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Inflammation is the body's response to injury and is characterized by pain, swelling, redness, and heat. Eicosanoids are lipid mediators of inflammation. Leukotrienes (LT) are 20-carbon eicosanoids produced ...
Citation Citation
- Title:
- Dietary polyunsaturated fatty acids and leukotriene production in poultry
- Author:
- Jha, Shantibhushan
Inflammation is the body's response to injury and is characterized by pain, swelling, redness, and heat. Eicosanoids are lipid mediators of inflammation. Leukotrienes (LT) are 20-carbon eicosanoids produced from arachidonic acid (AA), an n-6 fatty acid (FA), and eicosapentaenoic acid (EPA), an n-3 FA. LT produced from AA are proinflammatory (LTB₄) and those produced from EPA (LTB₅) are less inflammatory. Two experiments were conducted. The objective of the first experiment was to optimize the assay conditions for LT production by platelets from chickens, and neutrophils from horses and dogs. Optimal production of LT from equine and canine neutrophils and chicken platelets was characterized in terms of incubation time (2.5, 5, 10, 15 or 20 minutes), temperature (25 or 37°C), and calcium ionophore A23187 concentration (0.1, 1, 10 or 20 μM). In all species, incubation at 37°C resulted in optimal LTB₄ production compared to 25°C (p≤0.05). Production of LTB₄ was maximum when neutrophils were stimulated with 20 μM calcium ionophore A23187 in all species (p≤0.05). Incubation times greater than 2.5 minutes did not further increase LTB₄ production in chickens and horses; in dogs, incubation for 2.5 and 10 minutes resulted in the highest concentrations of LTB₄ (p≤0.05). These results indicate that platelets from chickens, and neutrophils from horses and dogs, are capable of producing LTB₄; optimum conditions for LTB₄ production are similar in all three species. In the second study, the effect of feeding diets that differed in n-6 and n-3 FA ratios to breeder hens was investigated with regard to changes in composition of immune tissue, alteration of delayed-type-hypersensitivity (DTH) response, and LT production by platelets. Chicks hatched to hens fed these diets were also studied with regard to fatty acid composition of immune tissues and LT production by platelets at various stages of growth (7, 14, 21 days). A total of 72 breeder hens were randomly divided into three groups (n=24) and fed diets supplemented with either 3.0% (by weight) sunflower oil (SF0; rich in n-6 FA; Diet I), a mixture of 1.5% SF0 and 1.5% fish oil (Diet II), or 3.0% fish oil (FO; rich in n-3 FA; Diet III). Production of LTB₄ and LTB₅ by platelets stimulated with calcium ionophore A23187 were assessed by RP-HPLC. The hens fed Diet I synthesized 43.9 ± 2.5 ng of LTB₄ per 5x10⁶ cells compared to 13.3 ± 0.9 ng of LTB₄ from hens fed Diet II (p≤0.05). However, no LTB₄ was produced by hens fed Diet III. Production of LTB₅ by platelets of hens fed Diet III was 36.7 ± 4.9 ng compared to 47.4 ± 5.7 ng of LTB₅ from hens fed Diet II. No LTB₅ was produced by hens fed Diet I. The DTH reaction was smaller at 48 hrs post injection of bovine serum albumin in hens fed the 3% FO Diet III (p≤0.05). Fatty acid composition spleen and platelets in hens reflected the fatty acid composition of diets consumed by them (p≤0.05). Hatched chicks from hens fed Diet I produced significantly less LTB₄ at 14 days (p≤0.05) compared to 7- and 21-day-old chicks, which were not different from each other. Chicks from hens fed Diet II produced more LTB₄ at 21 days (p≤0.05) compared chicks from hens fed Diet III produced more LTB₄ at 7 and 21 days (p≤0.05) compared to 14-day-old chicks. There were no significant differences in LTB₅ production from chicks hatched to hens fed Diet III at 7 and 14 days of growth. By 21 days of growth, chicks hatched to hens fed Diet III showed decreased production of LTB₅ compared to 7- and 14-day-old chicks. The spleen and bursa tissue fatty acid composition in chicks at 7 and 14 days of age were similar to the maternal diet fatty acid composition, however, there were no significant differences in platelet fatty acid composition between the groups at different stages of growth. These results indicate that the type of fat in diets fed to breeder hens may alter the inflammatory response in hatched chicks, which could lead to less mortality and increased production performance in poultry.
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4152. [Article] Distribution and life history of the spiny dogfish (Squalus acanthias) off the Oregon and Washington coasts
This study examines the spatial and temporal distribution and life history of the "offshore" component of the Northeastern Pacific spiny dogfish (Squalus acanthias) population. Distribution was examined ...Citation Citation
- Title:
- Distribution and life history of the spiny dogfish (Squalus acanthias) off the Oregon and Washington coasts
- Author:
- Richards, Jaclyn M.
This study examines the spatial and temporal distribution and life history of the "offshore" component of the Northeastern Pacific spiny dogfish (Squalus acanthias) population. Distribution was examined in relation to latitude, depth, the Columbia River plume and large-scale climate changes. Fishery and survey data indicate that the Northeastern Pacific spiny dogfish population has a broad range along the Washington and Oregon coasts, with the highest abundance occurring off the northern Washington and central Oregon coasts. Catches, however, were patchy throughout the 37-year period of available survey data. In terms of depth, the greatest abundances of spiny dogfish were captured in shallow waters (55-184 m). An examination of the influence of the Columbia River plume using a generalized additive model (GAM) indicated that the fish were influenced significantly by the salinity, chlorophyll and surface temperature patterns associated with the plume, preferring the oceanic zone to the plume zone. In contrast, there was no indication that the catch-per-unit-effort of spiny dogfish was influenced by the Pacific Decadal Oscillation (PDO) or the El-Niño (ENSO) over 24-year period of the National Marine Fisheries (NMFS) triennial shelf groundfish survey (1977-2001). The multi-cohort age structure of the population, due to the spiny dogfish's late age at maturity and long lifespan, as well as the low fecundity make it difficult to detect the loss of a single cohort or two when examining abundance trends. Moreover, effects on abundance may be time-lagged, especially if, as is likely, the youngest cohort(s) is the most vulnerable life stage. Their absence would not become evident until they were large enough to have been captured by the survey gear. Sensitive abundance data and/or age-structured data would be needed to identify a pattern. I quantified the age, maturation and fecundity of the spiny dogfish and use these data to develop an age-structured matrix model to examine the sensitivity of the population's growth rate to changes in mortality (i.e. fishing). Female spiny dogfish in this population have an average age at 50% maturity of 28 years and males 20 years. Average length at 50% maturity was 85.0 cm for females and 71.5 cm for males. Female fecundity was extremely low, averaging eight pups per clutch biennially and ranging from four to 14. The number of pups increased with length, but not age. Using these data, a deterministic, female-based model was developed. Asymptotic population growth rate (λ) was determined to be very low, 1.01, and comparable to population growth rates calculated for "coastal" populations. When fishing mortality was incorporated into the model, the fishery was only sustainable when exploitation was low and strict size limits enforced. When fecundity was doubled, the population growth rate increased from 1% to 3% per year. This 33% increase in population growth was equivalent to the effect of a decrease in the age at first maturity of three years. Given that responses to changes in population demographics through shifts in fecundity or spawning frequency are likely constrained, responses would then seem likely to involve changes in age at maturity. These life history traits translate into a low potential population growth and as a consequence high susceptibility to overfishing. My findings indicate that the Northeastern Pacific spiny dogfish are relatively slow growing, late to mature, and have low fecundity and a patchy distribution, with large catches occurring off the northern Washington and central Oregon coasts in shallow waters (55-184 m). These life history traits and distributional patterns are useful in the development of population models to predict responses to environmental fluctuations or increased mortality and thus the management of the population. It is evident from my findings that periodic monitoring is necessary to track possible catch declines off the northern Washington and central Oregon coasts and prevent collapse of the population should it be targeted by a fishery and overfishing occur.
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4153. [Article] Flavor chemistry of blue cheese
Numerous attempts have been made to identify the flavor compounds in Blue cheese, however, duplication of Blue cheese flavor has not yet been accomplished. Therefore, it was desirable to make a qualitative ...Citation Citation
- Title:
- Flavor chemistry of blue cheese
- Author:
- Anderson, Dale Fredrick
Numerous attempts have been made to identify the flavor compounds in Blue cheese, however, duplication of Blue cheese flavor has not yet been accomplished. Therefore, it was desirable to make a qualitative and quantitative investigation of Blue cheese flavor compounds and to study the effect of certain microorganisms on Blue cheese flavor. The aroma fraction of Blue cheese was isolated by centrifugation of the cheese and molecular distillation of the recovered fat. The volatiles were separated by gas chromatography on packed columns containing polar and nonpolar phases and by temperature programmed capillary column gas chromatography. Relative retention time data and fast scan mass spectral analysis of the capillary column effluent were used to identify compounds in the aroma fraction. Compounds positively identified were as follows: 2-pentanone, 2-hexanone, 2-heptanone, 2-octanone, 2-nonanone, 2-decanone, 2-undecanone, 2-tridecanone, 2-propanol, 2-pentanol, 2-heptanol, 2-octanol, 2-nonanol, methyl butanoate, methyl hexanote, methyl octanoate, methyl decanoate, methyl dodecanoate, ethyl formate, ethyl acetate, ethyl butanoate, ethyl hexanoate, ethyl octanoate, ethyl decanoate, ethanal, 3-methyl butanal, 2-methyl butanol, 3-methyl butanol, 1-pentanol, benzene, and toluene. Tentatively identified compounds included acetone, delta-octalactone, delta-decalactone, methyl acetate, isopropyl hexanoate, 3-methylbutyl butanoate, pentyl hexanoate, ethyl-2-methylnonanoate, isopropyl decanoate, furfural, 2-methyl propanal, methanol, ethanol, 2-phenylethanol, cresyl methyl ether, dimethylcyclohexane, diacetyl, methyl mercaptan, and hydrogen sulfide. A combination of liquid-liquid column chromatography and gas-liquid chromatography was utilized to quantitate the major free fatty acids in Blue and Roquefort cheese samples. The average concentration (mg acid/kg cheese) in three Blue cheese samples was as follows: 2:0, 826; 4:0, 1, 448; 6:0, 909; 8:0, 771; 10:0, 1,318; 12:0, 1,588; 14:0, 5,856; 16:0, 12,789; 18:0, 4,243; 18:1, 12,455; 18:2, 1,072; 18:3, 987. Roquefort cheese was found to be proportionately more abundant in 8:0 and 10:0 acids and low in 4:0 acid compared to Blue cheese. No formic, propionic, or isovaleric acid was detected in any of the cheeses tested. A quantitative procedure involving adsorption chromatography, liquid-liquid chromatography and absorption spectrophotometry was used to isolate and measure the concentration of the C₃, C₅, C₇, C₉, and C₁₁ methyl ketones in the fat of Blue and Roquefort cheese. The average methyl ketone concentration (micromoles ketone/10 g cheese fat) of five Blue cheese samples was as follows: acetone, 1.7; 2-pentanone, 5.9; 2-heptanone, 11.2; 2-nonanone, 9.3; 2-undecanone, 2. 4. Considerable variation in ketone concentration was noted between samples, but no consistent differences were observed between Blue and Roquefort cheese. One Roquefort sample contained no acetone. The annount of ketone formed during cheese curing does not depend directly on the amount of available fatty acid precursor. There appears to be a selective conversion of the 8:0, and to a lesser extent the 6:0 and 10:0, fatty acids to methyl ketones by the Penicillium roqueforti spores. The concentration of the C₅, C₇, and C₉ secondary alcohols was determined in the same cheeses used for ketone analysis. The previously measured ketones acted as internal standards and facilitated a semi-quantitative calculation of alcohol concentrations from peak areas of gas chrorriatograms. The average alcohol concentration (micromoles alcohol/10 g cheese fat) in five Blue cheese samples was as follows: 2-pentanol, 0. 3; 2-heptanol, 2. 1; 2-nonanol, 0. 8. The alcohols were present in approximately the same ratios as their methyl ketone analogs, but at much lower concentrations. A synthetic Blue cheese flavor was prepared using a blend of butterfat, dry curd cottage cheese, cream, and salt as a base. The most typical flavor was obtained using the following' compounds: the 2:0, 4:0, 6:0, and 8:0 fatty acids at two-thirds the average concentration found in cheese; twice the average concentration of the C₃, C₅, C₇, C₉, and C₁₁ methyl ketones and C₅, C₇, and C₉ secondary alcohols found in cheese: 2.0 mg/kg of base of 2-phenylethanol; 1.5 mg/kg of base of ethyl butanoate; 6.0 mg/kg of base of both methyl hexanoate and methyl octanoate. Incorporation of higher acids caused a soapy flavor. The presence of 2-phenylethanol and the esters was judged as very important in duplicating Blue cheese flavor. The mycelia of Penicillium roqueforti appear to be more active in the reduction of methyl ketones to secondary alcohols than the spores. Yeasts associated with Blue cheese are capable of reducing methyl ketones to secondary alcohols. Yeasts also may play a role in Blue cheese flavor by producing ethanol and other alcohols and certain esters.
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4154. [Article] Science basis for changing forest structure to modify wildfire behavior and severity
Fire, other disturbances, physical setting, weather, and climate shape the structure and function of forests throughout the Western United States. More than 80 years of fire research have shown that physical ...Citation Citation
- Title:
- Science basis for changing forest structure to modify wildfire behavior and severity
- Author:
- Graham, Russell T., McCaffrey, Sarah, Jain, Theresa B.
Fire, other disturbances, physical setting, weather, and climate shape the structure and function of forests throughout the Western United States. More than 80 years of fire research have shown that physical setting, fuels, and weather combine to determine wildfire intensity (the rate at which it consumes fuel) and severity (the effect fire has on vegetation, soils, buildings, watersheds, and so forth). Millions of acres of forestlands (mainly in dry forests dominated by ponderosa pine and/or Douglas-fir) contain a high accumulation of flammable fuels compared to conditions prior to the 20th century. Forests with high stem density and fuel loading combined with extreme fire weather conditions have led to severe and large wildfires (such as those seen in the summers of 2000, 2002, and 2003) that have put a number of important values at risk. Although homes in the path of a wildfire are perhaps the most immediately recognized value, these wildfires also put numerous other human and ecological values at risk, such as power grids, drinking water supplies, firefighter safety, critical habitat, soil productivity, and air quality. For a given set of weather conditions, fire behavior is strongly influenced by stand and fuel structure. Crown fires in the dry forest types represent an increasing challenge for fire management as well as a general threat to the ecology of these forests and the closely associated human values. Crown fires are dependent on the sequence of available fuels starting from the ground surface to the canopy. Limiting crown fire in these forests can be accomplished by actions that manage in concert the surface, ladder, and crown fuels. Reducing crown fire and wildland fire growth across landscapes decreases the chances of developing large wildfires that affect human values adjacent to forested areas. However, a narrow focus on minimizing crown fire potential will not necessarily reduce the damage to homes and ecosystems when fires do occur. Homes are often ignited by embers flying far from the fire front, and by surface fires. Fire effects on ecosystems can also occur during surface fires where surface and understory fuels and deep organic layers are sufficient to generate high temperatures for long periods. Fuel treatments can help produce forest structures and fuel characteristics that then reduce the likelihood that wildfires will cause large, rapid changes in biophysical conditions. Fuel treatments can also help modify fire behavior sufficiently so that some wildfires can be suppressed more easily. Subsequent, sustained fuel treatments can maintain these conditions. Different fuel reduction methods target different components of the fuel bed. Thinning mainly affects standing vegetation, and other types of fuel treatments such as prescribed fire and pile burning woody fuels are needed to modify the combustion environment of surface fuels. In forests that have not experienced fire for many decades, multiple fuel treatments—that is, thinning and surface fuel reduction—may be required to significantly affect crown fire and surface fire hazard. Fuel treatments cannot guarantee benign fire behavior but can reduce the probability that extreme fire behavior will occur. Fuel treatments can be designed to restore forest conditions to a more resilient and resistant condition than now exists in many forests, and subsequent management could maintain these conditions, particularly in dry forests (ponderosa pine and Douglas-fir) where crown fires were historically infrequent. The degree of risk reduction will depend to some degree on the level of investment, social and economic acceptability of treatments, and concurrent consideration of other resource values (for example, wildlife). This report describes the kinds, quality, amount, and gaps of scientific knowledge for making informed decisions on fuel treatments used to modify wildfire behavior and effects in dry forests of the interior Western United States (especially forests dominated by ponderosa pine and Douglas-fir). A review of scientific principles and applications relevant to fuel treatment primarily for the dry forests is provided for the following topics: fuels, fire hazard, fire behavior, fire effects, forest structure, treatment effects and longevity, landscape fuel patterns, and scientific tools useful for management and planning.
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4155. [Article] Science basis for changing forest structure to modify wildfire behavior and severity
Fire, other disturbances, physical setting, weather, and climate shape the structure and function of forests throughout the Western United States. More than 80 years of fire research have shown that physical ...Citation Citation
- Title:
- Science basis for changing forest structure to modify wildfire behavior and severity
- Author:
- Graham, Russell T., McCaffrey, Sarah, Jain, Theresa B.
Fire, other disturbances, physical setting, weather, and climate shape the structure and function of forests throughout the Western United States. More than 80 years of fire research have shown that physical setting, fuels, and weather combine to determine wildfire intensity (the rate at which it consumes fuel) and severity (the effect fire has on vegetation, soils, buildings, watersheds, and so forth). Millions of acres of forestlands (mainly in dry forests dominated by ponderosa pine and/or Douglas-fir) contain a high accumulation of flammable fuels compared to conditions prior to the 20th century. Forests with high stem density and fuel loading combined with extreme fire weather conditions have led to severe and large wildfires (such as those seen in the summers of 2000, 2002, and 2003) that have put a number of important values at risk. Although homes in the path of a wildfire are perhaps the most immediately recognized value, these wildfires also put numerous other human and ecological values at risk, such as power grids, drinking water supplies, firefighter safety, critical habitat, soil productivity, and air quality. For a given set of weather conditions, fire behavior is strongly influenced by stand and fuel structure. Crown fires in the dry forest types represent an increasing challenge for fire management as well as a general threat to the ecology of these forests and the closely associated human values. Crown fires are dependent on the sequence of available fuels starting from the ground surface to the canopy. Limiting crown fire in these forests can be accomplished by actions that manage in concert the surface, ladder, and crown fuels. Reducing crown fire and wildland fire growth across landscapes decreases the chances of developing large wildfires that affect human values adjacent to forested areas. However, a narrow focus on minimizing crown fire potential will not necessarily reduce the damage to homes and ecosystems when fires do occur. Homes are often ignited by embers flying far from the fire front, and by surface fires. Fire effects on ecosystems can also occur during surface fires where surface and understory fuels and deep organic layers are sufficient to generate high temperatures for long periods. Fuel treatments can help produce forest structures and fuel characteristics that then reduce the likelihood that wildfires will cause large, rapid changes in biophysical conditions. Fuel treatments can also help modify fire behavior sufficiently so that some wildfires can be suppressed more easily. Subsequent, sustained fuel treatments can maintain these conditions. Different fuel reduction methods target different components of the fuel bed. Thinning mainly affects standing vegetation, and other types of fuel treatments such as prescribed fire and pile burning woody fuels are needed to modify the combustion environment of surface fuels. In forests that have not experienced fire for many decades, multiple fuel treatments—that is, thinning and surface fuel reduction—may be required to significantly affect crown fire and surface fire hazard. Fuel treatments cannot guarantee benign fire behavior but can reduce the probability that extreme fire behavior will occur. Fuel treatments can be designed to restore forest conditions to a more resilient and resistant condition than now exists in many forests, and subsequent management could maintain these conditions, particularly in dry forests (ponderosa pine and Douglas-fir) where crown fires were historically infrequent. The degree of risk reduction will depend to some degree on the level of investment, social and economic acceptability of treatments, and concurrent consideration of other resource values (for example, wildlife). This report describes the kinds, quality, amount, and gaps of scientific knowledge for making informed decisions on fuel treatments used to modify wildfire behavior and effects in dry forests of the interior Western United States (especially forests dominated by ponderosa pine and Douglas-fir). A review of scientific principles and applications relevant to fuel treatment primarily for the dry forests is provided for the following topics: fuels, fire hazard, fire behavior, fire effects, forest structure, treatment effects and longevity, landscape fuel patterns, and scientific tools useful for management and planning.
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Several aspects of the potent inhibition of bovine plasma amine oxidase (PAO) by hydrazines were investigated by kinetic and preparative means. The inhibition was classified as pseudo-irreversible by the ...
Citation Citation
- Title:
- Studies on the inhibition of bovine plasma amine oxidase by hydrazines
- Author:
- Hucko-Haas, Jacqueline Elizabeth
Several aspects of the potent inhibition of bovine plasma amine oxidase (PAO) by hydrazines were investigated by kinetic and preparative means. The inhibition was classified as pseudo-irreversible by the method of Ackerman and Potter (Proc. Soc. Exptl. Biol. Med. 72, 1 (1949), and was found to exhibit Zone B kinetic behavior (Straus and Goldstein, J. Gen. Physiol. 26, 559 (1943)). The constancy of the mole ratio of inhibitor to enzyme which produced 50% inhibition, (I/E)₅₀, for PAO preparations of different degrees of purity demonstrated the unique specificity of these inhibitors for PAO. Inhibitor potency as a function of structure was found to parallel the reactivity of these hydrazines towards carbonyls in model systems. The kinetically determined amount of (unsubstituted) hydrazine which produced 100% inhibition was found to correspond exactly with the reported pyridoxal phosphate (PLP) content of the enzyme. The isolation of a ¹⁴C-labelled EI complex confirmed this stoichiometry. These results, coupled with the spectral observations of Yamada and Yasunobu (J. Biol. Chem. 238, 2669 (1963)) led to the conclusion that the inhibition most likely proceeded from a nucleophilic attack of the hydrazine molecule on the carbonyl of the enzyme's PLP to form a stable azomethine via a transaldiminization reaction. The kinetic competition observed between hydrazines and substrate indicated that they react with PAO at the same site, PLP, thus confirming the proposal originated by Tabor, Tabor, and Rosenthal (J. Biol. Chem. 208, 645 (1954)) that PLP is involved in the active site. Inhibitor potency was found to decrease with increasing N-methyl substitution in a manner which could not be related exclusively to either steric or inductive effects of the substituents, but rather, depended on the presence or absence of a hydrogen alpha to the attacking nucleophilic -NH₂ on the hydrazine molecule. Thus, binding of hydrazines to the catalytic site of PAO may involve a three-point attachment. Therefore, the active site of PAO can be visualized to contain two subsites: one which binds the α-H of hydrazines or substrates by non-covalent forces, which functions to optimally orient the molecule for the chemical reaction at the enzyme's primary site, PLP. The titration of PAO by hydrazines was found to exhibit a biphasic response. Low inhibitor concentrations enhanced PAO activity, but high concentrations inhibited. This apparent homotropic cooperative effect suggested the presence of an allosteric site for the binding of these inhibitors. PAO was found to exhibit anomalous kinetic order with respect to substrate in the presence of hydrazines; v vs. (S) curves were sigmoidal. Normal Michaelis-Menten kinetics were followed in the absence of these inhibitors, indicating that the binding of a hydrazine molecule by the enzyme potentiated an effect which resulted in the binding of more than substrate molecule. High substrate inhibition of PAO was found to conform to the Haldane mechanism. The dissymmetry of v vs. log (S) plots indicated that at high substrate concentrations PAO binds more than two substrate molecules. Thus, PAO may contain an allosteric site for substrate as well as for hydrazines. A hypothetical model is presented which accounts for these experimental observations in terms of the nature and interaction of PAO's inhibitor and substrate binding sites. PAO was found to undergo a time- and concentration-dependent activation in dilute solution at room temperature, pH 7.0, in the presence or absence of hydrazines which could not be attributed to the presence of an endogenous activator or inhibitor (v vs. (E) plots were linear). Gel-filtration experiments revealed that the activation in the absence of hydrazines was not caused by a shift in the monomer- polymer equilibrium or the dissociation of PAO into subunits. Only one species was eluted from the column (which had a molecular weight corresponding to that of the monomer) whether the enzyme was activated or not. This peak was likewise independent of PAO concentration. These results led to the conclusion that the activation of the enzyme in the absence of inhibitor is most likely due to a conformational change. The activation of the inhibited enzyme was found to be greater than that of the "enzyme alone" control; in other words, the inhibition appeared to be reversed. This reversal of inhibition was found to follow first order (with respect to (EI) kinetics indicating that it was caused by the catalytic decomposition of the hydrazine inhibitors by the enzyme.
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4157. [Article] Biological interrelationships between the Ambrosia beetle Xyleborus dispar with its symbiotic fungus Ambrosiella hartigii
Biological interrelationships between the ambrosia beetle Xyleborus dispar (F.) (Coleoptera:Scolytidae) with its symbiotic fungus, Ambrosiella hartigii Batra (Fungi Imperfecti) were investigated in western ...Citation Citation
- Title:
- Biological interrelationships between the Ambrosia beetle Xyleborus dispar with its symbiotic fungus Ambrosiella hartigii
- Author:
- French, John Richard Joseph
Biological interrelationships between the ambrosia beetle Xyleborus dispar (F.) (Coleoptera:Scolytidae) with its symbiotic fungus, Ambrosiella hartigii Batra (Fungi Imperfecti) were investigated in western Oregon. Postdiapause adults of X. dispar collected in March through June with rotary nets, and excised from overwintered and newly attacked host material, produced a single generation when the beetle was reared in vitro with A. hartigii. Diapause beetles excised from host materials in the fall failed to oviposit. This study is the first record of rearing a temperate zone scolytid in vitro and on a fungus in the genus Ambrosiella. Such in vitro rearing allowed controlled studies of ecological, behavioral, developmental and physiological aspects of this ectosymbiosis. Comparisons were made between wild and in vitro populations. Seasonal variations of the fungus within the female beetles mesonotal mycangium, and the synchronization of ovariole development were demonstrated. Comparative concentrations of solube proteins and free amino acids suggested that the fungus in the mycangia was built up from free amino acids of the insects. At the period of emergence, flight and attack of new hosts, the females were found to have a concentration of soluble proteins more than double that found in the beetles during the remainder of the year. Whereas, the free amino acids were the lowest values recorded during this period (March-October). Ovariole development and oviposition only occurred after the post-diapause female had fed on the ambrosial form of A. hartigii. These beetles attacked a new host with empty intestinal tracts. The relationship between the number of progeny and the volume of the galleries was linear. Experiments were conducted in an attempt to terminate maturation diapause in this univoltine species of ambrosia beetle using temperature, Juvenile Hormone Analogs (JHA) and an olfactometer. Termination of the maturation diapause was not achieved with these procedures. Qualitative and quantitative analyses of the major nitrogenous excretory products were made on the various life stages of X. dispar. The main nitrogenous product found in excreta and hindguts of beetles, larvae and pupae, was uric acid (range 7.6-14.8 μg uric acid/beetle). No ninhydrin-positive compounds were located in excreta of the beetles. The concentration of ammonia-nitrogen in the various life stages averaged between 0.70-1.13 μg NH₃-N/beetle. Total nitrogen determinations were made on sapwood samples of Malus sylvestris (0.34 ± 0.005% N by dry weight), attacked wood, "pre-brood" (0.31 ± 0.005% N by dry weight) and attacked wood-"post-brood" (0.17 + 0.02% N). Similar determinations of the artificial medium (L-asparagine) indicated that a nitrogen requirement of about 0.08 -0.1% N by dry weight was necessary before oviposition could occur. Fixation of atmospheric nitrogen by individual X. dispar beetles in vitro was not indicated using the acetylene ethylene reductase method. In vivo situations may be different, but were not investigated. Proteolytic enzyme activity was not found on examination of dispause beetles, their excreta, larval and pupal excreta, and the ambrosial and mycelial forms of A. hartigii. Bioassays were used to study the interactions and effects of the various life stages of X. dispar on the induction of the ambrosial form of its symbiotic fungus, A. hartigii. Postdiapause adults and pupae of X. dispar were able to cause a change from the mycelial to the ambrosial form of A. hartigii in culture. Larvae fed on the mycelia' form in vitro, but ambrosia is required by larvae to develop and pupate. One of the main factors inducing the ambrosial form of A. hartigii is probably a secretory product of X. dispar. Nitrogenous compounds are considered necessary for the cause of ambrosial induction, but not the primary factor alone for the continued growth of the ambrosia. Morphogenic compounds that caused ambrosial induction in vitro responded negatively to the Azocoll procedure, indicating no proteolytic activity. The symbiotic association of X. dispar and its sole food fungus, A. hartigii is a reciprocal biochemical alliance based on carbon and nitrogen metabolic integration. The beetles contribute their free amino acids and nitrogenous excretions, and the fungus con - tributes its cellulose-degrading enzymic ability to the association, plus synthesizing proteins, sterols, vitamins and other growth factors. The beetle-fungus symbiosis has been depicted in the form of an abstract pattern.
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The results of the research presented in this work are related to synthesis and investigations of novel color inorganic pigments having various structures and shades. Inorganic pigments play a major role ...
Citation Citation
- Title:
- The Role of Materials Chemistry in Designing Advanced Color Inorganic Pigments
- Author:
- Medina, Elena A.
The results of the research presented in this work are related to synthesis and investigations of novel color inorganic pigments having various structures and shades. Inorganic pigments play a major role in contemporary life. They are used in paints, rubber, plastic, cosmetics etc. Searching for new, stable, environmentally benign and cheap pigments is an important task of materials science. Several classes of colored inorganic oxides have been prepared and studied using various methods and techniques including powder X-ray (XRD) and neutron diffraction, color characterization (L*a*b* parameters), optical (UV-VIS diffuse reflectance and near-IR (NIR) reflectance), magnetic and dielectric properties measurements, infrared (IR) spectroscopy. Pigments A₅Mʹ₃₋ₓMₓO₁₂X (A = Sr, Ba; Mʹ = Cr, Mn; M = V, P; X = F, Cl) with apatite-type structure were prepared using standard solid state, sol-gel and microwave synthesis methods. All samples have bright colors varying from white (x = 3.0) through turquoise (x = 1.5) to dark green (x = 0). The color arises due to a combination of d-d interatomic transitions of Mn⁵⁺/Cr⁵⁺ cations and transition metal–O²⁻ charge transfer. Mn⁵⁺, V⁵⁺ and P⁵⁺ occupy the tetrahedral sites in the structure as shown by Rietveld structure refinement of neutron data. Hibonite – type colored oxides with a general formula of AAl₁₂₋ₓMₓO₁₉ (A = Ca, Sr, RE (rare earths) or any combination thereof; M = Ni, Fe, Mn, Cr, Cu coupled with one of the following: Ga, In, Ti, Sn, Ge, Nb, Ta, Sb) were synthesized through A-site and M-site substitutions. Ni, Fe, Mn, Cr and Cu are chromophore ions and they are responsible for the color of the compounds. Ni²⁺ gives bright sky-blue to royal-blue colors; samples containing different amounts of Fe, Mn, Cr or Cu have diverse colors: ivory, brown, creamy, tan, pink, light turquoise and green. Ni²⁺, Mn²⁺ and Fe³⁺ prefer to occupy the tetrahedral site, Mn³⁺ has a preference for both tetrahedral and octahedral sites, Ti⁴⁺ and Sn⁴⁺ for octahedral site in the hibonite structure. Compounds belong to Li₂Mn₁₋ₓTiₓO₃ (x = 0–1.0) series show bright orange colors varying from dark brick red (x = 0) to orange (x = 0.5) and light orange (x = 0.8). d-d transitions of d electrons of octahedral Mn⁴⁺ and M(IV)–O²⁻ charge transfer are responsible for the colors. Pigments with sillenite-type structure, Bi₁₂₋ₓInₓTiO₂₀ (x = 0–1.5), Bi₁₂₋ₓInₓMn₀.₂Ti₀.₈O₂₀ (x = 0–5.5) and Bi₁₂Mn₁₋ₓMxO₂₀ (M = Ti, Si, Ge), were prepared using standard solid state synthesis through Bi-site and M-site substitutions. Bi₁₂-ₓInₓTiO₂₀ compounds have shades changing from light yellow (x = 0) to beige (x = 1.5); Bi₁₂-ₓInₓMn₀.₂Ti₀.₈O₂₀ series: from forest green (x = 0) to dark sea green (x = 2.5) and light olive drab (x = 5.5); Bi₁₂Mn₁₋ₓMₓO₂₀ (M = Ti, Si, Ge): from dark green (x = 0) to forest green (x = 0.5) and lawn green (x = 0.8); Bi₁₂MO₂₀ (M = Ti, Si, Ge) are light yellow. Mn⁴⁺ (Td) is a chromophore element of the solid solutions, samples become lighter when amount of manganese decreases. Bi₁₂Mn₁₋ₓTiₓO₂₀ (x = 0.2; 0.6; 0.8) phases show paramagnetic behavior in the measured temperature region (5–300 K). All synthesized samples have relatively high reflectance in the near-IR region (700–2500 nm) and are promising candidates for “Cool pigments” applications.
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4159. [Article] Single Phase and Flow Boiling Heat Transfer and Flow Characterization in Microscale Pin Fin Heat Sinks
The ever increasing requirements for heat dissipation in various thermal management applications such as computer chip cooling and high power electronics have necessitated the need for novel thermal management ...Citation Citation
- Title:
- Single Phase and Flow Boiling Heat Transfer and Flow Characterization in Microscale Pin Fin Heat Sinks
- Author:
- Rasouli, Erfan
The ever increasing requirements for heat dissipation in various thermal management applications such as computer chip cooling and high power electronics have necessitated the need for novel thermal management techniques. Thermal management using heat sinks with microscale features is amongst the prominent techniques developed over the past two decades. In this dissertation, single and phase change heat transfer and pressure drop through one such heat sink, namely microscale pin fin heat sinks (µPFHS), is examined experimentally. In particular, effects of pitch-to-diameter and aspect ratio variations are studied on the thermofluidic performance of studied µPFHSs. Single phase heat transfer and pressure drop of two distinct fluids, liquid nitrogen and Performance Fluid (PF5060) are characterized experimentally through the µPFHSs with staggered diamond shape pin fins. The LN₂ and PF5060 experiments' Reynolds number (Re_Dh, based on pin fin hydraulic diameter) is in range of 108-570 and 8-462, respectively. Results are presented in a non-dimensional form in terms of the friction factor (f), Nusselt (Nu), and Reynolds numbers and are compared with the predictions of existing correlations in the literature for micro pin fin heat sinks. Heat sinks with the higher pitch ratio (coarser array) not only show lower pressure drops at a fixed Re_Dh, but also enhance significantly heat transfer rate when compared against the heat sink of the same pin fin size but denser arrangement. Flow visualization experiments using an infrared camera on PF5060 single phase tests are performed to understand the counter-intuitive trends seen in the global results. Flow through heat sinks with the same aspect ratio but larger pitch ratio exhibit unsteady vortex shedding in the wake region of pin fins, which markedly enhances convective heat transfer rate. Existing correlations developed for µPFHSs (such as that by Prasher et al. [1] and Koşar and Peles [2]) are capable of predicting the f and Nu data with good agreement only in the absence of vortex shedding, while the unsteady flow past the transition Re_Dh results in poor comparison of correlations with experimental data. A comparison of the experimental Nu data of PF5060 (Pr≅12.2) with the data of LN₂ (Pr≅1.9) shows significant change between the slopes of the curves of two fluids only in the heat sinks without vortex shedding. In the heat sinks with unsteady vortex shedding, the Nu_Dh curves show significantly decreased dependency on Pr number. Consequently, separate correlations are developed for predicting Nu in the case with and without unsteady vortex shedding using data from two distinct fluids and four PFHS geometries over a range of Re_Dh from 8 to 643. Given the clear heat transfer enhancement that occurs for certain pitch ratio designs of PFHSs in single phase flows, flow boiling experiments with PF5060 are performed to clarify whether additional changes to the pressure drop and two-phase heat transfer coefficient occur upon the introduction of the unsteady vortex shedding. Subcooled (∆T_sub=12.5℃) and saturated flow boiling of PF5060 through the micro pin fins are investigated. The heat sinks are tested at three constant mass fluxes of 30, 60, and 100 kg/m².s with heat fluxes ranging from 1.1 to 17.8 W⁄(cm² ) based on the planform area of the heat sinks. Flow regimes are studied with high speed imaging. Nucleate boiling heat transfer is the dominant mechanism for exit vapor qualities less than 0.5; at higher qualities annular film evaporation becomes dominant. The salient effect of unsteady vortex shedding is in elimination of wall temperature overshoot. In nucleate boiling regime, the heat sinks with unsteady flow flapping show higher two-phase heat transfer coefficients. The predictions of existing correlations for h_tp in literature are not in good agreement with the experimental data (MAE>30%) and show a systematic deviation depending on the µPFHSs dimensions.
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The 4s³P₁ state of argon decays radiatively by a resonance transition to the 3p⁶¹S₀ ground state; the wavelength of this radiation is 1067A. By direct observation of the decay of the 1067A radiation from ...
Citation Citation
- Title:
- A direct lifetime measurement for a resonance transition in argon
- Author:
- Dickerson, George Fielden
The 4s³P₁ state of argon decays radiatively by a resonance transition to the 3p⁶¹S₀ ground state; the wavelength of this radiation is 1067A. By direct observation of the decay of the 1067A radiation from excited argon gas, a value of 0.93±0.06 x 10⁻⁵ seconds has been obtained for the natural lifetime of the 4s³P₁ state. The failure of this state to appear as a metastable state points up the inadequacy of a description of the argon atom by Russel-Saunders coupling. The calculated value (25) of 1.05 x 10⁻⁵ seconds for the natural lifetime of the 4s³P₁ state requires a larger degree of mixing of the strict Russel-Saunders terms than does the value measured in this experiment. The measurement was made using a modified delayed coincidence method (3). Bombardment of argon gas with a pulsed beam of controlled energy electrons was used to produce cyclic excitation and relaxation of the gas. The cyclic regeneration of the argon decay allowed the entire decay curve to be determined by examining it piecemeal. A small portion of the decay curve is repetetively examined by gating a detector such that it is active only during a small fraction of each cycle. During each cycle the location in time of this sampling interval is set by triggering the gating signal with a delayed pulse which is produced at the termination of the excitation. Different portions of the decay curve are examined by adjusting the delay of the trigger pulse. Because the detector output is a constant which varies only when the location of the sampling interval is shifted along the decay curve, this method avoids the problem of attempting to record a single transient. The atomic excitation is produced within a nine liter cylindrical volume. A slow molecular type flow of argon is maintained through this excitation chamber. The pressure is essentially uniform within this chamber and is varied over the range of 10⁻³ to 10⁻¹ Torr. The electron gun, located at the center of the excitation chamber, consists of the cathode and grid structure of a 6SJ7 electron tube. The spread in energy of electrons from this gun was small enough to allow selective excitation of the 4s multiplet of argon, but selective excitation of levels within this multiplet could not be achieved. Radiation from the excitation chamber was detected with a Bendix magnetic photomultiplier (20) which was separated from the excitation chamber by a thinly cleaved lithium fluoride window. This photomultiplier is sensitive only to radiation in the wavelength region between 2A and 1500A. Final identification of the observed radiation as that from the 4s³P₁-3p₆¹S₀ transition was made using a vacuum spectrograph. Since the intensity of radiation from the excitation chamber is directly proportional to the concentration of argon atoms in the 4s³P₁ state, it is the decay of these atoms that is determined. This decay will be governed by the radiative decay constant only if collisional transfer of excitation and trapping of resonance radiation can be neglected. Throughout the range of pressure used in this experiment the rate constants associated with both these processes are known to be pressure dependent (21, 22) and the effect of resonance trapping can be observed separately by its dependence upon the enclosure geometry. It is to be expected that the predominant collision process will be the two body collisions which result in the exchange of excitation between the 4s³P₁ level and the adjacent metastable levels. The experimental data consistently yield decay curves which represent the sum of two exponential decays having different decay constants. The larger of these decay constants is independent of gas pressure and the smaller one is approximately directly proportional to pressure. Neither is dependent upon enclosure geometry. Therefore, it is concluded that the effects of resonance trapping are negligible, and that the de-excitation of argon atoms in the 4s³P₁ state is governed predominantly by radiative decay and by two body collisions which result in the transfer of excitation to or from this state. The cross sections for collisional transfer is approximately 4 x 10⁻¹⁵cm² at room temperature. The fact that resonance radiation from the 4s¹P₁ state of argon was not observed indicates that this radiation is heavily trapped and that collisional transfer is primarily responsible for the decay of this state. It thus appears that there is a large difference in the natural lifetimes of the two radiative 4s levels. This implication is in disagreement with the experimental results obtained by Vaughan & Stacy (35).