The Experts below are selected from a list of 180825 Experts worldwide ranked by ideXlab platform
G Bech - One of the best experts on this subject based on the ideXlab platform.
-
bacteria associated with a marine planktonic copepod in culture i bacterial genera in seawater body surface intestines and fecal pellets and succession during fecal pellet degradation
Journal of Plankton Research, 1996Co-Authors: Benni Winding Hansen, G BechAbstract:In laboratory experiments, the bacterial flora of the zooplankton microbial environments seawater, fecal pellets and associated with the external and internal surfaces of the copepod Acartia tonsa (Dana) were examined. The bacteria associated with fecal pellets were dominated by Bacillus spp., Cytophaga/Flavobacterium spp., Vibrio spp. and Pscudomonas spp. The same genera were found in the seawater (0.22 u.m filtered) in which the pellets were incubated. The bacteria showed a characteristic growth succession, and the abundance increased several orders of magnitude in the seawater during incubation of the pellets, indicating growth and prolifeRation based on the disintegrating/degrading fecal pellets. A carbon budget calculation revealed that organic matter from degrading fecal pellets could cover the carbon demand for the growing bacterioplankton. The composition of the bacterial community in the seawater and the fecal pellets also indicated a colonization of the pellets from bacterioplankton. The composition of the bacteria associated with the copepods showed that bacterial genera characterized as surface associated were preferentially associated with fecal pellets, animal surfaces and intestines. This suggests a specific intestinal flora in the cultivated copepods composed of 10 culturable bacteria per intestine (colony-forming units, c.f.u.) or 10 bacteria per intestine (acridine orange direct counts, AODC), possibly colonizing the intestine passively during filtRation of algae. The activity of the bacterial communities was examined by the Numerical Ratio c.f.u.:AODC, where 1-19% of the bacteria were found active, with no significant difference between microbial environments.
Daniel Ansari - One of the best experts on this subject based on the ideXlab platform.
-
The role of the left intraparietal sulcus in the relationship between symbolic number processing and children's arithmetic competence.
Developmental cognitive neuroscience, 2012Co-Authors: Stephanie Bugden, Gavin R. Price, D. Adam Mclean, Daniel AnsariAbstract:The neural foundations of arithmetic learning are not well understood. While behavioral studies have revealed relationships between symbolic number processing and individual differences in children's arithmetic performance, the neurocognitive mechanisms that bind symbolic number processing and arithmetic are unknown. The current fMRI study investigated the relationship between children's brain activation during symbolic number comparison (Arabic digits) and individual differences in arithmetic fluency. A significant correlation was found between the Numerical Ratio effect on reaction times and accuracy and children's arithmetic scores. Furthermore, children with a stronger neural Ratio effect in the left intraparietal sulcus (IPS) during symbolic number processing exhibited higher arithmetic scores. Previous research has demonstrated that activation of the IPS during Numerical magnitude processing increases over the course of development, and that the left IPS plays an important role in symbolic number processing. The present findings extend this knowledge to show that children with more mature response modulation of the IPS during symbolic number processing exhibit higher arithmetic competence. These results suggest that the left IPS is a key neural substrate for the relationship between the relative of precision of the representation of Numerical magnitude and school-level arithmetic competence.
-
using eye tracking to study Numerical cognition the case of the Ratio effect
Experimental Brain Research, 2010Co-Authors: Rebecca Merkley, Daniel AnsariAbstract:In both behavioural and brain-imaging studies, Numerical magnitude comparison tasks have been used to glean insights into the processing and representation of Numerical magnitude. The present study examined the extent to which eye movement data can be used to investigate the neurocognitive processes underlying Numerical magnitude processing. Twenty-two participants performed a Numerical comparison task (deciding which of two Arabic numerals represents the larger Numerical magnitude) while eye tracking data was recorded. The Ratio between numbers (smaller/larger) was manipulated and ranged from 0.11 to 0.89. Consistent with previous reaction time and accuracy studies, the present results demonstrated significant main effects of Ratio on the number of fixations, as well as a significant main effect of correct (Numerically larger) versus incorrect (Numerically smaller) number on the duRation of fixations. Furthermore, data from the present investigation also revealed that participants made significantly more saccades between the two numbers for large relative to small Ratio trials. Moreover, the Ratio effects on eye movements were uncorrelated with the effect of Numerical Ratio on reaction times, suggesting that eye tracking measures of number comparison may tap into a different level of Numerical magnitude processing than reaction time measures do.
Benni Winding Hansen - One of the best experts on this subject based on the ideXlab platform.
-
bacteria associated with a marine planktonic copepod in culture i bacterial genera in seawater body surface intestines and fecal pellets and succession during fecal pellet degradation
Journal of Plankton Research, 1996Co-Authors: Benni Winding Hansen, G BechAbstract:In laboratory experiments, the bacterial flora of the zooplankton microbial environments seawater, fecal pellets and associated with the external and internal surfaces of the copepod Acartia tonsa (Dana) were examined. The bacteria associated with fecal pellets were dominated by Bacillus spp., Cytophaga/Flavobacterium spp., Vibrio spp. and Pscudomonas spp. The same genera were found in the seawater (0.22 u.m filtered) in which the pellets were incubated. The bacteria showed a characteristic growth succession, and the abundance increased several orders of magnitude in the seawater during incubation of the pellets, indicating growth and prolifeRation based on the disintegrating/degrading fecal pellets. A carbon budget calculation revealed that organic matter from degrading fecal pellets could cover the carbon demand for the growing bacterioplankton. The composition of the bacterial community in the seawater and the fecal pellets also indicated a colonization of the pellets from bacterioplankton. The composition of the bacteria associated with the copepods showed that bacterial genera characterized as surface associated were preferentially associated with fecal pellets, animal surfaces and intestines. This suggests a specific intestinal flora in the cultivated copepods composed of 10 culturable bacteria per intestine (colony-forming units, c.f.u.) or 10 bacteria per intestine (acridine orange direct counts, AODC), possibly colonizing the intestine passively during filtRation of algae. The activity of the bacterial communities was examined by the Numerical Ratio c.f.u.:AODC, where 1-19% of the bacteria were found active, with no significant difference between microbial environments.
Jacqueline Leybaert - One of the best experts on this subject based on the ideXlab platform.
-
Relationships between approximate number system acuity and early symbolic number abilities
Trends in Neuroscience and Education, 2012Co-Authors: Christophe Mussolin, Julie Nys, Jacqueline LeybaertAbstract:Abstract The present study assessed the relationships between approximate and exact number abilities in children with little formal instruction to ask (1) whether individual differences in acuity of the approximate system are related to basic abilities with symbolic numbers; and (2) whether the link between non-symbolic and symbolic number performance changes over the development. To address these questions, four different age groups of 3- to 6-year-old children were asked to compare pairs of train wagons varying on Numerical Ratio, as well as to complete exact tasks including number words or Arabic numbers. When correlation analyses were conducted across age groups, results indicated that performance in numerosity comparison was associated with mastery of symbolic numbers, even when short-term memory, IQ and age were controlled for. Separate analyses by age group revealed that the precision in numerosity discrimination was related to both number word and Arabic number knowledge but differently across the development.
J C Nogueira - One of the best experts on this subject based on the ideXlab platform.
-
duRation of the cycle of the seminiferous epithelium and quantitative histology of the testis of the south american white belly opossum didelphis albiventris marsupialia
Reproduction Fertility and Development, 1992Co-Authors: G F Queiroz, J C NogueiraAbstract:The duRation of the cycle of the seminiferous epithelium of the South American white-belly opossum, as obtained by autoradiography after intratesticular injection of tritiated thymidine, was estimated to be 17.3 +/- 0.1 days (mean +/- s.d.). Quantitative histological analysis was performed on testes from animals caught both in mating and non-mating periods of the annual reproductive cycle. Significant differences were found in the volumetric proportion of Leydig cells, but the spermatogenic yield remained constant throughout the year. The Numerical Ratio between type A spermatogonia and zygotene primary spermatocytes (1:12.0), as well as daily sperm production (4.8 x 10(6) sperm cells per g of testis parenchyma per day), were found to be lower than those reported in most eutherian mammals.
