X-ray data collection from mineral crystals by means of a position-sensitive detector: Advantages and disadvantages

In order to check for the accuracy of X-ray diffracted data collected with an area-detector diffractometer (FAST-Nonius), we have carried out several data collections on a good-quality pyrope crystal (space group 1a3d; a = 11.479 \uc5) under different experimental settings and compared the results with those obtained with the same crystal mounted on a conventional Philips PW1100 diffractometer. Several parameters have been tested (detector gain, crystal-to-detector distance, frame width, integration time per image, beam intensity, shoebox size and re-measuring of overflow reflections), and four critical features of the system have been identified: the low thermal stability of the detector, its narrow dynamic range, the importance of the detector-to-crystal distance and the integration of the diffracted intensities. We are now able to select the best experimental settings in order to obtain a refinement from FAST diffraction data good as that from Philips data, in terms of Rsym, Robs and standard deviation of the refined parameters

Promoção de eventos culturais na Biblioteca da Embrapa Florestas: responsabilidade social e cultural.

Apresenta uma reflexão sobre a responsabilidade e compromisso social das bibliotecas e descreve ações desenvolvidas por uma biblioteca especializada na área de pesquisa com o objetivo de promover a biblioteca, incentivar atividades culturais, bem como de sociabilizar a mesma na empresa

Digestibilidade de dietas constantes de feno de capim mandante e milho, suplementadas com farelos de algodão e de mamona desintoxicada.

Foi realizado um estudo comparativo entre os farelos de algodão e de mamona desintoxicada, através de ensaio de digestibilidade com ovinos adultos, como suplementos proteícos de uma dieta básica constante de capim mandante e milho moido (grão)

Extra-matrix Mg\u3csup\u3e2+\u3c/sup\u3e Limits Ca\u3csup\u3e2+\u3c/sup\u3e Uptake and Modulates Ca\u3csup\u3e2+\u3c/sup\u3e Uptake-independent Respiration and Redox State in Cardiac Isolated Mitochondria

Cardiac mitochondrial matrix (m) free Ca2+ ([Ca2+]m) increases primarily by Ca2+ uptake through the Ca2+ uniporter (CU). Ca2+ uptake via the CU is attenuated by extra-matrix (e) Mg2+ ([Mg2+]e). How [Ca2+]m is dynamically modulated by interacting physiological levels of [Ca2+]e and [Mg2+]e and how this interaction alters bioenergetics are not well understood. We postulated that as [Mg2+]e modulates Ca2+ uptake via the CU, it also alters bioenergetics in a matrix Ca2+–induced and matrix Ca2+–independent manner. To test this, we measured changes in [Ca2+]e, [Ca2+]m, [Mg2+]e and [Mg2+]m spectrofluorometrically in guinea pig cardiac mitochondria in response to added CaCl2 (0–0.6 mM; 1 mM EGTA buffer) with/without added MgCl2 (0–2 mM). In parallel, we assessed effects of added CaCl2 and MgCl2 on NADH, membrane potential (ΔΨm), and respiration. We found that \u3e0.125 mM MgCl2 significantly attenuated CU-mediated Ca2+ uptake and [Ca2+]m. Incremental [Mg2+]e did not reduce initial Ca2+uptake but attenuated the subsequent slower Ca2+ uptake, so that [Ca2+]m remained unaltered over time. Adding CaCl2 without MgCl2 to attain a [Ca2+]m from 46 to 221 nM enhanced state 3 NADH oxidation and increased respiration by 15 %; up to 868 nM [Ca2+]m did not additionally enhance NADH oxidation or respiration. Adding MgCl2 did not increase [Mg2+]m but it altered bioenergetics by its direct effect to decrease Ca2+ uptake. However, at a given [Ca2+]m, state 3 respiration was incrementally attenuated, and state 4 respiration enhanced, by higher [Mg2+]e. Thus, [Mg2+]e without a change in [Mg2+]m can modulate bioenergetics independently of CU-mediated Ca2+ transport

NON-DARCY FLOW EVALUATION OF UNCONSOLIDATED POROUS MEDIA IN A CLOSED LOOP PERMEAMETER

A new closed loop permeameter was implemented in this work to study the fluid flow through two different unconsolidated porous media. An apparent permeability, similar to that proposed by Barree and Conway, was described in this work in terms of the absolute permeability combined with a new fluid property description, the inertial contribution factor that accounts for the domain of viscous and inertial forces. Such approach discriminate those properties of the rock as intrinsic permeability from those related to the fluid as the inertial contribution factor. The apparent permeability equation of Barree and Conway was applied to different intervals of the experimental data in which it was possible to obtain the Forchheimer coefficients as well as the inertial contribution factors according to each interval. Two different types of unconsolidated porous media materials were utilized in the new Closed Loop Permeameter, sand (1-2 mm) and glass spheres (3.96 mm). The equation of Barree and Conway provided a great agreement fitting the experimental data in a wide non-Darcy Reynolds number range. It was observed an increase in the Forchheimer coefficient and decrease in the apparent permeability with the flow rate increase. The results indicate a correlation between the permeability and the inertial effects in the non-Darcy turbulent regions in which the porous media materials with low permeability values are probably more subjected to flow losses due to the inertial effects

Sequence polymorphism can produce serious artefacts in real-time PCR assays: hard lessons from Pacific oysters

<p>Abstract</p> <p>Background</p> <p>Since it was first described in the mid-1990s, quantitative real time PCR (Q-PCR) has been widely used in many fields of biomedical research and molecular diagnostics. This method is routinely used to validate whole transcriptome analyses such as DNA microarrays, suppressive subtractive hybridization (SSH) or differential display techniques such as cDNA-AFLP (Amplification Fragment Length Polymorphism). Despite efforts to optimize the methodology, misleading results are still possible, even when standard optimization approaches are followed.</p> <p>Results</p> <p>As part of a larger project aimed at elucidating transcriptome-level responses of Pacific oysters (<it>Crassostrea gigas</it>) to various environmental stressors, we used microarrays and cDNA-AFLP to identify Expressed Sequence Tag (EST) fragments that are differentially expressed in response to bacterial challenge in two heat shock tolerant and two heat shock sensitive full-sib oyster families. We then designed primers for these differentially expressed ESTs in order to validate the results using Q-PCR. For two of these ESTs we tested fourteen primer pairs each and using standard optimization methods (i.e. melt-curve analysis to ensure amplification of a single product), determined that of the fourteen primer pairs tested, six and nine pairs respectively amplified a single product and were thus acceptable for further testing. However, when we used these primers, we obtained different statistical outcomes among primer pairs, raising unexpected but serious questions about their reliability. We hypothesize that as a consequence of high levels of sequence polymorphism in Pacific oysters, Q-PCR amplification is sub-optimal in some individuals because sequence variants in priming sites results in poor primer binding and amplification in some individuals. This issue is similar to the high frequency of null alleles observed for microsatellite markers in Pacific oysters.</p> <p>Conclusion</p> <p>This study highlights potential difficulties for using Q-PCR as a validation tool for transcriptome analysis in the presence of sequence polymorphism and emphasizes the need for extreme caution and thorough primer testing when assaying genetically diverse biological materials such as Pacific oysters. Our findings suggest that melt-curve analysis alone may not be sufficient as a mean of identifying acceptable Q-PCR primers. Minimally, testing numerous primer pairs seems to be necessary to avoid false conclusions from flawed Q-PCR assays for which sequence variation among individuals produces artifactual and unreliable quantitative results.</p