A method for determining minimal sets of markers for the estimation of center of mass,linear and angular momentum

A new method is proposed for finding small sets of points on the body giving sufficient information for estimating the whole body center of mass (CoM), as well as the linear momenta (LM) and angular momenta (AM). In the underlying model each point (whose trajectory is tracked by a marker) is a point mass: Hence the body is represented by a simple system of point masses. The first step is to determine the appropriate set of points and the mass of each point, which is assumed to be specific for the movement performed. The distribution of the mass to each marker is determined from training data for which the true (or reference) trajectories of the CoM, LM or AM are known. This leads to a quadratic optimization problem with inequality constraints. The use of the method is demonstrated on data from discus throw. Results indicate reasonably small errors, considering the magnitude of other error sources, in CoM position (average magnitude of estimation error 1–2 cm), and moderate errors in AM (13–20% of peak value).     

Using an extended kalman filter for rigid body pose estimation

Rigid body pose is commonly represented as the rigid body transformation from one (often reference) pose to another This is usually computed for each frame of data without any assumptions or restrictions on the temporal change of the pose. The most common algorithm was proposed by S?derkvist and Wedin (1993, "Determining the Movements of the Skeleton Using Well-configured Markers," J. Biomech., 26, pp. 1473-1477), and implies the assumption that measurement errors are isotropic and homogenous. This paper describes an alternative method based on a state space formulation and the application of an extended Kalman filter (EKF). State space models are formulated, which describe the kinematics of the rigid body. The state vector consists of six generalized coordinates (corresponding to the 6 degrees of freedom), and their first time derivatives. The state space models have linear dynamics, while the measurement function is a non-linear relation between the state vector and the observations (marker positions). An analytical expression for the linearized measurement function is derived. Tracking the rigid body motion using an EKF enables the use of a priori information on the measurement noise and type of motion to tune the filter. The EKF is time variant, which allows for a natural way of handling temporarily missing marker data. State updates are based on all the information available at each time step, even when data from fewer than three markers are available. Comparison with the method of S?derkvist and Wedin on simulated data showed a considerable improvement in accuracy with the proposed EKF method when marker data was temporarily missing. The proposed method offers an improvement in accuracy of rigid body pose estimation by incorporating knowledge of the characteristics of the movement and the measurement errors. Analytical expressions for the linearized system equations are provided, which eliminate the need for approximate discrete differentiation and which facilitate a fast implementation.     

Bias compensated least squares estimate of the center of rotation

It is shown that a recently published least squares method for the estimation of the average center of rotation is biased. Consequently, a correction term is proposed, and an iterative algorithm is derived for finding a bias compensated solution to the least squares problem.The accuracy of the proposed bias compensated least squares method is compared to the previously proposed least squares method by Monte-Carlo simulations. The tests show that the new method gives a substantial improvement in accuracy.     

Contamination of livestock due to the operation of a small waste incinerator: a case incident in Skutulsfjörður,Iceland, in 2010

Background

Declining fertility is a major concern for dairy farmers today. One explanation is shorter and weaker expression of oestrus in dairy cows making it difficult to determine optimal time for artificial insemination (AI). Chemical communication is of interest in the search for tools to detect oestrus or to synchronise or enhance oestrous periods. Pheromones, used in chemical communication within species, can influence reproduction in different ways. The aim here was to investigate whether oestrous cycle length, and duration and intensity of oestrous expression in dairy heifers could be manipulated through exposure to pheromones in oestrual substances from other females.

Methods

Beginning on day 16 of two consecutive control oestrous cycles, ten heifers of the Swedish Red Breed (SRB) were exposed to water. During the two following cycles the heifers were exposed to urine and vaginal mucus, obtained from cows in oestrus. Cyclicity parameters were monitored through hormone measurements, oestrus detection and ultrasonographic examination.

Results

We found no difference in cycle length or in duration of standing oestrus between control and treatment. We did, however, find a tendency of interaction between type of exposure (control or treatment) and cycle number within type of exposure for cycle length (p = 0.068), with the length differing less between the treatment cycles. We also found a tendency of effect of type of exposure on maximal concentration (p = 0.073) and sum of concentrations (p = 0.063) of LH during the LH surge, with values being higher for the control cycles. There were also significant differences in when the different signs of oestrus occurred and in the intensity of oestrous expression. The score for oedema and hyperaemia of external genitalia was significantly higher (p = 0.004) for the control cycles and there was also a significant interaction between type of exposure and time period for restlessness (p = 0.011), with maximum score occurring earlier for treatment cycles.

Conclusions

No evidence of altered oestrous cycle length or duration of oestrus after exposure of females to oestrous substances from other females was found. Expression of oestrus, and maybe also LH secretion, however, seemed influenced by the exposure, with the effect of treatment being suppressive rather than enhancing.     

The importance of plant relatedness for host utilization among phytophagous insects

Current methods for measuring similarity among phytophagous insect communities fail to consider the phylogenetic relationship between host plants. We analysed this relation based on 3580 host observations of 1174 beetle species associated with 100 species of angiosperms in two different forest types in Panama. We quantified the significance of genetic distance as well as taxonomic rank among angiosperms in relation to species overlap in beetle assemblages. A logarithmic model describing the decrease in beetle species similarity between host-plant species of increasing phylogenetic distance explains 35% of the variation. Applied to taxonomic rank categories the results imply that except for the ancient branching of monocots from dicots, only adaptive radiations of plants on the family and genus level are important for host utilization among phytophagous beetles. These findings enable improvements in estimating host specificity and species richness through correction for phylogenetic relatedness between hosts and consideration of the host-specific fauna associated with monocots.     

Interleukin-1beta swiftly down-regulates UCP-2 mRNA in beta-cells by mechanisms not directly coupled to toxicity

Regulation of uncoupling protein-2 (UCP-2) in beta-cells is presently unclear but may involve oxidative stress. We tested for regulation by beta-cell toxic cytokines. Exposure to interleukin-1beta (IL-1beta, 10 ng/ml) for 6 h down-regulated UCP-2 mRNA in clonal INS-1 cells, by 37 +/- 7%, and in rat pancreatic islets, by 55 +/- 8%. In contrast, a 6 h exposure to IL-1beta did not affect viability as assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, or mitochondrial membrane potential, or ATP cellular contents. Continued exposure to IL-1beta was accompanied by decreased viability and persisting down-regulation of UCP-2 mRNA. Exposure to a combination of IL-1beta and tumor necrosis factor (TNF)-alpha for 48 h additively decreased cell viability and UCP-2 mRNA. The constitutive nitric oxide (NO) synthase inhibitor N-omega-nitro-L-arginine methyl ester (L-NAME, 1 mM) partially protected against toxicity but failed to significantly affect UCP-2 mRNA expression. The inducible NO synthase inhibitor N(G)-monomethyl-L-arginine (L-NMMA, 1 mM) protected completely against cytokine-induced toxicity. L-NMMA per se down-regulated UCP-2 mRNA (by 64 +/- 7%). Transfection with a UCP-2-antisense nucleotide failed to affect IL-1beta induced toxicity. In conclusion, down-regulation of UCP-2 mRNA by IL-1beta is an early event of cytokine interaction with beta-cells which is not directly coupled to toxicity.     

Genetic characterization of the mitochondrial DNA from Lepeophtheirus salmonis (Crustacea; Copepoda). A new gene organization revealed

The mitochondrial DNA (mtDNA) from the salmon louse, Lepeophtheirus salmonis, is 15445 bp. It includes the genes coding for cytochrome B (Cyt B), ATPase subunit 6 and 8 (A6 and A8), NADH dehydrogenase subunits 1-6 and 4L (ND1, ND2, ND3, ND4, ND4L, ND5 and ND6), cytochrome c oxidase subunits I-III (COI, COII and COIII), two rRNA genes (12S rRNA and 16S rRNA) and 22 tRNAs. Two copies of tRNA-Lys are present in the mtDNA of L. salmonis, while tRNA-Cys was not identified. Both DNA strands contain coding regions in the salmon louse, in contrast to the other copepod characterized Tigriopus japonicus, but only a few genes overlap. In vertebrates, ND4 and ND4L are transcribed as one bicistronic mRNA, and are therefore localized together. The same organization is also found in crustaceans, with the exceptions of T. japonicus, Neocalanus cristatus and L. salmonis that deviate from this pattern. Another exception of the L. salmonis mtDNA is that A6 and A8 do not overlap, but are separated by several genes. The protein-coding genes have a bias towards AT-rich codons. The mitochondrial gene order in L. salmonis differs significantly from the copepods T. japonicus, Eucalanus bungii, N. cristatus and the other 13 crustaceans previously characterized. Furthermore, the mitochondrial rRNA genes are encoded on opposite strands in L. salmonis. This has not been found in any other arthropods, but has been reported in two starfish species. In a phylogenetic analysis, using an alignment of mitochondrial protein sequences, L. salmonis groups together with T. japonicus, being distant relatives to the other crustaceans.     

Closely related colon cancer cell lines display different sensitivity to polyunsaturated fatty acids, accumulate different lipid classes and downregulate sterol regulatory element-binding protein 1

N-6 polyunsaturated fatty acids (PUFAs) may be associated with increased risk of colon cancer, whereas n-3 PUFAs may have a protective effect. We examined the effects of docosahexaenoic acid (DHA), eicosapentaenoic acid and arachidonic acid on the colon carcinoma cell lines SW480 derived from a primary tumour, and SW620 derived from a metastasis of the same tumour. DHA had the strongest growth-inhibitory effect on both cell lines. SW620 was relatively more growth-inhibited than SW480, but SW620 also had the highest growth rate in the absence of PUFAs. Flow cytometry revealed an increase in the fraction of cells in the G2/M phase of the cell cycle, particularly for SW620 cells. Growth inhibition was apparently not caused by increased lipid peroxidation, reduced glutathione or low activity of glutathione peroxidase. Transmission electron microscopy revealed formation of cytoplasmic lipid droplets after DHA treatment. In SW620 cells an eightfold increase in total cholesteryl esters and a 190-fold increase in DHA-containing cholesteryl esters were observed after DHA treatment. In contrast, SW480 cells accumulated DHA-enriched triglycerides. Arachidonic acid accumulated in a similar manner, whereas the nontoxic oleic acid was mainly incorporated in triglycerides in both cell lines. Interestingly, nuclear sterol regulatory element-binding protein 1 (nSREBP1), recently associated with cell growth regulation, was downregulated after DHA treatment in both cell lines. Our results demonstrate cell-specific mechanisms for the processing and storage of cytotoxic PUFAs in closely related cell lines, and suggest downregulation of nSREBP1 as a possible contributor to the growth inhibitory effect of DHA.