Variation of the cumulative heat stored in n-hexadecane (C16), n-heptadecane (C18) and n-eicosane (C20) as function of temperature. Display omitted
•Thermal properties of n-hexadecane, n-octadecane ...and n-eicosane used as PCM are reported.•Thermal conductivity and thermal diffusivity were measured by the hot wire technique at different temperatures.•A discontinuity in thermal conductivity and diffusivity was detected near the melting temperature.•No literature data were found for the thermal diffusivity of the three n-alkanes considered in this study.•The cumulative heat stored increases with the number of carbon in the n-alkane hydrocarbon chain.
The thermal conductivity (λ) and thermal diffusivity (aT) of the solid/liquid phase change linear n-alkanes were measured simultaneously by the transient multi-current hot wire technique at atmospheric pressure in the range 258–348K. The same set-up was used to measure λ and aT of the liquid and the solid states at different electrical currents. Three n-alkanes, n-hexadecane (C16H34), n-octadecane (C18H38) and n-eicosane (C20H42) were studied. Differential scanning calorimetry was applied at the temperature range 248–348K to determine the melting/crystallization temperature, the heat of melting/crystallization and the specific heat of both the solid and liquid phases. Some results were compared with available literature data. The density of the n-alkanes at liquid state was also measured at different temperatures and their thermal diffusivity was estimated and compared to that obtained by the hot wire technique. The cumulative energy stored was estimated over a definite range of temperature for the three n-alkanes and this was found to be higher for eicosane.
The Plasma Environment Modeling in the Earth's Magnetosphere (PEMEM) is a European Space Agency activity supporting the development of a new specification model for the spacecraft surface charging ...risk assessment. This paper presents a description of the basic model version: the PEMEM percentile model. The model is intended to be used for space missions with near‐equatorial orbits. The model is based on the Van Allen Probes particle measurements inside the geostationary orbit. The model's primary input is a planned spacecraft trajectory. It outputs statistical characteristics of the plasma environment which are expected to be encountered during a mission lifetime. These characteristics include differential electron and proton flux percentiles for a set of energies (percentile spectra), and percentiles of the integrated electron flux. The model covers the energy range of 1–100 keV for electrons and 40 eV–51 keV for protons. Since extreme spacecraft charging usually occurs in the eclipse, the same characteristics can be separately output for the periods when the spacecraft is shadowed by the Earth.
Key Points
The new specification model of cis‐GEO near‐equatorial plasma environment aimed at the surface charging risk assessment is presented
The model covers the energy ranges 1–100 keV for electrons and 50 eV–50 keV for protons
For a given orbital scenario, the model outputs flux percentiles that are expected to be encountered during the mission lifetime
The growth and survival of Crassostrea gigas were evaluated in hanging culture in the Chone River estuary (Bahía de Caráquez), Manabí province, Ecuador. Oyster seeds (~10 mm) were confined in lantern ...nets at a density equal to the occupation of half the surface of the basket base, until reaching commercial size (80 mm). A sample for oyster biometric, parasitic and bacterial analysis was obtained monthly. Temperature, salinity, oxygen concentration, seston and phytoplankton biomass were determined. At the end of the study, the oysters were analysed for heavy metal concentration. The commercial oyster production was extrapolated to estimate the possible economic performance of a family production module (a 7 × 7 m bamboo raft). The results show a great biological feasibility of culture of C. gigas with harvests of commercial size oysters in only 5 months and acceptable survivals (accumulated >70%, after 3 weeks of crop seed selection). The heavy metal concentrations and the parasitological and bacteriological analyses did not indicate levels of contamination. The economic projections suggest that, even with a profitability of 57%, the initially invested capital could be recovered within the first harvest.
Spectroscopic and spectropolarimetric observations of the pre-main sequence early-G star HD 141943 were obtained at four observing epochs (in 2006, 2007, 2009 and 2010). The observations were ...undertaken at the 3.9-m Anglo-Australian Telescope using the UCLES echelle spectrograph and the SEMPOL spectropolarimeter visitor instrument. Brightness and surface magnetic field topologies were reconstructed for the star using the technique of least-squares deconvolution to increase the signal-to-noise ratio of the data.
The reconstructed brightness maps show that HD 141943 had a weak polar spot and a significant amount of low-latitude features, with little change in the latitude distribution of the spots over the 4 yr of observations. The surface magnetic field was reconstructed at three of the epochs from a high-order (l≤ 30) spherical harmonic expansion of the spectropolarimetric observations. The reconstructed magnetic topologies show that in 2007 and 2010 the surface magnetic field was reasonably balanced between poloidal and toroidal components. However, we find tentative evidence of a change in the poloidal/toroidal ratio in 2009 with the poloidal component becoming more dominant. At all epochs the radial magnetic field is predominantly non-axisymmetric while the azimuthal field is predominantly axisymmetric with a ring of positive azimuthal field around the pole similar to that seen on other active stars.
•Addressed an extended version of the truck loading problem.•Presented a novel mixed integer linear formulation.•Developed a two-phase exact solution approach, and a greedy heuristic.•Tested on 300 ...realistic random cases and 5 actual case studies.•Conducted extensive computational experiments to assess their performance.
In this work we address the problem of determining the optimal types of products and their quantities that should be loaded on a fleet of heterogeneous one or two level trucks so that the weighted sum of delivered products is maximized, with the weights being an exponential function of the lateness computed for each unit shipped. We propose a mixed integer linear formulation followed by a two-phase solution approach. During phase one the formulation is solved aiming at maximizing the weighted sum of products delivered, whereas for the second phase, the formulation is solved aiming at minimizing the number of trucks, while ensuring that the objective function attained in phase one is not compromised. A greedy heuristic is also proposed in order to better quantify the advantages of adopting the proposed exact approach with respect to solution quality. To assess the performance of the proposed approach we used two sets of test instances, a large set of randomly generated instances that resemble the practical application that motivated this research, and a small set of real instances provided by the company. The results of our computational experiments suggest that the proposed exact solution approach is very effective in solving realistic sized instances.
The objective of this study was to analyze the eco-epidemiological aspects of Leptospira seroprevalence and seroincidence and its associated factors in two municipalities of northwest Colombia. A ...prospective study was performed in rural areas of Urabá, Antioquia, Colombia. The study enrolled 597 people between November 2015 and January 2016, of which 274 were followed up 1 year later. Serologic testing was performed by a microscopic agglutination. The outcomes were seroprevalent and seroincident cases, and the primary exposure was an outdoor occupation. A binary and mixed-effect multinomial logistic regression model was used to estimate factors associated with seroprevalent or seroincident cases of Leptospira infection. The overall Leptospira seroprevalence was 27.81% (95% confidence interval: 23.62-32.49), and the overall cumulative seroincidence for Leptospira was 14.60% (95% confidence interval: 10.33-20.23). Multivariable analysis showed that factors associated with L. interrogans serogroups seropositivity were outdoor occupation, male gender, older age, the presence of dirt floor in the household, and the presence of piglets and opossums. It also showed that factors associated with other Leptospira species serogroups were the presence of pit latrines and of turkeys. In addition, the multivariable model of seroincident cases of L. interrogans serogroups evidenced outdoor occupations, the presence of rats, and corn cultivation as risk factors. Likewise, the multivariable model for seroincident cases of other Leptospira species showed that the presence of hunting canines and cassava cultivation were risk factors. We found specific factors associated with the transmission of Leptospira serogroups contribute to the understanding of the epidemiology of Leptospira infection in rural areas of Urabá, Colombia.
We present the photometry and spectropolarimetry of the pre-main-sequence star HD 106506. A photometric rotational period of ∼1.416 ± 0.133 d has been derived using observations at Mount Kent ...Observatory (MKO). Spectropolarimetric data obtained with the 3.9-m Anglo-Australian Telescope (AAT) were used to derive spot occupancy and magnetic maps of the star through the technique of Zeeman Doppler imaging (ZDI). The resulting brightness maps indicate that HD 106506 displays photospheric spots at all latitudes including a predominant polar spot. Azimuthal and radial magnetic images of this star have been derived, and a significant azimuthal magnetic field is indicated, in line with other active young stars. A solar-like differential rotation law was incorporated into the imaging process. Using Stokes I information the equatorial rotation rate, Ωeq, was found to be 4.54 ± 0.01 rad d−1, with a photospheric shear δΩ of 0.21+0.02
−0.03 rad d−1. This equates to an equatorial rotation period of ∼1.39 ± 0.01 d, with the equatorial region lapping the poles every ∼ 30+5
−3 d. Using the magnetic features, the equatorial rotation rate, Ωeq, was found to be 4.51 ± 0.01 rad d−1, with a photospheric shear δΩ of 0.24 ± 0.03 rad d−1. This differential rotation is approximately four times that observed on the Sun.
Aims and objectives
To explore aspects related to the fulfilment of the role of nurses in palliative sedation.
Background
Palliative sedation demands knowledge and a proper attitude for maintaining ...comfort, preserving dignity and contributing to a peaceful death. In some developed countries, nurses have a well‐established role in palliative sedation. However, studies on their role and its fulfilment are limited, particularly in the developing world.
Design
An exploratory, mixed, qualitative and quantitative study was conducted. A self‐administered questionnaire was used to examine the level of knowledge of palliative sedation and the level of confidence in skills and knowledge about palliative sedation. Also, focus groups were conducted to explore the emotional impact and the perceived role of nurses.
Methods
Forty‐one nurses from three advanced‐care hospitals with palliative care units in Colombia completed the questionnaire. Also, four focus groups were conducted with 22 participants selected from the first phase.
Results
A high level of knowledge regarding palliative sedation was found, but the level of confidence in skills was higher than the confidence in knowledge. The participants expressed their belief that their knowledge was derived from experience but believed that it was not enough to fulfil their role with confidence. A negative emotional impact about the patients' condition was found. For some, it served as motivation to provide better care. For others, it was difficult to face, especially when assisting children. They also expressed satisfaction and gratification about providing relief from suffering through sedation.
Conclusions
The role of nursing is essential in palliative sedation. Although the nurses' knowledge is adequate, it primarily derives from experience and not from formal training, which impacts on their perceived confidence and their distress.
Relevance to clinical practice
Formal training for the optimal fulfilling of the nursing role in palliative sedation is crucial to provide better end‐of‐life care, particularly in developing countries.
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