SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Experimental uncertainty analysis

180

Wrist-worn monitors claim to provide accurate measures of heart rate and energy expenditure. People wishing to lose weight use these devices to monitor energy balance, however the accuracy of these devices to measure such parameters has not been established.

Concepts: Measurement, Mass, Psychometrics, Force, Accuracy and precision, Experimental uncertainty analysis, Balance wheel, Monitor

146

Ovarian cancer (OC) is associated with non-specific symptoms such as bloating, making accurate diagnosis challenging: only 1 in 3 women with OC presents through primary care referral. National Institute for Health and Care Excellence guidelines recommends sequential testing with CA125 and routine ultrasound in primary care. However, these diagnostic tests have limited sensitivity or specificity. Improving accurate triage in women with vague symptoms is likely to improve mortality by streamlining referral and care pathways. The Refining Ovarian Cancer Test Accuracy Scores (ROCkeTS; HTA 13/13/01) project will derive and validate new tests/risk prediction models that estimate the probability of having OC in women with symptoms. This protocol refers to the prospective study only (phase III).

Concepts: Type I and type II errors, Hereditary nonpolyposis colorectal cancer, Ovarian cyst, BRCA2, Ovarian cancer, Experimental uncertainty analysis, CA-125, Bloating

30

Laughter is a nonverbal vocal expression that often communicates positive affect and cooperative intent in humans. Temporally coincident laughter occurring within groups is a potentially rich cue of affiliation to overhearers. We examined listeners' judgments of affiliation based on brief, decontextualized instances of colaughter between either established friends or recently acquainted strangers. In a sample of 966 participants from 24 societies, people reliably distinguished friends from strangers with an accuracy of 53-67%. Acoustic analyses of the individual laughter segments revealed that, across cultures, listeners' judgments were consistently predicted by voicing dynamics, suggesting perceptual sensitivity to emotionally triggered spontaneous production. Colaughter affords rapid and accurate appraisals of affiliation that transcend cultural and linguistic boundaries, and may constitute a universal means of signaling cooperative relationships.

Concepts: Psychology, Sociology, Culture, Linguistics, Anthropology, Accuracy and precision, Experimental uncertainty analysis, Humanities

28

Examinations for retinopathy of prematurity (ROP) are typically performed using binocular indirect ophthalmoscopy. Telemedicine studies have traditionally assessed the accuracy of telemedicine compared with ophthalmoscopy as a criterion standard. However, it is not known whether ophthalmoscopy is truly more accurate than telemedicine.

Concepts: Sample size, Accuracy and precision, Experimental uncertainty analysis, Retinopathy of prematurity

27

While laboratory monitoring is not required in patients treated with apixaban, a direct factor-Xa inhibitor, assessment of its concentration is useful in some critical situations. However, few data are available on its effect on coagulation tests and on the suitability of anti-Xa assays for its quantification. It was the objective of this study to identify laboratory tests suitable for apixaban concentration assessment. Coagulation tests - PT and aPTT- and anti-Xa assays were performed in apixaban-spiked plasma samples. To evaluate the sensitivity of PT and aPTT to apixaban, we conducted a first monocenter part, with a wide range of concentrations (50-1,000 ng/ml), a large panel of reagents (20 reagents), and two coagulometers (STAR®, Stago and ACL TOP®, IL), and a second multicenter part involving 13 laboratories using either a common PT reagent (RecombiPlastin2G®) or the local PT and aPTT reagents. In the multicentre part, five blinded apixaban-spiked plasma samples (0/100/200/400/800 ng/ml - checked by HPLC-MS/MS) were used; apixaban concentrations were measured with three anti-Xa assays, apixaban calibrators and controls (Stago). PT and aPTT tests using a large panel of reagents displayed a low sensitivity to a wide range of apixaban concentrations. The concentrations to double PT ranged from 400 to >1,000 ng/ml with the 10 reagents. With the three anti-Xa assays, inter-laboratory precision and accuracy were below 11% and 12%, respectively. In conclusion, whereas PT and aPTT tests were not sensitive enough to detect apixaban, the three anti-Xa assays tested using lyophilised apixaban calibrators and controls allowed to reliably quantify a wide range of apixaban concentrations.

Concepts: Coagulation, Concentration, Chemistry, Experiment, Accuracy and precision, Laboratory, Reagent, Experimental uncertainty analysis

26

The purpose of this study was to investigate step count and energy expenditure accuracy of the piezoelectric Omron (Walking Style X-HJ-304E)and spring-levered Yamax (DigiWalkerSW700/ 701) pedometers at different speeds and various inclinations.

Concepts: Accuracy and precision, Experimental uncertainty analysis, Walking, Gait, Human skills

25

Statistical rate theory calculations, in particular formulations of the chemical master equation, are widely used in order to calculate rate coefficients of interest in combustion environments as a function of temperature and pressure. However despite the increasing accuracy of electronic structure calculations, small uncertainties in the input parameters for these master equation models can lead to relatively large uncertainties in the calculated rate coefficients. Master equation input parameters may be constrained further using experimental data and the relationship between experiment and theory warrants further investigation. In this work the CH3OCH2 + O2 system, of relevance to the combustion of dimethyl ether (DME), is used as an example and the input parameters for master equation calculations on this system are refined through fitting to experimental data. Complementing these fitting calculations, global sensitivity analysis is used to explore which input parameters are constrained by which experimental conditions, and which parameters need to be further constrained in order to accurately predict key elementary rate coefficients. Finally, uncertainties in the calculated rate coefficients are obtained using both correlated and uncorrelated distributions of input parameters.

Concepts: Mathematics, Chemistry, Experiment, Hypothesis, Uncertainty, Experimental uncertainty analysis, Sensitivity analysis, Dimethyl ether

4

The recent release of the gene-targeted metagenomics assembler Xander has demonstrated that using the trained Hidden Markov Model (HMM) to guide the traversal of de Bruijn graph gives obvious advantage over other assembly methods. Xander, as a pilot study, indeed has a lot of room for improvement. Apart from its slow speed, Xander uses only 1 k-mer size for graph construction and whatever choice of k will compromise either sensitivity or accuracy. Xander uses a Bloom-filter representation of de Bruijn graph to achieve a lower memory footprint. Bloom filters bring in false positives, and it is not clear how this would impact the quality of assembly. Xander does not keep track of the multiplicity of k-mers, which would have been an effective way to differentiate between erroneous k-mers and correct k-mers.

Concepts: Bioinformatics, Model theory, Graph theory, Hidden Markov model, Experimental uncertainty analysis, De Bruijn graph, De Bruijn sequence, Nicolaas Govert de Bruijn

3

Structural variations (SVs) play a crucial role in genetic diversity. However, the alignments of reads near/across SVs are made inaccurate by the presence of polymorphisms. BatAlign is an algorithm that integrated two strategies called ‘Reverse-Alignment’ and ‘Deep-Scan’ to improve the accuracy of read-alignment. In our experiments, BatAlign was able to obtain the highest F-measures in read-alignments on mismatch-aberrant, indel-aberrant, concordantly/discordantly paired and SV-spanning data sets. On real data, the alignments of BatAlign were able to recover 4.3% more PCR-validated SVs with 73.3% less callings. These suggest BatAlign to be effective in detecting SVs and other polymorphic-variants accurately using high-throughput data. BatAlign is publicly available at https://goo.gl/a6phxB.

Concepts: Accuracy and precision, Experimental uncertainty analysis, Call option, Incremental backup

3

Precise MEG estimates of neuronal current flow are undermined by uncertain knowledge of the head location with respect to the MEG sensors. This is either due to head movements within the scanning session or systematic errors in co-registration to anatomy. Here we show how such errors can be minimised using subject-specific head-casts produced using 3D printing technology. The casts fit the scalp of the subject internally and the inside of the MEG dewar externally, reducing within session and between session head movement. Systematic errors in matching to MRI coordinate system are also reduced through the use of MRI-visible fiducial markers placed on the same cast. Bootstrap estimates of absolute co-registration error were of the order of 1mm. Estimates of relative co-registration error were <1.5mm between sessions. We corroborated these scalp based estimates by looking at the MEG data recorded over a 6month period. We found the between session sensor variability of the subject's evoked response was of the order of the within session noise, showing no appreciable noise due to between-session movement. Simulations suggest that the between-session sensor level amplitude SNR improved by a factor of 5 over conventional strategies. We show that at this level of coregistration accuracy there is strong evidence for anatomical models based on the individual rather than canonical anatomy; but that this advantage disappears for errors of greater than 5mm. This work paves the way for source reconstruction methods which can exploit very high SNR signals and accurate anatomical models; and also significantly increases the sensitivity of longitudinal studies with MEG.

Concepts: Longitudinal study, Biology, Measurement, Error, Anatomy, Accuracy and precision, Experimental uncertainty analysis, Observational error