bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preferential Siting of Iron Atoms in an MFI‐type Ferrisilicate Zeolite Framework: An Attempt to Explain Experimental Data with TPA‐Silicate Solution Chemistry
Authors: Theunissen Elisabeth , Kirschhock Christine E. A. , Kremer Sebastien P. B. , Habermacher David D. , Martens Johan A. 
Published: March 2003

AbstractIn this paper an attempt is made to explain the experimentally observed iron siting in ferrisilicate MFI‐type zeolites based on TPA‐silicate solution chemistry. A critical molecular step in the formation of Silicalite‐1 zeolite is the formation of the precursor, counting 36 T‐atoms, by condensation of three pentacyclic dodecamers around a TPA molecule. Incorporation of a tetracyclic undecamer instead of a pentacyclic dodecamer results in a precursor with a missing Si atom at a position that becomes a T9 or T10 site of the orthorhombic unit cell of the MFI‐type zeolite. The incorporation of iron at these empty positions of the precursor explains the experimentally observed preferred iron positions. Close examination of the precursor formation mechanism reveals that the iron is incorporated at the same T‐atom positions, viz. T9 and T10, when the precursor is formed from an iron‐containing pentacyclic dodecamer. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
A Novel Open‐Framework Gallium Phosphate Containing Two Different Building Units
Authors: Sun Daofeng , Cao Rong , Sun Yanqiong , Bi Wenhua , Hong Maochun 
Published: March 2003

AbstractA novel open‐framework fluorinated gallium phosphate has been prepared hydrothermally. X‐ray diffraction shows each double four‐ring (D4R) links four 1D gallium phosphate chains made up of single four‐rings (S4R) to form a 3D framework with eight‐ring channels where potassium ions reside. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
The Coordination Chemistry of the Pentadentate 2,2,6,6‐Tetrakis(aminomethyl)‐4‐azaheptane (ditame)
Authors: Hegetschweiler Kaspar , Maas Oliver , Zimmer Anja , Geue Rodney J. , Sargeson Alan M. , Harmer Jeffrey , Schweiger Arthur , Buder Irmgard , Schwitzgebel Günter , Reiland Vera , Frank Walter 
Published: March 2003

AbstractThe protonation and metal complex formation of the branched pentaamine ligand 2,2,6,6‐tetrakis(aminomethyl)‐4‐azaheptane (ditame, L) with CoII, CoIII, NiII, CuII, ZnII, and CdIIhave been studied. The crystal structures of [Ni(ditame)(EtOH)]Br2, [Co2(ditame)2(O2)]Cl4·4H2O, and [Co2(ditame)2(O2)]Cl2[ZnCl4][ZnCl3(H2O)]·H2O were determined by X‐ray diffraction analyses. The metal complexes showed octahedral coordination geometries with exclusive formation of six‐membered chelate rings, the four primary amino groups being in equatorial positions and the secondary amino group (Nsec) apical. This geometry enforces a relatively short M−Nsecbond. Complex formation in aqueous solution was evaluated by potentiometric titration. The ditame ligand forms a surprisingly stable NiIIcomplex with logKNiL= 17.8 (25 °C, 0.1MKNO3), and formation of protonated species [Ni(Hnditame)](n+2)+(n= 1, 2) is not significant. Different behavior is evident for ZnIIand CdII, with which protonated species are extensively formed, while the stability of [ML]2+is relatively low. Complex formation between ditame and CuIIin the range 3 < pH < 7 resulted in the formation of [Cu(H2ditame)]4+. In slightly alkaline solution, the dinuclear [Cu2(ditame)2]4+appears to be formed. The structural assignment of this dimer is based on its UV/Vis and EPR characteristics, with the EPR data indicating a CuII···CuIIseparation of about 5.9 Å. The redox behavior of the Ni and Co complexes was investigated by cyclic voltammetry. The mononuclear species showed quasi‐reversible electron transfer for the NiII/IIIand CoII/IIIcouples. For the dinuclear peroxo/ superoxo‐bridged CoIIIcomplexes, quasi‐reversible electron transfer corresponding to oxidation/reduction of the O22−/O2−bridge was observed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Studies of Pyridinyl‐Containing 14‐Membered Macrocyclic Copper(II) Complexes
Authors: Autzen Sabrina , Korth Hans‐Gert , Boese Roland , Groot Herbert de , Sustmann Reiner 
Published: March 2003

AbstractSix copper(II) complexes of tetracoordinating, pyridinyl‐containing 14‐membered macrocycles with varying ratios of nitrogen and oxygen donor atoms were prepared and characterized by IR, UV/Vis, and EPR spectroscopy and cyclic voltammetry. A distorted tetragonal coordination of the copper center in the solid‐state was established by X‐ray crystallography for the tetraazamacrocyclic complex Cu‐3 carrying a methoxybenzyl pendent arm and the trioxaaza complex Cu‐6. The superoxide dismutase‐like activity of the CuII complexes was investigated by inhibition of NADH oxidation. Although the UV/Vis and EPR spectra of the complexes were strongly affected when the coordinating nitrogen atoms were successively replaced by oxygen atoms, no significant change in their reactivity towards superoxide was observed. In all cases a 1:1 or 1:2 stoichiometry for the reaction with superoxide was found, with the exception of the methoxybenzyl‐substituted tetraaza complex, which showed a low catalytic activity with a turnover number of about 10. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Structural Manipulation of Hydrogen Bond Networks Using Sulfonated Phosphane Ligands and Their Complexes: Competition and Interplay Between Strong and Weak Hydrogen Bonds
Authors: Burrows Andrew D. , Harrington Ross W. , Mahon Mary F. , Teat Simon J. 
Published: March 2003

AbstractUsing the sulfonated phosphane [PPh2(C6H4‐m‐SO3)]−, L−, we have demonstrated that metal centres can readily be incorporated into guanidinium sulfonate (GS) hydrogen‐bonded networks, and that the increase in steric bulk on going from [C(NH2)3][L] (1) to [C(NH2)3][AuCl(L)] (2) leads to a flattening of the GS sheets. The crystal structures of [C(NH2)3][LS] 3 and [C(NH2)3][LSe] 4 (LS− = [SPPh2(C6H4‐m‐SO3)]−, LSe− = [SePPh2(C6H4‐m‐SO3)]−) reveal disorder in both the sulfonate groups and the guanidinium cations, which is a consequence of pseudo‐sixfold phenyl embraces between the anions. These interactions, identical to those observed in Ph3PS and Ph3PSe, position the sulfonate groups too close together for regular quasihexagonal hydrogen bonding motifs to be formed. The regular GS hydrogen bonding patterns can also be disrupted by using an anion containing two sulfonate groups such as that in [C(NH2)3]2{cis‐[PdCl2(L)2]} (5). In this case the incorporation of two sulfonate groups from each anion into the same hydrogen‐bonded sheet also serves to constrain the distance between the sulfur atoms to a value incommensurate with that enabling a guanidinium cation to hydrogen bond to both groups. In this case irregular GS sheets are formed involving fewer N−H···O hydrogen bonds than in 1 and 2. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Phosphorus‐Selenium Heterocycles from the Tetraphospholane (PhP)4CH2
Authors: Kilian Petr , Bhattacharyya Pravat , Slawin Alexandra M. Z. , Woollins J. Derek 
Published: March 2003

AbstractTwo new heterocyclic and one acyclic species were prepared by reduction/deselenation of the five‐membered heterocycle PhP(Se)CH2PhP(Se)Se2 (containing a PCPSe2 ring sequence). Deselenation with Me3SiCN led to the four‐membered heterocycle PhP(Se)CH2PPh(Se)Se (containing a PCPSe ring sequence), whereas reaction with Bu3P afforded the five‐membered heterocycle PhP(Se)CH2PhP(Se)SePPh (ring sequence PCPSeP) and reduction with K metal afforded the dipotassium salt of methylene‐bis(diselenophenylphosphinic) acid [K2(PhPSe2)2CH2]. The new compounds were characterised by a combination of NMR, MS and FT IR spectroscopic techniques; their structures were confirmed by single crystal X‐ray analyses. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
A box‐counting‐based algorithm for computing Shannon entropy in molecular dynamics simulations
Authors: Lorenzo Luis , Mosquera Ricardo A. 
Published: March 2003

AbstractA box‐counting‐based algorithm (SEBC) has been developed for the numerical computation of the Shannon entropy from samples of continuous functions. Its performance was tested by applying it to several samples of known continuous distribution functions. The results obtained with SEBC reproduced those obtained by analytical or numerical integration. SEBC was also employed for computing the Shannon entropies of the steric energy, Sh(ES), of several amino acids from their in vacuo NVE molecular dynamics simulations using the AMBER‐4 force field. The results obtained correlate linearly with the experimental standard thermodynamic entropies of these compounds. This work points to the possibility of introducing straightforward and reliable calculations of thermodynamic entropies from empirical linear relationships with Sh(ES) obtained from MD simulations. © 2003 Wiley Periodicals, Inc. J Comput Chem 24: 707–713, 2003
Binding of proteins to the minor groove of DNA: What are the structural and energetic determinants for kinking a basepair step?
Authors: Bosch David , Campillo Mercedes , Pardo Leonardo 
Published: March 2003

AbstractThe structural and energetic determinants for kinking a basepair step by minor groove–insertion of the protein side chains of PurR, LacI, LEF–1, IHF, Sac7d, and Sso7d, have been calculated by molecular dynamics/potential of mean force simulations. The structural determinants of the kinked structures are: two contiguous furanose rings achieve different conformations, in the region of C3′endo (A–DNA) and C2′endo (B–DNA); the χ torsion angle always takes values characteristic of the C2′endo conformation of B–DNA, independently of sugar puckering; and protein side chain insertion increases slide (from negative to positive values), rise, and roll, and decreases twist. The energetic determinants of DNA kinking are: the conformational transition of the sugar–phosphate backbone is not energetically demanding; the relative importance of the interbase parameters in the free energy penalty is slide, followed by twist and rise, and concluding with shift and roll; and the characteristic increase of roll and decrease of twist, upon side chain insertion, tends to stabilize the process of DNA kinking. © 2003 Wiley Periodicals, Inc. J Comput Chem 24: 682–691, 2003
Radial quadrature for multiexponential integrands
Authors: Gill Peter M. W. , Chien Siu‐Hung 
Published: March 2003

AbstractWe introduce a Gaussian quadrature, based on the polynomials that are orthogonal with respect to the weight function ln2x on the interval [0, 1], which is suitable for the evaluation of radial integrals. The quadrature is exact if the non‐Jacobian part of the integrand is a linear combination of a geometric sequence of exponential functions. We find that the new scheme is a useful alternative to existing approaches, particularly for integrands that exhibit multiexponential behavior. © 2003 Wiley Periodicals, Inc. J Comput Chem 24: 732–740, 2003
Small‐worlds: A review of recent books
Authors: Frommer I. , Pundoor G. 
Published: March 2003

AbstractSmall‐worlds research and related fields study a set of network structures with well‐defined properties. This new area has been gaining momentum lately. Theoretical studies have advanced our understanding of such networks while empirical studies have shown these networks to be ubiquitous in both nature and society. In particular, systems that appear to be well modeled by such networks include World Wide Web documents, Internet routers, the cellular metabolic network, ecological food webs, social networks, and many others. The two main structures being investigated are small‐world networks and scale‐free networks. Three recent books, including two just published this summer, describe the research being undertaken in this burgeoning field. We survey and review these books through a discussion of the field of small‐worlds research with numerous examples and considerations of the future of the field. © 2003 Wiley Periodicals, Inc.
Unequally spaced non‐periodic B‐spline finite strip method
Authors: Choi Chang‐Koon , Hong Hyun‐Seok , Kim Kyeong‐Ho 
Published: March 2003

AbstractThe unequally spaced non‐periodic B‐spline finite strip method (FSM) is presented. The motivation to investigate the irregularly spaced interior nodes in the longitudinal direction of strip is to generalize the concept of non‐periodic B‐spline FSM and to improve the general accuracy of the stress evaluation in the region of high stress gradients. In the present paper, the unequally spaced non‐periodic B3‐spline series with multiple knots at the boundary are introduced for the interpolation of displacement and description of geometry in the formulation of isoparametric spline FSM. The use of multiple knots at the boundary makes the shape function satisfy the Kronecker delta properties at the boundary. The unequally spaced B‐spline FSM is applied to the stress‐reduced shell problem with six degrees of freedom per node. The main purpose of this study is to find a way of ensuring that the geometry of strip is appropriately approximated when the interior nodes of the strip are not regularly spaced along the longitudinal direction. Some numerical results have been compared with those of the previous studies to evaluate the accuracy and efficiency of this method. Copyright © 2003 John Wiley & Sons, Ltd.
The Plasticisation Effect of Glycerol and Water on the Gelatinisation of Wheat Starch
Authors: Nashed Gena , Rutgers Rulande P. G. , Sopade Peter A. 
Published: March 2003

AbstractIn the extrusion manufacture of starch‐based thermoplastics, such as biodegradable packaging materials, glycerol is an effective additive as a plasticiser, that is, to diminish the brittle nature of the product and provide the desired extent of flexibility. However, the addition of glycerol may also affect the gelatinisation behaviour of the starchwater mixture, and hence the required processing conditions for producing a homogeneously gelatinised starch‐based material. The effect of glycerol on the gelatinisation of wheat starch was studied using differential scanning calorimetry (DSC). Mixtures of starch, water and glycerol were investigated with a water content ranging from 12 — 40% and a glycerol concentration up to 75%. Dependent on composition, the enthalpy of gelatinisation ranged from 1.7 — 12.6 J/g (on a dry starch basis), while the onset and peak temperatures varied from 54 to 86 °C and 60 to 90 °C, respectively. As expected, water acted as a plasticiser in that the onset temperature for gelatinisation (T0) decreased with increasing moisture content. Glycerol, however, increased T0. It is shown that the T0 of starch‐glycerol‐water mixtures may be predicted on the basis of the effective moisture content of the starch fraction of these mixtures resulting from the relative speed of moisture absorption by glycerol and starch, respectively. Moisture sorption kinetics of wheat starch and glycerol in 100% relative humidity were determined and used to predict the preferential water absorption by glycerol in starch‐glycerol‐water mixtures and hence the resulting T0 of the system.
Moderate‐to‐large injection and suction driven channel flows with expanding or contracting walls
Authors: Majdalani J. , Zhou C. 
Published: March 2003

AbstractWe consider in this paper the incompressible laminar flow in a porous channel with expanding or contracting walls. While the head‐end is closed by a compliant membrane, the downstream end is left unobstructed. For symmetric injection or suction along the uniformly expanding porous walls, the Navier‐Stokes equations are reduced to a single, nonlinear, ordinary differential equation. The latter is obtained via similarity transformations in both time and space. The resulting equation is then solved both numerically and asymptotically, using perturbations in the crossflow Reynolds number R. Two separate approaches are presented for each of the injection and suction cases, respectively. For the large injection case, the governing equation is first integrated and the resulting third‐order differential equation is solved using the method of variation of parameters. For the large suction case, the governing equation is first simplified near the wall and then solved using successive approximations. Results are then correlated and compared for variations in R and the dimensionless wall expansion rate α. For injection‐induced flow, the asymptotic solution becomes more accurate when R/α is increased. Its deviation from the classic sinusoidal profile arising in nonexpanding channels becomes less significant with successive increases in R. For suction‐induced flows, faster wall contractions increase the effective Reynolds number ‐(α+R), thus leading to more precise approximations. For the same absolute value of R, the suction‐flow approximation tends to be the most accurate of the two and the least sensitive to variations in α. As ‐(α+R) is increased, the suction profile approaches the linear form anticipated in nonexpanding channels. By comparison with the injection‐induced flow, suction is characterized by improved accuracy, sharper flow turning, and larger shear.
Appropriate Surgical Management of Small Hepatocellular Carcinomas in Patients Infected with Hepatitis C Virus
Authors: Kubo Shoji , Taukamoto Tadashi , Hirohashi Kazuhiro , Tanaka Hiromu , Shuto Taichi , Takemura Shigekazu , Kawai Shuichi , Wakasa Kenichi , Kinoshita Hiroaki 
Published: March 2003

AbstractWe investigated the incidence of recurrence after resection of small hepatocellular carcinomas (HCC) in patients infected with hepatitis C virus (HCV) to determine the appropriate surgical management of these patients. Sixty‐one patients with anti‐HCV antibody who underwent curative liver resection for small HCC (≦ 2.0 cm in greatest diameter) were categorized into two groups. Group 1 consisted of 27 patients with serum concentrations of type IV collagen 7S domain (7S collagen), a marker for hepatic fibrosis, < 8 ng/ml. Group 2 consisted of 34 patients with serum concentrations of 7S collagen ≧ 8 ng/ml. Serum concentration of 7S collagen correlated with the severity of active hepatitis and the degree of fibrosis in the noncancerous hepatic tissue, both of which are related to risk potential of hepatocarcinogenesis. Serum concentration of total bilirubin, aspartate aminotransferase activity, indocyanine green retention rate at 15 minutes, the proportion of patients who were Child‐Pugh class B, and the proportion of patients with severe active hepatitis or cirrhosis (determined by histologic examination) were significantly higher in group 2 than in group 1. Platelet count was significantly lower in group 2. Tumor‐free survival rates were not different between the groups. In group 1, nonanatomic resection was a risk factor for recurrence by univariate and multivariate analyses (odds ratio = 3.45, p = 0.040). In group 2, nonanatomic resection was not a risk factor for recurrence. In patients with small HCV‐related HCC, anatomic resection is recommended when the serum concentration of 7S collagen is low (< 8 ng/ml) because the potential of hepatocarcinogenesis may be low even after the operation.
Distribution of Lymph Node Metastasis Including Micrometastasis in Gastric Cancer with Submucosal Invasion
Authors: Higashi Hiroshi , Natsugoe Shoji , Ishigami Sumiya , Uenosono Yoshikazu , Matsumoto Masataka , Nakajo Akihiro , Miyazono Futoshi , Hokita Shuichi , Takao Sonshin , Aikou Takashi 
Published: March 2003

AbstractThe purpose of this retrospective study was to analyze the distribution of lymph node metastases, including micrometastases, according to the location of the gastric cancer with submucosal invasion. A total of 118 patients with submucosal gastric cancer were enrolled in this study. The distribution of lymph node metastases was examined according to tumor location. Immunohistochemical examination using anti‐cytokeratin antibody was performed to examine nodal micrometastases in 118 patients. Lymph node metastasis was found in 19.5% (23/118) of the patients. Significant differences were found for tumor size and depth, lymphatic invasion, and venous invasion for patients with and without nodal metastasis. The distribution of lymph node metastasis for tumors at upper or middle portions of the stomach was mainly found along the left gastric artery. The distribution of lymph node metastasis for tumors in the lower and lesser curvature varied. Immunohistochemical analysis found that 15 of 23 patients with lymph node metastasis found by histologic examination had micrometastases. The presence of two or more lymph node micrometastases was found in these 15 patients, and they were distributed in another stations, including distant nodes. The incidence of micrometastasis was 24.2% (23/95) in pN0 patients. Lymph node micrometastases were confined to regional nodes near the primary tumor. When planning minimally invasive treatment for submucosal gastric cancer, it is important to understand the distribution of lymph node metastasis, including micrometastasis, according to tumor location.
Long Saphenous Vein Stripping Reduces Local Level of Reactive Oxygen Metabolites in Patients with Varicose Disease of the Lower Limbs
Authors: Flore Roberto , Santoliquido Angelo , Antonio Dal Lago , Pola Enrico , Flex Andrea , Pola Roberto , Muzi Marco Gallinella , Farinon Attilio , Rulli Francesco , Gaetani Eleonora , Tondi Paolo , Gerardino Laura , Gasbarrini Antonio 
Published: March 2003

AbstractLong saphenous vein (LSV) stripping is the most common surgical procedure in patients affected by varicose disease of the lower limbs. Reactive oxygen metabolites (ROM) generation plays a crucial role in chronic venous insufficiency (CVI). The aim of this study was to investigate whether ROM generation is increased in patients affected by varicose disease versus healthy controls and whether LSV stripping has a positive effect on the local production of ROM. The local production of ROM was assessed measuring hydroperoxides in the blood collected from the leg of 30 patients consecutively undergoing LSV stripping and 30 controls. In both the patient group and the control group, the test was repeated 30 days later. We found that ROM levels before surgery are higher in varicose vein patients than in controls (p <. 0001) and that ROM are significantly reduced 30 days after LSV stripping (p <. 0001). At that time point, no significant differences between patients and controls was found. We also found that sex and age do not affect ROM concentration in patients and controls, either before or after surgery. In conclusion, our data indicate that CVI is characterized by significant oxidative stress and that LSV stripping is able to normalize local production of ROM in patients with varicose disease of the lower limbs. We suggest that measurement of ROM might be useful to test the positive effects of LSV stripping in these patients.