Liquid laser cavities

Liquid laser cavities have plenum chambers at the ends of the capillary cell which are terminated in transparent optical flats. By use of these cavities, several new europium chelates and a terbium chelate can provide laser action in solution at room temperature

Geology and Ground-Water Resources of the Lower South Platte River Valley Between Hardin, Colorado, and Paxton, Nebraska

The study of the geology and ground-water resources of the lower South Platte River valley was made by the Ground Water Branch of the U. S. Geological Survey at the request of the U. S. Bureau of Reclamation and with the endorsement of the Colorado Water Conservation Board. The area includes parts of Colorado and Nebraska, covers about 3,200 square miles, and ranges in altitude from about 3,000 to 5,000 feet above sea level. The average annual precipitation in the area is about 16 inches and is sufficient to support grasses and some grains. Irrigation utilizing water diverted from the river and pumped from wells is extensively developed in the valleys of the South Platte River and its tributaries. The principal agricultural products are Corn, sugar beets, alfalfa, beans, wheat, barley, and livestock. The rocks exposed in the area are sedimentary and range in age from Late Cretaceous to Recent. The Pierre shale underlies the entire area. The Fox Hills sandstone and the Laramie formation underlie the western part and the Chadron, Brule, and Ogallala formations underlie the eastern part. Pleistocene arid Recent alluvium underlies the valleys of the South Platte River and its tributaries. The Pierre shale ranges in thickness from about 2,500 feet near Paxton, Nebr., to about 6,500 feet near Hardin, Colo., and yields water in small quantities to wells in the vicinity of Sterling, Colo. Within the area, both the Fox Hills sandstone and the Laramie formation range in thickness from a featheredge to nearly 200 feet and yield small quantities of water to stock and domestic wells. Although a test hole near Proctor, Colo., was drilled 102 feet into the Chadron formation, the total thickness of the formation was not ascertained; no wells within the area covered by this investigation are known to derive water from the formation. The Brule formation ranges in thickness from a featheredge to more than 500 feet and yields water to wells from fractured or porous zones. The Ogallala formation ranges in thickness from a featheredge near Sedgwick, Colo., to about 350 feet near Paxton, Nebr., and yields large quantities of water to wells. The alluvium ranges in thickness from a featheredge at the edges of valleys to about 300 feet in some places in the valleys. The alluvium occurs in two physiographic forms Pleistocene and Recent terrace deposits and Recent floodplain deposits and yields abundant water to irrigation, public-supply, and other wells. Dune-sand deposits cover part of the area, range in thickness from a featheredge to about 100 feet, and yield water in small quantities to stock and domestic wells. Loess deposits cover much of the area and range in thickness from a featheredge to about 50 feet. Generally the loess is above the water table and is not known to yield water to wells

Analyzing false memories in children with associative lists specific for their age

Two experiments attempted to resolve previous contradictory findings concerning developmental trends in false memories within the Deese-Roediger-McDermott (DRM) paradigm by using an improved methodology-constructing age-appropriate associative lists. The research also extended the DRM paradigm to preschoolers. Experiment 1 (N = 320) included children in three age groups (preschoolers of 3-4 years, second-graders of 7-8 years, and preadolescents of 11-12 years) and adults, and Experiment 2 (N = 64) examined preschoolers and preadolescents. Age-appropriate lists increased false recall. Although preschoolers had fewer false memories than the other age groups, they showed considerable levels of false recall when tested with age-appropriate materials. Results were discussed in terms of fuzzy-trace, source-monitoring, and activation frameworks

Novel utilization of powder-suspension hybrid feedstock in HVAF spraying to deposit improved wear and corrosion resistant coatings

Deployment of a suspension feedstock has been known to alleviate problems associated with using sub-micron and nanosized powder feedstock for thermal spraying of monolithic as well as powder-suspension ‘hybrid’ composite coatings. However, a powder-suspension hybrid feedstock has never been previously used in high-velocity air-fuel (HVAF) spraying. In this work, for the very first time, a chromium carbide (Cr3C2) suspension has been co-sprayed along with an Inconel-625 (IN-625) powder by the HVAF process as an illustrative case study. Two variants of the IN-625 + Cr3C2 hybrid coatings were produced by varying relative powder-suspension feed rates. For comparison, pure IN-625 coating was also deposited utilizing identical spray parameters. Detailed microstructural characterization, porosity content, hardness measurement and phase analysis of the as-deposited coatings was performed. The suspension-derived carbides were retained in the bulk of the coating, resulting in higher hardness. In the dry sliding wear test, the hybrid coatings demonstrated lower wear rate and higher coefficient of friction (CoF) compared to the conventional, powder-derived IN-625 coatings. Furthermore, the wear rate improved slightly with an increase in Cr3C2 content in the hybrid coating. Post-wear analysis of the worn coating, worn alumina ball and the wear debris was performed to understand the wear mechanisms and material transfer in the investigated coatings. In the potentiodynamic polarization test, higher corrosion resistance for hybrid coatings than conventional IN-625 coatings was achieved, indicating that the incorporation of a secondary, carbide phase in the IN-625 matrix did not compromise its corrosion performance. This work demonstrates a novel approach to incorporate any finely distributed second phase in HVAF sprayed coatings to enhance their performance when exposed to harsh environments

Narrowband frequency tunable light source of continuous quadrature entanglement

We report the observation of non-classical quantum correlations of continuous light variables from a novel type of source. It is a frequency non-degenerate optical parametric oscillator below threshold, where signal and idler fields are separated by 740MHz corresponding to two free spectrum ranges of the parametric oscillator cavity. The degree of entanglement observed, - 3.8 dB, is the highest to-date for a narrowband tunable source suitable for atomic quantum memory and other applications in atomic physics. Finally we use the latter to visualize the Einstein-Podolsky-Rosen paradox.Comment: 11 pages, 9 figures, LaTe

Gain without population inversion in V-type systems driven by a frequency-modulated field

We obtain gain of the probe field at multiple frequencies in a closed three-level V-type system using frequency modulated pump field. There is no associated population inversion among the atomic states of the probe transition. We describe both the steady-state and transient dynamics of this system. Under suitable conditions, the system exhibits large gain simultaneously at series of frequencies far removed from resonance. Moreover, the system can be tailored to exhibit multiple frequency regimes where the probe experiences anomalous dispersion accompanied by negligible gain-absorption over a large bandwidth, a desirable feature for obtaining superluminal propagation of pulses with negligible distortion.Comment: 10 pages + 8 figures; To appear in Physical Review

Doppler-free frequency modulation spectroscopy of atomic erbium in a hollow cathode discharge cell

The erbium atomic system is a promising candidate for an atomic Bose-Einstein condensate of atoms with a non-vanishing orbital angular momentum ($L \neq 0$) of the electronic ground state. In this paper we report on the frequency stabilization of a blue external cavity diode laser system on the 400.91 $nm$ laser cooling transition of atomic erbium. Doppler-free saturation spectroscopy is applied within a hollow cathode discharge tube to the corresponding electronic transition of several of the erbium isotopes. Using the technique of frequency modulation spectroscopy, a zero-crossing error signal is produced to lock the diode laser frequency on the atomic erbium resonance. The latter is taken as a reference laser to which a second main laser system, used for laser cooling of atomic erbium, is frequency stabilized

Improving Strategies via SMT Solving

We consider the problem of computing numerical invariants of programs by abstract interpretation. Our method eschews two traditional sources of imprecision: (i) the use of widening operators for enforcing convergence within a finite number of iterations (ii) the use of merge operations (often, convex hulls) at the merge points of the control flow graph. It instead computes the least inductive invariant expressible in the domain at a restricted set of program points, and analyzes the rest of the code en bloc. We emphasize that we compute this inductive invariant precisely. For that we extend the strategy improvement algorithm of [Gawlitza and Seidl, 2007]. If we applied their method directly, we would have to solve an exponentially sized system of abstract semantic equations, resulting in memory exhaustion. Instead, we keep the system implicit and discover strategy improvements using SAT modulo real linear arithmetic (SMT). For evaluating strategies we use linear programming. Our algorithm has low polynomial space complexity and performs for contrived examples in the worst case exponentially many strategy improvement steps; this is unsurprising, since we show that the associated abstract reachability problem is Pi-p-2-complete