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Open access

Dorota Bród

Abstract

In this paper we present a new one parameter generalization of the classical Pell numbers. We investigate the generalized Binet's formula, the generating function and some identities for r-Pell numbers. Moreover, we give a graph interpretation of these numbers.

Open access

Bağdagül Kartal

Abstract

In the present paper, two theorems of absolute summability have been proved by using the definition of almost increasing sequence.

Open access

Matej Babič, Miłosz Andrzej Huber, Elzbieta Bielecka, Metin Soycan, Wojciech Przegon, Ljubomir Gigović, Siniša Drobnjak, Dragoljub Sekulović, Ivan Pogarčić, George Miliaresis, Matjaž Mikoš and Marko Komac

Abstract

Many problems in the analysis of natural terrain surface shapes and the construction of terrain maps to model them remain unsolved. Almost the whole process of thematic interpretation of aerospace information consists of a step-by-step grouping and further data conversion for the purpose of creating a completely definite, problematically oriented picture of the earth’s surface. In this article, we present application of a new method of drawing 3D visibility networks for pattern recognition and its application on terrain surfaces. For the determination of complexity of 3D surface terrain, we use fractal geometry method. We use algorithm for constructing the visibility network to analyse the topological property of networks used in complex terrain surfaces. Terrain models give a fast overview of a landscape and are often fascinating and overwhelmingly beautiful works by artists who invest all their interest and an immense amount of work and know-how, combined with a developed sense of the portrayed landscape, in creating them. At the end, we present modelling of terrain surfaces with topological properties of the visibility network in 3D space.

Open access

Paweł Gładki

Abstract

In this work we generalize the results of [9] to the higher level case: we define n-th root selections in fields of characteristic ≠ 2, that is subgroups of the multiplicative group of a field whose existence is equivalent to the existence of a partial inverse of the xxn function, provide necessary and sufficient conditions for such a subgroup to exist, study their existence under field extensions, and give some structural results describing the behaviour of maximal n-th root selection fields.

Open access

Benjamin Peet

Abstract

In this paper we consider the finite groups that act fiber- and orientation-preservingly on closed, compact, and orientable Seifert manifolds that fiber over an orientable base space. We establish a method of constructing such group actions and then show that if an action satisfies a condition on the obstruction class of the Seifert manifold, it can be derived from the given construction. The obstruction condition is refined and the general structure of the finite groups that act via the construction is provided.

Open access

Ivaylo Sirakov, Katya Velichkova, Stefka Stoyanova, Georgi Zhelyazkov and Yordan Staykov

Abstract

The aim of the current study was to test the effect of a diet supplemented with dandelion’s (Taraxacum officinale) extract on the productive traits and blood parameters in common carp (Cyprinus carpio L.) cultivated in an recirculation aquaculture system. The carps were cultivated at a stocking density of 7.2 kg/m3 in recirculation aquaculture system. The fish were split into the following two experimental groups: DF (the fish were fed with feed supplemented with dandelion’s extract) and CF (the fish were fed with feed without supplementation). Common carp fed with a diet added with dandelion’s extract at a quantity of 0.8% from daily feed ratio, did not affect the hydrochemical parameters (pH, dissolved oxygen, and electrical conductivity). The carps fed with feed supplemented with dandelion’s extract did not show better productive traits compared with these found for carp from the control variant. The carp from experimental groups had a higher survival rate, final weight, average individual weight gain and specific growth rate (SGR), respectively with 13.2%, 3.94%, 31.5% and 31.3%, compared with the average values of these parameters measured in individuals fed with the control feed, but the differences were not statistically significant (P≥0.05). Supplementation of feed with dandelion’s extract significantly decreased the plasma cholesterol (4.76%) and triglyceride (61.2%) content, promoting hypolipidemic status in fish (P≤0.05).

Open access

Rositsa Mileva

Abstract

A fast and sensitive HPLC method was validated in order to analyze doxycycline in plasma and milk of sheep and in plasma of rabbits. The samples were processed with trifluoroacetic acid (TFA). After the centrifugation step, a supernatant containing extracted doxycycline and internal standard oxytetracycline was injected into the HPLC system with PDA detection. The method showed linearity in the range of 0.125 - 2.5 μg/mL for ovine plasma, 0.125 – 5.0 μg/mL for ovine milk, and 0.125 – 1 μg/mL for rabbit plasma. The inter-assay precision varied between 5.69 – 13.55 %. Values for intraassay precision were between 0.62 – 8.67 %. Accuracy was higher than 90% in all of the tested concentrations in the three types of biological matrices. The mean extraction recovery was higher than 90 % for all matrices. In order to handle only with free drug concentrations, microfiltration of standard solutions with low (0.25mg/mL), medium (0.5mg/mL) and high (1.0mg/mL) concentration was performed. A percentage for correction of the quantified doxycycline was calculated. The most significant adjustments should be made at the low concentrations. The correction for rabbit plasma is 24.63±5.03%, for ovine plasma is 20.10±8.01% and for milk –16.68±0.04 %. This method can be used for routine determination of doxycycline concentrations for pharmacokinetic studies and further dosage adjustment.

Open access

Neil McDonnell and Nathan Wildman

Abstract

Are the objects and events that take place in Virtual Reality genuinely real? Those who answer this question in the affirmative are realists, and those who answer in the negative are irrealists. In this paper we argue against the realist position, as given by Chalmers (2017), and present our own preferred irrealist account of the virtual. We start by disambiguat- ing two potential versions of the realist position—weak and strong— and then go on to argue that neither is plausible. We then introduce a Waltonian variety of fictionalism about the virtual, arguing that this sort of irrealist approach avoids the problems of the realist positions, fits with a unifying theory of representational works, and offers a better ac- count of the phenomenology of engaging in virtual experiences.

Open access

Mark Silcox

Abstract

In “The Virtual and the Real,” David Chalmers argues that there is an epistemic and ontological parity between VR and ordinary reality. My argument here is that, whatever the plausibility of these claims, they provide no basis for supposing that there is a similar parity of value. Careful reflection upon certain aspects of the transition that individu- als make from interacting with real-world, physical environments to interacting with VR provides a basis for thinking that, to the extent that there are good reasons to deny the reality of virtual objects, there are also reasons to place a correspondingly higher value upon the ex- perience of interacting with a VR environment. Chalmers’ assump- tion to the contrary arises from a subtle misrepresentation of how the phenomenon of cognitive penetration works in the perception of virtual objects, and from an unwillingness to acknowledge how our attitudes toward virtual environments are conditioned by the values we adopt when engaged in gameplay.