bluuebunny/crossref_metadata_2025 huggingface dataset:
Integrating Reconfiguration Cost Into the Design of Multi-Period Scalable Reconfigurable Manufacturing Systems
Authors: Spicer Patrick , Carlo Hector J.
Published: February 2007

A reconfigurable manufacturing system (RMS) that is designed specifically to adapt to changes in production capacity, through system reconfiguration, is called a scalable-RMS. The set of system configurations that a scalable-RMS assumes as it changes over time is called its configuration path. This paper investigates how to determine the optimal configuration path of a scalable-RMS that minimizes investment and reconfiguration costs over a finite horizon with known demand. First, a practical cost model is presented to compute the reconfiguration cost between two scalable-RMS configurations. This model comprehends labor costs, lost capacity costs, and investment/salvage costs due to system reconfiguration and ramp up. Second, the paper presents an optimal solution model for the multiperiod scalable-RMS using dynamic programming (DP). Third, a combined integer programming/dynamic programming (IP-DP) heuristic is presented that allows the user to control the number of system configurations considered by the DP in order to reduce the solution time while still providing a reasonable solution. Numerical problems involving a two-stage and a three-stage scalable-RMS are solved using the DP and IP-DP methodologies. Experimental results suggest that the DP approach, although it is optimal, is not computationally efficient for large problem sizes. However, the combined IP-DP approach offers reasonable results with much less computational effort.
Drying of Dielectric Materials Using a Continuous Microwave Belt Drier (Case Study: Ceramics and Natural Rubber)
Authors: Rattanadecho P. , Suwannapum N. , Watanasungsuit A. , Duanduen A.
Published: February 2007

In this study, the drying of dielectric materials by a continuous microwave belt drier has been investigated experimentally. Most importantly, it focuses on the investigation of drying phenomena under microwave environment. In this analysis, the effect of the irradiation time, sample sizes, and microwave power level (number of magnetrons (800W∕1 magnetron)) on overall drying kinetics and mechanical properties are studied. The dielectric materials studied are classified into two types including ceramics (microwave demolding of tableware product) and natural rubber. The results showed that using the continuous microwave applicators technique has several advantages over the conventional method such as shorter processing times, volumetric dissipation of energy throughout a product, and high energy efficiency compared with other process, and it offers improvements in product quality. The results presented here provide a basis for fundamental understanding of microwave-heating of various kinds of dieletric materials. Further quantitative validation of experimental data could be very useful, especially in providing information for processing high performance microwave drying for developing the ceramics and rubber industries in Thailand.
From Incident Laser Pulse to Residual Stress: A Complete and Self-Closed Model for Laser Shock Peening
Authors: Wu Benxin , Shin Yung C.
Published: February 2007

Laser shock peening (LSP) is emerging as a competitive alternative technology to classical treatments to improve fatigue and corrosion properties of metals for a variety of important applications. LSP is often performed under a water confinement regime, which involves several complicated physical processes. A complete and self-closed LSP model is presented in this paper, which requires a sequential application of three submodels: a breakdown-plasma model, a confined-plasma model, and a finite element mechanics model. Simulation results are compared with experimental data in many aspects under a variety of typical LSP conditions, and good agreements are obtained.
Conjugate Mass Transfer in Gas Channels and Diffusion Layers of Fuel Cells
Authors: Beale S. B.
Published: February 2007

Prediction of mass transfer effects is a key element in fuel cell design. In this paper, the results of a generalized analysis appropriate to a wide range of designs and flow conditions are presented. Mass transfer in a rectangular gas passage, diffusion layer, and the combination of the two is considered. Fully developed viscous flow is presumed to occur within the passage, while the incompressible form of Darcy’s law is prescribed for the diffusion layer. The mathematical foundations for a simple mass transfer analysis are presented. Detailed calculations are then performed by means of a computational fluid dynamics code. These results are then correlated according to the analytical methodology in terms of nondimensional numbers appropriate to mass transfer analysis; namely, the overall mass transfer driving force as a function of the blowing parameter. Parametric studies are performed for a range of geometries, as characterized by the aspect ratio and blockage factor. It is shown that a simple solution for the overall driving force may readily be obtained from the two individual solutions for the conjugate mass transfer problem. This solution is quite general in its nature, and may readily be used to predict concentration polarization effects for a variety of fuel cells.
A Comparative Study Between Resistance Measurements in Model Experiments and Solid Oxide Fuel Cell Stack Performance Tests
Authors: Haanappel V. A. C. , Batfalsky P. , Gross S. M. , de Haart L. G. J. , Malzbender J. , Menzler N. H. , Shemet V. , Steinbrech R. W. , Vinke I. C.
Published: February 2007

Several combinations of glass-ceramic and steel compositions with excellent chemical and physical properties have been tested in the past in solid oxide fuel cell (SOFC) stacks, but there have also been some combinations exhibiting pronounced chemical interactions causing severe stack degradation. Parallel to the examination of these degradation and short-circuiting phenomena in stack tests, recently less complex model experiments have been developed to study the interaction of glass-ceramic sealants and interconnect steels. The sealants and steels were tested in the model experiments at operation temperature using a dual air/hydrogen atmosphere similar to stack conditions. The present work compares electrochemical performance under constant current load of SOFC stack tests with the resistance changes in model experiments. In addition, microstructural results of post-operation inspection of various sealant–steel combinations are presented. The model experiments have shown that under the chosen experimental conditions, distinct changes of the specific resistance of the specimens correlate well with the changes of the electrochemical performance of SOFC stacks, indicating that this method can be considered as an excellent comparative method to provide useful information on the physical and chemical interactions between glass-ceramic sealants and ferritic steels.
Characterization of Fuel Cells and Fuel Cell Systems Using Three-Dimensional X-Ray Tomography
Authors: Griesser Stefan , Buchinger G. , Raab T. , Claassen D. P. , Meissner Dieter
Published: February 2007

Three dimensional (3D) computer aided X-ray tomography (CT) has proven to be an extremely useful tool in developing our own as well as in examining commercially available solid oxide fuel cells. The results of 3D-CT measurements became very important for understanding the functionality of our first generation and improving the development of our second fuel cell generation. Also geometrical measurements, especially the roundness and the straightness of the tube, can be evaluated, both critical parameters when the stack is heated and mechanical stress has to be avoided. By using this technique the structure of the first generation cells proved to be of insufficient quality. Problems like the variation in thickness of the electrolyte tube as well as the homogeneity in thickness of the electrodes deposited can easily be detected by this nondestructive technique. Microscopic investigations of this problem of course provide equal results, but only after cutting the samples in many slices and many single measurements of different areas of the fuel cell. Using cells with inhomogeneous thickness of course results in drastic variations of the current densities along a single cell. Electrolyte layers that are too thick will result in power loss due to the increased resistance in the ionic conductivity of the electrolyte. If the electrolyte of an electrolyte supported cell is too thin, this can cause mechanical instability. Problems can also occur with the leak tightness of the fuel cell tube. Gas diffusion through the electrode layer can become a problem when the thickness of the electrode layer is too high. On the other hand, if the layers are too thin, the result can be a discontinuous layer, leading to a high electrical series resistance of the electrode. Besides determining the thickness variations also the porosity of the electrolyte needs careful attention. Larger cavities or shrink holes form insulating islands for the ion-stream and are therefore limiting the ionic conductivity. They are also diminishing the mechanical stability and provide problems for depositing a closed electrode film in electrode supported cells.
Effects of Mass Transport on the Performance of Solid Oxide Fuel Cells Composite Electrodes
Authors: Cannarozzo Marco , Grosso Simone , Agnew Gerry , Del Borghi Adriana , Costamagna Paola
Published: February 2007

Composite electrodes are of great interest in the field of solid oxide fuel cells because their use can improve the performance of these cells. However, an important correlation exists between composition, microstructure, and thickness of an electrode and its performance. This correlation has been investigated in this work using a theoretical model. The model, in order to consider all the losses occurring in an electrode, includes Ohm’s law for ionic and electronic charge transport, and the Butler-Volmer equation to evaluate the activation polarizations, and mass transport equations, taking into account diffusion through porous media, to evaluate the concentration losses. The model shows that the best electrode performance is a trade-off between activation and concentration losses. This is because a decrease in the dimensions of the particles or an increase in its thickness result, on the one hand, in a reduction of the activation polarizations, because of a larger active area for the electrochemical reaction, and, on the other hand, in an increase in the concentration losses due to a more difficult gas diffusion. In particular, in order to understand the impact of concentration losses on the performance of composite electrodes, the simulations have been run with two models, one including and the other one neglecting the mass transport equations. The results show that concentration losses play a role only with thick electrodes composed of small particles, operating at high fuel utilization.
Fixtureless Sensor Standoff Control for High-Precision Dimensional Inspection of Freeform Parts
Authors: Srivatsan Vijay , Katz Reuven , Dutta Debasish
Published: February 2007

High-precision, noncontact dimensional inspection requires sensor standoff control due to the working range limitation posed by high-precision range sensors. Constant sensor standoff with the surface of the part is necessary to ensure accurate measurement. This paper presents a novel computer-aided design (CAD) independent approach to sensor standoff control called “fixtureless sensor standoff control (FSC),” which contrary to current methods does not require a fixture or manual intervention for registration. This approach to sensor standoff control will enable rapid, flexible, and high-precision inspection of freeform parts, thus catering to the needs of future manufacturing systems. In the FSC methodology, the sensor’s position for the next measurement is estimated based on immediate previous measurements. The method was implemented on a four-axis machine used to inspect turbine blades. Results from measurement of an example turbine blade showed the deviation from desired standoff to be significantly smaller than the working range of the sensor.
Spherical and Aspheric Microlenses Fabricated by Excimer Laser LIGA-like Process
Authors: Lee Yung-Chun , Chen Chun-Ming , Wu Chun-Ying
Published: February 2007

This paper presents an effective and low-cost method for fabricating spherical and aspheric microlenses based on excimer laser LIGA-like processes. It is based on a newly developed excimer laser micromachining technique that can accurately machine a 3D microstructure with a predetermined continuous surface profile. The method is called the planetary scanning method since it is based on a combination of sample rotation and revolution and a concept of laser machining probability. Spherical and aspheric microlenses with precise and smooth surface profiles are fabricated by direct laser machining on polymer materials. Laser-machined microlenses are replicated by electroforming to obtain inverse metal molds. Finally, plastic microlenses are replicated from these metal molds using hot embossing method. The profile accuracy and surface roughness of the produced microlenses at each stage have been measured and monitored. The average surface profile accuracy is better than 1μm and average surface roughness is less than 10nm. Optical performance of the fabricated microlenses is evaluated by measuring the light intensity distribution at the focal plane and the focal length. Experimental data show that the characteristics of fabricated spherical and aspheric microlenses are well matched to the theoretical predictions, which demonstrates the controllability and accuracy of this micromachining process. Potential applications and further developments will be addressed.
Adaptive Nontransferred Plasma Charge Sensor and Its Applications
Authors: Lu Wei , Zhang Y. M. , Emmerson John
Published: February 2007

Practical welding control systems require durable/compact sensors to sense the welding process and appropriate control algorithms to produce smooth welds. A novel arc welding sensor, referred to as nontransferred plasma charge sensor, which requires no additional attachment to the torch, has been proved to be reliable for weld pool surface sensing. Aiming at eliminating the effect of manufacturing conditions on the sensor performance, this paper proposes two simple yet effective methods. Specifically, reference signals are sampled either from the bottom or the top surface of the work-piece and used to define relative signals, which can measure the depth of the weld pool with better accuracy. Using improved sensing methods, two groups of welding control experiments, keyhole plasma arc welding and all-position pipe welding, have been conducted, and the effectiveness of the developed sensing/control systems in producing quality welds under various conditions is verified.
Surface Roughness and Material Removal Rate in Machining Using Microorganisms
Authors: Johnson Daniel , Warner Roscoe , Shih Albert J.
Published: February 2007

The use of bacteria as a tool for machining, also known as biomachining, is a novel material removal process. This study characterizes the surface changes and relates the material removal rate to quantified bacterial concentrations resulting from machining of pure polycrystalline Cu using the bacterium Acidithiobacillus ferrooxidans. Cu blocks, polished to four levels of surface roughness, were utilized to examine the surface effects of bacterial machining. The mass change in Cu foil was measured to find the material removal rate. The most probable number method, a statistical enumeration technique, was applied to estimate bacterial concentrations. Scanning electron microscope (SEM) micrographs demonstrate that bacterial machining is anisotropic, and roughness measurements of the polycrystalline Cu samples showed a deterioration of Ra values of 1.5-2.5μm. Finally, suggestions for future work are presented that could potentially ameliorate current process problems.
Dependence of the Yield and Fatigue Strength of the Thread Rolled Mild Steel on Dislocation Density
Authors: Mohandesi J. Aghazadeh , Rafiee Mohammad A. , Maffi O. , Saffarzadeh P.
Published: February 2007

Dependence of the yield and fatigue strength of steel bolts with composition in accordance to AISI 1035 manufactured by thread rolling and machining process on dislocation density were investigated. The results indicate that the fatigue strength of the rolled bolts are 55% higher than the machined bolts and by full annealing at 850°C, it reduced to the extent of machined specimen. Partial annealing of the thread rolled bolts at 680°C caused a reduction of fatigue strength by approximately 61% due to reduction in the dislocation density. Fatigue strength was improved by deformation rate (i.e., rolling speed), which is also due to the increasing dislocation density. Yield stress of the studied specimens followed the same pattern as fatigue strength. Considering the obtained results from the low and high speed, partial and full annealed thread rolled specimens, yield stress of the thread rolled bolts has been modeled based on the dislocation density. The obtained results from the model are in good agreement with the experimental results. The contribution to fatigue strength by thread rolling stems from the strain hardening effect which would facilitate the formation of compressive residual stress near the surface layer. The strengthening may be attributed to increasing dislocation density in the ferrite phase (i.e., substructure formation), in addition to the formation of a fine layered structure consisting of elongated pearlite colonies and ferrite grains.
A pendulum experiment on added mass and the principle of equivalence
Authors: Neill Douglas , Livelybrooks Dean , Donnelly Russell J.
Published: February 2007

The concept of added mass in fluid mechanics has been known for many years. A familiar example is the accelerated motion of a sphere through an ideal (inviscid and irrotational) fluid, which has an added mass equal to one-half the mass of the fluid displaced. The period of oscillation of a simple pendulum in a vacuum is independent of its mass because of the equivalence of gravitational and inertial masses. In contrast, in a fluid both buoyancy and added mass affect the period. We present experimental results on simple pendula of different materials oscillating in various fluids. The results agree fairly well with the results obtained for the added mass in an ideal fluid.
Nonequivalent representations of canonical commutation relations in quantum mechanics: The case of the Aharonov-Bohm effect
Authors: Bracci Luciano , Picasso Luigi E.
Published: February 2007

We stress the role of nonequivalent representations of the canonical commutation relations in quantum mechanics. Such representations occur when the space accessible to the system is not simply connected. An example is the magnetic Aharonov-Bohm effect, which can be interpreted in terms of nonequivalent representations, without explicitly invoking the vector potential in the region accessible to the electrons.
Transmission and scattering by an absorptive potential
Authors: Maheswari A. Uma , Mahadevan S. , Prema P. , Shastry C. S. , Agarwalla S. K.
Published: February 2007

Transmission and scattering problems involving complex potentials are important in physics, in particular in describing nuclear collisions. We describe many pedagogical features of transmission in one dimension and scattering and absorption cross sections in three dimensions for a rectangular absorptive potential and compare the results with scattering from real barriers and a hard sphere. For a given energy in one dimension we show that the absorption reaches a maximum for a critical value of the absorption strength and then monotonically decreases with an increase in the absorption strength. An infinitely absorptive well becomes almost fully reflective and thus is similar to an infinitely high barrier. Similar results are found in three dimensions. We show that the absorption cross section in three dimensions diverges at a threshold energy, which is of critical importance for exothermic reactions.
The design and construction of a cost-efficient confocal laser scanning microscope
Authors: Xi Peng , Rajwa Bartlomiej , Jones James T. , Robinson J. Paul
Published: February 2007

The optical dissection ability of confocal microscopy makes it a powerful tool for biological materials. However, the cost and complexity of confocal scanning laser microscopy hinders its wide application in education. We describe the construction of a simplified confocal scanning laser microscope and demonstrate three-dimensional projection based on cost-efficient commercial hardware, together with available open source software.
Electromagnetics from a quasistatic perspective
Authors: Larsson Jonas
Published: February 2007

Quasistatic models provide intermediate levels of electromagnetic theory in between statics and the full set of Maxwell’s equations. Quasistatics is easier than general electrodynamics and in some ways more similar to statics, but exhibits more interesting physics and more important applications than statics. Quasistatics is frequently used in electromagnetic modeling, and the pedagogical potential of electromagnetic simulations gives additional support for the importance of quasistatics. Quasistatics is introduced in a way that fits into the standard textbook presentations of electrodynamics.
Lissajous curves and semiclassical theory: The two-dimensional harmonic oscillator
Authors: Doll Roland , Ingold Gert-Ludwig
Published: February 2007

The semiclassical treatment of the two-dimensional harmonic oscillator provides an instructive example of the relation between classical motion and the quantum mechanical energy spectrum. We extend previous work on the anisotropic oscillator with incommensurate frequencies and the isotropic oscillator to the case with commensurate frequencies for which the Lissajous curves appear as classical periodic orbits. Because of the three different scenarios depending on the ratio of its frequencies, the two-dimensional harmonic oscillator offers a unique way to explicitly analyze the role of symmetries in classical and quantum mechanics.
Optical Doppler shift measurement using a rotating mirror
Authors: Bernal Luis , Bilbao Luis
Published: February 2007

Optical Doppler shift experiments are not simple because the light source cannot easily be moved in a sufficiently smooth and uniform manner to keep the level of noise well below that of the signal. Thus, most Doppler shift experiments are performed with sound or microwaves. Instead of using a moving mirror to produce a moving light source, we use a rotating mirror in which one beam is reflected from the advancing side and the other beam is reflected from the receding part of a rotating mirror. This arrangement can overcome many noise generating effects.
Nodes of wavefunctions
Authors: Moriconi M.
Published: February 2007

We give a simple argument to show that the nth wavefunction for the one-dimensional Schrödinger equation has n−1 nodes. We also show that if n1<n2, then between two consecutive zeros of ψn1, there is a zero of ψn2.
Modeling student thinking: An example from special relativity
Authors: Scherr Rachel E.
Published: February 2007

Our understanding of the nature of student ideas informs our instructional and research agendas. In this paper, I characterize student ideas in terms of five observable properties (determinacy, coherence, context-dependence, variability, and malleability) and describe how those observable properties correspond to the “misconceptions” and “pieces” models of student reasoning. I then analyze instructional materials and student thinking in a particular topic area (special relativity) in terms of each of those two models. I show that specific instructional strategies reflect specific theoretical orientations, and explore the extent to which observed student behavior corresponds to predictions made by the theoretical models. The analysis suggests that while both the misconceptions and pieces models are flexible enough to accommodate all of the data, some aspects of student thinking seem best described in terms of pieces, and others seem better characterized as misconceptions. The purpose of the analysis is to illustrate the effect of theoretical orientation on instruction, instructional research, and curriculum development.
Accurate measurement of the position and velocity of a falling object
Authors: Garg Madhur , Kalimullah  , Arun P. , Lima F. M. S.
Published: February 2007

An object accelerates while it falls under the influence of the gravitational force. By using two sensors a precise and automated measurement of the velocity can be obtained. The analysis of these measurements may be insufficient if air resistance is important. We discuss how by increasing the number of sensors we can determine the velocity, terminal velocity, and acceleration due to gravity.
Path integrals and wavepacket evolution for damped mechanical systems
Authors: Jain Dharmesh , Das A. , Kar Sayan
Published: February 2007

Damped mechanical systems with various forms of damping are quantized using the path integral formalism. In particular, we obtain the path integral kernel for the linearly damped harmonic oscillator and a particle in a uniform gravitational field with linearly or quadratically damped motion. In each case, we study the evolution of Gaussian wave packets and discuss the characteristic features that help us distinguish between different types of damping. For quadratic damping we show the connection of the action and equation of motion to a zero-dimensional version of a scalar field theory. We also demonstrate that the equation of motion for quadratic damping can be identified as a geodesic equation in a fictitious two-dimensional space.
Time (in)dependence in general relativity
Authors: Deser S. , Franklin J.
Published: February 2007

We clarify the conditions for Birkhoff’s theorem, that is, time independence in general relativity. We work primarily at the linearized level where guidance from electrodynamics is particularly useful. As a bonus, we also review how the equivalence principle results from general relativity. The basic time-independent solutions due to Schwarzschild and Kerr provide concrete illustrations of the theorem. Only familiarity with Maxwell’s equations and tensor analysis is required.
Solid-liquid-gas state transducer: A study of an electro-mechanical system
Authors: Meyer H. O.
Published: February 2007

We describe a transducer that is sensitive to the state of its environment (gas, liquid, or solid). It consists of a piezoelectric bimorph immersed in a medium. A phase change of the medium affects the freedom of motion of the sensor, and thus changes its electrical properties. The observed behavior of the device is explained by a simple model. The device is easy to realize, can be analyzed theoretically, illustrates several important physics principles, and is well suited for an experiment in an intermediate-level teaching lab.
Retrospective baseline measurement of self-reported health status and health-related quality of life versus population norms in the evaluation of post-injury losses
Authors: Watson W L , Ozanne-Smith J , Richardson J
Published: February 2007

Background:Owing to the difficulty in prospectively measuring pre-injury health status and health-related quality of life (HRQL) in an injured cohort, population norms or retrospective baseline scores are often used as comparators for evaluating post-injury losses. However, there has been little discussion in the literature or research into the soundness of these approaches for this purpose.

Objectives:To investigate the appropriateness of the retrospectively measured baseline health status and HRQL in an injured population for the purpose of evaluating post-injury losses.

Methods:A cohort of injured admitted to hospital (n = 186) was followed up for 12 months after injury. Retrospectively measured pre-injury health status and HRQL scores were compared with those at 12 months after injury for participants who reported complete recovery (n = 61) and those who did not. Retrospective baseline scores for the whole cohort were also compared with Australian population norms.

Results:For participants who completely recovered, no significant difference was observed between scores at baseline (measured retrospectively) and those at 12 months after injury (36-item Short Form Questionnaire physical component summary z = −1.274, p = 0.203; 36-item Short Form Questionnaire mental component summary z = −1.634, p = 0.102; Short Form 6 Dimensions: z = −1.405, p = 0.296). A borderline significant difference was observed in HRQL as measured by the Assessment of Quality of Life (z = −1.970, p = 0.049). Retrospectively measured pre-injury scores were consistently higher than Australian norms for all measures.

Conclusions:The injured population may not be representative of the general population. Consequently, retrospective baseline measurement of pre-injury health states may be more appropriate than general population norms for the purpose of evaluating post-injury losses in this population.
Competency-based strategies for injury control and prevention curriculums in undergraduate medical education: Figure 1
Authors: Beth Phelan Mary , Falimirski Mark E , Simpson Deborah E , Czinner Mary L , Hargarten Stephen W
Published: February 2007

Injury, including unintentional injury and intentional injury, is the leading cause of death in people aged ⩽44 years. Doctors often treat acute injuries, assist in the rehabilitation process and provide injury prevention guidance to patients. Current undergraduate medical school curriculums lack content and consistency in providing training in this area. A matrix to show the integration of injury control and prevention principles into existing undergraduate medical school curriculums is proposed.
Evaluation of the health effects of the new driving penalty point system in the Lazio Region, Italy, 2001–4
Authors: Farchi Sara , Chini Francesco , Giorgi Rossi Paolo , Camilloni Laura , Borgia Piero , Guasticchi Gabriella
Published: February 2007

Objective:The penalty point system was introduced in Italy in June 2003. The aim of this study was to evaluate the health effects of this legislation in the Lazio region.

Methods:Poisson models were used to compare emergency department visits, hospitalizations and death between the pre-law and post-law periods (July 2001–June 2003; July 2003–June 2004).

Results:The emergency department visit rate ratio (RR) of the two periods was 0.87 (95% confidence interval (CI) 0.86 to 0.88); the corresponding hospital admission RR was 0.87 (95% CI 0.84 to 0.9). The death RR was 0.93 (95% CI 0.82 to 1.05).

Conclusion:After the legislation was introduced, there were fewer visits to the emergency department, hospitalizations and death from road traffic injuries. However, the effect was lower than expected, and it decreased over time.
Occupational physical demands and same-level falls resulting in fracture in female workers: an analysis of workers’ compensation claims
Authors: Verma S K , Sorock G S , Pransky G S , Courtney T K , Smith G S
Published: February 2007

Objectives:To examine the association between occupational physical demands and risk of same-level falls resulting in fracture in female workers’ compensation claimants.

Methods:From workers’ compensation claims for same-level falls, 7286 female workers from three age groups (18–49, 50–59 and 60–79 years) were randomly selected. Levels of occupational physical activity, standing and sitting were assigned using occupational codes. Fracture occurrence was determined using the International Classification of Diseases codes. Risks of same-level falls resulting in fracture were compared by quartiles of physical activity, standing and sitting.

Results:In the 18–49-year age group, physical activity, standing and sitting at work were not significantly associated with risk of same-level falls resulting in fracture (p value trend: 0.07, 0.18 and 0.10, respectively). In the 50–59 and 60–79-year age groups, increasing duration of standing and decreasing duration of sitting were associated with decreasing risk of same-level falls resulting in fracture (p value trend: standing <0.001, 0.01; sitting <0.001, 0.02). In the 50–59-year age group, the relative risks of same-level falls resulting in fracture were 0.53, 0.41 and 0.82 for the second, third and highest quartiles of physical activity, respectively, as compared with workers in the lowest quartile (95% confidence interval 0.35 to 0.80, 0.23 to 0.72, 0.56 to 1.21, respectively). In the 60–79-year age group, there was a similar, but not significant, U-shaped association between occupational physical activity and risk of same-level falls resulting in fracture.

Conclusion:Moderate occupational physical demands may be associated with a decreased risk of same-level fall resulting in fracture in female workers’ compensation claimants ⩾50 years of age.
Quality of hospital discharge data for injury prevention
Authors: Langley John D , Davie Gabrielle S , Simpson Jean C
Published: February 2007

Objective:To examine the use of unspecified codes for the circumstances of injury for New Zealand public hospital discharges at a district health board (DHB) level.

Methods:Hospital injury discharges for the period 2000–3 were examined. The use of the International Classification of Diseases unspecified categories was examined for mechanism of injury, activity and place of occurrence.

Results:For all DHBs, the combined age-adjusted and mechanism-adjusted usage of unspecified mechanism codes was 7% and ranged from 3% to 11%. Most (57%) of these cases were unspecified falls. The comparable usage for activity was 39% and ranged from 17% to 52%, and for place of occurrence the respective figures were 23% and 7–36%. Only 50% of hospital discharges were completely specified in terms of mechanism of injury, activity and place of occurrence; this varied from 36% to 74% between DHBs. For several DHBs a significant degree of inconsistency was found in performance across mechanism, activity and place of occurrence coding.

Conclusions:Those DHBs with a high proportion of cases coded as unspecified would serve the prevention efforts of their communities better by making efforts to determine the cause of this situation and implement measures to reduce the problem.
The US gun stock: results from the 2004 national firearms survey
Authors: Hepburn L , Miller M , Azrael D , Hemenway D
Published: February 2007

Objectives:To examine the size and composition of the privately held firearm stock in the US; and to describe demographic patterns of firearm ownership and motivations for ownership.

Design, setting and participants:A nationally representative household telephone survey of 2770 adults aged ⩾18 years living in the US, conducted in the spring of 2004.

Main outcome measure:Responses to questions regarding firearm ownership, the number and types of guns owned, and motivations for ownership.

Results:38% of households and 26% of individuals reported owning at least one firearm. This corresponds to 42 million US households with firearms, and 57 million adult gun owners. 64% of gun owners or 16% of American adults reported owning at least one handgun. Long guns represent 60% of the privately held gun stock. Almost half (48%) of all individual gun owners reported owning ⩾4 firearms. Men more often reported firearm ownership, with 45% stating that they personally owned at least one firearm, compared with 11% for women.

Conclusions:The US population continues to contain at least one firearm for every adult, and ownership is becoming increasingly concentrated. Long guns are the most prevalent type of gun in the US but handgun ownership is widespread. Ownership demographic patterns support findings of previous studies.
How many employees receive safety training during their first year of a new job?
Authors: Smith Peter M , Mustard Cameron A
Published: February 2007

Objective:To describe the provision of safety training to Canadian employees, specifically those in their first year of employment with a new employer.

Design:Three repeated national Canadian cross-sectional surveys.

Subjects:59 159 respondents from Statistics Canada’s Workplace and Employee Surveys (1999, 2001 and 2003), 5671 who were in their first year of employment.

Main outcome:Receiving occupational health and safety training, orientation training or office or non-office equipment training in either a classroom or on-the-job in the previous 12 months.

Results:Only 12% of women and 16% of men reported receiving safety training in the previous 12 months. Employees in their first 12 months of employment were more likely to receive safety training than employees with >5 years of job tenure. However, still only one in five new employees had received any safety training while with their current employer. In a fully adjusted regression model, employees who had access to family and support programs, women in medium-sized workplaces and in manufacturing, and men in large workplaces and in part-time employment all had an increased probability of receiving safety training. No increased likelihood of safety training was found in younger workers or those in jobs with higher physical demands, both of which are associated with increased injury risk.

Conclusions:From our results, it would appear that only one in five Canadian employees in their first year of a new job received safety training. Further, the provision of safety training does not appear to be more prevalent among workers or in occupations with increased risk of injuries.
Myometrial expression of small conductance Ca2+-activated K+ channels depresses phasic uterine contraction
Authors: Brown Amber , Cornwell Trudy , Korniyenko Iryna , Solodushko Viktoriya , Bond Chris T. , Adelman John P. , Taylor Mark S.
Published: February 2007

Mechanisms regulating uterine contractility are poorly understood. We hypothesized that a specific isoform of small conductance Ca2+-activated K+ (SK) channel, SK3, promotes feedback regulation of myometrial Ca2+ and hence relaxation of the uterus. To determine the specific functional impact of SK3 channels, we assessed isometric contractions of uterine strips from genetically altered mice (SK3T/T), in which SK3 is overexpressed and can be suppressed by oral administration of doxycycline (SK3T/T+Dox). We found SK3 protein in mouse myometrium, and this expression was substantially higher in SK3T/T mice and lower in SK3T/T+Dox mice compared with wild-type (WT) controls. Sustained contractions elicited by 60 mM KCl were not different among SK3T/T, SK3T/T+Dox, and WT mice. However, the rate of onset and magnitude of spontaneously occurring phasic contractions was muted significantly in isolated uterine strips from SK3T/T mice compared with those from WT mice. These spontaneous contractions were augmented greatly by blockade of SK channels with apamin or by suppression of SK3 expression. Phasic but not tonic contraction in response to oxytocin was depressed in uterine strips from SK3T/T mice, whereas suppression of SK3 channel expression or treatment with apamin promoted the predominance of large coordinated phasic events over tone. Spontaneous contractions and the phasic component of oxytocin contractions were blocked by nifedipine but not by cyclopiazonic acid. Our findings suggest that SK3 channels play an important role in regulating uterine function by limiting influx through L-type Ca2+ channels and disrupting the development of concerted phasic contractile events.
Genomic organization of the region spanning D14Mit262 and D14Mit86 on mouse chromosome 14 and exclusion of Adam28 and Adamdec1 as the cataract-causing gene, lr2
Authors: Kim E. , Rhee S.D. , Bae Y. , Okumoto M. , Yoon J.-B. , Song C.-W. , Yoon S.K.
Published: February 2007

Mice with recessive cataract, CXSD, show the first clinical symptoms of cataract at five weeks, with complete penetrance. We previously localized the cataract-causing lens rupture 2 gene (lr2) to mouse chromosome 14. In the process of positional cloning of the lr2 gene, we determined the genomic organization of the critical region, defined by D14Mit262 and D14Mit86, and compared it to recently published map information. In addition, mutational analysis using reverse transcription polymerase chain reaction (RT-PCR) followed by direct sequencing as well as quantitative realtime PCR (RQ-PCR) was performed to investigate Adam28 and Adamdec1 as lr2 candidate genes in this study. There was no mutation cosegregating with the phenotype of CXSD mice, which excluded these genes as the lr2 gene. Identification of more transcripts from this region and their mutation analyses are required to isolate the lr2 gene.
Increased skewing of X chromosome inactivation with age in both blood and buccal cells
Authors: Knudsen G.P.S. , Pedersen J. , Klingenberg O. , Lygren I. , Ørstavik K.H.
Published: February 2007

The X chromosome inactivation pattern in peripheral blood cells becomes more skewed after age 55, and a genetic effect on this age-related skewing has been reported. We investigated the effect of age on X inactivation phenotype in blood, buccal cells and tissue from duodenal biopsies in 80 females aged 19–90 years. The X inactivation pattern correlated positively with age in blood (r = 0.238, P = 0.034) and buccal cells (r = 0.260, P = 0.02). The mean degree of skewing was higher in the elderly (≧55 years) than in the young (<55 years) in blood (70.1 and 63.5%, respectively, P = 0.013) and in buccal cells (64.7 and 59.0%, respectively, P = 0.004). Correlation of X inactivation between the different tissues was high in all tissues with a tendency to increase with age for blood and buccal cells (P = 0.082). None of the duodenal biopsies had a skewed X inactivation, and the mean degree of skewing was similar in the two age groups. The tendency for the same X chromosome to be the preferentially active X in both blood and buccal cells with advancing age is in agreement with a genetic effect on age-related skewing and indicates that genes other than those involved in hematopoiesis should be investigated in the search for genes contributing to age related skewing.
RAD51C (RAD51L2) is involved in maintaining centrosome number in mitosis
Authors: Renglin Lindh A. , Schultz N. , Saleh-Gohari N. , Helleday T.
Published: February 2007

The RAD51C (RAD51L2) protein is one out of five RAD51 paralogs and forms a complex that includes either XRCC2 or XRCC3. Both of these complexes may have important functions in homologous recombination (HR). Here, we confirm that the frequency of DNA double-strand break (DSB)-induced HR is reduced in the RAD51C deficient cell line CL-V4B, in agreement with a role for RAD51C in HR. We report that mitotic RAD51C deficient CL-V4B cells also have an increased number of centrosomes in mitosis resulting in aberrant mitotic spindles. These data suggest that the RAD51C protein is important in maintaining correct centrosome numbers and that the complexes including RAD51C and XRCC2 or XRCC3 may be of importance in maintaining correct centrosome numbers in mitosis. Increased centrosome numbers following a RAD51C defect indicates that this protein might be important in preventing aneuploidy, suggesting that it could be a potential tumour suppressor in mammals.
Chromosomal speciation of humans and chimpanzees revisited: studies of DNA divergence within inverted regions
Authors: Szamalek J.M. , Cooper D.N. , Hoegel J. , Hameister H. , Kehrer-Sawatzki H.
Published: February 2007

The human and chimpanzee karyotypes are distinguishable in terms of nine pericentric inversions. According to the recombination suppression model of speciation, these inversions could have promoted the process of parapatric speciation between hominoid populations ancestral to chimpanzees and humans. Were recombination suppression to have occurred in inversion heterozygotes, gene flow would have been reduced, resulting in the accumulation of genetic incompatibilities leading to reproductive isolation and eventual speciation. In an attempt to detect the molecular signature of such events, the sequence divergence of non-coding DNA was compared between humans and chimpanzees. Precise knowledge of the locations of the inversion breakpoints permitted accurate discrimination between inverted and non-inverted regions. Contrary to the predictions of the recombination suppression model, sequence divergence was found to be lower in inverted chromosomal regions as compared to non-inverted regions, albeit with borderline statistical significance. Thus, no signature of recombination suppression resulting from inversion heterozygosity appears to be detectable by analysis of extant human and chimpanzee non-coding DNA. The precise delineation of the inversion breakpoints may nevertheless still prove helpful in identifying potential speciation-relevant genes within the inverted regions.
Rat gene mapping in the post-genome sequencing era: the continued utility of cell hybrids to localize rat genes (Cks2, Ephb4, Fabp5, Il13ra1, Rpl10, Ssr4)
Authors: Szpirer C. , van Vooren P. , Rivière M. , Szpirer J.
Published: February 2007

Finding the position of a gene is now easily done when the genome sequence is available: the gene position is generally found by a simple query of genomic databases such as those available at the Ensembl browser or the NCBI. We were interested in determining the position of 125 cancer-related rat genes and we found that the position of most of these genes (110) could indeed be identified in this manner. However, in 15 cases, the gene position was not available in these databases, or the results were ambiguous. We then explored a more specialized database, namely the Rat Genome Database, and experimentally mapped these genes using standard and radiation cell hybrids. The 15 genes in question could be localized unambiguously. In four cases, the radiation cell hybrids were indispensable: the sequence of these four genes could not be found in the rat genome sequence. On the basis of the sample we examined, it thus appears that a classical gene mapping method is still required to localize about 3% of the rat genes, as if 3% of the rat gene sequences were lacking in the current rat genome sequence.
Forward to a detailed sequence map of bovine chromosome 6
Authors: Weikard R. , Goldammer T. , Womack J.E. , Kuehn C.
Published: February 2007

Numerous QTL for a variety of phenotypic traits in dairy and beef cattle have been mapped on bovine chromosome 6 (BTA6). The complete and validated information on the molecular genome organization is an essential prerequisite for the conclusive identification of the causative sequence variation underlying the QTL. In our study we describe efforts to improve the genomic sequence map assembly of BTA6 by filling-in gaps and by suggesting sequence contig rearrangements. This is achieved by the generation and in silico mapping of BAC-end sequences (BESs) from clones containing sequences placed on our high-resolution radiation hybrid (RH) map of BTA6 onto the genome sequence map. Linking high-resolution RH mapping with in silico mapping of BESs on BTA6 enabled the detection of discrepancies in chromosomal assignments of genome sequence contigs and improved the resolution of non-conclusive assignments on the genome sequence assembly. Furthermore, 37% of BESs enabled chromosomal assignment of contigs previously unassigned. Anchoring of 66% of BESs onto HSA4 confirmed the synteny of the respective region of BTA6 including the known evolutionary breakpoints. The BESs will play an important role in the ongoing efforts to complete the sequence of the bovine genome and will also provide a source for the identification of new polymorphic sites in the genome sequence to resolve QTL-containing intervals.