New inroads in an old subject: Plasticity, from around the atomic to the macroscopic scale

Nonsingular, stressed, dislocation (wall) profiles are shown to be 1-d equilibria of a non-equilibrium theory of Field Dislocation Mechanics (FDM). It is also shown that such equilibrium profiles corresponding to a given level of load cannot generally serve as a travelling wave profile of the governing equation for other values of nearby constant load; however, one case of soft loading with a special form of the dislocation velocity law is demonstrated to have no ‘Peierls barrier’ in this sense. The analysis is facilitated by the formulation of a 1-d, scalar, time-dependent, Hamilton-Jacobi equation as an exact special case of the full 3-d FDM theory accounting for non-convex elastic energy, small, Nye-tensor-dependent core energy, and possibly an energy contribution based on incompatible slip. Relevant nonlinear stability questions, including that of nucleation, are formulated in a non-equilibrium setting. Elementary averaging ideas show a singular perturbation structure in the evolution of the (unsymmetric) macroscopic plastic distortion, thus pointing to the possibility of predicting generally rate-insensitive slow response constrained to a tensorial ‘yield’ surface, while allowing fast excursions off it, even though only simple kinetic assumptions are employed in the microscopic FDM theory. The emergent small viscosity on averaging that serves as the small parameter for the perturbation structure is a robust, almost-geometric consequence of large gradients of slip in the dislocation core and the persistent presence of a large number of dislocations in the averaging volume. In the simplest approximation, the macroscopic yield criterion displays anisotropy based on the microscopic dislocation line and Burgers vector distribution, a dependence on the Laplacian of the incompatible slip tensor and a nonlocal term related to a Stokes-Helmholtz-curl projection of an ‘internal stress’ derived from the incompatible slip energy.     

Continuity in the plastic strain rate and its influence on texture evolution

Classical plasticity models evolve state variables in a spatially independent manner through (local) ordinary differential equations, such as in the update of the rotation field in crystal plasticity. A continuity condition is derived for the lattice rotation field from a conservation law for Burgers vector content—a consequence of an averaged field theory of dislocation mechanics. This results in a nonlocal evolution equation for the lattice rotation field. The continuity condition provides a theoretical basis for assumptions of co-rotation models of crystal plasticity. The simulation of lattice rotations and texture evolution provides evidence for the importance of continuity in modeling of classical plasticity. The possibility of predicting continuous fields of lattice rotations with sharp gradients representing non-singular dislocation distributions within rigid viscoplasticity is discussed and computationally demonstrated.     

Near-field measurements and development of a new boundary layer over a flat plate with localized suction

Suction on a turbulent boundary layer is applied through a narrow strip in order to understand the effects suction can have on the boundary layer development and turbulent structures in the flow. Detailed two-component laser Doppler velocimetry (LDV) and laser-induced fluorescence (LIF) based measurements have been undertaken in regions close to the suction strip and further downstream. The region close to the strip involves a flow reversal accompanied by a change in sign for the Reynolds shear stress and strong gradients in the flow variables. The mean streamwise velocity after suction remains larger than its corresponding no-suction value. Relative to the no-suction case, the velocity fluctuations first decrease with suction followed by a slow recovery which may involve a slight overshoot. LIF visualizations indicate that compared to the no-suction case, the low-speeds streaks stay closer to the wall and exhibit a smaller amount of spanwise and wall-normal oscillations with suction. The visualization results are consistent with two-point velocity correlation measurements. The streamwise and spanwise correlation measurements indicate that the structures are disrupted or removed from the boundary layer due to suction suggesting that the original boundary layer has been strongly influenced by suction. The results are explained by the development of a new inner layer that forms downstream of the suction strip.     

Naphthoflavone propargyl ether inhibitors of cytochrome P450

Cytochrome P450 enzymes protect the body from foreign substances through a mechanism that involves oxidation of those substances into more readily excretable polar compounds. It has been shown that some naphthoflavones function as substrates of certain P450 enzymes (CYP1A1 and CYP1B1) and with appropriate structural changes may become inhibitors. Moreover, propargyl ether derivatives of adamantane have been shown to function as selective inactivators of some P450 enzymes (CYP2B1 and CYP2B5). In an attempt to improve the potency and selectivity of inhibition, we have designed and synthesized a series of naphthoflavone propargyl ethers. We report here the synthesis, X-ray crystal structures, and inhibition data (IC₅₀ of EROD inhibition in CYP1A1 and CYP1B1 enzymes) of α-naphthoflavone 2′-propargyl ether, β-naphthoflavone 2′-propargyl ether, α-naphthoflavone 4′-propargyl ether, and β-naphthoflavone 4′-propargyl ether. Crystallographic data: α-naphthoflavone 2′-propargyl ether, , a=7.775(1) ?, b=8.062(1) ?, c=13.110(1) ?, α=84.32(1)°, β=75.42(1)°, γ=86.56(1)°, V=790.8(2) ?³; β-naphthoflavone 2′-propargyl ether, , a=7.605(2) ?, b=7.793(1) ?, c=14.167(2) ?, α=77.06(1)°, β=75.41(1)°, γ=89.54(1)°, V=790.9(2) ?³; α-naphthoflavone 4′-propargyl ether, P21/n, a=14.595(2) ?, b=4.708(1) ?, c=24.745(6) ?, β=106.31(2)°, V=1631.8(7) ?³; β-naphthoflavone 4′-propargyl ether, P1, a=4.8871(5) ?, b= 7.9597(7) ?, c=21.788(3) ?, α=81.771(9)°, β=89.918(10)°, γ=72.223(8)°, V= 797.9(2) ?³.     

Natural and Synthetic Agents Targeting Reactive Carbonyl Species against Metabolic Syndrome

Reactive carbonyl species (RCS) may originate from the oxidation of unsaturated fatty acids and sugar in conditions of pathology. They are known to have high reactivity towards DNA as well as nucleophilic sites of proteins, resulting in cellular dysfunction. It has been considered that various pathological conditions are associated with an increased level of RCS and their reaction products. Thus, regulating the levels of RCS may be associated with the mitigation of various metabolic and neurodegenerative disorders. In order to perform a comprehensive review, various literature databases, including MEDLINE, EMBASE, along with Google Scholar, were utilized to obtain relevant articles. The voluminous review concluded that various synthetic and natural agents are available or in pipeline research that hold tremendous potential to be used as a drug of choice in the therapeutic management of metabolic syndrome, including obesity, dyslipidemia, diabetes, and diabetes-associated complications of atherosclerosis, neuropathy, and nephropathy. From the available data, it may be emphasized that various synthetic agents, such as carnosine and simvastatin, and natural agents, such as polyphenols and terpenoids, can become a drug of choice in the therapeutic management for combating metabolic syndromes that involve RCS in their pathophysiology. Since the RCS are known to regulate the biological processes, future research warrants detailed investigations to decipher the precise mechanism.     

Experimental and DFT Evidence for the Fractional Non‐Innocence of a β‐Diketonate Ligand

New compounds [Ru(pap)₂(L)](ClO₄), [Ru(pap)(L)₂], and [Ru(acac)₂(L)] (pap=2‐phenylazopyridine, L^?=9‐oxidophenalenone, acac^?=2,4‐pentanedionate) have been prepared and studied regarding their electron‐transfer behavior, both experimentally and by using DFT calculations. [Ru(pap)₂(L)](ClO₄) and [Ru(acac)₂(L)] were characterized by crystal‐structure analysis. Spectroelectrochemistry (EPR, UV/Vis/NIR), in conjunction with cyclic voltammetry, showed a wide range of about 2 V for the potential of the Ru^III/II couple, which was in agreement with the very different characteristics of the strongly π‐accepting pap ligand and the σ‐donating acac^? ligand. At the rather high potential of +1.35 V versus SCE, the oxidation of L^? into L^. could be deduced from the near‐IR absorption of [Ru^III(pap)(L^.)(L^?)]²⁺. Other intense long‐wavelength transitions, including LMCT (L^?→Ru^III) and LL/CT (pap^.?→L^?) processes, were confirmed by TD‐DFT results. DFT calculations and EPR data for the paramagnetic intermediates allowed us to assess the spin densities, which revealed two cases with considerable contributions from L‐radical‐involving forms, that is, [Ru^III(pap⁰)₂(L^?)]²⁺?[Ru^II(pap⁰)₂(L^.)]²⁺ and [Ru^III(pap⁰)(L^?)₂]⁺?[Ru^II(pap⁰)(L^?)(L^?)]⁺. Calculations of electrogenerated complex [Ru^II(pap^.?)(pap⁰)(L^?)] displayed considerable negative spin density (?0.188) at the bridging metal.     

Cyclization Dynamics and Competitive Processes of Photochromic Perfluorocyclopentene Dithienylethylene in Solution

Time-resolved absorption spectroscopy measurements were performed to study the dynamics of photochromic 1,2-Bis(2,4-dimethylthiophene-3-yl)perfluoro-cyclopentene (DMTPF) in chloroform, including antiparallel conformer ring-closure reaction and parallel conformer photophysics. All characteristic times are given, discussed and compared to a previous publication concerning the close molecule substituted with phenyl rings. (Hamdi et al., PCCP, 2016). Apart from the expected photocyclization process, condensed ring by-product formation is observed and hypotheses concerning the origin of this by-product are presented.     

Crystallization kinetics of compatibilized blends of polypropylene and polyethylenimine

Journal of Thermal Analysis and Calorimetry - In this paper, isothermal and non-isothermal crystallization behaviour of neat polypropylene (PP), blends of PP/maleic anhydride grafted polypropylene...     

UHPLC–Q-TOF–MS/MS-based metabolite profiling of duvelisib and establishment of its metabolism mechanisms

Duvelisib is a dual inhibitor of phosphoinositide 3 kinase that received global approval by the US Food and Drug Administration in 2018 to treat follicular lymphoma after at least two prior systemic therapies. An extensive literature search revealed that, to date, metabolites of duvelisib have not been characterized and information on them is not available in any of the literature. Moreover, the metabolism pathway is yet to be established. This study aimed to investigate and characterize the metabolites of duvelisib generated in microsomes and S9 fractions. In this study, five duvelisib metabolites were identified using UHPLC–Q-TOF–MS/MS analysis technique. The structural characterization of the metabolites was performed by comparing the fragmentation pattern of duvelisib and its metabolites through an accurate mass measurement technique. Three metabolites were generated through phase I hydroxylation and dechlorination reactions. The other two metabolites were generated through a phase II glucuronidation reaction. The metabolism mechanism established through this study can be useful to improve the safety profile of drugs of similar categories in the future after establishment of the toxicity profile of the identified metabolites.