Error analysis of the thermal cell for soil thermal conductivity measurement

Soil thermal conductivity is an important factor in the design of energy foundations and other ground heat exchanger systems. Laboratory tests in a thermal cell are often used to determine the thermal conductivity of soil specimens. Two interpretation methods have been suggested. Analysis can be based on the assumption of one-directional heat flow and the thermal conductivity calculated using Fourier's law. Alternatively the lumped capacitance method can be employed, using results generated as a specimen cools. In this study, six samples of London Clay were tested using a thermal cell. A finite-element model of the tests was then used to determine the validity of the assumptions made in analysis. The model showed substantial heat loss through the sides of the specimens, which would have a significant impact on the calculated thermal conductivity. The conditions required for the lumped capacitance method to be valid were also found not to be met. Consequently neither analysis method is recommended. A better approach would be to pursue apparatus with fewer heat losses or transient testing techniques

Cutaneous vascular responses to hypercapnia during whole-body heating

This article has been made available through the Brunel Open Access Publishing Fund and is available from the specified link - Copyright © 2008 Aerospace Medical Association (AsMA).Introduction: Hypercapnia may be encountered in lung disease as well as during situations involving rebreathing of previously expired air (e.g., occupational diving). Inhibitory effects of elevated arterial carbon dioxide partial pressure on the central nervous system may result in impaired thermoregulation. This study tested the hypothesis that in heat-stressed subjects, cutaneous vascular responsiveness [expressed as cutaneous vascular conductance (CVC)] would be reduced during hypercapnic exposure. Methods: Four men and three women (mean ± SD; age: 35 ± 7 yr) rested supine while wearing a tube-lined suit perfused with 34°C water (normothermia). Following normothermic data collection, 50°C water was perfused through the suit to increase internal temperature approximately 1°C (whole-body heating). In both thermal conditions, a normoxic-hypercapnic (5% CO2, 21% O2, balance N2) gas mixture was inspired while forearm skin blood flux (laser-Doppler flow-metry) was measured continuously and was used for calculation of CVC (skin blood flux/mean arterial pressure). Results: End-tidal CO2 increased similarly throughout hypercapnic exposure during both normothermic and whole-body heating conditions (7.9 ± 2.4 and 8.3 ± 1.9 mmHg, respectively). However, CVC was not different between normocapnia and hypercapnia under either thermal condition (normothermia: 0.42 ± 0.24 vs. 0.39 ± 0.21 flux units/mmHg for normocapnia and hypercapnia, respectively; heat stress: 1.89 ± 0.67 vs. 1.92 ± 0.63 flux units/mmHg for normocapnia and hypercapnia, respectively). Discussion: Based on these findings, mild hypercapnia is unlikely to impair heat dissipation by reducing cutaneous vasodilation

Interactions of the Bacillus subtilis DnaE polymerase with replisomal proteins modulate its activity and fidelity

During Bacillus subtilis replication two replicative polymerases function at the replisome to collectively carry out genome replication. In a reconstituted in vitro replication assay, PolC is the main polymerase while the lagging strand DnaE polymerase briefly extends RNA primers synthesized by the primase DnaG prior to handing-off DNA synthesis to PolC. Here, we show in vivo that (i) the polymerase activity of DnaE is essential for both the initiation and elongation stages of DNA replication, (ii) its error rate varies inversely with PolC concentration, and (iii) its misincorporations are corrected by the mismatch repair system post-replication. We also found that the error rates in cells encoding mutator forms of both PolC and DnaE are significantly higher (up to 15-fold) than in PolC mutants. In vitro, we showed that (i) the polymerase activity of DnaE is considerably stimulated by DnaN, SSB and PolC, (ii) its error-prone activity is strongly inhibited by DnaN, and (iii) its errors are proofread by the 30 . 50 exonuclease activity of PolC in a stable template-DnaE –PolC complex. Collectively our data show that protein –protein interactions within the replisome modulate the activity and fidelity of DnaE, and confirm the prominent role of DnaE during B. subtilis replication

Impact of the COVID-19 pandemic on the research activities of UK ophthalmologists

BACKGROUND: The COVID-19 pandemic has impacted negatively on many areas of biomedical research and there is concern that academic recovery will take several years. This survey aimed to define the impact of the COVID-19 pandemic on UK ophthalmologists' research activities and understand the implications for recovery. METHODS: An online survey comprising multiple choice and free-text questions was designed, piloted and then distributed to Royal College of Ophthalmologists (RCOphth) members in January 2021. Respondent characteristics, research expectations and experiences through the pandemic were captured. Descriptive and comparative statistics were applied to quantitative data alongside content analysis of qualitative data. RESULTS: In total, 148 respondents (3.7% of RCOphth membership) comprised 46 trainees (31.1%), 97 consultants (65.5%) and 5 SAS doctors (3.4%); 54 had clinical-academic roles (36.5%) and 65/94 (69.1%) ophthalmologists with fully clinical posts identified as research-active. Of 114 research-active respondents, 104 (91.2%) reported an impact on their research from COVID-19; negative impacts included loss of research time (n = 69), research delays (n = 96) and funding shortfalls (n = 63). Content analysis identified five common themes; type of research activity, clinical demands, institutional challenges, COVID-19 alignment and work-life balance. CONCLUSIONS: UK ophthalmology research has been adversely impacted by the pandemic. A substantial proportion of UK ophthalmologists are research active, but 20.4% of those surveyed felt that the pandemic had made research less attractive. Strategic steps must be taken to nurture UK ophthalmologists' engagement with research, especially for those who currently do no research, if the profession is to align itself with the Government vision of 'Research for All'

Coupling marine ecosystem state with environmental management and conservation: A risk-based approach

\ua9 2024 The Author(s)The sustainability of marine ecosystems demands a focus on ecological improvement, necessitating managers and conservationists to consider a range of actions from those that limit stressors to those that actively restore. Deciding the most appropriate action should be informed by environmental context, which includes assessing information on both degradation and recovery potential. Here, we provide an analysis of how the degree of ecological degradation coupled with the stressor regime can inform environmental management and conservation actions (e.g., stressor reductions, adaptive management, assisted recovery/restoration). With this analysis we design a risk framework combining principles that define ecosystem resilience and recovery times with those that characterize stressor regimes (i.e., the number, type, and impact). The combination of these principles defines where an ecosystem is placed along sliding scales of degradation and recovery and likely response to protective and restorative interventions. It is designed to facilitate place-based conversations regarding the risks of different management actions informed by the temporal dynamics of ecosystem degradation and recovery

Construction and analysis of causally dynamic hybrid bond graphs

Engineering systems are frequently abstracted to models with discontinuous behaviour (such as a switch or contact), and a hybrid model is one which contains continuous and discontinuous behaviours. Bond graphs are an established physical modelling method, but there are several methods for constructing switched or ‘hybrid’ bond graphs, developed for either qualitative ‘structural’ analysis or efficient numerical simulation of engineering systems. This article proposes a general hybrid bond graph suitable for both. The controlled junction is adopted as an intuitive way of modelling a discontinuity in the model structure. This element gives rise to ‘dynamic causality’ that is facilitated by a new bond graph notation. From this model, the junction structure and state equations are derived and compared to those obtained by existing methods. The proposed model includes all possible modes of operation and can be represented by a single set of equations. The controlled junctions manifest as Boolean variables in the matrices of coefficients. The method is more compact and intuitive than existing methods and dispenses with the need to derive various modes of operation from a given reference representation. Hence, a method has been developed, which can reach common usage and form a platform for further study

Deletion of the gabra2 gene results in hypersensitivity to the acute effects of ethanol but does not alter ethanol self administration

Human genetic studies have suggested that polymorphisms of the GABRA2 gene encoding the GABA(A) α2-subunit are associated with ethanol dependence. Variations in this gene also convey sensitivity to the subjective effects of ethanol, indicating a role in mediating ethanol-related behaviours. We therefore investigated the consequences of deleting the α2-subunit on the ataxic and rewarding properties of ethanol in mice. Ataxic and sedative effects of ethanol were explored in GABA(A) α2-subunit wildtype (WT) and knockout (KO) mice using a Rotarod apparatus, wire hang and the duration of loss of righting reflex. Following training, KO mice showed shorter latencies to fall than WT littermates under ethanol (2 g/kg i.p.) in both Rotarod and wire hang tests. After administration of ethanol (3.5 g/kg i.p.), KO mice took longer to regain the righting reflex than WT mice. To ensure the acute effects are not due to the gabra2 deletion affecting pharmacokinetics, blood ethanol concentrations were measured at 20 minute intervals after acute administration (2 g/kg i.p.), and did not differ between genotypes. To investigate ethanol's rewarding properties, WT and KO mice were trained to lever press to receive increasing concentrations of ethanol on an FR4 schedule of reinforcement. Both WT and KO mice self-administered ethanol at similar rates, with no differences in the numbers of reinforcers earned. These data indicate a protective role for α2-subunits, against the acute sedative and ataxic effects of ethanol. However, no change was observed in ethanol self administration, suggesting the rewarding effects of ethanol remain unchange

Differential immunogenicity of homologous versus heterologous boost in Ad26.COV2.S vaccine recipients.

BACKGROUND: Protection offered by coronavirus disease 2019 (COVID-19) vaccines wanes over time, requiring an evaluation of different boosting strategies to revert such a trend and enhance the quantity and quality of Spike-specific humoral and cellular immune responses. These immunological parameters in homologous or heterologous vaccination boosts have thus far been studied for mRNA and ChAdOx1 nCoV-19 vaccines, but knowledge on individuals who received a single dose of Ad26.COV2.S is lacking. METHODS: We studied Spike-specific humoral and cellular immunity in Ad26.COV2.S-vaccinated individuals (n = 55) who were either primed with Ad26.COV2.S only (n = 13) or were boosted with a homologous (Ad26.COV2.S, n = 28) or heterologous (BNT162b2, n = 14) second dose. We compared our findings with the results found in individuals vaccinated with a single (n = 16) or double (n = 44) dose of BNT162b2. FINDINGS: We observed that a strategy of heterologous vaccination enhanced the quantity and breadth of both Spike-specific humoral and cellular immunity in Ad26.COV2.S-vaccinated individuals. In contrast, the impact of the homologous boost was quantitatively minimal in Ad26.COV2.S-vaccinated individuals, and Spike-specific antibodies and T cells were narrowly focused to the S1 region. CONCLUSIONS: Despite the small sample size of the study and the lack of well-defined correlates of protection against COVID-19, the immunological features detected support the utilization of a heterologous vaccine boost in individuals who received Ad26.COV2.S vaccination. FUNDING: This study is partially supported by the Singapore Ministry of Health's National Medical Research Council under its COVID-19 Research Fund (COVID19RF3-0060, COVID19RF-001, and COVID19RF-008), The Medical College St. Bartholomew's Hospital Trustees - Pump Priming Fund for SMD COVID-19 Research