SciCombinator

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Carbon-fiber microelectrodes are an instrumental tool in neuroscience, used for electroanalysis of neurochemical dynamics and recordings of neural activity. However, performance is variable and dependent on fabrication strategies, the biological response to implantation, and the physical and chemical composition of the recording environment. This presents an analytical challenge, as electrode performance is difficult to quantitatively assess in situ, especially when electrodes are permanently implanted or cemented in place. We previously reported that electrode impedance directly impacts electrochemical performance for molecular sensing. In this work, we investigate the impact of individual components of the electrochemical system on impedance. Equivalent circuit models for glass- and silica-insulated carbon-fiber microelectrodes were determined using electrochemical impedance spectroscopy (EIS). The models were validated based on the ability to assign individual circuit elements to physical properties of the electrochemical system. Investigations were performed to evaluate the utility of the models in providing feedback on how changes in ionic strength and carbon fiber material alter impedance properties. Finally, EIS measurements were used to investigate the electrode/solution interface prior to, during, and following implantation in live brain tissue. A significant increase in impedance and decrease in capacitance occur during tissue exposure and persist following implantation. Electrochemical conditioning, which occurs continually during fast-scan cyclic voltammetry recordings, etches and renews the carbon surface, mitigating these effects. Overall, the results establish EIS as a powerful method for characterization of carbon-fiber microelectrodes, providing unprecedented insight into how real-world factors affect the electrode/solution interface.

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Droplet jumping phenomenon widely exists in the fields of self-cleaning, anti-frosting and heat transfer enhancement. Numerous studies have been reported on the static droplet jumping while the rolling droplet jumping still remains unnoticed although it is very common in practice. Here, we used the volume of fluid (VOF) method to simulate the droplet jumping induced by coalescence of a rolling droplet and a stationary one with corresponding experiments conducted to validate the correctness of the simulation model. The departure velocity of the jumping droplet was mainly concerned here. The results show that when the center velocity of the rolling droplet (V0 =ωR, where ω is the angular velocity of the rolling droplet and R is the droplet radius) is fixed, the vertical departure velocity satisfies a power law which can be expressed as Vz, depar = aRb. When the droplet radius is fixed, the vertical departure velocity first decreases, and then increases if the center velocity exceeds a critical value. Interestingly, the critical center velocity is demonstrated to be approximately 0.76 times of the capillary-inertial velocity, corresponding to a constant Weber number of 0.58. Different from the vertical departure velocity, the horizontal departure velocity is basically proportional to the center velocity of the rolling droplet. These results deepen the understanding of the droplet jumping physics, which shall further promote related applications in engineering fields.

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A novel porous organic cage (POC) was prepared via condensation reaction between 1,3,5-triformylbenzene (TFB) and (1R, 2R)-4-cyclohexene-1,2-diamine (CHEDA). This POC could pack in either an amorphous structure or a crystalline. Atomically precise structure determination of POC was achieved through Ab initio powder X-ray diffraction (PXRD) structure analysis in chiral trigonal space group of R3. The same atomically precise structure determination of POC from single crystal X-ray diffraction (SXRD) structure analysis could be obtained independently with a slight difference in cell parameter, indicating that the refinement method through Ab initio PXRD structure analysis is reliable and may serve as an essential method for atomically precise structure determination. The cage could adsorb up to 8 mmol/g CO2 at 298 K and 1 bar. Furthermore, 1-thioglycerol and 1-octadecanethiol were chosen to prove that post-modification of this POC was flexible. After post-synthetic modification (PSM) via highly efficient photoinitiated thiol-ene click reaction, the products still kept porous with relatively higher special surface area (337 m2/g of 5T and 156 m2/g of 5O) than mostly reported cages via reduced-amine approach.

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Nature provides various exquisite photonic structures of antireflection. Here, we investigate the color and structure of the inner surface of the shell edge (ISSE) of blue mussel shells, using fiber optical spectrometer, scanning electron microscope (SEM), and X-ray diffraction (XRD). We demonstrate that the structurally assisted black color of the ISSE is produced by pyramidal microstructure. Furthermore, we use the two-step bio-template (TSBT) method to successfully replicate this microstructure. Particularly, we modify this method by using a poly (vinyl alcohol) (PVA) film as the negative replica and an epoxy resin film as the positive replica both fabricated without vacuum treatment. We show that the natural and replicated structures show the reflectivity of ~ 4% and of ~ 3% in the visible wavelength. Finally, we hope our investigation can provide basic data for the study of the bioinspired antireflective structures, which have a promising application in smart windows and optical devices.

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The hydroazidation of alkynes is the most straightforward way to access vinyl azides - versatile building blocks in organic synthesis. We previously realized such a fundamental reaction of terminal alkynes using Ag2CO3 as a catalyst. However, the high catalyst loading seriously limits its practicality, and moreover the exact reaction mechanism remains unclear. Here, on the basis of X-ray diffraction studies on the conversion of silver salts, we report the identification of AgN3 as the real catalytic species in this reaction, and therefore developed a AgN3-catalyzed hydroazidation of terminal alkynes. AgN3 proved to be a highly robust catalyst, as the loading of AgN3 could be as low as 5 mol%, and such a small proportion of AgN3 is still highly efficient even at a 50 mmol reaction scale. Further, the combination of experimental investigations and theoretical calculations disclosed that the concerted addition mechanism via a six-membered transition state is more favored than the classical silver acetylide mechanism.

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Microbial transformations of two tetracyclic beyerane-type diterpenes, ent-16β-oxobeyeran-19-oic acid (1) and its chemical reduction product, ent-16β-hydroxybeyeran-19-oic acid (2), by the filamentous fungus Cunninghamella echinulata ATCC 8688a yielded eight metabolites (3-10). Incubation of the substrate 2 with C. echinulata afforded three new hydroxylated ones (3-5) along with two known ones (6-7), while incubation of 1 gave three known ones (8-10). The new compounds were characterized by 1D and 2D NMR as well as HRESIMS analysis, and the stereostructures of 3 and 4 were confirmed by X-ray crystallography. The bio-reactions were involved not only in stereoselective incorporation of hydroxyl groups at inert positions C-7, -9, -12, and -14 of the two beyerane diterpenes but also in glucosidation at C-19 of 2. This is the first report on the biotransformation of the diterpenes by using C. echinulata. All compounds were assayed for their α-glucosidase inhibitory, neurotrophic, anti-inflammatory, and phytotoxic activity, and only in neurotrophic assay compounds 2 and 9 were found to display NGF-mediated neurite-outgrowth promoting effects in PC12 cells; the others were inactive.

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Reversible addition-fragmentation chain transfer (RAFT) dispersion polymerization of benzyl methacrylate is used to prepare a series of well-defined poly(stearyl methacrylate)-poly(benzyl methacrylate) (PSMA-PBzMA) diblock copolymer nanoparticles in mineral oil at 90 °C. A relatively long PSMA54 precursor acts as a steric stabilizer block and also ensures that only kinetically-trapped spheres are obtained, regardless of the target degree of polymerization (DP) for the core-forming PBzMA block. This polymerization-induced self-assembly (PISA) formulation provides good control over the particle size distribution over a wide size range (24 to 459 nm diameter). 1H NMR spectroscopy studies confirm that high benzyl methacrylate monomer conversions (≥ 96%) are obtained for all PISA syntheses while transmission electron microscopy (TEM) and dynamic light scattering (DLS) analyses show well-defined spheres with a power law relationship between the target PBzMA DP and the mean particle diameter. Gel permeation chromatography (GPC) studies indicate a gradual loss of control over the molecular weight distribution as higher DPs are targeted, but well-defined morphologies and narrow particle size distributions can be obtained for PBzMA DPs up to 3500, which corresponds to an upper particle size limit of 459 nm. Thus, these are amongst the largest well-defined spheres with reasonably narrow size distributions (standard deviation ≤ 20%) produced by any PISA formulation. Such large spheres show promise as model nanoparticles for analytical centrifugation studies.

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Hypochlorite (ClO-) and singlet oxygen (1O2) are commonly coexisted in living system, and exert important interplaying roles in many diseases. To dissect their complex inter-relationship, it is urgently required to construct a fluorescent probe that can dis-criminate ClO- and 1O2 in living organism. Herein, by taking 3-(aliphaticthio)-propan-1-one group as the unique recognition unit for both ClO- and 1O2, we proposed the first fluorescent probe, Hy-2, to simultaneously discriminate ClO- and 1O2 with high sensi-tivity and selectivity. Probe Hy-2 itself showed fluorescence in blue channel. After treatment with ClO- and 1O2 respectively, pro-nounced fluorescence enhancements were observed in the green channel and red channel correspondingly. Moreover, upon de-velopment of the probe with aggregation-induced emission (AIE) characteristics, the probe could work well in a solution with high water volume fraction. Probe Hy-2 was also able to accumulate into mitochondria and was utilized as an effective tool to image exogenous and endogenous ClO- and 1O2 in mitochondria. Significantly, as the first trial, probe Hy-2 was employed to sim-ultaneously monitor the variation of ClO- and 1O2 level in cecum tissues of rat in the cecal ligation and puncture (CLP)-induced polymicrobial sepsis model. The results demonstrated that the expressed ClO- and 1O2 levels were tightly correlated with the sever-ity of sepsis, inferring the overproduction of ClO- and 1O2 is an important factor for the pathogenesis of sepsis. The probe illus-trated herein may provide a guide for further exploring the functions of ClO- and 1O2 in various diseases.

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Ruthenium pyrochlores, i.e. oxides of composition A2Ru2O7-δ, have emerged recently as state-of-the-art catalysts for the oxygen evolution reaction (OER) in acidic conditions. Here, we demonstrate that the A-site substituent in yttrium ru-thenium pyrochlores Y1.8M0.2Ru2O7-δ (M = Cu, Co, Ni, Fe, Y) controls the concentration of surface oxygen vacancies (VO) in these materials whereby an increased concentration of VO sites correlates with a superior OER activity. DFT calcula-tions rationalize these experimental trends demonstrating that the higher OER activity and VO surface density originate from a weakened strength of the M-O bond, scaling with the formation enthalpy of the respective MOx phases and the coupling between the M d states and O 2p states. Our work introduces a novel catalyst with improved OER perfor-mance, Y1.8Cu0.2Ru2O7-δ, and provides general guidelines for the design of active electrocatalysts.

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This work reports a novel dual-phase glass containing Tm: NaYbF4 upconverting nanocrystals (UCNCs) and CsPbBr3 perovskite NCs (PNCs). The advantages of this kind of nanocomposite are to provide a solid inorganic glass host for in-situ co-growth of UCNCs and PNCs as well as to protect PNCs against decomposition affected by external environment. Tm: NaYbF4 NCs sensitized photon UC in PNCs is achieved under the irradiation of 980 nm near-infrared (NIR) laser and the mechanism is evidenced to be radiative energy transfer (ET) from Tm3+: 1G4 state to PNCs rather than non-radiative Förster resonance ET. Consequently, decay lifetime of exciton recombination is remarkably lengthened from intrinsic nanoseconds to milliseconds since carriers in PNCs are fed from long-lifetime Tm3+ intermediate state. Under simultaneous excitation of ultraviolet (UV) light and NIR laser, dual-modal photon UC and downshifting (DS) emissions from ultra-stable CsPbBr3 PNCs in glass are observed, and the combined UC/DS emitting color can be easily altered by modifying pumping light power. In addition, UC exciton recombination and Tm3+ 4f-4f transitions are found to be highly temperature sensitive. All these unique emissive features enable the developed dual-phase glass find practical applications in advanced anticounterfeit and accurate temperature detection.