bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analytical models for the mean flow inside dense canopies on gentle hilly terrain
Authors: Poggi D. , Katul G. G. , Finnigan J. J. , Belcher S. E. 
Published: August 2008

AbstractSimplifications and scaling arguments employed in analytical models that link topographic variations to mean velocity perturbations within dense canopies are explored using laboratory experiments. Laser Doppler anemometry (LDA) measurements are conducted in a neutrally‐stratified boundary‐layer flow within a large recirculating flume over a train of gentle hills covered by a dense canopy. The hill and canopy configuration are such that the mean hill slope is small and the hill is narrow in relation to the canopy (H/L ≪ 1 and Lc/L ≈ 1, where H is the hill height, L the half‐length, and Lc the canopy adjustment length‐scale). The LDA data suggest that the often‐criticized linearizations of the advective terms, turbulent‐shear‐stress gradients and drag force appear reasonable except in the deep layers of the canopy. As predicted by a previous analytical model, the LDA data reveal a recirculation region within the lower canopy on the lee slope. Adjusting the outer‐layer pressure perturbations by a virtual ground that accounts for the mean streamline distortions induced by this recirculation zone improves this model's performance. For the velocity perturbations in the deeper layers of the canopy, a new analytical model, which retains a balance between mean horizontal advection, mean pressure gradient and mean drag force but neglects the turbulent‐shear‐stress gradient, is developed. The proposed model reproduces the LDA measurements better than the earlier analytical model, which neglected advection but retained the turbulent‐shear‐stress gradient in the lower layers of the canopy and near the hill top. This finding is consistent with the fact that the earlier model was derived for tall hills in which advection inside the canopy remains small. In essence, the newly‐proposed model for the narrow hill studied here assumes that in the deeper layers of the canopy the spatial features of the mean flow perturbations around their background state can be approximated by the inviscid mean‐momentum equation. We briefly discuss how to integrate all these findings with recent advances in canopy lidar remote‐sensing measurements of general topography and canopy height. Copyright © 2008 Royal Meteorological Society
Model error and sequential data assimilation: A deterministic formulation
Authors: Carrassi A. , Vannitsem S. , Nicolis C. 
Published: August 2008

AbstractData assimilation schemes are confronted with the presence of model errors arising from the imperfect description of atmospheric dynamics. These errors are usually modelled on the basis of simple assumptions such as bias, white noise, and first‐order Markov process. In the present work, a formulation of the sequential extended Kalman filter is proposed, based on recent findings on the universal deterministic behaviour of model errors in marked contrast with previous approaches. This new scheme is applied in the context of a spatially distributed system proposed by Lorenz. First, it is found that, for short times, the estimation error is accurately approximated by an evolution law in which the variance of the model error (assumed to be a deterministic process) evolves according to a quadratic law, in agreement with the theory. Moreover, the correlation with the initial condition error appears to play a secondary role in the short‐time dynamics of the estimation error covariance. Second, the deterministic description of the model error evolution, incorporated into the classical extended Kalman filter equations, reveals that substantial improvements of the filter accuracy can be gained compared with the classical white‐noise assumption. The universal short‐time quadratic law for the evolution of the model error covariance matrix seems very promising for modelling estimation error dynamics in sequential data assimilation. Copyright © 2008 Royal Meteorological Society
Power‐law velocity profile in a turbulent Ekman layer on a transitional rough surface
Authors: Afzal Noor 
Published: August 2008

AbstractA two‐layer asymptotic theory of mean momentum in a turbulent Ekman layer without any closure model (such as eddy viscosity, mixing length, or k − ϵ) for large Rossby numbers is proposed. The flow in the inner wall layer and the outer wake layer are matched, using the Izakson–Millikan–Kolmogorov hypothesis; this leads to an open functional equation. Another open functional equation is obtained from the ratio of two successive derivatives of the basic functional equation; this admits two functional solutions, with power‐law and log‐law velocity profiles. The envelope of the geostrophic‐drag power law leads to the log law, and determines the power‐law index and prefactor as a function of the surface Rossby number or the drag coefficient. The log laws and power laws for velocity and friction velocity, including the power‐law constants, are universal, and independent of the wall roughness. This universality is well supported by extensive experimental and laboratory data. In traditional smooth‐wall variables, there is no universality of scalings, and different expressions are needed for different types of roughness. Approximate solutions of the power‐law geostrophic drag and cross‐isobaric angle are also obtained. The power‐law geostrophic‐drag solution for each prescribed value of the power‐law index is valid for a limited domain of Rossby numbers. Copyright © 2008 Royal Meteorological Society
Soft reliability: an interdisciplinary approach with a user–system focus
Authors: Koca A. , Funk M. , Karapanos E. , Rozinat A. , van der Aalst W. M. P. , Corporaal H. , Martens J. B. O. S. , van der Putten P. H. A. , Weijters A. J. M. M. , Brombacher A. C. 
Published: August 2008

AbstractA recent trend in technological innovation is towards the development of increasingly multifunctional and complex products to be used within rich socio‐cultural contexts such as the high‐end office, the digital home, and professional or personal healthcare. One important consequence of the development of strongly innovative products is a growing market uncertainty regarding ‘if’, ‘how’, and ‘when’ users can and will adopt such products. Often, it is not even clear to what extent these products are understood and interacted with in the intended manner. The mentioned problems have already become an evident concern in the field, where there is a significant rise in the numbers of seemingly sound products being complained about, signaling a lack of soft reliability. In this paper, we position soft reliability as a growing and critical industrial problem, whose solution requires new academic expertise from various disciplines. We illustrate potential root causes for soft reliability problems, such as discrepancy between the perceptions of users and designers. We discuss the necessary approach to effectively capture subjective feedback data from actual users, e.g. when they contact call centers. Furthermore, we present a novel observation and analysis approach that enables insight into actual product usage, and outline opportunities for combining such objective data with the subjective feedback provided by users. Copyright © 2008 John Wiley & Sons, Ltd.
Effect of phase‐breaking events on electron transport in mesoscopic and nanodevices
Authors: Jayasekera Thushari , Pillalamarri Pavan K. , Mintmire J. W. , Meunier V. 
Published: August 2008

AbstractExisting ballistic models for electron transport in mesoscopic and nanoscale systems break down as the size of the device becomes longer than the phase coherence length of electrons in the system. Krstic et al. experimentally observed that the current in single‐wall carbon nanotube systems can be regarded as a combination of a coherent part and a noncoherent part. In this article, we discuss the use of Büttiker phase‐breaking technique to address partially coherent electron transport, generalize that to a multichannel problem, and then study the effect of phase‐breaking events on the electron transport in two‐terminal graphene nanoribbon devices. We also investigate the difference between the pure‐phase randomization and phase/momentum randomization boundary conditions. While momentum randomization adds an extra resistance caused by backward scattering, pure‐phase randomization smooths the conductance oscillations because of interference. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
N‐bands Hubbard models. IV. Comparisons of electron‐ or hole‐doped quaternary oxypictides LaOMPn superconductors with cuprates
Authors: Yamaguchi K. , Yamanaka S. , Isobe H. , Hagihara M. , Yamaki D. , Nishihara M. , Kitagawa Y. , Kawakami T. , Okumura M. 
Published: August 2008

AbstractA lot of theoretical and experimental results are examined to obtain a unified picture of magnetism and superconductivity in strongly correlated electron systems. First principle computational results reported recently have been used to elucidate electronic structures of strongly correlated electron systems. In this series of articles theoretical efforts for the systems such as transition metal oxides have been extended to search high‐Tc superconductors (HTSC) other than cuprates in relation to possible mechanism(s) of high‐Tc superconductivity. Very recently, Kamihara et al. have found that quaternary oxypictides LaOMPn (M = V, Cr, Mn, Fe, Co, Ni, and Pn = P, As) are a new family of high‐Tc superconductors, exhibiting high‐transition temperature Tc = 26 K for the case of M = Fe and Pn = As. Since iron has been believed to be magnetic in many systems, their finding raises extremely interesting question concerning with relationships between magnetism and superconductivity. Moreover, coexistence of antiferromagnetism (AF) and superconductivity (SC) is also discovered in the recently synthesized cuprates with five CuO2 planes. This may indicate the uniformly mixed phase of AF and SC in cuprates without disorder corresponds to spin glass, instead of other complex phases resulting from random potentials in disordered cuprates. Coexistence of AF and SC phases and multiband effects are also suggested for quaternary oxypictides LaOMPn. Here, comparison between quaternary oxypictides LaOMPn and cuprates is carried out from both theoretical and experimental grounds, leading to an extension of our magnetic (J) model for LaOMPn. Implications of these analyses are discussed in relation to possible candidates of HTSC with multi (N)‐layers consisted of iso‐electronic π‐d, π‐R, and σ‐R systems, for which similar electronic phases are expected from the theoretical grounds. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Some simple explicit examples of correlated one‐electron theory and density matrix functionals
Authors: Weiner B. 
Published: August 2008

AbstractSome examples are presented displaying how general spin orbitals (GSOs) and their occupation numbers uniquely determine N‐electron antisymmetrized geminal power states. This provides a correlated one‐electron model that generalizes the independent particle model that is universally used in picturing chemical behavior. These examples also demonstrate that one‐electron models, involving GSOs and occupation numbers, and the one based on a first order density matrix are not equivalent. This difference is shown by displaying sets of different GSOs that have the same occupation numbers that correspond to the same density matrix but different N‐electron states. This observation also leads to the explicit construction of a density matrix functional. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Study on the photostability of guaiazulene by high‐performance liquid chromatography/mass spectrometry and gas chromatography/mass spectrometry
Authors: Fiori Jessica , Gotti Roberto , Albini Angelo , Cavrini Vanni 
Published: August 2008

AbstractThe photostability of guaiazulene (1,4‐dimethyl‐7‐isopropylazulene; GA), a natural azulenic compound used in cosmetic and health‐care products, as well as in pharmaceutical preparations, was investigated in solution (methanol, ethanol, acetonitrile), by different techniques: gas chromatography/mass spectrometry (GC/MS) and high‐performance liquid chromatography combined with atmospheric pressure chemical ionization mass spectrometry and UV detection (LC/APCI‐MS and HPLC/UV). A solar simulator (xenon‐arc lamp) was used as UV‐A radiation source. The study involved: monitoring compound decomposition, identifying products of photodegradation (PPs), assessing the role of oxygen and evaluating the kinetics of the process. Minor PPs are volatile compounds and were characterized by GC/MS, while oligomeric polyoxygenated compounds, tentatively characterized on the basis of MS and MS/MS spectra, were found to be the main photoproducts. The photodegradation was found to be enhanced by the presence of oxygen; nevertheless, determination of the singlet oxygen quantum yield for GA gave a lower value than that for the reference standard Rose Bengal. The obtained results and the developed stability‐indicating methods (GC/MS and LC/MS) are of interest for stability studies and/or quality control purposes of GA as raw material or cosmetic products. Copyright © 2008 John Wiley & Sons, Ltd.
Fetus‐supporting flexible manipulator with balloon‐type stabilizer for endoscopic intrauterine surgery
Authors: Liao Hongen , Suzuki Hirokazu , Matsumiya Kiyoshi , Masamune Ken , Dohi Takeyoshi , Chiba Toshio 
Published: August 2008

AbstractBackgroundMinimally invasive endoscopic fetal surgery enables intrauterine intervention with reduced risk to the mother and fetus. A novel surgical manipulator is described for stabilizing the fetus and restraining it from floating free during endoscopic intrauterine surgery.MethodsWe designed and fabricated a prototype fetus‐supporting manipulator equipped with flexible joint and bending mechanisms and a soft balloon stabilizer. The flexible joint and bending mechanisms enable the stabilizer to reach the target sites within the confined space of the uterus under the guidance of an ultrasound device. The balloon stabilizer could be inserted into the uterus through a small incision.ResultsThe accuracy evaluation showed that the maximum error of the bending mechanism was as small as 7 mm and the standard deviation of the joint mechanism was just 1.6° . In the experiments using a fetus model, the manipulator could be well controlled with guidance from ultrasound images and its bending mechanism with the balloon stabilizer could be clearly visualized while stabilizing the fetus model.ConclusionsThe manipulator has the potential to be used in minimally invasive intrauterine surgery, although further improvements and experiments remain to be carried out. Copyright © 2008 John Wiley & Sons, Ltd.
Accuracy of MRI vs CT imaging with particular reference to patient specific templates for total knee replacement surgery
Authors: White D. , Chelule K. L. , Seedhom B. B. 
Published: August 2008

AbstractBackgroundThe present study compares the accuracy of MRI and CT imaging for the manufacture of patient‐specific templates for total knee replacement surgery.MethodsA total of 10 ovine knees were imaged using MRI and CT scanners. Each set of images was reconstructed in 3D and then used to manufacture physical models of each bone, using rapid prototyping technology. After imaging the soft tissues were removed and specific measurements of the bony anatomy compared with measurements from the MRI and CT models.ResultsBone models generated from MRI scans were dimensionally less accurate than those generated from CT scans. Furthermore, the bone models generated from MRI scans were visibly inferior to those generated from the CT scans.ConclusionsCurrent MRI scans do not offer a viable alternative to CT. Although adaptation of the template system to accommodate MRI imaging is possible, the changes required are neither practical nor desirable. Copyright © 2008 John Wiley & Sons, Ltd.
Noninferiority hypotheses and choice of noninferiority margin
Authors: Ng Tie‐Hua 
Published: August 2008

AbstractNg (Drug Inf. J. 1993; 27:705–719; Drug Inf. J. 2001; 35:1517–1527) proposed that the noninferiority (NI) margin should be a small fraction of the therapeutic effect of the active control as compared with placebo in the setting of testing the NI hypothesis of the mean difference with a continuous outcome. For testing the NI hypothesis of the mean ratio with a continuous outcome, a similar NI margin on a log scale is proposed. This approach may also be applied in the setting of testing the NI hypotheses for survival data based on hazard ratios. Some pitfalls of testing the NI hypotheses with binary endpoints based on the difference or the ratio of proportions will be discussed. Testing the NI hypothesis with binary endpoints based on the odds ratio is proposed. Copyright © 2008 John Wiley & Sons, Ltd.
Finite sample adjustments in estimating equations and covariance estimators for intracluster correlations
Authors: Preisser John S. , Lu Bing , Qaqish Bahjat F. 
Published: August 2008

AbstractBias‐corrected covariance estimators are introduced in the context of an estimating equations approach for intracluster correlations among binary outcomes. Simulation study results show that the bias‐corrected covariance estimators perform better than uncorrected sandwich estimators in terms of bias and coverage probabilities. Additionally, introduction of a matrix‐based bias‐correction into the estimating equations considerably improves point and interval estimation for the intracluster correlations. The methods are illustrated using data from a nested cross‐sectional cluster trial on reducing underage drinking. Copyright © 2008 John Wiley & Sons, Ltd.
Software process re‐engineering: a model and its application to an industrial case study
Authors: Napier Nannette P. , Kim Jonathan , Mathiassen Lars 
Published: August 2008

AbstractMany software organizations engage in software process improvement (SPI), but process descriptions may soon become outdated especially if the organization, for a while, has given low priority to SPI. As a result, software organizations may need to re‐engineer process descriptions that are inconsistent with desired process practices. While the literature addresses how organizations can re‐engineer business processes and legacy systems, no guidance exists on re‐engineering legacy process descriptions. Software process re‐engineering (SPR) is a transitional activity that helps organizations effectively re‐engage in SPI by assessing legacy process descriptions; selecting process descriptions that need to be removed, innovated, or implemented; and defining a plan to align process descriptions with desired process practices. SPR results in a repository of managed process descriptions and a plan for disciplined software process management. In this article, we derive principles for SPR, use these principles to propose a model for re‐engineering legacy process descriptions, and present an industrial case study to demonstrate the effectiveness of the model. In the presented case, SPR had several benefits: it leveraged earlier investments in SPI; it engaged key stakeholders in revitalizing improvement efforts; it created a shared understanding of the organization's desired process practices; and, it established a solid platform for continued SPI. Copyright © 2008 John Wiley & Sons, Ltd.
From Cocoa to CSR: Finding sustainability in a cup of hot chocolate
Authors: Long John C. 
Published: August 2008

AbstractSustainability definitely has become a hot topic in recent years. Clearly, it is a subject that is not going away and whose importance in the corporate world is gaining currency. The notion of “doing well by doing good” is moving incrementally into mainstream business practice. In what might be considered a sea change, some very important customers now want to talk to supplier company CEOs and managers about their sustainability efforts, as do a growing number of consumers. And while it's hard to tell whether consumers are leading or following when it comes to the importance of sustainability, it's definitely on their radar. Business success increasingly is going to depend upon conducting operations today with a clear view to their impact on future generations. For this, and other valid reasons, we, as business leaders, need to arrive at a practical, workable model of sustainability. © 2008 Wiley Periodicals, Inc.
Inorganic and black carbon aerosol concentrations at a high altitude on Mt Kenya
Authors: Gatari Michael J. , Pettersson Jan B. C. , Kimani Wilson , Boman Johan 
Published: August 2008

AbstractAerosol samples were collected at an altitude of 3678 m on Mt Kenya in August 2001. A virtual impactor was used to collect particles in fine (aerodynamic diameter, da < 2.5 µm) and coarse (2.5 µm < da < 10 µm) size fractions. The samples were analyzed for particulate mass (PM), black carbon (BC) and 15 elements. The PM concentrations varied in the ranges 3.3 ± 1.1–7.8 ± 2.5 µg m−3 (in fine fraction) and 3.7 ± 1.2–9.6 ± 3.0 µg m−3 (in coarse fraction). The fine fraction was dominated by high concentrations of BC, S and K due to particles formed during biomass burning and sulfate particles from secondary processes in the atmosphere. The coarse fraction was dominated by high concentrations of Si, S, Cl, K, Ca and Fe indicative of the presence of soil dust particles. This was further verified by enrichment factors (EFs) calculated using the elemental content of the average crustal rock. Chemical mass balance (CMB) calculations indicated that the PM was largely attributable to biomass burning, mineral dust and sulfate, while contributions from anthropogenic sources were small. Source apportionment of elemental concentrations compared well with that of an earlier study on the southwestern slope of Mt Kenya, while PM and sulfate concentrations were comparable with those observed at high‐altitude sites in North America and Europe. The observed concentrations were 5–50 times lower than those of urban Kenya. Copyright © 2008 John Wiley & Sons, Ltd.
Glycogen storage disease type I in Tunisia: An epidemiological analysis
Authors: Chehida A. Ben , Tebib N. , Cherif W. , Turkia H. Ben , Abdelmoula S. , Azzouz H. , Ben Dridi M. F. 
Published: August 2008

SummaryObjective: Analysis of epidemiological data concerning GSD I in Tunisia. Subjects and methods: All the cases diagnosed as GSD I between 1992 and 2005 in a paediatric department recruiting all the metabolic diseases referred from the North of Tunisia were reviewed. Individual data (sex, socioeconomic and educational background, geographic origins, insurance coverage) were collected and pedigrees were reconstituted. Results: Twenty‐two cases (9 boys and 13 girls from 20 homes) were identified. Fourteen belonged to 11 families originating from the North of Tunisia; ten of them are still alive. Both parents in 4 homes (21%) and one parent in 9 homes (47%) were illiterate. Most of the homes (60%) had a low income and 45% comprised at least 3 children. Only 7 homes (35%) had health insurance. Pedigrees indicated 44 infant deaths and at least 10 other cases fulfilling the clinical features of GSD I but not diagnosed. Conclusion: The paediatric prevalence of GSD I in the North of Tunisia can be estimated to 7.93 cases per one million inhabitants and its incidence to 1/100 000 births. However, it is likely to be more frequent because of underreporting or underdiagnosis leading to precocious deaths.