Showing papers by "University of Maine published in 1998"

Chemical alarm signalling in aquatic predator-prey systems: A review and prospectus

Abstract: The importance of chemical cues in predator-prey interactions has recently received increasing attention from ecologists. The sources of chemicals to which prey species respond often originate as cues released by the predator (reviewed by Kats and Dill, this issue). Alternatively, cues may be released by other prey animals when they detect or are attacked by a predator. Such cues, known as chemical alarm signals, are particularly common in aquatic systems. These signals provide the basis of our current review. Short-term behavioural responses of prey animals to alarm signals have received the most attention. Behavioural responses of prey resemble those exhibited to known predators, and are therefore likely to make receivers less vulnerable to predation. More recently, studies have shown that benefits to alarm signal receivers extend beyond the immediate behavioural response of nearby conspecifics over a few minutes. For example, alarm signals are important in mediating the learning of unknown pred...

Disturbance of the Seabed by Mobile Fishing Gear: A Comparison to Forest Clearcutting

Abstract: Bottom trawling and use of other mobile fishing gear have effects on the seabed that resemble forest clearcutting, a terrestrial disturbance recognized as a major threat to biological diversity and economic sustainability. Structures in marine benthic communities are generally much smaller than those in forests, but structural complexity is no less important to their biodiversity. Use of mobile fishing gear crushes, buries, and exposes marine animals and structures on and in the substratum, sharply reducing structural diversity. Its severity is roughly comparable to other natural and anthropogenic marine disturbances. It also alters biogeochemical cycles, perhaps even globally. Recovery after disturbance is often slow because recruitment is patchy and growth to maturity takes years, decades, or more for some structure-forming species. Trawling and dredging are especially problematic where the return interval—the time from one dredging or trawling event to the next—is shorter than the time it takes for the ecosystem to recover; extensive areas can be trawled 100–700% per year or more. The effects of mobile fishing gear on biodiversity are most severe where natural disturbance is least prevalent, particularly on the outer continental shelf and slope, where storm-wave damage is negligible and biological processes, including growth, tend to be slow. Recent advances in fishing technology (e.g., rockhopper gear, global positioning systems, fish finders) have all but eliminated what were de facto refuges from trawling. The frequency of trawling (in percentage of the continental shelf trawled per year) is orders of magnitude higher than other severe seabed disturbances, annually covering an area equivalent to perhaps half of the world’s continental shelf, or 150 times the land area that is clearcut yearly. Mobile fishing gear can have large and long-lasting effects on benthic communities, including young stages of commercially important fishes, although some species benefit when structural complexity is reduced. These findings are crucial for implementation of “Essential Fish Habitat” provisions of the U.S. Magnuson-Stevens Fishery Conservation and Management Act which aim to protect nursery and feeding habitat for commercial fishes. Using a precautionary approach to management, modifying fishing methods, and creating refuges free of mobile fishing gear are ways to reduce effects on biological diversity and commercial fish habitat. Perturbaciones del Lecho Marino por Artes de Pesca Mobiles: Una Comparacion con la Tala Forestals Los arrastres de fondo y el uso de otras artes de pesca moviles tienen efectos en el lecho marino que se asemejan a la tala total de bosques, que es a su vez una pertubacion terrestre reconocida como una de las mayores amenazas a la diversidad biologica y la sustentabilidad economica. Las estructuras en comunidades marinas benticas son generalmente mucho mas pequenas que aquellas en los bosques, pero la complejidad estructural no es menos importante que la biodiversidad. El uso de artes de pesca moviles quiebra, sepulta y expone animales marinos y estructuras sobre y en el substrato, reduciendo marcadamente la diversidad estructural. Su severidad es burdamente comparable con otras perturbaciones marinas de orden natural o antropogenico. Tambien altera los ciclos biogeoquimicos, de hecho a nivel mundial. La recuperacion despues de una pertubacion es frecuentemente lenta debido a que el reclutamiento es por parches y el crecimiento para alcanzar la madurez toma anos, decadas o aun mas para algunas especies que forman estructuras. Los arrastres de fondo y dragados son especialmente problematicos donde el intervalo de retorno (tiempo entre un evento de dragado o arrastre y otro) es mas corto que el tiempo que toma a un ecosistema recuperarse;arears extensas son arrastradas entre un 100 y 700% por ano o mas. Los efectos de las artes de pesca moviles en la biodiversidad son mas severos cuando las perturbaciones naturales son menos prevalentes, particularmente en las afueras de la plataforma continental y la pendiente, donde el dano del oleaje por tormentas es negligible y los procesos biologicos (incluyendo crecimiento) tienden a ser lentos. Recientes avances en tecnologia pesquera (e.g., sistemas de posicionamiento global, detectores de peces) aparentemente tienen todo, pero eliminan lo que de facto fueran refugios contra arrastres. La frecuencia de los arrastres (en porcentaje de la plataforma continental arrastrada por ano) es ordenes de magnitud mayor que otras perturbaciones severas al lecho marino, anualmente la cobertura de area es equivalente quiza a la mitad de la plataforma continental marina, o 150 veces el area de tierra que es talada anualmente. Las artes de pesca moviles pueden tener impactos grandes y de larga duracion en las comunidades bentonicas, incluyendo estadios jovenes de peces de importancia comercial, aunque algunas especies se benefician cuando la complejidad estructural es reducida. Estos descubrimientos son cruciales para la implementacion de el “habitat esencial para peces” del Acta de Conservacion y Manejo de Pesquerias Magnuson-Stevens de los Estados Unidos y que pretende establecer habitats de reproduccion y alimentacion para peces comerciales. El uso de una aproximacion precautoria de manejo, la modificacion de metodos de pesca y la creacion de refugios libres de artes de pesca moviles son formas para reducir los efectos en la diversidad biologica y el habitat para peces comerciales.

Modeling failure time data by lehman alternatives

Abstract: The proportional hazards model has been extensively used in the literature to model failure time data. In this paper we propose to model failure time data by F*(f) = [F(t)]θ where F(t) is the baseline distribution function and θ is a positive real number. This model gives rise to monotonic as well as non-monotonic failure rates even though the baseline failure rate is monotonic. The monotonicity of the failure rates are studied, in general, and some order relations are examined. Some examples including exponentiated Weibull, exponential, gamma and Pareto distributions are investigated in detail.

Biological bases of creativity.

Abstract: Creativity is a rare trait. This is presumably because it requires the simultaneous presence of a number of traits (e.g., intelligence, perseverance, unconventionality, the ability to think in a particular manner). None of these traits is especially rare. What is quite uncommon is to find them all present in the same person. One imagines that all of these traits have biological bases. In this chapter, I shall focus upon the type of thought involved in creative insight. First, I describe the nature of this type of thought; then I present arguments as to why it must be based upon specific physiological states; finally, I review evidence that it is in fact so based. A creative idea is one that is both original and appropriate for the situation in which it occurs. It would seem that creative productions always consist of novel combinations of pre-existing mental elements. As Poincaree (1913) noted, “To create consists of making new combinations of associative elements which are useful” (p. 286). Creative ideas, he further remarked, “reveal to us unsuspected kinships between other facts well known but wrongly believed to be strangers to one another” (p. 115). To create, then, involves the realization of an analogy between previously unassociated mental elements. On the verbal level, creativity involves production of novel statements of the form “A is like B” or statements involving novel modifiers for A. Hugo's image, “I climbed the bitter stairs” is more creative than, say, “I climbed the steep stairs.”

Psychometric Approaches to the Study of Human Creativity

Abstract: The study of human creativity, although historically extensive, is in the midst of a second golden age as the century comes to a close. Authors and researchers from a variety of backgrounds publish hundreds of articles and books on creativity every year, conferences that cross disciplines frequently include sessions on creativity, and programs for increasing the creative productivity of young people and adults are introduced on a regular basis. And while several distinct approaches are used to examine creative phenomenon, a majority of work dealing with creativity relies on psychometric methods - the direct measurement of creativity and/or its perceived correlates in individuals. Indeed, practically all current work on creativity is based upon methodologies that either are psychometric in nature or were developed in response to perceived weaknesses of creativity measurement. As such, the psychometric studies of creativity conducted in the past few decades form the foundation of current understandings of creativity. Yet the psychometric approach is significantly more complex and comprehensive than its critics (and many of its proponents) would have us believe, and alternatives to the psychometric approach are wrought with many of the same difficulties posed during the direct measurement of creativity. A thorough review of psychometric techniques for the study of creativity benefits both those individuals attempting to measure creativity and those individuals studying creativity via other techniques.

Review—ultraviolet radiation-absorbing mycosporine-like amino acids in coral reef organisms: a biochemical and environmental perspective

Abstract: The clear waters surrounding tropical coral reefs typically are oligotrophic, yet these reefs are highly productive and support dense populations of marine organisms. This paradox is resolved in part because many coral reef invertebrates accommodate unicellular autotrophs (‘‘zooxanthellae,’’ Symbiodinium spp.; Prochlorales, Prochloron sp.; cyanobacteria) within their tissues. These photoautotrophic symbioses entail an exchange of nutrients between the endosymbionts and the animal hosts. Organic compounds produced by the microalgal partners are released to the hosts for their nutrition while inorganic metabolic wastes are recycled to fertilize the algae (Muscatine 1990). The requirement for photosynthetically active radiation (PAR, 400–700 nm) also exposes such algalinvertebrate symbioses and other primary producers to high levels of environmental ultraviolet radiation (UVR 5 295–400 nm) in tropical waters (Smith and Baker 1979, Fleischmann 1989). These waters are often low in UV-absorbing particulate and dissolved organic matter, and sea level fluences of solar UV are high because of the short atmospheric path length and thinness of the stratospheric ozone layer above the tropics (Baker et al. 1980). Photoautotrophic symbiosis thus presents an evolutionary challenge by precluding the morphological development of an optically opaque barrier (such as hair, scales, and feathers in higher vertebrates) and potentially allows damaging UV radiation to reach vulnerable biomolecules in both partners. The problem is exacerbated because the tissues are hyperoxic (.250% air saturation: Kuhl et al.

Principles of glacier mechanics

Abstract: Why study glaciers? some basic concepts mass balance flow of a crystalline material the velocity field in a glacier temperature distribution in polar ice sheets the coupling between a glacier and its bed water flow in and under glaciers - geomorphic implications stress and deformation stress and velocity distribution in an idealized glacier applications of stress and deformation principles to classical problems response of glaciers to changes in mass balance problems

Fe(0)-Supported Autotrophic Denitrification

Abstract: Proof of concept was obtained that Fe(0) can stoichio metrically reduce nitrate to ammonium and that cathodic hydrogen [produced during anaerobic Fe(0) corrosion by water] can sustain microbial den...

Effects of Silvicultural Edges on the Distribution and Abundance of Amphibians in Maine

Abstract: Amphibians share several biological characteristics that may cause them to be sensitive to abrupt transitions in microhabitat and microclimate that occur across forest edges. To better understand the impor- tance of edge effects on amphibians in a forested landscape, we sampled the distribution of populations along drift fences placed perpendicular to silvicultural edges of varying contrast in central Maine. Within the com- munity of amphibians sampled (14 species), salamanders generally were more sensitive to even-aged harvest- ing and associated edge effects than were anurans, but forest habitat generalists and specialists were identi- fied within both groups. We conservatively estimated the depth of edge effects at 25-35 m for a subset of management-sensitive species ( Plethodon cinereus, Ambystoma maculatum, A. laterale, and Rana sylvatica ). An index of edge contrast, calculated using ambient light penetration levels, was valuable in predicting the mag- nitude of edge effects among sites that included silvicultural edges of different age and origin (old field plan- tations versus recent clearcuts). Some structural microhabitat variables relevant to forest management were identified as potentially limiting to amphibians near forest edges, including canopy cover, litter cover, and a measure of stumps, snags, and their root channels. Our observations are consistent with the results of other work on biotic edge effects in the eastern United States and suggest that impacts from intensive forest man- agement practices extend beyond the boundaries of harvested stands.

Antarctic Glacial History Since the Last Glacial Maximum: An Overview of the Record on Land

Abstract: This overview examines available circum-Antarctic glacial history archives on land, related to developments after the Last Glacial Maximum (LGM). It considers the glacial-stratigraphic and morphologic records and also biostratigraphical information from moss banks, lake sediments and penguin rookeries, with some reference to relevant glacial marine records. It is concluded that Holocene environmental development in Antarctica differed from that in the Northern Hemisphere. The initial deglaciation of the shelf areas surrounding Antarctica took place before 10 000 14C yrs before present(BP), and was controlled by rising global sea level. This was followed by the deglaciation of some presently ice-free inner shelf and land areas between 10 000 and 8000 yr BP. Continued deglaciation occurred gradually between 8000 yr BP and 5000 yr BP. Mid-Holocene glacial readvances are recorded from various sites around Antarctica. There are strong indications of a circum-Antarctic climate warmer than today 4700–2000 yr BP. The best dated records from the Antarctic Peninsula and coastal Victoria Land suggest climatic optimums there from 4000–3000 yr BP and 3600–2600 yr BP, respectively. Thereafter Neoglacial readvances are recorded. Relatively limited glacial expansions in Antarctica during the past few hundred years correlate with the Little Ice Age in the Northern Hemisphere.

Relationship marketing effectiveness: The role of involvement

Abstract: The term relationship marketing has been used to describe a wide range of marketing tactics. In this article, three dimensions that may be used to categorize these tactics are identified: personalization, individualization, and continuity. Research is presented demonstrating that the effectiveness of each type of tactic is influenced by buyer involvement in the product category, although the nature of this influence differs by country and gender. This suggests that managers contemplating relationship marketing programs should consider buyer involvement levels, and that researchers studying relationship marketing effectiveness should control for this variable. © 1998 John Wiley & Sons, Inc.

Upper ocean export of particulate organic carbon in the Arabian Sea derived from thorium-234

Abstract: Thorium-234 is used in the Arabian Sea as a tracer of sinking particle fluxes. Samples were collected from January to August 1995 on four cruises during the Northeast Monsoon, the Spring Intermonsoon and the mid- and late-Southwest Monsoon periods. In this study, 234Th activity distributions are used to quantify the 234Th flux on sinking particles, and the measured ratio of particulate organic carbon (POC) to particulate 234Th is used to convert from 234Th to POC export at 100 m. The calculated POC fluxes range from 25 mmols C m-2 d-1, and strong seasonal and spatial gradients are observed. The single largest feature is a basinwide export maximum associated with the late-SW Monsoon cruise when POC export rates are 17–28% of the observed primary production rates along the southern sampling line. During all other cruises, this export ratio is

A Meta‐Analysis of Forest Cover, Edge Effects, and Artificial Nest Predation Rates

Abstract: Landscape fragmentation has been among the most intensely studied topics in conservation biology for decades (Gates & Gysel 1978; Murcia 1995). The influence of habitat edge has often been investigated as an important feature in fragmented areas, especially with respect to bird nesting success, as evidenced by three recent reviews. Paton (1994) concluded that "current evidence, although equivocal, suggests that predation and parasitism rates are often significantly greater within 50 m of an edge." Andren (1995) examined edge (or patch size) effects in a review of 40 papers and concluded that "edge-related increase in predation seems to be most commonly found inside forests surrounded by farmland and was rarely found in forest mosaics." Major and Kendal (1996) showed that a preponderance of studies "demonstrated a positive correlation between predation rate and the degree of habitat fragmentation," but found "more variable results" regarding edge effects. We believe that none of these papers adequately addressed the issue of whether or not predation rates and edge effects differ between deforested versus forested landscapes. Thus, we decided to evaluate relationships between degree of forest cover in a landscape and (1) avian nest success rates and (2) the existence of elevated predation rates near habitat edges. We combined data from 13 previous studies in 33 U.S. landscapes to explore patterns of nest predation and landscape composition.

Resuspension of Sediment by Bottom Trawling in the Gulf of Maine and Potential Geochemical Consequences

Abstract: The benthic environment of the Gulf of Maine is characterized by a thick and basin-wide nepheloid layer, classically defined as a near-bottom region of permanent sediment resuspension. The high frequency of commercial bottom trawling in particular regions of the Gulf of Maine, documented by records compiled by the National Marine Fisheries Service, may strongly affect measured resuspension fluxes and contribute to the maintenance of the nepheloid layer. Indirect evidence of the effects of bottom trawling on sediment resuspen- sion is observed in the seasonal collection of large, benthic infaunal worms, along with substantial amounts of resuspended bottom sediment, in a sediment trap deployed 25 m off the bottom in the western gulf region of Wilkinson Basin. These collections appear to be coincident with seasonal periods of intensive bottom trawl- ing in this area. By comparison, the western gulf region of Jordan Basin is typified by significantly reduced annual bottom-trawling activity, and very few infaunal worms are found in the seasonal collections of a sed- iment trap located 25-30 m off the bottom. The extent to which trawling-induced bottom sediment excava- tion and resuspension occurs has important implications for regional nutrient budgets in terms of the input of sedimentary nitrogen and silica into the water column via this anthropogenic activity. Sediment mixing and frequent bottom disturbance from trawling activity may also produce changes in the successional orga- nization of soft-sediment infaunal communities. The potential effects of trawling require serious examination and quantification to accurately determine the impact of such anthropogenic activity on the benthic ecosys- tems of continental margin environments.

Using simulated annealing to solve a multiobjective assembly line balancing problem with parallel workstations

Abstract: This research presents a Simulated Annealing based technique to address the assembly line balancing problem for multiple objective problems when paralleling of workstations is permitted. The Simulated Annealing methodology is used for 23 line balancing strategies across seven problems. The resulting performance of each solution was studied through a simulation experiment. Many of the problems consisted of multiple products, which were sequenced in a mixed model fashion, task times were assumed to be stochastic, and parallel workstations were permitted. Two primary performance objectives were of most interest: total cost (labour and equipment) per part, and the degree to which the desired cycle time was achieved. Other traditional line balancing and production performance measures were also collected. This paper demonstrates how Simulated Annealing can be used to obtain line balancing solutions when one or more objectives are important. The experimental results showed that Simulated Annealing approaches yi...

Effects of Ultraviolet Radiation on Amphibians: Field Experiments

Abstract: SYNOPSIS. Numerous reports suggest that populations of amphibians from a wide variety of locations are experiencing population declines and/or range reductions. In some cases, unusually high egg mortality has been reported. Field experiments have been used with increasing frequency to investigate ultraviolet radiation as one of the potential factors contributing to these declines. Results from field experiments illustrate that hatching success of eggs is hampered by ultraviolet radiation in a number of species, while other species appear to be unaffected. Continued mortality in early life-history stages may ultimately contribute to a population decline. Although UV-B radiation may not contribute to the population declines of all species, it may play a role in the population decline of some species, especially those that lay eggs in open shallow water subjected to solar radiation and in those that have a poor ability to repair UV-induced DNA damage.

Thermal stability of DNA

Abstract: Tij and Delta Hij for stacking of pair i upon j in DNA have been obtained over the range 0.034-0.114 M Na+from high-resolution melting curves of well-behaved synthetic tandemly repeating inserts in recombinant pN/MCS plasmids. Results are consistent with neighbor-pair thermodynamic additivity, where the stability constant, sij , for different domains of length N depend quantitatively on the product of stability constants for each individual pair in domains, sijN . Unit transition enthalpies with average errors less than +/-5%, were determined by analysis of two-state equilibria associated with the melting of internal domains and verified from variations of Tij with [Na+]. Enthalpies increase with Tij , in close agreement with the empirical function: Delta Hij = 52.78@ Tij - 9489, and in parallel with a smaller increase in Delta Sij . Delta Hij and Delta Sij are in good agreement with the results of an extensive compilation of published Delta Hcal and Delta Scal for synthetic and natural DNAs. Neighbor-pair additivity was also observed for (dA@dT)-tracts at melting temperatures; no evidence could be detected of the familiar and unusual structural features that characterize tracts at lower temperatures. The energetic effects of loops were determined from the melting behavior of repeating inserts installed between (G+C)-rich barrier domains in the pN/MCS plasmids. A unique set of values for the cooperativity, loop exponent and stiffness parameters were found applicable to internal domains of all sizes and sequences. Statistical mechanical curves calculated with values of Tij([Na+]) , Delta Hij and these loop parameters are in good agreement with observation.

Paleozoic orogens in New England, USA

Abstract: Stratigraphy and isotope geochronology in the crystalline core of the Appalachians suggest revised interpretations of the extent, nature and timing of Paleozoic orogens in New England. Five major episodes of magmatism, deformation, and high-grade regional metamorphism are recognized: Taconian (455-442 Ma), Acadian (423-385 Ma), Neo-Acadian (366-350 Ma), Late Pennsylvanian (300-290 Ma) and Alleghanian (280-260 Ma). In the Taconian, the passive margin of Laurentia was subducted below a complex magmatic arc lasting from 480 to 442 Ma, founded in part on continental crust of a Medial New England terrane with possible affinities with Amazonia. Questions about Medial New England involve its coherence as a single plate, and the nature of its underlying crust. The Acadian began in Late Silurian as a collision between the amalgamated Laurentia-Medial New England and outer belts of Composite Avalon along a cryptic suture in coastal Maine, and progressed northwestward to the Connecticut Valley basin by mid-...

Three-Dimensional Simulation of Scour-Inducing Flow at Bridge Piers

Abstract: Presently available formulas for estimating the maximum depth of scour near bridge piers often lead to unreliable results. A fully three-dimensional hydrodynamic model is therefore used in this study to simulate the flow occurring at the base of a cylindrical bridge pier within a scour hole. The results of the numerical simulation are compared with laboratory observations by Melville and Raudkivi (1977). Quantitative and qualitative agreement between the studies is quite good. Discrepancies between the results of the two studies are of an order that may be attributed to choices in numerical model parameters. The simulations may be supplemented by Lagrangian particle-tracking to estimate the depth of the equilibrium scour condition.

Influence of landscape pattern on habitat use by American Marten in an industrial forest

Abstract: Few studies have examined the potential for clearcutting to fragment habitat of area-sensitive, forest-dependent mammals such as American marten (Martes americana). We examined relationships among measures of landscape pattern and spatial use of habitat by 33 resident and 32 nonresident, adult marten that were radio-monitored in an extensively logged landscape. Size and distribution of forest patches (trees over 6 m in height) were associated with patch use by marten. Patches of forest used by resident marten (median = 27 ha, n = 12) were larger ( p < 0.003) than patches with no observed use (median = 1.5 ha, n = 128). Further, patches used by residents were closer to the nearest patch larger than 2.7 ha (38 m versus 55 m;p = 0.057) and to an adjacent forest preserve (2.5 km versus 3.5 km;p = 0.075) than patches with no observed use. At four spatial scales (10, 65, 125, and 250 ha), grid cells used by resident marten comprised a greater percentage of residual forest over 6 m in height ( p≤ 0.008) and intersected forest patches of greater area ( p≤ 0.006) than cells with no observed use. Edge indices were not different ( p≥ 0.490) between used grid cells and cells with no observed use at any of the four spatial scales. Analyses of forest edge associations indicated that marten did not avoid residual-regenerating forest edge within home ranges or within the study area. Home ranges ( n = 27) of all resident, adult marten were composed of more than 60% forest cover over 6 m in height; median values were 78–80% for both sexes. The median size of the largest forest patch in marten home ranges was 150 ha for females and 247 ha for males. Our results suggest that reducing fragmentation by consolidating clearcuts and retaining large residual patches would help to maintain resident marten in extensively logged landscapes. Influencia del Patron del Paisaje en el Uso del Habitat por la Marta Americana en un Bosque Industrial Pocos estudios han examinado el efecto de la tala en habitats fragmentados de mamiferos sensibles al area y dependientes del bosque como lo es la marta americana ( Martes americana). Examinamos las relaciones entre mediciones de patrones del paisaje y uso espacial de habitat por 33 martas adultas residentes y 32 no residentes monitoreadas por radiotelemetria en un pasaje extensivamente talado. El tamano y la distribucion de parches de bosque (arboles > 6 m de altura) fueron asociados con parches usados por las martas. Los parches de bosque usados por martas residentes (mediana = 27 ha, n = 12) fueron mayores ( p 6 m de altura ( p≤ 0.008) y de parches que interceptaron bosque de area mayor ( p≤ 0.006) que las celdas en las que no se observo. Los indices de borde no fueron significativamente diferentes ( p≥ 0.49) entre celdas usadas y las celdas que no mostraron uso a ninguna de las cuatro escalas espaciales usadas. Los analisis de asociaciones en el borde del bosque indicaron que las martas no evitaron bordes de bosque residual en regeneracion dentro de los rangos de hogar o dentro del area de estudio. Los rangos de hogar ( n = 27) de todas las martas residentes estuvieron compuestos por un 60% de cobertura forestal> 6 m de altura; los valores de la mediana para ambos sexos estuvieron entre 78 y 80%. El valor de la mediana para los parches de bosque mas grandes usados por las martas fue de 150 ha para hembras y 247 ha para machos. Nuestros resultados sugieren que la reduccion de la fragmentacion al consolidar la tala intensiva y retener parches residuales grandes podria ayudar a mantener poblaciones de martas residentes en paisajes talados extensivamente.

Intracellular oxygen diffusion: the roles of myoglobin and lipid at cold body temperature.

Abstract: Cold temperature can constrain the rate of oxygen movement through muscle cells of ectothermic animals because the kinetic energy of the solvent-solute system decreases and the viscosity of the aqueous cytoplasm increases during cooling within the physiological range of body temperatures. These factors affect the movement of both dissolved oxygen and oxymyoglobin, the two predominant routes of intracellular oxygen diffusion in vertebrate oxidative muscles. In addition, reductions in temperature have been shown to increase the affinity of myoglobin for oxygen and to slow the rate of Mb O2-dissociation, compromising the ability of this oxygen-binding protein to facilitate intracellular oxygen diffusion. Experiments with both seasonally cold-bodied fishes and polar fish species suggest that several factors combine to overcome these limitations in delivery of oxygen from the blood to the mitochondria. First, reductions in body temperature induce increases in mitochondrial density of oxidative muscle cells, reducing the mean diffusional pathlength for oxygen between capillaries and mitochondria. Second, cold body temperature in both temperate-zone and polar fishes is frequently correlated with a high content of neutral lipid in oxidative muscles, providing an enhanced diffusional pathway for oxygen through the tissue. Third, recent data indicate that myoglobins from fish species bind and release oxygen more rapidly at cold temperature than do those from mammals. Data from both oxidative skeletal muscle and cardiac muscle of fishes suggest that these factors in various combinations contribute to enhance the aerobically supported mechanical performance of the tissues at cold cellular temperatures.

Late Onset Canonical Babbling: A Possible Early Marker of Abnormal Development

Abstract: By their 10th month of life, typically developing infants produce canonical babbling, which includes the well-formed syllables required for meaningful speech. Research suggests that emerging speech or language-related disorders might be associated with late onset of canonical babbling. Onset of canonical babbling was investigated for 1,536 high-risk infants, at about 10-months corrected age. Parental report by open-ended questionnaire was found to be an efficient method for ascertaining babbling status. Although delays were infrequent, they were often associated with genetic, neurological, anatomical, and/or physiological abnormalities. Over half the cases of late canonical babbling were not, at the time they were discovered, associated with prior significant medical diagnoses. Late canonical-babbling onset may be a predictor of later developmental disabilities, including problems in speech, language, and reading.

Metric details for natural-language spatial relations

Abstract: Spatial relations often are desired answers that a geographic information system (GIS) should generate in response to a user's query. Current GIS's provide only rudimentary support for processing and interpreting natural-language-like spatial relations, because their models and representations are primarily quantitative, while natural-language spatial relations are usually dominated by qualitative properties. Studies of the use of spatial relations in natural language showed that topology accounts for a significant portion of the geometric properties. This article develops a formal model that captures metric details for the description of natural-language spatial relations. The metric details are expressed as refinements of the categories identified by the 9-intersection, a model for topological spatial relations, and provide a more precise measure than does topology alone as to whether a geometric configuration matches with a spatial term or not. Similarly, these measures help in identifying the spatial term that describes a particular configuration. Two groups of metric details are derived: splitting ratios as the normalized values of lengths and areas of intersections; and closeness measures as the normalized distances between disjoint object parts. The resulting model of topological and metric properties was calibrated for 64 spatial terms in English, providing values for the best fit as well as value ranges for the significant parameters of each term. Three examples demonstrate how the framework and its calibrated values are used to determine the best spatial term for a relationship between two geometric objects.

Context-mediated behavior for intelligent agents

Abstract: Humans and other animals are exquisitely attuned to their context. Context affects almost all aspects of behavior, and it does so for the most part automatically, without a conscious reasoning effort. This would be a very useful property for an artificial agent to have: upon recognizing its context, the agent's behavior would automatically adjust to fit it. This paper describescontext-mediated behavior(CMB), an approach to context-sensitive behavior we have developed over the past few years for intelligent autonomous agents. In CMB, contexts are represented explicitly ascontextual schemas(c-schemas). An agent recognizes its context by finding the c-schemas that match it, then it merges these to form a coherent representation of the current context. This includes not only a description of the context, but also information about how to behave in it. From that point until the next context change, knowledge for context-sensitive behavior is available with no additional effort. This is used to influence perception, make predictions about the world, handle unanticipated events, determine the context-dependent meaning of concepts, focus attention and select actions. CMB is being implemented in the Orca program, an intelligent controller for autonomous underwater vehicles.

Breast Talk in Breast Cancer Narratives

Abstract: Breast cancer often involves uniquely mutilating treatments and is frequently assumed to produce problems specifically associated with feminine identity: body image and sexuality. But empirical research to support this assumption is sometimes mixed and nearly always quantitative in method. This study examines breast talk--specific references to breasts and breast cancer in women's illness narratives--collected in 20 open-ended, in-depth interviews with 17 White, middle-class survivors in Maine. Participants varied in age, marital status, motherhood sexual orientation, family history of breast cancer, medical diagnoses, and treatments. Phenomenological analysis of the breast talk resulted in four interrelated clusters of meanings: the medicalized breast, the functional breast, the gendered breast, and the sexualized breast. The analysis suggests both greater and fewer problems with femininity, sexuality, and body image than presumed by much research, and it urges researchers not to reproduce the objectifications and stereotyping of sexist culture.

A double-stranded RNA element from a hypovirulent strain of Rhizoctonia solani occurs in DNA form and is genetically related to the pentafunctional AROM protein of the shikimate pathway

Abstract: M2 is a double-stranded RNA (dsRNA) element occurring in the hypovirulent isolate Rhs 1A1 of the plant pathogenic basidiomycete Rhizoctonia solani. Rhs 1A1 originated as a sector of the virulent field isolate Rhs 1AP, which contains no detectable amount of the M2 dsRNA. The complete sequence (3,570 bp) of the M2 dsRNA has been determined. A 6.9-kbp segment of total DNA from either Rhs 1A1 or Rhs 1AP hybridizes with an M2-specific cDNA probe. The sequences of M2 dsRNA and of PCR products generated from Rhs 1A1 total DNA were found to be identical. Thus this report describes a fungal host containing full-length DNA copies of a dsRNA element. A major portion of the M2 dsRNA is located in the cytoplasm, whereas a smaller amount is found in mitochondria. Based on either the universal or the mitochondrial genetic code of filamentous fungi, one strand of M2 encodes a putative protein of 754 amino acids. The resulting polypeptide has all four motifs of a dsRNA viral RNA-dependent RNA polymerase (RDRP) and is phylogenetically related to the RDRP of a mitochondrial dsRNA associated with hypovirulence in strain NB631 of Cryphonectria parasitica, incitant of chestnut blight. This polypeptide also has significant sequence similarity with two domains of a pentafunctional polypeptide, which catalyzes the five central steps of the shikimate pathway in yeast and filamentous fungi.