bluuebunny/crossref_metadata_2025 huggingface dataset:
A Spatial Approach to Environmental Risk Assessment of PAH Contamination
Authors: Bengtsson Göran , Törneman Niklas
Published: September 2008

The extent of remediation of contaminated industrial sites depends on spatial heterogeneity of contaminant concentration and spatially explicit risk characterization. We used sequential Gaussian simulation (SGS) and indicator kriging (IK) to describe the spatial distribution of polycyclic aromatic hydrocarbons (PAHs), pH, electric conductivity, particle aggregate distribution, water holding capacity, and total organic carbon, and quantitative relations among them, in a creosote polluted soil in southern Sweden. The geostatistical analyses were combined with risk analyses, in which the total toxic equivalent concentration of the PAH mixture was calculated from the soil concentrations of individual PAHs and compared with ecotoxicological effect concentrations and regulatory threshold values in block sizes of 1.8 × 1.8 m. Most PAHs were spatially autocorrelated and appeared in several hot spots. The risk calculated by SGS was more confined to specific hot spot areas than the risk calculated by IK, and 40–50% of the site had PAH concentrations exceeding the threshold values with a probability of 80% and higher. The toxic equivalent concentration of the PAH mixture was dependent on the spatial distribution of organic carbon, showing the importance of assessing risk by a combination of measurements of PAH and organic carbon concentrations. Essentially, the same risk distribution pattern was maintained when Monte Carlo simulations were used for implementation of risk in larger (5 × 5 m), economically more feasible remediation blocks, but a smaller area became of great concern for remediation when the simulations included PAH partitioning to two separate sources, creosote and natural, of organic matter, rather than one general.
Analysis of Forensic SNPs in the Canine mtDNA HV1 Mutational Hotspot Region*
Authors: Baute Danielle T. , Satkoski Jessica A. , Spear Theresa F. , Smith David G. , Dayton Melody R. , Malladi Venkat S. , Goyal Vivek , Kou Alexander , Kinaga Jennifer L. , Kanthaswamy Sreetharan
Published: September 2008

Abstract:  A 60 bp sequence variation hotspot in the canine mitochondrial DNA hypervariable region 1 was evaluated for its use in forensic investigations. Nineteen haplotypes containing 18 single nucleotide polymorphisms were observed among laboratory‐generated and GenBank‐derived domestic dog sequences representing five regional localities in the U.S. Samples from the different localities were highly variable with the levels of intra‐population variability being similar among the populations studied. AMOVA further confirmed that there was no significant genetic structuring of the populations. Assays using these haplotypes were robust, canid specific and portend a rapid method for correctly excluding individual dogs as noncontributors of forensic evidence. Species‐specificity of the primers was confirmed by means of in‐tube polymerase chain reaction of human and cat DNA and in‐silico assessment of the genomes of several animal species. Breed‐specific fragments were not detected among the common haplotypes but there is evidence that this assay may be capable of differentiating domestic dog, wolf, and coyote sequences.
An Updated Validation of Promega’s PowerPlex® 16 System: High Throughput Databasing Under Reduced PCR Volume Conditions on Applied Biosystem’s 96 Capillary 3730xl DNA Analyzer*
Authors: Spathis Rita , Lum J. Koji
Published: September 2008

Abstract:  The PowerPlex® 16 System from Promega Corporation allows single tube multiplex amplification of sixteen short tandem repeat (STR) loci including all 13 core combined DNA index system STRs. This report presents an updated validation of the PowerPlex® 16 System on Applied Biosystem’s 96 capillary 3730xl DNA Analyzer. The validation protocol developed in our laboratory allows for the analysis of 1536 loci (96 × 16) in c. 50 min. We have further optimized the assay by decreasing the reaction volume to one‐quarter that recommended by the manufacturer thereby substantially reducing the total cost per sample without compromising reproducibility or specificity. This reduction in reaction volume has the ancillary benefit of dramatically increasing the sensitivity of the assay allowing for accurate analysis of lower quantities of DNA. Due to its substantially increased throughput capability, this extended validation of the PowerPlex® 16 System should be useful in reducing the backlog of unanalyzed DNA samples currently facing public DNA forensic laboratories.
Histologic Evidence of Repetitive Blunt Force Abdominal Trauma in Four Pediatric Fatalities
Authors: Dye Daniel W. , Peretti Frank J. , Kokes Charles P.
Published: September 2008

Abstract:  In cases of acute fatal child abuse, certain injuries, including cutaneous blunt force trauma, skull fractures, subdural hematomas, intra‐abdominal hemorrhage, and retinal hemorrhages are common and well described in the pediatric and forensic literature. These gross findings at autopsy, when taken into consideration with scene investigation and interviews with caregivers, may indicate both a clear manner and cause of death. In such cases, the discovery of additional pathologic changes attributable to older abusive injuries helps support a conclusion of death due to inflicted trauma. We discuss four cases of fatal child abuse in which acute blunt force abdominal trauma was the cause of death. In each of these cases, careful examination with proper sectioning and microscopy of select abdominal tissues revealed that the acute tissue trauma was superimposed on a background of older, healing injury. This older trauma was characterized by classic histologic elements of tissue repair, including fibroblast proliferation, early scar formation, increased vascularity, and hemosiderin‐laden macrophages. Iron and trichrome stains were used to confirm the presence of hemosiderin and fibrosis in all four cases, but the recognition of fibroblast proliferation and a reactive vascular pattern was best seen on routine hematoxylin and eosin stains. The gross and microscopic autopsy findings, along with available investigative information, established the diagnosis of chronic physical abuse.
Time‐Lapse Geophysical Investigations over a Simulated Urban Clandestine Grave*
Authors: Pringle Jamie K. , Jervis John , Cassella John P. , Cassidy Nigel J.
Published: September 2008

Abstract:  A simulated clandestine shallow grave was created within a heterogeneous, made‐ground, urban environment where a clothed, plastic resin, human skeleton, animal products, and physiological saline were placed in anatomically correct positions and re‐covered to ground level. A series of repeat (time‐lapse), near‐surface geophysical surveys were undertaken: (1) prior to burial (to act as control), (2) 1 month, and (3) 3 months post‐burial. A range of different geophysical techniques was employed including: bulk ground resistivity and conductivity, fluxgate gradiometry and high‐frequency ground penetrating radar (GPR), soil magnetic susceptibility, electrical resistivity tomography (ERT), and self potential (SP). Bulk ground resistivity and SP proved optimal for initial grave location whilst ERT profiles and GPR horizontal “time‐slices” showed the best spatial resolutions. Research suggests that in complex urban made‐ground environments, initial resistivity surveys be collected before GPR and ERT follow‐up surveys are collected over the identified geophysical anomalies.
COMT Val158Met moderation of cannabis‐induced psychosis: a momentary assessment study of ‘switching on’ hallucinations in the flow of daily life
Authors: Henquet C. , Rosa A. , Delespaul P. , Papiol S. , Faňanás L. , Van Os J. , Myin‐Germeys I.
Published: September 2008

Objective:  A functional polymorphism in the catechol‐o‐methyltransferase gene (COMT Val158Met) may moderate the psychosis‐inducing effects of cannabis. In order to extend this finding to dynamic effects in the flow of daily life, a momentary assessment study of psychotic symptoms in response to cannabis use was conducted.

Method:  The experience sampling technique was used to collect data on cannabis use and occurrence of symptoms in daily life in patients with a psychotic disorder (n = 31) and healthy controls (n = 25).

Results:  Carriers of the COMT Val158Met Val allele, but not subjects with the Met/Met genotype, showed an increase in hallucinations after cannabis exposure, conditional on prior evidence of psychometric psychosis liability.

Conclusion:  The findings confirm that in people with psychometric evidence of psychosis liability, COMT Val158Met genotype moderates the association between cannabis and psychotic phenomena in the flow of daily life.
Adjunctive lithium treatment in the prevention of suicidal behaviour in depressive disorders: a randomised, placebo‐controlled, 1‐year trial
Authors: Lauterbach E. , Felber W. , Müller‐Oerlinghausen B. , Ahrens B. , Bronisch T. , Meyer T. , Kilb B. , Lewitzka U. , Hawellek B. , Quante A. , Richter K. , Broocks A. , Hohagen F.
Published: September 2008

Objective:  Evidence based on controlled studies is still limited for treatment strategies that prevent recurrence of suicide attempts. Findings from observational as well as meta‐analytic studies strongly suggest that lithium may have suicide‐protective properties.

Method:  Patients with a recent suicide attempt in the context of an affective spectrum disorder (n = 167) were treated with either lithium or placebo during a 12‐month period.

Results:  Survival analysis showed no significant difference of suicidal acts between lithium and placebo‐treated individuals (adjusted hazard ratio 0.517; 95% CI 0.18–1.43). However, post hoc analysis revealed that all completed suicides had occurred in the placebo group accounting for a significant difference in incidence rates (P = 0.049).

Conclusion:  Results indicate that lithium treatment might be effective in reducing the risk of completed suicide in adult patients with affective disorders. Our findings contribute to the growing body of evidence suggesting a specific antisuicidal effect of lithium.
Ludwig II, King of Bavaria: a royal medical history
Authors: Förstl H. , Immler G. , Seitz M. , Hacker R.
Published: September 2008

Objective:  The case of Ludwig II, King of Bavaria, had soon become synonymous with paranoia, after he had drowned at the age of 40 together with the neuropsychiatrist Gudden.

Method:  We were granted access to the Secret Archive of the House of Wittelsbach to study documents on Ludwig’s medical history.

Results:  The documents underlying Gudden’s expert opinion which led to Ludwig being deposed would be insufficient for a diagnosis of schizophrenia according to contemporary standards. The autopsy revealed prominent prefrontal brain atrophy.

Conclusion:  The evidence is compatible with a diagnosis of schizotypal personality and suspected frontotemporal degeneration.
Insulin sensitivity, VO2max and body composition in severely obese Swedish children and adolescents
Authors: Morinder Gunilla , Larsson Ulla Evers , Norgren Svante , Marcus Claude
Published: September 2008

Aim: The aim of this study was to identify relationships between insulin sensitivity (SI), cardiorespiratory fitness and body composition in severely obese Swedish children and adolescents.

Methods: Two hundred and twenty‐eight obese children (119 girls, 8–16 years, body mass index (BMI) 23.2–57.0 kg/m2) performed a frequently sampled intravenous glucose tolerance test (FSIVGTT), a submaximal bicycle ergometry test and a dual‐energy X‐ray absorptiometry (DEXA).

Results: Mean SI (SD) was 0.38 (0.32) (×10−5/min/pM). SI correlated positively with relative body mass (BM) VO2max (r = 0.42) (p < 0.001), relative fat‐free mass (FFM) VO2max (r = 0.36) (p < 0.001) and negatively with body mass index standard deviation score (BMI SDS) (r =−0.22) (p = 0.001). SI did not correlate with percent body fat (r =−0.01) and absolute VO2max (r = 0.01). In multiple regression analyses with SI as dependent variable, VO2max and body composition, together with gender, age and Tanner stage, explained 20–26% of the variance.

Conclusion: Relative (BM) VO2max and relative (FFM) VO2max were stronger predictors of SI than percent body fat in severely obese children and adolescents. The study confirms that cardiorespiratory fitness is of importance for the metabolic syndrome in the studied population. Efforts to improve SI should include physical activity targeting cardiorespiratory fitness also in severely obese children and adolescents.
Comparison of a coq7 deletion mutant with other respiration‐defective mutants in fission yeast
Authors: Miki Risa , Saiki Ryoichi , Ozoe Yoshihisa , Kawamukai Makoto
Published: September 2008

Among the steps in ubiquinone biosynthesis, that catalyzed by the product of the clk‐1/coq7 gene has received considerable attention because of its relevance to life span in Caenorhabditis elegans. We analyzed the coq7 ortholog (denoted coq7) in Schizosaccharomyces pombe, to determine whether coq7 has specific roles that differ from those of other coq genes. We first confirmed that coq7 is necessary for the penultimate step in ubiquinone biosynthesis, from the observation that the deletion mutant accumulated the ubiquinone precursor demethoxyubiquinone‐10 instead of ubiquinone‐10. The coq7 mutant displayed phenotypes characteristic of other ubiquinone‐deficient Sc. pombe mutants, namely, hypersensitivity to hydrogen peroxide, a requirement for antioxidants for growth on minimal medium, and an elevated production of sulfide. To compare these phenotypes with those of other respiration‐deficient mutants, we constructed cytochrome c (cyc1) and coq3 deletion mutants. We also assessed accumulation of oxidative stress in various ubiquinone‐deficient strains and in the cyc1 mutant by measuring mRNA levels of stress‐inducible genes and the phosphorylation level of the Spc1 MAP kinase. Induction of ctt1, encoding catalase, and apt1, encoding a 25 kDa protein, but not that of gpx1, encoding glutathione peroxidase, was indistinguishable in four ubiquinone‐deficient mutants, indicating that the oxidative stress response operates at similar levels in the tested strains. One new phenotype was observed, namely, loss of viability in stationary phase (chronological life span) in both the ubiquinone‐deficient mutant and in the cyc1 mutant. Finally, Coq7 was found to localize in mitochondria, consistent with the possibility that ubiquinone biosynthesis occurs in mitochondria in yeasts. In summary, our results indicate that coq7 is required for ubiquinone biosynthesis and the coq7 mutant is not distinguishable from other ubiquinone‐deficient mutants, except that its phenotypes are more pronounced than those of the cyc1 mutant.
Topical negative pressure wound therapy: a review of its role and guidelines for its use in the management of acute wounds
Authors: Bovill Estas , Banwell Paul E , Teot Luc , Eriksson Elof , Song Colin , Mahoney Jim , Gustafsson Ronny , Horch Raymund , Deva Anand , Whitworth Ian
Published: September 2008

Over the past two decades, topical negative pressure (TNP) wound therapy has gained wide acceptance as a genuine strategy in the treatment algorithm for a wide variety of acute and chronic wounds. Although extensive experimental and clinical evidence exists to support its use and despite the recent emergence of randomised control trials, its role and indications have yet to be fully determined. This article provides a qualitative overview of the published literature appertaining to the use of TNP therapy in the management of acute wounds by an international panel of experts using standard methods of appraisal. Particular focus is applied to the use of TNP for the open abdomen, sternal wounds, lower limb trauma, burns and tissue coverage with grafts and dermal substitutes. We provide evidence‐based recommendations for indications and techniques in TNP wound therapy and, where studies are insufficient, consensus on best practice.
Late complication after tropic storm accident: subcutaneous and intracranial actinomycetoma
Authors: Verma Shyam B , Nayak Suresh , Pasale Ravindra K , Kittner Thomas , Wollina Uwe
Published: September 2008

We report a 53‐year‐old farmer who developed subcutaneous and cerebral masses 24 years after penetrating trauma during a tropic storm. Computed tomography scans, magnetic resonance imaging and histopathology disclosed actinomycetoma, a disease that rarely develops after trauma and is only occasionally seen with intracranial manifestation. Clinically, the cutaneous manifestation resembled acne keloidalis nuchae or dissecting folliculitis of the scalp. He was treated by neurosurgery and antibiosis.
Phenological growth stages of roses (Rosa sp.): codification and description according to the BBCH scale
Authors: Meier U. , Bleiholder H. , Brumme H. , Bruns E. , Mehring B. , Proll T. , Wiegand J.
Published: September 2008

The phenological development stages of plants and their BBCH (Biologische Bundesanstalt, Bundessortenamt, CHemische Industrie)‐coding system are used in agricultural and horticultural science and practice, botanical sciences, meteorology and climatic science as well as agricultural insurance, each with their own varying individual objectives. A proposal for a code for the phenological development of roses in general on the basis of the BBCH extended scale is presented. Ten principal growth stages have been defined from germination/sprouting, through leaf and shoot production to bud, flower and fruit production and to senescence and dormancy. Every principal growth stage has been subdivided into secondary growth stages. Under special conditions, it is helpful to use mesostages with three‐digit codes. The mesostages are particularly relevant to roses, as many rose plants have more than one flower per plant. Descriptive keys with illustration aids for the use of the system are included.
The type IIb SN 2008ax: the nature of the progenitor
Authors: Crockett R. M. , Eldridge J. J. , Smartt S. J. , Pastorello A. , Gal-Yam A. , Fox D. B. , Leonard D. C. , Kasliwal M. M. , Mattila S. , Maund J. R. , Stephens A. W. , Danziger I. J.
Published: September 2008

A source coincident with the position of the type IIb supernova (SN) 2008ax is identified in pre-explosion Hubble Space Telescope (HST) Wide Field Planetary Camera 2 observations in three optical filters. We identify and constrain two possible progenitor systems: (i) a single massive star that lost most of its hydrogen envelope through radiatively driven mass-loss processes, prior to exploding as a helium-rich Wolf–Rayet star with a residual hydrogen envelope, and (ii) an interacting binary in a low-mass cluster producing a stripped progenitor. Late time, high-esolution observations along with detailed modelling of the SN will be required to reveal the true nature of this progenitor star.
Polymorphic microsatellite markers isolated from the neptune whelk Neptunea arthritica
Authors: AZUMA N. , MIRANDA R. M. , GOSHIMA S. , ABE S.
Published: September 2008

Eight polymorphic microsatellite DNA loci were isolated from the neptune whelk Neptunea arthritica, which is an important fishery resource in northern Japan. The number of alleles at the loci ranged from two to six, with observed and expected heterozygosities of 0.192–0.807 and 0.233–0.738, respectively. The observed variations suggest that these loci can be used as markers for population and kinship analyses in this species.
TRPML3 mutations cause impaired mechano‐electrical transduction and depolarization by an inward‐rectifier cation current in auditory hair cells of varitint‐waddler mice
Authors: Van Aken Alexander F. J. , Atiba‐Davies Margaret , Marcotti Walter , Goodyear Richard J. , Bryant Jane E. , Richardson Guy P. , Noben‐Trauth Konrad , Kros Corné J.
Published: September 2008

TRPML3 (mucolipin‐3) belongs to one of the transient‐receptor‐potential (TRP) ion channel families. Mutations in the Trpml3 gene cause disorganization of the stereociliary hair bundle, structural aberrations in outer and inner hair cells and stria vascularis defects, leading to deafness in the varitint‐waddler (Va) mouse. Here we refined the stereociliary localization of TRPML3 and investigated cochlear hair cell function in varitint‐waddler (VaJ) mice carrying the TRPML3 mutations. Using a TRPML3‐specific antibody we detected a ∼68 kDa protein with near‐equal expression levels in cochlea and vestibule of wild‐type and VaJ mutants. At postnatal days 3 and 5, we observed abundant localization of TRPML3 at the base of stereocilia near the position of the ankle links. This stereociliary localization domain was absent in VaJ heterozygotes and homozygotes. Electrophysiological recordings revealed reduced mechano‐electrical transducer currents in hair cells from VaJ/+ and VaJ/VaJ mice. Furthermore, FM1‐43 uptake and [3H]gentamicin accumulation were decreased in hair cells in cultured organs of Corti from VaJ/+ and VaJ/VaJ mice. We propose that TRPML3 plays a critical role at the ankle‐link region during hair‐bundle growth and that an adverse effect of mutant TRPML3 on bundle development and mechano‐electrical transduction is the main cause of hearing loss in VaJ/+ mutant mice. Outer hair cells of VaJ/VaJ mice additionally had depolarized resting potentials due to an inwardly rectifying leak conductance formed by the mutant channels, leading over time to hair‐cell degeneration and contributing to their deafness. Our findings argue against TRPML3 being a component of the hair‐cell transducer channel.
Kinetics of Rab27a‐dependent actions on vesicle docking and priming in pancreatic β‐cells
Authors: Merrins Matthew J. , Stuenkel Edward L.
Published: September 2008

The small GTPase Rab27a, along with the isoforms of Rab3, is present on insulin secretory granules and has been implicated in regulation of Ca2+‐triggered exocytosis. We have used membrane capacitance measurements to define the role of Rab27a in regulating the size and refilling of distinct pools of insulin granules by comparison of evoked secretory responses from Rab27a‐null ashen and strain‐matched wild‐type control pancreatic β‐cells. We find that ashenβ‐cells display a kinetic defect in refilling of readily releasable and immediately releasable vesicle pools (RRP and IRP, respectively) in response to depolarization‐evoked Ca2+ influx. The deficit in IRP refilling was not observed in the presence of stimulatory glucose concentrations (16.7 mm), though incomplete refilling of the RRP persisted. Comparatively, β‐cells from Rab3a−/− mice exhibited complete refilling of the IRP and RRP, demonstrating that Rab27a and Rab3a exert distinct roles in the insulin granule secretory pathway. Further, depletion of the RRP in ashenβ‐cells was twofold faster than that of control β‐cells. These deficits in refilling and exocytotic rate in ashenβ‐cells were absent when cAMP‐regulatory pathways were activated. Elevated cAMP increased the RRP pool size, and complete refilling of the RRP occurred in ashenβ‐cells; responses were comparable to wild‐type controls. These effects of cAMP were largely eliminated by Rp‐cAMP inhibition of PKA, indicating that PKA acts on vesicle priming downstream or via pathways independent of Rab27a. In summary, Rab27a exerts dual roles in glucose‐mediated insulin granule exocytosis, facilitating refilling of releasable granule pools while also limiting the rate of release from these pools.
Discharges in human muscle spindle afferents during a key‐pressing task
Authors: Dimitriou Michael , Edin Benoni B.
Published: September 2008

Most manual tasks demand a delicate control of the wrist. Sensory information for this control, e.g. about the position and movement velocity of the hand, is assumed to be primarily provided by muscle spindle afferents. It is known that human muscle spindles in relaxed muscles behave as stretch receptors but it is unclear how they discharge during ‘natural’ hand movements, since their discharges can also be affected by extrafusal contractions and fusimotor activity. We therefore let subjects perform a centre‐out‐centre key‐pressing task on buttons laid out in a 3 × 3 pattern, a task that allowed unconstrained hand and finger movements and required precise control of the wrist. Microneurography recordings from muscle spindle afferents of the wrist extensor muscles were obtained along with wrist kinematics and electromyographic signals. The discharge rates of afferents were more phase advanced than expected on the length of the radial wrist extensor, which acted as an anti‐gravity muscle in the key‐pressing task. As such, both acceleration and velocity had significant impacts on the discharge rate of primary afferents, velocity on that of secondary afferents, and length had no impact on either afferent type. The response patterns were different for the two types of muscle spindle afferents from the predominantly eccentrically contracting ulnar wrist extensor: muscle length and velocity had significant impacts on the ensemble response of secondary afferents whereas the primary afferents showed highly variable responses. Accordingly, good predictions of the radial ulnar angular velocity were possible from spindle ensemble responses (R2= 0.85) whereas length could be predicted only for phases with lengthening of the ulnar wrist extensor. There are several possible explanations for the unexpectedly large phase advance of spindle afferents in the radial wrist extensor. Given the compliance of tendons, for instance, the phase relationship between the muscle fascicle length and the whole muscle length is conjectured to depend on the load. While additional phase advances are advantageous in motor control, it is concluded that if the central nervous system estimates length or velocity of a muscle from its muscle spindle discharges, this would require additional information about not only the concomitant extrafusal and fusimotor drive but also about the mechanical properties of the load on which the muscle acts.
Orientation and Path Dependence of Formability in the Stress- and the Extended Stress-Based Forming Limit Curves
Authors: Simha C. Hari Manoj , Inal Kaan , Worswick Michael J.
Published: September 2008

This article analyzes the formability data sets for aluminum killed steel (Laukonis, J. V., and Ghosh, A. K., 1978, “Effects of Strain Path Changes on the Formability of Sheet Metals,” Metall. Trans. A., 9, pp. 1849–1856), for Al 2008-T4 (Graf, A., and Hosford, W., 1993, “Effect of Changing Strain Paths on Forming Limit Diagrams of Al 2008-T4,” Metall. Trans. A, 24A, pp. 2503–2512) and for Al 6111-T4 (Graf, A., and Hosford, W., 1994, “The Influence of Strain-Path Changes on Forming Limit Diagrams of Al 6111 T4,” Int. J. Mech. Sci., 36, pp. 897–910). These articles present strain-based forming limit curves (ϵFLCs) for both as-received and prestrained sheets. Using phenomenological yield functions, and assuming isotropic hardening, the ϵFLCs are transformed into principal stress space to obtain stress-based forming limit curves (σFLCs) and the principal stresses are transformed into effective stress and mean stress space to obtain the extended stress-based forming limit curves (XSFLCs). A definition of path dependence for the σFLC and XSFLC is proposed and used to classify the obtained limit curves as path dependent or independent. The path dependence of forming limit stresses is observed for some of the prestrain paths. Based on the results, a novel criterion that, with a knowledge of the forming limit stresses of the as-received material, can be used to predict whether the limit stresses are path dependent or independent for a given prestrain path is proposed. The results also suggest that kinematic hardening and transient hardening effects may explain the path dependence observed in some of the prestrain paths.
Sliding Direction Dependence of Polyethylene Wear for Metal Counterface Traverse of Severe Scratches
Authors: Glennon Liam P. , Baer Thomas E. , Martin James A. , Lack William D. , Brown Thomas D.
Published: September 2008

Third-body effects appear to be responsible for an appreciable portion of the wear rate variability within cohorts of patients with metal-on-polyethylene joint replacements. The parameters dominating the rate of polyethylene debris liberation by counterface scratches are not fully understood, but one seemingly contributory factor is the scratch’s orientation relative to the direction of instantaneous local surface sliding. To study this influence, arrays of 550 straight parallel scratches each representative of the severe end of the clinical range were diamond stylus-ruled onto the surface of polished stainless steel plates. These ruled plates were then worn reciprocally against polyethylene pins (both conventional and highly cross-linked) at traverse angles varied parametrically relative to the scratch direction. Wear was measured gravimetrically, and particulate debris was harvested and morphologically characterized. Both of the polyethylene variants tested showed pronounced wear rate peaks at acute scratch traverse angles (15deg for conventional and 5deg for cross-linked), and had nominally comparable absolute wear rate magnitudes. The particulate debris from this very aggressive test regime primarily consisted of extremely large and elongated strands, often tens or even hundreds of microns in length. These data suggest that counterface damage regions with preferential scratch directionality can liberate large amounts of polyethylene debris, apparently by a slicing/shearing mechanism, at critical (acute) attack angles. However, the predominant manifestation of this wear volume was in the form of particles far beyond the most osteolytically potent size range.
Three-Dimensional Finite Element Simulations of the Dynamic Response of a Fingertip to Vibration
Authors: Wu John Z. , Krajnak Kristine , Welcome Daniel E. , Dong Ren G.
Published: September 2008

Although excessive dynamic deformation of the soft tissues in the fingertip under vibration loading is thought to induce hand-arm vibration syndrome, the in vivo distributions of the dynamic stress/strain of the tissues in the fingertip under vibration conditions have not been studied because they cannot be measured experimentally. In the present study, we analyzed the dynamic responses of a fingertip to vibrations by extending our previously proposed three-dimensional finite element (FE) model. The FE model of the fingertip contains the essential anatomical structures of a finger, such as skin layers (dermis and epidermis), subcutaneous tissue, bone, and nail. Our analysis indicated that the fingertip has a major local resonance around 100Hz and that the vibration displacement in the soft tissues under the nail bed is less than 10% of those in the finger pad for all precompression levels and vibration range. The resonant frequency of the fingertip was found to increase from 88Hzto125Hz with the static precompression increasing from 0.5mmto2.0mm. These results suggest that structural and functional changes in vascular function will likely initiate from the fingerpad, the location that undergoes the greatest deformation during vibration exposure. The current predictions are qualitatively consistent with the physiological data collected from workers with vibration white finger.
Characterization of Forces on the Sternal Midline Following Median Sternotomy in a Porcine Model
Authors: Pai Shruti , Dunn Raymond M. , Babbitt Russell , Strom Heather M. , Lalikos Janice F. , Pins George D. , Billiar Kristen L.
Published: September 2008

The development of more effective fixation devices for reapproximating and immobilizing the sternum after open-heart surgery is limited by current methods for evaluating these devices. In particular, precise emulation of in vivo sternal loading has not been achieved in controlled model systems. The present study is an initial effort to determine the in vivo loading parameters needed to improve current in vitro and in silico (computational) models. Towards this goal, the direction, magnitude, and distribution of loading along a midline sternotomy were characterized in a porcine model. Two instrumented plating systems were used to measure the forces across the bisected sternum in four anaesthetized Yorkshire pigs during spontaneous breathing, ventilated breathing, and coughing for four treatments: live, cadaveric, embalmed, and refrigerated. Changes in forces incurred by death and embalming were also investigated to evaluate the potential applicability of cadavers as models for testing sternal fixation devices. The magnitudes of the respiratory forces in three orthogonal directions ranged from 0.4Nto43.8N, many fold smaller than previously estimated. Dynamic forces were highest in the lateral direction during coughing and low in all directions during normal breathing. No significant differences in force were found between the four treatments, most likely due to the unexpectedly low magnitude of forces in all groups. These results provide the first measurements of in vivo sternal forces and indicate that small cyclic fatigue loads rather than large quasistatic loads should be applied in future model systems to best evaluate the mechanical performance of fixation devices.
Rheological Effects of Blood in a Nonplanar Distal End-to-Side Anastomosis
Authors: Wang Qian-Qian , Ping Bao-Hong , Xu Qing-Bo , Wang Wen
Published: September 2008

This study investigates rheological effects of blood on steady flows in a nonplanar distal end-to-side anastomosis. The shear-thinning behavior of blood is depicted by a Carreau–Yasuda model and a modified power-law model. To explore effects of nonplanarity in vessel geometry, a curved bypass graft is considered that connects to the host artery with a 90deg out-of-plane curvature. Navier–Stokes equations are solved using a finite volume method. Velocity and wall shear stress (WSS) are compared between Newtonian and non-Newtonian fluids at different flow rates. At low flow rate, difference in axial velocity profiles between Newtonian and non-Newtonian fluids is significant and secondary flows are weaker for non-Newtonian fluids. At high flow rate, non-Newtonian fluids have bigger peak WSS and WSS gradient. The size of the flow recirculation zone near the toe is smaller for non-Newtonian fluids and the difference is significant at low flow rate. The nonplanar bypass graft introduces helical flow in the host vessel. Results from the study reveal that near the bed, heel, and toe of the anastomotic junction where intimal hyperplasia occurs preferentially, WSS gradients are all very big. At high flow rates, WSS gradients are elevated by the non-Newtonian effect of blood but they are reduced at low flow rates. At these locations, blood rheology not only affects the WSS and its gradient but also secondary flow patterns and the size of flow recirculation near the toe. This study reemphasizes that the rheological property of blood is a key factor in studying hemodynamic effects on vascular diseases.
Control of Circumferential Wall Stress and Luminal Shear Stress Within Intact Vascular Segments Perfused Ex Vivo
Authors: El-Kurdi Mohammed S. , Vipperman Jeffrey S. , Vorp David A.
Published: September 2008

Proportional, integral, and derivative (PID) controllers have proven to be robust in controlling many applications, and remain the most widely used control system architecture. The purpose of this work was to use this architecture for designing and tuning two PID controllers. The first was used to control the physiologic arterial circumferential wall stress (CWS) and the second to control the physiologic arterial shear stress (SS) imposed on intact vascular segments that were implanted into an ex vivo vascular perfusion system (EVPS). In order to most accurately control the stresses imposed onto vascular segments perfused ex vivo, analytical models were derived to calculate the CWS and SS. The mid-vein-wall CWS was calculated using the classical Lamé solution for thick-walled cylinders in combination with the intraluminal pressure and outer diameter measurements. Similarly, the SS was calculated using the Hagen–Poiseuille equation in combination with the flow rate and outer diameter measurements. Performance of each controller was assessed by calculating the root mean square of the error (RMSE) between the desired and measured process variables. The performance experiments were repeated ten times (N=10) and an average RMSE was reported for each controller. RMSE standard deviations were calculated to demonstrate the reproducibility of the results. Sterile methods were utilized for making blood gas and temperature measurements in order to maintain physiologic levels within the EVPS. Physiologic blood gases (pH, pO2, and pCO2) and temperature within the EVPS were very stable and controlled manually. Blood gas and temperature levels were recorded hourly for several (N=9)24h perfusion experiments. RMSE values for CWS control (0.427±0.027KPa) indicated that the system was able to generate a physiologic CWS wave form within 0.5% error of the peak desired CWS over each cardiac cycle. RMSE values for SS control (0.005±0.0007dynes∕cm2) indicated that the system was able to generate a physiologic SS wave form within 0.3% error of the peak desired SS over each cardiac cycle. Physiologic pH, pO2, pCO2, and temperature levels were precisely maintained within the EVPS. The built-in capabilities and overall performance of the EVPS described in this study provide us with a novel tool for measuring molecular responses of intact vascular segments exposed to precisely simulated arterial biomechanical conditions.
Development and Validation of Patient-Specific Finite Element Models of the Hemipelvis Generated From a Sparse CT Data Set
Authors: Shim Vickie B. , Pitto Rocco P. , Streicher Robert M. , Hunter Peter J. , Anderson Iain A.
Published: September 2008

To produce a patient-specific finite element (FE) model of a bone such as the pelvis, a complete computer tomographic (CT) or magnetic resonance imaging (MRI) geometric data set is desirable. However, most patient data are limited to a specific region of interest such as the acetabulum. We have overcome this problem by providing a hybrid method that is capable of generating accurate FE models from sparse patient data sets. In this paper, we have validated our technique with mechanical experiments. Three cadaveric embalmed pelves were strain gauged and used in mechanical experiments. FE models were generated from the CT scans of the pelves. Material properties for cancellous bone were obtained from the CT scans and assigned to the FE mesh using a spatially varying field embedded inside the mesh while other materials used in the model were obtained from the literature. Although our FE meshes have large elements, the spatially varying field allowed them to have location dependent inhomogeneous material properties. For each pelvis, five different FE meshes with a varying number of patient CT slices (8–12) were generated to determine how many patient CT slices are needed for good accuracy. All five mesh types showed good agreement between the model and experimental strains. Meshes generated with incomplete data sets showed very similar stress distributions to those obtained from the FE mesh generated with complete data sets. Our modeling approach provides an important step in advancing the application of FE models from the research environment to the clinical setting.
Modeling of Saccular Aneurysm Growth in a Human Middle Cerebral Artery
Authors: Kroon Martin , Holzapfel Gerhard A.
Published: September 2008

Saccular aneurysm growth in a human middle cerebral artery is modeled. The aneurysm growth model was presented in a companion paper by Kroon and Holzapfel (“A Model for Saccular Cerebral Aneurysm Growth by Collagen Fibre Remodelling,” J. Theor. Biol., in press) and was assessed there for axisymmetric growth. The aneurysm growth model is now evaluated for a more realistic setting. The middle cerebral artery is modeled as a two-layered cylinder, where the layers correspond to the media and the adventitia. An instant loss of the media in a region of the artery wall initiates the growth of the saccular aneurysm. The aneurysm wall is assumed to be a development of the adventitia of the original healthy artery, and collagen is assumed to be the only load-bearing constituent in the adventitia and in the aneurysm wall. The collagen is organized in a number of distinct layers where fibers in a specific layer are perfectly aligned in a certain fiber direction. The production of new collagen is taken to depend on the stretching of the aneurysm wall, and the continuous remodeling of the collagen fibers is responsible for the aneurysm growth. The general behavior of the growth model is investigated and also the influence of the structural organization of the collagen fabric. The analysis underlines the fact that the material behavior of aneurysmal tissue cannot be expected to be isotropic. The model predictions agree well with clinical and experimental results, for example, in terms of aneurysm size and shape, wall stress levels, and wall thickness.
Analysis of Space Shuttle External Tank Spray-On Foam Insulation With Internal Pore Pressure
Authors: Bednarcyk Brett A. , Aboudi Jacob , Arnold Steven M. , Sullivan Roy M.
Published: September 2008

The polymer spray-on foam insulation used on NASA’s Space Shuttle external fuel tank is analyzed via the high-fidelity generalized method of cells micromechanical model. This model has been enhanced to include internal pore pressure, which is applied as a boundary condition on the internal faces of the foam pores. The pore pressure arises due to both ideal gas expansion during a temperature change as well as outgassing of species from the foam polymer material. Material creep and elastic stiffening are also incorporated via appropriate constitutive models. Due to the lack of reliable properties for the in situ foam polymer material, these parameters are backed out from foam thermomechanical test data. Parametric studies of the effects of key variables (both property-related and microstructural) are presented as is a comparison of model predictions for the thermal expansion behavior of the foam with experimental data.
Multiscale Thermodynamic Basis of Plastic Potential
Theory
Authors: Yang Q. , Xue L. J. , Liu Y. R.
Published: September 2008

In this paper, the multiscale thermodynamic basis of the plastic potential theory is addressed within the irreversible thermodynamic framework with internal variables by Rice (1971, “Inelastic Constitutive Relations for Solids: An Internal Variable Theory and Its Application to Metal Plasticity,” J. Mech. Phys. Solids, 19, pp. 433–455). It is shown that the condition of free or complementary energy equivalence leads to the full equivalence of the microscale and macroscale thermodynamic formulations as soon as the multiscale kinematic relation is prescribed. The condition of dissipation equivalence by Rice is not an independent condition. The thermodynamic significance and counterparts of plastic potentials and multipliers, Koiter’s and Mises’ flow rules, the intrinsic time in the work of Valanis (1975, “On the Foundations of the Endochronic Theory of Viscoplasticity,” Arch. Mech., 27, pp. 857–868), the viscoplasticity, and the J2 plasticity can all be revealed and recovered within the multiscale thermodynamic framework.
Characterization and Modeling of Large Displacement Micro-/Nano-Indentation of Polymeric Solids
Authors: Lu Y. C. , Shinozaki D. M.
Published: September 2008

Large displacement micro-indentation tests have been performed on various polymeric solids to measure the plastic properties. Cylindrical flat-ended indenters with diameter in the range of 10–90 μm are mostly used. The mechanism of large-strain indentation has been examined with optical microscopy and finite element simulations. Results show that under a flat-tipped indenter, the material can quickly reach a fully plastic state. The size (diameter) of the plastic zone is constant in large-strain regions and unaffected by the exact tip profile (flat, spherical, and conical). The indentation stress-displacement curve at large strains is linear as a result of the steady-state plastic flow, from which the mean indentation pressure, a measure of yield strength, can be readily extrapolated. The indentation stress-displacement response is independent of the indenter diameters but strongly dependent on the strain-hardening behavior of the material and the friction between a material and an indenter. Compared with other shaped indenters, the flat-ended indenter requires the least penetration depth in order to probe the plastic properties of a material or structure.
The Influence of Ultrasonic Energy on Chemical Treatment of Surface Properties and the Properties of Composites Made of Luffa Cylindrical Fiber-Polyester Resin
Authors: Koçak E. Dilara
Published: September 2008

Producing composites from natural fibers is known to be common. These fibers benefit from their mechanical performances, low density, and their biodegradability. However, it is necessary for the fibers to form adhesion in the matrix. Therefore, it is necessary to apply a chemical process to the surface of the fibers. In this study, four different processes in conventional and ultrasonic energies were applied on luffa cylindrical fibers. At the end of the application, a composite structure was formed on the fibers that were obtained by using unsaturated polyester resin. The changes in the characteristics of the composite structure were recorded by mechanical tests, Fourier transform infrared, X-ray diffractometer, and their morphological characteristics by means of scanning electron microscopy. Considering all the results, formic acid and acetic acid process results were found to adequately modify the fiber surfaces.
Impact Damage Tolerance and Fatigue Durability of GLARE Laminates
Authors: Seo Hyoungseock , Hahn H. T. , Yang Jenn-Ming
Published: September 2008

The fatigue behavior and residual strength of postimpacted GLARE 4-3/2, GLARE 5-2/1, and monolithic aluminum 2024-T3 alloy were investigated experimentally. Drop-weight impact was applied at a variety of energy levels to inflict a barely visible impact damage, a clearly visible impact damage, and a penetration damage. After the impact test, constant-amplitude tension-tension fatigue was done to delineate the modes of damage initiation and growth and the effect of damage on fatigue life and residual strength. The results showed that GLARE laminates exhibit superior postimpact fatigue durability when compared with the monolithic 2024-T3 aluminum alloy.
Influence of Cartilaginous Matrix Accumulation on Viscoelastic Response of Chondrocyte/Agarose Constructs Under Dynamic Compressive and Shear Loading
Authors: Miyata Shogo , Tateishi Tetsuya , Ushida Takashi
Published: September 2008

A method has been developed to restore cartilage defects by culturing autologous chondrocytes to create a three dimensional tissue and then implanting the cultured tissue. In this kind of approach, it is important to characterize the dynamic mechanical behavior of the regenerated cartilaginous tissue, because these tissues need to bear various dynamic loadings in daily life. The objectives of this study were to evaluate in detail the dynamic viscoelastic responses of chondrocyte-seeded agarose gel cultures in compression and torsion (shear) and to determine the relationships between these mechanical responses and biochemical composition. The results showed that both the dynamic compressive and shear stiffness of the cultured constructs increased during culture. The relative energy dissipation in dynamic compression decreased, whereas that in dynamic shear increased during culture. Furthermore, correlation analyses showed that the sulfated glycosaminoglycan (sGAG) content of the cultured construct showed significant correlations with the dynamic modulus in both compression and shear situations. On the other hand, the loss tangent in dynamic compression, which represents the relative energy dissipation capability of the constructs, showed a low correlation with the sGAG content, whereas this capability in shear exhibited moderate correlation. In conclusion, we explored the dynamic viscoelasticity of the tissue-engineered cartilage in dynamic compression and shear, and determined correlations between viscoelasticity and biochemical composition.