4,474 research outputs found
Transverse Gradient Undulator in a Storage Ring X-ray Free Electron Laser Oscillator
Modern electron storage rings produce bright X-rays via spontaneous
synchrotron emission, which is useful for a variety of scientific applications.
The X-ray free-electron laser oscillator (XFELO) has the potential to amplify
this output, both in terms of peak power and photon coherence. However, even
current 4th generation storage rings (4GSRs) lack the requisite electron beam
brightness to drive the XFELO due to its electron energy spread. The transverse
gradient undulator (TGU) can overcome this issue, thus providing a practical
means to couple the 4GSR to the XFELO. In this study, we first examine the
theoretical basis of the TGU interaction by deriving the 3D TGU gain formula in
the low gain approximation. Then, we perform an optimization study of the gain
formula in order to determine optimal beam and machine parameters. Finally, we
construct a hypothetical storage ring TGU-XFELO based on near-optimal
parameters and report on its projected performance using multi-stage numerical
simulation. We also discuss potential implementation challenges associated with
the ring-FEL coupling.Comment: 17 pages, 11 figure
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NRG1 functions downstream of EDS1 to regulate TIR-NLR-mediated plant immunity in Nicotiana benthamiana.
Effector-triggered immunity (ETI) in plants involves a large family of nucleotide-binding leucine-rich repeat (NLR) immune receptors, including Toll/IL-1 receptor-NLRs (TNLs) and coiled-coil NLRs (CNLs). Although various NLR immune receptors are known, a mechanistic understanding of NLR function in ETI remains unclear. The TNL Recognition of XopQ 1 (Roq1) recognizes the effectors XopQ and HopQ1 from Xanthomonas and Pseudomonas, respectively, which activates resistance to Xanthomonas euvesicatoria and Xanthomonas gardneri in an Enhanced Disease Susceptibility 1 (EDS1)-dependent way in Nicotiana benthamiana In this study, we found that the N. benthamiana N requirement gene 1 (NRG1), a CNL protein required for the tobacco TNL protein N-mediated resistance to tobacco mosaic virus, is also essential for immune signaling [including hypersensitive response (HR)] triggered by the TNLs Roq1 and Recognition of Peronospora parasitica 1 (RPP1), but not by the CNLs Bs2 and Rps2, suggesting that NRG1 may be a conserved key component in TNL signaling pathways. Besides EDS1, Roq1 and NRG1 are necessary for resistance to Xanthomonas and Pseudomonas in N. benthamiana NRG1 functions downstream of Roq1 and EDS1 and physically associates with EDS1 in mediating XopQ-Roq1-triggered immunity. Moreover, RNA sequencing analysis showed that XopQ-triggered gene-expression profile changes in N. benthamiana were almost entirely mediated by Roq1 and EDS1 and were largely regulated by NRG1. Overall, our study demonstrates that NRG1 is a key component that acts downstream of EDS1 to mediate various TNL signaling pathways, including Roq1 and RPP1-mediated HR, resistance to Xanthomonas and Pseudomonas, and XopQ-regulated transcriptional changes in N. benthamiana
Critical elements of synthesis questions are incompletely reported: survey of systematic reviews of intervention effects
Objectives: To examine the characteristics of population, intervention and outcome groups and the extent to which they were completely reported for each synthesis in a sample of systematic reviews (SRs) of interventions. Study design and setting: We coded groups that were intended (or used) for comparisons in 100 randomly sampled SRs of public health and health systems interventions published in 2018 from the Health Evidence and Health Systems Evidence databases. Results: Authors commonly used population, intervention and outcome groups to structure comparisons, but these groups were often incompletely reported. For example, of 41 SRs that identified and/or used intervention groups for comparisons, 29 (71%) identified the groups in their methods description before reporting of the results (e.g., in the Background or Methods), 12 (29%) defined the groups in enough detail to replicate decisions about which included studies were eligible for each synthesis, 6 (15%) provided a rationale, and 24 (59%) stated that the groups would be used for comparisons. Sixteen (39%) SRs used intervention groups in their synthesis without any mention in the methods. Reporting for population, outcome and methodological groups was similarly incomplete. Conclusion: Complete reporting of the groups used for synthesis would improve transparency and replicability of reviews, and help ensure that the synthesis is not driven by what is reported in the included studies. Although concerted effort is needed to improve reporting, this should lead to more focused and useful reviews for decision-makers
Network-Level Structural Abnormalities of Cerebral Cortex in Type 1 Diabetes Mellitus
Type 1 diabetes mellitus (T1DM) usually begins in childhood and adolescence and causes lifelong damage to several major organs including the brain. Despite increasing evidence of T1DM-induced structural deficits in cortical regions implicated in higher cognitive and emotional functions, little is known whether and how the structural connectivity between these regions is altered in the T1DM brain. Using inter-regional covariance of cortical thickness measurements from high-resolution T1-weighted magnetic resonance data, we examined the topological organizations of cortical structural networks in 81 T1DM patients and 38 healthy subjects. We found a relative absence of hierarchically high-level hubs in the prefrontal lobe of T1DM patients, which suggests ineffective top-down control of the prefrontal cortex in T1DM. Furthermore, inter-network connections between the strategic/executive control system and systems subserving other cortical functions including language and mnemonic/emotional processing were also less integrated in T1DM patients than in healthy individuals. The current results provide structural evidence for T1DM-related dysfunctional cortical organization, which specifically underlie the top-down cognitive control of language, memory, and emotion. © 2013 Lyoo et al
The depression in visual impairment trial (DEPVIT): trial design and protocol
<b>Background</b>
The prevalence of depression in people with a visual disability is high but screening for depression and referral for treatment is not yet an integral part of visual rehabilitation service provision. One reason for this may be that there is no good evidence about the effectiveness of treatments in this patient group. This study is the first to evaluate the effect of depression treatments on people with a visual impairment and co morbid depression.<p></p>
<b>Methods/design</b>
The study is an exploratory, multicentre, individually randomised waiting list controlled trial. Participants will be randomised to receive Problem Solving Therapy (PST), a ‘referral to the GP’ requesting treatment according to the NICE’s ‘stepped care’ recommendations or the waiting list arm of the trial. The primary outcome measure is change (from randomisation) in depressive symptoms as measured by the Beck’s Depression Inventory (BDI-II) at 6 months. Secondary outcomes include change in depressive symptoms at 3 months, change in visual function as measured with the near vision subscale of the VFQ-48 and 7 item NEI-VFQ at 3 and 6 months, change in generic health related quality of life (EQ5D), the costs associated with PST, estimates of incremental cost effectiveness, and recruitment rate estimation.<p></p>
<b>Discussion</b>
Depression is prevalent in people with disabling visual impairment. This exploratory study will establish depression screening and referral for treatment in visual rehabilitation clinics in the UK. It will be the first to explore the efficacy of PST and the effectiveness of NICE’s ‘stepped care’ approach to the treatment of depression in people with a visual impairment.<p></p>
Faster Maximum Inner Product Search in High Dimensions
Maximum Inner Product Search (MIPS) is a ubiquitous task in machine learning
applications such as recommendation systems. Given a query vector and atom
vectors in -dimensional space, the goal of MIPS is to find the atom that has
the highest inner product with the query vector. Existing MIPS algorithms scale
at least as , which becomes computationally prohibitive in
high-dimensional settings. In this work, we present BanditMIPS, a novel
randomized MIPS algorithm whose complexity is independent of . BanditMIPS
estimates the inner product for each atom by subsampling coordinates and
adaptively evaluates more coordinates for more promising atoms. The specific
adaptive sampling strategy is motivated by multi-armed bandits. We provide
theoretical guarantees that BanditMIPS returns the correct answer with high
probability, while improving the complexity in from to
. We also perform experiments on four synthetic and real-world datasets
and demonstrate that BanditMIPS outperforms prior state-of-the-art algorithms.
For example, in the Movie Lens dataset (=4,000, =6,000), BanditMIPS is
20 faster than the next best algorithm while returning the same answer.
BanditMIPS requires no preprocessing of the data and includes a hyperparameter
that practitioners may use to trade off accuracy and runtime. We also propose a
variant of our algorithm, named BanditMIPS-, which achieves further
speedups by employing non-uniform sampling across coordinates. Finally, we
demonstrate how known preprocessing techniques can be used to further
accelerate BanditMIPS, and discuss applications to Matching Pursuit and Fourier
analysis.Comment: 23 page
FeII4L4 Tetrahedron Binds to Nonpaired DNA Bases.
A water-soluble self-assembled supramolecular FeII4L4 tetrahedron binds to single stranded DNA, mismatched DNA base pairs, and three-way DNA junctions. Binding of the coordination cage quenches fluorescent labels on the DNA strand, which provides an optical means to detect the interaction and allows the position of the binding site to be gauged with respect to the fluorescent label. Utilizing the quenching and binding properties of the coordination cage, we developed a simple and rapid detection method based on fluorescence quenching to detect unpaired bases in double-stranded DNA.The authors acknowledge support from the UK Engineering and Physical Sciences Research Council (EPSRC EP/M008258/1, EPSRC EP/P027067/1, and EPSRC EP/L015978/1). This project has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No 64219
Exploring the Universe with Metal-Poor Stars
The early chemical evolution of the Galaxy and the Universe is vital to our
understanding of a host of astrophysical phenomena. Since the most metal-poor
Galactic stars (with metallicities down to [Fe/H]\sim-5.5) are relics from the
high-redshift Universe, they probe the chemical and dynamical conditions of the
Milky Way and the origin and evolution of the elements through nucleosynthesis.
They also provide constraints on the nature of the first stars, their
associated supernovae and initial mass function, and early star and galaxy
formation. The Milky Way's dwarf satellites contain a large fraction (~30%) of
the known most metal-poor stars that have chemical abundances that closely
resemble those of equivalent halo stars. This suggests that chemical evolution
may be universal, at least at early times, and that it is driven by massive,
energetic SNe. Some of these surviving, ultra-faint systems may show the
signature of just one such PopIII star; they may even be surviving first
galaxies. Early analogs of the surviving dwarfs may thus have played an
important role in the assembly of the old Galactic halo whose formation can now
be studied with stellar chemistry. Following the cosmic evolution of small
halos in simulations of structure formation enables tracing the cosmological
origin of the most metal-poor stars in the halo and dwarf galaxies. Together
with future observations and additional modeling, many of these issues,
including the reionization history of the Milky Way, may be constrained this
way. The chapter concludes with an outlook about upcoming observational
challenges and ways forward is to use metal-poor stars to constrain theoretical
studies.Comment: 34 pages, 11 figures. Book chapter to appear in "The First Galaxies -
Theoretical Predictions and Observational Clues", 2012 by Springer, eds. V.
Bromm, B. Mobasher, T. Wiklin
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