Star clusters are key age-dateable tracers of the chemical history of the Milky Way. Star clusters can provide significant constraints on galaxy chemical evolution models. The large discrepancies between different small studies limit the accuracy of these constraints, so a large uniform study is needed. To create a large uniform sample, we observed stars in 63 clusters with the same telescope. We then determined the chemical makeup of these stars using a machine learning tool called The Cannon. Using this sample, we examine the change in chemical abundance over the radius of our galaxy.

Nano- and microcrystalline ZnO is a low-cost material, employed in many applications due to its optoelectronic, structural and chemical properties as well as a great variety of synthesis methods. Among these applications, antibacterial action of ZnO is a budding field of interdisciplinary research. Despite numerous studies of this antibacterial action, the physical and chemical mechanisms behind it are still largely not understood. In particular, the influence of the crystal surface morphology and surface-surface interactions between the bacteria and ZnO are largely unknown. Hexagonal (wurtzite) ZnO crystals terminate with three different types of crystallographic surfaces: charged polar hexagonal (Zn or O), electrically neutral nonpolar rectangular and partially polar pyramidal slanted. In our studies we employ a hydrothermal growth procedure to synthesize nanocrystals and microcrystals of ZnO with tunable morphology to investigate the influence of surface types on interactions with bacteria as well as surface charge dynamics. To quantify the antibacterial action we employ minimum inhibitory concentration (MIC) assays of staphylococcus aureus with hydrothermally-grown ZnO microcrystals. Scanning electron microscopy (SEM) is used to characterize the morphology of the as-grown ZnO specimens as well as the organization of these particles after their interactions with bacteria. To characterize electronic structure and dominant charge transport mechanisms at ZnO surfaces we performed photovoltage (SPV) experiments. Our results confirm that antibacterial action is a result of ZnO surface interactions with extracellular material, whereas internalization of ZnO particles (happening in the case of nanoscale ZnO) is not necessary for inhibition. We also report that the electronic transitions at the surface of the ZnO particles are consistent the theoretically predicted electronic structure of ZnO, with the spectral signatures of surface states which could be the source of the antimicrobial action.

Reportedly, hydrophobic surfaces of polysulfone (PSu) thin films become hydrophilic following exposure to UV radiation and it can affect PSu novel applications in microfluidics and biophysics. Fundamental mechanisms behind this effect remain unknown. To elucidate them, in our work we study surface charge transport employing surface photovoltage (SPV) on thin PSu polysulfone films spin-cast on silicon substrates. Since exposure of PSu even to an ambient UV light could affect the surface properties we ran SPV spectroscopy as well as SPV transient experiments on both as-received samples fabricated in darkness and UV-irradiated films of varying and controllable thicknesses. We report on the comparison of the SPV response in the as-deposited and UV-irradiated polysulfone samples.

Modern astronomical catalogs consist of up to billions of stars and measure various properties of these objects. There have been recent data releases from two of these surveys, GAIA which measures positions and distances, and APOGEE which measures radial velocities and stellar physical properties. By combining these datasets we have the full 6D phase space information for each star and can compute orbital characteristics and kinematics properties. APOGEE targeted specific stellar populations in our Milky Way and determined some of their physical properties. By cross matching with GAIA, we are able to fully describe the orbits of these populations and look for potential new members that have the same physical and kinematic properties but are not located in the immediate vicinity. We will present kinematic properties of the full cross matched dataset as well as information on the targeted stellar populations of the Milky Way.

Metal nanoparticles on a substrate have gained significant attention in recent years as novel systems for new generations of catalysts. Among other metals, iron attracts constant attention due to its low cost. Iron possess either the body-centered cubic (bcc) or the face-centered cubic (fcc) structure. Up to 917 °C, iron exists in its α-form (α-Fe) with the thermodynamically bcc lattice. At 917 °C, α-Fe transforms into the fcc lattice, and this allotrope is termed as γ-iron (γ-Fe) (austenite) with diamagnetic properties. According to the iron-carbon phase diagram, γ-Fe can incorporate up to 2.03% carbon. Lowering the temperature below 917 °C, carbon atoms diffuse out of the structure, and γ-Fe turns back to α-Fe. Up to now, γ-Fe could not be stabilized without such impurities as Mn, Cr, Ni at room temperature. We have obtained of iron nanoparticles with the face-centered cubic structure with diameters of up to 200 nm without impurities on the substrate of graphene oxide by thermal annealing in an inert gas. In our work we show that phases formation of iron depends on the temperature of annealing. At the annealing temperature from 300 ºC through 600 ºC only iron oxides are formed. We established the unexpected formation of the γ-phase already at 700°C by X-Ray diffraction and Mössbauer spectroscopy. These methods clearly identify the stability of the γ-phase at room temperature. The rather low transition temperature of α-Fe to γ-Fe already starting at 700 °C suggests that the mechanism for the transformation is different from that observed for bulk iron. The maximum γ-iron nanoparticles content on the substrate of graphene oxide was fixed at an annealing temperature of 950 °C.