Influence of electrospinning parameters on poly(hydroxybutyrate) electrospun membranes fiber size and distribution

Poly(hydroxybutyrate) (PHB) obtained from sugar cane waste was dissolved in a blend of chloroform and dimethylformamide (DMF) and electrospun at 40°C. By adding DMF to the solution, the electrospinning process for the PHB polymer becomes more stable, allowing complete polymer crystallization during the jet travelling between the tip and the grounded collector. The influence of processing parameters on fiber size and distribution was systematically studied. It was observed that an increase of tip inner diameter promotes a decrease of the fiber average size and a broader distribution. Conversely, an increase of the electric field and flow rate produces an increase of fiber diameter until a maximum of ～2.0 µm but for electric fields higher than 1.5 kV cm^?1, a decrease of the fiber diameter was observed. Polymer crystalline phase seems to be independent of the processing conditions and a crystallinity degree of 53% was found. Moreover, thermal degradation of the as‐spun membrane occurs in single step degradation with activation energy of 91 kJ mol^?1. Furthermore, MC‐3T3‐E1 cell adhesion was not inhibited by the fiber mats preparation, indicating their potential use for biomedical applications. POLYM. ENG. SCI., 54:1608–1617, 2014. © 2013 Society of Plastics Engineers     

The semiotic turn

This paper reports the author's personal collaboration with Piero Mussio. It begins with an analysis of Mussio's increasing involvement with semiotic concepts while working with visual languages. In conclusion, the author proposes follow-up questions, in continuation to an ongoing intellectual conversation that current and future researchers may help to sustain.     

The infrared spectral signature of volcanic ash determined from high-spectral resolution satellite measurements

High-spectral resolution infrared spectra of the earth's atmosphere and surface are routinely available from satellite sensors, such as the Atmospheric Infrared Sounder (AIRS) and the Infrared Atmospheric Sounding Interferometer (IASI). We exploit the spectral content of AIRS data to demonstrate that airborne volcanic ash has a unique signature in the infrared (8-12 μm) that can be used to infer particle size, infrared opacity and composition. The spectral signature is interpreted with the aid of a radiative transfer model utilizing the optical properties of andesite, rhyolite and quartz. Based on the infrared spectral signature, a new volcanic ash detection algorithm is proposed that can discriminate volcanic ash from other airborne substances and we show that the algorithm depends on particle size, optical depth and composition. The new algorithm has an improved sensitivity to optically thin ash clouds, and hence can detect them for longer (~ 4 days) and at greater distances from the source(~ 5000 km).     

Comparison of iterative and monte carlo methods for calculation of the Aureole about a point source in the earth's atmosphere

Point sources in the atmosphere are surrounded by aureoles because of atmospheric scattering. The properties of an aureole were calculated by use of a Monte Carlo approach and an iterative method for an isotropic source and an axially symmetric emission source inside an infinite homogeneous atmosphere. The influence of single-scattering albedo, optical depth between source and observer, and source intensity anisotropy were studied from both approaches. For each situation, the limits and advantages of the Monte Carlo technique and the iterative method are described.     

Mercury contamination in the vicinity of a chlor-alkali plant and potential risks to local population

A mercury-cell chlor-alkali plant operated in Estarreja (North-western Portugal) for 50 years causing widespread environmental contamination. Although production by this process ceased in 2002, mercury contamination from the plant remains significant. The main objective of this study was to investigate mercury impact on the nearby environment and potential risks to local population. To assess the level of contamination soil samples were collected from agricultural fields in the vicinity of the plant, extending the study by taking samples of the predominant vegetation suitable for animal and human consumption, water samples, and fish species from a nearby coastal lagoon, to gain a preliminary insight into the potential for contamination of the terrestrial and aquatic food web. To determine population exposure to mercury, hair samples were collected from local residents. Total mercury concentration in the 0-15 cm layer of soil was found to be highly variable, ranging between 0.010 and 91 mg kg^− 1, although mercury contamination of soils was found to be restricted to a confined area. Lolium perenne roots contained between 0.0070 and 2.0 mg kg^− 1, and there is evidence that root systems uptake mercury from the soil. Levels of mercury in the aerial parts of plants ranged between 0.018 and 0.98 mg kg^− 1. It appears that plants with higher mercury concentration in soils and roots also display higher mercury concentration in leaves.Total mercury concentration in water samples ranged between 12 and 846 ng L^− 1, all samples presenting concentrations below the maximum level allowable for drinking water defined in the Portuguese law (1.0 μg L^− 1).Mercury levels in fish samples were below the maximum limit defined in the Portuguese law (0.5 mg kg^− 1), ranging from 0.0040 to 0.24 mg kg^− 1. Vegetables collected presented maximum mercury concentration of 0.17 mg kg^− 1. In general, food is not contaminated and should not be responsible for major human exposure to the metal.Mercury determined in human hair samples (0.090-4.2 mg kg^− 1; mean 1.5 mg kg^− 1) can be considered within normal limits, according to WHO guidelines suggesting that it is not affecting the local population. Despite being subject to decades of mercury emissions, nowadays this pollutant is only found in limited small areas and must not constitute a risk for human health, should these areas be restricted and monitored.Considering the present data, it appears that the population from Estarreja is currently not being affected by mercury levels that still remain in the environment.     

Impact of Phenolic Compounds and Related Enzymes in Sorghum Varieties for Resistance and Susceptibility to Biotic and Abiotic Stresses

Contents of phenolic compounds and related enzymes before and after sorghum grain germination were compared between varieties either resistant or susceptible to biotic (sooty stripe, sorghum midge, leaf anthracnose, striga, and grain molds) and abiotic (lodging, drought resistance, and photoperiod sensitivity) stresses. Independent of grain germination, sorghum varieties resistant to biotic and abiotic stresses had on average higher contents of proanthocyanidins (PAs), 3-deoxyanthocyanidins (3-DAs), and flavan-4-ols than susceptible varieties. Results show that content of 3-DAs is a good marker for sorghum resistance to both biotic and abiotic stresses because it correlates with resistance to all stresses except for photoperiod sensitivity. The second good marker for stress resistance is content of PAs. Total phenolic compounds and the activities of related enzymes are not good markers for stress resistance in sorghum grains.     

Circular switched monopole arrays for beam steering wirelesscommunications

Future mobile communication services which will operate at microwave/millimetre wavelengths require advanced antenna design. The authors here propose circular arrays of monopoles, for beam steering based on electronic switching. They provide appreciable directivity gain, and may allow implementation of angular diversity in communications systems. Satisfactory radiation patterns are computed and measured     

Demonstration of anisotropic composites with tuneable microwavepermeability manufactured from ferromagnetic thin films

Recently, we presented the microwave properties of laminated insulator ferromagnetic on the edge (LIFE) composites. For the fundamental mode propagating in a coaxial line, they exhibit large permeability and low permittivity. In this paper we investigate the properties of LIFE composites in the 0.1 to 18 GHz range when a static magnetic field is applied along the propagation direction. We show that the evolution of the resonance frequency with the external field can be described by conventional gyromagnetic resonance models. The effect of demagnetizing fields is analyzed. In particular, it is shown that LIFE materials exhibit comparatively low demagnetizing effects and large permeabilities. The evolution of the resonance linewidth with the external field is investigated. LIFE material may be used for a variety of microwave applications in a coaxial line or in a guide. In particular, we demonstrate a tuneable coaxial absorbing termination with peak attenuation frequency tuneable from 1.7 to 18 GHz with more than -15 dB maximum attenuation, and a switchable termination that can be either reflective or absorbing. The operation of a field-driven variable attenuator is also presented     

Morphology of the stifle in agouti (Dasyprocta prymnolopha,Wagler 1831)

The agouti (Dasyprocta prymnolopha, Wagler 1831) is a wild rodent of great zootechnical potential, a fact that enables anatomical and morphological studies to support management actions with this animal. In this perspective, this study aimed to describe the anatomy and histology of the agouti stifle joint. Four adult agoutis were used, two females and two males. The animals were submitted to dissection and identification of the structures of the stifle joint. For light microscopy study, samples of the patellar ligament, cranial and caudal cruciate ligaments, medial and lateral collateral ligaments were used. Agouti has a highly congruent patellofemoral joint; elongated patella; medial and lateral fabellae at the proximal insertion of the gastrocnemius muscle; medial and lateral meniscus with lunula; in addition to the presence of the following ligament structures: patellar ligament, cranial and caudal cruciate ligaments, medial and lateral collateral ligaments, meniscofemoral ligament, caudal meniscal ligament of the medial meniscus, and medial and lateral cranial ligaments. The patellar ligament presents bundles of parallel collagen fibers with a straight path and coated fibroblasts; collateral and cruciate ligaments had loose and dense connective tissue, coated fibroblasts and collagen bundle undulations, the latter most expressive in the caudal cruciate ligament. Thus, except for the shape and angulation of the stifle, which allows specific movements, the agouti stifle has structures analogous to that of other rodents and domestic animals.