Direct effects of increased CO2 concentrations in seawater on the net primary production of charophytes in a shallow, coastal, brackish-water ecosystem

Charophytes are found in fresh and brackish waters across the globe and play key roles in coastal ecosystems. However, their response to increasing CO2 is not well understood. The aim of the study was to detect the effects of elevated CO2 on the physiology of charophyte species growing in the brackish Baltic Sea by measuring net primary production. Mesocosm experiments were conducted in the Kõiguste Bay (N Gulf of Riga) during the field season of 2012. Separate mesocosms were maintained at different pCO2 levels: 2000, 1000 and 200 µatm. The experiments were carried out with three species of charophytes: Chara aspera, C. tomentosa and C. horrida. The short-term photosynthetic responses of charophytes to different treatments were measured by the oxygen method. The results show that elevated CO2 levels in brackish water may enhance the photosynthetic activity of charophyte species and suggest that increasing CO2 in the Baltic Sea could have implications for interspecific competition and community structure in a future high CO2 world.

The Impact of United States Sanctions on the Myanmar Garment Industry

The United States imposed trade sanctions against the military regime in Myanmar in July 2003. The import ban damaged the garment industry in particular. This industry exported nearly half of its products to the United States, and more than eighty percent of United States imports from Myanmar had been clothes. The garment industry was probably the main target of the sanctions. Nevertheless, the impact on the garment industry and its workers has not been accurately evaluated or closely examined. The purpose of this paper is to evaluate the impact of the sanctions and to further understand the present situation. This is done using several sources of information, including the author's field and questionnaire surveys. This paper also describes the process of selection and polarization underway in the garment industry, an industry that now has more severe competition fueled by the sanctions. Through such a process, the impact was inflicted disproportionately on small and medium-sized domestic firms and their workers.

On the Evolution of the Spatial Economy with Multi-unit/Multi-plant Firms: The Impact of IT Development

This paper examines how the decline of communication costs between management and production facilities within firms and the decrease in trade costs of manufactured goods affect the spatial organization of a two-region economy with multi-unit/multi-plant firms. The development of information technology decreases the costs of communication and trade costs. Thus, the fragmentation of firms is promoted. Our result indicates that, with decreasing communication costs, firms producing low trade-cost products (such as consumer electronics) tend to concentrate their manufacturing plants in low wage countries. In contrast, firms producing high trade-cost products (such as automobiles) tend to have multiple plants serving to segmented markets, even in the absence of wage differentials.

China's Impact on the Exports of Other Asian Countries: A Note

Despite widespread interest in China's growing trade surplus and its impact on other countries, empirical research in these issues is handicapped by the lack of reliable statistics on aggregate import and export prices. Although researchers estimate the trade volumes of China and other East Asian countries using a variety of surrogate price indices, an inappropriate deflator can give rise to a significant bias in econometric analysis. This paper discusses the potential seriousness of this problem by examining recent studies on the export competition between China and other Asian countries.

Parameterization of applied general equilibrium models with flexible trade specifications based on the Armington, Krugman, and Melitz models

This paper explains how the Armington-Krugman-Melitz supermodel developed by Dixon and Rimmer can be parameterized, and demonstrates that only two kinds of additional information are required in order to extend a standard trade model to include Melitz-type monopolistic competition and heterogeneous firms. Further, it is shown how specifying too much additional information leads to violations of the model constraints, necessitating adjustment and reconciliation of the data. Once a Melitz-type model is parameterized, a Krugman-type model can also be parameterized using the calibrated values in the Melitz-type model without any additional data. Sample code for the General Algebraic Modeling System (GAMS) has also been prepared to promote the innovative supermodel in the AGE community.

On the sustainability of a monocentric city : lower transport costs from new transport facilities

This paper proposes a general equilibrium model of a monocentric city based on Fujita and Krugman (1995). Two rates of transport costs per distance and for the same good are introduced. The model assumes that lower transport costs are available at a few points on a line. These lower costs represent new transport facilities, such as high-speed motorways and railways. Findings is that new transport facilities connecting the city and hinterlands strengthen the lock-in effects, which describes whether a city remains where it is forever after being created. Furthermore, the effect intensifies with better agricultural technologies and a larger population in the economy. The relationship between indirect utility and population size has an inverted U-shape, even if new transport facilities are used. However, the population size that maximizes indirect utility is smaller than that found in Fujita and Krugman (1995).

Influence of the molecular architecture on the secondary relaxations of Poly(styrene-co-methylmethacrylate) copolymers

The processes of adsorption of grafted copolymers onto negatively charged surfaces were studied using a dissipative quartz crystal microbalance (D-QCM) and ellipsometry. The control parameters in the study of the adsorption are the existence or absence on the molecular architecture of grafted polyethyleneglycol (PEG) chains with different lengths and the chemical nature of the main chain, poly(allylamine) (PAH) or poly(L-lysine) (PLL). It was found out that the adsorption kinetics of the polymers showed a complex behavior. The total adsorbed amount depends on the architecture of the polymer chains (length of the PEG chains), on the polymer concentration and on the chemical nature of the main chain. The comparison of the thicknesses of the adsorbed layers obtained from D-QCM and from ellipsometry allowed calculation of the water content of the layers that is intimately related to the grafting length. The analysis of D-QCM results also provides information about the shear modulus of the layers, whose values have been found to be typical of a rubber-like polymer system. It is shown that the adsorption of polymers with a charged backbone is not driven exclusively by the electrostatic interactions, but the entropic contributions as a result of the trapping of water in the layer structure are of fundamental importance.

On the spatial distribution of woody plant species in a tropical montane cloud forest

Abstract The cloud forest is a special type of forest ecosystem that depends on suitable conditions of humidity and temperature to exist; hence, it is a very fragile ecosystem. The cloud forest is also one of the richest ecosystems in terms of species diversity and rate of endemism. However, today, it is one of the most threatened ecosystems in the world. Little is known about tree species distribution and coexistence among cloud forest trees. Trees are essential to understanding ecosystem functioning and maintenance because they support the ecosystem in important ways. For this dissertation, an analysis of woody plant species distribution at a small scale in a north-Peruvian Andean cloud forest was performed, and some of the factors implicated in the observed patterns were identified. Towards that end, different natural factors acting on species distribution within the forest were investigated: (i) intra-specific arrangements, (ii) heterospecific spatial relationships and (iii) relationships with external environmental factors. These analyses were conducted first on standing woody plants and then on seedlings. The woody plants were found to be clumped in the forest, either considering all the species together or each species separately. However, each species presented a specific pattern and specific spatial relationship among different-age individuals. Dispersal mode, growth form and shade tolerance played roles in the final distribution of the species. Furthermore, spatial associations among species, either positive or negative, were observed. These associations were more numerous when considering individuals of the interacting species at different developmental stages, i.e., younger individuals from one species and older individuals from another. Accordingly, competition and facilitation are asymmetric processes and vary throughout the life of an individual. Moreover, some species appear to prefer certain habitat conditions and avoid other habitats. The habitat definition that best explains species distribution is that which includes both environmental and stand characteristics; thus, a combination of these factors is necessary to understanding species' niche preferences. Seedling distribution was also associated with habitat conditions, but these conditions explained less than the 30% of the spatial variation. The position of conspecific adult individuals also affected seedling distribution; although the seedlings of many tree species avoid the vicinity of conspecifics, a few species appeared to prefer the formation of cohorts around their parent trees. The importance of habitat conditions and distance dependence with conspecifics varied among regions within the forest as well as on the developmental stage of the stand. The results from this thesis suggest that different species can coexist within a given space, forming a “puzzle” of species as a result of the intra- and interspecific spatial relationships along with niche preferences and adaptations that operate at different scales. These factors not only affect each species in a different way, but specific preferences also vary throughout species' lifespans. Resumen Resumen El bosque de niebla es uno de los ecosistemas más amenazados del mundo además de ser uno de los más frágiles. Son formaciones azonales que dependen de la existencia de unas condiciones de humedad y temperatura que permitan la formación de nubes que cubran el bosque; lo que dificulta en gran medida su conservación. También es uno de los ecosistemas con mayor riqueza de especies además de tener uno de los mayores porcentajes de endemismos. Uno de los aspectos más importantes para entender el ecosistema, es identificar y entender los elementos que lo componen y los mecanismos que regulan las relaciones entre ellos. Los árboles son el soporte del ecosistema. Sin embargo, apenas hay información sobre la distribución y coexistencia de los árboles en los bosques de niebla. Esta tesis presenta un análisis de la distribución a pequeña escala de las plantas leñosas en un bosque de niebla situado en la cordillera andina del norte de Perú; así como el análisis de algunos de los factores que pueden estar implicados en que se origine la distribución observada. Para este propósito se estudia cómo influyen factores de diferente naturaleza en la distribución de las especies (i) organización intra-específica (ii) relaciones espaciales heterospecíficas y (iii) relación con factores ambientales externos. En estos análisis se estudiaron primero las plantas jóvenes y las adultas, y después las plántulas. Los árboles aparecieron agregados en el bosque, tanto considerando todos a la vez como cuando se estudió cada especie por separado. Sin embargo, cada especie mostró un patrón distinto así como una particular relación espacial entre individuos jóvenes y adultos. El modo de dispersión, la forma de vida y la tolerancia de la especies estuvieron relacionados con el patrón general observado. Se vio también que ciertas especies aparecían relacionadas con otras, tanto de forma positiva (compartiendo zonas) como negativa (apareciendo en áreas distintas). Las asociaciones fueron mucho más numerosas cuando se consideraron los pares de especies en diferente estado de desarrollo, es decir, individuos jóvenes de una especie e individuos mayores de la otra. Eso indicaría que los procesos de competencia y facilitación son asimétricos y además varían durante la vida de la planta. Por otro lado, algunas especies aparecen preferentemente bajo ciertas condiciones de hábitat y evitan otras. La definición de hábitat a la que mejor responden las especies es cuando se incluyen tanto variables ambientales como de masa; así que ambos tipos de variables son necesarias para entender la preferencia de las especies por ciertos nichos. La distribución de las plántulas también estuvo relacionada con condiciones de hábitat, pero eso sólo llegaba a explicar hasta un 30% de la variabilidad espacial. La posición de los adultos de la misma especie también afectó a la distribución de las plántulas. En bastantes especies las plántulas evitan la cercanía de adultos de su misma especie, padres potenciales, aunque algunas especies aisladas mostraron el patrón contrario y aparecieron preferentemente en las mismas áreas que sus padres. La importancia de las condiciones de hábitat y posición de los adultos en la disposición de las plántulas varía de una zona a otra del bosque y además también varía según el estado de desarrollo de la masa.

An empirical mixed model to quantify climate influence on the growth of Pinus halepensis Mill. stands in South-Eastern Spain

The influence of climate on forest stand composition, development and growth is undeniable. Many studies have tried to quantify the effect of climatic variables on forest growth and yield. These works become especially important because there is a need to predict the effects of climate change on the development of forest ecosystems. One of the ways of facing this problem is the inclusion of climatic variables into the classic empirical growth models. The work has a double objective: (i) to identify the indicators which best describe the effect of climate on Pinus halepensis growth and (ii) to quantify such effect in several scenarios of rainfall decrease which are likely to occur in the Mediterranean area. A growth mixed model for P. halepensis including climatic variables is presented in this work. Growth estimates are based on data from the Spanish National Forest Inventory (SNFI). The best results are obtained for the indices including rainfall, or rainfall and temperature together, with annual precipitation, precipitation effectiveness, Emberger?s index or free bioclimatic intensity standing out among them. The final model includes Emberger?s index, free bioclimatic intensity and interactions between competition and climate indices. The results obtained show that a rainfall decrease about 5% leads to a decrease in volume growth of 5.5?7.5% depending on site quality.

A methodology to measure the interface shear strength by means of the fiber push-in test

A methodology is presented to measure the fiber/matrix interface shear strength in composites. The strategy is based on performing a fiber push-in test at the central fiber of highly-packed fiber clusters with hexagonal symmetry which are often found in unidirectional composites with a high volume fraction of fibers. The mechanics of this test was analyzed in detail by means of three-dimensional finite element simulations. In particular, the influence of different parameters (interface shear strength, toughness and friction as well as fiber longitudinal elastic modulus and curing stresses) on the critical load at the onset of debonding was established. From the results of the numerical simulations, a simple relationship between the critical load and the interface shear strength is proposed. The methodology was validated in an unidirectional C/epoxy composite and the advantages and limitations of the proposed methodology are indicated.

Assessing the impact of adaptive accessibility on the optimal transport policy implementation by using an integrated land-use/transport model for Madrid

Accessibility is an essential concept widely used to evaluate the impact of land-use and transport strategies in transport and urban planning. Accessibility is typically evaluated by using a transport model or a land-use model independently or successively without a feedback loop, thus neglecting the interaction effects between the two systems and the induced competition effects among opportunities due to accessibility improvements. More than a mere methodological curiosity, failure to account for land- use/transport interactions and the competition effect may result in large underestimation of the policy effects. With the recent development of land-use and transport interaction (LUTI) models, there is a growing interest in using these models to adequately measure accessibility and evaluate its impact. The current study joins this research stream by embedding an accessibility measure in a LUTI model with two main aims. The first aim is to account for adaptive accessibility, namely the adjustment of the potential accessibility due to the effect of competition among opportunities (e.g., workplaces) as a result of improved accessibility. LUTI models are particularly suitable for assessing adaptive accessibility because the competition factor is a function of the number of jobs, which is related to land-use attractiveness and the number of workers which is related, among other factors, to the transport demand. The second aim is to identify the optimal implementation scenario of policy measures on the basis of the potential and adaptive accessibility and analyse the results in terms of social welfare and accessibility. The metropolitan area of Madrid is used as a case-study and two transport policy instruments, namely a cordon toll and bus frequency increase, have been chosen for the simulation study in order to present the usefulness of the approach to urban planners and policy makers. The MARS model (Metropolitan Activity Relocation Simulator) calibrated for Madrid was employed as the analysis tool. The impact of accessibility is embedded in the model through a social welfare function that includes not only costs and benefits to both road users and transport operators, but also costs and benefits for the government and society in general (external costs). An optimisation procedure is performed by the MARS model for maximizing the value of objective function in order to find the best (optimal) policy imp lementations intensity (i.e., price, frequency). Last, the two policy strategies are evaluated in terms of their accessibility. Results show that the accessibility with competition factor influences the optimal policy implementation level and also generates different results in terms of social welfare. In addition, mapping the difference between the potential and the adaptive accessibility indicators shows that the main changes occur in areas where there is a strong competition among land-use opportunities.

Mach-Zehnder interferometer based on all-fiber multimode interference device for DPSK signal demodulation

Differential Phase Shift Keying (DPSK) modulation format has been shown as a robust solution for next-generation optical transmission systems. One key device enabling such systems is the delay interferometer, converting the signal phase information into intensity modulation to be detected by the photodiodes. Usually, Mach-Zehnder interferometer (MZI) is used for demodulating DPSK signals. In this paper, we developed an MZI which is based on all-fiber Multimode Interference (MI) structure: a multimode fiber (MMF) located between two single-mode fibers (SMF) without any transition zones. The standard MZI is not very stable since the two beams go through two different paths before they recombine. In our design the two arms of the MZI are in the same fiber, which will make it less temperature-sensitive than the standard MZI. Performance of such MZI will be analyzed from transmission spectrum. Finally such all-fiber MI-based MZI (MI-MZI) is used to demodulate 10 Gbps DPSK signals. The demodulated signals are analyzed from eye diagram and bit error rate (BER).

Influence of the Fiber Alignment in the Ballistic Performance of Dyneema Non-Woven Fabrics

The aim of this study was the determination of the deforming micromechanisms of needlepunched felts subjected to impact loads. A large experimental campaign has been carried out to analyze the influence of the fiber alignment in the ballistic performance. Ballistic limit curves of predeformed samples were compared. The fiber realignment was experimentally measure by means of 2D X-Ray diffraction. Higher specific absorption was observed for samples with a more isotropic mechanical response. A constitutive physicallybased model was developed within the context of the finite element method, which provided the constitutive response for a mesodomain including micromechanical aspects as fiber alignment, fiber sliding and pull-out. The macroscopic response has been validated with the experimental results, showing a very good agreement. The absorbed energy by the material during the impact was predicted and the fiber realignment evolution was also obtained.

Investigations on the distribution of air transport traffic and CO2 emissions within the European Union

This study analyses the structure of air traffic and its distribution among the different countries in the European Union, as well as traffic with an origin or destination in non-EU countries. Data sources are Eurostat statistics and actual flight information from EUROCONTROL. Relevant variables such as the number of flights, passengers or cargo tonnes and production indicators (RPKs) are used together with fuel consumption and CO2 emissions data. The segmentation of air traffic in terms of distance permits an assessment of air transport competition with surface transport modes. The results show a clear concentration of traffic in the five larger countries (France, Germany, Italy, Spain and UK), in terms of RPKs. In terms of distance the segment between 500 and 1000 km in the EU, has more flights, passengers, RTKs and CO2 emissions than larger distances. On the environmental side, the distribution of CO2 emissions within the EU Member States is presented, together with fuel efficiency parameters. In general, a direct relationship between RPKs and CO2 emissions is observed for all countries and all distance bands. Consideration is given to the uptake of alternative fuels. Segmenting CO2 emissions per distance band and aircraft type reveals which flights contribute the most the overall EU CO2 emissions. Finally, projections for future CO2 emissions are estimated, according to three different air traffic growth and biofuel introduction scenarios.

Natural regeneration in mediterranean mixed forests: effect of environmental conditions on the physiological optimum niche of the species = Regeneración natural en masas mixtas mediterráneas: efecto de las condiciones ambientales en el nicho óptimo fisiológico de las especies

Los montes Mediterráneos han experimentado múltiples cambios en las últimas décadas (tanto en clima como en usos), lo que ha conducido a variaciones en la distribución de especies. El aumento previsto de las temperaturas medias junto con la mayor variabilidad intra e inter anual en cuanto a la ocurrencia de eventos extremos o disturbios naturales (como periodos prolongados de sequía, olas de frío o calor, incendios forestales o vendavales) pueden dañar significativamente al regenerado, llevándolo hasta la muerte, y jugando un papel decisivo en la composición de especies y en la dinámica del monte. La amplitud ecológica de muchas especies forestales puede verse afectada, de forma que se esperan cambios en sus nichos actuales de regeneración. Sin embargo, la migración latitudinal de las especies en busca de mejores condiciones, podría ser una explicación demasiado simplista de un proceso mucho más complejo de interacción entre la temperatura y la precipitación, que afectaría a cada especie de un modo distinto. En este sentido tanto la capacidad de adaptación al estrés ambiental de una determinada especie, así como su habilidad para competir por los recursos limitados, podría significar variaciones dentro de una comunidad. Las características fisiológicas y morfológicas propias de cada especie se encuentran fuertemente relacionadas con el lugar donde cada una puede surgir, qué especies pueden convivir y como éstas responden a las condiciones ambientales. En este sentido, el conocimiento sobre las distintas respuestas ecofisiológicas observadas ante cambios ambientales puede ser fundamentales para la predicción de variaciones en la distribución de especies, composición de la comunidad y productividad del monte ante el cambio global. En esta tesis investigamos el grado de tolerancia y sensibilidad que cada una de las tres especies de estudio, coexistentes en el interior peninsular ibérico (Pinus pinea, Quercus ilex y Juniperus oxycedrus), muestra ante los factores abióticos de estrés típicos de la región Mediterránea. Nuestro trabajo se ha basado en la definición del nicho óptimo fisiológico para el regenerado de cada especie a través de la investigación en profundidad del efecto de la sequía, la temperatura y el ambiente lumínico. Para ello, hemos desarrollado un modelo de predicción de la tasa de asimilación de carbono que nos ha permitido identificar las condiciones óptimas ambientales donde el regenerado de cada especie podría establecerse con mayor facilidad. En apoyo a este trabajo y con la idea de estudiar el efecto de la sequía a nivel de toda la planta hemos desarrollado un experimento paralelo en invernadero. Aquí se han aplicado dos regímenes hídricos para estudiar las características fisiológicas y morfológicas de cada especie, sobre todo a nivel de raíz y crecimiento del tallo, y relacionarlas con las diferentes estrategias en el uso del agua de las especies. Por último, hemos estudiado los patrones de aclimatación y desaclimatación al frio de cada especie, identificando los periodos de sensibilidad a heladas, así como cuellos de botella donde la competencia entre especies podría surgir. A pesar de que el pino piñonero ha sido la especie objeto de la gestión de estas masas durante siglos, actualmente se encuentra en la posición más desfavorable para combatir el cambio global, presentado el nicho fisiológico más estrecho de las tres especies. La encina sin embargo, ha resultado ser la especie mejor cualificada para afrontar este cambio, seguida muy de cerca por el enebro. Nuestros resultados sugieren una posible expansión en el rango de distribución de la encina, un aumento en la presencia del enebro y una disminución progresiva del pino piñonero a medio plazo en estas masas. ABSTRACT Mediterranean forests have undergone multiple changes over the last decades (in both climate and land use), which have lead to variations in the distribution of species. The expected increase in mean annual temperature together with the greater inter and intra-annual variability in extreme events and disturbances occurrence (such as prolonged drought periods, cold or heat waves, wildfires or strong winds) can significantly damage natural regeneration, up to causing death, playing a decisive role on species composition and forest dynamics. The ecological amplitude for adaptation of many species can be affected in such a way that changes in the current regeneration niches of many species are expected. However, the forecasted poleward migration of species seeking better conditions could be an oversimplification of what is a more complex phenomenon of interactions among temperature and precipitation, that would affect different species in different ways. In this regard, either the ability to adapt to environmental stresses or to compete for limited resources of a single species in a mixed forest could lead to variations within a community. The ecophysiological and morphological traits specific to each species are strongly related to the place where each species can emerge, which species can coexist, and how they respond to environmental conditions. In this regard, the understanding of the ecophysiological responses observed against changes in environmental conditions can be essential for predicting variations in species distribution, community composition, and forest productivity in the context of global change. In this thesis we investigated the degree of tolerance and sensitivity that each of the three studied species, co-occurring in central of the Iberian Peninsula (Pinus pinea, Quercus ilex and Juniperus oxycedrus), show against the typical abiotic stress factors in the Mediterranean region. Our work is based on the optimal physiological niche for regeneration of each species through in-depth research on the effect of drought, temperature and light environment. For this purpose, we developed a model to predict the carbon assimilation rate which allows us to identify the optimal environmental conditions where regeneration from each species could establish itself more easily. To obtain a better understanding about the effect of low temperature on regeneration, we studied the acclimation and deacclimation patterns to cold of each species, identifying period of frost sensitivity, as well as bottlenecks where competition between species can arise. Finally, to support our results about the effect of water availabilty, we conducted a greenhouse experiment with a view of studying the drought effect at the whole plant level. Here, two watering regimes were applied in order to study the physiological and morphological traits of each species, mainly at the level of the root system and stem growth, and so relate them to the different water use strategies of the species. Despite the fact that stone pine has been the target species for centuries, nowadays this species is in the most unfavorable position to cope with climate change. Holm oak, however, resulted the species that is best adapted to tolerate the predicted changes, followed closely by prickly juniper. Our results suggest a feasible expansion of the distribution range in holm oak, an increase in the prickly juniper presence and a progressive decreasing of stone pine presence in the medium term in these stone pine-holm oak-prickly juniper mixed forests.