2,963,351 research outputs found
High-Resolution Nanoscale Solid-State Nuclear Magnetic Resonance Spectroscopy
We present a new method for high-resolution nanoscale magnetic resonance
imaging (nano-MRI) that combines the high spin sensitivity of nanowire-based
magnetic resonance detection with high spectral resolution nuclear magnetic
resonance (NMR) spectroscopy. By applying NMR pulses designed using optimal
control theory, we demonstrate a factor of reduction of the proton spin
resonance linewidth in a volume of polystyrene and
image proton spins in one dimension with a spatial resolution below
.Comment: Main text: 8 pages, 6 figures; supplementary information: 10 pages,
10 figure
Living Liquid Crystals
Collective motion of self-propelled organisms or synthetic particles often
termed active fluid has attracted enormous attention in broad scientific
community because of it fundamentally non-equilibrium nature. Energy input and
interactions among the moving units and the medium lead to complex dynamics.
Here we introduce a new class of active matter, living liquid crystals (LLCs)
that combine living swimming bacteria with a lyotropic liquid crystal. The
physical properties of LLCs can be controlled by the amount of oxygen available
to bacteria, by concentration of ingredients, or by temperature. Our studies
reveal a wealth of new intriguing dynamic phenomena, caused by the coupling
between the activity-triggered flow and long-range orientational order of the
medium. Among these are (a) non-linear trajectories of bacterial motion guided
by non-uniform director, (b) local melting of the liquid crystal caused by the
bacteria-produced shear flows, (c) activity-triggered transition from a
non-flowing uniform state into a flowing one-dimensional periodic pattern and
its evolution into a turbulent array of topological defects, (d)
birefringence-enabled visualization of microflow generated by the
nanometers-thick bacterial flagella. Unlike their isotropic counterpart, the
LLCs show collective dynamic effects at very low volume fraction of bacteria,
on the order of 0.2%. Our work suggests an unorthodox design concept to control
and manipulate the dynamic behavior of soft active matter and opens the door
for potential biosensing and biomedical applications.Comment: 32 pages, 8 figures, Supporting Information include
Structured volume-law entanglement in an interacting, monitored Majorana spin liquid
Monitored quantum circuits allow for unprecedented dynamical control of
many-body entanglement. Here we show that random, measurement-only circuits,
implementing the competition of bond and plaquette couplings of the Kitaev
honeycomb model, give rise to a structured volume-law entangled phase with
subleading liquid scaling behavior. This interacting Majorana liquid
takes up a highly-symmetric, spherical parameter space within the entanglement
phase diagram obtained when varying the relative coupling probabilities. The
sphere itself is a critical boundary with quantum Lifshitz scaling separating
the volume-law phase from proximate area-law phases, a color code or a toric
code. An exception is a set of tricritical, self-dual points exhibiting
effective (1+1)d conformal scaling at which the volume-law phase and both
area-law phases meet. From a quantum information perspective, our results
define error thresholds for the color code in the presence of projective error
and stochastic syndrome measurements. We show that an alternative realization
of our model circuit can be implemented using unitary gates plus ancillary
single-qubit measurements only.Comment: 4.5 + 3 pages; 4 + 8 figure
Cell Volume Regulation Studies with the Electron Microprobe
Lumbricals from the hind feet of young rats are dissected free, stretched to approximately 125% of resting length, and mounted on individual, simple plastic forms. After recovery in physiological saline, the isolated muscles are incubated for periods of 40 to 60 min. in one of a series of hypertonic bathing solutions. The composition of each bathing solution is identical, except for osmolality which is increased with lactose. At least one muscle from each animal is incubated in a control solution to serve as a control muscle for that particular set of 5 to 8 muscles. Mounted muscles are removed from the bathing solutions and quickly plunged into chilled liquid propane. Tissue is freeze-dried at low temperature, fixed with osmium tetroxide vapor, and embedded in brominated EPON 826. Dilution of the embedding medium by tissue solids, assessed by reduction of the embedding plastic Br Lα signal, is used to establish intracellular hydration; or conversely, intracellular solids fractions. The Br Lα signal is monitored along with S Kα, K Kα, Cl Kα, Na Kα, and the continuum region from 4.2 to 7.2 keV using a simultaneous ED-WD spectrometer electron probe microanalyzer. This provides sufficient information to present intracellular concentrations in units of mmol/kg wet weight, mmol/kg water, or mmol/kg dry weight. Cell volume change relative to a suitable control is determined from the ratio of sulfur signals from the experimental and control cells. The response of cells to hypertonic challenge is assessed by comparing actual cell volume change with the change expected of a simple osmotic bag. Simultaneously, the intracellular electrolyte data provides information on the mechanism of cellular response to osmotic shifts
Geometric Hydrodynamics: from Euler, to Poincar\'e, to Arnold
These are lecture notes for a short winter course at the Department of
Mathematics, University of Coimbra, Portugal, December 6--8, 2018. The course
was part of the 13th International Young Researchers Workshop on Geometry,
Mechanics and Control.
In three lectures I trace the work of three heroes of mathematics and
mechanics: Euler, Poincar\'e, and Arnold. This leads up to the aim of the
lectures: to explain Arnold's discovery from 1966 that solutions to Euler's
equations for the motion of an incompressible fluid correspond to geodesics on
the infinite-dimensional Riemannian manifold of volume preserving
diffeomorphisms. In many ways, this discovery is the foundation for the field
of geometric hydrodynamics, which today encompasses much more than just Euler's
equations, with deep connections to many other fields such as optimal
transport, shape analysis, and information theory.Comment: Lecture notes for PhD winter course in Coimbra, December 6-8, 201
Controlling spin relaxation with a cavity
Spontaneous emission of radiation is one of the fundamental mechanisms by
which an excited quantum system returns to equilibrium. For spins, however,
spontaneous emission is generally negligible compared to other non-radiative
relaxation processes because of the weak coupling between the magnetic dipole
and the electromagnetic field. In 1946, Purcell realized that the spontaneous
emission rate can be strongly enhanced by placing the quantum system in a
resonant cavity -an effect which has since been used extensively to control the
lifetime of atoms and semiconducting heterostructures coupled to microwave or
optical cavities, underpinning single-photon sources. Here we report the first
application of these ideas to spins in solids. By coupling donor spins in
silicon to a superconducting microwave cavity of high quality factor and small
mode volume, we reach for the first time the regime where spontaneous emission
constitutes the dominant spin relaxation mechanism. The relaxation rate is
increased by three orders of magnitude when the spins are tuned to the cavity
resonance, showing that energy relaxation can be engineered and controlled
on-demand. Our results provide a novel and general way to initialise spin
systems into their ground state, with applications in magnetic resonance and
quantum information processing. They also demonstrate that, contrary to popular
belief, the coupling between the magnetic dipole of a spin and the
electromagnetic field can be enhanced up to the point where quantum
fluctuations have a dramatic effect on the spin dynamics; as such our work
represents an important step towards the coherent magnetic coupling of
individual spins to microwave photons.Comment: 8 pages, 6 figures, 1 tabl
Motion corrected fetal body magnetic resonance imaging provides reliable 3D lung volumes in normal and abnormal fetuses
Objectives: To calculate 3D-segmented total lung volume (TLV) in fetuses with thoracic anomalies using deformable slice-to-volume registration (DSVR) with comparison to 2D-manual segmentation. To establish a normogram of TLV calculated by DSVR in healthy control fetuses.
Methods: A pilot study at a single regional fetal medicine referral centre included 16 magnetic resonance imaging (MRI) datasets of fetuses (22–32 weeks gestational age). Diagnosis was CDH (n = 6), CPAM (n = 2), and healthy controls (n = 8). Deformable slice-to-volume registration was used for reconstruction of 3D isotropic (0.85 mm) volumes of the fetal body followed by semi-automated lung segmentation. 3D TLV were compared to traditional 2D-based volumetry. Abnormal cases referenced to a normogram produced from 100 normal fetuses whose TLV was calculated by DSVR only.
Results: Deformable slice-to-volume registration-derived TLV values have high correlation with the 2D-based measurements but with a consistently lower volume; bias −1.44 cm3 [95% limits: −2.6 to −0.3] with improved resolution to exclude hilar structures even in cases of motion corruption or very low lung volumes.
Conclusions: Deformable slice-to-volume registration for fetal lung MRI aids analysis of motion corrupted scans and does not suffer from the interpolation error inherent to 2D-segmentation. It increases information content of acquired data in terms of visualising organs in 3D space and quantification of volumes, which may improve counselling and surgical planning
A micro-optical module for multi-wavelength addressing of trapped ions
The control of large-scale quantum information processors based on arrays of
trapped ions requires a means to route and focus multiple laser beams to each
of many trapping sites in parallel. Here, we combine arrays of fibres, 3D
laser-written waveguides and diffractive microlenses to demonstrate the
principle of a micro-optic interconnect suited to this task. The module is
intended for use with an ion microtrap of 3D electrode geometry. It guides ten
independent laser beams with unique trajectories to illuminate a pair of
spatially separated target points. Three blue and two infrared beams converge
to overlap precisely at each desired position. Typical relative crosstalk
intensities in the blue are and the average insertion loss
across all channels is dB. The module occupies times less
volume than a conventional bulk-optic equivalent and is suited to different ion
species
Foreword: Control and Conservation of Lampreys Beyond 2020 – Proceedings from the 3rd Sea Lamprey International Symposium (SLIS III)
This special issue summarizes outcomes from the 3rd Sea Lamprey International Symposium (SLIS III; Fig. 1) held 28 July – 2 August 2019 at Wayne State University in Detroit, Michigan, U.S.A. The first two symposia (SLIS I and SLIS II) were held 30 July – 8 August 1979 at Northern Michigan University in Marquette, Michigan and 14–18 August 2000 at Lake Superior State University in Sault Ste. Marie, Michigan, respectively. The published volumes from these symposia in 1980 (Canadian Journal of Fisheries and Aquatic Sciences, Volume 37, Issue 11) and 2003 (Journal of Great Lakes Research Volume 29, Supplement 1) have been invaluable references for the broader scientific community and for management agencies around the Laurentian Great Lakes; cited over 4800 and 3300 times, respectively. SLIS III was attended by over 150 scientists, biologists, resource managers, graduate students, and Commission advisors, including participants from Australia, Canada, China, Japan, New Zealand, Portugal, Spain, the United Kingdom, and the United States (Fig. 2). Similar to SLIS I and SLIS II, the goals of SLIS III were to provide a forum to (i) update and publish information on sea lamprey control and research on lampreys since SLIS II, (ii) exchange knowledge and ideas to bring practitioners to a common plateau of understanding, and (iii) develop innovative initiatives and stimulate new vigor in efforts to control sea lamprey in the Great Lakes and to conserve lampreys in their native ranges. The emphasis on conservation of lampreys is unique to SLIS III and reflects a heightened international recognition that scientific and management advances supporting sea lamprey control in the Great Lakes can benefit the global effort to conserve native lampreys and vice versa
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