1,022 research outputs found
Synthesis of atomically thin hexagonal boron nitride films on nickel foils by molecular beam epitaxy
Hexagonal boron nitride (h-BN) is a layered two-dimensional material with
properties that make it promising as a dielectric in various applications. We
report the growth of h-BN films on Ni foils from elemental B and N using
molecular beam epitaxy. The presence of crystalline h-BN over the entire
substrate is confirmed by Raman spectroscopy. Atomic force microscopy is used
to examine the morphology and continuity of the synthesized films. A scanning
electron microscopy study of films obtained using shorter depositions offers
insight into the nucleation and growth behavior of h-BN on the Ni substrate.
The morphology of h-BN was found to evolve from dendritic, star-shaped islands
to larger, smooth triangular ones with increasing growth temperature
Origin of the Mosaicity in Graphene Grown on Cu(111)
We use low-energy electron microscopy to investigate how graphene grows on
Cu(111). Graphene islands first nucleate at substrate defects such as step
bunches and impurities. A considerable fraction of these islands can be
rotationally misaligned with the substrate, generating grain boundaries upon
interisland impingement. New rotational boundaries are also generated as
graphene grows across substrate step bunches. Thus, rougher substrates lead to
higher degrees of mosaicity than do flatter substrates. Increasing the growth
temperature improves crystallographic alignment. We demonstrate that graphene
growth on Cu(111) is surface diffusion limited by comparing simulations of the
time evolution of island shapes with experiments. Islands are dendritic with
distinct lobes, but unlike the polycrystalline, four-lobed islands observed on
(100)-textured Cu foils, each island can be a single crystal. Thus, epitaxial
graphene on smooth, clean Cu(111) has fewer structural defects than it does on
Cu(100).Comment: Article revised following reviewer comment
Real estate stock selection and attribute preferences
The majority of studies that explore property portfolio construction and management strategies utilise highly aggregated ex-post data, but stock selection is known to be a significant determinant of portfolio performance. Thus, here we look at stock selection, focusing on the choices faced by investors, necessitating the collection and analysis of primary data, carried out utilising conjoint analysis. This represents a new step in property research, with the data collection undertaken using a simulation exercise. This enables fund managers to make hypothetical purchase decisions, viewing properties comprising a realistic bundle of attributes and making complex contemporaneous trade-offs between attributes, subject to their stated market and economic forecasts and sector specialism. In total 51 fund managers were surveyed, producing 918 purchase decisions for analysis, with additional data collected regarding fund and personal characteristics. The results reveal that âfixedâ property characteristics (location and obsolescence) are dominant in the decision-making process, over and above âmanageableâ tenant and lease characteristics which can be explicitly included within models of probabilities of income variation. This reveals investors are making ex-ante risk judgements and are considering post acquisition risk management strategies. The study also reveals that behavioural factors affect acquisition decisions
The Spectroscopy and Molecular Dynamics of the High Frequency ν1 6 Intermolecular Vibrations in HCNâââHF and DCNâââDF
Gas phase rovibrational analysis of the high frequency intermolecular hydrogen bonded bending overtone 2ν0 6 [ν0=1132.4783(2) cmâ 1] in HCNâââHF and its corresponding perdeuterated fundamental ν1 6 [ν0=409.1660(2) cmâ 1] are reported. Evaluated rovibrational parameters provide the basis for quantitative modeling of the molecular dynamics associated with this vibration. A quantum mechanical calculation permits determination of the quadratic and quartic force constants K 6 6=537(17) and K 6 6 6 6=4.98(12) cmâ 1 which in turn are used to estimate the pertinent cubic band stretching interaction constants K 4 6 6=â149.3(50) cmâ 1 and account for the unexpected behavior in the rotational constantB 1 6. Second order expansion of the vibrational term energies, give X 4 6=â21.61(2), X 6 7=â7.694(1), X 6 6=â14.84(90), g 6 6=â31.04(90) cmâ 1, neglecting corrections for Fermi resonance. The common isotopic species equilibrium rotational constantB e is evaluated to be 3681.1(11) MHz
Erratum: Determination of Dissociation Energies and Thermal Functions of Hydrogen Bond Formation Using High Resolution FTIR Spectroscopy [J. Chem. Phys. 8 7, 5674 (1987)]
Erratu
Determination of Dissociation Energies and Thermal Functions of Hydrogenâbond Formation using High Resolution FTIR Spectroscopy
A technique which employs high resolution Fourier transform infrared spectroscopy is demonstrated for evaluation of hydrogen bonddissociation energiesD 0 and D e . Results for HCNââHF give a D 0=20.77(22) and D e =28.77(45) kJ/mol which are compared with previously determined values obtained from microwave absolute intensity measurements and a b i n i t i o molecular orbital calculations. Rovibrational band information available for HCNââHF also permits evaluation of thermal functions of dimer formation in kJ/mol: ÎU â 298.2 =20.1(2), ÎH â 298.2 =22.6(2), ÎG â 298.2 =59.4(2), ÎS â 298.2 =â0.1235
Finding a Fit: Biological Science Doctoral Studentsâ Selection of a Principal Investigator and Research Laboratory
In the laboratory-based disciplines, selection of a principal investigator (PI) and research laboratory (lab) indelibly shapes doctoral studentsâ experiences and educational outcomes. Framed by the theoretical concept of personâenvironment fit from within a socialization model, we use an inductive, qualitative approach to explore how a sample of 42 early-stage doctoral students enrolled in biological sciences programs made decisions about fitting with a PI and within a lab. Results illuminated a complex array of factors that students considered in selecting a PI, including PI relationship, mentoring style, and professional stability. Further, with regard to studentsâ lab selection, peers and research projects played an important role. Students actively conceptualized trade-offs among various dimensions of fit. Our findings also revealed cases in which students did not secure a position in their first (or second) choice labs and had to consider their potential fit with suboptimal placements (in terms of their initial assessments). Thus, these students weighted different factors of fit against the reality of needing to secure financial support to continue in their doctoral programs. We conclude by presenting and framing implications for students, PIs, and doctoral programs, and recommend providing transparency and candor around the PI and lab selection processes
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