First Direct Observation of Nanometer size Hydride Precipitations on Superconducting Niobium

Superconducting niobium serves as a key enabling material for superconducting radio frequency (SRF) technology as well as quantum computing devices. At room temperature, hydrogen commonly occupies tetragonal sites in the Nb lattice as metal (M)-gas (H) phase. When the temperature is decreased, however, solid solution of Nb-H starts to be precipitated. In this study, we show the first identified topographical features associated with nanometer-size hydride phase (Nb1-xHx) precipitates on metallic superconducting niobium using cryogenic-atomic force microscopy (AFM). Further, high energy grazing incidence X-ray diffraction reveals information regarding the structure and stoichiometry that these precipitates exhibit. Finally, through time-of-flight secondary ion mass spectroscopy (ToF-SIMS), we are able to locate atomic hydrogen sources near the top surface. This systematic study further explains localized degradation of RF superconductivity by the proximity effect due to hydrogen clusters

Contexto geocronológico y paleoclimático de la formación de playas fósiles sumergidas en el Mediterráneo Occidental

This article describes the geomorphological and petrological characteristics of 19 submerged beachrocks located on the north Catalan coast (western Mediterranean Sea). Their length ranges between 8 and 1039 m, their width between 1.5 and 86.5 m and their thickness between 0.4 and 3.25 m. They are siliciclastic beachrocks consisting of well-rounded gravels with a very coarse sand matrix, and they have a low proportion of bioclasts (<1%). Cementation occurred in the swash zone and adjacent foreshore due to the precipitation of high magnesium calcite. From absolute dates (14C and optically stimulated luminescence) and anthropic artifacts, three phases of formation attributable to the Late Holocene were identified. Phase I corresponds to the warm and humid Roman Period and was recorded at a level below -3.75 m mean sea level (MSL). Phase II corresponds to the warm and arid Medieval Climate Anomaly and was recorded at +0.25 m to -2.5 m MSL. Phase III corresponds to the Little Ice Age and Industrial Period and was recorded at levels ranging from +0.5 m to -3.0 m MSL. Good temporal correspondence between the chronology of the cementation phases and warm and/or dry palaeoclimatic conditions can be established.En este artículo se describen las características geomorfológicas y petrológicas de 19 playas fósiles sumergidas localizadas en la costa norte catalana (Mediterráneo Occidental). Su longitud oscila entre 1039 m y 8 m, y su anchura entre 86.5 m y 1.5 m. Su espesor varía entre un mínimo de 0.4 m y un máximo de 3.25 m. Se trata de playas fósiles siliciclásticas, constituidas por gravas bien redondeadas, con matriz de arena muy gruesa. Presentan una baja proporción de bioclastos (<1%). La cementación se produjo en la zona de batida de la playa debido a la precipitación de calcita magnesiana. A partir de dataciones absolutas (14C y OSL) y de artefactos antrópicos, se han identificado tres fases de formación atribuibles al Holoceno superior. La fase I corresponde al periodo cálido y húmedo romano, y ha sido registrada en un nivel situado por debajo de los -3.75 m respecto del nivel medio del mar (MSL). La fase II encaja con la anomalía climática cálida y árida medieval, la cual ha sido registrada entre +0.25 m y -2.5 m MSL. La fase III corresponde a la pequeña edad del hielo y al periodo industrial, y ha sido registrada en niveles situados entre +0.5 m y -3.0 m MSL. Se puede establecer una buena correspondencia temporal entre la cronología de las distintas fases de cementación y las condiciones paleoclimáticas cálidas y/o áridas. &nbsp

Exposure to non-English languages : a look at children’s metalinguistic skills

This dissertation presents 3 studies that investigate the metalinguistic skills of monolingual children in relation to their exposure to non-native languages. In Study 1, children with large amounts of past exposure to non-English languages were more likely than minimally exposed children to endorse both English and Spanish labels for the same objects. This finding was not explained by fluency in a non-English language. In Study 2, English-speaking children’s multilingual awareness (i.e., their understanding that non-native speakers can communicate meaningful information) was assessed. The majority of children had some past experience with Spanish but no experience with Tagalog or Lithuanian. Children were asked to compare the speech of an English speaker to that of a Lithuanian speaker. Half of these children also heard a Spanish speaker as part of the task, while the remaining half heard Tagalog. Results suggest that only children who heard a Spanish speaker in the study were able to scaffold from their past Spanish experience to make the further inference that the Lithuanian speaker could be saying the same thing as the English speaker. This finding suggests that children might be able to use past non-native language experience to make inferences about the content of new non-native speakers. Finally, Study 3 expanded upon Study 1 by manipulating the language exposure that children received, and assessing children’s subsequent willingness to endorse both native and non-native labels. Results show that children willing to endorse labels across languages are also more willing to learn additional vocabulary from both speakers. This suggests that children’s metalinguistic awareness might have behavioral consequences with respect to their willingness to learn from speakers of non-native languages. Altogether, the findings from this dissertation highlight the importance of language exposure in understanding the development of metalinguistic awareness, and suggest that we may have historically underestimated these skills in monolingual children.Psycholog

Embroidered Meteorology

Weathering is a series of embroidered works that explore the symbolic and cartographic language of meteorology. Through research, mentorship and the physical work, my understanding and anxiety around weather has grown. Making art is a learning process for me: the haptic is a means for understanding. From embroidered world maps to animation to painted laundry, I conflate the intricacy of textiles with the complicated nature of the atmosphere

Picture Superiority Effect and its Detrimental Effect in Memory Updating with Road Signs

Classic studies found advantages of pictures over words in memory (picture superiority effect). This paper applied the picture superiority effect to road signs to examine whether people remembered picture road signs better than word road signs. People remembered picture road signs better than word road signs, as evidenced on a recognition test. However, in real driving situations drivers do not need to remember the meaning of one road sign for a long time; rather, they need to continuously update information from sequentially encountered road signs. Therefore, Experiment 2 explored the differences in updating memory between pictures and words. Memory for the most recently viewed road signs was different depending on the form (picture, word) of the previously encountered road sign. Previously encountered picture items impaired memory significantly more than previously encountered words. These findings demonstrate that superior picture memory sometimes can be detrimental, especially when remembering recent information

Epitaxial Electrodeposition Of Ordered Inorganic Materials

Conspectus The quality of technological materials generally improves as the crystallographic order is increased. This is particularly true in semiconductor materials, as evidenced by the huge impact that bulk single crystals of silicon have had on electronics. Another approach to producing highly ordered materials is the epitaxial growth of crystals on a single-crystal surface that determines their orientation. Epitaxy can be used to produce films and nanostructures of materials with a level of perfection that approaches that of single crystals. It may be used to produce materials that cannot be grown as large single crystals due to either economic or technical constraints. Epitaxial growth is typically limited to ultrahigh vacuum (UHV) techniques such as molecular beam epitaxy and other vapor deposition methods. In this Account, we will discuss the use of electrodeposition to produce epitaxial films of inorganic materials in aqueous solution under ambient conditions. In addition to lower capital costs than UHV deposition, electrodeposition offers additional levels of control due to solution additives that may adsorb on the surface, solution pH, and, especially, the applied overpotential. We show, for instance, that chiral morphologies of the achiral materials CuO and calcite can be produced by electrodepositing the materials in the presence of chiral agents such as tartaric acid. Inorganic compound materials are electrodeposited by an electrochemical-chemical mechanism in which solution precursors are electrochemically oxidized or reduced in the presence of molecules or ions that react with the redox product to form an insoluble species that deposits on the electrode surface. We present examples of reaction schemes for the electrodeposition of transparent hole conductors such as CuI and CuSCN, the magnetic material Fe3O4, oxygen evolution catalysts such as Co(OH)2, CoOOH, and Co3O4, and the n-type semiconducting oxide ZnO. These materials can all be electrodeposited as epitaxial films or nanostructures onto single-crystal surfaces. Examples of epitaxial growth are given for the growth of films of CuI(111) on Si(111) and nanowires of CuSCN(001) on Au(111). Both are large mismatch systems, and the epitaxy is explained by invoking coincidence site lattices in which x unit meshes of the film overlap with y unit meshes of the substrate. We also discuss the epitaxial lift-off of single-crystal-like foils of metals such as Au(111) and Cu(100) that can be used as flexible substrates for the epitaxial growth of semiconductors. The metals are grown on a Si wafer with a sacrificial SiOx interlayer that can be removed by chemical etching. The goal is to move beyond the planar structure of conventional Si-based chips to produce flexible electronic devices such as wearable solar cells, sensors, and flexible displays. A scheme is shown for the epitaxial lift-off of wafer-scale foils of the transparent hole conductor CuSCN. Finally, we offer some perspectives on possible future work in this area. One question we have not answered in our previous work is whether these epitaxial films and nanostructures can be grown with the level of perfection that is achieved in UHV. Another area that is ripe for exploration is the epitaxial electrodeposition of metal-organic framework materials from solution precursors

Nanostructured graphene:Forms, synthesis, properties and applications

This thesis describes the synthesis, properties and applications of the nanostructured graphene with different dimensionalities from 3D foams to, 2D film, and 0D graphene quantum dots (GQDs), and from micron-porous to nanoporous. The applications of the nanostructured graphene include batteries, photoluminescence and cell imaging. Specifically, the thesis comprises the following contents: (1) Nanoporous metallic templates are crucial for the synthesis of nanoporous graphene. A novel method for the synthesis of nanoporous metals was developed and is suitable for industrial production. The growth mechanism, kinetics and microstructures of porous metallic templates were investigated. In addition, the porous metals were synthesized as binder-free current collectors for high-capacity electrodes of lithium-ion batteries. (2) A new solid-state-growth approach is developed for controllable synthesis of nanoporous graphene with interconnected tubular pores and tunable porosities at relatively low temperatures. Nanoporous graphene greatly enhanced the electrochemical performances of high-energy-density Li-S batteries. (3) Large-area graphene film is successfully synthesized at near room temperatures from conversion of amorphous carbon using metallic catalysts. The nucleation, growth process and growth kinetics of graphene were investigated. The results point at several attractive strategies for the facile synthesis of graphene-based carbon films for industrial applications. (4) GQDs were successfully exfoliated from abundant carbon feedstocks such as carbon black in liquid phases with the assistance of ultrasonication. The new approach is eco-friendly and promising for large-scale production. GQDs delivered photoluminescence and light absorption properties, which are firmly associated with their microstructures. The as-synthesized GQDs show good performances as fluorescence nanoprobes for bioimaging