261 research outputs found
A multilevel control system for the large space telescope
A multilevel scheme was proposed for control of Large Space Telescope (LST) modeled by a three-axis-six-order nonlinear equation. Local controllers were used on the subsystem level to stabilize motions corresponding to the three axes. Global controllers were applied to reduce (and sometimes nullify) the interactions among the subsystems. A multilevel optimization method was developed whereby local quadratic optimizations were performed on the subsystem level, and global control was again used to reduce (nullify) the effect of interactions. The multilevel stabilization and optimization methods are presented as general tools for design and then used in the design of the LST Control System. The methods are entirely computerized, so that they can accommodate higher order LST models with both conceptual and numerical advantages over standard straightforward design techniques
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A Blind Comparative Study of Focused Wave Interactions with a Fixed FPSO-like Structure (CCP-WSI Blind Test Series 1)
Results from Blind Test Series 1, part of the Collaborative ComputationalProject in Wave Structure Interaction (CCP-WSI), are presented. Partici-pants, with a range of numerical methods, simulate blindly the interactionbetween a fixed structure and focused waves ranging in steepness and di-rection. Numerical results are compared against corresponding physicaldata. The predictive capability of each method is assessed based on pres-sure and run-up measurements. In general, all methods perform well inthe cases considered, however, there is notable variation in the results(even between similar methods). Recommendations are made for appro-priate considerations and analysis in future comparative studies
Bayesian test for colocalisation between pairs of genetic association studies using summary statistics.
Genetic association studies, in particular the genome-wide association study (GWAS) design, have provided a wealth of novel insights into the aetiology of a wide range of human diseases and traits, in particular cardiovascular diseases and lipid biomarkers. The next challenge consists of understanding the molecular basis of these associations. The integration of multiple association datasets, including gene expression datasets, can contribute to this goal. We have developed a novel statistical methodology to assess whether two association signals are consistent with a shared causal variant. An application is the integration of disease scans with expression quantitative trait locus (eQTL) studies, but any pair of GWAS datasets can be integrated in this framework. We demonstrate the value of the approach by re-analysing a gene expression dataset in 966 liver samples with a published meta-analysis of lipid traits including >100,000 individuals of European ancestry. Combining all lipid biomarkers, our re-analysis supported 26 out of 38 reported colocalisation results with eQTLs and identified 14 new colocalisation results, hence highlighting the value of a formal statistical test. In three cases of reported eQTL-lipid pairs (SYPL2, IFT172, TBKBP1) for which our analysis suggests that the eQTL pattern is not consistent with the lipid association, we identify alternative colocalisation results with SORT1, GCKR, and KPNB1, indicating that these genes are more likely to be causal in these genomic intervals. A key feature of the method is the ability to derive the output statistics from single SNP summary statistics, hence making it possible to perform systematic meta-analysis type comparisons across multiple GWAS datasets (implemented online at http://coloc.cs.ucl.ac.uk/coloc/). Our methodology provides information about candidate causal genes in associated intervals and has direct implications for the understanding of complex diseases as well as the design of drugs to target disease pathways
Pathophysiology, diagnosis, and treatment of patients with concomitant severe aortic stenosis and coronary artery disease. A closer look to the unresolved perplexity
Degenerative aortic stenosis (AS) and coronary artery disease (CAD) are the most prevalent cardiovascular diseases in developed countries, and they coexist in up to 50% of patients. The pathophysiological rationale behind concomitant AS and CAD is discussed in detail in this review, together with prognostic implications. Detecting CAD in patients with AS may be challenging, as AS may mask the existence and symptoms of CAD. The safety and reliability of invasive and non-invasive physiological assessment for epicardial coronary disease are also a matter of debate. Finally, the selection and timing of optimal treatment of CAD in patients with severe AS are still unclear. Given the aging of the population, the increase in the prevalence of AS, and the ongoing paradigm shift in its treatment, controversies in the diagnosis and treatment of CAD in the setting of AS are deemed to grow in importance. In this paper, we present contemporary issues in the diagnosis and management of CAD in patients with severe AS who are transcatheter aortic valve implantation (TAVI) candidates and provide perspective on the treatment approach
Reperfusion therapy for ST elevation acute myocardial infarction 2010/2011: current status in 37 ESC countries
Aims Primary percutaneous coronary intervention (PPCI) is the preferred reperfusion therapy in ST-elevation myocardial infarction (STEMI). We conducted this study to evaluate the contemporary status on the use and type of reperfusion therapy in patients admitted with STEMI in the European Society of Cardiology (ESC) member countries. Methods and results A cross-sectional descriptive study based on aggregated country-level data on the use of reperfusion therapy in patients admitted with STEMI during 2010 or 2011. Thirty-seven ESC countries were able to provide data from existing national or regional registries. In countries where no such registries exist, data were based on best expert estimates. Data were collected on the use of STEMI reperfusion treatment and mortality, the numbers of cardiologists, and the availability of PPCI facilities in each country. Our survey provides a brief data summary of the degree of variation in reperfusion therapy across Europe. The number of PPCI procedures varied between countries, ranging from 23 to 884 per million inhabitants. Primary percutaneous coronary intervention and thrombolysis were the dominant reperfusion strategy in 33 and 4 countries, respectively. The mean population served by a single PPCI centre with a 24-h service 7 days a week ranged from 31 300 inhabitants per centre to 6 533 000 inhabitants per centre. Twenty-seven of the total 37 countries participated in a former survey from 2007, and major increases in PPCI utilization were observed in 13 of these countries. Conclusion Large variations in reperfusion treatment are still present across Europe. Countries in Eastern and Southern Europe reported that a substantial number of STEMI patients are not receiving any reperfusion therapy. Implementation of the best reperfusion therapy as recommended in the guidelines should be encourage
MiR-137-derived polygenic risk: effects on cognitive performance in patients with schizophrenia and controls
Variants at microRNA-137 (MIR137), one of the most strongly associated schizophrenia risk loci identified to date, have been associated with poorer cognitive performance. As microRNA-137 is known to regulate the expression of ~1900 other genes, including several that are independently associated with schizophrenia, we tested whether this gene set was also associated with variation in cognitive performance. Our analysis was based on an empirically derived list of genes whose expression was altered by manipulation of MIR137 expression. This list was cross-referenced with genome-wide schizophrenia association data to construct individual polygenic scores. We then tested, in a sample of 808 patients and 192 controls, whether these risk scores were associated with altered performance on cognitive functions known to be affected in schizophrenia. A subgroup of healthy participants also underwent functional imaging during memory (n=108) and face processing tasks (n=83). Increased polygenic risk within the empirically derived miR-137 regulated gene score was associated with significantly lower performance on intelligence quotient, working memory and episodic memory. These effects were observed most clearly at a polygenic threshold of P=0.05, although significant results were observed at all three thresholds analyzed. This association was found independently for the gene set as a whole, excluding the schizophrenia-associated MIR137 SNP itself. Analysis of the spatial working memory fMRI task further suggested that increased risk score (thresholded at P=10−5) was significantly associated with increased activation of the right inferior occipital gyrus. In conclusion, these data are consistent with emerging evidence that MIR137 associated risk for schizophrenia may relate to its broader downstream genetic effects
The influence of sighing respirations on infant lung function measured using multiple breath washout gas mixing techniques
There is substantial interest in studying lung function in infants, to better understand the early life origins of chronic lung diseases such as asthma. Multiple breath washout (MBW) is a technique for measuring lung function that has been adapted for use in infants. Respiratory sighs occur frequently in young infants during natural sleep, and in accordance with current MBW guidelines, result in exclusion of data from a substantial proportion of testing cycles. We assessed how sighs during MBW influenced the measurements obtained using data from 767 tests conducted on 246 infants (50% male; mean age 43 days) as part of a large cohort study. Sighs occurred in 119 (15%) tests. Sighs during the main part of the wash‐in phase (before the last 5 breaths) were not associated with differences in standard MBW measurements compared with tests without sighs. In contrast, sighs that occurred during the washout were associated with a small but discernible increase in magnitude and variability. For example, the mean lung clearance index increased by 0.36 (95% CI: 0.11–0.62) and variance increased by a multiplicative factor of 2 (95% CI: 1.6–2.5). The results suggest it is reasonable to include MBW data from testing cycles where a sigh occurs during the wash‐in phase, but not during washout, of MBW. By recovering data that would otherwise have been excluded, we estimate a boost of about 10% to the final number of acceptable tests and 6% to the number of individuals successfully tested
Relationship between mentalizing and teacher burnout: A cross sectional study
Background Teaching is considered a high-risk profession due to the high impact of occupational risk factors which can endanger educators' mental health and lead to burnout syndrome. This study aimed to examine whether the capacity for mentalizing in teachers explains the degree of their burnout syndrome. The expectation was that a low capacity for mentalizing increases the degree of burnout. Methods A cross-sectional study was conducted on a sample of 823 teachers. The Maslach Burnout Inventory-Educators Survey was used to examine the burnout syndrome. The capacity for mentalizing was examined using hypomentalizing and hypermentalizing scales from the Reflective Functioning Questionnaire. Results The expectation that a low capacity for mentalizing increases teachers' burnout confirms the finding that hypomentalizing is a positive predictor of their emotional exhaustion as a dimension of burnout (ß = 0.09; p < 0.01). Unexpectedly, hypomentalizing proved to be a positive predictor of personal accomplishment (ß = 0.09; p < 0.05), which indicates that with a lower capacity for mentalizing, teachers experience greater personal accomplishment. Also, hypermantalizing was a negative predictor of emotional exhaustion (ß = -0.17; p < 0.01) and depersonalization (ß = -0.31; p < 0.01), and a positive predictor of personal accomplishment (ß = 0.30; p < 0.01). The findings showed that with higher socioeconomic status, with marriage and having children, the burnout of teachers is lower, as expected. Conclusions Capacity for mentalizing and burnout syndrome in teachers are interrelated phenomena. With a good capacity for mentalizing, emotional exhaustion and burnout in teachers are reduced. Knowledge and skills that enable a good capacity for mentalizing should be included in educational and teacher training programs
Characterisation of surface oxygen groups on different carbon materials by the Boehm method and temperature-programmed desorption
The surface characteristics of different carbon materials: activated carbon, carbon felt, glassy carbon and a porous carbon monolith were investigated. The specific surface area was examined by the BET method with N(2) adsorption, the amount and the type of surface oxygen groups by Boehm titration as well as by temperature-programmed desorption (TPD). By comparing the results obtained using BET analysis with those of TPD and the Boehm method, it was found that the number of surface groups was not proportional to the specific surface area. The total amount of oxygen groups, obtained by TPD, is higher than the amount obtained by Boehms method for porous samples. The inconsistencies between these results originate from the fact that the Boehm method is limited to the determination of acidic and basic groups, whereas TPD provides information on the total number of all surface oxygen groups. In addition, the presence of porosity could reduce the solvent-accessible surface in the Boehm method. The TPD profiles of CO evolution showed the presence of a low temperature maximum, below 650 K, which originates from CO(2) reduction on the carbon material surface
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