1,669 research outputs found
Three-dimensional nuclear spin positioning using coherent radio-frequency control
Distance measurements via the dipolar interaction are fundamental to the
application of nuclear magnetic resonance (NMR) to molecular structure
determination, but they only provide information on the absolute distance
and polar angle between spins. In this Letter, we present a protocol
to also retrieve the azimuth angle . Our method relies on measuring the
nuclear precession phase after application of a control pulse with a calibrated
external radio-frequency coil. We experimentally demonstrate three-dimensional
positioning of individual carbon-13 nuclear spins in a diamond host crystal
relative to the central electronic spin of a single nitrogen-vacancy center.
The ability to pinpoint three-dimensional nuclear locations is central for
realizing a nanoscale NMR technique that can image the structure of single
molecules with atomic resolution.Comment: 5 pages, 4 figure
High-bandwidth microcoil for fast nuclear spin control
The active manipulation of nuclear spins with radio-frequency (RF) coils is
at the heart of nuclear magnetic resonance (NMR) spectroscopy and spin-based
quantum devices. Here, we present a microcoil transmitter system designed to
generate strong RF pulses over a broad bandwidth, allowing for fast spin
rotations on arbitrary nuclear species. Our design incorporates: (i) a planar
multilayer geometry that generates a large field of 4.35 mT per unit current,
(ii) a 50 Ohm transmission circuit with a broad excitation bandwidth of
approximately 20 MHz, and (iii) an optimized thermal management for removal of
Joule heating. Using individual 13C nuclear spins in the vicinity of a diamond
nitrogen-vacancy (NV) center as a test system, we demonstrate Rabi frequencies
exceeding 70 kHz and nuclear pi/2 rotations within 3.4 us. The extrapolated
values for 1H spins are about 240 kHz and 1 us, respectively. Beyond enabling
fast nuclear spin manipulations, our microcoil system is ideally suited for the
incorporation of advanced pulse sequences into micro- and nanoscale NMR
detectors operating at low (<1 T) magnetic field.Comment: 8 pages, 5 figures. Submitted to Rev. Sci. Inst
Quantum sensing with arbitrary frequency resolution
Quantum sensing takes advantage of well controlled quantum systems for
performing measurements with high sensitivity and precision. We have
implemented a concept for quantum sensing with arbitrary frequency resolution,
independent of the qubit probe and limited only by the stability of an external
synchronization clock. Our concept makes use of quantum lock-in detection to
continuously probe a signal of interest. Using the electronic spin of a single
nitrogen vacancy center in diamond, we demonstrate detection of oscillating
magnetic fields with a frequency resolution of 70 uHz over a MHz bandwidth. The
continuous sampling further guarantees an excellent sensitivity, reaching a
signal-to-noise ratio in excess of 10,000:1 for a 170 nT test signal measured
during a one-hour interval. Our technique has applications in magnetic
resonance spectroscopy, quantum simulation, and sensitive signal detection.Comment: Manuscript resubmitted to Science. Includes Supplementary Material
Elastometry of deflated capsules elastic moduli from shape and wrinkle analysis
Elastic capsules, prepared from droplets or bubbles attached to a capillary (as in a pendant drop tensiometer), can be deflated by suction through the capillary. We study this deflation and show that a combined analysis of the shape and wrinkling characteristics enables us to determine the elastic properties in situ. Shape contours are analyzed and fitted using shape equations derived from nonlinear membrane-shell theory to give the elastic modulus, Poisson ratio and stress distribution of the membrane. We include wrinkles, which generically form upon deflation, within the shape analysis. Measuring the wavelength of wrinkles and using the calculated stress distribution gives the bending stiffness of the membrane. We illustrate this method on two very different capsule materials: polymerized octadecyltrichlorosilane (OTS) capsules and hydrophobin (HFBII) coated bubbles. Our results are in agreement with the available rheological data. For hydrophobin coated bubbles the method reveals an interesting nonlinear behavior consistent with the hydrophobin molecules having\ud
a rigid core surrounded by a softer shell
Genetic conservation within managed forests in Amazonia: dendrogene project.
Editado por Bernd Degen, Marilyn D. Loveless e Antoine Kremer
Evolutionary implications of a high selfing rate in the freshwater snail Lymnaea truncatula.
Self-compatible hermaphroditic organisms that mix self-fertilization and outcrossing are of great interest for investigating the evolution of mating systems. We investigate the evolution of selfing in Lymnaea truncatula, a self-compatible hermaphroditic freshwater snail. We first analyze the consequences of selfing in terms of genetic variability within and among populations and then investigate how these consequences along with the species ecology (harshness of the habitat and parasitism) might govern the evolution of selfing. Snails from 13 localities (classified as temporary or permanent depending on their water availability) were sampled in western Switzerland and genotyped for seven microsatellite loci. F(IS) (estimated on adults) and progeny array analyses (on hatchlings) provided similar selfing rate estimates of 80%. Populations presented a low polymorphism and were highly differentiated (F(ST) = 0.58). Although the reproductive assurance hypothesis would predict higher selfing rate in temporary populations, no difference in selfing level was observed between temporary and permanent populations. However, allelic richness and gene diversity declined in temporary habitats, presumably reflecting drift. Infection levels varied but were not simply related to either estimated population selfing rate or to differences in heterozygosity. These findings and the similar selfing rates estimated for hatchlings and adults suggest that within-population inbreeding depression is low in L. truncatula
Entwicklung eines Messverfahrens auf Thermodesorptionsbasos zur Detektion schwerflüchtiger Kohlenwasserstoffe in Spurenkonzentrationen mit Gassensoren
In der Halbleiterindustrie ist eine unbelastete Umgebungsluft Voraussetzung für eine effiziente und störungsfreie Produktion. Von besonderem Interesse ist die Überwachung der Qualität der gefilterten Zuluft in den Reinräumen im Hinblick auf ihre Belastung mit kondensierbaren Kohlenwasserstoffen. Das im Rahmen dieser Arbeit entwickelte Messsystem Air Check ermöglicht mit einem neuartigen Messverfahren die selelktive Überwachung von Spurenkonzentrationen dieser schwerflüchtigen Sunbstanzen mit Gassensoren durch zeitaufgelöste Thermodesorption. das Messverfahren gliedert sich in einen adsorptiven Probenanreicherungsprozess, die Desortption der angereicherten Probe und die Messung der angereicherten Substanzen mit einem Array von Gassensoren.
Die verfahrensparameter Trägergasgeschwindigkeit und Aufheizgeschwindigkeit während der Thermodesroption sowie Adsorbensmenge wurden hinsichtlich ihres Einfluss auf Empfindlichkeit und Selektivität des Messverfahrens systematisch untersucht.
Das Verfahren ist unempfindlich gegen den Einfluss der Luftfeuchtigkeit und ermöglicht bei geeigneter Wahl der verfahrensparameter die Überwachung der kondensierbaren Kohlenwasserstoffe und ist dabei selbst in Konzentrationen bis hinab zu wenigen Parts per Billion (ppb) möglich
High resolution quantum sensing with shaped control pulses
We investigate the application of amplitude-shaped control pulses for
enhancing the time and frequency resolution of multipulse quantum sensing
sequences. Using the electronic spin of a single nitrogen vacancy center in
diamond and up to 10,000 coherent microwave pulses with a cosine square
envelope, we demonstrate 0.6 ps timing resolution for the interpulse delay.
This represents a refinement by over 3 orders of magnitude compared to the 2 ns
hardware sampling. We apply the method for the detection of external AC
magnetic fields and nuclear magnetic resonance signals of carbon-13 spins with
high spectral resolution. Our method is simple to implement and especially
useful for quantum applications that require fast phase gates, many control
pulses, and high fidelity.Comment: 5 pages, 4 figures, plus supplemental materia
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