Flows of gas through a protoplanetary gap Casassus, Simon; van der Plas, Gerrit; Sebastian Perez, M ...
Nature (London),
01/2013, Letnik:
493, Številka:
7431
Journal Article
Recenzirano
The formation of gaseous giant planets is thought to occur in the first few million years after stellar birth. Models predict that the process produces a deep gap in the dust component (shallower in ...the gas). Infrared observations of the disk around the young star HD 142527 (at a distance of about 140 parsecs from Earth) found an inner disk about 10 astronomical units (AU) in radius (1 AU is the Earth-Sun distance), surrounded by a particularly large gap and a disrupted outer disk beyond 140 AU. This disruption is indicative of a perturbing planetary-mass body at about 90 AU. Radio observations indicate that the bulk mass is molecular and lies in the outer disk, whose continuum emission has a horseshoe morphology. The high stellar accretion rate would deplete the inner disk in less than one year, and to sustain the observed accretion matter must therefore flow from the outer disk and cross the gap. In dynamical models, the putative protoplanets channel outer-disk material into gap-crossing bridges that feed stellar accretion through the inner disk. Here we report observations of diffuse CO gas inside the gap, with denser HCO(+) gas along gap-crossing filaments. The estimated flow rate of the gas is in the range of 7 × 10(-9) to 2 × 10(-7) solar masses per year, which is sufficient to maintain accretion onto the star at the present rate.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Neovascular age-related macular degeneration (AMD) has undergone substantial break-throughs in diagnostic as well as therapeutic respect, with optical coherence tomography (OCT) allowing to identify ...disease morphology in great detail, and intravitreal anti-vascular endothelial growth factor therapy providing unprecedented benefit. However, these two paths have yet not been combined in an optimal way, real-world outcomes are inferior to expectations, and disease management is largely inefficient in the real-world setting. This dilemma can be solved by identification of valid biomarkers relevant for visual function, disease activity and prognosis, which can provide solid guidance for therapeutic management on an individual level as well as on the population base.
Qualitative and quantitative morphological features obtained by advanced OCT provide novel insight into exudative and degenerative stages of neovascular AMD. However, conclusions from structure/function correlations evolve differently from previous paradigms. While central retinal thickness was used as biomarker for guiding retreatment management in clinical trials and practice, fluid localization in different compartments offers superior prognostic value: Intraretinal cystoid fluid has a negative impact on visual acuity and is considered as degenerative when persisting through the initial therapeutic interval. Subretinal fluid is associated with superior visual benefit and a lower rate of progression towards geographic atrophy. Detachment of the retinal pigment epithelium was identified as most pathognomonic biomarker, often irresponsive to therapy and responsible for visual decline during a pro-re-nata regimen. Alterations of neurosensory tissue are usually associated with irreversible loss of functional elements and a negative prognosis. Novel OCT technologies offer crucial insight into corresponding changes at the level of the photoreceptor – retinal pigment epithelial – choriocapillary unit, identifying the biological limits of therapeutic interventions.
To optimally benefit from high-resolution multi-modal imaging, an integrated analysis of all functional and structural features is required involving reliable automated algorithms and computational data analyses. Using innovative analysis methods, retinal biomarkers can be used to provide efficient personalized therapy for the individual patient, predictive disease- and population-based models for large-scale management and identifying promising targets for the development of novel therapeutic strategies.
Test beds and living labs have emerged as a prominent approach to foster innovation across geographical regions and technical domains. They feed on the popular “grand societal challenges” discourse ...and the growing insight that adequate policy responses to these challenges will require drastic transformations of technology and society alike. Test beds and living labs represent an experimental, co-creative approach to innovation policy that aims to test, demonstrate, and advance new sociotechnical arrangements and associated modes of governance in a model environment under real-world conditions. In this paper, we develop an analytic framework for this distinctive approach to innovation. Our research draws on theories from Science and Technology Studies (STS) and Innovation Studies, as well as in-depth empirical analysis from two case studies – an urban smart energy campus and a rural renewable energy network. Our analysis reveals three characteristic frictions that test beds face: (1) the limits of controlled experimentation due to messy social responses and co-creation activity; (2) a tension between lab-like open-ended experimentation and pressures to demonstrate success; (3) the opposing needs of local socio-cultural specificity and scalability, i.e. the inherent promise of test bed outcomes being generalizable or transferrable because the tested “model society” is presumed to represent a future society at large. These tensions suggest that thinking of test beds as mere technology tests under real-world conditions is insufficient. Rather, test beds both test and re-configure society around a new set of technologies, envisioned futures, and associated modes of governance – occasionally against considerable resistance. By making social order explicitly available for experimentation, test beds tentatively stabilize new socio-technical orders on a local scale in an “as-if” mode of adoption and diffusion. Symmetric attention to the simultaneous co-production of new technical and social orders points to new opportunities and challenges for innovation governance in test-bed settings: Rather than mere enablers of technology, test beds could serve as true societal tests for the desirability of certain transformations. This will require rethinking notions of success and failure, planning with a view towards reversibility, and greater scrutiny of how power is distributed within such settings. Likewise, rather than envisioning test beds as low-regulation zones to drive innovation, they could be strategically deployed to co-develop socially desirable governance frameworks in tandem with emerging technologies in real-time.
The spliceosome excises introns from pre-messenger RNAs using an RNA-based active site that is cradled by a dynamic protein scaffold. A recent revolution in cryo-electron microscopy (cryo-EM) has led ...to near-atomic-resolution structures of key spliceosome complexes that provide insight into the mechanism of activation, splice site positioning, catalysis, protein rearrangements and ATPase-mediated dynamics of the active site. The cryo-EM structures rationalize decades of observations from genetic and biochemical studies and provide a molecular framework for future functional studies.
Abstract
Many processes during the evolution of protoplanetary disks and during planet formation are highly sensitive to the sizes of dust particles that are present in the disk: the efficiency of ...dust accretion in the disk and volatile transport on dust particles, gravoturbulent instabilities leading to the formation of planetesimals, or the accretion of pebbles onto large planetary embryos to form giant planets are typical examples of processes that depend on the sizes of the dust particles involved. Furthermore, radiative properties like absorption or scattering opacities depend on the particle sizes. To interpret observations of dust in protoplanetary disks, a proper estimate of the dust particle sizes is needed. We present
DustPy:
a
Python
package to simulate dust evolution in protoplanetary disks.
DustPy
solves gas and dust transport including viscous advection and diffusion as well as collisional growth of dust particles.
DustPy
is written with a modular concept, such that every aspect of the model can be easily modified or extended to allow for a multitude of research opportunities.
•“Innovation deficits” are regularly diagnosed to justify policy intervention.•We develop an analytic framework to explore deficit logics of innovation in public policy.•We demonstrate the impact of ...framings in three national innovation strategies (Luxembourg, Singapore, Denmark).•A more democratic, inclusive, and political approach to innovation policy is needed to avoid the pitfalls of PUS•Sound innovation policy should consider alternative framings to innovation.
As innovation is increasingly becoming an imperative for policymakers around the globe, there is a growing tendency to frame policy problems as problems of innovation. This logic suggests that we are unable to address grand societal challenges and ensure economic competitiveness because our societies, institutions, scientific activities or individual predispositions are not sufficiently geared towards innovation. In this paper, we analyze this “deficit model” of innovation in which a lack of innovation is routinely invoked as the main obstacle to social progress. Drawing parallels to research on the deficit model of public understanding of science (PUS), we develop a theoretical framework that captures the dynamics and normative implications of deficit construction, highlighting five salient dimensions: problem diagnoses, proposed remedies, the role of expertise, implied social orders, and measures of success. We apply this framework to three empirical case studies of recent innovation strategies in Luxembourg, Singapore, and Denmark. Attention to this deficit framing around innovation is important, we argue, because it is an essential part of how innovation transforms societies in the 21st century: not only through new technological possibilities or economic growth, but also by shaping public discourse, narrowing policy options, and legitimizing major institutional interventions. The implied pro-innovation bias tends to marginalize other rationales, values, and social functions that do not explicitly support innovation. It further delegates decisions about sweeping social reconfigurations to innovation experts, which raises questions of accountability and democratic governance. Experiences from the history of PUS suggest that, without a dedicated effort to transform innovation policy into a more democratic, inclusive, and explicitly political field, the present deficit logic and its technocratic overtones risks significant social and political conflict.
Here, we review the structure and function of a core region in the vestibular cortex of humans that is located in the midposterior Sylvian fissure and referred to as the parieto-insular vestibular ...cortex (PIVC). Previous studies have investigated PIVC by using vestibular or visual motion stimuli and have observed activations that were distributed across multiple anatomical structures, including the temporo-parietal junction, retroinsula, parietal operculum, and posterior insula. However, it has remained unclear whether all of these anatomical areas correspond to PIVC and whether PIVC responds to both vestibular and visual stimuli. Recent results suggest that the region that has been referred to as PIVC in previous studies consists of multiple areas with different anatomical correlates and different functional specializations. Specifically, a vestibular but not visual area is located in the parietal operculum, close to the posterior insula, and likely corresponds to the nonhuman primate PIVC, while a visual-vestibular area is located in the retroinsular cortex and is referred to, for historical reasons, as the posterior insular cortex area (PIC). In this article, we review the anatomy, connectivity, and function of PIVC and PIC and propose that the core of the human vestibular cortex consists of at least two separate areas, which we refer to together as PIVC+. We also review the organization in the nonhuman primate brain and show that there are parallels to the proposed organization in humans.
Small, light weight and multifunctional electronic components are attracting much attention because of the rapid growth of the wireless communication systems and microwave products in the consumer ...electronic market. The component manufacturers are thus forced to search for new advanced integration, packaging and interconnection technologies. One solution is the low temperature cofired ceramic (LTCC) technology enabling fabrication of three-dimensional ceramic modules with low dielectric loss and embedded silver electrodes. During the past 15 years, a large number of new dielectric LTCCs for high frequency applications have been developed. About 1000 papers were published and ∼500 patents were filed in the area of LTCC and related technologies. However, the data of these several very useful materials are scattered. The main purpose of this review is to bring the data and science of these materials together, which will be of immense help to researchers and technologists all over the world. The commercially available LTCCs, low loss glass phases and researched novel materials are listed with properties and references. Additionally, their high frequency and thermal performances are compared with the other substrate material options such as high sintering temperature ceramics and polymers, and further improvements in materials' development required are discussed.
•A fast, generative adversarial network (GAN) based anomaly detection approach.•f−AnoGAN is suitable for real-time anomaly detection applications.•Enables anomaly detection on the image level and ...localization on the pixel level.•Wasserstein GAN (WGAN) training and subsequent encoder training via unsupervised learning on normal data.•Comprehensive experimental evaluation and comparison with alternative approaches.
Obtaining expert labels in clinical imaging is difficult since exhaustive annotation is time-consuming. Furthermore, not all possibly relevant markers may be known and sufficiently well described a priori to even guide annotation. While supervised learning yields good results if expert labeled training data is available, the visual variability, and thus the vocabulary of findings, we can detect and exploit, is limited to the annotated lesions. Here, we present fast AnoGAN (f-AnoGAN), a generative adversarial network (GAN) based unsupervised learning approach capable of identifying anomalous images and image segments, that can serve as imaging biomarker candidates. We build a generative model of healthy training data, and propose and evaluate a fast mapping technique of new data to the GAN’s latent space. The mapping is based on a trained encoder, and anomalies are detected via a combined anomaly score based on the building blocks of the trained model – comprising a discriminator feature residual error and an image reconstruction error. In the experiments on optical coherence tomography data, we compare the proposed method with alternative approaches, and provide comprehensive empirical evidence that f-AnoGAN outperforms alternative approaches and yields high anomaly detection accuracy. In addition, a visual Turing test with two retina experts showed that the generated images are indistinguishable from real normal retinal OCT images. The f-AnoGAN code is available at https://github.com/tSchlegl/f-AnoGAN.
•Cryo-EM structures reveal a more complex proteome for the human spliceosome compared to budding yeast.•Movements of three loop-like elements of the core protein Prp8 underlie association of ...step-specific factors.•Specific human proteins modulate plasticity of splice site selection during assembly and catalysis by the human spliceosome.•Novel human exon ligation factors may regulate splicing of specific transcripts.•Additional human ATPases, such as Aquarius, may function as general spliceosome remodelling chaperones.
Introns are excised from pre-messenger RNAs by the spliceosome, which produces mRNAs with continuous protein-coding information. In humans, most pre-mRNAs undergo alternative splicing to expand proteomic diversity. Cryo-electron microscopy (cryo-EM) structures of the yeast spliceosome elucidated how proteins stabilize and remodel an RNA-based active site to effect splicing catalysis. More recent cryo-EM snapshots of the human spliceosome reveal a complex protein scaffold and provide insights into the role of specific human proteins in modulating spliceosome activation, splice site positioning, and the ATPase-mediated dynamics of the active site. The emerging molecular picture highlights how, compared to its yeast counterpart, the human spliceosome has coopted additional protein factors to allow increased plasticity of splice site recognition and remodeling, and potentially to regulate alternative splicing.
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