A Frequency-Dependent Equivalence Between Groove Gap Waveguide and Rectangular Waveguide

Recently gap waveguides have been shown as a potential alternative to conventional waveguides in the millimeter-wave band. Groove Gap Waveguide (GGW) has until now been studied though direct correspondence with rectangular waveguide with the same propagation channel dimensions. However there have been observed differences in the above cutoff propagation characteristics between these waveguide types. Furthermore, the behaviour of GGW below cutoff remains unknown. This work presents a discussion of below and above cutoff propagation characteristics, and introduces a simple model that explains observed GGW behavior and establishes its propagation characteristics.

Strengthening an in-service reinforcement concrete bridge with prestressed CFRP bar

Carbon fiber reinforced polymer (CFRP) bars were prestressed for the structural strengthening of 8 T-shaped reinforced concrete (RC) beams of a 21-year-old bridge in China. The ultimate bearing capacity of the existing bridge after retrofit was discussed on the basis of concrete structures theory. The flexural strengths of RC beams strengthened with CFRP bars were controlled by the failure of concrete in compression and a prestressing method was applied in the retrofit. The field construction processes of strengthening with CFRP bars—including grouting cracks, cutting groove, grouting epoxy and embedding CFRP bars, surface treating, banding with the U-type CFRP sheets, releasing external prestressed steel tendons—were introduced in detail. In order to evaluate the effectiveness of this strengthening method, field tests using vehicles as live load were applied before and after the retrofit. The test results of deflection and concrete strain of the T-shaped beams with and without strengthening show that the capacity of the repaired bridge, including the bending strength and stiffness, is enhanced. The measurements of crack width also indicate that this strengthening method can enhance the durability of bridges. Therefore, the proposed strengthening technology is feasible and effective.

Development and clinical validation of multiplex TaqMan® assays for rapid diagnosis of viral gastroenteritis.

There is a need to provide rapid, sensitive, and often high throughput detection of pathogens in diagnostic virology. Viral gastroenteritis is a serious health issue often leading to hospitalization in the young, the immunocompromised and the elderly. The common causes of viral gastroenteritis include rotavirus, norovirus (genogroups I and II), astrovirus, and group F adenoviruses (serotypes 40 and 41). This article describes the work-up of two internally controlled multiplex, probe-based PCR assays and reports on the clinical validation over a 3-year period, March 2007 to February 2010. Multiplex assays were developed using a combination of TaqMan™ and minor groove binder (MGB™) hydrolysis probes. The assays were validated using a panel of 137 specimens, previously positive via a nested gel-based assay. The assays had improved sensitivity for adenovirus, rotavirus, and norovirus (97.3% vs. 86.1%, 100% vs. 87.8%, and 95.1% vs. 79.5%, respectively) and also more specific for targets adenovirus, rotavirus, and norovirus (99% vs. 95.2%, 100% vs. 93.6%, and 97.9% vs. 92.3%, respectively). For the specimens tested, both assays had equal sensitivity and specificity for astrovirus (100%). Overall the probe-based assays detected 16 more positive specimens than the nested gel-based assay. Post-introduction to the routine diagnostic service, a total of 9,846 specimens were processed with multiplex 1 and 2 (7,053 pediatric, 2,793 adult) over the 3-year study period. This clinically validated, probe-based multiplex testing algorithm allows highly sensitive and timely diagnosis of the four most prominent causes of viral gastroenteritis.

A chiton without a foot

The palaeoloricate ‘polyplacophorans’ are an extinct paraphyletic group of basal chiton-like organisms known primarily from their fossilized valves. Their phylo- genetic placement remains contentious, but they are likely to include both stem-group Polyplacophora and stem- group Aplacophora. Candidates for the latter position include ‘Helminthochiton’ thraivensis from the Ordovician of Scotland, which we redescribe here through a combined optical and micro-CT (XMT) restudy of the type material. The 11 specimens in the type series are all articulated, presenting partial or complete valve series as well as moul- dic preservation of the girdle armature; they demonstrate a vermiform body plan. The valves are typically palaeolori- cate in aspect, but differ in detail from all existing palaeol- oricate genera; we hence erect Phthipodochiton gen. nov. to contain the species. The most notable feature of the fossils is the spicular girdle; this is impersistently preserved, but demonstrably wraps entirely around the ventral surface of the animal, implying that a ‘true’ (i.e. polyplacophoran like) foot was absent, although we do not exclude the pos- sibility of a narrow solenogastre-like median pedal groove having been present. Phthipodochiton thraivensis presents an apparent mosaic of aplacophoran and polyplacophoran features and as such will inform our understanding of the relationship between these groups of extant molluscs. An inference may also be drawn that at least some other pal- aeoloricates possessed an ‘armoured aplacophoran’ body plan, in contrast to the ‘limpet-like’ body plan of extant Polyplacophora.

A charged-particle microbeam .2. A single-particle micro-collimation and detection system.

The use of a charged-particle microbeam provides a unique opportunity to control precisely, the number of particles traversing individual cells and the localization of dose within the cell. The accuracy of 'aiming' and of delivering a precise number of particles crucially depends on the design and implementation of the collimation and detection system. This report describes the methods available for collimating and detecting energetic particles in the context of a radiobiological microbeam. The arrangement developed at the Gray Laboratory uses either a 'V'-groove or a thick-walled glass capillary to achieve 2-5 mu m spatial resolution. The particle detection system uses an 18 mu m thick transmission scintillator and photomultiplier tube to detect particles with >99% efficiency.

Experimental and numerical studies on rock breaking with TBM tools under high stress confinement

The understanding of rock breaking and chipping due to the TBM cutter disks mechanism in deep tunnels is considered in this paper. The interest stems from the use of TBMs for the excavation of long Trans-Alpine tunnels. Some tests that simulate the disk cutter action at the tunnel face by means of an indenter, acting on a rock specimen are proposed. The rock specimen is confined through a flat-jack and a confinement-free area on one side of the specimen simulates the formation of a groove near the indenter, like it occurs in TBM excavation conditions. Results show a limited influence of the confinement stress versus the thrust increment required for breaking the rock between the indenter and the free side of the specimen. Numerical modelling of the cutter disk action on confined material has also been carried out in order to investigate further aspects of the fracture initiation. Also in this case the importance of the relative position between disk cutter and groove is pointed out. © 2006 Springer-Verlag.

Laboratory tests to study the influence of rock stress confinement on the performances of TBM discs in tunnels

To clarify some aspects of rock destruction with a disc acting on a high confined tunnel face, a series of tests were carried out to examine fracture mechanisms under an indenter that simulates the tunnel boring machine (TBM) tool action, in the presence of an adjacent groove, when a state of stress (lateral confinement) is imposed on a rock sample. These tests proved the importance of carefully establishing the optimal distance of grooves produced by discs acting on a confined surface, and the value (as a mere order of magnitude) of the increase of the thrust to produce the initiation of chip formation, as long as the confinement pressure becomes greater. © University of Science and Technology Beijing and Springer-Verlag Berlin Heidelberg 2011.

Numerical modelling of laboratory tests for TBM cutter indentation process analysis

Considering that TBMs are nowadays used for long Trans-Alpine tunnels, the
understanding of rock breaking and chipping due to TBM cutter disks mechanism, for deep tunnelling operations, becomes very interesting. In this paper, the results from carried out laboratory tests that simulate the disk cutter action at the rock tunnel face by means of an indentation tool, acting on a rock
specimen with proper size, and the related three-dimensional and two-dimensional numerical modelling are proposed. The developed numerical models simulate the different test conditions (applied load, boundary conditions) allowing the analysis of the stresses distributions along possible breaking planes.
The influence of a confinement-free area on one side of the specimen, simulating the formation of a groove near the tool, is pointed out.
The obtained results from numerical modelling put in evidence a satisfactory agreement with the experimental observations.

BROAD-BAND EXCITATION AND EMISSION OF SURFACE-PLASMONS

The well known advantages of using surface plasmons, in particular the high sensitivity to surface adsorbates, are nearly always compromised in practice by the use of monochromatic excitation and the consequent lack of proper spectroscopic information. This limitation arises from the angle/wavelength selective nature of the surface plasmon resonance. The work described here uses an elegant broadband excitation/decay scheme in a substrate(silica)-grating profiled photoresist-Ag film geometry. Laser radiation of wavelength 488 nm, incident through the silica substrate, excites by near-field coupling a broad band of surface plasmons at the photoresist-Ag interface within the spectral range of the photoresist fluorescence. With a judicious choice of grating period this mode can cross-couple to the mode supported at the Ag-air interface. This latter mode can, in turn, couple out to light by virtue of the same grating profile. The spectral distribution of the light emitted due to this three-step process has been studied as a function of the angle of emission and depth of the grating profiled surface for each polarization. It is found that the optimum emission efficiency occurs with a groove depth in the region of 65 nm. This is considerably greater than the optimum depth of 40 nm required for surface plasmon-photon coupling at a Ag-air interface or, in other words, for the last step of the process in isolation.