Characterization of bidimensional polymeric films at the air–water interface in the Langmuir trough, despite being a recurrent topic, usually refers to films of already formed polymeric materials, ...with very scarce reports on direct polymerization at the air–water interface. In the present work, we studied the photo-polymerization of stearyl methacrylate directly at the air–water interface under a nitrogen atmosphere, with the radical initiator solubilized in the aqueous phase. Two-dimensional (2D) polymerization was monitored by measuring the pressure–area isotherm at different irradiation times. The polymerization leads to a film with an isotherm different from that observed for the monomer, where the surface pressure is directly related to the irradiation time. The shape of this isotherm confirms the presence of a compressed liquid phase, where a higher order can be attained as a consequence of stronger packing forces involving polymer chains. The presence of inter-chain interactions allows rearrangements on the surface of the subphase, and even before the collapse a dense 2D ordering (with a solid phase-like behavior) can be observed. We present a new one-step, solvent-free procedure to obtain a photo-polymeric film directly at the air–water interface, which can be transferred to a solid surface by the Langmuir–Blodgett method, allowing film preparation of controlled thickness. Films were characterized by measuring properties such as thickness, roughness, and hydrophobicity and comparing them with films obtained from a conventional polymer. We report the differences between the interfacial behavior of amphiphilic molecules and nanomaterials such as films obtained by photo-polymerization, PSMA, directly on the air–water interface.
One major challenge for the legacy measurements at the LHC is that the likelihood function is not tractable when the collected data is high-dimensional and the detector response has to be modeled. We ...review how different analysis strategies solve this issue, including the traditional histogram approach used in most particle physics analyses, the Matrix Element Method, Optimal Observables, and modern techniques based on neural density estimation. We then discuss powerful new inference methods that use a combination of matrix element information and machine learning to accurately estimate the likelihood function. The MadMiner package automates all necessary data-processing steps. In first studies we find that these new techniques have the potential to substantially improve the sensitivity of the LHC legacy measurements.
Likelihood ratio tests are a key tool in many fields of science. In order to evaluate the likelihood ratio the likelihood function is needed. However, it is common in fields such as High Energy ...Physics to have complex simulations that describe the distribution while not having a description of the likelihood that can be directly evaluated. In this setting it is impossible or computationally expensive to evaluate the likelihood. It is, however, possible to construct an equivalent version of the likelihood ratio that can be evaluated by using discriminative classifiers. We show how this can be used to approximate the likelihood ratio when the underlying distribution is a weighted sum of probability distributions (e.g. signal plus background model). We demonstrate how the results can be considerably improved by decomposing the ratio and use a set of classifiers in a pairwise manner on the components of the mixture model and how this can be used to estimate the unknown coefficients of the model, such as the signal contribution.
Surfaces were prepared with polyelectrolyte derivatives of poly(styrene-alt-maleic anhydride) (PSMA) functionalized with amino acids of different hydropathy indices, with the aim of evaluating the ...effect of the chemical functionality of polyelectrolytes on SH-SY5Y neuroblastoma cell adhesion. Functionalizing PSMA derivatives with l-glutamine, l-methionine, and l-tyrosine yielded PSMA-Gln, PSMA-Met, and PSMA-Tyr polyelectrolytes, respectively. We first studied the adsorption behavior of PSMA functionalized with amino acids on silicon wafer surfaces modified with 3-aminopropyltriethoxysilane at pH 4.0 and 7.0 and at low and high ionic strengths. The highest rate of polyelectrolyte adsorption was at pH 4.0 and high ionic strength and was higher with the glutamine and tyrosine films. The advance contact angles (θA) of the polyelectrolyte surfaces showed a moderate effect of ionic strength and pH on polyelectrolyte film wettability, with PSMA-Tyr being slightly more hydrophobic. Atomic force microscopy images of the polyelectrolyte surfaces showed two types of morphology: the well-defined globular nanostructure of PSMA-Met and PSMA-Tyr and densely packed nanofibrous-like structure of PSMA-Gln. The highest level of ionic strength caused a slight decrease in the size of the nanostructure that formed the surface domains, which was reflected in the degree of surface roughness. Cell adhesion assays with the polyelectrolyte film showed that SH-SY5Y neuroblastoma cells cultured on PSMA-Met present a well-extended morphology characterized by a stellate shape, with five or more actin-rich thin processes, whereas SH-SY5Y cells that were seeded on PSMA-Gln and PSMA-Tyr have a round morphology, with fewer and shorter processes. These results indicate that it is possible to modulate the surface characteristics of polyelectrolyte films based on their chemical functionality and environmental parameters such as pH and ionic strength in order to evaluate their effect on cell adhesion. Thus, surfaces prepared from polyelectrolytes functionalized with amino acids are an attractive and simple platform for cell adhesion, which can be used in developing biomaterials with modulated surface properties.
• A new silanol-based hybrid coating has been synthesized. • The incorporation of CeO
2 and ZrO
2 nanoparticles into the coating greatly improves the corrosion resistance of the coated aluminium ...alloy. • The effectiveness of the coating is increasingly evident for long term exposure to the sodium chloride solution. • The silanol-based nanocomposite coatings have self-healing ability.
A new hybrid sol–gel type film, composed of tetraethylorthosilicate (TEOS) and tetraocthylorthosilicate (TEOCS), and modified with different nanoparticle systems, has been investigated as a coating for protection of AA-2024-T3 aluminium alloy. The nanoparticle systems considered were either ZrO
2 or CeO
2 or their combination
. The zirconia nanoparticles were prepared from a Zr (IV) propoxide sol (TPOZ), using an organic stabilizer, and the CeO
2 nanoparticles were developed spontaneously after adding cerium nitrate solution to the hybrid sol. The chemical composition and the structure of the hybrid sol–gel films were examined by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The corrosion resistance of the coated AA-2024 alloy was examined by potentiodynamic polarization. The results revealed that, for short exposure times in the electrolyte, incorporation of ZrO
2 or CeO
2 nanoparticles in the hybrid film does not provide an increase in the corrosion resistance of the coated AA-2024 alloy. Further, the resistance was significantly reduced by increasing the nanoparticle content. Conversely, by incorporating both nanoparticles (ZrO
2 and CeO
2), the corrosion resistance of the resulting hybrid films increased slightly. The behavior changed significantly when the coated alloy was exposed to the electrolyte for 5 days. The corrosion resistance of the coatings, unmodified and modified with CeO
2 or ZrO
2 nanoparticles, decreased by two or three orders of magnitude, while the film modified with both nanoparticles (CrO
2 and ZrO
2) showed a relatively high corrosion resistance and responsiveness to activation processes during anodic polarization.
► MIC on stainless by catalase deficient Escherichia coli bacteria reveals the enzyme influence. ► The localized damage was greater in the presence of the wild E. coli. ► Catalase assists oxygen ...generation by disproportionation of H2O2 to H2O and O2.
The role of catalase on the microbiologically influenced corrosion mechanism by Escherichia coli (E. coli) has been examined, employing wild type and catalase-deficient cells. The bacteria were cultured for different times in the presence of AISI 316L stainless steel samples. The morphologies of the metallic surfaces covered by biofilms were studied by optical microscopy. The localized corrosion catalyzed by the bacteria was followed by scanning electron microscopy after immersion in the bacterial culture for different times. Susceptibility to corrosion was further investigated by potentiodynamic measurements. It was found that wild type E. coli is more aggressive than the mutant one, suggesting a role for catalase in increasing the kinetics of the cathodic reaction and, consequently, the global corrosion process. This correlates with oxygen uptake kinetics, as determined by differential pulse voltammetry on a pyrolytic graphite electrode modified with cobalt phthalocyanine, which was higher in the presence of wild type E. coli. When H2O2 was deliberately added to the culture medium, wild type E. coli catalyzed oxygen disproportionation more efficiently than the mutant derivative, thus limiting H2O2 accumulation in the medium and, hence, bacterial poisoning. In fact, the reduced adhesion of mutant cells to the metal substrate is apparently the result of H2O2 accumulation in the culture broth. Thus, the rapid consumption of oxygen and peroxide in the presence of wild type E. coli is associated with the catalysis of H2O2 disproportionation to water and oxygen. On the stainless steel, however, a dual mechanism of oxygen reduction, i.e. through formation of hydrogen peroxide and by formation of water, is also considered.
We have investigated the electrocatalytic activity of cobalt tetra-aminophthalocyanine (CoTAPc) for the one-electron oxidation of 2-mercaptoethanol (2-ME) using adsorbed monomeric CoTAPc and ...electropolymerized poly-CoTAPc films of different thickness on vitreous carbon electrode. Our results show that the activity of poly-CoTAPc increases slightly with the thickness of the film, while the activity of the adsorbed monomeric CoTAPc is still greatest. The trend in activities, analysed by cyclic voltammetry, is the same for the electro-oxidation of 2-ME and for the electroreduction of the corresponding disulphide. Tafel plots obtained from rotating disk measurement for adsorbed CoTAPc and poly-CoTAPc film modified electrodes show slopes close to
RT/
F (ca. 70 mV) at low polarisation potentials which increase gradually with potential to values close to 2
RT/
F (120 mV). This suggests that at low polarisation the rate-determining step is a chemical step (formation of a metal complex–thiol adduct) preceded by a fast electron-transfer step involving the CoTAPc. At higher polarisations the one electron oxidation of the adduct to give the thiyl radical becomes rate controlling. Even though monomeric CoTAPc adsorbed on glassy carbon presents higher activity for the electro-oxidation of 2-ME, the high stability of the electropolymerized poly-CoTAPc makes them more attractive for applications in the activation and/or the amperometric detection of thiols.
We report on the interaction of the thiocyanate ion (SCN–) with Co macrocyclics. In order to modulate the electron density located on the metal center, we used several phthalocyanine and macrocyclic ...molecules with electron-donating or electron-withdrawing groups located on the phthalocyanine ligand. We studied the following substituted Cobalt-macrocycles (CoPc’s): cobalt-tetraamino-phthalocyanine (4β(NH 2 )CoPc), cobalt-phthalocyanine (CoPc), cobalt-octahydroxyethylthio-phthalocyanine (8β(SC 2 H 4 OH)CoPc), cobalt-tetrapentylopyrrol-phthalocyanine (4β(PenPyr)CoPc), cobalt-tetrapyridino-phorphyrazine (4β(Pyr)CoPc), cobalt-octaethylhexyloxy-phthalocyanine (8β(EH)CoPc), cobalt-octamethoxyphthalocyanine (8β(OCH 3 )CoPc), and cobalt-hexadecafluorophthalocyanine (16(F)CoPc). Our results for the formation of a CoPc-SCN adduct indicate that the electron-withdrawing groups favors the formation of an adduct between thiocyanate and the Co center, with an increase of the thiocyanate-binding energy. When the adducts are formed, they exhibit an increasing chemical potential, thus indicating the feasibility to produce the catalysis once the adducts are formed. The molecular hardness values suggest that the CoPc’s with electron-withdrawing substituents will show low catalytic activity while those with electron-donor substituents will show an enhanced catalytic activity. The functionalized Co-phthalocyanine shows the highest catalytic activity for the thiocyanate electroxidation, which presents an appropriate energy gap (HOMO SCN– – LUMO CoPc's ) for the adduct formation and the subsequent electronic transfer.
This article proposes a simple method to calculate a current vector trajectory for the enhanced operation of the electric power generation system based on a synchronous reluctance machine (SynRM). ...Owing to magnetic saturation and cross magnetization, the performance and the torque capability of a SynRM vary according to the position and the value of the stator current. State-of-the-art control methods usually assume parameters with constant values, especially the inductance, neglecting saturation, leading to possible uncertainty in the machine operation. Therefore, a current vector trajectory to operate this type of machine, as a generator, in an extended speed range, with enhanced performance and considering magnetic saturation is proposed. A straightforward algorithm based on the inductance characteristic of the machine is used to calculate the trajectory of the stator current vector. This trajectory is evaluated via the numerical simulation of an experimentally validated finite-element model of a SynRM. The results show that the proposed current vector trajectory can improve the torque capability to 5% concerning the estimated trajectory without considering saturation. Experimental results are also provided to demonstrate the enhanced operation of the generator.
This paper presents the solution of the optimal power flow (OPF) using the simulated annealing (SA) technique. The main goal of this paper is to verify the viability of using SA to solve the OPF ...problem simultaneously composed by the load flow and the economic dispatch problem. Definitions on the objective function, weights and norms are given here as well as criteria for solving the load flow. Two test systems (Six and IEEE30 buses) are used to highlight the goodness of this solution technique.
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