bluuebunny/crossref_metadata_2025_split huggingface dataset:
Improving mechanical performance of injection molded PLA by controlling crystallinity
Authors: Harris Angela M. , Lee Ellen C. 
Published: November 2007

AbstractCurrently, use of poly(lactic acid) (PLA) for injection molded articles is limited for commercial applications because PLA has a slow crystallization rate when compared with many other thermoplastics as well as standard injection molding cycle times. The overall crystallization rate and final crystallinity of PLA were controlled by the addition of physical nucleating agents as well as optimization of injection molding processing conditions. Talc and ethylene bis‐stearamide (EBS) nucleating agents both showed dramatic increases in crystallization rate and final crystalline content as indicated by isothermal and nonisothermal crystallization measurements. Isothermal crystallization half‐times were found to decrease nearly 65‐fold by the addition of only 2% talc. Process changes also had a significant effect on the final crystallinity of molded neat PLA, which was shown to increase from 5 to 42%. The combination of nucleating agents and process optimization not only resulted in an increase in final injection molded crystallinity level, but also allowed for a decreased processing time. An increase of over 30°C in the heat distortion temperature and improved strength and modulus by upwards of 25% were achieved through these material and process changes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Polyurethanes with monodisperse rigid segments based on a diamine–diamide chain extender
Authors: Biemond G. J. E. , Braspenning K. , Gaymans R. J. 
Published: November 2007

AbstractPolyether(bisurethane‐bisurea‐bisamide)s (PEUUA) based on poly(tetramethylene oxide) (PTMO) were synthesized by chain extension of PTMO endcapped with a diisocyanate (DI), and a diamine–diamide extender. The prepolymers were PTMOs with molecular weights between 1270 and 2200 g mol−1, either endcapped with 4,4′‐diphenylmethane diisocyanate (MDI), 2,4‐toluene diisocyanate (2,4‐TDI), or 1,6‐hexane diisocyante (HDI) and with a low content of free diisocyanate (<0.1 wt %). The diamine–diamide (6A6) extender was based on hexamethylene diamine (6) and adipic acid (A). In this way, segmented polyurethanes with monodisperse rigid segments (DI‐6A6‐DI) were obtained. The PEUUAs were characterized by DSC as well as temperature‐dependent FTIR and DMTA. The mechanical properties of the polymers were evaluated by compression set and tensile test measurements. The polyurethanes with monodisperse rigid segments displayed low glass transition temperatures, almost temperature‐independent rubbery plateaus and sharp melting temperatures. The crystallinities of the hard segments were 70–80% upon heating and 40–60% upon cooling. The rate of crystallization was moderately fast as the supercooling (Tm − Tc) was in the order 36–54°C. The polyurethanes based on HDI had a much higher rubber modulus as compared to the MDI and 2,4‐TDI‐based polymers, because of a higher degree of crystallinity and/or a higher aspect ratio of the crystallites. The HDI residues are flexible and not sterically hindered and could therefore be more easily packed than MDI or 2,4‐TDI residues. Polyurethanes with monodisperse DI‐6A6‐DI hard segments have interesting properties. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Gelation of methylcellulose hydrogels under isothermal conditions
Authors: Joshi S. C. , Su J. C. , Liang C. M. , Lam Y. C. 
Published: November 2007

AbstractThe current work deals with the gelation of methylcellulose (MC) in aqueous solutions under isothermal conditions. The isothermal gelation was monitored during two consecutive heating and cooling cycles. The gelation was observed to occur early during the second cycle and progress at a higher rate. Micelle‐like structures were found to form in MC solutions during the first gelation cycle. These were largely responsible for the accelerated gelation during the second heating cycle. The influence from the state of water was examined by studying the gelation phenomenon for MC using either cold or hot DI water as solvent. The possible mechanism involved is discussed. A gel indexing method was established to provide a quantitative measure for the state of gelation achievable using different MC concentrations with either cold or hot water solvent. Stabilization kinetics for the gel under isothermal conditions was described using the Malkin and Kulichikhin model. The kinetics parameters were determined. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Light‐triggered reversible solubility of α‐cyclodextrin and azobenzene moiety complexes in PDMAA‐co‐PAPA via molecular recognition
Authors: Luo Chunhua , Zuo Fang , Ding Xiaobin , Zheng Zhaohui , Cheng Xu , Peng Yuxing 
Published: November 2007

AbstractPhotoresponsive polymer with azobenzene pendant group (PDMAA‐co‐PAPA) was synthesized by radical polymerization of N,N‐dimethylacrylamide (DMAA) and N‐4‐phenylazophenyl acrylamide (PAPA), and the characterization of the inclusion complexes of the PDMAA‐co‐PAPA with α‐cyclodextrin (α‐CD) were performed by FTIR, GPC, 1H NMR, 2D NOESY, and UV–vis spectroscopy. It was found that the solubility of PDMAA‐co‐PAPA and α‐CD inclusion complexes in aqueous solution showed tunable property, which could be triggered by alternating UV–vis light irradiation at a certain temperature due to the effect of molecular recognition of α‐CD with azobenzene moiety in the polymer. After UV irradiation, the lower critical solution temperature (LCST) of the polymer aqueous solution increased slightly without α‐CD while the LCST decreased sharply at presence of α‐CD. Furthermore, UV spectroscopy showed that the photoisomerization of the polymer solution went on rapidly and reversibly, and 2D NOESY data suggested that the inclusion complexation of α‐CD with trans azobenzene moiety and the decomplexation with cis azobenzene resulted in reversible solubility behavior when objected to UV and Vis light irradiation alternately. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Coarse‐grained lattice model simulations of sequence‐structure fitness of a ribosome‐inactivating protein
Authors: Olson Mark A. , Yeh In‐Chul , Lee Michael S. 
Published: November 2007

AbstractMany realistic protein‐engineering design problems extend beyond the computational limits of what is considered practical when applying all‐atom molecular‐dynamics simulation methods. Lattice models provide computationally robust alternatives, yet most are regarded as too simplistic to accurately capture the details of complex designs. We revisit a coarse‐grained lattice simulation model and demonstrate that a multiresolution modeling approach of reconstructing all‐atom structures from lattice chains is of sufficient accuracy to resolve the comparability of sequence‐structure modifications of the ricin A‐chain (RTA) protein fold. For a modeled structure, the unfolding–folding transition temperature was calculated from the heat capacity using either the potential energy from the lattice model or the all‐atom CHARMM19 force‐field plus a generalized Born solvent approximation. We found, that despite the low‐resolution modeling of conformational states, the potential energy functions were capable of detecting the relative change in the thermodynamic transition temperature that distinguishes between a protein design and the native RTA fold in excellent accord with reported experimental studies of thermal denaturation. A discussion is provided of different sequences fitted to the RTA fold and a possible unfolding model. © 2007 Wiley Periodicals, Inc. Biopolymers 89: 153–159, 2008.This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Analysis of structural changes in normal and aneurismal human aortic tissues using FTIR microscopy
Authors: Rubin S. , Bonnier F. , Sandt C. , Ventéo L. , Pluot M. , Baehrel B. , Manfait M. , Sockalingum G. D. 
Published: November 2007

AbstractAortic aneurisms are frequently asymptomatic but can induce dramatic complications. The diagnosis is only based on the aortic diameter and not on a structural and compositional basis. In this preliminary study, we propose infrared microspectroscopy to nondestructively probe normal and aneurismal human aortas. Spectra from 19 human ascending aortic biopsies (10 normal and 9 aneurismal) were acquired using infrared microspectroscopy. A 1500 × 150 μm2 area of each 7‐μm thick cryosection was investigated using a 30‐μm spatial resolution with a total of about 200 spectra per sample. Spectral differences between normal and aneurismal tissues were mainly located in spectral regions related to proteins, such as elastin and collagen, and proteoglycans (1750–1000 cm−1). Tissue heterogeneity and sample classification have been evaluated using hierarchical cluster analysis of individual or mean spectra and their second derivative. Using spectral range related to proteins, 100% of good classification was obtained whereas the proteoglycan spectral range was less discriminant. This in vitro study demonstrates the potential of such technique to differentiate between normal and aneurismal aortas using selected spectral ranges. Future investigations will be focused on these specific spectral regions to determine the role of elastin and collagen in the discrimination of normal and pathological aortas. © 2007 Wiley Periodicals, Inc. Biopolymers 89: 160–169, 2008.This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Contrast‐induced nephropathy
Authors: Pucelikova Tereza , Dangas George , Mehran Roxana 
Published: November 2007

AbstractContrast induced nephropathy (CIN) is an iatrogenic disorder, resulting from exposure to contrast media. Contrast‐induced hemodynamic and direct cytotoxic effects on renal structures are highly evident in its pathogenesis, whereas other mechanisms are still poorly understood. CIN is typically defined as an increase in serum creatinine by either ≥0.5 mg/dl or by ≥25% from baseline within the first 2–3 days after contrast administration. Although rare in the general population, CIN has a high incidence in patients with an underlying renal disorder, in diabetics, and the elderly. The risk factors are synergistic in their ability to produce CIN. The best way to prevent CIN is to identify the patients at risk and to provide adequate peri‐procedural hydration. The role of various drugs in prevention of CIN is still controversial and warrants future studies. Despite remaining uncertainty regarding the degree of nephrotoxicity produced by various contrast agents, in current practice non‐ionic low‐osmolar contrast media are preferred over the high‐osmolar contrast media in patients with renal impairment. © 2007 Wiley‐Liss, Inc.
Rheolytic mechanical thrombectomy for pulmonary artery thrombus in children with complex cyanotic congenital heart disease
Authors: Menon Shaji C. , Hagler Donald J. , Cetta Frank , Cabalka Allison K. 
Published: November 2007

AbstractAcute thrombosis of the pulmonary arteries (PA) can occur during operative or catheter based interventions. This may have serious consequences especially in patients with palliated single ventricle physiology. Traditional therapy for PA thrombosis includes use of local or systemic thrombolytic therapy and surgical thrombectomy. Percutaneous transcatheter mechanical thrombectomy can be broadly divided into three categories based on their mechanisms of action: (a) mechanical fragmentation of the embolus using guide‐wires, pigtail catheters, or balloons (flossing technique), (b) extraction using cup or basket devices, or (c) hydrodynamic fragmentation and aspiration of the embolus. Rheolytic thrombectomy using AngioJet system (Possis Medical, Minneapolis, MN) uses hydrodynamic thrombus fragmentation and aspiration technique, and provides an alternative solution in management of acute thrombosis. We report three patients with complex congenital heart disease of single ventricle physiology palliated by cavopulmonary anastomosis or central shunts and PA thrombosis treated with AngioJet system. © 2008 Wiley‐Liss, Inc.
On the free boundary problem of three‐dimensional incompressible Euler equations
Authors: Zhang Ping , Zhang Zhifei 
Published: November 2007

AbstractIn this paper, we consider in three dimensions the motion of a general inviscid, incompressible fluid with a free interface that separates the fluid region from the vacuum. We assume that the fluid region is below the vacuum and that there is no surface tension on the free surface. Then we prove the local well‐posedness of the free boundary problem in Sobolev space provided that there is no self‐intersection point on the initial surface and under the stability assumption that ${{\partial p}\over {\partial {\bf n}}}(\xi)|_{t=0}\leq -2c_{0}<0$ with ξ being restricted to the initial surface. © 2007 Wiley Periodicals, Inc.
Rat pancreatic islet is formed by unification of multiple endocrine cell clusters
Authors: Hara Akemi , Kadoya Yuichi , Kojima Itaru , Yamashina Shohei 
Published: November 2007

AbstractThe organogenesis of islets in rat pancreas was studied by three‐dimensional reconstructions from serial section micrographs. On embryonic day (E) 12, an endocrine cluster consisting mainly of glucagon‐expressing cells maintained connection with the pancreatic endoderm at several regions. On E15–E17, the cluster enlarged by fusion of newly formed buds. Although the proportion of insulin‐expressing cells increased, they were located in the periphery of the cluster. On the day of birth, insulin‐expressing cell clusters enlarged and fused to form several cores within the islet. The glucagon‐expressing cell mass expanded to form a thin mantle covering the cores. During islet organogenesis, proliferation activity was high in the exocrine duct system. Moreover, the endocrine cell clusters maintained contact with the duct epithelium throughout. We conclude that the pancreatic islet is generated by the unification of multiple endocrine clusters originated from separate regions of the duct system. The mechanism of mantle–core formation is discussed. Developmental Dynamics 236:3451–3458, 2007. © 2007 Wiley‐Liss, Inc.
Output‐only structural identification in time domain: Numerical and experimental studies
Authors: Perry M. J. , Koh C. G. 
Published: November 2007

AbstractBy identifying changes in stiffness parameters, structural damage can be detected and monitored. Although considerable progress has been made in this research area, many challenges remain in achieving robust structural identification based on incomplete and noisy measurement signals. The identification task is made even more difficult if measurement of input force is to be eliminated. To this end, an output‐only structural identification strategy is proposed to identify unknown stiffness and damping parameters. A non‐classical approach based on genetic algorithms (GAs) is adopted. The proposed strategy makes use of the recently developed GA‐based method of search space reduction, which has shown to be able to accurately and reliably identify structural parameters from measured input and output signals. By modifying the numerical integration scheme, input can be computed as the parameter identification task is in progress, thereby eliminating the need to measure forces. Numerical and experimental results demonstrate the power of the strategy in accurate and efficient identification of structural parameters and damage using only incomplete acceleration measurements. Copyright © 2007 John Wiley & Sons, Ltd.
Assessment of the access selection gain in multi‐radio access networks
Authors: Sachs Joachim , Magnusson Per 
Published: November 2007

AbstractIn this paper, we investigate the capacity gain of access selection in a multi‐radio access network with heterogeneous radio access technologies (RATs). We classify the kinds of gain that can be achieved by access selection: statistical multiplexing in the multi‐access system leads to a trunking gain, spatial transmission diversity results from the geographic capacity distribution of the cell layout, stochastic transmission diversity exploits the multi‐path fading characteristics. We show how these different properties are affected by the cell layout of the different RATs, the characteristics of each RAT and the traffic load distribution in the network. In a simulation environment the system capacity for the combination of two wide‐area access technologies, as well as, for the combination of a wide‐area and a local‐area access technology is investigated. For this, we compare two different access selection algorithms. One uses the radio link quality as an input parameter, while the other also considers the cell load. We derive quantitative figures for the capacity gain in a large number of scenarios and show that load‐based access selection can significantly increase the capacity. We show that the gain of an overlay of local‐area access cells provides little capacity gain for uniform geographic load distribution, whereas significant gain can be achieved when most users are located at hotspots. Copyright © 2007 John Wiley & Sons, Ltd.
Modelling of virtual‐circuit switching nodes with multicast connections
Authors: Głąbowski Mariusz , Stasiak Maciej , Zwierzykowski Piotr 
Published: November 2007

AbstractThis paper presents an approximate calculation methodology of the occupancy distribution and the blocking probability in a virtual circuit switching node with multi‐rate unicast and multicast traffic streams. Particular traffic streams are generated by an infinite as well as by a finite population of traffic sources. The model enables calculations of any structure of the groups forming the outgoing directions of the node. Additionally, bandwidth reservation algorithms are also proposed in order to improve traffic characteristics of different traffic classes. The results of the analytical calculations have been compared with the simulation results of a switching node carrying multicast and unicast traffic streams. Copyright © 2007 John Wiley & Sons, Ltd.
Mutational inactivation of TGFBR2 in microsatellite unstable colon cancer arises from the cooperation of genomic instability and the clonal outgrowth of transforming growth factor β resistant cells
Authors: Biswas Swati , Trobridge Patricia , Romero‐Gallo Judith , Billheimer Dean , Myeroff Lois L. , Willson James K. V. , Markowitz Sanford D. , Grady William M. 
Published: November 2007

AbstractThe mutational inactivation of transforming growth factor β receptor type II (TGFBR2) occurs in ∼30% of colon cancers and promotes the formation of colon cancer by inhibiting the tumor suppressor activity of the TGFB signaling pathway. TGFBR2 mutations occur in >90% of microsatellite unstable (MSI) colon cancers and affect a polyadenine tract in exon 3 of TGFBR2, called BAT‐RII, which is vulnerable to mutation in the setting of DNA mismatch repair (MMR) system deficiency. In light of the vulnerable nature of the BAT‐RII tract in the setting of MMR inactivation and the favorable effects of TGFBR2 inactivation in colon cancer, analysis of TGFBR2 inactivation provides an opportunity to assess the roles of genomic instability vs. clonal selection in cells acquiring TGFBR2 BAT‐RII tract mutations in MSI colon cancer formation. The contribution of genomic instability and/or clonal evolution to the mutational inactivation of TGBFR2 in MSI colon cancers has not been studied in a systematic way that would allow a determination of the relative contribution of these two mechanisms in the formation of MSI colon cancer. It has not been demonstrated whether the BAT‐RII tract mutations are strictly a consequence of the BAT‐RII region being hypermutable in the setting of MMR deficiency or if the mutations are rather a consequence of clonal selection pressure against the TGFB receptor. Through the use of defined cell line systems, we show that both genomic instability and clonal selection of TGFB resistant cells contribute to the high frequency of TGFBR2 mutations in MSI colon cancer. © 2007 Wiley‐Liss, Inc.
Geomorphology, hydrology, and aquatic vegetation drive seasonal hyporheic flow patterns across a gravel‐dominated floodplain
Authors: Jones Krista L. , Poole Geoffrey C. , Woessner William W. , Vitale Matt V. , Boer Brian R. , O'Daniel Scott J. , Thomas Steven A. , Geffen Brook A. 
Published: November 2007

AbstractAcross 1·7 km2 of the Umatilla River floodplain (Oregon, USA), we investigated the influences of an ephemeral tributary and perennial ‘spring channel’ (fed only by upwelling groundwater) on hyporheic hydrology. We derived maps of winter and summer water‐table elevations from data collected at 46 monitoring wells and 19 stage gauges and used resulting maps to infer groundwater flow direction. Groundwater flow direction varied seasonally across the floodplain and was influenced by main channel stage, flooding, the tributary creek, and the location and direction of hyporheic exchange in the spring channel. Hyporheic exchange in the spring channel was evaluated with a geochemical mixing model, which confirmed patterns of floodplain groundwater movement inferred from water‐table maps and showed that the spring channel was fed predominantly by hyporheic water from the floodplain aquifer (87% during winter, 80% during summer), with its remaining flow supplied by upslope groundwater from the adjacent catchment aquifer. Summertime growth of aquatic macrophytes in the spring channel also influenced patterns of hyporheic exchange and groundwater flow direction in the alluvial aquifer by increasing flow resistance in the spring channel, locally raising surface water stage and adjacent water‐table elevation, and thereby altering the slope of the water‐table in the hyporheic zone. The Umatilla River floodplain is larger than most sites where hyporheic hydrology has been investigated in detail. Yet, our results corroborate other research that has identified off‐channel geomorphic features as important drivers of hyporheic hydrology, including previously published modeling efforts from a similar river and field observations from smaller streams. Copyright © 2007 John Wiley & Sons, Ltd.