Hollow lithiated metal oxide particles as lithium-ion battery cathode materials

We report the synthesis and characterization of the hollow micrometer-sized (Mn_0.5Ni_0.4Co_0.1)CO₃ precursor, and one of its promising lithium-enriched phases. The chemical composition of the resulting lithiated final material was Li_1.2(Mn_0.5Ni_0.4Co_0.1)O_2+y. Lithium half cells with cathodes comprised of these hollow particles as the active intercalation material showed a reversible capacity of 183 mAh/g when cycled between 2.0 V and 4.6 V. X-ray diffraction patterns and the electrochemical data of Li_1.2(Mn_0.5Ni_0.4Co_0.1)O_2+y were consistent with the existence of the Li₂MnO₃-type integrated component that was activated during the initial charging of the cells. The results presented herein demonstrate a method to synthesize multicomponent, multiphase materials with hollow internal morphologies that can reversibly and stably be cycled with high gravimetric capacities as the active cathode material in lithium-ion batteries.     

Toughness of HDPE/CaCO3 microcomposites prepared from masterbatch by melt blend method

In this study, a series of high‐density polyethylene and micro/nanocalcium carbonate polymer composites (HDPE/CaCO₃ nanocomposites) were prepared via melt blend technique using a twin screw extruder. Nanocomposite samples were prepared via injection molding for further testing. The effect of % loading of CaCO₃ on mechanical and fracture toughness of these composites has been investigated in details. The effect of precrack length variation on the fracture toughness of the composite samples was evaluated, and the morphology of the fractured samples was also observed using scanning electron microscopy (SEM). It was found that increasing the % of CaCO₃ and precrack length decreased the fracture toughness. Fracture surface examination by SEM indicated that the diminished fracture properties in the composites were caused by the aglomerization of CaCO₃ particles which acted as stress concentrators. A finite element analysis using ANSYS was also carried out to understand the effect of agglomeration size, interaction between the particles and crack tip length on the fracture properties of these composites. Finally, a schematic presentation of the envisioned fracture processes was proposed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Spatial and Time Variation and Effect of Some Meteorological Parameters in Polycyclic Aromatic Hydrocarbons in Athens Greece

Abstract

The PAH concentrations determined on 650 samples of airborne particulates collected from four locations in the Athens area have been studied for two years starting in February 1984. The sampling sites covered both the center and the industrial area of the city. Higher values of PAH were found at the site located in the center of the city than at sites located in the industrial areas. The height of the sampling place has a negative effect on PAH concentrations. The mean yearly concentration values of benzo(a)pyrene varied between 1.8 and 4.0 ng m^?3 for the various sites and can be characterised as median levels. Higher PAH concentrations were found during winter months, while on Sundays the levels of PAH were lower. PAH concentrations increased during days with temperature inversions and when light winds from the Southwest direction prevailed. The main source of PAH in Athens seemed to be fuel burning either for central heating or industrial use in winter and for diesel powered vehicles in summer.     

Milk quality characteristics of Boutsiko,Frisarta and Karagouniko sheep breeds reared in the mountainous and semimountainous areas of Western and Central Greece

In this study, the chemical and microbiological characteristics of ovine milk from three indigenous Greek breeds was assessed. The breeds selected for this study were Boutsiko, Frisarta and Karagouniko. The milk yield of each breed was recorded at the early, mid‐ and late stages of lactation for two consecutive years. Among the three breeds, the average milk compositions obtained were similar for protein, lactose and total solids; however, fat values were significantly lower in Frisarta milk compared with Boutsiko and Karagouniko milk. The major fatty acids (FAs) in ovine milk were palmitic and oleic. The microbiological quality of Boutsiko and Karagouniko milk was superior to Frisarta milk.     

Time-dependent opportunities in energy business: A comparative study of locally available renewable and conventional fuels

This work investigates and compares energy-related, private business strategies, potentially interesting for investors willing to exploit either local biomass sources or strategic conventional fuels. Two distinct fuels and related power-production technologies are compared as a case study, in terms of economic efficiency: the biomass of cotton stalks and the natural gas. The carbon capture and storage option are also investigated for power plants based on both fuel types. The model used in this study investigates important economic aspects using a “real options” method instead of traditional Discounted Cash Flow techniques, as it might handle in a more effective way the problems arising from the stochastic nature of significant cash flow contributors’ evolution like electricity, fuel and CO₂ allowance prices. The capital costs have also a functional relationship with time, thus providing an additional reason for implementing “real options” as well as the learning-curves technique. The methodology as well as the results presented in this work, may lead to interesting conclusions and affect potential private investment strategies and future decision making. This study indicates that both technologies lead to positive investment yields, with the natural gas being more profitable for the case study examined, while the carbon capture and storage does not seem to be cost efficient with the current CO₂ allowance prices. Furthermore, low interest rates might encourage potential investors to wait before actualising their business plans while higher interest rates favor immediate investment decisions.     

Theoretical and experimental analysis of a novel low emissivity water pond in summer

The present study focuses on the research of a new passive roof cooling technique, based on the combination of low emissivity materials and water. A novel roof pond is chosen as the most advantageous in terms of both energy efficiency and less maintenance or functional demands. The pond – referred as “Roof Pond with Gunny Bag” (RPWGB) – is covered by a cloth floating on water level, encouraging evaporative heat losses. A mathematical model describing the energy flux through the RPWGB is developed. The following sensitivity analysis marks the parameters that reduce bottom pond temperature thus improving the efficiency of the system. The experimental study analyses alternative ways to reduce bottom pond temperature. For this purpose, the low emissivity material is placed in different positions, above, below and floating on water level. Heat dissipation occurs by means of radiation losses and water evaporation.     

Evaluation of porous silicon carbide monolithic honeycombs as volumetric receivers/collectors of concentrated solar radiation

Porous monolithic multi-channeled silicon carbide (SiC) honeycombs employed as open volumetric receivers of concentrated solar radiation, were evaluated with respect to their porous structure and thermomechanical properties before and after long-time operation. Proper “tuning” of porosity, pore size distribution and microstructure can provide SiC honeycombs with improved mechanical properties (higher bending and compressive strength) in the “as-manufactured” state. Exposure under solar irradiation was found to affect both their pore structure and their mechanical characteristics. During the first stages of exposure, a re-structuring of the porous structure takes place shifting the mean pore size to higher values and slightly decreasing the total porosity; this re-structuring ceases after some “characteristic” exposure time. After solar exposure the honeycombs become harder and exhibit significantly higher compressive strength. Extension of anticipated lifetime can be achieved by materials with enhanced mechanical properties like silicon-infiltrated (siliconized) SiC.     

The polymerization of propargyl halides (Cl,Br) using M(CO)5PPh3/R x AlCl3-x (M=Mo,W) as catalysts

Summary Propargylchloride (PCl) and propargylbromide (PBr) were polymerized in good yields using M(CO)₅PPh₃/R_xAlCl_3-x as catalysts (M=W, Mo). Mo was found to be more effective than W. The presence of chlorine atoms in co-catalyst was important for the activation of the catalyst. The obtained polymers were coloured, insoluble in all organic solvents and stable until 150°C. From their IR and ESR spectra is concluded that the polymers have highly conjugated structures. The oligomeric products were constituted mainly from cyclotrimers. In the case of Mo-catalyst only 1,2,4-cyclotrimer was obtained; a mixure of 1,2,4 and 1,3,5-derivatives were formed using W-catalysts.     

Buspirone vs amitriptyline in the treatment of chronic tension-type headache

The human sexual response is a complicated biopsychosocial phenomenon in which internal and external stimuli are modulated by the central and peripheral nervous system, resulting in a cascade of biochemical, hormonal and circulatory changes that lead to cognitive and physical sexual arousal. In this article, current knowledge of the relationships between central processes, mediated by neuropeptides and neurotransmitters, and the hypothalamo-pituitary-gonadal axis is explored. Hormonal aspects of sexual arousability and sexual excitement are mainly related to androgens. The possible influences of hormonal therapies such as hormonal contraception and perimenopausal hormone substitution are described. The main conclusion is that clinicians should be aware of possible sexual problems resulting from changes in circulating sex hormone binding globulin and free testosterone in men and women due to endogenous or exogenous hormonal changes.