The Drude‐Smith equation is widely used for treating the frequency‐dependent electrical conductivity of materials in the terahertz region. An attractive feature is its sparsity of adjustable ...parameters. A significant improvement over Drude theory for these materials, the theory includes backscattering of the charge carriers. It has nevertheless been criticized, including by Smith himself, because of the arbitrariness of a step in the derivation. We recall a somewhat similar behavior of back scattering in fluids observed in molecular dynamics computations and discussed in terms of memory functions. We show how theories such as Drude‐Smith and Cocker et al. are examples of a broader class of theories by showing how they also arise as particular cases of a memory function formalism that divides the interactions into short and long range.
Insight into the Drude‐Smith equation commonly used to treat terahertz electrical conductivity of solids and the role of backscattering is obtained using extensive computer‐based studies of a related quantity, the velocity autocorrelation function of fluids. The latter has been interpreted using a memory function formalism which is then used here to analyze and extend the Drude‐Smith equation.
•To the best of our knowledge, Mask-CNN is the first end-to-end model that selects deep convolutional descriptors for object recognition, especially for fine-grained image recognition.•We present a ...novel and efficient part-based three-stream model for fine-grained recognition. By discarding the fully connected layers, the proposed M-CNN is computationally efficient (cf. Table 1 and Table 4 in experiments). Additionally, comparing with state-of-the-art methods, M-CNN has smaller feature dimensionality. Beyond those, it achieves the highest classification accuracy on CUB200-2011 and Birdsnap among published methods.•The part localization performance of the proposed model outperforms other part-based finegrained approaches which requires additional bounding boxes. In particular, M-CNN is 12.76% higher than state-of-the-art for head localization on CUB200-2011.
Fine-grained image recognition is a challenging computer vision problem, due to the small inter-class variations caused by highly similar subordinate categories, and the large intra-class variations in poses, scales and rotations. In this paper, we prove that selecting useful deep descriptors contributes well to fine-grained image recognition. Specifically, a novel Mask-CNN model without the fully connected layers is proposed. Based on the part annotations, the proposed model consists of a fully convolutional network to both locate the discriminative parts (e.g., head and torso), and more importantly generate weighted object/part masks for selecting useful and meaningful convolutional descriptors. After that, a three-stream Mask-CNN model is built for aggregating the selected object- and part-level descriptors simultaneously. Thanks to discarding the parameter redundant fully connected layers, our Mask-CNN has a small feature dimensionality and efficient inference speed by comparing with other fine-grained approaches. Furthermore, we obtain a new state-of-the-art accuracy on two challenging fine-grained bird species categorization datasets, which validates the effectiveness of both the descriptor selection scheme and the proposed Mask-CNN model.
A novel photo‐responsive protein–graphene–protein (PGP) capsule that doubles as a photothermal agent with core/shell structure is constructed by anchoring reduced graphene oxide nanosheets on ...one‐component protein (lactoferrin) shell through a double emulsion method. PGP capsules can transport fully concealed hydrophilic anticancer cargo, doxorubicin (Dox), with a large payload (9.43 μmol g‐1) to be later unloaded in a burst‐like manner by photo‐actuation triggered by near‐infrared irradiation. Being biocompatible yet with a high cancer cell targeting efficiency, PGP capsules have successfully eradicated subcutaneous tumors in 10 d following a single 5 min NIR irradiation without distal damage. Besides, the photochemothermal therapy of PGP capsules eradicates tumor cells not only in the light‐treating area but also widely light‐omitted tumor cells, overcoming the tumor recurrence due to efficient cell killing efficacy. These results demonstrate that the PGP capsule is a potential new drug delivery platform for local‐targeting, on‐demand, photoresponsive, combined chemotherapy/hyperthermia for tumor treatment and other biomedical applications.
Core–shell photoresponsive protein–graphene–protein capsules supported on a reduced graphene oxide substrate and one‐single component of protein display targeted chemotherapy with synergistic hyperthermia effects, eradicating not only the targeted cells but also cancerous cells omitted near infrared irradiation in vivo and in vitro.
In recent years, China has made strides in adopting student-oriented teaching approaches, particularly in tertiary English education, through the integration of enhanced technology. This study aimed ...to investigate the impact of flipped classroom on the English proficiency of first-year pre-service teachers at a Chinese normal university. It also sought to determine whether educational background (urban or rural) interacted with the teaching approach (flipped or traditional) in affecting the language proficiency of the learners.
A quasi-experimental design was utilized with two treatments: a flipped classroom approach and a traditional teacher-centered teaching approach. Both approaches were implemented in the Integrated English Course over a 12-week semester. Two randomly selected classes, consisting of 60 pre-service teachers in each class, were assigned to either the experimental or control group. Data were collected from pretest and post-test assessments and analyzed using two-way ANOVA.
The results revealed a positive impact of the flipped classroom and a significant interaction between educational background and teaching approach on English proficiency. Specifically, urban pre-service teachers achieved higher English proficiency than their rural peers when taught in the flipped classroom, but not in the traditional classroom. Furthermore, urban pre-service teachers in the flipped classroom outperformed their urban peers in the traditional classroom, while rural pre-service teachers did not show any significant difference in their performance between the two classes.
The findings suggested that the flipped classroom approach was more effective than the traditional approach for Chinese pre-service teachers, particularly those with an urban educational background. However, it is important to ensure that rural learners receive sufficient support to benefit equally from this innovative teaching approach. Accordingly, implications and recommendations for future research are discussed.
Carbon-based supercapacitors can provide high electrical power, but they do not have sufficient energy density to directly compete with batteries. We found that a nitrogen-doped ordered mesoporous ...few-layer carbon has a capacitance of 855 farads per gram in aqueous electrolytes and can be bipolarly charged or discharged at a fast, carbon-like speed. The improvement mostly stems from robust redox reactions at nitrogen-associated defects that transform inert graphene-like layered carbon into an electrochemically active substance without affecting its electric conductivity. These bipolar aqueous-electrolyte electrochemical cells offer power densities and lifetimes similar to those of carbon-based supercapacitors and can store a specific energy of 41 watt-hours per kilogram (19.5 watt-hours per liter).
Recently, diverse functional materials that take subcellular structures as therapeutic targets are playing increasingly important roles in cancer therapy. Here, particular emphasis is placed on four ...kinds of therapies, including chemotherapy, gene therapy, photodynamic therapy (PDT), and hyperthermal therapy, which are the most widely used approaches for killing cancer cells by the specific destruction of subcellular organelles. Moreover, some non‐drug‐loaded nanoformulations (i.e., metal nanoparticles and molecular self‐assemblies) with a fatal effect on cells by influencing the subcellular functions without the use of any drug molecules are also included. According to the basic principles and unique performances of each treatment, appropriate strategies are developed to meet task‐specific applications by integrating specific materials, ligands, as well as methods. In addition, the combination of two or more therapies based on multifunctional nanostructures, which either directly target specific subcellular organelles or release organelle‐targeted therapeutics, is also introduced with the intent of superadditive therapeutic effects. Finally, the related challenges of critical re‐evaluation of this emerging field are presented.
The rapid development in the field of subcellular targeted cancer therapy is reviewed systemically and comprehensively on account of six sets of treatment modalities: chemotherapy, gene therapy, PDT, hyperthermia, non‐drug‐loaded nanoformulations, and synergistic combined therapy.
In this work, we report a green and simple strategy for the in situ growth of surfactant-free Au nanoparticles (Au NPs) on nitrogen-doped graphene quantum dots (Au NPs–N-GQDs). The formation of ...hybrid was achieved by just mixing the N-GQDs and HAuCl4·4H2O without addition of any other reductant and surfactant. High-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) characterizations clearly showed the formation of Au nanoparticles with predominantly exposed (111) facets which can provide more adsorption sites. Such nonsurfactant-capped Au NPs can provide naked catalytic surface with highly electrocatalytic activity. The Au NPs–N-GQDs exhibit high sensitivity and selectivity for electrochemical detection of hydrogen peroxide (H2O2) with a low detection limit of 0.12 μM and sensitivity of 186.22 μA/mM cm2. Importantly, the Au NPs–N-GQDs-based electrochemical biosensor has shown great potential applications for detection of H2O2 levels in human serum samples and that released from human cervical cancer cells with satisfactory results. The present study demonstrates that such novel Au NPs–N-GQDs nanocomposite is promising for fabrication of nonenzymatic H2O2 biosensors.
A 16-channel closed-loop neuromodulation system-on-chip (SoC) for human epileptic seizure control is proposed and designed. In the proposed SoC, a 16-channel neural-signal acquisition unit (NSAU), a ...biosignal processor (BSP), a 16-channel high-voltage-tolerant stimulator (HVTS), and wireless power and bidirectional data telemetry are designed. In the NSAU, the input protection circuit is used to prevent MOSFET from overstressing by the high-voltage stimulations. Hence, NSAUs can share electrodes with stimulators. The auto-reset chopper-stabilized capacitive-coupled instrumentation amplifiers (AR-CSCCIAs) are designed with the chopper-stabilized technique with a new offset reduction loop. The measured input-referred noise is 2.09 <inline-formula> <tex-math notation="LaTeX">\mu \textrm {V}_{\mathrm {rms}} </tex-math></inline-formula> and the noise-efficiency factor (NEF) is 3.78. The entropy-and-spectrum seizure detection algorithm is implemented in the BSP with 0.76-s seizure detection latency and 97.8% detection accuracy. When the seizure onset is detected by the BSP, the HVTS with adaptive supply control delivers 0.5-3-mA biphasic current stimulation to suppress the seizure onset. The proposed SoC is powered wirelessly, and the bidirectional data telemetry is realized through the same pair of coils in 13.56 MHz. The downlink data rate is 211 Kb/s with the binary phase-shift keying (BPSK) modulation and a new BPSK demodulator. The uplink data rate is 106 Kb/s with the load-shift keying (LSK) modulation. The proposed SoC is fabricated in a 0.18-<inline-formula> <tex-math notation="LaTeX">\mu \text{m} </tex-math></inline-formula> CMOS technology and occupies 25 mm 2 . Electrical tests have been performed to characterize the SoC performance. In vivo animal experiments using mini-pigs have been performed to successfully verify the closed-loop neuromodulation functions on epileptic seizure suppression.
Herein, it is reported the influence of solution processing and treatments, such as adding marginal solvent, ultrasonication, and UV treatment, on the resulting perovskite (CsPbBr3) quantum dot ...(QD)/poly(3‐hexylthiophene) (P3HT) composite nanofibril films (CNFs) to improve the charge dissociation and photonic synaptic performance. A photonic synaptic transistor with CNFs can perform fundamental functions, including short‐term plasticity, long‐term plasticity, spike‐number‐dependent, and spike‐time‐dependent plasticity, to mimic sensing, computing, and memory functions. Notably, a synaptic device with CNFs presents an ultralow energy consumption of 0.18 fJ and zero‐gate operation. The superior performance of synaptic devices with CNFs can be attributed to two factors: (i) homogeneous axial distribution of the QDs and (ii) the formation of P3HT nanofibrils and co‐aggregates. Therefore, enhanced interfacial charge transfer between QDs and P3HT, ensuring decent carrier transport capability, is achieved. Collectively, the composite artificial synapse successfully provides an effective guide that offers a new perspective for the fabrication of one‐dimensional self‐assembled nanostructure‐based artificial synapses emulating human‐like memory, neuromorphic computing, and artificial intelligent systems.
Semiconducting self‐assembled composite nanostructures via solution processing is a promising strategy to improve the charge dissociation and photonic synaptic performance. In this study, quantum dot/poly(3‐hexylthiophene) nanofibrils are studied to understand the morphology/optoelectronic relation. The composite artificial synapse exhibits fundamental functions, including short‐term plasticity, long‐term plasticity, and spike‐number‐dependent and spike‐time‐dependent plasticity with ultralow energy consumption of 0.18 fJ and zero‐gate operation.
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