Economic performance,environmental concerns,and renewable energy consumption: drivers of renewable energy development in Sub-Sahara Africa

This paper analyzes the drivers of renewable energy development and consumption in Sub-Sahara African countries for the period, 1980–2011. The fully modified ordinary least squares, dynamic ordinary least squares, and fixed-effects estimation techniques are used to evaluate the statistical significance of the determinants of renewable energy consumption. Results indicate that income has the desired positive, albeit statistically insignificant contribution to renewable energy consumption growth. This indicates that recent economic strength in the region has not been accompanied by increased development and consumption of renewable energy, in contrast to empirical evidence in other developing economies. A review of the possible reasons for this incongruence is presented. Also, increased consumption of renewable energy is associated with heightened concerns for climate change caused by pollutants such as carbon dioxide. Population and industrial expansion are statistically significant determinants of renewable consumption, and oil prices correlate negatively with renewable energy consumption.     

Wind Velocity Sensorless Maximum Power Point Tracking Algorithm in Grid-connected Wind Energy Conversion System

This article proposes a wind velocity sensorless hill-climb searching algorithm in the grid-connected field-oriented controlled permanent magnet synchronous generator based wind energy conversion system. The proposed method improves the speed and accuracy of initial tracking. Pseudo-optimum points are used to track the exact optimum points using the power versus speed characteristics of a wind turbine for various wind velocities. This research emphasizes that the pseudo-optimum points using the power versus speed characteristics are always less than and much nearer to the exact optimum points. The small-step forward tracking after pseudo-optimum points improves the accuracy of this algorithm. Moreover, this method improves the tracking speed for various wind velocities. The system used for this research consists of a back-to-back sinusoidal pulse-width modulation converter between the generator and the grid. The performance of the proposed method is analyzed mathematically and verified by simulation using MATLAB/Simulink software (The Mathworks, Natick; Massachusetts, USA).     

Analysis of microRNAs in Exosomes of Breast Cancer Patients in Search of Molecular Prognostic Factors in Brain Metastases

Brain metastases are the most severe tumorous spread during breast cancer disease. They are associated with a limited quality of life and a very poor overall survival. A subtype of extracellular vesicles, exosomes, are sequestered by all kinds of cells, including tumor cells, and play a role in cell-cell communication. Exosomes contain, among others, microRNAs (miRs). Exosomes can be taken up by other cells in the body, and their active molecules can affect the cellular process in target cells. Tumor-secreted exosomes can affect the integrity of the blood-brain barrier (BBB) and have an impact on brain metastases forming. Serum samples from healthy donors, breast cancer patients with primary tumors, or with brain, bone, or visceral metastases were used to isolate exosomes and exosomal miRs. Exosomes expressed exosomal markers CD63 and CD9, and their amount did not vary significantly between groups, as shown by Western blot and ELISA. The selected 48 miRs were detected using real-time PCR. Area under the receiver-operating characteristic curve (AUC) was used to evaluate the diagnostic accuracy. We identified two miRs with the potential to serve as prognostic markers for brain metastases. Hsa-miR-576-3p was significantly upregulated, and hsa-miR-130a-3p was significantly downregulated in exosomes from breast cancer patients with cerebral metastases with AUC: 0.705 and 0.699, respectively. Furthermore, correlation of miR levels with tumor markers revealed that hsa-miR-340-5p levels were significantly correlated with the percentage of Ki67-positive tumor cells, while hsa-miR-342-3p levels were inversely correlated with tumor staging. Analysis of the expression levels of miRs in serum exosomes from breast cancer patients has the potential to identify new, non-invasive, blood-borne prognostic molecular markers to predict the potential for brain metastasis in breast cancer. Additional functional analyzes and careful validation of the identified markers are required before their potential future diagnostic use.     

Modified Atmosphere Packaging Technology of Fresh and Fresh-cut Produce and the Microbial Consequences—A Review

Modified atmosphere packaging (MAP) technology offers the possibility to retard the respiration rate and extend the shelf life of fresh produce, and is increasingly used globally as value adding in the fresh and fresh-cut food industry. However, the outbreaks of foodborne diseases and emergence of resistant foodborne pathogens in MAP have heightened public interest on the effects of MAP technology on the survival and growth of pathogenic organisms. This paper critically reviews the effects of MAP on the microbiological safety of fresh or fresh-cut produce, including the role of innovative tools such as the use of pressurised inert/noble gases, predictive microbiology and intelligent packaging in the advancement of MAP safety. The integration of Hazard Analysis and Critical Control Points-based programs to ensure fresh food quality and microbial safety in packaging technology is highlighted.     

国外电脑销售模式一览：美国

英国的3C环境和国内有很大不同。首先，英国用户对电脑的要求喜好和国内不同。以台式机为例．DIY在英国并不是很流行，花心思装配一台电脑是很多人不愿意去做的。他们重视的是享受到什么服务和附加价值．例如一些店铺举行促销的话有时候买电脑还会送一年宽带。因此英国人买电脑都是以买品牌机为主。     

Effect of nanofillers on the flame retardant properties of a polyethylene–calcium carbonate–silicone elastomer system

This study shows the effects of three different nanofillers on the viscosity properties and fire behavior of a halogen‐free flame retardant system. The original system, based on ethylene‐acrylate copolymer, calcium carbonate, and a silicone elastomer, shows good flame retardant properties. One of the nanofillers, montmorillonite (MMT), significantly increases the viscosity above 250^°C, resulting in reduced dripping and decreased heat release rate. The ash residue, however, is very brittle, indicating poor interactions between the MMT and other components of the system. The second nanofiller, sepiolite, shows no improvement on the flame retardant properties of the system. Reduced dripping is observed when a small amount of the third nanofiller, polyhedral oligomeric silsesquioxane, POSS, is incorporated into the system. In this case, high silica content on the surface indicates char formation originating from the POSS. However, an increased heat release is observed when POSS is used in the system. Copyright © 2010 John Wiley & Sons, Ltd.     

The nature and impacts of fines in smelter-grade alumina

Fines in smelter-grade aluminas are recognized as a significant process problem in aluminum smelting. However, understanding the nature of this fine material and how it impacts the reduction process are less clearly understood. The combination of new analytical methods such as variable pressure scanning electron microscopy and very high field solid state nuclear magnetic resonance provide new insights into the phases present and their spatial distribution within aluminas, and suggest how such fine materials are generated, particularly during calcination in the alumina refinery.