Plateau Shape Research Articles

Dielectric relaxation of PVC/PMMA/NiO blends as a function of DC bias

We have prepared poly vinyl chloride (PVC)/poly-methyl methacrylate (PMMA) blend with loading of Nickel oxide (NiO) by solution cast technique. X-ray diffraction reveals the interaction between NiO, PVC and PMMA in the blend form. The weak interaction between PVC, PMMA and NiO was confirmed by Fourier transform infrared spectroscopy. The miscibility of PVC and PMMA has been confirmed by differential scanning calorimetry. The results demonstrate that the 2 wt% NiO loaded PVC/PMMA blend exhibits lowest crystallinity which leads to better NiO dispersion, also observed by atomic force microscopy and scanning electron microscopy. The performance of electrical properties were evaluated under wide band of frequency (10–107 Hz) as a function of DC bias voltage (0–25 V). The dielectric property was characterized via electrical modulus formalism. The present blend systems show good dielectric property as well as considerable conductivity which differs by frequency and DC bias. The variation of AC conductivity as a function of frequency and DC bias shows plateau shape at higher frequency which obeys Jonscher’s power law. It demonstrates that the AC electrical conductivity is directly proportional to the applied DC bias potential. It may be developed for electrolyte application.

Numerical modelling of open-cell metal foam with Kelvin cell

The paper presents an investigation study of the mechanical properties of metal foam. In this investigation, a numerical simulation by finite element method is used. For this purpose, the foam structure is modelled by a regular network of Kelvin cells. In these cells, the strands are modelled as a three-dimensional (3D) finite element beam. In particular, we consider four types of strands cross sections: (1) circular (2) square (3) triangular and (4) Plateau shape. Our numerical results are in agreement with the experimental results obtained on a real Nickel metallic foam. In addition, we perform a parametric analysis to study the effect of some geometrical characteristics on the elasticity of a metal foam. Among these geometrical characteristics, we consider the shape and dimensions of strands cross section as well as the inertia variation.

Basis for the Induction of Tissue-Level Phase-2 Reentry as a Repolarization Disorder in the Brugada Syndrome.

Aims. Human action potentials in the Brugada syndrome have been characterized by delayed or even complete loss of dome formation, especially in the right ventricular epicardial layers. Such a repolarization pattern is believed to trigger phase-2 reentry (P2R); however, little is known about the conditions necessary for its initiation. This study aims to determine the specific mechanisms that facilitate P2R induction in Brugada-affected cardiac tissue in humans. Methods. Ionic models for Brugada syndrome in human epicardial cells were developed and used to study the induction of P2R in cables, sheets, and a three-dimensional model of the right ventricular free wall. Results. In one-dimensional cables, P2R can be induced by adjoining lost-dome and delayed-dome regions, as mediated by tissue excitability and transmembrane voltage profiles, and reduced coupling facilitates its induction. In two and three dimensions, sustained reentry can arise when three regions (delayed-dome, lost-dome, and normal epicardium) are present. Conclusions. Not only does P2R induction by Brugada syndrome require regions of action potential with delayed-dome and lost-dome, but in order to generate a sustained reentry from a triggered waveback multiple factors are necessary, including heterogeneity in action potential distribution, tissue coupling, direction of stimulation, the shape of the late plateau, the duration of lost-dome action potentials, and recovery of tissue excitability, which is predominantly modulated by tissue coupling.

Influence of the Cavity Length on the Behavior of Hybrid Fixed-Point Cells Constructed at INRIM

Hybrid cells with double carbon/carbon sheets are used at the Istituto Nazionale di Ricerca Metrologica (INRIM) for the realization of both pure metal fixed points and high-temperature metal–carbon eutectic points. Cells for the Cu and Co–C fixed points have been prepared to be used in the high-temperature fixed-point project of the Comite Consultatif de Thermometrie. The results of the evaluation processes were not completely satisfactory for the INRIM cells because of their low transition temperatures with respect to the best cells, and of a rather large melting range for the Co–C cell. A new design of the cells was devised, and considerable improvements were achieved with respect to the transition temperature, and the plateau shape and duration. As for the Cu point, the duration of the freezing plateaux increased by more than 50 % and the freezing temperature increased by 18 mK. As for the Co–C point, the melting temperature, expressed in terms of the point of inflection of the melting curve, increased by about 70 mK. The melting range of the plateaux, expressed as a difference \((T_{\mathrm{liquidus}} - T_{\mathrm{solid}})\) was reduced from about 180 mK to about 130 mK, with melting times \((t_{\mathrm{liquidus}} - t_{\mathrm{solid}})\) increased by about 50 %, as a consequence of an improvement of flatness and run-off of the plateaux.

The influence of tibial morphology on the design of an anatomical tibial baseplate for TKA

BackgroundFinding the right balance between tibial coverage and minimal implant overhang is an important factor in TKA. Another significant cause of failure is component malrotation. MethodsAn average master shape of the proximal tibia at TKA resection level was calculated using fine slice computed tomographies of 117 cadaveric knees. To find out whether alternate implant contours would be necessary depending on the patient's body size, we established five subgroups to compare. CAD-Analysis was performed to simulate the overhang produced after ±4°/±7°/±10° rotation. ResultsA master shape for the tibial resection cut (with a 5° posterior slope, 7mm under lateral joint line) could be determined. Neither left vs. right knee joint, nor male vs. female nor the size subdivision appears to alter the calculated master shape significantly. The optimized shape allowing for ±4° of rotational freedom was found to be the best variant. ConclusionsValid methods have been obtained to design a two-dimensional average shape of the tibial plateau. The modifications described in this study might come in useful, when designing future implant designs. Clinical relevanceAn optimized fit at the tibial plateau and lower rates of component malrotation may result in better outcomes after TKA.

Dependence of Harmonic Spectrum Shape on Laser Beam Intensity in Interaction With Atoms

We present a method to calculate the harmonic spectrum of the radiation emitted at the interactions between intense laser beams and atoms. Our relations describe accurately, in good agreement with the experiment, important features of the harmonic spectrum and the evolution of its shape with the increase of the laser beam intensity. More specifically, for low intensities, of the order of $10^{13}~{\rm W}/{\rm cm}^{2}$ , the spectrum has the well-known plateau shape, after which follows a sharp decrease at the cutoff edge. When the beam intensity is increased, toward $10^{15}~{\rm W}/{\rm cm}^{2}$ , the slope of the plateau increases, corresponding to a decrease by one or two orders of magnitude of the harmonic intensities. When the beam intensity is increased more, toward $10^{17}~{\rm W}/{\rm cm}^{2}$ , there is a maximum at the left edge of the spectrum, which is followed by a strong decrease of many orders of magnitude, and the spectrum concentrates in a very limited domain, under a certain frequency, far lower than the theoretical cutoff frequency. These theoretical results are in good agreement with numerous experimental data from the literature, for many atoms and ions, and for a large spectrum of intensities of laser beams. This result has important implications in the emerging field of generation of high intensity hard X-rays.

Development and investigation of WC–C fixed-point cells

Three cells of the WC–C peritectic fixed point with a temperature of about 3021 K were built and investigated. Two different sources of tungsten with nominal purities of 5N and 3N were used, and two different filling techniques were applied. There was no difference in plateau shapes between the cells. The 3N purity cell showed a small difference (0.22 K) in the melting temperature from the 5N cell, which indicates significant purification of initially contaminated tungsten. The typical melting range and repeatability of the observed peritectic melting plateaux were 100 mK and 15 mK, respectively. The melting point was stable and reproducible within 25 mK per two weeks. T90 temperature of the WC–C melting point was found to be (2747.6 ± 1.1) °C (k = 2). The observed freezing plateaux were flat and repeatable within 50 mK and 15 mK, respectively. The WC1−x–WC eutectic transition showed a melting temperature about 29 K lower than the peritectic one with a repeatability of about 0.2 K. The problem of deep supercooling is discussed and a method for its solution is shown and tested.

Paper # 277: Biomechanical Consequence of Posterior Medial Meniscal Root Tears with Subsequent Repair Using a Physiologic Loading Model

A physiologic load, simulating a knee squat and a pressure sensitive, capacitive, electronic sensor were used to investigate the biomechanical consequence of a meniscal root tear, subsequent repair and total meniscectomy. Posterior root tears of the medial meniscus cause a detachment of the meniscus at its insertion onto the posterior tibial plateau. Recent literature has identified these tears as common and clinically significant entities associated with meniscal extrusion and the development of degenerative arthritis. Recent studies demonstrated that meniscal root tears are biomechanically equivalent to total meniscectomy in axial load models, while these same studies also report that repair of the meniscal root corrects compartment loading (Marzo, 2008; Allaire et. al. 2008). The current study investigates the effect of posterior medial meniscal root tears on medial compartment loading using a physiologic model that recreates a knee squat. An all arthroscopic meniscal root repair technique which uses a retrograde reaming device (FlipCutterTM, Arthrex, Naples, FL, USA) to create a blind socket at the tibial insertion into which the meniscal root is advanced, recreating the tibial attachment, was then performed to repair the posterior root tear(Nicholas et al 2009). The knees were then similarly loaded after root repair and subsequent total meniscectomy, examining their effect on medial compartment loading. Nine fresh-frozen cadaver knees were dissected of soft tissue to the joint capsule while preserving the insertion and entire length of the quadriceps and hamstring tendons. Knee moments during squatting were simulated in a custom testing jig by application of angle specific loads to the quadriceps and hamstring tendons (based on body mass) with an axial compressive load at the tibia used to flex the knee to the desired angle (simulating the ground reaction force). Anterior and posterior, submeniscal arthrotomies were made allowing for passage of a pressure sensitive, capacitive, electronic sensor, custom made to approximate the medial tibial plateau shape and surface area. This sensor measures both contact area and peak pressures. Each specimen was then tested in four conditions: medial meniscus intact, after creation of posterior root tear, after repair of the meniscal root, and after total medial meniscectomy. Each condition was tested at 15, 45 and 90 degrees of knee flexion. Transection of the meniscal root significantly decreased the contact area of the medial compartment by 13% (p=0.002). After meniscal root repair, contact area was not significantly different from the intact meniscal state (decreased 6%, p=0.302). Additionally, total meniscectomy reduced contact area by 53% (p=0.025). Root transection also resulted in an overall increase in peak contact pressure of 21% (p=0.167) in the medial compartment. Meniscal root repair showed no difference when compared to the intact meniscal state (increased 10% p=0.425) and total meniscectomy increased peak contact pressure by 97% at 15 degrees (p=0.015) with no significant effect at 45 or 90 degrees of knee flexion. Our study differs from previous studies in the use of a physiologic load model that recreates the loads seen in the knee during the performance of a squat rather than an axial load model using supraphysiological loads and/or non-angle specific loading. In contrast to previous reports, our results show that meniscal root tears are not equivalent to total meniscectomies. The reduction in tibiofemoral contact area with meniscal root transection was approximately 25% of that seen with total meniscectomy. The previously described meniscal root repair technique (Nicholas et al 2009) recreated normal compartment loading.

Pressure influence on crystallization kinetics during injection molding

This work presents the measurement of the temperature at the center of the cavity during the molding of PP material using an embedded thermocouple probe. The measured temperature curves show a plateau shape related to the crystallization phenomenon. Measurements, done at various pressures show an increase in the crystallization plateau temperature depending on the cavity pressure. The change in the measured crystallization temperature allows the identification of the pressure dependence on the Hoffman–Lauritzen crystallization kinetics parameters: T m and T g . The T m pressure dependence leads to a good agreement with the data of reported studies that used other experimental devices. The obtained results also show a decrease in cavity pressure duration related to the increase in the gate freezing speed as a result of the pressure increase. The identified pressure dependence laws for T m and T g introduced in the crystallization kinetics and the thermal model, allow to describe a temperature change in good agreement with the temperature measured down to the crystallization plateau.

New Method of Filling of High-Temperature Fixed-Point Cells Based on Metal-Carbon Eutectics/Peritectics

A new method of filling of high-temperature fixed-point cells based on metal-carbon eutectics and peritectics is suggested and tested. In this method a metal and carbon powder mixture is introduced not directly into the crucible, but into an additional container located just above the crucible. The mixture melts inside the container, and the already molten eutectic drops through a small hole in the bottom of the container and fills the crucible drop by drop. The method can be used to obtain a uniform ingot without porous or foundry cavities, to minimize the risk of contamination, and to avoid some other disadvantages. The method was applied to fabricate Re-C and WC-C cells using 5N purity materials. The cells demonstrated a good plateau shape with melting ranges of 0.2 K and 80 mK for Re-C and WC-C, respectively. The Re-C cell was compared with a cell built at NMIJ and showed good agreement with a difference of melting temperatures of only 45 mK.

Biomechanical Consequence of Posterior Medial Meniscal Root Tears with Subsequent Repair Using a Physiologic Loading Model (SS-32)

<h3>Introduction</h3> Posterior root tears of the medial meniscus cause a detachment of the meniscus at its insertion to the posterior tibia. These tears have been identified as clinically significant entities associated with meniscal extrusion and the development of degenerative arthritis. Recent studies demonstrated that meniscal root tears are biomechanically equivalent to total meniscectomy in axial load models, while also reporting that root repair can correct compartment loading (Marzo, 2008; Allaire et al., 2008). This study investigates the effect of posterior medial meniscal root tears on medial knee compartment loading using a physiologic model that recreates a knee squat. A meniscal root repair technique which uses a retrograde reaming device to create a socket at the tibial insertion, into which the meniscal root is advanced, recreating the tibial attachment, was then performed (Nicholas et al., 2009). The knees were then loaded after the root repair and subsequent total meniscectomy examining the effect on medial compartment loading. <h3>Methods</h3> Nine fresh-frozen cadaver knees were dissected of soft tissue to the joint capsule while preserving the insertion and entire quadriceps and hamstring tendons. Knee moments during squatting were simulated in a custom testing jig by application of angle specific loads to the quadriceps and hamstring tendons (based on body mass) with an axial compressive load at the tibia used to flex the knee to the desired angle (simulating ground reaction force). Anterior and posterior submeniscal arthrotomies allowed for passage of a pressure sensitive, capacitive, electronic sensor, made to approximate the medial tibial plateau shape and surface area. This sensor measures both contact area and peak pressures. Each specimen was then tested in four conditions: medial meniscus intact, after creation of posterior root tear, after repair of the meniscal root, and after total meniscectomy. Each condition was tested at 15, 45, and 90 degrees of knee flexion. <h3>Results</h3> Transection of the meniscal root decreased the contact area of the medial compartment by 13% (p=0.002). After meniscal root repair, contact area was not significantly different from the intact meniscal state (decreased 6%, p=0.302). Additionally, total meniscectomy reduced contact area by 53% (p=0.025). Root transection also resulted in an overall increase in peak contact pressure of 21% (p=0.167) in the medial compartment. Meniscal root repair showed no difference when compared to the intact meniscal state (increased 10%, p=0.425) and total meniscectomy increased peak contact pressure by 97% at 15 degrees (p=0.015) with no significant effect at 45 or 90 degrees of knee flexion. <h3>Conclusion</h3> Our study differs from others in the use of a physiologic load model that recreates the loads seen in the knee during the performance of a squat rather than an axial load model using supraphysiological loads and/or non-angle specific loading. In contrast to previous reports, our results show that meniscal root tears are not equivalent to total meniscectomies. The reduction in tibiofemoral contact area with meniscal root transaction was approximately 25% of that seen with total meniscectomy. The previously described meniscal root repair technique (Nicholas et al., 2009) recreated normal compartment loading.

MR-Mammografie vor und nach neoadjuvanter Systemtherapie – Enhancementcharakteristika und T 2-Signalinintensität von Mammakarzinomen und Drüsenparenchym

PURPOSE: Analysis of enhancement characteristics and T 2 signal intensity (SI) of breast cancers and normal breast parenchyma on MR imaging (MRI) before and after neoadjuvant treatment (NT) to improve the assessment of therapy response. MATERIALS AND METHODS: Retrospective data analysis of 43 consecutive patients (mean age 49.9 years) with invasive breast cancers (T2 /T3) who received NT. Evaluation of breast MRI before and after NT with assessment of therapy response according to RECIST criteria as well as calculation of the maximum initial enhancement (Enh max ), delayed enhancement (Enh post ) and T 2 SI by ROI analyses of breast cancers and breast parenchyma. Comparison of therapy response and enhancement characteristics. RESULTS: Therapy response on MRI: 16.3 % (n = 7) complete remission (CR MRT ), 53.5 % (n = 23) partial remission (PR MRT ), 27.9 % (n = 12) stable disease (SD MRT ) und 2.3 % (n = 1) progressive disease (PD MRT ). Breast cancers showed a significant decrease in Enh max and T 2 SI as well as a significant increase in Enh post after NT (p 0.05). All cases with CR MRT had wash out or plateau shape of the SI time curve before NT and showed continuous enhancement thereafter. CONCLUSION: Breast MRI shows significant changes in enhancement characteristics and T 2 SI of breast cancers after NT, whereas normal breast parenchyma remains unchanged. SI data could possibly help to improve the assessment of therapy response by MRI. Prospective trials with larger study cohorts and MRI monitoring during NT are necessary to validate these results.

MR-Mammografie vor und nach neoadjuvanter Systemtherapie – Enhancementcharakteristika und T 2-Signalinintensität von Mammakarzinomen und Drüsenparenchym

Analysis of enhancement characteristics and T 2 signal intensity (SI) of breast cancers and normal breast parenchyma on MR imaging (MRI) before and after neoadjuvant treatment (NT) to improve the assessment of therapy response. Retrospective data analysis of 43 consecutive patients (mean age 49.9 years) with invasive breast cancers (T2 /T3) who received NT. Evaluation of breast MRI before and after NT with assessment of therapy response according to RECIST criteria as well as calculation of the maximum initial enhancement (Enh (max)), delayed enhancement (Enh (post)) and T 2 SI by ROI analyses of breast cancers and breast parenchyma. Comparison of therapy response and enhancement characteristics. Therapy response on MRI: 16.3 % (n = 7) complete remission (CR (MRT)), 53.5 % (n = 23) partial remission (PR (MRT)), 27.9 % (n = 12) stable disease (SD (MRT)) und 2.3 % (n = 1) progressive disease (PD (MRT)). Breast cancers showed a significant decrease in Enh (max) and T 2 SI as well as a significant increase in Enh (post) after NT (p < 0.01). Not any SI parameter of normal breast parenchyma showed a significant change after NT (p > 0.05). All cases with CR (MRT) had wash out or plateau shape of the SI time curve before NT and showed continuous enhancement thereafter. Breast MRI shows significant changes in enhancement characteristics and T 2 SI of breast cancers after NT, whereas normal breast parenchyma remains unchanged. SI data could possibly help to improve the assessment of therapy response by MRI. Prospective trials with larger study cohorts and MRI monitoring during NT are necessary to validate these results.

Camera-based investigation of high-temperature fixed points for radiometric application

A radiance camera was used to investigate the radiation field emitted by high-temperature blackbodies and fixed-point cavities up to temperatures of 3000 K. In a first step the applicability of the camera to measure the spectral radiance at such high temperatures was investigated. In a second step the radiation characteristics of several sources were studied using the camera system, in particular, large area fixed-point blackbodies of Cu, Pt–C and ZrC–C. Especially for the ZrC–C fixed points the radiation field at the cavity opening was found to be non-uniform. This observation explains systematic differences in the plateau shape of large aperture eutectic fixed-point cells for radiometers with different fields of view. Using the two-dimensional radiance distribution measured with the camera system the deviation of the temperatures measured with interference filter radiometers and radiation thermometers was studied.

The mean anatomical shape of the tibial plateau at the knee arthroplasty resection level: An investigation using MRI

Clinical assessments after Total Knee Arthroplasty (TKA) show persisting pain after implantation in over 20% of patients. Impingement of soft tissue around the knee, due to imprecise geometry of the tibial implant, can be one reason for persisting ailment. Two hundred and thirty seven MRI scans were evaluated using an active contour detection algorithm (snake) to obtain a high-resolution mean anatomical shape of the tibial plateau. Differences between female and male, older and younger (≤ 40/> 40) and left and right averaged shapes were determined. The shapes obtained were asymmetric throughout. Absolute differences between the subgroups fell short of inter-individual variations represented by calculated one- σ confidence intervals. Our results indicate that a differentiation in TKA tibial plateau design by gender, age, or side is of minor relevance.

Improvement of crunchiness of battered fish nuggets

In this study, two strategies to improve the crunchiness of fish nuggets for microwave final cooking were employed: addition of dextrin into batter formulation, and using a package containing a susceptor material, which improves heat transmission and increases the temperatures reached in the microwave. In this work, two dextrins (one of high solubility and other of medium solubility) were used to study their effect in battered, prefried fish nuggets, finally cooked by three different procedures: deep frying, microwaving and microwaving with susceptor packaging. In addition, all tests were performed with and without batters containing methylcellulose in order to assess the effect of oil uptake. The crunchiness of fish nuggets was evaluated by a recently developed method which simultaneously registered texture and sound measurements during the cutting of the nuggets. The profiles of the fried nuggets had numerous force and sound peaks and a typical jagged plateau shape, whereas those of the microwaved samples had force peaks that disappeared and the profiles adopted a smooth ascending curve. However, the use of the susceptor slightly improved the number of sound peaks. In addition, sensory crunchiness and other sensory attributes were measured by a trained panel. When the dextrins-containing nuggets were cooked by microwave and susceptor, they were perceived as crunchier as and oilier than the other samples.

Demagnetization of crust by magmatic intrusion near the Arsia Mons volcano: Magnetic and thermal implications for the development of the Tharsis province, Mars

A sharp crustal magnetic field contrast of almost two orders of magnitude at 185 km altitude, as determined by electron reflection (ER) magnetometry, exists between the nonmagnetic bulk of the Tharsis province and its relatively strongly magnetized southwestern region. The 3 nT magnetic field contour passes west of Ulysses Patera, south of Arsia Mons, through Thaumasia Planum and appears largely unmodified by impact craters, suggesting a post-Noachian origin. This sharp magnetic boundary is most easily explained by thermal demagnetization caused by pervasive magmatic intrusion throughout the upper crust on its nonmagnetic side. Using a best guess range of assumptions, we model these intrusions and their demagnetizing effects on preexisting crustal magnetization distributions and fit the resulting model magnetic field magnitudes to ER magnetic profiles across the boundary. Within the framework of our assumptions, we find that the magmatic boundary may not be as sharp as its magnetic counterpart, extending over 0–600 km, and that a minimum of ∼ 10–35 km average accumulated thickness of intrusions are required to completely demagnetize the crust on the northeast side of the boundary. The best-fit modeled intrusions extend horizontally between ∼ 120 km and 220 km beyond the magnetic boundary to the southwest for most of its length, with the inferred intrusion thickness and penetration distance being larger for minerals with higher magnetic blocking temperatures (magnetite vs. pyrrhotite). Such thicknesses of intrusion are consistent with magma production rates similar to those at Hawaii, if we allow accumulation over 0.1 to 1 Ga. If the volume of intrusion is representative of most of Tharsis, these thicknesses imply average intrusive–extrusive ratios higher than previously estimated, and in closer agreement with previous magma production estimates based on heat flow. Mapped fields of late Amazonian small volcanic vents, with diverse morphologies and a wide spatial distribution, may represent the latest stages of volcanism and record some of the polybaric processes that likely have occurred as magma intruded multiple levels of the crust. Also, intrusions are inferred to extend beneath most of the length of the upper southwest rift apron of Arsia Mons, implying that localized extrusion may be responsible, along with volcanism from the rift zone, for the apron's plateau shape. Lastly, within our model, the maximum pre-intrusion lateral magnetization coherence scale in this region is found to be less than ∼ 200 km.

Uroflow Findings in Older Boys with Tubularized Incised-Plate Urethroplasty

Aim: To analyze uroflow findings in older boys with tubularized incised-plate urethroplasty (TIPU). Materials and Methods: 79 toilet-trained patients who had TIPU were evaluated by studying their voiding history, a physical examination, suprapubic ultrasound and uroflowmetry, both pre- and postoperatively. The obstructive urinary flow pattern (OUFP) was accepted as low maximum urinary flow rate with plateau, staccato or intermittent shape. Results: The mean age was 7 years (range 5–11). The mean follow-up was 30 months (range 6–36). Of the 79 patients, 70 recovered. A permanent OUFP was found in 10 of 63 patients, as follows: 7 were detected in the 6th month after operation, and 1 each in the 9th, 18th and 36th months.Ten patients had no voiding abnormality and significant residual urine. The mean interval from initial surgery to presentation with an OUFP was 10.5 months. Conclusions: An occult urethral obstruction develops in some asymptomatic children with TIPU and commonly occurrs in the first year after operation.

Lateral versus medial tibial plateau: morphometric analysis and adaptability with current tibial component design

The purpose of this study was to analyze the in vivo dimensions of each tibial plateau for planning of unicompartmental knee arthroplasty (UKA), and to compare the morphometric data to the dimensions of nine current designs of UKA tibial components. Thirty-seven knees (31 females and 6 males) operated on with UKA were studied. All patients were examined postoperatively using computed tomography (CT). There were 18 lateral and 19 medial UKAs. On the CT scan, each operated tibial plateau was measured in the transverse plane at the resection level, just below the full polyethylene tibial component. We measured the length of the anteroposterior (AP) cut as well as the maximal mediolateral dimension of the resected plateau (perpendicular to the AP cut). We compared the measurements with nine current UKA systems: Accuris (Smith and Nephew), Advance (Wright Medical), HLS Uni Evolution (Tornier), Miller-Galante and "ZUK" (Zimmer), Oxford and Oxford alpha (Biomet), Preservation (DePuy) and Unix (Stryker). There was good correlation between patient height and mediolateral dimension (r=0.6), and between patient height and area of total tibial plateau (r=0.7). The anteroposterior dimension was greater for the medial plateau (mean 50.8 mm, SD 3.3) than for the lateral plateau (mean 47.2 mm, SD 3.3). This difference was statistically significant (P=0.0016). Some UKA implants are designed with an asymmetric femoral component, but none have an asymmetric tibial component. The present study suggests, however, that the shape of the medial tibial plateau differs from that of the lateral plateau. This difference can lead to mediolateral overhang for medial UKA, if the surgeon aims for optimal anteroposterior coverage.

Thermal Effects in the HTBB-3200pg Furnace on Metal-Carbon Eutectic Point Implementation

The general statement that a temperature fixed-point cell will show better melting and freezing plateaux with better temperature uniformity along the dimensions of the fixed point is understood to be valid for metal-carbon (M-C) eutectics as well as for pure metal fixed points. In this article, it is shown that improved temperature uniformity in the central part of the high-temperature blackbody BB3200pg (HTBB), where the M-C fixed point is implemented, results in flatter and longer plateaux. Pyrolitic graphite rings, clamped together by a spring, form the heated cavity of the HTBB. As a first step, the relative electrical resistivity of each pyrolitic graphite ring was measured using a method advised by the furnace manufacturer. Next, the ring positions were optimized, taking into account their relative resistivities, in order to obtain a more homogeneous temperature distribution. Subsequent measurement of the temperature uniformity at the furnace walls confirmed the improvement. Measuring the melting plateaux of the Pt-C eutectic with different arrangements of the rings, and thereby operating the fixed-point cell in different temperature distributions, confirmed the influence of the temperature distribution on the plateau shape, with the best plateau shape corresponding to the most homogeneous temperature distribution.