Measurement of incidence rates of childhood cancer in Africa is difficult. The study 'Cancer of Childhood in sub Saharan Africa' brings together results from 16 population-based registries which, as ...members of the African Cancer Registry Network (AFCRN), have been evaluated as achieving adequate coverage of their target population. The cancers are classified according to the third revision of the International Classification of Childhood Cancer (ICCC-3) and recorded rates in Africa are compared with those in childhood populations in the UK, France, and the USA. It is clear that, in many centres, lack of adequate diagnostic and treatment facilities leads to under-diagnosis (and enumeration) of leukaemias and brain cancers. However, for several childhood cancers, incidence rates in Africa are higher than those in high-income countries. This applies to infection-related cancers such as Kaposi sarcoma, Burkitt lymphoma, Hodgkin lymphoma and hepatocellular carcinoma, and also to two common embryonal cancers - retinoblastoma and nephroblastoma. These (and other) observations are unlikely to be artefact, and are of considerable interest when considering possible aetiological factors, including ethnic differences in risk (and hence genetic/familial antecedents). The data reported are the most extensive so far available on the incidence of cancer in sub Saharan Africa, and clearly indicate the need for more resources to be devoted to cancer registration, especially in the childhood age range, as part of an overall programme to improve the availability of diagnosis and treatment of this group of cancers, many of which have-potentially-an excellent prognosis.
The thermodynamic stability and electronic structure of 40 surfaces of lithium peroxide (Li2O2) and lithium oxide (Li2O) were characterized using first-principles calculations. As these compounds ...constitute potential discharge products in Li–oxygen batteries, their surface properties are expected to play a key role in understanding electrochemical behavior in these systems. Stable surfaces were identified by comparing 23 distinct Li2O2 surfaces and 17 unique Li2O surfaces; crystallite areal fractions were determined through application of the Wulff construction. Accounting for the oxygen overbinding error in density functional theory results in the identification of several new Li2O2 oxygen-rich {0001} and {11̅00} terminations that are more stable than those previously reported. Although oxygen-rich facets predominate in Li2O2, in Li2O stoichiometric surfaces are preferred, consistent with prior studies. Surprisingly, surface-state analyses reveal that the stable surfaces of Li2O2 are half-metallic, despite the fact that Li2O2 is a bulk insulator. Surface oxygens in these facets are ferromagnetic with magnetic moments ranging from 0.2 to 0.5 μB. In contrast, the stable surfaces of Li2O are insulating and nonmagnetic. The distinct surface properties of these compounds may explain observations of electrochemical reversibility for systems in which Li2O2 is the discharge product and the irreversibility of systems that discharge to Li2O. Moreover, the presence of conductive surface pathways in Li2O2 could offset capacity limitations expected to arise from limited electron transport through the bulk.
We present a multiscale integrationist interpretation of the boundaries of cognitive systems, using the Markov blanket formalism of the variational free energy principle. This interpretation is ...intended as a corrective for the philosophical debate over internalist and externalist interpretations of cognitive boundaries; we stake out a compromise position. We first survey key principles of new radical (extended, enactive, embodied) views of cognition. We then describe an internalist interpretation premised on the Markov blanket formalism. Having reviewed these accounts, we develop our positive multiscale account. We argue that the statistical seclusion of internal from external states of the system—entailed by the existence of a Markov boundary—can coexist happily with the multiscale integration of the system through its dynamics. Our approach does not privilege any given boundary (whether it be that of the brain, body, or world), nor does it argue that all boundaries are equally prescient. We argue that the relevant boundaries of cognition depend on the level being characterised and the explanatory interests that guide investigation. We approach the issue of how and where to draw the boundaries of cognitive systems through a multiscale ontology of cognitive systems, which offers a multidisciplinary research heuristic for cognitive science.
With the cancer burden rising in sub-Saharan Africa, countries in the region need surveillance systems to measure the magnitude of the problem and monitor progress in cancer control planning. Based ...on the national estimates built from data provided by cancer registries in sub-Saharan Africa, we summarise key patterns of the regional burden and argue for investments in locally produced data.
To present national estimates of the cancer incidence and mortality burden in sub-Saharan Africa countries, new cancer cases and deaths were extracted from International Agency for Research on Cancers' GLOBOCAN database for the year 2020. Given weak vital statistics systems, almost all of the information on the cancer burden in sub-Saharan Africa was derived from population-based cancer registries. Of the 48 countries included in GLOBOCAN (national populations must be larger than 150 000 inhabitants in 2020), relatively recent cancer registry data (up to 2019) were directly used to produce national incidence estimates in 25 countries, while the absence of such data for 16 meant that estimates were based on data from neighbouring countries. Tables and figures present the estimated numbers of new cases and deaths, as well as age-standardised (incidence or mortality) rates per 100 000 person-years and the cumulative risk of developing or dying from cancer before the age of 75 years.
801 392 new cancer cases and 520 158 cancer deaths were estimated to have occurred in sub-Saharan Africa in 2020. Cancers of the breast (129 400 female cases) and cervix (110 300 cases) were responsible for three in ten of the cancers diagnosed in both sexes. Breast and cervical cancer were the most common cancers, ranking first in 28 and 19 countries, respectively. In men, prostate cancer led in terms of incidence (77 300 cases), followed by liver cancer (24 700 cases) and colorectal cancer (23 400 cases). Prostate cancer was the leading incident cancer in men in 40 sub-Saharan Africa countries. The risk of a woman in sub-Saharan Africa developing cancer by the age of 75 years was 14·1%, with breast cancer (4·1%) and cervical cancer (3·5%) responsible for half of this risk. For men, the corresponding cumulative incidence was lower (12·2%), with prostate cancer responsible for a third of this risk (4·2%). Cervical cancer was the leading form of cancer death among women in 27 countries, followed by breast cancer (21 countries). Prostate cancer led as the most common type of cancer death in 26 countries, with liver cancer ranking second (11 countries).
The estimates indicate substantial geographical variations in the major cancers in sub-Saharan Africa. Rational cancer control planning requires capacity to be built for data production, analysis, and interpretation within the countries themselves. Cancer registries provide important information in this respect and should be prioritised for sustainable investment in the region.
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The performance of high-capacity Li/O2 batteries is limited by the high overpotential associated with the oxygen evolution reaction (OER) during charging. These losses have been attributed to ...sluggish charge transport within the solid lithium peroxide (Li2O2) discharge phase. Recent experiments have shown that use of Co3O4-containing Li/O2 electrodes enhances rechargeability, but the mechanism responsible for this effect is unclear, as are the general prospects for the promotion of the Li/O2 OER. Here first-principles calculations are combined with continuum-scale transport theory to build a multiscale model which demonstrates that the incorporation of trace Co into Li2O2 is a plausible mechanism for OER promotion. These calculations suggest that doping at equilibrium levels (tens of ppm) can enhance charge transport by shifting the balance of Li-ion vacancies and hole polarons. This mechanism could rationalize the improved rechargeability observed in Li/O2 electrodes containing Co. On the basis of a computational assessment of 22 additional dopants, we speculate that Ni may also be an effective OER promoter.
In this paper we outline a framework for the study of the mechanisms involved in the engagement of human agents with cultural affordances. Our aim is to better understand how culture and context ...interact with human biology to shape human behavior, cognition, and experience. We attempt to integrate several related approaches in the study of the embodied, cognitive, and affective substrates of sociality and culture and the sociocultural scaffolding of experience. The integrative framework we propose bridges cognitive and social sciences to provide (i) an expanded concept of 'affordance' that extends to sociocultural forms of life, and (ii) a multilevel account of the socioculturally scaffolded forms of affordance learning and the transmission of affordances in patterned sociocultural practices and regimes of shared attention. This framework provides an account of how cultural content and normative practices are built on a foundation of contentless basic mental processes that acquire content through immersive participation of the agent in social practices that regulate joint attention and shared intentionality.
The aim of this paper is twofold: (1) to assess whether the construct of neural representations plays an explanatory role under the variational free-energy principle and its corollary process theory, ...active inference; and (2) if so, to assess which philosophical stance-in relation to the ontological and epistemological status of representations-is most appropriate. We focus on non-realist (deflationary and fictionalist-instrumentalist) approaches. We consider a deflationary account of mental representation, according to which the explanatorily relevant contents of neural representations are mathematical, rather than cognitive, and a fictionalist or instrumentalist account, according to which representations are scientifically useful fictions that serve explanatory (and other) aims. After reviewing the free-energy principle and active inference, we argue that the model of adaptive phenotypes under the free-energy principle can be used to furnish a formal semantics, enabling us to assign semantic content to specific phenotypic states (the internal states of a Markovian system that exists far from equilibrium). We propose a modified fictionalist account-an
. We argue that, under the free-energy principle, pursuing even a deflationary account of the content of neural representations licenses the appeal to the kind of semantic content involved in the 'aboutness' or intentionality of cognitive systems; our position is thus coherent with, but rests on distinct assumptions from, the realist position. We argue that the free-energy principle thereby explains the aboutness or intentionality in living systems and hence their capacity to parse their sensory stream using an ontology or set of semantic factors.
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