Home About us Contact
|
Home About us Contact | ||
|
|
||
Specific Variation (specific + variation)
Selected AbstractsSolution of the linear diffusion equation for modelling erosion processes with a time varying diffusion coefficientEARTH SURFACE PROCESSES AND LANDFORMS, Issue 10 2008Georgios Aim. Abstract In the present paper the differential equation of the temporal development of a landform (mountain) with a time dependent diffusion coefficient is solved. It is shown that the shape and dimensions of the landform at time t are independent of the specific variation of the diffusion coefficient with time; they only depend on the mean value of the diffusion coefficient in the time interval where the erosion process takes place. Studying the behaviour of the solution of the differential equation in the wave number domain, it is concluded that Fourier analysis may help in estimating, in quantitative terms, the initial dimensions, the age or, alternatively, the value of the diffusion coefficient of the landform. The theoretical predictions are tested on a hill of the southern part of the Ural mountainous region, in order to show how the results of the mathematical analysis can be used in describing, in quantitative terms, the morphological development of landforms due to erosion processes. Copyright © 2007 John Wiley & Sons, Ltd. [source] The effect of genetic and environmental variation on metabolic gene expressionMOLECULAR ECOLOGY, Issue 13 2009CINDA P. SCOTT Abstract What is the relationship between genetic or environmental variation and the variation in messenger RNA (mRNA) expression? To address this, microarrays were used to examine the effect of genetic and environmental variation on cardiac mRNA expression for metabolic genes in three groups of Fundulus heteroclitus: (i) individuals sampled in the field (field), (ii) field individuals acclimated for 6 months to laboratory conditions (acclimated), or (iii) individuals bred for 10 successive generations in a laboratory environment (G10). The G10 individuals have significantly less genetic variation than individuals obtained in the field and had a significantly lower variation in mRNA expression across all genes in comparison to the other two groups (P = 0.001). When examining the gene specific variation, 22 genes had variation in expression that was significantly different among groups with lower variation in G10 individuals than in acclimated individuals. Additionally, there were fewer genes with significant differences in expression among G10 individuals vs. either acclimated or field individuals: 66 genes have statistically different levels of expression vs. 107 or 97 for acclimated or field groups. Based on the permutation of the data, these differences in the number of genes with significant differences among individuals within a group are unlikely to occur by chance (P < 0.01). Surprisingly, variation in mRNA expression in field individuals is lower than in acclimated individuals. Relative to the variation among individual within a group, few genes have significant differences in expression among groups (seven, 2.3%) and none of these are different between acclimated and field individuals. The results support the concept that genetic variation affects variation in mRNA expression and also suggests that temporal environmental variation associated with estuarine environments does not increase the variation among individuals or add to the differences among groups. [source] Assessment of Salivary Flow Rate: Biologic Variation and Measure Error,THE LARYNGOSCOPE, Issue 10 2004Peter H. Jongerius MD Abstract Objective: To investigate the applicability of the swab method in the measurement of salivary flow rate in multiple-handicap drooling children. To quantify the measurement error of the procedure and the biologic variation in the population. Study Design: Cohort study. Methods: In a repeated measurements design, a baseline series of salivary flow rates were obtained from 45 children. The within-subject SD (SW) was calculated to express the measurements error according to a procedure introduced by Bland and Altman. Results: Two hundred twenty-four samples (mean 0.40 mL/min, SD 0.19 mL/min) were obtained and analyzed. The results of this study indicate that consistent scores were obtained at subsequent measurements, and good parity existed between the two measurements of salivary flow rate at each session. The SW could be estimated (0.11 mL/min), which was applied to quantify the specific variation of the salivary flow rate in our population. Conclusion: According to Bland and Altman, the SW, which is a quantification of the measurement error and biologic variation, was found to be a useful tool to evaluate the obtained baseline salivary flow rate measurements. The swab method can be used to evaluate salivary flow rates in drooling children with cerebral palsy during interventional studies that aim to reduce saliva production. [source] Age-specific size of the normal adenoid pad on magnetic resonance imagingCLINICAL OTOLARYNGOLOGY, Issue 5 2000R.C. Vogler Conclusions regarding the significance and appearance of the adenoids incidentally noted on magnetic resonance (MR) scans of the brain largely rely on observations of previously published plain film data. In order to determine the age specific appearance of normal adenoid tissue as measured on sagittal T1-weighted midline MR images, we evaluated 189 patients without a history or clinical evidence of adenoid disease, who were sequentially referred for an MR scan of the brain. The thickness of the adenoid pad was measured to the nearest 1 mm along a line through the pharyngeal tubercle constructed perpendicular to the anterior clival surface. Patients were grouped according to age. Normal subjects demonstrated an age specific variation in the size of the pad with the maximal size being attained in early childhood and then steadily decreasing in later childhood and adulthood (P = 0.0001). The adenoids were largest in the 7,10 years age group (mean, 14.59 mm) and steadily declined to 4.83 mm by 60 years of age. Previous surgery had no effect on adenoid measurement (P = 0.582). Magnetic resonance scans provide an excellent method for assessing the adenoid pad. [source] Interleukin-1 gene polymorphisms and experimental gingivitisJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 2 2003Søren Jepsen Abstract Background: Recently, an association between the severity of periodontitis and specific variations in the interleukin-1 (IL1) , and , genes has been demonstrated. Aim: The purpose of this study was to evaluate the relationship of the IL1 genotype to the development of experimental gingivitis. Materials and Methods: Twenty young adult subjects presenting with healthy gingival conditions participated after giving their informed consent. The group included 10 risk genotype positive (P+) and 10 risk genotype negative (P,) individuals. The IL1 genotypes were determined on DNA samples from peripheral blood using PCR-RFLP analyses for the IL1, and IL1, polymorphisms. Experimental gingivitis was allowed to develop in two posterior sextants per subject. Bleeding on probing (BOP%) and gingival crevicular fluid volume (GCF) were assessed at baseline and days 2, 7, 9, 14, 16 and 21. The day 21 results for BOP and GCF as well as the rate of increase of these parameters , mean area under the curve (AUC) and mean increase per day (slope) , were evaluated using risk analyses for IL1 genotype, smoking status and gender. Results: Experimental gingivitis developed with a gradual increase in BOP scores and GCF values (expressed as Periotron units=PU) from baseline to day 21 (BOP, P+: 0.5 to 26.0%; P,: 1.0 to 28.1%; GCF, P+: 36.8 to 138.5 PU, P,: 43.1 to 143.4 PU). No significant risk was associated with P+ and P, for day 21 results, AUC or slope. Conclusion: The results of this study failed to provide evidence that the IL1 risk genotype was associated with higher GCF volume and percentage BOP during the development of experimental gingivitis. Zusammenfassung Hintergrund: Kürzlich ist eine Beziehung zwischen dem Schweregrad von Parodontitis und speziellen Varianten der Interleukin-1 (IL1),- und -,-Gene gezeigt worden. Zielsetzung: Untersuchung des Zusammenhanges zwischen dem ILl-Genotyp und der Entwicklung einer experimentellen Gingivitis. Material und Methoden: 20 junge Erwachsene mit gesunden parodontalen Verhältnissen, von denen 10 für den Risikogenotyp positiv (P+) und 10 negativ (P-) waren, nahmen an der Studie teil, nachdem sie ihr Einverständnis dazu gegeben hatten. Die IL1 -Genotypen wurden aus DNS-Proben aus peripherem Blut mittels PCR-RFLP-Analyse auf ILl,- und IL1/,-Polymorphismen untersucht. In 2 Seitenzahnsextanten ließ jeder Proband eine experimentelle Gingivitis entwickeln. Bluten auf Sondieren (BOP%) und Sulkiksfiüssigkeitsvolumen (SFV) wurden zu Beginn der Studie und nach 2, 7, 9, 14, 16 und 21 Tagen bestimmt. Sowohl die Ergebnisse für BOP und SFV an Tag 21 als auch die Zunahme dieser Werte , mittlere Fläche unter der Kurve (AUC) und mittlere Zunahme pro Tag (Steigung) , wurden mittels Risikoanalyse fur IL1 -Genotyp, Rauchen und Gescnlecht bestimmt. Ergebnisse: Die experimentelle Gingivitis entwickelte sich mit einem stetigen Anstieg der BOP- und SFV-Werte (ausgedrückt als Periotroneinheiten=PU) vom Beginn der Studie bis zum 21. Tag (BOP, P+: 0,5% to 26,0%, P-: 1,0% to 28,1%; GCF, P+: 36,8 to 138,5 PU, P-: 43,1 to 143,4 PU). Mit P+und P- war kein signifikantes Risiko für die Werte am 21. Tag, die AUC oder die Steigung verbunden. Schlussfolgerung: Die Ergebnisse dieser Studie konnten keine Beziehung zwischen dem IL1 -Risikogenotype und erhöhtem SFV bzw. Anteil von Stellen mit BOP in % während der Entwicklung einer experimentellen Gingivitis zeigen. Résumé Contexte: Récemment, une association entre la sévérité de la parodontite et des variations spéifiques des gènes codant pour l'interleukin-1 (IL1) , et , a été démontrée. But: Cette étude se propose d'évaluer la relation entre le génotype IL1 dans le developpment de la gingivite expérimentale. Méthods: 20 jeunes sujets adultes présentant une bonne santé gingivale ont participé cette étude après consentement éclairé. Dans ce groupe, il y avait 10 individus à risque positif (P+) et 10 individus à génotype de risque négatif (P,). génotypes lL1 furent déterminés sur des échantillons d'ADN prélevés du sang périphérique par analyse en PCR-RFLP pour les polymorphismes d' IL1, et IL1,. On a laissé se développer une gingivite expérimentale sur 2 sextants postérieurs chez chaque sujet. Le saignement au sondage (BOP%) et le volume de fluide gingival (GCF) furent notes au départ et aux jours 2, 7, 9, 14, 16, et 21. Au vingt et unième jour, les résultats pour BOP et GCF ainsi que le taux d'augmentation de ces paramètres- La surface moyenne sous la courbe (AUC) et l'augmentation moyenne par jour (pente) - furent évalués par analyses du risque pour les génotypes IL1, le tabagisme et le sexe. Résultats: gingivite expérimentale se développa avec une augmentation graduelle des et scores de BOP et des valeurs de GCF (exprimées en unités Periotron=PU) du début de l'étude jusqu'au jour 21 (BOP, P+: 0.5%à 26.0%, P-: 1.0%à 28.1%; GCF, P+: 36.8 à 43.1 à 143.4 PU). Aucun risque significatif ne fut associe avec P+et P-ats à 21 jours, AUC ou la pente. Conclusion: -es résultats de cette étude n'ont pas pu donner de preuves d'associations entre le génotype de risque IL1 et un volume accru de GCF et le % BOP lors du t d'une gingivite expérimentale. [source] Timing and nature of late Quaternary mountain glaciation,JOURNAL OF QUATERNARY SCIENCE, Issue 6-7 2008Glenn D. Thackray Abstract Compilations of regional- to subcontinental-scale mountain glacier chronologies from five continents, plus Hawaii, examine the temporal and spatial patterns of mountain glaciation. The compilations yield key insights into the nature of past fluctuations in temperature and precipitation in mountains and adjacent regions, and provide baseline data for examining the dynamics of glacier responses to climate change. Key insights from these compilations include the wide variability of glacier responses to fluctuations in insolation, temperature and precipitation and the regionally specific variations in climatic variables through late Quaternary time. The compilations highlight the need to improve the density and quality of geochronological data and to enhance the understanding of the links between climate and glaciation. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||