In--out intermittency in PDE and ODE models

We find concrete evidence for a recently discovered form of intermittency, referred to as in--out intermittency, in both PDE and ODE models of mean field dynamos. This type of intermittency (introduced in Ashwin et al 1999) occurs in systems with invariant submanifolds and, as opposed to on--off intermittency which can also occur in skew product systems, it requires an absence of skew product structure. By this we mean that the dynamics on the attractor intermittent to the invariant manifold cannot be expressed simply as the dynamics on the invariant subspace forcing the transverse dynamics; the transverse dynamics will alter that tangential to the invariant subspace when one is far enough away from the invariant manifold. Since general systems with invariant submanifolds are not likely to have skew product structure, this type of behaviour may be of physical relevance in a variety of dynamical settings. The models employed here to demonstrate in--out intermittency are axisymmetric mean--field dynamo models which are often used to study the observed large scale magnetic variability in the Sun and solar-type stars. The occurrence of this type of intermittency in such models may be of interest in understanding some aspects of such variabilities.Comment: To be published in Chaos, June 2001, also available at http://www.eurico.web.co

The model of dynamo with small number of modes and magnetic activity of T Tauri stars

The model that describes operation of dynamo in fully convective stars is presented. It is based on representation of stellar magnetic field as a superposition of finite number of poloidal and toroidal free damping modes. In the frame of adopted low of stellar differential rotation we estimated minimal value of dynamo number D, starting from which generation of cyclic magnetic field in stars without radiative core is possible. We also derived expression for period of the cycle. It was found that dynamo cycles of fully convective stars and stars with thin convective envelopes differ in a qualitative way: 1) distribution of spots over latitude during the cycle is different in these stars; 2) the model predicts that spot formation in fully convective stars should be strongly suppressed at some phases of the cycle. We have analyzed historical lightcurve of WTTS star V410 Tau and found that long term activity of the star is not periodic process. Rather one can speak about quasi cyclic activity with characteristic time of $\sim 4$ yr and chaotic component over imposed. We concluded also that redistribution of cool spots over longitude is the reason of long term variations of V410 Tau brightness. It means that one can not compare directly results of photometric observations with predictions of our axially symmetric (for simplicity) model which allows to investigate time evolution of spot's distribution over latitude. We then discuss what kind of observations and in which way could be used to check predictions of the dynamo theory.Comment: 18 pages, 5 figures, accepted to Astron. Let

Solar Grand Minima and random fluctuations in dynamo parameters

We consider to what extent the long-term dynamics of cyclic solar activity in the form of Grand Minima can be associated with random fluctuations of the parameters governing the solar dynamo. We consider fluctuations of the alpha-coefficient in the conventional Parker migratory dynamo, and also in slightly more sophisticated dynamo models, and demonstrate that they can mimic the gross features of the phenomenon of the occurrence of Grand Minima over a suitable parameter range. The temporal distribution of these Grand Minima appears chaotic, with a more or less exponential waiting time distribution, typical of Poisson processes. In contrast however, the available reconstruction of Grand Minima statistics based on cosmogenic isotope data demonstrates substantial deviations from this exponential law. We were unable to reproduce the non-Poissonic tail of the waiting time distribution either in the framework of a simple alpha-quenched Parker model, or in its straightforward generalization, nor in simple models with feedback on the differential rotation. We suggest that the disagreement may only be apparent and is plausibly related to the limited observational data, and that the observations and results of numerical modeling can be consistent and represent physically similar dynamo regimes.Comment: Solar Physics, in prin

Sensing and Integration of Erk and PI3K Signals by Myc

The transcription factor Myc plays a central role in regulating cell-fate decisions, including proliferation, growth, and apoptosis. To maintain a normal cell physiology, it is critical that the control of Myc dynamics is precisely orchestrated. Recent studies suggest that such control of Myc can be achieved at the post-translational level via protein stability modulation. Myc is regulated by two Ras effector pathways: the extracellular signal-regulated kinase (Erk) and phosphatidylinositol 3-kinase (PI3K) pathways. To gain quantitative insight into Myc dynamics, we have developed a mathematical model to analyze post-translational regulation of Myc via sequential phosphorylation by Erk and PI3K. Our results suggest that Myc integrates Erk and PI3K signals to result in various cellular responses by differential stability control of Myc protein isoforms. Such signal integration confers a flexible dynamic range for the system output, governed by stability change. In addition, signal integration may require saturation of the input signals, leading to sensitive signal integration to the temporal features of the input signals, insensitive response to their amplitudes, and resistance to input fluctuations. We further propose that these characteristics of the protein stability control module in Myc may be commonly utilized in various cell types and classes of proteins

Production of buckwheat sowing seeds on soil classified to good wheat complex

In the period 1993-1995 in the Experimental Station belonging to Olsztyn University of Agriculture and Technology the experiment was carried out aimed to study of growing buckwheat on soil of good wheat complex (cultivars Hruszowska, Emka and Kora) and rate of nitrogen applying (40 kg N ha before sowing + 0 during flowering, 20 + 20 or 0 + 40) effects on yield and seed sowing value of buckwheat. Seed yields ranged from 0,71 to 2,71 t/ha and significantly higher yielded cv. Kora and the lowest yield was noted for Emka. В iological yield (harvested using human force from microplots) amounted above 3,0 t/ha. Losses of buckwheat seeds during the growing period amounted to 44% on average. Nitrogen applied during buckwheat flowering limited crop lodging, but on the other hand adversely affected sowing value of obtained yield, compared to treatment where whole rate of N was applied before sowing. In the above ground mass of buckwheat yield seeds of Raphanus raphanistrum were not found

Ocena wartosci siewnej nasion roslin straczkowych i ich wschodow w polu

Nasiona bobiku, grochu siewnego pastewnego, wyki ozimej i seradeli poddano analizie zdolności kiełkowania, przeprowadzono testy Hiltnera i elektroprzewodnictwa oraz wysiano je w polu i określono procent wschodów roślin. U nasion bobiku i wyki najwyższą zgodność wyników oceny ze wschodami w polu, potwierdzoną wysokim współczynnikiem korelacji stwierdzono w teście Hiltnera, u grochu ze zdolnością kiełkowania i elektroprzewodnictwem wód nastoinowych. Po wysiewie w polu wschodziło: bobiku około 90 %, grochu około 95 %, wyki 72 % i seradeli 80 % kiełkujących w laboratorium nasion, co oznacza potrzebę korekty ilości wysiewu nasion w celu otrzymania planowanej obsady roślin.The analysis of seed germination, Hiltner’s and conductivity tests of faba bean, fodder pea, winter vetch and serradella were carried out. Next the seeds were sown and the numbers of emerged plants were recorded. For faba bean and winter vetch seeds the highest agreement between laboratory tests and field emergence, confirmed by the high values of correlation coefficients was found for Hiltner’s test, whereas for fodder pea by germination capacity and conductivity of exudates. The field emergence was as follows: 90 % for faba bean, 95 % for fodder pea, 72 % for winter vetch and 80 % for serradella in relation to seed germinating in laboratory. Those differences indicate the need of correcting the number of seeds sown to obtain planned plant density in the field

Gospodarcze i przyrodnicze znaczenie krzewiastych wierzb Salix sp.

W Polsce istnieją uzasadnione podstawy do szerszego zainteresowania się krzewiastymi wierzbami - wikliną w uprawie polowej i wykorzystaniem jej biomasy na cele energetyczne (ekologiczne paliwo), surowca dla przemysłu chemicznego (celuloza). Wysoka zawartość salicylanów i garbników w korze wierzb krzewiastych stanowi potencjalny surowiec dla przemysłu farmaceutycznego i chemicznego. Włókno organiczne pozyskiwane z kory krzewiastych wierzb (32-57%) może stanowić substytut dla włókna szklanego. Duża plastyczność ekologiczna krzewiastych gatunków wierzb daje możliwość ich wykorzystania w kształtowaniu krajobrazu, przy rekultywacji stanowisk zdewastowanych działalnością przemysłową i komunalną. Pędy Salix sp. mogą być używane do wykonywania zabezpieczeń przed erozją stromych brzegów cieków wodnych i skarp przy szlakach komunikacyjnych oraz do produkcji ekranów akustycznych tłumiących hałas (przy drogach biegnących przez osiedla). Rośliny te można sadzić w strefach buforowych wokół ujęć wody, oczyszczalni ścieków, wysypisk śmieci.It seems justifiable to claim that the shrubby willow may attract increasing attention in Poland - for field cultivation, for production of biomass used as energy source (ecological fuel) or as a raw material for chemical industry (cellulose). Bark of shrubby willow is a potentially valuable raw material for pharmaceutical and chemical industries because of high salicylates and tannins contents. Organic fibre produced from shrubby willow bark (32-57%) may substitute glass fibre. High ecological adaptability of shrubby species of willow makes it possible to apply this plant in landscaping and reclamation of areas devastated by industrial and urban activities. Willow shoots can be used to prevent erosion of river gorges and escarpments by roadsides or to make acoustic screens to reduce noise (by roads crossing housing estates). Willows can be planted in buffer zones around water intakes, sewage treatment plants, landfills

Plonowanie słonecznika zwyczajnego (Helianthus annus L.) uprawianego na nasiona w północno-wschodniej Polsce

W Zakładzie Dydaktyczno-Doświadczalnym w Tomaszkowie ART Olsztyn, prowadzono doświadczenie z uprawą słonecznika zwyczajnego na nasiona. Wysiewano 5 odmian: Lech, Wielkopolski, Eurosol, Frankasol, Negra de Clui w zagęszczeniu 60 x 15 i 60 x 30 cm. Najwyższy plon nasion wydała odmiana Frankasol, rosnąca w obsadzie około 100 tys. roślin na 1 ha, najniższy zaś Negra de Clui. Słonecznik rosnący w rzadszym łanie wytwarzał większe koszyczki, dorodniejsze nasiona oraz większą masę nasion z rośliny, czym rekompensował plon nasion z jednostki powierzchni w stosunku do rosnącego prawie dwukrotnie gęściej W okresie zbioru koszyczki i nasiona miały wysoką wilgotność i wymagały sztucznego dosuszania. Najwięcej silnie porażonych roślin zgnilizną twardzikową było u odmiany Negra de Clui, o połowę mniej u odmian Eurosol i Frankasol.Field experiment on seed production of sunflower was carried out at Tomaszkowo Experimental Station in belonging to Olsztyn University of Agriculture and Technology. Five sunflower cultivars were tested: Lech, Wielkopolski, Eurosol, Frankasol, Negra de Clui. Seeds were sown at spacing 60 x 15 and 60 x 30 cm. The highest seed yield was obtained for Frankasol cv. at density of 100 000 plants per ha while the lowest for Negra de Clui cv. Cultivated on a sparser stand sunflower set bigger anthodia, larger seeds, giving higher seed weight per plant, what resulted in a higher seed yield per ha as compared to twice denser stands, and compensated the higher stand density. Because of their high moisture content the seeds had to be artificially dried after harvesting. The highest rate of stalk break (Sclerotinia sclerotiorum) infestation was recorded for Negra de Clui cv. plants whereas the Eurosol and Frankasol cultivars were half less infested

Plon i wartość nasion facelii błękitnej (Phacelia tanacaetifolia Benth.) w zależności od wybranych czynników agrotechnicznych

Facelia błękitna wysiewana w terminie wczesnym - odpowiadającym terminowi siewu zbóż jarych, wschodziła liczniej i wydała wyższy plon nasion niż siana w terminie późnym - po zbiorze poplonów ozimych. Wzrost ilości wysiewu nasion z 5 do 15 kg·ha⁻¹ dawał nieproporcjonalny do wysiewu wzrost obsady roślin. Facelia rosnąca w mniejszym zagęszczeniu wytwarzała liczniejsze rozgałęzienia, wytwarzała więcej nasion i wydała z jednostki powierzchni zbliżony plon nasion do rosnącej gęściej. Zbiór facelii sposobem dwuetapowym, jednoetapowym po wcześniejszej desykacji oraz jednoetapowym bez desykacji nie powodował istotnych różnic w plonie nasion. Najwyższy plon nasion uzyskano z wczesnego terminu siewu w ilości 10 kg·ha⁻¹, przy zbiorze dwufazowym. Nie stwierdzono istotnego wpływu czynników doświadczenia na masę 1000 nasion i ich zdolność kiełkowania.Phacelia tanacaetifolia Benth. sown at early date, i.e. the same as for spring cereals, showed better emergence and gave higher seed yield as compared to later sowing term after harvest of winter aftercrops. Increase of seed sowing rate from 5 to 15 kg per ha resulted in disproportionate increase of plant density. When Phacelia tanacaetifolia Benth. was grown in lower density more branches were developed, more seeds were set per plant and final yield was similar to that obtained on more dense stand. None studied method of harvesting i.e.: two stages, one stage after desiccation or one-stage without desiccation, did affect the seed yield. The highest seed yield was obtained when plants were sown in the early date at the rate of 10 kg per ha and two stage method of harvesting was used. Seed germination capacity and weight of 1000 seeds were not affected by experimental treatments