Development of an Open-Source Tractor Driving Simulator for Tractor Stability Tests.

Developing devices for stability monitoring and rollover alerts is a promising possibility to prevent overturn events, which pose a severe risk to tractor operators. However, performing relevant tests with operators in the field is dangerous and impractical. As an alternative, this work identifies the challenges of simulating a tractor driving environment in a laboratory and details the solutions put in place to develop a tractor driving simulator at Penn State University. The simulator includes an instrumented tractor cab mounted on a custom motion base, a 2.43 m tall, 360° high-definition screen, a sound system, and a nine-computer network running open-source software that can be used to conduct experiments and simulate driving scenarios relevant to tractor instabilities. The system is used for an experiment that evaluates the driver's ability to perceive tilt angles at various tilt and roll combinations. Pilot-test results show that roll and pitch are systematically overestimated, producing perceptual errors that are unbiased, independent for roll and pitch, and typically have magnitudes of 4°. These results can aid the development of instability monitoring systems by considering human tilt perception to set alert thresholds. Future projects and applications of the tractor driving simulator are also discussed.

Operator assessment of tractor roll angle with and without a tractor stability visual feedback device.

According to a 2004 National Institute for Occupational Safety and Health (NIOSH) report, approximately 250 to 350 fatalities occur each year due to incidents involving production agriculture workers and tractors. Tractor overturns account for about 150 to 200 of these deaths. The goals of this project were to study operators' understanding of tractor roll angles and test a device to effectively deliver stability information to the tractor operator. This project required the design and construction of a full-scale tractor cab roll simulator that was used to identify lateral roll angles at which volunteer participants felt uncomfortable, as well as lateral roll angles at which they would no longer operate a tractor. In addition, the participants performed a series of tasks to test the functionality of a visual slope indicator that was designed to help them estimate slope angles. The project tested 231 tractor operators' perceptions of safe operation on side slopes and 128 participants' interactions with the visual slope indicator. Testing showed that the visual slope indicator was able to influence the angle estimations of the novice tractor operator population and helped the entire population of participants more accurately rank the simulator scenarios.

Moment coefficients of skewness in the femoral neck cortical bone distribution of BAR 1002'00.

The cortical bone distributions in the femoral necks of apes and humans differ as a result of different loading environments caused by the realignment of the hip abductor apparatus. Femoral neck cortical bone in extant humans is very thin superiorly and thicker inferiorly, while the cortical bone in apes tends to be more uniformly thick. The unique internal anatomy of extant humans allows inferences to be made about primary locomotor function from incomplete femora. Here the differences in cortical bone distributions are quantified using moment coefficient of skewness. Skewness coefficients at two locations along the neck of the 6 million years old African femoral specimen BAR 1002'00 were compared to samples of 9 extant adult humans and 10 adult chimpanzees. The skewness coefficients of cortical bone in the femoral neck of BAR 1002'00 are more similar to those of chimpanzees than to humans, although the contrast is less pronounced in the region closer to the neck-shaft junction than more proximally toward the femoral head; this pattern indicates that in at least one respect this specimen attributed to Orrorin tugenensis manifests structural features suggesting influences of a hip abductor apparatus that had not yet evolved to the same extent as in extant humans.

In vitro assessment of a motion-based optimization method for locating the talocrural and subtalar joint axes.

The locations of the joint axes of the ankle complex vary considerably between subjects, yet no noninvasive method with demonstrated accuracy exists for locating these axes. The moments of muscle and ground reaction forces about the joint axes are dependent on axis locations, making knowledge of these locations critical to accurate musculoskeletal modeling of the foot and ankle. The accuracy of a computational optimization method that fits a two-revolute model to measured motion was assessed using computer-generated data, a two-revolute mechanical linkage, and three lower-leg cadaver specimens. Motions were applied to cadaver specimens under axial load while bone-mounted markers attached to the tibia, talus, and calcaneus were tracked using a video-based motion analysis system. Estimates of the talocrural and subtalar axis locations were computed from motions of the calcaneus relative to the tibia using the optimization method. These axes were compared to mean helical axes computed directly from tibia, talus, and calcaneus motions. The optimization method performed well when the motions were computer-generated or measured in the mechanical linkage, with angular differences between optimization and mean helical axes ranging from 1 deg to 5 deg. In the cadaver specimens, however, these differences exceeded 20 deg. Optimization methods that locate the anatomical joint axes of the ankle complex by fitting two revolute joints to measured tibia-calcaneus motions may be limited because of problems arising from non-revolute behavior.

Superquadric modeling of cranial and cerebral shape and asymmetry.

A new method for quantifying cranial and cerebral shape and asymmetry fits symmetric superquadric geometric models to three-dimensional coordinate measurements. Asymmetry is quantified as radial residuals of the surface data points from their best-fit superquadric models. Twenty human crania, 10 magnetic resonance imaging (MRI) exocranial surfaces, and 10 corresponding MRI cerebral surfaces as well as two infant head casts were digitized and modeled using superquadrics. Superquadric parameters have simple geometric interpretation, are very reproducible, and demonstrated statistically significant differences between crania of Amerindian ancestry and MRI exocranial surfaces of European ancestry used in this study. Superquadric models demonstrated strong congruence between MRI exocranial and cerebral surfaces. Typical asymmetry was 1-5 mm. Lastly, polar contour plots of radial residuals for head casts before and after orthotic cranioplasty demonstrated the efficacy of using superquadrics to quantify positional plagiocephaly and synostosis of infant crania.

Simplified overturn stability monitoring of agricultural tractors.

Agricultural tractors are the most common source of farm work fatalities in the U.S., with overturns the most common type of incident. For the year 2001, there were 15 tractor-related fatalities in Pennsylvania, 9 of which were due to tractor rollover. A new device using low-cost sensors and microcomputers was developed around a simplified mathematical model of an agricultural tractor to inform the operator of potential tractor instability. This device communicates the current rollover potential, along with a recent history of rollover potential, to the operator of the tractor via a simple bar-graph display. The device uses a single-chip accelerometer to sense the current rollover potential and a small microprocessor to analyze the accelerometer data, compensate for variations due to temperature, and then send this information to a visual display. The use of these low-cost "off the shelf" components enabled the fabrication of a very inexpensive sensor system. Because agricultural tractors have a long service life, it was important to make the device low cost and flexible. This could enable it to be sold as an aftermarket add-on for a variety of tractor models. The device is also capable of interfacing with newer on-board tractor systems via a CAN bus to make it more attractive to tractor manufacturers who may want to incorporate this device into new models. Work is continuing on the development of an improved display to inform the tractor operator of possible instability, including display ergonomic studies, investigation of threshold levels for alerting an operator of potential instability, and investigation into audible warning signals.

Anesthesiology and intensive care during epilepsy surgery in children and adolescents.

Thus far there are no known studies of the management of anesthesiology and intensive care in cases of implantation of subdural plates for the purpose of determining the epileptogenic areal and of subsequent epilepsy surgery. Such operative measures are still considered too risky, especially in the case of small children. The authors report on cases of 45 children and adolescents who underwent this kind of surgery between December 1992 and December 1997 in Gilead hospital. In order to judge the anesthesiological risk the children were divided into three age groups: A, 1-5 years (n = 12); B, 6-11 years (n = 14); C, 12-18 years (n = 19). In none of these groups were there complications which in retrospect would have shed a negative light on the operation.

Evaluation of a Treadmill with Vibration Isolation and Stabilization (TVIS) for use on the International Space Station.

A treadmill with vibration isolation and stabilization designed for the International Space Station (ISS) was evaluated during Shuttle mission STS-81. Three crew members ran and walked on the device, which floats freely in zero gravity. For the majority of the more than 2 hours of locomotion studied, the treadmill showed peak to peak linear and angular displacements of less than 2.5 cm and 2.5 degrees, respectively. Vibration transmitted to the vehicle was within the microgravity allocation limits that are defined for the ISS. Refinements to the treadmill and harness system are discussed. This approach to treadmill design offers the possibility of generating 1G-like loads on the lower extremities while preserving the microgravity environment of the ISS for structural safety and vibration free experimental conditions.

Cost analysis of hospital material management systems.

Integrated healthcare material management begins with manufactures of medical/surgical supplies, uses distributors and ends at the point of use at hospitals. Recent material management philosophies in the healthcare industry, such as just-in-time and stockless systems, are yet to be fully evaluated. In order to evaluate the cost effectiveness of each type of material management technique, a cost model for hospital materials management has been designed. Several case scenarios are analyzed and results are reported.

A three-dimensional musculoskeletal database for the lower extremities.

A three-dimensional musculoskeletal database of the lower extremities has been developed for use in human musculoskeletal models. The locations of idealized muscle attachments on the pelvis, both femurs, both tibias and fibulas, and both feet were accurately digitized for 52 dried skeletal specimens. The mean specimen heights were 177.5 cm (male) and 166.2 cm (female) and the mean specimen age at the time of death was 48.8 yr. Statistical accumulation and scaling techniques were used to generate highly representative normative models, which were divided into groups and tested for differences based on gender and race. From the test results, the pelvis was divided into a male model (RMS = 8.6 mm), a black female model (RMS = 7.0 mm) and a white female model (RMS = 7.3 mm). The foot was separated into black (RMS = 3.7 mm) and white models (RMS = 3.6 mm). Single models were used for the femur (RMS = 6.5 mm) and the tibia/fibula (RMS = 3.7). Containing over 12000 anatomical landmarks digitized from 52 dried skeletons, this study represents an improvement over previous databases by an order of magnitude.

Comparative ontogenetic shape changes in the skull of Caiman species (Crocodylia, Alligatoridae).

Ontogenetic shape changes in the skull of three species of the genus Caiman (C. latirostris, C. sclerops, and C. yacare) are compared by geometric morphometrics for three-dimensional configurations (the least-squares analysis). The technique for obtaining the landmark coordinates is a simplification of the algorithm for multidimensional scaling. The ontogenetic nonlinear shape changes are similar in the three species but occur in a lesser extent in C. latirostris. These seem to be correlated with functional changes in the skull. The uniform shape change corresponds to an elongation of the skull, dorsoventral flattening, and lateral compression in C. sclerops and C. yacare. There is some lateral broadening in C. latirostris. Differences in the ontogenetic processes probably cause the differences in diet observed between C. latirostris and the other two species. Neotenic evolution seems to have acted in the skull of C. latirostris, and a posterior amplification of the early divergence led to a repatterning of the shape ontogenetic trajectory in this species. J. Morphol. 231:53-62, 1997. © 1997 Wiley-Liss, Inc.

Ground reaction forces during locomotion in simulated microgravity.

BACKGROUND: Significant losses in bone density and mineral, primarily in the lower extremities, have been reported following exposure to weightlessness. Recent investigations suggest that mechanical influences such as bone deformation and strain rate may be critically important in stimulating new bone formation. HYPOTHESIS: It was hypothesized that velocity, cadence, and harness design would significantly affect lower limb impact forces during treadmill exercise in simulated zero-gravity (0G). METHODS: A ground-based hypogravity simulator was used to investigate which factors affect limb loading during tethered treadmill exercise. A fractional factorial design was used and 12 subjects were studied. RESULTS: The results showed that running on active and passive treadmills in the simulator with a tethering force close to the maximum comfortable level produced similar magnitudes for the peak ground reaction force. It was also found that these maximum forces were significantly lower than those obtained during overground trials, even when the speeds of locomotion in the simulator were 66% greater than those in 1G. Cadence had no effect on any of the response variables. The maximum rate of force application (DFDTmax) was similar for overground running and exercise in simulated 0G, provided the "weightless" subjects ran on a motorized treadmill. CONCLUSIONS: These findings have implications for the use of treadmill exercise as a countermeasure for hypokinetic osteoporosis. As the relationship between mechanical factors and osteogenesis becomes better understood, results from human experiments in 0G simulators will help to design in-flight exercise programs that are more closely targeted to generate appropriate mechanical stimuli.

Adaptation of the tear film to work in air-conditioned rooms (office-eye syndrome).

To detect mechanisms of tear-film adaptation to a dry climate, we investigated co-workers in our hospital with air-conditioned rooms. Three groups were formed according to the time of occupancy (6 months to 2 years, 2-4 years, and 4-6 years) and were compared with a control group. The number of patients with frequent dry-eye complaints increased up to 48%, reaching a steady state after 2-4 years. The breakup time was slightly reduced (decrease, 17.5%; P < 0.01) and also reached a steady state after 2-4 years. The tear-ferning test, however, showed a highly significant improvement (P < 0.01). A slight reduction in the Schirmer test was found. Our study indicates that improved tear quality is important for adaptation to long-standing increased evaporation of the tear film.

Foot inversion-eversion and knee kinematics during walking.

The purpose of this study was to monitor selected aspects of the three-dimensional kinematics of the knee during walking with regular shoes and with modified shoes that induced either pronation or supination of the foot. Steinmann traction pins were inserted into the right tibia and femur of five adult men who had apparently normal lower extremities. Target clusters mounted onto the pins were filmed by four cine cameras operating at 100 frames/sec. Two trials per subject were analyzed for each of the three experimental conditions: regular running shoes, running shoes with a 10 degree valgus wedge, and running shoes with a 10 degree varus wedge. The different types of footwear induced only minor kinematic changes at the knee during the stance phase of walking. The angular patterns of the tibiofemoral joint were modified by less than 1 degree, whereas the translatory patterns were altered by 2 mm. Immediately following foot-strike, the valgus-wedge shoes caused the tibia to rotate internally 4 degrees more than the varus-wedge shoes, but at the tibiofemoral joint no consistent differences in the pattern of internal-external rotation between normal and modified footwear were measureable. These findings suggest that, in the healthy lower extremity, increased internal and external tibial rotation is resolved at the hip joint, with changes at the tibiofemoral joint that barely are detectable with the techniques used in this study.

Three-dimensional kinematics of the human knee during walking.

Three-dimensional kinematics of the tibiofemoral joint were studied during normal walking. Target markers were fixed to tibia and femur by means of intra-cortical traction pins. Radiographs of the lower limb were obtained to compute the position of the target markers relative to internal anatomical structures. High-speed cine cameras were used to measure three-dimensional coordinates of the target markers in five subjects walking at a speed of 1.2 m s-1. Relative motion between tibia and femur was resolved according to a joint coordinate system (JCS). The measurements have identified that substantial angular and linear motions occur about and along each of the JCS axes during walking. The results do not, however, support the traditional view that the so-called 'screw home' mechanism of the knee joint operates during gait.

[Aggressive fibromatosis--a surgical problem disease]. / Aggressive Fibromatose--eine chirurgische Problemerkrankung.

The aggressive fibromatosis is a surgical problem disease. Two remarkable cases serve as examples to demonstrate the aggressive forms of extraabdominal fibromatosis. There is a tendency to locally invasive destructive growth without metastasising at any time and a markedly high relapse rate after surgery, a tendency that showed up clearly in our patients, too. The very multivarious nomenclature points out that about histiogenesis, pathogenesis and benignity of this excrescence still exists great obscurity. We report on the pathology and clinic of an aggressive fibromatosis of the thyroid gland region and of a thoracal aggressive fibromatosis in the right shoulderblade-region.

[CT portography in malignant space-occupying lesions of the liver]. / CT-Portographie bei malignen Raumforderungen der Leber.

CT portography was performed in 32 patients with liver tumours and in four patients with cirrhosis of the liver, but without evidence of tumour, after angiographic injection of contrast into the superior mesenteric or splenic arteries. Compared with CT using no contrast, or contrast by intravenous injection, CT portography has the following advantages: better tumour detection, better detection of tumour size, better demarcation and localisation of tumours, better demonstration of the portal system, more inhomogeneity of the parenchyma. Of 12 patients with a number of tumours shown on CT, CT portography demonstrated tumours in four cases, which could not be shown by any other imaging method. Problems concerning CT portography in patients with cirrhosis of the liver are discussed.

[The subphrenic abscess. Surgical and/or percutaneous drainage]. / Der subphrenische Abszess. Operative und/oder perkutane Drainage.

The results indicate that the low risk percutaneous drainage of subphrenic abscesses is only feasible in carefully selected patients. The surgical intervention remains the method of choice for the drainage of subphrenic abscesses in conditions such as multiple and complicated abscesses, unfavourable access to the abscess cavities or other pathological conditions. An early and decisive diagnosis is crucial for effective treatment of subphrenic abscesses either by percutaneous drainage or surgical intervention and antibiotic therapy.

[Primary infrapapillary leiomyosarcoma of the duodenum]. / Primäres infrapapilläres Leiomyosarkom des Duodenums.

The primary infrapapillary leiomyosarcoma of the duodenum is very rare. In spite of the rarity and often uncharacteristical symptomatology of these tumors the knowledge of the clinical symptoms and diagnostical possibilities is for all the greater importance, because a radical operation with good late results is possible at early recognition.