17 research outputs found
Measuring the Sterile Neutrino CP Phase at DUNE and T2HK
The CP phases associated with the sterile neutrino cannot be measured in the
dedicated short-baseline experiments being built to test the sterile neutrino
hypothesis. On the other hand, these phases can be measured in long-baseline
experiments, even though the main goal of these experiments is not to test or
measure sterile neutrino parameters. In particular, the sterile neutrino phase
affects the charged-current electron appearance data in
long-baseline experiment. In this paper we show for the first time how well the
sterile neutrino phase can be measured by the next-generation
long-baseline experiments DUNE, T2HK (and T2HKK). We also show the expected
precision with which this sterile phase can be measured by combining the DUNE
data with data from T2HK or T2HKK. We also present the sensitivity of these
experiments to the sterile mixing angles, both by themselves, as well as when
DUNE is combined with T2HK or T2HKK.Comment: Published in EPJ C with minor correction
Exploring fake solutions in the sterile neutrino sector at long-baseline experiments
Active-sterile neutrino mixing is known to affect the neutrino oscillation
probabilities at both short as well as long-baselines. In particular,
constraints on active-sterile neutrino oscillation parameters can be obtained
from long-baseline experiments such as T2HK and DUNE. We present here existence
of fake solution in the appearance channel for the 3+1 scenario at
long-baseline experiments. We show that the appearance probability is same for
values of for which the fast oscillations are averaged out
and for . The fake solution does not
appear for the disappearance channel.Comment: 17 pages, 6 figures, accepted with some modification
Sterile Neutrinos: Propagation in Matter and Sensitivity to Sterile Mass Ordering
We analytically calculate the neutrino conversion probability in
the presence of sterile neutrinos, with exact dependence on
and with matter effects explicitly included. Using perturbative expansion in
small parameters, the terms involving the small mixing angles and
can be separated out, with dependence only arising
due to matter effects. We express in terms of the quantities of the
form , which helps in elucidating its dependence on matter effects
and a wide range of values. Our analytic expressions allow us
to predict the effects of the sign of at a long baseline
experiment like DUNE. We numerically calculate the sensitivity of DUNE to the
sterile mass ordering and find that this sensitivity can be significant in the
range eV, for either mass
ordering of active neutrinos. The dependence of this sensitivity on the value
of for all mass ordering combinations can be explained by
investigating the resonance-like terms appearing due to the interplay between
the sterile sector and matter effects.Comment: 25 pages, 5 figure
Apomyoglobin Sequesters Heme from Heme Bound Aβ Peptides
A combination of absorption, electron
paramagnetic resonance (EPR), and resonance Raman (rR) spectroscopy
has been used to study the interaction of heme-Aβ and apomyoglobin
(apoMb). The absorption spectrum of oxidized heme bound Aβ,
characterized by a split Soret band at 364 and 394 nm, shifts to 408
nm on incubation with apoMb, characteristic of Myoglobin (Mb). The
ν<sub>4</sub>, ν<sub>3</sub>, and ν<sub>2</sub> bands
in the rR spectrum of heme-Aβ are observed at 1376, 1495, and
1570 cm<sup>–1</sup>, which shift to 1371, 1482, and 1563 cm<sup>–1</sup>, respectively on incubating with apoMb, implying
formation of Mb. Similarly, heme transfer from reduced heme-Aβ
to apoMb resulting in the formation of deoxyMb was also observed.
Thus, spectroscopic data show that apoMb can sequester heme from heme-Aβ
complexes both in oxidized and in reduced forms. Heme uptake by apoMb
from native heme-Aβ(1–40) and Aβ(1–16) in
both oxidized and reduced forms follow a biphasic reaction kinetics
likely representing heme transfer from two dominating conformers of
heme-Aβ in solution. The rate constants for the two steps involved
in heme uptake by apoMb from heme-Aβ(1–40) are 11.5 ×
10<sup>4</sup> M<sup>–1</sup> s<sup>–1</sup> and 7.5
× 10<sup>3</sup> M<sup>–1</sup> s<sup>–1</sup> while
from heme-Aβ(1–16) are 6.0 × 10<sup>4</sup> M<sup>–1</sup> s<sup>–1</sup> and 7.5 × 10<sup>3</sup> M<sup>–1</sup> s<sup>–1</sup>. The rate constants
for heme uptake by apoMb from reduced heme-Aβ(1–40) are
3.7 × 10<sup>4</sup> M<sup>–1</sup> s<sup>–1</sup> and 6.8 × 10<sup>3</sup> M<sup>–1</sup> s<sup>–1</sup> while for reduced heme-Aβ(1–16) are 2.0 × 10<sup>4</sup> M<sup>–1</sup> s<sup>–1</sup> and 6.0 ×
10<sup>3</sup> M<sup>–1</sup> s<sup>–1</sup>. The heme
uptake from heme-Aβ by apoMb leads to a dramatic reduction of
PROS generation by the reduced heme-Aβ complexes
Interaction of NO with Cu and Heme-Bound Aβ Peptides Associated with Alzheimer’s Disease
Reduced Cu and heme has been invoked to be involved in
Alzheimer’s
disease (AD). Recently the Aβ peptides have been demonstrated
to bind heme and Cu simultaneously, and this complex produces significantly
more toxic partially reduced oxygen species (PROS) than the Cu or
heme-bound Aβ peptides. Here a combination of absorption, EPR,
and resonance Raman spectroscopy along with kinetic assays are used
to investigate the interaction of nitric oxide (NO) with the physiologically
relevant form of Cu and heme-bound Aβ peptides, since a down-regulation
of nitric oxide synthase activity is observed in patients suffering
from AD. The data indicate that NO oxidizes the Cu(I) sites, making
them less toxic toward PROS generation and releases heme from the
Aβ peptides ameliorating the effects of heme binding to Aβ
peptides associated with AD. This process involves a tyrosine-mediated
electron transfer between the Cu and heme sites. These results provide
a mechanistic pathway for the possible protective role of NO in AD
Artificial maturation of [FeFe] hydrogenase in a redox polymer film
International audienceWe demonstrate that the insertion of the dinuclear active site of [FeFe] hydrogenase into the apo-enzyme can occur when the enzyme is embedded in a film of redox polymer, under conditions of mediated electron transfer. The maturation can be monitored by electrochemistry, and is as fast as under conditions of direct electron transfer. This new approach clears further the way to the implementation of hydrogenases in large scale real life processes