A Brownian particle in a microscopic periodic potential

We study a model for a massive test particle in a microscopic periodic potential and interacting with a reservoir of light particles. In the regime considered, the fluctuations in the test particle's momentum resulting from collisions typically outweigh the shifts in momentum generated by the periodic force, and so the force is effectively a perturbative contribution. The mathematical starting point is an idealized reduced dynamics for the test particle given by a linear Boltzmann equation. In the limit that the mass ratio of a single reservoir particle to the test particle tends to zero, we show that there is convergence to the Ornstein-Uhlenbeck process under the standard normalizations for the test particle variables. Our analysis is primarily directed towards bounding the perturbative effect of the periodic potential on the particle's momentum.Comment: 60 pages. We reorganized the article and made a few simplifications of the conten

Instability of Democracy as Resource Curse

We suggest a dynamic game theoretic model to explain why resource abundance may lead to instability of democracy. Stationary Markov perfect equilibria of this game with four players – Politician, Oligarch, Autocrat and Public (voters) – are analyzed. Choosing a rate of resource rent tax, potential Autocrat competes with conventional Politician for the office, and Oligarch, the owner of the resource wealth, bribes Politician to influence her decisions. Actual Autocrat's tax policy may be different from the announced one. If the difference is large, then Public may revolt or Oligarch may organize a coup to throw Autocrat down. It is shown that the probability of democracy preservation is decreasing in the amount of resources if the institutional quality is low enough. It does not depend on the amount of resources, if the institutional quality is higher than a threshold. The level of the threshold, however, depends positively on the resource wealth. We have found also that under very low institutional quality, a paradoxical effect takes place: the probability of democracy preservation may decrease with small improvements of institutional quality. It is shown as well that Oligarch earns larger part of rent under democracy than under autocracy. This result conforms to empirical observation which is demonstrated in the paper: under low quality of institutions, democratization leads to higher inequality and inequality entails worsening of the attitude to democracy

Fueling the gender gap? Oil and women's labor and marriage market outcomes

This paper analyzes the effect of resource-based economic specialization on women's labor market outcomes. Using information on the location and discovery of major oil fields in the Southern United States coupled with a county-level panel derived from US Census data for 1900-1940, we specifically test the hypothesis that the presence of mineral resources can induce changes in the sectoral composition of the local economy that are detrimental to women's labor market outcomes. We find evidence that the discovery of oil at the county level may constitute a substantial male biased demand shock to local labor markets, as it is associated with a higher gender pay gap. However, we find no evidence that oil wealth lowers female labor force participation or has any impact on local marriage and fertility patterns. While our results are consistent with oil shocks limiting female labor market opportunities in some sectors (mainly manufacturing), this effect tends to be compensated by the higher availability of service sector jobs for women who are therefore not driven out of the labor market

First-trimester cesarean scar pregnancy: a comparative analysis of treatment options from the international registry

Background: A cesarean scar pregnancy is an iatrogenic consequence of a previous cesarean delivery. The gestational sac implants into a niche created by the incision of the previous cesarean delivery, and this carries a substantial risk for major maternal complications. The aim of this study was to report, analyze, and compare the effectiveness and safety of different treatments options for cesarean scar pregnancies managed in the first trimester through a registry. Objective: This study aimed to evaluated the ultrasound findings, disease behavior, and management of first-trimester cesarean scar pregnancies. Study design: We created an international registry of cesarean scar pregnancy cases to study the ultrasound findings, disease behavior, and management of cesarean scar pregnancies. The Cesarean Scar Pregnancy Registry collects anonymized ultrasound and clinical data of individual patients with a cesarean scar pregnancy on a secure, digital information platform. Cases were uploaded by 31 participating centers across 19 countries. In this study, we only included live and failing cesarean scar pregnancies (with or without a positive fetal heart beat) that received active treatment (medical or surgical) before 12+6 weeks' gestation to evaluate the effectiveness and safety of the different management options. Patients managed expectantly were not included in this study and will be reported separately. Treatment was classified as successful if it led to a complete resolution of the pregnancy without the need for any additional medical interventions. Results: Between August 29, 2018, and February 28, 2023, we recorded 460 patients with cesarean scar pregnancies (281 live, 179 failing cesarean scar pregnancy) who fulfilled the inclusion criteria and were registered. A total of 270 of 460 (58.7%) patients were managed surgically, 123 of 460 (26.7%) patients underwent medical management, 46 of 460 (10%) patients underwent balloon management, and 21 of 460 (4.6%) patients received other, less frequently used treatment options. Suction evacuation was very effective with a success rate of 202 of 221 (91.5%; 95% confidence interval, 87.8-95.2), whereas systemic methotrexate was least effective with only 38 of 64 (59.4%; 95% confidence interval, 48.4-70.4) patients not requiring additional treatment. Overall, surgical treatment of cesarean scar pregnancies was successful in 236 of 258 (91.5%, 95% confidence interval, 88.4-94.5) patients and complications were observed in 24 of 258 patients (9.3%; 95% confidence interval, 6.6-11.9). Conclusion: A cesarean scar pregnancy can be managed effectively in the first trimester of pregnancy in more than 90% of cases with either suction evacuation, balloon treatment, or surgical excision. The effectiveness of all treatment options decreases with advancing gestational age, and cesarean scar pregnancies should be treated as early as possible after confirmation of the diagnosis. Local medical treatment with potassium chloride or methotrexate is less efficient and has higher rates of complications than the other treatment options. Systemic methotrexate has a substantial risk of failing and a higher complication rate and should not be recommended as first-line treatment

Residency patterns and migration dynamics of adult bull sharks (Carcharhinus leucas) on the east coast of southern Africa:

Bull sharks (Carcharhinus leucas) are globally distributed top predators that play an important ecological role within coastal marine communities. However, little is known about the spatial and temporal scales of their habitat use and associated ecological role. In this study, we employed passive acoustic telemetry to investigate the residency patterns and migration dynamics of 18 adult bull sharks (195–283 cm total length) tagged in southern Mozambique for a period of between 10 and 22 months. The majority of sharks (n = 16) exhibited temporally and spatially variable residency patterns interspersed with migration events. Ten individuals undertook coastal migrations that ranged between 433 and 709 km (mean  = 533 km) with eight of these sharks returning to the study site