The Hi content of compact groups of galaxies

The Hi content of Hickson Compact Groups in the southern hemisphere is measured using data from the Hi Parkes All-Sky Survey (HIPASS), and dedicated observations using the narrow band filter on the Multibeam instrument on the Parkes telescope. The expected Hi mass of these groups was estimated using the luminosity, diameter, and morphological types of the member galaxies, calibrated from published data. Taking careful account of non-detection limits, the results show that the compact group population that has been detected by these observations has an Hi content similar to that of galaxies in the reference field sample. The upper limits for the undetected groups lie within the normal range; improvement of these limits will require a large increase in sensitivity.

Compact tunable microfluidic interferometer

We demonstrate a compact tunable filter based on a novel microfluidic single beam Mach-Zehnder interferometer. The optical path difference occurs during propagation across a fluid-air interface ( meniscus), the inherent mobility of which provides tunability. Optical losses are minimized by optimizing the meniscus shape through surface treatment. Optical spectra are compared to a 3D beam propagation method simulations and good agreement is found. Tunability, low insertion loss and strength of the resonance are well reproduced. The device performance displays a resonance depth of - 28 dB and insertion loss maintained at - 4 dB. (C) 2004 Optical Society of America.

Optofluidics enables compact tunable interferometer

An optofluidic interferometer - in which a beam propagates across an interface between fluid and air - modulates at high extinction ratios and is only microns in size.

Packing-dependent pore structure in single-walled carbon nanotube arrays

Based on a self-similar array model of single-walled carbon nanotubes (SWNTs), the pore structure of SWNT bundles is analyzed and compared with that obtained from the conventional triangular model and adsorption experimental results. In addition to the well known cylindrical endo-cavities and interstitial pores, two types of newly defined pores with diameters of 2-10 and 8-100 nm are proposed, inter-bundle pores and inter-array pores. In particular, the relationship between the packing configuration of SWNTs and their pore structures is systematically investigated. (c) 2005 American Institute of Physics.

A wave equation technique for designing compact gradient coils

A primary purpose of this research is to design a gradient coil that is planar in construction and can be inserted within existing infrastructure. The proposed wave equation method for the design of gradient coils is novel within the field. it is comprehensively shown how this method can be used to design the planar x-, y-, and z-gradient wire windings to produce the required magnetic fields within a certain domain. The solution for the cylindrical gradient coil set is also elucidated. The wave equation technique is compared with the well-known target held method to gauge the quality of resultant design. In the case of the planar gradient coil design, it is shown that using the new method, a set of compact gradient coils with large field of view can be produced. The final design is considerably smaller in dimension when compared with the design obtained using the target field method, and therefore the manufacturing costs and materials required are somewhat reduced.

Compact ultra-wideband planar tapered slot antenna for use in a microwave imaging system

The design of an ultra-wideband planar tapered slot antenna for use in a circular cylindrical microwave imaging system is pre-sented. The antenna was designed assuming high dielectric substrate material Rogers RT6010LM to achieve its compact size. The developed antenna element (50 X 50 mm(2)) features a 10-dB return loss bandwidth from 2.75 GHz to more than 11 GHz. The gain of the antenna is between 3.5 and 9.4 dBi over the 3-10 GHz band. The experimental tests showed that the manufactured antenna element supports transmission of narrow pulses with negligible distortions, as required in the microwave imaging system. (c) 2006 Wiley Periodicals, Inc.

Design of a compact ultra-wideband antenna

A simple method for the design of ultra-wideband antennas in planar format is presented. This method is demonstrated for a high-dielectric-constant substrate material, which allows for a considerable antenna size reduction. Simulations are performed using Ansoft's High-Frequency Structure Simulator (HFSS) for antennas assuming Du-Pont951 (epsilon(r) = 7.8) and RT6010LM (epsilon(r) = 10.2) substrates. For the 1-mm-thick DuPont951, the designed antenna with 22 X 28 nun dimensions features a 10-dB return-loss band width front 2.7 GHz to more than 15 GHz. For the 0.64-mm-thick RT6010LM a 20 X 26 nun antenna exhibits a 10-dB return loss bandwidth from 3.1 to 15 GHz. Both antennas feature nearly omnidirectional properties across the whole 10-dB return-loss bandwidth. The validity of the presented UWB antenna design strategy is confirmed by measurements performed on a prototype developed on RT6010LM substrate. (c) 2006 Wiley Periodicals, Inc.

Design of compact directive ultra wideband antipodal antenna

In this paper, a novel design procedure for designing a compact UWB antipodal Vivaldi antenna is presented. The antenna operates over the UWB frequency, band from 3.1 to more than 10.6 GHz. Its measured far-field radiation is directive and its peak gain is 10.2 dBi in the specified band. The antenna pulse response shows negligible distortion, indicating that it can be useful in a precision ranging and imaging instrumentation. (c) 2006 Wiley Periodicals, Inc.

Interfacial behavior of tetrapyridylporphyrin monolayer arrays

The behavior of monolayer films of free base 5,10,15,20-tetrapyridylporphinato (TPyP) and 5,10,15,20-tetrapyridylporphinato zinc(II) (ZnTPyP) on pure water, 0.1 M CdCl2, and 0.1 M CuCl2 subphases was investigated by surface pressure-area isotherms, specular X-ray reflectometry, and polarized total reflection X-ray absorption spectroscopy (PTRXAS). Surface pressure-area isotherms showed significant differences in the area per molecule on pure water compared to that on salt subphases, with a marked increase in the area observed on the salt solutions. This behavior was noted for both forms of the porphyrin and both salts investigated. Modeling of specular X-ray reflectometry data indicated that thinner and more electron dense layers on salt subphases best fit the observed profiles. These data suggest that the porphyrin macrocycle is oriented parallel to the interface on salt subphases and takes on a tilted conformation on pure water. In the case of ZnTPyP, PTRXAS was used to determine the orientation of the porphyrin moiety relative to the surface and to probe the coordination of the central Zn ion. In agreement with the pressure-area isotherms and reflectometry, the PTRXAS data indicate a change in orientation on the salt subphases.

Matching commercial clips from TV streams using a unique, robust and compact signature

One of critical challenges in automatic recognition of TV commercials is to generate a unique, robust and compact signature. Uniqueness indicates the ability to identify the similarity among the commercial video clips which may have slight content variation. Robustness means the ability to match commercial video clips containing the same content but probably with different digitalization/encoding, some noise data, and/or transmission and recording distortion. Efficiency is about the capability of effectively matching commercial video sequences with a low computation cost and storage overhead. In this paper, we present a binary signature based method, which meets all the three criteria above, by combining the techniques of ordinal and color measurements. Experimental results on a real large commercial video database show that our novel approach delivers a significantly better performance comparing to the existing methods.