Shape of an elastica under growth restricted by friction

We investigate the quasi-static growth of elastic fibers in the presence of dry or viscous friction. An unusual form of destabilization beyond a critical length is described. In order to characterize this phenomenon, a new definition of stability against infinitesimal perturbations over finite time intervals is proposed and a semi-analytical method for the determination of the critical length is developed. The post-critical behavior of the system is studied by using an appropriate numerical scheme based on variational methods. We find post-critical shapes for uniformly distributed as well as for concentrated growth and demonstrate convergence to a figure-8 shape for large lengths when self-crossing is allowed. Comparison with simple physical experiments yields reasonable accuracy of the theoretical predictions

Explaining the elongated shape of 'Oumuamua by the Eikonal abrasion model

The photometry of the minor body with extrasolar origin (1I/2017 U1) 'Oumuamua revealed an unprecedented shape: Meech et al. (2017) reported a shape elongation b/a close to 1/10, which calls for theoretical explanation. Here we show that the abrasion of a primordial asteroid by a huge number of tiny particles ultimately leads to such elongated shape. The model (called the Eikonal equation) predicting this outcome was already suggested in Domokos et al. (2009) to play an important role in the evolution of asteroid shapes.Comment: Accepted by the Research Notes of the AA

A Universal Voltammetric Cell

In eleotroanalytical research it is desirable to wor·k with a cell which is easily used for various electrochemical measurements. The requirem~μts for such a cell are: 1) ability to function with different types of electrodes,, 2) perfectly reproducible hydrodynamic conditions, 3) ·simple replacement \u27of the sample and electrodes, and 4) construction material which is inert in respect to the sample

Countinuous and discrete models for abrasion processes

The origin of the shapes of stones and other particles formed by water or wind has always attracted the attention of geologists and mathematicians. A classical model of abrasion due to W. J. Firey leads to a geometric partial differential equation representing the continuum limit of the process. This model predicts convergence to spheres from an arbitrary initial form; analogously, the two-dimensional version of the model predicts convergence to circles. The shapes of real stones are, however, not always round. Most notably, coastal pebbles tend to be smooth but somewhat flat, and ventifacts (e.g. pyramidal dreikanters) often have completely different shapes with sharp edges. Inspired by Firey´s results, a new PDE is derived in this paper, which not only appears to be a natural mathematical generalization of Firey´s PDE, but also represents the continuum limit of a genezalized abrasion model based on recurrent loss of material due to collisions of nearby pebbles. We also introduce a related, mezo-scale discre te random model which is ideally suited for analyzing wear processes in specific geometric scenarios. Preliminary results suggest that our model is capable to predict a broad range of limit shapes: polygonal shapes with sharp edges develop due to sand blasting (big stone surrounded by infinitesimally small particles), round stones emerge due to collisions with relatively big stones, and flat shapes are the typical outcome in the intermediate case. The results show nice agreement with real data despite the model´s simplicity

Biomass potential assessment for locating biorefinery plant in Hungary

To find a suitable site for a 150,000 metric ton dry material per year (t dm/yr) input capacity biorefinery plant in Hungary is a challenging task. Not only biomass potentials have to be assessed, competing uses, sustainability aspects, public opinion and future threats to feedstock availability should be also taken into account. As a result of our calculations, currently there is enough feedstock available for the targeted input capacity to operate in an ecologically sustainable way. However, several factors may threaten the future of feedstock availability. In the long run enhanced price competition is anticipated for biomass among biorefinery, livestock keeping, timber industry and biomass based renewable energy production. The majority of stakeholders accept in general biorefinery as a promising solution for substituting fossil based plastics, still local interests give priority to a balanced agricultural production including higher shares of husbandry

Genetic Diversity of Serine Protease Inhibitors in Myxozoan (Cnidaria, Myxozoa) Fish Parasites

We studied the genetic variability of serine protease inhibitors (serpins) of Myxozoa, microscopic endoparasites of fish. Myxozoans affect the health of both farmed and wild fish populations, causing diseases and mortalities. Despite their global impact, no effective protection exists against these parasites. Serpins were reported as important factors for host invasion and immune evasion, and as promising targets for the development of antiparasitic therapies. For the first time, we identified and aligned serpin sequences from high throughput sequencing datasets of ten myxozoan species, and analyzed 146 serpins from this parasite group together with those of other taxa phylogenetically, to explore their relationship and origins. High intra- and interspecific variability was detected among the examined serpins. The average sequence identity was 25-30% only. The conserved domains (i.e. motif and signature) showed taxon-level differences. Serpins clustered according to taxonomy rather than to serpin types, and myxozoan serpins seemed to be highly divergent from that of other taxa. None of them clustered with their closest relative free-living cnidarians. The genetic distinction of myxozoan serpins further strengthens the idea of an independent origin of Myxozoa, and may indicate novel protein functions potentially related to parasitism in this animal group

Mid-infrared interferometric variability of DG Tau: implications for the inner-disk structure

Context. DG Tau is a low-mass pre-main sequence star, whose strongly accreting protoplanetary disk exhibits a so-far enigmatic behavior: its mid-infrared thermal emission is strongly time-variable, even turning the 10 $\mu$m silicate feature from emission to absorption temporarily. Aims. We look for the reason for the spectral variability at high spatial resolution and at multiple epochs. Methods. We study the temporal variability of the mid-infrared interferometric signal, observed with the VLTI/MIDI instrument at six epochs between 2011 and 2014. We fit a geometric disk model to the observed interferometric signal to obtain spatial information about the disk. We also model the mid-infrared spectra by template fitting to characterize the profile and time dependence of the silicate emission. We use physically motivated radiative transfer modeling to interpret the mid-infrared interferometric spectra. Results. The inner disk (r<1-3 au) spectra exhibit a 10 $\mu$m absorption feature related to amorphous silicate grains. The outer disk (r>1-3 au) spectra show a crystalline silicate feature in emission, similar to the spectra of comet Hale-Bopp. The striking difference between the inner and outer disk spectral feature is highly unusual among T Tauri stars. The mid-infrared variability is dominated by the outer disk. The strength of the silicate feature changed by more than a factor of two. Between 2011 and 2014 the half-light radius of the mid-infrared-emitting region decreased from 1.15 to 0.7 au. Conclusions. For the origin of the absorption we discuss four possible explanations: a cold obscuring envelope, an accretion heated inner disk, a temperature inversion on the disk surface and a misaligned inner geometry. The silicate emission in the outer disk can be explained by dusty material high above the disk plane, whose mass can change with time, possibly due to turbulence in the disk.Comment: 16 pages, 13 figure

A hangulatstabilizáló gyógyszerek (lítium, valproinsav, karbamazepin) hatásai a kalcium ionok által közvetített intracelluláris jelátvitelre = Effects of mood stabilizer drugs (lithium, valproic acid, carbamazepine) on the calcium ion mediated intracellular signal transduction

A lítium bipoláris betegek kezelésére használt gyógyszer, azonban pontos hatásmechanizmusa máig nem tisztázott. Korábbi kutatásokból ismert, hogy a lítium gátolja a foszfoglukomutázt, mely a galaktóz metabolizmus egyik kulcsenzime. Mivel a galaktóz tápanyagforrásul szolgálhat, valamint metabolitjai elengedhetetlen építőkövei a glikoproteineknek, glikolipideknek, tanulmányunkban a lítium galaktóz metabolizmusra kifejtett hatását vizsgáltuk, valamint ezen hatások celluláris válaszreakcióit. Munkánk eredményeként megállapítottuk, hogy a lítium kezelés jelentősen befolyásolja a galaktóz metabolizmust. Ennek következtében olyan poszt-transzlációs fehérje módosulások jöhetnek létre, melyek hypoglikémiás állapotra hasonlítanak. Ezzel magyarázatot találtunk arra a kérdésre, hogy miért aktiválódik az unfolded protein response galaktózon növesztett, lítiummal kezelt sejtekben. | Lithium is a known mood stabilizer in the therapy of bipolar disorders however its exact molecular mechanism is not clarified yet. It was shown earlier that lithium inhibits phosphoglucomutase, one of the key enzyme of galactose metabolism. Since galactose is an important nutrient resource and its metabolites are essential for glycoprotein, glycolipid synthesis, inn this study we examined the effect of lithium on galactose metabolism and subsequent changes in the protein post-translational modification. We demonstrated that lithium significantly influences galactose metabolism and due to this, causing disturbances in the post-translational protein modification similar to hypoglycemic conditions. This process could be the missing link that leads to UPR activation in cells grown on galactose and treated by lithium

Differentiation Potential of Pancreatic Fibroblastoid Cells/Stellate Cells: Effects of Peroxisome Proliferator-Activated Receptor Gamma Ligands

Pancreatic stellate cells have been investigated mostly for their activation process, supposed to support the development of pancreatic disease. Few studies have been presented on reversal of the activation process in vitro. Thiazolidinediones (TZDs) have been used as antidiabetics and have now been reported to exert antifibrotic activity. We tested effects of natural and synthetic ligands of peroxisome proliferator-activated receptor gamma (PPARγ) on human pancreatic fibroblastoid cells (hPFCs) in search for specificity of action. Ciglitazone, as a prototype of TZDs, was shown to have reversible growth inhibitory effects on human pancreatic fibroblastoid cells/stellate cells. Cells treated with ciglitazone for three days showed enhanced lipid content and induction of proteins involved in lipid metabolism. Collagen synthesis was reduced in hPFC. Interaction of PPARγ with DNA binding sites upon ligand binding was shown by gel shift analysis. These findings point toward a potential for adipocyte differentiation in human pancreatic fibroblastoid cells