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Apparent Density (apparent + density)
Kinds of Apparent Density Selected AbstractsApparent density of the primate calcaneo-cuboid joint and its association with locomotor mode, foot posture, and the "midtarsal break"AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 2 2010Matthew G. Nowak Abstract Primates use a range of locomotor modes during which they incorporate various foot postures. Humans are unique compared with other primates in that humans lack a mobile fore- and midfoot. Rigidity in the human foot is often attributed to increased propulsive and stability requirements during bipedalism. Conversely, fore- and midfoot mobility in nonhuman primates facilitates locomotion in arboreal settings. Here, we evaluated apparent density (AD) in the subchondral bone of human, ape, and monkey calcanei exhibiting different types of foot loading. We used computed tomography osteoabsorptiometry and maximum intensity projection (MIP) maps to visualize AD in subchondral bone at the cuboid articular surface of calcanei. MIPs represent 3D volumes (of subchondral bone) condensed into 2D images by extracting AD maxima from columns of voxels comprising the volumes. False-color maps are assigned to MIPs by binning pixels in the 2D images according to brightness values. We compared quantities and distributions of AD pixels in the highest bin to test predictions relating AD patterns to habitual locomotor modes and foot posture categories of humans and several nonhuman primates. Nonhuman primates exhibit dorsally positioned high AD concentrations, where maximum compressive loading between the calcaneus and cuboid likely occurs during "midtarsal break" of support. Humans exhibit less widespread areas of high AD, which could reflect reduced fore- and midfoot mobility. Analysis of the internal morphology of the tarsus, such as subchondral bone AD, potentially offers new insights for evaluating primate foot function during locomotion. Am J Phys Anthropol, 2010. © 2009 Wiley-Liss, Inc. [source] Longitudinal Study of Changes in Hip Bone Mineral Density in Caucasian and African-American WomenJOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 2 2005Jane A. Cauley DrPH Objectives: To determine whether changes in hip bone mineral density (BMD) differ in Caucasian and African American women. Design: Longitudinal study of changes in hip BMD. Setting: Four U.S. clinical centers. Participants: Six thousand seven Caucasian (mean age 73) and 482 African-American (mean age 75) women enrolled in the Study of Osteoporotic Fractures. Measurements: Total hip and femoral neck BMD were measured an average of 3.5 years apart (Caucasian) and 2.0 years apart (African American). Annual absolute and percentage changes in BMD and bone mineral apparent density (BMAD) were calculated. Results: The multivariate adjusted annual percentage change in BMD was greater in Caucasian than African-American women at the total hip (,0.574%/y vs ,0.334%/y) and femoral neck (,0.515%/y vs ,0.203%/y) (both, P<.001). Similar findings were observed for BMAD. The average annualized rate of BMD loss was twice as high in women aged 75 and older as in women younger than 75 in both ethnic groups. The annual percentage loss in femoral neck BMD in nonusers versus hormone therapy users was (,0.57% vs ,0.22%) in Caucasians and (,0.35% vs 0.64%) in African Americans (interaction P=.03). Conclusion: The average rate of hip BMD loss is approximately twice as great in Caucasian as African-American women and increases with age in both groups. The hormonal and biochemical factors that contribute to ethnic differences and the increase in bone loss with advancing age need to be identified. [source] Habitual use of the primate forelimb is reflected in the material properties of subchondral bone in the distal radiusJOURNAL OF ANATOMY, Issue 6 2006Kristian J. Carlson Abstract Bone mineral density is directly proportional to compressive strength, which affords an opportunity to estimate in vivo joint load history from the subchondral cortical plate of articular surfaces in isolated skeletal elements. Subchondral bone experiencing greater compressive loads should be of relatively greater density than subchondral bone experiencing less compressive loading. Distribution of the densest areas, either concentrated or diffuse, also may be influenced by the extent of habitual compressive loading. We evaluated subchondral bone in the distal radius of several primates whose locomotion could be characterized in one of three general ways (quadrupedal, suspensory or bipedal), each exemplifying a different manner of habitual forelimb loading (i.e. compression, tension or non-weight-bearing, respectively). We employed computed tomography osteoabsorptiometry (CT-OAM) to acquire optical densities from which false-colour maps were constructed. The false-colour maps were used to evaluate patterns in subchondral density (i.e. apparent density). Suspensory apes and bipedal humans had both smaller percentage areas and less well-defined concentrations of regions of high apparent density relative to quadrupedal primates. Quadrupedal primates exhibited a positive allometric effect of articular surface size on high-density area, whereas suspensory primates exhibited an isometric effect and bipedal humans exhibited no significant relationship between the two. A significant difference between groups characterized by predominantly compressive forelimb loading regimes vs. tensile or non-weight-bearing regimes indicates that subchondral apparent density in the distal radial articular surface distinguishes modes of habitually supporting of body mass. [source] Structural characterization of undoped and Sb-doped SnO2 thin films fired at different temperaturesJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3-1 2003Alessandro P. Rizzato SnO2 thin films were obtained by the sol-gel method starting from inorganic precursor solutions. In this work, we compare the structure of undoped and Sb-doped SnO2 films prepared by dip-coating. The films were deposited on quartz substrates and then fired at different temperatures ranging from 383 up to 1173 K. The density and the thickness of the films were determined by X-ray reflectivity (XRR) and their porous nanostructure was characterized by grazing-incidence small angle X-ray scattering (GISAXS). XRR results corresponding to undoped and Sb-doped samples indicate a monotonous decrease in film thickness when they are fired at increasing temperatures. At same time, the apparent density of undoped samples exhibits a progressive increase while for Sb-doped films it remains invariant up to 973 K and then increases for T = 1173 K. Anisotropic GISAXS patterns of both films, Sb-doped and undoped, fired above 573 K indicate the presence of elongated pores with their major axis perpendicular to the film surface. For all firing temperatures the nanopores in doped samples are larger than in undoped ones. This suggests that Sb-doping favours the pore growth hindering the film densification. At the highest firing temperature (1173 K) this effect is reversed. [source] Adjusting Bone Mass for Differences in Projected Bone Area and Other Confounding Variables: An Allometric Perspective,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 4 2002Alan M. Nevill B.Sc., Ph.D. Abstract The traditional method of assessing bone mineral density (BMD; given by bone mineral content [BMC] divided by projected bone area [Ap], BMD = BMC/Ap) has come under strong criticism by various authors. Their criticism being that the projected bone "area" (Ap) will systematically underestimate the skeletal bone "volume" of taller subjects. To reduce the confounding effects of bone size, an alternative ratio has been proposed called bone mineral apparent density [BMAD = BMC/(Ap)3/2]. However, bone size is not the only confounding variable associated with BMC. Others include age, sex, body size, and maturation. To assess the dimensional relationship between BMC and projected bone area, independent of other confounding variables, we proposed and fitted a proportional allometric model to the BMC data of the L2-L4 vertebrae from a previously published study. The projected bone area exponents were greater than unity for both boys (1.43) and girls (1.02), but only the boy's fitted exponent was not different from that predicted by geometric similarity (1.5). Based on these exponents, it is not clear whether bone mass acquisition increases in proportion to the projected bone area (Ap) or an estimate of projected bone volume (Ap)3/2. However, by adopting the proposed methods, the analysis will automatically adjust BMC for differences in projected bone size and other confounding variables for the particular population being studied. Hence, the necessity to speculate as to the theoretical value of the exponent of Ap, although interesting, becomes redundant. [source] Glucocorticoid Excess During Adolescence Leads to a Major Persistent Deficit in Bone Mass and an Increase in Central Body FatJOURNAL OF BONE AND MINERAL RESEARCH, Issue 10 2001Veronica Abad Abstract Endogenous Cushing's syndrome (CS) in children causes growth retardation, decreased bone mass, and increased total body fat. No prospective controlled studies have been performed in children to determine the long-term sequelae of CS on peak bone mass and body composition. A 15-year-old girl with Cushing disease (CD), and her healthy identical co-twin, were followed for 6 years after the CD was cured. At the 6-year follow-up both twins had areal bone mineral density (BMD) and body composition determined by dual-energy X-ray absorptiometry (DXA) and three-dimensional quantitative computed tomography (3DQCT). Z scores for height, weight, and body mass index (BMI) were ,2.3, ,0.8 and 0.2, and 1.2, 0.2, and ,0.6, in the twin with CD and her co-twin, respectively. In the twin with CD, areal BMD and bone mineral apparent density (BMAD) at different sites varied from 0.7 to 3 SD below her co-twin. Volumetric lumbar spine bone density Z score was ,0.75 and 1.0, and total body, abdominal visceral, and subcutaneous fat (%) was 42, 10, and 41 versus 26, 4, and 17 in the twin with CD and her co-twin, respectively. The relationship between total body fat and L2-L4 BMAD was inverse in the twin with CD (p < 0.05), which by contrast in her co-twin was opposite and direct (p < 0.001). In the twin with CD, despite cure, there was a persistent deficit in bone mass and increase in total and visceral body fat. These observations suggest that hypercortisolism (exogenous or endogenous) during adolescence may have persistent adverse effects on bone and fat mass. [source] Quantitative Ultrasound Does Not Reflect Mechanically Induced Damage in Human Cancellous BoneJOURNAL OF BONE AND MINERAL RESEARCH, Issue 12 2000P. H. F. Nicholson Abstract This study investigated the ability of quantitative ultrasound (QUS) to detect reductions in the elastic modulus of cancellous bone caused by mechanical damage. Ultrasonic velocity and attenuation were measured using an in-house parametric imaging system in 46 cancellous bone cores from the human calcaneus. Each core was subjected to a mechanical testing regime to (a) determine the predamage elastic modulus, (b) induce damage by applying specified strains in excess of the yield strain, and (c) measure the postdamage elastic modulus. The specimens were divided into four groups: a control group subjected to a nominally nondestructive 0.7% maximum strain (,m) and three damage groups subjected to increasing strain levels (,m = 1.5, 3.0, and 4.5%). QUS measurements before and after the mechanical testing showed no significant differences between the control group and damage groups, despite highly significant (p < 0.001) reductions in the elastic modulus of up to 72%. These results indicate that current QUS techniques do not intrinsically reflect the elastic properties of cancellous bone. This is consistent with ultrasonic properties being determined by other factors (apparent density and/or architecture), which normally are associated strongly with elastic properties, but only when bone is mechanically intact. Clinically, this implies that ultrasound cannot be expected to detect bone fragility in the absence of major changes in bone density and/or trabecular architecture. [source] More Broken Bones: A 4-Year Double Cohort Study of Young Girls With and Without Distal Forearm FracturesJOURNAL OF BONE AND MINERAL RESEARCH, Issue 10 2000A. Goulding Abstract Predictors of childhood fractures have not been investigated previously. This study was undertaken to determine whether a previous history of forearm fracture, low bone mineral density (BMD; both areal bone mineral density [aBMD, g/cm2] and volumetric bone mineral apparent density [BMAD, g/cm3]), or anthropometry, influence fracture risk in young girls. At baseline, two cohorts of girls, aged 3,15 years, were evaluated: 100 had recently broken a forearm (group 1) and 100 were fracture free (group 2). Four years later we restudied 170 of these girls (82 from group l and 88 from group 2). We now report the relationships of previous fracture history, baseline BMD (measured by dual-energy X-ray absorptiometry), baseline weight, and height to risk of new fracture. More new fractures occurred in group l (37 fractures in 24 girls) than in group 2 (8 fractures in 7 girls; p = 0.0007). The independent predictors for occurrence of a new fracture at any skeletal site in a multivariate model adjusting for age, weight, total body aBMD, and fracture history were previous fracture (hazard ratio [HR], 3.28; 95% CI, 1.41-7.64); age (HR per l-year increase, 0.91; 95% CI, 0.84-0.99); total body aBMD (HR per l SD decrease, 1.92; 95% CI, 1.31-2.81); and body weight (HR per l SD increase, 1.49; 95% CI, 1.06-2.08). Girls with two risk factors together had substantially greater fracture risk: previous fracture and low spinal BMAD (HR, 9.4; 95% CI, 2.8-32.0), previous fracture and high body weight (HR, 10.2; 95% CI, 2.8-37.6), or previous fracture and low total body aBMD (HR, 13.0; 95% CI, 3.9-43.1). We conclude that previous forearm fracture, low total body aBMD, low spinal BMAD, and high body weight each increase risk of new fractures within 4 years in young girls. Interventions to reduce the risk of fractures, particularly forearm fractures, in girls warrant further study. [source] Effect of Co-Precipitation on the Low-Temperature Sintering of Biphasic Calcium PhosphateJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2006Youn-Ki Jun Three types of biphasic calcium phosphate (BCP) powders were prepared and their sintering behavior was investigated. The specific surface area and HA/TCP ratio were similar in all three specimens. Most of the densification in the co-precipitated s-BCP occurred before the ,- to ,-TCP phase transformation, and a maximum density of ,95% was obtained at 1100°C. The mixture of separately precipitated and calcined hydroxyapatite (HA) and tricalcium phosphate (TCP) (m-BCP) showed a poor sintering behavior, and the apparent density was below 70% at temperatures up to 1200°C. In the commercial HA and TCP mixture (c-BCP), the low temperature sintering was poor, but densification continued without the phase transformation due to the presence of MgO, achieving almost full densification at 1200°C. [source] Use of deltamethrin ,pour-on' insecticide for the control of cattle trypanosomosis in the presence of high tsetse invasionMEDICAL AND VETERINARY ENTOMOLOGY, Issue 1 2001G. J. Rowlands Summary A deltamethrin ,pour-on' insecticide was applied monthly to over 2000 cattle exposed to a high challenge of drug-resistant trypanosomes and high tsetse re-invasion pressure in the Ghibe valley, south-west Ethiopia. Blood samples were taken monthly from an average of 760 cattle for determination of PCV and presence of trypanosomes. The area of the valley is approximately 350 km2 and the cattle grazed in roughly four locations covering about a quarter to half of the area. Two years before the trial commenced, Glossina morsitans submorsitans Newstead (Diptera: Glossinidae) began to invade the valley. Despite the use of the pour-on the mean apparent density of G. m. submorsitans continued to rise, and, during the 4 years of tsetse control, was more than three-fold higher than that recorded during the previous 18 months. Over the same period there was little change in the apparent density of Glossina pallidipes Austen (Diptera: Glossinidae). By contrast, the mean monthly prevalence of trypanosome infections in cattle over 36 months of age decreased from 38.3 to 29.0%, the incidence of new infections decreased from 26.6 to 16.0% (a reduction of 40%), and packed cell volume in cattle increased from 21.7 to 24.1%. Evidence of a change in apparent parasite transmission rate was demonstrated by regression of infection incidence in cattle on the logarithm of apparent density of G. m. submorsitans. Before the trial started the regression coefficient was 45.8 ± 6.3 and this reduced to 9.2 ± 2.5% incidence per loge (flies/trap/day) during the period of tsetse control. It was concluded that this indicated reductions in tsetse numbers in the immediate vicinities of cattle in a way that was not reflected in overall tsetse catches. Nevertheless, the comparatively high levels of trypanosome prevalence that persisted in the cattle demonstrates that, where invasion prevalence is high, treatment of small pockets of cattle will not eradicate tsetse. To achieve more significant reduction in trypanosome prevalence in cattle, integrated methods of control utilizing target barriers in the major routes of invasion will be needed. [source] Preparation, characterization and preliminary calcium release study of floating sodium alginate/dextran-based hydrogel beads: part IPOLYMER INTERNATIONAL, Issue 1 2008Sunil Kumar Bajpai Abstract Ionically crosslinked calcium alginate/dextran-based floating beads were prepared using NaHCO3 as porogen. Various micrometric properties such as tapped density, apparent density, compressibility index, etc., were determined for beads with different compositions. The beads were also evaluated for their mechanical strength. The percent buoyancy of the beads was measured as a function of time in simulated gastric fluid (pH = 1.2 at 37 °C). The beads prepared with higher concentrations of NaHCO3 porogen and CaCl2 crosslinker possessed 100% buoyancy and remained buoyant for nearly 20 h, or even more. Finally, the release of calcium from the beads was observed to follow diffusion-controlled Higuchi kinetics. Copyright © 2007 Society of Chemical Industry [source] Apparent density of the primate calcaneo-cuboid joint and its association with locomotor mode, foot posture, and the "midtarsal break"AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 2 2010Matthew G. Nowak Abstract Primates use a range of locomotor modes during which they incorporate various foot postures. Humans are unique compared with other primates in that humans lack a mobile fore- and midfoot. Rigidity in the human foot is often attributed to increased propulsive and stability requirements during bipedalism. Conversely, fore- and midfoot mobility in nonhuman primates facilitates locomotion in arboreal settings. Here, we evaluated apparent density (AD) in the subchondral bone of human, ape, and monkey calcanei exhibiting different types of foot loading. We used computed tomography osteoabsorptiometry and maximum intensity projection (MIP) maps to visualize AD in subchondral bone at the cuboid articular surface of calcanei. MIPs represent 3D volumes (of subchondral bone) condensed into 2D images by extracting AD maxima from columns of voxels comprising the volumes. False-color maps are assigned to MIPs by binning pixels in the 2D images according to brightness values. We compared quantities and distributions of AD pixels in the highest bin to test predictions relating AD patterns to habitual locomotor modes and foot posture categories of humans and several nonhuman primates. Nonhuman primates exhibit dorsally positioned high AD concentrations, where maximum compressive loading between the calcaneus and cuboid likely occurs during "midtarsal break" of support. Humans exhibit less widespread areas of high AD, which could reflect reduced fore- and midfoot mobility. Analysis of the internal morphology of the tarsus, such as subchondral bone AD, potentially offers new insights for evaluating primate foot function during locomotion. Am J Phys Anthropol, 2010. © 2009 Wiley-Liss, Inc. [source] Body size and joint posture in primatesAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 2 2009John D. Polk Abstract Body mass has been shown in experimental and comparative morphological studies to have a significant effect on joint posture in major limb joints. The generalizability of experimental studies is limited by their use of small sample sizes and limited size ranges. In contrast, while comparative morphological studies often have increased sample sizes, the connection between joint posture and morphological variables is often indirect. The current study infers joint postures for a large sample of primates using an experimentally validated method, and tests whether larger primates use more extended joint postures than smaller species. Postures are inferred through the analysis of patterns of subchondral bone apparent density on the medial femoral condyle. Femora from 94 adult wild-shot individuals of 28 species were included. Apparent density measurements were obtained from CT scans using AMIRA software, and the angular position of the anterior-most extent of the region of maximum apparent density on the medial femoral condyle was recorded. In general, the hypothesis that larger-bodied primates use more extended knee posture was supported, but it should be noted that considerable variation exists, particularly at small body sizes. This indicates that smaller species are less constrained by their body size, and their patterns of apparent density are consistent with a wide range of knee postures. The size-related increase in inferred joint posture was observed in most major groups of primates, and this observation attests to the generalizability of Biewener's model that relates body size and joint posture. Am J Phys Anthropol, 2009. © 2009 Wiley-Liss, Inc. [source] Decreased hippocampal NMDA, but not kainate or AMPA receptors in bipolar disorderBIPOLAR DISORDERS, Issue 4 2003E Scarr Objectives:, The purpose of this study was to determine whether there are changes in the density of ionotropic glutamate receptors in the hippocampus of subjects with bipolar disorder. Methods:, Using in situ radioligand binding with semiquantitative autoradiography, we measured the density of [3H]MK-801, [3H]CGP39653, [3H]AMPA and [3H]kainate binding in hippocampi, obtained postmortem, from eight subjects with type 1 bipolar disorder and 8 age- and sex-matched controls. Results:, In subjects with bipolar disorder there were significant decreases in the density of [3H]MK-801 binding in the Cornu Ammonis (CA) 3 (mean ± SEM; 108.8 ± 12.2 versus 166.2 ± 18.0 fmol/mg ETE, p < 0.005) as well as the pyramidal (102.8 ± 9.2 versus 136.6 ± 11.2 fmol/mg ETE, p < 0.05) and polymorphic (21.73 ± 6.5 versus 53.26 ± 11.6 fmol/mg ETE, p < 0.05) layers of the subiculum. In addition, two-way analysis of variance (ANOVA) revealed a decrease in the density of [3H]CGP39653 binding across the hippocampal formation in bipolar subjects, which did not reach significance in any subregion. There were no changes in the densities of [3H]AMPA or [3H]kainate binding in these subjects. Conclusions:, [3H]CGP39653 and [3H]MK-801 bind to the glutamate binding site and open ion channel of the n -methyl- d -aspartate (NMDA) receptor, respectively. Therefore, these data suggest that there is a decrease in the number of open ion channels associated with no significant change in the apparent density of NMDA receptors in regions of the hippocampus from subjects with bipolar disorder. [source] Effect of Volume Fraction of Material on Separation by Density Difference in a Liquid-Fluidized Bed of Inert ParticlesCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 7 2010Y. Tatemoto Abstract A liquid-fluidized bed was used to separate a pure material from a mixture. A quantity of relatively large sized material was immersed in an inert-particle fluidized bed and the behavior of materials was examined for different liquid velocities. In particular, the volume fraction of the material was varied and its effect on the separation characteristics was examined. The material floats on the inert-particle fluidized bed when the density of the material is lower than the apparent density of the bed, regardless of the volume fraction of the material. The apparent density of the bed can be adjusted by changing the liquid velocity. The materials in the upper portion of the bed affect the properties of the bed below them, i.e., the void fraction decreases and the apparent density increases in the inert-particle suspension when materials are present in the upper portion of the bed. Therefore, the materials float on the bed although the apparent density of the inert-particle suspension obtained from the case without material is less than the density of the material at a relatively high volume fraction of material. This phenomenon occurs more easily for lighter and smaller materials. This means that small inert particles and low liquid velocities are the optimum operating conditions for the separation. [source] Volumetric bone mineral density is an important tool when interpreting bone mineralization in healthy childrenACTA PAEDIATRICA, Issue 2 2009Susanne Eriksson Abstract In adults, it is well known that gender influences bone mass, but studies in children have shown contradictory results. Also, conflicting results have been reported regarding bone mineral density in obese children. Objective: To investigate bone parameters in healthy 8-year-old children and relate them to anthropometry and self-reported physical activity (PA). Design: Bone measurements were performed with dual X-ray absorptiometry in 96 children, and questionnaires were used to assess self-reported PA. Results: Bone mineral content and density differed by gender. Eighteen percent of the children were overweight/obese and they had higher bone mineral content and density than children with normal weight. Bone mineral apparent density (g/cm3) of the lumbar spine did not differ, since the vertebral size differed, as was also the case between genders. Self-reported weight-bearing PA influenced bone mass in the hip. Conclusion: PA influenced bone mineralization at this age. The differences in bone mineral content and density in healthy children would mainly be explained by the differences in bone size, reflected in body height and the width of the vertebrae. This indicates the importance of determining volumetric bone mineralization in children. [source] Anisotropic elastic properties of cancellous bone from a human edentulous mandibleCLINICAL ORAL IMPLANTS RESEARCH, Issue 5 2000Aisling M. O'Mahony The elastic moduli have not been reported for cancellous bone from the edentulous mandible. Accurate values are needed for finite element modeling of the mandible. The aim of this study was to determine elastic modulus values in three orthogonal directions for cancellous bone taken from an edentulous jaw and to relate these values to apparent density and volume fraction. Seven samples were obtained from the edentulous mandible of a 74-year-old female. Young's modulus was determined by compression testing of cubes cut with the faces aligned with the anatomic axes. Bone volume fraction averaged 0.33 (SD 0.14) and apparent density averaged 0.55 g/cc (SD 0.29). Young's modulus was greatest in the mesio-distal direction (mean 907 MPa, SD 849 MPa), followed by the bucco-lingual (mean 511 MPa, SD 565 MPa) and infero-superior direction (mean 114 MPa, SD 78 MPa). The infero-superior direction was less than the bucco-lingual (P=0.03) and mesio-distal (P=0.002). The mesio-distal and bucco-lingual directions could not be shown to be different (P=0.32). This suggests a model of transverse isotropy for cancellous bone in the jaw, where the symmetry axis is along the infero-superior (weakest) direction. [source] | |||||||||||||||||||