39 research outputs found
Recent innovations in silk biomaterials
Silk contains a fibre forming protein, fibroin, which is biocompatible, particularly after removing the potentially immunogenic non-fibroin proteins. Silk can be engineered into a wide range of materials with diverse morphologies. Moreover, it is possible to regenerate fibroin with a desired amount of crystallinity, so that the biodegradation of silk materials can be controlled. These advantages have sparked new interest in the use of silk fibroin for biomedical applications, including tissue engineering scaffolds and carriers for sustained release of biologically active molecules. This article summarizes the current research related to the formation of silk materials with different morphologies, their biocompatibility, and examples of their biomedical applications. Recent work on the preparation of silk particles by mechanical milling and their applications in silk composite scaffolds is also discussed
Bid Optimization by Multivariable Control in Display Advertising
Real-Time Bidding (RTB) is an important paradigm in display advertising,
where advertisers utilize extended information and algorithms served by Demand
Side Platforms (DSPs) to improve advertising performance. A common problem for
DSPs is to help advertisers gain as much value as possible with budget
constraints. However, advertisers would routinely add certain key performance
indicator (KPI) constraints that the advertising campaign must meet due to
practical reasons. In this paper, we study the common case where advertisers
aim to maximize the quantity of conversions, and set cost-per-click (CPC) as a
KPI constraint. We convert such a problem into a linear programming problem and
leverage the primal-dual method to derive the optimal bidding strategy. To
address the applicability issue, we propose a feedback control-based solution
and devise the multivariable control system. The empirical study based on
real-word data from Taobao.com verifies the effectiveness and superiority of
our approach compared with the state of the art in the industry practices
Budget Constrained Bidding by Model-free Reinforcement Learning in Display Advertising
Real-time bidding (RTB) is an important mechanism in online display
advertising, where a proper bid for each page view plays an essential role for
good marketing results. Budget constrained bidding is a typical scenario in RTB
where the advertisers hope to maximize the total value of the winning
impressions under a pre-set budget constraint. However, the optimal bidding
strategy is hard to be derived due to the complexity and volatility of the
auction environment. To address these challenges, in this paper, we formulate
budget constrained bidding as a Markov Decision Process and propose a
model-free reinforcement learning framework to resolve the optimization
problem. Our analysis shows that the immediate reward from environment is
misleading under a critical resource constraint. Therefore, we innovate a
reward function design methodology for the reinforcement learning problems with
constraints. Based on the new reward design, we employ a deep neural network to
learn the appropriate reward so that the optimal policy can be learned
effectively. Different from the prior model-based work, which suffers from the
scalability problem, our framework is easy to be deployed in large-scale
industrial applications. The experimental evaluations demonstrate the
effectiveness of our framework on large-scale real datasets.Comment: In The 27th ACM International Conference on Information and Knowledge
Management (CIKM 18), October 22-26, 2018, Torino, Italy. ACM, New York, NY,
USA, 9 page
Graphene oxide nanoparticles for enhanced photothermal cancer cell therapy under the irradiation of a femtosecond laser beam
Nano-sized graphene and graphene oxide (GO) are promising for biomedical applications, such as drug delivery and photothermal therapy of cancer. It is observed in thiswork that the ultrafast reduction of GO nanoparticles (GONs)with a femtosecond laser beam creates extensive microbubbling. To understand the surface chemistry of GONs on the microbubble formation, the GONs were reduced to remove
most of the oxygen-containing groups to get reduced GONs
(rGONs). Microbubbling was not observed when the rGONs
were irradiated by the laser. The instant collapse of the
microbubbles may produce microcavitation effect that brings
about localized mechanical damage. To understand the
potential applications of this phenomenon, cancer cells
labeled with GONs or rGONs were irradiated with the laser.
Interestingly, the microbubbling effect greatly facilitated the
destruction of cancer cells. When microbubbles were produced,
the effective laser power was reduced to less than
half of what is needed when microbubbling is absent. This
finding will contribute to the safe application of femtosecond
laser in the medical area by taking advantage of the ultrafast
reduction of GONs. It may also find other important applications
that need highly localized microcavitation effects
Control of crystallization in supramolecular soft materials engineering
As one class of the most important supramolecular functional materials, gels formed by low molecular weight gelators (LMWGs) have many important applications. The key important parameters affecting the in-use performance of a gel are determined by the hierarchical fiber network structures. Fiber networks consisting of weakly interacting multiple domains are commonly observed in gels formed by LMWGs. The rheological properties, particularly the elasticity, of a gel with such a fiber network are weak due to the weak interactions between the individual domains. As achieving desirable rheological properties of such a gel is practically relevant, in this work, we demonstrate the engineering of gels with such a type of fiber network by controlling crystallization of the gelator. Two example gels formed by a glutamic acid derivative in a non-ionic surfactant Tween 80 and in propylene glycol were engineered by controlling the thermodynamic driving force for crystallization. For a fixed gelator concentration, the thermodynamic driving force was manipulated by controlling the temperature for fiber crystallization. It was observed that there exists an optimal temperature at which a gel with maximal elasticity can be fabricated. This will hopefully provide guidelines for producing high performance soft materials by engineering their fiber network structures
Control of crystallization in supramolecular soft materials engineering
As one class of the most important supramolecular functional materials, gels formed by low molecular weight gelators (LMWGs) have many important applications. The key important parameters affecting the in-use performance of a gel are determined by the hierarchical fiber network structures. Fiber networks consisting of weakly interacting multiple domains are commonly observed in gels formed by LMWGs. The rheological properties, particularly the elasticity, of a gel with such a fiber network are weak due to the weak interactions between the individual domains. As achieving desirable rheological properties of such a gel is practically relevant, in this work, we demonstrate the engineering of gels with such a type of fiber network by controlling crystallization of the gelator. Two example gels formed by a glutamic acid derivative in a non-ionic surfactant Tween 80 and in propylene glycol were engineered by controlling the thermodynamic driving force for crystallization. For a fixed gelator concentration, the thermodynamic driving force was manipulated by controlling the temperature for fiber crystallization. It was observed that there exists an optimal temperature at which a gel with maximal elasticity can be fabricated. This will hopefully provide guidelines for producing high performance soft materials by engineering their fiber network structures
Photochromic wool fabrics with enhanced durability and photochromic performance
In our previous work, we have produced a photochromic wool fabric by applying a thin layer of hybrid silica-photochromic dye onto the wool surface. The coating showed a very fast optical response, but had little influence on the fabric handle, however durability was low. In this context, we reported that durability of the hybrid layer can be improved by introducing epoxy groups into the silica matrix via co-hydrolysis and co-condensation of an alkyl trialkoxysilane (ATAS) and 3-glycidoxypropyltrimethoxysilane (GPTMS). The presence of epoxy groups in the silica enhanced both washing and abrasion durabilities. Also, the optical response speed was slightly increased as well. Effects of the type of alkyl silane and the GPTMS:alkyl silane ratio on the coating durability, fabric handle and optical response were examined.<br /
Kinetically controlled homogenization and transformation of crystalline fiber networks in supramolecular materials
Supramolecular materials with three-dimensional fiber networks have applications in many fields. For these applications, a homogeneous fiber network is essential in order to get the desired performance of a material. However, such a fiber network is hard to obtain, particularly when the crystallization of fiber takes place nonisothermally. In this work, a copolymer is used to kinetically control the nucleation and fiber network formation of a small molecular gelling agent, N-lauroyl-L-glutamic acid di-nbutylamide (GP-1) in benzyl benzoate. The retarded nucleation and enhanced mismatch nucleation of the gelator by the additive leads to the conversion of a mixed fiber network into a homogeneous network consisting of spherulites only. The enhanced structural mismatch of the GP-1 during crystallization is quantitatively characterized using the rheological data. This effect also leads to the transformation of an interconnecting (single) fiber network of GP-1 into a multidomain fiber network in another solvent, isostearyl alcohol. The approach developed is significant to the production of supramolecular materials with homogeneous fiber networks and is convenient to switch a single fiber network to a multidomain network without adjusting the thermodynamic driving force