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Size Characteristics (size + characteristic)
Selected AbstractsFetal size in mid- and late pregnancy is related to infant alertness: The generation R studyDEVELOPMENTAL PSYCHOBIOLOGY, Issue 2 2009Jens Henrichs Abstract The vulnerability for behavioral problems is partly shaped in fetal life. Numerous studies have related indicators of intrauterine growth, for example, birth weight and body size, to behavioral development. We investigated whether fetal size in mid- and late pregnancy is related to infant irritability and alertness. In a population-based birth cohort of 4,255 singleton full-term infants ultrasound measurements of fetal head and abdominal circumference in mid- and late pregnancy were performed. Infant irritability and alertness scores were obtained by the Mother and Baby Scales at 3 months and z -standardized. Multiple linear regression analyses revealed curvilinear associations (inverted J-shape) of measures of fetal size in both mid- and late pregnancy with infant alertness. Fetal size characteristics were not associated with infant irritability. These results suggest that alterations of intrauterine growth affecting infant alertness are already detectable from mid-pregnancy onwards. © 2008 Wiley Periodicals, Inc. Dev Psychobiol 51: 119,130, 2009 [source] Soil detachment and transport on field- and laboratory-scale interrill areas: erosion processes and the size-selectivity of eroded sedimentEARTH SURFACE PROCESSES AND LANDFORMS, Issue 8 2006O. Malam Issa Abstract Field- and laboratory-scale rainfall simulation experiments were carried out in an investigation of the temporal variability of erosion processes on interrill areas, and the effects of such variation upon sediment size characteristics. Poorly aggregated sandy soils from the semi-arid environment of Senegal, West Africa, were used on both a 40 m2 field plot and a 0·25 m2 laboratory plot; rainfall intensity for all experiments was 70 mm h,1 with a duration of 1 to 2 hours. Time-series measurements were made of the quantity and the size distribution of eroded material: these permitted an estimate of the changing temporal balance between the main erosion processes (splash and wash). Results from both spatial scales showed a similar temporal pattern of runoff generation and sediment concentration. For both spatial scales, the dominant erosional process was detachment by raindrops; this resulted in a dynamic evolution of the soil surface under raindrop impact, with the rapid formation of a sieving crust followed by an erosion crust. However, a clear difference was observed between the two scales regarding the size of particles detached by both splash and wash. While all measured values were lower than the mean weight diameter (MWD) value of the original soil (mean 0·32 mm), demonstrating the size-selective nature of wash and splash processes, the MWD values of washed and splashed particles at the field scale ranged from 0·08 to 0·16 mm and from 0·12 to 0·30 mm respectively, whereas the MWD values of washed and splashed particles at the laboratory scale ranged from 0·13 to 0·29 mm and from 0·21 to 0·32 mm respectively. Thus only at the field scale were the soil particles detached by splash notably coarser than those transported by wash. This suggests a transport-limited erosion process at the field scale. Differences were also observed between the dynamics of the soil loss by wash at the two scales, since results showed wider scatter in the field compared to the laboratory experiments. This scatter is probably related to the change in soil surface characteristics due to the size-selectivity of the erosion processes at this spatial scale. Copyright © 2006 John Wiley & Sons, Ltd. [source] A study of Holocene floodplain particle size characteristics with special reference to palaeochannel infills from the upper Severn basin, Wales, UKGEOLOGICAL JOURNAL, Issue 2 2001Mark Patrick Taylor Abstract Multiple sedimentary units from floodplain reaches at Welshpool on the upper River Severn and at the confluence of the Afon Tanat and Afon Vyrnwy (mid-Wales, UK) were examined to ascertain if they have distinctive particle size characteristics. Changes in particle size characteristics and their possible relationship to known human and climatic impacts are also discussed. Ellipse plots of particle size characteristics from the River Severn floodplain at Welshpool show that coarse-grained outwash deposits can be clearly discriminated from channel margin or palaeochannel sediments. In contrast, at the Afon Tanat,Vyrnwy study reach, this discrimination is not seen so clearly. The relationships between age and particle size characteristics from the most sampled sedimentary environment, palaeochannel infills, were also examined. The data from the River Severn floodplain at Welshpool show that palaeochannel sediments reveal a gradual but clear increase in particle size from the mid- to late Holocene towards the present day. Sediments deposited in the period 90,160 years BP are markedly coarser. It is suggested that these changes may be related to the combined effect of land-use changes, metal mining impacts and changes in flood frequency and magnitude that occurred at this time within the upper Severn basin. In contrast, the particle size characteristics of post Late Devensian/Early Holocene units from Tanat,Vyrnwy palaeochannels were random with no discernible age,size patterns. It is suggested that the non-systematic grain size distribution may be due to the steeper valley gradients of the Tanat,Vyrnwy system (and by inference higher stream powers) and its relatively narrow valley form enabling more effective coupling between coarser outwash deposits found on and at the edges of hillslopes and the valley floor. Although the two study reaches have undergone comparable environmental change during the Holocene and lie in the piedmont zone of their catchments, palaeochannel units of the same age possess distinctly different characteristics. Intrinsic reach-scale geomorphic factors would appear to preclude the uniform application of particle size characteristics to determine alluvial response to environmental change. Consequently, care needs to be applied to the use of such data for environmental discrimination because the phenomenon of equifinality means that a specific set of sediment characteristics is not necessarily exclusive to specific fluvial environments in either space or time. Copyright © 2001 John Wiley & Sons, Ltd. [source] Composite suspended sediment particles and flocculation in glacial meltwaters: preliminary evidence from Alpine and Himalayan basinsHYDROLOGICAL PROCESSES, Issue 9 2002J. C. Woodward Abstract Research over the last decade has shown that the suspended sediment loads of many rivers are dominated by composite particles. These particles are also known as aggregates or flocs, and are commonly made up of constituent mineral particles, which evidence a wide range of grain sizes, and organic matter. The resulting in situ or effective particle size characteristics of fluvial suspended sediment exert a major control on all processes of entrainment, transport and deposition. The significance of composite suspended sediment particles in glacial meltwater streams has, however, not been established. Existing data on the particle size characteristics of suspended sediment in glacial meltwaters relate to the dispersed mineral fraction (absolute particle size), which, for certain size fractions, may bear little relationship to the effective or in situ distribution. Existing understanding of composite particle formation within freshwater environments would suggest that in-stream flocculation processes do not take place in glacial meltwater systems because of the absence of organic binding agents. However, we report preliminary scanning electron microscopy data for one Alpine and two Himalayan glaciers that show composite particles are present in the suspended sediment load of the meltwater system. The genesis and structure of these composite particles and their constituent grain size characteristics are discussed. We present evidence for the existence of both aggregates, or composite particles whose features are largely inherited from source materials, and flocs, which represent composite particles produced by in-stream flocculation processes. In the absence of organic materials, the latter may result solely from electrochemical flocculation in the meltwater sediment system. This type of floc formation has not been reported previously in the freshwater fluvial environment. Further work is needed to test the wider significance of these data and to investigate the effective particle size characteristics of suspended sediment associated with high concentration outburst events. Such events make a major contribution to suspended sediment fluxes in meltwater streams and may provide conditions that are conducive to composite particle formation by flocculation. Copyright © 2002 John Wiley & Sons, Ltd. [source] | ||||||||||