972 research outputs found
Copyright Laws in the Music Industry
This assignment was to write an argumentative research paper on a topic related to the course theme, which was Remix Culture. After browsing through a list of suggested topics and reading about a number of famous copyright cases, I finally chose my topic. My biggest struggle during the composition of this paper was figuring out how to organize all of my thoughts and weave them into the research that I gathered. Having both a peer review day in class and a conference with my professor was very helpful and gave me a fresh perspective on my work, making it much easier to revise my draft
Kohn-Sham decomposition in real-time time-dependent density-functional theory: An efficient tool for analyzing plasmonic excitations
The real-time-propagation formulation of time-dependent density-functional
theory (RT-TDDFT) is an efficient method for modeling the optical response of
molecules and nanoparticles. Compared to the widely adopted linear-response
TDDFT approaches based on, e.g., the Casida equations, RT-TDDFT appears,
however, lacking efficient analysis methods. This applies in particular to a
decomposition of the response in the basis of the underlying single-electron
states. In this work, we overcome this limitation by developing an analysis
method for obtaining the Kohn-Sham electron-hole decomposition in RT-TDDFT. We
demonstrate the equivalence between the developed method and the Casida
approach by a benchmark on small benzene derivatives. Then, we use the method
for analyzing the plasmonic response of icosahedral silver nanoparticles up to
Ag. Based on the analysis, we conclude that in small nanoparticles
individual single-electron transitions can split the plasmon into multiple
resonances due to strong single-electron-plasmon coupling whereas in larger
nanoparticles a distinct plasmon resonance is formed.Comment: 11 pages, 3 figure
Pressure-induced phase transition in the electronic structure of palladium nitride
We present a combined theoretical and experimental study of the electronic
structure and equation of state (EOS) of crystalline PdN2. The compound forms
above 58 GPa in the pyrite structure and is metastable down to 11 GPa. We show
that the EOS cannot be accurately described within either the local density or
generalized gradient approximations. The Heyd-Scuseria-Ernzerhof
exchange-correlation functional (HSE06), however, provides very good agreement
with experimental data. We explain the strong pressure dependence of the Raman
intensities in terms of a similar dependence of the calculated band gap, which
closes just below 11 GPa. At this pressure, the HSE06 functional predicts a
first-order isostructural transition accompanied by a pronounced elastic
instability of the longitudinal-acoustic branches that provides the mechanism
for the experimentally observed decomposition. Using an extensive Wannier
function analysis, we show that the structural transformation is driven by a
phase transition of the electronic structure, which is manifested by a
discontinuous change in the hybridization between Pd-d and N-p electrons as
well as a conversion from single to triple bonded nitrogen dimers. We argue for
the possible existence of a critical point for the isostructural transition, at
which massive fluctuations in both the electronic as well as the structural
degrees of freedom are expected.Comment: 9 pages, 12 figures. Revised version corrects minor typographical
error
Surface potential at a ferroelectric grain due to asymmetric screening of depolarization fields
Nonlinear screening of electric depolarization fields, generated by a stripe
domain structure in a ferroelectric grain of a polycrystalline material, is
studied within a semiconductor model of ferroelectrics. It is shown that the
maximum strength of local depolarization fields is rather determined by the
electronic band gap than by the spontaneous polarization magnitude.
Furthermore, field screening due to electronic band bending and due to presence
of intrinsic defects leads to asymmetric space charge regions near the grain
boundary, which produce an effective dipole layer at the surface of the grain.
This results in the formation of a potential difference between the grain
surface and its interior of the order of 1 V, which can be of either sign
depending on defect transition levels and concentrations. Exemplary acceptor
doping of BaTiO3 is shown to allow tuning of the said surface potential in the
region between 0.1 and 1.3 V.Comment: 14 pages, 11 figures, submitted to J. Appl. Phy
Maine’s Potential to Be a Global Leader in Sustainable Seaweed Harvesting and Management
A multitude of macroalgae (i.e., seaweed) species that are harvested in Maine are economically and ecologically important. Currently, management of these resources in Maine is focused on rockweed (Ascophyllum nodosum). This seaweed grows in abundance along intertidal rocky shores and provides a number of benefits including serving as habitat and nursery for many species including fin-fish, coastal protection from storms and sea level rise, carbon sequestration, and is a harvestable natural resource used primarily in fertilizer and animal feed production. It is critical that these functions and benefits are maintained and harvesting activities managed to ensure a sustainable fishery and healthy ecosystem. In 2014, Maine drafted a rockweed fisheries management plan; however, this plan has yet to be adopted. The delay in adoption is now an opportunity to re-examine the plan from an ecosystem-based management (EBM) perspective. We compare EBM strategies to the existing rockweed fisheries management plan, and identify areas of synergy as well as gaps in the management of Maine’s seaweeds and harvesting activities. Based on this analysis we propose Maine adopt an EBM approach and strategies for wild as well as farmed seaweeds
Nonlinear microwave absorption in Ba1-xKxBiO3
Nonlinear, field-modulated, direct microwave absorption (FMMA) was observed in copper-free Ba1-xKxBiO3 powder samples. The high-field, low-temperature results were compared to previous measurements of YBa CuO and BiSrCaCuO. The microwave wave determined critical field μ0H* = 0.7 μT and depinning current density J* c ≈ 1 × 107 A/m2 were obtained from the "Portis" model of flux pinning and depinning. These values were lower than the values obtained previously for YBaCuO and BiSrCaCuO as anticipated for a material with larger coherence length and comparable London penetration depth. A previously unobserved asymmetry of the FMMA in the field scan direction was also noted. © 1994
Direct field modulated microwave absorption in Ba1-xKxBiO3
Non linear, field modulated, direct microwave absorption (MA) was studied in the high-Tc copper-free isotropic Ba1-xKxBiO3 (BaKBiO) powder samples. The microwave determined critical magnetic field gradient and the corresponding depinning current density were compared with the values obtained previously for YBaCuO (YBCO) and BiSrCaCuO (BSCCO). © 1994
Investigation of the chemical vicinity of crystal defects in ion-irradiated Mg and AZ31 with coincident Doppler broadening spectroscopy
Crystal defects in magnesium and magnesium based alloys like AZ31 are of
major importance for the understanding of their macroscopic properties. We have
investigated defects and their chemical surrounding in Mg and AZ31 on an atomic
scale with Doppler broadening spectroscopy of the positron annihilation
radiation. In these Doppler spectra the chemical information and the defect
contribution have to be thoroughly separated. For this reason samples of
annealed Mg were irradiated with Mg-ions in order to create exclusively
defects. In addition Al- and Zn-ion irradiation on Mg-samples was performed in
order to create samples with defects and impurity atoms. The ion irradiated
area on the samples was investigated with laterally and depth resolved positron
Doppler broadening spectroscopy (DBS) and compared with preceding
SRIM-simulations of the vacancy distribution, which are in excellent agreement.
The investigation of the chemical vicinity of crystal defects in AZ31 was
performed with coincident Doppler broadening spectroscopy (CDBS) by comparing
Mg-ion irradiated AZ31 with Mg-ion irradiated Mg. No formation of
solute-vacancy complexes was found due to the ion irradiation, despite the high
defect mobility.Comment: Submitted to Physical Review B on March 20 20076. Revised version
submitted on September 28 2007. Accepted on October 19 200
Vitrification of octonary perylene mixtures with ultralow fragility
Strong glass formers with a low fragility are highly sought-after because of the technological importance of vitrification. In the case of organic molecules and polymers, the lowest fragility values have been reported for single-component materials. Here, we establish that mixing of organic molecules can result in a marked reduction in fragility. Individual bay-substituted perylene derivatives display a high fragility of more than 70. Instead, slowly cooled perylene mixtures with more than three components undergo a liquid-liquid transition and turn into a strong glass former. Octonary perylene mixtures display a fragility of 13 \ub1 2, which not only is a record low value for organic molecules but also lies below values reported for the strongest known inorganic glass formers. Our work opens an avenue for the design of ultrastrong organic glass formers, which can be anticipated to find use in pharmaceutical science and organic electronics
Recommended from our members
Does mode of administration affect health-related quality-of-life outcomes after stroke?
Telephone interviews and postal surveys may be a resource-efficient way of assessing health-related quality-of-life post-stroke, if they produce data equivalent to face-to-face interviews. This study explored whether telephone interviews and postal surveys of the Stroke and Aphasia Quality of Life Scale (SAQOL-39g) yielded similar results to face-to-face interviews. Participants included people with aphasia and comprised two groups: group one (n =22) were 3-6 months post-stroke; group two (n =26) were ≥1 year post-stroke. They completed either a face-to-face and a telephone interview or a face-to-face interview and a postal survey of the SAQOL-39g. Response rates were higher for group two (87%) than for group one (72-77%). There were no significant differences between respondents and non-respondents on demographics, co-morbidities, stroke severity, or communication impairment. Concordance between face-to-face and telephone administrations (.90-.98) was excellent; and very good-excellent between face-to-face and postal administrations (.84-.96), although scores in postal administrations were lower (significant for psychosocial domain and overall SAQOL-39g in group two). These findings suggest that the SAQOL-39g yields similar results in different modes of administration. Researchers and clinicians may employ alternative modes, particularly in the longer term post-stroke, in order to reduce costs or facilitate clients with access difficulties
- …