Aliment Pharmacol Ther 2011; 33: 585–591
Summary
Background Temporal changes in the incidence of cause‐specific gastrointestinal (GI) complications may be one of the factors underlying changing ...medical practice patterns.
Aim To report temporal changes in the incidence of five major causes of specific gastrointestinal (GI) complication events.
Methodology Population‐based study of patients hospitalised due to GI bleeding and perforation from 1996 to 2005 in Spain. We report crude rates, and estimate regression coefficients of temporal trends, severity and recorded drug use for five frequent GI events. GI hospitalisation charts were validated by independent review of large random samples.
Results The incidence per 100 000 person‐years of hospitalisations due to upper GI ulcer bleeding and perforation decreased over time from 54.6 and 3.9 in 1996 (R2 = 0.944) to 25.8 and 2.9 in 2005 (R2 = 0.410) respectively. On the contrary, the incidence per 100 000 person‐years of colonic diverticular and angiodysplasia bleeding increased over time 3.3 and 0.9 in 1996 (R2 = 0.443) and 8.0 and 2.6 in 2005 (R2 = 0.715) respectively. A small increasing trend was observed for the incidence per 100 000 person‐years of intestinal perforations (from 1.5 to 2.3 events). Based on data extracted from the validation process, recent recorded drug intake showed an increased frequency of anticoagulants with colonic diverticular and angiodysplasia bleeding, whereas NSAID and low‐dose aspirin use were more prevalent in peptic ulcer bleeding and colonic diverticular bleeding respectively.
Conclusions From 1996 to 2005, hospitalisations due to peptic ulcer bleeding and perforation have decreased significantly, whereas the number of cases of colonic diverticular and angiodysplasia bleeding have increased.
Self-heating of rolled ZnCuTi sheets MILESI, M; MUÑOZ, D PINO; LAGROUM, A ...
Sadhana (Bangalore),
12/2020, Letnik:
45, Številka:
1
Journal Article
Recenzirano
Self-heating effect for thermomechanical forming processes turns out to be dramatically significant for material with a very low melting point, such as zinc alloys. Zinc low melting point temperature ...(419.54°C) accentuates metallurgical effects when it is formed in cold or warm manufacturing processes. During deformation, self-heating can therefore induce a relative softening in the behavior law (that could improve formability) which competes with the conventional plastic hardening of the material. Hence, the correct identification of zinc material behavior has to account for both softening and hardening phenomena. This paper studies the effect of plastic work energy in the material identified by means of tensile tests by combining digital image correlation and infrared thermography technique.
Phytoplankton blooms in the Barents Sea are highly sensitive to seasonal and interannual changes in sea ice extent, water mass distribution, and oceanic fronts. With the ongoing increase of Atlantic ...Water inflows, we expect an impact on these blooms. Here, we use a state‐of‐the‐art collection of in situ hydrogeochemical data for the period 1998–2014, which includes ocean color satellite‐derived proxies for the biomass of calcifying and noncalcifying phytoplankton. Over the last 17 years, sea ice extent anomalies were evidenced having direct consequences for the spatial extent of spring blooms in the Barents Sea. In years of minimal sea ice extent, two spatially distinct blooms were clearly observed: one along the ice edge and another in ice‐free water. These blooms are thought to be triggered by different stratification mechanisms: heating of the surface layers in ice‐free waters and melting of the sea ice along the ice edge. In years of maximal sea ice extent, no such spatial delimitation was observed. The spring bloom generally ended in June when nutrients in the surface layer were depleted. This was followed by a stratified and oligotrophic summer period. A coccolithophore bloom generally developed in August, but was confined only to Atlantic Waters. In these same waters, a late summer bloom of noncalcifying algae was observed in September, triggered by enhanced mixing, which replenishes surface waters with nutrients. Altogether, the 17 year time‐series revealed a northward and eastward shift of the spring and summer phytoplankton blooms.
Key Points
A 17 year time‐series of remotely sensed and in situ observations is used to describe the variability of phytoplankton blooms
At least three distinct blooms were revealed and are partly controlled by the position of the sea ice edge and the polar front
A north‐eastward shift of the spring and summer blooms was observed
Oxygen minimum zones (OMZs), known as suboxic layers which are mainly localized in the Eastern Boundary Upwelling Systems, have been expanding since the 20th "high CO2 " century, probably due to ...global warming. OMZs are also known to significantly contribute to the oceanic production of N2 O, a greenhouse gas (GHG) more efficient than CO2 . However, the contribution of the OMZs on the oceanic sources and sinks budget of CO2 , the main GHG, still remains to be established. We present here the dissolved inorganic carbon (DIC) structure, associated locally with the Chilean OMZ and globally with the main most intense OMZs (O2 <20 μmol kg-1 ) in the open ocean. To achieve this, we examine simultaneous DIC and O2 data collected off Chile during 4 cruises (2000-2002) and a monthly monitoring (2000-2001) in one of the shallowest OMZs, along with international DIC and O2 databases and climatology for other OMZs. High DIC concentrations (>2225 μmol kg-1 , up to 2350 μmol kg-1 ) have been reported over the whole OMZ thickness, allowing the definition for all studied OMZs a Carbon Maximum Zone (CMZ). Locally off Chile, the shallow cores of the OMZ and CMZ are spatially and temporally collocated at 21° S, 30° S and 36° S despite different cross-shore, long-shore and seasonal configurations. Globally, the mean state of the main OMZs also corresponds to the largest carbon reserves of the ocean in subsurface waters. The CMZs-OMZs could then induce a positive feedback for the atmosphere during upwelling activity, as potential direct local sources of CO2 . The CMZ paradoxically presents a slight "carbon deficit" in its core (~10%), meaning a DIC increase from the oxygenated ocean to the OMZ lower than the corresponding O2 decrease (assuming classical C/O molar ratios). This "carbon deficit" would be related to regional thermal mechanisms affecting faster O2 than DIC (due to the carbonate buffer effect) and occurring upstream in warm waters (e.g., in the Equatorial Divergence), where the CMZ-OMZ core originates. The "carbon deficit" in the CMZ core would be mainly compensated locally at the oxycline, by a "carbon excess" induced by a specific remineralization. Indeed, a possible co-existence of bacterial heterotrophic and autotrophic processes usually occurring at different depths could stimulate an intense aerobic-anaerobic remineralization, inducing the deviation of C/O molar ratios from the canonical Redfield ratios. Further studies to confirm these results for all OMZs are required to understand the OMZ effects on both climatic feedback mechanisms and marine ecosystem perturbations.
The goal of this work is to predict ductile failure of pipe-ring notched AISI 316L specimens, where notches mimic the geometry of corrosion defects. Uncoupled damage models are used to that end. The ...Johnson-Cook and Lou-Huh criteria are calibrated.
The uncoupled damage models are calibrated using experimental results from testing pipe-ring notched specimens. Calibration was achieved using a hybrid experimental-numerical approach. Six notch shapes are studied. Experimental matrices are designed to determine these shapes, and the pipe-ring notched specimen is inspired from the literature.
Calibration of the uncoupled damage models require a ductile crack initiation indicator. The first indicator was based on the derivative curves of the force versus the connectors displacement curve. The second was based on the raw images of the gage section. The third was based on a percentage of the connectors displacement at fracture.
Results show that ductile fracture depends on the Lode paramater. As a consequence, the Lou-Huh criterion is more effective at predicting ductile fracture than the Johnson-Cook criterion.
•Notched samples were designed to mimic the corrosion defects observed on 316L pipes.•A methodology was developed to cover η and L locally underwent by pressurized pipes.•Ductile fracture models were calibrated using a hybrid approach.•The experimental crack initiation indicator reliability requires further improvement.•A slight Lode parameter influence was observed at high η.
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•3D full field FE simulations of DRX up to high strain considering grain topology•CPFEM coupled with a level-set framework and with a nucleation phenomenological law.•Information ...provided by CPFEM is used to define new criteria for nuclei position.•Simulation of industrial forming processes possible in this framework.
This work describes the coupling of a level-set (LS) based numerical framework for microstructural evolutions modeling with a crystal plasticity finite element method (CPFEM), in order to propose a new full field approach dedicated to dynamic recrystallization (DRX) modeling. These developments are proposed for 3D polycrystalline metals subjected to large deformations at high temperatures.
CPFEM is one of the best available alternatives to model the evolution of dislocation densities and misorientation during plastic deformation. The dislocation density and misorientation is then used as input data for the recrystallization model. Grain boundary migration (GBM) is modeled by using a kinetic law which links the velocity of the grain boundaries, described by LS functions, with the thermodynamic driving pressures. The nucleation of new grains is modeled by using phenomenological laws, which define the number of nucleation sites as a function of the dislocation density and the misorientation. The link between the CPFEM and the GBM model gives an accurate description of the DRX phenomenon, which is intended to model industrial processes.
In this work the methods and the coupling algorithm are presented, along with an analysis of the different numerical parameters and strategies to define nucleation. The calibration and validation of the model against experimental data for 304L steel will be presented in a future work.
The presence of voids after casting processes of large metal workpieces requires the use of adapted hot metal forming processes to deliver sound products. Yet, there is at present a lack of knowledge ...regarding void closure mechanisms and there is no reliable model that can accurately predict void closure. The main aim of this work is to develop a highly accurate mean field model able to predict the evolution of the voids volume after each forming stage. This proposed model is accounting for both stress triaxiality ratio Tx and Lode angle θ in order to override the hypothesis of axisymmetric loading, which is generally considered in the existing models handling void closure in the literature. Based on an advanced multiscale approach, this model also accounts for voids shape and orientation. An optimization method, using a database of explicit RVE simulations, is developed in order to calibrate the new proposed model. Several void morphological parameters and an industrial range of mechanical loading parameters are analyzed regarding void closure. The proposed mean field model is validated by comparison with explicit full field simulations and with a recent pre-existing mean field model, named Cicaporo1 model hereafter (Saby et al., 2015 19). In comparison with Cicaporo1, the new model, named Cicaporo2 hereafter, uses less constants and is more accurate.
•The modelling of void closure in hot metal forming processes is addressed.•The Lode angle is used to define the stress state in general cases.•A model accounting for both stress triaxiality and Lode angle is proposed.•This model also accounts for voids shape and orientation.
We investigate the decay of planetary boundary layer (PBL) turbulence in the afternoon, from the time the surface buoyancy flux starts to decrease until sunset. Dense observations of mean and ...turbulent parameters were acquired during the Boundary Layer Late Afternoon and Sunset Turbulence (BLLAST) field experiment by several meteorological surface stations, sounding balloons, radars, lidars and two aircraft during the afternoon transition. We analysed a case study based on some of these observations and large-eddy simulation (LES) data focusing on the turbulent vertical structure throughout the afternoon transition. The decay of turbulence is quantified through the temporal and vertical evolution of (1) the turbulence kinetic energy (TKE), (2) the characteristic length scales of turbulence and (3) the shape of the turbulence spectra. A spectral analysis of LES data, airborne and surface measurements is performed in order to characterize the variation in the turbulent decay with height and study the distribution of turbulence over eddy size. This study highlights the LES ability to reproduce the turbulence evolution throughout the afternoon. LESs and observations agree that the afternoon transition can be divided in two phases: (1) a first phase during which the TKE decays at a low rate, with no significant change in turbulence characteristics, and (2) a second phase characterized by a larger TKE decay rate and a change in spectral shape, implying an evolution of eddy size distribution and energy cascade from low to high wave number. The changes observed either in TKE decay (during the first phase) or in the vertical wind spectra shape (during the second phase of the afternoon transition) occur first in the upper region of the PBL. The higher within the PBL, the stronger the spectra shape changes.
Due to the major role of the sun in heating the earth's surface, the atmospheric planetary boundary layer over land is inherently marked by a diurnal cycle. The afternoon transition, the period of ...the day that connects the daytime dry convective boundary layer to the night-time stable boundary layer, still has a number of unanswered scientific questions. This phase of the diurnal cycle is challenging from both modelling and observational perspectives: it is transitory, most of the forcings are small or null and the turbulence regime changes from fully convective, close to homogeneous and isotropic, toward a more heterogeneous and intermittent state. These issues motivated the BLLAST (Boundary-Layer Late Afternoon and Sunset Turbulence) field campaign that was conducted from 14 June to 8 July 2011 in southern France, in an area of complex and heterogeneous terrain. A wide range of instrumented platforms including full-size aircraft, remotely piloted aircraft systems, remote-sensing instruments, radiosoundings, tethered balloons, surface flux stations and various meteorological towers were deployed over different surface types. The boundary layer, from the earth's surface to the free troposphere, was probed during the entire day, with a focus and intense observation periods that were conducted from midday until sunset. The BLLAST field campaign also provided an opportunity to test innovative measurement systems, such as new miniaturized sensors, and a new technique for frequent radiosoundings of the low troposphere. Twelve fair weather days displaying various meteorological conditions were extensively documented during the field experiment. The boundary-layer growth varied from one day to another depending on many contributions including stability, advection, subsidence, the state of the previous day's residual layer, as well as local, meso- or synoptic scale conditions. Ground-based measurements combined with tethered-balloon and airborne observations captured the turbulence decay from the surface throughout the whole boundary layer and documented the evolution of the turbulence characteristic length scales during the transition period. Closely integrated with the field experiment, numerical studies are now underway with a complete hierarchy of models to support the data interpretation and improve the model representations.
Most of the contaminant conceptual models in weathered crystalline bedrock aquifers in Brazil rely on data collected using conventional site investigation methods, at insufficient spatial resolution ...for associating contaminant distributions with observed heterogeneity. The DFN methodology was adapted for the characterization of a chlorinated solvent contaminated weathered crystalline bedrock aquifer, located in the region of the Jurubatuba district, Sao Paulo city, Brazil. The objective of this research is to establish a detailed 1-D conceptual model to show variable contaminant distribution within the bedrock matrix under different fracture and weathering conditions. The numerous depth-discrete rock sample analyses, assigned to specific geologic features, indicate the presence of PCE-Dense Non-Aqueous Phase Liquid (DNAPL) at discrete-depth intervals along the profile. These zones are mainly related to the lithological contacts and interfaces among the weathered bedrock. The soft and hard weathered-bedrock transition zone does not indicate a sharp decrease in the contaminant mass retention within the bedrock matrix for the studied area. This indicates that contaminant mass storage in the bedrock remains beyond this drilling method-defined interface, which can potentially sustain dissolved VOC concentrations over time and maintain the continuous vertical mass flux into deeper parts of the aquifer. There is a demonstrated need for an appropriate characterization methodology including high-resolution soil coring and sampling to delineate contaminant distribution over crystalline weathered bedrock aquifers. This is a key assumption for the definition of appropriate remedial and groundwater management strategies.
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