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Wheelchair users who live in cold climates are faced with daily difficulties related to personal independence and societal inclusion as their assistive devices are unable to overcome the physical barriers created by snow and ice. The purpose of the research was to evaluate four commercially available casters to determine which caster performed best on snow-covered surfaces. Performance measures included: travel time, force transfer through the palms of the hands, number of propulsive movements, static resistance to movement, kinetic resistance to movement, and caster penetration into the packed snow. On a snow-covered incline, the FreeWheel™ caster enabled travel time to be decreased by 10 s, requiring 3 fewer propulsive movements and 60% of the amount of force to propel the wheelchair compared with solid casters. Static and kinetic resistance tests did not differentiate the four caster types. Penetration into packed snow was reduced from 11.9 mm to approximately 1 mm by changing from solid casters to the FreeWheel™ or Wheelblades™ caster types on flat surfaces. Similar results were observed on a snow-covered incline for the Wheelblades™, however, the FreeWheel™ penetrated approximately 8 mm. Considering the entire body of evidence, the FreeWheel™ performed the best on snow-covered surfaces.

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Drivers' inadequate mental workload has been reported as one of the negative effects of driving assistant systems and in-vehicle automation. The increasing trend of automation in agricultural vehicles raises some concerns about drivers' mental workload in such vehicles. Thus, a human factors perspective is needed to identify the consequences of such automated systems. In this simulator study, the effects of vehicle steering task automation (VSTA) and implement control and monitoring task automation (ICMTA) were investigated using a tractor-air seeder system as a case study. Two performance parameters (reaction time and accuracy of actions) were measured to assess drivers' perceived mental workload. Experiments were conducted using the tractor driving simulator (TDS) located in the Agricultural Ergonomics Laboratory at the University of Manitoba. Study participants were university students with tractor driving experience. According to the results, reaction time and number of errors made by drivers both decreased as the automation level increased. Correlations were found among performance parameters and subjective mental workload reported by the drivers.

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During monitoring of rear-mounted equipment, frequent rearward turning of tractor drivers causes awkward postures that can cause musculoskeletal disorders related to the back, neck, and shoulders. The objective of this study was to compare three implement monitoring strategies (direct viewing via physical turning, indirect viewing via rear-view mirrors, and indirect viewing via a camera-monitor system) in a lab environment using a tractor and air seeder driving simulator Comparison was based on monitoring performance of the operator (i.e., response error), physical impact on the operator (i.e., head/neck acceleration and increase in neck muscle temperature), and operator preference. Indirect viewing via a camera-monitor system caused the least physical impact on subjects and was the preferred implement monitoring strategy. No significant differences (alpha = 0.05) in monitoring performance were observed.

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Tractor operators are prone to neck and back discomfort and disorders. It is well known that awkward posture is a major contributor to this problem. Previous studies have investigated the prevalence of awkward posture and the resulting discomfort and disorders among tractor operators. They have also suggested various ways to mitigate this problem. With the introduction of new autosteer guidance systems, the tractor operator is relieved from the task of steering the tractor for most of the time during field work. Therefore, it is expected that the operator's posture will change. The goal of this study was to investigate the changes in the eye-glance behavior and posture of tractor operators as a result of using autosteer guidance systems. An eye-tracking system and a camcorder were used to record the eye-glance behavior and posture of 13 tractor operators as they performed seeding operations. The experiment with each operator consisted of two sessions. In one session, the operator used an autosteer system, while in the other session the operator steered the tractor manually. Analysis of the data showed that the eye-glance behavior and posture of the operators were significantly different between the autosteer and manual steering sessions. With the autosteer system, the operators spent less time in an awkward posture, and they changed their posture less frequently. However, even with the autosteer system, the operators spent 1/3 of their time in an awkward posture. Subjective feedback from the operators indicated that more than half of them experienced back or neck/shoulder discomfort during or after seeding. It is essential that the recommendations of the previous studies, such as using large rear-view mirrors or a rotating tractor seat, be evaluated when the operator is using an autosteer system. Other tools, such as video cameras that show the attached equipment, should also be tested to evaluate their effectiveness in reducing the operator's exposure to awkward postures.

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Agricultural spraying involves two major tasks: guiding a sprayer in response to a GPS navigation device, and simultaneous monitoring of rear-attached booms under various illumination and terrain difficulty levels. The aim of the present study was to investigate the effect of illumination, task difficulty, and task level on the mental workload of an individual operating an agricultural sprayer in response to a commercial GPS lightbar, and to explore the sensitivity of the NASA-TLX and SSWAT subjective rating scales in discriminating the subjective experienced workload under various task, illumination, and difficulty levels. Mental workload was measured using performance measures (lateral root mean square error and reaction time), physiological measures (0.1 Hz power of HRV, latency of the P300 component of event-related potential, and eye-glance behavior), and two subjective rating scales (NASA-TLX and SSWAT). Sixteen male university students participated in this experiment, and a fixed-base high-fidelity agricultural tractor simulator was used to create a simulated spraying task. All performance measures, the P300 latency, and subjective rating scales showed a common trend that mental workload increased with the change in illumination from day to night, with task difficulty from low to high, and with task type from single to dual. The 0.1 Hz power of HRV contradicted the performance measures. Eye-glance data showed that under night illumination, participants spent more time looking at the lightbar for guidance information. A similar trend was observed with the change in task type from single to dual. Both subjective rating scales showed a common trend of increasing mental workload with the change in illumination, difficulty, and task levels. However, the SSWAT scale was more sensitive than the NASA-TLX scale. With the change in illumination, difficulty, and task levels, participants spent more mental resources to meet the increased task demand; hence, the illumination, task difficulty, and task level affected the mental workload of an agricultural sprayer operator operating a sprayer in response to a GPS lightbar.

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Despite the existence of the slow-moving vehicle (SMV) emblem for almost 50 years, there continues to be a large number of preventable accidents between SMVs and other motorists. In this study, the current SMV emblem was tested against other common road signs as well as alternative slow-moving vehicle emblems to determine motorist comprehension of the signs. An open-ended test method was used to determine the level of comprehension by Manitoba motorists. Written answers from 50 participants were classified as either "correct" or "incorrect" by the authors based on the meaning of the traffic signs provided in a driver's handbook. Only 3 of the 16 Manitoba traffic signs attained the 85% level of comprehension required by ANSI standards. Only 22% of participants correctly identified the current SMV emblem. Two alternatives to the SMV emblem found in the literature, both iconic in nature, were understood to mean "slow-moving vehicle" by only 2% and 8% of participants, respectively. Two alternatives to the SMV developed for this project were evaluated with levels of comprehension of 68% and 84%: however, these levels of comprehension were likely biased by the presence of text. There is insufficient evidence to suggest that the current symbolic SMV emblem should be replaced by an alternative emblem that is iconic in nature.

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The objective of this study was to perform a complete task analysis to measure the workload associated with operating an agricultural sprayer equipped with a navigation device. The task analysis included a written questionnaire and subsequent observation of sprayer operators. The questionnaire revealed that the lightbar was the most important source of guidance information (as opposed to relying on guidance information from external field cues). Observation consisted of recording eye-glance behaviour and heart rate variability while operators were spraying in a field setting. The eye-glance data suggest that external cues are more important than the lightbar for providing the necessary navigation information. Thus, the questionnaire and observation data contradict each other. Based on heart rate variability, operators who used a lightbar navigation device experienced more mental workload than operators who used an auto-steer navigation device.

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The overall accessibility of controls is one of the most important issues to consider when designing a control layout. Well-arranged controls, whose operational characteristics are based on both design guidelines and on human factors considerations, allow the operator to efficiently interact with the system in question. The objective of this article is to introduce a numerical index, referred to as the "index of functionality", capable of comparing, on a mathematical basis, different control arrangements in agricultural tractors. The model is based on information that has been gleaned from the published literature, with input from both professional ergonomists and experienced agricultural tractor operators. The numerical index may take any value between 0 and +1, with +1 being defined as an optimum value in terms of the functionality of a workstation. Data were collected from six old (pre-1982) and six modern (post-2003) tractor workstations to determine whether the model would recognize improvements that have occurred in the ergonomic design of tractor control layouts over the past 20 years. An average score of 0.19 +/- 0.07 was calculated for the pre-1982 tractor workstations. By contrast, an average score of 0.63 +/- 0.10 was calculated for the post-2003 tractor workstations. A number of limitations have been identified with the current model; despite these limitations, the index of functionality clearly recognized the ergonomic improvements in tractor workstations that have occurred over the past 20 years.

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Many farmers with disabilities choose to modify their work environments to accommodate their personal abilities; however, modified tractors may present greater risk to the operator as they are often one-of-a-kind designs that have not been subjected to rigorous safety testing. The objective of this research was to evaluate mechanical tractor pedal , extensions from a safety perspective. This objective was achieved by identifying potential hazards associated with the introduction of a pedal extension into the cab environment so that both existing and novel designs could be compared using a common methodology. Based on review of the published literature, 19 potential hazards associated with the introduction of a pedal extension into the cab of a tractor were identified. A hazard self-assessment worksheet (HSAW), created based on the 19 hazards, was validated through a pilot study. The overall inter-rater reliability and concurrent criterion validity proved to be acceptable. With the use of the HSAW six pedal extensions (three existing designs and three novel designs) were evaluated by 14 experts. Statistical analysis of the results did not identify a "best" design; however, several important trends were observed. Four of the six designs tended to block access to the exit path. The two designs that did not block access to the exit path might be considered to be the best designs for the tractors used in this study, but other designs likely would have been acceptable if they had been custom-fit for these tractors. The results of this research suggest that custom fabrication of pedal extensions for each specific tractor will likely yield the safest work environment for those who choose to use this assistive technology.

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The operation of agricultural vehicles is a multitask activity that requires proper distribution of attentional resources. Human factors theories suggest that proper utilization of the operator's sensory capacities under such conditions can improve the operator's performance and reduce the operator's workload. Using a tractor driving simulator, this study investigated whether auditory cues can be used to improve performance of the operator of an agricultural vehicle. Steering of a vehicle was simulated in visual mode (where driving error was shown to the subject using a lightbar) and in auditory mode (where a pair of speakers were used to convey the driving error direction and/or magnitude). A secondary task was also introduced in order to simulate the monitoring of an attached machine. This task included monitoring of two identical displays, which were placed behind the simulator, and responding to them, when needed, using a joystick. This task was also implemented in auditory mode (in which a beep signaled the subject to push the proper button when a response was needed) and in visual mode (in which there was no beep and visual, monitoring of the displays was necessary). Two levels of difficulty of the monitoring task were used. Deviation of the simulated vehicle from a desired straight line was used as the measure of performance in the steering task, and reaction time to the displays was used as the measure of performance in the monitoring task. Results of the experiments showed that steering performance was significantly better when steering was a visual task (driving errors were 40% to 60% of the driving errors in auditory mode), although subjective evaluations showed that auditory steering could be easier, depending on the implementation. Performance in the monitoring task was significantly better for auditory implementation (reaction time was approximately 6 times shorter), and this result was strongly supported by subjective ratings. The majority of the subjects preferred the combination of visual mode for the steering task and auditory mode for the monitoring task.

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This article reviews some ergonomic factors associated with agricultural guidance displays. Any technology or management decision that improves the efficiency of an agricultural operation can be considered an aspect of precision farming. Agricultural guidance displays are one such tool because they help to reduce guidance error (i.e., skipping and overlapping of implements within the field), which result in improper application of crop inputs at increased cost. Although each of the guidance displays currently available functions using a different principle, their key objective is to communicate useful guidance information to the operator of the agricultural machine. The case with which the operator obtains the required information depends on a number of ergonomic factors, such as color perceptibility, flash rate, attentional demand, display size, viewing distance, and height of placement of the display in the cab. Ergonomics can be defined as the application of knowledge to create a safe, comfortable, and effective work environment. Consequently, it is critical to consider ergonomics when designing guidance displays or when locating a display in the tractor cab. Without considering ergonomics, it is unlikely that the efficiency of the human-machine system can be optimized.

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A guidance aid is a device that provides guidance information to the driver rather than replacing the driver. With a camera-based guidance aid, the view seen by a forward-looking video camera is displayed on a monitor situated within the operator station of the vehicle. As the vehicle moves forward, images of the ground scroll vertically across the monitor. The rate at which the image scrolls, the image velocity, is related to the forward velocity of the vehicle, the placement of the camera (height and tilt angle), and the optical characteristics of the guidance camera. When tested with a tractor at forward velocities between 1.6 and 12.8 km/h, lateral error increased linearly as image velocity increased. Driver self-confidence decreased linearly as image velocity increased. Based on subjective feedback, drivers preferred a camera tilt angle of 20 degrees (over either 30 degrees or 40 degrees) because it yielded the greatest look-ahead distance. Statistically, a tilt angle of 30 degrees was best for a camera with a narrow field of view (narrow FOV, 20 degrees in the lateral direction). For a camera with a wide field of view (wide FOV, 39 degrees in the lateral direction), there was no statistical difference. For the narrow FOV camera, a camera height of 1.1 m yielded statistically smaller lateral errors than a camera height of 1.5 m. There was no statistical difference for the wide FOV camera. Overall, the lateral error was statistically smaller for the narrow FOV camera than for the wide FOV camera due to the difference in the lateral ratio for each camera, where the lateral ratio is the ratio of the lateral field of view of the camera to the fixed monitor width.

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Several recent studies document the declining use of osteopathic manipulative treatment (OMT) in clinical practice. In this article, the authors contend that developing new teaching materials based on the mastery learning approach can augment time-tested methods of teaching OMT and help to stop or reverse this decline. The Spencer technique for shoulder manipulation is used to demonstrate the development and evaluation of OMT mastery learning materials. These materials could be developed as part of a progressive teaching sequence requiring increasing diagnostic acumen, palpatory skill, and therapeutic subtlety. Such a program could be used throughout osteopathic medical training and for continuing medical education to increase skills and confidence in the use of OMT.

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Medical education has not kept pace with the evolving healthcare system. Criticism from industry and policy observers focuses on four major areas requiring reform: the curriculum, the fragmented educational infrastructure, the specialist-to-generalist mix, and the alienation from community and public health. The dominance of managed care organizations in the delivery and financing of healthcare is forcing a new set of physician competencies to the fore and changing projections of physician manpower and specialty needs. The authors address the four major criticisms from a uniquely osteopathic point-of-view. In this first of two articles, the authors describe the evolving osteopathic medical education model, and then employ a medical analogy to diagnose the causes of and propose treatments for curricular issues and infrastructure fragmentation. In the second article of the pair, they explore the causes of and propose strategies to address the generalist-to-specialist imbalance and the alienation of medicine from community and public health; the article also explores the role of technology in support of reform. In each article, the authors propose treatments to correct the problems in the osteopathic medical education model, and conclude that the profession is well-positioned to lead medical education reform.

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Pharmacokinetic values of a new quinolone antimicrobial, danofloxacin, were studied in cattle and swine. Plasma concentration was detected within 15 minutes after IM administration, peaked by 1 hour, and subsequently decreased, with half-life of 2.9 and 6.8 hours for cattle and swine, respectively. In swine, danofloxacin was absorbed, whether orally administered by gavage, in feed, or in drinking water. Danofloxacin concentrated in lung tissue at 4 to 7 times the plasma concentration. Lung tissue concentration exceeded the minimal inhibitory concentrations for im90portant respiratory tract pathogens for extended periods after administration of the drug by any of the routes studied. The major routes of excretion were in urine and bile.

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A series of novel 6-fluoro-7-diazabicycloalkylquinolonecarboxylic acids substituted with various C8 (H, F, Cl, N) and N1 (ethyl, cyclopropyl, vinyl, 2-fluoroethyl, 4-fluorophenyl, 2,4-difluorophenyl) substituents, as well as, 9-fluoro-10-diazabicycloalkylpyridobenzoxazinecarboxylic acids, were prepared and evaluated for antibacterial activity against a range of important veterinary pathogenic bacteria. The diazabicycloalkyl side chains investigated at the 7-position (benzoxazine 10-position) include (1S,4S)-5-methyl-2,5-diazabicyclo[2.2.1]heptane (2), (1S,4S)-2,5-diazabicyclo[2.2.1]heptane (3), (1R,4R)-5-methyl-2,5-diazabicyclo[2.2.1]heptane (4), 8-methyl-3,8-diazabicyclo[3.2.1]octane (5), 9-methyl-3,9-diazabicyclo[4.2.1]nonane (6), 1,4-diazabicyclo[3.2.2]nonane (7), 1,4-diazabicyclo[3.3.1]nonane (8), and 9-methyl-3,9-diazabicyclo[3.3.1]nonane (9). Among these side chains, in vitro potency was not highly variable; other properties therefore proved more critical to the selection of possible development candidates. However, the relative potencies observed for several of these compounds in mouse, swine, and cattle infection models correlated well with those seen in vitro. A combination of the N1 cyclopropyl group and the C7 (1S,4S)-5-methyl-2,5-diazabicyclo[2.2.1]hept-2-yl appendage conferred the best overall antibacterial, physiochemical, and pharmacodynamic properties. Hence, danofloxacin (Advocin, 2c) (originally CP-76,136, 1-cyclopropyl-6-fluoro-7-[(1S,4S)-5-methyl-2,5-diazabicyclo[2.2.1] hept-2-yl]-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid) was selected as a candidate for development as a therapeutic antibacterial agent for veterinary medicine.

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The effect of subclinical levels of mycotoxin T-2 on the cells of the bovine immune system was investigated in two in vivo experiments. In experiment 1, five calves were orally dosed with 0.3 mg/kg/day of T-2 toxin for 56 days and five calves were pair fed controls. The neutrophil function as measured by nitroblue tetrazolium reduction was reduced in the mycotoxin treated calves. The cutaneous reaction to intradermally injected phytohemagglutinin was reduced in the T-2 toxin treated calves. B-cell (SIg+) numbers increased slightly, but T-cell (PNA+) numbers were not affected during the experimental period. In the second experiment, six calves were given 0.5 mg/kg/day T-2 toxin orally for 28 days and six calves were pair fed controls. B-cell numbers and the response of a B-cell enriched fraction to phytohemagglutinin increased after toxin administration. T-cell numbers and the response of a T-cell enriched fraction and the whole mononuclear cell population to phytohemagglutinin was reduced only on day 19 posttoxin administration. The in vitro (T-2 toxin) exposure of the mononuclear cell population, B-cell enriched, or T-cell enriched fraction reduced their lymphoblastic response to mitogens. A 50% reduction was induced by as little as 1.4 ng/mL of T-2 toxin.

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An experiment was designed to compare the efficacy of an IM modified live vaccine, an IN temperature-sensitive vaccine, an IN modified live vaccine, and an aerosolized modified live vaccine (two concentrations) to stimulate specific serum antibody and protect calves from a known viral challenge. All vaccines except the IM vaccine contained IBR virus and PI3 virus. The IM vaccine and the IN vaccines provided excellent protection to an IBR challenge, but both concentrations of aerosolized vaccine provided only patial protection. The use of IN modified live vaccine resulted in IBR serum Ab titers in all the test calves (100%), while the IM preparation elicited a response in only 60% of test calves and the IN temperature sensitive vaccine resulted in serum Ab titers in 40% of test calves. The aerosolized vaccine induced IBR serum antibody titers in only 20% of the calves. The use of IN modified live and the aerosolized vaccine resulted in a greater immune response to the PI3 virus (60-80% sero-conversion) than did the temperature sensitive vaccine (20% sero-conversion).

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Mycotoxin T-2 (0.5 mg/kg of body weight) was administered orally to mixed-breed beef calves. Serum protein fractions, immunoglobulin (Ig) G, IgM, and several complement protein concentrations were studied in control and toxin-treated calves. Total protein, albumin, and globulin concentrations all decreased in toxin-treated calves as compared with that in controls. Similarly, the concentrations of alpha-, beta 1-, and beta 2-globulin fractions were reduced in the toxin-treated calves more than those in controls. The IgG and IgM values were lower in toxin-treated calves than those in the controls. Complement proteins Bbov (of the alternate pathway) and the 3rd component of complement were lower in the toxin-treated calves. The fragment of Bbov activation, B gamma 2, was increased after toxin treatment, indicating that activation of the alternate complement pathway was responsible for at least some of the reduction of the 3rd component of complement.

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