Availability and safety assessment of infrared neural stimulation at high repetition rate through an implantable optrode

An implantable optrode with micro-thermal detectors was designed to investigate the availability and safety of INS using high repetition rates.Optical auditory brainstem responses(oABRs)were recorded in normal-hearing guinea pigs,and the energy thresholds,pulse durations,and ampli-tudes evoked by the varied stimulus repetitions were analyzed.Stable oABRs could be evoked through INS even as the repetition rate of stimulation reached 19 kHz.The energy threshold of oABRs was elevated,the amplitudes decreased as pulse durations increased and repetition rates were higher,and the latencies were delayed as the pulse durations increased.The temperature variation curves on the site of stimulation significantly increased as the pulse duration increased to 400μs.INS elevated the temperature around the stimulus site area via thermal accumulation during radiation,especially when higher repetition stimuli were used.Our results demonstrate that high repetition infrared stimulations can safely evoke stable and available oABRs in normal-hearing guinea pigs.

In vivo auditory nerve stimulation with visible light

Background:Infrared laser stimulation has been proposed as an innovative method to elicit an auditory nerve response.Most studies have focused on usi ng long-wavelength infrared(>980 nm)pulsod lasers with high water absoption cofficients.This paper sought to assts8 whether a short-wavelength laser(465 nm)with an absorption cofficient as low as 103 cm^(-1) would activate the auditory nerve and studied its potential mechanism.Method:Optical compound action potentials(OCAPs)were recorded when synchronous triger laser pulses st imulate the cochlea before and after deafening,varying the pulse durations(from 8001us to 36001us)and the amount of radiant enengy(fom 18.05 mJ/cm^(2) to 107.91 mJ/cm^(2)).A thermal infrared imager was applied to monitor the tempenature change of the guinea pig cochlea.Results:The results showed that pulsed laser stimulation at 465 nm could invoke OCAPs and had a similar waveform compared to the acoustical compound action potentials.The amplitude of OCAPs had a poaitive correlation with the in-creasi ng laser peak power,while the latency of OCAPs showed a negative correlation.The imager data showed that the temperature in thecochlea rose quickly by about 0.3℃ right after stimulating the cochlea and decreased quickly back to the initial temperature as the stimulation ended.Con-clusions:This paper demonstrates that 465-nm laser st imulation can successfully induce OCAPs outside the cochlea,and that the amplitude and latency of the invoked OCAPs are highly affected by laser peak power.This paper proposes that a photothermal efect might be the main mechanism for the auditory nerve response induced by short-wavelength laser stimulation.

Late Pleistocene aeolian activity in Haitan Island, Southeast China: Insights from optically stimulated luminescence dating of coastal dunes on marine terraces

The 'Old Red Sand' is a type of semicemented medium-fine sandy sediment that is red(10R_4/8) or brown red(2.5YR_4/8) in colour and is found in late Quaternary deposits. The sediments have distinctive characteristics and are a critical archive for understanding climatic changes in the coastal areas of East Asia. The ages of the late Quaternary aeolian sand dunes from Haitan Island in the coastal area of South China are still in debate. In this study, three sets of marine terraces were identified in the northern region of Haitan Island. Aeolian dune sands are well preserved on the top of these terraces. Quartz Optically Stimulated Luminescence dating and the distribution of the formation ages demonstrated that the palaeo-dunes are deposits from the middle-late period of the Late Pleistocene(Q_3^(2-3)). The period may be divided into three stages, 100-90 ka, 70-60 ka, and 40-20 ka, in which the palaeo-dunes of the first two stages are more widespread and were formed separately during a low-sea level period of the Marine Isotope Stages 5 b and 4. Several depositional palaeo-flood event records were preserved during the last stage due to the increasing gradient of mountain gullies formed during the Last Glacial Maximum.

The study on optically stimulated luminescence dosimeter based on the SrS:Eu,Sm and CaS:Eu,Sm

With the increasing use of nuclear energy, there is a need for a wider range of efficient dosimeters for radiation detection and assessment. There has been a tremendous growth in the development of radiation detectors and devices in the past few decades. In recent years, the development of new materials for radiation dosimetry has progressed significantly. Alkaline earth sulfides （AES） have been known for a long time as excellent and versatile phosphor materials. In the present investigation, a number of phosphor samples such as mono-, binary and ternary sulfides of alkaline earths （II^a-VI^b） have been prepared and their TL properties have been studied with respect to exposure （x-ray） response and fading. In this paper, some results on SrS：Eu, Sm and CaS：Eu, Sm phosphors are presented. A type of novel OSL dosimeter is described. The dosimeter takes advantage of the characteristics of charge trapping materials SrS：Eu, Sm and CaS：Eu, Sm that exhibit optically stimulated luminescence （OSL）. The measuring range of the dosimeter is from 0.01 to 1000 Gy. The OSL dosimeters provide capability for remote monitoring radiation locations which are difficult to access and hazardous. This equipment is relatively simple, small in size and has low power consumption. The device is suitable for space radiation dose exploration. In addition, it also can be used in IC and other radiation occasions and has good prospects.

Optically stimulated luminescence dating of young glacial sediments from the eastern Qinghai-Tibetan Plateau

Poor bleaching is a significant problem for Optically Stimulated Luminescence(OSL) dating of glacial sediments. Five young glacial samples(including two modern analogues) from different depositional settings were collected beyond the Yingpu Glacier in the eastern Qinghai-Tibetan Plateau. De was determined using different OSL methods. The luminescence characteristics and dating results showed that the large aliquot quartz Blue Stimulated Luminescence(BSL) is more applicable than polymineral infrared stimulated luminescence(IRSL) method. Small aliquot quartz BSL results showed poor luminescence properties due to low luminescence sensitivity of quartz in this area. The dating results also indicated that glaciofluvial samples deposited close to ice margin(~40 m and ~700 m) and supraglacial debris dominated lateral moraine samples are relatively well-bleached, whereas samples from ground moraine and low terminal moraine were poorly bleached, probably due to containing subglacial and englacial debris. The residual doses of glaciofluvial and lateral moraine crest samples were below a few Gy and age overestimations were below a few hundred years. The ground moraine and low terminal moraine samples had residual doses as high as ~110 Gy, and ages were overestimated by ~15-17 ka.

Assessing conservation practices in Amalacaxco Gorge (Izta-Popo National Park, Central Mexico) using fallout 137Cs and Optically Stimulated Luminescence (OSL)

This study aims to assess conservation practices in Izta-Popo National Park(Central Mexico) by evaluating the mechanisms of sediment transfer. We applied a methodology based on fallout ^(137)Cs and optically stimulated luminescence(OSL) analysis. This was tested in the upper catchment of Amalacaxco Gorge, selected for being one of the sectors of the park in which man-made actions have been implemented in last decades to favor forest growth in the alpine grassland and to reduce the effect of water runoff. We quantified the ^(137)Cs activity using gamma and beta spectrometry of fine sediment grains extracted from the surface of parcels of 0.4 m2 in areas of natural forest, natural alpine grassland, alpine grassland with conservation practices, ravines and trails. In general, ^(137)Cs values increases as local slope decreases as it was expected. The natural forest is the most stable area in terms of soil erosion and sediment accumulation and, mean ^(137)Cs activity was taken as reference to assess cumulative zones, with higher ^(137)Cs values and erosive, with lower. We found that trails are accumulative surfaces but in other areas, erosion predominates. Man-made ditches, trenches and afforestation in the alpine grassland have higher ^(137)Cs values than thenatural grassland, which indicates that conservation practices are limiting the sediment transfer from hillslopes to channels, however, soil retention is less than in the natural grassland. Additionally, we evaluated the luminescence(OSL) values obtained from samples extracted from the sediment transported in ravines that are cutting into different sectors of the study area to assess the grade of resetting of fluvial materials. These luminescence results indicated that the sediment transported in ravines that are cutting into the natural forest and alpine grassland is bleached more efficiently than the sediment transported in the alpine grassland with conservation practices. Results of fallout ^(137)Cs and luminescence strongly suggest that man-made actions in this part of the Izta-Popo National Park are dramatically modifying the natural mechanisms of sediment transfer and favoring soil erosion. We conclude that made ditches, trenches and afforestation are not an effective conservation practice in Amalacaxco Gorge because they are promoting soil erosion instead of reducing it.

Thermoluminescence and optically stimulated luminescence disadvantages of α-Al_2O_3:C crystal grown by the temperature gradient technique

Recently, α-Al2O3：C crystal with highly sensitive thermoluminescence （TL） and optically stimulated luminescence （OSL） has been successfully grown by the temperature gradient technique. This paper investigates the heating rate dependence of TL sensitivity, light-induced fading of TL signals and thermal stability of OSL of α-Al2O3：C crystals. As the heating rate increases, the integral TL response decreases and the dosimetric glow peak shifts to higher temperatures in α-Al2O3：C crystals. Light-induced fading of TL increases with the irradiation dose, and TL response decreases as the exposure time increases, especially in the first 15 minutes. With the increasing intensity of the exposure light, the TL fading of α-Al2O3：C crystal increases sharply. The OSL response of as-grown α-Al2O3：C crystal is quite stable below 373 K and decreases sharply for higher temperatures.

Wireless closed-loop deep brain stimulation using microelectrode array probes

Deep brain stimulation(DBS),including optical stimulation and electrical stimulation,has been demonstrated considerable value in exploring pathological brain activity and developing treatments for neural disorders.Advances in DBS microsystems based on implantable microelectrode array(MEA)probes have opened up new opportunities for closed-loop DBS(CL-DBS)in situ.This technology can be used to detect damaged brain circuits and test the therapeutic potential for modulating the output of these circuits in a variety of diseases simultaneously.Despite the success and rapid utilization of MEA probe-based CL-DBS microsystems,key challenges,including excessive wired communication,need to be urgently resolved.In this review,we considered recent advances in MEA probe-based wireless CL-DBS microsystems and outlined the major issues and promising prospects in this field.This technology has the potential to offer novel therapeutic options for psychiatric disorders in the future.

Late Quaternary fluvial terrace formation in the Luan River drainage basin,north China and its possible linkages with climate change and tectonic activation

The Luan River is the most important water system in north-eastern Hebei Province,China and is located in the transitional zone of the Eastern Yan Mountains,North China Plain and Songliao Plain.The well-developed river terraces of its tributary,the Yixun River,provide excellent information for studying neotectonics and climate change.There are seven terraces in the lower reaches of the Yixun River,numbered T7-T1.The optically stimulated luminescence dating results of 23 samples show that terraces T7-T2 formed at 111.36±5.83 ka,78.20±4.45 ka,65.29±4.15 ka,56.44±3.07 ka,40.08±2.66 ka,and 13.14±0.76 ka,respectively.A comparison with the oxygen isotope curves of deep-sea sediments reveals that the sediment formation of each terrace corresponded to cold periods of marine isotope stages MIS 4 and MIS 2 and the relatively cold periods of MIS 5e,MIS 3,and MIS 1.Since the Late Pleistocene,the incision rate of the Yixun River has ranged from 0.371-1.740 mm/a.During the formation of T7-T6,T5-T4,T4-T3,and T3-T2,the incision rate was low.However,in the two stages during which T6-T5 and T2-T1 formed(13.14±0.76 ka to 0.58±0.08 ka and 10.79±0.64 ka to 0.16±0.01 ka),these rates reached 1.554 mm/a and 1.592-1.740 mm/a,respectively.At approximately 30 ka,the activity of the Langying Fault increased,leading to footwall uplift.The river gathered in the north of Langying to form the ancient Erdaowan Lake,which resulted in the drying of the river in the lower reaches of the Yixun River during the last glacial maximum without forming river deposits.In the Early Holocene,headward erosion in the lower reaches of the Yixun River was enhanced,which resulted in the disappearance of the lake,and incised meandering formed due to increased neotectonism.Based on the analyses of river incision and the formation of ancient lakes and incised meandering,it was inferred that there have been three periods of strong tectonism in the river basin since the Late Pleistocene.

Chronology of coastal aeolian deposition and its paleo-environmental implications on the Liuao Peninsula of South China

Coastal dunes are a common geomorphic type in sandy coastal zones.They are a record of the coupled evolutionary processes of the wind and ocean waves.Many coastal dune fields have developed on the east coast of Fujian China and now occur as widespread typical coastal aeolian sand landforms on the Liuao Peninsula,Gulei Peninsula and Dongshan Island,but it is difficult to evaluate the dynamic geomorphologic process of sandy coast due to the lack of systematic and accurate chronological data.In this study,we selected the Hutoushan(HTS)aeolian dune on the Liuao Peninsula as the research object.Optical dating and grain-size analysis were applied to sand samples from the aeolian sequence of a profile of the HTS dune.The results show that the ages of seven samples of this profile were in the range of 37.8–0.19 ka from 4.0 to 0.2 m deep.These correspond to the Marine Isotope Stage 3(MIS3),abrupt climatic change events of 4.2 and 1.1 ka and the Little Ice Age(LIA),respectively.These samples displayed evidence of a longer-term climate trend in this area.The period of formation of this coastal aeolian dune corresponds to a cold and arid climate associated with the East Asia Winter Monsoon(EAWM).Periods of dune fixation and rubification are evidence of a hot and humid climate.Mobilization and stabilization of the aeolian dune is an important characteristic of the coastal evolution in South China since the late Pleistocene.

Initiation and Development of the Late Cenozoic Uplift of Daluo Mountains,Northeastern Margin of the Tibetan Plateau

Daluo Mountains lie at front of the arcuate tectonic belt at the northeastern margin of the Tibetan Plateau,and are the landform boundary zone between the active Tibetan Plateau and the stable North China Craton.Studying of the late Cenozoic uplift evolution of Daluo Mountains is important for understanding the expansion mechanism of the northeastern margin of the Tibetan Plateau and its influence on the western North China Craton.In this study,the late Cenozoic uplift of Daluo Mountains is constructed from the development of the late Cenozoic alluvial fan around Daluo Mountains.The entire sedimentary sequence and framework of the fan was revealed by the newly obtained drilling core data.The cosmogenic nuclide,optically stimulated luminescence,and detrital zircon U-Pb dating results provide new evidences for discussion about the initial timing of the late Cenozoic uplift of Daluo Mountains and the key stages of uplift during the Pleistocene.The late Cenozoic alluvial fan at front of Daluo Mountains overlies a set of fluvial-facies strata;therefore,development of the alluvial-fan marks the start of late Cenozoic uplift of Daluo Mountains.The timing of this event can be constrained to~4.64 Ma.Two extensive gravel layers(dated to ca.0.76–0.6 Ma and~0.05 Ma)developed during the Pleistocene,indicating two episodes of considerable uplift.This study provides a new time scale for the uplift and expansion of the arcuate tectonic belt at the northeastern margin of the Tibetan Plateau.

Age and Provenance of Loess deposits on the Northern Flank of Tianshan Mountain

The distribution, optically stimulated luminescence dating and granulometric properties suggest that the loess on the northern flank of Tian Shan should be divided into two types. One which is like mantle and is named type A, is located on the windward slopes and dated to about 54.5±5.73 Ka. The other, called type B, lies flatly on the terraces of the rivers or low hills and penetrated 30.8±2.05 Ka ago. Here we study the origin and the age of two types of loess, and a model of loess formation is proposed. The dust was entrained from the Gobi Desert located to the north of Tian Shan by the monsoon from Mongolia, obstructed by the high mountains and deposited on the windward slopes of the mountains. The rivers and flows then transported the aeolian loess to low terraces and piedmont alluvial plains.

Coastal environment of the past millennium recorded by a coastal dune in Fujian,China

Coastal dune is a common aeolian geomorphology in a sandy coast,which records the evolution process of the aeolian landscape system and reflects the complex interaction among land surface,atmosphere and ocean.Coast is a sensitive area to global climate change.Restricted by chronology,most previous researches in China focused only on the cause of formation of coastal dunes.In recent years,the development of optically stimulated luminescence （OSL） dating provides a good method and acts as a carrier for coastal dunes to paleoclimate and paleoenvironmental studies.In this study,we selected an aeolian dune at the Anshan archaeological site,Fujian,China as the research object based on field observations.For determining their sedimentary stages and the primary influencing factors,we used the OSL dating method to construct a chronological framework for the aeolian dune.In addition,the sizes of grains were analyzed for identifying factors influencing the winter monsoon during the Medieval Warm Period （MWP） and the Little Ice Age （LIA） in this area.The results showed that the deposition of the aeolian dune was closely related to variations in the winter monsoon intensity.The changes of the winter monsoon were similar to the tendency of the East Asian winter monsoon,although there were several sub-fluctuations.From an overall perspective,the winter monsoon was strengthened during the MWP （1050–1300） .The results of a power spectrum analysis showed that the intensity of the East Asian winter monsoon is correlated with sunspot activity.

The progress in optic nerve regeneration, where are we?

Optic nerve regeneration is an important area of research. It can be used to treat patients suffering from optic neuropathy and provides insights into the treatment of numerous neurodegenerative diseases. There are many hurdles impeding optic regeneration in mammals. The mammalian central nervous system is non-permissive to regeneration and intrinsically lacks the capacity for axonal regrowth. Any axonal injury also triggers a vicious cycle of apoptosis. Understanding these hurdles provides us with a rough framework to appreciate the essential steps to bring about optic nerve regeneration： enhancing neuronal survival, axon regeneration, remyelination and establishing functional synapses to the original neuronal targets. In this review article, we will go through current potential treatments for optic nerve regeneration, which includes neurotrophic factor provision, inflammatory stimulation, growth inhibition suppression, intracellular signaling modification and modeling of bridging substrates.

Quartz luminescence dating of a centennial coastal foredune from Changle in Fujian Province,East China Sea

The Aeolian foredunes in the southern coast of China are records of paleoenvironmental changes for marine monsoon region. Intensive studies have been conducted to decipher their formation and paleoenvironmental implications in which chronology played a key role. However, robust dating results are still limited due to the scarcity of organic materials for radiocarbon and the limited application of quartz optically stimulated luminescence(OSL). Here, we collected 11 OSL samples and 140 grainsize samples from the Changle section with a thickness of 7 m from a coastal foredune in Fujian Province. The dating results indicated that the section spanned a time period from 0.32±0.04 ka(depth of 700 cm) to 0.18±0.02 ka(depth of 80 cm), after removal of age outliers. According to the OSL ages and sedimentary structural characteristics, the section could be divided into two stages, i.e. the stable accumulation period with an age range of 0.32-0.18 ka from the depth of 700 cm to 80 cm, and the activation period above the depth of 60 cm, at which the dune erosion was retained. The foredune development due to increased transport of dune sediment at the top part of the section was the result of recent human activities.Inside the foredunes, normal cross-bedding was generated by seasonal changes in wind direction.Seasonal changes in the wind direction were the primary cause for various sedimentary bedding within the dunes.

The fluorescence and thermoluminescence characteristics of α-Al_2O_3:C ceramics

This paper reports that polycrystalline （α-Al2O3：C ceramics are fabricated by conventional ceramics process. The excitation, emission spectra, thermoluminescence （TL） and optical stimulated luminescence （OSL） of α-Al2O3：C polycrystalline ceramics are investigated. There exists 410nm maximum emission peak which is caused by recombination of an electron with F＋ centre to produce an excited F centre. The samples show three clear TL glow peaks at 405, 493 and 610 K. The attenuation constant of exponentially decaying fast component （τ1） and slow component（τ2） of OSL curve are 8.43s and 41.73s, respectively. Those fluorescence and thermoluminescence characteristics are similar with α-Al2O3：C crystal.

OSL Dating of Coastal Post-Barreiras Sediments from Northern Brazil

In the present work, luminescence dating of sedimentary deposits, from the coast of the State of Maranh^o, in northeast Brazil, was done. Samples were collected from the Post-Barreiras sediments, a quartzose sandy unit that is extensive along the entire northeast and northern Brazilian coast, where they occur overlying early to middle Miocene Barreiras Formation. A great part of the Post-Barreiras sediments is massive, which precludes its depositional setting interpretation. However, this unit consists of three successions, the lowermost one including highly bioturbated deposits suggestive of marine influence, and the two uppermost ones displaying dune dissipative structures related to eolian processes along coastal areas. The study aimed to compare MAR （multiple aliquot regeneration） and SAR （single aliquot regeneration） protocols for dating these deposits. Discussion involving origins of depositions will also include single aliquot measurements. The ages obtained by OSL （optical stimulated luminescence）-SAR protocol range from （0.5 ± 0.1） ka to （84 ± 6） ka.

Dose-Dependence of Trap Parameters of OSL Decay from Al_(2)O_(3):C

Optically Stimulated Luminescence (OSL) trap parameters can only be reliably determined through the detailed analy- sis of OSL decay curves. In this study the kinetic parameters of a blue-light stimulated luminescence (BLS) decay curve from Al2O3:C sample irradiated at 0.1, 0.15, 0.2, 0.4 and 0.6 Gy beta doses were obtained using the same basic methods with some modifications applied and also by using our suggestion: Active-OSL Approximation (AOSL). The results were compared with those of other studies on the trap parameters of Al2O3:C material.

Optically stimulated luminescence of Dy^3+-doped NaCaPO4 glass-ceramics

Dy^3+-doped glass-ceramics containing NaCaPO4 crystals were successfully fabricated by heat treatment at base glass,and the luminescence properties were investigated for potential applications in radiation measurements.The photo luminescence(PL)excitation and emission spectra exhibit transitions related to Dy^3+ions corresponding to the strongest excitation and emission wavelengths at 351 and 575 nm,respectively.The CW-OSL properties as a function of dopant concentration,pre-heating temperature,pre-heating time and signal fading were investigated.The most appropriate Dy^3+ion concentration was found to be 0.25 mol%.The TL glow curves have a broad peak feature peaking at 195±5℃.The fading of the OSL signal would keep stable in five days with the intensity value of about 76.11%.The samples also exhibit good signal reusability and a broad linear dose response range(0.02-1000 Gy).

A study on the real-time radiation dosimetry measurement system based on optically stimulated luminescence

The optically stimulated luminescent （OSL） radiation dosimeter technically surveys a wide dynamic t range and a high sensitivity. Optical fiber dosimeters provide capability for remote monitoring of the radiation in the locations which are difficult-to-access and hazardous. In addition, optical fiber dosimeters are immune to electrical and radio-frequency interference. In this paper, a novel remote optical fiber radiation dosimeter is described. The optical fiber dosimeter takes advantage of the charge trapping materials CaS：Ce, Sm that exhibit OSL. The measuring range of the dosimeter is from 0.1 to 100 Gy. The equipment is relatively simple and small in size, and has low power consumption. This device is suitable for measuring the space radiation dose and also can be used in high radiation dose condition and other dangerous radiation occasions.