1,185 research outputs found
Electrical Tuning of Single Nitrogen-Vacancy Center Optical Transitions Enhanced by Photoinduced Fields
We demonstrate precise control over the zero-phonon optical transition
energies of individual nitrogen-vacancy (NV) centers in diamond by applying
multiaxis electric fields, via the dc Stark effect. The Stark shifts display
surprising asymmetries that we attribute to an enhancement and rectification of
the local electric field by photoionized charge traps in the diamond. Using
this effect, we tune the excited-state orbitals of strained NV centers to
degeneracy and vary the resulting degenerate optical transition frequency by
>10 GHz, a scale comparable to the inhomogeneous frequency distribution. This
technique will facilitate the integration of NV-center spins within photonic
networks.Comment: 10 pages, 6 figure
An Arctic Alaskan Kelp Bed
Reports the discovery of a kelp bed near Point Barrow and describes its composition, both red and brown algae and associated fauna: a few polychaetous annelids, arthropods and six fishes, one, Enophrys diceraus new to arctic waters and kelp beds are rare in arctic Alaska waters limited in species and in number of individuals. The general poverty of marine algae is thought due to the prevalence of sediments north of Alaska and to silting effects by sea ice in winter
Modulation of Cross-Frequency Coupling by Novel and Repeated Stimuli in the Primate Ventrolateral Prefrontal Cortex
Adaptive behavior depends on an animalās ability to ignore uninformative stimuli, such as repeated presentations of the same stimulus, and, instead, detect informative, novel stimuli in its environment. The primate prefrontal cortex (PFC) is known to play a central role in this ability. However, the neural mechanisms underlying the ability to differentiate between repeated and novel stimuli are not clear. We hypothesized that the coupling between different frequency bands of the local field potential (LFP) underlies the PFCās role in differentiating between repeated and novel stimuli. Specifically, we hypothesized that whereas the presentation of a novel-stimulus induces strong cross-frequency coupling, repeated presentations of the same stimulus attenuates this coupling. To test this hypothesis, we recorded LFPs from the ventrolateral PFC (vPFC) of rhesus monkeys while they listened to a novel vocalization and repeated presentations of the same vocalization. We found that the cross-frequency coupling between the gamma-band amplitude and theta-band phase of the LFP was modulated by repeated presentations of a stimulus. During the first (novel) presentation of a stimulus, gamma-band activity was modulated by the theta-band phase. However, with repeated presentations of the same stimulus, this cross-frequency coupling was attenuated. These results suggest that cross-frequency coupling may play a role in the neural computations that underlie the differentiation between novel and repeated stimuli in the vPFC
Speech and Prosody Characteristics of Adolescents and Adults With High-Functioning Autism and Asperger Syndrome
Speech and prosody-voice profiles for 15 male speakers with High-Functioning Autism (HFA) and 15 male speakers with Asperger syndrome (AS) were compared to one another and to profiles for 53 typically developing male speakers in the same 10- to 50-years age range. Compared to the typically developing speakers, significantly more participants in both the HFA and AS groups had residual articulation distortion errors, uncodable utterances due to discourse constraints, and utterances coded as inappropriate in the domains of phrasing, stress, and resonance. Speakers with AS were significantly more voluble than speakers with HFA, but otherwise there were few statistically significant differences between the two groups of speakers with pervasive developmental disorders. Discussion focuses on perceptual-motor and social sources of differences in the prosody-voice findings for individuals with Pervasive Developmental Disorders as compared with findings for typical speakers, including comment on the grammatical, pragmatic, and affective aspects of prosody
Quantitative nanoscale vortex-imaging using a cryogenic quantum magnetometer
Microscopic studies of superconductors and their vortices play a pivotal role
in our understanding of the mechanisms underlying superconductivity. Local
measurements of penetration depths or magnetic stray-fields enable access to
fundamental aspects of superconductors such as nanoscale variations of
superfluid densities or the symmetry of their order parameter. However,
experimental tools, which offer quantitative, nanoscale magnetometry and
operate over the large range of temperature and magnetic fields relevant to
address many outstanding questions in superconductivity, are still missing.
Here, we demonstrate quantitative, nanoscale magnetic imaging of Pearl vortices
in the cuprate superconductor YBCO, using a scanning quantum sensor in form of
a single Nitrogen-Vacancy (NV) electronic spin in diamond. The sensor-to-sample
distance of ~10nm we achieve allows us to observe striking deviations from the
prevalent monopole approximation in our vortex stray-field images, while we
find excellent quantitative agreement with Pearl's analytic model. Our
experiments yield a non-invasive and unambiguous determination of the system's
local London penetration depth, and are readily extended to higher temperatures
and magnetic fields. These results demonstrate the potential of quantitative
quantum sensors in benchmarking microscopic models of complex electronic
systems and open the door for further exploration of strongly correlated
electron physics using scanning NV magnetometry.Comment: Main text (5 pages, 4 figures) plus supplementary material (5 pages,
6 figures). Comments welcome. Further information under
http://www.quantum-sensing.c
The global decline of reptiles, dejaā vu amphibians
Reptile species are declining on a global scale. Six significant threats to reptile populations are habitat loss and degradation, introduced invasive species, environmental pollution, disease, unsustainable use, and global climate change
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