18 research outputs found
New Experimental Limit on the Electric Dipole Moment of the Electron in a Paramagnetic Insulator
We report results of an experimental search for the intrinsic Electric Dipole
Moment (EDM) of the electron using a solid-state technique. The experiment
employs a paramagnetic, insulating gadolinium gallium garnet (GGG) that has a
large magnetic response at low temperatures. The presence of the eEDM would
lead to a small but non-zero magnetization as the GGG sample is subject to a
strong electric field. We search for the resulting Stark-induced magnetization
with a sensitive magnetometer. Recent progress on the suppression of several
sources of background allows the experiment to run free of spurious signals at
the level of the statistical uncertainties. We report our first limit on the
eEDM of 10ecm with 5 days of
data averaging.Comment: 9 pages, 9 figures, Revtex 4.
Microtesla MRI of the human brain combined with MEG
One of the challenges in functional brain imaging is integration of
complementary imaging modalities, such as magnetoencephalography (MEG) and
functional magnetic resonance imaging (fMRI). MEG, which uses highly sensitive
superconducting quantum interference devices (SQUIDs) to directly measure
magnetic fields of neuronal currents, cannot be combined with conventional
high-field MRI in a single instrument. Indirect matching of MEG and MRI data
leads to significant co-registration errors. A recently proposed imaging method
- SQUID-based microtesla MRI - can be naturally combined with MEG in the same
system to directly provide structural maps for MEG-localized sources. It
enables easy and accurate integration of MEG and MRI/fMRI, because microtesla
MR images can be precisely matched to structural images provided by high-field
MRI and other techniques. Here we report the first images of the human brain by
microtesla MRI, together with auditory MEG (functional) data, recorded using
the same seven-channel SQUID system during the same imaging session. The images
were acquired at 46 microtesla measurement field with pre-polarization at 30
mT. We also estimated transverse relaxation times for different tissues at
microtesla fields. Our results demonstrate feasibility and potential of human
brain imaging by microtesla MRI. They also show that two new types of imaging
equipment - low-cost systems for anatomical MRI of the human brain at
microtesla fields, and more advanced instruments for combined functional (MEG)
and structural (microtesla MRI) brain imaging - are practical.Comment: 8 pages, 5 figures - accepted by JM
Photosynthesis-dependent HâOâ transfer from chloroplasts to nuclei provides a high-light signalling mechanism
Chloroplasts communicate information by signalling to nuclei during acclimation to fluctuating light. Several potential operating signals originating from chloroplasts have been proposed, but none have been shown to move to nuclei to modulate gene expression. One proposed signal is hydrogen peroxide (H2O2) produced by chloroplasts in a light-dependent manner. Using HyPer2, a genetically encoded fluorescent H2O2 sensor, we show that in photosynthetic Nicotiana benthamiana epidermal cells, exposure to high light increases H2O2 production in chloroplast stroma, cytosol and nuclei. Critically, over-expression of stromal ascorbate peroxidase (H2O2 scavenger) or treatment with DCMU (photosynthesis inhibitor) attenuates nuclear H2O2 accumulation and high light-responsive gene expression. Cytosolic ascorbate peroxidase over-expression has little effect on nuclear H2O2 accumulation and high light-responsive gene expression. This is because the H2O2 derives from a sub-population of chloroplasts closely associated with nuclei. Therefore, direct H2O2 transfer from chloroplasts to nuclei, avoiding the cytosol, enables photosynthetic control over gene expression
SQUIDs in biomagnetism : A roadmap towards improved healthcare
This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 686865.Peer reviewedPublisher PD
A New Cryogenic Apparatus to Search for the Neutron Electric Dipole Moment
A cryogenic apparatus is described that enables a new experiment, nEDM@SNS,
with a major improvement in sensitivity compared to the existing limit in the
search for a neutron Electric Dipole Moment (EDM). It uses superfluid He to
produce a high density of Ultra-Cold Neutrons (UCN) which are contained in a
suitably coated pair of measurement cells. The experiment, to be operated at
the Spallation Neutron Source at Oak Ridge National Laboratory, uses polarized
He from an Atomic Beam Source injected into the superfluid He and
transported to the measurement cells as a co-magnetometer. The superfluid
He is also used as an insulating medium allowing significantly higher
electric fields, compared to previous experiments, to be maintained across the
measurement cells. These features provide an ultimate statistical uncertainty
for the EDM of e-cm, with anticipated systematic
uncertainties below this level
Electric dipole moments and the search for new physics
Static electric dipole moments of nondegenerate systems probe mass scales for
physics beyond the Standard Model well beyond those reached directly at high
energy colliders. Discrimination between different physics models, however,
requires complementary searches in atomic-molecular-and-optical, nuclear and
particle physics. In this report, we discuss the current status and prospects
in the near future for a compelling suite of such experiments, along with
developments needed in the encompassing theoretical framework.Comment: Contribution to Snowmass 2021; updated with community edits and
endorsement