807 research outputs found
Beyond Worst-Case Analysis for Joins with Minesweeper
We describe a new algorithm, Minesweeper, that is able to satisfy stronger
runtime guarantees than previous join algorithms (colloquially, `beyond
worst-case guarantees') for data in indexed search trees. Our first
contribution is developing a framework to measure this stronger notion of
complexity, which we call {\it certificate complexity}, that extends notions of
Barbay et al. and Demaine et al.; a certificate is a set of propositional
formulae that certifies that the output is correct. This notion captures a
natural class of join algorithms. In addition, the certificate allows us to
define a strictly stronger notion of runtime complexity than traditional
worst-case guarantees. Our second contribution is to develop a dichotomy
theorem for the certificate-based notion of complexity. Roughly, we show that
Minesweeper evaluates -acyclic queries in time linear in the certificate
plus the output size, while for any -cyclic query there is some instance
that takes superlinear time in the certificate (and for which the output is no
larger than the certificate size). We also extend our certificate-complexity
analysis to queries with bounded treewidth and the triangle query.Comment: [This is the full version of our PODS'2014 paper.
Role of buffer surface morphology and alloying effects on the properties of InAs nanostructures grown on InP(001)
International audienceWe show the role played by the buffer surface morphology and by alloying effects on the size, shape and lateral distribution of InAs nanostructures grown on InP001 substrates by molecular beam epitaxy. Three buffers, viz., In 0.53 Ga 0.47 As, In 0.52 Al 0.48 As, and InP lattice matched on InP have been studied. Differences in nanostructure morphology and in carrier confinement have been evaluated by atomic force microscopy and by low-temperature photoluminescence measurements, respectively. Alongside the classical relaxation mode through two-dimensional/three-dimensional surface morphology change, a chemical relaxation mode has to be introduced as a competitive mode of relaxation of strained layers. This chemical relaxation mode, due to alloying between the InAs deposit and the buffer, is thought to be responsible for most of the observed differences in the InAs nanostructure properties
First evidence for a gravitational lensing-induced echo in gamma rays with Fermi LAT
Aims. This article shows the first evidence for gravitational lensing
phenomena in high energy gamma-rays. This evidence comes from the observation
of a gravitational lens induced echo in the light curve of the distant blazar
PKS 1830-211. Methods. Traditional methods for the estimation of time delays in
gravitational lensing systems rely on the cross-correlation of the light curves
of the individual images. In this paper, we use 300 MeV-30 GeV photons detected
by the Fermi-LAT instrument. The Fermi-LAT instrument cannot separate the
images of known lenses. The observed light curve is thus the superposition of
individual image light curves. The Fermi-LAT instrument has the advantage of
providing long, evenly spaced, time series. In addition, the photon noise level
is very low. This allows to use directly Fourier transform methods. Results. A
time delay between the two compact images of PKS 1830-211 has been searched for
both by the autocorrelation method and the "double power spectrum" method. The
double power spectrum shows a 3 {\sigma} evidence for a time delay of 27.5
1.3 days, consistent with the result from Lovell et al. (1998). The
relative uncertainty on the time delay estimation is reduced from 20% to 5%.Comment: submitted to A&
The effects of Cstb duplication on APP/amyloid-β pathology and cathepsin B activity in a mouse model
People with Down syndrome (DS), caused by trisomy of chromosome 21 have a greatly increased risk of developing Alzheimer's disease (AD). This is in part because of triplication of a chromosome 21 gene, APP. This gene encodes amyloid precursor protein, which is cleaved to form amyloid-β that accumulates in the brains of people who have AD. Recent experimental results demonstrate that a gene or genes on chromosome 21, other than APP, when triplicated significantly accelerate amyloid-β pathology in a transgenic mouse model of amyloid-β deposition. Multiple lines of evidence indicate that cysteine cathepsin activity influences APP cleavage and amyloid-β accumulation. Located on human chromosome 21 (Hsa21) is an endogenous inhibitor of cathepsin proteases, CYSTATIN B (CSTB) which is proposed to regulate cysteine cathepsin activity in vivo. Here we determined if three copies of the mouse gene Cstb is sufficient to modulate amyloid-β accumulation and cathepsin activity in a transgenic APP mouse model. Duplication of Cstb resulted in an increase in transcriptional and translational levels of Cstb in the mouse cortex but had no effect on the deposition of insoluble amyloid-β plaques or the levels of soluble or insoluble amyloid-β42, amyloid-β40, or amyloid-β38 in 6-month old mice. In addition, the increased CSTB did not alter the activity of cathepsin B enzyme in the cortex of 3-month or 6-month old mice. These results indicate that the single-gene duplication of Cstb is insufficient to elicit a disease-modifying phenotype in the dupCstb x tgAPP mice, underscoring the complexity of the genetic basis of AD-DS and the importance of multiple gene interactions in disease
Strong normal-incidence infrared absorption in self-organized InAs/InAlAs quantum dots grown on InP(001)
International audienceInAs self-assembled quantum dots in InAlAs matrix grown on InP001 substrates have been fabricated using Stranski-Krastanov growth mode. A strong in-plane polarized intraband absorption in the 10.6-20 m wavelength region has been observed and ascribed to a transition from the ground electron state to an excited state confined in the layer plane along the 110 direction. The absorption at normal-incidence reaches 7.8% for ten layers of n-doped quantum dots. The oscillator strength of the intraband transition is comparable to that achieved in quantum wells for a conduction band intersubband transition. The dependence of the intraband absorption on carrier concentration and temperature suggests a quantum-wire type confinement potential
Ringing effects reduction by improved deconvolution algorithm Application to A370 CFHT image of gravitational arcs
We develop a self-consistent automatic procedure to restore informations from
astronomical observations. It relies on both a new deconvolution algorithm
called LBCA (Lower Bound Constraint Algorithm) and the use of the Wiener
filter. In order to explore its scientific potential for strong and weak
gravitational lensing, we process a CFHT image of the galaxies cluster Abell
370 which exhibits spectacular strong gravitational lensing effects. A high
quality restoration is here of particular interest to map the dark matter
within the cluster. We show that the LBCA turns out specially efficient to
reduce ringing effects introduced by classical deconvolution algorithms in
images with a high background. The method allows us to make a blind detection
of the radial arc and to recover morphological properties similar to
thoseobserved from HST data. We also show that the Wiener filter is suitable to
stop the iterative process before noise amplification, using only the
unrestored data.Comment: A&A in press 9 pages 9 figure
Real-world Experience With Sunitinib Treatment in Patients With Metastatic Renal Cell Carcinoma: Clinical Outcome According to Risk Score.
BACKGROUND: ADONIS is an ongoing observational study in 9 European countries, designed to evaluate treatment patterns/outcomes in patients with metastatic renal cell carcinoma (mRCC) treated with first-line sunitinib and/or second-line axitinib post sunitinib. We present an evaluation of sunitinib efficacy by risk group, in the real-world setting examined in ADONIS. PATIENTS AND METHODS: Patients were enrolled at the start of first-line sunitinib treatment or second-line axitinib post sunitinib treatment. Evaluation of sunitinib efficacy was assessed by International Metastatic Renal Cell Carcinoma Database Consortium (IMDC) and Memorial Sloan Kettering Cancer Center risk criteria. RESULTS: For all patients in this analysis (N = 467), the median progression-free survival was 23.8 months (95% confidence interval [CI], 16.5-28.5 months), 11.8 months (95% CI, 8.1-17.4 months), and 4.6 months (95% CI, 2.5-7.7 months) for IMDC favorable-, intermediate-, and poor-risk groups, respectively. The median overall survival was 97.1 months (95% CI, 46.3 months-not evaluable [NE]), 33.5 months (95% CI, 20.5-46.6 months), and 10.0 months (95% CI, 4.5-19.8 months) for the respective risk groups. Data on individual risk factors were available for a subgroup of patients, allowing analysis by intermediate risk by 1 versus 2 risk factors. When including this subgroup (n = 120), the median overall survival for IMDC favorable-, intermediate-1, and intermediate-2 risk factors was 21.6 months (95% CI, 16.3 months-NE), 20.5 months (15.5 months-NE), and 15.1 months (4.1 months-NE), respectively. CONCLUSIONS: For patients overall and by risk-group stratification, survival estimates were aligned with previously published data. In patients with intermediate-1 risk, overall survival was very similar to patients with favorable risk. However, further exploration of outcome data from different sources is needed to confirm these observations
Plasma membrane-associated receptor like kinases relocalize to plasmodesmata in response to osmotic stress
Plasmodesmata act as key elements in intercellular communication, coordinating processes related to plant growth, development, and responses to environmental stresses. While many of the developmental, biotic, and abiotic signals are primarily perceived at the plasma membrane (PM) by receptor proteins, plasmodesmata also cluster receptor-like activities; whether these two pathways interact is currently unknown. Here we show that specific PM-located Leucine-Rich-Repeat Receptor-Like-Kinases (LRR-RLKs), QSK1 and IMK2, which under optimal growth conditions are absent from plasmodesmata, rapidly relocate and cluster to the pores in response to osmotic stress. This process is remarkably fast, is not a general feature of PM-associated proteins, and is independent of sterol- and sphingolipid- membrane composition. Focusing on QSK1, previously reported to be involved in stress responses, we show that relocalisation in response to mannitol depends on QSK1 phosphorylation. Loss-of-function mutation in QSK1 results in delayed lateral root (LR) development and the mutant is affected in the root response to mannitol stress. Callose-mediated plasmodesmata regulation is known to regulate LR development. We found that callose levels are reduced in the qsk1 mutant background with a root phenotype resembling ectopic expression of PdBG1, an enzyme that degrades callose at the pores. Both the LR and callose phenotypes can be complemented by expression of wild-type and phosphomimic QSK1 variants, but not by phosphodead QSK1 mutant which fails to relocalise at plasmodesmata. Together the data indicate that re-organisation of RLKs to plasmodesmata is important for the regulation of callose and LR development as part of the plant response to osmotic stress
Improved Laboratory Transition Probabilities for Neutral Chromium and Re-determination of the Chromium Abundance for the Sun and Three Stars
Branching fraction measurements from Fourier transform spectra in conjunction
with published radiative lifetimes are used to determine transition
probabilities for 263 lines of neutral chromium. These laboratory values are
employed to derive a new photospheric abundance for the Sun: log (Cr
I) = 5.640.01 (). These Cr I solar abundances do
not exhibit any trends with line strength nor with excitation energy and there
were no obvious indications of departures from LTE. In addition, oscillator
strengths for singly-ionized chromium recently reported by the FERRUM Project
are used to determine: log (Cr II) = 5.770.03 (). Transition probability data are also applied to the spectra of three
stars: HD 75732 (metal-rich dwarf), HD 140283 (metal-poor subgiant), and CS
22892-052 (metal-poor giant). In all of the selected stars, Cr I is found to be
underabundant with respect to Cr II. The possible causes for this abundance
discrepancy and apparent ionization imbalance are discussed.Comment: 44 pages, 6 figure
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