Evaporation of liquids on chemically patterned surfaces

We studied evaporation rates of volatile liquids deposited onto chemically patterned surfaces by means of experiments and numerical simulations. We quantified the influence of the droplet geometry, in particular circular, triangular, rectangular and square shapes, as well as the influence of contact angles. We considered the two cases of vaporization both in stagnant atmospheres as well as in the presence of well-defined laminar airflows. While lateral air-convection enhances evaporation, it causes a dependence of the evaporation rate on the pattern orientation with respect to the airflow. Neighboring droplets and rivulets tend to mutually reduce their evaporation rate relative to isolated patterns.     

Dynamic State Estimation for Microgrid Structures

Abstract

In this article, the dynamic state estimation of the islanded microgrids problem is addressed. The electrical network and energy sources are represented as a set of Nonlinear Differential Algebraic Equations, with the aim to capture the nonlinear phenomena and a novel solution, by using a variation of the Kalman Filter ad hoc for differential algebraic systems, is presented. In this representation, the state is given by the voltage phasors at each bus and the variables related to the energy sources. The proposed algorithm permits not only to effectively obtain an estimate of the state variables but also it allows to recover these variables during the microgrid transient behavior. Moreover, the estimation may be carried out using fewer measurements than those needed by conventional static estimators. The performance of the proposed dynamic state estimator is evaluated via numerical experiments using two practical microgrids containing wind power and hydroelectric generators. This novel method has been tested for load variations and wind speed changes demonstrating its capabilities and efficiency.     

Kernicterus. Anatomo clinical correlation in 64 newborn infants

The case histories and autopsy reports of 64 neonates who died from kernicterus were reviewed. The most outstanding findings were: high incidence of kernicterus with serum indirect bilirubin less than 15 mg.; different clinical picture of the premature in comparison with term neonate; predisposing factors such as respiratory distress and intrauterine malnutrition were often associated in the premature. Preventive, educational and therapeutic measures were discussed at the end.     

Biodegradability of polyethylene–starch blends prepared by extrusion and molded by injection: Evaluated by response surface methodology

Low density polyethylene (LDPE)–starch blends were prepared by extrusion. Starch content ranged between 0 and 50% under different conditions of temperature and extrusion speed. Each blend was injected into a commercial mold of a 250 mL cup. Cups were cut into 5 cm × 5 cm coupons. Biodegradability was assessed placing the coupons in the middle of a 50 cm pile of compost. Samples were recovered, washed, dried, and weighed after 25, 50, 75, 100, and 125 days under compost. Weight loss was determined and structural modifications were evaluated by SEM. Mechanical properties as tensile strength, elongation to break, and yield point were assessed before and after compost treatment. Experimental design and characterization were performed using a central composite design (CCD) and results were modeled with surface response methodology. SEM analysis revealed fractures and pores as a consequence of microorganism degradation. Pure LDPE samples remained unchanged. Mechanical, physical, and thermal properties of LDPE–starch blends are slightly different from that of pure LDPE. Environmental exposure, measured by accelerated intemperism, does not modify blend properties; consequently, they are suitable for the same industrial applications of LDPE.     

Study of the Solidification Dynamic of a Photocurable Resin by Photoacoustic

This paper reports on the photoacoustic (PA) study of a photopolymer (resin) that changes its physical properties when being irradiated with ultraviolet light from a xenon lamp. The wavelength range necessary for the curing of the resin, characterized by the PA technique, was found to be between 300 nm and 400 nm. PA measurements show a sigmoidal change of heat transport properties as a function of time during the curing process. By describing the PA signal evolution by a parametrized model, a characteristic curing time was introduced. The PA measurements were complemented with UV–Vis Spectroscopy, which was used to characterize the polymer in order to study the optical absorption. The proposed method can support the optimization of the settings of curing parameters in applications of stereolithography and 3D printing.     

Thermoplastic biodegradable material elaborated from unripe banana flour reinforced with metallocene catalyzed polyethylene

To meet the challenge of procuring new sources of natural polymers without affecting the demands for food crops, a thermoplastic unripe banana flour (TPF) was produced, characterized, and blended with metallocene‐catalyzed polyethylene (mPE). Both the pulp and peels of unripe banana were used to produce flour, whose stability and thermoplastic properties allowed blending with mPE in high proportions, that is, 50, 60, 70, and 80%. The blends were injection molded, and the thermal, mechanical, microstructural, and infrared spectral properties of the resulting samples were characterized. The blend containing 50% TPF yielded a robust, elastic, and nonbrittle material. Maleic anhydride grafting on mPE (mPE‐g‐MA) promoted interphase adhesion of the polymers and homogeneity in the blends. Grafting also influenced the mechanical, thermal, and microstructural properties of the blends. The characteristics of the blends make them ideal for designing biodegradable plastics while exploiting banana peels, which are usually considered agricultural waste. POLYM. ENG. SCI., 55:866–876, 2015. © 2014 Society of Plastics Engineers     

Biodegradation process of a blend of thermoplastic unripe banana flour—polyethylene under composting: Identification of the biodegrading agent

Starch‐based biodegradable polymers are obtained by incorporating plant‐derived polymers into plastics. This blending allows for a reduction in the polymer's resistance to microbial degradation. Assessing biodegradability is a key step in the characterization of newly designed polymers. Composting has been taken into consideration in waste management strategies as an alternative technology for plastic disposal. This study analyzed the biodegradability of an injection‐molded plastic material in which thermoplastic unripe banana flour (TPF) acts as a matrix (70%) and metallocene catalyzed polyethylene acts as a reinforcing filler (30%). This plastic was termed 70 TPF, and the structural, physical, and mechanical changes associated with its degradation were analyzed. The characterization of the microorganism that contributes to 70 TPF biodegradation was also performed. After composting, 70 TPF decreased in tensile strength and the TPF moiety in the blend was lost, greatly affecting the microstructure of the sample. Based on these indicators of degradation, this study identified the fungus Mortierella elongata as the microorganism responsible for the degradation of the plastic, a finding that supports the role of fungal communities in the biodegradation of designed materials. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42258.     

Urban agriculture in Mexico City:: Functions provided by the use of space for dairy based livelihoods

This paper examines the use of urban space by dairy production activities in two areas of Mexico City with different degrees of urbanization (east and south). These activities have adapted to the recent urban conditions, from an original rural state. Dairy production is carried out in the house area, and producers pay for urban services as other residents. In the eastern zone, the activity is the sole form of income, while in the south, livelihoods are more diversified. In the east, a wide variety of food wastes from various sources are used, while in the south grass remains an important part of the diet. Raw milk in the east is usually sold direct to the consumer, while intermediaries are more common in the south. Herds tend to be larger and more specialized in the east than the south. In both cases there is important use of local resources both for housing and feeding the animals. Manure is used in pre-Hispanic agricultural systems in sub and peri-urban areas. Based on the range of functions provided to the city by these systems, and the present unnecessary dependence of Mexico City on imported milk, the options for policy and development support are discussed.     

An Uneasy Match: Neoliberalism, Gentrification and Heritage Conservation in Bo-Kaap, Cape Town, South Africa

It is increasingly argued that gentrification is incorporated into public policy and the by-product of a range of contemporary neoliberal urban development policies intent on attracting investment capital. However, gentrification can also be the unintended outcome of well-meaning urban policy frameworks, such as urban densification, inner-city regeneration and urban heritage conservation but with arguably negative consequences. Focusing on Cape Town, the argument of this paper is that one of the outcomes of a neoliberalist approach to urban regeneration in the city centre is the impact it has on conserving the living and built environment heritage of the historic Bo-Kaap district. The last remaining inner-city neighbourhood that has not yet gentrified appears to be succumbing to this process. The outcome is a neighbourhood which is in economic and social flux and challenging the coherence of this once “indigenous” community.