Axis Placement Research Articles

Design of Gearings from Involute-Bevel Gears

The article presents formulas for determining the dimensions of involute-bevel gears and the gearings composed of them. It examines the most general cases of gearings formation, consisting of two involute-bevel gears with crossing axes (hyperboloid gearings), with intersecting axes (bevel gearings), and with parallel axes (cylindrical gearings). Gearings composed of involute-bevel gears have design, technological, and operational advantages compared to gearings composed of conventional cylindrical and bevel gears. The use of involute-bevel gearings with crossing axes allows for achieving the required contact character of the teeth from localized contact to linear contact, reducing sensitivity to manufacturing and assembly errors, and increasing the load capacity of the gearing compared to helical gearings from cylindrical gears. Bevel gearings with involute-bevel gears allow for the creation of gearings with any desired small shaft angles, which is difficult to achieve with conventional bevel gears. The use of internal meshing bevel gearings with modified tooth profiles in planetary reducers allows for gearings comparable to harmonic drives in terms of power and kinematic characteristics, but with a higher operational life. The use of involute-bevel gears in cylindrical gearings improves the smoothness of the mechanism and allows for adjusting the center distance and backlash in the meshing, making them suitable for backlash-free drives. By combining the taper angles of the gears and the inclination of the teeth, it is possible to create a one-way rotation mechanism - a freewheel mechanism. Modern CAD systems do not take into account the geometry features of gearings composed of involute-bevel gears, which limits their application in technology. The article proposes an algorithm for calculating the main geometric parameters of gearings composed of involute-bevel gears with arbitrary axis placement in space. Examples of geometric calculations of various types of gearings based on the proposed algorithm are provided.

Comprehensive performance analysis of CST-PV system based on spectral beam splitting film

Abstract In this paper, a novel linear Fresnel concentrator (LFC) with a rotating platform was constructed, and a novel concentrated solar thermal and photovoltaic (CST-PV) hybrid system utilizing spectral beam splitting was established on the LFC. A spectral beam-splitting film (SBSF) was coated on the PV cell’s inner glass wall, replacing the LFC’s primary reflector. The SBSF can transmit the solar spectrum of 300-1100 nm to the photovoltaic (PV) cells and reflect the remaining solar wavelengths to the absorber to generate heat. The LFC’s cosine efficiency and end efficiency after azimuthal compensation by a rotating platform were calculated through theoretical analysis. The effects of temperature on the efficiency of PV and linear Fresnel solar systems were studied through experimental and numerical simulations. The comprehensive utilization efficiency evaluation method was established. The results show that the LFC’s end efficiency and cosine efficiency in this paper, after azimuthal compensation, increased by 31.7% and 33.7%, respectively, compared with the east-west and north-south axis placement. The comprehensive utilization efficiency of the CST-PV system based on SBS is 61.58%, which increased by 13.47% compared to that of the single fixed PV system.

Detection of a Rotating Conveyor Roller Casing Vibrations on a Laboratory Machine

The article describes the basic parts and the overall design of the laboratory machine, which can be used to measure vibrations generated by a rotating conveyor roller attached to the flattened parts of its axis in the cut-outs of the conveyor idler support. On the structurally modified support of the conveyor idler consisting of the insertion of a plastic element placed between the roller axis and the support cut-out, the vibration acceleration values of the rotating roller from symmetric analysis were measured and compared with the values from asymmetric analysis of the traditional roller axis placement in the steel support. The size of the peripheral speed of the roller was determined, during the experimental measurements, by controlling the speed of the electric motor using a frequency converter. The obtained results of the measured values of vibration velocities in three mutually perpendicular planes showed a reduction in vibration values of about 15% when using plastic holders. The paper aims to present one of the possible technical solutions that can limit the vibration values transmitted to the supporting structure of the conveyor belt, generated by the rotating casing of the conveyor roller.

On a model-based approach to improve intranasal spray targeting for respiratory viral infections

The nasopharynx, at the back of the nose, constitutes the dominant initial viral infection trigger zone along the upper respiratory tract. However, as per the standard recommended usage protocol (“Current Use”, or CU) for intranasal sprays, the nozzle should enter the nose almost vertically, resulting in sub-optimal nasopharyngeal drug deposition. Through the Large Eddy Simulation technique, this study has replicated airflow under standard breathing conditions with 15 and 30 L/min inhalation rates, passing through medical scan-based anatomically accurate human airway cavities. The small-scale airflow fluctuations were resolved through use of a sub-grid scale Kinetic Energy Transport Model. Intranasally sprayed droplet trajectories for different spray axis placement and orientation conditions were subsequently tracked via Lagrangian-based inert discrete phase simulations against the ambient inhaled airflow field. Finally, this study verified the computational projections for the upper airway drug deposition trends against representative physical experiments on sprayed delivery performed in a 3D-printed anatomic replica. The model-based exercise has revealed a new “Improved Use” (or, IU) spray usage protocol for viral infections. It entails pointing the spray bottle at a shallower angle (with an almost horizontal placement at the nostril), aiming slightly toward the cheeks. From the conically injected spray droplet simulations, we have summarily derived the following inferences: (a) droplets sized between 7–17 μm are relatively more efficient at directly reaching the nasopharynx via inhaled transport; and (b) with realistic droplet size distributions, as found in current over-the-counter spray products, the targeted drug delivery through the IU protocol outperforms CU by a remarkable 2 orders-of-magnitude.

BATTLE AXES OF AMAZONS OF EUROPEAN SCYTHIA

Weapons are one of the most important elements of the material culture of the North Pontic nomads. Archaeological finds from the steppe kurhans testify that the Scythians were armed with bows and arrows, spears and javelins, slings, swords and daggers, battle axes, horseman’s picks (pick axe), hammers and maces. However, not all types of weapons were equally common, and battle axes were less popular.
 Relatively few battle axes came from burial assemblages on the territory of European Scythia — from 50 to 100 items, according to the data of various researchers. By morphological features, two groups are distinguished: battle axes (three divisions) and axes with hammers (two divisions). The length of the wooden handles in most cases is about 50―70 cm. Battle axes are known in Scythian burial sites from the 7th to the 2nd century BC. Finds of early specimens are correlated mainly with antiquities of the Forest Steppe, while later specimens are concentrated in the central part of the territories of European Scythia. Until recently, it was believed that this type of weapon marked only male Scythian burials, however, the presence of axes in several female burials proves otherwise.
 The use of axes by the Amazons is mentioned in the works of several ancient authors, the works of ancient art demonstrate this phenomenon as well. According to archaeological materials, battle axes were found in only six (2 %) women’s graves: two in the Lower Dnipro Steppe Group and four in the Lower Dniester Steppe Group. An examination of the burial complexes of Scythian female warriors with axes made it possible to note several characteristic features.
 
 All axes are iron. Five of them have a single blade, from 16.5 to 22 cm long. And only one axe has a double blade. It is also stand out by its small size — 14.6 cm. Typologically and in terms of size, all these axes fully correspond to samples from other Scythian graves of European Scythia.
 An examination of the placement of axes in the graves showed a variety of its options. This means that there were no clear canons for the location of axes regarding the dead.
 The nature and size of the burials, as well as the assortment and number of grave goods testify that Scythian female warriors armed with axes were mainly representatives of the middle class of nomadic society.
 The age of women who were buried with axes is determined to be between 20 and 35 years old. This means that we are talking about the most active members of military units.
 Only ordinary iron axes were found in women’s graves, usually in sets with other weapons, mainly arrows. Gala and artistically decorated pick axes or sceptre axes, which served as symbols of high social status and power, are not known in women’s graves.
 Axes from women’s graves typologically and chronologically do not differ from those found in men’s graves.
 
 Therefore, iron axes from women’s graves, along with other types of weapons, were obviously used for their intended purpose. They were not part of the insignia of power but marked the belonging of women to the military state.

Are Different Two-Dimensional Models of Culture Just a Matter of Different Rotations? Evidence From the Analysis Based on the WVS/EVS

There is a need for a simple and graspable model of culture covering the main cultural differences across modern nations. A two-dimensional model might be a reasonable choice. We analyzed data from the World Values Survey and the European Values Study to test whether different two-dimensional models are factor rotations of each other. We took into account criticisms regarding the choice of items in Inglehart’s analysis of the same data source. Nevertheless, we replicated his dimensions. By means of factor rotation by various angles we aligned our dimensions and those of Inglehart with other previously published sets of dimensions. Thus, although different studies seem to have produced different two-dimensional solutions depending on the study design, those solutions are actually related to each other. There is no right or wrong placement of axes—they describe the same relationships between cultural elements. By showing the positions of various sets of cultural dimensions relative to each other, this study adds another viewpoint that can help researchers make sense of the huge variety of cultural dimensions in the literature.

Effect of Soil Resistivity Measurement on the Safe Design of Grounding Systems

A prerequisite for the proper and safe designing of a grounding system is the full knowledge of the ground structure in the terrain of installation. Through soil resistivity measurements, engineers are able to illustrate the ground profile, which constitutes the most significant parameter for the design of a grounding system and for determining the maximum permissible limits of step and touch voltages. This paper highlights the high importance and necessity for engineers to choose the proper measurement axes of soil resistivity in the terrain of interest and to choose suitable measurement depths, as well the combination of axes for the final determination of the ground profile. The variance of soil resistivity values, as a function of axis distance and the impact of axis placement on determining the uncertainty of measurements, is also analyzed in detail in this study. Furthermore, this work studies the value variance of step and touch voltages as a function of measurement axes, considering two- and three-layer soil models, based on soil resistivity field measurements performed at the university campus. Therefore, the proper and premeditated measurement of soil resistivity, particularly in anisotropic ground, is proved to be of major importance for the full designing of a safe grounding system.

Distribution of posterior corneal astigmatism and its effect on the calculation of Toric intraocular lens

Objective To analysis the distribution of posterior corneal astigmatism (PA) and evaluate the influence of keratometric astigmatism (KA) and total corneal astigmatism (TCA) on the calculation of Toric intraocular lens (Toric IOL) in patients with age-related cataract (ARC) and high corneal astigmatism. Methods An observational study design was adopted.Pentacam was used to measure 200 eyes of 181 patients with ARC and KA>0.75 D in Affiliated Hospital of Nantong University from August 2016 to April 2017.KA, PA, TCA and anterior corneal astigmatism (AA) were recorded.The astigmatism magnitude and axis of PA was studied.The subjects were divided into astigmatism with the rule group, astigmatism against the rule group and oblique astigmatism group according to the axis of AA.The correlations of decomposition values between PA and AA or KA and TCA in each group were analyzed by Pearson linear correlation analysis.The difference of decomposition values between KA and TCA in each group was compared by paired sample t test.The type and axis of Toric IOL were calculated by online formula according to KA and TCA.This study followed the Declaration of Helsinki and written informed consent was obtained from each patient prior to any medical examination. Results The mean astigmatic magnitudes of PA was -0.32 D×93.1°.PA exceeded 0.5 D in 22 eyes (11%). The steepest posterior corneal meridian was vertically aligned in 163 eyes (81.5%). The decomposition value KP(0) and KP(45) of PA were positively correlated with those of AA (r=0.480, P<0.001; r=0.251, P<0.001). The mean astigmatic magnitudes of KA and TCA were 1.44 D×89.6° and 1.32 D×89.5° in astigmatism with the rule group, 1.39 D×153.4° and 1.71 D×154.4° in astigmatism against the rule group and 1.13 D×122.0° and 1.24 D×124.2° in oblique astigmatism group.53 eyes (69.7%) had KA higher than TCA in astigmatism with the rule group.82 eyes (87.3%) had KA lower than TCA in astigmatism against the rule group; 20 eyes (66.7%) had KA lower than TCA in oblique astigmatism group.There were significant differences in KP (0) between KA and TCA in different astigmatism groups (all at P<0.001). The calculated Toric IOL type were inconsistent in 85 eyes(42.5%) and the calculated axis were inconsistent in 176 eyes (88.2%). Conclusions In patients with high corneal astigmatism, the astigmatism type of PA is mostly astigmatism against the rule.Ignoring the PA can lead to deviation of Toric IOL type selection and axis placement in some patients.For patients who cannot measure PA or TCA, the type of Toric IOL should be adjusted appropriately. Key words: Cataract; Posterior corneal astigmatism; Total corneal astigmatism; Keratometric astigmatism; Toric intraocular lens

Patterns of Wave Deformational Multicontact Half-Subspace Loading

It was experimentally found that during the passage of the impact momentum through multi-indentor impact system the distortion of energy transfer in the deformation zone is influenced by such factors as the number of indentures (waveguides), their shape and distance position relative to the impact axis. Thus, the increase in the number of indentures in the impact system, on the one hand, leads to a decrease in the proportion of energy of the impact pulse per an isolated indenter, and on the other hand allows to increase the total value of energy transfer in the deformation zone compared to one-indentor scheme. The distance increase between impact axis and indentors placement regardless of their number and form, leads to a decrease in the proportion of energy transmitted to the deformation zone.

2A2-D04 4軸駆動型電動船舶における船体推力を考慮した各プロペラ推力制御に関する研究

Recently, electric ship is being actively conducted in marine industry. Benefits are reduction of environmental impact and improved maneuverability and controllability. A ship that specializes in motility attention to control of the motor has been attracting attention. It is a 4-axis electric propulsion ship with four motors to the driving force. 4-axis electric propulsion ship tracks the magnitude of the direction and magnitude of thrust of the hull utilizing the control of the motor speed. This paper proposes a thrust estimation method that focuses on the axis placement of 4-axis electric propulsion ship. This paper evaluates thrust control using the estimation method by thrust measurement. Results of experiments suggest that the proposed method works properly and effectively.

Abstract 19192: Utility of Cardiac Computed Tomography in Detecting Malposition of Left Ventricular Assist Devices Associated With Pump Thrombosis

Introduction: Pump thrombosis is a potentially life-threatening event that currently presents a diagnostic challenge. We therefore sought to explore the diagnostic utility and the association of measured cardiac computed tomography (CT) parameters in patients with LVAD malfunction due to pump thrombosis. Methods: From 2009 to 2013, 150 patients underwent placement of Heart Mate II continuous flow pump at our institution. Of these 52 patients, underwent cardiac CT with contrast either as part of a prospective protocol or for suspected malfunction. 14 patients had pump thrombosis per the INTERMACS criteria and the remaining were used as controls. Rigorous linear and area measurements for the inflow and outflow tracts of LVADs were performed. Results: The mean age of the population was 55 ± 11, 36 were male, and 28 had ischemic cardiomyopathy. Results are shown in table 1. For inflow cannula, measurement of axial area shown in figure 1, was significantly higher in the pump thrombosis group compared to the control group 31±16 cm2 vs 20 ± 12 cm2 (p=.02). Although, the difference in the acute angle for the inflow cannula relative to the perpendicular axis between the midpoint of the mitral annulus and tip of inflow cannulas was not significantly different between the two groups, there was a trend towards greater angulation in the pump thrombosis group (60 ± 6 vs 53 ± 15) and there was a positive correlation between both measurements r=0.513, p-value= 0.003. Conclusions: Area in the axial view of the ventricle at the site of the inflow cannula tip may be a surrogate for off axis placement of the cannula. This area may be helpful in predicting pump thrombosis in patients.

Rotational stability of a toric intraocular lens: Influence of axial length and alignment in the capsular bag

To evaluate the rotational stability of a toric intraocular lens (IOL) using purpose-designed software and to determine the influence of axial length (AL) and in-the-bag IOL alignment on IOL rotation. Iladevi Cataract & IOL Research Centre, Ahmedabad, India. Prospective observational case series. This study enrolled eyes that had AcrySof toric IOL implantation. The AL was measured using optical coherence biometry or immersion A-scan biometry. Corneal astigmatism was determined by manual keratometry and topography. The IOL alignment was vertical, horizontal, or oblique. Rotational stability was measured using the purpose-designed software, and the mean absolute difference was determined. The effect of AL and IOL alignment on rotational stability was determined 6 months postoperatively. The study evaluated 168 eyes (168 patients). The mean AL was 23.86 mm ± 1.63 (SD), (range 19.50 to 29.03 mm). The median IOL rotation was 0.3 degree from baseline to 1 week, 1.0 degree from 1 week to 1 month, 0.2 degree from 1 to 3 months, and 0.1 degree from 3 to 6 months. The maximum rotation occurred between 1 week and 1 month. There was a strong correlation between AL and IOL rotation at 6 months (r = 0.93, P<.001). The mean absolute difference at 6 months was not significantly different between the 3 axis placement categories when correlated with the rotation (P=.102, analysis of variance). Toric IOL rotation was greater in eyes with a longer AL. Alignment of the IOL in the capsular bag had no influence on rotation.

Optical collection efficiency and orientation of a solar trough medium-power plant installed in Italy

Parabolic trough collectors were investigated, applying the study results to a plant prototype installed in Florence (Italy) for residential supply. Ray tracing simulations examined optical characteristics and collection performance on the base of prototype geometry and functionality. The purpose was to control the realisation errors and overcome the difficulties arising in the development of the solar trough plant. The paper summarises the results of several studies analysing the interactions between collection efficiency, angular misalignments, mirror deformations, sun tracking and trough placement. The mirror deformations are reproduced introducing an original procedure. The unusual subject of imprecision in trough axis placement is discussed.

Scaphoid AARIF Arthroscopically Assisted Reduction and Internal Fixation of Scaphoid Fractures

The unstable scaphoid fracture can be treated by a variety of different methods including open reduction and internal fixation (ORIF), percutaneous fixation with either K-wires or cannulated screws, and arthroscopic-assisted reduction and internal fixation (AARIF) with various cannulated screw systems. The drawbacks of ORIF include extensive soft-tissue dissection, disruption of the nondominant volar blood supply, division of the radioscaphocapitate and / or radiolunate ligaments and volar capsule, and prolonged rehabilitation. Percutaneous fixation avoids the aforementioned drawbacks yet relies on fluoroscopic guidance alone to ensure accurate reduction of the scaphoid fracture fragments and optimal positioning of the implant in the central third axis of the scaphoid. The frank technical limitations of plain radiography as well as fluoroscopy in detailed visualization of the oddly oriented scaphoid finitely limit the accuracy of the percutaneous technique. AARIF avoids all the limitations of ORIF yet allows direct visualization of the scaphoid fracture site and ensures accurate reduction of the fragments before and during definitive arthroscopically assisted internal fixation. AARIF also assists in accurate targeting of the proximal pole apex or “sweet spot” assuring central third scaphoid axis placement in addition to allowing detection of concurrent pathology in the radiocarpal or midcarpal joints. Scaphoid AARIF is a convenient therapeutic alternative that avoids many of the inherent pitfalls of ORIF and percutaneous fixation.

Optimal Sensor Positioning to Track Rib Deflections from an Optical System in the Hybrid III Dummy

Objectives: The objective of the study was to determine the optimal use of a new optical device, the RibEye system, intended to obtain internal ribcage deflections from tests using anthropomorphic test dummies. Specifically, the study was designed to determine the most efficacious mounting location of light emitting diodes (LEDs) on the ribs and sternum in the 50th percentile male Hybrid III dummy. Methods: Optical signal drop-out and accuracy assessment tests were conducted. In the former series, symmetric antero-posterior chest compressive loading was accomplished using cylindrical and square indenters, and asymmetrical compressive loading was accomplished using unilateral offset and diagonal belt-type loadings. LEDs were mounted to multiple ribs bilaterally at varying locations on the ribcage. The internal chest potentiometer available in the Hybrid III dummy was used. The latter series, aimed at examining the system accuracy, consisted of tests with LEDs mounted to the 4 corners of the sternum, termed sternum-mounted LED tests; rib-mounted tests wherein LEDs were mounted either to a specific rib or in the intercostal space of two successive ribs; rib-mounted tests with rotated chest simulating oblique loading; and indenter-mounted isolated LED tests. An electro-hydraulic testing device was used to apply compressive loads via an indenter in all tests. Displacement profiles were extracted from the optical system records, drop-out evaluations were conducted, and the system accuracy was evaluated by comparing data from the indenter and/or internal chest potentiometer. Results: In general, results indicated that the RibEye system captures rib cage deformations effectively. Under symmetric loading, LEDs on the sternum responded similar to the internal chest potentiometer. The accuracy of the system depended on the location of position of the LEDs on the rib, magnitude of rib deformation, and potential interference from internal dummy structures such as the presence of the internal chest potentiometer. Optimum locations for LED placement were found to be at a distance of 9 cm, measured along the outer curvilinear path of the rib from the mid-sternum on either side. At this location, the system showed no signal drop-out at deflections representative of the United States current frontal impact Injury Assessment Reference Values. Signal drop-out was also depended on the type of loading: diagonal belt-type loading produced more signal loss. Mounting LEDs away from the center of the rib representing eccentric superior-inferior (z) axis placement also resulted in loss of accuracy. Conclusions: These controlled evaluations provide a fundamental understanding of the performance of the system as installed in the 50th percentile male Hybrid III dummy and its ability to measure both antero-posterior and lateral components of deflections at multiple ribs, including the sternum for frontal impact applications. The system may be optimally used to gather rib deflection data without signal drop-out under symmetrical and asymmetrical loadings when LEDs are mounted on the superior-inferior centerline of the ribs with no eccentricity along the z-axis and at the 9-cm location from the mid-sternum on either side of the ribcage and at any corner on the sternum to obtain sternum deflections.

Skiing‐Skating

An articulated boot design is commonly used in skiing and skating sports because it allows sagittal plane ankle mobility while still providing critical frontal plane stability. Although articulated boots have been in use for several decades, current manufacturers of these boots differ in their articulation placement. In this study we determined an optimal position of the ankle articulation axis. We also calculated the amount of anterior skin movement that a boot tongue must account for during a full range of ankle motion. Three‐dimensional kinematic data were collected and analyzed from 40 participants moving their right foot through a full range of sagittal plane motion. The calculated horizontal position of the articulation axis was found to be highly predictable from foot length (r = 0.87, standard error of estimate = 3.44 mm), while its vertical component displayed less predictability (r = 0.49, standard error of estimate = 7.46 mm). The expansion required by the boot tongue had a moderate association with foot length and low variability (r = 0.58, standard error of estimate = 0.07 mm). An accurate axis placement will minimize relative motion between the boot cuff and the ankle, reducing friction and motion resistance. An expandable tongue will accommodate full plantar flexion and reduce pressure on the anterior ankle during dorsiflexion, eliminating common pressure‐related injuries.

The influence of axis placement and subject position on measurement of isokinetic peak moment while using the Lido Active Back System 1

The influence of axis placement and subject position on measurement of isokinetic peak moment while using the Lido Active Back Systems Purpose: The purpose of this study was to assess the effect of varying the measurement axis of the subject relative to an isokinetic dynamometer on the peak flexion and extension moment of the trunk. The effect of testing position (sitting or standing) on peak moment was also investigated. Methods: Thirty healthy young subjects [8 male, 22 female] were selected at random from a pool of 90 volunteers and asked to perform concentric sagittal flexion-extension cycles at velocities of 60 deg/s, 120 deg/s and 180 deg/s in both the seated and standing position with respect to 5 measurement axes. The subjects were initially aligned with the highest point on the iliac crest (reference axis) and then aligned with 4 measurement axes displaced from the reference axis (25 mm anterior/posterior and 50mm superior/inferior). Results: Two-way repeated measures AN()VA revealed significant differences (a < 0.05) between peak moments recorded between axes and velocity for flexion and extension, however no difference with respect to testing position, i.e., sitting versus standing. Post hoc multiple comparison tests by the Scheff?f method revealed that all measurement axes tested were statistically different [P < 0.001] from the reference axis, however there were no differences between the two inferior axes [P =0.999] and the two superior axes [P = 0.982]. The inferior measurement axes consistently produced greater peak moments than the reference axis while the superior axes consistently produced lower peak moments than the reference axis. Males produced significantly greater peak moments than did females [P = 0.000]. Conclusions: Measurement axis alignment significantly effects the peak moment recorded. Furthermore, these results reinforce the need for accurate and consistent alignment between the subject and the dynamometer. The position of the subject [seated/standing] did not significantly affect the measured peak moment when using the Lido Active Back System in this study.

On coordinate systems and the representation of articulatory movements

Hypothetical examples are used to demonstrate how certain quantitative characterizations of kinematic events can be affected by the placement and orientation of reference axes against which measurements are made. The variation in coordinate systems among a representative sample of recent publications describing speech movements and postures is summarized, and a standard, easily defined coordinate system for future descriptions is proposed. Interpretative benefits associated with the proposed representational standard are noted.

Proteins at interfaces: Principles, multivariate aspects, protein resistant surfaces, and direct imaging and manipulation of adsorbed proteins

The principles of protein adsorption are briefly reviewed with emphasis on model proteins at model interfaces. Using a data set for protein behavior at the air/water interface, a multi-variate, multi-axes treatment of protein adsorption behavior is developed: the Tatra plot. By the careful placement and scaling of radial axes, representing 12 protein, surface, and interface parameters, one can begin to deduce various correlations between these parameters. The correlations are then used to formulate hypotheses with which to design additional experiments. The treatment is extended to the solid/liquid interface using data available in the literature for model proteins on model solid surfaces. We then present brief discussion of the extension of the technique to more complex surfaces, including means to parameterize solid/liquid interfacial properties, before proceeding to more complex proteins based on a structural domain approach to protein structure and function. A preliminary analysis employing albumin is briefly presented. We move on to protein resistant surfaces based on polyethylene oxide and present a rationale for the properties and behavior of such interfaces, including a preliminary theoretical model which may be useful for the design and optimization of protein resistant surfaces. Finally, we briefly present some preliminary atomic force microscopy studies of immunoglobulins on mica surfaces, demonstrating not only direct imaging of proteins at interfaces in an aqueous environment but, perhaps even more importantly, their manipulation, processing, and ordering.

Implementation of a Five Degree of Freedom Automated System to Determine Knee Flexibility In Vitro

This article describes an automated system designed to study the complete flexibility functions of the knee in vitro. The system allows five degrees of freedom with flexion angle being fixed, though adjustable from 0 to 45 deg. Loads corresponding to each of the five motions can be applied independently and in any combination. The effect of weight bearing on knee flexibility can also be studied by including axial force as one of the five loads. The relative motions are measured with LVDT's and RVDT's, and the loads are measured with strain gage transducers. The system is digitally controlled with a closed feedback loop, allowing for any combination of programmed loads. A control algorithm on an IBM PC/AT monitors the loads on each axis and continuously adjusts stepping motors to correctly follow programmed loads. The machine coordinate system corresponds to clinically accepted definitions of motion yet retains sequence independence for rotations. Results are presented demonstrating the repeatability of using a functional definition of axis placement to align the leg within the machine. Results are also presented demonstrating the utility of the full flexibility functions of the knee, notably in the determination of significant load interactions between anterior/posterior force and internal/external torque, and varus/valgus torque and internal/external torque.