bluuebunny/crossref_metadata_2025_split huggingface dataset:
Model predictions of increased knee joint loading in regions of thinner articular cartilage after patellar tendon adhesion
Authors: Fernandez Justin W. , Akbarshahi Massoud , Crossley Kay M. , Shelburne Kevin B. , Pandy Marcus G. 
Published: March 2011

AbstractPatellar tendon adhesion is a complication from anterior cruciate ligament (ACL) reconstruction that may affect patellofemoral and tibiofemoral biomechanics. A computational model was used to investigate the changes in knee joint mechanics due to patellar tendon adhesion under normal physiological loading during gait. The calculations showed that patellar tendon adhesion up to the level of the anterior tibial plateau led to patellar infera, increased patellar flexion, and increased anterior tibial translation. These kinematic changes were associated with increased patellar contact force, a distal shift in peak patellar contact pressure, a posterior shift in peak tibial contact pressure, and increased peak tangential contact sliding distance over one gait cycle (i.e., contact slip). Postadhesion, patellar and tibial contact locations corresponded to regions of thinner cartilage. The predicted distal shift in patellar contact was in contrast to other patellar infera studies. Average patellar and tibial cartilage pressure did not change significantly following patellar tendon adhesion; however, peak medial tibial pressure increased. These results suggest that changes in peak tibial cartilage pressure, contact slip, and the migration of contact to regions of thinner cartilage are associated with patellar tendon adhesion and may be responsible for initiating patellofemoral pain and knee joint structural damage observed following ACL reconstruction. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 29: 1168–1177, 2011
Long‐term outcome and cost‐effectiveness of complete versus assisted video‐assisted thoracic surgery for non‐small cell lung cancer
Authors: He Jianxing , Shao Wenlong , Cao Christopher , Yan Tristan , Wang Daoyuan , Xiong Xin‐guo , Yin Weiqiang , Xu Xin , Chen Hanzhang , Qiu Yuan , Zhong Baoliang 
Published: March 2011

AbstractBackgroundTo compare the outcomes and costs of two methods of video‐assisted thoracoscopic surgery (VATS) major pulmonary resection in patients with clinically resectable non‐small cell lung cancer (NSCLC).MethodsBetween January 2000 and December 2007, 1,058 patients with proven stages I–IIIA NSCLC underwent complete VATS (c‐VATS) or assisted VATS (a‐VATS) major pulmonary resection together with a systematic nodal dissection.ResultsThe study cohort consisted of 736 men and 322 women. Mean operative time was shorter for the a‐VATS cohort compared with the c‐VATS group (P = 0.038). Overall survival (OS) at 5 years based on Kaplan–Meier analysis was 55.3% (95%CI, 50.6–60.0%) for those who underwent c‐VATS and 47.7% (95%CI, 41.2–54.2%) for those who underwent a‐VATS (P = 0.404). Gender, final pathology, TNM stage, and pT status were significant predictive factors for OS according to multivariate analysis. The total cost of a‐VATS lobectomy was lower than that of c‐VATS lobectomy.Conclusionsc‐VATS and a‐VATS yield similar results in patients with clinically resectable NSCLC. a‐VATS, however, may be less expensive and easier to adopt, making it a particularly attractive option for thoracic surgeons in developing countries. J. Surg. Oncol. 2011;104:162–168. © 2011 Wiley‐Liss, Inc.
In vivo volumetric imaging of microcirculation within human skin under psoriatic conditions using optical microangiography
Authors: Qin Jia , Jiang Jingying , An Lin , Gareau Daniel , Wang Ruikang K. 
Published: March 2011

AbstractBackground and ObjectiveThere is a growing body of evidence suggesting that vascular abnormalities may play crucial role in several dermatologic diseases, such as psoriasis, port wine stain, and skin cancer. To improve our understanding of vascular involvement in these skin conditions, there is a need for a non‐invasive imaging modality capable of assessing 3D microcirculations within skin tissue beds in vivo. This study aims to demonstrate whether ultra‐high sensitive optical microangiography (UHS‐OMAG) is feasible to visualize skin microcirculations in 3D and to quantify microvascular vessel density under normal and psoriatic conditions in vivo.Study Design/Material and MethodsAn UHS‐OMAG system operating at 1,310 nm wavelength was used for in vivo imaging of microcirculation in human skin. The system has a spatial resolution of ∼10 µm × 20 µm (axial × lateral), running at 280 fps to acquire 3D imaging dataset to represent morphology and capillary level microvascular blood perfusion within the scanned skin tissue volume. The sensitivity of the system to the blood flow is as low as ∼4 µm/second. With this system, we performed the imaging experiments on the skin of a volunteer with stable plaque‐type psoriasis. The microcirculation and structural information of normal and diseased skins were compared both qualitatively and quantitatively.ResultsThe UHS‐OMAG is capable of differentiating the microcirculation within the normal skins from that in the psoriatic skins. The 3D optical images show that the blood vessel elongation and the dense network in the psoriatic lesion skin, the appearance of which is not observed within the normal skin. Based on the results obtained from one subject, the statistical analyses show that higher blood vessel density presented within the psoriasis lesion skin than that of the normal skin.ConclusionsUHS‐OMAG can be a valuable tool for imaging skin microcirculations non‐invasively with high‐speed and high‐sensitivity, and therefore may have a useful role in future clinical diagnosis and treatment of dermatologic diseases such as psoriasis in human subjects. Lasers Surg. Med. 42:122–129, 2011 © 2011 Wiley‐Liss, Inc.
Chain transfer and living functionalization of polymethacrylates by group transfer polymerization using ethyl 2‐Phenyl‐2‐butenoate
Authors: Quirk Roderic P. , Ren Jie 
Published: March 2011

AbstractA living functionalization method has been investigated for group transfer polymerization (GTP) of poly(alkyl methacrylates) using ethyl 2‐phenyl‐2‐butenoate (EPB). The end‐capping reactions of EPB to living trimethylsilyl ketene acetal‐ended poly(methyl methacrylate) (PMMA) chain ends have been systematically studied and characterized by SEC, VPO, UV‐visible spectrosocopy, 1H and 13c NMR spectroscopy. The results of sequential monomer addition, varying stoichiometry and copolymerization indicate that EPB effects efficient chain end functionalization only at stoichiometric concentrations; chain transfer reactions (chain transfer constant = 0.4) occur with excess EPB and during copolymerization with MMA. Chain transfer reactions (chain transfer constant = 0.1) also occur when copolymerizing ethyl 2‐methyl‐2‐butenoate with MMA.
Intramolecular chelation as a factor in the stereochemistry of anionic vinyl polymerization
Authors: Hogen‐Esch T. E. , Meverden C. 
Published: March 2011

AbstractThe methylation (CH3I) of 1,3‐bis(2‐pyridyl)butyllithium in THF at −78°C is highly meso‐selective (>98%) but the selectivity decreases with increasing cation‐size or ‐coordination. The reaction of 1,3‐bis(2‐pyridyl)butyllithium with other electrophiles such as i‐C3H7Br, PhCH2Cl, Me3SiCl (CD3)2CO and 4‐vinylpyridine is also stereoselective under these conditions giving meso‐like products. On the other hand, addition of 2‐vinylpyridine is only slightly selective (64%) and this is consistent with the 65% meso content of P2VP formed by polymerization in the presence of Li ion. The chemistry of the above reactions is rationalized by intramolecular coordination of Li or other cations by the penultimate 2‐pyridyl group and this is supported by equilibria involving proton abstraction of 1,3‐bis(2‐pyridyl)butane and similar compounds by bases having Li, Na or K counterions. It is shown that the tendency for intramolecular chelation is highest for Li and lowest for K ion. Temperature dependence of the above equilibrium shows that intramolecular chelation of Li and Na ions is exothermic (−1.4 and −1.3 kcal respectively) whereas the AH for K ion is very small (−0.5 kcal). Entropies of chelation are slightly positive for Li (0.8 e.u.) and negative for Na and K ions (‐2.60 and −0.40 e.u. respectively). The lack of stereoregular polymerization of 2‐VP in the presence of Li ion is most likely due to the requirement that the Li ion of the newly formed 2‐pyridyl anion is coordinated with the 2‐pyridyl group of the previous asymmetric center. Thus it would appear that intramolecular coordination of metal ion by penultimate 2‐pyridine does not necessarily lead to isotactic‐polymerization.
Group‐transfer polymerization: Recent advances and applications
Authors: Hertler Walter R. 
Published: March 2011

AbstractAbstract: Catalysis of GTP of MMA with nucleophilic anions on cross‐linked polystyrene supports was studied. With anion‐bound supported catalyst, evidence is presented for formation in solution of ester enolates as reaction intermediates. Study of the cyanide‐catalyzed initiation of GTP of MMA by TMSCN, has provided quantitative data for the association constant Ka for the complexation of cyanide by TMSCN and, by inference, an upper limit for the Ka for the association of this nucleophilic anion with silyl ketene acetals. The effects of i‐propyl‐ and t‐butoxy‐silyl analogs of TMSCN on anion‐complexation and on initiation and propagation of GTP are discussed. Coordination by hydrogen‐bonding of nucleophilic anions to acetonitrile is shown to be the mechanism for “livingness‐enhancement” of anion‐catalyzed GTP at low concentrations of acetonitrile. GTP was used to prepare an ABC triblock dispersant, poly(methacrylic acid)‐block‐poly(2‐phenylethyl methacrylate)‐block‐poly(ethoxytriethylene glycol methacrylate), and the surface activity of an aqueous solution of the potassum salt was compared with that of other polymer architectures.
Breathing new life into the free radical polymerization process
Authors: Georges Michael K. , Veregin Richard P.N. , Hamer Gordon K. , Kazmaier Peter M. 
Published: March 2011

AbstractConventional free radical polymerization processes are limited by their inability to be used for the synthesis of resins of controlled molecular weights and complex architecture. New processes are being developed in which the free radical propagating chain is reversibly terminated, allowing the free radical polymerization to behave in a living fashion. A review of these processes is presented, along with preliminary results of chain extension studies of nitroxide‐terminated polystyrene as a model for block copolymer synthesis.
Novel catalyst system for the synthesis of poly(alkylene oxide) with controlled molecular weight
Authors: Inoue Shohei , Aida Takuzo , Sugimoto Hiroshi , Kawamura Chikara , Kuroki Masakatsu 
Published: March 2011

AbstractAn organoaluminum compound with bulky phenoxide groups as a Lewis acid can accelerate much the living polymerization of alkylene oxide initiated with aluminum porphyrin by the coordinative activation of the monomer. This concept can be extented to the polymerization initiated with aluminum Schiff base and tetraazaannulene complexes.
Starburst® dendrimers: A conceptual approach to nanoscopic chemistry and architecture
Authors: Dvornic Petar R. , Tomalia Donald A. 
Published: March 2011

AbstractThe nanoscopic domain of structural complexity, which ranges from 1 to 100 run on a particle size scale includes a relatively unexplored area of science which resides between classical chemistry and molecular biology. This rapidly growing area of science is referred to as nanoscopic chemistry and architecture. Concepts evolving in this area lead to a rich variety of precise structures, architecture and properties. These concepts are based on dendritic macromolecules in general and on Starburst® dendrimers in particular. They envision dendrimers as fundamental building blocks which may be used to synthesize nanoscopic compounds, clusters, polymers, etc. Accordingly, dendrimers are regarded architecturally as functional analogues of atoms; therefore, their potential role in nanoscopic chemistry may be compared to that of the atoms in classical chemistry.
Heterogeneous catalysis for ring opening anionic oligomerisation
Authors: Hamaide T. , Spitz R. , Letourneux J. P. , Clavene J. , Guyot A. 
Published: March 2011

AbstractNew heterogeneous catalysts for ring opening oligomerization are obtained by grafting alkyl aluminium moieties on silica. Adding alcohol in excess causes the formation of aluminium alkoxides and allows the catalytic mode, because of a rapid exchange reaction between the grafted active centers and the free alcohols present in the medium. All the polymer chains are end‐capped by these alcohol molecules, which give functionalized oligomers.
Novel evidence on the chemistry of β‐Lactone anionic polymerization
Authors: Jedliński Zbigniew J. , Kowalczuk Marek , Kurcok Piotr 
Published: March 2011

AbstractThe mechanistic aspects of the β‐lactones anionic polymerization initiated by both classical initiators, i.e. alkali metal alkoxides, and non‐traditional ones, such as supramolecular complexes of alkali metals and alkali metal naphthalenes, are discussed in this paper.
Polymerization of glycolide promoted by ω‐Al‐alkoxide poly(ϵ‐caprolactone) macro‐initiators and formation of stable colloidal dispersions
Authors: Barakat Ibrahim , Dubois Philippe , Jérǒme Robert , Teyssié Philippe , Mazurek Mieczyslaw 
Published: March 2011

AbstractBlock polymerization of glycolide (GA) and ϵ‐caprolactone (ϵ‐CL) has been initiated with aluminum alkoxides, such as Al(OiPr)3 and Et2AlOCH2X (where X = ‐CH2‐Br and ‐CH2O‐C(O)‐C(Me)=CH2), in THF at 40°C. Structure and composition of block copolyesters have been characterized with respect to the molecular weight by NMR spectroscopy and thermal analysis. Copolymerization is typically living, so that block copolyesters have been synthesized with predictable molecular weight and composition. The inherent insolubility of polyglycolide block is responsible for the heterogeneity of the polymerization medium and formation of stable, non‐aqueous colloidal dispersions. This effect is especially pronounced at high GA/ϵ‐CL molar ratios. Colloidal dispersions have been analyzed by transmission electron microscopy (TEM) and photocorrelation spectroscopy (PCS).
Conditions for secondary particle formation in emulsion polymerization systems
Authors: Morrison Bradley R. , Gilbert Robert G. 
Published: March 2011

AbstractA simple means is deduced for determining conditions for secondary particle formation in emulsion polymerization systems in systems where the amount of added surfactant is below the cmc. A new radical formed from initiator in the aqueous phase will undergo some polymerization with aqueous‐phase monomer, but must have three possible eventual fates: aqueous‐phase termination, entry into a preexisting particle, or creation of a new particle. The means for determining the onset and extent of secondary nucleation is to modify HUFT theory to take into account a successful model for entry [ Macromolecules, 24, 1629 (1991)] which states that entry occurs if and only if the aqueous‐phase radical has achieved a critical degree of polymerization z. Particle formation below the cmc is by homogeneous/coagulative nucleation which (if coagulation is ignored) gives an upper bound to the rate of formation of precursor particles; these are of a degree of polymerization Jcrit > z. The resulting equations are readily solved, and require only a knowledge of the aqueous‐phase propagation and termination rate coefficients (the latter is very high: ca. 109 dm3 mol−1 s−1 for termination between the very small radicals), z and jcrit. Easily applied means are given for estimating all these quantities. The treatment gives good accord with experimentally observed conditions for the onset of secondary nucleation in low‐surfactant systems (including taking in situ micellization into account).
Pulsed laser polymerization of styrene in compartmentalized systems
Authors: Schweer Johannes , van Herk Alex M. , Pijpers Ralf J. , Manders Bart G. , German Anton L. 
Published: March 2011

AbstractPulsed laser polymerizations of styrene were performed in microemulsion droplets and in latex particles. From the molecular weight distribution of the resultant polymer either the propagation rate coefficient in the droplets or the monomer concentration in the particles could be determined. Furthermore for microemulsion droplets with a low initiator concentration the rate coefficient for transfer to monomer could be determined. Because in very small particles the termination rate can be very high, instantaneous termination may occur, leading to a shift of the low molecular weight inflection point as the best measure of the propagation rate coefficient to the maximum in the molecular weight distribution.forming pulsed laser polymerization experiments directly in emulsion systems gives specific information on the special features associated with doing polymerizations in heterogeneous and compartmentalized systems.
Challenges in predicting and controlling particle morphology in latices of commercial complexity
Authors: Sundberg Donald C. , Durant Yvon G. 
Published: March 2011

AbstractIndependent, quantitative models for free energy associated with crosslinked seed latices, and monomer and surfactant at the polymer/water interface have been integrated into a predictive model for latex particle morphology. It has been found that very low levels of crosslinking are predicted to influence the particle morphology in a dramatic fashion. Free energy calculation also highlight the often critical role played by surfactant. Highly active surfactants tend to equalize the two polymer/water interfacial tensions and allow the polymer/water interfacial energy to significantly influence the particle morphology.
An overview of the preparation and use of emulsion polymer particles for the toughening of plastics
Authors: Lovell Peter A. 
Published: March 2011

AbstractThe rationale for rubber‐toughening of brittle plastics is presented together with a discussion of the advantages of using pre‐formed toughening particles prepared by emulsion polymerisation. Rubber‐toughened acrylic and epoxy resin materials are used to illustrate the preparation and use of pre‐formed emulsion polymer particles for toughening. For both types of material, tensile properties are controlled by the volume fraction of rubbery polymer, essentially independent of the size and morphology of the toughening particles. However, under the additional constraint ahead of propagating cracks, toughening particle size and morphology are shown to be important, and to have different effects in the two types of material due to inherent differences in the mechanism of yielding of the matrix polymer.
Synthesis and characterization of core‐shell latexes with microscopic and solid‐state NMR methods
Authors: Landfester K. , Boeffel C. , Lambla M. , Spiess H. W. 
Published: March 2011

AbstractCore‐shell latexes based on poly (butyl acrylate) and poly(methyl methacrylate) were synthesized with varying shell content at high and low temperature. Electron microscopy combined with advanced solid‐state NMR techniques have been used to investigate the entire structure and the interphase morphology in these core‐shell particles depending on the reaction conditions. Distinct differences of the interphase morphology were found for particles synthesized at high and low temperature.
Miniemulsion polymerization: An approach to control copolymer composition
Authors: Kitzmiller Ervin L. , Miller Christopher M. , David Sudol E. , El‐Aasser Mohamed S. 
Published: March 2011

AbstractThe copolymerization of vinyl acetate (VAc) and vinyl 2‐ethylhexanoate (V2EH) via miniemulsion polymerization is being investigated with the goal of better copolymer composition control. The reaction kinetics and final particle sizes were compared for homopolymerizations and copolymerizations of the two monomers. Enhanced polymerization rates were seen for the miniemulsion polymerizations over their conventional counterparts despite a decreased number of particles. This was attributed to the influence of the reactive surfactant sodium dodecyl allyl sulfosuccinate and low water solubility of the V2EH monomer. Increased nucleation of miniemulsion droplets was sought by incorporation of small amounts of polymer into the droplets. This was first shown to be effective for styrene miniemulsion polymerizations and was subsequently successfully extended to the VAc/V2EH system
Characterization of emulsion polymerizations through ultrasound propagation velocity measurements
Authors: Apostolo M. , Canegallo S. , Siani A. , Morbidelli M. 
Published: March 2011

AbstractThe application of the measurement of ultrasound waves propagation velocity for characterizing emulsion polymerization systems is discussed. The ultrasound velocity sensor provides informations about various properties of interest in emulsion polymerization systems. These include the evaluation of monomer solubility and emulsifier critical micellar concentration in water, the in‐situ and on‐line monitoring of conversion in homo‐ and co‐polymerizations, the investigation of the polymer glass transition and finally the measure of monomer solubility in submicron polymer particles.
Modelling of glass transition and molecular weight distribution in emulsion and suspension copolymerisation
Authors: Guillot Jean 
Published: March 2011

AbstractSUMMARY. Modelling of emulsion copolymerisation is now more and more used for both mechanistic investigations and process control. Many specific characteristics of monomers, as well as polymerisation in heterogeneous medium can be quite accurately taken into account (temperature, pH, gel effect, crosslinking, inhibition, e.g.). However, a major problem is the extensive number of required parameters. But, depending on the main informations sought (kinetics, microstructure or properties), the number of parameters actually required can be decreased considerably by providing the computer either on‐line or even off‐line with global information on conversion and particle size, from reliable sensors. In addtion to kinetics, many distributions characterising the copolymers can be derived, which in turn lead to the accurate simulation and control of end‐use properties such as glass transition or molecular weight distribution, as shown in this work.
Kinetics of polyelectrolyte network formation in free‐radical copolymerization of acrylic acid and bisacrylamide
Authors: Zhao X. , Zhu S. , Hamielec A. E. , Pelton R. H. 
Published: March 2011

AbstractRecently, a research/development program has been initiated to investigate the kinetics of synthesis, characterization and applications of polyelectrolyte networks. The research on crosslinking involves both theoretical development and experimentation. Herein, is provided a summary of this work. In the experimental polymerization done to date, acrylic acid (AA)/N.N'‐methylenebisacrylamide (BAM) was studied in considerable detail. The polymerization conditions were: temperature, 50°C; initial monomer concentration, 5 wt%, of which 1.0 mol% is BAM; K2S2O8(KPS) as the initiator, 10−3 mol/L; pH range, 1 − 13; sodium chloride concentrations up to 3.1 mol/L. Measurements included: monomer conversion, polymer composition, sol/gel fraction, swelling ratio, and the densities of primary cyclization, secondary cyclization and crosslinking. It was found that the effect of polymerization parameters on the resulting polymer network microstructure was dramatic, and in particular, the pH and ionic strength of the reaction medium were important parameters. In the theoretical studies, the Tobita‐Hamielec kinetic gelation model was extended to incorporate the concept of ion pair interaction and the divinyl loop formation. The system was treated as a multi‐component polymerization of acrylic acid, acrylate ion, acrylate ion pair and bisacrylamide. The model permits one to investigate the development of the crosslinking density distribution among primary polymer chains during the course of polymerization as a function of pH and ionic strength.