Nylon Mesh Screen Research Articles

Periodic Flow Purging System for Harvesting Fibers from Screens

ABSTRACT Fiber length is believed to be an important factor in determining various toxicological responses to asbestos and other bio-persistent fibers. Length classification of fibers thus is crucial for toxicological assessment. Nylon mesh screens have been shown to be effective in separating fibers by length. In this note, we report development of a purging flow system for harvesting fibers from a nylon net screen, with the aim of separating airborne fibers by length. We evaluated the performance of this purging flow system by examining the lengths of glass fibers collected on a screen. Fibers aerosolized by vortex shaking were provided to 10 µm and 20 µm mesh screens, and the fibers collected on each screen were purged periodically with a backflow. The length of the purged fibers was measured and compared to that of fibers washed from the screen. The mean length of fibers on the screen is larger than that of the fibers in the original test aerosol. The mean length of the backflow purged fibers is smaller than that of the fibers from the washed screen. The results indicate that the purging flow system with screens can harvest the longer fibers from the original aerosol.

Harvesting microalgal-bacterial biomass from biogas upgrading process and evaluating the impact of flocculants on their growth during repeated recycling of the spent medium

Microalgal-bacterial consortium can be used to upgrade biogas by removing CO2 and H2S. Photosynthetic biogas upgrading requires harvesting microalgal-bacterial biomass in order to use the biomass-free cultivation medium as scrubbing liquid in the absorption column. In this study, the efficiency of different flocculants (Zetag 8125, cationically modified cellulose nanocrystals, Tanfloc, chitosan, and FeCl3) to harvest microalgal-bacterial biomass used for biogas upgrading in alkaline medium (inorganic carbon concentration up to 1800 mg L−1 and a pH ~10) was evaluated. Zetag and cationic cellulose nanocrystals resulted in maximum flocculation efficiencies of 95% (optimal dose 30 mg g−1) and 93% (optimal dose 20 mg g−1), respectively. Low flocculation was observed with other flocculants at doses as high as 200 mg g−1, which can be ascribed to the high pH of the alkaline medium. Zetag and cationic cellulose nanocrystals were selected for harvesting the biomass during semi-continuous cultivation of the microalgal consortium. Both Zetag and cationic cellulose nanocrystals were effective in flocculating the biomass with efficiencies of over 90% during five successive harvesting cycles. Gravity settling of the flocs formed by Zetag and cationic cellulose nanocrystals resulted in low biomass concentration factors of 7.7 and 2.0, respectively. Screening of flocs using a nylon mesh screen (pore size of 180 μm) resulted in a biomass concentration factor as high as 19.8. Zetag and cationic cellulose nanocrystals could be useful in harvesting biomass under high alkaline conditions without detrimental effects on biomass growth.

Collection efficiency of airborne fibers on nylon mesh screens with different pore sizes and configurations

AbstractAerodynamic behavior of airborne fibers including high-aspect ratio particles plays an important role in aerosol filtration and lung deposition. Fiber length is considered to be an importan...

Intercropping with sweet corn (Zea mays L. var. rugosa Bonaf.) expands P acquisition channels of chili pepper (Capsicum annuum L.) via arbuscular mycorrhizal hyphal networks

Intercropping of chili pepper (Capsicum annuum L.) with corn (Zea mays L.) is one of the main valuable intercropping patterns. However, the potential contribution of arbuscular mycorrhizal (AM) fungal hyphal networks is still poorly understood. The purpose of this work was to resolve the changes of AM fungal propagation and colonization in the pepper/corn intercropping systems due to the constitution of hyphal networks and the networks’ effects on plant nutrient uptake and interspecific competitive relations. An 18-week pot experiment on an unsterilized soil was carried out to test mycorrhizal performance and P acquisition of chili pepper and sweet corn (Zea mays L. var. rugosa Bonaf.) in two compartments, which were absolutely separated (Sep) by polyvinyl chloride (PVC) layer or semi-separated (Semi-Sep) by nylon mesh (30 μm) screen that only allows the passage of AM fungal hyphae but not plant roots. Root mycorrhizal colonization rates and the biomasses and P concentrations of shoots, roots, and fruits of pepper and corn were all measured. The total P acquisition of each crop per pot and the acquisition ratio of one to two crops were assessed. Soil pH, organic C, total P, available P, AM fungal abundance, and acid phosphatase activity were also tested. In the Sep system, root mycorrhizal colonization, P acquisition amount, shoot biomass, and rhizosphere AM fungal abundance of corn were all higher (P < 0.05) than those of pepper, but soil available P concentration was lower (P < 0.05) in corn compartment than in pepper one. Compared with Sep, Semi-Sep had higher (P < 0.05) mycorrhizal colonization rates with both intercrops and higher (P < 0.05) soil acid phosphatase activity and AM fungal abundance in corn and pepper compartments, respectively. Semi-Sep decreased (P < 0.05) soil available P concentrations with both compartments, but did not narrow the difference of soil available P concentration between compartments, suggesting there was no gradient diffusion of soil available P between compartments. Semi-Sep increased (P < 0.05) the P acquisition ratio and fruit yield of pepper, but not corn. Constitution of hyphal networks increased mycorrhizal colonization with both intercrops, and corn supplied part of photosynthetic C for increasing AM fungal propagules in pepper compartment by gradient expansion since AM fungi formed better symbioses with corn. Hyphal networks increased pepper fruit yield via improving P distribution to pepper, but acquired relatively higher P from corn compartment via elevating the soil acid phosphatase activity, suggesting enhanced P competitive ability of pepper against corn upon hyphal networks.

Embryonic, Larval, and Early Postlarval Development of the Tropical Black-Lip Rock Oyster Saccostrea echinata

The black-lip rock oyster, Saccostrea echinata, has considerable potential for aquaculture in tropical Australia and the Indo-Pacific region because of its large size, rapid growth rates, and established market acceptance. This article is the first to report on embryonic and larval development of this species reared under hatchery conditions. Developmental biology was examined across three larval cultures over a 21-day period. Newly fertilized eggs had a mean (±SE) diameter of 50 ± 0.4 µm, and postfertilization, the first polar body formed within 20 min. The earliest actively swimming trochophore appeared from 12.5 h postfertiliszation (hpf) and D-stage larvae appeared by 18 hpf. Rapid shell growth resulted in the presence of early umbo larvae at 5–7 days post fertilization (dpf). Pediveliger larvae were present from 18 dpf and the larvae settled with induction by epinephrine bitartrate from 21 dpf when they had reached an anteroposterior shell measurement of approximately 280 µm and could be retained on a 200-µm nylon mesh screen. Despite minor differences, overall, the early ontogeny of S. echinata is consistent with that of other members of the genus. This study fills an important knowledge gap in the literature and will aid the advancement of hatchery protocols for this developing aquaculture species.

Screen collection efficiency of airborne fibers with monodisperse length

Fiber length is believed to be an important variable in determining various toxicological responses to asbestos and other elongate mineral particles. In this study we investigated screen collection characteristics using monodisperse-length glass fibers (i.e., 11, 15, 25, and 53µm in length), to better understand the collection of fibers with different lengths on screens with different mesh sizes. A well-dispersed aerosol of glass fibers (geometric mean length ~ 20µm), generated by vortex shaking, was fed directly into the Baron Fiber Length Classifier, in order to produce monodisperse length fibers. With nylon mesh screens (10, 20, 30, 41 and 60µm mesh sizes), the screen collection efficiency was measured using an aerodynamic particle sizer. As the screen mesh size decreases from 60µm to 10µm, the screen collection efficiency for 53µm fibers increases (from 0.3 to 0.9) while 11µm fibers exhibited a collection efficiency independent of screen mesh size. The collection efficiency for the longest fibers was found to be nearly constant for aerodynamic diameters 1–4µm for screens 20 and 30µm, but to rise significantly at aerodynamic diameters larger than 4µm. For the 20µm screen, the collection efficiency for fibers with lengths > 20µm is a factor of two to five larger than that for spherical particles with the same aerodynamic diameter. We believe that fibers are collected on the screen primarily by interception below 4µm in aerodynamic diameter, and by impaction above 4µm. This study represents a fundamental advance in the understanding of the interaction of screens with a fibrous aerosol.

Longevity of Sclerotinia sclerotiorum sclerotia on the soil surface under field conditions

ABSTRACT The longevity of Sclerotinia sclerotiorum sclerotia was quantified in an experiment carried out in the field. Sclerotia naturally formed in soybean plants in an infested commercial field were collected in a grain-cleaning machine and those present in the stem pith, with c.a. 8 mm in length and 1.9 mm in diameter were selected. Fifty sclerotia were kept inside a white nylon mesh (0.25mm) screen bag (25 x 25cm). Eighty bags were laid on the soil surface-simulating no till farming. At monthly intervals, four bags were taken and brought to the laboratory. Sclerotia were washed with tap water and surface desinfested with sodium hypochlorite and exposed to germinate on sterilized moist river sand in a growth chamber at 15oC and 12h photoperiod. After 12 months, sclerotia kept on the soil surface, lost their viability. It may be concluded that under no till, crop rotation with nonsusceptible crops, can reduce the sclerotia bank in the soil.

A Granular Bed for Use in a Nanoparticle Respiratory Deposition Sampler.

A granular bed was designed to collect nanoparticles as an alternative to nylon mesh screens for use in a nanoparticle respiratory deposition (NRD) sampler. The granular bed consisted of five layers in series: a coarse mesh, a large-bead layer, a small-bead layer, a second large-bead layer, and a second coarse mesh. The bed was designed to primarily collect particles in the small-bead layer, with the coarse mesh and large-bead layers designed to hold the collection layer in position. The collection efficiency of the granular bed was measured for varying depths of the small-bead layer and for test particles with different shape (cuboid, salt particles; and fractal, and stainless steel and welding particles). Experimental measurements of collection efficiency were compared to estimates of efficiency from theory and to the nanoparticulate matter (NPM) criterion, which was established to reflect the total deposition in the human respiratory system for particles smaller than 300 nm. The shape of the collection efficiency curve for the granular bed was similar to the NPM criterion in these experiments. The collection efficiency increased with increasing depth of the small-bead layer: the particle size associated with 50% collection efficiency, d50, for salt particles was 25 nm for a depth of 2.2 mm, 35 nm for 3.2 mm, and 45 nm for 4.3 mm. The best-fit to the NPM criterion was found for the bed with a small-bead layer of 3.2 mm. Compared to cubic salt particles, the collection efficiency was higher for fractal-shaped particles larger than 50 nm, presumably due to increased interception.

A Novel Method for Assessing Respiratory Deposition of Welding Fume Nanoparticles

Welders are exposed to high concentrations of nanoparticles. Compared to larger particles, nanoparticles have been associated with more toxic effects at the cellular level, including the generation of more reactive oxygen species activity. Current methods for welding-fume aerosol exposures do not differentiate between the nano-fraction and the larger particles. The objectives of this work are to establish a method to estimate the respiratory deposition of the nano-fraction of selected metals in welding fumes and test this method in a laboratory setting. Manganese (Mn), Nickel (Ni), Chromium (Cr), and hexavalent chromium (Cr(VI)) are commonly found in welding fume aerosols and have been linked with severe adverse health outcomes. Inductively coupled plasma mass spectrometry (ICP-MS) and ion chromatography (IC) were evaluated as methods for analyzing the content of Mn, Ni, Cr, and Cr(VI) nanoparticles in welding fumes collected with nanoparticle respiratory deposition (NRD) samplers. NRD samplers collect nanoparticles at deposition efficiencies that closely resemble physiological deposition in the respiratory tract. The limits of detection (LODs) and quantitation (LOQs) for ICP-MS and IC were determined analytically. Mild and stainless steel welding fumes generated with a robotic welder were collected with NRD samplers inside a chamber. LODs (LOQs) for Mn, Ni, Cr, and Cr(VI) were 1.3 μg (4.43 μg), 0.4 μg (1.14 μg), 1.1 μg (3.33 μg), and 0.4 μg (1.42 μg), respectively. Recovery of spiked samples and certified welding fume reference material was greater than 95%. When testing the method, the average percentage of total mass concentrations collected by the NRD samplers was ∼30% for Mn, ∼50% for Cr, and ∼60% for Ni, indicating that a large fraction of the metals may lie in the nanoparticle fraction. This knowledge is critical to the development of toxicological studies aimed at finding links between exposure to welding fume nanoparticles and adverse health effects. Future work will involve the validation of the method in workplace settings.[Supplementary materials are available for this article. Go to the publisher's online edition of Journal of Occupational and Environmental Hygiene for the following free supplemental resource: Digestion, extraction, and analysis procedures for nylon mesh screens.]

Spawning detection device for the black tiger shrimp Penaeus monodon broodstock

This research is aimed at developing an automatic spawning detection system for the black tiger shrimp, Penaeus monodon. This system is composed of instruments which are attached to the inner wall of the spawning tank that contains light sensing circuits which change light intensity into electrical signals. The detection unit is composed of a polyvinyl chloride (PVC) pipe containing a light emitting diode (LED) bulb that serves as a light source transmitter, and a light-dependent resistor (LDR) that serves as a light receiver which transforms light intensity into electrical resistance. Placed between the LED bulb and the LDR is a 135μm nylon mesh screen that is stretched horizontally inside the pipe to filter out shrimp eggs. Changing signals from the LDR turns on (or off) a 220V bulb. This device detects spawning activity as early as 22s after the onset of spawning. There is a correlation that exists between the number of spawned eggs and the time of the onset of spawning, with earliest detection occurring with the highest number of eggs.

P47phox Directs Murine Macrophage Cell Fate Decisions

Macrophage differentiation and function are pivotal for cell survival from infection and involve the processing of microenvironmental signals that determine macrophage cell fate decisions to establish appropriate inflammatory balance. NADPH oxidase 2 (Nox2)-deficient chronic granulomatous disease (CGD) mice that lack the gp91(phox) (gp91(phox-/-)) catalytic subunit show high mortality rates compared with wild-type mice when challenged by infection with Listeria monocytogenes (Lm), whereas p47(phox)-deficient (p47(phox-/-)) CGD mice show survival rates that are similar to those of wild-type mice. We demonstrate that such survival results from a skewed macrophage differentiation program in p47(phox-/-) mice that favors the production of higher levels of alternatively activated macrophages (AAMacs) compared with levels of either wild-type or gp91(phox-/-) mice. Furthermore, the adoptive transfer of AAMacs from p47(phox-/-) mice can rescue gp91(phox-/-) mice during primary Lm infection. Key features of the protective function provided by p47(phox-/-) AAMacs against Lm infection are enhanced production of IL-1α and killing of Lm. Molecular analysis of this process indicates that p47(phox-/-) macrophages are hyperresponsive to IL-4 and show higher Stat6 phosphorylation levels and signaling coupled to downstream activation of AAMac transcripts in response to IL-4 stimulation. Notably, restoring p47(phox) protein expression levels reverts the p47(phox)-dependent AAMac phenotype. Our results indicate that p47(phox) is a previously unrecognized regulator for IL-4 signaling pathways that are important for macrophage cell fate choice.

Particle Collection Efficiency for Nylon Mesh Screens.

Mesh screens composed of nylon fibers leave minimal residual ash and produce no significant spectral interference when ashed for spectrometric examination. These characteristics make nylon mesh screens attractive as a collection substrate for nanoparticles. A theoretical single-fiber efficiency expression developed for wire-mesh screens was evaluated for estimating the collection efficiency of submicrometer particles for nylon mesh screens. Pressure drop across the screens, the effect of particle morphology (spherical and highly fractal) on collection efficiency and single-fiber efficiency were evaluated experimentally for three pore sizes (60, 100 and 180 μm) at three flow rates (2.5, 4 and 6 Lpm). The pressure drop across the screens was found to increase linearly with superficial velocity. The collection efficiency of the screens was found to vary by less than 4% regardless of particle morphology. Single-fiber efficiency calculated from experimental data was in good agreement with that estimated from theory for particles between 40 and 150 nm but deviated from theory for particles outside this size range. New coefficients for the single-fiber efficiency model were identified that minimized the sum of square error (SSE) between the values estimated with the model and those determined experimentally. Compared to the original theory, the SSE calculated using the modified theory was at least one order of magnitude lower for all screens and flow rates with the exception of the 60-μm pore screens at 2.5 Lpm, where the decrease was threefold.

Occurrence of the Wheat Stem Maggot, Meromyza americana Fitch (Diptera: Chloropidae), in Intermediate Wheatgrass, Thinopyrum intermedium (Host) Barkworth and D. R. Dewey (Poaceae), in Oklahoma1

The wheat stem maggot is primarily an economic pest of wheat, Triticum aestivum L.; barley, Hordeum vulgare L.; and cereal rye, Secale cereale L. (Poaceae) (Gilbertson, 1925; Allen and Painter, 1937; Rockwood et al., 1947). The larva of the wheat stem maggot enters the culm above the terminal node and feeds within the culm. Consequently, the developing inflorescence withers and dies and turns white in color. The aborted inflorescences are very noticeable among non-infested inflorescences. In Oklahoma, wheat stem maggot infestations have been reported to occur in seed production fields of bermudagrass, Cynodon dactylon var. dactylon (L.) Pers., and weeping love grass, Eragrostis curvula (Schrad.) Nees (Arnold and Ahring, 1987; Kindler et al., 1989). These were the first reported cases of wheat stem maggot to economically impact important warm-season forage grasses. Kindler et al. (1989) reported the percentage of aborted inflorescence in weeping lovegrass ranged from 3.2 to 22.6%. Intermediate wheatgrass, Thinopyrum intermedium (Host) Barkworth and D.R. Dewey, is an introduced forage grass that is used for pasture and hay for livestock in the Northern Great Plains, the Central and Southern High Plains, and much of the western United States. In the Southern Plains, research has shown that perennial, cool-season forage grasses do not persist through prolonged drought. Gillen and Berg (2005) reported a 95% reduction in stand due to drought where precipitation from September 2001 through May 2002 measured 62% of normal. Seeds from surviving plants from pastures used by Gillen and Berg were harvested in June 2002 and increased at the USDA-ARS Southern Plains Range Research Station, Woodward, Oklahoma. It was anticipated that progeny from these plants would have increased tolerance to drought. In late June 2006, aborted inflorescences of intermediate wheatgrass were found in a seed production block at Woodward. Aborted inflorescences were collected from the plot on 30 June, placed in Erlenmeyer flasks containing about 300 ml of tap water, and caged by placing them in a clear plastic bag with a nylon mesh screen on two sides to determine which insect was responsible (Kindler et al., 1989). Adult flies emerged 15–20 days later and were identified as wheat stem maggot using the keys of Sabrosky (1935) and Fedoseeva (1971). The percentage of aborted inflorescences was determined from randomly sampling 10 quadrats (30 3 30 cm) and ranged from 10 to 28%. Accordingly, the wheat stem maggot was confirmed as a pest of intermediate wheatgrass in Oklahoma which is a new host record. Voucher specimens were deposited at the K. C. Emerson Entomological Museum, Oklahoma State University, Stillwater.

Nylon Mesh Screens Reduce Incidence of Leaf Curl Virus and Improve Yield in Sweet Pepper

Abstract Leaf Curl Virus (LCV) is a limiting factor in production of solanaceous vegetables. The virus is transmitted by the whitefly (Bemisia tabaci Gen.) to tomato, and chili and sweet peppers. A mechanical barrier provided by enclosures covered with nylon nets with different mesh densities was tested for its effectiveness in controlling LCV. Sweet pepper grown under a 50 × 50 holes·cm−1 mesh net had the lowest LCV incidence (16.8%), followed by the 40 × 40 holes·cm−1 (22.7%) and the 30 × 30 holes·cm−1 (55.2%) mesh nets. Control plants, no netting, had the highest LCV incidence (95.1%). Plants grown under mesh nets had similar fruit yields, which were higher than plants grown without nets. Use of net screens could reduce the need for application of insecticides.

Uso de micorrizas e rizóbio em cultivo consorciado de eucalipto e sesbânia: I - Crescimento, absorção e tranferência de nitrogênio entre plantas

Realizou-se um experimento em casa de vegetação para avaliar os efeitos de fungos micorrízicos arbusculares (FMAs) e rizóbio na produção de matéria seca, na absorção e na eficiência de utilização de N por plantas de Eucalyptus grandis e Sesbania virgata, cultivadas em consorciação. Avaliou-se, também, a transferência de N da sesbânia para o eucalipto, utilizando-se o isótopo 15N. Os tratamentos constaram da inoculação, ou não, com FMAs em ambas as espécies de plantas e da inoculação, ou não, com rizóbio na sesbânia. Utilizaram-se vasos plásticos subdivididos em três compartimentos (A, B e C), cada um com 2 L de capacidade. Os compartimentos A e B foram separados por uma parede plástica e entre os compartimentos B e C foi colocada uma tela com poros de 40 mm que permitiu somente a passagem de hifas, mas não de raízes. A sesbânia foi cultivada com suas raízes subdivididas entre o compartimento A e B e o eucalipto foi cultivado no compartimento C. No compartimento A, foram adicionados 7 mg kg-1 de 15N-(NH4)2SO4 com 99 % de 15N. As plantas foram avaliadas aos 100 dias. Nos tratamentos com inoculação com o rizóbio, com FMAs ou com FMAs + rizóbio, foram observados, nas plantas de eucalipto, aumentos na produção de matéria seca total de 119, 223 e 209 %, respectivamente, e aumentos no conteúdo de N de 125, 247 e 310 %, respectivamente, quando comparados aos resultados do tratamento-controle. Nas plantas de sesbânia, foram observados aumentos no conteúdo de N e decréscimo na relação C/N em todos os tratamentos inoculados com os microrganismos. A eficiência de utilização de N foi maior nas plantas de eucalipto quando inoculadas com FMAs e não variou com os tratamentos nas plantas de sesbânia. Foi observada a transferência de 15N das plantas de sesbânia para o eucalipto em todos os tratamentos.

Spatial, Seasonal, and Annual Variation of Fine Root Mass in a Forested Wetland

live and dead fine root mass. Nylon mesh screens were used in the second year to determine if microtopographic position influenced rates of new root production. Samples were collected from 20 replicates each of three microsite types: well-drained hummocks, flats with intermediate drainage, and poorly-drained hollows. Overall live root mass was lower in the second year of the study, possibly because of greater flooding then. Within each year, microsites did not differ significantly in mean live root mass; however, hummocks had significantly less seasonal variation than did flats or hollows. When microsites were compared across years, seasonal fluctuations in live root mass overlapped more strongly in the second year. Dead root mass was significantly less in hollows than in hummocks in both years. Screen data showed that hummocks had the greatest productivity. Overall, results show that some spatial and seasonal patterns of root distribution are similar across years, while others change from year to year, possibly in response to hydrology.

The Role of the external mycelial network of arbuscular mycorrhizal fungi: III. a study of nitrogen transfer between plants interconnected by a common mycelium

An experiment under greenhouse conditions was carried out to evaluate the relative contribuition of arbuscular mycorrhizal fungi (AMF) in the process of nitrogen transfer from cowpea to maize plants, using the isotope 15N. Special pots divided in three sections (A, B and C), were constructed and a nylon mesh screen of two diameters: 40µm (which allowed the AMF hyphae to pass but not the plant roots) or 1µm (which acted as a barrier to AM hyphae and plant roots) was inserted between the sections B and C. Section A had 25.5 mg of N/kg using (15NH4)2SO4 as N source. Two cowpea seedlings inoculated with Rhizobium sp. were transplanted with their root systems divided between the sections A and B. Ten days later, 2 seeds of maize were sown into the section C which was inoculated with Glomus etunicatum. Thirty-five days after transplanting, the maize plants were harvested. AMF inoculation increased dry weight and 15N and P content of maize plant shoots. Direct transfer of 15N via AMF hyphae was 21.2%; indirect transfer of 15N mediated by AMF mycelium network, was 9.6%, and indirect transfer not mediated by AM mycelium network , was 69.2%.

Transferência de nitrogênio entre plantas interconectadas por fungos micorrízicos arbusculares (FMAS)

Este trabalho, desenvolvido em casa de vegetação da Universidade Estadual do Norte Fluminense (UENF), em Campos (RJ), no primeiro semestre de 1996, objetivou avaliar a importância dos fungos micorrízicos arbusculares (FMAS) no processo de transferência de N do feijão para o milho, utilizando o isótopo 15N. Foram construídos três tipos de vasos especiais, divididos em três seções, A, B e C, com 2 dm³ de capacidade: sem barreira, com tela de nylon de 40 ∝m (permitiu a passagem de hifas fúngicas, mas não a de raízes) e com tela de nylon de 1 ∝m (não permitiu a passagem de hifas e raízes) entre as seções B e C. Adicionaram-se 25 mg kg-1 de N somente na seção A de cada vaso, utilizando-se, como fonte (15NH4)2SO4. Duas plantas de feijão pré-germinadas e inoculadas com Rhizobium tropici foram plantadas com suas raízes divididas entre as seções A e B. Após 10 dias, efetuou-se o plantio do milho, diretamente, na seção C dos vasos, e a inoculação micorrízica nos tratamentos com o FMA foi feita pela adição de propágulos de Glomus etunicatum somente na seção C. O experimento foi coletado 35 dias após o transplantio do feijão, e os resultados demonstraram que a colonização micorrízica se mostrou satisfatória, tanto no milho quanto no feijão. A presença da micorriza aumentou a produção de matéria seca, conteúdo de 15N e P da parte aérea das plantas de milho. A transferência direta de 15N do feijão para o milho através do micélio fúngico foi de 16,6%; a transferência indireta envolvendo o FMA - ou seja, a absorção do 15N excretado pelas raízes do feijão na solução do solo que foi absorvido e transferido através do micélio do FMA para o milho - foi de 34,1%; e a transferência indireta não envolvendo o FMA - ou seja, a absorção de 15N pelas raízes de milho da solução do solo sem envolvimento do FMA - foi de 49,3%.

A direct method for assessing sediment load in epilithic algal communities

S. W. Purcell Department of Marine Biology, James Cook University, Townsville Qld. 4811, Australia Accepted: 14 March 1996 Mobile sediments within coral reef environments can be deleterious to coral (Rogers 1990), and their deposition onto reef surfaces may directly affect other benthic biota. Epi- lithic algal communities (EACs), which cover significant proportions of coral reef surfaces, can trap sediments which may deleteriously affect neighbouring biota such as corals (Walker and Ormond 1982). Furthermore, sediments can remain in coral reef systems for long periods (Chansang et al. 1992) and via resuspension events, may be transported through other biotopes. The ability to measure sediment loads on hard reef surfaces, such as EAC-covered substra- ta, where they are directly influencing reef biota, is therefore important to assessing sediment disturbance on coral reefs. The principal methodology used to assess sedimenta- tion on coral reefs has been the deployment of sediment traps (Rogers 1990). Sediment traps collect suspended sediments over a given time; these values are interpreted as the gross downward flux rates of particles in the water column. Within this context, sediment traps have been invaluable as research tools for documenting gross sedi- ment inputs to reef systems. Problems can arise, however, when sediment trap data are extended to infer accrual rates of sediments to reef substrata (Cort6s and Risk 1985), since a sediment trap does not approximate the nature in which particules are bound to the benthos (Gardner 1980). More- over, the technique does not provide any information about the amount of sediment deposited on natural sub- strata, in contact with sessile biota. Ideally, studies should incorporate direct sampling of accumulated sediments on reef substrata to provide base- line assessments of natural loads and supplement informa- tion on sedimentation rates during disturbances. I outline here a portable apparatus and sampling technique which allows a diver to collect sediments on reef surfaces, and a test of its efficiency at removing sediments held within EACs of natural coral reef substrata. This rapid method permits the measurement of the instantaneous (net) load, rather than the sedimentation rate, of terrigenous and reef-derived sediments on algae-covered substrata. The sediment sampler (Fig. 1) is a submersible appar- atus which uses a bilge pump to vacuum particulate material from substrata. It can be viewed as four connected components; a brush to loosen bound sediments from algae, a filter to retain coarse sediments, a pump which produces an intake current, and a collection bag to retain water and fine sediments. The electric rotary bilge pump (Whale ® Superline 99) is powered by a 12V dryfit battery and associated electronics contained within a waterproof housing. An adjustable timer and current regulator circuit, which maintains a constant voltage (10.5V), standardises the water flow speed and duration for each sample. A voltmeter mounted within the housing can be checked periodically, to indicate when the battery power is insuf- ficient to run the current regulator. The sediment filter used for sampling is contained within a 250 ml plastic sample vial, which has two tapered fittings attached to the lid. The filter houses an intake hose which is fitted through the centre of five perforated PVC baffles stacked 10 mm apart within the vial, with a 200 gm nylon mesh screen below the uppermost baffle. The central hose carries water and particulate material to the bottom of the vial, and as they passes through the filter, the perforated baffles impede turbulence, and retain the coarse sediments. A brush (25mm diameter) with soft, nylon bristles around the perimeter, is attached to the intake hose. The brush attachment has a central opening (20 mm diameter) which results in an intake current speed of about 28 cm s- 1 at the opening. A circular sampling ring of 6 mm thick PVC is pinned to the substrate to outline a 100cm 2 sampling area and partition the enclosed sediments from those on neighbouring surfaces. The brush is applied to the substratum within the sampling unit and, once the pump is switched on, it is used to brush/dab the algae (or other epilithic biota) to release bound sediments which are im- mediately vacuumed through the filter. Fine sediment grains and water (5.4 I) pass through the bilge pump and fill a plastic collection bag (530 x 300mm, 100 gauge). Upon

A Container for Eclosion and Holding Adult Insects Prior to Mass Release

The mass release of adult insects requires containers for eclosing pupae and, at times, for holding adults for several days (e.g., Tanaka boxes used in the release of sterile fruit flies illus. in Holler, et al. 1984). These units can be both bulky and expensive. Casual observation of large numbers of confined insects has shown that the majority of their time is spent resting on cage walls or on objects in the cage. The large air volume of a cage is essentially wasted space. With this in mind, a container in the shape of a bag roughly the size of a pillow case was designed for eclosing and holding large numbers of adult braconid parasites. The eclosion bag is mostly walls, takes up little room, and is easy to move about, both within the rearing/eclosion facility and during transportation to release sites. The bags are made from pieces of 32 x 32 nylon mesh screen (Lumite, Inc., Gainesville, GA.) that are sewn together and closed continuously across the bottom and the length of one side by velcro strips. For our purposes, we found that a bag 60 cm wide and 90 cm long was ideal, but smaller as well as larger bags (up to 2m long) have been constructed, and insects have been successfully maintained in them. Earlier designs had rounded edges on the bottom to prevent insects from accumulating in corners and milling. The parasite being held in our research, Diachasmimorpha longicaudata (Ashmead), did not display this behavior to any significant extent, and bags with square-edges proved easier to sew and cheaper to produce. Should these bags be adapted for use with insects in which milling is typically a problem, e.g., tephritid fruit flies, the inclusion of rounded bottom corners might be considered. During the holding/maturation period, parasites were fed a solution of honey and water that was poured into 30 cm polyethylene tubes with an inner diam of 10 mm. The tube ends were closed with 3 cm cotton wicks. The diluted honey seeped through the wick and provided a feeding surface for the insects. To prevent either dripping or incomplete absorbance, we found it necessary to vary the proportions of honey and water with changes in temperature and relative humidity. The tube was held along the upper margin of the bag with a large (#5) binder clip. Cages were then hung from lines, sometimes at two levels in rooms of normal height (2.5 m). An S-hook or open paper clip fitted through the binder clip and then over the line made an effective hanger. Parasitized Caribbean fruit fly pupae (Anastrepha suspensa (Loew)) were poured evenly on the bottom of the bag. A typical volume was 375 ml, which gave rise to approximately 5000 adult parasites. For our needs, adults were maintained in the bags for five days after the first eclosion. They were then taken by vehicle to the release sites. Lines strung in the back of a van provided a convenient method of suspending them during transportation, although bags could be laid flat and stacked several deep with no apparent ill effects on the parasites. At the release site, the feeding tube was removed, the velcro opened, and the pupal remains poured into a bucket. The bag was spread open and shaken in the air. This was a particularly useful technique in releasing D. longicaudata, which have a rela-