Natural Insect Repellents: Activity against Mosquitoes and Cockroaches

Recent research has focused on the repellent properties of extracts from the catnip plant (Nepeta cataria) and the Osage orange (Madura pomifera) fruit. This chapter includes results on German cockroach (Blattella germanica), and house fly (Musca domestica) contact irritancy to catnip essential oil, and its major components, Z,E-nepetalactone and E,Z-nepetalactone, compared with the commercial standard, N,Ndiethyl-m-toluamide (DEET). Both species showed high percentage repellency values when exposed to filter paper treated with catnip essential oil or the individual nepetalactone isomers. Of the two nepetalactone isomers evaluated, German cockroaches were most responsive to the E,Z isomer. House flies showed similar trends in contact irritancy, responding to surfaces treated with the predominant catnip isomer, Z,E-nepetalactone, more intensely than to the catnip essential oil. Catnip and Osage orange essential oils, and a sesquiterpene found in Osage orange, elemol, were evaluated for repellency to the northern house mosquito (Culex pipiens) and are presented here. Two mosquito bioassays were used to measure percentage and contact repellecy. Mosquitoes responded initially with high percentage repellency to surfaces treated with catnip essential oil. From the residual repellency study, this trend in repellency by the catnip oil significantly decreased over the 180-minute test period. Elemol, and DEET initially had lower percentage repellency values than catnip essential oil, but did not show the negative relationship between percentage repellency and time, retaining excellent repellency throughout the 3-hour bioassay. Solutions with elemol and DEET exhibited greater significance in contact repellency compared to catnip essential oil. These results show that catnip essential oil is a potent mosquito repellent, but does not provide the same residual effects as the commercial standard, DEET, Elemol, a sesquiterpene extracted from the fruit of the Osage orange, shows excellent promise as a mosquito repellent with comparable activity to DEET in contact and residual repellency

Statistical properties of a linear stochastic system

In this paper a random linear system of the form of y(t; ω = ∫t∁K(t, τ; ω)x(τ; ω)dr is studied, where the kernel is a stochastic process defined on a probability space. The concept of the modified characteristic function for the output process is introduced. These characteristic functions are used to identify the distribution of the output process over certain subsets of the probability space, Ω, in order to study the statistical properties of the process. Several examples are given to illustrate the usefulness of the resulting theory. These results extend the previous theory of random linear systems, in that until now, the kernel was deterministic in nature

Visualizing Large Datasets on Memory and Performance Constrained Mobile Devices

Graphics hardware in mobile devices has become more powerful, allowing rendering techniques such as ray-cast volume rendering to be done at interactive rates. This increase of performance provides desktop capabilities combined with the portability of a tablet. Volumes can demand a high amount of memory in order to be loaded in. This becomes problematic when dealing with mobile operating systems, such as Android, while trying to load large volumes into an application. Even though tablets on the market today contain 1 – 3 gigabytes of memory, Android allocates only a fraction of the total memory per application. Cases in which the dataset does fit into memory, but the resolution of the volume surpasses the capabilities of the mobile GPU, results in an unresponsive application. Although downscaling the data is a remedy to both the lack of memory and GPU performance, it is sacrificing potentially useful information. This loss of data is undesired in scientific fields, such as medical imaging. Combining both downsizing and data division tactics, this research project introduces a method that allows the user to view the entirety of the dataset as a whole and zoom in on the native resolution sub-volumes. Additionally, our method allows the GPU to perform at an effective level to achieve interactive frame rates

Proudman resonance with tides, bathymetry and variable atmospheric forcings

Proudman resonance is a primary amplification mechanism for meteotsunamis, which are shallow-water waves generated by atmospheric forcings. The effect of tides, sloping bathymetry and the speed, amplitude and aspect ratio of the atmospheric forcing on Proudman resonant wave growth are investigated using analytical approximations and numerical models. With tides included, maximum wave growth through Proudman resonance occurred when the atmospheric-forcing speed matched the tidal-wave speed. Growth greater than Proudman resonance occurred with a positive tidal elevation together with a tidal current in the opposite direction to wave propagation, due to linear growth combined with further amplification from wave-flux conservation. Near-Proudman resonant growth occurred when the forced-wave speed or free-wave speed varied by either a small amount, or varied rapidly, around a speed appropriate for Proudman resonance. For a forcing moving at Proudman resonant speed, resultant wave growth was proportional to the total, time-integrated forcing amplitude. Finally, Proudman resonant wave growth was lower for forcings with lower aspect ratios (AP), partly because forced-wave heights are proportional to 1 + A 2P , but also because free waves could spread in two dimensions. Whilst the assumptions of strict Proudman resonance are never met, near-Proudman resonant growth may occur over hundreds of kilometres if the effective Froude number is near 1 and the resultant wave propagates predominantly in one dimension

Practical considerations for in vivo MRI with higher dimensional spatial encoding

Object: This work seeks to examine practical aspects of in vivo imaging when spatial encoding is performed with three or more encoding channels for a 2D image. Materials and methods: The recently developed 4-Dimensional Radial In/Out (4D-RIO) trajectory is compared in simulations to an alternative higher-order encoding scheme referred to as O-space imaging. Direct comparison of local k-space representations leads to the proposal of a modification to the O-space imaging trajectory based on a scheme of prephasing to improve the reconstructed image quality. Data were collected using a 4D-RIO acquisition in vivo in the human brain and several image reconstructions were compared, exploiting the property that the dense encoding matrix, after a 1D or 2D Fourier transform, can be approximated by a sparse matrix by discarding entries below a chosen magnitude. Results: The proposed prephasing scheme for the O-space trajectory shows a marked improvement in quality in the simulated image reconstruction. In experiments, 4D-RIO data acquired in vivo in the human brain can be reconstructed to a reasonable quality using only 5% of the encoding matrix—massively reducing computer memory requirements for a practical reconstruction. Conclusion: Trajectory design and reconstruction techniques such as these may prove especially useful when extending generalized higher-order encoding methods to 3D image

Automated versus non-automated weaning for reducing the duration of mechanical ventilation for critically ill adults and children: a cochrane systematic review and meta-analysis

Automated weaning systems may improve adaptation of mechanical support for a patient's ventilatory needs and facilitate systematic and early recognition of their ability to breathe spontaneously and the potential for discontinuation of ventilation. Our objective was to compare mechanical ventilator weaning duration for critically ill adults and children when managed with automated systems versus non-automated strategies. Secondary objectives were to determine differences in duration of ventilation, intensive care unit (ICU) and hospital length of stay (LOS), mortality, and adverse events. Electronic databases were searched to 30 September 2013 without language restrictions. We also searched conference proceedings; trial registration websites; and article reference lists. Two authors independently extracted data and assessed risk of bias. We combined data using random-effects modelling. We identified 21 eligible trials totalling 1,676 participants. Pooled data from 16 trials indicated that automated systems reduced the geometric mean weaning duration by 30% (95% confidence interval (CI) 13% to 45%), with substantial heterogeneity (I(2) = 87%, P <0.00001). Reduced weaning duration was found with mixed or medical ICU populations (42%, 95% CI 10% to 63%) and Smartcare/PS (28%, 95% CI 7% to 49%) but not with surgical populations or using other systems. Automated systems reduced ventilation duration with no heterogeneity (10%, 95% CI 3% to 16%) and ICU LOS (8%, 95% CI 0% to 15%). There was no strong evidence of effect on mortality, hospital LOS, reintubation, self-extubation and non-invasive ventilation following extubation. Automated systems reduced prolonged mechanical ventilation and tracheostomy. Overall quality of evidence was high. Automated systems may reduce weaning and ventilation duration and ICU stay. Due to substantial trial heterogeneity an adequately powered, high quality, multi-centre randomized controlled trial is neede