1,720,964 research outputs found
Dike emplacement and flank instability at Mount Etna: Constraints from a poro-elastic-model of flank collapse
No full textMany volcanic edifices are subject to flank failure, usually produced by a combination of events, rather than any single process. From a dynamic point of view, the cause of collapse can be divided into factors that contribute to an increase in shear stress, and factors that contribute to the reduction in the friction coefficient μ of a potential basal failure plane. We study the potential for flank failure at Mount Etna considering a schematic section of the eastern flank, approximated by a wedge-like block. For such geometry, we perform a (steady state) limit equilibrium analysis: the resolution of the forces parallel to the possible basal failure plane allows us to determine the total force acting on the potentially unstable wedge. An estimate of the relative strength of these forces suggests that, in first approximation, the stability is controlled primarily by the balance between block weight, lithostatic load and magmatic forces. Any other force (sea load, hydrostatic uplift, and the uplift due to mechanical and thermal pore-fluid pressure) may be considered of second order. To study the model sensitivity, we let the inferred slope α of the basal surface failure vary between -10° and 10°, and consider three possible scenarios: no magma loading, magmastatic load, and magmastatic load with magma overpressure. We use error propagation to include in our analysis the uncertainties in the estimates of the mechanics and geometrical parameters controlling the block equilibrium. When there is no magma loading, the ratio between destabilizing and stabilizing forces is usually smaller than the coefficient of friction of the basal failure plane. In the absence of an initiating mechanism, and with the nominal values of the coefficient of friction μ= 0.7. ±. 0.1 proposed, the representative wedge will remain stable or continue to move at constant speed. In presence of magmastatic forces, the influence of the lateral restraint decreases. If we consider the magmastatic load only, the block will remain stable (or continue to move at constant speed), unless the transient mechanical and thermal pressurization significantly decrease the friction coefficient, increasing the instability of the flank wedge for α>. 5° (seaward dipping decollement). When the magma overpressure contribution is included in the equilibrium analysis, the ratio between destabilizing and stabilizing forces is of the same order or larger than the coefficient of friction of the basal failure plane, and the block will become unstable (or accelerate), especially in the case of the reduction in friction coefficient. Finally, our work suggests that the major challenge in studying flank instability at Mount Etna is not the lack of an appropriate physical model, but the limited knowledge of the mechanical and geometrical parameters describing the block equilibrium. © 2010 Elsevier B.V
Presacral myelolipoma in a patient with colon carcinoma
No full textMyelolipoma is an uncommon benign tumor, composed of an admixture of adipose tissue and hematopoietic cells, usually discovered within the adrenal glands. Extra-adrenal myelolipomas are rare and approximately half of the reported cases were presacral. We report a case of an asymptomatic presacral myelolipoma measuring 9x8x7 cm., incidentally found in a 71-year-old woman with a stenosing colon cancer. Ultrasonography, computed tomography and magnetic resonance imaging of the presacral mass evidenced a well circumscribed tumor with heterogeneous features due to a nonuniform composition. Surgical excision of the mass was performed
Synchronous colon and gastric advanced carcinomas
No full textAn unusual case of advanced synchronous colon and gastric carcinoma is described. A 36 year old female was admitted to our Department with a stenosing right colon cancer diagnosed at endoscopy which was performed for lower crampy abdominal pain and gross blood in the stool. Multiple colon polyps, distal to the tumor, were also detected. On preoperative abdominal computed tomography, a stenosing right colon cancer, without evidence of abdominal diffusion, was confirmed. At laparotomy, in addition to colon cancer, an antral gastric cancer was incidentally found. En bloc hemigastrectomy and subtotal colectomy were performed. Digestive continuity was restored by gastrojejunal and ileosigmoid anastomoses. At histology, a poorly differentiated gastric adenocarcinoma with signet ring-cell component (pT2, pN0; stage IB) and a moderately differentiated colon adenocarcinoma with a tubolovillous component (pT3, pN1; stage III, Stage Dukes C) were revealed. Both tumors showed a low expression of p53 and c-erb2 oncoproteins. No genetic defect was identified in the APC and MMR genes. The patient is alive, without recurrence, two years after the operation
Thermal anomaly at the Earth's surface associated with a lava tube
Full text linkLava tubes are frequently encountered in volcanic areas. The formation of lava tubes has strong implications on the volcanic hazard during effusive eruptions. The thermal dissipation of lava flowing in a tube is reduced in respect to the lava flowing in an open channel so the lava may threaten areas that would not be reached by flows in open channels: for this reason it is important to detect the presence of lava tubes.
In this work we propose a model to detect the presence and the characteristics of lava tubes by their thermal footprint at the surface. We model numerically the temperature distribution and the heat flow, both in the steady and the transient state, and we take into account the principal thermal effects due to the presence of an active lava tube, i.e. the conduction to the ground and the atmosphere, the convection and the radiation in the atmosphere. We assume that lava fluid is at high temperature, in motion inside a sloping tube under the gravity force.
The thermal profile across the tube direction, in particular the width of the temperature curve, allows to evaluate the depth of the tube. The values of maximum temperature and of tube depth allow to estimate the area of the tube section. The shape of the temperature curve and its asymmetry can give information about the geometry of the tube.
If we observe volcanic areas at different times by thermal cameras, we can detect anomalies and evaluate their causes during an eruption; in particular, we can evaluate whether they are due to active lava flows or not and what is their state. For lava tubes, we can connect thermal anomalies with lava tube position, characteristics and state
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Lymphadenectomy in gastric cancer: influence on prognosis of lymph node count.
No full textTo better understand the role of the number of lymph nodes retrieved on long-term outcome of gastric cancer treatment, 154 patients who had undergone curative resection, with dissection of >15 nodes were retrospectively studied. Dissection of perigastric and extraperigastric lymph nodes, defined as 'extended' (>26 nodes dissected) in 39 cases and 'limited' (7). The cumulative 5-year survival rate was 47% in patients without lymph node metastases; 29% in those with 1-7 nodes involved and 17% in those with >8 nodes involved (p=0.002). Receiver operating characteristic (ROC) curve analysis, in 65 nodenegative cancer cases, demonstrated an area under the curve for vital status (alive or dead) of 0.602 (95% CI: 0.473 - 0.721). All node-negative cases with a number equivalent to or exceeding the cutoff point of 23 nodes were alive. ROC analysis showed 11 to be the cutoff number of metastasized lymph nodes in correlation with vital status. Almost all those patients in whom the number of positive nodes was equivalent to, or exceeded the cutoff point had died (area under the ROC curve 0.633; 95% CI: 0.524 - 0.733). ROC analysis showed that the cutoff lymph node ratio, in relation to vital status, was 0.33. The majority of patients at or above this cutoff point had died (area under ROC curve 0.682; 95% CI: 0.574 - 0.776). Multivariate survival analysis showed that lymph node ratio was the only independent prognostic factor (p=0.001). The present findings suggest that, in lymphadenectomy with at least 15 nodes, the number and status of regional nodes dissected, irrespective of the location, provide reliable prognostic information on curatively resected gastric carcinomas
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