Rotating gravity currents: small-scale and large-scale laboratory experiments and a geostrophic model

Laboratory experiments simulating gravity-driven coastal surface currents produced by estuarine fresh-water discharges into the ocean are discussed. The currents are generated inside a rotating tank filled with salt water by the continuous release of buoyant fresh water from a small source at the fluid surface. The height, the width and the length of the currents are studied as a function of the background rotation rate, the volumetric discharge rate and the density difference at the source. Two complementary experimental data sets are discussed and compared with each other. One set of experiments was carried out in a tank of diameter 1 m on a small-scale rotating turntable. The second set of experiments was conducted at the large-scale Coriolis Facility (LEGI, Grenoble) which has a tank of diameter 13 m. A simple geostrophic model predicting the current height, width and propagation velocity is developed. The experiments and the model are compared with each other in terms of a set of non-dimensional parameters identified in the theoretical analysis of the problem. These parameters enable the corresponding data of the large-scale and the small-scale experiments to be collapsed onto a single line. Good agreement between the model and the experiments is found

The ionization structure of the Orion nebula: Infrared line observations and models

Observations of the (O III) 52 and 88 micron lines and the (N III) 57 micron line have been made at 6 positions and the (Ne III) 36 micron line at 4 positions in the Orion Nebula to probe its ionization structure. The measurements, made with a -40" diameter beam, were spaced every 45" in a line south from and including the Trapezium. The wavelength of the (Ne III) line was measured to be 36.013 + or - 0.004 micron. Electron densities and abundance ratios of N(++)/O(++) have been calculated and compared to other radio and optical observations. Detailed one component and two component (bar plus halo) spherical models were calculated for exciting stars with effective temperatures of 37 to 40,000K and log g = 4.0 and 4.5. Both the new infrared observations and the visible line measurements of oxygen and nitrogen require T sub eff approx less than 37,000K. However, the double ionized neon requires a model with T sub eff more than or equal to 39,000K, which is more consistent with that inferred from the radio flux or spectral type. These differences in T sub eff are not due to effects of dust on the stellar radiation field, but are probably due to inaccuracies in the assumed stellar spectrum. The observed N(++)/O(++) ratio is almost twice the N(+)/O(+) ratio. The best fit models give N/H = 8.4 x 10 to the -5 power, O/H = 4.0 x 10 to the -4 power, and Ne/H = 1.3 x 10 to the -4 power. Thus neon and nitrogen are approximately solar, but oxygen is half solar in abundance. From the infrared O(++) lines it is concluded that the ionization bar results from an increase in column depth rather than from a local density enhancement

Determination of the Telluric Water Vapor Absorption Correction for Astronomical Data Obtained from the Kuiper Airborne Observatory

The amount of telluric water vapor along the line of sight of the Kuiper Airborne Observatory telescope as obtained concommitantly on 23 flights is compared with the NASA-Ames Michelson interferometer and with the NOAA-Boulder radiometer. A strong correlation between the two determinations exists, and a method for computing the atmospheric transmission for a given radiometer reading is established

The effect of metapopulation processes on the spatial scale of adaptation across an environmental gradient

We show that the butterfly Aricia agestis (Lycaenidae) is adapted to its thermal environment in via integer changes in the numbers of generations per year (voltinism): it has two generations per year in warm habitats and one generation per year in cool habitats in north Wales (UK). Voltinism is an “adaptive peak” since individuals having an intermediate number of generations per year would fail to survive the winter, and indeed no populations showed both voltinism types in nature. In spite of this general pattern, 11% of populations apparently possess the “wrong” voltinism for their local environment, and population densities were lower in thermally intermediate habitat patches. Population dynamic data and patterns of genetic differentiation suggest that adaptation occurs at the metapopulation level, with local populations possessing the voltinism type appropriate for the commonest habitat type within each population network. When populations and groups of populations go extinct, they tend to be replaced by colonists from the commonest thermal environment nearby, even if this is the locally incorrect adaptation. Our results illustrate how stochastic population turnover can impose a limit on local adaptation over distances many times larger than predicted on the basis of normal dispersal movements

Ambient mixing ratios of nonmethane hydrocarbons (NMHCs) in two major urban centers of the Pearl River Delta (PRD) region: Guangzhou and Dongguan

The Pearl River Delta (PRD) region can be considered one of the most economically developed areas of mainland China. In September 2005, a total of 96 whole air samples were collected in Guangzhou and Dongguan, two important urban centers of the PRD region. Guangzhou is considered the economic center of Guangdong province, and Dongguan is a rapidly expanding industrial city. Here, we report mixing ratios of 50 nonmethane hydrocarbons (NMHCs) that were quantified in the ambient air of these PRD centers. The discussion focuses on understanding the main sources responsible for NMHC emissions, and evaluating the role of the identified sources towards ozone formation. Propane was the most abundant species in Guangzhou, with an average mixing ratio of 6.8 ppbv (±0.7 ppbv S.E.), compared to 2.5±0.2 ppbv in Dongguan. Toluene was the most abundant hydrocarbon in Dongguan (6.1±0.8 ppbv, compared to 5.9±0.7 ppbv in Guangzhou). Based on an analysis of the correlation between vehicular-emitted compounds and the measured NMHCs, together with the benzene-to-toluene (B/T) ratio, vehicular emission appears to be the dominant source of NMHCs measured in Guangzhou. By contrast, selected species (including toluene) in many of the Dongguan samples were influenced by an additional source, most likely related to industrial activities. A specific B/T ratio (<0.20) is proposed here and used as indicator of samples strongly affected by industrial emissions. The ozone formation potential (OFP) is calculated, and the role of the different NMHCs associated with industrial and combustion sources is evaluated. © 2008 Elsevier Ltd. All rights reserved

Neurologists' lived experiences of communicating the diagnosis of a motor neurodegenerative condition: an interpretative phenomenological analysis

BACKGROUND Receiving the diagnosis of a motor neurodegenerative condition (MNDC) can be a life-changing experience. Although several studies of individuals' experiences have indicated dissatisfaction with aspects of how an MNDC diagnosis was communicated, few studies have addressed doctors' experiences of breaking bad news for these conditions, especially from a qualitative perspective. This study explored UK neurologists' lived experience of delivering an MNDC diagnosis. METHODS Interpretative phenomenological analysis was used as the overarching method. Eight consultant neurologists working with patients with MNDCs took part in individual, semi-structured interviews. RESULTS Two themes were constructed from the data: 'Meeting patients' emotional and information needs at diagnosis: a balancing act between disease, patient and organization-related factors', and 'Empathy makes the job harder: the emotional impact and uncovered vulnerabilities associated with breaking bad news'. Breaking the news of an MNDC diagnosis was challenging for participants, both in terms of achieving a patient-centred approach and in terms of dealing with their own emotions during the process. CONCLUSIONS Based on the study's findings an attempt to explain sub-optimal diagnostic experiences documented in patient studies was made and how organizational changes can support neurologists with this demanding clinical task was discussed

Neurologists' current practice and perspectives on communicating the diagnosis of a motor neurodegenerative condition: a UK survey

Background The communication of a life-changing diagnosis can be a difficult task for doctors with potential long-term effects on patient outcomes. Although several studies have addressed the experiences of individuals with motor neurodegenerative diseases in receiving this diagnosis, a significant research gap exists regarding professionals’ perspectives, especially in the UK. This study aimed to assess UK neurologists’ current practice and perspectives on delivering the diagnosis of a motor neurodegenerative disease, explore different aspects of the process and detail the potential challenges professionals might face. Methods We conducted an anonymised online survey with 44 questions, grouped into four sections; basic demographic information, current practice, the experience of breaking bad news and education and training needs. Results Forty-nine professionals completed the survey. Overall, participants seemed to meet the setting-related standards of good practice; however, they also acknowledged the difficulty of this aspect of their clinical work, with about half of participants (46.5%) reporting moderate levels of stress while breaking bad news. Patients’ relatives were not always included in diagnostic consultations and participants were more reluctant to promote a sense of optimism to patients with poorer prognosis. Although professionals reported spending a mean of around 30–40 min for the communication of these diagnoses, a significant proportion of participants (21–39%) reported significantly shorter consultation times, highlighting organisational issues related to lack of capacity. Finally, the majority of participants (75.5%) reported not following any specific guidelines or protocols but indicated their interest in receiving further training in breaking bad news (78.5%). Conclusions This was the first UK survey to address neurologists’ practice and experiences in communicating these diagnoses. Although meeting basic standards of good practice was reported by most professionals, we identified several areas of improvement. These included spending enough time to deliver the diagnosis appropriately, including patients’ relatives as a standard, promoting a sense of hope and responding to professionals’ training needs regarding breaking bad news