5,240 research outputs found

    Distribution, age, and growth of young-of-the year greater amberjack (Seriola dumerili) associated with pelagic Sargassum

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    Patterns of distribution and growth were examined for young-of-the-year (YOY) greater amberjack (Seriola dumerili) associated with pelagic Sargassum in the NW Gulf of Mexico. Seriola dumerili were collected off Galveston, Texas, from May to July over a two-year period (2000 and 2001) in both inshore (<15 nautical miles [nmi]) and offshore zones (15−70 nmi). Relative abundance of YOY S. dumerili (32−210 mm standard length) from purse-seine collections peaked in May and June, and abundance was highest in the offshore zone. Ages of S. dumerili ranged from 39 to 150 days and hatching-date analysis indicated that the majority of spawning events occurred from February to April. Average daily growth rates of YOY S. dumerili for 2000 and 2001 were 1.65 mm/d and 2.00 mm/d, respectively. Intra-annual differences in growth were observed; the late-season (April) cohort experienced the fastest growth in both years. In addition, growth was significantly higher for S. dumerili collected from the offshore zone. Mortality was approximated by using catch-curve analysis, and the predicted instantaneous mortality rate (Z) of YOY S. dumerili was 0.0045 (0.45%/d)

    Diet of the Blacktip Shark (Carcharhinus limbatus) in the Northwestern Gulf of Mexico

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    The stomach contents of 90 Blacktip Shark (Carcharhinus limbatus) specimens caught in the northwestern Gulf of Mexico (GOM) were examined. Stomach contents were identified to the lowest possible taxon, and quantified using percent weight, percent number, percent frequency of occurrence, and percent index of relative importance (IRI). Teleosts were the dominant prey group (98.95% IRI), although most were unidentified (61.70% IRI). Of identified teleost species, Atlantic Croaker (Micropogonias undulatus) (28.43% IRI), and Gulf Menhaden (Brevoortia patronus) (2.31% IRI) were the most important. Crustaceans (0.65% IRI), mollusks (0.46% IRI), and elasmobranchs (0.03% IRI) formed a minor component of the diet. Suspected shrimp fishery discards were found in 11% of stomachs, highlighting the potential importance of this food source for the Blacktip Shark. Diet composition did not differ between male and female sharks, but did between juveniles and adults. Juvenile shark diets had greater proportions of unidentified teleost, Clupeidae and Penaeidae, while adult diets had greater proportions of Sciaenidae, Ariidae and cephalopods. Our results were similar, although not identical to, other studies of Blacktip Shark diets in the northwestern GOM. Of note is finding of the mantis shrimp Squilla empusa, a species previously unreported in Blacktip Shark stomach contents. This new finding, the high importance of unidentified teleosts, and the lack of asymptote in the prey accumulation curve emphasize the need for further study of the Blacktip Shark diet in the northwestern GOM

    Structural behaviour of copper chloride catalysts during the chlorination of CO to phosgene

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    The interaction of CO with an attapulgite-supported Cu(II)Cl2 catalyst has been examined in a micro-reactor arrangement. CO exposure to the dried, as-received catalyst at elevated temperatures leads to the formation of CO2 as the only identifiable product. However, phosgene production can be induced by a catalyst pre-treatment where the supported Cu(II)Cl2 sample is exposed to a diluted stream of chlorine. Subsequent CO exposure at ~ 370°C then leads to phosgene production. In order to investigate the origins of this atypical set of reaction characteristics, a series of x-ray absorption experiments were performed that were supplemented by DFT calculations. XANES measurements establish that at the elevated temperatures connected with phosgene formation, the catalyst is comprised of Cu+ and a small amount of Cu2+. Moreover, the data show that unique to the chlorine pre-treated sample, CO exposure at elevated temperature results in a short-lived oxidation of the copper. On the basis of calculated CO adsorption energies, DFT calculations indicate that a mixed Cu+/Cu2+ catalyst is required to support CO chemisorption

    Cosmic Strings from Supersymmetric Flat Directions

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    Flat directions are a generic feature of the scalar potential in supersymmetric gauge field theories. They can arise, for example, from D-terms associated with an extra abelian gauge symmetry. Even when supersymmetry is broken softly, there often remain directions in the scalar field space along which the potential is almost flat. Upon breaking a gauge symmetry along one of these almost flat directions, cosmic strings may form. Relative to the standard cosmic string picture based on the abelian Higgs model, these flat-direction cosmic strings have the extreme Type-I properties of a thin gauge core surrounded by a much wider scalar field profile. We perform a comprehensive study of the microscopic, macroscopic, and observational characteristics of this class of strings. We find many differences from the standard string scenario, including stable higher winding mode strings, the dynamical formation of higher mode strings from lower ones, and a resultant multi-tension scaling string network in the early universe. These strings are only moderately constrained by current observations, and their gravitational wave signatures may be detectable at future gravity wave detectors. Furthermore, there is the interesting but speculative prospect that the decays of cosmic string loops in the early universe could be a source of ultra-high energy cosmic rays or non-thermal dark matter. We also compare the observational signatures of flat-direction cosmic strings with those of ordinary cosmic strings as well as (p,q) cosmic strings motivated by superstring theory.Comment: 58 pages, 16 figures, v2. accepted to PRD, added comments about baryogenesis and boosted decay products from cusp annihilatio

    A photometricity and extinction monitor at the Apache Point Observatory

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    An unsupervised software ``robot'' that automatically and robustly reduces and analyzes CCD observations of photometric standard stars is described. The robot measures extinction coefficients and other photometric parameters in real time and, more carefully, on the next day. It also reduces and analyzes data from an all-sky 10μm10 \mu m camera to detect clouds; photometric data taken during cloudy periods are automatically rejected. The robot reports its findings back to observers and data analysts via the World-Wide Web. It can be used to assess photometricity, and to build data on site conditions. The robot's automated and uniform site monitoring represents a minimum standard for any observing site with queue scheduling, a public data archive, or likely participation in any future National Virtual Observatory.Comment: accepted for publication in A

    High-Risk Environmental Conditions Attenuates Performance Efficiency Index in NCAA DI Female Soccer Players

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    International Journal of Exercise Science 15(6): 442-454, 2022. The purpose of this study was to evaluate the effects of environmental conditions on running performance and performance efficiency index (Effindex). Performance data recorded using Polar Team Pro sensors from eight collegiate female soccer players in nine matches were analyzed during the 2019 competitive season. Effindex and running performance, including total distance covered (TDREL) and distance covered in five speed thresholds relative to minutes played, were examined for indications of fatigue with respect to environmental conditions, including ambient temperature and relative humidity. Matches were separated into three groups based on environmental conditions: Low-Risk (n = 2 matches), Moderate-Risk (n = 3 matches), or High-Risk (n = 4 matches). Speed thresholds were grouped as follows: walking (WALKREL), jogging (JOGREL), low-speed running (LSRREL), high-speed running (HSRREL), and sprinting (SPRINTREL). A significant effect was observed for TDREL in all environmental conditions (η2 = 0.614). TDREL was significantly lower in the High-Risk (p = 0.002; 95.32 ± 12.04 m/min) and Moderate-Risk conditions (p = 0.004; 94.85 ± 9.94 m/min) when compared to Low-Risk (105.61 ± 9.95 m/min). WALKREL (p = 0.005), JOGREL (p = 0.005) LSRREL (p = 0.001), HSRREL (p = 0.035), SPRINTREL (p = 0.017), and Effindex (p = 0.0004) were significantly greater in Low-Risk conditions when compared to Moderate-Risk conditions. WALKREL (p = 0.005), HSRREL (p = 0.029), SPRINTREL (p = 0.005), and Effindex (p = 0.0004) were significantly greater in Low-Risk conditions when compared to High-Risk conditions. High-Risk environmental conditions may result in adverse performance in female collegiate soccer players

    Trophic Ecology of Meso- and Bathypelagic Predatory Fishes in the Gulf of Mexico

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    The trophic ecology of eight circumglobal meso- and bathypelagic fishes (Anoplogaster cornuta, Chauliodus sloani, Coccorella atlantica, Gigantura chuni, G. indica, Omosudis lowii, Photostomias guernei, and Stomias affinis) with contrasting vertical migration habits (vertical migrators vs. non-migrators) were examined using stable isotope analysis (SIA). Mean δ13C values of these predators were similar among species, ranging from –18.17 to –18.99 ‰, suggesting that all species are supported by a similar carbon source. This finding was supported by mixing-model analysis; all of these deep-living predators received the majority (\u3e73%) of their carbon from epipelagic food resources. Mean δ15N values of the predators ranged from 9.18 to 11.13 ‰, resulting in trophic position estimates between the third and fourth trophic level, although significant shifts in δ15N with increasing body size suggest that some of these species undergo ontogenetic shifts in trophic position. Bayesian standard ellipses, used to estimate isotopic niche areas, differed in size among species, with those occupying the highest relative trophic positions possessing the largest isotopic niches. These results, which provide the first trophic descriptions using dietary tracers for several of these species, offer insight into the trophic structure of deep-sea ecosystems and will help inform the construction of ecosystem-based models

    Importance of low-relief nursery habitat for reef fishes

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    Coastal restoration projects to mitigate environmental impacts have increased global demand for sand resources. Unfortunately, these resources are often extracted from sand/shell banks on the inner continental shelf, resulting in significant alteration or loss of low-relief reefs in coastal oceans. Experimental reefs (oyster shell, limestone rubble, composite) were deployed in the western Gulf of Mexico to assess their potential value as nurseries for newly settled reef fishes. Occurrence, abundance, and species richness of juvenile fishes were significantly higher on all three types of low-relief reefs compared with unconsolidated sediment. Moreover, reefs served as nursery habitat for a range of reef fish taxa (angelfishes, grunts, sea basses, snappers, and triggerfishes). Red snapper (Lutjanus campechanus) was the dominant species present on all experimental reefs (100% occurrence), and mean density of this species was markedly higher on each of the three low-relief reefs (\u3e40.0 individuals/reef) relative to comparable areas over unconsolidated sediment (0.2 individuals). Our results suggest creation or restoration of structurally complex habitat on the inner shelf has the potential to markedly increase early life survival and expedite the recovery of exploited reef fish populations, and therefore may represent a critical conservation tool for increasing recruitment and maintaining reef fish diversity

    Fish assemblages associated with artificial reefs assessed using multiple gear types in the northwest Gulf of Mexico

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    Quantitative surveys of fishes associated with artificial reefs in the northwest Gulf of Mexico were conducted over a 4-yr period (2014-2017). Artificial reefs surveyed were comprised of three types: concrete structures, rig jackets, and decommissioned ships. All reefs were surveyed using vertical long line ( VLL), fish traps, and Adaptive Resolution Imaging Sonar (ARIS 1800). Mean fish abundance did not significantly differ using VLL [1.7 ind set(-1) (SD 2.2)] among the three reef types. However, relative abundance among all fishes collected was significantly highest on rig reefs using traps [6.2 ind soak(-1) (SD 3.8)], while results from sonar surveys indicated that the mean relative fish density was highest on concrete reefs [15.3 fish frame(-1) (SD 26.8)]. Red snapper (n = 792), followed by gray triggerfish (n = 130), pigfish (n = 70), tomtate (n = 69), and hardhead catfish (n = 57) were the most numerically abundant species using VLL and traps; red snapper comprised 90.7% of total catch using VLL and 43.9% using traps. Mean Brillouin\u27s diversity (HB) was highest on ships using VLL [0.41 (SD 0.14)] and highest on rigs using traps [0.87 (SD 0.58)] compared to the lowest diversity found on concrete [VLL 0.07 (SD 0.11); traps 0.36 (SD 0.32)]. Findings from this study can be used to inform the planning of future artificial reefs and their effect on the assemblages of reef-associated fishes. Additionally, these results highlight the value of using multiple gear types to survey reef fish assemblages associated with artificial reefs

    Mediators of Monocyte Migration in Response to Recovery Modalities following Resistance Exercise

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    Mediators of monocyte migration, complement receptor-3 (CR3), and chemokine ligand-4 (CCL4) were measured in response to recovery modalities following resistance exercise. Thirty resistance-trained men (23.1 +/- 2.9 y; 175.2 +/- 7.1 cm; 82.1 +/- 8.4 kg) were given neuromuscular electric stimulation (NMES), cold water immersion (CWI), or control (CON) treatments immediately following resistance exercise. Blood samples were obtained preexercise (PRE), immediately (IP), 30 minutes (30 P), 24 hours (24 H), and 48 hours (48 H) after exercise for measurement of circulating CCL4 and CR3 expression on CD14+ monocytes, by assay and flow cytometry. Circulating CCL4 showed no consistent changes. Inferential analysis indicated that CR3 expression was likely greater in CON at 30 P than NMES (90.0%) or CWI (86.8%). NMES was likely lower than CON at 24H (92.9%) and very likely lower at 48H (98.7%). Expression of CR3 following CWI was very likely greater than CON (96.5%) at 24H. The proportion of CR3+ monocytes was likely greater following CWI than NMES (85.8%) or CON (85.2%) at 24 H. The change in proportion of CR3+ monocytes was likely (86.4%) greater following NMES than CON from IP to 30 P. The increased expression of CR3 and increased proportion of CR3+ monocytes following CWI at 24 H indicate a potentially improved ability for monocyte adhesion to the endothelium, possibly improving phagocytosis of damaged tissues
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