bluuebunny/crossref_metadata_2025_split huggingface dataset:
Allostery of the two‐state model of hemoglobin studied by ECEPP energy minimization
Authors: Seno Yasunobu 
Published: March 2006

AbstractRecently, a powerful parallel‐vector processor became available for molecular science. A new FORTRUN program was coded to treat the whole hemoglobin molecule with twofold symmetry. Using the X‐ray coordinates of deoxyhemoglobin and oxyhemoglobin, minimum energy conformations were obtained for both the T‐state and the R‐state on the two‐state model of allostery. From them, further energy minimization was performed with simple perturbation to bring the proximal region close to the heme group instead of oxygen binding, and the structural changes and energy changes were investigated. The difference of calculated energy changes between T and R was semiquantitatively in agreement with the experimental value 2.7 kcal/mol for one oxygen binding. When the perturbation was exerted on the α‐subunits, the energy change within the perturbed α‐subunits in the T‐state gave a main contribution, and in the R‐state, the structural changes of the α‐subunits were specifically large. When the perturbation was exerted on the β‐subunits, the intersubunit interaction energy between α1 and β2 (α2 and β1) was dominant in the difference of the energy changes between T and R. © 2006 Wiley Periodicals, Inc. J Comput Chem 27: 701–710, 2006
Direct constructions for cyclically relative difference matrices with five rows
Authors: Ding Cunsheng , Yin Jianxing 
Published: March 2006

AbstractIn this article, we construct a (6p, 5, 1) cyclic difference matrix with one hole of size 6 for any prime p > 5 and a (2p, 5, 1) cyclic difference matrix with one hole of size 2 for any prime p ≡ 1, 13 or 17 (mod 24). © 2006 Wiley Periodicals, Inc. J Combin Designs 14: 391–399, 2006
Small latin squares, quasigroups, and loops
Authors: McKay Brendan D. , Meynert Alison , Myrvold Wendy 
Published: March 2006

AbstractWe present the numbers of isotopy classes and main classes of Latin squares, and the numbers of isomorphism classes of quasigroups and loops, up to order 10. The best previous results were for Latin squares of order 8 (Kolesova, Lam, and Thiel,1990), quasigroups of order 6 (Bower,2000), and loops of order 7 (Brant and Mullen,1985). The loops of order 8 have been independently found by “QSCGZ” and Guérin (unpublished,2001).We also report on the most extensive search so far for a triple of mutually orthogonal Latin squares (MOLS) of order 10. Our computations show that any such triple must have only squares with trivial symmetry groups. © 2006 Wiley Periodicals, Inc. J Combin Designs
Quasi‐symmetric designs with fixed difference of block intersection numbers
Authors: Pawale Rajendra M. 
Published: March 2006

AbstractThe following results for proper quasi‐symmetric designs with non‐zero intersection numbers x,y and λ > 1 are proved.

Let D be a quasi‐symmetric design with z = y − x and v ≥ 2k. If x ≥ 1 + z + z3 then λ < x + 1 + z + z3.
Let D be a quasi‐symmetric design with intersection numbers x, y and y − x = 1. Then D is a design with parameters v = (1 + m) (2 + m)/2, b = (2 + m) (3 + m)/2, r = m + 3, k = m + 1, λ = 2, x = 1, y = 2 and m = 2,3,… or complement of one of these design or D is a design with parameters v = 5, b = 10, r = 6, k = 3, λ = 3, and x = 1, y = 2.
Let D be a triangle free quasi‐symmetric design with z = y − x and v ≥ 2k, then x ≤ z + z2.
For fixed z ≥ 1 there exist finitely many triangle free quasi‐symmetric designs non‐zero intersection numbers x, y = x + z.
There do not exist triangle free quasi‐symmetric designs with non‐zero intersection numbers x, y = x + 2.
© 2006 Wiley Periodicals, Inc. J Combin Designs 15: 49–60, 2007
Radiological and pathological changes in hemiballism‐hemichorea with striatal hyperintensity
Authors: Nath Jaya , Jambhekar Kedar , Rao Chandrakanth , Armitano Erik 
Published: March 2006

AbstractWe report CT and MRI findings in a 50‐year‐old African‐American woman with hemichorea‐hemiballism (HCHB) and hyperglycemia with striatal hyperintensity. Histopathologic findings following autopsy are also described, and possible explanations for the MR findings of this unique syndrome are presented. J. Magn. Reson. Imaging 2006. © 2006 Wiley‐Liss, Inc.
Why lateral meniscectomy is more dangerous than medial meniscectomy. A finite element study
Authors: Peña Estefania , Calvo Begoña , Martinez Miguel Angel , Palanca Daniel , Doblaré Manuel 
Published: March 2006

AbstractTotal meniscectomies are commonly thought to cause progressive degenerative arthrosis pathology in articular cartilage in a period of a few years because of alteration of the biomechanical environment including increased joint instability. This concern has lead to a preference for partial meniscectomies, although lateral partial meniscectomies sometimes lead to catastrophic results. We performed a three‐dimensional finite element model of the human tibiofemoral joint to examine the effect of lateral meniscectomy on knee biomechanics. The results were compared to those from modeling a medial meniscectomy. Under axial femoral compressive loads, the peak contact stress and maximum shear stress in the articular cartilage increased 200% more after a lateral than a medial meniscectomy. These increased stresses could partly explain the higher cartilage degeneration observed after a lateral meniscectomy. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res
High‐dose gamma irradiation for soft tissue allografts: High margin of safety with biomechanical integrity
Authors: Grieb Teri A. , Forng Ren‐Yo , Bogdansky Simon , Ronholdt Chad , Parks Brent , Drohan William N. , Burgess Wilson H. , Lin Jack 
Published: March 2006

AbstractScreening and processing methods currently in place have made the risk of bacterial and viral infections from allograft tissues extremely low. However, the development of a terminal sterilization method that does not adversely affect tissue function would provide an added safety to tissues for transplantation. We assessed whether high‐dose gamma irradiation could be used as an effective terminal sterilization method for allografts without impairing the preimplantation mechanical integrity of the tissues. Semitendinosus tendons were pretreated with a radioprotectant solution and then irradiated to 50 kGy under well‐defined conditions that included a tight dose range and maintained low temperatures. Maximum force, strain, stress, modulus, and strain energy density for tendons irradiated to 50 kGy were compared to nonirradiated control tendons and tendons irradiated to 18 kGy by a commercial tissue bank using their existing method. The preimplantation biomechanical properties of the 50‐kGy group compared favorably to the nonirradiated and 18 kGy groups. A study to evaluate the postimplantation mechanical and biological performance of grafts irradiated to 50 kGy is ongoing. Pathogen inactivation was also quantified following 50 kGy of irradiation, with ≥4.5 logs of Sindbis virus and 4.9 logs of parvovirus kill achieved. Analysis of Clostridium sordellii inactivation kinetics indicated that a 16 log10 reduction is predicted with 50 kGy of irradiation. A high dose of gamma irradiation using the described conditions can reduce infectious risks associated with soft tissue allografts while maintaining the preimplantation biomechanical performance of the tissues. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res
Early healing of flexor tendon insertion site injuries: Tunnel repair is mechanically and histologically inferior to surface repair in a canine model
Authors: Silva Matthew J. , Thomopoulos Stavros , Kusano Nozomu , Zaegel Melissa A. , Harwood Frederick L. , Matsuzaki Hironori , Havlioglu Necat , Dovan Thomas T. , Amiel David , Gelberman Richard H. 
Published: March 2006

AbstractOrthopedic injuries often require surgical reattachment of tendon to bone. Tendon ends can be sutured to bone by direct apposition to the bone surface or by placement within a bone tunnel. Our objective was to compare early healing of a traditional surface versus a novel tunnel method for repair of the flexor digitorum profundus (FDP) tendon insertion site in a canine model. A total of 70 tendon–bone specimens were analyzed 0, 5, 10 or 21 days after injury and repair, using tensile and range of motion mechanical testing, histology and densitometry. Ultimate force (a measure of repair strength) did not differ between surface and tunnel repairs at day 0. Both repair types had reduced strength at 10 and 21 days compared to 0 days, indicative of deterioration of suture grasping strength (tendon softening). At 21 days, tendons repaired in a bone tunnel had 38% lower ultimate force compared to surface repairs (p = 0.017). Histological findings were comparable between repair groups at 5 and 10 days but differed at 21 days, when we saw evidence of maturation of the tendon–bone interface in the surface repairs compared to an immature fibrous interface with no evidence of tendon–bone integration in the tunnel repairs. After accounting for bone removed by the tunnel, no difference in bone mineral density or trabecular bone volume existed between surface and tunnel repairs. If the results of our animal study extend to healing of the human FDP insertion, they indicate that FDP tendons should be reattached to the distal phalanx by suture to the cortical surface rather than suture in a bone tunnel. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res
Functional Beads of Polyvinylpyrrolidone: Promising Support Materials for Solid‐Phase Synthesis
Authors: Engström Jonas U. A. , Helgee Bertil 
Published: March 2006

AbstractSummary: The solubility properties of polyvinylpyrrolidone (PVP) make it an attractive material for several different polymer‐assisted synthesis applications. However, PVP lacks reactive groups necessary for attaching compounds to the polymer. Furthermore, the radical reactivity of 1‐vinylpyrrolidin‐2‐one (NVP) is different from most other monomers, which results in compositional drift during copolymerization. Therefore, introducing reactive groups into the polymer using this method is intricate. Smaller differences in radical reactivity are expected from monomers that are derivatives of NVP itself. Hence, such monomers provide a way of preparing PVP with adjustable properties. Four new monomers containing pendant double bonds, all derivatives of NVP, were synthesized and used in the preparation of a new type of hydrophilic polymer bead by aqueous suspension polymerization. We also found that undec‐10‐en‐1‐ol can be used as a comonomer for the introduction of functional groups. The lightly crosslinked beads contain hydroxyl groups at a functional loading of 0.28 mmol/g and swell extensively in a broad range of solvents. Their potential as support materials has previously been demonstrated in a five‐step solid‐phase synthesis of 5‐(2,4,6‐trimethoxy‐phenyl)‐cyclohexa‐1,3‐dienecarboxylic acid.Scanning electron microscopy image of dry beads from PVP‐[B]2.magnified imageScanning electron microscopy image of dry beads from PVP‐[B]2.
IUPAC International Symposium on Ionic Polymerization Goa, India, IP2005, October 23–28, 2005
Authors: Baskaran Durairaj , Sivaram Swaminathan 
Published: March 2006

AbstractConference Reports: This section contains reports on topical conferences. Reports are usually written at the request of the editorial office, but unsolicited contributions are also welcome. Suggestions should be sent to the editorial office of the Macromolecular journals, preferably by E‐mail to macromol@wiley‐vch.de.
Styrenics/Polyamide‐Blends – Reactive Blending and Properties
Authors: Weber Martin , Heckmann Walter , Goeldel Andreas 
Published: March 2006

AbstractThe combination of polyamide 6 (PA 6) and styrene‐butadiene‐acrylonitrile (ABS) to polymer alloys with co‐continuous morphology leads to an interesting combination of properties. Using recent development in the sampling technique for Twin Screw Extruders, the morphology formation in ABS/PA 6 blends and alloys was studied by microscopy and chemical analysis. It could be shown, that the morphology of the alloys is formed in the initial phase of the extrusion step, while in the physical blend a clear correlation between the dispersion of the phases and the residence time could be observed. By chemical analysis further details of the process could be detected.
Influence of the Curing Temperature in the Mechanical and Thermal Properties of Nanosilica Filled Epoxy Resin Coating
Authors: Pascual‐Sánchez Verónica , Martín‐Martínez José Miguel 
Published: March 2006

Abstract0.5–3 wt% nanosilica was added to an epoxy resin based on diglycidyl ether of bisphenol A (DGEBA) and cured at 25, 40 or 60 °C using isophoronediamine (IPDA) as hardener. Aggregates of nanosilica were properly dispersed into the DGEBA‐IPDA resin and agglomerates formation was avoided. Addition of nanosilica increased the storage modulus E′ and the area and height of the tan δ curve of DGEBA‐IPDA resin cured at 25 °C, but no significant differences were found by curing at higher temperature. Gel time measurements and the results obtained by applying the Kamal model to isotherm DSC curing of DGEBA‐IPDA‐nanosilica revealed that nanosilica catalysed the curing reaction between DGEBA and IPDA, in less extent by increasing the curing temperature.
Mechanical Properties and Morphology of Melt‐mixed PA6/SWNT Composites: Effect of Reactive Coupling
Authors: Bhattacharyya Arup R. , Pötschke Petra 
Published: March 2006

AbstractAn interfacial reaction during melt mixing of maleic anhydride copolymer (SMA) encapsulated single wall carbon nanotubes (SWNT) and polyamide 6 (PA6) was used in order to disperse SWNT homogeneously and to enhance interfacial adhesion. The intended reactive coupling between PA6 and SMA was evident from IR spectroscopy. Nanocomposites with SMA encapsulated SWNT showed increased elongation at break as compared to PA6/SWNT composites. SEM investigation of tensile fractured surfaces of PA6/SWNT+SMA composites indicated enhanced interfacial adhesion between PA6 and SMA modified SWNT.
Brittle‐Ductile Transition in Reactive PBT/SAN Blends
Authors: Lumlong Saisamorn , Kuboyama Keiichi , Chiba Tsuneo , Ougizawa Toshiaki 
Published: March 2006

AbstractToughening of reactive poly(butylene terephthalate) (PBT)/styrene‐acrylonitrile copolymer (SAN) blends was studied. PBT/SAN with glycidyl methacrylate (SAN‐GMA) (70/30) behaved in ductile manner on tensile test, while PBT/SAN (70/30) blend failed in brittle manner. Additionally, poly[methylene (phenylene isocyanate)] (PMPI) was added to the PBT/SAN‐GMA blend, where it was expected that PMPI would assist the reaction between PBT and SAN‐GMA, and then the strain at break was improved. PBT/SAN/PMPI (70/30/4) also behaved in ductile manner, although the interfacial adhesion strength between matrix and dispersed phase was extremely weaker than that in PBT/SAN‐GMA blend. From the results, it was found that PMPI acted as a compatibilizer without copolymer formation at the interface and then PBT/SAN behaved in ductile manner in higher SAN content by PMPI effect.
Novel Copolymers as Dispersants/Intercalants/Exfoliants for Polypropylene‐Clay Nanocomposites
Authors: Moad Graeme , Dean Katherine , Edmond Lex , Kukaleva Natalia , Li Guoxin , Mayadunne Roshan T A , Pfaendner Rudolf , Schneider Armin , Simon George , Wermter Hendrik 
Published: March 2006

AbstractThe use of various copolymers as dispersants/intercalants/exfoliants in polypropylene (PP)‐clay nanocomposites based on unmodified montmorillonite clays (NaMMT) has been explored. The primary objective of this research has been to find dispersants that allow PP nanocomposites to be formed by direct melt mixing, that are effective with unmodified clays and that comprise only a minor component of the overall composition both with respect to both clay and PP. Two classes of dispersants were investigated: PEO‐based nonionic surfactants and amphiphilic copolymers based on a long chain (meth)acrylate (e.g. octadecyl acrylate) and a more polar comonomer (e.g. maleic anhydride, N‐vinylpyrrolidone, methyl methacrylate). The state of dispersion achieved and the properties of the derived nanocomposites were found to depend strongly on both on the level of dispersant and its overall composition but interestingly properties are not particularly dependent on the dispersant architecture (i.e. whether statistical, gradient or block copolymer). The nanocomposites possess a tensile modulus up to 40% greater that the precursor PP while elongation at break and impact strength are significantly improved over “clay alone” composites and reference organoclay‐based nanocomposites. Also notable are significantly better thermal and thermo‐oxidative stability as compared to both PP and “clay alone” composites. For optimal properties, it is both necessary and desirable that the surfactant should only be a minor constituent (20–50 wt‐%) of the composition with respect to clay.
Polymer Nanocomposites: How to Reach Low Flammability?
Authors: Bourbigot Serge , Duquesne Sophie , Jama Charaf 
Published: March 2006

AbstractThe paper investigates critically the feasibility to make fire proof polymer using nanoparticles. It includes organoclay, polyhedral oligomeric silsesquioxanes (POSS) and carbon nanotube (CNT). It is shown that they can be used to make material exhibiting low heat release rate (HRR) when they undergo heat. We have developed novel approaches to characterize quantitatively the nanodispersion by solid state NMR and by TEM associated with image analysis and we have demonstrated that the dispersion at the nanoscale is essential to achieve the best performance. On the other hand, low flammability of nanocomposites is only achieved in terms of HRR but they fail in terms of UL‐94 and limiting oxygen index (LOI). To overcome this problem, we have combined nanoparticles with traditional flame retardants (intumescents) or with plasma treatment. The nanofillers act as synergists and offer an exceptional way for making fire safe polymers.
Optimization of Biodegradable Nanocomposites Based on aPLA/PCL Blends for Food Packaging Applications
Authors: Cabedo Lluís , Luis Feijoo José , Pilar Villanueva María , Lagarón José María , Giménez Enrique 
Published: March 2006

AbstractBiodegradable blends of amorphous poly(lactic acid) (aPLA) and polycaprolactone (PCL) and nanocomposites of these blends were developed by melt blending. A morphological study of the bioblends was carried out by means of WAXS and SEM showing immiscible behavior. The nanocomposites were also characterized morphologically by WAXS, TEM and SEM, revealing high degree of interaction of the nanoclays with the aPLA. Mechanical, thermal and gas barrier properties of the different blends and nanocomposites were studied and the effect of blending and clay addition on the above‐mentioned properties was evaluated.
Influence of the Nanoscale Morphology on the Photovoltaic Properties of Fullerene/MEH‐PPV Composites
Authors: Davenas Joël , Alcouffe Pierre , Ltaief Adnen , Bouazizi Abdelaziz 
Published: March 2006

AbstractThe relation between morphology and photoelectric properties of PPV derivatives/fullerene composites forming bulk heterojunction solar cells has been investigated. The solvent used to spin cast the photoactive layers has a main influence on the quenching of the MEH‐PPV fluorescence, which could be attributed to different dispersion abilities of C60 in the polymer layer shown by AFM microscopy. Formation of large fullerene aggregates is observed at fullerene concentrations of the order of 10% leading to phase separation for composite layers processed in THF, whereas more dispersed distributions of fullerenes are observed in an aromatic solvent like ODCB which accounts for a more efficient luminescence quenching with increasing filler concentrations. However the improvement of the dissociation of photogenerated charge pairs is counterbalanced by a less efficient charge transport in the composite shown by lower short circuit currents probably due to unfavorable polymer chain arrangement in ODCB. Thin film processing conditions have been modified by the preparation of blends of solutions of the polymer in THF and fullerene in ODCB. The resulting spin casted layers show improved morphologies implying better dispersion of the fullerenes and increased short circuit currents. The improvement of the photovoltaic properties of the MEH‐PPV/C60 composites has been attributed to the nanosized fullerene domains formed upon phase separation.
Fire Retarded Insulating Sheets from Recycled Materials
Authors: Matkó Szabolcs , Keszei Sándor , Csontos István , Anna Péter , Marosi György , Zsuga Miklós , Borda Jenő , Nagy Gábor 
Published: March 2006

AbstractIn this work we aimed at forming partially recycled polymer composites of appropriate mechanical properties and flame retardancy. Multilayer composite structures proved to be suitable to fulfill all of these requirements. Core‐shell structures presented here contain two‐component thermosets, i.e. epoxy, recycled polyurethane and polyisocyanurate, as matrices reinforced with waste fillers such as short basalt fibers and wood chips. Flame retardancy and mechanical properties of the core‐shell structures were investigated by the conventional methods of characterization. The developed cost‐effective multilayer composites can be applied as heat and sound insulating panels e.g. multifunctional sheets for construction or automotive industry.
Rheology and Morphology of Highly Compatibilized Polymer Blends
Authors: Van Hemelrijck Ellen , Van Puyvelde Peter , Moldenaers Paula 
Published: March 2006

AbstractThe rheology and morphology of highly compatibilized droplets has been studied, using both rheology and small angle light scattering. It is shown that linear viscoelastic measurements are a powerful tool to investigate the effectiveness of a compatibilizer to suppress coalescence. Moreover, such highly compatibilized droplets are insensitive to deformation and breakup. The consequences for the rheological behaviour of the blend are discussed.
Reaction and Morphology Development Influenced by Diffusion in a Thermoplastic/Thermoset Blend
Authors: Bella Redha , Cassagnau Philippe , Fenouillot Françoise 
Published: March 2006

AbstractDiglycidyl ether of bisphenol A (DGEBA) and 4,4′‐methylenebis [2,6‐diethylaniline] (MDEA) are miscible in polystyrene at 177 °C. We have studied how their diffusion rate in a molten polystyrene matrix influences their polymerization rate and the morphology of the thermoset particles formed at the end of the reaction. The global composition of the blend was 60 wt% of PS and 40 wt% of epoxy‐amine. The diffusional control of the reaction was evidenced by comparing the time of reaction of an initially homogeneous mixture with that of different bi‐layer samples. The reaction was controled by the diffusion for relatively thick layers (>0.3. mm). A gradient of morphology was obtained due to the diffusionnal control of the reaction. The asymetricity of this gradient may be explained by three factors: differences in diffusion coefficients, in thermodynamic interactions and in viscosity.