Magnetic Field Effects in Quantum Biology: Beyond the Radical Pair Mechanism

The effects of weak magnetic fields on biological systems have become an area of burgeoning research and interest in recent years. Specifically, the Radical Pair Mechanism (RPM) has been quite successful at beginning to explain phenomena such as avian magnetoreception, the magnetosensitivity of lipid peroxidation reactions and other such biological magnetic field effects (MFEs) - but there are still many questions to answer. This thesis addresses such questions, by proposing a new mechanism (D3M) to offer a new perspective on radical spin dynamics, and methods for amplifying biological MFEs

On the magnetosensitivity of lipid peroxidation: two- versus three-radical dynamics

This is the final version. Available on open access from the Royal Society of Chemistry via the DOI in this recordData availability: The datasets generated during the current study are available from the corresponding author on reasonable request.We present a theoretical analysis of the putative magnetosensitivity of lipid peroxidation. We focus on the widely accepted radical pair mechanism (RPM) and a recently suggested idea based on spin dynamics induced in three-radical systems by the mutual electron–electron dipolar coupling (D3M). We show that, contrary to claims in the literature, lipid peroxides, the dominant chain carriers of the autoxidation process, have associated non-zero hyperfine coupling interactions. This suggests that their recombination could, in principle, be magnetosensitive due to the RPM. While the RPM indeed goes a long way to explaining magnetosensitivity in these systems, we show that the simultaneous interaction of three peroxyl radicals via the D3M can achieve larger magnetic field effects (MFE), even if the third radical is remote from the recombining radical pair. For randomly oriented three-radical systems, the D3M induces a low-field effect comparable to that of the RPM. The mechanism furthermore immunizes the spin dynamics to the presence of large exchange coupling interactions in the recombining radical pair, thereby permitting much larger MFE at magnetic field intensities comparable to the geomagnetic field than would be expected for the RPM. Based on these characteristics, we suggest that the D3M could be particularly relevant for MFE at low fields, provided that the local radical concentration is sufficient to allow for three-spin radical correlations. Eventually, our observations suggest that MFEs could intricately depend on radical concentration and larger effects could ensue under conditions of oxidative stress.Engineering and Physical Sciences Research Council (EPSRC

Children and young adults who received tracheostomies or were initiated on long-term ventilation in PICUs

Objectives: To characterize patients who received tracheostomies for airway compromise or were initiated on long-term ventilation for chronic respiratory failure in pediatric intensive care units (PICU), and to examine variation in the incidence of initiation, patient characteristics, and modalities across sites. Design: Retrospective cross-sectional analysis. Settings: Seventy three North American PICUs that participated in the Virtual Pediatric Intensive Care Unit Performance System. Patients: PICU patients admitted between 2009 and 2011. Interventions: None. Measurements and Main Results: Among 115,437 PICU patients, 1.8% received a tracheostomy or were initiated on long-term ventilation; 1034 received a tracheostomy only, 717 were initiated on invasive ventilation (IV), and 381 were initiated on noninvasive ventilation (NIV). Ninety percent had substantial chronic conditions and comorbidities, including more than 50% with moderate or worse cerebral disability upon discharge. Seven percent were initiated after a catastrophic injury/event. Across sites, there was variation in incidence of tracheotomy and initiation of long-term ventilation, ranging 0–4.6%. There also was variation in patient characteristics, time to tracheotomy, number of extubations prior to tracheostomy, and the use of IV versus NIV. Conclusions: While the PICU incidence of initiation of tracheostomies and long-term ventilation was relatively uncommon, it suggests that thousands of children and young adults receive these interventions each year in North American PICUs. The majority of them have conditions and comorbidities that impose on-going care needs, beyond those required by artificial airways and long-term ventilation themselves

Addition of a channel for XCO observations to a portable FTIR spectrometer for greenhouse gas measurements

The portable FTIR (Fourier transform infrared) spectrometer EM27/SUN, dedicated to the precise and accurate observation of column-averaged abundances of methane and carbon dioxide, has been equipped with a second detector channel, which allows the detection of additional species, especially carbon monoxide. This allows an improved characterisation of observed carbon dioxide enhancements and makes the extended spectrometer especially suitable as a validation tool of ESA's Sentinel 5 Precursor mission, as it now covers the same spectral region as used by the infrared channel of the TROPOMI (TROPOspheric Monitoring Instrument) sensor. The extension presented here does not rely on a dichroic, but instead a fraction of the solar beam is decoupled near the aperture stop of the spectrometer using a small plane mirror. This approach allows maintaining the camera-controlled solar tracker set-up, which is referenced to the field stop in front of the primary detector. Moreover, the upgrade of existing instruments can be performed without alterating the optical set-up of the primary channel and resulting changes of the instrumental characteristics of the original instrument

Myosin heavy chain and physiological adaptation of the rat diaphragm in elastase-induced emphysema

BACKGROUND: Several physiological adaptations occur in the respiratory muscles in rodent models of elastase-induced emphysema. Although the contractile properties of the diaphragm are altered in a way that suggests expression of slower isoforms of myosin heavy chain (MHC), it has been difficult to demonstrate a shift in MHCs in an animal model that corresponds to the shift toward slower MHCs seen in human emphysema. METHODS: We sought to identify MHC and corresponding physiological changes in the diaphragms of rats with elastase-induced emphysema. Nine rats with emphysema and 11 control rats were studied 10 months after instillation with elastase. MHC isoform composition was determined by both reverse transcriptase polymerase chain reaction (RT-PCR) and immunocytochemistry by using specific probes able to identify all known adult isoforms. Physiological adaptation was studied on diaphragm strips stimulated in vitro. RESULTS: In addition to confirming that emphysematous diaphragm has a decreased fatigability, we identified a significantly longer time-to-peak-tension (63.9 ± 2.7 ms versus 53.9 ± 2.4 ms). At both the RNA (RT-PCR) and protein (immunocytochemistry) levels, we found a significant decrease in the fastest, MHC isoform (IIb) in emphysema. CONCLUSION: This is the first demonstration of MHC shifts and corresponding physiological changes in the diaphragm in an animal model of emphysema. It is established that rodent emphysema, like human emphysema, does result in a physiologically significant shift toward slower diaphragmatic MHC isoforms. In the rat, this occurs at the faster end of the MHC spectrum than in humans

R. L. Keens

"V64590 Lt. Keens. R.L. 7th Aust. Inf. Btn Feb 1942 - Feb 1944".V64590 Lieutenant Keens, R.L. 7th Australian Infantry Battalion. February 1942 - February 1944

Introduction to technical communications of the 26th Int'l. Conference on logic programming (ICLP'10)

Abstract is not available