Mining Pool Selection under Block WithHolding Attack

In current Proof-of-Work (PoW) blockchain systems, miners usually form mining pools to compete with other pools/miners in the mining competition. Forming pools can give miners steady revenues but will introduce two critical issues. One is mining pool selection, where miners select the pools to join in order to maximize their revenues. The other is a Block WithHolding (BWH) attack, where pools can inject part of their hash/mining power into other pools to obtain additional revenues without contributing to the mining process of the attacked pools. Reasoning that the BWH attack will have significant impacts on the pool selection, we therefore investigate the mining pool selection issue in the presence of a BWH attack in this paper. In particular, we model the pool selection process of miners as an evolutionary game and find the Evolutionarily Stable States (ESSs) of the game (i.e., stable pool population states) as the solutions. Previous studies investigated this problem from the perspective of pool managers and neglected the revenues from attacked pools (attacking revenues), leading to less accurate and insightful findings. This paper, however, focuses on the payoffs of miners and carefully takes the attacking revenues into consideration. To demonstrate how the problem is solved, we consider the scenario with two mining pools and further investigate the case where one pool attacks the other and the case where the two pools attack each other. The results in this paper show that pools can attract more miners to join by launching a BWH attack and the attack power significantly affects the stable pool populations.

The Future of Intelligence Outsourcing

This chapter considers the outcome of the US government’s efforts to reform the accountability regime for intelligence contractors. The chapter shows that further efforts are and will be needed to continue fill accountability gaps and adapt the national intelligence effort to the security environment. To avoid past mistakes and provide greater coherence to this effort, adaptation should focus on three essential questions: What (not) to outsource? When to outsource? How to outsource? Answers to these questions emphasize the need for more coherent policies and planning in the domain of human resources, and in particular a more stable pool of government personnel to cope with the ebb and flow of intelligence requirements.

Even worms matter: cave habitat restoration for a planarian species increased environmental suitability but not abundance

Invertebrates living in underground environments often have unusual and sometimes unique adaptations and occupy narrow ranges, but there is a lack of knowledge about most micro-endemic cave-dwelling invertebrate species. An illustrative case is that of the flatworm Dendrocoelum italicum, the first survey of which was performed 79 years after its description. The survey revealed that the underground stream supplying water to the pool from which the species was first described had been diverted into a pipe for human use, thus severely reducing the available habitat for the species. Here we describe the results of what we believe is the first habitat restoration action performed in a cave habitat for the conservation of a flatworm. The water-diverting structure was removed, with the involvement of local protected area administrators, citizens and volunteers from local organizations. The intervention resulted in the restoration of a large, stable pool inside the cave, thus creating an optimal habitat for this threatened planarian, with increased availability of prey and a stable population. This report of habitat restoration for a neglected invertebrate offers insights for the protection of other micro-endemic species.

Importin-β modulates the permeability of the nuclear pore complex in a Ran-dependent manner

Soluble karyopherins of the importin-β (impβ) family use RanGTP to transport cargos directionally through the nuclear pore complex (NPC). Whether impβ or RanGTP regulate the permeability of the NPC itself has been unknown. In this study, we identify a stable pool of impβ at the NPC. A subpopulation of this pool is rapidly turned-over by RanGTP, likely at Nup153. Impβ, but not transportin-1 (TRN1), alters the pore's permeability in a Ran-dependent manner, suggesting that impβ is a functional component of the NPC. Upon reduction of Nup153 levels, inert cargos more readily equilibrate across the NPC yet active transport is impaired. When purified impβ or TRN1 are mixed with Nup153 in vitro, higher-order, multivalent complexes form. RanGTP dissolves the impβ•Nup153 complexes but not those of TRN1•Nup153. We propose that impβ and Nup153 interact at the NPC's nuclear face to form a Ran-regulated mesh that modulates NPC permeability.

Mean Residence Time of Soil Organic Carbon in Aggregates Under Contrasting Land Uses Based on Radiocarbon Measurements

Radiocarbon is a useful tool for studying carbon dynamics in soil aggregates. The objective of the current study was to determine the mean residence time (MRT) of soil organic carbon (SOC) in macroaggregates and microaggregates under contrasting land uses. Contrasting land uses investigated at Alfisol (equivalent to Dermosol in Australian Soil Classification) sites were native pasture (NP), crop-pasture rotation (CP), and Eucalypt woodland (WL), whereas in Oxisol (Ferrosol in Australian Soil Classification) sites, land uses comprised improved pasture (IP), cropping (CR), and forest (FR). Soil aggregates were separated into macroaggregates (250–2000 μm) and microaggregates (53–250 μm) by wet-sieving, and their14C signatures were determined by accelerator mass spectrometry (AMS). The14C activity in both macro- and microaggregates was >100 pMC, indicating the presence of post-bomb carbon in the soil. The mean residence time (MRT) of SOC in macro- and microaggregates (MRTagg) was on average 68 yr longer in the Oxisol compared with that in the Alfisol. The MRTaggin microaggregates was 10 yr longer than that of macroaggregates in the Alfisol. However, the MRTaggin microaggregates was 50 yr shorter compared to macroaggregates in the Oxisol.The MRT of macro- and microaggregates can be separated into active, slow, and stable SOC pools. Among the 3 SOC pools, the MRT of the stable pool is of higher significance in terms of SOC stabilization in soil aggregates because of its longer MRT. However, isolation and direct MRT estimation of the stable SOC pool is difficult. The MRT of active and slow SOC pools associated with macro- and microaggregates was measured using a SOC mineralization experiment to estimate the MRT of the stable SOC pool under contrasting land uses by applying a mass balance criterion. The MRT of active (MRTA) and slow (MRTS) SOC pools in macro- and microaggregates varied between 1–50 days and 13–38 yr, respectively. The estimated MRT of the stable pool carbon (MRTP) in microaggregates was 897 yr longer compared to that of macroaggregates in the Alfisol. However, in the Oxisol, MRTPin microaggregates was 568 yr shorter than that of macroaggregates. Among the land uses, WL in Alfisol and CR in Oxisol had longer MRTaggand MRTPcompared to other land uses.