4,150 research outputs found
NT1-Tau Is Increased in CSF and Plasma of CJD Patients, and Correlates with Disease Progression
This study investigates the diagnostic and prognostic potential of different forms of tau in biofluids from patients with Creutzfeldt-Jakob disease (CJD). Extracellular tau, which is molecularly heterogeneous, was measured using ultra-sensitive custom-made Simoa assays for N-terminal (NT1), mid-region, and full-length tau. We assessed cross-sectional CSF and plasma from healthy controls, patients with Alzheimer’s disease (AD) and CJD patients. Then, we evaluated the correlation of the best-performing tau assay (NT1-tau) with clinical severity and functional decline (using the MRC Prion Disease Rating Scale) in a longitudinal CJD cohort (n = 145). In a cross-sectional study, tau measured in CSF with the NT1 and mid-region Simoa assays, separated CJD (n = 15) from AD (n = 18) and controls (n = 21) with a diagnostic accuracy (AUCs: 0.98–1.00) comparable to or better than neurofilament light chain (NfL; AUCs: 0.96–0.99). In plasma, NT1-measured tau was elevated in CJD (n = 5) versus AD (n = 15) and controls (n = 15). Moreover, in CJD plasma (n = 145) NT1-tau levels correlated with stage and rate of disease progression, and the effect on clinical progression was modified by the PRNP codon 129. Our findings suggest that plasma NT1-tau shows promise as a minimally invasive diagnostic and prognostic biomarker of CJD, and should be further investigated for its potential to monitor disease progression and response to therapies
Observation of isotonic symmetry for enhanced quadrupole collectivity in neutron-rich 62,64,66Fe isotopes at N=40
The transition rates for the 2_{1}^{+} states in 62,64,66Fe were studied
using the Recoil Distance Doppler-Shift technique applied to projectile Coulomb
excitation reactions. The deduced E2 strengths illustrate the enhanced
collectivity of the neutron-rich Fe isotopes up to N=40. The results are
interpreted by the generalized concept of valence proton symmetry which
describes the evolution of nuclear structure around N=40 as governed by the
number of valence protons with respect to Z~30. The deformation suggested by
the experimental data is reproduced by state-of-the-art shell calculations with
a new effective interaction developed for the fpgd valence space.Comment: 4 pages, 2 figure
High-mass star formation at high luminosities: W31 at >10^6 L_sun
Context: High-mass star formation has been a very active field over the last
decade, however, most studies targeted regions of luminosities between 10^4 and
10^5 L_sun. Methods: We selected the W31 star-forming complex with a total
luminosity of ~6x10^6 L_sun for a multi-wavelength spectral line and continuum
study covering wavelengths from the near- and mid-infrared via (sub)mm
wavelength observations to radio data in the cm regime. Results: While the
overall structure of the multi-wavelength continuum data resembles each other
well, there are several intriguing differences. The 24mum emission stemming
largely from small dust grains follows tightly the spatial structure of the cm
emission tracing the ionized free-free emission. Hence warm dust resides in
regions that are spatially associated with the ionized hot gas (~10^4 K) of the
HII regions. Furthermore, we find several evolutionary stages within the same
complexes, ranging from infrared-observable clusters, via deeply embedded
regions associated with active star formation traced by 24\,m and cm
emission, to at least one high-mass gas clump devoid of any such signature. The
13CO(2-1) and C18O(2-1) spectral line observations reveal a large kinematic
breadth in the entire region with a total velocity range of approximately 90
km/s. While the average virial mass ratio for W31 is close to unity, the line
width analysis indicates large-scale evolutionary differences between the
southern and northern sub-regions (G10.2-0.3 and G10.3-0.1) of the whole W31
complex. The clump mass function - tracing cluster scales and not scales of
individual stars - derived from the 875mum continuum data has a slope of
1.5+-0.3, consistent with previous cloud mass functions.Comment: 13 pages, 11 figures, accepted for Astronomy and Astrophysics,
high-resolution version of paper at
http://www.mpia.de/homes/beuther/papers.htm
Observation of Bound Surface States in Grain Boundary Junctions of High Temperature Superconductors
We have performed a detailed study of the tunneling spectra of bicrystal
grain boundary junctions (GBJs) fabricated from the HTS YBCO, BSCCO, LSCO, and
NCCO. In all experiments the tunneling direction was along the CuO planes. With
the exception of NCCO, for all materials a pronounced zero bias conductance
peak was observed which decreases with increasing temperature and disappears at
the critical temperature. These results can be explained by the presence of a
dominating d-wave symmetry of the order parameter resulting in the formation of
zero energy Andreev bound states at surfaces and interfaces of HTS. The absence
of a ZBCP for NCCO is consistent with a dominating s-wave symmetry of the pair
potential in this material. The observed nonlinear shift of spectral weight to
finite energies by applying a magnetic field is in qualitative agreement with
recent theoretical predictions.Comment: 4 pages, 4 figures, to be published in Phys. Rev.
On the Identification of High Mass Star Forming Regions using IRAS: Contamination by Low-Mass Protostars
We present the results of a survey of a small sample (14) of low-mass
protostars (L_IR < 10^3 Lsun) for 6.7 GHz methanol maser emission performed
using the ATNF Parkes radio telescope. No new masers were discovered. We find
that the lower luminosity limit for maser emission is near 10^3 Lsun, by
comparison of the sources in our sample with previously detected methanol maser
sources. We examine the IRAS properties of our sample and compare them with
sources previously observed for methanol maser emission, almost all of which
satisfy the Wood & Churchwell criterion for selecting candidate UCHII regions.
We find that about half of our sample satisfy this criterion, and in addition
almost all of this subgroup have integrated fluxes between 25 and 60 microns
that are similar to sources with detectable methanol maser emission. By
identifying a number of low-mass protostars in this work and from the
literature that satisfy the Wood & Churchwell criterion for candidate UCHII
regions, we show conclusively for the first time that the fainter flux end of
their sample is contaminated by lower-mass non-ionizing sources, confirming the
suggestion by van der Walt and Ramesh & Sridharan.Comment: 8 pages with 2 figures. Accepted by Ap
Adaptive Lévy processes and area-restricted search in human foraging
A considerable amount of research has claimed that animals’ foraging behaviors display movement lengths with power-law distributed tails, characteristic of Lévy flights and Lévy walks. Though these claims have recently come into question, the proposal that many animals forage using Lévy processes nonetheless remains. A Lévy process does not consider when or where resources are encountered, and samples movement lengths independently of past experience. However, Lévy processes too have come into question based on the observation that in patchy resource environments resource-sensitive foraging strategies, like area-restricted search, perform better than Lévy flights yet can still generate heavy-tailed distributions of movement lengths. To investigate these questions further, we tracked humans as they searched for hidden resources in an open-field virtual environment, with either patchy or dispersed resource distributions. Supporting previous research, for both conditions logarithmic binning methods were consistent with Lévy flights and rank-frequency methods–comparing alternative distributions using maximum likelihood methods–showed the strongest support for bounded power-law distributions (truncated Lévy flights). However, goodness-of-fit tests found that even bounded power-law distributions only accurately characterized movement behavior for 4 (out of 32) participants. Moreover, paths in the patchy environment (but not the dispersed environment) showed a transition to intensive search following resource encounters, characteristic of area-restricted search. Transferring paths between environments revealed that paths generated in the patchy environment were adapted to that environment. Our results suggest that though power-law distributions do not accurately reflect human search, Lévy processes may still describe movement in dispersed environments, but not in patchy environments–where search was area-restricted. Furthermore, our results indicate that search strategies cannot be inferred without knowing how organisms respond to resources–as both patched and dispersed conditions led to similar Lévy-like movement distributions
The Origin of T Tauri X-ray Emission: New Insights from the Chandra Orion Ultradeep Project
We use the data of the Chandra Orion Ultradeep Project (COUP) to study the
nearly 600 X-ray sources that can be reliably identified with optically well
characterized T Tauri stars (TTS) in the Orion Nebula Cluster. We detect X-ray
emission from more than 97% of the optically visible late-type (spectral types
F to M) cluster stars. This proofs that there is no ``X-ray quiet'' population
of late-type stars with suppressed magnetic activity. All TTS with known
rotation periods lie in the saturated or super-saturated regime of the relation
between activity and Rossby numbers seen for main-sequence (MS) stars, but the
TTS show a much larger scatter in X-ray activity than seen for the MS stars.
Strong near-linear relations between X-ray luminosities, bolometric
luminosities and mass are present. We also find that the fractional X-ray
luminosity rises slowly with mass over the 0.1 - 2 M_sun range. The plasma
temperatures determined from the X-ray spectra of the TTS are much hotter than
in MS stars, but seem to follow a general solar-stellar correlation between
plasma temperature and activity level. The large scatter about the relations
between X-ray activity and stellar parameters seems to be related to the
influence of accretion on the X-ray emission. While the X-ray activity of the
non-accreting TTS is consistent with that of rapidly rotating MS stars, the
accreting stars are less X-ray active (by a factor of ~2-3 on average) and
produce much less well defined correlations than the non-accretors. We discuss
possible reasons for the suppression of X-ray emission by accretion and the
implications of our findings on long-standing questions related to the origin
of the X-ray emission from young stars.Comment: accepted for ApJS, COUP Special Issu
Factor H autoantibody is associated with atypical hemolytic uremic syndrome in children in the United Kingdom and Ireland
Factor H autoantibodies can impair complement
regulation, resulting in atypical hemolytic uremic
syndrome, predominantly in childhood. There are no trials
investigating treatment, and clinical practice is only
informed by retrospective cohort analysis. Here we
examined 175 children presenting with atypical hemolytic
uremic syndrome in the United Kingdom and Ireland for
factor H autoantibodies that included 17 children with
titers above the international standard. Of the 17, seven
had a concomitant rare genetic variant in a gene encoding
a complement pathway component or regulator. Two
children received supportive treatment; both developed
established renal failure. Plasma exchange was associated
with a poor rate of renal recovery in seven of 11 treated. Six
patients treated with eculizumab recovered renal function.
Contrary to global practice, immunosuppressive therapy to
prevent relapse in plasma exchange–treated patients was
not adopted due to concerns over treatment-associated
complications. Without immunosuppression, the relapse
rate was high (five of seven). However, reintroduction of
treatment resulted in recovery of renal function. All
patients treated with eculizumab achieved sustained
remission. Five patients received renal transplants without
specific factor H autoantibody–targeted treatment with
recurrence in one who also had a functionally significant CFI mutation. Thus, our current practice is to initiate
eculizumab therapy for treatment of factor H
autoantibody–mediated atypical hemolytic uremic
syndrome rather than plasma exchange with or without
immunosuppression. Based on this retrospective analysis
we see no suggestion of inferior treatment, albeit the
strength of our conclusions is limited by the small sample siz
Warm H2O and OH in the disk around the Herbig star HD 163296
We present observations of far-infrared (50-200 micron) OH and H2O emission
of the disk around the Herbig Ae star HD 163296 obtained with Herschel/PACS in
the context of the DIGIT key program. In addition to strong [OI] emission, a
number of OH doublets and a few weak highly excited lines of H2O are detected.
The presence of warm H2O in this Herbig disk is confirmed by a line stacking
analysis, enabled by the full PACS spectral scan, and by lines seen in Spitzer
data. The line fluxes are analyzed using an LTE slab model including line
opacity. The water column density is 10^14 - 10^15 cm^-2, and the excitation
temperature is 200-300 K implying warm gas with a density n > 10^5 cm^-3. For
OH we find a column density of 10^14 - 2x10^15 cm^-2 and T_ex ~ 300-500 K. For
both species we find an emitting region of r ~ 15-20 AU from the star. We argue
that the molecular emission arises from the protoplanetary disk rather than
from an outflow. This far-infrared detection of both H2O and OH contrasts with
near- and mid-infrared observations, which have generally found a lack of water
in the inner disk around Herbig AeBe stars due to strong photodissociation of
water. Given the similarity in column density and emitting region, OH and H2O
emission seems to arise from an upper layer of the disk atmosphere of HD
163296, probing a new reservoir of water. The slightly lower temperature of H2O
compared to OH suggests a vertical stratification of the molecular gas with OH
located higher and water deeper in the disk, consistent with thermo-chemical
models.Comment: Accepted for publication in A&
ALMA Reveals the Anatomy of the mm-sized Dust and Molecular Gas in the HD 97048 Disk
Transitional disks show a lack of excess emission at infrared wavelengths due to a large dust cavity, that is often corroborated by spatially resolved observations at ∼mm wavelengths. We present the first spatially resolved ∼ mm-wavelength images of the disk around the Herbig Ae/Be star, HD 97048. Scattered light images show that the disk extends to ≈640 au. ALMA data reveal a circular-symmetric dusty disk extending to ≈350 au, and a molecular disk traced in CO J = 3-2 emission, extending to ≈750 au. The CO emission arises from a flared layer with an opening angle ≈30°–40°. HD 97048 is another source for which the large (∼ mm-sized) dust grains are more centrally concentrated than the small (∼μm-sized) grains and molecular gas, likely due to radial drift. The images and visibility data modeling suggest a decrement in continuum emission within ≈50 au, consistent with the cavity size determined from mid-infrared imaging (34 ± 4 au). The extracted continuum intensity profiles show ring-like structures with peaks at ≈50, 150, and 300 au, with associated gaps at ≈100 and 250 au. This structure should be confirmed in higher-resolution images (FWHM ≈ 10–20 au). These data confirm the classification of HD 97048 as a transitional disk that also possesses multiple ring-like structures in the dust continuum emission. Additional data are required at multiple and well-separated frequencies to fully characterize the disk structure, and thereby constrain the mechanism(s) responsible for sculpting the HD 97048 disk
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