Improved SVD + + Recommendation Algorithm Based on Fusion Time Factor

Collaborative filtering algorithm is widely used in recommendation system. Aiming at the problems of data sparsity and low recommendation accuracy in traditional collaborative filtering algorithm, an improved recommendation algorithm is proposed PT _ SVD++. Firstly, the attribute information of users and the implicit feedback information of items are introduced to improve the SVD++ algorithm, which solves the insufficient utilization of information and alleviates the problem of sparse data；Secondly the time effect model is established to further improve the accuracy of the prediction results. The experimental results on MovieLens dataset show that compared with other algorithms, the average absolute error and root mean square error of this algorithm are lower, and its recommendation accuracy is higher

Website Service Quality and Shopping Website Stickiness: The Mediating Effect of Website Involvement

Website service quality has been considered to be important to increase users’ stickiness toward website in online shopping context. However, the underlying mechanism through which website service quality can influence shopping website stickiness remains unclear. In this study, the concept of website involvement was introduced to explain why people tend to favor sticking a shopping website. Also, four dimensions of website service quality (i.e. recovery , reliability, personalization, and responsiveness) were identified from existing related literature to influence consumers’ website involvement. Unlike prior studies, the “Stimulus-Organism- Response” model and an integrated framework combining the transactional view and the relational view of consumer-website interaction were used to test the relationship among website service quality , website involvement (cognitive involvement and affective involvement), and website stickiness. Empirical result shows that website service quality has no significant direct impact on website stickiness. However, it has significantly positive effects on both cognitive involvement and affective involvement, which in turn significantly correlate to website stickiness, indicating that website involvement plays full mediating role in the relation between website service quality and website stickiness. The results also indicate that consumer affective involvement strongly influences their cognitive involvement toward a shopping website

Enhanced large-scale production of laccases from Coriolopsis polyzona for use in dye bioremediation

Pollution from synthetic dyes, released by textile and paper pulping plants, draws major concern. Textile effluents have negative impact both on the environment and human health because they are toxic and some are carcinogenic. Apart from the textile industry, dyes are also widely used in manufacturing industries for leather products, cosmetics, pharmaceuticals, foods and beverages. It is known that white rot fungi can decolourise and detoxify various industrial effluents through the production of extracellular lignin modifying enzymes, a major class of which are laccases (EC 1.10.3.2). Considering the above, three strains of white rot fungi, Coriolopsis polyzona (MUCL 38443), Pleurotus ostreatus (ATCC no. MYA-2306) and Pycnoporus sanguineus (MUCL 41582) were studied for their ability to produce laccases in liquid media. The effects of mannan oligosaccharides (MO) as elicitor and ferulic acid as inducer were studied using central composite experimental design in liquid cultures of the three strains. The results showed that MO, either added alone or combined with ferulic acid, enhanced laccase activity in the three different cultures and the enhancement was species specific. The highest increase was in liquid cultures of P. sanguineus (88-fold) followed by P. ostreatus (3-fold) and C. polyzona (2-fold), among which C. polyzona resulted in the highest laccase activity. The combined addition of 150 mg/l of MO and 1 mM ferulic acid resulted in the optimal laccase activity by C. polyzona, whereas additions of 75 mg/l MO to the cultures of P. sanguineus and P. ostreatus led to the optimal activity. Extracellular laccase activity was considerably increased when C. polyzona was grown in glucose-bactopetone based culture medium induced by ferulic acid. The effect of inoculum conditions on laccase production was studied at reactor scales. Laccase activity achieved with conidia inoculation was higher compared with mycelium inoculation at the early stage of fermentation. However, the laccase levels were similar after 23 days of fermentation (110 U/ml and 100 U/ml for the conidia and mycelia pre-culture respectively). The conidia inoculation is preferred in scale-up when time-cost is considered. The maximal laccase activity with conidia inoculation in a 2 litre stirred tank reactor was 27% higher compared to that in shaken flasks. This showed that C. polyzona cultures have the potential to be scaled-up for increased laccase activity by applying conidia inoculum. The fermentation of C. polyzona was scaled-up to 20 litre and 150 litre stirred tank reactors applying fed-bath strategy. This resulted in 100 % enhancement of laccase activity. Addition of oak wood powder in the culture medium increased total laccase activity indicating the potential of lignocellulosic wastes as alternative substrates for enhanced laccase production with reducing cost. In order to investigate the application of laccases in dye decolourisation, two major laccase isozymes (Lac I & II) from C. polyzona were purified to apparent eletrophoretic homogenetity using hydrophobic interaction chromatography and ionexchange chromatography. Both enzymes were found to be monomeric proteins with the same molecular mass of 63 kDa, and isoelectronic point of 4.3. Their catalytic activities were studied under various substrates, pHs and temperatures. The highest enzyme affinity and efficiency were obtained with 2,2′-azino-bis- (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS). Compared with other fungal laccases, the laccases from C. polyzona have very low Km values with ABTS as a susbtrate. The optimum pHs were 2.8, 3.0 and 5.0 on ABTS, 2, 6-dimethoxyphenol (DMP) and syringaldazine, respectively. Both isozymes had acidic optimal pH values. However, they were more stable in netural pH rather than at acidic pH. Moreover, mass spectrometry (MS) analysis of tryptic digestion products of the two isozymes was performed, which showed further similarity of these two isozymes. As common physical or chemical methods for dye removal are expensive, have low efficiency and sometimes generate other pollutants, the decolourisation of industrial effluents containing single and mixed dyes was investigated using purified laccase (Lac I) from C. polyzona as well as whole cell culture. The method appeared to be an attractive alternative for dye removal. Anthraquinone dyes were found to be more easily decolourised by Lac I compared to azo dyes. The addition of redox mediator ABTS and violuric acid (VA) improved considerably the catalytic efficiencies of azo dyes. Decolourisation, 40-50 %, was achieved for the reactive and the direct dye baths. Response surface technology (RSM) was applied to optimise the decolourisation of the diazo dye reactive black 5 (RB 5) by Lac I. Box-Behnken experimental design with three variables including laccase activity (100, 200, 300 U/l), pH (5, 7, 9) and VA concentration (0, 1.25, 2.5 mM) was studied to identify a significant correlation between the effect of these variables on decolourisation of RB5. The experimental values were in good agreement with the predicted values with the correlation coefficient of 97.4%.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Biogeography of Free-living and Particle-Associated Bacteria in the St. Lawrence Estuary

The St. Lawrence Estuary (SLE) is a productive ecosystem characterized by steep gradients in salinity and dissolved oxygen (DO). The SLE has been well studied in terms of physical and chemical properties, however bacterial diversity and community structure have not been documented in this large estuarine system. Here, we used 16S rRNA gene surveys to assess the bacterial community structure of both the free-living (FL) and particle-associated (PA) fractions of the bacterial community. Non-metric multidimensional scaling (NMS) ordinations and ANOSIM analysis showed that bacterial communities inhabiting particles were distinct from those found free-living in the water column, and this structure held true for both surface communities and those inhabiting the bottom waters. Taxonomic assignment of 16S DNA sequences revealed a shift in the bacterial community structure along the surface salinity gradient of the SLE. In general, Proteobacteria were more common in the free-living fraction, while Bacteroidetes were more commonly associated with particles. Moreover, particleassociated bacterial communities had an abundance of Alteromonadales in the deep hypoxic waters and free-living bacteria exhibited a greater abundance of Marine Group A and Delta-proteobacteria. These findings are shedding light on the diversity of bacterial taxa inhabiting the SLE and further metagenomic analysis will elucidate the metabolic contribution of these bacterial communities

Porcine rotavirus mainly infects primary porcine enterocytes at the basolateral surface

Intestinal epithelium functions as a barrier to protect multicellular organisms from the outside world. It consists of epithelial cells closely connected by intercellular junctions, selective gates which control paracellular difusion of solutes, ions and macromolecules across the epithelium and keep out pathogens. Rotavirus is one of the major enteric viruses causing severe diarrhea in humans and animals. It specifcally infects the enterocytes on villi of small intestines. The polarity of rotavirus replication in their target enterocytes and the role of intestinal epithelial integrity were examined in the present study. Treatment with EGTA, a drug that chelates calcium and disrupts the intercellular junctions, (i) signifcantly enhanced the infection of rotavirus in primary enterocytes, (ii) increased the binding of rotavirus to enterocytes, but (iii) considerably blocked internalization of rotavirus. After internalization, rotavirus was resistant to EGTA treatment. To investigate the polarity of rotavirus infection, the primary enterocytes were cultured in a transwell system and infected with rotavirus at either the apical or the basolateral surface. Rotavirus preferentially infected enterocytes at the basolateral surface. Restriction of infection through apical inoculation was overcome by EGTA treatment. Overall, our fndings demonstrate that integrity of the intestinal epithelium is crucial in the host’s innate defense against rotavirus infection. In addition, the intercellular receptor is located basolaterally and disruption of intercellular junctions facilitates the binding of rotavirus to their receptor at the basolateral surface

Algebraic Key-Recovery Attacks on Reduced-Round Xoofff

Farfalle, a permutation-based construction for building a pseudorandom function (PRF), is really versatile. It can be used for message authentication code, stream cipher, key derivation function, authenticated encryption and so on. Farfalle construction relies on a set of permutations and on so-called rolling functions: it can be split into a compression layer followed by a two-step expansion layer. As one instance of Farfalle, Xoofff is very efficient on a wide range of platforms from low-end devices to high-end processors by combining the narrow permutation Xoodoo and the inherent parallelism of Farfalle. In this paper, we present key-recovery attacks on reduced-round Xoofff. After identifying a weakness in the expanding rolling function, we first propose practical attacks on Xoofff instantiated with 1-/2-round Xoodoo in the expansion layer. We next extend such attack on Xoofff instantiated with 3-/4-round Xoodoo in the expansion layer by making use of Meet-in-the-Middle algebraic attacks and the linearization technique. All attacks proposed here -- which are independent of the details of the compression and/or middle layer -- have been practically verified (either on the real Xoofff or on a toy-version Xoofff with block-size of 96 bits). As a countermeasure, we discuss how to slightly modified the rolling function for free to reduce the number of attackable rounds

Role of Porcine Aminopeptidase N and Sialic Acids in Porcine Coronavirus Infections in Primary Porcine Enterocytes.

Porcine epidemic diarrhea virus (PEDV) and transmissible gastroenteritis virus (TGEV) have been reported to use aminopeptidase N (APN) as a cellular receptor. Recently, the role of APN as a receptor for PEDV has been questioned. In our study, the role of APN in PEDV and TGEV infections was studied in primary porcine enterocytes. After seven days of cultivation, 89% of enterocytes presented microvilli and showed a two- to five-fold higher susceptibility to PEDV and TGEV. A significant increase of PEDV and TGEV infection was correlated with a higher expression of APN, which was indicative that APN plays an important role in porcine coronavirus infections. However, PEDV and TGEV infected both APN positive and negative enterocytes. PEDV and TGEV Miller showed a higher infectivity in APN positive cells than in APN negative cells. In contrast, TGEV Purdue replicated better in APN negative cells. These results show that an additional receptor exists, different from APN for porcine coronaviruses. Subsequently, treatment of enterocytes with neuraminidase (NA) had no effect on infection efficiency of TGEV, implying that terminal cellular sialic acids (SAs) are no receptor determinants for TGEV. Treatment of TGEV with NA significantly enhanced the infection which shows that TGEV is masked by SAs

Role of porcine amino peptidase N and sialic acids in porcine coronavirus infections in primary porcine enterocytes

Porcine epidemic diarrhea virus (PEDV) and transmissible gastroenteritis virus (TGEV) have been reported to use aminopeptidase N (APN) as a cellular receptor. Recently, the role of APN as a receptor for PEDV has been questioned. In our study, the role of APN in PEDV and TGEV infections was studied in primary porcine enterocytes. After seven days of cultivation, 89% of enterocytes presented microvilli and showed a two- to five-fold higher susceptibility to PEDV and TGEV. A significant increase of PEDV and TGEV infection was correlated with a higher expression of APN, which was indicative that APN plays an important role in porcine coronavirus infections. However, PEDV and TGEV infected both APN positive and negative enterocytes. PEDV and TGEV Miller showed a higher infectivity in APN positive cells than in APN negative cells. In contrast, TGEV Purdue replicated better in APN negative cells. These results show that an additional receptor exists, different from APN for porcine coronaviruses. Subsequently, treatment of enterocytes with neuraminidase (NA) had no effect on infection efficiency of TGEV, implying that terminal cellular sialic acids (SAs) are no receptor determinants for TGEV. Treatment of TGEV with NA significantly enhanced the infection which shows that TGEV is masked by SAs