1,317 research outputs found
Ultrasensitive Label-Free Nanosensing and High-Speed Tracking of Single Proteins
: Label-free detection, analysis, and rapid tracking
of nanoparticles is crucial for future ultrasensitive sensing
applications, ranging from understanding of biological
interactions to the study of size-dependent classical-quantum
transitions. Yet optical techniques to distinguish nanoparticles
directly among their background remain challenging. Here we
present amplified interferometric scattering microscopy (aiSCAT)
as a new all-optical method capable of detecting
individual nanoparticles as small as 15 kDa proteins that is
equivalent to half a GFP. By balancing scattering and reflection
amplitudes the interference contrast of the nanoparticle signal
is amplified 1 to 2 orders of magnitude. Beyond high
sensitivity, a-iSCAT allows high-speed image acquisition exceeding several hundreds of frames-per-second. We showcase the
performance of our approach by detecting single Streptavidin binding events and by tracking single Ferritin proteins at 400
frames-per-second with 12 nm localization precision over seconds. Moreover, due to its extremely simple experimental
realization, this advancement finally enables a cheap and routine implementation of label-free all-optical single nanoparticle
detection platforms with sensitivity operating at the single protein level.Peer ReviewedPostprint (author's final draft
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Eve Unsell
In June of 1937, Los Angeles Times writer Alma Whitaker told a heartwarming anecdote in her regular society column. Eve Unsell, Hollywood dramatist, she wrote, had “been adopted by” a motherless seal pup camped out on the beach near her Malibu home. Although the pup had already been rescued, nursed back to health, and released back into the ocean by the volunteers at Los Flores Inn, the seal had not returned to sea. When Unsell started to feed the animal every day, the pup somehow crossed the highway from the beach to the former screenwriter’s front door. “Eve now understands what is expected of her,” teased Whitaker (D7)
Fasti Ecclesiae Gallicanae (1200-1500). XIV: Diocèse de Châlons-en-Champagne
This is a prosopographical repertory of bishops, canons and office-holders of the French dioceses from 1200 to 1500, giving for each a biographical and a bibliographical entry. The geographical limits are those of present-day France. Each volume presents the central institutions of the bishopric, and, depending on the availability of sources or research, gives a description of the cathedral borough, books, treasure, relics and ornaments
Auditory stream segregation of amplitude-modulated narrowband noise in cochlear implant users and individuals with normal hearing
Voluntary stream segregation was investigated in cochlear implant (CI) users and normal-hearing (NH) listeners using a segregation-promoting objective approach which evaluated the role of spectral and amplitude-modulation (AM) rate separations on stream segregation and its build-up. Sequences of 9 or 3 pairs of A and B narrowband noise (NBN) bursts were presented which differed in either center frequency of the noise band, the AM-rate, or both. In some sequences (delayed sequences), the last B burst was delayed by 35 ms from their otherwise-steady temporal position. In the other sequences (no-delay sequences), the last B bursts were temporally advanced from 0 to 10 ms. A single interval yes/no procedure was utilized to measure participants’ sensitivity (d\u27) in identifying delayed vs. no-delay sequences. A higher d\u27 value showed the higher ability to segregate the A and B subsequences. For NH listeners, performance improved with each spectral separation. However, for CI users, performance was only significantly better for the condition with the largest spectral separation. Additionally, performance was significantly poorer for the largest AM-rate separation than for the condition with no AM-rate separation for both groups. The significant effect of sequence duration in both groups indicated that listeners made more improvement with lengthening the duration of stimulus sequences, supporting the build-up effect. The results of this study suggest that CI users are less able than NH listeners to segregate NBN bursts into different auditory streams when they are moderately separated in the spectral domain. Contrary to our hypothesis, our results indicate that AM-rate separation may interfere with the segregation of streams of NBN. Additionally, our results add evidence to the literature that CI users build up stream segregation at a rate comparable to NH listeners, when the inter-stream spectral separations are adequately large
Control of Vibronic Transition Rates by Resonant Single-Molecule-Nanoantenna Coupling
Plasmonic nanostructures dramatically alter the radiative and nonradiative properties of single molecules in their vicinity. This coupling-induced change in decay channels selectively enhances specific vibronic transitions, which can enable plasmonic control of molecular reactivity. Here, we report coupling-dependent spectral emission shaping of single Rhodamine 800 molecules in the vicinity of plasmonic gold nanorods. We show that the relative vibronic transition rates of the first two vibronic transitions of the spontaneous emission spectrum can be tuned in the weak coupling regime, by approximately 25-fold, on the single molecule level.Peer ReviewedPostprint (author's final draft
Isolating strong nanoantenna-molecule interactions by ensemble-level single-molecule detection
Traditionally, the nanoscale interaction between single photon emitters and plasmonic nanostructures is studied by relying on deterministic, near-perfect, nanoscale-control, either top-down or bottom-up. However, these approaches are ultra-low throughput thus rendering systematic studies difficult and time-consuming. Here, we show a highly parallelised far-field tactic, combining multiplexed super-resolution fluorescence localization microscopy and data-driven statistical analysis, to study near-field interactions between gold nanorods and single molecules, even at bulk concentrations. We demonstrate that ensemble-level single molecule detection allows separating individual emitters according to their coupling strength with tailored resonant structures, which ultimately permits the reconstruction of super-resolved 2D interaction maps around individual nanoantennas.Peer ReviewedPostprint (author's final draft
Compton Echoes from Gamma-ray Bursts
Recent observations of gamma-ray bursts (GRBs) have provided growing evidence
for collimated outflows and emission, and strengthened the connection between
GRBs and supernovae. If massive stars are the progenitors of GRBs, the hard
photon pulse will propagate in the pre-burst, dense environment. Circumstellar
material will Compton scatter the prompt GRB radiation and give rise to a
reflection echo. We calculate luminosities, spectra, and light curves of such
Compton echoes in a variety of emission geometries and ambient gas
distributions, and show that the delayed hard X-ray flash from a pulse
propagating into a red supergiant wind could be detectable by Swift out to
z~0.2. Independently of the gamma-ray spectrum of the prompt burst, reflection
echoes will typically show a high-energy cutoff between m_ec^2/2 and m_ec^2
because of Compton downscattering. At fixed burst energy per steradian, the
luminosity of the reflected echo is proportional to the beaming solid angle,
Omega_b, of the prompt pulse, while the number of bright echoes detectable in
the sky above a fixed limiting flux increases as Omega_b^{1/2}, i.e. it is
smaller in the case of more collimated jets. The lack of an X-ray echo at one
month delay from the explosion poses severe constraints on the possible
existence of a lateral GRB jet in SN 1987A. The late r-band afterglow observed
in GRB990123 is fainter than the optical echo expected in a dense red
supergiant environment from a isotropic prompt optical flash. Significant MeV
delayed emission may be produced through the bulk Compton (or Compton drag)
effect resulting from the interaction of the decelerating fireball with the
scattered X-ray radiation.Comment: LaTeX, 18 pages, 4 figures, revised version accepted for publication
in the Ap
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