Online network monitoring

An important problem in network analysis is the online detection of anomalous behaviour. In this paper, we introduce a network surveillance method bringing together network modelling and statistical process control. Our approach is to apply multivariate control charts based on exponential smoothing and cumulative sums in order to monitor networks generated by temporal exponential random graph models (TERGM). The latter allows us to account for temporal dependence while simultaneously reducing the number of parameters to be monitored. The performance of the considered charts is evaluated by calculating the average run length and the conditional expected delay for both simulated and real data. To justify the decision of using the TERGM to describe network data, some measures of goodness of fit are inspected. We demonstrate the effectiveness of the proposed approach by an empirical application, monitoring daily flights in the United States to detect anomalous patterns. © 2021, The Author(s)

Online network monitoring

An important problem in network analysis is the online detection of anomalous behaviour. In this paper, we introduce a network surveillance method bringing together network modelling and statistical process control. Our approach is to apply multivariate control charts based on exponential smoothing and cumulative sums in order to monitor networks generated by temporal exponential random graph models (TERGM). The latter allows us to account for temporal dependence while simultaneously reducing the number of parameters to be monitored. The performance of the considered charts is evaluated by calculating the average run length and the conditional expected delay for both simulated and real data. To justify the decision of using the TERGM to describe network data, some measures of goodness of fit are inspected. We demonstrate the effectiveness of the proposed approach by an empirical application, monitoring daily flights in the United States to detect anomalous patterns

Mendelian nightmares: The germline-restricted chromosome of songbirds

Germline-restricted chromosomes (GRCs) are accessory chromosomes that occur only in germ cells. They are eliminated from somatic cells through programmed DNA elimination during embryo development. GRCs have been observed in several unrelated animal taxa and show peculiar modes of non-Mendelian inheritance and within-individual elimination. Recent cytogenetic and phylogenomic evidence suggests that a GRC is present across the species-rich songbirds, but absent in non-passerine birds, implying that over half of all 10,500 bird species have extensive germline/soma genome differences. Here, we review recent insights gained from genomic, transcriptomic, and cytogenetic approaches with regard to the genetic content, phylogenetic distribution, and inheritance of the songbird GRC. While many questions remain unsolved in terms of GRC inheritance, elimination, and function, we discuss plausible scenarios and future directions for understanding this widespread form of programmed DNA elimination

Abstracts from the 20th International Symposium on Signal Transduction at the Blood-Brain Barriers

https://deepblue.lib.umich.edu/bitstream/2027.42/138963/1/12987_2017_Article_71.pd

Essays on New Income Opportunities for Disadvantaged Populations in the U.S.

89 pagesAlthough historically Native Americans were displaced from resource-rich areas to resource-poor areas, substantial reserves of shale oil, gas, uranium, and some other resources were subsequently discovered on reservations. In the second chapter of this thesis I study how extraction of shale oil, gas, and uranium has contributed to disparities in today's economic outcomes across Native American reservations. Since extraction of resources on a reservation might be endogenous to the economic development of the reservation or political institutions of the tribes populating it, I instrument for shale drilling with whether a reservation is sitting on a shale oil or gas tight play and use a similar approach to instrument for uranium mining. I find that shale drilling on reservations, which has been a relatively recent phenomenon, is associated with a significant reduction in today's unemployment rate and an increase in today's mean household income, though these findings are not robust to the Bonferroni correction. At the same time, I find that uranium mining, which peaked during the Cold War, is associated with a significant decline in today's mean household income on reservations (and this finding is robust to the Bonferroni correction). Using the same instrumental variable approach, I explore whether the persistent negative income effect of a history of uranium mining on reservations is at least partly driven by health consequences and find that a history of uranium mining increases the availability of hospitals on the affected reservations, which I interpret as evidence that the health channel is at least partly responsible for the persistent negative income effect of uranium mining. Other potential channels for the negative income effect of uranium mining are also discussed. This year Uber Technologies Inc. has celebrated a 10-year anniversary since the launch of the app in San Francisco in May of 2010, yet little is still known about the micro-economic effects of Uber. In the third chapter of this thesis I exploit two sources of plausibly exogenous variation - the geographical spread of UberX across about 90 largest Metropolitan Statistical Areas (MSAs) during 2010-2017 and Uber bans in 8 MSAs - in a difference-in-differences research design to test whether Uber availability affected weekly hours worked by males with lower levels of educational attainment. I find that both the initial introduction of UberX and lifting of Uber bans raised hours worked by males of color with less than a bachelor's degree. No significant effects for white males with lower levels of educational attainment are observed. These results are robust to a variation in the model specification, definition of treatment as the introduction of Uber as opposed to UberX, and a falsification test in which each MSA is assigned an incorrect date for UberX entry or lifting of an Uber ban. Possible mechanisms for the effect of Uber on males of color with no college education include employment with Uber and other ride-hailing companies that followed Uber as well as improved access to employment opportunities

Architecture of the EU Emissions Trading System in Phase 3 and the Distribution of Allowance Asset Values

Recent changes to the EU Emissions Trading System introduce structural changes regarding the initial distribution of emissions allowances, which are worth tens of billions of euros. A key change is the expanding role for auctions, which account for about half of the allowance allocation now and will be a growing share going forward. The use of revenue from auctions is a decision left to EU Member States and appears increasingly important. Well over half of auction revenue to date has been directed to energy and climate related purposes. Further, we do not find evidence that Member States have used state aid to electricity-intensive firms to strategically support domestic industry. The trading system is evolving in a way that is likely to improve its performance, but there remain important questions related the future price of allowances and the distribution and use of asset value created under the trading system.JEL: H23, P48, Q5

Statistical learning for change point and anomaly detection in graphs

Complex systems which can be represented in the form of static and dynamic graphs arise in different fields, e.g., communication, engineering and industry. One of the interesting problems in analysing dynamic network structures is monitoring changes in their development. Statistical learning, which encompasses both methods based on artificial intelligence and traditional statistics, can be used to progress in this research area. However, the majority of approaches apply only one or the other framework. In this chapter, we discuss the possibility of bringing together both disciplines in order to create enhanced network monitoring procedures focussing on the example of combining statistical process control and deep learning algorithms. Together with the presentation of change point and anomaly detection in network data, we propose to monitor the response time of ambulance service, applying jointly the control chart for quantile function values and a graph convolutional network

Statistical process monitoring of artificial neural networks

The rapid advancement of models based on artificial intelligence demands innovative monitoring techniques which can operate in real time with low computational costs. In machine learning, especially if we consider artificial neural networks (ANNs), the models are often trained in a supervised manner. Consequently, the learned relationship between the input and the output must remain valid during the model’s deployment. If this stationarity assumption holds, we can conclude that the ANN provides accurate predictions. Otherwise, the retraining or rebuilding of the model is required. We propose considering the latent feature representation of the data (called “embedding”) generated by the ANN to determine the time when the data stream starts being nonstationary. In particular, we monitor embeddings by applying multivariate control charts based on the data depth calculation and normalized ranks. The performance of the introduced method is compared with benchmark approaches for various ANN architectures and different underlying data formats

Karyotypes and recombination patterns of the Common Swift (Apus apus Linnaeus, 1758) and Eurasian Hobby (Falco subbuteo Linnaeus, 1758)

Abstract Background Meiotic recombination is an important source of genetic variability. Studies on mammals demonstrate a substantial interspecies variation in overall recombination rate, which is dependent mainly on chromosome (2n) and chromosome arm number (FN). Bird karyotypes are very conservative with 2n being about 78–82 and FN being 80–90 in most species. However, some families such as Apodidae (swifts) and Falconidae (falcons) show a substantial karyotypic variation. In this study, we describe the somatic and pachytene karyotypes of the male Common Swift (Apus apus) and the pachytene karyotype of the male Eurasian Hobby (Falco subbuteo) and estimate the overall number and distribution of recombination events along the chromosomes of these species. Methods The somatic karyotype was examined in bone marrow cells. Pachytene chromosome spreads were prepared from spermatocytes of adult males. Synaptonemal complexes and mature recombination nodules were visualized with antibodies to SYCP3 and MLH1 proteins correspondingly. Results The karyotype of the Common Swift consists of three metacentric, three submetacentric and two telocentric macrochromosomes and 31 telocentric microchromosomes (2n = 78; FN = 90). It differs from the karyotypes of related Apodidae species described previously. The karyotype of the Eurasian Hobby contains one metacentric and 13 telocentric macrochromosomes and one metacentric and ten telocentric microchromosomes (2n = 50; FN = 54) and is similar to that described previously in 2n, but differs for macrochromosome morphology. Despite an about 40% difference in 2n and FN, these species have almost the same number of recombination nodules per genome: 51.4 ± 4.3 in the swift and 51.1 ± 6.7 in the hobby. The distribution of the recombination nodules along the macrochromosomes was extremely polarized in the Common Swift and was rather even in the Eurasian Hobby. Conclusions This study adds two more species to the short list of birds in which the number and distribution of recombination nodules have been examined. Our data confirm that recombination rate in birds is substantially higher than that in mammals, but shows rather a low interspecies variability. Even a substantial reduction in chromosome number does not lead to any substantial decrease in recombination rate. More data from different taxa are required to draw statistically supported conclusions about the evolution of recombination in birds