Search results for "force"
showing 10 items of 3423 documents
An Efficient Synthesis of Rubin’s Aldehyde and its Precursor 1,3,5-Tribromo-2,4,6-tris(dichloromethyl)benzene
2011
2,4,6-Tribromobenzene-1,3,5-tricarboxaldehyde (4) can be efficiently prepared in two reaction steps from 1,3,5-tribromobenzene. The intermediate 1,3,5-tribromo-2,4,6-tris(dichloromethyl)benzene (3) crystallizes from petroleum ether in its C3h structure. However, in CDCl3 solution it exists at room temperature in two isomeric forms: 3a (C3h) and 3b (Cs) (1:1.15).The intramolecular Br・・・Cldistances are much smaller than the sum of the van der Waals radii. Therefore, the exocyclic C-C bonds show a hindered rotation.
Bis-, Tris-, and Tetrakis(squaraines) Linked by Stilbenoid Scaffolds
2001
The oligosquaraines 1−5, with stilbenoid scaffolds, were prepared by multistep syntheses in which the final steps consisted of condensation reactions between the semisquaric acid 21 and multiple resorcinols 12b−15b and 17b. The target compounds exhibit intense (ϵ > 250000 L·mol−1·cm−1) and sharp absorption bands with maxima between 687 to 778 nm, depending on the conjugation in the stilbenoid scaffold. Comparison with the monosquaraine 6 as a model compound reveals intramolecular interactions between different donor−acceptor−donor moieties, which give rise to increased absorption intensities.
ChemInform Abstract: Bis-, Tris-, and Tetrakis(squaraines) Linked by Stilbenoid Scaffolds.
2010
The oligosquaraines 1−5, with stilbenoid scaffolds, were prepared by multistep syntheses in which the final steps consisted of condensation reactions between the semisquaric acid 21 and multiple resorcinols 12b−15b and 17b. The target compounds exhibit intense (ϵ > 250000 L·mol−1·cm−1) and sharp absorption bands with maxima between 687 to 778 nm, depending on the conjugation in the stilbenoid scaffold. Comparison with the monosquaraine 6 as a model compound reveals intramolecular interactions between different donor−acceptor−donor moieties, which give rise to increased absorption intensities.
More Than Just “Stressful”? Testing the Mediating Role of Fatigue on the Relationship Between Job Stress and Occupational Crashes of Long-Haul Truck …
2021
Sergio A Useche,1,2 Francisco Alonso,1,2 Boris Cendales,3 Javier Llamazares4 1Faculty of Psychology, University of Valencia, Valencia, Spain; 2DATS (Development and Advising in Traffic Safety) Research Group, INTRAS (Research Institute on Traffic and Road Safety), University of Valencia, Valencia, Spain; 3Faculty of Economic and Administrative Sciences, El Bosque University, Bogotá, Colombia; 4Department of Technology, ESIC Business and Marketing School, Madrid, SpainCorrespondence: Sergio A UsecheDATS, Carrer del Serpis 29, 3rd Floor, Valencia, 46022, SpainTel +34 611317890Email sergio.useche@uv.esIntroduction: Recent evidence consistently highlights the adverse work environment of long-h…
Double asymmetric intramolecular aza-Michael reaction: a convenient strategy for the synthesis of quinolizidine alkaloids.
2021
A new methodology to access the quinolizidine skeleton in an asymmetric fashion was devised. It involves two consecutive intramolecular aza-Michael reactions of sulfinyl amines bearing a bis-enone moiety, in turn generated by a monodirectional cross metathesis reaction. The sequence, which takes place with excellent yields and diastereocontrol, was applied to the total synthesis of alkaloids lasubine I and myrtine.
Supramolecular self-assembly on the B-Si(111)-(√3x√3) R30° surface: From single molecules to multicomponent networks
2017
Abstract Understanding the physical and chemical processes in which local interactions lead to ordered structures is of particular relevance to the realization of supramolecular architectures on surfaces. While spectacular patterns have been demonstrated on metal surfaces, there have been fewer studies of the spontaneous organization of supramolecular networks on semiconductor surfaces, where the formation of covalent bonds between organics and adatoms usually hamper the diffusion of molecules and their subsequent interactions with each other. However, the saturation of the dangling bonds at a semiconductor surface is known to make them inert and offers a unique way for the engineering of m…
Residual out-of-plane capacity of infills damaged by in-plane cyclic loads
2020
Abstract During earthquakes, infills are subjected to In-Plane (IP) and Out-Of-Plane (OOP) actions. In the case of strong earthquakes, infills may progressively change their mechanical behavior resulting in a reduction of IP and OOP stiffness and strength. Recent earthquakes have proved that the OOP collapse of infills is a diffused mechanism also for buildings designed to resist seismic events in agreement to the most modern codes. This is potentially a very dangerous event with risk for human health. The strong interaction between IP and OOP behavior of infills traduces in a progressive reduction of the OOP strength. The IP damaging loads may cause a loss of the OOP capacity not predicted…
Flexural Response of Reinforced Concrete Beam on Elastic Foundation under Vertical Load and Bending Moment: Review of Existing Methods and Proposed N…
2021
AbstractThis work examined the behavior of a RC beam on a soil foundation subject to concentrated vertical loads and bending moment in both the elastic and the plastic phases. Some of the simplifie...
Elastic Deformation of Dispersely Failing Unidirectionally Reinforced Composites
2003
A phenomenological model is proposed for describing the elastic deformation of a unidirectionally reinforced composite capable of accumulating scattered microdamages during its loading. The composite is considered as a homogeneous transversely isotropic solid. Its damaged state at every point is characterized by a centrally symmetric scalar function on the unit sphere (the damage function), which is used to account for variations in the elastic properties of the material during its deformation. The damage itself depends on the history of some equivalent strain, for which four simplified variants are suggested. The relation between strains and stresses is defined in a differential form. Depe…
Shear force comparative evaluation for surface treated and non- treated 3D interim printed materials with different types of glass-ionomer cements
2020
Background The purpose of this investigation was to compare shear force of different glass-ionomer cements on 3D printed interim material in combination with and without surface pretreatment. Material and Methods 120 rectangular specimens made of printable provisional material (Bego, Bremen, Germany) were used. After post-processing the specimens were blasted with aluminum oxide 110µm (Bego, Bremen, Germany). Extra 120 non-surface treated specimens were used as an experimental negative test group. All 240 specimens were divided randomly into 6 groups. All were cemented with a compressive load of 20 N using universal testing machine Z010 (Zwick/Roell, Ulm, Germany) to ensure a comparable cem…