Reimann Brake Ramp for planar flow casting processes and analysis of ribbon gluing

Planar flow casting is a rapid solidification process used to manufacture thin, metallic ribbons, and foil. Liquid metal is forced through a nozzle against a heat-sink wheel, and it rapidly solidifies into thin ribbons. A puddle of molten metal, held by surface tension, forms between the nozzle and wheel. This study examines a well-defined periodic surface defect called herringbone (HB), which is commonly produced when casting zirconium based alloys. The presence of this defect is related to processing conditions and puddle dynamics. Its formation has been correlated with the pinning of the liquid puddle at the nozzle edge. Here, the uniformity of thickness along a ribbon was successfully controlled (over a length of 50 m) using the Reimann Brake Ramp, which reduces the wheel speed at the start of the cast. For the alloy used in this study, the variation in the dimensionless thickness parameter, , with the Euler number () at assigned values of followed an allometric scaling, with an exponent value close to the theoretical value of 1/3. Furthermore, the nozzle inclination was related to the ribbon thickness, , and the ribbon quality. Moreover, a newly developed automatized melt spinner permitted monitoring and controlling of the process parameters, elucidating the gluing phenomenon of the ribbon observed during the starting phase. The ribbon gluing was influenced by the puddle geometry, the recirculation in the puddle, and later, to the ribbon cooling rate. Within these results, high-quality ribbons with control thickness over a considerable length are achieved

Persistent memory for a Brownian walker in a random array of obstacles

We show that for particles performing Brownian motion in a frozen array of scatterers long-time correlations emerge in the mean-square displacement. Defining the velocity autocorrelation function (VACF) via the second time-derivative of the mean-square displacement, power-law tails govern the long-time dynamics similar to the case of ballistic motion. The physical origin of the persistent memory is due to repeated encounters with the same obstacle which occurs naturally in Brownian dynamics without involving other scattering centers. This observation suggests that in this case the VACF exhibits these anomalies already at first order in the scattering density. Here we provide an analytic solution for the dynamics of a tracer for a dilute planar Lorentz gas and compare our results to computer simulations. Our result support the idea that quenched disorder provides a generic mechanism for persistent correlations irrespective of the microdynamics of the tracer particle.Comment: 11 pages, 4 figures, accepted in Chemical Physic

High Magnetic Field Microwave Conductivity of 2D Electrons in an Array of Antidots

We measure the high magnetic field ($B$) microwave conductivity, Re$\sigma_{xx}$, of a high mobility 2D electron system containing an antidot array. Re$\sigma_{xx}$ vs frequency ($f$) increases strongly in the regime of the fractional quantum Hall effect series, with Landau filling $1/3<\nu<2/3$. At microwave $f$, Re$\sigma_{xx}$ vs $B$ exhibits a broad peak centered around $\nu=1/2$. On the peak, the 10 GHz Re$\sigma_{xx}$ can exceed its dc-limit value by a factor of 5. This enhanced microwave conductivity is unobservable for temperature $T \gtrsim 0.5$ K, and grows more pronounced as $T$ is decreased. The effect may be due to excitations supported by the antidot edges, but different from the well-known edge magnetoplasmons.Comment: 4 pages, 3 figures, revtex

Brownian motion: a paradigm of soft matter and biological physics

This is a pedagogical introduction to Brownian motion on the occasion of the 100th anniversary of Einstein's 1905 paper on the subject. After briefly reviewing Einstein's work in its contemporary context, we pursue some lines of further developments and applications in soft condensed matter and biology. Over the last century Brownian motion became promoted from an odd curiosity of marginal scientific interest to a guiding theme pervading all of the modern (live) sciences.Comment: 30 pages, revie

Sadržaj toksičnih i esencijalnih metala u ljekovitom bilju koje raste u onečišćenim i neonečišćenim područjima u Makedoniji

The aim of this study was to determine and compare Ba, Cr, Cd, Fe, Sr, Pb, and Zn content in medicinal herbs Urtica dioica L., Taraxacum officinale, and Matricaria recutita growing in polluted and unpolluted areas of the Republic of Macedonia. The metal content was determined using inductively coupled plasma atomic emission spectroscopy (ICP-AES). In the unpolluted area of Mt. Plačkovica the metal content in Taraxacum officinale was in the descending order: Fe>Sr>Zn>Ba>Cr, while Pb and Cd were below the limit of detection. In the polluted area of Veles, the order was as follows: Fe>Zn>Sr>Pb>Ba>Cd>Cr. Our results suggest that quality assurance and monitoring of toxic metals is needed for plants intended for human use and consumption. Medicinal plants should be picked in areas free of any contamination sources.Cilj je ovoga istraživanja bio utvrditi i usporediti sadržaj Ba, Cr, Cd, Fe, Sr, Pb i Zn u ljekovitom bilju Urtica dioica L., Taraxacum offi cinale i Matricaria recutita koje raste u onečišćenome odnosno neonečišćenome području u Republici Makedoniji. Sadržaj metala utvrdili smo s pomoću atomske emisijske spektroskopije induktivno spregnutom plazmom (engl. inductively coupled plasma atomic emission spectroscopy, krat. ICP-AES). U neonečišćenome području planine Plačkovice, sadržaj metala u Taraxacum offi cinale kretao se kako slijedi: Fe>Sr>Zn>Ba>Cr, dok su Pb i Cd bili ispod granice detekcije. U onečišćenome području blizu talionice olova i cinka u Velesu redoslijed je bio ovakav: Fe>Zn>Sr>Pb>Ba>Cd>Cr. Naši rezultati upućuju na potrebu za osiguranjem kakvoće i praćenjem razina toksičnih metala u biljaka namijenjenih ljudskoj uporabi. Ljekovito bilje valja brati u područjima bez izvora onečišćenja

Sustainability reporting practices and their social impact to NGO funding in Italy

This study analyses the growing social trends of sustainability reporting practices in non-governmental organisations (NGOs). Taking a preliminary step toward NGO funding, we consider the current lack of information disclosure in existing reporting practices, which are diverse and unsustainable. We investigate key organisational information in order to discover any potential links between funding sources and disclosure practices. In Italy, today there is an on-going effort to encourage public engagement in civil society. A percentage-tax law allows taxpayers to dedicate ‘cinque per mille’ (one-half percent)of their income to NGOs, which is then deducted from their tax obligation (Hereafter, ‘5 per thousand’). Our primary research objective is to understand if there is a link between the ‘5 per thousand’ donations that NGOs receive for providing social impact, and their reporting practices. Therefore, we critically analyse if and how sustainable reporting practices are achieved within the top 100 most funded NGOs that receive the ‘5 per thousand’ donation. We examine public data from official government records published by the Italian Revenue Agency. The findings suggest that sustainability reporting offers a number of financial and social advantages, including social impact that builds trust towards the idea of civil society and its funders. © 2019 Elsevier Lt

Relativistic Brownian Motion

Stimulated by experimental progress in high energy physics and astrophysics, the unification of relativistic and stochastic concepts has re-attracted considerable interest during the past decade. Focusing on the framework of special relativity, we review, here, recent progress in the phenomenological description of relativistic diffusion processes. After a brief historical overview, we will summarize basic concepts from the Langevin theory of nonrelativistic Brownian motions and discuss relevant aspects of relativistic equilibrium thermostatistics. The introductory parts are followed by a detailed discussion of relativistic Langevin equations in phase space. We address the choice of time parameters, discretization rules, relativistic fluctuation-dissipation theorems, and Lorentz transformations of stochastic differential equations. The general theory is illustrated through analytical and numerical results for the diffusion of free relativistic Brownian particles. Subsequently, we discuss how Langevin-type equations can be obtained as approximations to microscopic models. The final part of the article is dedicated to relativistic diffusion processes in Minkowski spacetime. Due to the finiteness of velocities in relativity, nontrivial relativistic Markov processes in spacetime do not exist; i.e., relativistic generalizations of the nonrelativistic diffusion equation and its Gaussian solutions must necessarily be non-Markovian. We compare different proposals that were made in the literature and discuss their respective benefits and drawbacks. The review concludes with a summary of open questions, which may serve as a starting point for future investigations and extensions of the theory.Comment: review article, 159 pages, references updated, misprints corrected, App. A.4. correcte

Abstracts from the 8th International Conference on cGMP Generators, Effectors and Therapeutic Implications

This work was supported by a restricted research grant of Bayer AG