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Rapid and Efficient Arsenic Removal by Iron Electrocoagulation Enabled with in Situ Generation of Hydrogen Peroxide.
Millions of people are exposed to toxic levels of dissolved arsenic in groundwater used for drinking. Iron electrocoagulation (FeEC) has been demonstrated as an effective technology to remove arsenic at an affordable price. However, FeEC requires long operating times (âŒhours) to remove dissolved arsenic due to inherent kinetics limitations. Air cathode Assisted Iron Electrocoagulation (ACAIE) overcomes this limitation by cathodically generating H2O2 in situ. In ACAIE operation, rapid oxidation of Fe(II) and complete oxidation and removal of As(III) are achieved. We compare FeEC and ACAIE for removing As(III) from an initial concentration of 1464 ÎŒg/L, aiming for a final concentration of less than 4 ÎŒg/L. We demonstrate that at short electrolysis times (0.5 min), i.e., high charge dosage rates (1200 C/L/min), ACAIE consistently outperformed FeEC in bringing arsenic levels to less than WHO-MCL of 10 ÎŒg/L. Using XRD and XAS data, we conclusively show that poor arsenic removal in FeEC arises from incomplete As(III) oxidation, ineffective Fe(II) oxidation and the formation of Fe(II-III) (hydr)oxides at short electrolysis times (<20 min). Finally, we report successful ACAIE performance (retention time 19 s) in removing dissolved arsenic from contaminated groundwater in rural California
Distributed Cyber-Attack Detection in the Secondary Control of DC Microgrids
The paper considers the problem of detecting
cyber-attacks occurring in communication networks typically
used in the secondary control layer of DC microgrids. The proposed
distributed methodology allows for scalable monitoring of
a microgrid and is able to detect the presence of data injection
attacks in the communications among Distributed Generation
Units (DGUs) - governed by consensus-based control - and
isolate the communication link over which the attack is injected.
Each local attack detector requires limited knowledge regarding
the dynamics of its neighbors. Detectability properties of the
method are analyzed, as well as a class of undetectable attacks.
Some results from numerical simulation are presented to
demonstrate the effectiveness of the proposed approach
Near-field diffraction of fs and sub-fs pulses: super-resolutions of NSOM in space and time
The near-field diffraction of fs and sub-fs light pulses by nm-size slit-type
apertures and its implication for near-field scanning optical microscopy (NSOM)
is analyzed. The amplitude distributions of the diffracted wave-packets having
the central wavelengths in the visible spectral region are found by using the
Neerhoff and Mur coupled integral equations, which are solved numerically for
each Fourier's component of the wave-packet. In the case of fs pulses, the
duration and transverse dimensions of the diffracted pulse remain practically
the same as that of the input pulse. This demonstrates feasibility of the NSOM
in which a fs pulse is used to provide the fs temporal resolution together with
nm-scale spatial resolution. In the sub-fs domain, the Fourier spectrum of the
transmitted pulse experiences a considerable narrowing that leads to the
increase of the pulse duration in a few times. This imposes a limit on the
simultaneous resolutions in time and space.Comment: 5 figure
Terahertz imaging and spectroscopy of large-area single-layer graphene
We demonstrate terahertz (THz) imaging and spectroscopy of a 15x15-mm^2
single-layer graphene film on Si using broadband THz pulses. The THz images
clearly map out the THz carrier dynamics of the graphene-on-Si sample, allowing
us to measure sheet conductivity with sub-mm resolution without fabricating
electrodes. The THz carrier dynamics are dominated by intraband transitions and
the THz-induced electron motion is characterized by a flat spectral response. A
theoretical analysis based on the Fresnel coefficients for a metallic thin film
shows that the local sheet conductivity varies across the sample from {\sigma}s
= 1.7x10^-3 to 2.4x10^-3 {\Omega}^-1 (sheet resistance, {\rho}s = 420 - 590
{\Omega}/sq).Comment: 6 pages, 5 figure
iNucs:Inter-nucleosome interactions
[Motivation] Deciphering nucleosomeânucleosome interactions is an important step toward mesoscale description of chromatin organization but computational tools to perform such analyses are not publicly available. [Results] We developed iNucs, a user-friendly and efficient Python-based bioinformatics tool to compute and visualize nucleosome-resolved interactions using standard pairs format input generated from pairtools
DC-electric-field-induced and low-frequency electromodulation second-harmonic generation spectroscopy of Si(001)-SiO interfaces
The mechanism of DC-Electric-Field-Induced Second-Harmonic (EFISH) generation
at weakly nonlinear buried Si(001)-SiO interfaces is studied experimentally
in planar Si(001)-SiO-Cr MOS structures by optical second-harmonic
generation (SHG) spectroscopy with a tunable Ti:sapphire femtosecond laser. The
spectral dependence of the EFISH contribution near the direct two-photon
transition of silicon is extracted. A systematic phenomenological model of the
EFISH phenomenon, including a detailed description of the space charge region
(SCR) at the semiconductor-dielectric interface in accumulation, depletion, and
inversion regimes, has been developed. The influence of surface quantization
effects, interface states, charge traps in the oxide layer, doping
concentration and oxide thickness on nonlocal screening of the DC-electric
field and on breaking of inversion symmetry in the SCR is considered. The model
describes EFISH generation in the SCR using a Green function formalism which
takes into account all retardation and absorption effects of the fundamental
and second harmonic (SH) waves, optical interference between field-dependent
and field-independent contributions to the SH field and multiple reflection
interference in the SiO layer. Good agreement between the phenomenological
model and our recent and new EFISH spectroscopic results is demonstrated.
Finally, low-frequency electromodulated EFISH is demonstrated as a useful
differential spectroscopic technique for studies of the Si-SiO interface in
silicon-based MOS structures.Comment: 31 pages, 14 figures, 1 table, figures are also available at
http://kali.ilc.msu.su/articles/50/efish.ht
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