Kinds Of Reactions Research Articles

Crosslinked polybenzimidazole via a Diels–Alder reaction for proton conducting membranes

The crosslinking of polybenzimidazole (PBI) is a potential strategy to improve the mechanical properties and dimensional stability of acid-doped membranes, as well as to retain additives in the membranes. An effective method to prepare crosslinked PBI with a well-defined structure via a Diels–Alder reaction between vinylbenzyl functionalized PBI (PBI–VB) and α,α′-difurfuryloxy-p-xylene (DFX) is proposed. The chemical structure of PBI–VB is confirmed by FTIR and 1H NMR. The model reaction of styrene and DFX is employed to clarify the crosslinking reaction of PBI and DFX. During the crosslinking process, three kinds of chemical reaction may happen. The first is a Diels–Alder reaction of DFX with the vinyl groups of PBI–VB. The second is the self-polymerization of vinyl groups. The third is the grafting of difuran groups via a Diels–Alder reaction. The first two reactions contribute the most to the crosslinking of the PBI membrane. With the addition of DFX, there is competition between these two kinds of crosslinking reactions. When the feed ratio of DFX is below 20%, the tensile strength of the crosslinked membranes increases with increasing content of DFX. The crosslinking of the membrane is mainly a results of Diels–Alder reactions. When the feed ratio of DFX exceeds 20%, the tensile strength decreases slightly. Besides the crosslinking via Diels–Alder reactions, the crosslinking of the membrane is also contributed by the self-polymerization of vinyl groups and the grafting of difuran groups. The crosslinked PBI membrane exhibits improved mechanical strength, higher physical and chemical stability, as well as higher phosphoric acid (PA) retention ability. After doping with PA, the crosslinked membrane exhibits good proton conductivity over a temperature range of 60 to 180 °C.

Reactivity for boryl(phosphino)carbenyl carbene analogues with group 14 elements (C, Si, Ge, Sb, and Pb) as a heteroatom: a theoretical study

The potential energy surfaces for the chemical reactions of group 14 carbenes have been studied using density functional theory (B3LYP/LANL2DZ). Five boryl(phosphino)-based carbene (B-Ë-P) species, where Ë = C, Si, Ge, Sn, and Pb, have been chosen as model reactants in this work. Also, four kinds of chemical reactions; intramolecular 1,2-migration, water insertion, alkene cycloaddition, and intermolecular dimerization, have been used to study the chemical reactivities of these group 14 carbenes. The present theoretical investigations suggest that the relative carbenic reactivity decreases in the order C > Si > Ge > Sn > Pb. That is, the heavier the group 14 atom (E), the more stable is the boryl(phosphino)-based B-Ë-P species towards chemical reactions. Our theoretical findings thus demonstrate that all boryl(phosphino)-based carbenes are isolable at room temperature because they are quite inert to chemical reactions, except that they are also moisture-sensitive molecules. Furthermore, the singlet-triplet energy splitting of the B-Ë-P, as described in the configuration mixing model attributed to the work of Pross and Shaik, can serve as a diagnostic tool for a better understanding and predicting of their chemical reactivities, kinetically and thermodynamically. The results obtained allow a number of predictions to be made.

The Rabe amination after a century: direct addition of N-heterocycles to carbonyl compounds

A catalytic version of the Rabe electrophilic amination is presented. This kind of reaction was originally employed in 1918 in a key step for the conversion of quinotoxine to quinine. Ketones and α-substituted aldehydes give the corresponding α-aminated carbonyl compounds in moderate yield. α,α-Unsubstituted aldehydes give rise to amino ketones via a novel rearrangement.

Are Radiopharmaceuticals Safe? The Case of FDG-18

Too many false-positive and adverse reactions related to radiopharmaceuticals take place every day in hospitals routine, but many are not reported or even sensed. Information concerning these kind of reactions is not abundant and nuclear medicine staff is usually overwhelmed by this information. As every healthcare intervention carries some risk of harm, clinical decision making needs to be supported by a systematic assessment of the balance of benefit to harm. A systematic review that considers only the favorable outcomes of an intervention, without also assessing the adverse effects and false positives reactions, can mislead by introducing a bias favoring the intervention that in the case o radiopharmaceuticals may to render a important factor related not even to the quality of the drug but even to the quality of the diagnosis. The results suggest a logical framework to make decisions in reviews that incorporate false positive and adverse reactions. Also, was explored situations where a comprehensive investigation of false positive reactions and adverse effects was warranted and suggest strategies to identify practicable and clinically useful outcomes. We concluded that there is the necessity to include and to recognize how strategic choices made in the review process determine what harms are found, and how the findings may affect clinical decisions. Researchers undertaking a systematic review that incorporates false positive reaction and adverse reactions must understand the rationale for the suggested methods and be able to implement them in their review. Beyond a world effort should be made to report as many cases of false positive and adverse reactions with radiopharmaceuticals as possible. Only if this is done a complete picture of false positive reactions with radiopharmaceuticals can be drawn.

The Different Clinical Expressions of the Aspergillus/Host Interactions in Humans

Aspergillus is very ubiquitous. It is a highly aerobic fungus and found as mold on surfaces. It spreads most commonly through spores in the air that are not detected with the naked eye. These spores get into the respiratory tract where they colonize and often cause different kinds of reactions. Human beings respond to these inhalations in several ways depending upon the status of one’s immune system. In fact some of these responses are diametrically opposed from each other to the point that we decided to report our experience of the different expressions of the Aspergillus/human interaction in a spectral fashion. We have represented these findings in a parabola pictured below where to the right of the parabola from 0 to 90, we included the interactions of Aspergillus with an immune deficient host, and to the left of the parabola from 90 to 180, we considered the interactions of Aspergillus with a host of a hyperergic immune system.

A simple and sensitive method for lipoprotein and lipids profiles analysis of individual micro-liter scale serum samples

A simple and sensitive method to determine lipoprotein and lipids profiles in micro-liter scale individual serum sample is not presently available. Traditional lipoprotein separation techniques either by ultra-centrifugation or by liquid chromatography methods have their disadvantages in both lipoprotein separation and lipids component quantification. In this study we used small volume needing size-exclusion fast protein liquid chromatography to separate different lipoprotein subclasses in 50μL serum. And lipids contents, such as cholesterol, cholesterol ester and triacylglycerol, were measured by using two different fluorescence-based lipid detection methods. With this method, very low density lipoprotein, low density lipoprotein and high density lipoprotein could be easily separated, and follow-up lipid detection was completed by simple kinds of reactions. Serum lipoprotein and lipids profiling from C57BL/6 mice (n=5) and human (n=5) were analyzed. The elution profiles of five individuals were highly reproducible, and there were lipoprotein and lipids distribution variations between C57BL/6 mice and human beings. In conclusion, this method which combined small volume needing size-exclusion fast protein liquid chromatography and fluorescence-based lipids measurement, provided a simple, efficient, integrity and reproducible procedure for determining serum lipoprotein and lipids profiles in micro-liter scale levels. It becomes possible that determination of lipoprotein profiles and gaining information of lipids in different lipoproteins can be accomplished simultaneously.

Studies on the Coordination Reactions of Polyphenols and Vanadium (IV) Using pH-Potentiometry

Protonation constants of pyrocatechol, pyrogallol and gallic acid, and stability constants, thermodynamic properties of their complexes with tetravalent vanadium VO2+ have been calculated by using pH-potentiometry at different temperatures and ionic strength of 0.1mol•L-1NaCl. The results indicated protonation constants and stability constants decrease with increasing temperature. Higher temperature is unfavorable to the complexation reactions. This kind of reaction is exothermic reaction that was spontaneous. Compared with all thermodynamic properties, the enthalpy change is the driving force for the reaction.

A study of chemical reactions in coarse-grained simulations

We introduce a reaction model for use in coarse-grained simulations to study the chemical reactions in polymer systems at mesoscopic level. In this model, we employ an idea of reaction probability in control of the whole process of chemical reactions. This model has been successfully applied to the studies of surface initiated polymerization process and the network structure formation of typical epoxy resin systems. It can be further modified to study different kinds of chemical reactions at mesoscopic scale.

Theoretical investigations of the reactivities of four-membered N-heterocyclic carbene analogues of the group 13 elements

The potential energy surfaces for the chemical reactions of four-membered N-heterocyclic group 13 heavy carbeneoid species have been studied using density functional theory (Becke, 3-parameter, Lee-Yang-Parr (B3LYP)/Los Alamos National Laboratory 2-Double-Zeta (LANL2DZ)). Five four-membered group 13 heavy carbeneoid species, iPr2NC(NAr)2E:, where E ¼ B, Al, Ga, In, and Tl, have been chosen as model reactants in this work. Also, three kinds of chemical reactions, CAH bond insertion, alkene cycloaddition, and dimerization, have been used to study the chemical reactivities of these group 13 fourmembered N-heterocyclic carbeneoid species. In principle, our present theoretical work predicts that the larger the ffNEN bond angle of the four-membered group 13 iPr2NC(NAr)2E: species, the smaller the singlet–triplet splitting, the lower the activation barrier, and, in turn, the more rapid its chemical reactions to various chemical species. Moreover, our theoretical investigations suggest that the relative carbenic reactivity decreases in the following order: B > Al > Ga > In > Tl. That is, the heavier the group 13 atom (E), the more stable its fourmembered carbeneoid toward chemical reactions is. As a result, our computations predict that the four-membered heavy group 13 iPr2NC(NAr)2E: species (E ¼ Al, Ga, In, and Tl) should be both kinetically and thermodynamically stable, and can be readily synthesized and isolated at room temperature. Furthermore, the singlet–triplet energy splitting of the four-membered group 13 iPr2NC(NAr)2E: species, as described in the configuration mixing model attributed to the work of Pross and Shaik, can be used as a diagnostic tool to predict their reactivities. The results obtained allow a number of predictions to be made.

Calculation of the Complete Sets of Nuclear Data for n + 32,34S Below 20 MeV

Based on the available experimental data for total cross section, nonelastic cross section, and elastic scattering angular distribution of n + 32,natS, a set of neutron optical potential parameters is obtained. The complete sets of nuclear data for n + 32,34S < 20 MeV are calculated. These sets include cross sections, angular distributions of elastic scattering, energy spectra and/or double-differential cross sections of all emitted particles, and gamma production data (production cross sections and multiplicity, energy spectra) in all kinds of reactions. The calculated results are generally in good accordance with experimental data and are compared with JENDL-3.3.

Mechanisms for the Reaction of Water, Butadiene, and Palladium Complex with 1,2-Dimetallacyclohexene (R2M═MR2, M = C, Si, Ge, Sn, Pb). A Theoretical Study

The potential energy surfaces for the chemical reactions of six-membered cyclic dimetallaalkenes containing the M═M doubly bonded species Rea-M═M, where M = C, Si, Ge, Sn, and Pb, were studied, using the density functional theory (B3LYP/LANL2DZ) method. Three kinds of chemical reaction, water addition, [2+4] Diels–Alder cycloaddition, and palladium complexation, were also used to study the chemical reactivity of these group 14 Rea-M═M molecules. In principle, our present theoretical work suggests that the smaller the singlet–triplet splitting of the Rea-M═M, the lower are its activation barriers and, in turn, the more rapid are its chemical reactions with other molecules. These theoretical investigations indicate that the relative chemical reactivity increases in the order Rea-M═M-C < Rea-M═M-Si < Rea-M═M-Ge < Rea-M═M-Sn < Rea-M═M-Pb. That is, the smaller the atomic weight of the group 14 atom (M), the more stable is its Rea-M═M to chemical reaction. As a result, we predict that the group 14 Rea-M═M (M = ...

Key aroma compounds in Shanxi aged tartary buckwheat vinegar and changes during its thermal processing

ABSTRACTShanxi aged vinegar differs from other vinegars in that it has a unique thermal process (6 days at 85°C) which creates its typical flavour. The present study evaluated the key aroma compounds of Shanxi aged vinegar made from tartary buckwheat by gas chromatography–olfactometry–mass spectrometry. The influence of the thermal processing on product aroma was also studied. A total of 45 compounds were detected of which 24 were correctly identified while 21 were tentatively identified: the remaining six were unknown. Of the 45 compounds detected, 13 have not been previously reported in other vinegars. Most of the aroma compounds identified increased significantly during the first 3 days of heating and then decreased from the fourth day onwards. The changes may have resulted from different kinds of reactions, such as the Maillard reaction and other associated reactions such as degradation of amino acids. This study would be helpful for optimizing the processing conditions of Shanxi aged vinegar. Copyright © 2011 John Wiley &amp; Sons, Ltd.

3-Dimensional optical frequency domain imaging for the evaluation of primary percutaneous coronary intervention in ST-segment elevation myocardial infarction

occasion she was also found affected by allergy to iodinated contrast media”, but the paper provides no information concerning the kind of reaction (clinical features [4]), the severity, the number of reactions, the time of onset after the contrast medium has been injected, the results of an allergological work-out (was it true allergic reaction or a non-allergic reaction? [5]), possible risk factors (e.g. allergic asthma [6]) and last but not least the time point of the last CM-reaction is also missing. Especially, the last fact is of great importance for this case. A CM-hypersensitivity reaction that occurred more than 7 days before the onset of the Kounis syndrome seems to be an isolated reaction without causative connection to a contrast medium injection. This assumption is further supported by the fact that the authorswrote: “... chemotherapy with cisplatin and cyclophosphamide. After the second administration of these drugs she developed intense chest pain...” [1]. This is a clear hint for the assumption that the presented patient could have a hypersensitivity to chemotherapy that could be also related to the Kounis syndrome. In conclusion, cardiac complaint after iodinated contrast medium injection is currently an unsolved problem, and “allergic angina” could be the reason for it in some patients. Detailed clinical information on allergic reactions in general or hypersensitivity reactions to iodinated contrast media in particular are necessary to clearly relate reactions to suspected compounds. Furthermore, to facilitate a safe use of iodinated contrast media in patients with previous reactions detailed clinical information is very important. The authors of this manuscript have certified that they comply with the Principles of Ethical Publishing in the International Journal of Cardiology (Shewan and Coats 2010;144:1–2).

A study of reaction rates of (n, f ) , (n, $ \gamma$ ) and (n, 2n) reactions in natU and 232Th by the neutron fluence produced in the graphite set-up (GAMMA-3) irradiated by 2.33 GeV deuteron beam

Spallation neutrons produced in the collision of a 2.33GeV deuteron beam with a large lead target are moderated by a thick graphite block surrounding the target and used to activate the radioactive samples of natU and Th put at three different positions, identified as holes “a”, “b” and “c” in the graphite block. Rates of the (n, f), (n, \( \gamma\) and (n, 2n) reactions in the two samples are determined using the gamma spectrometry. The ratios of the experimental reaction rates, R (n, 2n)/R (n, f), for 232Th and natU are estimated in order to understand the role of the (n, x n) kind of reactions in Accelerator-Driven Sub-critical Systems. For the Th-sample, the ratio is ∼ 54 (10)% in the case of hole “a” and ∼ 95 (57)% in the case of hole “b” compared to 1.73(20)% for hole “a” and 0.710(9)% for hole “b” in the case of the natU sample. Also the ratio of fission rates in uranium to thorium, natU (n, f)/ 232Th (n, f), is ∼ 11.2 (17) in the case of hole “a” and 26.8(85) in hole “b”. Similarly, the ratio 238U (n, 2n)/ 232Th (n, 2n) is 0.36(4) for hole “a” and 0.20(10) for hole “b” showing that 232Th is more prone to the (n, x n) reaction than 238U . All the experimental reaction rates are compared with the simulated ones by generating neutron fluxes at the three holes from MCNPX 2.6c and making use of the LA150 library of cross-sections. The experimental and calculated reaction rates of all the three reactions are in reasonably good agreement. The transmutation power, Pnorm as well as Pnorm/Pbeam of the set-up is estimated using the reaction rates of the (n, \( \gamma\) and (n, 2n) reactions for both the samples in the three holes and compared with some of the results of the “Energy plus Transmutation” set-up and TARC experiment.

DFT Study of Mechanism of Extraction Reaction Between Germylene Carbene (H2Ge=C:) and Its Derivatives and Ethylene Oxide

The mechanism of the oxide extraction reaction between singlet germylene carbene and its derivatives X2Ge=C: (X=H, F, Cl, CH3) and ethylene oxide has been investigated with B3LYP/6-311G(d,p) method. The results show that this kind of reaction has similar mechanism, the shift of 2p lone electron pair of O in ethylene oxide to the 2p unoccupied orbital of C in X2Ge=C: gives a p→p donor-acceptor bond, thereby leading to the formation of intermediate. As the p→p donor-acceptor bond continues to strengthen, that is the C—O bond continues to shorten, the intermediate generates product (P+C2H4) via transition state. It is the substituent electronegativity that mainly affect the extraction reactions. When the substituent electronegativity is greater, the energy barrier is lower, and the reaction rate is greater.

Diversity of wild legumes and associated rhizobia in the coastal regions of Andaman

The present study was undertaken to uncover the diversity of root nodulating Rhizobium and associated wild legumes growing in coastal regions of Bay Islands. The exploration of coastal areas of South Andaman showed occurrence of 5 unique wild legumes and in that two viz., Vigna marina and Mucuna monosperma were found to grow in seashore areas. The earlier had abundant canopy and pods even under submergence of sea water during high tide and the second one was capable of growing in the backwater of sea. Results show that the five Rhizobum isolates associated with these wild legumes exhibit similar kind of reaction to various biochemical test with few exceptions. Among the isolates WL1 and WL12 associated with V. marina and M. monosperma, respectively showed high salt tolerance and that grew up to 1000mM NaCl in vitro, which is unique finding.

Mn(III)-Catalyzed Synthesis of Pyrroles from Vinyl Azides and β-Keto Acids

Reported is the synthesis of highly substituted pyrroles through a Mn(III)-catalyzed radical-based cycloaddition. The proposed mechanism proceeds by Mn(III)-catalyzed decarboxylation to generate an α-carbonyl radical, which then undergoes reaction with the vinyl azide, forming a new carbon-carbon bond and ejecting N2 to generate an iminyl radical. This iminyl radical then undergoes a Mn(II)-driven condensation with the remaining carbonyl to generate the desired products and regenerate the Mn(III) catalyst. Although this mechanism is presented without evidence (e.g. no indication of byproducts), each of the steps is entirely reasonable and it represents a good working hypothesis for the further utility of vinyl azides in this kind of reaction.

Study on the Microstructure and Behaviour of Unburnt Pulverized Coal in BF

Using the sampling device for unburnt pulverized coal(UPC) before the tuyere and combining the UPC microscopic morphology which are in BF dust, there is a detailed study of the combustion process of coal before the tuyere. Analyze the behavior of the UPC for effective use and ineffective use in BF, and then get the conclusion, that it can relax the size of the PCI appropriately, and make it to produce proper UPC, which can participate in all kinds of reaction in BF, so that it can replace a part of coke; but in the slag and dust the UPC is hoped not too much.

A computational study of the reactivities of four-membered heavy carbene systems

The potential energy surfaces for the chemical reactions of four-membered N-heterocyclic group 14 heavy carbene species have been studied using density functional theory (B3LYP/LANL2DZ). Five four-membered group 14 heavy carbene species, (i-Pr)(2) NP(NR)(2) E:, in which E = C, Si, Ge, Sn, and Pb, were chosen as the model reactants in this work. Also, four kinds of chemical reactions, C-H bond insertion, water addition, alkene cycloaddition, and dimerization, have been used to study the chemical reactivities of these group 14 four-membered N-heterocyclic carbene species. Basically, our present theoretical work predicts that the larger the ∠NEN bond angle of the four-membered group 14 heavy carbene species, the smaller the singlet-triplet splitting, the lower the activation barrier, and, in turn, the more rapid, its chemical reactions to various chemical species. Moreover, our theoretical investigations suggest that the relative carbenic reactivity decreases in the order: C > Si > Ge > Sn > Pb. That is, the heavier the group 14 atom (E), the more stable is its four-membered carbene toward chemical reactions. As a result, our results predict that the four-membered group 14 heavy carbene species (E = Si, Ge, Sn, and Pb) should be more kinetically stable than the observed carbene species and, thus, can be also readily synthesized and isolated at room temperature. Furthermore, the singlet-triplet energy splitting of the four-membered group 14 carbene species, as described in the configuration mixing model attributed to the work of Pross and Shaik, can be used as a diagnostic tool to predict their reactivities. The results obtained allow a number of predictions to be made.

Il grande dittatore di Charlie Chaplin: i settant'anni di un film tra storia e critica

The great dictator is the first Charlie Chaplin’s film which doesn’t belong to the silent movie age and is also the only one work with political and international reflections about the years of the second world war. For these reasons it’s really very important to see how it was born, when it was represented all over the world and, of course, which kind of reactions it produced in different countries. We tried, as well, to give an idea of how quickly comedy get old and how it has been used for political goals as it can be seen by the words of authors who appreciated and criticized The great dictator.