1,579 research outputs found
Calcite covering of sediment as a possible way of curbing blue-green algae
Natural calcite precipitation in lakes is a well-known control mechanism of eutrophication. In hard-water lakes, calcite deposits on the flat bottoms of shallow lakes and near the shores of deeper lakes resulted from biogenic decalcification during the millenia after the last glacial period. The objective of a new restoration technology is to intensify the natural process of precipitation by utilizing the different qualities of calcareous mud layers. In a pilot experiment in Lake Rudower See, East Germany, phosphorus-poor deeper layers of the sediments were flushed out and spread over the phosphorus-rich uppermost sediments, to promote the co- precipitation of calcite with phosphorus from the water-column
ΠΠ»ΠΈΡΠ½ΠΈΠ΅ ΠΏΠ°ΡΠ°ΠΌΠ΅ΡΡΠΎΠ² ΠΈΡΠΊΡΠΎΠ²ΠΎΠ³ΠΎ ΠΏΠ»Π°Π·ΠΌΠ΅Π½Π½ΠΎΠ³ΠΎ ΡΠΏΠ΅ΠΊΠ°Π½ΠΈΡ Π½Π° ΡΡΡΡΠΊΡΡΡΠ½ΠΎ-ΡΠ°Π·ΠΎΠ²ΠΎΠ΅ ΡΠΎΡΡΠΎΡΠ½ΠΈΠ΅ ΠΊΠ΅ΡΠ°ΠΌΠΈΡΠ΅ΡΠΊΠΈΡ ΠΊΠΎΠΌΠΏΠΎΠ·ΠΈΡΠΎΠ² Π½Π° ΠΎΡΠ½ΠΎΠ²Π΅ MAX-ΡΠ°Π·, ΠΏΠΎΠ»ΡΡΠ΅Π½Π½ΡΡ ΠΈΠ· ΠΏΡΠ΅ΠΊΠ΅ΡΠ°ΠΌΠΈΡΠ΅ΡΠΊΠΎΠΉ Π±ΡΠΌΠ°Π³ΠΈ
ΠΠΎΠΌΠΏΠΎΠ·ΠΈΡΠ½ΡΠ΅ ΠΌΠ°ΡΠ΅ΡΠΈΠ°Π»Ρ Π½Π° ΠΎΡΠ½ΠΎΠ²Π΅ MAX β ΡΠ°Π· ΡΠΎΡΠ΅ΡΠ°ΡΡ Π² ΡΠ΅Π±Π΅ ΠΎΡΠΎΠ±Π΅Π½Π½ΠΎΡΡΠΈ ΠΊΠ΅ΡΠ°ΠΌΠΈΠΊ ΠΈ ΠΌΠ΅ΡΠ°Π»Π»ΠΎΠ². ΠΠ°Π½Π½ΠΎΠ΅ ΡΠΎΡΠ΅ΡΠ°Π½ΠΈΠ΅ ΠΏΠΎΠ·Π²ΠΎΠ»ΡΠ΅Ρ ΠΈΡΠΏΠΎΠ»ΡΠ·ΠΎΠ²Π°ΡΡ ΠΈΡ
Π² ΡΠ°Π·Π»ΠΈΡΠ½ΡΡ
ΠΎΠ±Π»Π°ΡΡΡΡ
ΠΏΡΠΎΠΈΠ·Π²ΠΎΠ΄ΡΡΠ²Π°, ΡΠ°ΠΊΠΈΡ
ΠΊΠ°ΠΊ ΡΠ»Π΅ΠΊΡΡΠΎΠ½ΠΈΠΊΠ°. Π Π΄Π°Π½Π½ΠΎΠΉ ΡΠ°Π±ΠΎΡΠ΅ ΠΈΠ·ΡΡΠ°Π΅ΡΡΡ Π²Π»ΠΈΡΠ½ΠΈΠ΅ ΠΏΠ°ΡΠ°ΠΌΠ΅ΡΡΠΎΠ² ΠΈΡΠΊΡΠΎΠ²ΠΎΠ³ΠΎ ΠΏΠ»Π°Π·ΠΌΠ΅Π½Π½ΠΎΠ³ΠΎ ΡΠΏΠ΅ΠΊΠ°Π½ΠΈΡ Π½Π° ΡΡΡΡΠΊΡΡΡΠ½ΠΎ-ΡΠ°Π·ΠΎΠ²ΠΎΠ΅ ΡΠΎΡΡΠΎΡΠ½ΠΈΠ΅ ΠΊΠ΅ΡΠ°ΠΌΠΈΡΠ΅ΡΠΊΠΈΡ
ΠΊΠΎΠΌΠΏΠΎΠ·ΠΈΡΠΎΠ² Π½Π° ΠΎΡΠ½ΠΎΠ²Π΅ MAX β ΡΠ°Π·, ΠΏΠΎΠ»ΡΡΠ΅Π½Π½ΡΡ
ΠΈΠ· ΠΏΡΠ΅ΠΊΠ΅ΡΠ°ΠΌΠΈΡΠ΅ΡΠΊΠΎΠΉ Π±ΡΠΌΠ°Π³ΠΈ. Π ΡΠ΅Π·ΡΠ»ΡΡΠ°ΡΠ΅ Π±ΡΠ»ΠΈ ΠΏΠΎΠ»ΡΡΠ΅Π½Ρ Π΄Π°Π½Π½ΡΠ΅ ΠΎΠ± ΠΈΠ·ΠΌΠ΅Π½Π΅Π½ΠΈΠΈ ΡΠ°Π·ΠΎΠ²ΠΎΠ³ΠΎ ΡΠΎΡΡΠ°Π²Π°, ΠΌΠΈΠΊΡΠΎΡΡΡΡΠΊΡΡΡΡ, ΠΏΠ»ΠΎΡΠ½ΠΎΡΡΠΈ ΠΈ ΠΏΠΎΡΠΈΡΡΠΎΡΡΠΈ ΠΊΠΎΠΌΠΏΠΎΠ·ΠΈΡΠ° ΠΏΡΠΈ ΡΠ°Π·Π»ΠΈΡΠ½ΡΡ
Π·Π½Π°ΡΠ΅Π½ΠΈΡΡ
Π΄Π°Π²Π»Π΅Π½ΠΈΡ ΠΈ ΡΠ΅ΠΌΠΏΠ΅ΡΠ°ΡΡΡ ΠΈΡΠΊΡΠΎΠ²ΠΎΠ³ΠΎ ΠΏΠ»Π°Π·ΠΌΠ΅Π½Π½ΠΎΠ³ΠΎ ΡΠΏΠ΅ΠΊΠ°Π½ΠΈΡ.Composite materials based on MAX - phases combine the features of ceramics and metals. This combination allows you to use them in various areas of production, such as electronics. In this work, we study the effect of spark plasma sintering parameters on the structural phase state of ceramic composites based on MAX phases obtained from preceramic paper. As a result, data were obtained on changes in the phase composition, microstructure, density and porosity of the composite at various values ??of pressure and spark plasma sintering temperatures
The Viscous Nonlinear Dynamics of Twist and Writhe
Exploiting the "natural" frame of space curves, we formulate an intrinsic
dynamics of twisted elastic filaments in viscous fluids. A pair of coupled
nonlinear equations describing the temporal evolution of the filament's complex
curvature and twist density embodies the dynamic interplay of twist and writhe.
These are used to illustrate a novel nonlinear phenomenon: ``geometric
untwisting" of open filaments, whereby twisting strains relax through a
transient writhing instability without performing axial rotation. This may
explain certain experimentally observed motions of fibers of the bacterium B.
subtilis [N.H. Mendelson, et al., J. Bacteriol. 177, 7060 (1995)].Comment: 9 pages, 4 figure
Twirling and Whirling: Viscous Dynamics of Rotating Elastica
Motivated by diverse phenomena in cellular biophysics, including bacterial
flagellar motion and DNA transcription and replication, we study the overdamped
nonlinear dynamics of a rotationally forced filament with twist and bend
elasticity. Competition between twist injection, twist diffusion, and writhing
instabilities is described by a novel pair of coupled PDEs for twist and bend
evolution. Analytical and numerical methods elucidate the twist/bend coupling
and reveal two dynamical regimes separated by a Hopf bifurcation: (i)
diffusion-dominated axial rotation, or twirling, and (ii) steady-state
crankshafting motion, or whirling. The consequences of these phenomena for
self-propulsion are investigated, and experimental tests proposed.Comment: To be published in Physical Review Letter
Accurate laboratory rest frequencies of vibrationally excited CO up to and up to 2 THz
Astronomical observations of (sub)millimeter wavelength pure rotational
emission lines of the second most abundant molecule in the Universe, CO, hold
the promise of probing regions of high temperature and density in the innermost
parts of circumstellar envelopes. The rotational spectrum of vibrationally
excited CO up to \varv = 3 has been measured in the laboratory between 220
and 1940 GHz with relative accuracies up to , corresponding
to kHz near 1 THz. The rotational constant and the quartic
distortion parameter have been determined with high accuracy and even the
sextic distortion term was determined quite well for \varv = 1 while
reasonable estimates of were obtained for \varv = 2 and 3. The present
data set allows for the prediction of accurate rest frequencies of
vibrationally excited CO well beyond 2 THz.Comment: Astron. Astrophys, accepted; 5 pages, 2 Figures, 2 Table
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