The black hole dynamical horizon and generalized second law of thermodynamics

The generalized second law of thermodynamics for a system containing a black hole dynamical horizon is proposed in a covariant way. Its validity is also tested in case of adiabatically collapsing thick light shells.Comment: JHEP style, 8 pages, 2 figures, version to appear in JHEP with typos correcte

Evaluating the use of the autodiametric method for estimating fecundity of Reinhardtius hippoglossoides, a species with an unusual oocyte development strategy

The autodiametric method is a highly streamlined method for estimating fecundity of fish with determinate oocyte development pattern. Greenland halibut presents a peculiar reproductive strategy with two simultaneously cohorts one of large vitellogenic oocytes (for the current year) and another one of small vitellogenic oocytes (for the subsequent year). Results of this study showed that autodiametric method can be applied to estimate fecundity in Greenland halibut. Additionally, spatial differences in the autodiametric calibration curve were observed in the Northwest Atlantic, but did not translate into differences in fecundity at length. This is the first time that spatial differences between ACCs of the same species have been reported, what could be the result of (i) the unusual oocyte development pattern, or (ii) spatial differences in oocyte biochemistry. More research on the relative dynamics of oocyte cohorts simultaneously present in Greenland halibut ovaries and the factors (endo- or exogenous) influencing oocyte packing density could provide a better understanding of observed geographical differences.En prens

Black Hole Thermodynamics and Statistical Mechanics

We have known for more than thirty years that black holes behave as thermodynamic systems, radiating as black bodies with characteristic temperatures and entropies. This behavior is not only interesting in its own right; it could also, through a statistical mechanical description, cast light on some of the deep problems of quantizing gravity. In these lectures, I review what we currently know about black hole thermodynamics and statistical mechanics, suggest a rather speculative "universal" characterization of the underlying states, and describe some key open questions.Comment: 35 pages, Springer macros; for the Proceedings of the 4th Aegean Summer School on Black Hole

Coded imaging systems for X-ray astronomy

Available from British Library Document Supply Centre-DSC:DX213220 / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo

Variation in the frequency of skipped spawning in Atlantic cod (Gadus morhua) off Newfoundland and Labrador

Macroscopic maturity data collected between January and March of 1978–2004 during groundfish surveys were analysed to determine the frequency of skipped spawning for Atlantic cod (Gadus morhua) populations in the Northwest Atlantic. Nearly 18% of the 6583 potential female spawners sampled during this period would not have spawned in the subsequent spawning season. The frequency of skipped spawning was much higher on the Flemish Cap (NAFO Division 3M, ∼33%) and off the south coast of Newfoundland (Subdivision 3Ps, ∼21%) than that in three areas off eastern Newfoundland and southern Labrador (Divisions 3L, ∼8%; 3K, ∼3%; and 2J, <1%). Annual variation in the frequency of skipped spawning was apparent in all areas. Skipped spawning was most common in fish of medium size (60–79 cm). Non-reproductive cod were characterized by lower liver condition than reproductive cod, but not a lower gutted condition. Generalized linear models suggested that relative liver weight was the best predictor of spawning probability, and that age, length, and relative body condition were not good predictors. Models of spawning probability based on relative liver condition suggest that female fish in poor condition in 3KL are more likely to spawn than fish of equal condition in areas 3M and 3Ps

Assessing the status of the cod (Gadus morhua) stock in NAFO Subdivision 3Ps in 2020

The status of the cod stock in the Northwest Atlantic Fisheries Organization (NAFO) Subdivision (Subdiv.) 3Ps was assessed during a Fisheries and Oceans Canada (DFO) Regional Peer Review Process meeting held November 2–7, 2020. An integrated state space model resulting from the 2019 3Ps Cod Framework meeting was used to assess the status of the stock and estimate fishing mortality. The Limit Reference Point (LRP) is 66,000 t of Spawning Stock Biomass (SSB). SSB at January 1, 2021, is estimated to be 25 kt (18 kt–35 kt). The stock is in the Critical Zone (38% of Blim [27–53%]) as defined by the DFO Precautionary Approach (PA) Framework. Natural mortality (ages 5–8) was estimated to be 0.43 (0.35–0.52) in 2019. Values of natural mortality (M) during the last four years are the among the highest in the time series. Recruitment (age 2) estimates have been below the long term average since the mid-1990s.L’état du stock de morue dans la sous-division 3Ps de l’Organisation des pêches de l’Atlantique Nord-Ouest (OPANO) a fait l’objet d’une évaluation lors d’une réunion du processus régional d’examen par les pairs de Pêches et Océans Canada (MPO) qui s’est tenue du 2 au 7 novembre 2020. Un modèle intégré de type état-espace élaboré à la suite de la réunion sur le cadre relatif à la morue de la sous-division 3Ps de 2019 a été utilisé pour évaluer l’état du stock et estimer la mortalité par pêche. Le point de référence limite (PRL) est de 66 000 t de biomasse du stock reproducteur (BSR). La biomasse du stock reproducteur au 1 er janvier 2021 est estimée à 25 kt (18 kt à 35 kt). Le stock se situe dans la zone critique (38 % de la valeur B lim [27 à 53 %]), selon la définition du cadre intégrant l’approche de précaution (AP) établi par le MPO. Les valeurs de la mortalité naturelle (M) au cours des quatre dernières années sont parmi les plus élevées de la série chronologique. Les estimations du recrutement (âge 2) sont inférieures à la moyenne à long terme depuis le milieu des années 1990.

Oocyte development and vitellogenin production in Northwest Atlantic Greenland halibut Reinhardtius hippoglossoides

Histological data presented here supports the notion of an uncommon oocyte development pattern for Greenland halibut, with two simultaneous groups of developing oocytes in the ovary, the larger group developing for the upcoming spawning season and the smaller group developing for next year (i.e. the duration of vitellogenesis is > 1 yr.). We analyzed blood samples collected from wild fish as well as fish that were part of the first documented study of Greenland halibut reproductive development in captivity in order to explore the annual cycle of vitellogenin production for this species. Despite the unusual oocyte development strategy there were no obvious differences in seasonal vitellogenin profiles versus fish with more traditional oocyte development strategies. Blood plasma vitellogenin levels generally peaked prior to or during spawning for those fish that successfully spawned, while patterns were highly variable for fish that did not spawn. Maximum plasma vitellogenin levels observed were 25 mg/ml and within the range of values observed for other fish species. Continued refinements in husbandry and experimental protocols for the study of Greenland halibut in captivity will provide a valuable tool for examining aspects of the species' biology that are difficult to ascertain based on sampling of only wild fish. \ua9 Her Magesty the Queen in right of Canada, 2012.Peer reviewed: YesNRC publication: Ye

Evaluation de l'état du stock de morue (Gadus morhua) de la sous-division 3Ps de l'OPANO en 2017

The status of the cod stock in the Northwest Atlantic Fisheries Organization (NAFO) Subdivision 3Ps was assessed during a Fisheries and Oceans Canada (DFO) Regional Peer Review Process meeting held October 17-18, 2017. Estimates of Spawning Stock Biomass (SSB) derived from a survey-based (SURBA) cohort model increased considerably over 2009-12 but have since declined. The stock is currently estimated to be in the Cautious Zone (54% above Blim) as defined by the DFO Precautionary Approach (PA) Framework. Short-term projections of the stock were performed to 2020 assuming mortality rates will be within +/- 20% of current values (2014 to 2016 average). Projected SSB shows a continuous decline to 2020 in most cases, with the decrease ranging from 23 to 58% (2017-20). The risk of being below Blim by 2019 ranges from 0.09 and 0.73, and by 2020 from 0.25 to 0.94.L'état du stock de morue dans la sous-division 3Ps de l'Organisation des pêches de l'Atlantique Nord-Ouest (OPANO) a fait l'objet d'une évaluation lors d'une réunion du processus régional d'examen par les pairs de Pêches et Océans Canada (MPO) qui s'est tenue les 17 et 18 octobre 2017. Les estimations de la biomasse du stock reproducteur (BSR) calculées à partir d'un modèle de cohorte basé sur les relevés (SURBA) ont augmenté de façon importante au cours de la période 2009-2012, mais ont connu un déclin depuis. On estime actuellement que le stock se situe dans la zone de prudence (54 % inférieur à la valeur Blim), selon la définition du cadre intégrant l'approche de précaution (AP) établi par le MPO. Des prévisions à court terme relatives au stock ont été effectuées jusqu'en 2020 en supposant que les taux de mortalité varieraient d'environ 20 % par rapport aux valeurs actuelles (moyenne de 2014 à 2016). La projection de la BSR montre un déclin continu jusqu'en 2020 dans la plupart des cas, avec une diminution variant entre 23 % et 58 % (de 2017 à 2020). Le risque que sa valeur soit inférieure à Blim d'ici 2019 varie entre 0,09 et 0,73. D'ici 2020, ce risque varie entre 0,25 et 0,94

Assessing the status of the cod (Gadus morhua) stock in NAFO Subdivision 3Ps in 2018

The status of the cod stock in the Northwest Atlantic Fisheries Organization (NAFO) Subdivision 3Ps was assessed during a Fisheries and Oceans Canada (DFO) Regional Peer Review Process meeting held October 16-17, 2018. Total landings for the 2017-18 management year (April 1-March 31) were 5,031 t or 77% of the Total Allowable Catch (TAC). This marks the eighth consecutive season that the entire TAC has not been taken. Survey abundance and biomass estimates from the DFO research vessel (RV) spring survey were below average during 2016 to 2018. Sentinel gillnet catch rates have been very low and stable since 1999. Sentinel linetrawl catch rates have been below average for the past eight years and the 2017 catch rate was among the lowest in the time series. Spawning stock biomass (SSB) has increased since 2015. In 2018, 71% of the SSB is comprised of ages 6 and 7. Recruitment has generally been at or above the time-series average since 2005, with a particularly strong cohort produced in 2011. Estimated total mortality remains high. Over 2015-17, total mortality averaged 0.61 (54% survival per year); however, the relative contributions of natural and fishing mortality to total mortality are unknown. Projection of the stock to 2021 was conducted assuming mortality rates will be within +/- 20% of current values (2015 to 2017 average). All projections show SSB in 2021 to be lower than SSB in 2018. Where total mortality is assumed to remain at or above current levels, projections indicate that SSB in 2020 and 2021 to be at or below Blim.L’état du stock de morue dans la sous-division 3Ps de l’Organisation des pêches de l’Atlantique Nord-Ouest (OPANO) a fait l’objet d’une évaluation lors d’une réunion du processus régional d’examen par les pairs de Pêches et Océans Canada (MPO) qui s’est tenue les 16 et 17 octobre 2018. Les débarquements totaux de l’année de gestion 2017-2018 (du 1er avril au 31 mars) se chiffraient à 5 031 t, soit 77 % du total autorisé des captures (TAC). Il s’agit de la huitième saison consécutive au cours de laquelle le TAC n’a pas été atteint. Les estimations de l’abondance et de la biomasse obtenues lors des relevés printaniers par navire de recherche du MPO étaient inférieures à la moyenne de 2016 à 2018. Depuis 1999, les taux de prise des pêches sentinelles au filet maillant sont très faibles et stables. Depuis huit ans, les taux de prise des pêches sentinelles à la palangre sont inférieurs à la moyenne. L’année 2017 figure parmi les années où le taux de prise a été le plus faible. La biomasse du stock reproducteur (BSR) a augmenté depuis 2015. En 2018, 71 % de la BSR est composée de poissons âgés de 6 et 7 ans. Le recrutement s’avère généralement supérieur ou égal à la moyenne de la série chronologique depuis 2005, avec une cohorte particulièrement abondante en 2011. Le taux estimé de mortalité totale demeure élevé. Entre 2015 et 2017, la mortalité totale s’élevait à 0,61 en moyenne (taux de survie de 54 % par année); toutefois, les contributions relatives de la mortalité naturelle et de la mortalité par pêche à la mortalité totale sont inconnues. Les prévisions relatives au stock de 2021 ont été effectuées en supposant que les taux de mortalité varieront d’environ 20 % par rapport aux valeurs actuelles (moyenne de 2015 à 2017). Toutes les projections indiquent que la BSR en 2021 sera inférieure à celle de 2018. Lorsque l’on présume que la mortalité totale demeurera égale ou supérieure aux niveaux actuels, les projections indiquent qu’en 2020 et 2021, la BSR sera égale ou inférieure à la valeur Blim

Evaluating the use of the autodiametric method for estimating fecundity of Reinhardtius hippoglossoides, a species with an unusual oocyte development strategy

The autodiametric method is a highly streamlined method for estimating fecundity of fish with determinate oocyte development pattern. Greenland halibut presents a peculiar reproductive strategy with two simultaneously cohorts one of large vitellogenic oocytes (for the current year) and another one of small vitellogenic oocytes (for the subsequent year). Results of this study showed that autodiametric method can be applied to estimate fecundity in Greenland halibut. Additionally, spatial differences in the autodiametric calibration curve were observed in the Northwest Atlantic, but did not translate into differences in fecundity at length. This is the first time that spatial differences between ACCs of the same species have been reported, what could be the result of (i) the unusual oocyte development pattern, or (ii) spatial differences in oocyte biochemistry. More research on the relative dynamics of oocyte cohorts simultaneously present in Greenland halibut ovaries and the factors (endo- or exogenous) influencing oocyte packing density could provide a better understanding of observed geographical differences.S