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Query: UMLS:C0851184 (thinning)
 11,252 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The production of pullulan from beet molasses by a pigment-free strain of Aztreobasidium pullulans on shake-flask culture was investigated. Combined pretreatment of molasses with sulfuric acid and activated carbon to remove potential fermentation inhibitors present in molasses resulted in a maximum pullulan concentration of 24 g/L, a biomass dry wt of 14 g/L, a pullulan yield of 52.5%, and a sugar utilization of 92% with optimum fermentation conditions (initial sugar concentration of 50 g/L and initial pH of 7.0). The addition of other nutrients as carbon and nitrogen supplements (olive oil, ammonium sulfate, yeast extract) did not further improve the production of the exopolysaccharides. Structural characterization of the isolated polysaccharides from the fermentation broths by 13C-nuclear magnetic resonance spectroscopy and pullulanase digestion combined with size-exclusion chromatography confirmed the identity of pullulan and the homogeneity (>93% dry basis) of the elaborated polysaccharides by the microorganism. Using multiangle laser light scattering and refractive index detectors in conjunction with high-performance size-exclusion chromatography molecular size distributions and estimates of the molecular weight (Mw = 2.1-4.1 x 10(5)), root mean square of the radius of gyration (R = 30-38 nm), and polydispersity index (Mw/Mn = 1.4-2.4) were obtained. The fermentation products of molasses pretreated with sulfuric acid and/or activated carbon were more homogeneous and free of contaminating proteins. In the concentration range of 2.8-10.0 (w/v), the solution's rheologic behavior of the isolated pullulans was almost Newtonian (within 1 and 1200 s(-1) at 20 degrees C); a slight shear thinning was observed at 10.0 (w/v) for the high molecular weight samples. Overall, beet molasses pretreated with sulfuric acid and activated carbon appears as an attractive fermentation medium for the production of pullulan by A. pullulans.
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PMID:Production and characterization of pullulan from beet molasses using a nonpigmented strain of Aureobasidium pullulans in batch culture. 1190 Jan 13

Low-elevation ponderosa pine (Pinus ponderosa Dougl. ex. Laws.) forests of the northern Rocky Mountains historically experienced frequent low-intensity fires that maintained open uneven-aged stands. A century of fire exclusion has contributed to denser ponderosa pine forests with greater competition for resources, higher tree stress and greater risk of insect attack and stand-destroying fire. Active management intended to restore a semblance of the more sustainable historic stand structure and composition includes selective thinning and prescribed fire. However, little is known about the relative effects of these management practices on the physiological performance of ponderosa pine. We measured soil water and nitrogen availability, physiological performance and wood radial increment of second growth ponderosa pine trees at the Lick Creek Experimental Site in the Bitterroot National Forest, Montana, 8 and 9 years after the application of four treatments: thinning only; thinning followed by prescribed fire in the spring; thinning followed by prescribed fire in the fall; and untreated controls. Volumetric soil water content and resin capsule ammonium did not differ among treatments. Resin capsule nitrate in the control treatment was similar to that in all other treatments, although burned treatments had lower nitrate relative to the thinned-only treatment. Trees of similar size and canopy condition in the three thinned treatments (with and without fire) displayed higher leaf-area-based photosynthetic rate, stomatal conductance and mid-morning leaf water potential in June and July, and higher wood radial increment relative to trees in control units. Specific leaf area, mass-based leaf nitrogen content and carbon isotope discrimination did not vary among treatments. Our results suggest that, despite minimal differences in soil resource availability, trees in managed units where basal area was reduced had improved gas exchange and growth compared with trees in unmanaged units. Prescribed fire (either in the spring or in the fall) in addition to thinning, had no measurable effect on the mid-term physiological performance and wood growth of second growth ponderosa pine.
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PMID:Physiological responses of ponderosa pine in western Montana to thinning, prescribed fire and burning season. 1563 82

A modified back-etch method is described that has been successfully used to prepare samples of thin films and nanoparticles on Si wafer substrates for examination by high-resolution transmission electron microscopy (HRTEM). This process includes ultrasonic cutting, abrasive pre-thinning and a two-stage etching procedure. Unlike previous reports of back-etching methods, tetramethyl ammonium hydroxide, which has a very high-etching selectivity of Si to SiO(2), is used for the final etching to allow removal of the Si without degradation of the SiO(2) membrane. An innovative wrapping method is also described. This novel approach reduces the preparation time for HRTEM samples to <1 h per sample for groups of 10 or more samples. As an example, the preparation of FePt nanoparticle samples for HRTEM imaging is described.
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PMID:A modified back-etch method for preparation of plan-view high-resolution transmission electron microscopy samples. 1704 Sep 30

We investigated the impacts of forest thinning, prescribed fire, and contour ripping on community level physiological profiles (CLPP) of the soil microbial population in postmining forest rehabilitation. We hypothesized that these management practices would affect CLPP via an influence on the quality and quantity of soil organic matter. The study site was an area of Jarrah (Eucalyptus marginata Donn ex Sm.) forest rehabilitation that had been mined for bauxite 12 years previously. Three replicate plots (20 x 20 m) were established in nontreated forest and in forest thinned from 3,000-8,000 stems ha(-1) to 600-800 stems ha(-1) in April (autumn) of 2003, followed either by a prescribed fire in September (spring) of 2003 or left nonburned. Soil samples were collected in August 2004 from two soil depths (0-5 cm and 5-10 cm) and from within mounds and furrows caused by postmining contour ripping. CLPP were not affected by prescribed fire, although the soil pH and organic carbon (C), total C and total nitrogen (N) contents were greater in burned compared with nonburned plots, and the coarse and fine litter mass lower. However, CLPP were affected by forest thinning, as were fine litter mass, soil C/N ratio, and soil pH, which were all higher in thinned than nonthinned plots. Furrow soil had greater coarse and fine litter mass, and inorganic phosphorous (P), organic P, organic C, total C, total N, ammonium, microbial biomass C contents, but lower soil pH and soil C/N ratio than mound soil. Soil pH, inorganic P, organic P, organic C, total C and N, ammonium, and microbial biomass C contents also decreased with depth, whereas soil C/N ratio increased. Differences in CLPP were largely (94%) associated with the relative utilization of gluconic, malic (greater in nonthinned than thinned soil and mound than furrow soil), L-tartaric, succinic, and uric acids (greater in thinned than nonthinned, mound than furrow, and 5-10 cm than 0-5 cm soil). The relative utilization of amino acids also tended to increase with increasing soil total C and organic C contents but decreased with increasing nitrate content, whereas the opposite was true for carboxylic acids. Only 45% of the variance in CLPP was explained using a multivariate multiple regression model, but soil C and N pools and litter mass were significant predictors of CLPP. Differences in soil textural components between treatments were also correlated with CLPP; likely causes of these differences are discussed. Our results suggest that 1 year after treatment, CLPP from this mined forest ecosystem are resilient to a spring prescribed fire but not forest thinning. We conclude that differences in CLPP are likely to result from complex interactions among soil properties that mediate substrate availability, microbial nutrient demand, and microbial community composition.
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PMID:Impact of ecosystem management on microbial community level physiological profiles of postmining forest rehabilitation. 1789 48

Oil-in-water emulsions stabilised by anionic surfactant and gelatin provide the bulk of photographic coating fluids. Their rheology is of crucial importance to the fluids' performance in coating and their concentration in drying. Gelatin complexes with non-adsorbed micelles and adsorbs to the oil-surfactant-water interface, which effects an increase in the viscosity of the continuous phase and the volume of the nano-sized oil droplets, respectively. The consequences of these interactions are high viscosity and strong shear thinning. Here, the effects on the emulsion rheology of a series of bulk, commercially available surfactants were studied. These co-surfactants were chosen so as to weaken the interactions between gelatin and the anionic surfactant and hence reduce viscosity and thinning thus enabling the emulsions to be concentrated. The co-surfactants had polar head groups of three types: simple nonionic based on polyethylenenoxide, simple cationic based on a quaternary alkyltrimethyl ammonium, and combined nonionic-cationic based on a quaternised bis-ethoxylated primary amine. This last type proved the most effective at reducing the low-shear viscosity of the emulsion and reducing the shear thinning, although, at high concentrations the polyethoxylated cationic surfactants induced flocculation and coalescence of the oil droplets.
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PMID:Rheology and stability of oil-in-water nanoemulsions stabilised by anionic surfactant and gelatin 1) addition of nonionic, cationic and ethoxylated-cationic co-surfactants. 1883 65

1. In all age groups the effects of ammonium chloride administration were found to be strikingly dependent upon the calcium intake. 2. Dogs receiving an adequate calcium diet and ammonium chloride showed less decalcification than those receiving a low calcium diet with or without ammonium chloride. 3. In the younger groups the added effect of ammonium chloride to calcium-low diet brought out more striking changes than a low calcium diet alone. 4. When the decalcification was less severe-in the oldest dogs on the low calcium diet with or without ammonium chloride, and in the younger dogs on an adequate calcium intake with ammonium chloride -generalized thinning of the bones without marrow fibrosis resulted (osteoporosis). 5. When the decalcification was rapid and severe-in the youngest dogs on low calcium diet, particularly with ammonium chloride- generalized decalcification and secondary marrow fibrosis resulted (ostitis fibrosa). 6. Generalized ostitis fibrosa is a rather inclusive term and may be applied to the histologic picture which results when clinical or experimental decalcification is rapid, and therefore leads to extensive marrow fibrosis. 7. The special underlying causes of the decalcification may incidentally contribute features to modify the generalized osteoporosis or ostitis fibrosa as in rickets and in von Recklinghausen's disease.
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PMID:AMMONIUM CHLORIDE DECALCIFICATION, AS MODIFIED BY CALCIUM INTAKE: THE RELATION BETWEEN GENERALIZED OSTEOPOROSIS AND OSTITIS FIBROSA. 1987 Jan 5

High-internal phase aqueous-in-oil emulsions of two surfactant concentrations were studied using small-angle neutron scattering (SANS) and simultaneous in situ rheology measurements. They contained a continuous oil phase with differing amounts of hexadecane and d-hexadecane (for contrast matching experiments), a deuteroaqueous phase almost saturated with ammonium nitrate, and an oil-soluble stabilizing polyisobutylene-based surfactant. The emulsions' macroscopic rheological behavior has been related to quantify changes in microscale and nanoscale structures observed in the SANS measurements. The emulsions are rheologically unexceptional and show, inter alia, refinement to higher viscosity after high shear, and shear thinning. These are explained by changes observed in the SANS model parameters. Shear thinning is explained by SANS-observed shear disruption of interdroplet bilayer links, causing deflocculation to more spherical, less linked, aqueous droplets. Refinement to higher viscosity is accompanied by droplet size reduction and loss of surfactant from the oil continuous phase. Refinement occurs because of shear-induced droplet anisotropy, which we have also observed in the SANS experiment. This observed anisotropy and the emulsion refinement cannot be reproduced by either isolated molecule or mean-field models but require a more detailed consideration of interdroplet forces in the sheared fluid.
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PMID:Nano- and microstructure of high-internal phase emulsions under shear. 2018 May 79

Taking a dense spruce pure plantation as test object and simulating the formation of natural forest gap, this paper studied the effects of low intensity thinning by gap creation on the ground temperature, ground humidity, and nutrient contents in different soil layers of the plantation. In the first year of gap creation, the mean diurnal temperature in the gap across the growth season (May - September) increased, while the mean diurnal humidity decreased. The soil organic matter (SOM) and NH4(+) -N contents in O-horizon (humus layer) increased by 19.62% and 283.85%, and the dissolved organic carbon (DOC) and NO3(-) -N contents decreased by 77.86% and 23.60%, respectively. The SOM, total nitrogen (TN), and NO3(-) -N contents in 0-10 cm soil layer increased by 45.77%, 37.14%, and 75.11%, and the NH4(+) -N, DOC, and total phosphorus (TP) contents decreased by 48.56%, 33.33%, and 13.11%, respectively. All the results suggested that low intensity thinning by gap creation could rapidly improve the ground microclimate of the plantation, and consequently, promote the soil microbial activity and mineralization processes in O-horizon, the release of soil nutrients, and the restoration of soil fertility.
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PMID:[Short-term effects of low intensity thinning simulated by gap on ground microclimate and soil nutrients of pure spruce plantation]. 2056 Mar 5

Sodium laurate (SL), which is otherwise sparingly soluble in water at room temperature, forms viscoelastic fluids when mixed with cationic cetyl trimethylammonium bromide (CTAB) micelles. This originates from a cooperative assembly of CTAB and SL through electrostatic interaction and the ability of the tetralkyl ammonium headgroup in decreasing the Kraft point of SL. Addition of SL to CTAB induces the formation of rod-like micelles, the length of which can be controlled by the composition of the mixture. The effects of electrostatic repulsion of ionic moieties and steric repulsion of hydrocarbon chains in controlling the packing of surfactant molecules within the aggregate have been identified. The variation in the optimum interfacial area occupied by the surfactant as a function of electrolyte concentration is consistent with the model predicted by Nagarajan. Small angle neutron scattering studies indicate that the micelles undergo composition dependent uniaxial growth without any significant change in the cross section radius, in the absence of electrolytes. However, in the presence of NaCl, both the length and cross section radius of the elongated micelles are sensitive to composition. At small axial ratio, these micelles behave like Newtonian fluids, while long polymer-like micelles show shear thinning behavior. The dynamic rheological responses of long micelles are consistent with a Maxwell type viscoelastic behavior.
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PMID:Viscoelastic fluids originated from enhanced solubility of sodium laurate in cetyl trimethyl ammonium bromide micelles through cooperative self-assembly. 2066 52

Poly([stearyl methacrylate]-stat-[2-(dimethylamino) ethyl methacrylate]) was synthesised through radical polymerisation using 1,1-diphenyl ethylene (DPE) as a molecular weight controlling agent. The amino groups were further quaternised into a cationic form in order to increase water solubility. Solubility of the polymers in water and a mixed solvent was studied with rotational rheometry. The resulting poly[(stearyl methacrylate)-stat-([2-(methacryloyloxy)ethyl] trimethyl ammonium iodide)] was soluble in water when the amount of stearyl methacrylate (SMA) in the polymer was less than 17 mol%. At higher SMA content, solubility strongly decreased but could be improved by using an organic co-solvent. Viscosity of the SMA-based statistical co-polymers is strongly dependent on polymer composition but solvent quality also has an influence, and the fluidic character can be either Newtonian or shear-thinning, or a weak gel can be formed. Concentration dependence behaviour deviates from that of typical polyelectrolytes. SMA polymers retain low viscosity up to rather high concentrations, but above a certain limiting concentration, the viscosity rapidly increases. This phenomenon is stronger with a higher amount of hydrophobic side-chain. At high co-polymer concentrations no entanglement formation was observed, and rheological behaviour indicates that SMA segments form aggregates in water solution.
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PMID:Synthesis and solution rheology of poly[(stearyl methacrylate)-stat-([2-(methacryloyloxy)ethyl] trimethyl ammonium iodide)]. 2072 32


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