Stochastic model of hysteresis

The methods of the probability theory have been used in order to build up a new model of hysteresis. It turns out that the reversal points of the control parameter (e. g., the magnetic field) are Markov points which determine the stochastic evolution of the process. It has been shown that the branches of the hysteresis loop are converging to fixed limit curves when the number of cyclic back-and-forth variations of the control parameter between two consecutive reversal points is large enough. This convergence to limit curves gives a clear explanation of the accommodation process. The accommodated minor loops show the return-point memory property but this property is obviously absent in the case of non-accommodated minor loops which are not congruent and generally not closed. In contrast to the traditional Preisach model the reversal point susceptibilities are non-zero finite values. The stochastic model can provide a good approximation of the Raylaigh quadratic law when the external parameter varies between two sufficiently small values.Comment: 13 pages, 14 figure

Tápanyagellátás hatása 13 éves telepített gyep fejlődésére és botanikai összetételére a Mezőföldön.

Egy műtrágyázási kísérlet 40. évében, 2013-ban vizsgáltuk az eltérő N, P, K, ellátottsági szintek és kombinációik hatását a réti csenkesz (Festuca pratensis) vezérnövényű, nyolckomponensű pillangósnélküli gyepkeverék fejlődésére, termésére és botanikai összetételére a telepítés utáni 13. évben. A termőhely talaja a szántott rétegben 3% humuszt, 3˗5% CaCO3 -ot és 20˗22% agyagot tartalmazott, N és K elemekben eredetileg közepesen, P és Zn elemekkel viszonylag gyengén ellátottnak minősült. A kísérlet 4N×4P×4K = 64 kezelést x2 ismétlést = 128 parcellát foglal magában. A talajvíz 13‒15 m mélyen helyezkedik el, a terület aszályérzékeny. A vizsgált 2013. évben a tenyészidő kezdetén a talaj 1 m rétege kb. 170 mm csapadékot tárolt, a tenyészidő alatt lehullott csapadék 381 mm-t tett ki. A gyep mintegy 551 mm vízkészlettel rendelkezhetett a június 17-i kaszálás idejéig. Az elöregedő gyep második kaszáláshoz sarjút nem képezett ebben az aszályos évben. Az átlagos növénymagasság kaszálás előtt 2013. június 17-én a kontroll talajon 10 cm, az optimális NPK ellátott parcellákon 100 cm volt. Döntőnek a N-trágyázás bizonyult. A K átlagosan 40, a P 25%-kal igazolhatóan növelte a magasságot. A szénahozam a kontrollon mért 1,8 t·ha-1 mennyiségről 8,2 t·ha-1-ra emelkedett az optimális NPK kínálattal. Meghatározó az N × P kölcsönhatás volt, a K-hatások csak 0,7 t·ha-1 növekményt eredményeztek az NP-kezelések átlagaiban. A 13 évvel korábban elvetett 8 gyepalkotó fűfaj közül csupán 3 faj volt fellelhető, valamint az azóta betelepült árva rozsnok (Bromus inermis). A taréjos búzafű (Agropyron pectinatum) kitűnt extrém N-igényével: N-hiányos talajon nyomokban fordult elő, míg a maximális N-kínálattal 53% borítást adott a PK-kezelések átlagaiban. Ugyanitt az árva rozsnok 6%-ról 19%-ra növelte arányát. A nádképű csenkesz (Festuca arundinacea) aránya 10%-ról 16%-ra nőtt a 100 kg·ha-1·év-1 N-adaggal, majd a N-túlsúly nyomán borítása 1-2%-ra csökkent. A csomós ebír (Dactylis glomerata) előfordulása a kezelésektől függetlenül jelentéktelen maradt. A nem pillangós gyomok borítása a N-kontroll parcellákon 26%-ot ért el, majd az emelkedő N-kínálattal 10%-ra süllyedt. A pillangós gyomok 32%-os borítást mutattak a nitrogénnel 40 éve nem trágyázott, de növénytermesztéssel hasznosított talajon. Összességében a fűfélék aránya négyszeresére nőtt, míg a gyomoké egyötödére esett a növekvő N-adagolással. A tápelemek közötti kölcsönhatásokat vizsgálva azt találtuk, hogy a taréjos búzafű maximális borítása 50%-kal nőtt az N×P pozitív kölcsönhatások eredményeképpen. A P-hatások N-hiányos talajon ugyanis teljesen elmaradtak. A büdös zörgőfű (Crepis rhoeadifolia) esetén 18% körüli volt az NP-kontrollon mért borítás, de az együttesen és bőségesen NP-trágyázott kezelések a faj eltűnését eredményezték. Hasonló jelenség figyelhető meg a molyhos madárhúr (Cerastium tomentosum) fajnál. A fedél rozsnok (Bromus tectorum) borítása 14%-os a mérsékelt NP-kínálatnál, majd az NP hiánya vagy túlsúlya egyaránt a faj kiszorulását eredményezi. Az egyes fajok versenyképességét a tápláltsági szituáció alapvetően befolyásolhatja

Seasonal dynamics, age structure and reproduction of four Carabus species (Coleoptera: Carabidae) living in forested landscapes in Hungary

Seasonal dynamics and reproductive phenological parameters of four Carabus species (C. convexus, C. coriaceus, C. germarii and C. hortensis) common in Hungary were studied by pitfall trapping and dissection. Beetles were collected in an abandoned apple orchard and in the bordering oak forest near Budapest (Central Hungary), in 1988–1991. The sex ratio was male-dominated, but this was significant only for C. coriaceus. The catch of C. germarii adults showed relatively short activity period with unimodal curve, but activity was longer and bimodal for the other three species. Adults of C. germarii and C. hortensis reached sexual maturity in July, and C. coriaceus adults were matured by early August. We did not find newly hatched individuals of C. coriaceus or C. germarii. The reproductive period was approximately four weeks in C. hortensis, five weeks for C. coriaceus and six weeks for C. germarii. Reproduction lasted much longer, for about four months, in C. convexus. The mean number of ripe eggs per female were 4.2 in C. convexus, 5.4 in C. coriaceus, 6.6 in C. germarii, and 7.4 in C. hortensis. The maximum number found was about three times the average in all studied species. The reproductive allocation (ratio of egg complement mass/body mass) was lowest in C. germarii (0.133) and highest in C. hortensis (0.196), and did not depend on body size. There was minimal overlap of the activity and reproductive periods of the four species

European studies: Taking stock and looking ahead

This essay is an attempt to generalize experiences of Central and Eastern European universities in the field of European Studies over the past 20 years. The paper follows the logic of business analysis in order to come up with proposals for future action

And the first shall be the last

This study analyzes the puzzle of Hungarian economic drifting in a long run perspective. The underlying puzzle for the investigation is why bad policies are invariably popular and good policies unpopular, thus why political and economic rationality never overlap. The first part of the article summarizes in eight points the basic features of the postwar period. Then six lessons are offered, which might be useful for other countries in transition or for students of comparative economics and politics, lessons that can be generalized on the basis of the individual country experience

Microstructure formation in electrodeposited Co-Cu/Cu multilayers with GMR effect: influence of current density during the magnetic layer deposition

The influence of the current density applied during the deposition of the magnetic layers on the microstructure formation in electrodeposited Co-Cu/Cu multilayers and on their giant magnetoresistance (GMR) was investigated using a combination of magnetoresistance measurements, wide-angle and small-angle X-ray scattering, high-resolution transmission electron microscopy, atomic force microscopy and chemical analysis. The magnetoresistance measurements revealed that a reduction of the current density stimulates a transition from the formation of the magnetic layers with predominantly ferromagnetic character to the formation of superparamagnetic regions. As based on electrochemical considerations, it was supposed that such a change in the magnetic properties can be caused by an increased amount of Cu codeposited with Co at low current densities. It turned out from the structural studies that a pronounced segregation of Co and Cu occurs at low current densities. In accordance with their very low mutual solubility at room temperature, no atomic scale intermixing of Co and Cu could be detected. The segregation of Cu and Co was related to the fragmentation of the magnetic layers, to the enhancement of the local lattice strains, to the increase of the interface corrugations, to the partial loss of the multilayer periodicity and finally to the formation of Co precipitates in the Cu matrix

Propagation of travelling waves in sub-excitable systems driven by noise and periodic forcing

It has been reported that traveling waves propagate periodically and stably in sub-excitable systems driven by noise [Phys. Rev. Lett. \textbf{88}, 138301 (2002)]. As a further investigation, here we observe different types of traveling waves under different noises and periodic forces, using a simplified Oregonator model. Depending on different noises and periodic forces, we have observed different types of wave propagation (or their disappearance). Moreover, the reversal phenomena are observed in this system based on the numerical experiments in the one-dimensional space. As an explanation, we regard it as the effect of periodic forces. Thus, we give qualitative explanations to how reversal phenomena stably appear, which seem to arise from the mixing function of the periodic force and the noise. And the output period and three velocities (the normal, the positive and the negative) of the travelling waves are defined and their relationship with the periodic forces, along with the types of waves, are also studied in sub-excitable system under a fixed noise intensity.Comment: Some references and information are added in the modified version. Accepted, The European Physical Journal

The Effect of Surfactants and pH Modifying Agents on the Dissolution and Permeation of Pimobendan

Solubility and permeability are key parameters for establishing in vitro-in vivo correlation for poorly water-soluble active pharmaceutical ingredients (APIs). Recent studies demonstrate that not only solubility, but also effective permeability of the API may change due to the addition of solubilizing agents, and there is a certain mathematical relation between these physicochemical parameters. The aim of this study was to show the importance of early screening of solubility and permeability in presence of additives in order to achieve the expected bioavailability of the API. In this work, the effect of surfactants and microenvironmental pH modifiers were in focus, and pimobendan was chosen as model drug.In the case of pH modifiers, the equilibrium solubility of the API increased, while the permeability decreased significantly. No negative effect was observed for two surfactants at low additive levels, but these two additives also exhibited a slightly negative effect on permeability when used at higher concentrations. In the simultaneous dissolution-permeation studies the surfactants-containing formulation was found to have slightly higher flux than the pH-modifier-containing one. It can be due to the phenomenon that the dissolution of the active substance can be enhanced by these surfactants without any significant permeability reducing effect.The results obtained from the present study clearly demonstrate the importance of studying drug-additive interactions in every step of formulation development and based on these, the selection of the appropriate quality and quantity of additives. In addition, the results also underline the significance of performing simultaneous dissolution-permeation studies to predict bioavailability

Timelike surfaces in Lorentz covariant loop gravity and spin foam models

We construct a canonical formulation of general relativity for the case of a timelike foliation of spacetime. The formulation possesses explicit covariance with respect to Lorentz transformations in the tangent space. Applying the loop approach to quantize the theory we derive the spectrum of the area operator of a two-dimensional surface. Its different branches are naturally associated to spacelike and timelike surfaces. The results are compared with the predictions of Lorentzian spin foam models. A restriction of the representations labeling spin networks leads to perfect agreement between the states as well as the area spectra in the two approaches.Comment: a wrong sign corrected in equation (65