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Variables
Kinds of Variables Terms modified by Variables Selected AbstractsHIGH POTENCY CANNABIS: THE FORGOTTEN VARIABLEADDICTION, Issue 10 2005NEIL SMITH No abstract is available for this article. [source] SUCROSE DETECTION AND THE STABILITY OF THE 2-AFC PROCEDURE IN THE PRESENCE OF A CONFOUNDING VARIABLEJOURNAL OF SENSORY STUDIES, Issue 5 2008DANIEL SHEPHERD ABSTRACT This study attempted to measure absolute thresholds for sucrose in aqueous solution for 51 experienced judges. Two experiments utilizing the two-alternative forced-choice (2-AFC) procedure generated 6-point psychometric functions plotting percentage correct as a function of sucrose concentration. In both experiments, the judges were divided into two groups and tested in either purpose-built sensory booths or on open tables situated in a laboratory. In the first experiment, the influence of a confounding variable was apparent, with nonmonotonic psychometric functions being obtained. In experiment II, the confounding variable was eliminated, permitting the estimation of absolute thresholds. In both experiments, there was no main effect of gender or session, though there was an effect of testing locality (P < 0.05). Data are reported to emphasize the importance of controlling extraneous variables and to demonstrate the robustness of the 2-AFC procedure. PRACTICAL APPLICATIONS This research contributes to an otherwise impoverished database on the detection of sucrose in a solution. The uses of the research include estimates of sucrose detection thresholds for comparative purposes; confirmation of the stability of the two-alternative forced-choice procedure; the utility of using formal testing areas as opposed to ad hoc testing stations; and the dangers of utilizing substandard experimental equipment while conducting research of this nature. [source] GENDER, STRUCTURAL DISADVANTAGE, AND URBAN CRIME: DO MACROSOCIAL VARIABLES ALSO EXPLAIN FEMALE OFFENDING RATES?,CRIMINOLOGY, Issue 2 2000DARRELL STEFFENSMEIER Building on prior macrosocial-crime research that sought to explain either total crime rates or male rates, this study links female offending rates to structural characteristics of U.S. cities. Specifically, we go beyond previous research by: (1) gender disaggregating the Uniform Crime Report (UCR) index-crime rates (homicide, robbery, aggravated assault, burglary, larceny-theft) across U.S. cities; (2) focusing explicitly on the effects of structural disadvantage variables on the index-offending rates of females; and (3) comparing the effects of the structural variables on female rates with those for male rates. Alternative measures of structural disadvantage are used to provide more theoretically appropriate indicators, such as gender-specific poverty and joblessness, and controls are included for age structure and structural variables related to offending. The main finding is consistent and powerful: The structural sources of high levels of female offending resemble closely those influencing male offending, but the effects tend to be stronger on male offending rates. [source] WHICH VARIABLES EXPLAIN DECISIONS ON IMF CREDIT?ECONOMICS & POLITICS, Issue 2 2005AN EXTREME BOUNDS ANALYSIS This paper analyses which economic and political factors affect the chance that a country receives IMF credit or signs an agreement with the Fund. We use a panel model for 118 countries over the period 1971,2000. Our results, based on extreme bounds analysis, suggest that it is mostly economic variables that are robustly related to IMF lending activity, while most political variables that have been put forward in previous studies on IMF involvement are non-significant. To the extent that political factors matter, they seem more closely related to the conclusion of IMF agreements than to the disbursement of IMF credits. [source] PHYLOGENETICALLY NESTED COMPARISONS FOR TESTING CORRELATES OF SPECIES RICHNESS: A SIMULATION STUDY OF CONTINUOUS VARIABLESEVOLUTION, Issue 1 2003NICK J. B. ISAAC Abstract., Explaining the uneven distribution of species among lineages is one of the oldest questions in evolution. Proposed correlations between biological traits and species diversity are routinely tested by making comparisons between phylogenetic sister clades. Several recent studies have used nested sister-clade comparisons to test hypotheses linking continuously varying traits, such as body size, with diversity. Evaluating the findings of these studies is complicated because they differ in the index of species richness difference used, the way in which trait differences were treated, and the statistical tests employed. In this paper, we use simulations to compare the performance of four species richness indices, two choices about the branch lengths used to estimate trait values for internal nodes and two statistical tests under a range of models of clade growth and character evolution. All four indices returned appropriate Type I error rates when the assumptions of the method were met and when branch lengths were set proportional to time. Only two of the indices were robust to the different evolutionary models and to different choices of branch lengths and statistical tests. These robust indices had comparable power under one nonnull scenario. Regression through the origin was consistently more powerful than the t -test, and the choice of branch lengths exerts a strong effect on both the validity and power. In the light of our simulations, we re-evaluate the findings of those who have previously used nested comparisons in the context of species richness. We provide a set of simple guidelines to maximize the performance of phylogenetically nested comparisons in tests of putative correlates of species richness. [source] RELATION BETWEEN VEGETATION CHANGES, CLIMATE VARIABLES AND LAND-USE POLICY IN SHAANXI PROVINCE, CHINAGEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 4 2007MADELENE OSTWALD ABSTRACT Shaanxi Province in China has been exposed to climate variability and dramatic land-use policies. The aim here is to examine vegetation changes in this area on a regional scale from 2000 to 2004 in relation to land-use changes and climate traits. The data in this assessment include remote sensing information from moderate-resolution imaging spectro-radiometer normalized difference vegetation index from 2000 to 2004, and climate data (precipitation and temperature) from 1956 to 2000. The results show an increase in vegetation production from 2000 to 2004, particularly in the north, which cannot be explained solely by climate impacts. Since the vegetation in the north is more dependent on climate variation than the other parts of Shaanxi due to more serious water limitation, the results suggest that the large-scale land-use policy implemented over the last decade, with a focus on northern Shaanxi, is possibly having an impact on the overall vegetation. [source] PAIRWISE DIFFERENCE ESTIMATION WITH NONPARAMETRIC CONTROL VARIABLES,INTERNATIONAL ECONOMIC REVIEW, Issue 4 2007Andres Aradillas-Lopez This article extends the pairwise difference estimators for various semilinear limited dependent variable models proposed by Honoré and Powell (Identification and Inference in Econometric Models. Essays in Honor of Thomas Rothenberg Cambridge: Cambridge University Press, 2005) to permit the regressor appearing in the nonparametric component to itself depend upon a conditional expectation that is nonparametrically estimated. This permits the estimation approach to be applied to nonlinear models with sample selectivity and/or endogeneity, in which a "control variable" for selectivity or endogeneity is nonparametrically estimated. We develop the relevant asymptotic theory for the proposed estimators and we illustrate the theory to derive the asymptotic distribution of the estimator for the partially linear logit model. [source] ANALYSIS OF VARIABLES AND MODELING OF GEVUINA AVELLANA OIL EXTRACTION WITH ETHANOL NEAR AZEOTROPE CONDITIONSJOURNAL OF FOOD PROCESS ENGINEERING, Issue 5 2009DANIEL FRANCO ABSTRACT Oil extraction from Gevuina avellana Mol. (Chilean hazelnut) with ethanol, near the conditions of its azeotrope with water, was carried out in this work. The effects of solubility, liquid-to-solid ratio and moisture content of ethanol were studied using 92% ethanol, azeotropic (96%) and absolute ethanol (99.9%) as solvents. Water content had a high effect on oil solubility, which reached 140 g/L in 99.9% ethanol, whereas it was 40 g/L with azeotropic ethanol. Oil accounted for 93% of total extractable compounds with absolute ethanol. Kinetics studies of the extraction process were performed at 50C, giving as a result apparent diffusivity values near 10,11 m2/s, being the highest values obtained for ethanol 92% (7.5,16 × 10,11). It was also found that the higher the liquid-to-solid ratio, the higher the diffusivity. Simulation of four-stage countercurrent extraction with azeotropic ethanol yielded 23.5% oil extraction, whereas simulation of four-stage cross-flow extraction yielded 40.7%. Ethanol can be an alternative to batch cold pressing or hexane solvent extraction, for G. savellana seeds or meal processing. PRACTICAL APPLICATIONS The results presented in this paper are applicable for obtaining oil from oilseeds by extraction with ethanol. It includes relevant results for the optimization of extraction conditions and particularly those regarding liquid-to-solid ratio and percentage of water. Considering the more specific focus of this research, the results are applicable to obtaining Gevuina avellana oil by using an ethanol-based process, which will allow to avoid one of the cold-pressing process drawbacks: the high oil content of the meal, which is a factor limiting its lifetime. [source] EFFECTS OF RAW MATERIALS AND PROCESS VARIABLES ON THE HEAT PENETRATION TIMES, FIRMNESS, AND PECTIC ENZYME ACTIVITY OF DICED TOMATOES (HALLEY BOS 3155 CV)JOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 2 2001WENDY H. MA The effects of raw materials and process variables on the heat penetration times into diced tomatoes (Halley Bos 3155 cv) were evaluated. Variables included dice size (1.27 and 2.54 cm), maturity at harvest (red and red+2 weeks), and processing temperature (88 and 92C). Heat penetration times between dice sizes were significantly different, but not between maturities or processing temperatures. Tomatoes were also evaluated for firmness, pectin-methylesterase (PME) and polygalacturonase (PG) activities. Half-inch size diced tomatoes were processed at 88 and 92C, and evaluated for firmness using the shear-compression method. Firmness decreased to 60% of the initial raw firmness from 8.8 × 105 to 5.3 × 105 g-mm after 15 s at 88C, and to 50% from 8.8 × 105 to 4.4 × 105 g-mm after 15 s at 92C. Diced tomato firmness showed a slight firming trend after 150 s at both temperatures. PME was inactivated after 45 s, while 5% residual PG activity remained after 3 min. [source] III. SUBSTANCE-USE PATTERNS AND CORRELATIONS AMONG VARIABLESMONOGRAPHS OF THE SOCIETY FOR RESEARCH IN CHILD DEVELOPMENT, Issue 3 2009Article first published online: 17 NOV 200 First page of article [source] OMITTED VARIABLES, CONFIDENCE INTERVALS, AND THE PRODUCTIVITY OF EXCHANGE RATESPACIFIC ECONOMIC REVIEW, Issue 1 2007Jonathan E. Leightner This paper develops confidence intervals for BD-RTPLS and uses BD-RTPLS to estimate the relationship between the exchange rate (e) and gross domestic product (GDP) using annual data from 1984 to 2000 for 23 developing Asian and Pacific countries. BD-RTPLS produces estimates for the exchange rate multiplier (dGDP/de) for these countries and shows how omitted variables affected these multipliers across countries and over time. [source] THE INVESTMENT OPPORTUNITY SET AND ITS PROXY VARIABLESTHE JOURNAL OF FINANCIAL RESEARCH, Issue 1 2008Tim Adam Abstract We use a real options approach to evaluate the performance of several proxy variables for a firm's investment opportunity set. The results show that, on a relative scale, the market-to-book assets ratio has the highest information content with respect to investment opportunities. Although both the market-to-book equity and the earnings,price ratios are related to investment opportunities, they do not contain information that is not already contained in the market-to-book assets ratio. Consistent with this finding, a common factor constructed from several proxy variables does not improve the performance of the market-to-book assets ratio. [source] WARRANT PRICING USING OBSERVABLE VARIABLESTHE JOURNAL OF FINANCIAL RESEARCH, Issue 3 2004Andrey D. Ukhov Abstract The classical warrant pricing formula requires knowledge of the firm value and of the firm-value process variance. When warrants are outstanding, the firm value itself is a function of the warrant price. Firm value and firm-value variance are then unobservable variables. I develop an algorithm for pricing warrants using stock prices, an observable variable, and stock return variance. The method also enables estimation of firm-value variance. A proof of existence of the solution is provided. [source] A STOCHASTIC ORDERING FOR RANDOM VARIABLES WITH APPLICATIONSAUSTRALIAN & NEW ZEALAND JOURNAL OF STATISTICS, Issue 1 2010Miguel López-Díaz Summary A new univariate stochastic ordering is introduced. Some characterization results for such an ordering are stated. It is proved that the ordering is an integral stochastic ordering, obtaining a maximal generator. By means of this generator, the main properties of the ordering are deduced. A method for introducing univariate stochastic orderings, suggested by the new ordering, is analysed. Relationships with other stochastic orderings are also developed. To conclude, an example of an application of the new ordering to the field of medicine is proposed. [source] KERNEL DENSITY ESTIMATION WITH MISSING DATA AND AUXILIARY VARIABLESAUSTRALIAN & NEW ZEALAND JOURNAL OF STATISTICS, Issue 3 2009Suzanne R. Dubnicka Summary In most parametric statistical analyses, knowledge of the distribution of the response variable, or of the errors, is important. As this distribution is not typically known with certainty, one might initially construct a histogram or estimate the density of the variable of interest to gain insight regarding the distribution and its characteristics. However, when the response variable is incomplete, a histogram will only provide a representation of the distribution of the observed data. In the AIDS Clinical Trial Study protocol 175, interest lies in the difference in CD4 counts from baseline to final follow-up, but CD4 counts collected at final follow-up were incomplete. A method is therefore proposed for estimating the density of an incomplete response variable when auxiliary data are available. The proposed estimator is based on the Horvitz,Thompson estimator, and the propensity scores are estimated nonparametrically. Simulation studies indicate that the proposed estimator performs well. [source] WEIGHTED SUMS OF NEGATIVELY ASSOCIATED RANDOM VARIABLESAUSTRALIAN & NEW ZEALAND JOURNAL OF STATISTICS, Issue 1 2006Han-Ying Liang Summary In this paper, we establish strong laws for weighted sums of negatively associated (NA) random variables which have a higher-order moment condition. Some results of Bai Z.D. & Cheng P.E. (2000)[Marcinkiewicz strong laws for linear statistics. Statist. and Probab. Lett.43, 105,112,] and Sung S.K. (2001)[Strong laws for weighted sums of i.i.d. random variables, Statist. and Probab. Lett.52, 413,419] are sharpened and extended from the independent identically distributed case to the NA setting. Also, one of the results of Li D.L. et al. (1995)[Complete convergence and almost sure convergence of weighted sums of random variables. J. Theoret. Probab.8, 49,76,] is complemented and extended. [source] FORECASTING AUSTRALIAN MACROECONOMIC VARIABLES USING A LARGE DATASETAUSTRALIAN ECONOMIC PAPERS, Issue 1 2010SARANTIS TSIAPLIAS This paper investigates the forecasting performance of the diffusion index approach for the Australian economy, and considers the forecasting performance of the diffusion index approach relative to composite forecasts. Weighted and unweighted factor forecasts are benchmarked against composite forecasts, and forecasts derived from individual forecasting models. The results suggest that diffusion index forecasts tend to improve on the benchmark AR forecasts. We also observe that weighted factors tend to produce better forecasts than their unweighted counterparts. We find, however, that the size of the forecasting improvement is less marked than previous research, with the diffusion index forecasts typically producing mean square errors of a similar magnitude to the VAR and BVAR approaches. [source] What is the Dependent Variable in Corporate Governance Research?CORPORATE GOVERNANCE, Issue 5 2008William Judge No abstract is available for this article. [source] Optimal Contracts when Enforcement is a Decision Variable: A ReplyECONOMETRICA, Issue 1 2003Stefan Krasa No abstract is available for this article. [source] Variable smoothing in Bayesian intrinsic autoregressionsENVIRONMETRICS, Issue 8 2007Mark J. Brewer Abstract We introduce an adapted form of the Markov random field (MRF) for Bayesian spatial smoothing with small-area data. This new scheme allows the amount of smoothing to vary in different parts of a map by employing area-specific smoothing parameters, related to the variance of the MRF. We take an empirical Bayes approach, using variance information from a standard MRF analysis to provide prior information for the smoothing parameters of the adapted MRF. The scheme is shown to produce proper posterior distributions for a broad class of models. We test our method on both simulated and real data sets, and for the simulated data sets, the new scheme is found to improve modelling of both slowly-varying levels of smoothness and discontinuities in the response surface. Copyright © 2007 John Wiley & Sons, Ltd. [source] The Bold and the Variable: Fish with High Heterozygosity Act Recklessly in the Vicinity of PredatorsETHOLOGY, Issue 1 2008Sampsa Vilhunen Variation in the innate behavioral response to predation threat is often assumed to reflect genetic differences among the prey individuals. To date, no published results, however, exist that would offer explanation for the origin of this behavioral variation within populations. Using microsatellites as markers, we estimated the genetic variability of juvenile brown trout (Salmo trutta) individuals whose behavior had been individually recorded in a trade-off situation where both predator chemical cues and food were present. Mean overall heterozygosity and the internal relatedness of fish associated significantly with their activity and foraging, so that the genetically more variable individuals showed more risk-prone behavior under predation risk. No association between genetic variability and behavior was found in trials where predator odors were not present. These results were consistent over the three study populations of brown trout with different backgrounds, suggesting that the phenomenon is of general nature in this species. Of the possible mechanisms suggested to enable the existence of the positive association between neutral microsatellite variation and fitness-related trait, the local effect hypothesis gained more support from our data than the general effect hypothesis. [source] Power of Tests for a Dichotomous Independent Variable Measured with ErrorHEALTH SERVICES RESEARCH, Issue 3 2008Daniel F. McCaffrey Objective. To examine the implications for statistical power of using predicted probabilities for a dichotomous independent variable, rather than the actual variable. Data Sources/Study Setting. An application uses 271,479 observations from the 2000 to 2002 CAHPS Medicare Fee-for-Service surveys. Study Design and Data. A methodological study with simulation results and a substantive application to previously collected data. Principle Findings. Researchers often must employ key dichotomous predictors that are unobserved but for which predictions exist. We consider three approaches to such data: the classification estimator (1); the direct substitution estimator (2); the partial information maximum likelihood estimator (3, PIMLE). The efficiency of (1) (its power relative to testing with the true variable) roughly scales with the square of one less the classification error. The efficiency of (2) roughly scales with the R2 for predicting the unobserved dichotomous variable, and is usually more powerful than (1). Approach (3) is most powerful, but for testing differences in means of 0.2,0.5 standard deviations, (2) is typically more than 95 percent as efficient as (3). Conclusions. The information loss from not observing actual values of dichotomous predictors can be quite large. Direct substitution is easy to implement and interpret and nearly as efficient as the PIMLE. [source] Comparison of estimated breeding values, daughter yield deviations and de-regressed proofs within a whole genome scan for QTLJOURNAL OF ANIMAL BREEDING AND GENETICS, Issue 6 2001H. Thomsen An important issue in quantitative trait loci (QTL) detection is the use of phenotypic measurement as a dependent variable. Daughter yield deviations (DYDs) as the unit of choice are not available for all traits of interest. The use of de-regressed proofs (DRPFs) of estimated breeding values (EBVs) is an alternative to using daughter yield deviations. The objective of this study was to examine possible differences between DYDs and DRPFs within the use of QTL detection. The pedigree used was part of the granddaughter design of the German QTL effort. Consisting marker maps for livestock species were derived from all available data of 16 German Holstein paternal half-sib families with a total of 872 sires. The number of progeny ranged from 19 to 127. A whole genome scan was performed using weighted and unweighted multimarker regression with DYDs, DRPFs and EBVs as dependent variables for the traits milk, fat and protein yields. Results were compared with respect to the number of QTL detected. A similar number of QTL was detected with DRPFs and DYDs. Also, when dependent variables were weighted according to the variance of the trait, a higher number of QTL was detected at the desired level of significance as compared to using unweighted variables. Vergleich von Zuchtwerten, Daughter Yield Deviation und deregressierten Zuchtwerten bei der Genomanalyse zum Nachweis für QTL Ein bedeutender Einflussfaktor in der QTL-Analyse (QTL: Genorte für quantitativemarkmale) ist die Wahl der abhängigen Leistungsvariablen. Da Daughter Yield Deviations (DYDs) aber nicht für jedes Leistungsmerkmal zur Verfügung stehen, sollte untersucht werden, ob die De-regression von Zuchtwerten als alternative Variable in der QTL Analyse verwendet werden kann. Für die Untersuchung wurde ein Teil des Tiermaterials verwendet, das im Rahmen des Genomanalyseprojektes der Arbeitsgemeinschaft Deutscher Rinderzüchter untersucht wurde. Es standen 872 Bullen aus 16 väterlichen Halbgeschwisterfamilien der Rasse Deutsche Holsteins zur Verfügung. Die Zahl der Nachkommen pro Familie variierte von 19 bis 127. Unter Verwendung eines gewichteten als auch ungewichteten Multi-Marker Regressionsansatzes wurde ein Genomscan für die Leistungsmerkmale Milch-kg, Fett-kg und Eiweiss-kg durchgeführt, wobei als abhängige Variablen Zuchtwerte (EBV), Daughter Yield Deviations (DYD) und de-regressierte Zuchtwerte (DRPF) verwendet wurden. Die De-regression wurde auf der Basis der effektiven Töchterzahl, der Heritabilität des Merkmals und der additiv genetischen Verwandtschaftsmatrix durchgeführt. Alle Ergebnisse wurden in Hinblick auf die Anzahl der entdeckten QTL verglichen. Es zeigten sich dabei keine wesentlichen Unterschiede bei der Verwendung von DYDs und DRPFs. Die Rate der QTL Entdeckungen war bei beiden verwendeten Zuchtwerten annähernd gleich. Über den Vergleich unterschiedlicher Leistungsvariablen hinaus wurden die Ergebnisse der ungewichteten und gewichteten Analyse einander gegenübergestellt. Es konnte gezeigt werden, dass bei einer Gewichtung des Merkmals die Rate der QTL-Entdeckungen bei einem bestimmten Signifikanzniveau deutlich höher ist. [source] Chromogenic in situ hybridization analysis of melastatin mRNA expression in melanomas from American Joint Committee on Cancer stage I and II patients with recurrent melanomaJOURNAL OF CUTANEOUS PATHOLOGY, Issue 9 2006L. Hammock Objective:, To determine whether loss of melastatin (MLSN) is a universal phenomenon in American Joint Committee on Cancer (AJCC) stage I and II melanoma patients who experienced recurrence. Material and methods:, Paraffin blocks of primary melanomas (PMs) were retrieved from 30 patients who had a negative sentinel lymph node biopsy and developed recurrent melanoma (AJCC stage I and II). Chromogenic in situ hybridization (CISH) methods were utilized to evaluate the expression of MLSN mRNA. These results were correlated with clinicopathologic data. Results:, Variable, heterogeneous expression of MLSN mRNA was identified in normal, in situ and invasive melanocytes within and between cases. For the invasive PM component, 24 (80%) had focal, regional or complete loss of MLSN mRNA. The remaining 20% had either regional or total partial downregulation of MLSN mRNA. Intact MLSN mRNA expression was present regionally in 14/30 (47%), with mean relative tumor area of 38%, range 5,85%. Increasing loss of MLSN mRNA significantly correlated with increasing tumor depth and microsatellites (r = 0.1/0.4, p = 0.04). However, thin, AJCC T stage 1a PM had higher relative mean loss than intermediate AJCC T stage 2a/2b/3a thickness PM (65% vs. 34%/48%/25%). Increasing loss of MLSN mRNA significantly impacted on disease free survival (DFS) by multivariate analysis (58 vs. 0% 2 years DFS, , 75 vs. >75% mRNA loss, p = 0.02). Decreased overall survival significantly correlated with increasing age and vascular invasion on multivariate analysis. Conclusion:, Extensive loss of MLSN in PM correlated with aggressive metastatic melanoma. Ancillary testing for MLSN mRNA expression by CISH could offer a means to more accurately identify AJCC stage I and II patients at risk for metastatic disease, who could benefit from adjuvant therapy. [source] Balancing fertility management and economics in organic field vegetable rotationsJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 15 2007Ulrich Schmutz Abstract BACKGROUND: Organic field-scale vegetables are among the most profitable enterprises in organic farming systems. They are also some of the most nutrient-demanding crops, and many organic arable systems with field-scale vegetables are stockless. Without livestock manure inputs, nutrient supply depends on fertility-building crops, which generate only costs and no income. Different strategies of fertility management were compared on a central England research farm. Fertility management treatments consisted of different lengths of fertility building with green waste compost additions. Outputs and inputs in terms of nutrients and economics were monitored for 31 rotations during 1996,2002. RESULTS: N, P and K rotational nutrient balances, as well as C inputs, showed a negative relationship with rotational gross margins. Variable and allocated fixed costs of fertility building were low, between 2 and 5% of variable costs (£0.5,2 ha,1 for 1 kg N ha,1 supplied to the rotation). The intensity of vegetable cropping in these rotations was moderate (25,40% vegetable crops in the rotation) and balancing of fertility management and economics was possible at this intensity without livestock manure or other permitted fertiliser additions. CONCLUSION: Completely stockless systems (in analogy may be called vegan) are possible in organic vegetable production without compromising on fertility or economics. However, for a higher vegetable-cropping intensity (up to 90%) a more sophisticated mix of short-term fertility-building and N-trapping crops will be needed and such rotations may require further external addition of green waste or livestock manure. Copyright © 2007 Society of Chemical Industry [source] Variable but predictable prey availability affects predator breeding success: natural versus experimental evidenceJOURNAL OF ZOOLOGY, Issue 4 2008A. Millon Abstract Food supply is a major source of variation in breeding success for predators, and to what extent individuals are able to cope with temporal variability in food availability remains an outstanding question in life-history studies. We confronted the natural variation in clutch size and breeding success with results from a food supplementation experiment during egg formation, conducted over several contrasted years of natural food supply in an avian specialist predator, the Montagu's harrier Circus pygargus. This raptor mainly preys on common vole Microtus arvalis a cyclic microtine under temperate latitudes. Vole abundance together with timing of breeding accounted for most of the variance in clutch size and number of fledglings. Results from empirical and experimental data were overall in agreement. Fed pairs consistently increased clutch size compared with controls in all experimental years, whereas no effect of food supplementation on egg volume was detected. Supplemented pairs, however, did not fledge significantly more chicks than controls. The costs entailed by the increase in clutch size appear nevertheless to be limited compared with previous studies. Food supply seemed therefore to display sufficient predictability throughout a breeding season to afford individuals the opportunity to adjust their breeding effort to an optimal number of offspring, in agreement with Lack's anticipation hypothesis. [source] Effect of chlorhexidine mouth rinse on Streptococci counts of tooth-tissue-borne palatal expander biofilmORTHODONTICS & CRANIOFACIAL RESEARCH, Issue 3 2008IT Maruo Structured Abstract Authors,,, Maruo IT, Rosa EAR, Maruo H, Tanaka O, Guariza Filho O, Ignácio SA, Camargo ES Objectives,,, To assess total Streptococci (TS) counts and biofilm mass over tooth-tissue-borne palatal expander (TTBPE), as well as the effect of chlorhexidine (CHX) mouth rinse on these variables. Design,,, A cross-sectional study design employed clinical procedures and laboratorial techniques. Setting and Sample Population,,, Patients who had TTBPE removal indicated were divided into two groups: a CHX group (n = 26) in which three times a day of 0.2% CHX digluconate mouth rinses were prescribed 7 days before TTBPE removal; and a control (CON) group (n = 25) in which no antimicrobial treatment was applied. Experimental Variable,,, ,Gender', ,Age', and ,TTBPE wear time' were recorded. After TTBPE removal, biofilm mass was determined by the difference between (TTBPE + biofilm) and (TTBPE only) masses. TS counts were determined by biofilm suspension followed by progressive dilutions and culture on Mitis Salivarius agar with incubation at 37°C for 72 h. Outcome Measure,,, Biofilm mass (mg) and Colony Forming Units of TS,/,mg of biofilm (CFU-TS,/,mg) were calculated. Results,,, Total Streptococci mean values in CHX (6.77 × 106CFU-TS,/,mg) were statistically lower (p < 0.01) than those in CON (3.82 × 107CFU-TS,/,mg), but there was no statistical difference (p > 0.05) between CHX (168.88 mg) and CON (182.04 mg) masses nor statistical correlation (p > 0.05) between biofilm mass and CFU-TS,/,mg in the two groups. Conclusion,,, Chlorhexidine reduces the TS counts in TTBPE, but has no effect on biofilm mass. [source] Design and assessment of a tissue-engineered model of human phalanges and a small jointORTHODONTICS & CRANIOFACIAL RESEARCH, Issue 4 2005WJ Landis Structured Abstract Authors ,, Landis WJ, Jacquet R, Hillyer J, Lowder E, Yanke A, Siperko L, Asamura S, Kusuhara H, Enjo M, Chubinskaya S, Potter K, Isogai N. Objectives ,, To develop models of human phalanges and small joints by suturing different cell-polymer constructs that are then implanted in athymic (nude) mice. Design ,, Models consisted of bovine periosteum, cartilage, and/or tendon cells seeded onto biodegradable polymer scaffolds of either polyglycolic acid (PGA) or copolymers of PGA and poly-L-lactic acid (PLLA) or poly- , -caprolactone (PCL) and PLLA. Constructs were fabricated to produce a distal phalanx, middle phalanx, or distal interphalangeal joint. Setting and Sample Population ,, Studies of more than 250 harvested implants were conducted at the Northeastern Ohio Universities College of Medicine. Experimental Variable ,, Polymer scaffold, cell type, and implantation time were examined. Outcome Measure ,, Tissue-engineered specimens were characterized by histology, transmission electron microscopy, in situ hybridization, laser capture microdissection and qualitative and quantitative polymerase chain reaction analysis, magnetic resonance microscopy, and X-ray microtomography. Results ,, Over periods to 60 weeks of implantation, constructs developed through vascularity from host mice; formed new cartilage, bone, and/or tendon; expressed characteristic genes of bovine origin, including type I, II and X collagen, osteopontin, aggrecan, biglycan, and bone sialoprotein; secreted corresponding proteins; responded to applied mechanical stimuli; and maintained shapes of human phalanges with small joints. Conclusion ,, Results give insight into construct processes of tissue regeneration and development and suggest more complete tissue-engineered cartilage, bone, and tendon models. These should have significant future scientific and clinical applications in medicine, including their use in plastic surgery, orthopaedics, craniofacial reconstruction, and teratology. [source] Tissue reaction to orthodontic tooth movement in different bone turnover conditionsORTHODONTICS & CRANIOFACIAL RESEARCH, Issue 3 2003C. Verna Structured Abstract Authors , Verna C, Melsen B Objectives , To study the tissue reaction to orthodontic load in normal, high, and low bone turnover states. Design , ,Split mouth' design performing orthodontic tooth movement in 52, 6-month-old male rats with: normal (n = 19), high (n = 16), and low bone turnover (n = 17), the latter two being obtained by induction of hyperthyroidism and hypothyroidism, respectively. Performed at the Department of Orthodontics at Aarhus University. Experimental Variable , The upper left first molar was moved for 21 days. Bone markers were administered 7 and 2 days before killing. Histological sections were cut at the coronal and apical levels. Outcome Measure , Alveolar socket area, periodontal ligament width, the relative extension of alveolar wall with erosion surfaces, and the mineralizing surfaces were measured and compared in the three groups. Results , Alveolar socket, periodontal ligament width, and erosion surface were larger on the treated than on the control side in the three groups. The normal and hypothyroid groups showed a wider periodontal ligament at the bucco-distal site at the coronal level, while the hyperthyroid group showed a widening which was not spatially oriented. The normal and hyperthyroid groups showed higher erosion at the corono-mesial site. The mineralizing surfaces were larger on the treated than on the control side in the normal and hypothyroid groups, but not in the hyperthyroid group. Conclusion , In the hyperthyroid group, the widening of the periodontal ligament was not spatially oriented and the increased erosion was not accompanied by increased formation, as observed in the normal and hypothyroid groups. [source] Upregulation of immunoreactivity of endothelin-1 and ,-SMA in PDL microvasculature following acute tooth loading: an immunohistochemical study in the marmosetORTHODONTICS & CRANIOFACIAL RESEARCH, Issue 2 2003MR Sims Structured Abstract Authors , Sims MR, Ashworth JF, Sampson WJ Objectives , To test the hypothesis that a continuous mechanical tooth load would elevate immunoreactivity of endothelin-1 (ET-1) and alpha-smooth muscle actin (,-SMA) in the periodontal ligament (PDL) microvasculature. Design , A randomized control study employing 1.5 h of loading to first molars. Setting and Sample Population , Orthodontic Research Laboratory, Dental School, Adelaide University. Four young adult, male marmoset monkeys were consecutively anaesthetized and treated. Experimental Variable , An external telescoping frame applied a jaw closing load (120,200 g) transmitted occlusally, via a rubber pad, to randomly assigned mandibular left or right first molars. Contralateral molars were used as controls. Outcome Measure , Undemineralized, midsagittal, mandibular molar slices, ,150 ,m thick were immunolabelled with ET-1 and ,-SMA antibodies and examined in a confocal laser scanning microscope (CLSM) for vascular endothelium and smooth muscle immunolabelling. Results , Three categories of post-capillary-sized venule endothelial cell immunolabelling occurred: endothelium labelled solely with ET-1; endothelium labelled solely with ,-SMA; endothelium labelled with both ET-1 and ,-SMA. In endothelial cells, the ,-SMA showed a moderate cytoplasmic distribution with dense peripheral concentration. Loading increased arteriole ,-SMA actin labelling. Conclusion , Scattered expression of ET-1 is the default state in primate PDL endothelial cells. Increased antigenicity of endothelial cells to both ET-1 and ,-SMA, and of arteriolar smooth muscle to ,-SMA, is a response to shear and compression loads. [source] | |||||||||||||||||||||||||||||||||||||