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At least 973 records · Page 54Linked to original sources
PubMed2006

Optimisation of integrated biodiesel production. Part I. A study of the biodiesel purity and yield.

This study consists of the development and optimisation of the potassium hydroxide-catalysed synthesis of fatty acid methyl esters (biodiesel) from sunflower oil. A factorial design of experiments and a central composite design have been used. The variables chosen were temperature, initial catalyst concentration by weight of sunflower oil and the methanol:vegetable oil molar ratio, while the responses were biodiesel purity and yield. The initial catalyst concentration is the most important factor, having a positive influence on biodiesel purity, but a negative one on biodiesel yield. Temperature has a significant positive effect on biodiesel purity and a significant negative influence on biodiesel yield. The methanol:vegetable oil molar ratio is only significant for the biodiesel purity, having a positive influence. Second-order models were obtained to predict biodiesel purity and yield as a function of these variables. The best conditions are 25 degrees C, a 1.3%wt for the catalyst concentration and a 6:1 methanol:sunflower oil molar ratio.

Bioreactors↗
PubMed2006

Yield, size and bacterial blotch resistance of Pleurotus eryngii grown on cottonseed hulls/oak sawdust supplemented with manganese, copper and whole ground soybean.

Experiments were performed to determine effects of supplementation of cottonseed hull/sawdust substrate with Mn, Cu, and ground soybean on yield, mushroom size, and bacterial blotch resistance of two commercial strains of Pleurotus eryngii. A basal formulation (d.w.) of cottonseed hulls (62%), aged red oak sawdust (27%), whole ground soybean (6%), corn distiller's waste (4%) and calcium sulfate (1%) was supplemented to 50, 150 or 250 microg/g Mn or Cu and to 4%, 8% and 12% whole ground soybean. The cottonseed hulls content in the basal substrate was adjusted to compensate for the addition of ground soybean. Formulated substrates were mixed, placed in 1050ml bottles, and sterilized at 121 degrees C for 90min. Mushroom yields were significantly higher from substrates containing Mn at 50 microg/g and soybean at 8% and 12% supplementation compared to the basal substrate. As the level of soybean addition to substrate increased, yield also increased. The addition of Mn at levels of 150 and 250 microg/g significantly enhanced yield as well, although less than did the 50 microg/g treatment. To assess the influence of mushroom strain and substrate composition on blotch disease severity, pilei of P. eryngii were inoculated with Pseudomonas tolaasii. Strain WC888 was more resistant to disease than WC846. Disease severity was greater when substrates were amended with Cu to 150 or 250 microg/g. There was a significant difference in inherent levels of Cu in the basidiomata of different strains, but P. eryngii did not accumulate Cu and disease severity was not correlated with Cu content of the basidiomata.

Analysis of Variance↗
PubMed2006

Accumulation of copper in brown rice and effect of copper on rice growth and grain yield in different rice cultivars.

A pot experiment with 38 commonly cultured rice cultivars showed that the effect of Cu (100 mg kg(-1)) on rice growth, grain yield and accumulation of Cu in brown rice varied greatly with different cultivars. Although the average Cu concentration in brown rice of the 38 cultivars was significantly increased (P<0.01) compared with the control, in none of the cultivars did Cu concentration in brown rice exceed the maximum permissible limit of 10 mg Cu kg(-1). This suggests that rice grown in Cu-contaminated paddy soil (100 mg Cu kg(-1)) will not adversely affect human health through the food chain. Because of the significant negative correlation between grain weight and Cu concentration in brown rice with the soil Cu treatment, screening for cultivars with low Cu accumulation in brown rice and high grain yield for Cu-contaminated areas is feasible. The present research led to the recommendation of three such cultivars: Jiahua, Zhenxian 866, Zhe 733. The average grain yield under Cu treatment (100 mg Cu kg(-1) soil) was significantly (P<0.01) reduced compared with the control. The decreases or increases of grain yields mainly resulted from the combined effects of the panicles per pot, spikelets per panicle and filled spikelets per panicle under the soil Cu treatment. Furthermore, there were significant (r=0.869, P<0.01) positive correlations between the RC (relative changes) of spikelets per panicle and filled spikelets per panicle under the soil Cu treatment.

Copper↗
PubMed2005

Hardness and yield strength of dentin from simulated nano-indentation tests.

The finite element method (FEM) is applied for studying the hardness (H) and yield strength (Y) of dentin subjected to a nano-indentation process. The nano-indentation experiments were simulated with the ABAQUS finite element software package. This test, performed with a spherical indenter, was simulated by axisymmetric finite element analysis. The load versus displacement was calculated during loading-unloading sequence for different elastic modulus (E) and yield strength. Hardness and maximum principal compressive and tensile stresses were plotted for different elastic modulus depending on yield strength. The dentin was assumed to be isotropic, homogenous and elasto-plastic. The theoretical results outlined in this study were compared with the experimental works reported in the literature and then hardness and yield strength of dentin was estimated.

Dentin↗
PubMed2005

The initiating radical yields and the efficiency of polymerization for various dental photoinitiators excited by different light curing units.

OBJECTIVES: To evaluate the efficiency of the photopolymerization of dental resins it is necessary to know to what extent the light emitted by the light curing units is absorbed by the photoinitiators. On the other hand, the efficiency of the absorbed photons to produce species that launch the polymerization process is also of paramount importance. Therefore, the previously determined PAE (photon absorption efficiency) is used in conjunction with the polymerization quantum yields for the photoinitiators, in order to be able to compare the total process on an equivalent basis. This parameter can be used to identify the best performance for the photochemical process with specific photoinitiators. METHODS: The efficiency of LED (Ultrablue IS) and QTH (Optilux 401) lamps were tested comparing their performances with the photoinitiators camphorquinone (CQ); phenylpropanedione (PPD); monoacylphosphine oxide (Lucirin TPO); and bisacylphosphine oxide (Irgacure 819). The extent of photopolymerization per absorbed photon was determined from the polymerization quantum yields obtained by using the photoinitiators to polymerize methyl methacrylate, and afterwards combined with the previously determined PAEs. RESULTS: Although CQ presents a rather low polymerization quantum yield, its photopolymerization efficiency is practically the highest when irradiated with the Ultrablue LED. On the other hand, Lucirin is much more efficient than the other photoinitiators when irradiated with a QTH lamp, due to its high quantum yield and the overlap between its absorption spectrum and the output of the visible lamp light. SIGNIFICANCE: Difference in photopolymerization efficiencies arise when combinations of photoinitiators are used, and when LED sources are used in preference to QTH. Mechanistic understanding is essential to optimal initiator formulation.

4-Aminobenzoic Acid↗
PubMed2006

Quantum yield of conversion of the photoinitiator camphorquinone.

The primary absorber in dental resins is the photoinitiator, which starts the photo polymerization process. We studied the quantum yield of conversion of camphorquinone (CQ), a blue light photoinitiator, in dental resin composites using a LED lamp (3M FreeLight) and a Quartz Tungsten Halogen (QTH) lamp (VIP) as the light curing units at five different irradiances. The molar extinction coefficient, epsilon(469), of CQ was 46+/-2 cm(-1)/(mol/L) at 469 nm. The reciprocity of irradiance and exposure time holds for changes of CQ absorption coefficient, that is, irradiance x exposure time (=radiant exposure)=constant. Both LED and QTH lamps yielded the same curing threshold (the radiant exposure when CQ absorption drops to 1/e) and the same quantum yield conversion under different irradiances. In our dental resin formulation (0.7 wt.% CQ with reducing agents 0.35 wt.% dimethylaminoethyl methacrylate (DMAEMA) and 0.05 wt.% butylated hydroxytoluene (BHT)) the quantum yield was measured as 0.07+/-0.01 CQ conversion per absorbed photon.

Absorption↗
PubMed2005

To what extent do variabilities in hormones, metabolites and energy intake explain variability in milk yield?

The objective of the present paper is to describe the extent to which variability in milk yield can be explained by variability in plasma hormones, metabolites and DE intake. Results from a study including 317 cows and 634 lactations were used. Detailed registration of performance was carried out on these cows and 10,809 plasma samples analyzed for selected hormones and metabolites. Univariate analysis was carried out on energy-corrected milk yield and concentrations of selected plasma hormones (insulin, growth hormone (GH) and triiodothyronine (T3)), metabolites (non-esterified fatty acids (NEFA)), glucose, beta-hydroxybutyrate (BOHB) and urea nitrogen (BUN), and digestible energy intake (DE intake) to estimate between-cow variation through lactations. Partial least square (PLS) models were subsequently run to estimate the extent to which between-cow differences in energy-corrected milk yield could be explained by between-cow differences in hormone concentrations, metabolite concentration or DE intake. The between-cow variability in energy-corrected milk yield and the hormones and metabolites were generally found to be considerable and total variance changed through lactation, particularly for GH, T3, NEFA and BOHB. In this study, the total variance was highest in third lactation cows. When analyzed separately using partial least square models, hormones, metabolites and DE intake accounted for 24, 25 and 26% of the variability in ECM, respectively. Insulin and glucose were the single most important predictors among the selected hormones and metabolites. When including both the hormones and metabolites, the model explained 36% of the between-cow variability in ECM and this figure was increased to 53% if DE intake was also included. The lack of additivity in the variability explained shows that hormones, metabolites and DE intake were correlated illustrating the integration and orchestration of metabolism and intake. Perspectives of the analysis for use in prevention of diseases and reproduction are briefly discussed.

3-Hydroxybutyric Acid↗
PubMed2005

Microemulsion and diafiltration approaches: an attempt to maximize the global yield of DNA-loaded nanospheres.

The yield of DNA-loaded nanospheres in its widest definition includes encapsulation efficiency and the integrity of the loaded molecules plus the production yield of fabricated nanospheres. The former aspect could be considerably improved by adopting the microemulsion concept to enhance the stability of the primary emulsion during the preparation of nanospheres by the double emulsion solvent-removal method. The droplet size of the mentioned emulsion was monitored by means of photon electron correlation spectroscopy and could serve as an index for emulsion fineness and stability. DNA stability as a function of applied mechanical stress was monitored by horizontal agarose gel electrophoresis. The impact of the primary emulsion on nanosphere porosity was assessed as well. Regarding the second aspect of the global yield of nanospheres, i.e. production yield, a modified diafiltration technique was adopted for the washing and recovery processes in comparison with the traditional and for the conservation of particle size characteristics of the recovered nanospheres.

1-Butanol↗
PubMed2006

A prospective control study of the safety and cellular yield of EUS-guided FNA or Trucut biopsy in patients taking aspirin, nonsteroidal anti-inflammatory drugs, or prophylactic low molecular weight heparin.

BACKGROUND: Although the ASGE recommends that high-risk endoscopic procedures can safely be performed on patients taking aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) in standard doses, there is a paucity of data on EUS-FNA per se in this setting. OBJECTIVE: We studied the safety and cellular yield of EUS-FNA and/or Trucut biopsy (TCB) in patients taking aspirin, NSAIDS, or prophylactic low molecular weight heparins (LMWH). DESIGN: Prospective control study. PATIENTS: Consecutive patients undergoing EUS-FNA and/or TCB were recruited over an 18-month period. The usage of aspirin, NSAIDS, or LMWH were recorded and patients who were not taking these medications served as controls. MAIN OUTCOME MEASUREMENTS: The bleeding events (endosonographic findings of extraluminal bleeding, intraluminal bleeding requiring hemostatic procedures, hematemesis, or melena) and cellular yield were compared between patients and controls. RESULTS: Two hundred fourteen patients (8 had repeat procedures) underwent EUS-FNA and/or TCB on 241 lesions. Bleeding events occurred in none (0 of 26), 33.3% (2 of 6), and 3.7% (7 of 190) of the patients in the aspirin/NSAIDS, LMWH, and control groups, respectively (p = 0.023). The mean numbers of FNA passes, applications of suction, bloody specimens, and cellular yield were not significantly different between patients who were or were not receiving medications. No significant difference in bleeding events was noted between the FNA and TCB groups. CONCLUSION: EUS-FNA or TCB is safe in patients taking aspirin or NSAIDS. Consideration should be given to stopping LMWH before the procedure. The cellular yield and blood contamination of the specimen from FNA are similar to those in controls.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2006

Repeat colonoscopy has a low yield even in symptomatic patients.

BACKGROUND: In many regions, the demand for colonoscopy exceeds its availability. Patients undergoing repeat examinations comprise a significant proportion of those on waiting lists. OBJECTIVE: To assess the yield of repeat colonoscopy in varied clinical settings. DESIGN: Cohort study. SETTING: Endoscopic database of an Australian tertiary referral hospital. PATIENTS: Adults who had >/=2 colonoscopies between 1992 and 2004. Patients were excluded if the repeat procedure was for completion or for high-risk surveillance. MAIN OUTCOME MEASUREMENTS: Yield for neoplasia by indication, interval to repeat examination, and appropriateness for surveillance (determined by National Australian guidelines). RESULTS: A total of 4974 colonoscopies in 2075 patients were studied. The mean age was 63.1 years (range, 19.2-92.4 years). The mean number of examinations was 2.4 (range, 2-8), with a mean interval between examinations of 2.9 years. Colorectal cancer (CRC) was significantly more prevalent at initial colonoscopy compared with subsequent colonoscopies (7.9% vs 0.6%; prevalence ratio 14.2, 95% confidence interval [CI] 8.5-23.7, P < .001), as were advanced adenomas (15.3% vs 4.8%; prevalence ratio 3.2, 95% CI 2.6-3.9, P < .001). No CRCs were detected in symptomatic patients undergoing polyp surveillance examinations performed before the recommended interval. LIMITATIONS: Retrospective design. CONCLUSIONS: Yield of repeat colonoscopy is significantly lower than for initial colonoscopy, irrespective of indication. In symptomatic patients within a polyp surveillance program, the yield is negligible when a colonoscopy is performed before the recommended surveillance interval. The need for a repeat colonoscopy should be carefully considered, and patients who have never had a colonoscopy must take priority on waiting lists over those awaiting repeat examinations.

Adult↗
PubMed2004

Yield of surveillance bronchoscopy for acute rejection and lymphocytic bronchitis/bronchiolitis after lung transplantation.

BACKGROUND: Better understanding of the timing and pattern of surveillance bronchoscopy findings after lung transplantation could influence the timing and frequency of surveillance bronchoscopy. We present our surveillance bronchoscopy experience and test the hypothesis that patients not encountering early acute rejection or lymphocytic bronchitis/bronchiolitis are less likely to have subsequent occult occurrences in the 1st year after lung transplantation. METHODS: We conducted a retrospective study of 204 patients who underword transplantation between 1996 and 2000. Based on contemporary biopsy-specimen grading in the first 100 days, we formed 2 groups: No Early Rejection and Early Rejection. We compared subsequent yields of surveillance bronchoscopy and the incidence of acute rejection or of lymphocytic bronchitis/bronchiolitis. RESULTS: We reviewed 645 biopsies taken from 204 recipients during the first 100 days to classify patients into a No Early Rejection Group (n=67) or an Early Rejection Group (n=137). Yield of surveillance bronchoscopy for acute rejection or lymphocytic bronchitis/bronchiolitis was 31% with the greatest yield during the first 30 days (45%), and then decreasing to 26% (p <0.001). After Day 100, 71% of occult acute rejection episodes involved minimal (A1) lesions. Yield of surveillance bronchoscopy after Day 100 was 20% in the No Early Rejection Group and was 27% in the Early Rejection Group (p=0.22). Incidence of acute rejection or lymphocytic bronchitis/bronchiolitis after Day 100 was 41% in the No Early Rejection Group and was 50% in the Early Rejection Group (p=0.17). CONCLUSION: Surveillance bronchoscopy detects occult acute rejection or lymphocytic bronchitis/bronchiolitis in approximately one-third of biopsy specimens during the 1st year, with the majority of late abnormalities being minimal (A1) rejection. The absence of acute rejection or lymphocytic bronchitis/bronchiolitis during the first 100 days does not predict freedom from such events in the remainder of the 1st year.

Acute Disease↗
PubMed2006

A simple method for estimating activation energies using the fragmentation yield: collision-induced dissociation of iron(II)-phenanthroline complexes in an electrospray ionization mass spectrometer.

The gas-phase stabilities of Fe(Phi)3(2+) complexes, where Phi represents the 1,10-phenanthroline, 5-chloro-1,10-phenanthroline, 5-methyl-1,10-phenanthroline, 3,4,7,8-tetramethyl-1,10-phenanthroline, and 4,7-diphenyl-1,10-phenanthroline ligands were investigated by collision-induced dissociation (CID) in the capillary-first skimmer region upon changing the voltage difference between the capillary and the skimmer. The loss of only one ligand from the Fe(Phi)3(2+) complexes was observed with each of the phenanthroline ligands studied. An increase in the voltage difference between the capillary and the skimmer resulted in a higher fragmentation yield as calculated from the intensity of the precursor and the fragment ion. The fragmentation yield versus capillary-skimmer voltage difference plots were evaluated by means of the Arrhenius and the Rice-Ramsperger-Kassel (RRK) model by fitting the model parameters to the experimental data. Both models yielded practically the same results. In addition, if the internal energy gained through the capillary-skimmer region is estimated correctly, the approximate value of the critical energy (activation energy) for fragmentation can be extracted from the fragmentation yield versus capillary-skimmer voltage difference plots. It was found that the gas-phase stabilities of the Fe(Phi)3(2+) complexes are nearly identical except for the more stable Fe(II)-4,7-diphenyl-1,10-phenanthroline complex. The critical energy for fragmentation was estimated to be approximately 1.2 and 0.9 eV for the Fe(II)- 4,7-diphenyl-1,10-phenanthroline, and the other complexes, respectively.

Journal Article↗
PubMed2007

A novel approach to assess post-yield energy dissipation of bone in tension.

In this study, we proposed a novel approach to assess the energy dissipation during the post-yield deformation of bone. Based on the stress-strain behavior in an incremental and cyclic loading-unloading-reloading scheme in uniaxial tension, we partitioned the post-yield energy dissipation of bone into three distinct pathways: released elastic strain energy (U(er)); irreversible energy (U(i)); and hysteresis energy (U(h)). Among them, U(er) depends on the stiffness loss, U(i) is the energy permanently consumed, and U(h) reflects changes in the viscoelastic behavior of bone in the process of post-yield deformation. As an example, bone specimens from human cadaveric femurs of middle-aged and elderly donors were tested using this approach. The results of this study indicate that there exist age-related differences in post-yield energy dissipation and modulus degradation. These results implicate that this novel approach could detect the age-related differences in energy dissipation of bone and may aid in understanding the underlying mechanisms of such changes.

Aged↗
PubMed2005

Yield stress and zeta potential of nanoparticulate silica dispersions under the influence of adsorbed hydrolysis products of metal ions--Cu(II), Al(III) and Th(IV).

The effects of hydrolysable Cu2+, Al3+ and Th4+ ions on the zeta potential and yield stress behaviour of silica dispersions were evaluated as a function of pH and metal ions concentration. Silica dispersion remained dispersed at its point of zero charge (pzc) of pH approximately 2.0 (CR1). Adsorbed hydrolysis products of Cu2+ and Al3+ caused the dispersion to display two further points of charge reversal (CR2 and CR3) at moderate ions concentration. CR2 occurred near the pH for the formation of the first hydrolysis product. This pH is about 2.8 for Al3+ and 5.0 for Cu2+. For all three metal ions, CR3 approached the pzc of the metal hydroxides at complete surface coverage. At CR3, the dispersions displayed a maximum yield stress. As many as three type of attractive forces; bridging, charged patch and van der Waals, may account for the maximum yield stress at low surface coverage. At complete coverage, only the van der Waals force is in play--the adsorbed hydrolysis products must have increased significantly the effective Hamaker constant of silica. With Al3+ the yield stress was absent at CR2 because particle bridging and charged patch attraction are unimportant as the silica surface charge is near zero. Adsorption of strongly hydrolysed Th4+ ions at pH<2.0 caused the dispersion to display only one pzc (CR3).

Adsorption↗
PubMed2006

A comparative study of quantum yield and electrical energy per order (E(Eo)) for advanced oxidative decolourisation of reactive azo dyes by UV light.

This paper evaluates the quantum yield and electrical energy per order (E(Eo)) efficiency of Reactive Orange 4 (RO4) and Reactive Yellow 14 (RY14) azo dyes by three advanced oxidation processes (AOPs). Both dyes were completely decolourised by all these processes. The relative decolourisation efficiencies of these processes were in the following order: Fe(2+)/H(2)O(2)/UV>UV/TiO(2)>UV/H(2)O(2). The low efficiency of UV/H(2)O(2) process is mainly due to low UV absorption by hydrogen peroxide at the 365nm. The figure of merit E(Eo) values showed that UV/H(2)O(2) process consumes more electrical energy than the other two processes. The electrical energy consumption is in the following order: UV/H(2)O(2)>UV/TiO(2)>Fe(2+)/H(2)O(2)/UV. At low initial dye concentration higher quantum yield was observed in UV/TiO(2) process, whereas in photo-Fenton process higher quantum yield was observed at high initial dye concentration. The structure of dye molecule also influences the quantum yield and E(Eo) value.

Azo Compounds↗
PubMed2004

A chaperone-assisted high yield system for the production of HLA-DR4 tetramers in insect cells.

MHC tetramers have become essential tools for the analysis of antigen specific responses of CD8+ and CD4+ T cells. However, the use of MHC class II tetramers is hampered by the relatively low yields of most current expression systems. We have devised an insect cell/baculovirus expression system in which yields of 50-70 mg of recombinant HLA-DR4 molecules, with or without covalently linked peptide, per liter of insect cell supernatant, are routinely obtained. These yields are rendered possible by an optimized design and use of DRalpha and DRbeta expression cassettes and by co-expression of a housekeeping chaperone of the endoplasmic reticulum, calreticulin, which, due to its co-secretion, increases secretion of HLA-DR molecules two- to threefold. A tetramer produced in the system specifically was shown to stain an HLA-DR4 restricted T cell line obtained from a healthy donor by in vitro priming, but which recognizes a type I diabetes autoantigen. Co-expression of chaperones may represent a general strategy for enhancing yields of recombinant proteins expressed in insect cells and facilitate production of MHC class II tetramers in the future.

Amino Acid Sequence↗
PubMed2006

Increased yield of high purity recombinant human interferon-gamma utilizing reversed phase column chromatography.

Increasing therapeutic applications for recombinant human interferon-gamma (rhIFN-gamma), an antiviral proinflammatory cytokine, has broadened interest in optimizing methods for its production and purification. We describe a reversed phase chromatography (RPC) procedure using Source-30 matrix in the purification of rhIFN-gamma from Escherichia coli that results in a higher yield than previously reported. The purified rhIFN-gamma monomer from the RPC column is refolded in Tris buffer. Optimal refolding occurs at protein concentrations between 50 and 100 microg/ml. This method yields greater than 90% of the dimer form with a yield of 40 mg/g cell mass. Greater than 99% purity is achieved with further purification over a Superdex G-75 column to obtain specific activities of from 2 x 10(7) to 4 x 10(7)IU/mg protein as determined via cytopathic antiviral assay. The improved yield of rhIFN-gamma in a simple chromatographic purification procedure promises to enhance the development and therapeutic application of this biologically potent molecule.

Chromatography↗
PubMed2005

Influence of UV-B exclusion and selenium treatment on photochemical efficiency of photosystem II, yield and respiratory potential in pumpkins (Cucurbita pepo L.).

The influence of ambient and filtered solar ultraviolet-B (UV)-B radiation and of selenium treatment was determined on photochemical efficiency, respiratory potential measured by electron transport system (ETS) activity, and yield in pumpkins, Cucurbita pepo L. Yield and ETS activity were higher when solar UV-B was filtered out. The results suggested that the decreased yield was related to the UV-B impaired flow of electrons in the respiratory chain. Selenium increased yield under ambient radiation conditions. However, no significant effect of excluding UV-B radiation or of treatment with selenium was observed on the photochemical efficiency of photosystem II (PSII).

Cucurbita↗