794 resultados para Continuity of attractors
Resumo:
The impact of recent changes in climate on the arctic environment and its ecosystems appear to have a dramatic affect on natural populations (National Research Council Committee on the Bering Sea Ecosystem 1996) and pose a serious threat to the continuity of indigenous arctic cultures that are dependent on natural resources for subsistence (Peterson D. L., Johnson 1995). In the northeast Pacific, winter storms have intensified and shifted southward causing fundamental changes in sea surface temperature patterns (Beamish 1993, Francis et al. 1998). Since the mid 1970’s surface waters of the central basin of the Gulf of Alaska (GOA) have warmed and freshened with a consequent increase in stratification and reduced winter entrainment of nutrients (Stabeno et al. 2004). Such physical changes in the structure of the ocean can rapidly affect lower trophic levels and indirectly affect fish and marine mammal populations through impacts on their prey (Benson and Trites 2002). Alaskan natives expect continued and perhaps accelerating changes in resources due to global warming (DFO 2006).and want to develop strategies to cope with their changing environment.
Resumo:
Since the commencement of the exploitation of oceanic tuna resources of the Indian Ocean seventeen years ago, the hooked rates for the tuna species have declined in many areas of the Ocean but there are no evidences of such a trend in the case of the sharks. As a result, the percentage composition of sharks in the longline catches and the percentage of the tuna catch damaged by sharks show an increase. Hence there is an urgent need for innovation of the existing longline gear in order to increase the fishing efficiency for hooking the tuna species with a corresponding reduction in its efficiency for hooking sharks. At the beginning of this fishery, hooked sharks were discarded at sea, at a later stage the liver and fins were taken and the carcass discarded and presently the sharks are also brought along with the tuna catch. Though the shark meat has a very low market value it is brought in order to cover up for the declining tuna catches. Thus it has become very necessary to increase the demand for shark meat by developing products or by-products utilizing shark meat and ensuring the successful continuity of the tuna longline fishery. The pattern of distribution of shark species in the time grounds of the Pacific, Indian and Atlantic Oceans and also the predation of hooked tunas by sharks were discussed earlier (Sivasubranianiam 1963, 1964 and 1966). Some contribution to these studies is made in this paper based on new data become available.
Resumo:
East Asia is one of the few regions in the world where a large number of human fossils have been unearthed. The continuity of hominid fossils in East Asia, particularly in China has been presented as strong evidence supporting an independent origin of mod
Resumo:
In most recent substructuring methods, a fundamental role is played by the coarse space. For some of these methods (e.g. BDDC and FETI-DP), its definition relies on a 'minimal' set of coarse nodes (sometimes called corners) which assures invertibility of local subdomain problems and also of the global coarse problem. This basic set is typically enhanced by enforcing continuity of functions at some generalized degrees of freedom, such as average values on edges or faces of subdomains. We revisit existing algorithms for selection of corners. The main contribution of this paper consists of proposing a new heuristic algorithm for this purpose. Considering faces as the basic building blocks of the interface, inherent parallelism, and better robustness with respect to disconnected subdomains are among features of the new technique. The advantages of the presented algorithm in comparison to some earlier approaches are demonstrated on three engineering problems of structural analysis solved by the BDDC method.
Resumo:
The details of the Element Free Galerkin (EFG) method are presented with the method being applied to a study on hydraulic fracturing initiation and propagation process in a saturated porous medium using coupled hydro-mechanical numerical modelling. In this EFG method, interpolation (approximation) is based on nodes without using elements and hence an arbitrary discrete fracture path can be modelled.The numerical approach is based upon solving two governing partial differential equations of equilibrium and continuity of pore water simultaneously. Displacement increment and pore water pressure increment are discretized using the same EFG shape functions. An incremental constrained Galerkin weak form is used to create the discrete system of equations and a fully implicit scheme is used for discretization in the time domain. Implementation of essential boundary conditions is based on the penalty method. In order to model discrete fractures, the so-called diffraction method is used.Examples are presented and the results are compared to some closed-form solutions and FEM approximations in order to demonstrate the validity of the developed model and its capabilities. The model is able to take the anisotropy and inhomogeneity of the material into account. The applicability of the model is examined by simulating hydraulic fracture initiation and propagation process from a borehole by injection of fluid. The maximum tensile strength criterion and Mohr-Coulomb shear criterion are used for modelling tensile and shear fracture, respectively. The model successfully simulates the leak-off of fluid from the fracture into the surrounding material. The results indicate the importance of pore fluid pressure in the initiation and propagation pattern of fracture in saturated soils. © 2013 Elsevier Ltd.
Resumo:
Thin poly(3-butylthiophene) (P3BT) film composed of aligned lamellae attached to the edge of the original film has been achieved via a controlled solvent vapor treatment (C-SVT) method. The polarized optical microscopy operated at both single-polarization and cross-polarization modes has been used to investigate the alignment of the fiber-like lamellae. A numerical simulation method is used to quantitatively calculate angle distributions of the lamellae deviated from the film growth direction. Prepatterned P3BT film edge acts as nuclei which densely initialize subsequent crystal growth by exhausting the materials transported from the partially dissolved film. The growth of new film upon crystallization is actually a self-healing process where the two-dimensional geometric confinement is mainly responsible for this parallel alignment of P3BT crystals. The solvent vapor pressure should be carefully chosen so as to induce crystal growth but avoid liquid instability which will destroy the continuity of the film.
Resumo:
The ZnO/TiO2 core/shell structure was formed through deposition of a TiO2 coating layer on the hydrothermally fabricated ZnO nanorod arrays through radio frequency magnetron sputtering. The effects of the TiO2 shell's characteristics on the current-voltage behaviors of the core/shell-based dye-sensitized solar cells (CS-DSSC) were investigated. As the rates of injection, transfer, and recombination of electrons of such CS-DSSC were affected significantly by the crystallization, morphology, and continuity of the TiO2 shells, the photovoltaic efficiency was accordingly varied remarkably. In addition, the efficiency was further improved by enhancing the surface area in the core/shell electrode.
Resumo:
This study investigates the meanings and significance of the seventh-day Sabbath for worship in the Seventh-day Adventist Church. In recent years, both the day and concept of Sabbath have attracted ecumenical attention, but the focus of scholarship has been placed on Sunday as the Lord's Day or Sabbath with little consideration given to the seventh-day Sabbath. In contrast, this project examines the seventh-day Sabbath and worship on that day from theological, liturgical, biblical and historical perspectives. Although not intended as an apology for Seventh-day Adventist practices, the work does strive to promote a critical and creative conversation with other theological and liturgical traditions in order to promote mutual, ecumenical understanding. Historical research into the origins and nature of the principal day for weekly Christian worship provides a starting point for discussion on Sabbath. Reconsideration of the relationship between Judaism and early Christianity in recent studies suggests that the influence of Judaism lasted longer than previously supposed, thereby prolonging the developmental process of Sabbath (seventh day) to Sunday. A possible coexistence of Sabbath and Sunday in early Christianity offers an alternative to perspectives that dichotomize Sabbath and Sunday from Christian antiquity onward, and thus for the Seventh-day Adventist Church, suggests biblical and historical validity for their Sabbath worship practice. Recent theological perspectives on Sabbath and Sunday are examined, particularly those of Karl Barth, Jürgen Moltmann and Pope John Paul II. While all three of these theologians stress the continuity of Sabbath and Sunday and speak mainly to a theology of Sunday, they do highlight the significance of Sabbath—which is relevant to an interpretation of seventh-day Sabbath worship. The study concludes that the seventh-day Sabbath is significant for worship in the Seventh-day Adventist Church because it symbolizes the relationship between God and human beings, reminds humanity of the creating and redeeming God who acts in history, and invites persons to rest and fellowship with God on a day sanctified by God.
Resumo:
In this paper, two methods for constructing systems of ordinary differential equations realizing any fixed finite set of equilibria in any fixed finite dimension are introduced; no spurious equilibria are possible for either method. By using the first method, one can construct a system with the fewest number of equilibria, given a fixed set of attractors. Using a strict Lyapunov function for each of these differential equations, a large class of systems with the same set of equilibria is constructed. A method of fitting these nonlinear systems to trajectories is proposed. In addition, a general method which will produce an arbitrary number of periodic orbits of shapes of arbitrary complexity is also discussed. A more general second method is given to construct a differential equation which converges to a fixed given finite set of equilibria. This technique is much more general in that it allows this set of equilibria to have any of a large class of indices which are consistent with the Morse Inequalities. It is clear that this class is not universal, because there is a large class of additional vector fields with convergent dynamics which cannot be constructed by the above method. The easiest way to see this is to enumerate the set of Morse indices which can be obtained by the above method and compare this class with the class of Morse indices of arbitrary differential equations with convergent dynamics. The former set of indices are a proper subclass of the latter, therefore, the above construction cannot be universal. In general, it is a difficult open problem to construct a specific example of a differential equation with a given fixed set of equilibria, permissible Morse indices, and permissible connections between stable and unstable manifolds. A strict Lyapunov function is given for this second case as well. This strict Lyapunov function as above enables construction of a large class of examples consistent with these more complicated dynamics and indices. The determination of all the basins of attraction in the general case for these systems is also difficult and open.
Resumo:
This thesis focuses on two Western European cinematic cities, and two unique periods of their respective nations’ histories, in a bid to “locate” the transnational within a contemporary European milieu. I argue that my geo-cinematic case studies are emblematic of broader questions of the problematics of national identity in contemporary Europe in the face of cross-national flows yet, as a result of their representations as cities both “anchored” and “in flux”, they reject a European postnational identity. Through its engagement with cinematic Rome as the “Eternal City” of Europe and cinematic Dublin as the “newly Europeanised” city, my thesis traces how representations and aesthetics of the urban spaces of these two cities correspond with the tensions at the heart of the respective eras in question. Via the figures that inhabit it, navigate it and search for it, the city is utilised to highlight fixity and mobility, centrality and dislocation, in explicit and implicit ways, amid the rapidly changing landscape of its national terrain. It is through my analyses of the filmed places and sociopolitical, socioeconomic and sociocultural spaces of these capital cities under the rubric of the transnational that this research demonstrates the “pluralities” of the construct in its cinematic manifestations. It is also my aim to evaluate the concept of cinematic transnationalism when identifying and accounting for representations of a specific national, historical timeframe, when the momentousness of the changes that occur is not bound by the national, but rather is reflective of the influence of both domestic and external forces. To this end, my thesis draws attention to instances in which the nation is shown to persist and resist dilution, arguing that it is only against the backdrop and continuity of the nation (in its evershifting guises) that the transnational can be conceived in representative and aesthetic terms.
Variation in use of surveillance colonoscopy among colorectal cancer survivors in the United States.
Resumo:
BACKGROUND: Clinical practice guidelines recommend colonoscopies at regular intervals for colorectal cancer (CRC) survivors. Using data from a large, multi-regional, population-based cohort, we describe the rate of surveillance colonoscopy and its association with geographic, sociodemographic, clinical, and health services characteristics. METHODS: We studied CRC survivors enrolled in the Cancer Care Outcomes Research and Surveillance (CanCORS) study. Eligible survivors were diagnosed between 2003 and 2005, had curative surgery for CRC, and were alive without recurrences 14 months after surgery with curative intent. Data came from patient interviews and medical record abstraction. We used a multivariate logit model to identify predictors of colonoscopy use. RESULTS: Despite guidelines recommending surveillance, only 49% of the 1423 eligible survivors received a colonoscopy within 14 months after surgery. We observed large regional differences (38% to 57%) across regions. Survivors who received screening colonoscopy were more likely to: have colon cancer than rectal cancer (OR = 1.41, 95% CI: 1.05-1.90); have visited a primary care physician (OR = 1.44, 95% CI: 1.14-1.82); and received adjuvant chemotherapy (OR = 1.75, 95% CI: 1.27-2.41). Compared to survivors with no comorbidities, survivors with moderate or severe comorbidities were less likely to receive surveillance colonoscopy (OR = 0.69, 95% CI: 0.49-0.98 and OR = 0.44, 95% CI: 0.29-0.66, respectively). CONCLUSIONS: Despite guidelines, more than half of CRC survivors did not receive surveillance colonoscopy within 14 months of surgery, with substantial variation by site of care. The association of primary care visits and adjuvant chemotherapy use suggests that access to care following surgery affects cancer surveillance.
Resumo:
BACKGROUND: Little is known about the constraints of optimizing health care for prostate cancer survivors in Alaska primary care. OBJECTIVE: To describe the experiences and attitudes of primary care providers within the Alaska Tribal Health System (ATHS) regarding the care of prostate cancer survivors. DESIGN: In late October 2011, we emailed a 22-item electronic survey to 268 ATHS primary care providers regarding the frequency of Prostate Specific Antigen (PSA) monitoring for a hypothetical prostate cancer survivor; who should be responsible for the patient's life-long prostate cancer surveillance; who should support the patient's emotional and medical needs as a survivor; and providers' level of comfort addressing recurrence monitoring, erectile dysfunction, urinary incontinence, androgen deprivation therapy, and emotional needs. We used simple logistic regression to examine the association between provider characteristics and their responses to the survivorship survey items. RESULTS: Of 221 individuals who were successfully contacted, a total of 114 responded (52% response rate). Most ATHS providers indicated they would order a PSA test every 12 months (69%) and believed that, ideally, the hypothetical patient's primary care provider should be responsible for his life-long prostate cancer surveillance (60%). Most providers reported feeling either "moderately" or "very" comfortable addressing topics such as prostate cancer recurrence (59%), erectile dysfunction (64%), urinary incontinence (63%), and emotional needs (61%) with prostate cancer survivors. These results varied somewhat by provider characteristics including female sex, years in practice, and the number of prostate cancer survivors seen in their practice. CONCLUSIONS: These data suggest that most primary care providers in Alaska are poised to assume the care of prostate cancer survivors locally. However, we also found that large minorities of providers do not feel confident in their ability to manage common issues in prostate cancer survivorship, implying that continued access to specialists with more expert knowledge would be beneficial.
Resumo:
© 2015 Elsevier Ltd.Sedimentological, ichnological and paleontological analyses of the Early Miocene uppermost Monte León Formation and the lower part of the Santa Cruz Formation were carried out in Rincón del Buque (RDB), a fossiliferous locality north of Río Coyle in Santa Cruz Province, Patagonia, Argentina. This locality is of special importance because it contains the basal contact between the Monte Léon (MLF) and the Santa Cruz (SCF) formations and because it preserves a rich fossil assemblage of marine invertebrates and marine trace fossils, and terrestrial vertebrates and plants, which has not been extensively studied. A ~90m-thick section of the MLF and the SCF that crops out at RDB was selected for this study. Eleven facies associations (FA) are described, which are, from base to top: subtidal-intertidal deposits with Crassotrea orbignyi and bioturbation of the Skolithos-Cruziana ichnofacies (FA1); tidal creek deposits with terrestrial fossil mammals and Ophiomorpha isp. burrows (FA2); tidal flat deposits with Glossifungites ichnofacies (FA3); deposits of tidal channels (FA4) and tidal sand flats (FA5) both with and impoverish Skolithos ichnofacies associated; marsh deposits (FA6); tidal point bar deposits recording a depauperate mixture of both the Skolithos and Cruziana ichnofacies (FA7); fluvial channel deposits (FA8); fluvial point bar deposits (FA9); floodplain deposits (FA10); and pyroclastic and volcaniclastic deposits of the floodplain where terrestrial fossil mammal remains occur (FA11).The transition of the MLF-SCF at RDB reflects a changing depositional environment from the outer part of an estuary (FA1) through the central (FA2-6) to inner part of a tide-dominated estuary (FA7). Finally a fluvial system occurs with single channels of relatively low energy and low sinuosity enclosed by a broad, low-energy floodplain dominated by partially edaphized ash-fall, sheet-flood, and overbank deposits (FA8-11). Pyroclastic and volcaniclastic materials throughout the succession must have been deposited as ash-fall distal facies in a fluvial setting and also were carried by fluvial streams and redeposited in both estuarine and fluvial settings. These materials preserve most of the analyzed terrestrial fossil mammals that characterize the Santacrucian age of the RDB's succession. Episodic sedimentation under volcanic influence, high sedimentation rates and a relatively warm and seasonal climate are inferred for the MLF and SCF section.Lateral continuity of the marker horizons at RDB serve for correlation with other coastal localities such as the lower part of the coastal SCF south of Río Coyle (~17.6-17.4Ma) belonging to the Estancia La Costa Member of the SCF.
Resumo:
A physically open, but electrically shielded, microwave open oven can be produced by virtue of the evanescent fields in a waveguide below cutoff. The below cutoff heating chamber is fed by a transverse magnetic resonance established in a dielectric-filled section of the waveguide exploiting continuity of normal electric flux. In order to optimize the fields and the performance of the oven, a thin layer of a dielectric material with higher permittivity is inserted at the interface. Analysis and synthesis of an optimized open oven predicts field enhancement in the heating chamber up to 9.4 dB. Results from experimental testing on two fabricated prototypes are in agreement with the simulated predictions, and demonstrate an up to tenfold improvement in the heating performance. The open-ended oven allows for simultaneous precision alignment, testing, and efficient curing of microelectronic devices, significantly increasing productivity gains.
Resumo:
As is known, there are everywhere discontinuous infinitely Frechet differentiable functions on the real locally convex spaces D(R) and V(R) of finitely supported infinitely differentiable functions and, respectively, of generalized functions. In this paper the relationship between the complex differentiability and continuity of a function on a complex locally convex space is considered. We describe a class of complex locally convex spaces, which includes the complex space V(R), such that every Gateaux complex-differentiable function on a space of this class is continuous. We also describe another class of locally convex spaces, which includes the complex space D(R), such that on every space of this class there is an everywhere discontinuous infinitely Frechet complex-differentiable function whose derivatives are continuous.