ABSTRACT
The contemporary removal of organic pollutants from aqueous solution and electricity generation is studied in the present work by means of an experimental device resulting from the combination of a photocatalytic reactor and an electrochemical cell. The proposed system relies on the capability of Cu2+ ions to reduce in the presence of TiO2, (solar) UV radiations and a sacrificial organic agent. In the anodic solution of the combined photoreactor-cell, Cu0 is oxidized to Cu2+ and the latter is reduced again to the lowest oxidation state. The use of different sacrificial agents ranging from formic acid (FA) to glycerol (GLY) to glucose (GLU) is investigated along with the adoption of two different cathodes for the cell, the first based again on the couple Cu2+/Cu0 and the second on the couple O2/H2O.
Subject(s)
Bioelectric Energy Sources , Photochemistry/methods , Waste Disposal, Fluid/methods , Copper/chemistry , Formates/chemistry , Glucose/chemistry , Glycerol/chemistry , Oxidation-Reduction , Titanium/chemistry , Ultraviolet RaysABSTRACT
Runaway phenomena and thermal explosions can originate during the nitration of salicylic acid by means of a nitric acid/acetic acid mixture when the thermal control is lost, mainly as a result of the formation and thermal decomposition of picric acid. The prediction of the behaviour of this system is thus of great importance in view of possible industrial applications and the need to avoid the occurrence of unwanted dangerous events. During a previous investigation a model was developed to simulate its behaviour when the starting concentration of the substrate is too low, thus, preventing the precipitation of poor soluble intermediates. In this work this model is extended to deal with more concentrated systems even in case of a solid phase separating during the process. To this purpose the previously assessed dependence of the solubility of 3-nitro and 5-nitrosalicylic acids upon temperature and nitric acid concentration is included in the model. It is assumed that when 3-nitro and 5-nitrosalicylic acids are partially suspended in the reacting medium a kinetic regime of "dissolution with reaction" is established; that is, the redissolution of these species is a fast process compared to the successive nitration to give dinitroderivatives. Good results are obtained in the comparison of the experimental data with those calculated both in isoperibolic and adiabatic conditions when the revised model is used.
Subject(s)
Acetic Acid/chemistry , Models, Chemical , Nitric Acid/chemistry , Salicylic Acid/chemistry , Reproducibility of Results , Temperature , ThermodynamicsABSTRACT
The nitration process of salicylic acid for the production of the important intermediate 5-nitrosalicylic acid is studied from thermokinetic and safety points of view. Investigations carried out by considering, as process deviations, the loss of the thermal control point out the possibility of runaway phenomena due to the occurrence of polynitration reactions. Isothermal experiments are carried out in various conditions to assess the involved reaction network and reaction kinetics.
Subject(s)
Acetic Acid/chemistry , Nitrates/chemistry , Nitric Acid/chemistry , Salicylic Acid/chemistry , Kinetics , Nitrophenols/chemistry , Safety , TemperatureABSTRACT
The present work aims at assessing both thermodynamic and kinetic parameters of the esterification process of the (S)-carnitine, using calorimetric techniques. The use of the system acetic anhydride/nitric acid/acetic acid as esterifying agent and the explosive behaviour of nitric esters lead to safety considerations that have been investigated by hypothesizing some common process deviations. In particular, it has been investigated in adiabatic conditions both the batch addition of acetic anhydride and the effect of an initial temperature higher than those required by the process.
Subject(s)
Acetic Acid/chemistry , Acetic Anhydrides/chemistry , Carnitine/analogs & derivatives , Carnitine/chemistry , Nitrates/chemical synthesis , Safety Management/methods , Calorimetry/methods , Esterification , Explosions/prevention & control , Kinetics , Models, Chemical , Nitric Acid/chemistryABSTRACT
The ozonation of pyruvic acid (2-ketopropionic acid) in aqueous solutions, catalyzed by Mn(II) and Mn(IV) ions, has been studied at three different pH values (pH = 1.1, 2.0 and 3.0). A mathematical model of the unsteady operation of the experimental reactor has been developed, which takes into account the reactions occurring in the liquid phase and the ozone mass transfer from the gas bubbles. Those reactions have been described with two alternative kinetic models, both made out of four elementary steps. The two kinetic models correlate the experimental data with a fair accuracy, respectively at the lowest and at the highest pH examined. In particular, at pH = 3.0, the ozonation results are inhibited by the acetate ions produced by the reaction itself. This effect has been correctly described in the terms of a complex formed with the low oxidation-state manganese, which successively reacts with the dissolved ozone.
Subject(s)
Manganese , Ozone/chemistry , Pyruvic Acid/chemistry , Hydrogen-Ion Concentration , Kinetics , Models, Chemical , Pyruvic Acid/isolation & purification , Solutions , Water Purification/methodsABSTRACT
The bis-dimethylaminoethyl derivative of quindoline (10H-indolo[3,2-b]quinoline), an alkaloid from the West African shrub Cryptolepis sanguinolenta, has been synthesised. This has been shown to have modest cytotoxicity, as well as inhibitory activity against the telomerase enzyme. It is hypothesised that the latter activity is due to stabilisation of an intermediate guanine-quadruplex complex, in accordance with computer modelling.
Subject(s)
Quinolines , Telomerase/antagonists & inhibitors , Aminoquinolines/chemical synthesis , Aminoquinolines/pharmacology , Antineoplastic Agents/chemical synthesis , Antineoplastic Agents/pharmacology , Cell Death/drug effects , Humans , Indoles/chemical synthesis , Indoles/pharmacology , Inhibitory Concentration 50 , Models, Molecular , Reverse Transcriptase Inhibitors/chemical synthesis , Reverse Transcriptase Inhibitors/pharmacology , Tumor Cells, Cultured/drug effectsABSTRACT
Electromechanical nonphysiologic signals caused by the movement of intracardiac metal portions of an endocardial grasping electrode were shown to be "falsely" recycling an implanted pacemaker. The signals were similar in amplitude and slew rate to the ventricular electrogram and were terminated by ending the movement of the two metallic surfaces.
Subject(s)
Arrhythmias, Cardiac/etiology , Pacemaker, Artificial/adverse effects , Atrial Fibrillation/complications , Atrial Fibrillation/therapy , Cardiomegaly/complications , Electrodes/standards , Female , Heart Failure/complications , Humans , Middle Aged , Pacemaker, Artificial/instrumentationABSTRACT
Endocardial electrograms in 77 acute cases (at time of pacemaker implant) and 56 chronic cases (at time of pulse generator replacement, with electrodes in service for at least 6 months) were recorded. The peak-to-peak voltage and rate of rise, or slew rate, were compared acutely and chronically. Both parameters must simultaneously exceed given thresholds to trigger the sensing circuits of implantable pacemakers. The average chronic slew rate was half the average acute value. The maximum slew rate and voltage swing occur during the intrinsic deflection as a virtually straight line segment of the electrogram. The findings are consistent with the predictions of a mathematical model for genesis of the electrogram, and also with a model for explaining acute-to-chronic changes in stimulation current thresholds.
