Realization of Zero-Refractive-Index Lens with Ultralow Spherical Aberration

Optical complex materials offer unprecedented opportunity to engineer fundamental band dispersion which enables novel optoelectronic functionality and devices. Exploration of photonic Dirac cone at the center of momentum space has inspired an exceptional characteristic of zero-index, which is similar to zero effective mass in fermionic Dirac systems. Such all-dielectric zero-index photonic crystals provide an in-plane mechanism such that the energy of the propagating waves can be well confined along the chip direction. A straightforward example is to achieve the anomalous focusing effect without longitudinal spherical aberration, when the size of zero-index lens is large enough. Here, we designed and fabricated a prototype of zero-refractive-index lens by comprising large-area silicon nanopillar array with plane-concave profile. Near-zero refractive index was quantitatively measured near 1.55 um through anomalous focusing effect, predictable by effective medium theory. The zero-index lens was also demonstrated to perform ultralow longitudinal spherical aberration. Such IC compatible device provides a new route to integrate all-silicon zero-index materials into optical communication, sensing, and modulation, and to study fundamental physics on the emergent fields of topological photonics and valley photonics.Comment: 14 pages, 4 figure

DeepCF: A Unified Framework of Representation Learning and Matching Function Learning in Recommender System

In general, recommendation can be viewed as a matching problem, i.e., match proper items for proper users. However, due to the huge semantic gap between users and items, it's almost impossible to directly match users and items in their initial representation spaces. To solve this problem, many methods have been studied, which can be generally categorized into two types, i.e., representation learning-based CF methods and matching function learning-based CF methods. Representation learning-based CF methods try to map users and items into a common representation space. In this case, the higher similarity between a user and an item in that space implies they match better. Matching function learning-based CF methods try to directly learn the complex matching function that maps user-item pairs to matching scores. Although both methods are well developed, they suffer from two fundamental flaws, i.e., the limited expressiveness of dot product and the weakness in capturing low-rank relations respectively. To this end, we propose a general framework named DeepCF, short for Deep Collaborative Filtering, to combine the strengths of the two types of methods and overcome such flaws. Extensive experiments on four publicly available datasets demonstrate the effectiveness of the proposed DeepCF framework

The Evaluation of Financing Efficiency of China’s Stock Market

Financing is the main way for listed companies to obtain funds in China, and it is the “reservoir” which can guarantee enterprises to operate continuously. Financing efficiency can be used to measure the efficiency in using enterprises’ own funds, and it is one of the main indicators which are concerned by the stakeholders of listed companies. This paper mainly researches on the impact of equity financing on the financing efficiency of listed companies as a whole and selects 300 listed companies in the Shanghai and Shenzhen Stock Exchange as decision-making units. Then this paper analyzes the financial data of sample companies in 2008–2014. Finally, it can be concluded that the financing efficiency of listed companies in China is generally low, and the total factor productivity in the stock market continued to decline between 2003 and 2005 and then rose rapidly

Determination of the top-quark on-shell mass MtM_t via the scale-invariant perturbative relation to its MS‾\overline{\rm MS} mass

In the paper, we firstly improve the scale-setting procedures of the principle of maximum conformality (PMC) such that the correct magnitudes of the $\alpha_s$ and the $\overline{\rm MS}$ running mass ${\overline m}$ of the perturbative QCD series are determined simultaneously with the help of the renormalization group equation. By using the derived formulas, we determine the top-quark on-shell mass via the four loop $\overline{\rm MS}$-on-shell quark mass relation. Its prediction avoids the conventional renormalization scale ambiguity, and a more precise pQCD prediction can be achieved. By taking the top-quark $\overline{\rm MS}$ mass fixed-point ${\overline m}_t({\overline m}_t)=162.5^{+2.1}_{-1.5}$ GeV as an input, we obtain, $M_t\simeq 172.41^{+2.21}_{-1.57}$ GeV, in which the error is the squared average of those from $\Delta \alpha_s(M_Z)$, $\Delta {\overline m}_t({\overline m}_t)$, and the approximate error from the uncalculated five-loop terms predicted by using the Pad\'{e} approximation approach.Comment: 11 pages, 2 figure

In vitro drug release behavior from a novel thermosensitive composite hydrogel based on Pluronic f127 and poly(ethylene glycol)-poly(ε-caprolactone)-poly(ethylene glycol) copolymer

<p>Abstract</p> <p>Background</p> <p>Most conventional methods for delivering chemotherapeutic agents fail to achieve therapeutic concentrations of drugs, despite reaching toxic systemic levels. Novel controlled drug delivery systems are designed to deliver drugs at predetermined rates for predefined periods at the target organ and overcome the shortcomings of conventional drug formulations therefore could diminish the side effects and improve the life quality of the patients. Thus, a suitable controlled drug delivery system is extremely important for chemotherapy.</p> <p>Results</p> <p>A novel biodegradable thermosensitive composite hydrogel, based on poly(ethylene glycol)-poly(ε-caprolactone)-poly(ethylene glycol) (PEG-PCL-PEG, PECE) and Pluronic F127 copolymer, was successfully prepared in this work, which underwent thermosensitive sol-gel-sol transition. And it was flowing sol at ambient temperature but became non-flowing gel at body temperature. By varying the composition, sol-gel-sol transition and <it>in vitro </it>drug release behavior of the composite hydrogel could be adjusted. Cytotoxicity of the composite hydrogel was conducted by cell viability assay using human HEK293 cells. The 293 cell viability of composite hydrogel copolymers were yet higher than 71.4%, even when the input copolymers were 500 μg per well. Vitamin B₁₂(VB₁₂), honokiol (HK), and bovine serum albumin (BSA) were used as model drugs to investigate the <it>in vitro </it>release behavior of hydrophilic small molecular drug, hydrophobic small molecular drug, and protein drug from the composite hydrogel respectively. All the above-mentioned drugs in this work could be released slowly from composite hydrogel in an extended period. Chemical composition of composite hydrogel, initial drug loading, and hydrogel concentration substantially affected the drug release behavior. The higher Pluronic F127 content, lower initial drug loading amount, or lower hydrogel concentration resulted in higher cumulative release rate.</p> <p>Conclusion</p> <p>The results showed that composite hydrogel prepared in this paper were biocompatible with low cell cytotoxicity, and the drugs in this work could be released slowly from composite hydrogel in an extended period, which suggested that the composite hydrogel might have great potential applications in biomedical fields.</p