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At least 1,171 records · Page 65Linked to original sources
PubMed1975

Emission control of gas effluents from geothermal power plants.

Geothermal steam at the world's five largest power plants contains from 0.15 to 30% noncondensable gases including CO(2), H(2)S, H(2), CH(4), N(2), H(3)BO(3), and NH(3). At four of the plants the gases are first separated from the steam and then discharged to the environment; at the fifth, the noncondensables exhaust directly to the atmosphere along with spent steam. Some CO(2) and sulfur emission rates rival those from fossil-fueled plants on a per megawatt-day basis. The ammonia and boron effluents can interfere with animal and plant life. The effects of sulfur (which emerges as H(2)S but may oxidize to SO(2)) on either ambient air quality or longterm human health are largely unknown. Most geothermal turbines are equipped with direct contact condensers which complicate emission control because they provide two or more pathways for the effluents to reach the environment. Use of direct contact condensers could permit efficient emission control if coupled to processes that produce saleable quantities of purified carbon dioxide and elemental sulfur.

Air Pollution↗
PubMed2002

Irradiating or autoclaving chitosan/polyol solutions: effect on thermogelling chitosan-beta-glycerophosphate systems.

The effects of steam sterilization and gamma-irradiation on chitosan and thermogelling chitosan-beta-glycerophosphate (GP) solutions containing polyol additives were investigated. The selected polyols were triethylene glycol, glycerol, sorbitol, glucose and poly(ethylene glycol) (PEG). They were incorporated to chitosan solutions prior to sterilization in a proportion ranging from 1 to 5% (w/v). The solutions were characterized with respect to their viscosity, thermogelling properties, compressive stress relaxation behavior and chitosan degradation. All polyols reduced the autoclaving-induced viscosity loss and had a positive impact on the solution thermogelling properties and compressive performance of the gels. Steam sterilization in the presence of glucose resulted in a substantial increase in the solution viscosity and gel strength. This was associated with a strong discoloration suggesting chemical alteration of the system. PEG was the most effective agent in preventing hydrolytic degradation of chitosan chains. Gamma-irradiation strongly decreased the chitosan solution viscosity regardless of the presence of additives, even when sterilization was carried out at -80 degrees C. Moreover, the thermogelling properties were dramatically altered, and thus, gamma-irradiation would not be an appropriate method to sterilize chitosan solutions. In conclusion, polyols are potentially useful additive to maximise the viscoelastic and mechanical properties of chitosan-GP after steam sterilization.

Chitin↗
PubMed2000

Two-stage dilute-acid pretreatment of softwoods.

Whole tree chips obtained from softwood forest thinnings were pretreated via single- and two-stage dilute-sulfuric acid pretreatment. Whole-tree chips were impregnated with dilute sulfuric acid and steam treated in a 4-L steam explosion reactor. In single-stage pretreatment, wood chips were treated using a wide range of severity. In two-stage pretreatment, the first stage was carried out at low severity to maximize hemicellulose recovery. Solubilized sugars were recovered from the first-stage prehydrolysate by washing with water. In the second stage, water-insoluble solids from first-stage prehydrolysate were impregnated with dilute sulfuric acid, then steam treated at more severe conditions to hydrolyze a portion of the remaining cellulose to glucose and to improve the enzyme digestibility. The total sugar yields obtained after enzymatic hydrolysis of two-stage dilute acid-pretreated samples were compared with sugar yields from single-stage pretreatment. The overall sugar yield from two-stage dilute-acid pretreatment was approx 10% higher, and the net enzyme requirement was reduced by about 50%. Simultaneous saccharification and fermentation using an adapted Saccharomyces cerevisiae yeast strain further improved cellulose conversion yield and lowered the enzyme requirement.

Cellulase↗
PubMed1998

Medical waste autoclaves: not just a lot of hot air.

Over the past ten years, the treatment of medical waste has received much attention. During this time, an entire new industry to develop "alternate medical waste treatment technologies" has emerged. Much of this has been in response to increasingly stringent air quality standards along with public sentiment opposed to incineration, with a resultant decline in the use of on-site medical waste incinerators. However, in between incinerators and alternative treatment systems is a technology that is as much a part of American healthcare as hospitals themselves. Medical waste regulation in all fifty states recognize steam sterilization as an acceptable method of treatment prior to disposal. Within this category of medical waste treatment technology, there is a wide array of systems available, many of which have altered the basic, simple principles of steam treatment to make it more conducive to this application. This Professional Development Series reviews some the basic and newer innovative techniques of steam treatment of medical waste.

Cross Infection↗
PubMedDate not supplied

Measurement of critical properties of muslin and nonwoven sterile-wraps.

Empirical evaluations closely simulating actual use conditions were employed to compare critical property levels of commonly used muslin (140-thread) and nonwoven sterile-wraps. Critical properties and experimental methods used to measure these properties are: (a) ease of steam penetration determined by time-temperature measurements in large, double-wrapped packs subjected to steam sterilization, (b) bacterial barrierness measured by microbiological assay of initially sterile double- and single-wrapped packs contents after pack storage in hospitals, (c) compatibility with ethylene oxide sterilization measured by inactivation of spore strips and by quantities of ethylene oxide residuals after aeration of packs and (d) generation of lint by counting particles generated by flexing wrap materials. It was concluded that the nonwoven steril-wrap was superior in ease of steam penetration, bacterial barrierness, and linting. No differnece was detected between materials in ethylene oxide sterilization.

Air Microbiology↗
PubMedDate not supplied

Analysis of factors influencing the Bowie-Dick-type test.

Investigations were conducted to determine the air-detecting capacity of the Bowie-Dick-type test for prevacuum steam autoclaves. The results indicate that the limitations in air detection are related to the specific type of sterilizer and test procedure being used, rather than some theoretical consideration. The chemical indicators on the test sheet appear to respond to incomplete steam penetration, rather than to the presence of air. The so-called small-load effect should be attributed to other than the commonly accepted causes. It appears that the causes of the small load effect are (a) air trapped by a condensate layer, and (b) the reluctance of steam a and air to mix.

Bedding and Linens↗
PubMed1994

Effect of inhalation of hot humidified air on experimental rhinovirus infection.

OBJECTIVE: Nasal inhalation of steam has been proposed as treatment of viral colds on the assumption that increased intranasal temperature will inhibit replication of rhinovirus (RV). The effect of steam inhalation on RV shedding by infected volunteers was examined in this study. DESIGN: Randomized controlled trial. Volunteers experimentally infected with RV were treated with machine-generated humidified air, which was either hot (active) or at room temperature (placebo). Viral shedding was assessed over the 4 days following treatment. SETTING: Local hotel. PARTICIPANTS: Twenty volunteers from the university community who were susceptible to the challenge virus. INTERVENTION: Two 30-minute intranasal treatments, the first at 24 hours after inoculation and the second at 48 hours. The temperature of active vapor was 42 degrees C to 44 degrees C and of placebo vapor was 22 degrees C. MAIN OUTCOME MEASURES: Viral titers in nasal washings on each of 5 days following inoculation. RESULTS: Mean viral titers prior to the first treatment were 10(1.7) tissue culture infectious doses per milliliter in the active group and 10(1.5) in the placebo group. Mean titers for the next 4 days were 10(1.7), and 10(1.7), 10(1.2), and 10(0.9)/mL in the active group and 10(1.8), 10(1.9), 10(1.6), and 10(0.7)/mL in the placebo group (no significant difference). The proportion of volunteers who shed virus on each day was also similar in the two groups. CONCLUSION: Two nasal inhalation treatments with steam had no effect on viral shedding in volunteers with experimental RV colds.

Administration, Inhalation↗
PubMed1995

[Hygienic processing of dental transmission instruments (handpieces and instruments, turbines) in dental practice].

The efficacy of a steam disinfection method for the processing of used instruments in dental practice was tested with 274 high-speed turbines and handpieces. The instruments treated with streaming steam were both taken out of the dental practice of treatment and artificially contaminated with five different test-microorganisms (E. coli, P. aeruginosa, S. aureus, E. faecium, C. albicans) and different concentrations of serum (1%, 10%, 20%). In spite of the narrow channels of these instruments a microbial reduction of more than 5 log10 steps could be achieved in all cases. Thus dental high-speed turbines and handpieces can reliably be disinfected with streaming steam.

Colony Count, Microbial↗
PubMedDate not supplied

Color change and fracture resistance of two preveneered stainless-steel crowns after sterilization.

PURPOSE: This study compared the fracture resistance and color stability of two commercially available, preveneered stainless-steel crowns before and after four sterilization techniques. METHODS: Thirty-five crowns from each of two manufacturers were divided into five groups. Four groups were sterilized twice using one of the following techniques: steam autoclave at both 121 degrees C (15 PSI) for 20 min and 132 degrees C (30 PSI) for 8 min; Chemiclave with formaldehyde at 132 degrees C for 20 min; and 2% gluteraldehyde for 10 h. The fifth group from each manufacturer was the control. Color of facings was measured before and after each sterilization in triplicate using a colorimeter, and the variance of each color parameter was analyzed for significance. Fracture resistance was measured for each group and differences between the control and experimental groups analyzed for significance. RESULTS: The results of this study show that high heat and chemical sterilizations have little effect on color and fracture resistance of the preveneered stainless-steel crowns. Student's t test analysis revealed a significantly decreased resistance to fracture with Kinder Krowns sterilized in 2% gluteraldehyde. Chemiclave sterilization caused the most negative color change in all three color parameters measured for both types of crowns. CONCLUSIONS: As neither steam technique produced significant changes in fracture resistance or color changes that were clinically detectable, the results of this study indicate that the two steam techniques tested can be used by clinicians to sterilize either Kinder Krowns or Nu Smile preveneered stainless-steel crowns.

Color↗
PubMed1996

Injury control in practice. Home radiator burns in inner-city children.

OBJECTIVE: To describe thermal burns from radiators in the homes of children in the inner city and an intervention to decrease the risk for this pediatric injury. SETTING: Academic medical center in Chicago. PATIENTS: Case series of 10 radiator-related burns. RESULTS: The burns described were found to be clustered in an area of a public housing project served by steam radiators. No burns were associated with hot water radiators. Just 14% of housing units with young children had adequate radiator covers and radiator pipe insulation. Radiator covers and insulation have now been replaced or repaired in all units of the 11 housing project buildings served by steam radiators. CONCLUSIONS: Steam radiators in the home represent a particular childhood burn hazard. Community-based clinicians are in a unique position to recognize local patterns of injury and work with other agencies in injury control efforts.

Accidents, Home↗
PubMed2000

2D CSI proton MR spectroscopy of human spinal vertebra: feasibility studies.

This report focuses on proton magnetic resonance spectroscopy (1H MRS) of spine vertebra acquired with two-dimensional chemical shift imaging (2D CSI), utilizing the stimulated echo acquisition mode (STEAM) sequence. Both validity and reproducibility studies were performed. To validate the 2D CSI method, its spectra were compared with those obtained with the single-voxel (SV) method. Five normal volunteers were scanned. The reproducibility of 2D CSI was examined by performing spectroscopy on two different occasions, on three normal volunteers. Data show that the STEAM 2D CSI technique results in MRI spectra comparable to those obtained with the STEAM SV method. 2D CSI offers significant time savings and convenient multi-voxel spectral analysis at a substantially higher signal-to-noise ratio. The 2D CSI method was then applied to a patient with a small vertebral hemangioma. The results demonstrated that the voxels containing the hemangioma exhibit different spectra than the neighboring voxels of the same vertebra. Additionally, a case of vertebral osteoporosis was investigated. Results showed a significant increase in the lipid-to-water ratio (LWR). It is suggested that 2D CSI may be powerful in identifying physiological as well as pathological changes of the bone marrow. Furthermore, covering a more extensive area of the vertebral body will maximize the chances of depicting a small focus of pathologic tissue. A more detailed bone marrow pattern was noticed in on one subject whose spectra show more lipid peaks.

Adult↗
PubMed2004

Effect of initial moisture content and chip size on the bioconversion efficiency of softwood lignocellulosics.

Previous optimization strategies for the bioconversion of lignocellulosics by steam explosion technologies have focused on the effects of temperature, pH, and treatment time, but have not accounted for changes in severity brought about by properties inherent in the starting feedstock. Consequently, this study evaluated the effects of chip properties, feedstock size (40-mesh, 1.5 x 1.5 cm, 5 x 5 cm), and moisture content (12% and 30%) on the overall bioconversion process, and more specifically on the efficacy of removal of recalcitrant lignin from the lignocellulosic substrates following steam explosion. Increasing chip size resulted in an improvement in the solids recovery, with concurrent increases in the water soluble, hemicellulose-derived sugar recovery (7.5%). This increased recovery is a result of a decrease in the "relative severity" of the pretreatment as chip size increases. Additionally, the decreased relative severity minimized the condensation of the recalcitrant residual lignin and therefore increased the efficacy of peroxide fractionation, where a 60% improvement in lignin removal was possible with chips of larger initial size. Similarly, increased initial moisture content reduced the relative severity of the pretreatment, generating improved solids and hemicellulose-derived carbohydrate recovery. Both increased chip size and higher initial moisture content results in a substrate that performs better during peroxide delignification, and consequently enzymatic hydrolysis. Furthermore, a post steam-explosion refining step increased hemicellulose-derived sugar recovery and was most effectively delignified (to as low as 6.5%). The refined substrate could be enzymatically hydrolyzed to very high levels (98%) and relatively fast rates (1.23 g/L/h).

Biotransformation↗
PubMed2004

Low-temperature destruction of carbon tetrachloride over lanthanide oxide-based catalysts: from destructive adsorption to a catalytic reaction cycle.

The catalytic destruction of carbon tetrachloride in the presence of steam, CCl(4) + 2 H(2)O-->4 HCl + CO(2), was investigated at 200-350 degrees C over a series of lanthanide (La, Ce, Pr and Nd) and alkaline-earth metal (Mg, Ca, Sr and Ba) oxide-based catalysts with kinetic experiments, Raman spectroscopy, X-ray photoelectron spectroscopy, IR spectroscopy, X-ray diffraction, and DFT calculations. This new catalytic reaction was achieved by combining destructive adsorption of CCl(4) on a basic oxide surface and concurrent dechlorination of the resulting partially chlorinated solid by steam. The combination of the two noncatalytic reactions into a catalytic cycle provided a rare opportunity in heterogeneous catalysis for studying the nature and extent of surface participation in the overall reaction chemistry. The reaction is proposed to proceed over a terminal lattice oxygen site with stepwise donation of chlorine atoms from the hydrocarbon to the surface and formation of the gas-phase intermediate COCl(2), which is readily readsorbed at the catalyst surface to form CO(2). In a second step, the active catalyst surface is regenerated by steam with formation of gas-phase HCl. Depending on the reaction conditions, the catalytic material was found to transform dynamically from the metal oxide state to the metal oxide chloride or metal chloride state due to the bulk diffusion of oxygen and chlorine atoms. A catalyst obtained from a 10 wt % La(2)O(3)/Al(2)O(3) precursor exhibited the highest destruction rate: 0.289 g CCl(4) h(-1) g(-1) catalyst at 350 degrees C, which is higher than that of any other reported catalyst system.

Adsorption↗
PubMed1983

Detoxification and nutritional evaluation of solvent extracted Egyptian cottonseed meal.

Attempts for degossypolization of the solvent extracted Egyptian cottonseed meal (CSM) and evaluation of its nutritional value as a possible protein supplement for human feeding were undertaken. Three methods were applied for degossypolization: Steaming, addition of iron(II)-sulphate dihydrate, and steaming after addition of iron(II)-sulphate dihydrate. Steaming was done for varying periods of time. Nutritional evaluation was undertaken by chemical analysis and by feeding experiments. Chemically, the third method for degossypolization was the most effective. Feed efficiency and protein efficiency for diets containing 15 and 10% levels of CSM protein indicated that all treatments used for detoxification caused a decrease in diet and protein quality. Diets containing iron-supplemented CSM at the same level were the best of all. Mixing CSM with casein to form a diet containing 10% protein increases the protein quality of both casein and CSM.

Animals↗
PubMed2004

Effects of various sterilization methods on the setting and mechanical properties of apatite cement.

Sterilization capability is a necessary requirement for any material that is to be used in a medical application. Therefore, it is necessary for apatite cement (AC) to be sterilized. Because there is little information on the sterilization methods of AC, the aims of this investigation were to evaluate the effects of various sterilization methods, including steam, dry heat, ethylene oxide (EtO) gas, and gamma irradiation sterilizations, on the setting and mechanical properties of AC. In the case of steam sterilization, because AC powder aggregated before setting-time measurements, the setting time could not be measured. When the powder was sterilized by dry heat or EtO gas, the setting time was prolonged significantly and the wet diametral tensile strength (DTS) value decreased significantly. Therefore, sterilizations with steam, dry heat, or EtO gas were suggested to be inappropriate methods for AC. Accordingly, the following experiments focused on gamma sterilization. The setting time of AC was retarded with an increase in gamma irradiation dose. The wet DTS value decreased with the increase in gamma irradiation dose. There was no compositional change due to the gamma irradiation. The following tests were carried out in order to examine the effect of the gamma irradiation on the setting reaction of AC in detail. Tetracalcium phosphate [TTCP: Ca(4)(PO(4))(2)O] and dicalcium phosphate anhydrous (DCPA: CaHPO(4)) were separately irradiated, and the cements were produced with the use of irradiated powder and nonirradiated powder. Although the wet DTS value of AC produced from irradiated TTCP and nonirradiated DCPA decreased with increasing gamma irradiation dose, there was no significant difference. In contrast, the wet DTS value of AC produced from irradiated DCPA and nonirradiated TTCP significantly decreased with the increase in gamma irradiation dose. In conclusion, although the detailed mechanism of the delayed setting time and decreased DTS value was not clarified by the present study, it was found that gamma irradiation affected DCPA more than TTCP.

Adhesives↗
PubMedDate not supplied

Comparison of conventional single echo and multi-echo sequences with a fast spin-echo sequence for quantitative T2 mapping: application to the prostate.

The accuracy of water T2 maps generated from a fast spin-echo (FSE) sequence was compared with data obtained by conventional single and multi-echo spin-echo pulse sequences using a commercial gel phantom. Spatially localized stimulated echo acquisition mode (STEAM) proton spectroscopy was also used to confirm the reported water T2 values of the gels contained in the phantom. The FSE sequence was shown to be superior in accuracy to both the single and multi-echo spin echo sequences and comparable to STEAM, producing results that were within 10% of known values. The effectiveness of the FSE sequence was further demonstrated by generating T2 maps of the normal and diseased prostate in clinically acceptable imaging times, resulting in comparable T2 values to those obtained using STEAM. Accurate quantitative T2 maps can be produced with the FSE sequence.

Carcinoma↗
PubMed2002

Laser-tattoo removal--a study of the mechanism and the optimal treatment strategy via computer simulations.

BACKGROUND AND OBJECTIVE: The physical mechanisms for laser-tattoo interactions and the tattoo particle breakup process are not well understood. This study investigates whether the mechanism of the breakup process can be identified via computer simulations and proposes a treatment strategy that can potentially minimize the collateral damage to the surrounding tissues. Note that the "removal" of tattoo particles is defined here as breakup of particles into smaller ones with sizes approaching or smaller than the visible wavelength of light so that they become less visible. STUDY DESIGN/MATERIALS AND METHODS: The radiation-hydrodynamics code LATIS is used for the modeling. We first identify the magnitude of the tensile stress generated inside graphite tattoo particles as functions of laser pulse length and particle size. We then calculate the relationship between the surface laser fluence (defined as the time integrated energy flux) and the tensile strength of the tattoo particle at a given depth. RESULTS: If the laser pulse length is sufficiently short, strong acoustic waves with tensile strengths exceeding the fracture thresholds for graphite are generated. The strength of the wave decreases with particle size and increases as the laser pulse length decreases. Simulation results are in general agreement with clinical studies. Although temperatures of the tattoo particles never reach the melting point, a cavitation bubble around the particle can be formed. The steam generated can get into the cracked particles and induce steam-carbon reactions. Laser energy density decreases rapidly with the skin depth. Therefore, the minimum surface laser fluence, for a given pulse length, required for breaking up tattoo particles at a given skin depth, increases with particle depth. CONCLUSIONS: Computer simulations confirm that the breakup of tattoo particles is photoacoustic. For the same amount of laser energy, a shorter pulse is more efficient. The optimal pulse length is approximately 10-100 picosecond to minimize the laser fluence and the collateral damage. It is more difficult to break up the smallest tattoo particles that have diameters smaller than 10 nm; however, smaller particles are less important because they are less visible. Tissue surrounding the tattoo particles can be damaged by cavitation bubbles. These bubbles could be the cause of the empty vacuoles in the ash-white lesions throughout the dermis seen after treatment. Steam-carbon reactions can be induced. Particles then become grossly transparent because of this reaction. Different laser intensity should be used for pigments at different depths in order to minimize the collateral damage to the dermis.

Computer Simulation↗
PubMed1993

Effects of pulse width on erbium:YAG laser photothermal trabecular ablation (LTA).

An erbium (Er):YAG laser can remove trabecular meshwork (TM) by photothermal ablation with minimal contiguous thermal damage. A variable pulse width Er:YAG laser was used to investigate the effect of varying pulse width on ablation of human TM. Trabecular photothermal ablation was performed on tissue obtained from eye bank eyes at pulse widths of 50, 150, and 250 microseconds, with energy held constant at 4 mJ. At this energy, a single laser pulse was sufficient for full-thickness ablation of TM. Laser energy was delivered through a 200-microns diameter optical fiber held in apposition to the tissue sample, which was immersed in physiologic saline. High-speed photography of the resultant steam bubbles also was performed. Light microscopy and scanning electron microscopy of TM ablated at 50 microseconds revealed the greatest variability in size (0-140 microns) of the full-thickness ablated areas and demonstrated blast effects, tissue shredding and < or = 10 microns thermal damage. At 150 microseconds, the full-thickness ablated areas were more consistent size (115-120 microns), showed no blast effects and 10 to 20 microns thermal damage. At 250 microseconds, the largest ablations were found (180-220 microns) and showed no blast damage; however, a significant amount of thermal damage (< or = 50 microns) was evident. The steam bubbles produced by the laser energy were largest at 50 microseconds and did not begin to collapse until well over twice the original pulse interval. At 150 and 250 microseconds, the steam bubbles were successively smaller and dissipated at the end of the laser pulse.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗