3,229 research outputs found
AnĂĄlise SedimentolĂłgica de Recifes do GĂȘnero Phragmatopoma Mörch, 1863 (Annelida: Polychaeta) da RegiĂŁo Metropolitana de Fortaleza (CE)
AnelĂdeos do gĂȘnero Phragmatopoma sĂŁo animais marinhos de hĂĄbito bentĂŽnico sĂ©ssil encontrados por quase toda a costa brasileira, onde constroem recifes via agregação de areias litorĂąneas. Seu habitat e a preservação de seus recifes auxiliam em estudos holocĂȘnicos de variação do nĂvel relativo do mar, alĂ©m de outros aspectos biolĂłgicos, oceanogrĂĄficos e atĂ© econĂŽmicos, despertando assim grande interesse em suas construçÔes biossedimentares. Este trabalho analisou a sedimentologia de sete recifes do gĂȘnero Phragmatopoma de diferentes locais na zona costeira da RegiĂŁo Metropolitana de Fortaleza (RMF), comparando suas propriedades entre si, com as areias das praias locais e com uma regiĂŁo livre de influĂȘncia da urbanização (SĂŁo Miguel do Gostoso, RN). As anĂĄlises incluĂram o zoneamento biolĂłgico de um costĂŁo rochoso natural, alĂ©m da contagem dos principais componentes detrĂticos das areias por lupa, quantificação de teores brutos de carbonato de cĂĄlcio e de matĂ©ria orgĂąnica, granulometria e petrografia de minerais pesados. Os resultados sugerem que nĂŁo hĂĄ preferĂȘncia por tipos especĂficos de substrato duro de fixação. Na RMF, o zoneamento biolĂłgico foi semelhante ao da RegiĂŁo Sudeste para metade dos organismos da zona infralitoral, sendo a diferença concentrada na diversidade de algas da RMF. Em termos de matĂ©ria orgĂąnica, granulometria e minerais pesados, as areias de recifes e das praias em que se encontravam foram muito semelhantes. Valores mais elevados no teor de carbonato de cĂĄlcio e na quantidade e diversidade de bioclastos nas areias dos recifes em relação Ă s praias em que se encontravam apontam para uma clara predileção do poliqueta por componentes biodetrĂticos calcĂĄrios das areias, seja por uma questĂŁo de forma e/ou disponibilidade hidrodinĂąmica. O resultado geral pode ser considerado semelhante ao de estudos preliminares realizados na costa atlĂąntica da AmĂ©rica do Norte e na RegiĂŁo Sudeste do Brasil para poliquetas do mesmo gĂȘnero
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The influence of the atmospheric boundary layer on nocturnal layers of noctuids and other moths migrating over southern Britain
Insects migrating at high altitude over southern Britain have been continuously monitored by automatically-operating, vertical-looking radars over a period of several years. During some occasions in the summer months, the migrants were observed to form well-defined layer concentrations, typically at heights of 200-400 m, in the stable night-time atmosphere. Under these conditions, insects are likely to have control over their vertical movements and are selecting flight heights which are favourable for long-range migration. We therefore investigated the factors influencing the formation of these insect layers by comparing radar measurements of the vertical distribution of insect density with meteorological profiles generated by the UK Met. Officeâs Unified Model (UM). Radar-derived measurements of mass and displacement speed, along with data from Rothamsted Insect Survey light traps provided information on the identity of the migrants. We present here three case studies where noctuid and pyralid moths contributed substantially to the observed layers. The major meteorological factors influencing the layer concentrations appeared to be: (a) the altitude of the warmest air, (b) heights corresponding to temperature preferences or thresholds for sustained migration and (c), on nights when air temperatures are relatively high, wind-speed maxima associated with the nocturnal jet. Back-trajectories indicated that layer duration may have been determined by the distance to the coast. Overall, the unique combination of meteorological data from the UM and insect data from entomological radar described here show considerable promise for systematic studies of high-altitude insect layering
Costs of Reproduction and Terminal Investment by Females in a Semelparous Marsupial
Evolutionary explanations for life history diversity are based on the idea of costs of reproduction, particularly on the concept of a trade-off between age-specific reproduction and parental survival, and between expenditure on current and future offspring. Such trade-offs are often difficult to detect in population studies of wild mammals. Terminal investment theory predicts that reproductive effort by older parents should increase, because individual offspring become more valuable to parents as the conflict between current versus potential future offspring declines with age. In order to demonstrate this phenomenon in females, there must be an increase in maternal expenditure on offspring with age, imposing a fitness cost on the mother. Clear evidence of both the expenditure and fitness cost components has rarely been found. In this study, we quantify costs of reproduction throughout the lifespan of female antechinuses. Antechinuses are nocturnal, insectivorous, forest-dwelling small (20â40 g) marsupials, which nest in tree hollows. They have a single synchronized mating season of around three weeks, which occurs on predictable dates each year in a population. Females produce only one litter per year. Unlike almost all other mammals, all males, and in the smaller species, most females are semelparous. We show that increased allocation to current reproduction reduces maternal survival, and that offspring growth and survival in the first breeding season is traded-off with performance of the second litter in iteroparous females. In iteroparous females, increased allocation to second litters is associated with severe weight loss in late lactation and post-lactation death of mothers, but increased offspring growth in late lactation and survival to weaning. These findings are consistent with terminal investment. Iteroparity did not increase lifetime reproductive success, indicating that terminal investment in the first breeding season at the expense of maternal survival (i.e. semelparity) is likely to be advantageous for females
Extragalactic Radio Continuum Surveys and the Transformation of Radio Astronomy
Next-generation radio surveys are about to transform radio astronomy by
discovering and studying tens of millions of previously unknown radio sources.
These surveys will provide new insights to understand the evolution of
galaxies, measuring the evolution of the cosmic star formation rate, and
rivalling traditional techniques in the measurement of fundamental cosmological
parameters. By observing a new volume of observational parameter space, they
are also likely to discover unexpected new phenomena. This review traces the
evolution of extragalactic radio continuum surveys from the earliest days of
radio astronomy to the present, and identifies the challenges that must be
overcome to achieve this transformational change.Comment: To be published in Nature Astronomy 18 Sept 201
Histone deacetylases as new therapy targets for platinum-resistant epithelial ovarian cancer
Introduction: In developed countries, ovarian cancer is the fourth most common cancer in women. Due to the nonspecific symptomatology associated with the disease many patients with ovarian cancer are diagnosed late, which leads to significantly poorer prognosis. Apart from surgery and radiotherapy, a substantial number of ovarian cancer patients will undergo chemotherapy and platinum based agents are the mainstream first-line therapy for this disease. Despite the initial efficacy of these therapies, many women relapse; therefore, strategies for second-line therapies are required. Regulation of DNA transcription is crucial for tumour progression, metastasis and chemoresistance which offers potential for novel drug targets. Methods: We have reviewed the existing literature on the role of histone deacetylases, nuclear enzymes regulating gene transcription. Results and conclusion: Analysis of available data suggests that a signifant proportion of drug resistance stems from abberant gene expression, therefore HDAC inhibitors are amongst the most promising therapeutic targets for cancer treatment. Together with genetic testing, they may have a potential to serve as base for patient-adapted therapies
CT Scan Screening for Lung Cancer: Risk Factors for Nodules and Malignancy in a High-Risk Urban Cohort
Low-dose computed tomography (CT) for lung cancer screening can reduce lung cancer mortality. The National Lung Screening Trial reported a 20% reduction in lung cancer mortality in high-risk smokers. However, CT scanning is extremely sensitive and detects non-calcified nodules (NCNs) in 24-50% of subjects, suggesting an unacceptably high false-positive rate. We hypothesized that by reviewing demographic, clinical and nodule characteristics, we could identify risk factors associated with the presence of nodules on screening CT, and with the probability that a NCN was malignant.We performed a longitudinal lung cancer biomarker discovery trial (NYU LCBC) that included low-dose CT-screening of high-risk individuals over 50 years of age, with more than 20 pack-year smoking histories, living in an urban setting, and with a potential for asbestos exposure. We used case-control studies to identify risk factors associated with the presence of nodules (n=625) versus no nodules (n=557), and lung cancer patients (n=30) versus benign nodules (n=128).The NYU LCBC followed 1182 study subjects prospectively over a 10-year period. We found 52% to have NCNs >4 mm on their baseline screen. Most of the nodules were stable, and 9.7% of solid and 26.2% of sub-solid nodules resolved. We diagnosed 30 lung cancers, 26 stage I. Three patients had synchronous primary lung cancers or multifocal disease. Thus, there were 33 lung cancers: 10 incident, and 23 prevalent. A sub-group of the prevalent group were stable for a prolonged period prior to diagnosis. These were all stage I at diagnosis and 12/13 were adenocarcinomas.NCNs are common among CT-screened high-risk subjects and can often be managed conservatively. Risk factors for malignancy included increasing age, size and number of nodules, reduced FEV1 and FVC, and increased pack-years smoking. A sub-group of screen-detected cancers are slow-growing and may contribute to over-diagnosis and lead-time biases
Renormalization Group Functions of the \phi^4 Theory in the Strong Coupling Limit: Analytical Results
The previous attempts of reconstructing the Gell-Mann-Low function \beta(g)
of the \phi^4 theory by summing perturbation series give the asymptotic
behavior \beta(g) = \beta_\infty g^\alpha in the limit g\to \infty, where
\alpha \approx 1 for the space dimensions d = 2,3,4. It can be hypothesized
that the asymptotic behavior is \beta(g) ~ g for all values of d. The
consideration of the zero-dimensional case supports this hypothesis and reveals
the mechanism of its appearance: it is associated with a zero of one of the
functional integrals. The generalization of the analysis confirms the
asymptotic behavior \beta(g)=\beta_\infty g in the general d-dimensional case.
The asymptotic behavior of other renormalization group functions is constant.
The connection with the zero-charge problem and triviality of the \phi^4 theory
is discussed.Comment: PDF, 17 page
Maroon Archaeology Beyond the Americas: A View From Kenya
Archaeological research on Maroonsâthat is, runaway slavesâhas been largely confined to the Americas. This essay advocates a more global approach. It specifically uses two runaway slave communities in 19th-century coastal Kenya to rethink prominent interpretive themes in the field, including âAfricanisms,â Maroonsâ connections to indigenous groups, and Maroon group cohesion and identity. This articleâs analysis demonstrates that the comparisons enabled by a more globalized perspective benefit the field. Instead of eliding historical and cultural context, these comparisons support the development of more localized and historically specific understandings of individual runaway slave communities both in Kenya and throughout the New World
Evolutionary connectionism: algorithmic principles underlying the evolution of biological organisation in evo-devo, evo-eco and evolutionary transitions
The mechanisms of variation, selection and inheritance, on which evolution by natural selection depends, are not fixed over evolutionary time. Current evolutionary biology is increasingly focussed on understanding how the evolution of developmental organisations modifies the distribution of phenotypic variation, the evolution of ecological relationships modifies the selective environment, and the evolution of reproductive relationships modifies the heritability of the evolutionary unit. The major transitions in evolution, in particular, involve radical changes in developmental, ecological and reproductive organisations that instantiate variation, selection and inheritance at a higher level of biological organisation. However, current evolutionary theory is poorly equipped to describe how these organisations change over evolutionary time and especially how that results in adaptive complexes at successive scales of organisation (the key problem is that evolution is self-referential, i.e. the products of evolution change the parameters of the evolutionary process). Here we first reinterpret the central open questions in these domains from a perspective that emphasises the common underlying themes. We then synthesise the findings from a developing body of work that is building a new theoretical approach to these questions by converting well-understood theory and results from models of cognitive learning. Specifically, connectionist models of memory and learning demonstrate how simple incremental mechanisms, adjusting the relationships between individually-simple components, can produce organisations that exhibit complex system-level behaviours and improve the adaptive capabilities of the system. We use the term âevolutionary connectionismâ to recognise that, by functionally equivalent processes, natural selection acting on the relationships within and between evolutionary entities can result in organisations that produce complex system-level behaviours in evolutionary systems and modify the adaptive capabilities of natural selection over time. We review the evidence supporting the functional equivalences between the domains of learning and of evolution, and discuss the potential for this to resolve conceptual problems in our understanding of the evolution of developmental, ecological and reproductive organisations and, in particular, the major evolutionary transitions
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