Spatial and temporal variation of fish assemblage associated with aquatic macrophyte patches in the littoral zone of the Ayapel Swamp Complex, Colombia

ABSTRACT: Aim: The purpose of the present study was to examine spatial and temporal variation in fish assemblage structure associated with aquatic macrophytes in the littoral zone of the ASC. Methods: Specimens were caught between January 2008 and February 2009, over four limnimetric moments, using both cast net and seine net. Data on the temperature, electrical conductivity, pH and dissolved oxygen was recorded for the characterization of the water mass in the sites. Results: A total of 34,151 specimens from 44 species were collected. The most abundant species were Eigenmannia virescens, Astyanax caucanus, Astyanax fasciatus, Roeboides dayi and Cyphocharax magdalenae, which together accounted for more than 75% of the sample. Temporal and spatial comparisons showed variation in the environmental conditions and highlighted the existence of heterogeneous abiotic conditions (p0.05) regarding the fish assemblage structure. The multivariate analysis showed no significant relationship between existing environmental conditions and the fish assemblage (p=0.04). The analysis also showed the absence of a relationship between the fish assemblage and environmental variables with respect to the flood pulse and sampling sites (p>0.05). Conclusion: The uniformity of the fish communities that inhabit aquatic macrophyte patches in the littoral region of the ASC may be related to the availability of suitable habitat in structural terms, that probably supports a more abundant and varied wildlife

Representational predicaments for employees: Their impact on perceptions of supervisors\u27 individualized consideration and on employee job satisfaction

A representational predicament for a subordinate vis-à-vis his or her immediate superior involves perceptual incongruence with the superior about the subordinate\u27s work or work context, with unfavourable implications for the employee. An instrument to measure the incidence of two types of representational predicament, being neglected and negative slanting, was developed and then validated through an initial survey of 327 employees. A subsequent substantive survey with a fresh sample of 330 employees largely supported a conceptual model linking being neglected and negative slanting to perceptions of low individualized consideration by superiors and to low overall job satisfaction. The respondents in both surveys were all Hong Kong Chinese. Two case examples drawn from qualitative interviews illustrate and support the conceptual model. Based on the research findings, we recommend some practical exercises to use in training interventions with leaders and subordinates. © 2013 Copyright Taylor and Francis Group, LLC

Emission-Line Imaging of QSOS with High Resolution

We report the first detection of emission line gas within the host galaxies of high redshift QSOs. This was done using narrow-band imaging at the redshifted wavelengths of [O III] and H alpha, using the PUEO adaptive optics camera of the CFHT. The QSOs are all radio-quiet or very compact radio sources. In all five observed QSOs, which have redshifts 0.9 to 2.4, we find extended line emission that lies within 0.5" (a few Kpc) of the nucleus. The emission (redshifted) equivalent widths range from 35 to 300A. Where there is radio structure, the line emission is aligned with it. We also report on continuum fluxes and possible companions. Two of the QSOs are very red, and have high resolved continuum flux.Comment: 17 pages including 2 tables, 6 diagrams; to appear in A

Performance modeling of a wide-field ground-layer adaptive optics system

Using five independent analytic and Monte Carlo simulation codes, we have studied the performance of wide-field ground-layer adaptive optics (GLAO), which can use a single, relatively low order deformable mirror to correct the wave-front errors from the lowest altitude turbulence. GLAO concentrates more light from a point source in a smaller area on the science detector, but unlike with traditional adaptive optics, images do not become diffraction-limited. Rather, the GLAO point-spread function (PSF) has the same functional form as a seeing-limited PSF and can be characterized by familiar performance metrics such as full width at half-maximum (FWHM). The FWHM of a GLAO PSF is reduced by 0 1 or more for optical and near-infrared wavelengths over different atmospheric conditions. For the Cerro Pachón atmospheric model, this correction is even greater when the image quality is poorest, which effectively eliminates “bad seeing” nights; the best seeing-limited image quality, available only 20% of the time, can be achieved 60%–80% of the time with GLAO. This concentration of energy in the PSF will reduce required exposure times and improve the efficiency of an observatory up to 30%–40%. These performance gains are relatively insensitive to a number of trade-offs, including the exact field of view of a wide-field GLAO system, the conjugate altitude and actuator density of the deformable mirror, and the number and configuration of the guide stars

Avaliação de cinco híbridos de milho (Zea mays, L.) em diferentes estádios de maturação: 3. Composição químico-bromatológica Evaluation of five corn hybrids (Zea mays, L.) at different maturity stages: 3. Chemical-bromatology composition

O objetivo do presente estudo foi avaliar cinco híbridos de milho (Zea mays L.) Pioneer: superprecoce P32R21, os precoces P30R07, P3041 e P30F33 e o semiprecoce P30F80, quanto à composição química, em diferentes estádios de maturação. O delineamento utilizado foi de blocos ao acaso, com cinco tratamentos e quatro repetições. A colheita das amostras dos híbridos de milho foi adotada estimando-se os cinco estádios de maturação da planta: 30, 34, 38, 42 e 46% de matéria seca (MS). Para cada estádio de maturação, procedeu-se à separação de colmo + bainha, lâmina foliar e do grão para posteriores analises químicas. Da fração grão, foram determinados os teores de nitrogênio total e de amido, nos cinco estádios de maturação. Nas frações de lâmina foliar e colmo + bainha, foram determinados os teores de fibra em detergente ácido (FDA), fibra em detergente neutro (FDN), lignina, nitrogênio insolúvel em detergente ácido (NIDA) e nitrogênio total. Para os parâmetros avaliados observou-se diferença entre os híbridos de milho e efeito de dias pós-plantio. Com o avanço do estádio de maturação, observou-se que houve ligeira redução nos teores de proteína bruta (PB) e os teores de amido praticamente não variaram no grão. Para a fração lâmina foliar, verificou-se que, com o aumento nos teores de matéria seca da planta, houve queda nos teores de PB e NIDA, ao contrário da fração colmo + bainha, cujos teores aumentaram. Os teores de FDN, FDA e lignina na lâmina foliar aumentaram, porém esses nutrientes na fração colmo + bainha dos híbridos de milho, praticamente, não variaram com o avanço do estádio de maturação.<br>The objective of this study was evaluate, of the chemical composition of five corn (Zea mays L.) hybrids Pioneer: P32R21, P30R07, P3041, P30F33 and P30F80, at different maturity stages. The treatments were used in plots of 7 x 8 m in a randomized block design, with four replicates. The samples collected of corn hybrid were adopted trying to estimate phases of maturity of the plant: 30, 34, 38, 42 and 46% of dry matter (DM)). For stages of maturity, proceed separation stem + sheath, lamina leaf, and grain at analysis chemicals. In fraction grain, was determinated levels total nitrogen and starch in the different maturation stages. In the fractions of leaf lamina and stem + sheath, levels the following analysis chemicals was determinated: acid detergent fiber (ADF), neuter detergent fiber (NDF), lignin, acid detergent insoluble nitrogen (ADIN) and total nitrogen. All the variables presented differences between the hybrids and days after seeding (DAS). With the advance of the maturity, observed a decrease of crude protein (CP) and of crude starch practicably not varied. For fraction lamina leaf, verification that, increased levels the dry matter at plant, and decreased the levels starch, CP and ADID, contrary the fraction stem + sheath, increased levels. The levels NDF, ADF and lignin the lamina leaf increased, but this nutrition at fraction stem + sheath the corn hybrid, practicably, not varied with advance the maturity of stages