2,419 research outputs found
Influence of Surface Active Agents on the Interaction in Disperse Systems
The behaviour and the properties of a dispersion are determined
by the forces of interaction developing at the phase boU111dary
due to the asymmetry of the intermolecular forces. The forces of
longer ranges, the electrostatic repulsive forces, and the London
dispersion forces will determine whether the dispersed particles will
continue to exist as individuals or coagulate into particles aggregates
(flocculation process). The behaviour of the particle networks,
the question whether the individuals continue to exist in the aggregate
form, separated by thin films of the dispersion medium,
or flow or grow together to larger particles (coalescence), is influenced
by dipole tnteractions, steric forces, and eventually by
hydrogen bridge linkages, in addition to the electrostatic and
dispersion interaction forces. To modify the interparticle forces
surfactants or macromolecular compounds are used, which will both
influence the long~range inter-particle forces and to a high de1gree,
govern the interaction over short distances, expecially the »steric
hindrance«
Influence of Surface Active Agents on the Interaction in Disperse Systems
The behaviour and the properties of a dispersion are determined
by the forces of interaction developing at the phase boU111dary
due to the asymmetry of the intermolecular forces. The forces of
longer ranges, the electrostatic repulsive forces, and the London
dispersion forces will determine whether the dispersed particles will
continue to exist as individuals or coagulate into particles aggregates
(flocculation process). The behaviour of the particle networks,
the question whether the individuals continue to exist in the aggregate
form, separated by thin films of the dispersion medium,
or flow or grow together to larger particles (coalescence), is influenced
by dipole tnteractions, steric forces, and eventually by
hydrogen bridge linkages, in addition to the electrostatic and
dispersion interaction forces. To modify the interparticle forces
surfactants or macromolecular compounds are used, which will both
influence the long~range inter-particle forces and to a high de1gree,
govern the interaction over short distances, expecially the »steric
hindrance«
Band structures of rare gas solids within the GW approximation
Band structures for solid rare gases (Ne, Ar) have been calculated using the
GW approximation. All electron and pseudopotential ab initio calculations were
performed using Gaussian orbital basis sets and the dependence of particle-hole
gaps and electron affinities on basis set and treatment of core electrons is
investigated. All electron GW calculations have a smaller particle-hole gap
than pseudopotential GW calculations by up to 0.2 eV. Quasiparticle electron
and hole excitation energies, valence band widths and electron affinities are
generally in very good agreement with those derived from optical absorption and
photoemission measurements.Comment: 7 pages 1 figur
Reforestation in a high-CO2 world - Higher mitigation potential than expected, lower adaptation potential than hoped for
We assess the potential and possible consequences for the global climate of a strong reforestation scenario for this century. We perform model experiments using the Max Planck Institute Earth System Model (MPI-ESM), forced by fossil-fuel CO2 emissions according to the high-emission scenario Representative Concentration Pathway (RCP) 8.5, but using land use transitions according to RCP4.5, which assumes strong reforestation. Thereby, we isolate the land use change effects of the RCPs from those of other anthropogenic forcings. We find that by 2100 atmospheric CO2 is reduced by 85 ppm in the reforestation model experiment compared to the reference RCP8.5 model experiment. This reduction is higher than previous estimates and is due to increased forest cover in combination with climate and CO2 feedbacks. We find that reforestation leads to global annual mean temperatures being lower by 0.27 K in 2100. We find large annual mean warming reductions in sparsely populated areas, whereas reductions in temperature extremes are also large in densely populated areas
Enhanced rates of regional warming and ocean acidification after termination of large-scale ocean alkalinization
Termination effects of large‐scale Artificial Ocean Alkalinization (AOA) have received little attention because AOA was assumed to pose low environmental risk. With the Max‐Planck‐Institute Earth System Model, we use emission‐driven AOA simulations following the Representative Concentration Pathway 8.5 (RCP8.5). We find that after termination of AOA warming trends in regions of the Northern hemisphere become ∼50% higher than those in RCP8.5 with rates similar to those caused by termination of solar geoengineering over the following three decades after cessation (up to 0.15 K/year). Rates of ocean acidification after termination of AOA outpace those in RCP8.5. In warm shallow regions where vulnerable coral reefs are located, decreasing trends in surface pH double (0.01 units/year) and the drop in the carbonate saturation state (Ω) becomes up to one order of magnitude larger (0.2 units/year). Thus, termination of AOA poses higher risks to biological systems sensitive to fast‐paced environmental changes than previously thought. <br
Oral mucositis caused by Candida glabrata biofilms: failure of the concomitant use of fluconazole and ascorbic acid
Objectives: Candida glabrata is becoming one of the most prevalent pathogenic yeasts in cases of oral diseases. Mucositis is an recurrent oral infection in immunocompromised patients, and the actual guidelines recommend the use of fluconazole (Flu) for many cases. However, the azole resistance by C. glabrata is renowned, causing a reduced therapeutic response, especially when it occurs in biofilms. In this study, we performed an in vitro evaluation of an alternative pharmacotherapy for C. glabrata biofilm infections, combining ascorbic acid (AA) with Flu. AA is recognized for degrading -glucans, an important compound of the biofilm matrices, which prevent drug diffusion. Materials and Methods: Thus, routine clinical 30 or 40mg/l doses of Flu were applied to C. glabrata biofilms simultaneously with 200 or 300mg/l of AA. Results: The results showed that this combination effectively promoted the degradation of the biofilm network, but unfortunately, also stimulated the growth of the yeasts population due to release of several glucose monomers during -glucans hydrolysis. Conclusions: As a result, it was proven that, contrary to what happens in treatment of bacterial infection, AA should not be used together with Flu in the treatment of oral mucositis caused by Candida.The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by the Programa Operacional, Fatores de competitividade – COMPETE and by national funds through FCT – Fundação para a Ciência e a Tecnologia on the scope of the projects FCT PTDC/SAU-MIC/119069/2010, RECI/EBBEBI/0179/2012 and PEst-OE/EQB/LA0023/2013 and Célia F. Rodrigues’ SFRH/BD/93078/2013 PhD grant
Comparative analysis of 2D and 3D models of turbulent natural convection and thermal surface radiation in closed areas
Turbulent natural convection with surface thermal radiation in air-filled enclosures has been investigated. The equations of conservation of mass, momentum and energy are solved using both finite difference and control volume methods. It should be noted that the working medium is Newtonian and heat conducting fluid, where the Boussinesq approximation is valid. The walls are supposed to be gray, diffuse emitters and reflectors of radiation. The left and right surfaces of the enclosure are isothermal walls, while other surfaces are adiabatic walls. The considered fluid flow is turbulent. The main aim of the present research is to compare the heat transfer process in 2D and 3D enclosures. Detailed results including flow profiles, temperature fields, and average Nusselt numbers have been presented
Ab initio many-body calculation of excitons in solid Ne and Ar
Absorption spectra, exciton energy levels and wave functions for solid Ne and
Ar have been calculated from first principles using many-body techniques.
Electronic band structures of Ne and Ar were calculated using the GW
approximation. Exciton states were calculated by diagonalizing an exciton
Hamiltonian derived from the particle-hole Green function, whose equation of
motion is the Bethe-Salpeter equation. Singlet and triplet exciton series up to
n=5 for Ne and n=3 for Ar were obtained. Binding energies and
longitudinal-transverse splittings of n=1 excitons are in excellent agreement
with experiment. Plots of correlated electron-hole wave functions show that the
electron-hole complex is delocalised over roughly 7 a.u. in solid Ar.Comment: 6 page
LMGP: Lifted Multicut Meets Geometry Projections for Multi-Camera Multi-Object Tracking
Multi-Camera Multi-Object Tracking is currently drawing attention in the
computer vision field due to its superior performance in real-world
applications such as video surveillance in crowded scenes or in wide spaces. In
this work, we propose a mathematically elegant multi-camera multiple object
tracking approach based on a spatial-temporal lifted multicut formulation. Our
model utilizes state-of-the-art tracklets produced by single-camera trackers as
proposals. As these tracklets may contain ID-Switch errors, we refine them
through a novel pre-clustering obtained from 3D geometry projections. As a
result, we derive a better tracking graph without ID switches and more precise
affinity costs for the data association phase. Tracklets are then matched to
multi-camera trajectories by solving a global lifted multicut formulation that
incorporates short and long-range temporal interactions on tracklets located in
the same camera as well as inter-camera ones. Experimental results on the
WildTrack dataset yield near-perfect performance, outperforming
state-of-the-art trackers on Campus while being on par on the PETS-09 dataset.Comment: Official version for CVPR 202
Computer simulation of crystallization kinetics with non-Poisson distributed nuclei
The influence of non-uniform distribution of nuclei on crystallization
kinetics of amorphous materials is investigated. This case cannot be described
by the well-known Johnson-Mehl-Avrami (JMA) equation, which is only valid under
the assumption of a spatially homogeneous nucleation probability. The results
of computer simulations of crystallization kinetics with nuclei distributed
according to a cluster and a hardcore distribution are compared with JMA
kinetics. The effects of the different distributions on the so-called Avrami
exponent are shown. Furthermore, we calculate the small-angle scattering
curves of the simulated structures which can be used to distinguish
experimentally between the three nucleation models under consideration.Comment: 14 pages including 7 postscript figures, uses epsf.sty and
ioplppt.st
- …