7,680 research outputs found
Evaluating two concepts for the modelling of intermediates accumulation during biological denitrification in wastewater treatment
The accumulation of the denitrification intermediates in wastewater treatment systems is highly undesirable, since both nitrite and nitric oxide (NO) are known to be toxic to bacteria, and nitrous oxide (N2O) is a potent greenhouse gas and an ozone depleting substance. To date, two distinct concepts for the modelling of denitrification have been proposed, which are represented by the Activated Sludge Model for Nitrogen (ASMN) and the Activated Sludge Model with Indirect Coupling of Electrons (ASM-ICE), respectively. The two models are fundamentally different in describing the electron allocation among different steps of denitrification. In this study, the two models were examined and compared in their ability to predict the accumulation of denitrification intermediates reported in four different experimental datasets in literature. The N-oxide accumulation predicted by the ASM-ICE model was in good agreement with values measured in all four cases, while the ASMN model was only able to reproduce one of the four cases. The better performance of the ASM-ICE model is due to that it adopts an “indirect coupling” modelling concept through electron carriers to link the carbon oxidation and the nitrogen reduction processes, which describes the electron competition well. The ASMN model, on the other hand, is inherently limited by its structural deficiency in assuming that carbon oxidation is always able to meet the electron demand by all denitrification steps, therefore discounting electron competition among these steps. ASM-ICE therefore offers a better tool for predicting and understanding intermediates accumulation in biological denitrification
Voltage-independent SK-channel dysfunction causes neuronal hyperexcitability in the hippocampus of Fmr1 knock-out mice
Neuronal hyperexcitability is one of the major characteristics of fragile X syndrome (FXS), yet the molecular mechanisms of this critical dysfunction remain poorly understood. Here we report a major role of voltage-independent potassium (
The Charge Collection Properties of CVD Diamond
The charge collection properties of CVD diamond have been investigated with
ionising radiation. In this study two CVD diamond samples, prepared with
electrical contacts have been used as solid state ionisation chambers. The
diamonds have been studied with beta particles and 10 keV photons, providing a
homogeneous ionisation density and with protons and alpha particles which are
absorbed in a thin surface layer. For the latter case a strong decrease of the
signal as function of time is observed, which is attributed to polarisation
effects inside the diamond. Spatially resolved measurements with protons show a
large variation of the charge collection efficiency, whereas for photons and
minimum ionising particles the response is much more uniform and in the order
of 18%. These results indicate that the applicability of CVD diamond as a
position sensitive particle detector depends on the ionisation type and appears
to be promising for homogeneous ionisation densities as provided by
relativistic charged particles.Comment: 26 pages (Latex), submitted to NIM
Development of Test-Bed AUV \u27ISiMI\u27 and Underwater Experiments on Free Running and Vision Guided Docking
Characterization and Modeling of Non-Uniform Charge Collection in CVD Diamond Pixel Detectors
A pixel detector with a CVD diamond sensor has been studied in a 180 GeV/c
pion beam. The charge collection properties of the diamond sensor were studied
as a function of the track position, which was measured with a silicon
microstrip telescope. Non-uniformities were observed on a length scale
comparable to the diamond crystallites size. In some regions of the sensor, the
charge drift appears to have a component parallel to the sensor surface (i.e.,
normal to the applied electric field) resulting in systematic residuals between
the track position and the hits position as large as 40 m. A numerical
simulation of the charge drift in polycrystalline diamond was developed to
compute the signal induced on the electrodes by the electrons and holes
released by the passing particles. The simulation takes into account the
crystallite structure, non-uniform trapping across the sensor, diffusion and
polarization effects. It is in qualitative agreement with the data. Additional
lateral electric field components result from the non-uniform trapping of
charges in the bulk. These provide a good explanation for the large residuals
observed.Comment: Accepted by Nucl. Instr. and Met
An experimental observation of geometric phases for mixed states using NMR interferometry
Examples of geometric phases abound in many areas of physics. They offer both
fundamental insights into many physical phenomena and lead to interesting
practical implementations. One of them, as indicated recently, might be an
inherently fault-tolerant quantum computation. This, however, requires to deal
with geometric phases in the presence of noise and interactions between
different physical subsystems. Despite the wealth of literature on the subject
of geometric phases very little is known about this very important case. Here
we report the first experimental study of geometric phases for mixed quantum
states. We show how different they are from the well understood, noiseless,
pure-state case.Comment: 4 pages, 3 figure
All-inorganic core-shell silica-titania mesoporous colloidal nanoparticles showing orthogonal functionality
Colloidal mesoporous silica (CMS) nanoparticles with a thin titania-enriched outer shell showing a spatially resolved functionality were synthesized by a delayed co-condensation approach. The titaniashell can serve as a selective nucleation site for the growth of nanocrystalline anatase clusters. These fully inorganic pure silica-core titania-enriched shell mesoporous nanoparticles show orthogonal functionality, demonstrated through the selective adsorption of a carboxylate-containing ruthenium N3-dye. UV-Vis and fluorescence spectroscopy indicate the strong interaction of the N3-dye with the titania-phase at the outer shell of the CMS nanoparticles. In particular, this interaction and thus the selective functionalization are greatly enhanced when anatase nanocrystallites are nucleated at the titania-enriched shell surface
Transcriptome analysis reveals new insight into appressorium formation and function in the rice blast fungus Magnaporthe oryzae
Analysis of genome-wide gene-expression changes during spore germination and appressorium formation in Magnaporthe oryzae revealed that protein degradation and amino-acid metabolism are essential for appressorium formation and subsequent infection
Gain-bandwidth characteristics of thin avalanche photodiodes
The frequency-response characteristics of avalanche photodiodes (APDs) with thin multiplication layers are investigated by means of a recurrence technique that incorporates the history dependence of ionization coefficients. In addition, to characterize the autocorrelation function of the impulse response, new recurrence equations are derived and solved using a parallel computer. The mean frequency response and the gain-bandwidth product are computed and a simple model for the dependence of the gain-bandwidth product on the multiplication-layer width is set forth for GaAs, InP, Al/sub 0.2/Ga/sub 0.8/As, and In/sub 0.52/Al/sub 0.48/As APDs. It is shown that the dead-space effect leads to a reduction (up to 30%) in the bandwidth from that predicted by the conventional multiplication theory. Notably, calculation of the power-spectral density of the photocurrent reveals that the presence of dead space also results in a reduction in the fluctuations in the frequency response. This result is the spectral generalization of the reduction in the excess noise factor in thin APDs and reveals an added advantage of using thin APDs in ultrafast receivers
Selective and potent proteomimetic inhibitors of intracellular protein–protein interactions
Inhibition of protein–protein interactions (PPIs) represents a major challenge in chemical biology and drug discovery. α-Helix mediated PPIs may be amenable to modulation using generic chemotypes, termed “proteomimetics”, which can be assembled in a modular manner to reproduce the vectoral presentation of key side chains found on a helical motif from one partner within the PPI. In this work, it is demonstrated that by using a library of N-alkylated aromatic oligoamide helix mimetics, potent helix mimetics which reproduce their biophysical binding selectivity in a cellular context can be identified
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