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Recent Submissions

Access status: Open Access ,
Mechanical properties of multi-walled beryllium-oxide nanotubes: a molecular dynamics simulation study
(Nazarbayev University, 2025-11-24) Amin Hamed Mashhadzadeh; Christos Spitas; Navid Shahab; Yaser Rostamiyan
Molecular dynamic (MD) simulation was employed to take the molecular fingerprint of mechanical properties of beryllium-oxide nanotubes (BeONTs). In this regard, the effect of the radius, the number of walls (single-, double-, and triple-walled), and the interlayer distance, as well as the temperature on the Young’s modulus, failure stress, and failure strain, are visualized and discussed. It was unveiled that larger single-walled BeONTs have lower Young’s modulus in zigzag and armchair direction, and the highest Young’s modulus was obtained for the (8,0) zigzag and (4,4) armchair SWBeONTs as of 645.71 GPa and 624.81 GPa, respectively. Unlike Young’s modulus, however, the failure properties of the armchair structures were higher than those of zigzag ones. Furthermore, similar to SWBEONTs, an increase in the interlayer distance of double-walled BeONTs (DWBeONTs) led to a slight reduction in Young’s modulus value, while no meaningful trend was found among failure behavior. For double-walled BeONTs (TWBeONTs), the elastic modulus was obviously higher in both armchair and zigzag directions compared to DWBeONTs.
Access status: Open Access ,
Study of the effect of the introduction of Tris(bipyridine)ruthenium(II) chloride into silicon dioxide particles by spectrofluorometry methods
(Nazarbayev University, 2025-11-24) I. I. Barashkova; Svetlana Mendigaliyeva; Anuar Aldongarov; Akbota Yensebayeva; Olga Lu; N. N. Barashkov; Arthur Mantel; Irina Irgibayeva
The Stoeber reaction was used to grow silica microparticles in the presence of the fluorescent dye Tris(bipyridine)ruthenium (II) chloride. The diameter of the obtained particles varies from about 150 to 280 nm depending on the dye concentration. Using spectrofluorometry methods, concentration quenching of fluorescence of dye solutions was studied before and after growing the microparticles. It was found out that the concentration quenching of fluorescence decreases significantly after its incorporation into the silicon dioxide microparticles upon excitation in the short-wavelength region of the spectrum.
Access status: Open Access ,
Porous carbon nanotubes microspheres decorated with strong catalyst cobalt nanoparticles as an effective sulfur host for lithium-sulfur battery
(Nazarbayev University, 2025-11-24) Zhumabay Bakenov; Arailym Nurpeissova; Yan Zhao; Guoliang Cui; Tong Wang
The commercialization of lithium-sulfur (Li–S) battery is largely obstructed by the slow redox kinetics of sulfur cathode and the shuttle effect of polysulfides during its operation, which negatively affect the battery rate capability and cycle life. Herein, a porous CNTs/Co microsphere is synthesized and applied as sulfur host material to boost the electrochemical performance of sulfur cathode. The porous conductive CNTs spherical network can realize a rapid charge and mass transfer via fast conduction of Li+-ions and mitigate the cathode volume expansion in the course of the cycles. Importantly, the Co metal nanoparticles can attain intense chemical adsorption and fast catalytic conversion of polysulfides. Because of the above merits, the high initial discharge specific capacity 1242.5 mAh g−1 was obtained for S-CNTs/Co composite at 0.2C. The capacity decay rate was only 0.066% per cycle at 1C over 300 cycles and the excellent rate performance at up to 3C could also be obtained. Moreover, the S-CNTs/Co composite delivered a high initial areal capacity of 5.7 mAh cm−2 at a high sulfur loading (5.9 mg cm−2), indicating broad perspectives of CNTs/Co as a sulfur host in lithium-sulfur battery.
Access status: Open Access ,
Bioturbation, heavy mineral concentration, and high gamma-ray activity in the Lower Cretaceous McMurray Formation, Canada
(Nazarbayev University, 2025-11-24) Jagos R. Radovic; Manuel Bringue; Raphael A.J. Wust; W. A. Matthews; Raza A. Siddiqui; Andreas Wetzel; Rajeev Nair; Milovan Fustic
In the Lower Cretaceous McMurray Formation (Alberta, Canada), many intervals of intensely bioturbated (Bioturbation Index = 5–6) fine-grained sediments are characterized by high gamma-ray (GR) readings. Several methods, including sedimentary facies analysis, thin-section petrography, handheld spectral gamma-ray, portable X-ray fluorescence, X-ray diffraction, inductively coupled plasma-mass spectrometry, microprobe of K-feldspar, energy dispersive spectroscopy, and detrital zircon geochronology by laser ablation-inductively coupled plasma-mass spectrometry, were used to investigate the interval of interest in core samples. The mineralogical analysis shows that these intervals are enriched in heavy mineral grains, and particularly in zircons. The content of radioactive elements is variable. Thorium is commonly elevated up to three times, uranium nil to two times, and potassium content usually remains normal. The studied intervals consist of interbedded, bitumen-saturated cross-bedded and/or ripple cross-laminated sandstone (high-energy deposits) and light-gray bioturbated mudstone (low-energy deposits), commonly addressed as inclined heterolithic strata (IHS). IHS represent tidally influenced, brackish-water, upper point-bar deposits. The zircon grains become concentrated while hydraulic processes interact with bioturbation: the burrowing animals cause significant sediment mixing that allows the lightest sediment particles to go back into the suspension. Additionally, bioturbation increases the surface roughness along the sediment-water interface and, causes more turbulent flow, allowing for quartz and other light grains to be removed by traction and/or saltation, while dispersed heavier zircon grains become trapped and concentrated in open burrows. So far, this study is the first to demonstrate the importance of bioturbation in the enrichment of zircon grains in IHS. The interaction of bioturbation and hydraulic processes explains the apparently counter-intuitive enrichment of heavy minerals in a low-energy depositional setting. This scenario likely applies to numerous intervals characterized by similar GR and/or zirconium spikes across the McMurray Formation. Furthermore, it can be expected that in other sedimentary basins and stratigraphic units, similar studies will demonstrate that the proposed mechanism is universal.
Access status: Open Access ,
Global connectedness of local NGOs: do different types of funding create barriers for cooperation?
(Nazarbayev University, 2025-11-24) K.N. Rodionova; Darkhan Medeuov; Adil Rodionov
How does international financial aid affect the cooperative behavior of local non-governmental organizations (NGOs)? Can NGOs, while turning global, preserve peer connections with local actors and be engaged in local issues? The civil society literature contains competing perspectives on and reports of how international financial aid may restructure local civic networks. Some scholars argue that international support comes at the expense of local integration as inclusion in global networks takes local NGOs out of the local context, while others find evidence that organizations do not have to face “a forced choice”, and may well be integrated both globally and locally. Drawing on this scholarship, we examine two hypotheses on how transnational funding influences cooperation patterns among NGOs. The hierarchy argument states that public entities tend to cooperate with internationally funded NGOs as external contact signals quality and trustworthiness. The segregation argument, on the contrary, suggests financial homophily according to which organizations are more likely to choose peers similar in sources of funding. To test these hypotheses, we apply Exponential Random Graph Models to the data on cooperation among 221 Kazakhstani NGOs. Results support the segregation hypothesis implying that NGOs are likely to have a bias towards similarly funded peers.