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An even leaky mode in a microstrip line loaded with periodic shorting vias at the centre is investigated. The even leaky mode has a lower cutoff frequency than that of the first higher mode (odd mode). Thus, it is a fundamental leaky mode. The even leaky mode can generate dual symmetrical side beams that scan with frequency, similar to the second higher mode (even mode) in a non-loaded microstrip line. The dispersion characteristic of the even leaky mode is analysed efficiently with the method of auxiliary sources and validated with HFSS. Based on the leaky even mode, two leaky-wave antennas with different feeding structures are designed. Measured results for the two antennas are consistent with simulated and theoretical results. [ABSTRACT FROM AUTHOR]

The periodic half-width microstrip leaky wave antenna (MLWA) with a backward to forward scanning capability is presented in this paper. The proposed antenna consists of a series of half-width MLWA. The radiating periods place on the different sides of the transmission line. The radiating period works in cutoff region of the first higher order mode, the periodic construction radiates the slow wave out along the edge. The experimental results show the main lobe scans electronically and continuously from 149° to 28° in H-plane (y-z plane) toward end fire (+z direction) when the operating frequency increases from 4.2-.9 GHz. [ABSTRACT FROM AUTHOR]

A quasi microstrip leaky-wave antenna (QMLWA) with a two-dimensional (2-D) beam-scanning capability is presented in this paper. QMLWA consists of two half-width microstrip leaky-wave antennas with a phase-shifter. This new type of microstrip leaky-wave antenna has the advantages of reducing size, 2-D beam-scanning and suppressing back lobes. The main lobe scanning in H-plane (y - z plane) is achieved through varying the operating frequency. When the operating frequency increases from 4.4-6 GHz, the main lobe scans from 84° to 26° in H-plane continuously. The main lobe steers in quasi-E-plane with varying the phase difference between two half-width microstrip leaky-wave antennas. The lobe scans from 78° to 103° in quasi-E-plane at 5.4 GHz. The experimental results show this short QMLWA (about 2 wavelengths) leaks power effectively. The back lobe in H-plane of QMLWA is suppressed 13 dB as compared with the conventional whole width MLWA at 5.4 GHz as example. The H-plane radiation characteristics of QMLWA are mainly determined by the width s of half-width MLWA and the distance D between two half-width MLWA together. This size-reduced QMLWA is useful in the automotive radar system and air traffic control. [ABSTRACT FROM AUTHOR]

A fixed-frequency dual-beam steering microstrip leaky-wave antenna is presented in this paper. A novel equation with finite-difference time-domain method is proposed to calculate the complex propagation constant of microstrip leaky-wave antenna. The microstrip leaky-wave antenna is excited by multiterminals. By control the novel feeding configuration, the microstrip leaky-wave antenna has the advantage of main lobe's dual-beam and steering at fixed-frequency. The main lobe steers from 41° to 63° for right beam and from 117° to 139° for left beam symmetrically when operating frequency fixes at 7 GHz. This new microstrip leaky-wave antenna can easily be used as collision avoidance or automobile radar system. [ABSTRACT FROM AUTHOR]

A beam-patterns switchable microstrip leaky-wave antenna (MLWA) is presented in this letter. A new feeding configuration of MLWA has been shown. MLWA fed with two feeding terminals on different sides radiates out single-beam radiation patterns. Through controlling SPDT switch, the beam-patterns change from single-beam mode to dual-beam mode. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 3060–3063, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22949 [ABSTRACT FROM AUTHOR]

A novel forward and backward periodic microstrip antenna is presented and tested in this article. The experimental results show that the main lobe scans electronically from 140° to 30° in y–z plane when the operating frequency increases from 3.2 to 8 GHz. The measured results show that the slotted ground plane affects the radiation characteristics of the antenna efficiently. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2608–2610, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25525 [ABSTRACT FROM AUTHOR]

A microstrip leaky-wave antenna (MLWA) with parasitic elements is presented in this letter. The short MLWA is the basic element, and two microstrip patches with a short-circuit edge worked as the parasitic elements. The main lobe scans from 66° to 42° when operating frequency increases from 5.9 to 6.9 GHz. In contrast to the conventional MLWA, the reflected wave of the short MLWA (about two wavelengths) with parasitic elements is suppressed 12 dB at 6.9 GHz. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1565–1567, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23428 [ABSTRACT FROM AUTHOR]

The analysis of noncovalent interactions in several complexes constructed from 2,3,5,6-tetramethylpyrazine with different acid ligands, 1,4-cyclohexanedicarboxylic acid, 2,6-dihydroxybenzoic acid, 2,6-pyridinedicarboxylic acid, 6-hydroxy-2-naphthoic acid, 3-nitrophthalic acid, o-phthalic acid and 3-hydroxybenzoic acid, supported by single crystal X-ray diffraction analysis is presented. It reveals that all of these forms except 2 are organic supramolecular cocrystals without charge-transfer between the multicomponent acids and the base. The noncovalent interactions directing the assemblies of the eight structures are managed by classical O-H⋯O, O-H⋯N, weak C-H⋯O and π-π stacking interactions to generate 2D or 3D supermolecular architectures. For 5, 6, 7 and 8, carboxyl/pyrazine supramolecular heterosynthons R2² (6) and R2² (8) containing classical O-H⋯N and weak C-H⋯O interactions, usually observed in organic cocrystals of carboxylic acid and heterocyclic base, are again confirmed to participate in constructing these hydrogen-bonding supermolecular networks. In addition, weak C-H⋯O interactions were involved in building and consolidating their structures in all organic complexes. The thermal stability of crystals 1-8 has been investigated by thermogravimetric analysis (TGA) of mass loss. [ABSTRACT FROM AUTHOR]

An in-depth knowledge of the interaction of water with amorphous silica is critical to fundamental studies of interfacial hydration water, as well as to industrial processes such as catalysis, nanofabrication, and chromatography. Silica has a tunable surface comprising hydrophilic silanol groups and moderately hydrophobic siloxane groups that can be interchanged through thermal and chemical treatments. Despite extensive studies of silica surfaces, the influence of surface hydrophilicity and chemical topology on the molecular properties of interfacial water is not well understood. In this work, we controllably altered the surface silanol density, and measured surface water diffusivity using Overhauser dynamic nuclear polarization (ODNP) and complementary silica-silica interaction forces across water using a surface forces apparatus (SFA). The results show that increased silanol density generally leads to slower water diffusivity and stronger silica-silica repulsion at short aqueous separations (less than ~4 nm). Both techniques show sharp changes in hydration properties at intermediate silanol densities (2.0-2.9 nm-2). Molecular dynamics simulations of model silica-water interfaces corroborate the increase in water diffusivity with silanol density, and furthermore show that even on a smooth and crystalline surface at a fixed silanol density, adjusting the spatial distribution of silanols results in a range of surface water diffusivities spanning ~10%. We speculate that a critical silanol cluster size or connectivity parameter could explain the sharp transition in our results, and can modulate wettability, colloidal interactions, and surface reactions, and thus is a phenomenon worth further investigation on silica and chemically heterogeneous surfaces. [ABSTRACT FROM AUTHOR]

Background: The management of an enterocutaneous fistula poses a significant challenge to surgeons and is often associated with a costly hospital stay and long-term discomfort. The use of fibrin glue in the fistula tract has been shown to promote closure of low output enterocutaneous fistulas. Our previous nonrandomized study demonstrated that autologous platelet-rich fibrin glue treatment significantly decreased time to fistula closure and promoted closure rates. However, there are several limitations in the study, which may lead to bias in our conclusion. Thus, a multicenter, randomized, controlled clinical trial is required.Methods/design: The study is designed as a randomized, open-label, three-arm, multicenter study in nine Chinese academic hospitals for evaluating the efficacy and safety of fibrin glue for sealing low-output fistulas. An established number of 171 fistula patients will undergo prospective random assignment to autologous fibrin glue, commercial porcine fibrin sealants or drainage cessation (1:1:1). The primary endpoint is fistula closure time (defined as the interval between the day of enrollment and day of fistula closure) during the 14-day treatment period.Discussion: To our knowledge, this is the first study to evaluate the safety and efficacy of both autologous and commercial fibrin glue sealing for patients with low-output volume fistulas.Trial Registration: NCT01828892 . Registration date: April 2013. [ABSTRACT FROM AUTHOR]