Spherically symmetric dissipative anisotropic fluids: A general study

The full set of equations governing the evolution of self--gravitating spherically symmetric dissipative fluids with anisotropic stresses is deployed and used to carry out a general study on the behaviour of such systems, in the context of general relativity. Emphasis is given to the link between the Weyl tensor, the shear tensor, the anisotropy of the pressure and the density inhomogeneity. In particular we provide the general, necessary and sufficient, condition for the vanishing of the spatial gradients of energy density, which in turn suggests a possible definition of a gravitational arrow of time. Some solutions are also exhibited to illustrate the discussion.Comment: 28 pages Latex. To appear in Phys.Rev.

Multi-ancestry genome-wide association analyses improve resolution of genes and pathways influencing lung function and chronic obstructive pulmonary disease risk.

Lung-function impairment underlies chronic obstructive pulmonary disease (COPD) and predicts mortality. In the largest multi-ancestry genome-wide association meta-analysis of lung function to date, comprising 580,869 participants, we identified 1,020 independent association signals implicating 559 genes supported by ≥2 criteria from a systematic variant-to-gene mapping framework. These genes were enriched in 29 pathways. Individual variants showed heterogeneity across ancestries, age and smoking groups, and collectively as a genetic risk score showed strong association with COPD across ancestry groups. We undertook phenome-wide association studies for selected associated variants as well as trait and pathway-specific genetic risk scores to infer possible consequences of intervening in pathways underlying lung function. We highlight new putative causal variants, genes, proteins and pathways, including those targeted by existing drugs. These findings bring us closer to understanding the mechanisms underlying lung function and COPD, and should inform functional genomics experiments and potentially future COPD therapies

Multi-ancestry genome-wide association analyses improve resolution of genes and pathways influencing lung function and chronic obstructive pulmonary disease risk

Lung-function impairment underlies chronic obstructive pulmonary disease (COPD) and predicts mortality. In the largest multi-ancestry genome-wide association meta-analysis of lung function to date, comprising 580,869 participants, we identified 1,020 independent association signals implicating 559 genes supported by ≥2 criteria from a systematic variant-to-gene mapping framework. These genes were enriched in 29 pathways. Individual variants showed heterogeneity across ancestries, age and smoking groups, and collectively as a genetic risk score showed strong association with COPD across ancestry groups. We undertook phenome-wide association studies for selected associated variants as well as trait and pathway-specific genetic risk scores to infer possible consequences of intervening in pathways underlying lung function. We highlight new putative causal variants, genes, proteins and pathways, including those targeted by existing drugs. These findings bring us closer to understanding the mechanisms underlying lung function and COPD, and should inform functional genomics experiments and potentially future COPD therapies

The effect of three different (-135-degrees-C) whole body cryotherapy exposure durations on elite rugby league players

Background: Whole body cryotherapy (WBC) is the therapeutic application of extreme cold air for a short duration. Minimal evidence is available for determining optimal exposure time. Purpose: To explore whether the length of WBC exposure induces differential changes in inflammatory markers, tissue oxygenation, skin and core temperature, thermal sensation and comfort. Method: This study was a randomised cross over design with participants acting as their own control. Fourteen male professional first team super league rugby players were exposed to 1, 2, and 3 minutes of WBC at -135°C. Testing took place the day after a competitive league fixture, each exposure separated by seven days. Results: No significant changes were found in the inflammatory cytokine interleukin six. Significant reductions (p<0.05) in deoxyhaemoglobin for gastrocnemius and vastus lateralis were found. In vastus lateralis significant reductions (p<0.05) in oxyhaemoglobin and tissue oxygenation index (p<0.05) were demonstrated. Significant reductions (p<0.05) in skin temperature were recorded. No significant changes were recorded in core temperature. Significant reductions (p<0.05) in thermal sensation and comfort were recorded. Conclusion: Three brief exposures to WBC separated by 1 week are not sufficient to induce physiological changes in IL-6 or core temperature. There are however significant changes in tissue oxyhaemoglobin, deoxyhaemoglobin, tissue oxygenation index, skin temperature and thermal sensation. We conclude that a 2 minute WBC exposure was the optimum exposure length at temperatures of -135°C and could be applied as the basis for future studies

Differences in skin temperature responses during three different (-135°c) whole body cryotherapy exposure durations in elite rugby league players

Background Growing ever popular within elite sports, Whole Body Cryotherapy (WBC) is the therapeutic application of extreme cold air for a short duration. Minimal evidence is available for determining the physiological effects of WBC, including observation of skin surface and core temperature changes, in particular across specific pre-determined regions of interest. This study aimed to investigate the effects of three different (-135°C) whole body cryotherapy exposure durations on skin surface and core body temperatures in a group of elite rugby league players. Methods and Results 14 male professional first team super league rugby players were exposed to 1, 2 and 3 minutes of WBC at -135°C. Each WBC exposure was separated by seven days, and followed a competitive league fixture. Via ingestion of a core temperature pill, core body temperature was recorded pre, immediately post and 20 minutes post WBC. Non-contact, digital infrared thermal imaging measured skin surface temperature (Tsk). Tsk was measured pre, immediately post and every five minutes post WBC exposure, up to 20 minutes. Regions of interest were defined by attaching wooden markers to specific anatomical landmarks. Four regions of interest were defined; anterior triangle of the neck (A), torso (B), lower abdomen (C) and the back (D). Significant reductions (p=<0.05) in mean Tsk were noted after each exposure duration. Average Tsk over time demonstrated significant differences (p=<0.05) between pre and immediately post exposure time points, for each exposure. When comparing regions of interest significant differences (p=<0.05) were found in mean Tsk. When comparing average Tsk of lower abdomen with A, B and D, significant differences (p=<0.05) were determined. No significant differences were noted between B and D. No Significant differences were noted in core temperature. Discussion and Conclusion In all four regions of interest, Tsk was reduced following all exposure durations of WBC. The effectiveness of WBC in reducing Tsk has been demonstrated in previous studies; in the current study the lowest Tsk recorded was 12.1°C, in the lower abdomen following a 3 minute exposure of WBC. This demonstrates the ability of WBC to achieve skin cooling within a desired therapeutic range, which is a key claim of WBC, as part of a recovery method within elite sport. The pattern of change and differences in average Tsk across C against A, B and D was interesting. In particular vascular shunting to protect vital organs in areas A and B could be a suggestion as to why Tsk differed following WBC exposures. Core temperature did not significantly fluctuate following exposures of WBC. However, a small rise was observed in all exposures, illustrating a relationship with the drop in Tsk, and the body’s ability to maintain the function of vital organs. A phase of rewarming occurred following WBC exposures with post mean Tsk at 20 minutes not reaching pre exposure mean Tsk. Although lower limb Tsk was not measured in this study, these findings may have implications for clinicians deciding when it is safe to return an athlete to functional tasks following WBC, to reduce the risk of potential injury

Specialization of rainforest canopy beetles to host trees and microhabitats: not all specialists are leaf-feeding herbivores

Reliable estimates of host specificity in tropical rainforest beetles are central for an understanding of food web dynamics and biodiversity patterns. However, it is widely assumed that herbivores constitute the majority of host specific species, and that most herbivore species feed on leaves. We tested the generality of this assumption by comparing both plant host- and microhabitat-specificity between beetle communities inhabiting the foliage (flush and mature), flowers, fruit, and suspended dead wood from 23 canopy plant species in a tropical rainforest in north Queensland, Australia. Independent of host tree identity, 76/77 of the most abundant beetle species (N ≥ 12 individuals) were aggregated on a particular microhabitat. Microhabitat specialization (measured by Sm and Lloyd's indices) was very high and did not differ between flower and foliage communities, suggesting that each newly-sampled microhabitat has a large additive effect on total species richness. In accordance with previous studies, host specificity of foliage-inhabiting beetles was most pronounced among herbivorous families (Curculionidae, Chrysomelidae). By contrast, host specificity among flower-visitors was equally high among herbivorous and nonherbivorous families (e.g. Nitidulidae, Staphylinidae, Cleridae). Effective specialization (FT) measures showed that traditional correction factors used to project total species richness in nonherbivorous groups fail to fully capture diversity in the flower-visiting beetle fauna. These results demonstrate that host specialization is not concentrated within folivores as previously assumed