Two-dimensional shear modulus of a Langmuir foam

We deform a two-dimensional (2D) foam, created in a Langmuir monolayer, by applying a mechanical perturbation, and simultaneously image it by Brewster angle microscopy. We determine the foam stress tensor (through a determination of the 2D gas-liquid line tension, 2.35 $\pm$ 0.4 pJ$\cdot$m$^{-1}$) and the statistical strain tensor, by analyzing the images of the deformed structure. We deduce the 2D shear modulus of the foam, $\mu= 38 \pm 3 \mathrm{nN}\cdot \mathrm{m}^{-1}$. The foam effective rigidity is predicted to be $35 \pm 3 \mathrm {nN}\cdot \mathrm {m}^{- 1}$, which agrees with the value $37.5 \pm 0.8 \mathrm {nN}\cdot \mathrm {m}^{-1}$ obtained in an independent mechanical measurement.Comment: submitted May 12, 2003 ; resubmitted Sept 9, 200

Energy generation from full strength domestic wastewater using a sandwich dual chamber microbial fuel cell with an uncatalyzed mesh current collector cathode

A sandwich domestic wastewater fed dual-chamber microbial fuel cell (MFC) was designed for energy generation and wastewater treatment. Power density for the MFC increased with increasing domestic wastewater concentration, reaching a maximum of 251 mW/m2 for full strength wastewater (3400 mg/L chemical oxygen demand (COD)) at a current density of 0.054 mA/cm2 at an external resistance of 200Ω. These values dropped to 60 mW/m2 (76% lower) and 0.003 mA/cm2 using wastewater 91% diluted to 300 mg/L COD. Maximum removals were: of COD, 89%; nitrite, 60%; nitrate, 77%; total nitrogen, 36%; and phosphate, 26%

A collaborative and evolving response to the needs of frontline workers, patients and families during the COVID-19 pandemic at Tygerberg Hospital, Western Cape Province, South Africa

The global devastation caused by the COVID-19 pandemic and its mental health impact is undeniable. The physical and psychological consequences are wide-ranging – affecting patients fighting the disease, frontline workers in the trenches with them, healthcare staff deployed in high-care settings, and families disconnected from their loved ones in their darkest hours. Within 6 weeks of the COVID-19 outbreak in South Africa, the Department of Psychiatry at Stellenbosch University established the TBH/SU COVID Resiliency Clinic to provide psychological support to frontline workers at Tygerberg Hospital. Identified barriers in healthcare workers accessing mental healthcare resulted in moving towards an on-site visibility to try to remove some of these barriers. This greater on-site presence enabled networking and building of relationships with frontline staff that over time highlighted other frontline needs, such as providing psychosocial and spiritual support to patients and their families. We share challenges, lessons learned and recommendations from two initiatives: the TBH/SU COVID-19 Resiliency Clinic, and an embedded COVID Care Team (CCT). We describe the establishment, roll-out and progress of the Clinic and the subsequent CCT

Thermal and electrical conductivity of iron at Earth's core conditions

The Earth acts as a gigantic heat engine driven by decay of radiogenic isotopes and slow cooling, which gives rise to plate tectonics, volcanoes, and mountain building. Another key product is the geomagnetic field, generated in the liquid iron core by a dynamo running on heat released by cooling and freezing to grow the solid inner core, and on chemical convection due to light elements expelled from the liquid on freezing. The power supplied to the geodynamo, measured by the heat-flux across the core-mantle boundary (CMB), places constraints on Earth's evolution. Estimates of CMB heat-flux depend on properties of iron mixtures under the extreme pressure and temperature conditions in the core, most critically on the thermal and electrical conductivities. These quantities remain poorly known because of inherent difficulties in experimentation and theory. Here we use density functional theory to compute these conductivities in liquid iron mixtures at core conditions from first principles- the first directly computed values that do not rely on estimates based on extrapolations. The mixtures of Fe, O, S, and Si are taken from earlier work and fit the seismologically-determined core density and inner-core boundary density jump. We find both conductivities to be 2-3 times higher than estimates in current use. The changes are so large that core thermal histories and power requirements must be reassessed. New estimates of adiabatic heat-flux give 15-16 TW at the CMB, higher than present estimates of CMB heat-flux based on mantle convection; the top of the core must be thermally stratified and any convection in the upper core driven by chemical convection against the adverse thermal buoyancy or lateral variations in CMB heat flow. Power for the geodynamo is greatly restricted and future models of mantle evolution must incorporate a high CMB heat-flux and explain recent formation of the inner core.Comment: 11 pages including supplementary information, two figures. Scheduled to appear in Nature, April 201

Modelling the effects of boundary walls on the fire dynamics of informal settlement dwellings

AbstractCharacterising the risk of the fire spread in informal settlements relies on the ability to understand compartment fires with boundary conditions that are significantly different to normal residential compartments. Informal settlement dwellings frequently have thermally thin and leaky boundaries. Due to the unique design of these compartments, detailed experimental studies were conducted to understand their fire dynamics. This paper presents the ability of FDS to model these under-ventilated steel sheeted fire tests. Four compartment fire tests were modelled with different wall boundary conditions, namely sealed walls (no leakage), non-sealed walls (leaky), leaky walls with cardboard lining, and highly insulated walls; with wood cribs as fuel and ISO-9705 room dimensions. FDS managed to capture the main fire dynamics and trends both qualitatively and quantitatively. However, using a cell size of 6 cm, the ability of FDS to accurately model the combustion at locations with high turbulent flows (using the infinitely fast chemistry mixing controlled combustion model), and the effect of leakage, was relatively poor and both factors should be further studied with finer LES filter width. Using the validated FDS models, new flashover criteria for thermally thin compartments were defined as a combination of critical hot gas layer and wall temperatures. Additionally, a parametric study was conducted to propose an empirical correlation to estimate the onset Heat Release Rate required for flashover, as current knowledge fails to account properly for large scale compartments with thermally thin boundaries. The empirical correlation is demonstrated to have an accuracy of ≈ ± 10% compared with the FDS models

Hybrid inorganic-organic capsules for efficient intracellular delivery of novel siRNAs against influenza A (H1N1) virus infection

This work was supported by ARUK project grant 21210 ‘Sustained and Controllable Local Delivery of Anti-inflammatory Therapeutics with Nanoengineered Microcapsules’. The work was also supported in part by Russian Foundation of Basic Research grants No. 16-33-50153 mol_nr, No. 16-33-00966 mol_a, Russian Science Foundation grant No. 15-15-00170 and Russian Governmental Program ‘‘Nauka’’, No. 1.1658.2016, 4002