Search

Due to the contradiction between limited bandwidth and huge transmission parameters, federated Learning (FL) has been an ongoing challenge to reduce the model parameters that need to be transmitted to server in clients for fast transmission. Existing works that attempt to reduce the amount of transmitted parameters have limitations: 1) the reduced number of parameters is not significant; 2) the performance of the global model is limited. In this paper, we propose a novel method called Fed-KGF that significantly reduces the amount of model parameters while improving the global model performance. Our goal is to reduce those transmitted parameters by reducing the number of convolution kernels. Specifically, we construct an incomplete model with a few representative convolution kernels, and propose Kernel Generation Function (KGF) to generate other convolution kernels to render the incomplete model to be a complete one. We discard those generated kernels after training local models, and solely transmit those representative kernels during training, thereby significantly reducing the transmitted parameters. Furthermore, there is a client-drift in the traditional FL because of the averaging method, which hurts the global model performance. We innovatively select one or few modules from all client models in a permutation way, and only aggregate the uploaded modules rather than averaging all modules to reduce client-drift, thus improving the global model performance and further reducing the transmitted parameters. Experimental results on both non-Independent and Identically Distributed (non-IID) and IID scenarios for image classification and object detection tasks demonstrate that our Fed-KGF outperforms SOTA FL models.

Rational control of the supramolecular aggregation of π-conjugated molecules plays an important role in determining their optoelectronic properties and applications. Here, we report a systematic study of the factors, including solvent polarity, concentration, and surfactants, that affect the aggregation behavior of a brominated hydroazaheptacene tetraimide (HATI) and its thiophene-substituted derivative, Th-HATI, as near-infrared fluorophores, in both nonpolar and polar solvents. The thermal stability of the aggregates is also studied by monitoring their optical absorption against temperature change. Our results indicate that the aggregation of HATI is highly sensitive to the solvent polarity. Moreover, the average aggregation number of HATI inside the colloidal nanoparticles formed in aqueous media can be controlled by surfactants. The substitution of the bromo groups in HATI by thiophene units induces a slight blue shift of the optical absorption, enhanced crystallinity, distinct aggregation behavior in both nonpolar and polar solvents, and improved thermal stability. The multifacet understanding of the supramolecular aggregation of these systems may offer insight for other π-conjugated molecular chromophores with various optoelectronic properties and applications.

Designing an efficient nanocarrier to target multiple types of cancer remains a major challenge in the development of cancer nanomedicines. The majority of systemically administered nanoparticles (NPs) are rapidly cleared by the liver, resulting in poor tumor-targeting efficiency and severe side effects. Here, we present a delicately tailored design and synthesis of fluorescent bottle-brush polymers and screen nine derived NPs, each varying in size and surface coatings, for tumor imaging and targeted delivery. Our optimized polymer bearing (oligo(ethylene glycol) methyl ether methacrylate) in the side chains shows reduced macrophage uptake, prolonged blood-circulation time (up to 27 h), and exceptionally high accumulation in the tumor compared to the liver, elucidating an immune-evasion-induced tumor-targeting mechanism. High tumor accumulation significantly improved the antitumor efficacy. The outstanding tumor-targeting ability has been further validated across five distinct tumor models, including orthotopic glioblastoma and pancreatic cancer, which demonstrate the universality of our polymeric nanocarrier for tumor-targeting delivery.

Titanium (Ti) alloys have been widely applied clinically due to their good biocompatibility, corrosion resistance and mechanical stability. However, how to improve the weak osteointegration caused by their intrinsic bio-inertness has been a long-standing puzzle. Osteogenic-related cells, endothelial cells (ECs) and macrophages are the main cells involved in osteointegration. In recent years, surface topography based on Ti alloys, which mimics the topographical cues of the extracellular matrix (ECM), has been confirmed to precisely regulate these cells' fate to improve osteointegration. More importantly, while serving as a physicomechanical stimuli, topographic surface modification is considered more biosafe and stable than biochemical cues. Nevertheless, how different topographic modifications affect cell behavior and the specific mechanisms involved remain elusive. In this review, we highlight the regulation of surface topography based on Ti alloys on the behaviors of bone repair-related cells, such as osteogenic-related cells, ECs and macrophages, and summarize the activated intracellular mechanotransduction pathways, which aims to provide basis and support for further research on osteointegration of Ti alloys.

In this study, the combustion experiments were carried out in a simultaneous thermogravimetric analyzer and in an oxidizing atmosphere at four heating rates of 5, 10, 15, and 20 °C/min, respectively. The thermal decomposition kinetics of pyrolysis char of torrefied treatment (T-P-char) from camellia shell were invested by the isoconversional methods of Friedman and Ozawa. The results showed that the correlation coefficients of the experiment data fitting were all over 0.99, and both the average values of activation energy and pre-exponential from Ozawa were higher than those of Friedman method. The enthalpy analysis indicated that the energy difference between the activated complex and the reagent was consistent with activation energy. The Gibbs free energy changed from 185.08 kJ/mol to 204.87 kJ/mol, and the entropy changes were negative, implying that the disorder degree of the products was lower than that of the initial reactants. Moreover, the reaction mechanism transformed from the random nucleation and growth reaction to the nth order reaction when the pyrolysis temperature exceeded 450 °C.

In this study, the nitrogen-releasing characteristics and mechanism of the biochar-based urea infiltration fertilizer (BUF) were investigated. The crushing resistance of BUF increased with the increased proportion of urea-biochar, which at maximum reached 502.93 ± 6.47 N. BUF had the excellent slow-release performance. Urea was completely released after third leaching, while the urea in BUF1-2was not completely released after tenth leaching. The release process of BUF1-2is divided into three stages, which corresponded to the release of P-urea (dispersed on the biochar surface without physic force and chemical bonds), F-urea (connected with biochar through intermolecular forces, hydrogen bonds, etc.), and C-urea (connected with biochar through chemical bonds) in BUF1-2. The release rate of P-urea, F-urea, and C-urea decreased gradually. Moreover, the physicochemical performances of biochar and Re biochar were similar, although their apparent morphologies were different. The pores of biochar filled with urea collapsed in the nitrogen-release process, reducing the number of pores on Re-biochar surface. As a new type of biochar-based fertilizer, its effects on soil improvement, crop yield increase, and fertilization methods still need to be further studied.

Current robotic laser weeding systems mostly rely on serial mechanisms with one or two actuated axes, which can barely meet the requirements of high precision and dynamic performances. In this article, a novel laser weeding gimbal is proposed based on a two-degree-of-freedom 5-revolute rotational parallel manipulator to perform a dynamic intrarow laser weeding operation. Comprehensive analyses consisting of kinematics, workspace, singularity, and dynamics are carried out to evaluate the performance of the proposed design. Finally, experimental tests were conducted both in lab and field environments and the results are provided, in which the positioning accuracy has been evaluated as in average errors of 0.62 mm in position at the distance of 535 mm, and the dynamic weeding efficiency is around 0.72 s/weed with a dwell time of 0.64 s at the tracking speed of 0.1 m/s. The effectiveness of the proposed dynamic intrarow weeding mechanism has been evaluated in a real field trial.

Current research on walking robots strives to achieve a higher efficiency, a better load capacity, and an increased adaptability. Parallel kinematic manipulators (PKMs) are characterized by high payload and accuracy, but conventional PKMs with fixed configurations are limited to constrained workspaces in known structured environments. In this article, we propose a parallel reconfigurable walking machine tool that overcomes these limits by adapting its configuration and gaits to different scenarios. A lightweight and compact positioning system with shape memory alloy actuation is presented to achieve reconfiguration capabilities. Furthermore, kinematic, stability, and force analyses are reported to determine the optimal walking gaits in three different scenarios (with inclined slopes at different angles) and four robot configurations. Finally, a set of experiments with the physical prototype validates the proposed models. The results show that symmetric configurations present a better performance at lower ground inclinations (0.5% error), whereas asymmetric configurations can climb on slope conditions that would prevent the use of conventional PKMs (18% or 10°).

AbstractAs an emerging global city, Shanghai has experienced significant growth in its creative economy over the past two decades. By reconstructing a large number of old constructions into creative industry clusters, Shanghai has attracted a significant number of creative talents from across the globe. Informed by the theoretical discourse on the social network- based understanding of the production of creative spaces, this paper engages in a semi-structured interview analysis to shed light on the formation mechanism of place-anchored networks in Shanghai’s design industries. Creative spaces for the design industry in Shanghai are largely concentrated in inner-city areas and consist of six functional types: design enterprises or studios, arts and creative parks, educational institutions, exhibition centres, social networking spaces, and cultural and business areas. These multi-layered creative spaces are formed through intensive social interactions, knowledge spillovers, and functional complementation among creative designers and institutions. Finally, the implications of place-anchored networks for creative industries are discussed within the context of the planning and design of creative cities.

We report a mussel-inspired strategy of polydopamine (PDA) coating to stabilize and functionalize J-aggregate nanotubes (NTs) formed by supramolecular self-assembly of an amphiphilic cyanine dye called C8S3 in aqueous media. Optimization of the coating condition by changing the incubation time in a slightly basic media of dopamine with different concentrations leads to conformal wrapping of the PDA layer with controllable thickness on the surface of the NTs. Compared to noncoated pristine C8S3 NTs, these PDA-coated NTs show enhanced stability against dilution, heating, and photobleaching. Moreover, the PDA layer wrapping around the NTs serves as an adhesive for the adsorption of a variety of metal ions and electroless deposition of the metal nanoparticles. Such stabilized and functionalized NT composites may offer a robust synthetic J-aggregate system to mimic the structure and function of light-harvesting complexes and reaction centers in photosynthetic systems.

Recently, studies on non-Hermitian topologic physics have attracted considerable attention. The non-Hermitian skin effect (NHSE), as a remarkable phenomenon in the non-Hermitian lattice, has been demonstrated in coupled ring resonators and photonic mesh lattices. However, there is a scarcity of work on the realization of NHSEs in synthetic dimensions, owing to inaccessible anisotropic coupling. This limits the potential for exploring non-Hermitian topologic physics in on-chip integrated optical systems. In this work, we implement a non-Hermitian Su–Schrieffer–Heeger topologic insulator in the synthetic frequency dimension, and the NHSE and topologic edge state are manifested. Furthermore, we demonstrate that the exotic chiral Zener tunneling can also be realized. Our system provides a versatile platform to explore and exploit non-Hermitian topologic physics on a chip and can have impacts on flexible light manipulation in frequency domains.

Identifying the variation of fracture structure and coal permeability with effective stress is important for protecting coalbed methane (CBM) reservoirs and formulating a reasonable drainage system. This study characterizes the coal fracture and permeability variations with effective stress using three-dimensional (3-D) micro-CT and digital core techniques. Dual-resolution scanning is adopted to characterize the variation of three types of fractures with effective stress and to clarify the stress sensitivity of the porosity of each type of fracture. Type-A fractures (>109μm3) are most sensitive to effective stress and tend to close as effective stress increases. Moreover, the porosity of this fracture has a negative exponential relationship with effective stress. Type-B fractures (107–109μm3) are moderately sensitive to effective stress and have the highest contribution of total porosity at high effective stress. Type-C fractures (<107μm3) are least sensitive to effective stress, and the porosity of this fracture changes slightly. The seepage simulation in the two directions with digital core techniques confirms that the permeability of coal samples presents an exponential decrease with effective stress and shows an anisotropic behavior with space. Combined with the quantitative analysis of variation of pore–fracture models, the compression model of coal under effective stress can be established, which can reveal the reason that the permeability loss rate in the y-axis is more than that in the z-axis. The sensitivity of porosity and permeability is stronger under low stress and weaker under high stress. Therefore, digital core technology can quantitatively analyze the stress sensitivity of coal fracture structure and permeability based on 3-D models. This method is more intuitive to study the stress sensitivity of coal compared with traditional methods.

The measurement sensitivity of quantum probes using Nuncorrelated particles is restricted by the standard quantum limit1, which is proportional to 1/N. This limit, however, can be overcome by exploiting quantum entangled states, such as spin-squeezed states2. Here we report the measurement-based generation of a quantum state that exceeds the standard quantum limit for probing the collective spin of 1011rubidium atoms contained in a macroscopic vapour cell. The state is prepared and verified by sequences of stroboscopic quantum non-demolition (QND) measurements. We then apply the theory of past quantum states3,4to obtain spin state information from the outcomes of both earlier and later QND measurements. Rather than establishing a physically squeezed state in the laboratory, the past quantum state represents the combined system information from these prediction and retrodiction measurements. This information is equivalent to a noise reduction of 5.6 decibels and a metrologically relevant squeezing of 4.5 decibels relative to the coherent spin state. The past quantum state yields tighter constraints on the spin component than those obtained by conventional QND measurements. Our measurement uses 1,000 times more atoms than previous squeezing experiments5–10, with a corresponding angular variance of the squeezed collective spin of 4.6 × 10−13radians squared. Although this work is rooted in the foundational theory of quantum measurements, it may find practical use in quantum metrology and quantum parameter estimation, as we demonstrate by applying our protocol to quantum enhanced atomic magnetometry.

The Free-Leg Hexapod (Free-Hex) machine tool is an advancement from the conventional Stewart platform, which has the fixed base platform removed to enable the limbs to be attached to a wider range of surfaces (e.g. non-flat and curved). However, in some scenarios (e.g. in-situ repair of industrial installations), the limbs of the Free-Hex need to be attached to the surfaces with unequal stiffness, which brings the challenge of predicting the dynamics of the system for conducting machining operations under dynamically stable conditions. In this paper, after introducing the attachment stiffness (i.e. feet attached to the environment with different materials) in the conventional dynamic model of the parallel manipulator, the dynamic behavior of the Free-Hex machine tools devoted to the in-situ operation environments was studied. Then, the experimental validation was conducted to prove the dynamic model developed in this paper. It was found that the errors of the proposed model are under 6% (i.e. 5.1% at symmetrical limb configuration and 5.8% at the arbitrary configuration) when the limbs are attached to the surfaces with unequal stiffness. Further, by applying the validated model, the dynamic performance of the Free-Hex with a wider range of attachment stiffness was analyzed. Overall, it was found that the attachment stiffness has a remarkable influence on the natural frequencies of the machine tool (e.g. the frequency of mode 4 at the symmetrical configuration is increased by 36.8% when the attachment stiffness of one limb changes from 0 to 1e+12 N/m). Thus, the work discussed in this paper can be utilized to avoid the dynamically unstable configurations of parallel kinematic machine tools (e.g. Free-Hex) when mounting on the surface with unequal stiffness in the in-situ operation environments.

Digital image of pipeline weld is an important basis for the reliability management of pipeline welds. However, the error rate of artificial discrimination is high. In order to increase the defect identification accuracy of digital image of pipeline weld, we adopted several methods (e.g. multiple edge detection, detection channel and threshold segmentation) to carry out image processing on the image defects of pipeline welds. Then, a defect characteristic database on the digital images of pipeline welds was constructed, including grayscale difference, equivalent area (S/C), circularity, entropy, correlation and other parameters. Furthermore, a multi-classifier construction (SVM) model was established. Thus, the classification and evaluation on the defects in the digital images of pipeline welds were realized. Finally, an automatic defect identification software for digital image of pipeline weld was developed and verified on site. And the following research results were obtained. First, after image processing, the edge detection results obtained by Canny and other algorithms are satisfactory when there is no noise. In the case of noise, however, pseudo-edge emerges in the detection results. In this case, the automatic threshold selection method shall be adopted to detect the image edge to obtain the rational threshold. Second, there are 14 parameters in the defect characteristic database, including shape characteristic, lamination characteristic and image length pixel. Third, by virtue of the SVM classification model, the shape characteristics of each type of defect can be clarified, and the defect characteristics can be identified, such as crack, slag inclusion, air hole, incomplete penetration, non-fusion and strip. Based on field application, the following results were obtained. First, this automatic defect identification technology is applicable to quality identification and evaluation of various defects in pipeline welds. Second, its identification accuracy is higher than 90%. Third, by virtue of this technology, automatic defect identification and evaluation of digital image of pipeline weld is realized. In conclusion, these research results help to ensure the safe operation of pipelines.

We report a solution-processable π-conjugated molecular building block (denoted as PhDPP) consisting of a rigid and planar core of phenyl-flanked diketopyrrolopyrrole and “soft” branched alkoxy chains that endow the solubility in a variety of organic solvents. Intermolecular hydrogen bonding in PhDPP was revealed in nonpolar solvents above a threshold of concentration and below a critical point of temperature. The strong intermolecular interaction mainly contributed by the hydrogen-bonding and π–π interaction between PhDPP molecules promoted the formation of supramolecular polymeric structures in both solution and solid states and at interfaces. The supramolecular polymeric properties enabled solution-based processing of PhDPP under a variety of conditions into different structures including fibers and uniform thin films. The structure–property relationship that we established in the present system of PhDPP from the molecular to supramolecular level will be important to solution-process this type of H-bonding π-conjugated molecules for a variety of applications such as optoelectronic devices.

The newly invented triboelectric nanogenerator (TENG) shows a significant potential to be a powerful technology for converting mechanical energy into electricity as a complementary usage for solving our future energy demanded for micro- and macro- grid. However, packaging and robustness are critical factors for TENG toward practical applications since the performance of TENG is affected by environmental conditions such as humidity. Here, a full-packaged waterwheel-like rolling triboelectric–electromagnetic hybrid nanogenerator (TEHNG) for harvesting mechanical energy in harsh environment has designed. The integrated silicone rubber-magnet rods and electrodes laminated by a layer of nylon film, which worked as the triboelectric material, are used to fabricate a rolling friction free-standing triboelectric layer mode triboelectric nanogenerator (RFS-TENG) and combining with copper coils subtly, electromagnetic generator (EMG) is achieved. The rolling friction causes almost no damage to the triboelectric layers and there is no obvious normalized current decay found after 3-days continuous working at 0.5 Hz. Thus, this novel design makes the TEHNG easier to be packaged, and prevent from water interference revealing a superior robustness. It is also found that the developed TEHNG broadens the working frequency range as TENG can work more effectively for converting the mechanical energy at lower-frequencies less than 5 Hz energy scavenging while EMG can work much better at higher-frequencies above 5 Hz. Moreover, combining with hand shaking and water wheel, the device can be demonstrated to collect the energy of handy and water-flow flexibly. Furthermore, using current output signals of the EMG, a self-powered wireless frequency and revolution sensor systems are also demonstrated. This work presents a new platform of hybrid generator for harvesting mechanical energy in harsh environments with several desirable features such as the broadened frequency bands, better portability and for building up self-powered wireless sensor systems.

Molecular spins, owing to their vast synthetic variety and ease of scalability, have emerged as promising qubits for quantum computation and information processing. However, a major challenge is to disperse the spin moieties into solid matrices in a well-defined and controllable way. Limited success has been achieved in previously developed strategies such as diluting the spin moieties into diamagnetic matrices of crystals, frozen solvents, or metal–organic frameworks. Herein, we present a powerful strategy of tuning the spin–spin coherence and spin–lattice interaction by covalently tethering star-like polymer chains from molecular spins, using metal-coordinated porphyrins as an example. Specifically, we have designed and synthesized a series of four-arms star-like polyesters, each of which contains a copper-porphyrin core serving as a single molecular spin and qubit. We have employed both continuous wave and pulse electron paramagnetic resonance spectroscopy (EPR) to study the impact of chemical composition and chain lengths on the quantum coherence and spin–lattice relaxation of these polymer-attached molecular spins, so-called PAMS, in solid states. The structure–property relationship that we have revealed in the present PAMS polymers will offer insight into molecular design and structural control for constructing ordered arrays of a large number of molecular qubits in the future.

We report multiscale structured fibers and patterned films based on a semiconducting polymer, poly(3-hexylthiophene) (P3HT), as photoconductive biointerfaces to promote neuronal stimulation upon light irradiation. The micro/nanoscale structures of P3HT used for neuronal interfacing and stimulation include nanofibers with an average diameter of 100 nm, microfibers with an average diameter of about 1 μm, and lithographically patterned stripes with width of 3, 25, and 50 μm, respectively. The photoconductive effect of P3HT upon light irradiation provides electrical stimulation for neuronal differentiation and directed growth. Our results demonstrate that neurons on P3HT nanofibers showed a significantly higher total number of branches, while neurons grown on P3HT microfibers had longer and thinner neurites. Such a combination strategy of topographical and photoconductive stimulation can be applied to further enhance neuronal differentiation and directed growth. These photoconductive polymeric micro/nanostructures demonstrated their great potential for neural engineering and development of novel neural regenerative devices.

A base‐promoted and metal‐/oxidant‐free one‐pot three‐component tandem annulation of amidines, aryl/alkyl isothiocyanates, and α‐bromoesters/ketones to 2,4,5‐trisubstituted thiazoles is described. This operationally simple protocol involves a base‐promoted C−N bond cleavage of amidines and features readily available starting materials, excellent functional group tolerance, and high step‐economy. It leads to the preparation of 2,4,5‐trisubstituted thiazoles efficiently and has potential applications in the field of drug screening and modification. 3 in 1: A base‐promoted and metal‐/oxidant‐free one‐pot three‐component tandem annulation of amidines, aryl/alkyl isothiocyanates, and α‐bromoesters/ketones to 2,4,5‐trisubstituted thiazoles is described herein.

Collecting mechanical energy in the surrounding environment to power small electronic devices is an ideal method as a green and clean power source. Based on the working mechanism and the advantages of triboelectric nanogenerator (TENG), a robust rolling friction contact-separation mode TENG (CS-TENG) has been fabricated for harvesting vertical rotation energy by utilizing the integrated cylindrical surface with the conjunction of rolling contact electrification and electrostatic induction. The output current of the CS-TENG can maintain 96% (origin: 1.72 μA, final: 1.66 μA) after two days continuous work a rotation speed of 300 r/min. Furthermore, an electromagnetic and triboelectric hybrid contact-separation mode nanogenerator (HCS-TENG) has been further designed by coupling magnets in the rolling cylinders with copper coils as an electromagnetic generator (EMG) in the acrylic cylinder to implement the multi-functional properties. The gear transmission structure makes the device more facile to be installed on the rotation objects. The output performances of CS-TENG and EMG under various rotation speeds were systematically studied. It shows that the CS-TENG with six units can deliver an output power of 0.15 mW/cm2and the 100 μF capacitor can be charged to 6 V in less than 1 min by the hybridized nanogenerator at a rotating rate of 700 r/min. In addition, utilizing the output signal's intrinsic characteristics of CS-TENG, a self-powered rotation speed and displacement sensor using the dual cylinder structure TENG has been achieved for these rotating mobile devices that are inconvenient to get an additional power supply in the grimmest circumstances such as moon car or other celestial and tough environment detection equipment. This multifunctional TENG device reveals a significantly potential application in the grimmest circumstances as power source, self-powered electronics and sensor systems.

Multifunctional stable and stimuli-responsive drug delivery systems are important for efficient cancer treatment due to their advantages such as enhanced cancer-targeting efficiency, improved pharmacokinetics, minimized drug leaching, and reduced undesirable side effects. Here we report a robust and pH-responsive anticancer drug delivery system based on unimolecular micelles of star-like amphiphilic copolymers. The polymers (denoted as CPOFs) were facilely synthesized via one-step atom transfer radical polymerization of functionalizable benzoaldehyde and hydrophilic poly[(oligo ethylene glycol) methyl ether methacrylate] as comonomers from the core of heptakis [2,3,6-tri-o-(2-bromo-2-methyl propionyl]-β-cyclodextrin as the initiator. Doxorubicin (DOX) as an anticancer drug was covalently linked to the benzoaldehyde groups of CPOFsthrough pH-sensitive Schiff-base bonds. The DOX-conjugated polymers, denoted as CPOF–DOX, formed robust unimolecular micelles with an average diameter of 18 nm in aqueous media. More importantly, these unimolecular micelles showed higher drug loading capacity and more controllable drug release characteristics, compared to our previous unimolecular micelles of β-cyclodextrin-poly(lactic acid)-b-poly[(oligo ethylene glycol) methyl ether methacrylates] that physically encapsulated DOX via hydrophobic interaction. Moreover, the CPOF–DOXunimolecular micelles could be internalized by human cervical cancer HeLa cells in a stepwise way and showed less cytotoxicity compared to carrier-free DOX. We foresee that CPOF–DOXwould provide a promising robust and controllable anticancer drug delivery system for future animal study and clinical trials for cancer treatment.

Near-infrared (NIR) light-responsive hydrogels are important for biomedical applications, such as remote-controlled release, but the NIR agents previously used were largely limited to heavy-metal inorganic materials such as gold nanoparticles. In this article, we report a new type of NIR photothermal-responsive hydrogel that can undergo structural changes in response to NIR light for biomedical applications in drug delivery and controlled release. The hydrogels synthesized by integrating a narrow-bandgap semiconductor polymer poly(diketopyrrolopyrrole-alt-3,4-ethylenedioxythiophene) with the polymerization of N-isopropylacrylamide show rapid and reversible mechanical shrinkage upon NIR light irradiation and can serve as carriers for anticancer drug loading and spatial/temporal control of drug release. These stimuli-responsive hydrogels, which can be prepared in different sizes and shapes, integrate photothermal properties and hydrogel characteristics and can provide on-demand, repeated, remote-controlled drug delivery for biomedical applications such as cancer treatment.

Scrap tires were pyrolyzed in a continuously stirred batch reactor in the presence and absence of catalysts. The maximum yield of derived oil was up to 55.65 wt% at the optimum temperature, 500 °C. The catalytic pyrolysis was performed using 1.0 wt% (on a scrap tire weight basis) of catalysts based on ZSM-5, USY, β, SAPO-11, and ZSM-22. The oil products were characterized using simulation distillation, elemental analysis, and gas chromatography-mass spectrometry. The results show that using a catalyst can increase the conversion of scrap tires to gas and decrease char by-products; the yield of derived oil remains unchanged or a little lower. The oils derived from catalytic pyrolysis had H/C ratios of 1.55–1.65 and contained approximately 70–75 wt% light oil, 0.3–0.58 wt% S and 0.78–1.0 wt% N. Catalysts with high acid strengths and appropriate pore sizes, such as ZSM-5, USY, β, and SAPO-11, increased the amount of single-ring aromatics in the light-middle-fraction oil to 45 wt%. The derived oil can therefore be used as a petrochemical feedstock for producing high-value-added chemical products or fuel oil.

π-Conjugated narrow-band-gap polymers (NBPs), characterized by their intrinsically electrical, optical, spintronic, and mechanical properties, have attracted broad interest since the development of the first generation of conducting polymers. The current synthesis of NBPs, nevertheless, largely relies on traditional Suzuki or Stille coupling, which often requires preactivation of aryl C–H bonds involving highly flammable organometallic reagents, such as butyl lithium and highly toxic stannyl agents, which are often involved in Stille coupling. Here, we report the synthesis of a series of NBPs consisting of benzobisthiadiazole (BBT) or thiadiazoloquinoxaline (BBQ) units via a “greener chemistry” of direct arylation polymerization (DArP). Free of toxic organotin compounds or extra borylation, our DArP protocol, in the presence of a Pd2(dba)3catalyst, phosphine ligands, and carboxylic acid additives enables efficient polymerization with monomers of BBT or BBQ with comonomers containing opposite reactive sites. Consequently, a series of donor–acceptor (D–A) or acceptor–acceptor (A–A) alternating copolymers have been synthesized in decent yields and with minimal defects. These polymers with narrow optical band gaps below 1.3 eV can achieve near-infrared (NIR) absorption and fluorescence emission, as well as stable electrochemical performance. Moreover, the scope of open-shell BBT- and BBQ-based polymers has been broadened, including a series of spin density and spin–orbit coupling, as well as tunable electron, hole, or ambipolar charge transport behavior.

The purpose of this study is to investigate the catalytic effects of alkali and alkaline earth metallic species (AAEM) on char conversion during the gasification in steam and the changes in ex-situ char reactivity in oxygen after the gasification in steam using different forms (i.e. H-form, Na-form) of Shengli brown coal. The surface area, AAEM concentration and carbon crystallite of chars were obtained to understand the change in char reactivity. It was found that not only Na concentration and carbon structure were the main factors governing the char reactivity in the atmosphere of steam and oxygen, but also they interacted each other. The presence of Na could facilitate the formation of disordering carbon structure in char, and the amorphous carbon structure would in turn affect the distribution of Na and thus its catalytic performance. The surface area and pore volume had very little relationship with the char’s reactivity. Additionally, the morphology of chars from different forms of coals were observed using scanning electron microscope (SEM).

This article presents a novel glutathione (GSH)-responsive poly(ethylene glycol)-b-polycarbonate-b-poly(ethylene glycol) triblock copolymer that self-assembles into micellar nanoparticles and simutaneously carry hydrophobic anticancer drugs such as doxirubicin. These drug-loading micelles show glutathione-triggered decomposition that leads to controlled drug release and cytotoxicity to cancer cells. This polymeric drug-carrier system integrates features of facile synthesis, stimuli-responsive drug release, good biocompatibility, and relatively low toxicity of the dissociated segments, thus representing a promising anticancer drug carrier for potential clinical applications.

Three-degree of freedom(3-DOF) translational parallel manipulators(TPMs) have been widely studied both in industry and academia in the past decades. However, most architectures of 3-DOF TPMs are created mainly on designers’ intuition, empirical knowledge, or associative reasoning and the topology synthesis researches of 3-DOF TPMs are still limited. In order to find out the atlas of designs for 3-DOF TPMs, a topology search is presented for enumeration of 3-DOF TPMs whose limbs can be modeled as 5-DOF serial chains. The proposed topology search of 3-DOF TPMs is aimed to overcome the sensitivities of the design solution of a 3-DOF TPM for a LARM leg mechanism in a biped robot. The topology search, which is based on the concept of generation and specialization in graph theory, is reported as a step-by-step procedure with desired specifications, principle and rules of generalization, design requirements and constraints, and algorithm of number synthesis. In order to obtain new feasible designs for a chosen example and to limit the search domain under general considerations, one topological generalized kinematic chain is chosen to be specialized. An atlas of new feasible designs is obtained and analyzed for a specific solution as leg mechanisms. The proposed methodology provides a topology search for 3-DOF TPMs for leg mechanisms, but it can be also expanded for other applications and tasks.

The stable presence of fluorophores within the biocompatible and biodegradable elastomer poly(glycerol-co-sebacate) acrylate (PGSA) is critical for monitoring the transplantation, performance, and degradation of the polymers in vivo. However, current methods such as physically entrapping the fluorophores in the polymer matrix or providing a fluorescent coating suffer from rapid leakage of fluorophores. Covalent conjugation of fluorophores with the polymers and the subsequent core-cross-linking are proposed here to address this challenge. Taking rhodamine as the model dye and PGSA nanoparticles (NPs) as the model platform, we successfully showed that the synthesized rhodamine-conjugated PGSA (PGSAR) NPs only released less than 30% rhodamine at day 28, whereas complete release of dye occurred for rhodamine-encapsulated PGSA (PGSA-p-R) NPs at day 7 and 57.49% rhodamine was released out for the un-cross-linked PGSAR NPs at day 28. More excitingly, PGSAR NPs showed a strong quantum yield enhancement (26.24-fold) of the fluorophores, which was due to the hydrophobic environment within PGSAR NPs and the restricted rotation of (6-diethylamino-3H-xanthen-3-ylidene) diethyl group in rhodamine after the conjugation and core-cross-linking. The stable presence of dye in the NPs and enhanced fluorescence allowed a longitudinal tracking of stem cells both in vitroand in vivofor at least 28 days.

Transition-metal-catalyzed aryl-aryl coupling though C-H bonds activation, termed direct arylation, has been widely used in synthesis of a broad range of small molecules. In contrast to traditional coupling methods such as Suzuki coupling and Stille coupling, direct arylation does not involve tedious preparation of unstable, toxic organometallic reagents. Despite these advantages, direct arylation has not been applied to synthesis of π-conjugated polymers until recently. In this perspective, we summarize the progress of direct arylation polymerization for synthesis of various π-conjugated polymers, including homopolymers of polythiophene derivatives and donoracceptor alternating copolymers. We also discuss present challenges and future directions of this nascent methodology of polymerization for synthesis of functional π-conjugated polymers that can find applications in optoelectronic devices such as solar cells and field effect transistors.

This paper addresses the control problem of the 6-DOF motion simulator which is designed for a deep-sea mining ship. In this research, we first analyse the inverse kinematics and the hydraulic driving system of the 6-DOF motion simulator. Based on the conventional PID control, we develop a fuzzy-PID controller for the simulator. Experimental results have shown that the designed fuzzy-PID controller can drive the deep-sea mining ship 6-DOF motion simulator accurately, smoothly, and stably.

Abstract: We propose an effective method to realize the quantum phase gate of one qubit simultaneously controlling N qubits. We use the system in which the transmon qubits are capacitively coupled to a superconducting transmission line resonator driven by a strong microwave field. In our scheme, the phase gate can be realized in a time (nanosecond-scale) much shorter than decoherence time (microsecond-scale), and it is more immune to the 1/f charge noise and has longer dephasing time due to the favorable properties of the transmon qubits in the system.

The effect of molecular self-assembly on nanoscale photoinduced charge generation of fullerene-capped poly(3-hexylthiophene) (PCB-c-P3HT) films and its effectiveness as a molecular additive in bulk heterojunction P3HT:[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) is investigated through photoconductive atomic force microscopy. ortho-Dichlorobenzene-cast films of PCB-c-P3HT are found to form interconnected fibrous networks that show high photocurrent generation, while tetrahydrofuran-cast films show nanospheres with relatively low photocurrent generation. The nanofiber size and current generated from these nanowires are shown to vary with additions of PCBM. The PCB-c-P3HT amphiphile is shown to be a successful molecular additive in P3HT:PCBM films. These observations demonstrate how the self-assembly of PCB-c-P3HT into specific nanostructures is crucial to charge generation and transport.

A new dyad of fullerene/disperse-red, denoted as PCBDR, strongly absorbs visible light in the range of 400–600 nm. PCBDR showed advantages over PCBM in several aspects such as enhanced visible-light absorption, improved solubility, and the possibility to facilitate cascaded electron transfer. P3HT:PCBDR bulk heterojunction (BHJ) solar cells, nevertheless, so far have not outperformed P3HT:PCBM BHJ solar cells under similar conditions. Among factors that affect the efficiency of P3HT:PCBDR BHJ solar cells, the suppression of the interchain interaction of P3HT in the P3HT:PCBDR blend played a major role, presumably due to better interfacial miscibility between P3HT and PCBDR than that in blends of P3HT:PCBM. In contrast, benzoporphyrin (BP), due to its unique crystallinity, morphology, and nonsolubility, afforded a better control of the morphology and the interface of the p/n junctions. As a consequence, the performance of solar cells with BP/PCBDR as the active layer was comparable to that of BP/PCBM solar cells. These results suggest that a synergistic approach of synthetic design and morphological control in devices is critical to develop new electron acceptors for highly efficient organic/polymer solar cells.

This paper describes the co-self-assembly of a polystyrene-poly(4-vinylpyridine)-poly(ethylene oxide) triblock copolymer with CdSe nanocrystals (quantum dots, QDs) and with a styrene compatible phenylenevinylene conjugated polymer (MEH-PPV) in mixtures of chloroform and 2-propanol. The polymer itself (PS577−P4VP302−PEO852, where the subscripts refer to the number average degree of polymerization) forms worm-like micelles when 2-propanol is added to a solution of the polymer in CHCl3. In the presence of increasing amounts of QDs, the structures become shorter and form only spherical hybrid micelles (with QDs bound to the surface) at 4:1 QD/polymer w/w, accompanied by free QDs. These structures retain their colloidal stability in 2-PrOH, suggesting that even the free QDs bear a surface shell of block copolymer. The presence of MEH-PPV has no affect on this self assembly. One of the most remarkable observations occurred when the samples in 2-PrOH were centrifuged to remove the free QDs accompanying the hybrid micelles. The micelles sedimented, but upon redispersion in 2-PrOH, rearranged to form colloidally stable long branched cylindrical structures including cylindrical networks.

We report the preparation and characterization of two comblike graft copolymers, polythiophenegraftpolyN,Ndimethylaminoethyl methacrylates PT700gPDMA60and PT220gPDMA16, where the subscripts represent the number average degree of polymerization, and an investigation of their interaction with CdSe nanorods. Each polymer contains a regiorandom polythiophene PT as the backbone, from which polyN,Ndimethylaminoethyl methacrylate PDMA chains are densely grafted. The PDMA arms serve as multidentate ligands for CdSe semiconductor nanocrystals and increase the compatibility between the PT backbone and the nanocrystals. Using electron microscopy, we examined the morphology and the internal structure of the nanorodpolymer composites formed in toluene. The morphology and the internal structure of the composites vary with a change in the nanorodpolymer ratio as well as with the concentration of each component. The results of steadystate fluorescence spectroscopy indicate that the presence of the nanocrystals in toluene leads to photoluminescence PL quenching of the PT backbone in the graft copolymer with relatively short PDMA arms PT220gPDMA16. In contrast, no PL quenching could be detected in composites formed from a similar polymer with longer PDMA arms PT700gPDMA60. A likely explanation of this result is that in composites formed with PT700gPDMA60, the nanocrystals are held too far from the PT backbone for energy transfer or charge transfer to take place.

The expectation–maximization (EM) algorithm is a very general and popular iterative computational algorithm to find maximum likelihood estimates from incomplete data and broadly used to statistical analysis with missing data, because of its stability, flexibility and simplicity. However, it is often criticized that the convergence of the EM algorithm is slow. The various algorithms to accelerate the convergence of the EM algorithm have been proposed. The vector ε algorithm of Wynn (Math Comp 16:301–322, 1962) is used to accelerate the convergence of the EM algorithm in Kuroda and Sakakihara (Comput Stat Data Anal 51:1549–1561, 2006). In this paper, we provide the theoretical evaluation of the convergence of the ε-accelerated EM algorithm. The ε-accelerated EM algorithm does not use the information matrix but only uses the sequence of estimates obtained from iterations of the EM algorithm, and thus it keeps the flexibility and simplicity of the EM algorithm.

We report passivation of CdSe and CdSe/ZnS nanocrystals (NCs) with poly(N,N-dimethylaminoethyl methacrylate) (PDMA) through a ligand exchange process. We present the results from various techniques that were used to verify that ligand exchange occurred, including 1H NMR, 31P NMR, and changes in solubility/colloidal properties, hydrodynamic radius, and photoluminescence. We have examined the effect of polymer molecular weight on the surface passivation and quantum yields of the NCs. As additional evidence for the binding of the polymer to the surface of the NC, we were able to modify the polymer chemically to render the NC−polymer moiety water-soluble.

We report passivation of CdSe and CdSe/ZnS nanocrystals (NCs) with poly(N,N-dimethylaminoethyl methacrylate) (PDMA) through a ligand exchange process. We present the results from various techniques that were used to verify that ligand exchange occurred, including 1H NMR, 31P NMR, and changes in solubility/colloidal properties, hydrodynamic radius, and photoluminescence. We have examined the effect of polymer molecular weight on the surface passivation and quantum yields of the NCs. As additional evidence for the binding of the polymer to the surface of the NC, we were able to modify the polymer chemically to render the NC−polymer moiety water-soluble.

No Abstract

No Abstract

We describe the synthesis and characterization of the mesogen-bearing bolaform amphiphile 4,4'-dihydroxybiphenylbis(11-pyridinium-N-yl-undecanoic ester) dibromide (BP-10) and its solid/liquid interfacial self-assembly. Cylindrical micelles are directly observed by atomic force microscopy (AFM) at the interface between mica and the aqueous solution above the critical micelle concentration (cmc). In situ and ex situ AFM studies indicate that the cylindrical micelles are stable both at the mica/solution interface and in the dry state. The enhanced stability of the micellar structures enables a detailed investigation of their self-assembly behavior and supramolecular structures at the interface. The adsorption model proposed here is supported by the variation of the interfacial self-assemblies on changing the solution concentration and substrate temperature.

We describe the synthesis and characterization of the mesogen‐bearing bolaform amphiphile 4,4′‐dihydroxybiphenylbis(11‐pyridinium‐N‐yl‐undecanoic ester) dibromide (BP‐10) and its solid/liquid interfacial self‐assembly. Cylindrical micelles are directly observed by atomic force microscopy (AFM) at the interface between mica and the aqueous solution above the critical micelle concentration (cmc). In situ and ex situ AFM studies indicate that the cylindrical micelles are stable both at the mica/solution interface and in the dry state. The enhanced stability of the micellar structures enables a detailed investigation of their self‐assembly behavior and supramolecular structures at the interface. The adsorption model proposed here is supported by the variation of the interfacial self‐assemblies on changing the solution concentration and substrate temperature.

Stable organic radicals represent a unique type of functional materials for a broad scope of applications in optoelectronic and spintronic devices. A central challenge toward these applications is how to suppress the inter-radical aggregation that often causes aggregation-induced photoluminescence quenching and limits the correlation lifetime of the electron spins from the radicals. Here, we report an effective approach to fine-tuning luminescence and spin dynamics using a series of polyester-tethered single radicals, with a common core of carbazole-triphenylmethyl radical but different chains of polyesters with distinct glass transition temperature and rigidity. The rigidity of the polymeric matrices plays a critical role in tuning the luminescence and electron spin resonance of the radicals. The tunable properties of luminescence and electron spin dynamics as well as the robust photostability of such polymer-tethered single radicals represent important attributes for cutting-edge applications in optoelectronic devices and quantum information technologies.

This paper presents a transient computational fluid dynamics (CFD) model of a reciprocating compressor to study the interaction of the thermodynamic process and pressure pulsation. To realize the interaction between the thermodynamics and the pressure pulsation, the most difficult procedure lies in dealing with the valve motion and flow through the valve channel both precisely and effectively. Therefore, a discretization method for the flow channel of the ring valve to generate structured grids is proposed. Then, the subsequent model is embedded in the flow channel of the compressor model. User-defined functions are employed to calculate the independent velocity of each valve plate based on the real-time pressure differences across the valve plates. After verified, the influences of the discharge pipeline configuration, pressure ratio, and rotational speed were examined. The results of the numerical model agreed well with the experiment. The maximal deviation between predictions and experiments at the pressure ratio of 3 was 6.14% of indicated power. The maximum deviation increased to 7.42% at the rotational speed of 480 rpm. The results for the discharge pipeline configuration verified that the buffer tank directly following the nozzle of the compressor contributed greatly to attenuating the pressure pulsation. A fast Fourier transform analysis of pressure pulsation showed that at all speeds, the amplitudes were almost the same below the eighth harmonic, and then gradually increased for the higher harmonics.

Melt ponds occupy a large fraction of the Arctic sea ice surface during spring and summer. The fraction and distribution of melt ponds have considerable impacts on Arctic climate and ecosystem by reducing the albedo. There is an urgency to obtain improved accuracy and a wider coverage of melt pond fraction (MPF) data for studying these processes. MPF information has generally been acquired from optical imagery. Conventional MPF algorithms based on high‐resolution optical sensors have treated melt ponds as features with constant reflectance; however, the spectral reflectance of ponds can vary greatly, even at a local scale. Here we use Sentinel‐2 imagery to demonstrate those previous algorithms assuming fixed melt pond‐reflectance greatly underestimate MPF. We propose a new algorithm (“LinearPolar”) based on the polar coordinate transformation that treats melt ponds as variable‐reflectance features and calculates MPF across the vector between melt pond and bare ice axes. The angular coordinate θof the polar coordinate system, which is only associated with pond fraction rather than reflectance, is used to determinate MPF. By comparing the new algorithm and previous methods with IceBridge optical imagery data, across a variety of Sentinel‐2 images with melt ponds at various stages of development, we show that the RMSE value of the LinearPolar algorithm is about 30% lower than for the previous algorithms. Moreover, based on a sensitivity test, the new algorithm is also less sensitive to the subjective threshold for melt pond reflectance than previous algorithms. Melt ponds are pools of open water that form on the sea ice surface in the Arctic in summer months. Sea ice covered by melt ponds absorbs more solar heat than solid ice which speeds up the rate of sea ice melt. To study this process, we need melt pond coverage data that are generally obtained from satellite observations. There are several methods to calculate the melt pond fraction from high‐resolution optical satellite imagery but these methods assume that melt ponds have constant optical properties, which is not true. In this study, we show that these existing methods significantly underestimate melt pond fraction. To address this problem, we present a new method that treats melt ponds as features having variable optical properties. Images of sea ice from aircraft are used to assess the new algorithm and two previous methods, demonstrating that the new algorithm has higher accuracy and precision. Sentinel‐2 and IceBridge imagery are used to show that algorithms assuming fixed melt pond‐reflectance largely underestimate melt pond fractionA new algorithm based on the polar coordinate transformation that treats melt ponds as variable‐reflectance has been developedThe accuracy and precision of the new Sentinel‐2 algorithm, assessed with IceBridge DMS imagery, are higher than previous algorithms

In this work, the Cassino Biped Locomotor, a biped walking robot, is presented as the leg design by using reduced parallel mechanisms. The proposed biped locomotor consists of two identical tripod leg mechanisms with a three degree-of-freedom parallel manipulator architecture. Kinematics analysis is carried out in terms of the forward and inverse kinematics of one leg mechanism and inverse kinematics of the biped locomotor. The walking operation is discussed in detail with gait planning and trajectories of feet and waist. A CAD model is elaborated in solidworks® environment and the corresponding prototype is fabricated with low-cost user-oriented features by using commercial components and structural parts that are manufactured by using 3D printing. An experimental layout and corresponding test modes are illustrated for characterizing the walking operation performance. Experimental results are analyzed for an operation performance evaluation and architecture design characterization of the Cassino Biped Locomotor.

A new polymerizable surfactant 1-[11-(lipoyloxy)-undecyl]-pyridinium bromide was synthesized, which provides a new approach for polymerizing micelles under mild conditions.

This paper presents a new three-degrees-of-freedom spherical parallel manipulator, which is designed to be used as a prosthetic wrist. The inverse position problem is solved and a closed form equation is obtained. Afterward, using the screw theory approach, the mobility analysis is performed to demonstrate that the proposed mechanism performs spherical motion. The velocity analysis is carried out by means of screw theory, and an input–output velocity equation is obtained. Furthermore, a preliminary virtual design of the mechanism is presented and the workspace and analytical static analysis is performed. Finally, a set of dynamic simulations are carried out to demonstrate the three movements (i.e., pronation–supination, flexion–extension, and ulnar–radial deviation) of the wrist, and the simulation results show that the proposed mechanism is capable of performing the full range of motion required for daily living and the required actuation torques are obtained for the future development.