Investigation of Amorphous Carbon in Nanostructured Carbon Materials (A Comparative Study by TEM, XPS, Raman Spectroscopy and XRD).

Amorphous carbon (AC) is present in the bulk and on the surface of nanostructured carbon materials (NCMs) and exerts a significant effect on the physical, chemical and mechanical properties of NCMs. Thus, the determination of AC in NCMs is extremely important for controlling the properties of a wide range of materials. In this work, a comparative study of the effect of heat treatment on the structure and content of amorphous carbon in deposited AC film, nanodiamonds, carbon black and multiwalled carbon nanotube samples was carried out by TEM, XPS, XRD and Raman spectroscopy. It has been established that the use of the 7-peak model for fitting the Raman spectra makes it possible not only to isolate the contribution of the modes of amorphous carbon but also to improve the accuracy of fitting the fundamental G and D2 (D) modes and obtain a satisfactory convergence between XPS and Raman spectroscopy. The use of this model for fitting the Raman spectra of deposited AC film, ND, CB and MWCNT films demonstrated its validity and effectiveness for investigating the amorphous carbon in various carbon systems and its applicability in comparative studies of other NCMs.

Fuels, power and chemical periodicity.

The insatiable-and ever-growing-demand of both the developed and the developing countries for power continues to be met largely by the carbonaceous fuels comprising coal, and the hydrocarbons natural gas and liquid petroleum. We review the properties of the chemical elements, overlaid with trends in the periodic table, which can help explain the historical-and present-dominance of hydrocarbons as fuels for power generation. However, the continued use of hydrocarbons as fuel/power sources to meet our economic and social needs is now recognized as a major driver of dangerous global environmental changes, including climate change, acid deposition, urban smog and the release of many toxic materials. This has resulted in an unprecedented interest in and focus on alternative, renewable or sustainable energy sources. A major area of interest to emerge is in hydrogen energy as a sustainable vector for our future energy needs. In that vision, the issue of hydrogen storage is now a key challenge in support of hydrogen-fuelled transportation using fuel cells. The chemistry of hydrogen is itself beautifully diverse through a variety of different types of chemical interactions and bonds forming compounds with most other elements in the periodic table. In terms of their hydrogen storage and production properties, we outline various relationships among hydride compounds and materials of the chemical elements to provide some qualitative and quantitative insights. These encompass thermodynamic and polarizing strength properties to provide such background information. We provide an overview of the fundamental nature of hydrides particularly in relation to the key operating parameters of hydrogen gravimetric storage density and the desorption/operating temperature at which the requisite amount of hydrogen is released for use in the fuel cell. While we await the global transition to a completely renewable and sustainable future, it is also necessary to seek CO2 mitigation technologies applied to the use of fossil fuels. We review recent advances in the strategy of using hydrocarbon fossil fuels themselves as compounds for the high capacity storage and production of hydrogen without any CO2 emissions. Based on these advances, the world may end up with a hydrogen economy completely different from the one it had expected to develop; remarkably, with 'Green hydrogen' being derived directly from the hydrogen-stripping of fossil fuels. This article is part of the theme issue 'Mendeleev and the periodic table'.

Effects of carbon and silicon nanotubes and carbon nanofibers on marine microalgae Heterosigma akashiwo.

The effect of carbon and silicon nanotubes (CNTs and SiNTs) and carbon nanofibers (CNFs) to microscopic marine algae Heterosigma akashiwo was studied, using algal growth inhibition for 3 days (acute effect) and 7 days (chronic effect) as toxicity endpoints. The criterion of the toxic effect was the statistically significant reduction of the number of algal cells in the exposed samples compared to the control. Samples did not demonstrate toxic effects at doses 1 mg/l and 10 mg/l. CNTs and SiNTs samples at 100 mg/l exhibited both acute and chronic toxic effects. We assume that the main cause of cell death in these samples was related to the mechanical damage of cell integrity. CNFs at concentrations of 100 mg/l did not inhibit algal growth, but cells with irregular shapes were observed, which were not observed after exposure to CNTs and SiNTs. Nickel impurities present in CNFs samples are presumably the main cause of observed cell deformations.

Microwaves effectively examine the extent and type of coking over acid zeolite catalysts.

Coking leads to the deactivation of solid acid catalyst. This phenomenon is a ubiquitous problem in the modern petrochemical and energy transformation industries. Here, we show a method based on microwave cavity perturbation analysis for an effective examination of both the amount and the chemical composition of cokes formed over acid zeolite catalysts. The employed microwave cavity can rapidly and non-intrusively measure the catalytically coked zeolites with sample full body penetration. The overall coke amount is reflected by the obtained dielectric loss (ε″) value, where different coke compositions lead to dramatically different absorption efficiencies (ε″/cokes' wt%). The deeper-dehydrogenated coke compounds (e.g., polyaromatics) lead to an apparently higher ε″/wt% value thus can be effectively separated from lightly coked compounds. The measurement is based on the nature of coke formation during catalytic reactions, from saturated status (e.g., aliphatic) to graphitized status (e.g., polyaromatics), with more delocalized electrons obtained for enhanced Maxwell-Wagner polarization.Catalyst deactivation by coke deposition is a major drawback in industrial processes. Here, the authors show a non-intrusive microwave cavity perturbation technique as a powerful tool to determine the nature and extent of coke accumulation in industrially-relevant zeolite catalysts.

Wax: A benign hydrogen-storage material that rapidly releases H2-rich gases through microwave-assisted catalytic decomposition.

Hydrogen is often described as the fuel of the future, especially for application in hydrogen powered fuel-cell vehicles (HFCV's). However, its widespread implementation in this role has been thwarted by the lack of a lightweight, safe, on-board hydrogen storage material. Here we show that benign, readily-available hydrocarbon wax is capable of rapidly releasing large amounts of hydrogen through microwave-assisted catalytic decomposition. This discovery offers a new material and system for safe and efficient hydrogen storage and could facilitate its application in a HFCV. Importantly, hydrogen storage materials made of wax can be manufactured through completely sustainable processes utilizing biomass or other renewable feedstocks.

Contrasting the grain boundary-affected performance of zinc and indium oxide transparent conductors.

Zinc oxide-based transparent conductors have long been advanced for their potential as low-cost, earth-abundant replacements for the indium oxide-based materials that currently dominate in practical applications. However, this potential has yet to be realized because of the difficulties in producing zinc oxide thin films with the necessary high levels of electrical conductivity and environmental stability that are readily achieved using indium oxide. To better understand the fundamental reasons for this, polycrystalline zinc and indium oxide thin films were prepared across a range of deposition temperatures using the technique of spray pyrolysis. Electrical transport measurements of these samples both as a function of temperature and UV irradiation were correlated with film morphology to illustrate that the different grain boundary behaviour of these two materials is one of the key reasons for their divergent performance. This is a critical challenge that must be addressed before any substantial increase in the adoption of ZnO-based transparent conductors can take place.

The impact of multi-walled carbon nanotubes with different amount of metallic impurities on immunometabolic parameters in healthy volunteers.

The impact of two types of multi-walled carbon nanotubes (MWCNTs) (12-14 nm) with different content of metallic impurities (purified and unpurified nanotubes) on peroxidation processes, the status of immune cells in healthy volunteers and gene expression combined to pathway analysis was studied in vitro. From the study it was shown that the main mechanism of action for both types of MWCNTs is induction of oxidative stress, the intensity of which is directly related to the amount of metallic impurities. Unpurified MWCNTs produced twice as high levels of oxidation than the purified CNTs inducing thus more intense mitochondrial dysfunction. All the above were also verified by gene expression analysis of 2 different human cellular cultures (lung epithelium and keratinoma cells) and the respective pathway analysis; modulation of genes activating the NFkB pathway is associated to inflammatory responses. This may cause a perturbation in the IL-6 signaling pathway in order to regulate inflammatory processes and compensate for apoptotic changes. A plausible hypothesis for the immunological effects observed in vivo, are considered as the result of the synergistic effect of systemic (mediated by cells of the routes of exposure) and local inflammation (blood cells).

Multi-walled carbon nanotubes increase anxiety levels in rats and reduce exploratory activity in the open field test.

The results of the first study on the effects of multi-walled carbon nanotubes (MWNTs) on the exploratory activity and the emotional state in laboratory rats assessed by the open field test are reported. During three or ten days, rats received 8-10 nm MWNTs added to their food at a dose of 500 mg/kg. It was demonstrated that, in the group of rats which were fed with MWNTs, the integrated anxiety level index began to increase as early as the third day of the experiment; on the tenth day, it appeared to be twice increased. It was also demonstrated that MWNTs decreased the integrated exploratory activity index nearly twofold on the third day and nearly fourfold on the tenth day.

Catalytic dehydrogenation of propane by carbon dioxide: a medium-temperature thermochemical process for carbon dioxide utilisation.

The dehydrogenation of C3H8 in the presence of CO2 is an attractive catalytic route for C3H6 production. In studying the various possibilities to utilise CO2 to convert hydrocarbons using the sustainable energy source of solar thermal energy, thermodynamic calculations were carried out for the dehydrogenation of C3H8 using CO2for the process operating in the temperature range of 300-500 °C. Importantly, the results highlight the enhanced potential of C3H8 as compared to its lighter and heavier homologues (C2H6 and C4H10, respectively). To be utilised in this CO2 utilisation reaction the Gibbs free energy (ΔrGθm) of each reaction in the modelled, complete reacting system of the dehydrogenation of C3H8 in the presence of CO2 also indicate that further cracking of C3H6 will affect the ultimate yield and selectivity of the final products. In a parallel experimental study, catalytic tests of the dehydrogenation of C3H8 in the presence of CO2 over 5 wt%-Cr2O3/ZrO2 catalysts operating at 500 °C, atmospheric pressure, and for various C3H8 partial pressures and various overall GHSV (Gas Hourly Space Velocity) values. The results showed that an increase in the C3H8 partial pressure produced an inhibition of C3H8 conversion but, importantly, a promising enhancement of C3H6 selectivity. This phenomenon can be attributed to competitive adsorption on the catalyst between the generated C3H6 and inactivated C3H8, which inhibits any further cracking effect on C3H6 to produce by-products. As a comparison, the increase of the overall GHSV can also decrease the C3H8 conversion to a similar extent, but the further cracking of C3H6 cannot be limited.

[Use of diagnostic nanosecond X-ray pulse apparatuses].

OBJECTIVE: The study the specific features of using diagnostic nanosecond X-ray pulse apparatuses versus X-ray diagnostic apparatuses using direct current X-ray tubes. MATERIAL AND METHODS: Dosimetric tests of ARDP-01 and Yasen-01 X-ray pulse apparatuses versus RUM2O and Siemens Axiom Iconos R200 apparatuses using direct current X-ray tubes were carried out. RESULTS: The tests established that the patient radiation dose by a Yasen-01 apparatus is 2.5-3 times lower than that by a Siemens Axiom Iconos R200 apparatus. The radiation dose by an ARDP-01 apparatus was 10-20 times lower than that by a RUM20 apparatus when using film radiation detectors. CONCLUSION: The performed investigations demonstrate a manifold reduction in the lower X-ray radiation with the use of nanosecond X-ray pulse apparatuses as compared to the continuous radiation. Without changing the characteristics of a radiation detector, the dose can be further reduced by increasing the amplitude and decreasing the duration of the pulse of X-ray tube current, and raising the pulse ratio.

[Recombinant strain producing thermostable lipase from Thermomyces lanuginosus immobilized into nanocarbon silica matrices and properties of the prepared biocatalyzers].

Multicomponent composite biocatalyzers with lipolytic activity have been studied. These biocatalyzers were prepared through the immobilization of a recombinant producer strain of thermostable lipase from Thermomyces lanuginosus into SiO2 xerogel, which contains a nanocarbon component, i.e., multilayered carbon nanotubes with varying diameters, and also bulblike structured carbon nanospheres ("nanobulb"). The properties of lipase were studied both in cell suspensions of a recombinant producer strain constructed based on E. coli BL21(DE3) and in the immobilized state with regard to the structure and dispersibility of the nanocarbon component used in the composition of the biocatalyzers. It was shown that the recombinant intracellular lipase exerted its activity in a reaction of tributirin hydrolysis on average comprising 50 U/mg of dried cells and had a high level of thermostability. Upon heating in olive oil at 100 degrees C, the inactivation constant and the period of semi-inactivation comprised 6 x 10(-3) min(-1) and 2 h, respectively, exceeding by one order the thermostability of lipase in a buffer solution. Biocatalyzers that contained aggregated "thick" nanotubes with a diameter of 20-22 nm had the maximum initial activity-250 U/g.

Turning carbon dioxide into fuel.

Our present dependence on fossil fuels means that, as our demand for energy inevitably increases, so do emissions of greenhouse gases, most notably carbon dioxide (CO2). To avoid the obvious consequences on climate change, the concentration of such greenhouse gases in the atmosphere must be stabilized. But, as populations grow and economies develop, future demands now ensure that energy will be one of the defining issues of this century. This unique set of (coupled) challenges also means that science and engineering have a unique opportunity-and a burgeoning challenge-to apply their understanding to provide sustainable energy solutions. Integrated carbon capture and subsequent sequestration is generally advanced as the most promising option to tackle greenhouse gases in the short to medium term. Here, we provide a brief overview of an alternative mid- to long-term option, namely, the capture and conversion of CO2, to produce sustainable, synthetic hydrocarbon or carbonaceous fuels, most notably for transportation purposes. Basically, the approach centres on the concept of the large-scale re-use of CO2 released by human activity to produce synthetic fuels, and how this challenging approach could assume an important role in tackling the issue of global CO2 emissions. We highlight three possible strategies involving CO2 conversion by physico-chemical approaches: sustainable (or renewable) synthetic methanol, syngas production derived from flue gases from coal-, gas- or oil-fired electric power stations, and photochemical production of synthetic fuels. The use of CO2 to synthesize commodity chemicals is covered elsewhere (Arakawa et al. 2001 Chem. Rev. 101, 953-996); this review is focused on the possibilities for the conversion of CO2 to fuels. Although these three prototypical areas differ in their ultimate applications, the underpinning thermodynamic considerations centre on the conversion-and hence the utilization-of CO2. Here, we hope to illustrate that advances in the science and engineering of materials are critical for these new energy technologies, and specific examples are given for all three examples. With sufficient advances, and institutional and political support, such scientific and technological innovations could help to regulate/stabilize the CO2 levels in the atmosphere and thereby extend the use of fossil-fuel-derived feedstocks.

Functional materials for sustainable energy technologies: four case studies.

The critical topic of energy and the environment has rarely had such a high profile, nor have the associated materials challenges been more exciting. The subject of functional materials for sustainable energy technologies is demanding and recognized as a top priority in providing many of the key underpinning technological solutions for a sustainable energy future. Energy generation, consumption, storage, and supply security will continue to be major drivers for this subject. There exists, in particular, an urgent need for new functional materials for next-generation energy conversion and storage systems. Many limitations on the performances and costs of these systems are mainly due to the materials' intrinsic performance. We highlight four areas of activity where functional materials are already a significant element of world-wide research efforts. These four areas are transparent conducting oxides, solar energy materials for converting solar radiation into electricity and chemical fuels, materials for thermoelectric energy conversion, and hydrogen storage materials. We outline recent advances in the development of these classes of energy materials, major factors limiting their intrinsic functional performance, and potential ways to overcome these limitations.

Hydrogen energy.

The problem of anthropogenically driven climate change and its inextricable link to our global society's present and future energy needs are arguably the greatest challenge facing our planet. Hydrogen is now widely regarded as one key element of a potential energy solution for the twenty-first century, capable of assisting in issues of environmental emissions, sustainability and energy security. Hydrogen has the potential to provide for energy in transportation, distributed heat and power generation and energy storage systems with little or no impact on the environment, both locally and globally. However, any transition from a carbon-based (fossil fuel) energy system to a hydrogen-based economy involves significant scientific, technological and socio-economic barriers. This brief report aims to outline the basis of the growing worldwide interest in hydrogen energy and examines some of the important issues relating to the future development of hydrogen as an energy vector.

[Mathematical model of the digestion process regulation and its computer presentation]. / Matematicheskaia model' reguliatsii protsessa pishchevareniia i ee komp'iuternaia realizatsiia.

The article presents a mathematic model, which describes regulation of the digestion process. The simulation was based on data on mutual influence of the factors participating in digestion regulation, which were acquired from analysis of over 1200 sources of experimental observations on digestion in dogs published in Russia and abroad, and on own experimental studies. The simulation includes 67 factors and about 400 interactions observed between them. The computer implementation of this simulation demonstrated descriptive coincidence of patterns of the variables respective to the factors of the model with experimental research data; the coincidence was observed in individual patterns and in combined patterns, as well as in coordinated responses in time.

[Analysis of antibacterial activity of a new antiseptic for therapy of maxillofacial inflammations]. / Analiz antibakterial'noi aktivnosti novogo antisepticheskogo sredstva dlia terapii vospalitel'nykh zabolevanii cheliustno-litsevoi oblasti.

Clinical and experimental studies of polydimethyldiallylammonium chloride (PDMDAAC) experimentally validated the choice of optimal concentration and composition of this agent. The results indicate a high antiseptic activity of 1% PDMDAAC and the possibility of using it in local therapy of periodontitis and posttraumatic infection.

45Ca exchange in rat cortex slices in conditions of long-term potentiation.

Existing data on the role of Ca2+ ions in the development of long-term potentiation were used as a basis for studying changes in different Ca2+ compartments in cells in living rat olfactory cortex slices during potentiation. The kinetics of 45Ca2+ exchange were studied at 5, 15, and 30 min of potentiation. During the induction phase (1-5 min) of long-term potentiation, the fraction of tightly-bound intracellular Ca2+ decreased. There were no changes in the content of Ca2+ ions in other fractions at this stage. During maintenance of potentiation, which lasted 15-25 min, Ca2+ levels in the extracellular and intracellular compartments did not differ from controls. At 30 min, during extinction of long-term potentiation, there was a significant redistribution of Ca2+ in cells: the levels of free and loosely-bound Ca increased, as did extracellular Ca2+.

[45Ca metabolism in slices of rat cerebral cortex during long-term potentiation]. / Obmen 45Ca v srezakh kory mozga krys v usloviiakh dolgovremennoi potentsiatsii.

Ca45 kinetics was studied in 5, 15 and 30 min after potentiation. In the induction phase (1-5 min), the potentiation decreased the fraction of intracellular bound Ca. The 15-25 min potentiation the intra- and extracellular Ca levels was equal to the control ones. In 30 min, a considerable redistribution of Ca in the cells occurred.

[Glucose and galactose absorption in the small intestine of rats in vivo]. / Vsasyvanie gliukozy i galaktozy v tonkoi kishke krys in vivo.

In mathematical models, competition between glucose and galactose in the course of their active transport across the apical membrane of the erythrocytes, was studied. Both substances seem to share the same means of transmembrane transport, although the affinity of glucose in 6-fold higher.