Browsing by Subject "Lithium"
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Item Open Access High-capacity hydrogen storage by metallized graphene(AIP Publishing, 2008) Ataca, C.; Aktürk, E.; Çıracı, Salim; Ustunel H.First-principles plane wave calculations predict that Li can be adsorbed on graphene forming a uniform and stable coverage on both sides. A significant part of the electronic charge of the Li 2s orbital is donated to graphene and is accommodated by its distorted π* -bands. As a result, semimetallic graphene and semiconducting graphene ribbons change into good metals. It is even more remarkable that Li covered graphene can serve as a high-capacity hydrogen storage medium with each adsorbed Li absorbing up to four H2 molecules amounting to a gravimetric density of 12.8 wt %.Item Open Access Identification of RNA-based biomarkers associated with manic episodes and lithium response in bipolar disorder(Bilkent University, 2022-12) Niaz, NoorBipolar disorder (BD) is one of the major mood disorders. A person afflicted with this neuropsychiatric disease undergoes episodes of depression and mania. BD ranks as the highest amongst all the mood disorders for having the most negative affect on a person's life. It is a lifelong illness, which requires constant monitoring and medication. From psychotic behaviours to suicide ideation, this disease is a burden on the afflicted and their families. Although, BD has been shown to have a high heritability factor, none of the studies done so far have been able to identify any biomarkers that could be causative for this disease. It is due to the fact that this disease is multifactorial, in which environment is a major contributing factor. Therefore, we believe that a more 'pattern-seeking' approach would lead to novel findings. We performed gene-set enrichment analysis (GSEA) with BD datasets that consisted of 3 different biological phenotypes; euthymic BD, manic BD and lithium treated BD samples. Since a long time, lithium has been used as 'the leading' drug to treat BD because it functions as a mood stabilizer. Therefore, we also included BD cohorts that had undergone lithium treatment in our analysis. As a result of GSEA, we were able to discover 2 novel patterns. In pattern 1, specific genes were found to up-regulated in euthymic BD and lithium treated cohorts, while the same genes were down-regulated in manic BD cohorts. In pattern 2, the opposite trend was observed, that is; another list of specific genes was down-regulated in euthymic BD and lithium treated cohorts, while they were found to be up-regulated in manic BD. The novelty of utilizing GSEA in our analysis was in the fact that we created our own custom gene-sets. The gene-sets were formed after performing differential gene expression (DEG) analysis on all the 3 types of BD datasets. The advantage of using custom gene-sets was that these were genes representing differential expression in different BD phenotypes, therefore, they were biologically relevant to BD. In the publically available curation of gene-sets on various databases, very few gene-sets represent BD. Hence, the custom gene-sets are more relevant and specific to the disease. Then we proceeded to extract core-enriched genes and performed further analysis, such as, plotting fold-change graphs and performing non-parametric tests. In light of these results, we propose putative biomarkers associated with manic episodes and lithium response in bipolar disorder. We put forth the hypothesis that these patterns can diagnose BD accurately, indicate if a patient is responding to lithium or not, and predict an oncoming manic episode. Therefore, we propose the genes adhering to the discovery patterns as putative biomarkers. Simultaneously, we performed biological analyses and literature review with the list of putative biomarkers. We found out inflammation as a potential underlying cause of pathogenicity in BD. We hypothesize that the process of inflammation is disrupted in BD patients, especially between the different mood states and that in order to treat this disease, inflammation as a pathway should also be targeted. We highlight TNFa as one of the main cytokines that 3 of our biomarkers; ADAMTS9, IL-1 B and STCJ are associated through various pathways, and this disruption of the inflammatory pathway may occur due to alteration in TNFa and biomarkers' levels. We hope that after further, subsequent research, the inclusion of our biomarkers in the clinics will help with the issue of BD misdiagnosis, help save precious treatment time, help with the choice of medication, and help indicate a patient's mood state. Overall, it will help the clinicians to tailor the treatment to every patient's specific profile, making the it easier to design a more personalized treatment strategy.Item Open Access Lithium-mediated downregulation of PKB/Akt and cyclin E with growth inhibition in hepatocellular carcinoma cells(Wiley-Liss, Inc, 2005) Erdal, E.; Ozturk, N.; Cagatay, T.; Eksioglu-Demiralp, E.; Ozturk, M.We studied in vitro effects of glycogen synthase kinase 3β (GSK3β)-inhibitor lithium on the growth of hepatocellular carcinoma (HCC) cells. Lithium induced strong growth inhibition (>70%) in 75% (n = 9 of 12) of cell lines, apparently independent from the status of major genes that are mutated in HCC including p53, p16INK4a, β-catenin and Axin1. Comparative studies with a growth-sensitive Huh7 and growth-resistant Hep40 cell lines showed that lithium induces growth arrest in Huh7 cells but not in Hep40 cells. Lithium induced the accumulation of N-terminally phosphorylated inactive form of GSK3β with concomitant increase in β-catenin and β-catenin/TCF transcriptional activity in both cell lines. This suggests that lithium-mediated HCC growth inhibition is independent of its well-known stimulatory effect on Wnt-β-catenin signaling. The main differences between Huh7 and Hep40 responses to lithium treatment were observed at the levels PKB/Akt and cyclin E proteins. Lithium induced depletion of both proteins in growth-sensitive Huh7, but not in growth-resistant Hep40 cells. PKB/Akt and Cyclin E are 2 major proteins that are known to be constitutively active in HCC. The targeting of both proteins with lithium may be the main reason why most HCC cells are responsive to lithium-mediated growth inhibition, independent of their p53, retinoblastoma and Wnt-β-catenin pathways. The exploration of molecular mechanisms involved in lithium-mediated growth inhibition in relation with PKB/Akt and cyclin E downregulation may provide new insights for therapy of liver tumors. © 2005 Wiley-Liss, Inc.Item Open Access Lyotropic liquid crystalline mesophases of lithium dihydrogen phosphate and 10-lauryl ether stabilized with water or phosphoric acid(Wiley, 2023-01) Topuzlu, Ezgi Yılmaz; Ulgut, Burak; Dağ, ÖmerItem Open Access Lyotropic liquid-crystalline mesophase of lithium triflate-nonionic surfactant as gel electrolyte for graphene optical modulator(American Chemical Society, 2023) Balci, F. M.; Balci, S.; Kocabas, C.; Dag, Ö.Lithium salt (noncoordinating anions, such as lithium triflate (Ltf)) gel electrolytes may be key for the practical use of electrochemical devices. We introduce a new lyotropic liquid-crystalline (LLC) mesophase using Ltf, a small amount of water (as low as 1.3 water per Ltf), and nonionic surfactant (C18H37(OCH2CH2)10OH, C18E10). The LLC phase forms over a broad range of Ltf/C18E10 mole ratios, 2-18. The clear ethanol solution of the ingredients can be either directly spin-coated over a glass substrate to form a gel phase or it can be prepared as a gel by mixing Ltf, water, and C18E10. The mesophase leaches out surfactant molecules at low salt concentrations, but at a salt/surfactant mole ratio of above 8, the phase is homogeneous with a cubic mesostructure, fully transparent in the visible optical region, mechanically flexible, and an effective gel electrolyte. We have observed a large electrostatic doping on graphene with the Fermi energy level of ∼1.0 eV using Ltf-C18E10 gel electrolytes. The Ltf-based gels demonstrate better properties than commonly used ionic liquid electrolyte in graphene optical modulators. The stability of the new gel electrolytes and their superior performance make them suitable electrolytes for use in graphene-based optical modulators.Item Open Access Mo2C as a high capacity anode material: a first-principles study(Royal Society of Chemistry, 2016) Çakir, D.; Sevik, C.; Gülseren, O.; Peeters, F. M.The adsorption and diffusion of Li, Na, K and Ca atoms on a Mo2C monolayer are systematically investigated by using first principles methods. We found that the considered metal atoms are strongly bound to the Mo2C monolayer. However, the adsorption energies of these alkali and earth alkali elements decrease as the coverage increases due to the enhanced repulsion between the metal ions. We predict a significant charge transfer from the ad-atoms to the Mo2C monolayer, which indicates clearly the cationic state of the metal atoms. The metallic character of both pristine and doped Mo2C ensures a good electronic conduction that is essential for an optimal anode material. Low migration energy barriers are predicted as small as 43 meV for Li, 19 meV for Na and 15 meV for K, which result in the very fast diffusion of these atoms on Mo2C. For Mo2C, we found a storage capacity larger than 400 mA h g-1 by the inclusion of multilayer adsorption. Mo2C expands slightly upon deposition of Li and Na even at high concentrations, which ensures the good cyclic stability of the atomic layer. The calculated average voltage of 0.68 V for Li and 0.30 V for Na ions makes Mo2C attractive for low charging voltage applications.Item Open Access A new, highly conductive, lithium salt/nonionic surfactant, lyotropic liquid-crystalline mesophase and its application(Wiley-VCH Verlag, 2012) Albayrak, C.; Cihaner, A.; Dag, Ö.Salty water! Lithium salts (LiCl, LiNO3, and LiClO4) at very high concentrations in water form lyotropic liquid crystalline (LLC) mesophases with a nonionic surfactant (10-lauryl ether) and display high ionic conductivities (10−2–10−4 S cm−1) over a broad temperature range (−10 to 80 °C) with excellent behavior as gel electrolytes in electrochemical applications.Item Open Access Synthesis of mesoporous lithium titanate thin films and monoliths as an anode material for high-rate lithium-ion batteries(Wiley-VCH Verlag, 2016) Balcı, F. M.; Kudu, Ö. U.; Yılmaz, E.; Dag, Ö.Mesoporous Li4Ti5O12 (LTO) thin film is an important anode material for lithium-ion batteries (LIBs). Mesoporous films could be prepared by self-assembly processes. A molten-salt-assisted self-assembly (MASA) process is used to prepare mesoporous thin films of LTOs. Clear solutions of CTAB, P123, LiNO3, HNO3, and Ti(OC4H9)4 in ethanol form gel-like meso-ordered films upon either spin or spray coating. In the assembly process, the CTAB/P123 molar ratio of 14 is required to accommodate enough salt species in the mesophase, in which the LiI/P123 ratio can be varied between molar ratios of 28 and 72. Calcination of the meso-ordered films produces transparent mesoporous spinel LTO films that are abbreviated as Cxx-yyy-zzz or CAxx-yyy-zzz (C=calcined, CA=calcined–annealed, xx=LiI/P123 molar ratio, and yyy=calcination and zzz=annealing temperatures in Celsius) herein. All samples were characterized by using XRD, TEM, N2-sorption, and Raman techniques and it was found that, at all compositions, the LTO spinel phase formed with or without an anatase phase as an impurity. Electrochemical characterization of the films shows excellent performance at different current rates. The CA40-350-450 sample performs best among all samples tested, yielding an average discharge capacity of (176±1) mA h g−1 at C/2 and (139±4) mA h g−1 at 50 C and keeping 92 % of its initial discharge capacity upon 50 cycles at C/2.Item Open Access TL/OSL studies of Li2B4O7:Cu dosimetric phosphors(2013) Aydin, T.; Demirtaş H.; Aydin, S.Dosimetric phosphors of Cu-doped lithium tetraborate (Li2B 4O7:Cu) were produced using a sintering technique in a laboratory environment and characterized using Scanning Electron Microscopy (SEM) and X-ray Diffractometry (XRD). The thermoluminescence (TL) and optically stimulated luminescence (OSL) properties of powdered (Li2B 4O7) phosphor doped with copper at different concentrations (0.020-0.025 wt %) were studied. The Cu-doped Li 2B4O7 phosphor material has two dominant TL glow peaks, and the maximum TL responses of the peaks are at 115 C and 243 C in the range of 0 C-310 C. The TL response of the Cu-doped lithium tetraborate is approximately 900 times more sensitive than undoped lithium tetraborate. The TL and OSL signal intensities increase as the beta radiation doses increase up to approximately 150.00 Gy and 76.50 Gy, respectively. The OSL dose-response curve is linear up to a dose range of 12.00 Gy for Cu-doped Li2B 4O7 dosimetric phosphors. The time-dependent fading behavior of the Cu-doped lithium tetraborate was found to be quite stable over long time durations. In addition, the repeatability of the OSL dose measurements were determined to be 2/3 lower compared to the TL measurements. The reproducibility of the OSL measurements was approximately 5%. Based on the TL and OSL results, the prepared phosphors can be used to measure beta doses ranging from 10 μGy to 150.00 Gy and 76.50 Gy, respectively, by using the TL and OSL techniques, with confidence limits of approximately 7% and 3-4%, respectively. © 2013 Elsevier Ltd. All rights reserved.