Evaporation-driven convective flows in suspensions of non-motile bacteria

We report a novel form of convection in suspensions of the bioluminescent marine bacterium Photobacterium phosphoreum. Suspensions of these bacteria placed in a chamber open to the air create persistent luminescent plumes most easily visible when observed in the dark. These flows are strikingly similar to the classical bioconvection pattern of aerotactic swimming bacteria, which create an unstable stratification by swimming upwards to an air-water interface, but they are a puzzle since the strain of P. phosphoreum used does not express flagella and therefore cannot swim. When microspheres were used instead of bacteria, similar flow patterns were observed, suggesting that the convective motion was not driven by bacteria but instead by the accumulation of salt at the air-water interface due to evaporation of the culture medium. Even at room temperature and humidity, and physiologically relevant salt concentrations, the water evaporation was found to be sufficient to drive convection patterns. To prove this hypothesis, experiments were complemented with a mathematical model that aimed to understand the mechanism of plume formation and the role of salt in triggering the instability. The simplified system of evaporating salty water was first studied using linear stability analysis, and then with finite element simulations. A comparison between these three approaches is presented. While evaporation-driven convection has not been discussed extensively in the context of biological systems, these results suggest that the phenomenon may be broadly relevant, particularly in those systems involving microorganisms of limited motility

Pressure coefficients of Raman modes of carbon nanotubes resolved by chirality: Environmental effect on graphene sheet

Studies of the mechanical properties of single-walled carbon nanotubes are hindered by the availability only of ensembles of tubes with a range of diameters. Tunable Raman excitation spectroscopy picks out identifiable tubes. Under high pressure, the radial breathing mode shows a strong environmental effect shown here to be largely independent of the nature of the environment . For the G-mode, the pressure coefficient varies with diameter consistent with the thick-wall tube model. However, results show an unexpectedly strong environmental effect on the pressure coefficients. Reappraisal of data for graphene and graphite gives the G-mode Grueuneisen parameter gamma = 1.34 and the shear deformation parameter beta = 1.34.Comment: Submitted to Physical Review

The tumour stroma of oral squamous cell carcinomas show increased vascularity compared with adjacent host tissue.

For tumours to grow they must acquire an adequate blood supply, and the use of drugs to inhibit tumour vascularization is one promising approach to anti-cancer therapy. Clear information is therefore required on the vascular architecture of human tumours and animal tumour models used for testing anti-angiogenic therapies. Many previous studies on animal tumour models have shown that carcinomas are least vascular in their centres and that host tissues become more vascular with proximity to the tumour. However, we have previously found that many human colorectal carcinomas do not show this pattern. The present study on human oral squamous cell carcinomas (SCCs) again reveals significant differences. Paraffin sections from 24 SCCs were immunostained using the QBEnd-10 monoclonal antibody to demonstrate blood vessels, and these were quantified by interactive morphometry using a Kontron Videoplan system. In most carcinomas, viable tumour tissue was no less vascular in the tumour centre than in the tumour periphery. Although tumours are known to release angiogenic factors, viable tumour tissue was less vascular than adjacent host tissues. However, the tumour stroma, by itself, was more vascular than adjacent host tissues. Host tissue adjacent to tumour showed no obvious increase in vascular density with increasing proximity to the tumour edge, which suggests that tumour-released angiogenic factors are only effective over a short distance

Predictors of unfavourable treatment outcome in patients diagnosed with drug-resistant tuberculosis in the Torres Strait / Papua New Guinea border region

Drug-resistant tuberculosis (DR-TB) is an ongoing challenge in the Torres Strait Islands (TSI) / Papua New Guinea (PNG) border region. Treatment success rates have historically been poor for patients diagnosed with DR-TB, leading to increased transmission. This study aimed to identify variables associated with unfavourable outcome in patients diagnosed with DR-TB to inform programmatic improvements. A retrospective study of all DR-TB cases who presented to Australian health facilities in the Torres Strait between 1 March 2000 and 31 March 2020 was performed. This time period covers four distinct TB programmatic approaches which reflect Australian and Queensland Government decisions on TB management in this remote region. Univariate and multivariate predictors of unfavourable outcome were analysed. Unfavourable outcome was defined as lost to follow up, treatment failure and death. Successful outcome was defined as cure and treatment completion. In total, 133 patients with resistance to at least one TB drug were identified. The vast majority (123/133; 92%) of DR-TB patients had pulmonary involvement; and of these, 41% (50/123) had both pulmonary and extrapulmonary TB. Unfavourable outcomes were observed in 29% (39/133) of patients. Patients living with human immunodeficiency virus, renal disease or diabetes (4/133; 4/133; 3/133) had an increased frequency of unfavourable outcome (p <0.05), but the numbers were small. Among all 133 DR-TB patients, 41% had a low lymphocyte count, which was significantly associated with unfavourable outcome (p <0.05). We noted a 50% increase in successful outcomes achieved in the 2016–2020 programmatic period, compared to earlier periods (OR 5.3, 95% Confidence Interval [1.3, 20.4]). Being a close contact of a known TB case was associated with improved outcome. While DR-TB treatment outcomes have improved over time, enhanced surveillance for DR-TB, better cross border collaboration and consistent diagnosis and management of comorbidities and other risk factors should further improve patient care and outcomes

Mild recessive epidermolytic hyperkeratosis associated with a novel keratin 10 donor splice-site mutation in a family of Norfolk terrier dogs

Background  Epidermolytic hyperkeratosis in humans is caused by dominant-negative mutations in suprabasal epidermal keratins 1 and 10. However, spontaneous keratin mutations have not been confirmed in a species other than human. Objectives  To describe an autosomal recessive, mild, nonpalmar/plantar epidermolytic ichthyosis segregating in an extended pedigree of Norfolk terrier dogs due to a splice-site mutation in the gene encoding keratin 10 (KRT10). Methods  Dogs were evaluated clinically, and skin samples were examined by light and electron microscopy. Genomic DNA samples and cDNA from skin RNA were sequenced and defined a mutation in KRT10. Consequences of the mutation were evaluated by assessing protein expression with immunohistochemistry and Western blotting and gene expression with real-time RT-PCR (reverse transcriptase-polymerase chain reaction). Results  Adult dogs with the disease had generalized, pigmented hyperkeratosis with epidermal fragility. Light microscopic examination defined epidermolysis with hyperkeratosis; ultrastructural changes included a decrease in tonofilaments and abnormal filament aggregation in upper spinous and granular layer keratinocytes. Affected dogs were homozygous for a single base GT→TT change in the consensus donor splice site of intron 5 in KRT10. Keratin 10 protein was not detected with immunoblotting in affected dogs. Heterozygous dogs were normal based on clinical and histological appearance and keratin 10 protein expression. The mutation caused activation of at least three cryptic or alternative splice sites. Use of the cryptic sites resulted in transcripts containing premature termination codons. One transcript could result in shortening of the proximal portion of the 2B domain before the stutter region. Quantitative real-time PCR indicated a significant decrease in KRT10 mRNA levels in affected dogs compared with wild-type dogs. Conclusions  This disease is the first confirmed spontaneous keratin mutation in a nonhuman species and is the first reported recessive form of epidermolytic hyperkeratosis.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74670/1/j.1365-2133.2005.06735.x.pd

Biogeochemical Control of Phosphorus Cycling and Primary Production in Lake Michigan

A 3-yr study in Lake Michigan has shown a 27 mmol P m-2 increase in the mass of total P (TP) in the water during spring when the lake is mixed from surface to sediment. This value is an order of magnitude greater than the annual P input from external sources. TP changed in concert with increases in chlorophyll a and organic N and decreases in nitrate and soluble Si. The concentration of soluble reactive PO4-3 (SRP) remained relatively constant throughout the study. We hypothesize that the SRP concentration is maintained by a chemical equilibrium with calcium-phosphate species. The increased mass of TP arises from the sequestering of P by algae which displaces the chemical equilibrium and allows more P to be released to the water from the sediments. Solar irradiance and the duration of mixing determine the magnitude of the spring bloom and the demand for P that must be supplied through the flux of P from the sediments to the overlying water

Critical Consideration of Tuberculosis Management of Papua New Guinea Nationals and Cross-Border Health Issues in the Remote Torres Strait Islands, Australia

The international border between Australia and Papua New Guinea (PNG) serves as a gateway for the delivery of primary and tertiary healthcare for PNG patients presenting to Australian health facilities with presumptive tuberculosis (TB). An audit of all PNG nationals with presumptive TB who presented to clinics in the Torres Strait between 2016 and 2019 was conducted to evaluate outcomes for PNG patients and to consider the consistency and equity of decision-making regarding aeromedical evacuation. We also reviewed the current aeromedical retrieval policy and the outcomes of patients referred back to Daru General Hospital in PNG. During the study period, 213 PNG nationals presented with presumptive TB to primary health centres (PHC) in the Torres Strait. In total, 44 (21%) patients were medically evacuated to Australian hospitals; 26 met the evacuation criteria of whom 3 died, and 18 did not meet the criteria of whom 1 died. A further 22 patients who met the medical evacuation criteria into Australia were referred to Daru General Hospital of whom 2 died and 10 were lost to follow-up. The cross-border movement of people from PNG into Australia is associated with an emergent duty of care. Ongoing monitoring and evaluation of patient outcomes are necessary for transparency and justice

Enhanced diffusion due to active swimmers at a solid surface

We consider two systems of active swimmers moving close to a solid surface, one being a living population of wild-type \textit{E. coli} and the other being an assembly of self-propelled Au-Pt rods. In both situations, we have identified two different types of motion at the surface and evaluated the fraction of the population that displayed ballistic trajectories (active swimmers) with respect to those showing random-like behavior. We studied the effect of this complex swimming activity on the diffusivity of passive tracers also present at the surface. We found that the tracer diffusivity is enhanced with respect to standard Brownian motion and increases linearly with the activity of the fluid, defined as the product of the fraction of active swimmers and their mean velocity. This result can be understood in terms of series of elementary encounters between the active swimmers and the tracers.Comment: 4 pages, 2 figures in color, Physical Review Letters (in production