Simple Coupling Research Articles

Synthesis of a novel CCR1 antagonist for treatment of glioblastoma

Glioblastoma is a brain cancer caused by the presence of a fast-growing, malignant tumor in the brain. As of now, this cancer is universally lethal due to lack of efficacious treatment options. C-C chemokine receptor 1 (CCR1) is a G-protein coupled receptor that controls chemotaxis, the movement of cells in response to chemical stimuli. Inhibiting these receptors could retard the growth of the malignant tumor by inhibiting chemotaxis. This research aims to synthesize potential CCR1 antagonists by coupling carboxylic acids with a triazole core. We synthesized these compounds using a simple carboxylic acid coupling and confirmed the identity of the final compounds using nuclear magnetic resonance (NMR) spectroscopy. Further testing of these compounds in inhibition bioassays is planned to be done when lab space becomes accessible again.

Robust in-phase synchronization in repressor-based coupled gene oscillators

Abstract Inside living cells, proteins or mRNA can show oscillations even without a periodic driving force. Such genetic oscillations are precise timekeepers for cell-cycle regulations, pattern formation during embryonic development in higher animals, and daily cycle maintenance in most organisms. The synchronization between oscillations in adjacent cells happens via intercellular coupling, which is essential for periodic segmentation formation in vertebrates and other biological processes. While molecular mechanisms of generating sustained oscillations are quite well understood, how do simple intercellular coupling produces robust synchronizations are still poorly understood? To address this question, we investigate two models of coupled gene oscillators - activator-based coupled oscillators (ACO) and repressor-based coupled oscillators (RCO) models. In our study, a single autonomous oscillator (that operates in a single cell) is based on a negative feedback, which is delayed by intracellular dynamics of an intermediate species. For the ACO model (RCO), the repressor protein of one cell activates (represses) the production of another protein in the neighbouring cell after a intercellular time delay. We investigate the coupled models in the presence of intrinsic noise due to the inherent stochasticity of the biochemical reactions. We analyze the collective oscillations from stochastic trajectories in the presence and absence of explicit coupling delay and make careful comparison between two models. Our results show no clear synchronizations in the ACO model when the coupling time delay is zero. However, a non-zero coupling delay can lead to anti-phase synchronizations in ACO. Interestingly, the RCO model shows robust in-phase synchronizations in the presence and absence of the coupling time delay. Our results suggest that the naturally occurring intercellular couplings might be based on repression rather than activation where in-phase synchronization is crucial.

Anticancer Activity of the Host-Guest Complex of Camptothecin with β-Cyclodextrin-Folate Conjugate. Encapsulation and Efficacy

Cyclodextrins are cyclic oligosachcharides that act as molecular hosts and accommodate drug molecules forming host: guest complexes. They aid in the sustained release of the encapsulated drugs through diffusion in solution and protect their unstable forms. In this paper, we report the synthesis of a β-cyclodextrin-folate by a simple coupling reaction. The compound is characterized using IR, NMR, and mass spectroscopic techniques. The amide carbonyl band is observed at 1680 cm-1. The mass spectrum shows the molecular ion peak of the β-cycloxetrin-folate conjugate at an m/z value of 1615.35. An inclusion complex of the anticancer drug, camptothecin, with the β-cycloxetrin-folate is formed on the stepwise addition of the β-cycloxetrin-folate to the guest molecule. The complex formation is studied using UV-visible and fluorescence spectroscopy. The formation of host: guest complexes is known to enable the sustained release of the encapsulated drug molecule. Herein, we examined the in vitro anticancer activity of the host: guest complex against cervical cancer (HeLa) cells. The host: guest complex formation results in enhanced efficacy of the drug. Dose-dependent cytotoxicity is observed for the β-cyclodextrin-folate: camptothecin complex. The cytotoxicity is more for the complex than for the free drug in solution.

Antimicrobial and antitumor activity of peptidomimetics synthesized from amino acids

Thirteen cationic peptidomimetics derived from amino acids bearing an alkyl or ethynylphenyl moiety that mimic the structure of cationic antibacterial peptides were designed and synthesized using a simple coupling reaction of an amino acid with a substituted amine. Antibacterial activities of the resulting peptidomimetics against drug-sensitive bacteria, such as Gram-positive Staphylococcus aureus (S. aureus) and Bacillus subtilis, Gram-negative Escherichia coli (E. coli) and Salmonella enterica, and a drug-resistant bacterium, methicillin-resistant S. aureus (MRSA), were systematically evaluated. Most peptidomimetics show significant broad-spectrum antibacterial activity. A-L-Iso-C12 (isoleucine derivative bearing a dodecyl moiety) show MICs of 2.5 μg/mL against S. aureus and 4 μg/mL against MRSA and A-L-Val-C12 (valine derivative bearing a dodecyl moiety) show MICs of 1.67 μg/mL against E. coli and 8.3 μg/mL against MRSA. A-L-Val-C12 showed low cytotoxicity toward L929 cells in comparison with SGC 7901 cells, indicating tumor-directed killing by peptidomimetics while avoiding toxicity to normal cells. The influences of type of amino acid and substituent, length of substituent, and stereochemistry of amino acids on antibacterial activity and cytotoxicity of peptidomimetics were systematically investigated. The results indicate that this series of cationic peptidomimetics derived from amino acids display antitumor activity and may be useful for treatment of bacterial infections.

Ab initio comparative study of the magnetic, electronic and optical properties of AB2O4 (A, B= Mn, Fe) spinels

The comparison of the magnetic, electronic, and optical properties of the spinel transition-metal oxides AB2O4 (A, B = Fe, Mn) and their relationship with the structure and composition were studied within DFT-GGA + U approximation. The spinels were considered both in the normal and inverse structure. We have found that regardless of composition and structure, the studied spinels are ferrimagnetic with antiparallel magnetic moments on A- and B-site cations. Electronic and structural properties of spinels depend on the composition: FeMn2O4 has a tetragonal structure and half-metallic properties; however, in the inverse FeMn2O4, the bandgap opens for the spin-up channel. MnFe2O4 is a cubic insulator with a bandgap of about 1.5 eV, which decreases in the inverse structure. The superexchange constants estimate within the simple indirect coupling model and have values close to the experimental ones. The total magnetization of FeMn2O4 is drop-down to zero under hydrostatic pressure above 60 GPa due to the strong dependence of the magnetic moment of octahedral manganese ion on the pressure. The microscopic mechanisms of the relationship between the structure, composition and properties are studied.

Insight into Buffer Trap-Induced Current Saturation and Current Collapse in GaN RF Heterojunction Field-Effect Transistors

Buffer traps in GaN RF heterostructure field-effect transistors (HFETs) provide a high dc output resistance on one hand but induce the current collapse effect on the other hand. Here, we show that traps do not merely confine the carriers into the channel, but serve to pin the Fermi level. Only by pinning the Fermi level a high saturated dc output resistance can be obtained in short channel devices. If carriers are confined into the channel by a back-barrier, and no traps are present, then short channel effects still severely reduce the saturated dc output resistance. In addition, we show that the buffer-related current collapse, which manifests as an output conductance under RF or pulse conditions, can straightforwardly be explained by a simple capacitive coupling model between the drain and the channel under the gate. The trapped charge under the gate results in a pulse voltage step-dependent shift in threshold voltage. Based on this picture, current collapse at pulsed condition can be approximately evaluated from dc simulations or from capacitance measurements.

Ultra-trace Extraction of Two Bactericides Via Ultrasound-Assisted Dispersive Liquid-Liquid Microextraction.

A simple, rapid and sensitive method coupling ultrasound-assisted dispersive liquid-liquid microextraction (DLLME) with ultra-high performance liquid chromatography-tandem mass spectrometry was developed for the simultaneous determination of malachite green (MG) and crystal violet (CV) in different water samples. In ultrasound-assisted DLLME procedure, several parameters affecting the extraction efficiency, including pH, type and volume of the extraction and dispersive solvents, extraction time, ionic strength, were optimized to improve the accuracy and precision of this method. MG and CV were extracted and preconcentrated using dichloromethane and acetonitrile as the extraction and dispersive solvents, respectively. Under the optimum conditions, the proposed method affords good linearity in the range of 0.40-20.0ng/L, and the limit of detections were 0.21 and 0.32ng/L for MG and CV, respectively. The recoveries of the method at three spiked levels were in the range of 83.4-94.2% with relative standard deviations lower than 4.7% (n=3). Satisfactorily, no significant matrix effect has been found as the data ranged between 68% and 102%.

Simple and effective coupling technique for polarization maintaining fibers.

We present a simple and effective technique for coupling free-space laser beams into polarization maintaining fibers (PMFs) with high coupling efficiency. We measure both input and output laser beam sizes near the PMF by using the knife-edge method and build a suitable two-lens system for beam shaping according to the difference between those two beam sizes. For tapered amplifiers, we achieve high coupling efficiency above 70% with the help of the seeding mirrors. For external cavity diode lasers, we obtain high coupling efficiency above 80%. In addition, we demonstrate that theoretical maximum coupling efficiency can be approached by using a mode-filtered beam. Our technique is easy to implement and suitable for many applications such as coherent optical communication, atomic physics experiments, and precision measurements.

In-fiber zigzag excitation for whispering-gallery modes via evanescent wave and free space coupling.

In this paper, we demonstrate a simple capillary-based coupler with optical zigzag transmission to excite whispering-gallery modes (WGMs) in a passive deformed microcavity. The coupler is just composed sections of a single mode fiber, a microsphere and a capillary, while neither corrosion nor tapering process is necessary. Based on the ray optics model, we obtain the criterion between the cone-apex angle and capillary wall thickness for the zigzag beams to excite WGMs effectively. This proper cone-apex angle range can be obtained by only setting the appropriate welding parameters. The smaller and larger cone-apex angles correspond to evanescent wave and free space coupling, respectively. The former has a clear free spectral range (FSR) envelope of WGMs, while the latter has no but compact and fairly intensity-uniform WGM peaks because it first directly excites chaotic sea which then couples into WGMs by dynamical tunneling. Moreover, the modified equations of motion for the photon counts are brought forward to analyze the energy distribution for the free space coupling. The excitation unit can work as a pure and basic building block, which is a simple and flexible coupling scheme for WGMs and has great potential in photonic integrated devices.

Mass production of high-performance single atomic FeNC electrocatalysts via sequenced ultrasonic atomization and pyrolysis process

Mass production of highly efficient, durable, and inexpensive single atomic catalysts is currently the major challenge associated with the oxygen reduction reaction (ORR) for fuel cells. In this study, we develop a general strategy that uses a simple ultrasonic atomization coupling with pyrolysis and calcination process to synthesize single atomic FeNC catalysts (FeNC SACs) at large scale. The microstructure characterizations confirm that the active centers root in the single atomic Fe sites chelating to the four-fold pyridinic N atoms. The identified specific Fe active sites with the variable valence states facilitate the transfer of electrons, endowing the FeNC SACs with excellent electrochemical ORR activity. The FeNC SACs were used as cathode catalysts in a homemade Zn-air battery, giving an open-circuit voltage (OCV) of 1.43 V, which is substantially higher than that of commercial Pt/C catalysts. This study provides a simple approach to the synthesis of single atomic catalysts at large scale.

Synthesis of high-density flammable hydrocarbon as potential hypergolic fuel and ignition additive of high-density fuels

Flammable liquid fuels are potential candidates to replace hydrazine derivatives as hypergolic fuel and to promote ignition and combustion of high-density fuels as additives. Here 1,4-dicyclopropylbuta-1,3-diyne (DCPB) with high density (0.932 g/mL) and net heating value (42.47 MJ/kg) was synthesized by simple copper-catalyzed alkyne coupling reaction. As hypergolic fuel, DCPB has a short ignition delay time of 19 ± 0.11 ms when contacting with fuming nitric acid. The calculated enthalpy of formation (ΔfH) of DCPB and specific impulse (Isp) using O2(L), N2O4(L) and HNO3(L) as oxidants are 499.2 kJ/mol, 394.7 s, 355.4 s and 334.7 s, respectively, much higher than that of hydrazine (50.9 kJ/mol, 379.0 s, 350.2 s and 333.5 s). The high Isp and short ignition delay time supported DCPB can be used as hypergolic fuel. As ignition additive, high temperature droplet plate and shock tube tests confirm that DCPB is effective to reduce the ignition delay time and lower the apparent ignition activation energy of high-density fuels like JP-10. Therefore, DCPB can be used as potential hypergolic fuel and ignition additive of high-density fuel.

Potential-driven inflation with disformal coupling to gravity

In this paper, we investigate the potential-driven inflation models with a disformal coupling to Einstein Gravity, to find out the effects of such a coupling on these models. We consider a simple coupling form which introduces only one parameter, and three inflation models, namely the chaotic inflation, the Higgs inflation, and the monodromy inflation. We find that the disformal coupling can have some modifications to the observational variables of these models such as the power spectrum, the spectral index as well as the tensor/scalar ratio, although not too large due to the constraints on the disformal coupling parameter. With these modifications, one has the opportunity of improving models that lie on the edge of the favorable regions of Planck observational data, such as monodromy inflation. Moreover, the non-trivial sound speed of tensor perturbations (gravitational waves) may come out, due to the coupling of gravity and kinetic terms of the field.

Efficient method for the computation of lightning current distributions in wind turbine blades using the Fourier transform and the finite element method

Rotor blades of large, modern wind turbines are susceptible to lightning strikes. In order to produce a design that resists lightning strikes, it is crucial to simulate lightning current propagation in the blade components. Since the current in the blade is generated by the superposition of potential and induced electric fields, a coupling exists between electric and magnetic fields which need to be calculated by an imposed integral constraint at each time step. Commercial software packages can deal with such constraints, but it results in time-consuming computations. Therefore, this work aims to develop a numerical methodology able to compute the voltage which drives the lightning current through the structure. In this way, the problem is reformulated as a voltage-driven one which in turn allows a simple subsequent coupling of electrical and magnetic problems. The computation of the voltage waveform was accomplished using the fast Fourier transform and the finite element method (FEM) to compute the structure impedance in the frequency domain. The developed procedure showed high efficiency for a blade subjected to different lightning impulses. It allows a description of the time-dependent lightning current to be given, as well as the distribution of current within the blade conductors.

Configurationally Random Polythiophene for Improved Polymer Ordering and Charge-Transporting Ability.

Random polythiophene polymers are characterized by the arbitrary sequences of monomeric units along polymer backbones. These untailored orientations generally result in the twisting of thiophene rings out of the conjugation planarity in addition to steric repulsions experienced among substituted alkyl chains. These tendencies have limited close polymer packing, which has been detrimental to charge transport in these moieties. To ameliorate charge transport in these classes of polymers, we make use of simple Stille coupling polymerization to synthesize highly random polythiophene polymers. We induced a positive microstructural change between polymer chains by attuning the ratio between alkyl-substituted and nonalkyl-substituted monomer units along the backbones. The optimized random polythiophene was found to have enhanced intermolecular interaction, increased size of crystallites, and stronger tendency to take edge orientation compared with both regiorandom and regioregular poly(3-hexylthiophene) polymers. Incorporation of the optimized random polythiophene as an active material in solid-state electrolyte-gated organic field-effect transistors exhibited better performance than the control device using regioregular poly(3-hexylthiophene), with a high hole mobility up to 4.52 cm2 V-1 s-1 in ambient conditions.

On the fate of sinking diatoms: the transport of active buoyancy-regulating cells in the ocean.

Diatoms are one of the most abundant, diverse and ecologically relevant phytoplanktonic group, contributing enormously to global biogeochemical processes like the carbon and silica cycles. This large success has been partly attributed to the mechanical and optical properties of the silica shell (the frustule) that envelops their body. But since they lack motility it is difficult to conceive how they cope with the fast-fluctuating environment they live in and where distributions of resources are very heterogeneous and dynamical. This pinpoints an important but yet poorly understood feature of diatoms physiology: buoyancy regulation that helps them controlling their sinking speed and position in the water column. While buoyancy regulation by light and nutrients availability has been well studied, the effect of hydromechanical stress via fluid shear has been rather overlooked when considering diatoms dynamics. Here, we aim to start filling this gap by first presenting direct experimental evidences for buoyancy control in response to hydro-mechanical stress and then review recent theoretical models where simple couplings between local shear and buoyancy control always result in heterogeneous cell distributions, specific accumulation regions within complex flows and increased sedimentation times to the depths, features of direct ecological relevance. We conclude by suggesting future experiments aiming to unveil such coupling and therefore gain better understanding on the fate of these fascinating microorganisms in their natural habitat. This article is part of the theme issue 'Stokes at 200 (part 2)'.

A new tail-switching superharmonic multiphase LC-VCO

PurposeMultiphase and quadrature voltage-controlled oscillators (QVCOs) play key roles in modern communication systems and their phase noise performance affects the performance of the overall system. Different studies are devoted to efficient quadrature signals generation. This paper aims to present a new low-phase noise superharmonic injection-locked QVCO.Design/methodology/approachThe proposed QVCO is comprised of two identical inductor-capacitor circuit (LC)-voltage-controlled oscillators (VCOs) in which second harmonics, with 180° phase shift, are injected from one core VCO to the gate of tail current source of the other VCO via a coupling capacitor. Using second harmonics with high amplitude will switch the tail from the inversion to the accumulation, and therefore, flicker noise is reduced. Also, because of the use of lossless and noiseless coupling elements, that is, coupling capacitors, and also because of the existence of an inherent high-pass filter, the proposed LC-QVCO has a good phase noise performance.FindingsThe introduced technique is designed and simulated in a commercial 0.18 µm radio frequency complementary metal oxide semiconductor (RF-CMOS) technology and 10 dB improvement of close-in phase noise is achieved (compared to the conventional method). Simulation results show that the phase noise of the proposed QVCO is −130.3 dBc/Hz at 3 MHz offset from 5.76 GHz center frequency, while the total direct current (DC) current drawn from a 0.9-V power supply is 4.25 mA (figure of merit = −190.2 dBc). Monte Carlo simulation results show that the figure of merit of the circuit has a Gaussian distribution with mean value and standard deviation of −189.97 dBc and 0.183, respectively.Originality/valueThis technique provides a new simple but efficient superharmonic coupling and noise shaping method that reduces close-in phase noise of superharmonic multiphase VCOs by switching of tail transistors with 2 ω0 (second harmonic of oscillation frequency). No extra devices such as area-consuming transformer or additional power-hungry oscillator are used for coupling.

Room-Temperature Synthesis of Hollow Carbazole-Based Covalent Triazine Polymers with Multiactive Sites for Efficient Iodine Capture-Catalysis Cascade Application

In this work, we report a room temperature synthesis of multifunctional hollow carbazole-based covalent triazine polymers (H-C-CTPs) via a simple FeCl3-catalyzed oxidative coupling reaction using t...

Entropy-stable p-nonconforming discretizations with the summation-by-parts property for the compressible Navier–Stokes equations

The entropy-conservative/stable, curvilinear, nonconforming, p-refinement algorithm for hyperbolic conservation laws of Del Rey Fernández et al. (2019) is extended from the compressible Euler equations to the compressible Navier–Stokes equations. A simple and flexible coupling procedure with planar interpolation operators between adjoining nonconforming elements is used. Curvilinear volume metric terms are numerically approximated via a minimization procedure and satisfy the discrete geometric conservation law conditions. Distinct curvilinear surface metrics are used on the adjoining interfaces to construct the interface coupling terms, thereby localizing the discrete geometric conservation law constraints to each individual element. The resulting scheme is entropy conservative/stable, element-wise conservative, and freestream preserving. Viscous interface dissipation operators that retain the entropy stability of the base scheme are developed. The accuracy and stability of the resulting numerical scheme are shown to be comparable to those of the original conforming scheme in Carpenter et al. (2014) and Parsani et al. (2016), i.e., this scheme achieves ∼p+1/2 convergence on geometrically high-order distorted element grids; this is demonstrated in the context of the viscous shock problem, the Taylor–Green vortex problem at a Reynolds number of Re=1,600, and a subsonic turbulent flow past a sphere at Re=2,000.

All-Optical 2 $ \times $ 2-Bit Multiplier at 40 Gb/s Based on Canonical Logic Units-based Programmable Logic Array (CLUs-PLA)

Multiplication is an important function of logic operation, and all-optical high-speed multiplication logic operation will lay the foundation for future high-speed optical computing and optical logic processing chip. In this article, by introducing the structure of canonical logic units-based programmable logic array (CLUs-PLA), we propose a scheme to realize all-optical 2 × 2-bit multiplier. In our scheme, different types of CLUs are generated using bidirectional multichannel four-wave mixing (FWM), then the results of multiplier at the operation of 40 Gb/s can be obtained by simple power coupling of corresponding CLUs. Eye diagrams of logic results are widely open, and the extinction ratios are more than 9.4 dB. Comparing with multiplier based on traditional hierarchical computing, multiplier based on parallel computing in our scheme can reduce the number of AND gate by 4, and avoid further deterioration of signal quality due to three-order cascade of AND gate. Moreover, the scheme has the potential to realize m × n-bit (m + n ≤ 9, m and n are positive integers) multiplier at higher operation rate in the integrated platform, paving the way towards multi-bit high-speed compact complex logic devices for future high-performance optical computing and optical logic processing chip.

Particles with Magnetic Patches: Synthesis, Morphology Control, and Assembly

AbstractThe concept of patchy particles is revolutionizing the research field of colloidal assembly, by the design of particles whose surface is purposely patterned to promote attractive interactions with their neighbors in limited number, and in privileged and programmed directions. The idea of magnetic patches makes it possible to imagine assemblies not only spontaneous by simple magnetic coupling but also triggered and canceled at will due to external magnetic fields. This review shows that studies published until now mainly deal with particles with a single magnetic patch, often called Janus particles. The very diverse synthetic routes have been brought together into four main strategies, covering the size range from 100 nm to 100 µm. Their assembly capacity is described both from experimental and simulation viewpoints. The orientation of the magnetic moment of the patch and its decentering extent with respect to the particle are the key parameters for controlling the morphology of clusters, loops, staggered chains, double chains, helices, microtubes, etc. The review offers some perspectives to generalize these studies to multipatch particles, examples of which are still too rare, and to make assemblies sustainable, especially after the removal of the structuring magnetic fields.