bluuebunny/crossref_metadata_2025 huggingface dataset:
An evaluation of the replicate pool method: quick estimation of genome‐wide linkage peak p‐values
Authors: Wigginton Janis E. , Abecasis Gonçalo R.
Published: April 2006

The calculation of empirical p‐values for genome‐wide non‐parametric linkage tests continues to present significant computational challenges for many complex disease mapping studies. The gold standard approach is to use gene dropping to simulate null genome scans. Unfortunately, this approach is too computationally expensive for many data sets of interest. An alternative, more efficient method for sampling null genome scans is to pre‐calculate pools of family‐specific statistics and then resample from these replicate pools to generate “pseudo‐replicate” genome scans. In this study, we use simulations to explore properties of the replicate pool p‐value estimator p̂RP and show that it provides an excellent approximation to the traditional gene‐dropping estimator for significantly less computational effort. While the computational efficiency of the replicate pool estimator is noticeable in almost all data sets, by applying the replicate pool method to several previously characterized data sets we show that savings in computational effort can be especially significant (on the order of 10,000‐fold or more) when one or more large families are analyzed. We also estimate replicate pool p‐values for the schizophrenia data described by Abecasis et al. and show that p̂RP closely approximates gene‐drop p‐values for all linkage peaks reported for this study. Lastly, we expand upon Song et al.'s previous work by deriving a conservative estimator of the variance for p̂RP that can easily be computed in practical settings.We have implemented the replicate pool method along with our variance estimator in a new program called Pseudo, which is the first widely available automated implementation of the replicate pool method. Genet. Epidemiol. 30, 2006. © 2006 Wiley‐Liss, Inc.
Testing for genetic heterogeneity in the genome search meta‐analysis method
Authors: Lewis Cathryn M. , Levinson Douglas F.
Published: April 2006

The Genome Search Meta‐Analysis (GSMA) method is widely used to detect linkage by pooling results of previously published genome‐wide linkage studies. The GSMA uses a non‐parametric summed rank statistic in 30 cM bins of the genome. Zintzaras and Ioannidis ([2005] Genet. Epidemiol. 28:123–137) developed a method of testing for heterogeneity of evidence for linkage in the GSMA, with three heterogeneity statistics (Q, Ha, B). They implement two testing procedures, restricted versus unrestricted for the summed rank within the bin. We show here that the rank‐unrestricted test provides a conservative test for high heterogeneity and liberal test for low heterogeneity in linked regions. The rank‐restricted test should therefore be used, despite the extensive simulations needed. In a simulation study, we show that the power to detect heterogeneity is low. For 20 studies of affected sib pairs, simulated assuming linkage in all studies to a gene with sibling relative risk of 1.3, the power to detect low heterogeneity using the Q statistic was 14%. With linkage present in 50% of the studies (to a gene with sibling relative risk of 1.4), the Q heterogeneity statistic had power of 29% to detect high heterogeneity. The power to detect linkage using the summed rank was high in both of these situations, at 98% and 79%, respectively. Although testing for heterogeneity in the GSMA is of interest, the currently available method provides little additional information to that provided by the summed rank statistic. Genet. Epidemiol. 2006. © 2006 Wiley‐Liss, Inc.
Facies development, depositional settings and sequence stratigraphy across the Ordovician–Silurian boundary: a new perspective from the Barrandian area of the Czech Republic
Authors: Štorch Petr
Published: April 2006

The Hirnantian and Llandovery sedimentary succession of the Barrandian area has been assigned to middle and outer clastic‐shelf depositional settings, respectively. Deposition was influenced by the remote Gondwanan glaciation and subsequent, long‐persisting, post‐glacial anoxia triggered by a current‐driven upwelling system. High‐resolution graptolite stratigraphy, based upon 19 formally defined biozones—largely interval zones—and five subzones, enabled a detailed correlation between 42 surface sections and boreholes, and enabled linking of the sedimentary record, graptoloid fauna dynamics, organic‐content fluctuations and spectral gamma‐ray curves. The Hirnantian and Llandovery succession has been subdivided into four biostratigraphically dated third‐order sequences (units 1–4). Time–spatial facies distribution recorded early and late Hirnantian glacio‐eustatic sea‐level lowstands separated by a remarkable mid‐Hirnantian rise in sea‐level. A major part of the post‐glacial sea‐level rise took place within the late Hirnantian. The highstand of Unit 2 is apparently at the base of the Silurian succession. Short‐term relative sea‐level drawdown and a third‐order sequence boundary followed in the early Rhuddanian upper acuminatus Zone. Early Aeronian and late Telychian sea‐level highstands and late Aeronian drawdown of likely eustatic origin belong to units 3 and 4. Sea‐level rise culminated in the late Telychian, which may also be considered as a highstand episode of a second‐order Hirnantian–early Silurian cycle. Facies and sequence‐stratigraphic analysis supports recent interpretations on nappe structures in the core part of the Ordovician–Middle Devonian Prague Synform of the Barrandian. Copyright © 2006 John Wiley & Sons, Ltd.
Stratigraphy and volcanology of the Türkbükü volcanics: products of a stratovolcano in the Bodrum Peninsula, SW Anatolia
Authors: Karacik Zekiye
Published: April 2006

The Middle‐Upper Miocene Bodrum magmatic complex of the Aegean region, southwestern Turkey, is mainly represented by intermediate stocks, lavas, pyroclastic and volcaniclastic deposits. Monzonitic stocks and connected porphyry intrusions and extrusions are the first products of the magmatism. These are followed by a volcanic succession consisting of andesitic‐latitic lavas, autobrecciated lavas, pyroclastic and volcaniclastic deposits. The final stage is represented by basaltic and basaltic andesitic flows and dykes intruded into previous units.

The volcanic succession crops out in the northern part of the Bodrum peninsula. In the lower part of this succession are widespread pyroclastic deposits, composed of pyroclastic fall and flow units, alternating with epiclastic deposits. Grain size, volume and thickness of the pyroclastic deposits were mainly controlled by the type, magnitude and intensity of the eruption. Further up the section, there are two horizons of debris avalanche deposits forming the coarsest and thickest deposits of the volcaniclastic succession. The debris avalanche deposits indicate at least two different flank collapses coeval with the volcanism. The stratigraphy and map pattern of these volcanic units imply that the northern part of the Bodrum peninsula was the north‐facing flank of a stratovolcano during the mid‐Late Miocene. Copyright © 2006 John Wiley & Sons, Ltd.
Analytical solution of water table fluctuations above an inclined leaky layer due to ditch recharge
Authors: Hung Chien‐Jen , Tan Yih‐Chi , Chen Chu‐Hui , Chen Jiann‐Mou , Chang Po‐Wen
Published: April 2006

Ditch recharge is a method used for raising a water table. However, if the aquifer lies above a leaky layer, then the leaky bed will have an effect on the height of the water table. This paper attempts to provide an analytical solution of the transient state to the linearized Boussinesq equation. The solution proposed in this paper is intended for a generalized form of the leaky layer, with the boundary condition of the water level moving according to an exponential form. The results of theoretical analysis and experimental studies can provide a much better explanation of ditch recharge on an inclined leaky layer. Copyright © 2006 John Wiley & Sons, Ltd.
Regionalizing mean annual flow and daily flow variability for basin‐scale sediment and nutrient modelling
Authors: Wilkinson Scott N. , Young William J. , DeRose Ron C.
Published: April 2006

River discharges vary strongly through time and space, and quantifying this variability is fundamental to understanding and modelling river processes. The river basin is increasingly being used as the unit for natural resource planning and management; to facilitate this, basin‐scale models of material supply and transport are being developed. For many basin‐scale planning activities, detailed rainfall‐runoff modelling is neither necessary nor tractable, and models that capture spatial patterns of material supply and transport averaged over decades are sufficient. Nevertheless, the data to describe the spatial variability of river discharge across large basins for use in such models are often limited, and hence models to predict river discharge at the basin scale are required. We describe models for predicting mean annual flow and a non‐dimensional measure of daily flow variability for every river reach within a drainage network. The models use sparse river gauging data, modelled grid surfaces of mean annual rainfall and mean annual potential evapotranspiration, and a network accumulation algorithm. We demonstrate the parameterization and application of the models using data for the Murrumbidgee basin, in southeast Australia, and describe the use of these predictions in modelling sediment transport through the river network. The regionalizations described contain less uncertainty, and are more sensitive to observed spatial variations in runoff, than regionalizations based on catchment area and rainfall alone. Copyright © 2006 John Wiley & Sons, Ltd.
Groundwater quality in Mesogea basin in eastern Attica (Greece)
Authors: Stamatis G. , Lambrakis N. , Alexakis D. , Zagana E.
Published: April 2006

Studies on the hydrogeological conditions of the Mesogea basin in east Attica reveal that the aquifers developed on the post‐alpine formations at the inner part of the coastal brackish zone exhibit positive hydraulic head. These Neogene and Quaternary deposits present high salt concentrations. Selected points were sampled (total 85: 51 wells and 34 boreholes) in order to obtain hydrogeological and hydrochemical data for a better understanding of the structure, operation and dynamics of the aquifer of the area. Statistical methods, R‐mode factor analysis and scatter‐plot diagrams were used for the hydrochemical analysis and presentation of the data. The groundwater resources are relatively weak and there is significant quality degradation due to the geological structure of the greater area, as well as the bad management of the aquifer and anthropogenic activities. Groundwater is characterized by high salt concentrations. Electrical conductivity values range between 260 and 6970 µS cm−1. High salt concentrations at the coastal aquifers are due to sea intrusion, whereas they are attributed to the dissolution of minerals of the geological environment in the inland area. The groundwaters of the study area can be classified into five water types: Ca–HCO3, Mg–HCO3, Na–HCO3, Na–Cl and Mg–Cl. They are saturated in dolomite and calcite, whereas they are unsaturated in anhydrite. High ion concentrations, e.g. $\hbox{NO}_{3}^{-}$] (0‐221 mg l−1), $\hbox{NH}_{4}^{+}$] (0·01‐1·88 mg l−1), $\hbox{PO}_{4}^{3-}$] (0·01‐6·75 mg l−1), as well as high heavy metals concentrations are attributed to anthropogenic impacts. Copyright © 2006 John Wiley & Sons, Ltd.
Uncertainties in DRAINMOD predictions of subsurface drain flow for an Indiana silt loam using the GLUE methodology
Authors: Wang X. , Frankenberger J. R. , Kladivko E. J.
Published: April 2006

Good modelling practice requires the incorporation of uncertainty analysis into hydrologic/water quality models. The generalized likelihood uncertainty estimation procedure was used to evaluate the uncertainty in DRAINMOD predictions of daily, monthly, and yearly subsurface drain flow. A variance‐based sensitivity analysis technique, the extended Fourier amplitude sensitivity test, was used to identify the main sources of prediction uncertainty. The analysis was conducted for the experimental drainage field at the Southeast Purdue Agricultural Center in Indiana. Six years of data were used and the uncertainties in eight model parameters were considered to analyse how uncertainties in input parameters propagate to model outputs. The width of 90% confidence interval bands of drain flow ranged from 0 to 0·6 cm day−1for daily predictions, from 0 to 3·1 cm month−1for the monthly predictions, and from 7·6 to 12·4 cm year−1for yearly predictions. Annual drain flow predicted by DRAINMOD fell well within the 90% confidence bounds. Model results were most sensitive to the vertical saturated hydraulic conductivity of the restrictive layer and the lateral hydraulic conductivity of the deepest soil layer, followed by the lateral hydraulic conductivity of the top soil layer and surface micro‐storage. Parameter interactions also contributed to the prediction uncertainty. Copyright © 2006 John Wiley & Sons, Ltd.
Multiple injected and natural conservative tracers quantify mixing in a stream confluence affected by acid mine drainage near Silverton, Colorado
Authors: Schemel Laurence E. , Cox Marisa H. , Runkel Robert L. , Kimball Briant A.
Published: April 2006

The acidic discharge from Cement Creek, containing elevated concentrations of dissolved metals and sulphate, mixed with the circumneutral‐pH Animas River over a several hundred metre reach (mixing zone) near Silverton, CO, during this study. Differences in concentrations of Ca, Mg, Si, Sr, and SO42− between the creek and the river were sufficiently large for these analytes to be used as natural tracers in the mixing zone. In addition, a sodium chloride (NaCl) tracer was injected into Cement Creek, which provided a Cl− ‘reference’ tracer in the mixing zone. Conservative transport of the dissolved metals and sulphate through the mixing zone was verified by mass balances and by linear mixing plots relative to the injected reference tracer. At each of seven sites in the mixing zone, five samples were collected at evenly spaced increments of the observed across‐channel gradients, as determined by specific conductance. This created sets of samples that adequately covered the ranges of mixtures (mixing ratios, in terms of the fraction of Animas River water, %AR). Concentratis measured in each mixing zone sample and in the upstream Animas River and Cement Creek were used to compute %AR for the reference and natural tracers. Values of %AR from natural tracers generally showed good agreement with values from the reference tracer, but variability in discharge and end‐member concentrations and analytical errors contributed to unexpected outlier values for both injected and natural tracers. The median value (MV) %AR (calculated from all of the tracers) reduced scatter in the mixing plots for the dissolved metals, indicating that the MV estimate reduced the effects of various potential errors that could affect any tracer. Copyright © 2006 John Wiley & Sons, Ltd.
Isotopic variations in precipitation at Bangkok and their climatological significance
Authors: He Yuanqing , Pang Hongxi , Theakstone W. H. , Zhang Zhonglin , Lu Aigang , Gu Juan
Published: April 2006

The stable isotopic composition of precipitation from low to mid latitudes contains information about changes of some climatic factors, such as temperature, precipitation and atmospheric circulation patterns. However, the isotopic variations in the area are very complicated because of the combined influences of these factors. Proper interpretation of the patterns of isotopic variations for palaeoclimate reconstructions in this area requires a detailed understanding of these complex stable isotope controls. The isotopic data (δ18O and δ2D) in precipitation at the International Atomic Energy Agency–World Meteorological Organization Bangkok station were collected and analysed because of the relatively long and unbroken isotopic records and the particular geographical location. The isotopic variations at Bangkok have strong seasonal patterns owing to distinct source regions in different seasons. In summer, the remote sources of water there can influence the δ18O values significantly, which is verified by the simple Rayleigh model. In winter, the mixing of isotopically distinct air masses with different origins, i.e. the continental and oceanic air masses, accounts for the isotopic variations. In the transition periods of the Asia–Australia monsoon, namely in May and October, the local vapour contribution may play a role in the isotopic ratios. On the interannual time‐scale, the influences of El Niño–southern oscillation (ENSO) and the Indian Ocean dipole (IOD) on isotopic composition are examined. The indications are that both the ENSO and IOD indices have a significant correlation with the δ18O ratios, and that the δ18O ratio in summer rains is significantly more enriched (depleted) during the warm (cold) phase of ENSO/IOD events. All the results suggest that it is useful for us in understanding the water cycling process and may be helpful in palaeoclimate reconstruction in this monsoon region. Copyright © 2006 John Wiley & Sons, Ltd.
River suspended sediment modelling using a fuzzy logic approach
Authors: Kisi Ozgur , Karahan M. Emin , Şen Zekai
Published: April 2006

Correct estimation of sediment volume carried by a river is very important for many water resources projects. Conventional sediment rating curves, however, are not able to provide sufficiently accurate results. In this paper, a fuzzy logic approach is proposed to estimate suspended sediment concentration from streamflow. This study provides forecasting benchmarks for sediment concentration prediction in the form of a numerical and graphical comparison between fuzzy and rating‐curve models. Benchmarking was based on a 5‐year period of continuous streamflow and sediment concentration data of Quebrada Blanca Station operated by the United States Geological Survey. The benchmark results showed that the fuzzy model was able to produce much better results than rating‐curve models. The fuzzy model proposed in the study is site specific and does not simulate the hysteresis effects. Copyright © 2006 John Wiley & Sons, Ltd.
Overview of the European and North American studies on HPV testing in primary cervical cancer screening
Authors: Cuzick Jack , Clavel Christine , Petry Karl‐Ulrich , Meijer Chris J.L.M. , Hoyer Heike , Ratnam Samuel , Szarewski Anne , Birembaut Philippe , Kulasingam Shalini , Sasieni Peter , Iftner Thomas
Published: April 2006

Several studies suggest that HPV testing is more sensitive than cytology in primary cervical screening. These studies had different designs and were reported in different ways. Individual patient data were collected for all European and North American studies in which cytology was routinely performed and HPV testing was included as an additional parallel test. More than 60,000 women were included. The sensitivity and specificity of HPV testing were compared with routine cytology, both overall and for ages <35, 35–49 and 50+. The age‐specific prevalence of high risk HPV (hr‐HPV) was also analysed. HPV testing was substantially more sensitive in detecting CIN2+ than cytology (96.1% vs. 53.0%) but less specific (90.7% vs. 96.3%). The sensitivity of HPV testing was similar in all studies carried out in different areas of Europe and North America, whereas the sensitivity of cytology was highly variable. HPV sensitivity was uniformly high at all ages, whereas the sensitivity of cytology was substantially better in women over the age of 50 than in younger women (79.3% vs. 59.6%). The specificity of both tests increased with age. Positivity rates for HPV testing in women without high‐grade CIN were region dependent. These results support the use of HPV testing as the sole primary screening test, with cytology reserved for women who test HPV positive. Large demonstration projects are needed to fully evaluate this strategy. © 2006 Wiley‐Liss, Inc.
“A gold mine and a tool for democracy”: George Gallup, Elmo Roper, and the business of scientific polling, 1935–1955
Authors: Igo Sarah E.
Published: April 2006

“Scientific” public opinion polls arrived on the American scene in 1936. Examining the work of opinion surveyors George Gallup and Elmo Roper, this essay tracks the early career of a new social scientific technology, one that powerfully shaped conceptions of “the public.” Pollsters described their craft as a democratic one that could accurately represent the U.S. populace. Yet, their assumptions about that same public—and the techniques they employed to measure it—undermined such claims, and even risked calling the polling profession into question. To understand why Gallup and Roper fell short of their stated ambitions, one must turn not only to the state of midcentury sampling methods but also to the corporate sponsors and commercial pressures underlying their enterprise. © 2006 Wiley Periodicals, Inc.
The historiography of Swedish sociology and the bounding of disciplinary identity
Authors: Larsson Anna , Wisselgren Per
Published: April 2006

Bounding a scientific discipline is a way of regulating its cognitive direction as well as its relations to neighboring disciplines and extra‐academic authorities. In this process of identity making, disciplinary history often is a crucial element. In this article, focusing on the historiography of Swedish sociology and the reception of Gustaf Steffen, Sweden's first professional sociologist, it is argued that Steffen's marginalized role in the traditional accounts should be understood not only with reference to his supposed theoretical shortcomings, but also in the historical context of the early postwar reestablishment of sociology as an academic discipline and its prevalent need for a new disciplinary identity, strategically adjusted to the contemporary institutional and political settings. © 2006 Wiley Periodicals, Inc.
“A new deal for the drug addict”: The Addiction Research Center, Lexington, Kentucky
Authors: Campbell Nancy D.
Published: April 2006

This article describes the social organization of knowledge production in the formative moments of the substance abuse research enterprise. It describes the institutional arrangements and material conditions of a U.S. Public Health Service laboratory that was housed in a facility run jointly with the federal Bureau of Prisons. The Addiction Research Center (ARC) in Lexington, Kentucky, was dedicated to elucidating the basic underlying mechanisms of drug addiction. The ARC was housed on the rural campus of a prison‐hospital called “Narco,” one of two “narcotics farms” in Lexington, Kentucky, and Fort Worth, Texas. For its studies on drug effects, the ARC had access to a pool of drug‐experienced human subjects drawn from the ranks of convicted felons. Given their unparalleled access to human subjects, the scientists who worked at the ARC made conceptual contributions still acknowledged today. Based on archival work as well as dozens of oral history interviews with individuals who began their research careers at Lexington, the article presents an analytic, intellectual history of the early work of Abraham Wikler, whose lifelong pursuit of the underlying mechanisms of opiate addiction led him to hypothesize the role of conditioning in relapse, as an exemplar of the kind of scientific research that depended on closely listening to and observing “post‐addicts,” as subject participants were called. © 2006 Wiley Periodicals, Inc.
Evaluation and standardisation of small‐scale canning methods for small white beans (Phaseolus vulgaris L.) canned in tomato sauce
Authors: van der Merwe Daleen , Osthoff Garry , Pretorius Apie J
Published: April 2006

Canning and evaluation procedures should be standardised to ensure that beans selected, based on canning quality, meet the requirements set by the market and processors. For the purpose of evaluating the canning qualities of small white beans in tomato sauce, three small‐scale canning techniques were evaluated, one of which was found to deliver a product with quality parameters similar to those of international standards. Using South African small white bean cultivars and the selected method, Teebus, the cultivar used by industry as the standard to indicate acceptable canning quality, displayed better visual appearance and less split beans than with the other two methods. The percentage washed drained weight and texture values of Teebus were also in agreement with international standards. The evaluation procedure for the small white beans after canning was also optimised, by comparing two procedures, which identified texture, visual appearance (scale 1 to 10), splits (scale 1 to 10), hydration coefficient, clumping, size and colour as the statistically most suitable quality parameters. With the aid of the developed method, it was possible to define standard values for South African ‘choice’ and ‘standard’ grade beans, which previously was based only on ‘visual inspection’ by a trained inspection panel. Copyright © 2006 Society of Chemical Industry
Relativistic dipole and non-relativistic quadrupole generation of the second harmonic at the irradiation of atomic clusters by the femtosecond laser pulses
Authors: Rastunkov V S , Krainov V P
Published: April 2006

The power of the second harmonic irradiated by the cluster at the interaction with a femtosecond laser pulse is derived. The main contribution is produced by the relativistic oscillations of the electron cloud along the direction of the propagation of the laser pulse. The contribution into radiation power produced by the quadrupole surface oscillations of the electron cloud along the polarization axis of the laser pulse can be neglected.
Comparison of electrooptically Q-switched Er:Cr:YSGG
lasers by two polarizers: Glan-Taylor prism and Brewster angle
structure
Authors: Wang T-J , He Q-Y , Gao J-Y , Kang Z-H , Jiang Y , Sun H
Published: April 2006

Two types of electro-optically Q-switched Er:Cr:YSGG
lasers with different polarizing mechanisms have been operated.
For the one Q-switching and polarizing are realized with only a
LiNbO3 crystal with both ends cut at Brewster's angle and for
the other they are achieved by a cubic LiNbO3 crystal and a
Glan-Taylor prism, respectively. The two schemes are compared with
regard to both the mechanical and laser Q-switched properties.
Collision induced photon echo in ytterbium vapour
Authors: Rubtsova N N , Khvorostov E B , Kochubei S A , Ishchenko V N , Yevseyev I V
Published: April 2006

Collision induced photon echo is observed in ytterbium
vapour at the inter-combination transition (6s6p) 3P1
↔ (6s2) 1S0 in the presence of Kr gas as
buffer. Collision echo is generated by two unidirectional resonant
dye laser pulses of linear mutually orthogonal polarizations.
There is practically no echo in the absence of buffer. Photon echo
power increases with Kr pressure in the range from 0 to 20 mTorr
and decreases at higher Kr pressures. Experimental results are
compared with theoretical predictions accounting for relaxation
matrix dependence on the direction of the velocity of active
atoms.
Poly(ε‐caprolactone) Biomaterial Sterilized by E‐Beam Irradiation
Authors: Filipczak Katarzyna , Wozniak Magdalena , Ulanski Piotr , Olah Laszlo , Przybytniak Grazyna , Olkowski Radoslaw M. , Lewandowska‐Szumiel Malgorzata , Rosiak Janusz M.
Published: April 2006

Summary: The effects of ionizing radiation (electron beam) on poly(ε‐caprolactone) (PCL) were studied by analyzing changes in viscosity‐average and weight‐average molecular weight and radius of gyration, and by performing sol‐gel analysis and swelling tests. Samples were irradiated under various conditions: solid and molten PCL in the presence or absence of air. The overall efficiency of crosslinking is higher for samples irradiated in the molten state than in the solid state, and is reduced in the presence of oxygen. Based on three kinds of experiments (molecular weight dependence on the dose in the pre‐gelation region, sol‐gel analysis, and swelling study), radiation‐chemical yields of intermolecular crosslinking and scission were determined and are discussed in terms of the mechanism of radiation‐induced reactions in PCL. Properties of the gels formed by high‐dose irradiation and mechanical properties of irradiated PCL were analyzed. Irradiation causes an increase in the compression modulus of PCL. This process occurs at the pre‐gelation stage and continues in the gel‐containing system. We have demonstrated, for the first time, that irradiation of solid PCL is accompanied by a pronounced post‐effect, which manifests itself by changes in the average molecular weight. EPR data indicate that this effect, at least in part, is caused by the presence of long‐lived radicals trapped in the crystalline regions. Irradiation with the sterilizing dose does not cause a statistically significant change in the biocompatibility of PCL after subsequent storage for 79 d, as determined by preliminary osteoblast vitality tests.

Changes in the molecular weight upon irradiation and subsequent storage of poly(ε‐caprolactone).

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Changes in the molecular weight upon irradiation and subsequent storage of poly(ε‐caprolactone).
EIS characterisation of the layer of corrosion products on various substrates in differing atmospheric environments
Authors: Rodriguez J. J. Santana , Álvarez C. Motesdeoca , González J.E. González
Published: April 2006

The layer of corrosion products forming on zinc in atmospheric environments of varying aggressivity have been characterised and compared with previous results obtained for carbon steel. The characteristics of said layers have been linked to the nature of the products found. Likewise, we have found that EIS is a useful tool towards characterising the layers of corrosion products of carbon steel and zinc. The equivalent circuit which gives the best fit of impedance data for both metals is type R(C(R(C(R(CR))))), where the Nyquist diagrams are composed of two time constants. It is observed that the value of the capacitance of the corrosion product layer (Cpc) diminishes as the time of exposure increases, which is directly related with an increase in the thickness of the corrosion product layer. Also, it is observed that when the nature of the corrosion products doesn't vary with the time of exposure, the decrease of the charge transfer resistance is related with the increase in the thickness of the corrosion product layer.
Unmodified and Modified Surface Sisal Fibers as Reinforcement of Phenolic and Lignophenolic Matrices Composites: Thermal Analyses of Fibers and Composites
Authors: Faulstich de Paiva Jane Maria , Frollini Elisabete
Published: April 2006

Summary: The study and development of polymeric composite materials, especially using lignocellulosic fibers, have received increasing attention. This is interesting from the environmental and economical viewpoints as lignocellulosic fibers are obtained from renewable resources. This work aims to contribute to reduce the dependency on materials from nonrenewable sources, by utilizing natural fibers (sisal) as reinforcing agents and lignin (a polyphenolic macromolecule obtained from lignocellulosic materials) to partially substitute phenol in a phenol‐formaldehyde resin. Besides, it was intended to evaluate how modifications applied on sisal fibers influence their properties and those of the composites reinforced with them, mainly thermal properties. Sisal fibers were modified by either (i) mercerization (NaOH 10%), (ii) esterification (succinic anhydride), or (iii) ionized air treatment (discharge current of 5 mA). Composites were made by mould compression, of various sisal fibers in combination with either phenol‐formaldehyde or lignin‐phenol‐formaldehyde resins. Sisal fibers and composites were characterized by thermogravimetry (TG) and DSC to establish their thermal stability. Scanning electron microscopy (SEM) was used to investigate the morphology of unmodified and modified surface sisal fibers as well as the fractured composites surface. Dynamic mechanical thermoanalysis (DMTA) was used to examine the influence of temperature on the composite mechanical properties. The results obtained for sisal fiber‐reinforced phenolic and lignophenolic composites showed that the use of lignin as a partial substitute of phenol in phenolic resins in applications different from the traditional ones, as for instance in other than adhesives is feasible.

Micrograph of the impact fracture surface of phenolic composite reinforced with mercerized sisal fiber (500 X).

magnified image

Micrograph of the impact fracture surface of phenolic composite reinforced with mercerized sisal fiber (500 X).
The relative weights of Internet shopping fundamental objectives: Effect of lifestyle differences
Authors: Wang Eric T.G. , Yeh His‐Yin , Jiang James J.
Published: April 2006

Internet commerce should be viewed as a new way of value creation and provision. To attract consumers to visit Web sites, a critical question is: What are their major concerns in Internet shopping? Nine fundamental objectives to describe the bottom line concerns to Internet consumers have been proposed in the literature. From the perspective of the means–end chain theory and by focusing on the shopping goods, this study proposed that different weights on these nine fundamental concerns are assigned by different lifestyle individuals. Based on the results of a survey of 181 on‐line respondents who provided consistent data, this study indicated that privacy, safety, and product quality were the most critical concerns of on‐line consumers, contradicting the conventional wisdom that cost and convenience are the key concerns for consumers shopping on‐line. Furthermore, for those consumers with active style, privacy factor received significantly more concern than safety and product quality. Respondents who preferred variety and excited lifestyle put more weights on these three Internet fundamental objectives than consumers with other lifestyles. However, principle lifestyle individuals put more weight on other factors, such as shopping enjoyment, environmental impacts, time to receive products, and less weight on cost and convenience. Implications are discussed. © 2006 Wiley Periodicals, Inc.
The effect of Flash banners on multiattribute decision making: Distractor or source of arousal?
Authors: Day Rong‐Fuh , Shyi Gary C.‐W. , Wang Jyun‐Cheng
Published: April 2006

The role of peripheral flash advertisements in decision making as a distractor or a source of arousal was examined. Participants were asked to perform multiattribute decision making in a display environment with or without banners of advertisement flashing occasionally in the peripheral region of the display. The flash banners accelerated the speed of decision making, although the participants rarely made eye movements in response to the banners or fixated their eyes on them. It was interesting to note that the participants' pupil sizes increased with the presence of flash banners. These findings suggest that rather than distracting participants' attention, flash banners appear to elevate the general level of arousal of the participants, which in turn led to making faster on‐line decisions. © 2006 Wiley Periodicals, Inc.
Investigating initial trust toward e‐tailers from the elaboration likelihood model perspective
Authors: Yang Shu‐Chen , Hung Wan‐Chiao , Sung Kai , Farn Cheng‐Kiang
Published: April 2006

This study investigates initial trust formation in Internet shopping from the perspective of the elaboration likelihood model (ELM) by conducting a 2 2 factorial laboratory experiment. Based on data collected from 160 respondents, the results indicate that display of third‐party seals and product information quality positively affects consumers' trust toward an e‐tailer through assurance perception and result demonstrability, respectively. Besides, one's product involvement and trait anxiety play moderating roles. As predicted in ELM, consumers with high involvement and low anxiety build their trust via central route exclusively, whereas consumers with low involvement or high anxiety build their trust via peripheral route exclusively. The results suggest that customizing the persuasive arguments for different consumers is a critical strategy for initial on‐line trust building. © 2006 Wiley Periodicals, Inc.
Why on‐line customers remain with a particular e‐retailer: An integrative model and empirical evidence
Authors: Tsai Hsien‐Tung , Huang Heng‐Chiang , Jaw Yi‐Long , Chen Wen‐Kuo
Published: April 2006

This article formulates and empirically tests a conceptual framework that considers the antecedents of switching barriers and overall satisfaction, and their roles as drivers of customer retention in on‐line settings. To test the proposed hypotheses, structural equation modeling based on data obtained from a large on‐line retailing store in Taiwan is used. The results suggest that perceived switching costs and community building exert the greatest impact on repurchase intentions through switching barriers and overall satisfaction. Furthermore, relational orientations significantly moderate the link between switching barriers and repurchase intentions. Finally, the theoretical and practical implications of the findings are discussed. © 2006 Wiley Periodicals, Inc.
Uniform stabilization of a nonlinear structural acoustic model with a Timoshenko beam interface
Authors: Dalsen Marié Grobbelaar‐Van
Published: April 2006

This paper is concerned with a nonlinear model which describes the interaction of sound and elastic waves in a two‐dimensional acoustic chamber in which one flat ‘wall’, the interface, is flexible. The composite dynamics of the structural acoustic model is described by the linearized equations for a gas defined on the interior of the chamber and the nonlinear Timoshenko beam equations on the interface. Uniform stability of the energy associated with the interactive system of partial differential equations is achieved by incorporating a nonlinear feedback boundary damping scheme in the equations for the gas and the beam. Copyright © 2006 John Wiley & Sons, Ltd.
The point source method for inverse scattering in the time domain
Authors: Russell Luke D. , Potthast Roland
Published: April 2006

Many recent inverse scattering techniques have been designed for single frequency scattered fields in the frequency domain. In practice, however, the data is collected in the time domain. Frequency domain inverse scattering algorithms obviously apply to time‐harmonic scattering, or nearly time‐harmonic scattering, through application of the Fourier transform. Fourier transform techniques can also be applied to non‐time‐harmonic scattering from pulses. Our goal here is twofold: first, to establish conditions on the time‐dependent waves that provide a correspondence between time domain and frequency domain inverse scattering via Fourier transforms without recourse to the conventional limiting amplitude principle; secondly, we apply the analysis in the first part of this work toward the extension of a particular scattering technique, namely the point source method, to scattering from the requisite pulses. Numerical examples illustrate the method and suggest that reconstructions from admissible pulses deliver superior reconstructions compared to straight averaging of multi‐frequency data. Copyright © 2006 John Wiley & Sons, Ltd.
Long‐circulating liposomal contrast agents for magnetic resonance imaging
Authors: Ayyagari Ananta Laxmi , Zhang Xiaodong , Ghaghada Ketan B. , Annapragada Ananth , Hu Xiaoping , Bellamkonda Ravi V.
Published: April 2006

Contrast‐enhanced magnetic resonance imaging (CE‐MRI) is a dynamic technique for imaging vasculature. However, the currently used gadolinium (Gd) chelates, such as Gd‐DTPA, restrict the time window for image acquisition due to their rapid elimination from blood and their rapid diffusion into the extravascular space, which prevents their use in steady‐state imaging, particularly for MR angiography (MRA). The goal of this study was to prepare long‐circulating polyethylene glycol‐bearing ((PEG)ylated) liposomes encapsulating Gd chelate, and characterize and demonstrate their utility for MRA. The liposomes were prepared by hydrating a mixture of lipids with gadodiamide (Omniscan®). The liposomes were sized down to around 100 nm by extruder and exhaustively dialysed to remove the unencapsulated gadodiamide. The Gd liposomes exhibited a significant sustained (>4 hr) contrast enhancement of the vasculature with improved spatial details in a rat model with little leakage relative to Gd‐DTPA controls as shown by MRI. We suggest that such long‐circulating liposomal formulations allow for high spatial resolution imaging without the confounding effects of clearance and extravascular diffusion of the agent complicating the data and image analysis. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.
Quantification of vitamin C in the rat brain in vivo using short echo‐time 1H MRS
Authors: Terpstra Melissa , Tkác̆ Ivan , Rao Raghavendra , Gruetter Rolf
Published: April 2006

Both ultrashort echo‐time STEAM and MEGA‐PRESS‐edited spectroscopy were used to validate noninvasive quantification of vitamin C (ascorbate) in the developing rat brain, where changes in ascorbate concentration have been reported. Despite strong overlap with resonances from glutamine, glutamate, glutathione, and macromolecules, reliable quantification of ascorbate (Cramer‐Rao lower bounds < 0.2 μmol/g) by LCModel analysis of STEAM (TE = 2 ms) spectra was possible at 9.4 T. Ascorbate concentrations quantified from the STEAM spectra were in very good agreement with concentrations calculated from fully resolved ascorbate resonances in MEGA‐PRESS‐edited spectra measured from identical volumes of interest. Ascorbate concentrations measured using STEAM decreased with increasing postnatal rat age, in agreement with published brain ascorbate concentrations measured in vitro using high‐performance liquid chromatography (HPLC). Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.
Advantages of parallel imaging in conjunction with hyperpolarized helium—A new approach to MRI of the lung
Authors: Lee Ray F. , Johnson Glyn , Grossman Robert I. , Stoeckel Bernd , Trampel Robert , McGuinness Georgeann
Published: April 2006

Hyperpolarized helium (3He) gas MRI has the potential to assess pulmonary function. The non‐equilibrium state of hyperpolarized 3He results in the continual depletion of the signal level over the course of excitations. Under non‐equilibrium conditions the relationship between the signal‐to‐noise ratio (SNR) and the number of excitations significantly deviates from that established in the equilibrium state. In many circumstances the SNR increases or remains the same when the number of data acquisitions decreases. This provides a unique opportunity for performing parallel MRI in such a way that both the temporal and spatial resolution will increase without the conventional decrease in the SNR. In this study an analytical relationship between the SNR and the number of excitations for any flip angle was developed. Second, the point‐spread function (PSF) was utilized to quantitatively demonstrate the unconventional SNR behavior for parallel imaging in hyperpolarized gas MRI. Third, a 24‐channel (24ch) receive and two‐channel (2ch) transmit phased‐array system was developed to experimentally prove the theoretical predictions with 3He MRI. The in vivo experimental results prove that significant temporal resolution can be gained without the usual SNR loss in an equilibrium system, and that the entire lung can be scanned within one breath‐hold (∼13 s) by applying parallel imaging to 3D data acquisition. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.
Linear combination filtering for T2‐selective imaging of the knee
Authors: Vidarsson Logi , Gold Garry E. , Hargreaves Brian , Pauly John M.
Published: April 2006

Recently a novel T2 selective imaging method based on linear combination (LC) filtering was developed. By linearly combining images acquired with different echo times LC filtering is able to generate images showing only tissues with a preselected range of T2 relaxation times. In this study the use of LC filtering in knee imaging was investigated. Three LC filters were designed: a short LC filter for imaging the knee meniscus, a medium LC filter for articular cartilage, and a long LC filter for synovial fluid. To verify the filter designs, eight phantoms with different T2 relaxation times were imaged. In addition, in vivo images were acquired from four asymptomatic volunteers and a subject with cartilage damage. T2 maps were also generated using the same source images. Signal‐to‐noise ratio (SNR) measurements were made of the meniscus, cartilage, and fluid regions on the three LC filtered images. The highest SNR was seen in the target tissue on each of the LC filtered images. LC filtering is a new method that can selectively image knee tissues based on their T2. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.
Elasto‐plastic finite element analysis of shells with damage due to microvoids
Authors: Woelke Pawel , Voyiadjis George Z. , Perzyna Piotr
Published: April 2006

This paper presents a non‐linear finite element analysis for the elasto‐plastic behaviour of thick/thin shells and plates with large rotations and damage effects. The refined shell theory given by Voyiadjis and Woelke (Int. J. Solids Struct.2004;41:3747–3769) provides a set of shell constitutive equations. Numerical implementation of the shell theory leading to the development of theC0quadrilateral shell element (Woelke and Voyiadjis, Shell element based on the refined theory for thick spherical shells. 2006, submitted) is used here as an effective tool for a linear elastic analysis of shells. The large rotation elasto‐plastic model for shells presented by Voyiadjis and Woelke (General non‐linear finite element analysis of thick plates and shells. 2006, submitted) is enhanced here to account for the damage effects due to microvoids, formulated within the framework of a micromechanical damage model. The evolution equation of the scalar porosity parameter as given by Duszek‐Perzyna and Perzyna (Material Instabilities:Theory and Applications,ASME Congress, Chicago, AMD‐Vol. 183/MD‐50, 9–11 November 1994; 59–85) is reduced here to describe the most relevant damage effects for isotropic plates and shells, i.e. the growth of voids as a function of the plastic flow. The anisotropic damage effects, the influence of the microcracks and elastic damage are not considered in this paper. The damage modelled through the evolution of porosity is incorporated directly into the yield function, giving a generalized and convenient loading surface expressed in terms of stress resultants and stress couples. A plastic node method (Comput. Methods Appl. Mech. Eng.1982;34:1089–1104) is used to derive the large rotation, elasto‐plastic‐damage tangent stiffness matrix. Some of the important features of this paper are that the elastic stiffness matrix is derived explicitly, with all the integrals calculated analytically (Woelke and Voyiadjis, Shell element based on the refined theory for thick spherical shells. 2006, submitted). In addition, a non‐layered model is adopted in which integration through the thickness is not necessary. Consequently, the elasto‐plastic‐damage stiffness matrix is also given explicitly and numerical integration is not performed. This makes this model consistent mathematically, accurate for a variety of applications and very inexpensive from the point of view of computer power and time. Copyright © 2006 John Wiley & Sons, Ltd.