Search

In this review, we discuss approaches for learning causal structure from data, also called causal discovery. In particular, we focus on approaches for learning directed acyclic graphs and various generalizations which allow for some variables to be unobserved in the available data. We devote special attention to two fundamental combinatorial aspects of causal structure learning. First, we discuss the structure of the search space over causal graphs. Second, we discuss the structure of equivalence classes over causal graphs, i.e., sets of graphs which represent what can be learned from observational data alone, and how these equivalence classes can be refined by adding interventional data., Author(s): Chandler Squires [sup.1], Caroline Uhler [sup.2] Author Affiliations: (1) https://ror.org/042nb2s44, grid.116068.8, 0000 0001 2341 2786, Massachusetts Institute of Technology, , 02139, Cambridge, MA, USA (2) grid.66859.34, 0000 0004 0546 [...]

Trade is a critical component of the U.S. seafood industry's supply and demand. In 2018 total seafood imports were $22.4 billion and total exports were $5.6 billion with a trade deficit of approximately $16.8 billion. Furthermore, imports and re-imports are reported to constitute greater than 85% of domestic seafood consumption. Recognizing the importance of the U.S. seafood trade, an interagency Seafood Trade Task Force, cochaired by the U.S. Department of Commerce and the Office of the United States Trade Representative, was initiated in May of 2020 through the 'Executive Order on Promoting American Seafood Competitiveness and Economic Growth.' The objectives of the Executive Order are to explore policies to improve access to foreign markets, reduce barriers to exports, and more generally to promote seafood trade. Given this recent focus on the seafood trade deficit, we thought it important to describe critical aspects of the deficit. We do this by providing detailed case studies of eight U.S. harvest species categories with large trade flows., Introduction The NMFS Strategic Plan for 2019-2022 (1) identified 'increasing U.S. seafood production and reducing the seafood trade deficit' as one of its challenges that must be addressed. The first [...]

An interdisciplinary team of academics and representatives of fishing fleets and government collaborated to study the emerging requirements for sustainability in Canada's fisheries. Fisheries assessment and management has focused on biological productivity with insufficient consideration of social (including cultural), economic, and institutional (governance) aspects. Further, there has been little discussion or formal evaluation of the effectiveness of fisheries management. The team of over 50 people (i) identified a comprehensive set of management objectives for a sustainable fishery system based on Canadian policy statements, (ii) combined objectives into an operational framework with relevant performance indicators for use in management planning, and (iii) undertook case studies that investigated some social, economic, and governance aspects in greater detail. The resulting framework extends the suite of widely accepted ecological aspects (productivity and trophic structure, biodiversity, and habitat-ecosystem integrity) to include comparable economic (viability and prosperity, sustainable livelihoods, distribution of access and benefits, regional-community benefits), social (health and well-being, sustainable communities, ethical fisheries), and institutional (legal obligations, good governance structure, effective decision-making) aspects of sustainability. This work provides a practical framework for implementation of a comprehensive approach to sustainability in Canadian fisheries. The project also demonstrates the value of co-construction of collaborative research and co-production of knowledge that combines and builds on the strengths of academics, industry, and government. Une equipe interdisciplinaire d'universitaires et de representants gouvernementaux et de flottes de peche a collabore a l'etude des nouvelles exigences en matiere de perennite des ressources halieutiques canadiennes. L'evaluation et la gestion de ces ressources ont mis l'accent sur la productivite biologique en ne tenant pas suffisamment compte d'aspects sociaux (y compris des aspects culturels), economiques et institutionnels (de gouvernance). L'efficacite de la gestion des peches a en outre fait l'objet de tres peu de discussions ou d'evaluations formelles. L'equipe composee de plus de 50 membres a (i) cerne un ensemble exhaustif d'objectifs de gestion pour un systeme de peches perenne reposant sur des enonces de principes canadiens, (ii) regroupe ces objectifs en un cadre operationnel comptant des indicateurs de rendement pertinents a utiliser dans la planification de la gestion et (iii) realise des etudes de cas pour examiner plus en detail certains aspects sociaux, economiques et de gouvernance. Le cadre en decoulant elargit l'ensemble des aspects ecologiques (productivite et structure trophique, biodiversite et integrite des habitats et ecosystemes) largement acceptes pour y inclure des aspects economiques (viabilite et prosperite, moyens de subsistance durables, repartition de l'acces et des benefices, avantages pour les regions-collectivites), sociaux (sante et bien-etre, collectivites durables, peches ethiques) et institutionnels (obligations legales, structure de bonne gouvernance, processus decisionnel efficace) comparables de la perennite. Ces travaux fournissent un cadre pratique pour la mise en oeuvre d'une approche integree visant la perennite des ressources halieutiques canadiennes. Le projet demontre egalement la valeur de la construction collective de recherches collaboratives et de la production collective de connaissances qui mettent en commun les forces des universitaires, de l'industrie et des gouvernements. [Traduit par la Redaction], Introduction Canada's legislation and international commitments require attention to ecological, social (including cultural), economic, and institutional (governance) aspects of fisheries. The Federal Sustainable Development Strategy (ECCC 2016), which, along with [...]

In 2010, more than 20 associations representing harvesters from five provinces bordering the range of American lobster (Homarus americanus) in Canada, from the Gulf of Maine to southern Labrador, joined government research scientists at Fisheries and Oceans Canada (and one provincial department) and researchers from Canadian universities (two English- and four French-speaking) to establish the Lobster Node. This partnership was formed to address knowledge gaps on lobster productivity, stock structure, and connectivity through collaborative research under the auspices of the Canadian Fisheries Research Network (CFRN), which was funded by the Natural Sciences and Engineering Research Council of Canada. In so doing, the research partners overcame barriers of geography, language, culture, education, and, in some cases, longstanding disputes around management and conservation measures. This paper reviews why and how the Lobster Node was formed, what it achieved scientifically, what benefits (and challenges) it provided to the partners, and why it succeeded. It concludes by advocating for the creation of a permanent collaborative platform to conduct research in support of lobster fisheries in Canada. En 2010, plus de 20 associations representant des pecheurs de cinq provinces bordant l'aire de distribution du homard Americain (Homarus americanus) au Canada, du Golfe du Maine au sud du Labrador, se sont joints a des chercheurs gouvernementaux au Ministere des Peches et Oceans Canada (et un ministere provincial) et des chercheurs d'universites canadiennes (deux anglophones et quatre francophones) pour etablir le Groupe Homard. Ce partenariat fut forme afin de combler des lacunes de connaissances au niveau de la productivite, de la structure et de la connectivite des stocks de homard par l'entremise de recherche collaborative sous les auspices du Reseau canadien de recherche sur la peche (RCRP), finance par le Conseil de recherches en sciences naturelles et en genie du Canada. Ce faisant, les partenaires ont du surmonter des obstacles lies a la geographie, la langue, la culture, l'education et, dans certains cas, des differends historiques autour des mesures de gestion et de conservation. Cet article explique pourquoi et comment le Groupe Homard a ete forme, ce qu'il a accompli scientifiquement, quels avantages (et defis) il a donnes aux partenaires, et pourquoi cette initiative fut couronnee de succes. Nous concluons en plaidant pour la creation d'une plate-forme collaborative permanente pour mener des recherches en appui a la peche au homard au Canada., Introduction It has been argued that Canada does not invest sufficient resources in research on the American lobster (Homarus americanus; hereinafter lobster), considering the species' socioeconomic importance to the country [...]

The Cambrian Tally Pond volcanic belt in central Newfoundland contains numerous volcanogenic massive sulphide (VMS) deposits and prospects associated with exhalative metalliferous mudstones. Deposits in the belt are bimodal felsic VMS eposits that are both base metal bearing (e.g., Duck Pond-Boundary), and base metaland precious metal bearing (Lemarchant). At the Lemarchant deposit, metalliferous mudstones are stratigraphically and genetically associated with mineralization. In the remainder of the Tally Pond belt, detrital shales occur predominantly in the northeastern part of the belt (mostly as unrelated mid-Ordovician structural blocks) in the upper sections of the Cambrian volcanic stratigraphy, but locally also are intercalated with metalliferous mudstones. Their relationships to massive sulphides are less obvious, with many spatially, but not necessarily genetically, related to mineralization. Upper Cambrian to Lower Ordovician black shales from Bell Island, which represent pelagic sedimentation not associated with hydrothermal activity and volcanism, are compared with the Tally Pond belt mudstones and shales. Exhalative mudstones, like those at Lemarchant, have elevated Fe/Al and base-metal values, and have shale-normalized negative Ce and positive Eu anomalies, indicative of deposition from high-temperature (>250°C) hydrothermal fluids within an oxygenated water column. Mudstones and shales sampled from other Tally Pond prospects have more variable signatures, ranging from hydrothermal to nonhydrothermal black shales (no positive Eu anomalies, flat rare earth element patterns, low Fe/Al and base-metal contents), to those that have mixed signatures. Accordingly, mudstones from areas with a Lemarchant-like hydrothermal and vent-proximal character are more attractive exploration targets than mudstones and shales with predominantly detrital signatures. La ceinture volcanique cambrienne de Tally Pond, dans le centre de Terre-Neuve, renferme de nombreux gisements et prospects de sulfures massifs volcanogenes (SMV) associes a des mudstones metalliferes exhalatifs. Les gisements dans cette ceinture sont des gisements SMV bimodaux felsiques qui contiennent, d'une part, des metaux de base (p. ex. Duck Pond Boundary) et, d'autre part, des metaux de base et des metaux precieux (Lemarchant). Au gisement de Lemarchant, des mudstones metalliferes sont associes stratigraphiquement et genetiquement a la mineralisation. Dans le reste de la ceinture de Tally Pond, des shales detritiques sont presents principalement dans la partie nord-est de la ceinture (surtout sous forme de blocs structuraux non associes d'age ordovicien moyen) dans les sections superieures de la stratigraphie volcanique cambrienne, mais sont egalement intercales par endroits avec des mudstones metalliferes. Leurs liens avec les sulfures massifs sont moins evidents, bon nombre etant relies dans l'espace, mais pas necessairement genetiquement, a une mineralisation. Des shales noirs d'age cambrien superieur a ordovicien inferieur de Tile Bell, qui representent une sedimentation pelagique non associee a de l'activite hydrothermale ou du volcanisme, sont compares aux mudstones et shales de la ceinture de Tally Pond. Les mudstones exhalatifs, comme ceux du gite de Lemarchant, presentent des valeurs de Fe/Al et de metaux de base elevees et des anomalies de Ce negatives et d'Eu positives normalisees aux valeurs de shales, refletant une precipitation a partir de fluides hydrothermaux de haute temperature (>250°C) dans une colonne d'eau oxygenee. Les mudstones et shales preleves d'autres prospects de la ceinture de Tally Pond ont des signatures plus variables allant de shales noirs hydrothermaux a non hydrothermaux (pas d'anomalie d'Eu positive, spectres de terres rares plats, faibles valeurs de Fe/Al et de metaux de base) a des signatures hybrides. Les mudstones de zones presentant un caractere hydrothermal et proximal aux cheminees s'apparentant a celui du gite de Lemarchant constituent des cibles d'exploration plus interessantes que les mudstones et shales caracterises par des signatures principalement detritiques. [Traduit par la Redaction], Introduction Exhalative metalliferous mudstones and detrital shales are abundant in the Tally Pond volcanic belt, central Newfoundland Appalachians, and are spatially and (or) genetically associated with numerous massive sulphide deposits, [...]

Disease outbreaks in resource-limited or remote areas pose unique challenges to outbreak responses. These challenges are exemplified by the ongoing Ebola virus (EBOV) outbreak in West Africa that began in [...]

Are we going to have a white Christmas? That is a question that scientists at the National Oceanic and Atmospheric Administration (NOAA) receive each autumn from members of the media [...]

ABSTRACT This paper describes a new snowfall index that quantifies the impact of snowstorms within six climate regions in the United States. The regional snowfall index (RSI) is based on [...]

The Late Cretaceous marine gastropod Sycodes glabra (Shumard, 1858) from the northeast Pacific has been poorly known because the type, which was never figured, was lost in a fire in 1892, and the type locality was very poorly located. A neotype is selected from specimens collected by the early Canadians, geologist J. Richardson and eminent British Columbian naturalist Dr. C.F. Newcombe. Newly discovered material, as well as museum specimens, provide fundamental geologic and paleontologic information. The number of available specimens is 19, and nearly all are from submarine-fan deposits in the Upper Cretaceous Nanaimo Group exposed along the southeastern-coastal region of Vancouver Island, British Columbia, and on Big Sucia Island, northwestern Washington State, with nearly half of the specimens from the latter locale. A single specimen is from northern California. This present study better establishes the type locality for S. glabra and documents this name as the senior subjective synonym of ?Ficus cypraeoides Gabb, 1864. The geologic range of S. glabra is early Campanian (Submortoniceras chicoense ammonite Zone) to early late Campanian (Metaplacenticeras cf. pacificum ammonite Zone). Sycodes seems to be a monotypic genus, but Pyrula (Protopirula) capensis Rennie, 1930, from mid-Santonian to lower Campanian strata in South Africa, might be congeneric. Sycodes is questionably assigned herein to the family Ficidae Meek, 1864, and could be the earliest known ficid. Le gasteropode marin Sycodes glabra (Shumard, 1858) du Cretace tardif du nord-est du bassin Pacifique etait meconnu etant donne que le type, qui n'avait jamais ete figure, s'est perdu dans un incendie en 1892, et que l'emplacement precis de la localite-type etait tres mal situe. Un neotype est selectionne parmi des specimens preleves par des Canadiens de la premiere heure, le geologue J. Richardson et l'eminent naturaliste britanno-colombien C.F. Newcombe. Du materiau decouvert recemment, ainsi que des specimens de musee, fournissent de renseignements geologiques et paleontologiques fondamentaux. Dix-neuf specimens sont disponibles, dont la presque totalite provient de depots de cone alluvial dans le Groupe de Nanaimo du Cretace superieur, exposes dans la region cotiere du sud-est de l'ile de Vancouver (Colombie-Britannique) et dans la grande ile Sucia, dans le nord-ouest de l'Etat de Washington, cette derniere localite ayant fourni pres de la moitie des specimens. Un unique specimen provient du nord de la Californie. L'etude permet de mieux etablir la localite-type pour S. glabra et determine que ce nom est le synonyme subjectif senior de ?Ficus cypraeoides Gabb, 1864. L'etendue stratigraphique de S. glabra va du Campanien precoce (zone a ammonite Submortoniceras chicoense) au debut de Campanien tardif (zone a ammonite Metaplacenticeras cf. pacificum). Sycodes semble etre un genre monotypique, mais Pyrula (Protopirula) capensis Rennie, 1930, de strates du milieu du Santonien au Campanien inferieur en Afrique du Sud, pourrait etre congenere. Sycodes est affecte sous reserve a la famille des Ficides Meek, 1864, et pourrait representer le plus ancien ficide connu. [Traduit par la Redaction], Introduction Marine gastropods from the Upper Cretaceous Nanaimo Group in the Vancouver Island area of British Columbia, Canada, are understudied. This present paper provides sorely needed, new fundamental paleontologic and [...]

Similarities between lambda and rRNA transcription antitermination have led to suggestions that they involve the same Nus factors. However, direct in vivo confirmation that rRNA antitermination requires all of the lambda Nus factors is lacking. We have therefore analyzed the in vivo role of NusB and NusG in rRNA transcription antitermination and have established that both are essential for it. We used a plasmid test system in which reporter gene mRNA was measured to monitor rRNA antiterminator-dependent bypass of a Rhodependent terminator. A comparison of terminator read-through in a wild-type Escherichia coli strain and that in a nusB::IS10 mutant strain determined the requirement for NusB. In the absence of NusB, antiterminator-dependent terminator read-through was not detected, showing that NusB is necessary for rRNA transcription antitermination. The requirement for NusG was determined by comparing rRNA antiterminator-dependent terminator read-through in a strain overexpressing NusG with that in a strain depleted of NusG. In NusG-depleted cells, termination levels were unchanged in the presence or absence of the antiterminator, demonstrating that NusG, like NusB, is necessary for rRNA transcription antitermination. These results imply that NusB and NusG are likely to be part of an RNA-protein complex formed with RNA polymerase during transcription of the rRNA antiterminator sequences that is required for rRNA antiterminator-dependent terminator read-through.

Research has been conducted on the growth rate-independent rrn P1 promoter mutants. The ability of these mutants to respond to the changes in rrn gene dosage has been tested.

Background: Previous epidemiological studies have been suggestive but inconclusive in demonstrating inverse associations of calcium, vitamin D, dairy product intakes with risk of colorectal cancer (CRC). We conducted a large population-based comparison of such associations in Newfoundland and Labrador (NL) and Ontario (ON). Methods: A case control study design was used. Colorectal cancer cases were new CRC patients aged 20-74 years. Controls were a sex and age-group matched random sample of the population in each province. 1760 cases and 2481 controls from NL and ON were analyzed. Information on dietary intake and lifestyle was collected using self-administered food frequency and personal history questionnaires. Results: Controls reported higher mean daily intakes of total calcium and total vitamin D than cases in both provinces. In ON, significant reduced CRC risk was associated with intakes of total calcium (OR of highest vs. lowest quintiles was 0.57, 95% CI 0.42-0.77, [p.sub.trend]=0.03), total vitamin D (OR=0.73, 95% CI 0.54-1.00), dietary calcium (OR=0.76, 95% CI 0.60-0.97), dietary vitamin D (OR=0.77, 95% CI 0.61-0.99), total dairy products and milk (OR=0.78, 95% CI 0.60-1.00), calcium-containing supplements use (OR=0.76). In NL, the inverse associations of calcium, vitamin D with CRC risk were most pronounced among calcium- or vitamin D-containing supplement users (OR=0.67, 0.68, respectively). Conclusions: Results of this study add to the evidence that total calcium, dietary calcium, total vitamin D, dietary vitamin D, calcium- or vitamin D-containing supplement use may reduce the risk of CRC. The inverse associations of CRC risk with intakes of total dairy products and milk may be largely due to calcium and vitamin D. Key words: Calcium; vitamin D; dairy products; colorectal cancer Contexte : Des etudes epidemiologiques anterieures, bien que peu concluantes, donnent a penser que les apports en calcium, en vitamine D et en produits laitiers sont inversement associes au risque de cancer colorectal (CCR). Nous avons mene une vaste comparaison populationnelle de telles associations a Terre-Neuve-et-Labrador (T.-N.-L.) et en Ontario. Methode : Nous avons utilise un plan d'etude cas/temoins. Nos cas de cancer colorectal etaient des patients nouvellement atteints de CCR ages de 20 a 74 ans. Nos temoins etaient un echantillon aleatoire de la population de chaque province, assortis selon le sexe et le groupe d'age. Nous avons analyse 1 760 cas et 2 481 temoins de T.-N.-L. et de l'Ontario. Des renseignements sur leurs apports alimentaires et leurs modes de vie ont ete recueillis au moyen de questionnaires autoadministres sur la frequence de consommation des produits alimentaires et les antecedents personnels. Resultats : Dans les deux provinces, les temoins ont declare des apports moyens quotidiens plus eleves en calcium total et en vitamine D totale. En Ontario, un risque de CCR significativement reduit etait associe aux apports en calcium total (RC des quintiles superieur et inferieur = 0,57, IC de 95% = 0,42-0,77, P=0,03), en vitamine D totale (RC=0,73, IC de 95% = 0,541,00), en calcium alimentaire (RC=0,76, IC de 95% = 0,60-0,97), en vitamine D alimentaire (RC=0,77, IC de 95% = 0,61-0,99), en lait et produits laitiers totaux (RC=0,78, IC de 95% = 0,60-1,00) et a la consommation de supplements contenant du calcium (RC=0,76). A T.-N.-L., les associations inverses entre le calcium, la vitamine D et le risque de CCR etaient plus prononcees chez les consommateurs de supplements contenant du calcium ou de la vitamine D (RC=0,67, 0,68, respectivement). Conclusion : Les resultats de cette etude tendent a confirmer que le calcium total, le calcium alimentaire, la vitamine D totale, la vitamine D alimentaire et la consommation de supplements contenant du calcium ou de la vitamine D peuvent reduire le risque de CCR. Les associations inverses entre le risque de CCR et les apports en lait et produits laitiers totaux pourraient s'expliquer dans une large mesure par le calcium et la vitamine D. Mots cles : calcium; vitamine D; produits laitiers; tumeurs colorectales, Diet has long been regarded as one of the most important environmental factors associated with colorectal cancer (CRC). (1) Since 1980 when Garland and Garland proposed that the inverse association [...]

Controlling the complex spatio-temporal dynamics underlying life-threatening cardiac arrhythmias such as fibrillation is extremely difficult, because of the nonlinear interaction of excitation waves in a heterogeneous anatomical substrate (1-4). In the absence of a better strategy, strong, globally resetting electrical shocks remain the only reliable treatment for cardiac fibrillation (5-7). Here we establish the relationship between the response of the tissue to an electric field and the spatial distribution of heterogeneities in the scale-free coronary vascular structure. We show that in response to a pulsed electric field, E, these heterogeneities serve as nucleation sites for the generation of intramural electrical waves with a source density ρ(E) and a characteristic time, τ, for tissue depolarization that obeys the power law τ [varies] [E.sup.α]. These intramural wave sources permit targeting of electrical turbulence near the cores of the vortices of electrical activity that drive complex fibrillatory dynamics. We show in vitro that simultaneous and direct access to multiple vortex cores results in rapid synchronization of cardiac tissue and therefore, efficient termination of fibrillation. Using this control strategy, we demonstrate low-energy termination of fibrillation in vivo. Our results give new insights into the mechanisms and dynamics underlying the control of spatio-temporal chaos in heterogeneous excitable media and provide new research perspectives towards alternative, life-saving low-energy defibrillation techniques., Spatially extended non-equilibrium systems display spatio-temporal dynamics that can range from ordered to turbulent. Controlling such systems is one of the central problems in nonlinear science and has far-reaching technological [...]