Biomimetic apatite coating on P(EMA-co-HEA)/SiO2 hybrid nanocomposites

P(EMA-co-HEA)/SiO₂ nanocomposites with silica contents in the range of 0-30 wt% were prepared by co-polymerization of the organic monomers during the simultaneous sol-gel polymerization of the silica precursor. The ability of the hybrids to form hydroxyapatite (HAp) on their surfaces was tested in vitro by soaking the samples in a simulated body fluid (SBF) solution for different times up to 35 days. On the one hand, the composition and morphology of the HAp layer formed were characterized by SEM, EDS, FTIR and XRD; on the other, the exchange of soluble silicates and calcium and phosphate ions, and the structural changes taking place in the nanohybrids when immersed in SBF were analyzed by SEM/EDS. This is, up to our knowledge, the first time the HAp nucleation mechanism has been proposed for organic-silica nanohybrids and correlated with their respective nanostructures. The results revealed that the formation of a HAp coating was in all cases limited by the nucleation induction time, but the mechanism and rate of HAp nucleation were found to be different depending on the nanostructure of the samples, which differs, in turn, with the silica content as a consequence of the differing connectivity of the silica network. The nanohybrids with silica contents in the range of 10-20 wt% proved to be the most suitable for the development of bioactive synthetic scaffolds for bone or other mineralized tissues.     

NRN1 Gene as a Potential Marker of Early-Onset Schizophrenia: Evidence from Genetic and Neuroimaging Approaches

Included in the neurotrophins family, the Neuritin 1 gene (NRN1) has emerged as an attractive candidate gene for schizophrenia (SZ) since it has been associated with the risk for the disorder and general cognitive performance. In this work, we aimed to further investigate the association of NRN1 with SZ by exploring its role on age at onset and its brain activity correlates. First, we developed two genetic association analyses using a family-based sample (80 early-onset (EO) trios (offspring onset ≤ 18 years) and 71 adult-onset (AO) trios) and an independent case–control sample (120 healthy subjects (HS), 87 EO and 138 AO patients). Second, we explored the effect of NRN1 on brain activity during a working memory task (N-back task; 39 HS, 39 EO and 39 AO; matched by age, sex and estimated IQ). Different haplotypes encompassing the same three Single Nucleotide Polymorphisms(SNPs, rs3763180–rs10484320–rs4960155) were associated with EO in the two samples (GCT, TCC and GTT). Besides, the GTT haplotype was associated with worse N-back task performance in EO and was linked to an inefficient dorsolateral prefrontal cortex activity in subjects with EO compared to HS. Our results show convergent evidence on the NRN1 association with EO both from genetic and neuroimaging approaches, highlighting the role of neurotrophins in the pathophysiology of SZ.     

Ab initio study of lithium decoration of popgraphene and hydrogen storage capacity of the hybrid nanostructure

The successful realization of extended ‘5-5-8’ line defects in graphene in a controlled way has suggested the possible formation of a new 2D carbon allotrope consisting in pentagonal-octagonal-pentagonal carbon rings. The mechanical and thermal stability of this nanostructure, called popgraphene, has recently been confirmed on the basis of first-principles calculations. Moreover, it has been proposed as a promising anode material for use in Li-ion batteries with fast charge/discharge rates. In the present paper we perform density functional theory calculations to investigate the hydrogen storage ability of popgraphene. Our calculations show that popgraphene can be decorated in a very stable way by placing Li atoms on the pentagonal carbon rings of both sides of the sheet, leaving free the octagonal carbon rings. In that condition, the Li-decorated popgraphene sheet can bind up to four H₂ molecules per unit cell, with an average adsorption energy in a range between physisorption and atomic chemisorption, which would allow for reversible hydrogen storage at moderate temperatures and pressures. Moreover, the gravimetric density of the Li-decorated popgraphene is 4.24 wt%, which is almost equal to the threshold specified by the U.S. Department of Energy for novel hydrogen-storage materials. All these results show that Li-decorated popgraphene nanostructures could be good materials for hydrogen storage.     

Determination of several common disinfection by-products in frozen foods

Disinfected water and/or disinfectants are commonly used by the freezing industry in such processes as sanitising, washing, blanching, cooling and transporting the final product. For this reason, disinfection by-products (DBPs) can be expected in frozen foods. This study focused on the presence of DBPs in a wide variety of frozen vegetables, meats and fish. For this purpose, the 14 halogenated DBPs more prevalent in disinfected water were selected (four trihalomethanes, seven haloacetic acids, two haloacetonitriles and trichloronitromethane). Up to seven DBPs were found in vegetables, whereas only four DBPs were present in meats and fish, and at lower concentrations, since their contact with disinfected water is lower than in frozen vegetables. It is important to emphasise that trichloronitromethane (the most abundant nitrogenous DBP in disinfected water) was found for the first time in foods. Finally, it was concluded that the freezing process can keep the compounds stable longer than other preservation processes (viz. sanitising, canning) and, therefore, frozen foods present higher DBP concentrations than other food categories (minimally processed vegetables, or canned vegetables and meats).     

A dataset of regressions in web applications detected by end-to-end tests

Software Quality Journal - End-to-end tests present many challenges in the industry. The long-running times of these tests make it unsuitable to apply research work on test case prioritization or...     

A fast and efficient contact algorithm for fretting problems applied to fretting modes I,II and III

A computational contact algorithm is presented to solve both the normal and tangential contact problems that describe fretting contacts between two elastic half-spaces. The coupling between the normal and tangential contact problems can or not be taken into account. Nevertheless the coupling should be introduced when materials are dissimilar. Fast and efficient methods are used. The contact solver is based on a conjugate gradient method and acceleration techniques based on the Fast Fourier transforms (FFT) are employed. Very good agreements are found with analytical solutions of three fretting examples representing each fretting mode. However it is shown that these analytical solutions are based on approximations that can be too strong when materials are dissimilar.     

Advances in centerless grinding technology

This paper reviews the history of centerless grinding and its contribution to industry. It summarizes the evolution of centerless grinding theory including advanced modeling and simulation. Then, it discusses the design of main elements of a centerless grinding machine such as spindles, bed, guideways and positioning system, and provides design guidelines for future machines. The paper presents the state-of-the-art centerless grinding technologies: advanced machines, advanced process monitoring and the latest developments in grinding wheels. Finally, in conclusion, future trends and research work in centerless grinding technology are discussed.     

Friction pressure correlations for turbulent flow of drag reducing polymer solutions in straight and coiled tubing

Accurate determination of friction pressure losses of dilute drag reducing polymer solutions remains to be a challenge in many practical applications. These include a wide variety of hydraulic operations performed on a daily basis in the oil and gas industry. Most drilling, completions, and stimulation jobs require pumping fluids at high flow rates, which in turn generates high frictional pressure losses, enhanced by the use of small diameter tubing or coiled tubing. Curvature in this latter is believed to generate secondary flows and thus extra flow resistance. Therefore, good drag reduction characteristics of fluids are desirable.In this study, energy dissipation by eddies in turbulent flow of viscoelastic fluids is assumed to be the mechanism causing drag reduction. Various concentrations of Nalco ASP-700 and Nalco ASP-820 dilute polymer solutions are tested at ambient temperature in laboratory-scale and full-scale flow loops installed with straight and coiled tubing sections exhibiting different values of diameter, curvature ratio and pipe roughness. In addition, flow tests are conducted at 100 °F and 130 °F using the laboratory-scale flow loop.Effects of concentration, temperature, curvature ratio, and pipe roughness on drag reduction are discussed in light of Fanning friction factor versus solvent Reynolds number plots. Results show that drag reduction in coiled tubing is lower than in straight tubing. As curvature ratio increases, drag reduction decreases. The effect of increasing temperature is to decrease drag reduction in straight tubing and increase it in coiled tubing. In turn, the effect of increasing pipe roughness is to slightly decrease drag reduction in straight tubing up to a certain Reynolds number value and then it starts to increase. For coiled tubing, the effect of increasing pipe roughness is to decrease drag reduction.In this study, generalized correlations for the prediction of drag reduction in dilute polymer solutions flowing in straight and coiled tubing are developed on the basis of the energy dissipation of eddies in turbulent flow field and a shear rate dependent relaxation time. In addition, correlations are validated using experimental data for a low concentration guar fluid flowing through full-scale flow loop.