Numerical Simulation of Single‐Bubble Dynamics in High‐Viscosity Ionic Liquids Using the Level‐Set Method

Two numerical models for studying the dynamics of formation and rise of single bubbles in high‐viscosity ionic liquids were implemented using the level‐set method. The models describe two stages of bubble dynamics: bubble formation at the inlet nozzle and bubble displacement across the column. The models were experimentally validated through a laboratory‐scale bubble column using water‐glycerol mixtures and two imidazolium‐type ionic liquids. The models were consistent with the experimental tests for Reynolds numbers < 5. Outside this range, the models tend to underestimate the bubble terminal velocity, which can be explained by the effect of the high velocity and pressure gradients close to the gas‐liquid interface. The models also predicted the velocity and pressure fields near the bubble surface before and after detachment.     

Thrombosis of the great cerebral vein in a hemodialysis patient

Cerebral venous thrombosis is a rare condition with various clinical presentations which may delay diagnosis. It is frequently associated with severe consequences. We present the first documented case of thrombosis of the great cerebral vein in a hemodialysis patient. A 29‐year‐old female patient with end‐stage renal disease of unknown etiology was admitted to a hospital with altered consciousness and nausea. Severe headache in the right parietal area had started 2 days before. On examination, she was in the poor overall condition, dysartric, with a severe nystagmus. Urgent brain multislice computerized tomography and magnetic resonance imaging revealed thrombosis of the great cerebral vein with hypodense zones in hypothalamus, thalamus and basal ganglia. She was treated with heparin bolus of 25000 IU with a favorable outcome. Detailed examination demonstrated increased lupus anticoagulant (LA) 1 and LA2 and increased LA1/LA2. Control magnetic resonance imaging performed 1 year later revealed multiple vascular lesions within the brain. Acetylsalicylate was introduced in therapy. Thrombosis of the cerebral veins should be suspected in patients with end‐stage renal disease, altered neurological status and signs of increased intracranial pressure.     

A BEM formulation based on Reissner’s theory to perform simple bending analysis of plates reinforced by rectangular beams

In this work, the plate bending formulation of the boundary element method (BEM), based on the Reissner’s hypothesis, is extended to the analysis of plates reinforced by rectangular beams. This composed structure is modelled by a zoned plate, being the beams represented by narrow sub-regions with larger thickness. The integral equations are derived by applying the weighted residual method to each sub-region, and summing them to get the equation for the whole plate. Equilibrium and compatibility conditions are automatically imposed by the integral equations, which treat this composed structure as a single body. In order to decrease the number of degrees of freedom, some approximations are considered for both displacements and tractions along the beam width. The accuracy of the proposed model is illustrated by simple examples whose exact solution are known as well as by more complex examples whose numerical results are compared with a well-known finite element code.     

Chemical and antimicrobial analyses of essential oil of Lippia origanoides H.B.K

Lippia origanoides H.B.K. (Verbenaceae) is a plant known in Oriximiná (Brazil) as “Salva-de-Marajó”. Its leaves are widely used as of a spice in cooking and in traditional medicine. The chemical composition of the essential oil obtained from its leaves, analyzed by GC and GC/MS, showed a high content of oxygenated monoterpenes (66.0%), carvacrol (38.6%) and thymol (18.5%) being the major constituents. Considering that previous studies on the same plant species showed carvacrol as a trace or absent compound, we propose the existence of a new chemotype for this species. A high carvacrol content in the essential oil determines the plant’s suitability for the preparation of oregano condiment. The antimicrobial activity of this essential oil was determined by the drop diffusion method, showing highly significant inhibition zones for all microorganisms tested.     

Availability evaluation of system service hosted in private cloud computing through hierarchical modeling process

The Journal of Supercomputing - Cloud computing provides an abstraction of the physical tiers, allowing a sense of infinite resources. However, the physical resources are not unlimited and need to...     

Defining amplifier’s gain to maximize the transmission rate in optical systems using evolutionary algorithms and swarm intelligence

Optical networks are currently the only technology capable of providing extremely high data transmission rates. Because of this, systems must be increasingly efficient and immune to failures. One way to improve network efficiency is to use dynamic approaches like Adaptive Control of Operating Point, which consists of autonomously choosing the best operating point for optical amplifiers on the link, thus providing the best configuration concerning Quality of transmission. Unlike the previous works that focused on optimizing Optical Signal-To-Noise Ratio, our proposal and analysis are focused on maximizing the transmission rate. In this paper, we compare the results obtained by five different and widely used evolutionary and swarm-based algorithms in the search for maximizing the transmission rate in optical links. We have observed that the differential evolution provided the best results in the analyzed scenarios.

     

Effect of Zn2TiO4 and ZnB2O4 additions on the microstructure and dielectric properties of AgNb1 ? xTaxO3 solid solutions

We report the preparation and characterization of AgNb_0.6Ta_0.4O₃ (ANT) based materials. The addition of Zn₂TiO₄ and ZnB₂O₄ influences the sintering temperature, phase composition, and microstructure of ANT ceramics. ANT doped with 1 wt % Zn₂TiO₄ or ZnB₂O₄ has high dielectric permittivity (400–470), low dielectric losses (tanδ ∼ 10⁻³), and a nonlinearity coefficient n _R ≅ 3–9% (at a field strength E = 3 × 10⁶ V/m).     

Dilute oxalic acid pretreatment for biorefining giant reed (Arundo donax L.)

Biomass pretreatment is essential to overcome recalcitrance of lignocellulose for ethanol production. In the present study we pretreated giant reed (Arundo donax L.), a perennial, rhizomatous lignocellulosic grass with dilute oxalic acid. The effects of temperature (170-190 °C), acid loading (2-10% w/w) and reaction time (15-40 min) were handled as a single parameter, combined severity. We explored the change in hemicellulose, cellulose and lignin composition following pretreatment and glucan conversion after enzymatic hydrolysis of the solid residue. Two different yeast strains, Scheffersomyces (Pichia) stipitis CBS 6054, which is a native xylose and cellobiose fermenter, and Saccharomyces carlsbergensis FPL-450, which does not ferment xylose or cellobiose, were used along with commercial cellulolytic enzymes in simultaneous saccharification and fermentation (SSF). S. carlsbergensis attained a maximum ethanol concentration of 15.9 g/l after 48 h at pH 5.0, while S. stipitis, at the same condition, took 96 h to reach a similar ethanol value; increasing the pH to 6.0 reduced the S. stipitis lag phase and attained 18.0 g/l of ethanol within 72 h.     

Light and electron microscopy study of the spermatheca of Eupholidoptera chabrieri bimucronata (Ramme, 1927) and Uromenus brevicollis trinacriae La Greca 1964 (Orthoptera: Tettigoniidae)

A study by both optical and electron microscopy has been carried out on the spermatheca of Eupholidoptera chabrieri bimucronata and Uromenus brevicollis trinacriae (Orthoptera: Tettigoniidae). In both the examined species, the spermatheca consists of a sac/kidney‐shaped seminal receptacle and a more or less tortuous spermathecal duct that opens into the common oviduct. The wall of both the organs consists of a pseudostratified epithelium surmounted by a cuticular intima; the latter is made up of a thicker endocuticle and an epicuticle. The epithelium shows two different cell types, irregularly arranged and with well differentiated functions: cuticle‐forming and gland cells. In both the species, the cuticle‐forming cells perform other functions, in addition to producing the cuticular intima. The gland cells never come in contact with the cuticular intima, have inside the reservoir a secretion whose appearance can diversify also in contiguous zones of the seminal receptacle. Based on our findings in both the species, the functions of the seminal receptacle would differ from those of the spermathecal duct. In the latter, some areas of the wall of the connecting tract show an activity of lysis, by contiguous epithelial cells, that could play a role in control and selection of spermatozoa. As for the feather‐shaped spermatodesms, similar in both the species, freeze‐fracture observations have shown that the acrosome of each spermatozoon regularly covers three‐quarters of the extension of the acrosome of the following spermatozoon. Finally, the significance of our findings, compared with what is known in literature, is discussed. Microsc. Res. Tech. 78:577–586, 2015. © 2015 Wiley Periodicals, Inc.