Rapid Reservoir Sedimentation of Four Historic Thin Arch Dams in Australia

Waters flowing in streams and rivers have the ability to scour channel beds, to carry particles (heavier than water) and to deposit materials. This phenomenon of sediment transport can affect substantially the design of reservoirs. The paper describes four case studies of siltation which rendered useless water storage structures in less than 25 years. Although each dam had advanced structural features, the hydrology of the catchment and sediment transport processes were not properly taken into account. The study highlights practical situations in which a reservoir must be analysed as a complete system, taking into account structural features, hydraulics, hydrology, sediment transport, catchment erosion and catchment management. The case studies may used as teaching examples to increase student interest on the significance of sediment transport problems and to emphasise the design procedure to professionals. They may serve also to alert the community at large to basic errors caused by improper soil conservation policy and the inability to predict sediment-load process

Characterizing CO Fourth Positive Emission in Young Circumstellar Disks

Carbon Monoxide is a commonly used IR/sub-mm tracer of gas in protoplanetary disks. We present an analysis of ultraviolet CO emission in {HST}-COS spectra for 12 Classical T Tauri stars. Several ro-vibrational bands of the CO A^1\Pi - X^1\Sigma^+ (Fourth Positive) electronic transition system are spectrally resolved from emission of other atoms and H_2. The CO A^1\Pi v'=14 state is populated by absorption of Ly\alpha photons, created at the accretion column on the stellar surface. For targets with strong CO emission, we model the Ly\alpha radiation field as an input for a simple fluorescence model to estimate CO rotational excitation temperatures and column densities. Typical column densities range from N_{CO} = 10^{18} - 10^{19} cm^{-2}. Our measured excitation temperatures are mostly below T_{CO} = 600 K, cooler than typical M-band CO emission. These temperatures and the emission line widths imply that the UV emission originates in a different population of CO than that which is IR-emitting. We also find a significant correlation between CO emission and the disk accretion rate M_{acc} and age. Our analysis shows that ultraviolet CO emission can be a useful diagnostic of CTTS disk gas

Experimental quantum tomography of photonic qudits via mutually unbiased basis

We present the experimental quantum tomography of 7- and 8-dimensional quantum systems based on projective measurements in the mutually unbiased basis (MUB-QT). One of the advantages of MUB-QT is that it requires projections from a minimal number of bases to be performed. In our scheme, the higher dimensional quantum systems are encoded using the propagation modes of single photons, and we take advantage of the capabilities of amplitude- and phase-modulation of programmable spatial light modulators to implement the MUB-QT.Comment: Published versio

The Far-Ultraviolet "Continuum" in Protoplanetary Disk Systems II: CO Fourth Positive Emission and Absorption

We exploit the high sensitivity and moderate spectral resolution of the $HST$-Cosmic Origins Spectrograph to detect far-ultraviolet spectral features of carbon monoxide (CO) present in the inner regions of protoplanetary disks for the first time. We present spectra of the classical T Tauri stars HN Tau, RECX-11, and V4046 Sgr, representative of a range of CO radiative processes. HN Tau shows CO bands in absorption against the accretion continuum. We measure a CO column density and rotational excitation temperature of N(CO) = 2 +/- 1 $\times$ 10$^{17}$ cm$^{-2}$ and T_rot(CO) 500 +/- 200 K for the absorbing gas. We also detect CO A-X band emission in RECX-11 and V4046 Sgr, excited by ultraviolet line photons, predominantly HI LyA. All three objects show emission from CO bands at $\lambda$ $>$ 1560 \AA, which may be excited by a combination of UV photons and collisions with non-thermal electrons. In previous observations these emission processes were not accounted for due to blending with emission from the accretion shock, collisionally excited H$_{2}$, and photo-excited H2; all of which appeared as a "continuum" whose components could not be separated. The CO emission spectrum is strongly dependent upon the shape of the incident stellar LyA emission profile. We find CO parameters in the range: N(CO) 10$^{18-19}$ cm$^{-2}$, T_{rot}(CO) > 300 K for the LyA-pumped emission. We combine these results with recent work on photo- and collisionally-excited H$_{2}$ emission, concluding that the observations of ultraviolet-emitting CO and H2 are consistent with a common spatial origin. We suggest that the CO/H2 ratio in the inner disk is ~1, a transition between the much lower interstellar value and the higher value observed in solar system comets today, a result that will require future observational and theoretical study to confirm.Comment: 12 pages, 7 figures, 3 tables. ApJ - accepte

Adaptive optics imaging and optical spectroscopy of a multiple merger in a luminous infrared galaxy

(abridged) We present near-infrared (NIR) adaptive optics imaging obtained with VLT/NACO and optical spectroscopy from the Southern African Large Telescope (SALT) of a luminous infrared galaxy (LIRG) IRAS 19115-2124. These data are combined with archival HST imaging and Spitzer imaging and spectroscopy, allowing us to study this disturbed interacting/merging galaxy, dubbed the Bird, in extraordinary detail. In particular, the data reveal a triple system where the LIRG phenomenon is dominated by the smallest of the components. One nucleus is a regular barred spiral with significant rotation, while another is highly disturbed with a surface brightness distribution intermediate to that of disk and bulge systems, and hints of remaining arm/bar structure. We derive dynamical masses in the range 3-7x10^10 M_solar for both. The third component appears to be a 1-2x10^10 M_solar mass irregular galaxy. The total system exhibits HII galaxy-like optical line ratios and strengths, and no evidence for AGN activity is found from optical or mid-infrared data. The star formation rate is estimated to be 190 M_solar/yr. We search for SNe, super star clusters, and detect 100-300 km/s outflowing gas from the Bird. Overall, the Bird shows kinematic, dynamical, and emission line properties typical for cool ultra luminous IR galaxies. However, the interesting features setting it apart for future studies are its triple merger nature, and the location of its star formation peak - the strongest star formation does not come from the two major K-band nuclei, but from the third irregular component. Aided by simulations, we discuss scenarios where the irregular component is on its first high-speed encounter with the more massive components.Comment: 24 pages, 16 figures. Accepted MNRAS version, minor corrections only, references added. Higher resolution version (1.3MB) is available from http://www.saao.ac.za/~petri/bird/ulirg_bird_highres_vaisanen_v2.pd

The Cosmic Origins Spectrograph

The Cosmic Origins Spectrograph (COS) is a moderate-resolution spectrograph with unprecedented sensitivity that was installed into the Hubble Space Telescope (HST) in May 2009, during HST Servicing Mission 4 (STS-125). We present the design philosophy and summarize the key characteristics of the instrument that will be of interest to potential observers. For faint targets, with flux F(sub lambda) approximates 1.0 X 10(exp -14) ergs/s/cm2/Angstrom, COS can achieve comparable signal to noise (when compared to STIS echelle modes) in 1-2% of the observing time. This has led to a significant increase in the total data volume and data quality available to the community. For example, in the first 20 months of science operation (September 2009 - June 2011) the cumulative redshift pathlength of extragalactic sight lines sampled by COS is 9 times that sampled at moderate resolution in 19 previous years of Hubble observations. COS programs have observed 214 distinct lines of sight suitable for study of the intergalactic medium as of June 2011. COS has measured, for the first time with high reliability, broad Lya absorbers and Ne VIII in the intergalactic medium, and observed the HeII reionization epoch along multiple sightlines. COS has detected the first CO emission and absorption in the UV spectra of low-mass circumstellar disks at the epoch of giant planet formation, and detected multiple ionization states of metals in extra-solar planetary atmospheres. In the coming years, COS will continue its census of intergalactic gas, probe galactic and cosmic structure, and explore physics in our solar system and Galaxy

The Cosmic Origins Spectrograph

The Cosmic Origins Spectrograph (COS) is a moderate-resolution spectrograph with unprecedented sensitivity that was installed into the Hubble Space Telescope (HST) in May 2009, during HST Servicing Mission 4 (STS-125). We present the design philosophy and summarize the key characteristics of the instrument that will be of interest to potential observers. For faint targets, with flux F_lambda ~ 1.0E10-14 ergs/s/cm2/Angstrom, COS can achieve comparable signal to noise (when compared to STIS echelle modes) in 1-2% of the observing time. This has led to a significant increase in the total data volume and data quality available to the community. For example, in the first 20 months of science operation (September 2009 - June 2011) the cumulative redshift pathlength of extragalactic sight lines sampled by COS is 9 times that sampled at moderate resolution in 19 previous years of Hubble observations. COS programs have observed 214 distinct lines of sight suitable for study of the intergalactic medium as of June 2011. COS has measured, for the first time with high reliability, broad Lya absorbers and Ne VIII in the intergalactic medium, and observed the HeII reionization epoch along multiple sightlines. COS has detected the first CO emission and absorption in the UV spectra of low-mass circumstellar disks at the epoch of giant planet formation, and detected multiple ionization states of metals in extra-solar planetary atmospheres. In the coming years, COS will continue its census of intergalactic gas, probe galactic and cosmic structure, and explore physics in our solar system and Galaxy.Comment: 17 pages, 15 figure

Unrestricted generation of pure two-qubit states and entanglement diagnosis by single-qubit tomography

We present an experimental proof-of-principle for the generation and detection of pure two-qubit states which have been encoded in degrees of freedom that are common to both classical-light beams and single photons. Our protocol requires performing polarization tomography on a single qubit from a qubit pair. The degree of entanglement in the qubit pair is measured by concurrence, which can be directly extracted from intensity measurements – or photon counting – entering single-qubit polarization tomography

The Apache Point Observatory Galactic Evolution Experiment (APOGEE)

The Apache Point Observatory Galactic Evolution Experiment (APOGEE), one of the programs in the Sloan Digital Sky Survey III (SDSS-III), has now completed its systematic, homogeneous spectroscopic survey sampling all major populations of the Milky Way. After a three-year observing campaign on the Sloan 2.5 m Telescope, APOGEE has collected a half million high-resolution (R ~ 22,500), high signal-to-noise ratio (>100), infrared (1.51–1.70 μm) spectra for 146,000 stars, with time series information via repeat visits to most of these stars. This paper describes the motivations for the survey and its overall design—hardware, field placement, target selection, operations—and gives an overview of these aspects as well as the data reduction, analysis, and products. An index is also given to the complement of technical papers that describe various critical survey components in detail. Finally, we discuss the achieved survey performance and illustrate the variety of potential uses of the data products by way of a number of science demonstrations, which span from time series analysis of stellar spectral variations and radial velocity variations from stellar companions, to spatial maps of kinematics, metallicity, and abundance patterns across the Galaxy and as a function of age, to new views of the interstellar medium, the chemistry of star clusters, and the discovery of rare stellar species. As part of SDSS-III Data Release 12 and later releases, all of the APOGEE data products are publicly available