Wind dynamic range video camera

A television camera apparatus is disclosed in which bright objects are attenuated to fit within the dynamic range of the system, while dim objects are not. The apparatus receives linearly polarized light from an object scene, the light being passed by a beam splitter and focused on the output plane of a liquid crystal light valve. The light valve is oriented such that, with no excitation from the cathode ray tube, all light is rotated 90 deg and focused on the input plane of the video sensor. The light is then converted to an electrical signal, which is amplified and used to excite the CRT. The resulting image is collected and focused by a lens onto the light valve which rotates the polarization vector of the light to an extent proportional to the light intensity from the CRT. The overall effect is to selectively attenuate the image pattern focused on the sensor

Fabrication of extruded vertical axis turbine blades

Important characteristics of the extruded aluminum blade for the Vertical Axis Wind Turbine are presented. Their weight, structural strength, shape, and maintainability are pointed out

Visco-resistive shear wave dissipation in magnetic X-points

We consider the viscous and resistive dissipation of perpendicularly polarized shear waves propagating within a planar magnetic X-point. To highlight the role played by the two-dimensional geometry, the damping of travelling Alfvèn waves that propagate within an unbounded, but non-orthogonal X-point topology is analyzed. It is shown that the separatrix geometry affects both the dissipation time and the visco-resistive scaling of the energy decay. Our main focus, however, is on developing a theoretical description of standing wave dissipation for orthogonal, line-tied X-points. A combination of numerical and analytic treatments confirms that phase mixing provides a very effective mechanism for dissipating the wave energy. We show that wave decay comprises two main phases, an initial rapid decay followed by slower eigenmode evolution, both of which are only weakly dependent on the visco-resistive damping coefficients

Rapid dissipation in a current sheet driven by footpoints motions

Context.Wave energy dissipation by viscous and resistive damping in magnetic coronal plasmas is addressed. A two and one half dimensional, line-tied magnetic channel is considered whose footpoints are disturbed by buffeting motions of the photosphere. Aims.The aim of the analysis is to determine how effectively shear Alfvén waves, driven by footpoint motions and resonating in the channel, can be damped by visco-resistive friction. Methods.The problem is analyzed using a mixture of numerical and analytic techniques. Dynamic simulations, based on a cyclic footpoint driver, show that phase mixing resulting from variations in the magnetic field of the channel is instrumental in setting up a permanent "resonance regime" for the system. Analytic methods are used to analyze the resonance regime and to develop scaling laws for the rate of energy dissipation. Results.We show that in the general case where the Alfvén velocity profile may be linearized around the resonance, the dissipation rate is "fast" in that it is not limited by small damping coefficients. Although large energies can accumulate within the channel in the limit of very small damping, we show that by tuning the driver to low frequencies, both the energy level and the dissipation rate can be made insensitive to the level of the damping

Mothering at a distance and disclosure of maternal HIV to children in Kingston, Jamaica

Accepted for publication in a forthcoming issue of Population Horizons, an open access peer-reviewed journal by The Oxford Institute of Population Ageing.Existing guidelines (WHO, 2011) advise caretakers and professionals to disclose children’s and their caretakers’ HIV status to children, despite a lack of evidence concerning the potential implications in resource-constrained settings. Our research uses feminist Interpretative Phenomenological Analysis (IPA) to explore the experiences of HIV positive mothers in Kingston, Jamaica, focusing on their lived experiences of talking to their children about maternal HIV. This paper will focus on the concept of mothering at a distance and how this presents additional challenges for HIV positive mothers who are trying to establish emotional closeness in relation to talking to their children about their HIV. Using Hochschild’s concept of emotion work and examples from the interviews, we highlight the difficult contexts informing women’s decisions when negotiating discussions about their HIV. Women may choose full, partial or differential disclosure or children may be told their mother’s HIV status by others. Disclosure policy, we argue, reflects Anglo-Northern constructions of the family and parenting which may not adequately reflect the experiences of poor urban mothers in low and middle income countries. We argue that policy needs to recognise culturally-specific family formations, which, in Jamaica includes absent fathers, mothering at a distance and mothering non-biological children. This article reflects on the experiences of an under-researched group, poor urban Jamaican women practising mothering at a distance, using a novel methodological approach (IPA) to bring into relief unique insights into their lived experiences and will contribute to the global policy and research literature on HIV disclosure. Keywords: Feminist IPA, HIV disclosure, mothering, emotion workPeer reviewedFinal Accepted Versio

Primer selection impacts specific population abundances but not community dynamics in a monthly time-series 16S rRNA gene amplicon analysis of coastal marine bacterioplankton.

Primers targeting the 16S small subunit ribosomal RNA marker gene, used to characterize bacterial and archaeal communities, have recently been re-evaluated for marine planktonic habitats. To investigate whether primer selection affects the ecological interpretation of bacterioplankton populations and community dynamics, amplicon sequencing with four primer sets targeting several hypervariable regions of the 16S rRNA gene was conducted on both mock communities constructed from cloned 16S rRNA genes and a time-series of DNA samples from the temperate coastal Santa Barbara Channel. Ecological interpretations of community structure (delineation of depth and seasonality, correlations with environmental factors) were similar across primer sets, while population dynamics varied. We observed substantial differences in relative abundances of taxa known to be poorly resolved by some primer sets, such as Thaumarchaeota and SAR11, and unexpected taxa including Roseobacter clades. Though the magnitude of relative abundances of common OTUs differed between primer sets, the relative abundances of the OTUs were nonetheless strongly correlated. We do not endorse one primer set but rather enumerate strengths and weaknesses to facilitate selection appropriate to a system or experimental goal. While 16S rRNA gene primer bias suggests caution in assessing quantitative population dynamics, community dynamics appear robust across studies using different primers

The 2009 analysis of information remaining on USB storage devices offered for sale on the second hand market

The use of the USB storage device, also known as the USB drive, a thumb drive, a keychain drive and a flash drive has, for the most part, replaced the floppy disk and to some extent the Compact Disk (CD), the DVD (Digital Video Disk or Digital Versatile Disk) and the external hard disk. Their robustness, size and weight make them easy to transport, but also to lose or misplace. They are inexpensive and are often given away as promotional items by organisations. Over the last few years there has been a dramatic increase in the storage capacity of these devices, going from a few tens of megabytes to a current capacity of around 64 gigabytes (equal to around 13 DVDs). The larger capacity and continued low cost has vastly increased the potential uses of the devices and also the volumes and types of data that they may contain