IR Stimulation Research Articles

Improved separation of quartz optically stimulated luminescence from a mixed sample using pulsed green light

In the luminescence dating of samples containing both quartz and feldspar (e.g. fine silt, or unseparated rock), the infra-red stimulated luminescence (IRSL) from feldspar is most often used, even though the luminescence characteristics of the OSL from quartz are better understood, and quartz OSL is known to be more stable than feldspar IRSL and more readily reset when exposed to daylight. Unfortunately, in almost all unseparated samples giving both quartz and feldspar luminescence signals, the feldspar OSL (stimulated by blue or green wavelengths) intensity is similar to, or greater than, that from quartz. Separation of quartz and feldspar signals has been achieved before using prior IR and/or pulsed visible light stimulation. This study investigates whether using pulsed green stimulation after IR stimulation gives better discrimination in favour of quartz optically stimulated luminescence (OSL) than using post-IR pulsed blue stimulation, by using the luminescence response of single mineral rocks (quartzite, potassium feldspar) at various temperatures. The results presented here support the view that pulsed blue and pulsed green stimulation of quartz (quartzite or calibration quartz grains) both excite charge to the conduction band, resulting in only a minor dependence on the temperature of the blue or green stimulation. We also confirm that IR depletes the quartz OSL signal only if undertaken at elevated temperature (>125 °C). In contrast, all 3 light sources can result in luminescence from potassium-rich feldspar, but the post-infrared pulsed blue light stimulated luminescence (post-IR PBSL) signal is significantly less dependent on the prior IR stimulation temperature than the post-infrared pulsed green light stimulated luminescence (post-IR PGSL) signal. This is presumably because green stimulation excites mainly into the band-tails. As a consequence, it is shown that the contribution of feldspar OSL to pulsed-green light stimulated luminescence (PGSL) is reduced more by a prior IR stimulation at elevated temperature, than the corresponding pulsed-blue light stimulated luminescence (PBSL). These results are consistent with the band models used to describe the origins of quartz and feldspar luminescence proposed by previous studies. We conclude that the post-IR PGSL provide better discrimination in favour of quartz OSL than does the corresponding post-IR PBSL, and that this should be taken advantage of in future studies on samples with mixed sources of luminescence.

Mitochondrial responses to intracellular Ca2+ release following infrared stimulation.

Many studies of Ca2+ effects on mitochondrial respiration in intact cells have used electrical and/or chemical stimulation to elevate intracellular [Ca2+], and have reported increases in [NADH] and increased ADP/ATP ratios as dominant controllers of respiration. This study tested a different form of stimulation: brief temperature increases produced by pulses of infrared light (IR, 1,863 nm, 8-10°C for ∼5 s). Fluorescence imaging techniques applied to single PC-12 cells in low µM extracellular [Ca2+] revealed IR stimulation-induced increases in both cytosolic (fluo5F) and mitochondrial (rhod2) [Ca2+]. IR stimulation increased O2 consumption (porphyrin fluorescence), and produced an alkaline shift in mitochondrial matrix pH (Snarf1), indicating activation of the electron transport chain (ETC). The increase in O2 consumption persisted in oligomycin, and began during a decrease in NADH, suggesting that the initial increase in ETC activity was not driven by increased ATP synthase activity or an increased fuel supply to ETC complex I. Imaging with two potentiometric dyes [tetramethyl rhodamine methyl ester (TMRM) and R123] indicated a depolarizing shift in ΔΨm that persisted in high [K+] medium. High-resolution fluorescence imaging disclosed large, reversible mitochondrial depolarizations that were inhibited by cyclosporin A (CSA), consistent with the opening of transient mitochondrial permeability transition pores. IR stimulation also produced a Ca2+-dependent increase in superoxide production (MitoSox) that was not inhibited by CSA, indicating that the increase in superoxide did not require transition pore opening. Thus, the intracellular Ca2+ release that follows pulses of infrared light offers new insights into Ca2+-dependent processes controlling respiration and reactive oxygen species in intact cells.NEW & NOTEWORTHY Pulses of infrared light (IR) provide a novel method for rapidly transferring Ca2+ from the endoplasmic reticulum to mitochondria in intact cells. In PC12 cells the resulting ETC activation was not driven by increased ATP synthase activity or NADH. IR stimulation produced a Ca2+-dependent, reversible depolarization of ΔΨm that was partially blocked by cyclosporin A, and a Ca2+-dependent increase in superoxide that did not require transition pore opening.

Characteristics of TL Signal and Multi-wavelength OSL Signal against Firing Temperature of White Porcelain

We analyzed the characteristics of white porcelain fired at different temperatures (800, 1200, 1350℃) by measuring changes in thermal luminescence(TL) and multi-wavelength (IR, orange, green, blue, UVA) optically stimulated luminescence(OSL) signal. White porcelain fired at 800℃ showed high intensity TL signals over a wide temperature range of 100 to 400℃, whereas white porcelain fired at 1200 and 1350℃ showed TL peaks at 100 and 210℃. Moreover, the OSL signals of white porcelain fired at 800℃, increased linearly according to the amount of irradiation, under IR, orange, green, blue and UVA stimulation. However, the OSL signals of white porcelain fired at 1200℃ increased linearly only under blue and UVA stimulation, while those of white porcelain fired at 1350℃ increased linearly only under UVA stimulation. In general, the strength of the TL/OSL signal was weakened as the firing temperature increased, which seems to be due to the vitrification caused by the high-temperature firing process. Therefore, it was found that it is important to select the optical stimulation source of the proper wavelength during TL/OSL dating to white porcelain.

Isolating quartz-dominated OSL signal of rock slice by using pulsed stimulation: Implications for dating burial age of cobbles

Although the OSL signal sourced from quartz is expected to be more stable and bleached more rapidly than the IRSL signal sourced from feldspar in a general sense, the former is much less investigated than the latter for rock surface related luminescence dating. It is mainly due to the difficulty in isolating quartz-dominated OSL signals from rock slices, and the low sensitivity and non-fast component dominated OSL signals for quartz in most of rocks. In merit of the sub-conduction band transition of trapped electrons of feldspar under both green light stimulation and IR stimulation at elevated temperature (Jain and Ankjӕrgaard, 2011), it is expected that the contribution of feldspars to the green light stimulated luminescence could be substantially reduced by a prior IR stimulation at elevated temperature. Meanwhile, more fast-component dominated quartz OSL signal (if there is any) could be obtained by green light stimulation (Bailey et al., 2011). Therefore, in this study, we investigated the feasibility of using the post-IR pulsed green stimulation, which is performed at 25 °C (PGLSL 25 ) following two IR stimulations (IR 50 IR 225 ), to isolate the quartz-dominated OSL signals from rock slices of granite cobbles for burial dating. The decay characteristics of stimulation curve, characteristic saturation dose and thermal stability of the pIR 50 IR 225 PGLSL 25 signal suggest that this signal is quartz-dominated, but still not fast-component dominated. We tentatively validated the equivalent dose (D e ) measurement protocol by dose recovery experiment. The luminescence-depth profiles show that the bleaching depths of pIR 50 IR 225 PGLSL 25 signals are slightly smaller than or close to that of the IR 50 signals, while they are much shallower for the pIR 50 IR 225 signals. The pIR 50 IR 225 PGLSL 25 procedure enables multiple D e values determined from luminescence signals, with different bleachabilities and stabilities, from both feldspars and quartz in one measurement, which is of potential for buried age dating of cobbles. • The pIR 50 IR 225 PGLSL 25 method could be used to isolate the quartz-dominated signal from rock slice. • The bleaching depth of the pIR 50 IR 225 PGLSL 25 signalis slightly less than or close to that of the IR 50 signal. • The pIR 50 IR 225 and the pIR 50 IR 225 PGLSL 25 D e values could be obtained in one measurement.

Using Infra-red stimulated luminescence and phototransferred thermoluminescence to investigate electron trapping and charge transport in feldspars

Previous studies have observed mineral specific variations in the ratios of IRSL signals stimulated at the different discrete wavelengths of lines corresponding to Xe lamp emission lines, which fall within the broad excitation spectrum of IRSL. Meanwhile recent accounts of IRSL have referred to single trapping systems within the excitation band, and modelled excitation spectra as continuous gaussian distributions. A simple single trap model should not result in variations in the ratio of IRSL intensities produced at different wavelengths. In the study reported here 22 different feldspar samples, which have all been characterised by SEM and x-ray analysis, were measured using a portable OSL instrument equipped with 890 nm and 940 nm diode arrays to confirm and extend the previous observations of variations in IRSL intensity ratios. Of the samples investigated the sensitivity varied over 3–4 orders of magnitude. Albite samples in this selection showed consistently high responses. The plagioclase samples show significant variations, and the microcline and K-feldspar samples produced a large range of responses. Excitation ratios of 940 nm–890 nm show mineralogically linked variations which together with the earlier Xe lamp data point to distributions of trapping systems within the variable environments of these minerals. These results do not readily fit simple single trap models for luminescence from feldspars; instead, they suggest multiple traps or a series of similar traps which are significantly perturbed by their local lattice structural environments. Post Stimulation Phosphorescence (PSP) was observed for all samples, and phototransferred thermoluminescence (PTTL) has also been confirmed following IR stimulation suggesting that recombination mechanisms involve charge mobility and interactions with shallow traps in band-tail states rather than primarily being associated with direct quantum tunnelling recombination. The relative proportions of PSP to prior IRSL also varied between the two stimulation wavelengths which further emphasises the physical differentiation between processes influencing different subpopulations of the trapping states associated with IRSL and their local lattice environments.

Pulsed infrared stimulation evoked electrical potential in mouse vestibular system

To improve accuracy of VsEP and avoid the inherent limitation of mechanical vibration, we designed an infrared optical stimulation approach to stimulate mouse vestibular system and measured the evoked potential. IR pulses (1871 nm, 30 pps and 100 μs pulse width) were delivered to mice with different vestibular dysfunction levels and the evoked potential was recorded. The result suggests that the amplitude and latency of the IR-evoked potential (IR-VsEP) were significantly associated with vestibular function integrity. Immunofluorescence staining confirmed that magnitude of IR-VsEP decreased was consistent with the loss of HCs. Micro-CT imaging revealed that the optical fiber was orientating towards the vestibular system. Taken together, we found that: 1) IR stimulation can generate VsEP evoked potential in vestibular system (IR-VsEP), which can be potentially used for vestibular function evaluation; 2) intact HCs and fully functional synaptic transmission are crucial for efficient IR-induced vestibular system stimulation.

Pulsed Infrared Stimulation of Vertical Semicircular Canals Evokes Cardiovascular Changes in the Rat.

A variety of stimuli activating vestibular end organs, including sinusoidal galvanic vestibular stimulation, whole body rotation and tilt, and head flexion have been shown to evoke significant changes in blood pressure (BP) and heart rate (HR). While a role for the vertical semicircular canals in altering autonomic activity has been hypothesized, studies to-date attribute the evoked BP and HR responses to the otolith organs. The present study determined whether unilateral activation of the posterior (PC) or anterior (AC) semicircular canal is sufficient to elicit changes in BP and/or HR. The study employed frequency-modulated pulsed infrared radiation (IR: 1,863 nm) directed via optical fibers to PC or AC of adult male Long-Evans rats. BP and HR changes were detected using a small-animal single pressure telemetry device implanted in the femoral artery. Eye movements evoked during IR of the vestibular endorgans were used to confirm the stimulation site. We found that sinusoidal IR delivered to either PC or AC elicited a rapid decrease in BP and HR followed by a stimulation frequency-matched modulation. The magnitude of the initial decrements in HR and BP did not correlate with the energy of the suprathreshold stimulus. This response pattern was consistent across multiple trials within an experimental session, replicable, and in most animals showed no evidence of habituation or an additive effect. Frequency modulated electrical current delivered to the PC and IR stimulation of the AC, caused decrements in HR and BP that resembled those evoked by IR of the PC. Frequency domain heart rate variability assessment revealed that, in most subjects, IR stimulation increased the low frequency (LF) component and decreased the high frequency (HF) component, resulting in an increase in the LF/HF ratio. This ratio estimates the relative contributions of sympathetic nervous system (SNS) and parasympathetic nervous system (PNS) activities. An injection of atropine, a muscarinic cholinergic receptor antagonist, diminished the IR evoked changes in HR, while the non-selective beta blocker propranolol eliminated changes in both HR and BP. This study provides direct evidence that activation of a single vertical semicircular canal is sufficient to activate and modulate central pathways that control HR and BP.

Characteristics of Pulsed Blue and Green Light Stimulated Luminescence Signals of Quartz and Feldspars

The post-infrared (post-IR) pulsed blue light stimulated luminescence (PBLSL) signal has been employed to determine the equivalent dose (D<sub>e</sub>) of feldspar contaminated quartz grains, but it sometimes suffers from the interference of feldspars. Since the green light stimulated luminescence (GLSL) signal of feldspars might be more reduced by a prior IR stimulation, we compared the characteristics of post-IR PBLSL and post-IR pulsed GLSL (post-IR PGLSL) signals of quartz and feldspars in this study to evaluate the feasibility of employing the green light for pulsed stimulation. We investigated the effect of the signal integration period, pulsed stimulation temperature, and prior IR stimulation temperature on the intensities of post-IR PBLSL and post-IR PGLSL of quartz and feldspars, and evaluated the potential feldspar interference on these two signals for the hypothetical and artificial quartz-feldspar mixture. The results demonstrate a lower feldspars contribution for the post-IR PGLSL signal. The feldspar interference only slightly increases with the increase of integration period for the post-IR PGLSL signal measured at low stimulation temperature, which permits a long integration period to be employed to enhance the signal to noise ratio. This study shows that the green light is a promising alternative for pulsed stimulation to suppress the feldspar contribution.

Sequential two-step optical stimulation in K-feldspars: Correlation among the luminescence signals and implications for modeling parameters

Luminescence signals from feldspars are of importance in luminescence dosimetry and dating. The present study attempts a correlation between two specific experimental parameters, such as the lifetime of luminescence components and the dimensionless acceptor density parameter ρ′, as well as the influence of the crystal structure on the luminescence signals. The analysis of the above parameters was completed in three different K-feldspar samples, each one belonging to the structural group of microcline, sanidine and orthoclase. The stimulations in this manuscript were carried out using blue optically stimulated luminescence (BLOSL) and infrared (IRSL) optically stimulated luminescence, in two different two step experimental protocols. A comparison of these two step protocols is applied for the first time in the literature. A de-convolution analysis was completed with the use of two components, a slow component which can be described by general order kinetics (GOK), and a tunneling component which is necessary to describe the blue light stimulation. The GOK component describes recombination processes taking place only through the conduction band. In order to describe the results of the IR stimulation protocol, two tunneling components were used. The results from this study are encouraging and are in full correlation with published studies in the luminescence literature.

Circumvention of anomalous fading in feldspar luminescence dating using Post-Isothermal IRSL

Abstract In luminescence dating of feldspar, laboratory induced luminescence necessary to assess the naturally acquired dose in the environment suffers from a poorly understood instability over time, known as anomalous fading (AF). AF is the source of commonly observed age underestimation in optical dating of feldspar. Approaches to circumvent AF include correction methods as well as attempts to measure directly an unfading component of feldspar luminescence, e.g. post-IR IRSL protocols. The former has the advantage of measuring the easily bleachable traps but requires extrapolations of fading rates. Post-IR IRSL methods can be limited by the use of more difficult-to-bleach traps and hence by potential age overestimations. In this paper, we show how post-isothermal laboratory induced luminescence (pIt-IR) allows measuring an equivalent dose (De) that is not dependent on time elapsed since irradiation. In this procedure, one measures two IRSL signals, first from an IR stimulation at low temperature (i.e. IR50) followed by a second one, at a higher temperature (i.e. IR225). Since both signals fade at different rates, De from IR50 is lower than that of IR225. In pIt-IR, a succession of thermal treatments is carried out before the measurement of laboratory-induced IR50 and IR225 luminescence. The dependence of De on thermal annealing is different for each IR signal so one can find which thermal treatment will yield the same De for both signals. This De is assumed to be the true total radiation dose received by the feldspar minerals in nature, more properly known as the paleodose (P). This new methodology is herein applied to three samples of different ages and different geological contexts. Post-isothermal luminescence is thus proposed as a way to circumvent AF, even though extended isothermal annealing treatment is not shown to eradicate AF.

Review of the Post-IR IRSL Dating Protocols of K-Feldspar.

Compared to quartz, the infrared stimulated luminescence (IRSL) of K-feldspar saturates at higher dose, which has great potential for extending the dating limit. However, dating applications with K-feldspar has been hampered due to anomalous fading of the IRSL signal. The post-IR IRSL (pIRIR) signal of K-feldspar stimulated at a higher temperature after a prior low-temperature IR stimulation has significantly lower fading rate. Different dating protocols have been proposed with the pIRIR signals and successful dating applications have been made. In this study, we review the development of various pIRIR dating protocols, and compare their performance in estimating the equivalent dose (De). Standard growth curves (SGCs) of the pIRIR signals of K-feldspar are introduced. Single-grain K-feldspar pIRIR dating is presented and the existing problems are discussed.

Synthesis and characterization of finely dispersed phosphors doped with rare-earth metal ions for enhanced photodynamic therapy of cancer

Finely dispersed NaBaPO4:Eu2+, NaGdF4:Eu3+, BaGdF5:Eu3+, GdF3:Yb3+, Er3+ and YF3:Yb3+, Er3+ phosphors are synthesized using a sol–gel procedure and hydrothermal method. A process is developed for obtaining NaBaPO4:Eu2+ phosphors with enhanced dispersion via sol–gel precipitation followed by a high-temperature annealing in molten NaCl. The applied annealing technique provided a 3.8-fold decrease in the phosphor particle size and 11-fold increase in the finely dispersed (less than 1 μm) fraction compared with the phosphors prepared using a conventional sol–gel method. In addition to already known luminescence centers comprising Eu2+ ions located in NaBaPO4 lattice sites with coordination numbers 10 and 12, these phosphors are found to contain two more types of luminescence centers supposedly corresponding to Eu2+ ions in the same positions locating on the phosphor particle surface. According to the obtained data, the energy levels of luminescence centers in the NaBaPO4:Eu2+ phosphor are summarized in a chart. NaGdF4:Eu3+ phosphor is shown to be mostly appropriate for X-ray stimulated photodynamic therapy (PDT), while GdF3:Yb3+, Er3+ phosphor is promising for IR-activated PDT. The efficiency of 980 nm IR laser-induced generation of active oxygen by a medicine involving the YF3:Yb3+, Er3+ phosphor, and Radachlorin photosensitizer is studied. A finely dispersed NaBaPO4:Eu2+ phosphor is synthesized using a modified sol-gel method and studied to make a detailed energy chart of luminescence centers, including specific energy levels of surface sites. A nanosized (particles below 100 nm) YF3:Yb3+,Er3+ phosphor synthesized via hydrothermal technique is found to be useful for photodynamic therapy of abdominal cancer in couple with Radachlorin photosensitizer by generating active oxygen upon IR stimulation.

Two-dimensional plasmonic biosensing platform: Cellular activity detection under laser stimulation

Combining biosensors with nanoscience provides great advantages such as being label-free and real time, highly sensitive, and small in size, as well as providing a low limit of detection and integration to other systems. That is why plasmonics finds various applications in drug detection, food safety, agriculture, photothermal therapy, etc. In this paper, we have fabricated a two-dimensional plasmonic grating biosensor using a soft lithography technique, which has eliminated some disadvantages of conventional plasmonic structures like expensive fabrication cost, inflexibility, and lack of mass production. On the other hand, we benefited from infrared neural stimulation for regulating membrane depolarization, which was based on photothermal mechanism and provided a contact-free and high spatial/temporal resolution. Eventually, the membrane depolarization of two different cell types of Hep G2 and mesenchymal stem cells cultured on two-dimensional plasmonic structure has been investigated under infrared neural stimulation. After preparing the soft plasmonic crystal, its reflection spectra and respective ellipsometry parameters were analyzed before and after cell culture with/without stimulation (near-infrared immune region ∼1450 nm). By comparing the obtained ellipsometry results for HEP G2 and mesenchymal stem cells, it is observed that the behavior of two cell types with respect to IR stimulation was the same as well as providing us the possibility of distinguishing the level of membrane depolarization under various stimulating frequencies. The strength of this integrated system for membrane depolarization detection has been shown experimentally, which can open new avenues toward neuroplasmonic application in the future.

Landscape dynamics revealed by luminescence signals of feldspars from fluvial terraces

Luminescence signals of quartz and feldspar minerals are widely used to determine the burial age of Quaternary sediments. Although luminescence signals bleach rapidly with sunlight exposure, incomplete bleaching may affect luminescence ages, in particular in fluvial settings where an unbleached remnant signal is commonly encountered in modern alluvium. Here, we use feldspar single-grain post-infrared IR stimulation (pIRIR) dating to show that recent (<11 ka) fluvial terraces of the Rangitikei River (New Zealand) were formed in a context of non-linear incision rate. We relate this pattern to the rapid reinstatement of steady-state incision following the formation of a major, climate-driven, aggradation terrace, causing a phase of accelerated incision. In addition, we show systematic variations in the proportion of unbleached grains in the fluvial sediments over time, mirroring incision rate at the time of deposition. Deposits formed during rapid incision contain fewer bleached grains, which we attribute to large input of unbleached material and limited bleaching opportunities during fluvial transport. This finding demonstrates that the luminescence signals recorded in fluvial terraces not only yield age information, but also inform us on past fluvial transport and ultimately, landscape dynamics.

Optical and Electrical Properties of CdS Material in a Microplasma Cell Under IR Stimulation

CdS has a wide range of applications for explorations of its optical and electrical behaviors. A microplasma cell with a CdS electrode has been constructed. The measurements on discharge currents under various gas pressures, interelectrode distances and excitation voltages have been studied theoretically and experimentally. The 2D electron densities under different parameter ranges along the gas discharge volume have been examined. The structural and optical features have been analyzed using scanning electron microscopy, atomic force spectroscopy and Fourier transform infrared spectroscopy for complementary information. Experimentally, as an additional optical test, CVC measurements have also been performed under IR stimulation to verify the infrared sensitivity of the sample. The CdS cathode sample has been damaged by the high energetic current value around 10−1 A following the plasma transition from the glow to the arc.

Component-resolved bleaching correlation between OSL and IRSL signals in various geological materials

The primary aim of the present study includes establishing a qualitative as well as quantitative correlation between OSL and IRSL signals in various materials of geological origin, by investigating the influence of the IR stimulation to the OSL signal. The materials which are the subject of the present study include one K-feldspar belonging to the group of microcline, two different grain size fractions of Durango apatite at the edge of the nano-scale and gypsum. A two-step stimulation protocol was applied, including an exposure of the irradiated sample to infrared stimulation for various time and a subsequent continuous wave OSL using blue light. In the framework of a component-resolved analysis, the IRSL decay curves were fitted using analytical equations describing the localized tunneling recombination model; the subsequent OSL decay curves were also fitted using a linear superposition of analytical expressions describing both delocalized and localized recombination processes. The selection of number and type of components in the latter case is also elaborated, based on the physical meaningfulness of the de-convolution results.

Thermogenetic stimulation of single neocortical pyramidal neurons transfected with TRPV1-L channels

Thermogenetics is a promising innovative neurostimulation technique, which enables robust activation of single neurons using thermosensitive cation channels and IR stimulation. The main advantage of IR stimulation compared to conventional visible light optogenetics is the depth of penetration (up to millimeters). Due to physiological limitations, thermogenetic molecular tools for mammalian brain stimulation remain poorly developed. Here, we tested the possibility of employment of this new technique for stimulation of neocortical neurons. The method is based on activation gating of TRPV1-L channels selectively expressed in specific cells. Pyramidal neurons of layer 2/3 of neocortex were transfected at an embryonic stage using a pCAG expression vector and electroporation in utero. Depolarization and spiking responses of TRPV1L+ pyramidal neurons to IR radiation were recorded electrophysiologically in acute brain slices of adult animals with help of confocal visualization. As TRPV1L-expressing neurons are not sensitive to visible light, there were no limitations of the use of this technique with conventional fluorescence imaging. Our experiments demonstrated that the TRPV1-L+ pyramidal neurons preserve their electrical excitability in acute brain slices, while IR radiation can be successfully used to induce single neuronal depolarization and spiking at near physiological temperatures. Obtained results provide important information for adaptation of thermogenetic technology to mammalian brain studies in vivo.

Establishing a high-resolution luminescence chronology for the Zhenbeitai sand-loess section at Yulin, North-Central China

Sand-loess sequences in the desert-loess transition zone are sensitive terrestrial archives for recording past climatic changes and atmospheric dust activities. However, a high-resolution chronology for relative long-term sand-loess sequences is still rare. In this study, we used quartz SAR OSL and K-feldspar pIRIR (pIRIR290) methods to date a 16.8 m sand-loess sequence at Zhenbeitai in Yulin (North-Central China). The quartz is sensitive, fast component dominated but saturates at ∼150 Gy. The measured K-feldspar pIRIR290 De showed no dependency on the first IR stimulation temperature between 50 °C and 260 °C. Dose recovery results were consistent with unity up to ∼800 Gy for a test dose of approximately 30% of the equivalent dose to be measured. The resulting pIRIR290 ages are consistent with the stratigraphy up to ∼121 ka. Thus, a high-resolution chronology up to the last interglacial could be established for the Zhenbeitai sand-loess section. Derived mass accumulation rates show sedimentation rates of ∼10–80 cm/ka for the upper loess (<10 ka) and ∼15–30 cm/ka for the loess deposits between 57 and 111 ka. Interbedded sands (∼10–65 cm/ka) suggest active dunes in the Mu Us desert during ∼17–10 ka. We found a depositional hiatus of loess between ∼47 ka and 17 ka. The Zhenbeitai sand-loess sequence provides a sensitive record of regional climatic changes in this semiarid zone since last interglacial period.

Post-IR IRSL dating of K-feldspar from last interglacial marine terrace deposits on the Kamikita coastal plain, northeastern Japan

To establish a suitable luminescence dating protocol for marine terrace deposits in Japan, we tested the applicability of K-feldspar post-infrared (IR) infrared stimulated luminescence (IRSL) (pIRIR) dating using a marine isotope stage (MIS) 5e terrace deposit from the Kamikita coastal plain (NE Japan), where independent age control from a tephra is available. One of the most commonly used pIRIR signals, measured at 290°C with the first IR stimulation temperature at 50°C (pIRIR&lt;sub&gt;50/290&lt;/sub&gt;), faded with a mean g&lt;sub&gt;2days&lt;/sub&gt; value of 1.94 ± 0.19%/decade. In contrast, the pIRIR signal with a higher first IR stimulation temperature of 200°C (pIRIR&lt;sub&gt;200/290&lt;/sub&gt;) had a much lower fading rate (g&lt;sub&gt;2days&lt;/sub&gt; = 0.16 ± 0.49%/decade). The average fading-uncorrected and -corrected pIRIR&lt;sub&gt;200/290&lt;/sub&gt; ages of MIS 5e subtidal sediments obtained from two sampling sites were 126 ± 3 ka and 132 ± 2 ka, which is in good agreement with the independent age control. We conclude that is it is now possible to use pIRIR protocol to estimate the ages of not only marine terraces formed during MIS 5 substages (5a, 5c) but also of older marine terraces, for which age evidence is limited.

Timing of fluvial sedimentation in the Upper Rhine Graben since the Middle Pleistocene: constraints from quartz and feldspar luminescence dating

The Heidelberg Basin (HDB) hosts one of the thickest Quaternary sediment successions in central Europe. To establish a reliable Middle and Upper Pleistocene chronology for a recently drilled core from the depocentre of the Heidelberg Basin, we applied multiple luminescence dating approaches, including quartz optically stimulated luminescence (OSL), two feldspar post‐IR IRSL protocols using second IR stimulation temperatures of 225 °C (pIRIR225) and 290 °C (pIRIR290), and two fading correction models. Relatively high anomalous fading was observed for both the pIRIR225 and pIRIR290 signals, with mean fading rates of 2.13±0.27 and 2.08±0.49%/decade, respectively. Poor dose recovery behaviour of the pIRIR290 signal suggests that the pIRIR290 ages are not reliable. The comparison of two fading correction methods for the K‐feldspar ages indicates that the correction method proposed by Kars et al. (2008) Radiation Measurements 43, 786, yields reliable ages, whereas the dose‐rate correction method proposed by Lamothe et al. (2003) Radiation Measurements 37, 493, does not. A chronology for the HDB is established using the quartz ages and reliable fading corrected feldspar pIRIR225 ages. Our chronology shows that the sediments in the upper Mannheim Formation were deposited during Marine Isotope Stage (MIS) 4 (c. 70 ka), constrained by two quartz ages in the upper 20 m of the core. Four fading corrected pIRIR225 ages of c. 400 ka show that the upper Ludwigshafen Formation was deposited during MIS 12–11, correlated with the Elsterian‐Holsteinian stage. Two ages of 491±76 and 487±79 ka indicate that the Middle and Upper Ludwigshafen Formation were probably deposited during the Cromerian Complex. This luminescence chronology is consistent with palynological results. It also indicates that the IR‐RF ages reported earlier are probably underestimated due to anomalous fading.