Microbes exert extensive control on redox element cycles. They participate directly orindirectly in the concentration and fractionation of elements by influencing the partitioningbetween soluble and insoluble species. Putative microbially mediated manganese (Mn) oxidesof the birnessite-type, enriched in rare earth elements (REE) + yttrium (Y) were recentlyfound in the Ytterby mine, Sweden. A poorly crystalline birnessite-type phyllomanganate isregarded as the predominant initial phase formed during microbial Mn oxidation. Owing to ahigher specific surface area, this biomineral also enhances the known sorption property of Mnoxides with respect to heavy metals (e.g. REE) and therefore has considerable environmentalimpact.The concentration of REE + Y (2±0.5% of total mass, excluding oxygen, carbon and silicon)in the Ytterby Mn oxide deposit is among the highest ever observed in secondary precipitateswith Mn and/or iron. Sequential extraction provides evidence of a mineral structure where theREE+Y are firmly included, even at pH as low as 1.5. Concentration ratios of Mn oxideprecipitates to fracture water indicate a strong preference for the trivalent REE+Y overdivalent and monovalent metals. A culture independent molecular phylogenetic approach wasadopted as a first step to analyze the processes that microbes mediate in this environment andspecifically how the microbial communities interact with the Mn oxides. Plausible players inthe formation of the investigated birnessite-type Mn oxides are mainly found within theferromanganese genera Hyphomicrobium and Pedomicrobium and a newly identified YtterbyBacteroidetes cluster most closely related to the Terrimonas. Data also indicate that thedetected microorganisms are related to the environmental constraints of the site including lowconstant temperature (8°C), absence of light, high metal content and possibly proximity to theformer storage of petroleum products.

No description available.

Nasopharyngeal Carcinoma (NPC) as a typical malignancy that occurs in high-incidence areas, e.g. southern China region, including Hong Kong, and it has aroused wide interests for local researchers to study. The Epstein-Barr virus (EBV) was reported as a vital herpes virus for the growth of NPC. Two significant proteins in EBV, namely Epstein-Barr Nuclear Antigen 1 (EBNA1) and latent infection membrane protein 1 (LMP1) are crucial for virus maintenance and EBV-infected cell development, and essential for cell proliferation and differentiation of EBV latent life cycle, respectively. Thus, inhibition of EBNA1 and LMP1 can be regarded as effective and potent therapy on EBV-associated cancers. In this thesis, the conjugation of core-shell structured upconversion nanoparticles (UCNPs) with distinct EBV-specific peptides including EBNA1 and LMP1 targeting peptides to achieve both impressive inhibition on EBV-positive cancers in vitro/in vivo and visualization on EBV-positive cells with responsive upconversion emission signals were investigated. Taking advantage of lanthanide-based UCNPs, their unique photophysical properties offer deep tissue penetration depth, negligible photobleaching and photocytotoxicity, and therefore provides a solid foundation for convincible theranostic studies. Furthermore, desired inhibitory performance was achieved, it was shown that ~50 mg/mL of nanoprobes can inhibit half of EBV-infected cell viability and only 0.25 mg/tumor of nanoprobes dosage via intravenous injection can prohibit 64.7% of growth inhibition of an EBV-positive tumor

During the past decade, lanthanide doped alkali metal rare earth fluorides have been intensively studied due to their unique properties. Also, nanoparticles of these materials have gained much importance because NaYF4, NaGdF4, NaLuF4 and LiYF4 nanocrystals doped with Yb/Er or Yb/Tm display efficient upconversion emission. The synthesis of NaREF4 nanocrystals (RE = rare earths) has therefore attracted many researchers worldwide. While a large number of procedures is already available for the synthesis of NaREF4 particles of the heavier rare earth ions and for NaYF4, only a very limited number of methods exists for nanocrystals of the lighter rare earth ions, RE = La, Ce, Pr and Nd. In this work, a synthesis method was therefore developed to produce monodisperse sub-10 nm sodium rare earth fluoride nanocrystals of the lighter rare earths, NaREF4 (RE = La, Ce, Pr and Nd) from single-source precursors. Based on this method, the Ostwald ripening, the size focusing and the stability of these nanocrystals were studied; also, the versatility of the method was demonstrated by developing doped nanocrystals of these particles. The procedures developed in this thesis not only allow to prepare the hexagonal β-phase of these materials but also the meta-stable cubic α-phase. The latter is found to be very sensitive to decomposition. This decomposition affects also the synthesis of NaREF4 particles of the hexagonal β-phase where particles of the cubic α-phase form an intermediate product. This thesis also shows that highly sodium deficient α-NaYF4 nanocrystals with a size of less than 10 nm can be prepared which contain much less sodium than the bulk material. These nanocrystals were used as precursor to produce monodisperse sub-10 nm lithium rare earth fluoride (LiREF4, RE = Y, Gd, Lu) nanocrystals. Using this new approach also LiYF4:Yb,Er/LiYF4 core/shell upconversion nanocrystals were prepared, displaying a 35 times enhancement in luminescence intensity compared to the corresponding core particles. Further, this approach provided new insights on intermediate phases formed during the synthesis. Our studies confirmed, for instance, that LiREF4 nanocrystals were formed through an ‘available intermediate phase’, that is, a phase having a composition which is determined by the available cations in the reaction mixture.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第18983号 / 工博第4025号 / 新制||工||1620(附属図書館) / 31934 / 京都大学大学院工学研究科材料工学専攻 / (主査)教授 田中 功, 教授 宇田 哲也, 教授 白井 泰治 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第20389号 / 工博第4326号 / 新制||工||1670(附属図書館) / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 江口 浩一, 教授 陰山 洋, 教授 阿部 竜 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

No description available.

Neutron-rich rare-earth nuclei around the maximum of collectivity are predicted to exist with an extremely stable intrinsic configuration in their ground-state structure. Due to the high degree of axial symmetry and large deformation, these nuclei are also excellent candidates for having long-lived high-K isomers. The present work concerns a study of the structure of the yrast bands and a search for isomers in the neutron-rich 68Er isotopes. Excited states of 68Er isotopes were populated via multi-nucleon transfer reactions. A 859 MeV 136Xe-beam was used to bombard a 170Er-target. The experimental setup consisted of the high-resolution γ-ray spectrometer AGATA coupled to the heavy-ion magnetic spectrometer PRISMA. The experiment collected 2 TB of useful data corresponding to 3 days of effective beam time. Beam-like fragments were identified by the PRISMA specrometer placed at the grazing angle of 44 degrees. PRISMA allows for Z, A and q identification as well as TOF and velocity vector determination. This is required for the Doppler correction of the emitted γ rays detected in time coincidence with AGATA. A good Z and very clean A separation has been achieved in PRISMA. Making use of two-body kinematics, Doppler corrected γ-ray spectra for target-like fragments were obtained as well. Due to the novel techniques of PSA and γ-ray tracking, AGATA provided high-quality γ-ray spectra for both beam-like xenon and target-like erbium isotopes. Known yrast bands and isomeric states in neutron-rich erbium isotopes were observed. A candidate for the decay of an isomeric state with Eγ=184 keV  in 173Er, which has no previously known excited states, was identified.

This paper explores the relationship between Chinese rare earth metals (REMs) and the industries in the U.S and Europe that heavily rely on them. The study uses the EGARCH(1,1)-ARMA(1,0) process for conditional volatility and incorporates it into VAR(8) framework for forecast error variance decomposition to evaluate the static and dynamic volatility spillovers using daily data from the 2nd of January 2018 to the 3rd of March 2023. The liaison of risk management is also consolidated through the incorporation of Value at Risk and Event Study. Our findings indicate that the volatility interconnectedness between the Chinese REMs market and computer and electronics, electric vehicle, and wind energy industries exhibits relatively low volatility spillover to and from each other. Value at Risk measures suggests complexity in assessing the potential short-term losses for REM equity, leading to difficulties in risk management. Establishing and utilizing a derivatives market could be beneficial for future notice. However, the study also highlights that severe geopolitical risk or conflict could enable extreme levels of financial risk due to the global supply dominance of the Chinese quasi-monopolistic construct and the elements' overall criticality in the sustainable energy transition. The study also highlights the infeasibility of Western nations decoupling themselves from the Chinese REM supply. Various factors such as the pace of advancement in sourcing alternatives, technological advancements, and recycling technology are the main drivers of ineligibility. The forecasted global demand for REMs is also expected to increase significantly, primarily driven by the renewable and sustainable energy transition worldwide, further straining the possibility of independence. Therefore, the pace of advancement of these factors must collectively supersede that of the forecasted demand to mitigate the risk. Keywords: Rare Earth Metals, Interconnectedness, Conditional Volatility, Risk Management, Value at Risk, Event Study.

In this thesis, group IV material oxides for silicon photonics applications were deposited using novel deposition techniques. Erbium and terbium doped silicon oxide thin films were deposited through a novel hybrid radio frequency (RF) magnetron sputtering source in an electron cyclotron resonance (ECR)-plasma enhanced chemical vapour deposition (PECVD) reactor chamber. This approach contrasts with traditional doping methods which use metal-organic precursors to introduce rare-earth dopant species into the host matrix. The effects of sputtering power applied to the rare-earth target and system plasma pressure on the thin film properties were investigated. It was found that the sputtering power strongly influences the rare-earth incorporation, and a wide range of control over the doping level can be achieved. The effect of sputtering power on the refractive index, stoichiometry, and film density were also investigated. Doped thin films deposited with this technique showed low as-deposited hydrogen concentrations. In the case of terbium doped silicon oxide (SiOx), photoluminescence (PL) studies were conducted finding bright emission due to 5D4 → 7F5 transitions visible with the naked eye in films annealed above 1150 °C. Further investigation found that silicon nanostructures formed at the high annealing temperatures and were likely sensitizing the Tb3+ ions. These results demonstrate that hybrid sputtering in ECR-PECVD can be an effective tool for integrating optically active rare-earth dopants into silicon-based thin films. Using alternating current (AC) plasma assisted reactive magnetron sputtering (PARMS), low optical loss germanium oxide (GeO2) thin films were also produced. The films were fabricated at low temperature and high deposition rates of 6–38 nm/min on silicon and thermally oxidized silicon substrates. Prism coupling measurements demonstrated losses of 0.1 dB/cm at wavelengths ranging from 638 to 980 nm attributed to good uniformity and low surface roughness demonstrated through atomic force microscopy (AFM) measurements. The thin films materials developed here are highly promising for their applications in silicon photonics devices, including light sources and amplifiers. / Thesis / Candidate in Philosophy