In vitro evaluation of natural hydroxyapatite from Osteoglossum bicirrhosum fish scales for biomedical application

This study reports the obtainment of bioactive hydroxyapatite (HAp) extracted from scales of arowana fish (FSHA) (Osteoglossum bicirrhosum) by alkaline treatment followed by calcination at 600 and 800°C. The cell viability and bioactivity of hydroxyapatite particles (FSHA) were investigated and compared with those of HAp synthesized (s.HA) by the precipitation method. The HAp particles from fish scales showed non-toxic behavior to dental pulp stem cells similar to HAp synthesized. Additionally, bioactivity assays show that the Hap from natural source forms the bone-like apatite layer faster than s.HA sample, after being incubated in McCoy medium for 3 days. The results illustrate that HAp obtained from Osteoglossum bicirrhosum fish scale bio-waste showed excellent biocompatibility. Besides, this study provides an effective method for converting low-cost bio-waste into a value-added and it can be a potential alternative biomaterial for various biomedical applications.     

The declining scientific wealth of Hong Kong and Singapore

Scientometrics - At a time when the knowledge race is at its most intense, the scientific wealth of nations is increasingly relevant to ensure the preparedness and competitiveness of societies in a...     

Alkali activation of a novel calcium‐silicate hydraulic binder with CaO/SiO2 = 1.1

A quasi‐amorphous low‐calcium‐silicate hydraulic binder, with an overall CaO/SiO₂ (C/S) molar ratio of 1.1, was produced. This cementitious material was then hydrated with aqueous solutions containing 3 wt% alkalis (either NaOH, Na₂CO₃ or Na₂SiO₃). The evolution of the hydration processes of the samples were monitored by compressive strength testing, XRD, FTIR, ²⁹Si and ²⁷Al MAS NMR, isothermal calorimetry and TGA. It was found that the nearly exclusive hydration product formed was a C‐S‐H phase with a semi‐crystalline structure. More importantly, the paste prepared with the Na₂SiO₃ solution developed compressive strength values similar to those of ordinary portland cements (OPC) with faster early age kinetics. In addition, the isothermal calorimetry results indicated that these new hydraulic binders present much lower heat of hydration values compared with a traditional OPC. The results presented here open the possibility of producing cement with a compressive strength comparable to that of OPC but with lower CO₂ emissions during the production process and with lower hydration heat related problems during the production of concrete structures.     

Toward the characterization of software testing practices in South America: looking at Brazil and Uruguay

Software testing is an important activity in the software development life cycle. Several previous studies reported the results of surveys on software testing practices among practitioners from different countries. In this paper, we analyze these surveys aiming to get their main questions, and replicate a survey with practitioners from Brazil and Uruguay, two emerging South American software development scenarios. This survey was previously conducted in Manaus/Brazil in 2006 and Buenos Aires/Argentina in 2013. The replication’s scope includes three regions (Northern Brazil, Southern Brazil, and Uruguay). A total of 150 software testing practitioners responded to the survey. Its results are compared with the previous executions and other software testing surveys identified in the technical literature, strengthening previous findings. The Brazilian and Uruguayan participants indicate that: (1) documentation of test artifacts (plan, cases, procedures, results) are useful and important for software testing practitioners; (2) system and regression testing are the two test types deemed most useful and important; (3) tools for monitoring and management of test process tasks and bug reports are considered useful and important; (4) it is usual for software companies to have a definition of a testing process and to have a dedicated testing team; (5) there is a lack of measurement of test tasks and coverage in the industry; and (6) tools to support automation of test case generation and execution or code coverage are still poorly used in their organizations.     

The effect of variable renewable energy sources on electricity price volatility: the case of the Iberian market

The relationship between variable renewable energy supply (V-RES) and electricity price volatility is a controversial issue in the economic literature. In general, the literature has been inconclusive about the sign of the impact of installed capacity of these technologies on price volatility. This paper investigates the impact of V-RES on price volatility for the Iberian Market of Electricity (MIBEL), in the period ranging from 2010 to 2015. Using regression analysis and EGARCH models, we conclude that V-RES, and more specifically wind power supply, heightens price volatility. Likewise, greater intraday variability of V-RES also induces higher price volatility. Finally, following an analysis of the connection with the French market, we find that market coupling could help alleviate the sensitivity of price volatility to wind power supply variability.     

Water sorption isotherms and thermodynamic properties of pearl millet grain

The water sorption isotherms of pearl millet grain and the thermodynamic properties obtaining during the process of drying pearl millet were examined. Equilibrium moisture content (X_eq) was determined under several temperature (T) and relative humidity (RH) conditions. The X_eq data were correlated by six mathematical models. The modified Henderson was the model that best fitted the experimental data. The X_eq decreased with an increase in T at constant RH. Hysteresis was also studied; increasing T led to a decrease in this phenomenon. Integral isosteric heat of sorption (Q_st), differential entropy (ΔS) and the enthalpy–entropy compensation theory were studied. Q_st values decreased when X_eq increased because the Q_st values of adsorption were lower than Q_st desorption values. The values of ΔS decreased with increases in X_eq, because ΔS values were higher for desorption than for adsorption. The enthalpy–entropy compensation theory is valid for describing the water sorption processes of pearl millet grain.     

Effect of solidification times on crack opening displacement of aluminum alloy castings

The effects of mold temperature, solidification time, and metallurgical structure on both the crack-tip opening displacement (COD) at maximum load and ultimate tensile strength (UTS) of Al-10.6Si, 0.9Mg, 0.9Cu alloy have been investigated. Seven alloy melt samples poured into a copper mold, which was pre-heated at different temperatures, were allowed to solidify at different cooling rates. Even though it was found that the COD values increase and the UTS decreases as the mold temperature and solidification time increase, these parameters could be related to microstructural differences such as silicon crystals size in an α-aluminum matrix.     

Scientific research ontology to support systematic review in software engineering

The term systematic review is used to refer to a specific methodology of research, developed in order to gather and evaluate the available evidence pertaining to a focused topic. It represents a secondary study that depends on primary study results to be accomplished. Several primary studies have been conducted in the field of Software Engineering in the last years, determining an increasing improvement in methodology. However, in most cases software is built with technologies and processes for which developers have insufficient evidence to confirm their suitability, limits, qualities, costs, and inherent risks. Conducting systematic reviews in Software Engineering consists in a major methodological tool to scientifically improve the validity of assertions that can be made in the field and, as a consequence, the reliability degree of the methods that are employed for developing software technologies and supporting software processes. This paper aims at discussing the significance of experimental studies, particularly systematic reviews, and their use in supporting software processes. A template designed to support systematic reviews in Software Engineering is presented, and the development of ontologies to describe knowledge regarding such experimental studies is also introduced.     

Low birthweight, preterm births and intrauterine growth retardation in relation to maternal smoking

Penile erection is a complex neurovascular event that represents a balance between corporal smooth muscle relaxation and contraction. This balance is determined by the interaction between proerectile and antierectile neurotransmitters. It is believed that nitric oxide is the primary erectogenic neurotransmitter and that noradrenaline (norepinephrine) is the primary erectolytic neurotransmitter. There are a number of pharmacological approaches to the management of erectile dysfunction and manipulation of the neurotransmitter systems. These involve direct delivery of drugs into the erectile chambers (intracavernosal injection therapy), administration of medications into the urethra (transurethral delivery), application of medications to the skin (transdermal delivery) and it is hoped that oral agents will be available in the very near future. This article reviews the world literature on the medications that have been investigated to date and their delivery routes.