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- Fatollahzadeh, Kianoush, 1956-
(författare)
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A laboratory vehicle mock-up research work on truck driver’s selected seat position and posture : A mathematical model approach with respect to anthropometry, body landmark locations and discomfort
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Professional truck drivers are highly exposed to fatigue and work related injuries. Truck drivers are common victims of musculoskeletal disorders, frequently suffering from pain symptoms particularly in the neck, shoulder and lower back. This situation is believed to be a contributor to the high absenteeism in this job category. A high percentage of this problem is due to the adoption of an unhealthy driving posture resulting from inappropriate seat design. This incorrect and poor design is owing to the insufficient and obsolete anthropometrical data which has been used for decades for arranging and positioning components in the driver environment. The main objective of the present study was to create and construct a mathematical model which clarifies and predicts the drivers’ comfortable sitting posture and position. It was hypothesized that the length and height characteristics of some body segments as well as the body weight and waist circumference of the driver have a great impact on the selection of a specific sitting posture. The steering wheel positions as well as the pedal/floor locations were hypothesized to be highly correlated to the driver’s selected posture and the corresponding comfort. The effect of the seat position on posture selection and related comfort assessments constituted the other hypothesis of the study which received extra attention. A laboratory experiment on a Scania truck cab mock-up was conducted. The seat track travel along a vertical as well as horizontal forward-backward path was obtained by mounting the seat on the motorized rigid frame which allowed unrestricted vertical and fore-aft travel. The seat cushion angle and backrest angle were adjusted by pivoting the entire seat and backrest around a lateral axis and independently. The pedal components were mounted on a motorized platform, thus allowing unrestricted fore-aft and height travel without any changes in the pedal angles. The steering wheel was mounted on the instrument panel by two independent pneumatic axes which allowed a wide range of adjustments including tilting and moving along the sagittal plane for adjusting the height and distance. The test plan called for 55 international highly experienced heavy truck drivers. The drivers were recruited to span a large range of body weight and stature, in particular to ensure adequate representation of both the extreme as well as the normal group of drivers. The drivers filled in a general information questionnaire before undergoing the anthropometrical measurements and thereafter the test trials. The experiment contained a subset of test conditions with five different trials using random selection sampling procedure. Drivers were asked to adjust the components in a wide range of trajectory according to a written protocol. A sparse set of threedimensional body landmark locations and the corresponding comfort assessments were recorded. As the main part of the result, the mathematical models using multiple regression analyses on selected body landmarks as well as anthropometrical measures were developed which proposed a linear correlation between parameters. The differences between the observed data and the corresponding predicted data using the model were found to be minimal and almost dispensable. Additionally, the drivers preferred to sit in the rearmost position and at a rather high level relative to the rest of the available and adjustable area. Considering the normal adjustable seat area of the cab, only a very small part of the observed Hpoint data lies within this area while a large remaining amount of data lies outside of it. Moreover, the difference between the observation (plotted H-point data) and the neutral H-point was found to be significant. Furthermore, and since some of the data lies almost on the border of the adjustable area, it may indicate a reasonable tendency for even more seat adjustment in the backward direction. A conceptual model consisting of four different parameters was developed and presented in the end. These parameters of the model suggest being as key factors which play a central role on process of decision making regarding the selection of a desirable sitting posture. Any eventual modifications and adjustments for elimination or minimizing discrepancies, biases or obscured factors affecting the quality of the mathematical model would be a case for future study. The investigation of a complete assessment of comfort should be supplemented with an analysis of how many truck drivers are satisfied with the comfort in the end.
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- Karalexi, M. A., et al.
(författare)
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Maternal fetal loss history and increased acute leukemia subtype risk in subsequent offspring : a systematic review and meta-analysis
- 2017
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Ingår i: Cancer Causes and Control. - : SPRINGER. - 0957-5243 .- 1573-7225. ; 28:6, s. 599-624
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Forskningsöversikt (refereegranskat)abstract
- Purpose History of fetal loss including miscarriage and stillbirth has been inconsistently associated with childhood (0-14 years) leukemia in subsequent offspring. A quantitative synthesis of the inconclusive literature by leukemia subtype was therefore conducted. Methods Eligible studies (N = 32) were identified through the screening of over 3500 publications. Random-effects meta-analyses were conducted on the association of miscarriage/stillbirth history with overall (AL; 18,868 cases/35,685 controls), acute lymphoblastic (ALL; 16,150 cases/38,655 controls), and myeloid (AML; 3042 cases/32,997 controls) leukemia. Sensitivity and subgroup analyses by age and ALL subtype, as well as meta-regression were undertaken. Results Fetal loss history was associated with increased AL risk [Odds Ratio (OR) 1.10, 95% Confidence Intervals (CI) 1.04-1.18]. The positive association was seen for ALL (OR 1.12, 95%CI 1.05-1.19) and for AML (OR 1.13, 95%CI 0.91-1.41); for the latter the OR increased in sensitivity analyses. Notably, stillbirth history was significantly linked to ALL risk (OR 1.33, 95%CI 1.02-1.74), but not AML. By contrast, the association of ALL and AML with previous miscarriage reached marginal significance. The association of miscarriage history was strongest in infant ALL (OR 2.34, 95%CI 1.19-4.60). Conclusions In this meta-analysis involving > 50,000 children, we found noteworthy associations by indices of fetal loss, age at diagnosis, and leukemia type; namely, of stillbirth with ALL and miscarriage history with infant ALL. Elucidation of plausible underlying mechanisms may provide insight into leukemia pathogenesis and indicate monitoring interventions prior to and during pregnancy.
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- Kvarnström, Björn
(författare)
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Traceability methods for continuous processes
- 2008
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The subject of this thesis is traceability in continuous processes, i.e. the ability to trace products or batches through a certain process. Examples of the benefits from traceability are that it minimises the extent to which products are affected by product recalls and assures lot uniformity in production. The traceability in part production is often high, since various kinds of identification markers can be attached to a product or batch and followed. Further, the literature in the traceability field is dominated by descriptions of traceability issues in parts production. However, creating traceability in continuous processes implies vast challenges: process flows can be parallel, serial and reflux; sub processes can be continuous as well as batch-wise. These challenges are not commonly addressed in the research literature about traceability. Continuous processes are commonly found in process industries such as the mining, dairy and food, paper, and steel industries. The purpose of this thesis is to explore and describe how traceability can be improved in continuous processes. A research study consisting of a case study was designed and performed to fulfil the purpose. The results from the study are described in four papers. In Paper 1, various traceability methods that could be used to improve traceability in continuous processes are identified and described together with their advantages and disadvantages. A mind map connecting different terms of traceability found in the literature is also presented. Further, the mind map describes how traceability may be improved in a continuous process. In Paper 2, a procedure to develop a flow simulation model for a process section to improve traceability is presented. The constructed flow model is then used to simulate the product flow in the pelletizing plants at LKAB. In Paper 3, a novel method to create traceability in a granular product flow using radio frequency identification (RFID) technique is presented. RFID is a wireless and automatic data capturing technique. The method showed promising results when it was initially tested at a conveyor. In Paper 4, the RFID technique is tested in two full scale experiments in a distribution chain of iron ore pellets at LKAB. Different types of RFID- tags and tag containers are tested in the experiments. The results of the experiments show that the RFID technique can be used to improve traceability in the distribution chain. Finally, the results from the research study illustrate that it may be possible to improve traceability in continuous processes by applying the presented traceability methods.
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- Landeck, Natalie, et al.
(författare)
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Two C-terminal sequence variations determine differential neurotoxicity between human and mouse α-synuclein
- 2020
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Ingår i: Molecular Neurodegeneration. - : Springer Science and Business Media LLC. - 1750-1326. ; 15:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: α-Synuclein (aSyn) aggregation is thought to play a central role in neurodegenerative disorders termed synucleinopathies, including Parkinson's disease (PD). Mouse aSyn contains a threonine residue at position 53 that mimics the human familial PD substitution A53T, yet in contrast to A53T patients, mice show no evidence of aSyn neuropathology even after aging. Here, we studied the neurotoxicity of human A53T, mouse aSyn, and various human-mouse chimeras in cellular and in vivo models, as well as their biochemical properties relevant to aSyn pathobiology. Methods: Primary midbrain cultures transduced with aSyn-encoding adenoviruses were analyzed immunocytochemically to determine relative dopaminergic neuron viability. Brain sections prepared from rats injected intranigrally with aSyn-encoding adeno-associated viruses were analyzed immunohistochemically to determine nigral dopaminergic neuron viability and striatal dopaminergic terminal density. Recombinant aSyn variants were characterized in terms of fibrillization rates by measuring thioflavin T fluorescence, fibril morphologies via electron microscopy and atomic force microscopy, and protein-lipid interactions by monitoring membrane-induced aSyn aggregation and aSyn-mediated vesicle disruption. Statistical tests consisted of ANOVA followed by Tukey's multiple comparisons post hoc test and the Kruskal-Wallis test followed by a Dunn's multiple comparisons test or a two-tailed Mann-Whitney test. Results: Mouse aSyn was less neurotoxic than human aSyn A53T in cell culture and in rat midbrain, and data obtained for the chimeric variants indicated that the human-to-mouse substitutions D121G and N122S were at least partially responsible for this decrease in neurotoxicity. Human aSyn A53T and a chimeric variant with the human residues D and N at positions 121 and 122 (respectively) showed a greater propensity to undergo membrane-induced aggregation and to elicit vesicle disruption. Differences in neurotoxicity among the human, mouse, and chimeric aSyn variants correlated weakly with differences in fibrillization rate or fibril morphology. Conclusions: Mouse aSyn is less neurotoxic than the human A53T variant as a result of inhibitory effects of two C-terminal amino acid substitutions on membrane-induced aSyn aggregation and aSyn-mediated vesicle permeabilization. Our findings highlight the importance of membrane-induced self-assembly in aSyn neurotoxicity and suggest that inhibiting this process by targeting the C-terminal domain could slow neurodegeneration in PD and other synucleinopathy disorders.
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