Control Enclosure Research Articles

Particles in a box: novel design and evaluation of an adaptable engineering control enclosure for a common split tube furnace to eliminate occupational exposure to refractory ceramic insulation fibers

Split tube furnaces routinely used in nanotechnology laboratories to generate C-based nanomaterials rely on refractory ceramic insulation fibers, which can pose an inhalation risk to operators.

Performance improvement of an industrial control enclosure cooling system

Following the trend of high accuracy machining, thermal management of industrial control enclosures become a critical issue. Therefore, a well-designed enclosure cooling system is essential to manage the heat generation inside the enclosure. In this study, to improve the performance of cooling system and the air-flow distribution inside the enclosure, CFD simulation has been used to evaluate the application of using the auxiliary circulation fan and air baffler. Furthermore, this study also investigates the lay-out design for both supply air vent and return air vent arrangement by two types of commercialized cooling systems through field measurements. The simulation results show the short circulation of air-flow is improved when the air baffler is installed. It also shows that the auxiliary circulation fan is suggested. Besides, air baffler is used to enhance the temperature distribution. The experimental results reveal the upper supply vent arrangement will cause the short circulation of air-flow slightly. The auxiliary circulation fans can improve the heat dissipation of cooling systems. There is no short circulation of air-flow for the lower supply vent arrangement, but the supply air cannot be distributed smoothly by the auxiliary circulation fans because the shape of the air baffler is not properly designed.

Brandt’s vole (Lasiopodomys brandtii) affects its habitat quality by altering plant community composition

The selective feeding of plants and excavation of soil by small mammals, especially rodents, have important effects on plant-animal interactions, but few studies have explored these effects and their potential mechanisms. In the present study, large-scale enclosure manipulative experiments were performed to explore the effects of Brandt’s vole (Lasiopodomys brandtii) on plant community composition and soil nutrients in Inner Mongolia, China. The results suggested that Brandt’s vole significantly decreased community biomass compared to the control enclosure, reducing it by 21.42% at the end of the experiments. Further analysis showed that the rhizome grass biomass was significantly reduced by 86.82%, while the biomass of bunch grasses and forbs was higher in the vole enclosure by 18.35% and 49.64%, respectively. Furthermore, Brandt’s vole significantly decreased species richness and the density, coverage, and importance value of the main forage species available. However, the soil main nutrient content and ammonium nitrogen mineralization rate were not significantly affected by the presence of Brandt’s vole, whereas nitrification rate significantly increased in the vole enclosure. Finally, we conclude that Brandt’s vole activity may affect the species’ habitat quality by creating plant communities dominated by less preferred forage species.

Performance of water transfer in response to water environment issues in Wuxi, China

The continuous development of industrialization and urbanization resulted in increased pollution in plain river network areas. In response to water environment issues, water transfer can be a countermeasure to improve water environment. There are five basic elements to be determined of water transfer, i.e., water sources, water transfer patterns, regulating rules, water transfer routes, and flow rate of water transfer. In Wuxi City, needs for water transfer were analyzed from the five aspects above. The former three elements were determined based on the results of water transfer measurements. The water source was Yangtze River, the pattern was continuous water transfer, and regulating rules were water transferred by pumping stations and drained by sluices and pumping stations. Besides, a water quantity and quality coupling model was constructed to analyze routes and flow rate of water transfer. Different flow rate of water transfer, from 80 to 130m3/s, were analyzed. According to the characteristics of regional river system and the requirements of flood control, the Baiqugang River was taken as the clean water route, and the urban flood control enclosure was taken as the clean water transfer station. In the end, it was concluded that the optimal flow rate is 110m3/s based on the results of different schemes. It indicates that a proper scheme of water transfer can better improve the water environment in plain river network areas.

Mouse Hind Limb Skeletal Muscle Functional Adaptation in a Simulated Fine Branch Arboreal Habitat.

The musculoskeletal system is remarkably plastic during growth. The purpose of this study was to examine the muscular plasticity in functional and structural properties in a model known to result in significant developmental plasticity of the postcranial skeleton. Fifteen weanling C57BL/6 mice were raised to 16 weeks of age in one of two enclosures: a climbing enclosure that simulates a fine branch arboreal habitat and is traversed by steel wires crossing at 45° relative to horizontal at multiple intersections, and a control enclosure that resembles a parking deck with no wires but the same volume of habitable space. At killing, ex vivo contractility properties of the soleus (SOL) and extensor digitorum longus (EDL) muscles were examined. Our results demonstrate that EDL muscles of climbing mice contracted with higher specific forces and were comprised of muscle fibers with slower myosin heavy chain isoforms. EDL muscles also fatigued at a higher rate in climbing mice compared to controls. SOL muscle function is not affected by the climbing environment. Likewise, mass and architecture of both EDL and SOL muscles were not different between climbing and control mice. Our data demonstrate that functional adaptation does not require concomitant architectural adaptation in order to increase contractile force. Anat Rec, 301:434-440, 2018. © 2018 Wiley Periodicals, Inc.

Effects of in situ CO2 enrichment on epibiont settlement on artificial substrata within a Posidonia oceanica meadow

Alterations to colonization or early post-settlement stages may cause the reorganization of communities under future ocean acidification conditions. Yet, this hypothesis has been little tested by in situ pH manipulation. A Free Ocean Carbon Dioxide Enrichment (FOCE) system was used to lower pH by a ~0.3unit offset within a partially enclosed portion (1.7m3) of a Posidonia oceanica seagrass meadow (11m depth) between 21 June and 3 November 2014. Epibiont colonization and early post settlement stages were assessed within the FOCE setup, as part of the larger community-level study, to better understand the outcome for a multispecies assemblage and the ecological processes that result in reported community shifts under altered carbonate chemistry. Two types of artificial collectors (tiles and scourers) were placed within three treatments: a pH-manipulated enclosure, an un-manipulated control enclosure, and an open plot in the ambient meadow. Tiles and scourers were collected after one to four months. Additionally, to see whether the outcome differed for communities in a later successional stage, previously settled scourer-collectors were also placed in the same three treatments. Enclosures acted to reduce settlement and migrant colonization. Scourers deployed for one to four months within the open-plot contained a community assemblage that could be distinguished from the assemblages within the enclosures. However, a comparison of enclosure assemblages on tiles showed evidence of a pH effect. There was lowered coverage of crustose coralline algae and fewer calcareous tube-forming polychaetes (Spirorbis sp. and Spirobranchus sp.) on tiles placed in the pH-manipulated enclosure compared to the un-manipulated enclosure. For assemblages in scourer collectors, shared and common taxa, in all treatments, were invertebrate polychaetes Psamathe fusca, Sphaerosyllis sp., Chrysopetalum sp., arthropods Harpacticoida, and Amphipoda, and the juvenile bivalve Lyonsia sp. Similar organism composition and abundance, as well as taxonomic richness and evenness, were found in scourers from both enclosures. Pre-settled scourers contained greater numbers of individuals and more calcified members, but the assemblage, as well as the growth rate of a juvenile bivalve Lyonsia sp., appeared unaffected by a two-month exposure to lowered pH and calcium carbonate saturation state. Results from this case study support the hypothesis that early stages of specific calcifiers (crustose coralline algae and calcareous tube-forming polychaetes) are sensitive to near future ocean acidification conditions yet suggest that negative effects on sessile micro-invertebrate assemblages will be minimal.

Effects of in situ CO2 enrichment on Posidonia oceanica epiphytic community composition and mineralogy

Alterations in seagrass epiphytic communities are expected under future ocean acidification conditions, yet this hypothesis has been little tested in situ. A Free Ocean Carbon Dioxide Enrichment system was used to lower pH by a ~0.3 unit offset within a partially enclosed portion (1.7 m3) of a Posidonia oceanica meadow (11 m depth) between June 21 and November 3, 2014. Leaf epiphytic community composition (% cover) and bulk epiphytic mineralogy were compared every 4 weeks within three treatments, located in the same meadow: a pH-manipulated (experimental enclosure) and a control enclosure, as well as a nearby ambient area. Percent coverage of invertebrate calcifiers and crustose coralline algae (CCA) did not appear to be affected by the lowered pH. Furthermore, fleshy algae did not proliferate at lowered pH. Only Foraminifera, which covered less than 3% of leaf surfaces, declined in manner consistent with ocean acidification predictions. Bulk epiphytic magnesium carbonate composition was similar between treatments and percentage of magnesium appeared to increase from summer to autumn. CCA did not exhibit any visible skeleton dissolution or mineral alteration at lowered pH and carbonate saturation state. Negative impacts from ocean acidification on P. oceanica epiphytic communities were smaller than expected. Epiphytic calcifiers were possibly protected from the pH treatment due to host plant photosynthesis inside the enclosure where water flow is slowed. The more positive outcome than expected suggests that calcareous members of epiphytic communities may find refuge in some conditions and be resilient to environmentally relevant changes in carbonate chemistry.

Why didn't the lizard cross the road? Dunes sagebrush lizards exhibit road-avoidance behaviour

Context Research has shown many negative effects of roads and traffic on wildlife and other biodiversity. The direct and indirect mechanisms through which roads and traffic harm animal populations vary across taxa, making mitigation of road effects a great challenge for conservation. As such, a large toolkit of species-specific management techniques may be needed to mitigate the negative effects of roads for wildlife and other biodiversity. The dunes sagebrush lizard, Sceloporus arenicolus, is a psammophilic (sand-loving) habitat specialist endemic to the Mescalero–Monahans Sandhills ecosystem of New Mexico and Texas. Within this ecosystem, roads fragment shinnery oak sand-dune landforms occupied by the species. Aims In the present study, we conducted behaviour trials in experimental enclosures to test whether the smallest roads restrict movements of the dunes sagebrush lizard. In addition, we also conducted trials to evaluate whether a sand-filled wildlife-crossing feature could facilitate road crossing. Methods We conducted behavioural trials on 24 dunes sagebrush lizards in our control enclosure and 22 lizards in our road and sand-filled wildlife-crossing enclosure. Movements were recorded for 15min. The final locations at the end of each trial were analysed using circular statistics to determine whether movements in the road or the sand-filled wildlife-crossing enclosures were different from the control. Key results Our results supported the hypotheses that dunes sagebrush lizards avoid roads and do so according to a surface-avoidance mechanism. We also found that the wildlife crossing-feature design tested here had no effect on the movements or road-crossing frequency of dunes sagebrush lizard. Conclusions Surface-avoidance behaviour indicated that roads will persistently affect the movements of dunes sagebrush lizard, even when traffic is not present. Also, more research into an effective wildlife crossing is needed to increase connectivity of fragmented populations. Implications These findings help evaluate the impact of roads in creating isolated populations that experience increased demographic stochasticity and, in some instances, localised extirpation in this species. Our study can guide conservation plans for the dunes sagebrush lizard, and contribute to our understanding of road effects on biodiversity in general.

Effect of two macrophyte species on phytoplankton growth and water quality in a eutrophic pond

To evaluate the ecological restoration effect of floating and submerged macrophytes on phytoplankton inhibition and water quality improvement, an enclosure experiment was undertaken in situ including Hydrilla verticillata mono enclosure, Eichhornia crassipes mono enclosure, and H. verticillata plus E. crassipes mixed enclosure. Concentrations of total nitrogen, ammonia nitrogen, nitrate nitrogen and total phosphorus were significantly lower in the vegetated enclosures than those in the control enclosure. Eichhorniacrassipes mono enclosure had significantly lower concentrations of ammonia nitrogen and nitrate nitrogen compared to the mixed enclosure. Purification ability was higher for faster growing macrophytes. The density and biomass of the phytoplankton in the plant enclosures were lower than those in the control enclosure, while the values in the mixed enclosures were significantly higher than those in the mono enclosures. Chlorophyta were the dominant algae in all the enclosures. Pyrrophyta and Cryptophyta were the co-dominant algae in the control enclosure. Therefore, macrophytes had a significantly inhibitory effect on phytoplankton, with the mono enclosures showing a stronger inhibitory effect compared to the mixed enclosures.

Effects on cyanobacterial growth and water quality after harvesting accumulated cyanobacteria in autumn: an <i>in-situ</i> experiment in Lake Chaohu

An in-situ enclosure experiment was conducted to study the effect of harvesting of algae on cyanobacteria growth and water quality in the northwestern Lake Chaohu in autumn. The gill type filter was used to harvest cyanobacteria in two enclosures and no treatment was conducted in control enclosure. The growth rates of cyanobacteria and the concentrations of nutrients and organic matters were investigated after harvesting compared with that in the control. The initial concentrations of chlorophyll-a,total nitrogen and total phosphorus reached 309. 5 ± 3. 7 μg / L,3. 32 ± 0. 14 mg / L and 0. 30 ± 0. 04 mg / L,respectively. Algogenic organic matter became a major source of dissolved organic matter in the enclosures,and fluorescent dissolved organic matter was dominated by proteinoid materials. Harvesting reduced the cyanobacterial biomass by 41. 7%,which relieved the "density dependence of growth"of cyanobacteria,and then resulted in an increase in diel frequency of dividing cells and the in-situ growth rates of cyaobacteria. Algogenic organic matters were reduced due to harvesting increased the viability of cyanobacterial cells in a short term.What's more,cyanobacteria tended to decline in autumn and chlorophyll-a concentration dropped gradually in the enclosures,which testified that harvesting in autumn would not cause a second outbreak of algal bloom. Primary productivity,nitrogen and phosphorus nutrients,Potassium permanganate index were controlled significantly in the harvesting enclosures due to the reduction of cyanobacterial biomass. Furthermore,the release of algogenic organic matters was controlled and macromolecular organic compound was degraded easily to low-molecular-weight organics. Therefore,harvesting the accumulated cyanobacteria shoreside in autumn could control the amount of algae,nitrogen and phosphorus nutrients as well as the release of algogenic organic matters,which could reduce the ecological risk in lakes.

Risk of spider predation alters food web structure and reduces local herbivory in the field.

Predators can indirectly enhance plant performance via herbivore suppression, with both prey consumption and changes in prey traits (e.g. changes in foraging behaviour) contributing to the reduction in herbivory. We performed a field experiment to determine the extent of such non-consumptive effects which consisted of repeatedly placing spiders (Pisaura mirabilis) on enclosed plants (Urtica dioica) for cue deposition. Control plants were enclosed in the same way but without spiders. After cue deposition, the enclosures were removed to allow arthropods to colonize the plants and feed on them. Arthropods were removed from the plants before the subsequent spider deposition or control enclosure. During six cycles of enclosure, we quantified leaf damage on the plants. After a seventh cycle, the colonizing arthropods were sampled to determine community composition in relation to the presence/absence of spider cues. We found that the presence of chemotactile spider cues reduced leaf damage by 50 %. In addition, spider cues led to changes in the arthropod community: smaller spiders avoided plants with spider cues. In contrast, the aphid-tending ant Myrmica rubra showed higher recruitment of workers on cue-bearing plants, possibly to protect aphids. Our results show that the risk of spider predation can reduce herbivory on wild plants and also demonstrate that non-consumptive effects can be particularly strong within the predator guild.

Improvement of Detection Method and Power Supply Device of Vehicle Detector

Automatic Vehicle Classification (AVC) detector, among traffic data collection devices, is very useful but operation failure or damage is often occurred due to unstable power supply, weather changes and poor road pavement condition, causing deteriorated data quality. In case of AVC detector currently used for detecting the vehicle type, 2 or more detectors are installed at the sections with similar traffic pattern, causing unnecessary cost. This study thus is intended to identify the problems with existing vehicle detector so as to develop the improved detector as well as evaluate the performance. This study is intended to identify the problems with existing vehicle detector and develop and evaluate the improved detector. The failure with AVC detector was mostly attributable to unstable power supply and environmental change and complex sensor and controller results in the high cost. Thus, to stabilize the power supply and reduce the failure by environmental change, improvement of the control part and enclosure was made and the cost was reduced by simplifying the sensor and control system and as a result of test, data accuracy, power stability and cost reduction could be achieve, proving high potential applicability to the site in the future.

O021: Infection control enclosure (ICE) POD: meeting the need for more single rooms

An increase in single occupancy rooms reduces transmission, improves hand hygiene compliance and increases patient satisfaction. Thus, there is a demand for more single rooms, particularly in hospitals with a low proportion of single rooms as is common in Europe. Furthermore, where the previous room occupant was infected or colonised with a pathogen, the subsequent admission is significantly less likely to acquire that pathogen if the room is decontaminated using hydrogen peroxide vapour (HPV) rather than being cleaned and disinfected using standard methods.

Ecosystem response to a salmon disturbance regime: Implications for downstream nutrient fluxes in aquatic systems

Recent work in salmon spawning streams has shown that sediment resuspended during nest construction flocculates with salmon organic matter to form suspended composite particles characterized by increased size and settling velocities. In a river system, these flocs have the potential to interact with benthic biofilms, suggesting a mechanism for the incorporation of organic matter into aquatic food webs. Using the Horsefly River spawning channel in central British Columbia, the spatial scale of biofilm floc trapping was evaluated for a salmon disturbance regime, which consists of the active digging of redds, spawning, and carcass decay. We stocked two sequential enclosures in the spawning channel with sockeye salmon (Oncorhynchus nerka) and established one upstream control enclosure. Biofilms were sampled for chlorophyll a, trapped sediment, and marine isotope tracers (δ15N and δ13C). In the active‐spawn period, biofilm abundance was reduced due to spawning disturbance, with isotope values indicating low utilization of marine‐derived nutrients (MDNs). During the post‐spawn period, downstream biofilm abundance exceeded pre‐spawn values, indicating a near‐field nutrient pulse with isotope values reflecting biofilm utilization of MDNs. At the same time, an increase in biofilm trapping efficiency occurred in concert with a significant increase in the in situ particle size of suspended sediment, suggesting that flocs were a temporary storage site of MDNs. The retention of MDNs over short spatial scales acts to retard the flushing of MDNs to downstream rearing lakes. The magnitude of these processes has ecological implications on the downstream lake's productivity, thereby influencing the success of future salmon stocks.

Concentrated Solar Power Harvesting Using Self-powered, Wireless, Thin-profile, Lightweight Solar Tiles

This paper presents a modular and scalable approach to concentrated solar power (CSP) harvesting by using low-profile, light-weight, sun-tracking, millimeter-to-centimeter-scale mirror arrays that can be wirelessly controlled to reflect the incident solar energy to a central receiver. Conventional, utility-scale CSP plants use large-area heliostats, parabolic troughs, or dish collectors that are not only heavy and bulky, but also require significant labor for installation and maintenance infrastructure. Furthermore, form-factors of current heliostats are not compatible with low-profile roof-mountable systems, as seen by the dominance of the conventional Photovoltaic systems for roof-top installations. Solar TILE (STILE) technology to be presented in this work enables concentrated solar power harvesting on a given surface with form factor and weight per unit area comparable to those of ceramic tiles used on walls/floors or that of Photovoltaic modules. Self-powered operation by integrated solar cells, elimination of wiring for power transfer, wireless control, and weather-proof enclosure of moving parts help STILE technology promise lower installation and maintenance costs than PV approaches, while enabling novel beam-redirection applications over large surfaces. As the STILEs are made of mostly plastic, which costs at least an order of magnitude less than solar grade silicon, associated material costs could potentially be much cheaper than silicon PV cells. After a description of the STILE technology and a discussion of mirror scaling, we present a prototype tile with dimensions 33 × 33 × 6.4 cm3 and detail its wireless operation.

Phytoremediation facilitates removal of nitrogen and phosphorus from eutrophicated water and release from sediment

Phosphorus (P) fractions and the effect of phytoremediation on nitrogen and phosphorus removal from eutrophicated water and release from sediment were investigated in the eco-remediation experiment enclosures installed in the Hua-jia-chi pond (Hangzhou city, Zhejiang province, China). The main P fraction in the sediment was inorganic phosphorus (IP). For the mesotrophic sediments, IP mainly consisted of HCl-extractable P (Ca-P). The annual-average concentration of total nitrogen (TN), total phosphorus (TP) in water and the content of TN, TP in different vertical depth of sediment in the experiment enclosures with hydrophyte were always much lower than those in the control enclosure without hydrophyte and those outside of experiment enclosures. It is suggested that phytoremediation was an effective technology for N and P removal from eutrophicated water and release from sediment.

CCGA packages for space applications

Commercial-off-the-shelf (COTS) area array packaging technologies in high reliability versions are now being considered for applications, including use in a number of NASA electronic systems being utilized for both the Space Shuttle and Mars Rover missions. Indeed, recently a ceramic package version specifically tailored for high reliability applications was used to provide the processing power required for the Spirit and Opportunity Mars Rovers built by NASA-JPL. Both Rovers successfully completed their 3-months mission requirements and continued exploring the Martian surface for many more moths, providing amazing new information on previous environmental conditions of Mars and strong evidence that water exists on Mars. Understanding process, reliability, and quality assurance (QA) indicators for reliability are important for low risk insertion of these newly available packages in high reliability applications. In a previous investigation, thermal cycle test results for a non-functional daisy-chained peripheral ceramic column grid array (CCGA) and its plastic ball grid array (PBGA) version, both having 560 I/Os, were gathered and are presented here. Test results included environmental data for three different thermal cycle regimes (−55/125 °C, −55/100 °C, and −50/75 °C). Detailed information on these—especially failure type for assemblies with high and low solder volumes—are presented. The thermal cycle test procedure followed those recommended by IPC-9701 for tin–lead solder joint assemblies. Its revision A covers guideline thermal cycle requirements for Pb-free solder joints. Key points on this specification are also discussed. In a recent investigation a fully populated CCGA with 717 I/Os was considered for assembly reliability evaluation. The functional package is a field-programmable gate array that has much higher processing power than its previous version. This new package is smaller in dimension, has no interposer, and has a thinner column wrapped with copper for reliability improvement. This paper will also present thermal cycle test results for assemblies of this and its plastic package version with 728 I/Os, both of which were exposed to four different cycle regimes. Two of these cycle profiles are specified by IPC-9701A for tin–lead, namely, −55 to 100 °C and −55 to 125 °C. One is a cycle profile specified by Mil-Std-883, namely, −65/150 °C, generally used for ceramic hybrid packages screening and qualification. The last cycle is in the range of −120 to 85 °C, a representative of electronic systems directly exposed to the Martian environment without use in a thermal control enclosure. Per IPC-9701A, test vehicles were built using daisy chain packages and were continuously monitored and/or manually checked for opens at intervals. The effects of many process and assembly variables—including corner staking commonly used for improving resistance to mechanical loading such as drop and vibration loads—were also considered as part of the test matrix. Optical photomicrographs were taken at various thermal cycle intervals to document damage progress and behavior. Representative samples of these are presented along with cross-sectional photomicrographs at higher magnification taken by scanning electron microscopy (SEM) to determine crack propagation and failure analyses for packages.

IMPORTANCE OF PROTOZOA AS FOOD TO ZOOPLANKTON AND SOME FISH SPECIES IN LAKE QAROUN, EGYPT

The relationship between the protozoan organisms and zooplankton in addition to fish predation of Lake Qaroun were herby studied. An experiment was conducted in the aquatic laboratory of Shakshouk Station-Fayoum close to Lake Qaroun using cylindrical fiberglass enclosures of 1000 liters capacity that were filled with water pumped from 0.5m depth of Lake Qaroun. The numbers and net population growth and production of the dominant protozoan organisms in absence and presence of small and large- sized zooplankton as well as two native fishes namely, Mitgil cephalus and Tilapia zillii were described. The average air and water temperatures were 27.7±2.1 and 22.6±l.lsC (mean ±SD) respectively. PH values ranged from 7.39 to 8.00 (7.74±0.13, mean±SD) while ammonium ranged from 64.39^gf 1 to 1.05mgmrl during the experiment At the start, the protozoan organisms, constituted numerically 48.12% of total zooplankton organisms that dominated by three species; Tintinnopsis kofoidi, Helicostomella subulata, and Euplots vannus. In the presence of the small-sized organisms (SS), the total protozoan number was decreased. In the presence of small and large sized organisms (SLS) the protozoan number returned to the control level The impact of the fishes was more pronounce in presence of M. cephalus than T. zilli compared to the control enclosure. Protozoan organisms were observed in the gut contents of M cephalus and T. zilli, representing 1429% and 4.69% respectively. The net population growth (NPG) was higher in control. (2.15 day') followed by SLS (2.10 day1). NPGR of T. kofoidi was the highest especially in presence of the SLS

Effects of inorganic and organic nutrient addition on a coastal microbial community (Isefjord, Denmark)

Using flow cytometry (FCM), microbial populations were followed in a mesoscosm experiment manipulated with daily additions of mineral nutrients (as phosphates and nitrates in Red- field equilibrium), of degradable organic carbon (as glucose-C), or with the 2 treatments combined. Intensive sampling was performed in order to assess the short time-scale variability of the microbial community. Five autotrophic groups (including Synechococcus spp. and cryptophytes), 2 groups of heterotrophic bacteria, and 2 groups of viruses could be discriminated by FCM. The control enclosure (no addition) revealed that heterotrophic bacteria were carbon-limited. Synechococcus spp. abun- dance increased in the control, presumably because they experienced little competition from hetero- trophic bacteria (which were C-limited) and from larger phytoplankton (which were not as efficient in nutrient uptake at low nutrient concentration and could not, therefore, sustain high growth rates). When N and P were added, however, larger-celled autotrophic populations were favoured. When glucose was added, alone or together with inorganic elements, the abundance of Synechococcus spp. and small eukaryotes was reduced, suggesting that, when released from C-limitation, heterotrophic bacteria are the best competitors for mineral nutrients. The addition of both inorganic and organic nutrients also enhanced cryptophytes in contrast to all other autotrophs, probably because of their heterotrophic capacity. Our results agree with recent evidence suggesting that heterotrophic bac- teria are limited by both carbon and mineral nutrients, and demonstrate how this has important con- sequences for the success of their trophic neighbours in the microbial food web.

NASA Glenn Research Center Acoustical Testing Laboratory

The Acoustical Testing Laboratory (ATL) at the National Aeronautics and Space Administration (NASA) John H. Glenn Research Center in Cleveland, Ohio supports the low-noise design of science experiment payloads developed for the International Space Station (ISS). The ATL consists of a 100-Hz vibration-isolated hemianechoic test chamber with 21-ft by 17-ft by 17-ft (h) interior working dimensions and removable floor wedges that allow the facility to be configured as either a hemianechoic or fully anechoic chamber. A separate, sound-isolated control room with outside dimensions of 23-ft by 11-ft by 12-ft (h) doubles as a noise control enclosure when testing articles that require remote connections to high-noise support equipment and services. These characteristics, along with very low design background sound levels, enable the acquisition of accurate and repeatable acoustical measurements on test articles, up to a full ISS rack in size, that produce very little noise. The ATL provides a comprehensive array of acoustical testing services, including sound power level in accordance with precision and engineering grade standards. These capabilities employ a PC-based acoustical data acquisition system that has been customized to perform simultaneous acquisition and real-time analysis of multiple channels of acoustical signals.