Large sets of long distance equienergetic graphs

Distance energy of a graph is a recent energy-type invariant, defined as the absolute deviation of the eigenvalues of the distance matrix of the graph. Two graphs of the same order are said to be distance equienergetic if they have equal distance energy, while they have distinct spectra of their distance matrices. Examples of pairs of distance equienergetic graphs appear in the literature already, but most of them have diameter two only. We describe here the distance spectrum of a special composition of regular graphs, and, as an application, we show that for any ▫$n ge 3$▫, there exists a set of ▫$n + 1$▫ distance equienergetic graphs which have order ▫$6n$▫ and diameter ▫$n - 1$▫ each

Influence of Different Degradation Medium on Release of Ascorbic Acid from PLGA Nano ans Microspheres

Poster presented at PHYSICAL CHEMISTRY 2008. 9th International Conference on Fundamental and Applied Aspects of Physical Chemistry, Belgrade, September 24-26, 200

Poly(lactide-co-glycolide)-based Micro and Nanoparticles for the Controlled Drug Delivery of Vitamins

Controlled drug delivery systems and polymeric carriers have undergone significant development in recent years. Polymers like polylactides (PLA), polyglycolides (PGA), poly(lactide-co-glycolides) (PLGA), are approved by the World Health Organization (WHO) and Food and Drug Administration (FDA) as materials that can be used in medicine and pharmacy. Owing to their biodegradable nature, polymer materials, such as copolymer poly(DL-lactide-co-glycolide), are widely used in various medical applications; controlled release of delivering drugs, carriers in the tissue engineering, fixation of bone fractures, chirurgical strings, etc. Polymeric particles are used for the controlled delivery of several types of medicaments, including anticancer agents, antihypertensive agents, immunomodulatory drugs, hormones, vitamins and macromolecules, such as nucleic acid, proteins, peptides, antibodies, etc. Preparation of poly(lactide-co-glycolide) submicron spheres poses serious challenges. The present review attempts to address some important issues related to micro/nanoparticle-based delivery systems comprising poly(lactide-co-glycolide), with a special reference to PLGA for the controlled delivery of vitamins. A range of topics is discussed, including formulation aspects of micro- and nanoparticles, the effects of particle size and size distribution, most commonly used incorporation techniques, surface modification with stabilizers, surface functionalization, and factors affecting degradation and drug release rate.\ud \ud A post-print version of the article: Uskokovic, Dragan, and Magdalena Stevanovic. 2009. “Poly(lactide-Co-Glycolide)-Based Micro and Nanoparticles for the Controlled Drug Delivery of Vitamins.” Current Nanoscience 5 (1) (February 1): 1–14. doi:10.2174/157341309787314566

Lathrobium joncooteri, novo ime za Lathrobium cooteri Stevanović, Hlaváč & Pavićević (Coleoptera, Staphylinidae, Paederinae)

A new name, Lathrobium joncooteri, is proposed for Lathrobium cooteri Stevanović, Hlaváč & Pavićević, 2008, a primary homonym of L. cooteri Watanabe 1999.Novo ime, Lathrobium joncooteri, predlaže se za vrstu Lathrobium cooteri Stevanović, Hlaváč & Pavićević, 2008, primarni homonim vrste L. cooteri Watanabe 1999

A note on extremal Sombor indices of trees with a given degree sequence

We note here that the problem of determining extremal values of Sombor index for trees with a given degree sequence fits within the framework of results by Hua Wang from [Cent. Eur. J. Math. 12 (2014) 1656-1663], implying that the greedy tree has the minimum Sombor index, while an alternating greedy tree has the maximum Sombor index

Thermal-hydraulics of evaporating tubes in the forced circulation loop of a steam boiler

Elektroprivreda Srbije je u toku 2005. godine nastavila radove na izgradnji TE Kolubara B snage 350 MW, koji su započeti još davne 1989. godine. Sam kotao je toranjske konstrukcije, a za isparivač kotla predviđeno je cirkulaciono kolo sa prinudnim strujanjem. Osim toga, ekranske cevi u ložištu su ožljebljene sa unutrašnje strane, što predstavlja jedinstveni slučaj u kotlovima termoelektrana u Srbiji. Da bi se izvršile termohidrauličke analize ovog isparivača urađeni su termički proračuni kotla, kao i hidraulički proračuni isparivača za različita radna opterećenja. U ovom radu prikazana je metodologija hidrauličkog proračuna isparivača sa prinudnom cirkulacijom. Na osnovu dobijenih rezultata, za spomenuti kotao, izvršena je analiza uticaja ožljebljenja cevi na povećanje hidrauličkog otpora u cirkulacionom kolu. S obzirom da ožljebljene cevi obezbeđuju sigurniji rad isparivača, održavajući nisku temperaturu zida cevi i pri visokim sadržajima pare, vršeno je njihovo upoređivanje sa glatkim cevima za slučajeve ravnomernog i neravnomernog toplotnog opterećenja u ložištu.Rifled evaporating tubes are applied in a steam boiler with the aim to increase the steam-water mixture turbulization and to prevent tubes' wall burnout. The evaporating rifled tubes and the working fluid forced circulation are applied in the steam boiler at the Thermal Power Plant 'Kolubara B' that is being built by the Electric Power Utility of Serbia. In order to investigate operating characteristics of the steam boiler of such an advanced design, a simulation and analysis of complex coupled thermal processes on the furnace gas side and thermal-hydraulics in the evaporating tubes were performed for the whole range of the plant designed operating loads. In this paper the methodology for the hydraulic calculations of forced circulation loops is presented. The rifled tubes thermal-hydraulics is calculated. An acceptable temperature of the evaporating tube wall, even under a high void fraction of the coolant is obtained. It is shown that the rifled tubes prevent the occurrence of the critical heat transfer conditions. The obtained increased thermal safety margin of the rifled tubes is compared with the safety margin of the smooth tubes for uniform and variable heat loads between walls of the boiler furnace. The influence of the rifled tubes on the increase of the hydraulic resistance in the circulation loop is analyzed