bluuebunny/crossref_metadata_2025 huggingface dataset:
Model equation for strongly focused finite-amplitude sound beams
Authors: Kamakura Tomoo , Ishiwata Tsuneo , Matsuda Kazuhisa
Published: July 2002

A model equation that describes the propagation of sound beams in a fluid is developed using the oblate spheroidal coordinate system. This spheroidal beam equation (SBE) is a parabolic equation and has a specific application to a theoretical prediction on focused, high-frequency beams from a circular aperture. The aperture angle does not have to be small. The theoretical background is basically along the same analytical lines as the composite method (CM) reported previously [B. Ystad and J. Berntsen, Acustica 82, 698–706 (1996)]. Numerical examples are displayed for the amplitudes of sound pressure along and across the beam axis when sinusoidal waves are radiated from the source with uniform amplitude distribution. The primitive approach to linear field analysis is readily extended to the case where harmonic generation in finite-amplitude sound beams becomes significant due to the inherent nonlinearity of the medium. The theory provides the propagation and beam pattern profiles that differ from the CM solution for each harmonic component.
Flow of Gelling Materials in a Uniform Layer on a Vertical Plane
Authors: Fischer F. J. , Paslay P. R.
Published: July 2002

The motion of a general class of gelling materials was investigated under a particular physical configuration. The gelling material was hypothesized to be a Bingham type body of constant viscosity and variable yield stress. The form of the time-past deformation dependent yield stress has been proposed by Slibar and Paslay and incorporates an exponential memory function, which “weights” current deformation rates more heavily than those occurring at a previous time. The general constitutive equations used in this study were proposed earlier by Slibar and Paslay and in essence infer that no motion within the body is permissible for values of the square root of the quadratic invariant of the reduced stress tensor less than the yield stress. The physical configuration treated is that of a uniform layer of the proposed material extending over an infinite vertical plane. Hence, the stress field is a function of the material density and layer thickness only. The steady-state solution was found for incipient flow and the necessary and sufficient criterion for solidification of the flow was determined. A numerical technique was used to obtain the time elapsed and total vertical displacement during the interim of relative motion, for various material parameters, felt by the authors to be in the practical range of interest. The results were found to meet all physically motivated anticipations; however, many different mechanisms are active in various gelling materials and the applicability of the proposed constitutive equations has to be verified in each case of a different material.
The Influence of Additional Orientation Mechanisms on the Theory of Streaming Birefringence
Authors: Argyropoulos George S.
Published: July 2002

The problem of determining the orientation distribution function of rigid particles of arbitrary shape is formulated in a general stochastic approach to consider any acting orientation mechanism, stochastic or deterministic. The effect of the various orientation mechanisms on the partial differential equation of the problem is analysed. A particular orientation mechanism acting on rigid ellipsoidal macromolecules in addition to the hydrodynamic and the Brownian effects is considered in Couette flow: a force field in the radial direction x, varying linearly with x. It is shown that the effect of a uniform electric field in the radial direction on polarizable ellipsoidal particles is of this nature. The corresponding steady-state orientation distribution function is determined to the third order for the case of predominant Brownian influence, and the theory of streaming birefringence of a dilute suspension of rigid ellipsoidal macromolecules in Couette flow is generalised to include the influence of the additional orientation mechanism: the direction of the isocline and the amount of birefringence are calculated to the second order.
Analog Study of the Dynamics of a Nonlinear Maxwell Model Material
Authors: Gruntfest I. J. , Mueller G. E.
Published: July 2002

As part of a continuing study of the mechanical behavior of materials which have temperature-dependent properties, electric analog experiments on a nonlinear Maxwell Model Material are described. The circuit that is used contains thermistor elements which simulate the temperature-dependent viscosity of the mechanical model. The inertial and elastic elements are simulated by electronic integrators instead of inductors and capacitors which assures the ideality of the elements and increases the versatility of the analog. The work leads to the identification of a natural “property” of the material which has advantages over the use of the viscosity coefficients and elastic moduli alone. The results show how, because of heating, the responses of the model change from elastic to viscous as the severity or duration of the excitation increases. The heating also leads to stress reduction in the trailing part of the disturbance. Since elements of the analog may be identified with elements of atomic scale models of material, the work relates to material development programs as well as to mechanical design studies.
The State of Stress and Strain in an Orthotropic Heterogeneous Viscoelastic Cylinder with Burning Inner Boundary
Authors: Soliman F.
Published: July 2002

The analysis of stress and strain in an orthotropic heterogeneous linear viscoelastic cylinder which has a burning inner boundary and which is subjected to a time-dependent internal pressure, has been worked out. The assumptions of isothermal conditions and infinitesimal strains are consistently made and the conditions of a quasistatic plane strain are adopted. Numerical solution for an orthotropic heterogeneous viscoelastic cylinder is established and which was anticipated to be quite stable. The established solution can be reduced to that of a homogeneous orthotropic cylinder. As special cases from the general problem, solutions for an isotropic compressible cylinder and an isotropic incompressible cylinder can also be derived. Numerical examples have been worked out to illustrate the influence of anisotropy, heterogeneity, and viscosity on the deformation of a burning cylindrical grain in a solid propellant rocket. The results for both short-time and long-time behavior are presented for a relaxation function of a form similar to that obtainable from a seven-parameter Maxwell model which has been shown to represent the rheological behavior of a filled elastomer fairly well.
Elementary Flows of Anisotropic Fluids
Authors: Denn M. M. , Metzner A. B.
Published: July 2002

The Ericksen theory of anisotropic fluids is examined with respect to its usefulness for describing the constitutive properties of real fluids. It is found that except in the limit of low shear rates, anisotropic effects may not be observed in simple laminar shearing flows or in helical flows, in both of which the behavior of these materials is indistinguishable from the predictions of the isotropic theory of simple fluids, and such flows do not suffice to determine uniquely all the material functions needed to describe other configurations. In unsteady flows, the theory as presently developed is limited to applications in which the fluid time constant is much smaller than the characteristic time of the flow field, i.e., to flows for which the Deborah number is sufficiently small. In these, the theory of simple fluids again appears to suffice with but the same exception.
Some Almost-Parallel Viscoelastic Flows
Authors: Tanner R. I.
Published: July 2002

Viscoelastic flows with a type of small controlled deviation from viscometricity are investigated. The calculations provide a basis for exploring the use of simple constitutive equations in some steady flows. The two-dimensional flow of a low-order Rivlin-Ericksen fluid through a channel of slowly varying width is worked out. Inversion formulas enabling the deduction of material functions from experimental observations are also given, which may provide a new means of measuring one normal stress difference.
The Mechanical Behavior of a Filled Elastomer at High Strain Rates
Authors: Nicholas T. , Freudenthal A. M.
Published: July 2002

The mechanical properties of a salt-filled polyurethane elastomer have been investigated at high rates of strain and at several temperatures. Constant strain-rate tests up to 27 in./in./sec at temperatures from 40 to 160°F have been performed to determine the relaxation modulus in tension and the effects of strain and temperature on this modulus. The effects of time, strain, and temperature have been found to be separable for this highly filled material even after de-wetting has occurred and the stress-strain curve becomes highly nonlinear. The relaxation modulus has been evaluated over a time range from 10−4 to 102 sec at 70°F.
Fluid Suspensions: Flow Near an Oscillating Plate
Authors: Allen S. J. , Kline K. A.
Published: July 2002

The problem of an infinite plate oscillating harmonically in an infinite fluid with rigid, spherical substructure is considered. Expressions are obtained for the fluid velocity and substructure spin. The limiting cases of dilute and concentrated suspensions of rigid spheres are examined and estimates made of the depth of penetration of viscous effects.
The Visco-Elastic Behavior of Confined Liquid Films in the Direction Normal to the Plane of the Film
Authors: Dickinson E. J.
Published: July 2002

When a thin film of liquid is confined between parallel rigid plates and stressed in a direction normal to the plane of the film, visco-elastic behavior is obtained provided the rate of loading is sufficiently high. The measured (apparent) complex modulus is always higher than three times the complex shear modulus (the value to be expected for shear behavior) but less than the complex bulk modulus. For sinusoidal loading, linear visco-elastic theory predicts an approximate relationship between the measured complex modulus, the complex shear modulus, and the degree of confinement of the liquid as given by the radius/thickness ratio of the film. The ratio of the measured complex modulus to the complex shear modulus, when both are measured at the same temperature and rate of loading (frequency), is predicted to be proportional to the square of the radius/thickness ratio of the film when this ratio is greater than one. Complex modulus measurements under sinusoidal loading on a petroleum bitumen, a silicone oil, and water have confirmed the validity of this relationship.
Rheological Properties of Dispersions of Spherical Particles in Polymer Solutions
Authors: Onogi Shigeharu , Matsumoto Takayoshi , Warashina Yoshiro
Published: July 2002

The steady flow and dynamic viscoelastic properties of disperse systems consisting of polystyrene copolymer particles of different sizes in polystyrene solutions were measured by means of rotating cylinder type rheometers over wide ranges of temperature, rate of shear, and frequency. The yield values, evaluated by use of the modified Casson equation for disperse systems, were found to be independent of temperature. Time-temperature superposition was applied to the flow curves and the frequency dependence curves of the dynamic properties, giving identical shift factors which obeyed the WLF type equation and were almost independent of the size and content of the particles. The yield value increased with increasing particle content and polymer concentration in the disperse medium. The smaller the particle size, the larger the yield value. The frequency dependence curves of the storage shear modulus G′ and the loss modulus G″ showed second plateaus lower than the rubbery plateau at lower frequencies. The correlation between the yield value and the complex shear stress is discussed.
Tensile Failure of Viscoelastic Materials Under Multiaxial Loading at Various Temperatures
Authors: Dong Richard G.
Published: July 2002

The failure-envelope description for tensile failure of viscoelastic materials under uniaxial stress was generalized to multiaxial stresses in a previous paper by the author. In the current paper, the theory is refined and the temperature of application extended from 70°F to the range −35° to 165°F. The material studied was LX-04-1, a high explosive composed of 85% HMX crystalline particles and 15% Viton polymer. Data for experimental verification were obtained with biaxial tests on hollow cylindrical specimens. Parameters describing multiaxial failure are determined as a function of temperature. In the strict sense, the theory should be applied only to stress states not far from biaxial since experimental verification is carried out only for biaxial stresses. Experimental limitations prevented a more general verification at this time.
The First Normal Stress Function at High Shear Rates Using Pressure-Driven Angular Annular Flow
Authors: Osmers H. R. , Lobo P. F.
Published: July 2002

A new device has been built and tested which provides for pressure-driven flow at high shear rates in the angular direction within the annulus between two concentric cylinders. Analysis of this viscometric flow demonstrates that the measured difference between the normal stresses at the inner and outer surfaces of the annulus is related to the first normal stress function. The data interpretation corrects for pressure hole errors and inertial effects. First normal stress function data for aqueous polymeric solutions are presented and discussed. Significant advantages over commonly used testing procedures are realised. These include the ability to conduct tests on both polymer solutions and melts over a broad range of shear rates (comparable to that realized in capillary flows), improved temperature control, and the minimization of changes in the sample due to solvent evaporation and polymer degradation. Surmountable difficulties include the need for relatively large sample size, the possibility of secondary flows under some conditions, and data analysis that requires inversion of an integral.
Viscosity of critical mixtures: Isopycnic polymer blendsa)
Authors: Cerny L. C. , Cerny E. L. , Sutter J. K. , Czerniawski D.
Published: July 2002

In many multicomponent systems, a transition from a single phase of uniform composition to a multiphase state with separated regions of different composition can be induced by changes in temperature and shear. The density difference between the phase and thermal and/or shear gradients within the system results in buoyancy driven convection. These differences affect kinetics of the phase separation if the system has a sufficiently low viscosity. This investigation presents more preliminary developments of a theoretical model in order to describe effects of the buoyancy-driven convection in phase separation kinetics. Polymer solutions were employed as model systems because of the ease with which density differences can be systematically varied and because of the importance of phase separation in the processing and properties of polymeric materials. Isopycnic polymer solutions were used to determine the viscosity and density difference limits for polymer phase separation. From these methods, it was possible to examine polymer–polymer interactions in a θ solvent. The rheological measurements were extended to detect the phase separation and to define the critical temperature.
Are different reading problems associated with different anxiety types?
Authors: Francis Deanna A. , Hudson Jennifer L. , Robidoux Serje , McArthur Genevieve M.
Published: May 2022

There is a reliable association between poor reading and anxiety, but we do not completely understand the specifics of this relationship. The current study included a sample of children (N = 284; Mage = 9.30, SDage = 1.31) who completed a reading (word, nonword, and text reading accuracy, word, nonword, and text reading fluency, passage reading comprehension) and anxiety (social anxiety, generalized anxiety, separation anxiety, physical injury fears/phobias, panic, obsessive compulsive symptoms) assessment. Analyses included bivariate and partial correlations, principal components analysis, and hierarchical clustering. We found a very tentative suggestion in the data that there may be a specific yet weak association between reading accuracy and social anxiety. The clinical implications and directions for future research are discussed.
Microstructure and Thermal Stability of High‐Temperature Titanium Alloy with Hf Element
Authors: Wang Congcong , Li Bolong , Wang Tongbo , Qi Peng , Qiao Xu , Yin Jiaming , Nie Zuoren
Published: May 2022

The influence of partial substitution of Hf for Zr on the microstructure and thermal stability of near‐α high‐temperature titanium alloys is systematically investigated. The results show that the addition of Hf promotes the refinement of precipitated phases of the silicides and α2 phase and the (Ti,Zr,Hf)6(Si,Sn)3 S2‐type silicides were formed in alloys after aging treatment. During thermal exposure, both silicides and α2 phase in alloy with 2.5 wt% Hf exhibited excellent anti‐coarsening ability, which may be attributed to the slow diffusion of Hf in Ti that significantly inhibited the growth rate of the precipitated phase. The loss of plasticity of near‐α titanium alloys after thermal exposure is mainly due to the precipitation and coarsening of silicides and α2 phase, therefore, the Hf‐containing titanium alloy has more excellent thermal stability, i.e., the plasticity loss rate is decreased from 34.8% (the alloy without Hf) to 7.4% (the alloy with 2.5 wt% Hf).
Ultra‐Broadband Strong Electromagnetic Interference Shielding with Ferromagnetic Graphene Quartz Fabric
Authors: Xie Yadian , Liu Shan , Huang Kewen , Chen Bingbing , Shi Pengcheng , Chen Zhaolong , Liu Bingzhi , Liu Kaihui , Wu Zhiqiang , Chen Ke , Qi Yue , Liu Zhongfan
Published: May 2022

Flexible electromagnetic interference (EMI) shielding materials with ultrahigh shielding effectiveness (SE) are highly desirable for high‐speed electronic devices to attenuate radiated emissions. For hindering interference of their internal or external EMI fields, however, a metallic enclosure suffers from relatively low SE, band‐limited anti‐EMI responses, poor corrosion resistance, and non‐adaptability to the complex geometry of a given circuit. Here, a broadband, strong EMI shielding response fabric is demonstrated based on a highly structured ferromagnetic graphene quartz fiber (FGQF) via a modulation‐doped chemical vapor deposition (CVD) growth process. The precise control of the graphitic N‐doping configuration endows graphene coatings on specifically designable quartz fabric weave with both high conductivity (3906 S cm−1) and high magnetic responsiveness (a saturation magnetization of ≈0.14 emu g−1 under 300 K), thus attaining synergistic effect of EMI shielding and electromagnetic wave (EMW) absorption for broadband anti‐EMI technology. The large‐scale durable FGQF exhibits extraordinary EMI SE of ≈107 dB over a broadband frequency (1–18 GHz), by configuring ≈20 nm‐thick graphene coatings on a millimeter‐thick quartz fabric. This work enables the potential for development of an industrial‐scale, flexible, lightweight, durable, and ultra‐broadband strong shielding material in advanced applications of flexible anti‐electronic reconnaissance, antiradiation, and stealthy technologies.
Amino Termination of Ti3C2 MXene Induces its Graphene Hybridized Film with Enhanced Ordered Nanostructure and Excellent Multiperformance
Authors: Peng Mengyi , Wu Zhenwang , Wei Wei , Xu Huajie , Liu Chuntai , Shen Changyu
Published: May 2022

The strategy of nacre‐inspired structures or the introduction of polymers can only strengthen and toughen 2D inorganic nanosheets‐based flexible films while mitigating their other properties. Herein, based on bending rigidity discrepancy of reduced graphene oxides (rGO) and Ti3C2 nanosheets, the introduction of amino termination on Ti3C2 (Ti3C2‐NH2) endows 3rGO/7Ti3C2‐NH2 films with enhanced ordered nanostructure and excellent multiperformance. Its interlayer‐ordered nanostructures are consistently confirmed by both wide‐angle X‐ray scattering and polarized Raman spectroscopy. The tensile strength and fracture energy increase by 84.7% and 156.3% compared with those of traditional 3rGO/7Ti3C2 film, respectively. The higher remained stress (81%) after relaxation agrees well with its better nanosheet orientation. The average fatigue cycles to failure approach 16 951 times under 150 MPa maximum tensile loading. Due to a large decrease in the interface thermal resistance, its thermal conductivity approaches ≈48.9 W m−1 K−1. The results also show that the absorbance of Ti3C2‐NH2 based films greatly surpass the maximum of the components in both X‐band frequency and middle infrared range. Particularly, 3rGO/7Ti3C2‐NH2 films exhibit anomalously high absorbance in the middle infrared range (55% for 22 µm thickness). It suggests that this film has good promise as flexible electronic devices with excellent mechanical, EMI shielding, heat dissipation, and thermal accumulation monitoring capabilities.
Ultrasensitive Near‐Infrared MoTe2 Photodetectors with Monolithically Integrated Fresnel Zone Plate Metalens
Authors: Qiao Jie , Feng Fu , Cao Guiyuan , Wei Shibiao , Song Shuang , Wang Tao , Yuan Xiaocong , Somekh Michael G.
Published: May 2022

Atomic layers of group‐VI 2D transition metal dichalcogenides (TMDCs) with substantial materials system and unique physicochemical properties have exhibited excellent performances in electronics and optoelectronics. However, photodetectors based on TMDCs suffer from poor sensitivity and optical absorption due to the weak phonon conversion efficiency and optical absorption due to their atomically thin feature. Here, taking advantages of miniaturization and integrability, all‐dielectric TiO2 metalenses are designed based on the Fresnel diffraction effect and integrated with molybdenum ditelluride (MoTe2) photodetectors. Owing to the enhancement of photon utilization efficiency, the corresponding integrated devices exhibit a high responsivity of 135.0 A W–1, an excellent external quantum efficiency of 202.0%, and a specific detectivity of ≈4.05 × 1012 Jones. These results indicate that the optoelectrical properties of 2D materials can be significantly optimized by integration with metalens and will accelerate the evolution of metalens in 2D optoelectronics fields.
Well‐Defined Ni−SNS Complex Catalysed Borrowing Hydrogenative α‐Alkylation of Ketones and Dehydrogenative Synthesis of Quinolines
Authors: Sharma Rahul , Mondal Avijit , Samanta Arup , Biswas Nandita , Das Babulal , Srimani Dipankar
Published: May 2022

The “borrowing hydrogen” (BH) method for C‐alkylation reactions using alcohol as alkylating agents is an important synthetic transformation. In this respect, designing cheap and bench stable earth abundant metal catalyst for borrowing hydrogen transformation is a key challenge to be witnessed. Herein we have presented a synthesis of non‐phosphine, easily accessible and bench stable SNS−Ni complexes. The Ni‐catalyst was successfully applied for the C‐alkylation of ketone enolates to α‐alkylated ketones. Primary alcohol with different functional groups and various heteroaromatic alcohols are well tolerated. The present catalyst system was efficiently applied to gram scale synthesis and also the green chemistry metrics of the reaction were calculated. The present protocol was also extended successfully for the synthesis of biologically important quinoline moieties. Finally, various control experiments and deuterium labelled experiments suggest that the reaction proceeds via borrowing hydrogen pathway.

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Metal‐Organic Framework Nanosheets as Templates to Enhance Performance in Semi‐Crystalline Organic Photovoltaic Cells
Authors: Sasitharan Kezia , Kilbride Rachel C. , Spooner Emma L.K. , Clark Jenny , Iraqi Ahmed , Lidzey David G. , Foster Jonathan A.
Published: May 2022

Optimizing the orientation, crystallinity, and domain size of components within organic photovoltaic (OPV) devices is key to maximizing their performance. Here a broadly applicable approach for enhancing the morphology of bulk heterojunction OPV devices using metal–organic nanosheets (MONs) as additives is demonstrated. It is shown that addition of porphyrin‐based MONs to devices with fully amorphous donor polymers lead to small improvements in performance attributed to increased light absorption due to nanosheets. However, devices based on semi‐crystalline polymers show remarkable improvements in power conversion efficiency (PCE), more than doubling in some cases compared to reference devices without nanosheets. In particular, this approach led to the development of PffBT4T2OD‐MON‐PCBM device with a PCE of 12.3%, which to the authors’ knowledge is the highest performing fullerene based OPV device reported in literature to date. Detailed analysis of these devices shows that the presence of the nanosheets results in a higher fraction of face‐on oriented polymer crystals in the films. These results therefore demonstrate the potential of this highly tunable class of two‐dimensional nanomaterials as additives for enhancing the morphology, and therefore performance, of semi‐crystalline organic electronic devices.
A High‐Performance Bidirectional Direct Current TENG by Triboelectrification of Two Dielectrics and Local Corona Discharge
Authors: Shan Chuncai , He Wencong , Wu Huiyuan , Fu Shaoke , Tang Qian , Wang Zhao , Du Yan , Wang Jian , Guo Hengyu , Hu Chenguo
Published: May 2022

Triboelectric nanogenerators (TENGs) are regarded as a promising technology to convert ambient low‐frequency mechanical energy into electricity for distributed power supply. Although TENGs based on triboelectrification (TE) of metal–dielectric and air breakdown have the advantage of direct current (DC) output, the unidirectional and single‐channel output mode limits their energy utilization efficiency. Here, a bidirectional and double‐channel (BDC‐TENG) based on TE of dielectric–dielectric and local corona discharge is proposed. Different from traditional DC‐TENGs, the TE process of the BDC‐TENG occurs in two dielectrics, and the double‐channel output is generated from simultaneous discharge between each dielectric and its adjacent electrode fixed on both sides of the slider. The BDC‐TENG shows unique characteristics, in that the current direction is tunable by adjusting the slider movement direction and electronegativity difference of two dielectric materials, and the average output power density is up to 3 W m–2 which is 14 times higher than that of traditional DC‐TENGs. This work provides a feasible strategy to boost the output performance of DC‐TENGs.
AI models for correlation of physical properties in system of 1DMA2P‐CO2‐H2O
Authors: Liu Helei , Jiang Xiaotong , Idem Raphael , Dong Shoulong , Tontiwachwuthikul Paitoon
Published: May 2022

In this work, the density, viscosity, and specific heat capacity of pure 1‐dimethylamino‐2‐propanol (1DMA2P) as well as aqueous unloaded and CO2‐loaded 1DMA2P solution (with a CO2 loading of 0.04–0.70 mol CO2/mol amine) were measured over the 1DMA2P concentration range of 0.5–3.0 mol/L and temperature range of 293–323 K. The observed experimental results of these thermophysical properties of the 1DMA2P‐H2O‐CO2 system were correlated using empirical models as well as artificial neural network (ANN) models (namely, back‐propagation neural network [BPNN] and radial basis function neural network [RBFNN] models). It was found that the developed BPNN and RBFNN models could predict the experimental results of 1DMA2P‐H2O‐CO2 better than correlations using empirical models. The results could be treated as one of the accurate and potential methods to predict the physical properties for aqueous amine CO2 absorption systems.
Modeling vapor–liquid equilibrium and liquid–liquid extraction of deep eutectic solvents and ionic liquids using perturbed‐chain statistical associating fluid theory equation of state. Part II
Authors: Aminian Ali
Published: May 2022

This study aims to use perturbed‐chain statistical associating fluid theory (PC‐SAFT) to describe the phase behavior of systems containing deep eutectic solvents (DESs) and ionic liquids (ILs). The DESs are based on tetrabutylammonium chloride and tetrabutylammonium bromide as hydrogen bond acceptors, and levulinic acid and diethylene glycol as hydrogen bond donors in the mole ratio of 1:2 and 1:4, respectively. Predictions of phase equilibria by PC‐SAFT were compared with the results of COnductor like Screening MOdel for Real Solvents (COSMO‐RS) and non‐random two‐liquid (NRTL). In this work, low viscosity ether‐ and pyridinium‐based ILs [EnPy][NTf2] and [CmPy][NTf2] were used for vapor–liquid equilibrium systems, while 1‐(2‐methoxyethyl)‐1‐methylpyrrolidinium bis(trifluoromethylsulfonyl)‐amide and 1‐propyl‐3‐methylimidazolium bis{trifluoromethylsulfonyl}imide with n‐heptane + thiophene and n‐hexane + ethylbenzene were used in the liquid–liquid extraction, respectively. In the last part, the phase behavior of the mixtures of perfluoroalkylalkanes with their linear alkane counterparts was studied and compared with the SAFT‐Mie pair potential.
Bioinspired Soft Robotic Fish for Wireless Underwater Control of Gliding Locomotion
Authors: Lee Jinwoo , Yoon Yeosang , Park Huijae , Choi Joonhwa , Jung Yeongju , Ko Seung Hwan , Yeo Woon-Hong
Published: May 2022

Animal locomotion offers valuable references as it is a critical component of survival as animals adapting to a specific environment. Especially, underwater locomotion poses a challenge because water exerts a high antagonistic drag force against the direction of progress. However, marine vertebrates usually use much lower aerobic energy for locomotion than aerial or terrestrial vertebrates due to their unique intermittent gliding locomotion. None of the prior works demonstrate the locomotive strategies of marine vertebrates. Herein, an untethered soft robotic fish capable of reconstructing the marine vertebrates’ effective locomotion and traveling underwater by controlling localized buoyancy with thermoelectric pneumatic actuators is introduced. The actuators enable both heating and cooling to control a localized buoyancy while providing a substantial driving force to the system. Besides mimicking the locomotion, the bidirectional communication system enables the untethered delivery of commands to the underwater subject and real‐time acquisition of the robotic fish's physical information. Underwater imaging validates the fish's practical use as a drone, allowing for inspecting the aquatic environment that is not easily accessible to humans. Future work studies the operation of the robotic fish as a collective swarm to examine a broader range of the underwater area and conduct various strategic missions.
Recent Advances in Light‐Induced Carboxylation of Organic (Pseudo)Halides with CO2
Authors: Fan Zhengning , Yi Yaping , Xi Chanjuan
Published: May 2022

Carbon dioxide is an ideal C1 source in organic synthesis as a precursor for the carboxyl group. With the development of photocatalysis, the carboxylation reactions with CO2 incorporation could be carried out in a more environmental and sustainable manner without the addition of stoichiometric metallic reductants. This minireview summarizes the recent development in light‐induced carboxylation of organic (pseudo)halides and analogues with CO2 via C−X (X=Br, Cl, O, N, etc.) bond cleavage.
Synthesis of a Negatively Curved Nanocarbon Molecule with an Octagonal Omphalos via Design‐of‐Experiments Optimizations Supplemented by Machine Learning
Authors: Ikemoto Koki , Akiyoshi Misato , Mio Tatsuru , Nishioka Kaito , Sato Sota , Isobe Hiroyuki
Published: May 2022

A saddle‐shaped nanocarbon molecule was synthesized, which revealed the existence of negative Gauss curvatures on a >3‐nm molecular structure possessing 192 π‐electrons. The synthesis was facilitated by a protocol developed with Design‐of‐Experiments optimizations and machine‐learning predictions, and spectroscopy and crystallography were used to reveal the saddle‐shaped structure of the molecule. Solution‐phase analyses showed the presence of dimeric assembly, and crystallographic analyses revealed the stacked dimeric structures. The stacked crystal structure was scrutinized by various methods, including Gauss curvatures derived from the discrete surface theory of geometry, to reveal the important role of the molecular Gauss curvature in dimeric assembly.
Zinc‐Catalyzed Enantioselective [3+2] Cycloaddition of Azomethine Ylides Using Planar Chiral [2.2]Paracyclophane‐Imidazoline N,O‐ligands
Authors: Kumar Sundaravel Vivek , Guiry Patrick J.
Published: May 2022

We present a facile synthetic route toward a novel series of imidazolinyl‐[2.2]paracyclophanol (UCD‐Imphanol) ligands possessing central and planar chirality. Both sets of diastereomeric ligands were successfully purified by column chromatography. The preliminary application of this family of ligands showed excellent activities in the asymmetric Zn‐catalyzed azomethine ylide cycloaddition. Enantioenriched pyrrolidines, in a substrate scope of 20 examples, were accessed in high levels of endo/exo ratios (up to >99/1) and enantioselectivities (up to >99 % ee) with excellent yields (up to 99 %) by using (S,S,SP)‐UCD‐Imphanol/(S,S,RP)‐UCD‐Imphanol, respectively.
Facile Synthesis of a Fluorinated‐Squaramide Covalent Organic Framework for the Highly Efficient and Broad‐Spectrum Removal of Per‐ and Polyfluoroalkyl Pollutants
Authors: Huang Junlong , Shi Yueru , Huang Guo‐zhang , Huang Shuyao , Zheng Juan , Xu Jianqiao , Zhu Fang , Ouyang Gangfeng
Published: May 2022

The escalating contamination by per‐ and polyfluoroalkyl substances (PFAS) has become an urgent issue in recent years, and the structural diversity of PFAS is the major challenge for effective pollution control. Herein, we take the intrinsic advantages of squaramide and prepare a new two‐dimensional covalent organic framework (FSQ‐1) that exhibits broad‐spectrum PFAS affinity. The tailor‐made linker forges hydrogen‐bond donors, hydrogen‐bond acceptors, and fluorophilic segments into one framework. The obtained material exhibits multipoint and multitype affinity to PFAS with different structures, by which high‐efficient and broad‐spectrum removal of various PFAS can be simultaneously achieved. Notably, the thermodynamic profiles provided by isothermal titration calorimetry (ITC) experiments further illustrate the underlying mechanism of the broad‐spectrum affinity. FSQ‐1 can also be applied for efficient PFAS extraction in trace‐level PFAS analysis.
Jojoba seed powder as eco‐friendly antioxidant for rubber products
Authors: Kandil Heba , Nashar Doaa E. El. , Ward Azza A. , Khalaf Aman I.
Published: May 2022

In search of a new class of antioxidants for rubber products, plant based antioxidants have emerged as a suitable alternative to traditional antioxidants. Therefore, this study aimed to explore the efficiency of jojoba seed meal (JSM) as a natural antioxidant in rubber compounds. Hence, JSM was ground and sieved into a very fine powder (JSMP) where it was applied here in silica‐filled acrylonitrile butadiene rubber (NBR) composite at different loadings. Its effect on the curing, swelling, physico‐mechanical, aging and dielectric properties of the resulting composites was investigated. It was found that the incorporation of JSMP into silica‐NBR composites enhanced the curing, mechanical, and swelling properties compared to those of the composite prepared with the commercial antioxidant 2,2,4‐trimethyl‐1,2‐dihydroquinoline (TMQ) and the optimum concentration of JSMP was 4 phr. This result was proved by SEM which showed that using up to 4 phr of JSMP enhanced the dispersion of silica within the NBR matrix. Aging process results showed that the composites with JSMP exhibited a high resistance to the aging process compared to that with TMQ. Furthermore, the dielectric results revealed that the presence of JSMP caused an increase in the permittivity, dielectric loss, and conductivity of the resulting composites. The conductivity value reached to 8 × 10−7 S/cm which recommends the use of such composites for electrostatic dissipation applications.
The effect of curricular reform on gross anatomy laboratory examination performance: An institutional analysis
Authors: Taylor Melissa A. , Loder Danielle M. , Herr Michael J. , Nichols Richard A.
Published: May 2022

Many medical schools have undergone curricular reform recently. With these reforms, time spent teaching anatomy has been reduced, and there has been a general shift to a pass/fail grading system. At Indiana University School of Medicine (IUSM), a new curriculum was implemented in fall 2016. The year‐long human gross anatomy course taught in 2015 was condensed into an integrated, semester‐long course starting in 2016. Additionally, the grading scale shifted to pass/fail. This study examined first‐year medical student performance on anatomy practical laboratory examinations—specifically, among lower‐order (pure identification) questions and higher‐order (function, innervation) questions. Participants included medical students from a pre‐curricular reform cohort (year 2015, 34 students) and two post‐curricular reform cohorts (years 2016, 30 students and 2017, 33 students). A Kruskal–Wallis ANOVA test was used to determine differences of these questions among the three cohorts. Additionally, 40 of the same lower‐order questions that were asked on gross anatomy laboratory examinations from medical student cohort year 2015 and year 2016 were further analyzed using an independent samples t‐test. Results demonstrated that the pre‐curricular reform cohort scored significantly higher on both lower‐order (median = 81, p < 0.001) and higher‐order questions (median = 82.5, p < 0.05) than both post‐curricular reform cohorts. Additionally, when reviewing the selected 40 similar questions, it was found that the pre‐curricular reform cohort averaged significantly higher (82.1 ± 16.1) than the post‐curricular reform cohort from 2016 (69.3 ± 21.8, p = 0.004). This study provides evidence about the impact of curricular reform on medical student anatomical knowledge.
Recent Advances of Chemosensors for Nerve Agents
Authors: Wang Xiao , Wang Xuechuan , Feng Rong , Fu Tao , Jiang Ying , Zhang Jie , Sun Xiaolong
Published: May 2022

Nerve agents are a branch of organophosphorus (OP) compounds that chemically cause irreversible inhibition of acetylcholinesterase, thereby failing the hydrolysis of acetylcholine, resulting in severe neurological disease and death in organisms. Thus, the unreasonable use of such compounds threatens public and national security, so it is a high demand to establish portable, low‐cost, sensitive, and highly selective methods for their precise detection. In this review, we introduced the recent development of spectroscopy‐based optical chemosensors that aimed for the detection of nerve agents, focusing on the progress made in the molecular design, sensing principle and applications. We conclude this Review by highlighting the current challenges associated with the future development and outlook.
Quadruple Functionalized Pyrazole Pharmacophores by One‐pot Regioselective [3+2] Cycloaddition of Fluorinated Nitrile Imines and Dicyanoalkenes
Authors: Zhou Yin , Gao Cheng‐Feng , Ma Hai , Nie Jing , Ma Jun‐An , Zhang Fa‐Guang
Published: May 2022

Here we present a quadruple functionalization approach for the modular construction of fully substituted N1‐aryl 3‐di/trifluoro‐methyl‐4/5‐cyanopyrazole pharmacophores from readily available hydrazonyl chlorides and dicyanoalkenes. The realization of this [3+2] cycloaddition reaction hinges upon the employment of N‐aryl di/trifluoromethyl nitrile imines as the 1,3‐dipoles to bypass external synthetic steps and dicyanoalkenes as the dipolarophiles to tune the regioselectivity. This one‐pot strategy offers access to a divergent library of cyano analogues of prevalent 3‐di/trifluoromethyl pyrazole pharmacophores, among which several compounds have shown potent inhibitory activity towards cyclooxygenase 2 (COX‐2) compared with marketed drug Celecoxib.
The medial prefrontal cortex to the medial amygdala connections may affect the anxiety level in aged rats
Authors: Sotoudeh Narges , Namavar Mohammad Reza , Bagheri Farshid , Zarifkar Asadollah
Published: May 2022

Background

Aging changes brain function and behavior differently in male and female individuals. Changes in the medial prefrontal cortex (mPFC)–medial amygdala (MeA) connectivity affect anxiety‐like behavior.

Objectives

Therefore, this study aimed to investigate the effect of aging and sex on the mPFC–MeA connection and its association with the level of anxiety‐like behavior.

Methods

We divided the Wistar rats into the male and female young rats (2‐3‐month‐old) and male and female old rats (18–20 months old). First, the open field test (OFT) was performed, and then 80 nl of Fluoro‐Gold (FG) was injected by stereotaxic surgery in the right or left MeA. After 10 days, the animals were perfused, their brain removed, coronal sections cut, and the number of FG‐labeled cells in the right and left mPFC of each sample was estimated.

Results

Based on our results, old animals revealed less anxiety‐like behavior than young ones, and young females were less anxious than young males, too. Interestingly, MeA of old male rats received more fibers from the bilateral mPFC than young ones. Also, this connection was stronger in the young females than young males. Altogether, the present study indicated that old individuals had less anxiety‐like behavior and stronger mPFC–MeA connection, and young female rats were less anxious and had a stronger connection of mPFC–amygdala than males of the same age.

Conclusion

Thus, it seems that there is a negative relationship between anxiety levels based on the rat's performance in the OFT apparatus and the mPFC–MeA connection.
Examining organic acid production potential and growth‐coupled strategies in Issatchenkia orientalis using constraint‐based modeling
Authors: Suthers Patrick F. , Maranas Costas D.
Published: May 2022

Growth‐coupling product formation can facilitate strain stability by aligning industrial objectives with biological fitness. Organic acids make up many building block chemicals that can be produced from sugars obtainable from renewable biomass. Issatchenkia orientalis is a yeast strain tolerant to acidic conditions and is thus a promising host for industrial production of organic acids. Here, we use constraint‐based methods to assess the potential of computationally designing growth‐coupled production strains for I. orientalis that produce 22 different organic acids under aerobic or microaerobic conditions. We explore native and engineered pathways using glucose or xylose as the carbon substrates as proxy constituents of hydrolyzed biomass. We identified growth‐coupled production strategies for 37 of the substrate‐product pairs, with 15 pairs achieving production for any growth rate. We systematically assess the strain design solutions and categorize the underlying principles involved.
Anti‐Aging Potential of a Rosa centifolia Stem Extract with Focus on Phytochemical Composition by Bioguided Fractionation
Authors: Dubois Camille , Plainfossé Hortense , Delcroix Maïlys , Trinel Manon , Verger‐Dubois Grégory , Azoulay Stéphane , Burger Pauline , Fernandez Xavier
Published: May 2022

Agricultural practices generate huge amounts of by‐products, often simply discarded as waste that must be processed at some cost. The natural by‐products revalorisation as raw material to produce high‐added value ingredients for various industrial sectors may pave the way towards more sustainable industrial practices, via an optimised utilisation of natural resources. Integrating the circular economy precepts to production systems is considered to be a more and more promising management solution to significantly reduce the environmental impact of economic activities. This article discusses the valorisation of Rosa centifolia stem to produce a natural extract with cosmetic anti‐aging potential. To do so, the cosmetic potential of 30 extracts obtained by maceration of agricultural by‐products in a hydroalcoholic solvent was evaluated: their activities, as well as their inhibitory activities of specific enzymes were assessed in vitro to identify those that could be used effectively as anti‐ageing actives while meeting the consumer's expectations in terms of sustainability, naturality, transparency and traceability.[1] A hydroalcoholic extract of R. centifolia stem revealed itself particularly promising due to its valuable anti‐hyaluronidase and antioxidant activities, and its interesting anti‐elastase and anti‐inflammatory potential. The bio‐guided fractionation of this extract allows the characterisation of three major compounds, e. g., isoquercitrin, quercitrin and euscaphic acid, never identified in R. centifolia previously.
Hupertimines A–E, Fawcettimine‐Type Lycopodium Alkaloids from Huperzia serrata
Authors: Deng Zhen‐Tao , Liu Yu‐Chen , Zhu Qin‐Feng , Jiang Shuai , Wu Xing‐De , Zhao Qin‐Shi
Published: May 2022

Five new fawcettimine‐type Lycopodium alkaloids, hupertimines A–E (1–5), were discovered from the whole plant of Huperzia serrata, along with two known alkaloids, 8α‐hydroxyphlegmariurine B (6) and 8β‐hydroxyphlegmariurine B (7). The structures of 1–7 were identified through HR‐MS, IR, 1H, 13C, and 2D NMR, and single‐crystal X‐ray diffraction analysis. Structurally, compound 1 was the fourth example of Lycopodium alkaloid with an ether linkage between C‐5 and C‐13 and 2 was the third example of Lycopodium alkaloid with a 5/5/5/5/6 pentacyclic ring system and featuring a 1‐aza‐7‐oxabicyclo[2.2.1]heptane unit. Compounds 1–7 were tested for their BACE1 inhibitory activity. In addition, the correct 1H‐ and 13C‐NMR data for 7 were reported in current study.
Computational targeting of allosteric site of MEK1 by quinoline‐based molecules
Authors: Singh Rahul , Bhardwaj Vijay K. , Purohit Rituraj
Published: May 2022

MEK1 is an attractive target due to its role in selective extracellular‐signal‐regulated kinase phosphorylation, which plays a pivotal role in regulating cell proliferation. Another benefit of targeting the MEK protein is its unique hydrophobic pocket that can accommodate highly selective allosteric inhibitors. To date, various MEK1 inhibitors have reached clinical trials against several cancers, but they were discarded due to their severe toxicity and low efficacy. Thus, the development of allosteric inhibitors for MEK1 is the demand of the hour. In this in‐silico study, molecular docking, long‐term molecular dynamics (5 µs), and molecular mechanics Poisson–Boltzmann surface area analysis were undertaken to address the potential of quinolines as allosteric inhibitors. We selected four reference MEK1 inhibitors for the comparative analysis. The drug‐likeness and toxicity of these molecules were also examined based on their ADMET and Toxicity Prediction by Komputer Assisted Technology profiles. The outcome of the analysis revealed that the quinolines (4m, 4o, 4s, and 4n) exhibited better stability and binding affinity while being nontoxic compared to reference inhibitors. We have reached the conclusion that these quinoline molecules could be checked by experimental studies to validate their use as allosteric inhibitors against MEK1.