Why Do Smart Contracts Self-Destruct? Investigating the Selfdestruct Function on Ethereum

The selfdestruct function is provided by Ethereum smart contracts to destroy a contract on the blockchain system. However, it is a double-edged sword for developers. On the one hand, using the selfdestruct function enables developers to remove smart contracts ( SCs ) from Ethereum and transfers Ethers when emergency situations happen, e.g., being attacked. On the other hand, this function can increase the complexity for the development and open an attack vector for attackers. To better understand the reasons why SC developers include or exclude the selfdestruct function in their contracts, we conducted an online survey to collect feedback from them and summarize the key reasons. Their feedback shows that 66.67% of the developers will deploy an updated contract to the Ethereum after destructing the old contract. According to this information, we propose a method to find the self-destructed contracts (also called predecessor contracts) and their updated version (successor contracts) by computing the code similarity. By analyzing the difference between the predecessor contracts and their successor contracts, we found five reasons that led to the death of the contracts; two of them (i.e., Unmatched ERC20 Token and Limits of Permission ) might affect the life span of contracts. We developed a tool named LifeScope to detect these problems. LifeScope reports 0 false positives or negatives in detecting Unmatched ERC20 Token . In terms of Limits of Permission , LifeScope achieves 77.89% of F-measure and 0.8673 of AUC in average. According to the feedback of developers who exclude selfdestruct functions, we propose suggestions to help developers use selfdestruct functions in Ethereum smart contracts better.

Does Recruitment trigger negative Density-Dependent Feedback loops in Stream-Dwelling Salmonids?

I explored the hypothesis that recruitment may stabilize the numerical dynamics of stream-dwelling salmonids by triggering density-dependent feedback loops through the operation of recruitment-dependence on individual growth, mortality, life span and maximum size and their effects on fecundity. I examined 98 cohorts of two Salmo trutta populations of northern Spain and a population of Jutland (Denmark) located 2400 km apart Recruitment, growth, mortality, life span and maximum size were inter-related, were recruitment-dependent and described negative power trajectories. In the Spanish populations, faster growing individuals of weakly recruited cohorts with lower mortality attain longer life span and larger size. Hence, larger females spawning more abundant, larger eggs that, in turn, induce stronger cohorts of higher spawners’ abundance, recruitment and mortality. The mortality patterns match the self-thinning patterns, an ultimate expression of competition. Significant relationships among self-thinning slopes and mortalities rates with increasing recruitment demonstrate that the rate at which density-driven mortality is higher, the stronger the intensity of intraspecific competition. Space-limited habitat and size-dependent resource availability underpinning site-specific carrying capacities suggest that interference competition is the primary mechanism underpinning population regulation.

Imaging and tracing the pattern of adult ovarian angiogenesis implies a strategy against female reproductive aging

Unique model of adult ovarian angiogenesis implies a strategy to extend female reproductive life span.

Protective Effects of Transient Glucose Exposure in Adult C. elegans

C. elegans are used to study molecular pathways, linking high glucose levels (HG) to diabetic complications. Persistent exposure of C. elegans to a HG environment induces the mitochondrial formation of reactive oxygen species (ROS) and advanced glycation endproducts (AGEs), leading to neuronal damage and decreased lifespan. Studies suggest that transient high glucose exposure (TGE) exerts different effects than persistent exposure. Thus, the effects of TGE on ROS, AGE-formation and life span were studied in C. elegans. Four-day TGE (400 mM) as compared to controls (0mM) showed a persistent increase of ROS (4-days 286 ± 40 RLUs vs. control 187 ± 23 RLUs) without increased formation of AGEs. TGE increased body motility (1-day 0.14 ± 0.02; 4-days 0.15 ± 0.01; 6-days 0.16 ± 0.02 vs. control 0.10 ± 0.02 in mm/s), and bending angle (1-day 17.7 ± 1.55; 3-days 18.7 ± 1.39; 6-days 20.3 ± 0.61 vs. control 15.3 ± 1.63 in degree/s) as signs of neuronal damage. Lifespan was increased by 27% (21 ± 2.4 days) after one-day TGE, 34% (22 ± 1.2 days) after four-days TGE, and 26% (21 ± 1.4 days) after six-days TGE vs. control (16 ± 1.3 days). These experiments suggest that TGE in C. elegans has positive effects on life span and neuronal function, associated with mildly increased ROS-formation. From the perspective of metabolic memory, hormetic effects outweighed the detrimental effects of a HG environment.

The dynamics of mitochondrial-linked gene expression among tissues and life stages in two contrasting strains of laying hens

The cellular energy metabolism is one of the most conserved processes, as it is present in all living organisms. Mitochondria are providing the eukaryotic cell with energy and thus their genome and gene expression has been of broad interest for a long time. Mitochondrial gene expression changes under different conditions and is regulated by genes encoded in the nucleus of the cell. In this context, little is known about non-model organisms and we provide the first large-scaled gene expression analysis of mitochondrial-linked genes in laying hens. We analysed 28 mitochondrial and nuclear genes in 100 individuals in the context of five life-stages and strain differences among five tissues. Our study showed that mitochondrial gene expression increases during the productive life span, and reacts tissue and strain specific. In addition, the strains react different to potential increased oxidative stress, resulting from the increase in mitochondrial gene expression. The results suggest that the cellular energy metabolism as part of a complex regulatory system is strongly affected by the productive life span in laying hens and thus partly comparable to model organisms. This study provides a starting point for further analyses in this field on non-model organisms, especially in laying-hens.

Highly efficient multiplex genome editing in dicot plants using improved CRISPR/Cas systems

CRISPR/Cas9-mediated gene editing provides a powerful tool for dissecting gene function and improving important traits in crops. However, there are still persisting challenges to obtain high homozygous/bi-allelic (ho/bi) mutations in dicot plants. Here, we develop an improved CRISPR/Cas9 system harboring a calreticulin-like gene promoter, which can boost targeted mutations in dicots. Additionally, the pDC45_dsg construct, combining a 35Spro-tRNA_sgRNA-EU unit and PCE8pro-controlled Cas9, can achieve more than 80.0% ho/bi mutations at target sites in allotetraploid tobacco. We construct pDC45_Fast system that can simultaneously fulfill gene editing and shorten the life span of T0 generation tobacco and tomato. This study provides new tools for improving targeted gene mutagenesis in dicots, and makes manipulations of genes in Solanum more feasible.

The Persistence of the Victorian Prison: Alteration, Inhabitation, Obsolescence, and Affirmative Design

Prior scholarship tracing the origins and architecture of prisons has tended to focus on how and why prisons are built—what they are intended to achieve and their construction as an expression of the punitive philosophies of their age. It does not consider how prisons persist as time passes, perhaps beyond their anticipated operational life span, and into “obsolescence.” Focusing on the archetypal Victorian prison, and considering the alteration and inhabitation of such prisons through time, this article critically reinterprets notions of obsolescence in the built environment and explores an enduring cultural attachment to a particular and arguably archaic material manifestation of punishment.

Sustainability Factors Affecting the Implementation of Design for Dis-assembly and Re-manufacturing Principles in Automobile Sector Using ISM

With the automobile sector pacing the tracks among their competitors to lead the market and adopting eco-friendly technologies, a much economic and vital field of making use of the manufactured product beyond its useful life span is widely neglected. This paper throws light on the necessity for implementing and highlights the various reasons for which these guidelines have not come to the attention of the responsible organizations including law making agencies, automobile manufacturers and as well the consumers. An interpretive structural modelling analysis is made to point out ten driving factors in consultation with various experts from the relevant fields and the results provide guidance to how far the idea of design for dis-assembly and re-manufacturing has sought the world for the sustainability of the automobile manufacturers in the industry, for the days to come.