The excessive and unsustainable exploitation of our marine resources has led to the promotion of marine reserves as a fisheries management tool. Marine reserves, areas in which fishing is restricted or prohibited, can offer opportunities for the recovery of exploited stock and fishery enhancement. This study examines the impact of the creation of marine protected areas, from both economic and biological perspectives. The consequences of reserve establishment on the long-run equilibrium fish biomass and fishery catch levels are evaluated. We include (...) reserve size as control variable to maximize catch at equilibrium. A continuous time model is used to simulate the effects of reserve size on fishing catch. Fish movements between the sites is assumed to take place at a faster time scale than the variation of the stock and the change of the fleet size. We take advantage of these two time scales to derive a reduced model governing the dynamics of the total fish stock and the fishing effort. Simulation results suggest that the establishment of a protected marine reserve will always lead to an increase in total fish biomass, an optimal size of a marine reserve can achieve to maximize the catch at equilibrium. (shrink)

Steven Vogel and Albert Borgmann have much in common. Both thinkers agree we collectively and materially build our environment. Both also believe communal discussion is essential for constructing better environments. Yet Borgmann does not hesitate to speak of “eloquent things,” while Vogel insists on nature’s silence. This essay examines that disagreement, arguing Vogel’s position is made stronger by the inclusion of what Borgmann calls “deictic discourse.” Such discourse testifies to the goodness of things, but without being either straightforward first-person speech, (...) or the kind of ventriloquism that worries Vogel. Deictic discourse does not eschew responsibility; it accepts a deep responsibility not only for the practices it advocates, but for the wellbeing of its subject. The essay concludes by arguing deictic discourse plays a crucial and ineliminable role in the type of transparent conversations about practice Vogel promotes. (shrink)

Falsafat wa-ḥayāt Abī Hāshim al-Jubbāʼī wa-madrasatuh -- al-Tawallud ʻinda al-Muʻtazilah.

The usual definition of (non-contextual) hidden variables is found to be too restrictive, in the sense that, according to it, even some classical systems do not admit hidden variables. A more general concept is introduced and the term “approximate hidden variables” is used for it. This new concept avoids the aforementioned problems, since all classical systems admit approximate hidden variables. Standard quantum systems do not admit approximate hidden variables, unless the corresponding Hilbert space is 2-dimensional. However, an appropriate non-standard quantum (...) system, which arises by focussing on momentum and position and neglecting the remaining observables, admits approximate hidden variables. Systems associated with JBW-algebras (resp. von Neumann algebras) and satisfying some mild conditions admit approximate hidden variables iff they are classical, that is, iff the corresponding JBW-algebra (resp. von Neumann algebra) is associative (resp. commutative). (shrink)

In this article we, given a free ultrafilter p on ω, consider the following classes of ultrafilters:(1) T(p) - the set of ultrafilters Rudin-Keisler equivalent to p,(2) S(p)={q ∈ ω*:∃ f ∈ ω ω , strictly increasing, such that q=f β (p)},(3) I(p) - the set of strong Rudin-Blass predecessors of p,(4) R(p) - the set of ultrafilters equivalent to p in the strong Rudin-Blass order,(5) P RB (p) - the set of Rudin-Blass predecessors of p, and(6) P RK (p) (...) - the set of Rudin-Keisler predecessors of p,and analyze relationships between them. We introduce the semi-P-points as those ultrafilters p ∈ ω* for which P RB (p)=P RK (p), and investigate their relations with P-points, weak-P-points and Q-points. In particular, we prove that for every semi-P-point p its α-th left power α p is a semi-P-point, and we prove that non-semi-P-points exist in ZFC. Further, we define an order ⊴ in T(p) by r⊴q if and only if r ∈ S(q). We prove that (S(p),⊴) is always downwards directed, (R(p),⊴) is always downwards and upwards directed, and (T(p),⊴) is linear if and only if p is selective.We also characterize rapid ultrafilters as those ultrafilters p ∈ ω* for which R(p)∖S(p) is a dense subset of ω*.A space X is M-pseudocompact (for ) if for every sequence (U n ) n < ω of disjoint open subsets of X, there are q ∈ M and x ∈ X such that x=q-lim (U n ); that is, for every neighborhood V of x. The P RK (p)-pseudocompact spaces were studied in [ST].In this article we analyze M-pseudocompactness when M is one of the classes S(p), R(p), T(p), I(p), P RB (p) and P RK (p). We prove that every Frolik space is S(p)-pseudocompact for every p ∈ ω*, and determine when a subspace with is M-pseudocompact. (shrink)

carrington places race and racism at the center of his densely written analysis of science fiction, fantasy, utopia, and other forms of popular culture. He moves easily between a broad range of forms, which include memoirs, television series, comic books, novels, novelizations, fandom and fanzines, and short fiction and fiction circulated on the Internet. Popular culture helps us to construct notions of identity and race, and for carrington many constituent groups, notably fans, develop its key concepts and values.Speculative fiction is (...) for carrington a framework that links these various forms of popular culture. Here, SF is a genre different from literature, as it is situated closer to, and is more deeply... (shrink)

In lieu of an abstract, here is a brief excerpt of the content: Classics and Complexity in Walden’s “Spring” M. D. USHER In 1843, two years before Henry Thoreau built his cabin at Walden Pond, the Fitchburg Railroad laid down tracks through the woods near the Pond for its line connecting Boston to Fitchburg. The original Fitchburg Line, at 54 miles long, was, until 2010, the longest run in the present -day MBTA Commuter Rail system. And it is one of (...) the oldest railways in New England. By 1900, fortunes swelled and the Fitchburg’s Hoosac Tunnel Line took passengers and goods westward toward Chicago. The Lake Champlain Route connected Boston to points north like Burlington, Vermont. (See Figure 1.) arion 27.1 spring/summer 2019 Figure 1 (left): Advertisement for the Hoosac Tunnel Route in The New England Magazine (Vol. 21, Issue 6, February, 1900). Figure 2 (right): Herbert Wendell Gleason. The Fitchburg Railroad and Walden Pond in winter, Concord, Mass., March 24, 1920. Courtesy Concord Free Public Library. The Railroad was literally a fixture in Thoreau’s landscape. Its tracks pass remarkably close to Walden Pond (Figure 2), and the Fitchburg Line—both its reality and the specter of it—is practically a character in his writing: “I usually go to the village along its causeway, and am, as it were, related to society by this link,” Thoreau writes in “Sounds,” a chapter of Walden that contains what must be one of the most picturesque odes (or laments) to rail travel and commerce in all of American literature: The engine’s whistle, Thoreau complains, pierces the still silence of his idyllic retreat like a screaming hawk circling a farmer’s field, its billows of steam an ominous harbinger of “this travelling demi-god, this cloud-compeller.”1 Thoreau’s frequent, customary walks into Concord along the railroad tracks took him through a heavily excavated stretch of the line known as the Deep Cut, to which he returned again and again each year in early spring, even after leaving the cabin, to observe and to record his observations. The leaf-shaped sand flows and trickling surface erosion caused by melting frost in the banks of the Deep Cut are elaborately described in Thoreau’s chapter in Walden entitled “Spring,” what Laurence Buell calls the “high point of Thoreau’s epic.”2 And yet, in spite of the universal acclaim of this passage as a literary tour de force, it has not received the full attention it deserves. What warrants fresh consideration first and foremost is “Spring”’s deep-rootedness in classical sources. Many classical influences, allusions, and a good deal of etymological word play have gone so far unnoticed. The chapter is also important because it describes, by intimation, what contemporary scientists now call emergence. Emergent phenomena are properties or behaviors that arise in systems as a result of complex, dynamic interactions amongst constituent parts, including changes to a system brought about by human interventions3—not only, e.g., climate change and wildfires, but also traffic patterns and terrorist networks; kidney function in the body; the rings of Saturn. As he tries to capture the essence of the 114 classics and complexity in WALDEN’s “spring” Deep Cut and interpret its significance, Thoreau adumbrates this concept, but also grapples ingeniously with broader issues of perennial concern—the relationship of Nature to Culture, for example, of Wilderness to Civilization, of Science to the Humanities—making “Spring” not only a probing work of eco-criticism and environmental philosophy, but of scientific reflection and poetic experiment as well. In short, Thoreau’s “Spring” is that rare work of classical reception that transmits both literary and scientific insight. Perhaps at this point, in lieu of accolades, it is best to let Thoreau start speaking for himself. What I offer in the following pages is a commentary on the Deep Cut passage from “Spring.” Classical references and aspects of systems theory will be explained and contextualized as they emerge, as it were, from Thoreau’s text. The whole chapter corresponds to pages 289–308 in Cramer’s edition of Walden—26 paragraphs all told, of which only the relevant ones are printed and annotated here. (Transitions and extraneous material are briefly summarized, as needed, in paraphrase... (shrink)

Kalam philosophy, theological thought in Islam on postmodernism.

On various principles of economics in an Islamic society.

Após a obrigatoriedade da educação sexual (ES) nas escolas portuguesas em 2009, pretendemos conhecer que perspectiva têm os professores ( N = 307) sobre a ES. Através de um questionário on-line , analisado através de estatística descritiva e de análise factorial e inferencial, avaliámos as atitudes ..