Synthesis of CdS/L-cys nanoparticles colloid solutions with predetermined optical properties

The purpose of this paper is to summarize experimental data of CdS/L-cystein nanoparticles (NPs) colloid solutions optical properties as function of 3-component mixture (Cd2+–S2 –L-cys) content. The NPs synthesis was carried out at pH 11 in the wide composition range based on literature data. The influence of the solutions composition on the colloids stability and the CdS/l-cys NPs size was monitored by absorption and fluorescence spectra observation at room temperature and studied by TEM. A polynomial model was used for the responses produced from Scheffe’s simplex lattice design with fourth degree terms. The paper also compares the results of two statistical-experimental methods, namely 2D Scheffe’s simplex-lattice design and 3D-plot by STATISTICA v6 program. Both models were found to be adequate for prediction the optical properties of the solutions but with various approximation level

Synthesis of CdS/L-cys nanoparticles colloid solutions with predetermined optical properties

The purpose of this paper is to summarize experimental data of CdS/L-cystein nanoparticles (NPs) colloid solutions optical properties as function of 3-component mixture (Cd2+–S2 –L-cys) content. The NPs synthesis was carried out at pH 11 in the wide composition range based on literature data. The influence of the solutions composition on the colloids stability and the CdS/l-cys NPs size was monitored by absorption and fluorescence spectra observation at room temperature and studied by TEM. A polynomial model was used for the responses produced from Scheffe’s simplex lattice design with fourth degree terms. The paper also compares the results of two statistical-experimental methods, namely 2D Scheffe’s simplex-lattice design and 3D-plot by STATISTICA v6 program. Both models were found to be adequate for prediction the optical properties of the solutions but with various approximation levels

Electron magnetotransport in GaAs/AlGaAs superlattices with weak and strong inter-well coupling

We report on magnetotransport measurements in two MBE-grown GaAs/AlGaAs superlattices formed by wide and narrow quantum wells and thin Si-doped barriers subject to tilted magnetic fields. It has been shown that illumination of the strongly coupled superlattice with narrow wells leads to reduction of its dimensionality from the 3D to 2D. The illumination-induced transition is revealed by remarkable change of magnetoresistance curves as compared to those measured before illumination. The experimental data along with tight-binding model calculations indicate that the illumination not only enhances the electron concentration but also suppresses the electron tunneling through the barriers.Comment: 3 pages, 3 figures, elsart/PHYEAUTH macros; presented on the LDSD 2007 Conference in the Caribbean Archipelago San Andres, Colombia. To be published as a special issue of Microelectronics Journal (Elsevier

In-plane Magnetic Field Dependent Magnetoresistance of Gated Asymmetric Double Quantum Wells

We have investigated experimentally the magnetoresistance of strongly asymmetric double-wells. The structures were prepared by inserting a thin Al$_{0.3}$Ga$_{0.7}$As barrier into the GaAs buffer layer of a standard modulation-doped GaAs/Al$_{0.3}$Ga$_{0.7}$As heterostructure. The resulting double-well system consists of a nearly rectangular well and of a triangular well coupled by tunneling through the thin barrier. With a proper choice of the barrier parameters one can control the occupancy of the two wells and of the two lowest (bonding and antibonding) subbands. The electron properties can be further influenced by applying front- or back-gate voltage.Comment: 4 pages, 5 figures, elsart/PHYEAUTH macros; to be presented on the EP2DS-15 Conference in Nara, Japan. Revised version. To appear in Physica

Magnetoresistance oscillations in GaAs/AlGaAs superlattices subject to in-plane magnetic fields

The MBE-grown GaAs/AlGaAs superlattice with Si-doped barriers has been used to study a 3D-2D transition under the influence of the in-plane component of applied magnetic field. The longitudinal magnetoresistance data measured in tilted magnetic fields have been interpreted in terms of a simple tight-binding model. The data provide values of basic parameters of the model and make it possible to reconstruct the superlattice Fermi surface and to calculate the density of states for the lowest Landau subbands. Positions of van Hove singularities in the DOS agree excellently with magnetoresistance oscillations, confirming that the model describes adequately the magnetoresistance of strongly coupled semiconductor superlattices.Comment: 4 pages, 3 figures, elsart/PHYEAUTH macros; presented on the EP2DS-16 Conference in Albuquerque, New Mexico USA. To be published in Physica

Kerr non-linearity in a superconducting Josephson metamaterial

We present a detailed experimental and theoretical analysis of the dispersion and non-linear Kerr frequency shifts of plasma modes in a one-dimensional Josephson junction chain containing 500 SQUIDs in the regime of weak nonlinearity. The measured low-power dispersion curve agrees perfectly with the theoretical model if we take into account the Kerr renormalisation of the bare frequencies and the long-range nature of the island charge screening by a remote ground plane. We measured the self- and cross-Kerr shifts for the frequencies of the eight lowest modes in the chain. We compare the measured Kerr coefficients with theory and find good agreement

Three-body correlations in direct reactions: Example of 6^{6}Be populated in (p,n)(p,n) reaction

The $^{6}$Be continuum states were populated in the charge-exchange reaction $^1$H($^{6}$Li,$^{6}$Be)$n$ collecting very high statistics data ($\sim 5 \times 10^6$ events) on the three-body $\alpha$+$p$+$p$ correlations. The $^{6}$Be excitation energy region below $\sim 3$ MeV is considered, where the data are dominated by contributions from the $0^+$ and $2^+$ states. It is demonstrated how the high-statistics few-body correlation data can be used to extract detailed information on the reaction mechanism. Such a derivation is based on the fact that highly spin-aligned states are typically populated in the direct reactions.Comment: submitted to Physical Review

New insight into the low-energy 9^9He spectrum

The spectrum of $^9$He was studied by means of the $^8$He($d$,$p$)$^9$He reaction at a lab energy of 25 MeV/n and small center of mass (c.m.) angles. Energy and angular correlations were obtained for the $^9$He decay products by complete kinematical reconstruction. The data do not show narrow states at $\sim$1.3 and $\sim$2.4 MeV reported before for $^9$He. The lowest resonant state of $^9$He is found at about 2 MeV with a width of $\sim$2 MeV and is identified as $1/2^-$. The observed angular correlation pattern is uniquely explained by the interference of the $1/2^-$ resonance with a virtual state $1/2^+$ (limit on the scattering length is obtained as $a > -20$ fm), and with the $5/2^+$ resonance at energy $\geq 4.2$ MeV.Comment: 5 pages, 4 figures, 2 table