Asymptotic silence-breaking singularities

We discuss three complementary aspects of scalar curvature singularities: asymptotic causal properties, asymptotic Ricci and Weyl curvature, and asymptotic spatial properties. We divide scalar curvature singularities into two classes: so-called asymptotically silent singularities and non-generic singularities that break asymptotic silence. The emphasis in this paper is on the latter class which have not been previously discussed. We illustrate the above aspects and concepts by describing the singularities of a number of representative explicit perfect fluid solutions.Comment: 25 pages, 6 figure

Effect of silicic acid and other silicon compounds on fungal growth in oligotrophic and nutrient-rich media

Mycelium grew from a spore-mycelial inoculum of Aspergillus oryzae added to ultra-pure water (upw) containing silicon compounds, but did not grow in upw alone. Growth of other fungi also occurred in upw only when silicon compounds were added. Increased growth of A. oryzae, and other fungi, also followed the addition of silicic acid and other silicon compounds to Czapek Dox. Aspergillus oryzae solubilized silicon compounds in both upw and nutrient-rich media. Although interactions between microorganisms and silicon have been generally neglected, the results show that silicon compounds can increase fungal growth under both oligotrophic and nutrient-rich conditions

How do microorganisms reach the stratosphere?

A number of studies have demonstrated that bacteria and fungi are present in the stratosphere. Since the tropopause is generally regarded as a barrier to the upward movement of particles it is difficult to see how such microorganisms can reach heights above 17 km. Volcanoes provide an obvious means by which this could be achieved, but these occur infrequently and any microorganisms entering the stratosphere from this source will rapidly fall out of the stratosphere. Here, we suggest mechanisms by which microorganisms might reach the stratosphere on a more regular basis; such mechanisms are, however, likely only to explain how micrometre to submicrometre particles could be elevated into the stratosphere. Intriguingly, clumps of bacteria of size in excess of 10 μm have been found in stratospheric samples. It is difficult to understand how such clumps could be ejected from the Earth to this height, suggesting that such bacterial masses may be incoming to Earth. We suggest that the stratospheric microflora is made up of two components: (a) a mixed population of bacteria and fungi derived from Earth, which can occasionally be cultured; and (b) a population made up of clumps of, viable but non-culturable, bacteria which are too large to have originated from Earth; these, we suggest, have arrived in the stratosphere from space. Finally, we speculate on the possibility that the transfer of bacteria from the Earth to the highly mutagenic stratosphere may have played a role in bacterial evolution

How does 'banter' influence trainee doctors' choice of career? A qualitative study

Following publication of the original article, the authors reported an error in the first paragraph of the 'Results' section. The correction details are available at https://bmcmededuc.biomedcentral.com/articles/10.1186/s12909-019-1707-7Peer reviewedPublisher PD

Tricyclic Cationic Chromophores as Models for New Photoantimicrobials

Despite the preponderance of literature pertaining to photosensitisers based on the porphyrin system, many other chemical classes are available with similar or improved characteristics and potential for use in photodynamic medicine. Several of these classes are based on small, tricyclic, heteroaromatic chromophores, often originally developed from textile dyes or biological stains. The latter classification is useful in providing a basis for biological uptake and antimicrobial activity. The current review covers the chemistry and photoantimicrobial applications of established and novel cationic bisamino derivatives of the acridine, phenazine, phenoxazine, phenothiazine and xanthene systems and related compounds. The range covered is considerable and demonstrates photodynamic performance to rival the porphyrin class. In addition, the chemical synthesis of new analogues of lead compounds such as methylene blue or acridine orange is relatively straightforward and inexpensive, and compound series with varying physicochemical profiles have been produced for structure-activity studies in order to furnish improved photosensitisers for clinical triallin

Imaging and imagining chronic obstructive pulmonary disease (COPD): Uruguayans draw their lungs

Purpose: This anthropological study investigated what people imagined chronic obstructive pulmonary disease to look like in their lungs, what may be influencing these images and how this imagery shapes embodiment. Method: Employing graphic elicitation, in one of multiple ethnographic interviews, participants were asked to draw their lungs: “If we could look inside your chest now, what would we see?” Lung drawings and accompanying narratives and fieldnotes from 14 participants were analyzed for themes and patterns. Results: The theme of “imaging/imagining” emerged and three distinct patterns within this theme were identified: the microscope perspective, the X-ray perspective and the reduced pulmonary capacity perspective. These patterns demonstrate how embodiment can be shaped by an integration and reinterpretation of the medical images that form part of everyday clinic visits and pulmonary rehabilitation. Conclusions: Medical technology and images impact patients’ embodiment. Understanding this is important for rehabilitation practitioners who work in a challenging space created by potentially conflicting medical narratives: on the one hand, chronic obstructive pulmonary disease is incurable permanent damage, and on the other, improvement is possible through rehabilitation. Drawing could be integrated into pulmonary rehabilitation and may help identify perceptions of the body that could hinder the rehabilitation process. * Implications for rehabilitation * Drawings, when combined with interviews, can lead to a deeper and more complex understanding of patients’ perspectives and embodiment. * Rehabilitation practitioners should be concerned with how patients embody the medical technology and imagery they are exposed to as part of the educational component of pulmonary rehabilitation and healthcare generally. * Asking patients to visualize their illness through drawing may help pulmonary rehabilitation practitioners identify perceptions of the body which could hinder the patient’s ability to reap the full benefit of their treatmen

Did silicon aid in the establishment of the first bacterium?

Silicic acid increased numbers of both aerobic and facultatively anaerobic bacteria in ultrapure water incubated under strict oligotrophic conditions; soil extracts acted as the bacterial inoculum. The results are discussed in relation to the possibility that silicic acid, produced by the hydrolysis of silicates on the early Earth, could have stimulated the growth of the first bacterium, thereby allowing it to become established in the then prevailing conditions (presumed to be oligotrophic)