bluuebunny/crossref_metadata_2025 huggingface dataset:
Computed Tomography Findings in Xanthogranulomatous Pyelonephritis
Authors: Rajesh Arumugam , Jakanani George , Mayer Nick , Mulcahy Kevin
Published: August 2011

Background:

Xanthogranulomatous pyelonephritis (XGN) is an uncommon condition characterized by chronic suppurative renal inflammation that leads to progressive parenchymal destruction.

Purpose:

To review the computed tomography (CT) findings of patients diagnosed with XGN.

Materials and Methods:

A retrospective review of CT findings in patients with histologically proven XGN was carried out.

Results:

Thirteen CT examinations of 11 patients were analyzed. Renal enlargement was demonstrable on the affected side in all patients. Nine patients (82%) had multiple dilated calyces and abnormal parenchyma. Six patients (55%) had a renal pelvis or upper ureteric calculus causing obstruction. Three patients (27%) had focal fat deposits identifiable within the inflamed renal parenchyma. Two patients had renal abscesses. Ten patients (91%) had extrarenal extension of the inflammatory changes. Three patients (27%) demonstrated extensive retroperitoneal inflammation.

Conclusion:

Unilateral renal enlargement and inflammation were the most consistent findings of XGN on CT. Perinephric inflammation and collections or abscess should also alert the radiologist to the possibility of this diagnosis.
Portal Asiático de Información: un servicio transcontinental de intercambio de artículos
Authors: Mantilla Martha E.
Published: August 2011

El Portal Asiático de Información de la Universidad de Pittsburgh es un innovador servicio de cooperación entre bibliotecas de Estados Unidos y bibliotecas de la China, Japón, y Corea, que facilita el acceso rápido a artículos publicados en revistas académicas, utilizando tecnología de bajo costo.
Electrical and Photo‐Induced Degradation of ZnO Layers in Organic Photovoltaics
Authors: Manor Assaf , Katz Eugene A. , Tromholt Thomas , Krebs Frederik C.
Published: August 2011

We present the case of degradation of organic solar cells by sunlight concentrated to a moderate level (∼4 suns). This concentration level is not enough for sufficient acceleration of the photobleaching or trap‐generation in the photoactive layer and therefore such short treatment (100 minutes) does not affect the short‐circuit current of the device. However, a significant degradation of VOC and FF has been recorded by measurements of the cell current‐voltage curves with a variation of light intensity, for the devices before and after the treatment. The same degradation was found to occur after short application of forward voltage biases in the dark. This kind of degradation is found to be repairable, and could even be prevented by simple electrical treatment (short pulses of the reverse bias). Moreover, even the fresh cells can be improved by the same process. Generation and degeneration of shunts in ZnO hole‐blocking layer as underlying physical mechanisms for the cell degradation and restoration, respectively, can explain the results.
Direct numerical simulations of aggregation of monosized spherical particles in homogeneous isotropic turbulence
Authors: Derksen J. J.
Published: August 2011

Direct numerical simulations of turbulent solid–liquid suspensions have been performed. The liquid is Newtonian, and the particles are identical spheres. The spheres have a tendency to aggregate since they are attracted to one another as a result of a square‐well potential. The size of the particles is typically larger than the Kolmogorov scale, albeit of the same order of magnitude. In such situations, the particle dynamics (including the aggregation process), and turbulence strongly interact which explains the need for direct simulations. The lattice‐Boltzmann method combined with an immersed boundary method for representing the no‐slip conditions at the spherical solid–liquid interfaces was used. The results show that the aggregate size distributions depend on both the strength of particle–particle interactions and the intensity of the turbulence. © 2011 American Institute of Chemical Engineers AIChE J, 58: 2589–2600, 2012
Sensitivity analysis of a proposed model mechanism for newly created glucose‐6‐oxidases
Authors: Moon Tae Seok , Nielsen David R. , Prather Kristala L. Jones
Published: August 2011

Parametric sensitivity analysis of a proposed model mechanism can serve as a valuable diagnostic for studying the fundamental characteristics of an enzymatic reaction. As the first step toward understanding the kinetics of a series of newly engineered glucose‐6‐oxidases, the activity of which has never been found in nature, we have proposed a mechanistic kinetic model and performed a parametric sensitivity analysis. The mechanism of our model consists of two enzyme conformations, namely “less active” and “more active,” and is shown to be consistent with experimental observations of prolonged periods of enzyme induction. The extended lag phase phenomenon was found to be well described mechanistically by a slow rate of interconversion between the two enzyme conformations (relative to the rate of product formation), and this prediction was further supported by our experimental results. The proposed enzymatic model will serve as a blueprint with which to better understand the mechanistic behavior of newly generated glucose‐6‐oxidases. © 2011 American Institute of Chemical Engineers AIChE J, 58: 2303–2308, 2012
The coexistence of chronic lymphocytic leukemia and myeloproliperative neoplasms: A retrospective multicentric GIMEMA experience
Authors: Laurenti Luca , Tarnani Michela , Nichele Ilaria , Ciolli Stefania , Cortelezzi Agostino , Forconi Francesco , Rossi Davide , Mauro Francesca Romana , D'Arena Giovanni , Del Poeta Giovanni , Montanaro Marco , Morabito Fortunato , Musolino Caterina , Callea Vincenzo , Falchi Lorenzo , Tedeschi Alessandra , Ambrosetti Achille , Gaidano Gianluca , Leone Giuseppe , Foà Robin
Published: August 2011

Although the coexistence of chronic lymphocytic leukemia (CLL) and myeloproliferative neoplasms (MPN) has been sporadically reported in the literature, no systematic studies on this disease association are available. We retrospectively analyzed 46 patients affected by CLL/MPN referred by 15 Italian GIMEMA centers. The aim of this retrospective multicenter study was to define the following: clinico‐biological characteristics, possible familiarity, clinical course of both diseases, and influence of MPN chemotherapy on the course of CLL. Among 46 patients, 30 patients were males, 16 patients were females; median age was 71 years. Only one case had familiar CLL. Myeloproliferative disorders consisted of essential thrombocytemia in 18 cases, polycythemia vera in 10 cases, chronic myeloid leukemia in 9 cases, primary myelofibrosis in 6 cases, and MPN/myelodysplastic syndrome in 3 cases. The lymphoproliferative disorder was diagnosed as monoclonal B‐cell lymphocytosis in 8 patients and as Binet Stage A CLL in 38 patients. After a median follow‐up of 49 months, 9 patients experienced progressive CLL and only 6 patients required treatment after a median of 57.5 months. The biological profile confirmed a subset of low‐risk CLL. Twenty patients received chemotherapy for MPN without influence on the course of CLL: lymphocyte counts remained unchanged after 3, 6, and 12 months of treatment. This series is the largest so far reported in literature. The diagnosis of concomitant CLL/MPN is a rare event and lymphoproliferative disorders present a clinical indolent course with a low‐risk biological profile. MPN therapy does not interfere with the prognosis of patients with CLL. Am. J. Hematol. 2011. © 2011 Wiley‐Liss, Inc.
Preparation and characterization of polyimide and polyethersulfone blend membrane for gas separation
Authors: Madaeni S. S. , Mohammadi Nooripour R. , Vatanpour V.
Published: August 2011

Polyimides (PI) have been studied as the basic materials for preparing gas separation membranes attributable to their high gas selectivity. This paper deals with the preparation and characterization of blended polyimide membranes with polyethersulfone (PES) to study separation of ethylene from nitrogen gas at different feed pressures. For improving performance of PI membranes, two procedures were used. First, using polymeric additives such as polyvinylidene fluoride (PVDF) and PES in low content and second, blending of PI casting solution with high amount of PES. Infrared spectroscopy and scanning electron microscopy (SEM) images were employed to characterize the membranes. Pyromellitic dianhydride‐co‐4, 4′‐oxy dianiline (PMDA/ODA) polyimide membranes was synthesized using polyamic acid (PAA) as precursor materials. The ideal selectivity of 100% (ethylene permeation only) was achieved at 1 bar using PMDA/ODA polyimide membranes containing 1 wt% PVDF. Addition of PES did not have any significant influence on ideal selectivity of the prepared membranes. PES‐(PMDA/ODA) polyamic acid blend membranes were prepared using different blending ratios of PES (25 wt%) and PAA (15 wt%). The blending ratio of casting solutions of PES/PAA solutions exhibited a main influence on the ideal selectivity. The ideal selectivity of 2.9 for ethylene was achieved at 3 bar using blend membranes with 0.5 wt% PAA solution. PES‐PMDA/ODA polyimide membranes were also prepared from blend casting solutions by thermal imidization. Immiscible blend membranes were obtained at different blending ratios of the casting solutions with high gas permeance and poor selectivity. © 2011 Curtin University of Technology and John Wiley & Sons, Ltd.
Influence of plasma surface treatments on kink band formation in PBO fibers during compression
Authors: Lorenzo‐Villafranca Eduardo , Tamargo‐Martínez Katia , Molina‐Aldareguia Jon M. , González Carlos , Martínez‐Alonso Amelia , Tascón Juan M. D. , Gracia Mercedes , Llorca Javier
Published: August 2011

The effect of nitrogen and oxygen plasma surface treatments on the compressive strength of PBO fibers has been studied. To this end, the nucleation and propagation of compression‐induced kink bands was carefully monitored by means of in situ bending tests inside a scanning electron microscope. The micromechanisms of deformation were identical irrespective of fiber surface condition (either as‐received or modified by plasma) but the critical stress necessary to induce irreversible damage in compression in the nitrogen‐plasma treated fibers was 40% higher than in the as‐received fibers. This improvement occurred without any reduction in the fiber tensile properties. The source of this behavior is discussed in the light of the morphological and chemical changes induced by the plasma treatments on the fiber surface, as studied by AFM and XPS. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Characterization and physical properties investigation of conducting polypyrrole/TiO2 nanocomposites prepared through a one‐step “in situ” polymerization method
Authors: Babazadeh Mirzaagha , Rezazad Gohari Faezeh , Olad Ali
Published: August 2011

Nowadays, nanocomposites are a special class of materials having unique physical properties and wide application potential in diverse areas. The present research work describes an efficient method for synthesis of a series of polypyrrole/titanium dioxide (PPy/TiO2) nanocomposites with different TiO2 ratios. These nanocomposites were prepared by one‐step in situ deposition oxidative polymerization of pyrrole hydrochloride using ferric chloride (FeCl3) as an oxidant in the presence of ultra fine grade powder of anatase TiO2 nanoparticles cooled in an ice bath. The obtained nanocomposites were characterized by Fourier‐transform infrared (FTIR), thermogravimetric analysis (TGA), X‐ray diffraction (XRD), and scanning electron microscope (SEM) techniques. The obtained results showed that TiO2 nanoparticles have been encapsulated by PPy with a strong effect on the morphology of PPy/TiO2 nanocomposites. Also, the synthesized PPy/TiO2 nanocomposites had higher thermal stability than that of pure PPy. The investigation of electrical conductivity of nanocomposites by four‐point probe instrument showed that the conductivity of nanocomposite at low TiO2 content is much higher than of neat PPy, while with the increasing contents of TiO2, the conductivity decreases. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Novel high‐performance wave‐transparent aluminum phosphate/cyanate ester composites
Authors: Sun Zhouqiang , Huang Pingzhen , Gu Aijuan , Liang Guozheng , Yuan Li , Dai Shankai
Published: August 2011

Advanced wave‐transparent composites are the key materials for many cutting‐edge industries including aviation and aerospace, which should have outstanding heat resistance, low dielectric constant and loss as well as good mechanical properties. A novel kind of high‐performance wave‐transparent composites based on surface‐modified aluminum phosphate AlPO4(KH‐550) and cyanate ester (CE) was first developed. The dielectric and dynamic mechanical properties of AlPO4(KH‐550)/CE composites were investigated intensively. Results show that AlPO4(KH‐550)/CE composites have decreased dielectric loss and higher storage moduli than pure CE resin; in addition, the composites with suitable AlPO4(KH‐550) concentration remain the outstanding thermal property and low dielectric constant of pure CE resin. The reasons attributing to these results are discussed from the effects of AlPO4(KH‐550) on the key aspects such as morphology, curing mechanism, and interfacial adhesion of composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Effects of lithium perchlorate on poly(ethylene oxide) spherulite morphology and spherulite growth kinetics
Authors: Zhang Yao , Li Jingqing , Huo Hong , Jiang Shichun
Published: August 2011

Effects of lithium perchlorate (LiClO4) on the crystallization behaviors of poly(ethylene oxide) (PEO) were investigated by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and polarized optical microscopy (POM) in PEO/LiClO4 system. DSC results indicate that there are nucleation effects of LiClO4 on the crystallization of PEO. But, on the other hand, the coordination of lithium ion with the oxygen ether atoms of PEO can obviously reduce the crystallinity and spherulite growth rate of PEO. This contrary effect of LiClO4 on the crystallization of PEO in PEO/LiClO4 complexes system was analyzed and discussed in detail. The Laurizen–Hoffman theory was used to describe the Li‐coordinated crystallization kinetics of PEO spherulite. It showed that the nucleation constant (Kg) and folding surface free energy (σe) decreased with increasing LiClO4 contents, and the energy necessary for the transport of segments across the liquid–solid interface (ΔE) increased on increasing the contents of LiClO4. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Using a polymer‐supported azide ion in [2+3] cycloaddition reaction of azide ion with nitriles
Authors: Karimi Zarchi Mohammad Ali , Nazem Fatemeh.
Published: August 2011

The [2+3] cycloaddition between various nitriles and crosslinked poly(4‐vinylpyridine) supported azide ion proceeds smoothly in the presence of ammonium bromide or ammonium chloride in N,N‐dimethyl formamide, to give the corresponding 5‐substituted‐1H‐tetrazoles in good to high yields. Conventional heating was used to promote reaction. It was found that using nitriles with electron‐withdrawing groups result in bout higher yields and lower reaction times. The present procedure offers advantages, such as shorter reaction time, and simple workup. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Effects of material and treatment parameters on noise‐control performance of compressed three‐layered multifiber needle‐punched nonwovens
Authors: Yilmaz Nazire Deniz , Michielsen Stephen , Banks‐Lee Pamela , Powell Nancy B.
Published: August 2011

The effects of material and treatment parameters on airflow resistivity and normal‐incidence sound absorption coefficient (NAC) of compressed three‐layer nonwoven composites have been studied. Material parameters included fiber size and porosity, and treatment factors included applied pressure and duration of compression. Fibers used included poly(lactic acid) (PLA), polypropylene (PP), glassfiber, and hemp. Three‐layered nonwoven composites were classified based on material content and fiber blend. LHL and PGP were sandwiched structures consisting of PLA/Hemp/PLA and PP/glassfiber/PP layers, respectively. PGI consisted of three layers of an intimate blend of PP and glassfiber. Statistical models were developed to predict air flow resistivity from material parameters and the change in air flow resistivity from compression parameters. Independent variables in the first model were porosity and fiber size and, in the latter model, were compressibility, pressure, and initial material parameters. An increase in air flow resistivity was found with increased compression. No significant effect of compression duration was detected. Two additional statistical models were developed for the prediction of sound absorption coefficient based on material and treatment parameters. The independent variables of the first model were air flow resistivity, thickness, and frequency, and those of the second model were compressibility, initial thickness, and initial density of the composite, diameter and density of the fiber, compression pressure, and frequency. A decrease in sound absorption coefficient was detected with increasing compression, while no effect of duration was detected. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Isothermal rheokinetic study of a precured resol resin beyond gelation by torsion
Authors: Domínguez J. C. , Oliet M. , Alonso M. V. , Rojo E. , Rodríguez F.
Published: August 2011

The rheokinetics of the curing process of a resol resin was studied through isothermal analysis. The resin was subjected to a curing pretreatment until gelation was reached. Rectangular torsion was chosen as the appropriate strain form to carry out the study of the resin's curing kinetics, because the viscoelastic behavior of the material was closer to an ideal solid than to a Newtonian fluid. Seven operating temperatures were selected for analysis (80–110°C). The Arrhenius and Kiuna rheokinetic models were applied to the resin's complex viscosity (η*) evolution during the crosslinking of polymer. The resol resin had curing activation energies of 62.6 and 65.8 kJ/mol when the Arrhenius model was applied in four‐ and six‐parameter forms, respectively. The Kiuna model was proposed to fit the nonlinear viscosity region found at the highest temperatures. This model was suitable to predict changes in the resin's complex viscosity, obtaining a curing activation energy of 69.5 kJ/mol for the resin. In addition, the evolution of the degree of mechanical curing was obtained from the elastic modulus, rather than from the more common DSC technique. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Novel phenolic resins with improved mechanical and toughness properties
Authors: Cardona Francisco , Kin‐Tak Alan Lau , Fedrigo Jessica
Published: August 2011

Novel phenolic type of thermoset resins were synthesized, and their mechanical and toughness properties were evaluated. Phenol Formaldehyde (PF) phenolic resins were modified to broaden their applications for modern composite structures. A first modification consisted of copolymerization of Phenol with Cardanol during the synthesis of resole phenolic (CPF) resins. The modified phenolic resins (CPF) were prepared at various molar ratios of total Phenol to Formaldehyde (F : P ratio) and with different weight ratios of Phenol to Cardanol. CPF resins with a maximum content of 40 wt % of Cardanol were synthesized and used. The CPF resins were applied as a plasticizer and toughening agent to the base PF resins. Both resins (CPF/PF) were mixed in different proportions, and their thermal and mechanical properties were then established. A full miscibility of the two resins was observed with the formation of a single‐phase system. An increase in the content of Cardanol resulted in a proportional increase of the flexural strength and fracture toughness together with a decrease of the flexural modulus of the cured CPF/PF resins. Further increased plasticizing and toughening effect was also observed by the blending of the CPF resins with propylene glycol. The higher toughness and flexibility effect of the CPF resins was obtained with a F : P molar ratio equal to 1.25 and with a Cardanol content of 40% (w/w). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Modification of cellulosic fabrics to impart flame retardancy properties
Authors: Waly A. I. , Abou Elmaaty T. M. , Abd El‐Shakour S. A.
Published: August 2011

Graft copolymerization of dimethylaminoethyl methacrylate (DMAEMA) onto cotton‐cellulose in the fabric form was carried out using a cellulose‐thiocarbonate‐ammonium persulphate redox initiation system. Effects of the concentration of the monomer, effect of liquor ratio, grafting time, and temperature were studied. The results point out the following important aspects of flame retardation of cellulose fabrics. (1) The graft polymerization of DMAEMA can improve the flame retardant properties of cellulose fabrics. (2) Tertiary amine grafted to cellulosic fabrics is suitable for nitrogen compounds that can effectively operate as synergists. The flame retardant properties of the poly‐DMAEMA‐ grafted‐phosphorylated cellulosic materials were found to be excellent even after 25 dry clean washings. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Investigation of tensile properties and dyeing behavior of various polypropylene/amine modifier blends
Authors: Asiaban Saeed , Moradian Siamak
Published: August 2011

Polypropylene is utilized in manifold applications due to its unique properties. However, its use has been limited in the textile industry because conventional dyestuffs have no affinity for this polymer. Amine modifiers, generally improve the dye‐ability of polypropylene. Polyamide 6 (PA6) is a traditional amine modifier which improves the dyeing ability of polypropylene with disperse dyes. In this investigation, polyetheramine (PEA) is introduced as a novel amine modifier which improves the dye‐ability of polypropylene with disperse and acid dyestuffs. To this end, the dyeing behavior as well as possible impairments of tensile properties of PEA modified polypropylene were studied and compared to PA6 modified polypropylene. As with the PA6 containing blends, the tensile properties of the incompatible PP/PEA blends decreased due to weak interfacial adhesions between the components of the blends. However, the incorporation of a compatibilizer into such blends led to better dispersions of modifiers in the matrix as well as formation of amide or imide linkages which in turn reincreased the tensile properties almost to their initial values. Both PEA and PA6 modifiers improved the disperse dye uptake of the blends. However, Only Jeffamine ED‐2003 (i.e., PEA) was capable of enhance the acid dye uptake of modified polypropylene. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Fatigue life prediction for circular rubber bearings subjected to cyclic compression
Authors: Chou Hsoung‐Wei , Huang Jong‐Shin
Published: August 2011

The fatigue life of circular rubber bearings under cyclic compression is theoretically and numerically analyzed based on a previously proposed fatigue failure mechanism. The energy release rate at any point in circular rubber bearings under cyclic compression, which depends on the cracking energy density and crack length along the predicted crack propagation path, is derived first theoretically. Then, the corresponding fatigue crack growth rate and fatigue life are determined numerically by introducing the fatigue parameters of three different rubber compounds before and after suffering from thermal aging. Meanwhile, the effects of intrinsic flaw size and maximum compressive stress on the fatigue life of circular rubber bearings are also investigated. It is found that the enlargement in the Regime 1 range of the crack growth rate of rubber increases the fatigue resistance of circular rubber bearings. Therefore, the effects of the mechanical properties, intrinsic flaw size, threshold value, and maximum cyclic compressive stress on fatigue life are significant and should be taken into account in designing rubber bearings. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
An investigation about solid equal channel angular extrusion on polypropylene/organic montmorillonite composite
Authors: Li Hong , Huang Xun , Huang Chengya , Zhao Yaoming
Published: August 2011

The solid equal channel angular extrusion (ECAE) process on polypropylene (PP)/organic montmorillonite (OMMT) was carried out. Scanning electron microscopy, polarized optical microscopy, transmission electron microscopy, and X‐ray diffraction were used to observe and characterize the samples structures. Experimental results show that both PP spherulites and OMMT particles were significantly deformed and orientated toward the shearing direction, and OMMT agglomeration particles were broken into needle‐like primary particles, some even exfoliated into nanosilicate layers after twice ECAE processes due to the immense solid shear force. This solid process approach introduces a new way to prepare PP/OMMT nanocomposites. The mechanism of exfoliation between PP and OMMT was also discussed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Mathematical modeling for the pultrusion of polymethyl methacrylate based composites
Authors: Chen Chin‐Hsing
Published: August 2011

The thermokinetic behavior of polymethyl methacrylate (PMMA)‐based composites during the pultrusion of glass fiber reinforced composites was investigated using a mathematical model accounting for the heat transfer and heat generation during the reaction. The equations of continuity and energy balance, coupled with a kinetic expression for the reaction system were solved using a finite difference method to calculate the temperature profiles in the thickness direction in a rectangular pultrusion die. A kinetic model,
$ {dP\over dt} = -\eta A_{o}{\rm exp}\left(-{E_{p}\over {\rm RT}}\right)$
$(2[I]_{o}- [Z]_{o})P^m \left(1- {P\over P_{f}} \right)^n(1-{\rm exp}(-k_{d}(t-t_{z})))$, was proposed to describe the reaction behavior of a PMMA resin. Kinetic parameters for the model were found from isothermal differential scanning calorimetry (DSC) scans using a multiple regression technique. The kinetic parameters ηAo = 1.459 × 109 min−1, Ep = 10.62 kcal/mol, m = 1.095, and n = 0.893 were obtained. The predictions of the model will be compared with experimental results. It can be found that the theoretical predicted values of temperature profiles along the pultrusion die length were in good agreement with experimental data, which implies that the mathematical model was suitable for the pultrusion processes. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Information behavior and decision making in time‐constrained practice: A dual‐processing perspective
Authors: Allen David
Published: August 2011

This article reviews results from a research project designed to understand the mediating influence of information technology on information behavior. During the analysis of the data, five modes of information behavior were uncovered. These provide us with a reconceptualization of core information‐seeking and search activities, as well as a fruitful opening to redevelop, augment, or complement existing models of information behavior. The findings resonate with emerging theories of decision making and judgement and illustrate the need for information behavior researchers to undertake research in differing contexts. The work illuminates an issue of current concern for public policy: police use of information in decision making.
Semiparametric estimation in copula models for bivariate sequential survival times
Authors: Lawless Jerald F. , Yilmaz Yildiz E.
Published: August 2011

Sequentially observed survival times are of interest in many studies but there are difficulties in analyzing such data using nonparametric or semiparametric methods. First, when the duration of followup is limited and the times for a given individual are not independent, induced dependent censoring arises for the second and subsequent survival times. Non‐identifiability of the marginal survival distributions for second and later times is another issue, since they are observable only if preceding survival times for an individual are uncensored. In addition, in some studies a significant proportion of individuals may never have the first event. Fully parametric models can deal with these features, but robustness is a concern. We introduce a new approach to address these issues. We model the joint distribution of the successive survival times by using copula functions, and provide semiparametric estimation procedures in which copula parameters are estimated without parametric assumptions on the marginal distributions. This provides more robust estimates and checks on the fit of parametric models. The methodology is applied to a motivating example involving relapse and survival following colon cancer treatment.
A two‐part mixed‐effects pattern‐mixture model to handle zero‐inflation and incompleteness in a longitudinal setting
Authors: Maruotti Antonello
Published: August 2011

Two‐part regression models are frequently used to analyze longitudinal count data with excess zeros, where the same set of subjects is repeatedly observed over time. In this context, several sources of heterogeneity may arise at individual level that affect the observed process. Further, longitudinal studies often suffer from missing values: individuals dropout of the study before its completion, and thus present incomplete data records. In this paper, we propose a finite mixture of hurdle models to face the heterogeneity problem, which is handled by introducing random effects with a discrete distribution; a pattern‐mixture approach is specified to deal with non‐ignorable missing values. This approach helps us to consider overdispersed counts, while allowing for association between the two parts of the model, and for non‐ignorable dropouts. The effectiveness of the proposal is tested through a simulation study. Finally, an application to real data on skin cancer is provided.
Evaluation of the antioxidant activity of tetracycline antibiotics in vitro
Authors: Kładna Aleksandra , Michalska Teresa , Berczyński Paweł , Kruk Irena , Aboul‐Enein Hassan Y.
Published: August 2011

Tetracyclines are the second most common antibiotic family in medicine usage. These antibiotics exhibit antioxidant potential; however, the exact mechanism remains unclear. The antiradical activity of the seven tetracyclines (TCs; tetracycline, chlortetracycline, oxytetracycline, doxocycline, methacycline, demeclocycline, minocycline) was determined using the free radical 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH•) and hydroxyl radicals (HO•) generated in a Fenton reaction. Electron spin resonance (ESR), ESR spin‐trapping, chemiluminescence and spectrophotometry techniques were applied. It was found that the TCs showed high DPPH antiradical activity in the range 26–96% at 2.5 mmol/L concentration. The second‐order rate constants for the reaction between HO• and TCs were calculated, in the range (3.6–9.6) × 109 L/mol/s. The tetracycline compounds also exhibited a strong decrease in light emission (range 61–85% at concentration of 1 mmol/L). This study also showed that TCs promote the generation of singlet oxygen in the presence of and Fe(II)/Fe(III) ions. Our findings suggest direct scavenging activity of the examined tetracyclines towards free radicals, and may be relevant to therapeutic strategy. Copyright © 2011 John Wiley & Sons, Ltd.
Enzyme precipitate coatings of glucose oxidase onto carbon paper for biofuel cell applications
Authors: Fischback Mike , Kwon Ki Young , Lee Inseon , Shin Su Jeong , Park Hyun Gyu , Kim Byoung Chan , Kwon Yongchai , Jung Hee‐Tae , Kim Jungbae , Ha Su
Published: August 2011

Enzymatic biofuel cells (BFC) have a great potential as a small power source, but their practical applications are being hampered by short lifetime and low power density. This study describes the direct immobilization of glucose oxidase (GOx) onto the carbon paper in the form of highly stable and active enzyme precipitation coatings (EPCs), which can improve the lifetime and power density of BFCs. EPCs were fabricated directly onto the carbon paper via a three‐step process: covalent attachment (CA), enzyme precipitation, and chemical crosslinking. GOx‐immobilized carbon papers via the CA and EPC approaches were used as an enzyme anode and their electrochemical activities were tested under the BFC‐operating mode. The BFCs with CA and EPC enzyme anodes produced the maximum power densities of 50 and 250 µW/cm2, respectively. The BFC with the EPC enzyme anode showed a stable current density output of >700 µA/cm2 at 0.18 V under continuous operation for over 45 h. When a maple syrup was used as a fuel under ambient conditions, it also produced a stable current density of >10 µA/cm2 at 0.18 V for over 25 h. It is anticipated that the direct immobilization of EPC on hierarchical‐structured electrodes with a large surface area would further improve the power density of BFCs that can make their applications more feasible. Biotechnol. Bioeng. 2012; 109:318–324. © 2011 Wiley Periodicals, Inc.
Randomized clinical trial of fibrin sealant versus titanium tacks for mesh fixation in laparoscopic umbilical hernia repair
Authors: Eriksen J R , Bisgaard T , Assaadzadeh S , Nannestad Jorgensen L , Rosenberg J
Published: August 2011

Background

The use of tacks for mesh fixation may induce pain after surgery for ventral hernia. The aim of this study was to compare postoperative pain after laparoscopic ventral hernia repair (LVHR) with conventional mesh fixation using titanium tacks versus fibrin sealant (FS).

Methods

This randomized clinical trial included patients with an umbilical hernia defect ranging from 1·5 to 5 cm at three Danish hernia centres. Participants were assigned randomly to FS or titanium tack fixation. The primary outcome was acute pain, defined as the mean pain score on days 0–2 after surgery, measured on a 0–100-mm visual analogue scale (VAS).

Results

Forty patients were included, of whom 38 were available for intention-to-treat analysis after 1 month. Patients in the FS group reported less pain than those in the tack group on days 0–2, both at rest (median 19 versus 47 mm; P = 0·025) and during activity (38 versus 60 mm; P = 0·014). The absolute difference in pain score between groups was 19 (95 per cent confidence interval 3 to 34) and 20 (4 to 35) mm at rest and during activity respectively. Patients in the FS group resumed normal daily activity earlier (after median 7 versus 18 days; P = 0·027) and reported significantly less discomfort. No recurrences were observed.

Conclusion

Mesh fixation with FS in LVHR was associated with less acute postoperative pain, discomfort and a shorter convalescence than tack fixation. Long-term follow-up is needed to show whether the effect of FS fixation persists in terms of chronic pain and recurrence. Registration number: NCT00842842 (http://www.clinicaltrials.gov).
Pathogenesis of postoperative adhesion formation
Authors: Hellebrekers B W J , Kooistra T
Published: August 2011

Background

Current views on the pathogenesis of adhesion formation are based on the ‘classical concept of adhesion formation’, namely that a reduction in peritoneal fibrinolytic activity following peritoneal trauma is of key importance in adhesion development.

Methods

A non-systematic literature search (1960–2010) was performed in PubMed to identify all original articles on the pathogenesis of adhesion formation. Information was sought on the role of the fibrinolytic, coagulatory and inflammatory systems in the disease process.

Results

One unifying concept emerged when assessing 50 years of studies in animals and humans on the pathogenesis of adhesion formation. Peritoneal damage inflicted by surgical trauma or other insults evokes an inflammatory response, thereby promoting procoagulatory and antifibrinolytic reactions, and a subsequent significant increase in fibrin formation. Importantly, peritoneal inflammatory status seems a crucial factor in determining the duration and extent of the imbalance between fibrin formation and fibrin dissolution, and therefore in the persistence of fibrin deposits, determining whether or not adhesions develop.

Conclusion

Suppression of inflammation, manipulation of coagulation as well as direct augmentation of fibrinolytic activity may be promising antiadhesion treatment strategies.
A strategy for extending the applicability of a validated plasma calibration curve to quantitative measurements in multiple tissue homogenate samples: a case study from a rat tissue distribution study of JI‐101, a triple kinase inhibitor
Authors: Gurav Sandip Dhondiram , Jeniffer Sherine , Punde Ravindra , Gilibili Ravindranath Reddy , Giri Sanjeev , Srinivas Nuggehally R , Mullangi Ramesh
Published: August 2011

A general practice in bioanalysis is that, whatever the biological matrix the analyte is being quantified in, the validation is performed in the same matrix as per regulatory guidelines. In this paper, we are presenting the applicability of a validated LC‐MS/MS method in rat plasma for JI‐101, to estimate the concentrations of JI‐101 in various tissues that were harvested in a rat tissue distribution study. A simple protein precipitation technique was used to extract JI‐101 and internal standard from the tissue homogenates. The recovery of JI‐101 in all the matrices was found to be >70%. Chromatographic separation was achieved using a binary gradient using mobile phase A (acetonitrile) and B (0.2% formic acid in water) at a flow rate of 0.30 mL/min on a Prodigy ODS column with a total run time of 4.0 min. The MS/MS ion transitions monitored were 466.1 → 265 for JI‐101 and 180.1 → 110.1 for internal standard. The linearity range was 5.02–4017 ng/mL. The JI‐101 levels were quantifiable in the various tissue samples harvested in this study. Therefore, the use of a previously validated JI‐101 assay in plasma circumvented the tedious process of method development/validation in various tissue matrices. Copyright © 2011 John Wiley & Sons, Ltd.
Validated high‐performance liquid chromatographic enantioseparation of selenomethionine using isothiocyanate based chiral derivatizing reagents
Authors: Bhushan Ravi , Dubey Rituraj
Published: August 2011

A high‐performance liquid chromatographic (HPLC) method for enantioseparation of selenomethionine (SeMet) was developed using two isothiocyanate‐based chiral derivatizing reagents [(R)‐methyl benzyl isothiocyanate (MBIC) and (S)‐1‐(1‐naphthyl) ethyl isothiocyanate (NEIC)] and UV detection. Diastereomers of selenomethionine were synthesized either via stirring (using MBIC) or by microwave irradiation (using NEIC). Derivatization conditions were optimized and the synthesized diastereomers were successfully resolved using triethyl ammonium phosphate buffer and acetonitrile on a reversed‐phase column. The method was validated for accuracy, precision and limit of detection. The mechanism of separation is also discussed. Copyright © 2011 John Wiley & Sons, Ltd.
Development and validation of a HPAE‐PAD method for the quantification of CGP69669A, a sialyl Lewisx mimetic, in skin permeation studies
Authors: Gratieri Taís , Wagner Beatrice , Kalaria Dhaval , Ernst Beat , Kalia Yogeshvar N.
Published: August 2011

A simple, rapid, precise and specific isocratic HPAE‐PAD method for quantification of CGP69669A was developed and validated. CGP69669A is a glycomimetic of sialyl Lewisx and an antagonist of E‐selectin with potential application in the treatment of inflammatory skin disease. Quantification was performed using a Dionex CarboPacTM PA‐200 anion‐exchange column (3 × 250 mm) with 100 mm NaOH solution as mobile phase, a flow rate of 0.50 mL/min and an injection volume of 10 μL. A quadruple potential waveform was used to detect the carbohydrate (+0.1 V from 0.00 to 0.40 s, −2.0 V from 0.41 to 0.42 s, +0.6 V at 0.43 s and −0.1 V from 0.44 to 0.50 s with current integrated between 0.20 and 0.40 s for detection) and rafinose was employed as an internal standard. The optimized conditions enabled rapid elution of CGP69669A (at 3.0 min) without interference from solvent peaks or substances present in the skin. The method showed good intra‐ and inter‐day precision and accuracy and the response was linear from 1.0 to 25 µg/mL. This is the first validated direct method for the quantification of CGP69669A. It will now be employed in studies investigating the topical and transdermal delivery of CGP69669A in vitro and in vivo and it should also be of use for other applications of this molecule. Copyright © 2011 John Wiley & Sons, Ltd.
Proteomic understanding of intracellular responses of recombinant chinese hamster ovary cells adapted to grow in serum‐free suspension culture
Authors: Baik Jong Youn , Ha Tae Kwang , Kim Young Hwan , Lee Gyun Min
Published: August 2011

To understand the intracellular responses in recombinant Chinese hamster ovary (rCHO) cells adapted to grow in serum‐free suspension culture, a proteomic approach was employed. After rCHO cells producing erythropoietin were adapted to grow in suspension culture with the two different serum‐free media (SFM4CHO™ and SF‐L1), proteome analyses were carried out using 2‐D PAGE and based on spot intensities, 58 high‐intensity protein spots were selected. Of the 58 protein spots, which represented 34 different kinds of proteins, 55 were identified by MALDI‐TOF‐MS, and MS/MS. Compared with the results in serum‐containing medium, six proteins, four de novo synthesis of nucleotides‐related proteins (dihydrolipoamide S‐acetyltransferase, transaldolase, inosine‐5′‐monophosphate dehydrogenase 2, and lymphoid‐restricted membrane protein) and two molecular chaperones (heat shock protein 70 kDa and 60 kDa [HSC70, HSP60]) were significantly increased in SFM4CHO™. From the results of proteomic analysis, HSP60 and HSC70, which were increased in both SFM, were selected as candidate proteins for engineering and rCHO cell lines overexpressing these genes were constructed. Cells overexpressing HSP60 and/or HSC70 showed 10–15% enhanced cell concentration during serum‐free adaptation and 15–33% reduction in adaptation time. Taken together, identification of differentially expressed proteins in rCHO cells by a proteomic study can provide insights into understanding the intracellular events and clues to find candidate genes for cell engineering for improved performance of rCHO cells during adaptation to serum‐free suspension culture. © 2011 American Institute of Chemical Engineers Biotechnol. Prog., 2011
Enzyme activity evaluation of organic solvent‐treated phenylalanine ammonia lyase
Authors: Quinn Andrew J. , Pickup Margaret J. , D'Cunha Godwin B.
Published: August 2011

The direct one‐step synthesis of L‐phenylalanine methyl ester in an organic‐aqueous biphasic system using phenylalanine ammonia lyase (E.C.4.3.1.5, PAL) containing Rhodotorula glutinis yeast whole cells was reported earlier. We report here further optimization of this biotransformation using isolated PAL, when the lyophilized enzyme is treated with different water miscible and water immiscible organic solvents. Use of isolated PAL enzyme is advantageous in overcoming diffusion barriers encountered when using PAL containing R. glutinis whole cells, and resulted in increased product yield due to better interaction of enzyme with the substrate. Among the water miscible solvents, ethanol treated and methanol treated enzymes supported maximum PAL forward and reverse activities; respectively. In the water immiscible solvents category, heptane‐treated enzyme exhibited maximal activity for both PAL forward and reverse reactions. PAL activity obtained with enzyme specimens treated with methanol, ethanol, and heptane varied in the range of 91–99% of that observed in aqueous buffer medium for the forward reaction; and 89–95% for the reverse reaction. n‐butanol, acetone, and benzene were found to have a inhibitory effect on PAL enzyme, in that, it resulted in only 31–33% activity of that obtained with aqueous solution. Raman spectroscopy was used to monitor amide I and II bands which are sensitive to changes in the secondary structure of proteins. No changes in structure could be detected from the analyses of AI and AII bands of PAL spectra. This data obtained for PAL, a tetramer, could be significant in predicting how solvent interactions affect the structure and function of multimeric proteins and enzymes in nonaqueous media. © 2011 American Institute of Chemical Engineers Biotechnol. Prog., 2011
Dynamic Multicomponent Hemiaminal Assembly
Authors: You Lei , Long S. Reid , Lynch Vincent M. , Anslyn Eric V.
Published: August 2011

A simple approach to generating in situ metal‐templated tris‐(2‐picolyl)amine‐like multicomponent assemblies with potential applications in molecular recognition and sensing is reported. The assembly is based on the reversible covalent association between di‐(2‐picolyl)amine and aldehydes. Zinc ion is best for inducing assembly among the metal salts investigated, whereas 2‐picolinaldehyde is the best among the heterocyclic aldehydes studied. Although an equilibrium constant of 6.6×103 M−1 was measured for the assembly formed by 2‐picolinaldehdye, di‐(2‐picolyl)amine, and zinc triflate, the equilibrium constants for other systems are in the 102 M−1 range. X‐ray structural analysis revealed that zinc adopts trigonal‐bipyramidal geometry within the assembled ligand. The diversity and equilibrium of the assemblies are readily altered by simply changing concentrations, varying components, or adding counteranions.
SrP3N5O: A Highly Condensed Layer Phosphate Structure Solved from a Nanocrystal by Automated Electron Diffraction Tomography
Authors: Sedlmaier Stefan J. , Mugnaioli Enrico , Oeckler Oliver , Kolb Ute , Schnick Wolfgang
Published: August 2011

The oxonitridophosphate SrP3N5O has been synthesized by heating a multicomponent reactant mixture that consisted of phosphoryl triamide OP(NH2)3, thiophosphoryl triamide SP(NH2)3, SrS, and NH4Cl enclosed in evacuated and sealed silica‐glass ampoules up to 750 °C. The compound was obtained as nanocrystalline powder with needle‐shaped crystallites. The crystal structure was solved ab initio on the basis of electron diffraction data by means of automated electron diffraction tomography (ADT) and verified by Rietveld refinement with X‐ray powder diffraction data. SrP3N5O crystallizes in the orthorhombic space group Pnma (no. 62) with unit‐cell data of a=18.331(2), b=8.086(1), c=13.851(1) Å and Z=16. The compound is a highly condensed layer phosphate with a degree of condensation κ=1/2. The corrugated layers ${{{\hfill 2\atop \hfill \infty }}}${(P3N5O)2−} consist of linked, triangular columns built up from P(O,N)4 tetrahedra with 3‐rings and triply binding nitrogen atoms. The Sr2+ ions are located between the layers and exhibit six‐, eight‐, and ninefold coordination. FTIR and solid‐state NMR spectra of SrP3N5O are discussed as well.
Preparation of Mononuclear, Homodinuclear, and Heterotrinuclear Complexes by Salicylaldiminato‐Functionalized Imidazolium Salt: Approach to Multifunctional Catalysts
Authors: Zhong Rui , Wang Ya‐Nong , Guo Xu‐Qing , Chen Zhen‐Xia , Hou Xiu‐Feng
Published: August 2011

A salicylaldiminato imidazolium salt that bears both a Schiff base and imidazolium salt moiety was used to synthesize heterometallic compounds that could serve as multifunctional catalysts in certain reactions. The successful preparation of seven mononuclear compounds with a variety of transition metals (Pd, Ir, Ru, Zn, Ni) illustrated the high versatility of this class of ligands, which is crucial for the design of catalysts. Synthesis of homodinuclear compounds and heterotrinuclear compounds provided practical methods to connect multiple metal fragments through these ligands. The heterotrinuclear complex (Ni/Ir) was employed as a catalyst in the reaction of dehalogenation/transfer hydrogenation of halo‐acetophenones. The preliminary catalytic study showed that this heterometallic species is more active than a combination of the corresponding monometallic species.