Two-step Transfer Research Articles

Multichannel experimental and theoretical constraints for the Cd116(Ne20,F20)In116 charge exchange reaction at 306 MeV

Charge exchange (CE) reactions offer a major opportunity to excite nuclear isovector modes, providing clues about the nuclear interaction in the medium. Moreover, double charge exchange (DCE) reactions are proving to be a tempting tool to access nuclear transition matrix elements (NME) related to double beta-decay processes. Through a multi-channel experimental analysis and a consistent theoretical approach of the $^{116}$Cd($^{20}$Ne,$^{20}$F)$^{116}$In single charge exchange (SCE) reaction at 306 MeV, we aim at disentangling from the experimental cross section the contribution of the competing mechanisms, associated with second or higher order sequential transfer and inelastic processes. We measured excitation energy spectra and absolute cross sections for elastic + inelastic, one-proton transfer and SCE channels, using the MAGNEX large acceptance magnetic spectrometer to detect the ejectiles. For the first two channels, we also extracted the experimental cross section angular distributions. The experimental data are compared with theoretical predictions obtained by performing two-step distorted wave Born approximation and coupled reaction channel calculations. We employ spectroscopic amplitudes for single-particle transitions derived within a large-scale shell model approach and different optical potentials for modeling the initial and the final state interactions. The present study significantly mitigates the possible model dependence existing in the description of these complex reaction mechanisms, thanks to the reproduction of several channels at once. In particular, our work demonstrates that the two-step transfer mechanisms produce a non negligible contribution to the total cross section of the $^{116}$Cd($^{20}$Ne,$^{20}$F)$^{116}$In reaction channel, although a relevant fraction is still missing, being ascribable to the direct SCE mechanism, which is not addressed here.

Superior peroxidase mimetic activity induced by topological surface states of Weyl semimetal WTe2

Nanozymes, as promising alternatives that integrate the advantage of natural enzymes and nanomaterials are attracted enormous interest due to their low cost, environmental tolerance, high stability, as well as significant catalytic activity. Two-dimensional materials, transition metal dichalcogenides (TMDs) harbor the potential as peroxidase mimic which is attributed to the active edge sites and surface electron transfer capability. However, a challenge faced in peroxidase mimetic of TMDs is the low catalytic activity which originates from the inert structures. Here, we, for the first time, report that the typical Weyl semimetal WTe2 possesses the superior peroxidase-like performance toward H2O2, which derives from the two-step electron-pathway. We demonstrate a novel functionality of the Weyl semimetal through introducing topologically protected surface states (TSSs) for regulating the electron transfer processes. The underlying mechanism for TSSs promoting enzyme mimetic catalysis is attributed to the effective electron bath provided by the robust TSSs. Experiments and the first-principles calculations show that TSSs of WTe2 which serve as effective electron baths are directly involved in the two-step electron transfer process. In the first step, TSSs accept the electrons donated by the substrate which further enhances the substrate’s absorption. Upon H2O2 adsorption, the electrons are transferred out of TSSs and injected into the absorbed H2O2 orbitals. These findings offer a new linkage between the topological matters with TSSs and nanomaterials for enzyme mimicking.

Self-healable and reprocessable networks involving diblock copolymer and hindered urea bonds

In this contribution, we reported a novel design of the self-healable (and/or reprocessable) networks involving diblock copolymers and hindered urea bonds (HUBs). The diblock copolymers were crosslinked with a crosslinker bearing hindered urea bonds (HUBs). Toward this end, a novel crosslinker (denoted HUDA) was synthesized via the reaction of 2-isocyanatoethylacrylate with N,N′-di-tert-butylethylenediamine, a hindered diamine. The diblock copolymers were composed of polystyrene (PS) and poly(n-butyl acrylate-stat-HUDA) [denoted P(BA-stat-HUDA)] blocks, which were synthesized via a two-step sequential reversible addition-fragmentation chain transfer (RAFT) polymerization approach. In the P(BA-stat-HUDA) blocks, HUDA acted as not only one of the copolymerization monomers but also the crosslinker bearing HUBs. In the networks, the PS microdomains behaved as the nanoreinforcement of P(BA-stat-HUDA) matrix. It was found that the PS-b-P(BA-stat-HUDA) networks displayed the self-healing properties or/and reprocessing properties. The self-healing properties were quite dependent on the concentration of hindered urea bonds. The self-healing behavior is attributable to the intense metathesis of HUBs in the crosslinked networks.

Enhanced visible to near-infrared photodetectors made from MoS2-based mixed-dimensional structures

Two-dimensional (2D) photodetectors based on semiconducting transitional metal chalcogenides (TMDs) have attracted much attention because of its unique mechanical and opto-electronic properties which can be integrated into nanoscale-sized opto-electronic devices and complex circuits. However, the photodetection range of 2D TMDs materials based detectors are generally limited within the visible range due to its intrinsic relatively large band-gap. In addition, 2D TMDs materials also suffers from weak light absorption inherited from their atomically thin layers, resulting in a photoresponsivity that can be further improved. Herein, by combining 2D MoS2 with zero-dimensional (0D) PbSe quantum dots (QDs) and Au nanocrystals (NCs), a novel 2D-0D photodetector (i.e., MoS2/PbSe@Au) is fabricated. Our MoS2/PbSe@Au photodetector exploits the 2D MoS2 as the conduction channels and PbSe@Au NCs as light sensitizer, which promote the absorption of the entire device and enable appreciable photodetection extending to the near-infrared (NIR). Prominently, the mixed-dimensional photodetector exhibits high responsivity of 1.22 A/W and detectivity of 1.56*109 Jones (cm·Hz1/2·W−1) at NIR (e.g., 1064 nm) compared with the MoS2 photodetector with PbSe QDs only, which are ascribed to the more efficient two-step charge transfer process between PbSe and MoS2 with the presence of Au NCs. We further identify the new carrier multiplication mechanism when comparing the photoresponse of our photodetectors at 405 nm and 635 nm. We found the extremely high EQE of MoS2/PbSe@Au photodetector at the wavelength of 405 nm (268.1%) could be ascribed to the synergism of carrier multiplication (CM) in PbSe QDs and the photo-gating effect induced by Au nanoparticles. Our study demonstrates that the novel mixed-dimensional photodetectors based on CVD-grown MoS2 may provide a new route for designing and realizing high-performance optoelectronic devices with harvesting merits of hybrid nanomaterials.

Multi-Aircraft Formation Recognition Method of Over-the-Horizon Radar Based on Deep Transfer Learning

Over-the-horizon radar (OTHR) is an important equipment for the ultralong-range early warning in the military, but the use of constant false-alarm rate (CFAR), which is a traditional detection method, makes it difficult in multi-aircraft formation recognition. To solve this problem, a multi-aircraft formation recognition method based on deep transfer learning in OTHR is proposed. First, the range-Doppler images of aircraft formation in OTHR are simulated, which are composed of four categories of samples. Secondly, a recognition model based on Convolutional Neural Network (CNN) and CFAR detection technology is constructed, whose training method is designed as a two-step transfer. Finally, the trained model can well distinguish the spectral characteristics of aircraft formation, and then recognize the aircraft number of a formation. Experiments show that the proposed method is better than the traditional CFAR detection method, and can detect the number of aircraft more accurately in the formation with the same false alarm rate.

An artificial light-harvesting system with sequential energy transfer for information dual encryption and anticounterfeiting

The artificial light-harvesting system (MPy1–ESY–SR101) with two-step sequential energy transfer constructed in this work serves as a privileged platform for multilevel data encryption and anticounterfeiting.

Effect of the Time Delay between Spin State Preparation and Measurement on Electron Spin Teleportation in a Covalent Donor-Acceptor-Radical System.

We recently demonstrated photodriven quantum teleportation of an electron spin state in a covalent donor-acceptor-radical (D-A-R•) system. Following specific spin state preparation on R• with a microwave pulse, photoexcitation of A results in two-step electron transfer producing D•+-A-R-, where the spin state on R• is teleported to D•+. This study examines the effects of varying the time (τD) between spin state preparation and photoinitiated teleportation. Using pulse electron paramagnetic resonance spectroscopy, the spin echo of D•+ resulting from teleportation shows a damped oscillation as a function of τD that is simulated using a density matrix model, which provides a fundamental understanding of the echo behavior. Teleportation fidelity calculations also show oscillatory behavior as a function of τD due to the accumulation of a phase factor between ⟨Sx⟩ and ⟨Sy⟩. Understanding experimental parameters intrinsic to quantum teleportation in molecular systems is crucial to leveraging this phenomenon for quantum information applications.

A bimodal BI-RADS-guided GoogLeNet-based CAD system for solid breast masses discrimination using transfer learning

Numerous solid breast masses require sophisticated analysis to establish a differential diagnosis. Consequently, complementary modalities such as ultrasound imaging are frequently required to evaluate mammographically further detected masses. Radiologists mentally integrate complementary information from images acquired of the same patient to make a more conclusive and effective diagnosis. However, it has always been a challenging task. This paper details a novel bimodal GoogLeNet-based CAD system that addresses the challenges associated with combining information from mammographic and sonographic images for solid breast mass classification. Each modality is initially trained using two distinct monomodal models in the proposed framework. Then, using the high-level feature maps extracted from both modalities, a bimodal model is trained. In order to fully exploit the BI-RADS descriptors, different image content representations of each mass are obtained and used as input images. In addition, using an ImageNet pre-trained GoogLeNet model, two publicly available databases, and our collected dataset, a two-step transfer learning strategy has been proposed. Our bimodal model achieves the best recognition results in terms of sensitivity, specificity, F1-score, Matthews Correlation Coefficient, area under the receiver operating characteristic curve, and accuracy metrics of 90.91%, 89.87%, 90.32%, 80.78%, 95.82%, and 90.38%, respectively. The promising results indicate that the proposed CAD system can facilitate bimodal suspicious mass analysis and thus contribute significantly to improving breast cancer diagnostic performance.

Porous Functional Graded Bioceramics with Integrated Interface Textures

Porous functional graded ceramics (porous FGCs) offer immense potential to overcome the low mechanical strengths of homogeneously porous bioceramics used as bone grafts. The tailored manipulation of the graded pore structure including the interfaces in these materials is of particular interest to locally control the microstructural and mechanical properties, as well as the biological response of the potential implant. In this work, porous FGCs with integrated interface textures were fabricated by a novel two-step transfer micro-molding technique using alumina and hydroxyapatite feedstocks with varied amounts of spherical pore formers (0–40 Vol%) to generate well-defined porosities. Defect-free interfaces could be realized for various porosity pairings, leading to porous FGCs with continuous and discontinuous transition of porosity. The microstructure of three different periodic interface patterns (planar, 2D-linear waves and 3D-Gaussian hills) was investigated by SEM and µCT and showed a shape accurate replication of the CAD-designed model in the ceramic sample. The Young’s modulus and flexural strength of bi-layered bending bars with 0 and 30 Vol% of pore formers were determined and compared to homogeneous porous alumina and hydroxyapaite containing 0–40 Vol% of pore formers. A significant reduction of the Young’s modulus was observed for the porous FGCs, attributed to damping effects at the interface. Flexural 4-point-testing revealed that the failure did not occur at the interface, but rather in the porous 30 Vol% layer, proving that the interface does not represent a source of weakness in the microstructure.

A Selective-Response Bioinspired Strain Sensor Using Viscoelastic Material as Middle Layer.

Flexible strain sensors have an irreplaceable role in critical and emerging fields, such as electronic skins, flexible robots, and prosthetics. Although numerous efforts have been made to improve sensor sensitivity to meet specific application scenarios, the signal-to-noise ratio (SNR) is an extremely critical and non-negligible indicator, which takes into account higher sensitivity, meaning that they can also detect the noise signals with high sensitivity. Coincidentally, scorpions with ultrasensitive vibration sensilla also face such a dilemma. Here, it is found that the scorpion ingeniously uses the viscoelastic material in front of its slit sensilla to realize efficient preprocessing of the signal. Its mechanism is that the loss factor of materials changes with frequency, affecting energy storage and transmission. Inspired by this ingenious strategy, a bioinspired strain sensor insensitive to a low strain rate was designed using a two-step template transfer method. As a result, its relative change in resistance reached 110% under the same strain (0.3197%) but with different strain rates (0.1 Hz and ∼20 Hz). The noncontact vibration experiments also show different responses to low-frequency vibration and high-frequency impact. Moreover, it can also be used as a typical flexible strain sensor. Under the tensile state, it has a gauge factor (GF) as high as 4596 upon 0.6% strain, and the response time is 140 ms. Therefore, it is expected that this strain sensor will be used in many important ultraprecision measurement fields, especially when the measured signal is small.

Polystyrene microsphere assisted synthesis of a Co/PEG comodified PbO2 anode and its electrocatalytic oxidation performance

• The Co-PEG-PbO 2 electrode was prepared by PS-assisted electrodeposition. • The electrode possess porous structure and high electrocatalytic performance. • The degradation of p-chlorophenol follows the CE mechanism. Highly performed electrode is one of the key factors affecting the efficiency of oxidation toward organic pollutants. To improve the electrocatalytic performance and stability of PbO 2 electrode, a Co-PEG-PbO 2 electrode modified by Co 2+ ion and polyethylene glycol (PEG 6000) was prepared by polystyrene microspheres assisted electrodeposition combined with surface structure adjustment and active substance doping, and used for the effective degradation of p-chlorophenol in water. The results showed that the Co-PEG-PbO 2 electrode surface was composed of small spherical particles β-PbO 2 , containing a small amount of Co 2 O 3 and PEG, and its grain size (8.985 nm) was the smallest in the same series of electrodes. The electrochemical tests results showed that the oxygen evolution reaction in Na 2 SO 4 solution was a sequential two-step charge transfer process, which was controlled by charge transfer and diffusion. The electrode had smaller oxygen evolution potential (1.40 V), larger exchange current density (j 0 = 1.164 × 10 −4 mA · cm −2 ), smaller charge transfer resistance (0.8778 Ω · cm 2 ) and larger concentration polarization resistance (1.335 Ω · cm 2 ), indicating that the Co-PEG-PbO 2 electrode had better electrocatalytic performance. The degradation of p-chlorophenol was controlled by diffusion and was oxidized by strong oxidizing · OH, which conforms to CE mechanism. Within the same degradation time, the electrode had a higher p-chlorophenol removal efficiency η (97.34%), higher TOC removal efficiency (64.25%), higher mineralization current efficiency (23.45%), and lower cell voltage. The accelerated life test showed that Co-PEG-PbO 2 electrode had the longest service life (280 min), which was 2.8, 1.8 and 2 times of PbO 2 electrode, Co-PbO 2 electrode and PEG-PbO 2 electrode, respectively. The electrocatalytic activity and stability of PbO 2 electrode can be effectively improved by structural adjustment and co-doping with Co 2+ and PEG, which can be used for the effective degradation of p-chlorophenol.

Predicting Breast Cancer Gene Expression Signature by Applying Deep Convolutional Neural Networks From Unannotated Pathological Images.

We proposed a highly versatile two-step transfer learning pipeline for predicting the gene signature defining the intrinsic breast cancer subtypes using unannotated pathological images. Deciphering breast cancer molecular subtypes by deep learning approaches could provide a convenient and efficient method for the diagnosis of breast cancer patients. It could reduce costs associated with transcriptional profiling and subtyping discrepancy between IHC assays and mRNA expression. Four pretrained models such as VGG16, ResNet50, ResNet101, and Xception were trained with our in-house pathological images from breast cancer patient with recurrent status in the first transfer learning step and TCGA-BRCA dataset for the second transfer learning step. Furthermore, we also trained ResNet101 model with weight from ImageNet for comparison to the aforementioned models. The two-step deep learning models showed promising classification results of the four breast cancer intrinsic subtypes with accuracy ranging from 0.68 (ResNet50) to 0.78 (ResNet101) in both validation and testing sets. Additionally, the overall accuracy of slide-wise prediction showed even higher average accuracy of 0.913 with ResNet101 model. The micro- and macro-average area under the curve (AUC) for these models ranged from 0.88 (ResNet50) to 0.94 (ResNet101), whereas ResNet101_imgnet weighted with ImageNet archived an AUC of 0.92. We also show the deep learning model prediction performance is significantly improved relatively to the common Genefu tool for breast cancer classification. Our study demonstrated the capability of deep learning models to classify breast cancer intrinsic subtypes without the region of interest annotation, which will facilitate the clinical applicability of the proposed models.

Photoinduced Irreversible Intramolecular Proton Transfer of Arnebinones B, D, and E: The Case of Photoenolization at the p-Benzoquinone-CH2/CH-π System.

Arnebinones B, E, and D (1-3) have been found to be sensitive to light, generating complex and diverse proton transfer products when triggered by light. A unique two-step irreversible intramolecular proton transfer of 1 produced five scalemic mixtures, of which four possessed intriguing dual planar chirality. The unprecedented orientation epimerization equilibrium of the intra-annular double bond was first observed and researched in the homologous meroterpenoids by HPLC monitoring and DFT calculations. A "p-benzoquinone-CH2/CH-π" moiety in the structure was the common key feature for the occurrence of this type of photoenolization reaction. The product transformation processes and universality of this photoinduced irreversible proton transfer reaction were analyzed together with the cytotoxic activities of arnebinones B, D, and E, and their photoreaction products.

New Mobilization Pathway of Antimonite: Thiolation and Oxidation by Dissimilatory Metal-Reducing Bacteria via Elemental Sulfur Respiration.

Antimony (Sb) mobilization is widely explored with dissimilatory metal-reducing bacteria (DMRB) via microbial iron(III)-reduction. Here, our study found a previously unknown pathway whereby DMRB release adsorbed antimonite (SbIII-O) from goethite via elemental sulfur (S0) respiratory reduction under mild alkaline conditions. We incubated SbIII-O-loaded goethite with Shewanella oneidensis MR-1 in the presence of S0 at pH 8.5. The incubation results showed that MR-1 reduced S0 instead of goethite, and biogenic sulfide induced the formation of thioantimonite (SbIII-S). SbIII-S was then oxidized by S0 to mobile thioantimonate (SbV-S), resulting in over fourfold greater Sb release to water compared with the abiotic control. SbIV-S was identified as the intermediate during the oxidation process by Fourier transform ion cyclotron resonance mass spectrometry and electron spin resonance analysis. The existence of SbIV-S reveals that the oxidation of SbIII-S to SbV-S follows a two-step consecutive one-electron transfer from Sb to S atoms. SbV-S then links with SbIII-S by sharing S atoms and inhibits SbIII-S polymerization and SbIII2S3 precipitation like a "capping agent". This study clarifies the thiolation and oxidation pathway of SbIII-O to SbV-S by S0 respiration and expands the role of DMRB in the fate of Sb.

Gaseous Elemental Mercury [Hg(0)] Oxidation in Poplar Leaves through a Two-Step Single-Electron Transfer Process

Gaseous Elemental Mercury [Hg(0)] Oxidation in Poplar Leaves through a Two-Step Single-Electron Transfer Process

Isomeric sp2-C-conjugated porous organic polymer-mediated photo- and sono-catalytic detoxification of sulfur mustard simulant under ambient conditions

Isomeric sp2-C-conjugated porous organic polymer-mediated photo- and sono-catalytic detoxification of sulfur mustard simulant under ambient conditions

Two-step sequential energy transfer of molecular assemblies based on host-guest interactions for the construction of photochemically catalyzed artificial light-harvesting systems

In the present work, a highly efficient artificial light-harvesting system with a two-step sequential energy transfer process based on host-guest interactions between cyano-substituted p-phenylenevinylene derivative (PPTA) and cucurbit [7]uril (CB [7]) has been constructed in an aqueous media, in which the molecular assemblies was employed as energy donors, two dyes including eosin Y (EY) and sulforhodamine (SR101) were used as energy acceptors. The obtained PPTA-CB [7] supramolecular assemblies have aggregation-induced emission (AIE) effect and can be used as an ideal donor to transfer energy to EY. Then, inspired by the multi-step energy transfer in nature, the PPTA-CB [7]+EY system was chosen as the energy donor while SR101 was selected as the energy acceptor to construct an efficient light-harvesting system with a two-step sequential energy transfer, which demonstrated high FRET efficiencies of 38% and 33% in the two-step process, respectively. The light-harvesting systems also exhibit high antenna efficiencies of 23.7 and 20.1 with a 100:1 donor/acceptor ratio, respectively. More importantly, the PPTA-CB [7]+EY + SR101 system exhibited high activity for the photocatalytic dehalogenation of 2-bromo-1-phenylethanone with a yield of up to 86% in an aqueous solution.

Theoretical Investigation of Excited-State Intramolecular Double-Proton Transfer Mechanism of Substituent Modified 1, 3-Bis (2-Pyridylimino)-4,7-Dihydroxyisoindole in Dichloromethane Solution

In this paper, density functional theory (DFT) and time-dependent DFT (TDDFT) methods were used to investigate substituent effects and excited-state intramolecular double-proton transfer (ESIDPT) in 1, 3-bis (2-pyridylimino)-4, 7-dihydroxyisoindole (BPI–OH) and its derivatives. The results of a systematic study of the substituent effects of electron-withdrawing groups (F, Cl and Br) on the adjacent sites of the benzene ring were used to regulate the photophysical properties of the molecules and the dynamics of the proton-transfer process. Geometric structure comparisons and infrared (IR) spectroscopic analysis confirmed that strengthening of the intramolecular hydrogen bond in the first excited state (S1) facilitated proton transfer. Functional analysis of the reduced density gradient confirmed these conclusions. Double-proton transfer in BPI–OH is considered to occur in two steps, i.e., BPI–OH (N) [Formula: see text] BPI–OH (T1) [Formula: see text] BPI–OH (T2), in the ground state (S0) and the S1 state. The potential-energy curves (PECs) for two-step proton transfer were scanned for both the S0 and S1 states to clarify the mechanisms and pathways of proton transfer. The stepwise path in which two protons are consecutively transferred has a low energy barrier and is more rational and favorable. This study shows that the presence or absence of coordinating groups, and the type of coordinating group, affect the hydrogen-bond strength. A coordinating group enhances hydrogen-bond formation, i.e., it promotes excited-state intramolecular proton transfer (ESIPT).

Preparation and photoluminescence of functionalized cotton fabric by double luminescent guests-encapsulated ZnBDC metal-organic framework

A series of functionalized cotton fabrics (LG-ZnBDC-CCtn) were prepared by attachment of ZnBDC metal-organic framework with LbL deposition method on carboxylated cotton fabric (CCtn) and further encapsulation of ZnBDC with different luminescent guests (LG = Tb3+, La3+, Rhodanmine B or/and acridine orange). The characterization of LG-ZnBDC-CCtn by XRD, SEM and EDS showed that the structural integrity and morphology of ZnBDC on the CCtn surface were not destroyed after encapsulation. The photoluminescence behavior of sample LG-ZnBDC-CCtn was investigated by fluorescence excitation and emission spectra. After encapsulated with different luminescent guests, samples LG-ZnBDC-CCtn emitted different fluorescence. Although sample Tb/RhB-ZnBDC-CCtn with double LGs (Tb3+ and RhB) showed almost same visible color with RhB-ZnBDC-CCtn under sunlight, the orange yellow fluorescence of sample Tb/RhB-ZnBDC-CCtn was quite different with that of the single LG encapsulated sample Tb-ZnBDC-CCtn (green) or RhB-ZnBDC-CCtn (rose). A similar phenomenon was also observed in La/AO-ZnBDC-CCtn system. The fluorescence change of sample Tb/RhB-ZnBDC-CCtn could be due to a two-step fluorescence resonance energy transfer (FRET) among ZnBDC framework and luminescent guests. The visible color-change properties and technical performance of sample LG-ZnBDC-CCtn were evaluated with LAB color space and color strength.

Mimicking the Energy Funnel of the Photosynthetic Unit Using a Dendrimer-Dye Supramolecular Assembly.

Photosynthesis involves light-harvesting complexes where an array of antenna pigment channels the absorbed solar energy to the reaction centre of a photosystem. This work reports a supramolecular dendrimer-dye assembly that mimics the natural light-harvesting mechanism. A dendrimeric molecule based on two-fluorophores has been constructed with three coumarin units at the end of three long arms and a 7-diethylaminocoumarin unit at the interior. The molecule self-aggregates in water into spherical micelles, which can encapsulate a rose-bengal dye (RB). On excitation, peripheral coumarin units shuttled the energy to the loaded RB dye reaction center via a two-step cascade resonance energy transfer (RET). The energy absorbed in the periphery is funnelled efficiently, resulting in a strong emission from the dye that resembles an energy funnel. The energy transfer cascade has been studied with both steady-state and time-resolved fluorescence spectroscopy. Molecular dynamics simulations of the self-assembled aggregates in water were also in agreement with the experimental observations.