GIS-based models for the development of sustainable aquaculture of native fish species in central Mexico: a catchment level approach for the protection of biodiversity.

Over the last 3 decades, freshwater aquaculture has become one of the most important food industries. However the constant introduction of a reduced number of very successful species for aquaculture has been identified as one of the main activities related to the alarming decline of fish biodiversity worldwide. This issue has raised awareness amongst the scientific community, governmental authorities and the general public towards freshwater fish biodiversity. This new awareness has promoted the development of “green” markets and environmentally friendly strategies, aiming for a reliable production of protein sources. The development of native species aquaculture has been presented as a strong alternative for sustainable aquaculture and the protection of biodiversity. However, it seems clear that unplanned native species aquaculture developments can be as detrimental on local biodiversity as the introduction of exotic fish, if not more dangerous. Therefore, the advantages and disadvantages of native species aquaculture have to be clearly analysed before any aquaculture development. This study aimed to establish a philosophical background regarding the use of native fish species in aquaculture in contrast to the introduction of exotic species that may compete for a similar niche as food in local markets. The main ecological impacts that exotic fish species may have on natives, such as competition, predation, and hybridization were discussed. In addition, a well planned native species Aquaculture Strategy for the Protection of Biodiversity was produced, at catchment level, within a Geographic Information System (GIS). For the development of the native species aquaculture strategy in central Mexico, four species of Atherinids (Chirostoma estor, C. Jordani, C. promelas and Atherinella balsana) and two species of native Ictalurids (Ictalurus balsanus and Ictalurus dugesii) were included in this study. These six species are relatively new to aquaculture and they were selected on the basis of their importance in local fisheries and markets in their native basins of the Lerma-Santiago and Balsas rivers. Both of these basins are of great importance in central Mexico, not only because of their biodiversity but also because of their high human population densities and socio-economic status. The use of Geographic Information Systems was a fundamental factor in the development of the native species aquaculture strategy at catchment level, consisting of site suitability models (SSM) for each species in their corresponding native catchments. Overall, SSM identified 13,916 km2 and 11,178 km2 highly suitable for aquaculture of the studied Atherinids and Ictalurids respectively, based on Water, Soil and Terrain, Infrastructure and Risk sub-models. A set of predictive species distribution models (PSDM), which related ecological characteristics for each studied species with relevant environmental and topographic parameters into a GIS, were also produced. Such models were developed for the establishment of potential natural ranges of distribution for each species, as well as their potential to become exotic in new environments, as a potential for invasion model (PI). Based on a partial verification, both PSDM and PI models produced results that were satisfactorily consistent with the known distribution of each modelled species. The combination of SSM and PSDM produced an Aquaculture Strategy for the Protection of Biodiversity model (ASPB) which identified the most environmentally friendly suitable areas for aquaculture sites. In contrast, the combination of the SSM with PI models into an ASPB model identified the site suitability potential for non-native species that are genetically close to native ones, in an attempt to reduce the known impacts that exotic species have on local biodiversity. In this way the ASPB model identified 7,651 km2 suitable for aquaculture of I. balsanus in its native Balsas basin and 15,633 km¬2 suitable for aquaculture of the non-native I. dugesii. ASPB models were produced for all the studied species. The final results were used to produce a set of guidelines for the development of sustainable aquaculture of native species at catchment level that cover genetic and ecological implications, as well as a well planned decision making tool produced in a GIS

LA EXPERIENCIA ANTIOQUEÑA EN HISTORIA REGIONAL

Antes de entrar en materia debo hacer dos observaciones preliminares que enmarcan los argumentos que expondré. La primera es aclaratoria sobre el sentido de mi charla, pues por razones diversas en Antioquia hemos aprendido que cada uno de nosotros no es mas que el heredero de una tradición, y por tanto, ésta no es una reflexión personal de Victor Alvarez sino la herencia que nuestra generación ha recibido en el terreno de los estudios regionales.. La segunda es para puntualizar lo significativo que resulta presentar aquí en Santander la experiencia deAntioquia, pues desde elsiglo XIX ha sido lugar común pensar que las dos regiones que más se parecen en el país son Antioquia y Santander. Justamente en 1890 Salvador Camacho Roldan decia, palabras más, palabras menos, que si existían dos pueblos importantes en el territorio de la República éstos eran el Antioqueño y el "Socorrano", como llamabanen aquella época a lossantandereanos. Al parecer, lo decía en aquel momento por razones diversas, pero fundamentalmente porque se experimentaba la dinámica colonizadora del Magdalena. Sinembargo, sabemos que después existieron procesos comunes muy importantes: el desarrollo de la economía cafetera, los primerosintentos de industrialización, y aún podemos pensar que mientras Santander era el imperio del radicalismo liberal, Antioquia era a su vez el imperio del conservadurismo radical. Yal mismo tiempo, mientras allá se estaba construyendo el ferrocarril en la época de Pedro Justo Berrío, aquí se estaba abriendo el ferrocarril por la época de Salón Wilches. En fin, existen una serie de situaciones que hacen que para nosotros la comprensión de nuestro papel en el contexto nacional pase por pensar el papel regional santandereano

On round-off error for adaptive finite element methods

Round-off error analysis has been historically studied by analyzing the condition number of the associated matrix. By controlling the size of the condition number, it is possible to guarantee a prescribed round-off error tolerance. However, the opposite is not true, since it is possible to have a system of linear equations with an arbitrarily large condition number that still delivers a small round-off error. In this paper, we perform a round-off error analysis in context of 1D and 2D hp-adaptive Finite Element simulations for the case of Poisson equation. We conclude that boundary conditions play a fundamental role on the round-off error analysis, specially for the so-called 'radical meshes'. Moreover, we illustrate the importance of the right-hand side when analyzing the round-off error, which is independent of the condition number of the matrix. © 2012 Published by Elsevier Ltd

Most \u3cem\u3eCaenorhabditis elegans\u3c/em\u3e MicroRNAs are Individually Not Essential for Development or Viability

MicroRNAs (miRNAs), a large class of short noncoding RNAs found in many plants and animals, often act to post-transcriptionally inhibit gene expression. We report the generation of deletion mutations in 87 miRNA genes in Caenorhabditis elegans, expanding the number of mutated miRNA genes to 95, or 83% of known C. elegans miRNAs. We find that the majority of miRNAs are not essential for the viability or development of C. elegans, and mutations in most miRNA genes do not result in grossly abnormal phenotypes. These observations are consistent with the hypothesis that there is significant functional redundancy among miRNAs or among gene pathways regulated by miRNAs. This study represents the first comprehensive genetic analysis of miRNA function in any organism and provides a unique, permanent resource for the systematic study of miRNAs

Experimental evolution of the coral algal endosymbiont, Cladocopium goreaui: lessons learnt across a decade of stress experiments to enhance coral heat tolerance

Projected increases in sea surface temperatures will exceed corals' ability to withstand heat stress within this century. Experimental evolution of cultured symbionts (Symbiodiniaceae) at high temperatures followed by reintroduction into corals can enhance coral heat tolerance. Several studies have selected for enhanced tolerance in Cladocopium goreaui (C1) over multiple time scales and then compared the performance of coral juveniles infected with the heat-tolerant C1 selected strain (SS) to the performance of juveniles infected with the C1 wild type (WT). To derive lessons about host benefits when symbionts are experimentally selected, here we compare the performance of SS- and WT-juveniles after 21 cell generations of heat selection versus longer periods (73–131) in recently published experiments. After 21 generations, we found rapid improvement in heat tolerance of SS through an overall shift in the mean tolerance to temperature. This did not translate to improved growth and survivorship of the coral. Specifically, survival did not differ significantly between juveniles of Acropora tenuis hosting WT versus SS at any temperature. Juveniles infected with WT exhibited greater skeletal growth than those infected with SS at 27 and 31°C but not at 32.5°C. SS-juvenile symbiont cell densities increased significantly at 27°C relative to SS-juveniles in the 31 and 32.5°C. Photosynthetic efficiencies in SS-juveniles were higher compared to WT-juveniles at 31°C, equal at 27°C, and lower at 32.5°C. These results suggest that selection over longer generation (>130) times will be needed to confer host benefits and will be dependent on the stability of this association being maintained in nature

The tyrosyl-tRNA synthetase like gene located in the tyramine biosynthesis cluster of Enterococcus durans is transcriptionally regulated by tyrosine concentration and extracellular pH

<p>Abstract</p> <p>Background</p> <p>The tyramine producer <it>Enterococcus durans </it>IPLA655 contains all the necessary genes for tyramine biosynthesis, grouped in the TDC cluster. This cluster includes <it>tyrS</it>, an aminoacyl-tRNA synthetase like gene.</p> <p>Results</p> <p>This work shows that <it>tyrS </it>was maximally transcribed in absence of tyrosine at acidic pH, showing a greater than 10-fold induction in mRNA levels over levels occurring in presence of tyrosine. Mapping of the <it>tyrS </it>transcriptional start site revealed an unusually long untranslated leader region of 322 bp, which displays the typical features of the T box transcriptional attenuation mechanism. The tyrosine concentration regulation of <it>tyrS </it>was found to be mediated by a transcription antitermination system, whereas the specific induction at acidic pH was regulated at transcription initiation level.</p> <p>Conclusions</p> <p>The expression of the <it>tyrS </it>gene present in the TDC cluster of <it>E. durans </it>is transcriptionally regulated by tyrosine concentration and extracelular pH. The regulation is mediated by both an antitermination system and the promoter itself.</p

Vertically illuminated TW-UTC photodiodes for terahertz generation

More efficient and powerful continuous-wave photonic mixers as terahertz sources are motivated by the need of more versatile local oscillators for submillimeter/terahertz receiver systems. Uni-Travelling Carrier (UTC) photodiodes are very prospective candidates for reaching this objective, but so far only have been reported as lumped-elements or as edge-illuminated optical-waveguide travelling-wave (TW) devices. To overcome the associated power limitations of those implementations, we are developing a novel implementation of the UTC photodiodes which combines a traveling-wave photomixer with vertical velocity-matched illumination in a distributed structure. In this implementation called velocity-matched travelling-wave uni-travelling carrier photodiode, it is possible to obtain in-situ velocity matching of the beat-fringes of the two angled laser beams with the submm/THz-wave on the stripline. In this way, minimum frequency roll-off is achieved by tuning the angle between the two laser beams. A first design of these TW-UTC PDs from our Terahertz Photonics Laboratory at University of Chile has been micro-fabricated at the MC2 cleanroom facility at Chalmers Technical University

Is Subdural Peritoneal Shunt Placement an Effective Tool for the Management of Recurrent/Chronic Subdural Hematoma?

Objectiveæ To describe a surgical techniqueæand to report using a retrospective studyæthe efficacy of peritoneal shunts for the treatment of recurrent/chronic subdural hematoma (CSDH). We describeæthe considerations, complications, and outcomes related to this technique. Methodsæ In a retrospectiveæcohort study, 125 charts with a diagnosis of subacute/chronic subdural hematoma were assigned for evaluation. Of the charts reviewed, 18 charts were found from subjects with a diagnosis of recurrent sub-acute or chronic subdural hematoma. All patients had undergone initial surgical treatment of their condition followed by peritoneal shunt placement to help alleviate intracranial pressure. Factors including the age, size of subdural hematoma, number of previous events, BMI, complications, survival, and clinical course were analyzed. Resultsæ After subdural peritoneal shunt placement all patients had full neurological recovery with no complaints of headaches, lethargy, weakness, confusion or seizures. None of the cases had new subdural hematoma episodes after placement for a minimum of a two-year period (mean 26.1 months) (range 24.3-48.6 months). No postoperative complications were reported. The rates of postoperative hemorrhage, infection, distal catheter revision, and perioperative seizures was found to be zero percent. Shunt drainage was successful in all cases, draining 85% of the blood in the first 48 hours. There was no significant relationship between complications and the use of anticoagulants four weeks after surgery. Conclusions Peritoneal shunts, though rarely used, are a viable option in the treatment of sub-acute/chronic subdural hematomas. When pursuing this treatment, this technique is recommended to mitigate the risks of repeat surgical intervention and lessen perioperative time in high-risk patients

Optimum relative concentrations of phosphorus and sulfur in coffee fertilization in a Dark-Red Latosol, at Machado, MG, Brazil

Para estudar as doses relativas P - S, na adubação do cafeeiro (Coffea arabica L.) (cv. Catuaí), num Latossolo Vermelho-Escuro, fase cerrado, de Machado, MG, foi instalado um experimento no campo. Os tratamentos foram escolhidos de acordo com o método de cortes de Richard. Os valores dos cortes (0,8, 0,4 e 0,2) foram definidos em função da capacidade máxima de adsorção de P e S. Dentro de cada corte foram estudadas quatro doses relativas. As fontes de P e S, aplicadas no enchimento das covas, foram o superfosfato triplo e o gesso. Os efeitos dos tratamentos foram avaliados no segundo e terceiro anos após o plantio. A altura da planta e os diâmetros do tronco e da copa, no segundo ano após o plantio, mostraram ser a aplicação de S necessária somente na presença de níveis elevados de P (corte 0,8). Resultados obtidos no início da fase produtiva (terceiro ano após o plantio) mostraram que para aplicação de níveis baixos de P (corte 0,2) a disponibilidade de S do solo foi suficiente. Entretanto, para níveis mais elevados de P (cortes 0,4 e 0,8), foi necessária a adição conjunta de P e S. Considerando a produção, no corte 0,4 o equilíbrio ótimo ocorreu com a aplicação de 70 g de P2O5 e 4 g de S, por cova, e no corte 0,8, com a aplicação de 135 g de P2O5 e 9 g de S, por cova, As observações obtidas indicam ser o P mais exigido do que o S, na fase de formação do cafeeiro. O desenvolvimento da cultura e o aumento da dose de P aplicada na cova exigem a complementação com S.To study the P - S equilibria in coffee (Coffea arabica L.) fertilization (Catuai cultivar) in a Dark-Red Latosol, "cerrado" phase, at Machado, MG, Brazil, a field experiment was carried out with the treatments selected according to "Richard's cut method". The cut values (0.8, 0.4 and 0.2) were defined as a function of the soil P and S maximum adsorptions. In each cut, four equilibria were studied. The sources of P and S were concentrated superphosphate and gypsum. The treatment effects were evaluated in the second and third years after planting. The plant height and the stem and top diameter, in the second year after planting showed the application of S as necessary only in the presence of high levels of P (cut 0.8). In the yielding phase (third year after planting) the results showed that for the low levels of P applied the soil S was enough. On the other hand, for high levels of P (cuts 0.4 and 0.8), the application of both P and S was necessary. Considering yield, for the cut 0.4, the optimum equilibrium was observed with the applications of 70 g P2O5 of and 4 g of S per planting hole, and for the cut 0.8, with 135 and 9 g, respectively. The results indicate that P is more required than S during the growth phase of coffee. With the plant growth and with the increase in the rate of P applied per plant, the S requirement becomes more important