Region Of Maximum Sensitivity Research Articles

Vertically-resolved observations of Jupiter’s quasi-quadrennial oscillation from 2012 to 2019

Over the last eight years, a rich dataset of mid-infrared CH4 observations from the TEXES instrument at IRTF has been used to characterize the thermal evolution of Jupiter’s stratosphere. These data were used to produce vertically-resolved temperature maps between latitudes of 50∘S and 50∘N, allowing us to track approximately two periods of Jupiter’s quasi-quadrennial oscillation (QQO). During the first five years of observations, the QQO has a smooth sinusoidal pattern with a period of 4.0 ± 0.2 years and an amplitude of 7 ± 1 K at 13.5 mbar (our region of maximum sensitivity). In 2017, we note an abrupt change to this pattern, with the phase being shifted backwards by ∼1 year. Searching for possible causes of this QQO delay, we investigated the TEXES zonally-resolved temperature retrievals and found that in May/June 2017, there was an unusually warm thermal anomaly located at a latitude of 28∘N and a pressure of 1.2 mbar, moving westward with a velocity of 19 ± 4 ms−1. We suggest that there may be a link between these two events.

Luminescent optical fibers with CdS(Se) quantum dots for spark detectors

We present results of studying the luminescent characteristics of optical fibers with CdS and CdSSe quantum dots (QDs) for spark detectors with up-conversion of the spark flashing spectrum to the long-wavelength range. It is shown that, by selecting a proper QD composition and size, it is possible to shift the luminescence band position toward the region of maximum sensitivity of a Si photodetector.

Room-temperature photodiodes based on InAs/InAs0.88Sb0.12/InAsSbP heterostructures for extended (1.5–4.8 μm) spectral range

Photodiodes with a photosensitive area of 0.45 × 0.45 mm2 operating at room temperature in a wavelength range bounded by 4.9 μm have been created on the basis of InAs/InAs0.94Sb0.06/InAsSbP/InAs0.88Sb0.12/InAsSbP/InAs heterostructures grown by liquid phase epitaxy. A distinguishing feature of the proposed photodiodes is extended (λmax = 1.5–4.8 μm) spectral sensitivity range, in which the photodiode is characterized by a monochromatic responsivity of 0.5–0.8 A/W and a dark current density of 1.0–1.5 A/cm2 at a reverse bias of 0.2 V. The differential resistance at zero bias reaches up to 20–100 Ω. The detection ability of photodiodes in the region of maximum sensitivity reaches (1–2) × 108 cm Hz1/2 W−1.

Directional sensitivity and hearing pathways in the beluga whale, Delphinapterus leucas

Although much variation exists in jaw morphology among species, odontocetes are believed to receive sound primarily through the pan bone region of the lower jaw. In order to further examine this jaw hearing hypothesis, we tested the head receiving sensitivity and directional hearing of a beluga whale, Delphinapterus leucas. Hearing measurements were conducted with a 9‐yr‐old female beluga using the auditory evoked potential technique. A preliminary audiogram indicated that the subject had very sensitive hearing (45‐55dB from 32‐80 kHz) and heard up to 128 kHz. The pathway investigation used a piezo‐electric transducer to present the click stimuli, whereas the hearing directivity was measured in the far field, also using broadband clicks. Like the bottlenose dolphin, the subject had a region of high sensitivity around the pan bone region (78 dB), however, unlike the bottlenose dolphin, we found that the region of maximum sensitivity was at the tip of the lower jaw (75dB). The subject also proved to have highly directional hearing. This study supports the shaded receiver hypothesis and also shows that hearing pathway variations appear to exist among odontocete species and are at least partially dependent on head morphology.

Selective Responsiveness to Long-Range Acoustic Signals in Insects and Anurans

SYNOPSIS. Insects and anurans show various patterns of selective responsiveness to playbacks of natural and synthetic sounds. Preferences and tuning of the auditory system most often match one or more strongly emphasized frequency components in long-range, mate-attracting signals typical of conspecific individuals, but exceptions, in which frequencies lower or higher than the mean are preferred, occur in some species. In some insects the most preferred frequencies may correspond to regions that maximize localizability of signals rather than regions of maximum sensitivity. Patterns of preference for fine-temporal properties are typically stabilizing within a population; females prefer values near the mean and few males produce calls with values that deviate sufficiently to make them less attractive than calls with average values. Preferences for gross temporal properties {e.g., the rate and duration of signaling) are usually highly directional, with much higher than mean values preferred. In anurans, call rate is a better predictor of male mating success than dominant frequency. Nevertheless, a variety of factors, especially close-range assessments that are common in insects, may modify or negate the advantages of producing long-range signals of high relative attractiveness. The evolutionary consequences of selective responsiveness in anurans and insects are discussed

5-HT receptors and hyper- or hypothermia: Elucidation by catecholamine antagonists injected into the cat hypothalamus

The receptor mechanisms in the hypothalamus and preoptic area which mediate thermoregulatory changes produced by serotonin (5-HT) were examined in the unrestrained cat. Stainless steel guide tubes were implanted just above the rostral diencephalon or preoptic area in each of twelve cats. 5-HT in a dose of 1.5 to 10.5 μg was micro-injected in a volume of 0.75 to 1.5 μl into a total of 256 test sites in the hypothalamus. An individual site at which 5-HT evoked a rise or a fall in core temperature of ⩾ 0.5°C within 30 min was considered to be reactive to the indoleamine. Within such a region of maximum sensitivity, i.e., the cat's anterior hypothalamic, preoptic area (AH/POA), either norepinephrine (NE) or dopamine (DA) micro-injected in a dose of 2.33 to 14.0 μg in similar volumes evoked only a dose-dependent decline in the body temperature of the cat. 5-HT was found to cause either hyper- or hypothermia. The direction of temperature change caused by 5-HT was dependent principally upon the neuroanatomical locus of injection. Each of the 5-HT reactive sites was characterized pharmacologically by their pre-treatment with phentolamine (PHT), d-butaclamol (BUTAC) or methysergide (METHY) in doses of 1.0 to 10.0 μg. At the most rostral sites in POA, the catecholamine receptor antagonists selectively delayed the onset of the 5-HT hypothermia and limited the magnitude of the response. Within sites located in the AH in which 5-HT induced only a rise in body temperature, prior treatment of the site with the catecholamine receptor antagonists PHT or BUTAC failed to modify the response. These results indicate that 5-HT in producing hypothermia not only may saturate the 5-HT receptor sites but also may be taken up by catecholamine receptors which mediate the diencephalic heat loss pathway.

Tentacle responses of the sea anemone Anthopleura xanthogrammica to ultraviolet and visible radiations.

WE have observed that exposure of anemones to ultraviolet and visible radiations can elicit two specific responses, flexion and retraction of the tentacles. A detailed investigation revealed that these responses were readily differentiated by their spectral region of maximum sensitivity.

Construction and theoretical analysis of a direct-reading hot-wire vacuum gauge with zero point control

A hot-wire vacuum gauge connected to a special bridge (fig. 2), indifferent to voltage fluctuations or changes in the temperature of the surroundings, is described. The balance point of the bridge can be controlled independently of the actual gas pressure in the vacuum system. The heating current is adjusted in the region of maximum sensitivity for very low pressures. The instrument has been calibrated from 10−5 up to 0.1 mm Hg. Calibration curves for air, hydrogen, helium and argon are shown (fig. 6 and 7).