The properties of the Li2O2 discharge phase are expected to impact strongly the performance of Li–air batteries. Although both crystalline Li2O2 (c-Li2O2) and amorphous Li2O2 (a-Li2O2) have been ...reported to form in Li–air cells, little is known regarding possible differences in charge and mass transport within these phases. To reveal these differences, here we predict the properties of a-Li2O2 using first-principles “melt-and-quench” molecular dynamics and percolation theory. We find that the band gaps and equilibrium electrochemical potentials of c-Li2O2 and a-Li2O2 are similar; nevertheless, their transport properties are quite different. Importantly, the ionic conductivity of a-Li2O2 is predicted to be 2 × 10–7 S/cm, which is 12 orders of magnitude larger than that in the crystalline phase. This enhancement arises from increases in both the concentration and mobility of negative lithium vacancies. The electronic conductivity of a-Li2O2 is also enhanced, but to a much smaller extent (4 orders of magnitude), and remains low overall, 2 × 10–16 S/cm. These data suggest that the formation of amorphous Li2O2 during discharge may enhance cell performance if charge or mass transport through the discharge product is a rate-limiting process.
Cancer in Africa 2012 Parkin, D Maxwell; Bray, Freddie; Ferlay, Jacques ...
Cancer epidemiology, biomarkers & prevention,
06/2014, Letnik:
23, Številka:
6
Journal Article
Recenzirano
Odprti dostop
Noncommunicable diseases, and especially cancers, are recognized as an increasing problem for low and middle income countries. Effective control programs require adequate information on the size, ...nature, and evolution of the health problem that they pose.
We present estimates of the incidence and mortality of cancer in Africa in 2012, derived from "GLOBOCAN 2012," published by the International Agency for Research on Cancer.
There were 847,000 new cancer cases (6% of the world total) and 591,000 deaths (7.2% of the world total) in the 54 countries of Africa in 2012, with about three quarters in the 47 countries of Sub-Saharan Africa. While the cancer profiles often differ markedly between regions, the most common cancers in men were prostate (16.4% of new cancers), liver (10.7%), and Kaposi sarcoma (6.7%); in women, by far the most important are cancers of the breast (27.6% of all cancers) and cervix uteri (20.4%).
There are still deficiencies in surveillance systems, particularly in Sub-Saharan Africa and, specifically, of their most vital component, population-based cancer registries. With the number of annual cancer cases and deaths likely to increase by at least 70% by 2030, there is a pressing need for a coordinated approach to improving the extent and quality of services for cancer control in Africa, and better surveillance systems with which they can be planned and monitored.
The results are the best data currently available and provide a reasonable appraisal of the cancer situation in Africa.
A variational approach to niche construction Constant, Axel; Ramstead, Maxwell J. D.; Veissière, Samuel P. L. ...
Journal of the Royal Society interface,
04/2018, Letnik:
15, Številka:
141
Journal Article
Recenzirano
Odprti dostop
In evolutionary biology, niche construction is sometimes described as a genuine evolutionary process whereby organisms, through their activities and regulatory mechanisms, modify their environment ...such as to steer their own evolutionary trajectory, and that of other species. There is ongoing debate, however, on the extent to which niche construction ought to be considered a bona fide evolutionary force, on a par with natural selection. Recent formulations of the variational free-energy principle as applied to the life sciences describe the properties of living systems, and their selection in evolution, in terms of variational inference. We argue that niche construction can be described using a variational approach. We propose new arguments to support the niche construction perspective, and to extend the variational approach to niche construction to current perspectives in various scientific fields.
Cholesterol reduction from statin therapy has been one of the greatest public health successes in modern medicine. Simvastatin is among the most commonly used prescription medications. A ...non‐synonymous coding single‐nucleotide polymorphism (SNP), rs4149056, in SLCO1B1 markedly increases systemic exposure to simvastatin and the risk of muscle toxicity. This guideline explores the relationship between rs4149056 (c.521T>C, p.V174A) and clinical outcome for all statins. The strength of the evidence is high for myopathy with simvastatin. We limit our recommendations accordingly.
Clinical Pharmacology & Therapeutics (2012); 92 1, 112–117. doi:10.1038/clpt.2012.57
The processes underwriting the acquisition of culture remain unclear. How are shared habits, norms, and expectations learned and maintained with precision and reliability across large-scale ...sociocultural ensembles? Is there a unifying account of the mechanisms involved in the acquisition of culture? Notions such as "shared expectations," the "selective patterning of attention and behaviour," "cultural evolution," "cultural inheritance," and "implicit learning" are the main candidates to underpin a unifying account of cognition and the acquisition of culture; however, their interactions require greater specification and clarification. In this article, we integrate these candidates using the variational (free-energy) approach to human cognition and culture in theoretical neuroscience. We describe the construction by humans of social niches that afford epistemic resources called cultural affordances. We argue that human agents learn the shared habits, norms, and expectations of their culture through immersive participation in patterned cultural practices that selectively pattern attention and behaviour. We call this process "thinking through other minds" (TTOM) - in effect, the process of inferring other agents' expectations about the world and how to behave in social context. We argue that for humans, information from and about other people's expectations constitutes the primary domain of statistical regularities that humans leverage to predict and organize behaviour. The integrative model we offer has implications that can advance theories of cognition, enculturation, adaptation, and psychopathology. Crucially, this formal (variational) treatment seeks to resolve key debates in current cognitive science, such as the distinction between internalist and externalist accounts of theory of mind abilities and the more fundamental distinction between dynamical and representational accounts of enactivism.
Accurate information on the extent of disease around the time of diagnosis is an important component of cancer care, in defining disease prognosis, and evaluating national and international cancer ...control policies. However, the collection of stage data by population-based cancer registries remains a challenge in both high-income and low and middle-income countries. We emphasise the lack of availability and comparability of staging information in many population-based cancer registries and propose Essential TNM, a simplified staging system for cancer registries when information on full Tumour, Node, Metastasis (TNM) is absent. Essential TNM aims at staging cancer in its most advanced disease form by summarising the extent of disease in the order of distant metastasis (M), regional lymph node involvement (N), and tumour size or extension, or both (T). Flowcharts and rules have been developed for coding these elements in breast, cervix, prostate, and colon cancers, and combining them into stage groups (I–IV) that correspond to those obtained by full TNM staging. Essential TNM is comparable to the Union for International Cancer Control TNM stage groups and is an alternative to providing staging information by the population-based cancer registries that complies with the objectives of the Global Initiative for Cancer Registry Development.
The degrees of freedom associated with orbital, spin, and charge ordering can strongly affect the properties of many crystalline solids, including battery materials, high-temperature superconductors, ...and naturally occurring minerals. This work reports on the development of a computational framework to systematically explore the ordering of electronic degrees of freedom and presents results on orbital ordering associated with Jahn–Teller distortions in four layered oxides relevant for Li- and Na-ion batteries: LiNiO2, NaNiO2, LiMnO2, and NaMnO2. Our calculations reveal a criterion for the stability of orbital orderings in these layered materials: each oxygen atom must participate in two short and one long transition-metal/oxygen bond. The only orderings that satisfy this stability criterion are row orderings, such as the “zigzag” ordering. The near degeneracy of such row-orderings in LiNiO2 suggests that boundaries between domains with distinct but symmetrically equivalent Jahn–Teller distortions will be relatively low in energy. Based on this result, we speculate that a microstructure consisting of nanoscale Jahn–Teller domains could be responsible for the apparent absence of a collective distortion in experiments on LiNiO2.
The performance of Na-ion batteries is sensitive to the nature of cation ordering and phase transformations that occur within the intercalation compounds used as electrodes. In order to elucidate ...these effects in layered Na intercalation compounds, we have carried out a first-principles statistical mechanics study of Na ordering and stacking-sequence preferences in the model compound Na x TiS2. Our calculations predict a series of structural phase transitions at room temperature between O3, P3, O1, O1–O3 staged hybrid, and O1–P3 staged hybrid. We further explore the ordering of Na ions in P3 and O3 and find that these host structures favor very distinct Na-vacancy patterns. Low energy orderings on the honeycomb lattice in P3 consist of triangular island domains with vacancies coalescing at antiphase boundaries. This results in a devil’s staircase of ground-state Na orderings within P3 that are unlike the orderings possible in the triangular lattice of Na sites in O3. We explore the role that antiphase boundaries play in mediating Na diffusion in the P3 host.
The performance of many technologies, such as Li- and Na-ion batteries as well as some two-dimensional (2D) electronics, is dependent upon the reversibility of stacking-sequence-change phase ...transformations. However, the mechanisms by which such transformations lead to degradation are not well understood. This study explores lattice-invariant shear as a source of irreversibility in stacking-sequence changes, and through an analysis of crystal symmetry shows that common electrode materials (graphitic carbon, layered oxides, and layered sulfides) are generally susceptible to lattice-invariant shear. The resulting irreversible changes to microstructure upon cycling (“electrochemical creep”) could contribute to the degradation of the electrode and capacity fade.
PDF
