Bar Vacuum Research Articles

Impregnation Effect of Synthesized Fe3O4 Nanoparticles on the Jabon Wood’s Physical Properties

This study focused on characterizing synthetic magnetite (Fe3O4-NP) and evaluating the impregnated jabon wood’s physical properties. The co-precipitation method used for the synthesis of Fe3O4-NP, namely by mixing the iron solution (n/n Fe2+:Fe3+=1:2) with the strong base of sodium hydroxide (NaOH) (MG-S) and weak base of ammonium hydroxide (NH4OH) (MG-W) as precursors. The impregnation stage uses parameters of a -0.5 bar vacuum for half an hour and 2 bar pressure for 2 hours with magnetite concentrations of 1; 2.5; 5% w/v in a demineralized water solvent. Scanning electron microscopy-energy dispersive x-ray spectroscopy (SEM-EDX) and Fourier transform infrared spectrometry (FTIR) confirmed the presence of Ferrum content and Fe-O functional group in both Fe3O4-NPs produced. The Fe3O4-NP size was also measured via the X-ray diffraction analysis, namely 34.54 nm for the MG-S and 39.24 nm for the MG-W. Magnetic strength obtained was 7.51 mT for the MG-S and 8.58 mT for the MG-W. The impregnated jabon wood’s physical properties also improved with indications of an increase in wood density, weight percent gain (WPG), bulking effect (BE), anti-swelling efficiency (ASE), and a decrease in water absorption (WA). The results showed the best treatments were MG-S 2.5% and MG-W 5%.

Coke oven gases processing by vacuum swing adsorption: Carbon capture and methane recovery

Coke oven gas (COG), a by-product gas from the steel industry with great potential for chemical utilization, contains multiple high-value gases including H2, CO2, and CH4. Our previous work has successfully achieved hydrogen production from COG with a purity greater than 99.99 %. For further separation of COG-to-hydrogen tail gas, a two-phase vacuum swing adsorption (VSA) strategy for CO2 capture and CH4 upgrading was carried out in this study. The accuracy of the 4-bed 8-step and 4-bed 7-step cycles established in the in-house mathematical model was verified through a series of multi-component breakthrough and VSA experiments for the two-stage CO2 capture and CH4 upgrading processes employing zeolite NaY and activated carbon RB3, respectively. To achieve more excellent separation performance, several novel VSA cycles were designed and developed in terms of each stage, and the Pareto fronts of purity and recovery of CO2 or CH4 for each cycle were obtained through a multi-objective optimization framework. Based on this, the separation performance and energy consumption of the optimal cycle for each stage were parametrically analyzed under various feed gas concentrations, vacuum pressures, and feed velocities. Moreover, the CO2 product with a purity of 95.58 % and a recovery of 90.11 % can be obtained ultimately by using a 4-bed 8-step cycle for the first stage and a 4-bed 7-step cycle for the second stage of the CO2 capture process under 0.1 bar vacuum pressure. The CH4 upgrading process using a 4-bed 7-step cycle at 0.1 bar vacuum pressure produced a product with 92.07 % purity and 98.81 % recovery. The specific energy consumption was 32.17 kJ/mol and 1.80 kJ/mol for CO2 capture and CH4 upgrading, respectively. Recovery of high-purity CO2 and CH4 at such medium vacuum pressure and low energy consumption through a two-phase VSA strategy from COG has great application potential.

Amine-functionalized MIL-101(Cr) fibers for direct air capture at cold temperatures using rapid temperature vacuum swing adsorption

Given that most of the world shows annual temperatures lower than 25 °C and some regions exhibit a large diurnal temperature difference in a single day, it is desirable to explore the CO2 sorption behavior of materials not only at ambient (25 °C) but also at cooler, “sub-ambient” conditions (defined here as < 25 °C). These cold temperatures may offer advantages for DAC such as higher gas adsorption capacities and lower absolute humidity, reducing concomitant water adsorption. Here, amine-functionalized MIL-101(Cr) fibers are evaluated at cold temperatures using rapid temperature vacuum swing adsorption (RTVSA). MIL-101(Cr)/cellulose acetate fibers loaded with macromolecular amines are evaluated as practical gas–solid contactors. As spun MIL-101(Cr) fibers show desirable properties for use as structured contactors such as high permeance and low pressure drop. Breakthrough and RTVSA experiments are conducted in the presence of humidity at sub-ambient temperatures to understand the CO2 adsorption and desorption behavior of the sorbent/contactor under conditions approaching practical operation. With optimized amine loading, the PEI-MIL-101(Cr) fibers give CO2 capacities comparable to the powder form of the sorbent, as well as sharp breakthrough curves at fast flow rates (1.4 m/s superficial velocity) suggesting the system is not limited by additional mass transfer resistances under the tested conditions. RTVSA shows fast desorption kinetics (14.4 mmol of CO2/g of fiber/h) at moderate desorption conditions, at 0.1 bar vacuum with temperatures below 80 °C. The entire cycle during RTVSA finishes in ∼ 25 min with ∼ 76 mol% CO2 purity as the product in this initial, modestly optimized study.

Enhancing phytochemical parameters in broccoli through vacuum impregnation and their prediction with comparative ANN and RSM models

Amidst increasing demand for nutritious foods, the quest for effective methods to enhance health-promoting attributes has intensified. Vacuum impregnation (VI) is a promising technique to augment produce properties while minimizing impacts on biochemical attributes. In light of broccoli’s growing popularity driven by its nutritional benefits, this study explores the impact of VI using ascorbic acid and calcium chloride as impregnation agents on enhancing its phytochemical properties. Response surface methodology (RSM) was used for optimization of the vacuum impregnation process with Vacuum pressure (0.6, 0.4, 0.2 bar), vacuum time (3, 7, 11 min), restoration time (5, 10, 15 min), and concentrations (0.5, 1.0, 1.5%) as independent parameters. The influence of these process parameters on six targeted responses viz. total phenolic content (TPC), total flavonoid content (TFC), ascorbic acid content (AAC), total chlorophyll content (TCC), free radical scavenging activity (FRSA), and carotenoid content (CC) were analysed. Levenberg–Marquardt back propagated neural network (LMB-ANN) was used to model the impregnation process. Multiple response optimization of the vacuum impregnation process indicated an optimum condition of 0.2 bar vacuum pressure, 11 min of vacuum time, 12 min of restoration time, and 1.5% concentration of solution for vacuum impregnation of broccoli. The values of TPC, TFC, AAC, TCC, FRSA, and CC obtained at optimized conditions were 291.20 mg GAE/100 g, 11.29 mg QE/100 g, 350.81 mg/100 g, 1.21 mg/100 g, 79.77 mg, and 8.51 mg, respectively. The prediction models obtained through ANN was found suitable for predicting the responses with less standard errors and higher R2 value as compared to RSM models. Instrumental characterization (FTIR, XRD and SEM analysis) of untreated and treated samples were done to see the effect of impregnation on microstructural and morphological changes in broccoli. The results showed enhancement in the TPC, TFC, AAC, TCC, FRSA, and CC values of broccoli florets with impregnation. The FTIR and XRD analysis also supported the results.

Optimization of a novel spray flash desalination system integrated with concentrated solar power utilizing response surface methodology

In the present study, the performance of a novel spray flash desalination system integrated with concentrated solar power is experimentally investigated and optimized. The effect of four factors, namely, flow rate (0.2–0.4 LPM), feed water temperature (30–50 °C), salinity (15,000–35,000 PPM), and vacuum pressure (0.1–0.5 bar), was examined on three responses (i.e., condenser exit temperature, boiler exit temperature, and distillate production). Mathematical models are developed for each response, and optimization is performed with Design Expert software using response surface methodology. The results revealed that the feed water temperature and vacuum pressure positively impacted condenser and boiler exit temperatures and vice versa for salinity and flow rate. However, the flow rate, feed water temperature, and vacuum pressure were found to impact the distillate production positively. The optimum factor settings are 0.4 LPM flow rate, 50 °C feed temperature, 15,000 PPM salinity, and 0.5 bar vacuum pressure for optimal condenser exit temperature of 55 °C, boiler exit temperature of 58.8 °C, and distillate 7010 mLPH. The energy and exergy analyses were conducted, and the mean efficiencies were found to be 55.6 % and 2.2 %, respectively.

Fast-Growing Wood-Polymer Nano Composite Characteristics through Nano-SiO2 Impregnation

Ganitri (Elaeocarpus sphaericus (Gaertn.) K. Schum.) and jabon (Anthocephalus cadamba) are fast-growing wood species that have low strength and durability class. One of methods for improving the characteristics of ganitri and jabon woods is impregnation. This study objectives were to analyze the effect of impregnation of Melamine Formaldehyde Furfuryl Alcohol (MFFA) copolymer and 0.5% Nano-SiO2 on the physical, mechanical and durability properties of ganitri and jabon woods. The impregnation process was carried out by applying a 0.5 bar vacuum for 1 hour and followed by 2 bar pressure for 2 hours. The results showed that impregnation with MFFA and Nano-SiO2 could improve optimally the physical and mechanical properties and durability of fast-growing woods

Physical Properties of Impregnated Ganitri Wood by Furfuryl Alcohol and Nano-SiO2

Ganitri wood (Elaeocarpus sphaericus) is a fast-growing wood that has low dimensional stability and density. This study aims were to analyze the effect of Furfuryl Alcohol (FA) and nano-SiO2 impregnation on the dimensional stability and density of ganitri wood and also examine the characteristics of impregnated ganitri wood. Impregnation used three treatments, including untreated (water), FA, and 0.5% FA-SiO2. The impregnation process was initiated by giving a 0.5 bar vacuum for 60 minutes, followed by applying a pressure of 2.5 bar for 120 minutes. Weight percent gain, leachability, anti-swelling efficiency, water uptake, bulking effect, and density were affected by the treatment. It was due to the coverage of FA and nano-SiO2 on vessels of ganitri wood (SEM analysis). Also, the presence of nano-SiO2 in wood treated (SEM-EDX analysis). FT-IR showed there were no FA bonds with ganitri wood cell wall components or between Nano- SiO2 and ganitri wood. The crystallinity of ganitri wood decreases because FA is amorphous and nano-SiO2 is semi-crystalline. The optimum dimensional stability and density were obtained at FA treatment.

Predicting effects of selected impregnation processes on the observed bending strength of wood, with use of data mining models

Wood materials have been used in many products such as furniture, stairs, windows, and doors for centuries. There are differences in methods used to adapt wood to ambient conditions. Impregnation is a widely used method of wood preservation. In terms of efficiency, it is critical to optimize the parameters for impregnation. Data mining techniques reduce most of the cost and operational challenges with accurate prediction in the wood industry. In this study, three data-mining algorithms were applied to predict bending strength in impregnated wood materials (Pinus sylvestris L. and Millettia laurentii). Models were created from real experimental data to examine the relationship between bending strength, diffusion time, vacuum duration, and wood type, based on decision trees (DT), random forest (RF), and Gaussian process (GP) algorithms. The highest bending strength was achieved with wenge (Millettia laurentii) wood in 10 bar vacuum and the diffusion condition during 25 min. The results showed that all algorithms are suitable for predicting bending strength. The goodness of fit for the testing phase was determined as 0.994, 0.986, and 0.989 in the DT, RF, and GP algorithms, respectively. Moreover, the importance of attributes was determined in the algorithms.

Process optimization and energy analysis of vacuum degasifier systems for the simultaneous removal of dissolved methane and hydrogen sulfide from anaerobically treated wastewater

The control of dissolved methane (CH4) and hydrogen sulfide (H2S) emissions in anaerobic effluents is essential for minimizing the environmental implications of greenhouse gases, odor, and carbon footprint, as well as for preventing energy loss in the form of unrecovered dissolved methane. This study assessed the feasibility of a vacuum degasifier for the removal of CH4 and H2S from staged anaerobic fluidized membrane bioreactor (SAF-MBR) effluent. The optimization results showed that the efficiency of the nozzle fitted degasifiers were superior to the media packed ones. In three-stage vacuum degasifiers at a −0.8 bar vacuum pressure, H2S removal was mostly pH dependent and 88% removal efficiency was achieved with an initial concentration of 13.6 mg/L. Methane removal was dependent primarily on the number of degasifier units, and approximately 94% efficiency was achieved in a three-stage degasifier. Energy balance analysis showed that energy production exceeded the system energy requirements with 0.05–0.07 kWh/m3 of surplus energy. These results provide deep insights into this new technology for simultaneous removal of dissolved CH4 and H2S, which can be referred for potential future applications.

Upgrading biogas to biomethane: Alkaline recovery of absorbed solution by thermal decomposition

A process to upgrade a biogas product to biomethane has been investigated. Recycling of an absorbent is important for low-cost upgrading of biogas by chemical absorption. This study investigated the alkaline recovery of absorbent solution by thermal decomposition at various temperatures (75, 85 and 95 °C) and various vacuum levels (0.2, 0.4 and 0.6 bar). During heating, CO2 and H2S were released from the absorbent solution, which increased the pH. The highest pH 10.58 was reached for NaHCO3 solution from initial pH 8.86 when treated at 95 °C and 0.6 bar vacuum level (gauge pressure). The mass fraction of CO32− in the solution increased from 0.06 to 0.78. Experiments on H2S removal from NaHS solution gave the highest pH 10.38 at 95 °C and 0.6 bar vacuum pressure. Moreover, the performance of the recovered alkaline solution was tested in biogas absorption. The results show that CO2 and H2S removal efficiencies of alkaline solution before and after recovery were similar, at 80 and 99 % respectively. This study demonstrated that thermal decomposition has high potential for recovering the alkaline used absorbent, for recirculation back into the absorption process.

Simulation of two-step redox recycling of non-stoichiometric ceria with thermochemical dissociation of CO2/H2O in moving bed reactors – Part II: Techno-economic analysis and integration with 100 MW oxyfuel power plant with carbon capture

This paper presents the model of a solar thermochemical looping CO2/H2O dissociation (CL) unit with commercial ceria as the redox oxygen carrier. The CL unit is integrated in an oxy-fuelled combined cycle power plant as an add-on unit to a 100 MW oxy-fuelled natural gas power plant with carbon capture. The efficiency benefit obtained was investigated. A moving bed counter-current reactor model, developed in ASPEN Plus®, consisting of a series of rigorous continuous stirred reactors (RCSTRs) was used for the simulation of both reduction and oxidation reactors of the CL unit. A kinetic subroutine was developed in FORTRAN and linked with each RCSTR for both reduction and oxidation reactions. It is found that the efficiency of the CL unit varies widely with reduction reactor temperature and operating pressure. Considering three different compositions of the feed gas to the oxidation reactor, the CL unit efficiency is obtained as: 35.41% with CO2 only; 30.84% with H2O only; and 35.26% for a mixture of 86% CO2 and 14% H2O. The lower efficiency for H2O-only operation is due to the heat requirement for water vaporization and the higher compression work required for compressing H2 than CO. The maximum solar to electrical efficiency for the whole add-on unit is found to be 25.44% with a reduction reactor operating at a temperature of 1600 °C and 10−7 bar vacuum pressure. With 0.5 m3 reduction reactor volume and 5 m3 oxidation reactor volume, the maximum net electricity produced by the CL add-on unit is 12.85 MWe. Economic analysis revealed that the major contributors to total plant cost are the hydrogen compressor and solar field and tower, which are the 19% and 39% of the total equipment cost, giving a specific overnight capital cost of 12,136 $/kW with an LCOE of 1321 $/MWh with a capacity factor of 21%. The LCOE drops to 628 $/MWh with a carbon tax of 80 $/tonne of CO2 and increased capacity factor of 26%.

Simulation of two-step redox recycling of non-stoichiometric ceria with thermochemical dissociation of CO2/H2O in moving bed reactors – Part I: Model development with redox kinetics and sensitivity analysis

Chemical looping syngas production is a two-step process that produces CO and H2 from water and CO2 splitting. This is performed by exploiting a metal oxide as oxygen carrier material, which is thermally reduced and releases oxygen in a subsequent step. The core-process layout is composed of two reactors (oxidation reaction and reduction reactor) and oxygen carriers (metal oxides) circulating between the two reactors. A comprehensive moving-bed reactor model is developed and applied to simulate both the syngas production from water and carbon dioxide by ceria oxidation as well as the thermal reduction of metal oxide. An extensive FORTRAN model is developed to appropriately simulate the complexities of ceria reaction kinetics and implemented as subroutine into an ASPEN Plus® reactor model. The kinetics has been validated with the model developed by comparing experimental and simulated data on the reduction reactor. The sensitivity of both the reduction and oxidation reactors have been performed. The reduction reactor temperature and pressure were varied between 1200–1600 °C and 10−3–10−7 bar, respectively. The oxidation reactor was evaluated by varying the inlet temperatures of the reactants as well as the relative gas composition between CO2 and H2O. Results indicate a non-stoichiometry achievable from the reduction of ceria of 0.198 at 1600 °C and 10−7 bar vacuum pressure. In the oxidation reactor, water splitting yields significantly better solid conversion (metal oxide conversion) of 97%, as compared to 91% by CO2 splitting with 5% excess gas flow than the stoichiometric requirements. The metal oxide inlet temperature significantly improves the yield of the oxidation reactor, in contrast to the minimal impact of variation of gas inlet temperature. A selectivity of over 90% can be achieved irrespective of gas composition with over 90% metal oxide conversion in the oxidation reactor.

Fiber-coupled ultrashort-pulse-laser-based electronic-excitation tagging velocimetry.

Transmission of intense ultrashort laser pulses through hollow-core fibers (HCFs) is investigated for molecular-tagging velocimetry. A low-vacuumed HCF beam-delivery system is developed to transmit high-peak-power pulses. Vacuum pressure effects on transmission efficiency and nonlinear effects at the fiber output are studied for 100ps and 100fs laser beams. With a 0.1bar vacuum in the fiber, transmission efficiency increases by ∼30%, while spectral broadening is reduced. A 1m long, 1mm core metal-dielectric-coated HCF can transmit ∼45 mJ/pulse and ∼2.9 mJ/pulse for 100ps laser pulses (at 532nm) and 100fs laser pulses (at 810nm), respectively. Proof-of-principle, single-laser-shot, fiber-coupled, ps and fs laser-based, nitrogen electronic-excitation tagging velocimetry is demonstrated in a free jet. Flow velocities are measured at 200kHz to capture high-frequency flow events.

Optimización de la temperatura de secado y presión de vacío en la decoloración y composición del aceite crudo de pescado

The objective of this study was to determine the optimal parameters of decolorization of crude oil to obtain a semi-refined fish oil of acceptable quality; response surface methodology was used, considering a central composite design with two factors: Vacuum pressure (0.13-0.7 bar) and drying temperature (96-124°C); having as dependent variables the percentage of free fatty acids (% AGL) and color of the oil. The raw material and the optimum finished product were characterized physico-chemically, which was obtained under the operating conditions: drying temperature of 110 ° C and 0.13 bar vacuum. The finished product indicated a percentage of free fatty acids of 0.27 ± 0.01% and CieLab colour with coordinates L: 48.69 ± 0.88, a: -4.28 ± 0.26 and b: 35.03 ± 0.85, which Is equivalent to color 6 -7 in Gardner scale, compliance with the industrial specifications.

Effect of drying methods and pre-treatments on phytonutrients of tomato slices

Tomato slices pre-treated with 4% potassium metabisulphite (KMS) and dried by hot air drying at 58 C and freeze drying at 0.008 m Bar vacuum were assessed for phytonutrient quality. Freeze drying was found to retain better antioxidant activity and phytonutrients in tomato slices compared to the hot air dried tomato slices. Sulphur dioxide exerted beneficial effect (antioxidative) on retention of phytonutrients during hot air drying but had negligible effect during freeze drying. Total carotenoids in pretreated hot air dried tomato slices were 17.49% higher than control samples whereas in case of freeze drying, carotenoids were 3.01% higher in control samples than pretreated samples Rehydration ratio was the highest in pretreated freeze dried tomato slices (6.69) compared to pretreated hot air dried tomato slices (5.77). Maximum nutrients were retained by KMS treated slices during storage.

Effect of Operating Parameters on Ethanol–Water Vacuum Separation in an Ethanol Dehydration Apparatus and Process Modeling with ANN

Abstract Bioethanol has been found to be a suitable substitute for gasoline in internal combustion engines. It could be used either in an undiluted form or blended with gasoline. To blend the ethanol and gasoline, the water content of ethanol should reach 0.5% or less. In the present research work, 3A Zeolite was used as an absorbent with vacuum distillation. The effects of the operating parameters such as temperature, vacuum pressure and vapor flow rate on ethanol–water separation were investigated. Final ethanol concentration was obtained at the end of every run as well as the concentration of outlet ethanol. Both linear regression and ANN design were used to determine the best fit for two final parameters. The optimum condition was obtained at 0.4 bar vacuum pressure and 20 l/min ethanol–water vapor flow rate. ANN model is more qualified to the simulation of outspread data while the linear regression is not. L10L10 mode and L5T10 mode provide the best results for final concentration and total time, respectively. The Trainlm Algorithm like the previous research training algorithm is the best.

Wettability of Aluminum on Alumina

The wettability of molten aluminum on solid alumina substrate has been investigated by the sessile drop technique in a 10−8 bar vacuum or under argon atmosphere in the temperature range from 1273 K to 1673 K (1000 °C to 1400 °C). It is shown that the reduction of oxide skin on molten aluminum is slow under normal pressures even with ultralow oxygen potential, but it is enhanced in high vacuum. To describe the wetting behavior of the Al-Al2O3 system at lower temperatures, a semiempirical calculation was employed. The calculated contact angle at 973 K (700 °C) is approximately 97 deg, which indicates that aluminum does not wet alumina at aluminum casting temperatures. Thus, a priming height is required for aluminum to infiltrate a filter. Wetting in the Al-Al2O3 system increases with temperature.

Mercury isotope fractionation during liquid–vapor evaporation experiments

Liquid–vapor mercury isotope fractionation was investigated under equilibrium and dynamic conditions. Equilibrium evaporation experiments were performed in a closed glass system under atmospheric pressure between 0 and 22 °C, where vapor above the liquid was sampled at chemical equilibrium. Dynamic evaporation experiments were conducted in a closed glass system under 10 −5 bar vacuum conditions varying (1) the fraction of liquid Hg evaporated at 22 °C and (2) the temperature of evaporation (22–100 °C). Both, residual liquid and condensed vapor fractions were analyzed using stannous chloride CV-MC-ICP-MS. Equilibrium evaporation showed a constant liquid–vapor fractionation factor ( α 202/198) of 1.00086 ± 0.00022 (2SD, n = 6) within the 0–22 °C range. The 22 °C dynamic evaporations experiments displayed Rayleigh distillation fractionation behavior with liquid–vapor α 202/198 = 1.0067 ± 0.0011 (2SD), calculated from both residual and condensed vapor fractions. Our results confirm historical data (1920s) from Brönsted, Mulliken and coworkers on mercury isotopes separation using evaporation experiments, for which recalculated δ 202Hg′ showed a liquid–vapor α 202/198 of 1.0076 ± 0.0017 (2SD). This liquid–vapor α 202/198 is significantly different from the expected kinetic α 202/198 value ((202/198) 0.5 = 1.0101). A conceptual evaporation model of back condensation fluxes within a thin layer at the liquid–vapor interface was used to explain this discrepancy. The δ 202Hg′ of condensed vapor fractions in the 22–100 °C temperature range experiments showed a negative linear relationship with 10 6/ T 2, explained by increasing rates of exchange within the layer with the increase in temperature. Evaporation experiments also resulted in non-mass-dependent fractionation (NMF) of odd 199Hg and 201Hg isotopes, expressed as Δ 199Hg′ and Δ 201Hg′, the deviation in ‰ from the mass fractionation relationship with even isotopes. Liquid–vapor equilibrium yielded Δ 199Hg′/Δ 201Hg′ relationship of 2.0 ± 0.6 (2SE), which is statistically not different from the one predicted for the nuclear field shift effect (Δ 199Hg/Δ 201Hg ≈ 2.47). On the other hand, evaporation under dynamic conditions at 22 °C led to negative anomalies in the residual liquid fractions that are balanced by positive anomalies in condensed vapors with lower Δ 199Hg′/Δ 201Hg′ ratios of 1.2 ± 0.4 (2SD). This suggests that either magnetic isotope effects may have occurred without radical chemistry or an unknown NMF process on odd isotopes operated during liquid mercury evaporation.

The influence of vacuum mixing on methylmethacrylate liberation from acrylic cement powder

Polymethylmethacrylate (PMMA) bone cement is a biomaterial used to anchor prostheses during joint replacement surgery. Residual methylmethacrylate monomer (MMA) may be related with the cytotoxic effect of PMMA. The aim of the present paper was to investigate the effect of two different cement mixing methods: hand stirring at atmospheric pressure and under partial vacuum (0.330 and 0.154 bar) on residual monomer liberation in phosphate buffer saline solution from acrylic cement powder. Residual MMA content was determined by high-performance liquid chromatography. Mathematical models were applied to experimental dissolution data revealing that monomer release was significantly reduced in bone cement powder obtained at 0.154 bar vacuum pressure compared to the other mixing conditions. The kinetic models applied are consistent with a simple diffusion mechanism of the monomer from the polymer matrix.

Mass Spectrometer Source Loading Lock and Isolation Valve

An all metal sliding bar vacuum lock is described employing a new type of vacuum seal involving the deflection of the wall of the lock housing. A pressure of 2×10−7 Torr can be maintained in the main source region of a mass spectrometer during the introduction of solid samples into the source. An isolation valve utilizing a similar principle is also described.