scholarly journals The rapid generation of isothiocyanates in flow

2013 ◽  
Vol 9 ◽  
pp. 1613-1619 ◽  
Author(s):  
Marcus Baumann ◽  
Ian R Baxendale
Keyword(s):  
Chemical Transformation ◽  
Chemical Reactions ◽  
Direct Conversion ◽  
Wide Range ◽  
Rapid Generation ◽  
Work Up ◽  
Immobilised Reagents

Isothiocyanates are versatile starting materials for a wide range of chemical reactions. However, their high nucleophilic susceptibility means they are best prepared and used immediately. We report here on a flow platform for the fast and efficient formation of isothiocyanates by the direct conversion of easily prepared chloroximes. To expedite this chemistry a flow insert cartridge containing two immobilised reagents is used to affect the chemical transformation which typically eliminates the requirements for any conventional work-up or purification of the reaction stream.

Microwaves: Application in Electron Microscopy

1990 ◽  
Vol 48 (3) ◽  
pp. 140-141
Author(s):  
Anthony S-Y Leong ◽  
David W Gove
Keyword(s):  
Electron Microscopy ◽  
Light Microscopy ◽  
Chemical Reactions ◽  
Electromagnetic Waves ◽  
Tissue Fixation ◽  
Primary Method ◽  
Dipolar Molecules ◽  
Wide Range ◽  
Time Required ◽  
Cryostat Sections

Microwaves (MW) are electromagnetic waves which are commonly generated at a frequency of 2.45 GHz. When dipolar molecules such as water, the polar side chains of proteins and other molecules with an uneven distribution of electrical charge are exposed to such non-ionizing radiation, they oscillate through 180° at a rate of 2,450 million cycles/s. This rapid kinetic movement results in accelerated chemical reactions and produces instantaneous heat. MWs have recently been applied to a wide range of procedures for light microscopy. MWs generated by domestic ovens have been used as a primary method of tissue fixation, it has been applied to the various stages of tissue processing as well as to a wide variety of staining procedures. This use of MWs has not only resulted in drastic reductions in the time required for tissue fixation, processing and staining, but have also produced better cytologic images in cryostat sections, and more importantly, have resulted in better preservation of cellular antigens.

Advances in Triazole Synthesis from Copper-catalyzed Azide-alkyne Cycloadditions (CuAAC) Based on Eco-friendly Procedures

2019 ◽  
Vol 16 (2) ◽  
pp. 244-257 ◽  
Author(s):  
Marcus Vinicius Nora de Souza ◽  
Cristiane França da Costa ◽  
Victor Facchinetti ◽  
Claudia Regina Brandão Gomes ◽  
Paula Mázala Pacheco
Keyword(s):  
Biological Activities ◽  
Reaction Times ◽  
Water Extract ◽  
Fish Bone ◽  
New Drugs ◽  
Bone Powder ◽  
Wide Range ◽  
Recoverable Catalysts ◽  
Egg Shell ◽  
Work Up

Background: 1,2,3-triazoles are an important class of organic compounds and because of their aromatic stability, they are not easily reduced, oxidized or hydrolyzed in acidic and basic environments. Moreover, 1,2,3-triazole derivatives are known by their important biological activities and have drawn considerable attention due to their variety of properties. The synthesis of this nucleus, based on the click chemistry concept, through the 1,3-dipolar addition reaction between azides and alkynes is a well-known procedure. This reaction has a wide range of applications, especially on the development of new drugs. Methods: The most prominent eco-friendly methods for the synthesis of triazoles under microwave irradiation published in articles from 2012-2018 were reviewed. Results: In this review, we cover some of the recent eco-friendly CuAAC procedures for the click synthesis of 1,2,3-triazoles with remarks to new and easily recoverable catalysts, such as rhizobial cyclic β-1,2 glucan; WEB (water extract of banana); biosourced cyclosophoraose (CyS); egg shell powder (ESP); cyclodextrin (β- CD); fish bone powder; nanoparticle-based catalyst, among others. Conclusion: These eco-friendly procedures are a useful tool for the synthesis of 1,2,3-triazoles, providing many advantages on the synthesis of this class, such as shorter reaction times, easier work-up and higher yields when compared to classical procedures. Moreover, these methodologies can be applied to the industrial synthesis of drugs and to other areas.

scholarly journals A General Fitting Function to Estimate Apparent Reaction Orders of Kinetic Profiles

2019 ◽  
Author(s):  
Robert Pollice
Keyword(s):  
Chemical Reactions ◽  
Catalyst Deactivation ◽  
Rapid Development ◽  
Product Inhibition ◽  
Time Profile ◽  
Time Data ◽  
Concentration Time ◽  
Wide Range ◽  
Reaction Orders

The rapid development of analytical methods in recent decades has resulted in a wide range of readily available and accurate reaction-monitoring techniques, which allow for easy determination of high-quality concentration-time data of chemical reactions. However, while the acquisition of kinetic data has become routine in the development of new chemical reactions and the study of their mechanisms, not all the information contained therein is utilized because of a lack of suitable analysis tools which unnecessarily complicates mechanistic studies. Herein, we report on a general method to analyze a single concentration-time profile of chemical reactions and extract information regarding the reaction order with respect to substrates, the presence of multiple kinetic regimes, and the presence of kinetic complexities, such as catalyst deactivation, product inhibition, and substrate decomposition.<br>

Hot-Pressed Barium Sulphate Ceramic Waste Forms for Direct Immobilisation of Medium Level Magnox Waste

1981 ◽  
Vol 6 ◽  
Author(s):  
A. Briggs ◽  
D.V.C. Jones ◽  
G.B. Cole
Keyword(s):  
Hot Pressing ◽  
Open Porosity ◽  
Matrix Material ◽  
Direct Conversion ◽  
Barium Sulphate ◽  
Reduction Factor ◽  
Waste Form ◽  
Internal Surfaces ◽  
Wide Range ◽  
Leaching Behaviour

ABSTRACTA possible method of treatment for Magnox cladding waste is by dissolution in nitric acid and precipitation of barium sulphate-based floc with which radioactive ions are co-precipitated. The floc could then be immobilised in a matrix material such as cement or bitumen to give the waste form, or alternatively can be converted directly into a waste form by hot pressing.This paper describes the direct conversion of barium sulphate floc, containing simulated radwaste, into a synthetic, ceramic version of the natural mineral barite by a hot-pressing route. By variation of the parameters pressure, temperature and time, optimum conditions for consolidation of the floc to > 90% theoretical density on a laboratory scale are found to be 22.5 MPa, 900°C for 10 minutes. Using a pressure of 15 MPa, at 900°C for 30 min., hot-pressed billets of BaSO4 have been made on a 5 kg scale. In going from the Magnox waste to the hot-pressed barium sulphate a volume reduction factor ∼ 18 is achieved. The principal phases in the product are found to be BaSO4 , MgO and Fe3O4, and the degree of consolidation achieved depends on the MgO content.The leaching behaviour of the hot-pressed materials in 100°C, 3 day Soxhlet tests also depends on the MgO content, and on the consequent level of open porosity. If there is porosity accessible to the leach water, MgO at the internal surfaces is converted to Mg(OH)2, which deposits within the pores, and a weight gain is registered in the Soxhlet test. If, however, there is no open porosity, a weight loss occurs, and leach rates ∼ 4 × 10−7 kg/m2/sec are found. In contrast, pure BaSO4, hot-pressed to similar densities, shows no variation in leaching behaviour over a wide range of o en porosities, and gives Soxhlet leach rates ∼ 8 × 10−8 kg/m2/sec.

Rapid generation of Hybrid Biochemical/Mechanical Cues in Heterogeneous Droplets for High-Throughput Screening of Cellular Response

Lab on a Chip ◽  
2021 ◽  
Author(s):  
Xing Zhao ◽  
Gaozhi Ou ◽  
Mengcheng Lei ◽  
Yang Zhang ◽  
Lina Li ◽  
...  
Keyword(s):  
Signaling Pathways ◽  
High Throughput ◽  
High Throughput Screening ◽  
Cellular Response ◽  
Wide Range ◽  
Rapid Generation ◽  
P Cells

Cells in native microenvironment are subjected to varying combinations of biochemical cues and mechanical cues in a wide range. Despite many signaling pathways have been found to be responsive for...

scholarly journals Ultraviolet Irradiation Enhances the Microbicidal Activity of Silver Nanoparticles by Hydroxyl Radicals

2020 ◽  
Vol 21 (9) ◽  
pp. 3204 ◽  
Author(s):  
Shingo Nakamura ◽  
Naoko Ando ◽  
Masahiro Sato ◽  
Masayuki Ishihara
Keyword(s):  
Silver Nanoparticles ◽  
Uv Radiation ◽  
Hydroxyl Radicals ◽  
Healthcare Workers ◽  
Direct Detection ◽  
Ultraviolet A ◽  
Microbicidal Activity ◽  
Wide Range ◽  
Spin Resonance ◽  
Rapid Generation

It is known that silver has microbicidal qualities; even at a low concentration, silver is active against many kinds of bacteria. Silver nanoparticles (AgNPs) have been extensively studied for a wide range of applications. Alternately, the toxicity of silver to human cells is considerably lower than that to bacteria. Recent studies have shown that AgNPs also have antiviral activity. We found that large amounts of hydroxyl radicals—highly reactive molecular species—are generated when AgNPs are irradiated with ultraviolet (UV) radiation with a wavelength of 365 nm, classified as ultraviolet A (UVA). In this study, we used electron spin resonance direct detection to confirm that UV irradiation of AgNPs produced rapid generation of hydroxyl radicals. As hydroxyl radicals are known to degrade bacteria, viruses, and some chemicals, the enhancement of the microbicidal activity of AgNPs by UV radiation could be valuable for the protection of healthcare workers and the prevention of the spread of infectious diseases.

scholarly journals Ionic liquids. Green solvents for the future

2000 ◽  
Vol 72 (7) ◽  
pp. 1391-1398 ◽  
Author(s):  
Martyn J. Earle ◽  
Kenneth R. Seddon
Keyword(s):  
Ionic Liquids ◽  
Vapor Pressure ◽  
Chemical Reactions ◽  
Green Solvents ◽  
Wide Range ◽  
The Future

Ionic liquids, being composed entirely of ions, were once mainly of interest to electrochemists. Recently, however, it has become apparent that, inter alia, their lack of measurable vapor pressure characterizes them as green solvents, and that a wide range of chemical reactions (reviewed here) can be performed in them.

scholarly journals Emulating the global 21-cm signal from Cosmic Dawn and Reionization

2020 ◽  
Vol 495 (4) ◽  
pp. 4845-4859 ◽  
Author(s):  
Aviad Cohen ◽  
Anastasia Fialkov ◽  
Rennan Barkana ◽  
Raul A Monsalve
Keyword(s):  
Neutral Hydrogen ◽  
Mean Free Path ◽  
Microwave Background ◽  
Star Forming ◽  
Global Signal ◽  
Wide Range ◽  
The Mean ◽  
Rapid Generation ◽  
Minimal Mass ◽  
Formation Efficiency

ABSTRACT The 21-cm signal of neutral hydrogen is a sensitive probe of the Epoch of Reionization (EoR), Cosmic Dawn, and the Dark Ages. Currently, operating radio telescopes have ushered in a data-driven era of 21-cm cosmology, providing the first constraints on the astrophysical properties of sources that drive this signal. However, extracting astrophysical information from the data is highly non-trivial and requires the rapid generation of theoretical templates over a wide range of astrophysical parameters. To this end emulators are often employed, with previous efforts focused on predicting the power spectrum. In this work, we introduce 21cmgem– the first emulator of the global 21-cm signal from Cosmic Dawn and the EoR. The smoothness of the output signal is guaranteed by design. We train neural networks to predict the cosmological signal using a database of ∼30 000 simulated signals which were created by varying seven astrophysical parameters: the star formation efficiency and the minimal mass of star-forming haloes; the efficiency of the first X-ray sources and their spectrum parametrized by spectral index and the low-energy cut-off; the mean-free path of ionizing photons, and the cosmic microwave background optical depth. We test the performance with a set of ∼2000 simulated signals, showing that the relative error in the prediction has an rms of 0.0159. The algorithm is efficient, with a running time per parameter set of 0.16 s. Finally, we use the database of models to check the robustness of relations between the features of the global signal and the astrophysical parameters that we previously reported.

NMR studies of enzymatic rates in vitro and in vivo by magnetization transfer

1984 ◽  
Vol 17 (1) ◽  
pp. 83-124 ◽  
Author(s):  
J. R. Alger ◽  
R. G. Shulman
Keyword(s):  
Creatine Kinase ◽  
Chemical Reactions ◽  
Magnetization Transfer ◽  
Living Systems ◽  
Nmr Studies ◽  
Wide Range ◽  
Potential Applications

Magnetization transfer techniques are specialized NMR experiments which can measure the rate of chemical reactions while concentrations of products and reactants are maintained constant. These techniques are being used to measure the rates of enzyme catalysed reactions in a variety of living systems and in vitro. The magnetization transfer measurements in vivo of the ATP synthetase and the creatine kinase reactions have been particularly useful in describing rates of major energy transducing reactions involving ATP and phosphocreatine. As a result, a wide range of biomedicai scientists are becoming aware of the potentials of these techniques. The purpose of this review is thus threefold: first, to present a concise, conceptual review of the underlying principles for these non-specialists; secondly, to review the important biochemical applications of the method which have appeared, and thirdly, to discuss potential applications and limitations of the method.

Autocatalysis: At the Root of Self-Replication

2011 ◽  
Vol 17 (3) ◽  
pp. 219-236 ◽  
Author(s):  
Raphaël Plasson ◽  
Axel Brandenburg ◽  
Ludovic Jullien ◽  
Hugues Bersini
Keyword(s):  
Chemical Reactions ◽  
Chemical Compound ◽  
Dynamic Properties ◽  
General Definition ◽  
Mathematical Form ◽  
Fundamental Level ◽  
Autopoietic Systems ◽  
Wide Range ◽  
Kinetic Pattern ◽  
Self Replication

Autocatalysis is a fundamental concept, used in a wide range of domains. From its most general definition, that is, a process in which a chemical compound is able to catalyze its own formation, several different systems can be described. We detail the different categories of autocatalyses, and compare them on the basis of their mechanistic, kinetic, and dynamic properties. It is shown how autocatalytic patterns can be generated by different systems of chemical reactions. The notion of autocatalysis covers a large variety of mechanistic realizations with very similar behaviors; it is proposed that its key signature is its kinetic pattern expressed in a mathematical form. This notion, while describing dynamic behaviors at the most fundamental level, is at the basis for developing higher-level concepts towards life: autocatalytic sets, and autopoietic systems.

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