bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Finishing/Polishing Systems on the Surface Roughness of Novel Posterior Composites
Authors: MARGHALANI HANADI Y.
Published: April 2010

Purpose:  The aim of this in vitro study was to evaluate and compare the surface finish of some direct posterior resin composites with new novel ones, which are based on a resin matrix other than the ordinary dimethacrylate, after fine finishing and polishing with eight different systems.

Materials and Methods:  Forty‐eight disk‐shaped specimens of the posterior composites were prepared in a split Teflon mold and irradiated by an Astralis 10 light cure (560 mW/cm2 for 10 seconds) at four quadrants on each sample's side. The specimens were divided into eight groups according to the designed finishing and/or polishing protocols. The surface roughness in the form of surface finish (Ra) was recorded using a contact profilometer. The surface of the specimens was observed under the scanning electron microscope.

Results:  Analysis of variance revealed highly significant differences between the materials for the Ra roughness parameter at each finishing and polishing system used (p < 0.05). On the one hand, Filtek P90 (3M ESPE Dental Products, Seefeld, Germany) and Definite (Degussa, Dental Centrum, Hanau, Germany) provided the smoothest surface finish (Ra) when they were finished and polished with a series of Sof‐Lex pop‐on disks (3M ESPE Dental Products) and Astropol (Ivoclar Vivadent, Schaan, Liechtenstein), respectively. On the other hand, Filtek P60 (3M ESPE Dental Products) presented the roughest surface when it was finished with Fini disks (Jeneric/Pentron Clinical Technologies, Wallingford, CT, USA). Scanning electron microscope images indicated a uniform surface topography for Filtek P90 with most finishing/polishing systems. Contrary to CompoSite polishers (Shofu Inc., Kyoto, Japan), Astropol showed the smoothest surface finish with most of the investigated composites.

CLINICAL SIGNIFICANCE

The smoothest surface finish was achieved by most of the finishing/polishing systems investigated specifically on cationic (Filtek P90) and organically modified ceramics (Definite) composites compared with dimethacrylate‐based composites, suggesting their successful clinical use.

(J Esthet Restor Dent 22:127–138, 2010)
One‐Year Clinical Evaluation of the Efficacy of a New Daytime At‐Home Bleaching Technique
Authors: TÜRKÜN MURAT , ÇELİK ESRA UZER , ALADAĞ AKIN , GÖKAY NECMI
Published: April 2010

The aim of this study was to compare the clinical efficacy and side effects of a new daytime at‐home bleaching technique (28% carbamide peroxide [CP] gel) with the overnight application of 10% CP and to determine the change of tooth color 1‐year post‐treatment. Twenty healthy volunteers were assigned to one of two sample groups of 10. All participants employed one of the two at‐home bleaching systems: (1) the new daytime at‐home bleaching system including 28% CP gel with a non‐custom‐fit tray (Meta Tray, Remedent, Deurle, Belgium) for 20 minutes, and (b) the conventional overnight at‐home bleaching system with a 10% CP gel and a custom‐fit tray (Opalescence PF, Ultradent, South Jordan, UT, USA) for 6 to 8 hours. Digital images and CIE (International Commission on Illumination) L*, a*, and b* spectrophotometric measurements were taken at baseline, after the bleaching treatment and 1‐year post‐treatment. Tooth and gingival sensitivity was measured with a specially designed 4‐point scale. Significant differences were found in L*, a*, and b* values, between initial and post‐treatment, for both bleaching systems (p < 0.05). However, no significant difference was detected between post‐treatment and 1‐year follow‐up. The bleaching effectiveness of Opalescence PF was found to be superior to that of Meta Tray, considering the color parameter of ΔE (p < 0.05). Meta Tray provoked less tooth sensitivity (p < 0.05), however gingival sensitivity appeared more in this group (p < 0.05). Within the limitations of this study, it can be concluded that the new daytime at‐home bleaching system tested (Meta Tray) produced significant bleaching effects. However, the clinical efficacy of the overnight bleaching system was found to be superior to the daytime at‐home bleaching system evaluated in this study. The whitening effect remained similar 1‐year after the bleaching treatment for both at‐home bleaching systems.

CLINICAL SIGNIFICANCE

Although the new daytime at‐home bleaching system tested exhibited significant bleaching effects, overnight bleaching with a 10% CP gel resulted in a higher bleaching effectiveness than this new system. Although the participants using the new bleaching system exhibited less tooth sensitivity probably because of the reduced contact time of bleaching gel with tooth surfaces, the application of the bleaching agent with a non‐customized tray provoked more gingival sensitivity in this group.

(J Esthet Restor Dent 22:139–148, 2010)
OPTIONS FOR DENTIN/ENAMEL BONDING: PART II
Authors: Swift Edward J.
Published: April 2010

Four categories of resin‐based dentin/enamel adhesives are currently available. These include the three‐step etch‐and‐rinse, “one‐bottle” etch‐and‐rinse, two‐step self‐etch primer systems, and “all‐in‐one” self‐etch adhesives. In consecutive issues of the journal, the Critical Appraisal series will present salient publications on research in each of the categories. The first installment focused on the three‐step etch‐and‐rinse systems and the series continues with this paper on the one‐bottle etch‐and‐rinse systems.
Downregulation of oxytocin receptors in right ventricle of rats with monocrotaline‐induced pulmonary hypertension
Authors: Broderick T. L. , Wang Y. , Gutkowska J. , Wang D. , Jankowski M.
Published: April 2010

Aim:  Pulmonary hypertension (PH) in the rat leads to right ventricular (RV) hypertrophy, inflammation and increased natriuretic peptide (NP) levels in plasma and RV. Because the release of nitric oxide (NO) and atrial natriuretic peptide (ANP) is a function of the oxytocin receptor (OTR), we examined the effect of PH on gene and protein expression of OTR, NP (A, atrial; B, brain) and receptors (NPRs), nitric oxide synthases (NOS), interleukin (IL)‐1β, IL‐6 and tumour necrosis factor‐α in the hypertrophied RV in a model of PH.

Methods:  RV hypertrophy was induced in male Sprague–Dawley rats with monocrotaline (MCT; 60 mg kg−1) and was confirmed by the presence of an increased RV weight and RV‐to‐[left ventricle (LV) and septum] ratio.

Results:  In the RV of MCT‐treated rats, a ∼40% reduction in OTR mRNA and protein was observed compared with the RV of control rats. This reduction was associated with increased transcripts of ANP and BNP in both ventricles and a corresponding increase in NP receptor mRNA expression for receptors A, B and C. Protein expression of inducible NOS was increased in the RV, whereas endothelial NOS transcripts were increased only in the LV of MCT‐treated rats. In the RV of MCT‐treated rats, downregulation of OTR was also associated with increased mRNA expression of IL‐1β and IL‐6.

Conclusion:  Our results show that downregulation of the OTR in the RV of MCT‐treated rats is associated with increased expression of NP and their receptors as well as IL‐1β and IL‐6. This reduction in OTR in RV myocardium may have an impact on cardiac function in the MCT‐induced model of PH.
Telemetry in a motion‐sickness model implicates the abdominal vagus in motion‐induced gastric dysrhythmia
Authors: Percie du Sert Nathalie , Chu Kit M. , Wai Man K. , Rudd John A. , Andrews Paul L. R.
Published: April 2010

In humans, motion sickness is associated with disruption of normal gastric myoelectric activity, and it has been proposed that this results from an imbalance of autonomic nervous system activity. We used the established Suncus murinus (house musk shrew) model of motion‐induced emesis to investigate the effect of horizontal motion on gastric myoelectric activity (recorded using telemetry) and the involvement of the abdominal vagi. Surgical vagotomy increased baseline dysrhythmia and reduced the dominant power of the gastric myoelectric signals. In response to motion, normal gastric myoelectric activity was reduced in sham‐operated animals but not in vagotomized animals. Vagotomy, however, failed to affect motion‐induced emesis. In conclusion, motion had a differential effect in sham‐operated and vagotomized animals, which is consistent with the hypothesis that motion‐induced dysrhythmia arises from an autonomic nervous system imbalance.
Ciliary beat frequency controlled by oestradiol and progesterone during ovarian cycle in guinea‐pig Fallopian tube
Authors: Nishimura Ayumi , Sakuma Ko , Shimamoto Chikao , Ito Shigenori , Nakano Takashi , Daikoku Eriko , Ohmichi Masahide , Ushiroyama Takahisa , Ueki Minoru , Kuwabara Hiroko , Mori Hiroshi , Nakahari Takashi
Published: April 2010

The ciliary beat frequency (CBF) of guinea‐pig fimbria during the ovarian cycle was measured by video microscopy using a high‐speed camera (500 Hz). In the follicular phase, with increasing concentrations of β‐oestradiol ([βE2]) and a low concentration of progesterone ([PRG]), CBF increased from 13.5 to 16 Hz. In the ovulatory phase, with further increase of [βE2], CBF decreased gradually from 16 to 13.5 Hz. In the early luteal phase, with low [PRG] and [βE2], CBF increased to ∼17 Hz; however, in the middle luteal phase, with increasing [PRG], CBF decreased (∼12 Hz), and in the late luteal phase, with decreasing [PRG], CBF increased to ∼15 Hz. Then, in the resting phase, with low [βE2] and [PRG], CBF decreased immediately to ∼14 Hz. The CBF of the fimbria was measured in guinea‐pigs treated with β‐oestradiol benzoate (βE2B) or medroxyprogesterone (mPRG). A low dose of βE2B increased CBF to ∼14.5 Hz, whereas a high dose decreased it to ∼11 Hz. A βE2 receptor blocker, ICI‐182,780, abolished the βE2B‐induced CBF changes and maintained CBF at ∼12.0 Hz. Medroxyprogesterone decreased CBF to ∼12.5 Hz, and mifepristone (a PRG receptor blocker) abolished the mPRG‐induced CBF decrease and maintained CBF at ∼15 Hz. The addition of both blockers increased CBF to ∼18 Hz, suggesting that activation of βE2 or PRG receptors decreases the CBF of the fimbria. In conclusion, a moderate [βE2] increase maintains a high CBF (15.5 Hz) in the follicular phase, and then further [βE2] increase decreases CBF to 13.5 Hz in the ovulatory phase. In the early and late luteal phase, low [βE2] and [PRG] increase CBF to 17 and 15 Hz, respectively, and in the middle luteal phase a high [PRG] decreases CBF (to ∼12 Hz). Thus, the CBF of the fimbria was controlled by signals via βE2 and PRG receptors in guinea‐pigs.
Similar metabolic perturbations during all‐out and constant force exhaustive exercise in humans: a 31P magnetic resonance spectroscopy study
Authors: Burnley Mark , Vanhatalo Anni , Fulford Jonathan , Jones Andrew M.
Published: April 2010

It is not possible to attain a metabolic steady state during exercise above the so‐called critical force or critical power. We tested the hypothesis that the muscle metabolic perturbations at the end of a bout of maximal isometric contractions, which yield a stable end‐test force (equal to the critical force), would be similar to that at task failure following submaximal contractions performed above the critical force. Eight healthy subjects (four female) performed isometric single knee‐extension exercise in the bore of a 1.5 T superconducting magnet on two occasions. Following familiarization, subjects performed the following exercises: (1) 60 maximal contractions (3 s contraction, 2 s rest); and (2) submaximal contractions (the same contraction regime performed at 54 ± 8% maximal voluntary contraction) to task failure. Phosphocreatine (PCr), inorganic phosphate (Pi) and diprotonated phosphate (H2PO4−) concentrations and pH were determined using 31P magnetic resonance spectroscopy throughout both tests. During the maximal contractions, force production fell from 213 ± 33 N to reach a plateau in the last 30 s of the test at 100 ± 20 N. The muscle metabolic responses at the end of each test were substantial, but not different between conditions: [PCr] was reduced (to 21 ± 12 and 17 ± 7% of baseline for maximal and submaximal contractions, respectively; P= 0.17), [Pi] was elevated (to 364 ± 98 and 363 ± 135% of baseline, respectively; P= 0.98) and pH reduced (to 6.64 ± 0.16 and 6.69 ± 0.17, respectively; P= 0.43). The [H2PO4−] was also elevated at the end of both tests (to 607 ± 252 and 556 ± 269% of baseline, respectively; P= 0.22). These data suggest that the exercise‐induced metabolic perturbations contributing to force depression in all‐out exercise are the same as those contributing to task failure during submaximal contractions.
Modelling Complex Force Systems, Part 1: The Cutting and Pad Forces in Deep Drilling
Authors: Griffiths B. J.
Published: April 2010

This paper is the first part of a two-part series which analyzes the complex force system existing within a deep hole drilling operation where cutting forces exist at a single cutting edge and burnishing and friction forces exist at two pads. In this first paper the forces at the pads and cutting edge are determined by (1) assuming that the pad forces are related by coefficients and (2) by the use of complimentary dynamometers.
The Computer Simulation and Experimental Analysis of Chip Monitoring for Deep Hole Drilling
Authors: Chin Jih-Hua , Wu Jang-Shyong , Young Rouh-Song
Published: April 2010

Chip congestion is a long time bottleneck in deep hole drilling. This paper addresses the problem of chip state monitoring in single-edge deep hole drilling by computer simulation and experimental analysis. Two phenomenological models were proposed to interpret the physics of chip discharging in normal and congested states, respectively. Length and diameter of the chip are chosen to represent the geometric features of the chip, and the formation of a chip signal is discussed. Based on the two models different types of chips are used to simulate the monitoring process. Computer simulation shows that the normal chip discharging in a real drilling process can be interpreted by the proposed slug flow model. Also, the experiments with cylindrical form chips confirms model II proposed for a congested chip state in which the diametral effect develops due to chip congestion. The experimental analyses also find out the dependence of pressure signals on the various parameters of chips as well as the cutting process.
A Unified Transfer Function (UTF) Approach for the Modeling and Stability Analysis of Long Slender Bars in 3-D Turning Operations
Authors: Tansel I. N.
Published: April 2010

A new approach is introduced to model 3-D turning operations that are used for the stability analysis of long slender bars. This approach utilizes the unique relationship between externally created feed direction tool displacements (input) and the resultant thrust direction workpiece vibrations (output) to estimate stability limits in three-dimensional turning operations from the data of a single dynamic cutting test. In this paper, this unique relationship is referred to as the “Unified Transfer Function ” (UTF) and its expressions are derived from conventional cutting and structural dynamics transfer functions. For the stability analysis, the uncut chip area variations of oblique cutting are represented by a linear model having different coefficients at different depths of cuts. These coefficients are found by using a tool geometry simulation program. An iterative procedure is developed for the stability analysis. The proposed approach considers in-process structural and cutting dynamics and can be automatically implemented without any input from the operator for the traverse turning of a long slender bar. Experimental studies have validated the proposed modeling and stability analysis techniques. The UTFs can also be used to monitor machine tool structure, tool wear, and the machinability of the material.
Statistical Analysis of the Dynamic Cutting Coefficients and Machine Tool Stability
Authors: El Baradie M. A.
Published: April 2010

Machine tool chatter is a statistical phenomenon since it is dependent on the interaction of two statistical quantities, these being the dynamic characteristics of the machine tool structure and the transfer function of the cutting process. In this paper, a generalized statistical theory of machine tool chatter has been developed. This takes into consideration the scatter of the dynamic data of the machine structure and/or that of the cutting process. The dynamics of the cutting process have been represented by a mathematical model which derives the cutting coefficients from steady state cutting data, based on a nondimensional analysis of the cutting process. The dynamics of the machine tool structure and the cutting process, being the input data to the theory, were determined experimentally. The predicted stability charts were plotted to take into consideration the scatter in the machine structure dynamics and/or the cutting process. At the threshold of stability, the statistical variations due to the dynamic cutting coefficients amount to ±29.5 percent at 99 percent confidence level, while the statistical variations due to the structure dynamics amount to ±4.5 percent only, at the same confidence level. Therefore, the threshold of stability can be specified only in terms of mean values with confidence limits.
Production of Tapered Cups by Sequential Deep Drawing of Sheet Metals Using Drawn Cups as a Part of Punch
Authors: Yamaguchi K. , Kanayama K. , Parsa M. H. , Takakura N.
Published: April 2010

A new deep drawing process of sheet metals is developed to facilitate small-lot production of deep cups with large drawing ratio. In this process, unlike the conventional deep drawing method, a few drawn cups are always stacked on the punch and used as a part of punch for the subsequent deep drawing of a given blank. Before drawing a new blank, a drawn cup which is in contact with the punch is stripped off. The repetition of such stripping and drawing operations makes it possible to carry out both the first-stage drawing and the subsequent slight redrawings in one drawing operation using only one pair of punch and die. In this paper, this new deep drawing process is applied to the production of tapered cups and the main feature of the process is shown.
Knowledge-Based Expert System for Ballscrew Grinding
Authors: Billatos S. B. , Webster J. A.
Published: April 2010

This paper discusses the ballscrew grinding process and provides a newly structured knowledge-based expert system (KBES) developed to automate the process based on fuzzy pattern recognition techniques for shape control with recommendations for further optimization considering practical machining constraints. The KBES offers several advantages including the use of semiskilled operators who can monitor several machines simultaneously, the consistent production of high quality parts, and the significant reduction in cycle time due to automatic adjustment of steadies. A new stepper motor steady design and in-process measuring system are also described.
A Study of Friction Feed Paper Separation
Authors: Stack K. D. , Benson R. C.
Published: April 2010

An understanding of the mechanics of paper separation is very important to the design of reliable photocopiers, and in this paper a model is developed to simulate friction feed paper separation. The importance of such system parameters as roller acceleration and compressive load is demonstrated. The variability of friction coefficients is shown to have a significant effect on feeding reliability. Experimental data are shown to be in good agreement with predicted results. Recommendations are made for the design of reliable friction feed paper separators.
A Study of the Anisotropy and Tension/Compression Behavior of Human Cervical Tissue
Authors: Myers Kristin M. , Socrate Simona , Paskaleva Anastassia , House Michael
Published: April 2010

The cervix plays a crucial role in maintaining a healthy pregnancy, acting as a mechanical barrier to hold the fetus in utero during gestation. Altered mechanical properties of the cervical tissue are suspected to play a critical role in spontaneous preterm birth. Both MRI and X-ray data in the literature indicate that cervical stroma contains regions of preferentially aligned collagen fibers along anatomical directions (circumferential/longitudinal/radial). In this study, a mechanical testing protocol is developed to investigate the large-strain response of cervical tissue in uniaxial tension and compression along its three orthogonal anatomical directions. The stress response of the tissue along the different orthogonal directions is captured using a minimal set of model parameters generated by fitting a one-dimensional time-dependent rheological model to the experimental data. Using model parameters, mechanical responses can be compared between samples from patients with different obstetric backgrounds, between samples from different anatomical sites, and between the different loading directions for a single specimen. The results presented in this study suggest that cervical tissue is mechanically anisotropic with a uniaxial response dependent on the direction of loading, the anatomical site of the specimen, and the obstetric history of the patient. We hypothesize that the directionality of the tissue mechanical response is primarily due to collagen orientation in the cervical stroma, and provides an interpretation of our mechanical findings consistent with the literature data on preferential collagen alignment.
Effect
of Return Bend and Entrance on Heat Transfer in Thermally Developing Laminar Flow in Round Pipes of
Some Heat Transfer Fluids With High Prandtl
Numbers
Authors: Hrnjak Predrag
S. , Hong S. H.
Published: April 2010

The paper presents experimental results and analysis of heat transfer in a thermally developing region of round pipes for three fluids typically used as low temperature coolants, in the range of 0–−40°C. The experiments were performed at low Re (200–1000) and high Pr (80–140) numbers that are typically found in secondary refrigeration loop conditions. The effect of horizontal U-bend is also presented. It is shown that the positive effect of thermal development (high Nu number) lasts long because of the technically significant length of the thermally developing region. Secondary flows developed in and after the U-bend are so significant that they have almost an identical effect as the thermal development at the pipe entrance. That is a reason for the extremely good performance of the heat exchangers with secondary refrigerants in laminar flow regimes. Experimental data are presented with developed empirical correlations, which show good relationships to several existing correlations.
Thermal Hydraulic Study of a Single Row Heat Exchanger With Helically Finned Tubes
Authors: Huisseune H. , T’Joen C. , Brodeoux P. , Debaets S. , De Paepe M.
Published: April 2010

In this study, the heat transfer and friction correlation of a single row heat exchanger with helically finned tubes are experimentally determined. The transversal tube pitch was parametrically varied. A detailed description of the test rig and the data reduction procedure is given. A thorough uncertainty analysis was performed to validate the results. The proposed heat transfer correlation can describe 95% of the data within ±11% and shows a 4.49% mean deviation. The friction correlation predicts 95% of the data within ±19% with a mean deviation of 6.84%. The new correlations show the same trend as most correlations from open literature, but none of the literature correlations are able to accurately predict the results of this study.
Effect of Particle Migration on Flow and Convective Heat Transfer of Nanofluids Flowing Through a Circular Pipe
Authors: Heyhat M. M. , Kowsary F.
Published: April 2010

This paper aims to study the effect of particle migration on flow and heat transfer of nanofluids flowing through a circular pipe. To do this, a two-component model proposed by Buongiorno (2006, “Convective Transport in Nanofluids,” ASME J. Heat Transfer, 128, pp. 240–250) was used and a numerical study on laminar flow of alumina-water nanofluid through a constant wall temperature tube was performed. The effects of nonuniform distribution of particles on heat-transfer coefficient and wall shear stress are shown. Obtained results illustrate that by considering the particle migration, the heat-transfer coefficient increases while the wall shear stress decreases, compared with uniform volume fraction. Thus, it can be concluded that the enhancement of the convective heat transfer could not be solely attributed to the enhancement of the effective thermal conductivity, and beside other reasons, which may be listed as this higher enhancement, particle migration is proposed to be an important reason.
Semi-Analytical Solution for Heat Transfer in a Water Film Flowing Over a Heated Plane
Authors: Aubert Adrien , Candelier Fabien , Solliec Camille
Published: April 2010

Film flow coupled with heat and mass transfer is a widely open domain due to the range of its applications. However, the coupling between the different phenomena makes the analytical resolution difficult, and thus, coerces most authors into performing numerical studies. Although efficient, the numerical approach does not reveal the real link between the different parameters when studying heat transfer. This lack of meaningful formulation motivates the present paper, which proposes a semi-analytical solution for the establishment of the thermal boundary layer of a film flowing down an inclinated heated plane. The formula is obtained by a truncated sum of Whittaker’s functions, and is validated by comparison with a full numerical solution of the problem (assuming the same hypotheses). The semi-analytical nature of the equation provides better understanding of the physical phenomena and could help in reducing numerical computational time.
Simultaneous
Measurement of Three-Dimensional Soot Temperature and Volume Fraction Fields in Axisymmetric or
Asymmetric Small Unconfined Flames With CCD
Cameras
Authors: Liu D. , Huang Q.
X. , Wang F. , Chi Y. , Cen K. F. , Yan J.
H.
Published: April 2010

A nonintrusive measurement technique is presented numerically for simultaneous measurement of three-dimensional (3D) soot temperature and volume fraction fields in the axisymmetric or asymmetric flames with charge-coupled device (CCD) cameras. CCD cameras were introduced to capture the flame images for obtaining the line-of-sight radiation intensities. The distributions of local emission source under two wavelengths can be deduced through solving the reconstruction matrix equation by the least-square QR decomposition method from the knowledge of the line-of-sight radiation intensities of the flames. The two-color distributions of the local emission source were used to retrieve the soot temperature and volume fraction distributions. The effects of the discrete ray number of CCD cameras, the number of CCD cameras, and the system signal-to-noise ratio (SNR) on the measurement were investigated. The results show that for accurate measurement of soot volume fraction field, the CCD cameras number should not be less than four and the system SNR can be as low as 54 dB. The proposed technique can be capable for reconstructing the 3D soot temperature and volume fraction fields in both axisymmetric and asymmetric flames well.
Design and Validation of a General Purpose Robotic Testing System for Musculoskeletal Applications
Authors: Noble Lawrence D. , Colbrunn Robb W. , Lee Dong-Gil , van den Bogert Antonie J. , Davis Brian L.
Published: April 2010

Orthopaedic research on in vitro forces applied to bones, tendons, and ligaments during joint loading has been difficult to perform because of limitations with existing robotic simulators in applying full-physiological loading to the joint under investigation in real time. The objectives of the current work are as follows: (1) describe the design of a musculoskeletal simulator developed to support in vitro testing of cadaveric joint systems, (2) provide component and system-level validation results, and (3) demonstrate the simulator’s usefulness for specific applications of the foot-ankle complex and knee. The musculoskeletal simulator allows researchers to simulate a variety of loading conditions on cadaver joints via motorized actuators that simulate muscle forces while simultaneously contacting the joint with an external load applied by a specialized robot. Multiple foot and knee studies have been completed at the Cleveland Clinic to demonstrate the simulator’s capabilities. Using a variety of general-use components, experiments can be designed to test other musculoskeletal joints as well (e.g., hip, shoulder, facet joints of the spine). The accuracy of the tendon actuators to generate a target force profile during simulated walking was found to be highly variable and dependent on stance position. Repeatability (the ability of the system to generate the same tendon forces when the same experimental conditions are repeated) results showed that repeat forces were within the measurement accuracy of the system. It was determined that synchronization system accuracy was 6.7±2.0 ms and was based on timing measurements from the robot and tendon actuators. The positioning error of the robot ranged from 10 μm to 359 μm, depending on measurement condition (e.g., loaded or unloaded, quasistatic or dynamic motion, centralized movements or extremes of travel, maximum value, or root-mean-square, and x-, y- or z-axis motion). Algorithms and methods for controlling specimen interactions with the robot (with and without muscle forces) to duplicate physiological loading of the joints through iterative pseudo-fuzzy logic and real-time hybrid control are described. Results from the tests of the musculoskeletal simulator have demonstrated that the speed and accuracy of the components, the synchronization timing, the force and position control methods, and the system software can adequately replicate the biomechanics of human motion required to conduct meaningful cadaveric joint investigations.
Multiplane Loading of the Extensor Mechanism Alters the Patellar Ligament Force/Quadriceps Force Ratio
Authors: Powers Christopher M. , Chen Yu-Jen , Scher Irving S. , Lee Thay Q.
Published: April 2010

Since the direction of the quadriceps force and location of the patellofemoral contact point likely differ between axial and multiplane loadings, the force and moment balance solutions for a multiplane loading condition may not yield the same patella ligament force/quadriceps force ratio (FPL/FQ ratio) when compared with an axial loading condition. The purpose of this study was to compare the effects of an axial loading condition and an anatomical, multiplane loading condition on the FPL/FQ ratio at various knee flexion angles. Ten cadaver knees were used in this investigation. Each was mounted on a custom jig that was fixed to an Instron frame. Quadriceps muscle loads were applied with same resultant force magnitudes under two force directions, as follows: (1) axial loading (central quadriceps tendon loading parallel to the femoral axis), and (2) an anatomically based, multiplane loading condition (individual vasti loaded, taking into consideration physiologic muscle fiber orientation). Patellar ligament tension was measured using a buckle transducer. The patellar ligament force/quadriceps force ratio (FPL/FQ ratio) was calculated for both loading conditions at 0 deg, 20 deg, 40 deg, and 60 deg of knee flexion. Across the range of knee motion evaluated, the FPL/FQ ratio for the axial loading condition was significantly greater than the FPL/FQ ratio for the multiplane loading condition. Our results suggest that loading orientation affects the transfer of forces from the quadriceps tendon to the patellar ligament.
Repair of Periprosthetic Pelvis Defects With Porous Metal Implants: A Finite Element Study
Authors: Levine Danny L. , Dharia Mehul A. , Siggelkow Eik , Crowninshield Roy D. , Degroff Dale A. , Wentz Douglas H.
Published: April 2010

Periacetabular osteolysis is a potentially difficult surgical challenge, which can often drive the choice of reconstruction methods used in revision hip replacement. For smaller defects, impaction of bone grafts may be sufficient, but larger defects can require filler materials that provide structural support in addition to filling a void. This study utilized finite element analysis (FEA) to examine the state of stress in periprosthetic pelvic bone when subjected to a stair-climbing load and in the presence of two simulated defects, to show the effect of implanting a defect repair implant fabricated from Trabecular Metal™. Even a small medial bone defect showed a local stress elevation of 4× compared with that seen with an acetabular implant supported by intact periacetabular bone. Local bone stress was much greater (8× the baseline level) for a defect case in which the loss of bone superior to the acetabular implant permitted significant migration. FEA results showed that a repair of the small defect with a Trabecular Metal™ restrictor lowered periprosthetic bone stress to a level comparable to that in the case of a primary implant. For the larger defect case, the use of a Trabecular Metal™ augment provides structural stabilization and helps to restore the THR head center. However, stress in the adjacent periprosthetic bone is lower than that observed in the defect-free acetabulum. In the augment case, the load path between the femoral head and the pelvis now passes through the augment as the superior rim of the acetabulum has been replaced. Contact-induced stress in the augment is similar in magnitude to that seen in the superior rim of the baseline case, although the stress pattern in the augment is noticeably different from that in intact bone.
Flow Field Analysis in Expanding Healthy and Emphysematous Alveolar Models Using Particle Image Velocimetry
Authors: Oakes Jessica M. , Day Steven , Weinstein Steven J. , Robinson Risa J.
Published: April 2010

Particulates that deposit in the acinus region of the lung have the potential to migrate through the alveolar wall and into the blood stream. However, the fluid mechanics governing particle transport to the alveolar wall are not well understood. Many physiological conditions are suspected to influence particle deposition including morphometry of the acinus, expansion and contraction of the alveolar walls, lung heterogeneities, and breathing patterns. Some studies suggest that the recirculation zones trap aerosol particles and enhance particle deposition by increasing their residence time in the region. However, particle trapping could also hinder aerosol particle deposition by moving the aerosol particle further from the wall. Studies that suggest such flow behavior have not been completed on realistic, nonsymmetric, three-dimensional, expanding alveolated geometry using realistic breathing curves. Furthermore, little attention has been paid to emphysemic geometries and how pathophysiological alterations effect deposition. In this study, fluid flow was examined in three-dimensional, expanding, healthy, and emphysemic alveolar sac model geometries using particle image velocimetry under realistic breathing conditions. Penetration depth of the tidal air was determined from the experimental fluid pathlines. Aerosol particle deposition was estimated by simple superposition of Brownian diffusion and sedimentation on the convected particle displacement for particles diameters of 100–750 nm. This study (1) confirmed that recirculation does not exist in the most distal alveolar regions of the lung under normal breathing conditions, (2) concluded that air entering the alveolar sac is convected closer to the alveolar wall in healthy compared with emphysematous lungs, and (3) demonstrated that particle deposition is smaller in emphysematous compared with healthy lungs.
A Triphasic Orthotropic Laminate Model for Cartilage Curling Behavior: Fixed Charge Density Versus Mechanical Properties Inhomogeneity
Authors: Wan Leo Q. , Guo X. Edward , Mow Van C.
Published: April 2010

Osmotic pressure and associated residual stresses play important roles in cartilage development and biomechanical function. The curling behavior of articular cartilage was believed to be the combination of results from the osmotic pressure derived from fixed negative charges on proteoglycans and the structural and compositional and material property inhomogeneities within the tissue. In the present study, the in vitro swelling and curling behaviors of thin strips of cartilage were analyzed with a new structural model using the triphasic mixture theory with a collagen-proteoglycan solid matrix composed of a three-layered laminate with each layer possessing a distinct set of orthotropic properties. A conewise linear elastic matrix was also incorporated to account for the well-known tension-compression nonlinearity of the tissue. This model can account, for the first time, for the swelling-induced curvatures found in published experimental results on excised cartilage samples. The results suggest that for a charged-hydrated soft tissue, such as articular cartilage, the balance of proteoglycan swelling and the collagen restraining within the solid matrix is the origin of the in situ residual stress, and that the layered collagen ultrastructure, e.g., relatively dense and with high stiffness at the articular surface, play the dominate role in determining curling behaviors of such tissues.
Boundary-Condition-Independent Reduced-Order Modeling of Heat Transfer in Complex Objects by POD-Galerkin Methodology: 1D Case Study
Authors: Raghupathy Arun P. , Ghia Urmila , Ghia Karman , Maltz William
Published: April 2010

This technical note presents an introduction to boundary-condition-independent reduced-order modeling of complex electronic components using the proper orthogonal decomposition (POD)-Galerkin approach. The current work focuses on how the POD methodology can be used along with the finite volume method to generate reduced-order models that are independent of their boundary conditions. The proposed methodology is demonstrated for the transient 1D heat equation, and preliminary results are presented.
Combined Effects of Joule Heating and Viscous Dissipation on Magnetohydrodynamic Flow Past a Permeable, Stretching Surface With Free Convection and Radiative Heat Transfer
Authors: Chen Chien-Hsin
Published: April 2010

The combined effects of Joule heating and viscous dissipation on the momentum and thermal transport are studied for the Magnetohydrodynamic (MHD) flow over a stretching sheet. Effects of free convection, thermal radiation, and surface suction/blowing on the flow and heat transfer characteristics are also examined. Results demonstrate that the reduction in heat transfer due to Joule and viscous heating is more pronounced at a higher Prandtl number. The Eckert number changes appreciably the velocity profile as the buoyancy effect becomes significant, while the Eckert number has an unimpressive effect on the velocity when the free convection is week. Increasing the radiation parameter will increase the temperature profile noticeably, and thus reduce the heat transfer rate accordingly. The heat transfer is enhanced markedly by imposing surface fluid suction, while the opposite trend is observed for blowing.
Effect of Pin Density on Heat-Mass Transfer and Fluid Flow at Low Reynolds Numbers in Minichannels
Authors: Selvarasu N. K. C. , Tafti Danesh K. , Blackwell Neal E.
Published: April 2010

Previous investigations on the performance of straight pins, pins with tip clearance, and profiled fins showed that closely packed cylindrical pin fins are very competitive with the modified pins. Therefore, the objective of this paper is to investigate the effect of pin density on performance. Steady/time-dependent calculations are performed to investigate the effect of pin density on friction and heat transfer. Pins packed at distances of SD=1.1, 1.2, 1.3, 1.4, 1.5, 2.0, 2.5, and 3 pin diameters (D) are investigated for 10≤ReD≤600. Two performance measures are used to compare the different pin fin densities. The first measure is to maximize heat transfer capacity for a given pumping power compared with a plane channel. The second measure used is based on entropy generation minimization (EGM), where the objective is to reduce the total irreversibility of the pin fin array to obtain an optimal spacing. Based on the performance measure of maximizing heat capacity, it is shown that for plain channels operating in the laminar range using denser pin packing has distinct advantages with SD=1.1 providing the best augmentation. However, the augmentation in heat capacity becomes relatively independent of the pin density for a channel operating in the turbulent regime. Based on the EGM method, at ReD>200, SD=1.3, 1.4, and 1.5 are the most suitable, with the least entropy generation observed at SD=1.4. At ReD<200, SD=1.1, 1.2, and 1.3 are also suitable for keeping entropy generation low.
Heat and Mass Transfer on the Unsteady Magnetohydrodynamic Flow Due to a Porous Rotating Disk Subject to a Uniform Outer Radial Flow
Authors: Turkyilmazoglu Mustafa
Published: April 2010

An unsteady flow and heat transfer of an incompressible electrically conducting fluid over a porous rotating infinite disk impulsively set into motion are studied in the present paper. The disk finds itself subjected to a uniform normal magnetic field. The particular interest lies in searching for the effects of an imposed uniform outer radial flow far above the disk on the behavior of the physical flow. The governing Navier–Stokes and Maxwell equations of the hydromagnetic fluid, together with the energy equation, are converted into self-similar forms using suitable similarity transformations. A compact, unconditionally stable, and highly accurate implicit spectral numerical integration algorithm is then employed in order to resolve the transient behavior of the velocity and temperature fields. The time evolution and steady state case of some parameters of fundamental physical significance such as the surface shear stresses in the radial and tangential directions and the heat transfer rate are also fully examined for the entire family of magnetic interaction, radial flow, and suction/blowing parameters.
Heat Transfer Augmentation of Parallel Flows by Means of Electric Conduction Phenomenon in Macro- and Microscales
Authors: Yazdani Miad , Seyed-Yagoobi Jamal
Published: April 2010

Electrohydrodynamic conduction phenomenon takes advantage of the electrical Coulomb force exerted on a dielectric liquid generated by externally applied electric field and dissociated charges from electrolytes. The electric conduction phenomenon can be applied to enhance or control mass transport and heat transfer in both terrestrial and microgravity environments with advantages of simplicity and no degradation of fluid properties for isothermal as well as nonisothermal liquids. This paper numerically studies the heat transfer augmentation of externally driven macro- and microscale parallel flows by means of electric conduction phenomenon. The electric conduction is generated via electrode pairs embedded against the channel wall to mainly enhance the heat transfer and not necessarily to pump the liquid. Two cases of Poiseuille and Couette parallel flows are considered where for the former, a constant external pressure gradient is applied along the channel and for the latter, the channel wall moves with a constant velocity. The electric field and electric body force distributions along with the resultant velocity fields are presented. The heat transfer enhancements are illustrated under various operating conditions for both macro- and microscales.
Field emission microscopy of Al-deposited carbon nanotubes: Emission stability improvement and image of an Al atom cluster
Authors: Saito Yahachi , Matsukawa Tomohiro , Asaka Koji , Nakahara Hitoshi
Published: April 2010

Aluminum (Al) was deposited on multiwall carbon nanotubes (MWNTs) with mean thicknesses ranging from 1to11nm in vacuum, and the influence of deposited Al on field electron emission was investigated by field emission microscopy (FEM). Al deposition significantly suppressed the fluctuations of emission current after a simple conditioning process. Interestingly, FEM images revealing the atomic detail of an Al cluster with the cubo-octahedron structure were observed. The discussion on the spatial resolution in FEM for MWNTs suggests the probable observation of some atomic structures with a resolution of the order of 0.3nm.
Revealing real images of cloverleaf pattern emission sites by using field ion microscopy
Authors: Neo Yoichiro , Matsumoto Takahiro , Tomita Makoto , Sasaki Masahiro , Aoki Toru , Mimura Hidenori
Published: April 2010

The authors have attempted to reveal the origins of the characteristic cloverleaf patterns that often emerge in field emission microscopy studies from various organic materials. These phenomena were first reported by Müller [Z. Naturforsch. 59a, 473 (1950)], and many theories for their propagation have been proposed. However, their formation mechanism is still not completely understood because “real” images of the emission sites where the patterns are formed still remain unclear. In this article, the authors describe how images of the emission sites can be clarified by using field ion microscopy. Pentacene, copper phthalocyanine, and graphite nanoneedles were adopted as promising materials that might develop cloverleaf patterns. The results clarified that the emission sites were also cloverleaf shaped, including two- and four-lobed patterns. Important information revealing how the cloverleaf patterns are formed is presented in this article.
Nanosmoothing of single crystal diamond chips by 1 keV Ar+ ion bombardment
Authors: Nagase Takashi , Kato Hiroyuki , Pahlovy S. A. , Miyamoto Iwao
Published: April 2010

In this article the authors have studied the smoothing of diamond chips by irradiating them with 1 keV Ar ion beam at ion incident angles of 0°, 30°, 45°, 60°, and 80° with ion doses from 3.4×1018 to 6.8×1018 ions/cm2. They found that using ion dose of 6.8×1018 ions/cm2 at incident angles from 0° to 45°, the unprocessed surface (rms=0.14–1.2 nm) turned into ultrasmooth processed surface (rms=0.1 nm). Their results also confirmed the formation of ripples on diamond surface when the surface was irradiated with 1 keV Ar+ ion at incident angles of 60°–80°. They have also discussed the mechanism of smoothing and roughening of the surface by employing Bradley and Harper model and equations. These studies led to the understanding of the role of induced viscous flow in the smoothing process. Therefore, by choosing right conditions, 1.0 keV Ar+ ion beam machining can be employed to make diamond tools with nanofinished surface without any ripple effect.
Early stages of direct L10 FePt nanocluster formation: The effects of plasma characteristics
Authors: Patterson M. M. , Cochran A. , Ferina J. , Rui X. , Zimmerman T. A. , Sun Z. , Kramer M. J. , Sellmyer D. J. , Shield J. E.
Published: April 2010

The formation of FePt nanoclusters via gas condensation has attracted a great deal of attention. The clusters normally form with the magnetically soft A1 structure rather than the desired L10 structure with high magnetocrystalline anisotropy. This work has examined the effects of plasma characteristics on the early stages of order in the formation L10 FePt nanoclusters via inert gas condensation. The plasma characteristics have been modified to control ion density in the nanocluster condensation region. Increased ion density results in more cluster-ion collisions. The energy imparted to the clusters as a result of these collisions allows atomic rearrangements to form the ordered structure. The results indicate that controlled ion density directly impacts the early stages of FePt nanocluster ordering, according to high-resolution electron microscopy structure observations and coercivity measurements.