Using Ego Network Data to Inform Agent-based Models of Diffusion

Agent-based modeling holds great potential as an analytical tool. Agent-based models (ABMs) are, however, also vulnerable to critique, as they often employ stylized social worlds, with little connection to the actual environment in question. Given these concerns, there has been a recent call to more fully incorporate empirical data into ABMs. This article falls in this tradition, exploring the benefits of using sampled ego network data in ABMs of cultural diffusion. Thus, instead of relying on full network data, which can be difficult and costly to collect, or no empirical network data, which is convenient but not empirically grounded, we offer a middle-ground, one combining ABMs with recent work on network sampling. The main question is whether this approach is effective. We provide a test of the approach using six complete networks; the test also includes a range of diffusion models (where actors follow different rules of adoption). For each network, we take a random ego network sample and use that sample to infer the full network structure. We then run a diffusion model through the known, complete networks, as well as the inferred networks, and compare the results. The results, on the whole, are quite strong: Across all analyses, the diffusion curves based on the sampled data are very similar to the curves based on the true, complete network. This suggests that ego network sampling can, in fact, offer a practical means of incorporating empirical data into an agent-based model

Gender quotas in the boardroom: New evidence from Germany

We examine the introduction of a gender quota law in Germany, mandating a minimum 30% of the underrepresented gender on the supervisory boards of a particular type of firms. We exploit the fact that Germany has a two-tier corporate system consisting of the affected supervisory boards and unaffected management boards within the same firm. We find a positive effect on the female share on supervisory boards of affected firms, but no effect on presidency of the board or its size. We also study whether the increased female representation has had an effect on the financial performance of the firm and conclude that, unlike some previous studies in other countries, there has not been any negative effect on the profitability of the firm, neither at the time when the law was announced nor when it was passed

Attenuated Codon Optimality Contributes to Neural-Specific mRNA Decay in Drosophila.

Tissue-specific mRNA stability is important for cell fate and physiology, but the mechanisms involved are not fully understood. We found that zygotic mRNA stability in Drosophila correlates with codon content: optimal codons are enriched in stable transcripts associated with metabolic functions like translation, while non-optimal codons are enriched in unstable transcripts, including those associated with neural development. Bioinformatic analyses and reporter assays revealed that similar codons stabilize or destabilize mRNAs in the nervous system and other tissues, but the link between codon content and stability is attenuated in the nervous system. We confirmed that optimal codons are decoded by abundant tRNAs while non-optimal codons are decoded by less abundant tRNAs in embryos and in the nervous system. We conclude that codon optimality is a general determinant of zygotic mRNA stability, and attenuation of codon optimality allows trans-acting factors to exert greater influence over mRNA decay in the nervous system

Differential partitioning of thiols and glucosinolates between shoot and root in Chinese cabbage upon excess zinc exposure

Zinc (Zn) is one of the important elements of plant growth, however, at elevated level it is toxic. Exposure of Chinese cabbage to elevated Zn2+ concentrations (5 and 10 μM ZnCl2) resulted in enhancement of total sulfur and organic sulfur concentration. Transcript level of APS reductase (APR) as a key enzyme in biosynthesis of primary sulfur compounds (cysteine and thiols), was up-regulated in both shoot and root upon exposure to elevated Zn2+, which was accompanied by an increase in the concentration of cysteine in both tissues. In contrast, the concentration of thiols increased only in the root by 5.5 and 15-fold at 5 and 10 μM Zn2+, respectively, which was in accompanied by an upregulation of ATP sulfurylase, an enzyme responsible for activation of sulfate. An elevated content of glucosinolates, mostly indolic glucosinolates, only in the shoot of plants exposed to excess level of Zn2+ coincided with an increase in gene expression of key biosynthetic enzymes and regulators (CYP79B3, CYP83B1, MYB34). Thus distinct acuumulation patterns of sulfur containing compounds in root and shoot of Chinese cabbage may be a strategy for Chinese cabbage to combat with exposure to excess Zn

Sulfur metabolism in <i>Allium cepa</i> is hardly affected by chloride and sulfate salinity

Salinity as a major agricultural problem can affect crop growth and quality. Onion (Allium cepa L.) plant contains a wide variety of sulfur-containing compounds which may be involved in plant protection against salt stress. In the current study, a similar reduction in growth caused by chloride and sulfate salts was observed when onion was exposed to equimolar concentrations of Na+. Also, no difference was observed for shoot/root ratio and dry matter content of roots and shoots. Plants accumulated Na+ and the respective anions (chloride and sulfate) which in turn caused changes in the content of other nutrients. The content of potassium and calcium was decreased more than the other elements by both sodium salts. Sulfate salinity resulted in substantial increase in total sulfur and sulfate content but chloride salinity affected neither the total sulfur nor sulfate content of the roots and shoots, only in onion exposed to 200 mM chloride salt, those of roots and shoots were reduced. Furthermore, the water-soluble non-protein thiol content as well as the content of alliin remained rather unaffected. In conclusion, either salts affected the uptake and distribution of sulfate in onion, but had no or only a minor effect on the plant sulfur metabolism

The Deep Space Network: A Radio Communications Instrument for Deep Space Exploration

The primary purpose of the Deep Space Network (DSN) is to serve as a communications instrument for deep space exploration, providing communications between the spacecraft and the ground facilities. The uplink communications channel provides instructions or commands to the spacecraft. The downlink communications channel provides command verification and spacecraft engineering and science instrument payload data