Uncovering Download Fraud Activities in Mobile App Markets

Download fraud is a prevalent threat in mobile App markets, where fraudsters manipulate the number of downloads of Apps via various cheating approaches. Purchased fake downloads can mislead recommendation and search algorithms and further lead to bad user experience in App markets. In this paper, we investigate download fraud problem based on a company's App Market, which is one of the most popular Android App markets. We release a honeypot App on the App Market and purchase fake downloads from fraudster agents to track fraud activities in the wild. Based on our interaction with the fraudsters, we categorize download fraud activities into three types according to their intentions: boosting front end downloads, optimizing App search ranking, and enhancing user acquisition&retention rate. For the download fraud aimed at optimizing App search ranking, we select, evaluate, and validate several features in identifying fake downloads based on billions of download data. To get a comprehensive understanding of download fraud, we further gather stances of App marketers, fraudster agencies, and market operators on download fraud. The followed analysis and suggestions shed light on the ways to mitigate download fraud in App markets and other social platforms. To the best of our knowledge, this is the first work that investigates the download fraud problem in mobile App markets.Comment: Published as a conference paper in IEEE/ACM ASONAM 201

Greener, Safer and Better Performing Aqueous Binder for Positive Electrode Manufacturing of Sodium Ion Batteries

P2-type cobalt-free MnNi-based layered oxides are promising cathode materials for sodium-ion batteries (SIBs) due to their high reversible capacity and well chemical stability. However, the phase transformations during repeated (dis)charge steps lead to rapid capacity decay and deteriorated Na+ diffusion kinetics. Moreover, the electrode manufacturing based on polyvinylidene difluoride (PVDF) binder system has been reported with severely defluorination issue as well as the energy intensive and expensive process due to the use of toxic and volatile N-methyl-2-pyrrolidone (NMP) solvent. It calls for designing a sustainable, better performing, and cost-effective binder for positive electrode manufacturing. In this work, we investigated inorganic sodium metasilicate (SMS) as a viable binder in conjunction with P2-Na0.67Mn0.55Ni0.25Fe0.1Ti0.1O2 (NMNFT) cathode material for SIBs. The NMNFT-SMS electrode delivered a superior electrochemical performance compared to carboxy methylcellulose (CMC) and PVDF based electrodes with a reversible capacity of ~161 mAh/g and retaining ~83 % after 200 cycles. Lower cell impedance and faster Na+ diffusion was also observed in this binder system. Meanwhile, with the assistance of TEM technique, SMS is suggested to form a uniform and stable nanoscale layer over the cathode particle surface, protecting the particle from exfoliation/cracking due to electrolyte attack. It effectively maintained the electrode connectivity and suppressed early phase transitions during cycling as confirmed by operando XRD study. With these findings, SMS binder can be proposed as a powerful multifunctional binder to enable positive electrode manufacturing of SIBs and to overall reduce battery manufacturing costs

Overexpression of Na ؉ -Dependent Myo-inositol Transporter Gene in Mouse Lens Led to Congenital Cataract

PURPOSE. Maintaining appropriate osmotic pressure is essential for maintaining lens transparency. This study was performed to investigate whether high levels of myo-inositol, one of the major organic osmolytes in the lens, would lead to cataract development. METHODS. Transgenic mouse lines carrying the bovine Na ϩ -dependent myo-inositol transporter (bSMIT) cDNA under the control of the mouse ␣A-crystallin promoter were generated. RESULTS. Increased bSMIT expression was accompanied by increased myo-inositol level in the lens and increased uptake of ( 3 H) myo-inositol by the lens in culture. The transgenic mice developed observable cataract under normal rearing conditions beginning at 2 to 8 weeks of age, and the severity of cataract development was correlated to the level of bSMIT gene expression and lens myo-inositol accumulation. For transgenic mouse line 3352, heterozygous mice did not develop cataract, whereas homozygous ones did. Prenatal feeding of heterozygous 3352 mice with high myo-inositol diet led to cataract development, indicating that cataract development was not merely due to a nonspecific effect of SMIT overexpression. Introducing aldose reductase overexpressing transgene into heterozygous 3352 mice also led to cataract development, indicating that this type of cataract is primarily due to osmotic stress. CONCLUSIONS. The present results indicate that high levels of myo-inositol and sorbitol in the lens contribute to cataract development. This is a useful model to study the role of osmotic stress in cataractogenesis during lens development. (Invest Ophthalmol Vis Sci. 2000;41:1467-1472 C ataract is the most important cause of blindness in the world. Nearly 16 million people are estimated to be blind because of cataract. 1 There are a number of causes for cataract, including congenital cataract, cataract from infection, cataract from UV and X-ray irradiation and oxidation damage, and cataract associated with several diseases, particularly diabetes. The transparency in mammalian lenses is due to the presence of crystallin structures formed by highly ordered association of several proteins. Changes in ionic environment, a reduction in the level of antioxidants such as reduced glutathione and ascorbic acid, and changes in the level of other solutes may lead to random protein aggregation and disruption of the crystallin structures, resulting in lens opacity and cataract. Therefore, the lens needs to stabilize the intracellular osmotic pressure by regulating the influx and efflux of water, osmolytes, and other solutes. Osmotic stress due to the accumulation of sorbitol in the lens is most likely the cause of diabetic cataract. This is based on the fact that sorbitol accumulates to high levels in the lenses of diabetic animals 6 Development of lens opacity in vitro can be prevented by AR inhibitors or if the medium is made hypertonic to balance the increased sorbitol accumulation in the lens, indicating that osmotic stress is the cause of diabetic cataract. 9 To determine whether cataract caused by sorbitol accumulation is a consequence of osmotic stress rather than the toxic effect of sorbitol, we wanted to increase the lens myoinositol (MI) level to see if that also causes cataract. Myoinositol is one of the three major osmolytes in the lens besides sorbitol and taurine. 10 Influx of MI into lens is dependent on the Na ϩ -dependent MI transporter (SMIT). 11 In this study, we produced transgenic mice that overexpress SMIT constitutively in lens cells and found that they developed congenital cataract under normal rearing condition beginning at 2 to 8 weeks of age. These results provide strong evidence that a high level o

The characterisation of diesel exhaust particles - composition, size distribution and partitioning

A number of major research questions remain concerning the sources and properties of road traffic generated particulate matter. A full understanding of the composition of primary vehicle exhaust aerosol and its contribution to secondary organic aerosol (SOA) formation still remains elusive, and many uncertainties exist relating to the semi-volatile component of the particles. Semi-Volatile Organic Compounds (SVOCs) are compounds which partition directly between the gas and aerosol phases under ambient conditions. The SVOCs in engine exhaust are typically hydrocarbons in the C15–C35range, and are largely uncharacterised because they are unresolved by traditional gas chromatography, forming a large hump in the chromatogram referred to as Unresolved Complex Mixture (UCM). In this study, thermal desorption coupled to comprehensive Two Dimensional Gas-Chromatography Time-of-Flight Mass-Spectrometry (TD-GC × GC-ToF-MS) was exploited to characterise and quantify the composition of SVOCs from the exhaust emission. Samples were collected from the exhaust of a diesel engine, sampling before and after a diesel oxidation catalyst (DOC), while testing at steady state conditions. Engine exhaust was diluted with air and collected using both filter and impaction (nano-MOUDI), to resolve total mass and size resolved mass respectively. Adsorption tubes were utilised to collect SVOCs in the gas phase and they were then analysed using thermal desorption, while particle size distribution was evaluated by sampling with a DMS500. The SVOCs were observed to contain predominantlyn-alkanes, branched alkanes, alkyl-cycloalkanes, alkyl-benzenes, PAHs and various cyclic aromatics. Particle phase compounds identified were similar to those observed in engine lubricants, while vapour phase constituents were similar to those measured in fuels. Preliminary results are presented illustrating differences in the particle size distribution and SVOCs composition when collecting samples with and without a DOC. The results indicate that the DOC tested is of very limited efficiency, under the studied engine operating conditions, for removal of SVOCs, especially at the upper end of the molecular weight range.</p

Activated dissociation of O2 on Pb(111) surfaces by Pb adatoms

We investigate the dissociation of O2 on Pb(111) surface using first-principles calculations. It is found that in a practical high-vacuum environment, the adsorption of molecular O2 takes place on clean Pb surfaces only at low temperatures such as 100 K, but the O2 easily desorbs at (elevated) room temperatures. It is further found that the Pb adatoms enhance the molecular adsorption and activate the adsorbed O2 to dissociate during subsequent room-temperature annealing. Our theory explains the observation of a two-step oxidation process on the Pb surfaces by the unique role of Pb adatoms

Continuity of transcriptomes among colorectal cancer subtypes based on meta-analysis

Background: Previous approaches to defining subtypes of colorectal carcinoma (CRC) and other cancers based on transcriptomes have assumed the existence of discrete subtypes. We analyze gene expression patterns of colorectal tumors from a large number of patients to test this assumption and propose an approach to identify potentially a continuum of subtypes that are present across independent studies and cohorts. Results: We examine the assumption of discrete CRC subtypes by integrating 18 published gene expression datasets and \u3e3700 patients, and contrary to previous reports, find no evidence to support the existence of discrete transcriptional subtypes. Using a meta-analysis approach to identify co-expression patterns present in multiple datasets, we identify and define robust, continuously varying subtype scores to represent CRC transcriptomes. The subtype scores are consistent with established subtypes (including microsatellite instability and previously proposed discrete transcriptome subtypes), but better represent overall transcriptional activity than do discrete subtypes. The scores are also better predictors of tumor location, stage, grade, and times of disease-free survival than discrete subtypes. Gene set enrichment analysis reveals that the subtype scores characterize T-cell function, inflammation response, and cyclin-dependent kinase regulation of DNA replication. Conclusions: We find no evidence to support discrete subtypes of the CRC transcriptome and instead propose two validated scores to better characterize a continuity of CRC transcriptomes

IκBα polymorphism at promoter region (rs2233408) influences the susceptibility of gastric cancer in Chinese

<p>Abstract</p> <p>Background</p> <p>Nuclear factor of kappa B inhibitor alpha (IκBα) protein is implicated in regulating a variety of cellular process from inflammation to tumorigenesis. The objective of this study was to investigate the susceptibility of rs2233408 T/C genotype in the promoter region of <it>IκBα </it>to gastric cancer and the association of this polymorphism with clinicopathologic variables in gastric cancer patients.</p> <p>Methods</p> <p>A population-based case-control study was conducted between 1999 and 2006 in Guangdong Province, China. A total of 564 gastric cancer patients and 566 healthy controls were enrolled in this study. rs2233408 genotypes in <it>IκBα </it>were analyzed by TaqMan SNP genotyping assay.</p> <p>Results</p> <p>Both rs2233408 T homozygote (TT) and T heterozygotes (TC and TT) had significantly reduced gastric cancer risk (TT: OR = 0.250, 95% CI = 0.069-0.909, <it>P </it>= 0.035; TC and TT: OR = 0.721, 95% CI = 0.530-0.981, <it>P </it>= 0.037), compared with rs2233408 C homozygote (CC). rs2233408 T heterozygotes were significantly associated with reduced risk of intestinal-type gastric cancer with ORs of 0.648 (95% CI = 0.459-0.916, <it>P </it>= 0.014), but not with the diffuse or mix type of gastric cancer. The association between rs2233408 T heterozygotes and gastric cancer appeared more apparent in the older patients (age>40) (OR = 0.674, 95% CI = 0.484-0.939, <it>P </it>= 0.02). rs2233408 T heterozygotes was associated with non-cardiac gastric cancer (OR = 0.594, 95% CI = 0.411-0.859, <it>P </it>= 0.006), but not with cardiac gastric cancer. However, rs2233408 polymorphism was not associated with the prognosis of gastric cancer patients.</p> <p>Conclusions</p> <p><it>IκBα </it>rs2233408 T heterozygotes were associated with reduced risk of gastric cancer, especially for the development of certain subtypes of gastric cancer in Chinese population.</p