To send content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about sending content to .
To send content items to your Kindle, first ensure email@example.com
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about sending to your Kindle.
Note you can select to send to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
We apply two methods to estimate the 21-cm bispectrum from data taken within the Epoch of Reionisation (EoR) project of the Murchison Widefield Array (MWA). Using data acquired with the Phase II compact array allows a direct bispectrum estimate to be undertaken on the multiple redundantly spaced triangles of antenna tiles, as well as an estimate based on data gridded to the uv-plane. The direct and gridded bispectrum estimators are applied to 21 h of high-band (167–197 MHz; z = 6.2–7.5) data from the 2016 and 2017 observing seasons. Analytic predictions for the bispectrum bias and variance for point-source foregrounds are derived. We compare the output of these approaches, the foreground contribution to the signal, and future prospects for measuring the bispectra with redundant and non-redundant arrays. We find that some triangle configurations yield bispectrum estimates that are consistent with the expected noise level after 10 h, while equilateral configurations are strongly foreground-dominated. Careful choice of triangle configurations may be made to reduce foreground bias that hinders power spectrum estimators, and the 21-cm bispectrum may be accessible in less time than the 21-cm power spectrum for some wave modes, with detections in hundreds of hours.
The Pentland Hills sponge fauna (Llandovery, Telychian) consists of an unusual, aberrant assemblage, but of low diversity. A new specimen of a unique sponge, Eoghanospongia carlinslowpensis gen. et sp. nov., is described from the classic locality of R82. The mushroom-shaped, probably stalked body (peduncle attachment to body not exposed) resembles that of some living rossellids, especially Caulophacus. The sponge also shows prominent projecting pentactins and monaxon derivatives – a spicule type diagnostic of the Rossellidae among living taxa, albeit in a robust form not described from extant sponges, including Caulophacus or other pedunculate lyssacinosidans. Certain attribution to the Rossellidae is not possible from the single specimen, largely because of weak preservation of the primary spicule skeleton, but no other fossil or modern sponges show any significant similarity to it. Although similarly early relatives of the Rossellidae have recently been described from elsewhere, the new sponge is even more unexpected in being from a shallow-water environment, making the absence of rossellids through the rest of the Palaeozoic much more problematic.
Biological tissues have complex, three-dimensional (3D) organizations of cells and matrix factors that provide the architecture necessary to meet morphogenic and functional demands. Disordered cell alignment is associated with congenital heart disease, cardiomyopathy, and neurodegenerative diseases and repairing or replacing these tissues using engineered constructs may improve regenerative capacity. However, optimizing cell alignment within engineered tissues requires quantitative 3D data on cell orientations and both efficient and validated processing algorithms. We developed an automated method to measure local 3D orientations based on structure tensor analysis and incorporated an adaptive subregion size to account for multiple scales. Our method calculates the statistical concentration parameter, κ, to quantify alignment, as well as the traditional orientational order parameter. We validated our method using synthetic images and accurately measured principal axis and concentration. We then applied our method to confocal stacks of cleared, whole-mount engineered cardiac tissues generated from human-induced pluripotent stem cells or embryonic chick cardiac cells and quantified cardiomyocyte alignment. We found significant differences in alignment based on cellular composition and tissue geometry. These results from our synthetic images and confocal data demonstrate the efficiency and accuracy of our method to measure alignment in 3D tissues.
The aim of this study was to determine the factors associated with a feeling of well-being using the Edmonton Symptom Assessment Scale (ESAS)–Feeling of Well-Being item (ESAS–FWB; where 0 = best and 10 = worst) among advanced lung or non-colonic gastrointestinal cancer patients who were referred to an outpatient palliative care clinic (OPCC). We also examined the association of performance on the ESAS–FWB with overall survival (OS).
We reviewed the records of consecutive patients with incurable advanced lung cancer and non-colonic gastrointestinal cancer presenting to an OPCC from 1 January 2008 through to 31 December 2013. Descriptive statistics were employed to summarize patient characteristics. Multivariate regression analysis was used to determine the factors associated with ESAS–FWB severity. We also examined the association of ESAS–FWB scores and survival using Kaplan–Meier survival analysis.
A total of 826 evaluable patients were analyzed (median age = 62 years, 57% male). Median ESAS–FWB scores were five times the interquartile range (5 × IQR; 3–7). ESAS–FWB score was found to be significantly associated with ESAS fatigue (OR = 2.31, p < 0.001); anxiety (OR = 1.98, p < 0.001); anorexia (OR = 2.31, p < 0.001); cut down, annoyed, guilty, eye opener (CAGE) score (hazard ratio [HR] = 1.80, p = 0.008); and family caregiver distress (HR = 1.93, p = 0.002). A worse ESAS–FWB score was significantly associated with decreased OS (r = –0.18, p < 0.001). However, ESAS–FWB score was not independently associated with OS in the final multivariate model (p = 0.35), which included known major clinical prognostic factors.
Worse ESAS–FWB scores were significantly associated with high scores on ESAS fatigue, anorexia, anxiety, CAGE, and family caregiver distress. More research is necessary to understand how palliative care interventions are capable of improving the contributory factors related to ESAS–FWB score.
Decametric wavelength imaging has been largely neglected in the quest for higher angular resolution because ionospheric structure limited interferometric imaging to short (< 5 km) baselines. The long wavelength (LW, 2—20 m or 15—150 MHz) portion of the electromagnetic spectrum thus remains poorly explored. The NRL-NRAO 74 MHz Very Large Array has demonstrated that self-calibration techniques can remove ionospheric distortions over arbitrarily long baselines. This has inspired the Low Frequency Array (LOFAR)—-a fully electronic, broad-band (15—150 MHz)antenna array which will provide an improvement of 2—3 orders of magnitude in resolution and sensitivity over the state of the art.
We have completed a near-infrared spectral survey of more than 40 planetary nebulae (PN). The data were obtained using the KSPEC spectrometer on the University of Hawaii 2.2m telescope on Mauna Kea. KSPEC is a cross-dispersed spectrograph that provides simultaneous sampling of the 1.1–2.4 μm range at a resolution of approximately 700. We used a 1 × 7 arcsec slit and a slit-viewing camera with a second NICMOS3 detector operating in the K-band for positioning and tracking of the source. The survey sample consists of compact IR-bright PN with a range of ages and morphological classifications. For many PN in the survey, spectra of several positions, such as the central star and one or more positions in the nebula, were obtained. There are many spectral features of interest within this wavelength range, such as HI recombination lines, emission lines of HeI, FeI, OI, and [FeII]; molecules such as H2, CN, C2, and CO; and continuum emission from the central star and hot dust in the nebula. A typical spectrum is shown in Figure 1. Emission from H2 was detected for the first time in several PN, including NGC 40, NGC 7026, M 1-92, and Vy 2-2. The survey data will be used to compare the properties of the sample PN, including H2 excitation mechanisms (shocks versus excitation by UV photons) and temperatures, and to correlate the properties with morphology class and age.
We present the first results of a deep near-infrared narrowband imaging study of several planetary nebulae. The data were acquired using the University of Hawaii 2.2m telescope on Mauna Kea and the “QUIRC” 1024 × 1024 array camera. With these sensitive high spatial resolution imaging data, we are able to explore in detail where H2 is found relative to the ionized region in planetary nebulae at various stages of evolution (See Figure 1, for an example). The objects were selected from previous studies to have evidence for extended emission from H2, and they are at several differing phases of central star evolution. The presence of molecules in the UV–flooded environment of a planetary nebula cannot be explained without highly non-spherical geometries and high densities, or clumping. Although there can be an ambiguity in the excitation mechanism (UV photons or shocks), the location of H2 emission identifies regions of the nebula with sufficient dust shielding and density for the survival of molecular species. The emission morphology also provides information that helps identify which excitation mechanism is most likely. When combined with data provided by other molecular studies, we can examine how the photodissociation region evolves through the circumstellar envelope as the planetary nebula tracks across the top of the HR diagram. We can also consider how morphological evolution of the nebula, through interacting winds and shocks, might provide the conditions necessary for molecular survival.
The evolution of planetary nebulae is controlled largely by hardening of the radiation field from the central star and by hydrodynamic interactions between the “fast wind” and the slower red giant wind. These processes also result in the heating and dissociation of H2 and in the production of H2 vibration–rotation lines in the near-infrared. Both mechanisms tend to produce high gas temperatures and, at high densities, a thermal population of states. Kinematic studies provide vital information on the geometry and expansion of the nebulae and offer a discriminant between shocked and photodissociated regions.
Actors in high-reliability organizations often form meetings to discuss incidents and learn from them. Such after-action reviews (AARs) are structured opportunities for shared retrospective learning, innovation development, and continuous improvement. Research on AARs has examined the meeting-level antecedents and outcomes associated with various elements of AARs, but has generally stopped short of considering how they should influence and respond to the organizations in which they are situated. After connecting the functions of AARs using the theoretical frameworks of collective sensemaking, organizational learning, and knowledge management, this chapter presents an input-process-output model of AAR systems that accounts for a range of extra-meeting factors that influence and are influenced by the content of retrospective discussion. It also describes best practices and directions for future research associated with these inputs, processes, and outputs.
We studied the energy cost of egg production in two flea species (Parapulex chephrenis and Xenopsylla ramesis) feeding on principal (Acomys cahirinus and Meriones crassus, respectively) and auxiliary (M. crassus and A. cahirinus, respectively) rodent hosts. We predicted that fleas feeding on principal as compared with auxiliary hosts will (a) expend less energy for egg production; (b) produce larger eggs and (c) live longer after oviposition. Both fleas produced more eggs and spent less energy per egg when exploiting principal hosts. Parapulex chephrenis produced larger eggs after exploiting auxiliary hosts, while the opposite was true for X. ramesis. After oviposition, P. chephrenis fed on the auxiliary hosts survived for a shorter time than those fed on the principal hosts, while in X. ramesis the survival time did not differ among hosts. Our results suggested that one of the proximate causes for lower reproductive performance and subsequent lower abundance of fleas on auxiliary hosts is the higher energy cost of egg production. However, in some species, lower offspring number may be compensated to some extent by their size, although this compensation may also compromise their future reproduction via decreased survival. In addition, the reproductive strategy of exploitation of low profitable (i.e. auxiliary) hosts may differ between flea species.
Significant new opportunities for astrophysics and cosmology have been identified at low radio frequencies. The Murchison Widefield Array is the first telescope in the southern hemisphere designed specifically to explore the low-frequency astronomical sky between 80 and 300 MHz with arcminute angular resolution and high survey efficiency. The telescope will enable new advances along four key science themes, including searching for redshifted 21-cm emission from the EoR in the early Universe; Galactic and extragalactic all-sky southern hemisphere surveys; time-domain astrophysics; and solar, heliospheric, and ionospheric science and space weather. The Murchison Widefield Array is located in Western Australia at the site of the planned Square Kilometre Array (SKA) low-band telescope and is the only low-frequency SKA precursor facility. In this paper, we review the performance properties of the Murchison Widefield Array and describe its primary scientific objectives.