1,756 research outputs found
Kinematic modelling of a 3-axis NC machine tool in linear and circular interpolation
Machining time is a major performance criterion when it comes to high-speed
machining. CAM software can help in estimating that time for a given strategy.
But in practice, CAM-programmed feed rates are rarely achieved, especially
where complex surface finishing is concerned. This means that machining time
forecasts are often more than one step removed from reality. The reason behind
this is that CAM routines do not take either the dynamic performances of the
machines or their specific machining tolerances into account. The present
article seeks to improve simulation of high-speed NC machine dynamic behaviour
and machining time prediction, offering two models. The first contributes
through enhanced simulation of three-axis paths in linear and circular
interpolation, taking high-speed machine accelerations and jerks into account.
The second model allows transition passages between blocks to be integrated in
the simulation by adding in a polynomial transition path that caters for the
true machining environment tolerances. Models are based on respect for path
monitoring. Experimental validation shows the contribution of polynomial
modelling of the transition passage due to the absence of a leap in
acceleration. Simulation error on the machining time prediction remains below
1%
Combined use of mitochondrial and nuclear genetic markers further reveal immature marine turtle hybrids along the South Western Atlantic
Marine turtle hybridization is usually sporadic and involves reports of only a few individuals; however, Brazilian populations have high hybridization rates. Here we investigated the presence of hybrids in morphologically identified immature hawksbills (Eretmochelys imbricate) along the South Western Atlantic (SWA). We sequenced one mitochondrial (D-Loop) and three nuclear DNA (RAG1, RAG2, and CMOS) markers to better understand the patterns and characteristics of hybrids. We identified 22 hybrids (n = 270), 11 of them at the extreme South of the SWA. Uruguay had the highest hybrid frequency in the SWA (similar to 37.5%) followed by southern Brazil with 30%. These are common areas for loggerheads (Caretta caretta) but uncommon for hawksbills, and these hybrids may be adopting the behavior of loggerheads. By analyzing nuclear markers, we can infer that 50% of the sampled hybrids are first generation (F1) and 36% are the result of backcrosses between hybrids and pure E. imbricate (> F1). We also report for the first time immature E. imbricate x Lepidochelys olivacea hybrids at the Brazilian coast. Considering the high frequency of hybrids in the SWA, continuous monitoring should be performed to assess the fitness, genetic integrity, and extent of changes in the gene pools of involved populations
Intercalation of aromatic sulfonates in âgreen rustâ via ion exchange
âGreen rustâ intercalated with aromatic sulfonates can potentially be effective materials for the treatment of soil and groundwater polluted with chlorinated benzenes. We investigated the potential intercalation of benzene sulfonate (BzS) and 1,3-benzene disulfonate (BzDS) into green rust sulfate (GRSO4) via ion exchange. The GRSO4 reacted with various concentrations of sulfonates were characterized by X-ray diffraction, X-ray scattering and transmission electron microscopy. GR interacted with BzDS did not result in intercalation due to stearic hindrance and electrostatic repulsion. For BzS, mixtures of GRSO4 and GR-BzS (d001 = 14.3 Ă
) were obtained at molar equivalents of ion exchange capacity >5. The intercalation of BzS in the GR structure is limited (~18% intercalation) since BzS cannot fully replace SO42-. The BzS molecules are likely arranged in the interlayer as a dehydrated monolayer with the âSO3 groups facing away in alternate directions
Robust singleâwalled carbon nanotubeâinfiltrated carbon fiber electrodes for structural supercapacitors: from reductive dissolution to high performance devices
Multifunctional electrodes for structural supercapacitors are prepared by vacuum infiltration of single-walled carbon nanotubes (SWCNTs) into woven carbon fibers (CFs); the use of reductive charging chemistry to form nanotubide solutions ensured a high degree of individualization. The route is highly versatile, as shown by comparing four different commercial nanotube feedstocks. In film form, the pure nanotubide networks (âbuckypapersâ) are highly conductive (up to 2000 S cmâ1) with high surface area (>1000 m2 gâ1) and great electrochemical performance (capacitance of 101 F gâ1, energy density of 27.5 Wh kgâ1 and power density of 135 kW kgâ1). Uniformly integrating these SWCNT networks throughout the CF fabrics significantly increased electrical conductivity (up to 318 S cmâ1), surface area (up to 196 m2 gâ1), and in-plane shear properties, all simultaneously. The CNT-infiltrated CFs electrodes exhibited intrinsically high specific energy (2.6â4.2 Wh kgâ1) and power (6.0â8.7 kW kgâ1) densities in pure 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM TFSI) electrolyte. Multifunctional structural supercapacitors based on CNT-coated CFs offer a substantial increase in capacitive performance while maintaining the tensile mechanical properties of the as-received CF-based composite. This non-damaging approach to modify CFs with highly graphitic, high surface area nanocarbons provides a new route to structural energy storage systems
Pharmacoeconomic analysis of adjuvant oral capecitabine vs intravenous 5-FU/LV in Dukes' C colon cancer: the X-ACT trial
Oral capecitabine (Xeloda<sup>®</sup>) is an effective drug with favourable safety in adjuvant and metastatic colorectal cancer. Oxaliplatin-based therapy is becoming standard for Dukes' C colon cancer in patients suitable for combination therapy, but is not yet approved by the UK National Institute for Health and Clinical Excellence (NICE) in the adjuvant setting. Adjuvant capecitabine is at least as effective as 5-fluorouracil/leucovorin (5-FU/LV), with significant superiority in relapse-free survival and a trend towards improved disease-free and overall survival. We assessed the cost-effectiveness of adjuvant capecitabine from payer (UK National Health Service (NHS)) and societal perspectives. We used clinical trial data and published sources to estimate incremental direct and societal costs and gains in quality-adjusted life months (QALMs). Acquisition costs were higher for capecitabine than 5-FU/LV, but higher 5-FU/LV administration costs resulted in 57% lower chemotherapy costs for capecitabine. Capecitabine vs 5-FU/LV-associated adverse events required fewer medications and hospitalisations (cost savings ÂŁ3653). Societal costs, including patient travel/time costs, were reduced by >75% with capecitabine vs 5-FU/LV (cost savings ÂŁ1318), with lifetime gain in QALMs of 9 months. Medical resource utilisation is significantly decreased with capecitabine vs 5-FU/LV, with cost savings to the NHS and society. Capecitabine is also projected to increase life expectancy vs 5-FU/LV. Cost savings and better outcomes make capecitabine a preferred adjuvant therapy for Dukes' C colon cancer. This pharmacoeconomic analysis strongly supports replacing 5-FU/LV with capecitabine in the adjuvant treatment of colon cancer in the UK
A population-based controlled experiment assessing the epidemiological impact of digital contact tracing
While Digital contact tracing (DCT) has been argued to be a valuable complement to manual tracing in the containment of COVID-19, no empirical evidence of its effectiveness is available to date. Here, we report the results of a 4-week population-based controlled experiment that took place in La Gomera (Canary Islands, Spain) between June and July 2020, where we assessed the epidemiological impact of the Spanish DCT app Radar Covid. After a substantial communication campaign, we estimate that at least 33% of the population adopted the technology and further showed relatively high adherence and compliance as well as a quick turnaround time. The app detects about 6.3 close-contacts per primary simulated infection, a significant percentage being contacts with strangers, although the spontaneous follow-up rate of these notified cases is low. Overall, these results provide experimental evidence of the potential usefulness of DCT during an epidemic outbreak in a real population
Laboratory comparison of aging characteristics of warm mix asphalts involving natural and synthetic water containing additives
When comparing the aging characteristics of hot and warm mix asphalts from a technical point of view, it can intuitively be expected that a warm mix asphalt would be less subjected to aging-induced failures due to lower application temperatures. Since the side effects of warm asphalt technology should be investigated distinctly. This study addresses the aging investigation of properties of bituminous mixtures containing two (i.e., natural and synthetic zeolite) water based additives available on the market. Within the scope of this study, short- and long-term aging conditions were simulated on mixtures containing various contents of additives as well as on control specimens. The aging indices were determined based on the hardness ratio employing indirect tensile strength values in order to investigate the aging induced failures betide by time. Aging indices showed that the specimens with water containing additives demonstrate relatively better resistance against hardening than conventional hot mix asphalt specimens
Accuracy in Copy Number Calling by qPCR and PRT: A Matter of DNA
The possible implication of copy number variation (CNV) in the genetic susceptibility to human disease needs to be assessed using robust methods that can be applied at a population scale. In this report, we analyze the performance of the two major techniques, quantitative PCR (qPCR) and paralog ratio test (PRT), and investigate the influence of input DNA amount and template integrity on the reliability of both methods. Analysis of three genes (PRELID1, SYNPO and DEFB4) in a large sample set showed that both methods are prone to false copy number assignments if sufficient attention is not paid to DNA concentration and quality. Accurate normalization of samples is essential for reproducible qPCR because it avoids the effect of differential amplification efficiencies between target and control assays, whereas PRT is generally more sensitive to template degradation due to the fact that longer amplicons are usually needed to optimize sensitivity and specificity of paralog sequence PCR. The use of normalized, high quality genomic DNA yields comparable results with both methods
Pattern Formation in Interface Depinning and Other Models: Erratically Moving Spatial Structures
We study erratically moving spatial structures that are found in a driven
interface in a random medium at the depinning threshold. We introduce a
bond-disordered variant of the Sneppen model and study the effect of extremal
dynamics on the morphology of the interface. We find evidence for the formation
of a structure which moves along with the growth site. The time average of the
structure, which is defined with respect to the active spot of growth, defines
an activity-centered pattern. Extensive Monte Carlo simulations show that the
pattern has a tail which decays slowly, as a power law. To understand this sort
of pattern formation, we write down an approximate integral equation involving
the local interface dynamics and long-ranged jumps of the growth spot. We
clarify the nature of the approximation by considering a model for which the
integral equation is exactly derivable from an extended master equation.
Improvements to the equation are considered by adding a second coupled equation
which provides a self-consistent description. The pattern, which defines a
one-point correlation function, is shown to have a strong effect on ordinary
space-fixed two-point correlation functions. Finally we present evidence that
this sort of pattern formation is not confined to the interface problem, but is
generic to situations in which the activity at succesive time steps is
correlated, as for instance in several other extremal models. We present
numerical results for activity-centered patterns in the Bak-Sneppen model of
evolution and the Zaitsev model of low-temperature creep.Comment: RevTeX, 18 pages, 19 eps-figures, To appear in Phys. Rev.
The D-score: a metric for interpreting the early development of infants and toddlers across global settings
Introduction: Early childhood development can be described by an underlying latent construct. Global comparisons of childrenâs development are hindered by the lack of a validated metric that is comparable across cultures and contexts, especially for children under age 3âyears. We constructed and validated a new metric, the Developmental Score (D-score), using existing data from 16 longitudinal studies. /
Methods: Studies had item-level developmental assessment data for children 0â48 months and longitudinal outcomes at ages >4â18 years, including measures of IQ and receptive vocabulary. Existing data from 11 low-income, middle-income and high-income countries were merged for >36â000 children. Item mapping produced 95 âequate groupsâ of same-skill items across 12 different assessment instruments. A statistical model was built using the Rasch model with item difficulties constrained to be equal in a subset of equate groups, linking instruments to a common scale, the D-score, a continuous metric with interval-scale properties. D-score-for-age z-scores (DAZ) were evaluated for discriminant, concurrent and predictive validity to outcomes in middle childhood to adolescence. /
Results: Concurrent validity of DAZ with original instruments was strong (average r=0.71), with few exceptions. In approximately 70% of data rounds collected across studies, DAZ discriminated between children above/below cut-points for low birth weight (<2500âg) and stunting (â2 SD below median height-for-age). DAZ increased significantly with maternal education in 55% of data rounds. Predictive correlations of DAZ with outcomes obtained 2â16 years later were generally between 0.20 and 0.40. Correlations equalled or exceeded those obtained with original instruments despite using an average of 55% fewer items to estimate the D-score. /
Conclusion: The D-score metric enables quantitative comparisons of early childhood development across ages and sets the stage for creating simple, low-cost, global-use instruments to facilitate valid cross-national comparisons of early childhood development
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