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Comparison of cultivable acetic acid bacterial microbiota in organic and conventional apple cider vinegar
Aleksandra Mori Štornik, Barbara Skok, Janja Trček, 2016, izvirni znanstveni članek

Opis: Organic apple cider vinegar is produced from apples that go through very restricted treatment in orchard. During the first stage of the process, the sugars from apples are fermented by yeasts to cider. The produced ethanol is used as a substrate by acetic acid bacteria in a second separated bioprocess. In both, the organic and conventional apple cider vinegars the ethanol oxidation to acetic acid is initiated by native microbiota that survived alcohol fermentation. We compared the cultivable acetic acid bacterial microbiota in the production of organic and conventional apple cider vinegars from a smoothly running oxidation cycle of a submerged industrial process. In this way we isolated and characterized 96 bacteria from organic and 72 bacteria from conventional apple cider vinegar. Using the restriction analysis of the PCR-amplified 16S-23S rRNA gene ITS regions, we identified four different HaeIII and five different HpaII restriction profiles for bacterial isolates from organic apple cider vinegar. Each type of restriction profile was further analyzed by sequence analysis of the 16S-23S rRNA gene ITS regions, resulting in identification of the following species: Acetobacter pasteurianus (71.90 %), Acetobacter ghanensis (12.50 %), Komagataeibacter oboediens (9.35 %) and Komagataeibacter saccharivorans (6.25 %). Using the same analytical approach in conventional apple cider vinegar, we identified only two different HaeIII and two different HpaII restriction profiles of the 16S‒23S rRNA gene ITS regions, which belong to the species Acetobacter pasteurianus (66.70 %) and Komagataeibacter oboediens (33.30 %). Yeasts that are able to resist 30 g/L of acetic acid were isolated from the acetic acid production phase and further identified by sequence analysis of the ITS1-5.8S rDNA‒ITS2 region as Candida ethanolica, Pichia membranifaciens and Saccharomycodes ludwigii. This study has shown for the first time that the bacterial microbiota for the industrial production of organic apple cider vinegar is clearly more heterogeneous than the bacterial microbiota for the industrial production of conventional apple cider vinegar. Further chemical analysis should reveal if a difference in microbiota composition influences the quality of different types of apple cider vinegar.
Ključne besede: microbiology, acetic acid bacteria, apple cider vinegar
Objavljeno: 24.07.2017; Ogledov: 9; Prenosov: 0
.pdf Polno besedilo (289,47 KB)

16S rRNA in situ hybridization followed by flow cytometry for rapid identification of acetic acid bacteria involved in submerged industrial vinegar production
Janja Trček, Luka Lipoglavšek, Gorazd Avguštin, 2016, izvirni znanstveni članek

Opis: Acetic acid bacteria are involved in many biotechnological processes such as vitamin C, gluconic acid, miglitol or acetic acid production, and others. For a technologist trying to control the industrial process, the ability to follow the microbiological development of the process is thus of importance. During the past few years hybridization in a combination with flow cytometry has oft en been used for this purpose. Since vinegar is a liquid, it is an ideal matrix for flow cytometry analysis. In this work we have constructed a specific probe for highly acetic acid-resistant species of the acetic acid bacteria and a protocol for in situ hybridization, which in combination with flow cytometry enables direct monitoring of bacteria producing vinegar with >10 % of acetic acid. The approach was successfully applied for monitoring microbiota during industrial vinegar production.
Ključne besede: microbiology, acetic acid bacteria, flow cytometry
Objavljeno: 24.07.2017; Ogledov: 9; Prenosov: 0
.pdf Polno besedilo (500,81 KB)

Curvature-controlled topological defects
Luka Mesarec, Pavlo Kurioz, Aleš Iglič, Wojciech Góźdź, Samo Kralj, izvirni znanstveni članek

Opis: Effectively, two-dimensional (2D) closed films exhibiting in-plane orientational ordering (ordered shells) might be instrumental for the realization of scaled crystals. In them, ordered shells are expected to play the role of atoms. Furthermore, topological defects (TDs) within them would determine their valence. Namely, bonding among shells within an isotropic liquid matrix could be established via appropriate nano-binders (i.e., linkers) which tend to be attached to the cores of TDs exploiting the defect core replacement mechanism. Consequently, by varying configurations of TDs one could nucleate growth of scaled crystals displaying different symmetries. For this purpose, it is of interest to develop a simple and robust mechanism via which one could control the position and number of TDs in such atoms. In this paper, we use a minimal mesoscopic model, where variational parameters are the 2D curvature tensor and the 2D orientational tensor order parameter. We demonstrate numerically the efficiency of the effective topological defect cancellation mechanism to predict positional assembling of TDs in ordered films characterized by spatially nonhomogeneous Gaussian curvature. Furthermore, we show how one could efficiently switch among qualitatively different structures by using a relative volume v of ordered shells, which represents a relatively simple naturally accessible control parameter.
Ključne besede: topological defects, Gaussian curvature, self-assembling, crystal growth nucleation
Objavljeno: 20.07.2017; Ogledov: 19; Prenosov: 0
.pdf Polno besedilo (6,77 MB)

Optimal distribution of incentives for public cooperation in heterogeneous interaction environments
Xiaojie Chen, Matjaž Perc, 2014, izvirni znanstveni članek

Opis: In the framework of evolutionary games with institutional reciprocity, limited incentives are at disposal for rewarding cooperators and punishing defectors. In the simplest case, it can be assumed that, depending on their strategies, all players receive equal incentives from the common pool. The question arises, however, what is the optimal distribution of institutional incentives? How should we best reward and punish individuals for cooperation to thrive? We study this problem for the public goods game on a scale-free network. We show that if the synergetic effects of group interactions are weak, the level of cooperation in the population can be maximized simply by adopting the simplest "equal distribution" scheme. If synergetic effects are strong, however, it is best to reward high-degree nodes more than low-degree nodes. These distribution schemes for institutional rewards are independent of payoff normalization. For institutional punishment, however, the same optimization problem is more complex, and its solution depends on whether absolute or degree-normalized payoffs are used. We find that degree-normalized payoffs require high-degree nodes be punished more lenient than low-degree nodes. Conversely, if absolute payoffs count, then high-degree nodes should be punished stronger than low-degree nodes.
Ključne besede: public cooperation, institutional reciprocity, scale-free network, punishment, reward
Objavljeno: 10.07.2017; Ogledov: 34; Prenosov: 0
.pdf Polno besedilo (3,26 MB)

Linear recognition of generalized Fibonacci cubes $Q_h (111)$
Yoomi Rho, Aleksander Vesel, 2016, izvirni znanstveni članek

Opis: The generalized Fibonacci cube $Q_h(f)$ is the graph obtained from the $h$-cube $Q_h$ by removing all vertices that contain a given binary string $f$ as a substring. In particular, the vertex set of the 3rd order generalized Fibonacci cube $Q_h(111)$ is the set of all binary strings $b_1b_2 ... b_h$ containing no three consecutive 1’s. We present a new characterization of the 3rd order generalized Fibonacci cubes based on their recursive structure. The characterization is the basis for an algorithm which recognizes these graphs in linear time.
Ključne besede: graph theory, Fibonacci cubes, recognition algorithm
Objavljeno: 10.07.2017; Ogledov: 21; Prenosov: 0
.pdf Polno besedilo (803,81 KB)

Guarded subgraphs and the domination game
Gašper Košmrlj, Douglas F. Rall, Sandi Klavžar, Boštjan Brešar, 2015, izvirni znanstveni članek

Opis: V članku vpeljemo koncept zaščitenega podgrafa. Množica le-teh po definicji leži med množico konveksnih in 2-izometričnih podgrafov, hkrati pa ni primerljiva z množico izometričnimih podgrafov. Dokažemo nekatere metrične lastnosti zaščitenih podgrafov ter koncept uporabimo v dominacijski igri, v kateri dva igralca, Dominator in Zavlačevalka, izmenično izbirata vozlišča grafa, tako da vsako izbrano vozlišče poveča množico dominiranih vozlišč. Dominatorjev cilj je končati igro, tj. dominirati celoten graf, čim hitreje, medtem ko je Zavlačevalkin cilj odigrati čim več potez. Igralno dominacijsko število je število potez v igri, ko Dominator začne in oba igralca igrata optimalno. Kot glavni rezultat članka dokažemo, da igralno dominacijsko število grafa ni nikoli manjše, kot igralno dominacijsko število njegovega zaščitenega podgrafa. Predstavljenih je tudi več aplikacij tega rezultata.
Ključne besede: dominacijska igra, igralno dominacijsko številko, konveksni podgraf, (2-)izometrični podgraf
Objavljeno: 10.07.2017; Ogledov: 19; Prenosov: 0
.pdf Polno besedilo (690,85 KB)

Covering codes in Sierpiński graphs
Michel Mollard, Laurent Beaudou, Sandi Klavžar, Sylvain Gravier, Matjaž Kovše, 2010, izvirni znanstveni članek

Opis: Za dani graf ▫$G$▫ in celi števili ▫$a$▫ in ▫$b$▫ je ▫$(a,b)$▫-koda grafa ▫$G$▫ množica vozlišč ▫$C$▫, tako da ima vsako vozlišče iz ▫$C$▫ natanko ▫$a$▫ sosedov v ▫$C$▫, vsako drugo vozlišče pa natanko ▫$b$▫ sosedov v ▫$C$▫. V tem prispevku klasificiramo števila ▫$a$▫ in ▫$b$▫, za katera obstajajo ▫$(a,b)$▫-kode v grafih Sierpińskega.
Ključne besede: graph theory, codes in graphs, perfect codes, Sierpiński graphs
Objavljeno: 10.07.2017; Ogledov: 21; Prenosov: 0
.pdf Polno besedilo (786,68 KB)

Connectivity of Fibonacci cubes, Lucas cubes, and generalized cubes
Jernej Azarija, Sandi Klavžar, Jaehun Lee, Yoomi Rho, 2015, izvirni znanstveni članek

Opis: If ▫$f$▫ is a binary word and ▫$d$▫ a positive integer, then the generalized Fibonacci cube ▫$Q_d(f)$▫ is the graph obtained from the ▫$d$▫-cube ▫$Q_d$▫ by removing all the vertices that contain ▫$f$▫ as a factor, while the generalized Lucas cube ▫$Q_d(\stackrel{\leftharpoondown}{f})$▫ is the graph obtained from ▫$Q_d$▫ by removing all the vertices that have a circulation containing ▫$f$▫ as a factor. The Fibonacci cube ▫$\Gamma_d$▫ and the Lucas cube ▫$\Lambda_d$▫ are the graphs ▫$Q_d({11})$▫ and ▫$Q_d(\stackrel{\leftharpoondown}{11})$▫, respectively. It is proved that the connectivity and the edge-connectivity of ▫$\Gamma_d$▫ as well as of ▫$\Lambda_d$▫ are equal to ▫$\left\lfloor \frac{d+2}{3}\right\rfloor$▫. Connected generalized Lucas cubes are characterized and generalized Fibonacci cubes are proved to be 2-connected. It is asked whether the connectivity equals minimum degree also for all generalized Fibonacci/Lucas cubes. It was checked by computer that the answer is positive for all ▫$f$▫ and all ▫$d \le9$▫.
Ključne besede: Fibonacci cube, Lucas cube, generalized Fibonacci cube, generalized Lucas cube, connectivity, combinatorics on words
Objavljeno: 10.07.2017; Ogledov: 22; Prenosov: 0
.pdf Polno besedilo (740,04 KB)

A new characterization and a recognition algorithm of Lucas cubes
Andrej Taranenko, 2013, izvirni znanstveni članek

Opis: Fibonacci and Lucas cubes are induced subgraphs of hypercubes obtained by excluding certain binary strings from the vertex set. They appear as models for interconnection networks, as well as in chemistry. We derive a characterization of Lucas cubes that is based on a peripheral expansion of a unique convex subgraph of an appropriate Fibonacci cube.This serves as the foundation for a recognition algorithm of Lucas cubes that runs in linear time.
Ključne besede: graph theory, Lucas cubes, characterization, recognition algorithm
Objavljeno: 10.07.2017; Ogledov: 20; Prenosov: 0
.pdf Polno besedilo (563,10 KB)

Biology students' teacher opinions about the integration of ICT into the learning and teaching process
Andreja Špernjak, 2014, izvirni znanstveni članek

Opis: Biology laboratory work can be performed in various ways, even using information and communication technologies (ICT). Whether a teacher incorporates it into laboratory work is related to different factors, but educators can influence students’ beliefs about the value of ICT through their pedagogical practice. In our study, student teachers of biology gave opinions on how successfully university professors use ICT in the classroom, where they acquired most knowledge about ICT and their attitude towards using of ICT in laboratory work. Student teachers were critical about the knowledge and usage of ICT of university professors in class. During their student teachers mostly failed to acquire knowledge about ICT and practice in incorporating it into daily routines. These results will be presented to our university professors, at which time we will suggest how they could use ICT more effectively in daily practice because, on the one hand, they are responsible for students teacher attitudes and for the level of student teacher knowledge, while, on the others, they precipitate indirectly in forming the pupils’ attitudes and determining the level of the pupils’ knowledge of ICT. The study was done on 85 student teachers of biology. Attitudes toward ICT are statistically significant by gender.
Ključne besede: education, information and communication technology, ICT, gender studies
Objavljeno: 06.07.2017; Ogledov: 17; Prenosov: 0
.pdf Polno besedilo (166,92 KB)

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