Multiband theory of multi-exciton complexes in self-assembled quantum dots

We report on a multiband microscopic theory of many-exciton complexes in self-assembled quantum dots. The single particle states are obtained by three methods: single-band effective-mass approximation, the multiband $k\cdot p$ method, and the tight-binding method. The electronic structure calculations are coupled with strain calculations via Bir-Pikus Hamiltonian. The many-body wave functions of $N$ electrons and $N$ valence holes are expanded in the basis of Slater determinants. The Coulomb matrix elements are evaluated using statically screened interaction for the three different sets of single particle states and the correlated $N$-exciton states are obtained by the configuration interaction method. The theory is applied to the excitonic recombination spectrum in InAs/GaAs self-assembled quantum dots. The results of the single-band effective-mass approximation are successfully compared with those obtained by using the of $k\cdot p$ and tight-binding methods.Comment: 10 pages, 8 figure

Od karcinoida do biološki i prognostički značajne klasifikacije neuroendokrinih tumora probavnog trakta i gušterače

Although well established in the medical terminology, the term carcinoid is no longer adequate to cover the entire morphological and biological spectrum of neoplasms of the disseminated neuroendocrine cell system. Instead of "carcinoid" the WHO classification published in 2000 therefore uses the general terms "neuroendocrine tumor" and "neuroendocrine carcinoma". In this review we describe a classification of gastroenteropancreatic neuroendocrine tumors based on the WHO criteria. We also classify and comment on the most important tumor entities. On the basis of localization and of various morphological and biological criteria we distinguish between benign neuroendocrine tumors, tumors with uncertain malignant potential, and tumors showing low grade and high grade malignancy.Iako je dobro poznat u medicinskoj terminologiji, pojam karcinoid nije više dovoljan da bi pokrio eitav morfološki i biološki spektar neoplazma diseminiranog neuroendokrinog staničnog sustava. Stoga se u klasifikaciji što ju je 2000. godine objavila SZO umjesto "karcinoidi" rabe opći pojmovi "neuroendokrini tumor" i "neuroendokrini karcinom". U ovom preglednom članku opisujemo klasifikaciju gastroenteropankreatičnih neuroendokrinih tumora, koja se temelji na kriterijima SZO. Također dajemo klasifikaciju i primjerene napomene o najvažnijim tumorskim entitetima. Na osnovi lokalizacije i različitih morfoloških i bioloških kriterija razlikujemo benigne neuroendokrine tumore, tumore neodređenog malignog potencijala, te tumore koji pokazuju nizak i visok stupanj malignosti

Effect of quantum confinement on exciton-phonon interactions

We investigate the homogeneous linewidth of localized type-I excitons in type-II GaAs/AlAs superlattices. These localizing centers represent the intermediate case between quasi-two-dimensional (Q2D) and quasi-zero-dimensional localizations. The temperature dependence of the homogeneous linewidth is obtained with high precision from micro-photoluminescence spectra. We confirm the reduced interaction of the excitons with their environment with decreasing dimensionality except for the coupling to LO-phonons. The low-temperature limit for the linewidth of these localized excitons is five times smaller than that of Q2D excitons. The coefficient of exciton-acoustic-phonon interaction is 5 ~ 6 times smaller than that of Q2D excitons. An enhancement of the average exciton-LO-phonon interaction by localization is found in our sample. But this interaction is very sensitive to the detailed structure of the localizing centers.Comment: 6 pages, 4 figure

Impact of bromide and iodide during drinking water disinfection and potential treatment processes for their removal or mitigation

In this study, the impact of bromide and iodide on disinfected waters was examined and potential treatment technologies for their removal or mitigation were investigated. Distributed waters from two Western Australian drinking water sources were evaluated in terms of their bromide and iodide concentrations, disinfection by-product (DBP) formation, halogen-specific adsorbable organic halogen (AOX) formation and chlorinous odours after disinfection. In both systems, the brominated DBPs dominated the measured DBPs and, in both cases, the known DSPs accounted for only 30% of total organohalogens. Chloramination with a sufficient free chlorine contact time followed by ammonia addition, rather than preformed monochloramine, may be a viable mitigation strategy for the minimisation of I-OBPs, since exposure to free chlorine should promote the conversion of iodide to iodate, a safe form of iodine. This study has shown that bromide plays an important role in this process, mainly by enhancing the preferred conversion' of iodide to iodate. Ozone pre-treatment selectively oxidised iodide to iodate and minimised the formation of I-OB Ps. Complete conversion of iodide to iodate, while minimising the bromate formation to below the guideline value of 10 µg L-1 was achieved for a wide range of ozone concentrations in raw waters, including raw waters with high bromide concentrations

Equilibrium shapes and energies of coherent strained InP islands

The equilibrium shapes and energies of coherent strained InP islands grown on GaP have been investigated with a hybrid approach that has been previously applied to InAs islands on GaAs. This combines calculations of the surface energies by density functional theory and the bulk deformation energies by continuum elasticity theory. The calculated equilibrium shapes for different chemical environments exhibit the {101}, {111}, {\=1\=1\=1} facets and a (001) top surface. They compare quite well with recent atomic-force microscopy data. Thus in the InP/GaInP-system a considerable equilibration of the individual islands with respect to their shapes can be achieved. We discuss the implications of our results for the Ostwald ripening of the coherent InP islands. In addition we compare strain fields in uncapped and capped islands.Comment: 10 pages including 6 figures. Submitted to Phys. Rev. B. Related publications can be found at http://www.fhi-berlin.mpg.de/th/paper.htm

Multiplicities of charged pions and unidentified charged hadrons from deep-inelastic scattering of muons off an isoscalar target

Multiplicities of charged pions and unidentified hadrons produced in deep-inelastic scattering were measured in bins of the Bjorken scaling variable $x$, the relative virtual-photon energy $y$ and the relative hadron energy $z$. Data were obtained by the COMPASS Collaboration using a 160 GeV muon beam and an isoscalar target ($^6$LiD). They cover the kinematic domain in the photon virtuality $Q^2$ > 1(GeV/c$)^2$, $0.004 < x < 0.4$, $0.2 < z < 0.85$ and $0.1 < y < 0.7$. In addition, a leading-order pQCD analysis was performed using the pion multiplicity results to extract quark fragmentation functions

α-Fetoprotein and human chorionic gonadotrophin-β as prognostic markers in neuroendocrine tumour patients

Serum chromogranin A is the most useful general and prognostic tumour marker available for neuroendocrine tumour (NET) patients. The role of other tumour markers is less clear. In order to determine the diagnostic and prognostic value of serum α-fetoprotein (AFP) and human chorionic gonadotrophin-β (hCGβ) in NETs, a database containing biochemical, histological, and survival data on 360 NET patients was constructed. This data was statistically assessed, using Statistical Package for the Social Sciences, to determine the utility of commonly measured tumour markers with particular emphasis on AFP and hCGβ. α-Fetoprotein and hCGβ were raised in 9.5 and 12.3% of patients respectively and jointly raised in 9.1% of patients in whom it was measured. α-Fetoprotein levels associated strongly and positively with tumour grade, serum CgA and hCGβ levels, and worse survival. Human chorionic gonadotrophin-β levels also associated strongly and positively with serum CgA and AFP levels, and worsening survival. α-Fetoprotein and hCGβ are elevated in high-grade NETs, with a rapidly progressive course and poorer survival. They also correlate with chromogranin-A, which is known to be a marker of tumour burden and to have prognostic value. Thus AFP and hCGβ are clinically important in NETs and when elevated are poor prognostic markers