Infrared Stimulation Research Articles

Gold Nanorod-assisted Optical Stimulation of Neuronal Cells.

Recent studies have demonstrated that nerves can be stimulated in a variety of ways by the transient heating associated with the absorption of infrared light by water in neuronal tissue. This technique holds great potential for replacing or complementing standard stimulation techniques, due to the potential for increased localization of the stimulus and minimization of mechanical contact with the tissue. However, optical approaches are limited by the inability of visible light to penetrate deep into tissues. Moreover, thermal modelling suggests that cumulative heating effects might be potentially hazardous when multiple stimulus sites or high laser repetition rates are used. The protocol outlined below describes an enhanced approach to the infrared stimulation of neuronal cells. The underlying mechanism is based on the transient heating associated with the optical absorption of gold nanorods, which can cause triggering of neuronal cell differentiation and increased levels of intracellular calcium activity. These results demonstrate that nanoparticle absorbers can enhance and/or replace the process of infrared neural stimulation based on water absorption, with potential for future applications in neural prostheses and cell therapies.

High resolution OSL and post-IR IRSL dating of the last interglacial–glacial cycle at the Sanbahuo loess site (northeastern China)

Northeastern China is located in the East Asian monsoon region; it is sensitive to both high and low latitude global climate systems. Loess deposits in the region have considerable potential as sensitive archives of past climate changes. However, research into loess deposition and climate change in this region is restricted by the lack of independent age control. In this study, coarse-grained quartz SAR OSL and K-feldspar post-IR infrared (IR) stimulated luminescence (post-IR IRSL; pIRIR290) methods have been used to date the Sanbahuo loess site in northeastern China. The quartz OSL characteristics are satisfactory. The measured pIRIR290 De's do not vary significantly with IR stimulation temperatures between 50 °C and 260 °C; a first IR stimulation temperature of 200 °C was adopted. Dose recovery tests were performed by adding different laboratory doses to both laboratory bleached (300 h SOL2) samples and natural samples; the results are satisfactory up to ∼800 Gy. Resulting quartz OSL and feldspar pIRIR290 ages are in good agreement at least back to ∼44 ka; beyond this feldspar pIRIR290 ages are older. The feldspar ages are consistent with the expected age of the S1 palaeosol (MIS 5). There appears to have been a period of fast loess deposition at ∼62 ka, perhaps indicative of winter monsoon intensification with a very cold and dry climate that lead to a serious desertification of dunefields in northeastern China.

Fluvial tufa evidence of Late Pleistocene wet intervals from Santa Barbara, California, U.S.A.

Past pluvials in the western United States provide valuable context for understanding regional hydroclimate variability. Here we report evidence of conditions substantially wetter than today from fluvial tufa deposits located near Zaca Lake, Santa Barbara County, California that have been dated by radiocarbon ( 14 C) and Infra-Red Stimulated Luminescence (IRSL). Two successions of tufa deposition occur within a small catchment that drains Miocene Monterey Formation bedrock : 1) a fluvial deposit (0–0.5 m thick, 200 m in extent) that formed along a narrow valley below a modern spring, and 2) a perched deposit ~ 10 m higher (2 m thick, 15 m in extent). IRSL and radiocarbon dating of the perched carbonates suggest at least two episodes of carbonate growth: one at 19.4 ± 2.4 (1σ) through 17.8 ± 2.8 (1σ) ka and another at 11.9 ± 1.5 (1σ) ka verified with a charcoal 14 C age of 10.95 ± 0.12 (2σ) cal ka BP. The relationship between the perched and fluvial spring deposits is inferred to represent a drop in the water table of more than 10 m associated with a transition from a wet climate in the late glacial to a dry Holocene today. The wet period indicated by the perched tufa deposit between 19.4 and 17.8 ka is relatively consistent with other California climate records both north and south of Zaca Lake. However, tufa growth ca. 12 to 11 ka demonstrates wet conditions occurred as far south as Zaca Lake during the Younger Dryas event, in contrast to climate records farther south in Lake Elsinore that indicate a drying trend through this interval. A small shift north in the average position of the winter season storm track could explain wet winters at Zaca while at the same time generating dry winters at Lake Elsinore, ~ 275 km southwest of Zaca. If true, these data indicate that rather small latitudinal shifts in the average winter season storm track can produce large changes in regional hydroclimate. • Spring-associated carbonates (tufa) in Santa Barbara, CA were dated via 14 C and IRSL. • Fossil perched tufa ~ 10 m above a modern spring indicates past pluvial conditions. • IRSL ages suggest tufa growth at 19.4 ± 2.4 to 17.8 ± 2.8 (1σ) ka and 11.9 ± 1.5 (1σ) ka. • 14 C from embedded charcoal suggests tufa deposition at 10.95 ± 0.12 (2σ) cal ka BP. • IRSL and 14 C of perched tufa provide terrestrial evidence of Late Pleistocene pluvial.

Further studies on the relationship between IRSL and BLSL at relatively high temperatures for potassium-feldspar from sediments

In optical dating of potassium-feldspar, the luminescence signals can be stimulated by both infrared (IR) light and blue light (BL). To develop reliable dating methods using different stimulation light sources for feldspars, it is important to understand the sources of the traps associated with the infrared stimulated luminescence (IRSL) and blue light stimulated luminescence (BLSL) and their relationship. In this study, we explored the luminescence characteristics of IRSL and BLSL at different stimulation temperatures (from 60°C to 200°C) and their relationship based on five sets of experiments, i.e. post-IR BLSL, post-BL IRSL experiments, pulse annealing test, dose–response test and laboratory fading rate test. Our results suggest that the luminescence characteristics of IRSL and BLSL and their relationship are dependent on stimulation temperature. For IR stimulation at a relatively high temperature of 200°C, at least two components of IRSL signals are involved in the process. One component of IRSL signals can be easily bleached by BL stimulation at 60°C, while the other is relatively hard to be bleached by BL stimulation at 60°C. The two components have different luminescence properties, such as thermal stability, dose–response and laboratory fading rate.

Plasma membrane nanoporation as a possible mechanism behind infrared excitation of cells

Objective. Short infrared (IR) laser pulses have been used to stimulate action potentials in neurons both in vivo and in vitro. However, the mechanism(s) underlying this phenomenon has remained elusive. In vitro studies have found that pulsed IR exposure generates a nearly instant change in capacitance in the plasma membrane, characterized by inward rectification, a common feature in pore-forming exposures, such as electrical pulses and acoustic shock waves. Based on this similarity, we hypothesize that the mechanism of IR stimulation is the formation of short-lived nanopores in the plasma membrane. These transient, small-diameter pores allow the influx of extracellular ions that lead to action potential generation, possibly through activation of secondary messenger pathways or depolarization of the cell membrane resulting in activation of voltage-gated ion channels. Approach. A variety of fluorescent markers are used to observe the cell response to IR stimulation to monitor for effects indicative of nanoporation in other modalities. Main results. We observe rapid, transient rises in intracellular Ca2+, influx of YO-PRO-1 and propidium iodide into the cell signifying membrane permeabilization, cellular blebbing and swelling, and activation of the intracellular phosphoinositides lipid signaling pathway. Significance. This conclusion better explains the experimental observations and limitations of IR-induced neurological stimulation and represents a distinct theoretical shift in the understanding of the mechanism of IR-induced stimulation.

Investigation of the spectral improvement of a capacitive Frisch-grid CdZnTe detector by using infrared stimulation

A capacitive Frisch-grid CdZnTe detector with different lengths of the Frisch rings has been fabricated, and the influence of infrared (IR) stimulation on the spectral performance of the detector has been investigated. IR stimulation at a wavelength (940 nm), close to the absorption edge of the CdZnTe, was found to improve the detector’s spectral performance significantly. IR radiation was noted to influence the detector’s sensitivity, changing the equilibrium between free and trapped carriers and improving the charge collection. The degree of improvement was different for detectors with different lengths of the Frisch rings and depended on the weighting potential distribution and the IR illumination intensity. For example, improvement was obtained in the energy resolution (FWHM) at 662 keV from 3.3% without illumination to 2.3% with a low intensity (120 μW) of IR illumination for the capacitive Frisch-grid CdZnTe detector with an 8-mm-long Frisch ring. Good energy resolution could be obtained even at low operating voltages.

Photoluminescence, reddish orange long persistent luminescence and photostimulated luminescence properties of praseodymium doped CdGeO3 phosphor

Praseodymium doped CdGeO3 phosphors were prepared successfully by a conventional high temperature solid-state reaction method. It showed reddish orange long persistent luminescence (LPL) after the short UV-irradiation. The reddish orange photostimulated luminescence (PSL) was also observed upon near infrared stimulation at 980nm after per-exposure into UV light. The origin of LPL and PSL was identified with the emission from Pr3+ ions with the aid of traps in host lattice. The optimal concentration of Pr3+ ions for the brightest photoluminescence (PL) emission and the best LPL characteristic were experimentally to be about 3% and 0.5mol%, respectively. The trapping and de-trapping processes of charge carriers between shallower and deep traps were illustrated. A model was proposed on the basis of experimental results to study the mechanisms of LPL and PSL.

Enhanced infrared neural stimulation using localized surface plasmon resonance of gold nanorods.

An advanced optical activation of neural tissues is demonstrated using pulsed infrared light and plasmonic gold nanorods. Photothermal effect localized in plasma membrane triggers action potentials of in vivo neural tissues. Compared with conventional infrared stimulation, the suggested method can increase a neural responsivity and lower a threshold stimulation level significantly, thereby reducing a requisite radiant exposure and the concern of tissue damage.

Optical stimulation enables paced electrophysiological studies in embryonic hearts.

Cardiac electrophysiology plays a critical role in the development and function of the heart. Studies of early embryonic electrical activity have lacked a viable point stimulation technique to pace in vitro samples. Here, optical pacing by high-precision infrared stimulation is used to pace excised embryonic hearts, allowing electrophysiological parameters to be quantified during pacing at varying rates with optical mapping. Combined optical pacing and optical mapping enables electrophysiological studies in embryos under more physiological conditions and at varying heart rates, allowing detection of abnormal conduction and comparisons between normal and pathological electrical activity during development in various models.

Luminescence chronology of the Grub-Kranawetberg site, Austria

Abstract. Das Alter von acht Proben aus einem Lössprofil der Freilandfundstelle Grub-Kranawetberg (Niederösterreich) wurde mittels der Lumineszenzmethoden der IRSL-Datierungen an der polymineralischen Feinkornfraktion und der OSL-Datierungen an der Mittelkornfraktion von Quarzen bestimmt. Kalibrierte Radiokohlenstoffalter von ca. 30 ka für den archäologischen Hauptfundhorizont AH4 werden innerhalb der Fehlergrenzen durch IRSL- und OSL-Alter bestätigt. Anomales Ausheilen der feldspat-dominierten Feinkornfraktion konnte im Labor nicht nachgewiesen werden, weshalb die MAAD-IRSL Alter nicht korrigiert wurden. Während die meisten IRSL- und OSL-Alter innerhalb ihrer Fehlergrenzen übereinstimmen, unterschätzen einige IRSL-Alter die OSL-Alter aus bisher unbekannten Gründen signifikant, wobei die Mittelwerte der OSL-Resultate tendenziell älter als die IRSLDatierungen sind. Nach den OSL-Altern wurde der aufgeschlossene Löss einschließlich eines interstadialen Bodenkomplexes („Stillfried B“) im Zeitraum zwischen ca. 47 ka und ca. 30 ka gebildet. Mögliche edostratigraphische Korrelationen mit einigen europäischen Lössgebieten sowie paläoökologische Überlegungen zur menschlichen Besiedlung im Jungpaläolithikum werden diskutiert.

Combined ESR/U-series chronology of Acheulian hominid-bearing layers at Trinchera Galería site, Atapuerca, Spain

The Sierra de Atapuerca, northern Spain, is known from many prehistoric and palaeontological sites documenting human prehistory in Europe. Three major sites, Gran Dolina, Galería and Sima del Elefante, range in age from the oldest hominin of Western Europe dated to 1.1 to 1.3 Ma (millions of years ago) at Sima del Elefante to c.a. 0.2 Ma on the top of the Galería archaeological sequence. Recently, a chronology based on luminescence methods (Thermoluminescence [TL] and Infrared Stimulated Luminescence [IRSL]) applied to cave sediments was published for the Gran Dolina and Galería sites. The authors proposed for Galería an age of 450 ka (thousands of years ago) for the units lower GIII and GII, suggesting that the human occupation there is younger than the hominid remains of Sima de los Huesos (>530 ka) around 1 km away.In this paper, we present new results obtained by combined Electron Spin Resonance/Uranium-series (ESR/U-series) dating on 20 herbivorous teeth from different levels at the Galería site. They are in agreement with the TL results for the upper part of the stratigraphic sequence (GIV and GIIIb), in the range of between 200 and 250 ka. But for the GIIIa to GIIb levels, the TL ages become abruptly older by 200 ka while ESR ages remain relatively constant. Finally, the TL and ESR data agree in the lowest part of the section (GIIa); both fall in the range of around 350–450 ka. Our results suggest a different interpretation for the GII, GIII and GIV units of Galería and the upper part of Gran Dolina (TD10 and TD11) than obtained by TL. The ESR/U-series results are supported by a Bayesian analysis, which allows a better integration between stratigraphic information and radiometric data.

Improving the Performance of Quasi-Hemispherical CdZnTe Detectors Using Infrared Stimulation

The influence of monochromatic optical stimulation with wavelengths from 400 to 1100 nm on the characteristics of CdZnTe quasi-hemispherical detectors was studied. It was found that illumination with infrared (IR) light with wavelengths of 870-900 nm close to the absorption edge of the CdZnTe significantly improves the performance of the detector at room temperature. Improvement can be achieved with low-intensity IR illumination at 1-300 μW depending on the chosen wavelength of illumination. Higher intensity illumination was observed to lead to the degradation of the detector's spectrometric characteristics. IR radiation was noted to influence the detector's sensitivity, changing the equilibrium between free and trapped carriers and improving charge collection. For practical purposes, the use of an IR light-emitting diode (LED) as the IR source is suggested. We tested various LEDs with light wavelengths of 770 to 1020 nm. The degree of improvement was different for different detectors due to the different source materials used in the detectors and their dimensions. For example, the performance of a detector that was 10 mm × 10 mm × 5 mm in size with an initial energy resolution (FWHM) of 14.9 keV at 662 keV was improved with an IR LED illumination of up to 8.6 keV. IR stimulation improved the spectrometric characteristics for a wide range of energies starting at 59.6 keV without decreasing detection efficiency and over the temperature range from - 30°C to + 70°C. We found that the use of IR illumination with a properly chosen wavelength not only improves the performance of detectors at low temperatures but also stabilizes them over time.

Optical bleaching and radiation response of feldspar TL glow peaks separated by using computerized glow curve deconvolution

The thermoluminescence (TL) peaks of feldspar were separated using the computerized glow curve deconvolution (CGCD) method combined with the second-derivative technique and were investigated not only for bleaching with different light sources (blue and infrared) but also for luminescence response to radiation dose. In the results, the TL glow peak was separated into four peaks at 280 °C, 315 °C, 360 °C, and 440 °C. Each separated TL glow peak exhibited two exponential decays in the signal bleached using blue or infrared stimulation. In view of all four separated glow peaks, the bleaching of the first (second) exponential component was faster (slower) for both the blue and the infrared stimulation as the peak temperature increased, and the bleaching of the first (second) exponential component with blue stimulation was faster (slower) than that with infrared stimulation. In addition, we found that with added beta dose, the shapes of the growth curves showed no substantial differences for the separated glow peaks.

Effects of thermal treatments on luminescence features of three natural feldspars

Abstract The effects of prior infrared stimulation on the TL emission of three feldspar minerals (albite, sanidine and orthoclase) were studied. Different reductions in the TL signal were observed in the three samples: albite (Na-rich feldspar) was only partially affected by stimulation while there was an important decrease of TL signal in sanidine and orthoclase (K-rich and intermediate K–Na feldspars). A similar behaviour was also detected when the samples were illuminated at different temperatures. Moreover, when the IR stimulation was performed at temperatures below 100 °C, there was a charge transfer effect (PTTL) that progressively rose, moving from albite to sanidine to orthoclase. A dose recovery experiment was also performed, varying both preheat and measurement temperature. Our results are a further confirmation of the complexity and variability of the luminescence processes in feldspars. They also indicate that the luminescence characteristics of the albite we dealt with are particularly useful for dosimetric application.

Modeling of the shape of infrared stimulated luminescence signals in feldspars

This paper presents a new empirical model describing infrared (IR) stimulation phenomena in feldspars. In the model electrons from the ground state of an electron trap are raised by infrared optical stimulation to the excited state, and subsequently recombine with a nearest-neighbor hole via a tunneling process, leading to the emission of light. The model explains the experimentally observed existence of two distinct time intervals in the luminescence intensity; a rapid initial decay of the signal followed by a much slower gradual decay of the signal with time. The initial fast decay region corresponds to a fast rate of recombination processes taking place along the infrared stimulated luminescence (IRSL) curves. The subsequent decay of the simulated IRSL signal is characterized by a much slower recombination rate, which can be described by a power-law type of equation. Several simulations of IRSL experiments are carried out by varying the parameters in the model. It is found that the shape of the IRSL signal is remarkably stable when the kinetic parameters are changed within the model; this is in agreement with several previous studies of these signals on feldspars, which showed that the shape of the IRSL curves does not change significantly under different experimental conditions. The relationship between the simulated IRSL signal and the well-known power-law dependence of relaxation processes in solids is also explored, by fitting the IRSL signal at long times with a power-law type of equation. The exponent in this power-law is found to depend very weakly on the various parameters in the model, in agreement with the results of experimental studies. The results from the model are compared with experimental IRSL curves obtained using different IR stimulating power, and good quantitative agreement is found between the simulation results and experimental data. ► A new empirical model describing infrared stimulation phenomena in feldspars. ► The shape of the IRSL signal is remarkably stable when the parameters are changed. ► The simulated IRSL signal follows the power-law of relaxation processes in solids. ► The simulated exponent of the power-law depends very weakly on the intrinsic properties of the crystal. ► The simulated results are compared with experimental data for different stimulating IR power.

Infrared light excites cells by changing their electrical capacitance.

Optical stimulation has enabled important advances in the study of brain function and other biological processes, and holds promise for medical applications ranging from hearing restoration to cardiac pace making. In particular, pulsed laser stimulation using infrared wavelengths >1.5 μm has therapeutic potential based on its ability to directly stimulate nerves and muscles without any genetic or chemical pre-treatment. However, the mechanism of infrared stimulation has been a mystery, hindering its path to the clinic. Here we show that infrared light excites cells through a novel, highly general electrostatic mechanism. Infrared pulses are absorbed by water, producing a rapid local increase in temperature. This heating reversibly alters the electrical capacitance of the plasma membrane, depolarizing the target cell. This mechanism is fully reversible and requires only the most basic properties of cell membranes. Our findings underscore the generality of pulsed infrared stimulation and its medical potential.

Infrared Light Excites Cells via Transient Changes in Membrane Electrical Capacitance

Control of excitable cells using optical technologies such as optogenetics has enabled important advances in neuroscience and the development of clinical applications. Most existing methods of optical control require the use of genetic or chemical sensitizers that enable light to alter the ionic conductance of cell membranes. By contrast, infrared (IR) light of wavelengths > 1.5μm has been shown in vivo to excite neural and muscle tissue without any pre-treatment. Unfortunately, the mechanism of IR stimulation is unknown. Here, we describe how IR light excites cells by transiently altering their membrane electrical capacitance. Our data from voltage clamped Xenopus laevis oocytes, mammalian cells and artificial lipid bilayers shows that IR energy absorbed by water produces a rapid local increase in temperature at the cell membrane, transiently increasing its electrical capacitance, and generating depolarizing currents. Correspondingly, under current clamp conditions, IR pulses produce rapid changes in membrane potential. This unexpected mechanism is fully reversible and requires only the most basic properties of cell membranes. Changes in capacitance were verified by direct measurement in mammalian cells and artificial bilayers, and are consistent with a classical theoretical description of cell membranes as coupled double-layer capacitors. In shedding light on the mechanism of IR stimulation, our findings point to this technology's unique generality as a means to control excitable cells, and raise questions about other thermal phenomena that may meaningfully affect membrane electrostatics. Supported by the NIH: GM030376 and DC011481-01A1.

Optical dating of alluvial deposits at the orogenic front of the andean precordillera (Mendoza, Argentina)

Well constrained numerical ages of alluvial fan sediments are key to understanding the chronology of alluvial episodes and tectonic activity at the front of the Andean Precordillera. We tested the application of radiocarbon and optically stimulated luminescence (OSL) dating in the distal part of an alluvial fan five kilometers north of Mendoza. For OSL dating a large number of aliquots (n > 70) — each composed of ∼50 quartz grains — were measured in order to obtain reliable burial ages despite scattered dose distributions. Owing to a feldspar contamination in all samples, an infrared stimulation was inserted before each OSL measurement, which reduced the feldspar OSL signal successfully. By using the minimum age model we obtained stratigraphically consistent burial ages of alluvial deposits in a depth profile. The uppermost ∼1 m of sediment is composed of debris flow deposits buried 770±76 years ago. Three plant remnants used for radiocarbon dating from the same layer, however, yielded ages younger than 350 years, which are interpreted to underestimate the depositional age. Underneath the debris flow, a major unconformity cuts a series of distal alluvial fan sediments with interstratified floodplain deposits, which are composed of sandy and calciterich silt layers, respectively. Three samples from this unit which were distributed over one meter of sediment thickness yielded statistically concordant OSL ages of 12.3±1.2 ka, 12.3±1.2 ka, and 11.7±1.1 ka. The deposition of these sediments during the latest Pleistocene coincides with a phase of cool and humid climate, which occurred before the alluvial fan propagated farther into the foreland. The overlying debris flow sediments are associated with alluvial fan incision during the arid Late Holocene.

Luminescence dating of young coastal deposits from New Zealand using feldspar

A new measurement protocol has been tested on K-feldspars from Whanganui Inlet and Parengarenga Harbour, New Zealand. A Single Aliquot Regenerative (SAR) dose protocol, using two successive infrared (IR) stimulations (post-IR IR SAR protocol) is setup for these young (<1000 years) coastal sediments. Significant anomalous fading (g2days=7 %/decade) is observed using the conventional IR signal measured at 50°C. In contrast, the fading rate of the IR signal measured at elevated temperature (150°C) after the IR stimulation at 50°C (a post-IR IR signal) is not significant (g2days≤ 1 %/decade). Surprisingly low residual infrared stimulated luminescence (IRSL) signals were observed for a surface sample, suggesting that accurate ages as young as ∼50 years can be obtained for these recent deposits. IRSL ages ranging between 48±6 years and 1050±50 years are obtained from six samples, indicating that sediment accumulation has occurred at the two sites during the last millennia, despite a falling trend in relative sea-level in Whanganui Inlet and a stable relative sea-level at Parengarenga Harbour.

Towards a non-fading signal in feldspar: Insight into charge transport and tunnelling from time-resolved optically stimulated luminescence

Feldspars are an attractive alternative to quartz for extending the dose range, and for dating volcanic terrains such as on Mars and Iceland. Unfortunately, charge stored in the feldspar lattice undergoes anomalous fading leading to an underestimation in the dose estimates. In this paper we use the time-resolved optically stimulated luminescence (TR-OSL) technique to investigate the processes that give rise to the signal following infrared (IR), green and blue stimulation, with an objective to understand tunnelling and charge transport during thermo-optical excitations. We show that the TR-OSL shape is governed by the energy of excitation and the subsequent charge recombination route through the excited state of the trap, the band tail states or the conduction band. The role of band tail states in charge recombination is specifically examined using the signal shown to decay over several ms; we identify two dominant recombination routes, viz., phonon (0.05–0.06 eV) assisted diffusion, and quantum mechanical tunnelling, depending on the energy state of the detrapped electron. As would be expected, diffusion in the band tails is identical for both resonant and non-resonant excitations, where in the latter case the band tail state occupancy likely arises from thermalisation of conduction band electrons. The important outcome of this study is a comprehensive physical model based on a single dosimetric trap that successfully explains wide-ranging luminescence phenomena in feldspars, in particular, the luminescence efficiency and thermal partitioning of charge in different energy states and the subsequent recombination routes. The model predicts three different systematic approaches to preferentially sampling the most stable signal. We finally present evidence for a non-fading signal using one of these methods based on pulsed IR stimulation.