Search results for "BEARING"

ChemInform Abstract: A Theoretical Study of the Selectivity for the Domino [5 + 2]/[4 + 2] Cycloadditions of γ-Pyrones Bearing Tethered Alkenes with …

2010

Abstract Selectivity of the domino [5+2]/[4+2] cycloaddition reactions of a β-silyloxy-γ-pyrone bearing a tethered alkene with two substituted 1,3-butadienes have been theoretically studied at the B3LYP/6-31G∗//AM1 and B3LYP/6-31G∗ computational levels. Analysis of these results allow explaining the regio, stereo and chemoselectivity observed experimentally at these domino reactions. Selectivity outcome is reproduced by these calculations.

SUL METABOLISMO DEGLI ORGANI DI RATTO PORTATORE DI SARCOMA DA BENZOPIRENE

1955

Free aminoacids were estimated in benzopyrene sarcoma of rats and in some organs of the tumour-bearing rats (brain, heart, muscle, lung, liver, spleen, kidney). In the tumour the content changes according to the growth stage; in the advanced tumour a strong increase of serine-glycine, glutammic acid and treonine is observed. In the organs the free amino acid contents are diminished in the first stages of the tumour growth, while in the advanced stages there is a tendency to an increase with different values according to the organs. The oxidation process in the organ homogenate (with or without substrate addition) varies according to the stage of the tumour growth, more evidently in the org…

[3+2] Cycloaddition Reaction of C -Phenyl-N -methyl Nitrone to Acyclic-Olefin-Bearing Electron-Donating Substituent: A Molecular Electron Density The…

2018

Dipolar Relaxation in Functionalized Poly-p-phenylenes Bearing Ultrastrong Dipoles Perpendicular to the Backbone

2018

Local polymer dynamics are studied in polymers bearing dipoles rigidly attached to the backbone. The compounds are based on cyano-substituted dihydrobenzimidazoles bearing ultrastrong dipole moments (∼12 D per repeat unit) incorporated in a poly-p-phenylene backbone, giving rise to polymers with rigid dipoles perpendicular to the chain. They belong to type B polymers according to the Stockmayer classification. They are ideal model systems for studying rotational isomers in the gas phase and the self-assembly and local dynamics in the solid state. Gas phase calculations (DFT) provided the dipole moments, the energetic barriers, and the backbone conformation as a function of the dipole streng…

Steel Fibres: Effective Way to Prevent Failure of the Concrete Bonded with FRP Sheets

2016

Although the efficiency of steel fibres for improving mechanical properties (cracking resistance and failure toughness) of the concrete has been broadly discussed in the literature, the number of studies dedicated to the fibre effect on structural behaviour of the externally bonded elements is limited. This experimental study investigates the influence of steel fibres on the failure character of concrete elements strengthened with external carbon fibre reinforced polymer sheets. The elements were subjected to different loading conditions. The test data of four ties and eight beams are presented. Different materials were used for the internal bar reinforcement: in addition to the conventiona…

ChemInform Abstract: Organocatalytic Enantioselective Synthesis of Pyrazoles Bearing a Quaternary Stereocenter.

2016

An efficient one-pot asymmetric synthesis of pyrazoles bearing a chiral quaternary stereocenter has been developed. Quinine-derived thiourea catalyzed the enantioselective addition of pyrazolones to isatin-derived ketimines, providing the corresponding acetylated pyrazoles after in situ treatment with Ac2 O/Et3 N. The corresponding pyrazoles were afforded in high yields and excellent enantioselectivities.

Non-uniformity of displacement and strain within the Achilles tendon is affected by joint angle configuration and differential muscle loading.

2020

Although the Achilles tendon (AT) has been studied for more than a century, a complete understanding of the mechanical and functional consequences of AT structural organization is currently lacking. The aim of this study was to assess how joint angle configuration affects subtendon displacement and strain of soleus (SOL) and lateral gastrocnemius (LG) muscles. Knots sutured onto SOL and LG subtendons of 12 Wistar rats, were videotaped to quantify displacements and the ankle torque was assessed for different isometric activation conditions (i.e., individual and simultaneous) of the triceps surae muscles. Changing ankle and knee joint angle affected the magnitude of displacement, relative dis…

Bearing fault detection based on time-frequency representations of vibration signals

2015

To prevent failures of a rolling bearing in the gearbox drive system, acceleration sensors are used to detect fault-related signals of the bearing. It is a big challenge to observe and identify signals caused by bearing defects in the time domain or the frequency spectrum by a conventional Fourier analysis. The time-frequency representation of the fault-related signals implemented by the windowed Fourier transform is studied in this work. It is shown that the fault characteristic frequencies can be clearly identified in the time-frequency spectrum if a fault occurs in the bearing of the gearbox at different speeds. Otherwise, the shaft frequency and its multiples are the main harmonics in t…

Dynamic Refolding of Ion-Pair Catalysts in Response to Different Anions.

2019

Four distinct folding patterns were identified in two foldamer-type urea-thiourea catalysts bearing a basic dimethylamino unit by a combination of X-ray crystallography, solution NMR studies, and computational studies (DFT). These patterns are characterized by different intramolecular hydrogen bonding schemes that arise largely from different thiourea conformers. The free base forms of the catalysts are characterized by folds where the intramolecular hydrogen bonds between the urea and the thiourea units remain intact. In contrast, the catalytically relevant salt forms of the catalyst, where the catalyst forms an ion pair with the substrate or substrate analogues, appear in two entirely dif…

Solai ad orditura metallica. Per una storia della costruzione

2016

Sommario: Il saggio approfondisce gli aspetti storici e costruttivi dei solai ad orditura metallica dalla fine del XVIII secolo all’ultima guerra. Dopo una parte generale in cui vengono delineate le motivazioni e le fasi iniziali dell’uso dei materiali ferrosi in edilizia, si traccia ed analizza una serie di linee evolutive della trave metallica, fino al raggiungimento della sezione a doppio T che, a pieno titolo, si considera il punto di arrivo della ricerca sulla forma più conveniente per evidenti motivi di efficienza statica, pur coi successivi affinamenti nella produzione, nel calcolo e nella messa in opera. Si è ipotizzata l’evoluzione attraverso le strade della combinazione legno-ferr…