Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “STEAM”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 415 records · Page 23Linked to original sources
PubMed2004

Influence of morphology and composition of fumed oxides on changes in their structural and adsorptive characteristics on hydrothermal treatment in steam phase at different temperatures.

A series of fumed oxides such as silica, titania, alumina, silica/alumina (SA), silica/titania (ST), and alumina/silica/titania (AST), initial and hydrothermally treated (HTT) in the steam phase at T(HTT)=150, 250, and 350 degrees C was studied by adsorption, AFM, XRD, FTIR, and theoretical methods. Diminution of the size of primary particles (corresponding to increasing S(BET)) of initial silica and mixed oxides results in enhancement of their structural changes on HTT with elevating T(HTT) and increasing density of packing of primary particles in the secondary structures. Relative changes in the texture of treated fumed silicas are smaller than those of mesoporous silica gels occurring under similar HTT conditions. On HTT, aggregates of primary particles and their agglomerates become denser but their surface layers become looser because of transfer of silica fragments from one particle to another, and the smaller the initial primary particles, the greater the relative diminution of the specific surface area S(BET) for the same type of primary particle packing in aggregates. Relative changes in the pore volume V(p) (or V(BJHd)) on HTT are more complex than that of S(BET), as for many samples the V(p) value increases especially at T(HTT)=150 degrees C. Alumina and titania partially inhibit structural changes on HTT, which decrease in the series silica > SA > AST approximately ST.

Journal Article↗
PubMed2006

One-step incorporation of Pd-Zn catalytic sites into organized mesoporous alumina for use in the oxidative steam reforming of methanol.

In this paper we report the preparation of an organized mesoporous Pd-Zn/alumina system, by a new surfactant-assisted single-step sol-gel synthesis, performed in alcohol, using stearic acid as a chemical template, aluminum sec-butoxide as Al source and metal stearates both as Pd-Zn sources and as structural directing agents. The prepared materials have been characterized using a variety of techniques such as thermogravimetric analysis, atomic absorption spectroscopy, X-ray powder diffraction and N2 adsorption-desorption, and preliminarily tested in the oxidative steam reforming of methanol (OSRM) in the temperature range 100-400 degrees C.

Journal Article↗
PubMed2000

Simulation modeling of nuclear steam generator water level process--a case study

Simulation modeling of the nuclear steam generator (SG) water level process in Qinshan Nuclear Power Plant (QNPP) is described in this paper. A practical methodology was adopted so that the model is both simple and accurate for control engineering implementation. The structure of the model is in the form of a transfer function, which was determined based on first-principles analysis and expert experience. The parameters of the model were obtained by taking advantage of the recorded historical response curves under the existing closed-loop control system. The results of process dimensional data verification and experimental tests demonstrate that the simulation model depicts the main dynamic characteristics of the SG water level process and is in accordance with the field recorded response curves. The model has been successfully applied to the design and test of an advanced digital feedwater control system in QNPP.

Journal Article↗
PubMed2001

Capillary electrophoresis for measuring major and trace anions in thermal water and condensed-steam samples from hydrothermal springs and fumaroles.

A new application of capillary electrophoresis for measuring major and trace anions in thermal water and condensed-steam samples is presented. Ten fluid samples were collected from hydrothermal springs and fumaroles located in a volcanic zone of Deception Island, Antarctica. Anion separation was achieved in less than 6 min using indirect UV detection at 254 nm with a negative power supply (-15 kV). The electrolyte consisted of 4.7 mM sodium chromate, 4.0 mM electroosmotic flow modifier (OFM) hydroxide, 10 mM 2-(N-cyclohexylamino)ethanesulfonic acid and 0.1 mM calcium gluconate (pH 9.1). Major anions (Cl-, SO4(2), PO4H2+, and CO3H-) were measured using hydrostatic injection (10 cm for 30 s) at 25 degrees C. Trace amounts of anions (F-, Br-, and NO3-) were better determined by electromigration injection (4 kV, 10 s) at 15 degrees C. Good reproducibility of the migration times (<0.72% RSD), a satisfactory linear response and accuracy as well as acceptable detection limits were successfully obtained.

Anions↗
PubMed2003

Evaluation of a low-temperature steam and formaldehyde sterilizer.

We evaluated a low-temperature steam and formaldehyde (LTSF) sterilizer based on the draft European Standard prEN 14180. Microbiological tests were conducted on small and full loads using process challenge devices in five programs (P1-P5). With small loads all tests showed no growth of Bacillus stearothermophilus (ATCC7953) spores. However, positive cultures were observed with full-load tests using P5 (sterilization temperature, 50 degrees C). Our data indicated that the load influenced the efficacy of the LTSF sterilizer. Desorption tests were conducted to determine residual formaldehyde in indicator strips. The mean concentrations of formaldehyde in P1-P5 were 31.9, 56.3, 54.9, 82.2 and 180.6 microg, respectively, which are below the limits allowed by the draft Standard. Our results indicate that the LTSF sterilizer is useful for sterilization because of its excellent efficacy, short handling time, and safety.

Disinfectants↗
PubMed2000

The steam volatile oil of Wollemia nobilis and its comparison with other members of the Araucariaceae (Agathis and Araucaria).

The leaf essential oil of Wollemia nobilis (Wollemi Pine) has been investigated and compared with other members of the family Araucariaceae. All araucaroids examined yielded steam volatile oils in low yields. The oil from Wollemia nobilis was composed mainly of (+)-16-kaurene (60%), together with alpha-pinene (9%) and germacrene-D (8%). Oils from Agathis species endemic to Australia were high in monoterpenes, in contrast to those isolated from extra-Australian species. The major constituents of A. atropurpurea oil were phyllocladene (13%) and 16-kaurene (19%), followed by alpha-pinene (8%) and delta-cadinene (9%). A. microstachya yielded oil in which alpha-pinene (18%) was the major component; the only other components in excess of 5% were myrcene (7%), bicyclogermacrene (6%) and delta-cadinene (6%). A. robusta oil contained spathulenol (37%) and rimuene (6%). Approximately 40% of the oil was unidentified sesquiterpenes. A. australis oil contained 16-kaurene (37%), sclarene (5%) and an unidentified oxygenated diterpene K (12%) as major components; the only other compound in excess of 5% was germacrene-D (9%). 5,15-Rosadiene (60%), and 16-kaurene (7%) were the major constituents of A. macrophylla oil. A. moorei oil was rich in sesquiterpenes, but the only compounds in excess of 5% were allo-aromadendrene (6%), germacrene-D, delta-cadinene (10%), an unidentified sesquiterpene (12%) and 16-kaurene (6%). In A. ovata oil the most significant compounds were caryophyllene oxide (15%) and phyllocladene (39%). Araucaria angustifolia contained germacrene-D (9%) and the diterpenes hibaene (30%) and phyllocladene (20%) as major components of its essential oil. Oils of A. bidwillii, A. columnaris and A. cunninghamii were all low in mono- and sesquiterpenes and high in diterpenes. In the first, hibaene (76%) was the major constituent; the second contained hibaene (9%), sclarene (6%), luxuriadiene (13-epi-dolabradiene)(23%) and two unidentified diterpene hydrocarbons (B) (33%) and (E) (10%). In the last, 16-kaurene (53%) was the most significant component followed by hibaene (29%). A. heterophylla was unusual in that over half the oil was made up of the monoterpenoid alpha-pinene (52%), with phyllocladene (32%) being the only other compound of significance. alpha-Pinene (18%) was a significant component of A. hunsteinii oil; sclarene (11%) and germacrene-D (5%) were the only other compounds present in concentrations of more than 5%. A. luxurians oil was composed of 5,15-rosadiene (20%) and luxuriadiene (13-epi-dolabradiene) (66%), previously unreported from natural sources. The major components of A. montana were phyllocladene (61%) and 16-kaurene (23%). Sclarene (20%), luxuriadiene (19%) and the unidentified diterpene hydrocarbons (B) (25%) and (E) (10%) were the most important constituents of A. muelleri oil. A. scopulorum contained large amounts of 16-alpha-phyllocladanol (41%) as well as luxuridiene (10%) and delta-cadinene and alpha-copaene, both at 6%.

Journal Article↗
PubMed2001

Analysis of 3,5,6-trichloro-2-pyridinol in urine samples from the general population using gas chromatography-mass spectrometry after steam distillation and solid-phase extraction.

We have developed a new method for the quantitative trace determination of 3,5,6-trichloro-2-pyridinol (TCPyr). TCPyr is a urinary metabolite specific to the organophosphorus pesticides chlorpyrifos and chlorpyrifos-methyl. After hydrolysis and separation of TCPyr from the urinary matrix using semi-automated steam distillation and solid-phase extraction on a new polystyrol-divinylbenzene copolymer (Isolute 101) the analyte was converted into its tert-butyldimethylsilyl derivative by N-tert-butyldimethylsilyl-N-methyltrifluoroacetamide (MTBSTFA). Separation and quantitative analysis were carried out by capillary gas chromatography and mass selective detection in selected ion monitoring mode. 2,6-Dibromophenol (DBP) was used as the internal standard. The detection limit was 0.05 microg/l; the limit of quantification was 0.1 microg/l urine. The relative standard deviation of the within-series imprecision was 4.2% at a concentration of 3.5 microg/l. The relative recovery was 104%. The new method was used to analyse the urine samples of 12 persons from the general population without known exposure to the above-mentioned pesticides. TCPyr concentrations between 0.27 and 6.6 microg/l urine were detected in all urine samples. This indicates that there is a baseline excretion of TCPyr in the general population. Four urine samples collected from workers who had applied chlorpyrifos were also analysed. In these samples TCPyr was found in concentrations from 4.7 to 7.9 microg/l.

Calibration↗
PubMed2001

Solid-state production of lignin peroxidase (LiP) and manganese peroxidase (MnP) by Phanerochaete chrysosporium using steam-exploded straw as substrate.

In the used media mainly consisting of steam-exploded wheat straw, the straw, which could replace expensive veratryl alcohol, might act not only as nutrient, but also as inducer of lignin enzymes. The activities of the enzymes lignin peroxidase (LiP) and manganese peroxidase (MnP) in solid-state fermentation (SSF) were far higher than in submerged fermentation (SmF). Under optimal conditions of SSF, the maximum activities of the enzymes Lip and MnP were 2600 and 1375 U/L, respectively. Thus, this would pave the way for production and application of lignin enzymes on a large scale.

Benzyl Alcohols↗
PubMed2002

Production of ribonucleotides by autolysis of Hansenula anomala grown on Korean ginseng steaming effluent.

Hansenula anomala KCCM 11473, which grew well in Korean ginseng steaming effluent, was selected for the production of 5'-ribonucleotides. This strain had high RNA content. Optimal autolysis conditions were established to produce 5'-ribonucleotides (13.9 approximately 28.5 mg/g of biomass) at 55 degrees C and pH 5.0 for 24 h. 5'-Phosphodiesterase and adenyl deaminase were not effective in increasing the yield of 5'-ribonucleotides, but the yield of IMP increased significantly only after the addition of 1.0% adenyl deaminase.

Journal Article↗
PubMedDate not supplied

Flash extraction of pectin from orange albedo by steam injection.

Pectin was acid extracted from orange albedo by steam injection heating under pressure. Extraction times ranged from 2 to 6 min at a pressure of about 15 psi. Solubilized pectin was characterized by HPSEC with online light scattering and viscosity detection. Molar mass (M), radius of gyration (R(g)), and intrinsic viscosity ([eta]) all decreased with increasing extraction time when heating temperature was 120 degrees C. At heating times of 3 min, M(w) ranged from 4.9 to 4.5 x 10(5), R(gz) was about 44 nm, and [eta](w) ranged from 8.4 to 7.9 dL/g. Chromatography revealed that solubilized pectin distributions were bimodal in nature at 3 min extraction time and trimodal when the extraction time was 6 min. Scaling law exponents obtained for the highest molar mass fractions were consistent with a very compact spherical structure. For the intermediate fraction, scaling law exponents were consistent with a less compact spherical structure comparable to a random coil. In the case of the low molar mass fractions, scaling law exponents were consistent with a structure more asymmetric in shape. These results are consistent with earlier results which indicated that pectin distributions were mixtures of two or more of the following due to disaggregation during extraction: spherical aggregates, hydrogen bonded network structures, and partially or fully disaggregated components of network structures which could include branched structures, rods, segmented rods, and kinked rods.

Chromatography↗
PubMed2006

Study on the conversion of wool keratin by steam explosion.

A wool fiber sample was submitted to chemical-free steam explosion in view of potential exploitation of keratin-based industrial and farm wastes. Fiber keratin was converted into a dark-yellow sludge that was submitted to phase separation by filtration, centrifugation, and precipitation of the soluble materials from the supernatant liquid. The resulting products, when compared with the original wool, showed the extent of disruption of the histology structure, reduction of the molecular weight to water-soluble peptides and free amino acids, and change of the structure of the remainder of the protein associated with breaking of disulfide bonds and decomposition of the high-sulfur-content protein fraction.

Animals↗
PubMed2003

Extraction of essential oil and pigments from Curcuma longa [L] by steam distillation and extraction with volatile solvents.

Curcuma longa [Linn] (turmeric), of the Zingiberaceae family, has a great importance in the food, textile, and pharmaceutical industries. The aim of this work was to identify the best processing conditions to maximize the yields of essential oil and pigments, as well as their content of ar-turmerone, (alpha and beta)-turmerone, and the curcuminoids, respectively. Autoclave pressure and distillation time were the variables studied for the steam distillation process. The highest yields of essential oil (0.46 wt %) and pigment (0.16 wt %)-expressed as curcumin, demethoxycurcumin, and bisdemethoxycurcumin-were obtained at a pressure of 1.0 x 10(5) Pa and a time of 2 h. On the other hand, with extraction by volatile solvents, the best yield of essential oil (5.49 wt %) was obtained when using 0.175, 0.124, 0.088 mm particles (Foust, A. S.; Wenzel, L. A.; Clump, C. W.; Maus, L.; Andersen, L. B. Princípios das Operações Unitárias; Editora Guanabara Dois S.A.: Rio de Janeiro, Brazil, 1982), at 40 degrees C, and 6 h of extraction. However, the best yield of pigment (7.98 wt %) was obtained under the same conditions, except for the temperature (30 degrees C).

Curcuma↗
PubMed1999

Characterization of residual lignin after SO(2)-catalyzed steam explosion and enzymatic hydrolysis of Eucalyptus viminalis wood chips.

The lignin component found in both water insoluble (WI) and water and alkali insoluble (WIA) fractions derived from SO(2)-impregnated steam-exploded eucalyptus chips (SEE) was isolated and characterized. Dioxane lignins with a sugar content lower than 2% (w/w) were obtained after each material was treated with commercial cellulases. The C9 formulas of both SEE-WI and SEE-WIA dioxane lignins were C(9)H(6.83)N(0.04)O(2.24)(OCH(3))(1.21)(OH(aro))(0.56)(OH(ali))(0. 77) and C(9)H(8.65)N(0.29)O(1.97)(OCH(3))(0.90)(OH(aro))(0. 46)(OH(ali))(1.02), respectively. The weight-average molecular weight (M(w)) of the SEE-WI lignin corresponded to 3.85 kDa, whereas the SEE-WIA lignin had an M(w) of 3.66 kDa for the same polydispersity of 2.4. The SEE-WIA lignin was shown to be more thermally stable than the SEE-WI lignin, requiring temperatures in the range of 520 degrees C for complete degradation. FTIR and (1)H NMR analyses of both untreated and peracetylated lignin fractions showed that (a) the alkali insoluble lignin contained a relatively higher degree of substitution in aromatic rings per C9 unit and that (b) alkaline extraction removed lignin fragments containing appreciable amounts of phenolic hydroxyl groups.

Cellulase↗
PubMed2005

Framework composition effects on the performance of steam-activated FeMFI zeolites in the N2O-mediated propane oxidative dehydrogenation to propylene.

The N(2)O-mediated oxidative dehydrogenation of propane (ODHP) to propylene has been investigated in the temperature range of 673-773 K over steam-activated FeMFI zeolites with different framework compositions (Si-Al, Si-Ga, Si-Ge, and pure Si). The catalysts, which were characterized by ICP-OES, XRD, SEM, N(2) adsorption, NH(3)-TPD, and FTIR of pyridine adsorbed, HRTEM, and UV/vis, have a very similar iron content (0.6-0.7 wt %). A tapered element oscillating microbalance (TEOM) coupled to on-line analysis of products has been applied to simultaneously monitor activity and mass changes during the ODHP reaction. FeAlMFI and FeGaMFI zeolites display higher propylene yields (up to 25%) and a much slower deactivation due to coking than do FeGeMFI and FeMFI zeolites. The higher density and strength of acid sites in the former samples did not induce a faster catalyst deactivation. In general, catalyst deactivation was accelerated upon decreasing the reaction temperature. The total amount of coke formed in the samples during 400 min on stream ranged from 6 to 23 wt %, increasing linearly with the amount of propylene produced. The distinct performance of both groups of zeolites is likely related to the different iron speciation, which is influenced by the composition of the framework. The smaller primary crystallites of FeAlMFI and FeGaMFI, as well as the presence of mesopores in these samples, which are created by dislodgement of aluminum and gallium to extraframework positions, appear to be also beneficial for higher catalyst effectiveness and a reduced deactivation.

Journal Article↗
PubMed2006

Structural and diffusion characterizations of steam-stable mesostructured zeolitic UL-ZSM-5 materials.

A series of mesoporous UL-ZSM-5 materials (Si/Al = 50) with different micro- and mesoporosity as well as crystallinity was prepared following the procedure proposed in one of our recent studies (Trong-On, D.; Kaliaguine, S. Angew. Chem. Int. Ed. 2001, 40, 3248-3251. Trong-On, D.; Kaliaguine, S. U.S. Patent 6,669,924, B1, 2003). These materials have zeolitic structure in the form of nanoparticles intergrown in the walls of the amorphous wormhole-like aluminosilicate mesopores of Al-Meso-50, which was used as a precursor in the synthesis. The structure, crystallinity, and textural properties of the synthesized materials, as well as a reference ZSM-5 zeolite sample, were determined by X-ray diffraction (XRD), transmission electron microscopy (TEM)/scanning electron microscoy (SEM) analyses, Fourier transform infrared spectroscopy (FTIR), 27Al magic angle spinning (MAS) nuclear magnetic resonance (NMR), and nitrogen adsorption/desorption techniques. The acid properties were examined by FTIR of adsorbed pyridine. UL-ZSM-5 materials were shown to be highly hydrothermally stable. The diffusion of two C7 hydrocarbons, i.e., n-heptane and toluene, in four UL-ZSM-5 materials with different microporosities, related acidities, and crystallinities were investigated using the zero-length column (ZLC) method. Furthermore, the wormhole-like mesostructured aluminosilicate precursor (Al-Meso-50) and a reference MFI zeolite sample were also investigated using the same technique. A theoretical model considering a combination of mesopore diffusion (with surface slip in the main channels) with an activated, mainly surface diffusion mechanism in the intrawall biporous structure, was proposed and employed to interpret the experimental ZLC results. A classical Knudsen type of diffusion was replaced by an activated surface slip type of diffusion mechanism in the mesopores. The transport of n-heptane in UL-ZSM-5 materials was found to be mainly controlled by mesopore diffusion in the main-channel structure, while that of toluene was dominated by the intrawall diffusion process. Diffusion activation energies of n-heptane are about 2 times higher in comparison to toluene, which has a larger kinetic diameter. The main mesopore channel structure seems to appreciably contribute to the overall mass transport. Furthermore, the effect of hydrothermal treatment (20% steam at 800 degrees C for 24 h) on the diffusion of these two sorbates on UL-ZSM-5 materials was also evaluated.

Journal Article↗
PubMed1999

Use of two varieties of hard-to-cook beans (Phaseolus vulgaris) and cowpeas (Vigna unguiculata) in the processing of koki (a steamed legume product).

Koki is a nutritious cowpea-based food product usually processed by steam cooking whipped cowpea (Vigna unguiculata) paste mixed with spices and palm oil. A study was carried out to investigate the effect of the partial replacement of cowpeas (CP) with hard-to-cook (HTC) beans on the chemical, nutritional and sensory characteristics of koki. Towards this objective, two varieties of beans--Phaseolus vulgaris (red kidney beans--RKB and mottled brown beans--MBB), each with the HTC defect, were separately incorporated into cowpea paste in the following Bean:CP ratios 0:100, 20:80, 30:70, 40:60, 50:50, 60:40 and processed into koki. Incorporation of dry HTC beans into cowpeas in the making of koki affected the bulking properties of the uncooked paste, the nutrient composition, essential amino acid content, antinutritional factors, digestibility as well as the sensory attributes of cooked koki. Sensory tests showed that a highly acceptable, nutritious and digestible koki can be processed from cowpeas partially replaced with dry HTC bean paste up to levels of about 40-50% depending on the variety of dry bean used.

Amino Acids↗
PubMed2002

The effects of supplementing Napier grass (Pennisetum purpureum) with rock phosphate and steamed bone meal compared with a commercial mineral mix on phosphorus absorption in cattle.

Twelve Boran steers with a mean live weight of 215.8 +/- 13.9 kg were used in an incomplete Latin Square experiment to compare the apparent phosphorus (P) absorption in cattle when Napier grass (Pennisetum purpureum) was supplemented with Busumbu rock phosphate (BRP), Minjingu rock phosphate (MRP), steamed bone meal (SBM) or a commercial mineral mix (CMM). The steers were housed individually and supplemented with P at 0, 4.5 or 17.5 g P/day. Dry matter intake (DMI) and dry matter digestibility (DMD) were not affected (p > 0.05) by the source of P. Live weight gains (LWG) were different (p < 0.05) across the sources of P. The coefficient for apparent P absorption from the supplement (CAPA), DMD and LWG decreased linearly (p < 0.05) with period. Dry matter intakes were not significantly different (p > 0.05) across periods. The level of P supplementation had no significant effect (p > 0.05) on DMI or LWG. However, increasing the level of P supplementation significantly increased (p < 0.05) the DMD of the basal diet. There was also a significant (p < 0.05) source x level interaction for CAPA. The CMM had the highest CAPA, which decreased from 106% to 74.7% with increasing level of P supplementation. For SBM, BRP and MRP, increasing P supplementation also increased CAPA. The CAPA for SBM and BRP and BRP and MRP were not significantly (p > 0.05) different from each other. These results suggest that BRP has potential as a source of P for ruminants.

Animal Nutritional Physiological Phenomena↗
PubMed2003

Vulgarone B, the antifungal constituent in the steam-distilled fraction of Artemisia douglasiana.

Antifungal activity of the steam distilled essential oil fraction of Artemisia douglasiana was detected by bioautography on silica gel TLC plates against three Colletotrichum spp. The active principle was isolated by bioassay-directed fractionation using column chromatography followed by crystallization and was characterized as vulgarone B by 1H and 13C NMR and GC-MS. Antifungal activity of vulgarone B was further evaluated using 96-well microtiter assay against Colletotrichum acatatum, C. fragariae, C. gloeosporioides, and Botrytis cinerea. In addition, the antifungal activity of vulgarone B and verbenone, and their corresponding alcohols was tested by bioautography and microtiter assay. Structure-activity studies revealed that the alpha, beta-unsaturated carbonyl functionality is a prerequisite for the antifungal activity of these mono and sesquiterpene ketones. This is the first report of antifungal activity of vulgarone B. The yield of essential oil from A. douglasiana is about 0.6-0.8% by weight of the dry material, including plant stems.

Antifungal Agents↗