3,543 research outputs found
Ovarian reserve and anti-Mullerian hormone (AMH) in mothers of dizygotic twins
This study aimed to explore if natural dizygotic (DZ) twinning is associated with earlier menopause and lower anti-Mullerian hormone (AMH) values. We investigated if advanced biological reproductive aging, which can be responsible for the multiple follicle growth in familial twinning, is similar to mechanisms that occur in normal ovarian aging, reflected by earlier menopause in mothers of DZ twins and lower levels of AMH. A total of 16 mothers of DZ twins enrolled with the Netherlands Twin Register (average age at first assessment: 35.9 +/- 3.0 years) and 14 control mothers (35.1 +/- 3 years) took part in a prospective study. Fifteen years after entry into the study, which included follicle-stimulating hormone (FSH) assessment, AMH was measured in stored serum samples and menopause status was evaluated. Average AMH levels were not significantly different between DZ twin mothers and controls (2.1 +/- 2.4 mu g/L vs. 1.9 +/- 1.9 mu g/L). Among the 16 mothers of twins, 7 had an elevated (FSH) value over 10 U/L at first assessment. Their AMH levels were lower than the nine twin mothers with normal FSH values: 0.6 +/- 0.4 versus 3.4 +/- 2.6 mu g/L (p = .01). Of the mothers of twins, eight mothers had entered menopause at the second assessment compared with only one control mother (p = .07). Thus, slightly more DZ mothers were in menopause than the control mothers, although this difference was not significant. The subgroup of DZ twin mothers who had an increased FSH concentration 15 years ago had a limited ovarian reserve as reflected by lower AMH levels. These data indicate that advanced ovarian aging can be a feature in familial DZ twinning, particularly with elevated early follicular phase FSH
A large-deviations principle for all the cluster sizes of a sparse Erdős–Rényi graph
Let (Formula presented.) be the Erdős–Rényi graph with connection probability (Formula presented.) as N → ∞ for a fixed t ∈ (0, ∞). We derive a large-deviations principle for the empirical measure of the sizes of all the connected components of (Formula presented.), registered according to microscopic sizes (i.e., of finite order), macroscopic ones (i.e., of order N), and mesoscopic ones (everything in between). The rate function explicitly describes the microscopic and macroscopic components and the fraction of vertices in components of mesoscopic sizes. Moreover, it clearly captures the well known phase transition at t = 1 as part of a comprehensive picture. The proofs rely on elementary combinatorics and on known estimates and asymptotics for the probability that subgraphs are connected. We also draw conclusions for the strongly related model of the multiplicative coalescent, the Marcus–Lushnikov coagulation model with monodisperse initial condition, and its gelation phase transition
Conductance plateau in quantum spin transport through an interacting quantum dot
Quantum spin transport is studied in an interacting quantum dot. It is found
that a conductance "plateau" emerges in the non-linear charge conductance by a
spin bias in the Kondo regime. The conductance plateau, as a complementary to
the Kondo peak, originates from the strong electron correlation and exchange
processes in the quantum dot, and can be regarded as one of the characteristics
in quantum spin transport.Comment: 5 pages, 5 figure
Correlation induced switching of local spatial charge distribution in two-level system
We present theoretical investigation of spatial charge distribution in the
two-level system with strong Coulomb correlations by means of Heisenberg
equations analysis for localized states total electron filling numbers taking
into account pair correlations of local electron density. It was found that
tunneling current through nanometer scale structure with strongly coupled
localized states causes Coulomb correlations induced spatial redistribution of
localized charges. Conditions for inverse occupation of two-level system in
particular range of applied bias caused by Coulomb correlations have been
revealed. We also discuss possibility of charge manipulation in the proposed
system.Comment: 6 pages, 4 figures Submitted to JETP Letter
Computational and experimental analysis identified 6-diazo-5-oxonorleucine as a potential agent for treating infection by Plasmodium falciparum
Plasmodium falciparum (PF) is the most severe malaria parasite. It is developing resistance quickly to
existing drugs making it indispensable to discover new drugs. Effective drugs have been discovered targeting
metabolic enzymes of the parasite. In order to predict new drug targets, computational methods
can be used employing database information of metabolism. Using this data, we performed recently a
computational network analysis of metabolism of PF. We analyzed the topology of the network to find
reactions which are sensitive against perturbations, i.e., when a single enzyme is blocked by drugs. We
now used a refined network comprising also the host enzymes which led to a refined set of the five
targets glutamyl–tRNA (gln) amidotransferase, hydroxyethylthiazole kinase, deoxyribose–phophate
aldolase, pseudouridylate synthase, and deoxyhypusine synthase. It was shown elsewhere that glutamyl–
tRNA (gln) amidotransferase of other microorganisms can be inhibited by 6-diazo-5-oxonorleucine.
Performing a half maximal inhibitory concentration (IC50) assay, we showed, that 6-diazo-5-oxonorleucine
is also severely affecting viability of PF in blood plasma of the human host. We confirmed this by an
in vivo study observing Plasmodium berghei infected mice
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The need for a marker predicting benefit following cardiovascular disease risk reduction treatment
Developing a robust method to study characteristics of vascular flow using ultrasound may be useful to assess endothelial function and vasodilatation. There are four stages in this proposal. 1.The first stage is to standardise and validate the methodology to enable computational risk flow data and other flow characteristics to be used clinically. (Current Study). Further development of fluid modelling methods will enable particulate haemodynamics to be investigated, and incorporate detailed endothelial structure together with cellular pathways. 2. This should be followed up by studies in different patient groups investigating the association between the derived values and estimated risk (using other methods such as Framingham risk score). 3. Then, associated with underlying cardiovascular risk, prospective studies would be made to establish whether computational flow dynamic data can predict outcome. If successful it could prove to be a very useful marker of benefit following treatment in a clinical setting
Synchronized dynamics of cortical neurons with time-delay feedback
The dynamics of three mutually coupled cortical neurons with time delays in
the coupling are explored numerically and analytically. The neurons are coupled
in a line, with the middle neuron sending a somewhat stronger projection to the
outer neurons than the feedback it receives, to model for instance the relay of
a signal from primary to higher cortical areas. For a given coupling
architecture, the delays introduce correlations in the time series at the
time-scale of the delay. It was found that the middle neuron leads the outer
ones by the delay time, while the outer neurons are synchronized with zero lag
times. Synchronization is found to be highly dependent on the synaptic time
constant, with faster synapses increasing both the degree of synchronization
and the firing rate. Analysis shows that presynaptic input during the
interspike interval stabilizes the synchronous state, even for arbitrarily weak
coupling, and independent of the initial phase. The finding may be of
significance to synchronization of large groups of cells in the cortex that are
spatially distanced from each other.Comment: 21 pages, 11 figure
Origin of the quasi-quantized Hall effect in ZrTe5
The quantum Hall effect (QHE) is traditionally considered a purely
two-dimensional (2D) phenomenon. Recently, a three-dimensional (3D) version of
the QHE has been reported in the Dirac semimetal ZrTe5. It was proposed to
arise from a magnetic-field-driven Fermi surface instability, transforming the
original 3D electron system into a stack of 2D sheets. Here, we report
thermodynamic, thermoelectric and charge transport measurements on ZrTe5 in the
quantum Hall regime. The measured thermodynamic properties: magnetization and
ultrasound propagation, show no signatures of a Fermi surface instability,
consistent with in-field single crystal X-ray diffraction. Instead, a direct
comparison of the experimental data with linear response calculations based on
an effective 3D Dirac Hamiltonian suggests that the quasi-quantization of the
observed Hall response is an intrinsic property of the 3D electronic structure.
Our findings render the Hall effect in ZrTe5 a truly 3D counterpart of the QHE
in 2D systems
INDEPENDENT DISCOVERIES IN GRAPH THEORY *
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72829/1/j.1749-6632.1979.tb17761.x.pd
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