Relationships between environmental factors,periphyton biomass and nutrient content in Garças Reservoir,a hypereutrophic tropical reservoir in southeastern Brazil

This study focused on evaluating the factors related to seasonal variations of periphyton biomass and nutrient content (N, P) in Garças Reservoir, a tropical, shallow hypereutrophic tropical reservoir in southeastern Brazil that exhibits a permanent cyanobacteria bloom. Artificial substrata were placed in the subsurface water (20 cm) of the lake on a monthly basis (incubation time of 28 days) over a 1‐year period. Two limnological periods were characterized, including: (i) a period of decreased water clarity, higher levels of soluble reactive phosphorus and higher phytoplankton biomass; and (ii) a period of relatively higher water clarity (as measured by Secchi depth), higher nitrate concentration and lower phytoplankton biomass. The periphyton chlorophyll‐a levels were lower during the first period, being negatively correlated with phytoplankton biomass. The results of this study suggest that during the period of decreased water clarity, periphyton was primarily light‐limited. In contrast, the periphyton biomass was higher during the second period, regardless of P limitation of periphyton growth. Rehabilitation of this highly degraded tropical reservoir must consider the light regime, which is controlled by phytoplankton abundance. Thus, a reduction in the P loading to the lake should be considered to suppress its cyanobacterial blooms, thereby improving conditions for submerged macrophytes and the re‐establishment of periphyton.     

Crystallization of Rhenium Salts in a Simulated Low‐Activity Waste Borosilicate Glass

This study presents the characterization of salt phases that formed on simulated low‐activity waste glass melts during a rhenium solubility study. This study with rhenium salts is also applicable to real applications involving radioactive technetium salts. In this synthesis method, oxide glass powder is mixed with the volatile species, vacuum‐sealed in a fused quartz ampoule, and then heated in a furnace. This technique restricts the volatile species to the headspace above the melt but still within the sealed ampoule, thus maximizing the concentration of these species that are in contact with the glass. Above the previously determined solubility of Re⁷⁺ in this glass, a molten salt phase segregated to the top of the melt and crystallized into a solid layer. This salt was analyzed with X‐ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, as well as wavelength dispersive spectroscopy and was found to be composed of alkali perrhenates (NaReO₄, KReO₄) and alkali sulfates. Similar crystalline inclusions were found in the bulk of some glasses as well.     

SOLVENT EXTRACTION EQUILIBRIUM OF NICKEL FROM AMMONIACAL SOLUTIONS BY LIX 64N

Equilibrium data for the solvent extraction of nickel from amraoniacal solutions by LIX 64N (10 vol%) dissolved in kerosene (15% aromatic content) are reported. The effect of NH3/aq) concentration, LIX 64N concentration, pH and temperature are shown. The stoichiometry of the Ni-active oxime in LIX 64N complex was ascertained by spectrophotometry studies. A mathematical mechanistic model was developed for the prediction of extraction distribution coefficients as a function of pH. The model predicts more accurate results at high pH values, as could be expected taking into consideration the assumptions made in developing the model.     

Microstructure dependence of magnetization mechanisms in Co-Fe thick films

Journal of Materials Science - Magnetization reversal mechanisms in electrodeposited Co100?xFex (x?=?0; 20; 30; 50) films are investigated by measuring the angular dependence of...     

3D-Printed Carrageenan-Based Nanocomposites for Force-Sensing Applications

Technological development is leading to an exponential growth in the implementation of sensors and actuators where the concern about environmental problems is also focusing on electronic waste (e-waste), which is composed of hazardous materials, corresponding to a large part of urban waste, and has a strong environmental impact. Therefore, more environmentally friendly electronic components are required, natural polymers being a suitable approach to solve or attenuate those problems. This work reports on a bio-based polymer, carrageenan, embedded with dielectric barium titanate (BTO) nanoparticles to tailor the electrical response. The inclusion of the filler induces slight modifications in the thermal characteristics and on the physicochemical properties of the polymer matrix. On the other hand, the mechanical and dielectric properties improve with the addition of BTO and a high dielectric constant of ε′ ≈13 000 is obtained for the composite with 20 wt% BTO content. The increase of the dielectric constant is accompanied by a high AC electrical conductivity, leading to a high-ε′–high-loss material. The 20 wt% BTO composite is used to produce a force measuring sensor, due to the highest dielectric response. The functional response of the sensing system shows good stability over cycling.     

Analysing the lag-growth rate relationship of Yersinia enterocolitica

A generalised z-value concept has been applied to analyse the relationship between the lag and the growth rate of Yersinia enterocolitica at a range of temperature, atmospheric carbon dioxide and oxygen percentages. The product of the specific growth rate and the lag (the "work to be done" during the lag phase) is found to be independent of temperature. However, it does depend on the CO2 and O2 concentrations, though the effect of oxygen was less noticeable than the effect of carbon dioxide.     

Construction and qualitative assessment of a bibliographic portfolio using the methodology Methodi Ordinatio

Methodi Ordinatio is a methodology used to accomplish systematic literature reviews, to build bibliographical portfolios, and to map the state of the art of a research theme. It is composed of nine phases. The 7th phase, named InOrdinatio, applies an equation that orders the papers according to its scientific relevance. The equation applies the alpha (α) element, which can vary from 0 to 10 depending on the research need of currentness and according to the researcher’s perception for its variation. Therefore, the aim of this paper is to test and analyse the variations of the alpha (α) values in the equation InOrdinatio and its influence in the qualification of the items that composes a portfolio. In order to reach this purpose, a practical application was performed and a bibliographic portfolio on the theme Horizontal Business Networks and Trust was built. Using the data from the bibliographic portfolio, the alpha values from 0 to 10 were applied and their influence on the final qualification of the articles was analysed. As a complementary objective, the areas where the methodology was successfully applied until now are also identified. The results show that the methodology is coherent, reproducible and useful to sort the most relevant articles in accordance with what is internationally recognized as valid scientific criteria: the impact factor, year of publication, and number of citations.     

Spin-spin relaxation times in myocardial hypertrophy induced by endocrine agents in rat

Magnetic resonance techniques afford a significant advantage for noninvasive diagnosis of cardiovascular pathology. The purpose of our present study was to assay the proton nuclear magnetic resonance (¹H-NMR) sensitivity in the differential diagnosis of certain endocrine cardiovascular complications. In this context, we investigated the water state and content in the hypertrophied myocardium. Male and female Wistar rats were treated with different hormones (hydrocortisone acetate, testosterone, estradiol, thyroid hormones) in combination with isoproterenol (a synthetic catecholamine that induces myocardial ischemia and hypertrophy). The animals were sacrificed after 20 days of treatment and samples of integral myocardium and left ventricular myocardium were analyzed on a¹H-NMR AREMI spectrometer (0.6 T; proton resonance at 25 MHz). The estimation ofT ₂ was made by Carr-Purcell-Meiboom-Gill pulse sequence. The data were fitted to a bi-exponential curve, yielding short (T ₂₁) values forbound water and long (T ₂₂) values forfree water. In order to evaluate the myocardial hypertrophy, the following ratios were calculated: integral myocardium to body weight; left ventricle to body weight; left ventricle to integral myocardium. The first two ratios were also calculated for dried tissue, in order to estimate its contribution to myocardial hypertrophy. Our findings demonstrate that myocardial hypertrophy is associated with a decrease ofT ₂₂, as a consequence of the increase in the dried component (i.e. proteins) of the tissue, while the total tissue, while the total tissue water (H₂O_t%, measured by gravimetry) was not significantly modified. Nevertheless, it is reasonable that the increase in the protein content would be proportional with the increase in H₂O_t%. The decrease ofT ₂₁ seems to be proportional with the level of left ventricle hypertrophy in female groups. The¹H-NMR measurements were much sensitive for the differential diagnosis of myocardial hypertrophy in the case of left ventricle.