Quantifying resonant activation like phenomenon in non-Markovian systems

Resonant activation is an effect of a noise-induced escape over a modulated potential barrier. The modulation of a energy landscape facilitates the escape kinetics and makes it optimal as measured by the mean first passage time. A canonical example of resonant activation is a Brownian particle moving in a time-dependent potential under action of Gaussian white noise. Resonant activation is observed not only in typical Markovian-Gaussian systems but also in far from equilibrium and far from Markovianity regimes. We demonstrate that using an alternative to the mean first passage time, robust measures of resonant activation, the signature of this effect can be observed in general continuous time random walks in modulated potentials even in situations when the mean first passage time diverges.Comment: 7 pages, 9 figure

Stationary states in 2D systems driven by bi-variate L\'evy noises

Systems driven by $\alpha$-stable noises could be very different from their Gaussian counterparts. Stationary states in single-well potentials can be multimodal. Moreover, a potential well needs to be steep enough in order to produce stationary states. Here, it is demonstrated that 2D systems driven by bi-variate $\alpha$-stable noises are even more surprising than their 1D analogs. In 2D systems, intriguing properties of stationary states originate not only due to heavy tails of noise pulses, which are distributed according to $\alpha$-stable densities, but also because of properties of spectral measures. Consequently, 2D systems are described by a whole family of Langevin and fractional diffusion equations. Solutions of these equations bear some common properties but also can be very different. It is demonstrated that also for 2D systems potential wells need to be steep enough in order to produce bounded states. Moreover, stationary states can have local minima at the origin. The shape of stationary states reflects symmetries of the underlying noise, i.e. its spectral measure. Finally, marginal densities in power-law potentials also have power-law asymptotics.Comment: 9 pages, 8 figure

Non-Gaussian, non-dynamical stochastic resonance

The archetypal system demonstrating stochastic resonance is nothing more than a threshold triggered device. It consists of a periodic modulated input and noise. Every time an output crosses the threshold the signal is recorded. Such a digitally filtered signal is sensitive to the noise intensity. There exist the optimal value of the noise intensity resulting in the "most" periodic output. Here, we explore properties of the non-dynamical stochastic resonance in non-equilibrium situations, i.e. when the Gaussian noise is replaced by an $\alpha$-stable noise. We demonstrate that non-equilibrium $\alpha$-stable noises, depending on noise parameters, can either weaken or enhance the non-dynamical stochastic resonance.Comment: 5 pages, 6 figurure

Escape from bounded domains driven by multi-variate α\alpha-stable noises

In this paper we provide an analysis of a mean first passage time problem of a random walker subject to a bi-variate $\alpha$-stable L\'evy type noise from a 2-dimensional disk. For an appropriate choice of parameters the mean first passage time reveals non-trivial, non-monotonous dependence on the stability index $\alpha$ describing jumps' length asymptotics both for spherical and Cartesian L\'evy flights. Finally, we study escape from $d$-dimensional hyper-sphere showing that $d$-dimensional escape process can be used to discriminate between various types of multi-variate $\alpha$-stable noises, especially spherical and Cartesian L\'evy flights.Comment: 8 pages, 5 figure

A patient with polycythaemia, hypersplenism and kidney cirrhosis caused by renal artery stenosis

Zwężenie tętnicy nerkowej powodujące marskość nerki jest rzadko uwzględnianą przyczyną czerwienicy wtórnej. Zwiększona na skutek nieadekwatnego wydzielania erytropoetyny liczba czerwonych krwinek po wielu latach trwania choroby prowadzi do rozwinięcia się hipersplenizmu z wtórną małopłytkowością. Jednocześnie dochodzi do kompensacyjnego przerostu zdrowej nerki, w wyniku czego stężenia mocznika i kreatyniny oraz GFR są długo prawidłowe. W niniejszej pracy zaprezentowano przypadek pacjenta, u którego w przebiegu miażdżycowego zwężenia prawej tętnicy nerkowej doszło do marskości nerki, a następnie wystąpienia poliglobulii i splenomegalii.Renal artery stenosis causing kidney cirrhosis is uncommon reason of secondary polycythaemia. Red blood cells amount incerased due to inadequate erythropoietin secretion leads to the development of hypersplenism and secondary thrombocytopenia. Additionally it comes to compensatory healthy kidney hypertrophia resulting in the urea and creatinine levels being normal for a long time. The following article describes the case of a patient with stenosis of right renal artery which caused kidney cirrhosis and later polycythaemia and splenomegaly

Mechanisms underlying outbreaks of spider mites following applications of imidacloprid

Imidacloprid is a widely used neonicotinoid insecticide with high efficacy and long residual activity, and it is frequently applied to manage insect pests in urban landscapes. Recent reports of secondary outbreaks of spider mites after imidacloprid applications have prompted research endeavors to explain the driving force of the abrupt increases in abundance of mites. In this research, I documented outbreaks of spider mites in field and greenhouse experiments, and explored the three main mechanisms that have been proposed to explain the outbreaks: elimination of natural enemies, direct stimulation of spider mite fecundity and changes in plant quality, specifically, changes in defense pathways. To this end, I examined if the outbreaks occur in field and greenhouse experiments, and tested if imidacloprid applications disrupted communities of beneficial insects and caused increased reproductive performance of spider mites in two woody ornamental systems, elm trees and boxwood shrubs. Additionally, I used a model organism, tomato plants, to address the hypothesis of altered plant defenses in plants treated with imidacloprid. I found overwhelming evidence that outbreaks of spider mites occur consistently following applications of imidacloprid in landscape and greenhouse experiments. Moreover, surveys of arthropods on elms and boxwoods showed no evidence of disruption of a key predator of spider mites that could explain the outbreaks. Importantly, I found a plant-mediated effect of imidacloprid on fecundity of spider mites, while there was no evidence that the insecticide applied directly to the mites exerted the same effect on their reproductive performance. Lastly, two genes involved in jasmonic and salicylic acid showed a differential expression in tomatoes treated with imidacloprid, indicating that it affected plants' defense pathways in ways that could render plants more suitable for spider mites. This research demonstrated that changes in quality of plants brought about by imidacloprid seem to be the driving mechanism of secondary outbreaks of spider mites

The role of the βKlotho gene in uterine endometrial cancer

Objectives: Endometrial cancer is the most common cancer of the female genital organs in developed countries, accounting for approximately 50% of all gynecological cancers. The Klotho gene was discovered in 1997 as an anti-aging gene that, when overexpressed, may extend the lifespan, but when disrupted, may be a factor responsible for premature aging syndrome. The aim of the study is to assess the relationship between the clinical and pathological features of endometrial cancer and βKlotho gene expression.Material and methods: The expression of βKlotho gene was studied in 138 cases of endometrioid endometrial carcinoma specimens using Real Time PCR reaction in RNA isolated tissue samples by commercial tests. The expression profile was correlated with the clinicopathological characteristics of endometrial carcinoma. The chi-square independence test and Fisher’s test for four-field tables were used to assess the statistical significance of the observed relationships.Results: Significant relationships were found between βKlotho gene expression and FIGO clinical stage, the degree of histological differentiation and the presence of metastases in the lymph nodes. Higher levels of gene expression correlate with lower degrees of clinical staging according to FIGO, the presence of highly-differentiated endometrial cancer (G1) and the absence of lymph node metastases.Conclusions: The βKlotho gene expression might be involved in endometrioid endometrial cancer tumorgenesis. TheβKlotho may in future be used as an useful indicator for endometrial cancer, although further studies are needed