THE TOXICITY AND ABSORPTION OF 2-SULFANILAMIDOPYRIDINE AND ITS SOLUBLE SODIUM SALT     

Marshall EK  Bratton AC  Litchfield JT 《Science (New York, N.Y.)》1938,88(2295):597-599

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THE DETERMINATION OF SULFANILAMIDE     

Marshall EK  Litchfield JT 《Science (New York, N.Y.)》1938,88(2273):85-86

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Direct inhibition of maintenance respiration in western hemlock roots exposed to ambient soil carbon dioxide concentrations     

McDowell NG  Marshall JD  Qi J  Mattson K 《Tree physiology》1999,19(9):599-605

Root respiration often exhibits a direct and immediate decline with increasing concentrations of ambient soil carbon dioxide concentration ([CO(2)]), and recent evidence suggests this decline may be attributable to a decline in maintenance respiration within the root. If true, this concept could provide a clue to the biochemical process underlying respiratory inhibition as well as improve our knowledge of the timing and degree to which this inhibition occurs in nature. To test the hypothesis that maintenance respiration exhibits a direct, negative response to increasing [CO(2)], we measured total respiration in intact root systems of western hemlock (Tsuga heterophylla (Raf.) Sarg.) seedlings grown at different relative growth rates and exposed to soil [CO(2)]s ranging from 91 to 7008 &mgr;mol mol(-1). Analysis of covariance was used to separate maintenance from total respiration. Total respiration declined exponentially with increasing [CO(2)]. Maintenance respiration, which comprised 85% of total respiration over all treatments, also declined exponentially with increasing [CO(2)]. Growth respiration was not inhibited at any [CO(2)]. These findings may explain why roots of some fast-growing species do not show [CO(2)] inhibition.  相似文献   

A regression-based equivalence test for model validation: shifting the burden of proof     

Robinson AP  Duursma RA  Marshall JD 《Tree physiology》2005,25(7):903-913

Model validation is often realized as a test of how well model predictions match a set of independent observations. One would think that the burden of proof should rest with the model, to force it to show that it can make accurate predictions. Further, one would think that increasing the sample size ought to increase the model's ability to demonstrate its utility. Traditional statistical tools are inappropriate for this because they default to the case that the model and the data are no different, and their ability to detect differences increases with the sample size. These traditional tools are optimized to detect differences, rather than similarities. We present an alternative strategy for model validation that is based on regression and statistical tests of equivalence. Equivalence tests reverse the usual null hypothesis: they posit that the populations being compared are different and use the data to prove otherwise. In this sense, equivalence tests are lumping tests, whereas the traditional statistical tests are splitting tests. To date, model validation with equivalence tests has focused on comparisons of means. Our proposed test checks not only for similarity of means, but also for similarity between individual predictions and observations. The strategy is demonstrated using three case studies that differ in their modeling objectives, and for varied sample sizes. The proposed strategy provides a formal means of model validation that is superior to traditional statistical tests in each case.  相似文献   

Time-series analysis of delta13C from tree rings. I. Time trends and autocorrelation     

Monserud RA  Marshall JD 《Tree physiology》2001,21(15):1087-1102

Univariate time-series analyses were conducted on stable carbon isotope ratios obtained from tree-ring cellulose. We looked for the presence and structure of autocorrelation. Significant autocorrelation violates the statistical independence assumption and biases hypothesis tests. Its presence would indicate the existence of lagged physiological effects that persist for longer than the current year. We analyzed data from 28 trees (60-85 years old; mean = 73 years) of western white pine (Pinus monticola Dougl.), ponderosa pine (Pinus ponderosa Laws.), and Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. glauca) growing in northern Idaho. Material was obtained by the stem analysis method from rings laid down in the upper portion of the crown throughout each tree's life. The sampling protocol minimized variation caused by changing light regimes within each tree. Autoregressive moving average (ARMA) models were used to describe the autocorrelation structure over time. Three time series were analyzed for each tree: the stable carbon isotope ratio (delta(13)C); discrimination (delta); and the difference between ambient and internal CO(2) concentrations (c(a) - c(i)). The effect of converting from ring cellulose to whole-leaf tissue did not affect the analysis because it was almost completely removed by the detrending that precedes time-series analysis. A simple linear or quadratic model adequately described the time trend. The residuals from the trend had a constant mean and variance, thus ensuring stationarity, a requirement for autocorrelation analysis. The trend over time for c(a) - c(i) was particularly strong (R(2) = 0.29-0.84). Autoregressive moving average analyses of the residuals from these trends indicated that two-thirds of the individual tree series contained significant autocorrelation, whereas the remaining third were random (white noise) over time. We were unable to distinguish between individuals with and without significant autocorrelation beforehand. Significant ARMA models were all of low order, with either first- or second-order (i.e., lagged 1 or 2 years, respectively) models performing well. A simple autoregressive (AR(1)), model was the most common. The most useful generalization was that the same ARMA model holds for each of the three series (delta(13)C, delta, c(a) - c(i)) for an individual tree, if the time trend has been properly removed for each series. The mean series for the two pine species were described by first-order ARMA models (1-year lags), whereas the Douglas-fir mean series were described by second-order models (2-year lags) with negligible first-order effects. Apparently, the process of constructing a mean time series for a species preserves an underlying signal related to delta(13)C while canceling some of the random individual tree variation. Furthermore, the best model for the overall mean series (e.g., for a species) cannot be inferred from a consensus of the individual tree model forms, nor can its parameters be estimated reliably from the mean of the individual tree parameters. Because two-thirds of the individual tree time series contained significant autocorrelation, the normal assumption of a random structure over time is unwarranted, even after accounting for the time trend. The residuals of an appropriate ARMA model satisfy the independence assumption, and can be used to make hypothesis tests.  相似文献   

Estimating CO(2) flux from snowpacks at three sites in the Rocky Mountains     

McDowell NG  Marshall JD  Hooker TD  Musselman R 《Tree physiology》2000,20(11):745-753

Soil surface CO(2) flux (F(s)) is the dominant respiratory flux in many temperate forest ecosystems. Snowpacks increase this dominance by insulating the soil against the low temperature to which aboveground components are exposed. However, measurement of F(s) in winter may be impeded by snow cover. Likewise, developing annual F(s) models is complicated by seasonal variation in root and microbial metabolism. We compared three methods of measuring sub-snow F(s): (1) dynamic chamber measurements at the upper snowpack surface (F(snow)), (2) dynamic chamber measurements at the soil surface via snowpits (F(soil)), and (3) static estimates based on measured concentrations of carbon dioxide ([CO(2)]) and conductance properties of the snowpack (F(diffusional)). Methods were compared at a mid-elevation forest in northeastern Washington, a mid-elevation forest in northern Idaho, and a high-elevation forest and neighboring meadow in Wyoming. The methods that minimized snowpack disturbance, F(diffusional) and F(snow), yielded similar estimates of F(s). In contrast, F(soil) yielded rates two to three times higher than F(snow) at the forested sites, and seven times higher at the subalpine meadow. The ratio F(soil)/F(snow) increased with increasing snow depth when compared across all sites. Snow removal appears to induce elevated soil flux as a result of lateral CO(2) diffusion into the pit. We chose F(snow) as our preferred method and used it to estimate annual CO(2) fluxes. The snowpack was present for 36% of the year at this site, during which time 132 g C m(-2), or 17% of the annual flux, occurred. We conclude that snowpack CO(2) flux is quantitatively important in annual carbon budgets for these forests and that the static and dynamic methods yield similar and reasonable estimates of the flux, as long as snowpack disturbance is minimized.  相似文献   

Demographic factors associated with the diet quality of older US men: baseline data from the Osteoporotic Fractures in Men (MrOS) study     

Shannon J  Shikany JM  Barrett-Connor E  Marshall LM  Bunker CH  Chan JM  Stone KL  Orwoll E;Osteoporotic Fractures in Men 《Public health nutrition》2007,10(8):810-818

OBJECTIVE: Throughout the world, the proportion of the male population aged 65 years and older is increasing. Yet, we have limited information regarding diet quality and predictors of diet quality in this segment of the population. The objectives of the current analyses are to describe the diet quality of a cohort of men >65 years of age, and identify lifestyle factors associated with poor diet quality. METHODS: We present a cross-sectional analysis of the diet quality of 5928 men, aged 65-100 years, who are participants in the Osteoporotic Fractures in Men (MrOS) cohort study. Dietary intake was determined using a modified Block 98 food-frequency questionnaire. Diet quality was calculated using the previously validated Diet Quality Index-Revised (DQI-R). Univariate and multivariate modelling was used to estimate the variance in diet quality predicted by a number of sociodemographic factors, including age, race/ethnicity, body mass index (BMI), marital status, education, smoking status, physical activity, self-perceived health and nutritional supplement use. RESULTS: Overall, we found that in this geographically diverse group of older men, diet quality was low, with a mean modified DQI-R for the entire study population of 62.5 (standard deviation 13.1) out of an ideal of 100. Further, younger age, very low total calorie intake (< or = 1187 kcal day- 1), higher BMI, residence in a North or Southeast community, being of African-American or Hispanic race, being less educated, not using dietary supplements and smoking were each significant independent predictors of a poorer diet. CONCLUSION: These data may prove useful in both understanding the dietary intake of older US men as it relates to published dietary guidelines, and for targeting future dietary intervention programmes.  相似文献   

Optimizing the use of breed types in developing country livestock production systems: a neglected research area     

K. Marshall 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2014,131(5):329-340

Developing country livestock production systems are diverse and dynamic, and include those where existing indigenous breeds are currently optimal and likely to remain so, those where non‐indigenous breed types are already in common use, and systems that are changing, such as by intensification, where the introduction of new breed types represents significant opportunities. These include opportunities to improve the livelihood of the world's poor, increase food and nutrition security and enhance environmental sustainability. At present, very little research has focused on this issue, such that significant knowledge gaps in relation to breed‐change interventions remain. The purpose of this study is to raise awareness of this issue and suggests strategic research areas to begin filling these knowledge gaps. Such strategic research would include (i) assessing the impact of differing breed types in developing country livestock productions systems, from a range of viewpoints including intrahousehold livelihood benefit, food and nutrition security at different scales, and environmental sustainability; (ii) identification of specific livestock production systems within developing countries, and the type of livestock keepers within these system, that are most likely to benefit from new breed types; and (iii) identification of new breed types as candidates for in‐situ testing within these systems, such as through the use of spatial analysis to identify similar production environments combined with community acceptance studies. Results of these studies would primarily assist stakeholders in agriculture, including both policy makers and livestock keepers, to make informed decisions on the potential use of new breed types.  相似文献   

Control of ion transport by the sperm duct epithelium of brook trout (Salvelinus fontinalis)     

William S. Marshall  Sharon E. Bryson  David R. Idler 《Fish physiology and biochemistry》1989,7(1-6):331-336

The sperm duct epithelium of brook trout (Salvelinus fontinalis), mountedin vitro in Ussing-style epithelial chambers actively absorbs Na⁺ (measured as the short-circuit current, I_sc) and secretes K⁺ (measured using⁸⁶Rb⁺ as tracer). Dibutyryl-cyclic-adenosine monophosphate (db-cAMP) and 3-isobutyl-1-methylxanthine (IMX) produce a rapid, sustained stimulation of both ion transport processes, but the hormone connected to the response is unknown. Purified sockeye salmon CON A2 gonadotropin (GtH) produces a dose-dependent, rapid and sustained rise in Na⁺ uptake and K⁺ secretion. The time course, electrophysiological and transport characteristics are similar to those evoked by IMX. Carbohydrate-poor (chum salmon CON A1) GtH is ineffective. Pretreatment of fish with 17α,20β-dihydroxy-4-pregnen-3-one (17α,20β-P) significantly increases milt volume but is without effect on resting or stimulated (IMX + db-cAMP) levels of sperm duct ion transport. This is the first indication of a direct, rapid action of GtH on ion transport by the vertebrate blood-testis barrier. The results suggest direct involvement of GtH in control of later stages of sperm maturation.  相似文献   

Crude glycerol,a biodiesel byproduct,used as a soil amendment to temporarily immobilise and then release nitrogen     

Mriganka De  John E. Sawyer  Marshall D. McDaniel 《European Journal of Soil Science》2022,73(3):e13241

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