Two more things about compositional biplots: quality of projection and inclusion of supplementary elements

The biplot is a widely and powerful methodology used with multidimensional data sets to describe and display the relationships between observations and variables in an easy way. Compositional data consist of positive vectors each of which is constrained to have a constant sum; due to this property standard biplots can not be performed with compositional data, instead of a previous transformation of the data is performed. Due to this constant sum constraint, a transformation of data is needed before performing a biplot and, consequently, special interpretation rules are required. However, these rules can only be safely applied when the elements of a biplot have a good quality of projection, for which a new measure is introduced in this paper. Also, we extend the compositional biplot defined by Aitchison and Greenacre on 2002, in order to include the display supplementary elements that are not used in the definition of the compositional biplot. Different types of supplementary elements are considered: supplementary parts of the composition, supplementary continuous variables external to the composition, supplementary categorical variables and supplementary observations. The projection of supplementary parts of the composition is done by means of the equivalence of clr and lr biplots. The other supplementary projections are done by classical methodology. Both the qualities of projections and the supplementary projections are explained using real geological data: a sample of 72 observations of soil in an area about 20 km west of Kiev in the area south of Kiev Polessie

Tourist development and efficient water management. An opportunity for sustainable tourism in the Costa Brava (Girona)

La solución a la crisis económica actual pasa por el establecimiento de un nuevo paradigma de gestión sostenible de los recursos. El turismo depende de la disponibilidad de agua, de la misma manera que el agua condiciona los usos que el turista hace del territorio. Las restricciones de agua o la falta de la misma pueden afectar la imagen de los destinos turísticos, perjudicando su desarrollo socioeconómico. Sin embargo, los distintos episodios de sequías acaecidos en los últimos años en el litoral mediterráneo peninsular y las predicciones climáticas, señalan que estos fenómenos serán cada vez más recurrentes y muestran claramente la necesidad de introducir cambios sustanciales en las estrategias de gestión de los recursos hídricos. La sostenibilidad económica, social y ambiental del turismo debe acompañarse de una gestión eficiente de los recursos hídricos. El objetivo del presente artículo es determinar cuáles son los factores relacionados con la oferta turística que determinan el consumo de agua en la Costa Brava (Girona). La hipótesis inicial de este trabajo parte de que el consumo de agua viene determinado no sólo por el número de usuarios conectados a la red de suministro sino que es necesario tener en cuenta otros aspectos sociales y territoriales como la tipología urbano turística para comprender y mejorar la gestión del agua en los municipios turísticos del litoral mediterráneo.The establishment of a new paradigm of sustainable resource management must be one of the solutions to the current economic crisis. Tourism depends on the availability of water, in the same way that water determines the uses that tourists develop on the territory. Water restrictions, or the lack of water, can affect the image of tourist destinations, damaging their socioeconomic development. However, the different episodes of drought occurred in recent years in the peninsular Mediterranean coastline and climate predictions, which indicate that these phenomena will increase, clearly show the need for substantial changes in management strategies of water resources. The economic, social and environmental sustainability of tourism should be accompanied by an efficient management of water resources. The main goal of this work is to identify the factors related to tourism that determine water consumption in the Costa Brava (Girona). The hypothesis is that not only the number of users connected to the water supply network determines water consumption. Actually, it is necessary to consider other social and territorial aspects for understanding and improving water management in tourist municipalities over the Mediterranean coast

Could CODA methodology be useful in control chart techniques?

On standard control charts, the hypothesis of normality is usually assumed without any additional veri cation. Nevertheless, in some cases this assumption is not accurate and might cause errors in process quality monitoring. In particular, for the control of the proportion of nonconforming units (p-chart) the normality is doubtful when p is small and consequently, lower control limit less than or equal to zero are frequent. Some authors have proposed new techniques to de ne limits in the p-chart. Others have proposed transformations to improve the detection of special causes

On the interpretation of differences between groups for compositional data

Social polices are designed using information collected in surveys; such as the Catalan TimeUse survey. Accurate comparisons of time use data among population groups are commonlyanalysed using statistical methods. The total daily time expended on different activities by asingle person is equal to 24 hours. Because this type of data are compositional, its sample spacehas particular properties that statistical methods should respect. The critical points required tointerpret differences between groups are provided and described in terms of log-ratio methods.These techniques facilitate the interpretation of the relative differences detected in multivariateand univariate analysis

Analysis of fossil planktonic foraminifera: the sieve mesh effect

The choice of the sediment size fraction in the analysis of fossil planktonic foraminifera is of great importance in determining the composition of assemblages. In past studies several size fractions have been utilised. Imbrie and Kipp (1971) stated that “smaller fractions give rise to too many uncertainties in the identification of small specimens and require too long to process. Large mesh size yield undesiderable loss of small species, and small specimens of larger species”. The adoption of coarser sieve meshes has the effect to reduce the percentages of small sized (usually living in cold waters) species (Bé and Hutson, 1977). In a comparison between >63 μm and >150 μm size-fraction of planktonic foraminifera assemblages from NW Atlantic Ocean, Smart (2002), stated that because particular smaller species are either under-represented or even absent from the larger (>150 μm) size-fraction, the smaller (>63 μm) size-fraction must be included in studies of planktonic foraminifera. Di Donato et al. (2008) highlighted in the >150 μm size fraction of a core from the Tyrrhenian Sea, a great loss of the small-sized species Turborotalita quinqueloba in glacial samples, where this species is very abundant. This caused an increase in warm water species such as Globigerinoides ruber, apparently reaching typical Holocene values in some full glacial levels. From the above mentioned statements, it is clear that treatment changes can strongly influence the results of palaeoclimatic reconstructions based on planktonic foraminiferal assemblages. As stated by Aitchison (1986, 1992) scale invariance and subcompositional coherence are fundamental properties of the compositional data analysis (CODA). The main goal of this paper is to verify if the variable relationships pointing out from CODA of foraminiferal assemblages are or not influenced by the size fraction and, more in general, to test the robustness of CODA respect to treatment changes related to different preparation techniques for the analysis of planktonic foraminifera

Environmental heterogeneity in human health studies. A compositional methodology for Land Use and Land cover data

Altres ajuts: Acord transformatiu CRUE-CSICUnidad de excelencia María de Maeztu CEX2019-000940-MThe use of Land use and Land cover (LULC) data is gradually becoming more widely spread in studies relating the environment to human health. However, little research has acknowledged the compositional nature of these data. The goal of the present study is to explore, for the first time, the independent effect of eight LULC categories (agricultural land, bare land, coniferous forest, broad-leaved forest, sclerophyll forest, grassland and shrubs, urban areas, and waterbodies) on three selected common health conditions: type 2 diabetes mellitus (T2DM), asthma and anxiety, using a compositional methodological approach and leveraging observational health data of Catalonia (Spain) at area level. We fixed the risk exposure scenario using three covariates (socioeconomic status, age group, and sex). Then, we assessed the independent effect of the eight LULC categories on each health condition. Our results show that each LULC category has a distinctive effect on the three health conditions and that the three covariates clearly modify this effect. This compositional approach has yielded plausible results supported by the existing literature, highlighting the relevance of environmental heterogeneity in health studies. In this sense, we argue that different types of environment possess exclusive biotic and abiotic elements affecting distinctively on human health. We believe our contribution might help researchers approach the environment in a more multidimensional manner integrating environmental heterogeneity in the analysis

Intravoxel Incoherent Motion Metrics as Potential Biomarkers for Survival in Glioblastoma.

Intravoxel incoherent motion (IVIM) is an MRI technique with potential applications in measuring brain tumor perfusion, but its clinical impact remains to be determined. We assessed the usefulness of IVIM-metrics in predicting survival in newly diagnosed glioblastoma. Fifteen patients with glioblastoma underwent MRI including spin-echo echo-planar DWI using 13 b-values ranging from 0 to 1000 s/mm2. Parametric maps for diffusion coefficient (D), pseudodiffusion coefficient (D*), and perfusion fraction (f) were generated for contrast-enhancing regions (CER) and non-enhancing regions (NCER). Regions of interest were manually drawn in regions of maximum f and on the corresponding dynamic susceptibility contrast images. Prognostic factors were evaluated by Kaplan-Meier survival and Cox proportional hazards analyses. We found that fCER and D*CER correlated with rCBFCER. The best cutoffs for 6-month survival were fCER>9.86% and D*CER>21.712 x10-3mm2/s (100% sensitivity, 71.4% specificity, 100% and 80% positive predictive values, and 80% and 100% negative predictive values; AUC:0.893 and 0.857, respectively). Treatment yielded the highest hazard ratio (5.484; 95% CI: 1.162-25.88; AUC: 0.723; P = 0.031); fCER combined with treatment predicted survival with 100% accuracy. The IVIM-metrics fCER and D*CER are promising biomarkers of 6-month survival in newly diagnosed glioblastoma

Combined Approach to Stroke Thrombectomy Using a Novel Short Flexible Aspiration Catheter with a Stent Retriever

Background: Large-bore aspiration catheters enabling greater flow rates and suction force for mechanical thrombectomy might improve outcomes in patients with stroke secondary to large-vessel occlusion. Complete or near-complete reperfusion after a single thrombectomy pass (first-pass effect) is associated with improved clinical outcomes. We assessed the efficacy and safety of novel MIVI Q™ aspiration catheters in combination with stent-retriever devices. Methods: We retrospectively analyzed demographics, procedure characteristics, and clinical data from consecutive patients with acute anterior large-vessel occlusion treated with a combined approach using MIVI Q™ aspiration catheters and stent retrievers. Reperfusion was defined according to the modified thrombolysis in cerebral infarction (mTICI) score. Clinical outcomes were measured by the National Institute of Health Stroke Scale (NIHSS) and modified Rankin scale (mRS) scores. Results: We included 52 patients (median age, 75 y IQR: 64-83); 31 (59.6%) women; 14 (26.9%) with terminal internal carotid artery occlusions, 26 (50%) middle cerebral artery (MCA) segment M1 occlusions, and 12 (23.1%) MCA segment M2 occlusions; median NIHSS score at admission was 19 (IQR: 13-22). After the first pass, 25 (48%) patients had mTICI ≥ 2c. At the end of the procedure, 47 (90.4%) had mTICI ≥ 2b and 35 (67.3%) had mTICI ≥ 2c. No serious device-related adverse events were observed. Symptomatic intracranial hemorrhage developed in 1 patient. Mean NIHSS score was 13 at 24 h and 5 at discharge. At 90 days, 24 (46.2%) patients were functionally independent (mRS 0-2). Conclusion: This preliminary study found good efficacy and safety for MIVI Q™ aspiration catheters used in combination with stent-retriever devices