Multivariate Nonparametric Estimation of the Pickands Dependence Function using Bernstein Polynomials

Many applications in risk analysis, especially in environmental sciences, require the estimation of the dependence among multivariate maxima. A way to do this is by inferring the Pickands dependence function of the underlying extreme-value copula. A nonparametric estimator is constructed as the sample equivalent of a multivariate extension of the madogram. Shape constraints on the family of Pickands dependence functions are taken into account by means of a representation in terms of a specific type of Bernstein polynomials. The large-sample theory of the estimator is developed and its finite-sample performance is evaluated with a simulation study. The approach is illustrated by analyzing clusters consisting of seven weather stations that have recorded weekly maxima of hourly rainfall in France from 1993 to 2011

The efficiency of briefly presenting word forms in a computerized repeated spelling training

Contains fulltext : 203623.pdf (publisher's version ) (Open Access)We investigated the efficiency of briefly presenting word forms (visual dictation) over and above word copying in 5 computerized repeated spelling training sessions of Dutch rule-based and loan words in advanced spellers in primary school. Using repeated measures analyses of variance, we compared the effects of 2 spelling feedback conditions in a between-subjects pretest/posttest control group design on growth in spelling accuracy and speed for trained and comparable untrained words. Children in the visual dictation condition (n = 29) had to spell a word from memory after briefly seeing the correct form, whereas children in the word copying condition (n = 30) just had to copy the correct form. In an additional control condition (n = 31), children only received feedback on correctness. We assessed improvement in the reading of trained words and in the reading and spelling of comparable untrained words via pre- and posttest. By the end of the training, children in the visual dictation condition outperformed the control group on spelling accuracy of both rule-based words and loan words (both ps < .001), whereas the word copying group only did so for loan words (p < .001). In contrast to the control group, the word copying group caught up with the visual dictation group on both word types; however, children in the visual dictation group attained higher spelling accuracy earlier during training. We found no differential transfer effects. We can thus conclude that visual dictation was the most efficient way of memorizing spelling representations of both rule-based words and loan words.18 p

Developing reference material for validation of hair spectral analysis reliability

Mineral analysis of human hair is increasingly proposed as a estimation method for the human contamination with environmental mineral pollutants and even as a diagnostic tool for related health problems. It offers a good way of investigating long-term variation in trace element concentration. Many minor and trace elements can be determined in hair samples with good precision and sensitivity by a variety of analytical techniques. An important requirement in such work is the application of suitable analytical quality control, for which the availability of a hair reference material is important. In paper the preparation of the human hair reference material and the initial stages which were taken to confirm its certification are described

Characterization of defects in a martensitic CuAlNi shape-memory alloy

A water-quenched martensitic CuAlNi shape-memory alloy was investigated by a combination of coincidence Doppler broadening and positron-lifetime spectroscopy, supported by positron-lifetime calculations. We find a high defect concentration in the as-quenched samples. The positron-lifetime calculations suggest that the defects are not only single vacancies but also vacancies associated with dislocations and stacking faults. Annealing in the martensitic phase has no significant influence on the vacancy concentration but results in a different chemical environment around the vacancies. After aging in the austenitic phase the vacancy concentration decreases significantl

Aging is associated with an earlier arrival of reflected waves without a distal shift in reflection sites

Background-Despite pronounced increases in central pulse wave velocity (PWV) with aging, reflected wave transit time (RWTT), traditionally defined as the timing of the inflection point (T-INF) in the central pressure waveform, does not appreciably decrease, leading to the controversial proposition of a "distal-shift" of reflection sites. T-INF, however, is exceptionally prone to measurement error and is also affected by ejection pattern and not only by wave reflection. We assessed whether RWTT, assessed by advanced pressure-flow analysis, demonstrates the expected decline with aging. Methods and Results-We studied a sample of unselected adults without cardiovascular disease (n=48; median age 48 years) and a clinical population of older adults with suspected/established cardiovascular disease (n=164; 61 years). We measured central pressure and flow with carotid tonometry and phase-contrast MRI, respectively. We assessed RWTT using wave-separation analysis (RWTTWSA) and partially distributed tube-load (TL) modeling (RWTTTL). Consistent with previous reports, T-INF did not appreciably decrease with age despite pronounced increases in PWV in both populations. However, aging was associated with pronounced decreases in RWTTWSA (general population -15.0 ms/decade, P<0.001; clinical population -9.07 ms/decade, P=0.003) and RWTTTL (general -15.8 ms/decade, P<0.001; clinical -11.8 ms/decade, P<0.001). There was no evidence of an increased effective reflecting distance by either method. TINF was shown to reliably represent RWTT only under highly unrealistic assumptions about input impedance. Conclusions-RWTT declines with age in parallel with increased PWV, with earlier effects of wave reflections and without a distal shift in reflecting sites. These findings have important implications for our understanding of the role of wave reflections with aging