Effects of Pacing When Using Material Handling Manipulators

Common manipulator-assisted materials handling tasks were performed in a laboratory simulation at self-selected and faster (paced) speeds. The effects of pacing on peak hand forces, torso kinematics, spine moments and forces, and muscle antagonism were determined, along with any influences of several task variables on these effects. The faster trials were performed 20% more rapidly than the self-paced trials. It was found that (a) achieving this level of performance required 10% higher hand forces and 5%-10% higher torso moments, (b) consistent torso postures and motions were used for both speed conditions, and (c) the faster trials resulted in 10% higher spine forces and 15% higher levels of lumbar muscle antagonism. On whole, these results suggest a higher risk of musculoskeletal injury associated with performance of object transfers at faster than self-selected speeds with and without a manipulator. Further analysis provided evidence that the use of manipulators involves higher levels of motor coordination than do manual tasks. Several implications regarding the use of material handling manipulators in paced operations are discussed. Results from this investigation can be used in the design, evaluation, and selection of material handling manipulators.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67067/2/10.1518_001872099779591240.pd

Fatigue evaluation in maintenance and assembly operations by digital human simulation

Virtual human techniques have been used a lot in industrial design in order to consider human factors and ergonomics as early as possible. The physical status (the physical capacity of virtual human) has been mostly treated as invariable in the current available human simulation tools, while indeed the physical capacity varies along time in an operation and the change of the physical capacity depends on the history of the work as well. Virtual Human Status is proposed in this paper in order to assess the difficulty of manual handling operations, especially from the physical perspective. The decrease of the physical capacity before and after an operation is used as an index to indicate the work difficulty. The reduction of physical strength is simulated in a theoretical approach on the basis of a fatigue model in which fatigue resistances of different muscle groups were regressed from 24 existing maximum endurance time (MET) models. A framework based on digital human modeling technique is established to realize the comparison of physical status. An assembly case in airplane assembly is simulated and analyzed under the framework. The endurance time and the decrease of the joint moment strengths are simulated. The experimental result in simulated operations under laboratory conditions confirms the feasibility of the theoretical approach

Effects of Aging on the Biomechanics of Slips and Falls

Although much has been learned in recent decades about the deterioration of muscular strength, gait adaptations, and sensory degradation among older adults, little is known about how these intrinsic changes affect biomechanical parameters associated with slip-induced fall accidents. In general, the objective of this laboratory study was to investigate the process of initiation, detection, and recovery of inadvertent slips and falls. We examined the initiation of and recovery from foot slips among three age groups utilizing biomechanical parameters, muscle strength, and sensory measurements. Forty-two young, middle-age, and older participants walked around a walking track at a comfortable pace. Slippery floor surfaces were placed on the track over force platforms at random intervals without the participants’ awareness. Results indicated that younger participants slipped as often as the older participants, suggesting that the likelihood of slip initiation is similar across all age groups; however, older individuals’ recovery process was much slower and less effective. The ability to successfully recover from a slip (thus preventing a fall) is believed to be affected by lower extremity muscle strength and sensory degradation among older individuals. Results from this research can help pinpoint possible intervention strategies for improving dynamic equilibrium among older adults

Cytosolic Sequestration of Prep1 Influences Early Stages of T Cell Development

Objective: Prep1 and Pbx2 are the main homeodomain DNA-binding proteins of the TALE (three amino acid loop extension) family expressed in the thymus. We previously reported reduced Pbx2 expression and defective thymocyte maturation in Prep1 hypomorphic mice. To further investigate the role of this homeodomain DNA-binding protein in T cell development, we generated transgenic mice expressing the N-terminal fragment of Pbx1 (Pbx1NT) under the control of the Lck proximal promoter. Principal Findings: Pbx1NT causes Prep1 cytosolic sequestration, abolishes Prep1-dependent DNA-binding activity and results in reduced Pbx2 expression in developing thymocytes. Transgenic thymi reveal increased numbers of CD4 2 CD8 2 CD44 2 (DN3 and DN4) thymocytes, due to a higher frequency of DN2 and DN4 Pbx1NT thymocytes in the S phase. Transgenic thymocytes however do not accumulate at later stages, as revealed by a normal representation of CD4/CD8 double positive and single positive thymocytes, due to a higher rate of apoptotic cell death of DN4 Pbx1NT thymocytes. Conclusion: The results obtained by genetic (Prep1 hypomorphic) and functional (Pbx1NT transgenic) inactivation of Prep

A Long-Term Vision for an Ecologically Sound Platte River

The Platte River extends about 310 mi (499 km) from North Platte, Nebraska, to its terminus at the Missouri River confluence near Plattsmouth, Nebraska. The Platte River Valley is a continentally significant ecosystem that serves as a major stopover for migratory waterbirds in the Central Flyway including the endangered Whooping Crane (Grus americana) and \u3e1 million Sandhill Cranes (Antigone canadensis) at the peak of spring migration. However, the Platte River Valley also supports a great diversity of avifauna including grassland breeding birds, native stream fish, vascular plants, herpetofauna, mammals, pollinators, and aquatic macroinvertebrates. Despite ongoing conservation efforts since the mid-1970s the ecosystem remains largely conservation dependent and an increasing number of species across taxa are being considered at risk of regional extirpation or outright extinction. However, given the attention provided to conservation in the Platte River Valley and the need to maintain ecologically functional stopover sites in the Central Flyway, there is a great opportunity to create a resilient refugium for biodiversity conservation in the central Great Plains. To that end we convened a working group of \u3e18 individuals representing \u3e9 organizations including representatives from non-profit conservation organizations, universities, and state and federal natural resource agencies to develop a long-term vision for an ecologically sound Platte River Valley (PRV). We met in groups of varying size for \u3e170 hours throughout a more than 3-year period and developed conservation priorities and objectives using a landscape design process. Landscape design is an interdisciplinary conservation planning process that incorporates components of landscape ecology and social dimensions of natural resources with the explicit intention of improving conservation implementation.https://digitalcommons.unl.edu/zeabook/1128/thumbnail.jp

Deep coverage whole genome sequences and plasma lipoprotein(a) in individuals of European and African ancestries.

Lipoprotein(a), Lp(a), is a modified low-density lipoprotein particle that contains apolipoprotein(a), encoded by LPA, and is a highly heritable, causal risk factor for cardiovascular diseases that varies in concentrations across ancestries. Here, we use deep-coverage whole genome sequencing in 8392 individuals of European and African ancestry to discover and interpret both single-nucleotide variants and copy number (CN) variation associated with Lp(a). We observe that genetic determinants between Europeans and Africans have several unique determinants. The common variant rs12740374 associated with Lp(a) cholesterol is an eQTL for SORT1 and independent of LDL cholesterol. Observed associations of aggregates of rare non-coding variants are largely explained by LPA structural variation, namely the LPA kringle IV 2 (KIV2)-CN. Finally, we find that LPA risk genotypes confer greater relative risk for incident atherosclerotic cardiovascular diseases compared to directly measured Lp(a), and are significantly associated with measures of subclinical atherosclerosis in African Americans

Publisher Correction: Deep coverage whole genome sequences and plasma lipoprotein(a) in individuals of European and African ancestries.

The original version of this article contained an error in the name of the author Ramachandran S. Vasan, which was incorrectly given as Vasan S. Ramachandran. This has now been corrected in both the PDF and HTML versions of the article

A meta‐analysis of change in applicants' perceptions of fairness

Using an event‐triggered multi‐stage framework, this random‐effects meta‐analysis examined the changes in applicants' perceptions of fairness between consecutive stages and throughout the entire personnel selection process. We integrated findings of studies with at least two measurement points, resulting in 45 effect sizes (overall N = 3,038). Trajectories of perceptions of fairness decreased nonlinearly across the process, with a steeper decrease for people who held high levels of initial fairness expectations. Unjust treatment produced a decrease in perceptions of fairness from pretest to posttest and an increase from posttest to postdecision. Furthermore, the length of the time interval moderated the changes in fairness perceptions between the posttest and postdecision stage. Practical implications and an agenda for future research are discussed

Evidence-based clinical practice guideline for the use of pit-and-fissure sealants

AbstractBackgroundThis article presents evidence-based clinical recommendations for the use of pit-and-fissure sealants on the occlusal surfaces of primary and permanent molars in children and adolescents. A guideline panel convened by the American Dental Association (ADA) Council on Scientific Affairs and the American Academy of Pediatric Dentistry conducted a systematic review and formulated recommendations to address clinical questions in relation to the efficacy, retention, and potential side effects of sealants to prevent dental caries; their efficacy compared with fluoride varnishes; and a head-to-head comparison of the different types of sealant material used to prevent caries on pits and fissures of occlusal surfaces.Types of Studies ReviewedThis is an update of the ADA 2008 recommendations on the use of pit-and-fissure sealants on the occlusal surfaces of primary and permanent molars. The authors conducted a systematic search in MEDLINE, Embase, Cochrane Central Register of Controlled Trials, and other sources to identify randomized controlled trials reporting on the effect of sealants (available on the US market) when applied to the occlusal surfaces of primary and permanent molars. The authors used the Grading of Recommendations Assessment, Development, and Evaluation approach to assess the quality of the evidence and to move from the evidence to the decisions.ResultsThe guideline panel formulated 3 main recommendations. They concluded that sealants are effective in preventing and arresting pit-and-fissure occlusal carious lesions of primary and permanent molars in children and adolescents compared with the nonuse of sealants or use of fluoride varnishes. They also concluded that sealants could minimize the progression of noncavitated occlusal carious lesions (also referred to as initial lesions) that receive a sealant. Finally, based on the available limited evidence, the panel was unable to provide specific recommendations on the relative merits of 1 type of sealant material over the others.Conclusions and Practical ImplicationsThese recommendations are designed to inform practitioners during the clinical decision-making process in relation to the prevention of occlusal carious lesions in children and adolescents. Clinicians are encouraged to discuss the information in this guideline with patients or the parents of patients. The authors recommend that clinicians reorient their efforts toward increasing the use of sealants on the occlusal surfaces of primary and permanent molars in children and adolescents