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Aromatic macromolecules tend to form a compact conformation after physically adsorbed on graphene and it brings about great entropy loss for physisorption, due to the strong interaction between aromatic macromolecules and graphene. However, previous researches have validated the availability of aromatic macromolecules to stabilize graphene based on physisorption. In order to clarify the underlying mechanism of this physisorption process on graphene, a series of aromatic polyamide copolymers are used as models in this research. Apart from their adsorbed conformations on graphene, the conformations of these copolymers as the free states in diluted solutions are taken into consideration. Although these copolymers present the fully extended conformation on graphene, their conformations in diluted solutions vary largely with the copolymer composition. It is verified that the copolymer with smaller conformational change could have the better stabilization effectiveness for graphene, rather than the one having stronger interaction with graphene. Therefore, the entropy-tailored behavior for the adsorption of aromatic macromolecules on graphene is put forward. Based on this mechanism, the chemical structure of aromatic polyamide is optimized and furthermore it is utilized to directly exfoliate natural graphite flakes. Eventually, high-quality graphene nanosheets with a large dimension and low defects are obtained. Moreover, its exfoliating effectiveness is superior to those of the commonly used exfoliating agents nowadays.

Weak transverse interaction of aramid fiber leads to low compressive strength, which is a prominent problem for its further application. In this study, a novel strategy by constructing dendritic structure in aramid fiber was conducted to solve the problem. Hyperbranched aromatic polyamide and linear aromatic polyamide are grafted on nano-SiO2 respectively, which will present absolutely different conformations. Structure of the SiO2 derivates was analyzed in detail by Fourier transform infrared spectroscopy (FTIR), dynamic laser scattering (DLS) and X-ray photoelectron spectroscopy (XPS). Compared with linear polyamide, hyperbranched polyamide tends to grow in multiple directions during polymerization due to significant steric effect, which can be confirmed by molecular simulation. When the SiO2 derivates were blended in aramid fiber, three-dimensional dendritic structure will be constructed by utilizing distinctive conformation of the hyperbranched polyamide. When loading content of nano-SiO2 derivate modified by hyperbranched polyamide in aramid fiber is 0.5 wt%, compressive strength of the fiber is improved by nearly 114%. Moreover, tensile strength and modulus are improved by nearly 13% and 9% respectively. Therefore, comprehensive performance of the aramid fiber can be remarkably improved by utilizing unique conformation of the hyperbranched polyamide, even if loading content of the SiO2 derivate is relatively low.

Superparamagnetic tunnel junctions (STJs) are nanostructures with very low turnover barriers. The barrier height of an STJ is generally equal to the heat energy at room temperature; thus, it can oscillate automatically without external driving. Previous studies have shown that the randomness of an STJ can be driven by a subthreshold voltage. This synchronization can be adjusted using electrical noise, which is often considered as zero-field Gaussian white noise. However, the actual circuit and environment are inevitably associated with colored noise, which has not been considered previously. In this work, numerical simulations were performed to study the phase-locking characteristics of a single STJ with the aid of several typical types of colored noise. The results show that the phase-locked behavior of an STJ can be effectively enhanced by colored noise whose power spectral density per unit of bandwidth is proportional to its frequency. Meanwhile, colored noise whose power spectral density per unit of bandwidth and frequency are inversely proportional can suppress the synchronization of STJs by suppressing the increase in junction frequency.

Superparamagnetic tunnel junctions (SMTJs) are spintronic nanodevices that can oscillate spontaneously under the influence of thermal noise. Studies have proposed that SMTJs can be modeled as magnetic neurons by subjecting them to electrical Gaussian white noise and can be subsequently synchronized under subthreshold driving. Considering the non-Gaussian background noise in industrial applications, this study investigated the influence of levy noise on SMTJ subthreshold synchronization. The results revealed that levy noise with weak pulse characteristics can be used to promote the subthreshold synchronization of the SMTJs, whereas levy noise with enhanced pulse characteristics cannot be used. Under the same conditions, enhanced levy noise asymmetry is advantageous for achieving SMTJ synchronization under subthreshold driving.

Rigid-chain polymeric gels with excellent performance and multi-functions are rarely reported due to the difficulty in balancing solubility and precipitation caused by π-π stacking. Herein, a rigid aromatic polyamide organogel containing benzimidazole moiety was prepared successfully by utilizing protonation effect of protic acid HCl. Due to protonation, coplanarity of stacking structures was destroyed and the dissolution interaction of benzimidazole moiety and solvent was weakened. With increasing temperature, the further decreased solvation capacity led to the formation of interchain hydrogen bonds with a self-assembly process that induced gelation. What’ s more, due to weakened conjugation of protonated PABI, aggregation-induced quenching (ACQ) was suppressed, and this LCST-type organogel showed aggregation-induced emission (AIE) phenomenon with enhanced blue-light emission. This paper provides an ingenious approach via regulating conjugation and solvation for constructing functional rigid-chain polymer gels.

PURPOSE: To compare machine learning methods for classifying mass lesions on mammography images that use predefined image features computed over lesion segmentations to those that leverage segmentation-free representation learning on a standard, public evaluation dataset. METHODS: We apply several classification algorithms to the public Curated Breast Imaging Subset of the Digital Database for Screening Mammography (CBIS-DDSM), in which each image contains a mass lesion. Segmentation-free representation learning techniques for classifying lesions as benign or malignant include both a Bag-of-Visual-Words (BoVW) method and a Convolutional Neural Network (CNN). We compare classification performance of these techniques to that obtained using two different segmentation-dependent approaches from the literature that rely on specific combinations of end classifiers (e.g. linear discriminant analysis, neural networks) and predefined features computed over the lesion segmentation (e.g. spiculation measure, morphological characteristics, intensity metrics). RESULTS: We report area under the receiver operating characteristic curve (A(Z)) values for malignancy classification on CBIS-DDSM for each technique. We find average A(Z) values of 0.73 for a segmentation-free BoVW method, 0.86 for a segmentation-free CNN method, 0.75 for a segmentation-dependent linear discriminant analysis of Rubber-Band Straightening Transform features, and 0.58 for a hybrid rule-based neural network classification using a small number of hand-designed features. CONCLUSIONS: We find that malignancy classification performance on the CBIS-DDSM dataset using segmentation-free BoVW features is comparable to that of the best segmentation-dependent methods we study, but also observe that a common segmentation-free CNN model substantially and significantly outperforms each of these (p

A fluorescence paper-based sensor method by simply using thiomalic acid modified CdTe (TMA-capped CdTe) was proposed for visual detection of silver ions (Ag+). Red-emission TMA-capped CdTe with a large amount of carboxyl groups on the surface could be combined with Ag+ by electrostatic interaction, thus leading to the fluorescence quenching. It was found that the adding of amino acids contributed to fluorescence recovery by the leaving of Ag+ on the surface of TMA-capped CdTe. Moreover, the more amino group, benzene and thiol group equipped in the structure of amino acid, the stronger fluorescence restoring of CdTe could be achieved. This fluorescence spectrometry method for Ag+ showed low detection of limit with the value of 13.16 nmol/L, with no response to other heavy metals, which demonstrating its high sensitivity and high selectivity for Ag+. More importantly, this paper-based sensor method combined with chemometrics could accurately identify and quantify different concentrations of Ag+ in different complex matrices. This fast, economical, accurate and effective approach exhibited a new idea for the on-site detection of Ag+, and was expected to be extended to the on-site detection of Ag+ in biological and environmental fields.

Rigid macromolecular chains possess weak mobility and have difficulty with conformational adjustment, resulting in some “free intermolecular interaction sites” of hydrogen bonds. Herein, aramid oligomers (OPBIA) with different average polymerization degree (DP) were synthesized and added in aramid fiber (PBIA) to fill these free interaction sites, aiming to form stronger interchain hydrogen bonding interactions and achieve self-enhancement in mechanical properties of aramid fiber. Variable-temperature Fourier transform infrared spectrometer was employed to in situ monitor the evolution of hydrogen bonds in aramid from 30 °C to 360 °C. The results show that the value of hydrogen bonding enthalpy change is −19.37 kJ mol−1 after adding OPBIA5 (DP = 5) in PBIA, whose absolute value is obviously larger than that of PBIA (−13.14 kJ mol−1). This demonstrates that the oligomer improves intermolecular hydrogen bonding interactions effectively. Correspondingly, the tensile strength and compressive strength of PBIA/OPBIA5 fiber increases by 23.1% and 29.4%, respectively, compared to those of PBIA fiber. Besides, the enhancement of properties is related to the DP of oligomers, OPBIA with low DP has stronger effect on intermolecular hydrogen bonds than OPBIA with high DP. Nevertheless, the oligomer tends to self-aggregate when its DP is too low. In addition, the oligomers can plasticize the macromolecules at high temperatures, which is advantageous for further increasing the orientation and tensile strength of aramid fibers.