George Eliot: Beyond feminism

The three central conflicts of George Eliot\u27s life--an emotional conflict with male rejection, an intellectual conflict with orthodox Christianity, and a gender conflict with the limitations imposed on women--can be attributed largely to the nineteenth-century feminine ideologies. While Eliot used her nonfiction to criticize the ideas responsible for her conflicts, she used her poetry and fiction to dramatize the conflicts and develop an ideal of humanity. Eliot considered feminism, in Romola, as a resolution to these conflicts, then moved beyond feminism to develop her human ideal. This ideal, which transcends gender ideologies in response to natural and moral law, posits a whole of androgynous female and male, in which each completes and frees the other for development through self-giving love and duty, for a reciprocity of temporal salvation. For Eliot, this whole comprises the human Christ, or divinity, capable of effecting moral and political reform for humanity\u27s greater self-consciousness and unity

Lightweight, self-evacuated insulation panels

Multilayer insulation of prefabricated panels is developed for cryogenic storage tanks. System utilizes panels of aluminized Mylar separated by sheets of low conductivity polyurethane foam. Panels are self-evacuated by cryopumping of gaseous carbon dioxide at time of use

Confocal Ellipsoidal Reflector System for a Mechanically Scanned Active Terahertz Imager

We present the design of a reflector system that can rapidly scan and refocus a terahertz beam for high-resolution standoff imaging applications. The proposed optical system utilizes a confocal Gregorian geometry with a small mechanical rotating mirror and an axial displacement of the feed. For operation at submillimeter wavelengths and standoff ranges of many meters, the imaging targets are electrically very close to the antenna aperture. Therefore the main reflector surface must be an ellipse, instead of a parabola, in order to achieve the best imaging performance. Here we demonstrate how a simple design equivalence can be used to generalize the design of a Gregorian reflector system based on a paraboloidal main reflector to one with an ellipsoidal main reflector. The system parameters are determined by minimizing the optical path length error, and the results are validated with numerical simulations from the commercial antenna software package GRASP. The system is able to scan the beam over 0.5 m in cross-range at a 25 m standoff range with less than 1% increase of the half-power beam-width

The detection of automated perimetric stimuli in ocular disease

Automated perimetry has made viable a rapid threshold examination of the visual field and has reinforced the role of perimetry in the diagnostic procedure. The aim of this study was twofold: to isolate the influence of certain extraneous factors on the sensitivity gradient, since these might limit the early detection and accurate monitoring of visual field loss and to investigate the efficacy of certain novel combinations of stimulus parameters in the detection of early visual field loss. The work was carried out with particular reference to glaucoma and to ocular hypertension. The effects of media opacities on the visual field were assessed by forward intraocular light scatter (n= 15) and were found to mask diffuse glaucomatous visual field loss and underestimate focal loss. Correction of the visual field indices for the effects of forward intraocular light scatter (n= 26) showed the focal losses to be, in reality, unaffected. Measurements of back scatter underestimated forward intraocular light scatter (n= 60) and the resultant depression of the visual field. Perimetric sensitivity improved with patient learning (n= 25) and exhibited eccentricity- and depth-dependency effects whereby improvements in sensitivity were greatest for peripheral areas of the field and for those areas which initially demonstrated the lowest sensitivity. The effects of practice were retained over several months (n= 16). Perimetric sensitivity decreased during prolonged examination due to fatigue effects (n&61 19); these demonstrated a similar eccentricity-dependency, being greatest for eccentricities beyond 30o. Mean sensitivities over the range of adaptation levels employed obeyed the Weber-Fechner law (n= 10) and, as would be expected, were independent of pupil size. No relationship was found between short-term fluctuation and adaptation level. Detection of diffuse glaucomatous visual field loss was facilitated using a size III stimulus of duration 200msec at an adaptation level of 31.5asb, compared with a size III stimulus of duration 100msec at an adaptation level of 4asb (n= 20). In a pilot study (n= 10), temporal summation was found to be higher in glaucomatous patients compared with age-matched controls, although the difference was not statistically significant

Terahertz heterodyne imager for biomedical applications

Terahertz heterodyne imaging is an established technique that offers the potential for extremely large dynamic range and high signal-to-noise ratio while maintaining fast data acquisition, stable magnitude and phase measurements, reasonable frequency flexibility and mm level penetration in tissue and other materials. The authors have set up an imaging system based around a custom fabricated 2.5 THz planar Schottky diode mixer pair and two optically pumped far IR lasers. One laser is used for the signal beam and supplies as much as 70mW at 2.5 THz. The other laser acts as a local oscillator (LO) source for the two mixers. Line pairs very close to each other (CH3OH and CH2F2) are chosen to provide a workable intermediate frequency output (IF=24 GHz). Broader RF bandwidth is possible with tunable signal sources and wider IF band amplifiers. A novel frequency stabilization scheme has been implemented to track and calibrate the laser power (magnitude and phase) over a sample run. The system uses the second THz mixer, a low frequency (GHz) reference oscillator and a lock-in amplifier to monitor and normalize the two lasers (LO and Signal). Stability of ~0.1 dB and <5 degrees have been achieved with a dynamic range of more than 90dB. The present system scans the sample through the focused beam and measures transmission or reflection at a fixed RF frequency. Applications to date include establishing contrast mechanisms in a range of test and biological materials. The measurement system is described and the merits and demerits discussed. Early results on a variety of samples are presented as well as plans to enhance the performance in the near future

Time-Delay Multiplexing of Two Beams in a Terahertz Imaging Radar

We demonstrate a time-delay multiplexing technique that doubles the frame rate of a 660–690-GHz imaging radar with minimal additional instrument complexity. This is done by simultaneously projecting two offset, orthogonally polarized radar beams generated and detected by a common source and receiver. Beam splitting and polarization rotation is accomplished with a custom designed waveguide hybrid coupler and twist. A relative time lag of approximately 2 ns between the beams’ waveforms is introduced using a quasi-optical delay line, followed by spatial recombination using a selectively reflective wire grid. This delay is much longer than the approximately 20-ps time-of-flight resolution of the 30-GHz bandwidth radar, permitting the two beams’ reflected signals from a compact target to be easily distinguished in digital post-processing of the single receiver channel

A planar quasi-optical SIS receiver for array applications

A planar, quasi-optical SIS receiver operating at 230 GHz is described. The receiver consists of a 2 x 5 array of half wave dipole antennas with ten niobium-aluminum oxide-niobium SIS junctions on a quartz dielectric-filled parabola. The 1.4 GHz intermediate frequency is coupled from the mixer via coplanar strip transmission lines and 4:1 balun transformers. The receiver is operated at 4.2 K in a liquid helium immersion cryostat. We report accurate measurements of the performance of single receiver elements. A mixer noise temperature of 89 K DSB, receiver noise temperature of 156 K DSB, and conversion loss of 3 dB into a matched load have been obtained

Species–area relationships in continuous vegetation : evidence from Palaearctic grasslands

Aim: Species-area relationships (SARs) are fundamental scaling laws in ecology although their shape is still disputed. At larger areas power laws best represent SARs. Yet, it remains unclear whether SARs follow other shapes at finer spatial grains in continuous vegetation. We asked which function describes SARs best at small grains and explored how sampling methodology or the environment influence SAR shape. Location: Palaearctic grasslands and other non-forested habitats. Taxa: Vascular plants, bryophytes and lichens. Methods: We used the GrassPlot database, containing standardised vegetation-plot data from vascular plants, bryophytes, and lichens spanning a wide range of grassland types throughout the Palaearctic and including 2057 nested-plot series with at least seven grain sizes ranging from 1 cm2 to 1024 m². Using non-linear regression, we assessed the appropriateness of different SAR functions (power, power quadratic, power breakpoint, logarithmic, Michaelis-Menten). Based on AICc, we tested whether the ranking of functions differed among taxa, methodological settings, biomes or vegetation types. Results: The power function was the most suitable function across the studied taxonomic groups. The superiority of this function increased from lichens to bryophytes to vascular plants to all three taxonomic groups together. The sampling method was highly influential as rooted-presence sampling decreased the performance of the power function. By contrast, biome and vegetation type had practically no influence on the superiority of the power law. Main conclusions: We conclude that SARs of sessile organisms at smaller spatial grains are best approximated by a power function. This coincides with several other comprehensive studies of SARs at different grain sizes and for different taxa, thus supporting the general appropriateness of the power function for modelling species diversity over a wide range of grain sizes. The poor performance of the Michaelis-Menten function demonstrates that richness within plant communities generally does not approach any saturation, thus calling into question the concept of minimal area