Correlation of Foundation Vibration Results

The vibration a paper machine generates during normal operation presents a complicated challenge to engineers of paper machine support structures. The modeling and the analysis procedure inevitably involves many simplifications and assumptions. Therefore, a comparison of the calculated and the measured results is very helpful in assessing the validity of the overall approach. This paper discusses correlation of calculated paper machine vibration with actual field measurements for a specific paper machine installation. A force-response analysis was performed using a commonly accepted industry practice which is generally considered to be conservative in several areas. Subsequently, field vibration measurements were made. The vibration data were recorded at strategic locations of the paper machine and compared with the calculated values. The comparison confirms that the measured results are indeed conservative as compared to the calculated values. Key parameters that affect the predicted results are also discussed in the paper

The role of shawn, the Drosophila homolog of SLC25A39 and SLC25A40, in neuronal function and survival

The brain consists out of billions of neurons all connected in functional circuits. Good interplay between the individual units and networks forms the basis for our daily life. Exposure to intrinsic and extrinsic factors such as environmental toxins might disturb correct functioning of these networks eventually inducing severe pathologies. Proper understanding of neuronal function under normal and pathological conditions is therefore key to understand and eventually improve neurological disorders. Drosophila melanogaster is a model system frequently used to perform large scale forward genetic screens, a strategy applied by scientists to identify novel components or concepts for a given process of interest. In this work we performed a large scale forward genetic screen in Drosophila and generated a large mutant population using the chemical mutagen ethyl methanesulfonate. We subsequently used a simple electrophysiological recording, the electroretinogram to isolate those mutants that affect synaptic function. In total we identified 119 mutants with defects in synaptic transmission that we, after genetic mapping, assigned into 15 complementation groups. One of the genes we identified is, shawn, a mitochondrial carrier protein of the SLC25 family. Shawn has two human homologs, slc25a39 and slc25a40, and was previously unstudied in the brain. We show that in Drosophila Shawn localizes to mitochondria. Loss of shawn results in reduced mitochondrial function, increased amount of reactive oxygen species (ROS) and eventually mitochondrial swelling. At the level of the brain we found that shawn is necessary for neuronal function and survival because its absence leads to severe toxicity. In yeast shawn was associated with iron and manganese homeostasis and in Drosophila we found accumulations of manganese in the cytosol and an increase in free iron in the mitochondria. The combination of increased ROS and labile iron results in highly redox-active iron that induces more oxidative stress. The increased redox active environment in shawn mutants forms a trigger for neuronal and neuromuscular death. Functionally we found that in contrast to other mitochondrial mutants shawn displays facilitation of glutamatergic transmission. While this could be a homeostatic response, Pink1, a mitochondrial mutant with similar neuromuscular pathology does not show this facilitation. Our mutants display increased cytosolic Mn2+ levels and this metal could either substitute for Ca2+ in the release process or contribute to the release of Ca2+ from intracellular stores. Interestingly both human homologs of shawn have been found in susceptibility loci of epilepsy. Epileptic episodes are often initiated or triggered by an imbalance in glutamatergic and GABAergic transmission. Human diseases involving mitochondrial carrier proteins are rare and very severe. Considering the severity of our phenotypes it is therefore not unlikely that mutations in humans are not viable. However, decreased activity of the carrier can and might be a risk factor for neurodegeneration and epilepsy by sensitizing the cell for toxic insults. Towards the future identifying factors that might improve the activity of shawn might prove beneficial to prevent or delay neurological disorders.nrpages: 175status: publishe

Stroke volume variation and pulse pressure variation measured at pulmonary arterial level versus pulse pressure variation measured at systemic arterial level : an exploratory study

Problem: Optimized fluid management reduces morbidity and mortality in major operations, including cardiac surgery (1, 2). Validated dynamic parameters were developed to predict fluid responsiveness but have limitations (3-5). This study explores the potential added value of stroke volume variation and pulse pressure variation measured at pulmonary arterial level in predicting fluid responsiveness (6). Methods: In twenty adult patients undergoing coronary artery bridging and/or aortic valve replacement, the systemic and pulmonary arterial (SA and PA) pressure curves were stored using Datagrabber software. A custom-made MATLAB code automatically analyzed the pulse pressures, from which the SA and PA pulse pressure variations (PPV_SA and PPV_PA) were calculated. Simultaneously, stroke volumes in the pulmonary artery were measured and PA stroke volume variation (SVV_PA) was calculated. These three parameters were determined in both closed and open chest situations and further analyzed using RStudio software. Results: No correlation could be established between SVV_PA and fluid responsiveness as defined by PPV_SA above 12% (3). In the case of PPV_PA, a mild correlation was seen with the above-mentioned fluid responsiveness, with an R-2 of 25%. Bland Altman analysis of PPV_PA and PPV_SA showed proportional bias with broad limits of agreement. ROC curve analysis attempted to determine a new cutoff value for PPV_PA, which was 33% (sensitivity 100%, specificity 86%). Conclusions: SVV_PA could not be correlated with fluid responsiveness as previously defined. PPV_PA appears to be mildly correlated with fluid responsiveness and has a relatively faster increase in variation than PPV_SA. Therefore, a new fluid responsiveness cutoff for PPV_ PA is proposed. Further research is needed to confirm these findings and to explore further the sensitivity and specificity regarding fluid responsiveness