DBU‐Mediated Intermolecular 5‐exo‐dig Cyclization of PropargylAlcohols and Carbon Disulfide to [1,3]‐Oxathiole‐2‐thiones

5‐exo‐dig is a versatile Baldwin tool to predict and make useful heterocyclic compounds from nucleophiles and electrophiles. In order to aid this, a novel metal‐free method is proposed to produce [1,3]‐oxathiole‐2‐thiones from a readily synthesized propargyl alcohols and easily accessible carbon disulfide, where both secondary and primary propargyl alcohols are compatible to this methodology. This procedure is simple, versatile, atom economy and functional group tolerance resulting in moderate to excellent yields. Finally, the process was screened on different mode of reaction operation

Highly Z-selective synthesis of 1,3-oxathiol-2-ylidenes and 4-methylene-oxazolidine-2-thiones via atom-specific 5-exo-dig cyclization of propargyl alcohol with isothiocyanate

DBU mediated 5-exo-dig cyclization of isothiocyanate and propargyl alcohol leading to valuable heterocyclic compounds has been accomplished. The different modes of nucleophilicity (either S-selective or N-selective) of isothiocyanates were found to depend on the substitution pattern of propargyl alcohol. The terminal propargyl alcohol and isothiocyanate underwent an N-nucleophilic attack to afford 3-substituted 4-methylene oxazolidine-2-thiones. In contrast, exclusive S-nucleophilic cyclization was observed with internal propargyl alcohol to produce (Z)-1,3-oxathiol-2-ylidenes and (Z)-N-(Z)-4-ethylidene-1,3-oxathiolan-2-ylidenes from secondary and primary propargyl alcohols, respectively. The formation of high Z-selectivity in the imine motif and alkene is the highlight of this new method as multiple selectivities over C[double bond, length as m-dash]N and C[double bond, length as m-dash]C in a single system are synthetically highly challenging. The Z-selectivity in imine and alkene may be attributed to electronic and steric factors respectively

PINNsFormer: A Transformer-Based Framework For Physics-Informed Neural Networks

Physics-Informed Neural Networks (PINNs) have emerged as a promising deep learning framework for approximating numerical solutions for partial differential equations (PDEs). While conventional PINNs and most related studies adopt fully-connected multilayer perceptrons (MLP) as the backbone structure, they have neglected the temporal relations in PDEs and failed to approximate the true solution. In this paper, we propose a novel Transformer-based framework, namely PINNsFormer, that accurately approximates PDEs' solutions by capturing the temporal dependencies with multi-head attention mechanisms in Transformer-based models. Instead of approximating point predictions, PINNsFormer adapts input vectors to pseudo sequences and point-wise PINNs loss to a sequential PINNs loss. In addition, PINNsFormer is equipped with a novel activation function, namely Wavelet, which anticipates the Fourier decomposition through deep neural networks. We empirically demonstrate PINNsFormer's ability to capture the PDE solutions for various scenarios, in which conventional PINNs have failed to learn. We also show that PINNsFormer achieves superior approximation accuracy on such problems than conventional PINNs with non-sensitive hyperparameters, in trade of marginal computational and memory costs, with extensive experiments.Comment: 15 pages (including 9 pages of main text, 3 pages of references, and 3 pages of appendix), 4 figures, 5 table

Designa and Evaluation of Microsponge Drug Delivery of Psoralen - Isolated from Psoralea Corylifolia

The present study was to produce ethylcellulose microparticles containing BPO which were able to control the release of BPO to the skin and reduces the side effect of commercial BPO such as irritation and percutaneous absorption. Generally, an increase in the ratio of drug: polymer resulted in a reduction in the release rate of BPO from Microsponges. The aim of the present study was to produce ethylcellulose microparticles containing BPO which were able to control the release of BPO to the skin and reduces the side effect of commercial BPO such as irritation and percutaneous absorption. Generally, an increase in the ratio of drug: polymer resulted in a reduction in the release rate of BPO from Microsponges

Microstructure and texture evolution during thermomechanical processing of β-quenched Zr

The microstructure and texture evolution of an α-Zr alloy during thermomechanical processing was investigated, starting from the β-quenched microstructure. The material was rolled at 550 °C to reductions of 10, 20, 40 and 60%, and held at 550 °C for 24 h. EBSD was used to measure the texture at the different reductions and characterize the microstructural evolution, and crystal plasticity finite element modelling was used as a theoretical framework to help understand the changes in texture observed. Our results show that slip, twinning and recrystallization all play a role in the microstructure development during hot rolling. Their contribution to texture development, lamellae break-up and the ultimate development of a bimodal microstructure are discussed

Fracture toughness of cemented carbides obtained by electrical resistance sintering

The unique combination of hardness, toughness and wear resistance exhibited by WC-Co cemented carbides (hardmetals) has made them a preeminent material choice for extremely demanding applications, such as metal cutting/forming tools or mining bits, in which improved and consistent performance together with high reliability are required. The high fracture toughness values exhibited by hardmetals are mainly due to ductile ligament bridging and crack deflection (intrinsic to carbides). In this work two WC-Co grades obtained by using the electric resistance sintering technique are studied. The relationships between the process parameters (cobalt volume fraction, sintering current and time, die materials, etc.), the microstructural characteristics (porosity, cobalt volume fraction, carbide grain size, binder thickness and carbide contiguity) and mechanical properties (Vickers hardness and fracture toughness) are established and discussed. Also the presence of microstructural anisotropy and residual stresses is studied. The sintering process at 7 kA, 600 ms and 100 MPa, in an alumina die, followed by a treatment of residual stress relief (800 °C, 2 h in high vacuum), allows to obtain WC-Co pellets with the best balance between an homogeneous microstructure and mechanical behaviour.EU for funding this research with in the framework of the EU 7th Framework FoF.NMP.2013-10 608729 EFFIPRO Projec

The Relativistic Dirac-Brueckner Approach to Asymmetric Nuclear Matter

The properties of asymmetric nuclear matter have been investigated in a relativistic Dirac-Brueckner-Hartree-Fock framework using the Bonn A potential. The components of the self-energies are extracted by projecting on Lorentz invariant amplitudes. Furthermore, the optimal representation scheme for the $T$ matrix, the subtracted $T$ matrix representation, is applied and the results are compared to those of other representation schemes. Of course, in the limit of symmetric nuclear matter our results agree with those found in literature. The binding energy $E_b$ fulfills the quadratic dependence on the asymmetry parameter and the symmetry energy is 34 MeV at saturation density. Furthermore, a neutron-proton effective mass splitting of $m_n^* < m_p^*$ is found. In addition, results are given for the mean-field effective coupling constants.Comment: 28 pages, 7 figures, to appear in Nucl. Phys. A, added additional reference

The effect of loading direction and Sn alloying on the deformation modes of Zr: An in-situ neutron diffraction study

Deformation modes (slip and twining) in a strongly textured model hcp alloy system (Zr–Sn) have been investigated using in-situ neutron diffraction and deformation along with complementary electron microscopy. Analysis of the evolution of the intergranular strain evolutions and intensity of specific reflections from neutron diffraction show differential influence of Sn on the extent of twinning too, depending on the deformation direction. While Sn displayed very noticeable influence on twin activity when samples were compressed along a direction that predominantly activates prismatic slip, this effect was not seen when samples were compressed along other different directions. These experimental observations were successfully simulated using a CPFE (crystal plasticity finite element) model that incorporates composition sensitive CRSS (critical resolved shear stress) for slip and composition insensitive CRSS activation of twinning. The success of the CPFE model in capturing the experimental observations with respect to twin evolution suggests that the twinning in Zr is chiefly governed by the initial crystallographic texture and the associated intergranular stress state generated during plastic deformation

The effect of aluminium on twinning in binary alpha-titanium

The deformation mechanisms of binary Ti–Al model alloys (0–13.1 at.% Aluminium) have been investigated with respect to the twinning activity using in-situ loading in combination with neutron diffraction as well as detailed post mortem electron backscatter diffraction analysis. A consistent starting grain size and texture was generated for all alloys promoting tensile twinning during compression testing. Long-wavelength neutron diffraction and selected area diffraction transmission electron microscopy analysis were carried out to detect evidence of Aluminium ordering and Ti3Al formation.It was found that raising the Aluminium content in Titanium does first slightly enhance twinning, with {10View the MathML source2} tensile twinning being by far the dominant type, while the critical residual intergranular strains for twin initiation decreases. This suggests that either the lowering of stacking fault energy by Aluminium or its solute solution strengthening effect are important factors. At around 7 at.% Aluminium a turning point in twinning activity was noticed and a further increase in Aluminium did result in a dramatic loss of twinning activity particularly when the material had been exposed to an additional low temperature age. The dramatic decrease of twinning activity is strongly correlated with increasing evidence of short range ordering and also early signs of Ti3Al-formation in case of the highest Aluminium content. In addition, electron backscatter diffraction analysis revealed that the formation of Aluminium ordered zones do severely hinder growth of twin boundaries

Oscillations of neutrinos and mesons in quantum field theory

This report deals with the quantum field theory of particle oscillations in vacuum. We first review the various controversies regarding quantum-mechanical derivations of the oscillation formula, as well as the different field-theoretical approaches proposed to settle them. We then clear up the contradictions between the existing field-theoretical treatments by a thorough study of the external wave packet model. In particular, we show that the latter includes stationary models as a subcase. In addition, we explicitly compute decoherence terms, which destroy interferences, in order to prove that the coherence length can be increased without bound by more accurate energy measurements. We show that decoherence originates not only in the width and in the separation of wave packets, but also in their spreading through space-time. In this review, we neither assume the relativistic limit nor the stability of oscillating particles, so that the oscillation formula derived with field-theoretical methods can be applied not only to neutrinos but also to neutral K and B mesons. Finally, we discuss oscillations of correlated particles in the same framework.Comment: v2, 124 pages, 10 figures (7 more); updated review of the literature; complete derivation of the oscillation probability at short and large distance; more details on the influence of the spreading of the amplitude on decoherence; submitted to Physics Report