bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetic Investigation of Poly(ethylene glycol) Hydrogel Formation via Perfusion‐Based Frontal Photopolymerization: Influence of Free‐Radical Polymerization Conditions on Frontal Velocity and Swelling Gradients
Authors: Turturro Michael V. , Rendón Daniela María Vélez , Teymour Fouad , Papavasiliou Georgia
Published: January 2013

Poly(ethylene glycol) diacrylate (PEGDA) hydrogels are extensively used as scaffolds in tissue engineering. The ability to spatially control hydrogel properties is critical for designing scaffolds that direct cell behavior and tissue regeneration. To this end, we have recently developed a polymerization technique, perfusion‐based frontal photopolymerization, to generate tunable gradients in PEG hydrogels. This study explores the effects of polymerization conditions on the velocity of the propagating front and its influence on gradients in hydrogel swelling. Alterations in photoinitiator perfusion rate result in the largest variations in frontal velocity and in the magnitude of the swelling gradient among all polymerization conditions investigated.

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Generalized poroelastic wellbore problem
Authors: Mehrabian Amin , Abousleiman Younane N.
Published: January 2013

This paper presents a novel analytical solution to the transient, z‐dependent, and asymmetric problem of an infinite wellbore drilled into a fluid‐saturated porous medium. The formulations are based on Biot's linear theory of poroelasticity, in which the dependency of poroelastic field variables to spatial coordinates as well as time domain is considered in the most general form. This gives flexibility to the solution in cases that cannot be analyzed using the conventional plane strain or symmetric models. One such case is when calculating the stress variations around an inclined wellbore where the far‐field stresses are acting over a finite vertical section. The results of our solution to this case with a three‐dimensional state of far‐field stress are used to analyze the stability of inclined wellbores passing through abnormally stressed formations.

The presented solution is capable of finding expressions for fundamental solutions with stress or flow boundary conditions at the wellbore. These solutions are here adopted to analyze the pressure disturbances generated by multiprobe formation tester, a standard wireline device that is designed for downhole fluid sampling as well as estimating the directional permeabilities of subsurface earth formations. A comparison with the conventional solution for the relevant pressure diffusion equation indicates that the poroelastic effect is relatively significant in relation to the transient response of the pore pressure. Further, it is shown that the finite dimensions of sink probe would, to a great extent, contribute to the formation's pore pressure variations at its immediate proximity. Copyright © 2013 John Wiley & Sons, Ltd.
A stabilized assumed deformation gradient finite element formulation for strongly coupled poromechanical simulations at finite strain
Authors: Sun WaiChing , Ostien Jakob T. , Salinger Andrew G.
Published: January 2013

An adaptively stabilized finite element scheme is proposed for a strongly coupled hydro‐mechanical problem in fluid‐infiltrating porous solids at finite strain. We first present the derivation of the poromechanics model via mixture theory in large deformation. By exploiting assumed deformation gradient techniques, we develop a numerical procedure capable of simultaneously curing the multiple‐locking phenomena related to shear failure, incompressibility imposed by pore fluid, and/or incompressible solid skeleton and produce solutions that satisfy the inf‐sup condition. The template‐based generic programming and automatic differentiation (AD) techniques used to implement the stabilized model are also highlighted. Finally, numerical examples are given to show the versatility and efficiency of this model. Copyright © 2013 John Wiley & Sons, Ltd.
Soil‐pile interaction in the pile vertical vibration considering true three‐dimensional wave effect of soil
Authors: Wu W.B. , Wang K.H. , Zhang Z.Q. , Leo Chin Jian
Published: January 2013

The dynamic response of an end bearing pile embedded in a linear visco‐elastic soil layer with hysteretic type damping is theoretically investigated when the pile is subjected to a time‐harmonic vertical loading at the pile top. The soil is modeled as a three‐dimensional axisymmetric continuum in which both its radial and vertical displacements are taken into account. The pile is assumed to be vertical, elastic and of uniform circular cross section. By using two potential functions to decompose the displacements of the soil layer and utilizing the separation of variables technique, the dynamic equilibrium equation is uncoupled and solved. At the interface of soil‐pile system, the boundary conditions of displacement continuity and force equilibrium are invoked to derive a closed‐form solution of the vertical dynamic response of the pile in frequency domain. The corresponding inverted solutions in time domain for the velocity response of a pile subjected to a semi‐sine excitation force applied at the pile top are obtained by means of inverse Fourier transform and the convolution theorem. A comparison with two other simplified solutions has been performed to verify the more rigorous solutions presented in this paper. Using the developed solutions, a parametric study has also been conducted to investigate the influence of the major parameters of the soil‐pile system on the vertical vibration characteristics of the pile. Copyright © 2013 John Wiley & Sons, Ltd.
Axial kinematic response of end‐bearing piles to P waves
Authors: Anoyatis George , Di Laora Raffaele , Mylonakis George
Published: January 2013

Kinematic pile–soil interaction under vertically impinging seismic P waves is revisited through a novel continuum elastodynamic solution of the Tajimi type. The proposed model simulates the steady‐state kinematic response of a cylindrical end‐bearing pile embedded in a homogeneous viscoelastic soil stratum over a rigid base, subjected to vertically propagating harmonic compressional waves. Closed‐form solutions are obtained for the following: (i) the displacement field in the soil and along the pile; (ii) the kinematic Winkler moduli (i.e., distributed springs and dashpots) along the pile; (iii) equivalent, depth‐independent, Winkler moduli to match the motion at the pile head. The solution for displacements is expressed in terms of dimensionless transfer functions relating the motion of the pile head to the free‐field surface motion and the rock motion. It is shown that (i) a pile foundation may significantly alter (possibly amplify) the vertical seismic excitation transmitted to the base of a structure and (ii) Winkler moduli pertaining to kinematic loading differ from those for inertial loading. Simple approximate expressions for kinematic Winkler moduli are derived for use in applications. Copyright © 2013 John Wiley & Sons, Ltd.
A polyhedral study of the capacity formulation of the multilayer network design problem
Authors: Mattia Sara
Published: January 2013

A multilayer network is a hierarchical network where each layer is built using the components of the previous one. Optical networks are an example of two layered networks. The multilayer network design problem consists of installing minimum cost integer capacities on the edges of all the layers so that a set of demands can be routed on the network. In this article, two versions of the optical network design problem are studied, and polyhedral results for the corresponding capacity formulations are presented. We also show how to extend the results to a network with an arbitrary number of layers. © 2013 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2013
Parametrized relocation of low‐mobility resources
Authors: Wildstrom D. Jacob
Published: January 2013

Relocation of service‐providers in response to changing real‐time needs is suboptimal due to limited foreknowledge of client requests. Simple cost schedules for relocation and remote‐service provision have been investigated both for the possibility of complete optimizability and the degree of inefficiency introduced by imperfect future knowledge. This work further explores a parametrization developed for reflecting limitations in the mobility of some resources. The optimizability response to this parameter exhibits two significant thresholds. Below the first threshold, optimization is trivial, but many real‐world resource‐location problems correspond to parameter values past the second threshold. This work explores both the value of the second threshold and the behavior of optimal limited‐lookahead responses for resources whose immobility places them past this threshold. It is determined that, for resources of sufficiently high immobility α, it is possible with finite lookahead to achieve a relocation schedule which is within a ratio of (1+α) of the optimal omniscient schedule. © 2013 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2013
In vitro sealing of iatrogenic fetal membrane defects by a collagen plug imbued with fibrinogen and plasma
Authors: Engels A. C. , Hoylaerts M. F. , Endo M. , Loyen S. , Verbist G. , Manodoro S. , DeKoninck P. , Richter J. , Deprest J. A.
Published: January 2013

Objectives

We aimed to demonstrate local thrombin generation by fetal membranes, as well as its ability to generate fibrin from fibrinogen concentrate. Furthermore, we aimed to investigate the efficacy of collagen plugs, soaked with plasma and fibrinogen, to seal iatrogenic fetal membrane defects.

Methods

Thrombin generation by homogenized fetal membranes was measured by calibrated automated thrombography. To identify the coagulation caused by an iatrogenic membrane defect, we analyzed fibrin formation by optical densitometry, upon various concentrations of fibrinogen. The ability of a collagen plug soaked with fibrinogen and plasma was tested in an ex vivo model for its ability to seal an iatrogenic fetal membrane defect.

Results

Fetal membrane homogenates potently induced thrombin generation in amniotic fluid and diluted plasma. Upon the addition of fibrinogen concentrate, potent fibrin formation was triggered. Measured by densiometry, fibrin formation was optimal at 1250 µg/mL fibrinogen in combination with 4% plasma. A collagen plug soaked with fibrinogen and plasma sealed an iatrogenic membrane defect about 35% better than collagen plugs without these additives (P = 0.037).

Conclusions

These in vitro experiments suggest that the addition of fibrinogen and plasma may enhance the sealing efficacy of collagen plugs in closing iatrogenic fetal membrane defects. © 2013 John Wiley & Sons, Ltd.
Low‐temperature cure high‐performance cyanate ester resins/microencapsulated catalyst systems
Authors: Chen Feng , Yuan Li , Gu Aijuan , Lin Chao , Liang Guozheng
Published: January 2013

The encapsulated catalyst can be released under stimulation conditions to control the polymerization reaction. In this study, poly(urea‐formaldehyde) (PUF) microcapsules (MCs) filled with dibutyltin dilaurate (DBTDL) catalyst (PUF/DBTDL MCs) were applied to bisphenol A dicyanate ester (BADCy) resins to develop a novel low temperature cure high performance BADCy/MCs systems. The effect of PUF/DBTDL MCs on the reactivity of BADCy was investigated. The mechanical property, the thermal property, the water uptake, and the dielectric property of cured BADCy/MCs resin systems were discussed in detail. Results indicate that roughly varying the content of the encapsulated DBTDL can easily and safely adjust the polymerization temperature. The BADCy systems with proper content of MCs cured at low temperature show excellent mechanical property, good thermal property, low water uptake, and low dielectric property. When the content of MCs is 0.125 wt%, the cured BADCy/MCs system has the optimal integrated properties owing to the formation of more uniform crosslinked structure and high conversion of cyanate ester (OCN) groups resulting from the slow release of DBTDL catalyst through the wall shell under heating condition. POLYM. ENG. SCI., 2013. © 2013 Society of Plastics Engineers
Electrodeposited Cu2ZnSnSe4 thin film solar cell with 7% power conversion efficiency
Authors: Guo Lian , Zhu Yu , Gunawan Oki , Gokmen Tayfun , Deline Vaughn R. , Ahmed Shafaat , Romankiw Lubomyr T. , Deligianni Hariklia
Published: January 2013

High performance Cu2ZnSnSe4 (CZTSe) photovoltaic materials were synthesized by electrodeposition of metal stack precursors followed by selenization. A champion solar cell with 7.0% efficiency is demonstrated. This is the highest efficiency among all of the CZTSe solar cells prepared from electrodeposited metallic precursors reported to‐date. Device parameters are discussed from the perspective of material microstructure and composition in order to improve performance. In addition, a high performance electrodeposited CZTS (S only) solar cell was demonstrated and its device characteristics were compared against the CZTSe (Se only) cell. Using secondary ion mass spectrometry for the analysis of the chemical composition of the absorber layer, a higher concentration of oxygen in the electrodeposited absorber is thought to be the root cause of the lower performance of the electrodeposited CZTS or CZTSe solar cells with respect to a solar cell fabricated by evaporation. The grain boundary areas of Sn‐rich composition are thought to be responsible for the lower shunt resistance commonly observed in CZTSe devices. We measured the longest minority carrier lifetime of 18 ns among all reported kesterite devices. This work builds a good baseline for obtaining higher efficiency earth‐abundant solar cells, while it highlights electrodepositon as a low cost and feasible method for earth‐abundant thin film solar cell fabrication. Copyright © 2013 John Wiley & Sons, Ltd.
EFFECTIVE SCHOOL‐BASED SERVICE DELIVERY FOR STUDENTS WITH AUTISM SPECTRUM DISORDERS: WHERE WE ARE AND WHERE WE NEED TO GO
Authors: Sansosti Frank J. , Sansosti Jenine M.
Published: January 2013

School psychologists increasingly are called on to assess academic, behavioral, and social functioning of students with autism spectrum disorders (ASDs), as well as advocate for and assist in the development, implementation, and evaluation of evidence‐based instructional strategies across a wide variety of education contexts. In this study, we obtained information from trainers of school psychology and school psychologists to ascertain the current state of practice and to identify areas of change required for future training and practice. Overall, results of the study were encouraging and demonstrated that both trainers and practitioners engage in a variety of evidence‐based assessment and intervention practices. However, several areas for improvement were identified. Recommendations are provided for increased awareness and application of empirically validated assessment and intervention approaches specific to ASD populations. Areas of future recommended research also are provided.
A water soluble macromolecular nanobox having porphyrinic walls as a large host for giant guests
Authors: Mineo Placido , Spitaleri Fabiola , Scamporrino Emilio
Published: January 2013

Cyclic tetra{5,15‐di‐[p(ω‐methoxypolyethyleneoxy)phenyl]‐10,20‐[p‐oxyphenyl] methylen porphyrin}, cy‐[O‐(H2‐PTPEG2)‐O‐CH2‐]4, a water soluble macromolecule consisting of four porphyrin units [each with two long ω‐methoxypolyethyleneoxy (PEG) branches bound on its peripheral positions] linked by means of four methylenoxy bridges, was prepared by an interfacial etherification reaction. Structural and spectroscopic characterization of cy‐[O‐(H2‐PTPEG2)‐O‐CH2‐]4 and of its cobalt‐derivative {cy‐[O‐(Co‐PTPEG2)‐O‐CH2‐]4} was performed by means of MALDI‐TOF mass spectrometry, NMR, UV–vis, and circular dichroism spectroscopy. The data obtained from the cy‐[O‐(Co‐PTPEG2)‐O‐CH2‐]4/Gramicidin‐S mixture showed that some evident spectral changes were compatible with the formation of a supramolecular structure between the porphyrinic nanobox and the Gramicidin S (a polypeptide having a relevant pharmacological importance). These preliminary data highlight how cy‐[O‐(H2‐PTPEG2)‐O‐CH2‐]4 and/or its metalled derivatives, for their both chemical composition and structural arrangement, have promising properties for applications as a drug carrier in aqueous media. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013
A renaissance of color: New structures and building blocks for organic electronics
Authors: Robb Maxwell J. , Ku Sung‐Yu , Brunetti Fulvio G. , Hawker Craig J.
Published: January 2013

Natural dyes and pigments like indigo and its derivatives valued for their bright colors and photochemical stability has been used since antiquity. Recently, the need for better performing materials in the organic electronics field has inspired a resurgence of these historical molecules and their subsequent transformation into new families of π‐conjugated building blocks used to construct new (macro)molecular semiconductors. This Highlight will explore the renaissance of notable building blocks including diketopyrrolopyrrole, (iso)indigo, benzodipyrrolidone, and benzodifuranone, as well as nonfullerene acceptor structures 9,9′‐bifluorenylidene and quinacridone. In addition, as the organic electronics field continues to evolve, the design of molecules with precise structure and function embodies a new paradigm for the next generation of materials. Representative examples will be described that embrace this new model and point the direction for advanced technologies. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013
Novel pH‐responsive mixed‐charge copolymer brushes based on carboxylic acid and quaternary amine monomers
Authors: Demirci Serkan , Kinali‐Demirci Selin , Caykara Tuncer
Published: January 2013

In this study, we report on the fabrication of tunable mixed‐charged copolymer brushes consisting of negatively charged carboxylic acid monomer (4‐vinylbenzoic acid, VBA) and positively charged quaternary amine monomer ((ar‐vinylbenzyl)trimethylammonium chloride) via reversible addition–fragmentation chain transfer‐mediated polymerization. The copolymer brushes have negative charge under neutral and basic conditions, and are positively charged under acidic conditions owing to the protonation of the carboxylate groups. The copolymer brushes revealed a unique reversible wetting behavior with pH. The reversible properties of the copolymer brushes can be employed to regulate the adsorption of charged biomacromolecules such as DNA and proteins. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013
Dual behavior of excess electrons in rutile TiO2
Authors: Janotti A. , Franchini C. , Varley J. B. , Kresse G. , Van de Walle C. G.
Published: January 2013

The behavior of electrons in the conduction band of TiO2 and other transition‐metal oxides is key to the many applications of these materials. Experiments seem to produce conflicting results: optical and spin‐resonance techniques reveal strongly localized small polarons, while electrical measurements show high mobilities that can only be explained by delocalized free electrons. By means of hybrid functional calculations we resolve this apparent contradiction and show that small polarons can actually coexist with delocalized electrons in the conduction band of TiO2, the former being energetically only slightly more favorable. We also find that small polarons can form complexes with oxygen vacancies and ionized shallow‐donor impurities, explaining the rich spectrum of Ti3+ species observed in electron spin resonance experiments. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Wind‐gust parametrizations at heights relevant for wind energy: a study based on mast observations
Authors: Suomi I. , Vihma T. , Gryning S.‐E. , Fortelius C.
Published: January 2013

Wind gusts are traditionally observed and reported at the reference height of 10 m and most gust parametrization methods have been developed only for this height. In many practical applications, e.g. in wind energy, the relevant heights are, however, up to a few hundred metres. In this study, mean gustiness conditions were studied using observations from two coastal/archipelago weather masts in the Gulf of Finland (northern Europe) with observation heights between 30 and 143 m. Only moderate and strong wind cases were addressed. Both masts were located over relatively flat terrain but the local environment, and hence the surface roughness length, differed between the mast locations. The observations showed that above all the gust factor depended on the surface roughness. Stability had a more pronounced effect over the rough forested surface than over the smooth sea surface. At both locations the stability had a larger effect on gusts than the observation height. Two existing parametrization methods, developed for a 10 m reference height, were validated against the observations and a new parametrization was proposed. In the new method, the gust factor depends on the standard deviation of the wind speed, which is parametrized on the basis of the surface friction velocity, the Obukhov length and height and the boundary‐layer height. The new gust parametrization method outperformed the two older methods: the effects of surface roughness, stability and the height above the surface were well represented by the new method.
On‐line calibration of the vertical distribution of ensemble spread
Authors: Flowerdew Jonathan , Bowler Neill E.
Published: January 2013

The Met Office Global and Regional Ensemble Prediction System (MOGREPS) uses an on‐line inflation factor calculation to calibrate the spread of the ensemble in space and time and counteract the tendency of the Ensemble Transform Kalman Filter (ETKF) to underestimate analysis uncertainty. Sonde measurements are augmented with ATOVS brightness temperature observations to provide sufficient coverage across the globe. This paper describes how the scheme has been extended to improve the vertical distribution of spread. Separate inflation factors are derived for each of three ‘bands’ of model levels, loosely representing the boundary layer, troposphere and stratosphere. A continuous profile is ensured by linearly interpolating between the band centres. The error/spread relationship observed in each ATOVS channel is mapped onto the three bands using a set of weights obtained by integrating the appropriate Jacobians over the range of pressures covered by each band. These weights are found to be approximately constant, thanks to the small number of bands and the fact that near‐surface channels are not used over land. The revised initial perturbations lead to increased near‐surface spread which persists throughout the 72 h forecast and carries through to improved probabilistic scores. However, the near‐surface spread remains too small due to insufficient growth of spread by the forecast model. This suggests perturbation of sea‐surface temperatures, soil initial conditions, soil properties and boundary‐layer physics as priorities for future work.
The formation of ice in a long‐lived supercooled layer cloud
Authors: Westbrook C. D. , Illingworth A. J.
Published: January 2013

This article focuses on the characteristics of persistent thin single‐layer mixed‐phase clouds. We seek to answer two important questions: (i) how does ice continually nucleate and precipitate from these clouds, without the available ice nuclei becoming depleted? (ii) how do the supercooled liquid droplets persist in spite of the net flux of water vapour to the growing ice crystals? These questions are answered quantitatively using in situ and radar observations of a long‐lived mixed‐phase cloud layer over the Chilbolton Observatory.

Doppler radar measurements show that the top 500 m of cloud (the top 250 m of which is mixed‐phase, with ice virga beneath) is turbulent and well‐mixed, and the liquid water content is adiabatic. This well‐mixed layer is bounded above and below by stable layers. This inhibits entrainment of fresh ice nuclei into the cloud layer, yet our in situ and radar observations show that a steady flux of ≈︁100 m−2s−1 ice crystals fell from the cloud over the course of ∼1 day. Comparing this flux to the concentration of conventional ice nuclei expected to be present within the well‐mixed layer, we find that these nuclei would be depleted within less than 1 h. We therefore argue that nucleation in these persistent supercooled clouds is strongly time‐dependent in nature, with droplets freezing slowly over many hours, significantly longer than the few seconds residence time of an ice nucleus counter.

Once nucleated, the ice crystals are observed to grow primarily by vapour deposition, because of the low liquid water path (21 g m−2) yet vapour‐rich environment. Evidence for this comes from high differential reflectivity in the radar observations, and in situ imaging of the crystals. The flux of vapour from liquid to ice is quantified from in situ measurements, and we show that this modest flux (3.3 g m−2h−1) can be readily offset by slow radiative cooling of the layer to space.
Mobile Underwater Sensor Networks for Protection and Security: Field Experience at the UAN11 Experiment
Authors: Caiti Andrea , Calabrò Vincenzo , Munafò Andrea , Dini Gianluca , Lo Duca Angelica
Published: January 2013

The EU‐funded project UAN (Underwater Acoustic Network) was aimed at conceiving, developing, and testing at sea an innovative and operational concept for integrating underwater and above‐water sensors in a unique communication system to protect offshore and coastline critical infrastructures. This work gives details on the underwater part of the project. It introduces a set of original security features and gives details on the integration of autonomous underwater vehicles (AUVs) as mobile nodes of the network and as surveillance assets, acoustically controlled by the command and control center to respond against intrusions. Field results are given of the final UAN project sea trial, UAN11, held in May 2011 in Norway. During the experimental activities, a UAN composed of four fixed nodes, two AUVs, and one mobile node mounted on the supporting research vessel was operated continuously and integrated into a global protection system. In this article, the communication performance of the network is reported in terms of round‐trip time, packet loss, and average delivery ratio. The major results of the experiment can be thus summarized: the implemented network structure was successful in continuously operating over five days with nodes seamlessly entering and exiting the network; the performance of the network varied greatly with fluctuations in the acoustic channel; the addition of security features induced a minor degradation in network performance with respect to channel variation; the AUVs were successfully controlled from a remote station through acoustic signals routed by the network. © 2013 Wiley Periodicals, Inc.
Interval‐censored parametric regression survival models and the analysis of longitudinal trials
Authors: MacKenzie Gilbert , Peng Defen
Published: January 2013

This paper develops interval censoring likelihood methods in the context of parametric proportional hazard (PH) and non‐PH regression models in the longitudinal study setting to reanalyze the medical research council's randomized controlled trial of teletherapy in age‐related macular degeneration. We compare the performance of the interval censoring likelihood with proxy likelihoods that were used to analyze the original data. It is shown, analytically, that the use of such proxy likelihoods in selected PH models leads to biased estimators. Such estimators are artificially precise; further, the magnitude of their percentage bias is quantified in a data‐directed simulation study. For non‐PH models, we demonstrate that these results obtained from PH models do not hold uniformly and explain the implications of this finding for the reanalysis of proxy likelihood trial data. Our final analysis, of the age‐related macular degeneration trial data, based on fitting PH and non‐PH models, reassuringly confirms the published findings from the original trial. Copyright © 2013 John Wiley & Sons, Ltd.
Semiparametric transformation models for panel count data with correlated observation and follow‐up times
Authors: Li Ni , Zhao Hui , Sun Jianguo
Published: January 2013

The statistical analysis of panel count data has recently attracted a great deal of attention, and a number of approaches have been developed. However, most of these approaches are for situations where the observation and follow‐up processes are independent of the underlying recurrent event process unconditional or conditional on covariates. In this paper, we discuss a more general situation where both the observation and the follow‐up processes may be related with the recurrent event process of interest. For regression analysis, we present a class of semiparametric transformation models and develop some estimating equations for estimation of regression parameters. Numerical studies under different settings conducted for assessing the proposed methodology suggest that it works well for practical situations, and the approach is applied to a skin cancer study that motivated the study. Copyright © 2013 John Wiley & Sons, Ltd.
Testing for improvement in prediction model performance
Authors: Pepe Margaret Sullivan , Kerr Kathleen F. , Longton Gary , Wang Zheyu
Published: January 2013

Authors have proposed new methodology in recent years for evaluating the improvement in prediction performance gained by adding a new predictor,Y, to a risk model containing a set of baseline predictors,X, for a binary outcomeD. We prove theoretically that null hypotheses concerning no improvement in performance are equivalent to the simple null hypothesis thatYis not a risk factor when controlling forX,H0:P(D = 1 | X,Y) = P(D = 1 | X). Therefore, testing for improvement in prediction performance is redundant ifYhas already been shown to be a risk factor. We also investigate properties of tests through simulation studies, focusing on the change in the area under the ROC curve (AUC). An unexpected finding is that standard testing procedures that do not adjust for variability in estimated regression coefficients are extremely conservative. This may explain why the AUC is widely considered insensitive to improvements in prediction performance and suggests that the problem of insensitivity has to do with use of invalid procedures for inference rather than with the measure itself. To avoid redundant testing and use of potentially problematic methods for inference, we recommend that hypothesis testing for no improvement be limited to evaluation ofYas a risk factor, for which methods are well developed and widely available. Analyses of measures of prediction performance should focus on estimation rather than on testing for no improvement in performance. Copyright © 2013 John Wiley & Sons, Ltd.
Impact of a virtual resistor on the input admittance of a grid‐connected inverter
Authors: Rizqiawan Arwindra , Fujita Goro , Funabashi Toshihisa , Nomura Masakatsu
Published: January 2013

A grid‐connected inverter offers good operation and controllability; however, there is a risk of local instabilities due to particular control schemes. As long as the input admittance is positive at a particular resonance frequency, the risk of local instability can be suppressed. In this paper, an attempt to improve the input admittance of the grid‐connected inverter (GCI)[vnsn1] using a virtual resistor is proposed. The impact of the virtual resistor on the inverter's passivity is analyzed by observing the input admittance of the inverter. Numerical analysis shows that the employment of the virtual resistor gives better input admittance to the GCI, particularly in the low‐frequency regions. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
Wind Energy literature survey no. 27
Authors: Henriksen Lars Christian
Published: January 2013

As a service to readers, Wind Energy regularly conducts literature surveys and publishes lists of relevant articles drawn from recent issues of a large number of periodicals including: Journal of Wind Engineering and Industrial Aerodynamics, International Journal of Energy Research, Renewable Energy, Energy Sources, Journal of Solar Energy Engineering, American Institute of Aeronautics and Astronautics Journal, and Electric Power Components and Systems along with a number of periodicals published by the Institute of Electrical and Electronics Engineers and so on. The list is limited exclusively to journals not specifically devoted to wind energy and its applications. To assist the reader, the list is separated into broad categories. Although many papers fit several categories, each paper is listed only once under the category thought most appropriate. Please note that the inclusion in the list is not an endorsement of a paper's quality. Compiled by Lars Christian Henriksen, Department of Wind Energy, Technical University of Denmark, PO Box 49, DK‐4000 Roskilde, Denmark. Please e‐mail any suggestions to larh@dtu.dk. Copyright © 2012 John Wiley & Sons, Ltd.
Role of physical activity in tumor patients and possible underlying mechanisms
Authors: Bloch Wilhelm , Zopf Eva , Zimmer Philipp , Baumann Freerk T.
Published: January 2013

A growing knowledge regarding the influence of exercise on adverse physiologic outcomes associated with cancer and its treatment exists. Aside from its effects on psychological behavior, quality of life, and cancer-related fatigue, physical exercise can target physical and cardio-respiratory fitness, insulin regulation and metabolic syndrome, body weight and composition, and immune function in tumor patients. The increasing number of study results for different cancer types, which prove the positive influences of physical activity in cancer patients, changed the contradictory opinions which existed until the end of the last century. Although an increasing number of studies showing the positive effects of physical activity and more specifically of endurance and resistance training in cancer patients have been published, the underlying mechanisms are mostly unknown. Thus, we summarized the current knowledge of the effects of physical activity and specific training in different tumor entities with specific respect to the possible underlying mechanisms. Especially, the association between physical activity and (1) the improvement of fatigue and the role of free radicals in this process, (2) the counterbalance of tumor-induced cachexia, (3) the improvement of the immune system for supportive tumor treatment, and (4) the possible role of epigenetic modulation against tumor and tumor treatment-dependent adverse physiologic outcomes is focused.
Exercise in the setting of hematopoietic stem cell transplantation
Authors: Wiskemann Joachim
Published: January 2013

The procedure of hematopoietic stem cell transplantation (HSCT) is an intense treatment approach to cure patients from leukemia or lymphoma. Prior, during, and after HSCT, patients experience considerable physical and psychosocial distress. In light of the increasing number of successfully treated patients, the need is growing for evidence-based adjuvant therapy options, which are able to reduce treatment-related side effects and enhance the rehabilitation process. Exercise constitutes to be a promising intervention in this setting due to its multidimensional effectiveness. The purpose of this article was to review the current knowledge in the field of exercise and HSCT. Therefore, an electronic literature search in PubMed on the topic was performed. Twenty-nine articles could be identified and classified as relevant for this paper. Reviewed studies suggest that exercise training is an important therapeutic approach in the supportive care for transplant patients. Significant benefits from the exercise interventions have been reported for physical performance, quality of life (QoL), and fatigue status. Several other benefits, such as a more rapid immune recovery or alleviation of therapy-related side effects have been reported in some studies. Future studies should address existing methodological problems, identify further effect levels of exercise and integrate a long-term perspective for the participants in the context of hematopoietic stem cell transplantation. Furthermore, potential biological pathways of exercise in HSCT patients should be investigated.
Orthopaedic manifestations and diagnostic clues in children with Guillain–Barré syndrome
Authors: Matsushita Masaki , Kitoh Hiroshi , Itomi Kazuya , Kitakoji Takahiko , Iwata Koji , Mishima Kenichi , Ishiguro Naoki , Hattori Tadashi
Published: January 2013

Introduction

Guillain–Barré syndrome (GBS) is an acute inflammatory demyelinating polyneuropathy characterized by symmetric limb weakness. Children with GBS sometimes consult the orthopaedists because of limb pain and gait disturbance. The orthopaedists, however, are unfamiliar with GBS, since it has rarely been delineated in detail in the orthopaedic literature. In the present study, we specifically describe orthopaedic manifestations and diagnostic clues in pediatric GBS.

Methods

We reviewed seven patients with pediatric GBS in regard to age, gender, clinical symptoms, department at the first medical consultation, initial diagnosis, physical and laboratory findings, medical interventions, and the latest clinical outcome.

Results

There were five boys and two girls, with a mean age at presentation of 7.2 years. Gait disturbance associated with lower limb pain and weakness was the most frequent early clinical symptom. Among the five patients who presented initially at the orthopaedic department, three were misdiagnosed. Loss of deep tendon reflexes was seen in all patients. Anti-ganglioside antibodies were positive in three and protein levels of cerebrospinal fluid were elevated in five patients. Six patients recovered completely after intravenous immunoglobulin (IVIG) treatment, while one patient who had not undergone IVIG treatment showed minor residual disability.

Conclusions

Acute symmetrical limb pain and gait disturbance associated with loss of tendon reflexes were important clinical manifestations of pediatric GBS. Early diagnosis is essential to prevent delayed recovery, long-term weakness, and permanent functional disabilities.
Reduction osteoplasty for treating pneumosinus dilatans of the maxillary sinus
Authors: Hyun S M , Min J-Y , Jang Y J
Published: January 2013

Objective:

To report a patient with maxillary pneumosinus dilatans and facial deformity treated by reduction osteoplasty and reconstruction.

Case report:

This study describes the successful management of facial deformity in a 17-year-old male with maxillary pneumosinus dilatans. The patient's facial deformity of the maxillary sinus, which had been slowly progressing over a 10-year period, was managed by reduction osteoplasty and reconstruction using the maxillary bone, conchal cartilage and Tutoplast-processed fascia lata via a sublabial approach. This treatment yielded satisfactory functional and aesthetic outcomes.

Conclusion:

As pneumosinus dilatans of the maxillary sinus is uncommon, there is no established surgical treatment protocol. This surgical technique was less invasive than other described procedures and revealed good cosmetic results.
X.—The Genus Primula: Section Petiolares
Authors: Smith W. Wright , Fletcher H. R.
Published: January 2013

The establishment of Primula petiolaris and its allies as representing a distinct section of the genus was the work of Pax in Engler's Bot. Jahrb., x, 173 (1889). His definition of the section was reasonably adequate, allowance being made for the scanty material available to him. The main information at his disposal came from Wallich's diagnosis (1) of P. petiolaris in 1824 and Hooker's treatment (2) of that species and its varieties in 1882. The chief diagnostic marks instanced by Pax were the membranous leaves with very broad midrib and with sharply and closely erose-denticulate margin, the great variability in leaf-shape and in the degree of development of the scape, the rose-coloured flowers and the globose capsule. Very apposite were his comments on the difficulty in distinguishing the component species and his conviction that the many varieties of P. petiolaris may quite well represent individual species, although the lack of careful observations on living material compelled him to leave within that aggregate even such plants as P. Tanneri. Pax's conception of the confines of his section was better exemplified by his choice of its components than by his diagnosis.
MEDICAL TECHNOLOGY AT HOME: SAFETY-RELATED ITEMS IN TECHNICAL DOCUMENTATION
Authors: Hilbers Ellen S.M. , de Vries Claudette G.J.C.A , Geertsma Robert E.
Published: January 2013

Objectives: This study aimed to investigate the technical documentation of manufacturers on issues of safe use of their device in a home setting.

Methods: Three categories of equipment were selected: infusion pumps, ventilators, and dialysis systems. Risk analyses, instructions for use, labels, and post market surveillance procedures were requested from manufacturers. Additionally, they were asked to fill out a questionnaire on collection of field experience, on incidents, and training activities.

Results: Specific risks of device operation by lay users in a home setting were incompletely addressed in the risk analyses. A substantial number of user manuals were designed for professionals, rather than for patients or lay carers. Risk analyses and user information often showed incomplete coherence. Post market surveillance was mainly based on passive collection of field experiences.

Conclusions: Manufacturers of infusion pumps, ventilators, and dialysis systems pay insufficient attention to the specific risks of use by lay persons in home settings. It is expected that this conclusion is also applicable for other medical equipment for treatment at home. Manufacturers of medical equipment for home use should pay more attention to use errors, lay use and home-specific risks in design, risk analysis, and user information. Field experiences should be collected more actively. Coherence between risk analysis and user information should be improved. Notified bodies should address these aspects in their assessment. User manuals issued by institutions supervising a specific home therapy should be drawn up in consultation with the manufacturer.
Human metapneumovirus infections are associated with severe morbidity in hospitalized children of all ages
Authors: HAHN A. , WANG W. , JAGGI P. , DVORCHIK I. , RAMILO O. , KORANYI K. , MEJIAS A.
Published: January 2013

The impact of human metapneumovirus (HMPV) in children aged >5 years and the risk factors associated with disease severity for all ages have not been well characterized. A retrospective cohort study of 238 children aged 0–15 years hospitalized over a 3-year period was performed. Medical records were reviewed for demographic information, clinical parameters and outcomes. Multivariable analyses were performed to identify independent factors associated with worse disease severity assessed by length of hospital stay (LOS), need for ICU care, respiratory support, and a disease severity score. Pulmonary diseases were associated with all outcomes of care, while congenital heart disease (CHD) and neuromuscular disorders were associated with longer LOS, and CHD and trisomy 21 were associated with worse severity scores independent of other covariables. Fever, retractions, use of steroids and albuterol were also associated with enhanced disease severity. Understanding the determinants of HMPV disease in children may help design targeted preventive strategies.
Recurrent epidemic cholera with high mortality in Cameroon: persistent challenges 40 years into the seventh pandemic
Authors: CARTWRIGHT E. J. , PATEL M. K. , MBOPI-KEOU F. X. , AYERS T. , HAENKE B. , WAGENAAR B. H. , MINTZ E. , QUICK R.
Published: January 2013

Cameroon has experienced recurrent cholera epidemics with high mortality rates. In September 2009, epidemic cholera was detected in the Far North region of Cameroon and the reported case-fatality rate was 12%. We conducted village-, healthcare facility- and community-level surveys to investigate reasons for excess cholera mortality. Results of this investigation suggest that cholera patients who died were less likely to seek care, receive rehydration therapy and antibiotics at a healthcare facility, and tended to live further from healthcare facilities. Furthermore, use of oral rehydration salts at home was very low in both decedents and survivors. Despite the many challenges inherent to delivering care in Cameroon, practical measures could be taken to reduce cholera mortality in this region, including the timely provision of treatment supplies, training of healthcare workers, establishment of rehydration centres, and promotion of household water treatment and enhanced handwashing with soap.
Prevalence and genetic diversity of two adhesion-related genes, pilE and nadA, in Neisseria meningitidis in China
Authors: SUN X. , ZHOU H. , XU L. , YANG H. , GAO Y. , ZHU B. , SHAO Z.
Published: January 2013

The main Neisseria meningitidis adhesion molecules, type IV pili (Tfp) and Neisseria adhesion A (NadA), play important roles in the pathogenesis of invasive meningococcal disease. PilE is the major Tfp subunit. In this study, the prevalence and genetic diversity of pilE and nadA were investigated in the prevalent serogroups and clonal complexes (CC) of N. meningitidis isolated in China. All serogroup A strains belonging to CC1 and CC5 and all CC11 serogroup W135 strains were clustered into class II PilE clades. All serogroup C and most of serogroup B isolates except CC8 and ST5642 were class I PilE clades. Class II pilE sequences were highly conserved. All isolates belonging to class I PilE isolates were nadA negative. However, nadA-positive strains were exclusively found in CC5 and CC11 isolates (class II PilE). This study showed that PilE and NadA may be related to epidemic or endemic meningococcal disease.
Environmental Migration in the Asia-Pacific Region: Could We Hang Out Sometime?
Authors: MAYER Benoît
Published: January 2013

Several proposals for global legal governance of environmental migration have recently been published, almost exclusively by Western scholars. The present article denounces the geographical and intellectual disconnect between descriptive works on environmental migration as a phenomenon and the normative studies on the developments in law and governance. It suggests that this disconnect has resulted in a post-colonial approach towards tackling environmental migration, which could impede the protection of environmental migrants. While recalling that governance of environmental migration is most likely to succeed within a regional framework, this article pleads for a home-grown legal approach of environmental migration in the Asia-Pacific. Participating in a multilateral discussion is a unique opportunity for the rising countries of Asia and the Pacific to strengthen their growing diplomatic roles and to demonstrate their capacity in the development of liberal forms of transnational governance.