Violet stimulated luminescence dating of quartz from Luochuan (Chinese loess plateau): Agreement with independent chronology up to ∼600 ka

Luminescence dating at the Luochuan loess type (China) section is at present limited to ∼0.1 Ma using quartz blue light stimulated luminescence (BLSL), but can be extended back in time to ∼0.5 Ma by resorting to the more developmental post-infrared infrared stimulated luminescence (post-IR IRSL) and thermally transferred OSL (TT-OSL) signals. Since both the latter are associated with systematic uncertainties due to the potential (a)-thermal instability of these signals, a search continues for alternative, and demonstrably stable luminescence signals that can cover the entire Quaternary timescale. Here we explore the violet stimulated luminescence (VSL) signal at the Luochuan section, which provides a continuous archive of homogenous sediment with favourable luminescence characteristics and a solid independent age framework. By testing several VSL protocols and their associated performance, we demonstrate that the Multi-Aliquot Additive-Dose (MAAD) protocol produces a VSL chronology at Luochuan which is in agreement with independent ages up to ∼0.6 Ma. For a more representative environmental dose rate of ∼2 Gy/ka (∼35% lower than at Luochuan), the documented range of MAAD-VSL sensitivity (200-1800 Gy) would correspond to the ability to date sediment up to ∼1 Ma back in time, offering a remarkable advance over existing methods.</p

Muscle damage response in female collegiate athletes following repeated sprint activity

Exercise induced muscle damage (EIMD) is a well-investigated area, however there is a paucity of data surrounding the damage response in females. The aim of this study was to examine the damage responses from a sport-specific bout of repeated sprints in female athletes. Eleven well-trained females (mean ± SD; age 22 ± 3 y, height 166.6 ± 5.7 cm, mass 62.7 ± 4.5 kg) in the luteal phase of the menstrual cycle completed a repeated sprint protocol designed to induce EIMD (15 × 30 m sprints). Creatine kinase (CK), countermovement jump height (CMJ), knee extensor maximum voluntary contraction force (MVIC), muscle soreness (DOMS), 30 m sprint time and limb girth were recorded pre, post, 24 h, 48 h and 72 h post exercise. CK was elevated at 24, 48 and 72 h (p < 0.05), peaking at 24 h (+418%) and returning towards baseline at 72 h. CMJ height was reduced immediately post, 24 and 48 h (p < 0.05). Sprint performance was also negatively affected immediately post, 24 h, 48 h and 72 h post exercise. Muscle soreness peaked at 48 h (p<0.01) and remained significantly elevated at 72 h post exercise (p<0.01). Limb girth and MVIC did not alter over time. The current study provides new information on the EIMD response in trained females following a sport specific bout of repeated sprints. Importantly, this damage response has the potential to negatively affect performance for several days post-exercise

Метод интегрирования дифференциальных уравнений динамики электрических машин с вращающимся ротором

Для исследования переходных процессов в электротехнических системах, содержащих статические электромагнитные устройства, включенные в сложные электрические схемы, разработан программный комплекс Colo, функционирующий на основе магнитоэлектрических схем замещения в матричной форме. Главная матрица комплекса Colo содержит коэффициенты при искомых токах или магнитных потоках. Моделирование динамических процессов в электрических машинах с вращающимся ротором связано с интегрированием дифференциальных уравнений, в которые входят произведения искомых величин, поэтому непосредственно эти уравнения не могут решаться в программном комплексе Colo

Exploring multiple-aliquot methods for quartz violet stimulated luminescence dating

In the pursuit of extending the dating range of quartz, violet stimulated luminescence (VSL) has been proposed as a possible candidate. VSL samples traps deeper than those accessible by blue stimulated luminescence (BSL), the latter often limited to the past 100 ka. This study investigates 51 samples from three different type sections in the central part of the Chinese Loess Plateau with depositional ages between 1 and 2500 ka. Results indicate that the natural VSL signal grows to ∼2700 Gy, is best fitted with a double saturating exponential plus a constant, and its shape can be reproduced with the MAAD protocol. Using a ∼900 ka sample, the bleaching decay is recorded over 53 days of light exposure in a solar simulator to further understand the origin of the VSL signal, and to test a multiple-aliquot regenerative (MAR) protocol. The results of the MAAD and the MAR protocols are evaluated against the independent age control. For samples between 20 and 900 ka, 74% were in agreement with expected age using the MAAD protocol. The MAR protocol was tested by building dose response curves (DRCs) using two samples with ages of ∼75 ka and ∼900 ka. Ages calculated by interpolating natural signals onto these two DRCs for all samples within the same 20–900 ka range show 45% and 81% agreement, respectively, with independent age control. The MAR protocol obtained a ∼900 ka VSL age in agreement with independent age control within 1σ of joint uncertainties.</p

Optically stimulated phosphorescence in quartz over the millisecond to second time scale: insights into the role of shallow traps in delaying luminescent recombination

International audienceTelephone: +45 4677 4920 ABSTRACT Time-resolved OSL curves from quartz are usually measured over a few hundred µs because this time range best illustrates the main component in quartz which lies in the range of 30-45 µs. In this study we present the decay form of quartz time-resolved optically stimulated luminescence (TR-OSL) and optically stimulated phosphorescence (OSP) covering over 8 orders of magnitude from 50 ns to ~8 s. A detailed characterisation of the previously unstudied slowly decaying signals (ms-s time scales) is undertaken to understand the origin of these components and the role of re-trapping following optical stimulation. We present preheat and stimulation temperature dependence for both the TR-OSL and OSP curves in these time ranges and use the latter data to determine the E and s values for the participating shallow traps. We observe an abnormal decay behaviour seen as a sudden increase in the decay rate (a 'kink ') conspicuous at about 2 – 3 s in the OSP curves measured at 75 and 100°C. We satisfactorily reproduce this behaviour with a numerically solved kinetic model consisting of 4 energy levels. The physical interpretation of the kinetic rate equations is discussed in terms a three trap – one centre model or a one trap – two centres model involving localised charge transfer