Flow and acoustic characteristics of subsonic and supersonic jets from convergent nozzle

Acoustic and flow characteristics of subsonic and supersonic jets from convergent nozzle

Coping with the Cold: An Ecological Context for the Abundance and Distribution of Rock Sandpipers during Winter in Upper Cook Inlet, Alaska

Shorebirds are conspicuous and abundant at high northern latitudes during spring and summer, but as seasonal conditions deteriorate, few remain during winter. To the best of our knowledge, Cook Inlet, Alaska (60.6˚ N, 151.6˚ W), is the world’s coldest site that regularly supports wintering populations of shorebirds, and it is also the most northerly nonbreeding location for shorebirds in the Pacific Basin. During the winters of 1997–2012, we conducted aerial surveys of upper Cook Inlet to document the spatial and temporal distribution and number of Rock Sandpipers (Calidris ptilocnemis) using the inlet. The average survey total was 8191 ± 6143 SD birds, and the average of each winter season’s highest single-day count was 13 603 ± 4948 SD birds. We detected only Rock Sandpipers during our surveys, essentially all of which were individuals of the nominate subspecies (C. p. ptilocnemis). Survey totals in some winters closely matched the population estimate for this subspecies, demonstrating the region’s importance as a nonbreeding resource to the subspecies. Birds were most often found at only a handful of sites in upper Cook Inlet, but shifted their distribution to more southerly locations in the inlet during periods of extreme cold. Two environmental factors allow Rock Sandpipers to inhabit Cook Inlet during winter: 1) an abundant bivalve (Macoma balthica) food source and 2) current and tidal dynamics that keep foraging substrates accessible during all but extreme periods of cold and ice accretion. C. p. ptilocnemis is a subspecies of high conservation concern for which annual winter surveys may serve as a relatively inexpensive population-monitoring tool that will also provide insight into adaptations that allow these birds to exploit high-latitude environments in winter.Le printemps et l’été, les oiseaux de rivage abondent et sont bien en vue dans les latitudes de l’extrême nord, mais au fur et à mesure que les conditions saisonnières se détériorent, peu d’entre eux hivernent dans ces régions. Au meilleur de nos connaissances, l’anse Cook, en Alaska (60,6˚ N, 151,6˚ O), est l’endroit le plus froid du monde où l’on trouve régulièrement des populations d’oiseaux de rivage l’hiver. Il s’agit aussi de l’emplacement le plus nordique du bassin du Pacifique à ne pas être consacré à la reproduction des oiseaux de rivage. Au cours des hivers allant de 1997 à 2012, nous avons réalisé des levés aériens de la partie supérieure de l’anse Cook afin d’être en mesure de répertorier la répartition spatiale, la répartition temporelle et le nombre de bécasseaux des Aléoutiennes (Calidris ptilocnemis) dans l’anse. Le total moyen des levés a permis de repérer8 191 ± 6 143 (DS) oiseaux, tandis que la moyenne du dénombrement le plus élevé au cours d’une seule journée d’hiver était de 13 603 ± 4 948 (DS) oiseaux. Dans le cadre de nos levés, nous n’avons détecté que des bécasseaux des Aléoutiennes, dont tous étaient essentiellement des individus de la sous-espèce désignée (C. p. ptilocnemis). Au cours de certains hivers, les totaux des levés se rapprochaient beaucoup des estimations de population de cette sous-espèce, ce qui laisse entrevoir l’importance de cette région en tant que ressource de non-reproduction pour cette sous-espèce. La plupart du temps, ces oiseaux ne se retrouvaient qu’à quelques endroits de la partie supérieure de l’anse Cook, bien qu’ils se répartissaient plus au sud de l’anse pendant les périodes de froid extrême. Deux facteurs environnementaux permettent aux bécasseaux des Aléoutiennes d’évoluer dans l’anse Cook l’hiver : 1) une source abondante de nourriture acéphale (Macoma balthica) et 2) une dynamique de courants et de marées qui a constamment pour effet d’alimenter les oiseaux en substrat pendant toutes les périodes, sauf celles de froid extrême et d’accrétion de glace. C. p. ptilocnemis est une sous-espèce dont la conservation présente de grandes inquiétudes et pour laquelle les levés hivernaux annuels peuvent constituer un outil de surveillance de population relativement abordable qui permettra également d’en savoir plus sur les adaptations qui permettent à ces oiseaux d’exploiter les milieux de haute latitude l’hiver

Birds of the Northcentral Alaska Peninsula, 1976-1980

Between spring 1976 and fall 1980 we studied the occurrence, abundance, and habitat use of birds over a 2000 square km segment of the northcentral Alaska Peninsula. During this period observers were present 473 days and obtained records for all seasons. A total of 125 species was recorded; 63% (79 of 125) were water-associated. The breeding avifauna was found to be a mixture of Panboreal (49%), North American (34%), and Aleutican (17%) species. The Aleutican group was dominant in terms of biomass and numbers of individuals during the nonbreeding period. Forty-two species were confirmed breeding in the area and another 19 were suspected of breeding. The majority of birds occurred as migrants; 14 species were considered permanent residents and an additional 20 were winter residents. ... The area is a principal late summer and fall molting and staging area for several species of arctic and subarctic nesting waders and seaducks and emperor geese .... From late September through mid-October the density of water birds over the entire littoral and nearshore area approached 1000 birds square km. This density was exceeded many fold for certain species on particular segments of habitats in the area.Key words: birds, Alaska Peninsula, abundance, migration, nesting, habitat, distribution, zoogeographyMots clés: oiseaux, péninsule d'Alaska, abondance, migration, saison des nids, habitat, distribution, zoogéographi

The Pacific as the world’s greatest theater of bird migration:Extreme flights spark questions about physiological capabilities, behavior, and the evolution of migratory pathways

The Pacific Basin, by virtue of its vastness and its complex aeroscape, provides unique opportunities to address questions about the behavioral and physiological capabilities and mechanisms through which birds can complete spectacular flights. No longer is the Pacific seen just as a formidable barrier between terrestrial habitats in the north and the south, but rather as a gateway for specialized species, such as shorebirds, to make a living on hemispherically distributed seasonal resources. This recent change in perspective is dramatic, and the research that underpins it has presented new opportunities to learn about phenomena that often challenge a sense of normal. Ancient Polynesians were aware of the seasonal passage of shorebirds and other landbirds over the Pacific Ocean, incorporating these observations into their navigational “tool kit” as they explored and colonized the Pacific. Some ten centuries later, systematic visual observations and tracking technology have revealed much about movement of these shorebirds, especially the enormity of their individual nonstop flights. This invites a broad suite of questions, often requiring comparative studies with bird migration across other ocean basins, or across continents. For example, how do birds manage many days of nonstop exercise apparently without sleep? What mechanisms explain birds acting as if they possess a Global Positioning System? How do such extreme migrations evolve? Through advances in both theory and tracking technology, biologists are poised to greatly expand the horizons of movement ecology as we know it. In this integrative review, we present a series of intriguing questions about trans-Pacific migrant shorebirds and summarize recent advances in knowledge about migratory behavior operating at temporal scales ranging from immediate decisions during a single flight, to adaptive learning throughout a lifetime, to evolutionary development of migratory pathways. Recent advances in this realm should stimulate future research across the globe and across a broad array of disciplines

Not fitting in and getting out : psychological type and congregational satisfaction among Anglican churchgoers in England

Listening to the motivations reported by individuals for ceasing church attendance and becoming church leavers, Francis and Richter identified high on the list the sense of "not fitting in". Drawing on psychological type theory, several recent studies have documented the way in which some psychological types are over-represented in church congregations and other psychological types are under-represented. Bringing these two observations together, the present study tested the hypothesis that church congregations have created type-alike communities within which individuals displaying the opposite type preferences are more likely to feel marginalised and to display lower levels of satisfaction with the congregations they attend. Data were provided by 1867 churchgoers who completed a measure of psychological type, together with measures of frequency of attendance and congregational satisfaction. These data confirmed that congregations were weighted towards preferences for introversion, sensing, feeling and judging, and that individuals displaying the opposite preferences (especially intuition, thinking and perceiving) recorded lower levels of congregational satisfaction. The implications of these findings are discussed for promoting congregational retention by enhancing awareness of psychological type preferences among those who attend

Fourier Magnetic Imaging with Nanoscale Resolution and Compressed Sensing Speed-up using Electronic Spins in Diamond

Optically-detected magnetic resonance using Nitrogen Vacancy (NV) color centres in diamond is a leading modality for nanoscale magnetic field imaging, as it provides single electron spin sensitivity, three-dimensional resolution better than 1 nm, and applicability to a wide range of physical and biological samples under ambient conditions. To date, however, NV-diamond magnetic imaging has been performed using real space techniques, which are either limited by optical diffraction to 250 nm resolution or require slow, point-by-point scanning for nanoscale resolution, e.g., using an atomic force microscope, magnetic tip, or super-resolution optical imaging. Here we introduce an alternative technique of Fourier magnetic imaging using NV-diamond. In analogy with conventional magnetic resonance imaging (MRI), we employ pulsed magnetic field gradients to phase-encode spatial information on NV electronic spins in wavenumber or k-space followed by a fast Fourier transform to yield real-space images with nanoscale resolution, wide field-of-view (FOV), and compressed sensing speed-up.Comment: 31 pages, 10 figure

An addressable quantum dot qubit with fault-tolerant control fidelity

Exciting progress towards spin-based quantum computing has recently been made with qubits realized using nitrogen-vacancy (N-V) centers in diamond and phosphorus atoms in silicon, including the demonstration of long coherence times made possible by the presence of spin-free isotopes of carbon and silicon. However, despite promising single-atom nanotechnologies, there remain substantial challenges in coupling such qubits and addressing them individually. Conversely, lithographically defined quantum dots have an exchange coupling that can be precisely engineered, but strong coupling to noise has severely limited their dephasing times and control fidelities. Here we combine the best aspects of both spin qubit schemes and demonstrate a gate-addressable quantum dot qubit in isotopically engineered silicon with a control fidelity of 99.6%, obtained via Clifford based randomized benchmarking and consistent with that required for fault-tolerant quantum computing. This qubit has orders of magnitude improved coherence times compared with other quantum dot qubits, with T_2* = 120 mus and T_2 = 28 ms. By gate-voltage tuning of the electron g*-factor, we can Stark shift the electron spin resonance (ESR) frequency by more than 3000 times the 2.4 kHz ESR linewidth, providing a direct path to large-scale arrays of addressable high-fidelity qubits that are compatible with existing manufacturing technologies

Electron affinities of the first- and second- row atoms: benchmark ab initio and density functional calculations

A benchmark ab initio and density functional (DFT) study has been carried out on the electron affinities of the first- and second-row atoms. The ab initio study involves basis sets of $spdfgh$ and $spdfghi$ quality, extrapolations to the 1-particle basis set limit, and a combination of the CCSD(T), CCSDT, and full CI electron correlation methods. Scalar relativistic and spin-orbit coupling effects were taken into account. On average, the best ab initio results agree to better than 0.001 eV with the most recent experimental results. Correcting for imperfections in the CCSD(T) method improves the mean absolute error by an order of magnitude, while for accurate results on the second-row atoms inclusion of relativistic corrections is essential. The latter are significantly overestimated at the SCF level; for accurate spin-orbit splitting constants of second-row atoms inclusion of (2s,2p) correlation is essential. In the DFT calculations it is found that results for the 1st-row atoms are very sensitive to the exchange functional, while those for second-row atoms are rather more sensitive to the correlation functional. While the LYP correlation functional works best for first-row atoms, its PW91 counterpart appears to be preferable for second-row atoms. Among ``pure DFT'' (nonhybrid) functionals, G96PW91 (Gill 1996 exchange combined with Perdew-Wang 1991 correlation) puts in the best overall performance. The best results overall are obtained with the 1-parameter hybrid modified Perdew-Wang (mPW1) exchange functionals of Adamo and Barone [J. Chem. Phys. {\bf 108}, 664 (1998)], with mPW1LYP yielding the best results for first-row, and mPW1PW91 for second-row atoms. Indications exist that a hybrid of the type $a$ mPW1LYP + $(1-a)$ mPW1PW91 yields better results than either of the constituent functionals.Comment: Phys. Rev. A, in press (revised version, review of issues concerning DFT and electron affinities added