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With the increasing application of polyvinyl alcohol (PVA) films in the field of food packaging, it is important to improve its mechanical and antibacterial properties. This paper focuses on the preparation of PVA nanocomposite films and how their properties are affected by a silver-loaded nanocellulose solution. Cellulose nanocrystals (CNCs) were used as both the carrier and the dispersant of silver nanoparticles (AgNPs) prepared using glucose as the reducing agent. Ag+ was stabilized by the many hydroxyl groups located in the CNCs, and then the Ag+ was reduced to AgNPs in situ. After addition of silver-loaded nanocellulose, the tensile strength of the CNC-PVA-AgNP films increased from 47 MPa to 73 MPa, and the nanocomposite films displayed reduced moisture absorption and good antibacterial properties.

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In a searchable public-key encryption scheme with a designated tester (dPEKS), only the designated server can test which dPEKS ciphertext is related with a given trapdoor generated by a user with a keyword $w$ by using the server's private key, but learn nothing else. In this paper, we study the keyword guessing attack of dPEKS and shows that two dPEKS schemes are insecure against this type of attack. Then an enhanced scheme is proposed and proved secure against chosen keyword attack and keyword guessing attack. To resolve the problem that dPEKS scheme does not allow the user to decrypt the encrypted keyword which limits its applicability, we give the definition of decryptable searchable public key encryption with a designated tester which enables keyword decryption from keyword ciphertext and get a concrete construction based on our dPEKS scheme. At last, we extend the dPEKS scheme to a bidirectional searchable proxy re-encryption with a designated tester scheme(Re-dPEKS)

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In this work, hydrogels composed of cellulose nanofibril (CNF) and sodium alginate (SA) were prepared as a pH-responsive release system by controlling the amount of CNF and SA. Scanning electron microscopy, thermogravimetric analysis, and swelling rate methods were used to characterize. The results showed that when the mass ratio of CNF to SA was 2:1, CNF/SA hydrogels with better morphology were obtained. Due to the deprotonation or protonation of calcium alginate, as the pH changing from 1.5 to 11.0, the swelling ratio increased from 7 times to 19 times compared with its dry weight. The

Variations in temperature and precipitation affect local ecosystems. Considerable spatial and temporal heterogeneity exists in arid ecosystems such as desert steppes. In this study, we analyzed the spatiotemporal dynamics of climate and vegetation phenology in the desert steppe of Inner Mongolia, China using meteorological data (1961-2010) from 11 stations and phenology data (2004-2012) from 6 ecological observation stations. We also estimated the gross primary production for the period of 1982-2009 and found that the annual mean temperature increased at a rate of 0.47ºC/decade during 1961-2010, with the last 10 years being consistently warmer than the 50 years as an average. The most significant warming occurred in winters. Annual precipitation slightly decreased during the 50-year period, with summer precipitation experiencing the highest drop in the last 10 years, and spring precipitation, a rise. Spatially, annual precipitation increased significantly in the northeastern and eastern central areas next to the typical steppe. From 2004 to 2012, vegetation green-up and senescence date advanced in the study area, shortening the growing season. Consequently, the primary productivity of the desert steppe decreased along the precipitation gradient from southeast to northwest. Temporally, productivity increased during the period of 1982-1999 and significantly decreased after 2000. Overall, the last decade witnessed the most dramatic climatic changes that were likely to negatively affect the desert steppe ecosystem. The decreased primary productivity, in particular, decreases ecosystem resilience and impairs the livelihood of local farmers and herdsmen.

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