Electrical Properties of Zinc-Kaolin Composites below its Percolation Threshold

In this paper, we present some electrical properties of the zinc-kaolin cermet resistors with zinc metal fillers below the percolation threshold. Rectangular cermet rods of dimensions 65 mm by 6.5 mm by 3.2 mm were produced in a mould with semi-dry the zinc/kaolin powder mixture which is compressed with a force of about 1.32 x 105 N. Percolation threshold was found to be both a function of the metal-kaolin ceramic mixture and the annealing temperature. The percolation threshold for cermets annealed at 300and 4000C is between 70 and 80% (vol.) while the cermets annealed at temperatures between 500 and 9000C is between 15 and 20% (vol.). The electrical conduction mechanism of the zinc-kaolin cermet below the percolation threshold is a mixture of both the hopping and the tunneling model with the hopping mechanism dominating. The temperature coefficient of resistance (TCR) is predominantly positive and large (30000-45000 ppmK-1) when cermet temperature is below 1000C. It is observed that changes in the measurement of TCR can be used to determine percolation threshold in cermets.Keywords: Cermet, Percolation threshold, Electrical properties, Composite, Hopping and Tunneling

Characterization of Marble-Clay Composite as Alternative To Conventional Bricks in Building

The usability of marble as an additive material with clay in industrial brick has been investigated. Marble was collected from the marble deposit located at Igbeti (latitude 80 451 longitude 40 81 E.), and the red clay was collected at University of Ilorin, Ilorin (latitude 80 321 N and longitude 40 341 E), both in Nigeria. Marble and Clay were processed for the preparation of the composite. The two materials were mixed in varying proportion of marble, ranging from 0 wt. % to 45 %. The mixture was made into bricks with size 6.0 x 7.0 x 2.0 cm. Ten sample bricks of different marble composition were prepared. These bricks were compressed and heated at a temperature of 950 0C for 2 hours. Water absorption and thermal conductivity tests were carried out on the samples. It was observed that the amount of marble added had positive effect on the physical and mechanical strength of the produced brick. The results also show that increase in percentage of marble will be of good advantage in keeping the house warm during raining season as observed from the thermal conductivity test.Keywords: Marble, Clay, Physico-mechanical, Thermal conductivity, Water Absorptio

Environmental Ionizing Radiation Survey of Quarry Sites in Ilorin Industrial Area, Nigeria

An environmental ionizing radiation survey around quarry sites in Ilorin was carried out using three Radalert Nuclear Radiation Monitors and Global  Positioning System (GPS) in order to assess and provide up to date  information on radiation levels in the environment. Measured mean radiation levels ranged from 1.11±0.05 to 1.72±0.03 mSv/yr with an average of  1.49±0.04 mSv/yr in the study area. The radiation levels have surpassed the standard level of 1 mSv/yr by 50%, but fall below the global average of 2.4 mSv/yr for the general public and 20 mSv/yr for occupational environment.Keywords: Radiation, Environment, Industry, Health, Nigeri

The SLUGGS survey: the mass distribution in early-type galaxies within five effective radii and beyond

We study mass distributions within and beyond 5 effective radii (Re) in 23 early-type galaxies from the SAGES Legacy Unifying Globulars and Galaxies Survey, using their globular cluster (GC) kinematic data. The data are obtained with Keck/DEep Imaging Multi-Object Spectrograph, and consist of line-of-sight velocities for ̃3500 GCs, measured with a high precision of ̃15 km s-1 per GC and extending out to ̃13 Re. We obtain the mass distribution in each galaxy using the tracer mass estimator of Watkins et al. and account for kinematic substructures, rotation of the GC systems and galaxy flattening in our mass estimates. The observed scatter between our mass estimates and results from the literature is less than 0.2 dex. The dark matter fraction within 5 Re (fDM) increases from ̃0.6 to ̃0.8 for low- and high-mass galaxies, respectively, with some intermediate-mass galaxies (M* ̃ 1011 M☉) having low fDM ̃ 0.3, which appears at odds with predictions from simple galaxy models. We show that these results are independent of the adopted orbital anisotropy, stellar mass-to-light (M/L) ratio, and the assumed slope of the gravitational potential. However, the low fDM in the ̃1011 M☉ galaxies agrees with the cosmological simulations of Wu et al. where the pristine dark matter distribution has been modified by baryons during the galaxy assembly process. We find hints that these M* ̃ 1011 M☉ galaxies with low fDM have very diffuse dark matter haloes, implying that they assembled late. Beyond 5 Re, the M/L gradients are steeper in the more massive galaxies and shallower in both low and intermediate mass galaxies

Tau association with synaptic vesicles causes presynaptic dysfunction

Tau is implicated in more than 20 neurodegenerative diseases, including Alzheimer's disease. Under pathological conditions, Tau dissociates from axonal microtubules and missorts to pre- and postsynaptic terminals. Patients suffer from early synaptic dysfunction prior to Tau aggregate formation, but the underlying mechanism is unclear. Here we show that pathogenic Tau binds to synaptic vesicles via its N-terminal domain and interferes with presynaptic functions, including synaptic vesicle mobility and release rate, lowering neurotransmission in fly and rat neurons. Pathological Tau mutants lacking the vesicle binding domain still localize to the presynaptic compartment but do not impair synaptic function in fly neurons. Moreover, an exogenously applied membrane-permeable peptide that competes for Tau-vesicle binding suppresses Tau-induced synaptic toxicity in rat neurons. Our work uncovers a presynaptic role of Tau that may be part of the early pathology in various Tauopathies and could be exploited therapeutically.status: publishe

Globular cluster systems and galaxy formation

Globular clusters are compact, gravitationally bound systems of up to a million stars. The GCs in the Milky Way contain some of the oldest stars known, and provide important clues to the early formation and continuing evolution of our Galaxy. More generally, GCs are associated with galaxies of all types and masses, from low-mass dwarf galaxies to the most massive early-type galaxies which lie in the centres of massive galaxy clusters. GC systems show several properties which connect tightly with properties of their host galaxies. For example, the total mass of GCs in a system scales linearly with the dark matter halo mass of its host galaxy. Numerical simulations are at the point of being able to resolve globular cluster formation within a cosmological framework. Therefore, GCs link a range of scales, from the physics of star formation in turbulent gas clouds, to the large-scale properties of galaxies and their dark matter. In this Chapter we review some of the basic observational approaches for GC systems, some of their key observational properties, and describe how GCs provide important clues to the formation of their parent galaxies.Comment: 32 pages, 6 figures. Accepted for publication in the book "Reviews in Frontiers of Modern Astrophysics: From Space Debris to Cosmology" (eds Kabath, Jones and Skarka; publisher Springer Nature) funded by the European Union Erasmus+ Strategic Partnership grant "Per Aspera Ad Astra Simul" 2017-1-CZ01-KA203-03556

Trait emotional intelligence and problematic social media use among adults: the mediating role of social media use motives

There are many contributing factors to problematic social media use including personality differences, psychosocial factors, and specific use motivations. The present study (N = 444 emerging adults, 75% women) investigated the direct and indirect relationships between trait emotional intelligence and problematic social media use via social media use motives by testing a complex mediation model. Path analyses suggested that trait emotional intelligence was directly and indirectly associated with problematic social media use via two social media use motives: (i) expressing or presenting a more popular self, and (ii) passing time. Results of the present study indicate that trait emotional intelligence may have a role in the motives for using social media as well as the development and maintenance of problematic social media use. Moreover, future studies should focus mediator risk factors between trait emotional intelligence and problematic social media use

Replacement Models Revisited

Replacement is an aspect of operations research. In this paper various aspects of replacement have been considered. They include reasons for replacement, replacement assumptions and replacement policies, single and group types of replacement and some of the existing quantitative techniques of replacement. The objective is to review the annual total cost and the cumulative annual total cost average hitherto used as replacement methods. The study showed some disparity in the optimal age of single replacement as used by some authors. Hence, an arithmetic mean method of finding the optimal single- replacement- age of an asset has been proposed with an assumption that the asset is fit for the first n years, the value of n depending on the prevailing situation; examples of this newly proposed arithmetic-mean method are compared to the results of some of the existing ones. It is concluded that the method is more reliable and simpler than the older ones. JORIND Vol. 5 (1) 2007: pp. 23-2

Symbolic Logic: The Construction Of An Initial Truth Table Revisited

The paper provided three alternative methods of constructing an initial truth table for an n-sentence argument in logic. The first method provides the construction by a modified binomial expansion. The second method provides a formula or a model for constructing or filling any column. The third method is the conversion of the column modeling to a frequency distribution table. These three methods serve as alternatives to the existing heuristic approach and in a way they are better as using them has shown. Keywords: Modified binomial expansion, frequency distribution of T,s and F's on a truth table, a heuristic approach JORIND Vol. 6 (1) 2008: pp. 24-2