An Efficient Viologen-Based Electron Donor to Nitrogenase

Nitrogenase catalyzes the reduction of N2 to NH3, supporting all biological nitrogen fixation. Electron donors to this enzyme are ferredoxin or flavodoxin (in vivo) and sodium dithionite (in vitro). Features of these electron donors put a limit on spectrophotometric studies and electrocatalytic applications of nitrogenase. Although it is common to use methyl viologen as an electron donor for many low-potential oxidoreductases, decreased nitrogenase activity is observed with an increasing concentration of methyl viologen, limiting its utility under many circumstances. In this work, we suggest that this concentration-dependent decrease in activity can be explained by the formation of a dimer of the radical cation of methyl viologen (Me2V•+)2 at higher methyl viologen concentrations. In addition, viologens functionalized with positively and negatively charged groups were synthesized and studied using spectroscopy and cyclic voltammetry. A sulfonated viologen derivative, 1,1′-bis(3-sulfonatopropyl)-4,4′-bipyridinium radical {[(SPr)2V•]−}, was found to support full nitrogenase activity up to a mediator concentration of 3 mM, while the positively charged viologen derivative was not an efficient reductant of nitrogenase due to the high standard redox potential. The utility of [(SPr)2V•]− as an electron donor for nitrogenase was demonstrated by a simple, sensitive spectrophotometric assay for nitrogenase activity that can provide accurate values for the specific activity and turnover rate constant under argon. Under N2, the formation of ammonia was confirmed. Because of the observed full activity of nitrogenase and low overpotential, [(SPr)2V•]− should also prove to be valuable for nitrogenase electrocatalysis, including bioelectrosynthetic N2 reduction

Genetic Variations rs859, rs4646, and rs372883 in the 3′-Untranslated Regions of Genes Are Associated with a Risk of IgA Nephropathy

Background: Previous studies indicate that genetic factors play an important role in the pathogenesis of IgA nephropathy (IgAN). To evaluate the association between single nucleotide polymorphisms (SNPs) in the 3′-untranslated region (3′-UTR) of genes and IgAN risk, we performed a case-control study in a Chinese Han population. Materials: Twelve SNPs were selected and genotyped in 384 IgAN patients and 357 healthy controls. Odds ratio (OR) and 95% confidence intervals (CI) were calculated by logistic regression adjusted for age and gender. Multifactor dimensionality reduction (MDR) was used to analyze the interaction of SNP-SNP with IgAN risk. Results: Our study demonstrated that IL-16 rs859 (OR = 0.75, p = 0.040) and CYP19A1 rs4646 (OR = 2.58, p = 0.017) polymorphism were related to the risk of IgAN. In stratified analyses by gender, CYP19A1 rs4646 (OR = 2.96, p = 0.015) and BACH1 rs372883 (OR = 1.81, p = 0.038) polymorphisms conferred susceptibility to IgAN in males. Besides, rs372883 reduced IgAN risk in females (OR = 0.44, p = 0.042). We also found rs859 polymorphism was correlated with grade I-II (OR = 0.42, p = 0.028) in subgroup analysis of Lee’s classification. Additionally, we found rs4646 polymorphism was correlated with serum creatinine (p = 0.035). Conclusion: Our results suggested that the IL-16 rs859, CYP19A1 rs4646, and BACH1 rs372883 polymorphisms have potential roles in the genetic susceptibility to IgAN in Chinese Han population

Host Phylogeny and Diet Shape Gut Microbial Communities Within Bamboo-Feeding Insects

The gut microbiome plays an important role in a host’s development and adaption to its dietary niche. In this study, a group of bamboo-feeding insects are used to explore the potential role of the gut microbiota in the convergent adaptation to extreme diet specialization. Specifically, using a 16S rRNA marker and an Illumina sequencing platform, we profiled the microbial communities of 76 gut samples collected from nine bamboo-feeding insects, including both hemimetabolous (Orthoptera and Hemiptera) and holometabolous (Coleoptera and Lepidoptera) species, which are specialized in three distinct dietary niches: bamboo leaf, shoot, and sap. The gut microbiota of these insects were dominated by Proteobacteria, Firmicutes, and Bacteroidetes and were clustered into solid (leaf and shoot) and liquid (sap) dietary niches. The gut bacterial communities of insects feeding on solid diet overlapped significantly, even though these insects belong to phylogenetically distant lineages representing different orders. In addition, the presence of cellulolytic bacterial communities within the gut microbiota allows bamboo-feeding insects to adapt to a highly specialized, fiber-rich diet. Although both phylogeny and diet can impact the structure and composition of gut microbiomes, phylogeny is the primary driving force underlying the convergent adaptation to a highly specialized diet, especially when the related insect species harbor similar gut microbiomes and share the same dietary niche over evolutionary timescales. These combined findings lay the foundation for future research on how convergent feeding strategies impact the interplays between hosts and their gut microbiomes and how the gut microbiota may facilitate convergent evolution in phylogenetically distant species in adaptation to the shared diet

North Expansion of Winter Wheat Planting Area in China under Different Emissions Scenarios

Suitable planting areas for winter wheat in north China are expected to shift northwardly due to climate change, however, increasing extreme events and the deficient water supply are threatening the security of planting systems. Thus, based on predicted climate data for 2021–2050 under the Shared Socioeconomic Pathways (SSP1-2.6, SSP3-7.0, and SSP5-8.5) emission scenarios, as well as historical data from 1961–1990, we use four critical parameters of percentages of extreme minimum temperature years (POEMTY), first day of the overwintering period (FD), sowing date (SD), and precipitation before winter (PBW), in order to determine the planting boundary of winter wheat. The results show that the frequency of extreme minimum temperature occurrences is expected to decrease in the North winter wheat area, which will result in a northward movement of the western part of northern boundary by 73, 94, and 114 km on average, in addition to FD delays ranging from 6.0 to 10.5 days. Moreover, agrometeorological conditions in the Huang-Huai winter wheat area are expected to exhibit more pronounced changes than the rest of the studied areas, especially near the southern boundary, which is expected to retreat by approximately 213, 215, and 233 km, northwardly. The north boundary is expected to move 90–140 km northward. Therefore, the change in southern and northern boundaries will lead the potential planting areas of the entire North winter wheat area to increase by 10,700 and 28,000 km2 on average in the SSP3-7.0 and SSP5-8.5 scenarios, respectively, but to decrease by 38,100 km2 in the SSP1-2.6 scenario; however, the lack of precipitation remains a limitation for extending planting areas in the future

North Expansion of Winter Wheat Planting Area in China under Different Emissions Scenarios

Suitable planting areas for winter wheat in north China are expected to shift northwardly due to climate change, however, increasing extreme events and the deficient water supply are threatening the security of planting systems. Thus, based on predicted climate data for 2021–2050 under the Shared Socioeconomic Pathways (SSP1-2.6, SSP3-7.0, and SSP5-8.5) emission scenarios, as well as historical data from 1961–1990, we use four critical parameters of percentages of extreme minimum temperature years (POEMTY), first day of the overwintering period (FD), sowing date (SD), and precipitation before winter (PBW), in order to determine the planting boundary of winter wheat. The results show that the frequency of extreme minimum temperature occurrences is expected to decrease in the North winter wheat area, which will result in a northward movement of the western part of northern boundary by 73, 94, and 114 km on average, in addition to FD delays ranging from 6.0 to 10.5 days. Moreover, agrometeorological conditions in the Huang-Huai winter wheat area are expected to exhibit more pronounced changes than the rest of the studied areas, especially near the southern boundary, which is expected to retreat by approximately 213, 215, and 233 km, northwardly. The north boundary is expected to move 90–140 km northward. Therefore, the change in southern and northern boundaries will lead the potential planting areas of the entire North winter wheat area to increase by 10,700 and 28,000 km2 on average in the SSP3-7.0 and SSP5-8.5 scenarios, respectively, but to decrease by 38,100 km2 in the SSP1-2.6 scenario; however, the lack of precipitation remains a limitation for extending planting areas in the future

Security Implications of Password Discretization for Click-based Graphical Passwords*

Discretization is a standard technique used in click-based graphical passwords for tolerating input variance so that approximately correct passwords are accepted by the system. In this paper, we show for the first time that two representative discretization schemes leak a significant amount of password information, undermining the security of such graphical passwords. We exploit such information leakage for successful dictionary attacks on Persuasive Cued Click Points (PCCP), which is to date the most secure click-based graphical password scheme and was considered to be resistant to such attacks. In our experiments, our purely automated attack successfully guessed 69.2 % of the passwords when Centered Discretization was used to implement PCCP, and 39.4 % of the passwords when Robust Discretization was used. Each attack dictionary we used was of approximately 2 ��� � entries, whereas the full password space was of 2 ��� � entries. For Centered Discretization, our attack still successfully guessed 50 % of the passwords when the dictionary size was reduced to approximately 2 ��� � entries. Our attack is also applicable to common implementations of other click-based graphical password systems such as PassPoints and Cued Click Points – both have been extensively studied in the research communities

Captcha as graphical passwords:a new security primitive based on hard AI problems

Many security primitives are based on hard mathematical problems. Using hard AI problems for security is emerging as an exciting new paradigm, but has been under-explored. In this paper, we present a new security primitive based on hard AI problems, namely, a novel family of graphical password systems built on top of Captcha technology, which we call Captcha as graphical passwords (CaRP). CaRP is both a Captcha and a graphical password scheme. CaRP addresses a number of security problems altogether, such as online guessing attacks, relay attacks, and, if combined with dual-view technologies, shoulder-surfing attacks. Notably, a CaRP password can be found only probabilistically by automatic online guessing attacks even if the password is in the search set. CaRP also offers a novel approach to address the well-known image hotspot problem in popular graphical password systems, such as PassPoints, that often leads to weak password choices. CaRP is not a panacea, but it offers reasonable security and usability and appears to fit well with some practical applications for improving online security

Security analyses of click-based graphical passwords via image point memorability

We propose a novel concept and a model of image point memorability (IPM) for analyzing click-based graphical passwords that have been studied extensively in both the security and HCI communities. In our model, each point in an image is associated with a numeric index that indicates the point's memorability level. This index can be approximated either by automatic computer vision algorithms or via human assistance. Using our model, we can rank-order image points by their relative memorability with a decent accuracy. We show that the IPM model has both defensive and offensive applications. On the one hand, we apply the model to generate high-quality graphical honeywords. This is the first work on honeywords for graphical passwords, whereas all previous methods are only for generating text honeywords and thus inapplicable. On the other hand, we use the IPM model to develop the first successful dictionary attacks on Persuasive Cued Click Points (PCCP), which is the state-of-the-art click-based graphical password scheme and robust to all prior dictionary attacks. We show that the probability distribution of PCCP passwords is seriously biased when it is examined with the lens of the IPM model. Although PCCP was designed to generate random passwords, its effective password space as we measured can be as small as 30.58 bits, which is substantially weaker than its theoretical and commonly believed strength (43 bits). The IPM model is applicable to all click-based graphical password schemes, and our analyses can be extended to other graphical passwords as well

A Kinetic and Mechanismic Study of Plasma-Induced Degradation of Monochloropropionic Acids in Water by Means of Anodic Contact Glow Discharge Electrolysis

Decomposition of aqueous monochloropropionic acids (MCPAs) was investigated by means of anodic contact glow discharge electrolysis (CGDE). With the decay of MCPAs, the corresponding total organic carbon (TOC) also decreased smoothly. Furthermore, it was found that chlorine atoms in the MCPAs were released as chloride ions. As the main by-products, oxalic acid and formic acid were detected. The acetic acid (CA), monochloroacetic acid (MCA), and propanedioic acid (PDA) were also detected as the primary intermediates for decomposition of the corresponding MCPAs. The decay of both MCPAs and TOC obeyed the first-order kinetics, respectively. The apparent rate constant for the decay of MCPAs increased with the increase in pKa values of MCPAs, while that for the decay of TOC was substantially unaffected. The reaction pathway involving the successive attack of hydroxyl radical and the carbon chain cleavage were discussed based on the products and kinetics