Diffusion-controlled annihilation A+B→0A + B \to 0: The growth of an AA particle island from a localized AA-source in the BB particle sea

We present the growth dynamics of an island of particles $A$ injected from a localized $A$-source into the sea of particles $B$ and dying in the course of diffusion-controlled annihilation $A+B\to 0$. We show that in the 1d case the island unlimitedly grows at any source strength $\Lambda$, and the dynamics of its growth {\it does not depend} asymptotically on the diffusivity of $B$ particles. In the 3d case the island grows only at $\Lambda > \Lambda_{c}$, achieving asymptotically a stationary state ({\it static island}). In the marginal 2d case the island unlimitedly grows at any $\Lambda$ but at $\Lambda < \Lambda_{*}$ the time of its formation becomes exponentially large. For all the cases the numbers of surviving and dying $A$ particles are calculated, and the scaling of the reaction zone is derived.Comment: 5 REVTEX pages, no figure

ROLE OF THE NEW MEDIA AS A DISTRIBUTION CHANNEL FOR ACCOMMODATION SERVICES IN TOURISM

The new media has changed the tourism and hospitality industry on many levels bringing an unprecedented change in the way consumers purchase the accommodation services. More and more consumers in a tourism industry use the new media in order to seek information and purchase. At the same time companies that sell accommodation services, or are intermediaries in their sales, are adapting and rapidly increasing an implementation of the new media in their business as a new and innovative channel of distribution. Use of the new media is therefore widely accepted by accommodation providers in a tourism today. This paper gives a brief review of main forms of the new media, which are used in purchasing and selling of the accommodation services, including web sites (and blogs), e-mail, social medias and mobile commerce. An empirical research have been conducted in order to investigate the role of the new media as a channel for distribution of accommodation services in tourism. Exploratory research used for survey a highly structured questionnaire answered by a sample of 102 respondents. The objective was to explore their experience and perspective of their use of the new media in seeking information and purchasing. According to the research, it can be concluded that the new media is the core and the key to a successful business, not only in the sale of accommodation services, but in the whole tourism and accommodation industry. As a result large share of the sales have moved to the new media as a dominant channel for distribution of such services

A large deviation theory-based analysis of heat waves and cold spells in a simplified model of the general circulation of the atmosphere

We study temporally persistent and spatially extended extreme events of temperature anomalies, i.e. heat waves and cold spells, using large deviation theory. To this end, we consider a simplified yet Earth-like general circulation model of the atmosphere and numerically estimate large deviation rate functions of near-surface temperature in the mid-latitudes. We find that, after a renormalisation based on the integrated autocorrelation, the rate function one obtains at a given latitude by looking, locally in space, at long time averages agrees with what is obtained, instead, by looking, locally in time, at large spatial averages along the latitude. This is a result of scale symmetry in the spatial-temporal turbulence and of the fact that advection is primarily zonal. This agreement hints at the universality of large deviations of the temperature field. Furthermore, we discover that the obtained rate function is able to describe spatially extended and temporally persistent heat waves or cold spells, if we consider temporal averages of spatial averages over intermediate spatial scales. Finally, we find out that large deviations are relatively more likely to occur when looking at these spatial averages performed over intermediate scales, thus pointing to the existence of weather patterns associated to the low-frequency variability of the atmosphere. Extreme value theory is used to benchmark our results

Klinički i ultrazvučni pregled vimena krava nakon primenelaktoferina u periodu involucije

Kontrola zdravlja vimena krava je bitan element u procesu proizvodnje zdravstveno bezbednog mleka, te se na farmama visokomlečnih krava, kroz program kontrole mastitisa, redovno sprovode mere otkrivanja i prevencije bolesti vimena. Klinički pregled vimena predstavlja osnovni metod koji pruţa korisne informacije o zdravstvenom statusu vimena krava, ali nailazi na poteškoće u otkrivanju patoloških promena unutar parenhima i papile vimena. U cilju otkrivanja promena u parenhimu vimena moţe se primeniti ultrazvučni pregled koji omogućava vizualizaciju strukturnih promena vimena nastalih kao posledica upalnih procesa i tako olakšava dijagnostiku oboljenja. Tokom poslednjih godina, javio se problem povećanja rezistencije bakterija na antimikrobne lekove, što oteţava lečenje bolesti, ali i ugroţava zdravlje ţivotinja i ljudi. Najčešći uzroci toga su nepravilna upotreba i eventualna zloupotreba antimikrobnih lekova. Mnoga istraţivanja vršena su u in vitro i in vivo uslovima na primeni laktoferina samog ili u kombinaciji sa antibioticima u terapiji i prevenciji mastitisa krava. Laktoferin, gvoţĎe vezujući antimikrobni glikoprotein koji se nalazi u mleku i drugim sekretima, predstavlja bitan deo sistema odbrane mlečne ţlezde. Cilj istraţivanja u okviru ove disertacije je procena dijagnostičke mogućnosti ultrazvučnog pregleda u detekciji subkliničkog mastitisa i poremećene sekrecije vimena, kao i razmatranje opravdanosti primene laktoferina u prevenciji i lečenju mastitisa. Kliničkim pregledom izvršena je procena opšteg zdravstvenog stanja krava, kao i ispitivanje mlečne ţlezde adspekcijom i palpacijom. Za otkrivanje poremećene sekrecije vimena i subkliničkih mastitisa korišćeni su brzi testovi, Kalifornija mastitis test i Draminski test, kao i ultrazvučni pregled mlečne ţlezde krava. OdreĎivanje broja somatskih ćelija u uzorcima mleka uraĎeno je metodom protočne citometrije. Za identifikaciju uzročnika mastitisa korišćene su klasične mikrobiološke metode. Krave sa pozitivnim bakteriološkim nalazom podeljene su u dve ogledne grupe. Krave ogledne grupe I su tretirane intramamarnom aplikacijom antibiotika, dok je kravama ogledne grupe II aplikovana kombinacija antibiotika i laktoferina. OdreĎivanje koncentracije imunoglobulina G u mlečnom serumu krava vršeno je metodom radioimunodifuzije, a odreĎivanje koncentracije laktoferina u mleku krava ELISA testom. U istraţivanjima u okviru ove disertacije, najčešće izolovani major mastitis patogeni bile su bakterije Staphylococcus aureus i Streptococcus agalactiae, a najčešće izolovani minor mastitis patogeni Corynebacterium spp. i koagulaza negativne stafilokoke. Ultrasonografija mlečne ţlezde krava pokazala se kao efikasna metoda u dijagnostici poremećaja sekrecije vimena. Veće vrednosti koncentracije imunoglobulina G u mlečnom serumu krava uočene su tokom perioda predzasušenja i zasušenja, u odnosu na period rane laktacije. Najveći uticaj na porast koncentracije laktoferina u mleku krava su imali bakterijski uzročnici mastitisa. Efikasnost antibiotske terapije primenjene tokom perioda zasušenja kod krava ogledne grupe I iznosila je 52,7%, dok je efikasnost primenjene terapije sa goveĎim laktoferinom i antibiotikom kod krava ogledne grupe II iznosila 60%. Aplikacija laktoferina tokom perioda zasušenja doprinela je efikasnosti terapije intramamarnih infekcija, ali nije imala uticaj na koncentraciju laktoferina u mleku tokom perioda rane laktacije. Dalja istraţivanja su neophodna kako bi se u potpunosti potvrdila efikasnost intramamarne terapije sa goveĎim laktoferinom i antibiotikom u cilju eliminacije uzročnika mastitisa i da se precizno odredi terapijska koncentracija laktoferina.Control of udder health is an essential element in the process of safe milk production, thus, through the mastitis control program, dairy farms regularly conduct measures of detection and prevention of udder diseases. Clinical examination of the udder is a basic method that provides useful information about the health status of cow udders, but this method is limited in its ability to detect pathological changes in the udder parenchyma and teat. In order to detect changes in the parenchyma of the udder, an ultrasound can be applied which allows visualization of udder structural changes incurred as a result of inflammatory processes, thus facilitating diagnosis of diseases. Over the last few years, the problem of increasing resistance to antimicrobial drugs has appeared, making it difficult to treat disease and also threaten the health of animals and humans. The incorrect and widespread use of antimicrobial drugs are the most common cause of this. Many studies were conducted in vitro and in vivo conditions on the use of lactoferrin alone or in combination with antibiotics in the treatment and prevention of mastitis. Lactoferrin, an iron-binding antimicrobial glycoprotein which is found in milk and other secretions, represents an important part of the mammary gland defense system. The aim of the research within this thesis was to evaluate the diagnostic possibilities of udder ultrasonography in the detection of subclinical mastitis and udder secretion disorders, as well as considering the feasibility of lactoferrin application in the prevention and treatment of mastitis. The general condition of the animals was evaluated by clinical examination, as well as udder examination by adspection and palpation. The California mastitis test, Draminski test and ultrasound examination of the cow's mammary glands were used for detection of udder secretion disorders and subclinical mastitis. Somatic cell count in milk samples was determined by flow cytometry method. Classical microbiological methods were used for the isolation and identification of mastitis causative agents. Cows with positive bacteriological findings were divided into two experimental groups. Cows in experimental group I were treated with intramammary applications of antibiotics, while the cows in experimental group II were treated with a combination of antibiotics and lactoferrin. Immunoglobulin G concentration in bovine milk serum was determined by the immunodiffusion method, while lactoferrin concentration in bovine milk was determined using the ELISA test. In this study, the most common isolated major mastitis pathogens were Staphylococcus aureus and Streptococcus agalactiae, while Corynebacterium spp. and coagulase-negatice staphilococci were the most commonly detected minor mastitis pathogens. Ultrasonography of the bovine mammary gland proved to be an effective method in the diagnosis of udder secretion disorders. Higher immunoglobulin G concentrations were observed in milk serum from cows during pre-dry and dry period, relative to early lactation period. The biggest influence on the increase in the concentration of lactoferrin in the bovine milk had mastitis pathogens. The efficacy of antibiotic therapy during the dry period in cows of experimental group I was 52.7%, while the efficacy of the applied therapy with lactoferrina and antibiotics in cows of experimental group II was 60%. Application of lactoferrin during the dry period contributed to the effectiveness of the treatment of intramammary infections, but had no influence on lactoferrin concentration in the milk during the early lactation period. Further studies are necessary to in order to fully confirm the efficacy of intramammary therapy with bovine lactoferrin and antibiotic to eliminate the mastitis pathogens and to determine the therapeutic concentration of lactoferrin

Convergence of extreme value statistics in a two-layer quasi-geostrophic atmospheric model

We search for the signature of universal properties of extreme events, theoretically predicted for Axiom A flows, in a chaotic and high dimensional dynamical system by studying the convergence of GEV (Generalized Extreme Value) and GP (Generalized Pareto) shape parameter estimates to a theoretical value, expressed in terms of partial dimensions of the attractor, which are global properties. We consider a two layer quasi-geostrophic (QG) atmospheric model using two forcing levels, and analyse extremes of different types of physical observables (local, zonally-averaged energy, and the average value of energy over the mid-latitudes). Regarding the predicted universality, we find closer agreement in the shape parameter estimates only in the case of strong forcing, producing a highly chaotic behaviour, for some observables (the local energy at every latitude). Due to the limited (though very large) data size and the presence of serial correlations, it is difficult to obtain robust statistics of extremes in case of the other observables. In the case of weak forcing, inducing a less pronounced chaotic flow with regime behaviour, we find worse agreement with the theory developed for Axiom A flows, which is unsurprising considering the properties of the system

ROLE OF THE NEW MEDIA AS A DISTRIBUTION CHANNEL FOR ACCOMMODATION SERVICES IN TOURISM

The new media has changed the tourism and hospitality industry on many levels bringing an unprecedented change in the way consumers purchase the accommodation services. More and more consumers in a tourism industry use the new media in order to seek information and purchase. At the same time companies that sell accommodation services, or are intermediaries in their sales, are adapting and rapidly increasing an implementation of the new media in their business as a new and innovative channel of distribution. Use of the new media is therefore widely accepted by accommodation providers in a tourism today. This paper gives a brief review of main forms of the new media, which are used in purchasing and selling of the accommodation services, including web sites (and blogs), e-mail, social medias and mobile commerce. An empirical research have been conducted in order to investigate the role of the new media as a channel for distribution of accommodation services in tourism. Exploratory research used for survey a highly structured questionnaire answered by a sample of 102 respondents. The objective was to explore their experience and perspective of their use of the new media in seeking information and purchasing. According to the research, it can be concluded that the new media is the core and the key to a successful business, not only in the sale of accommodation services, but in the whole tourism and accommodation industry. As a result large share of the sales have moved to the new media as a dominant channel for distribution of such services

Agnostic detection of large-scale weather patterns in the northern hemisphere: from blockings to teleconnections

Detecting recurrent weather patterns and understanding the transitions between such regimes are key to advancing our knowledge on the low-frequency variability of the atmosphere and have important implications in terms of weather and climate-related risks. We adapt an analysis pipeline inspired by Markov State Modelling and detect in an unsupervised manner the dominant winter mid-latitude Northern Hemisphere weather patterns in the Atlantic and Pacific sectors, defined by the slowest decaying modes of a suitable projection on a discrete basis of the weather dynamics. When focusing on a longitudinal window of 60$^\circ$, we recognise, first and foremost, a longitude-dependent estimate of the slowest relaxation times, which are often related with transitions between blocked regimes and zonal flow. We analyze in detail the Atlantic and Pacific sectors, finding, additionally, clear evidence of the strong connection between blockings in the two regions. When the analysis is performed in a broader geographical region of the Atlantic sector, we detect teleconnection patterns like the North Atlantic Oscillation and a large-scale mode of variability alternating between Scandinavian and Greenland blocking. The approach proposed here has great potential for intercomparing climate models and for assessing the impact of climate change on the low-frequency variability of the atmosphere.Comment: 14 pages, 4 figures, plus supplementary materia

Atmospheric jet stream variability reflects vegetation activity in Europe

Jet streams are a key component of the climate system, whose dynamics couple closely to regional climate variability. Yet, the link between jet stream variability and vegetation activity has received little attention. Here, we leverage our understanding of the mid-latitude jet stream dynamics over the Euro-Atlantic sector to probe climate-vegetation interactions across Europe. We link indices related to the meridional location of the jet and the large-scale zonal wind speed with remotely-sensed vegetation greenness anomalies during locally-defined growing seasons. Correlations between greenness anomalies and jet latitude anomalies point to a control of the jet stream's variability on vegetation activity over large parts of Europe. This potential control is mediated by the jet latitude anomalies' correlations with temperature, soil moisture and downward surface solar radiation. The sign and strength of these correlations depend on location and time of the year. Furthermore, jet stream variability modulates conditions at the onset and end of the growing season. The link between jet latitude anomalies and vegetation greenness is not only specific to the climate zone, but also to the landclass and subperiod within the growing season. It is thus important to use a locally-defined growing season for interpreting the atmospheric controls on regional vegetation phenology. Results consistent with the correlation analysis emerge when focussing on local high or low greenness months only or on zonal wind speed anomalies, confirming the relevance of jet variability for vegetation activity

CLEANING AND PREVENTION OF INORGANIC DEPOSITS IN PLATE HEAT EXCHANGERS USING PULSATING CURRENT

Fouling of heat exchangers is a major problem in many industrial processes. The higher temperature of the heat exchange surface compared with the liquid containing precipitable compounds causes the formation of inorganic deposits. Removing the deposits on plate heat exchangers is most often carried out by high-pressure cleaning. This is a laborious task and often increases the corrosion rate of the plates by increasing the roughness of the cleaned surface. This study presents an electrochemical method to clean heat exchange surfaces fouled by deposits and to prevent formation of deposits. This method utilizes pulsating current to polarize heat exchange surfaces with periodic anodic and cathodic DC current. The shape of the pulse and the current density are adjusted to maximize the deposit removal rate, thus minimizing plate corrosion. The optimal pulsating current depends on the material of the heat exchange surface, as well as the composition of the deposits and the solution. For cleaning, the current densities and the frequency of the current pulse are typically higher than those used for preventing deposition. Pulsating current can effectively remove deposits with low solubility, such as TiO2 on titanium heat exchange plates or dense gypsum deposits on stainless steel plates. For cleaning titanium, the cathodic pulse and formation of hydrogen is more essential than in the cleaning of stainless steels. However, the risk of corrosion limits the use of high current densities. Experiments have until now been carried out mainly in the laboratory, though industrial pilot cleaning equipment has also been constructed. An application has already been submitted to patent the method

The becoming of a Prehistoric Landscape: Palaeolithic Occupations and Geomorphological Processes at Lojanik (Serbia)

Accomplishing long-term plans to harvest and modify natural resources has been a crucial skill for the survival of our species since early Prehistory. Research on this first step of production mostly focuses on the provenience study of lithic artifacts uncovered at archaeological sites, using petrographic and geochemical analyses to correlate the artifacts with potential geological outcrops. Although fundamental for understanding key aspects of landscape use and mobility, regional raw material economy, and extraction technology, Palaeolithic raw material sources have been less intensively investigated, as they are often difficult to locate and challenging to tackle with traditional archaeological approaches. Lojanik in the Central Balkans is one of the largest Prehistoric quarrying areas known in Europe, showing numerous lithic raw material outcrops exploited from the Middle Palaeolithic to the Chalcolithic periods, over an area of 18 hectares. In this paper, we present the results from our renewed research program in this region. Combining airborne LIDAR mapping, geomorphological and archaeological survey, and techno-typological analysis of lithic artifacts, we were able to reconstruct the geomorphological evolution of the landscape and its use by prehistoric societies.info:eu-repo/semantics/publishedVersio