Color-coded area sensitivity maps of photomultipliers

Technique was devised specifically for testing photomultipliers and other photodetectors, but it could also be used to color code any type of mapping data, such as weather or topographical maps, thermal or pressure distributions on reentry surfaces, or any other three-dimensional data to be displayed in two-dimensional form

Versatile LDV burst simulator

A device for generating burst signals is reported that can be used to determine whether or not a laser Doppler velocimeter is operating properly. A high frequency signal which corresponds to the information frequency of the laser Doppler velocimeter is modulated by a low frequency signal to provide an envelope for the high frequency signal. The high frequency signal is modulated by any modulator means such as, for example, an analog multiplier. The low frequency signal is added to the modulated signal to provide pedestals for the resulting series of burst pulses. The means are provided for selecting different combinations of these burst signals. Also means are provided for making the burst signals asymmetrical as desired. In addition, means are provided for varying the frequencies, and amplitudes of the information, envelope and pedestal frequency signals in the burst signals

Long-Term Effects of the Cleaner Fish Labroides dimidiatus on Coral Reef Fish Communities

Cleaning behaviour is deemed a mutualism, however the benefit of cleaning interactions to client individuals is unknown. Furthermore, mechanisms that may shift fish community structure in the presence of cleaning organisms are unclear. Here we show that on patch reefs (61–285 m2) which had all cleaner wrasse Labroides dimidiatus (Labridae) experimentally removed (1–5 adults reef−1) and which were then maintained cleaner-fish free over 8.5 years, individuals of two site-attached (resident) client damselfishes (Pomacentridae) were smaller compared to those on control reefs. Furthermore, resident fishes were 37% less abundant and 23% less species rich per reef, compared to control reefs. Such changes in site-attached fish may reflect lower fish growth rates and/or survivorship. Additionally, juveniles of visitors (fish likely to move between reefs) were 65% less abundant on removal reefs suggesting cleaners may also affect recruitment. This may, in part, explain the 23% lower abundance and 33% lower species richness of visitor fishes, and 66% lower abundance of visitor herbivores (Acanthuridae) on removal reefs that we also observed. This is the first study to demonstrate a benefit of cleaning behaviour to client individuals, in the form of increased size, and to elucidate potential mechanisms leading to community-wide effects on the fish population. Many of the fish groups affected may also indirectly affect other reef organisms, thus further impacting the reef community. The large-scale effect of the presence of the relatively small and uncommon fish, Labroides dimidiadus, on other fishes is unparalleled on coral reefs

Lidar and Balloon-Borne Cascade Impactor Measurements of Aerosols: A Case Study

Aerosol size distributions, elemental components, complex refractive indices, extinction profiles and extinctionto- backscatter ratios have been measured and inferred from balloon-borne cascade impactor and lidar observations made during a cooperative joint experiment conducted during the period 4-10 April, 1980 in Tucson, AZ. Size distributions obtained from quartz crystal microbalance (QCM) cascade impactor measurements at different heights (1 to 1000 m) and times over a period of several days were fairly similar in form, being clearly bimodal in their mass distributions with the coarse particle mode being dominant. Electron microscope and energy dispersive X-ray analyses of particles deposited on the QCM stages over the particle radii range ~0.5-4.0 µm revealed that the particle samples were elementally dominated by both sulfur and crustal type (Al, Ca, Mg and Si) elements. Complex refractive index estimates for a wavelength of 649 nm were obtained by comparing the lidar inferred aerosol extinction-to-backscatter ratios with theoretically computed values calculated for the impactor-derived size distributions. The real part of the index was estimated to be 1.45 for most cases, while the estimates for the imaginary part ranged between 0.000 and 0.01. Aerosol extinction coefficients calculated for the impactor-derived size distributions were found to be somewhat smaller but in fair agreement with the extincti

Analysis of Organic Pollutants in Gulf of Mexico Gelatinous Zooplankton

Organic pollutants in gelatinous zooplankton species have yet to be studied as potential bioindicators for surface to bathypelagic depths in the Gulf of Mexico (GoM). These fauna could be used to assess water quality more accurately than vertebrate species (e.g., fishes) due to their thin integumentary system, lifestyle, and lack of xenobiotic-metabolic enzymes. Additionally, these organisms possess a mucus layer that can store organic chemicals, presenting an alternative method for coping with oil exposure. To test if gelatinous zooplankton accumulates more organic pollutants than fishes, we analyzed polycyclic aromatic hydrocarbons (PAHs) and pesticides in Atolla wyvillei, Aurelia aurita, and Sigmops elongatus. Samples were collected in the northern GoM in 2018 as part of the Deep Pelagic Nekton Dynamics Consortium (DEEPEND). Ultra-sonication and ASE extraction methods were utilized, followed by gas-chromatography analysis in reaction monitoring mode (GC/MS/MS-MRM). Statistically higher (~50 times) concentrations of organic compounds occurred in A. aurita as compared to A. wyvillei and S. elongatus. Also, high molecular weight PAHs (HMW PAHs) were 3.5 times higher in the two cnidarian species than in S. elongatus. However, no significant differences in low molecular weight PAHs (LMW PAHs) were found. These results showed that the medusae are unable to metabolize HMW PAHs as efficiently as S. elongatus. Therefore, these gelata can be used to assess bioavailability of chemicals in offshore waters due to their increased ability to accumulate organic contaminants as compared to vertebrates. In addition, we will present results for the tunicate Pyrosoma atlanticum collected before (2010) and after (2011, 2016, 2018) the Deepwater Horizon oil spill to better evaluate exposure, uptake, and storage capacity of hydrocarbons in deep-pelagic gelatinous zooplankton

Spatial patterns in the vertical structure of euphausiids in Gullmarsfjord, Sweden: Identifying influences on bilayer formation and distribution

The formation of two vertically discrete layers (bilayers) at night-time is a commonly observed phenomenon in zooplankton and is regularly found in Gullmarsfjord, a fjord with a 50 m sill depth, deep basin and a three-layered water column. In an acoustic and net sampling survey in September 2003, night-time euphausiid layers occurred at 15 and 45 m, with the deeper layer containing relatively higher concentrations of adult Northern krill (Meganyctiphanes norvegica). The main night-time predatory threat came from the upward migration of demersal fish, which reached the deeper but not the shallower euphausiid layer. Shoreward advection of coastal waters across the sill creates a layer of resuspended organic matter between 40 and 50 m. The deeper bilayer was located at those depths, particularly at the mouth of the fjord where this organic matter was most concentrated. Krill in the lower bilayer experienced waters that were 4°C cooler than in the upper bilayer, which can decrease the cost of respiration by around 20%. Accompanying studies have shown significantly higher growth rates in krill consuming sedimentary organic material and benthic filamentous algae. Combined, it appears that energetic benefit and predatory threat were greatest in the deeper rather than the shallower bilayer in Gullmarsfjord. This is the reverse of most other euphausiid habitats, where the highest risk and reward is in the upper bilayer, illustrating that euphausiids adapt their stereotypic vertical migration pattern to local environmental conditions