Are daily financial data useful for forecasting GDP? Evidence from Mexico

This article evaluates the use of financial data sampled at high frequencies to improve short-term forecasts of quarterly GDP for Mexico. The model uses both quarterly and daily sampling frequencies while remaining parsimonious. In particular, the mixed data sampling (MIDAS) regression model is employed to deal with the multi-frequency problem. To preserve parsimony, factor analysis and forecast combination techniques are used to summarize the information contained in a data set containing 392 daily financial series. Our findings suggest that the MIDAS model incorporating daily financial data leads to improvements in quarterly forecasts of GDP growth over traditional models that either rely only on quarterly macroeconomic data or average daily frequency data. The evidence suggests that this methodology improves the forecasts for the Mexican GDP notwithstanding its higher volatility relative to that of developed countries. Furthermore, we explore the ability of the MIDAS model to provide forecast updates for GDP growth (nowcasting)

A Qualitative Exploration of Entrepreneurial Learning Among Southern Arizona Small-Scale Farmers and Ranchers

Small-scale farmers and ranchers who participate in local food enterprise are challenged by a number of market uncertainties. These uncertainties include unpredictable consumer purchasing patterns, seasonal production variations, and relatively small customer bases. Moreover, farmers and ranchers turned local food entrepreneurs have limited access to business training and, thus, rely on experience and experimentation to guide their business decision making. This article draws on qualitative data to explore how farmers and ranchers who participate in Southern Arizona farmers\u27 markets develop entrepreneurial knowledge and skills. Recommendations for how Extension educators can enhance the entrepreneurial learning of small-scale farmers and ranchers are provided

The effect of plant age on the chemical composition of fresh and ensiled Agave salmiana leaves

In the first study dry matter (DM), organic matter, crude protein (CP), neutral detergent fibre (NDF) and soluble carbohydrate (SC) concentrations were determined in whole leaves and the upper and lower sections of whole leaves of the Agave salmiana (Otto ex. Salm-Dyck) plant. The pH and saponin concentration were measured in aqueous extracts from these leaves. The leaves were collected from plants at the young (ca. 12 years old), bud (ca. 14 years old) and mature (ca. 16 years old) stages of growth. The CP level of young Agave (48 g/kg DM) leaves was higher than in leaves from the bud (38 g/kg DM) and mature (43 g/kg DM) stages, and higher in the upper (51 g/kg DM) than in the lower (35 g/kg DM) leaf sections. The leaves at the bud stage contained lower NDF (189 g/kg DM) but higher SC (358 g/kg DM) levels than those of mature (272 g NDF, 247 g SC/kg DM) and young (273 g NDF, 189 g SC) plants. The saponin content of leaves was higher in the mature (11.1 g/kg DM) than in the bud stage (7.5 g/kg DM). In the second study the chemical composition of whole leaves from young, bud and mature micro-ensilaged (3.5 kg as fed) Agave was determined over a 36 weeks fermentation period. Agave silage had acceptable chemical characteristics. As time of fermentation increased, a linear decrease in DM and saponin concentration, a linear increase in NDF and lactic acid levels and a quadratic increase of pH values and ammonia-N concentrations were recorded. Both fresh and ensilaged leaves of the mature and the bud stages were the most desirable maturity stages of Agave to be utilised as feed for ruminants. Keywords: Agave salmiana, chemical composition, magueySouth African Journal of Animal Science Vol. 38 (1) 2008: pp. 43-5

Direct Observation of High-Spin States in Manganese Dimer and Trimer Cations by X-ray Magnetic Circular Dichroism Spectroscopy in an Ion Trap

The electronic structure and magnetic moments of free Mn$_2^+$ and Mn$_3^+$ are characterized by $2p$ x-ray absorption and x-ray magnetic circular dichroism spectroscopy in a cryogenic ion trap that is coupled to a synchrotron radiation beamline. Our results show directly that localized magnetic moments of 5 $\mu_B$ are created by $3d^5 (^6\mathrm{S})$ states at each ionic core, which are coupled in parallel to form molecular high-spin states via indirect exchange that is mediated in both cases by a delocalized valence electron in a singly-occupied $4s$ derived orbital with an unpaired spin. This leads to total magnetic moments of 11 $\mu_B$ for Mn$_2^+$ and 16 $\mu_B$ for Mn$_3^+$, with no contribution of orbital angular momentum

The exotic weevil Stenopelmus rufinasus Gyllenhal, 1835 (Coleoptera: Curculionidae) across a "host-free" pond network

The presence of the exotic weevil Stenopelmus rufinasus (Coleoptera: Curculionidae) is closely related to the occurrence of the exotic red water fern, Azolla filiculoides. In this paper, we present the first records of S. rufinasus in Doñana National Park (SW Spain), based on sampling of macroinvertebrates in 91 temporary ponds, including monthly samples of 22 ponds, during two successive years (2005-2007). The exotic weevil was present in 21% of the sampled ponds where the host plant, A. filiculiodes, was not detectable. Because A. filiculoides can reach high densities in an adjacent area of marsh, we suggest that the occurrence of the exotic weevil in these ponds is a consequence of dispersal from nearby marshes. Our study demonstrates that S. rufinasus adults can occur at relatively high densities in ponds where the host plant is not present, suggesting that such apparently “host-free” sites may act as stepping stones for the spread of this speciesLa presencia de la especie de gorgojo exótico Stenopelmus rufinasus (Coleoptera: Curculionidae) está íntimamente rela- cionada con la planta acuática exótica Azolla filiculoides. En este estudio se registró por primera vez la presencia de S. rufinasus en el Parque Nacional de Doñana (SO España) tras realizar un muestreo de macroinvertebrados en 91 lagunas que incluye muestreos mensuales de 22 de las mismas durante dos años consecutivos (2005-2007). El gorgojo exótico estuvo presente en el 21% de las lagunas muestreadas a pesar de que su supuesto hospedador, A. filiculiodes, no fue detectado. Dado que A. filiculiodes puede alcanzar grandes densidades en la marisma adyacente, sugerimos que la presencia del gor- gojo exótico en las lagunas temporales se debe a su dispersión desde la marisma. Este estudio demuestra que individuos adultos de S. rufinasus pueden aparecer con densidades relativamente altas en lagunas donde su hospedador potencial no está presente, lo que sugiere que estos sitios libres de hospedador podrían actuar como zonas de paso para la dispersión de la especiePeer reviewe

Coordination-driven magnetic-to-nonmagnetic transition in manganese doped silicon clusters

The interaction of a single manganese impurity with silicon is analyzed in a combined experimental and theoretical study of the electronic, magnetic, and structural properties of manganese-doped silicon clusters. The structural transition from exohedral to endohedral doping coincides with a quenching of high-spin states. For all geometric structures investigated, we find a similar dependence of the magnetic moment on the manganese coordination number and nearest neighbor distance. This observation can be generalized to manganese point defects in bulk silicon, whose magnetic moments fall within the observed magnetic-to-nonmagnetic transition, and which therefore react very sensitively to changes in the local geometry. The results indicate that high spin states in manganese-doped silicon could be stabilized by an appropriate lattice expansion

Interannual variation in filling season affects zooplankton diversity in Mediterranean temporary ponds

In Mediterranean temporary ponds, the timing of annual flooding is highly variable and depends on heavy seasonal rains. Ponds can flood in the autumn, winter, or spring, and thus the environmental conditions faced by emerging zooplankton can be very different. We performed an experiment in a climatic chamber where we simulated annual variation in natural temperature and light conditions to study how differences in pond-filling season affected zooplankton assemblage composition. We sampled sediments from a temporary pond and placed them in aquariums that were filled with water during three different seasons: autumn (October), winter (January), and spring (March). Zooplankton abundance, species richness, diversity, and assemblage composition differed significantly among treatments, and post-inundation temperature and pH appeared to be the main drivers of these differences. Diversity was highest in the winter treatment. It was lower in the autumn treatment and the spring treatment, and no indicator species were present in the latter. Our results suggest that interannual variability in initial inundation conditions favours the emergence of different species and thus contributes to high species richness in the egg bank. However, climate change and/or groundwater drawdown could delay pond flooding, impoverishing the zooplankton assemblage in the long ter