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Synchrotron radiation was used to obtain a high-resolution powder diffraction pattern of the high-density form of BeH2, a material whose unit-cell dimensions have not previously been determined. The observed d-spacing values were presented to three different computer indexing programs. All three programs returned as best solution a body-centered orthorhombic unit cell with a = 9.082, b = 4.160, c = 7.707 Å and V = 292 Å3. Interpretation of the three-dimensional Patterson led to 12 BeH2 molecules per unit cell; thus, the theoretical density is 0.755 g/cm3. The molecular structure is based on a network of corner-sharing BeH4 tetrahedra rather than flat, infinite chains with hydrogen bridges previously assumed.
Spray drying is shown to be an effective and rapid method for preparing samples for quantitative analysis by x-ray powder diffraction. Previously intractable problems like the simultaneous analysis of multiple phases in orientation prone systems can be carried out. Using this method, and a computer controlled diffractometer, five and six phase analyses of Devonian shales can be accomplished in approximately forty minutes. A rapid and convenient method for using the absorption diffraction technique for x-ray quantitative analysis is described.
The spray drying of powders is a method of forming spherical or torroidal shaped agglomerates. A relatively simple method is given for preparing spray dried samples of the quantities used in x-ray diffraction analysis. This technique is shown to minimize preferred orientation effects on diffraction intensities from materials of widely differing symmetry and crystallite habit.
Adverse pregnancy outcomes including prematurity and low birth weight (LBW) have been associated with life-long chronic disease risk for the infant. Stress during pregnancy increases the risk of adverse pregnancy outcomes. Many studies have reported the incidence of adverse pregnancy outcomes in Indigenous populations and a smaller number of studies have measured rates of stress and depression in these populations. This study sought to examine the potential association between stress during pregnancy and the rate of adverse pregnancy outcomes in Australian Indigenous women residing in rural and remote communities in New South Wales. This study found a higher rate of post-traumatic stress disorder, depression and anxiety symptoms during pregnancy than the general population. There was also a higher incidence of prematurity and LBW deliveries. Unfortunately, missing post-traumatic stress disorder and depressive symptomatology data impeded the examination of associations of interest. This was largely due to the highly sensitive nature of the issues under investigation, and the need to ensure adequate levels of trust between Indigenous women and research staff before disclosure and recording of sensitive research data. We were unable to demonstrate a significant association between the level of stress and the incidence of adverse pregnancy outcomes at this stage. We recommend this longitudinal study continue until complete data sets are available. Future research in this area should ensure prioritization of building trust in participants and overestimating sample size to ensure no undue pressure is placed upon an already stressed participant.
Childhood obesity rates are higher among Indigenous compared with non-Indigenous Australian children. It has been hypothesized that early-life influences beginning with the intrauterine environment predict the development of obesity in the offspring. The aim of this paper was to assess, in 227 mother–child dyads from the Gomeroi gaaynggal cohort, associations between prematurity, Gestation Related-Optimal Weight (GROW) centiles, maternal adiposity (percentage body fat, visceral fat area), maternal non-fasting plasma glucose levels (measured at mean gestational age of 23.1 weeks) and offspring BMI and adiposity (abdominal circumference, subscapular skinfold thickness) in early childhood (mean age 23.4 months). Maternal non-fasting plasma glucose concentrations were positively associated with infant birth weight (P=0.005) and GROW customized birth weight centiles (P=0.008). There was a significant association between maternal percentage body fat (P=0.02) and visceral fat area (P=0.00) with infant body weight in early childhood. Body mass index (BMI) in early childhood was significantly higher in offspring born preterm compared with those born at term (P=0.03). GROW customized birth weight centiles was significantly associated with body weight (P=0.01), BMI (P=0.007) and abdominal circumference (P=0.039) at early childhood. Our findings suggest that being born preterm, large for gestational age or exposed to an obesogenic intrauterine environment and higher maternal non-fasting plasma glucose concentrations are associated with increased obesity risk in early childhood. Future strategies should aim to reduce the prevalence of overweight/obesity in women of child-bearing age and emphasize the importance of optimal glycemia during pregnancy, particularly in Indigenous women.
The Neotoma Paleoecology Database is a community-curated data resource that supports interdisciplinary global change research by enabling broad-scale studies of taxon and community diversity, distributions, and dynamics during the large environmental changes of the past. By consolidating many kinds of data into a common repository, Neotoma lowers costs of paleodata management, makes paleoecological data openly available, and offers a high-quality, curated resource. Neotoma’s distributed scientific governance model is flexible and scalable, with many open pathways for participation by new members, data contributors, stewards, and research communities. The Neotoma data model supports, or can be extended to support, any kind of paleoecological or paleoenvironmental data from sedimentary archives. Data additions to Neotoma are growing and now include >3.8 million observations, >17,000 datasets, and >9200 sites. Dataset types currently include fossil pollen, vertebrates, diatoms, ostracodes, macroinvertebrates, plant macrofossils, insects, testate amoebae, geochronological data, and the recently added organic biomarkers, stable isotopes, and specimen-level data. Multiple avenues exist to obtain Neotoma data, including the Explorer map-based interface, an application programming interface, the neotoma R package, and digital object identifiers. As the volume and variety of scientific data grow, community-curated data resources such as Neotoma have become foundational infrastructure for big data science.
In 1968 the FAA adopted a high density rule for the allocation of scarce landing and take-off slots at four major airports (La Guardia,Washington National, Kennedy International, and O'Hare International). This rule establishes slot quotas for the control of airspace congestion at these airports.
Airport runway slots, regulated by these quotas, have a distinguishing feature which any proposed allocation procedure must accommodate: an airline's demand for a takeoff slot at a flight originating airport is not independent of its demand for a landing slot at the flight destination airport. Indeed, a given flight may take off and land in a sequence of several connected demand interdependent legs. For economic efficiency it is desirable to develop an airport slot allocation procedure that allocates individual slots to those airline flights for which the demand (willingness to pay) is greatest.
Grether, Isaac, and Plott (hereafter, GIP) (1979, 1981) have proposed a practical market procedure for achieving this goal. Their procedure is based upon the growing body of experimental evidence on the performance of (1) the competitive (uniform price) sealed-bid auction and (2) the oral double auction such as is used on the organized stock and commodity exchanges. Under their proposal an independent primary market for slots at each airport would be organized as a sealed-bid competitive auction at timely intervals. Since the primary market allocation does not make provision for slot demand interdependence, a computerized form of the oral double auction (with block transaction capabilities) is proposed as an “after market” to allow airlines to purchase freely and sell primary market slots to each other. This continuous after market exchange would provide the institutional means by which individual airlines would acquire those slot packages which support their individual flight schedules. Thus, an airline that acquired slots at Washington National which did not flight-match the slots acquired at O'Hare could either buy additional O'Hare slots or sell its excess Washington slots in the after market.
Over the past 30 years, the number of US doctoral anthropology graduates has increased by about 70%, but there has not been a corresponding increase in the availability of new faculty positions. Consequently, doctoral degree-holding archaeologists face more competition than ever before when applying for faculty positions. Here we examine where US and Canadian anthropological archaeology faculty originate and where they ultimately end up teaching. Using data derived from the 2014–2015 AnthroGuide, we rank doctoral programs whose graduates in archaeology have been most successful in the academic job market; identify long-term and ongoing trends in doctoral programs; and discuss gender division in academic archaeology in the US and Canada. We conclude that success in obtaining a faculty position upon graduation is predicated in large part on where one attends graduate school.
To develop consensus recommendations for training future clinician educators (CEs) in emergency medicine (EM).
A panel of EM education leaders was assembled from across Canada and met regularly by teleconference over the course of 1 year. Recommendations for CE training were drafted based on the panel’s experience, a literature review, and a survey of current and past EM education leaders in Canada. Feedback was sought from attendees at the Canadian Association of Emergency Physicians (CAEP) annual academic symposium. Recommendations were distributed to the society’s Academic Section for further feedback and updated by a consensus of the expert panel.
Recommendations were categorized for one of three audiences: 1) Future CEs; 2) Academic departments and divisions (AD&D) that support training to fulfill their education leadership goals; and 3) The CAEP Academic Section. Advanced medical education training is recommended for any emergency physician or resident who pursues an education leadership role. Individuals should seek out mentorship in making decisions about career opportunities and training options. AD&D should regularly perform a needs assessment of their future CE needs and identify and encourage potential individuals who fulfill education leadership roles. AD&D should develop training opportunities at their institution, provide support to complete this training, and advocate for the recognition of education scholarship in their institutional promotions process. The CAEP Academic Section should support mentorship of future CEs on a national scale.
These recommendations serve as a framework for training and supporting the next generation of Canadian EM medical educators.
The Internet offers a number of advantages as a survey mode: low marginal cost per completed response, capabilities for providing respondents with large quantities of information, speed, and elimination of interviewer bias. Those seeking these advantages confront the problem of representativeness both in terms of coverage of the population and capabilities for drawing random samples. Two major strategies have been pursued commercially to develop the Internet as a survey mode. One strategy, used by Harris Interactive, involves assembling a large panel of willing respondents who can be sampled. Another strategy, used by Knowledge Networks, involves using random digit dialing (RDD) telephone methods to recruit households to a panel of Web-TV enabled respondents. Do these panels adequately deal with the problem of representativeness to be useful in political science research? The authors address this question with results from parallel surveys on global climate change and the Kyoto Protocol administered by telephone to a national probability sample and by Internet to samples of the Harris Interactive and Knowledge Networks panels. Knowledge and opinion questions generally show statistically significant but substantively modest difference across the modes. With inclusion of standard demographic controls, typical relational models of interest to political scientists produce similar estimates of parameters across modes. It thus appears that, with appropriate weighting, samples from these panels are sufficiently representative of the U.S. population to be reasonable alternatives in many applications to samples gathered through RDD telephone surveys.
Survey-based contingent valuation (CV) techniques are commonly used to value the potential effects of a policy change when market-based valuation of those effects is not possible. The results of these analyses are often intended to inform policy decisions, which are made within the context of formal policymaking institutions. These institutions are typically designed to reduce the large number of potential options for addressing any given policy problem to a binary choice between the continuation of current policy and a single, specified alternative. In this research we develop an approach for conducting CV exercises in a manner consistent with the decision structure typically faced by policymakers. The data generated from this approach allow for an estimate of willingness to pay (WTP) for a defined policy alternative, relative to leaving policy unchanged, which we argue is of direct interest to policymakers. We illustrate our approach within the context of policy governing the storage of used nuclear fuel in the United States. We value the policy option of constructing an interim storage facility relative to continuation of current policy, wherein used nuclear fuel is stored on-site at or near commercial nuclear generating plants. We close the paper with a discussion of the implications for future research and the role of CV in the policymaking process.
The linear polarization of the Crab pulsar as a function of pulse phase was observed by the High Speed Photometer on the Hubble Space Telescope in March, 1993. Observations were obtained in a bandpass centered on 2770 A using a 0.25 ms sample time, corresponding to a time resolution of 0.0075 in pulse phase. The UV polarization of the pulsar [Fig. 1] is strikingly similar to that observed in the visible (cf. Smith et al. 1988). The same values of polarization and the same swing of position angle occur through the main and secondary pulses. The polarization pulse profile must be essentially wavelength independent at frequencies above the infrared.
We previously reported an association between 5HTTLPR genotype and
outcome following cognitive–behavioural therapy (CBT) in child anxiety
(Cohort 1). Children homozygous for the low-expression short-allele
showed more positive outcomes. Other similar studies have produced mixed
results, with most reporting no association between genotype and CBT
To replicate the association between 5HTTLPR and CBT outcome in child
anxiety from the Genes for Treatment study (GxT Cohort 2,
n = 829).
Logistic and linear mixed effects models were used to examine the
relationship between 5HTTLPR and CBT outcomes. Mega-analyses using both
cohorts were performed.
There was no significant effect of 5HTTLPR on CBT outcomes in Cohort 2.
Mega-analyses identified a significant association between 5HTTLPR and
remission from all anxiety disorders at follow-up (odds ratio 0.45,
P = 0.014), but not primary anxiety disorder
The association between 5HTTLPR genotype and CBT outcome did not
replicate. Short-allele homozygotes showed more positive treatment
outcomes, but with small, non-significant effects. Future studies would
benefit from utilising whole genome approaches and large, homogenous
Emerald ash borer (EAB), Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), is a non-native, wood-boring beetle that has caused widespread mortality of ash (Fraxinus Linnaeus (Oleaceae)) in eastern North America. During 2004–2007, we determined whether forest community composition and structure of black (F. nigra Marshall), green (F. pennsylvanica Marshall), and white (F. americana Linnaeus) ash stands influenced their susceptibility to EAB invasion in southeast Michigan, United States of America. There was no relationship between EAB-induced ash decline or percentage mortality and any measure of community composition (tree species diversity, stand/ash density, total basal area, or relative dominance of ash). There was also no relationship between measures of EAB impact (density of EAB signs, ash decline rating, percentage ash mortality, or percentage infested ash) and forest attributes (ash/total stand density, basal area, ash importance, or stand diversity). Decline and mortality of black ash advanced more rapidly than that of white and green ash. Percentage mortality of ash increased from 51% to 93% during 2004–2007. Distance from the epicentre of the invasion was negatively correlated with ash mortality, but this relationship dissipated over time. Stand composition data suggests that ash will be replaced by Quercus Linnaeus (Fagaceae), Acer Linnaeus (Sapindaceae), and Tilia Linnaeus (Malvaceae); such vegetation changes will irreversibly alter the structure and function of these forests.