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1.
Komagataeibacter sp. nov. T5K1: ocetnokislinska bakterija, izolirana iz kvasovke Saccharomycodes ludwigii
Mateja Polc, 2017, magistrsko delo

Opis: Ocetnokislinske bakterije so skupina mikroorganizmov, ki jih v naravi pogosto najdemo na substratih, bogatih s sladkorji, alkoholi in kislinami. Število opisanih rodov ocetnokislinskih bakterij je v zadnjih 30 letih iz prvotno dveh narastlo na 19. Med njimi je največje število vrst opisanih znotraj rodov Acetobacter, Gluconobacter, Gluconacetobacter in Komagataeibacter. V magistrskem delu smo iz kvasovke Saccharomycodes ludwigii T5K1 osamili ocetnokislinsko bakterijo Komagataeibacter sp. T5K1_A in jo nadalje okarakterizirali s preiskovanjem nukleotidnega zaporedja genov za 16S rRNA in medgenske regije 16S-23S rDNA. Odkrili smo, da je njen najbližji sorodnik vrsta Gluconacetobacter entanii; njuni sekvenci gena za 16S rRNA sta si podobni v 99 %, sekvenci medgenskih regij 16S-23S rDNA pa v 94 %. Glede na do sedaj poznane podatke o podobnosti teh DNA-regij med vrstami ocetnokislinskih bakterij smo domnevali, da bi sev Komagataeibacter sp. T5K1_A lahko bila nova vrsta ocetnokislinske bakterije. Odločili smo se, da naredimo natančno fenotipsko analizo in poiščemo fenotipske lastnosti, ki omogočajo razlikovanje seva Komagataeibacter sp. T5K1_A od njemu najbolj sorodnih vrst. Sev Komagataeibacter sp. T5K1_A je mogoče razlikovati od dveh filogenetsko najbolj sorodnih vrst Gluconacetobacter entanii in Komagataeibacter maltaceti po zmožnosti tvorbe 2-keto-D-glukonske kisline, uporabe sorbitola, D- manitola, D-glukonata in glicerola kot edinega vira ogljika za rast, fermentaciji D-manitola do kisline in še nekaterih drugih biokemijskih lastnostih. Sev Komagataeibacter sp. T5K1_A raste tudi pri višjih koncentracijah ocetne kisline ob prisotnosti 1 % in 3 % etanola v gojišču RAE, v primerjavi s tipskim sevom Komagataeibacter maltaceti. Sev Komagataeibacter sp. T5K1_A producira na gojišču RAE celulozo. Zaradi vseh teh lastnosti je sev Komagataeibacter sp. T5K1_A zelo verjetno nova vrsta ocetnokislinske bakterije. Za dokončno potrditev te hipoteze bo potrebno razlike seva Komagataeibacter sp. T5K1 od njemu najbolj sorodnih vrst potrditi še na nivoju celokupne DNA genomov. Sekvenciranje genoma seva Komagataeibacter sp. T5K1 in genomov njemu najbolj sorodnih vrst trenutno poteka v sodelavi z raziskovalno skupino iz Belgije.
Ključne besede: Ocetnokislinske bakterije, rod Komagataeibacter, industrijski bioprocesi, kis, 16S rRNA, 16S-23S rDNA, identifikacija
Objavljeno: 18.04.2017; Ogledov: 44; Prenosov: 4
.pdf Polno besedilo (1,79 MB)

2.
Uporaba in posplošitve Anderson-Choquetovega izreka
Daša Štesl, 2016, magistrsko delo

Opis: V magistrskem delu dokažemo Anderson-Choquetov izrek za enolične funkcije in tip Anderson-Choquetovega izreka za večlične funkcije. Natančno je predstavljena tudi njuna uporaba.
Ključne besede: kontinuum, inverzna limita, enolične funkcije, večlične funkcije, Anderson-Choquetov izrek, Varšavski lok
Objavljeno: 18.04.2017; Ogledov: 28; Prenosov: 2
.pdf Polno besedilo (967,63 KB)

3.
High potential of sub-Mediterranean dry grasslands for sheep epizoochory
Mitja Kaligarič, Jožica Brecl, Sonja Škornik, 2016, izvirni znanstveni članek

Opis: There is a general decline of grasslands across Europe due to habitat loss and degradation. Ensuring plant dispersal thus becomes a key process for preserving grassland patches in all scales. We examined diaspore dispersal by sheep epizoochory in the pastures of the North Adriatic Karst (NW Slovenia) and determined the qualitative and quantitative features of diaspores in fur. We recorded 25,650 diaspores of 141 plant taxa (with 107 taxa and 23,350 diaspores determined to species level), using three different methods: (i) the “whole-coat method”, (ii) the “part-of-thecoat method” and (iii) a “seedling emergence method”. A comparison of these techniques revealed that the “wholecoat method” provided the highest number of diaspores and plant species. All diaspores were clustered into five emergent groups based on seven functional traits (diaspore weight, length, width, height, volume, specific weight and the diaspore surface structure). Our research revealed that sheep represent an important dispersal vector, since about half of the plant species recorded in the pastures were found as diaspores in fur. This study contributes to knowledge about the modes of seed dispersal in seminatural grasslands. Taking into account that livestock play a key role in vegetation dynamics, understanding their effects on seed dispersal is essential for conservation and restoration of these species-rich grassland communities.
Ključne besede: community assembly, diaspore traits, plant dispersal, seedling emergence method, transhumance
Objavljeno: 03.04.2017; Ogledov: 27; Prenosov: 0
.pdf Polno besedilo (173,31 KB)

4.
The periphery graph of a median graph
Boštjan Brešar, Manoj Changat, Ajitha R. Subhamathi, Aleksandra Tepeh, 2010, izvirni znanstveni članek

Opis: The periphery graph of a median graph is the intersection graph of its peripheral subgraphs. We show that every graph without a universal vertex can be realized as the periphery graph of a median graph. We characterize those median graphs whose periphery graph is the join of two graphs and show that they are precisely Cartesian products of median graphs. Path-like median graphs are introduced as the graphs whose periphery graph has independence number 2, and it is proved that there are path-like median graphs with arbitrarily large geodetic number. Peripheral expansion with respect to periphery graph is also considered, and connections with the concept of crossing graph are established.
Ključne besede: mathematics, graph theory, median graph, Cartesian product, geodesic, periphery, peripheral expansion
Objavljeno: 31.03.2017; Ogledov: 43; Prenosov: 0
.pdf Polno besedilo (145,86 KB)

5.
On the rainbow connection of Cartesian products and their subgraphs
Sandi Klavžar, Gašper Mekiš, 2012, izvirni znanstveni članek

Opis: Rainbow connection number of Cartesian products and their subgraphs are considered. Previously known bounds are compared and non-existence of such bounds for subgraphs of products are discussed. It is shown that the rainbow connection number of an isometric subgraph of a hypercube is bounded above with the rainbow connection number of the hypercube. Isometric subgraphs of hypercubes with the rainbow connection number smaller as much as possible than the rainbow connection of the hypercube are constructed. The concept of c-strong rainbow coloring is introduced. In particular it is proved that the so-called ▫$\Theta$▫-coloring of an isometric subgraph of a hypercube is its unique optimal c-strong rainbow coloring.
Ključne besede: graph theory, rainbow connection, strong rainbow connection, Cartesian product of graphs, isometric subgraph, hypercube
Objavljeno: 31.03.2017; Ogledov: 18; Prenosov: 0
.pdf Polno besedilo (125,60 KB)

6.
On [Theta]-graphs of partial cubes
Sandi Klavžar, Matjaž Kovše, 2007, izvirni znanstveni članek

Opis: The ▫$\Theta$▫-graph ▫$\Theta(G)$▫ of a partial cube ▫$G$▫ is the intersection graph of the equivalence classes of the Djokovic-Winkler relation. ▫$\Theta$▫-graphs that are 2-connected, trees, or complete graphs are characterized. In particular, ▫$\Theta(G)$▫ is complete if and only if ▫$G$▫ can be obtained from ▫$K_1$▫ by a sequence of (newly introduced) dense expansions. ▫$\Theta$▫-graphs are also compared with familiar concepts of crossing graphs and ▫$\tau$▫-graphs.
Ključne besede: mathematics, graph theory, intersection graph, partial cube, median graph, expansion theorem, Cartesian product of graphs
Objavljeno: 31.03.2017; Ogledov: 18; Prenosov: 1
.pdf Polno besedilo (150,56 KB)

7.
Edge-transitive lexicographic and cartesian products
Wilfried Imrich, Ali Iranmanesh, Sandi Klavžar, Abolghasem Soltani, 2016, izvirni znanstveni članek

Opis: In this note connected, edge-transitive lexicographic and Cartesian products are characterized. For the lexicographic product ▫$G \circ H$▫ of a connected graph ▫$G$▫ that is not complete by a graph ▫$H$▫, we show that it is edge-transitive if and only if ▫$G$▫ is edge-transitive and ▫$H$▫ is edgeless. If the first factor of ▫$G \circ H$▫ is non-trivial and complete, then ▫$G \circ H$▫ is edge-transitive if and only if ▫$H$▫ is the lexicographic product of a complete graph by an edgeless graph. This fixes an error of Li, Wang, Xu, and Zhao (Appl. Math. Lett. 24 (2011) 1924--1926). For the Cartesian product it is shown that every connected Cartesian product of at least two non-trivial factors is edge-transitive if and only if it is the Cartesian power of a connected, edge- and vertex-transitive graph.
Ključne besede: edge-transitive graph, vertex-transitive graph, lexicographic product of graphs, Cartesian product of graphs
Objavljeno: 31.03.2017; Ogledov: 21; Prenosov: 1
.pdf Polno besedilo (150,33 KB)

8.
Domination game critical graphs
Csilla Bujtás, Sandi Klavžar, Gašper Košmrlj, izvirni znanstveni članek

Opis: The domination game is played on a graph ▫$G$▫ by two players who alternately take turns by choosing a vertex such that in each turn at least one previously undominated vertex is dominated. The game is over when each vertex becomes dominated. One of the players, namely Dominator, wants to finish the game as soon as possible, while the other one wants to delay the end. The number of turns when Dominator starts the game on ▫$G$▫ and both players play optimally is the graph invariant ▫$\gamma_g(G)$▫, named the game domination number. Here we study the ▫$\gamma_g$▫-critical graphs which are critical with respect to vertex predomination. Besides proving some general properties, we characterize ▫$\gamma_g$▫-critical graphs with ▫$\gamma_g =2$▫ and with ▫$\gamma_g =3$▫, moreover for each ▫$n$▫ we identify the (infinite) class of all ▫$\gamma_g$▫-critical ones among the ▫$n$▫th powers ▫$C_N^n$▫ of cycles. Along the way we determine ▫$\gamma_g(C_N^n)$▫ for all ▫$n$▫ and ▫$N$▫. Results of a computer search for ▫$\gamma_g$▫-critical trees are presented and several problems and research directions are also listed.
Ključne besede: domination game, domination game critical graphs, powers of cycles, trees
Objavljeno: 31.03.2017; Ogledov: 21; Prenosov: 0
.pdf Polno besedilo (194,74 KB)

9.
1-factors and characterization of reducible faces of plane elementary bipartite graphs
Andrej Taranenko, Aleksander Vesel, 2012, izvirni znanstveni članek

Opis: As a general case of molecular graphs of benzenoid hydrocarbons, we study plane bipartite graphs with Kekulé structures (1-factors). A bipartite graph ▫$G$▫ is called elementary if ▫$G$▫ is connected and every edge belongs to a 1-factor of ▫$G$▫. Some properties of the minimal and the maximal 1-factor of a plane elementary graph are given. A peripheral face ▫$f$▫ of a plane elementary graph is reducible, if the removal of the internal vertices and edges of the path that is the intersection of ▫$f$▫ and the outer cycle of ▫$G$▫ results in an elementary graph. We characterize the reducible faces of a plane elementary bipartite graph. This result generalizes the characterization of reducible faces of an elementary benzenoid graph.
Ključne besede: mathematics, graph theory, plane elementary bipartite graph, reducible face, benzenoid graph
Objavljeno: 31.03.2017; Ogledov: 21; Prenosov: 0
.pdf Polno besedilo (139,73 KB)

10.
On derivations of operator algebras with involution
Nejc Širovnik, Joso Vukman, 2014, izvirni znanstveni članek

Opis: The purpose of this paper is to prove the following result. Let X be a complex Hilbert space, let L(X) be an algebra of all bounded linear operators on X and let A(X) ⊂ L(X) be a standard operator algebra, which is closed under the adjoint operation. Suppose there exists a linear mapping D : A(X) → L(X) satisfying the relation 2D(AA*A) = D(AA*)A + AA*D(A) + D(A)A*A + AD(A*A) for all A ∈ A(X). In this case, D is of the form D(A) = [A,B] for all A ∈ A(X) and some fixed B ∈ L(X), which means that D is a derivation.
Ključne besede: mathematics, prime rings, semiprime rings, derivation, Jordan derivation, Banach space
Objavljeno: 31.03.2017; Ogledov: 19; Prenosov: 0
.pdf Polno besedilo (343,43 KB)

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