bluuebunny/crossref_metadata_2025 huggingface dataset:
Systematic Coarse Graining of a High‐Performance Polyimide
Authors: Pandiyan Sudharsan , Parandekar Priya V. , Prakash Om , Tsotsis Thomas K. , Basu Sumit
Published: June 2015

An important high‐temperature polyimide, namely HFPE‐30, has been coarse grained to three different levels of detail. It has been shown that while it is possible to successfully calibrate bonded and non‐bonded forcefields and attain realistic densities with all levels of coarse graining, reproducing chain structures and dynamic properties requires an adequate level of atomistic detail to be retained. A model that coarse grains the HFPE‐30 molecule into eight beads, approximates both chain structure and dynamic properties well. Alternately, the unrealistically fast dynamics in coarse‐grained models can be slowed down by increasing the thermal coupling constant by a scaling factor that is estimated by comparing mean square displacements in detailed atomistic and coarse‐grained simulations. In general, stress‐strain responses of coarse‐grained systems do not match those of the detailed atomic systems except when the coarse graining involves eight beads. In cases where lesser number of beads are used, slowing the dynamics down by the estimated scaling factor takes the stress‐strain response of the coarse‐grained system close to that of the detailed atomistic one.
Levodopa Is a Double‐Edged Sword for Balance and Gait in People With Parkinson's Disease
Authors: Curtze Carolin , Nutt John G. , Carlson‐Kuhta Patricia , Mancini Martina , Horak Fay B.
Published: June 2015

Background

The effects of levodopa on balance and gait function in people with Parkinson's disease (PD) is controversial. This study compared the relative responsiveness to l‐dopa on six domains of balance and gait: postural sway in stance; gait pace; dynamic stability; gait initiation; arm swing; and turning in people with mild and severe PD, with and without dyskinesia.

Methods

We studied 104 subjects with idiopathic PD (H & Y II [n = 52] and III–IV [n = 52]) and 64 age‐matched controls. Subjects performed a mobility task in the practical off state and on l‐dopa: standing quietly for 30 seconds, initiating gait, walking 7 meters, and turning 180 degrees. Thirty‐four measures of mobility were computed from inertial sensors. Standardized response means were used to determine relative responsiveness to l‐dopa.

Results

The largest improvements with l‐dopa were found for arm swing and pace‐related gait measures. Gait dynamic stability was unaffected by PD and not responsive to l‐dopa. l‐dopa reduced turning duration, but only in subjects with severe PD. In contrast to gait, postural sway in quiet standing increased with l‐dopa, especially in the more severely affected subjects. The increase in postural sway, as well as decrease in turning duration and exaggerated arm swing with l‐dopa was observed only for subjects with dyskinesia at the time of testing.

Conclusions

The observed spectrum of l‐dopa responsiveness in balance and gait measures suggests that multiple neural circuits control balance and gait. Many of the negative effects of l‐dopa may be directly or indirectly caused by dyskinesia. © 2015 International Parkinson and Movement Disorder Society
GDNF gene is associated with tourette syndrome in a family study
Authors: Huertas‐Fernández Ismael , Gómez‐Garre Pilar , Madruga‐Garrido Marcos , Bernal‐Bernal Inmaculada , Bonilla‐Toribio Marta , Martín‐Rodríguez Juan Francisco , Cáceres‐Redondo María Teresa , Vargas‐González Laura , Carrillo Fátima , Pascual Alberto , Tischfield Jay A. , King Robert A. , Heiman Gary A. , Mir Pablo
Published: June 2015

Background

Tourette syndrome is a disorder characterized by persistent motor and vocal tics, and frequently accompanied by the comorbidities attention deficit hyperactivity disorder and obsessive‐compulsive disorder. Impaired synaptic neurotransmission has been implicated in its pathogenesis. Our aim was to investigate the association of 28 candidate genes, including genes related to synaptic neurotransmission and neurotrophic factors, with Tourette syndrome.

Methods

We genotyped 506 polymorphisms in a discovery cohort from the United States composed of 112 families and 47 unrelated singletons with Tourette syndrome (201 cases and 253 controls). Genes containing significant polymorphisms were imputed to fine‐map the signal(s) to potential causal variants. Allelic analyses in Tourette syndrome cases were performed to check the role in attention deficit hyperactivity disorder and obsessive‐compulsive disorder comorbidities. Target polymorphisms were further studied in a replication cohort from southern Spain composed of 37 families and three unrelated singletons (44 cases and 73 controls).

Results

The polymorphism rs3096140 in glial cell line–derived neurotrophic factor gene (GDNF) was significant in the discovery cohort after correction (P = 1.5 × 10−4). No linkage disequilibrium was found between rs3096140 and other functional variants in the gene. We selected rs3096140 as target polymorphism, and the association was confirmed in the replication cohort (P = 0.01). No association with any comorbidity was found.

Conclusions

As a conclusion, a common genetic variant in GDNF is associated with Tourette syndrome. A defect in the production of GDNF could compromise the survival of parvalbumin interneurons, thus altering the excitatory/inhibitory balance in the corticostriatal circuitry. Validation of this variant in other family cohorts is necessary. © 2015 International Parkinson and Movement Disorder Society
Modifications of resting state networks in spinocerebellar ataxia type 2
Authors: Cocozza Sirio , Saccà Francesco , Cervo Amedeo , Marsili Angela , Russo Cinzia Valeria , Giorgio Sara Maria delle Acque , De Michele Giuseppe , Filla Alessandro , Brunetti Arturo , Quarantelli Mario
Published: June 2015

Purpose

We aimed to investigate the integrity of the Resting State Networks in spinocerebellar ataxia type 2 (SCA2) and the correlations between the modification of these networks and clinical variables.

Methods

Resting‐state functional magnetic resonance imaging (RS‐fMRI) data from 19 SCA2 patients and 29 healthy controls were analyzed using an independent component analysis and dual regression, controlling at voxel level for the effect of atrophy by co‐varying for gray matter volume. Correlations between the resting state networks alterations and disease duration, age at onset, number of triplets, and clinical score were assessed by Spearman's coefficient, for each cluster which was significantly different in SCA2 patients compared with healthy controls.

Results

In SCA2 patients, disruption of the cerebellar components of all major resting state networks was present, with supratentorial involvement only for the default mode network. When controlling at voxel level for gray matter volume, the reduction in functional connectivity in supratentorial regions of the default mode network, and in cerebellar regions within the default mode, executive and right fronto‐parietal networks, was still significant. No correlations with clinical variables were found for any of the investigated resting state networks.

Conclusions

The SCA2 patients show significant alterations of the resting state networks, only partly explained by the atrophy. The default mode network is the only resting state network that shows also supratentorial changes, which appear unrelated to the cortical gray matter volume. Further studies are needed to assess the clinical significance of these changes. © 2015 International Parkinson and Movement Disorder Society
Zonisamide improves wearing‐off in Parkinson's disease: A randomized, double‐blind study
Authors: Murata Miho , Hasegawa Kazuko , Kanazawa Ichiro , Fukasaka Junichi , Kochi Kenji , Shimazu Rieko ,   The Japan Zonisamide on PD Study Group
Published: June 2015

Background

Previously, we reported 50 mg/d zonisamide improved wearing‐off without increasing dyskinesia in patients with Parkinson's disease (PD).

Methods

To determine the efficacy of zonisamide for treatment of “off” time in PD patients, we conducted a multicenter, randomized, double‐blind, parallel‐group, placebo‐controlled study in Japan. Patients with PD and wearing‐off received placebo for 4 weeks and then were treated for 12 weeks with zonisamide 25 or 50 mg/d or placebo, in addition to their previous therapy. The primary endpoint was the change from baseline in daily “off” time as determined by patients’ diaries at the final assessment. Secondary endpoints included changes from baseline in the total scores of the Unified Parkinson's Disease Rating Scale Parts I, II, III, and IV, the dyskinesia duration, and PDQ‐39 score.

Results

Of 422 patients enrolled, 389 (131 for placebo, 130 for zonisamide 25 mg, and 128 for zonisamide 50 mg) were randomized, and 354 (120, 119, and 115, respectively) completed the study. The “off” time significantly reduced by 0.719 ± 0.179 h for zonisamide, 50 mg compared with placebo (0.011 ± 0.173 h, P = 0.005). Although the incidence of somnolence was higher for zonisamide (3.1% for zonisamide 25 mg, 6.3% for zonisamide 50 mg) than for placebo (2.3%), the incidences of the other adverse events, including dyskinesia or hallucination, for both zonisamide treatments were comparable to those for placebo.

Conclusion

The study provides evidence that confirms the efficacy of zonisamide 50 mg/d for reduction in “off” time in PD patients with wearing‐off phenomena. © 2015 International Parkinson and Movement Disorder Society
Molecular Docking Study on Galantamine Derivatives as Cholinesterase Inhibitors
Authors: Atanasova Mariyana , Yordanov Nikola , Dimitrov Ivan , Berkov Strahil , Doytchinova Irini
Published: June 2015

A training set of 22 synthetic galantamine derivatives binding to acetylcholinesterase was docked by GOLD and the protocol was optimized in terms of scoring function, rigidity/flexibility of the binding site, presence/absence of a water molecule inside and radius of the binding site. A moderate correlation was found between the affinities of compounds expressed as pIC50 values and their docking scores. The optimized docking protocol was validated by an external test set of 11 natural galantamine derivatives and the correlation coefficient between the docking scores and the pIC50 values was 0.800. The derived relationship was used to analyze the interactions between galantamine derivatives and AChE.
NMR‐Assisted Molecular Docking Methodologies
Authors: Sturlese Mattia , Bellanda Massimo , Moro Stefano
Published: June 2015

Nuclear magnetic resonance (NMR) spectroscopy and molecular docking are regularly being employed as helpful tools of drug discovery research. Molecular docking is an extremely rapid method to evaluate possible binders from a large chemical library in a fast and cheap manner. NMR techniques can directly detect a protein‐ligand interaction, can determine the corresponding association constant, and can consistently identify the ligand binding cavity. Consequently, molecular docking and NMR techniques are naturally complementary techniques where the combination of the two has the potential to improve the overall efficiency of drug discovery process. In this review, we would like to summarize the state of the art of docking methods which have been recently bridged to NMR experiments to identify novel and effective therapeutic drug candidates.
Acceleration of Binding Site Comparisons by Graph Partitioning
Authors: Krotzky Timo , Klebe Gerhard
Published: June 2015

The comparison of protein binding sites is a prominent task in computational chemistry and has been studied in many different ways. For the automatic detection and comparison of putative binding cavities the Cavbase system has been developed which uses a coarse‐grained set of pseudocenters to represent the physicochemical properties of a binding site and employs a graph‐based procedure to calculate similarities between two binding sites. However, the comparison of two graphs is computationally quite demanding which makes large‐scale studies such as the rapid screening of entire databases hardly feasible. In a recent work, we proposed the method Local Cliques (LC) for the efficient comparison of Cavbase binding sites. It employs a clique heuristic to detect the maximum common subgraph of two binding sites and an extended graph model to additionally compare the shape of individual surface patches. In this study, we present an alternative to further accelerate the LC method by partitioning the binding‐site graphs into disjoint components prior to their comparisons. The pseudocenter sets are split with regard to their assigned phyiscochemical type, which leads to seven much smaller graphs than the original one. Applying this approach on the same test scenarios as in the former comprehensive way results in a significant speed‐up without sacrificing accuracy.
Effects of ignoring clustered data structure in confirmatory factor analysis of ordered polytomous items: a simulation study based on PANSS
Authors: Stochl Jan , Jones Peter B. , Perez Jesus , Khandaker Golam M. , Böhnke Jan R. , Croudace Tim J.
Published: June 2015

Statistical theory indicates that hierarchical clustering by interviewers or raters needs to be considered to avoid incorrect inferences when performing any analyses including regression, factor analysis (FA) or item response theory (IRT) modelling of binary or ordinal data. We use simulated Positive and Negative Syndrome Scale (PANSS) data to show the consequences (in terms of bias, variance and mean square error) of using an analysis ignoring clustering on confirmatory factor analysis (CFA) estimates. Our investigation includes the performance of different estimators, such as maximum likelihood, weighted least squares and Markov Chain Monte Carlo (MCMC). Our simulation results suggest that ignoring clustering may lead to serious bias of the estimated factor loadings, item thresholds, and corresponding standard errors in CFAs for ordinal item response data typical of that commonly encountered in psychiatric research. In addition, fit indices tend to show a poor fit for the hypothesized structural model. MCMC estimation may be more robust against clustering than maximum likelihood and weighted least squares approaches but further investigation of these issues is warranted in future simulation studies of other datasets. Copyright © 2015 John Wiley & Sons, Ltd.
Galectin signature of the choriocarcinoma JAr cells: Galectin‐1 as a modulator of invasiveness in vitro
Authors: Kolundžić Nikola , Ćujić Danica , Abu Rabi Tamara , Bojić‐Trbojević Žanka , Kadoya Toshihiko , Vićovac Ljiljana
Published: June 2015

Our previous findings showed that galectin‐1 (LGALS1) plays an important role in the in vitro invasion of normal human trophoblast cells. In the present study, choriocarcinoma JAr cells were found to express LGALS1, ‐2, ‐3, ‐8, ‐10, and ‐13 mRNA and at least LGALS1, ‐3, and ‐8 protein, as determined by reverse‐transcriptase PCR and Western blot, respectively. The galectin mRNA signature of JAr cells thus differed from that of normal first‐trimester extravillous trophoblasts. A Matrigel migration assay was also used to investigate and confirm the relevance and effect of LGALS1 on the invasive potential of JAr cells, as observed in other trophoblast models. This modulation in behavior was achieved by specific lectin‐glycan binding. Mol. Reprod. Dev. 82: 765–773, 2015. © 2015 Wiley Periodicals, Inc.
Meiotic wave adds extra asymmetry to the development of female chicken gonads
Authors: de Melo Bernardo Ana , Heeren A. Marijne , van Iperen Liesbeth , Fernandes Maria Gomes , He Nannan , Anjie Stafford , Noce Toshiaki , Ramos Ester Silveira , de Sousa Lopes Susana M. Chuva
Published: June 2015

Development of female gonads in the chicken is asymmetric. This asymmetry affects gene expression, morphology, and germ cell development; consequently only the left ovary develops into a functional organ, whereas the right ovary remains vestigial. In males, on the other hand, both gonads develop into functional testes. Here, we revisited the development of asymmetric traits in female (and male) chicken gonads between Hamburger Hamilton stage 16 (HH16) and hatching. At HH16, primordial germ cells migrated preferentially to the left gonad, accumulating in the left coelomic hinge between the gut mesentery and developing gonad in both males and females. Using the meiotic markers SYCP3 and phosphorylated H2AFX, we identified a previously undescribed, pronounced asymmetryc meiotic progression in the germ cells located in the central, lateral, and extreme cortical regions of the left female gonad from HH38 until hatching. Moreover, we observed that—in contrast to the current view—medullary germ cells are not apoptotic, but remain arrested in pre‐leptotene until hatching. In addition to the systematic analysis of the asymmetric distribution of germ cells in female chicken gonads, we propose an updated model suggesting that the localization of germ cells—in the left or right gonad; in the cortex or medulla of the left gonad; and in the central part or the extremities of the left cortex—has direct consequences for their development and participation in adult reproduction. Mol. Reprod. Dev. 82: 774–786, 2015. © 2015 The Authors. Molecular Reproduction and Development published by Wiley Periodicals, Inc.
A constitutive model for unsaturated soil–structure interfaces
Authors: Lashkari Ali , Kadivar Mehdi
Published: June 2015

A constitutive model for simulation of the behavior of unsaturated interfaces is presented here. The model is an extension of an existing critical state compatible interface model for dry and saturated interfaces that was already proposed by one of the authors [Lashkari, A. 2013. Int. J. Numer. Anal. Meth. Geomech.37(8): 904–931]. For a proper simulation of the behavior of partially saturated interfaces, the extended model is formulated in terms of two pairs of work conjugate stress–strain‐like variables. The modified model simulations are compared with the existing data of dry, unsaturated, and saturated interfaces. For each interface type, it is shown that the proposed model can capture the essential elements of the behavior using a unique set of parameters. Copyright © 2015 John Wiley & Sons, Ltd.
Gated Silica Mesoporous Materials in Sensing Applications
Authors: Sancenón Félix , Pascual Lluís , Oroval Mar , Aznar Elena , Martínez‐Máñez Ramón
Published: June 2015

Silica mesoporous supports (SMSs) have a large specific surface area and volume and are particularly exciting vehicles for delivery applications. Such container‐like structures can be loaded with numerous different chemical substances, such as drugs and reporters. Gated systems also contain addressable functions at openings of voids, and cargo delivery can be controlled on‐command using chemical, biochemical or physical stimuli. Many of these gated SMSs have been applied for drug delivery. However, fewer examples of their use in sensing protocols have been reported. The approach of applying SMSs in sensing uses another concept—that of loading pores with a reporter and designing a capping mechanism that is selectively opened in the presence of a target analyte, which results in the delivery of the reporter. According to this concept, we provide herein a complete compilation of published examples of probes based on the use of capped SMSs for sensing. Examples for the detection of anions, cations, small molecules and biomolecules are provided. The diverse range of gated silica mesoporous materials presented here highlights their usefulness in recognition protocols.
Voltammetric Study of the Influence of Various Phosphate Anions on Silver Nanoparticle Oxidation
Authors: Navolotskaya Daria V. , Toh Her Shuang , Batchelor–McAuley Christopher , Compton Richard G.
Published: June 2015

The antibacterial properties of silver are strongly controlled by the redox couple of silver/silver(I). This work reports the influence of phosphate anions on silver nanoparticle oxidation, which is important given the abundance of phosphate species in biological systems. The three different species of anions were found to have a varying degree of influence on silver oxidation with the order PO43−>HPO42−>H2PO4−. It was found that in the presence of phosphate anions, the silver oxidation potential shifts to a less positive value, which indicated the increasing ease of the oxidation reaction of silver. Given that the interplay between silver and its cation is crucial to its antibacterial properties and significant concentrations of the HPO42− anion are present at biological pH (near neutral), it is essential that the influence of the dibasic anion (HPO42−) on silver oxidation dynamics be considered for biological systems.
Internal audit public sector capability: a case study
Authors: Janse van Rensburg Jacobus Oosthuizen , Coetzee Philna
Published: June 2015

Internal auditing is an essential part of governance and can be a valuable asset to public sector institutions. However, for public sector internal auditing to effectively support management, the internal audit function (IAF) should be capable. The question arises as to how the capability of public sector IAFs can be measured. The Institute of Internal Auditors Research Foundation published the Internal Audit Capability Model (IA‐CM) in 2009 to provide a capability self‐assessment tool for public sector IAFs. The main objective of the study is to determine whether the IA‐CM can be used successfully to measure internal audit capability levels, and a secondary objective is to determine whether the tool can be successfully adapted for a specific public sector organisation and/or country. To achieve these objectives, the model was applied in a South African public sector organisation by means of a case study, where the IAF of the case was ranked against the key process areas (KPAs) of the model. The ranking was conducted based on a documentary review and interviews with applicable officials within the case. The model was successfully tested in measuring the internal audit capability level of a South African public sector organisation; however, a total of eight potential feasibility hindrances or considerations have been identified that could negatively affect the implementation of seven of the KPAs of the IA‐CM. Copyright © 2015 John Wiley & Sons, Ltd.
Transparency and accountability: principles and rules for the construction of publicity
Authors: Filgueiras Fernando
Published: June 2015

Western countries have experienced a growing demand for accountability as a key element to the democratization of the State. This demand has given rise to an advocacy towards a transparency of State institutions and its subsequent public policies. This advocacy, in turn, aims to make governments accountable before the public. The goal of this article is to establish a critical perspective towards what we call transparency policy in favor of what we call publicity policy. The latter provides a normative argument for the concept of accountability aimed towards a deeper democracy and stronger public management processes. Copyright © 2015 John Wiley & Sons, Ltd.
Mechanical properties of poly(styrene‐co‐acrylonitrile) nanocomposites containing organically modified layered double hydroxides
Authors: Kim Seogjun , Ryu Chang Y.
Published: June 2015

Zn2Al layered double hydroxides (LDHs) modified with stearic acid, oleic acid, or caproic acid were synthesized by the co‐precipitation method for the compounding with poly(styrene‐co‐acrylonitrile) (SAN) at 0 to 6 wt% contents using a co‐rotating twin screw extruder. Melt flow indices (MFI) and mechanical properties of SAN nanocomposites were measured to know the effect of organic modifier. MFI of SAN nanocomposites reinforced with stearic acid modified LDH (SA‐Zn2Al LDH) were multiplied by the lubrication effect of considerably released organic modifier over 5 wt%. Mechanical properties of SAN nanocomposites showed the maximum values at the contents of organically modified LDH between 1 and 5 wt%. The optimum contents of organically modified LDHs (OLDHs) for tensile modulus were measured as 1 or 2 wt%, significantly less than the percolation threshold calculated as 4.7 wt% for an aspect ratio of 25. Except the flexural strength and notched Izod impact strength, caproic acid modified LDH (CA‐Zn2Al LDH) showed the best mechanical performance. SAN nanocomposites containing oleic acid modified LDH (OA‐Zn2Al LDH) showed the slightly largest values in both flexural strength and notched Izod impact strength. These results show that the strategy of organically modified LDH (OLDH) can be used to reinforce the SAN polymer without compromising mechanical properties. Copyright © 2015 John Wiley & Sons, Ltd.
Activation of the FGFR1 signalling pathway by the Epstein–Barr virus‐encoded LMP1 promotes aerobic glycolysis and transformation of human nasopharyngeal epithelial cells
Authors: Lo Angela Kwok‐Fung , Dawson Christopher W , Young Lawrence S , Ko Chuen‐Wai , Hau Pok‐Man , Lo Kwok‐Wai
Published: June 2015

Non‐keratinizing nasopharyngeal carcinoma (NPC) is closely associated with Epstein–Barr virus (EBV) infection. The EBV‐encoded latent membrane protein 1 (LMP1) is believed to play an important role in NPC pathogenesis by virtue of its ability to activate multiple cell signalling pathways which collectively promote cell proliferation, transformation, angiogenesis, and invasiveness, as well as modulation of energy metabolism. In this study, we report that LMP1 increases cellular uptake of glucose and glutamine, enhances LDHA activity and lactate production, but reduces pyruvate kinase activity and pyruvate concentrations. LMP1 also increases the phosphorylation of PKM2, LDHA, and FGFR1, as well as the expression of PDHK1, FGFR1, c‐Myc, and HIF‐1α, regardless of oxygen availability. Collectively, these findings suggest that LMP1 promotes aerobic glycolysis. With respect to FGFR1 signalling, LMP1 not only increases FGFR1 expression, but also up‐regulates FGF2, leading to constitutive activation of the FGFR1 signalling pathway. Furthermore, two inhibitors of FGFR1 (PD161570 and SU5402) attenuate LMP1‐mediated aerobic glycolysis, cellular transformation (proliferation and anchorage‐independent growth), cell migration, and invasion in nasopharyngeal epithelial cells, identifying FGFR1 signalling as a key pathway in LMP1‐mediated growth transformation. Immunohistochemical staining revealed that high levels of phosphorylated FGFR1 are common in primary NPC specimens and that this correlated with the expression of LMP1. In addition, FGFR1 inhibitors suppress cell proliferation and anchorage‐independent growth of NPC cells. Our current findings demonstrate that LMP1‐mediated FGFR1 activation contributes to aerobic glycolysis and transformation of epithelial cells, thereby implicating FGF2/FGFR1 signalling activation in the EBV‐driven pathogenesis of NPC. Copyright © 2015 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Experimental study of dielectric properties of composite materials pozzolan/DGEBA
Authors: Irekti Amar , Bezzazi Boudjema , Smith Agnès , Aribi Chouaib
Published: June 2015

The subject of composite materials with reinforced filler has been studied recently. This study to improve both the dielectric and structural characteristics of diglycidyl ether of bisphenol a (DGEBA) focused on the appropriate use (from 5% to 60 wt%) of pozzolan filler mechanically grinded to obtain a very fine particle size (Ø < 10 μm) and area surface of 23.5 m2 g−1. The dielectric properties were investigated at great filler concentrations by weight. Epoxy microcomposite samples with a good dispersion of nanoparticles in the epoxy matrix were prepared and experiments were performed to measure the capacitance (C), the electrical resistance (R), and impedance (Z) as a function of frequency (1 kHz–10 kHz). Measurements were made using dielectric spectroscopy over the temperature range 25–80°C. Using the scanning electron microscope (SEM), the morphologies and structure of the surface and fracture surfaces of Pozzolan/DGEBA composites were observed. POLYM. COMPOS., 38:324–331, 2017. © 2015 Society of Plastics Engineers
Effect of high‐shear mixing by twin‐screw extruder on the dispersion and homogeneity of polyacrylonitrile/carbon nanotube composite solution
Authors: Yan Xuejia , Dong Hongming , Xiao Zhiwei , Liu Yaodong , Liu Tao , Chae Han Gi , Kumar Satish
Published: June 2015

High‐shear mixing experiments using twin‐screw extruder were conducted to study the effect of shearing on carbon nanotube (CNT) dispersion in polyacrylonitrile (PAN) polymer solution. Different types of CNTs (few‐wall carbon nanotube and single‐wall carbon nanotube) were used to prepare composite solution at 0.5 wt% with respect to the PAN polymer through various preparation conditions. The resulting PAN/CNT composite solution was characterized using various techniques including dynamic light scattering, preparative ultracentrifuge method, optical microscopy, solution rheology, and high‐resolution transmission electron microscopy. With increasing the number of extrusion cycle, it was observed that the CNT bundle size was moderately reduced, while solution homogeneity and macroscopic CNT dispersion was significantly improved. POLYM. COMPOS., 38:719–726, 2017. © 2015 Society of Plastics Engineers
Surface and spectroscopic properties of CdSe/ZnS/PVC nanocomposites
Authors: Ahmed R.M.
Published: June 2015

It is valuable to understand the way the wettability is affected by the solid and the liquid surface free energies. For this study, transparent films of CdSe/ZnS/PVC nanocomposites have been prepared and characterized by FTIR and contact angle measurements. Moreover, the presence of polar interactions at the liquid/polymer interfaces, which show a proportionality to the polar components of the liquid surface energy for pure polyvinyl chloride (PVC) and all CdSe/ZnS/PVC nanocomposites, is also studied. By using the surface polarizability hypothesis, there is possibility to obtain the dispersion component of surface‐free energies of pure PVC and also its nanocomposites from the contact angles measurement of only polar liquids. This approximately is coincident with that published data for pure PVC obtained from both polar and nonpolar liquids' contact angles. In addition to this, the absorption spectra and the photoluminescence illustrate clearly the effect of CdSe/ZnS quantum dots on their host matrix. The calculated values of the optical parameters, such as energy gap and Urbach energy, illustrate an inverse proportionality between them. POLYM. COMPOS., 38:749–758, 2017. © 2015 Society of Plastics Engineers
Preparation and characterization of silica/polyimide nanocomposite films based on water‐soluble poly(amic acid) ammonium salt
Authors: Weng Ling , Li Hong‐Xia , Yang Xiao‐Peng , Liu Li‐Zhu
Published: June 2015

In this article, a series of new silica/polyimide (SiO2/PI) nanocomposite films with high dielectric constant (>4.0), low dielectric loss (<0.0325), high breakdown strength (288.8 kV mm−1), and high volume resistivity (2.498 × 1014 Ω m) were prepared by the hydrolysis of tetraethyl orthosilicate in water‐soluble poly(amic acid) ammonium salt (PAAS). The chemical structure of nanocomposite films compared with the traditional pure PI was confirmed by Fourier transform infrared spectroscopy and X‐ray diffraction patterns. The results indicated that both the PAAS and the polyamide acid (PAA) material were effectively converted into the corresponding PI material through the thermal imidization and the amorphous SiO2 was embedded in the nanocomposite films without structural changes. Thermal stability of the nanocomposite films was increased though mechanical property was generally decreased with increasing the mass fraction of SiO2. All the nanocomposite films exhibited an almost single‐step thermal decomposition behavior and the average decomposition temperature was about 615°C. It was concluded that the effective dispersion of SiO2 particles in PI matrix vigorously improved the comprehensive performance of the SiO2/PI nanocomposite films and expanded their applications in the electronic and environment‐friendly industries. POLYM. COMPOS., 38:774–781, 2017. © 2015 Society of Plastics Engineers
Fabrication and performance of a polyethersulfone nanofiltration membrane impregnated with a mesoporous silica–poly(1‐VInylpyrrolidone) nanocomposite
Authors: Huang Jian , Shu Zengnian , Zhang Yu
Published: June 2015

Fouling is a serious problem in the membrane formation process. Adding hydrophilic polymers or inorganic particles into the membrane is an effective way for improving the antifouling performance. However, most of the water‐soluble polymeric additives leach out during the phase inversion process, and the inorganic particles are prone to agglomerate in the membrane, which decreases the antifouling property of the membrane. In this study, poly(1‐vinylpyrrolidone) (PVP) was grafted onto mesoporous silica (MS) nanoparticle surface, and polyethersulfone (PES)/MS–PVP nanocomposite membranes were fabricated by the phase inversion method. MS–PVP dispersed well on the membrane surface, and the hydrophilicity of the PES/MS–PVP membranes increased with increasing content of MS–PVP. PES/MS–PVP membranes exhibited higher water flux than that of the bare PES membrane without any loss in NaCl rejection, and water flux of 25 L/m2h could be achieved by the membrane containing 3% of MS–PVP, which is almost 1.5 times as high as that of bare PES membrane at 0.6 MPa. The protein adsorption onto the membrane surface declined significantly from 49 to 25 mg/cm2 when the MS–PVP loading increased from 0% to 3%. POLYM. COMPOS., 38:908–917, 2017. © 2015 Society of Plastics Engineers
The effect of molecular weight on the separation of semiconducting single‐walled carbon nanotubes using poly(2,7‐carbazole)s
Authors: Rice Nicole A. , Subrahmanyam Ayyagari V. , Laengert Scott E. , Adronov Alex
Published: June 2015

The use of selective interactions between conjugated polymers and single‐walled carbon nanotubes has emerged as a promising method for the separation of nanotubes by electronic type. Although much attention has been devoted to investigating polyfluorenes and their ability to disperse semiconducting carbon nanotubes under specific conditions, other polymer families, such as poly(2,7‐carbazole)s, have been relatively overlooked. Poly(2,7‐carbazole)s have been shown to also preferentially interact with semiconducting carbon nanotubes, however a detailed investigation of polymer parameters, such as molecular weight, has not been performed. We have prepared seven different molecular weights of a poly(2,7‐carbazole), from short chain oligomers to high molecular weight polymers, and have investigated their effectiveness at dispersing semiconducting single‐walled carbon nanotubes. Although all polymer chain lengths were able to efficiently exfoliate carbon nanotube bundles using a mild dispersion protocol, only polymers above a certain threshold molecular weight (Mn ∼ 27 kDa) were found to exhibit complete selectivity for semiconducting nanotubes, with no observable signals from metallic species. Additionally, we found the quality of separation to be strongly dependent on the ratio of polymer to carbon nanotube. Contrary to previous reports, we have found that an excess of poly(2,7‐carbazole) leads to incomplete removal of metallic carbon nanotubes. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 2510–2516
Effect of oxidant on electronic transport in polypyrrole nanotubes synthesized in the presence of methyl orange
Authors: Varga Martin , Kopecká Jitka , Morávková Zuzana , Křivka Ivo , Trchová Miroslava , Stejskal Jaroslav , Prokeš Jan
Published: June 2015

Polypyrrole nanotubes with diameter 60–400 nm are synthesized with methyl orange as template and various oxidants, iron(III) chloride hexahydrate, iron(III) sulfate hydrate, and ammonium peroxydisulfate. The highest electrical conductivity of compressed pellets, 66 S cm−1, is found for iron(III) chloride. Regions with 3D variable range hopping in series with ordered regions near metal–insulator transition govern the charge transport. Other oxidants and globular morphology provide less conducting samples, <10 S cm−1. The transport mechanism is identified with the heterogeneous model of tunneling between (bi)polaronic clusters with parallel contribution of Arrhenius‐like activated conductivity. The results of conductivity are correlated with the protonation level reflected in the infrared spectra and with the ratio of bipolaron/polaron bands revealed by Raman spectroscopy. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 1147–1159
Protein structure refinement by optimization
Authors: Carlsen Martin , Røgen Peter
Published: June 2015

Knowledge‐based protein potentials are simplified potentials designed to improve the quality of protein models, which is important as more accurate models are more useful for biological and pharmaceutical studies. Consequently, knowledge‐based potentials often are designed to be efficient in ordering a given set of deformed structures denoted decoys according to how close they are to the relevant native protein structure. This, however, does not necessarily imply that energy minimization of this potential will bring the decoys closer to the native structure. In this study, we introduce an iterative strategy to improve the convergence of decoy structures. It works by adding energy optimized decoys to the pool of decoys used to construct the next and improved knowledge‐based potential. We demonstrate that this strategy results in significantly improved decoy convergence on Titan high resolution decoys and refinement targets from Critical Assessment of protein Structure Prediction competitions. Our potential is formulated in Cartesian coordinates and has a fixed backbone potential to restricts motions to be close to those of a dihedral model, a fixed hydrogen‐bonding potential and a variable coarse grained carbon alpha potential consisting of a pair potential and a novel solvent potential that are b‐spline based as we use explicit gradient and Hessian for efficient energy optimization. Proteins 2015; 83:1616–1624. © 2015 Wiley Periodicals, Inc.
Polarization effect on time‐of‐flight measurements performed on a CVD diamond single crystal
Authors: Valentin Audrey , Tardieu André , Mille Vianney , Tallaire Alexandre , Achard Jocelyn , Gicquel Alix
Published: June 2015

Time‐of‐flight experiments have been performed on a freestanding CVD diamond sample with Ti–Au contacts. Electron–hole pairs are generated with alpha rays from an 241Am source. A low‐field mobility of 2972 cm2/Vs and a saturation velocity of 12.3 × 106 cm/s have been extracted from the hole current pulses. However, the obtained electrons pulse shapes do not allow a clear determination of the mobility. The electrons appear to be slowed down by space‐charges located near the contacts. This clear polarization effect is attributed to negative charges trapped at the metal/diamond interface. Its influence has been investigated by comparing the current pulses obtained when applying a negative or positive bias. This bias influences the electric field inside the sample. Two competitive effects can be identified: a bulk effect and a contact effect. Time‐of‐flight can thus be used to identify the presence of defects in diamond crystals for electronic applications.
A novel 3D composite structure with tunable Poisson's ratio and stiffness
Authors: Hou Xiaonan , Hu Hong
Published: June 2015

A composite structure with tunable mechanical properties is introduced. The composite consists of matrix material and a stack of inclusions. The specific hollow re‐entrant shell inclusions could exhibit ‘expansion effect’ and ‘closure effect’ as responses to tensile and compressive loadings, respectively. Due to the special deformation mechanism of the inclusions, the global structure exhibits unusual properties over a wide range of applied deformations. The overall Poisson's ratio of the composite is significantly reduced comparing with its constituents, and an overall hardening effect is achieved. Moreover, according to the results of a parametric finite element analysis, the specific properties of this composite structure can be tailored by controlling the geometry features and density of the inclusions.
A force‐field based analysis of the deformation mechanism in α‐cristobalite
Authors: Gatt Ruben , Mizzi Luke , Azzopardi Keith M. , Grima Joseph N.
Published: June 2015

α‐cristobalite is a metastable polymorph of silica which has the remarkable property of exhibiting a negative Poisson's ratio (auxetic). In this study, the mechanical properties and deformation mechanisms of this system were investigated through a force‐field based approach. Besides simulations on the actual structure of α‐cristobalite, a number of simulations where the rigidity of SiO2 tetrahedra was increased, were also conducted. This was done in order to obtain a clearer picture of the role which these tetrahedra play in determining the mechanical properties of this system. These systems were loaded in an off‐axis direction in a number of planes about the [001] direction and the deformations observed were compared with those of type II rotating rectangle systems. It was discovered that the mechanical properties of α‐cristobalite can be accurately described through the semi‐rigid version of this model, even for cases where the tetrahedra were fully rigid.
Significance of urethral fibrosis evaluated by preoperative magnetic resonance imaging as a predictor of continence status after robot‐assisted radical prostatectomy
Authors: Momozono Hiroyuki , Miyake Hideaki , Miyazaki Akira , Fujisawa Masato
Published: June 2015

Background

The objective of this study was to assess the impact of urethral fibrosis on the continence status following robot‐assisted radical prostatectomy (RARP).

Methods

The findings of fibrosis of the urethral wall and periurethral tissue in 185 patients undergoing RARP were each divided into grade 0 to 3 based on preoperative T2‐weighted magnetic resonance imaging. Urethral fibrosis was defined as the sum of both grades, and scores ≤ 2 and ≥ 3 were considered as ‘no/mild’ and ‘severe’ fibrosis, respectively.

Results

The incidences of continence in patients with no/mild fibrosis were significantly higher at 3, 6, and 12 months after RARP than those with severe fibrosis. Furthermore, urethral fibrosis was identified as an independent predictor of the postoperative continence status at 3, 6, and 12 months after RARP.

Conclusions

Assessment of urethral fibrosis could be a significant predictor of recovery of the urinary continence status after RARP. Copyright © 2015 John Wiley & Sons, Ltd.
Application of a laser‐guided docking system in robot‐assisted urologic surgery
Authors: Guo Fei , Zhang Chao , Wang Hui‐qing , Sheng Xia , Xiao Liang , Sun Ying‐hao , Yang Bo
Published: June 2015

Background

This work explores the clinical significance of a laser‐guided docking system for robot‐assisted urologic surgery.

Materials and Methods

Between July 2013 and June 2014, 40 patients underwent robot‐assisted laparoscopic prostatectomy (RALP), and 32 patients underwent robot‐assisted laparoscopic partial nephrectomy (RAPN) performed by a single surgeon. In the RALP and RAPN groups, the robot was docked in the traditional way in 20 and 16 cases, respectively. A laser guiding system was used in the other cases. The docking time and the time required to adjust the angles were recorded.

Result

The docking time was significantly shorter for the laser‐guided process performed by inexperienced nurses. The time required to adjust the angles was also lower. There were no significant differences between the processes performed by experienced nurses.

Conclusion

A laser‐guided docking system may simplify and standardize the docking process and shorten the learning curve. Copyright © 2015 John Wiley & Sons, Ltd.
Post‐Spawning Survival and Downstream Passage of Landlocked Atlantic Salmon (Salmo salar) in a Regulated River: Is There Potential for Repeat Spawning?
Authors: Nyqvist D. , Calles O. , Bergman E. , Hagelin A. , Greenberg L. A.
Published: June 2015

Repeat salmonid spawners may make large contributions to total recruitment and long term population stability. Despite their potential importance, relatively little is known about this phase of the life history for anadromous populations, and nothing has been reported for landlocked populations. Here, we studied post‐spawning behaviour and survival of landlocked Atlantic salmon in relation to downstream dam passage in the River Klarälven, Sweden. Eight hydropower stations separate the feeding grounds in Lake Vänern from the spawning grounds in the River Klarälven, and no measures to facilitate downstream migration are present in the river. Forty‐nine percent of the salmon survived spawning and initiated downstream migration. Females and small fish had higher post‐spawning survival than males and large fish. The post‐spawners migrated downstream in autumn and spring and remained relatively inactive in the river during winter. Downstream migration speed in the free flowing part of the river was highly variable with a median of 9.30 km/day. Most fish passed the first hydropower station via upward‐opening spill gates after a median residence time in the forebay of 25 min. However, no tagged fish survived passage of all eight hydropower stations to reach Lake Vänern. This result underscores the need for remedial measures to increase the survival of downstream migrating kelts. Copyright © 2015 John Wiley & Sons, Ltd.
The long‐term benefits of organizational resilience through sustainable business practices
Authors: Ortiz‐de‐Mandojana Natalia , Bansal Pratima
Published: June 2015

Research summary: Prior work on the benefits of business sustainability often applies short‐term causal logic and data analysis. In this article, we argue that the social and the environmental practices (SEPs) associated with business sustainability not only contribute to short‐term outcomes, but also to organizational resilience, which we define as the firm's ability to sense and correct maladaptive tendencies and cope positively with unexpected situations. Because organizational resilience is a latent, path‐dependent construct, we assess it through the long‐term outcomes, including improved financial volatility, sales growth, and survival rates. We tested these hypotheses with data from 121 U.S.‐based matched‐pairs (242 individual firms) over a 15‐year period. We also tested, but did not find support for, the relationship between SEPs and short‐term financial performance.

Managerial summary: Most managers look for short‐term financial benefits to justify socially responsible or sustainable practices. In this article, we argue that such practices also help firms become more resilient, which helps them avoid crises and bounce back from shocks. However, it is difficult to measure the avoidance of shocks, so we analyzed long‐term outcomes. We show that firms that adopt responsible social and environmental practices, relative to a carefully matched control group, have lower financial volatility, higher sales growth, and higher chances of survival over a 15‐year period; yet, we were unable to find any differences in short‐term profits. We hope this research provides good reasons for firms to practice sustainability beyond the pursuit of short‐term profits. Copyright © 2015 John Wiley & Sons, Ltd.