Use Of Isolation Research Articles

CMOS Programmable Gain Distributed Amplifier With 0.5-dB Gain Steps

A new CMOS programmable gain distributed amplifier with 0.5-dB gain steps is fabricated in a 130-nm process. The circuit is designed to demonstrate broadband (>1 decade) programmable gains with excellent matching and high isolation for use in RF integrated-circuit testing. The measured slope of <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</sub> loss is approximately 3 dB/decade over frequencies from 0.8 to 9 GHz where input and output return losses are better than roughly 10 dB; the measured input 1-dB compression point and third-order intermodulation intercept point at 2.78 GHz for the maximum 2.5-dB gain is 1 and 12.5 dBm, respectively. The measured noise figure is below 9.5 dB at 9 GHz. The circuit consumes approximately 40 mW total from 3.1-V analog and 1.5-V digital supplies.

Biocontrol potential of native Trichoderma isolates against root-knot nematodes in West African vegetable production systems

Seventeen isolates of the free-living soil fungus Trichoderma spp., collected from Meloidogyne spp. infested vegetable fields and infected roots in Benin, were screened for their rhizosphere competence and antagonistic potential against root-knot nematodes, Meloidogyne incognita , in greenhouse pot experiments on tomato. The five isolates expressing greatest reproductive ability and nematode suppression in pots were further assessed in a typical double-cropping system of tomato and carrot in the field in Benin. All seventeen isolates were re-isolated from both soil and roots at eight weeks after application, with no apparent crop growth penalty. In pots, a number of isolates provided significant nematode control compared with untreated controls. Field assessment demonstrated significant inhibition of nematode reproduction, suppression of root galling and an increase of tomato yield compared with the non-fungal control treatments. Trichoderma asperellum T-16 suppressed second stage juvenile (J 2 ) densities in roots by up to 80%; Trichoderma brevicompactum T-3 suppressed egg production by as much as 86%. Tomato yields were improved by over 30% following the application of these biocontrol agents, especially T. asperellum T-16. Although no significant effects were observed on carrot galling and yield, soil J 2 densities were suppressed in treated plots, by as much as 94% ( T. asperellum T-12), compared with the non-fungal controls. This study provides the first information on the potential of West-African Trichoderma spp. isolates for use against root-knot nematodes in vegetable production systems. The results are highly encouraging, demonstrating their strong potential as an alternative and complementary crop protection component. ► West African Trichoderma spp. isolates significantly suppressed root-knot nematodes. ► Trichoderma spp. isolates persisted in soil for at least eight weeks after application. ► Tomato yield was improved by 30% following Trichoderma application in field. ► Soil nematode densities were suppressed by up to 94% in follow-on carrot crops. ► The most effective Trichoderma spp. isolates were sourced from nematode egg masses.

Principles of scaling and similarity for testing of lead–rubber bearings

AbstractLead–rubber bearings are seismic isolators that have been extensively used to protect buildings, bridges and mission‐critical infrastructure from the damaging effects of earthquake shaking. Testing of isolators, including lead–rubber bearings, is conducted either for research purposes (for example, shake table testing) or for determination of their properties before their use in applications (prototype and quality‐control testing). Testing is of significance as it (a) provides the data needed to validate complex models for analysis, and (b) results in basic mechanical properties of the tested isolators for use in analysis and design. Often testing has to be performed on reduced‐size bearings and/or at conditions of reduced speed of motion due, primarily, to unavailability of testing equipment capable of testing full‐size specimens at realistic dynamic conditions. When testing at reduced size, the conditions of testing need to be adjusted on the basis of scientific analysis so that the test results represent the behavior of the full‐size prototype bearing. This paper examines the issue of testing of lead–rubber bearings at reduced scale and presents the necessary conditions for testing in order to correctly reproduce the critical effects of lead core heating on the characteristic strength of the bearing. Experimental results on large‐size and reduced‐size bearings are used to demonstrate the concepts. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Antigenic Categorization of Contemporary H3N2 Swine Influenza Virus Isolates Using a High-Throughput Serum Neutralization Assay

In vivo, neutralizing antibodies are critical for viral clearance. A high-throughput serum neutralization (HTSN) assay was developed to antigenically categorize Swine influenza virus (SIV) isolates. Uncategorized viruses were tested using a panel of antisera representing the H3N2 SIV subtypes and the results expressed as a serum neutralization ratio. Antisera were generated against contemporary isolates representing circulating H3N2 SIV subtypes (clusters I, III, IV). Reference viruses and the corresponding antisera were evaluated using traditional hemagglutination inhibition (HI) and the HTSN assays and good correlation (r = 0.84) was observed between the 2 tests. Categorical clustering of 40 recent (2008-2009) SIV isolates was assessed using the HTSN assay. The H3N2 SIV isolates with amino acid similarity >97% to the commonly used H3N2 cluster IV reference strain A/Swine/Ontario/33853/2005 (ON05) showed strong reactivity with cluster IV antisera. Isolates with <97% amino acid similarity to ON05 sporadically or completely failed to react with any antiserum. A cluster of 3 isolates with weak reaction with cluster III antiserum may be a potential emerging cluster of H3N2 with moderate genetic similarity to cluster II H3N2 (93% similarity). Potential uses of the HTSN assay include identification of broadly cross-reactive or antigenically distinct SIV isolates for use in vaccine virus selection or as part of surveillance efforts monitoring antigenic drift.

Isolation of a novel strain of Bacillus pumilus from penaeid shrimp that is inhibitory against marine pathogens.

A bacterium was isolated from the mid-gut of healthy black tiger shrimp, Penaeus monodon, based on a large zone of inhibition in mixed culture on solid medium. The isolate was a Gram-positive, motile spore former, with an optimum pH range for growth in tryptone soya broth containing 2% NaCl of between pH 6 and 9. The bacterium was highly salt tolerant with concentrations between 0% and 8% having no detrimental effect on growth. The isolate was identified as Bacillus pumilus based on physiological capabilities using the API50CHB and Biolog systems. Amplification and sequencing of the 16S rRNA gene followed by phylogenetic analysis confirmed its identity. The Bacillus pumilus isolate was strongly inhibitory against the marine bacterial pathogens Vibrio alginolyticus, V. mimicus and V. harveyi, and weakly inhibitory against V. parahaemolyticus in cross-streaking assays on solid medium. The organism was marginally self-inhibitory, and inhibited B. licheniformis and B. subtilis. The suitability of the B. pumilus isolate for use as a probiotic in farmed shrimp was further supported by the absence of any of the known B. cereus enterotoxin genes. Based on these in vitro results, in vivo safety and efficacy trials are underway to determine suitability of the novel strain as a commercial probiotic.

Compact vibration isolation and suspension for Australian International Gravitational Observatory: Performance in a 72 m Fabry Perot cavity

This paper describes the first demonstration of vibration isolation and suspension systems, which have been developed with view to application in the proposed Australian International Gravitational Observatory. In order to achieve optimal performance at low frequencies new components and techniques have been combined to create a compact advanced vibration isolator structure. The design includes two stages of horizontal preisolation and one stage of vertical preisolation with resonant frequencies approximately 100 mHz. The nested structure facilitates a compact design and enables horizontal preisolation stages to be configured to create a superspring configuration, where active feedback can enable performance close to the limit set by seismic tilt coupling. The preisolation stages are combined with multistage three-dimensional (3D) pendulums. Two isolators suspending mirror test masses have been developed to form a 72 m optical cavity with finesse approximately 700 in order to test their performance. The suitability of the isolators for use in suspended optical cavities is demonstrated through their ease of locking, long term stability, and low residual motion. An accompanying paper presents the local control system and shows how simple upgrades can substantially improve residual motion performance.

Isolator mount for shock and vibration

An isolator mount for the active dissipation of shocks and vibrations is presented. The invention includes at least one energy dissipating element disposed between deflectable elements so as to provide soft damping for small disturbance excitations, yet remaining sufficiently stiff to mitigate large shocks. The mount transfers mechanical energy to the dissipating element via the device structure. Dissipating element mitigates the energy in shocks and vibrations as either heat or magnetic energy. A snap-together modular embodiment enables the coupling of two or more isolators for use within a wide variety of shock and vibration applications. Quasi-static tuning of one or more mounts comprising a snap-together module facilitates an active response to changing conditions.

Storage rack vibration isolators and related storage rack systems

A storage rack system to be installed on a floor has a plurality of columns, is more flexible in a down aisle dimension than it is in a cross aisle dimension, and has at least a first column and a second column adjacent one another in the cross aisle dimension. A storage rack vibration isolator for use with this storage rack system comprises at least one seismic vibration absorption and dissipation structure constructed to be located primarily between the first and second columns to reduce the storage rack system's natural frequency in at least the cross aisle dimension. The seismic vibration absorption and dissipation structure includes a first member connectable 'to the storage rack system and a second member connectable to the floor. At least one column support assembly is mountable to at least the first and second columns to enable them to move with respect to the floor. A structure limits the movement of the first and second columns to substantially the cross aisle dimension.

Effects of temperature and water activity on Lecanicillium spp. conidia germination and growth, and mycosis of Pissodes strobi

Selecting entomopathogenic fungal isolates for use as biocontrol agents requires an assessment of their growth and virulence characteristics as affected by environmental conditions. Here we demonstrate a wide temperature and moisture range for colony growth, effective conidial germination and virulence against Pissodes strobi Peck (white pine weevil) of several isolates of Lecanicillium Gams and Zare, an entomopathogenic fungus distributed worldwide and indigenous to forests on Vancouver Island, British Columbia, Canada. In order to examine the potential Lecanicillium as a biological control agent, the pathogenicity of isolates collected from different geographical locations on P. strobi cadavers was assessed, and colony growth at different temperatures was evaluated. Colony growth was evident between 5 and 30°C, with optimal growth occurring at 25°C. Various combinations of water activity (0.55, 0.76, 0.85 and 0.99 a w) and temperature (10, 15, 20, and 25°C) were also used to evaluate environmental impacts on conidial germination and cumulative mycosis of adult P. strobi. Certain Lecanicillium isolates displayed xerophilic (0.85 a w) or psychrophilic (10°C) growth optima. Ultimately, identifying the abiotic limits of this entomopathogenic fungus will be used to determine which isolates have potential for future in situ biocontrol trials.

Study of polymorphic variable-number of tandem repeats loci in the ECOR collection and in a set of pathogenic Escherichia coli and Shigella isolates for use in a genotyping assay

The Escherichia coli ( E. coli) reference collection, ECOR, consists of 72 strains that are representative of the genotypic diversity, as indexed by multilocus enzyme electrophoresis (MLEE), in the species as a whole. MLEE revealed 4 main phylogenetic groups designated A, B1, B2 and D. We present a study of the relationship between the ECOR strains as determined by polymorphisms in seven variable-number of tandem repeats (VNTR) loci. Seven tandem repeats that were present in more than one of the fully sequenced E. coli strains were selected, and primers were constructed in order to amplify the targets in all species where the loci were present. The combined result for all VNTR loci was adapted as a multiple-locus variable-number tandem repeats analysis (MLVA) and showed that the ECOR collection was divided into 63 distinct genotypes. The ECOR phylogenetic groups defined by MLEE were not well conserved by MLVA. A set of 61 pathogenic isolates of both E. coli and Shigella spp. was then tested with the same set of VNTR loci, and revealed 54 distinct genotypes. In addition, the MLVA method was used to genotype isolates from patients and suspected sources in a recent outbreak of E. coli O103 in Norway. The pathogenic E. coli isolates contained the diarrhea causing categories EIEC, EAEC, STEC, ETEC and EPEC. Shigella isolates were of species S. flexneri, S. boydii, S. sonnei and S. dysenteriae. The MLVA method rapidly genotyped all isolates in the study at a Simpson's index of diversity of D = 0.98.

Genetic Diversity and Carriage Dynamics ofNeisseria lactamicain Infants

Neisseria lactamica, a harmless human commensal found predominantly in the upper respiratory tracts of infants, is closely related to Neisseria meningitidis, a pathogen of global significance. Colonization with N. lactamica may be responsible for the increase in immunity to meningococcal disease that occurs during childhood, when rates of meningococcal carriage are low. This observation has led to the suggestion that N. lactamica whole cells or components are potential constituents of novel meningococcal vaccines. However, the dynamics of carriage and population diversity of N. lactamica in children are poorly understood, presenting difficulties for the choice of representative isolates for use in vaccine development. This problem was addressed by the multilocus sequence typing of N. lactamica isolates from two longitudinal studies of bacterial carriage in infants. The studies comprised 100 and 216 subjects, with N. lactamica carriage monitored from age 4 weeks until age 96 weeks and from age 2 weeks until age 24 weeks, respectively. The maximum observed carriage rate was 44% at 56 weeks of age, with isolates obtained on multiple visits for the majority (54 of 75, 72%) of carriers. The N. lactamica isolates were genetically diverse, with 69 distinct genotypes recovered from the 75 infants. Carriage was generally long-lived, with an average rate of loss of under 1% per week during the 28 weeks following acquisition. Only 11 of the 75 infants carried more than one genotypically unique isolate during the course of the study. Some participants shared identical isolates with siblings, but none shared identical isolates with their parents. These findings have implications for the design of vaccines based on this organism.

Effect of high temperature and water stress on in vitro germination and growth in isolates of the entomopathogenic fungus Beauveria bassiana (Bals.) Vuillemin

In non-irrigated agricultural fields in tropical zones, high temperature and water stress prevail during the main cropping season. Natural epizootics of Beauveria bassiana on lepidopteran pests occur during winter. Application of B. bassiana during hot months when pest populations are at their climax may prove an effective management strategy. Therefore, 29 isolates of B. bassiana were tested for their ability to germinate and grow in temperature and water availability conditions prevailing during the pest season in these fields. The effect of temperature cycles with 8 h duration of high temperature fluctuating with 16 h duration of lower temperature (similar to field conditions); low water availability; and a combination of these two stress conditions was studied. Germination and growth assays were done at fluctuating temperature cycles of 32, 35, 38, and 42 ± 1 °C (8 h)/25 ± 1 °C (16 h) and in media with water stress created by 10, 20, 30, and 40% polyethylene glycol (PEG 6000). Assays set at a continuous temperature of 25 ± 1 °C with no PEG in the medium served as controls. Stress was assessed as percentage germination or as growth relative to control. Isolates showing 90% growth relative to the control at temperature cycles including high temperatures of 35 and 38 ± 1 °C were identified. One isolate (ARSEF 2860) had a thermal threshold above 43 °C. At 25 °C, all but one isolate of B. bassiana showed >90% growth relative to the control in 10% PEG (−0.45 MPa). Some isolates were found with >90% growth relative to control in medium having 30% PEG with water availability (1.33 MPa), nearly equivalent to that in soils which induce permanent wilting point of plants. When isolates that showed >90% growth relative to the control at both stress conditions, were stressed simultaneously, a decrease in growth was observed. Growth was reduced by ∼20% at 35 ± 1 °C (8 h)/25 ± 1 °C (16 h) and 10% PEG and was affected to a greater degree in combinations of harsher stress conditions. The isolate ARSEF 2860 with a thermal threshold of >43 °C showed ∼80% relative growth at a combined stress of 38 ± 1 °C (8 h)/25 ± 1 °C (16 h) and 10% PEG. These findings will aid the selection of isolates for use in field trials in hot or dry agricultural climates.

Effects of antibiotic-producing Streptomyces on nodulation and leaf spot in alfalfa

The ability of antibiotic-producing streptomycetes to colonize alfalfa ( Medicago sativa L.) plants and influence the activities of a fungal plant pathogen ( Phoma medicaginis var. medicaginis) and a mutualistic symbiont ( Sinorhizobium meliloti) was investigated. Streptomyces strains were introduced around seeds at the time of planting. Hyphal filaments and spore chains were observed by scanning electron microscopy on roots of alfalfa seedlings receiving the streptomycete amendment. Streptomyces strain densities on leaves decreased 10–100-fold over an 8-week period, while densities on roots remained constant over time. The Streptomyces strains also colonized alfalfa root nodules. We then tested the ability of 15 antibiotic-producing strains of Streptomyces to inhibit in vitro growth of Phoma medicaginis var. medicaginis Malbr. & Roum., the causal agent of spring blackstem and leaf spot of alfalfa. The majority of the Streptomyces strains inhibited growth of three diverse strains of P. medicaginis. In a detached leaf assay, one Streptomyces strain decreased leaf spot symptoms caused by P. medicaginis when inoculated onto leaves 24 h before the pathogen. Two Streptomyces strains decreased defoliation caused by P. medicaginis when the streptomycetes were introduced around seeds at the time of planting. We also examined inhibitory activity of Streptomyces strains against 11 strains of S. meliloti. Eight of the 15 Streptomyces strains inhibited in vitro growth of five or more of the S. meliloti strains, while four Streptomyces strains had no effect on growth of any test strains. In a growth chamber assay, two of six Streptomyces strains, when inoculated into the planting mix, significantly reduced plant dry weight compared to the treatment with S. meliloti alone, but did not significantly reduce the number of nodules. These results suggest that careful selection of Streptomyces isolates for use in biological control of plant diseases will limit the potential negative impacts on rhizobia.

Influence of Material Stiffening on Stability of Elastomeric Bearings at Large Displacements

Experiments conducted to determine the mechanical characteristics of low shape factor bearings demonstrated that low shape factor elastomeric bearings that were bolted to their endplates—as opposed to bearings with doweled-type endplate connections—showed an increase in horizontal stiffness at large shear strains. This strain-induced crystallization at large shear strains offers a good reserve of shear resistance for bearings subjected to large deformation, thereby providing a high safety factor against failure under earthquake loads that exceed the design level. Modeling this property would be invaluable for structural engineers designing isolators for use in highly seismic areas. This paper presents an analytical method that adequately models the strain-induced crystallization of the elastomer at large shear strains. This model extends the linear elastic relationship developed in earlier studies to predict the buckling load of an elastomeric bearing in the case of material nonlinearity. Here, the nonlinear elastic response of the rubber is taken into account by replacing the shear modulus, G, by a shear modulus-shear strain relationship and calculating the shear strain from a root mean square average of the shear strains of the elastomeric bearing that is due to compression, bending, and shearing.

Effects of temperature on growth of Metarhizium flavoviride and virulence to the variegated grasshopper, Zonocerus variegatus

The temperature optima for germination, radial hyphal extension rate and sporulation were determined for two isolates of Metarhizium flavoviride from acridoid hosts. I91–609 exhibited lower temperature optima for hyphal extension (25.5°C) and sporulation (24°) than IMI 330189 (27° and 25°, respectively), although temperature optima for germination were similar ( ca 30°). The temperature optimum for sporulation was lower than that for hyphal extension. Further studies were carried out on I91–609 to investigate the effect of temperature and dose on the infection mortality rate of the grasshopper pest, Zonocerus variegatus . Increasing dose resulted in a decrease in mean survival time regardless of incubation temperature. Dose and temperature were shown to interact, with the effects of dose increasing at temperatures either side of the optimum. Furthermore, for each dose, the optimum temperature for infection was estimated to be ca 5° higher than the optimum for growth, and no significant relationship was identified between hyphal extension rate in vitro and host survival time. The implications of these results are discussed with regard to the selection of isolates for use in biological control.

Rapid identification of measles virus strains by the heteroduplex mobility assay

The continued endemic presence of measles virus (MV), and the large number of isolates which are made in South Africa each year, demanded the use of a rapid and reliable pre-screening technique to select isolates for molecular epidemiological studies by sequence analysis. The heteroduplex mobility assay (HMA) was used to genetically characterize 47 MV isolates collected from three different provinces in South Africa, made between 1986 and 1995. The carboxyl-terminal 590 nt of the nucleocapsid (N) gene—the most variable region of the genome—was amplified by polymerase chain reaction (PCR) and subsequently subjected to HMA analysis for initial genotyping. The results showed three different patterns of heteroduplex formation by gel electrophoresis, representing two distinct wild-type lineages and one group of vaccine-like viruses. Comparison of HMA results with phylogenetic analysis of sequence data for several of the South African MV strains showed a complete correlation of results. The HMA proved to be a useful tool for screening MV isolates for use in molecular epidemiological studies.

Production of alkaline protease by a new Bacillus subtilis isolate for use as a bating enzyme in leather treatment

Bacillus subtilis, isolated from tannery waste, produced an alkaline protease at optimal activity when grown in a casein/gelatine medium in a stirred tank fermenter at 37°C with the dissolved oxygen tension at 40% air saturation. Optimum protease activity (223 U ml(-1)) was at pH 8.5 and was stable for 1 h up to 45°C but at 60°C lost 80% activity. Use of the crude protease as a bating agent for producing high quality leather is indicated. Tensile strength, bursting strength, tear strength and elongation at break of prepared leather were increased with increasing amounts of protease used for bating.

Permanent magnet film magneto-optic waveguide isolator

Recent advances in high-coercivity planar-magnetization film magnets and Bi-YIG (bismuth-substituted yttrium iron garnet) film technology have opened up the possibility of fabricating very small magneto-optic devices. In this article we demonstrate that these two technologies can be brought together to fabricate a high performance waveguide magneto-optic isolator for use in integrated optical circuits. The device operates at 1.55-μm wavelength and consists of a waveguide etched into a Bi-YIG film whose magnetization is saturated by a 22-μm-thick TbCu7-type SmCo magnet with a coercivity of 4 kOe. Isolation ratios of 25 dB have been obtained in the wavelength region between 1490 and 1555 nm.

Thin-film-magnet magnetooptic waveguide isolator

Recent advances in thin-film-magnet and Bi-YIG film technologies have opened up the possibility of fabricating very compact magnetooptic structures. It is demonstrated for the first time that these new technologies can be brought together to make a thin-film-magnet magnetooptic isolator for use in optical packaging and integrated optical circuits. The device operates at a 1.55- mu m wavelength and uses a waveguide etched into a Bi-YIG film whose linear birefringence has been tuned to near zero at this wavelength. The Bi-YIG's magnetization is saturated by a thin ferromagnetic film. Isolation ratios of -21 dB have been obtained. >

Membrane-associated proteins from nematodes: Haemonchus contortus H11OD protein doublet isolation for use in vaccine

Membrane-associated proteins from nematodes: Haemonchus contortus H11OD protein doublet isolation for use in vaccine