Wave Threshold Research Articles

High performance continuous wave 1.3 μm quantum dot lasers on silicon

We demonstrate record performance 1.3 μm InAs quantum dot lasers grown on silicon by molecular beam epitaxy. Ridge waveguide lasers fabricated from the as-grown material achieve room temperature continuous wave thresholds as low as 16 mA, output powers exceeding 176 mW, and lasing up to 119 °C. P-modulation doping of the active region improves T0 to the range of 100–200 K while maintaining low thresholds and high output powers. Device yield is presented showing repeatable performance across different dies and wafers.

Serca Stimulation Increases Intra-Sr Ca2+Threshold for Ca2+ Waves in Cadiomyocytes

In cardiac muscle, stimulation of β-adrenergic receptors leads to activation of PKA via the second messenger cAMP. PKA-dependent phosphorylation of several targets subsequently amplifies the L-type Ca2+ current, relieves the SERCA inhibition by PLB and is proposed to increase the Ca2+ sensitivity of the RyRs (by phosphorylation at serine 2808). Together, these mechanisms account for positive inotropy, but can also be arrhythmogenic via facilitation of spontaneous Ca2+ waves. Unexpectedly, the level of Ca2+ inside the SR ([Ca2+]SR) needed to initiate such waves has been reported to increase upon β-adrenergic stimulation, an observation which cannot be easily reconciled with elevated Ca2+ sensitivity of the RyRs. We tested the hypothesis that this change of Ca2+ wave threshold could occur indirectly, subsequent to SERCA disinhibition. Cytosolic and intra-SR Ca2+ waves were simultaneously recorded with confocal line-scans in permeabilized mouse cardiomyocytes with rhod-2 and fluo-5-N, respectively. We analyzed changes of SR Ca2+ content and several Ca2+ wave parameters. Ochratoxin A (OTA) was used to specifically stimulate the SERCA and the findings were compared to those in the presence of cAMP, which besides SERCA stimulation also leads to RyR phosphorylation. While cAMP resulted in a modest increase of Ca2+ wave thresholds (F/F0 9%±3.5%), OTA lead to a substantial increase (30±5.1%). Both compounds resulted in an acceleration of SR refilling (OTA earlier than cAMP), confirming SERCA stimulation. While cAMP provoked in the occurrence of Ca2+ sparks and mini waves, possibly accounting for the less pronounced SR loading, this was not observed in OTA. Together these results suggest that SERCA stimulation alone can elevate the intra-SR threshold for the generation of Ca2+ waves, independently of RyR phosphorylation. Supported by SNF.

Continuous Wave Threshold Characteristics of Coupled-Cavity VCSELs: Experiment and Model

We carry out a detailed characterization of continuous wave threshold behavior of coupled-cavity vertical-cavity surface-emitting lasers with various radii of the ion-implantation and oxide apertures. We obtain modal threshold current maps and wavelength at threshold and identify three groups of lasers with qualitatively different behavior, i.e. 1) lasing only on the short, 2) on both short and long and 3) only on the long wavelength fundamental mode. All lasers show profound impact of the current induced self-heating. In order to elucidate this impact, we improve the existing rate equation model by considering nonuniform longitudinal temperature distribution and adding the gain and refractive index temperature dependencies. We are able to reproduce the experimentally observed switchings between different longitudinal modes, as well as all the three different types of modal behavior.

The Characteristic of Heat Wave Effects on Coronary Heart Disease Mortality in Beijing, China: A Time Series Study

BackgroundThere is limited evidence for the impacts of heat waves on coronary heart disease (CHD) mortality in Beijing, capital city of China.ObjectivesWe aimed to find a best heat wave definition for CHD mortality; and explore the characteristic of heat wave effects on CHD in Beijing, China.MethodsWe obtained daily data on weather and CHD mortality in Beijing for years 2000–2011. A quasi-Poisson regression model was used to assess the short-term impact of heat waves on CHD mortality in hot season (May–September), while controlling for relative humidity, day of the week, long-term trend and season. We compared 18 heat wave definitions by combining heat wave thresholds (87.5th, 90.0th, 92.5th, 95th, 97.5th, and 99th percentile of daily mean temperature) with different duration days (≥ 2 to ≥ 4 days), using Akaike information criterion for quasi-Poisson. We examined whether heat wave effects on CHD mortality were modified by heat wave duration and timing.ResultsHeat wave definition using 97.5th percentile of daily mean temperature (30.5 °C) and duration ≥ 2 days produced the best model fit. Based on this heat wave definition, we found that men and elderly were sensitive to the first heat waves of the season, while women and young were sensitive to the second heat waves. In general, the longer duration of heat waves increased the risks of CHD mortality more than shorter duration for elderly. The first two days of heat waves had the highest impact on CHD mortality. Women and elderly were at higher risks than men and young when exposed to heat waves, but the effect differences were not statistically significant.ConclusionsHeat waves had significant impact on CHD mortality. This finding may have implications for policy making towards protecting human health from heat waves.

Increased anesthesia time using 2,2,2-tribromoethanol–chloral hydrate with low impact on mouse psychoacoustics

BackgroundTo examine psychoacoustics in mice, we have used 2,2,2-tribromoethanol anesthesia in multiple studies. We find this drug is fast-acting and yields consistent results, providing 25–30min of anesthesia. Our recent studies in binaural hearing prompted development of a regimen to anesthesia time to 1h. We tested a novel cocktail using 2,2,2-tribromoethanol coupled with low dose chloral hydrate to extend the effective anesthesia time. New methodWe have established an intraperitoneal dosing regimen for 2,2,2-tribromoethanol–chloral hydrate anesthesia. To measure efficacy of the drug cocktail, we measured auditory brainstem responses (ABRs) at 10min intervals to determine the effects on hearing thresholds and wave amplitudes and latencies. ResultsThis novel drug combination increases effective anesthesia to 1h. ABR Wave I amplitudes, but not latencies, are marginally suppressed. Additionally, amplitudes of the centrally derived Waves III and V show significant inter-animal variability that is independent of stimulus intensity. These data argue against the systematic suppression of ABRs by the drug cocktail. Comparison with existing methodsUsing 2,2,2-tribromoethanol–chloral hydrate combination in psychoacoustic studies has several advantages over other drug cocktails, the most important being preservation of latencies from centrally- and peripherally-derived ABR waves. In addition, hearing thresholds are unchanged and wave amplitudes are not systematically suppressed, although they exhibit greater variability. ConclusionsWe demonstrate that 375mg/kg 2,2,2-tribromoethanol followed after 5min by 200mg/kg chloral hydrate provides an anesthesia time of 60min, has negligible effects on ABR wave latencies and thresholds and non-systematic effects on amplitudes.

β-adrenergic stimulation increases the intra-SR Ca termination threshold for spontaneous Ca waves in cardiac myocytes

β-adrenergic stimulation of cardiac myocytes enhances intracellular calcium cycling, which frequently associates with pro-arrhythmic Ca waves. The threshold level of free calcium in the sarcoplasmic reticulum ([Ca]SR) where waves initiate is increased during β-adrenergic stimulation.1 Here, we measured [Ca]SR directly to monitor the [Ca]SR level at which spontaneous Ca waves terminated (termination threshold) during β-adrenergic stimulation. Compared with control conditions, application of the β-adrenergic receptor agonist isoproterenol (ISO; 1 μM) resulted in an increase in basal [Ca]SR and an increase in the [Ca]SR at which spontaneous Ca waves terminated. When [Ca]SR was experimentally matched, ISO stimulation resulted in a decrease in the depletion amplitude of the waves. Sensitization of ryanodine receptor SR Ca release channels to Ca with a low dose of caffeine in the presence of ISO was able to decrease the termination threshold compared with control conditions. Therefore, the Ca wave termination level may represent an important mode of altering Ca depletion from the SR and reducing the arrhythmogenic potential during β-adrenergic stimulation.

Numerical simulation of thermal and reaction waves for in situ combustion in hydrocarbon reservoirs

New in situ combustion (ISC) method variants hold much promise in the way of ultimate oil recovery and recovery rates. The interactions of thermal and reaction waves for ISC recovery of heavy oils are here investigated numerically. A set of dimensionless screening parameters is developed in order to investigate important ISC phenomena, i.e. ignition delay time, flame thickness and propagation, ultimate recovery, and recovery efficiency. Defining a heavy oil Damköhler number (DaO) allows the identification of three performance regions of ignition delay: thermal diffusion limited, chemistry limited, and oxygen supply limited. There exists also a coke Damköhler number (DaC) threshold for the combustion wave to propagate or else extinguish. The ISC process efficiency and recovery rate are observed to be functions mainly of the DaC number and less so of the DaO number.

Coronary Wave Energy

Revascularization after acute coronary syndromes provides prognostic benefit, provided that the subtended myocardium is viable. The microcirculation and contractility of the subtended myocardium affect propagation of coronary flow, which can be characterized by wave intensity analysis. The study objective was to determine in acute coronary syndromes whether early wave intensity analysis-derived microcirculatory (backward) expansion wave energy predicts late viability, defined by functional recovery. Thirty-one patients (58±11 years) were enrolled after non-ST elevation myocardial infarction. Regional left ventricular function and late-gadolinium enhancement were assessed by cardiac magnetic resonance imaging, before and 3 months after revascularization. The backward-traveling (microcirculatory) expansion wave was derived from wave intensity analysis of phasic coronary pressure and velocity in the infarct-related artery, whereas mean values were used to calculate hyperemic microvascular resistance. Twelve-hour troponin T, left ventricular ejection fraction, and percentage late-gadolinium enhancement mass were 1.35±1.21 µg/L, 56±11%, and 8.4±6.0%, respectively. The infarct-related artery backward-traveling (microcirculatory) expansion wave was inversely correlated with late-gadolinium enhancement infarct mass (r=-0.81; P<0.0001) and strongly predicted regional left ventricular recovery (r=0.68; P=0.001). By receiver operating characteristic analysis, a backward-traveling (microcirculatory) expansion wave threshold of 2.8 W m(-2) s(-2)×10(5) predicted functional recovery with sensitivity and specificity of 0.91 and 0.82 (AUC 0.88). Hyperemic microvascular resistance correlated with late-gadolinium enhancement mass (r=0.48; P=0.03) but not left ventricular recovery (r=-0.34; P=0.07). The microcirculation-derived backward expansion wave is a new index that correlates with the magnitude and location of infarction, which may allow for the prediction of functional myocardial recovery. Coronary wave intensity analysis may facilitate myocardial viability assessment during cardiac catheterization.

Investigating the Effects of a Cardiotoxic Drug on Calcium Homeostasis in the Heart

Contractile dysfunction and arrhythmogenic activity can arise if there are perturbations to calcium (Ca) homeostasis in the heart, such as in response to cardiotoxic substances. This investigation focuses on changes in cellular Ca homeostasis in response to the acute application of the cardiotoxic drug Clozapine (an atypical anti-psychotic).Rat ventricular myocytes were isolated and stimulated under voltage clamp control. Various parameters of Ca handling were measured both in control conditions and in the presence of 10 μM clozapine. Ca-sensitive indicators fluo3-AM or fura-2 were used to quantify cytosolic Ca. Sarcoplasmic reticulum (SR) Ca content was measured by applying 10 mM caffeine. Activity of Ca extrusion mechanisms (SERCA - sarco-endoplasmic reticulum ATP-ase, NCX - sodium-calcium exchanger) were calculated from Ca transient decay rates. The current-voltage (I-V) relationship of the L-type Ca channel was also measured.Acute application of clozapine significantly reduced mean Ca transient amplitude by 48% and L-type Ca current (ICaL) density by 50%. SR content was decreased by 18 % and SERCA activity (rate constant) was reduced by 34 %. NCX rate constant was reduced by 17%. The effect of clozapine on SERCA was also present in phospholamban knockout myocytes suggesting that the effect on SERCA is not dependent on phospholamban.It remains unclear if or how the observed effects on Ca handling contribute to the cardiotoxicity of clozapine observed in the clinical setting (arrhythmogenesis and myocarditis). We speculate that effects on ICaL may predispose to refractory heterogeneity and reduced SERCA activity may increase the chance for Ca wave propagation. Current work focuses on effects of clozapine on calcium spark activity and SR threshold for Ca waves.

Scalar Mesons, $\pi \pi $ $D$-wave Photo-production and Threshold Parameters --- All from the Roy-like Dispersion Relations

Scalar Mesons, $\pi \pi $ $D$-wave Photo-production and Threshold Parameters --- All from the Roy-like Dispersion Relations

β‐Adrenergic stimulation increases the intra‐sarcoplasmic reticulum Ca2+ threshold for Ca2+ wave generation

β-Adrenergic signalling induces positive inotropic effects on the heart that associate with pro-arrhythmic spontaneous Ca(2+) waves. A threshold level of sarcoplasmic reticulum (SR) Ca(2+) ([Ca(2+)](SR)) is necessary to trigger Ca(2+) waves, and whether the increased incidence of Ca(2+) waves during β-adrenergic stimulation is due to an alteration in this threshold remains controversial. Using the low-affinity Ca(2+) indicator fluo-5N entrapped within the SR of rabbit ventricular myocytes, we addressed this controversy by directly monitoring [Ca(2+)](SR) and Ca(2+) waves during β-adrenergic stimulation. Electrical pacing in elevated extracellular Ca(2+) ([Ca(2+)](o) = 7 mM) was used to increase [Ca(2+)](SR) to the threshold where Ca(2+) waves were consistently observed. The β-adrenergic agonist isoproterenol (ISO; 1 μM) increased [Ca(2+)](SR) well above the control threshold and consistently triggered Ca(2+) waves. However, when [Ca(2+)](SR) was subsequently lowered in the presence of ISO (by lowering [Ca(2+)](o) to 1 mM and partially inhibiting sarcoplasmic/endoplasmic reticulum calcium ATPase with cyclopiazonic acid or thapsigargin), Ca(2+) waves ceased to occur at a [Ca(2+)](SR) that was higher than the control threshold. Furthermore, for a set [Ca(2+)](SR) level the refractoriness of wave occurrence (Ca(2+) wave latency) was prolonged during β-adrenergic stimulation, and was highly dependent on the extent that [Ca](SR) exceeded the wave threshold. These data show that acute β-adrenergic stimulation increases the [Ca(2+)](SR) threshold for Ca(2+) waves, and therefore the primary cause of Ca(2+) waves is the robust increase in [Ca(2+)](SR) above this higher threshold level. Elevation of the [Ca(2+)](SR) wave threshold and prolongation of wave latency represent potentially protective mechanisms against pro-arrhythmogenic Ca(2+) release during β-adrenergic stimulation.

Torque and temperature dependence of the hysteretic voltage-induced torsional strain in tantalum trisulfide

We have measured the dependence of the hysteretic voltage-induced torsional strain (VITS) in crystals of orthorhombic tantalum trisulfide on temperature and applied torque. In particular, applying square-wave voltages above the charge density wave (CDW) threshold, so as to abruptly switch the strain across its hysteresis loop, we have found that the time constant for the VITS to switch (at different temperatures and voltages) varied as the CDW current. Application of torque to the crystal could also change the VITS time constant, magnitude, and sign, suggesting that, at least in part, the VITS is a consequence of residual torsional strain in the sample which twists the CDW. Application of voltage changes the pitch of these CDW twists, which then act back on the lattice. However, it remains difficult to understand the sluggishness of the response.

On wave–particle interaction in axisymmetric toroidal systems

A general formalism is developed to describe the interaction of charged particles with electromagnetic waves in terms of coupled finite difference mapping equations that incorporate tokamak topology. The approach is based on considering non-adiabatic changes in the constants of particle motion and it covers a range of wave–particle resonance frequencies, from the precessional to cyclotron frequencies of both passing and trapped ions. The concept of overlapping resonances is used to estimate the threshold for a single plane wave to cause stochastic particle motion. In the stochastic regime, the process is Markovian, and particle diffusion in three-dimensional phase space takes place. Estimations of diffusion coefficients are carried out in the two cases of waves interacting with passing and trapped ions by means of the cyclotron and bounce resonances, respectively, and previously known results are recovered in the proper limits.

Beta-Adrenergic Stimulation Increases the Intra-Sarcoplasmic Reticulum Ca Threshold for Spontaneous Ca Waves

Beta-adrenergic signaling induces positive inotropic effects on the heart that frequently associate with spontaneous arrhythmogenic Ca release events including Ca waves. It remains unclear if the greater incidence of Ca waves is due to increased sarcoplasmic reticulum (SR) Ca content ([Ca]SR) or a change in the function of ryanodine receptors. To address this controversy we utilized dynamic [Ca]SR measurements (fluo-5N) to test if beta-adrenergic stimulation alters the [Ca]SR level where Ca waves initiate (wave threshold) during rest after action potential stimulation. Under control conditions [Ca]SR was progressively increased to the wave threshold via incremental increases in pacing frequency in a high extracellular Ca (7 mM) environment. In the presence of the beta-adrenergic agonist isoproterenol (ISO, 1 microM) [Ca]SR increased and Ca waves were observed. When [Ca]SR was subsequently lowered using low extracellular Ca (1 mM) and SERCA inhibition (3 microM cyclopiazonic acid), Ca waves were no longer observed, even at [Ca]SR levels above the control wave threshold. In parallel experiments we found that resting cytosolic [Ca] (indo-1) was similar between the respective experimental conditions. Indirect assessment of [Ca]SR using the amplitude of the cytosolic Ca transient induced by 10 mM caffeine confirmed our observation that in the presence of ISO Ca waves only occur when [Ca]SR is above the control wave threshold. Furthermore, spontaneous Ca spark measurements (fluo-4) showed a tendency towards spark inhibition in the presence of ISO at experimentally matched [Ca]SR. Together, these data show that acute beta-adrenergic stimulation increases the [Ca]SR threshold for Ca waves, and therefore the primary cause of Ca waves is the robust increase in [Ca]SR above this higher threshold level. Elevation of the [Ca]SR wave threshold may be interpreted as a protective mechanism against pro-arrhythmogenic Ca release during beta-adrenergic stimulation.

Dantrolene Restores Altered RyR2-Mediated Ca Signaling in Heart Failure

In heart failure (HF) arrhythmogenic Ca release and chronic [Ca]SR depletion arise due to altered function of ryanodine receptors. Dantrolene, a therapeautic agent used to treat malignant hyperthermia associated with mutations of the type 1 ryanodine receptor (RyR1), is purported to be without effects on the cardiac type 2 ryanodine receptor (RyR2). However, recent investigations suggest that dantrolene may correct abnormal RyR2-mediated calcium release associated with HF. In this investigation, we tested if dantrolene exerts anti-arrhythmic effects on heart failure ventricular myocytes by examining the intra-SR Ca threshold for arrhythmogenic Ca waves. Using the low-affinity calcium indicator fluo-5N entrapped in the SR, direct measurement of [Ca]SR showed that in normal rabbit myocytes dantrolene (1 microM) had no effect on SR Ca content, the amplitude of action potential induced intra-SR Ca depletions, or on the threshold for spontaneous Ca wave initiation (i.e., the SR Ca content at which spontaneous waves initiate). Furthermore, in field stimulated (0.5 Hz and 1.0 Hz) normal cardiomyocytes loaded with indo-1, dantrolene treatment had no effect on Ca transient amplitude, SR Ca load, or post-rest decay of SR Ca content. In cardiomyocytes from failing rabbit hearts, SR Ca content and the wave initiation threshold were decreased compared to normal myocytes. Interestingly, treatment of HF cardiomyocytes with dantrolene restored the SR Ca content and increased the wave initiation threshold. Together, these data suggest that dantrolene may exert anti-arrhythmic effects in heart failure cardiomyocytes by increasing the intra-SR Ca threshold at which spontaneous Ca waves occur.

In the RyR2 R4496C Mouse Model of CPVT, β-Adrenergic Stimulation Induces Ca Waves by Increasing SR Ca Content and Not by Decreasing the Threshold for Ca Waves

mutations of the ryanodine receptor (RyR) cause catecholaminergic polymorphic ventricular tachycardia (CPVT). These mutations predispose to the generation of Ca waves and delayed afterdepolarizations during adrenergic stimulation. Ca waves occur when either sarcoplasmic reticulum (SR) Ca content is elevated above a threshold or the threshold is decreased. Which of these occurs in cardiac myocytes expressing CPVT mutations is unknown. we tested whether the threshold SR Ca content is different between control and CPVT and how it relates to SR Ca content during β-adrenergic stimulation. ventricular myocytes from the RyR2 R4496C(+/-) mouse model of CPVT and wild-type (WT) controls were voltage-clamped; diastolic SR Ca content was measured and compared with the Ca wave threshold. The results showed the following. (1) In 1 mmol/L [Ca(2+)](o), β-adrenergic stimulation with isoproterenol (1μmol/L) caused Ca waves only in R4496C. (2) SR Ca content and Ca wave threshold in R4496C were lower than those in WT. (3) β-Adrenergic stimulation increased SR Ca content by a similar amount in both R4496C and WT. (4) β-Adrenergic stimulation increased the threshold for Ca waves. (5) During β-adrenergic stimulation in R4496C, but not WT, the increase of SR Ca was sufficient to reach threshold and produce Ca waves. in the R4496C CPVT model, the RyR is leaky, and this lowers both SR Ca content and the threshold for waves. β-Adrenergic stimulation produces Ca waves by increasing SR Ca content and not by lowering threshold.

High order harmonic balance formulation of free and encapsulated microbubbles

The radial responses of free and encapsulated microbubbles excited by an ultrasonic plane wave with a large wavelength in comparison with the bubble size are governed by NonLinear Ordinary Differential Equations (NL-ODEs). The nonlinear frequency response gives the harmonic content of the time response and constitutes the expected outcome of a high order harmonic analysis. In this paper, high order harmonic balance analysis of modified “RPNNP” (bubble), Hoff and Marmottant (contrast agents) models is performed with an open-source software program. For this purpose, the original NL-ODEs are recast into nonlinear systems in which the nonlinearities are at most quadratic. In the spectral domain, this recast provides close form and aliasing-free solutions of arbitrarily large numbers of harmonics. Relevant quantities such as primary and secondary resonances and the nonlinear amplitude threshold of the excitation wave are evaluated. The frequency curves drawn up characterize the bending and quantify the jump frequencies and amplitudes of each harmonic component. The results obtained with this predictive method confirm that it should provide a useful tool for nonlinear bubble detection and sizing and for contrast agent designing.

Multiple channels for horizontal, but only one for vertical corrugations? A new look at the stereo anisotropy

Stereo vision displays a well-known anisotropy: disparity-defined slant is easier to detect for rotations about a horizontal axis than about a vertical axis, and low-frequency sinusoidal depth corrugations are easier to detect when the corrugations are horizontal than when they are vertical. Here, we determined disparity thresholds for vertically and horizontally oriented depth corrugations with both sinusoidal and square-wave profiles. We found that the orientation anisotropy for square waves is much weaker than for sine waves and is almost independent of frequency. This weaker anisotropy for square waves can be explained by considering the Fourier harmonics present in the stimulus. Using linear models imported from the luminance and texture perception domain, the disparity thresholds for square waves can be very well predicted from those for sine waves, for both horizontally and vertically oriented corrugations. For horizontally oriented corrugations, models based on the root mean square of the output of a single linear channel or the output of multiple linear channels worked equally well. This is consistent with previous evidence suggesting that stereo vision has multiple channels tuned to different spatial frequencies of horizontally oriented disparity modulations. However, for vertically oriented corrugations, only the root mean squared output of a single linear channel explained the data. We suggest that the stereo anisotropy may arise because the stereo system possesses multiple spatial frequency channels for detecting horizontally oriented modulations in horizontal disparity, but only one for vertically oriented modulations.

Thresholds for morphological changes on an exposed sandy beach as a function of wave height

AbstractA sandy beach in the south of Portugal (Faro beach, Ria Formosa) was surveyed from the dune crest seaward to 15 m depth 20 times over a period of 26 months. Wave time‐series between surveys were analysed to obtain relationships between wave height and vertical profile variations and to define wave thresholds for important morphological changes. Results show that the active zone of the profile lies between 5 m above and 10·4 m below mean sea level, and that there are clear cross‐shore differences in the vertical variability of the profile. Based on the pattern of vertical variability, the profile was divided into four cross‐shore sectors: A (berm), 20–80 m from the profile origin; B (sub‐tidal terrace), 80–170 m; C (long‐shore bar), 170–360 m; and D, 360–700 m. The relationship between the modulus of the maximum vertical change in each sector and the 99th percentile of significant wave height between surveys was always significant. Calculated thresholds for significant wave height generating important morphological changes were 2·3 m in sector A, 3·2 m in sectors B and C, and 4·1 m in sector D. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Electron affinity of indium and the fine structure of In−measured using infrared photodetachment threshold spectroscopy

Binding energies of the fine-structure levels of the indium negative ion In${}^{\ensuremath{-}}$ are measured using infrared photodetachment threshold spectroscopy. The relative cross section for neutral atom production is measured with a crossed ion-beam--laser-beam apparatus over selected photon energy ranges between 300 and 700 meV. An $s$-wave threshold is observed due to the opening of the In${}^{\ensuremath{-}}$ ($5{p}^{2}$${}^{3}{P}_{0}$) to In($5p$${}^{2}{P}_{1/2}$) ground-state-to-ground-state transition, which determines the electron affinity of In to be 383.92(6) meV. The present result is in good agreement with previous theoretical calculations, but it differs substantially from the previously measured electron affinity and reduces the uncertainty by a factor of 150. $s$-wave thresholds are also observed for detachment from the excited fine-structure levels of In${}^{\ensuremath{-}}$, permitting accurate determination of the fine-structure intervals of 76.06(7) meV for $J=0--1$ and 170.6(6) meV for $J=0--2$, which are in good agreement with the previous measurements and substantially reduce the uncertainties.