11,734 research outputs found
Excitonic effects in the optical properties of CdSe nanowires
Using a first-principle approach beyond density functional theory we
calculate the electronic and optical properties of small diameter CdSe
nanowires.Our results demonstrate how some approximations commonly used in bulk
systems fail at this nano-scale level and how indispensable it is to include
crystal local fields and excitonic effects to predict the unique optical
properties of nanowires. From our results, we then construct a simple model
that describes the optical gap as a function of the diameter of the wire, that
turns out to be in excellent agreement with experiments for intermediate and
large diameters.Comment: submitte
Construction of the B88 exchange-energy functional in two dimensions
We construct a generalized-gradient approximation for the exchange-energy
density of finite two-dimensional systems. Guided by non-empirical principles,
we include the proper small-gradient limit and the proper tail for the
exchange-hole potential. The observed performance is superior to that of the
two-dimensional local-density approximation, which underlines the usefulness of
the approach in practical applications
Notational types in scores for guitar and electronics
Notation is one of the factors upon which the longevity of mixed music is dependent. In this paper, I first discuss how academic production has conceived representation in works with electronics and dealt with inherent problems. After, I present the nine representational strategies I have identified in repertoire for guitar and electronics. These notational types aid understanding how composers conceive the interaction between the acoustic and electroacoustic parts in mixed music performance. Their simultaneous use, even if redundant, can help understanding instrumental performance issues and contribute to the preservation of the electronic part. I conclude with some considerations about the relevant strategies and their importance for the performance and permanence in the repertoire
Spin filtering in nanowire directional coupler
The spin transport characteristics of a nanowire directional electronic
coupler have been evaluated theoretically via a transfer matrix approach. The
application of a gate field in the region of mixing allows for control of spin
current through the different leads of the coupler via the Rashba spin-orbit
interaction. The combination of spin-orbit interaction and applied gate
voltages on different legs of the coupler give rise to a controllable
modulation of the spin polarization. Both structural factors and field strength
tuning lead to a rich phenomenology that could be exploited in spintronic
devices.Comment: 9 pages, 4 figure
A Giant Hand Lipoma As a Rare Cause of Secondary Carpal Tunnel Syndrome - a Case Report
Introduction: Lipomas are a rare cause of compressive neuropathy and they lead to atypical clinical presentation that can mimic carpal tunnel syndrome.
Case presentation: The authors describe a rare presentation of a carpal tunnel syndrome recurrence after a hand giant lipoma, presenting with rapidly compression neuropathy of the median nerve, 6 months after de primary surgery.
Discussion: Lipomas are common benign soft tumours. Their occurrence in the hand remains rare and they rarely cause secondary entrapment neuropathies. Carpal tunnel syndrome is mostly idiopathic and bilateral. Local factors should be suspected when these neuropathies present with atypical symptomatology or even when they recur after primary conventional surgical release. Investigation should consider images studies as this correct preoperative assessment leads to successful diagnosis and treatment.info:eu-repo/semantics/publishedVersio
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