bluuebunny/crossref_metadata_2025 huggingface dataset:
Robust pole assignment for linear time-invariant systems using state-derivative feedback
Authors: Abdelaziz T H S
Published: December 2008

In this paper, a technique for computing robust controller for multivariable time-invariant linear systems via state-derivative feedback is introduced such that the sensitivity of the closed-loop system eigenvalues to perturbations in the system and gain matrices is minimized. The proposed technique can be applied for any controllable system with some restrictions when assigning zero poles. This article focuses on the derivation of feedback gain when the open-loop state matrix is singular. The available degrees of freedom offered by state-derivative feedback for multivariable system are utilized to improve robustness of the closed-loop system. Finally, a computational algorithm and a numerical example are introduced to demonstrate the effectiveness of the proposed technique.
An electrohydraulic vibration exciter using a two-dimensional valve
Authors: Ruan J , Burton R T
Published: December 2008

A scheme for an electrohydraulic vibrator excited by a two-dimensional valve is proposed, which significantly extends the frequency range compared to that of vibrators excited by conventional servo valves. In the two-dimensional valve, the rotary motion of the spool coordinates the relative motion of the grooves on the spools area with respect to the windows on the sleeve which in turn, alternates the oil flowrate into and out of the chambers of the hydraulic cylinder (motor) and subsequently excites the piston (rotor) to vibrate. The linear motion of the two-dimensional valve spool is used to vary the peak flowrate and thus the amplitude of the output vibration. The frequency of the vibration excited by the two-dimensional valve is related to the rotary speed of the spool and the number of the grooves on the spool area (windows on the sleeve). This configuration extends the frequency of the hydraulic vibrator by increasing the number of the grooves on the spool area (windows on the sleeve) and the rotary speed of the spool which are in the perfect lubrication of oil.

A model of the two-dimensional vibrator is developed and compared to its experimental counterpart. The vibration excited by the two-dimensional valve is influenced by pressure saturation, the elastic force, and the hydraulic resonance. There is a critical valve linear opening, beyond which the output force (torque) reaches a saturation value in both a positive and negative sense. Both simulation and experimental results show that at lower frequencies the ascent and descent slopes of the output force show some inconsistency which becomes more significant above the critical valve linear opening but drops off with a reduction in the valve linear opening. In a higher frequency range, the vibration excited by the two-dimensional valve is mainly influenced by hydraulic resonance. As the input frequency approaches the hydraulic resonant frequency, the output excited vibration essentially becomes the hydraulic resonance. Therefore, the effective frequency range of the hydraulic vibration is not only decided by the frequency bandwidth of the two-dimensional valve, but is influenced by the hydraulic resonance. Nevertheless, the study does provide an access to the high-frequency excitation of the hydraulic vibration.
Almost disturbance decoupling and tracking control for multi-input multi-output non-linear uncertain systems: Application to a half-car active suspension system
Authors: Chien T-L , Chen C-C , Tsai M-C , Chen Y-C
Published: December 2008

This study presents a novel feedback linearization control of non-linear multi-input multi-output uncertain systems for the tracking and almost disturbance decoupling performances. The main contribution of this study is to construct a controller, under appropriate conditions, such that the resulting closed-loop system is valid for any initial condition and bounded tracking signal with the following characteristics: input-to-state stability with respect to disturbance inputs and almost disturbance decoupling. In addition, a new theorem on robust stability is proposed in this study to provide a new criterion for closed-loop stability. A typical case, which cannot be solved by any previous study on the almost disturbance decoupling problem, is proposed in this study to exploit the fact that the tracking and the almost disturbance decoupling performances can be easily achieved by the proposed approach. Finally, the proposed control law is simulated in a half-car active suspension system on which the effectiveness of the design is verified.
A partial pole placement approach to proportional-integral observer design
Authors: Hu J-S , Hu F-R , Cheng M-Y
Published: December 2008

This paper deals with the partial pole placement design of a proportional-integral (PI) observer. The proposed partial pole placement approach offers a new method for designers to assign the PI observer gains on a detectable system. Analysis and design of the PI observer are discussed in detail. A crucial lemma and discussions to the proposed approach are presented, and an illustrative numerical example is given to verify the proposed design approach.
An algebraic method for designing controllers for multi-input multi-output linear systems via s-domain input-output decoupling
Authors: Özgören M K
Published: December 2008

The method introduced here is applicable for multi-input multi-output, linear, and time-invariant systems. The state and output equations of the system, which are originally expressed in the t-domain, are first transformed into the s-domain. Then, input-output decoupling is achieved by generating the actual control variables as combinations of virtual control variables in such a way that each output is controlled by only the dedicated one of the virtual control variables. As the next stage, appropriate linear controllers are designed to generate the virtual control variables with feedback, feedforward, and disturbance rejection features. The design method is algebraic and involves the assignment of not only the closed-loop poles but also the type numbers associated with the reference and disturbance inputs. The multivariable transformation filter that converts the virtual control variables into actual ones is formed properly to prevent any possibility of internal instability.
About the validity of Reynolds equation and inertia effects in textured sliders of infinite width
Authors: Dobrica M B , Fillon M
Published: December 2008

Numerous recent studies focus on modelling the lubricant flow in macro-textured configurations, using the Navier-Stokes, Stokes, and Reynolds equations. Several of these studies show that important, lift generating inertia effects are present in textured configurations, and conclude that Reynolds assumptions do not hold true for such contacts. A similar analysis is performed in this paper, for parallel sliders of infinite width, but with quite different conclusions. Two main observations are made based on the results presented herein: (a) inertia effects cannot be analysed by single texture cell models - for example, in the case of partial inlet texturing, inertia shows a clear negative influence, contradicting the previously reported lift generating effects; (b) the validity of Reynolds equation in textured sliders cannot be decided by the Reynolds number ( Re) alone, and the texture aspect ratio (λ) has an equally important influence on Reynolds equation validity. Finally, charts presenting the relative difference between Reynolds and Navier-Stokes solutions in terms of λ and Re are discussed.
Sound of a ball spline operated at a certain linear velocity
Authors: Ohta H , Iwasaki S , Kazama T , Hoshino K
Published: December 2008

This article deals with the sound of light or medium-preloaded ball splines operating at a certain linear velocity. Experimental results showed that the sound waveforms of the ball splines are pulse-like with ball passage period Tp, and sound peaks f1- f8 and f1- f7 appear in the 20 kHz range sound spectra of the light- and medium-preloaded ball splines, respectively. A supplemental experiment showed that the main cause of the ball spline sound is the collision between the ball and the spline shaft or spline nut at the entrance of the load zone. The measured frequencies of the sound peaks nearly matched the natural radial-bending frequencies of the spline shaft or nut obtained by finite-element method (FEM). This means that the sound peaks are caused by the natural radial-bending vibrations of the spline shaft and nut. Finally, based on the experimental and FEM results, the sound-generating mechanism of the ball splines has been elucidated.
Dynamic stiffness and damping characteristics of one-dimensional magneto-hydrodynamic inclined-plane slider bearings
Authors: Lin J-R , Hung C-R , Hsu C-H , Lai C
Published: December 2008

Considering the transient squeezing motion, the magneto-hydrodynamic (MHD) steady and dynamic characteristics of one-dimensional slider bearings lubricated with an electrically conducting fluid in the consideration of a transverse magnetic field are numerically investigated. Using the MHD motion equations and, the continuity equation, we have derived a MHD dynamic Reynolds-type equation, which is applicable to slider bearings taking into account the squeezing effect ∂ h/ ∂ t, in which the general film-shape function is described by h= h( x, t). A closed-form solution for the pressure of an inclined-plane slider is obtained and applied to predict the MHD dynamic stiffness and damping characteristics of bearings. According to the results obtained, the application of externally applied magnetic fields signifies an apparent increase in the MHD steady film pressure. Comparing with the classical non-conducting-lubricant case, the applied magnetic-field effects characterized by the Hartmann number provide significant improvement in the MHD steady load-carrying capacity, the MHD dynamic stiffness coefficient, and the MHD dynamic damping coefficient. The improvement of dynamic characteristics of MHD bearings is more pronounced with large Hartmann numbers and small minimum film thicknesses. For guiding the use of the present study, a design example is illustrated. Further results shown in the tables are provided for engineering application.
Coupling between structural deformations and wheel—rail contact geometry in railroad vehicle dynamics
Authors: Sanborn G , Tobaa M , Shabana A A
Published: December 2008

This investigation aims to demonstrate the effect of structural flexibility on the wheel—rail contact location and forces in railroad vehicle dynamics. It is shown that there is a strong dynamic coupling between the car body deformation coordinates and the wheel—rail contact parameters and geometry that depend on the wheel and rail surface profiles. In particular, two wheel profiles are considered in this study in order to examine the coupling between the geometry and structural flexibility. The first profile allows for a second point of contact on the flange of the wheel, while the second profile is designed such that the wheel cannot have more than one point of contact with the rail. The coupling between the deformation of the car body and the contact geometry is demonstrated through the comparison of computer simulations of a railroad tank car modelled with a flexible tank and a rigid tank. The simulations are performed using the methods of multi-body dynamics utilizing a fully non-linear multi-body framework and an elastic three-dimensional wheel—rail contact methodology. Structural flexibility is incorporated into the equations of motion by means of the floating frame of reference formulation, allowing for a small deformation, linear finite-element mesh to undergo arbitrarily large reference displacement and rotation. The resulting coupled, non-linear differential-algebraic equations are solved using well-known methods of numerical time integration.
Stabilization of singularly perturbed systems using acceleration-dependent forces
Authors: Zhechev M M
Published: December 2008

One of the most important properties of the Lagrange equations is their regularity, i.e. the non-singularity of their inertia matrix, as a result of which they can always be brought to normal form. However, their inertia matrix may be ill-conditioned, and the equations themselves may be singularly perturbed. As a consequence, even relatively small errors in the parameters of the control actuators and moderate perturbing actions may result in a significant difference between the calculated and the actual motions of the system.

It is not always possible to remedy this situation using traditional control, which depends on the position, velocity, and time alone, thus calling for the development of special methods to control singularly perturbed systems.

This paper reports a new approach to the singularly perturbed system stabilization problem, in which the effect of permanent perturbations is reduced using acceleration-dependent forces.
Using graph theory and symbolic computing to generate efficient models for multi-body vehicle dynamics
Authors: Schmitke C , Morency K , McPhee J
Published: December 2008

Linear graph theory, invented in 1736 by Leonhard Euler, has been combined with principles of physics to develop algorithms for formulating the dynamic equations for multi-body multi-domain systems. This graph-theoretic formulation allows electrical, mechanical, and hydraulic systems to be modelled within a common framework. The formulation has been implemented in a symbolic computer program, DynaFlexPro, that automatically generates compact and efficient sets of system equations that lead to reduced simulation times compared with most commercial multi-body dynamics software.

In this article, models of pneumatic tyres are incorporated into the symbolic computer implementation, which is used to create real-time simulations of vehicle dynamics. The tyre component forms a list of symbolic expressions for important tyre variables, such as inclination and slip angle, that are used to calculate tyre forces and moments during simulation. If the transient behaviour of the tyre is important, the user can request that additional relaxation length equations be included in the model. The tyre component allows the user to choose from several tyre model functions that describe the generation of forces and moments at the tyre contact patch and can also accommodate user-developed tyre model functions.

A brief introduction to the linear graph formulation procedure used by DynaFlexPro is given, as well as an explanation of how the tyre component works within the linear graph framework. As an example, optimized simulation code is generated for a three-dimensional vehicle model, and results are validated using an equivalent model in the MSC.ADAMS® commercial software package.
Simulation of material tests using meshfree Lagrangian particle methods
Authors: Gaugele T , Fleissner F , Eberhard P
Published: December 2008

This contribution presents an enhanced discrete-element model with special focus on modelling of cohesive ductile materials. The model is based on a basic three-dimensional discrete-element model consisting of spherical rigid particles, which is used to model non-cohesive granular material. This basic model is enhanced by including special interactions. These interactions allow for the description of cohesive ductile behaviour of the modelled material. It is shown that by including these interactions in the discrete-element model, the failure modes of highly ductile materials like aluminium can be qualitatively as well as quantitatively described. The validity of the model is shown by the comparison of different simulated material tests with the experimental counterpart.
On explicit adaptive symplectic integration of separable Hamiltonian systems
Authors: Modin K
Published: December 2008

Based on a known observation that symplecticity is preserved under certain Sundman time transformations, adaptive symplectic integrators of an arbitrary order are constructed for separable Hamiltonian systems, for two classes of scaling functions. Due to symplecticity, these adaptive integrators have excellent long-time energy behaviour, which is theoretically explained using standard results on the existence of a modified Hamiltonian function.

In Contrast to reversible adaptive integration, the constructed methods have good long-time behaviour also for non-reversible systems. Numerical examples of this are given.
Dynamic safety of active trailer steering systems
Authors: Odhams A M C , Roebuck R L , Cebon D , Winkler C B
Published: December 2008

The dynamic safety of an active steering system for an articulated heavy goods vehicle is investigated. The vehicle is a tractor semi-trailer with two independently steerable axles on the trailer. Several different vehicle dynamics modelling approaches are used to investigate the aspects of the safety of the steering system. These include ‘back of envelope’ calculations, a single degree-of-freedom yaw model, a simplified yaw-plane model using Matlab SimMechanics, with realistic controller frequency response assumptions, and a complex multi-body model of the whole vehicle using TruckSim.

Specific safety issues of concern associated with the primary active steering function are: (a) the necessary actuation bandwidth for stable response at high speeds, and (b) the performance implications of disturbance rejection requirements, e.g. side winds and split friction braking. It is found that vehicle tracking improves with increased bandwidth up to 8.3 Hz, but beyond this, performance is limited by other factors. Also, the steering system is able to reject off-tracking disturbances from side winds and split-friction braking, although the latter has a small effect.

Additional ‘failsafe’ issues of concern are: (a) whether an independent centring system is necessary on each steerable axle or whether failure of an axle can be safely managed by steering the remaining axles in opposition, (b) the force levels needed in the automatic safety centring system, and (c) the maximum slew rate for centring the axles in an emergency. It is found that individual centring systems for each axle are necessary because axle ‘opposition’ is not a safe strategy for a trailer with two steered axles. The steering actuator is required to generate 32 kN during all modes of operation in order to maintain safety during the specified manoeuvre. A maximum steering slew rate of 11°/s is found to limit additional lateral acceleration to less than 0.2 g.
Erythroplasia of Queyrat with Zoon's balanitis: a diagnostic dilemma
Authors: Divakaruni A K , Rao A V C , Mahabir B
Published: December 2008

Chronic erythematous lesions of the penis may result from a variety of underlying causes that form a part of differential diagnosis. They are difficult to diagnose only upon clinical examination and may necessitate performing a biopsy to confirm the diagnosis and also identify the coexisting disease. We report a case of erythroplasia of Queyrat (EQ) with Zoon's balanitis and discuss the classification of the lesion through the analysis of overlapping histological features. A middle-aged uncircumcised man presented with two long-standing erythematous prepucial penile lesions unresponsive to antibiotics. Biopsy performed to establish the diagnosis revealed non-invasive severe dysplastic changes in the epithelium that is typical of EQ. Subepithelial histological features were characteristic of Zoon's balanitis. The extent and nature of inflammatory infiltrate in the dermis described in the literature is quite varied in EQ and in the spectrum of non-cicatricial balanoposthitis. The overlap of histological findings could result in the diagnostic dilemma of a coexistent lesion, as described in this case report.
Low seroprevalence of HIV and syphilis in pregnant women in refugee camps on the Thai-Burma border
Authors: Plewes K , Lee T , Kajeechewa L , Thwin M M , Lee S J , Carrara V I , Nosten F , Mcgready R
Published: December 2008

Refugee and migrant populations are considered to be at high risk from sexually transmitted infection (STI) and HIV. Cross-sectional surveys for syphilis and HIV were conducted in antenatal clinics (ANCs) on the Thai-Burmese border. In Mae La refugee camp, the seroprevalence of HIV and syphilis were 0.2% (one of 500) (95% CI 0–1.1) and 0% (0 of 404) (95% CI 0–0.9) in 1997; and 0.4% (two of 500) (95% CI 0.1–1.4) and 0.4% (three of 741) (95% CI 0.1–1.2) in 2005, respectively; syphilis seroprevalence in migrant women in 2005 was 0 (0 of 234) (95% CI 0–1.6). The seroprevalence was lower than that reported from surrounding ANCs for Thai or Burmese women. Focus group discussions with HIV-negative and -positive pregnant refugee women established that aspects of Karen culture and isolation (geographical and political) had a significant protective role from HIV and STI. This survey has resulted in programmatic changes in services to pregnant women in this area.
Foreskin length in uncircumcised men is associated with subpreputial wetness
Authors: O'Farrell N , Chung C-K , Weiss H A
Published: December 2008

This study was performed to identify possible factors associated with penile wetness, defined as the observation of a diffuse homogenous film of moisture on the surface of the glans and coronal sulcus, in men attending a sexually transmitted infection clinic. Genital examination was undertaken in 422 uncircumcised men and any degree of subpreputial wetness observed was recorded. The degree of visibility of the urinary meatus on direct inspection was also assessed. Subjects were asked whether they retracted the foreskin while urinating and how long since they had last passed urine. Penile wetness was observed in 13.0% of the men and was more common in those whose foreskin covered the urinary meatus on direct inspection (17.4% vs. 4.9%) and those with balanitis (33.3%). On multivariate analysis, penile wetness was independently associated with balanitis, nonspecific urethritis/ chlamydia, reporting sex with another man and having a visible urinary meatus on direct inspection. Penile wetness was not associated with retracting the foreskin while passing urine or duration since last passed urine. Men with a foreskin covering the urinary meatus on direct observation should be advised about the benefits of good genital hygiene if penile wetness was observed.
Audit on the success of partner notification for sexually transmitted infections in the West Midlands
Authors: Manavi K , Bhaduri S , Tariq A
Published: December 2008

The aim of this study is to investigate the success of partner notification (PN) among 13 genitourinary medicine centres in West Midlands. The West Midlands Audit Group conducted a regional audit between June and August 2007. Information on screening and management of patients with chlamydia, gonorrhoea, early syphilis and HIV were collected separately. Participating centres were asked to provide PN details for 10 index patients with each of chlamydia, gonorrhoea, early syphilis and HIV infections. For each index patient with chlamydia or gonorrhoea, 0.54 and 0.44 partners were screened, respectively. Among partners of patients with syphilis and HIV, 24% and 35% were screened, respectively. Only 9% of 311 screened partners were involved in casual partnerships with index patients. Acquisition of more robust targets for PN, better documentation, improved communication between genitourinary (GU) medicine centres, and provider referral may improve the performance of PN for Sexually transmitted infections.
Performance of direct fluorescent antibody tests for routine diagnosis of Chlamydia trachomatis in Russian sexually transmitted disease clinics
Authors: Renton A , Filatova E , Ison C , Meheus A , Dmitriev G , Akovbian V , Taylor-Robinson D
Published: December 2008

Testing for Chlamydia trachomatis in Russia is usually done by microscopic examination of genital smears stained with fluorescent antibody provided in locally produced kits. The aim was to assess the sensitivity and specificity of such direct fluorescent antibody (DFA) tests compared with a nucleic acid amplification test (NAAT) (ligase chain reaction) to detect C. trachomatis in 171 cervical smears and 201 urethral smears from men. The patients were at high risk of chlamydial infection and had been recruited at three sexually transmitted disease clinics in Moscow. Among women, DFA test sensitivity was 6% (95% CI 0–14) and the specificity was 92% (95% CI 88–97). Among men, the sensitivity was 9% (95% CI 2–16) and the specificity was 90% (95% CI 83–94). Poor DFA test performance was probably due to poor antibody quality and such tests are not adequate for routine examination of populations with either low or high chlamydial prevalence. As there may remain a place for DFA testing where few patients are seen, the Russian Ministry of Health should enforce registration of diagnostic tests, and Russian manufacturers should seek ways of improving DFA test performance. However, the mainstay of testing should depend on NAATs.
The limits of healthcare seeking behaviour: how long will patients travel for STI care? Evidence from England's ‘Patient Access and the Transmission of Sexually Transmitted Infections’ (‘PATSI’) study
Authors: Olonilua O , Ross J D C , Mercer C , Keane F , Brook G , Cassell J A
Published: December 2008

The objective of this study was to identify factors associated with (i) longer patient travel time to genitourinary (GU) medicine clinics and (ii) not attending the nearest clinic. Questionnaires were completed by 4600 new attendees from seven sociodemographically and geographically different GU clinics across England between October 2004 and March 2005. These data were then linked to the routine clinic database. Median travel time was 25 minutes and varied significantly by clinic (P < 0.001) but not by gender (P = 0.96). Of all the respondents, 10% spent at least one hour getting to a GU clinic and this was significantly more likely in patients with less education, those who travelled by public transport and those who did not attend their closest clinic. Longer travel times were not associated with delays in seeking care. Patients reporting a previous sexually transmitted infection (STI) diagnosis were more likely not to go to their nearest GU clinic (P = 0.0006), as were those who used/tried to use other healthcare providers prior to attending the clinic (P = 0.007). To facilitate access to STI care, comprehensive local services need to be provided to avoid long journey times, especially for those who have to rely on public transport to get to clinic.
Is there a reservoir of sub-clinical lymphogranuloma venereum and non-LGV Chlamydia trachomatis infection in men who have sex with men?
Authors: Tinmouth J , Gilmour M W , Kovacs C , Kropp R , Mitterni L , Rachlis A , Richards S , Salit I , Sikri R , Valencia G R , Wesson T , Wong T , Wood H
Published: December 2008

The aim of this study was to determine if a reservoir of sub-clinical LGV infection exists in men who have sex with men (MSM), as this finding might account for the recent rise in lymphogranuloma venereum (LGV) Chlamydia trachomatis infections among MSM in Canada. MSM without proctitis were enrolled between January and August 2006 in a cross-sectional study. Rectal, urine, serology and pharyngeal specimens were tested for specific C. trachomatis serovars. The median age of the 253 participants was 43 years; 53% were HIV+. We found no active cases of LGV infection; but 20 (8%) participants had positive serology. Thirteen participants (5%) had non-LGV C. trachomatis infections. Unprotected anopenetrative intercourse, rectal enema and drug use were associated with non-LGV C. trachomatis infection. Sub-clinical rectal non-LGV C. trachomatis infection was relatively common but LGV was not identified in our sample. Further studies of screening for non-LGV chlamydia infection in MSM are needed.
High Cortical Bone Mass Phenotype in Betacellulin Transgenic Mice Is EGFR Dependent
Authors: Schneider Marlon R , Mayer-Roenne Bettina , Dahlhoff Maik , Proell Verena , Weber Karin , Wolf Eckhard , Erben Reinhold G
Published: December 2008

Signaling through the epidermal growth factor receptor (EGFR) by ligands such as epidermal growth factor (EGF), transforming growth factor α (TGFA), and amphiregulin (AREG) has been reported to have effects on skeletal growth. The role of betacellulin (BTC), another EGFR ligand, in skeletal development and bone metabolism is unknown. In previous experiments, transgenic mice overexpressing BTC ubiquitously under the control of the chicken β-actin promoter (BTC-tg) exhibited stunted growth and disproportionately sized long bones. In this study, we performed a detailed phenotypic analysis of BTC-tg mice at 3, 6, and 9 wk of age. Osteoblastic cells from transgenic mice showed strong expression of BTC as determined by Western blots and by immunohistochemistry on bone sections. In femurs of male and female BTC-tg mice, we found reduced longitudinal bone growth and a pronounced increase in total volumetric BMD. The increased femoral BMD was mainly caused by augmented endocortical bone apposition and subsequent cortical bone thickening. In contrast, vertebral BMD was reduced in BTC-tg mice of both sexes. An overall similar phenotype was found in 6-mo-old BTC-tg mice. The increase in cortical bone mass in the appendicular skeleton of BTC-tg mice was largely blocked when they were crossed into the EgfrWa5 background characterized by a dominant negative EGFR. Our study showed that overexpression of BTC results in an EGFR-dependent upregulation of cortical bone mass in the appendicular skeleton of mice, uncovering a potential novel anabolic pathway for cortical bone.
Estimates of the Proportion of Older White Women Who Would Be Recommended for Pharmacologic Treatment by the New U.S. National Osteoporosis Foundation Guidelines
Authors: Donaldson Meghan G , Cawthon Peggy M , Lui Li-Yung , Schousboe John T , Ensrud Kristine E , Taylor Brent C , Cauley Jane A , Hillier Teresa A , Black Dennis M , Bauer Doug C , Cummings Steven R
Published: December 2008

The new U.S. National Osteoporosis Foundation Clinician's Guide to Prevention and Treatment of Osteoporosis includes criteria for recommending pharmacologic treatment based on history of hip or vertebral fracture, femoral neck (FN), or spine BMD T-scores ≤−2.5 and presence of low bone mass at the FN or spine plus a 10-yr risk of hip fracture ≥3% or of major osteoporotic fracture ≥20%. The proportion of women who would be recommended for treatment by these guidelines is not known. We applied the NOF criteria for treatment to women participating in the Study of Osteoporotic Fractures (SOF). To determine how the SOF population differs from the general U.S. population of white women ≥65 yr of age, we compared women in SOF with women who participated in the National Health and Nutrition Examination Survey (NHANES) III on criteria included in the NOF treatment guidelines that were common to both cohorts. Compared with NHANES III, women in SOF had higher FN BMD and were younger. Application of NOF guidelines to SOF data estimated that at least 72% of U.S. white women ≥65 yr of age and 93% of those ≥75 yr of age would be recommended for drug treatment. Application of the new NOF Guidelines would result in recommending a very large proportion of white women in the United States for pharmacologic treatment of osteoporosis.
Sclerostin Antibody Treatment Increases Bone Formation, Bone Mass, and Bone Strength in a Rat Model of Postmenopausal Osteoporosis
Authors: Li Xiaodong , Ominsky Michael S , Warmington Kelly S , Morony Sean , Gong Jianhua , Cao Jin , Gao Yongming , Shalhoub Victoria , Tipton Barbara , Haldankar Raj , Chen Qing , Winters Aaron , Boone Tom , Geng Zhaopo , Niu Qing-Tian , Ke Hua Zhu , Kostenuik Paul J , Simonet W Scott , Lacey David L , Paszty Chris
Published: December 2008

The development of bone-rebuilding anabolic agents for potential use in the treatment of bone loss conditions, such as osteoporosis, has been a long-standing goal. Genetic studies in humans and mice have shown that the secreted protein sclerostin is a key negative regulator of bone formation, although the magnitude and extent of sclerostin's role in the control of bone formation in the aging skeleton is still unclear. To study this unexplored area of sclerostin biology and to assess the pharmacologic effects of sclerostin inhibition, we used a cell culture model of bone formation to identify a sclerostin neutralizing monoclonal antibody (Scl-AbII) for testing in an aged ovariectomized rat model of postmenopausal osteoporosis. Six-month-old female rats were ovariectomized and left untreated for 1 yr to allow for significant estrogen deficiency-induced bone loss, at which point Scl-AbII was administered for 5 wk. Scl-AbII treatment in these animals had robust anabolic effects, with marked increases in bone formation on trabecular, periosteal, endocortical, and intracortical surfaces. This not only resulted in complete reversal, at several skeletal sites, of the 1 yr of estrogen deficiency-induced bone loss, but also further increased bone mass and bone strength to levels greater than those found in non-ovariectomized control rats. Taken together, these preclinical results establish sclerostin's role as a pivotal negative regulator of bone formation in the aging skeleton and, furthermore, suggest that antibody-mediated inhibition of sclerostin represents a promising new therapeutic approach for the anabolic treatment of bone-related disorders, such as postmenopausal osteoporosis.
Osteocyte Apoptosis Controls Activation of Intracortical Resorption in Response to Bone Fatigue
Authors: Cardoso Luis , Herman Brad C , Verborgt Olivier , Laudier Damien , Majeska Robert J , Schaffler Mitchell B
Published: December 2008

Osteocyte apoptosis is spatially and temporally linked to bone fatigue-induced microdamage and to subsequent intracortical remodeling. Specifically, osteocytes surrounding fatigue microcracks in bone undergo apoptosis, and those regions containing apoptotic osteocytes co-localize exactly with areas subsequently resorbed by osteoclasts. Here we tested the hypothesis that osteocyte apoptosis is a key controlling step in the activation and/or targeting of osteoclastic resorption after bone fatigue. We carried out in vivo fatigue loading of ulna from 4- to 5-mo-old Sprague-Dawley rats treated with an apoptosis inhibitor (the pan-caspase inhibitor Q-VD-OPh) or with vehicle. Intracortical bone remodeling and osteocyte apoptosis were quantitatively assessed by standard histomorphometric techniques on day 14 after fatigue. Continuous exposure to Q-VD-OPh completely blocked both fatigue-induced apoptosis and the activation of osteoclastic resorption, whereas short-term caspase inhibition during only the first 2 days after fatigue resulted in >50% reductions in both osteocyte apoptosis and bone resorption. These results (1) show that osteocyte apoptosis is necessary to initiate intracortical bone remodeling in response to fatigue microdamage, (2) indicate a possible dose-response relationship between the two processes, and (3) suggest that early apoptotic events after fatigue-induced microdamage may play a substantial role in determining the subsequent course of tissue remodeling.
Experimental Folate and Vitamin B12 Deficiency Does Not Alter Bone Quality in Rats
Authors: Herrmann Markus , Wildemann Britt , Wagner Alexandra , Wolny Martin , Schorr Heike , Taban-Shomal Omid , Umanskaya Natalia , Ross Steffen , Garcia Patric , Hübner Ulrich , Herrmann Wolfgang
Published: December 2008

Hyperhomocysteinemia (HHCY) has been linked to fragility fractures and osteoporosis. Folate and vitamin B12 deficiencies are among the main causes of HHCY. However, the impact of these vitamins on bone health has been poorly studied. This study analyzed the effect of folate and vitamin B12 deficiency on bone in rats. We used two groups of rats: a control group (Co, n = 10) and a vitamin-deficient group (VitDef, n = 10). VitDef animals were fed for 12 wk with a folate- and vitamin B12–free diet. Co animals received an equicaloric control diet. Tissue and plasma concentrations of homocysteine (HCY), S-adenosyl-homocysteine (SAH), and S-adenosyl-methionine (SAM) were measured. Bone quality was assessed by biomechanical testing (maximum force of an axial compression test; Fmax), histomorphometry (bone area/total area; B.Ar./T.Ar.], and the measurement of biochemical bone turnover markers (osteocalcin, collagen I C-terminal cross-laps [CTX]). VitDef animals developed significant HHCY (Co versus VitDef: 6.8 ± 2.7 versus 61.1 ± 12.8 μM, p < 0.001) that was accompanied by a high plasma concentration of SAH (Co versus VitDef: 24.1 ± 5.9 versus 86.4 ± 44.3 nM, p < 0.001). However, bone tissue concentrations of HCY, SAH, and SAM were similar in the two groups. Fmax, B.Ar./T.Ar., OC, and CTX did not differ between VitDef and Co animals, indicating that bone quality was not affected. Folate and vitamin B12 deficiency induces distinct HHCY but has no effect on bone health in otherwise healthy adult rats. The unchanged HCY metabolism in bone is the most probable explanation for the missing effect of the vitamin-free diet on bone.
Maternal Dietary Patterns During Pregnancy and Childhood Bone Mass: A Longitudinal Study
Authors: Cole Zoe A , Gale Catharine R , Javaid M Kassim , Robinson Sian M , Law Catherine , Boucher Barbara J , Crozier Sarah R , Godfrey Keith M , Dennison Elaine M , Cooper Cyrus
Published: December 2008

Maternal nutrition is a potentially important determinant of intrauterine skeletal development. Previous studies have examined the effects of individual nutrients, but the pattern of food consumption may be of greater relevance. We therefore examined the relationship between maternal dietary pattern during pregnancy and bone mass of the offspring at 9 yr of age. We studied 198 pregnant women 17–43 yr of age and their offspring at 9 yr of age. Dietary pattern was assessed using principal component analysis from a validated food frequency questionnaire. The offspring underwent measurements of bone mass using DXA at 9 yr of age. A high prudent diet score was characterized by elevated intakes of fruit, vegetables, and wholemeal bread, rice, and pasta and low intakes of processed foods. Higher prudent diet score in late pregnancy was associated with greater (p < 0.001) whole body and lumbar spine BMC and areal BMD in the offspring, after adjustment for sex, socioeconomic status, height, arm circumference, maternal smoking, and vitamin D status. Associations with prudent diet score in early pregnancy were weaker and nonsignificant. We conclude that dietary patterns consistent with current advice for healthy eating during pregnancy are associated with greater bone size and BMD in the offspring at 9 yr of age.
Once-Weekly Risedronate in Men With Osteoporosis: Results of a 2-Year, Placebo-Controlled, Double-Blind, Multicenter Study
Authors: Boonen Steven , Orwoll Eric S , Wenderoth Dietrich , Stoner Karen J , Eusebio Rachelle , Delmas Pierre D
Published: December 2008

Male osteoporosis is increasingly recognized as a major public health issue. This multinational, 2-yr, randomized, double-blind, placebo-controlled study was conducted to determine the efficacy and safety of 35 mg once-a-week risedronate in men with osteoporosis. Patients had to be men ≥30 yr old, with lumbar spine T-score ≤ −2.5 and femoral neck T-score ≤ −1 SD or lumbar spine T-score ≤ −1 and femoral neck T-score ≤ −2 SD (based on young normal men). Patients were randomized 2:1 to risedronate 35 mg once a week or placebo for 2 yr; all patients took 1000 mg elemental calcium and 400–500 IU vitamin D daily. Lumbar spine BMD at month 24 using last observation carried forward was the primary endpoint. Other endpoints included lumbar spine BMD at time points other than month 24, proximal femur BMD, bone turnover markers (BTMs), new vertebral fractures, clinical fractures, and adverse event (AE) assessment. There were 284 men enrolled in the study. Treatment with risedronate resulted in a significant increase from baseline to endpoint in lumbar spine BMD compared with placebo (4.5%; 95% CI: 3.5%, 5.6%; p < 0.001). Few new vertebral and nonvertebral fractures were reported, with no differences in fracture rates between the two groups. There was a significant (p < 0.01) reduction from baseline in BTMs for the risedronate group compared with placebo at all time points. No apparent differences in the pattern or distribution of AEs including serious and upper gastrointestinal AEs were observed. Risedronate therapy was well tolerated during this 2-yr study and was rapidly effective as indicated by significant BTM decreases at month 3 and BMD increases at month 6 (the earliest time points tested). The effects of risedronate treatment on BMD and BTMs in this study were similar to those previously shown to be associated with fracture risk reductions in women with postmenopausal osteoporosis.
Mineralization and Bone Resorption Are Regulated by the Androgen Receptor in Male Mice
Authors: Chiang Cherie , Chiu Maria , Moore Alison J , Anderson Paul H , Ghasem-Zadeh Ali , McManus Julie F , Ma Cathy , Seeman Ego , Clemens Thomas L , Morris Howard A , Zajac Jeffrey D , Davey Rachel A
Published: December 2008

Androgens play a key role in skeletal growth and bone maintenance; however, their mechanism of action remains unclear. To address this, we selectively deleted the androgen receptor (AR) in terminally differentiated, mineralizing osteoblasts using the Cre/loxP system in mice (osteocalcin-Cre AR knockouts [mOBL-ARKOs]). Male mOBL-ARKOs had decreased femoral trabecular bone volume compared with littermate controls because of a reduction in trabecular number at 6, 12, and 24 wk of age, indicative of increased bone resorption. The effects of AR inactivation in mineralizing osteoblasts was most marked in the young mutant mice at 6 wk of age when rates of bone turnover are high, with a 35% reduction in trabecular bone volume, decreased cortical thickness, and abnormalities in the mineralization of bone matrix, characterized by increased unmineralized bone matrix and a decrease in the amount of mineralizing surface. This impairment in bone architecture in the mOBL-ARKOs persisted throughout adulthood despite an unexpected compensatory increase in osteoblast activity. Our findings show that androgens act through the AR in mineralizing osteoblasts to maintain bone by regulating bone resorption and the coordination of bone matrix synthesis and mineralization, and that this action is most important during times of bone accrual and high rates of bone remodeling.
Normalized Deformation Parameters for Kaolin
Authors: Poulos HG
Published: December 2008

This paper presents the results of a series of tests in which undrained and drained strength and deformation parameters are normalized with respect to initial vertical effective strain and related to overconsolidation ratio. The validity of the normalization procedure is demonstrated by the agreement between normalized parameters derived from tests performed at different consolidation stresses.

The initial consolidation conditions are shown to have an important influence on the deformation parameters, with hydrostatic consolidation giving significantly larger Young's moduli than consolidation under conditions of zero lateral strain, for comparable stress levels. However, the procedure, subsequent to initial consolidation, for determining the deformation parameters appears to have only a small effect, particularly on the drained moduli.
Suggested Method for Soil Specimen Remolding by Wet-Raining
Authors: Chaney R , Mulilis JP
Published: December 2008

A method for remolding a granular soil material by a sedimentation process is proposed. The process may produce a soil structure which approximates that produced in a natural alluvium environment.
Some Effects of Test Configuration on Measured Soil Properties Under Cyclic Loading
Authors: Pyke R
Published: December 2008

The effects on soil properties measured under cyclic loading of some of the differences between the stress and deformation conditions in cyclic simple shear tests and cyclic triaxial tests are discussed. The importance of differences in the deformation conditions is emphasized. An approximate method is presented for computing the equivalent linear shear modulus of a cross-anisotropic triaxial test specimen. Experimental data on the properties of Monterey No. 0 sand measured in cyclic simple shear and cyclic triaxial tests are presented, and it is shown that in spite of some difficulties caused by the nonlinear behavior of the test specimens it was possible to obtain good agreement between the results of the two types of test.
Dielectric Constant Determination of Soils at L Band Microwave Frequencies
Authors: Okrasinski TA , Koerner RM , Lord AE
Published: December 2008

The use of microwaves as a nondestructive testing method for penetrating the ground and detecting subsurface details and anomalies is currently receiving active consideration. All variations of the technique require knowledge of the dielectric constant of the soil being penetrated by the microwaves. This paper presents a method for determining the dielectric constant of soils under various density and moisture conditions at L band frequencies, namely, 0.39 to 1.5 GHz. Using a technique based on open wire transmission line theory it was found that: 1. Dielectric constant decreases linearly as porosity increases. 2. Dielectric constant increases rapidly as moisture content increases. 3. Dielectric constant is soil type-dependent. 4. Microwave properties in soils are conveniently related to volumetric water content, a term which includes both porosity and water content characteristics. 5. Temperatures above freezing have little effect on dielectric constant. 6. The open wire transmission line test is convenient, rapid, and easy to perform for remolded soils in the laboratory.
A Modified California Bearing Ratio Test for Granular Materials
Authors: Livneh M , Greenstein J
Published: December 2008

It is known that laboratory and field tests, under saturation conditions, yield different California Bearing Ratio (CBR) test values for granular material. This is due primarily to the higher laboratory strength of the specimen confined in a rigid cylinder. A laboratory procedure is outlined by which specimens are subjected to controlled lateral pressure. A formula is proposed for determining design values from the modified laboratory data on the basis of theoretical bearing capacity considerations through the theory of plasticity. Test results are reported and the verification of the suggested method for determining the design CBR value of granular material is shown.
Geotechnical Properties of Hackensack Valley Varved Clays of New Jersey
Authors: Saxena SK , Hedberg J , Ladd CC
Published: December 2008

A special testing program was conduted on 127-mm (5-in.) diameter samples of varved clay from Hackensack Meadows, the site of a glacial lake near Secaucus, New Jersey. The program included constant rate-of-strain consolidation tests, measurement of K0 versus OCR, permeability tests on cubic samples to determine kh/kv, undrained-unconsolidated triaxial compression tests run on specimens cut at various inclinations, K0 consolidated-undrained direct simple shear tests to establish su (σvc)1/2 versus OCR, and K0 consolidated-undrained triaxial compression and extension tests on normally consolidated samples.

This paper presents the results of the tests and compares the data to that obtained on other varved clays. The basic properties of the Hackensack Valley varved clay are very similar to those for Connecticut Valley varved clays from Amherst and Northhampton, Massachusetts. Two major problems are still unresolved: the in-situ value of kh/kv versus that measured in the laboratory, and the value of undrained strength for horizontal loading, su(h).