224 research outputs found
Aquatic Environment
Environment and Development: Basic Principles, Human Activities, and Environmental Implications focuses on the adverse impact that human activities, developments, and economic growth have on both natural and inhabited environments. The book presents the associated problems, along with solutions that can be used to achieve a harmonic, sustainable development that provides for the co-existence of man and natural life
Aquatic Environment
Environment and Development: Basic Principles, Human Activities, and Environmental Implications focuses on the adverse impact that human activities, developments, and economic growth have on both natural and inhabited environments. The book presents the associated problems, along with solutions that can be used to achieve a harmonic, sustainable development that provides for the co-existence of man and natural life
Effects of 2-chlorophenol and 2,4,6-trichlorophenol on an activated sludge sequencing batch reactor
In the work, the effect of 2-chlorophenol and 2,4,6-trichlorophenol on the performance of a sequencing batch reactor operated with suspended municipal recycle activated sludge (RAS) in terms of total carbon and total nitrogen removal is presented. The total carbon removal achieved ranged in 80%–100% and total nitrogen removal in 10%–84%. The results showed that chlorophenols did not inhibit either the activated sludge growth or the total carbon removal significantly. However, inhibition is observed in total nitrogen removal. 2-chlorophenol inhibited the ammonium oxidation (nitrification) while such an effect was not observed in the case of 2,4,6-trichlorophenol indicating that the later inhibits the ammonification step. Moreover, the results indicated that total removal of both chlorophenols was achieved during the first day of the processing
Treatment of municipal solid waste landfill leachate by use of combined biological, physical and photochemical processes
The purpose of this work was to study the treatment of a leachate coming from the municipal solid waste landfill of Astana (Kazakhstan). Physical (striping and adsorption), biological and photochemical processes were applied separately or in combination, and the treatment efficiency was attended in terms of carbon and nitrogen removal. The leachate carbon was by 45%–60% inorganic while nitrogen was almost 100% inorganic in the form of ammonia. The results showed that inorganic carbon and ammonia can be almost entirely removed by air stripping at pH = 7 and pH = 12, respectively. The removal of organic carbon by stripping alone was lower than 4% but combined to adsorption reached 20%, and to biological treatment 30%. The removal of organic carbon by photochemical oxidation alone was 43%. The combination of stripping, adsorption and biological treatment resulted in 37% organic carbon and with the addition of photochemical oxidation step the removal was increased to 59%. In overall, total carbon removal reached 85% and total nitrogen removal almost 100%. The results showed that the decomposition of landfill leachate carbon is a challenging task requiring a combination of processes. On the contrary, as almost all nitrogen is inorganic, air stripping at elevated pH alone can sufficiently eliminate it
Proximity effecs and curie temperature enhancement in Co/EuS and Fe/EuS multilayers
Two identical Co/EuS and Fe/EuS multilayers of six periods each and with
individual layers of about 4 nm thick are grown by e-beam evaporation under
ultrahigh vacuum conditions. The films show polycrystalline structure with a
grain size limited by the individual layer thickness. Both multilayers consist
of almost continuous layers with some roughness. The surface peak-to-peak
roughness is about 4–5 nm. Magnetization measurements and calculations of the
loops based on a Stoner–Wohlfarth-like model allow us to determine the direct
antiferromagnetic exchange coupling constant between the 3d metal and EuS at 5
K. Both samples show strong enhancement of the Curie temperature of EuS up to
at least 50 K with a EuS magnetization tail, which persists up to about 100 K.
The J = 7/2 character of the EuS layers is shown to be responsible for the
large Curie temperature enhancement
Direct evidence for significant spin-polarization of EuS in Co/EuS multilayers at room temperature
The new era of spintronics promises the development of nanodevices, where the
electron spin will be used to store information and charge currents will be
replaced by spin currents. For this, ferromagnetic semiconductors at room
temperature are needed. We report on significant room-temperature spin
polarization of EuS in Co/EuS multilayers recorded by x-ray magnetic circular
dichroism (XMCD). The films were found to contain a mixture of divalent and
trivalent europium, but only Eu11 is responsible for the ferromagnetic
behavior of EuS. The magnetic XMCD signal of Eu at room temperature could
unambiguously be assigned to magnetic ordering of EuS and was found to be only
one order of magnitude smaller than that at 2.5 K. The room temperature
magnetic moment of EuS is as large as the one of bulk ferromagnetic Ni. Our
findings pave the path for fabrication of room–temperature spintronic devices
using spin polarized EuS layers
Band-gap tuning at the strong quantum confinement regime in magnetic semiconductor EuS thin films
Ultraviolet-visible absorption spectra of nanoscaled EuS thin films reveal a
blue shift of the energy between the top-valence and bottom-conduction bands.
This band-gap tuning changes smoothly with decreasing film thickness and
becomes significant below the exciton Bohr diameter ~3.5nm indicating strong
quantum confinement effects. The results are reproduced in the framework of
the potential morphing method in Hartree Fock approximation. The large values
of the effective mass of the holes, due to localization of the EuS ƒ-states,
limit the blue shift to about 0.35eV. This controllable band-gap tuning of
magnetic semiconductor EuS renders it useful for merging spintronics and
optoelectronics
Paramagnetic gold in a highly disordered Au-Ni-O alloy
Magnetic materials are usually classified into a distinct category such as diamagnets, paramagnets or ferromagnets. The enormous progress in materials science allows one nowadays, however, to change the magnetic nature of an element in a material. Gold, in bulk form, is traditionally a diamagnet. But in a ferromagnetic environment, it can adopt an induced ferromagnetic moment. Moreover, the growth of gold under certain conditions may lead to a spontaneous ferromagnetic or paramagnetic response. Here, we report on paramagnetic gold in a highly disordered Au–Ni–O alloy and focus on the unusual magnetic response. Such materials are mainly considered for plasmonic applications. Thin films containing Au, Ni and NiO are fabricated by co-deposition of Ni and Au in a medium vacuum of 2 × 10−2 mbar. As a result, Au is in a fully disordered state forming in some cases isolated nanocrystallites of up to 4 nm in diameter as revealed by high resolution transmission electron microscopy. The disorder and the environment, which is rich in oxygen, lead to remarkable magnetic properties of Au: an induced ferromagnetic and a paramagnetic state. This can be proven by measuring the x-ray magnetic circular dichroism. Our experiments show a way to establish and monitor Au paramagnetism in alloys
IL-10 and TGF-β1 gene polymorphisms in Greek patients with recurrent aphthous stomatitis
Recurrent aphthous stomatitis (RAS) is one of the most frequent inflammatory disorders of the oral mucosa. Cytokines, which play an important role in RAS pathogenesis, participate directly or indirectly in normal, immunological and inflammatory processes and are secreted from cells belonging to innate and adaptive immunity as a consequence of microbial and antigenic stimuli. Gene polymorphisms in specific cytokines may predispose to RAS development. The aim of this study was the investigation and association of IL-10 and TGF-β1 gene polymorphisms with RAS
Dipolar interaction between two-dimensional magnetic particles
We determine the effective dipolar interaction between single domain
two-dimensional ferromagnetic particles (islands or dots), taking into account
their finite size. The first correction term decays as 1/D^5, where D is the
distance between particles. If the particles are arranged in a regular
two-dimensional array and are magnetized in plane, we show that the correction
term reinforces the antiferromagnetic character of the ground state in a square
lattice, and the ferromagnetic one in a triangular lattice. We also determine
the dipolar spin-wave spectrum and evaluate how the Curie temperature of an
ensemble of magnetic particles scales with the parameters defining the particle
array: height and size of each particle, and interparticle distance. Our
results show that dipolar coupling between particles might induce ferromagnetic
long range order at experimentally relevant temperatures. However, depending on
the size of the particles, such a collective phenomenon may be disguised by
superparamagnetism.Comment: 11 pages, 5 figure
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