3,592 research outputs found

    On the variance of sums of arithmetic functions over primes in short intervals and pair correlation for L-functions in the Selberg class

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    We establish the equivalence of conjectures concerning the pair correlation of zeros of LL-functions in the Selberg class and the variances of sums of a related class of arithmetic functions over primes in short intervals. This extends the results of Goldston & Montgomery [7] and Montgomery & Soundararajan [11] for the Riemann zeta-function to other LL-functions in the Selberg class. Our approach is based on the statistics of the zeros because the analogue of the Hardy-Littlewood conjecture for the auto-correlation of the arithmetic functions we consider is not available in general. One of our main findings is that the variances of sums of these arithmetic functions over primes in short intervals have a different form when the degree of the associated LL-functions is 2 or higher to that which holds when the degree is 1 (e.g. the Riemann zeta-function). Specifically, when the degree is 2 or higher there are two regimes in which the variances take qualitatively different forms, whilst in the degree-1 case there is a single regime

    Chromosome Organization in Meiosis

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    Our objective is to understand the mechanics of homologous chromosome pairing during meiosis. Aberrant pairing can result in nondisjunction and birth defects in humans. This study used yeast, Saccharomyces cerevisiae, with chromosomally‐integrated arrays of tetO operators that bind TetR repressor proteins fused to GFP to produce a fluorescent signal. In diploid cells, the tetO/TetR‐GFP system allows homologous chromosomes to be identified as two foci (unpaired) or one focus (paired) as they progress through meiosis. We conducted three replicate timecourse experiments, analysing three different stages of meiosis, t=0 hours: pre‐meiotic, t=3 hours: pairing transition, and t=5 hours: synapsis. At each stage, the cells were imaged for 25 minutes, with z‐stacks taken at 30 second intervals. To analyse individual cells, we developed a 4D image analysis pipeline in MATLAB that allowed us to calculate the mean squared change in distance (MSCD), a metric describing the distance between two foci, and analyse deviations from normal diffusive motion

    Ice nucleation and cloud microphysical properties in tropical tropopause layer cirrus

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    In past modeling studies, it has generally been assumed that the predominant mechanism for nucleation of ice in the uppermost troposphere is homogeneous freezing of aqueous aerosols. However, recent in situ and remote-sensing measurements of the properties of cirrus clouds at very low temperatures in the tropical tropopause layer (TTL) are broadly inconsistent with theoretial predictions based on the homogeneous freezing assumption. The nearly ubiquitous occurence of gravity waves in the TTL makes the predictions from homogeneous nucleation theory particularly difficult to reconcile with measurements. These measured properties include ice number concentrations, which are much lower than theory predicts; ice crystal size distributions, which are much broader than theory predicts; and cloud extinctions, which are much lower than theory predicts. Although other explanations are possible, one way to limit ice concentrations is to have on the order of 50 L<sup>−1</sup> effective ice nuclei (IN) that could nucleate ice at relatively low supersaturations. We suggest that ammonium sulfate particles, which would be dry much of the time in the cold TTL, are a potential IN candidate for TTL cirrus. However, this mechanism remains to be fully quantified for the size distribution of ammonium sulfate (possibly internally mixed with organics) actually present in the upper troposphere. Possible implications of the observed cloud microphysical properties for ice sedimentation, dehydration, and cloud persistence are also discussed

    Advanced Multilevel Node Separator Algorithms

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    A node separator of a graph is a subset S of the nodes such that removing S and its incident edges divides the graph into two disconnected components of about equal size. In this work, we introduce novel algorithms to find small node separators in large graphs. With focus on solution quality, we introduce novel flow-based local search algorithms which are integrated in a multilevel framework. In addition, we transfer techniques successfully used in the graph partitioning field. This includes the usage of edge ratings tailored to our problem to guide the graph coarsening algorithm as well as highly localized local search and iterated multilevel cycles to improve solution quality even further. Experiments indicate that flow-based local search algorithms on its own in a multilevel framework are already highly competitive in terms of separator quality. Adding additional local search algorithms further improves solution quality. Our strongest configuration almost always outperforms competing systems while on average computing 10% and 62% smaller separators than Metis and Scotch, respectively

    CSIRO Marine and Atmospheric Research, 2

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    With over 84 % of Australians living in urban areas (populations over 30,000), the outcome of the current debate on water use in cities and how to match water demand to supply under both current and future climates, has the potential to affect many Australians. Lacking in this debate is a sound quantitative basis for assessing the environmental and economic benefits of water use in urban areas. As an example, while water sensitive urban design (WSUD) is widely accepted as a tool to manage the impacts of urbanisation by careful design at the house and street scale, its focus has largely been on managing and re-using the runoff (stormwater and wastewater) component of the water balance. Much less attention has been paid to the role of urban evapotranspiration (ET) by urban hydrologists, even though this it is often the biggest output in the water balance. Evapotranspiration is the process that links the movement of water through a landscape with the local climate, with the process using energy that would otherwise contribute to elevated air temperatures. This passive control of the local climate via urban vegetation and ET has a direct influence on quantities of energy used in space heating and cooling through the role of urban ET and also because trees provide shade and shelter. This link between the urban water and energy balances, and microclimate, is demonstrated by considering the following simplified expressions for i) the urban water balance: P+ I = ET + D+ΔS (1) where the inputs are: P = precipitation; I = piped water supply (for external and internal uses); and the outputs are: ET = urban evapotranspiration; D = stormwater and wastewater; ΔS = change in stored water on and within the surface materials; and ii) the urban energy balance: Q + QF = QH + QE +ΔQ

    Bayesian signaling game based efficient security model for MANETs

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    Game Theory acts as a suitable tool offering promising solutions to security-related concerns in Mobile Ad Hoc Networks (i.e., MANETs). In MANETs, security forms a prominent concern as it includes nodes which are usually portable and require significant coordination between them. Further, the absence of physical organisation makes such networks susceptible to security breaches, hindering secure routing and execution among nodes. Game Theory approach has been manipulated in the current study to achieve an analytical view while addressing the security concerns in MANETs. This paper offers a Bayesian-Signaling game model capable of analysing the behaviour associated with regular as well as malicious nodes. In the proposed model, the utility of normal nodes has been increased while reducing the utility linked to malicious nodes. Moreover, the system employs a reputation system capable of stimulating best cooperation between the nodes. The regular nodes record incessantly to examine their corresponding nodes’ behaviours by using the belief system of Bayes-rules. On its comparison with existing schemes, it was revealed that the presented algorithm provides better identification of malicious nodes and attacks while delivering improved throughput and reduced false positive rate
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