Versatile Digital GHz Phase Lock for External Cavity Diode Lasers

We present a versatile, inexpensive and simple optical phase lock for applications in atomic physics experiments. Thanks to all-digital phase detection and implementation of beat frequency pre-scaling, the apparatus requires no microwave-range reference input, and permits phase locking at frequency differences ranging from sub-MHz to 7 GHz (and with minor extension, to 12 GHz). The locking range thus covers ground state hyperfine splittings of all alkali metals, which makes this system a universal tool for many experiments on coherent interaction between light and atoms.Comment: 4.5 pages, 5 figures v3: fixed error in schematic: R10 connects to other end of C

A Monolithic Filter Cavity for Experiments in Quantum Optics

By applying a high-reflectivity dielectric coating on both sides of a commercial plano-convex lens, we produce a stable monolithic Fabry-Perot cavity suitable for use as a narrow band filter in quantum optics experiments. The resonant frequency is selected by means of thermal expansion. Owing to the long term mechanical stability, no optical locking techniques are required. We characterize the cavity performance as an optical filter, obtaining a 45 dB suppression of unwanted modes while maintaining a transmission of 60%.Comment: 4 pages, 4 figure

Coherent magnon optics in a ferromagnetic spinor Bose-Einstein condensate

We measure the mass, gap, and magnetic moment of a magnon in the ferromagnetic $F=1$ spinor Bose-Einstein condensate of $^{87}$Rb. We find an unusually heavy magnon mass of $1.038(2)_\mathrm{stat}(8)_\mathrm{sys}$ times the atomic mass, as determined by interfering standing and running coherent magnon waves within the dense and trapped condensed gas. This measurement is shifted significantly from theoretical estimates. The magnon energy gap of $h\times 2.5(1)_\mathrm{stat}(2)_\mathrm{sys}\;\mathrm{Hz}$ and the effective magnetic moment of $-1.04(2)_\mathrm{stat}(8)\,\mu_\textrm{bare}$ times the atomic magnetic moment are consistent with mean-field predictions. The nonzero energy gap arises from magnetic dipole-dipole interactions.Comment: 5 pages, 3 figure

Transverse multi-mode effects on the performance of photon-photon gates

The multi-mode character of quantum fields imposes constraints on the implementation of high-fidelity quantum gates between individual photons. So far this has only been studied for the longitudinal degree of freedom. Here we show that effects due to the transverse degrees of freedom significantly affect quantum gate performance. We also discuss potential solutions, in particular separating the two photons in the transverse direction.Comment: 5 pages, 3 figures, published versio

Novel enantiopure bis(pyrrolo)tetrathiafulvalene donors exhibiting chiral crystal packing arrangements

Two novel enantiopure bis(pyrrolo[3,4-d])tetrathiafulvalene derivatives, substrates for preparing chiral conducting materials, show chiral crystal packing arrangements in which successive layers are rotated in accordance with an exact or approximate 43 axis. The corresponding donors containing fused dihydropyrrolegroups, and thus four more hydrogen atoms, form stacks along a crystal axis

Fecal pollution in water from storm sewers and adjacent seashores in Natal, Rio Grande do Norte, Brazil

A study on the distribution patterns of enteropathogenic bacteria polluting the shoreline in Natal, Rio Grande do Norte, Brazil, was carried out based on 72 samples obtained from three storm sewers and adjoining beach locations, Praia do Meio (PM), Areia Preta (AP) and Ponta Negra (PN). From each location, 12 water samples were taken and analyzed for fecal coliforms (FC) and Escherichia coli. In AP, two (16.7%) of the seawater samples and five (41.7%) of the storm sewer samples yielded values above 1.1 × 107 FC/100 ml, whereas only one (8.3%) of the samples from PM reached this level. There was no correlation (p > 0.05) between rainfall indeces and FC values. A total of 64 E. coli isolates were obtained: 37 from the storm sewer samples and 27 from the seawater samples. Of these isolates, four (O143, two O112ac, and O124) were enteroinvasive and two (O111 and O125) were enteropathogenic. Resistance to antibiotics and to heavy metals was also analyzed. Almost 36% of the E. coli strains isolated were resistant to more than one antibiotic. All strains were resistant to zinc and copper at the highest concentration tested (250 μg/ml), and several (23.4%) were resistant to mercury at 50 μg/ml. Our results agreed with previous reports that antibiotic resistance is commonly associated with heavy-metal resistance in pathogens. [Int Microbiol 2004; 7(3):213–218

A multinuclear solid state NMR, density functional theory and X-Ray diffraction study of hydrogen bonding in Group I hydrogen dibenzoates

An NMR crystallographic approach incorporating multinuclear solid state NMR (SSNMR), X-ray structure determinations and density functional theory (DFT) are used to characterise the H bonding arrangements in benzoic acid (BZA) and the corresponding Group I alkali metal hydrogen dibenzoates (HD) systems. Since the XRD data often cannot precisely confirm the proton position within the hydrogen bond, the relationship between the experimental SSNMR parameters and the ability of gauge included plane augmented wave (GIPAW) DFT to predict them becomes a powerful constraint that can assist with further structure refinement. Both the 1H and 13C MAS NMR methods provide primary descriptions of the H bonding via accurate measurements of the 1H and 13C isotropic chemical shifts, and the individual 13C chemical shift tensor elements; these are unequivocally corroborated by DFT calculations, which together accurately describe the trend of the H bonding strength as the size of the monovalent cation changes. In addition, 17O MAS and DOR NMR form a powerful combination to characterise the O environments, with the DOR technique providing highly resolved 17O NMR data which helps verify unequivocally the number of inequivalent O positions for the conventional 17O MAS NMR to process. Further multinuclear MAS and static NMR studies involving the quadrupolar 7Li, 39K, 87Rb and 133Cs nuclei, and the associated DFT calculations, provide trends and a corroboration of the H bond geometry which assist in the understanding of these arrangements. Even though the crystallographic H positions in each H bonding arrangement reported from the single crystal X-ray studies are prone to uncertainty, the good corroboration between the measured and DFT calculated chemical shift and quadrupole tensor parameters for the Group I alkali species suggest that these reported H positions are reliable