Independent Temperature Control Research Articles

Solubility of Cr2O3 and Speciation of Chromium in Soda–Lime–Silicate Melts

Chromium oxide solubility was measured in soda–lime–silicate melts using a thermochemical reactor allowing an independent control of temperature, glass composition, and oxygen fugacity in a closed system. This investigation performed in the ternary Na2O–CaO–xSiO2 (NCS) system showed that the physicochemical and thermochemical models used for chromium chemistry description in binary melts are applicable in the ternary system. The presence of Cr(II), Cr(III), and Cr(VI) has been evidenced and their respective contributions in the total chromium content dissolved in the melt were determined. A new approach based on optical basicity allowed the quantification of the basicity of the melt and consequently the free oxygen ions activity (aO2−). The treatment of the obtained results led to the determination of thermodynamical properties of the system. The standard enthalpies and entropies corresponding to the oxidation and reduction reactions were determined.

Abstract 2119: Very high sensitivity detection of K-RAS exon 2 mutations using fast COLD-PCR

Abstract Therapeutic agents such as cetuximab and panitumumab are epidermal growth factor receptor (EGFR) antagonists that can be effective in the treatment of colorectal cancer. However some 40% of these tumors have activating K-RAS exon 2 codon 12 and 13 mutations that have a strong association with poor response to EGFR antagonists. Attempts have been made to detect the presence of K-RAS exon 2 mutations in free circulating DNA from plasma/serum from colorectal cancer patients with K-RAS exon 2 mutations in their tumors. The small amount of circulating DNA in serum and the low sensitivity of the detection techniques used have resulted in sporadic success in establishing this correlation. Co-amplification at Lower Denaturation Temperature-PCR (COLD-PCR) is a novel form of PCR that preferentially amplifies mutant alleles in a mutant/wild-type mixture with wild-type alleles in vast excess. Fast COLD-PCR, one of two forms of the method, is applied to point mutations or insertion/deletions that lower the melting temperature (Tm) of the mutant allele. In Fast COLD-PCR, preferential amplification of a mutant allele is achieved by setting the PCR denaturation temperature during each cycle at the critical temperature (Tc) at which mutant DNA duplexes but not wild-type duplexes are denatured. COLD-PCR is normally carried out in a thermocycler with independent temperature control of each well, ensuring that Tc is precisely achieved. Well-to-well temperature variation of standard, bench thermocyclers is often not within the narrow range required to achieve efficient COLD-PCR mutation enrichment. We have developed a variation of the Fast COLD-PCR method that reduces the need for precise well-to-well temperature control. In this study we have taken advantage of the Tm lowering of most of the K-RAS exon 2 mutations in codons 12 and 13 (G>A or G>T), and have successfully applied our variation of Fast COLD-PCR to their enrichment. A plasmid-based model system was established to measure the Limit of Detection (LOD) of the K-RAS exon 2 codon 12 mutation G12S (GGT>GAT). Mixtures of two plasmids, one bearing a wild-type copy of exon 2 and the other the G12S mutation were prepared at ratios of mutant/wild-type ranging from 1:10 to 1:1,000 (0.1%). A total of 10,000 plasmid copies alone or combined with purified human serum DNA were enriched. Two rounds of PCR were performed: standard PCR producing a 218-bp amplicon followed by enrichment using nested Fast COLD-PCR at a Tc of 80.9 °C producing a 161-bp amplicon. SURVEYOR® Nuclease/WAVE® HPLC and Sanger DNA sequencing were used to identify the G>A mutation in the enriched PCR product. The LOD for the G12S mutation before enrichment was 1% by SURVEYOR/WAVE and 5% by sequencing. After Fast COLD-PCR enrichment, the LOD was <0.1% in the absence and <0.4% in the presence of serum with both detection methods. This represents detection of less than 1 mutant in 1000 wild-type K-RAS copies. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2119.

Screening Robotics and Automation

Screening Robotics and Automation

Analysis of potential genotoxic impurities in pharmaceuticals by two-dimensional gas chromatography with Deans switching and independent column temperature control using a low-thermal-mass oven module

The analysis of potential genotoxic impurities (PGIs) in active pharmaceutical ingredients (APIs) is a challenging task. The target limit of detection for a PGI in an API is typically 1 ppm (1 microg/g API). This is about 500 times lower than for classical impurity analysis. Consequently, analytical methods for trace analysis, mostly in combination with MS detection, need to be applied for the qualitative and quantitative determination of these impurities. A two-dimensional capillary GC method is presented that can be used for the determination of some target PGIs. A concentrated solution of the API sample is directly introduced in the GC-MS system, using an apolar column for first-dimension separation. The fraction (heart-cut) containing the PGIs is transferred to a second capillary column, installed in a low-thermal-mass oven (LTM). The LTM focuses the heart-cut(s) and allows independent temperature-programmed analysis with a polar second-dimension column. The API, solvent, and derivatization agents are not introduced in the second column or in the MS detector, avoiding contamination, column degradation, and target analyte peak detection/integration issues. The performance of this set-up is illustrated by the analysis of some Michael-reactive acceptor PGIs and haloalcohols in carbamazepine as test matrix. Excellent reproducibility (<10% RSD) at the low parts per million level and low detection limits (<1 ppm) were obtained.

Impedance spectroscopy analysis of TiO 2 thin film gas sensors obtained from water-based anatase colloids

In this work impedance spectroscopy technique was employed in order to characterize the gas-sensing behavior of undoped titanium dioxide (TiO 2) polycrystalline thin films. The electrical measurements were performed in a sensor-testing chamber that allows independent control of temperature, pressure, gas composition and flow rate. Frequency measurements, in the range from 40 Hz to 110 MHz, were performed in order to evaluate the gas sensor response of the samples as a function of temperature (50–350 °C) and surrounding atmosphere (vacuum or air at atmospheric pressure). Impedance spectroscopy is a very useful and important technique due to the possibility of using this method for discriminating between grain boundary capacitance ( C gb) and grain boundary resistance ( R gb) contributions. Therefore, a simple model taking into account variations in the intergranular potential barriers is proposed in this work.

Multidimensional gas chromatography with capillary flow technology and LTM‐GC

2-D GC is a logical and cost effective extension to 1-D GC for improving the separation resolution, selectivity, and peak capacity of an analytical system. The advent of electronic pressure control systems that are accurate to the third decimal place, combined with recently innovated chromatographic devices such as capillary flow technology, has eliminated many deficiencies encountered in current conventional 2-D GC by making the technique reliable and simple to implement in both production and research analytical facilities. Low thermal mass GC (LTM-GC) was successfully integrated with capillary flow technology to further enhance overall 2-D GC chromatographic system performance by providing not only faster throughput via rapid heating and cooling, but independent temperature control for each dimension to maximize separation power. As an example, despite the enhanced peak capacity obtained from conventional 2-D GC, alkyl naphthalene isomers such as 2,3-dimethyl and 1,4-dimethyl naphthalene coeluted. These two critical compounds were well resolved (R = 5.2) using 2-D GC with LTM-GC with a similar analytical time. This paper demonstrates the benefits of combining capillary flow technology with LTM-GC to provide major enhancements to conventional 2-D GC. The synergy of these techniques is highlighted with practical industrial applications.

Direct-current cathodic vacuum arc system with magnetic-field mechanism for plasma stabilization

Filtered cathodic vacuum arc (FCVA) deposition is characterized by plasma beam directionality, plasma energy adjustment via substrate biasing, macroparticle filtering, and independent substrate temperature control. Between the two modes of FCVA deposition, namely, direct current (dc) and pulsed arc, the dc mode yields higher deposition rates than the pulsed mode. However, maintaining the dc arc discharge is challenging because of its inherent plasma instabilities. A system generating a special configuration of magnetic field that stabilizes the dc arc discharge during film deposition is presented. This magnetic field is also part of the out-of-plane magnetic filter used to focus the plasma beam and prevent macroparticle film contamination. The efficiency of the plasma-stabilizing magnetic-field mechanism is demonstrated by the deposition of amorphous carbon (a-C) films exhibiting significantly high hardness and tetrahedral carbon hybridization (sp3) contents higher than 70%. Such high-quality films cannot be produced by dc arc deposition without the plasma-stabilizing mechanism presented in this study.

High-throughput reactor system with individual temperature control for the investigation of monolith catalysts

A high-throughput parallel reactor system has been designed and constructed to improve the reliability of results from large diameter catalysts such as monoliths. The system, which is expandable, consists of eight quartz reactors, 23.5 mm in diameter. The eight reactors were designed with separate K type thermocouples and radiant heaters, allowing for the independent measurement and control of each reactor temperature. This design gives steady state temperature distributions over the eight reactors within 0.5 degrees C of a common setpoint from 50 to 700 degrees C. Analysis of the effluent from these reactors is performed using rapid-scan Fourier transform infrared (FTIR) spectroscopic imaging. The integration of this technique to the reactor system allows a chemically specific, truly parallel analysis of the reactor effluents with a time resolution of approximately 8 s. The capabilities of this system were demonstrated via investigation of catalyst preparation conditions on the direct epoxidation of ethylene, i.e., on the ethylene conversion and the ethylene oxide selectivity. The ethylene, ethylene oxide, and carbon dioxide concentrations were calibrated based on spectra from FTIR imaging using univariate and multivariate chemometric techniques. The results from this analysis showed that the calcination conditions significantly affect the ethylene conversion, with a threefold increase in the conversion when the catalyst was calcined for 3 h versus 12 h at 400 degrees C.

Oxidation of methane over a Rh/Al 2O 3 catalyst using microfabricated reactors with integrated heating

Microfabricated reactors with integrated local heating were fabricated for investigating fast exothermic reactions with independent control of temperature and flow rate. As an example, oxidation of methane over a supported rhodium catalyst was investigated. The reaction was studied at different oxygen-to-methane ratios, covering both fuel-lean and fuel-rich compositions with full and partial oxidation. Good agreement with previously reported results indicates that the microfabricated reactors are useful for studying fast exothermic reactions.

Compact extended-cavity diode laser for atomic spectroscopy and metrology

We report on a compact, inexpensive, and durable extended-cavity diode laser (ECDL) of an original mechanical concept. The independent temperature control of a laser diode and an extended cavity provides a low-frequency drift. The linewidth of a few hundred kilohertz was measured by taking a beating of two identical ECDLs. The continuous tuning range of about 1Å is achieved by the synchronous scan of two piezotransducers translating and rotating an external diffraction grating. The laser has been used in high-resolution spectroscopy, atom cooling, metrology, and precise interferometry.

Apparatus for μSR and μLCR experiments on fluids at high pressure and temperature

Apparatus has been developed to perform μSR and μLCR experiments on aqueous solutions at high pressure and high temperature (up to 400 bar, 400 °C). The target sample container is a 30 ml cylinder constructed of titanium alloy, with walls thick enough to withstand these temperature and pressure conditions without distortion, fitted with a specially shaped front window, thin enough to allow backward muons to penetrate and stop completely in the sample volume without reaching the end of the cell. The target and its support have been designed: (1) to fit in the very constrained geometry of the bore of a superconducting magnet; and (2) such that even at the highest rated temperature of the sample, the temperature at the outside surface of the assembly is low enough to accept regular positron plastic scintillators positioned in very close proximity. In addition, the sample cell can be connected to an adjustable ballast volume to accomodate fluid sample expansion, and thus allow independent control of temperature and pressure. With the ability to obtain μLCR data under these temperature and pressure conditions, new radical signals observed by μSR during muon irradiation of acetone can now be assigned unambiguously.

Wavelength monitor integrated laser modules for 25-GHz-spacing tunable applications

Integration of 25-GHz-spacing wavelength monitors into industry standard butterfly laser modules are successfully achieved through the use of a unique optics. The 2-thermoelectric cooler (TEC) design enables independent temperature control of the laser diode and the wavelength monitor, hence eliminating the temperature dependence of the etalon as well as wavelength variation due to temperature variation and aging. As a result of the independent temperature control, narrowband tuning is easily achieved. Results from a series of thorough wavelength stability tests show that the wavelength variation of these laser modules are well within the ITU-T recommended requirement for 25-GHz channel-spacing dense wavelength-division multiplexing (DWDM) applications throughout 25 years of usage.

Simulation and Design for a Tunable Dispersion Compensator Package

A novel optical model for a tunable dispersion compensator is realized by a deliberate packaging scheme ensuing from intensive interactions of mechanical design, materials science and numerical simulation techniques including computational fluid dynamics and finite element analysis. The compensator is comprised of multiple cascaded single cavity Gires-Tournois etalons, each under independent temperature control. Three critical issues are addressed: etalon temperature uniformity, thermal insulation and optical surface deformation of the etalons. With etalon optical surface deformation minimized and etalon temperature uniformity successfully controlled within a range of /spl plusmn/0.1/spl deg/C, this small (232 /spl times/ 139 /spl times/ 16 mm) compensator achieves extremely low group delay ripple (<2.0 ps), low insertion loss ripple (<0.5 dB, insertion loss <6.3 dB), low polarization dependent loss [(PDL),<0.15 dB] and low polarization mode dispersion [(PMD),<0.7 ps]. The dispersion tuning range is from -700 ps/nm to +700 ps/nm in a dispersion passband of 0.2 nm which is sufficient for 10-Gb/s transmission. Thermal insulation design makes the tuning process take effect within 1 min at maximum power consumption 5 W.

Development of a continuous generation/supply system of highly concentrated ozone gas for low-temperature oxidation process

A system is described which can continuously generate/supply highly concentrated (HC) ozone gas to satisfy the future need for practical low-temperature oxidation. This system comprises four ozone vessels, each with independent temperature control. The system can supply a constant flow of HC ozone gas by allocating one of four modes of operation, i.e., accumulation/storage, vaporization (supply), evacuation, and cooling, to each of the ozone vessels so that all the modes can be simultaneously addressed. The maximum flow rate is 60 sccm with a flux stability of ±1.1%, and an ozone concentration of over 99.5 vol % can be achieved at the system outlet. The system was applied to the formation of an ultrathin SiO2 film on a 4 in. diameter silicon wafer substrate.

Independent control of lower critical solution temperature and swelling behavior with pH for poly(N-isopropylacrylamide-co-maleic acid)

Polymer solutions that gel in response to changes in temperature and pH are of interest for various forms of drug delivery, and it is desirable to increase swelling for diffusion-controlled release without bringing the lower critical solution temperature (LCST) above 37°C. N-isopropylacrylamide (NIP) was polymerized with maleic acid (MAc), a diprotic acid, and acrylic acid (AAc), a monoprotic acid, to compare swelling and temperature response with changes in pH. For samples with equal acid contents and almost identical LCST responses to pH, poly(N-isopropylacrylamide-co-maleic acid) (pNIP MAc) demonstrated greater swelling than poly(N-isopropylacrylamide-co-acrylic acid) (pNIP AAc). The LCST increase for MAc occurred at a pH corresponding to the deprotonation of almost all of the first acid groups. Further increases in pH led to the deprotonation of the second COOH and only served to increase the charge concentration at a given location. These results provide strong support for the theory that LCST results largely from uninterrupted chain lengths of NIP and that swelling results from the actual charge density of acid groups along the chain. Because the use of a diprotic acid copolymer allows swelling to be decoupled from LCST, pNIP MAc may be an appropriate candidate for pH-sensitive drug-delivery applications. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2110–2116, 2004

Emissions of Batch Combustion of Waste Tire Chips: The Hot Flue-Gas Filtering Effect

A laboratory investigation was performed on the emissions from the batch combustion of waste tire chips in fixed beds. Techniques and conditions that minimize toxic emissions were identified. Tire-derived fuel (TDF), in the form of waste tire chips (1 cm in size), was burned in a two-stage combustor. Batches of tire chips were introduced to the primary furnace, where gasification and combustion occurred. The gaseous effluent of this furnace was mixed with streams of additional preheated air in a mixing venturi, and it was then passed through a silicon carbide (SiC) honeycomb wall-flow filter that had been placed inside this furnace. Subsequently, it was channeled into a secondary furnace (afterburner), where further oxidation occurred. The arrangement of the two furnaces in series allowed for independent temperature control; varying the temperature in the primary furnace influenced the type and the flux of pyrolysates. The hot-flue-gas filtering section, ahead of the exit of the primary furnace, allowed the retention and further oxidation of most of the generated particulates and, thus, prevented them from entering the afterburner. Results showed that the combination of the high-temperature ceramic filter with the afterburner treatment was successful in reducing the emissions from the combustion of waste tires. Depending on the temperature of the primary furnace, the final emissions of CO were reduced by factors of 2−6, NOx emissions were reduced by factors of 2−3, particulate emissions were reduced by 2 orders of magnitude (both PM2.5 and PM10), and most individual polycyclic aromatic hydrocarbon (PAH) species emissions were reduced by more than 1 order of magnitude, with the exception of naphthalene, whose reduction was less drastic. The overall combustion effectiveness was enhanced, as evidenced by higher CO2 yields.

Particle Temperature and Velocity Effects on the Porosity and Oxidation of an HVOF Corrosion-Control Coating

Independent control of particle velocity and temperature in the HVOF process has been achieved in this research, allowing these variables to change by 170 m/s and 200 °C, respectively. The independence was achieved using a specially designed nozzle with multiple powder injection ports and by an inert diluent added to the oxygen stream feeding the combustion. Within the available range, notable changes in splat morphology, porosity, and coating oxidation of sprayed 316L stainless steel are readily apparent. Increased particle velocity generally correlates with improved splat deformation but has a weak effect on porosity and no effect on oxidation. Particle temperature, on the other hand, correlates strongly with highly deformed splats, porosity, and oxidation. In fact, highly dense coatings having little oxidation can be formed with relatively low velocity particles if the average particle temperature is kept in the vicinity of the material melting point. This result suggests that particle temperature control is the key to creating dense, low-oxide HVOF-sprayed corrosion-control coatings. Because commercial HVOF equipment currently lacks this capability, the research indicates a useful direction for future development.

Effectiveness of the Cobra aortic catheter for dual-temperature management during adult cardiac surgery

Objectives: In animals the Cardeon Cobra catheter (Cardeon Corp, Cupertino, Calif) allows independent control of aortic arch and descending aortic temperatures and profoundly reduces cerebral embolization during bypass. This investigation describes the first clinical use of the device during adult cardiac surgery. The purpose of the study was to confirm that the Cobra catheter delivers adequate cerebral and systemic perfusion while providing simultaneous cerebral hypothermia and systemic normothermia during cardiopulmonary bypass. Methods: In a prospective multicenter study the Cobra aortic catheter was placed in 20 adults undergoing cardiopulmonary bypass. Arch and corporeal temperatures, bypass flows, and arterial blood pressures were recorded intraoperatively. Jugular bulb and mixed venous oxygen saturation was used to assess the adequacy of cerebral and systemic perfusion. Results: Surgeons at 3 institutions placed the Cobra catheter in patients undergoing coronary artery bypass grafting (n = 13), valve (n = 3), and combined valve-bypass (n = 4) operations. Mean total bypass flows of 2.1 ± 0.2 L · min−1 · −2 maintained mean arterial pressures in arch and descending aortic circulations of greater than 55 mm Hg. A mean differential of 4.3°C between arch and descending aortic temperatures was established before crossclamp application, and a mean maximum temperature differential of 7°C was established during bypass. A 2.4°C temperature differential was maintained at crossclamp removal. Cerebral and systemic venous oxygen saturation remained greater than 65% during bypass. Conclusions: The Cobra device met all expectations for an arterial cannula with adequate perfusion to the arch and corporeal circulations. Dual perfusion with the Cobra catheter allows for independent temperature control during cardiopulmonary bypass with simultaneous cerebral hypothermia and systemic normothermia.J Thorac Cardiovasc Surg 2003;125:378-84

Emissions of Batch Combustion of Waste Tire Chips: The Afterburner Effect

A laboratory investigation was performed on the emissions from batch combustion of waste tire chips in fixed beds to identify techniques and conditions that minimize toxic emissions. Tire derived fuel (TDF), in the form of waste tire chips (1 cm), was burned in a two-stage combustor. Batches of tire chips were introduced to the primary furnace where gasification and oxidative pyrolysis took place. The gaseous effluent of this furnace was mixed with streams of additional air and, subsequently, it was channeled into the secondary furnace (afterburner) where further oxidation took place. The arrangement of two furnaces in series allows for independent temperature control; varying the temperature in the primary furnace influences the type and the flux of pyrolysates. The additional-air mixing section between the two furnaces allows for mostly heterogeneous and fuel-lean combustion in the afterburner. Results showed that both the operating temperature of the primary furnace, in the range of 500-1000 °C, and the existence of the afterburner had marked influences on the emissions of pollutants. Results showed that for this fuel use of combustion staging, with an additional-air mixing section, had a very beneficial effect. It drastically reduced the emissions of CO (by factors of 3-10), the particulates (by factors of 2-5) and the cumulative PAH (by factors of 2-3). Many health-hazardous PAH components were practically eliminated. Overall oxidizing conditions prevailed and the minimum oxygen mole fraction never fell below 2% in the effluent of either furnace. The operating primary furnace temperature (pyrolysis temperature) also proved to be important, with temperatures at the low side of the 500-1000 °C range producing fewer pollutants, upon treatment in the afterburner.

Wafer temperature measurements during dielectric etching in a MERIE etcher

Using both chemical phase change and wireless thermistor temperature measurement techniques, wafer temperatures were measured during plasma processing in a MERIE dielectric etch tool. An inorganic low-k dielectric etch process was studied first, and many parameters were varied to determine their effect on wafer temperature. Wafer temperature rose rapidly when the plasma was turned on, approaching a stable temperature after about 30 s. When the lower electrode temperature setpoint or the rf power setting was increased, wafer temperature increased linearly. Wafer temperature decreased as backside He cooling pressure was increased. A dual-zone electrostatic chuck allowed separate control of center and edge He pressure, and these pressures were varied individually or together. Temperature measurements indicated that the zones give reasonably independent control of center and edge wafer temperature. Wafer temperature throughout a complete organic low-k dielectric stack etch process was also measured.