1,088 research outputs found
Effect of Grain Size on Differential Desorption of Volatile Species and on Non-ideal MHD Diffusivity
We developed a chemical network for modeling the chemistry and non-ideal MHD
effects from the collapsing dense molecular clouds to protostellar disks.
First, we re-formulated the cosmic-ray desorption rate by considering the
variations of desorption rate over the grain size distribution. We find that
the differential desorption of volatile species is amplified by the grains
larger than 0.1 m, because larger grains are heated to a lower temperature
by cosmic-rays and hence more sensitive to the variations in binding energies.
As a result, atomic nitrogen N is 2 orders of magnitude more abundant
than CO; NH also becomes a few times more abundant than HCO due to
the increased gas-phase N. However, the changes in ionization fraction due
to freeze-out and desorption only have minor effects on the non-ideal MHD
diffusivities. Our chemical network confirms that the very small grains (VSGs:
below a few 100 ) weakens the efficiency of both ambipolar diffusion and
Hall effect. In collapsing dense cores, a maximum ambipolar diffusion is
achieved when truncating the MRN size distribution at 0.1 m, and for a
maximum Hall effect, the truncation occurs at 0.04 m. We conclude that the
grain size distribution is crucial to the differential depletion between CO and
N related molecules, as well as to the non-ideal MHD diffusivities in dense
cores.Comment: 15 pages, 11 figures; Submitted to MNRA
An anti-cancer Smurf
A novel, cancer-fighting function was recently discovered for Smad ubiquitination regulatory factor 2 (Smurf2)
Blow up solutions to a viscoelastic fluid system and a coupled Navier-Stokes/Phase-Field system in R^2
We find explicit solutions to both the Oldroyd-B model with infinite
Weissenberg number and the coupled Navier-Stokes/Phase-Field system. The
solutions blow up in finite time.Comment: 5 page
Study on the Rheological Properties and Constitutive Model of Shenzhen Mucky Soft Soil
In order to obtain the basic parameters of numerical analysis about the time-space effect of the deformation occurring in Shenzhen deep soft-soil foundation pit, a series of triaxial consolidated-undrained shear rheology tests on the peripheral mucky soft soil of a deep foundation pit support were performed under different confining pressures. The relations between the axial strain of the soil and time, as well as between the pore-water pressure of the soil and time, were achieved, meanwhile on the basis of analyzing the rheological properties of the soil, the relevant rheological models were built. Analysis results were proved that the rheology of Shenzhen mucky soft soil was generally viscous, elastic, and plastic, and had a low yield stress between 90 and 150 kPa. The increase in pore-water pressure made the rheological time effect of the mucky soft soil more remarkable. Thus, the drainage performance in practical engineering should be improved to its maximum possibility extent to decrease the soft-soil rheological deformation. Lastly, a six-component extended Burgers model was employed to fit the test results and the parameters of the model were determined. Findings showed that the extended Burgers model could satisfactorily simulate the various rheological stages of the mucky soft soil. The constitutive model and the determination of its parameters can be served as a foundation for the time-space effect analysis on the deformation of deep soft-soil foundation pits
Dichlorido[N-(2-pyridylmethylidene)benzene-1,4-diamine]zinc(II)
In the title compound, [ZnCl2(C12H11N3)], the ZnII atom is four-coordinated by two N atoms from an N-(2-pyridylmethylene)benzene-1,4-diamine ligand and two Cl atoms in a distorted tetrahedral geometry. In the crystal, the complex molecules are connected by N—H⋯Cl and C—H⋯Cl hydrogen bonds into a two-dimensional layer structure parallel to (110)
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