Pere Serra

Post-classification change detection with data from different sensors : Some accuracy considerations

Change detection from remote sensing data is often done by simple overlay of classified maps. However, such analyses can contain a significant proportion of boundary errors, especially when combining data from different sensors. This paper presents a protocol that allows reliable post-classification comparisons by taking into account classification accuracies, landscape fragmentation, planimetric accuracies, pixel sizes and grid origins. The proposed protocol has been applied, with little extra effort, in a fragmented agricultural Mediterranean zone using MSS (1970s) and TM (1990s) images. Applying the protocol, change detection had an accuracy of 85.1%, while for a direct overlay it was only 43.9% accurate. The drawback of this method is that it reduces the useful area of comparison. As the accuracy of individual classifications is critical, the paper also describes and tests a hybrid classifier that combines an unsupervised classification approach with training areas. This approach has proved more successful than maximum likelihood classifiers.

Depth profiling characterisation of the surface layer obtained by pulsed Nd:YAG laser irradiation of titanium in nitrogen

We investigated the composition of the surface layer obtained by pulsed Nd:YAG laser (λ=1.064 μm, τ∼120 ns, ν=1 kHz) irradiation of Ti targets in high pressure nitrogen. The surface morphology, the crystalline state, and the depth distribution of the elements were analysed by scanning electron microscopy, X-ray diffractometry, secondary ion mass spectrometry, X-ray photoelectron spectroscopy (XPS), and Auger electron spectroscopy. The chemical binding states were studied by deconvolution of the XPS spectra. The layer has a uniform surface, and mainly consists of the tetragonal δ′-TiNx crystalline phase. The nitrogen concentration increases firstly in the depth until approximately 0.15 μm, and then decreases until the greatest measured depth of 2 μm. The TiNx stoichiometry changes from x≈0.8 close to the surface to x≈0.5 at a depth of approximately 0.2 μm, it remains around this value until approximately 0.5 μm, and for greater depths decreases until 0.1 at 1.6 μm. Furthermore, the oxygen concentration decreases quickly and reaches the concentration of bulk Ti at approximately 0.2 μm.

Deposition of hydroxyapatite thin films by excimer laser ablation

Abstract The influence of the pressure of a sole water atmosphere during the pulsed laser deposition of hydroxyapatite thin films on Ti–6Al–4V substrates has been studied. The rest of the technological parameters involved in the process have been fixed near the conditions where the best crystalline coatings are obtained. The pressure of the water atmosphere has been varied between 0.15 and 1.5 mbar. The films properties have been analysed by means of XRD, SEM, FT-IR spectroscopy and SIMS. An optimal region, in order to obtain thin films of highly crystalline hydroxyapatite, has been found near 0.5 mbar for the two excimer laser wavelengths (193 nm and 248 nm) used in this study. These films have a preferential orientation in the (100) direction.

Coloring of titanium by pulsed laser processing in air

Surface treatments of titanium in air were performed by scanning with a Nd:YAG (ls1.064 mm) pulsed laser beam at high repetition rate.Different colored samples were obtained depending on the laser accumulated fluence.The surface morphology and cross-sections of the coatings were studied by scanning electron microscopy, revealing the formation of a bi-layer structure consisting of a thin shallow layer covering a thicker layer.Compositional analyses performed by X-ray diffraction and Raman spectroscopy measurements revealed the presence of several oxide phases like Ti O, TiO, Ti O and TiO (rutile and anatase). 22 3 2 Although changes in the colors of the samples may be correlated with the coating composition, the influence of light interference within the thin surface layer should not be discarded. 2002 Elsevier Science B.V. All rights reserved.

Contribution of cell blocks obtained through endobronchial ultrasound-guided transbronchial needle aspiration to the diagnosis of lung cancer.

BackgroundConventional smears of samples obtained by endobronchial ultrasound with real-time transbronchial needle aspiration (EBUS-TBNA) have proven useful in lung cancer staging, but the value of additional information from cell-block processing of EBUS-TBNA samples has only been marginally investigated. This study focussed on the contribution of cell block analysis to the diagnostic yield in lung cancer.MethodsPatients referred for lung cancer diagnosis and/or staging by means of EBUS-TBNA were enrolled, the adequacy of the obtained samples for preparing cell blocks was assessed, and the additional pathologic or genetic information provided from cell block analysis was examined.ResultsIn 270 lung cancer patients referred for EBUS-TBNA (mean age, 63.3 SD 10.4 years) 697 aspirations were performed. Cell blocks could be obtained from 334 aspirates (47.9%) and contained diagnostic material in 262 (37.6%) aspirates, providing information that was additional to conventional smears in 50 of the 189 samples with smears that were non-diagnostic, corresponding 21 of these blocks to malignant nodes, and allowing lung cancer subtyping of 4 samples. Overall, cell blocks improved the pathologic diagnosis attained with conventional smears in 54 of the 697 samples obtained with EBUS-TBNA (7.7%). Cell blocks obtained during EBUS-TBNA also made epithelial growth factor receptor mutation analysis possible in 39 of the 64 patients with TBNA samples showing metastatic adenocarcinoma (60.1%). Overall, cell blocks provided clinically significant information for 83 of the 270 patients participating in the study (30.7%).ConclusionsCell-block preparation from EBUS-TBNA samples is a simple way to provide additional information in lung cancer diagnosis. Analysis of cell blocks increases the diagnostic yield of the procedure by nearly seven per cent and allows for genetic analysis in a sixty per cent of the patients with metastatic adenocarcinoma.

Single pulse Nd:YAG laser irradiation of titanium: influence of laser intensity on surface morphology

Abstract The interaction between single-pulse Nd:YAG (λ=1.064 μm) laser radiation and Ti target surfaces was studied by scanning electron microscopy and profilometry. The laser-assisted surface modification was analyzed and described as a function of incident laser pulse intensity. The evolution of the surface morphology was explained in terms of liquid phase material displacement, vaporization and plasma shielding. The laser intensities characteristic for the transition between these surface processes were studied for the particular laser-target system. The development of wave-like surface topography was accounted by non-linear hydrodynamic instabilities evolving on the molten target surface. The material transport and its accumulation at the border of the imprints was assigned mainly to the effect of ambient gas breakdown and vaporization plasma recoil pressure. At high laser intensities the surface morphology was influenced by the plasma shielding.

Monitoring farmers' decisions on Mediterranean irrigated crops using satellite image time series

The main purpose of this study is to present a methodology for mapping and monitoring temporal signatures of Mediterranean crops over several years in irrigated areas, and to study their inter‐annual dynamics. These goals were achieved by remote sensing using 36 Landsat images from 2002 to 2005. Four crop maps, one for each year, with six agricultural categories and a thematic accuracy of 93%, 95%, 96% and 94% were obtained using a hybrid classifier. A mean of nine images produced these highly accurate results, but the absence of one image in the growth period of 2002 resulted in lower accuracies, particularly in fruit trees (85% of user accuracy). This highlights the importance of a multi‐temporal approach based on a relatively large number of images. After the classification results were validated, two parameters were used to characterize the dynamics of the four crops (rice, maize, alfalfa and fruit trees): greenness, extracted from the Normalized Difference Vegetation Index (NDVI), and wetness, calculated from the Tasselled Cap Wetness (TCW) Index. In order to differentiate the wetness origin of crops, an analysis of local daily precipitation (which could cause significant anomalies in the TCW coefficients) and water stored in the Susqueda reservoir (which may result in farmers making important management decisions when water is limited) was conducted during this four‐year period. After applying statistical analysis, the results showed that, of the four crops analysed, rice, alfalfa and fruit trees had more stable dynamics than maize, which was planted later in case of water deficit at the beginning of the irrigation campaign (in 2002) and earlier when the deficit occurred later (in 2005).

Anemia is a Mortality Predictor in Hospitalized Patients for COPD Exacerbation

Abstract Background. Anemia is a recognized prognostic factor in many chronic illnesses, but there is limited information about its impact on outcomes in patients hospitalized for acute COPD exacerbation (AECOPD). Aim. To investigate whether anemia exerts an effect on mortality in patients admitted for AECOPD after one year of follow-up. Methods. From November 2007 to November 2009 we recruited 117 patients who required hospitalization due to an AECOPD. Clinical, functional and laboratory parameters on admission were prospectively assessed. Patients were followed up during one year. Mortality and days-to-death were collected. Results. Mean age 72 (SD ± 9); FEV1 37.4 (SD ± 12); mortality after 1 year was 22.2%. Mean survival: 339 days. Comparing patients who died to those who survived we found significant differences (p < 0,000) in hemoglobin (Hb) (12.4 vs 13.8 mg/dl) and hematocrit (Ht) (38 vs 41%). Anemia (Hb < 13 g.dl-1) prevalence was 33%. Those who died had experienced 3.5 exacerbations in previous year vs 1.5 exacerbations in the case of the survivors (p = 0.000). Lung function and nutritional status were similar, except for percentage of muscle mass (%) (35 vs 39%; p = 0.015) and albumin (33 vs 37mg/dl; p = 0.039). These variables were included in a Multivariate Cox Proportional Hazards Model; anemia and previous exacerbations resulted as independent factors for mortality. Mortality risk for patients with anemia was 5.9(CI: 1.9–19); for patients with > 1 exacerbation in the previous year was 5.9(CI: 1.3–26.5). Conclusion. Anemia and previous exacerbations were independent predictors of mortality after one year in patients hospitalized for AECOPD.

Spatial and Socio-environmental Dynamics of Catalan Regional Planning from a Multivariate Statistical Analysis Using 1980s and 2000s Data

Abstract This article summarizes the protocol applied to analyse the spatial consequences of diverse regional plans included in the General Spatial Planning of Catalonia (GSPC) municipalities since 1985. The main aims of the GSPC were to achieve a more balanced distribution of population, avoiding Barcelona metropolitan region congestion, coastal overcrowding and mountain areas depopulation, and to improve mobility infrastructures and social welfare. The methodology used was based on factor analysis that reduced 30 socioeconomic and geographic variables provided by different sources into a smaller number of common factors. Afterwards a non-hierarchical clustering was employed to simplify the analysis of dynamics. The six first common factors retained in the model explained the 82.6% of total variance. After labelling them, six clusters were mapped to describe the most important dynamics: urban sprawl, urbanalization, depopulation, reterritorialization and coastalization. Finally, some socio-environmental consequences of such dynamics are discussed.

Direct Laser Printing of Tailored Polymeric Microlenses

We report a laser-based approach for the fast fabrication of high-optical-quality polymeric microlenses and microlens arrays with controllable geometry and size. Our strategy consists of the direct laser printing of microdroplets of a highly viscous UV prepolymer at targeted positions, followed by photocuring. We study the morphological characteristics and imaging performance of the microlenses as a function of the substrate and laser parameters and investigate optimal printing conditions and printing mechanisms. We show that the microlens size and focusing properties can be easily tuned by the laser pulse energy, with minimum volumes below 20 fL and focal lengths ranging from 7 to 50 μm.