2,152 research outputs found
OH-selected AGB and post-AGB stellar objects II.Blue versus red evolution off the AGB
Using objects found in a systematic survey of the galactic Plane in the
1612-MHz OH line, we discuss in detail two ``sequences'' of post-AGB evolution,
a red and a blue. We argue that the red and the blue groups separate by initial
mass at 4Msun, based on evolutionary-sequence turn-off colours, spectral energy
distributions, outflow velocities and scaleheight. The higher-mass (blue)
objects may have earlier AGB termination. The lower-mass (red) objects undergo
very sudden reddening for IRAS colour R21\sim1.2; these sources must all
undergo a very similar process at AGB termination. The transition colour
corresponds to average initial masses of 1.7Msun. A combined IRAS-MSX colour
proves a very sensitive tool to distinguish lower-mass, early post-AGB objects
from sources still on the AGB and also to distinguish more evolved post-AGB
objects from star-forming regions. The high-mass blue objects are the likely
precursors of bipolar planetary nebulae, whereas the low-mass red objects will
evolve into elliptical planetary nebulae.Comment: 12 pages, LaTex, 7 figures (1 colour), AJ (accepted
HST Snapshot Survey of Post-AGB Objects
The results from a Hubble Space Telescope (HST) snapshot survey of post-AGB
objects are shown. The aim of the survey is to complement existing HST images
of PPN and to connect various types of nebulosities with physical and chemical
properties of their central stars. Nebulosities are detected in 15 of 33
sources. Images and photometric and geometric measurements are presented. For
sources with nebulosities we see a morphological bifurcation into two groups,
DUPLEX and SOLE, as previous studies have found. We find further support to the
previous results suggesting that this dichotomy is caused by a difference in
optical thickness of the dust shell. The remaining 18 sources are classified as
stellar post-AGB objects, because our observations indicate a lack of
nebulosity. We show that some stellar sources may in fact be DUPLEX or SOLE
based on their infrared colors. The cause of the differences among the groups
are investigated. We discuss some evidence suggesting that high progenitor-mass
AGB stars tend to become DUPLEX post-AGB objects. Intermediate progenitor-mass
AGB stars tend to be SOLE post-AGB objects. Most of the stellar sources
probably have low mass progenitors and do not seem to develop nebulosities
during the post-AGB phase and therefore do not become planetary nebulae.Comment: 21 pages, 11 figure
An evolutionary catalogue of Galactic post-AGB and related objects
With the ongoing AKARI infrared sky survey, of much greater sensitivity than
IRAS, a wealth of post-AGB objects may be discovered. It is thus time to
organize our present knowledge of known post-AGB stars in th galaxy with a view
to using it to search for new post-AGB objects among AKARI sources. We searched
the literature available on the NASA Astrophysics Data System up to 1 October
2006, and defined criteria for classifying sources into three categories: "very
likely", "possible" and "disqualified" post-AGB objects. The category of "very
likely" post-AGB objects is made up of several classes. We have created an
evolutionary, on-line catalogue of Galactic post-AGB objects, to be referred to
as "The Torun catalogue of Galactic post-AGB and related objects". The present
version of the catalogue contains 326 "very likely", 107 "possible" and 64
"disqualified" objects. For the very likely post-AGB objects, the catalogue
gives the available optical and infrared photometry, infrared spectroscopy and
spectral types, and links to finding charts and bibliography.Comment: 9 pages, 6 figures, accepted for publication in A&
Bioengineering of Improved Biomaterials Coatings for Extracorporeal Circulation Requires Extended Observation of Blood-Biomaterial Interaction under Flow
Extended use of cardiopulmonary bypass (CPB) systems is often
hampered by thrombus formation and infection. Part of these
problems relates to imperfect hemocompatibility of the CPB
circuitry. The engineering of biomaterial surfaces with genuine
long-term hemocompatibility is essentially virgin territory in
biomaterials science. For example, most experiments with the
well-known Chandler loop model, for evaluation of
blood-biomaterial interactions under flow, have been described for
a maximum duration of 2 hours only. This study reports a systematic
evaluation of two commercial CPB tubings, each with a
hemocompatible coating, and one uncoated control. The experiments
comprised (i) testing over 5 hours under flow, with human whole
blood from 4 different donors; (ii) measurement of essential blood
parameters of hemocompatibility; (iii) analysis of the luminal
surfaces by scanning electron microscopy and thrombin generation
time measurements. The dataset indicated differences in
hemocompatibility of the tubings. Furthermore, it appeared that
discrimination between biomaterial coatings can be made only after
several hours of blood-biomaterial contact. Platelet counting,
myeloperoxidase quantification, and scanning electron microscopy
proved to be the most useful methods. These findings are believed
to be relevant with respect to the bioengineering of
extracorporeal devices that should function in contact with blood
for extended time
Developing hierarchically porous MnO<sub><em>x</em></sub>/NC hybrid nanorods for oxygen reduction and evolution catalysis
Electrochemical oxygen reduction and evolution reactions (ORR and OER) play a vital role in the field of energy conversion and storage. The problem is that both processes are sluggish, requiring precious-metal catalysts. Here, starting from abundant precursors and using a simple synthesis approach, we report the preparation of a good bifunctional oxygen electro-catalyst: a composite nanorod of manganese oxides and nitrogen-doped carbon. This material has hierarchical porosity, facilitating the mass transfer within the electrode. The nitrogen-doped carbon forms contiguous 3D network, connecting the isolated MnOx nanoparticles and ensuring superior electrical conductivity. Importantly, the MnOx particles contain manganese of mixed oxidation states; aligned with the nitrogen-doped carbon, this hybrid is among the best non-noble-metal ORR/OER catalysts in alkaline media, outperforming even Pt and RuO2 catalysts.Peer reviewed: YesNRC publication: Ye
Zr-89-pembrolizumab biodistribution is influenced by PD-1-mediated uptake in lymphoid organs
Background To better predict response to immune checkpoint therapy and toxicity in healthy tissues, insight in the in vivo behavior of immune checkpoint targeting monoclonal antibodies is essential. Therefore, we aimed to study in vivo pharmacokinetics and whole-body distribution of zirconium-89 (Zr-89) labeled programmed cell death protein-1 (PD-1) targeting pembrolizumab with positron-emission tomography (PET) in humanized mice. Methods Humanized (huNOG) and non-humanized NOG mice were xenografted with human A375M melanoma cells. PET imaging was performed on day 7 post(89)Zr-pembrolizumab (10 mu g, 2.5 MBq) administration, followed by ex vivo biodistribution studies. Other huNOG mice bearing A375M tumors received a co-injection of excess (90 mu g) unlabeled pembrolizumab or(89)Zr-IgG(4)control (10 mu g, 2.5 MBq). Tumor and spleen tissue were studied with autoradiography and immunohistochemically including PD-1. Results PET imaging and biodistribution studies showed high(89)Zr-pembrolizumab uptake in tissues containing human immune cells, including spleen, lymph nodes and bone marrow. Tumor uptake of(89)Zr-pembrolizumab was lower than uptake in lymphoid tissues, but higher than uptake in other organs. High uptake in lymphoid tissues could be reduced by excess unlabeled pembrolizumab. Tracer activity in blood pool was increased by addition of unlabeled pembrolizumab, but tumor uptake was not affected. Autoradiography supported PET findings and immunohistochemical staining on spleen and lymph node tissue showed PD-1 positive cells, whereas tumor tissue was PD-1 negative. Conclusion Zr-89-pembrolizumab whole-body biodistribution showed high PD-1-mediated uptake in lymphoid tissues, such as spleen, lymph nodes and bone marrow, and modest tumor uptake. Our data may enable evaluation of(89)Zr-pembrolizumab whole-body distribution in patients
Routine versus on demand removal of the syndesmotic screw; a protocol for an international randomised controlled trial (RODEO-trial)
Background: Syndesmotic injuries are common and their incidence is rising. In case of surgical fixation of the syndesmosis a metal syndesmotic screw is used most often. It is however unclear whether this screw needs to be removed routinely after the syndesmosis has healed. Traditionally the screw is removed after six to 12 weeks as it is thought to hamper ankle functional and to be a source of pain. Some studies however suggest this is only the case in a minority of patients. We therefore aim to investigate the effect of retaining the syndesmotic screw on functional outcome. Design: This is a pragmatic international multicentre randomised controlled trial in patients with an acute syndesmotic injury for which a metallic syndesmotic screw was placed. Patients will be randomised to either routine removal of the syndesmotic screw or removal on demand. Primary outcome is functional recovery at 12 months measured with the Olerud-Molander Score. Secondary outcomes are quality of life, pain and costs. In total 194 patients will be needed to demonstrate non-inferiority between the two interventions at 80% power and a significance level of 0.025 including 15% loss to follow-up. Discussion: If removal on demand of the syndesmotic screw is non-inferior to routine removal in terms of functional outcome, this will offer a strong argument to adopt this as standard practice of care. This means that patients will not have to undergo a secondary procedure, leading to less complications and subsequent lower costs.Peer reviewe
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