243 research outputs found
Utilization of Boron Waste Borogypsum with Silica Fume as a Supplementary Cementitious Material in Mortar
In the current study, borogypsum and borogypsum with silica fume mixtures are added to cement clinker partially. Flexural tensile strength, compressive strength and water absorption tests are performed on mortar samples which contain borogypsum and silica fume and also high temperature effect on the mortars are investigated. As a result of the tests it is revealed that 5% addition of borogysum and borogypsum-silica fume mixtures to cement clinker are altered strength behaviors of the mortars
Magnetic resonance imaging of the quadriceps fat pad oedema pattern in relation to patellofemoral joint pathologies
Purpose: Quadriceps fat pad is located posterior to the quadriceps tendon. Increased signal intensity of this fat pad is seen on routine knee magnetic resonance imaging (MRI) examinations, but the exact mechanism and related pathologies are not clear. In this study we aimed to evaluate the relationship between MRI signal intensity and morphological features of quadriceps fat pad, as well as various pathologies of the patellofemoral joint. Material and methods: Sixty-one knees with quadriceps fat pad oedema out of 457 knee MRI examinations were included. Quadriceps fat pad signal intensity, dimensions, posterior indentation, and various parameters related to patellofemoral joint such as trochlear facet asymmetry, trochlear depth and sulcus angle, and the Insall-Salvati ratio were evaluated. Results: There was no statistically significant correlation between quadriceps fat pad oedema intensity and its dimensions, but it was significant when compared to posterior indentation. There was no correlation between fat pad oedema and each of the pathologies. However, there was a significant correlation between the presence of fat pad oedema and the presence of at least one of the pathologies related to patellofemoral joint. Conclusions: Quadriceps fat pad oedema detected in MRI examinations should warn the radiologist against the presence of various pathologies related to the patellofemoral joint
Lomna žilavost trenjem zavarenih spojeva iz AlCu4SiMg aluminijske legure
The objective of paper was to determine the fracture toughness of friction stir welding (FSW) joints of EN AW-2014 AlCu4SiMg) aluminium alloy, and to compare the fracture toughness of FSW with that of conventional metal inert gas (MIG) process. FSW of aluminium alloy was performed on a conventional semiautomatic milling machine. Defect free FSW welds were produced on alloy plates at constant tool rotation and traverse speed of 1600 rpm and 200 mm/min, respectively. The results of Vickers hardness and Charpy impact tests were used to evaluate the fracture toughness of welded joints. Low heat input, absence of melting and filler metal resulted in better fracture toughness for FSW joints
Utilization of Colemanite waste in Concrete Design
Waste material is formed in enormous quantities during the beneficiation of raw ore. These wastes can cause both economic loss and environmental pollution. Thus, in this study, the effect of CW obtained from Eti Mine Establishments Kütahya-Emet Boron Plants on the compressive strength and cylinder splitting tensile strength of concrete and its USAbility as a concrete admixture is investigated. The results found show that utilization of Colemanite Waste is possible when it is used as additive in concrete
Structural, Vibrational and Electronic Properties of Single Layer Hexagonal Crystals of Groups IV and V
Using first-principles density functional theory calculations, we investigate
a family of stable two-dimensional crystals with chemical formula ,
where and belong to groups IV and V, respectively ( = C, Si, Ge, Sn,
Pb; = N, P, As, Sb, Bi). Two structural symmetries of hexagonal lattices
and are shown to be dynamically stable, named as
- and -phases correspondingly. Both phases have similar cohesive
energies, and the -phase is found to be energetically favorable for
structures except CP, CAs, CSb and CBi, for which the -phase is favored.
The effects of spin-orbit coupling and Hartree-Fock corrections to
exchange-correlation are included to elucidate the electronic structures. All
structures are semiconductors except CBi and PbN, which have metallic
character. SiBi, GeBi and SnBi have direct band gaps, whereas the remaining
semiconductor structures have indirect band gaps. All structures have quartic
dispersion in their valence bands, some of which make the valence band maximum
and resemble a Mexican hat shape. SnAs and PbAs have purely quartic valence
band edges, i.e. , a property reported for the first
time. The predicted materials are candidates for a variety of applications.
Owing to their wide band gaps, CP, SiN, SiP, SiAs, GeN, GeP can find their
applications in optoelectronics. The relative band positions qualify a number
of the structures as suitable for water splitting, where CN and SiAs are
favorable at all pH values. Structures with quartic band edges are expected to
be efficient for thermoelectric applications
Tangled Nature: A model of emergent structure and temporal mode among co-evolving agents
Understanding systems level behaviour of many interacting agents is
challenging in various ways, here we'll focus on the how the interaction
between components can lead to hierarchical structures with different types of
dynamics, or causations, at different levels. We use the Tangled Nature model
to discuss the co-evolutionary aspects connecting the microscopic level of the
individual to the macroscopic systems level. At the microscopic level the
individual agent may undergo evolutionary changes due to mutations of
strategies. The micro-dynamics always run at a constant rate. Nevertheless, the
system's level dynamics exhibit a completely different type of intermittent
abrupt dynamics where major upheavals keep throwing the system between
meta-stable configurations. These dramatic transitions are described by a
log-Poisson time statistics. The long time effect is a collectively adapted of
the ecological network. We discuss the ecological and macroevolutionary
consequences of the adaptive dynamics and briefly describe work using the
Tangled Nature framework to analyse problems in economics, sociology,
innovation and sustainabilityComment: Invited contribution to Focus on Complexity in European Journal of
Physics. 25 page, 1 figur
Lomna žilavost trenjem zavarenih spojeva iz AlCu4SiMg aluminijske legure
The objective of paper was to determine the fracture toughness of friction stir welding (FSW) joints of EN AW-2014 AlCu4SiMg) aluminium alloy, and to compare the fracture toughness of FSW with that of conventional metal inert gas (MIG) process. FSW of aluminium alloy was performed on a conventional semiautomatic milling machine. Defect free FSW welds were produced on alloy plates at constant tool rotation and traverse speed of 1600 rpm and 200 mm/min, respectively. The results of Vickers hardness and Charpy impact tests were used to evaluate the fracture toughness of welded joints. Low heat input, absence of melting and filler metal resulted in better fracture toughness for FSW joints
Self-optimization, community stability, and fluctuations in two individual-based models of biological coevolution
We compare and contrast the long-time dynamical properties of two
individual-based models of biological coevolution. Selection occurs via
multispecies, stochastic population dynamics with reproduction probabilities
that depend nonlinearly on the population densities of all species resident in
the community. New species are introduced through mutation. Both models are
amenable to exact linear stability analysis, and we compare the analytic
results with large-scale kinetic Monte Carlo simulations, obtaining the
population size as a function of an average interspecies interaction strength.
Over time, the models self-optimize through mutation and selection to
approximately maximize a community fitness function, subject only to
constraints internal to the particular model. If the interspecies interactions
are randomly distributed on an interval including positive values, the system
evolves toward self-sustaining, mutualistic communities. In contrast, for the
predator-prey case the matrix of interactions is antisymmetric, and a nonzero
population size must be sustained by an external resource. Time series of the
diversity and population size for both models show approximate 1/f noise and
power-law distributions for the lifetimes of communities and species. For the
mutualistic model, these two lifetime distributions have the same exponent,
while their exponents are different for the predator-prey model. The difference
is probably due to greater resilience toward mass extinctions in the food-web
like communities produced by the predator-prey model.Comment: 26 pages, 12 figures. Discussion of early-time dynamics added. J.
Math. Biol., in pres
Genome-wide association study of problematic opioid prescription use in 132,113 23andMe research participants of European ancestry
The growing prevalence of opioid use disorder (OUD) constitutes an urgent health crisis. Ample evidence indicates that risk for OUD is heritable. As a surrogate (or proxy) for OUD, we explored the genetic basis of using prescription opioids \u27not as prescribed\u27. We hypothesized that misuse of opiates might be a heritable risk factor for OUD. To test this hypothesis, we performed a genome-wide association study (GWAS) of problematic opioid use (POU) in 23andMe research participants of European ancestry (N = 132,113; 21% cases). We identified two genome-wide significant loci (rs3791033, an intronic variant of KDM4A; rs640561, an intergenic variant near LRRIQ3). POU showed positive genetic correlations with the two largest available GWAS of OUD and opioid dependence (
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