Land degradation caused by deforestation, overgrazing, and inappropriate irrigation practices affects about 16% of Latin America and the Caribbean (LAC). This paper addresses issues related to the ...application of remote sensing technologies for the identification and mapping of land degradation features, with special attention to the LAC region. The contribution of remote sensing to mapping land degradation is analyzed from the compilation of a large set of research papers published between the 1980s and 2009, dealing with water and wind erosion, salinization, and changes of vegetation cover. The analysis undertaken found that Landsat series (MSS, TM, ETM+) are the most commonly used data source (49% of the papers report their use), followed by aerial photographs (39%), and microwave sensing (ERS, JERS-1, Radarsat) (27%). About 43% of the works analyzed use multi-scale, multi-sensor, multi-spectral approaches for mapping degraded areas, with a combination of visual interpretation and advanced image processing techniques. The use of more expensive hyperspectral and/or very high spatial resolution sensors like AVIRIS, Hyperion, SPOT-5, and IKONOS tends to be limited to small surface areas. The key issue of indicators that can directly or indirectly help recognize land degradation features in the visible, infrared, and microwave regions of the electromagnetic spectrum are discussed. Factors considered when selecting indicators for establishing land degradation baselines include, among others, the mapping scale, the spectral characteristics of the sensors, and the time of image acquisition. The validation methods used to assess the accuracy of maps produced with satellite data are discussed as well.
We study Lyapunov matrices for the class of integral delay systems with constant kernel and one delay. The uniqueness and computational issues of these Lyapunov matrices for exponentially stable ...systems are investigated.
Background Resting right heart catheterization can assess both left heart filling and pulmonary artery (PA) pressures to identify and classify pulmonary hypertension. Although exercise may further ...elucidate hemodynamic abnormalities, current pulmonary hypertension classifications do not consider the expected interrelationship between PA and left heart filling pressures. This study explored the utility of this relationship to enhance the classification of exercise hemodynamic phenotypes in pulmonary hypertension. Methods and Results Data from 36 healthy individuals (55, 50-60 years, 50% male) and 85 consecutive patients (60, 49-71 years, 48% male) with dyspnea and/or suspected pulmonary hypertension of uncertain etiology were analyzed. Right heart catheterization was performed at rest and during semiupright submaximal cycling. To classify exercise phenotypes in patients, upper 95% CIs were identified from the healthy individuals for the change from rest to exercise in mean PA pressure over cardiac output (ΔmPAP/ΔCO ≤3.2 Wood units WU), pulmonary artery wedge pressure over CO (ΔPAWP/ΔCO ≤2 mm Hg/L per minute), and exercise PA pulse pressure over PAWP (PP/PAWP ≤2.5). Among patients with a ΔmPAP/ΔCO ≤3.2 WU, the majority (84%) demonstrated a ΔPAWP/ΔCO ≤2 mm Hg/L per minute, yet 23% demonstrated an exercise PP/PAWP >2.5. Among patients with a ΔmPAP/ΔCO >3.2 WU, 37% had an exercise PP/PAWP >2.5 split between ΔPAWP/ΔCO groups. Patients with normal hemodynamic classification declined from 52% at rest to 36% with exercise. Conclusions The addition of PP/PAWP to classify exercise hemodynamics uncovers previously unrecognized abnormal phenotypes within each ΔmPAP/ΔCO group. Our study refines abnormal exercise hemodynamic phenotypes based on an understanding of the interrelationship between PA and left heart filling pressures.
This study presents the experiments, modeling and numerical simulations of an industrial aeronautical structure subjected to vibroacoustic excitation. In flight, especially during atmospheric ...re-entry, an aeronautical structure is exposed to major pressure fluctuations on its external surface. These fluctuations are described as a dynamic excitation which generates structural vibrations of the outer surface and of the components inside the aeronautical structure. Due to some of these internal components such as joints, the assembly may exhibit a nonlinear vibration response. The simulation of these nonlinear vibrations requires reliable modeling of the wall pressure fluctuations and a nonlinear vibration simulation method adapted to the nonlinear modeling of the structure. In this study, a modeling and simulation method is developed to compute the nonlinear vibration response of an industrial assembly to such a surface, random, correlated dynamic excitation. More specifically, numerical simulations are performed by proposing an extension of the well-known Harmonic Balance Method for nonlinear mechanical systems subjected to complex vibroacoustic excitation. The method is validated using a dedicated ground experiment. A metallic industrial assembly representing a ballistic vehicle and including friction joints is used. This structure is subjected to controlled vibroacoustic excitation: diffuse acoustic loading in a reverberant chamber. The structure exhibits a nonlinear vibration response due to friction. The finite element model is validated through an experimental modal analysis with an electrodynamic shaker. The vibroacoustic modeling of the excitation is then validated through a test-simulation comparison using diffuse acoustic field testing at low excitation level. Then the global nonlinear simulation process is validated using diffuse acoustic field testing at increasing excitation levels. Test and simulation results exhibit the same nonlinear behavior: increase of dissipation and softening effect at the main resonances. This work thus represents a new step towards the use of nonlinear vibration simulation methods with real industrial structures and real-life loading.
•Experimental and numerical analysis of a ballistic vehicle subjected to vibroacoustic excitation.•Modeling of a real industrial structure with friction joints and real-life loading.•Extension of the Harmonic Balance Method for solving a nonlinear problem with vibroacoustic excitation.
The hydrogen isotopic composition (δ2H) of leaf waxes, especially of n-alkanes (δ2Hn-alkanes), is increasingly used for paleohydrological and paleoclimate reconstructions. However, it is challenging ...to disentangle past changes in the isotopic composition of precipitation and changes in evapotranspirative enrichment of leaf water, which are both recorded in leaf wax δ2H values. In order to overcome this limitation, Zech M. et al. (2013) proposed a coupled δ2Hn-alkane–δ18Osugar biomarker approach. This coupled approach allows for calculating (i) biomarker-based “reconstructed”δ2H/δ18O values of leaf water (δ2H/δ18Oleaf water), (ii) biomarker-based reconstructed deuterium excess (d-excess) of leaf water, which mainly reflects evapotranspirative enrichment and which can be used to reconstruct relative air humidity (RH) and (iii) biomarker-based reconstructed δ2H/δ18Oprecipitation values. Here we present a climate transect validation study by coupling new results from δ2H analyses of n-alkanes and fatty acids in topsoils along a climate transect in Argentina with previously measured δ18O results obtained for plant-derived sugars. Accordingly, both the reconstructed RH and δ2H/δ18Oprecipitation values correlate highly significantly with actual RH and δ2H/δ18Oprecipitation values. We conclude that compared to single δ2Hn-alkane or δ18Osugar records, the proposed coupled δ2Hn-alkane–δ18Osugar biomarker approach will allow more robust δ2H/δ18Oprecipitation reconstructions in future paleoclimate research. Additionally, the proposed coupled δ2Hn-alkane–δ18Osugar biomarker approach allows for the establishment of a “paleohygrometer”, more specifically, the reconstruction of mean summer daytime RH changes/history.
Exercise imposes increased pulmonary vascular afterload based on rises in pulmonary artery (PA) wedge pressure, declines in PA compliance, and resistance‐compliance time. In health, afterload stress ...stabilizes during steady‐state exercise. Our objective was to examine alterations of these exercise‐associated stresses in states of pre‐ and post‐capillary pulmonary hypertension (PH). PA hemodynamics were evaluated at rest, 2 and 7 min of steady‐state exercise at moderate intensity in patients who exhibited Pre‐capillary (n = 22) and post‐capillary PH (n = 22). Patients with normal exercise hemodynamics (NOR‐HD) (n = 32) were also studied. During exercise in all groups, PA wedge pressure increased at 2 min, with no further change at 7 min. In post‐capillary PH and NOR‐HD, increases in PA diastolic pressure and diastolic pressure gradient remained stable at 2 and 7 min of exercise, while in pre‐capillary PH, both continued to increase at 7 min. The behavior of the diastolic pressure gradient was linearly related to the duration of resistance‐compliance time at rest (r2 = 0.843) and exercise (r2 = 0.760). Exercise resistance‐compliance time was longer in pre‐capillary PH associated with larger increases in diastolic pressure gradient. Conversely, resistance‐compliance time was shortest in post‐capillary PH compared to pre‐capillary PH and NOR‐HD and associated with limited increases in exercise diastolic pressure gradient. During steady‐state, modest‐intensity exercise‐specific patterns of pulmonary vascular afterload responses were observed in pre‐ and post‐capillary PH relative to NOR‐HD. Longer resistance‐compliance time related to greater increases in PA diastolic pressure and diastolic pressure gradients in pre‐capillary PH, while shorter resistance‐compliance time appeared to limit these increases in post‐capillary PH.
We assessed patterns of change in hemodynamics and pulmonary vascular afterload over a period of steady‐state exercise in patients with pre‐ and post‐capillary pulmonary hypertension. Patients with normal hemodynamics were also studied. The responses of the resistance‐compliance time, prolonged in pre‐capillary pulmonary hypertension and shortest in post‐capillary pulmonary hypertension, were strongly associated with the diastolic pressure gradient. These differences accounted for the distinctive patterns of change in pulmonary vascular afterload observed between pre‐ and post‐capillary pulmonary hypertension.
Contrast-induced acute kidney injury (CI-AKI) is a common event after percutaneous coronary intervention (PCI). Presently, the main strategy to avoid CI-AKI lies in saline hydration, since to date ...none pharmacologic prophylaxis proved beneficial. Our aim was to determine if a low complexity mortality risk model is able to predict CI-AKI in patients undergoing PCI after ST elevation myocardial infarction (STEMI). We have included patients with STEMI submitted to primary PCI in a tertiary hospital. The definition of CI-AKI was a raise of 0.3 mg/dL or 50% in post procedure (24–72 h) serum creatinine compared to baseline. Age, glomerular filtration and ejection fraction were used to calculate ACEF-MDRD score. We have included 347 patients with mean age of 60 years. In univariate analysis, age, diabetes, previous ASA use, Killip 3 or 4 at admission, ACEF-MDRD and Mehran scores were predictors of CI-AKI. After multivariate adjustment, only ACEF-MDRD score and diabetes remained CI-AKI predictors. Areas under the ROC curve of ACEF-MDRD and Mehran scores were 0.733 (0.68–0.78) and 0.649 (0.59–0.70), respectively. When we compared both scores with DeLong test ACEF-MDRDs AUC was greater than Mehran’s (
P
= 0.03). An ACEF-MDRD score of 2.33 or lower has a negative predictive value of 92.6% for development of CI-AKI. ACEF-MDRD score is a user-friendly tool that has an excellent CI-AKI predictive accuracy in patients undergoing primary percutaneous coronary intervention. Moreover, a low ACEF-MDRD score has a very good negative predictive value for CI-AKI, which makes this complication unlikely in patients with an ACEF-MDRD score of <2.33.
The spectrum of patients referred for suspected pulmonary arterial hypertension (PAH) includes a population with clinical features suggestive of pulmonary hypertension due to left heart disease ...(PH‐LHD). Even after right heart catheterization (RHC) performed at rest, it can be a challenge to identify patients who will clearly benefit from PAH drug therapy. Therefore, the objective of this study was to evaluate the role of exercise RHC to influence decisions regarding prescription of PAH drug therapy in this population. A retrospective cohort study was conducted of older adults with risk factors for PH‐LHD and suspected PH referred for exercise RHC. One year follow‐up was conducted to record clinical outcomes, all changes in PAH drug therapy, and changes in patient‐reported quality of life. The final cohort included 61 patients, mean age of 69 ± 10; 44% and 34% had a history of coronary artery disease and atrial fibrillation respectively. Exercise changed the proportional breakdown of hemodynamic diagnoses from 36% No PH, 44% PAH, and 20% PH‐LHD at rest to 15% No PH, 36% PAH, and 49% PH‐LHD. Although a significant proportion of patients were reclassified as PH‐LHD, there was an overall increase in the proportion of patients receiving PAH drug therapy, particularly for those with PAH confirmed by exercise RHC. A total of 11 PAH drug prescriptions were employed before exercise RHC increasing to 24 after (p = 0.002). Patients receiving PAH therapy demonstrated significant improvement in self‐reported quality of life. Exercise RHC appeared to influence selection of PAH drug therapy.
Recent studies of soil–landscape relationships in northeastern Patagonia identified fibrous-clay minerals in calcic and petrocalcic horizons developed on old fluvio-glacial plains called “Rodados ...Patagónicos” (RP). The objectives of this study were: i) to evaluate the occurrence of fibrous-clay minerals in the arid soil environment, and ii) to establish the relationship between the soil properties and degree of the calcic horizon development, including the age of the soils containing fibrous-clay minerals in extra-Andean Patagonia. The soil studied were Calciargids, Natrigypsids, and Petrocalcids, located at elevations of 50, 70, and 130 m a.s.l., respectively. The soils are polygenetic, where the clay mineralogy is related to the age of the pedogenetic periods that affected the formation of geomorphic surfaces. In the surface horizons, illite proved to be the dominant clay mineral and was slightly altered to interstratified illite–smectite and smectite. An older pedogenic episode was identified in argillic and calcic horizons, in which smectite was prevalent. The following soil-formation period was recorded in calcic and calcic-gypsic horizons appearing in the upper limit of the RP. In these horizons, palygorskite is the dominant clay mineral. Pedogenetic carbonate was qualified as low-Mg calcite, indicating that during its precipitation, the Mg
2+ activity increased in the soil solution, favoring the smectite
→
palygorskite transformation. The soil environment, favorable for this transformation, was the textural transition between the fine materials of sub-surface horizons and the coarsest deposit of RP, where temporary waterlogging occurred. The petrocalcic horizons, and their re-transported fragments, represent the oldest pedogenetic period, where sepiolite was the dominant clay mineral. During the calcretization processes, the sepiolite was precipitated from the soil solution following the formation of palygorskite. Fluorite was identified in the petrocalcic horizon, and its association with calcite and sepiolite indicated a successive precipitation of these minerals under alkaline conditions during evaporation processes.
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