An intensity-expansion method to treat non-stationary time series: an application to the distance between prime numbers

We study the fractal properties of the distances between consecutive primes. The distance sequence is found to be well described by a non-stationary exponential probability distribution. We propose an intensity-expansion method to treat this non-stationarity and we find that the statistics underlying the distance between consecutive primes is Gaussian and that, by transforming the distance sequence into a stationary one, the range of Gaussian randomness of the sequence increases.Comment: 11 pages, 7 figures, in press on 'Chaos, Solitons & Fractals

Determination of the Optical Properties of Secondary Organic Aerosol Particles

The enhanced greenhouse effect is currently considered to be our most important global environmental problem. While the magnitude of radiation absorbed by greenhouse gases is known to a high certainty, the absorption of radiation by atmospheric aerosol particles is not. In the initial Visiting Faculty Program application, we proposed the use of an ultraviolet-visible (UV/Vis) spectrometer equipped with a liquid waveguide capillary flow cell to determine the extent to which secondary organic aerosol particles (SOA) absorb visible light. Early in the research period, the UV/Vis technique was optimized for three solvent systems (methanol, water and 0.1 M hydrochloric acid). Using the optimized UV/Vis technique optical properties such as mass specific absorption cross-section and imaginary refractive index were determined for SOA dissolved in different solvent systems. The end result of the UV/Vis studies is the inclusion of SOA optical properties into climate models developed at the Pacific Northwest National Laboratory (PNNL). This knowledge will help to improve climate models, which currently do not include the effect of SOA. We also utilized Fourier Transform Infrared Spectroscopy to help elucidate the chemical composition of SOA. Finally, an experimental method was developed to determine the peroxide content of SOA. It is expected that these studies will connect the chemical composition of SOA to their optical properties. The research carried out at PNNL will be included in two undergraduate senior theses at Concordia University - Portland (CU). It is also expected that this research will be included in a peer-reviewed journal article. It is our hope that success of our work will result in future collaborations between PNNL and CU students

Detecting phenology change in the mayfly Ephemera danica: responses to spatial and temporal water temperature variations

1. Rising water temperatures under climate change are expected to affect the phenology of aquatic insects, including the mayfly Ephemera danica Müller which is widespread throughout Europe. 2. To assess temporal and spatial variability in mayfly emergence, E. danica were monitored at two thermally contrasting reaches in the River Dove, English Peak District over the period 2007–2013. Inter-annual variations in growing degree days (GDDs) were modelled for an upstream site with intermittent spring flow supplementing main channel flow (Beresford Dale) and downstream site dominated by near constant discharges of cool groundwater (Dovedale). 3. A strong association exists between the emergence cycle of E. danica and GDDs at each site. Beresford Dale accumulated on average 374 more GDDs than Dovedale. After warm summers E. danica emerged after only 1 year in Beresford Dale but began to revert to a bi-annual cycle after the particularly wet/cool year of 2012. In Dovedale, E. danica maintained a 2-year cycle throughout the monitoring period in spite of the phenology changes observed 8 km upstream. 4. Data from the present study suggest that habitats near cool groundwater may provide important refugia for populations of insects, potentially delaying permanent shifts in phenology under climate change. However, an ability to detect changes in the thermal triggers and phenological response may be hindered by conventional spot sampling protocols

Demographic Determinants of Residue Profiles of Fungicidal Compounds in Common Voles (Microtus arvalis) under Semi-Natural and Natural Conditions

Environmental risks from plant protection products (PPPs) need to be assessed to ensure safe use. The risk assessments are generally carried out using the common vole as a focal species with conservative theoretical estimates of external exposure. These are then compared to dose-related toxicity endpoints established in toxicity studies, often with laboratory species. The aim of the present study was to determine the actual internal dosimetry of PPPs’ active ingredients (AIs) in a population of common voles to provide the basis for informed higher tier risk assessment. As a proof of concept, two fungicidal AIs (fludioxonil and cyprodinil) were investigated using a range of application methodologies. Individuals were treated using oral gavage application (AI dose: 100/200 mg/kg) and fed treated grass (AI sprayed at 2 kg/ha) under laboratory, semi-natural, and natural conditions. Our results show that demographic factors play a significant role in the individual residue profile and that age structure is a key aspect that determines the overall exposure risk of a population. These results are consistent from laboratory to field conditions. Future approaches could establish dose–residue relationships that are reflective of natural food intake rates in wild common vole populations in the risk assessment of PPPs

Seasonal shifts and land-use impact: unveiling the gut microbiomes of bank voles (Myodes glareolus) and common voles (Microtus arvalis)

Gut microbial diversity influences the health and vitality of the host, yet it is itself affected by internal and external factors, including land-use. The impact of land-use practices on wild rodents' gut microbiomes remains understudied, despite their abundance and potential as reservoirs for zoonotic pathogens. We examined the bacterial and fungal gut microbiomes of bank voles (Myodes glareolus) and common voles (Microtus arvalis) across grassland and forest habitats with varying land-use intensities and types. We collected rodents seasonally and used 16S rRNA and ITS amplicon sequencing for microbe identification. We found significant differences in alpha and beta diversities between the species, with M. arvalis exhibiting higher diversity. Seasonality emerged as a prominent factor influencing microbial diversity, with significant variations between sampling months. While land-use affects the gut microbiome, its impact is subordinate to seasonal variations. Differential abundance analysis underscores the dynamic nature of microbial composition, with seasonal changes playing a predominant role. Overall, our findings highlight the significant influence of seasonality on gut microbiome diversity and composition in wild rodents, reflecting dietary shifts associated with seasonal changes. Understanding the interplay between environmental factors and microbial communities in wild rodents enahnces our knowledge of ecosystem health and resilience, warranting further investigation