Changes In Threshold Research Articles

Moxibustion for declined cardiorespiratory fitness of apparently healthy older adults: A study protocol for a randomized controlled trial.

Aging and age-related declines lead to varying degrees of decreased cardiorespiratory fitness (CRF) in apparently healthy older adults. Exercise training, the primary approach for enhancing CRF, encounters several constraints when used with elderly individuals. Existing evidence implies that moxibustion might enhance the CRF of older adults. However, clinical research in this area still needs to be improved. This study will employ a randomized, assessor-blinded, controlled trial design involving 126 eligible participants. These participants will be stratified and randomly assigned to one moxibustion group, one sham moxibustion group, and one blank control group. Acupoints of bilateral Zusanli (ST36), Shenque (CV8), and Guanyuan (CV4) are selected for both real and sham moxibustion groups. The treatment will last 60 min per session, 5 sessions a week for 12 weeks. The blank control group will not receive any intervention for CRF improvement. Primary outcomes will be the mean change in peak oxygen uptake (VO2peak), anaerobic threshold (AT), and serum central carbon metabolites (CCB) from the baseline to observation points. Secondary outcome measures involve the six-minute walk distance (6MWD), the Short Form 36 Health Survey (SF-36), and the Qi and Blood Status Questionnaire (QBSQ). Outcome assessments will be conducted at weeks 4, 8, 12, and 24 as part of the follow-up. Adverse events will be assessed at each visit. This trial can potentially ascertain moxibustion's effectiveness and safety in enhancing CRF among apparently healthy older adults. ChiCTR, ChiCTR2300070303. Registered on April 08, 2023.

Dynamic Triggering of Earthquakes in Northeast Japan before and after the 2011 M 9.0 Tohoku-Oki Earthquake

ABSTRACT Previous studies documented a relative scarcity of remote dynamic triggering of earthquakes in Japan and suggested that it could be related to Japan’s predominantly compressive tectonic regime or the more frequent occurrence of large earthquakes in Japan. For example, remote triggering in California, characterized by extensional tectonics, occurs at levels of stress change as small as 0.1 kPa, whereas in Japan, transient stresses ≥30 kPa are required. However, the dynamic triggering threshold in Japan, following the 2016 Mw 7.0 Kumamoto earthquake, has been found to be of just a few kilopascals, significantly smaller than reported previously. It was proposed that a decrease in the triggering threshold may have taken place in Japan, in particular at volcanic and geothermal areas, after the 2011 Mw 9.0 Tohoku-Oki earthquake. In this study, we analyze the possible change in dynamic triggering conditions in five areas in northeast Japan, where swarm earthquakes have occurred immediately after the Tohoku-Oki earthquake. The triggering thresholds in these five areas have been estimated based on the analysis of waveform recordings of 49 teleseismic earthquakes that occurred between 2004 and 2020. A decrease of the triggering threshold (or triggering ability) is apparent in all but one region. However, a statistical significance Kolmogorov–Smirnov test could not reject, at a 5% level, the null hypothesis stating that “the distribution of dynamic stress changes for triggering earthquakes that occurred before and after the Tohoku-Oki event is the same.” We interpret the changes in the triggering threshold to be related to the pore pressure increase (and thus a fault strength decrease) in the crust following the Tohoku-Oki earthquake. Our results also indicate that dynamic triggering in Japan is more common than reported previously.

Tailored Mass Spectral Data Exploration Using the SpecXplore Interactive Dashboard.

Untargeted metabolomics promises comprehensive characterization of small molecules in biological samples. However, the field is hampered by low annotation rates and abstract spectral data. Despite recent advances in computational metabolomics, manual annotations and manual confirmation of in-silico annotations remain important in the field. Here, exploratory data analysis methods for mass spectral data provide overviews, prioritization, and structural hypothesis starting points to researchers facing large quantities of spectral data. In this research, we propose a fluid means of dealing with mass spectral data using specXplore, an interactive Python dashboard providing interactive and complementary visualizations facilitating mass spectral similarity matrix exploration. Specifically, specXplore provides a two-dimensional t-distributed stochastic neighbor embedding embedding as a jumping board for local connectivity exploration using complementary interactive visualizations in the form of partial network drawings, similarity heatmaps, and fragmentation overview maps. SpecXplore makes use of state-of-the-art ms2deepscore pairwise spectral similarities as a quantitative backbone while allowing fast changes of threshold and connectivity limitation settings, providing flexibility in adjusting settings to suit the localized node environment being explored. We believe that specXplore can become an integral part of mass spectral data exploration efforts and assist users in the generation of structural hypotheses for compounds of interest.

Determination of change of direction deficit thresholds across a spectrum of angles in basketball players

ABSTRACT Change of direction deficit (CODD) offers valuable insights into a player’s balance between linear and multidirectional speed. However, there are still no established reference values for CODD. The objectives of this study were to determine CODD thresholds for various change of direction angles in basketball players according to gender and analyse the relationships between CODD and execution time in speed tests. One hundred and thirty basketball players (46% female; age: 23.7 ± 5.29 years; height: 189.1 ± 11.1 cm; body mass: 84.3 ± 15.7 kg) undertook 10-m linear and change of direction speed test at 45º, 90º and 180º. A k-means cluster analysis was conducted to standardise CODD thresholds and a one-way analysis of variance to identify the differences between clusters. The results revealed angulation-specific CODD thresholds, ranging from 3% to 8%, 17% to 25% and 43% to 51% for 45º, 90º and 180º cutting angles, respectively for the pooled sample. Furthermore, differences inter-clusters (p < 0.05) were observed for execution time at all cutting angles for both genders. Therefore, strength and conditioning coaches are encouraged to assess CODD as a highly valid variable for evaluating change of direction performance and to use current CODD thresholds to tailor training programmes according to each athlete’s needs.

Comparison of the hemoglobin variability in non-chronic kidney disease or end-stage renal disease participants and patients with CKD and ESRD.

Hemoglobin (Hb) variability occurs frequently in hemodialysis (HD) patients during erythropoietin (EPO) therapy. Guidelines define a narrow target range for the anemia treatment in these patients that is difficult to adhere to in practice. Our aim was to evaluate whether the Hb variability in HD patients is higher compared to non-chronic kidney disease or end-stage renal disease (ESRD) participants and patients with CKD stage I or II. Monthly blood samples were assessed prospectively in 100 non-CKD or ESRD participants and 57 patients with CKD stage I or II, and retrospectively in 74 HD patients without changes in EPO or iron dose for 6 months. Variability was calculated and compared between the different groups. Hb variability was significantly higher in HD patients compared to the other groups, corresponding to results of previous studies. There were no significant differences between non-CKD or ESRD participants and patients with CKD stage I or II in terms of standard deviation (SD), residual SD, fluctuations across threshold, Hb cycling, and mean absolute change of Hb every 30 days (p>0.05), but a significant difference compared to HD patients (p<0.001). There were no significant differences between the groups in time in target and area under the curve (AUC) (p>0.05). Hb variability is a common phenomenon in all groups independently of the method used for assessment and even without EPO therapy. The target range is difficult to achieve for HD patients and should be reconsidered in the future to avoid unsettling both the patients and the staff.

Cross-border Retail E-Commerce and De Minimis: The Case of Kazakhstan

The development of international e-commerce has expanded opportunities for business and consumption in Kazakhstan and worldwide. However, these rapid changes have challenged the governments’ regulation of the flow of cross-border goods, ranging from clearance to customs duty and taxes collection. Among concerns is the flow of low-value consignments, the impact of which had previously been seen as beneficial. This paper examines whether cross-border e-commerce and the de minimis threshold are advantageous in Kazakhstan based on context, description, cause-and-effect and statistical analysis. The findings show a partial impact of de minimis threshold changes on the increase in retail e-commerce goods imported and on the decrease in the value of mis-declared goods; however, in Kazakhstan the consequences from the import of mis-declared low-value goods on the tax revenue are insignificant. Misuse of the de minimis threshold in Kazakhstan is confirmed by the study. Government actions for solving this problem involve giving higher priority to people’s access to higher quality and/or cheaper personal use goods. Also, the potential for further improvement of statistics on cross-border e-commerce is identified.

Hypothesis Tests for Continuous Audiometric Threshold Data.

Hypothesis tests for hearing threshold data may be challenging due to the special structure of the response variable, which consists of the measurements from the participant's two ears at multiple frequencies. The commonly-used methods may have inflated type I error rates for the global test that examines whether exposure-hearing threshold associations exist in at least one of the frequencies. We propose using both-ear methods, including all frequencies in the same model for hypothesis testing. We compared the both-ear method to commonly used single-ear methods, such as the worse-ear, better-ear, left/right-ear, average-ear methods, and both-ear methods that evaluate individual audiometric frequencies in separate models, through both theoretical consideration and a simulation study. Differences between the methods were illustrated using hypothesis tests for the associations between the Dietary Approaches to Stop Hypertension adherence score and 3-year change in hearing thresholds among participants in the Conservation of Hearing Study. We found that (1) in the absence of ear-level confounders, the better-ear, worse-ear and left/right-ear methods have less power for frequency-specific tests and for the global test; (2) in the presence of ear-level confounders, the better-ear and worse-ear methods are invalid, and the left/right-ear and average-ear methods have less power, with the power loss in the left/right-ear much greater than the average-ear method, for frequency-specific tests and for the global test; and (3) the both-ear method with separate analyses for individual frequencies is invalid for the global test. For hypothesis testing to evaluate whether there are significant associations between an exposure of interest and audiometric hearing threshold measurements, the both-ear method that includes all frequencies in the same model is the recommended analytic approach.

4-octyl itaconate alleviates cisplatin-induced ferroptosis possibly via activating the NRF2/HO-1 signalling pathway.

Ferroptosis, characterized by iron-dependent lipid reactive oxygen species (ROS) accumulation, plays a pivotal role in cisplatin-induced ototoxicity. Existing research has suggested that in cisplatin-mediated damage to auditory cells and hearing loss, ferroptosis is partially implicated. 4-Octyl itaconate (4-OI), derived from itaconic acid, effectively permeates cell membranes, showcasing potent anti-inflammatory as well as antioxidant effects in several disease models. Our study aimed to investigate the effect of 4-OI on cisplatin-induced ferroptosis and the underlying molecular mechanisms. The survival rates of HEI-OC1 cells and mice cochlea hair cells were measured by CCK8 and immunofluorescence, respectively. The auditory brainstem response (ABR) audiometry was used to detect changes in hearing thresholds in mice before and after treatment. Levels of ROS were evaluated by DCFH-DA. Real-time PCR quantified inflammatory cytokines TNF-α, IL-6 and IL-1β. Network Pharmacology and RNA sequencing (RNA-seq) analysis of the potential mechanism of 4-OI resistance to cisplatin-induced ferroptosis. The expressions of ferroptosis-related factors (GPX4, SLC7A11 and PTGS2) and important antioxidant factors (NRF2, HO-1, GCLC and NQO1) were tested by real-time PCR, Western blot and immunofluorescence. Results demonstrated cisplatin-induced significant ROS and inflammatory factor release, reduced NRF2 expression, hindered nuclear translocation and activated ferroptosis. Pretreatment with 4-OI exhibited anti-inflammatory and antioxidant effects, along with resistance to ferroptosis, ultimately mitigating cisplatin-induced cell loss. In the present study, we show that 4-OI inhibits cisplatin-induced ferroptosis possibly through activation of the NRF2/HO-1 signalling pathway, thereby exerting a protective effect against cisplatin-induced damage to auditory cells, and providing a new therapeutic strategy for cisplatin-induced hearing loss.

Reliability assessment models for competing failure processes with two types of correlative thresholds

AbstractThe two dependent competing risks are soft failure due to aging degradation and fragmentation caused by shocks and hard failure due to spring breakage caused by the same shock process. Considering the complexity of the product itself and the instability of the working environment, this study proposed a generalized reliability model for systems experiencing dependent competing failure processes (DCFPs) of degradation and random shocks, which considered two kinds of DCFP: (1) shock process could affect soft failure thresholds; (2) degradation process could affect hard failure thresholds. In case (1), we considered the effect that a cumulative number of shocks above a certain magnitude could have on the change in the soft failure threshold. In case (2), we considered not only the shock process's impact on the soft failure threshold but also the total degradation (including continuous degradation and sudden degradation caused by shock) on the hard failure threshold. The model captures the features that the shocks experienced by the system affect the degradation process, accelerating the system degradation and causing soft failures; the degradation process of the system affects the shock process, making the system more susceptible to failure from external shocks. Finally, an example using micro‐electro‐mechanical systems devices illustrates the effectiveness of the proposed approach with sensitivity analysis.

Serum Prestin Level May Increase Following Music Exposure That Induces Temporary Threshold Shifts: A Pilot Study.

To determine if blood prestin level changes after exposure to music at high sound pressure levels, and if this change is associated with temporary threshold shift (TTS) and/or changes in distortion product (DP) amplitude. Participants were exposed to pop-rock music at 100 dBA for 15 min monaurally through headphones. Pure-tone audiometry, DP amplitude, and blood prestin level were measured before and after exposure. Fourteen adults (9 women; age range: 20 to 54 years, median age = 31 [Interquartile ratio = 6.75]) with normal hearing were included in the study. Mean prestin level increased shortly after exposure to music, then returned to baseline within 1 week, although this trend was not observed in all participants. All participants presented TTS or a decrease in DP amplitude in at least one frequency after music exposure. There was a statistically significant average threshold elevation at 4 min postexposure. Statistically significant DP amplitude shifts were observed at 4 and 6 kHz, 2 min following exposure. Mean baseline serum prestin level (mean: 140.00 pg/mL, 95% confidence interval (CI): 125.92 to 154.07) progressively increased following music exposure, reaching a maximum at 2 hr (mean: 158.29 pg/mL, 95% CI: 130.42 to 186.66) and returned to preexposure level at 1 week (mean: 139.18 pg/mL, 95% CI: 114.69 to 163.68). However, after correction for multiple comparisons, mean prestin level showed no statistically significant increase from baseline at any timepoint. No correlation between maximum blood prestin level change and average TTS or distortion product otoacoustic emission amplitude shift was found. However, in an exploratory analysis, TTS at 6 kHz (the frequency at which maximum TTS occurred) decreased significantly as baseline blood prestin level increased. The results suggest that blood prestin level may change after exposure to music at high sound pressure levels, although statistical significance was not reached in this relatively small sample after correction. Baseline serum prestin level may also predict the degree of TTS. These findings thus suggest that the role of baseline serum prestin level as a proxy marker of cochlear susceptibility to intense music exposure should be further explored.

A bolt defect detection method for transmission lines based on improved YOLOv5

To solve the problem of bolt defects in unmanned aerial vehicle inspection that are difficult to identify quickly and accurately, this paper proposes a defect detection method based on the improved YOLOv5 anchor mechanism. Firstly, the Normalized Wasserstein distance (NWD) evaluation metric and the Intersection over Union evaluation metric are combined, and the experiment determines the appropriate weight for this combination. This way, the sensitivity of using IoU alone to small objecet detection anchor box threshold changes was reduced. Furthermore, Convolutional Block Attention Module is included into the head network architecture of yolov5 in order to prioritize significant information and suppress irrelevant features. Omni-dimensional Dynamic Convolution (ODConv) is used to replace convolution in MobileNetv2. The combination module is used as the new backbone of the YOLOv5 model. It simultaneously enhances the model’s capability to extract bolt defect object information, minimizes calculation requirements, and achieves lightweight detection across the entire model. Compared with the original algorithm, the model detection Accuracy Precision (AP) is increased by 30.1%, the mean Accuracy Precision is increased by 30.4%. Other evaluation metrics of the model, such as GFlOPs and Parameters, all decreased slightly. The above results show that the improved algorithm proposed in this paper greatly improves the detection accuracy of the model on the premise of ensuring that the model is as small as possible.

Associations between dietary indices and hearing status among middle-older aged adults – results from the Baltimore Longitudinal Study of Aging

BackgroundHearing loss, a public health issue in older populations, is closely related to functional decline. ObjectiveTo investigate the longitudinal associations between 4 dietary indices and hearing status. MethodsData from the Baltimore Longitudinal Study of Aging were used and included 882 participants ≥45 y of age. Dietary intake was assessed using a validated food frequency questionnaire, and 4 dietary scores (Mediterranean-Dietary Approaches to Stop Hypertension Intervention for Neurodegenerative Delay diet [MIND], Mediterranean style diet score [MDS], Alternative Healthy Eating Index [AHEI], and Healthy Eating Index [HEI]) were calculated as averages over time. Hearing status was examined using pure-tone audiometry, and pure-tone average (PTA) of hearing thresholds were calculated at speech-level (PTA(500, 1000, 2000, 4000 Hz)), low (PTA(500, 1000 Hz)), and high (PTA(4000, 8000 Hz)) frequencies, with lower thresholds indicating better hearing. Multivariable linear mixed-effect models were used to examine associations between dietary indices and hearing threshold change over time adjusted for confounders. ResultsAt baseline, the mean age of participants was 67 y and 55% were female. Over a median of 8 y of follow-up, MDS ≥7 was associated with 3.5 (95% CI: –6.5, –0.4) and 5.0 (95% CI: –9.1, –1.0) dB lower PTA(500, 1000, 2000, 4000 Hz) and PTA(4000, 8000 Hz), respectively, compared with MDS ≤3; the highest tertile of the AHEI was associated with 2.3 (95% CI: –4.6, –0.1) and 5.0 (95% CI: –8.0, –2.0) dB lower PTA(500, 1000, 2000, 4000 Hz) and PTA(4000, 8000 Hz); and each standard deviation increment in HEI was associated with 1.6 dB (95% CI: –2.7, –0.6), 1.1 dB (95% CI: –2.1, –0.1), and 2.1 dB (95% CI: –3.5, –0.6) lower PTA(500, 1000, 2000, 4000 Hz), PTA(500, 1000 Hz), and PTA(4000, 8000 Hz), respectively. ConclusionsAdherence to healthy dietary patterns was associated with better hearing status, with stronger associations at high frequencies. Am J Clin Nutr 20xx;x:xx.

Impact of occupational noise exposure on the hearing level in hospital staffs: a longitudinal study.

The study aimed to evaluate the impact of occupational noise on hearing loss among healthcare workers using audiometry. A longitudinal study was conducted with a six-month follow-up period in a hospital with 21 participants, divided into high-noise-exposure (HNE) and low-noise-exposure (LNE) groups. Mean noise levels were higher in the HNE group (70.4 ± 4.5 dBA), and hearing loss was measured using pure-tone audiometry at baseline and follow-up. The HNE group had significantly higher mean threshold levels at frequencies of 0.25kHz, 0.5kHz, 4.0kHz, and an average of 0.5, 1, 2, and 4kHz (all p-values < 0.05) after the follow-up period. After adjusting for confounding factors, the HNE group had significantly higher hearing loss levels at 0.25kHz, 0.5kHz, and average frequencies of 0.5, 1, 2, and 4kHz compared to the LNE group at the second measurement. Occupational noise levels above 65 dBA over six months were found to cause significant threshold changes at frequencies of 0.25kHz, 0.5kHz, and an average of 0.5-4.0kHz. This study highlights the risk of noise-induced hearing loss among healthcare workers and emphasizes the importance of implementing effective hearing conservation programs in the workplace. Regular monitoring and assessment of noise levels and hearing ability, along with proper use of personal protective equipment, are crucial steps in mitigating the impact of occupational noise exposure on the hearing health of healthcare workers.

Transferability of bone phenotyping and fracture risk assessment by μFRAC from first-generation high-resolution peripheral quantitative computed tomography to second-generation scan data.

The continued development of high-resolution peripheral quantitative computed tomography (HR-pQCT) has led to a second-generation scanner with higher resolution and longer scan region. However, large multicenter prospective cohorts were collected with first-generation HR-pQCT and have been used to develop bone phenotyping and fracture risk prediction (μFRAC) models. This study establishes whether there is sufficient universality of these first-generation trained models for use with second-generation scan data. HR-pQCT data were collected for a cohort of 60 individuals, who had been scanned on both first- and second-generation scanners on the same day to establish the universality of the HR-pQCT models. These data were each used as input to first-generation trained bone microarchitecture models for bone phenotyping and fracture risk prediction, and their outputs were compared for each study participant. Reproducibility of the models were assessed using same-day repeat scans obtained from first-generation (n = 37) and second-generation (n = 74) scanners. Across scanner generations, the bone phenotyping model performed with an accuracy of 93.1%. Similarly, the 5-year fracture risk assessment by μFRAC was well correlated with a Pearson's (r) correlation coefficient of r > 0.83 for the three variations of μFRAC (varying inclusion of clinical risk factors, finite element analysis, and dual X-ray absorptiometry). The first-generation reproducibility cohort performed with an accuracy for categorical assignment of 100% (bone phenotyping) and a correlation coefficient of 0.99 (μFRAC), whereas the second-generation reproducibility cohort performed with an accuracy of 96.4% (bone phenotyping) and a correlation coefficient of 0.99 (μFRAC). We demonstrated that bone microarchitecture models trained using first-generation scan data generalize well to second-generation scans, performing with a high level of accuracy and reproducibility. Less than 4% of individuals' estimated fracture risk led to a change in treatment threshold, and in general, these dissimilar outcomes using second-generation data tended to be more conservative.

Fatigue and vigilance in medical experts detecting breast cancer

An abundance of laboratory-based experiments has described a vigilance decrement of reducing accuracy to detect targets with time on task, but there are few real-world studies, none of which have previously controlled the environment to control for bias. We describe accuracy in clinical practice for 360 experts who examined >1 million women's mammograms for signs of cancer, whilst controlling for potential biases. The vigilance decrement pattern was not observed. Instead, test accuracy improved over time, through a reduction in false alarms and an increase in speed, with no significant change in sensitivity. The multiple-decision model explains why experts miss targets in low prevalence settings through a change in decision threshold and search quit threshold and propose it should be adapted to explain these observed patterns of accuracy with time on task. What is typically thought of as standard and robust research findings in controlled laboratory settings may not directly apply to real-world environments and instead large, controlled studies in relevant environments are needed.

The frequency and level dependence of across-frequency binaural interference for interaural time differences

Binaural hearing enables listeners to localize sound in the horizontal plane, even when dealing with intricate speech-like signals characterized by distributed energy across a broad range of frequencies and varying sound pressure levels. Low-frequency interaural time differences (ITDs) are the most important cue for human horizontal-plane sound localization. Across-frequency binaural interference tasks (where changes in ITD discrimination thresholds of a target signal are measured in the presence of a remote interferer signal) can be used to measure how a listener weighs different frequency regions for ITD. While it is known that low-frequency (0.5 kHz) targets experience less binaural interference from higher-frequency (4 kHz) interferers than vice versa, the impact of the relative level of the two signals has remained mostly unexplored. ITD discrimination thresholds were measured in normal-hearing listeners with target/interferer intensities of 35, 55, and 75 dB-A and frequencies of 0.5, 4, and 8 kHz. Besides the expected frequency effects, data to date show binaural interference increases with increasing interferer level. These results help better understand how sound level variation and more realistic complex sounds like speech are localized.

Age-related changes in gap detection thresholds in adult cochlear-implant users: Effects of stimulus level and electrode-to-neural interface

Aging is associated with reduced sensitivity to brief temporal gaps in auditory stimuli. Although gap detection is a relative strength among late-deafened cochlear-implant users, aging and electrode-to-neural interface (ENI) factors may contribute to temporal processing difficulties. Because aging may negatively impact perception particularly at very low and very high input levels, we hypothesized larger gap detection thresholds (GDTs) at poor-ENI electrodes and an interaction between age and level such that GDT improvement with increased level would be less evident in older listeners. GDTs were measured on three electrodes selected to span a range of good-to-poor ENI based on electrically-evoked compound action potential amplitude growth or threshold sensitivity to increased pulse rate. GDTs were assessed using constant-amplitude single-electrode 1000-pps pulse trains presented at 40/60/80/100% dynamic range. In preliminary data (N = 4), GDTs averaged 3 ms at 100%DR and 40 ms at 40%DR. Listeners with better average ENI metrics displayed better GDTs. Within-subject, an advantage for best-ENI electrode over poorer-ENI electrodes was evident only at low levels. Finding an interaction between age and level such that temporal processing is impaired at both low and high (but not mid) levels for older listeners may help elucidate the contributions of peripheral versus central factors.

Application of near infra-red laser light increases current threshold in optic nerve consistent with increased Na+-dependent transport

Increases in the current threshold occur in optic nerve axons with the application of infra-red laser light, whose mechanism is only partly understood. In isolated rat optic nerve, laser light was applied near the site of electrical stimulation, via a flexible fibre optic. Paired applications of light produced increases in threshold that were reduced on the second application, the response recovering with increasing delays, with a time constant of 24 s. 3-min duration single applications of laser light gave rise to a rapid increase in threshold followed by a fade, whose time-constant was between 40 and 50 s. After-effects were sometimes apparent following the light application, where the resting threshold was reduced. The increase in threshold was partially blocked by 38.6 mM Li+ in combination with 5 μ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mu$$\\end{document}M bumetanide, a manoeuvre increasing refractoriness and consistent with axonal depolarization. Assessing the effect of laser light on the nerve input resistance ruled out a previously suggested fall in myelin resistance as contributing to threshold changes. These data appear consistent with an axonal membrane potential that partly relies on temperature-dependent electroneutral Na+ influx, and where fade in the response to the laser may be caused by a gradually diminishing Na+ pump–induced hyperpolarization, in response to falling intracellular [Na+].

Laser induced damage threshold of GaSe with antireflection microstructures at a wavelength of 5 µm.

Large GaSe crystals were grown and various antireflection microstructures (ARMs) were fabricated on their cleaved surfaces using optimized femtosecond laser ablation, which provided the antireflection effect in a wide wavelength range of 4-16µm. The influence of ARMs created on the GaSe surface on the change of the laser-induced damage threshold (LIDT) of the crystal at a wavelength of 5 μm was evaluated. The 5-µm Fe:ZnMgSe laser with the pulse duration of 135 ns was used for the LIDT test in conditions close to single pulse exposure. The measured values of LIDT of 56 ± 6MW/cm2 and 51 ± 9 MW/cm2 for two GaSe substrates, respectively, were comparable with the known data of single pulse LIDT of GaSe. The average LIDT intensities of 54 ± 6MW/cm2 and 52 ± 7 MW/cm2 for the ARMs at two GaSe plates, respectively, were close to LIDT intensities for the corresponding GaSe substrates. The ARMs with lower structural quality had lower LIDT (50-52 MW/cm2) in comparison with the high-quality ARMs (58-60 MW/cm2). High LIDT for high-quality ARMs can be caused by increased selenium content in the ARMs. In any case, all the tested ARMs on the GaSe plates with different surface quality are workable for development of widely tunable mid-infrared nonlinear optical converters.

Mechanisms of cone sensitivity loss in retinitis pigmentosa.

To explore the mechanisms of cone sensitivity loss in retinitis pigmentosa by combining two-colour perimetry with threshold versus intensity (tvi) testing. Seven subjects with autosomal recessive retinitis pigmentosa and 10 normal subjects were recruited and underwent perimetric testing of one eye using 480- and 640-nm Goldman size V targets presented under scotopic conditions (no background illumination) and against a white background ranging in luminance from -1.5 to 2 log cd m-2 in 0.5 log cd m-2 steps. Data were fitted with tvi functions of the form logT = logT0 + log ((A + A0)/A0)n, where T is the threshold, T0 is the absolute threshold, A is the background intensity, A0 is the 'dark-light' constant and n is a gain constant. Reliable tvi functions could not be obtained within the region of the visual field corresponding to loss of the ellipsoid zone on optical coherence tomography. At fixation, changes in both T0 and A0 were observed, consistent with a d1 mechanism loss, which resulted in an upwards and rightwards shift of the tvi function. Losses at [±3°, ±3°] demonstrated changes in T0, consistent with a d3 mechanism loss, resulting in an upwards translation of the tvi curve. Although the absolute cone threshold was elevated at each location, shifts in the tvi function (so-called d1 mechanism loss) at fixation minimise threshold elevation in the presence of white adapting backgrounds, such as those typically employed in standard two-colour perimetry. At more peripheral testing locations, changes in threshold occurred independent of background luminance (so-called d3 mechanism loss). These findings suggest that backgrounds which selectively adapt rods while maintaining cones at, or near, absolute threshold may be preferable to conventional two-colour perimetry for assessing loss of cone sensitivity, especially at the point of fixation.