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Measured Variables (measured + variable)
Selected AbstractsGremmeniella abietina types cannot be distinguished using ascospore morphologyFOREST PATHOLOGY, Issue 6 2006A. Uotila Summary Twenty-one Gremmeniella abietina var. abietina type A and 12 type B samples with ripened apothecia were collected in Sweden and Finland. Morphological dimensions of the ascospores were determined with an image analyser (Leica Qwin). Measured variables included length, width, perimeter and roundness of ascospores. Variations in these variables overlapped between the two types. Type A ascospores were significantly shorter (mean length 15.8 ,m) than the type B ascospores (mean length 17.1 ,m). Type A ascospores were also significantly rounder than type B ascospores. Differences between these morphological characters were, however, too small to distinguish the types as separate taxonomical species. Round-pointed and acute ascospores were found in the same apothecium but in different asci. According to the hypervariable marker GAAA1000, both round-pointed and acute ascospores originated from the same two parents in normal segregation. Résumé Vingt-et-un échantillons avec des apothécies matures du type A de Gremmeniella abietina var. abietina et 12 du type B ont été récoltés en Suède et Finlande. Les dimensions morphologiques des ascospores ont été déterminées avec un analyseur d'images (Leica Qwin). Les variables mesurées sont la longueur, la largeur, le périmètre et la rondeur des spores. Les gammes de variation de ces différentes variables se recouvrent entre les deux types. Les ascospores de type A sont significativement plus courtes (longueur moyenne de 15.8 ,m) que les ascospores de type B (longueur moyenne de 17.1 ,m). Les ascospores de type A sont aussi significativement plus rondes que celles de type B. Les différences pour ces caractères morphologiques sont toutefois trop faibles pour distinguer les types comme des espèces taxonomiques différentes. Des ascospores arrondies et pointues ont été trouvées dans la même apothécie mais dans des asques différents. En se basant sur le marqueur hypervariable GAAA1000, on peut établir que les ascospores arrondies et pointues proviennent des mêmes deux parents en ségrégation normale. Zusammenfassung In Schweden und Finnland wurden 21 Gremmeniella abietina var. abietina Typ A- und 12 Typ B- Proben mit reifen Apothecien gesammelt. Folgende morphologische Messgrössen der Ascosporen wurden mit einem Image Analyser (Leica Quin) bestimmt: Länge, Breite, Umfang und Form. Die Variation der Variablen überlappte bei den beiden Typen. Die Typ A-Ascosporen waren signifikant kürzer (15,8 ,m mittlere Länge) als die Typ B-Ascosporen (17,1 ,m). Der Typ A hatte signifikant rundere Ascosporen als der Typ B. Die Unterschiede in den morphologischen Merkmalen waren jedoch zu gering, um zwei taxonomische Arten zu unterscheiden. Ascosporen mit runden und spitzen Enden wurden im gleichen Apothecium, jedoch in verschiedenen Asci gefunden. Mit dem hypervariablen Marker GAAA1000 erwiesen sich Ascosporen mit rundem und spitzem Ende als Nachkommen der gleichen Eltern mit normaler Segregation. [source] Adults with cerebral palsy: walking ability after progressive strength trainingDEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 4 2003C Andersson MSc PT The purpose of this study was to evaluate effects of a progressive strength training programme on walking ability in adults with cerebral palsy. Ten individuals with spastic diplegia (seven males, three females; mean age 31, range 23,44 years) participated twice a week over 10 weeks. Seven individuals with spastic diplegia (four males, three females; mean age 33, range 25,47 years) who did not receive strength training served as controls. All individuals were ambulatory but motor ability ranged from functional walkers to individuals who always required walking aids and used a wheelchair regularly. Significant improvements were seen in isometric strength (hip extensorsp=0.006, hip abductors p=0.01), and in isokinetic concentric work at 30/s (knee extensors p=0.02) but not in eccentric work. Results also showed significant improvements in Gross Motor Function Measure (GMFM) dimensions D and E (p=0.005), walking velocity (p=0.005), and Timed Up and Go (p=0.01). There was no increase in spasticity for those who underwent strength training. Individuals in the control group did not show any significant improvement in any measured variable. The groups were small, however, and there was no significant difference between the groups in any measured variable. These findings suggest that a 10-week progressive strength training programme improves muscle strength and walking ability without increasing spasticity. [source] Predicting unit plot soil loss in Sicily, south ItalyHYDROLOGICAL PROCESSES, Issue 5 2008V. Bagarello Abstract Predicting soil loss is necessary to establish soil conservation measures. Variability of soil and hydrological parameters complicates mathematical simulation of soil erosion processes. Methods for predicting unit plot soil loss in Sicily were developed by using 5 years of data from replicated plots. At first, the variability of the soil water content, runoff, and unit plot soil loss values collected at fixed dates or after an erosive event was investigated. The applicability of the Universal Soil Loss Equation (USLE) was then tested. Finally, a method to predict event soil loss was developed. Measurement variability decreased as the mean increased above a threshold value but it was low also for low values of the measured variable. The mean soil loss predicted by the USLE was lower than the measured value by 48%. The annual values of the soil erodibility factor varied by seven times whereas the mean monthly values varied between 1% and 244% of the mean annual value. The event unit plot soil loss was directly proportional to an erosivity index equal to , being QRRe the runoff ratio times the single storm erosion index. It was concluded that a relatively low number of replicates of the variable of interest may be collected to estimate the mean for both high and particularly low values of the variable. The USLE with the mean annual soil erodibility factor may be applied to estimate the order of magnitude of the mean soil loss but it is not usable to estimate soil loss at shorter temporal scales. The relationship for estimating the event soil loss is a modified version of the USLE-M, given that it includes an exponent for the QRRe term. Copyright © 2007 John Wiley & Sons, Ltd. [source] Chest pain is inversely associated with blood pressure during exercise among individuals being assessed for coronary heart diseasePSYCHOPHYSIOLOGY, Issue 2 2007Blaine Ditto Abstract Acute and chronic increases in blood pressure have been related to decreases in pain perception. This phenomenon has been studied primarily using acute experimental pain stimuli. To extend the literature to naturalistic pain and in particular the problem of silent cardiac ischemia, this study examined the relationship between blood pressure and chest pain during exercise stress testing. Nine hundred seven (425 men, 482 women) individuals undergoing exercise stress testing for diagnosis of possible myocardial ischemia completed the McGill Pain Questionnaire (MPQ) immediately afterward and other questionnaires before and after testing. Blood pressure was measured before, during, and after exercise. Systolic blood pressure at the end of exercise was inversely related to a number of measures of pain such as total score on the MPQ. The relationship could not be explained by individual differences in exercise duration, medication use, sex, or other measured variable. In sum, the inverse relationship between blood pressure and sensitivity to pain that has been observed in other populations in experimental and naturalistic conditions was observed for chest pain during exercise. Blood pressure may contribute to episodes of silent ischemia. [source] Effects of dietary protein and lipid level, and water temperature, on the post-feeding oxygen consumption of Atlantic cod and haddockAQUACULTURE RESEARCH, Issue 2 2010Juan C Pérez-Casanova Abstract Tank respirometry was used to study the interactive effects of protein:lipid level (55%:11% vs. 42%:16%; both diets isoenergetic) and temperature (11, 6 and 2 °C) on the magnitude and duration of specific dynamic action (SDA) in juvenile Atlantic cod and haddock. The protein:lipid level did not affect any measured variable. However, numerous temperature and species effects were observed. For example, although the maximum post-feeding oxygen consumption (30,50% above routine metabolic rate; RMR) and SDA duration (,55,85 h; SDADUR) were not affected by temperature, SDADUR g,1 of food increased from 11 to 2 °C (from ,3 to 12 h g food,1). While absolute SDA (mg O2) decreased by ,60,65% in cod and ,75% in haddock from 11 to 2 °C, due to a concomitant decrease in food consumption from ,2.0% to 0.6% body mass, SDA comprised between 3.3% and 5.2% of the dietary energy content at all temperatures. Finally, RMR at 11 and 2 °C and SDADUR at 2 °C were 25,35% and 25% greater in cod, respectively, as compared with haddock. These results suggest that feeding reduced protein diets at low water temperatures is unlikely to improve the growth of these species. [source] Sterile Versus Nonsterile Gloves During Mohs Micrographic Surgery: Infection Rate is not AffectedDERMATOLOGIC SURGERY, Issue 2 2006BRANDON M. RHINEHART MC BACKGROUND: Mohs micrographic surgery (MMS) is an outpatient procedure, which has become the treatment of choice for certain cutaneous malignancies. Although the major steps in this procedure are relatively standardized, one difference involves the use of sterile or nonsterile, clean gloves during the tumor removal phase. OBJECTIVE: This retrospective, chart review study was performed to evaluate whether infection rates are affected by the use of sterile versus nonsterile gloves in the tumor extirpation phase of MMS. METHODS: This study evaluated the surgical records of 1,810 consecutive Mohs patients, of which 1,239 Mohs patients (1,400 Mohs procedures) met inclusion criteria. Age, sex, tumor diagnosis, anatomic location, number of Mohs stages, area of defect, closure type, cartilage exposure, and sterile versus nonsterile glove use were recorded and evaluated. RESULTS: Twenty-five infections were identified. Statistically significant infection rates were discovered for patients with cartilage fenestration with secondary healing and malignant melanoma diagnosis only. There was no statistical difference in infection rates with all other measured variables to include the use of sterile or clean, nonsterile gloves. CONCLUSION: Our study lends support that clean, nonsterile gloves are safe and effective for use in the tumor extirpation phase of MMS, at a significant cost savings. [source] Morphological development and nutritive value of herbage in five temperate grass species during primary growth: analysis of time dynamicsGRASS & FORAGE SCIENCE, Issue 2 2009Abstract In a 2-year field experiment, morphological development and measures of the nutritive value of herbage for livestock during primary growth in Meadow foxtail, Tall oatgrass, Cocksfoot, Perennial ryegrass and Yorkshire fog were investigated. All measured variables were affected significantly by both species and sampling date, and their interaction (P < 0·001), in the period of primary growth. Changes with time in mean stage weight for Meadow foxtail and Cocksfoot were different from the other species due to their indeterminate growth habits. Mean stage weight of Tall oatgrass and Yorkshire fog increased more rapidly than that of Perennial ryegrass with time. Changes in mean stage weight with time were described by linear, parabolic and sigmoid relationships. Crude protein (CP) concentration of herbage was higher for Cocksfoot and Meadow foxtail than for Perennial ryegrass. A parabolic relationship of CP concentration with time was typical for all the species. Concentrations of neutral-detergent fibre (NDF) and acid-detergent fibre (ADF) in herbage of the species differed most during the mid-period of primary growth. Their increases with time showed curvilinear (sigmoid and parabolic) relationships. Perennial ryegrass had lower concentrations of both NDF and ADF in herbage than the other species. Differences between the in vitro dry matter (DM) digestibility among the grasses increased in mid- and late periods of primary growth. Perennial ryegrass had higher values for in vitro DM digestibility but the difference from other species was small in the early period of primary growth and from cocksfoot in the late period of primary growth. In vitro DM digestibility showed, in most cases, a sigmoid and, in others, a linear decrease with time. Principal component analysis showed that perennial ryegrass and meadow foxtail were the most distinctive of the species in characteristics relating to morphological development and the nutritive value of herbage to livestock. [source] Are there correlates of male Australian Magpie Gymnorhina tibicen reproductive success in a population with high rates of extra-group paternity?IBIS, Issue 2 2006KATE L. DURRANT The reproductive success of a male bird is often correlated with measurable traits that predict his intrinsic quality. Females are thought to base their selection of mates on the latter's ,quality' in order to gain their ,good genes'. Male Australian Magpies Gymnorhina tibicen of the white-backed race tyrannica were trapped in two breeding seasons. Measurements were taken of morphometric and other characteristics in order to discover whether particular traits of males were associated with: (1) percentage of offspring sired in the territory, (2) number of fledglings produced in the territory per season and (3) whether females select males for their ,good genes'. There were no consistently significant correlations between any of the measured variables and male Magpie reproductive success within territories. In particular, none of the traits measured had any consistent correlation with the percentage of offspring sired in a territorial group. This was an unexpected result given that the species is strongly territorial but also engages regularly in extra-group copulations. These findings appear contrary to the predictions of the ,good genes' hypothesis. The general lack of correlation between the variables and level of genetic paternity may in fact be due to females engaging in extra-group mating primarily to avoid breeding with a close relative rather than to choose a high-quality male. In this case, males would not have to be ,high quality', but merely genetically different from the female's social mate. [source] Do male hoots betray parasite loads in Tawny Owls?JOURNAL OF AVIAN BIOLOGY, Issue 4 2000Stephen M. Redpath Bird song structure may honestly reveal the health and vigour of individual males to potential mates and competitors. If this is the case then song may reflect the level of parasitic infections in males. We initially examined the relationship between blood parasite infections and the time taken to respond by 22 male Tawny Owls to a broadcast hoot. We then examined the call structure (total length and frequency) in relation to parasite infection, an index of owl condition and an index of food abundance. Owls with higher parasite loads responded more slowly to an intruder, although this relationship was not significant once condition and vole abundance were controlled for. We found no relationship between call length and any of the measured variables. However, the high frequency and the range of frequencies used in calls decreased with increasing parasite load. Thus, there was the potential for individuals to assess male parasite load from the speed of response and the structure of the call. Experimental tests of these relationships are now required. [source] Coping strategies in farmed African catfish Clarias gariepinus.JOURNAL OF FISH BIOLOGY, Issue 10 2010Does it affect their welfare? The objective of this study was to assess whether and how coping strategies affect the welfare of African catfish Clarias gariepinus housed at low and high densities. Group composition influenced feed intake; re-active groups (comprised of 100% re-active fish) had a lower specific growth rate (G) and feed intake and a higher feed conversion ratio (RFC) than pro-active groups. Furthermore, re-active groups had a lower energy retention than pro-active groups. The latter was fully due to differences in feed intake, since energy partitioning (on % total gross energy intake basis) was similar among the group composition treatments. Fish held at high stocking density showed a higher RFC and feeding speed and a lower energy retention and agonistic behaviour. None of the measured variables was influenced by the interaction effect. In mixed groups, G and number of skin lesions seemed to be affected by different behavioural phenotypes at low stocking density, but not at high density. These results indicate that both stocking density and group composition affect physical and behavioural responses of C. gariepinus. Furthermore, physical and behavioural data of individual fish housed in mixed groups suggest that coping strategy affects the fitness of different behavioural phenotypes at low, but not at high, stocking density. [source] Size-specific growth of bluegill, largemouth bass and channel catfish in relation to prey availability and limnological variablesJOURNAL OF FISH BIOLOGY, Issue 1 2007D. E. Shoup Growth of sympatric populations of three important sport fish species: bluegill Lepomis macrochirus, largemouth bass Micropterus salmoides and channel catfish Ictalurus punctatus, in 14 Illinois reservoirs was assessed in an attempt to relate size-specific growth to environmental conditions. Multiple regression relationships for most species and size classes explained a large percentage of the variation in growth. Growth of small bluegill (50 mm total length, LT) showed a strong negative relationship with bluegill catch per unit effort (cpue), per cent littoral area and pH. Large bluegill (150 mm LT) growth was negatively related to Daphnia spp. and benthic macroinvertebrate abundance and lake volume, and positively related to bluegill cpue. Growth of small (100 mm LT) and large (250 mm LT) largemouth bass was not well explained by any of the measured variables. Growth of both small (300 mm LT) and large (450 mm LT) channel catfish was strongly positively related to forage fishes and ichthyoplankton abundance, and per cent littoral area while negatively related to benthic macroinvertebrates. By identifying environmental conditions associated with increased growth rates, these models provide direction for managing fish populations and suggest testable hypotheses for future study of the complex interactions between environmental conditions and growth. [source] Energy reserves during food deprivation and compensatory growth in juvenile roach: the importance of season and temperatureJOURNAL OF FISH BIOLOGY, Issue 1 2005P. L. M. Van Dijk The effect of 21 days of starvation, followed by a period of compensatory growth during refeeding, was studied in juvenile roach Rutilus rutilus during winter and summer, at 4, 20 and 27° C acclimation temperature and at a constant photoperiod (12L : 12D). Although light conditions were the same during summer and winter experiments and fish were acclimated to the same temperatures, there were significant differences in a range of variables between summer and winter. Generally winter fish were better prepared to face starvation than summer fish, especially when acclimated at a realistic cold season water temperature of 4° C. In winter, the cold acclimated fish had a two to three-fold larger relative liver size with an approximately double fractional lipid content, in comparison to summer animals at the same temperature. Their white muscle protein and glycogen concentration, but not their lipid content, were significantly higher. Season, independent of photoperiod or reproductive cycle, was therefore an important factor that determined the physiological status of the animal, and should generally be taken into account when fish are acclimated to different temperature regimes. There were no significant differences between seasons with respect to growth. Juvenile roach showed compensatory growth at all three acclimation temperatures with maximal rates of compensatory growth at 27° C. The replenishment of body energy stores, which were utilized during the starvation period, was responsible for the observed mass gain at 4° C. The contribution of the different energy resources (protein, glycogen and lipid) was dependent on acclimation temperature. In 20 and 27° C acclimated roach, the energetic needs during food deprivation were met by metabolizing white muscle energy stores. While the concentration of white muscle glycogen had decreased after the fasting period, the concentrations of white muscle lipid and protein remained more or less constant. The mobilization of protein and fat was revealed by the reduced size of the muscle after fasting, which was reflected in a decrease in condition factor. At 20° C, liver lipids and glycogen were mobilized, which caused a decrease both in the relative liver size and in the concentration of these substrates. Liver size was also decreased after fasting in the 4° C acclimated fish, but the substrate concentrations remained stable. This experimental group additionally utilized white muscle glycogen during food deprivation. Almost all measured variables were back at the control level within 7 days of refeeding. [source] Integrated estimation of measurement error with empirical process modeling,A hierarchical Bayes approachAICHE JOURNAL, Issue 11 2009Hongshu Chen Abstract Advanced empirical process modeling methods such as those used for process monitoring and data reconciliation rely on information about the nature of noise in the measured variables. Because this likelihood information is often unavailable for many practical problems, approaches based on repeated measurements or process constraints have been developed for their estimation. Such approaches are limited by data availability and often lack theoretical rigor. In this article, a novel Bayesian approach is proposed to tackle this problem. Uncertainty about the error variances is incorporated in the Bayesian framework by setting noninformative priors for the noise variances. This general strategy is used to modify the Sampling-based Bayesian Latent Variable Regression (Chen et al., J Chemom., 2007) approach, to make it more robust to inaccurate information about the likelihood functions. Different noninformative priors for the noise variables are discussed and unified in this work. The benefits of this new approach are illustrated via several case studies. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Soft-sensor development using correlation-based just-in-time modelingAICHE JOURNAL, Issue 7 2009Koichi Fujiwara Abstract Soft-sensors have been widely used for estimating product quality or other key variables, but their estimation performance deteriorate when the process characteristics change. To cope with such changes, recursive PLS and Just-In-Time (JIT) modeling have been developed. However, recursive PLS does not always function well when process characteristics change abruptly and JIT modeling does not always achieve the high-estimation performance. In the present work, a new method for constructing soft-sensors based on a JIT modeling technique is proposed. In the proposed method, referred to as correlation-based JIT modeling (CoJIT), the samples used for local modeling are selected on the basis of the correlation among measured variables and the model can adapt to changes in process characteristics. The usefulness of the proposed method is demonstrated through a case study of a CSTR process, in which catalyst deactivation and recovery are taken into account. In addition, its industrial application to a cracked gasoline fractionator is reported. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Hemostatic Changes in Dogs with Naturally Occurring SepsisJOURNAL OF VETERINARY INTERNAL MEDICINE, Issue 5 2003Armelle M. de Laforcade Sepsis is a frequent source of morbidity and mortality in critically ill patients. The goal of this case control study was to measure hemostatic changes in dogs with naturally occurring sepsis. Blood was collected within 24 hours of admission from 20 dogs that fulfilled the criteria for sepsis. Sepsis was defined as histologic or microbiological confirmation of infection and 2 or more of the following criteria: hypo- or hyperthermia, tachycardia, tachypnea, or leukopenia, leukocytosis, or >3% bands. Culture and sensitivities were performed on appropriate samples from all septic dogs. Twenty-eight control dogs were enrolled on the basis of normal results of physical examination, CBC, serum biochemistry, and coagulation profile. Plasma samples were analyzed for prothrombin time (PT), partial thromboplastin time (PTT), fibrin(ogen) degradation products (FDP), D-dimer (DD) concentrations, antithrombin (AT) activity, and protein C (PC) activity. Data were compared between groups by chi-square or independent t -tests. PC (P < .001) and AT (P < .001) activities were significantly lower in dogs with sepsis compared to controls. Dogs with sepsis had significantly higher PT (P= .007), PTT (P= .005), D-dimer (P= .005), and FDP (P= .001) compared to controls. Platelet counts were not significantly different between groups. Ten of the 20 septic dogs (50%) died, but no association was identified between any of the measured variables and outcome. These findings are consistent with previous studies in animals with experimentally induced disease and in clinical studies of humans. On the basis of these results, further investigation of the role of AT and PC in canine sepsis is warranted. [source] Determining the sex of bottlenose dolphins from Doubtful Sound using dorsal fin photographsMARINE MAMMAL SCIENCE, Issue 1 2009Lucy E. Rowe Abstract Sexing cetaceans usually requires time-consuming observation, or genetic sexing via biopsy sampling or skin swabbing. We developed a method to determine the sex of bottlenose dolphins (Tursiops sp.) in Doubtful Sound, Fiordland, using laser-metric dorsal fin photographs. From dorsal fin photographs of 43 bottlenose dolphins of known sex (25 females, 18 males) we analyzed the shape, proportion of fin area covered in scarring and epidermal lesions, and the number of fin nicks. Males had significantly higher rates of scarring (P < 0.001) and dorsal fin nicks (P < 0.01) than females, whereas the severity of epidermal lesions was higher in females (P < 0.05). A logistic regression applied to all measured variables, and measurements of dorsal fin size, indicated that the proportion of dorsal fin scarring (P < 0.001), number of fin nicks (P < 0.01), and dorsal fin surface area (P < 0.01) were significant variables and together correctly predicted the sex of 93% (40/43) of the dolphins. The classification function may not be applicable to other populations due to geographic variation in bottlenose dolphin morphology and social structure. The method is quick and noninvasive to apply, and further increases the value of dorsal fin photo-identification pictures. [source] Confounder summary scores when comparing the effects of multiple drug exposures,PHARMACOEPIDEMIOLOGY AND DRUG SAFETY, Issue 1 2010Suzanne M. Cadarette PhD Abstract Purpose Little information is available comparing methods to adjust for confounding when considering multiple drug exposures. We compared three analytic strategies to control for confounding based on measured variables: conventional multivariable, exposure propensity score (EPS), and disease risk score (DRS). Methods Each method was applied to a dataset (2000,2006) recently used to examine the comparative effectiveness of four drugs. The relative effectiveness of risedronate, nasal calcitonin, and raloxifene in preventing non-vertebral fracture, were each compared to alendronate. EPSs were derived both by using multinomial logistic regression (single model EPS) and by three separate logistic regression models (separate model EPS). DRSs were derived and event rates compared using Cox proportional hazard models. DRSs derived among the entire cohort (full cohort DRS) was compared to DRSs derived only among the referent alendronate (unexposed cohort DRS). Results Less than 8% deviation from the base estimate (conventional multivariable) was observed applying single model EPS, separate model EPS or full cohort DRS. Applying the unexposed cohort DRS when background risk for fracture differed between comparison drug exposure cohorts resulted in ,7 to,+,13% deviation from our base estimate. Conclusions With sufficient numbers of exposed and outcomes, either conventional multivariable, EPS or full cohort DRS may be used to adjust for confounding to compare the effects of multiple drug exposures. However, our data also suggest that unexposed cohort DRS may be problematic when background risks differ between referent and exposed groups. Further empirical and simulation studies will help to clarify the generalizability of our findings. Copyright © 2009 John Wiley & Sons, Ltd. [source] Grapevine productivity and yield components: A case study using field vines of Zante currantAUSTRALIAN JOURNAL OF GRAPE AND WINE RESEARCH, Issue 2 2004JOHN A. CONSIDINE Abstract Yield components of the parthenocarpic cultivar Zante were analysed for five vineyards of diverse age and management. The data was obtained as part of an experiment to improve fruit set and yield by applying combinations of gibberellin and 2-chloroethyltrimethyl ammonium chloride or 4-chlorophenoxyacetic acid. Four of the vineyards were located in the Brockman valley north of Perth, Western Australia, two of these were irrigated, one was rain fed and one received supplementary flood irrigation. The fifth lay in an adjacent area of coastal sand plain, at the foot of the Darling scarp, and was irrigated. The vines were aged from 6 to 50 years. Principal component analysis showed that vine age was negatively correlated with vigour (pruning weight) and with berry number per bunch. Vine age however was not strongly related to either yield or yield components (bunch number and berry volume). Sugar concentration was negatively correlated with all yield components but imprecisely modelled based on any combination of the measured variables. Berry number per vine appeared to be the underlying factor determining ,sink' strength though this was inextricably confounded with bunch number per vine. Interpretation of the data leads to the conclusion that increased berry volume is an inefficient means of increasing dried yield. This conclusion argues for caution in the application of plant growth regulators that act primarily to increase berry volume. Yield of sugar per vine was accurately modelled based on second order relationships with bunch number per vine, berry number per bunch, berry volume and pruning weight. Vine age also showed a second order relationship to yield although the range was relatively small. The observations are considered in terms of developing strategies for maximising dried yield and devising mathematical models to account for photoassimilate (dry matter) partitioning in Vitis. [source] Testing Measurement Invariance Using Item Response Theory in Longitudinal Data: An IntroductionCHILD DEVELOPMENT PERSPECTIVES, Issue 1 2010Roger E. Millsap Abstract, Item response theory (IRT) consists of a set of mathematical models for the probabilities of various responses to test items as a function of item and person characteristics. In longitudinal data, changes in measured variables can only be interpreted if important psychometric features of the measured variables are assumed invariant across time. Measurement invariance is invariance in the relation of a measure to the latent variable underlying it. Measurement invariance in longitudinal studies concerns invariance over time, and IRT provides a useful approach to investigating longitudinal measurement invariance. Commonly used IRT models are described, along with the representation of measurement invariance in IRT. The use of IRT for investigating invariance is then described, along with practical considerations in using IRT for this purpose. Conceptual issues, rather than technical details, are emphasized throughout. [source] | ||||||||||||||||||||||