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Biogenic volatile organic compounds (BVOCs) can be released from soils to the atmosphere through microbial decomposition of plant residues or soil organic carbon, root emission, evaporation of litter-stored BVOCs, and other physical processes. Soils can also act as a sink of BVOCs through biotic and abiotic uptake. Currently, the source and sink capabilities of soils have not been explicitly accou
This study focuses on quantitative long-term effects of Supplemental Instruction (SI) in terms of graduation and dropout rates. One of the main aims of SI is to introduce students to effective study strategies and techniques. If SI is introduced at an early stage for new students in higher education, it should therefore be expected that this action will promote timely graduation. This has also beeThis study focuses on quantitative long-term effects of SupplementalInstruction (SI) in terms of graduation and dropout rates. One of the main aimsof SI is to introduce students to effective study strategies and techniques. If SIis introduced at an early stage for new students in higher education, it shouldtherefore be expected that this action will promote timely graduation. This hasalso been ind
A field study on current structure and circulation characteristics in Lake Vendyurskoe, a small, shallow, icecovered lake in Karelia, Russia, is presented. The current velocity magnitudes were generally found to be small. The most pronounced currents had an oscillating character, with velocity amplitudes on the order of millimeters per second. The oscillation period, obtained from spectral density
Using water balance computations, the behavior of different kinds of lakes is discussed. Simple analytical expressions relating water level to hydrological conditions and lake bathymetry are given. The importance of knowing the river basin area when analyzing lake levels is stressed. A conceptual rainfall-runoff model including lake routing is used to simulate runoff and lake levels and to compute
The overall circulation pattern in spring is rather specific as density-induced currents may be of significance. The density-driven circulation perpendicular to the shore can be described as consisting of two circulation cells, with a zone of convergence, referred to as thermal bar, in between. The thermal bar, which coincides with the 4°C isotherm (the temperature of maximum density), inhibits ho
A study on characteristics of currents and mixing in a shallow ice‐covered Russian lake is presented. The current velocity data are separated into four main components, mean velocity, uninodal longitudinal and transverse seiche currents, and “high”‐frequency velocity fluctuations, using digital filters. The analysis of components shows that mean currents are most pronounced in early winter and are
During spring and autumn a special thermohydrodynamic phenomenon, called a thermal bar, can be observed in dimictic lakes. [A dimictic lake is a lake where a complete turnover of the water occurs twice a year (in spring and autumn).] The thermal bar is a zone of mixing that separates waters with temperatures above and below 4° C. Its practical importance is due to the possibility that it might iso
During late winter (18 March–7 April 1994), temperature and current measurements were made in Lake Vendyurskoe, Russia, including three surveys at six cross sections of the lake. Also, the temperature profile evolution was registered with two thermistor chains at two stations (bottom depths of 7.6 and 11.5 m) until the time of ice breakup. Temperature gradients were measured just below the ice cov
Field data on temperature and salt content structure in the vicinity of the bottom boundary in an ice‐covered lake are analyzed. A bottom boundary layer is identified, characterized by rapid increases in both temperature and salt concentration and having a thickness of ∼1 dm with respect to temperature and 2–4 cm with respect to salt content. A simple analytical model of the temperature distributi
We use a combination of field and satellite data to investigate the thermal regime in Lake Ladoga in spring 1992. The analysis concentrates mainly on the temperature structure in the convectively mixed region and the dynamics of a special thermo‐hydrodynamic phenomenon called “thermal bar” (a zone of descending water with the temperature of maximum density equal to ∼4°C). A theoretical model of th
During spring and autumn, many lakes in temperate latitudes experience intensive convective mixing in the vertical, which leads to almost isothermal conditions with depth. Thus the regime of turbulence appears to be similar with that characteristic of convective boundary layers in the atmosphere. In the present paper a simple analytical approach, based on boundary-layer theory, is applied to conve
The thermal bar in Lake Ladoga was studied during one week in May 1991. Temperature and current velocity distributions were measured. The movement of the thermal bar and the horizontal heat transport were examined.The temperature off-shore the thermal bar was found to be constant within a vertical. The velocity distributions were complex and dependent on wind conditions. Calculations of changes in
The present article is a study of the surface temperature distribution and its evolution during spring in Lake Ladoga, using NOAA-AVHRR Channel 4/Channel 5 (CH4/CH5) data, with special focus on a thermohydrodynamic phenomenon, called thermal bar. The split-window technique, where both constant and atmospheric-mass-dependent retrieval coefficients are tested, is used for calculating the atmospheric
The hierarchical pore systems of Pt/Al2O3 exhaust gas aftertreatment catalysts were analyzed with a collection of correlative imaging techniques to monitor changes induced by hydrothermal aging. Synergistic imaging with laboratory X-ray microtomography, synchrotron radiation ptychographic X-ray computed nanotomography, and electron tomography allowed quantitative observation of the catalyst pore a
INTRODUCTION: Central venous catheterisation is a common procedure in intensive care therapy and the use of central venous catheters is essential for treatment of many medical disorders. Although rare, central venous catheterisation is associated with mechanical complications that can be life-threatening if untreated. Real-time ultrasound guidance reduces the incidence of mechanical complications
