1,333 research outputs found
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 Chinaâs Stock Market
Financing is the main way for listed companies to obtain funds in China, and it is the âreservoirâ which can guarantee enterprises to operate continuously. Financing efficiency can be used to measure the efficiency in using enterprisesâ 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 2008â2014. 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 via the scale-invariant perturbative relation to its 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
and the running mass 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 -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 mass fixed-point GeV as an input, we obtain, GeV, in which the error is the squared average of those
from , , 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(Δ-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(Δ-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 Όg per well. Vitamin B<sub>12 </sub>(VB<sub>12</sub>), 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
- âŠ