1,550 research outputs found
ESMO Minimum Clinical Recommendations for diagnosis, treatment and follow-up of soft tissue sarcomas
ESMO Minimum Clinical Recommendations for diagnosis, treatment and follow-up of malignant glioma
Silent Flocks
Experiments find coherent information transfer through biological groups on
length and time scales distinctly below those on which asymptotically correct
hydrodynamic theories apply. We present here a new continuum theory of
collective motion coupling the velocity and density fields of Toner and Tu to
the inertial spin field recently introduced to describe information propagation
in natural flocks of birds. The long-wavelength limit of the new equations
reproduces Toner-Tu theory, while at shorter wavelengths (or, equivalently,
smaller damping), spin fluctuations dominate over density fluctuations and
second sound propagation of the kind observed in real flocks emerges. We study
the dispersion relation of the new theory and find that when the speed of
second sound is large, a gap sharply separates first from second sound modes.
This gap implies the existence of `silent' flocks, namely medium-sized systems
across which neither first nor second sound can propagate
ESMO Minimum Clinical Recommendations for diagnosis, treatment and follow-up of soft tissue sarcomas.
Wide-field LOFAR-LBA power-spectra analyses: Impact of calibration, polarization leakage and ionosphere
Contamination due to foregrounds (Galactic and Extra-galactic), calibration
errors and ionospheric effects pose major challenges in detection of the cosmic
21 cm signal in various Epoch of Reionization (EoR) experiments. We present the
results of a pilot study of a field centered on 3C196 using LOFAR Low Band
(56-70 MHz) observations, where we quantify various wide field and calibration
effects such as gain errors, polarized foregrounds, and ionospheric effects. We
observe a `pitchfork' structure in the 2D power spectrum of the polarized
intensity in delay-baseline space, which leaks into the modes beyond the
instrumental horizon (EoR/CD window). We show that this structure largely
arises due to strong instrumental polarization leakage () towards
{Cas\,A} ( kJy at 81 MHz, brightest source in northern sky), which is
far away from primary field of view. We measure an extremely small ionospheric
diffractive scale ( m at 60 MHz) towards {Cas\,A}
resembling pure Kolmogorov turbulence compared to
km towards zenith at 150 MHz for typical ionospheric conditions. This is one of
the smallest diffractive scales ever measured at these frequencies. Our work
provides insights in understanding the nature of aforementioned effects and
mitigating them in future Cosmic Dawn observations (e.g. with SKA-low and HERA)
in the same frequency window.Comment: 20 pages, 11 figures, accepted for publication in MNRA
Substrate binding disrupts dimerization and induces nucleotide exchange of the chloroplast GTPase Toc33
GTPases act as molecular switches to control many cellular processes, including signalling, protein translation and targeting. Switch activity can be regulated by external effector proteins or intrinsic properties, such as dimerization. The recognition and translocation of pre-proteins into chloroplasts [via the TOC/TIC (translocator at the outer envelope membrane of chloroplasts/inner envelope membrane of chloroplasts)] is controlled by two homologous receptor GTPases, Toc33 and Toc159, whose reversible dimerization is proposed to regulate translocation of incoming proteins in a GTP-dependent manner. Toc33 is a homodimerizing GTPase. Functional analysis suggests that homodimerization is a key step in the translocation process, the molecular functions of which, as well as the elements regulating this event, are largely unknown. In the present study, we show that homodimerization reduces the rate of nucleotide exchange, which is consistent with the observed orientation of the monomers in the crystal structure. Pre-protein binding induces a dissociation of the Toc33 homodimer and results in the exchange of GDP for GTP. Thus homodimerization does not serve to activate the GTPase activity as discussed many times previously, but to control the nucleotide-loading state. We discuss this novel regulatory mode and its impact on the current models of protein import into the chloroplast
ESMO Minimum Clinical Recommendations for diagnosis, treatment and follow-up of malignant glioma.
Atomic-Scale Terahertz Near Fields for Ultrafast Tunnelling Spectroscopy
Lightwave-driven terahertz scanning tunnelling microscopy (THz-STM) is
capable of exploring ultrafast dynamics across a wide range of materials with
angstrom resolution. In contrast to scanning near-field optical microscopy,
where photons scattered by the tip apex are analyzed to access the local
dielectric function on the nanoscale, THz-STM uses a strong-field single-cycle
terahertz pulse to drive an ultrafast current across a tunnel junction, thereby
probing the local density of electronic states. Yet, the terahertz field in a
THz-STM junction may also be spectrally modified by the electromagnetic
response of the sample. Here, we demonstrate a reliable and self-consistent
approach for terahertz near-field waveform acquisition in an atomic tunnel
junction that can be generally applied to electrically conductive surfaces. By
combining waveform sampling and tailoring with terahertz scanning tunnelling
spectroscopy (THz-STS), we comprehensively characterize the tunnel junction and
distinguish local sample properties from effects due to terahertz pulse
coupling and field enhancement. Through modelling, we verify the presence of an
isolated unipolar terahertz-induced current pulse, facilitating straightforward
interpretation for differential THz-STS with high spectral resolution. Finally,
we demonstrate the feasibility of atomic-scale terahertz time-domain
spectroscopy via the extremely localized near-fields in the tunnel junction
- …