Superparamagnetic relaxation in Cu_{x}Fe_{3-x}O_{4} (x=0.5 and x=1) nanoparticles

The scope of this article is to report very detailed results of the measurements of magnetic relaxation phenomena in the new Cu$_{0.5}$Fe$_{2.5}$O$_{4}$ nanoparticles and known CuFe$_{2}$O$_{4}$ nanoparticles. The size of synthesized particles is (6.5$\pm$1.5)nm. Both samples show the superparamagnetic behaviour, with the well-defined phenomena of blocking of magnetic moment. This includes the splitting of zero-field-cooled and field-cooled magnetic moment curves, dynamical hysteresis, slow quasi-logarithmic relaxation of magnetic moment below blocking temperature. The scaling of the magnetic moment relaxation data at different temperatures confirms the applicability of the simple thermal relaxation model. The two copper-ferrites with similar structures show significantly different magnetic anisotropy density and other magnetic properties. Investigated systems exhibit the consistency of all obtained results.Comment: 18 pages, 8 figure

Mechanical properties of Cr-containing PM steels sintered in industrial conditions

The objectives of this present research work are Cr-containing PM steels sintered in industrial conditions. The sintering was carried out in industrial furnace with 85%N2+15%H2 atmosphere at temperature of T=1140oC, during 40min. It is obtained information about the mechanical properties of the investigated alloys, which serve to further studies connected with the application of chemical heat treatments such as oxidation and  gas carbonitriding

Microwave properties of DyBa_2Cu_3O_(7-x) monodomains and related compounds in magnetic fields

We present a microwave characterization of a DyBa$_{2}$Cu$_{3}$O$_{7-x}$ single domain, grown by the top-seeded melt-textured technique. We report the (a,b) plane field-induced surface resistance, $\Delta R_s(H)$, at 48.3 GHz, measured by means of a cylindrical metal cavity in the end-wall-replacement configuration. Changes in the cavity quality factor Q against the applied magnetic field yield $\Delta R_s(H)$ at fixed temperatures. The temperature range [70 K ; T_c] was explored. The magnetic field $\mu_0 H <$ 0.8 T was applied along the c axis. The field dependence of $\Delta R_s(H)$ does not exhibit the steep, step-like increase at low fields typical of weak-links. This result indicates the single-domain character of the sample under investigation. $\Delta R_s(H)$ exhibits a nearly square-root dependence on H, as expected for fluxon motion. From the analysis of the data in terms of motion of Abrikosov vortices we estimate the temperature dependences of the London penetration depth $\lambda$ and the vortex viscosity $\eta$, and their zero-temperature values $\lambda(0)=$165 nm and $\eta(0)=$ 3 10$^{-7}$ Nsm$^{-2}$, which are found in excellent agreement with reported data in YBa$_{2}$Cu$_{3}$O$_{7-x}$ single crystals. Comparison of microwave properties with those of related samples indicate the need for reporting data as a function of T/T_c in order to obtain universal laws.Comment: 6 pages, 4 figures, LaTeX, submitted to Journal of Applied Physic

Orangerie – One Unique Museum in Paris

Located right in the heart of Paris in the Tuileries Gardens and renovated in 2006, the Musée de l'Orangerie offers the visitor a poetic and artistic presentation of two prestigious collections. This article will present only the collection of Claude Monet’s paintings Water Lilies (Les Nymphéas). Both monumental and intimate, Water Lilies are the ultimate expression of Claude Monet's artistic ideas, an incredible project by a painter who wanted to explore all the variations of light in his garden at Giverny. The paintings are housed in two elliptical halls, and encourage the visitor to gaze in endless contemplation. After the horror of the First World War, Monet wanted his work to take on this aesthetic and poetic dimension, and provide a haven for peaceful meditation

The Rise and Development of Art Museums

Most of the people associate the term „museum“ with the Louvre, the Hermitage, the Prado, i.e. art museums. This seems to be so natural because the mentioned museums are emblematic for the museum work all over the world. The brilliant exhibitions of these „temples“ of art annually attract millions of visitors from near and far. In front of museum visitors are revealed the artistic achievements of the human civilization from ancient times till modernity. Thus the art museums continue to be schools of humanism and aestheticism. The numerous experts in these museums: curators, restorers, conservators, researchers provide systematic care for the protection, preservation and exhibition of the movable cultural heritage worldwide. The study is chronological history of the emergence and development of the major art museums in Europe. The term „muzeyon“ originates from ancient Greece. The first antique museum is created in the famous library of Alexandria. It was known in antiquity as „muzeyon“ and was the first purposely built antique museum. By this time there were some beginnings of museum activity. It was in Ancient Greece where the first art galleries known as the Pinacotec and sculpture collections - Gliptotek. During the Italian Renaissance emerged and gradually formed a new cultural institution - the art museum, which acquired popularity of the unique Italian name - gallery. Florence is the city that creates the most favorable conditions for the flourishing of Italian Renaissance. There occurred the world-famous galleries Uffizi and Pitti. Until German unification in 1870, it is divided into small independent states. Their rulers are seeking to emulate the kings of European empires and create rich art collections located in special rooms for this purpose called in German - Kunstkamera. 62 These cabinets of art are most widespread in the seventeenth and eighteenth centuries. They do not differ from the Italian galleries. They kept mostly private collections of paintings and sculptures, as well as some examples of applied arts. The Kunstkamera was widely spread among the various German states and in neighboring countries. Following this model, Peter the Great created his famous Kunstkamera in St. Petersburg. The absolutist monarchies in the seventeenth and eighteenth centuries are among the traditional patrons of artists. The nobility collections are filled with orders, purchases, and often through conquest wars, the most striking evidence of this is the Napoleonic wars. Gradually they grew into the largest art museums in the world. The Louvre is a result of the French Revolution. By decision of the Covenant the largest art museum is opened to all citizens of the French Republic. Different is the history of the emergence of the largest museum in Russia - the Hermitage. Another museum that is created on the basis of regal collections in Russia is the Armory Chamber. Similar is the story of emergence of the Prado Museum. It is created on the basis of the Spanish royal collections in 1819. The Habsburg dynasty (Austrian branch) is the longest ruling in Europe - whole 693 years. These collections are the basis for the History and Art Museum in Vienna. By the late nineteenth century the largest and richest art museums in Europe and worldwide were created. Their story is the story of conservation, preservation and presentation of the greatest achievements of human civilization in the arts. The digitization of works of art is the modern way for their documentation and preservation. Publication in virtual museums on the World Wide Web helps for further promotion, especially among young people. Thus the art museums have become more popular in the virtual world. By most valuable and attractive exhibits they attend many websites as emblems of art museums

Integrated mapping of ecosystems and assessment of forest ecosystem services at river basin scale

Ecosystems provide various goods and services to society and their valuation is among the main objectives of the concept of ecosystem services (ES). The mapping of ecosystems is the main building block of the whole process of the Mapping and Assessment of Ecosystems and their Services (MAES). The analyses of the ecosystem data produced during the implementation of the national methodology for mapping ecosystems in Bulgaria (MAES BG) reveal some problems that may cause confusion in cases of integrated assessment of all ecosystem types. In this paper, we present an approach that enables formulation of a uniform spatial dataset based on the mapping of the main ecosystem types, that can be used for mapping of ES at a river basin scale. It has been applied to the upper part of the Ogosta River basin and the result is a topologically correct uniform spatial data layer. The approach gives one possible solution to problems related to the different sources of information and the discrepancies between ecosystem types in the national mapping of ecosystems in Bulgaria. It is based on the use of a uniform spatial framework that outlines the ecosystem types and sets the initial database for further mapping. This ensures a topologically correct spatial dataset for the ecosystems and a background for further updates for each ecosystem at the different levels of MAES typology. The most appropriate spatial basis for the territory of Bulgaria is the database for the physical blocks of the Ministry of Interior. Its application to the studied river basin gives encouraging results and can be used as an example for similar areas. Further development of the approach will ensure the mapping of the forest ecosystems at level 3 of the MAES BG typology and more precise delineation of the grassland, heathland, freshwater, and sparsely vegetated ecosystems

Surface Effects in Superparamagnetic Magnetite Particles *

Abstract. We have studied the properties of unshielded and shielded (hybrid) nanosized spherical magnetite particles with diameter 10 ± 2 nm, which are superparamagnetic at room temperature, through magnetometry, X-ray powder diffraction, magnetic force microscopy imaging and Mössbauer spectroscopy. The unshielded material was prepared by co-precipitation either in air or in inert atmosphere and part of it was shielded subsequently by β-cyclodextrin (β-C42H70O35). The studies indicated that in the unshielded particles there is a surface layer with a depth of 3 nm wherein an exponential rise in the number of vacancies is observed in the octahedral sublattice ([B]-sites), so that the particle surface is highly defective and could be represented by the general formula (Fe , where x = 0-0.3 and denotes vacancies. In contrast, the hybrid particles, being protected from oxidation, are structurally close to bulk magnetite so that the surface magnetic effects could be understood as due to the chaotic orientation of the magnetic moments at the magnetic-nonmagnetic material interface. An empirical model for a spherical single domain particle was developed in attempting to describe the evolution of structural defects in the surface layer