bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of heating and bleaching on formation of stigmastadienes in olive oil
Authors: Gordon Michael H , Firman Christopher
Published: January 2005

Extra virgin olive oil was heated at various temperatures in the range 187–253 °C. The stigmastadiene content was shown to increase linearly with time, and the energy of activation for sitosterol dehydration was calculated as 191.0 ± 9.0 kJ mol−1. The effect on stigmastadiene formation of bleaching extra virgin olive oil was studied using three bleaching earths at temperatures in the range 80–120 °C. The earth that was most active for pigment removal was also most active for sitosterol dehydration. The bleaching earths had a major catalytic effect on stigmastadiene formation, with the activation energy for the dehydration of β‐sitosterol being reduced to 70.8–80.6 kJ mol−1 in their presence. It was concluded that a common catalytic effect was exerted by all bleaching earths, but the number of active sites for sterol dehydration per unit surface area was greater for the Premiere bleaching earth than for the other bleaching earths, and this was the main cause of the greater catalytic activity of this earth.

© 2001 Society of Chemical Industry
Community knowledge in an emerging online professional community: the case of Sigchi.dk
Authors: Clemmensen Torkil
Published: January 2005

This paper focuses on community knowledge in an emerging online professional community. Members of a Danish human–computer interaction community, 120 usability professionals, designers and researchers, described in an online survey their interest in theory and familiarity with methods. The results are reported in detail, and show a unanimous interest in theory, with a variety of reasons behind. Furthermore, the results indicate that the community's body of theoretical knowledge is divided into clear‐cut faculties, with only general usability and human–computer interaction concepts available for communication and cooperation. This implies that a view of the Danish usability professionals as sharing a special discipline is wrong, and that attempts to create a special common language or general theoretical framework (e.g. Kuutti and Bannon, 1991) will be unfruitful. Rather, an online professional community should be interpreted as a community of interest (Fischer, 2001), and we should use tools developed for these kinds of communities as support tools. Copyright © 2005 John Wiley & Sons, Ltd.
Learning facilitating factors of teamwork on intellectual capital creation
Authors: Cegarra‐Navarro Juan Gabriel , Rodrigo‐Moya Beatriz
Published: January 2005

In the last few years, a trend has been observed that regards teamwork as a fundamental unit for develop learning processes and other production activities. Group learning is thus the bridge between individual and organizational learning. This paper examines the relative importance and significance of some common components of group learning on ‘group capital’ (i.e. objective and collective knowledge created by teams) and the effects of such capital on the creation of intellectual capital through an empirical investigation of 139 small to medium‐sized enterprises (SMEs) in the Spanish optometry sector using structural equation modelling validated by factor analysis. Copyright © 2005 John Wiley & Sons, Ltd.
A contextual theory of learning and the learning organization
Authors: Jensen Povl Erik
Published: January 2005

Learning and accumulation of new knowledge in an organization always require two transformation processes: one transformation process from data to information and another from information to (new) knowledge. This is so because only information, and not knowledge, can be shared and spread among the members of the organization. This article describes these transformations processes as social processes that take place in a concrete context. The processes lead from Data→Information→Knowledge→Action→Learning→New Knowledge. But not all these processes have the same progression or produce the same kind of results. One can differentiate between single‐loop, double‐loop and triple‐loop learning.

These findings are analysed for the consequences they provide for the learning individual and the learning organization. The qualitative difference between the learning organization and other organizations is shown to be the coordination and cooperation that the individuals perform in a close working relationship. Against this background achievements and shortcomings of attempts to become a learning organization are summarized. Copyright © 2005 John Wiley & Sons, Ltd.
The dimensions of process knowledge
Authors: Amaravadi Chandra S. , Lee In
Published: January 2005

Many researchers are of the view that a firm's knowledge assets include its structure, culture, processes, employees and physical artifacts. The knowledge management (KM) literature has tended to emphasize employee knowledge as a locus for KM efforts. While this viewpoint is perfectly rational and justifiable, there is also a considerable amount of knowledge embedded in the firm's operating procedures. In this paper, we espouse viewing organizational knowledge from this perspective and propose a framework to manage process knowledge. Starting with a definition, classification of processes, and a characterization of the knowledge generation process, we provide seven dimensions by which process knowledge can be viewed: structure, personnel and coordination, performance and tools, discourse, results, quality and implications. They are intended to serve as a starting point for managing process knowledge. The dimensions are illustrated with several examples and implications of the framework are pointed out. Copyright © 2005 John Wiley & Sons, Ltd.
Exploring secondary activities of the knowledge chain
Authors: Holsapple Clyde , Jones Kiku
Published: January 2005

Researchers, marketers, and pundits often assert that knowledge management (KM) is an important, or even essential, basis for competitiveness. The Knowledge Chain Model has been advanced as a basis for understanding linkages between KM activities and organizational performance. Based on a general ontology of KM, this model identifies five primary and four secondary activities as focal points for enhancing an organization's competitive position. Both anecdotes and survey results support the model. A prior paper explored the primary classes of activity found in the Knowledge Chain Model, finding that each is comprised of distinct subclasse's that are candidates for enhancing organizational performance. Here, we similarly explore the model's secondary KM activity classes to uncover the subclasses of which they are comprised, thereby arriving at a more detailed understanding of their potential for launching competitive initiatives. A literature review yielded over 300 variations of the four secondary activities. We consolidate these into 29 distinct activity types and organize them into the four secondary activity classes. A typology of activity types is developed for each class. The result is a more in‐depth version of the Knowledge Chain Model that gives greater guidance to practitioners in assessing current KM initiatives or striving to incorporate KM into their organizations and their competitive strategies. Together with the earlier primary activity class paper, a total of 61 distinct activity types have been identified for the Knowledge Chain Model. Copyright © 2005 John Wiley & Sons, Ltd.
Noninvasive ventilation for pediatric patients including those under 1-year-old undergoing liver transplantation
Authors: Chin Kazuo , Uemoto Shinji , Takahashi Ken-ichi , Egawa Hiroto , Kasahara Mureo , Fujimoto Yasuhiro , Sumi Kensuke , Mishima Michiaki , Sullivan Colin E. , Tanaka Kouichi
Published: January 2005

Pulmonary complications are an important cause of the mortality associated with liver transplantation. The efficacy of noninvasive ventilation (NIV) in pediatric patients following transplantation is unknown. The purpose of this retrospective study is to investigate the effects of NIV for pediatric patients undergoing liver transplantation. Of 102 pediatric patients who underwent liver transplantation, 15 patients (aged 73 months; range 2.5–179) were supported by NIV because of atelectasis, hypercapnia, hypoxemia, pneumonia, massive effusion, or postextubation ventilatory support. Of 15 patients, 5 were under the age of 1 year (range 2.5–12 months). Of the 15 patients, 7 had required multiple intubations before NIV treatment because of pulmonary complications. NIV treatment was administered to 6 patients because of hypercapnia. Partial pressure of arterial carbon dioxide (PaCO2) levels improved from 56.9 (95% confidence interval [CI]: 48.4–65.4) to 41.5 (95% CI: 36.8–46.2) mmHg (

P

= .028) within 2 days. NIV treatment was very effective for patients with atelectasis with and without other pulmonary complications. Mean inspiratory positive pressure (IPAP) was 7.2 (95% CI: 6.0–8.3) cm H2O and expiratory positive pressure (EPAP) was 3.5 (95% CI: 3.2–3.9) cm of H2O. Mean duration of NIV was 18.5 (95% CI: 8.6–28.4) days. IPAP and EPAP levels were closely and significantly correlated with height (IPAP: r = .65,

P

= .016; EPAP: r = .77,

P

= .004). A total of 13 patients recovered and 2 patients died. However, no patient died of respiratory complications. In conclusion, NIV is effective in pediatric patients undergoing liver transplantation with subsequent pulmonary complications. The IPAP and EPAP levels may be predicted by the height of the patient. (Liver Transpl 2005;11:188–195.)
How common is delayed cyclosporine absorption following liver transplantation?
Authors: Yantorno Silvina E. , Varela Eva B. , Raffa Sebastián R. , Descalzi Valeria I. , Gomez Carretero Maria L. , Pirola Daniel A. , Ruf Andres E. , Martinez Carabuz Gretel I. , Podesta Luis G. , Villamil Federico G.
Published: January 2005

The mean time to peak absorption of cyclosporine (CsA) in liver transplant patients is approximately 2 hours, but in some patients the peak occurs later. The goal of this study was, therefore, to investigate the incidence of delayed absorption in 27

de novo

liver transplant recipients receiving CsA ≥10 mg/kg/day (C2 monitoring) and in 15 maintenance patients. Patients were categorized as ‘normal’ absorbers (C2 exceeding C4 and C6) or ‘delayed’ absorbers (C4 or C6 exceeding C2), and as ‘good’ (>800 ng/mL at C0, C2, C4, or C6) or ‘poor’ absorbers (C0, C2, C4 and C6 <800 ng/mL) on the day of study. Among

de novo

patients, 15 (56%) had ‘normal’ CsA absorption and 12 (44%) ‘delayed’ absorption. Good CsA absorption occurred in 16 patients (59%) and poor absorption in 11 (41%). The proportion of poor absorbers was similar in patients with normal (6 / 15, 40%) or delayed (5 / 12, 42%) absorption. Among the 12 delayed absorbers, 11 had peak CsA concentration at C4. Mean C0 level was significantly higher in delayed absorbers (282 ± 96 ng/mL) than in normal absorbers (185 ± 88ng/mL;

P

= .01). Delayed absorbers reverted to normal absorption (C2 > C4) after a median of 6 days from the day of study, and no cases of delayed absorption were found among maintenance patients. In conclusion, almost 50% of the patients had delayed CsA absorption early posttransplant; around half of these exhibited normal CsA exposure. Measurement of C4 in addition to C2 differentiates effectively between delayed and poor absorbers of CsA such that over- or underimmunosuppression can be avoided. (Liver Transpl 2005;11:167–173.)
MELD fails to measure quality of life in liver transplant candidates
Authors: Saab Sammy , Ibrahim Ayman B. , Shpaner Alexander , Younossi Zobair M. , Lee Cindy , Durazo Francisco , Han Steven , Esrason Karl , Wu Victor , Hiatt Jonathan , Farmer Douglas G. , Ghobrial Mark R. , Holt Curtis , Yersiz Hasan , Goldstein Leonard I. , Tong Myron J. , Busuttil Ronald W.
Published: January 2005

Previous studies have demonstrated an association between Child Turcotte-Pugh (CTP) class and impaired quality of life. However, the relationship between the model for end-stage liver disease (MELD) score and quality of life (QOL) has not been well studied. In this study, quality of life questionnaires (Medical Outcomes Short Form 36 [SF-36] and the Chronic Liver Disease Questionnaire [CLDQ]) were administered to 150 adult patients awaiting liver transplantation. We also collected demographic data and laboratory results and recorded manifestations of hepatic decompensation. The study found that all domains of the SF-36 and CLDQ were significantly lower in our patient cohort than in normal controls (

P

< .001). There was a moderate negative correlation between CPT class and physical components of the SF-36 (

r

= −.30), while there was a weak negative correlation (

r

= −.10) between CPT class and the mental component. There was a negative moderate correlation between CPT class and overall CLDQ (

r

= −.39,

P

< .001) and a weak correlation (

r

= −.20) between MELD score and overall CLDQ score. Both encephalopathy (correlation coefficient = −.713,

P

= .004) and ascites (correlation coefficient = −.68,

P

= .006) were predictive of the QOL using CLDQ (adjusted

R

2 = .1494 and f = 0.000). In conclusion, in liver transplant candidates, the severity of liver disease assessed by the MELD score was not predictive of QOL. The presence of ascites and/or encephalopathy was significantly associated with poor quality of life. CTP correlates better to QOL, probably because it contains ascites and encephalopathy. (Liver Transpl 2005;11:218–223.)
The effects of ownership concentration on investment and performance in privatized firms in Russia
Authors: Filatotchev Igor , Kapelyushnikov Rostislav , Dyomina Natalya , Aukutsionek Sergey
Published: January 2005

This paper provides new survey evidence on effects of concentrated ownership on restructuring and performance in privatized firms in Russia. The major findings are that large‐block shareholding is negatively associated with the firm's investment and performance, and this relationship does not depend on the identity of controlling shareholders. These results are consistent with the assumption that when minority shareholders' rights are not adequately protected, the entrenched controlling shareholders may be engaged in extracting ‘control premium’ before pro rata distribution of dividends. The issues raised have relevance to other transitional economies where the privatization process has been followed by an increase in ownership concentration. Copyright © 2001 John Wiley & Sons, Ltd.
Cartelizing effects of horizontal shareholding interlocks
Authors: Merlone Ugo
Published: January 2005

Some models of industries with horizontal shareholding interlocks are generalized. First, we consider industries where firms exhibit different technologies and more general market demand functions. The cartelizing effects of financial interlocks are examined using both the Lerner index and the Herfindahl–Hirshman index. Furthermore, the model is extended to consider multiproduct oligopolies. We find a compact expression for the Lerner index and study the cartelizing effects of such an industry. Copyright © 2001 John Wiley & Sons, Ltd.
Internal markets and the theory of the firm
Authors: Ellig Jerry
Published: January 2005

A growing number of companies are explicitly replacing bureaucratic internal resource allocation with internal markets. But if markets work well within firms, why are there firms at all? Why does not all allocation take place on ‘external’ markets? This paper seeks to resolve this apparent anomaly by viewing the firm as a membership club rather than as a command structure. Members join the firm and pay its membership fee when the value of the local public goods they receive exceeds the opportunity cost of joining. Some of the most important public goods provided by firms are variously referred to as organizational capabilities, competencies, or routines. These can often be characterized as public goods because they are ultimately based on knowledge, and hence involve a degree of nonrival consumption. A firm survives when its internal environment generates value‐creating capabilities, competencies, and routines. The firm will continue to exist as long as the owners of its human and physical capital find it more profitable to transact inside this environment than outside. Copyright © 2001 John Wiley & Sons, Ltd.
Linking hypercompetition and strategic group theories: strategic maneuvering in the US insurance industry
Authors: Fiegenbaum Avi , Thomas Howard , Tang Ming‐Je
Published: January 2005

Focusing on the dynamics of strategic maneuvering, this paper draws parallels between the accumulated perspectives of strategic group theory and ideas drawn from evolutionary economics and from a recent strategy‐oriented book on hypercompetition (D'Aveni RA. 1994. Hypercompetition: Managing the Dynamics of Strategic Maneuvering. The Free Press: New York). Using insurance industry data, the paper first uses the methodological framework of strategic groups to define competitive positioning and the identity of close competitors. It then develops a Markovian model to analyse two important aspects of strategic maneuvering over time: the level of firm movement, and the determination of optimal maneuvering paths and their related long‐term performance. The results provide insights into industry competitive dynamics and rivalry. First, there is clear evidence of strategic maneuvering over the entire time period studied and a higher level of maneuvering in the long run. Second, for some competitive scenarios, there are optimal maneuvering trajectories that optimize a firm's long‐term economic performance. Copyright © 2001 John Wiley & Sons, Ltd.
Firm strategy, innovation and consumer demand: a market process approach
Authors: Robertson Paul L. , Yu Tony F.
Published: January 2005

Despite recent advances by economists such as Porter and those associated with the resource‐based school, the economics of demand rarely features in discussions of business strategy. Porter and the resource‐based school take the characteristics of demand as given, and place almost exclusive emphasis on the role of supply‐side factors in formulating strategy. Scholars in strategic marketing, by contrast, recognize the importance of demand factors, but do not analyse them from an economic standpoint. Moreover, none of the important schools of strategic management attempts to explore the relationship between supply and demand in much analytical depth. In this paper, we adopt a market process approach to strategy formulation as a preliminary step towards rectifying these problems. First, we explore the factors that affect the economics of demand, particularly in innovative situations. Second, we adapt Lancaster's attribute analysis to show how the interaction between supply and demand can be represented from a market process perspective. On the basis of our efforts, we conclude that further work in these areas would benefit students of both strategic management and economics. Copyright © 2001 John Wiley & Sons, Ltd.
Strategy in turbulent environments: the role of dynamic competence
Authors: SubbaNarasimha P.N
Published: January 2005

It is often observed that firm survival and success have become problematic in the turbulent environments that firms face today. Resource‐based theories propose that sustained competitive advantage is more a function of firm resources than of industry structure. In this paper, the nature of resources that help firms sustain (or try to sustain) a competitive advantage in turbulent environments is queried. Viewing the firm as a stock of knowledge, the argument that dynamic competence or the variety‐generating capability of knowledge is an important antecedent of superior performance in such turbulent environments is developed. Copyright © 2001 John Wiley & Sons, Ltd.
Innovation and firm‐level persistent profitability: a Schumpeterian framework
Authors: Roberts Peter W
Published: January 2005

Studies of firm‐level profit dynamics tend to attribute the variance in profit persistence to variability in the extent to which imitative pressures are resisted. This monopoly‐based explanation of persistent profitability implicitly assumes a one‐to‐one correspondence between firm‐level and product‐level profit dynamics. Following Schumpeter, this paper begins to develop a framework for firm‐level profit persistence that embraces product innovation, competitor imitation, and, more importantly, the prospect that several product innovations may be embodied within a single firm. Such an approach opens the door for an innovation‐based explanation of profit persistence to accompany the monopoly‐based arguments that are typically offered. Copyright © 2001 John Wiley & Sons, Ltd.
Modeling the competitive process
Authors: Jacobson Robert , Hansen Gary
Published: January 2005

Understanding the behavior of markets requires understanding not just the level of return but also its dynamics. The speed at which abnormal returns dissipate is one useful indicator of the competitive process. We model for US and Japanese firms the process of competition as reflected in the persistence of abnormal returns. While we find a similar aggregate distribution of firm persistence in both countries, we observe cross‐national differences manifesting themselves in terms of inter‐country differences in industry persistence. We find that both industry‐ and firm‐specific factors influence firm persistence. Copyright © 2001 John Wiley & Sons, Ltd.
An agency analysis of church–pastor relations
Authors: Zech Charles
Published: January 2005

Incentives are critical to the study of economics. But do they work in non‐traditional economic settings, such as religious organizations, in a manner consistent with economic theory? This study considers the agency relationship between churches and their clergy. This paper contends that pastor compensation is not typically tied directly to performance, but rather indirectly through promotion tournaments. Pastors whose performance is recognized as being exceptional are rewarded by being called to larger, more prestigious congregations. Given the difficulty of observing and measuring pastor performance this represents a sensible solution to the church–pastor principal–agent problem. Copyright © 2001 John Wiley & Sons, Ltd.
Chaos and mixing in micro‐biological fluid dynamics: blinking stokeslets
Authors: Orme B. A. A. , Otto S. R. , Blake J. R.
Published: January 2005

The motion of particles and feeding currents around micro‐organisms due to a flagellum are considered. The calculations are pertinent to a range of sessile organisms but we concentrate on fluid motion around Salpingoeca Amphoridium—a choanoflagellate; these are a class of organism in the phylum Protozoa. The flow field is characterized by a very small Reynolds number indicating that viscous forces dominate over inertia. The flow caused by the motion of the flagellum is modelled via a point force. The point of application is not stationary, and this movement is modelled using two stokeslets (appropriate to Stokes' flow) whose orientation and position is varied with time. These sessile micro‐organisms reside above a surface, which is modelled as an interface between two fluids having different properties. Efficiency of feeding currents generated by the flagellar motion is studied. The resulting dynamics is investigated using chaotic measures, which examine the stretching and consequent mixing of elements within the fluid. Different point force locations lead to a range of eddy structures such that their superposition results in chaotic advection. Copyright © 2001 John Wiley & Sons, Ltd.
Variations on the wave equation
Authors: Leis Rolf
Published: January 2005

A lot of vibration processes in mathematical physics are described by the wave equation or by related equations and systems, and plenty of research has been done on this subject. The results and methods obtained thereby have been very important in other fields of application, and they still are. They also had and still have an immense influence on the development of mathematics as a whole.

The following survey tries to convey an impression of how exciting the research in this field of partial differential equations has been in the 20th century, and it wants to present some of the interesting results achieved. The selection, of course, reflects personal tastes and interests. It starts reporting on the state of the art at the end of the last century. It then describes important solution methods typical for this century, as there are integral equation methods, Hilbert space methods, or spectral representation. Generalized solutions to initial–boundary‐value problems are mentioned, and some applications are indicated, e.g. on the asymptotic behaviour of solutions, in scattering theory, and in non‐linear analysis. Copyright © 2001 John Wiley & Sons, Ltd.
On the stability and convergence of the finite section method for integral equation formulations of rough surface scattering
Authors: Meier A. , Chandler‐Wilde S. N.
Published: January 2005

We consider the Dirichlet and Robin boundary value problems for the Helmholtz equation in a non‐locally perturbed half‐plane, modelling time harmonic acoustic scattering of an incident field by, respectively, sound‐soft and impedance infinite rough surfaces.Recently proposed novel boundary integral equation formulations of these problems are discussed. It is usual in practical computations to truncate the infinite rough surface, solving a boundary integral equation on a finite section of the boundary, of length 2A, say. In the case of surfaces of small amplitude and slope we prove the stability and convergence as A→∞ of this approximation procedure. For surfaces of arbitrarily large amplitude and/or surface slope we prove stability and convergence of a modified finite section procedure in which the truncated boundary is ‘flattened’ in finite neighbourhoods of its two endpoints. Copyright © 2001 John Wiley & Sons, Ltd.
Analysis of a time discretization for an implicit variational inequality modelling dynamic contact problems with friction
Authors: Ricaud Jean‐Marc , Pratt Elaine
Published: January 2005

Some dynamic contact problems with friction can be formulated as an implicit variational inequality. A time discretization of such an inequality is given here, thus giving rise to a so‐called incremental solution. The convergence of the incremental solution is established, and then the limit is shown to be the unique solution of the variational inequality. This paper contains therefore not only some new results concerning the numerical aspect of some models of contact and friction but also a constructive existence result. Copyright © 2001 John Wiley & Sons, Ltd.
1H NMR studies of copper binding by histidine‐containing peptides
Authors: Gaggelli Elena , D'Amelio Nicola , Valensin Daniela , Valensin Gianni
Published: January 2005

We review recent developments in the studies of Cu(II) complexes with histidine‐containing peptides in solution by NMR. An overview of the theoretical background of the effects of the paramagnetic metal on the NMR properties (relaxation and shift) of nearby nuclei is given. Particular attention is paid to the effect of exchange rates between free and metal‐bound forms of the ligand on detection of paramagnetic relaxation rates. General methods are underlined to determine the structure of the complexes (and thus the donor set to the metal) and to distinguish between the binding of copper(II) to either N‐1 or N‐3 of the imidazole ring of histidine. Examples are reported dealing with fragments of the amyloid precursor protein (a protein related to Alzheimer's disease) and of the prion protein (related to Creutzfeldt–Jakob disease) in which the binding of copper may be relevant for subsequent redox activities, protein aggregation or metal‐catalyzed protein damage. Copyright © 2003 John Wiley & Sons, Ltd.
A 19F relaxometric study of the competition of Gd(III) and Lu(III) towards DTPA in water
Authors: Bonnet Célia S. , Fries Pascal H.
Published: January 2005

Because of its strong Coulomb attraction by the positive Gd(III) aqua ion and its strong repulsion by the negative gadolinium diethylenetriaminepentaacetate (Gd‐DTPA) complex, the trifluoroacetate anion CF3COO− has very different relative spatial dynamics with respect to these two species. Therefore, the Gd(III) aqua ion and Gd‐DTPA complex cause very different longitudinal relaxivities of the trifluoroacetate 19F nuclei. In the presence of competitor Lu(III) ions, the relaxivity difference makes it possible to assay the concentrations of Gd(III) aqua ion and Gd‐DTPA complex from the measured paramagnetic relaxation rate enhancement of the trifluoroacetate 19F nuclei. This experimental method allows one to characterize the present transmetallation equilibrium and it can be easily generalized to other systems. Copyright © 2003 John Wiley & Sons, Ltd.
Solution NMR methods for quantitative identification of chemical exchange in 15N‐labeled proteins
Authors: Wang Chunyu , Palmer Arthur G.
Published: January 2005

Chemical exchange phenomena in NMR spectra reveal protein motions on microsecond to millisecond time scales that are associated with biological functions, including catalysis, ligand binding, allosteric conformational changes and protein folding. This review surveys solution NMR methods for identifying chemical exchange in proteins by measuring transverse relaxation rate constants for backbone 15N spins. The relaxation‐compensated‐IzSz and in‐phase Hahn echo methods are suitable for small‐ to medium‐sized proteins. The transverse relaxation optimized spectroscopy method is suitable for large, deuterated proteins. Differential multiple quantum relaxation is also a signature of chemical exchange and provides unique information about exchange processes. The various methods are illustrated by application to basic pancreatic trypsin inhibitor and triosephosphate isomerase. Copyright © 2003 John Wiley & Sons, Ltd.
Conformational analysis of N‐arachidonylethanolamide (anandamide) using nuclear magnetic resonance and theoretical calculations
Authors: Bonechi C. , Brizzi A. , Brizzi V. , Francioli M. , Donati A. , Rossi C.
Published: January 2005

The conformational properties of cis‐5,8,11,14‐eicosatetraenoylethanolamide (anandamide) were analysed by the combined use of NMR experimental results plus molecular simulations. The structure of anandamide was found to be a predominantly linear with a seven‐atom ring of the ethanolamine group having a hydrogen bond which stabilizes the molecule. The vinylic group present has a cis conformation in solution. The terminal chain has a linear conformation and undergoes isotropic fast motion typical of this structure. Copyright © 2001 John Wiley & Sons, Ltd.
Identifying environmental contributions to autism: Provocative clues and false leads
Authors: Lawler Cindy P. , Croen Lisa A. , Grether Judith K. , Van de Water Judy
Published: January 2005

The potential role of environmental factors in autism spectrum disorders (ASD) is an area of emerging interest within the public and scientific communities. The high degree of heritability of ASD suggests that environmental influences are likely to operate through their interaction with genetic susceptibility during vulnerable periods of development. Evaluation of the plausibility of specific neurotoxicants as etiological agents in ASD should be guided by toxicological principles, including dose–effect dependency and pharmacokinetic parameters. Clinical and epidemiological investigations require the use of sufficiently powered study designs with appropriate control groups and unbiased case ascertainment and exposure assessment. Although much of the existing data that have been used to implicate environmental agents in ASD are limited by methodological shortcomings, a number of efforts are underway that will allow more rigorous evaluation of the role of environmental exposures in the etiology and/or phenotypic expression of the disorder. Surveillance systems are now in place that will provide reliable prevalence estimates going forward in time. Anticipated discoveries in genetics, brain pathology, and the molecular/cellular basis of functional impairment in ASD are likely to provide new opportunities to explore environmental aspects of this disorder. © 2004 Wiley‐Liss, Inc. MRDD Research Reviews 2004;10:292–302.
Strength of two structured soils in triaxial compression
Authors: Wong Ron C. K.
Published: January 2005

Oil sands are dense granular materials with interlocked structure and clay shales are heavily overconsolidated clays. They are classified as structured soil or weak rock, exhibiting high peak strength with severe softening and dilation, particularly at low confining stress. The triaxial compression test results indicate that both materials yield linear Mohr–Coulomb envelopes with an apparent cohesion for peak and residual strengths. However, the strength components mobilized from these two materials are very different. This paper investigates if these strength parameters are intrinsic properties or responses derived in triaxial compression conditions. Computer tomography scanning technique is used to aid in examining the micro‐structural features of the sheared specimens such as shear banding pattern, shear band thickness, spatial porosity distributions inside and outside shear bands. These micro‐structural features are used to explain the macro‐deformation response observed in the triaxial compression tests. Mobilization of strength components derived from interlocked structure, cementation, dilation, rolling and critical state are analysed for pre‐, post‐peak softening and residual stages. It is found that the empirical correlation such as Mohr–Coulomb failure criterion based on triaxial compression test results does not necessarily reflect the intrinsic properties of the test materials. Testing conditions are embedded in the empirical correlation. Copyright © 2001 John Wiley & Sons, Ltd.
Finite element analysis of land subsidence above depleted reservoirs with pore pressure gradient and total stress formulations
Authors: Gambolati Giuseppe , Ferronato Massimiliano , Teatini Pietro , Deidda Roberto , Lecca Giuditta
Published: January 2005

The solution of the poroelastic equations for predicting land subsidence above productive gas/oil fields may be addressed by the principle of virtual works using either the effective intergranular stress, with the pore pressure gradient regarded as a distributed body force, or the total stress incorporating the pore pressure. In the finite element (FE) method both approaches prove equivalent at the global assembled level. However, at the element level apparently the equivalence does not hold, and the strength source related to the pore pressure seems to generate different local forces on the element nodes. The two formulations are briefly reviewed and discussed for triangular and tetrahedral finite elements. They are shown to yield different results at the global level as well in a three‐dimensional axisymmetric porous medium if the FE integration is performed using the average element‐wise radius. A modification to both formulations is suggested which allows to correctly solve the problem of a finite reservoir with an infinite pressure gradient, i.e. with a pore pressure discontinuity on its boundary. Copyright © 2001 John Wiley & Sons, Ltd.
A note on formulas for localized failure of frictional materials in compression and biaxial loading modes
Authors: Lambrecht Matthias , Miehe Christian
Published: January 2005

The paper investigates aspects of the localization analysis of frictional materials. We derive closed formulas and diagrams for the inclination angle of critical discontinuity surfaces which develop in homogeneous compression and biaxial loading tests. The localization analysis is based on a Drucker–Prager‐type elastoplastic hardening model for non‐associated plastic flow at small strains, which we represent in spectral form. For this type of constitutive model, general analytical formulas for the so‐called critical hardening modulus and the inclination angle of critical discontinuity surfaces are derived for the plane strain case. The subsequent treatment then specializes these formulas for the analysis of compression and biaxial loading modes. The key contribution here is a detailed analysis of plane strain deformation modes where the localized failure occurs after subsequent plastic flow. The derived formulas and diagrams can be applied to the checking of an accompanying localization analysis of frictional materials in finite‐element computations. Copyright © 2001 John Wiley & Sons, Ltd.
A modified Jacobi preconditioner for solving ill‐conditioned Biot's consolidation equations using symmetric quasi‐minimal residual method
Authors: Chan S. H. , Phoon K. K. , Lee F. H.
Published: January 2005

This paper identifies imbalanced columns (or rows) as a significant source of ill‐conditioning in the preconditioned coefficient matrix using the standard Jacobi preconditioner, for finite element solution of Biot's consolidation equations. A simple and heuristic preconditioner is proposed to reduce this source of ill‐conditioning. The proposed preconditioner modifies the standard Jacobi preconditioner by scaling the excess pore pressure degree‐of‐freedoms in the standard Jacobi preconditioner with appropriate factors. The performance of such preconditioner is examined using the symmetric quasi‐minimal residual method. To alleviate storage requirements, element‐by‐element iterative strategies are implemented. Numerical experiment results show that the proposed preconditioner reduces both the number of iteration and CPU execution time significantly as compared with the standard Jacobi preconditioner. Copyright © 2001 John Wiley & Sons, Ltd.
Linear coupled analysis of desiccation shrinkage in a double‐layer partially saturated medium: semi‐explicit solutions
Authors: Thouvenin G. , Giraud A. , Homand F.
Published: January 2005

Solutions are presented for the problem of isothermal dessiccation shrinkage in a double‐layer porous partially saturated medium. The rheological model taken into account is linear poroelastic. Hence the analysis is mainly focused on hydromechanical coupling effects and contrasts of mechanical and hydraulic properties between two materials: a low thickness skin comprised between the outer boundary and the reference porous material. Three one‐dimensional ideal structures are taken into account: a wall of finite thickness (cartesian geometry), a thick cylinder and a thick sphere. The solution of the time‐dependent problem is arrived at by applying Laplace transforms to the field variables. Exact solutions are obtained in Laplace transform space using Mathematica© to solve the field equations whilst taking into account the continuity equations at the interface and the boundary conditions. The Talbot's modified algorithm has been performed to invert the Laplace transform solutions. A bibliographical and numerical study shows that this method is remarkably precise, stable and close to the analytical inversion. Results are presented using poroelastic data representative of a concrete material and involve a strong coupling effect between hydraulical and mechanical behaviours. A first approach elastic modelling of degradation process have been presented using a thin outer layer. Apart from emphasising the semi‐explicit solution utility due to accurate speed calculation, this paper deals with more complex problems than those which can be solved using purely analytical solutions. Copyright © 2001 John Wiley & Sons, Ltd.
The optimal feedback control of the linear‐quadratic control problem with a control inequality constraint
Authors: Mao Yunying , Liu Zeyi
Published: January 2005

In this paper, we consider the linear‐quadratic control problem with an inequality constraint on the control variable. We derive the feedback form of the optimal control by the agency of the unconstrained linear‐quadratic control systems. Copyright © 2001 John Wiley & Sons, Ltd.
The dynamic efficiency of the Ramsey model with endogenous labour participation rate
Authors: Faria João Ricardo
Published: January 2005

This paper incorporates the hypothesis of labour participation rate into the Ramsey model. It is shown that the economy can be dynamically inefficient if the average productivity of capital is greater than the sum of the rate of time preference, the population growth rate, the depreciation rate and the marginal rate of substitution between labour and consumption. The modified golden rule holds when the wage rate is equal to the marginal rate of substitution between labour and consumption. However, there is no guarantee that it will happen, since labour supply is driven by capital allocation decisions. Copyright © 2001 John Wiley & Sons, Ltd.
A suboptimal learning control scheme for non‐linear systems with time‐varying parametric uncertainties
Authors: Xu Jian‐Xin , Tan Ying
Published: January 2005

In this paper, learning control is integrated with non‐linear optimal control to enhance control performance of a class of non‐linear systems with time‐varying parametric uncertainties. A suboptimal control strategy based on a control Lyapunov function (CLF) and Sontag's formula provides suboptimal performance as well as stability along the time horizon for the nominal part of the non‐linear dynamic system. The proposed learning mechanism learns the unknown time‐varying parametric uncertainties so as to eliminate uncertain effects. System information both in time horizon and learning repetition horizon are incorporated in a composite energy function (CEF). The proposed control scheme achieves asymptotic convergence along the learning repetition horizon and boundedness and pointwise convergence of the tracking error (perfect tracking performance) along the time horizon. Copyright © 2001 John Wiley & Sons, Ltd.
Minimum effort dead‐beat control of linear servomechanisms with ripple‐free response
Authors: Mošna Jiří , Melichar Jiří , Pešek Pavel
Published: January 2005

A new and systematic approach to the problem of minimum effort ripple‐free dead‐beat (EFRFDB) control of the step response of a linear servomechanism is presented. There is specified a set of admissible discrete error feedback controllers, complying with general conditions for the design of ripple‐free dead‐beat (RFDB) controllers, regardless of the introduced degree of freedom, defined as the number of steps exceeding their minimum number. The solution is unique for the minimum number of steps, while their increase enables one to make an optimal choice from a competitive set of controllers via their parametrization in a finite‐dimensional space. As an objective function, Chebyshev's norm of an arbitrarily chosen linear projection of the control variable was chosen. There has been elaborated a new, efficient algorithm for all stable systems of the given class with an arbitrary degree of freedom. A parametrized solution in a finite space of polynomials is obtained through the solution of a standard problem of mathematical programming which simultaneously yields the solution of a total position change maximization of servomechanism provided that a required number of steps and control effort limitation are given. A problem formulated in this way is consecutively used in solving the time‐optimal (minimum‐step) control of a servomechanism to a given steady‐state position with a specified limitation on control effort. The effect of EFRFDB control on the example of a linear servomechanism with torsion spring shaft, with the criterions of control effort and control difference effort, is illustrated and analysed. Copyright © 2001 John Wiley & Sons, Ltd.
A reduced‐order stochastic observer approach to optimal state estimation with noise‐free measurements
Authors: Yaz Edwin Engin , Yaz Yvonne Ilke
Published: January 2005

In a continuous‐time Kalman filter, it is required that the measurement noise covariance be non‐singular. If the measurements are noise‐free, then this condition does not hold and, in practice, the measurement data are differentiated to define a derived measurement function to build what is known as Deyst filter. It is proposed here that a reduced‐order observer be used in deriving the linear minimum‐variance filter to construct state estimates based on the original measurement data with no need for differentiation. This filter is of dimension (n−p) wherenandpare the state and measurement vector dimensions, respectively. In this work, we consider both the finite‐time and infinite‐time results. The set of all assignable estimation error covariances are characterized and the set of all estimator gains are parametrized in addition to the linear minimum variance optimal results. The conditions for the existence of the optimal steady‐state filter are obtained in terms of the system theoretic properties of the original signal model. A simple example is included to illustrate the effectiveness of the proposed technique. Copyright © 2001 John Wiley & Sons, Ltd.
Model reduction for singular systems via covariance approximation
Authors: Jing Wang , Liu Wanquan , Zhang QingLing
Published: January 2005

In this paper, model reduction problem for singular systems will be investigated. To solve the problem, the covariance for singular systems will be defined. Then, a model reduction method based on covariance approximation will be presented for obtaining a stable and impulse controllable models for singular systems. Third, the error criterion was explicitly derived via a free parameter and the optimization procedure was presented in terms of gradient flow. Finally, illustrative examples are given to show the effectiveness of the proposed approach. Copyright © 2005 John Wiley & Sons, Ltd.
Constitution‐making in Africa: assessing both the process and the content
Authors: Ndulo M.
Published: January 2005

This article examines the relationship between governance and development, and concludes that underlying the litany of Africa's development problems is a crisis of governance. Good governance would result in institutions that are more likely to adopt economic policies that would resolve the constraints that hinder economic development. In addition, it would make a major contribution to the reduction of war and conflict. It would do this by creating an environment for sustainable development to take place and thereby reduce poverty, the root cause of war and conflict. This calls for a critical examination of the question of governance in Africa with a view to identifying the obstacles to its establishment and the possible approaches to the development of systems of governance that give political space to all groups. Since the most important legal instrument in the scheme of good governance is the national constitution, the article seeks to identify some of the key issues that must be considered in the process of developing a national constitution if it is to be durable. It also addresses the conditions under which such constitutions should be developed if they are to be acceptable to the people of the country they are intended to govern. Running through the article is the theme that the establishment of good governance in Africa depends on the development of political systems that give people a sense of ownership of the political process. Copyright © 2001 John Wiley & Sons, Ltd.