bluuebunny/crossref_metadata_2025 huggingface dataset:
Radiation Reaction of Charged Particles Orbiting a Magnetized Schwarzschild Black Hole
Authors: Tursunov Arman , Kološ Martin , Stuchlík Zdeněk , Gal’tsov Dmitri V.
Published: June 2018

In many astrophysically relevant situations, radiation-reaction forces acting upon a charge cannot be ignored, and the question of the location and stability of circular orbits in such a regime arises. The motion of a point charge with radiation reaction in flat spacetime is described by the Lorenz–Dirac (LD) equation, while in curved spacetime it is described by the DeWitt–Brehme (DWB) equation containing the Ricci term and a tail term. We show that for the motion of elementary particles in vacuum metrics, the DWB equation can be reduced to the covariant form of the LD equation, which we use here. Generically, the LD equation is plagued by runaway solutions, so we discuss computational ways of avoiding this problem when constructing numerical solutions. We also use the first iteration of the covariant LD equation, which is the covariant Landau–Lifshitz equation, comparing the results of these two approaches and showing the smallness of the third-order Schott term in the ultrarelativistic case. We calculate the corresponding energy and angular momentum loss of a particle and study the damping of charged particle oscillations around an equilibrium radius. We find that, depending on the orientation of the Lorentz force, the oscillating charged particle either spirals down to the black hole or stabilizes the circular orbit by decaying its oscillations. The latter case leads to the interesting new result of the particle orbit shifting outwards from the black hole. We also discuss the astrophysical relevance of the presented approach and provide estimates of the main parameters of the model.
Multi-band Polarization of Type IIP Supernovae Due to Light Echo from Circumstellar Dust
Authors: Nagao Takashi , Maeda Keiichi , Tanaka Masaomi
Published: June 2018

Type IIP supernovae (SNe IIP) often show relatively high continuum polarization (∼1%) in the late phase. This polarization feature is generally believed to be due to an inner aspherical core revealed in the late phase, while this polarization feature can also be contributed by the effect of polarized-scattered echoes by circumstellar (CS) dust around the SN. In this paper, we propose a unique method to distinguish polarization from the SN ejecta and from the light echo. We quantitatively examine wavelength dependence of the polarization created by the scattered echoes for various geometries and amounts of CS dust. It is found that the polarization in the U-band has characteristic features, i.e., the polarization emerges at an earlier phase with higher polarization degree than that in longer wavelengths. These are due to the rapid evolution of the U-band light curve as well as higher optical depth of dust in shorter wavelengths. Except for the U band, the polarization increases after the plateau phase, and the polarization degree is generally higher for shorter wavelengths. These polarimetric features can be easily distinguished from the polarization expected from an aspherical core, which predicts almost no wavelength dependence. Moreover, we show that multi-band polarimetric observations for SNe IIP can constrain a parameter space in the CS dust mass and distance from the SNe. We thus encourage multi-band polarimetric observations for SNe IIP.
Mixing between Seyfert and H ii Region Excitation in Local Active Galaxies
Authors: Thomas Adam D. , Kewley Lisa J. , Dopita Michael A. , Groves Brent A. , Hopkins Andrew M. , Sutherland Ralph S.
Published: June 2018

We fit theoretical models to the emission-line spectra of 2766 Seyfert galaxies from the Sloan Digital Sky Survey (SDSS). The model line fluxes are derived by “mixing” photoionization model predictions of active galactic nucleus (AGN) narrow line region (NLR) emission and H ii region emission. The observed line fluxes in each spectrum were directly compared to the grid of mixed models using the Bayesian parameter estimation code NebulaBayes, thereby measuring the degree of mixing in each spectrum for the first time. We find that the majority of the Balmer line emission in the majority of Seyfert-classified SDSS spectra arises from contaminating H ii regions within the fixed-size aperture. Even for spectra with log [O iii]/Hβ ≳ 0.9, a median of ∼30% of the Balmer flux arises in H ii regions. We show that the results are qualitatively insensitive to the assumed Seyfert ionizing continuum, and that ionizing spectra with a peak energy of E
peak ∼ 40–50 eV produce the most plausible distributions of mixing fractions. The analysis cleanly quantifies how the starburst—AGN “mixing fraction” increases on the Baldwin, Phillips, & Terlevich (BPT) diagram for SDSS galaxies. Apart from the mixing fraction, the models also vary with the ionization parameter in the NLR, the gas pressure, and the metallicity. Measurements for the metallicity in particular will be presented in a companion paper.
On Detecting Repetition from Fast Radio Bursts
Authors: Connor Liam , Petroff Emily
Published: June 2018

Fast radio bursts (FRBs) are bright, millisecond-duration radio pulses of unknown origin. To date, only one (FRB 121102) out of several dozen has been seen to repeat, though the extent to which it is exceptional remains unclear. We discuss detecting repetition from FRBs, which will be very important for understanding their physical origin, and which also allows for host galaxy localization. We show how the combination of instrument sensitivity, beam shapes, and individual FRB luminosity functions affect the detection of sources with repetition that is not necessarily described by a homogeneous Poisson process. We demonstrate that the Canadian Hydrogen Intensity Mapping Experiment (CHIME) could detect many new repeating FRBs for which host galaxies could be subsequently localized using other interferometers, but it will not be an ideal instrument for monitoring FRB 121102. If the luminosity distributions of repeating FRBs are given by power laws with significantly more dim than bright bursts, CHIME’s repetition discoveries could preferentially come not from its own discoveries, but from sources first detected with lower-sensitivity instruments like the Australian Square Kilometer Array Pathfinder in fly’s eye mode. We then discuss observing strategies for upcoming surveys, and advocate following up sources at approximately regular intervals and with telescopes of higher sensitivity when possible. Finally, we discuss doing pulsar-like periodicity searching on FRB follow-up data, based on the idea that while most pulses are undetectable, folding on an underlying rotation period could reveal the hidden signal.
Assessment of Laser Biostimulation in Induction of Ovulation
Authors: El-Nourya Mohamed A. , El-Begawyb Mahmoud B. , Morsyc Mona E. , Al Sherbiny Ehab M.
Published: June 2018

AIM: This study aimed to evaluate a new modality of low power laser biostimulation in rat ovaries, in comparison with the conventional medical therapy by clomiphene citrate that depends on up-regulation of the hypothalamic-pituitary-ovarian axis to induce ovulation.STUDY DESIGN: A Prospective experimental study carried out from January 2014 to February 2016.SETTING: University-based photobiology laboratory.MATERIALS AND METHODS: Seventy-two (72) Female-Wistar Albino rats were used in this study, divided into three groups: 17 rats used as a control group, 19 rats received clomiphene citrate (Clomid group), 36 rats exposed to diode laser 660 nm wavelength (laser group).RESULTS: Biochemical assessment of serum Estradiol and serum Progesterone was done in the three study groups. Serum Estradiol & Progesterone levels were statistically significantly higher in clomiphene and laser treated groups than non-interventional controls, while no significant difference between clomiphene and laser groups as regard of both hormones.CONCLUSION: This study shows that ovarian laser biostimulation is a new encouraging method for induction of ovulation, at least in animals. This had been proven biochemically by a significant increase in serum Estradiol and serum Progesterone.
Gouverner et s’enrichir outre-mer. Entrepreneurs publics et privés dans la culture du pastel (Europe-Amérique, début du xvi e siècle)
Authors: Priotti Jean-Philippe
Published: June 2018

La culture du pastel toulousain en Nouvelle Espagne dans les années 1530, tandis que la conquête n’est pas encore terminée et que les échanges entre les deux rives de l’océan en sont à leur balbutiement, retient l’attention. À travers ses différentes modalités, sont étudiés les mécanismes de transfert d’une culture européenne en Amérique, et la façon dont l’empereur Charles Quint et un groupe de capitalistes l’utilisaient pour dominer un nouvel espace-temps, ainsi que pour étendre leur autorité outre-mer. L’analyse d’un contrat ( asiento ) permet d’observer les soubassements humains de cette alliance public-privé au Nouveau Monde et la réaction des populations indigènes face à l’implantation de cette nouvelle culture. Au-delà, ce travail dévoile les processus globaux de coopération et de concurrence à l’œuvre dans l’échec de l’entreprise.
Les Verts, une gauche alternative ? (1984 - fin des années 1980)
Authors: Repaire Sébastien
Published: June 2018

Héritiers de la mouvance écologiste des années 1970, les Verts, fondés en 1984, refusent originellement de prendre position sur l’axe gauche-droite. Celui-ci est en effet perçu comme suranné, en dépit même de l’origine politique d’un nombre important de responsables écologistes, passés par des organisations de gauche, en particulier par le PSU, dans la décennie précédente. Or, malgré la volonté affichée de dépasser le clivage gauche-droite, et peut-être en raison justement des itinéraires politiques de nombre d’entre eux, les Verts tentent d’instaurer, dans leurs premières années d’existence, un dialogue avec les gauches alternatives. Plus encore, ils se rêvent en parti pivot d’un camp alternatif en gestation, sans pour autant renoncer à leur identité politique, ni à l’idée que l’écologie constituerait un nouveau paradigme politique, par-delà le socialisme et le libéralisme. Dès lors, une relation ambiguë s’établit entre les écologistes et les gauches alternatives : si chaque acteur a pleinement conscience des bénéfices, notamment électoraux, qu’il pourrait retirer d’une telle alliance, les méfiances réciproques, et notamment la peur des écologistes d’être victimes d’un noyautage par l’extrême gauche, rendent la convergence difficile. Après 1986 et l’arrivée à la tête des Verts d’une majorité « environnementaliste », le rapprochement avec les gauches alternatives n’est d’ailleurs plus le projet du parti, mais simplement celui des militants les plus à gauche qui continuent de croire en une grande convergence « rouge-verte ». Face à la candidature de Pierre Juquin en 1988, ceux-ci ont d’ailleurs parfois du mal à se déterminer entre Juquin et le candidat des Verts, Antoine Waechter. À la fin de la décennie, si la convergence apparaît comme un échec, elle a néanmoins permis pour les Verts la captation d’un second héritage, venu de l’extrême gauche, par le biais d’ex-militants notamment trotskistes et maoïstes qui décident de poursuivre leur engagement dans l’écologie politique. Ils compteront pour certains d’entre eux parmi les principaux partisans d’une alliance avec le Parti socialiste dans la décennie suivante.
De la « charité investigatrice » à la science de la pauvreté : l’activisme du visiteur des pauvres
Authors: Rodriguez Jacques
Published: June 2018

Cet article présente la pratique de la visite domiciliaire aux pauvres telle qu’elle a été conçue par le baron de Gérando en France et ses contemporains européens, en particulier Thomas Chalmers et Daniel von der Heydt. Il rappelle que le schéma de la visite aux pauvres s’inscrit, au xix e  siècle, dans un vaste mouvement de rationalisation du geste charitable ; il souligne également que ce procédé relève d’une volonté de contrôler les familles déshéritées, mais aussi de mieux les connaître afin d’échafauder une véritable science de la pauvreté ; il s’interroge enfin sur la persistance ou, plus exactement, la rémanence de cette pratique, qui a survécu à la disparition des conditions de sa mise en œuvre.
La charité à l’épreuve du roman balzacien
Authors: Bierce Vincent
Published: June 2018

Dans La Comédie humaine , Balzac propose une remise en cause de la charité traditionnelle : il interroge sa place au sein d’une société contemporaine inquiète et propose des tentatives pour construire des solutions qui soient plus efficaces. Cette problématisation générale a une conséquence importante : la charité n’est plus seulement le fait du prêtre, et la réussite des projets charitables est alors transférée vers des tentatives émanant de personnages laïcs, comme des médecins, des juges ou des ingénieurs. Cette concurrence nouvelle, en plus de proposer des modèles de bienfaisance efficaces, souligne les limites de la charité traditionnelle et du personnel ecclésiastique. L’efficacité de la charité traditionnelle est ainsi remise en cause par l’émergence d’autres systèmes que prennent en charge les fictions en proposant une réflexion à la fois sur les modalités de représentation de ces nouvelles formes de bienfaisance et sur les acteurs de la charité moderne.
Lieux communs, refuges narratifs ? Le Rouge et le Noir et les Mémoires de Marmontel
Authors: Lammers Philipp
Published: June 2018

Le Rouge et le Noir , lu en tant que « récit de vie », peut être rapproché des Mémoires du temps de Stendhal, notamment des Mémoires d’un père de Jean-François Marmontel, ouvrage dont s’inspire le début du roman comme d’un contre-modèle. Le roman de Stendhal s’attaque, à travers la peinture de ses lieux et milieux, aux lieux communs et à l’esthétique d’embellissement très présents dans les Mémoires de Marmontel tout comme dans nombre de récits édifiants des xviii e et xix e siècles. En s’affrontant à ces modèles autobiographiques, le roman met en débat la forme biographique tout en l’adoptant, afin de penser les « leçons » à tirer d’un récit de vie. Stendhal construit son roman contre le geste d’allure paternelle commun à nombre de Mémoires de son époque, fondé sur la transmission d’un savoir et d’une morale, et lui oppose un programme poétique alternatif et critique.
A reply to Ponte et al (2016) Supply chain collaboration: Some comments on the nucleolus of the beer game
Authors: Mueller David
Published: June 2018

Purpose: The aim of the paper is to pick up the result of a previously published paper in order to deepen the discussion. We analyze the solution against the background of some well-known concepts and we introduce a newer one. In doing so we would like to inspire the further discussion of supply chain collaborationDesign/methodology/approach: Based on game theoretical knowledge we present and compare seven properties of fair profit sharing.Findings: We show that the nucleolus is a core-solution, which does not fulfil aggregate monotonicity. In contrast the Shapley value is an aggregate monotonic solution but does not belong to the core of every cooperative game. Moreover, we present the Lorenz dominance as an additional fairness criteria.Originality/value: We discuss the very involved procedure of establishing lexicographic orders of excess vectors for games with many players.
The contribution of global sourcing to the economic performance of organizations: Analysis of the points of view of the supply chain participants
Authors: Lahiani Nouha , Apedome Kouami Seli , Zhu Joelle
Published: June 2018

Purpose: This paper aims at investigating the reasons for the complex and long lead time from global suppliers that causes inventory shortages.  It  focuses on supply chain risk management in global sourcing.  This study  has revealed all the specific risks of a global sourcing project and has provided some solutions for risk management: three-step risk management, safety stock, data sharing and driving supplier performance.Design/methodology/approach: A qualitative study is conducted to propose concrete recommendations on three topics: risk management, safety stock and information sharing. A semi-structured survey-guided interview was used to collect related data, and the answers were assessed using syntactic, lexical, thematical and NVivo software analysis.Findings: This study  has revealed all the specific risks of a global sourcing project and has provided some solutions for risk management: three-step risk management, safety stock, data sharing and driving supplier performance.Originality/value: Through research work, we have noticed that the world of the Supply Chain is constantly evolving and that it is becoming more and more complex. Through these interviews, we have noticed that the role of purchasing is changing differently in each sector.
A reply to Mueller (2018) Supply chain collaboration: Further insights into incentive alignment in the Beer Game scenario
Authors: Ponte Borja , Fernández Isabel , Rosillo Rafael , Parreño José , García Nazario
Published: June 2018

Purpose: We expand a previous discussion in this journal by proposing a new solution concept, based on game theory, for profit allocation with the aim of aligning incentives in collaborative supply chains.Design/methodology/approach: Through the Gately’s notion of propensity to disrupt, we minimize the desire of the nodes to leave the grand coalition in the search of a self-enforcing allocation mechanism.Findings: We discuss the benefits and limitations of this solution in comparison with more established alternatives (e.g. nucleolus and Shapley value). We show that it considers the bargaining power of the nodes, but it may not belong to the core.Originality/value: Finding a fair and self-enforcing scheme for incentive alignment, and specifically profit allocation, is essential to ensure the long-term sustainability of collaborative supply chains.
Сomplex Industrial Wastes Based Admixture for Improved Properties of Fine-Grained Concrete
Authors: Vdovin Alexander Alexandrovich , Yakovlev Grigory Ivanovich , Zorin Alexander Nikolaevich , Pervushin Grigory Nikolaevich
Published: June 2018

In the process of development of architectural views on modern construction, there is a gradual change of urban planning policies and construction in general. One of the modern trends in design focusing on sustainable, energy efficient and environmentally friendly architecture creates a demand for new materials and products that reflect modern achievements in the field of building materials science. A variety of spatial planning options for buildings and structures emphasizes the diversification of building materials. At the same time, concrete as a basic building material has a huge potential in improving and adapting to solutions of environmental problems of the modern world.
Special Grout for Anchoring Steel Elements with High Proportion of Fly Ash Contaminated by Denitrification Process
Authors: Žlebek Tomáš , Hodul Jakub , Drochytka Rostislav
Published: June 2018

This paper focuses on the possible use of fly ash contaminated by denitrification process as filler for special grouts based on epoxy resin. This fly ash is contaminated by combined ammonia ions as a consequence of flue gas denitrification. When mixing this fly ash with water and silica materials, ammonia (NH3) is released, therefore its application in these materials is inappropriate. The use of such fly ash as filler in polymeric substances, e.g. epoxy, polyester or vinyl ester resin, seems to be appropriate. When mixing fly ash with these materials, fly ash particles become coated with a polymeric substance, therefore no toxic ammonia is released. In the experiment, the impact of two kinds of contaminated fly ashes (FA-1, FA-2) and different percentages of filler in a polymer grout was examined on the resulting physical and mechanical properties. It was found that the best properties were by the grout with fly ash from circulating fluidized bed combustion from the Kladno thermal power plant (FA-1) under 45% of filling. This material showed high compressive and three-point bending strength and the flexural modulus was even higher than in the case of the reference material, which contained reference silica sand with optimal round grain shape as filler. Furthermore, chemical resistance of these materials against aggressive liquid solutions used in industrial operations were examined. An ideal grout formula was checked in a cut of an embedded steel element under optical microscope. A pull-out strength test was also performed in the case of the best formulas to determine the anchoring rate of embedded steel rod.
Influence of Ammonia Content in SNCR Fly Ash on Phase Composition and Morphology of Autoclaved Aerated Concrete (AAC)
Authors: Galvánková Lucie , Lédl Matěj , Opravil Tomáš , Beranová Denisa , Tkacz Jakub
Published: June 2018

In production of AAC the fly ash was used as a source of SiO2 for many years. Now, after introducing a selective non-catalytic reduction (SNCR) technology to coal combustion process, the fly ash contain ammonia in a form of soluble salts, such as NH4HSO4 and (NH4)2SO4, which causes problems during manufacturing the AAC. Among all the influence of ammonia ions to the phase composition of the final product was not fully described. The main aim of this contribution is to describe the influence of ammonia to phase composition and morphology of autoclaved aerated concrete (AAC). For preparing AAC in laboratory conditions, the fly ash with various content of ammonia was used. The amount of ammonia before and after the hydrothermal reaction was measured by VIS spectrofotometry. The phase composition of prepared samples was determined by means of X-ray diffractometry and confirmed by TG-DTA analysis. The influence of the ammonia to the morphology of final products was studied by scanning electron microscopy.
Rheological Properties of Alkali-Activated Brick Powder Based Pastes: Effect of Alkali Activator and Silicate Modulus
Authors: Vyšvařil Martin , Rovnaníková Pavla , Keppert Martin
Published: June 2018

The rheological behaviour of alkali-activated materials prepared by activation of a brick powder by alkaline solution (alkali + water glass) is described. The influence of the composition of activation solution (NaOH vs. KOH, varied silicate modulus) on the flow properties (yield stress, consistency coefficient, fluidity index) and the evolution of the elastic modulus (G ́) and the viscous modulus (G ́ ́) over time were studied. The rheological characterization was completed by frequency sweep tests with the aim of investigating the material behaviour more in detail. The results show that the pastes are thixotropic suspensions with very low yield stress. The potassium activator decreases the yield stress and viscosity of the pastes and retards the polymerization kinetic. The brick pastes become more rigid and more viscous with increasing silicate modulus. This also leads to an acceleration of gel formation in brick pastes.
Nano-Structured Alkaline Aluminosilicate Binder by Carbonate Mineral Addition
Authors: Bodnárová Lenka , Guzii Sergii , Hela Rudolf , Kryvenko Pavlo V. , Vozniuk Grigorii
Published: June 2018

The influence of СаСО3 on nano-structured, flowability and plastic strength of alkali activated alumonosilicate binders based on metakaolin for the range of oxide ratios in a structural formula of the Na2O∙Al2O3∙(2.5-4.5)SiO2∙(12-17)H2O + (5-15%)CaCO3 system was studied. The results of the study showed that the ratios of SiO2/Al2O3 – 3.8, H2O/Al2O3 – 13.75, and content of СаСО3 of 5% by mass were the most optimal ones from the point of view of meeting requirements for these binders to be used as base in protective coatings.The results of the study showed that process flowability of the binder with optimal ratios of oxides and 5 % by mass of additive 2 hours after preparation was by 5.4% lower, being by 5 times lower than that of the binder without the additive (СаСО3). The binder containing 5% СаСО3 by mass during 2 hours after preparation exhibited the same plastic strength (37 Pa), whereas this value of the binder without CaCO3 has increased, in average by 5.5 times, affecting negatively shelf life of this binder to be used as base in protective coatings.A conclusion was made that the addition of СаСО3 intensified the nano-structured formation processes in the direction of formation of Na-Ca zeolite-like phases; shortening time required the cement stone to gain water resistance in normal conditions.
Influence of Polymer Admixtures on the Rheological Properties and Heat of Hydration of Alkali Activated Slag Pastes
Authors: Mikhailova Olesia , Rovnaník Pavel
Published: June 2018

The purpose of this study is to investigate the rheological properties of alkali-activated slag prepared as a paste modified by various amount of polymer admixtures. Four commercial admixtures VINNAPAS® 5023 L, 5111 L, 7016 F and 7220 E were used as polymer admixture in this study. These admixtures were incorporated to alkali activated slag pastes in quantities between 0.5 and 2% by mass of slag. Rheological properties as shear stress and viscosity of fresh pastes were examined by Discovery HR-1. Another main focus of this paper is the effect of selected admixtures on the heat of hydration of an alkali activated slag. Results indicate that addition of polymer admixtures affects the viscosity of the pastes and hydration process.
Nanomodified Organic-Inorganic Polymeric Binders for Polymer Building Materials
Authors: Galeev Ruslan , Abdrakhmanova Lyailya Abdullovna , Nizamov Rashid
Published: June 2018

Advances in the creation of new polymeric composites based on polyvinyl (PVC) with a specified range of technological and operational properties contribute to their expansion in the form of Viniplastov, Plasticates, Plastisols in the construction industry. At present, PVC provides about 70% of the construction-oriented plastics market. It occupies third place after polyethylene and polypropylene the volume of consumption among industrial polymers, but with the ability to modify properties and the large number of compositions and articles of various functional (from ... rubbery to tough shockproof) exceed all thermoplastic large polymers.
Behavior of High Strength Concrete at High Temperatures
Authors: Sovová Kateřina , Mikulica Karel , Hubáček Adam , Dvořák Karel
Published: June 2018

Concrete is considered as a non-combustible building material. However, at High-Performance Concrete (HPC) is due to its dense structure more likely to occur in explosive spalling. This results in lost of load bearing capacity function of concrete. This paper deals with design, production and testing of the cement-based concrete with the use of different fibers (polypropylene fibers and cellulose fibers). It also assesses the influence of high temperature on strength, visual changes of specimens, changes of surface and degradation of testing specimens due to heat loads according to normative heat curve and also according to hydrocarbon curve.
The Estimated Effect of Carbon Nanomaterials Implementation on the Formation of Hydration Products
Authors: Yakovlev Grigory Ivanovich , Grakhov Valery , Polyanskikh Irina Sergeevna , Gordina Anastasiya Fedorovna , Saidova Zarina , Plekhanova Tatyana , Buryanov Аleksandr F.
Published: June 2018

The article contains a short literature review of the effects that carbon nanosystems may have on the properties of building composite materials. Highlighted are the main problems hindering nanosystems from wide industrial implementation, such as coagulation tendency of a dispersed phase, and the need for preliminary processing of nano-elements when producing suspensions with a homogeneous particle distribution. Attempts have been made to explain the mechanism leading to an increase in the main technical characteristics of materials based on mineral binders and modified by multilayer carbon nanotubes. With certain model simplifications, a calculation was made, allowing to estimate the amount of material that nanoscale products involve in the composite formation process, and showing a direct relationship between the increase in the technical characteristics of the final product and the homogeneity of the multilayered carbon nanotubes distribution in modifying suspensions.
Effect of Humidity on the Properties of Cement Mortars with a Crystalline Additive
Authors: Žižková Nikol , Nevřivová Lenka , Lédl Matěj
Published: June 2018

The paper focuses on examining the properties of mortars in which secondary crystallization (crystalline additive) was used. Laboratory tests have found that the effect of secondary crystallization is influenced by conditions in which specimens have been stored during the first 28 days. The investigation focused on the physical-mechanical properties and microstructure of mortar specimens containing a crystalline additive and polypropylene fibres stored at different levels of humidity for 28 days. The influence of crystalline additive on strength was studied as well and the results show that crystalline additives improves the 28-day strength of the mortars.
Influence of Cellulose Ethers on Fresh State Properties of Lime Mortars
Authors: Vyšvařil Martin , Hegrová Michaela , Žižlavský Tomáš
Published: June 2018

Cellulose ethers (CEs) are widely used as viscosity enhancing, water retaining additives in cement based mortars. Nevertheless, studies about the effect of cellulose ethers on the properties of aerial lime-based mortars are very lack. The use of water retaining additives in lime mortars can influence not only their fresh state properties but also the pore structure and strength of hardened mortars. In this work, four different commercial cellulose ethers were added to lime mortars in order to test their influence on properties of mortars in the fresh state. Mortar rheological parameters (relative yield stress, consistency coefficient and fluidity index) were correlated with flow table tests, relative density measurements, water retention and air content in the mortars. It was found that CEs reduce the spread of lime mortars and increase air content in the mortars. The CEs are not so effective in water retention compared with other types of water retention agents. Most dosages of CEs change the behaviour of mortars from pseudoplastic to dilatant. In contrast to the effect of CEs in cement-based materials, their viscosity enhancing behavior in lime mortars is denied, due to the presence of large amounts of calcium hydroxide. From this point of view, the CEs are not so suitable to use as viscosity enhancing admixtures in lime mortars like derivatives of chitosan or guar gum.
Formation of Physic and Mechanical Composition of Dust Emission from the Ventilation Shaft of a Coal Mine as a Factor of Ecological Hazard
Authors: Kolesnyk Valeriy , Pavlychenko Artem , Borysovs’ka Olena , Buchavyy Yuriy
Published: June 2018

During operation of coal mines, polluted air is emitted from the ventilation shafts, it contains large amount of carbon and rock dust with various physical and mechanical composition. Dust contains freshly formed silicon dioxide and other components of the mineral product that are hazardous to human health, which are scattered in the surface layer of the atmosphere. Mainly fine dust comes from the mine workings, and the release of the total dust mass by 80 – 96 % is due to the operation of the loading and unloading complex. It is established that the level of dustiness decreases mainly due to the settling in the mine workings of the coarsely dispersed dust fraction. The environment receives mainly fine dust with a high content of fine particles, which can be intensively dispersed outside the sanitary protection zone of the mine. A mathematical model is obtained in the form of a differential equation of mass transfer, which takes into account the physic and mechanical composition of the dust emission from the ventilation shaft of the coal mine as a factor of ecological hazard. The obtained results determine the directions of effective struggle against dust emissions of coal mines.
Stress-Strain State of a Flat Tractive-Bearing Element of a Lifting and Transporting Machine at Operational Changes of its Parameters
Authors: Kolosov Dmytro , Bilous Olena , Tantsura Hanna , Onyshchenko Serhii
Published: June 2018

Main indicators of a stress-strain state of a rubber-cable belt, the rubber-cable rope for a random placement pattern and the size of the part with broken cables, including partially removed cables, with cable breakages and their random amount, different conditions of belt interaction in its cross-sections of connection to structural elements of a conveyor and a lifting machine to ensure control of its tractive ability during the life cycle. Performed researches clarify the idea of the interaction mechanism of reinforcing elements in composite materials of layered structure with hard and soft layers. Obtained results can be used for development and justification of a unified technology of creation and engineering support of operation of lifting and transporting machines with flat tractive-bearing elements with increased life-span, level of efficiency and operational safety in systems of extraction, transportation and processing of minerals.
Innovative Approach to the Integrated Use of Energy Resources of Underground Coal Gasification
Authors: Saik Pavlo , Petlovanyi Mykhailo , Lozynskyi Vasyl , Sai Kateryna , Merzlikin Artem
Published: June 2018

Topical issues concerning the low efficiency of underground coal mining from thin and very thin seams as well as the problems of reserves left in mine fields by the closed-down enterprises resulting in substantial coal reserve losses have been highlighted. Alternative use of the unextracted energy resources is their physical and chemical transformation with the change in aggregate state including the possibility to generate valuable chemical and energy products capable of substituting certain share of natural gas being imported. Attention has been paid to budget reallocation in the process of coal enterprise restructuring to invest the projects of nontraditional techniques aimed at physical and chemical coal transformation; among other things, it concerns in-place construction of energy generating enterprises for underground coal gasification. Results of the studies concerning the analysis of the world 50-year interest in the techniques of gasification and hydrate formation explained and described in the top scientific journals being among those added to such scientometric data bases as Scopus and Web of Science; they confirm the expediency of the scientific tendency development in Ukraine. Innovative conversion scheme for solid fuel has been proposed; the scheme involves the integrated use of the generated energy and chemical products in the process of in-place coal gasification. Development of systems to gasify, cogenerate, and form hydrates at the territory of coal mines will make it possible to process coal in place with energy, heat energy, and chemical raw material generation depending upon the situation in energy market and chemical market.
Respiratory Protection Provided by Negative Pressure Half Mask Filtering Respirators in Coal Mines
Authors: Cheberiachko Sergiy , Yavors’ka Olena , Radchuk Dmytro , Yavorskyi Andrii
Published: June 2018

Two studies were conducted in the coal mines to evaluate worker exposures to a dust, and the effectiveness of air-purifying negative-pressure half mask respirators and was found that miners’ protection were insufficient. An elastomeric and filtering half-mask negative pressure respirators with (mid-efficiency) filters P2 (FFP2) were studied. Measurements of total dust concentrations in the in-mask and outer air were conducted simultaneously. Not identical sampling system led to an underestimation of the actual total inside dust concentration in the first study. The results have been corrected to reduce the systematic error. The inside total dust concentrations Ci exceeded national Permissible Exposure Limit (PEL) in most cases in both studies; in first GM Ci=24.7 mg/m3; in second 8.6 mg/m3. Protection factors were: from 2.9 to 6.9 in first study; and from 5.6 to 34 in second. Low efficiency of respirators can be caused by its non-continuous usage. High risk of miners’ occupational diseases should be reduced by decreasing the dust concentration in the breathing zone. It is advisable to check the possibility of improving respiratory protection of miners by powered air-purifying respirators.
The Methodology of Use of the Mobile Crushing-and-Sorting Radiometric Complex in the Iron-Ore Pit
Authors: Azaryan Volodymyr
Published: June 2018

This paper justifies the use of the mobile crushing-and-sorting radiometric complexes (MCSRC) under conditions of iron-ore pits in order to increase the ore quality produced in the mine faces of the «ore-rock» contact zone and stabilize the content of the useful component in the general ore-flow. The patterns, which are used as a fundamental base of the radiometric sorting process, are given. The functional scheme of MCSRC is considered, the algorithm of operation is developed, and the main technological tasks of the complex are determined. The technological scheme of the face sloping using MCSRC and formation of the all-pit ore-flow is developed. The expected indicators from use of the mobile crushing-and-sorting radiometric complex in the form of the technological, economical, power-saving and ecological effect were considered.
Early changes in farmers’ adoption and use of an improved maize seed: An assessment of the impact of demos and field days
Authors: Kamau Mercy W. , Bagamba Fredrick , Riungu Claris , Mukundi John , Toel Robert
Published: June 2018

Background: Demonstration plots are widely used in the seed industry to create awareness and promote improved seed among smallholder farmers in sub-Saharan Africa. However, the magnitude of effects on farmers’ adoption behaviour is less known.Objectives: This study assessed the impact of demonstration plots and field days on farmers’ awareness, knowledge and use of the improved maize variety that was being promoted. The study also assessed the impact on maize yields and production.Method: A promotion campaign was mounted by a local seed company in eastern and western Uganda, where demonstration plots were established and field days were held for two seasons. These were aimed at augmenting effects of radio messages that were aired over the same period. We used quasi-experimental approaches to determine changes in farmers’ adoption behaviour towards a new maize variety, and the subsequent effects on productivity. Farm household data were collected at the baseline and midline from a sample of 2050 households.Results: The findings showed no effect on the proportion of farmers planting the promoted variety, the acreage or proportion of land planted with the promoted variety. This was not surprising as farmers’ awareness and knowledge about the variety remained very low.Conclusion: The early result shows that demonstration plots were not effective, suggesting that more effective approaches should be explored. It may also be the case that the assessment was too early in the adoption cycle, in which case results after two more seasons of promotion will provide a better estimate of the effect.
In vitro antioxidant and antimicrobial activity of Prunus africana (Hook. f.) Kalkman (bark extracts) and Harrisonia abyssinica Oliv. extracts (bark extracts): A comparative study
Authors: Madivoli Edwin S. , Maina Ernest G. , Kairigo Pius K. , Murigi Martin K. , Ogilo Joel K. , Nyangau Jared O. , Kimani Paul K. , Kipyegon Cheruiyot
Published: June 2018

Background: Plants are new sources of antibacterial agents, hence the need to determine and evaluate the antibacterial properties, antioxidant activity and gas chromatography – mass spectrometer (GC-MS) profile of medicinal plants. Methodology: In this study, sequential extraction of Prunus africana and Harrisonia abyssinica was used to obtain ethyl acetate and methanol extracts. Antioxidant activity was evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH), whereas the total phenolic and total flavonoid contents were estimated using Folin-Ciocalteu and aluminium chloride, respectively. Antibacterial properties of the extracts against Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, Escherichia coliand Candida albicans were estimated using the disc diffusion method and compared against streptomycin. Results: Screening of crude methanolic extracts revealed the presence of secondary metabolites which was further confirmed by Fourier transform infrared (FT-IR) characterisation that revealed the presence of H-bonded OH functional groups. The extracts revealed that P. africana had a higher total phenolic and total flavonoid contents compared to H. abyssinica. Methanolic extracts of both plants had moderate activity against selected microorganisms and both inhibited DPPH radical scavenging activity. GC-MS analysis of P. africana and H. abyssinica extracts revealed the presence of several phytochemicals that have been reported to have medicinal uses. Total phenolic and flavonoid contents showed positive correlations with the DPPH radical scavenging activity and negative correlations with EC50. Conclusion: Prunus africana and H. abyssinica extracts had moderate antimicrobial properties against the selected microorganisms because of the presence of secondary metabolites.
Blowflies as vectors of Bacillus anthracis in the Kruger National Park
Authors: Basson Lizanne , Hassim Ayesha , Dekker At , Gilbert Allison , Beyer Wolfgang , Rossouw Jennifer , Van Heerden Henriette
Published: June 2018

Anthrax, caused by Bacillus anthracis, is endemic in the Kruger National Park (KNP). The epidemiology of B. anthracis is dependent on various factors including vectors.The aims of this study were to examine non-biting blowflies for the presence of B. anthracis externally and internally after feeding on an anthrax-infected carcass and to determine the role of flies in disseminating B. anthracis onto the surrounding vegetation.During an anthrax outbreak in 2014 in the endemic Pafuri region, blowflies associated with two 2–3-day-old anthrax-positive carcasses (kudu and impala) as well as surrounding vegetation were collected and investigated for the presence of B. anthracis spores.The non-biting blowflies (n = 57) caught included Chrysomya albiceps, Ch. marginalis and Lucilia spp. Bacillus anthracis spores were isolated from 65.5% and 25.0% of blowflies collected from the kudu and impala carcasses, respectively.Chrysomya albiceps and Ch. marginalis have the potential to disseminate B. anthracis to vegetation from infected carcasses and may play a role in the epidemiology of anthrax in the KNP. No B. anthracis spores were initially isolated from leaves of the surrounding vegetation using selective media. However, 170 and 500 spores were subsequently isolated from Abutilon angulatum and Acacia sp. leaves, respectively, when using sheep blood agar.Conservation implications: The results obtained in this study have no direct conservation implications and only assist in the understanding of the spread of the disease.
Genotypic characterisation of Avian paramyxovirus type-1 viruses isolated from aquatic birds in Uganda
Authors: Wanyana Agnes , Mugimba Kizito K. , Bosco Omony J. , Kirunda Halid , Nakavuma Jessica L. , Teillaud Angélique , Ducatez Mariette F. , Byarugaba Denis K.
Published: June 2018

Avian paramyxovirus type-1 (APMV-1) viruses of the lentogenic pathotypes are often isolated from wild aquatic birds and may mutate to high pathogenicity when they cross into poultry and cause debilitating Newcastle disease. This study characterised AMPV-1 isolated from fresh faecal droppings from wild aquatic birds roosting sites in Uganda. Fresh faecal samples from wild aquatic birds at several waterbodies in Uganda were collected and inoculated into 9–10-day-old embryonated chicken eggs. After isolation, the viruses were confirmed as APMV-1 by APMV-1-specific polymerase chain reaction (PCR). The cleavage site of the fusion protein gene for 24 representative isolates was sequenced and phylogenetically analysed and compared with representative isolates of the different APMV-1 genotypes in the GenBank database. In total, 711 samples were collected from different regions in the country from which 72 isolates were recovered, giving a prevalence of 10.1%. Sequence analysis of 24 isolates revealed that the isolates were all lentogenic, with the typical 111GGRQGR’L117 avirulent motif. Twenty-two isolates had similar amino acid sequences at the cleavage site, which were different from the LaSota vaccine strain by a silent nucleotide substitution T357C. Two isolates, NDV/waterfowl/Uganda/MU150/2011 and NDV/waterfowl/Uganda/MU186/2011, were different from the rest of the isolates in a single amino acid, with aspartate and alanine at positions 124 and 129, respectively. The results of this study revealed that Ugandan aquatic birds indeed harbour APMV-1 that clustered with class II genotype II strains and had limited genetic diversity.
Genetic characterisation of African swine fever virus from 2017 outbreaks in Zambia: Identification of p72 genotype II variants in domestic pigs
Authors: Simulundu Edgar , Sinkala Yona , Chambaro Herman M. , Chinyemba Andrew , Banda Frank , Mooya Lynnfield E. , Ndebe Joseph , Chitanga Simbarashe , Makungu Chitwambi , Munthali Gift , Fandamu Paul , Takada Ayato , Mweene Aaron S
Published: June 2018

African swine fever (ASF) is a contagious haemorrhagic disease associated with causing heavy economic losses to the swine industry in many African countries. In 2017, Zambia experienced ASF outbreaks in Mbala District (Northern province) and for the first time in Isoka and Chinsali districts (Muchinga province). Meanwhile, another outbreak was observed in Chipata District (Eastern province). Genetic analysis of part of the B646L gene, E183L gene, CP204L gene and the central variable region of the B602L gene of ASF virus (ASFV) associated with the outbreaks in Mbala and Chipata districts was conducted. The results revealed that the ASFV detected in Mbala District was highly similar to that of the Georgia 2007/1 isolate across all the genome regions analysed. In contrast, while showing close relationship with the Georgia 2007/1 virus in the B646L gene, the ASFV detected in Chipata District showed remarkable genetic variation in the rest of the genes analysed. These results suggest that the Georgia 2007/1-like virus could be more diverse than what was previously thought, underscoring the need of continued surveillance and monitoring of ASFVs within the south-eastern African region to better understand their epidemiology and the relationships between outbreaks and their possible origin.