ABSTRACT
The transformation of olivine during the conversion of CO2 to light hydrocarbons activated by mechanochemical treatments at different impact frequencies was studied by a combination of several complementary characterization methods including X-ray diffraction, Raman and 57Fe Mössbauer spectroscopy. Several olivine samples were studied as a function of the milling time, indicating the gradual transformation of FeII-containing olivine into new FeIII-containing weathering products including iron oxides, magnesium iron carbonates and silicates. The results presented here complement those of a previous study on the weathering process of olivine promoted by mechanochemical activation, by demonstrating the role of the redox activity of the iron species during the activation process. These additional spectroscopic results allow us to thoroughly understand the complex weathering mechanism and to correlate it with the efficiency of the CO2 conversion and storage properties of mechanochemically activated olivine. Supplementary Information: The online version contains supplementary material available at 10.1007/s10853-022-06962-x.
ABSTRACT
Due to the considerable interest in vanadium niobium oxides as a lithium storage material, the kinetics and transformation processes of the V2O5-5Nb2O5 system have been investigated by in situ synchrotron powder X-ray diffraction. The diffraction data after the thermal treatments selected with a view on the most significant features were supplemented with specific ex situ experiments conducted using a laboratory rotating anode X-ray diffractometer. The morphological changes of the mixed powders assuming an amorphous and nanocrystalline solid solution structure as a function of the temperature were inspected by scanning electron microscopy observations. The structural solution of the powder diffraction pattern of the phase recorded in situ at a temperature of about 700 °C was compatible with an orthorhombic crystal structure with the space group Amm2. The obtained lattice parameters for this structure were a = 3.965 Å; b = 17.395 Å, c = 17.742 Å, and the cell composition was V4Nb20O60, Pearson symbol oA84, and density = 4.10 g cm-3. In this structure, while the niobium atoms may be four-, five-, and six-fold coordinated by oxygen atoms, the vanadium atoms were six-fold or seven-fold coordinated. At the temperature of 800 °C and just above, the selected 1 : 2 and 1 : 3 V2O5-Nb2O5 compositions, respectively, returned mostly a tetragonal VNb9O25 phase, in line with earlier observations conducted for determination of the stability phase diagram of such quasi-binary systems.
ABSTRACT
The effects of ball milling treatment on both the structure and properties of guar gum (GG), tara gum (TG), and methylcellulose (MC) were analyzed prior to assessing their potential interactions with starch components when they are used alone or in blends in a corn starch-rice flour system. X-ray diffraction profiles showed that the ball milling caused a reduction in the crystallin domain and, in turn, a diminished viscosity of the GG aqueous solutions. Despite an increase in its viscosity properties, effects on TG were minimal, while the milled MC exhibited reduced crystallinity, but similar viscosity. When both milled and un-milled hydrocolloids were individually added to the starch-flour system, the pasting properties of the resulting mixtures seemed to be affected by the type of hydrocolloid added rather than the structural changes induced by the treatment. All hydrocolloids increased the peak viscosity of the binary blends (especially pure GG), but only milled and un-milled MC showed values of setback and final viscosity similar to those of the individual starch. Ball milling seemed to be more effective when two combined hydrocolloids (milled GG and MC) were simultaneously used. No significant differences were observed in the viscoelastic properties of the blends, except for un-milled GG/starch, milled TG/starch, and milled MC/milled TG/starch gels.
ABSTRACT
INTRODUCTION: There has been a growing interest in addressing the surgical disease burden in low- and middle-income countries (LMICs). Assessing the current state of global surgery research activity is an important step in identifying gaps in knowledge and directing research efforts towards important unaddressed issues. The aim of this bibliometric analysis was to identify trends in the publication of global surgical research over the last 30 years. METHODS: Scopus® was searched for global surgical publications (1987-2017). Results were hand-screened, and data were collected for included articles. Bibliometric data were extracted from Scopus® and Journal Citation Reports. Country-level economic and population data were obtained from the World Bank. Descriptive statistics were used to summarise data and identify significant trends. RESULTS: A total of 1623 articles were identified. The volume of scientific production on global surgery increased from 14 publications in 1987 to 149 in 2017. Similarly, the number of articles published open access increased from four in 1987 to 68 in 2017. Observational studies accounted for 88.7% of the included studies. The three most common specialties were obstetrics and gynaecology 260 (16.0%), general surgery 256 (15.8%), and paediatric surgery 196 (12.1%). Over two times as many authors were affiliated to an LMIC institution than to a high-income country (HIC) institution (6628, 71.5% vs 2481, 28.5%, P < 0.001). A total of 965 studies (59.5%) were conducted entirely by LMIC authors, and 534 (32.9%) by collaborations between HICs and LMICs. CONCLUSION: The quantity of research in global surgery has substantially increased over the past 30 years. Authors from LMICs seemed the most proactive in addressing the global surgical disease burden. Increasing the funding for interventional studies, and therefore the quality of evidence in surgery, has the potential for greater impact for patients in LMICs.
