Why is Water so Efficient at Suppressing the Effects of Explosions?

When most experienced explosives engineers first observe an explosion suppressed by bags of water, they are convinced that there has been a misfire. Depending on the amount of water and the way it is contained, the overpressure can be reduced by a factor of ten, sometimes more than twenty. The number of fragments from shell cases can be one hundred times less. Their velocities can be seven times. Slugs from focal point charges are stopped. Safety distances around magazines can be cut. The number of people evacuated from a bomb disposal site can be reduced. In June 1999, engineers from 33 Regiment (Explosive Ordnance Disposal) saved an entire village in Kosovo from the detonation of a 2,000-pound NATO bomb by using water bags

Re-wiring the brain: Increased functional connectivity within primary somatosensory cortex following synchronous co-activation

AbstractThe primary somatosensory cortex shows precise topographical organisation, but can be quickly modified by alterations to sensory inputs. Temporally correlated sensory inputs to the digits can result in the merging of digit representations on the cortical surface. Underlying mechanisms driving these changes are unclear but the strengthening of intra-cortical synaptic connections via Hebbian mechanisms has been suggested. We use fMRI measures of temporal coherence to infer alterations in the relative strength of neuronal connections between digit regions 2 and 4 following 3hours of synchronous and asynchronous co-activation. Following synchronous co-activation we find a 20% increase in temporal coherence of the fMRI signal (p=0.0004). No significant change is seen following asynchronous co-activation suggesting that temporal coincidence between the two digit inputs during co-activation is driving this coherence change. In line with previous work we also find a trend towards reduced separation of the digit representations following synchronous co-activation and significantly increased separation for the asynchronous case. Increased coherence is significantly correlated with reduced digit separation for the synchronous case. This study shows that passive synchronous stimulation to the digits strengthens the underlying cortical connections between the digit regions in only a few hours, and that this mechanism may be related to topographical re-organisation

The Longevity of Behaviour Change: A Case Study of the London 2012 Olympic and Paralympic Games

Travel behaviour change is traditionally regarded as being difficult to achieve, with strategies and initiatives often generating only slow and incremental shifts in behaviour amongst the population. There is an emerging discussion in the literature that more radical approaches to travel behaviour change are needed, to contribute to achieving challenging decarbonisation targets. If a step change is required then one potential source of learning is the study of disruptions to systems of mobility provision, which may provide valuable insights into how more radical travel behaviour change is achieved and, potentially, sustained. This thesis provides an innovative approach to examining major-event disruption, in this case arising from the London 2012 Olympic and Paralympic Games, to understand the potential for change from such large, disruptive events. A four-wave longitudinal panel survey was applied to establish the extent, and longevity, of change in response to the Games. The research uses the Transtheoretical Model (TTM) to critically examine travel behaviour. The results show that change was extensive during the Games (54% made at least one change); however change was not often sustained afterwards. Reducing, relocating and re-timing were the most common changes. The key elements of the TTM were not well suited to studying change in such a context, however less commonly used constructs of the model contributed to the identification of four clusters within the sample that provided valuable insight into the behaviour observed. This research makes a valuable contribution to the growing literature around the potential for learning, and opportunities for change, when there is an imperative to do so. Whilst the longevity of changes to travel were limited, the research provided greater understanding of the adaptability and planning involved in response to major-event disruption, and what this means for future travel planning. The clusters generated helped to show the psychological constructs important for supporting different types of change, which can contribute to approaching and understanding travel behaviour change in broader contexts, when there is an imperative to change

Absolute calibration of the intramolecular site preference of 15N fractionation in tropospheric N2O by FT-IR spectroscopy

Nitrous oxide (N2O) plays important roles in atmospheric chemistry both as a greenhouse gas and in stratospheric ozone depletion. Isotopic measurements of N2O have provided an invaluable insight into understanding its atmospheric sources and sinks. The preference for 15N fractionation between the central and terminal positions (the “site preference”) is particularly valuable because it depends principally on the processes involved in N2O production or consumption, rather than the 15N content of the substrate from which it is formed. Despite the value of measurements of the site preference, there is no internationally recognized standard reference material of accurately known and accepted site preference, and there has been some lack of agreement in published studies aimed at providing such a standard. Previous work has been based on isotope ratio mass spectrometry (IRMS); in this work we provide an absolute calibration for the intramolecular site preference of 15N fractionation of working standard gases used in our laboratory by a completely independent technique—high-resolution Fourier transform infrared (FT-IR) spectroscopy. By reference to this absolute calibration, we determine the site preference for 25 samples of tropospheric N2O collected under clean air conditions to be 19.8‰ ± 2.1‰. This result is in agreement with that based on the earlier absolute calibration of Toyoda and Yoshida (Toyoda, S. and Yoshida, N. Anal. Chem. 1999, 71, 4711−4718) who found an average tropospheric site preference of 18.7‰ ± 2.2‰. We now recommend an interlaboratory exchange of working standard N2O gases as the next step to providing an international reference standard