2,319 research outputs found
Patterns of CT lung injury and toxicity after stereotactic radiotherapy delivered with helical tomotherapy in early stage medically inoperable NSCLC
To evaluate toxicity and patterns of radiologic lung injury on CT images after hypofractionated image-guided stereotactic body radiotherapy (SBRT) delivered with helical tomotherapy (HT) in medically early stage inoperable non-small-cell lung cancer (NSCLC)
Hangprinter for large scale additive manufacturing using fused particle fabrication with recycled plastic and continuous feeding
The life cycle of plastic is a key source of carbon emissions. Yet, global plastics production has quadrupled in 40 years and only 9 % has been recycled. If these trends continue, carbon emissions from plastic wastes would reach 15 % of global carbon budgets by 2050. An approach to reducing plastic waste is to use distributed recycling for additive manufacturing (DRAM) where virgin plastic products are replaced by locally manufactured recycled plastic products that have no transportation-related carbon emissions. Unfortunately, the design of most 3-D printers forces an increase in the machine cost to expand for recycling plastic at scale. Recently, a fused granular fabrication (FGF)/fused particle fabrication (FPF) large-scale printer was demonstrated with a GigabotX extruder based on the open source cable driven Hangprinter concept. To further improve that system, here a lower-cost recyclebot direct waste plastic extruder is demonstrated and the full designs, assembly and operation are detailed. The <$1,700 machineâs accuracy and printing performance are quantified, and the printed parts mechanical strength is within the range of other systems. Along with support from the Hangprinter and DUET3 communities, open hardware developers have a rich ecosystem to modify in order to print directly from waste plastic for DRAM
Ejection of Supermassive Black Holes from Galaxy Cores
[Abridged] Recent numerical relativity simulations have shown that the
emission of gravitational waves during the merger of two supermassive black
holes (SMBHs) delivers a kick to the final hole, with a magnitude as large as
4000 km/s. We study the motion of SMBHs ejected from galaxy cores by such kicks
and the effects on the stellar distribution using high-accuracy direct N-body
simulations. Following the kick, the motion of the SMBH exhibits three distinct
phases. (1) The SMBH oscillates with decreasing amplitude, losing energy via
dynamical friction each time it passes through the core. Chandrasekhar's theory
accurately reproduces the motion of the SMBH in this regime if 2 < ln Lambda <
3 and if the changing core density is taken into account. (2) When the
amplitude of the motion has fallen to roughly the core radius, the SMBH and
core begin to exhibit oscillations about their common center of mass. These
oscillations decay with a time constant that is at least 10 times longer than
would be predicted by naive application of the dynamical friction formula. (3)
Eventually, the SMBH reaches thermal equilibrium with the stars. We estimate
the time for the SMBH's oscillations to damp to the Brownian level in real
galaxies and infer times as long as 1 Gyr in the brightest galaxies. Ejection
of SMBHs also results in a lowered density of stars near the galaxy center;
mass deficits as large as five times the SMBH mass are produced for kick
velocities near the escape velocity. We compare the N-body density profiles
with luminosity profiles of early-type galaxies in Virgo and show that even the
largest observed cores can be reproduced by the kicks, without the need to
postulate hypermassive binary SMBHs. Implications for displaced AGNs and
helical radio structures are discussed.Comment: 18 pages, The Astrophysical Journal, in press. Replaced with revised
versio
The jet of the BL Lac object PKS 0521 -365 in the near-IR : MAD adaptive optics observations
BL Lac objects are low--power active nuclei exhibiting a variety of peculiar
properties that are caused by the presence of a relativistic jet and
orientation effects.
We present here adaptive optics near-IR images at high spatial resolution of
the nearby BL Lac object PKS 0521-365, which is known to display a prominent
jet both at radio and optical frequencies. The observations were obtained in
Ks--band using the ESO multi-conjugated adaptive optics demonstrator at the
Very Large Telescope. This allowed us to obtain images with 0.1 arcsec
effective resolution. We performed a detailed analysis of the jet and its
related features from the near-IR images, and combined them with images
previously obtained with HST in the R band and by a re-analysis of VLA radio
maps. We find a remarkable similarity in the structure of the jet at radio,
near-IR, and optical wavelengths. The broad--band emission of the jet knots is
dominated by synchrotron radiation, while the nucleus also exhibits a
significant inverse Compton component. We discovered the near-IR counterpart of
the radio hotspot and found that the near-IR flux is consistent with being a
synchrotron emission from radio to X-ray. The bright red object (red-tip),
detached but well aligned with the jet, is well resolved in the near-IR and has
a linear light profile. Since it has no radio counterpart, we propose that it
is a background galaxy not associated with the jet. The new adaptive optics
near-IR images and previous observations at other frequencies allow us to study
the complex environment around the remarkable BL Lac object PKS 0521-365. These
data exemplify the capabilities of multi conjugate adaptive optics observations
of extragalactic extended sources.Comment: accepted for publication in Astronomy and Astrophysics 9 pages. A & A
2009, in pres
How do psychiatrists address delusions in first meetings in acute care? A qualitative study
Licensed under the Creative Commons Attribution Licens
Hyperfast pulsars as the remnants of massive stars ejected from young star clusters
Recent proper motion and parallax measurements for the pulsar PSR B1508+55
indicate a transverse velocity of ~1100 km/s, which exceeds earlier
measurements for any neutron star. The spin-down characteristics of PSR
B1508+55 are typical for a non-recycled pulsar, which implies that the velocity
of the pulsar cannot have originated from the second supernova disruption of a
massive binary system. The high velocity of PSR B1508+55 can be accounted for
by assuming that it received a kick at birth or that the neutron star was
accelerated after its formation in the supernova explosion. We propose an
explanation for the origin of hyperfast neutron stars based on the hypothesis
that they could be the remnants of a symmetric supernova explosion of a
high-velocity massive star which attained its peculiar velocity (similar to
that of the pulsar) in the course of a strong dynamical three- or four-body
encounter in the core of dense young star cluster. To check this hypothesis we
investigated three dynamical processes involving close encounters between: (i)
two hard massive binaries, (ii) a hard binary and an intermediate-mass black
hole, and (iii) a single star and a hard binary intermediate-mass black hole.
We find that main-sequence O-type stars cannot be ejected from young massive
star clusters with peculiar velocities high enough to explain the origin of
hyperfast neutron stars, but lower mass main-sequence stars or the stripped
helium cores of massive stars could be accelerated to hypervelocities. Our
explanation for the origin of hyperfast pulsars requires a very dense stellar
environment of the order of 10^6 -10^7 stars pc^{-3}. Although such high
densities may exist during the core collapse of young massive star clusters, we
caution that they have never been observed.Comment: 11 pages, 6 figures, 1 table, accepted to MNRA
The Effects of Park Based Interventions on Health: The Italian Project âMoving Parksâ
Obesity and physical inactivity are global health problems responsible for the risk increment of noncommunicable diseases. To overcome these problems, interventions aimed at increasing physical activity (PA) are necessary. Green space can have a positive influence on promoting PA, so, the aim of the present study was to assess the effectiveness of the project âThe moving parks projectâ, which provides for the administration of PA to citizens within Bolognaâs parks (Italy). An ad hoc questionnaire was administered before and after three months of outdoor PA. A total of 329 adult subjects participated in the survey. At follow-up, all psychosocial parameters showed an improvement, with a reduction in the state of tension, sadness and fatigue, and an improvement in the state of energy, serenity, and vitality. The impact of the interventions carried out in the âMoving Parks projectâ was positive and appears to be a good strategy for improving health outcomes
Ram pressure feeding super-massive black holes
When supermassive black holes at the center of galaxies accrete matter
(usually gas), they give rise to highly energetic phenomena named Active
Galactic Nuclei (AGN). A number of physical processes have been proposed to
account for the funneling of gas towards the galaxy centers to feed the AGN.
There are also several physical processes that can strip gas from a galaxy, and
one of them is ram pressure stripping in galaxy clusters due to the hot and
dense gas filling the space between galaxies. We report the discovery of a
strong connection between severe ram pressure stripping and the presence of AGN
activity. Searching in galaxy clusters at low redshift, we have selected the
most extreme examples of jellyfish galaxies, which are galaxies with long
tentacles of material extending for dozens of kpc beyond the galaxy disk. Using
the MUSE spectrograph on the ESO Very Large Telescope, we find that 6 out of
the 7 galaxies of this sample host a central AGN, and two of them also have
galactic-scale AGN ionization cones. The high incidence of AGN among the most
striking jellyfishes may be due to ram pressure causing gas to flow towards the
center and triggering the AGN activity, or to an enhancement of the stripping
caused by AGN energy injection, or both. Our analysis of the galaxy position
and velocity relative to the cluster strongly supports the first hypothesis,
and puts forward ram pressure as another, yet unforeseen, possible mechanism
for feeding the central supermassive black hole with gas.Comment: published in Nature, Vol.548, Number 7667, pag.30
Characteristic promoter hypermethylation signatures in male germ cell tumors
BACKGROUND: Human male germ cell tumors (GCTs) arise from undifferentiated primordial germ cells (PGCs), a stage in which extensive methylation reprogramming occurs. GCTs exhibit pluripotentality and are highly sensitive to cisplatin therapy. The molecular basis of germ cell (GC) transformation, differentiation, and exquisite treatment response is poorly understood. RESULTS: To assess the role and mechanism of promoter hypermethylation, we analyzed CpG islands of 21 gene promoters by methylation-specific PCR in seminomatous (SGCT) and nonseminomatous (NSGCT) GCTs. We found 60% of the NSGCTs demonstrating methylation in one or more gene promoters whereas SGCTs showed a near-absence of methylation, therefore identifying distinct methylation patterns in the two major histologies of GCT. DNA repair genes MGMT, RASSF1A, and BRCA1, and a transcriptional repressor gene HIC1, were frequently methylated in the NSGCTs. The promoter hypermethylation was associated with gene silencing in most methylated genes, and reactivation of gene expression occured upon treatment with 5-Aza-2' deoxycytidine in GCT cell lines. CONCLUSIONS: Our results, therefore, suggest a potential role for epigenetic modification of critical tumor suppressor genes in pathways relevant to GC transformation, differentiation, and treatment response
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