Ultrasound assisted catalytic wet peroxide oxidation of phenol: kinetics and intraparticle diffusion effects

The combination of ultrasound irradiation and catalytic wet peroxide oxidation was used as a means to degrade phenol. Direct and indirect irradiation were employed, while experiments in the absence of ultrasound were used as reference. A mixed (Al-Fe) pillared clay named FAZA, was used as a catalyst in the form of powder, extrudates and crushed extrudates. Ultrasound was found to clearly enhance the extrudates performance, increasing the conversion at 4h by more than 6 times under direct and almost 11 times under indirect irradiation. This observation is attributed to the reduction of diffusion resistance within the catalyst pores. The overall sonication-catalytic wet peroxide oxidation process appears very promising for environmental purposes.     

Development of a novel method based on liquid chromatography-evaporative light scattering detection for the direct determination of streptomycin and dihydrostreptomycin in raw materials, pharmaceutical formulations, culture media and plasma

A novel method for the non-derivatization liquid chromatographic determination of streptomycin (STR) and dihydrostreptomycin (DHSTR) was developed and validated based on evaporative light scattering detection (ELSD). Utilizing a ThermoHypersil BetaBasic C18 analytical column, evaporation temperature of 50 degrees C and pressure of nebulizing gas (nitrogen) of 3.5 bar, the optimized mobile phase was 1.25 mL L(-1) TFA aqueous solution, in an isocratic mode at a rate of 1.0 mL min(-1). STR was eluted at 5.6 min and DHSTR at 7.8 min with a resolution of 4.4. Linear calibration curves were obtained from 2 to 120 microg mL(-1) (r > 0.9990) for STR and 2-75 microg mL(-1) (r > 0.9994) for DHSTR, with a LOD equal to 0.7 and 0.5 microg mL(-1), respectively. The developed method was applied for the assay of STR and DHSTR (sulfate) in pharmaceutical raw materials and formulations, while the simultaneous direct determination of sulfate was feasible (tR = 2.5 min, LOD = 1.4 microg mL(-1), double logarithmic calibration curve in the range of 4-50 microg mL(-1), r > 0.9998). Modified isocratic mobile phase (H2O-ACN, 90:10, v/v, containing 1.25 mL L(-1) TFA), was used for the determination of streptomycin B impurity in STR sulfate raw material and a gradient mobile phase (H2O-ACN containing TFA) was used for the determination of DHSTR in the presence of penicillinG procaine. The developed method was also applied for the assay of commercial formulations (STR powder and DHSTR injection solution and suspension) (%recovery 98-102, %RSD < 1.3, n = 3 x 3), for the determination of STR in bacteria culture medium (%recovery 99.6, %RSD = 0.8, n = 3 x 3), and for the determination of DHSTR in human plasma (2.0-23.0 microg mL(-1)) after solid phase extraction using carboxylate cartridges (%recovery 98.4-101.8, %RSD = 3.2, n = 3 x 3).     

A Novel Approach for Mixing ZnO Nanoparticles into Poly(ethyl methacrylate)

A novel and versatile approach for the mixing of ZnO nanofillers into a host polymer matrix, poly(ethyl methacrylate) (PEMA), is reported. Firstly, ZnO nanoparticles are deposited onto the surface of polystyrene (PS) colloidal particles in a “raspberry‐like” fashion and subsequently obtained PS/ZnO composite particles are mixed into the PEMA matrix in the range of 0.5 to 5 wt.‐%. Microscopic analyses reveal a homogenous distribution of PS/ZnO domains into the PEMA matrix even at 5 wt.‐% loading level. Thermogravimetric analysis and differential scanning calorimetry results indicate an improvement in thermal stability of PEMA matrix after mixing with PS/ZnO filler particles. A significant enhancement in mechanical properties of PEMA matrix in the presence of PS/ZnO particles has been evidenced by dynamic mechanical analysis and three point bending measurements.

     

Abruptly autofocusing waves

We introduce a new class of (2+1)D spatial and (3+1)D spatiotemporal waves that tend to autofocus in an abrupt fashion. While the maximum intensity of such a radial wave remains almost constant during propagation, it suddenly increases by orders of magnitude right before its focal point. These waves can be generated through the use of radially symmetric Airy waves or by appropriately superimposing Airy wave packets. Possible applications of such abruptly focusing beams are also discussed.     

Constant sign and nodal solutions for logistic-type equations with equidiffusive reaction

We consider a logistic-type equation driven by the p-Laplace differential operator with an equidiffusive reaction term. Combining variational methods based on critical point theory together with truncation techniques and Morse theory, we show that when ?? > ??₁, the problem has extremal solutions of constant sign and when ?? > ??₂ it has also a nodal (sign-changing) solution. Here ??₁?<???₂ are the first two eigenvalues of the negative Dirichlet p-Laplacian. In the semilinear case (i.e. p?=?2) we produce two nodal solutions.     

Chemical bonding of chlorophylls and plant aminic axial ligands impact harvesting of visible light and quenching of fluorescence

In the present work, we tested the mode of interaction of all three polyamines (putrescine, spermidine and spermine) with chlorophyll a and b, as well as pheophytin a and b. The results showed that all three polyamines bind to the Mg ion of chlorophyll ring as probed by Raman spectroscopy. The coordination of spermine with Chl b has the most interesting features from all pigments tested. Spermine induces reversible increases and decreases of the fluorescence yield of Chl b at about 661 nm. Interestingly, equilibrium between a high-fluorescence yield conformation and a low yield is feasible by the interaction of chlorophyll b and aminic ligands. Furthermore, absorption data for the diagnostic regions of 518 and 535 nm are provided for all combinations of pigments and ligands. The significance and consistence of these results with respect to photochemical and bioenergetic principles are discussed.     

A deterministic resource scheduling model in epidemic control: A case study

The resources available to tackle an epidemic infection are usually limited, while the time and effort required to control it are increasing functions of the starting time of the containment effort. The problem of scheduling limited available resources, when there are several areas where the population is infected, is considered. A deterministic model, appropriate for large populations, where random interactions can be averaged out, is used for the epidemic’s rate of spread. The problem is tackled using the concept of deteriorating jobs, i.e. the model represents increasing loss rate as more susceptibles become infected, and increasing time and effort needed for the epidemic’s containment. A case study for a proposed application of the model in the case of the mass vaccination against A(H1N1)_v influenza in the Attica region, Greece and a comparative study of the model’s performance vs. the applied random practice are presented.     

Periodic lattice-ordered pregroups are distributive

It is proved that any lattice-ordered pregroup that satisfies an identity of the form x ^ll···l = x ^rr···r (for the same number of ^l,r -operations on each side) has a lattice reduct that is distributive. It follows that every such ?-pregroup is embedded in an ?-pregroup of residuated and dually residuated maps on a chain.     

Evaluation of Cocaine Effect on Endogenous Metabolites of HepG2 Cells Using Targeted Metabolomics

Cocaine toxicity has been a subject of study because cocaine is one of the most common and potent drugs of abuse. In the current study the effect of cocaine on human liver cancer cell line (HepG2) was assessed. Cocaine toxicity (IC50) on HepG2 cells was experimentally calculated using an XTT assay at 2.428 mM. The metabolic profile of HepG2 cells was further evaluated to investigate the cytotoxic activity of cocaine at 2 mM at three different time points. Cell medium and intracellular material samples were analyzed with a validated HILIC-MS/MS method for targeted metabolomics on an ACQUITY Amide column in gradient mode with detection on a triple quadrupole mass spectrometer in multiple reaction monitoring. About 106 hydrophilic metabolites from different metabolic pathways were monitored. Multivariate analysis clearly separated the studied groups (cocaine-treated and control samples) and revealed potential biomarkers in the extracellular and intracellular samples. A predominant effect of cocaine administration on alanine, aspartate, and glutamate metabolic pathway was observed. Moreover, taurine and hypotaurine metabolism were found to be affected in cocaine-treated cells. Targeted metabolomics managed to reveal metabolic changes upon cocaine administration, however deciphering the exact cocaine cytotoxic mechanism is still challenging.     

A hybrid LP/NLP paradigm for global optimization relaxations

Polyhedral relaxations have been incorporated in a variety of solvers for the global optimization of mixed-integer nonlinear programs. Currently, these relaxations constitute the dominant approach in global optimization practice. In this paper, we introduce a new relaxation paradigm for global optimization. The proposed framework combines polyhedral and convex nonlinear relaxations, along with fail-safe techniques, convexity identification at each node of the branch-and-bound tree, and learning strategies for automatically selecting and switching between polyhedral and nonlinear relaxations and among different local search algorithms in different parts of the search tree. We report computational experiments with the proposed methodology on widely-used test problem collections from the literature, including 369 problems from GlobalLib, 250 problems from MINLPLib, 980 problems from PrincetonLib, and 142 problems from IBMLib. Results show that incorporating the proposed techniques in the BARON software leads to significant reductions in execution time, and increases by 30% the number of problems that are solvable to global optimality within 500 s on a standard workstation.