Photostabilization of oxolinic acid in hydroxypropyl-β-cyclodextrins; implications for the effect of molecular self-assembly phenomena

Oxolinic acid (OXA) is a first-generation quinolone antibacterial agent, known to cause drug induced photosensitivity. In the present work its photoinduced degradation was monitored under simulated solar irradiation. The effect of photoprotecting agents on OXA stability was also assessed by drug complexation with hydroxypropyl-β-cyclodextrin (HPβCD). The complex was studied by UV-Vis and ¹H (2D) NMR Spectroscopy. A photostability indicating chromatographic method was developed and validated. Because OXA is insoluble in acidic solutions, and because an acidic solvent is necessary for successful chromatographic separation, a procedure was developed to pre-treat the sample. This method is suitable for the separation of degradation products from OXA and from each other. The method was also evaluated in the presence of HPβCD, in order to ensure that inclusion complexation did not generate inaccuracies. Investigation of OXA photodegradation profiles confirms first order kinetics and acceleration at higher initial sample concentrations. A 94% photostabilization upon complexation with HPβCD was achieved. Furthermore, molecular self association phenomena were determined by self titration experiments, using ¹H NMR Spectroscopy and suggestions were made for the photostabilization mechanism of cyclodextrins.     

Adjoint wall functions: A new concept for use in aerodynamic shape optimization

The continuous adjoint method for the computation of sensitivity derivatives in aerodynamic optimization problems of steady incompressible flows, modeled through the k–ε turbulence model with wall functions, is presented. The proposed formulation leads to the adjoint equations along with their boundary conditions by introducing the adjoint to the friction velocity. Based on the latter, an adjoint law of the wall that bridges the gap between the solid wall and the first grid node off the wall is proposed and used during the solution of the system of adjoint (to both the mean flow and turbulence) equations. Any high Reynolds turbulence model, other than the k–ε one used in this paper, could also profit from the proposed adjoint wall function technique. In the examined duct flow problems, where the total pressure loss due to viscous effects is used as objective function, emphasis is laid on the accuracy of the computed sensitivity derivatives, rather than the optimization itself. The latter might rely on any descent method, once the objective function gradient has accurately been computed.     

Trace Elements in Pleurotus Ostreatus,P. Eryngii,and P. Nebrodensis Mushrooms Cultivated on Various Agricultural By-Products

Abstract

Mushrooms are efficient accumulators of essential and toxic elements. Although oyster (Pleurotus spp.) mushrooms are widely commercialized and consumed, few data exist regarding trace elements content and bioaccumulation in cultivated P. ostreatus and P. eryngii, while no data are available for P. nebrodensis. The contents of Al, As, Ba, Cd, Co, Cr, Cs, Cu, Fe, K, Mn, Na, Ni, Pb, Rb, Sr, V, and Zn were monitored using inductively coupled plasma-mass spectrometry (ICP-MS) and atomic emission spectrometry (AES) in P. ostreatus, P. eryngii, and P. nebrodensis mushrooms and their cultivation substrates that include wheat straw (WHS), grape marc (GMC), olive leaves (OLV), and two-phase olive mill wastes (OMW), separately or in mixtures. Bioaccumulation factors (BAFs) less than 0.3 were obtained for Al, Ba, Co, Cr, Fe, Mn, Ni, Pb, Sr, and V; BAFs exceeding 1 for K?>?Zn?>?Cd?>?Cr?>?Rb?>?As, while the BAFs for Na were less 0.7. Mushrooms grown on OLV and OMW presented lower BAFs than those grown on WHS and GMC for all elements except for K, Cd, and Cu. P. ostreatus was an effective accumulator for Cr, Fe, and Zn; P. eryngii for Al, Cs, Ni, and V; and P. nebrodensis for As and Cd. The estimated daily intakes (μg kg^?1 body weight) from mushroom consumption were less than 0.010 for As, Cd, Co, Cs, Pb, and V, 0.010–0.10 for Ba, Cr, Ni, and Sr, 0.10–5.0 for Al, Cu, Fe, Mn, Rb, and Zn, 65–83 for Na, and 858–1030 for K. Overall, the mushrooms studied provide significant amounts of K, adequate amounts of Mn and Zn and low amounts of Na and toxic elements.     

Correlation between structural and electrical properties of heavily lithiated boron oxide solid electrolytes

Infrared and impedance measurements have been carried out on high lithium content boron oxide solid electrolytes xLi₂O–B₂O₃, with x = 3.0–4.5, in order to establish the correlation between their structural and electrical properties. The samples are two-phase materials, in which crystalline islands are scattered throughout the vitreous background phase. The evolution of structural and electrical properties with increasing x exhibits a marked differentiation around x = 4.0, which is associated with increasing crystallization in the material.     

PFAS Degradation in Ultrapure and Groundwater Using Non-Thermal Plasma

Perfluoroalkyl substances (PFAS) represent one of the most recalcitrant class of compounds of emerging concern and their removal from water is a challenging goal. In this study, we investigated the removal efficiency of three selected PFAS from water, namely, perfluorooctanoic acid (PFOA), perfluorohexanoic acid (PFHxA) and pefluorooctanesulfonic acid (PFOS) using a custom-built non-thermal plasma generator. A modified full factorial design (with 2 levels, 3 variables and the central point in which both quadratic terms and interactions between couple of variables were considered) was used to investigate the effect of plasma discharge frequency, distance between the electrodes and water conductivity on treatment efficiency. Then, the plasma treatment running on optimized conditions was used to degrade PFAS at ppb level both individually and in mixture, in ultrapure and groundwater matrices. PFOS 1 ppb exhibited the best degradation reaching complete removal after 30 min of treatment in both water matrices (first order rate constant 0.107 min⁻¹ in ultrapure water and 0.0633 min⁻¹ in groundwater), while the degradation rate of PFOA and PFHxA was slower of around 65% and 83%, respectively. During plasma treatment, the production of reactive species in the liquid phase (hydroxyl radical, hydrogen peroxide) and in the gas phase (ozone, NO_x) was investigated. Particular attention was dedicated to the nitrogen balance in solution where, following to NO_x hydrolysis, total nitrogen (TN) was accumulated at the rate of up to 40 mg^N L⁻¹ h⁻¹.     

Exponential lower bounds for finding Brouwer fix points

The computation of Brouwer fixed points is a central tool in economic modeling. Although there have been several algorithms for computing a fixed point of a Brouwer map, starting with Scarf's algorithm of 1965, the question of worst-case complexity was not addressed. It has been conjectured that Scarf's algorithm has typical behavior that is polynomial in the dimension. Here we show that any algorithm for computing the Brouwer fixed point of a function based on function evaluations (a class that includes all known general purpose algorithms) must in the worst case perform a number of function evaluations that is exponential in both the number of digits of accuracy and the dimension. Our lower bounds are very close to the known upper bounds.     

Platinum(II) and platinum(IV) complexes of 2-amino-4, 6-dimethylpyrimidine

Summary Platinum(II) and platinum(IV) complexes of 2-amino-4, 6-dimethylpyrimidine, ADMPY, have been prepared. Solids of formula Pt(ADMPYH⁺)Cl₃, Pt(ADMPY)₂Cl₄ and Pt(ADMPY)₂Cl₄·2HCl have been isolated and characterized by elemental analyses in conjuction with i.r. and n.m.r. spectra. A paramagnetic tan to reddishbrown complex has been reproducibly prepared from the direct reaction of K₂PtCl₄ and ADMPY at pH 6.     

Application of solid-phase microextraction in the monitoring of priority pesticides in the Kalamas River (N.W. Greece)

A solid-phase microextraction (SPME) method was applied to an extended monitoring survey of priority pesticides for the European Union for a period of 12 months in water of the Kalamas River (Epirus region of northwestern Greece) in order to determine their concentrations and seasonal variations. Polydimethylsiloxane-coated fiber (100 microm) was used. The samples were screened using gas chromatography with flame thermionic detection. Detection was confirmed by gas chromatographymass spectroscopy. The most frequently detected pesticides were some of the more commonly used herbicides, such as S-ethyl-N,N-di-n-propylthiol carbamate (EPTC), trifluralin, atrazine, deethylatrazine, terbuthylazine and alachlor, and insecticides, such as carbofuran, diazinon, disulfoton, parathion methyl, parathion ethyl, fenthion and ethion. Concentrations of individual compounds ranged from 0.020 to 0.3 microg/L. Greater pesticide concentrations occurred during the seasons of application. A comparison with a well-established solid-phase extraction (C18 disks) procedure was performed for samples of high-season application (May-September) in order to confirm the effectiveness of the SPME technique. The results demonstrate the suitability of the SPME method for routine screening multiresidue analysis in natural waters.     

Normal and differential demasking flow-injection manifold for the direct spectrophotometric determination of zinc(II) in biological materials and pharmaceutical formulations

A normal and a differential demasking flow-injection (FI) manifold were developed and optimized for the spectrophotometric determination of microamounts of Zn(II) in biological materials and pharmaceutical formulations. The reported method is very sensitive, rapid, simple and it is based upon the reaction of Zn(II) with 2,2'-dipyridyl-2-pyridylhydrazone (DPPH) in a strongly basic medium to form a yellow-coloured complex (lambda max = 448 nm). By using the differential demasking manifold, the tolerance of the method to many cations was enhanced by a mean factor of 25. The obtained calibration graphs were linear in the range of 0-10 mg l-1 Zn(II), at a sampling rate of 120 injections h-1 in both cases. The precisions of both manifolds were very good (RSD = 0.6 and 0.8%, respectively) and the 3 sigma detection limits were quite satisfactory (cL = 4 and 6 ng ml-1 respectively). The method has been successfully applied to the determination of Zn(II) in serum, human hair and pharmaceutical formulations with recoveries ranging between 98.0 and 101.6%. The obtained results were also in excellent agreement with flame atomic absorption spectrometry (FAAS), since the mean relative error was er = 0.9%.     

Organotin flufenamates: Synthesis, characterization and antiproliferative activity of organotin flufenamates

The organotin flufenamates [Me₂(flu)SnOSn(flu)Me₂]₂ (1), [Bu₂(flu)SnOSn(flu)Bu₂]₂ (2) and [Bu₂Sn(flu)₂] (3) have been prepared and structurally characterized by means of vibrational and NMR (¹H, ¹³C and ¹¹⁹Sn) spectroscopy. The crystal structure of [Me₂(flu)SnOSn(flu)Me₂]₂ (1) has been determined by X-ray crystallography. Three distannoxane rings are present to the dimeric tetraorganodistannoxane of planar ladder arrangement. The structure is centro-symmetric and features a central rhombus Sn₂O₂ unit with two additional tin atoms linked at the O atoms. Six-coordinated tin centers are present in the dimer distannoxane. This structure is self-assembled via π → π and C-H → π stacking interactions. Flufenamic acid and flufenamates were evaluated for antiproliferative activity in vitro. Among the compounds tested [Bu₂(flu)SnOSn(flu)Bu₂]₂ (2) and [Bu₂Sn(flu)₂] (3) exhibited high cytotoxic activity against the cancer cell line A549 (non-small cell lung carcinoma).