Initial studies of array feeds for the 70-meter antenna at 32 GHz

The results of a study to determine the feasibility of using array feed techniques to improve the performance of the 70 m antenna at 32 GHz are presented. Changing from 8.4 to 32 GHz has the potential of increasing the gain by 11.6 dB, but recent measurements indicate that additional losses of from 3 to 7 dB occur at 32 GHz, depending on the elevation angle. Array feeds were proposed to recover some of the losses by compensating for surface distortions that contribute to these losses. Results for both surface distortion compensation and pointing error correction are discussed. These initial studies, however, had one significant restriction: The mechanical finite element model was used to characterize the surface distortions, not the measured distortions from three angle holography data, which would be more representative of the actual antenna. Further work is required to provide for a more accurate estimate of performance that utilizes holography data and, in particular, one that evaluates the performance in the focal plane region of the antenna

Conical quadreflex antenna analytical study

A method for evaluating the performance of a four-reflection or quadreflex antenna is reported. Geometrical optics was used initially to determine the ideal feed pattern required to produce uniform illumination on the aperture of the conical reflector and the reverse problem of quickly finding the aperture illumination given an arbitrary feed pattern. The knowledge of the aperture illumination makes it possible to compute the antenna efficiency, which is useful for comparing antenna performance during tradeoff studies. Scattering calculations, using physical optics techniques, were then used to more accurately determine the performance of a specific design

Matrix Algebras with a Certain Compression Property I

An algebra $\mathcal{A}$ of $n\times n$ complex matrices is said to be projection compressible if $P\mathcal{A}P$ is an algebra for all orthogonal projections $P\in\mathbb{M}_n(\mathbb{C})$. Analogously, $\mathcal{A}$ is said to be idempotent compressible if $E\mathcal{A}E$ is an algebra for all idempotents $E\in\mathbb{M}_n(\mathbb{C})$. In this paper we construct several examples of unital algebras that admit these properties. In addition, a complete classification of the unital idempotent compressible subalgebras of $\mathbb{M}_3(\mathbb{C})$ is obtained up to similarity and transposition. It is shown that in this setting, the two notions of compressibility agree: a unital subalgebra of $\mathbb{M}_3(\mathbb{C})$ is projection compressible if and only if it is idempotent compressible. Our findings are extended to algebras of arbitrary size in the sequel to this paper.Comment: 23 page

A spatially explicit and quantitative vulnerability assessment of ecosystem service change in Europe

Environmental change alters ecosystem functioning and may put the provision of services to human at risk. This paper presents a spatially explicit and quantitative assessment of the corresponding vulnerability for Europe, using a new framework designed to answer multidisciplinary policy relevant questions about the vulnerability of the human-environment system to global change. Scenarios were constructed for a range of possible changes in socio-economic trends, land uses and climate. These scenarios were used as inputs in a range of ecosystem models in order to assess the response of ecosystem function as well as the changes in the services they provide. The framework was used to relate the impacts of changing ecosystem service provision for four sectors in relation to each other, and to combine them with a simple, but generic index for societal adaptive capacity. By allowing analysis of different sectors, regions and development pathways, the vulnerability assessment provides a basis for discussion between stakeholders and policymakers about sustainable management of Europe¿s natural resource

Introduction of 4-chloro-alpha-cyanocinnamic acid liquid matrices for high sensitivity UV-MALDI MS

Matrix-assisted laser desorption/ionization (MALDI) is a key ionization technique in mass spectrometry (MS) for the analysis of labile macromolecules. An important area of study and improvements in relation to MALDI and its application in high-sensitivity MS is that of matrix design and sample preparation. Recently, 4-chloro-alpha-cyanocinnamic acid (ClCCA) has been introduced as a new rationally designed matrix and reported to provide an improved analytical performance as demonstrated by an increase in sequence coverage of protein digests obtained by peptide mass mapping (PMM) (Jaskolla, T. W.; et al. Proc. Natl. Acad. Sci. U.S.A. 2008, 105, 12200-12205). This new matrix shows the potential to be a superior alternative to the commonly used and highly successful alpha-cyano-4-hydroxycinnamic acid (CHCA). We have taken this design one step further by developing and optimizing an ionic liquid matrix (ILM) and liquid support matrix (LSM) using ClCCA as the principle chromophore and MALDI matrix compound. These new liquid matrices possess greater sample homogeneity and a simpler morphology. The data obtained from our studies show improved sequence coverage for BSA digests compared to the traditional CHCA crystalline matrix and for the ClCCA-containing ILM a similar performance to the ClCCA crystalline matrix down to 1 fmol of BSA digest prepared in a single MALDI sample droplet with current sensitivity levels in the attomole range. The LSMs show a high tolerance to contamination such as ammonium bicarbonate, a commonly used buffering agent

The influence of vision on susceptibility to acute motion sickness studied under quantifiable stimulus-response conditions

Twenty-four healthy men, 22 to 25 years of age, were exposed to stressful accelerations in a rotating room until acute mild motion sickness was elicited. Thirteen subjects in one group were exposed first with eyes open and later with eyes covered; the reverse order was used with the remaining eleven in the other group. The stressful accelerations were generated by requiring the subject to execute 120 standardized head movements at each 1-rpm increase in angular velocity until the desired endpoint was reached. When susceptibility to motion sickness with eyes open and covered is compared, 19 subjects were more susceptible with eyes open, three with eyes covered, and in the remaining two susceptibility was the same. The maximum difference in velocity between trial 1 and 2 was 7 rpm when susceptibility was greater with eyes open and 3 rpm when it was greater with eyes covered; the means, respectively, were 3.2 and 2.0 rpm. Among subjects manifesting greater susceptibility with eyes open than covered the group differences were small, indicating little or no adaptation effects. The findings are discussed mainly on the basis that vision may act also to decrease susceptibility under the stimulus conditions described