Three-dimensional (3D) printers are a developing technology penetrating a variety of markets, including the medical sector. Since its introduction to the medical field in the late 1980s, 3D printers ...have constructed a range of devices, such as dentures, hearing aids, and prosthetics. With the ultimate goals of decreasing healthcare costs and improving patient care and outcomes, neurosurgeons are utilizing this dynamic technology, as well. Digital Imaging and Communication in Medicine (DICOM) can be translated into Stereolithography (STL) files, which are then read and methodically built by 3D Printers. Vessels, tumors, and skulls are just a few of the anatomical structures created in a variety of materials, which enable surgeons to conduct research, educate surgeons in training, and improve pre-operative planning without risk to patients. Due to the infancy of the field and a wide range of technologies with varying advantages and disadvantages, there is currently no standard 3D printing process for patient care and medical research. In an effort to enable clinicians to optimize the use of additive manufacturing (AM) technologies, we outline the most suitable 3D printing models and computer-aided design (CAD) software for 3D printing in neurosurgery, their applications, and the limitations that need to be overcome if 3D printers are to become common practice in the neurosurgical field.
•Three 3D printers and their respective printing processes are described in detail.•The process of translating DICOM into a 3D printable format is outlined.•3D printing applications and the limitations 3D printers must overcome to significantly impact the field of neurosurgery are discussed.
Civic identity and public space , focussing on Belfast, and
bringing together the work of a historian and two social
scientists, offers a new perspective on the sometimes lethal
conflicts over ...parades, flags and other issues that continue to
disrupt political life in Northern Ireland. It examines the
emergence during the nineteenth century of the concept of public
space and the development of new strategies for its regulation, the
establishment, the new conditions created by the emergence in 1920
of a Northern Ireland state, of a near monopoly of public space
enjoyed by Protestants and unionists, and the break down of that
monopoly in more recent decades. Today policy makers and
politicians struggle to devise a strategy for the management of
public space in a divided city, while endeavouring to promote a new
sense of civic identity that will transcend long-standing sectarian
and political divisions.
BACKGROUND:Smooth muscle cells (SMC) play significant roles in atherosclerosis via phenotypic switching, a pathological process in which SMC dedifferentiation, migration and transdifferentiation into ...other cell types. Yet, how SMC contribute to pathophysiology of atherosclerosis remains elusive.
METHODS:To reveal the trajectories of SMC transdifferentiation during atherosclerosis and to identify molecular targets for disease therapy, we combined SMC fate mapping and single-cell RNA sequencing of both mouse and human atherosclerotic plaques. We also performed cell biology experiments on isolated SMC-derived cells, conducted integrative human genomics, and employed pharmacological studies targeting SMC-derived cells both in vivo and in vitro.
RESULTS:We found that SMC transitioned to an intermediate cell state during atherosclerosis, which was also found in human atherosclerotic plaques of carotid and coronary arteries. SMC- derived intermediate cells, termed “SEM” cells, were multipotent and could differentiate into macrophage-like and fibrochondrocyte-like cells, as well as return towards SMC phenotype. Retinoic acid (RA) signaling was identified as a regulator of SMC to SEM cell transition and RA signaling was dysregulated in symptomatic human atherosclerosis. Human genomics revealed enrichment of genome wide association study (GWAS) signals for coronary artery disease (CAD) in RA signaling target gene loci and correlation between CAD risk alleles and repressed expression of these genes. Activation of RA signaling by all-trans retinoic acid (ATRA), an anti- cancer drug for acute promyelocytic leukemia, blocked SMC transition to SEM cells, reduced atherosclerotic burden and promoted fibrous cap stability.
CONCLUSIONS:Integration of cell-specific fate mapping, single-cell genomics and human genetics adds novel insights into the complexity of SMC biology and reveals regulatory pathways for therapeutic targeting of SMC transitions in atherosclerotic cardiovascular disease.
We present X-ray spectral variability of 24 local active galactic nuclei (AGN) from the Palomar sample of nearby galaxies, as observed mainly by Swift. From hardness ratio measurements, we find that ...18 AGN with low accretion rates show hardening with increasing count rate, converse to the softer-when-brighter behaviour normally observed in AGN with higher accretion rates. Two AGN show softening with increasing count rate, two show more complex behaviour, and two do not show any simple relationship. Sufficient data were available for the spectra of 13 AGN to be summed in flux-bins. In nine of these sources, correlated luminosity-dependent changes in the photon index (Γ) of a power-law component are found to be the main cause of hardness variability. For six objects, with a low accretion rate as a fraction of the Eddington rate (
$\dot{m}_\mathrm{{Edd}}$
), Γ is anticorrelated with
$\dot{m}_\mathrm{{Edd}}$
, i.e. ‘harder-when-brighter’ behaviour is observed. The three higher
$\dot{m}_\mathrm{{Edd}}$
-rate objects show a positive correlation between Γ and
$\dot{m}_\mathrm{{Edd}}$
. This transition from harder-when-brighter at low
$\dot{m}_\mathrm{{Edd}}$
to softer-when-brighter at high
$\dot{m}_\mathrm{{Edd}}$
can be explained by a change in the dominant source of seed-photons for X-ray emission from cyclo-synchrotron emission from the Comptonizing corona itself to thermal seed-photons from the accretion disc. This transition is also seen in the ‘hard state’ of black hole X-ray binaries (BHXRBs). The results support the idea that low-ionization nuclear emission-line regions are analogues of BHXRBs in the hard state and that Seyferts are analogues of BHXRBs in either the high-accretion rate end of the hard state or in the hard-intermediate state.
Lags measured from correlated X-ray/UV/optical monitoring of AGN allow us to determine whether UV/optical variability is driven by reprocessing of X-rays or X-ray variability is driven by UV/optical ...seed photon variations. We present the results of the largest study to date of the relationship between the X-ray, UV and optical variability in an AGN with 554 observations, over a 750 d period, of the Seyfert 1 galaxy NGC 5548 with Swift. There is a good overall correlation between the X-ray and UV/optical bands, particularly on short time-scales (tens of days). The UV/optical bands lag the X-ray band with lags which are proportional to wavelength raised to the power 1.23 ± 0.31. This power is very close to the power (4/3) expected if short time-scale UV/optical variability is driven by reprocessing of X-rays by a surrounding accretion disc. The observed lags, however, are longer than expected from a standard Shakura–Sunyaev accretion disc with X-ray heating, given the currently accepted black hole mass and accretion rate values, but can be explained with a slightly larger mass and accretion rate, and a generally hotter disc. Some long-term UV/optical variations are not paralleled exactly in the X-rays, suggesting an additional component to the UV/optical variability arising perhaps from accretion rate perturbations propagating inwards through the disc.
Previous empirical research on tolerance suffers from a number of shortcomings, the most serious being the conceptual and operational conflation of (in)tolerance and prejudice. We design research to ...remedy this. First, we contribute to the literature by advancing research that distinguishes analytically between the two phenomena. We conceptualize tolerance as a value orientation towards difference. This definition—which is abstract and does not capture attitudes towards specific out-groups, ideas, or behaviors—allows for the analysis of tolerance within and between societies. Second, we improve the measurement of tolerance by developing survey items that are consistent with this conceptualization. We administer two surveys, one national (Sweden) and one cross-national (Australia, Denmark, Great Britain, Sweden, and the United States). Results from structural equation models show that tolerance is best understood as a three-dimensional concept, which includes acceptance of, respect for, and appreciation of difference. Analyses show that measures of tolerance have metric invariance across countries, and additional tests demonstrate convergent and discriminant validity. We also assess tolerance’s relationship to prejudice and find that only an appreciation of difference has the potential to reduce prejudice. We conclude that it is not only possible to measure tolerance in a way that is distinct from prejudice but also necessary if we are to understand the causes and consequences of tolerance.
The diversity, frequency, and scale of human impacts on coral reefs are increasing to the extent that reefs are threatened globally. Projected increases in carbon dioxide and temperature over the ...next 50 years exceed the conditions under which coral reefs have flourished over the past half-million years. However, reefs will change rather than disappear entirely, with some species already showing far greater tolerance to climate change and coral bleaching than others. International integration of management strategies that support reef resilience need to be vigorously implemented, and complemented by strong policy decisions to reduce the rate of global warming.
Networks of no-take reserves are important for protecting coral reef biodiversity from climate change and other human impacts. Ensuring that reserve populations are connected to each other and ...non-reserve populations by larval dispersal allows for recovery from disturbance and is a key aspect of resilience. In general, connectivity between reserves should increase as the distance between them decreases. However, enhancing connectivity may often tradeoff against a network's ability to representatively sample the system's natural variability. This “representation” objective is typically measured in terms of species richness or diversity of habitats, but has other important elements (e.g., minimizing the risk that multiple reserves will be impacted by catastrophic events). Such representation objectives tend to be better achieved as reserves become more widely spaced. Thus, optimizing the location, size and spacing of reserves requires both an understanding of larval dispersal and explicit consideration of how well the network represents the broader system; indeed the lack of an integrated theory for optimizing tradeoffs between connectivity and representation objectives has inhibited the incorporation of connectivity into reserve selection algorithms. This article addresses these issues by (1) updating general recommendations for the location, size and spacing of reserves based on emerging data on larval dispersal in corals and reef fishes, and on considerations for maintaining genetic diversity; (2) using a spatial analysis of the Great Barrier Reef Marine Park to examine potential tradeoffs between connectivity and representation of biodiversity and (3) describing a framework for incorporating environmental fluctuations into the conceptualization of the tradeoff between connectivity and representation, and that expresses both in a common, demographically meaningful currency, thus making optimization possible.
Swift monitoring of NGC 4151 with an ∼6 hr sampling over a total of 69 days in early 2016 is used to construct light curves covering five bands in the X-rays (0.3-50 keV) and six in the ultraviolet ...(UV)/optical (1900-5500 Å). The three hardest X-ray bands (>2.5 keV) are all strongly correlated with no measurable interband lag, while the two softer bands show lower variability and weaker correlations. The UV/optical bands are significantly correlated with the X-rays, lagging ∼3-4 days behind the hard X-rays. The variability within the UV/optical bands is also strongly correlated, with the UV appearing to lead the optical by ∼0.5-1 days. This combination of 3 day lags between the X-rays and UV and 1 day lags within the UV/optical appears to rule out the "lamp-post" reprocessing model in which a hot, X-ray emitting corona directly illuminates the accretion disk, which then reprocesses the energy in the UV/optical. Instead, these results appear consistent with the Gardner & Done picture in which two separate reprocessings occur: first, emission from the corona illuminates an extreme-UV-emitting toroidal component that shields the disk from the corona; this then heats the extreme-UV component, which illuminates the disk and drives its variability.
The world is currently facing the prospect of a severe global shortage of fresh water alongside finite energy resources and the development of energy-efficient desalination methods is of paramount ...importance to solve these complex problems. In this paper the basic principles of freeze concentration processes are presented. Even though the process has the advantage of low energy usage and high concentration factors, only lab and pilot scale studies have been conducted in the desalination industry and application of the process has been limited due to the dominance of more traditional thermal and membrane technologies. Finally, the paper looks at the future applications for freeze concentration and discusses the possibility of application to high saline brine wastes in hybrid-technology.
Display omitted
•Review of processes for desalination by freeze concentration•Developments in freeze concentration methodologies in food, wastewater and desalination industries•RO-freeze desalination hybrid process
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