bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetics of polymerization of methyl methacrylate initiated by Ce(IV) ‐ disaccharide redox systems
Authors: Fernández M. D. , Guzmán G. M. 
Published: March 2011

AbstractThe polymerization of methyl methacrylate (MMA) initiated by ceric ammonium nitrate ‐ disaccharide redox systems has been studied in aqueous nitric acid at 30°C. The rate of polymerization and the rate of ceric ion disappearance were measured. The dependence of the rates on disaccharide and Ce(IV) concentrations have been evaluated. The reaction involves the formation of a complex between the metal ion and the reductants, whose decomposition gives rise to the initiating free radicals. The termination step takes place predominantly by mutual interaction between growing polymeric radicals.
Determination of kinetic constants for bulk polymerization of octyl acrylate at different temperatures
Authors: Katime Issa A. , Nuño T. 
Published: March 2011

AbstractThe bulk self‐initiated polymerization kinetics, assuming complete conversion of the octyl acrylate was determined by DTA in the temperature range 463‐493 K. Likewise, the overall activation energy, EA, and the polymerization enthalpies involved in the process have been calculated, as well as the overall rate constants and the reaction order.
Helical and sheet structures in the nylon 4 derivatives poly (α‐benzyl‐L‐glutamate) and poly‐(α‐methyl‐L‐glutamate)
Authors: Puiggali J. , MuñOz‐Guerra S. , Rodríguez‐Galán A. , Alegre C. , Subirana J. A. 
Published: March 2011

AbstractWe have synthesized and characterized the two stereoregular title compounds with a chemical formula:magnified imageThey form helical structures, similar to α‐helices (Form II), which are rather stable, in spite of the lower density of hydrogen bonds when compared with the standard α‐helix, found in proteins. We have determined the helical parameters of these structures by X‐ ray diffraction, and electron microscopy. Thin (10–40 nm) cylindrical threads are observed by the latter technique. The helix‐coil transition has been studied by proton NMR in the system chloroform/dichloroacetic acid. In the case of poly (α‐benzyl‐L‐glutamate) we have also found a sheet structure (Form I), similar to the extended sheets found in polyamides. The benzyl rings in the side chains appear to be stacked between such sheets.
The physical state of polycarbonate/hytrel blends
Authors: Gaztelumendi M. , Mondragón I. , Nazábal J. 
Published: March 2011

AbstractBlends of bisphenol A polycarbonate (PC) with Hytrel (Hy), a thermoplastic elastomer, were melt mixed at different compositions and processing times. The blends thus obtained were progressively opaque as the Hy content of the blends increased due to the Hy crystallization, but showed a single Tg at all the blend contents. Torque of blending‐time and torque‐composition plots are discussed and related to the physical state of the blends.
Viscoelastic behaviour of poly (trimethylene terephthalate) and related polyesters
Authors: González César C. , Pereña José M. , Bello Antonio 
Published: March 2011

AbstractPoly(oxytrimethyleneoxyterephthaloyl) (PTMT), poly(oxytrimethyleneoxytrimethyleneoxyterephthaloyl) (PTMTMT) and two copolymers derived from them have been studied by the use of a dynamic viscoelastometer. The four polymers show three relaxations α, β and γ in the temperature range between −150 and 200 °C. The α relaxation is the glass transition of the polymers, the β relaxation normally occurs in the vicinity of −70 °C, and the γ relaxation, usually overlapped by the β one, takes place at temperatures around −120 °C. The influence of the thermal history on the nature, location and intensity of the three relaxations is discussed.
Sub‐Tg storage of amorphous polymers
Authors: Zhou Y. Q. , Tong G. , Qi Z. N. 
Published: March 2011

AbstractThe sub‐T storage of PET(polyethylene terephthalate) and PEN(gpolyethylene naphthalate) has been investigated by means of TSC(thermally stimulated current) and DSC(differential scanning calorimetry). An apparent activation energy of sub‐T storage equal to one fourth of the activation energyg of glass transition has been obtained.
Physical interpretation of the rheological behaviour of amorphous polymers in the glass transition temperature range
Authors: Perez J. , Cavaille J. Y. , Jourdan C. 
Published: March 2011

AbstractIn a previous work, we developed, from physical basis, a theory of the non‐elastic deformation of amorphous polymers which is observed through the glass transition temperature. In this model, it is assumed that density fluctuations (or defects) exist in thermal equilibrium (TTg) or are frozen in (T< Tg). The application of a stress results in the nucleation of shear ‐ microdomains (smd) near the defects (anelasticity). A subsequent Irreversible expansion of shear ‐ loops might occur thanks to monomer diffusion which is shown to be dependent on (I) the defect concentration Cd and (II) on hierarchical correlation effects. The dynamic modulus G' and G' (and tanφ) are calculated as a function of parameters which can be known from Independent experimental ways and all have a precise physical meaning. The most Important parameter is the mechanical relaxation time τm linked to Cd; thus, all changes in the microstructure (i. e. Cd) imply a variation of the dynamic modulus.The purpose of the present work is to make a comparison between the predictions of the model and experimental results obtained with polystyrene after different thermal histories.
Charge decay of corona‐charged electrets of amorphous polyethylene terephthalate
Authors: Belana J. , Pujal M. , Menéndez E. 
Published: March 2011

AbstractDuring the formation of corona‐charged electrets of amorphous poly(ethylene terephthalate) at Tp between room temperature and 100°C, the charge injected from the electrodes to the sample is trapped from Tp to temperatures higher than 100°C. This fact determines that the measure of the initial charge of the electret is homocharge which is unstable with the time. The stored charge in the deep levels is the main cause for the internal field limiting the decrease of the heterocharge which finishes dominating in the decay process. The application of the thermally stimulated discharge to these electrets gives three relaxations whose behaviour has been analysed and has helped to interpret the decay of the charge.
Polypyrrole films formation by square waves in NaClO4 aqueous medium: Consecutive potential steps study
Authors: Fernándezotero T. , De Larreta E. , Tejada R. 
Published: March 2011

AbstractThe electrosynthesis of polypyrrole films was devised by consecutive potential steps. The time of each anodic and cathodic step, the number of consecutive steps, and the anodic potential of polarization influence the structure of the obtained polymer film, its adherence to the metal electrode and its electrochromic answer. Larger anodic polarization times (per step) give a polymer film formed by dendrites. Shorter anodic polarization times (per step) give smooth and adherent films. Darker colours were obtained when the number of polymerization potential steps increases.
Physical properties of some BEDT‐TTF cation radical salts with polymeric anions
Authors: Graja Andrzej , Dyachenko Oleg A. 
Published: March 2011

AbstractThe most intensively examined and promising organic materials to show superconducting properties are ion‐radical salts in which a molecule of bis(ethylenedithio)tetrathiafulvalene (BEDT‐TTF or shorter ET) serves as an electron donor. ET is capable of creating salts with various anions. The search for an anion species for ET‐based organic superconductors is one of the approaches towards making progress in the design of these materials. Polymeric anions, which form a stable layer structure, are especially useful for this purpose.Conducting properties of the organic superconductors are determined mainly by ET packing, but the role of anions is also important. The thickness of anion layers, which effectively alters the interlayer transfer interactions of ET molecules, depends upon the anion organization. Since critical temperature of the organic superconductor increases with the decrease of the magnitude of the anisotropy of the intra‐ and interlayer interaction, the change of the layer thickness gives an opportunity to affect the Tc of the superconductor.In this paper we present characteristic structures of selected ET salts, give a survey of the anions, especially polymerized anions, review some more common structural types observed, and describe some physical properties of the ET‐based organic superconductors containing polymerized anions.
Melting Pressure Curves of Concentrated Peroxide Solutions up to 3 kbar
Authors: Berbée Otto , Buback Michael , Fischer Bart , Vögele Hans Peter 
Published: March 2011

AbstractThe crystallization of peroxide/solvent mixtures with peroxide contents from 10 to 65 wt.‐% is studied between −50 and +30 °C up to 3 000 bar for di‐tert‐butylperoxide, tert‐butyl peroxyacetate, tert‐butyl peroxypivalate, tert‐butyl peroxy‐2‐ethylhexanoate, and bis(tert‐butyl) peroxybutanoate with decane, octane, isododecane, isooctane, and isopar H as solvents. The liquid/solid phase behavior indicates miscibility in the liquid and immiscibility in the solid phase. With tert‐butyl peroxyacetate/isododecane, in addition, liquid/liquid immiscibility occurs. A few melting pressure curves are presented for ternary systems containing either two solvents or two peroxides. magnified image
Fast MR parameter mapping using k‐t principal component analysis
Authors: Petzschner Frederike H. , Ponce Irene P. , Blaimer Martin , Jakob Peter M. , Breuer Felix A. 
Published: March 2011

AbstractQuantification of magnetic resonance parameters plays an increasingly important role in clinical applications, such as the detection and classification of neurodegenerative diseases. The major obstacle that remains for its widespread use in clinical routine is the long scanning times. Therefore, strategies that allow for significant decreases in scan time are highly desired. Recently, the k‐t principal component analysis method was introduced for dynamic cardiac imaging to accelerate data acquisition. This is done by undersampling k‐t space and constraining the reconstruction of the aliased data based on the k‐t Broad‐use Linear Acquisition Speed‐up Technique (BLAST) concept and predetermined temporal basis functions. The objective of this study was to investigate whether the k‐t principal component analysis concept can be adapted to parameter quantification, specifically allowing for significant acceleration of an inversion recovery fast imaging with steady state precession (TrueFISP) acquisition. We found that three basis functions and a single training data line in central k‐space were sufficient to achieve up to an 8‐fold acceleration of the quantification measurement. This allows for an estimation of relaxation times T1 and T2 and spin density in one slice with sub‐millimeter in‐plane resolution, in only 6 s. Our findings demonstrate that the k‐t principal component analysis method is a potential candidate to bring the acquisition time for magnetic resonance parameter mapping to a clinically acceptable level. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.
Analytic expressions for the ultimate intrinsic signal‐to‐noise ratio and ultimate intrinsic specific absorption rate in MRI
Authors: Kopanoglu E. , Erturk V. B. , Atalar E. 
Published: March 2011

AbstractThe ultimate intrinsic signal‐to‐noise ratio is the highest possible signal‐to‐noise ratio, and the ultimate intrinsic specific absorption rate provides the lowest limit of the specific absorption rate for a given flip angle distribution. Analytic expressions for ultimate intrinsic signal‐to‐noise ratio and ultimate intrinsic specific absorption rate are obtained for arbitrary sample geometries. These expressions are valid when the distance between the point of interest and the sample surface is smaller than the wavelength, and the sample is homogeneous. The dependence on the sample permittivity, conductivity, temperature, size, and the static magnetic field strength is given in analytic form, which enables the easy evaluation of the change in signal‐to‐noise ratio and specific absorption rate when the sample is scaled in size or when any of its geometrical or electrical parameters is altered. Furthermore, it is shown that signal‐to‐noise ratio and specific absorption rate are independent of the permeability of the sample. As a practical case and a solution example, a uniform, circular cylindrically shaped sample is studied. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.
Simultaneous dual‐nuclei imaging for motion corrected detection and quantification of 19F imaging agents
Authors: Keupp Jochen , Rahmer Jürgen , Grässlin Ingmar , Mazurkewitz Peter C. , Schaeffter Tobias , Lanza Gregory M. , Wickline Samuel A. , Caruthers Shelton D. 
Published: March 2011

AbstractFluorine MRI offers broad potential for specific detection and quantification of molecularly targeted agents in diagnosis and therapy planning or monitoring. Because non‐proton MRI applications lack morphological information, accompanying proton images are needed to elucidate the spatial tissue context. Furthermore, low concentrations typical of targeted molecular imaging agents require long examinations for signal averaging during which physiological motion may lead to blurring, underestimation in signal quantification, and erroneous localization of the agent distribution. Novel methods for truly simultaneous acquisition of dual‐nuclei MR data are presented that offer efficient and precise anatomical localization of fluorine signals using accurate motion correction based on contemporaneous proton signals. The feasibility of simultaneous dual‐nuclei MRI motion correction and corresponding dual‐resolution reconstruction, providing nuclei‐specific spatial resolution to retrospectively optimize the balance between signal‐to‐noise ratio and resolution, is shown on a clinical 3 T MR system. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.
Evidence‐based guideline: Treatment of painful diabetic neuropathy—report of the american association of neuromuscular and electrodiagnostic medicine, the american academy of neurology, and the american academy of physical medicine & rehabilitation
Authors: Bril Vera , England John D. , Franklin Gary M. , Backonja Miroslav , Cohen Jeffrey A. , Del Toro David R. , Feldman Eva L. , Iverson Donald J. , Perkins Bruce , Russell James W. , Zochodne Douglas W. 
Published: March 2011

AbstractThe objective of this report was to develop a scientifically sound and clinically relevant evidence‐based guideline for the treatment of painful diabetic neuropathy (PDN). The basic question that was asked was: “What is the efficacy of a given treatment (pharmacological: anticonvulsants, antidepressants, opioids, others; non‐pharmacological: electrical stimulation, magnetic field treatment, low‐intensity laser treatment, Reiki massage, others) to reduce pain and improve physical function and quality of life (QOL) in patients with PDN?” A systematic review of literature from 1960 to August 2008 was performed, and studies were classified according to the American Academy of Neurology classification of evidence scheme for a therapeutic article. Recommendations were linked to the strength of the evidence. The results indicate that pregabalin is established as effective and should be offered for relief of PDN (Level A). Venlafaxine, duloxetine, amitriptyline, gabapentin, valproate, opioids (morphine sulfate, tramadol, and oxycodone controlled‐release), and capsaicin are probably effective and should be considered for treatment of PDN (Level B). Other treatments have less robust evidence, or the evidence is negative. Effective treatments for PDN are available, but many have side effects that limit their usefulness. Few studies have sufficient information on their effects on function and QOL. Muscle Nerve, 2011.
Factor of safety in a partially saturated slope inferred from hydro‐mechanical continuum modeling
Authors: Borja Ronaldo I. , White Joshua A. , Liu Xiaoyu , Wu Wei 
Published: March 2011

SUMMARYRainfall weakens an earth slope and triggers mass movement. Relevant triggering mechanisms are complex and include reduction of capillary pressure due to increased saturation and frictional drag on the sediment induced by fluid flow. Physics‐based continuum models utilizing modern computational tools are useful for understanding the mechanisms of deformation in partially saturated slopes; however, they do not provide a scalar indicator called ‘factor of safety’ that measures the potential of a given slope for mass movement. In the present work, we employ sequential calculations consisting of a physics‐based finite element model that couples solid deformation with fluid flow to quantify the stress and deformation fields in a steep hillside slope subjected to rainfall infiltration. This is followed by a limit‐equilibrium calculation based on the method of slices that evaluates the desired factor of safety. The field condition investigated is similar to the steep experimental catchment CB1 near Coos Bay, Oregon, which failed as a large debris flow from heavy rainfall. Copyright © 2011 John Wiley & Sons, Ltd.
Content validation of the patient‐reported outcomes measurement information system (PROMIS) framework in women with urinary incontinence
Authors: Sung Vivian W. , Marques Felisha , Rogers Rebecca R. , Williams David A. , Myers Deborah L. , Clark Melissa A. 
Published: March 2011

AbstractAimsTo assess whether the existing National Institutes of Health (NIH) Patient Reported Outcomes Measurement Information System (PROMIS) conceptual framework and item banks sufficiently capture the concerns of women with urinary incontinence (UI).MethodsThirty‐five women with UI were recruited between February‐April 2009 for 4 structured focus groups to develop and assess the content validity of a conceptual framework for the impact of UI. This framework included domains from the NIH PROMIS framework and item banks including broad domains of physical and social function and mental health. All sessions were transcribed, coded, and qualitatively and quantitatively analyzed using analytic induction and deductive analysis to identify new themes and domains relevant to women with UI.ResultsThe focus groups provided information that confirmed the relevance of existing PROMIS domains and identified new outcome domains that are important to this patient population. The groups confirmed the relevance of the physical and social functioning, and mental health domains. Additional themes that emerged included the distinction between ability versus participation and satisfaction, role functioning, external mediators, re‐calibration/coping, cognitive function and new possibilities. Participants also felt strongly that not all domains and items apply to all women with UI and an option to tailor questionnaires and skip non‐relevant items was important.ConclusionsThe PROMIS framework domains are relevant to women with UI, but additional patient‐important themes are identified that may improve the comprehensiveness of this assessment framework for measuring outcomes important to women with UI. These results will inform future item content development for UI. 30:503–509, 2011. © 2011 Wiley‐Liss, Inc.
A confidence paradigm for classification systems
Authors: Leap Nathan J. , Bauer Kenneth W. 
Published: March 2011

AbstractThere is no universally accepted methodology to determine how much confidence one should place in the output of a classification system. In this article, we develop a confidence paradigm. This is a theoretical framework that attempts to unite the viewpoints of the classification system developer (or engineer) and the classification system user (or warfighter). The developer designs and tests the classification system at a macro‐level. The user fields the system in an environment often quite different than the environment used to develop the system. The user operates at a micro‐level and is interested in the indications as they are made by the system. The paradigm is based on the assumptions that the system confidence acts like or can be modelled as value, and that indication confidence can be modelled as a function of the posterior probability estimates. The viewpoints of the developer and the user are unified through the fundamental proposition that the expected value of the user's confidence should be approximately equal to the developer's confidence. This paradigm provides a direct link between traditional decision analysis techniques and traditional pattern recognition techniques. This methodology is applied to an automatic target recognition data set, and the results demonstrate the sort of behavior that would be expected from a rational confidence measure. © 2011 Wiley Periodicals, Inc. Naval Research Logistics, 2011
A process for anticipating and shaping adversarial behavior
Authors: McKay Shawn C. , Chaturvedi Alok , Adams Douglas E. 
Published: March 2011

AbstractA new approach for anticipating and shaping adversarial behavior is developed and demonstrated. The approach extends the notion of prediction, which is a forecast of the future from a third party point of view, to anticipation, which is a forecast from the perspective of an entity having partial control in a domain. Shaping utilizes the models developed for anticipation to determine actions that influence another influential entity (e.g., an enemy) and actions to direct the emergent phenomena of a domain according to an entity's objectives. The approach is developed using principles of control theory and demonstrated in the southeastern region of Afghanistan. A key capability demonstrated by this approach is its ability to handle proactive adversaries when actionable intelligence is nonexistent. In the demonstration, Taliban (Red) combat actions are anticipated from the perspective of the coalition forces (Blue) across time, across space, and by the current state of the region and then shaped to Blue's desires. Shaping identifies periods of time that simultaneous or alternating Blue combat actions in different regions help meet Blue's military and nonmilitary objectives. © 2011 Wiley Periodicals, Inc. Naval Research Logistics, 2011
A convected particle domain interpolation technique to extend applicability of the material point method for problems involving massive deformations
Authors: Sadeghirad A. , Brannon R. M. , Burghardt J. 
Published: March 2011

AbstractA new algorithm is developed to improve the accuracy and efficiency of the material point method for problems involving extremely large tensile deformations and rotations. In the proposed procedure, particle domains are convected with the material motion more accurately than in the generalized interpolation material point method. This feature is crucial to eliminate instability in extension, which is a common shortcoming of most particle methods. Also, a novel alternative set of grid basis functions is proposed for efficiently calculating nodal force and consistent mass integrals on the grid. Specifically, by taking advantage of initially parallelogram‐shaped particle domains, and treating the deformation gradient as constant over the particle domain, the convected particle domain is a reshaped parallelogram in the deformed configuration. Accordingly, an alternative grid basis function over the particle domain is constructed by a standard 4‐node finite element interpolation on the parallelogram. Effectiveness of the proposed modifications is demonstrated using several large deformation solid mechanics problems. Copyright © 2011 John Wiley & Sons, Ltd.