bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.
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.
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.
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

Abstract
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

Abstract
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

AbstractThe 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

Abstract
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 &gt;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

Abstract
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 &lt; 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 &lt; 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

Abstract
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 &lt; 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

Abstract
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 &lt; 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 &lt; 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

Abstract
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

Abstract
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.