Showing papers by "University of Johannesburg published in 2015"
TL;DR: A measurement of the Higgs boson mass is presented based on the combined data samples of the ATLAS and CMS experiments at the CERN LHC in the H→γγ and H→ZZ→4ℓ decay channels.
Abstract: A measurement of the Higgs boson mass is presented based on the combined data samples of the ATLAS and CMS experiments at the CERN LHC in the H→γγ and H→ZZ→4l decay channels. The results are obtained from a simultaneous fit to the reconstructed invariant mass peaks in the two channels and for the two experiments. The measured masses from the individual channels and the two experiments are found to be consistent among themselves. The combined measured mass of the Higgs boson is mH=125.09±0.21 (stat)±0.11 (syst) GeV.
1,567 citations
TL;DR: The first IGRB measurement with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope (Fermi) used 10 months of sky-survey data and considered an energy range between 200 MeV and 100 GeV.
Abstract: The gamma-ray sky can be decomposed into individually detected sources, diffuse emission attributed to the interactions of Galactic cosmic rays with gas and radiation fields, and a residual all-sky emission component commonly called the isotropic diffuse gamma-ray background (IGRB). The IGRB comprises all extragalactic emissions too faint or too diffuse to be resolved in a given survey, as well as any residual Galactic foregrounds that are approximately isotropic. The first IGRB measurement with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope (Fermi) used 10 months of sky-survey data and considered an energy range between 200 MeV and 100 GeV. Improvements in event selection and characterization of cosmic-ray backgrounds, better understanding of the diffuse Galactic emission, and a longer data accumulation of 50 months, allow for a refinement and extension of the IGRB measurement with the LAT, now covering the energy range from 100 MeV to 820 GeV. The IGRB spectrum shows a significant high-energy cutoff feature, and can be well described over nearly four decades in energy by a power law with exponential cutoff having a spectral index of 2.32 plus or minus 0.02 and a break energy of (279 plus or minus 52) GeV using our baseline diffuse Galactic emission model. The total intensity attributed to the IGRB is (7.2 plus or minus 0.6) x 10(exp -6) cm(exp -2) s(exp -1) sr(exp -1) above 100 MeV, with an additional +15%/-30% systematic uncertainty due to the Galactic diffuse foregrounds.
680 citations
TL;DR: The third catalog of active galactic nuclei (AGNs) detected by the Fermi-LAT (3LAC) is presented in this paper, which is based on the 3FGL of sources detected between 100 MeV and 300 GeV.
Abstract: The third catalog of active galactic nuclei (AGNs) detected by the Fermi-LAT (3LAC) is presented. It is based on the third Fermi-LAT catalog (3FGL) of sources detected between 100 MeV and 300 GeV w ...
668 citations
TL;DR: In this paper, a facile and inexpensive route has been developed to synthesize a ternary ZnO/Ag/Mn2O3 nanocomposite having nanorod structures based on the thermal decomposition method.
Abstract: A facile and inexpensive route has been developed to synthesize a ternary ZnO/Ag/Mn2O3 nanocomposite having nanorod structures based on the thermal decomposition method. The as-synthesized ternary ZnO/Ag/Mn2O3 nanocomposite was characterized and used for visible light-induced photocatalytic, sensing and antimicrobial studies. The ternary ZnO/Ag/Mn2O3 nanocomposite exhibited excellent and enhanced visible light-induced photocatalytic degradation of industrial textile effluent (real sample analysis) compared to pure ZnO. Sensing studies showed that the ternary ZnO/Ag/Mn2O3 nanocomposite exhibited outstanding and improved detection of uric acid (UA) and ascorbic acid (AA). It also showed effective and efficient bactericidal activities against Staphylococcus aureus and Escherichia coli. These results suggest that the small size, high surface area and synergistic effect among ZnO, AgNPs and Mn2O3 induced visible light photocatalytic activity by decreasing the recombination of photogenerated electrons and holes, and extending the response of pure ZnO to visible light, enhanced sensing of UA and AA and antimicrobial activity. Overall, the ternary ZnO/Ag/Mn2O3 nanocomposite is a valuable material that can be used for a range of applications, such as visible light-induced photocatalysis, sensing and antimicrobial activity. Therefore, ternary nanocomposites could have important applications in environmental science, sensing, and biological fields.
401 citations
TL;DR: In this paper, a pencil graphite electrode was modified with polypyrrole/functionalized multiwalled carbon nanotubes for the determination of 6-mercaptopurine (6-MP) is presented.
Abstract: A novel and sensitive biosensor employing immobilized DNA on a pencil graphite electrode modified with polypyrrole/functionalized multiwalled carbon nanotubes for the determination of 6-mercaptopurine (6-MP) is presented. In the first step, we modified the pencil graphite surface with polypyrrole and functionalized multiwalled carbon nanotubes (MWCNT/COOH). The developed electrode was characterized by scanning electron microscopy, atomic force microscopy, reflection–absorption infrared spectroscopy, X-ray photoelectron spectroscopy, and electrochemical impedance spectroscopy. In the other step, we used decreases in the oxidation responses of guanine and adenine as a sign of the interaction of 6-MP with salmon sperm double-stranded DNA using differential pulse voltammetry. The signal of guanine oxidation was linear with respect to the 6-MP concentration in the range of 0.2–100 μmol L–1 with a detection limit of 0.08 μmol L–1. The modified electrode was utilized for the determination of 6-MP in real samples.
373 citations
TL;DR: It is proved that the formation of CS-Al(3+) complex is fully reversible and can sense to AcO(-)/F(-) via dissociation.
335 citations
TL;DR: A simple 4-Methyl-7-hydroxy-8-formyl Coumarin (CS) was used as a selective chemosensor for Mg 2+ in the presence of alkali and alkaline earth metal ions.
Abstract: A simple 4-Methyl-7-hydroxy-8-formyl Coumarin (CS) serves as a selective chemosensor for Mg 2+ in the presence of alkali and alkaline earth metal ions. It showed a significant fluorescence enhancement towards Mg 2+ . The receptor CS exhibited a good binding constant and lowest detection limit for Mg 2+ . The variation of emission signal exists via of reversible chelation enhanced fluorescence (CHEF) with this inherent quenching metal ion.
313 citations
TL;DR: An integrated theoretical account of how the unique demands of acquiring instrumental skills and cultural conventions provide insight into when children imitate, when they innovate, and to what degree is proposed.
290 citations
TL;DR: In this article, a search for narrow resonances decaying into WW, WZ, or ZZ boson pairs using 20.3 fb(-1) of proton-proton collision data at a center-of-mass energy of root s = TeV recorded with the AT...
Abstract: A search is performed for narrow resonances decaying into WW, WZ, or ZZ boson pairs using 20.3 fb(-1) of proton-proton collision data at a centre-of-mass energy of root s = TeV recorded with the AT ...
217 citations
TL;DR: In this article, the final ATLAS Run 1 measurements of Higgs boson production and couplings in the decay channel H -> ZZ* -> l(+)l(-)l(+) l'(-), where l, l' = e or mu, are presented.
Abstract: The final ATLAS Run 1 measurements of Higgs boson production and couplings in the decay channel H -> ZZ* -> l(+)l(-)l(+)l'(-), where l, l' = e or mu, are presented. These measurements were performed using pp collision data corresponding to integrated luminosities of 4.5 and 20.3 fb(-1) at center-of-mass energies of 7 and 8 TeV, respectively, recorded with the ATLAS detector at the LHC. The H -> ZZ* -> 4l signal is observed with a significance of 8.1 standard deviations, with an expectation of 6.2 standard deviations, at m(H) = 125.36 GeV, the combined ATLAS measurement of the Higgs boson mass from the H -> gamma gamma and H -> ZZ* -> 4l channels. The production rate relative to the Standard Model expectation, the signal strength, is measured in four different production categories in the H -> ZZ* -> 4l channel. The measured signal strength, at this mass, and with all categories combined, is 1.44(-0.33)(+0.40). The signal strength for Higgs boson production in gluon fusion or in association with (tt) over bar or (bb) over bar pairs is found to be 1.7(-0.4)(+0.5), while the signal strength for vector-boson fusion combined with WH/ZH associated production is found to be 0.3(-0.9)(+1.6).
213 citations
TL;DR: In this article, the results of a search for events containing at least one long-lived particle that decays at a significant distance from its production point into two leptons or into five or more charged particles are presented.
Abstract: Many extensions of the Standard Model posit the existence of heavy particles with long lifetimes. This article presents the results of a search for events containing at least one long-lived particle that decays at a significant distance from its production point into two leptons or into five or more charged particles. This analysis uses a data sample of proton-proton collisions at root s = 8 TeV corresponding to an integrated luminosity of 20.3 fb(-1) collected in 2012 by the ATLAS detector operating at the Large Hadron Collider. No events are observed in any of the signal regions, and limits are set on model parameters within supersymmetric scenarios involving R-parity violation, split supersymmetry, and gauge mediation. In some of the search channels, the trigger and search strategy are based only on the decay products of individual long-lived particles, irrespective of the rest of the event. In these cases, the provided limits can easily be reinterpreted in different scenarios.
TL;DR: This work presents nitrogen isotope ratios from marine and fluvial sedimentary rocks of prehnite–pumpellyite to greenschist metamorphic grade and suggests that molybdenum was bioavailable in the mid-Archaean ocean long before the Great Oxidation Event.
Abstract: Nitrogen isotope ratios from rocks between 3.2 and 2.75 billion years old are most readily explained by biological nitrogen fixation, most probably using the metal molybdenum as a cofactor, showing that nitrogen fixation is at least 3.2 billion years old and suggesting that molybdenum was available to organisms long before the Great Oxidation Event. The evolution of the enzyme nitrogenase, through which organisms can fix atmospheric nitrogen, was a clearly major step in the history of life. What is less certain is the timing. Eva Stueken et al. have determined nitrogen isotope ratios in marine and fluvial sedimentary rocks between 3.2 and 2.75 billion years old. The ratios are most readily explained by biological nitrogen fixation, probably with molybdenum as a cofactor. This suggests that nitrogen fixation is at least 3.2 billion years old, and contradicts previous suggestions that marine molybdenum was scarce before the Great Oxidation Event. Nitrogen is an essential nutrient for all organisms that must have been available since the origin of life. Abiotic processes including hydrothermal reduction1, photochemical reactions2, or lightning discharge3 could have converted atmospheric N2 into assimilable NH4+, HCN, or NOx species, collectively termed fixed nitrogen. But these sources may have been small on the early Earth, severely limiting the size of the primordial biosphere4. The evolution of the nitrogen-fixing enzyme nitrogenase, which reduces atmospheric N2 to organic NH4+, thus represented a major breakthrough in the radiation of life, but its timing is uncertain5,6. Here we present nitrogen isotope ratios with a mean of 0.0 ± 1.2‰ from marine and fluvial sedimentary rocks of prehnite–pumpellyite to greenschist metamorphic grade between 3.2 and 2.75 billion years ago. These data cannot readily be explained by abiotic processes and therefore suggest biological nitrogen fixation, most probably using molybdenum-based nitrogenase as opposed to other variants that impart significant negative fractionations7. Our data place a minimum age constraint of 3.2 billion years on the origin of biological nitrogen fixation and suggest that molybdenum was bioavailable in the mid-Archaean ocean long before the Great Oxidation Event.
TL;DR: Inclusive jet production is found to be suppressed by approximately a factor of 2 in central collisions compared to pp collisions, and the nuclear modification factor R(AA) shows a slight increase with p(T) and no significant variation with rapidity.
Abstract: Measurements of inclusive jet production are performed in pp and Pb+Pb collisions at √sNN = 2.76 TeV with the ATLAS detector at the LHC, corresponding to integrated luminosities of 4.0 pb−1 and 0.14 nb−1, respectively. The jets are identified with the anti-kt algorithm with R = 0.4, and the spectra are measured over the kinematic range of jet transverse momentum 32 < pT < 500 GeV, and absolute rapidity |y| < 2.1 and as a function of collision centrality. The nuclear modification factor, RAA, is evaluated and jets are found to be suppressed by approximately a factor of two in central collisions compared to pp collisions. The RAA shows a slight increase with pT and no significant variation with rapidity.
TL;DR: In this paper, the adsorption capacity of two efficient adsorbents namely MWCNTs and SWCNTs for the rapid removal of noxious Cr (VI) ion from the polluted aqueous source was well studied and optimized.
TL;DR: In this paper, a search for heavy Majorana neutrinos in events containing a pair of high-p(T) leptons of the same charge and high p(t) jets is presented, which is consistent with the background-only hypothesis based on the Standard Model expectation.
Abstract: A search for heavy Majorana neutrinos in events containing a pair of high-p(T) leptons of the same charge and high-p(T) jets is presented. The search uses 20.3 fb(-1) of pp collision data collected with the ATLAS detector at the CERN Large Hadron Collider with a centre-of-mass energy of root s = 8TeV. The data are found to be consistent with the background-only hypothesis based on the Standard Model expectation. In the context of a Type-I seesaw mechanism, limits are set on the production cross-section times branching ratio for production of heavy Majorana neutrinos in the mass range between 100 and 500 GeV. The limits are subsequently interpreted as limits on the mixing between the heavy Majorana neutrinos and the Standard Model neutrinos. In the context of a left-right symmetric model, limits on the production cross-section times branching ratio are set with respect to the masses of heavy Majorana neutrinos and heavy gauge bosons W-R and Z'.
TL;DR: In this paper, the authors explore and summarize recent efforts in the area of titania nanoparticle synthesis, modifications, and application for water treatment purposes, and conclude that Titania nanoparticles are intended to be both supplementary and complementary to the present water treatment technologies through the destruction or transformation of hazardous chemical wastes to innocuous end-products, that is, CO2 and H2O.
Abstract: The presence of both organic and inorganic pollutants in water due to industrial, agricultural, and domestic activities has led to the global need for the development of new, improved, and advanced but effective technologies to effectively address the challenges of water quality. It is therefore necessary to develop a technology which would completely remove contaminants from contaminated waters. TiO2 (titania) nanocatalysts have a proven potential to treat "difficult-to-remove" contaminants and thus are expected to play an important role in the remediation of environmental and pollution challenges. Titania nanoparticles are intended to be both supplementary and complementary to the present water-treatment technologies through the destruction or transformation of hazardous chemical wastes to innocuous end-products, that is, CO2 and H2O. This paper therefore explores and summarizes recent efforts in the area of titania nanoparticle synthesis, modifications, and application of titania nanoparticles for water treatment purposes.
TL;DR: In this paper, the authors examined the relationship between consumers' authenticity perception and four brand equity dimensions (brand awareness, brand association, perceived quality, brand loyalty), as well as how these four dimensions are interrelated with one another.
TL;DR: In this article, both resonant and nonresonant Higgs boson pair production were performed in the hh -> bb tau tau, gamma gamma WW* final states using 20.3 fb(-1) of collision data at a center-of-m...
Abstract: Searches for both resonant and nonresonant Higgs boson pair production are performed in the hh -> bb tau tau, gamma gamma WW* final states using 20.3 fb(-1) of pp collision data at a center-of-m ...
TL;DR: In this paper, a neural network is used to discriminate between signal and background events, the latter being dominated by +jets production, and an observed (expected) limit of 3.4 (2.2) times the Standard Model cross section is obtained at 95 % confidence level.
Abstract: A search for the Standard Model Higgs boson produced in association with a top-quark pair, , is presented. The analysis uses 20.3 fb(-1) of pp collision data at , collected with the ATLAS detector at the Large Hadron Collider during 2012. The search is designed for the decay mode and uses events containing one or two electrons or muons. In order to improve the sensitivity of the search, events are categorised according to their jet and b-tagged jet multiplicities. A neural network is used to discriminate between signal and background events, the latter being dominated by +jets production. In the single-lepton channel, variables calculated using a matrix element method are included as inputs to the neural network to improve discrimination of the irreducible background. No significant excess of events above the background expectation is found and an observed (expected) limit of 3.4 (2.2) times the Standard Model cross section is obtained at 95 % confidence level. The ratio of the measured signal cross section to the Standard Model expectation is found to be assuming a Higgs boson mass of 125 Gev.
TL;DR: Overall, ecological assemblages of C3-browsing, C3–C4 mixed feeding, and C4-grazing taxa in the Turkana Basin fossil record that are different from any modern ecosystem in East or Central Africa are found.
Abstract: A large stable isotope dataset from East and Central Africa from ca. 30 regional collection sites that range from forest to grassland shows that most extant East and Central African large herbivore taxa have diets dominated by C4 grazing or C3 browsing. Comparison with the fossil record shows that faunal assemblages from ca. 4.1–2.35 Ma in the Turkana Basin had a greater diversity of C3–C4 mixed feeding taxa than is presently found in modern East and Central African environments. In contrast, the period from 2.35 to 1.0 Ma had more C4-grazing taxa, especially nonruminant C4-grazing taxa, than are found in modern environments in East and Central Africa. Many nonbovid C4 grazers became extinct in Africa, notably the suid Notochoerus, the hipparion equid Eurygnathohippus, the giraffid Sivatherium, and the elephantid Elephas. Other important nonruminant C4-grazing taxa switched to browsing, including suids in the lineage Kolpochoerus-Hylochoerus and the elephant Loxodonta. Many modern herbivore taxa in Africa have diets that differ significantly from their fossil relatives. Elephants and tragelaphin bovids are two groups often used for paleoecological insight, yet their fossil diets were very different from their modern closest relatives; therefore, their taxonomic presence in a fossil assemblage does not indicate they had a similar ecological function in the past as they do at present. Overall, we find ecological assemblages of C3-browsing, C3–C4-mixed feeding, and C4-grazing taxa in the Turkana Basin fossil record that are different from any modern ecosystem in East or Central Africa.
TL;DR: In this paper, a functional graded titanium alloy composite was produced using optimized process parameters for each material combination as obtained through a model that was developed in an initial study and the FGM was characterized through metallurgical, mechanical and tribological studies.
TL;DR: The relationship between tourism development and citizens' trust in government is an under-researched area and as discussed by the authors developed a model that established theoretical relationships between important tourism development variables and two types of political trust.
TL;DR: In this article, the authors measured the inclusive jet cross-section in proton-proton collisions at a centre-of-mass energy of 7 TeV using a data set corresponding to an integrated luminosity of 4.5 fb−1 collected with the ATLAS detector at the Large Hadron Collider in 2011.
Abstract: The inclusive jet cross-section is measured in proton-proton collisions at a centre-of-mass energy of 7 TeV using a data set corresponding to an integrated luminosity of 4.5 fb−1 collected with the ATLAS detector at the Large Hadron Collider in 2011. Jets are identified using the anti-k t algorithm with radius parameter values of 0.4 and 0.6. The double-differential cross-sections are presented as a function of the jet transverse momentum and the jet rapidity, covering jet transverse momenta from 100 GeV to 2 TeV. Next-to-leading-order QCD calculations corrected for non-perturbative effects and electroweak effects, as well as Monte Carlo simulations with next-to-leading-order matrix elements interfaced to parton showering, are compared to the measured cross-sections. A quantitative comparison of the measured cross-sections to the QCD calculations using several sets of parton distribution functions is performed.
Islamic Azad University1, Shahid Beheshti University2, University of Johannesburg3, King Fahd University of Petroleum and Minerals4, Indian Institute of Technology Roorkee5, University of Texas–Pan American6, Lappeenranta University of Technology7, United States Environmental Protection Agency8, Clarkson University9, Beijing University of Chemical Technology10, Payame Noor University11
TL;DR: In this paper, the authors comprehensively review the latest progress in the development of carbon nanotubes and their applications for the removal of synthetic dyes from wastewater, including functionalized of CNTs and their researched counterparts.
Abstract: Rapid removal of noxious synthetic dyes from wastewater is of great concern in the scientific research field, this is due to the expansion of harmful effects of synthetic dyes traces in water streams on the environment and human health with the exponential rise in concentration of synthetic dye globally and demand in various industries that coincided with the implantation of more stringent water quality standards. Various technologies have been applied for the removal of synthetic dye from wastewater, including adsorption technology, which has a great potential in treating varieties of synthetic dyes. This article comprehensively reviews the latest progress in the development of carbon nanotubes (CNTs) and their applications for the removal of synthetic dyes from wastewater, including functionalized of CNTs and their researched counterparts. The emerging trends in the development of alternative adsorbents with different substrates, morphologies, and functional groups are also elucidated.
TL;DR: In this paper, a search for the b (b) over bar decay of the Standard Model Higgs boson is performed with the ATLAS experiment using the full dataset recorded at the LHC in Run 1.
Abstract: A search for the b (b) over bar decay of the Standard Model Higgs boson is performed with the ATLAS experiment using the full dataset recorded at the LHC in Run 1. The integrated luminosities used are 4.7 and 20.3 fb(-1) from pp collisions at root s = 7 and 8 TeV, respectively. The processes considered are associated (WIZ)H production, where W -> e nu/mu nu, Z -> ee/mu mu, and Z -> nu nu. The observed (expected) deviation from the backgroundonly hypothesis corresponds to a significance of 1.4 (2.6) standard deviations and the ratio of the measured signal yield to the Standard Model expectation is found to be mu = 0.52 +/- 0.32 (stat.) +/- 0.24 (syst.) for a Higgs boson mass of 125.36 GeV. The analysis procedure is validated by a measurement of the yield of (W/Z)Z production with Z -> b (b) over bar in the same final states as for the Higgs boson search, from which the ratio of the observed signal yield to the Standard Model expectation is found to be 0.74 +/- 0.09 (stat.) +/- 0.14 (syst.).
TL;DR: In this paper, the authors present a review of the papers published up to February 2015 that have been focussed upon the assessment of the environmental and energy impacts related to the use of hemp-based materials for building applications.
Abstract: Buildings significantly contribute to global environmental pollution due to consumption of both natural and primary-energy resources as well as to emission of carbon dioxide in their life-cycles. Therefore, to enable construction of more sustainable buildings, it is important and urgent that new low-environmental impact materials are developed, mainly by reducing the use of non-renewable resources. In this regard, the recent advances in the development of natural fibres represent a significant opportunity to produce improved-materials and energy from renewable resources. For this purpose, assessments of energy and environmental performances are needed to support both the design and the production of the aforementioned materials so as to identify solutions for enhanced contribution to global sustainability. In this context, this study presented a review of the papers published up to February 2015 that have been focussed upon the assessment of the environmental and energy impacts related to the use of hemp-based materials for building applications. The reviewed studies aimed at testing and improving hygro-thermal properties and eco-friendliness of these materials for reduction of both embodied and operational energy, whilst preserving both indoor air quality and comfort. Doing so would enable limiting the use of energy resources and, as a consequence, their impacts to human health and to the environment, so contributing to making buildings healthier and more environmentally sustainable throughout their life-cycles. Based upon the findings of the studies reviewed, these materials have strengths and weaknesses and their use is strictly dependent upon the given structural situation as well as upon specific requirements of thermal, moisture, fire and sound protection. In particular, all studies concluded that the main strength in the use of hemp-based materials comes from the production phase because of the “green” origin of these materials, mainly associated with the carbon sequestration during plantation growth.
TL;DR: In this paper, the photocatalytic and electrochemical activity of ZnO and CdO nanocomposites were determined by a vapor to solid mechanism and were characterized by different physical and chemical techniques.
TL;DR: In this article, a search for a heavy, CP-odd Higgs boson decaying into a Z boson and a 125 GeV h, with the ATLAS detector at the LHC is presented.
TL;DR: In this paper, the authors search for high-mass diphoton resonances in pp collisions at pffisffi root s=8 TeV with the ATLAS detector.
Abstract: Search for high-mass diphoton resonances in pp collisions at pffisffi root s=8 TeV with the ATLAS detector
Saint Petersburg State University1, Smithsonian Conservation Biology Institute2, University of California, Los Angeles3, University of Johannesburg4, University of Porto5, Duke University6, University of Idaho7, University of Turku8, University of Oulu9, Sichuan University10, University of California, Santa Cruz11, Tel Aviv University12, Spanish National Research Council13, National Museum of Natural History14, Nova Southeastern University Oceanographic Center15
TL;DR: Using morphologic data, a striking morphologic similarity between East African and Eurasian golden jackals is demonstrated, suggesting parallelism, which may have misled taxonomists and likely reflects uniquely intense interspecific competition in the East African carnivore guild.