51 research outputs found
An experimental and theoretical study of the enantioselective deprotonation of cyclohexene oxide with isopinocampheyl-based chiral lithium amides
The mechanism of the enantioselective deprotonation of cyclohexene oxide with isopinocampheyl-based chiral lithium amide was studied by quantum chemical calculations. The transition states of eight molecules were fully optimized at the ab initio HF/3-21G and density functional B3LYP/3-21G levels with Gaussian 98. The activation energies were calculated at the B3LYP/6-31+G(3df,2p)//B3LYP/3-21G level. We found the theoretical evaluation to be consistent with the experimental data. At the best case, an enantiomeric excess of up to 95% for (R)-2-scyclohexen-1-ol was achieved with (−)-N, N-diisopinocampheyl lithium amide
Search for solar flare neutrinos with the KamLAND detector
We report the result of a search for neutrinos in coincidence with solar flares from the GOES flare database. The search was performed on a 10.8 kton-year exposure of KamLAND collected from 2002 to 2019. This large exposure allows us to explore previously unconstrained parameter space for solar flare neutrinos. We found no statistical excess of neutrinos and established 90% confidence level upper limits of 8.4 × 10^7 cm^−2 (3.0 × 10^9 cm^−2) on the electron antineutrino (electron neutrino) fluence at 20 MeV normalized to the X12 flare, assuming that the neutrino fluence is proportional to the X-ray intensity.https://arxiv.org/abs/2105.0245
First measurement of the strange axial coupling constant using neutral-current quasi-elastic interactions of atmospheric neutrinos at KamLAND
We report a measurement of the strange axial coupling constant using
atmospheric neutrino data at KamLAND. This constant is a component of the axial
form factor of the neutral current quasi-elastic (NCQE) interaction. The value
of significantly changes the ratio of proton and neutron NCQE cross
sections. KamLAND is suitable for measuring NCQE interactions as it can detect
nucleon recoils with low energy thresholds and measure neutron multiplicity
with high efficiency. KamLAND data, including the information on neutron
multiplicity associated with the NCQE interactions, makes it possible to
measure with a suppressed dependence on the axial mass , which has
not yet been determined. For a comprehensive prediction of the neutron emission
associated with neutrino interactions, we establish a simulation of particle
emission via nuclear de-excitation of C, a process not considered in
existing neutrino Monte Carlo event generators. Energy spectrum fitting for
each neutron multiplicity gives , which is the
most stringent limit obtained using NCQE interactions without
constraints
Measurement of cosmic-ray muon spallation products in a xenon-loaded liquid scintillator with KamLAND
Cosmic-ray muons produce various radioisotopes when passing through material.
These spallation products can be backgrounds for rare event searches such as in
solar neutrino, double-beta decay, and dark matter search experiments. The
KamLAND-Zen experiment searches for neutrinoless double-beta decay in 745kg of
xenon dissolved in liquid scintillator. The experiment includes dead-time-free
electronics with a high efficiency for detecting muon-induced neutrons. The
production yields of different radioisotopes are measured with a combination of
delayed coincidence techniques, newly developed muon reconstruction and xenon
spallation identification methods. The observed xenon spallation products are
consistent with results from the FLUKA and Geant4 simulation codes
KamLAND's search for correlated low-energy electron antineutrinos with astrophysical neutrinos from IceCube
We report the results of a search for MeV-scale astrophysical neutrinos in
KamLAND presented as an excess in the number of coincident neutrino
interactions associated with the publicly available high-energy neutrino
datasets from the IceCube Neutrino Observatory. We find no statistically
significant excess in the number of observed low-energy electron antineutrinos
in KamLAND, given a coincidence time window of 500s, 1,000s,
3,600s, and 10,000s around each of the IceCube neutrinos. We use this
observation to present limits from 1.8 MeV to 100 MeV on the electron
antineutrino fluence, assuming a mono-energetic flux. We then compare the
results to several astrophysical measurements performed by IceCube and place a
limit at the 90% confidence level on the electron antineutrino isotropic
thermal luminosity from the TXS 0506+056 blazar.Comment: 12 pages, 5 figure
Limits on astrophysical antineutrinos with the KamLAND Experiment
We report on a search for electron antineutrinos (n¯e) from astrophysical sources in the neutrino energy range
8.3–30.8 MeV with the KamLAND detector. In an exposure of 6.72 kton-year of the liquid scintillator, we observe 18
candidate events via the inverse beta decay reaction. Although there is a large background uncertainty from neutral
current atmospheric neutrino interactions, we find no significant excess over background model predictions.
Assuming several supernova relic neutrino spectra, we give upper flux limits of 60–110 cm−2 s
−1 (90% confidence
level, CL) in the analysis range and present a model-independent flux. We also set limits on the annihilation rates for
light dark matter pairs to neutrino pairs. These data improve on the upper probability limit of 8B solar neutrinos converting into , (90% CL) assuming an undistorted shape. This corresponds to a solar flux of 60 cm−2 s−1 (90% CL) in the analysis energy range.https://arxiv.org/abs/2108.0852
Detecting pancreatic β-cell cfDNA
Aims/Introduction: Several research groups have reported methods for quantifying pancreatic beta cell (β-cell) injury by measuring β-cell-specific CpG unmethylation of the insulin gene in circulation using digital droplet PCR or next-generation sequencing. However, these methods have certain disadvantages, such as the need to consider the background signal owing to the small number of target CpG sites and the need for unique equipment.
Materials and Methods: We established a novel method for detecting four CpG unmethylations of the insulin gene using two-step amplification refractory mutation system PCR. We applied it to type 1 diabetes (T1D) patients with a wide range of disease durations and to healthy adults.
Results: The assay showed high linearity and could detect a single copy of unmethylated insulin DNA in experiments using methylated and unmethylated plasmid DNA. The unmethylated insulin DNA level in the type 1 diabetes group, whose β-cell mass was considerably reduced, was similar to that of healthy adults. An inverse correlation was observed between copy number and disease duration in patients with unmethylated insulin DNA-positive type 1 diabetes.
Conclusions: We developed a novel method for detecting unmethylated insulin DNA in circulation that can be performed using a conventional real-time PCR system. This method would be useful for analyzing dynamic profiles of β-cells in human disease such as type 1 diabetes
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