499 research outputs found
Characterisation of Carotenoids Involved in the Xanthophyll Cycle
Carotenoids are known for versatile roles they play in living organisms; however, their most pivotal function is involvement in scavenging reactive oxygen species (ROS) and photoprotection. In plant kingdom, an important photoprotective mechanism, referred to as the xanthophyll cycle, has been developed by photosynthetic organism to avoid excess light that might lead to photoinhibition and inactivation of photosystems and induce the formation of reactive oxygen species (ROS), resulting in photodamage and long-term changes in the cells caused by oxidative stress. Apart from high-light driven enzymatic conversion of violaxanthin (Viola) to zeaxanthin (Zea) that occurs mostly in higher plants, mosses and lichens, other less known types of the xanthophyll cycle have been hitherto described. The work is aimed at summarising the current knowledge on the pigments engaged in the xanthophyll cycles operating in various organisms
Is Meta-Learning the Right Approach for the Cold-Start Problem in Recommender Systems?
Recommender systems have become fundamental building blocks of modern online
products and services, and have a substantial impact on user experience. In the
past few years, deep learning methods have attracted a lot of research, and are
now heavily used in modern real-world recommender systems. Nevertheless,
dealing with recommendations in the cold-start setting, e.g., when a user has
done limited interactions in the system, is a problem that remains far from
solved. Meta-learning techniques, and in particular optimization-based
meta-learning, have recently become the most popular approaches in the academic
research literature for tackling the cold-start problem in deep learning models
for recommender systems. However, current meta-learning approaches are not
practical for real-world recommender systems, which have billions of users and
items, and strict latency requirements. In this paper we show that it is
possible to obtaining similar, or higher, performance on commonly used
benchmarks for the cold-start problem without using meta-learning techniques.
In more detail, we show that, when tuned correctly, standard and widely adopted
deep learning models perform just as well as newer meta-learning models. We
further show that an extremely simple modular approach using common
representation learning techniques, can perform comparably to meta-learning
techniques specifically designed for the cold-start setting while being much
more easily deployable in real-world applications
Molecular organization in MAPLEâdeposited conjugated polymer thin films and the implications for carrier transport characteristics
The morphological structure of poly(3âhexylthiophene) (P3HT) thin films deposited by both Matrix Assisted Pulsed Laser Evaporation (MAPLE) and solution spinâcasting methods are investigated. The MAPLE samples possessed a higher degree of disorder, with random orientations of polymer crystallites along the sideâchain stacking, ÏâÏ stacking, and conjugated backbone directions. Moreover, the average molecular orientations and relative degrees of crystallinity of MAPLEâdeposited polymer films are insensitive to the chemistries of the substrates onto which they were deposited; this is in stark contrast to the films prepared by the conventional spinâcasting technique. Despite the seemingly unfavorable molecular orientations and the highly disordered morphologies, the inâplane charge carrier transport characteristics of the MAPLE samples are comparable to those of spinâcast samples, exhibiting similar transport activation energies (56 vs. 54 meV) to those reported in the literature for high mobility polymers. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 39â48Molecular order in poly(3âhexylthiophene) (P3HT) films deposited by the novel vaporâassisted deposition technique Matrix Assisted Pulsed Laser Evaporation (MAPLE) was investigated. The structure of MAPLEâdeposited films is insensitive to the substrate chemistries and processes random crystallite orientation. The seemingly unfavorable morphology in MAPLEâdeposited samples however does not have detrimental effects on inâplane transport characteristics, suggesting that fieldâeffect carrier transport in conjugated polymer devices is resilient to structure.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135123/1/polb24237.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/135123/2/polb24237_am.pd
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