bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photoluminescence and photoluminescence excitation spectroscopy of CdSe/ZnS core‐shell free standing nanocrystals in the ultraviolet spectral range
Authors: Podhorodecki A. , Misiewicz J. , Nauka K. 
Published: November 2006

AbstractPhotoluminescence and photoluminescence excitation spectroscopy measurements of CdSe/ZnS nanocrystals have been carried out to investigate its optical properties. The effect of rapid decrease of the emission intensity at 570 nm has been explained when the excitation wavelengths are higher than about 300 nm. This behavior has been related to the presence of additional recombination channels in the core/shell structure. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nonlinear optical microscopy of a single self‐assembled InGaAs quantum dot
Authors: Wesseli M. , Ruppert C. , Trumm S. , Krenner H. J. , Finley J. J. , Betz M. 
Published: November 2006

AbstractCarrier dynamics in InGaAs/GaAs quantum dots is analyzed with highly sensitive two‐color femtosecond transmission spectroscopy. Especially, a single artificial atom is addressed in the optical near‐field of a nanometer scale shadow mask. Resonantly exciting the wetting layer beneath the nanoisland, we detect transmission changes of the quantum dot with narrowband femtojoule probe pulses. We find bleaching signals in the order of 10–5 that arise from individual interband transitions. Moreover, the nonlinear optical response reveals a picosecond dynamics associated with carrier relaxation in the quantum dot. As a result, we have demonstrated an ultrafast optical tool for both manipulation and read‐out of a single self‐assembled quantum dot. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation of InAs quantum dot growth for electrical spin injection devices
Authors: Passow T. , Li S. , Litvinov D. , Löffler W. , Fallert J. , Daniel B. , Lupaca‐Schomber J. , Kvietková J. , Gerthsen D. , Kalt H. , Hetterich M. 
Published: November 2006

AbstractThe influence of the growth conditions during molecular‐beam epitaxy on the properties of InAs/GaAs quantum dot structures were systematically investigated by low temperature photoluminescence spectroscopy and transmission electron microscopy. The circular polarization degree (CPD) of the electroluminescence was compared for two quantum‐dot spin‐injection light‐emitting diodes. The CPD depends on the position of the emission energy in the luminescence band. This correlation is similar for both samples despite the strongly different quantum dot morphologies. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Scanning transmission electron microscopy of vertically stacked self organized quantum structures
Authors: Sauerwald A. , Kümmell T. , Löffler A. , Somers A. , Reithmaier J. P. , Forchel A. , Bacher G. 
Published: November 2006

AbstractChemically sensitive scanning transmission electron microscopy in combination with electron energy loss spectroscopy is applied to investigate self organized quantum structures. The impact of vertical stacking on size and chemical composition of both quantum dots and quantum dashes is studied. In case of our InAs quantum dashes grown on an InP substrate, a strong increase of the structure size with layer number is found while the chemical composition of the quantum dashes remains constant. In contrast, we do not observe any significant change in both composition and size in case of vertically stacked InGaAs quantum dots grown on a GaAs substrate. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Infrared detector based on modulation‐doped quantum‐dot structures
Authors: Mitin V. , Vagidov N. , Sergeev A. 
Published: November 2006

AbstractWe investigate a detector model, where quantum dots are surrounded by potential barriers created by modulation doping. Strong separation of the localized ground states and continuum conducting states drastically increases the photoelectron capture time. At room temperatures the photoelectron capture is conditioned by electron diffusion in the potential relief. Monte‐Carlo modeling with diffusion‐limited capture in the modulation‐doped quantum‐dot structures is used to calculate carrier lifetime and photoconductive gain as functions of the electric field. We evaluate the photodetector characteristics and show that photoconductive gain is substantially improved due to longer lifetimes of photoelectrons. Optimized quantum‐dot structures have a strong potential for development IR room‐temperature detectors. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetically driven coupling of electronic states in quantum dot molecules
Authors: Voskobyonikov O. , Liu J. L. , Chen J. H. 
Published: November 2006

AbstractWe consider lowest energy states of electrons confined in asymmetrical circular vertically stacked double InAs/GaAs quantum dot molecule. The energies where computed by using the effective three‐dimensional one band Hamiltonian, the energy (non‐parabolic) and position dependent electronic effective mass approximation, and the Ben Daniel‐Duke boundary conditions with the finite hard wall confinement potential. We demonstrated theoretically a possibility to drive dynamically coupled electronic states (relocate electronic wave functions from one dot to another) by applying external magnetic field. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Morphology and photoluminescence of seeded three‐dimensional InAs/GaAs(001) quantum‐dot crystals
Authors: Kiravittaya S. , Rastelli A. , Schmidt O. G. 
Published: November 2006

AbstractWe investigate the morphology and photoluminescence (PL) of quantum dots (QDs) in seeded three‐dimensional InAs/GaAs quantum‐dot crystals (QDCs). The QDs in the QDC show a dome shape for the second QD layer and they have a pyramid shape in all subsequent layers. The PL from the QDC with 11‐fold stacked QD layers shows an intense PL signal with narrow inhomogeneous linewidth. Both ground state PL peak energy and PL linewidth remain almost constant over the patterned area. A power‐dependent PL measurement is performed and compared with a simple quantum disk model. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Radiation pressure induced splitting of resonant modes in a nanocrystal‐coated microcavity
Authors: Gerlach M. , Rakovich Yu. P. , Donegan J. F. , Gaponik N. , Rogach A. L. 
Published: November 2006

AbstractMelamine formaldehyde microspheres were coated with a soft polyelectrolyte multilayer (PAH/PSS) and one monolayer of CdTe nanocrystals. A micro‐PL setup was used to trap the sample within the tightly focused laser beam. The radiation pressure was used to deform the spherical shape of the polyelectrolyte multilayer which changes the optical properties of the resonance modes (whispering gallery modes) in the microcavity. Optically induced shifting and splitting of the resonances were observed with changing characteristics based on varying particular parameters such as laser intensity and focus position. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stark spectroscopy of Coulomb interactions in individual InAs/GaAs self‐assembled quantum dots
Authors: Kowalik K. , Krebs O. , Senellart P. , Lemaître A. , Eble B. , Kudelski A. , Gaj J. , Voisin P. 
Published: November 2006

AbstractWe present results of polarization‐resolved micro‐photoluminescence (μ‐PL) experiments on self‐organized InAs/GaAs (QDs). We have investigated how Coulomb interactions are modified by application of an electric field. We observed systematic variation of bright exciton splitting for different electric field configurations (applied in the quantum dot plane or along the sample growth axis). The results show also dependence of direct Coulomb interactions of carriers inside the dots, manifested by changes of PL line position of charged excitons (X+ and X‐) with respect to the neutral excitonic line. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Luminescence and photo‐excitation properties of laser heterostructures with CdSe/ZnSe quantum dots
Authors: Lyublinskaya O. G. , Sedova I. V. , Sorokin S. V. , Toropov A. A. , Ivanov S. V. 
Published: November 2006

AbstractWe report on the photoluminescence excitation studies of optically pumped Cd(Zn)Se/ZnMgSSe laser heterostructures with CdSe/ZnSe quantum dots (QDs) in the active region, grown by molecular beam epitaxy on GaAs substrates. The weak coupling of CdSe QD excitons with the standing‐wave modes of the cavity formed between the sample surface and the II‐VI/GaAs interface has been observed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Self‐organized dots of GaN:Mn grown by molecular beam epitaxy
Authors: Kuroda S. , Marcet S. , Halley D. , Ferrand D. , Cibert J. , Mariette H. , Yamamoto S. , Sakai T. , Ohshima T. , Itoh H. 
Published: November 2006

AbstractSelf‐organized dots of Mn‐doped GaN were grown on AlN by plasma‐assisted molecular beam epitaxy. The growth was performed in the nitrogen‐rich growth regime with the addition of small amount of Mn flux. The in‐situ surface observation using reflection high energy electron diffraction (RHEED) and the ex‐situ examination using atomic force microscope (AFM) revealed that the dot formation was observed only in the case where the amount of Mn flux was small. The estimate of Mn composition using particle induced X‐ray emission (PIXE) experiment showed that the Mn composition in the dots layer was much higher than in thick (Ga,Mn)N layers grown with the same amount of Mn flux. The maximum Mn composition for the high‐density dot formation was about x = 0.01. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Energy dependence of the electron‐hole in‐plane anisotropy in InAs/GaAs quantum dots
Authors: Testelin C. , Aubry E. , Chaouache M. , Maaref M. , Bernardot F. , Chamarro M. , Gérard J.‐M. , Ferreira R. 
Published: November 2006

AbstractIn pump‐probe experiments, we measured the anisotropic exchange energy splitting of the low‐lying electron‐hole pair states in an ensemble of as‐grown InAs/GaAs self‐assembled quantum dots. This splitting shows a monotonic decrease with the energy of interband emission. We discuss this result considering different parameters: shape anisotropy, wavefunction confinement, size of the quantum dots, and piezoelectric effect. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Onset of GaSb/GaAs quantum dot formation
Authors: Timm R. , Lenz A. , Eisele H. , Ivanova L. , Pötschke K. , Pohl U. W. , Bimberg D. , Balakrishnan G. , Huffaker D. L. , Dähne M. 
Published: November 2006

AbstractWe present cross‐sectional scanning tunneling microscopy results on GaSb nanostructures in GaAs, analyzing their shape, size and chemical composition. By comparing different quantum wells and quantum dot layers, grown both by metalorganic chemical vapor deposition and by molecular beam epitaxy, the onset of quantum dot evolution is studied. Quantum dots are found already after a deposition of 1 monolayer GaSb. Intermixing of the deposited GaSb with GaAs due to anion exchange as well as different effects of Sb segregation during overgrowth are demonstrated. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High efficiency photoluminescence from silicon nanocrystals prepared by plasma synthesis and organic surface passivation
Authors: Mangolini L. , Jurbergs D. , Rogojina E. , Kortshagen U. 
Published: November 2006

AbstractAn efficient synthesis route for highly luminescent silicon quantum dots is presented. Silicon nanocrystals were synthesized in the gas phase using an argon‐silane non‐thermal plasma in a continuous flow reactor. Liquid phase surface passivation was used to improve the optical properties and avoid surface oxidation of the silicon quantum dots. Various alkenes, such as octadecene, dodecene and styrene, were covalently bonded to the plasma‐produced particles, while strictly avoiding exposure of the raw powder to oxidizing agents. Stable colloidal solutions of silicon quantum dots with ensemble quantum yields between 60% and 70% were achieved. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Memory inhibition in quantum‐wire transistors controlled by quantum dots
Authors: Müller C. R. , Worschech L. , Forchel A. 
Published: November 2006

AbstractCurrent‐voltage characteristics of in‐plane gated quantum‐wire transistors with embedded InGaAs quantum dots are studied at low temperatures. Due to the floating gate function of the quantum dots, for small bias voltages a threshold hysteresis of up to 0.9 V is observed between the up sweep and the down sweep of the gate voltage. With increasing bias the threshold hysteresis decreases, is even suppressed for a critical bias voltage and inverts its sign for higher biasing. We associate this bias controlled memory function to a bias voltage dependent gate efficiency of the quantum‐wire transistor. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Tuning the magnetic properties of ZnCdSe/ZnSe quantum dots by thermal annealing
Authors: Margapoti E. , Worschech L. , Mahapatra S. , Brunner K. , Bougerol C. , Forchel A. 
Published: November 2006

AbstractPhotoluminescence of ZnCdSe/ZnSe quantum dots treated by thermal annealing is investigated in magnetic fields up to 6 T. Thermal annealing leads to considerable changes of the circular polarization properties, which we attribute to different spin relaxation times and exciton lifetimes. A negative diamagnetic shift is observed for quantum dots showing the largest TA‐induced shift of 80 meV. Possible origins are discussed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimisation of quantum dot resonant tunnelling diodes for fibre wavelength detection
Authors: Li H. W. , Simmonds P. , Beere H. E. , Kardynal B. E. , See P. , Ritchie D. A. , Shields A. J. 
Published: November 2006

AbstractWe report the development of a quantum dot (QD) based photon detector at a fibre optic compatible wavelength. The device structure is based upon a lattice matched InGaAs/InAlAs resonant tunnelling diodes (RTD), grown on an InP substrate, containing a layer of self‐assembled QDs. The principle of operation is based upon sensing the change in the tunnelling current due to the capture of photo‐excited charges in quantum dots. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Biexcitonic complexes and the decay dynamics of trion and exciton in a single CdSe quantum dot
Authors: Koch M. , Kheng K. , Robin I. C. , André R. 
Published: November 2006

AbstractWe report dynamical studies of a single CdSe quantum dot for various excitation densities. Exciton and trion states refilling by recombination of neutral and charged biexciton is revealed by the observation of a delayed decay for the sharp trion and exciton lines respectively for increasing excitation intensity. The biexcitonic complexes lifetimes are then estimated from the rise time of the excitonic decays. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
InAs/InP quantum dots: from single to coupled dots applications
Authors: Cornet C. , Schliwa A. , Hayne M. , Chauvin N. , Doré F. , Even J. , Moshchalkov V. V. , Bimberg D. , Bremond G. , Bru‐Chevallier C. , Gendry M. , Loualiche S. 
Published: November 2006

AbstractWe report a brief overview of recent research developments on InAs/InP quantum dots (QDs). Eight‐band k · p calculations are performed on single InAs/InP QDs, and the impact of substrate orientation ((311)B or (100)) on electronic and optical properties is studied. A configuration interaction model is used to determine few‐particle states of these dots and a comparison with micro‐photoluminescence experiments on single InAs/InP QDs is made. It is then demonstrated that high QDs density can be reached on such a system, leading to lateral coupling between dots. Calculations and (magnetophoto‐) (photo‐) (electro‐) luminescence experiments are used to demonstrate that the lateral coupling leads to miniband effects, and to a better charge carrier redistribution between QDs for laser applications. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Human milk: Quantitative gas‐liquid chromatographic analysis of triglyceride and cholesterol content during lactation
Authors: Watts Rodney , Dils R. 
Published: November 2006

AbstractGas‐liquid chromatography has been used to follow changes in the triglyceride composition of human colostrum and milk from one donor during the first 10 days postpartum and to compare the compositions obtained with those at later stages of lactation.New triglycerides of low molecular weight appeared during the first 5 days postpartum. Lower molecular weight triglycerides (<C48) continued to increase until the eighth day. Triglyceride C48 and total cholesterol content remained almost constant during the period of the study.Comparison of triglyceride fatty acid composition on the third, sixth, and ninth days postpartum showed considerable specificity in all cases, but a tendency for randomization to occur as lactation proceeded.The advantage of triglyceride over fatty acid analysis for this type of investigation is that in the former, new molecules appear. In the latter, only changes in the proportions of fatty acids occur.
Studies on the preparation and analysis of glyceryl ether derivatives and the isolation and reductive ozonolysis of unsaturated glyceryl ethers
Authors: Ramachandran S. , Sprecher Howard W. , Cornwell David G. 
Published: November 2006

AbstractGlyceryl ethers were identified and quantified by the GLC analysis of their alkyl iodide (special conditions described), acetonide and allyl alkyl ether derivatives. The acetoxy‐mercuri‐methoxy derivatives of unsaturated glyceryl ether swere separated from saturated glyceryl ethers by TLC and the fractions were analyzed as alkyl iodides. Monoiodides from saturated glyceryl ethers and diiodides from unsaturated glyceryl ethers were also separated by TLC and then analyzed. Allyl alkyl ethers had small retention volumes and these derivatives were separated into pure fractions by preparative GLC. Ozonides were reduced either to alcohols with lithium aluminum hydrodie or to aldehydes with dimethyl sulfide. The alcohols were converted to mono‐ and diiodides which were separated by TLC and analyzed by GLC. The recovery of n‐C6 and n‐C7 monoiodides was not quantitative. Diiodides and aldehydes were both identified and quantified by GLC. Ozonolysis data suggest that the 16∶1 glyceryl ethers from dogfish liver oil contain 7,8 and 9,10 isomers and the 18∶1 glyceryl ethers contain 9,10 and 11,12 isomers.
Fatty acids in lipids of maturing wheat
Authors: Klopfenstein W. E. , Pomeranz Y. 
Published: November 2006

AbstractTwo varieties of hard red winter wheat were sampled at various stages of maturity. The lipids in those samples were fractionated into free polar, free nonpolar and bound lipids. Fatty acids of those fractions were determined. Major acids present were palmitic, oleic, linoleic and linolenic. Both wheat samples showed similar qualitative, but not quantitative patterns in distribution of fatty acids during maturation. In the free polar lipid fraction, the palmitic acid content decreased with maturation while the linoleic acid content increased. The free nonpolar fractions showed a slight increase in linoleic acid; the concentration of other acids decreased slightly as the wheat matured. The bound lipid fraction showed a marked increase in linoleic acid, accompanied by decreases in the other major fatty acids, especially linolenic.
The effect of antioxidant deficiency on tissue lipid composition in the rat. II. Liver
Authors: Witting L. A. , Theron J. J. , Horwitt M. K. 
Published: November 2006

AbstractThe hepatic phospholipids of the antioxidant‐deficient rat fed a source of both linoleate and linolenate showed a progressive net decrease in eicosapentaenoate, a progressive net increase in arachidonate, and there was a concomitant accumulation of fluorescent pigment of the lipofuscin or ceroid type in the tissue. An increased incorporation of isotopically labeled acetate into both the tetraenoic and pentaplus hexaenoic acid fractions was also noted, indicating that the disappearance of polyunsaturated fatty acids was partially countered by increased synthesis. Comparable results were obtained on diets containing either suboptimum or adequate levels of biologically available selenium. Vesicular dilation of the endoplasmic reticulum was noted in animals fed the tocopherol‐deficient diet. In separate experiments using a necrogenic diet containing torula yeast, these subcellular alterations were found to be prevented by tocopherol but not by selenium, although selenium supplementation did prevent macroscopically observable damage.
Comparison of antioxidant activities of tocol and its methyl derivatives
Authors: Olcott H. S. , Van der Veen J. 
Published: November 2006

AbstractIn tests with purified menhaden oil at 37C and with squalene at 37C and 50C, unsubstituted tocol, 7,8‐dimethyl tocol (γ‐tocol), and 8‐methyl tocol (σ‐tocol) were superior antioxidants to 5,7‐dimethyl tocol and 5,7,8‐trimethyl tocol (α‐tocol). In contrast to previous reports, there were no differences in the order of the activities of the tocopherols at different temperatures.
Fatty acid metabolism in the chloroplast lipids of green and blue‐green algae
Authors: Nichols B. W. 
Published: November 2006

AbstractThe pattern of uptake of radioactivity into chloroplast lipids when a green alga (Chlorella vulgaris) was incubated with sodium 2‐14C‐acetate differed appreciably from that obtained when two blue‐green algae (Anabaena cylindrica andAnacystis nidulans) were incubated under similar conditions.The fatty acids of the digalactosyl diglyceride and sulphoquinovosyl diglyceride fractions from the blue‐green algae were labeled more rapidly than were those of the corresponding fractions fromC. vulgaris, whereas the activity in the acids of the phosphatidyl glycerol fraction fromA. cylindrica andA. nidulans was relatively lower than that in the green alga. The results indicate that the metabolic behavior of chloroplast lipids may vary considerably according to the class of alga concerned.In all three alga, the evidence points to an intermediary function for the chloroplast lipids in fatty acid synthesis.Only limited exchange of acyl groups between the different chloroplast lipids seemed to occur during photoautotrophic growth.
Liver lipids during development
Authors: Baldwin Jerry , Cornatzer W. E. 
Published: November 2006

AbstractThe fatty acid composition of the major liver microsomal phospholipids has been studied during pre‐ and postnatal development of the rabbit. The fatty acid composition of the total lipids, phosphatidyl choline, and phosphatidyl ethanolamine from animals −6, −3, 0, +3, +6, +9, +16, and +112 days of age was determined. Fatty acid composition is similar in phosphatidyl choline and phosphatidyl ethanolamine for oleic acid at +3, +6, +9, and +16 day old animals; palmitoleic acid at +9 day old animals and linoleic acid at −6, −3, and 0 day old animals.Palmitoleic acid demonstrated a uniform decrease during early development in the total lipids and in both phosphatidyl choline and phosphatidyl ethanolamine; however, in the 112 day animal, the amount was just slightly lower than that observed for the earliest prenatal animal studied. Oleic acid decreased considerably during early postnatal development in the total lipids, phosphatidyl choline and phosphatidyl ethanolamine, but an increase in the 112 day animal was observed. Linoleic acid fluctuated considerably throughout postnatal development in the total lipids as well as in the two major phosphatides.Lecithin biosynthesis has been studied by two pathways during development of rabbit liver from −6 days to +110 days. The two pathways of lecithin biosynthesis were evaluated by assaying the activities of the liver enzymes choline phosphotransferase and phosphatidylmethyltransferase at different time intervals during development. The greater enzymatic activity was observed in the cholinephosphotransferase during development.