bluuebunny/crossref_metadata_2025 huggingface dataset:
Local Knowledge and Natural Resource Management
Authors: Kelkar Meghana
Published: September 2007

Understanding local knowledge systems is fundamentally important to discern the complexities of natural resource management in any locality, and scientists are increasingly becoming interested in these. However, this interest stems from a narrow technology-centred focus. To broaden this focus, it is important to develop a robust conceptual framework that captures the dynamics of these systems. This article attempts to review various ways of conceptualising local knowledges and the intermeshing of gender and local knowledge in a variety of ways. A feminist gender perspective not only unravels the intricacies of the gendering of knowledge, but problematises the unequal distribution of power, control and skills as these are integral elements of the construction, valuation and marginalisation of local knowledge.
Erythema nodosum and glatiramer acetate treatment in relapsing-remitting multiple sclerosis
Authors: Thouvenot E. , Hillaire-Buys D. , Bos-Thompson M.A. , Rigau V. , Durand L. , Guillot B. , Camu W.
Published: September 2007

Glatiramer acetate (GA), a well tolerated immunomodulatory treatment for relapsing—remitting multiple sclerosis (RR-MS), consists of a 4-amino acid polymer that mimics the myelin basic protein (MBP). We report the first case of biopsy-proven erythema nodosum (EN) in a patient presenting RR-MS under GA treatment. Comprehensive exams were negative in the search of the etiology of EN, which spontaneously resolved despite treatment continuation. GA treatment is known to generate reactive polyclonal antibodies that can cross-react with myelin epitopes, like MBP. These antibodies may also be implicated in allergenic reactions and auto-immune adverse events, such as anaphylactic shock, lymphadenopathy, livedo-like dermatitis, or lymphocytic infiltration. EN is an unspecific skin reaction occurring in several disorders and induced by many treatments. As EN can result from a polyclonal antibody response or type I hypersensitivity mechanisms, we hypothesize that GA treatment could be responsible for the occurrence of EN. Multiple Sclerosis 2007; 13: 941—944. http://msj.sagepub.com
Observational analytic studies in multiple sclerosis: controlling bias through study design and conduct. The Australian Multicentre Study of Environment and Immune Function
Authors: Lucas RM , Ponsonby A-L. , McMichael AJ , van der Mei I. , Chapman C. , Coulthard A. , Dear K. , Dwyer T. , Kilpatrick TJ , Pender MP , Taylor B. , Valery P. , Williams D.
Published: September 2007

Rising multiple sclerosis incidence over the last 50 years and geographic patterns of occurrence suggest an environmental role in the causation of this multifactorial disease. Design options for epidemiological studies of environmental causes of multiple sclerosis are limited by the low incidence of the disease, possible diagnostic delay and budgetary constraints. We describe scientific and methodological issues considered in the development of the Australian Multicentre Study of Environment and Immune Function (the Ausimmune Study), which seeks, in particular, to better understand the causes of the well-known MS positive latitudinal gradient. A multicentre, case-control design down the eastern seaboard of Australia allows the recruitment of sufficient cases for adequate study power and provides data on environmental exposures that vary by latitude. Cases are persons with an incident first demyelinating event (rather than prevalent multiple sclerosis), sourced from a population base using a two tier notification system. Controls, matched on sex, age (within two years) and region of residence, are recruited from the general population. Biases common in case-control studies, eg, prevalence-incidence bias, admission-rate bias, non-respondent bias, observer bias and recall bias, as well as confounding have been carefully considered in the study design and conduct of the Ausimmune Study. Multiple Sclerosis 2007; 13 : 827—839. http://msj.sagepub.com
Long-term survival of patients with multiple sclerosis in West France
Authors: Leray E. , Morrissey SP , Yaouanq J. , Coustans M. , Le Page E. , Chaperon J. , Edan G.
Published: September 2007

In France no data have been published about comparing survival in multiple sclerosis (MS) patients with the general French population. We estimated survival probabilities in MS patients from a major centre for MS in West France. We also compared MS survival with the general population and assessed prognostic parameters. All patients with MS onset after January 1976 and classified as dead or alive on 1 January 2004 were included. One thousand eight-hundred and seventy-nine patients (sex ratio W: M 2.3; relapsing/progressive onset 77.4%/22.6%) fulfilled these criteria, disease duration ranged from one to 28 years. By 2004, 68 patients died (51 due to MS) and the 15 and 25-year survival probabilities were 96% and 88%. Male gender, progressive course (either primary or secondary), polysymptomatic onset, and increased annual relapse rate during the first two years of MS were related to a worse prognosis. After a mean follow-up duration of 12.7 years since clinical onset, MS increased the number of deaths compared with the general population. However taking into account disability status, we found that less disabled MS patients had a better survival and highly disabled patients a worse survival (eight-fold increase of mortality) compared with the French population. Multiple Sclerosis 2007; 13: 865—874. http://msj.sagepub.com
Developing an activity to aid informed assent when interviewing children and young people
Authors: Bray Lucy
Published: September 2007

It is now recognised that children as social actors, are competent witnesses to speak for themselves about their experiences of, and perspectives on, the social worlds in which they live (James et al., 1998). Consulting with children and young people directly is vital to gain an understanding of their experiences and it is important for their involvement in research to be appropriate and ethically sound. They should be guaranteed a clear explanation of the purpose of the research and a clear choice about whether they want to get involved based on a full knowledge and understanding of what is involved (Cohen and Emanuel, 1998). There is limited literature which addresses the practical process of obtaining assent from children and young people in social research. This article discusses the factors influencing the assent process and the development of an activity to aid obtaining assent from children and young people.
Designing and testing questionnaires for children
Authors: Bell Alice
Published: September 2007

Only in the last 10—15 years have social researchers acknowledged the importance of conducting survey research with children directly, rather than relying on qualitative findings plus prevalence data collected by proxy from adults. With reference to the question—answer model, I here present and consider a number of guiding principles for the design of appropriate and effective questions for younger respondents. Pretesting of questions is especially important when researching populations about which relatively little is known, or who are likely to be especially sensitive to failings of questionnaire design. Children fall into this category because relatively little is known about how the question—answer model applies to them, and because their cognitive, memory, communicative and social faculties are still developing. With this in mind, I describe two key methods of question-testing, namely review by expert panel and in-depth cognitive interviewing.
Attitudes to and knowledge about pain and pain management, of nurses working with children with cancer: A comparative study between UK, South Africa and Sweden
Authors: Enskär Karin , Ljusegren Gunilla , Berglund Gimbler , Eaton Nicola , Harding Rosemary , Mokoena Joyce , Chauke Motshedisi , Moleki Maria
Published: September 2007

Pain is among the most common effects of cancer and its treatment. Children and young people with cancer often consider pain from procedures and treatment to be the worst aspect of their illness.

This study aimed to i) identify and describe knowledge and attitudes to pain and pain management amongst nurses working with children with cancer and ii) compare the perspectives on pain and pain management of nurses from UK, South Africa and Sweden.

106 nurses working with children with cancer in UK, South Africa and Sweden completed Salanterä's (1999) questionnaire on nurses' attitudes to pain in children.

Nurses had good levels of knowledge and positive attitudes to pain management, with Swedish nurses' having higher levels of knowledge and a more positive attitude to pain management than nurses from UK or South Africa.

A high level of knowledge was correlated to a more positive attitude to pain management. Knowledge levels need to be improved to ensure more positive attitudes to pain management, especially for nurses in South Africa. Swedish nurses' level of knowledge about non-pharmacological pain management strategies has scope for improvement. British nurses may need to focus more on the sociology and psychology of pain.
Using art-based techniques in engaging children and young people in health care consultations and/or research
Authors: Coad Jane
Published: September 2007

This paper outlines how art-based techniques and activities can applied for use in consultation work and/or research projects with children and young people. First, the concept of what constitutes an art-based activity and how it might be used in consultation and/or research is explored. Following this, three art-based activities of using photographs, drawings/posters or collages and mapping techniques are considered in terms of application to field work. Literature and work undertaken by the author is drawn upon. Critical discussion of using art-based techniques includes pragmatic discussion relating to entering the field, time, resources, collecting the data, settings and feedback.
Fretting wear of SiAlON ceramic
Authors: Wani M. F.
Published: September 2007

Friction andwear properties of Si6- Z Al zO zN8- Z ( z = 0.5) were studied in case of fretting. SiAlON samples were prepared by hot pressing without any externally added liquid. The effect of running time, slip amplitude, and normal load on friction and wear were investigated. A constant coefficient of 0.45 was observed during running time; however, friction coefficient increased from 0.445 to 0.475 for normal load variation of 20N to 60N. Wear increased linearly with the increase in sliding time and normal load for both SiAlON and steel; however, it decreased with the increase in slip amplitude. Higher wear was observed at low amplitudes as compared with wear at higher amplitudes. Transition from higher wear to lower wear occurred at fretting amplitude of 100–150μm. Wear coefficient of 7.0 × 10−4 and 18 × 10−4 was observed for SiAlON and steel, respectively. Micrographs proved useful for understanding wear mechanism. The wear in SiAlON/steel tribopair was caused by a combination of third body abrasion, tribofilm formation, and minor scoring.
Heat generation in Fe-C-Cu-MoS2-sintered spur gears under unlubricated conditions
Authors: Dhanasekaran S , Gnanamoorthy R
Published: September 2007

In many applications, gears operate under unlubricated conditions and there is a need for new materials with a good friction and wear characteristics for use in these situations. A new alloy, Fe-C-Cu + MoS2, was developed using a powder metallurgy processing route for gear and bearing running under unlubricated operating conditions. Spur gears were compacted from the pre-alloyed powders and sintered. The gear performance was evaluated using a power absorption type gear test rig. The temperature rise measured during testing depends on the material composition, porosity, and coefficient of friction. A thin lubricant film formed in the MoS2-added gears affects the friction and thereby the heat generation during running. An optimum amount of MoS2 addition, 3 per cent, is found beneficial in reducing the surface temperature rise. The analytical model predicts the temperature rise with a reasonable accuracy.
Transient elastohydrodynamic lubrication analysis of an involute spur gear using couple-stress fluid
Authors: Kumar P , Saini P. K. , Tandon P
Published: September 2007

A complete numerical solution to the transient elastohydrodynamic lubrication (EHL) problem of an involute spur gear is obtained under isothermal condition. The lubricant is assumed to be couple-stress fluid and the transient Reynolds equation for the compressible couple-stress fluid is derived using Stokes theory. The EHL characteristics computed for couple-stress fluids are found to have strong dependence on couple-stress parameter. Significant increase in minimum film thickness due to couple-stress fluid is observed. Also, it is found that couple-stress fluids tend to smoothen the variation of film thickness along the line of action caused by transient effects.
Design of a tribotester for evaluation of polymer components under static and dynamic sliding conditions
Authors: Samyn P , Kalacska G , Keresztes R , Zsidai L , De Baets P
Published: September 2007

Coefficients of friction and wear lifetime for machine elements are usually estimated from pin-on-disc tests under fixed test conditions. The experimental design of a tribotester with variable sliding path, dynamically changing normal loads, and sliding velocities is presented in this paper together with a preliminary evaluation of sliding properties for engineering polymers. The design of a dynamic loading mechanism and control of the sliding motion are detailed. The importance of dynamic testing is illustrated for polyamides and polyacetals under pure, internally lubricated and glass fibre-reinforced conditions. Dynamic tests induce lower friction compared with static tests because of influences of visco-elastic deformation, inertia forces, and possibly molecular orientation on the sliding surface. Internal lubricants efficiently reduce friction and wear both under static and dynamic conditions. Glass fibres more effectively reduce wear rates on dynamic tests indicating different wear debris mobility in the interface.
Rail corrugation formation studied with a full-scale test facility and numerical analysis
Authors: Jin X , Wen Z
Published: September 2007

The current paper reviews and discusses the results of some important papers on rail corrugation in detail, and introduces the experimental study on mechanism of rail corrugation formation on curved track carried out using a full-scale test facility. The corrugation with different wavelengths on the test wheel tread is reproduced in the experiment. It is found that the passing frequency of the reproduced corrugation is the same as the excited natural frequency of the test rig. The natural frequencies of the test rig are identified through the modal experiment of the test rig using impulse method. The corrugation in the experiment is numerically analysed in the paper. In the analysis the contact geometry and steady creepage of the wheels/rollers in rolling contact are calculated. Kalker's rolling contact theory with non-Hertzian form is modified and used to calculate the frictional work density in the contact area of the wheel/roller. A model concerning the material loss per unit area proportional to the frictional work density is used to determine the wear on the contact surface of the wheel. The numerical results are in good agreement with the experimental results. They show that the test rig vibrating at high frequency can initiate a corrugation passing the same frequency on the smooth contact surface of the wheel under specific test conditions. The specific conditions include the non-zero steady creepage of the wheelset/rollers, the circumference of the wheel rolling circle approximately equal to multiple of the corrugation wavelength. The corrugation wavelength depends on the excited natural frequency of the test rig and the rolling speed of the wheelset. The depth and growth speed of corrugation depend on the fluctuation amplitude of the contact normal load of the wheelset/rollers.
A model for couple-stress fluid film mechanism with reference to human joints
Authors: Ahmad N , Singh J. P.
Published: September 2007

A theoretical model for couple-stress fluids film mechanism with reference to human joints has been considered in this study. A couple-stress fluid film is taken as a lubricant. The expression for load capacity has been obtained in terms of couple-stress parameter, film thickness, and porosity parameter. The dependence of load on these parameters has been studied graphically.
Effects of operating conditions and friction on the entrapment of spherical debris particles in elliptical contacts
Authors: Nikas G. K.
Published: September 2007

Based on a mechanistic model of entrapment and rejection of spherical debris particles in elliptical contacts of various machine elements, which has been recently published by the present author, a parametric study has been conducted to analyse the effects of the contact load and speed, lubricant viscosity (in the case of lubricated contacts) and particle-contact-counterface friction coefficients on the critical particle size for entrapment, rejection, and intermediate states. The simulation involved a conforming as well as a non-conforming elliptical contact. The parameters were varied in unequal steps as follows: contact load from 5 to 500 N, contact speed (average speed of the two counterfaces) from 0.005 to 5.500 m/s, the lubricant dynamic viscosity from 0.001 to 1.000 Pa s, and the friction coefficient between a particle and a contact counterface from 0.02 to 0.20 (with, generally, different coefficients used for the two counterfaces). The results are in the form of two- and three-dimensional graphs and contour maps, showing the zones of particle entrapment, rejection, ‘weak rejection’, etc. in the contact inlet; the critical particle sizes for entrapment and rejection; as well as graphs showing most of these parameters and effects together for quick assessment. The model has proved to be an efficient mathematical tool in predicting the risks of contact damage due to debris particles by offering both clear quantitative as well as qualitative answers, and can assist in the selection of proper filtration or sealing systems, or simply be used as a supplementary tool in life-expectancy calculations of concentrated contacts in machine-element applications.
Heat transfer analysis in mechanical seals using fin theory
Authors: Luan Z , Khonsari M. M.
Published: September 2007

A simple and efficient method for estimating the average seal contact face temperature, surface temperature, and heat partitioning factor between the rings of a mechanical seal is presented. The method takes into account both heat conduction and convection. Design charts applicable to a variety of ring shapes are developed, and a series of examples are presented to illustrate their validity.
Modelling and optimization of rotary vane seals
Authors: Nikas G. K. , Burridge G , Sayles R. S.
Published: September 2007

The present study deals with the formulation of the mechanics and elastohydrodynamics, and performance of composite vane seals of rectangular cross-section and goalpost shape, such as those used in rotary vane actuators in aviation, automotive, and industrial applications. After constructing the mathematical and computational model of such seals, results are obtained for an application involving a rotary vane actuator for aircraft wing control surfaces. Examples are presented for both steady-state and transient conditions (steady and unsteady motion). These are followed by an extensive parametric study to establish the effects of various parameters on sealing performance, such as the effects of the seal interferences, sealed pressure, speed, design clearances, operating temperature, and the degree of lubricant starvation. Sealing performance is assessed on the grounds of the mass leakage rate, hydrodynamic friction force and extrusion size during operation. The parametric study resulted in the construction of 144 diagrams with 432 performance curves in total. Based on this, the design and operational sealing parameters were optimized to maximize sealing performance, that is, to minimize leakage, friction, and extrusion. There was an excellent agreement between the theoretically derived optimum values and those recommended semi-empirically by the seal and actuator manufacturers as initial estimates. The parametric study showed that vane seals are objects of complex mechanical behaviour, requiring attention to details in their design and application, not only to maximize performance, but, primarily, to establish sufficient sealing and avoid premature failure that could prove very costly indeed.
Flow switching bifurcations on the separation boundary in discontinuous dynamical systems with flow barriers
Authors: Luo A C J
Published: September 2007

In this paper, the flow passability on the separation boundary is investigated in discontinuous dynamic systems with flow barriers. The concepts of the flow barriers in discontinuous dynamical systems are introduced first. Because of the flow barriers existing on the separation boundary, the singularities of the flow on such a separation boundary will be changed accordingly. Therefore, the switching bifurcations from passable to non-passable flow or fromnon-passable to passable flowon the discontinuous boundary are discussed in this paper. Further, the necessary and sufficient conditions for the switching bifurcation and sliding fragmentation in discontinuous dynamical systems with flow barriers are developed. A periodically forced friction oscillator with static dry-friction is investigated as a sample problem for illustration of a flow into the flow barrier. This sample problem can be used to the cutting dynamics in manufacturing and brake system in automobile industry. This paper presents an efficient method to determine the flow passability on the boundary in discontinuous dynamical systems. The sliding mode control can be easily realized through the appropriate conditions as in this paper.
Non-linear free transverse vibration of thin rotating discs
Authors: Hamidzadeh H R
Published: September 2007

An analytical method is adopted to determine modal characteristics of non-linear spinning discs. The disc is assumed to be isotropic and rotating under steady-state conditions. The effects of amplitude and rotating speed on natural frequencies are determined. The developed procedure is also capable of analysing natural frequencies of linear free vibration, which is independent of amplitude. Attention is confined to determine natural frequencies, mode shapes, stress distributions, and critical speeds for different numbers of nodal diameters. The developed procedure does not consider modes of vibration corresponding to nodal circles. Validity of this procedure is verified by comparing some of the computed results with those established for certain cases.
Prediction of friction-related power losses of hypoid gear pairs
Authors: Xu H , Kahraman A
Published: September 2007

A model to predict friction-related mechanical efficiency losses of hypoid gear pairs is proposed in this study. The model includes a gear contact model, a friction prediction model, and a mechanical efficiency formulation. The friction model uses a friction coefficient formula obtained by applying multiple linear regression analysis to a large number of elastohydrodynamic lubrication analyses covering typical ranges of key parameters associated with surface roughness, geometry, load, kinematics, and the lubricant. Formulations regarding the kinematic and geometric properties of the hypoid gear contact are presented. The load and friction coefficient distribution predictions are used to compute instantaneous torque/power losses and the mechanical efficiency of a hypoid gear pair at any given position. Results of a parametric study are presented at the end to highlight the influence of key operating conditions, surface finish, and lubricant properties on mechanical efficiency losses of hypoid gears.
A study on the scattering field of SH-waves in a topographical area consisting of a semi-cylindrical hill and a subsurface horizontal hole
Authors: Wang G , Dai L , Liu D
Published: September 2007

This research intends to investigate the scattering field of SH-wave in a half-space containing a semicylindrical hill and a subsurface horizontal hole. A mathematical model is established in a two-dimensional plane on the basis of the characteristics of SH-waves, the ‘division-conjunction’ concept, the complex function, and moving-coordinate methods. The whole domain considered is divided into two subdomains, and the wave expressions are assumed in each subdomain. In the cylindrical subdomain, the wave function is constructed with the satisfaction of the zero-stress condition on the hill's surface automatically. In the other subdomain, the solution of the scattering waves is postulated under the stress-free condition on the horizontal surface. The analytical solutions of themodel established are obtained through a series of infinite linear algebraic equations, under the conditions that both the stress and displacement across the conjunction interface of the two subdomains are continuous. The numerical solutions are developed by truncating the infinite linear algebraic equations. The numerical simulations are performed for quantifying the displacements of the horizontal and semicylindrical hill surfaces subjected to incident SH waves, and the numerical results are verified with a comparison to the existing results of a case without subsurface hole.
Design of a piecewise linear vibration isolator for jump avoidance
Authors: Jazar G N , Mahinfalah M , Deshpande S
Published: September 2007

Piecewise linear isolators are smart passive vibration isolators that provide effective isolation for high frequency/low amplitude excitation. This can be done by introducing a soft primary suspension and a relatively damped secondary suspension. Such a piecewise isolator prevents the system from a high relative displacement in low frequency/high amplitude excitation.

By employed an averaging method it is possible to obtain an implicit function for frequency response of a symmetric bilinear vibration isolator system under steady-state harmonic excitation. This function is examined for jump avoidance. A condition is derived which when met ensures that the undesirable phenomenon of ‘jump’ does not occur and the system response is functional. The jump avoidance and sensitivity of the condition are examined and investigated as the dynamic parameters vary. The results of this investigation can be directly employed in design of effective piecewise linear vibration isolators.

A linear vibration system is defined as one in which the quantities of mass (or inertia), stiffness, and damping are linear in behaviour and do not vary with time [1]. Although mathematical models employing a linear ordinary differential equation with constant coefficients portray a simple and manageable system for analytical study, in most cases they are an incomplete representation simplified for the sake of analysis. Most real physical vibration systems are more accurately depicted by non-linear governing equations, in which the non-linearity may stem from structural constraints causing a change in stiffness and damping characteristics, or from inherent non-linear behaviour of internal springs and dampers. This paper focuses on a general form of such a non-linear system. This study of piecewise-linear systems will allow hazardous system behaviour over operating frequency ranges to be gauged and controlled in order to avoid premature fatigue damage, and prolong the life of the system.
Using Bézier splines for design optimization of cams regarding valve train dynamics
Authors: Scheucher R , Hellinger W
Published: September 2007

The aim of this work is to present an optimization problem to design cams for automotive valve trains. The constrained optimization problem uses the control points of the cam profile as design variables. The cam profile is represented by harmonic splines. In addition to the optimization problem the advantages of the calculation of sensitivity information using the direct are determined.

The valve train model is defined by a multi-body system containing discontinuities because of the loss of contact between two consecutive components of the valve train. The objective is to maximize the area below the valve lift, which has a great influence on the gas flow. Constraints for dynamic force, the valve opening and closing phase and the valve lift based on the engine's thermodynamics considerations are taken into account. Furthermore, some constraints for the geometric coordinates of the control points of the cam profile must be imposed.
Experimental and finite element analyses of a sliding-tube-type driveshaft-induced vehicle vibration
Authors: Juang T B , Cheng M , Na L
Published: September 2007

Driveline noise, vibration, and harshness (NVH) has become an integral attribute in defining how the vehicle NVH performance is perceived by the customers of the automotive industry. The driveshaft component design requirements need to make sure that the designed driveline system is robust and reliable in order to achieve the vehicle NVH targets. They also need to ensure that the system maintains its durability performance as well.

A slip mechanism in the driveline system is needed to accommodate the movements caused by the rear axle and rear suspensions when the vehicle travels on a rough road or accelerates/ decelerates abruptly. One design option to accommodate the slip mechanism is to use a press-fitted sliding-tube design. This slip mechanism causes the fluctuation of the contact forces in the tubes, particularly in the vehicle coast down course, and becomes a non-linear contact force phenomenon. This paper uses experimental and finite element method linear tools to explain the non-linear behaviour of the sliding-tube driveshaft, and to provide design options to prevent vehicle vibration issues created by the current sliding-tube driveshaft design.
A multi-physics multi-scale approach in engine design analysis
Authors: Perera M S M , Theodossiades S , Rahnejat H
Published: September 2007

Vibration behaviour of an internal combustion engine depends on rigid body inertial dynamics, structural modal characteristics of its elastic members, tribological behaviour of loadbearing contacts, and piston-cylinder interactions. Therefore, it is essential to use a multi-physics approach that addresses all these physical properties in a single integrative model as presented in this paper. This approach can be regarded as holistic and a good aid for detailed design. Particular attention is paid to the critical elements in the system, such as load-bearing conjunctions (crankshaft main bearings) and piston-cylinder wall interactions. Another important feature is the integrated analysis across the physics of motion from microscale fluid film formation to submillimetre structural deformations and onto large displacements of inertial members. In order to succeed in predictions within sensible industrial time scales, analytical methods have been used as far as possible rather than numerical approaches. Model predictions show good agreement with fired engine test data.
Steady-state stability and bifurcations of friction oscillators due to velocity-dependent friction characteristics
Authors: Hetzler H , Schwarzer D , Seemann W
Published: September 2007

This article presents an analytical investigation on stability and bifurcation behaviour due to an exponential and a generalized friction characteristics in the sliding domain of a simple friction oscillator, which is commonly referred to as ‘mass-on-a-belt’ oscillator. The friction is described by a friction coefficient which depends on the relative velocity between the two tribological partners.

The standard way of examining the steady-state only gives very rough insight in the behaviour and is not able to provide further informations about the steady-state's basin of attraction or about limit-cycles. It is found that the system may undergo bifurcations of Hopf type. Hereby, the character of the bifurcations strongly depends on the parameters of the friction characteristic.
Self-Restraint, Invective, and Credibility in Cicero's First Catilinarian Oration
Authors: Craig Christopher P
Published: September 2007

The First Catilinarian, in comparison with other Ciceronian political speeches commonly considered invectives, is extraordinarily sparing in its use of the standard invective themes. This article will first demonstrate the remarkable paucity in the speech of the invective loci that Cicero's audiences would properly expect. Then it will offer an explanation for Cicero's restraint grounded in the circumstances of the speech and the expectations of Cicero's audience for the veracity of invective.
Improving the Safety Net for Single Mothers Who Face Serious Barriers to Work
Authors: Blank Rebecca M
Published: September 2007

Rebecca Blank explores a weakness of the welfare reforms of the mid-1990s—the failure of the Temporary Assistance to Needy Families program to address the plight of so-called "hard to employ" single mothers and their children. TANF has moved many women on the welfare caseload into work, but the services it provides are not intensive or flexible enough to meet the needs of women with multiple disadvantages who find it difficult to get and keep full-time employment. Blank notes that many of these women have lost welfare benefits because of their failure to find work. Increasingly, studies show that the number of single mothers who are neither working nor on welfare has grown significantly over the past ten years. Such "disconnected" women now make up 20 to 25 percent of all low-income single mothers, and reported income in these families is extremely low. Disconnected women are likely to report multiple and serious barriers to work, including low education, learning disabilities, health problems, or a history of domestic violence or substance abuse. Counting both longer-term welfare recipients and women who are neither working nor on welfare, Blank estimates that about 2.2 million women who head families are not able to find jobs or, if they do, cannot keep them. And almost 4 million children are in the care of these severely challenged single mothers. Blank proposes a Temporary and Partial Work Waiver Program to provide more effective employment assistance and other supports for these women and their children. The program she proposes would recognize that some women might be able to work only part-time or be temporarily unable to work. It would supplement their earnings while also offering referral to services that both address their own work barriers and provide help for their children. The support, however, would be temporary. Women would be regularly reassessed for their readiness to return to work or work more hours. Such a program, Blank notes, would require intensive case management. Estimating the cost of such a program is difficult, she explains, because costs would depend heavily on the number of women who participate. But she offers a rough estimate of $2.8 billion, some of which is already being spent as part of the current TANF program.
Trabecular Bone Gradient in Rat Long Bone Metaphyses: Mathematical Modeling and Application to Morphometric Measurements and Correction of Implant Positioning
Authors: Gabet Yankel , Kohavi David , Kohler Thomas , Baras Mario , Müller Ralph , Bab Itai
Published: September 2007

The distribution of trabecular structures in mammalian long bone metaphyses has been insufficiently explored. We show in rats that the trabecular bone structural parameters display a decreasing gradient, toward the diaphysis, that can be defined mathematically. This gradient is applicable for optimizing the reference volume in metabolic studies and for retrospective correction of implant positioning.

Introduction: The mammalian metaphyseal trabecular bone is unevenly distributed. Hence, defining a standard reference volume is critical for morphometric analyses in metaphyseal sites.

Materials and Methods: The distal femoral and proximal tibial metaphyses of adult orchietomized (ORX) or sham-ORX rats were scanned by νCT 6 wk postoperatively. Morphometric analysis based on 3D image data was performed in 450-νm-thick transversal segments defined consecutively from the primary spongiosa toward the diaphysis. The results were subjected to curve-fit analysis. A similar approach was used for proximal tibial metaphyseal sites carrying titanium implants inserted horizontally 6 wk post-ORX and examined 2-12 wk after implantation.

Results: The respective curve-fit analysis in both femur and tibia revealed decreasing linear/quadratic and logarithmic gradients for all morphometric parameters in the sham-ORX animals. The ORX animals showed similar gradients with roughly similar slopes but lower values. For the bone volume (BV/TV) and connectivity (Conn.D) densities, the magnitude of the ORX effect vastly increased toward the diaphysis. The trabecular number was unaffected in ORX femora and tibias. The trabecular thickness showed a constant decrease in the femur and was unchanged in the tibia. These findings are useful for the determination and reporting of reference volumes in morphometric studies. Implementing the curve-fit analysis for retrospective correction of implant positioning revealed differences in BV/TV, Tb.N, Conn.D, and percent implant surface in contact with bone (%OI) between the sham-ORX and ORX rats. These differences were otherwise undisclosed. In addition, a temporal increase in %OI was shown only for the corrected measurements.

Conclusions: We show the feasibility of modeling trabecular bone structures using mathematical tools. Such modeling may be used as an experimental tool. Moreover, if proven applicable to human skeletal structures, it may be further developed for the diagnosis of metabolic bone diseases and evaluation of therapeutic measures.
Comparison of Densitometric and Radiographic Vertebral Fracture Assessment Using the Algorithm-Based Qualitative (ABQ) Method in Postmenopausal Women at Low and High Risk of Fracture
Authors: Ferrar Lynne , Jiang Guirong , Clowes Jackie A , Peel Nicola F , Eastell Richard
Published: September 2007

Using ABQ diagnosis, the sensitivity to detect VF of densitometric versus radiographic assessment in 755 postmenopausal women was 71-81% and specificity was 97%. Misdiagnosis was influenced by image quality and was more common for mild deformities.

Introduction: Using densitometric vertebral fracture assessment (VFA), prevalent fractures are identified when vertebral height appears reduced by ≥20%. However, this approach does not discriminate between osteoporotic vertebral fracture (VF) and nonosteoporotic deformity, which increases the false-positive rate. Algorithm-based qualitative diagnosis (ABQ) focuses on vertebral endplate fracture to exclude these deformities but has not been applied in VFA. We wished to determine whether densitometric image quality is adequate for ABQ assessment. Our aims were to (1) calculate agreement between VFA and radiography using ABQ to identify prevalent VF and (2) identify the primary reasons for any discordant diagnosis.

Methods: Radiographic and densitometric spine images for postmenopausal women at low risk (LR; n = 459) and high risk (HR; n = 298) of VF were assessed using ABQ. Agreement between imaging modalities for VF diagnosis was assessed by κ statistics using ABQ radiographic readings as the gold standard.

Results: The prevalence of VF was 11-29% (radiography) and 9-26% (VFA) in the LR and HR groups, respectively. Agreement between imaging modalities was good or very good (κ = 0.62-0.81 in the LR and HR populations). The sensitivity to detect women with VF by VFA was 71% and 84% in the LR and HR populations, respectively, and specificity was 97%. Fifty-two (77%) and 60 (61%) of vertebrae misclassified by VFA in the LR and HR populations were mild fractures and 37 (54%) and 62 (63%) were wedge fractures. One third of fractures missed by VFA were related to poor or unreadable image quality (n = 27 and 28 vertebrae in the LR and HR populations, respectively).

Conclusions: There was good agreement between VFA and radiography using ABQ to identify prevalent VF in women at LR or HR of osteoporotic VF. Vertebrae misclassified by VFA were primarily mild fractures or deformities, and two thirds of all fractures missed by VFA were related to poor or unreadable image quality.
Calcifications in the Abdominal Aorta Predict Fractures in Men: MINOS Study
Authors: Szulc Pawel , Kiel Douglas P , Delmas Pierre D
Published: September 2007

In a cohort of 781 men ≥50 yr of age followed up for 10 yr, extended calcifications in the abdominal aorta were associated with a 2- to 3-fold increase in the risk of osteoporotic fractures regardless of BMD and falls.

Introduction: Cardiovascular disease and osteoporotic fractures are public health problems that frequently coexist.

Materials and Methods: We assessed the relation of the severity of aortic calcifications with BMD and the risk of fracture in 781 men ≥50 yr of age. During a 10-year follow-up, 66 men sustained incident clinical fractures. Calcifications in the abdominal aorta expressed as an aortic calcification score (ACS) were assessed by a semiquantitative method. BMD was measured at the lumbar spine, hip, whole body, and distal forearm.

Results: ACS > 2 was associated with a 2-fold increase in the mortality risk after adjustment for age, weight, smoking, comorbidity, and medications. After adjustment for age, body mass index (BMI), smoking, and comorbidity, men in the highest quartile of ACS (>6) had lower BMD of distal forearm, ultradistal radius, and whole body than men in the lower quartiles. Log-transformed ACS predicted fractures when adjusted for age, BMI, age by BMI interaction, prevalent fractures, BMD, and history of two or more falls (e.g., hip BMD; OR = 1.44; p < 0.02). ACS, BMD at all the skeletal sites, and history of two or more falls were independent predictors of fracture. Men with ACS > 6 had a 2- to 3-fold increased risk of fracture after adjustment for confounding variables (OR = 2.54-3.04; p < 0.005-0.001 according to the site).

Conclusions: This long-term prospective study showed that elevated ACS (>6) is a robust and independent risk factor for incident fracture in older men regardless of age, BMI, BMD, prevalent fractures, history of two or more falls, comorbidities, and medications.
Effects of Raloxifene on Fracture Risk in Postmenopausal Women: The Raloxifene Use for The Heart Trial
Authors: Ensrud Kristine E , Stock John L , Barrett-Connor Elizabeth , Grady Deborah , Mosca Lori , Khaw Kay-Tee , Zhao Qingwen , Agnusdei Donato , Cauley Jane A
Published: September 2007

Using data from a randomized placebo-controlled trial of 10,101 postmenopausal women not selected on the basis of osteoporosis, we examined whether the effect of raloxifene treatment on fractures was consistent across categories of fracture risk. Treatment with raloxifene for 5 yr reduced the risk of clinical vertebral fractures, but not nonvertebral fractures, irrespective of the presence or absence of risk factors for fracture.

Introduction: In The Raloxifene Use for The Heart (RUTH) trial, women assigned to raloxifene had a lower risk of clinical vertebral fractures but not nonvertebral fractures. However, it is uncertain whether the effect of raloxifene on fractures in this population not selected for low BMD differs according to risk factors for fractures.

Materials and Methods: We randomly assigned 10,101 postmenopausal women ≥55 yr of age with documented coronary heart disease or at high risk for coronary events to 60 mg raloxifene daily or placebo and followed them for a median of 5.6 yr. Fractures (nonvertebral and clinical vertebral) were prespecified secondary endpoints that were reported at semiannual visits. Fractures were adjudicated and confirmed using X-ray reports or medical records.

Results: There was no difference between raloxifene and placebo groups in risk of nonvertebral fractures (428 versus 438 events; hazard ratio [HR], 0.96; 95% CI, 0.84-1.10), including hip/femur (89 versus 103 events; HR, 0.85; 95% CI, 0.64-1.13) and wrist (107 versus 111 events; HR, 0.95; 95% CI, 0.73-1.24) fractures. Women treated with raloxifene had a lower risk of clinical vertebral fractures (64 versus 97 events; HR, 0.65; 95% CI, 0.47-0.89). The effect of treatment with raloxifene on risk of nonvertebral and clinical vertebral fractures was consistent across fracture risk categories defined at baseline by age, smoking status, physical activity level, prior history of fracture, family history of hip fracture, diabetes mellitus, previous use of hormone therapy, thyroid hormone use, statin use, weight loss, body mass index, or fracture specific summary risk score.

Conclusions: In older women with or at high risk of coronary heart disease not selected on the basis of osteoporosis or increased fracture risk, treatment with raloxifene for 5 yr reduced the risk of clinical vertebral fractures, but not nonvertebral fractures, irrespective of presence or absence of risk factors for fracture.
Race and Ethnic Variation in Proximal Femur Structure and BMD Among Older Men
Authors: Marshall Lynn M , Zmuda Joseph M , Chan Benjamin KS , Barrett-Connor Elizabeth , Cauley Jane A , Ensrud Kristine E , Lang Thomas F , Orwoll Eric S ,   for the Osteoporotic Fractures in Men (MrOS) Research Group
Published: September 2007

Femoral neck dimensions and vBMD from QCT were compared among 3305 black, Asian, Hispanic, and white men ≥65 yr of age. All had similar stature-adjusted mean femoral neck volume, but black and Asian men had thicker cortices and higher trabecular vBMD, which may increase bone strength.

Introduction: Hip fracture rates among elderly U.S. black and Asian men are lower than rates among white men. Structural characteristics or volumetric BMD (vBMD), which confer advantages for femoral neck bone strength, may vary by race/ethnicity. However, this topic has not been studied in detail.

Materials and Methods: In a cross-sectional study, dimensions and vBMD in the femoral neck and shaft were obtained from QCT scans among 3305 men ≥65 yr of age in the Osteoporotic Fractures in Men (MrOS) study. Femoral neck measures were cross-sectional area; integral, cortical, and medullary volumes and integral, cortical, and trabecular vBMD. Shaft measures were cross-sectional, cortical, and medullary areas and cortical vBMD. Self-reported race/ethnicity was classified as black, Asian, Hispanic, or white. We used multivariable linear regression models with adjustment for age, height, and body mass index to compare means of the outcome measures in black, Asian, and Hispanic men to those in whites.

Results: All groups had similar femoral neck integral volume. Among black and Asian men, mean cortical volume as a percent of integral volume was 6% greater, integral vBMD was 6-10% greater, and trabecular vBMD was 33-36% greater than means among whites. Shaft cross-sectional area was similar among blacks, but smaller among Asians, compared with whites. However, mean shaft cortical area was greater among blacks but similar among Asians and whites, resulting in mean cortical thickness being 5% greater among black and Asian men. Blacks also had greater mean cortical vBMD in both the femoral neck and shaft.

Conclusions: Black and Asian men ≥65 yr of age have features in the proximal femur that may confer advantages for bone strength. Specifically, greater cortical thickness and higher trabecular vBMD among black and Asian men could help explain the lower hip fracture rates in these populations. Discerning the mechanisms underlying these differences could provide advances for the prevention and treatment of osteoporosis.