Large-volume Chamber Research Articles

The Yubileinoe Porphyry Gold–Copper Deposit (Western Kazakhstan): Geological Position and Conditions of Formation

In the Uralian Fold Belt, there are quite numerous and well-studied porphyry copper (±Mo) deposits corresponding to the traditional “diorite” (most) or “monzonite” (Talitsa, Verkhneuralskoe) models. Along with them, there are relatively small but gold-rich massifs of porphyric granitoids, including the large Yubileinoe porphyry Au–Cu deposit, which is located at the southernmost extremity of the Urals. In this study, two main types of regional hydrothermal–metasomatic alteration were distinguished based on applying quantitative petrography and areal multielement geochemical studies in the scale of the ore district: (1) an earlier synvolcanic secondary alteration of volcanics, similar to those observed in volcanic massive sulfide-bearing fields (albitization, propylitic, and listvenitic alteration) and (2) a later plutonogenic alteration of the porphyry type. The plutonogenic hydrothermal–metasomatic (HM) complex is represented by K-feldspathization, hornfels and skarn alteration at the progressive phase, and propylitization, sericitization, and beresitization at the regressive phase. They are caused by hydrothermal alteration in the apical part of the stock, composed of the mineralizing Frasnian granite porphyry complex that hosts the Yubileinoe gold deposit. A lateral series of geochemical zonality (from the periphery of volcanotectonic structures to their center) has been established for the volcanogenic stage of hydrothermal activity: CrNiCo → PbZnCuCrNi → AuAg (CrNi) → BaAuAg. A large positive anomaly of the lithochalcophilic type was found for the HM plutonogenic complex in the ore field of the Yubileinoe deposit. The concentric zonality of this anomaly is characterized by the development of Ag, W, Sn, Pb, As, and Sb halos at its periphery, and Au, Cu, Bi and Mo at its focus (“core”). The stable and radiogenic isotope geochemical data for most of the porphyry copper deposits of the Urals indicate the predominant mantle source of their rocks and ore matter. Their paleotectonic position is reconstructed as a mature stage of intraoceanic island arcs. Unlike many other porphyry objects in the Urals, the totality of geochemical, isotope–geochemical and geological features of the Yubileinoe deposit indicate the predominantly crustal magma source. According to these features, this deposit is closer to Andean-type porphyry deposits, and its position can be reconstructed as an active margin of the Mugodzhar microcontinent, i.e., a suprasubduction regime, transitional from a mature island arc to the marginal continental one. According to the complex of features, this deposit in the Urals is a close analogue of the porphyry gold deposits of the Maricunga Belt in Chile. The magmatic complexes from the Silurian (Wenlock) to the Devonian (Frasnian) age, which are parental to the porphyry gold–copper systems of the Urals, correspond to the early phase of the Wilson cycle. This phase is the most ore-productive with the formation of giant Cr and Fe–Ti–V deposits associated with ultramafic–mafic complexes. It is likely that the differentiation of mafic magmas in the large-volume chambers occurring in the lower part of the lithosphere causes the appearance (as an extreme member) of diorite melts with a noticeable enrichment in gold and copper.

Controlled-release testing of the static chamber methodology for direct measurements of methane emissions

Abstract. Direct measurements of methane emissions at the component level provide the level of detail necessary for the development of actionable mitigation strategies. As such, there is a need to understand the magnitude of component-level methane emission sources and to test methane quantification methods that can capture methane emissions at the component level used in national inventories. The static chamber method is a direct measurement technique that has been applied to measure large and complex methane sources, such as oil and gas infrastructure. In this work, we compile methane emission factors from the Intergovernmental Panel on Climate Change (IPCC) Emission Factor Database in order to understand the magnitude of component-level methane flow rates, review the tested flow rates and measurement techniques from 40 controlled-release experiments, and perform 64 controlled-release tests of the static chamber methodology with mass flow rates of 1.02, 10.2, 102, and 512 g h−1 of methane. We vary the leak properties, chamber shapes, chamber sizes, and use of fans to evaluate how these factors affect the accuracy of the static chamber method. We find that 99 % of the component-level methane emission rates from the IPCC Emission Factor Database are below 100 g h−1 and that 77 % of the previously available controlled-release experiments did not test for methane mass flow rates below 100 g h−1. We also find that the static chamber method quantified methane flow rates with an overall accuracy of +14/-14 % and that optimal chamber configurations (i.e., chamber shape, volume, and use of fans) can improve accuracy to below ±5 %. We note that smaller chambers (≤20 L) performed better than larger-volume chambers (≥20 L), regardless of the chamber shape or use of fans. However, we found that the use of fans can substantially increase the accuracy of larger chambers, especially at higher methane mass flow rates (≥100 g h−1). Overall, our findings can be used to engineer static chamber systems for future direct measurement campaigns targeting a wide range of sources, including landfills, sewerage utility holes, and oil and natural gas infrastructure.

Experimental investigation of burning characteristics of porous combustible soaked in liquid oxidizer

Experimental investigations of burning characteristics of a tested specimen consisting of a polyethylene foam soaked in 100 wt% hydrogen peroxide are made. All experiments are carried out in a large volume chamber, which newly introduced in our previous work at an initial pressure range from p = 0.1 to p = 0.35 MPa in absolute with various fuel porosity range from ε = 0.6 to ε = 0.9, which corresponds to global equivalence ratios from φ = 0.51 to φ = 3.8. Temperature measurements using an R-type thermocouple embedded into the specimen are then conducted to investigate thermal structure (e.g., profiles of temperature and temperature gradients and burning surface temperature) of the burning specimen for deep understandings of the burning process. Following forced ignition at top surface of the specimen, steady successive-burning process is successfully observed for all conditions studied in this work. Burning rates (a rate at which the top surface moves downward) are measured by carefully tracking the top surface of the specimen by adopting an image processing software. Findings show that overall burning rates at the rate from 1 to 3.2 mm/s are obtained and influenced by pressure and the fuel porosity. Additionally, results of the direct temperature measurements reveal that the temperature gradient in the gas-phase layer near the top surface (burning surface) of the specimen increases as pressure increases, resulting in an increase in the overall burning rate. The top surface temperature and its pressure dependency, and a global activation energy at the top surface temperature of the specimen are experimentally measured accordingly.

Collar Properties and Measurement Time Confer Minimal Bias Overall on Annual Soil Respiration Estimates in a Global Database

AbstractMeasuring the soil‐to‐atmosphere carbon dioxide (CO2) flux (soil respiration, RS) is important to understanding terrestrial carbon balance and to forecasting climate change. Such measurements are frequently made using measurement collars permanently inserted into the soil surface. However, differences in measurement duration and frequency, as well as collar properties, may lead to biases in the estimation of annual RS. Using a newly updated global RS database (SRDB‐V5), we investigated the annual RS bias associated with five methodological factors: collar height, collar coverage area, collar insertion depth, measurement duration, and measurement frequency. We found that annual RS was negatively correlated with collar insertion depth, consistent with the idea that collar insertion cuts roots and thus reduces RS. Annual RS was also negatively related with collar height and collar coverage area, perhaps because uniform head‐space mixing is difficult to achieve in larger volume chambers; however, these effects were quantitatively small (bias of ~2% to 10% of mean RS). We found no correlation of measurement duration or measurement frequency with annual RS. These findings suggest that variation in RS methodology generally introduces minimal bias overall. Therefore, compilations of minimally adjusted annual RS measurements provide a reliable resource for synthesis studies, global annual RS modeling, and investigation of how soil carbon responds to climate change.

PIII Treatment of SS Samples Using a Current-Controlled High-Voltage Pulser

Plasma immersion ion implantation (PIII) was conducted in a large volume chamber with a current-controlled high-voltage pulser, to test the vacuum, plasma, and PIII conditions, in a preparation for the treatments of large workpieces or the batch-processing mode. For that purpose, a rugged high-power pulser (10 kW average) based on solid-state moderate voltage pulse system (1 kV) was coupled to a high-voltage transformer (1:22) to feed different loaded sample supports placed in different positions inside the chamber. It was found that the plasma, when produced by a hot filament enhanced glow discharge source, is not uniformly distributed in the chamber but despite that, implantation doses are locally uniform within 10% for 10-15-cm distances, along with the supports. Stainless steel 304 (SS304) -type samples were successfully treated with nitrogen PIII and different tests showed improvements on their mechanical and tribological properties.

Comparison of open chamber and pre-chamber ignition of methane/air mixtures in a large bore constant volume chamber: Effect of excess air ratio and pre-mixed pressure

Natural gas is an alluring choice to substitute the widely used diesel for environmental and economic reasons as it generates less particulate matter and carbon dioxide emissions. However, natural gas is comparatively difficult to be ignited and its flame penetrates slowly in a large bore combustion chamber especially for the lean condition. In order to analyze how the pre-chamber turbulent jet ignition promotes combustion in a large volume chamber, a comparative study with the traditional open chamber ignition mode was conducted to analyze the effect of excess air ratios and pre-mixed pressures on the combustion characteristics of methane/air mixtures. In rich fuel combustion, the advantage of pre-chamber is not obvious, and the flame propagation rate can only be increased by 2.8 times in maximum. In the case of lean combustion and stoichiometric combustion, the flame propagation speeds can be increased by 5–6 times, especially in lean combustion by pre-chamber. In general, the pre-chamber turbulent jet ignition technique can increase the flame propagation rate of methane/air, and improve combustion and thermal efficiency of natural gas large-bore engines under lean combustion conditions. With comparison to the open chamber ignition mode, the reduction percentage of ignition time by pre-chamber turbulent jet ignition decreases with the rise of initial pressure. However, the asymmetric placement of the spark plug inside the pre-chamber, results in the inhomogeneous spreading of flame jets in the constant volume chamber, which ought to be considered in the design of marine engine.

Experimental study on spray and atomization characteristics under subcritical, transcritical and supercritical conditions of marine diesel engine

In this research, detailed characteristics of diesel spray and atomization based on marine engine scale have been studied under subcritical, transcritical and supercritical conditions. A large constant volume chamber with an inner diameter of 300 mm and a 300 μm single-nozzle injector are used to mimic the in-cylinder thermodynamic condition of marine diesel engine. Sub/trans/supercritical conditions are composed of nine cases by means of different diesel phase transition regions. Optical diagnostic measurements are conducted through backlight illumination technology and schlieren imaging technology in an inert atmosphere. The images are processed with multi-threshold technique to obtain quantitative spray parameters, such as jet and liquid penetrations, averaged lengths, liquid steady time, spray cone angles and R-parameter. Moreover, some new finding about the structure of spray under supercritical condition is also discussed. The results show that the spray liquid periphery is quite smooth and stable with shorter penetration under supercritical condition, meanwhile, the jet of spray behaves as thinner periphery near the injector nozzle region and shows lower density at downstream region. Higher ambient pressure produces a negative effect on the increase of the tip velocity and development of spray. With the transition from transcritical condition to supercritical condition, the liquid length decreases by 32 mm and there exists an obvious decrease of 35 mm from jet length to liquid length. A trade-off relationship between the jet cone angle and jet penetration is also found. Generally, this work is helpful to understand the detailed process of diesel atomization under transcritical and supercritical conditions.

Effect of the volume of methane released into respiration chambers on full system methane recovery

The respiration chamber method is considered to be the most precise approach for measuring enteric methane emissions in cattle. A set of experimental runs was carried out in which increasing volumes of pure methane (168.5, 194.9, 234.9, 264.9, 301.0, 339.8, and 375.7 L per run) were gravimetrically released into open-circuit respiration chambers to simulate the volumes of methane eructated by cattle of different weights. The aim was to assess the effect of the volume of methane released into the chambers on percentage of methane recovered at the exit by the infrared methane analyzer. It was found that as the volume of methane released into the respiration chambers was decreased, methane recovery percentages were concomitantly reduced. The recovery percentages ranged from 103.7% down to 18.3% and from 102.7% down to 31.6% for chambers one and two, respectively. It can be concluded that the slow stabilization of methane inside the large volume chamber, when injected at low rates from the cylinder, led to low recoveries of the gas at an air extraction rate of 300 L/min. As a result, the recovery of methane was constrained, leading to underestimation of the actual volumes released from the pure methane cylinders. Poor mixing of air inside the chambers did also constrain the recovery of methane with the experimental approach employed. The possible implications for methane measurements in respiration chambers under in vivo conditions with cattle are discussed.

Investigation of the conditions for the formation of SiCN-based coatings in arc discharge with self-heated hollow cathode

Method for low-temperature (<200°C) deposition of SiCN-based coatings in a large volume chamber (0.3 m3) by decomposition of organosilicon precursor in nitrogen-argon plasma of discharge with self-heated hollow cathode and remote anode (40 cm) at pressure of ~1 mTorr was investigated. The analysis of the composition of coatings by IR spectroscopy and the analysis of plasma composition are carried out by optical emission spectroscopy. The influence of discharge current (10-40 A) and the flow of gas mixture (5-15 sccm hexamethyldisilazane and 60 sccm Ar-N2 mixture) on plasma composition and elemental composition of coatings was investigated. It is shown that the degree of decomposition of precursor molecules is increased with growth of the current and with increase of Ar content in the gas mixture.

Blast-Induced Traumatic Brain Injury Triggered by Moderate Intensity Shock Wave Using a Modified Experimental Model of Injury in Mice.

Background:The increasing frequency of explosive injuries has increased interest in blast-induced traumatic brain injury (bTBI). Various shock tube models have been used to study bTBI. Mild-to-moderate explosions are often overlooked because of the slow onset or mildness of the symptoms. However, heavy gas cylinders and large volume chambers in the model may increase the complexity and danger. This study sought to design a modified model to explore the effect of moderate explosion on brain injury in mice.Methods:Pathology scoring system (PSS) was used to distinguish the graded intensity by the modified model. A total of 160 mice were randomly divided into control, sham, and bTBI groups with different time points. The clinical features, imaging features, neurobehavior, and neuropathology were detected after moderate explosion. One-way analysis of variance followed by Fisher's least significant difference posttest or Dunnett's t 3-test was performed for data analyses.Results:PSS of mild, moderate, and severe explosion was 13.4 ± 2.2, 32.6 ± 2.7 (t = 13.92, P < 0.001; vs. mild group), and 56.6 ± 2.8 (t = 31.37, P < 0.001; vs. mild group), respectively. After moderate explosion, mice showed varied symptoms of malaise, anorexia, incontinence, apnea, or seizure. After bTBI, brain edema reached the highest peak at day 3 (82.5% ± 2.1% vs. 73.8% ± 0.6%, t = 7.76, P < 0.001), while the most serious neurological outcomes occurred at day 1 (Y-maze: 8.25 ± 2.36 vs. 20.00 ± 4.55, t = −4.59, P = 0.048; 29.58% ± 2.84% vs. 49.09% ± 11.63%, t = −3.08, P = 0.008; neurologic severity score: 2.50 ± 0.58 vs. 0.00 ± 0.00, t = 8.65, P = 0.016). We also found that apoptotic neurons (52.76% ± 1.99% vs. 1.30% ± 0.11%, t = 57.20, P < 0.001) and gliosis (2.98 ± 0.24 vs. 1.00 ± 0.00, t = 14.42, P = 0.021) in the frontal were significantly higher at day 3 post-bTBI than sham bTBI.Conclusions:We provide a reliable, reproducible bTBI model in mice that can produce a graded explosive waveform similar to the free-field shock wave in a controlled laboratory environment. Moderate explosion can trigger mild-to-moderate blast damage of the brain.

Introduction of a New Baffle-Plate Concept to Control the Gas Flow Behavior in a Large Volume PECVD Chamber

Achieving a reasonable homogeneity of the coating deposition rate within a low-pressure plasma process is a challenge, especially in large volume chambers. The local gas flow behavior is one key parameter in the coating deposition. Basically, with the exception of the product geometry and the electrode design, there are two main influences on the gas flow distribution inside a large volume chamber: 1) gas feed-in system and 2) gas exhaustion system. This work focuses on the gas exhaustion system with the aim to reduce its influence on the gas flow behavior inside a large plasma coater. In this sense, a solution with a perforated plate, named “Baffle-Plate”, is created. Thereby relevant construction parameters are identified and investigated to understand their influence in respect to the homogeneity of the gas exhaustion. Number of holes, hole diameter, distance of the Baffle-Plate to the top of the chamber, gas flow and chamber volume are evaluated parameters. Computational fluid dynamics (CFD) simulations are used as a tool to determine velocity and pressure distribution inside the PECVD-chamber and, consequently, to evaluate the layout parameters of the Baffle-Plate. Additionally, practical coating experiments with and without the Baffle-Plate installed are performed. The results show a correlation between the gas flow distribution and the homogeneity of the coating deposition rate. With these results construction guidelines have been formulated. Hence in future developments correct technical layouts of the Baffle-Plate can be applied, easily.

High pressure pulsed electric current activated equipment (HP-SPS) for material processing

An innovative new system under high pressure syntheses activated by pulsed electric current (HP-SPS) was designed and built in-house with belt type apparatus (HP-SPS-Belt). This new HP-SPS- Belt with large volume chamber is capable of reaching high pressures up to 6GPa and temperatures until 1800°C. This system was pressure and temperature calibrated by using different metal calibrants. To demonstrate the efficiency of this new equipment in the present work, we have successfully shown the structural γ to α phase transformation in alumina under less severe conditions than in conventional high pressure and temperature processes. Further, we have also used this new HP-SPS-Belt to fabricate shear cutter for drilling bits in an economical way of fabrication. This study shows the wide interest of our unique designed equipment for various applications in materials processing to better control their microstructure and their properties.

Impact of droplet evaporation rate on resulting in vitro performance parameters of pressurized metered dose inhalers

Pressurized metered dose inhalers (pMDIs) are widely used for the treatment of pulmonary diseases. The overall efficiency of pMDI drug delivery may be defined by in vitro parameters such as the amount of drug that deposits on the model throat and the proportion of the emitted dose that has particles that are sufficiently small to deposit in the lung (i.e., fine particle fraction, FPF). The study presented examines product performance of ten solution pMDI formulations containing a variety of cosolvents with diverse chemical characteristics by cascade impaction with three inlets (USP induction port, Alberta Idealized Throat, and a large volume chamber). Through the data generated in support of this study, it was demonstrated that throat deposition, cascade impactor deposition, FPF, and mass median aerodynamic diameter of solution pMDIs depend on the concentration and vapor pressure of the cosolvent, and the selection of model throat. Theoretical droplet lifetimes were calculated for each formulation using a discrete two-stage evaporation process model and it was determined that the droplet lifetime is highly correlated to throat deposition and FPF indicating that evaporation kinetics significantly influences pMDI drug delivery.

SU-G-TeP1-03: Beam Quality Correction Factors for Linear Accelerator with and Without Flattening Filter

Purpose: The impact of removing the flattening filter on absolute dosimetry based on IAEA's TPR-398 and AAPM's TG-51 was investigated in this study using Monte Carlo simulations. Methods: The EGSnrc software package was used for all Monte Carlo simulations performed in this work. Five different ionization chambers and nine linear accelerator heads have been modeled according to technical drawings. To generate a flattening filter free radiation field the flattening filter was replaced by a 2 mm thick aluminum layer. Dose calculation in a water phantom were performed to calculate the beam quality correction factor kQ as a function of the beam quality specifiers %dd(10)x, TPR20,10 and mean photon and electron energies at the point of measurement in photon fields with (WFF) and without flattening filter (FFF). Results: The beam quality correction factor as a function of %dd(10)x differs systematically between FFF and WFF beams for all investigated ionization chambers. The largest difference of 1.8% was observed for the largest investigated Farmer-type ionization chamber with a sensitive volume of 0.69 cm3. For ionization chambers with a smaller nominal sensitive volume (0.015 – 0.3 cm3) the deviation was less than 0.4% between WFF and FFF beams for %dd(10)x > 62%. The specifier TPR20,10 revealed only a good correlation between WFF and FFF beams (< 0.3%) for low energies. Conclusion: The results confirm that %dd(10)x is a suitable beam quality specifier for FFF beams with an acceptable bias. The deviation depends on the volume of the ionization chamber. Using %dd(10)x to predictkQ for a large volume chamber in a FFF photon field may lead to not acceptable errors according to the results of this study. This bias may be caused by the volume effect due to the inhomogeneous photon fields of FFF linear accelerators.

Attenuating characteristics of a multi-element buffer bottle in an aircraft piston pump

Pressure pulsation of an aircraft piston pump and accompanying vibrations are often sources of unreliability and fatigue of an aircraft hydraulic energy system. To reduce discharge pressure pulsation, a buffer bottle is usually installed inside the pump for space consideration that generally restricts its chamber volume resulting in a high working frequency range usually well exceeding the pressure pulsation frequencies corresponding to the normal operating speed range of the pump and hard to be adjusted once installed. To meet this challenge, this paper presents a method for designing a multi-element buffer bottle as an integrated fluid filter network formed by sub-elemental circuits (consisting of orifice, pipe and T-off) that can be assembled in an aircraft piston-pump. This design method of a compact fluid filter network is illustrated with a practical example based on a multi-element buffer bottle. Based on impedance models, results of an in-depth numerical investigation analyzing the effects of different buffer-bottle designs, geometrical parameters and adjustable orifice dimensions on pressure pulsation attenuation are discussed. The method for tuning the operating resonant frequency of a multi-element buffer bottle for pressure attenuation using a changeable orifice diameter is demonstrated experimentally confirming the buffer bottle as an attractive alternative to the conventional methods based on large-volume chambers.

Technical Note: Influence of Compton currents on profile measurements in small-volume ion chambers.

This work is to evaluate the effects of Compton current generation in three small-volume ionization chambers on measured beam characteristics for electron fields. Beam scans were performed using Exradin A16, A26, and PTW 31014 microchambers. Scans with varying chamber components shielded were performed. Static point measurements, output factors, and cable only irradiations were performed to determine the contribution of Compton currents to various components of the chamber. Monte Carlo simulations were performed to evaluate why one microchamber showed a significant reduction in Compton current generation. Beam profiles demonstrated significant distortion for two of the three chambers when scanned parallel to the chamber axis, produced by electron deposition within the wire. Measurements of ionization produced within the cable identified Compton current generation as the cause of these distortions. The size of the central collecting wire was found to have the greatest influence on the magnitude of Compton current generation. Microchambers can demonstrate significant (>5%) deviations from properties as measured with larger volume chambers (0.125 cm(3) and above). These deviations can be substantially reduced by averaging measurements conducted at opposite polarities.

Sterilization of Medical Devices Using Low Pressure N2/O2 Mixed Gas Plasma

Working at gas pressures in the 400-700 Pa range ensures, through species diffusion the uniform filling of large volume chambers with the species out flowing from the discharge possibly allowing batch processing within them. As a rule bacterial endospores are used as a biological indicator (BI) to validate sterilization processes. Under the present operating conditions Geobacillus stearothermophilus ATCC 7953 is found to be the most resistant one and is therefore utilized as BI.

Extracted ion current density in close-coupling multi-antenna type radio frequency driven ion source: CC-MATIS

Positive ions are extracted by using a small extractor from the Close-Coupling Multi-Antenna Type radio frequency driven Ion Source. Two types of RF antenna are used. The maximum extracted ion current density reaches 0.106 A/cm(2). The RF net power efficiency of the extracted ion current density under standard condition is 11.6 mA/cm(2)/kW. The efficiency corresponds to the level of previous beam experiments on elementary designs of multi-antenna sources, and also to the efficiency level of a plasma driven by a filament in the same chamber. The multi-antenna type RF plasma source is promising for all metal high density ion sources in a large volume chamber.

Sterilization/disinfection of medical devices using plasma: the flowing afterglow of the reduced-pressure N2-O2discharge as the inactivating medium

Potential sterilization/disinfection of medical devices (MDs) is investigated using a specific plasma process developed at the Université de Montréal over the last decade. The inactivating medium of the microorganisms is the flowing afterglow of a reduced-pressure N2-O2 discharge, which provides, as the main biocidal agent, photons over a broad ultraviolet (UV) wavelength range. The flowing afterglow is considered less damaging to MDs than the discharge itself. Working at gas pressures in the 400—700 Pa range (a few torr) ensures, through species diffusion, the uniform filling of large volume chambers with the species outflowing from the discharge, possibly allowing batch processing within them. As a rule, bacterial endospores are used as bio-indicators (BI) to validate sterilization processes. Under the present operating conditions, Bacillus atrophaeus is found to be the most resistant one and is therefore utilized as BI. The current paper reviews the main experimental results concerning the operation and characterization of this sterilizer/disinfector, updating and completing some of our previously published papers. It uses modeling results as guidelines, which are particularly useful when the corresponding experimental data are not (yet) available, hopefully leading to more insight into this plasma afterglow system. The species flowing out of the N2-O2 discharge can be divided into two groups, depending on the time elapsed after they left the discharge zone as they move toward the chamber, namely the early afterglow and the late afterglow. The early flowing afterglow from a pure N2 discharge (also called pink afterglow) is known to be comprised of N2+ and N4+ ions. In the present N2-O2 mixture discharge, NO+ ions are additionally generated, with a lifetime that extends over a longer period than that of the nitrogen molecular ions. We shall suppose that the disappearance of the NO+ ions marks the end of the early afterglow regime, thereby stressing our intent to work in an ion-free process chamber to minimize damage to MDs. Therefore, operating conditions should be set such that the sterilizer/disinfector chamber is predominantly filled by N and O atoms, possibly together with long-lived metastable-state O2(1 Δg) (singlet-delta) molecules. Various aspects related to the observed survival curves are examined: the actual existence of two “phases” in the inactivation rate, the notion of UV irradiation dose (fluence) and its implications, the UV photon best wavelength range in terms of inactivation efficiency, the influence of substrate temperature and the reduction of UV intensity through surface recombination of N and O atoms on the object/packaging being processed. To preserve their on-shelf sterility, MDs are sealed/wrapped in packaging material. Porous packaging materials utilized in conventional sterilization systems (where MDs are packaged before being subjected to sterilization) were tested and found inadequate for the N2-O2 afterglow system in contrast to a (non-porous) polyolefin polymer. Because the latter is non-porous, its corresponding pouch must be kept unsealed until the end of the process. Even though it is unsealed, but because the opening is very small the O2(1Δg) metastable-state molecules are expected to be strongly quenched by the pouch material as they try to enter it and, as a result, only N and O atoms, together with UV photons, are significantly present within it. Therefore, by examining a given process under pouch and no-pouch conditions, it is possible to determine what are the inactivating agents operating: (i) when packaged, these are predominantly UV photons, (ii) when unpackaged, O2(1Δg) molecules together with UV photons can be acting, (iii) comparing the inactivation efficiency under both packaged and unpackaged conditions allows the determination of the relative contribution of UV photons (if any) and O2(1Δg) metastable-state molecules. Such a method is applied to pyrogenic molecules and to the enzymatic activity of lysozyme proteins once exposed to the N2-O2 flowing afterglow. Finally, the activity of the infectious prion protein is shown to be reduced when exposed to the present flowing afterglow, as demonstrated by both in vitro and in vivo experiments.

FT-IR Product Study of the Reactions of NO3Radicals Withortho-,meta-, andpara-Cresol

Product analyses of the NO3 radical-initiated oxidation of ortho-, meta-, and para-cresol have been performed in large-volume chamber systems at the University of Wuppertal (1080 L quartz glass reactor: QUAREC) and the European Photoreactor (EUPHORE), Valencia, Spain. The reaction of O3 with NO2 was used for the in situ generation of NO3 radicals in both QUAREC and EUPHORE. In the QUAREC experiments the gas-phase reaction of ortho-cresol isomer with NO3 yielded (11.5 ± 0.8) % 6-methyl-2-nitrophenol (6M2NP), (4.4 ± 0.3) % methyl-1,4-benzoquinone (MQUIN) and (77.2 ± 6.3) % HNO3. The reaction of NO3 radicals with meta-cresol yielded (21.2 ± 1.4) % 3-methyl-2-nitrophenol (3M2NP), (22.8 ± 1.8) % 3-methyl-4-nitrophenol (3M4NP), (23.5 ± 1.8) % 5-methyl-2-nitrophenol (5M2NP), (4.2 ± 0.7) % MQUIN and (72.3 ± 6.4) % HNO3. In the reaction of NO3 radicals with para-cresol, 4-methyl-2-nitrophenol (4M2NP) and HNO3 were identified as products with yields of (41.3 ± 3.7) % and (85.0 ± 10.2) %, respectively. In the EUPHORE chamber not all products were formed at levels above the detection limit, however, in cases where detection was possible similar product yields were observed. The product formation yields determined in both chambers are compared with available literature data and a gas-phase mechanism is proposed to explain the formation of the products observed from the reaction of NO3 and with cresol isomers.