Synthetic, Crystallographic, and Computational Study of Copper(II) Complexes of Ethylenediaminetetracarboxylate Ligands

Copper(II) complexes of hexadentate ethylenediaminetetracarboxylic acid type ligands H4eda3p and H4eddadp (H4eda3p = ethylenediamine-N-acetic-N,N′,N′-tri-3-propionic acid; H4eddadp = ethylenediamine-N,N′-diacetic-N,N′-di-3-propionic acid) have been prepared. An octahedral trans(O6) geometry (two propionate ligands coordinated in axial positions) has been established crystallographically for the Ba[Cu(eda3p)]·8H2O compound, while Ba[Cu(eddadp)]·8H2O is proposed to adopt a trans(O5) geometry (two axial acetates) on the basis of density functional theory calculations and comparisons of IR and UV−vis spectral data. Experimental and computed structural data correlating similar copper(II) chelate complexes have been used to better understand the isomerism and departure from regular octahedral geometry within the series. The in-plane O−Cu−N chelate angles show the smallest deviation from the ideal octahedral value of 90°, and hence the lowest strain, for the eddadp complex with two equatorial β-propionate rings. A linear dependence between tetragonality and the number of five-membered rings has been established. A natural bonding orbital analysis of the series of complexes is also presented.

Symmetry of k·p Hamiltonian in pyramidal InAs/GaAs quantum dots: Application to the calculation of electronic structure

A method for the calculation of the electronic structure of pyramidal self-assembled InAs/GaAs quantum dots is presented. The method is based on exploiting the C-4 symmetry of the 8-band k·p Hamiltonian with the strain taken into account via the continuum mechanical model. The operators representing symmetry group elements were represented in the plane wave basis and the group projectors were used to find the symmetry adapted basis in which the corresponding Hamiltonian matrix is block diagonal with four blocks of approximately equal size. The quantum number of total quasiangular momentum is introduced and the states are classified according to its value. Selection rules for interaction with electromagnetic field in the dipole approximation are derived. The method was applied to calculate electron and hole quasibound states in a periodic array of vertically stacked pyramidal self-assembled InAs/GaAs quantum dots for different values of the distance between the dots and external axial magnetic field. As the distance between the dots in an array is varied, an interesting effect of simultaneous change of ground hole state symmetry, type, and the sign of miniband effective mass is predicted. This effect is explained in terms of the change of biaxial strain. It is also found that the magnetic field splitting of Kramer's double degenerate states is most prominent for the first and second excited state in the conduction band and that the magnetic field can both separate otherwise overlapping minibands and concatenate otherwise nonoverlapping minibands

Measuring the Superfluid Fraction of an Ultracold Atomic Gas

We propose a method to measure the superfluid fraction of an atomic gas. The method involves the use of a vector potential generated by optical beams with non-zero angular momentum to simulate uniform rotation. The induced change in angular momentum of the atomic gas can be measured spectroscopically. This allows a direct determination of the superfluid fraction.Comment: 4 pages, 2 figure

Efficient Production of Large 39K Bose-Einstein Condensates

We describe an experimental setup and the cooling procedure for producing 39K Bose-Einstein condensates of over 4x10^5 atoms. Condensation is achieved via a combination of sympathetic cooling with 87Rb in a quadrupole-Ioffe-configuration (QUIC) magnetic trap, and direct evaporation in a large volume crossed optical dipole trap, where we exploit the broad Feshbach resonance at 402 G to tune the 39K interactions from weak and attractive to strong and repulsive. In the same apparatus we create quasi-pure 87Rb condensates of over 8x10^5 atoms.Comment: 7 pages, 5 figures; figure font compatibility improve

An arbitrary-function light power controller

We describe the design, applications, and performance of a simple light power controller. The device is built on a fiber-coupled electro-optic modulator with an active electronic feedback. It can be used to actively stabilize laser power or to impress an arbitrary waveform onto the power. The bandwidth of the device is ∼70 kHz

Spectroscopic insensitivity to cold collisions in a two-state mixture of fermions

We have experimentally demonstrated the absence of spectroscopic resonance shifts in a mixture of two interacting Fermi gases. This result is linked to observations in an ultracold gas of thermal bosons. There, the measured resonance shift due to interstate collisions is independent of the coherence in the system, and twice that expected from the equilibrium energy splitting between the two states in a fully decohered cloud. We give a simple theoretical explanation of these observations, which elucidates the effect of coherent radiation on an incoherent mixture of atoms

Effects of Interactions on the Critical Temperature of a Trapped Bose Gas

We perform high-precision measurements of the condensation temperature of a harmonically-trapped atomic Bose gas with widely-tuneable interactions. For weak interactions we observe a negative shift of the critical temperature in excellent agreement with mean-field theory. However for sufficiently strong interactions we clearly observe an additional positive shift, characteristic of beyond-mean-field critical correlations. We also discuss non-equilibrium effects on the apparent critical temperature for both very weak and very strong interactions.Comment: 4 pages, 4 figure

Online burst detection in a water distribution system using the Kalman filter and hydraulic modelling

PublishedThis paper presents a burst detection methodology that utilizes distributed real time sensor data in a district metered area using a data assimilation method and a hydraulic model. A sensitivity analysis was applied to evaluate the performance of various burst detection metrics under different conditions, and to identify appropriate thresholds for online burst detection using artificial generated burst events. It was found that the best performing metrics are the corrected flow residual and normalized corrected flow residual. This metric can be effective to detect bursts in a timely and reliable manner within a district metering area under assumed test conditions

Hydro-geological properties of the Savian aquifer in the county Obrenovac

The paper presents a description of hydrogeological researches of alluvial layers of the Sava River in the area of the source "Vić Bare" near Obrenovac. This source supplies groundwater to that town. The depth of these layers amounts to 25 m. With regard to collecting capacity, the most significant are gravel-sand sediments of high filtration properties. Their average depth amounts to about 13 m with the underlying layer made of Pleistocene clays. Compact aquifer is formed within these sediments and it refills partly from the Sava River at places where river cuts its channel into the gravel-sand layer. The analysis of the groundwater regime in the riparian area points out that groundwater levels follow stages of the Sava River. Such an influence lessens with the distance. Established hydraulic connection between the river and the aquifer enables its permanent replenishment. On the other hand, due to certain pollutions this river flow might bring along, it represents a potential danger. Those pollutions could enter water-bearing layer of the aquifer as well as the exploitation well of the source. Such presumptions have been confirmed in the experiment of pollution transport carried out in the water-bearing layer. Unabsorbable chloride was used as a tracer whose movement velocity through exploitation well proved that there were real possibilities of intrusion of aggressive pollutants into the water-bearing layer and into the aquifer as well. Therefore, the protection of the source must be in the function of the protection of surface waters