2,009 research outputs found
Biological waste gas treatment with a modified rotating biological contactor. Ι. Control of biofilm growth and long-term performance
In this work, we introduce a modified rotating biological contactor (RBC) system and demonstrate its feasibility by applying the newly devised process to the biological treatment of artificial waste gas. In the proposed system, the waste gas is introduced to the bioreactor in the spacings between the rotating discs through a hollow shaft, thus allowing for intimate gas-liquid contact. A 91-l modified RBC containing 20 biofilm support discs 40cm in diameter was used in the experiments. Toluene was used as the model pollutant, and the system was operated under standard operating conditions for more than one year in order to investigate its long-term performance and assess its ability to control the growth of the biofilm. It was demonstrated that the proposed system allows to efficiently control the growth of the biofilm, thus overcoming the clogging problem inherent in most conventional methods for the biological treatment of waste gas. Moreover, the system was shown to exhibit stationary long-term performance for a period of more than one year, hence indicating its feasibility for industrial applicatio
Probing the pairing symmetry in the over-doped Fe-based superconductor Ba_0.35Rb_0.65Fe_2As_2 as a function of hydrostatic pressure
We report muon spin rotation experiments on the magnetic penetration depth
lambda and the temperature dependence of lambda^{-2} in the over-doped Fe-based
high-temperature superconductor (Fe-HTS) Ba_{1-x}Rb_ xFe_2As_2 (x = 0.65)
studied at ambient and under hydrostatic pressures up to p = 2.3 GPa. We find
that in this system lambda^{-2}(T) is best described by d-wave scenario. This
is in contrast to the case of the optimally doped x = 0.35 system which is
known to be a nodeless s^{+-}-wave superconductor. This suggests that the
doping induces the change of the pairing symmetry from s^{+-} to d-wave in
Ba_{1-x}Rb_{x}Fe_{2}As_{2}. In addition, we find that the d-wave order
parameter is robust against pressure, suggesting that d is the common and
dominant pairing symmetry in over-doped Ba_{1-x}Rb_{x}Fe_{2}As_{2}. Application
of pressure of p = 2.3 GPa causes a decrease of lambda(0) by less than 5 %,
while at optimal doping x = 0.35 a significant decrease of lambda(0) was
reported. The superconducting transition temperature T_c as well as the gap to
T_c ratio 2Delta/k_BT_c show only a modest decrease with pressure. By combining
the present data with those previously obtained for optimally doped system x =
0.35 and for the end member x = 1 we conclude that the SC gap symmetry as well
as the pressure effects on the SC quantities strongly depend on the Rb doping
level. These results are discussed in the light of the putative Lifshitz
transition, i.e., a disappearance of the electron pockets in the Fermi surface
of Ba_{1-x}Rb_{x}Fe_{2}As_{2} upon hole doping.Comment: Accepted for publication in Physical Review
Superconductivity and magnetism in RbxFe2-ySe2: Impact of thermal treatment on mesoscopic phase separation
An extended study of the superconducting and normal-state properties of
various as-grown and post-annealed RbxFe2-ySe2 single crystals is presented.
Magnetization experiments evidence that annealing of RbxFe2-ySe2 at 413 K, well
below the onset of phase separation Tp=489 K, neither changes the magnetic nor
the superconducting properties of the crystals. In addition, annealing at 563
K, well above Tp, suppresses the superconducting transition temperature Tc and
leads to an increase of the antiferromagnetic susceptibility accompanied by the
creation of ferromagnetic impurity phases, which are developing with annealing
time. However, annealing at T=488K=Tp increases Tc up to 33.3 K, sharpens the
superconducting transition, increases the lower critical field, and strengthens
the screening efficiency of the applied magnetic field. Resistivity
measurements of the as-grown and optimally annealed samples reveal an increase
of the upper critical field along both crystallographic directions as well as
its anisotropy. Muon spin rotation and scanning transmission electron
microscopy experiments suggest the coexistence of two phases below Tp: a
magnetic majority phase of Rb2Fe4Se5 and a non-magnetic minority phase of
Rb0.5Fe2Se2. Both microscopic techniques indicate that annealing the specimens
just at Tp does not affect the volume fraction of the two phases, although the
magnetic field distribution in the samples changes substantially. This suggests
that the microstructure of the sample, caused by mesoscopic phase separation,
is modified by annealing just at Tp, leading to an improvement of the
superconducting properties of RbxFe2-ySe2 and an enhancement of Tc.Comment: 13 pages, 12 figure
Low-temperature magnetic fluctuations in the Kondo insulator SmB6
We present the results of a systematic investigation of the magnetic
properties of the three-dimensional Kondo topological insulator SmB6 using
magnetization and muon-spin relaxation/rotation (muSR) measurements. The muSR
measurements exhibit magnetic field fluctuations in SmB6 below 15 K due to
electronic moments present in the system. However, no evidence for magnetic
ordering is found down to 19 mK. The observed magnetism in SmB6 is homogeneous
in nature throughout the full volume of the sample. Bulk magnetization
measurements on the same sample show consistent behavior. The agreement between
muSR, magnetization, and NMR results strongly indicate the appearance of
intrinsic bulk magnetic in-gap states associated with fluctuating magnetic
fields in SmB6 at low temperature.Comment: 5 pages, 5 figure
The cognitive-spiritual dimension - an important addition to the assessment of quality of life: Validation of a questionnaire (SELT-M) in patients with advanced cancer
Questions of meaning and challenge by illness, i.e., the spiritual dimension of quality of life (QL) traditionally played an important role in anthroposophically oriented medicine and have gained importance in palliative medicine and supportive care. In the context of a research project on QL in patients with advanced cancer, we therefore investigated the psychometric properties of a questionnaire covering spiritual QL issues, with the aim of providing a module for the assessment of cognitive-spiritual QL. Patients and methods: We investigated 89 patients with advanced breast and gastro-intestinal cancer. Construct validity of a modified version of the SELT (Skalen zur Erfassung von Lebensqualitat bei Tumorkranken), the SELT-M was tested by multitrait scaling analysis. Discriminant and convergent validity were also tested. The EORTC QLQ-C30 was used as a standard for validation. Results showed the SELT-M as feasible in administration. Four of the five SELT-M subscales were internally consistent (Cronbach's Alpha = ≥0.7). The subscale on spiritual QL showed higher within than outside subscale correlations for six of its eight items. Association of the SELT-M with the EORTC QLQ-C30 was good for the items and subscales covering the same aspects of QL in both questionnaires: emotional (Spearman r = 0.61), physical functioning (r= −0.54) and fatigue (r= −0.75). In accordance with expectations, there was no association between spiritual QL with any EORTC QLQ-C30 subscales. Self-assessed spiritual QL in the SELT-M corresponded well with interviewer assessments (test for trend accross ordered groups, P = 0.0023). Conclusions. Overall there is confirming evidence for the hypothesised structure of the SELT-M, especially for the newly developed module on spiritual QL. This module may be used as a module together with other cancer specific QL questionnaire
Applied environmental stresses to enhance the levels of polyphenolics in leaves of hawthorn plants
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72331/1/j.1399-3054.2004.00332.x.pd
Oxygen permeation, mechanical and structural properties of multilayer diffusion barrier coatings on polypropylene
To improve temperature durability for autoclaving of SiOx diffusion barrier coatings on polypropylene, plasma polymerized hexamethyldisiloxane (pp-HMDSO) is applied by plasma enhanced chemical vapour deposition as interlayer material and compared with results obtained with amorphous hydrogenated carbon-nitrogen (a-C : N : H) and a-Si : C : O : N : H interlayers. The influence of the O2/HMDSO ratio on the chemical structure and related mechanical and oxygen barrier properties is investigated by fragmentation tests, dilatometry, oxygen transmission rate, internal stress and mass density measurements as well as Fourier transform infrared and x-ray photoelectron spectroscopy. Carbon-rich, polymer-like coatings with low density, low internal stress and excellent adhesive and cohesive properties are found for pp-HMDSO at the expense of barrier performance. In the SiO x/pp-HMDSO coating a broad transition in chemical composition was observed, explaining improved mechanical properties responsible for good barrier performance after thermal cycling or autoclaving
A Test of Temporal Variation in Risk and Food Stimuli on Behavioral Tradeoffs in the Rusty Crayfish, Orconectes rusticus : Risk Allocation and Stimulus Degradation
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72936/1/j.1439-0310.2006.01156.x.pd
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