Constructing canopy-shaped molecular architectures to create local Pt surface sites with high tolerance to H2S and CO for hydrogen electrooxidation

2018 ◽  
Vol 11 (1) ◽  
pp. 166-171 ◽  
Author(s):  
Tao Wang ◽  
Zhi-Xin Chen ◽  
Song Yu ◽  
Tian Sheng ◽  
Hai-Bin Ma ◽  
...  
Keyword(s):  
Steric Hindrance ◽  
High Tolerance ◽  
Co Tolerance ◽  
Surface Sites ◽  
Molecular Architectures ◽  
Hydrogen Electrooxidation

Pt surface is modified with 2,6-diacetylpyridine, which exhibits high H2S and CO tolerance for H2oxidation through steric hindrance.

Hydrogen electrooxidation over palladium–gold alloy: Effect of pretreatment in ethylene on catalytic activity and CO tolerance

2012 ◽  
Vol 76 ◽  
pp. 344-353 ◽  
Author(s):  
Alexander N. Simonov ◽  
Pavel E. Plyusnin ◽  
Yury V. Shubin ◽  
Ren I. Kvon ◽  
Sergey V. Korenev ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Gold Alloy ◽  
Co Tolerance ◽  
Alloy Effect ◽  
Hydrogen Electrooxidation

Enhanced catalytic activity for hydrogen electrooxidation and CO tolerance of carbon-supported non-stoichiometric palladium carbides

2012 ◽  
Vol 353-354 ◽  
pp. 204-214 ◽  
Author(s):  
Alexander N. Simonov ◽  
Pavel A. Pyrjaev ◽  
Pavel A. Simonov ◽  
Boris L. Moroz ◽  
Svetlana V. Cherepanova ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Co Tolerance ◽  
Hydrogen Electrooxidation

Social representations of human rights violations: Further evidence

2001 ◽  
Vol 60 (2) ◽  
pp. 89-98 ◽  
Author(s):  
Alain Clémence ◽  
Thierry Devos ◽  
Willem Doise
Keyword(s):  
Cluster Analysis ◽  
Human Rights ◽  
Costa Rica ◽  
Young People ◽  
Social Representations ◽  
Social Reality ◽  
Questionnaire Study ◽  
Human Rights Violations ◽  
High Tolerance ◽  
Individual Actions

Social representations of human rights violations were investigated in a questionnaire study conducted in five countries (Costa Rica, France, Italy, Romania, and Switzerland) (N = 1239 young people). We were able to show that respondents organize their understanding of human rights violations in similar ways across nations. At the same time, systematic variations characterized opinions about human rights violations, and the structure of these variations was similar across national contexts. Differences in definitions of human rights violations were identified by a cluster analysis. A broader definition was related to critical attitudes toward governmental and institutional abuses of power, whereas a more restricted definition was rooted in a fatalistic conception of social reality, approval of social regulations, and greater tolerance for institutional infringements of privacy. An atypical definition was anchored either in a strong rejection of social regulations or in a strong condemnation of immoral individual actions linked with a high tolerance for governmental interference. These findings support the idea that contrasting definitions of human rights coexist and that these definitions are underpinned by a set of beliefs regarding the relationships between individuals and institutions.

High tolerance of progressive elastic compression in peripheral arterial disease

VASA ◽  
2019 ◽  
Vol 48 (5) ◽  
pp. 413-417 ◽  
Author(s):  
Serge Couzan ◽  
Jean-François Pouget ◽  
Claire Le Hello ◽  
Céline Chapelle ◽  
Silvy Laporte ◽  
...  
Keyword(s):  
Venous Insufficiency ◽  
Ankle Brachial Index ◽  
Arterial Disease ◽  
Return Flow ◽  
High Tolerance ◽  
Compression Stockings ◽  
Short Term ◽  
Poor Tolerance ◽  
The Mean ◽  
Peripheral Arterial

Summary. Background: Theoretically progressive compression stockings, which produce a higher compression at the calf than at the ankle level, improve venous return flow without exacerbating peripheral arterial insufficiency (PAD). We aimed to evaluate the short-term tolerance of elastic progressive compression stockings on peripheral arterial vascularisation in patients with symptomatic PAD and associated mild venous insufficiency. Patients and methods: Monocentric, prospective, open pilot study of 18 patients (acceptability study, 6 x 6 plan) evaluating the short-term tolerance of progressive compression stockings (18 ± 2 mmHg at calf and 8 ± 2 mmHg at ankle level) in patients with PAD (ankle brachial index ABI > 0.60 < 0.75) and chronic venous insufficiency (C1s–C4 stages of the CEAP classification). Day 15 tolerance was evaluated by a composite primary criteria comprising: no decrease > 15 % of ABI on each side, no decrease > 15 % of toe brachial index (TBI) on each side and no decrease > 25 % of the number of active plantar flexions performed while standing. Results: The proportion of men was 77.8 %, mean age was 77.3 ± 7.5 years and no patient were diabetic. At inclusion, the mean low ABI was 0.60 ± 0.04 and the mean high ABI was 0.77 ± 0.18. The mean low TBI was 0.32 ± 0.09 and the mean high TBI 0.46 ± 0.15. The mean number of active standing plantar flexions was 33.0 ± 5.0. The majority of the patients were classified in CEAP C2s and C3 classes (class 2: 16.7 %, class C2s: 27.8 %, class C3: 44.4 %, class C4: 5.6 % and class C4s: 5.6 %). Poor tolerance occurred in no patient. By day 30, no patient had worsening of their arterial and venous symptoms. No adverse events occurred during the study. Conclusions: These results suggest a high tolerance of progressive elastic stockings (18 ± 2 mmHg at calf and 8 ± 2 mmHg at ankle level) in symptomatic PAD.

Steric hindrance influence of a diazo link upon mesogenic properties of some ligands and related copper complexes

1997 ◽  
Vol 94 ◽  
pp. 1695-1714 ◽  
Author(s):  
P Lesot ◽  
F Perez ◽  
P Judeinstein ◽  
JP Bayle ◽  
H Allouchi ◽  
...  
Keyword(s):  
Steric Hindrance ◽  
Copper Complexes

METABOLISM OF 17α-HYDROXYPROGESTERONE-4-14C-17α-CAPROATE BY HOMOGENATES OF RAT LIVER AND HUMAN PLACENTA

1961 ◽  
Vol 36 (4) ◽  
pp. 511-519 ◽  
Author(s):  
Margaret Wiener ◽  
Charles I. Lupa ◽  
E. Jürgen Plotz
Keyword(s):  
Rat Liver ◽  
Human Placenta ◽  
Steric Hindrance ◽  
Placental Tissue ◽  
Caproic Acid ◽  
Major Product ◽  
Side Chain ◽  
Anaerobic Conditions ◽  
Prolonged Action ◽  
Long Acting

ABSTRACT 17α-hydroxyprogesterone-4-14C-17α-caproate (HPC), a long-acting progestational agent, was incubated with homogenates of rat liver and human placenta. The rat liver was found to reduce Ring A of HPC under anaerobic conditions to form allopregnane-3β,17α-diol-20-one-17α-caproate and pregnane-3β,17α-diol-20-one-17α-caproate, the allopregnane isomer being the major product. The caproic acid ester was neither removed nor altered during the incubation. Placental tissue did not attack HPC under conditions where the 20-ketone of progesterone was reduced. It is postulated that this absence of attack on the side chain is due to steric hindrance from the caproate ester, and that this may account for the prolonged action of HPC.

Tyrosine-Selective Bioconjugation with Iminoxyl Radicals

2020 ◽  
Author(s):  
Katsuya Maruyama ◽  
Takashi Ishiyama ◽  
Yohei Seki ◽  
Kounosuke Oisaki ◽  
Motomu Kanai
Keyword(s):  
Reaction Time ◽  
Steric Hindrance ◽  
Room Temperature ◽  
Water Soluble ◽  
Light Irradiation ◽  
Sodium Ascorbate ◽  
Iminoxyl Radical ◽  
Short Reaction Time ◽  
Modified Peptides ◽  
The Stability

A novel Tyr-selective protein bioconjugation using the water-soluble persistent iminoxyl radical is described. The conjugation proceeded with high Tyr-selectivity and short reaction time under biocompatible conditions (room temperature in buffered media under air). The stability of the conjugates was tunable depending on the steric hindrance of iminoxyl. The presence of sodium ascorbate and/or light irradiation promoted traceless deconjugation, restoring the native Tyr structure. The method is applied to the synthesis of a protein-dye conjugate and further derivatization to azobenzene-modified peptides.

Catalyst-Control over Sixfold Stereogenicity

2020 ◽  
Author(s):  
Xingxing Wu ◽  
Reto M. Witzig ◽  
Rodolphe Beaud ◽  
Christian Fischer ◽  
Daniel Häussinger ◽  
...  
Keyword(s):  
Conformational Analysis ◽  
Higher Order ◽  
Binary Codes ◽  
Rotational Barriers ◽  
Molecular Architectures

Governing higher-order stereogenicity is a long-standing goal in stereoselective catalysis, because it allows to achieve selectivity for more than a twofold number of stereoisomers per stereogenic unit. Current methods warrant control over the power of two stereoisomers and the configurations are routinely assigned using the descriptors ( R ) and ( S ), or related binary codes. In contrast, conformational analysis ranges beyond this dualistic treatment of stereoisomerism, which constitutes an unmet challenge for catalyst stereocontrolled processes. Herein, we now report that sixfold stereogenicity can be governed by stereoselective catalysis. By controlling a configurationally stable stereogenic axis with six large rotational barriers, a catalytic [2+2+2]-cyclotrimerization selectively governs the formation of one out of six stereoisomers with up to 0:0:2:98:0:0 stereocontrol. The underpinnings of conformational analysis and stereoselective catalysis are thereby conceptually reunited. Novel molecular architectures featuring distinct chemical topologies and unexplored chemical designs are anticipated from catalystcontrol over higher-order stereogenicities

Differentiation and Functionalization of Adjacent, Remote C–H Bonds

2019 ◽  
Author(s):  
Hang Shi ◽  
Lu Yi ◽  
Jiang Weng ◽  
Katherine Bay ◽  
Xiangyang Chen ◽  
...  
Keyword(s):  
Catalytic System ◽  
Functional Group ◽  
Hydrocinnamic Acid ◽  
Molecular Architectures ◽  
Site Selective ◽  
Developing Strategies

<p>Site-selective functionalizations of C–H bonds will ultimately afford chemists transformative tools for editing and constructing complex molecular architectures<sup>1-4</sup>. Towards this goal, developing strategies to activate C–H bonds that are distal from a functional group is essential<sup>4-6</sup>. In this context, distinguishing remote C–H bonds on adjacent carbon atoms is an extraordinary challenge due to the lack of electronic or steric bias between the two positions. Herein, we report the design of a catalytic system leveraging a remote directing template and a transient norbornene mediator to selectively activate a previously inaccessible remote C–H bond that is one bond further away. The generality of this approach has been demonstrated with a range of heterocycles, including a complex anti-leukemia agent, and hydrocinnamic acid substrates.</p>

Synthesis of Conjugated Triynes via Alkyne Metathesis

2019 ◽  
Author(s):  
Idriss Curbet ◽  
Sophie Colombel-Rouen ◽  
Romane Manguin ◽  
Anthony Clermont ◽  
Alexandre Quelhas ◽  
...  
Keyword(s):  
Steric Hindrance ◽  
High Selectivity ◽  
Alkyne Metathesis ◽  
Cross Metathesis ◽  
Synthetic Strategy ◽  
Sterically Hindered ◽  
Site Selective

<div> <div> <div> <div> <p>The synthesis of conjugated triynes by molybdenum-catalyzed alkyne metathesis is reported. Strategic to the success of this approach is the utilization of sterically-hindered diynes that allowed for the site- selective alkyne metathesis to produce the desired con- jugated triyne products. The steric hindrance of alkyne moiety was found to be crucial in preventing the for- mation of diyne byproducts. This novel synthetic strategy was amenable to self- and cross-metathesis providing straightforward access to the corresponding symmetrical and dissymmetrical triynes with high selectivity. </p> </div> </div> </div> </div>

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