850 research outputs found
Rectal Metastases from Squamous Cell Carcinoma: A Case Report and Review of the Literature
Non-small-cell lung cancer (NSCLC) represents 85% of lung cancer. The most frequent sites of distant metastasis are the liver, adrenal glands, bones and brain. Gastrointestinal metastases are uncommon and rectal metastases are extremely rare. Here we report a case of squamous cell carcinoma of the lung with rectal metastases
Nested species interactions promote feasibility over stability during the assembly of a pollinator community
The foundational concepts behind the persistence of ecological communities have been based on two ecological properties: dynamical stability and feasibility. The former is typically regarded as the capacity of a community to return to an original equilibrium state after a perturbation in species abundances and is usually linked to the strength of interspecific interactions. The latter is the capacity to sustain positive abundances on all its constituent species and is linked to both interspecific interactions and species demographic characteristics. Over the last 40 years, theoretical research in ecology has emphasized the search for conditions leading to the dynamical stability of ecological communities, while the conditions leading to feasibility have been overlooked. However, thus far, we have no evidence of whether species interactions are more conditioned by the community's need to be stable or feasible. Here, we introduce novel quantitative methods and use empirical data to investigate the consequences of species interactions on the dynamical stability and feasibility of mutualistic communities. First, we demonstrate that the more nested the species interactions in a community are, the lower the mutualistic strength that the community can tolerate without losing dynamical stability. Second, we show that high feasibility in a community can be reached either with high mutualistic strength or with highly nested species interactions. Third, we find that during the assembly process of a seasonal pollinator community located at The Zackenberg Research Station (northeastern Greenland), a high feasibility is reached through the nested species interactions established between newcomer and resident species. Our findings imply that nested mutualistic communities promote feasibility over stability, which may suggest that the former can be key for community persistence
Analysis of a three-component model phase diagram by Catastrophe Theory
We analyze the thermodynamical potential of a lattice gas model with three
components and five parameters using the methods of Catastrophe Theory. We find
the highest singularity, which has codimension five, and establish its
transversality. Hence the corresponding seven-degree Landau potential, the
canonical form Wigwam or , constitutes the adequate starting point to
study the overall phase diagram of this model.Comment: 16 pages, Latex file, submitted to Phys. Rev.
A multi-band AGN-SFG classifier for extragalactic radio surveys using machine learning
Extragalactic radio continuum surveys play an increasingly more important
role in galaxy evolution and cosmology studies. While radio galaxies and radio
quasars dominate at the bright end, star-forming galaxies (SFGs) and
radio-quiet Active Galactic Nuclei (AGNs) are more common at fainter flux
densities. Our aim is to develop a machine learning classifier that can
efficiently and reliably separate AGNs and SFGs in radio continuum surveys. We
perform supervised classification of SFGs vs AGNs using the Light Gradient
Boosting Machine (LGBM) on three LOFAR Deep Fields (Lockman Hole, Bootes and
ELAIS-N1), which benefit from a wide range of high-quality multi-wavelength
data and classification labels derived from extensive spectral energy
distribution (SED) analyses. Our trained model has a precision of 0.92(0.01)
and a recall of 0.87(0.02) for SFGs. For AGNs, the model has slightly worse
performance, with a precision of 0.87(0.02) and recall of 0.78(0.02). These
results demonstrate that our trained model can successfully reproduce the
classification labels derived from detailed SED analysis. The model performance
decreases towards higher redshifts, mainly due to smaller training sample
sizes. To make the classifier more adaptable to other radio galaxy surveys, we
also investigate how our classifier performs with a poorer multi-wavelength
sampling of the SED. In particular, we find that the far-infrared (FIR) and
radio bands are of great importance. We also find that higher S/N in some
photometric bands leads to a significant boost in the model's performance. In
addition to using the 150 MHz radio data, our model can also be used with 1.4
GHz radio data. Converting 1.4 GHz to 150 MHz radio data reduces performance by
about 4% in precision and 3% in recall. The final trained model is publicly
available at https://github.com/Jesper-Karsten/MBASCComment: 14 pages 9 figures Accepted for publication in A&
The role of nutrient loading and eutrophication in estuarine ecology.
Eutrophication is a process that can be defined as an increase in the rate of supply of organic matter (OM) to an ecosystem. We provide a general overview of the major features driving estuarine eutrophication and outline some of the consequences of that process. The main chemical constituent of OM is carbon (C), and therefore rates of eutrophication are expressed in units of C per area per unit time. OM occurs in both particulate and dissolved forms. Allochthonous OM originates outside the estuary, whereas autochthonous OM is generated within the system, mostly by primary producers or by benthic regeneration of OM. The supply rates of limiting nutrients regulate phytoplankton productivity that contributes to inputs of autochthonous OM. The trophic status of an estuary is often based on eutrophication rates and can be categorized as oligotrophic (<100 g C m(-2) y(-1), mesotrophic (100-300 g C m(-2) y(-1), eutrophic (300-500 g C m(-2) y(-1), or hypertrophic (>500 g C m(-2) y(-1). Ecosystem responses to eutrophication depend on both export rates (flushing, microbially mediated losses through respiration, and denitrification) and recycling/regeneration rates within the estuary. The mitigation of the effects of eutrophication involves the regulation of inorganic nutrient (primarily N and P) inputs into receiving waters. Appropriately scaled and parameterized nutrient and hydrologic controls are the only realistic options for controlling phytoplankton blooms, algal toxicity, and other symptoms of eutrophication in estuarine ecosystems
Global patterns of phosphatase activity in natural soils
Soil phosphatase levels strongly control the biotic pathways of phosphorus (P), an essential element for life, which is often limiting in terrestrial ecosystems. We investigated the influence of climatic and soil traits on phosphatase activity in terrestrial systems using metadata analysis from published studies. This is the first analysis of global measurements of phosphatase in natural soils. Our results suggest that organic P (Porg), rather than available P, is the most important P fraction in predicting phosphatase activity. Structural equation modeling using soil total nitrogen (TN), mean annual precipitation, mean annual temperature, thermal amplitude and total soil carbon as most available predictor variables explained up to 50% of the spatial variance in phosphatase activity. In this analysis, Porg could not be tested and among the rest of available variables, TN was the most important factor explaining the observed spatial gradients in phosphatase activity. On the other hand, phosphatase activity was also found to be associated with climatic conditions and soil type across different biomes worldwide. The close association among different predictors like Porg, TN and precipitation suggest that P recycling is driven by a broad scale pattern of ecosystem productivity capacity
Phytoplankton dynamics in relation to seasonal variability and upwelling and relaxation patterns at the mouth of Ria de Aveiro (West Iberian Margin) over a four-year period
From June 2004 to December 2007, samples were weekly collected at a fixed station located at the mouth of Ria de Aveiro (West Iberian Margin). We examined the seasonal and inter-annual fluctuations in composition and community structure of the phytoplankton in relation to the main environmental drivers and assessed the influence of the oceano-graphic regime, namely changes in frequency and intensity of upwelling events, over the dynamics of the phytoplankton assemblage. The samples were consistently handled and a final subset of 136 OTUs (taxa with relative abundance > 0.01%) was subsequently submitted to various multivariate analyses. The phytoplankton assemblage showed significant changes at all temporal scales but with an overriding importance of seasonality over longer-(inter-annual) or shorter-term fluctuations (upwelling-related). Sea-surface temperature, salinity and maximum upwelling index were retrieved as the main driver of seasonal change. Seasonal signal was most evident in the fluctuations of chlorophyll a concentration and in the high turnover from the winter to spring phytoplankton assemblage. The seasonal cycle of production and succession was disturbed by upwelling events known to disrupt thermal stratification and induce changes in the phytoplankton assemblage. Our results indicate that both the frequency and intensity of physical forcing were important drivers of such variability, but the outcome in terms of species composition was highly dependent on the available local pool of species and the timing of those events in relation to the seasonal cycle. We conclude that duration, frequency and intensity of upwelling events, which vary seasonally and inter-annually, are paramount for maintaining long-term phytoplankton diversity likely by allowing unstable coexistence and incorporating species turnover at different scales. Our results contribute to the understanding of the complex mechanisms of coastal phytoplankton dynamics in relation to changing physical forcing which is fundamental to improve predictability of future prospects under climate change.Portuguese Foundation for Science and Technology (FCT, Portugal) [SFRH/BPD/ 94562/2013]; FEDER funds; national funds; CESAM [UID/AMB/50017]; FCT/MEC through national funds; FEDERinfo:eu-repo/semantics/publishedVersio
Foliation and magnetic fabrics associated with fold interference in the Pyrenean Axial Zone (La Seu d’Urgell, Lleida)
La zona de estudio, en las inmediaciones de La Seu d’Urgell (Zona
Axial pirenaica), está constituida por una serie estratigráfica de rocas
Cambro-Ordovícicas, en su mayoría detríticas, donde la discordancia
Sarda se identifica claramente entre la Serie de Jujols y la Fm. Conglomerados de la Rabassa. Las principales estructuras son pliegues N-S
de plano axial subhorizontal que muestran una foliación asociada, bien
desarrollada en los niveles pelíticos (y claramente visibles en lámina
delgada) y pobremente desarrollada en los niveles de arenisca. En los
conglomerados suprayacentes a la discordancia Sarda (Fm. Conglomerados de la Rabassa) la foliación regional se caracteriza por tener sobreimpuestas bandas de cizalla conjugadas que rodean los clastos. Las
fábricas magnéticas (principalmente paramagnéticas) son coherentes
con las microestructuras observadas a pesar de que la correspondencia entre los ejes de las fábricas magnéticas y los ejes de las estructuras
observadas en el campo no es sencilla. El máximo de las direcciones de
lineación es bimodal (N-S y E-W), lo cual puede ser interpretado como el
resultado de una interferencia de pliegues (tipo 2 de RamsayThe study area, in the vicinity of La Seu d’Urgell (Pyrenean Axial
Zone), is composed of a stratigraphic series of Cambro-Ordovician
rocks, mostly detrital, where the Sardic unconformity can be clearly identified, between the Jujols Series and Rabassa conglomerates
Formation. The main structures are N-S folds with horizontal axial
surfaces, that show an associated cleavage, well developed in the
pelitic levels (and clearly distinguished in thin sections) and more
poorly developed in the sandstone levels. In the conglomerates
overlying the Sardic unconformity (Rabassa conglomerates Fm.) the
regional cleavage is characterized by superposed conjugate shear
bands surrounding the clasts. Magnetic fabrics (mainly paramagnetic) are consistent with the observed microstructures,although the
correspondence of axes between the magnetic fabric and the structures observed in the field is not straightforward. The orientation of
lineation directions are bimodal (N-S and E-W), a fact that can be
interpreted as the result of fold interference (type 2 of Ramsay
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