Opposite Faces Research Articles

Hydroxylation with Unusual Stereoinversion Catalyzed by an FeII/2‐OG Dependent Oxidase and 3,6‐Diene‐2,5‐diketopiperazine Formation in the Biosynthesis of Brevianamide K

AbstractNatural products with the 3,6‐diene‐2,5‐diketopiperazine core are widely distributed in nature; however, the biosynthetic mechanism of 3,6‐diene‐2,5‐diketopiperazine in fungi remains to be further elucidated. Through heterologous expression and biochemical investigation of an FeII/2‐oxoglutarate‐dependent oxidase (AspE) and a heme‐dependent P450 enzyme (AspF), we report that AspE, AspF and subsequent dehydration account for the formation of the 3,6‐diene‐2,5‐diketopiperazine substructure of brevianamide K from Aspergillus sp. SK‐28, a symbiotic fungus of mangrove plant Kandelia candel. More interestingly, in‐depth investigation of the enzymatic mechanism showed that AspE promotes hydroxylation of brevianamide Q with unprecedented stereoinversion through hydrogen atom abstraction and water nucleophilic attack from the opposite face of the resultant iminium cation intermediate.

Hydroxylation with Unusual Stereoinversion Catalyzed by an FeII /2-OG Dependent Oxidase and 3,6-Diene-2,5-diketopiperazine Formation in the Biosynthesis of Brevianamide K.

Natural products with the 3,6-diene-2,5-diketopiperazine core are widely distributed in nature; however, the biosynthetic mechanism of 3,6-diene-2,5-diketopiperazine in fungi remains to be further elucidated. Through heterologous expression and biochemical investigation of an FeII /2-oxoglutarate-dependent oxidase (AspE) and a heme-dependent P450 enzyme (AspF), we report that AspE, AspF and subsequent dehydration account for the formation of the 3,6-diene-2,5-diketopiperazine substructure of brevianamide K from Aspergillus sp. SK-28, a symbiotic fungus of mangrove plant Kandelia candel. More interestingly, in-depth investigation of the enzymatic mechanism showed that AspE promotes hydroxylation of brevianamide Q with unprecedented stereoinversion through hydrogen atom abstraction and water nucleophilic attack from the opposite face of the resultant iminium cation intermediate.

Measuring material thickness changes through tri-aperture digital speckle pattern interferometry

A configuration for the measurement of thickness changes in materials through one-shot digital speckle pattern interferometry (DSPI) was developed. The phase maps calculation was made by adding carrier fringes by the multiple aperture principle and Fourier Transform Method (FTM). With this setup, interferometry configurations verified that the simultaneous and instantaneous visualization of two opposite faces of a surface is possible. In addition, the combination of the simultaneous results obtained from both sides of the material makes it possible to determine displacements with greater sensitivity or to identify changes in their thickness. The validation and demonstrative tests were carried out with a 1-mm-thick aluminum plate with a 5-mm diameter through hole coated. Thickness changes to 2 μm were measured.

Simultaneous Treatment of Both Sides of the Polymer with a Conical-Shaped Atmospheric Pressure Plasma Jet.

A conical-shaped atmospheric pressure plasma jet (CS-APPJ) was developed to overcome a standard limitation of APPJs, which is their small treatment area. The CS-APPJs increase the treatment area but use the same gas flow. In the present work, polypropylene samples were treated by CS-APPJ and characterized by scanning electron microscope (SEM), the contact angle, Fourier-transformed infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). It was observed that the treatment co-occurs on the face directly in contact with the plasma and on the opposite face (OF) of the samples, i.e., no contact. However, the treatment changed the chemical composition on each side; the OF is rougher than the direct contact face (DCF), probably due to the oxygen groups in excess at the DCF and nitrogen in quantity at the OF. Although simultaneous treatment of both sides of the sample occurs for most atmospheric plasma treatments, this phenomenon is not explored in the literature.

Diamond Photoconductive Antenna for Terahertz Generation Equipped with Buried Graphite Electrodes

It has been shown recently that a photoconductive antenna (PCA) based on a nitrogen-doped diamond can be effectively excited by the second harmonic of a Ti:sapphire laser (λ = 400 nm). The THz emission performance of the PCA can be significantly increased if a much stronger electric field is created between the close-located electrodes. To produce a homogeneous electric field over the entire excited diamond volume, the laser fabrication of deep-buried graphite electrodes inside the diamond crystal was proposed. Several electrodes consisting of the arrays of buried pillars connected by the surface graphite stripes were produced inside an HPHT diamond crystal using femtosecond and nanosecond laser pulses. Combining different pairs of the electrodes, a series of PCAs with various electrode interspaces was formed. The THz emission of the PCAs equipped with the buried electrodes was measured at different values of excitation fluence and bias voltage (DC and pulsed) and compared with the emission of the same diamond crystal when the bias voltage was applied to the surface electrodes on the opposite faces. All examined PCAs have demonstrated the square-law dependencies of the THz fluence on the field strength, while the saturation fluence fluctuated in the range of 1200–1600 µJ/cm2. The THz emission performance was found to be approximately the same for the PCAs with the surface electrodes and with the buried electrodes spaced at a distance of 1.4–3.5 mm. However, it noticeably decreased when the distance between the buried electrodes was reduced to 0.5 mm.

Shrinkage of frame polymer concretes in road construction

It is known that with the same raw material composition, it is possible to obtain different structures of composite materials. So, for example, polymer concretes can be made using traditional technology and the method of phase-by-phase forming. At the same time, frame technology reduces material consumption without loss of strength properties and increases durability. Polymer composite materials of phase-forming by combining properties viscoelastic binder and rigid matrix. It has highly damping performance. The article considers the possibility of using the frame structure polymer composite material in road construction. The composition is also considered, the advantages are determined and a comparison with traditional materials is made. The shrinkage stresses of polymer concrete that occur during the polycondensation reaction of furan resin are quite large and can exceed the permissible ones, which leads to a violation of the monolithic nature of the structure due to the appearance of micro- and macrocracks. In this work, the kinetics of shrinkage within 28 days was studied. The composition of the frame polymer composite material includes the following components: furfural acetone monomer (FAM resin), benzosulfonic acid, granite crushed stone, andesite flour, quartz sand. Theshrinkage of phase-formed polymer concrete was measured on samples hardening under normal temperature-humidity conditions. The generally accepted technique was used, shrinkage deformations were installed along the axis of the sample on two opposite faces with a clock-type indicator with a division price of 0.001 mm. Also in the work is a diagram of the device for determining the deformations of the shrinkage of samples and the results of the study are given. Experimentally established the intensity of shrinkage, which manifests itself in the first three days of curing, in the future its change is insignificant and by the seventh day it fades. According to the test results, it was established that the linear shrinkage of frame polymer concretes is three times less than the shrinkage of polymer concretes with a conventional structure.

Angularly fused diaza-dinaphthopyrenes: regio-selective synthesis, crystal structures and isomer-dependent mechanochromic fluorescent properties.

We report a one-pot synthesis of a series of unprecedented angular-fused diaza-dinaphthopyrene isomers (1,8-DNPy and 1,6-DNPy) in high yields, which are enabled by regio-selective Bischler-Napieralski cyclization to fuse two quinolone rings either on the same or opposite faces of a pyrene core. Benefiting from the high reactivity of the 1- and 8-positions of the pyrene ring, steric effect from substitution and remarkably different dipole moments, high ring closure selectivity for the 1,8-form vs. the 1,6-form up to 6 : 1 is achieved with ease of separation. With differentiated molecular symmetry, conformation, intermolecular interactions and aromaticity, the two kinds of regio-isomers exhibit distinct single-crystal structures and optoelectronic properties. Impressively, isomer-dependent mechanochromic fluorescent properties of these 2D-azaacenes are identified, which are unique in their turn-on fluorescence feature and contrasting spectral shifts. These findings allow facile and modular access to regio-specific 2D-N-heteroarenes, which provide a way to create innovative optical sensors with improved sensitivity and fruitful fluorescent properties.

Effect of Replacement Ratio on Torsional Behaviour of Recycled Aggregate Concrete Beams

In the past two decade, researchers have studied the flexural, shear and bond behaviour of recycled aggregate concrete (RAC) beams. This work intends to analyze the behaviour of RAC beams under pure torsion, despite the lack of information on its behaviour under pure torsion. The coarse recycled concrete aggregates (RCA) extracted from construction and demolition (C & D) waste was used to replace natural coarse aggregates (NCA) in 0 %, 50 %, and 100 % ratio. Their recycling could help preserve the environment and promote sustainability through solid waste management. Six beams, each of size 150 x 250 x 1800 mm were prepared and tested. To detects minor deformation and to achieve the same strength through the out-of-plane direction, 250 mm inbuilt cantilever projections were provided on opposite faces of the beams at a span of 1000 mm along the longitudinal axis. The ultimate torsional capacity of tested beams was lower by 7.41 %, 8.60 % and 13.58 % than ATENA-3D (FEM) for 0 %, 50 % and 100 % RCA. The change in the replacement ratio of aggregate has a low impact on the ultimate torque and angle of twist. Based on the experimental and analytical results, it was established that the torque resistance capacity of the RAC beam was reduced as the % of RCA increased. Similar crack patterns and failure behaviour were observed in RAC and NAC beams in both studies. Therefore, it is practically possible to apply RAC in structural applications under pure torsional loading.

A Cyclic True Triaxial with Rigid-Rigid-Flexible Boundary for Determination of Cross-Anisotropic Nature of Geomaterials

Abstract This paper describes a custom-designed Soil Poly-Axial Test System, SPAX-3000, developed to investigate the cross-anisotropic material properties of geomaterials under varying loading conditions. SPAX-3000, a mixed-boundary type of large-scale cyclic true triaxial apparatus (CTTA), is capable of applying a wide range of principal stress combinations on prismatic specimens of dimensions 152 × 152 × 304 mm. Two vertical and two horizontal load actuators on two opposite faces apply principal major (σ1) and intermediate (σ2) stresses independently to evaluate the performance of pavement structures under anisotropic stress states through resilient modulus (MR) testing. SPAX-3000 is controlled through software (CATS Software, provided by the manufacturer to provide advanced digital servo control of stresses and deformations). In this study, SPAX-3000 capabilities were evaluated through MR testing of both isotropic (urethane rubber) and cross-anisotropic materials (base, subbase, and subgrade) for the development of stress histories. The test results showed that SPAX-3000 is capable of determining MR independently of the anisotropy characteristics of the tested materials. Stress-hardening and stress-softening behaviors were observed for the coarse- and fine-grained geomaterials under different loading conditions. Anisotropy ratios (ratio of horizontal MR [MhR] to the vertical MR [MvR]) were determined for the base, subbase, and subgrade materials. MR test results showed that higher MvR results were obtained than that of MhR regardless of the loading conditions. The anisotropy ratios ranged from 0.08 to 0.21, 0.38 to 0.87, and 0.05 to 0.50 for the base, subbase, and subgrade materials, respectively. The highest MvR values (200–590 MPa) were obtained for the base material, whereas subbase material yielded the highest MhR (35–169 MPa). In general, stress-hardening behavior was observed for the geomaterials tested in both directions except for the stiffness of subgrade and subbase materials in the vertical direction.

EVOLUTION OF THE FIELD OF DISTRIBUTED DEFECTS IN A CRYSTAL DURING CONTACT INTERACTION WITH A SYSTEM OF RIGID STAMPS

The article discusses the mathematical modeling for the evolution of the stress-strain state and fields of defects in crystals during their contact interaction with a system of rigid punches. From a macroscopic point of view, the redistribution of defects is characterized by inelastic (viscoplastic) deformation, and therefore the processes under study can be classified as elastic-viscoplastic. Elastic and inelastic deformations are assumed to be finite. To take into account inelastic deformations, it is proposed to use a differential-geometric approach, in which the evolution of the fields of distributed defects is completely characterized by measures of incompatible deformations and quantified by material connection invariants. This connection is generated by a non-Euclidean metric, which, in turn, is given by a field of symmetric linear mappings that define (inconsistent) deformations of the crystal. Since the development of local deformations depends both on thecontact interaction at the boundary and on the distribution of defects in the bulk of the crystal, the simulation problem turns out to be coupled. It is assumed that the local change in the defect density is determined by the first-order Alexander Haasen Sumino evolutionary law, which takes into account the deviatoric part of the stress field. An iterative algorithm has been developed to find coupled fields of local deformations and defects density. The numerical analysis for the model problem was provided for a silicon crystal in the form of a parallelepiped, one face of which is rigidly fixed, and a system of rigid stamps acts on the opposite face. The three-constant Mooney Rivlin potential was used to model the local elastic response.

Energy absorption characteristics of E-glass/epoxy over-wrapped aluminum pipes with induced holes: an experimental research

The effect of inducing circular holes into aluminum wrapped with glass/epoxy (Al/GFRP) pipes was investigated. Intact and holed specimens were evaluated in quasi-static axial compression after being constructed using the wet wrapping procedure. The effect of the induced holes' parameters i.e., hole diameter (d), number of holes (n), the hole position to specimen height ratio (L/H), on the crashworthiness of Al/GFRP structures was investigated. Results indicated that the existence of the cutouts visibly affects the values of crushing parameters. Increasing (d) remarkably reduces the total absorbed energy (U) and enhances the crushing force efficiency (CFE) of Al/GFRP pipes. Introducing two holes in two opposite faces with keeping their location constant reduces initial peak crush force {(mathrm{F}}_{mathrm{ip}}), mean crush force {(mathrm{F}}_{mathrm{m}}), and U of Al/GFRP pipes but increases CFE. As the hole location goes to the lower edge of the pipe i.e., L/H increases, U obviously increases. The specimens with 4 mm holes in one side at medium height and specimens with 12 mm holes on one side at L/H = 0.8 had the best crushing parameters, respectively. The adequate design of the induced cutouts in thin-walled constructions is valuable to enhance the crashworthy performance of engineering structures.

Determining the position of two cracks in a cantilever beam using artificial neural networks

During functioning time, structures such as beams are subjected to a variety of loads caused by the working conditions and environment, which can lead to the development of cracks. The current research is concerned with detecting the presence and location of two transverse breathing cracks, in cantilever beams. Starting from the known fact that damages produce a stiffness degradation in structures altering their dynamic parameters, we performed modal simulations of damaged beams to determine their natural frequencies. By using the simulation data, we trained an artificial neural network (ANN), using the feedforward backpropagation algorithm, that is capable to detect the presence of the cracks, their position and for the case when the damages are in proximity, the model can determine if the cracks occur on the same face or opposite faces.

Flocking in one dimension: Asters and reversals.

We study the one-dimensional active Ising model in which aligning particles undergo diffusion biased by the signs of their spins. The phase diagram obtained varying the density of particles, their hopping rate, and the temperature controlling the alignment shows a homogeneous disordered phase but no homogeneous ordered one, as well as two phases with localized dense structures. In the flocking phase, large ordered aggregates move ballistically and stochastically reverse their direction of motion. In what we termed the "aster" phase, dense immobile aggregates of opposite magnetization face each other, exchanging particles, without any net motion of the aggregates. Using a combination of numerical simulations and mean-field theory, we study the evolution of the shapes of the flocks, the statistics of their reversal times, and their coarsening dynamics. Solving exactly for the zero-temperature dynamics of an aster allows us to understand their coarsening, which shows extremal dynamics, while mean-field equationsaccount for their shape.

Asymmetrical Electrical Performance across Different Planes of Solution-Grown MAPbBr3 Crystals of mm Dimensions.

Throughout a few years, carrier transport studies across HaP single crystals have gained enormous importance for current generation photovoltaic and photodetector research with their superior optoelectronic properties compared to commercially available polycrystalline materials. Utilizing the room-temperature solution-grown method, we synthesized MAPbBr3 crystals and examined their electrical transport properties. Although the X-ray diffraction reveals the cubical nature of the crystals, we have observed anisotropy in the electrical transport behavior and variation in dielectric constant across the three opposite faces of the crystals of mm dimensions. The face with a higher dielectric constant depicts improved parameters from electrical characteristics such as lower trap densities and higher mobility values. We further explore the origin of its anisotropic nature by performing X-ray diffraction on three opposite faces of crystals. Our studies define the specific faces of cuboid-shaped MAPbBr3 crystals for efficient electrical contact in the fabrication of optoelectronic devices.

Crystal structure of a heterotrimetallic 12-metallacrown-4 with 2-propylvalerate anion bridges

The synthesis and single-crystal X-ray structure for tetraaquatetrakis(μ-2-propylvalerato)tetrakis(μ4-salicylhydroximato)dysprosiumtetramanganesesodium dimethylformamide tetrasolvate, [DyMn4Na(C7H4NO3)4(C8H15O2)4(H2O)4]·4C3H7NO or DyNa(2-PV)4[12-MCMnIII Nshi-4](H2O)4·4DMF, 1, where MC is metallacrown, shi3− is salicylhydroximate, 2-PV is 2-propylvalerate, and DMF is N,N-dimethylformamide, is reported. The slightly domed metallamacrocycle contains four ring MnIII ions and four shi3− ligands that generate an [MnIII—N—O] repeat unit that recurs four times. The ring MnIII ions are five-coordinate with a square-pyramidal shape. Furthermore, the metallacrown binds both a DyIII ion and a Na+ ion in the central cavity. The central ions are located on opposite faces of the cavity with the DyIII ion located on the convex side of the MC and the Na+ ion located on the concave side. Each central ion is eight-coordinate although they possess different geometries. The DyIII ion has a square-antiprismatic shape, while the Na+ ion has an extremely distorted biaugmented trigonal–prismatic shape. The four 2-propylvalerate anions help to tether the DyIII to the MC cavity by forming bridges between the DyIII ion and each ring MnIII ion. Moreover, the interstitial DMF molecules are hydrogen bonded to the water molecules that complete the coordination environment of the Na+ ion. The metallacrown framework (excluding the DyIII and Na+ ions), the bridging 2-propylvalerate, and the interstitial DMF molecule experience whole-molecule disorder due to the rotational orientation of the metallamacrocycle. Additionally, the main moiety alkyl chain of the 2-propylvalerate is disordered over two additional orientations, and the main moiety interstitial DMF molecule is disordered over one additional orientation. The main moiety of the metallacrown framework refined to 0.9030 (14), while the minor B-moiety refined to 0.0971 (14). The main moiety alkyl chain of the 2-propylvalerate refined to 0.287 (3): 0.309 (3): 0.307 (3), and the minor B-moiety alkyl chain refined to 0.0971 (14). Lastly, the main moiety interstitial DMF refined to 0.549 (3): 0.354 (3), and the minor B-moiety DMF refined to 0.0971 (14).

Adolescent ambivalence about diabetes technology-The Janus faces of automated care.

The Janus face metaphor approach highlights that a technology may simultaneously have two opposite faces or properties with unforeseen paradoxes within human-technology interaction. Suboptimal acceptance and clinical outcomes are sometimes seen in adolescents who use diabetes-related technologies. A traditional linear techno-determinist model of technology use would ascribe these unintended outcomes to suboptimal technology, suboptimal patient behavior, or suboptimal outcome measures. This paradigm has demonstratively not been successful at universally improving clinical outcomes over the last two decades. Alternatively, the Janus face metaphor moves away from a linear techno-determinist model and focuses on the dynamic interaction of the human condition and technology. Specifically, it can be used to understand variance in adoption or successful use of diabetes-related technology and to retrospectively understand suboptimal outcomes. The Janus face metaphor also allows for a prospective exploration of potential impacts of diabetes-related technology by patients, families, and their doctors so as to anticipate and minimize potential subsequent tensions.

Structural basis of activation and antagonism of receptor signaling mediated by interleukin-27.

SummaryInterleukin-27 (IL-27) uniquely assembles p28 and EBI3 subunits to a heterodimeric cytokine that signals via IL-27Rα and gp130. To provide the structural framework for receptor activation by IL-27 and its emerging therapeutic targeting, we report here crystal structures of mouse IL-27 in complex with IL-27Rα and of human IL-27 in complex with SRF388, a monoclonal antibody undergoing clinical trials with oncology indications. One face of the helical p28 subunit interacts with EBI3, while the opposite face nestles into the interdomain elbow of IL-27Rα to juxtapose IL-27Rα to EBI3. This orients IL-27Rα for paired signaling with gp130, which only uses its immunoglobulin domain to bind to IL-27. Such a signaling complex is distinct from those mediated by IL-12 and IL-23. The SRF388 binding epitope on IL-27 overlaps with the IL-27Rα interaction site explaining its potent antagonistic properties. Collectively, our findings will facilitate the mechanistic interrogation, engineering, and therapeutic targeting of IL-27.

An integrated approach of topological optimization with parametric validation and response surfaces, using ANSYS®

In industrial engineering practice, the use of cutting tools, or those of plastic deformation (dies), is known, involves high costs of materials, and requires, at the same time, conditions of high resistance to deformation. The reduction of the mass of the parts, ie the reduction of the costs with the materials, from the composition of the tools, at the same time with the constant maintenance, or, if possible, with the increase of the rigidity, which, in turn, is identical with the decrease of the metallic materials. when trying to optimize the shape of mechanical parts. To evaluate and to study the behavior of a plate material, also, elastic deformation of a tool component part, a specialized Computer Aided Engineering (CAE) software, Ansys Academic R22, was used. The load was applied to the holes contour of the plate to simulate “action” which determines the generation of permanent plate deformation.The boundary conditions, i.e. the fixed supports, are materialized in the lateral face of the piece and the upper edge of the opposite face. Both the applied load and the limit conditions simulate real situations from industrial practice.

Equilibrium problem for a thermoelastic Kirchhoff-Love plate with a delaminated flat rigid inclusion.

A new mathematical model describing an equilibrium of a thermoelastic heterogeneous Kirchhoff-Love plate is considered. A corresponding nonlinear variational problem is formulated with respect toa two-dimensional domain with a cut. This cut corresponds to an interfacial crack located on a given part of the boundary of a flat rigid inclusion. The flat inclusion is described by a cylindrical surface. Due tothe presence of the flat rigid inclusion in the plate, restrictions of the functions describing displacements to the corresponding curves satisfy special constraints having a linear form. Displacement boundary conditions of an inequality type are set on the crack faces that ensure a mutual non-penetration of opposite crack faces. Solvability of the problem is proved. Under the assumption that the solution of the variational problem is smooth enough, an equivalent differential formulation is found. This article is part of the theme issue 'Non-smooth variational problems and applications'.

Crashworthiness performance of hybrid energy absorbers using PET-G honeycomb structure

The authors report an experimental investigation on square thin-walled energy absorbers with different topologies and materials. The material was steel SAE 1010 and aluminum AL 6160. Some samples non-filled and filled with polymeric material received patterned windows placed in opposite faces with specific dimensions: 20x20, 15x30, and 20x30 mm2. Quasi-static axial loading crushes hollow specimens and hybrid specimens filled with PET-G honeycomb. The core filling was printed using the FDM technique. The crashworthy ability of specimens was evaluated based on the specific energy absorption (SEA), load ratio (LR) and structural efficiency (η), which showed that windowed-filled specimens with 20x30 mm2 perform better. The maximum increase of SEA was 212%, LR decreased from 4.02 to 1.78 and η increased from 0.45 to 0.89 for steel energy absorbers and in the same manner, the values for aluminum specimens were 123%, 2.97 to 1.28 and 0.46 to 0.71. The effects of the patterned windows and their combination with the honeycomb core for both metallic materials show that such a topology improved the performance in two factors. The windows reduced the peak force, and the PET-G honeycomb furnished a smoothing to the region at the end of the fold formation, contributing to the crashworthy ability. Future work envisages experimental testing of the samples in dynamic tests.