Temperature control - chambers

Experimentally DMTA is carried out on a small specimen of polymer held in a temperature-controlled chamber. The specimen is subjected to a sinusoidal mechanical loading (stress), which induces a corresponding extension (strain) in the material. The technique of DMTA essentially uses these measurements to evaluate a property known as the complex dynamic modulus, , which is resolved into two component parts, the storage modulus, E and the loss modulus, E . Mathematically these moduli are out of phase by an angle 5, the ratio of these moduli being defined as tan 5, Le. 

Figure 3. Recent version of the Portal Shield system housed in a temperature controlled chamber for long-term monitoring around fixed sites (www.dcfp.navy.mil/cbrd/ca/actd.htm, March 20, 2004).

Another approach to a source of vapors to calibration of instruments, and similar to that described above, was that of Davies et al. [67] who used a computer-controlled pulsed vapor generator with TNT, RDX, and PETN. The explosive solid was coated on quartz beads, which were then packed into a stainless steel tube. The tube was coiled and placed into a temperature-controlled chamber. Ultrapure air was passed through the coil at temperature and vapors of explosives were vented from the coil at rates or concentrations governed by coil temperature, airflow rate, and pulse width. Calibrations could reach the picogram to nanogram range when an IMS analyzer was used as the calibrating instrument. 

A fully automated system for performing detailed studies has been developed to improve the reproducibility and throughput (Fig. 12.2) [8]. It consists of two functional components a sample-deuteration device and a protein processing unit. The preparation operations (shown at the top of Fig. 12.2) are performed by two robotic arms equipped with low volume syringes and two temperature-controlled chambers, one held at 25 °C and the other held at 1 °C. To initiate the exchange experiment, a small amount of protein solution is mixed with a deuter-ated buffer and the mixture is then incubated for a programmed period of time in the temperature-controlled chamber. This on-exchanged sample is immediately transferred to the cold chamber where a quench solution is added to the mixture. 

Fig. 12.2 Diagram of a fully automated system for acquiring H/D exchange MS data starting with a stock solution of the nondeuterated protein. In this system [8], the liquid handler mixes a small amount of concentrated protein solution with a selected deuterated buffer and the mixture is incubated for a programmed period of time. The exchange reaction is conducted in a temperature-controlled chamber held at 25 °C. The mixture is then transferred to an acidic quench solution held at 1 °C. After quenching the exchange reaction, the entire sample is injected onto an LC-MS system...

Differential thermal analysis was performed with the DuPont 900 differential thermal analyzer the heating rate was usually 10°C. per minute. To determine heats of reaction, the calorimeter attachment to the Du Pont instrument was employed. Planimeter determinations of peak areas were converted to heat values by using standard calibration curves. For the infrared spectra either a Beckman IR5A instrument or a Perkin Elmer 521 spectrophotometer with a Barnes Engineering temperature-controlled chamber, maintained dry, was used. Specimens for infrared were examined, respectively, as Nujol mulls on a NaCl prism or as finely divided powders, sandwiched between two AgCl plates. For x-ray diffraction studies, the acid-soap samples were enclosed in a fine capillary. Exposures were 1.5 hours in standard Norelco equipment with Cu Ko radiation. For powder patterns the specimen-to-film distance was 57.3 mm. and, for long-spacing determinations, 156 mm. 

Eisele et al24 describe the so called tear analyzer using a strip test piece with a cut in one edge cycled in tension, which can be considered the classic geometry for obtaining fracture mechanics data on rubbers. This sophisticated instrument introduces nothing new in concept but has a temperature controlled chamber and can operate at different frequencies, pre-strains and strain amplitudes, with automatic compensation for set. 

NOTE Small temperature fluctuations can result in large errors in calculated densities. The temperature of all materials (bottle and solutions) should therefore be carefully controlled during all stages of the procedure using either a temperature-controlled chamber or a water bath. If a water bath is used, all excess water must be wiped off the specific gravity bottle prior to measurements to prevent evaporative cooling effects and errors in weight determination. 

Figure 4. A photograph of the thin him holder and temperature controlled chamber.

TMA consists of a quartz probe which rests on top of a flat sample (a few mms square) in a temperature controlled chamber. When setup in neutral buoyancy (with flat probe ) then as the temperature is increased the probe rises in direct response to the expansion of the sample yielding... 

Example 11.1 Chain Modification (Branching and Partial Cross-linking) of PET with Triglycidyl Isocyannrate (TGIC) Dhavalkikar (39) conducted the reaction cited in the Example title on samples placed between the rheometrics mechanical spectrometer (RMS) parallel disks in the temperature-controlled chamber under nitrogen. He followed the reaction dynamics chemorheologically by measuring, in-line, the in- and out-of-phase dynamic moduli G (t) and G"(t) they are indicative of the elastic and viscous nature of the molten reactive samples. 

Thermostatted water bath or temperature-controlled chamber (30-50°C). 

Inoculate 5-10 mL of fresh culture broth with a single colony of the bacterial strain of interest and incubate in a 37°C dry incubator or a temperature-controlled chamber. 

In these experiments a continuous record of locomotor activity was obtained from animals caged individually in the soundproof, temperature-controlled chamber described above. Each rat was kept in a Squirrel-Cage (E. K. Bowman Ltd., London) which consisted of an activity wheel, 16 in. in diameter and with a 5 in. rim, attached to a cage measuring 8 in. x 10 in. 

Careful temperature control is necessary so that ice crystals neither melt nor grow while they are imaged. This can be achieved by performing the sample preparation and microscopy inside temperature-controlled chambers or by carrying out the whole experiment in a cold room. The temperature of the cold chamber is set to the required imaging temperature, for example — 5 °C for ice cream that has just come out of the factory freezer, or —18 °C for ice cream that has been hardened and stored. A small sample of ice cream is smeared onto... 

A thermostat is required for temperature control. Temperature controlled chambers ensure more reproducible separations as they help to dissipate heat from Joule heating (section 3.1.2) and protect sensitive analytes from thermal degradation. 

A close tolerance on test temperature is required, and therefore the apparatus is usually placed in a temperature-controlled chamber. 

DMA is the most useful technique to study the viscoelastic properties of polymers [21], The sample is mounted in a temperature-controlled chamber. A sinusoidal stress is applied to the sample, and the resulting strain is measured for complex modulus analysis. For purely elastic materials, the stress and strain will be perfectly in phase, while for purely viscous material, there will be a 90° phase angle. The storage and loss moduli of the sample can be obtained. The storage modulus is the elastic part (i.e., stored energy), while the loss modulus is the viscous part (i.e., dissipated energy). The parameters obtained from DMA are listed in Table 20.1. 

For each pre-strain level and each temperature, the foam cylinder was first inserted into the double-waUed confining tube. After that, the confined specimen was put into a temperature-controlled chamber (ATS heating chamber) in a gear-driven MTS Q-TEST 150 machine. 

Fig. 14.16 X-ray diffraction patterns of a mixture of 0.6 LiFeP04 and 0.4 FeP04 recorded at 30 K steps from 298 to 633 K with magnification of 200 reflections. Bruker AXS D8 ADVANCE powdCT diffractomelCT was used with Co-Ka radiation and linear position-sensitive detector Vantec-1. Measurranent ranges were from 15° to 120°. The measurements were conducted under a high-purity He atmosphere in an Anton Paar HTK 450 temperature-controlled chamber...

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