Submillimeter wave frequency selective surface with polarisation independent spectral responses

This paper reports the design, construction and electromagnetic performance of a new freestanding frequency selective surface (FSS) structure which generates coincident spectral responses for dual polarisation excitation at oblique angles of incidence. The FSS is required to allow transmission of 316.5 - 325.5 GHz radiation with a loss = 0.6 dB and to achieve = 30 dB rejection from 349.5 - 358.5 GHz. It should also exhibit crosspolarisation levels below -25 dB, all criteria being satisfied simultaneously for TE and TM polarisations at 45° incidence. The filter consists of two identical, 30 mm diameter, 12.5 ?m thick, optically flat, perforated metal screens separated by 450 ?m. Each of the ˜5000 unit cells contains two nested, short circuited, rectangular loop slots and a rectangular dipole slot. The nested elements provide a passband spectral response centred at 320 GHz in the TE and TM planes; the dipole slot increases the filter roll-off above resonance. The FSS was fabricated from silicon-on-insulator wafers using precision micromachining and plating processes including the use of Deep Reactive Ion Etching (DRIE) to pattern the individual slots and remove the substrate under the periodic arrays. Quasi–optical transmission measurements in the 250 – 360 GHz range yielded virtually identical copolarised spectral responses, with the performance meeting or exceeding the above specifications. Experimental results are in excellent agreement with numerical predictions.

Thermal study of selectively plated nickel sulfamate coatings

Nickel sulfamate solution was applied to mild steel substrates by the process of selective plating. The coated samples were heated to temperatures in the range of 50–1000 °C. Thermal analysis, X-ray diffraction and microscopy techniques were used to investigate the effect of secondary heating on the microstructure, mechanical properties and the composition of the surface coatings.

The microscopy analysis showed that the secondary heating caused diffusion within the coating itself and diffusion between the coating and the substrate as concentrations of iron increased in the coating and nickel appeared in the substrate. This diffusion redistribution also caused a phase transformation in the coating as NiO formed on the surface when the coating was heated in a furnace fitted with a nitrogen flow. However this transformation was found not to occur when the coating was heated in a sealed helium environment. Layer and grain growth occurred as temperature increased with the grains taking their preferred orientation as they were heated.

The surface hardness was found to initially rise up from 565 HV to 600 HV when heated to 200 °C. After 200 °C the surface hardness decreased in two stages before falling to 110 HV by 1000 °C. During tensile testing the coated samples performed marginally better in tension than the uncoated samples, however the temperatures used were not elevated high enough to show any real degradation during the tensile testing of the nickel coating that was shown during hardness testing and the microscopy analysis

Abrasive wear resistance of electroless Ni-P coated aluminium after post treatment

Electroless nickel (EN) coatings are recognised for their hardness and wear resistance in automotive and aerospace industries. In this work, electroless Ni–P coatings were deposited on aluminium alloy substrate LM24 (Al–9 wt.% Si alloy) and the effect of post treatment on the wear resistance was studied. The post treatments included heat treatment and lapping with two different surface textures. Scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD) and micro-abrasion tester were used to analyse morphology, structure and abrasive wear resistance of the coatings. Post heat treatment significantly improved the coating density and structure, giving rise to enhanced hardness and wear resistance. Microhardness of electroless Ni–P coatings with thickness of about 15 μm increased due to the formation of Ni3P after heat treatment.

SEM-EDX of morphology of electroless nickel coatings with tin and tungsten

Electroless plating of binary Ni-P, ternary Ni-Sn-P and Ni-W-P, and quaternary Ni-W-Sn-P alloy coatings was carried out in alkalicitrate baths. After the plating, several kinds of test were carried out to determine the improvement in the characteristics and properties due to the additional elements as well as to study the change in behaviour when heat treatment was applied to these coatings. The coatings were subjected to X-ray diffraction analysis where it was found that all the coatings were amorphous. Interesting surface morphology features were examined using scanning electron microscopy. Addition of a third element improved the hardness.

Genomic instability in Chinese hamster cells after exposure to X rays or alpha particles of different mean linear energy transfer

Evidence has accumulated that radiation induces a transmissible persistent destabilization of the genome, which mag. result in effects arising in the progeny of irradiated but surviving cells. An enhanced death rate among the progeny of cells surviving irradiation persists for many generations in the form of a reduced plating efficiency. Such delayed reproductive death is correlated with an increased occurrence of micronuclei. Since it has been suggested that radiation-induced chromosomal instability might depend on the radiation quality, we investigated the effects of alpha particles of different LET by looking at the frequency of delayed micronuclei in Chinese hamster V79 cells after cytochalasin-induced block of cell division, A dose-dependent increase in the frequency of micronuclei was found in cells assayed 1 week postirradiation or later. Also, there was a persistent increase in the frequency of dicentrics in surviving irradiated cells, Moreover, we found an increased micronucleus frequency in all of the 30 clones isolated from individual cells which had been irradiated with doses equivalent to either one, two or three alpha-particle traversals per cell nucleus, We conclude that the target for genomic instability in Chinese hamster cells must be larger than the cell nucleus. (C) 1997 by Radiation Research Society

Bead array for Listeria monocytogenes detection using specific monoclonal antibodies

To develop a detection method for human pathogenic Listeria monocytogenes, novel specific antibodies were obtained from hybridoma libraries generated by using formalin-killed and heat-killed L. monocytogenes as immunogens. Several monoclonal antibodies found to be specific to Listeria spp or L. monocytogenes were evaluated for their applicability as binders for bead array and sandwichELISA for detection of L. monocytogenes in buffer and in 11 different food types. The bead array format consistently demonstrated lower detection limits and was less affected by interference from food matrices than the sandwich ELISA format. However, the obtained detection limits were not sufficient to satisfy the required standard for L. monocytogenes testing. Therefore, the international organizationfor standardization (ISO 11290-1:1996) methods for pre-enrichment and enrichment were employed to increase the bacteria numbers. When compared to the standard plating method, the bead array was able to detect the bacteria with the same accuracy even at the 1 CFU level after only 24 hours of the enrichment period. In addition, Listeria-specific 3C3 and L. monocytogenes-specific 7G4 antibodies were successfully employed to construct a multiplex detection for Listeria, Salmonella and Campylobacter in a bead array format by combining with commercial Salmonella-specific and available Campylobacter-specific antibodies.

A Novel Investigation of a Blister-Like Syndrome in Aquarium Echinopora lamellosa

This study investigates potential causes of a novel blister-like syndrome in the plating coral Echinopora lamellosa. Visual inspections of this novel coral syndrome showed no obvious signs of macroparasites and the blisters themselves manifested as fluid-filled sacs on the surface of the coral, which rose from the coenosarc between the coral polyps. Histological analysis of the blisters showed that there was no associated necrosis with the epidermal or gastrodermal tissues. The only difference between blistered areas and apparently healthy tissues was the presence of proliferated growth (possible mucosal cell hyperplasia) directly at the blister interface (area between where the edge of the blister joined apparently healthy tissue). No bacterial aggregates were identified in any histological samples, nor any sign of tissue necrosis identified. We conclude, that the blister formations are not apparently caused by a specific microbial infection, but instead may be the result of irritation following growth anomalies of the epidermis. However, future work should be conducted to search for other potential casual agents, including viruses. © 2014 Smith et al.

THE CULTURE MICROBIOME IN THE LUNGS OF PATIENTS WITH COPD

Introduction and Aims: Previous studies have shown that the lungs of Cystic Fibrosis (CF) and bronchiectasis (BE, not caused by CF) patients are colonised by a range of aerobic and anaerobic bacteria. As bacteria are also implicated in the pathogenesis and progression of chronic obstructive pulmonary disease (COPD), this study aimed to determine the culture microbiome of the COPD airways.

Methods: Samples were collected from 13 stable COPD patients during routine bronchoscopy. Bronchial washings were taken at a single location in the right middle lobe by flushing and removing 30 ml of sterile saline. Samples were cultured under strict anaerobic conditions with bacteria detected by plating on both selective and non-selective agar media and quantified by total viable count (TVC). Identification of the cultured bacteria was performed by amplification and subsequent sequencing of the 16sRNA gene.

Results: Mean FEV1 was 1.36 (range 0.84–2.26, mean per cent predicted FEV1, 54%), and the mean ratio (FEV1/FVC) was 51%. Bacteria were detected in 12/13 samples (92%) with bacteria from the genera Streptococcus [12/13 samples, 92%; mean (range) TVC 9.62×105 cfu/ml (1.50×103–1.42×107)] and Haemophilus [4/13 samples, 31%; mean (range) 6.40×104 cfu/ml (2.20×103–1.60×105)] most frequently detected. Anaerobic bacteria primarily from the genera Prevotella [8/13 samples, 62%; mean (range) TVC 1.12×104 cfu/ml (1.30×103–4.20×104)] and Veillonella [5/13 samples, 38%; mean (range) TVC 1.29×105 cfu/ml (4.20×103–3.60×105)] were also detected. Pseudomonas and Moraxella were not detected in any samples.

Conclusions: Our results show that bacteria from the genera Streptococcus, Haemophilus, Prevotella and Veillonella are frequently present the airways of patients suffering from COPD. Taking account of the dilutional effect of the bronchial wash procedure and extrapolating to allow comparison with sputum data in our laboratory for CF and BE, the relative load of bacteria from the genera Streptococcus, Prevotella and Veillonella is similar in these three airway diseases. The potential role of these bacteria in the progression and pathogenesis of COPD requires further investigation.