Sequential Transfer Research Articles

In-Situ Spectro-Electrochemistry of Conductive Polymers Using Plasmonics to Reveal Doping Mechanisms.

Conducting polymers are a key component for developing wearable organic electronics, but tracking their redox processes at the nanoscale to understand their doping mechanism remains challenging. Here we present an in-situ spectro-electrochemical technique to observe redox dynamics of conductive polymers in an extremely localized volume (<100 nm3). Plasmonic nanoparticles encapsulated by thin shells of different conductive polymers provide actively tuned scattering color through switching their refractive index. Surface-enhanced Raman scattering in combination with cyclic voltammetry enables detailed studies of the redox/doping process. Our data intriguingly show that the doping mechanism varies with polymer conductivity: a disproportionation mechanism dominates in more conductive polymers, while sequential electron transfer prevails in less conductive polymers.

The Augmented Social Scientist: Using Sequential Transfer Learning to Annotate Millions of Texts with Human-Level Accuracy

The last decade witnessed a spectacular rise in the volume of available textual data. With this new abundance came the question of how to analyze it. In the social sciences, scholars mostly resorted to two well-established approaches, human annotation on sampled data on the one hand (either performed by the researcher, or outsourced to microworkers), and quantitative methods on the other. Each approach has its own merits - a potentially very fine-grained analysis for the former, a very scalable one for the latter - but the combination of these two properties has not yielded highly accurate results so far. Leveraging recent advances in sequential transfer learning, we demonstrate via an experiment that an expert can train a precise, efficient automatic classifier in a very limited amount of time. We also show that, under certain conditions, expert-trained models produce better annotations than humans themselves. We demonstrate these points using a classic research question in the sociology of journalism, the rise of a “horse race” coverage of politics. We conclude that recent advances in transfer learning help us augment ourselves when analyzing unstructured data.

The scavenging mechanism of aminopyrines towards hydroxyl radical: A computational mechanistic and kinetics investigation

A DFT investigation was performed to characterize the scavenging mechanism of antipyrine and three of its aminopyrine derivatives i.e., Antipyrine (1), 4-Aminoantipyrine (2), 4-(N-Methyl)-aminoantipyrine (3), 4- (N, N-Dimethyl)-aminoantipyrine (4). Possible mechanisms e.g., hydrogen atom transfer, Single Electron Transfer Followed by Proton Transfer, and Sequential Proton Loss Electron Transfer were evaluated. QM-ORSA protocol has been used to analyze scavenging activity. Thermodynamic parameters e.g., bond dissociation energy, adiabatic ionization energy and proton dissociation enthalpy, and proton affinity and electron transfer enthalpies were computed to define the mechanism. HAT was found the most preferable mechanism among others and it shows the trend of reactivity 4 ∼ 3 > 2 > 1. Our results provide the de-methylated product as the major product for the reaction of compound 4 with OH radical which shows good agreement with the experiment. The acquired insights will be helpful for further characterizing the antioxidant activity of other compounds.

Light-induced energy and electron transfer occurring in tandem in tetra (bis(4′-tert-butylbiphenyl-4-yl)aniline)-zinc(II) porphyrin-fullerene supramolecular conjugates

[Formula: see text]-bis (4′-tert-butylbiphenyl-4-yl)aniline) tethered zinc porphyrins, (BBA)4- ZnP, (BBA- Ph)4- ZnP, and (BBA- OEtOPh)4- ZnP with varied spacer distances have been synthesized and photosynthetic antenna-reaction center models were constructed via axial co-ordination with fulleropyrrolidines, C60Im and C70Im. Selective excitation of the BBA moiety in the porphyrins at 355 nm resulted in the quenching of the emission intensity of the BBA followed by the concomitant appearance of the ZnP emission at 600–640 nm indicating the occurrence of the photoinduced energy transfer from 1BBA* to ZnP. When the zinc porphyrins are titrated with C60Im and C70Im, supramolecular complexes of the type, (BBA)4-ZnP:[Formula: see text]Im/[Formula: see text]Im are formed and the complex formation was monitored by UV-visible spectroscopic studies. Steady-state fluorescence studies involving the excitation of the ZnP at 550 nm displayed the diminished fluorescence intensity of the ZnP emission indicating the photoinduced electron transfer from 1ZnP* to fullerenes. More interestingly, when the BBA moiety is excited in the supramolecular complexes, the emission of both the BBA and ZnP were decreased gradually indicating the occurrence of PEnT from 1BBA* to ZnP followed by a sequential electron transfer from 1ZnP* to C60Im or C70Im indicating the formation of a charge-separated state in these complexes.

Elucidation of reactive oxygen species scavenging pathways of norbergenin utilizing DFT approaches.

Bergenin is a polyphenolic compound that contains isocoumarin skeletal derived from C-glycosylated 4-O-methylgallic acid. The biological activities of this compound and its derivatives are quite diverse. Recent studies reveal neuroprotective effects in vitro and in vivo in Alzheimer's. Norbergenin is a demethylated form of bergenin, known for better antioxidant capacity and associated with neuroprotective properties through oxidative stress inhibition. This study focused on investigating the scavenging mechanism of norbergenin with the •OH, •OOH, and as a radical model under physiological and lipid environments. The thermodynamic and kinetic parameters of the hydrogen transfer (HT), single electron transfer (SET), sequential proton lost-electron transfer (SPLET) and radical adduct formation (RAF) mechanisms were determined theoretically by the density functional theory (DFT) at M06-2X/6-311 + + G(d,p) level of theory. Based on the computational results, this compound has proved as an excellent •OOH and •OH scavenger under physiological conditions better than Trolox and vitamin C, whereas its radical demonstrated as an efficient scavenger.

Transfer of Phi6 bacteriophage between human skin and surfaces common to consumer-facing environments.

This study aimed to determine the extent of Phi6 (Φ6) transfer between skin and surfaces relevant to consumer-facing environments based on inoculum matrix, surface type and contact time. Φ6 transfer rates were determined from skin-to-fomite and fomite-to-skin influenced by inoculum matrix (artificial saliva and tripartite), surface type (aluminium, plastic, stainless steel, touchscreen, vinyl and wood) and contact time (5 and 10s). Significant differences in estimated means were observed based on surface type (both transfer directions), inoculum matrix (skin-to-fomite) and contact time (both transfer directions). During a sequential transfer experiment from fomite-to-skin, the maximum number of consecutive transfer events observed was 3.33 ± 1.19, 2.33 ± 1.20 and 1.67 ± 1.21 for plastic, touchscreen and vinyl, respectively. Contact time significantly impacted Φ6 transfer rates, which may be attributed to skin absorption dynamics. Surface type should be considered for assessing Φ6 transfer rates. Although the persistence of Φ6 on fomites has been characterized, limited data are available regarding the transfer of Φ6 among skin and fomites. Determining Φ6 transfer rates for surfaces in consumer-facing environments based on these factors is needed to better inform future virus transmission mitigation strategies.

Evolutionary Sequential Transfer Optimization for Objective-Heterogeneous Problems

Evolutionary sequential transfer optimization is a paradigm that leverages search experience from solved source optimization tasks to accelerate the evolutionary search of a target task. Even though many algorithms have been developed, they mainly focus on objective-homogeneous problems, where the source and target tasks possess a similar number of objectives. In this work, we explore objective-heterogeneous problems, in which knowledge transfers across single-objective optimization problems (SOPs), multiobjective optimization problems (MOPs), and many-objective optimization problems (MaOPs). Objective-heterogeneous problems challenge the existing methods due to the diverse search and objective spaces between the source and the target task. To address this issue, we present a decision variable analysis-based transfer method that can conduct knowledge transfer across problems with the different numbers of objectives. We first separate decision variables of MOPs and MaOPs into convergence-related variables (CVs) and diversity-related variables (DVs), according to their roles while treating variables of SOPs as CVs. Then, we propose a convergence transfer module to transfer knowledge of CVs to speed up the convergence. It aligns both solutions and fitness ranks for preserving fitness rank consistency between the source and target tasks, whereby accelerating search speed. Besides, a diversity transfer module is presented to refine the distribution of DVs to maintain the population diversity. The experimental results on objective-heterogeneous test problems and a real-world case study have demonstrated the effectiveness of the proposed algorithm.

Effects of sequential cleavage and blastocyst embryo transfer on pregnancy outcomes in patients with poor ovarian response

The management of patients with poor ovarian response (POR) remains a major challenge for fertility specialists in in vitro fertilization-embryo transfer (IVF-ET). In this retrospective cohort study, we aimed to evaluate the clinical effect of sequential transfer on pregnancy outcomes in patients with POR. A total of 3579 POR patients who underwent the first frozen embryo transfer (FET) cycle were enrolled from January 2018 to April 2021. The patients were divided into three groups according to the embryo transfer (ET) strategy adopted: a study group that included POR patients in whom a cleavage-stage embryo (day 3) and a blastocyst (day 5/6) were transferred (sequential transfer group), and two control groups in whom two cleavage-stage embryos (D3-dET group) or two blastocysts (D5/6-dET group) were transferred. The study group was matched with the control groups at a ratio of 1:4 by propensity score matching (PSM). The main pregnancy outcomes measured were the live birth rate and multiple pregnancy rate. After PSM, the live birth rate in the sequential transfer group was significantly higher than that in the D3-dET group (44.2% vs. 34.3%, P = 0.019), and was similar to that in the D5/6-dET group (44.2% vs. 45.3%; P = 0.90). In addition, there was no increase in the risk of multiple pregnancy among POR patients undergoing sequential transfer compared with both D3-dET (26.7% vs. 25.6%, P = 0.85) and D5/6-dET (26.7% vs. 28.4%, P = 0.97) groups. These findings imply that sequential transfer is an effective option for POR patients and could be utilized after careful consideration.

Paired electrolysis-enabled nickel-catalyzed enantioselective reductive cross-coupling between α-chloroesters and aryl bromides

Electrochemical asymmetric catalysis has emerged as a sustainable and promising approach to the production of chiral compounds and the utilization of both the anode and cathode as working electrodes would provide a unique approach for organic synthesis. However, precise matching of the rate and electric potential of anodic oxidation and cathodic reduction make such idealized electrolysis difficult to achieve. Herein, asymmetric cross-coupling between α-chloroesters and aryl bromides is probed as a model reaction, wherein alkyl radicals are generated from the α-chloroesters through a sequential oxidative electron transfer process at the anode, while the nickel catalyst is reduced to a lower oxidation state at the cathode. Radical clock studies, cyclic voltammetry analysis, and electron paramagnetic resonance experiments support the synergistic involvement of anodic and cathodic redox events. This electrolytic method provides an alternative avenue for asymmetric catalysis that could find significant utility in organic synthesis.

Two Theorems and Important Insight on How the Preferred Mechanism of Free Radical Scavenging Cannot Be Settled. Comment on Pandithavidana, D.R.; Jayawardana, S.B. Comparative Study of Antioxidant Potential of Selected Dietary Vitamins; Computational Insights. Molecules 2019, 24, 1646.

Totally ignoring that the five enthalpies of reaction-bond dissociation enthalpy (BDE), adiabatic ionization potential (IP), proton dissociation enthalpy (PDE), proton affinity (PA), and electron transfer enthalpy (ETE)-characterizing the three free radical scavenging mechanisms-direct hydrogen atom transfer (HAT), sequential electron transfer proton transfer (SET-PT), and stepwise proton loss electron transfer (SPLET)-are not independent of each other, a recent publication on the antioxidant activity of dietary vitamins compared various vitamins and "found" different quantities, which should be strictly equal by virtue of energy conservation. Aiming to clarify this point, as well as to avoid such mistakes in future studies and to unravel errors in the previous literature, in the present paper we formulate two theorems that any sound results on antioxidation should obey. The first theorem states that the sums of the enthalpies characterizing the individual steps of SET-PT and SPLET are equal: IP+PDE = PA+ETE (=H2). This is a mathematical identity emerging from the fact that both the reactants and the final products of SET-PT and SPLET are chemically identical. The second theorem, which is also a mathematical identity, states that H2 - BDE = IPH &gt; 0, where IPH is the ionization potential of the H-atom in the medium (e.g., gas or solvent) considered. Due to their general character, these theorems may/should serve as necessary sanity tests for any results on antioxidant activity, whatever the method employed in their derivation. From a more general perspective, they should represent a serious word of caution regarding attempts to assign the preferred free radical scavenging pathway based merely on thermochemical descriptors.

Pillar[5]arene-based light-harvesting assemblies with sequential energy-transfer for tunable emission and photocatalysis

Sequential energy transfer widely exists in natural light-harvesting systems (LHSs), which greatly benefits the full use of solar energy. In this work, we report an artificial light-harvesting platform derived from pillar (Wang et al., 2021) [5]arene-directed host-guest nanoparticles (WP5⊃G) in aqueous media. The WP5⊃G assembly can serve as a good donor owing to the excellent fluorescence behavior of G in the aggregated state, guaranteeing a two-step FRET from the WP5⊃G to the relay acceptor eosin Y (ESY) and then to the final acceptor Nile red (NiR) to form a WP5⊃G@ESY/NiR system with high efficiency. As a consequence of the flexibility of the system, tunable emission including a highly efficient white-light emission can be realized. The WP5⊃G@ESY/NiR system was further used as a photocatalyst to catalyze dehalogenation reaction in aqueous solution, exhibiting remarkable catalytic activity as compared with the WP5⊃G or ESY/NiR alone.

Radical scavenging capacity, UV activity, and molecular docking studies of 2ʹ, 5ʹ, 3, 4-Tetrahydroxychalcone: An insight into the photoprotection

A theoretical evaluation of radical scavenging activity and UV absorbing ability of chalcone named 2ʹ, 5ʹ, 3, 4-Tetrahydroxychalcone has been performed in the gas phase and aqueous media. The DFT-B3LYP/6–311+G (d, p) level of theory was utilized for geometry optimization and the calculation of reaction enthalpies, while the CAM-B3LYP/6–311+G (d, p) level of theory was employed for TDDFT analysis. Three potential working mechanisms of radical scavenging activity, hydrogen atom transfer mechanisms (HAT), stepwise electron transfer proton transfer (SET-PT), and sequential proton loss electron transfer mechanisms (SPLET) were investigated within the gas phase and aqueous phase. The results obtained demonstrate that the HAT will be the probable mechanism in the gas phase whereas SPLET will be in the water medium. Using the same level of theory, explicit surface analysis of the title compound was performed. The compound wave function analysis and molecular docking investigations were also performed in the optimized structure. The theoretical UV spectra were recorded in both the solvents and the compound's electronic absorption spectrum was analyzed using the TD-DFT method. The distribution of hole and electrons in the peaks of maximal oscillator strength corresponds to local excitation within the molecule. The Quantum Theory of Atoms in Molecule (QTAIM) was used to compute the strength of intramolecular hydrogen bonds and non-covalent interactions. The global reactivity parameters and electrostatic potential (ESP) were also included to define the reactivity of the whole molecule. The spin density distribution analysis was come upon to be complementary to the radical scavenging activity. Besides the radical scavenging activity of the compound, it can also be used as a potential UVA filter.

Silver Nanocrystal Array with Precise Control via Star-like Copolymer Nanoreactors.

Silver nanocrystal arrays had attracted much attention due to the unique plasmonic effect of their ordered nanostructure and the synergy among adjacent nanocrystals. Conventional preparation methods had several limitations, such as high cost, harsh preparation conditions, and complicated influencing factors, which could not be employed to fabricate the nanocrystal arrays in highly controlled fashion. To solve these issues, we reported ordered arrays of different Ag nanocrystals with precise control prepared by utilizing amphiphilic star-like poly(4-vinylpyridine)-block-polystyrene diblock copolymers as nanoreactors synthesized by sequential atom transfer radical polymerization. Moreover, this unimolecular nanoreactor method based on star-like copolymers with stable and predesigned nanostructures was proved to be a universal approach to prepare other nanocrystal arrays. This strategy had low cost, simple process flow, wide applicability, and structural stability that could fabricate nanocrystal array with precise control and continuously prepare more complex nanostructure units in a large scale to meet different functions and applications.

A Carbon Nanotube Binding BODIPY-C60 Nano Tweezer: Charge Stabilization through Sequential Electron Transfer.

Electron donor-acceptor (DA) hybrids comprised of single-wall carbon nanotubes (SWCNTs) are promising functional materials for light energy conversion. However, the DA hybrids built on SWCNTs have failed to reveal the much-sought long-lived charge separation (CS) due to the close proximity of the DA entities facilitating charge recombination. Here, we address this issue and report an elegant strategy to build multi-modular DA hybrids capable of producing long-lived CS states. For this, a nano tweezer featuring V-shape configured BODIPY was synthesized to host SWCNTs of different diameters via π-stacking. Supported by spectral, electrochemical, and computational studies, the established energy scheme revealed the possibility of sequential electron transfer. Systematic pump-probe studies covering wide spatial and temporal scales provided evidence of CS from the initial 1 BODIPY* ultimately resulting in C60 ⋅- -BODIPY-SWCNT⋅+ CS states of lifetimes in the 20-microsecond range.

A Carbon Nanotube Binding BODIPY‐C60 Nano Tweezer: Charge Stabilization through Sequential Electron Transfer

AbstractElectron donor–acceptor (DA) hybrids comprised of single‐wall carbon nanotubes (SWCNTs) are promising functional materials for light energy conversion. However, the DA hybrids built on SWCNTs have failed to reveal the much‐sought long‐lived charge separation (CS) due to the close proximity of the DA entities facilitating charge recombination. Here, we address this issue and report an elegant strategy to build multi‐modular DA hybrids capable of producing long‐lived CS states. For this, a nano tweezer featuring V‐shape configured BODIPY was synthesized to host SWCNTs of different diameters via π‐stacking. Supported by spectral, electrochemical, and computational studies, the established energy scheme revealed the possibility of sequential electron transfer. Systematic pump‐probe studies covering wide spatial and temporal scales provided evidence of CS from the initial 1BODIPY* ultimately resulting in C60⋅−‐BODIPY‐SWCNT⋅+ CS states of lifetimes in the 20‐microsecond range.

Glycopolymer Decorated pH-Dependent Ratiometric Fluorescent Probe Based on Förster Resonance Energy Transfer for the Detection of Cancer Cells.

Development of fluorescent imaging probes is an important topic of research for the early diagnosis of cancer. Based on the difference between the cellular environment of tumor cells and normal cells, several "smart" fluorescent probes have been developed. In this work, a glycopolymer functionalized Förster resonance energy transfer (FRET) based fluorescent sensor is developed, which can monitor the pH change in cellular system. One-pot sequential reversible addition-fragmentation chain transfer (RAFT)polymerization technique is employed to synthesize fluorescent active triblock glycopolymer that can undergo FRET change on the variation of pH. A FRET pair, fluorescein o-acrylate (FA) and 7-amino-4-methylcoumarin (AMC) is linked via a pH-responsive polymer poly [2-(diisopropylamino)ethyl methacrylate] (PDPAEMA), which can undergo reversible swelling/deswelling under acidic/neutral condition. The presence of glycopolymer segment provides stability, water solubility, and specificity toward cancer cells. The cellular FRET experiments on cancer cells (MDA MB 231) and normal cells (3T3 fibroblast cells) demonstrate that the material is capable of distinguishing cells as a function of pH change.

Sequential (two-step) day 3/day 5 frozen-thawed embryo transfer: does it improve the pregnancy rate of patients suffering recurrent implantation failure?

The best time of endometrial receptivity is the missing part of the implantation puzzle in patients with recurrent in vitro fertilization (IVF) failure. There are various treatment plans and strategies to meet the best endometrial timing for implantation. However, the lack of synchronization of the good-quality embryo with the patient's individual "window of implantation" is the hypothesis for most IVF failures so far. Sequential embryo transfer (ET) theoretically extends the availability time of embryos on the window of implantation. The study aimed to evaluate the improvement of pregnancy rate in sequential (two-step) frozen-thawed embryo transfer (FET) on day 3/day 5 in individuals who suffer from repeated IVF failures. This randomized controlled trial study was done in a university-affiliated infertility center for women with repeated consecutive IVF failures. Two hundred women aged 20-39 years who met our inclusion criteria were included in the study between January 2020 and September 2021. Participants were allocated with a 1:1 ratio to either sequential (two-step) ET on day 3/day 5 (study group, n=100) and conventional day 5 FET (n=100, control group). The frozen-thawed embryos were transferred to hormone replacement therapy-prepared endometrium in both groups. The primary outcomes were clinical pregnancy and implantation rates. The secondary outcomes were early pregnancy loss and multiple pregnancies. The demographic and clinical characteristics of the two groups were comparable. Clinical pregnancy rates were significantly higher in the sequential (two-step) FET group (40%) compared to the day 5 group (19%) (P<0.001). The sequential transfer of frozen-thawed embryos on day 3/day 5 was more effective than regular day 5 for patients suffering from repeated IVF failure.

Tetraphenylethene-Based Emissive Pt(II) Coordination Polymer toward Artificial Light-Harvesting Systems with Sequential Energy Transfer

Tetraphenylethene-Based Emissive Pt(II) Coordination Polymer toward Artificial Light-Harvesting Systems with Sequential Energy Transfer

Serial Femtosecond Crystallography Reveals the Role of Water in the One- or Two-Electron Redox Chemistry of Compound I in the Catalytic Cycle of the B-Type Dye-Decolorizing Peroxidase DtpB.

Controlling the reactivity of high-valent Fe(IV)-O catalytic intermediates, Compounds I and II, generated in heme enzymes upon reaction with dioxygen or hydrogen peroxide, is important for function. It has been hypothesized that the presence (wet) or absence (dry) of distal heme pocket water molecules can influence whether Compound I undergoes sequential one-electron additions or a concerted two-electron reduction. To test this hypothesis, we investigate the role of water in the heme distal pocket of a dye-decolorizing peroxidase utilizing a combination of serial femtosecond crystallography and rapid kinetic studies. In a dry distal heme site, Compound I reduction proceeds through a mechanism in which Compound II concentration is low. This reaction shows a strong deuterium isotope effect, indicating that reduction is coupled to proton uptake. The resulting protonated Compound II (Fe(IV)-OH) rapidly reduces to the ferric state, giving the appearance of a two-electron transfer process. In a wet site, reduction of Compound I is faster, has no deuterium effect, and yields highly populated Compound II, which is subsequently reduced to the ferric form. This work provides a definitive experimental test of the hypothesis advanced in the literature that relates sequential or concerted electron transfer to Compound I in wet or dry distal heme sites.

The antioxidative potential of procyanidin B1: DFT (density functional theory) and docking approaches.

Procyanidin B1 is one of the natural dimeric flavonoids. It has established a great role in antioxidative activity. In the current study, we wish to provide crucial information on its antioxidative action by the DFT computational and docking approaches. From point of thermodynamic view, at the M062X/6-311G(d,p) level, the HAT (hydrogen atom transfer) and SPL-ET (sequential proton loss-electron transfer) are principal antioxidative routes of this compound in gas and methanol, respectively. OH groups of two phenyl rings of this molecule are likely to be the best antiradical sites. In the kinetics of the interactions with HOO• radicals, OH groups of phenyl rings have also generated the best ΔG# (Gibbs free energy of activation) and rate constant K. The antioxidative action of procyanidin B1 is further confirmed by its chelation to metal ions, in which complex formation with Cu2+ having lower binding energy is more stable than complex formation with Zn2+. Docking study revealed that the antioxidative activity of procyanidin B1 involved human tyrosinase enzyme inhibition through interaction with essential residues, focusing on the OH groups of two phenyl rings.