3,111 research outputs found
Capacity loss of non-aqueous Li-Air battery due to insoluble product formation: Approximate solution and experimental validation
In this paper, we present a study of Lithium (Li)-air battery capacity by accounting for the voltage loss associated with the electrode passivation and transport resistance caused by insoluble product formation. Two regimes are defined, in which approximate formulas are developed to explicitly evaluate the battery capacity, along with extensive validation against experimental data of various cathode properties and materials from our and several other groups. The dependence of battery capacity on the surface coverage factor, tortuosity, and Damköhler numbers (Da) is explicitly expressed and discussed. The formulas provide a guideline for experimentalists and practitioners in air cathode design, analysis, and control
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Determinants of Phage Host Range in Staphylococcus Species.
Bacteria in the genus Staphylococcus are important targets for phage therapy due to their prevalence as pathogens and increasing antibiotic resistance. Here we review Staphylococcus outer surface features and specific phage resistance mechanisms that define host range - the set of strains an individual phage can potentially infect. Phage infection goes through five distinct phases - attachment, uptake, biosynthesis, assembly and lysis. Adsorption inhibition, encompassing outer surface teichoic acid receptor alteration, elimination, or occlusion, limits successful phage attachment and entry. Restriction-modification systems (in particular, type I and IV systems), which target phage DNA inside the cell, serve as the major barriers to biosynthesis as well as transduction and horizontal gene transfer between clonal complexes and species. Resistance to late stages of infection occurs through mechanisms such as assembly interference, in which staphylococcal pathogenicity islands siphon away superinfecting phage proteins to package their own DNA. While genes responsible for teichoic acid biosynthesis, capsule, and restriction-modification are found in most Staphylococcus strains, a variety of other host-range determinants (e.g., CRISPRs, abortive infection, and superinfection immunity) are sporadic. Fitness costs of phage resistance through teichoic acid structure alteration could make staphylococcal phage therapies promising, but host range prediction is complex because of the large number of genes involved, many with unknown roles. In addition, little is known about genetic determinants that contribute to host range expansion in the phages themselves. Future research must identify host range determinants, characterize resistance development during infection and treatment, and examine population-wide genetic background effects on resistance selection
Dark matter annihilation and decay in dwarf spheroidal galaxies: The classical and ultrafaint dSphs
Dwarf spheroidal (dSph) galaxies are prime targets for present and future
gamma-ray telescopes hunting for indirect signals of particle dark matter. The
interpretation of the data requires careful assessment of their dark matter
content in order to derive robust constraints on candidate relic particles.
Here, we use an optimised spherical Jeans analysis to reconstruct the
`astrophysical factor' for both annihilating and decaying dark matter in 21
known dSphs. Improvements with respect to previous works are: (i) the use of
more flexible luminosity and anisotropy profiles to minimise biases, (ii) the
use of weak priors tailored on extensive sets of contamination-free mock data
to improve the confidence intervals, (iii) systematic cross-checks of binned
and unbinned analyses on mock and real data, and (iv) the use of mock data
including stellar contamination to test the impact on reconstructed signals.
Our analysis provides updated values for the dark matter content of 8
`classical' and 13 `ultrafaint' dSphs, with the quoted uncertainties directly
linked to the sample size; the more flexible parametrisation we use results in
changes compared to previous calculations. This translates into our ranking of
potentially-brightest and most robust targets---viz., Ursa Minor, Draco,
Sculptor---, and of the more promising, but uncertain targets---viz., Ursa
Major 2, Coma---for annihilating dark matter. Our analysis of Segue 1 is
extremely sensitive to whether we include or exclude a few marginal member
stars, making this target one of the most uncertain. Our analysis illustrates
challenges that will need to be addressed when inferring the dark matter
content of new `ultrafaint' satellites that are beginning to be discovered in
southern sky surveys.Comment: 19 pages, 14 figures, submitted to MNRAS. Supplementary material
available on reques
Evidence and practice: a review of vignettes in qualitative research.
BACKGROUND: Developing and working through a PhD research study requires tenacity, continuous development and application of knowledge. It is paramount when researching sensitive topics to consider carefully the construction of tools for collecting data, to ensure the study is ethically robust and explicitly addresses the research question.
AIM: To explore how novice researchers can develop insight into aspects of the research process by developing vignettes as a research tool.
DISCUSSION: This article focuses on the use of vignettes to collect data as part of a qualitative PhD study investigating making decisions in the best interests of and on behalf of people with advanced dementia. Developing vignettes is a purposeful, conscious process. It is equally important to ensure that vignettes are derived from literature, have an evidence base, are carefully constructed and peer-reviewed, and are suitable to achieve the research's aims.
CONCLUSION: Using and analysing a vignette enables novice researchers to make sense of aspects of the qualitative research process and engage with it to appreciate terminology.
IMPLICATIONS FOR PRACTICE: Vignettes can provide an effective platform for discussion when researching topics where participants may be reluctant to share sensitive real-life experiences
Mitochondrial disease: Needs and problems of children, their parents and family. A systematic review and pilot study into the need for information of parents during the diagnostic phase
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51979.pdf (publisher's version ) (Closed access)OBJECTIVE: Firstly, this paper aims to systematically review the mitochondrial disease literature to identify studies assessing the needs and problems in the daily life of children with a mitochondrial disease and of their parents and family. The second aim is to provide more insight into the need for information by the parents of these children during the diagnostic process while in hospital. DESIGN: A systematic review and a pilot study, using a qualitative (focus group interviews; n = 7) and a quantitative (questionnaire; n = 37) design. RESULTS: Mothers reported great socioeconomic and psychoaffective strain and showed psychopathological symptoms in the two studies published with respect to this topic. The pilot study showed that parents considered an honest and interested attitude of the person who is giving the information as most important. Furthermore they wanted oral and written information and a central point where they could go with their questions at any time they felt the need. The need for information increased during the four phases of the diagnostic process and was highest in the fourth phase. CONCLUSIONS: The few studies found in the review, combined with expectations that having a mitochondrial disease must have a great impact on these children and their parents and family, call for more research in their needs and problems. Furthermore, there are gaps in the current information provision to parents of these children. A better understanding of the needs and problems of these children and their family is essential for effective care planning and might result in an improved quality of life
Luminance, colour, viewpoint and border enhanced disparity energy model
The visual cortex is able to extract disparity information through the use of binocular cells. This process is reflected by the Disparity Energy Model, which describes the role and functioning of simple and complex binocular neuron populations, and how they are able to extract disparity. This model uses explicit cell parameters to mathematically determine preferred cell disparities, like spatial frequencies, orientations, binocular phases and receptive field positions. However, the brain cannot access such explicit cell parameters; it must rely on cell responses. In this article, we implemented a trained binocular neuronal population, which encodes disparity information implicitly. This allows the population to learn how to decode disparities, in a similar way to how our visual system could have developed this ability during evolution. At the same time, responses of monocular simple and complex cells can also encode line and edge information, which is useful for refining disparities at object borders. The brain should then be able, starting from a low-level disparity draft, to integrate all information, including colour and viewpoint perspective, in order to propagate better estimates to higher cortical areas.Portuguese Foundation for Science and Technology (FCT); LARSyS FCT [UID/EEA/50009/2013]; EU project NeuroDynamics [FP7-ICT-2009-6, PN: 270247]; FCT project SparseCoding [EXPL/EEI-SII/1982/2013]; FCT PhD grant [SFRH-BD-44941-2008
Correcting pervasive errors in RNA crystallography through enumerative structure prediction
Three-dimensional RNA models fitted into crystallographic density maps
exhibit pervasive conformational ambiguities, geometric errors and steric
clashes. To address these problems, we present enumerative real-space
refinement assisted by electron density under Rosetta (ERRASER), coupled to
Python-based hierarchical environment for integrated 'xtallography' (PHENIX)
diffraction-based refinement. On 24 data sets, ERRASER automatically corrects
the majority of MolProbity-assessed errors, improves the average Rfree factor,
resolves functionally important discrepancies in noncanonical structure and
refines low-resolution models to better match higher-resolution models
Modeling the magnetospheric X-ray emission from solar wind charge exchange with verification from XMM-Newton observations
An MHDâbased model of terrestrial solar wind charge exchange (SWCX) is created and compared to 19 case study observations in the 0.5â0.7 keV emission band taken from the European Photon Imaging Cameras on board XMMâNewton. This model incorporates the Global Unified MagnetosphereâIonosphere Coupling Simulationâ4 MHD code and produces an Xâray emission datacube from O7+ and O8+ emission lines around the Earth using in situ solar wind parameters as the model input. This study details the modeling process and shows that fixing the oxygen abundances to a constant value reduces the variance when comparing to the observations, at the cost of a small accuracy decrease in some cases. Using the ACE oxygen data returns a wide ranging accuracy, providing excellent correlation in a few cases and poor/anticorrelation in others. The sources of error for any user wishing to simulate terrestrial SWCX using an MHD model are described here and include mask position, hydrogen to oxygen ratio in the solar wind, and charge state abundances. A dawnâdusk asymmetry is also found, similar to the results of empirical modeling. Using constant oxygen parameters, magnitudes approximately double that of the observed count rates are returned. A high accuracy is determined between the model and observations when comparing the count rate difference between enhanced SWCX and quiescent periods
A viscoelastic deadly fluid in carnivorous pitcher plants
Background : The carnivorous plants of the genus Nepenthes, widely
distributed in the Asian tropics, rely mostly on nutrients derived from
arthropods trapped in their pitcher-shaped leaves and digested by their
enzymatic fluid. The genus exhibits a great diversity of prey and pitcher forms
and its mechanism of trapping has long intrigued scientists. The slippery inner
surfaces of the pitchers, which can be waxy or highly wettable, have so far
been considered as the key trapping devices. However, the occurrence of species
lacking such epidermal specializations but still effective at trapping insects
suggests the possible implication of other mechanisms. Methodology/Principal
Findings : Using a combination of insect bioassays, high-speed video and
rheological measurements, we show that the digestive fluid of Nepenthes
rafflesiana is highly viscoelastic and that this physical property is crucial
for the retention of insects in its traps. Trapping efficiency is shown to
remain strong even when the fluid is highly diluted by water, as long as the
elastic relaxation time of the fluid is higher than the typical time scale of
insect movements. Conclusions/Significance : This finding challenges the common
classification of Nepenthes pitchers as simple passive traps and is of great
adaptive significance for these tropical plants, which are often submitted to
high rainfalls and variations in fluid concentration. The viscoelastic trap
constitutes a cryptic but potentially widespread adaptation of Nepenthes
species and could be a homologous trait shared through common ancestry with the
sundew (Drosera) flypaper plants. Such large production of a highly
viscoelastic biopolymer fluid in permanent pools is nevertheless unique in the
plant kingdom and suggests novel applications for pest control
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