bluuebunny/crossref_metadata_2025 huggingface dataset:
On the monotonicity of some singular integral operators
Authors: Junghanns Peter , von Wolfersdorf Lothar
Published: April 2012

The paper deals with the monotonicity of singular integral operators of the form where is the Cauchy singular integral operator on the interval (0,1) of the real axis and q is a power or logarithmic function. Under suitable assumptions, such singular integral operators are proved to be monotone and maximal monotone in spaces with power weights. Moreover, two related integral equations with weakly singular kernels of logarithmic type are studied. Copyright © 2012 John Wiley & Sons, Ltd.
Activation of – N=CH – bond in a Schiff base by divalent nickel monitored by NMR evidence
Authors: Chandrakala M. , Nanje Gowda N. M. , Murthy K. G. S. , Nagasundara K. R.
Published: April 2012

The Schiff base, 2–salicylidene–4–aminophenyl benzimidazole in ethanol undergoes activation of –N=CH– bond by Ni2+ in the presence of ammonia or primary alkyl amine to produce nickel complexes of the formula Ni{o–C6H4(O)CH NR}2 . n H2O [R = H, Me; n = 0; R = Et, n = 0.5] and 4–aminophenyl benzimidazole. The products have been identified by elemental analysis, magnetic susceptibility measurements and IR, ESR, mass and extensive NMR spectral studies. The possible mechanism for the activation of –N=CH – bond has also been proposed. Copyright © 2012 John Wiley & Sons, Ltd.
Peculiarities of intramolecular exchange and valence tautomerism in metal semiquinolates determined by high‐resolution NMR spectroscopy
Authors: Voronov Vladimir K. , Ushakov Igor A. , Shmelev Vadim V. , Sagdeev Dmitry R.
Published: April 2012

The 1H NMR spectra of semiquinalate cobalt complex have been analyzed in a wide range of temperatures. It has been established that the intramolecular exchange requires the obligatory presence of a paramagnetic structure containing non‐compensated electron spin localized on the carbon atom of the ligand aromatic ring, the cobalt atom being trivalent. The presence of such a structure leads to the appearance of satellite signals in the NMR spectra because of the superfine interactions. Copyright © 2012 John Wiley & Sons, Ltd.
Thermal Polymerization of Styrene, Part 2 – (Mini)emulsion Polymerization
Authors: Katzer Johannes , Pauer Werner , Moritz Hans‐Ulrich , Wulkow Michael
Published: April 2012

An experimental and theoretical study on the thermal (spontaneous) polymerization of styrene in compartmentalized systems is presented. Experimental data on thermally polymerized miniemulsions varying temperature and droplet size is provided. This data is used to test a new model approach to describe the thermal polymerization process of a disperse phase. The mathematical model is based on a chemical master equation balancing radical species that are capable of desorption (monomeric radicals) and ones that cannot leave a particle. Reasonable agreement between theory and experiment for the data provided here and for literature data can be achieved. Part 1 of this series is a review on the thermal bulk polymerization of styrene.

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Effect of Hydrogen and External Donor on Propylene Polymerization Kinetics with a 4th‐Generation Ziegler‐Natta Catalyst
Authors: Alshaiban Ahmad , Soares João B. P.
Published: April 2012

Apparent kinetic rate constants and activation energies for catalyst activation, deactivation, and propylene propagation with a 4th‐generation Ziegler‐Natta catalyst are estimated. The rate of polymerization in the presence of donor and hydrogen is higher than in their absence. Catalyst activation and propagation rate constants increase with the addition of hydrogen, likely because hydrogen frees 2–1‐terminated dormant sites. The deactivation term was the highest without electron donor, presumably because the nonspecific sites deactivate faster than the specific sites. Apparent activation energies for catalyst activation, deactivation, and propagation are not significantly influenced by the presence of hydrogen or external donor, indicating that they do not affect these mechanisms substantially.

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Construction of tetrahedral meshes of degree two
Authors: George P.L. , Borouchaki H.
Published: April 2012

There is a need for finite elements of degree two or more to solve various PDE problems. This paper discusses a method to construct such meshes in the case of tetrahedral element of degree two. The first section of this paper returns to Bézier curves, Bézier triangles and then Bézier tetrahedra of degree two. The way in which a Bézier tetrahedron and a P2 finite element tetrahedron are related is introduced. A validity condition is then exhibited. Extension to arbitrary degree and dimension is given. A construction method is then proposed and demonstrated by means of various concrete application examples. Copyright © 2012 John Wiley & Sons, Ltd.
Modified meshless local Petrov–Galerkin formulations for elastodynamics
Authors: Soares D. , Sladek V. , Sladek J.
Published: April 2012

This paper is concerned with the extension to the elastodynamic problems of the idea of analytical integrations in meshless local weak formulations. In this context, Taylor series expansions of the incognita fields are considered, and the related integrals of the meshless formulations are solved analytically, rendering a so‐called modified methodology. The moving least squares approximation is employed for the spatial variation of the displacement fields, and two variants of the meshless local Petrov–Galerkin (MLPG) formulation are discussed here, which are based on the use of Heaviside or Gaussian weight test functions. Once the spatial discretization is considered, the semi‐discretized ordinary differential equations for nodal unknowns that arise are treated in the time‐domain by the Houbolt's method. Considering the modified meshless methodology, it was found that the standard derivatives of the shape functions must also be modified to achieve numerically stable procedures, taking into account dynamic analyses. Thus, an efficient and easy‐to‐implement technique is developed to properly compute the shape function derivatives. As described in the paper, the proposed modified MLPG formulations are more effective than standard MLPG formulations, especially taking into account well refined large scale problems, providing much better computational efficiency, good accuracy and more robust convergence. Copyright © 2012 John Wiley & Sons, Ltd.
Geometrical design of thermoelectric generators based on topology optimization
Authors: Takezawa A. , Kitamura M.
Published: April 2012

This paper discusses an application of the topology optimization method for the design of thermoelectric generators. The proposed methodology provides the optimized geometry in accordance with various arbitrary conditions such as the types of materials, the volume of materials, and the temperature and shape of the installation position. By considering the coupled equations of state for the thermoelectric problem, we introduce an analytical model subject to these equations, which mimics the closed circuit composed of thermoelectric materials, electrodes, and a resistor. The total electric power applied to the resistor and the conversion efficiency are formulated as objective functions to be optimized. The proposed optimization method for thermoelectric generators is implemented as a geometrical optimization method using the solid isotropic material with penalization method used in topology optimizations. Simple relationships are formulated between the density function of the solid isotropic material with penalization method and the physical properties of the thermoelectric material. A sensitivity analysis for the objective functions is formulated with respect to the density function and the adjoint equations required for calculating it. Depending on the sensitivity, the density function is updated using the method of moving asymptotes. Finally, numerical examples are provided to demonstrate the validity of the proposed method. Copyright © 2012 John Wiley & Sons, Ltd.
Immersed smoothed finite element method for two dimensional fluid–structure interaction problems
Authors: Zhang Zhi‐Qian , Liu G. R. , Khoo Boo Cheong
Published: April 2012

A novel method called immersed smoothed FEM using three‐node triangular element is proposed for two‐dimensional fluid–structure interaction (FSI) problems with largely deformable nonlinear solids placed within incompressible viscous fluid. The fluid flows are solved using the semi‐implicit characteristic‐based split method. Smoothed FEMs are employed to calculate the transient responses of solids based on explicit time integration. The fictitious fluid with two assumptions is introduced to achieve the continuous form of the FSI conditions. The discrete formulations to calculate the FSI forces are obtained in terms of the characteristic‐based split scheme, and the algorithm based on a set of fictitious fluid mesh is proposed for evaluating the FSI force exerted on the solid. The accuracy, stability, and convergence properties of immersed smoothed FEM are verified by numerical examples. Investigations on the mesh size ratio indicate that the stability is fairly independent of the wide range of the mesh size ratio. No additional volume correction is required to satisfy the incompressible constraints. Copyright © 2012 John Wiley & Sons, Ltd.
A note on upper bound formulations in limit analysis
Authors: Muñoz J.J. , Huerta A. , Bonet J. , Peraire J.
Published: April 2012

In this paper, we study some recent formulations for the computation of upper bounds in limit analysis. We show that a previous formulation presented by the authors does not guarantee the strictness of the upper bound, nor does it provide a velocity field that satisfies the normality rule everywhere. We show that these deficiencies are related to the quadrature employed for the evaluation of the dissipation power. We derive a formulation that furnishes a strict upper bound of the load factor, which in fact coincides with a formulation reported in the literature. From the analysis of these formulations, we propose a post‐process, which consists in computing exactly the dissipation power for the optimum upper bound velocity field. This post‐process may further reduce the strict upper bound of the load factor in particular situations. Finally, we also determine the quadratures that must be used in the elemental and edge gap contributions, so that they are always positive and their addition equals the global bound gap. Copyright © 2012 John Wiley & Sons, Ltd.
Risk factors for pressure ulcer development in critically Ill patients: A conceptual model to guide research
Authors: Benoit Richard , Mion Lorraine
Published: April 2012

This paper presents a proposed conceptual model to guide research on pressure ulcer risk in critically ill patients, who are at high risk for pressure ulcer development. However, no conceptual model exists that guides risk assessment in this population. Results from a review of prospective studies were evaluated for design quality and level of statistical reporting. Multivariate findings from studies having high or medium design quality by the National Institute of Health and Clinical Excellence standards were conceptually grouped. The conceptual groupings were integrated into Braden and Bergstrom's (Braden and Bergstrom [1987] Rehabilitation Nursing, 12, 8–12, 16) conceptual model, retaining their original constructs and augmenting their concept of intrinsic factors for tissue tolerance. The model could enhance consistency in research on pressure ulcer risk factors. © 2012 Wiley Periodicals, Inc. Res Nurs Health 35:340–362, 2012
Reliability and validity of the 4‐item perceived stress scale among pregnant women: Results from the OTIS antidepressants study
Authors: Karam Fatiha , Bérard Anick , Sheehy Odile , Huneau Marie‐Claude , Briggs Gerald , Chambers Christina , Einarson Adrienne , Johnson Diana , Kao Kelly , Koren Gideon , Martin Brigitte , Polifka Janine E. , Riordan Sara H. , Roth Mark , Lavigne Sharon Voyer , Wolfe Lori ,   the OTIS Research Committee
Published: April 2012

We aimed to estimate the reliability of the 4‐item Perceived Stress Scale (PSS) and its validity in predicting maternal depression and quality of life (QoL). Data regarding stress, depression and QoL were collected during pregnancy among a sub‐sample from the Organization of Teratology Information Specialists Antidepressants in Pregnancy Cohort. The 4‐item PSS demonstrated acceptable internal consistency (Cronbach's alpha coefficient = .79), alternate forms stability reliability with the 10‐item PSS (Pearson correlation coefficient r = .63; p < .001), convergent validity with the Edinburgh Postnatal Depression Scale (r = .67; p < .001), and concurrent validity with the mental health component of the Short‐Form‐12 (r = −.62; p < .001) as a measure of QoL. The 4‐item PSS is a valid and useful tool for assessing maternal stress during pregnancy. © 2012 Wiley Periodicals, Inc. Res Nurs Health 35:363–375, 2012
How we make donors feel: the relationship between premium benefit level and donor identity esteem
Authors: Sargeant Adrian , Shang Jen
Published: April 2012

Previous studies on promotions have tended to focus on the benefit to the organization of using different promotional benefit levels to incentivize purchase. By contrast, we focus on how perceptions of different benefit levels make individuals feel. We focus on the context of NPR membership where a station uses promotional premiums to incentivize giving to its annual fund. Employing a field survey of 25 895 donors, we find that premium benefit level is positively correlated with the importance of donor identity and negatively correlated with the private donor esteem associated with the organization.

Copyright © 2012 John Wiley & Sons, Ltd.
The macro and micro views of political marketing: the underpinnings of a theory of political marketing
Authors: Cwalina Wojciech , Falkowski Andrzej , Newman Bruce I.
Published: April 2012

The multi‐disciplinary nature of political marketing lends itself to a micro/macro analysis. The goal of the article is to present the theoretical frames allowing one to develop an approach to political marketing, which may become the foundations of a general theory of political marketing. Like microeconomics and macroeconomics are the two major categories within the field of economics, so are micro and macro approach to political marketing the two major perspectives that allow one to better understand the workings of modern democracies and the processes taking place there. Such an approach can integrate various theories of particular political behavior considered as part of an external macrostructure, understood as broad social, political, legal, economic, and technological context, with the theories of political behavior of individuals and institutions considered as internal microstructure. Copyright © 2012 John Wiley & Sons, Ltd.
Morphology and properties of biodegradable and biosourced polylactide blends with poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate)
Authors: Han Lijing , Han Changyu , Zhang Huiliang , Chen Shan , Dong Lisong
Published: April 2012

Biodegradable polymer blends based on biosourced polymers, namely polylactide (PLA) and poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate) (P(3HB‐co‐4HB)), were prepared by melt compounding. The effects of P(3HB‐co‐4HB) on the miscibility, phase morphology, thermal behavior, mechanical properties, and biodegradability of PLA/P(3HB‐co‐4HB) blends were investigated. The blend was an immiscible system with the P(3HB‐co‐4HB) domains evenly dispersed in the PLA matrix. However, the Tg of P(3HB‐co‐4HB) component in the blends decreased compared with neat P(3HB‐co‐4HB), which might be attributed to that the presence of the phase interface between PLA and P(3HB‐co‐4HB) resulted in enhanced chain mobility near interface. The addition of P(3HB‐co‐4HB) enhanced the cold crystallization of PLA in the blends due to the nucleation enhancement of PLA caused by the enhanced chain mobility near the phase interface between PLA and P(3HB‐co‐4HB) in the immiscible blends. With the increase in P(3HB‐co‐4HB) content, the blends showed decreased tensile strength and modulus; however, the elongation at beak was increased significantly, indicating that the inherent brittlement of PLA was improved by adding P(3HB‐co‐4HB). The interesting aspect was that the biodegradability of PLA is significantly enhanced after blends preparation. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers
Relationship of first‐trimester uterine artery Doppler to late stillbirth
Authors: Iacovella C. , Franchi M. , Egbor M. , Bhide A. , Thilaganathan B.
Published: April 2012

Objective

The aim of this study was to investigate if increased first‐trimester uterine artery Doppler resistance indices (RI) are related to stillbirth.

Method

Uterine artery Doppler indices were assessed prospectively during a routine first‐trimester ultrasound scan. Patients were categorised as having a high uterine artery mean Doppler RI if the index was above the 90th centile for gestation. Stillbirth outcomes were ascertained from a mandatory national register of pregnancy losses.

Results

High RI uterine artery Doppler (>90th centile) was an independent risk factor for late (≥34 weeks) but not early stillbirth, with a hazard ratio of 2.61 (95% CI 1.13–6.03). The inclusion of uterine artery Doppler indices into Cox proportional hazard model negated the influence of conventional risk factors for stillbirth, such as parity, maternal age and body mass index (BMI), but not Afro‐Caribbean ethnicity or smoking.

Conclusion

High first‐trimester uterine artery Doppler RI is associated with late stillbirth after 34 weeks' gestation. This association supersedes those of conventional risk factors such as maternal age, parity and BMI, implying that these factors result in an increased risk of stillbirth by causing placental dysfunction. © 2012 John Wiley & Sons, Ltd.
Sphenoidal fontanelle area measurement on rendered three‐dimensional ultrasound
Authors: Ioannou Christos , Sarris Ippokratis , Javaid Muhammad K. , Papageorghiou Aris T.
Published: April 2012

Objective

Rendered three‐dimensional images of the fetal cranial vault permit the identification of sutures and measurement of the fontanelle surface area. The objective of this study was to establish the feasibility and repeatability of sphenoidal fontanelle area measurement.

Method

Head volumes were obtained using the biparietal diameter as the reference plane. These were displayed with maximum rendering and the surface area of the sphenoidal fontanelle was measured by one operator. Feasibility was expressed as the percentage of scans with a successful measurement at different gestational ages. Repeatability was expressed as coefficient of variation (CV), intraclass correlation coefficient (ICC) and Bland–Altman plots.

Results

Thirty women underwent 141 scans. Feasibility of sphenoidal fontanelle measurement is over 90% before 26 weeks, but drops gradually thereafter and becomes 0% at 34 weeks. Intraobserver repeatability of measurement on the same scan image demonstrated CV = 17.5% and ICC = 0.883; however, when measuring a newly acquired volume, the repeatability is poor, CV = 30.7% and ICC = 0.649.

Conclusion

Although it is feasible to visualize the sphenoidal fontanelle on rendered three dimensions, its surface area measurement is not reliable for clinical use. There is potential to overestimate repeatability when remeasuring the same volume. © 2012 John Wiley & Sons, Ltd.
Maternal serum human chorionic gonadotropin and pregnancy‐associated plasma protein‐A in pregnancies with fetal homozygous α‐thalassemia‐1 disease
Authors: Tongprasert Fuanglada , Wanapirak Chanane , Tongsong Theera
Published: April 2012

Objective

To compare the levels of maternal serum free β‐hCG and PAPP‐A between pregnancies with fetal homozygous α‐thalassemia‐1 disease and unaffected pregnancies.

Materials and Methods

One hundred and forty eight pregnancies at risk for fetal homozygous α‐thalassemia‐1 disease scheduled for cordocentesis at 18 to 22 weeks were recruited into the study. Maternal serum free β‐hCG and PAPP‐A concentrations were measured before cordocentesis, and the final fetal diagnosis of homozygous α‐thalassemia‐1 disease was based on fetal Hb typing using high‐performance liquid chromatography.

Results

Maternal serum concentration of free β‐hCG was significantly higher in women with fetal homozygous α‐thalassemia‐1 disease than those with unaffected fetuses (P = 0.018), whereas the concentrations of PAPP‐A was not significantly different (P = 0.184). The median MoM of free β‐hCG in the affected group was 1.38 MoM and in the unaffected group was 0.88 MoM (P = 0.020).

Conclusion

At midpregnancy, maternal serum free β‐hCG levels are significantly higher in pregnancies with fetal homozygous α‐thalassemia‐1 disease, signifying that the disease could be a confounder for interpretation free β‐hCG level in Down syndrome screening program. Nevertheless PAPP‐A level seems to be similar in both groups. © 2012 John Wiley & Sons, Ltd.
Curing behavior of Azo‐containing twin liquid crystalline epoxy resins with anhydride
Authors: Zhou Dewen , Lu Mangeng , Liang Liyan , Shen Tengfei , Xiao Wanping
Published: April 2012

A series of novel azo‐containing twin liquid crystalline (LC) epoxy monomers were cured with anhydrides without extra catalyst, and the curing kinetics was investigated by non‐isothermal differential scanning calorimetry (DSC) technique. The results showed that the effect of phase behavior on activation energy (Ea) was enormous, which increased first and then decreased quickly with the curing reaction processing. The chemical kinetic control and diffusion‐control mechanisms dominate the curing together, which gives large values of Ea. Azo group also served as a catalyst to accelerate the curing reaction. The curing mechanism was confirmed by the UV–Vis spectra of azo‐doped curing system in which the absorbance values at 366 nm and 475 nm changed with the curing reaction processing. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers
The effect of molecular structure of polypropylene on stretchability for biaxially oriented film
Authors: Tamura Satoshi , Kuramoto Itaru , Kanai Toshitaka
Published: April 2012

Biaxially oriented polypropylene films are widely used for food packaging and industrial films. Recently, machine speed has been increasing in order to obtain higher production rate, and film thickness has become thinner to reduce the environmental load. The customers' requirements for better production ability and thinner films have been becoming more demanding, but their demands are not always met because of lack of film stretchability in the final product. To meet the demands, research on stretchability has been conducted with the goal of finding the optimum polypropylene molecular structure for developing a new product by analyzing stretching force–strain data using a table tenter, which was thought to be the parameter of stretchability. It was found that low crystallinity and wide molecular weight distribution were effective in improving the stretchability from the table tenter test. By running the test with a sequential and biaxially oriented stretching machine, it was verified that samples produced by the above designed polymer indicated good thickness uniformity, which was considered to be the barometer of stretchability. Furthermore, it was concluded that analyzing the stretching force–strain data obtained from a table tenter is a good method to predict machine speed and film thickness. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers
Material deformation and fatigue behavior characterization for elastomeric component life predictions
Authors: Zarrin‐Ghalami Touhid , Fatemi Ali
Published: April 2012

Failure analysis and prediction of fatigue life of elastomers are important issues due to wide usage of elastomeric components in many applications. Material deformation and fatigue characterization including both crack nucleation and crack growth are typically required for such analysis and predictions. This article discusses relevant material deformation properties obtained from experiments conducted under stress states of simple tension and planar tension. Cyclic transient behavior including Mullin's effect is also discussed. Then, fatigue crack initiation approach and experimental procedure and obtained data are discussed including modeling of the R ratio effect. Finally, based on the fracture mechanics approach, fatigue crack growth test procedure and properties are presented, including a model for R‐ratio effect. It is also shown that using the crack growth approach as a total fatigue life predictor gives reasonable results, as compared with the crack nucleation approach. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers
Convex Geometry for the Morphological Modeling and Characterization of Crystal Shapes
Authors: Reinhold Alexander , Briesen Heiko
Published: April 2012

To characterize crystals and other particles not only with respect to their size but also to their shape there has been increasing interest over the last decade. Though there are several studies on the geometric problems for single crystals and studies using morphological population balance equations for specific cases there is a lack of a systematic way to construct models for the growth of crystal populations with arbitrary shape. This is due to the geometrical complexity. The aim of this work is to exploit mathematical theories in the area of convex geometry to overcome this deficiency. By introducing an algebra for convex bodies, any convex crystal shape can be decomposed into a set of simple shapes called structuring elements. The decomposition is a linear combination from which generic equations for the calculation of any measure, like volume, surface area or mean diameter, can be easily derived. Importantly, all the required parameters for these measure calculations can be calculated a priori to any dynamic simulation. Ultimately, this allows the generic construction of morphological population balances to model crystal growth. Additionally, the combinatorial complexity is explored with respect to the computational effort. Although the concepts are developed for faceted crystals only, the framework may apply to a much broader class of convex particles.
Particle Size Management Studies on Spherical 3‐Nitro‐1,2,4‐triazol‐5‐one
Authors: Vijayalakshmi Ramavat , Radhakrishnan Sarangapani , Rajendra Patil S. , Girish Gore M. , Arun Sikder K.
Published: April 2012

Particle shape and size of an energetic material play a vital role in achieving explosive formulations with optimal performance that decides the realization of high bulk and theoretical maximum density (TMD) and mix fluidity during their processing. 3‐Nitro‐1, 2, 4‐triazol‐5‐one (NTO) is an insensitive thermally stable high explosive and explored as a potential replacement of RDX in explosive formulations. This study investigates the preparation of spherical NTO in NTO: water: 1‐methyl‐2‐pyrolidone ternary system and the particle size management of spherical NTO by cooling crystallization technique. Crystallization operation variables like cooling rate, agitator configuration, speed, etc. have been systematically studied to understand their effect on the spheroidization process. Synthesized spherical NTO has been characterized by spectral, thermal and microscopic studies. The study established the process parameters to achieve selective particle size distribution ranging from 10 to 200 μm. Bulk density of the spherical NTO has been determined and correlated with particle size distribution.
Synthesis and Characterization of Carbon Nanotubes Wrapped on Anatase Microparticles
Authors: Barone Pasquale , Barberio Marianna , Oliva Antonino , Bonanno Assunta
Published: April 2012

In this work we present a study of growth and characterization of a composite based on TiO2 (anatase form) and carbon nanotubes (CNT). The composite was prepared by the chemical mix techniques suggested in [1], improved by changing the recipe for what concerns solvent type, sonication and heating time to obtain a greater carbon nanotubes solubility. The prepared samples were characterized by SEM analysis, energy dispersed X‐ray measurements (EDX) and X‐ray photoelectron spectroscopy (XPS). The analysis showed that the sample is formed by a direct contact between CNT and anatase, with CNTs wrapped around anatase micrometer particles. XPS analysis shows the typical lines of TiO2 and CNTs (Ti2p and C1s), without any indication for the Ti‐C chemical bond, instead the detection of the O1s line can be attributed to both bonds, Ti‐O and C‐O. Finally the composite was compared with a similar sample obtained by evaporating Ti on a CNT substrate, as discussed in [2]. The two different techniques produce very different composites, the first one (chemical mix) exhibits a strong contact between CNTs and anatase particles which appear uniformly distributed in the sample, while the other technique (evaporation) shows two separated and superimposed films (titanium dioxide on CNT).
Solution structure studies of monomeric human TIP47/perilipin‐3 reveal a highly extended conformation
Authors: Hynson Robert M. G. , Jeffries Cy M. , Trewhella Jill , Cocklin Simon
Published: April 2012

Tail‐interacting protein of 47 kDa (TIP47) has two putative functions: lipid biogenesis and mannose 6‐phosphate receptor recycling. Progress in understanding the molecular details of these two functions has been hampered by the lack of structural data on TIP47, with a crystal structure of the C‐terminal domain of the mouse homolog constituting the only structural data in the literature so far. Our studies have first provided a strategy to obtain pure monodisperse preparations of the full‐length TIP47/perilipin‐3 protein, as well as a series of N‐terminal truncation mutants with no exogenous sequences. These constructs have then enabled us to obtain the first structural characterization of the full‐length protein in solution. Our work demonstrates that the N‐terminal region of TIP47/perilipin‐3, in contrast to the largely helical C‐terminal region, is predominantly β‐structure with turns and bends. Moreover, we show that full‐length TIP47/perilipin‐3 adopts an extended conformation in solution, with considerable spatial separation of the N‐ and C‐termini that would likely translate into a separation of functional domains. Proteins 2012;. © 2012 Wiley Periodicals, Inc.
Yield‐Related Process Capability Indices for Processes of Multiple Quality Characteristics
Authors: Shiau Jyh‐Jen Horng , Yen Chia‐Ling , Pearn W. L. , Lee Wan‐Tsz
Published: April 2012

Process capability indices (PCIs) have been widely used in industries for assessing the capability of manufacturing processes. Castagliola and Castellanos (Quality Technology and Quantitative Management 2005, 2(2):201–220), viewing that there were no clear links between the definition of the existing multivariate PCIs and theoretical proportion of nonconforming product items, defined a bivariate Cpk and Cp (denoted by BCpk and BCp, respectively) based on the proportions of nonconforming product items over four convex polygons for bivariate normal processes with a rectangular specification region. In this paper, we extend their definitions to MCpk and MCp for multivariate normal processes with flexible specification regions. To link the index to the yield, we establish a ‘reachable’ lower bound for the process yield as a function of MCpk. An algorithm suitable for such processes is developed to compute the natural estimate of MCpk from process data. Furthermore, we construct via the bootstrap approach the lower confidence bound of MCpk, a measure often used by producers for quality assurance to consumers. As for BCp, we first modify the original definition with a simple preprocessing step to make BCp scale‐invariant. A very efficient algorithm is developed for computing a natural estimator of BCp. This new approach of BCp can be easily extended to MCp for multivariate processes. For BCp, we further derive an approximate normal distribution for , which enables us to construct procedures for making statistical inferences about process capability based on data, including the hypothesis testing, confidence interval, and lower confidence bound. Finally, the proposed procedures are demonstrated with three real data sets. Copyright © 2012 John Wiley & Sons, Ltd.
Comparative assessment of QSTR models based on density functional, hartree–fock, AM1, and PM3 methods for acute toxicity of aliphatic compounds toward Vibrio fischeri
Authors: Pandith Altaf Hussain , Islam Nasarul
Published: April 2012

Comparative quantitative‐structure‐toxicity‐relationship models developed using various quantum chemical descriptors calculated at semiempirical (AM1, PM3), Hartree–Fock and density functional theory (DFT) (B3LYP) methods, are compared for predicting the toxicity (pIGC50) of 69 aliphatic compounds toward Vibrio fischeri. The multiple linear regression equations, which can assist in modeling toxicity of these compounds, are developed using molecular descriptor, log P (1‐octanol/water partition coefficient) in conjunction with two quantum chemical descriptors, electrophilicity index (ω) and energy of the lowest unoccupied molecular orbital (ELUMO). The calculated toxicity values (PIGC50) based on the model equations are compared with the experimental data. In general, the stepwise model regression equations based on quantum chemical descriptor ω in combination with molecular descriptor log P, calculated at DFT(B3LYP) with 6‐311G (d,p) and DGDVZP basis sets show better agreement with the experimental data. The electronic origin of the toxicity dependence on descriptors like log P, ω and ELUMO is traced to the cumulative contribution of the lipophilicity and electrophilicity of the chemical moieties to their toxic behavior. © 2012 Wiley Periodicals, Inc.
Non‐orthogonal tool/flange and robot/world calibration
Authors: Ernst Floris , Richter Lars , Matthäus Lars , Martens Volker , Bruder Ralf , Schlaefer Alexander , Schweikard Achim
Published: April 2012

Background

For many robot‐assisted medical applications, it is necessary to accurately compute the relation between the robot's coordinate system and the coordinate system of a localisation or tracking device. Today, this is typically carried out using hand‐eye calibration methods like those proposed by Tsai/Lenz or Daniilidis.

Methods

We present a new method for simultaneous tool/flange and robot/world calibration by estimating a solution to the matrix equation AX = YB. It is computed using a least‐squares approach. Because real robots and localisation are all afflicted by errors, our approach allows for non‐orthogonal matrices, partially compensating for imperfect calibration of the robot or localisation device. We also introduce a new method where full robot/world and partial tool/flange calibration is possible by using localisation devices providing less than six degrees of freedom (DOFs).

The methods are evaluated on simulation data and on real‐world measurements from optical and magnetical tracking devices, volumetric ultrasound providing 3‐DOF data, and a surface laser scanning device. We compare our methods with two classical approaches: the method by Tsai/Lenz and the method by Daniilidis.

Results

In all experiments, the new algorithms outperform the classical methods in terms of translational accuracy by up to 80% and perform similarly in terms of rotational accuracy. Additionally, the methods are shown to be stable: the number of calibration stations used has far less influence on calibration quality than for the classical methods.

Conclusion

Our work shows that the new method can be used for estimating the relationship between the robot's and the localisation device's coordinate systems. The new method can also be used for deficient systems providing only 3‐DOF data, and it can be employed in real‐time scenarios because of its speed. Copyright © 2012 John Wiley & Sons, Ltd.
Adaptive consensus with a virtual leader of multiple agents governed by locally Lipschitz nonlinearity
Authors: Hu Yuebing , Su Housheng , Lam James
Published: April 2012

This paper is concerned with the second‐order consensus problem of multi‐agent systems with a virtual leader, where all agents and the virtual leader share the same intrinsic dynamics with a locally Lipschitz condition. It is assumed that only a small fraction of agents in the group are informed about the position and velocity of the virtual leader. A connectivity‐preserving adaptive controller is proposed to ensure the consensus of multi‐agent systems, wherein no information about the nonlinear dynamics is needed. Moreover, it is proved that the consensus can be reached globally with the proposed control strategy if the degree of the nonlinear dynamics is smaller than some analytical value. Numerical simulations are further provided to illustrate the theoretical results. Copyright © 2012 John Wiley & Sons, Ltd.
Computationally efficient simultaneous policy update algorithm for nonlinear H∞ state feedback control with Galerkin's method
Authors: Luo Biao , Wu Huai‐Ning
Published: April 2012

The main bottleneck for the application of H∞ control theory on practical nonlinear systems is the need to solve the Hamilton–Jacobi–Isaacs (HJI) equation. The HJI equation is a nonlinear partial differential equation (PDE) that has proven to be impossible to solve analytically, even the approximate solution is still difficult to obtain. In this paper, we propose a simultaneous policy update algorithm (SPUA), in which the nonlinear HJI equation is solved by iteratively solving a sequence of Lyapunov function equations that are linear PDEs. By constructing a fixed point equation, the convergence of the SPUA is established rigorously by proving that it is essentially a Newton's iteration method for finding the fixed point. Subsequently, a computationally efficient SPUA (CESPUA) based on Galerkin's method, is developed to solve Lyapunov function equations in each iterative step of SPUA. The CESPUA is simple for implementation because only one iterative loop is included. Through the simulation studies on three examples, the results demonstrate that the proposed CESPUA is valid and efficient. Copyright © 2012 John Wiley & Sons, Ltd.
Measurement feedback control for a class of feedforward nonlinear systems
Authors: Jo Hyun‐Wook , Choi Ho‐Lim , Lim Jong‐Tae
Published: April 2012

We propose a measurement feedback controller for a class of feedforward nonlinear systems under sensor noise. The sensor noise has unknown magnitude, frequency, and phase. Our proposed controller is coupled with a low‐pass filter in such a way that the sensor noise is attenuated. We show that the controlled system results in bounded states whose ultimate bounds are inversely proportional to the minimum frequency of the sensor noise. Our result is further generalized to work in a case where the sensor noise is only required to have a Fourier transform with finite energy. Moreover, if the sensor noise enters only at partial states, depending on the location of the sensor noise, the ultimate bounds of the particular states can be made arbitrarily small via the gain factor of the controller. Copyright © 2012 John Wiley & Sons, Ltd.
Canonical form of para‐Hermitian pencils, generalized spectral factorization, and optimal control over frequency region
Authors: Stefanovski Jovan
Published: April 2012

We generalize the J‐spectral factorization of para‐Hermitian proper rational matrix in the case when it has no constant inertia on the imaginary axis. This result and the presented numerical algorithm are based on a canonical form of para‐Hermitian matrix pencils. We apply the new spectral factorization to the optimal control of the proper plant by dynamic measurement feedback over a frequency region. Copyright © 2012 John Wiley & Sons, Ltd.
Novel delay‐derivative‐dependent stability criteria using new bounding techniques
Authors: Zhang Xian‐Ming , Han Qing‐Long
Published: April 2012

This paper studies the stability of linear systems with interval time‐varying delays. By constructing a new Lyapunov–Krasovskii functional, two delay‐derivative‐dependent stability criteria are formulated by incorporating with two different bounding techniques to estimate some integral terms appearing in the derivative of the Lyapunov–Krasovskii functional. The first stability criterion is derived by using a generalized integral inequality, and the second stability criterion is obtained by employing a reciprocally convex approach. When applying these two stability criteria to check the stability of a linear system with an interval time‐varying delay, it is shown through some numerical examples that the first stability criterion can provide a larger upper bound of the time‐varying delay than the second stability criterion. Copyright © 2012 John Wiley & Sons, Ltd.
Passive and active acoustics using an autonomous wave glider
Authors: Bingham Brian , Kraus Nicholas , Howe Bruce , Freitag Lee , Ball Keenan , Koski Peter , Gallimore Eric
Published: April 2012

The recently developed wave glider has the potential to be an effective unmanned platform for acoustic applications. We present the results of a variety of experiments that quantify this potential. The radiated self‐noise of the autonomous platform is evaluated using an integrated passive acoustic recorder during a set of field trials off the coast of Hawaii. We present the radiated noise spectra from these trials to illustrate the dependence on hydrophone location and sea state. Using the same instrumentation, we demonstrate the ability of a modified wave glider to detect marine mammals using passive acoustic monitoring techniques. We also evaluate the performance of the wave glider operating as an active acoustic gateway, highlighting the potential of this platform to serve as a navigation reference and communications relay for scientific, industrial, and military subsea assets. To demonstrate the potential of the wave glider platform to support acoustic navigation, we assess the performance of time‐of‐flight range estimation and seafloor transponder localization. These tests were performed using commercial off‐the‐shelf acoustic positioning hardware integrated with the wave glider to illustrate that the low self‐noise of the wave glider makes it possible to achieve acoustic positioning performance similar to previously reported results. Finally, we show that the glider can operate as a station‐keeping surface communications gateway and provide recommendations for its use. © 2012 Wiley Periodicals, Inc.
Direct Volume Rendering Methods for Cell Structures
Authors: Martišek* Dalibor , Martišek Karel
Published: April 2012

The study of the complicated architecture of cell space structures is an important problem in biology and medical research. Optical cuts of cells produced by confocal microscopes enable two‐dimensional (2D) and three‐dimensional (3D) reconstructions of observed cells. This paper discuses new possibilities for direct volume rendering of these data. We often encounter 16 or more bit images in confocal microscopy of cells. Most of the information contained in these images is unsubstantial for the human vision. Therefore, it is necessary to use mathematical algorithms for visualization of such images. Present software tools as OpenGL or DirectX run quickly in graphic station with special graphic cards, run very unsatisfactory on PC without these cards and outputs are usually poor for real data. These tools are black boxes for a common user and make it impossible to correct and improve them. With the method proposed, more parameters of the environment can be set, making it possible to apply 3D filters to set the output image sharpness in relation to the noise. The quality of the output is incomparable to the earlier described methods and is worth increasing the computing time. We would like to offer mathematical methods of 3D scalar data visualization describing new algorithms that run on standard PCs very well. SCANNING 34: 367‐377, 2012. © 2012 Wiley Periodicals, Inc.
The dynamics of wealth, profit, and sustainable advantage
Authors: Jacobides Michael G. , Winter Sidney G. , Kassberger Stefan M.
Published: April 2012

This paper shows how idiosyncratic resources can drive sustained profitability and persistent heterogeneity under competitive conditions. Generic inputs purchased in the market become idiosyncratic resources as the result of firms' investments in customization. Analytically, we show how heterogeneous firms coexist in equilibrium as a function of customization costs. Computationally, we show that sustainable profits can emerge without ‘monopolistic’ imperfections. We consider how capability heterogeneity, resource customization cost, and ease of expansion interact to drive short‐run and sustainable profits. Our results illustrate that sustainable profits may represent a small part of the total wealth created over time by a firm or industry, and that changes in factors shaping a sector's evolutionary trajectory may be more important than changes in factors that determine profits' ultimate sustainability. Copyright © 2012 John Wiley & Sons, Ltd.
High‐Throughput Transfection of Interfering RNA into a 3D Cell‐Culture Chip
Authors: Zhang Haiyuan , Lee Moo‐Yeal , Hogg Michael G. , Dordick Jonathan S. , Sharfstein Susan T.
Published: April 2012

A method for high‐throughput retroviral transfection of genes and interfering RNA into 3D cell‐culture microarrays is described. 3D cultures more closely mimic the in vivo cellular milieu, thus providing cellular responses to genetic manipulation more similar to the in vivo situation than 2D cultures. This technique is applied to transfect several “toxic” short‐hairpin RNAs (shRNAs) into 3D cell cultures. It is demonstrated that the toxicity is similar to that obtained by conventional (non‐high‐throughput) retroviral transfection of cells grown in similar 3D culture microarrays.
Fabrication of a Carbon‐Nanotube‐Based Field‐Effect Transistor by Microcontact Printing
Authors: Mehlich Jan , Miyata Yasumitsu , Shinohara Hisanori , Ravoo Bart Jan
Published: April 2012

The fabrication of a field‐effect transistor with both channel material and source and drain electrodes made from carbon nanotubes (CNTs) through patterned deposition of CNT films by microcontact printing is described. Surfactant‐dispersed single‐walled CNTs are first separated into semiconducting and metallic fractions by gel filtration. The semiconducting and metallic CNTs are then sequentially transferred by dendrimer‐coated polydimethylsiloxane stamps onto dendrimer‐coated silicon wafers following a printing protocol optimized for this purpose. The resulting CNT micropatterns are visualized by atomic force microscopy. Semiconducting as well as metallic CNTs preserve their characteristic electronic properties within the transferred films. A device composed of a rather thick (ca. 5 nm) and densely patterned film of metallic CNTs cross‐printed on top of a thinner (ca. 1.5 nm) and less dense film of semiconducting CNTs shows the typical properties of a field‐effect transistor with the metallic CNT stripes as electrodes, the semiconductive CNT stripes as channel material, and the silicon substrate as gate electrode.