scholarly journals Space and Time Crystal Engineering in Developing Futuristic Chemical Technology

2021 ◽  
Vol 5 (4) ◽  
pp. 67
Author(s):  
Pathik Sahoo ◽  
Subrata Ghosh
Keyword(s):  
Crystal Engineering ◽  
Chemical Engineering ◽  
Chemical System ◽  
Smart Devices ◽  
Active Centers ◽  
Reaction Cycle ◽  
Time Space ◽  
Catalytically Active ◽  
Reaction Cycles ◽  
Competitive Products

In the coming years, multipurpose catalysts for delivering different products under the same chemical condition will be required for developing smart devices for industrial or household use. In order to design such multipurpose devices with two or more specific roles, we need to incorporate a few independent but externally controllable catalytically active centers. Through space crystal engineering, such an externally controllable multipurpose MOF-based photocatalyst could be designed. In a chemical system, a few mutually independent secondary reaction cycles nested within the principal reaction cycle can be activated externally to yield different competitive products. Each reaction cycle can be converted into a time crystal, where the time consuming each reaction step could be converted as an event and all the reaction steps or events could be connected by a circle to build a time crystal. For fractal reaction cycles, a time polycrystal can be generated. By activating a certain fractal event based nested time crystal branch, we can select one of the desired competitive products according to our needs. This viewpoint intends to bring together the ideas of (spatial) crystal engineering and time crystal engineering in order to make use of the time–space arrangement in reaction–catalysis systems and introduce new aspects to futuristic chemical engineering technology.

Re-Programming Hydrogel Properties using a Fuel-driven Reaction Cycle

2019 ◽  
Author(s):  
Nishant Singh ◽  
Bruno Lainer ◽  
Georges Formon ◽  
Serena De Piccoli ◽  
Thomas Hermans
Keyword(s):  
Methionine Oxidation ◽  
Guanosine Triphosphate ◽  
Control Reaction ◽  
Reaction Cycle ◽  
Materials Properties ◽  
Assembly Kinetics ◽  
Control Assembly ◽  
Indispensable Tool ◽  
Reaction Cycles ◽  
Non Equilibrium

Nature uses catalysis as an indispensable tool to control assembly and reaction cycles in vital non-equilibrium supramolecular processes. For instance, enzymatic methionine oxidation regulates actin (dis)assembly, and catalytic guanosine triphosphate hydrolysis is found in tubulin (dis)assembly. Here we present a completely artificial reaction cycle which is driven by a chemical fuel that is catalytically obtained from a ‘pre-fuel’. The reaction cycle controls the disassembly and re-assembly of a hydrogel, where the rate of pre-fuel turnover dictates the morphology as well as the mechanical properties. By adding additional fresh aliquots of fuel and removing waste, the hydrogels can be re-programmed time after time. Overall, we show how catalysis can control fuel generation to control reaction / assembly kinetics and materials properties in life-like non-equilibrium systems.

Chemical Engineering of RNase Resistant and Catalytically Active Hammerhead Ribozymes

1997 ◽  
Vol 5 (11) ◽  
pp. 1999-2010 ◽  
Author(s):  
Fabienne Burlina ◽  
Alain Favre ◽  
Jean-Louis Fourrey
Keyword(s):  
Chemical Engineering ◽  
Hammerhead Ribozymes ◽  
Catalytically Active

scholarly journals Privacy-Protection Scheme Based on Sanitizable Signature for Smart Mobile Medical Scenarios

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Zhiyan Xu ◽  
Min Luo ◽  
Neeraj Kumar ◽  
Pandi Vijayakumar ◽  
Li Li
Keyword(s):  
Data Security ◽  
Privacy Protection ◽  
Medical Data ◽  
Security And Privacy ◽  
Smart Devices ◽  
Protection Scheme ◽  
Mobile Medicine ◽  
Time Space ◽  
Medical Network ◽  
Smart Mobile

With the popularization of wireless communication and smart devices in the medical field, mobile medicine has attracted more and more attention because it can break through the limitations of time, space, and objects and provide more efficient and quality medical services. However, the characteristics of a mobile smart medical network make it more susceptible to security threats such as data integrity damage and privacy leakage than those of traditional wired networks. In recent years, many digital signature schemes have been proposed to alleviate some of these challenges. Unfortunately, traditional digital signatures cannot meet the diversity and privacy requirements of medical data applications. In response to this problem, this paper uses the unique security attributes of sanitizable signatures to carry out research on the security and privacy protection of medical data and proposes a data security and privacy protection scheme suitable for smart mobile medical scenarios. Security analysis and performance evaluation show that our new scheme effectively guarantees data security and user privacy while greatly reducing computation and communication costs, making it especially suitable for mobile smart medical application scenarios.

scholarly journals Catalytic Behavior of Molybdenum Sulfide for the Hydrogen Evolution Reaction as a Function of Crystallinity and Particle Size Using Carbon Multiwall Nanotubes as Substrates

2020 ◽  
Vol 234 (5) ◽  
pp. 1021-1043 ◽  
Author(s):  
Diana Stellmach ◽  
Fanxing Xi ◽  
Ulrike Bloeck ◽  
Peter Bogdanoff ◽  
Sebastian Fiechter
Keyword(s):  
Carbon Nanotubes ◽  
Particle Size ◽  
Hydrogen Evolution ◽  
Hydrogen Evolution Reaction ◽  
Active Sites ◽  
Molybdenum Sulfide ◽  
Active Centers ◽  
Catalytically Active ◽  
Multi Walled Carbon Nanotubes ◽  
Different Diameters

AbstractMolybdenum sulfide is of interest as a noble metal-free catalyst for the hydrogen evolution reaction (HER). In crystallized form, it shows a typical stacking of planar S–Mo–S layers whereas the catalytically active centers are situated on the edges of these entities characterized by non-saturated bonds of the molybdenum atoms. In this study, 2H-MoS2 is investigated as HER catalyst as a function of particle size using powder electrodes of different grain sizes and morphology. HER was also determined as a function of growth defects (bending of layers) and as a function of active sites employing MoS2 nanoparticles (NP). To study the influence of the substrate on the perfection of the transition metal disulfide, MoS2 nanosheets were deposited on multi-walled carbon nanotubes (MWCNTs) of different diameters. Highest activity was found for MoS2 nanosheets deposited on MWCNTs with a diameter smaller than 8 nm. At diameters larger than 10 nm, a wrapping of the nanotubes by partially bended stacks of S–Mo–S layers occurs, while at diameters smaller than 10 nm, individual MoS2 nanosheets of 3–5 S–Mo–S stacks of 3–4 nm in height and 10–20 nm in lateral extension surround the carbon nanotubes in form of hexagonal cylinders. The ratio of catalytically active non-van-der-Waals and hexagonal basal planes was determined electrochemically by electro-oxidation and correlated with HER activity.

TYPES OF ACTIVE CENTERS ON SURFACE OF PROMOTED IRON OXIDE CATALYST

2018 ◽  
Vol 61 (6) ◽  
pp. 61 ◽  
Author(s):  
Nikolai V. Dvoretskii ◽  
Lyubov G. Anikanova ◽  
Zoya G. Malysheva
Keyword(s):  
Iron Oxide ◽  
Active Sites ◽  
Oxide Catalyst ◽  
Coke Formation ◽  
Reaction Medium ◽  
Active Centers ◽  
Iron Oxide Catalyst ◽  
Oxygen Ion ◽  
Catalytically Active ◽  
Potassium Monoferrite

The phase and chemical composition of compounds in the potassium-iron-oxygen system in a wide range of molar ratios of potassium and iron was studied by X-ray phase analysis and atomic absorption spectroscopy. The catalytic properties and the mass fraction of coke deposits on ferritic systems of various composition are determined. It has been shown that at least two types of active sites are present on the surface of the iron oxide catalyst. The dehydrogenation centers include oxygen ion, ions of a promoting alkali metal, and ions of bivalent and triply charged iron, between which electron exchange takes place. Most probably such center is realized in the structure of potassium-polyferrite (K2Fe2+Fe3+10O17). The coke formation centers contain an unpromoted cluster consisting of oxygen ion and iron (III) ion, are realized in Fe3O4 and KFe11O17. Coke deposits on the surface of the catalyst block non-selective active sites and increase the selectivity of action. The probability of realization of clusters corresponding to the dehydrogenation centers is three orders of magnitude higher than in the places of phase contact, the aggregate of which contains the whole set of ions corresponding to dehydrogenation centers, for example, "magnetite + potassium monoferrite". The pure potassium β"-polyferrite provides an optimal concentration of selective centers on the surface of the catalyst, operates highly efficiently in the absence of negative external influences (catalyst re-recovery, corrosion reaction of the reaction medium, poisoning effect). Individual b²-polyferrites, like any catalytically active phase, are unstable, however, being in equilibrium with potassium monoferrate and magnetite, it is able to operate effectively for a long time and to withstand the negative effects of redox properties of the surrounding reaction medium. The presence of potassium monoferrite in the catalytically active system ensures the polyfunctionality of the action of contact, i.e. ability to self-regeneration. It is likely that in the structure of potassium monoferrite, centers for preventing coke formation and annealing of coke are realized, containing oxygen ion, iron ion, and alkaline promoter.Forcitation:Dvoretskii N.V., Anikanova L.G., Malysheva Z.G. Types of active centers on surface of promoted iron oxide catalyst. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 6. P. 61-68

scholarly journals Modification of copper(I) – based activation solution with organic solvents and surfactants in the process of chemical copperplating

2019 ◽  
Vol 59 (8) ◽  
pp. 86-91
Author(s):  
Ludmila A. Brusnitsina ◽  
◽  
Elena I. Stepanovskih ◽  
Tatiana A. Aleхeeva ◽  
◽  
...  
Keyword(s):  
Organic Solvents ◽  
Printed Circuit Boards ◽  
Adhesive Layer ◽  
Dielectric Materials ◽  
Dielectric Surface ◽  
Colloidal Solutions ◽  
High Concentration ◽  
Active Centers ◽  
Catalytically Active ◽  
Activating Solution

In the processes of chemical and galvanic metallization of dielectric materials, in particular in the production of printed circuit boards, surface activation mainly uses compounds of precious metals and colloidal solutions characterized by limited stability during storage due to the coagulation process. To activate dielectric materials it is advisable to use true solutions based on monovalent copper compounds. For continuous metallization of the dielectric, it is necessary to obtain a sufficiently large number of catalytic active centers on the surface. This can be achieved in two ways: to create a high concentration of Cu(I) in the activation solution or to increase the thickness of the activating layer. The aim of this work is to modify the activating solution by introducing organic solvents and surfactants into its composition, contributing to an increase in the concentration of catalytically active centers on the dielectric surface. In order to better distribute the activating solution on the dielectric surface and in the holes, as well as to increase the sorption of copper(I) by the adhesive layer, the modifying effect of organic solvents on the activating composition was studied. As such solvents, dimethylformamide (DMFA) and dimethyl sulfoxide (DMSO) used in the preparation of the surface of the adhesive layer were studied. In the process of swelling, the solvent penetrates into the thickness of the adhesive layer. Due to this, the activator containing an organic solvent has the ability to be fixed on the surface not only due to the micro-roughness created in the etching process, but also able to penetrate deep into the swollen layer. It is established that the maximum thickness of the swollen layer for 10% solution is reached by the time of swelling 30-40 minutes, for 20% ‒ 20 minutes, for 50% ‒ more than 45 minutes. By the time of swelling, equal to 5 minutes, for 10, 20 and 50% solutions, the thickness of the swollen layer, respectively, is 1.00; 1.14; 1.55 microns. It is shown that the presence of organic solvents in the activator increases the adhesion of the metal coating by an average of 1.3 times. In order to better distribute the activator on the dielectric surface and in the holes, as well as to increase the adsorption of copper(I), it is advisable to introduce surfactants into the activator, which reduce the surface tension at the interface. Introduction to the composition of the surfactant activating solution affect the adhesion of the metal to the dielectric. It was found that the introduction of surfactant into the activating solution leads to an increase in the concentration of copper on the dielectric surface. Nonionic surfactant brand OP-10 in the activator provides a high concentration of catalytically active centers and get the highest adhesion of metal to the dielectric.

scholarly journals Stability of a Nonequilibrium Biochemical Cycle Revealed by Single-Molecule Spectroscopy

2021 ◽  
Author(s):  
Saurabh Talele ◽  
John T King
Keyword(s):  
Entropy Production ◽  
Single Molecule ◽  
Nonequilibrium Dynamics ◽  
Single Molecule Spectroscopy ◽  
Reaction Cycle ◽  
Central Interest ◽  
Thermodynamic Driving Force ◽  
Reaction Cycles ◽  
Thermal Stability Of

Biological machinery relies on nonequilibrium dynamics to maintain stable directional fluxes through complex reaction cycles. In stabilizing the reaction cycle, the role of microscopic irreversibility of elementary transitions, and the accompanying entropy production, is of central interest. Here, we use multidimensional single-molecule spectroscopy to demonstrate that the reaction cycle of bacteriorhodopsin is coupled through both reversible and irreversible transitions, with directionality of trans-membrane H+ transport being ensured by the entropy production of irreversible transitions. We observe that thermal destabilization of the process is the result of diminishing thermodynamic driving force for irreversible transitions, leading to an exponentially increasing variance of flux through the transitions. We show that the thermal stability of the reaction cycle can be predicted from the Gibbs-Helmholtz relation.

scholarly journals Re-Programming Hydrogel Properties using a Fuel-driven Reaction Cycle

2019 ◽  
Author(s):  
Nishant Singh ◽  
Bruno Lainer ◽  
Georges Formon ◽  
Serena De Piccoli ◽  
Thomas Hermans
Keyword(s):  
Methionine Oxidation ◽  
Guanosine Triphosphate ◽  
Control Reaction ◽  
Reaction Cycle ◽  
Materials Properties ◽  
Assembly Kinetics ◽  
Control Assembly ◽  
Indispensable Tool ◽  
Reaction Cycles ◽  
Non Equilibrium

Nature uses catalysis as an indispensable tool to control assembly and reaction cycles in vital non-equilibrium supramolecular processes. For instance, enzymatic methionine oxidation regulates actin (dis)assembly, and catalytic guanosine triphosphate hydrolysis is found in tubulin (dis)assembly. Here we present a completely artificial reaction cycle which is driven by a chemical fuel that is catalytically obtained from a ‘pre-fuel’. The reaction cycle controls the disassembly and re-assembly of a hydrogel, where the rate of pre-fuel turnover dictates the morphology as well as the mechanical properties. By adding additional fresh aliquots of fuel and removing waste, the hydrogels can be re-programmed time after time. Overall, we show how catalysis can control fuel generation to control reaction / assembly kinetics and materials properties in life-like non-equilibrium systems.

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