392 research outputs found
A necklace of Wulff shapes
In a probabilistic model of a film over a disordered substrate, Monte-Carlo
simulations show that the film hangs from peaks of the substrate. The film
profile is well approximated by a necklace of Wulff shapes. Such a necklace can
be obtained as the infimum of a collection of Wulff shapes resting on the
substrate. When the random substrate is given by iid heights with exponential
distribution, we prove estimates on the probability density of the resulting
peaks, at small density
CCS from industrial sources
The literature concerning the application of CCS to industry is reviewed. Costs are presented for different sectors including ``high purity'' (processes which inherently produce a high concentration of CO2), cement, iron and steel, refinery and biomass. The application of CCS to industry is a field which has had much less attention than its application to the electricity production sector. Costs range from less than 2011 100/tCO 2 . In the words of a synthesis report from the United Nations Industrial Development Organisation (UNIDO) ``This area has so far not been the focus of discussions and therefore much attention needs to be paid to the application of CCS to industrial sources if the full potential of CCS is to be unlocked''
Assessment of RNAi-induced silencing in banana (Musa spp.)
In plants, RNA- based gene silencing mediated by small RNAs functions at the transcriptional or post-transcriptional level to negatively regulate target genes, repetitive sequences, viral RNAs and/or transposon elements. Post-transcriptional gene silencing (PTGS) or the RNA interference (RNAi) approach has been achieved in a wide range of plant species for inhibiting the expression of target genes by generating double-stranded RNA (dsRNA). However, to our knowledge, successful RNAi-application to knock-down endogenous genes has not been reported in the important staple food crop banana
Metastable wetting
Consider a droplet of liquid on top of a grooved substrate. The wetting or
not of a groove implies the crossing of a potential barrier as the interface
has to distort, to hit the bottom of the groove. We start with computing the
free energies of the dry and wet states in the context of a simple
thermodynamical model before switching to a random microscopic version
pertaining to the Solid-on-Solid (SOS) model. For some range in parameter space
(Young angle, pressure difference, aspect ratio), the dry and wet states both
share the same free energy, which means coexistence. We compute these
coexistence lines together with the metastable regions. In the SOS case, we
describe the dynamic transition between coexisting states in wetting. We show
that the expected time to switch from one state to the other grows
exponentially with the free energy barrier between the stable states and the
saddle state, proportional to the groove's width. This random time appears to
have an exponential-like distribution
Interface Tensions and Perfect Wetting in the Two-Dimensional Seven-State Potts Model
We present a numerical determination of the order-disorder interface tension,
\sod, for the two-dimensional seven-state Potts model. We find
\sod=0.0114\pm0.0012, in good agreement with expectations based on the
conjecture of perfect wetting. We take into account systematic effects on the
technique of our choice: the histogram method. Our measurements are performed
on rectangular lattices, so that the histograms contain identifiable plateaus.
The lattice sizes are chosen to be large compared to the physical correlation
length. Capillary wave corrections are applied to our measurements on finite
systems.Comment: 8 pages, LaTex file, 2 postscript figures appended, HLRZ 63/9
Insulin Growth Factor-I in Protein-Energy Malnutrition during Rehabilitation in Two Nutritional Rehabilitation Centres in Burkina Faso
Objective. To investigate the relationship between IGF-I and the nutritional status of West-African children hospitalised for nutritional rehabilitation.
Patients and methods. A cohort study was performed in two centres for nutritional rehabilitation and education (CREN) in Burkina Faso. Children were followed and the anthropometric data as well as the capillary blood samples were taken on the 7th and on the 14th days after their admission. IGF-I levels were determined from dried blood spots on filter paper on IGF-I RIA, after separation of the IGF-I from its binding proteins, using Sep-Pak chromatography.
Results. A total of 59 children was included in the cohort. The IGF-I mean geometric values (SD) were 6.3 (1.4)
μg/L on admission, 8.6 (1.8) μg/L at day 7 and 13.6 (2.0) μg/L at day 14. The differences between these values were statistically significant (P < .001). There is a significant correlation between the changes of IGF-I with the change of weight for height Z-score (P = .01).
Conclusion. These results suggest that IGF-I can be considered as a potential marker to follow the nutritional status of children admitted in hospital for protein and energy malnutrition
Dynamics of Spreading of Chainlike Molecules with Asymmetric Surface Interactions
In this work we study the spreading dynamics of tiny liquid droplets on solid
surfaces in the case where the ends of the molecules feel different
interactions with respect to the surface. We consider a simple model of dimers
and short chainlike molecules that cannot form chemical bonds with the surface.
We use constant temperature Molecular Dynamics techniques to examine in detail
the microscopic structure of the time dependent precursor film. We find that in
some cases it can exhibit a high degree of local order that can persist even
for flexible chains. Our model also reproduces the experimentally observed
early and late-time spreading regimes where the radius of the film grows
proportional to the square root of time. The ratios of the associated transport
coefficients are in good overall agreement with experiments. Our density
profiles are also in good agreement with measurements on the spreading of
molecules on hydrophobic surfaces.Comment: 12 pages, LaTeX with APS macros, 21 figures available by contacting
[email protected], to appear in Phys. Rev.
Dewetting, partial wetting and spreading of a two-dimensional monolayer on solid surface
We study the behavior of a semi-infinite monolayer, which is placed initially
on a half of an infinite in both directions, ideal crystalline surface, and
then evolves in time due to random motion of the monolayer particles. Particles
dynamics is modeled as the Kawasaki particle-vacancy exchange process in the
presence of long-range attractive particle-particle interactions. In terms of
an analytically solvable mean-field-type approximation we calculate the mean
displacement X(t) of the monolayer edge and discuss the conditions under which
such a monolayer spreads (X(t) > 0), partially wets (X(t) = 0) or dewets from
the solid surface (X(t) < 0).Comment: 4 pages, 2 figures, to appear in PRE (RC
Appearance of a low superheat "quasi-Leidenfrost" regime for boiling on superhydrophobic surfaces
Pool boiling experiments were performed with degassed water on stainless steel substrates with different surface topographies and wettabilities. Boiling curves and visual observations of the boiling process have been carried out. The onset of nucleate boiling (ONB) has been measured and the influence of roughness and wettability has been quantified. Boiling curve shape is different between the hydrophilic and the superhydrophobic cases; superhydrophobic surfaces reaching the ONB heat flux at a lower superheat and presenting a "quasi-Leidenfrost" regime, without showing the typical boiling curve. Bubbles are easier to form on superhydrophobic surfaces, therefore the nucleation temperature is smaller, and bubbles are larger and stable. The ONB appears after less than 5 K of superheat on superhydrophobic surfaces, while on hydrophilic surfaces, with the same surface roughness, the superheat is above 7 K. Furthermore, superhydrophobic samples with a different roughness present the same boiling curve, meaning that, when the contact angle exceeds a certain value, the wettability has a predominant role on the surface roughness
Spreading of a Macroscopic Lattice Gas
We present a simple mechanical model for dynamic wetting phenomena. Metallic
balls spread along a periodically corrugated surface simulating molecules of
liquid advancing along a solid substrate. A vertical stack of balls mimics a
liquid droplet. Stochastic motion of the balls, driven by mechanical vibration
of the corrugated surface, induces diffusional motion. Simple theoretical
estimates are introduced and agree with the results of the analog experiments,
with numerical simulation, and with experimental data for microscopic spreading
dynamics.Comment: 19 pages, LaTeX, 9 Postscript figures, to be published in Phy. Rev. E
(September,1966
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