Qualification of Environmental Chambers

2004 ◽  
pp. 243-253
Author(s):  
Gilman Wong ◽  
Herman Lam
Keyword(s):  
Environmental Chambers

Side-entry differentially pumped environmental chamber for the AE1-EM7 HVEM

1986 ◽  
Vol 44 ◽  
pp. 888-889
Author(s):  
D. Barnard ◽  
D. Rexford ◽  
W.F. Tivol ◽  
J.N. Turner
Keyword(s):  
Electron Microscope ◽  
High Voltage ◽  
Environmental Chamber ◽  
Normal Operating ◽  
Voltage Electron ◽  
High Voltage Electron Microscope ◽  
High Voltage Electron ◽  
Environmental Chambers

A side-entry differentially pumped environmental chamber (SEDPEC) has been designed and constructed for the AEI-EM7 high-voltage electron microscope (HVEM). The SEDPEC has been tested in the same way as previous chambers for the HVEM. In contrast to the lengthy procedures necessary to install previous environmental chambers in the HVEM, the SEDPEC can be installed in about one half hour. Thus a user can install the SEDPEC, use it for a day and return the HVEM to normal operating status without causing delays for other HVEM users. This is particularly important for our facility, which is supported as a national biotechnology resource by the NIH.

scholarly journals Effect of oxidant concentration, exposure time, and seed particles on secondary organic aerosol chemical composition and yield

2015 ◽  
Vol 15 (6) ◽  
pp. 3063-3075 ◽  
Author(s):  
A. T. Lambe ◽  
P. S. Chhabra ◽  
T. B. Onasch ◽  
W. H. Brune ◽  
J. F. Hunter ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Gas Phase ◽  
Flow Reactor ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Short Exposure ◽  
Heterogeneous Oxidation ◽  
Seed Particles ◽  
Aerosol Mass ◽  
Environmental Chambers

Abstract. We performed a systematic intercomparison study of the chemistry and yields of secondary organic aerosol (SOA) generated from OH oxidation of a common set of gas-phase precursors in a Potential Aerosol Mass (PAM) continuous flow reactor and several environmental chambers. In the flow reactor, SOA precursors were oxidized using OH concentrations ranging from 2.0 × 108 to 2.2 × 1010 molec cm−3 over exposure times of 100 s. In the environmental chambers, precursors were oxidized using OH concentrations ranging from 2 × 106 to 2 × 107 molec cm−3 over exposure times of several hours. The OH concentration in the chamber experiments is close to that found in the atmosphere, but the integrated OH exposure in the flow reactor can simulate atmospheric exposure times of multiple days compared to chamber exposure times of only a day or so. In most cases, for a specific SOA type the most-oxidized chamber SOA and the least-oxidized flow reactor SOA have similar mass spectra, oxygen-to-carbon and hydrogen-to-carbon ratios, and carbon oxidation states at integrated OH exposures between approximately 1 × 1011 and 2 × 1011 molec cm−3 s, or about 1–2 days of equivalent atmospheric oxidation. This observation suggests that in the range of available OH exposure overlap for the flow reactor and chambers, SOA elemental composition as measured by an aerosol mass spectrometer is similar whether the precursor is exposed to low OH concentrations over long exposure times or high OH concentrations over short exposure times. This similarity in turn suggests that both in the flow reactor and in chambers, SOA chemical composition at low OH exposure is governed primarily by gas-phase OH oxidation of the precursors rather than heterogeneous oxidation of the condensed particles. In general, SOA yields measured in the flow reactor are lower than measured in chambers for the range of equivalent OH exposures that can be measured in both the flow reactor and chambers. The influence of sulfate seed particles on isoprene SOA yield measurements was examined in the flow reactor. The studies show that seed particles increase the yield of SOA produced in flow reactors by a factor of 3 to 5 and may also account in part for higher SOA yields obtained in the chambers, where seed particles are routinely used.

CONSTRUCTION OF INEXPENSIVE, WALK-IN ENVIRONMENTAL CHAMBERS FOR STUDYING INSECT-TEMPERATURE RELATIONSHIPS1

1985 ◽  
Vol 20 (3) ◽  
pp. 340-344
Author(s):  
M. C. Bell ◽  
R. G. Luttrell
Keyword(s):  
Large Scale ◽  
Low Cost ◽  
High Accuracy ◽  
Air Temperatures ◽  
Environmental Chambers

The construction of walk-in controlled environmental chambers that achieve high accuracy at low cost is described. These chambers are capable of maintaining air temperatures at 15 - 35° ± 0.5°C. Long term (weekly) humidity stability averages 75% RH at ±6%. The described units are useful for large-scale bioassay experiments.

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