Characterization using thermomechanical and differential thermal analysis of the sinterization of Portland clinker doped with CaF2

In this work, the sintering process of Portland cement was studied by combining thermomechanical analysis (TMA) and differential thermal analysis (DTA), together with X-ray diffraction (XRD) and scanning electron microscopy (SEM). Thermal analysis results employing both techniques indicted that phase transformations appeared at lower temperatures when CaF₂ was incorporated in the raw materials. Besides, it was observed at high temperature that in some phase transformations TMA conducts to better resolution compared with the DTA measurements. Furthermore, mechanical properties and X-ray diffraction patterns corroborate the TMA and DTA results, corroborating that the final amount of alite (Ca₃SiO₅) is higher when a certain amount of CaF₂ was present during the clinkerization process.     

Galacto‐Oligosaccharides: Production,Properties, Applications,and Significance as Prebiotics

Abstract: Galacto‐oligosaccharides (GOS) have now been definitely established as prebiotic ingredients after in vitro and animal and human in vivo studies. Currently, GOS are produced by glycoside hydrolases (GH) using lactose as substrate. Converting lactose into GOS by GH results in mixtures containing GOS of different degrees of polymerization (DP), unreacted lactose, and monomeric sugars (glucose and galactose). Recent and future developments in the production of GOS aim at delivering purer and more efficient mixtures. To produce high‐GOS‐content mixtures, GH should not only have good ability to catalyze the transgalactosylation reaction relative to hydrolysis, but also have low affinity for the GOS formed relative to the affinity for lactose. In this article, several microbial GH, proposed for the synthesis of GOS, are hierarchized according to the referred performance indicators. In addition, strategies for process improvement are discussed. Besides the differences in purity of GOS mixtures, differences in the position of the glycosidic linkages occur, because different enzymes have different regiochemical selectivity. Depending on oligosaccharide composition, GOS products will vary in terms of prebiotic activity, as well as other physiological effects. This review focuses on GOS production from synthesis to purification processes. Physicochemical characteristics, physiological effects, and applications of these prebiotic ingredients are summarized. Regulatory aspects of GOS‐containing food products are also highlighted with emphasis on the current process of health claims evaluation in Europe.     

The vulnerability of wind power to climate change in Brazil

The availability and reliability of wind power depend a great deal on current and future climate conditions, which may vary in light of possible global climate change (GCC). Long-term energy planning, however, does not normally take possible future GCC into consideration, which may turn out to be a risky exercise. In the case of Brazil, the untapped wind power potential is known to be impressive, provided that climate conditions remain the same over time. The focus of this study is to analyze some possible impacts of GCC on the wind power potential of Brazil, by simulating wind conditions associated with the IPCC A2 and B2 Scenarios. Results based on the HadCM3 general circulation model and the analysis of the country's wind database indicate that the wind power potential in Brazil would not be jeopardized in the future due to possible new climate conditions. On the contrary, improved wind conditions are expected, particularly in the Northeast coast of the country. Therefore, investments in wind power generation can be an interesting way to expand renewable energy production in Brazil. However, given the large uncertainties associated with GCC models and scenarios, the findings of this paper should be viewed as a possibility rather than as a projection.     

Effect of functionalized trititanate nanotubes on the properties of crosslinked cationic polymer nanocomposite

The synthesis and characterization of a crosslinked polymer nanocomposite containing titanium oxide nanotubes as filler are presented. First, the TiO₂ nanotubes were synthesized using a hydrothermal procedure and further functionalized using the organosilane reagent γ‐methacryloxypropyltrimethoxysilane. Subsequently, the modified nanotubes were incorporated into a polymer matrix using in situ polymerization of a mixture of monomer, crosslinker and initiator. Diverse characterization techniques were used at different stages of the synthesis, including transmission (TEM) and scanning electron microscopies, X‐ray diffraction (XRD), solid‐state ²⁹Si NMR and ¹³C NMR spectroscopy and nitrogen adsorption isotherms at 77 K. The as‐synthesized nanotubes correspond to the trititanate phase verified using XRD, and their presence within the nanocomposite was confirmed using TEM analysis. In addition, TiO₂ particles were detected on the surface of the nanocomposite. The nanocomposite exhibited a slight increase of Vickers microhardness while the water absorption decreased with oxide content attributed to trititanate nanotubes acting as multifunctional crosslinker.© 2015 Society of Chemical Industry     

Non-Alcoholic Steatohepatitis (NASH): Risk Factors in Morbidly Obese Patients

The aim was to investigate the prevalence of non-alcoholic steatohepatitis (NASH) and risk factors for hepatic fibrosis in morbidly obese patients submitted to bariatric surgery. This retrospective study recruited all patients submitted to bariatric surgery from January 2007 to December 2012 at a reference attendance center of Southern Brazil. Clinical and biochemical data were studied as a function of the histological findings of liver biopsies done during the surgery. Steatosis was present in 226 (90.4%) and NASH in 176 (70.4%) cases. The diagnosis of cirrhosis was established in four cases (1.6%) and fibrosis in 108 (43.2%). Risk factors associated with NASH at multivariate analysis were alanine aminotransferase (ALT) >1.5 times the upper limit of normal (ULN); glucose ≥ 126 mg/dL and triglycerides ≥ 150 mg/dL. All patients with ALT ≥1.5 times the ULN had NASH. When the presence of fibrosis was analyzed, ALT > 1.5 times the ULN and triglycerides ≥ 150 mg/dL were risk factors, furthermore, there was an increase of 1% in the prevalence of fibrosis for each year of age increase. Not only steatosis, but NASH is a frequent finding in MO patients. In the present study, ALT ≥ 1.5 times the ULN identifies all patients with NASH, this finding needs to be further validated in other studies. Moreover, the presence of fibrosis was associated with ALT, triglycerides and age, identifying a subset of patients with more severe disease.     

Reaction steps in the combustion synthesis of NiAl/TiB2 composites

The reaction steps in the formation of NiAl/TiB₂ composites produced by reaction synthesis have been determined using differential thermal analysis (DTA). The DTA technique reveals that the formation of NiAl/TiB₂ composites occurs in a two-step reaction. NiAl forms first at approximately 550 °C, followed by TiB₂, which forms at approximately 1050 °C. Both X-ray diffraction (XRD) and energy-dispersive spectroscopy (EDS) were performed on composites produced by reaction synthesis in a hot-press facility using the same heating rate used in the DTA experiments. It was found that the formation of NiAl and TiB₂ is preceded by the formation of intermediate compounds such as Ni₃Al, TiAl, Ti₃Al, Ti₂Ni, and TiB. The relative density measured in the composites with 0, 0.25, 0.50, and 0.75 volume fractions of TiB₂ was in excess of 96 pct of the theoretical density, since, during synthesis, NiAl is a transient liquid that acts as a binder phase for the TiB₂ particles.     

Supplemental water releases for fisheries restoration in a Brazilian floodplain river: a conceptual model

Highly productive floodplain rivers in Brazil and elsewhere provide livelihood and recreational fishing for millions of people around the world, but damming and controlled water discharge are a threat to these valuable ecosystems. Supplemental water releases (SWRs) at a dam are increasingly used for restoring fisheries productivity in many floodplain rivers. We proposed a conceptual model for a hypothetical water release to enhance fisheries using Três Marias Reservoir (TMR) on the São Francisco River (SFR), Brazil. The information needed by the model follows: (i) Biologically, what is the best release date? (ii) How much water will be released? (iii) What is the pattern of impoundment and how much impounded water will be released? (iv) What is the lost revenue to the power plant associated with SWR? (v) What is the relationship between river discharge and the area of floodplain that is flooded? (vi) What is the relationship between SWR and fisheries value? Ichthyoplankton studies in the SFR showed a clear positive relationship between fish density and water level (WL). While the relationship between WL and floodplain area flooded and recruitment is not known, we concluded the best date for release is when there is a natural flood, which naturally triggers fish spawning and the SWR will add to the natural flood and cover a greater floodplain area. The released volume will range from 0.302 km³ to 2.192 km³, depending on SWR duration. In most years from 1976 to 2003, TMR impounded enough water for SWR only in the second half of the fish‐spawning season (January–March). Lost revenue at TMR depended on release volume and ranged from US$ 0.493 million to US$ 3.452 million for the actual power rate. However, SWR could increase commercial fisheries income an estimated US$ 4.468 million. We forecast that SWR can bring fisheries benefits that surpass the lost revenue. Published in 2007 by John Wiley & Sons, Ltd.     

Thermal comfort criteria and building design: Field work in Portugal

The present paper focuses on the issue of thermal comfort adaptive criteria and its relevance to the implementation of passive design strategies, in the context of a field work carried out in Portugal. This field work involved monitoring and questionnaires in office buildings existing in Lisbon, as well as other types of buildings, such as homes for the elderly and educational buildings, during summer, winter and mid-season.     

‘Fragile Superconductivity’: A Kinetic Glass Transition in the Vortex Matter of the High-temperature Superconductor YBa2 Cu3O7-δ

Using high-resolution thermal expansion and magnetization measurements, we provide experimental evidence for a kinetic glass transition in the vortex matter of YBa₂Cu₃O_7-δ with some disorder. This transition, which represents the true superconducting transition in a magnetic field, exhibits many of the features of the usual glass transition found in supercooled structural liquids such as window glass. We demonstrate, using both kinetic and thermodynamic criteria, that this vortex matter is the most fragile system known to date, which we argue makes it possible to investigate the behavior very close to the Kauzmann temperature. Vortex matter, we suggest, may be a model system to study glassy behavior in general, which is expected to lead to a better understanding of the strong-fragile behavior in structural glasses.