3,975 research outputs found
Miniaturized Quadrature Hybrid Couplers based on Novel U-shaped Transmission Lines
In this paper, a miniaturized microstrip quadrature hybrid coupler (QHC) using U-shaped transmission lines (USTLs) is presented. The proposed approach replaces all arms of the conventional QHC with its equivalent USTL to achieve compactness. The proposed coupler structure is designed to operate in the 1.5 GHz (1427-1518 [MHz]) band which is one of the 5G bands of interest. At such low RF/microwave bands below 3-4 GHz, the size of the conventional coupler is considerably very large which raises a concern for the next generation networks. The pro- posed coupler is designed, simulated and fabricated using Rogers 5880 with thickness of 0.79 mm, dielectric con- stant (εr) of 2.2 and loss tangent of 0.0021. The proposed QHC size is 70% smaller in circuit area (30% relative area) than the conventional equivalent. Simulation and mea- sured results are presented and good matching between the results is observed, confirming the outstanding coupler performance properties. The proposed miniaturized QHC structure will play a vital role for next generation 4G and 5G wireless communication systems operating below 6 GHz
Microfabrication of Individual 200μm Diameter Transdermal Microconduits Using High Voltage Pulsing in Salicylic Acid and Benzoic Acid
We describe an extension of semiconductor fabrication methods that creates individual ≈ 200;μm diameter aqueous pathways through human stratum corneum at predetermined sites. Our hypothesis is that spatially localized electroporation of the multilamellar lipid bilayer membranes provides rapid delivery of salicylic acid to the keratin within corneocytes, leading to localized keratin disruption and then to a microconduit. A microconduit penetrating the isolated stratum corneum supports a volumetric flow of order 0.01;ml per s with a pressure difference of only 0.01;atm (about 102;Pa). This study provides a method for rapidly microengineering a pathway in the skin to interface future devices for transdermal drug delivery and sampling of biologically relevant fluids
Experimental observation of strong photon localization in disordered photonic crystal waveguides
We demonstrate experimentally that structural perturbations imposed on
highly-dispersive photonic crystal-based waveguides give rise to spectral
features that bear signatures of Anderson localization. Sharp resonances with
the effective Qs of over 30,000 are found in scattering spectra of disordered
waveguides. The resonances are observed in a ~20-nm bandwidth centered at the
cutoff of slowly-guided Bloch-modes. Their origin can be explained with
interference of coherently scattered electromagnetic waves which results in the
formation of a narrow impurity (or localization) band populated with spectrally
distinct quasistates. Standard photon localization criteria are fulfilled in
the localization band.Comment: first submitted to PRL on April 20th, 2007; 16 pages, 4 figure
Graphene-based photovoltaic cells for near-field thermal energy conversion
Thermophotovoltaic devices are energy-conversion systems generating an
electric current from the thermal photons radiated by a hot body. In far field,
the efficiency of these systems is limited by the thermodynamic
Schockley-Queisser limit corresponding to the case where the source is a black
body. On the other hand, in near field, the heat flux which can be transferred
to a photovoltaic cell can be several orders of magnitude larger because of the
contribution of evanescent photons. This is particularly true when the source
supports surface polaritons. Unfortunately, in the infrared where these systems
operate, the mismatch between the surface-mode frequency and the semiconductor
gap reduces drastically the potential of this technology. Here we show that
graphene-based hybrid photovoltaic cells can significantly enhance the
generated power paving the way to a promising technology for an intensive
production of electricity from waste heat.Comment: 5 pages, 4 figure
Towards a European framework for community engagement in higher education – a case study analysis of European universities
Purpose – This paper aims to examine the development and piloting of a novel European framework for community engagement (CE) in higher education, which has been purposefully designed to progress the CE agenda in a European context.
Design/methodology/approach – The proposed framework was co-created through the European Union (EU)-funded project towards a European framework for community engagement in higher education (TEFCE). The TEFCE Toolbox is an institutional self-reflection framework that centres on seven thematic dimensions of CE. This paper follows the development of the TEFCE Toolbox through empirical case study analysis of four European universities and their local communities.
Findings – The findings in this paper indicate that the TEFCE Toolbox facilitates context-specific applications in different types of universities and socioeconomic environments. Incorporating insights from engagement practitioners, students and community representatives the TEFCE Toolbox was successfully applied in universities with diverse profiles and missions. The process facilitated the recognition of CE achievements and the identification of potential areas for improvement.
Originality/value – Despite a range of international initiatives, there remains an absence of initiatives within the European higher education area that focus on developing tools to comprehensively support CE. The TEFCE Toolbox and case-study analysis presented in this paper address this gap in knowledge. The broader societal contribution and social responsibility of higher education have become increasingly prominent on the European agenda. The TEFCE Toolbox represents an innovative, robust and holistic European framework with the potential to support universities in reflecting upon their pursuit of addressing grand societal challenges, whilst promoting CE
Construction of PREMUX and preliminary experimental results, as preparation for the HCPB breeder unit mock-up testing
The elite judo female athlete’s heart
Purpose: There is a paucity of data on physiological heart adaptation in elite-level judo female athletes. This study aimed to assess left ventricular morphology and function in highly trained elite female judokas. Methods: The study prospectively included 18 females aged 23.5 ± 2.25 years, nine elite level judokas, and nine healthy non-athlete volunteers. All participants underwent a medical examination, electrocardiogram, and transthoracic 2D echocardiogram. Left ventricular diastolic and systolic diameters and volumes were determined, and parameters of left heart geometry and function (systolic and diastolic) were measured, calculated, and compared between groups. Results: When groups were compared, judokas had significantly increased left ventricular cavity dimensions p < 0.01, left ventricular wall thickness p < 0.01, and volumes p < 0.01. Elite female judokas exhibited left ventricular dilatation demonstrated as high prevalence increased end-diastolic volume/index, and increased end-systolic volume/index in 88.9% of judokas vs. 0% in controls, p < 0.01. Left ventricle mass/index was significantly increased in judokas, p < 0.01), with a 43.3% difference between groups. The majority (77.7%) of judokas had normal left ventricular geometry, although eccentric hypertrophy was revealed in 2 (22.2%) of judokas. Conclusion: Elite, highly trained female judokas exhibit significant changes in left heart morphology as a result of vigorous training compared to non-athletes. These findings suggest that female judokas athletes’ heart follows a pattern toward chamber dilatation rather than left ventricular wall hypertrophy
A picogram and nanometer scale photonic crystal opto-mechanical cavity
We describe the design, fabrication, and measurement of a cavity
opto-mechanical system consisting of two nanobeams of silicon nitride in the
near-field of each other, forming a so-called "zipper" cavity. A photonic
crystal patterning is applied to the nanobeams to localize optical and
mechanical energy to the same cubic-micron-scale volume. The picrogram-scale
mass of the structure, along with the strong per-photon optical gradient force,
results in a giant optical spring effect. In addition, a novel damping regime
is explored in which the small heat capacity of the zipper cavity results in
blue-detuned opto-mechanical damping.Comment: 15 pages, 4 figure
CapsID: a web-based tool for developing parsimonious sets of CAPS molecular markers for genotyping
BACKGROUND: Genotyping may be carried out by a number of different methods including direct sequencing and polymorphism analysis. For a number of reasons, PCR-based polymorphism analysis may be desirable, owing to the fact that only small amounts of genetic material are required, and that the costs are low. One popular and cheap method for detecting polymorphisms is by using cleaved amplified polymorphic sequence, or CAPS, molecular markers. These are also known as PCR-RFLP markers. RESULTS: We have developed a program, called CapsID, that identifies snip-SNPs (single nucleotide polymorphisms that alter restriction endonuclease cut sites) within a set or sets of reference sequences, designs PCR primers around these, and then suggests the most parsimonious combination of markers for genotyping any individual who is not a member of the reference set. The output page includes biologist-friendly features, such as images of virtual gels to assist in genotyping efforts. CapsID is freely available at . CONCLUSION: CapsID is a tool that can rapidly provide minimal sets of CAPS markers for molecular identification purposes for any biologist working in genetics, community genetics, plant and animal breeding, forensics and other fields
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