Bloggers Behavior and Emergent Communities in Blog Space

Interactions between users in cyberspace may lead to phenomena different from those observed in common social networks. Here we analyse large data sets about users and Blogs which they write and comment, mapped onto a bipartite graph. In such enlarged Blog space we trace user activity over time, which results in robust temporal patterns of user--Blog behavior and the emergence of communities. With the spectral methods applied to the projection on weighted user network we detect clusters of users related to their common interests and habits. Our results suggest that different mechanisms may play the role in the case of very popular Blogs. Our analysis makes a suitable basis for theoretical modeling of the evolution of cyber communities and for practical study of the data, in particular for an efficient search of interesting Blog clusters and further retrieval of their contents by text analysis

Spectral and Dynamical Properties in Classes of Sparse Networks with Mesoscopic Inhomogeneities

We study structure, eigenvalue spectra and diffusion dynamics in a wide class of networks with subgraphs (modules) at mesoscopic scale. The networks are grown within the model with three parameters controlling the number of modules, their internal structure as scale-free and correlated subgraphs, and the topology of connecting network. Within the exhaustive spectral analysis for both the adjacency matrix and the normalized Laplacian matrix we identify the spectral properties which characterize the mesoscopic structure of sparse cyclic graphs and trees. The minimally connected nodes, clustering, and the average connectivity affect the central part of the spectrum. The number of distinct modules leads to an extra peak at the lower part of the Laplacian spectrum in cyclic graphs. Such a peak does not occur in the case of topologically distinct tree-subgraphs connected on a tree. Whereas the associated eigenvectors remain localized on the subgraphs both in trees and cyclic graphs. We also find a characteristic pattern of periodic localization along the chains on the tree for the eigenvector components associated with the largest eigenvalue equal 2 of the Laplacian. We corroborate the results with simulations of the random walk on several types of networks. Our results for the distribution of return-time of the walk to the origin (autocorrelator) agree well with recent analytical solution for trees, and it appear to be independent on their mesoscopic and global structure. For the cyclic graphs we find new results with twice larger stretching exponent of the tail of the distribution, which is virtually independent on the size of cycles. The modularity and clustering contribute to a power-law decay at short return times

Epidemiology-clinical study of congenital hypothyroidism detected during 30 years of a screening programe in Serbia

Uvod: Kongenitalni hipotiroidizam (KH) je najčešće kongenitalno endokrinološko oboljenje, koje je u eri pre skrininga bilo vodeći uzrok mentalne retardacije. Program skrininga na KH, omogućio je pravovremeno postavljanje dijagnoze i rani početak supstitucione terapije, što je dovelo do skoro potpunog iščezavanja mentalne retardacije pouzrokovane ovim oboljenjem. U Srbiji, skrining na KH započet je 1983. godine jednogodišnjom pilot studijom u porodilištima grada Beograda, a potom se proširio na ostale regione Srbije. Ciljevi ovog istraživanja su bili određivanje kumulativne incidencije i prevalencije KH na teritoriji Srbije bez pokrajina u periodu od 1983. do 2013. godine, analiza kliničkih i laboratorijskih karakteristika dece sa KH, kao i definisanje glavnih kliničkih i laboratorijskih karakteristika dece sa trajnim i tranzitornim oblikom bolesti. Metodologija: U Srbiji, skrining na KH se bazira na određivanju koncentracije tireostimulišućeg hormona (TSH) iz uzorka kapilarne krvi. Tokom perioda 1983-1987. granična vrednost TSH je bila 30 mIJ/l (P1), 1988-1997. granična vrednost TSH je iznosila 15 mIJ/l (P2), 1998-2006. 10 mIJ/l (P3), a 2007- 2013. iznosila je 9 mIJ/l (P4). Koncentracija TSH između granične i 40 mIJ/l zahtevaju ponavljanje uzoraka, dok koncentracija TSH ≥40 mIJ/l ukazuje na verovatno postojanje primarnog KH i novorođenče se odmah hospitalizuje Na osnovu scintigrafskog nalaza, svi ispitanici su podeljeni u dve grupe, sa trajnim i tranzitornim oblikom KH. Trajni KH su imala novorođenčad s atireozom, ektopijom, hemiagenezijom i hipoplazijom tiroideje. Novorođenčad čija je tiroideja bila na mestu, normalne veličine ili uvećana, sa normalnom funkcijom posle reevaluacije u uzrastu od tri godine, svrstana su u grupu sa tranzitonim KH. Rezultati: U periodu 1983-2013. godine programom skrininga na KH na teritoriji Srbije bez pokrajina obuhvaćeno je 1.547.122 novorođenčeta. Primarni KH je dijagnostikovan kod 434, 59,7% (n=259) devojčica i 40,3% (n=175) dečaka. Kumulativna incidencija KH je iznosila 28,6 na 100 000 (1:3495), dok je prevalencije sa 1:5084 u P1 porasla na 1:1807 u P4...Introduction: Congenital hypothyroidism (CH) is the most frequent congenital endocrine disorder and the main cause of preventable mental retardation. Newborn screening (NBS) programs for CH have been established in most countries in order to enable early diagnosis and treatment of CH, thus preventing related neurodevelopmental complications. In Serbia, the CH screening program was initiated as a pilot study in Belgrade maternity hospitals in 1983 and then integrated into all maternity hospitals in Central Serbia. The purpose of the present study was to determine the incidence of CH from 1983 to 2013, and to assess changes in prevalence and etiology of CH during the study period. The secondary goal was to analyze clinical and laboratory characteristics of children with CH. Metodology: Newborn screening program for CH was based on measuring neonatal thyroid-stimulating hormone (TSH) levels using a 30 mU/l cutoff until 12/1987 (P1), 15 mU/l until 12/1997 (P2), 10 mU/l until 12/2006 (P3) and 9 mU/l thereafter (P4). When the TSH value was between cutoff and 40 mU/l, a positive was suspected and a new blood sample was extracted, while TSH result ≥ 40 mU/l was considered positive for CH and the newborn was immediately referred to the hospital. In regards to etiology, according to the scintigraphy result, all of the patients were classified as having permanent or transient CH. The patients with athyreosis, ectopy, hemiagenesis and hypoplasia in situ were considered to have permanent CH. The patients with eutopic normally sized gland and eutopic goiter whose thyroid function was within the normal range after a reevaluation at the age of 3, were considered to have transient CH. Results: During the study period from 1983 to 2013, there were 1,547,122 live births screened for CH. Primary CH was detected in 434 newborns, 59.7% (n=259) female and 40.3% (n=175) male, resulting in an overall incidence of 28.6 per 100 000 (1:3495). Among children with CH, 325 had permanent and 65 transient CH. The incidences standardized in regard to the number of screened newborns during each period showed significant increase (p<0.001) from 1:5084 in P1 to 1:1807 in P4..

Activities of antioxidant systems during germination of Chenopodium rubrum seeds

The activities of superoxide-dismutase (SOD), catalase (CAT) and peroxidase (POD), and concentrations of glutathione and ascorbate have been studied during the first stages of germination in Chenopodium rubrum L. seeds. The highest CAT and SOD activity was found prior to radicle Protrusion, while POD activity was maximal at the time of radicle protrusion and seedling development, new POD isozymes simultaneously appearing. The concentrations of total, reduced and oxidized glutathione showed similar changes during germination, the highest values being detected at the time of radicle protrusion. Ascorbic acid was present in the seeds in a detectable concentration only at the time preceding radicle protrusion, while its oxidized form dehydroascorbic acid was detected during the whole germination period studied. Gibberellic acid (GA(3), 160 muM) had no effect on germination percentage, but in presence of GA(3), SOD and CAT activity notably increased prior to radicle protrusion, and oxidized concentration decreased in further germination

Service life prediction of running steel wire ropes

Vrlo visoka čvrstoća omogućava žičanom užetu da prenese velike zatezne sile i da se kreće po koturima relativno malog prečnika. Žice od čelika vrlo visoke čvrstoće su postojale više od sto godina pre nego što su patentirane, kada je uveden specijalni postupak zagrevanja i usavršen postupak izvlačenja. Dalja poboljšanja posle toga su uvedena u relativno malim koracima. Žičana užad uvek imaju ograničen radni vek. Zbog toga ona moraju da se podvrgnu inspekciji i ispitaju u pravilnim intervalima da bi se zamenila znatno pre otkaza. Krajnji korisnik mašine sa čeličnim žičanim užetom u svakom slučaju želi da ima grubu ocenu radnog veka užeta već u ranoj fazi razvoja mašine. tako da bude u mogućnosti, ako zatreba, da poboljša sistem mašine. To je jedan od razloga zbog kojih su tokom niza godina izvedena obimna istraživanja kako bi se poboljšali postupci proračuna za predviđanje radnog veka žičanih užadi. Namena ovog rada je da ponudi pregled informacija o postupcima proračuna i da prikaže mogućnosti i ograničenja postupaka prognoziranja za predviđanja radnog veka čeličnih žičanih užadi u eksploataciji.Very high strength enables wire ropes to support large tensile forces and to run over sheaves with relative small diameters. Very high strength steel wires had already been in existence for more than a hundred years when patenting, a special heating process was introduced and the drawing process improved. Since then, further improvements have only occurred in relatively small steps. Wire ropes always have a limited service life. Therefore they must be inspected and examined at regular intervals so that they are replaced well before failure. End-users of machinery with steel wire ropes, however, would like to have a rough estimation of the service life of the ropes already in the early stages of conceiving their machines, so that they can, if necessary, improve the revving system. This is one of the reasons why for many years extensive research is carried out in order to improve calculations for predicting the service life of wire ropes. This paper is meant to offer an overview information on the method of calculation and to demonstrate the potential and limitations of the forecasting procedure for service-life prediction of running steel wire ropes

Influence of different nutritional preparations on morpho-anatomical characteristics of wild fruit seedlings : doctoral dissertation

Шумске воћкарице које су широко распрострањене, али и оне чије је присуство спорадично или ограничено на мања пространства, од огромне су важности и њихово очување, унапређење и одрживо коришћење генофонда на природним стаништима у складу је са општим интересом очувања биодиверзитета Србије. Основни научни циљеви везани су за истраживање морфолошко-анатомске грађе садница шумских воћкарица (црни орах, орах, мечја леска, оскоруша, дивља трешња) и утицај три различита типа препарата исхране на њихову примарну грађу, како би се одабрао онај препарат, чији је утицај на развој садног материјала био највећи и допринео правилном развоју и оптималном квалитету садница. Оглед је постављен 2011. године у Расаднику Института за шумарство у Београду, а поновљен 2012. и 2013. године. За сваку од пет истраживаних врста формирана су четири блока огледних површина, сваки са по три понављања: контролна површина (у коме биљке нису биле третиране препаратима исхране), и у зависности од типа препарата исхране којима је вршено третирање Osmocote® Exact Standard 5-6 М, контролисано разлагајуће минерално ђубриво, Bactofil® B 10, микробиолошки препарат и Florin 2, комплексно NPK минерално ђубриво. Сетва семена свих врста извршена је почетком априла. Семе је засејано у супстрату Tref PS fine brown, у који су (осим у контролном пољу) непосредно пред сетву додати наведени препарати исхране. За потребе истраживања ове докторске дисертације измерени су следећи морфометријски параметри: висина надземног дела садница, пречник у кореновом врату, дужина корена, маса надземног дела биљке (изданка) у апсолутно сувом стању, маса подземног дела биљке (корена) у апсолутно сувом стању, а осим њих, израчунати су и изведени параметри – однос пречник/висина и индекс квалитета садница...Widely spread forest fruit trees, but also those whose occurrence is sporadic or limited to smaller areas, have an enormous importance and their preservation, improvement and sustainable use in natural habitats are in accordance with the general interest for preservation of the biodiversity in Serbia. The primary scientific objectives are related to the study of morphologicalanatomical structure of seedlings of forest fruit trees (black walnut, walnut, Turkish hazelnut, service tree, and wild cherry) and the impact of three different type nutrition preparations on the primary structure of the said forest fruit trees, with the aim of selecting a preparation that exerts the strongest impact on development of planting material and contributes to adequate development and optimum quality of seedlings. A sample plot was established in 2011 at the seedling nursery of the Institute of Forestry in Belgrade and re-established in 2012 and 2013. For each of five studied species four blocks of sample plots with a repeated pattern were established, which were composed of the control plot (in which plants were not treated with nutrition preparations) and, depending on the type of nutrition preparation applied, plots treated with Osmocote® Exact Standard 5-6 М (controlled release mineral fertiliser), Bactofil® B 10 (micro-biological preparation) and Florin 2, (complex NPK mineral fertiliser). The sowing of seeds of all species was conducted in the beginning of April. The seeds were sown in the Tref PS fine brown substrate, into which, (with the exception of the control plot), the abovementioned nutrition preparations were immediately added. For the purpose of research of this doctoral dissertation, the following morphometric parameters were measured: The height of the surface part of the seedlings, diameter at the root collar, mass of the surface part of plant (sprout) in the absolutely dry condition, mass of the under surface part of plant (root) in the absolutely dry condition. In addition, the following parameters were calculated and obtained: the diameter/height ratio and seedling quality index..

Properties of the superconducting state in a two-band model

Eliashberg theory is used to investigate the range of thermodynamic properties possible within a two-band model for s-wave superconductivity and to identify signatures of its two-band nature. We emphasize dimensionless BCS ratios (those for the energy gaps, the specific heat jump and the negative of its slope near Tc, the thermodynamic critical field Hc(0), and the normalized slopes of the critical field and the penetration depth near Tc), which are no longer universal even in weak coupling. We also give results for temperature-dependent quantities, such as the penetration depth and the energy gap. Results are presented both for microscopic parameters appropriate to MgB2 and for variations away from these. Strong coupling corrections are identified and found to be significant. Analytic formulas are provided which show the role played by the anisotropy in coupling in some special limits. Particular emphasis is placed on small interband coupling and on the opposite limit of no diagonal coupling. The effect of impurity scattering is considered, particularly for the interband case.Comment: 20 pages, 14 figures, final version accepted in PR

Changes in Optical Conductivity due to Readjustments in Electronic Density of States

Within the model of elastic impurity scattering, we study how changes in the energy dependence of the electronic density of states (EDOS) $N(\epsilon)$ around the Fermi energy $\epsilon_F$ are reflected in the frequency-dependent optical conductivity $\sigma(\omega)$. While conserving the total number of states in $N(\epsilon)$ we compute the induced changes in $\sigma(\omega)$ as a function of $\omega$ and in the corresponding optical scattering rate $1/\tau_{\rm op}(\omega)$. These quantities mirror some aspects of the EDOS changes but the relationship is not direct. Conservation of optical oscillator strength is found not to hold, and there is no sum rule on the optical scattering rate although one does hold for the quasiparticle scattering. Temperature as well as increases in impurity scattering lead to additional changes in optical properties not seen in the constant EDOS case. These effects have their origin in an averaging of the EDOS around the Fermi energy $\epsilon_F$ on an energy scale set by the impurity scattering.Comment: 13 pages, 7 figure

Similar glassy features in the NMR response of pure and disordered La1.88Sr0.12CuO4

High Tc superconductivity in La2-xSrxCuO4 coexists with (striped and glassy) magnetic order. Here, we report NMR measurements of the 139La spin-lattice relaxation, which displays a stretched-exponential time dependence, in both pure and disordered x=0.12 single crystals. An analysis in terms of a distribution of relaxation rates T1^-1 indicates that i) the spin-freezing temperature is spatially inhomogeneous with an onset at Tg(onset)=20 K for the pristine samples, and ii) the width of the T1^-1 distribution in the vicinity of Tg(onset) is insensitive to an ~1% level of atomic disorder in CuO2 planes. This suggests that the stretched-exponential 139La relaxation, considered as a manifestation of the systems glassiness, may not arise from quenched disorder.Comment: 7 pages, to be published in Phys. Rev.

NMR relaxation time in a clean two-band superconductor

We study the spin-lattice relaxation rate of nuclear magnetic resonance in a two-band superconductor. Both conventional and unconventional pairing symmetries for an arbitrary band structure in the clean limit are considered. The importance of the inter-band interference effects is emphasized. The calculations in the conventional case with two isotropic gaps are performed using a two-band generalization of Eliashberg theory.Comment: 9 pages, 3 figure