bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic Stability of Passive Dynamic Walking on an Irregular Surface
Authors: Su Jimmy Li-Shin , Dingwell Jonathan B.
Published: December 2007

Falls that occur during walking are a significant health problem. One of the greatest impediments to solve this problem is that there is no single obviously “correct” way to quantify walking stability. While many people use variability as a proxy for stability, measures of variability do not quantify how the locomotor system responds to perturbations. The purpose of this study was to determine how changes in walking surface variability affect changes in both locomotor variability and stability. We modified an irreducibly simple model of walking to apply random perturbations that simulated walking over an irregular surface. Because the model’s global basin of attraction remained fixed, increasing the amplitude of the applied perturbations directly increased the risk of falling in the model. We generated ten simulations of 300 consecutive strides of walking at each of six perturbation amplitudes ranging from zero (i.e., a smooth continuous surface) up to the maximum level the model could tolerate without falling over. Orbital stability defines how a system responds to small (i.e., “local”) perturbations from one cycle to the next and was quantified by calculating the maximum Floquet multipliers for the model. Local stability defines how a system responds to similar perturbations in real time and was quantified by calculating short-term and long-term local exponential rates of divergence for the model. As perturbation amplitudes increased, no changes were seen in orbital stability (r2=2.43%; p=0.280) or long-term local instability (r2=1.0%; p=0.441). These measures essentially reflected the fact that the model never actually “fell” during any of our simulations. Conversely, the variability of the walker’s kinematics increased exponentially (r2⩾99.6%; p<0.001) and short-term local instability increased linearly (r2=88.1%; p<0.001). These measures thus predicted the increased risk of falling exhibited by the model. For all simulated conditions, the walker remained orbitally stable, while exhibiting substantial local instability. This was because very small initial perturbations diverged away from the limit cycle, while larger initial perturbations converged toward the limit cycle. These results provide insight into how these different proposed measures of walking stability are related to each other and to risk of falling.
Computational Modeling to Predict Mechanical Function of Joints: Application to the Lower Leg With Simulation of Two Cadaver Studies
Authors: Liacouras Peter C. , Wayne Jennifer S.
Published: December 2007

Computational models of musculoskeletal joints and limbs can provide useful information about joint mechanics. Validated models can be used as predictive devices for understanding joint function and serve as clinical tools for predicting the outcome of surgical procedures. A new computational modeling approach was developed for simulating joint kinematics that are dictated by bone/joint anatomy, ligamentous constraints, and applied loading. Three-dimensional computational models of the lower leg were created to illustrate the application of this new approach. Model development began with generating three-dimensional surfaces of each bone from CT images and then importing into the three-dimensional solid modeling software SOLIDWORKS and motion simulation package COSMOSMOTION. Through SOLIDWORKS and COSMOSMOTION, each bone surface file was filled to create a solid object and positioned necessary components added, and simulations executed. Three-dimensional contacts were added to inhibit intersection of the bones during motion. Ligaments were represented as linear springs. Model predictions were then validated by comparison to two different cadaver studies, syndesmotic injury and repair and ankle inversion following ligament transection. The syndesmotic injury model was able to predict tibial rotation, fibular rotation, and anterior/posterior displacement. In the inversion simulation, calcaneofibular ligament extension and angles of inversion compared well. Some experimental data proved harder to simulate accurately, due to certain software limitations and lack of complete experimental data. Other parameters that could not be easily obtained experimentally can be predicted and analyzed by the computational simulations. In the syndesmotic injury study, the force generated in the tibionavicular and calcaneofibular ligaments reduced with the insertion of the staple, indicating how this repair technique changes joint function. After transection of the calcaneofibular ligament in the inversion stability study, a major increase in force was seen in several of the ligaments on the lateral aspect of the foot and ankle, indicating the recruitment of other structures to permit function after injury. Overall, the computational models were able to predict joint kinematics of the lower leg with particular focus on the ankle complex. This same approach can be taken to create models of other limb segments such as the elbow and wrist. Additional parameters can be calculated in the models that are not easily obtained experimentally such as ligament forces, force transmission across joints, and three-dimensional movement of all bones. Muscle activation can be incorporated in the model through the action of applied forces within the software for future studies.
Modeling the Interaction of Coils With the Local Blood Flow After
Coil Embolization of Intracranial Aneurysms
Authors: Cha Kyung Se , Balaras Elias , Lieber Baruch B. , Sadasivan Chander , Wakhloo Ajay K.
Published: December 2007

Aneurysmal recanalization and coil compaction after coil embolization of intracranial aneurysms are seen in as many as 40% of cases. Higher packing density has been suggested to reduce both coil compaction and recanalization. Basilar bifurcation aneurysms remain a challenge due possibly to the hemodynamics of this specific aneurysm/parent vessel architecture, which subjects the coil mass at the aneurysm neck to elevated and repetitive impingement forces. In the present study, we propose a new modeling strategy that facilitates a better understanding of the complex interactions between detachable coils and the local blood flow. In particular, a semiheuristic porous media set of equations used to describe the intra-aneurysmal flow is coupled to the incompressible Navier–Stokes equations governing the dynamics of the flow in the involved vessels. The resulting system of equations is solved in a strongly coupled manner using a finite element formulation. Our results suggest that there is a complex interaction between the local hemodynamics and intra-aneurysmal flow that induces significant forces on the coil mass. Although higher packing densities have previously been advocated to reduce coil compaction, our simulations suggest that lower permeability of the coil mass at a given packing density could also promote faster intra-aneurysmal thrombosis due to increased residence times.
Robust Strategies for Automated AFM Force Curve Analysis—II: Adhesion-Influenced Indentation of Soft, Elastic Materials
Authors: Lin David C. , Dimitriadis Emilios K. , Horkay Ferenc
Published: December 2007

In the first of this two-part discourse on the extraction of elastic properties from atomic force microscopy (AFM) data, a scheme for automating the analysis of force-distance curves was introduced and experimentally validated for the Hertzian (i.e., linearly elastic and noninteractive probe-sample pairs) indentation of soft, inhomogeneous materials. In the presence of probe-sample adhesive interactions, which are common especially during retraction of the rigid tip from soft materials, the Hertzian models are no longer adequate. A number of theories (e.g., Johnson–Kendall–Roberts and Derjaguin–Muller–Toporov), covering the full range of sample compliance relative to adhesive force and tip radius, are available for analysis of such data. We incorporated Pietrement and Troyon’s approximation (2000, “General Equations Describing Elastic Indentation Depth and Normal Contact Stiffness Versus Load,” J. Colloid Interface Sci., 226(1), pp. 166–171) of the Maugis–Dugdale model into the automated procedure. The scheme developed for the processing of Hertzian data was extended to allow for adhesive contact by applying the Pietrement–Troyon equation. Retraction force-displacement data from the indentation of polyvinyl alcohol gels were processed using the customized software. Many of the retraction curves exhibited strong adhesive interactions that were absent in extension. We compared the values of Young’s modulus extracted from the retraction data to the values obtained from the extension data and from macroscopic uniaxial compression tests. Application of adhesive contact models and the automated scheme to the retraction curves yielded average values of Young’s modulus close to those obtained with Hertzian models for the extension curves. The Pietrement–Troyon equation provided a good fit to the data as indicated by small values of the mean-square error. The Maugis–Dugdale theory is capable of accurately modeling adhesive contact between a rigid spherical indenter and a soft, elastic sample. Pietrement and Troyon’s empirical equation greatly simplifies the theory and renders it compatible with the general automation strategies that we developed for Hertzian analysis. Our comprehensive algorithm for automated extraction of Young’s moduli from AFM indentation data has been expanded to recognize the presence of either adhesive or Hertzian behavior and apply the appropriate contact model.
Viscoelastic Properties of Ovine Adipose Tissue Covering the Gluteus Muscles
Authors: Gefen Amit , Haberman Einat
Published: December 2007

Pressure-related deep tissue injury (DTI) is a life-risking form of pressure ulcers threatening immobilized and neurologically impaired patients. In DTI, necrosis of muscle and enveloping adipose tissues occurs under intact skin, owing to prolonged compression by bony prominences. Modeling the process of DTI in the buttocks requires knowledge on viscoelastic mechanical properties of the white adipose tissue covering the gluteus muscles. However, this information is missing in the literature. Our major objectives in this study were therefore to (i) measure short-term (HS) and long-term (HL) aggregate moduli of adipose tissue covering the glutei of sheep, (ii) determine the effects of preconditioning on HS and HL, and (iii) determine the time course of stress relaxation in terms of the transient aggregate modulus H(t) in nonpreconditioned (NPC) and preconditioned (PC) tissues. We tested 20 fresh tissue specimens (from 20 mature animals) in vitro: 10 specimens in confined compression for obtaining the complete H(t) response to a ramp-and-hold protocol (ramp rate of 300mm∕s), and 10 other specimens in swift indentations for obtaining comparable short-term elastic moduli at higher ramp rates (2000mm∕s). We found that HS in confined compression were 28.9±14.9kPa and 18.1±6.9kPa for the NPC and PC specimens, respectively. The HL property, 10.3±4.2kPa, was not affected by preconditioning. The transient aggregate modulus H(t) always reached the plateau phase (less than 10% difference between H(t) and HL) within 2min, which is substantially shorter than the times for DTI onset reported in previous animal studies. The short-term elastic moduli at high indentation rates were 22.6±10kPa and 15.8±9.4kPa for the NPC and PC test conditions, respectively. Given a Poisson’s ratio of 0.495, comparison of short-term elastic moduli between the high and slow rate tests indicated a strong deformation-rate dependency. The most relevant property for modeling adipose tissue as related to DTI is found to be HL, which is conveniently unaffected by preconditioning. The mechanical characteristics of white adipose tissue provided herein are useful for analytical as well as numerical models of DTI, which are essential for understanding this serious malady.
In-Situ Deformation of the Aortic Valve Interstitial Cell Nucleus Under Diastolic Loading
Authors: Huang Hsiao-Ying Shadow , Liao Jun , Sacks Michael S.
Published: December 2007

Within the aortic valve (AV) leaflet resides a population of interstitial cells (AVICs), which serve to maintain tissue structural integrity via protein synthesis and enzymatic degradation. AVICs are typically characterized as myofibroblasts, exhibit phenotypic plasticity, and may play an important role in valve pathophysiology. While it is known that AVICs can respond to mechanical stimuli in vitro, the level of in vivo AVIC deformation and its relation to local collagen fiber reorientation during the cardiac cycle remain unknown. In the present study, the deformation of AVICs was investigated using porcine AV glutaraldehyde fixed under 0–90mmHg transvalvular pressures. The resulting change in nuclear aspect ratio (NAR) was used as an index of overall cellular strain, and dependencies on spatial location and pressure loading levels quantified. Local collagen fiber alignment in the same valves was also quantified using small angle light scattering. A tissue-level finite element (FE) model of an AVIC embedded in the AV extracellular matrix was also used explore the relation between AV tissue- and cellular-level deformations. Results indicated large, consistent increases in AVIC NAR with transvalvular pressure (e.g., from mean of 1.8 at 0mmHg to a mean of 4.8 at 90mmHg), as well as pronounced layer specific dependencies. Associated changes in collagen fiber alignment indicated that little AVIC deformation occurs with the large amount of fiber straightening for pressures below ∼1mmHg, followed by substantial increases in AVIC NAR from 4mmHgto90mmHg. While the tissue-level FE model was able to capture the qualitative response, it also underpredicted the extent of AVIC deformation. This result suggested that additional micromechanical and fiber-compaction effects occur at high pressure levels. The results of this study form the basis of understanding transvalvular pressure-mediated mechanotransduction within the native AV and first time quantitative data correlating AVIC nuclei deformation with AV tissue microstructure and deformation.
Self-Cooling Cavity Burs for Surgical Drills
Authors: Silverstein Calvin C.
Published: December 2007

In a self-cooled drill, an especially designed bur is used to transport heat generated at the cutting edge into the handpiece, where it is dissipated into an air heat sink. The bur contains a sealed cavity partially filled with water, which transports heat via the principle of rotating heat pipe technology. The heat transport capability of burs fitted out as rotating heat pipes was established. A conceptual design for a representative bur was prepared, based on surgical drill sculpting criteria. It appears that a self-cooled surgical drill for sculpting can limit bone temperatures below levels for the initiation of thermal damage in bone, nerve, and brain tissue, without the need to employ an externally applied coolant.
Smed-
β
catenin-1
Is Required for Anteroposterior Blastema Polarity in Planarian Regeneration
Authors: Petersen Christian P. , Reddien Peter W.
Published: December 2007

Planarian flatworms can regenerate heads at anterior-facing wounds and tails at posterior-facing wounds throughout the body. How this regeneration polarity is specified has been a classic problem for more than a century. We identified a planarian gene,
Smed-
β
catenin-1
, that controls regeneration polarity. Posterior-facing blastemas regenerate a head instead of a tail in
Smed-
β
catenin-1(RNAi)
animals.
Smed-
β
catenin-1
is required after wounding and at any posterior-facing wound for polarity. Additionally, intact
Smed-
β
catenin-1(RNAi)
animals display anteriorization during tissue turnover. Five Wnt genes and a secreted Frizzled-related Wnt antagonist-like gene are expressed in domains along the anteroposterior axis that reset to new positions during regeneration, which suggests that Wnts control polarity through
Smed-
β
catenin-1
. Our data suggest that β-catenin specifies the posterior character of the anteroposterior axis throughout the Bilateria and specifies regeneration polarity in planarians.
Treatment of Sickle Cell Anemia Mouse Model with iPS Cells Generated from Autologous Skin
Authors: Hanna Jacob , Wernig Marius , Markoulaki Styliani , Sun Chiao-Wang , Meissner Alexander , Cassady John P. , Beard Caroline , Brambrink Tobias , Wu Li-Chen , Townes Tim M. , Jaenisch Rudolf
Published: December 2007

It has recently been demonstrated that mouse and human fibroblasts can be reprogrammed into an embryonic stem cell–like state by introducing combinations of four transcription factors. However, the therapeutic potential of such induced pluripotent stem (iPS) cells remained undefined. By using a humanized sickle cell anemia mouse model, we show that mice can be rescued after transplantation with hematopoietic progenitors obtained in vitro from autologous iPS cells. This was achieved after correction of the human sickle hemoglobin allele by gene-specific targeting. Our results provide proof of principle for using transcription factor–induced reprogramming combined with gene and cell therapy for disease treatment in mice. The problems associated with using retroviruses and oncogenes for reprogramming need to be resolved before iPS cells can be considered for human therapy.
New Insights into Trehalose Metabolism by
Saccharomyces cerevisiae
:
NTH2
Encodes a Functional Cytosolic Trehalase, and Deletion of
TPS1
Reveals Ath1p-Dependent Trehalose Mobilization
Authors: Jules Matthieu , Beltran Gemma , François Jean , Parrou Jean Luc
Published: December 2007

In the yeast
Saccharomyces cerevisiae
, the synthesis of endogenous trehalose is catalyzed by a trehalose synthase complex, TPS, and its hydrolysis relies on a cytosolic/neutral trehalase encoded by
NTH1
. In this work, we showed that
NTH2
, a paralog of
NTH1
, encodes a functional trehalase that is implicated in trehalose mobilization. Yeast is also endowed with an acid trehalase encoded by
ATH1
and an H
+
/trehalose transporter encoded by
AGT1
, which can together sustain assimilation of exogenous trehalose. We showed that a
tps1
mutant defective in the TPS catalytic subunit cultivated on trehalose, or on a dual source of carbon made of galactose and trehalose, accumulated high levels of intracellular trehalose by its Agt1p-mediated transport. The accumulated disaccharide was mobilized as soon as cells entered the stationary phase by a process requiring a coupling between its export and immediate extracellular hydrolysis by Ath1p. Compared to what is seen for classical growth conditions on glucose, this mobilization was rather unique, since it took place prior to that of glycogen, which was postponed until the late stationary phase. However, when the Ath1p-dependent mobilization of trehalose identified in this study was impaired, glycogen was mobilized earlier and faster, indicating a fine-tuning control in carbon storage management during periods of carbon and energy restriction.
Gillnet catches as an estimate of fish abundance: a comparison between vertical gillnet catches and hydroacoustic abundances of Baltic Sea herring (Clupea harengus) and sprat (Sptattus sptattus)
Authors: Hansson Sture , Rudstam Lars G.
Published: December 2007

We compared the catches in a series of six vertical gill nets (6.25- to 18.75-mm bar mesh) with estimates of fish abundance derived from hydroacoustics. A total of 47 combined acoustic and gillnet surveys were collected between July and November 1987–1992 in archipelago areas of the northern Baltic Sea. Fish abundance determined by hydroacoustics was significantly correlated with gillnet catches but explained only 28% of the variance in catch per unit effort corrected for gillnet selectivity and fish swimming speed. Visibility (measured as Secchi disk depth) significantly decreased the likelihood of fish being caught in gill nets, while the effect of temperature was positive but nonsignificant. These data imply that gillnet catches will be a biased indicator of changes in fish abundance over time or space, if visibility and possibly also temperature change as well.
Efficiency and bias of estimators and sampling designs for determining length-weight relationships of fish
Authors: Hayes Daniel B. , Brodziak Jon K. T. , O'Gorman Joseph B.
Published: December 2007

The parameters of the allometric equation used to describe the length–weight relationship in fish are usually estimated by linear regression of log-transformed data. Simulation of length–weight regressions showed that for sample sizes commonly encountered in fisheries research, estimates of the intercept are biased high. In contrast with this, estimates of mean weight-at-length are biased low. As a result, different bias-correction factors are necessary to adjust for transformation bias. When the objective is to estimate the intercept of the length–weight equation, two existing methods correct for transformation bias. The appropriate bias-correction factor for mean weight-at-length, however, is exp(σ2/2) where σ2is the residual variance of the regression. As an alternative to the log-transformation method, the properties of nonlinear least-squares regression were explored. Estimates obtained with nonlinear regression are less efficient, but are relatively robust to departures from the assumed error structure. Simulation of several sampling designs showed that greater precision without loss of accuracy is obtained as subsampling is concentrated toward the extremes of the length distribution.
Time series bias in the estimation of density-dependent mortality in stock-recruitment models
Authors: Myers Ransom A. , Barrowman N. J.
Published: December 2007

Large biases can occur in parameter estimates for stock–recruitment models because the stock sizes are not chosen independently, being correlated with variability in recruitment. We examine the importance of this "time series bias" by a comprehensive analysis of available stock–recruitment data and the use of simulations. For semelparous species, i.e., species that reproduce only once, time series bias is important for all populations for which we had data. For iteroparous species, i.e., species that reproduce more than once, large biases occur if the populations are exploited at close to the maximum that is biologically possible. Notably, when there is autocorrelation in natural mortality, for univoltine species, the direction of bias is reversed due to model misspecification. Given moderate sample sizes and moderate levels of exploitation, time series bias is small for species such as Atlantic cod (Gadus morhua), for which α, the slope of the relationship between recruitment and number of spawners as the number of spawners goes to zero, is large. Time series bias will usually be important in species such as hakes (Merluccius) for which α appears to be relatively small.
Analytical study of special girder moment frames using a mixed shear–flexural link element
Authors: Kazemi M T , Erfani S
Published: December 2007

The present paper introduces a mixed shear–flexural (VM) link element that is capable of modelling shear yielding, flexural yielding, and their interaction under monotonic and cyclic loadings. The inelastic deformations are modelled using the multisurfaces approach with dissimilar yield surfaces and a stiffness matrix with nonzero off-diagonal components in shear–flexural space. A new kinematic hardening and new non-associated flow rules are employed. A special girder, which has an open web in the middle, is introduced and modelled using the developed VM link element. It is shown that the results of analyses using the VM link element are in good agreement with those from a finite element analysis. Nonlinear dynamic analyses are performed on a benchmark ordinary moment frame (OMF) and its improved versions with special girders. The special girder moment frame (SGMF), which consists of special girders at the lower storeys and ordinary girders at the roof level, has better seismic performance.Key words: mixed shear–flexural (VM) link element, inelastic zone, shear–flexural interaction, cyclic loading, multisurface, special girder, special girder moment frame (SGMF), ordinary moment frame (OMF).
Utilizing shape memory alloys to enhance the performance and safety of civil infrastructure: a review
Authors: Alam M S , Youssef M A , Nehdi M
Published: December 2007

Shape memory alloys (SMAs) are special materials with a substantial potential for various civil engineering applications. The novelty of such materials lies in their ability to undergo large deformations and return to their undeformed shape through stress removal (superelasticity) or heating (shape-memory effect). In particular, SMAs have distinct thermomechanical properties, including superelasticity, shape-memory effect, and hysteretic damping. These properties could be effectively utilized to substantially enhance the safety of various structures. Although the high cost of SMAs is still limiting their use, research investigating their production and processing is expected to make it more cost-competitive. Thus, it is expected that SMAs will emerge as an essential material in the construction industry. This paper examines the fundamental characteristics of SMAs, the constitutive material models of SMAs, and the factors influencing the engineering properties of SMAs. Some of the potential applications of SMAs are discussed, including the reinforcement and repair of structural elements, prestress applications, and the development of kernel components for seismic devices such as dampers and isolators. The paper synthesizes existing information on the properties of SMAs, presents it in concise and useful tables, and explains different alternatives for the application of SMAs, which should motivate researchers and practicing engineers to extend the use of SMAs in novel and emerging applications.Key words: shape memory alloy, superelasticity, shape-memory effect, construction, retrofitting.
Chart for edge stress in plate on elastic solid
Authors: Ioannides Anastasios M
Published: December 2007

A computerized chart is described for determination of the maximum bending stress, σe, under edge loading developing in a slab on an elastic solid. The solution used is akin to a closed-form solution. A predictive equation for σe is established, similar in form to the dense liquid formula of Westergaard. The variation of the load placement effect factor, i.e., the ratio of σe to the maximum stress under interior loading, is examined. This is shown to be solely a function of the load size ratio. The new solution is incorporated in a computer program (H51ES), which requires a relatively small memory core and can be implemented on a personal computer. The program can accommodate both single- and multi-wheel gears and promises to be useful to airport and highway pavement engineers.Key words: rigid pavements, elastic solid, edge loading, numerical solutions, slabs.
Establishing highway horizontal alignment to maximize design consistency
Authors: Easa Said M , Mehmood Atif
Published: December 2007

Highway design consistency is one of the important criteria in selecting the geometric features of proposed or existing alignments of two-lane rural highways. Operating-speed (OS) profile models have been used to evaluate design consistency by trial and error. For a proposed new highway, however, there may be geometric and physical constraints, and selection of these elements by trial and error to achieve optimal design consistency would be difficult, if not impossible. This paper presents an optimization model that establishes highway horizontal alignment to achieve maximum design consistency based on the OS profile. The decision variables of the model include radius of horizontal curves, spiral curve lengths, length of speed-change (SC) segments, and acceleration and deceleration rates. The objective function of the model minimizes the mean OS difference or the maximum OS difference for successive geometric features along the highway section. Application examples and sensitivity analysis are presented to illustrate the capabilities of the model in evaluating improvement strategies and to ensure that the model produces sound optimum alignments. The proposed model, which complements existing optimization models that mainly address highway construction cost, should be of interest to highway practitioners and engineers.Key words: design consistency, highway, geometric, horizontal alignment, optimization modeling, speed profile.
Equipment workspace analysis in infrastructure projects
Authors: Hammad Amin , Zhang Cheng , Al-Hussein Mohamed , Cardinal Germain
Published: December 2007

Workspace conflicts are one of the important problems that can delay construction activities, reduce productivity, or cause accidents that threaten the safety of workers. Workspace planning is particularly important in the case of large infrastructure projects, such as bridge construction, and rehabilitation projects where equipment with complex workspace requirement is required. This paper aims to extend the previous research on workspace representation and analysis in the case of large infrastructure projects focusing on the following issues: (i) specific representation of equipment workspaces using composite shapes, (ii) semiautomatic generation and analysis of workspaces, and (iii) development of a prototype system that can generate workspaces and detect spatiotemporal conflicts in a three-dimensional environment. The computational aspects of the proposed approach are discussed and demonstrated through the development of a prototype system, which has been applied in a case study of the deck replacement of Jacques Cartier Bridge in Montréal.Key words: workspace analysis, spatiotemporal conflicts, construction equipment, infrastructure projects, bridge redecking, constructive solid geometry.
Threshold values for reflective cracking based on continuous deflection measurements
Authors: Chen Dar-Hao , Zhou Fujie , Lee Jeffrey L , Hu Sheng , II Kenneth H. Stokoe , Yang Junsheng
Published: December 2007

The fundamental mechanisms leading to the development of reflective cracking are differential movements from the supporting pavement structure. In this study, the deflection profiles collected using the rolling dynamic deflectometer (RDD) were used to determine the threshold values for reflective cracking. This provides a quantitative method to determine the severity of the cracks (or joints), which controls the potential for reflective cracking. Three different deflection parameters were considered: (i) sensor 1 deflection (W1), (ii) differential deflection between sensor 1 and sensor 3 (W1-W3), and (iii) multiple of baseline deflection value. The reliability concept was also incorporated such that pavement engineers can select criteria (based on predefined confidence levels) to identify locations where reflective cracking is likely to take place. Threshold values were determined from a 4 year study conducted along US Interstate Highway 20 (IH-20), and case studies from overlay projects along State Highway 73 (SH-73) and US Highway 59 (US-59) were investigated to verify the proposed threshold values. Based on the findings in this study, the RDD can identify problematic areas but can also be used to optimize the rehabilitation strategy. As evident from the SH-73 and US-59 projects, the W1-W3 deflection and 2.5× baseline deflection are better criteria than W1 deflection alone.Key words: rolling dynamic deflectometer (RDD), reflective cracking, jointed concrete pavements, continuous deflection.
Modelling of three-dimensional flow velocities in a deep hole in the East Channel of the Mackenzie Delta, Northwest Territories
Authors: Gharabaghi Bahram , Inkratas Chris , Beltaos Spyros , Krishnappan Bommanna
Published: December 2007

The Mackenzie River has several anomalous deep scour holes in a number of river channels in its delta. Proposed gas pipeline crossings have renewed interest in studying the stability of these scour holes. The main goal of this research project was to study flow velocity and bed shear stress distributions for a 30 m deep hole in the East Channel of the Mackenzie Delta as a first step toward assessing the stability of the scour hole and the risk of its migration during various flow conditions. In this study, a three-dimensional (3D) finite element flow model, FLUENT, using the renormalization group (RNG) k-ε turbulence model (where k is the turbulent kinetic energy and ε is the turbulence dissipation rate) was set up for the scour hole and calibrated using detailed measurements of 3D flow velocities, obtained with an acoustic doppler current profiler. The numerical model was then applied to predict flow velocity and bed shear stress distributions in and around the scour hole for three flow conditions (720, 1000, and 1400 m3/s). Results indicate that two vortices are formed in the river elbow above the scour hole. As the flow rate changed, the sizes of the vortices varied. The region upstream of the hole experienced the greatest magnitudes of bed shear stress.Key words: computational fluid dynamics, finite element, bed shear stress, deep hole, flow reversal.
Monitoring of concrete building construction
Authors: Lin Shyh-Chyang
Published: December 2007

The collapses of concrete structures cause property loss, construction delays, and, more importantly, loss of human life. It is unlikely that a concrete construction failure is caused by a single factor. Presumably, a major cause combined with several secondary factors, such as rainfall, temperature fluctuations, uploading of formworks and rebars, and concrete placing, will have catastrophic consequences. This research tries to clarify the causes that increase the deformation of and stresses upon concrete members during construction stages. The marked strain increases, identified by daily readings of embedded gages, are due to either environmental changes or construction factors. The measured data shows that without unexpected external loadings, large rainfall causes a remarkable increase in the strain and stress on a concrete structure during construction. Other secondary factors affecting the concrete are: uploading of construction materials, removal of the support structure and formworks, change of temperature, and concrete placing. The results obtained by this study offer some precautions for in situ concrete construction.Key words: monitoring, strain gage, concrete construction, collapse.
New and improved single-arc unsymmetrical vertical curve for highways
Authors: Easa Said M
Published: December 2007

Existing unsymmetrical vertical curves consist of two parabolic arcs smoothly connected at the point of common curvature. As such, each arc has a constant rate of change in grade. This paper presents a new and improved single-arc unsymmetrical vertical curve for highways that takes the form of a cubic function. The curve has a rate of change in grade that varies gradually between the beginning and end of the curve. The new curve lies below the sharper arc and above the flatter arc of the existing equal-arc unsymmetrical (EAU) vertical curve, thus smoothing out the EAU curve. In addition, the new curve slightly improves highway sight distance in most of the cases studied. The single-arc curve exhibits several interesting properties. The forward and backward offsets are not equal, nor are the basic and reverse offsets. The offsets of the new and EAU curves are equal at the mid-point of the curve. Also, the rate of change in grade of the new curve at the mid-point equals the average of the rates of change in grade of the two arcs of the EAU curve. The new curve exhibits several important properties and, as such should be of interest to highway designers.Key words: unsymmetrical vertical curves, single arc, highways, offset, sight distance, driver comfort.
Clinical safety and efficacy of NG440: a novel combination of rho iso-alpha acids from hops, rosemary, and oleanolic acid for inflammatory conditionsThis article is one of a selection of papers published in this special issue (part 1 of 2) on the Safety and Efficacy of Natural Health Products.
Authors: Minich Deanna M. , Bland Jeffrey S. , Katke Jeffrey , Darland Gary , Hall Amy , Lerman Robert H. , Lamb Joseph , Carroll Brian , Tripp Matthew
Published: December 2007

In this report, we examine the clinical safety and efficacy of NG440, a phytochemical-based antiinflammatory formula consisting of a combination of rho iso-alpha acids from hops, rosemary, and oleanolic acid. In a previous study, we demonstrated that NG440 significantly decreased pain by 50% in patients with osteoarthritis. Consistent with these data, results from a multicentre trial indicate that NG440 reduced pain scores in patients with joint discomfort, as measured by VAS (visual analog scale) methodology. As demonstrated in an ex vivo clinical study, these effects on pain relief may be due to reduced inflammatory cytokine production including lower prostaglandin E2formation. Finally, strong data exist to suggest that NG440 is a safe formula for human consumption. Animal toxicity data revealed no adverse effects of NG440 at dosages ≤250 mg·kg–1·day–1for 21 days. Furthermore, human trial data suggest that NG440 does not negatively impact cardiovascular and gastrointestinal markers normally affected by selective COX-2 enzyme inhibitors, including platelet function, blood pressure, blood cell count, or fecal calprotectin, a measure of gastrointestinal injury. In conclusion, NG440 may serve as a safe and efficacious alternative in some areas where specific COX-2 inhibitors have been traditionally used.
Modulation of apolipoprotein A1 and B, adiponectin, ghrelin, and growth hormone concentrations by plant sterols and exercise in previously sedentary humansThis article is one of a selection of papers published in this special issue (part 1 of 2) on the Safety and Efficacy of Natural Health Products.
Authors: Collins Melissa , Varady Krista A. , Jones Peter J.H.
Published: December 2007

Plant sterols combined with exercise beneficially alter lipid levels in hypercholesterolemic adults. The effect of this combination therapy on other indicators of coronary heart disease risk, however, has yet to be determined. The objective of this trial was to investigate the effect of plant sterols and exercise, alone and in combination, on levels of apolipoprotein (apo) A1 and B, adiponectin, ghrelin, and growth hormone in previously sedentary hypercholesterolemic adults. In an 8 week, parallel-arm trial, 84 subjects were randomized to 1 of 4 groups: combination, exercise, plant sterols, or control. Body mass decreased by 1.1% (p < 0.01) and 0.9% (p < 0.05) in the combination and exercise group, respectively. Low-density lipoprotein cholesterol levels decreased (p < 0.01) by 0.30 mmol/L in the combination group and by 0.49 mmol/L in the plant sterol group. High-density lipoprotein cholesterol levels increased by 7.5% and 9.5% (p < 0.01) in the combination and exercise groups, respectively. Plant sterols increased (p < 0.05) adiponectin levels by 16%. No change in apoA1, apoB, ghrelin, or growth hormone levels were noted in any intervention group. ApoA1 was correlated with high-density lipoprotein cholesterol (r = 0.33, p = 0.01), whereas apoB was weakly related to low-density lipoprotein cholesterol levels (r = 0.13, p = 0.002). Adiponectin was associated with body mass index (r = –0.10, p = 0.006) and high-density lipoprotein cholesterol (r = 0.17, p = 0.0003). These findings suggest that plant sterols can increase adiponectin levels, thereby possibly reducing the risk of future coronary heart disease.
Fermented Canadian lowbush blueberry juice stimulates glucose uptake and AMP-activated protein kinase in insulin-sensitive cultured muscle cells and adipocytesThis article is one of a selection of papers published in this special issue (part 1 of 2) on the Safety and Efficacy of Natural Health Products.
Authors: Vuong Tri , Martineau Louis C. , Ramassamy Charles , Matar Chantal , Haddad Pierre S.
Published: December 2007

Extracts of the Canadian lowbush blueberry ( Vaccinium angustifolium Ait.) have recently been demonstrated to possess significant antidiabetic potential, in accordance with the traditional use of this plant as an antidiabetic natural health product. Fermentation of blueberry juice with the Serratia vaccinii bacterium is known to modify the phenolic content and increase antioxidant activity. The present study evaluated the effects of fermented blueberry juice on glucose uptake, adipogenesis, and the signaling pathways that regulate glucose transport in muscle cells and adipocytes. A 6-hour treatment with fermented juice potentiated glucose uptake by 48% in C2C12 myotubes and by 142% in 3T3-L1 adipocytes, in the presence or absence of insulin, whereas nonfermented juice had no effect on transport. Fermented juice dramatically inhibited triglyceride content during adipogenesis of 3T3-L1 cells. Chlorogenic acid and gallic acid, both major phenolic components of fermented juice, had no effect on glucose uptake. Western blot analysis of the insulin-independent AMP-activated protein kinase revealed increased phosphorylation resulting from a 6-hour treatment. This activation or the increase in glucose uptake could not be explained by increased cytosolic calcium. Fermentation with S. vaccinii is concluded to confer antidiabetic activities to blueberry juice. Although the active principles and their mechanisms of action remain to be identified, transformed blueberry juice may nevertheless represent a novel complementary therapy and a source of novel therapeutic agents against diabetes mellitus.
Modulation of human cytochrome P450 3A4 (CYP3A4) and P-glycoprotein (P-gp) in Caco-2 cell monolayers by selected commercial-source milk thistle and goldenseal productsThis article is one of a selection of papers published in this special issue (part 1 of 2) on the Safety and Efficacy of Natural Health Products.
Authors: Budzinski Jason W. , Trudeau Vance L. , Drouin Cathy E. , Panahi Mitra , Arnason J. Thor , Foster Brian C.
Published: December 2007

In this study, we used an in vitro Caco-2 cell monolayer model to evaluate aqueous extracts of commercial-source goldenseal ( Hydrastis canadensis ) and milk thistle ( Silybum marianum ) capsule formulations, their marker phytochemicals (berberine and silibinin, respectively), as well as dillapiol, vinblastine, and the HIV protease inhibitor saquinavir for their ability to modulate CYP3A4 and ABCB1 expression after short-term exposure (48 h). Both upregulation and downregulation of CYP3A4 expression was observed with extracts of varying concentrations of the two natural health products (NHPs). CYP3A4 was highly responsive in our system, showing a strong dose-dependent modulation by the CYP3A4 inhibitor dillapiol (upregulation) and the milk thistle flavonolignan silibinin (downregulation). ABCB1 was largely unresponsive in this cellular model and appears to be of little value as a biomarker under our experimental conditions. Therefore, the modulation of CYP3A4 gene expression can serve as an important marker for the in vitro assessment of NHP–drug interactions.
Characterizing the mechanism for ginsenoside-induced cytotoxicity in cultured leukemia (THP-1) cellsThis article is one of a selection of papers published in this special issue (part 2 of 2) on the Safety and Efficacy of Natural Health Products.
Authors: Kitts David D. , Popovich David G. , Hu Chun
Published: December 2007

Pure ginsenoside standards (saponins Rh2, PD, and PT), along with an Rh2-enhanced North American ginseng ( Panax quinquefolius ) leaf extract (LFRh2), were tested for cytotoxic activity in cultured THP-1 leukemia cells. Thermal treatment of ginseng leaf resulted in production of both Rh2 and Rg3 content that was confirmed by liquid chromatography – mass spectrometry (LC-MS). Flow cytometry of cells stained with annexin V – fluorescein isothiocyanate and propidium iodide showed that the LFRh2 significantly (p ≤ 0.05) increased apoptosis (18% ± 0.4%) after 23 h at a concentration that inhibited cell viability by 50% (LC50 (72 h) = 52 μg/mL. In comparison, a similar significant (p ≤ 0.05) increase in apoptotic cell numbers occurred at 41 h of exposure for pure ginsenoside standards, PD (LC50 (72 h) = 13 μg/mL), PT (LC50 (72 h) = 19 μg/mL), and Rh2 (LC50 (72 h) = 15 μg/mL). Although no further increase in apoptosis was observed in THP-1 cells after exposure to increasing concentrations of LFRh2 and pure Rh2, PD, and PT standards, a significant (p < 0.05) increase in the percentage of necrotic cells did occur after exposure of cells to different ginsenosides at elevated concentrations. THP-1 caspase-3 activity was greatest (p ≤ 0.05) with Rh2 (7.6 ± 1.1 nmol/L pNA), followed by LFRh2 (5.9 ± 1.0 nmol/L pNA) and PT (5.0 ± 0.8 nmol/L pNA), whereas PD was similar to control cells. We define for the first time the proportion of apoptotic to necrotic events that characterize the relative cytotoxicity and reduced cell proliferation of different ginsenosides in cultured THP-1 cells. Moreover, thermal treatment of North American ginseng leaf produced a marked transformation of ginsenoside, largely attributable to an increase in Rh2 content. This change was associated with cytotoxic properties in THP-1 cell that were related to alterations in cell membrane properties, which were also obtained with the pure ginsenosides PD, PT, and Rh2.
Survey of bioactive components in Western Canadian berriesThis article is one of a selection of papers published in this special issue (part 2 of 2) on the Safety and Efficacy of Natural Health Products.
Authors: Bakowska-Barczak Anna M. , Marianchuk Myles , Kolodziejczyk Paul
Published: December 2007

Berries native to Western Canada were analyzed for total anthocyanins, total phenolics, and trolox equivalent antioxidant activity (TEAC). Values ranged from 1.60 to 9.55 mmol trolox equivalent per 100 g fresh mass. Anthocyanin content ranged from 41.6 (in red twinberries) to 1081 mg cyanidin-3-glucoside equivalents per 100 g fresh mass (in honeysuckle fruits). Honeysuckle fruits contained the highest amount of total polyphenols, 1111 mg gallic acid equivalents per 100 g, among analyzed fruits. Additionally, anthocyanins in the investigated berries were identified and characterized by HPLC – electrospray ionization – tandem mass spectrometric method coupled with diode array detection. The number of anthocyanins varied from 4 in saskatoon berries ( Amelanchier alnifolia Nutt.) to 20 in bilberries ( Vaccinum myrtilloides Michx.). In all the samples analyzed, 6 common anthocyanidins:, cyanidin, delphinidin, pelargonidin, petunidin, peonidin, and malvidin, were found. Half the analyzed berries contained acylated anthocyanins, but a significant amount was found only in bilberries. The analyzed berry seed oils contained high amounts of unsaturated fatty acids (over 90%), but only the golden currant seed oil contained γ-linolenic acid.