scholarly journals Tuning Reactivity of Micellar Nanoreactors by Precise Adjustments of the Amphiphiles and Substrates Hydrophobicity

2021 ◽  
Author(s):  
Shahar Tevet ◽  
Shreyas Shankar Wagle ◽  
Gadi Slor ◽  
Roey Amir
Keyword(s):  
Structural Changes ◽  
Aqueous Media ◽  
Reaction Rates ◽  
Exponential Dependence ◽  
Bioorthogonal Chemistry ◽  
The Core ◽  
End Groups ◽  
Polymeric Assemblies ◽  
Further Development ◽  
Fine Tune

<p>Polymeric assemblies, such as micelles, are gaining increasing attention due to their ability to serve as nanoreactors for the execution of organic reactions in aqueous media. The ability to conduct transformations, which have been limited to organic media, in water is essential for the further development of the important fields of green</p><p>catalysis and bioorthogonal chemistry, among other fields. In light of the recent progress in the expanding the scopes of reactions that can be conducted using nanoreactors, we aimed to gain deeper understanding of the roles of the hydrophobicity of both the core of micellar nanoreactors and the substrates on the reaction rates in water. Towards this goal we designed a set of metal-loaded micelles, composed of PEG-dendron amphiphiles and studied their ability to serve as nanoreactors for a palladium mediated depropargylation reaction of four substrates with different LogP values. Using dendrons as the hydrophobic block, allowed us to fine tune the lipophilicity of the dendritic end-groups and study how precise structural changes in the hydrophobicity of the amphiphiles affect the reaction rates. The kinetic data revealed linear relations between the rate constants and the hydrophobicity of the amphiphiles (estimated by the dendron’s</p><p>cLogP), while exponential dependence was obtained for the lipophilicity of the substrates (estimated by their LogP values). Our results demonstrate the vital contributions of the hydrophobicity of both the substrates and amphiphiles on the lipo-selectivity of nanoreactors, illustrating the potential of tuning hydrophobicity as a tool for optimizing</p><p>the reactivity and selectivity of nanoreactors.</p>

scholarly journals Tuning Reactivity of Micellar Nanoreactors by Precise Adjustments of the Amphiphiles and Substrates Hydrophobicity

2021 ◽  
Author(s):  
Shahar Tevet ◽  
Shreyas Shankar Wagle ◽  
Gadi Slor ◽  
Roey Amir
Keyword(s):  
Structural Changes ◽  
Aqueous Media ◽  
Reaction Rates ◽  
Exponential Dependence ◽  
Bioorthogonal Chemistry ◽  
The Core ◽  
End Groups ◽  
Polymeric Assemblies ◽  
Further Development ◽  
Fine Tune

<p>Polymeric assemblies, such as micelles, are gaining increasing attention due to their ability to serve as nanoreactors for the execution of organic reactions in aqueous media. The ability to conduct transformations, which have been limited to organic media, in water is essential for the further development of the important fields of green</p><p>catalysis and bioorthogonal chemistry, among other fields. In light of the recent progress in the expanding the scopes of reactions that can be conducted using nanoreactors, we aimed to gain deeper understanding of the roles of the hydrophobicity of both the core of micellar nanoreactors and the substrates on the reaction rates in water. Towards this goal we designed a set of metal-loaded micelles, composed of PEG-dendron amphiphiles and studied their ability to serve as nanoreactors for a palladium mediated depropargylation reaction of four substrates with different LogP values. Using dendrons as the hydrophobic block, allowed us to fine tune the lipophilicity of the dendritic end-groups and study how precise structural changes in the hydrophobicity of the amphiphiles affect the reaction rates. The kinetic data revealed linear relations between the rate constants and the hydrophobicity of the amphiphiles (estimated by the dendron’s</p><p>cLogP), while exponential dependence was obtained for the lipophilicity of the substrates (estimated by their LogP values). Our results demonstrate the vital contributions of the hydrophobicity of both the substrates and amphiphiles on the lipo-selectivity of nanoreactors, illustrating the potential of tuning hydrophobicity as a tool for optimizing</p><p>the reactivity and selectivity of nanoreactors.</p>

St. Petersburg industrial policy: Determining the factors of structural changes in industry through Shift-Share Analysis

2020 ◽  
Vol 18 (5) ◽  
pp. 909-939
Author(s):  
M.V. Dement'ev
Keyword(s):  
Industrial Policy ◽  
Structural Transformation ◽  
Mechanical Engineering ◽  
Manufacturing Industry ◽  
Structural Changes ◽  
Analysis Method ◽  
Factor Analyses ◽  
Further Development ◽  
Positive Results

Subject. This article examines the theoretical and practical aspects of the implementation of industrial policy and the structural transformation of the manufacturing industry in St. Petersburg. Objectives. The article aims to justify the priority of the industry-based approach to industrial policy in St. Petersburg and determine its effectiveness by highlighting the factors of structural transformation of the city's manufacturing industry using the Shift-Share Analysis method. Methods. For the study, I used logical, statistical, and factor analyses. Results. Based on shift-share analysis, the study highlights positive results of industrial policy in the development of certain industries in St. Petersburg, as well as those industries that require further development of urban industrial policy. Conclusions. Despite the fact that the industry of St. Petersburg as a whole has become more stable, problems in the development of mechanical engineering and production of computers, electronic and optical products have not yet been solved.

Roughened gold electrode for in situ SERS analysis of structural changes accompanying the doping process of polyaniline in acidic aqueous media

2021 ◽  
Vol 882 ◽  
pp. 115034
Author(s):  
A. El Guerraf ◽  
M. Bouabdallaoui ◽  
Z. Aouzal ◽  
S. Ben Jadi ◽  
N.K. Bakirhan ◽  
...  
Keyword(s):  
Gold Electrode ◽  
Structural Changes ◽  
Aqueous Media

scholarly journals Ureido Functionalization through Amine-Urea Transamidation under Mild Reaction Conditions

Polymers ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1583
Author(s):  
Natalia Guerrero-Alburquerque ◽  
Shanyu Zhao ◽  
Daniel Rentsch ◽  
Matthias M. Koebel ◽  
Marco Lattuada ◽  
...  
Keyword(s):  
Aqueous Media ◽  
Reaction Times ◽  
Reaction Rates ◽  
Secondary Amines ◽  
Isocyanic Acid ◽  
Advantages And Disadvantages ◽  
Major Disadvantage ◽  
Wide Range ◽  
Potential Alternative ◽  
Full Conversion

Ureido-functionalized compounds play an indispensable role in important biochemical processes, as well as chemical synthesis and production. Isocyanates, and KOCN in particular, are the preferred reagents for the ureido functionalization of amine-bearing compounds. In this study, we evaluate the potential of urea as a reagent to graft ureido groups onto amines at relatively low temperatures (<100 °C) in aqueous media. Urea is an inexpensive, non-toxic and biocompatible potential alternative to KOCN for ureido functionalization. From as early as 1864, urea was the go-to reagent for polyurea polycondensation, before falling into disuse after the advent of isocyanate chemistry. We systematically re-investigate the advantages and disadvantages of urea for amine transamidation. High ureido-functionalization conversion was obtained for a wide range of substrates, including primary and secondary amines and amino acids. Reaction times are nearly independent of substrate and pH, but excess urea is required for practically feasible reaction rates. Near full conversion of amines into ureido can be achieved within 10 h at 90 °C and within 24 h at 80 °C, and much slower reaction rates were determined at lower temperatures. The importance of the urea/amine ratio and the temperature dependence of the reaction rates indicate that urea decomposition into an isocyanic acid or a carbamate intermediate is the rate-limiting step. The presence of water leads to a modest increase in reaction rates, but the full conversion of amino groups into ureido groups is also possible in the absence of water in neat alcohol, consistent with a reaction mechanism mediated by an isocyanic acid intermediate (where the water assists in the proton transfer). Hence, the reaction with urea avoids the use of toxic isocyanate reagents by in situ generation of the reactive isocyanate intermediate, but the requirement to separate the excess urea from the reaction product remains a major disadvantage.

scholarly journals Assembly of T-Antigen Double Hexamers on the Simian Virus 40 Core Origin Requires Only a Subset of the Available Binding Sites

1998 ◽  
Vol 18 (5) ◽  
pp. 2677-2687 ◽  
Author(s):  
Woo S. Joo ◽  
Henry Y. Kim ◽  
John D. Purviance ◽  
K. R. Sreekumar ◽  
Peter A. Bullock
Keyword(s):  
Structural Changes ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
Wild Type ◽  
The Core ◽  
Structural Distortions ◽  
In The Wild ◽  
Sv40 Dna ◽  
Initial Assembly

ABSTRACT Initiation of simian virus 40 (SV40) DNA replication is dependent upon the assembly of two T-antigen (T-ag) hexamers on the SV40 core origin. To further define the oligomerization mechanism, the pentanucleotide requirements for T-ag assembly were investigated. Here, we demonstrate that individual pentanucleotides support hexamer formation, while particular pairs of pentanucleotides suffice for the assembly of T-ag double hexamers. Related studies demonstrate that T-ag double hexamers formed on “active pairs” of pentanucleotides catalyze a set of previously described structural distortions within the core origin. For the four-pentanucleotide-containing wild-type SV40 core origin, footprinting experiments indicate that T-ag double hexamers prefer to bind to pentanucleotides 1 and 3. Collectively, these experiments demonstrate that only two of the four pentanucleotides in the core origin are necessary for T-ag assembly and the induction of structural changes in the core origin. Since all four pentanucleotides in the wild-type origin are necessary for extensive DNA unwinding, we concluded that the second pair of pentanucleotides is required at a step subsequent to the initial assembly process.

scholarly journals Quantifying Soil Compaction in Persimmon Orchards Using ISUM (Improved Stock Unearthing Method) and Core Sampling Methods

Agriculture ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 266 ◽  
Author(s):  
Ehsan Moradi ◽  
Jesús Rodrigo-Comino ◽  
Enric Terol ◽  
Gaspar Mora-Navarro ◽  
Alexandre Marco da Silva ◽  
...  
Keyword(s):  
Ecosystem Services ◽  
Soil Erosion ◽  
Bulk Density ◽  
Soil Compaction ◽  
Structural Changes ◽  
Low Cost ◽  
Positive Contribution ◽  
The Core ◽  
Core Sampling ◽  
Core Method

Agricultural activities induce micro-topographical changes, soil compaction and structural changes due to soil cultivation, which directly affect ecosystem services. However, little is known about how these soil structural changes occur during and after the planting of orchards, and which key factors and processes play a major role in soil compaction due to cultivation works. This study evaluates the improved stock unearthing method (ISUM) as a low-cost and precise alternative to the tedious and costly traditional core sampling method, to characterize the changes in soil compaction in a representative persimmon orchard in Eastern Spain. To achieve this goal, firstly, in the field, undisturbed soil samples using metallic core rings (in January 2016 and 2019) were collected at different soil depths between 45 paired-trees, and topographic variations were determined following the protocol established by ISUM (January 2019). Our results show that soil bulk density (Bd) increases with depth and in the inter-row area, due to the effect of tractor passes and human trampling. The bulk density values of the top surface layers (0–12 cm) showed the lowest soil accumulation, but the highest temporal and spatial variability. Soil consolidation within three years after planting as calculated using the core samples was 12 mm, whereas when calculated with ISUM, it was 14 mm. The quality of the results with ISUM was better than with the traditional core method, due to the higher amount of sampling points. The ISUM is a promising method to measure soil compaction, but it is restricted to the land where soil erosion does not take place, or where soil erosion is measured to establish a balance of soil redistribution. Another positive contribution of ISUM is that it requires 24 h of technician work to acquire the data, whereas the core method requires 272 h. Our research is the first approach to use ISUM to quantify soil compaction and will contribute to applying innovative and low-cost monitoring methods to agricultural land and conserving ecosystem services.

scholarly journals Production of radioisotopes within a plasma focus device

2005 ◽  
Vol 20 (1) ◽  
pp. 33-37 ◽  
Author(s):  
Ergisto Angeli ◽  
Agostino Tartari ◽  
Michele Frignani ◽  
Vincenzo Molinari ◽  
Domiziano Mostacci ◽  
...  
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Plasma Focus ◽  
Reaction Rates ◽  
Experimental Production ◽  
Endogenous Production ◽  
The Us ◽  
Further Development ◽  
Radio Isotopes ◽  
Very High

In recent years, research conducted in the US and in Italy has demonstrated production of radioisotopes in plasma focus devices, and particularly, on what could be termed "endogenous" production, to wit, production within the plasma it self, as opposed to irradiation of tar gets. This technique relies on the formation of localized small plasma zones characterized by very high densities and fairly high temperatures. The conditions prevailing in these zones lead to high nuclear reaction rates, as pointed out in previous work by several authors. Further investigation of the cross sections involved has proven necessary to model the phenomena involved. In this paper, the present status of research in this field is re viewed, both with regards to cross section models and to experimental production of radio isotopes. Possible out comes and further development are discussed.

The Ashkenazi Élite at the Beginning of the Modern Era: Manuscript versus Printed Book

1997 ◽  
pp. 85-98
Author(s):  
Elchanan Reiner
Keyword(s):  
Structural Changes ◽  
Central Issue ◽  
Literary Canon ◽  
General Attitude ◽  
Transmission Of Knowledge ◽  
The Core ◽  
European Culture ◽  
History Of ◽  
The Impact ◽  
Modern Era

This chapter evaluates the effect of printing on the Ashkenazi cultural élite. The shift from script to print in the sixteenth century heralded a reshaping of Ashkenazi literary models. The chapter traces some reactions amongst Ashkenazi intellectuals to this shift, which are indicative of their general attitude to the structural changes in patterns of the transmission of knowledge during the period. It focuses on certain developments within intellectual circles, primarily in connection with changes in the way halakhic literature — the core of the Ashkenazi literary canon — was written and transmitted. While the impact of the making of books and printing has long been a central issue in the history of European culture in general, it is genuinely surprising that Jewish culture, which is so profoundly literary, has not been examined in this light up to now.

scholarly journals Phosphorylated cellulose nanofibers exhibit exceptional capacity for uranium capture

Cellulose ◽  
2020 ◽  
Vol 27 (18) ◽  
pp. 10719-10732
Author(s):  
Janika Lehtonen ◽  
Jukka Hassinen ◽  
Avula Anil Kumar ◽  
Leena-Sisko Johansson ◽  
Roni Mäenpää ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Structural Changes ◽  
Cellulose Nanofibers ◽  
Aqueous Media ◽  
Isotherm Models ◽  
Batch Adsorption ◽  
Maximum Adsorption Capacity ◽  
Electron Microscopies ◽  
Network Scanning ◽  
Aqueous Matrices

AbstractWe investigate the adsorption of hexavalent uranium, U(VI), on phosphorylated cellulose nanofibers (PHO-CNF) and compare the results with those for native and TEMPO-oxidized nanocelluloses. Batch adsorption experiments in aqueous media show that PHO-CNF is highly efficient in removing U(VI) in the pH range between 3 and 6. Gelling of nanofiber hydrogels is observed at U(VI) concentration of 500 mg/L. Structural changes in the nanofiber network (scanning and transmission electron microscopies) and the surface chemical composition (X-ray photoelectron spectroscopy) gave insights on the mechanism of adsorption. The results from batch adsorption experiments are fitted to Langmuir, Freundlich, and Sips isotherm models, which indicate a maximum adsorption capacity of 1550 mg/g, the highest value reported so far for any bioadsorbent. Compared to other metals (Zn, Mn, and Cu) and typical ions present in natural aqueous matrices the phosphorylated nanofibers are shown to be remarkably selective to U(VI). The results suggest a solution for the capture of uranium, which is of interest given its health and toxic impacts when present in aqueous matrices.

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