Hydrodynamics of gas-solid fluidization of a homogeneous ternary mixture in a conical bed： Prediction of bed expansion and bed fluctuation ratios

Hydrodynamic characteristics of fluidization in a conical or tapered bed differ from those in a columnar bed because the superficial velocity in the bed varies in the axial direction. Fixed and fluidized regions could coexist and sharp variations in pressure drop could occur, thereby giving rise to a noticeable pressure drop-flow rate hysteresis loop under incipient fluidization conditions. To explore these unique properties, several experiments were carried out using homogeneous, well-mixed, ternary mixtures with three dif- ferent particle sizes at varying composition in gas-solid conical fluidized beds with varying cone angles. The hydrodynamic characteristics determined include the minimum fluidization velocity, bed fluctuation, and bed expansion ratios. The dependence of these quantities on average particle diameter, mass fraction of the fines in the mixture, initial static bed height, and cone angle is discussed. Based on dimensional analysis and factorial design, correlations are developed using the system parameters, i.e. geometry of the bed （cone angle）, particle diameter, initial static bed height, density of the solid, and superficial velocity of the fluidizing medium. Experimental values of minimum fluidization velocity, bed fluctuation, and bed expansion ratios were found to agree well with the developed correlations.     

Eine neue Reaktion auf Cholesterin

Ohne Zusammenfassung     

Stereoselective,solid phase-based synthesis of trans 3-alkyl-substituted β-lactams as analogues of cholesterol absorption inhibitors

A straightforward solid phase-based strategy for the rapid generation of two small libraries of trans 3-alkyl-substituted β-lactams is described. For the glycine-derived library, a controlled excess of nonactivated acid chlorides was used to prevent oxazinone formation. The second library involved the attachment of Fmoc-protected p-aminophenol to Wang resin for the preparation of structurally-closed analogues of known cholesterol absorption inhibitors. This strategy allowed us to introduce diversity in the three variable positions of the β-lactam ring.     

Closed range positive operators on Banach spaces

A bounded positive operator on a Hilbert space has closed range if and only if the operator and its square root have common ranges. We give an extension of this result for positive operators acting on reflexive Banach spaces. Some other results concerning positive operators on Hilbert spaces are carried over to this general case.     

Electrochemical Characterization and Quantification of the Strong Antioxidant and Antitumor Agent Pomiferin

The electrochemical behavior of pomiferin, a natural isoflavone with significant antioxidant, antidiabetic and antitumor properties, is reported here for the first time at a glassy carbon electrode (GCE). In order to understand the redox processes of this compound, its response was compared with the nonantioxidant isoflavone osajin. Based on cyclic and square‐wave voltammetric methods it was observed that pomiferin presents a quasireversible anodic peak, which was attributed to the oxidation of the catechol group, and that is strongly influenced by pH. This anodic process yields a well‐defined DPV response, which can be used for the analytical determination of this potential pharmotherapeutic isoflavone.     

Synthesis and electronic properties of terthienyls β-substituted by (thienyl)cyanovinylene groups

Terthienyls functionalized at their two outer β,β′-positions by 2- and 3-(thienyl)cyanovinyl groups have been synthesized by basic condensation. The analysis of their electronic properties by UV-vis spectroscopy and cyclic voltammetry shows that the mode of derivatization affects essentially the LUMO level of the conjugated system.     

Evidence for oxidative stress in the developing cerebellum of the rat after chronic mild carbon monoxide exposure (0.0025% in air)

Background  

The present study was designed to test the hypothesis that chronic very mild prenatal carbon monoxide (CO) exposure (25 parts per million) subverts the normal development of the rat cerebellar cortex. Studies at this chronic low CO exposure over the earliest periods of mammalian development have not been performed to date. Pregnant rats were exposed chronically to CO from gestational day E5 to E20. In the postnatal period, rat pups were grouped as follows: Group A: prenatal exposure to CO only; group B: prenatal exposure to CO then exposed to CO from postnatal day 5 (P5) to P20; group C: postnatal exposure only, from P5 to P20, and group D, controls (air without CO). At P20, immunocytochemical analyses of oxidative stress markers, and structural and functional proteins were assessed in the cerebellar cortex of the four groups. Quantitative real time PCR assays were performed for inducible (iNOS), neuronal (nNOS), and endothelial (eNOS) nitric oxide synthases.     

Voltammetric method for ultra-trace determination of total mercury and toxic metals in vegetables. Comparison with spectroscopy

A new procedure for the determination of mercury(II), copper(II), lead(II), cadmium(II) and zinc(II) traces in food matrices by square wave anodic stripping voltammetry and standard addition method is proposed. A rapid, inexpensive and multi-analyte analytical method suitable for food safety control is provided. Comestible vegetables were chosen as samples. A two-step, sequential determination was defined, employing two working electrodes: a gold electrode (GE) for mercury(II) and copper(II), and subsequently a hanging mercury drop electrode (HMDE) for copper(II), lead(II), cadmium(II) and zinc(II). No sample pre-treatment was needed. Spinach leaves, tomato leaves and apple leaves were employed as standard reference materials to optimize and defined the analytical procedure. The new method shows good selectivity, sensitivity, detectability and accuracy. A critical comparison with spectroscopic measurements is discussed. Spinach, lettuce and tomato samples sold on the market were analysed as real samples. Lead(II) and cadmium(II) concentration exceeded the relevant legal limits.      

Are Mobility and COVID-19 Related? A Dynamic Analysis for Portuguese Districts

In this research work, we propose to assess the dynamic correlation between different mobility indices, measured on a daily basis, and the new cases of COVID-19 in the different Portuguese districts. The analysis is based on global correlation measures, which capture linear and non-linear relationships in time series, in a robust and dynamic way, in a period without significant changes of non-pharmacological measures. The results show that mobility in retail and recreation, grocery and pharmacy, and public transport shows a higher correlation with new COVID-19 cases than mobility in parks, workplaces or residences. It should also be noted that this relationship is lower in districts with lower population density, which leads to the need for differentiated confinement policies in order to minimize the impacts of a terrible economic and social crisis.     

Bismuth modified carbon-based electrodes for the determination of selected neonicotinoid insecticides

Two types of bismuth modified electrodes, a bismuth-film modified glassy carbon (BiF-GCE) and a bismuth bulk modified carbon paste, were applied for the determination of selected nitroguanidine neonicotinoid insecticides. The method based on an ex situ prepared BiF-GCE operated in the differential pulse voltammetric (DPV) mode was applied to determine clothianidin in the concentration range from 2.5 to 23 μg cm?3 with a relative standard deviation (RSD) not exceeding 1.5%. The tricresyl phosphate-based carbon paste electrodes (TCP-CPEs), bulk modified with 5 and 20 w/w% of bismuth, showed a different analytical performance in the determination of imidacloprid, regarding the peak shape, potential window, and noise level. The TCP-CPE with 5% Bi was advantageous, and the developed DPV method based on it allowed the determination in the concentration range from 1.7 to 60 μg cm?3 with an RSD of 2.4%. To get a deeper insight into the morphology of the bismuth-based sensor surfaces, scanning electron microscopic measurements were performed of both the surface film and the bulk modified electrodes.