26,066 research outputs found
On the predominant mechanisms active during the high power diode laser modification of the wettability characteristics of an SiO2/Al2O3-based ceramic material
The mechanisms responsible for modifications to the wettability characteristics of a SiO2/Al2O3-based ceramic material in terms of a test liquid set comprising of human blood, human blood plasma, glycerol and 4-octonol after high power diode laser (HPDL) treatment have been elucidated. Changes in the contact angle, , and hence the wettability characteristics of the SiO2/Al2O3-based ceramic were attributed primarily to: modifications to the surface roughness of the ceramic resulting from HPDL interaction which accordingly effected reductions in ; the increase in the surface O2 content of the ceramic after HPDL treatment; since an increase in surface O2 content intrinsically brings about a decrease in , and vice versa and the increase in the polar component of the surface energy, due to the HPDL induced surface melting and resolidification which consequently created a partially vitrified microstructure that was seen to augment the wetting action. However, the degree of influence exerted by each mechanism was found to differ markedly. Isolation of each of these mechanisms permitted the magnitude of their influence to be qualitatively determined. Surface energy, by way of microstructural changes, was found to be by far the most predominant element governing the wetting characteristics of the SiO2/Al2O3-based ceramic. To a much lesser extent, surface O2 content, by way of process gas, was also seen to influence to a changes in the wettability characteristics of the SiO2/Al2O3-based ceramic, whilst surface roughness was found to play a minor role in inducing changes in the wettability characteristics
Wetting and bonding characteristics of selected liquid-metals with a high power diode laser treated alumina bioceramic
Changes in the wettability characteristics of an alumina bioceramic occasioned by high power diode laser (HPDL) surface treatment were apparent from the observed reduction in the contact angle. Such changes were due to the HPDL bringing about reductions the surface roughness, increases in the surface O2 content and increases in the polar component of the surface energy. Additionally, HPDL treatment of the alumina bioceramic surface was found to effect an improvement in the bonding characteristics by increasing the work of adhesion. An electronic approach was used to elucidate the bonding characteristics of the alumina bioceramic before and after HPDL treatment. It is postulated that HPDL induced changes to the alumina bioceramic produced a surface with a reduced bandgap energy which consequently increased the work of adhesion by increasing the electron transfer at the metal/oxide interface and thus the metal-oxide interactions. Furthermore, it is suggested that the increase in the work of adhesion of the alumina bioceramic after HPDL treatment was due to a correlation existing between the wettability and ionicity of the alumina bioceramic; for it is believed that the HPDL treated surface is less ionic in nature than the untreated surface and therefore exhibits better wettability characteristics
Quark charge balance function and hadronization effects in relativistic heavy ion collisions
We calculate the charge balance function of the bulk quark system before
hadronization and those for the directly produced and the final hadron system
in high energy heavy ion collisions. We use the covariance coefficient to
describe the strength of the correlation between the momentum of the quark and
that of the anti-quark if they are produced in a pair and fix the parameter by
comparing the results for hadrons with the available data. We study the
hadronization effects and decay contributions by comparing the results for
hadrons with those for the bulk quark system. Our results show that while
hadronization via quark combination mechanism slightly increases the width of
the charge balance functions, it preserves the main features of these functions
such as the longitudinal boost invariance and scaling properties in rapidity
space. The influence from resonance decays on the width of the balance function
is more significant but it does not destroy its boost invariance and scaling
properties in rapidity space either. The balance functions in azimuthal
direction are also presented.Comment: 9 figure
Theoretical studies of 63Cu Knight shifts of the normal state of YBa2Cu3O7
The 63Cu Knight shifts and g factors for the normal state of YBa2Cu3O7 in
tetragonal phase are theoretically studied in a uniform way from the high
(fourth-) order perturbation formulas of these parameters for a 3d9 ion under
tetragonally elongated octahedra. The calculations are quantitatively
correlated with the local structure of the Cu2+(2) site in YBa2Cu3O7. The
theoretical results show good agreement with the observed values, and the
improvements are achieved by adopting fewer adjustable parameters as compared
to the previous works. It is found that the significant anisotropy of the
Knight shifts is mainly attributed to the anisotropy of the g factors due to
the orbital interactions.Comment: 5 page
Sea flavor content of octet baryons and intrinsic five-quark Fock states
Sea quark contents of the octet baryons are investigated by employing an
extended chiral constituent quark approach, which embodies higher Fock
five-quark components in the baryons wave-functions. The well-known flavor
asymmetry of the nucleon sea , is used as input to predict the
probabilities of , and in the nucleon, ,
and baryons, due to the intrinsic five-quark components in the
baryons wave functions.Comment: 22 page
Investigations of the g factors and local structure for orthorhombic Cu^{2+}(1) site in fresh PrBa_{2}Cu_{3}O_{6+x} powders
The electron paramagnetic resonance (EPR) g factors g_x, g_y and g_z of the
orthorhombic Cu^{2+}(1) site in fresh PrBa_{2}Cu_{3}O_{6+x} powders are
theoretically investigated using the perturbation formulas of the g factors for
a 3d^9 ion under orthorhombically elongated octahedra. The local orthorhombic
distortion around the Cu^{2+}(1) site due to the Jahn-Teller effect is
described by the orthorhombic field parameters from the superposition model.
The [CuO6]^{10-} complex is found to experience an axial elongation of about
0.04 {\AA} along c axis and the relative bond length variation of about 0.09
{\AA} along a and b axes of the Jahn-Teller nature. The theoretical results of
the g factors based on the above local structure are in reasonable agreement
with the experimental data.Comment: 6 pages, 1 figur
Quark deconfinement phase transition for improved quark mass density-dependent model
By using the finite temperature quantum field theory, we calculate the finite
temperature effective potential and extend the improved quark mass
density-dependent model to finite temperature. It is shown that this model can
not only describe the saturation properties of nuclear matter, but also explain
the quark deconfinement phase transition successfully. The critical temperature
is given and the effect of - meson is addressed.Comment: 18 pages, 7 figure
- …