Electroanalysis of Natural Compounds as Copper Chelating Agents for Alzheimer’s Disease Therapy

The development of therapeutic compounds that can attenuate the toxicity exerted by the accumulation of metal ions has been an area of intensive research in neurodegenerative diseases. In this report, an electrochemical method was developed to determine the Cu(II)‐chelating ability of polyphenols that were implicated in Alzheimer’s disease (AD). The results suggested the strength of flavonoids to chelate Cu(II) as epigallocatechin‐3‐gallate (EGCG)>resveratrol>clioquinol>baicalein～scyllo‐inositol. Furthermore, the number of hydroxyl groups was found to play a role to lower Cu(II) oxidation signal using differential pulse voltammetry.     

Separation of glycosidic catiomers by TWIM‐MS using CO2 as a drift gas

Traveling wave ion mobility mass spectrometry (TWIM‐MS) is shown to be able to separate and characterize several isomeric forms of diterpene glycosides stevioside (Stv) and rebaudioside A (RebA) that are cationized by Na⁺ and K⁺ at different sites. Determination and characterization of these coexisting isomeric species, herein termed catiomers, arising from cationization at different and highly competitive coordinating sites, is particularly challenging for glycosides. To achieve this goal, the advantage of using CO₂ as a more massive and polarizable drift gas, over N₂, was demonstrated. Post‐TWIM‐MS/MS experiments were used to confirm the separation. Optimization of the possible geometries and cross‐sectional calculations for mobility peak assignments were also performed. Copyright © 2015 John Wiley & Sons, Ltd.     

Insights on beer volatile profile: Optimization of solid‐phase microextraction procedure taking advantage of the comprehensive two‐dimensional gas chromatography structured separation

The aroma profile of beer is crucial for its quality and consumer acceptance, which is modu‐lated by a network of variables. The main goal of this study was to optimize solid‐phase microextraction experimental parameters (fiber coating, extraction temperature, and time), taking advantage of the comprehensive two‐dimensional gas chromatography structured separation. As far as we know, it is the first time that this approach was used to the untargeted and comprehensive study of the beer volatile profile. Decarbonation is a critical sample preparation step, and two conditions were tested: static and under ultrasonic treatment, and the static condition was selected. Considering the conditions that promoted the highest extraction efficiency, the following parameters were selected: poly(dimethylsiloxane)/divinylbenzene fiber coating, at 40ºC, using 10 min of pre‐equilibrium followed by 30 min of extraction. Around 700–800 compounds per sample were detected, corresponding to the beer volatile profile. An exploratory application was performed with commercial beers, using a set of 32 compounds with reported impact on beer aroma, in which different patterns can be observed through the structured chromatogram. In summary, the obtained results emphasize the potential of this methodology to allow an in‐depth study of volatile molecular composition of beer.     

Dynamic behaviour of coal macerals during pyrolysis – Associations between physical,thermal and chemical changes

A fundamental study on the behaviour of heating coal macerals has been undertaken using two novel thermal analysis techniques. The apparent specific heat was determined during heating using an inverse calorimetric method (computer aided thermal analysis, CATA) and combined with pressure and displacement measurements to correlate endothermic and exothermic behaviour with measurement of swelling. The second technique used a post-oxidation stage to combust the tars and gases into products which were analysed. This method was used to study the elemental character of volatiles release from coal maceral concentrates in terms of carbon and hydrogen. Extents of swelling and exothermicity during primary devolatilisation were found to be correlated with vitrinite content and were associated with tar evolution. For the highest vitrinite fraction (of 86.4% vitrinite) swelling was initiated at the same temperature range for exothermic reactions, and maximum swelling coincided with the peak release of light gases. Tar evolution was found to change in chemical character (as defined by H/C ratio) during progressive heating, initially rising in the early stages of tar formation (<430 °C) to a maximum of 1.24, then gradually decreasing to a minimum of 0.64 at 550 °C.     

Experimental and numerical modelling of the fluid flow in the continuous casting of steel

This article gives an overview of recent research activities with respect to the mold flow in the continuous casting of steel in presence of DC magnetic fields. The magnetic fields appear to be an attractive tool for controlling the melt flow in a contactless way. Various kinds of magnetic systems are already in operation in industrial steel casting, but the actual impact on the melt flow has not been sufficiently verified by experimental studies. The rapid development of innovative diagnostic techniques in low-melting liquid metals over the last two decades enables new possibilities for systematic flow measurements in liquid metal model experiments. A new research program was initiated at HZDR comprising three experimental facilities providing a LIquid Metal Model for continuous CASTing of steel (LIMMCAST). The facilities operate in a temperature range from room temperature up to 400^°C using the low-melting alloys GaInSn and SnBi, respectively. The experimental program is focused on quantitative flow measurements in the mold, the submerged entry nozzle and the tundish. Local potential probes, Ultrasonic Doppler Velocimetry (UDV) and Contactless Inductive Flow Tomography (CIFT) are employed to measure the melt flow. The behavior of two-phase flows in case of argon injection is investigated by means of the Mutual Inductance Tomography (MIT) and X-ray radioscopy. The experimental results provide a substantial data basis for the validation of related numerical simulations. Numerical calculations were performed with the software package ANSYS-CFX with an implemented RANS-SST turbulence model. The non-isotropic nature of MHD turbulence was taken into account by specific modifications of the turbulence model. First results of the LIMMCAST program reveal important findings such as the peculiar, unexpected phenomenon that the application of a DC magnetic field may excite non-steady, non-isotropic large-scale flow oscillations in the mold. Another important result of our study is that electrical boundary conditions, namely the wall conductivity ratio, have a serious influence on the mold flow while it is exposed to an external magnetic field.     

Resourceful synthesis of pyrazolo[1,5-a]pyrimidines under ultrasound irradiation

Pyrazolo[1,5-a]pyrimidines were synthesized via the ultrasonic sonochemical method using the cyclocondensation reaction of 4-alkoxy-1,1,1-trifluoro-3-alken-2-ones [CF₃C(O)CH = C(R)(OMe) – where R = Me, Bu, i-Bu, Ph, 4-Me–C₆H₄, 4-F–C₆H₄, 4-Cl–C₆H₄, 4-Br–C₆H₄, naphth-2-yl and biphen-4-yl] – with 3-amino-5-methyl-1H-pyrazole in the presence of EtOH for 5 min. This methodology has several advantages, for example, it is a simple procedure, it has an easy work-up, mild conditions, short reaction times (5 min) and produces satisfactory yields (61–98%).     

An experimental study of the unsteady vortex structures in the wake of a root-fixed flapping wing

An experimental study was conducted to characterize the evolution of the unsteady vortex structures in the wake of a root-fixed flapping wing with the wing size, stroke amplitude, and flapping frequency within the range of insect characteristics for the development of novel insect-sized nano-air-vehicles (NAVs). The experiments were conducted in a low-speed wing tunnel with a miniaturized piezoelectric wing (i.e., chord length, C = 12.7 mm) flapping at a frequency of 60 Hz (i.e., f = 60 Hz). The non-dimensional parameters of the flapping wing are chord Reynolds number of Re = 1,200, reduced frequency of k = 3.5, and non-dimensional flapping amplitude at wingtip h = A/C = 1.35. The corresponding Strouhal number (Str) is 0.33, which is well within the optimal range of 0.2 < Str < 0.4 used by flying insects and birds and swimming fishes for locomotion. A digital particle image velocimetry (PIV) system was used to achieve phased-locked and time-averaged flow field measurements to quantify the transient behavior of the wake vortices in relation to the positions of the flapping wing during the upstroke and down stroke flapping cycles. The characteristics of the wake vortex structures in the chordwise cross planes at different wingspan locations were compared quantitatively to elucidate underlying physics for a better understanding of the unsteady aerodynamics of flapping flight and to explore/optimize design paradigms for the development of novel insect-sized, flapping-wing-based NAVs.     

An identity between the determinant and the permanent of Hessenberg-type matrices

In this short note we provide an extension of the notion of Hessenberg matrix and observe an identity between the determinant and the permanent of such matrices. The celebrated identity due to Gibson involving Hessenberg matrices is consequently generalized.     

On a conjecture of Murty and Simon on diameter 2-critical graphs

A graph G is diameter 2-critical if its diameter is two, and the deletion of any edge increases the diameter. Murty and Simon conjectured that the number of edges in a diameter 2-critical graph of order n is at most n²/4 and that the extremal graphs are complete bipartite graphs with equal size partite sets. We use an association with total domination to prove the conjecture for the graphs whose complements have diameter three.     

Existence and scattering theory for Boussinesq type equations with singular data

We study the initial value problem for the generalized Boussinesq equation and prove existence of local and global solutions with singular initial data in weak-Lp spaces. Our class of initial data for global existence is larger than that of Cho and Ozawa (2007) [7]. Long time behavior results are obtained and a scattering theory is proved in that framework. With more structure, we show Sobolev H¹ and Lorentz-type L(p,q) regularity properties for the obtained solutions. The approach employed is unified for all dimensions n?1.