Turbidimetric and intrinsic viscosity study of EVA copolymer–solvent systems

Both Hansen solubility parameter and Flory–Huggins interaction parameter of two EVA [Poly(ethylene-co-vinyl acetate)] copolymers with different vinyl acetate content have been obtained by means of intrinsic viscosity measurements. To calculate this last parameter it was also necessary to determine the theta solvent at different temperatures of the two EVA copolymers with turbidimetric measurements. The results indicate that the vinyl acetate content is a variable which influences the composition of the theta solvent and Flory–Huggins parameter (the higher the vinyl acetate content, the lower the Flory–Huggins parameter), although its influence over the Hansen solubility parameter is almost negligible.     

The LiyNi0.2Mn0.2Co0.6O2 electrode materials: A structural and magnetic study

Layered LiNi_0.2Mn_0.2Co_0.6O₂ phase, belonging to a solid solution between LiNi_1/2Mn_1/2O₂ and LiCoO₂ most commercialized cathodes, was prepared via the combustion method at 900 °C for a short time (1 h). Structural and magnetic properties of this material during chemical extraction were investigated. The powders adopted the α-NaFeO₂ structure with almost none of the well-known Li/Ni cation disorder. The analysis of the magnetic properties in the paramagnetic domain agrees with the combination of Ni²⁺ (S = 1), Co³⁺ (S = 0) and Mn⁴⁺ (S = 3/2) spin-only values. X-ray analysis of the chemically delithiated Li_yNi_0.2Mn_0.2Co_0.6O₂ reveals no structural transition. The process of lithium extraction from and insertion into LiNi_0.2Mn_0.2Co_0.6O₂ was discussed on the basis of ex situ EPR experiments and magnetic susceptibility. Oxidation of Ni²⁺ (S = 1) to Ni³⁺ (S = 1/2) and to Ni⁴⁺ (S = 0) was observed upon lithium removal.     

Photovoltaic device performance of single-walled carbon nanotube and polyaniline films on n-Si: device structure analysis

In this paper, we explore the use of two organic materials that have been touted for use as photovoltaic (PV) materials: inherently conducting polymers (ICPs) and carbon nanotubes (CNTs). Due to these materials' attractive features, such as environmental stability and tunable electrical properties, our focus here is to evaluate the use of polyaniline (PANI) and single wall carbon nanotube (SWNT) films in heterojunction diode devices. The devices are characterized by electron microscopy (film morphology), current-voltage characteristics (photovoltaic behavior), and UV/visible/NIR spectroscopy (light absorption). We have found that both PANI and SWNT can be utilized as photovoltaic materials in a simple bilayer configuration with n-type Silicon: n-Si/PANI and n-Si/SWNT. It was our aim to determine how photovoltaic performance was affected utilizing both PANI and SWNT layers in multilayer devices: n-Si/PANI/SWNT and n-Si/SWNT/PANI. The short-circuit current density increased from 4.91 mA/cm(2) (n-Si/PANI) to 12.41 mA/cm(2) (n-Si/PANI/SWNT), while an increase in power conversion efficiency by ~91% was also observed. In the case of n-Si/SWNT/PANI and its corresponding device control (n-Si/SWNT), the short-circuit current density was decreased by an order of magnitude. The characteristics of the device were affected by the architecture and the findings have been attributed to the more effective transport of holes from the PANI to SWNT and less effective transport of holes from PANI to SWNT in the respective multilayer devices.     

The effect of SiO<Subscript>2</Subscript> nanoparticles derived from hydrothermal solutions on the performance of portland cement based materials

The nanoparticles of SiO₂ were used in cement systems to modify the rheological behavior, to enhance the reactivity of supplementary cementitious materials, and also to improve the strength and durability. In this research, low-cost nano-SiO₂ particles from natural hydrothermal solutions obtained by membrane ultrafiltration and, optionally, by cryochemical vacuum sublimation drying, were evaluated in portland cement based systems.The SiO₂-rich solutions were obtained from the wells of Mutnovsky geothermal power station (Far East of Russia). The constant nano-SiO₂ dosage of 0.25% (as a solid material by weight of cementitious materials) was used to compare the cement systems with different nanoparticles against a reference mortar and a commercially available nano-SiO₂. Nanoparticles were characterized by X-Ray Diffraction (XRD), BET Surface Area, Scanning Electron Microscope (SEM) and Fourier Transform Infrared (FTIR) spectroscopy techniques. It was demonstrated that the addition of polycarboxylate ether superplasticizer and the dispersion treatment using an ultrasound processor can be used to facilitate the distribution of nano-SiO₂ particles in the mixing water. The effect of nano-SiO₂ particles in portland cement mortars was investigated by evaluating the flow, heat of hydration and compressive strength development. It was demonstrated that the use of nano-SiO₂ particles can reduce the segregation and improve strength properties.     

Top-Hat HELLISH-VCSOA for optical amplification and wavelength conversion for 0.85 to 1.3μm operation

The Top-Hat hot electron light emission and lasing in semiconductor heterostructure (HELLISH)-vertical cavity semiconductor optical amplifier (VCSOA) is a modified version of a HELLISH-VCSOA device. It has a shorter p-channel and longer n-channel. The device studied in this work consists of a simple GaAs p-i-n junction, containing 11 Ga_0.35In_0.65 N_0.02As_0.08/GaAs multiple quantum wells in its intrinsic region; the active region is enclosed between six pairs of GaAs/AlAs top distributed Bragg reflector (DBR) mirrors and 20.5 pairs of AlAs/GaAs bottom DBR mirrors. The operation of the device is based on longitudinal current transport parallel to the layers of the GaAs p-n junction. The device is characterised through I-V-L and by spectral photoluminescence, electroluminescence and electro-photoluminescence measurements. An amplification of about 25 dB is observed at applied voltages of around V = 88 V.     

Tolmetin sodium-loaded thermosensitive mucoadhesive liquid suppositories for rectal delivery; strategy to overcome oral delivery drawbacks

Tolmetin sodium (TS) is a nonsteroidal anti-inflammatory drug (NSAID) indicated for treatment of musculoskeletal issues. As other NSAID, TS displays a marked side effects on the gastro-intestinal (GI) tract after oral administration. Traditional solid suppositories can cause pain and discomfort for patients, may reach the end of the colon; consequently, the drug can undergo the first-pass effect. TS liquid suppository (TS-_LS) was developed to enhance patient compliance and rectal mucosal safety in high-risk patients receiving highly NSAID therapy. This work was conducted to optimize and evaluate Poloxamer P407/P188-based thermoresponsive TS-_LS by using mucoadhesive polymers such as methylcellulose (MC). TS-_LS was prepared by cold method and characterized their in vitro physicochemical properties as gelation temperature (GT), gel strength, bioadhesive properties, and in vitro release. The safety of the prepared suppository on rectum, stomach, and liver was evaluated histologically. Pharmacokinetic analyses were performed to compare rectal TS-_LS to orally Rhumtol^® capsules. The results showed that the optimized TS-_LS; composed of P407/P188/MC (21/9/0.5% w/w) displayed gelation at rectum temperature ～32.90?°C, gel strength of 21.35?s and rectal retention force at the administration site of 24.25?×?10²?dyne/cm². Moreover, TS-_LS did not cause any morphological damage to the rectal tissues. Pharmacokinetic parameters of optimized TS-_LS formulation revealed 4.6 fold increase in bioavailability as compared to Rhumtol^® capsules. Taken together, the results demonstrated that liquid suppository is a potential and physically safe rectal delivery carrier for improvement rectal bioavailability and in vivo safety of TS.     

A family of inequalities valid for the robust single machine scheduling polyhedron

We consider the problem of sequencing a set of jobs in a single machine to minimize the maximum of the total weighted completion time of the jobs over a number of scenarios, each corresponding to a set of job processing times. We give a large family of inequalities that are valid for the convex hull of the set of feasible schedules. We then present computational experience in which some of the inequalities are added to the original formulation. We demonstrate through the computational results that their addition to the formulation can substantially improve, among other things, the time required to solve difficult instances of the problem through branch-and-cut.     

An ACO-RFD hybrid method to solve NP-complete problems

In this paper we hybridize ant colony optimization (ACO) and river formation dynamics (RFD), two related swarm intelligence methods. In ACO, ants form paths (problem solutions) by following each other’s pheromone trails and reinforcing trails at best paths until eventually a single path is followed. On the other hand, RFD is based on copying how drops form rivers by eroding the ground and depositing sediments. In a rough sense, RFD can be seen as a gradient-oriented version of ACO. Several previous experiments have shown that the gradient orientation of RFD makes this method solve problems in a different way as ACO. In particular, RFD typically performs deeper searches, which in turn makes it find worse solutions than ACO in the first execution steps in general, though RFD solutions surpass ACO solutions after some more time passes. In this paper we try to get the best features of both worlds by hybridizing RFD and ACO. We use a kind of ant-drop hybrid and consider both pheromone trails and altitudes in the environment. We apply the hybrid method, as well as ACO and RFD, to solve two NP-hard problems where ACO and RFD fit in a different manner: the traveling salesman problem (TSP) and the problem of the minimum distances tree in a variable-cost graph (MDV). We compare the results of each method and we analyze the advantages of using the hybrid approach in each case.     

Cytogenomics Unveil Possible Transposable Elements Driving Rearrangements in Chromosomes 2 and 4 of Solea senegalensis

Cytogenomics, the integration of cytogenetic and genomic data, has been used here to reconstruct the evolution of chromosomes 2 and 4 of Solea senegalensis. S. senegalensis is a flat fish with a karyotype comprising 2n = 42 chromosomes: 6 metacentric + 4 submetacentric + 8 subtelocentric + 24 telocentric. The Fluorescence in situ Hybridization with Bacterial Artificial Chromosomes (FISH-BAC) technique was applied to locate BACs in these chromosomes (11 and 10 BACs in chromosomes 2 and 4, respectively) and to generate integrated maps. Synteny analysis, taking eight reference fish species (Cynoglossus semilaevis, Scophthalmus maximus, Sparus aurata, Gasterosteus aculeatus, Xiphophorus maculatus, Oryzias latipes, Danio rerio, and Lepisosteus oculatus) for comparison, showed that the BACs of these two chromosomes of S. senegalensis were mainly distributed in two principal chromosomes in the reference species. Transposable Elements (TE) analysis showed significant differences between the two chromosomes, in terms of number of loci per Mb and coverage, and the class of TE (I or II) present. Analysis of TE divergence in chromosomes 2 and 4 compared to their syntenic regions in four reference fish species (C. semilaevis, S. maximus, O. latipes, and D. rerio) revealed differences in their age of activity compared with those species but less notable differences between the two chromosomes. Differences were also observed in peaks of divergence and coverage of TE families for all reference species even in those close to S. senegalensis, like S. maximus and C. semilaevis. Considered together, chromosomes 2 and 4 have evolved by Robertsonian fusions, pericentric inversions, and other chromosomal rearrangements mediated by TEs.