Bacterial diversity and function within an epigenic cave system and implications for other limestone cave systems

There are approximately 48,000 known cave systems in the United States of America, with caves formed in carbonate karst terrains being the most common. Epigenic systems develop from the downward flow of meteoric water through carbonate bedrock and the solutional enlargement of interconnected subsurface conduits. Despite carbonate karst aquifers being globally extensive and important drinking water sources, microbial diversity and function are poorly understood compared to other Earth environments. After several decades of research, studies have shown that microorganisms in caves affect water quality, rates of carbonate dissolution and precipitation, and ecosystem nutrition through organic matter cycling. However, limited prior knowledge exists for the most common system, epigenic caves, regarding microbial taxonomic diversity, their metabolic capabilities, and how community function changes during and following environmental disturbances. To evaluate community development and succession, as well as potential roles in organic matter cycling, bacteria from the Cascade Cave System (CCS) in Kentucky were investigated. From geochemical and metagenomic data collected during a five-month colonization experiment, taxonomically distinct planktonic and sediment-attached bacterial communities formed along the epigenic cave stream. This represents one of the largest metagenomic studies done from any cave. Betaproteobacteria, Gammaproteobacteria, Alphaproteobacteria, and Opitutae were the most abundant groups. Planktonic bacteria pioneered sediment-attached communities, likely attributed to functional differences related to cell motility and attachment. Organic matter cycling affected exogenous heterotrophic community composition and function downstream because of diminished organic matter quality over time. This was reflected in significantly different abundances of genes encoding for carbohydrate and lignin degradation between habitats and depending on cave location. The ubiquity of environmental controls on bacteria functional diversity in karst is unknown because these environments have generally been left out of microbial biogeography research. In a spatial meta-analyses of bacterial diversity data from global cave systems, the ubiquity of some bacteria in karst is evident. Despite evidence for undersampling and difficulties comparing sequencing technologies and strategies, some caves appear to have novel lineages while other caves have taxonomically similar communities despite being 1000s of kilometers apart. The implications are that microbes in karst (i.e., carbonate) caves around the world are functionally comparable

A New Phillips Curve for Spain

En este trabajo se ha presentado evidencia de la Nueva Curva de Phillips (NCP) para la economia española durante las dos ultimas decadas (1980-1998). Algunos de los resultados alcanzados se pueden sintetizar de la siguiente forma : a) la NCP se ajusta bien a los datos de la economia españolab) todavia es importante el componente inercial implicito en la dinamica de esta variable: c) el grado de rigidez de los precios, implicito en las estimaciones, parece plausibled) la utilizacion de informacion independiente sobre precios de bienes intermedios importados (que se ve, a su vez, afectada por el tipo de cambio) afecta a la medicion de los costes marginales de las empresas y, por tanto, a la dinamica de la inflaciony, para concluir, e) las fracciones en el mercado de trabajo, tal y como se manifiesta en el comportamiento del margen salarial, parecen desempeñar un papel importante en la dinamica de los costes marginales. (jg) (ad

Efficiency or statistical illusion? The case for the Japanese Stock Market

The recent proliferation of hedge funds suggests that capital markets present windows of opportunity to realise substantial arbitrage profits thus violating the 'no arbitrage’ condition of efficient markets. This thesis examines several observed return patterns that have raised questions about the efficiency of capital markets and/or the validity of the asset pricing models used to analyse them. The study focuses on the Japanese stock market which is under-analysed despite being the second largest in the world. We first look at three stock attributes that can arguably differentiate between future winners and losers. These are size, price and book value to market. In contrast to older studies, we find no significant evidence of a size effect. The price and book value to market effects however are statistically significant although both appear to be cyclical in nature suggesting that they are at least partially driven by macroeconomic risk factors and so are not pure anomalies. The short term reversal of stock returns is investigated next. Unlike previous studies, a strategy that utilises optimal investment portfolios is simulated. By avoiding previously documented methodological problems, it is shown that contrarian profits are statistically and economically significant and that they are overwhelmingly attributed to investor over-reaction to firm-specific events, implying that significant short term inefficiencies occur in the Japanese stock market. Finally the effectiveness of the law of one price and its implications for the relative pricing of assets is examined. It is shown that the returns of securities with similar systematic risk are highly correlated and their relative prices oscillate around an equilibrium value. Large deviations from that value can be exploited by a trading strategy known as pairs trading. Simulations of several strategy variants generate statistically and economically significant profits which are not attributable to systematic risk. It is concluded that relative stock prices are not always efficient in the short term. Such inefficiencies can be profitably exploited as prices are eventually driven to equilibrium