Uncertainty estimation for operational ocean forecast products-a multi-model ensemble for the North Sea and the Baltic Sea

Multi-model ensembles for sea surface temperature (SST), sea surface salinity (SSS), sea surface currents (SSC), and water transports have been developed for the North Sea and the Baltic Sea using outputs from several operational ocean forecasting models provided by different institutes. The individual models differ in model code, resolution, boundary conditions, atmospheric forcing, and data assimilation. The ensembles are produced on a daily basis. Daily statistics are calculated for each parameter giving information about the spread of the forecasts with standard deviation, ensemble mean and median, and coefficient of variation. High forecast uncertainty, i.e., for SSS and SSC, was found in the Skagerrak, Kattegat (Transition Area between North Sea and Baltic Sea), and the Norwegian Channel. Based on the data collected, longer-term statistical analyses have been done, such as a comparison with satellite data for SST and evaluation of the deviation between forecasts in temporal and spatial scale. Regions of high forecast uncertainty for SSS and SSC have been detected in the Transition Area and the Norwegian Channel where a large spread between the models might evolve due to differences in simulating the frontal structures and their movements. A distinct seasonal pattern could be distinguished for SST with high uncertainty between the forecasts during summer. Forecasts with relatively high deviation from the multi-model ensemble (MME) products or the other individual forecasts were detected for each region and each parameter. The comparison with satellite data showed that the error of the MME products is lowest compared to those of the ensemble members

Tibio-femoral joint constraints for bone pose estimation during movement using multi-body optimization

The financial support of the Universita'Italo-Francese (Call Vinci) and of the Department of Human Movement and Sport Sciences of the University of Rome ''Foro Italico'' is gratefully acknowledged. The authors wish to acknowledge Dr. Sophie Lacoste for her technical support and John McCamley for his contribution to the refinement of the manuscriptWhen using skin markers and stereophotogrammetry for movement analysis, bone pose estimation may be performed using multi-body optimization with the intent of reducing the effect of soft tissue artefacts. When the joint of interest is the knee, improvement of this approach requires defining subject-specific relevant kinematic constraints. The aim of this work was to provide these constraints in the form of plausible values for the distances between origin and insertion of the main ligaments (ligament lengths), during loaded healthy knee flexion, taking into account the indeterminacies associated with landmark identification during anatomical calibration. Ligament attachment sites were identified through virtual palpation on digital bone templates. Attachments sites were estimated for six knee specimens by matching the femur and tibia templates to low-dose stereoradiography images. Movement data were obtained using stereophotogrammetry and pin markers. Relevant ligament lengths for the anterior and posterior cruciate, lateral collateral, and deep and superficial bundles of the medial collateral ligaments (ACL, PCL, LCL, MCLdeep, MCLsup) were calculated. The effect of landmark identification variability was evaluated performing a Monte Carlo simulation on the coordinates of the origin-insertion centroids. The ACL and LCL lengths were found to decrease, and the MCLdeep length to increase significantly during flexion, while variations in PCL and MCLsup length was concealed by the experimental indeterminacy. An analytical model is given that provides subject-specific plausible ligament length variations as functions of the knee flexion angle and that can be incorporated in a multi-body optimization procedure

The accuracy and precision of radiostereometric analysis in monitoring tibial plateau fractures

Background and purpose: The application of radiostereometric analysis (RSA) to monitor stability of tibial plateau fractures during healing is both limited and yet to be validated. We therefore evaluated the accuracy and precision of RSA in a tibial plateau fracture model. Methods: Combinations of 3, 6, and 9 markers in a lateral condyle fracture were evaluated with reference to 6 proximal tibial arrangements. Translation and rotation accuracy was assessed with displacement-controlled stages, while precision was assessed with dynamic double examinations. A comparison of error according to marker number and arrangement was completed with 2-way ANOVA models. Results: The results were improved using more tantalum markers in each segment. In the fracture fragment, marker scatter in all axes was achieved by a circumferential arrangement (medial, anterior, and lateral) of the tantalum markers above the fixation devices. Markers placed on either side of the tibial tuberosity and in the medial aspect of the fracture split represented the proximal tibial reference segment best. Using 6 markers with this distribution in each segment, the translation accuracy (root mean square error) was less than 37 μm in all axes. The precision (95% confidence interval) was less than ± 16 μm in all axes in vitro. Rotation, tested around the x-axis, had an accuracy of less than 0.123° and a precision of ± 0.024°. Interpretation: RSA is highly accurate and precise in the assessment of lateral tibial plateau fracture fragment movement. The validation of our center's RSA system provides evidence to support future clinical RSA fracture studies.Lucian B Solomon, Aaron W Stevenson, Stuart A Callary, Thomas R Sullivan, Donald W Howie, and Mellick J Chehad

Towards a piezoelectric vibration-powered microgenerator

As MEMS and Smart Material technologies advance, embedded and remote applications are becoming more widespread. Powering these systems can be a significant engineering problem, as traditional solutions such as batteries are not always appropriate. An inertial generator is developed that uses thick-film piezoelectric technologies to produce electrical power from vibrations in the environment of the device. The device validates the concept, and produces an output of 3uW. Predictions show that orders of magnitude increase in power output are possible

Mutation analysis of SLC7A9 in cystinuria patients in Sweden

Cystinuria is an autosomal recessive disorder characterized by increased urinary excretion of cystine and dibasic amino acids, which cause recurrent stone formation in affected individuals. Three subtypes of cystinuria have been described (type I, II, and III): type I is caused by mutations in the SLC3A1 gene, whereas nontype I (II and III) has been associated with SLC7A9 mutations. Of the 53 patients reported in our previous work, patients that showed SLC7A9 mutations in single-strand conformation polymorphism (SSCP) screening and/or either lacked or showed heterozygosity for SLC3A1 mutations were included in the present study. The entire coding region and the exon/intron boundaries of the SLC7A9 gene were analyzed by means of both SSCP and DNA sequencing in 16 patients, all but one of which were clinically diagnosed as homozygous cystinurics. Three novel SLC7A9 mutations were identified in the patient group: two missense mutations (P261L and V330M), and one single base-pair deletion (1009 delA). We also detected the previously reported A182T and nine novel polymorphisms in the patients. Mutations V330M and 1009delA occurred on different alleles in one individual, and we suggest that these mutations cause cystinuria in this patient. One patient that was homozygously mutated in the SLC3A1 gene carried the third novel mutation (P261L). We conclude that SLC3A1 is still the major disease gene among Swedish cystinuria patients, with only a minor contribution of SLC7A9 mutations as the genetic basis of cystinuria. The absence of SLC3A1 and SLC7A9 mutations in a substantial proportion of the patients implies that mutations in parts of the genes that were not analyzed may be present, as well as large deletions that escape detection by the methods used. However, our results raise the question of whether other, as yet unknown genes, may also be involved in cystinuria

Genetic deletion of mPGES-1 accelerates intestinal tumorigenesis in APC(Min/+) mice

The induced synthesis of bioactive prostanoids downstream of cyclooxygenase-2 (COX-2) and prostaglandin H(2) (PGH(2)) exerts a critical event in colorectal carcinogenesis. Here we demonstrate that APC(Min/+) mice with genetic deletion of microsomal prostaglandin E synthase-1 (mPGES-1), which catalyses the terminal conversion of PGH(2) into PGE(2), surprisingly develop more and generally larger intestinal tumors than do mPGES-1 wild type littermates (mean number of tumors/intestine 80 vs. 38, p <0.0005, mean tumor diameter 1.64 vs. 1.12 mm, p <0.0005). No deviation regarding the expression of other PGE2 related enzymes (COX-1, COX-2, mPGES-2, cPGES, and 15-PGDH) or receptors (EP1-4) was obvious among the mPGES-1 deficient mice. PGE(2) levels were suppressed in tumors of mPGES-1 deficient animals, but the concentrations of other PGH(2) derived prostanoids were generally enhanced, being most prominent for TxA(2) and PGD(2). Thus, we hypothesise that a redirected synthesis towards other lipid mediators might (over)compensate for loss of mPGES-1/PGE(2) during intestinal tumorigenesis. Nevertheless, our results question the suitability for mPGES-1 targeting therapy in the treatment or prevention of colorectal cancer. (C) 2008 Elsevier Inc. All rights reserved