Sum rules and physical bounds on passive metamaterials

Frequency dependence of the permittivity and permeability is inevitable in metamaterial applications such as cloaking and perfect lenses. In this paper, Herglotz functions are used as a tool to construct sum rules from which we derive physical bounds suited for metamaterial applications, where the material parameters are often designed to be negative or near zero in the frequency band of interest. Several sum rules are presented that relate the temporal dispersion of the material parameters with the difference between the static and instantaneous parameter values, which are used to give upper bounds on the bandwidth of the application. This substantially advances the understanding of the behavior of metamaterials with extraordinary material parameters, and reveals a beautiful connection between properties in the design band (finite frequencies) and the low- and high-frequency limit

Physical bounds and sum rules for high-impedance surfaces

High-impedance surfaces are artificial surfaces synthesized from periodic structures. The high impedance is useful as it does not short circuit electric currents and reflects electric fields without phase shift. Here, a sum rule is presented that relates frequency intervals having high impedance with the thickness of the structure. The sum rule is used to derive physical bounds on the bandwidth for high-impedance surfaces. Numerical examples are used to illustrate the result, and show that the physical bounds are tight

Sum rules and physical limitations for passive metamaterials

Bandwidth is an important parameter in many metamaterial applications. It has been shown that Herglotz functions and sum rules offer a powerful methodology to analyze the trade-off between bandwidth and design parameters. Here, this approach is described for the temporal dispersion of constitutive relations and high-impedance surfaces

Treatment of International Human Rights Violations in the United States

INTRODUCTION: Health-related quality of life (HRQoL) in patients treated in intensive care has been reported to be lower compared with age- and sex-adjusted control groups. Our aim was to test whether stratifying for coexisting conditions would reduce observed differences in HRQoL between patients treated in the ICU and a control group from the normal population. We also wanted to characterize the ICU patients with the lowest HRQoL within these strata. METHODS: We did a cross-sectional comparison of scores of the short-form health survey (SF-36) questionnaire in a multicenter study of patients treated in the ICU (n = 780) and those from a local public health survey (n = 6,093). Analyses were in both groups adjusted for age and sex, and data stratified for coexisting conditions. Within each stratum, patients with low scores (below -2 SD of the control group) were identified and characterized. RESULTS: After adjustment, there were minor and insignificant differences in mean SF-36 scores between patients and controls. Eight (n = 18) and 22% (n = 51) of the patients had low scores (-2 SD of the control group) in the physical and mental dimensions of SF-36, respectively. Patients with low scores were usually male, single, on sick leave before admission to critical care, and survived a shorter time after being in ICU. CONCLUSIONS: After adjusting for age, sex, and coexisting conditions, mean HRQoL scores were almost equal in patients and controls. Up to 22% (n = 51) of the patients had, however, a poor quality of life as compared with the controls (-2 SD). This group, which more often consisted of single men, individuals who were on sick leave before admission to the ICU, had an increased mortality after ICU. This group should be a target for future support

Hand Disinfectant Practice: The Impact of an Education Intervention

The primary hypothesis of this study was that a lecture on basic hygiene routines could be associated with an increase in the use of disinfectant for hand hygiene. A secondary hypothesis was that the lecture could positively affect the staff’s knowledge of and attitudes toward basic hygiene routines

Innehållsbaserad sökning av hierarkiska objekt med PicSOM

The amounts of multimedia content available to the public have been increasing rapidly in the last decades and it is expected to grow exponentially in the years to come. This development puts an increasing emphasis on automated content-based information retrieval (CBIR) methods, which index and retrieve multimedia based on its contents. Such methods can automatically process huge amounts of data without the human intervention required by traditional methods (e.g. manual categorisation, entering of keywords). Unfortunately CBIR methods do have a serious problem: the so-called semantic gap between the low-level descriptions used by computer systems and the high-level concepts of humans. However, by emulating human skills such as understanding the contexts and relationships of the multimedia objects one might be able to bridge the semantic gap. To this end, this thesis proposes a method of using hierarchical objects combined with relevance sharing. The proposed method can incorporate natural relationships between multimedia objects and take advantage of these in the retrieval process, hopefully improving the retrieval accuracy considerably. The literature survey part of the thesis consists of a review of content-based information retrieval in general and also looks at multimodal fusion in CBIR systems and how that has been implemented previously in different scenarios. The work performed for this thesis includes the implementation of hierarchical objects and multimodal relevance sharing into the PicSOM CBIR system. Also extensive experiments with different kinds of multimedia and other hierarchical objects (segmented images, web-link structures and video retrieval) were performed to evaluate the usefulness of the hierarchical objects paradigm. Keywords: content-based retrieval, self-organizing map, multimedia database

IR and Metasurface based mm-Wave Camera

We have developed a technique to measure low-power electromagnetic fields from mm-wave devices non-intrusively by combining a metasurface, designed to absorb power and focus the radiated power in a thermally isolated region, with an infrared camera. The metasurface consists of thermally isolated elements of low mass and highly emissive material for maximal IR conversion of the incident wave. The IR camera captures the converted energy and indirectly images the incident electromagnetic field on the metasurface. The setup combines multi-scale, multi-physical processes to conduct measurements of the incident electromagnetic fields in real time. In this work, the technique is presented and discussed. Measurements are carried out to demonstrate the technique and image the electromagnetic field of a radiating device. The results compare well with simulations and the technique can measure the low power density levels of consumer devices, as well as provide a general visualization of electromagnetic fields in a live setting