Published: October 2003

AbstractFT‐IR and FT‐Raman spectra of L‐ornithine nitrate were recorded and analyzed. The assignments of the fundamental vibrational modes due to COO−, NH3+, CH2, CH, CN and NO3− groups were made. The carboxylic group is found to exist as the COO− ion in the crystal. The formation of N–HO hydrogen bonds in the crystal contributes considerably to the crystal cohesion. The wavenumbers of several modes of vibrations were shifted from the expected values, indicating extensive intermolecular hydrogen bonding. Some of the forbidden modes of the nitrate group have been observed. The removal of degeneracy of the nitrate anion suggests that the symmetry of the nitrate group has been affected in the crystalline environment. Copyright © 2003 John Wiley & Sons, Ltd.
Kinetic and Mechanistic Studies of Carboxylic Acid–Bisoxazoline Chain‐Coupling Reactions
Authors: Néry Laurent , Lefebvre Hervé , Fradet Alain 
Published: October 2003

AbstractKinetic studies of the reactions between a model carboxylic acid and bisoxazoline coupling agents, namely 2,2′‐(1,3‐phenylene)bis(2‐oxazoline) (mbox), 2,2′‐(1,4‐phenylene)bis(2‐oxazoline) (pbox), and 2,2′‐(2,6‐pyridylene)bis(2‐oxazoline) (pybox), were carried out in bulk at 140–220 °C. A second‐order two‐step reaction mechanism was proposed and was verified by the experimental results. The results also indicate that the reactivity of the oxazoline groups is unchanged after the reaction of the other oxazoline group of the same coupling agent moiety, that is, oxazoline groups are equireactive. Rate constants and activation enthalpies and entropies were determined, allowing the comparison of bisoxazoline reactivity. The following reactivity order was found: pybox > mbox > pbox. The formation of a stabilized protonated complex is postulated to explain the much higher reaction rate observed with the new coupling agent pybox.Variation of the experimental concentrations of reactants and reaction products versus time.magnified imageVariation of the experimental concentrations of reactants and reaction products versus time.