bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of wood species on the mechanical and thermal properties of wood–plastic composites
Authors: Kim Jae‐Woo , Harper David P. , Taylor Adam M.
Published: February 2009

The effect of wood species on the mechanical and thermal properties of wood–plastic composites (WPCs) was explored. Various wood species, including cherry, sweet gum, hickory, yellow poplar, Osage orange, walnut, eastern red cedar, pine, maple, and red oak, were compounded with virgin isotactic polypropylene in a 50 : 50 weight ratio and injection‐molded. The tensile strength of WPCs made with cedar and hickory was higher than that of WPCs made with maple, oak, and Osage orange. The tensile modulus of WPCs made with gum and walnut was higher than that of oak WPCs. The tan δ peak temperatures and peak values from dynamic mechanical analysis indicated that pine and hickory WPCs had higher amorphous or void contents than walnut and cherry WPCs. The induction time during isothermal crystallization suggested that red cedar, cherry, and gum WPCs had higher nucleation density than walnut, pine, and oak WPCs. Dynamic mechanical properties of the WPCs appeared to be related to the crystallization behavior of the wood flour, which depends on the surface roughness. Although there were statistically significant differences in mechanical properties among the species, the differences were small, implying that wood flours from many species can be used successfully as raw materials for WPCs. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Investigations on pyridinium salts as a solid‐state ionics
Authors: Chetri Prafulla , Dass Narendra N. , Sarma Neelotpal Sen
Published: February 2009

The object of this work is to prepare polymer poly(2vinylpyridine), P‐2VP, and its salts like P‐2VP‐HI, P‐2VP‐HIO3, and P‐2VP‐HIO4. The formation of P‐2VP salts was confirmed by IR and 1H NMR techniques. Conductivities of these were determined in solid state at various temperatures from 30 to 90°C. Observations indicated that the addition of I− or IO3− or IO4− ions affect the ionic conductivity of P‐2VP. Molecular mass determination and analytical results indicated that 94, 92.5, and 95% of the pyridine molecules in the P‐2VP chain were hydroiodated, iodated, and periodated, respectively, with the corresponding acids of iodine. The total ionic transport number and activation energy of the polymers were also determined. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Leaching of plasticized PVC: Effect of irradiation
Authors: Colombani J. , Herbette G. , Rossi C. , Joussot‐Dubien C. , Labed V. , Gilardi T.
Published: February 2009

Highly irradiated (2–26 MGy) polyvinyl chloride (PVC) was leached in an alkaline solution to investigate the impact of high doses on the leaching process and on the nature of the leaching products. The results show that leaching is controlled by diffusion phenomena as described by Fick's second law. The apparent diffusion coefficient (Da) of plasticized PVC leaching products can be calculated for each sample. Irradiation at high dose causes Da to diminish; this can be attributed to crosslinking and grafting reactions occurring during irradiation. The material microstructure thus becomes less permeable during radiolysis, which slows down the migration of species. Organic products of leaching are plasticizers contained in plasticized PVC or their degradation products. The main organic leaching products are phthalic ions formed by the hydrolysis of phthalic esters in alkaline leaching solution. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Effect of aging conditions of neodymium‐based catalysts on cis‐1,4 polymerization of butadiene
Authors: Mello Ivana L. , Coutinho Fernanda M. B.
Published: February 2009

The aim of this work is to evaluate the effect of aging conditions catalysts based on neodymium salt on polymerization conversion, catalyst activity, and polymer characteristics. The synthesized catalysts were aged at 10, 25, 40, and 60°C for 24 and 48 h. The polybutadienes were characterized by size exclusion chromatography to determine the molecular weight characteristics and infrared spectroscopy to determine the microstructure. The results showed that the stereoselectivity of active catalyst sites was not affected by the aging conditions. However, the molecular weight increased with aging temperature. The catalysts aged at 25°C showed a trend to attain higher activities than those aged at 40 and 60°C. Moreover, a significant drop on polymerization reaction rate occurred as the catalyst aging temperature increased. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Preparation and characterization of lead monoxide filled unsaturated polyester based polymer composites for gamma radiation shielding applications
Authors: Harish V. , Nagaiah N. , Prabhu T. Niranjana , Varughese K. T.
Published: February 2009

Particulate polymer composites of Isophthalate based unsaturated polyester resin filled with different concentrations of lead monoxide were prepared. These composites were investigated for physical, thermal, mechanical, and gamma radiation shielding characteristics. The results of density evaluation, microscopic studies, and the radiation shielding properties for gamma rays of energy 0.662 MeV from Cs‐137 point source have been presented in this article. The results show that, the density of the composites was observed to increase with filler loading. The morphological analysis of the composites made using the scanning electron microscope showed that, the lead monoxide particles were observed to disperse uniformly in the polymer matrix with an average inter particle distance of about 10 μm and an average size of about 5.36 μm. The linear attenuation coefficient of the composites was found to increase with increased filler content in the composites. The highest value of 0.206 cm−1was found for 50 wt % of lead monoxide. These composites were observed to exhibit excellent % of heaviness and Half value layer in comparison with other conventional materials. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Crystallization kinetics of isotactic polypropylene nucleated with organic dicarboxylic acid salts
Authors: Zhao Shicheng , Xin Zhong
Published: February 2009

Bicyclo[2.2.1]hept‐5‐ene‐2,3‐dicarboxylate salts (BCHED) were synthesized by hydrothermal method. The crystallization kinetics of isotactic polypropylene (iPP) and nucleated iPP with BCHED were investigated by differential scanning calorimeter (DSC) under isothermal and nonisothermal conditions. Isothermal crystallization kinetics was described by Avrami equation and the fold surface free energy (σe) of iPP was calculated by Hoffman theory. The results showed Avrami exponents of nucleated iPP become smaller, the values of t1/2 dramatically decrease, the crystallization rate constants Z(T) greatly increase and the fold surface free energy (σe) of iPP decrease with the addition of the nucleating agents. Under nonisothermal condition the Caze method was applied to deal with the crystallization kinetics of iPP and the crystallization active energy of iPP was determined by Kissinger method. The results showed the crystallization peak temperatures (Tcp) of nucleated iPP greatly increase, but Avrami exponents of iPP were slightly influenced and the crystallization active energy of iPP increases by the addition of BCHED. It can be concluded that BCHED act as nucleating agents and BCHE11 shows the best nucleating effect. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
A Note on the Use of Unbiased Estimating Equations to Estimate Correlation in Analysis of Longitudinal Trials
Authors: Sun Wenguang , Shults Justine , Leonard Mary
Published: February 2009

Longitudinal trials can yield outcomes that are continuous, binary (yes/no), or are realizations of counts. In this setting we compare three approaches that have been proposed for estimation of the correlation in the framework of generalized estimating equations (GEE): quasi‐least squares (QLS), pseudo‐likelihood (PL), and an approach we refer to as Wang–Carey (WC). We prove that WC and QLS are identical for the first‐order autoregressive AR(1) correlation structure. Using simulations, we then develop guidelines for selection of an appropriate method for analysis of data from a longitudinal trial. In particular, we argue that no method is uniformly superior for analysis of unbalanced and unequally spaced data with a Markov correlation structure. Choice of the best approach will depend on the degree of imbalance and variability in the temporal spacing of measurements, value of the correlation, and type of outcome, e.g. binary or continuous. Finally, we contrast the methods in analysis of a longitudinal study of obesity following renal transplantation in children (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Likelihood Methods for Regression Models with Expensive Variables Missing by Design
Authors: Zhao Yang , Lawless Jerald F. , McLeish Donald L.
Published: February 2009

In some applications involving regression the values of certain variables are missing by design for some individuals. For example, in two‐stage studies (Zhao and Lipsitz, 1992), data on “cheaper” variables are collected on a random sample of individuals in stage I, and then “expensive” variables are measured for a subsample of these in stage II. So the “expensive” variables are missing by design at stage I. Both estimating function and likelihood methods have been proposed for cases where either covariates or responses are missing. We extend the semiparametric maximum likelihood (SPML) method for missing covariate problems (e.g. Chen, 2004; Ibrahim et al., 2005; Zhang and Rockette, 2005, 2007) to deal with more general cases where covariates and/or responses are missing by design, and show that profile likelihood ratio tests and interval estimation are easily implemented. Simulation studies are provided to examine the performance of the likelihood methods and to compare their efficiencies with estimating function methods for problems involving (a) a missing covariate and (b) a missing response variable. We illustrate the ease of implementation of SPML and demonstrate its high efficiency (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Some Methods of Propensity‐Score Matching had Superior Performance to Others: Results of an Empirical Investigation and Monte Carlo simulations
Authors: Austin Peter C.
Published: February 2009

Propensity‐score matching is increasingly being used to reduce the impact of treatment‐selection bias when estimating causal treatment effects using observational data. Several propensity‐score matching methods are currently employed in the medical literature: matching on the logit of the propensity score using calipers of width either 0.2 or 0.6 of the standard deviation of the logit of the propensity score; matching on the propensity score using calipers of 0.005, 0.01, 0.02, 0.03, and 0.1; and 5 → 1 digit matching on the propensity score. We conducted empirical investigations and Monte Carlo simulations to investigate the relative performance of these competing methods. Using a large sample of patients hospitalized with a heart attack and with exposure being receipt of a statin prescription at hospital discharge, we found that the 8 different methods produced propensity‐score matched samples in which qualitatively equivalent balance in measured baseline variables was achieved between treated and untreated subjects. Seven of the 8 propensity‐score matched samples resulted in qualitatively similar estimates of the reduction in mortality due to statin exposure. 5 → 1 digit matching resulted in a qualitatively different estimate of relative risk reduction compared to the other 7 methods. Using Monte Carlo simulations, we found that matching using calipers of width of 0.2 of the standard deviation of the logit of the propensity score and the use of calipers of width 0.02 and 0.03 tended to have superior performance for estimating treatment effects (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimal Response‐Adaptive Designs for Normal Responses
Authors: Biswas Atanu , Bhattacharya Rahul
Published: February 2009

Most of the available response‐adaptive designs in phase III clinical trial set up are not from any optimal consideration. An optimal design for binary responses is given by Rosenberger et al. (2001) and an optimal design for continuous responses is provided by Biswas and Mandal (2004). Recently, Zhang and Rosenberger (2006) [ZR] provided another design for normal responses. Biswas, Bhattacharya and Zhang (2007) pointed out that the design of ZR is not suitable for normally distributed responses, or any distribution having the possibility of negative mean, in general. But they only indicated the problem and bypassed the original problem and set up. In the present paper, we first start with the drawback of ZR. We then provide the appropriate optimal response‐adaptive design for normal or continuous distributions which provides the necessary correction for the ZR problem. The proposed methods are illustrated using some real data (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Hypoxia and stem cell‐based engineering of mesenchymal tissues
Authors: Ma Teng , Grayson Warren L. , Fröhlich Mirjam , Vunjak‐Novakovic Gordana
Published: February 2009

Stem cells have the ability for prolonged self‐renewal and differentiation into mature cells of various lineages, which makes them important cell sources for tissue engineering applications. Their remarkable ability to replenish and differentiate in vivo is regulated by both intrinsic and extrinsic cellular mechanisms. The anatomical location where the stem cells reside, known as the “stem cell niche or microenvironment,” provides signals conducive to the maintenance of definitive stem cell properties. Physiological condition including oxygen tension is an important component of the stem cell microenvironment and has been shown to play a role in regulating both embryonic and adult stem cells. This review focuses on oxygen as a signaling molecule and the way it regulates the stem cells' development into mesenchymal tissues in vitro. The physiological relevance of low oxygen tension as an environmental parameter that uniquely benefits stem cells' expansion and maintenance is described along with recent findings on the regulatory effects of oxygen on embryonic stem cells and adult mesenchymal stem cells. The relevance to tissue engineering is discussed in the context of the need to specifically regulate the oxygen content in the cellular microenvironment in order to optimize in vitro tissue development. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009
Vulnerable young people and substance misuse: expanding on the risk and protection‐focused approach using social psychology
Authors: Scaife Victoria , O'Brien Margaret , McEune Rhona , Notley Caitlin , Millings Abigail , Biggart Laura
Published: February 2009

This paper critically reviews recent research exploring risk and protective factors for the development of problematic substance use in populations of young people. Specific populations of young people who are most vulnerable to developing problematic patterns of use are identified, and alterations to methods of data collection which would improve the ability of local authorities to monitor these populations and more efficiently target them for early preventative interventions are highlighted. It is argued that social‐psychological research techniques and approaches should be used to complement a risk and protection‐focused approach in order to improve the design and evaluation of interventions, and provide decision‐aids for practitioners when assessing the needs of vulnerable young people. Examples are provided to demonstrate the utility of social psychology in this regard, and the paper concludes with specific recommendations for future research and services. Copyright © 2009 John Wiley & Sons, Ltd.
Impulsive donation decisions during online browsing of charity websites
Authors: Bennett Roger
Published: February 2009

Although online fundraising by charitable organisations is now commonplace, many aspects of effective online fundraising remain unexamined. In particular, little is known about the nature and determinants of impulsive donation decisions taken by browsers of charity websites. This empirical study attempted to help fill this important gap in current knowledge about online fundraising via an investigation of the antecedents of impulsive online giving to a hospice organisation in the south of England. Two hundred and thirty‐nine donors who stated that their gifts had been made impulsively and 223 donors whose online gifts were reported as having been pre‐planned completed a questionnaire that explored, inter alia, a person's socio‐demographic characteristics, level of impulsiveness and attitude towards impulsive behaviour, charity donation history, prior knowledge of hospice issues, subjective norms and personal involvement with charity giving. The main determinants of impulsive donations were identified and the profiles of various types of impulsive giver were established. Relevant matters were investigated in the contexts of two types of web page design: emotive and informative.

Copyright © 2009 John Wiley & Sons, Ltd.
Crystal Structure Analysis and in Silico pKa Calculations Suggest Strong pKa Shifts of Ligands as Driving Force for High‐Affinity Binding to TGT
Authors: Ritschel Tina , Hoertner Simone , Heine Andreas , Diederich François , Klebe Gerhard
Published: February 2009

Expanded lin‐benzoguanines exhibit binding affinities to tRNA‐guanine transglycosylase (TGT) in the low‐nanomolar range. A significant pKa shift is observed for the inhibitors moving from aqueous solution to protein environment. The protonation of the inhibitor facilitates a charge‐assisted hydrogen bond in the protein–ligand complex.

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A novel ligand series is presented to inhibit tRNA‐guanine transglycosylase (TGT), a protein with a significant role in the pathogenicity mechanism of Shigella flexneri, the causative agent of Shigellosis. The enzyme exchanges guanine in the wobble position of tRNAAsn,Asp,His,Tyr against a modified base. To prevent the base‐exchange reaction, several series of inhibitors have already been designed, synthesized, and tested. One aim of previous studies was to address a hydrophobic pocket with different side chains attached to the parent skeletons. Disappointingly, no significant increase in binding affinity could be observed that could be explained by the disruption of a conserved water cluster. The ligand series examined in this study are based on the known scaffold lin‐benzoguanine. Different side chains were introduced leading to 2‐amino‐lin‐benzoguanines, which address a different pocket of the protein and avoid disruption of the water cluster. With the introduction of an amino group in the 2‐position, a dramatic increase in binding affinity can be experienced. To explain this significant gain in binding affinity, Poisson–Boltzmann calculations were performed to explore pKa changes of ligand functional groups upon protein binding, they can differ significantly on going from aqueous solution to protein environment. For all complexes, a permanent protonation of the newly designed ligands is suggested, leading to a charge‐assisted hydrogen bond in the protein–ligand complex. This increased strength in hydrogen bonding takes beneficial effect on binding affinity of the ligands, resulting in low‐nanomolar binders. Crystal structures and docking emphasize the importance of the newly created charge‐assisted hydrogen bond. A detailed analysis of the crystal structures in complex with substituted 2‐amino‐lin‐benzoguanines indicate pronounced disorder of the attached side chains addressing the ribose 33 binding pocket. Docking suggests multiple orientations of these side chains. Obviously, an entropic advantage of the residual mobility experienced by these ligands in the bound state is beneficial and reveals an overall improved protein binding.
From Molecular Fragments to Crystals: A UV Raman Spectroscopic Study on the Mechanism of Fe‐ZSM‐5 Synthesis
Authors: Fan Fengtao , Sun Keju , Feng Zhaochi , Xia Haian , Han Bo , Lian Yuxiang , Ying Pinliang , Li Can
Published: February 2009

The nucleation process of iron‐exchanged zeolite Fe‐ZSM‐5, from the assembly of distorted tetrahedrally coordinated iron species and silicate rings in the precursor to the final Fe‐ZSM‐5 crystals, as well as variations in the coordination environment of iron, were studied by UV resonance Raman spectroscopy and complementary techniques.

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The entire sequence of crystallization events of Fe‐ZSM‐5 was monitored by UV Raman spectroscopy in combination with HRTEM, UV/Vis spectroscopy, X‐ray diffraction patterns, and periodic DFT calculations. Fe‐ZSM‐5 was synthesized by an organic‐free method to avoid signal interference from the organic template in Raman spectra. Framework iron atoms with resonance Raman bands at 516, 1115, and 1165 cm−1, and a Raman band at 1016 cm−1 are detected for Fe‐ZSM‐5. In the early stage of Fe‐ZSM‐5 synthesis, the precursor contains iron atoms in distorted tetrahedral coordination and five‐ and six‐membered silicate rings. Nucleation by aggregation of the precursor species was monitored by UV Raman spectroscopy based on the resonance Raman effect, and confirmed by periodic DFT calculations. Evolution of iron species on the surface and in the bulk phase was monitored by UV Raman spectroscopy with excitation at 244 and 325 nm, as well as HRTEM. Nucleation takes place first in the core of the amorphous particles, and crystalline nuclei with Fe‐ZSM‐5 structure are formed in the core by consuming the amorphous shell. Finally the amorphous particles are completely transformed into Fe‐ZSM‐5 crystals.
Synthesis, X‐ray Single‐Crystal Structure Determination, and Magnetic Properties of [Rb(benzo[18]crown‐6)]+ Salts Containing Well‐Ordered Fulleride Trianions C603−
Authors: Boeddinghaus M. Bele , Salzinger Michael , Fässler Thomas F.
Published: February 2009

Finally, a structure with well‐resolved C603− ions and S=1/2 spin system: The two novel title compounds have clearly S=1/2 and not S=3/2 electronic states, as expected for the occupation of the triply degenerate LUMO of C60. These structures with well‐ordered fullerene trianions show that the expected Jahn–Teller distortion is not observable in X‐ray diffraction experiments.

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Crystals of the composition [Rb(benzo[18]crown‐6)]3[η3‐C60](C7H8)(C3H7NO)4.5 (1) and [Rb(benzo[18]crown‐6)]3[C60](C3H7NO)5.33(C4H8O)1.66 (2) were synthesized by reduction of C60 with elemental rubidium in a mixture of dimethylformamide/tetrahydrofuran in the presence of benzo[18]crown‐6. X‐ray single‐crystal structure determinations reveal well‐ordered C60 trianions in both compounds. In contrast to previously reported structures of compounds containing C603− ions the present structure refinements allow the description of the buckyballs with good resolution (R1/wR2 for I>2σ(I) (all data) are 0.030/0.069 (0.051/0.071) and 0.042/0.101 (0.076/0.108) for 1 and 2, respectively). In 1 the C603− unit coordinates in an η3‐fashion to one Rb atom, whose coordination sphere is completed by one benzo[18]crown‐6 and one dimethylformamide molecule. In 2 no coordination of the alkali metal atom to the C60 trianion is observed. Magnetic measurements for 1 reveal a magnetic moment of 1.74 μB, as expected for an isolated S=1/2 spin system. The high‐quality data of the present studies allowed a comparison of structural details of C603− ions with other C60n− units (n=0, 2, 3) and a discussion of the structural Jahn–Teller distortions.
On the Signalling Pathways and CuII‐Mediated Anion Indication of N‐meso‐Substituted Heptamethine Cyanine Dyes
Authors: Descalzo Ana B. , Rurack Knut
Published: February 2009

Join or attack: meso‐Cyclam‐substituted heptamethine cyanine dye 1 responds very differently to the presence of metal ions and protons. Whereas the former are embraced in a host–guest complex, the latter attack the cyanine π system (see picture). In the presence of CuII, 1 selectively forms near‐infrared absorbing aggregates in buffered solution that allow the determination of citrate by using colourimetry.

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Three mid‐chain rigidified heptamethine cyanine dyes substituted with dimethylamino or cyclam groups at the meso position of the polymethine chain have been prepared and studied both experimentally and theoretically with respect to their spectroscopic response toward protons and various metal ions. Despite a potentially rich conformational ground‐state chemistry, the spectroscopic studies revealed that the behaviour of the dyes is in agreement with Kuhn's classic polymethine dye theory. Coordination of metal ions and protonation of the alkyl amino groups in the cyclam moiety accordingly lead to moderate bathochromic shifts in absorption and reduced Stokes shifts. In contrast, protonation of the dimethylamino‐substituted derivatives occurs at the polymethine chain, transforming the heptamethine into a trimethine‐type chromophore with concomitant gigantic spectral blueshifts. In the presence of CuII in buffered aqueous solution, the cyclam‐substituted dye selectively forms near‐infrared absorbing aggregates. The latter allow the determination of citrate under realistic conditions by changes in absorption at wavelengths greater than 800 nm, which results from a disruption of the aggregates when citrate binds to CuII. The copper ions thus act as mediators in a signalling reaction that constitutes a colourimetric displacement assay.
Reactions of Ruthenium Vinylidene and Acetylide Complexes Containing Trichloromethyl Groups: Preparation of a Cyclobutenonyl Complex by Solid‐State Photolysis
Authors: Wu Chung‐Yeh , Chou Hsien‐Hsin , Lin Ying‐Chih , Wang Yu , Liu Yi‐Hung
Published: February 2009

Solid‐state route to a cyclobutenone: Ruthenium perchlorocyclobutenonyl complex 2 is obtained by solid‐state photoisomerization of ruthenium trichloroacetyl acetylide complex 1. The four‐membered ring is sufficiently robust that transfer of the intact ligand could be readily achieved in a reaction of 2 with an enyne. Cyclobutenedionyl complex 3 was obtained by hydrolysis of 2 in H2O/THF.

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New reactions were observed for the cationic γ‐hydroxyvinylidene complex [Ru2]CCHC(OH)(CCl3)2+ (2, [Ru2]=CpRu(PPh3)2). A rare chloroform elimination was observed when 2 was treated with nBu4NOH to give neutral acetylide complex [Ru2]CCC(O)CCl3 (3). Solid‐state photoinduced isomerization of 3 generated ruthenium perchlorocyclobutenonyl complex [Ru2]C4Cl3O (4) in high yield. This transformation was analyzed by DFT calculations, and 4 was found to be 4.22 kcal mol−1 more stable in terms of Gibbs free energy than 3. In the coupling reaction of 4 with 2‐methyl‐1‐buten‐3‐yne the four‐membered cyclic ligand is transferred to the enyne to give substituted η3‐butadienyl complex 5 containing a cyclobutenonyl group. This coupling product could be removed from the metal by HCl. Deprotonation of 2 gave γ‐hydroxyacetylide complex [Ru2]CCC(OH)(CCl3)2 (9). In the photolysis of 9 phosphine dissociation is followed by addition of HCl to give neutral vinylidene complex Cl[Ru1]CCHC(OH)(CCl3)2 (10, [Ru1]=Cp(PPh3)Ru). Complex 4 catalyzed the coupling reaction of dimethyl acetylenedicarboxylate with styrene yielding the diene PhCHCHC(CO2Me)CHCO2Me. Solid‐state structures of 3–6 and 10 were determined by single‐crystal X‐ray diffraction analysis.
CuII–Hydrotalcite as an Efficient Heterogeneous Catalyst for Huisgen [3+2] Cycloaddition
Authors: Namitharan Kayambu , Kumarraja Mayilvasagam , Pitchumani Kasi
Published: February 2009

Top Cat! CuII–hydrotalcite (HT) is used as a catalyst for the regioselective synthesis of 1,4‐disubstituted 1,2,3‐triazoles by [3+2] cycloaddition of various azides and alkynes. The catalyst enjoys advantages such as faster reactivity, good stability, reusability, high catalytic activity without any additives at room temperature, and does not require a nitrogen atmosphere for this “click‐chemistry” transformation.

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Cyclotriphosphazene Ring as a Platform for Multiporphyrin Assemblies
Authors: Rao M. Rajeswara , Gayatri G. , Kumar Amit , Sastry G. Narahari , Ravikanth M.
Published: February 2009

Rings around a ring: The synthesis, characterization, material properties and biological studies of novel hexakis porphyrinato cyclotriphosphazene systems (see scheme) and their metal derivatives are described.

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A simple method has been employed to synthesize a cyclotriphosphazene appended with six porphyrins. The reaction of one equivalent of hexachlorocyclotriphosphazene with six equivalents of 5‐(4‐hydroxyphenyl)‐10,15,20‐tri(p‐tolyl)porphyrin or ‐21‐thiaporphyrin in tetrahydrofuran in the presence of cesium carbonate, followed by simple column‐chromatography purification, afforded the hexaporphyrinato cyclotriphosphazene systems as the single products in 80–90 % yields. The metal(II) derivatives (CuII, ZnII) of the hexaporphyrinato cyclotriphosphazene systems were prepared by treating the hexaporphyrin assemblies with the appropriate metal salts under standard metallation conditions. The compounds are freely soluble in common organic solvents and were characterized by mass spectrometry, NMR, absorption, and fluorescence spectroscopy, and electrochemical techniques. Material studies carried out by using fluorescence microscopy, SEM, and AFM techniques showed that the hexaporphyrinato cyclotriphosphazene systems form ringlike architectures. Preliminary biological studies indicate that the hexacopper(II) porphyrin assembly can be used as an artificial nuclease.
The effects of varying lengths and powers of co2 laser pulses transmitted through an optical fiber on atherosclerotic plaques
Authors: Eldar M. , Battler A. , Gal D. , Rath S. , Rotstein Z. , Neufeld H. N. , Akselrod S. , Katzir A. , Gaton E. , Wolman M.
Published: February 2009

We have studied the changes induced in atherosclerotic arteries by a CO2 laser beam delivered through a silver halide optical fiber. We found that the crater depth and diameter correlate with the total energy delivered and with the mode of delivery. Short‐duration high‐power pulses caused shallower and narrower craters and less damage to the arterial wall compared to the same energy delivered as low‐power pulses of long duration. Thus, high‐power pulses for short periods may be an effective and safe procedure for evaporization of atherosclerotic plaques.
Familial Migraine and Coronary Artery spasm in two siblings
Authors: Fournier J. A. , Fernandez‐Cortacero J. A. P. , Granado C. , Gascóon D.
Published: February 2009

A common pathophysiology for the clinical association of variant angina and migraine has been suggested, but the pathogenesis of both illnesses is yet unknown. Our report presents two siblings with both illnesses and a familial history of migraine where coronary artery spasm was documented, spontaneously in one and after the administration of ergonovine maleate in the other one. Our study strongly supports the hypothesis that genetic factors possibly play a role in the etiology of variant angina and migraine at least in some patients.
Urgent coronary artery bypass surgery in the presence of dressler's syndrome
Authors: Doble N. , Westaby S. , Goodwin J. F.
Published: February 2009

The clinical features of Dressler's syndrome which developed in a patient following a third myocardial infarction responded to a short course of prednisolone. However, angina at rest precipitated urgent coronary artery bypass surgery and pericardectomy.
Transient heart failure in an adult with kawasaki disease
Authors: Leclerc G. , Bégin P. , Laramée P. , Genest P.
Published: February 2009

Kawasaki disease is a mucocutaneous lymph node syndrome with important cardiovascular complications that usually afflicts young children. We describe a 31‐year‐old woman who developed transient heart failure during the acute phase of Kawasaki disease. The diagnosis was supported by the presence of all six criteria of the disease: fever, conjunctivitis, strawberry tongue, cervical lymphadenopathies, truncal exanthem, and periungual membranous desquamation. Related clinical and laboratory findings included heart failure, arthralgias, transverse nail grooves, thrombocytosis, and elevated serum glutamic oxaloacetic transaminase (SGOT), serum glutamic pyruvic transaminase (SGPT), and bilirubin. Alternative diagnoses were excluded. During her acute febrile illness, the patient developed tachycardia, hypotension, pulmonary rales, S3 gallop, and hepatojugular reflux. The chest roentgenogram showed new Kerley A and B lines. A first‐pass isotopic ventriculography showed diffuse hypokinesia and decreased ventricular ejection fractions; spontaneous recovery occurred after a few days. A coronarography performed two months later showed no aneurysmal dilatation. Kawasaki disease is a cause, albeit rare, of myocardial dysfunction in the adult human, and should be sought for actively in a patient with heart failure during the course of an acute febrile illness, associated with mucocutaneous changes.
Effects of pindolol therapy on the size of experimentally induced myocardial infarction in the pig
Authors: Friedli H. P. , Althaus U. , Magnenat L. , Gurtner H. P.
Published: February 2009

The effect of pindolol on experimental myocardial infarction was studied in a pig model. Intravenous application of 0.05 mg pindolol per kg body weight was initiated one hour after coronary ligation and repeated at 12‐hour intervals for five days. No significant difference in infarct size could be found between pindolol‐treated animals (20.4±0.6% SEM of whole ventricular mass, n = 6) and untreated controls (20.5 ± 1.2% SEM, n=9). Hemodynamic data did not change significantly throughout the experiment. These results differ in part from those reported by other investigators: The disagreement may be due to the specific pharmacological properties of the applied drug, to variations in the dosages of beta blockers, as well as to differences in the study design.
Familial hypercholesterolemia and HLA antigens
Authors: Donadon V. , Antonini CANTERIN A. , De PAOLI P. , Borean M. , Villalta D. , Zanata G. , Santini G. F.
Published: February 2009

Hereditary factors play an important role in the etiology and progression of coronary heart disease (CHD), most probably by causing the appearance and the levels of its risk factors. To investigate if there is a correlation between familial hypercholesterolemia and HLA system antigens, 25 subjects of 7 families with familial hypercholesterolemia were compared with 14 normocholesterolemic related subjects. Compared to normocholesterolemic kindreds, the familial hypercholesterolemic subjects have a significant increased HLA‐Bw35 antigen and a lack of HLA‐A1. Therefore, the correlation found with some HLA system phenotypes improves our knowledge about familial hypercholesterolemia and aids in the identification of subjects affected with this disorder of lipid metabolism, which is one of the most important CHD risk factors.
Prediction of left ventricular function in acute anterior myocardial infarction by serum creatine kinase activity and precordial ECG mapping
Authors: Marchionni N. , Moschi G. , Lombardi A. , Tozzi P. , Salani B. , Di. BARI M. , Ferrucci L. , Paoletti M.
Published: February 2009

Right cardiac catheterization, serial determination of creatine phosphokinase (CPK) and of CPK‐MB activities, and precordial 35‐lead ECG mapping were performed in 17 consecutive patients with a first anterior acute myocardial infarction (AMI) within 6 hours of the onset of symptoms. Left ventricular function as determined by the stroke index (SI, ml/m2) to mean pulmonary capillary wedge pressure (PCWP, mmHg) ratio inversely correlated either with the total CPK and CPK‐MB released and with peak enzymatic activity, or with the entity of early (6th hour ECG) ST‐segment elevation. Conversely, a direct correlation was found between the SI/PCWP ratio and the ratio of R to Q+S waves from late (48th hour) ECG. Residual left ventricular function after a first anterior AMI can therefore be estimated noninvasively in the individual patient by early precordial ECG mapping and by peak enzymatic activity.
The applicability of noninvasive his bundle electrogram to assessing the effect of digitalis on atrioventricular conduction
Authors: Otsuka K. , Otsuka K. , Nojima K. , Saito H. , Seto K. , Ozawa T.
Published: February 2009

His bundle electrograms were recorded by a signal averaging technique using the Takayasu vectorial lead system, and effects of ouabain on the atrioventricular conduction were investigated using Wistar rats. Ouabain was given intraperitoneally at 30 min intervals in doses of 1–40 mg/kg. When ouabain dosage was increased to 20 mg/kg, the prolongation of PQ interval became prominent and P waves were hidden on the preceding T waves. Dose‐related prolongation of PQ and AH intervals was observed in the 1–15 mg/kg dosages. Ouabain‐induced ventricular arrhythmias occurred in the 30 mg/kg dosage. Dose‐related prolongation of QRS duration and HV interval was observed in the 1–25 mg/kg dosages. These prolongations were significant by the analysis of variance (p<0.01). Prolongation of PQ and AH intervals is probably due to a digitalis‐induced increase in parasympathetic nerve activity. However, the reason for the prolongation of HV interval and QRS duration was uncertain. Direct effects of ouabain on the conduction system, or central nervous system effects of ouabain on cardiovascular function were speculated. These results suggest the applicability of the noninvasive record of His bundle electrogram to assessing the digitalis effect even on the human atrioventricular conduction.
Mechanical emergency recanalization of the left main coronary artery
Authors: Sigwart U. , Goy J.‐J. , Finci L. , Blanc M. , Grbic M. , Stumpe F.
Published: February 2009

Acute occlusion of the left main coronary artery is normally fatal. According to the literature, only a few cases have been treated by intracoronary thrombolysis; the prolonged period of ischemia, however, resulted in severe left ventricular dysfunction and numerous complications. Therefore, effort should be directed to recanalize the left main coronary artery within the shortest possible interval. We followed this approach in a case of acute occlusion of a subtotal stenosis of the left main coronary artery which could be mechanically reopened and dilated within a few minutes. The intervention resulted in immediate reversal of profound cardiogenic shock and complete restoration of normal left ventricular function. At hospital discharge, the patient was asymptomatic with a negative bicycle stress test. Immediate mechanical recanalization and angioplasty appear to be a feasible approach in life‐threatening coronary occlusion.
Echocardiographic and hemodynamic features of severe aortic regurgitation with diastolic opening of the aortic valve
Authors: Martinez E. E. , Herman M. V. , Kay R. H. , Pontes S. C. , Brandao A. C. , Pfefferman A. , Arroyo J. B. , Portugal O. P.
Published: February 2009

Severe aortic regurgitation may be associated with premature aortic valve opening. Several possible etiologies for this diastolic opening have been suggested. We present a patient with hemodynamic data, M‐mode and 2‐D echocardiography in the setting of severe aortic regurgitation and diastolic aortic valve opening. Our data lead us to conclude that aortic valve opening in this situation is neither from passive flotation nor dependent on atrial systole. We believe that active ventricular recoil mechanisms can facilitate increases in diastolic ventricular pressure which then can transiently exceed aortic pressure in the setting of severe aortic regurgitation. This hemodynamic observation suggests that the valve opening is an active process.
Application of a new spatial signal averaging device for the beat‐to‐beat detection of cardiac late potentials
Authors: Chen W‐C. , Zeng Z‐R. , Chow C. , Xine Q‐Z. , Kou L‐C.
Published: February 2009

A new high resolution digital signal averaging device was developed to record precordial late potentials. The subjects examined included 8 normals (including medical patients with normal cardiovascular status), and 21 patients with coronary artery disease (CAD) and myocarditis of probable viral origin. Late potentials were evident in 11 cases (CAD 8 cases and myocarditis in 3 cases). In 10 patients, multiple ventricular premature beats and in 3 others, attacks of ventricular tachycardia had been present. Sudden cardiac death occurred later in one patient. It was concluded that late potentials as recorded by this simple new device are predictive of ventricular arrhythmias — sometimes life threatening. As no triggering is necessary, both conventional and beat‐to‐beat signal averaging can be carried out and the presence of various arrhythmias is negligible.
Assessment of myocardial function by calculation of two energetic parameters from pressure‐volume relations and wall thickness in human ventricles
Authors: Holubarsch C H. , Hasenfuss G. , Just H.
Published: February 2009

For defining myocardial performance in chronic cardiac diseases and during acute pharmacological interventions we created a new index of performance based on myocardial mechanical and energetic counterparts. From angiocardiographic pressure‐volume data the pressure‐volume integral is analyzed and divided by left ventricular muscle mass, yielding work done by a unit of myocardium (E1). From pressure‐volume data the stress‐time integral σ.t is evaluated by using an ellipsoidal calculation model. In order to compare E1 with the σ.t the σ.t is transformed into energetic units on the basis of new physiologic myothermal findings (E2). Then, the sum of E1 and E2 (i.e., the maximum of mechanical performance), and the ratio of E1 to the sum of E1 and E2 can be defined (i.e., the myocardial work related to the energy consumed during a contraction). By calculating E1 and E2, we are able to analyze the myocardial efficiency of work production. These parameters are proposed for judging the myocardial performance and efficiency in congestive heart failure and the effects of positive inotropic substances and vasodilators.
Acute thrombosis of a composite ascending aortic conduit containing a bjork‐shiley valve during pregnancy: successful emergency cesarean section and operative repair
Authors: Shemin R. J. , Phillippe M. , Dzau V.
Published: February 2009

A 31‐year‐old female had an ascending aortic conduit with a Bjork‐Shiley valve placed for an aortic dissection. A year later she became pregnant and was placed on heparin instead of coumadin therapy. She then developed a distal aortic dissection and was hospitalized for close medical monitoring of fetal status and maturity. At 33 weeks of gestation the aortic valve thrombosed, resulting in pulmonary edema and cardiac arrest. Emergency cesarean section and replacement of the aortic valve and ascending aortic conduit was successful in salvaging mother and child. Both are well at 2 years followup. The case illustrates the hazards of prosthetic valves in pregnant patients and cardiac surgery during pregnancy. These issues are reviewed along with the details leading to successful surgical management.
Experimental study on the relationship between cardiac arrhythmias and sleep states by ambulatory ecg‐EEC monitoring
Authors: Otsuka K. , Ikari M. , Ichimaru Y. , Saito H. , Kawakami T. , Otsuka K. , Kaba H. , Seto K.
Published: February 2009

The relationship between cardiac arrhythmias and sleep states was investigated in rats using the ambulatory ECG‐EEG monitoring system under the 14/10 lightdark illumination schedule. Records of 14 rats obtained over 94 days were analyzed. Bradyarrhythmias (SA block and AV block) and ventricular arrhythmias [ventricular premature contraction (VPC) and short run of VPCs (ventricular tachycardia, VT)] were observed. Average number of episodes of bradyarrhythmia per day was 7.5, and the ratio of SA block to AV block was 34.9% to 65.1%. Average VPC or VT occurrence per day was 0.9 or 0.1 times, respectively. Sleep states were divided into alertness, slow‐wave sleep, and paradoxical sleep, and the relationship between sleep states and arrhythmias was investigated. Bradyarrhythmias appeared predominantly during paradoxical sleep, while ventricular arrhythmias appeared during alertness as well as paradoxical sleep. Bradyar‐rhythmic episodes decreased by right or left vagotomy 78% or 70%, respectively. Sinus bradyarrhythmias disappeared almost completely by the right vagotomy, while the occurrence of AV block decreased by the right or left vagotomy. Circadian rhythms in arrhythmias were also analyzed by the cosine‐fitting technique, and significant circadian rhythms were demonstrated in both bradyarrhythmias and ventricular arrhythmias. Acrophases were 9:56 A.M. and 1:47 A.M., respectively. Occurrence of VT was rare, but the most frequent incidental time zone was immediately following transition from light effects (rest) to dark (activity). This knowledge of circadian rhythm effects in arrhythmias must be incorporated into improved treatment of arrhythmias.
24‐Hour blood pressure differences in hypertension and normotension in bed‐confined subjects
Authors: Stamatelopoulos S. , Petrou P. , Papamichael C. , Mouskos C. , Sideris D. , Moulopoulos S.
Published: February 2009

This study investigates whether the degree of hypertension may be evaluated by information derived from the 24‐h blood pressure (BP) curve unrelated to the pressure height. We performed 24‐h BP intra‐arterial monitoring in 52 bed‐confined subjects (10 normotensives, 10 borderlines, and 32 hypertensives on WHO criteria). Computer analysis of 1152 BP values per subject per 24‐h revealed the following: (1) During the night hours, the percentage of the 1152 systolic BP values ≥160 (in mmHg) increased (or did not change if 100%) in all subjects with mean 24‐h systolic BP (24‐h BP) > 170 and it decreased (or did not change if 0%) in all subjects with 24‐h BP <150. The change in the percentage of the 1152 diastolic BP values≥95 during the night hours did not correlate to either the mean 24‐h diastolic or systolic BP. (2) The higher the mean 24‐h systolic BP, the lower the skewness of the distribution of the 1152 systolic BP values (p<0.01). No such correlation existed between the skewness of the distribution of the 1152 diastolic BP values and either the mean 24‐h diastolic or systolic BP. It is concluded that both the change in systolic BP during the night hours and the skewness of its distribution during the 24‐h monitoring period are correlated to the severity of hypertension.