NGC 6309, a Planetary Nebula that Shifted from Round to Multipolar

We present new narrow-band Ha, [N II], and [O III] high-resolution images of the quadrupolar planetary nebula (PN) NGC 6309 that show in great detail its bipolar lobes and reveal new morphological features. New high- and low-dispersion long-slit spectra have been obtained to help in the investigation of the new nebular components. The images and spectra unveil two diffuse blobs, one of them located at 55 arcsec from the central star along the NE direction (PA= +71) and the other at 78 arcsec in the SW direction (PA= -151). Therefore, these structures do not share the symmetry axes of the inner bipolar outflows. Their radial velocities relative to the system are quite low: +3 and -4 km/s, respectively. Spectroscopic data confirm a high [O III] to Ha ratio, indicating that the blobs are being excited by the UV flux from the central star. Our images convincingly show a spherical halo 60 arcsec in diameter encircling the quadrupolar nebula. The expansion velocity of this shell is low, 66 km/s. The software SHAPE has been used to construct a morpho-kinematic model for the ring and the bipolar flows that implies an age of 4,000 yrs, the expansion of the halo sets a lower limit for its age 46,000 yrs, and the very low expansion of the blobs suggests they are part of a large structure corresponding to a mass ejection that took place 150,000 yrs ago. In NGC 6309 we have direct evidence of a change in the geometry of mass-loss, from spherical in the halo to axially-symmetric in the two pairs of bipolar lobes.Comment: 8 pages, 7 figures, Accepted for publication in MNRA

An Empirical Analysis of Demand Interrelationships: An Application to Selected Agricultural Commodities in Venezuela

The primary objective of this study was to develop demand equations at retail for selected Venezuelan food commodities. Commodities included for analysis were rice, refined sugar, crude sugar, flour, potatoes, beef, pork, black beans, corn, and powdered milk. The basic statistical technique employed in the analysis was least squares multiple regression. Although several mathematical forms for these demand equations were evaluated, a log-log transform was found to be most useful. Independent variables included own price, prices of substitutes and complements, time and income. Observations were taken from Venezuelan time series data over the period 1945-1965. Development of these basic demand equations facilitated the treatment of a second objective which was to evaluate the degree of complementarity and substitution between each one of the commodities included in the model. Further, it provided the necessary structural framework to give exante examination to selected policy alternatives for Venezuelan agriculture. Alternatives examined included minimwn price and import policies. Interesting results and conclusions may be s ummarized as follows: 1. Difficult statistical problems are encountered in an attempt to estimate direct and cross elasticities of demand from time series data. 2. A less general approach utilizing principles of demand theory is advisable until further requirements are made in the data series. 3. A consistent demand model docs provide useful insights into the interrelationships of commodity demands in terms of direction of change in price and quantity if not in terms of their magnitude. 4. Regional and social stratification of price, income and consumption data should improve the reliability of any subsequent analyses. 5. Additional household expenditure surveys of a cross-sectional nature would provide useful and necessary checks on the demand estimates obtained from time series data

Propuesta de contextos geológicos para la catalogación del patriminio geológico y minero de la República Dominicana

El patrimonio geológico constituye el conjunto de recursos naturales no renovables de valor científico, cultural o educativo, ya sean formaciones y estructuras geológicas, formas del terreno o yacimientos paleontológicos y mineralógicos, que permiten reconocer, estudiar o interpretar la evolución de la historia geológica de la Tierra y los procesos que la han modelado (Gallego y García, 1996). Una de las dificultades para abordar la conservación del Patrimonio Geológico y Minero en una determinada región radica en definir una metodología adecuada para catalogar dicho patrimonio de forma rigurosa y científica teniendo en cuenta la geodiversidad propia de la zona.En este sentido el proyecto internacional Geosites (Wimbledon, 1996) define unas pautas para la catalogación del Patrimonio Geológico. Wimbledon (1996) propone la necesidad de definir los Contextos Geológicos (Geological Frameworks) representativos de la geodiversidad de cada territorio para luego catalogar los Lugares de Interés Geológico (LIGs) en el marco de dichos Contextos. Este sistema ha sido aplicado en numerosos países (p. ej. España, García-Cortés, 2008). En este trabajo se proponen y describen los Contextos Geológicos de la República Dominicana para así poder catalogar posteriormente los Lugares de Interés Geológico de este país. The geoheritageis the set of non-renewable natural resources of scientific, cultural or educational value, whether geological formations and structures, landforms or paleontological and mineralogical sites, who give us information to study and interpret the evolution of the geological history of the Earth and the processes that have modeled its surface (Gallego and Garcia, 1996). To make advances on geoconservation in a district it is necessary to define a methodology to catalog the Geological and Mining Heritage in a rigorous and scientific manner taking into account de geodiversity of this district. The international project Geosites (Wimbledon, 1996) defines a protocol to catalog the Geoheritage. Wimbledon (1996) proposes to divide a district in several Geological Frameworks representing its geodiversity and then catalog de Geosites (Places of Geological Interest) according to that Geological Frameworks. This method has been used in several countries (i.e. Spain, García-Cortés, 2008). In this study the Geological Frameworks of de Dominican Republic are proposed and described in order to catalog the Geosites of this country in the future.Peer ReviewedPostprint (published version

Some Problems in Density Functional Theory

Though calculations based on density functional theory (DFT) are used remarkably widely in chemistry, physics, materials science, and biomolecular research and though the modern form of DFT has been studied for almost 60 years, some mathematical problems remain. For context, we provide an outline of the basic structure of DFT, then pose several questions regarding both its time-independent and time-dependent forms. Progress on any of these would aid in development of better approximate functionals and in interpretation

Response to Neutrons and γ-rays of Two Liquid Scintillators

UltimaGoldTM AB and OptiphaseTrisafe are two liquid scintillators made by Perkin Elmer and EG & G Company respectively. Both are commercially promoted as scintillation detectors for α and β particles. In this work, the responses to γ-rays and neutrons of UltimaGoldTM AB and OptiphaseTriSafe liquid scintillators, without and with reflector, have been measured aiming to use these scintillators as γ-rays and neutron detectors. Responses to γ-rays and neutrons were measured as pulse shape spectra in a multichannel analyzer. Scintillators were exposed to gamma rays produced by 137Cs, 54Mn, 22Na and 60Co sources. The response to neutrons was obtained with a 241AmBe neutron source that was measured to 25 and 50 cm from the scintillators. The pulse height spectra due to gamma rays are shifted to larger channels as the photon energy increases and these responses are different from the response due to neutrons. Thus, UltimaGoldTM AB and OptiphaseTrisafe can be used to detect γ-rays and neutrons

Three-dimensional coarsening dynamics of a conserved, nematic liquid crystal-isotropic fluid mixture

We present a numerical investigation of the three-dimensional coarsening dynamics of a nematic liquid crystal-isotropic fluid mixture using a conserved phase field model. The model is a coupled system for a generalized Cahn–Hilliard equation for the order parameter ϕ, related to the volume fraction of the nematic component, and a simplified de Gennes–Prost evolution equation for the director field n, which describes the mean orientation of the rigid rod-like, liquid crystal molecules. We find that, as in the two-dimensional system, the orientational distortion induced by interfacial anchoring has profound effects both on the morphology and the coarsening rate. However, we identify significant differences in the three-dimensional and two-dimensional coarsening processes. In particular, we find a remarkable, new 3-stage late coarsening process with markedly different coarsening rates in the three-dimensional bicontinuous phase separation with homeotropic anchoring, unseen in the two-dimensional system

Antimicrobial resistance among migrants in Europe: a systematic review and meta-analysis

BACKGROUND: Rates of antimicrobial resistance (AMR) are rising globally and there is concern that increased migration is contributing to the burden of antibiotic resistance in Europe. However, the effect of migration on the burden of AMR in Europe has not yet been comprehensively examined. Therefore, we did a systematic review and meta-analysis to identify and synthesise data for AMR carriage or infection in migrants to Europe to examine differences in patterns of AMR across migrant groups and in different settings. METHODS: For this systematic review and meta-analysis, we searched MEDLINE, Embase, PubMed, and Scopus with no language restrictions from Jan 1, 2000, to Jan 18, 2017, for primary data from observational studies reporting antibacterial resistance in common bacterial pathogens among migrants to 21 European Union-15 and European Economic Area countries. To be eligible for inclusion, studies had to report data on carriage or infection with laboratory-confirmed antibiotic-resistant organisms in migrant populations. We extracted data from eligible studies and assessed quality using piloted, standardised forms. We did not examine drug resistance in tuberculosis and excluded articles solely reporting on this parameter. We also excluded articles in which migrant status was determined by ethnicity, country of birth of participants' parents, or was not defined, and articles in which data were not disaggregated by migrant status. Outcomes were carriage of or infection with antibiotic-resistant organisms. We used random-effects models to calculate the pooled prevalence of each outcome. The study protocol is registered with PROSPERO, number CRD42016043681. FINDINGS: We identified 2274 articles, of which 23 observational studies reporting on antibiotic resistance in 2319 migrants were included. The pooled prevalence of any AMR carriage or AMR infection in migrants was 25·4% (95% CI 19·1-31·8; I2 =98%), including meticillin-resistant Staphylococcus aureus (7·8%, 4·8-10·7; I2 =92%) and antibiotic-resistant Gram-negative bacteria (27·2%, 17·6-36·8; I2 =94%). The pooled prevalence of any AMR carriage or infection was higher in refugees and asylum seekers (33·0%, 18·3-47·6; I2 =98%) than in other migrant groups (6·6%, 1·8-11·3; I2 =92%). The pooled prevalence of antibiotic-resistant organisms was slightly higher in high-migrant community settings (33·1%, 11·1-55·1; I2 =96%) than in migrants in hospitals (24·3%, 16·1-32·6; I2 =98%). We did not find evidence of high rates of transmission of AMR from migrant to host populations. INTERPRETATION: Migrants are exposed to conditions favouring the emergence of drug resistance during transit and in host countries in Europe. Increased antibiotic resistance among refugees and asylum seekers and in high-migrant community settings (such as refugee camps and detention facilities) highlights the need for improved living conditions, access to health care, and initiatives to facilitate detection of and appropriate high-quality treatment for antibiotic-resistant infections during transit and in host countries. Protocols for the prevention and control of infection and for antibiotic surveillance need to be integrated in all aspects of health care, which should be accessible for all migrant groups, and should target determinants of AMR before, during, and after migration. FUNDING: UK National Institute for Health Research Imperial Biomedical Research Centre, Imperial College Healthcare Charity, the Wellcome Trust, and UK National Institute for Health Research Health Protection Research Unit in Healthcare-associated Infections and Antimictobial Resistance at Imperial College London

Climate Change, Global Food Security and the U.S. Food System

Food security—the ability to obtain and use sufficient amounts of safe and nutritious food—is a fundamental human need. Climate change is very likely to affect global, regional, and local food security by disrupting food availability, decreasing access to food, and making food utilization more difficult. Food security exists “when all people at all times have physical, social, and economic access to sufficient, safe, and nutritious food to meet their dietary needs and food preferences for an active and healthy life” and affects people through both under- and overconsumption. Food security requires that food be simultaneously (1) available—that it exist in a particular place at a particular time, (2) that people can access that food through economic or other means, (3) that people can utilize the food that is available and accessible to them, and (4) that each of these components be stable over time. Constrictions within any of these components can result in food insecurity. Food is provisioned through a food system that manifests in diverse ways across the globe. The food system includes all activities related to producing, transporting, trading, storing, processing, packaging, wholesaling, retailing, consuming, and disposing of food. Whether an individual food system includes few, many, or all of these elements, each is susceptible to risks from a changing climate. Human activities, such as burning fossil fuels and deforestation, have increased global greenhouse gas concentrations; atmospheric carbon dioxide levels have risen from 280 parts per million (ppm) in the late 1700s to today’s level of about 400 ppm. Concentrations continue to rise, though future levels depend on choices and development pathways yet to be determined. Additionally, the future condition of the food system depends upon socioeconomic trajectories that are external to the food system itself. For these reasons, a range of possible emissions futures and socioeconomic pathways have been considered by this assessment. The Climate Change, Global Food Security, and U.S. Food System assessment represents a consensus of authors and includes contributors from 19 Federal, academic, nongovernmental, and intergovernmental organizations in four countries, identifying climate-change effects on global food security through 2100, and analyzing the United States’ likely connections with that world. The assessment finds that climate change is likely to diminish continued progress on global food security through production disruptions leading to local availability limitations and price increases, interrupted transport conduits, and diminished food safety, among other causes. The risks are greatest for the global poor and in tropical regions. In the near term, some high-latitude production export regions may benefit from changes in climate. As part of a highly integrated global food system, consumers and producers in the United States are likely to be affected by these changes. The type and price of food imports from other regions are likely to change, as are export demands placed upon U.S. producers and the transportation, processing, and storage systems that enable global trade. Demand for food and other types of assistance may increase, as may demand for advanced technologies to manage changing conditions. Adaptation across the food system has great potential to manage climate-change effects on food security, and the complexity of the food system offers multiple potential points of intervention for decision makers at every level, from households to nations and international governance structures. However, effective adaptation is subject to highly localized conditions and socioeconomic factors, and the technical feasibility of an adaptive intervention is not necessarily a guarantee of its application if it is unaffordable or does not provide benefits within a relatively short time frame, particularly for smaller operations around the world with limited capacity for long-term investments. The accurate identification of needs and vulnerabilities, and the effective targeting of adaptive practices and technologies across the full scope of the food system, are central to improving global food security in a changing climate

The Eighteenth Data Release of the Sloan Digital Sky Surveys: Targeting and First Spectra from SDSS-V

The eighteenth data release of the Sloan Digital Sky Surveys (SDSS) is the first one for SDSS-V, the fifth generation of the survey. SDSS-V comprises three primary scientific programs, or "Mappers": Milky Way Mapper (MWM), Black Hole Mapper (BHM), and Local Volume Mapper (LVM). This data release contains extensive targeting information for the two multi-object spectroscopy programs (MWM and BHM), including input catalogs and selection functions for their numerous scientific objectives. We describe the production of the targeting databases and their calibration- and scientifically-focused components. DR18 also includes ~25,000 new SDSS spectra and supplemental information for X-ray sources identified by eROSITA in its eFEDS field. We present updates to some of the SDSS software pipelines and preview changes anticipated for DR19. We also describe three value-added catalogs (VACs) based on SDSS-IV data that have been published since DR17, and one VAC based on the SDSS-V data in the eFEDS field.Comment: Accepted to ApJ

Epidemiology of Invasive Fungal Infections in Latin America

The pathogenic role of invasive fungal infections (IFIs) has increased during the past two decades in Latin America and worldwide, and the number of patients at risk has risen dramatically. Working habits and leisure activities have also been a focus of attention by public health officials, as endemic mycoses have provoked a number of outbreaks. An extensive search of medical literature from Latin America suggests that the incidence of IFIs from both endemic and opportunistic fungi has increased. The increase in endemic mycoses is probably related to population changes (migration, tourism, and increased population growth), whereas the increase in opportunistic mycoses may be associated with the greater number of people at risk. In both cases, the early and appropriate use of diagnostic procedures has improved diagnosis and outcome