711 research outputs found
Adsorption of Escherichia coli Using Bone Char
The aim of study was providing a novel adsorbent for the removal of Escherichia coli (E.coli) as a microbial model from contaminated air especially in hospital units using bone char (BC). The BC was prepared from cattle animal bone by pyrolysis in a furnace at 450°C for 2 h. The characteristics of BC have been determined using scanning electron microscopy (SEM), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), pHzpc, apparent density and iodine number. Nebulizer system applied to convert the E.coli with different concentration into bioaerosols. The variables included: BC weights (4-10 g), the adsorbent pore size (20-40 mesh) and microbial concentrations (103-107 CFU/mL). Characteristics of the adsorbent show the ability of the BC to remove E.coli fromair. The results shows the higher amounts of BC, the more efficiency achieved to purify contaminate air and particles in the range of 20-40 mesh were more practical in removing bioaerosols. An efficient time for removing the more E.coli was 30 minutes. The maximum bacterial efficiency removal achieved was 99.99%. Comparison of removalefficiency with other literature showed that the BC particles were better mineral sorbents than other organic adsorbents and a commercial activated carbon. In this study, we investigated a novel air purification adsorbent and the information obtained in the paper is of fundamental significance for the mineral adsorbents especially bone charin cleaning of indoor bioaeroso
Theory of a two-level artificial molecule in laterally coupled quantum Hall droplets
We present a theory of laterally coupled quantum Hall droplets with electron
numbers (N1,N2) at filling factor . We show that the edge states of each
droplet are tunnel coupled and form a two-level artificial molecule. By
populating the edge states with one electron each a two electron molecule is
formed. We predict the singlet-triplet transitions of the effective
two-electron molecule as a function of the magnetic field, the number of
electrons, and confining potential using the configuration interaction method
(CI) coupled with the unrestricted Hartree-Fock (URHF) basis. In addition to
the singlet-triplet transitions of a 2 electron molecule involving edge states,
triplet transitions involving transfer of electrons to the center of individual
dots exist for .Comment: 5 pages, 10 figure
Piezomagnetic Quantum Dots
We study the influence of deformations on magnetic ordering in quantum dots
doped with magnetic impurities. The reduction of symmetry and the associated
deformation from circular to elliptical quantum confinement lead to the
formation of piezomagnetic quantum dots. The strength of elliptical deformation
can be controlled by the gate voltage to change the magnitude of magnetization,
at a fixed number of carriers and in the absence of applied magnetic field. We
reveal a reentrant magnetic ordering with the increase of elliptical
deformation and suggest that the piezomagnetic quantum dots can be used as
nanoscale magnetic switches.Comment: 4 pages, 3 figure
Casimir-Lifshitz Interaction between Dielectrics of Arbitrary Geometry: A Dielectric Contrast Perturbation Theory
The general theory of electromagnetic--fluctuation--induced interactions in
dielectric bodies as formulated by Dzyaloshinskii, Lifshitz, and Pitaevskii is
rewritten as a perturbation theory in terms of the spatial contrast in
(imaginary) frequency dependent dielectric function. The formulation can be
used to calculate the Casimir-Lifshitz forces for dielectric objects of
arbitrary geometry, as a perturbative expansion in the dielectric contrast, and
could thus complement the existing theories that use perturbation in
geometrical features. We find that expansion in dielectric contrast recasts the
resulting Lifshitz energy into a sum of the different many-body contributions.
The limit of validity and convergence properties of the perturbation theory is
discussed using the example of parallel semi-infinite objects for which the
exact result is known.Comment: 9 pages, 5 (combined) figures; to appear in Phys. Rev.
Spin transitions induced by a magnetic field in quantum dot molecules
We present a theoretical study of magnetic field driven spin transitions of
electrons in coupled lateral quantum dot molecules. A detailed numerical study
of spin phases of artificial molecules composed of two laterally coupled
quantum dots with N=8 electrons is presented as a function of magnetic field,
Zeeman energy, and the detuning using real space Hartree-Fock Configuration
Interaction (HF-CI) technique. A microscopic picture of quantum Hall
ferromagnetic phases corresponding to zero and full spin polarization at
filling factors and , and ferrimagnetic phases resulting from
coupling of the two dots, is presented.Comment: 12 pages, 18 figure
Statistical mechanics of double-stranded semi-flexible polymers
We study the statistical mechanics of double-stranded semi-flexible polymers
using both analytical techniques and simulation. We find a transition at some
finite temperature, from a type of short range order to a fundamentally
different sort of short range order. In the high temperature regime, the
2-point correlation functions of the object are identical to worm-like chains,
while in the low temperature regime they are different due to a twist
structure. In the low temperature phase, the polymers develop a kink-rod
structure which could clarify some recent puzzling experiments on actin.Comment: 4 pages, 3 figures; final version for publication - slight
modifications to text and figure
Electron-electron interactions in one- and three-dimensional mesoscopic disordered rings: a perturbative approach
We have computed persistent currents in a disordered mesoscopic ring in the
presence of small electron-electron interactions, treated in first order
perturbation theory. We have investigated both a contact (Hubbard) and a
nearest neighbour interaction in 1D and 3D. Our results show that a repulsive
Hubbard interaction produces a paramagnetic contribution to the average current
(whatever the dimension) and increases the value of the typical current. On the
other hand, a nearest neighbour repulsive interaction results in a diamagnetic
contribution in 1D and paramagnetic one in 3D, and tends to decrease the value
of the typical current in any dimension. Our study is based on numerical
simulations on the Anderson model and is justified analytically in the presence
of very weak disorder. We have also investigated the influence of the amount of
disorder and of the statistical (canonical or grand-canonical) ensemble.Comment: 7 pages in REVTEX, 4 figure
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