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Pollution of airborne metallic species in Seoul, Korea from 1998 to 2010
No full textA comprehensive analysis was made to characterize the long-term changes in concentration of seven key heavy metal species (iron (Fe), Copper (Cu), lead (Pb), manganese (Mn), chromium (Cr), nickel (Ni), and cadmium (Cd)) bound to total suspended particles (TSP) in Seoul, Korea, from 1998 to 2010. Their mean values over this period were: 1579 ± 652, 174 ± 54.3, 63.6 ± 8.60, 46.0 ± 15.2, 11.7 ± 9.58, 9.34 ± 8.87, and 1.78 ± 0.64 ng m−3, respectively. Most of the metals exhibited a strong seasonality with maxima in spring (Mn, Fe, and Ni), winter (Pb and Cd), or fall (Cr and Cu) but minima in summer. The most prominent reductions of 71.5% (Pb) and 91.1% (Cu) were seen from early in the study period (1999–2002) to the most recent year (2010). Despite many advances in air quality, these latest concentration values were still higher than in many Western cities. It is thus still desirable to reduce their levels even further to ensure air quality improvement in the coming years. © 2017 Elsevier B.V
Infinitely Adaptive Transition-Metal Ordering in Ln2O2MSe2-Type Oxychalcogenides
No full textA number of Ln2O2MSe2 (Ln = La and Ce; M = Fe, Zn, Mn, and Cd) compounds, built from alternating layers of fluorite-like [Ln2O2]2+ sheets and antifluorite-like [MSe2]2– sheets, have recently been reported in the literatures. The available MSe4/2 tetrahedral sites are half-occupied, and different compositions display different ordering patterns: [MSe2]2– layers contain MSe4/2 tetrahedra that are exclusively edge-sharing (stripe-like), exclusively corner-sharing (checkerboard-like), or mixtures of both. This paper reports 60 new compositions in this family. We reveal that the transition-metal arrangement can be systematically controlled by either Ln or M doping, leading to an “infinitely adaptive” structural family. We show how this is achieved in La2O2Fe1–xZnxSe2, La2O2Zn1–xMnxSe2, La2O2Mn1–xCdxSe2, Ce2O2Fe1–xZnxSe2, Ce2O2Zn1–xMnxSe2, Ce2O2Mn1–xCdxSe2, La2–yCeyO2FeSe2, La2–yCeyO2ZnSe2, La2–yCeyO2MnSe2, and La2–yCeyO2CdSe2 solid solutions. © 2015 American Chemical Societ
Neutron Laue diffraction study of the complex low-temperature magnetic behaviour of brownmillerite-type Ca2Fe2O5.
No full textThe atomic and magnetic structure of brownmillerite Ca2Fe2O5 has been refined against single-crystal neutron Laue diffraction data collected at 300, 100 and 10 K under zero-field and low-magnetic field (35 Oe = 35 × 103/4[pi] A m-1) conditions. Ca2Fe2O5 is a canted G-type antiferromagnet with Pcm'n' symmetry, the magnetic moments on Fe being directed approximately along the crystallographic c axis at room temperature. The refinement results show clearly that this magnetic structure persists down to T = 10 K, despite a previous suggestion that an anomalous magnetic susceptibility enhancement observed in Ca2Fe2O5 single crystals between 40 and 140 K might signify a reorientation of the antiferromagnetic easy axis from c to a below 40 K. Alternative explanations for this susceptibility anomaly are considered in terms of the evidence for partial or short-range loss of order in the anomalous regime, possibly due to the presence of multiple competing sublattice interactions. © International Union of Crystallograph
On the discovery of a cave lion from the Malyi Anyui River (Chukotka, Russia)
No full textAn incomplete postcranial skeleton (67 elements) of a cave lion, a lower jaw and a bundle of fine yellowish hair were found by a local resident in 2008 and 2009 washed out from the perennially frozen Pleistocene sediments in the lower reaches of the Malyi Anyui River (western Chukotka). This is the first skeleton of a cave lion (Panthera spelaea Goldfuss) to be found in Russia. The bone sizes are similar to finds of cave lion bones known from N–E Russia, but larger than East Beringian and smaller than West European ones. The remains have been studied using a variety of methods, including morphology, morphometry, SEM-examination, AMS-dating, and isotopic study, which included examination of over 100 samples of various members of the mammoth faunal assemblage (mammoth, wooly rhinoceros, bison, horse, bear, etc.). The results showed that the northeastern Asian cave lion hunted mainly bison and horses, but not reindeer, unlike its Western Europe counterpart. Bone and claw sheath dating showed an unexpectedly old geochronological age of over 61,000 years (OZQ290, OZQ291), while the hair was dated 28,690 ± 130 (OZQ292), which makes its affinity with the same individual as the skeleton questionable. Further studies to investigate possible unremoved contamination and obtain more reliable date are planned. © 2015 Elsevier Ltd. All rights reserved
On the structure-property relationships in framework materials: negative thermal expansion & lithium insertion behaviours
No full textA range of Prussian blue analogues were studied here incorporating both changes in bond strength (through variation of oxidation states) as well as more subtle changes such as those resulting from the introduction of vacancy sites. Three series of Prussian blue analogues were investigated here, FeM(CN)6, Fe3[M(CN)6]2 and M3[Co(CN)6]2, where M = two or more of Mn, Fe, Co, Ni, Cu, Zn, Cd, Ru and Ir.
In the FeM(CN)6 series, for M = Co and Ir, changing the carbon-bound metal results in variations in the magnitude of NTE, demonstrating that the strength of the M–C bond influences the magnitude of NTE. This result was supported by the behaviour of the Fe3[M(CN)6]2 series, for M = Fe and Ru, where the stronger bonds in the iron analogue result in a lesser degree of NTE.
For the M3[Co(CN)6]2 series, where M = Mn, Fe, Co, Ni, Cu, Zn and Cd, comparisons with the MPt(CN)6 series, where M = Mn, Fe, Co, Cu, Zn, and Cd, allowed for closer investigation of the vacancies in Prussian blue analogues. It was found that the introduction of vacancies introduces local disorder into these materials which impact on the bond energies in the frameworks and, consequently, the NTE.
Electrochemical investigations on FeFe(CN)6 and FeCo(CN)6 found both compounds able to reversibly insert lithium, with FeFe(CN)6 being able to incorporate three times more lithium in its structure than FeCo(CN)6. Structural studies found that FeIII is reduced in FeCo(CN)6 as lithium is inserted and the carbon-bound FeIII is being reduced in FeFe(CN)6. Powder neutron diffraction studies showed that in both cases lithium was found to prefer a site near the carbon of the cyanide when it is inserted into the framework, suggesting the carbon end of the cyanide is the most attractive force for lithium in the framework. This is a significant result to achieve as lithium sites have yet to be determined in any other Prussian blue analogues.
Finally, from investigation of the IRMOF series it was found that local distortions could be incorporated into these structures through addition of functional groups to the bridging ligands. This change in structure caused both a static disorder and a reduction of flexibility in the framework. The introduction of static disorder into these types of frameworks by the functionalisation of the ligand has not previously been observed, and while the effect is small it is still sufficient to have a noticeable effect on the NTE. This is an exciting new strategy for controlling the NTE in these compounds; with the use of more bulky functional groups potentially further perturbing the NTE properties.
The author retains copyright of this thesis. It may only be used for the purposes of research and study. It must not be used for any other purposes and may not be transmitted or shared with others without prior permission
Probing the effects of oxidative stress on biomimetic membrane interactions
No full textThis thesis studies the effects of oxidative stress on biomimetic membrane systems including their interaction with proteins relevant to oxidative stress. Two oxidation methods were used, in situ oxidation initiated using Fe(II) and ascorbate, and the incorporation of a synthetic “oxidised” phospholipid, PoxnoPC, into biomimetic membranes. The biomimetic systems employed included multi-bilayer stacks, tethered bilayers and phospholipid monolayers studied using a combination of reflectometry, attenuated total reflection infrared spectroscopy, electrochemical impedance spectroscopy, neutron diffraction and surface pressure-molecular area isotherms. Oxidation with Fe(II) and ascorbate, had a mild effect on membrane structure causing an increase in the order of the membrane, attributed to cross-linking of the phospholipids, but no significant impact on the thickness or completeness of the membrane. Incorporation of PoxnoPC, on the other hand, had a larger impact on the structure of the membrane. Inversion of the aldehyde-terminated truncated sn-2 chain of PoxnoPC into the head group region was observed, along with a slight decrease in the thickness and order of the membrane. Phospholipase A2 maintained activity on all oxidised membranes but did not show a lag phase for oxidised systems. There was, however, a decrease in the rate and extent of activity on oxidised membranes, with a larger decrease observed with the PoxnoPC incorporated membranes. Moreover, PLA2 was shown not to preferentially hydrolyse oxidised phospholipids. Plant annexin Gh1 was shown to bind strongly to membranes in a calcium dependent manner, contrary to previous reports, including penetration of the hydrophobic region. It was, however, found to bind with less affinity to oxidised membranes, with no binding to membranes containing 30 mol% PoxnoPC. There was also no evidence of protective crystalline domains. α-Synuclein also bound strongly to the head groups of the unoxidised membranes as well as penetrating into the hydrophobic region. Reduced binding was observed with the Fe(II) and ascorbate oxidised membranes as well as the 5 mol% PoxnoPC containing membranes, however, no binding was observed for the 30 mol% PoxnoPC containing membrane. ©, The Author, 2014
High temperature neutron diffraction studies of PrInO3 and the measures of perovskite structure distortion
No full textThe crystal structure of PrInO3 was investigated in the temperature range 303–1123 K by high-resolution neutron-powder diffraction. The PrInO3 adopts a highly distorted variant of the perovskite structure with the orthorhombic Pnma space group in the whole temperature range investigated. The bond length and bond-angle analysis revealed a very slow tendency to decrease structural distortion with increasing temperature. Comparison of different parameters quantifying perovskite structure distortion calculated for PrInO3 and the similar PrAlO3 and PrGaO3 shows the advantage of using the tolerance factor t12 calculated for the 12-fold coordinated Pr by geometrical averaging of the individual interatomic distances. An additional advantage of the tolerance factor method results from the possibility of extending it to predict the average structural distortion and the geometrical stability of the perovskites at various temperatures once the accurate dependence of t(x,T,d) on the composition, temperature and oxygen content is found. By comparing PrInO3 with several AMO3 perovskites containing ions in the fixed oxidation state on the A and M crystal sites it was found that structural distortion and the tolerance factor t12 for PrInO3 are consistent with the empirical thermal expansion coefficient based on the bond strength calculation [R. M. Hazen, and C. T. Prewitt, Am. Mineral., 1977, 62(3–4), 309]. In contrast to perovskites AMO3-d containing mixed-valent M ions, which allow for a wide range of changes of the tolerance factor t12(T,d) as a function of oxygen content, perovskites AMO3 with M ions in the fixed oxidation state show much less flexibility. This flexibility is further reduced for the A3+M3+O3 perovskites like PrInO3 for which even a large change of the synthesis temperature has a minor effect on controlling the resulting t12(T) and the structural phase in comparison with A2+M4+O3 perovskites. The only parameter left for A3+M3+O3 materials allowing formation of various perovskites and hexagonal phases is the total pressure, which may significantly change t12(T,P). © 2015, The Royal Society of Chemistry
Morphological and genetic identification and isotopic study of the hair of a cave lion (Panthera spelaea Goldfuss, 1810) from the Malyi Anyui River (Chukotka, Russia)
No full textWe present the first detailed analyses of the preserved hair of a cave lion (Panthera spelaea Goldfuss, 1810). The hair was found in association with a skeleton that was recovered recently from perennially frozen Pleistocene sediments in the lower reaches of the Malyi Anyui River (Chukotka, Russia). We extract mitochondrial DNA from the hair to confirm its taxonomic identity, and perform detailed morphological analyses of the color and structure of the hair using light optical microscopy and SEM. In addition, we compare the cave lion hair to hair taken from the back and mane of an African lion. We find that cave lion hair is similar but not identical to that of the present-day lion. In addition to slightly different coloration, cave lions had a very thick and dense undercoat comprising closed and compressed wavy downy hair with a medulla. In addition, while the microstructures of the medulla and cortex of cave lion hair are similar in extinct and living lions, the cuticular scales of cave lion hair are higher than those in living lions, suggesting that cave lion hair is stronger and more robust than that of living lions. We hypothesize that the differences between cave lion hair and present-day lion hair may be due to adaptations of cave lions to the harsh climatic and environmental conditions of the Pleistocene Ice Ages. © 2016, Elsevier Ltd
Palmitic acid induces central leptin resistance and impairs hepatic glucose and lipid metabolism in male mice
No full textThe consumption of diets rich in saturated fat largely contributes to the development of obesity in modern societies. A diet high in saturated fats can induce inflammation and impair leptin signaling in the hypothalamus. However, the role of saturated fatty acids on hypothalamic leptin signaling, and hepatic glucose and lipid metabolism remains largely undiscovered. In this study, we investigated the effects of intracerebroventricular (icv) administration of a saturated fatty acid, palmitic acid (PA, C16:0), on central leptin sensitivity, hypothalamic leptin signaling, inflammatory molecules and hepatic energy metabolism in C57BL/6 J male mice. We found that the icv administration of PA led to central leptin resistance, evidenced by the inhibition of central leptin's suppression of food intake. Central leptin resistance was concomitant with impaired hypothalamic leptin signaling (JAK2-STAT3, PKB/Akt-FOXO1) and a pro-inflammatory response (TNF-α, IL1-β, IL-6 and pIκBa) in the mediobasal hypothalamus and paraventricular hypothalamic nuclei. Furthermore, the pre-administration of icv PA blunted the effect of leptin-induced decreases in mRNA expression related to gluconeogenesis (G6Pase and PEPCK), glucose transportation (GLUT2) and lipogenesis (FAS and SCD1) in the liver of mice. Therefore, elevated central PA concentrations can induce pro-inflammatory responses and leptin resistance, which are associated with disorders of energy homeostasis in the liver as a result of diet-induced obesity. © 2015, Elsevier Inc
Arachidonic acid impairs hypothalamic leptin signaling and hepatic energy homeostasis in mice
No full textEpidemiological evidence suggests that the consumption of a diet high in n-6 polyunsaturated fatty acids (PUFA) is associated with the development of leptin resistance and obesity. We aim to examine the central effect of n-6 PUFA, arachidonic acid (ARA) on leptin sensitivity and leptin-regulated hepatic glucose and lipid metabolism. We found that intracerebroventricular injection of ARA (25 nmol/day) for 2.5 days reversed the effect of central leptin on hypothalamic JAK2, pSTAT3, pAkt, and pFOXO1 protein levels, which was concomitant with a pro-inflammatory response in the hypothalamus. ARA also attenuated the effect of central leptin on hepatic glucose and lipid metabolism by reversing the mRNA expression of the genes involved in gluconeogenesis (G6Pase, PEPCK), glucose transportation (GLUT2), lipogenesis (FAS, SCD1), and cholesterol synthesis (HMG-CoA reductase). These results indicate that an increased exposure to central n-6 PUFA induces central cellular leptin resistance with concomitant defective JAK2-STAT3 and PI3K-Akt signaling. © 2015, Elsevier Ireland Ltd