Low-velocity matter wave source for atom interferometry produced by Zeeman-tuned laser cooling and magneto-optic trapping

A continuous, low-velocity, nearly monochromatic atomic beam is created using laser cooling and two-dimensional magneto-optic trapping. Rubidium atoms from an effusive oven are slowed and cooled using Zeeman-tuned slowing. The scattering force from a counter-propagating, frequency-stabilized diode laser beam is used to decelerate the thermal beam of atoms to a velocity of ~ 20 m/s. A spatially varying magnetic field is used to Zeeman shift the resonance frequency of the atom to compensate for the changing Doppler shift, thereby keeping the slowing atoms resonant with the fixed frequency laser. This slowing process also cools the beam of atoms to a temperature of a few Kelvin. The slow beam of atoms is loaded into a two-dimensional magneto-optic trap or atomic funnel. The atoms are trapped along the axis of the funnel and experience a molassestype damping force in all three spatial dimensions. By frequency shifting the laser beams used to make the trap, the atoms are ejected at a controllable velocity. The continuous matter-wave source has a controllable beam velocity in the range of 2 to 15 m/s, longitudinal and transverse temperatures of approximately 500 μK, and a flux of 3.4 x10⁹ atoms/s. At 10 m/s, the de Broglie wavelength of the beam is 0.5 nm. The spatial profile of the atomic beam was characterized 30 cm from the exit of the atomic funnel using a surface ionization detector. The low-velocity atomic beam is an ideal source for atom interferometry and a variety of applications in the field of atom optics

Two-photon spectroscopy of rubidium using a grating-feedback diode laser

We describe an experiment for investigating the 5S1/2→5D5/2 two-photon transition in rubidium using a single grating-feedback diode laser operating at 778.1nm (385 THz). Continuous tuning of the laser frequency over 4GHz allows for the clear resolution of the Doppler-free spectral features and allows accurate measurement of the hyperfine ground-state splitting. A direct comparison between Doppler-broadened and Doppler-free spectral features is possible because both are distinctly evident in the two-photon spectra. By independently modifying the polarization state of the two laser fields, the impact of electric dipole selection rules on the two-photon transition spectra is investigated. This experiment is a valuable addition to the advanced undergraduate laboratory because it uses much of the same equipment as the single-photon saturated absorption spectroscopy experiment performed on the 5S1/2→5P3/2 transition in rubidium(λ=780.24nm) and provides students with an opportunity to investigate characteristics of atomic spectra not evident in the single-photon experiment

Rubidium atomic funnel

A low-velocity beam of rubidium atoms is produced from a two-dimensional magneto-optic trap or atomic funnel. Atoms from a thermal beam are slowed by chirped laser cooling and then loaded into the funnel. The cold atoms are ejected by moving molasses formed with frequency-shifted laser beams. The resultant atomic beam has a controllable velocity in the range of 3 to 10 m/s, a temperature of 500 μK, and a flux of 1010 atoms/s

Collimated blue light generation in rubidium vapor

We describe an experiment for generating and characterizing a beam of collimated blue light (CBL) in a rubidium vapor.Two low-power, grating-feedback diode lasers, operating at 780.2 nm (5S3/2 → 5D5/2) and 776.0 nm (5P3/2 → 5D5/2), respectively, provide step-wise excitation to the 5D excited state in rubidium. Under the right experimental conditions, cascade decay through the 6P excited state will yield a collimated blue (420-nm) beam of light with high temporal and spatial coherence. We investigate the production of a blue beam under a variety of experimental conditions and characterize the spatial coherence and spectral characteristics. This experiment provides advanced undergraduate students with a unique opportunity to investigate nonlinear optical phenomena in the laboratory and uses equipment that is commonly available in laboratories equipped to investigate diode-laser-based absorption spectroscopy in rubidium

Collimated blue light generation in rubidium vapor

We describe an experiment for generating and characterizing a beam of collimated blue light (CBL) in a rubidium vapor.Two low-power, grating-feedback diode lasers, operating at 780.2 nm (5S3/2 → 5D5/2) and 776.0 nm (5P3/2 → 5D5/2), respectively, provide step-wise excitation to the 5D excited state in rubidium. Under the right experimental conditions, cascade decay through the 6P excited state will yield a collimated blue (420-nm) beam of light with high temporal and spatial coherence. We investigate the production of a blue beam under a variety of experimental conditions and characterize the spatial coherence and spectral characteristics. This experiment provides advanced undergraduate students with a unique opportunity to investigate nonlinear optical phenomena in the laboratory and uses equipment that is commonly available in laboratories equipped to investigate diode-laser-based absorption spectroscopy in rubidium

Supermassive Black Hole Binaries: The Search Continues

Gravitationally bound supermassive black hole binaries (SBHBs) are thought to be a natural product of galactic mergers and growth of the large scale structure in the universe. They however remain observationally elusive, thus raising a question about characteristic observational signatures associated with these systems. In this conference proceeding I discuss current theoretical understanding and latest advances and prospects in observational searches for SBHBs.Comment: 17 pages, 4 figures. To appear in the Proceedings of 2014 Sant Cugat Forum on Astrophysics. Astrophysics and Space Science Proceedings, ed. C.Sopuerta (Berlin: Springer-Verlag

Gene content evolution in the arthropods

Arthropods comprise the largest and most diverse phylum on Earth and play vital roles in nearly every ecosystem. Their diversity stems in part from variations on a conserved body plan, resulting from and recorded in adaptive changes in the genome. Dissection of the genomic record of sequence change enables broad questions regarding genome evolution to be addressed, even across hyper-diverse taxa within arthropods. Using 76 whole genome sequences representing 21 orders spanning more than 500 million years of arthropod evolution, we document changes in gene and protein domain content and provide temporal and phylogenetic context for interpreting these innovations. We identify many novel gene families that arose early in the evolution of arthropods and during the diversification of insects into modern orders. We reveal unexpected variation in patterns of DNA methylation across arthropods and examples of gene family and protein domain evolution coincident with the appearance of notable phenotypic and physiological adaptations such as flight, metamorphosis, sociality, and chemoperception. These analyses demonstrate how large-scale comparative genomics can provide broad new insights into the genotype to phenotype map and generate testable hypotheses about the evolution of animal diversity

Effectiveness of a computer assisted learning (CAL) package to raise awareness of autism

<p>Abstract</p> <p>Background</p> <p>Promoting awareness of autism in populations who work with children may result in an earlier diagnosis of the condition. In this study, a computer assisted learning (CAL) package, containing educationally appropriate knowledge about autism was developed; and the effectiveness of this CAL package was evaluated.</p> <p>Methods</p> <p>The CAL package was developed using computer software, "Xerte" and "Flash Macromedia". The effectiveness of the CAL package was evaluated in 32 childcare students in the UK, who were randomised to watch the CAL package or to read the information leaflet containing the same information (n = 16 in each group). Retention performance, level of enjoyment, and level of confidence to identify a child with autism, after the interventions, were evaluated. The data obtained from two studied groups was analysed using unpaired Student's t-test, 95% confidence interval, and effect size.</p> <p>Results</p> <p>Students who watched the CAL package had superior retention performance percentage scores (p = 0.02, 95% CI = 0.83–12.19, effect size = 0.8) and level of enjoyment (p = 0.04, 95% CI = 0.03–2.75, effect size = 0.7) compared with students who read the information leaflet. However, there was no significant difference in level of confidence to identify a child with autism (p = 0.39, 95% CI = -1.80–0.72, effect size = -0.3).</p> <p>Conclusion</p> <p>The CAL package developed was an effective method of educating people who work with children about autism.</p