Sonar gain control and echo detection thresholds in the echolocating bat, Eptesicus fuscus

1992 ◽  
Vol 91 (2) ◽  
pp. 1150-1163 ◽  
Author(s):  
James A. Simmons ◽  
Anne J. M. Moffat ◽  
W. Mitch Masters
Keyword(s):  
Gain Control ◽  
Eptesicus Fuscus ◽  
Detection Thresholds ◽  
Echo Detection

Echo detection and target-ranging neurons in the auditory system of the bat Eptesicus fuscus

Science ◽  
1978 ◽  
Vol 202 (4368) ◽  
pp. 645-648 ◽  
Author(s):  
A. Feng ◽  
J. Simmons ◽  
S. Kick
Keyword(s):  
Auditory System ◽  
Eptesicus Fuscus ◽  
Echo Detection ◽  
Target Ranging

scholarly journals Detection and discrimination of flicker contrast in migraine

Cephalalgia ◽  
2011 ◽  
Vol 31 (6) ◽  
pp. 723-736 ◽  
Author(s):  
Olivera Karanovic ◽  
Michel Thabet ◽  
Hugh R Wilson ◽  
Frances Wilkinson
Keyword(s):  
Visual Stimulation ◽  
Gain Control ◽  
Healthy Controls ◽  
High Contrast ◽  
Detection Thresholds ◽  
Visual Discomfort ◽  
Flickering Light ◽  
Contrast Gain ◽  
Contrast Gain Control ◽  
Prior Adaptation

Aims: Flickering light is strongly aversive to many individuals with migraine. This study was designed to evaluate other abnormalities in the processing of temporally modulating visual stimulation. Methods: We measured psychophysical thresholds for detection of a flickering target and for the discrimination of suprathreshold flicker contrasts (increment thresholds) in 14 migraineurs and 14 healthy controls with and without prior adaptation to high-contrast flicker. Visual discomfort (aversion) thresholds were also assessed. Results: In the baseline (no adaptation) conditions, detection and discrimination thresholds did not differ significantly between groups. Following adaptation, flicker detection thresholds were elevated equivalently in both groups; however, discrimination thresholds were more strongly affected in migraineurs than in controls, showing greater elevation at moderate contrasts and greater threshold reduction (sensitisation) at high contrast (70%). Migraineurs also had significantly elevated discomfort scores, and these were significantly correlated with number of years with migraine. Discussion: We conclude that visual flicker not only causes discomfort but also exerts measurable effects on contrast processing in the visual pathways in migraine. The findings are discussed in the context of the existing literature on habituation, adaptation and contrast-gain control.

scholarly journals A temporal model for early vision that explains detection thresholds for light pulses on flickering backgrounds

2000 ◽  
Vol 17 (3) ◽  
pp. 449-462 ◽  
Author(s):  
H.P. SNIPPE ◽  
L. POOT ◽  
J.H. van HATEREN
Keyword(s):  
Feedback Loop ◽  
Light Adaptation ◽  
Full Range ◽  
Gain Control ◽  
Detection Thresholds ◽  
Pass Filter ◽  
Contrast Gain ◽  
Contrast Gain Control ◽  
Wide Range ◽  
Adaptation Processes

A model is presented for the early (retinal) stages of temporal processing of light inputs in the visual system. The model consists of a sequence of three adaptation processes, with two instantaneous nonlinearities in between. The three adaptation processes are, in order of processing of the light input: a divisive light adaptation, a subtractive light adaptation, and a contrast gain control. Divisive light adaptation is modeled by two gain controls. The first of these is a fast feedback loop with square-root behavior, the second a slow feedback loop with logarithm-like behavior. This can explain several aspects of the temporal behavior of photoreceptor outputs. Subtractive light adaptation is modeled by a high-pass filter equivalent to a fractional differentiation, and it can explain the attenuation of low frequencies observed in ganglion cell responses. Contrast gain control in the model is fast (Victor, 1987), and can explain the decreased detectability of test signals that are superimposed on dynamic backgrounds. We determine psychophysical detection thresholds for brief test pulses that are presented on flickering backgrounds, for a wide range of temporal modulation frequencies of these backgrounds. The model can explain the psychophysical data for the full range of modulation frequencies tested, as well as detection thresholds obtained for test pulses on backgrounds with increment and decrement steps in intensity.

Video-Enhanced Microscopy--Better Visibility of Plant Cell Structures

1982 ◽  
Vol 40 ◽  
pp. 182-185
Author(s):  
N.S. Allen ◽  
R.D. Allen
Keyword(s):  
Diffraction Pattern ◽  
Theoretical Basis ◽  
Numerical Aperture ◽  
Gain Control ◽  
Control Unit ◽  
Camera Control ◽  
Variable Gain ◽  
Contrast Method ◽  
Fine Detail ◽  
Cell Structures

Various methods of video-enhanced microscopy combine TV cameras with light microscopes creating images with improved resolution, contrast and visibility of fine detail, which can be recorded rapidly and relatively inexpensively. The AVEC (Allen Video-enhanced Contrast) method avoids polarizing rectifiers, since the microscope is operated at retardations of λ/9- λ/4, where no anomaly is seen in the Airy diffraction pattern. The iris diaphram is opened fully to match the numerical aperture of the condenser to that of the objective. Under these conditions, no image can be realized either by eye or photographically. Yet the image becomes visible using the Hamamatsu C-1000-01 binary camera, if the camera control unit is equipped with variable gain control and an offset knob (which sets a clamp voltage of a D.C. restoration circuit). The theoretical basis for these improvements has been described.

Orienting and Focusing in Voluntary and Involuntary Visuospatial Attention Conditions

2010 ◽  
Vol 24 (3) ◽  
pp. 198-209 ◽  
Author(s):  
Yan Wang ◽  
Jianhui Wu ◽  
Shimin Fu ◽  
Yuejia Luo
Keyword(s):  
Gain Control ◽  
Event Related Potentials ◽  
Stimulus Onset ◽  
Orientation Discrimination ◽  
Involuntary Attention ◽  
Attention Condition ◽  
Voluntary Attention ◽  
Visual Spatial ◽  
Related Potentials ◽  
Underlying Mechanisms

In the present study, we used event-related potentials (ERPs) and behavioral measurements in a peripherally cued line-orientation discrimination task to investigate the underlying mechanisms of orienting and focusing in voluntary and involuntary attention conditions. Informative peripheral cue (75% valid) with long stimulus onset asynchrony (SOA) was used in the voluntary attention condition; uninformative peripheral cue (50% valid) with short SOA was used in the involuntary attention condition. Both orienting and focusing were affected by attention type. Results for attention orienting in the voluntary attention condition confirmed the “sensory gain control theory,” as attention enhanced the amplitude of the early ERP components, P1 and N1, without latency changes. In the involuntary attention condition, compared with invalid trials, targets in the valid trials elicited larger and later contralateral P1 components, and smaller and later contralateral N1 components. Furthermore, but only in the voluntary attention condition, targets in the valid trials elicited larger N2 and P3 components than in the invalid trials. Attention focusing in the involuntary attention condition resulted in larger P1 components elicited by targets in small-cue trials compared to large-cue trials, whereas in the voluntary attention condition, larger P1 components were elicited by targets in large-cue trials than in small-cue trials. There was no interaction between orienting and focusing. These results suggest that orienting and focusing of visual-spatial attention are deployed independently regardless of attention type. In addition, the present results provide evidence of dissociation between voluntary and involuntary attention during the same task.

The process of investigating Diocesan Curia in Lublin by the PRL’s apparatus of repression in the years 1946-1974

2013 ◽  
Vol 67 (1) ◽  
Author(s):  
Elżbieta Kosobudzka
Keyword(s):  
Catholic Church ◽  
Gain Control ◽  
Source Analysis ◽  
Secret Police ◽  
Personal Lives ◽  
Catholic Clergy ◽  
Recorded Data ◽  
The Government ◽  
Operational Activities ◽  
Intensive Surveillance

SUMMARYThe article below focuses on the source analysis of the process of investigating Diocesan Curia in Lublin in the years 1946-1947, during the period when two Lublin ordinaries were in charge: Bishop Stefan Wyszyński (1946-1948) and Bishop Piotr Kałwa (1949-1974). Diocesan Curia, as the most important institution in the Church administrative hierarchy, was subject to intensive surveillance by PRL’s apparatus of repression.At the beginning, the process of investigating the management structure on the diocese level was not conducted by specially selected departments but was performed as a part of broadly conceived actions directed against Catholic clergy. In the years 1946-1948,when bishop Stefan Wyszyński was in charge, operational activities against the clergy and the bishops were led by 5th Section of 5th Department of Voivodeship Public Security Office (Sekcja V Wydziału V Wojewódzkiego Urzędu Bezpieczeństwa) in Lublin (until the February of 1953). It can be inferred from the recorded data that until 1949 the Diocesan Curia’s circle in Lublin was very poorly uncovered by Polish communist secret police and their activity amounted only to gathering and verifying data received from informants. The shortage of well-trained agents prevented taking more intensive actions against Bishop Wyszyński and Diocesan Curia in Lublin.In the years 1949-1974, when Bishop Piotr Kałwa was in charge, the 5th Section of the 5th Department of VPSO continued their operational activities aimed against the Lublin’s Curia. In 1953 a new department was created on the basis of 5th Section. The so-called 11th Department took over the entirety of cases pertaining to the Catholic Church. In 1955 the 11th Department was transformed into 6th Department of VPSO in Lublin. 3rd Department of VPSO in Lublin and 1st Section of 6th Department of Polish communist secret police of Voivodeship Polish Citizen Militia Headquarters in Lublin (referat Służby Bezpieczeństwa w Komendzie Wojewódzkiej Milicji Obywatelskiej), respectively, also conducted investigation activities concerning the bishops and Curia.As of 1949, the Diocesan Curia in Lublin was subject to intensive surveillance by the PRL’s security service apparatus. Its main aim at that point was to restrict the Curia’s activity so as to gain control over it. In order to achieve that, the activity of Curial employees and bishops was documented and revealed. Additionally, the conflicts between the bishops, Curial employees and KUL’s management were incited and deepened. What is more, the secret police attentively scrutinized bishops’ and Curial employees’ personal lives in order to gather compromising data, gained secret collaborators (47 secret agents were involved in the process) and limited Curia employees’ departures for studies abroad. Almost every type of operation activities was used against Bishop Piotr Kałwa. The secret police applied phone tapping, bugging, surveillance, reading mail and sending anonymous letters in order to undermine his authority. What is more, the secret police tried to set bishop Kałwa at variance with Primate Wyszyński. However, these actions did not change Bishops Kałwa’s stance who, until his death, unwaveringly defended the Catholic Church’s independence from the government.

Analysis and Identification of Off-Odor Compounds in Electronic Systems

2006 ◽  
Author(s):  
Mary Ann Nailos ◽  
Dan Stein ◽  
Lawrence T. Nielsen ◽  
Anna Iwasinska
Keyword(s):  
Volatile Compounds ◽  
Electronic Systems ◽  
Detection Thresholds ◽  
Detection And Identification ◽  
Odor Compounds ◽  
Novel Method ◽  
Odor Analysis ◽  
Analytical System ◽  
Task Perception ◽  
Analytical Tools

Abstract The detection and identification of substances that give rise to aromas and off-odors is often a difficult task. Perception of odors is very subjective and odor detection thresholds vary from person to person. The identification of trace levels of compounds responsible for perceived odors is difficult using conventional analytical tools. This paper will focus on a novel method for sampling and analyzing aromatic volatile compounds using an analytical system specifically designed for odor analysis.

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