Testing water pollution in a two layer aquifer

Water bodies around urban areas may be polluted with chemical elements from urban or industrial activities. We study the case of underground water pollution. This is a serious problem, since under- ground water is high qualified drinkable water in a world where this natural resource is increasingly reduced. This study is focused on a two-layer aquifer. If the superficial layer is contaminated, the deeper layer could be spoiled as well. This contribution checks the equality of the mean or centered composition of the two layers, with the aim of inferring their possible hydraulic conectivity. The data to be examined are different hydro-chemical components of water, such as nitrates and nitrites (related to nitrate/nitrite poisoning of animal stock), tensoactives (toxic to the ecosystem) or potassium (it promotes eutrophization of the water), represented in mg/l. As the data are compositional, we can group the pertinent elements and compare them applying ilr transformation. The ilr transformation is used for simplicity when comparing compositional vectors. MANOVA (Multivariate Analysis of Variance) is applied on the transformed data from the two layers. This provides a hypothesis test to discern whether the two aquifer layers can be considered a homogeneous continuum or, on the contrary, they should be considered as isolated layers. An illustrative example is presented. Used data sets, being synthetic, are inspired by a real case. These analyses suggest that the two aquifers are connected.Postprint (published version

Mean Reversion of Balance of Payments¡GEvidence from Sequential Trend Break Unit Root Tests

We analyze the G7 countries data set of real balance of payments series. The unit root tests with an endogenously determined break date in the trend function proposed by Zivot and Andrews (1992) is employed to characterize the balance of payments series. The empirical results show that allowing for a break in the trend function could alter the outcome of the standard unit root tests for some series.Balance of payments

Impartial comparative analysis of measurement of leukocyte telomere length/DNA content by Southern blots and qPCR.

Telomere length/DNA content has been measured in epidemiological/clinical settings with the goal of testing a host of hypotheses related to the biology of human aging, but often the conclusions of these studies have been inconsistent. These inconsistencies may stem from various reasons, including the use of different telomere length measurement techniques. Here, we report the first impartial evaluation of measurements of leukocyte telomere length by Southern blot of the terminal restriction fragments and quantitative PCR (qPCR) of telomere DNA content, expressed as the ratio of telomeric product (T)/single copy gene (S) product. Blind measurements on the same samples from 50 donors were performed in two independent laboratories on two different occasions. Both the qPCR and Southern blots displayed highly reproducible results as shown by r values > 0.9 for the correlations between results obtained by either method on two occasions. The inter-assay CV measurement for the qPCR was 6.45%, while that of the Southern blots was 1.74%. The relation between the results generated by Southern blots versus those generated by qPCR deviated from linearity. We discuss the ramifications of these findings with regard to measurements of telomere length/DNA content in epidemiological/clinical circumstances

Testing water pollution in a two layer aquifer

Water bodies around urban areas may be polluted with chemical elements from urban or industrial activities. We study the case of underground water pollution. This is a serious problem, since underground water is high qualified drinkable water in a world where this natural resource is increasingly reduced. This study is focused on a two-layer aquifer. If the superficial layer is contaminated, the deeper layer could be spoiled as well. This contribution checks the equality of the mean or centered composition of the two layers, with the aim of inferring their possible hydraulic conectivity. The data to be examined are different hydro-chemical components of water, such as nitrates and nitrites (related to nitrate/nitrite poisoning of animal stock), tensoactives (toxic to the ecosystem) or potassium (it promotes eutrophization of the water), represented in mg/l. As the data are compositional, we can group the pertinent elements and compare them applying ilr transformation. The ilr transformation is used for simplicity when comparing compositional vectors. MANOVA (Multivariate Analysis of Variance) is applied on the transformed data from the two layers. This provides a hypothesis test to discern whether the two aquifer layers can be considered a homogeneous continuum or, on the contrary, they should be considered as isolated layers. An illustrative example is presented. Used data sets, being synthetic, are inspired by a real case. These analyses suggest that the two aquifers are connected

Telomere Length, Proviral Load and Neurologic Impairment in HTLV-1 and HTLV-2-Infected Subjects.

Short or damaged telomeres have been implicated in degenerative conditions. We hypothesized that analysis of telomere length (TL) in human T-cell lymphotropic virus (HTLV) infection and HTLV-associated neuropathy might provide clues to the etiology of HTLV-associated disease and viral dynamics. A subset of 45 human T-cell lymphotropic virus type 1 (HTLV-1), 45 human T-cell lymphotropic virus type 2 (HTLV-2), and 45 seronegative subjects was selected from the larger HTLV Outcomes Study (HOST) cohort, matched on age, sex and race/ethnicity. Telomere-to-single-copy gene (T/S) ratio (a measure of TL) and HTLV-1 and HTLV-2 proviral loads were measured in peripheral blood mononuclear cells (PBMCs) using quantitative PCR (qPCR). Vibration sensation measured by tuning fork during neurologic examinations performed as part of the HOST study allowed for an assessment of peripheral neuropathy. TL was compared between groups using t-tests, linear and logistic regression. Mean T/S ratio was 1.02 ± 0.16 in HTLV-1, 1.03 ± 0.17 in HTLV-2 and 0.99 ± 0.18 in HTLV seronegative subjects (p = 0.322). TL was not associated with HTLV-1 or -2 proviral load. Shorter TL was significantly associated with impaired vibration sense in the HTLV-2 positive group only. Overall, we found no evidence that telomere length was affected by chronic HTLV-1 and HTLV-2 infection. That TL was only associated with peripheral neuropathy in the HTLV-2-positive group is intriguing, but should be interpreted cautiously. Studies with larger sample size and telomere length measurement in lymphocyte subsets may clarify the relationship between TL and HTLV-infection

The land–sea coastal border: a quantitative definition by considering the wind and wave conditions in a wave-dominated, micro-tidal environment

A quantitative definition for the land–sea (coastal) transitional area is proposed here for wave-driven areas, based on the variability and isotropy of met-ocean processes. Wind velocity and significant wave height fields are examined for geostatistical anisotropy along four cross-shore transects on the Catalan coast (north-western Mediterranean), illustrating a case of significant changes along the shelf. The variation in the geostatistical anisotropy as a function of distance from the coast and water depth has been analysed through heat maps and scatter plots. The results show how the anisotropy of wind velocity and significant wave height decrease towards the offshore region, suggesting an objective definition for the coastal fringe width. The more viable estimator turns out to be the distance at which the significant wave height anisotropy is equal to the 90th percentile of variance in the anisotropies within a 100 km distance from the coast. Such a definition, when applied to the Spanish Mediterranean coast, determines a fringe width of 2–4 km. Regarding the probabilistic characterization, the inverse of wind velocity anisotropy can be fitted to a log-normal distribution function, while the significant wave height anisotropy can be fitted to a log-logistic distribution function. The joint probability structure of the two anisotropies can be best described by a Gaussian copula, where the dependence parameter denotes a mild to moderate dependence between both anisotropies, reflecting a certain decoupling between wind velocity and significant wave height near the coast. This wind–wave dependence remains stronger in the central baylike part of the study area, where the wave field is being more actively generated by the overlaying wind. Such a pattern controls the spatial variation in the coastal fringe width.Peer ReviewedPostprint (published version

Essays on Chinese corporate tax avoidance

This thesis consists of three self-contained studies on corporate tax avoidance of Chinese firms around the 2008 Corporate Tax Reform. In Chapter 1, we describe the background of this thesis, provide a general introduction of the Tax Reform and outline the motivation of this research. Chapter 2 studies how multinationals’ decisions of foreign direct investment (FDI) into China responded to the tax reform where exemption from the dividend withholding tax was repealed and investors from various jurisdictions faced different withholding tax rates due to their existing double tax agreements (DTA) with China, providing incentives to adopt an indirect strategy for foreign affiliates and thus to reduce host country taxation of foreign income. We find a significant rise in FDI flows sourced from low tax conduit jurisdictions with favorable DTA subsequent to the tax reform, while there is no similar increase in FDI flows sourced from other jurisdictions. In addition, our results suggest that the pattern of FDI changes is similar for jurisdictions adopting divergent double tax relief mechanisms. Overall, our findings are supportive of the existence of indirect investment structures in which investors use conduit strategies via chains of ownership in order to minimize their corporate tax burden. Chapter 3 investigates whether and how firms shift income across consecutive years in response to a known schedule of tax rate changes. Both accruals-based and real earnings management models are tested for firms with tax rate increase or decrease. We find that firms expecting tax rate increase are more likely to manage their earnings upward via accruals instead of real activities, while firms facing tax rate reduction do not exhibit significant downward earnings management behavior via accruals or real activities. Our tests also show that state or institutional ownership do not have significant impact on the extent of accruals-based or real earnings management in response to tax rate changes. Chapter 4 studies the changes in effective tax rates (ETR) and book-tax differences (BTDs) of firms in response to a rise or cut in statutory tax rate during a major tax reform in an emerging market, and offers insights into the interaction of financial accounting considerations with corporate tax avoidance. We find that firms located in special economic zones (SEZ) with a rising statutory tax rate after tax reform exhibit a rise in ETRs and permanent BTDs, but the temporary BTDs of SEZ firms dropped after CTR-08, suggesting a trade-off of time value benefits of deferring tax payment for the advantage of accelerating tax payment during a period of rising tax rate. DR firms, on the other hand, show a decrease in ETRs and permanent BTDs when they face a decrease in statutory tax rate. In Chapter 5, the main findings and implications of the thesis are summarized and future research directions are discussed

Multivariate characterization of wave storms in coastal areas

Tesi per compendi de publicacions, amb diferents seccions retallades pels drets d'editorPremi extraordinari doctorat UPC curs 2017-2018. Àmbit d’Enginyeria Civil i AmbientalWave-storms are the responsible of the main changes in the Coast. Their detailed characterization results in a better design of any marine structure. The most common approach to describe wave-storms is to simplify the event by taking the significant wave-height (Hp), peak period (Tp) and direction (0p) at the peak of the storm and treating these variables independently. However, it is well accepted that some relationship should exist between them. What is more, the development of sophisticated numerical models in Coastal Engineering are demanding additional variables such as the duration of the wave-storm (D), the amount of associated energy (E), temporary evolution of the variables and their relationship to atmospheric climate-indices, to better reproduce the simulated processes. The main objectives and results of this thesis are as follows. First, wave-storms in the present wave climate of the Catalan Coast are characterized, assuming stationarity. The wave-storm variables modelled are: the energy at the peak of the wave-storm (Eu ), Tp , E, D, 0p and the proportions of time from the start to the storm peak and from the storm peak to the end (growth-decay rates). E, Eu , Tp and D are fit by generalized Pareto distributions (GPD). Their joint probability structure is characterized by a hierarchical Archimedean copula (HAC). 0p is characterized through a mixture of von Mises-Fisher probability distribution functions and related to E, T p and D through a multinomial logistic model. The growth-decay rates are related to D through third degree polynomials. A triangle and an irregular-trapezoid are proposed to model the wave-storm shape. In the present climate of the Catalan Coast, the constructed statistical model can serve to generate synthetic wave-storms. The most predominant 0p are north and east. The most appropriate geometric figure to describe the evolution of the wave-height is a irregular-trapezoid. For D over 100h, the peak of the wave-storm is generally closer to the end of the wave-storm than to the start. After establishing a stationary model, non-stationarity is incorporated into the characterization of wave-storms in the Catalan Coast. E, Hp , T p and D are characterized through non-stationary GPDs. The wave-storm threshold, the wave-storminess and the parameters of the GPDs are related to North Atlantic Oscillation (NAO), East Atlantic pattern (EA) and Scandinavian pattern (SC) and their first two time-derivatives, through Vectorial generalized additive models. The joint probability structure is characterized by a pseudo-time-dependent HAC. A severe greenhouse gas emission scenario is considered. The mean values of all wave-storm variables decrease in the 21st century, except for D in the northern part of the coast. A negative NAO may cause an increase in wave-storminess; the wave-storm threshold and the GPD parameters are most influenced by the dynamics of the climate-patterns, rather than by the climate-patterns themselves. The non-stationary methodology is repeated in the northwestern Black Sea, considering both a mild and a severe emission scenarios. Here, wave-storminess is not affected by the proposed climate-patterns, whereas the wave-storm threshold is strongly influenced by SC and EA. The average value of the wave-storm variables seem to have a more positive trend than in the Catalan Coast, and it is observed that an increase in mean values is related to an increase in variance. SC and EA also strongly influence the parameters of the GPDs. In the two study areas, the dependence between E and D is high, while the general dependence among the wave-storm variables is medium. In the Catalan Coast, it is expected that the dependence between E and D should increase with time. In the northwestern Black Sea, it is the dependence among all the wave-storm variables that increases with time, in both emission scenarios; the severe emission scenario presents less dependence among wave-storm variables.El enfoque más común para describir los temporales de mar es simplificar este suceso tomando la altura de ola significante (Hp), el periodo pico (Tp) y la dirección (0p) en el pico de la tormenta y tratándolas de forma independiente. Sin embargo, está ampliamente aceptado que exista al menos alguna relación entre ellas. Es más, el desarrollo de sofisticados modelos numéricos en la ingeniería de costas pide variables adicionales como la duración de tormenta (D), la cantidad de energía asociada (E), la evolución temporal de las variables y su relación con índices climáticos atmosféricos, todo para una mejor reproducción de los procesos simulados. Los objetivos y resultados principales de esta tesis son los siguientes: Primero, se caracteriza tormentas de mar en el clima de oleaje presente, de la costa catalana, suponiendo estacionalidad. Las variables modeladas son: la energía unitaria en el pico del temporal (Eu), Tp, E, D, 0p y la proporción de tiempo desde el inicio hasta el pico y desde el pico al final del temporal (ratios de crecimiento-decrecimiento). Se caracteriza E, E u, T p y D con distribuciones generalizadas de Pareto (GPD), y se caracteriza la estructura de probabilidades conjunta de estas variables vía una cópula jerárquica arquimedeana (HAC). Se caracteriza 0p con una combinación de distribución de probabilidad de von Mises-Fisher y se le relaciona con E, T p y D a través de un modelo logístico multinomial. Se propone una forma triangular o trapezoide-irregular para modelar la forma del temporal. En el clima presente de la costa catalana, el modelo estadístico construido puede generar temporales sintéticos. Las 0p principales son el norte y el este. La figura geométrica que mejor describe la evolución de la altura de ola es un trapezoide irregular. Para D mayor que 100h, el pico del temporal está generalmente más cerca del final que del principio. La media de cada variable decrece en el siglo XXI, excepto la de D, en el norte de la costa. Una NAO negativa puede causar una subida de la tormentosidad. Además, el umbral de tormenta y los parámetros de GPD están influenciados principalmente por la dinámica de los patrones climáticos, en vez de serlo por los propios patrones climáticos. Después de establecer un modelo estacionario, se incorpora la no estacionalidad a la caracterización de temporales de mar en la costa catalana. Se caracteriza E, Hp, Tp y D con GPDs no estacionarios. El umbral de temporal, la tormentosidad y los parámetros de los GPDs están relacionados con la Oscilación de Atlántico norte (NAO), el Patrón de Atántico oriental (EA) y el Patrón escandinavo (SC) y sus primeras dos derivadas temporales, a través de Modelos aditivos generalizados vectoriales. Se caracteriza la estructura de probabilidades conjunta con un HAC pseudo-dependiente del tiempo. Se considera un escenario grave de cambio climático. Se repite la metodología no estacionaria en el noroeste del Mar Negro, considerando tanto un escenario suave de cambio climático como otro grave. En el noroeste del Mar Negro, la tormentosidad de mar no está afectada por los patrones climáticos propuestos, todo y que el umbral de temporal está fuertemente influenciado por SC y EA. Los valores medios de las variables de temporal parecen tener una tendencia más positiva que en la costa catalana, y se observa que una subida de los valores medios se relaciona con otra subida de las varianzas. SC y EA afectan fuertemente a los parámetros de los GPDs. En las dos zonas de estudio, la dependencia entre E y D es alta, mientras que la dependencia general entre las variables de temporal es media. En la costa catalana, se espera que la dependencia entre E y D crezca con el tiempo. En el noroeste del Mar Negro, es la dependencia entre todas las variables de temporal la que crece con el tiempo, en ambos escenarios de cambio climático: el escenario grave presenta menos dependencia entre las variables.Award-winningPostprint (published version