46 research outputs found
Semiconductor quantum tubes: dielectric modulation and excitonic response
We study theoretically the optical properties of quantum tubes,
one-dimensional semiconductor nanostructures where electrons and holes are
confined to a cylindrical shell. In these structures, which bridge between 2D
and 1D systems, the electron-hole interaction may be modulated by a dielectric
substance outside the quantum tube and possibly inside its core. We use the
exact Green's function for the appropriate dielectric configuration and exact
diagonalization of the electron-hole interaction within an effective mass
description to predict the evolution of the exciton binding energy and
oscillator strength. Contrary to the homogeneous case, in dielectrically
modulated tubes the exciton binding is a function of the tube diameter and can
be tuned to a large extent by structure design and proper choice of the
dielectric media.Comment: 9 pages, 6 figures, in print for Phys. Rev.
Field-controlled suppression of phonon-induced transitions in coupled quantum dots
We calculate the longitudinal-acoustic phonon scattering rate for a vertical
double quantum dot system with weak lateral confinement and show that a strong
modulation of the single-electron excited states lifetime can be induced by an
external magnetic or electric field. The results are obtained for typical
realistic devices using a Fermi golden rule approach and a three-dimensional
description of the electronic quantum states.Comment: REVTex4 class, 6 pages, 3 figures, to be published in Applied Physics
Letter
Neutral and charged electron-hole complexes in artificial molecules: quantum transitions induced by the in-plane magnetic field
We theoretically investigate the properties of neutral and charged excitons and of the biexciton in vertically coupled quantum dots, as a function of the in-plane magnetic field B-parallel to. The main effect of the field consists in the suppression of the bonding-antibonding splitting, and in the resulting enhancement of the interdot correlations. As a consequence, the excitons form with the additional carrier a bound or an unbound complex depending on the sign of the charging, whereas the biexciton undergoes a transition between different quantum states with increasing B-parallel to. The discussed behaviors and transitions show up in the field dependence of experimentally accessible quantities, such as the charged-exciton and biexciton binding energies
Remote sensing investigation techniques for the analysis of rocky slope stability in remote areas: a test from the Sierra Madre Occidental, Mexico
Direct field survey to assess slope stability in steep and remote rocky cliffs is time demanding and highly consuming in term of human and economic resources. However, evolving technologies allow remotely sensed data integrated with GIS to theoretically provide equivalent information. Here we present a case study comparison of these methods applied to the Eastern valley-side of the Chinipas River, Sierra Madre Occidental, Mexico.
Results show that remote sensing procedures provides the same discontinuity sets and equivalent attitude information with respect to the data acquired during field survey
Spin-Spin Interaction In Artificial Molecules With In-Plane Magnetic Field
We investigate theoretically the spin-spin interaction of two-electrons in
vertically coupled QDs as a function of the angle between magnetic field and
growth axis. Our numerical approach is based on a real-space description of
single-particle states in realistic samples and exact diagonalization of
carrier-carrier Coulomb interaction. In particular, the effect of the in-plane
field component on tunneling and, therefore, spin-spin interaction will be
discussed; the singlet-triplet phase diagram as a function of the field
strength and direction is drawn.Comment: Proc. of EP2DS-15, Nara, Japan - 6 pages, 4 figure
Competing mechanisms for singlet-triplet transition in artificial molecules
We study the magnetic field induced singlet/triplet transition for two
electrons in vertically coupled quantum dots by exact diagonalization of the
Coulomb interaction. We identify the different mechanisms occurring in the
transition, involving either in-plane correlations or localization in opposite
dots, depending on the field direction. Therefore, both spin and orbital
degrees of freedom can be manipulated by field strength and direction. The
phase diagram of realistic devices is determined.Comment: To appear in Phys. Rev. B - Rapid Comm. - 5 pages, 3 figure
Cetuximab continuation after first progression in metastatic colorectal cancer (CAPRI-GOIM): A randomized phase II trial of FOLFOX plus cetuximab versus FOLFOX
Background: Cetuximab plus chemotherapy is a first-line treatment option in metastatic KRAS and NRAS wild-type colorectal cancer (CRC) patients. No data are currently available on continuing anti-epidermal growth factor receptor (EGFR) therapy beyond progression. Patients and methods: We did this open-label, 1:1 randomized phase II trial at 25 hospitals in Italy to evaluate the efficacy of cetuximab plus 5-fluorouracil, folinic acid and oxaliplatin (FOLFOX) as second-line treatment of KRAS exon 2 wild-type metastatic CRC patients treated in first line with 5-fluorouracil, folinic acid and irinotecan (FOLFIRI) plus cetuximab. Patients received FOLFOX plus cetuximab (arm A) or FOLFOX (arm B). Primary end point was progressionfree survival (PFS). Tumour tissues were assessed by next-generation sequencing (NGS). This report is the final analysis. Results: Between 1 February 2010 and 28 September 2014, 153 patients were randomized (74 in arm A and 79 in arm B). Median PFS was 6.4 [95% confidence interval (CI) 4.7-8.0] versus 4.5 months (95% CI 3.3-5.7); [hazard ratio (HR), 0.81; 95% CI 0.58-1.12; P = 0.19], respectively. NGS was performed in 117/153 (76.5%) cases; 66/117 patients (34 in arm A and 32 in arm B) had KRAS, NRAS, BRAF and PIK3CA wild-type tumours. For these patients, PFS was longer in the FOLFOX plus cetuximab arm [median 6.9 (95% CI 5.5-8.2) versus 5.3 months (95% CI 3.7-6.9); HR, 0.56 (95% CI 0.33-0.94); P = 0.025]. There was a trend in better overall survival: median 23.7 [(95% CI 19.4-28.0) versus 19.8 months (95% CI 14.9-24.7); HR, 0.57 (95% CI 0.32-1.02); P = 0.056]. Conclusions: Continuing cetuximab treatment in combination with chemotherapy is of potential therapeutic efficacy in molecularly selected patients and should be validated in randomized phase III trials