Search results for " Threshold"
showing 10 items of 497 documents
Small-sample characterization of stochastic approximation staircases in forced-choice adaptive threshold estimation
2007
Despite the widespread use of up—down staircases in adaptive threshold estimation, their efficiency and usability in forced-choice experiments has been recently debated. In this study, simulation techniques were used to determine the small-sample convergence properties of stochastic approximation (SA) staircases as a function of several experimental parameters. We found that satisfying some general requirements (use of the accelerated SA algorithm, clear suprathreshold initial stimulus intensity, large initial step size) the convergence was accurate independently of the spread of the underlying psychometric function. SA staircases were also reliable for targeting percent-correct levels far …
Continuous-wave mirrorless lasing at 221 μm in sodium vapors
2018
We demonstrate backward-directed continuous-wave (cw) emission at 2.21 {\mu}m generated on the 4P3/2-4S1/2 population-inverted transition in Na vapors two-photon excited with resonant laser light at 589 and 569 nm. Our study of power and atom-number-density threshold characteristics shows that lasing occurs at sub-10 mW total power of the applied laser light. The observed 6 mrad divergence is defined mainly by the aspect ratio of the gain region. We find that mirrorless lasing at 2.21 {\mu}m is magnetic field and polarization dependent that may be useful for remote magnetometry. The presented results could help determine the requirements for obtaining directional return from sodium atoms in…
Growth, percolation, and correlations in disordered fiber networks
1997
This paper studies growth, percolation, and correlations in disordered fiber networks. We start by introducing a 2D continuum deposition model with effective fiber-fiber interactions represented by a parameter $p$ which controls the degree of clustering. For $p=1$, the deposited network is uniformly random, while for $p=0$ only a single connected cluster can grow. For $p=0$, we first derive the growth law for the average size of the cluster as well as a formula for its mass density profile. For $p>0$, we carry out extensive simulations on fibers, and also needles and disks to study the dependence of the percolation threshold on $p$. We also derive a mean-field theory for the threshold ne…
Lasing characteristics of a new DCM derivative under flashlamp pumping
1991
Abstract A new DCM derivative (4-dicyanomethylene-2-methyl-6-p-diethanolamino-styryl 4H-pyran or DCM-OH), was tested under flashlamp pumping. This dye lased in the 600–700 nm range with efficiency up to 0.4% at maximum. Lasing performances of DCM-OH in methanol and water-methanol mixture are reported and compared to normal DCM.
Separate processing of “color” and “brightness” in goldfish
1991
Spectral sensitivity was measured under different adaptation levels using a behavioral training technique in which the fish had to discriminate between a dark test field and a test field illuminated with monochromatic light. Depending on which of the two test fields was used as training test field, two functions were obtained which differ (1) in absolute sensitivity and (2) in shape. When trained on the dark test field, the fish seems to discriminate on the basis of a "color" cue, but it uses a "brightness" cue when trained on the illuminated test field. This was concluded from measurements of wavelength discrimination. Under low levels of the adaptation light (1.5 and 0.2 lx instead of 20 …
Random Lasing of Rhodamine 6G Solution Containing TiO2:Silica Core:Shell Nanoparticles
2012
High efficiency and low rate of photodegradation was obtained in a random laser suspending TiO2@Silica nanoparticles in ethanol solution of Rhodamine 6G. The TiO2 nanoparticles were coated with a silica shell prepared via Stober method.
Umbrales de lluvia, daños y niveles de alerta en la Comunidad Valenciana
2016
Ponencia presentada en: X Congreso de la Asociación Española de Climatología celebrado en Alicante entre el 5 y el 8 de octubre de 2016. [ES]En el contexto de los riesgos climáticos, muchas de las alarmas tempranas de precipitaciones extremas se basan en umbrales de lluvia que, a su vez, están relacionados con niveles probables de daños. A pesar de los grandes esfuerzos que se han venido realizando en los últimos años para discriminar bien los umbrales de estas alertas, uno de los principales problemas es la emisión de un número excesivo de avisos, hecho que puede crear alarmismo. El presente trabajo constituye un estudio aplicado que aborda la detección de indicadores de lluvia y la estima…
Effect of diode laser irradiation on root surfaces in vitro.
2002
The objective of this study was to evaluate possible morphological alterations of root surfaces after GaAlAs-diode laser (809 nm) irradiation under standardized in vitro conditions.Root specimens obtained from extracted periodontally diseased teeth were scaled and root planed with curettes followed by air-powder abrasive treatment prior to lasing. The variable parameters were power output (0.5-2.5 W) and exposure time (10-30 sec per specimen). Additionally, the effect of a saline solution and a human blood film on the root surface was investigated. The root segments were analyzed by means of a reflected light microscope. Photographs before and after irradiation were taken and evaluated. The…
Increased serum miR-193a-5p during non-alcoholic fatty liver disease progression: Diagnostic and mechanistic relevance
2022
Background & Aims Serum microRNA (miRNA) levels are known to change in non-alcoholic fatty liver disease (NAFLD) and may serve as useful biomarkers. This study aimed to profile miRNAs comprehensively at all NAFLD stages. Methods We profiled 2,083 serum miRNAs in a discovery cohort (183 cases with NAFLD representing the complete NAFLD spectrum and 10 population controls). miRNA libraries generated by HTG EdgeSeq were sequenced by Illumina NextSeq. Selected serum miRNAs were profiled in 372 additional cases with NAFLD and 15 population controls by quantitative reverse transcriptase PCR. Results Levels of 275 miRNAs differed between cases and population controls. Fewer differences were seen wi…
Effects of Neuromuscular Electrical Stimulation (NMES) on salivary flow in healthy adults
2020
Background Neuromuscular electrical stimulation (NMES) is a method used for enhancing suprahyoid muscle activity and is widely applied as a treatment for dysphagia. Patients often complain of saliva pooling in the pharynx during NMES. Therefore, the purpose of this study was to investigate the changes in salivary flow during NMES. Material and methods Twenty healthy adults participated in this study. Electrical stimulation was applied at constant strength for 60 minutes to the suprahyoid muscles using VitalStim®. Participants were examined under three conditions of NMES: sensory threshold plus 75% of the difference between sensory and pain thresholds (75% Stim), SensoryStim, and Sham. Saliv…