Investigating Nonlinearity: A Note on the Estimation of Hamilton’s Random Field Regression Model

This is a revised and extended version of the authors’ 2003 Trinity Economic Paper. It describes Hamilton’s (2001) approach to nonlinear econometric modelling and some of the methods of nonlinear optimization, as before, but adds significantly to the investigation of Hamilton’s Gauss program for the implementation of his methodology. Specifically, it reports on the performance of this program using data relating to Hamilton’s US Phillips curve example, the use of two versions of the Gauss software and a range of numerical optimization options. It also examines the impact of changes in initial parameter estimates, the use of algorithm switching strategies, and the e?ects of changes in the sample data on the results produced by Hamilton’s procedure. The new results presented suggest some further clear conclusions that will be of value to those using Hamilton’s method.

Relative abundance and autecology of three piscivorous fishes in lakes of the upper basin of Salado River (Buenos Aires Province, Argentina)

El objetivo de este trabajo fue analizar la estructura de la comunidad de peces consumidores secundarios y terciarios, considerando aspectos autoecológicos que dieran cuenta del estado de estas poblaciones, en las lagunas de la cuenca superior del río Salado. Se registraron 14 especies de peces, de las cuales 3 eran depredadores piscívoros que representaban un 11.4% de la abundancia numérica y un 10.8% de la biomasa. La abundancia relativa de este nivel trófico fue de 89% (Oligosarcus jenynsii), 11% (Rhamdia sapo) y 0.5% (Hoplias malabaricus malabaricus). Considerando la biomasa, el 61% correspondió a Oligosarcus jenynsii, el 33% a Rhamdia sapo y el 6% a Hoplias malabaricus malabaricus. La relación longitud-peso, el factor de condición y el índice cefálico indicaron un desarrollo normal de las poblaciones de estas tres especies. Se clasificaron los estómagos de las mismas de acuerdo a la cantidad de alimento, observándose diferencias en el grado de repleción atribuibles al comportamiento alimentario de las especies. La abundancia relativa difirió de la encontrada en otros ambientes de la misma cuenca. Esta variación podría atribuirse a la competencia interespecífica o a las diferencias en la disponibilidad de recursos.The Salado River is an important watercourse in northern Pampean region of Argentina which includes several lakes in the upper part of its basin. This upper part shows lesser fish species richness than the lower section of the river. In this paper, an analysis of community structure of secondary and tertiary consumers and its autecology are presented. Among the 14 fish species recorded, 3 were mainly or totally piscivorous as adults. They constituted 11.4% of the numeric abundance and 10.8% of the biomass. Their numeric abundance was 89% (Oligosarcus jenynsii), 11% (Rhamdia sapo), and 0.5% (Hoplias malabaricus malabaricus), and their relative biomass was 61%, 33%, and 6%, respectively. Length/weight ratio, condition factor, and cephalic index indicate that the three populations presented normal development. Stomachs were classified according to the degree of repletion. Differences in repletion were attributable to the feeding behaviour of the different species. The relative abundance differed from the one observed in other environments within the same basin. This variation could be the result of interspecific competition or of differences in resource availability

Discussion of nuclear explosive operation process changes generated by a preliminary hazard assessment

Hazard assessments (HAs) are being used to support the US Department of Energy (DOE) Integrated Safety Process (SS-21), Nuclear Explosive Safety Study Group (NESSG), and Environmental Safety and Health (ES and H) initiatives. The HAs are used to identify hazards associated with nuclear explosive operations involving tooling and procedural processes. In general, a HA is a formal, systematic, in-depth method for evaluating a set of possible accident scenarios associated with a process. Two assessments of a nuclear explosive surveillance process have been performed or are in progress: (1) a preliminary HA of current operations to focus efforts on maximizing safety improvements during subsequent process redesign and track overall improvement following process redesign (completed) and (2) a rolling assessment of hazards present in conceptual solutions and solutions to improve safety (in progress). The preliminary HA was used to focus the process design teams on problem areas. The rolling assessment is evaluating how well problem areas were eliminated or mitigated. This paper summarizes the preliminary HA, how it focused the design teams on problem areas found by the assessment, and the rolling assessment of solutions generated by the process design team

CV20016

This report provides the main results and findings of the nineteenth annual underwater television survey on the Aran, Galway Bay and Slyne head Nephrops grounds, ICES assessment area; Functional Unit 17. The survey was multi-disciplinary in nature collecting UWTV, CTD and other ecosystem data. In 2020 a total of 44 UWTV stations were successfully completed, 34 on the Aran Grounds, 5 on Galway Bay and 5 on Slyne Head patches. The mean burrow density observed in 2020, adjusted for edge effect, was medium at 0.29 burrows/m². The final krigged burrow abundance estimate for the Aran Grounds was 359 million burrows with a CV (Coefficient of Variance; relative standard error) of 4%. The final abundance estimate for Galway Bay was 27 million and for Slyne Head was 7 million, with CVs of 13% and 4% respectively. The total abundance estimates have fluctuated considerably over the time series. The 2020 combined abundance estimate (394 million burrows) is 20% lower than in 2019, and it is below the MSY Btrigger reference point (540 million burrows). Using the 2020 estimate of abundance and updated stock data implies catches between 443 and 508 tonnes in 2021 that correspond to the F ranges in the EU multi annual plan for Western Waters, assuming that discard rates and fishery selection patterns do not change from the average of 2017–2019. Virgularia mirabilis was the only sea-pen species observed on the UWTV footage. Trawl marks were present at 7% of the Aran stations surveyed

CV19017

This report provides the results of the seventh underwater television on the ‘Porcupine Bank Nephrops grounds’ ICES assessment area; Functional Unit 16. The survey was multi-disciplinary in nature collecting UWTV, CTD and other ecosystem data. In total 65 UWTV stations were successfully completed in a randomised 6 nautical mile isometric grid covering the full spatial extent of the stock. The mean burrow density observed in 2019, adjusted for edge effect, was 0.14 burrows/m². The final krigged abundance estimate was 1010 million burrows with a relative standard error of 5% and an estimated stock area of 7,130 km2. The 2019 abundance estimate was 9.5% lower than in 2018. Using the 2019 estimate of abundance and updated stock data implies catches between 2127 and 2637 tonnes in 2020 that correspond to the F ranges in the EU multi annual plan for Western Waters (assuming that all catch is landed). Four species of sea-pen; Virgularia mirabilis, Funiculina quadrangularis, Pennatula phosphorea and the deepwater sea-pen Kophobelemnon stelliferum were observed during the survey. Trawl marks were also observed on 31% of the stations surveyed

CV19022

This report provides the main results of the 2019 underwater television survey on the ‘Labadie, Jones and Cockburn Banks’ ICES assessment area; Functional Unit 20-21. The 2019 survey was multi-disciplinary in nature collecting UWTV, and other ecosystem data. A total of 95 UWTV stations were completed at 6 nm intervals over a randomised isometric grid design. The mean burrow density was 0.06 burrows/m2 compared with 0.27 burrows/m2 in 2018. The 2019 geostatistical abundance estimate was 617 million, a 77% decrease on the abundance for 2018, with a CV of 5% which is well below the upper limit of 20% recommended by SGNEPS 2012. Low densities were observed throughout the ground. Using the 2019 estimate of abundance and updated stock data implies catch in 2020 that correspond to the F ranges in the EU multi annual plan for Western Waters are between 1131 and 1150 tonnes (assuming that discard rates and fishery selection patterns do not change from the average of 2016–2018). One species of sea-pen (Virgularia mirabilis) were recorded as present at the stations surveyed. Trawl marks were observed at 32% of the stations surveyed

Observations of Hercules X-1 during the 1998 July Short High State

We present RXTE monitoring of the eclipsing X-ray binary Hercules X-1 conducted over the short high state of 1998 July. This was one of the last major short high states before the source entered an anomalous low state of activity. A comparison with previous epochs Dnds no evidence for special behavior during these observations. We determine orbital and pulsar spin periods to facilitate measurements of (P)over dot(spin) and (P)over dot(orb) during the subsequent anomalous low state and the next epoch of high-state activity. Spectrally, the decay of the short high state and concurrent pre-eclipse dips are consistent with obscuration of a central X-ray source by a cloud of nonuniform column density. The standard model of a warped accretion disk of finite vertical scale height fits the characteristics of this absorber well. Pre-eclipse dips have durations a factor of a few longer than the characteristic durations of dips during main high states. Pulse profile structure increases in complexity toward the tail of the short high state, suggesting changes in accretion curtain geometry.</p

CE20006

The 2020 Irish Anglerfish and Megrim Survey (IAMS) took place from 23rd February to 18th March (area 7bcjk) and 12-21st April 2020 (area 6a) on RV Celtic Explorer. The main objective of the survey is to obtain biomass and abundance indices for anglerfish (Lophius piscatorius and L. budegassa) and megrim (Lepidorhombus whiffiagonis and L. boscii) in areas 6a (south of 58°N) and 7 (west of 8°W). Secondary objectives are to collect data on the distribution, relative abundance and biology of other commercially exploited species. For the second year, additional sampling took place in deep water (up to 1,500m) in order to monitor the recovery of exploited deep-water species following the decline of the deep-water fisheries in Irish waters. The IAMS survey is coordinated with the Scottish Anglerfish and Megrim Survey (SIAMISS) and uses the same gear and fishing practices

Physical interpretation of gauge invariant perturbations of spherically symmetric space-times

By calculating the Newman-Penrose Weyl tensor components of a perturbed spherically symmetric space-time with respect to invariantly defined classes of null tetrads, we give a physical interpretation, in terms of gravitational radiation, of odd parity gauge invariant metric perturbations. We point out how these gauge invariants may be used in setting boundary and/or initial conditions in perturbation theory.Comment: 6 pages. To appear in PR

CV20019

This report provides the main results of the eleventh underwater television survey of the various Nephrops patches in Functional Unit 19. The survey was multi-disciplinary in nature collecting UWTV, multi-beam and other ecosystem data. In 2020 a total 42 UWTV stations were successfully completed. The mean density estimates varied considerably across the different patches. The 2020 raised abundance estimate was a 20% decrease from the 2019 estimate and at 320 million burrows is below the MSY Btrigger reference point (430 million). Using the 2020 estimate of abundance and updated stock data implies catch in 2021 that correspond to the F ranges in the EU multi annual plan for Western Waters are between 531 and 595 tonnes (assuming that discard rates and fishery selection patterns do not change from the average of 2017–2019). Two species of sea pen were observed; Virgularia mirabilis and Pennatula phosphorea which have been observed on previous surveys of FU19. Trawl marks were observed at 26% of the stations surveyed