37 research outputs found
Surface Incommensurate Structure in an Anisotropic Model with competing interactions on Semiinfinite Triangular Lattice
An anisotropic spin model on a triangular semiinfinite lattice with
ferromagnetic nearest-neighbour interactions and one antiferromagnetic
next-nearest-neighbour interaction is investigated by the cluster
transfer-matrix method. A phase diagram with antiphase, ferromagnetic,
incommensurate, and disordered phase is obtained. The bulk uniaxial
incommensurate structure modulated in the direction of the competing
interactions is found between the antiphase and the disordered phase. The
incommensurate structure near the surface with free and boundary condition
is studied at different temperatures. Paramagnetic damping at the surface and
enhancement of the incommensurate structure in the subsurface region at high
temperatures and a new subsurface incommensurate structure modulated in two
directions at low temperatures are found.Comment: 13 pages, plainTex, 11 figures, paper submitted to J. Phys.
The Effect of Heating on Properties of Sandy Soils
Although burning grass and crop residues is prohibited in many countries, farmers perceive
it as a quick and inexpensive way to eliminate unwanted biomass. The aim of this study was to
estimate the impact of heating temperature (simulation of biomass burning) on the studied properties
(soil organic carbon (SOC) content, pH(H2O), water drop penetration time, WDPT, and contact
angle, CA) of acidic sandy soils. Soil samples were taken from the experimental sites S1, S2, and
S3 at Studienka village in the Borská nížina lowland (southwestern Slovakia). Experimental site S1
was arable land, experimental site S2 was arable land abandoned for approximately 10 years, and
experimental site S3 was arable land abandoned for approximately 30 years with scattered Scots pine
(Pinus sylvestris L.) trees. It was found that all the soil properties studied were strongly affected by
heating. A drop in SOC was observed in all the soils for the heating temperature between 20 and
600 °C. Due to the incomplete combustion of SOC, a small (0.1–0.7%) SOC content was recorded
even in soils heated to between 600 and 900 °C. An increase in pH(H2O) was observed in all the
soils for the heating temperature higher than 300 °C. Soil from the experimental site S1 was wettable
(WDPT < 5 s) for all of the heating temperatures. WDPT vs. heating temperature relationships for
the soils from the experimental sites S2 and S3 were more complex. After a decrease in the heating
temperature of 50 °C, an increase in WDPT for the heating temperature between 50 °C and 300 °C
(for S3 soil) and 350 C (for S2 soil) was registered. Finally, the WDPT dramatically dropped to 0 for
the heating temperature of 350 °C (for S3 soil) and 400 °C (for S2 soil). CA started to decrease at
300 °C in all the soils and dropped to 0° for all the soils at 800 °C. CA > 0° measured in soils for the
heating temperature between 400 and 800 °C, as a consequence of the small SOC contents due to
the incomplete combustion of SOC, is a novelty of this study which demonstrates that CA is more
sensitive to the changes in subcritical water repellency than WDPT