224 research outputs found
Random graph asymptotics on high-dimensional tori. II. Volume, diameter and mixing time
For critical bond-percolation on high-dimensional torus, this paper proves
sharp lower bounds on the size of the largest cluster, removing a logarithmic
correction in the lower bound in Heydenreich and van der Hofstad (2007). This
improvement finally settles a conjecture by Aizenman (1997) about the role of
boundary conditions in critical high-dimensional percolation, and it is a key
step in deriving further properties of critical percolation on the torus.
Indeed, a criterion of Nachmias and Peres (2008) implies appropriate bounds on
diameter and mixing time of the largest clusters. We further prove that the
volume bounds apply also to any finite number of the largest clusters. The main
conclusion of the paper is that the behavior of critical percolation on the
high-dimensional torus is the same as for critical Erdos-Renyi random graphs.
In this updated version we incorporate an erratum to be published in a
forthcoming issue of Probab. Theory Relat. Fields. This results in a
modification of Theorem 1.2 as well as Proposition 3.1.Comment: 16 pages. v4 incorporates an erratum to be published in a forthcoming
issue of Probab. Theory Relat. Field
Benzylic fluorination induced by a charge-transfer complex with a solvent-dependent selectivity switch
We present a divergent strategy for the fluorination of phenylacetic acid derivatives that is induced by a charge-transfer complex between Selectfluor and 4-(dimethylamino)pyridine. A comprehensive investigation of the conditions revealed a critical role of the solvent on the reaction outcome. In the presence of water, decarboxylative fluorination through a single-electron oxidation is dominant. Non-aqueous conditions result in the clean formation of α-fluoro-α-arylcarboxylic acids
Benzylic fluorination induced by N–F bond activation of Selectfluor<sup>®</sup> with a solvent-dependent selectivity switch
We present a divergent radical strategy for the fluorination of phenylacetic acid derivatives through N–F bond activation of Selectfluor® with 4-(dimethylamino)pyridine. Comprehensive reaction investigation revealed the critical role of reaction media on selectivity. In presence of water, decarboxylative fluorination through a single electron oxidation is dominant. Non-aqueous conditions result in the clean formation of α-fluoro-α-arylcarboxylic acids through hydrogen atom transfer
What is the super-sample covariance? A fresh perspective for second-order shear statistics
Cosmological analyses of second-order weak lensing statistics require precise
and accurate covariance estimates. These covariances are impacted by two
sometimes neglected terms: A negative contribution to the Gaussian covariance
due to finite survey area and the super-sample covariance (SSC) which for the
power spectrum contains the impact by Fourier modes larger than the survey
window. We show here that these two effects are connected and can be seen as
correction terms to the ``large-field-approximation'', the asymptotic case of
an infinitely large survey area. We describe the two terms collectively as
``Finite-Field-Terms''.
We derive the covariance of second-order shear statistics from first
principles. For this, we use an estimator in real space without relying on an
estimator for the power spectrum. The resulting covariance does not scale
inversely with the survey area, as naively assumed. This scaling is only
correct under the large-field approximation when the contribution of the
finite-field terms tends to zero. Furthermore, all parts of the covariance, not
only the SSC, depend on the power- and trispectrum at all modes, including
those larger than the survey. We also show that it is generally impossible to
transform an estimate for the power spectrum covariance into the covariance of
a real-space statistic. Such a transformation is only possible in the
asymptotic case of the `large-field approximation'.
Additionally, we find that the total covariance of a real-space statistic can
be calculated using correlation functions estimates on spatial scales smaller
than the survey window. Consequently, estimating covariances of real-space
statistics, in principle, does not require information on spatial scales larger
than the survey area. We demonstrate that this covariance estimation method is
equivalent to the standard sample covariance method.Comment: 8 pages + appendix, 3 figures, submitted to Astronomy & Astrophysics,
Major revision after comments by referee and communit
Metabolic Equivalent in Adolescents, Active Adults and Pregnant Women.
"Metabolic Equivalent" (MET) represents a standard amount of oxygen consumed by the body under resting conditions, and is defined as 3.5 mL O₂/kg × min or ~1 kcal/kg × h. It is used to express the energy cost of physical activity in multiples of MET. However, universal application of the 1-MET standard was questioned in previous studies, because it does not apply well to all individuals. Height, weight and resting metabolic rate (RMR, measured by indirect calorimetry) were measured in adolescent males (n = 50) and females (n = 50), women during pregnancy (gestation week 35-41, n = 46), women 24-53 weeks postpartum (n = 27), and active men (n = 30), and were compared to values predicted by the 1-MET standard. The RMR of adolescent males (1.28 kcal/kg × h) was significantly higher than that of adolescent females (1.11 kcal/kg × h), with or without the effects of puberty stage and physical activity levels. The RMR of the pregnant and post-pregnant subjects were not significantly different. The RMR of the active normal weight (0.92 kcal/kg × h) and overweight (0.89 kcal/kg × h) adult males were significantly lower than the 1-MET value. It follows that the 1-MET standard is inadequate for use not only in adult men and women, but also in adolescents and physically active men. It is therefore recommended that practitioners estimate RMR with equations taking into account individual characteristics, such as sex, age and Body Mass Index, and not rely on the 1-MET standard
8-Methoxyneorautenol and radical scavenging flavonoids from Erythrina abyssinica
A new pterocarpan (named 8-methoxyneorautenol) was isolated from the acetone extract of the root bark of Erythrina abyssinica. In addition, the known isoflavonoid derivatives eryvarin L, erycristagallin and shinpterocarpin were identified for the first time from the roots of this plant. The structures were determined on the basis of spectroscopic evidence. The new compound showed selective antimicrobial activity against Trichophyton mentagrophytes. The acetone extract of the root bark of E. abyssinica showed radical scavenging activity towards 2,2-diphenyl-1-picrylhydrazyl radical (DPPH). The pterocarpenes, 3-hydroxy-9-methoxy-10-(3,3- dimethylallyl)pterocarpene and erycristagallin, were the most active constituents of the roots of this plant and showing dose-dependent activities similar to that of the standard quercetin
Antiplasmodial and larvicidal flavonoids from Derris trifoliata
From the dichloromethane-methanol (1:1) extract of the seed pods of Derris trifoliata, a new flavanone derivative (S)-lupinifolin 4´-methyl ether was isolated. In addition, the known flavonoids lupinifolin and rotenone were identified. The structures were determined on the basis of spectroscopic evidence. Lupinfolin showed moderate in vitro antiplasmodial activity against the D6 (chloroquine-sensitive) and W2 (chloroquineresistant)strains of Plasmodium falciparum. The different parts of this plant showed larvicidal activities against Aedes aegypti and rotenoids were identified as the active principles
KiDS-1000 cosmology: Combined second- and third-order shear statistics
This paper performs the first cosmological parameter analysis of the
KiDS-1000 data with second- and third-order shear statistics. This work builds
on a series of papers that describe the roadmap to third-order shear
statistics. We derive and test a combined model of the second-order shear
statistic, namely the COSEBIs and the third-order aperture mass statistics
in a tomographic set-up. We validate our
pipeline with -body simulations that mock the fourth Kilo Degree survey data
release. To model the second- and third-order statistics, we use the latest
version of \textsc{HMcode2020} for the power spectrum and \textsc{BiHalofit}
for the bispectrum. Furthermore, we use an analytic description to model
intrinsic alignments and hydro-dynamical simulations to model the effect of
baryonic feedback processes. Lastly, we decreased the dimension of the data
vector significantly by considering for the
part of the data vector only equal smoothing radii, making a data analysis of
the fourth Kilo Degree survey data release using a combined analysis of COSEBIs
third-order shear statistic possible. We first validate the accuracy of our
modelling by analysing a noise-free mock data vector assuming the KiDS-1000
error budget, finding a shift in the maximum-a-posterior of the matter density
parameter and of the structure
growth parameter . Lastly, we performed the
first KiDS-1000 cosmological analysis using a combined analysis of second- and
third-order shear statistics, where we constrained
and
. The geometric average on the
errors of and of the combined statistics increased
compared to the second-order statistic by 2.2.Comment: 19 pages, 15 figures. Updated version with arXiv ID of our companion
paper Porth et at. 202
Oxidation of isodrimeninol with PCC yields drimane derivatives with activity against candida yeast by inhibition of lanosterol 14-alpha demethylase
Indexación: Scopus.Candida species cause an opportunistic yeast infection called Candidiasis, which is responsible for more than 50,000 deaths every year around the world. Effective treatments against candidiasis caused by non-albicans Candida species such as C. glabrata, C. parapsilosis, C. aureus, and C. krusei are limited due to severe resistance to conventional antifungal drugs. Natural drimane sesquiterpenoids have shown promising antifungal properties against Candida yeast and have emerged as valuable candidates for developing new candidiasis therapies. In this work, we isolated isodrimeninol (C1) from barks of Drimys winteri and used it as starting material for the hemi-synthesis of four sesquiterpenoids by oxidation with pyridinium chlorochromate (PCC). The structure of the products (C2, C3, C4, and C5) was elucidated by 1D and 2D NMR spectroscopy resulting in C4 being a novel compound. Antifungal activity assays against C. albicans, C. glabrata, and C. krusei revealed that C4 exhibited an increased activity (IC50 of 75 µg/mL) compared to C1 (IC50 of 125 µg/mL) in all yeast strains. The antifungal activity of C1 and C4 was rationalized in terms of their capability to inhibit lanosterol 14-alpha demethylase using molecular docking, molecular dynamics simulations, and MM/GBSA binding free energy calculations. In silico analysis revealed that C1 and C4 bind to the outermost region of the catalytic site of 14-alpha demethylase and block the entrance of lanosterol (LAN) to the catalytic pocket. Binding free energy estimates suggested that C4 forms a more stable complex with the enzyme than C1, in agreement with the experimental evidence. Based on this new approach it is possible to design new drimane-type sesquiterpenoids for the control of Candida species as inhibitors of 14-alpha demethylase. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.https://www.mdpi.com/2218-273X/10/8/110
The Alexander-Orbach conjecture holds in high dimensions
We examine the incipient infinite cluster (IIC) of critical percolation in
regimes where mean-field behavior has been established, namely when the
dimension d is large enough or when d>6 and the lattice is sufficiently spread
out. We find that random walk on the IIC exhibits anomalous diffusion with the
spectral dimension d_s=4/3, that is, p_t(x,x)= t^{-2/3+o(1)}. This establishes
a conjecture of Alexander and Orbach. En route we calculate the one-arm
exponent with respect to the intrinsic distance.Comment: 25 pages, 2 figures. To appear in Inventiones Mathematica
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