51,688 research outputs found
Cross-Country Evidence on the Link between the Level of Infrastructure and Capital Inflows
This paper empirically investigates the relationship between public infrastructrue and international capital flows. Out of a sample of thirty countries a cross-sectional econometric model is constructed to estimate the effects. Different components of infrastructure variables are tested in relation to their impact on different kinds of external capital liabilities. The resuts suggest a positive relationship between the level of infrastructure and capital inflows. However, statistical significance cannot be established for all variables in question.
Many Particle Hardy-Inequalities
In this paper we prove three differenttypes of the so-called many-particle
Hardy inequalities. One of them is a "classical type" which is valid in any
dimesnion . The second type deals with two-dimensional magnetic
Dirichlet forms where every particle is supplied with a soplenoid. Finally we
show that Hardy inequalities for Fermions hold true in all dimensions.Comment: 20 page
Analyticity of the density of electronic wavefunctions
We prove that the electronic densities of atomic and molecular eigenfunctions
are real analytic in away from the nuclei.Comment: 19 page
A small population of hypothalamic neurons govern fertility: the critical role of VAX1 in GnRH neuron development and fertility maintenance.
Fertility depends on the correct maturation and function of approximately 800 gonadotropin-releasing hormone (GnRH) neurons in the brain. GnRH neurons are at the apex of the hypothalamic-pituitary-gonadal axis that regulates fertility. In adulthood, GnRH neurons are scattered throughout the anterior hypothalamic area and project to the median eminence, where GnRH is released into the portal vasculature to stimulate release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) from the pituitary. LH and FSH then regulate gonadal steroidogenesis and gametogenesis. Absence of GnRH neurons or inappropriate GnRH release leads to infertility. Despite the critical role of GnRH neurons in fertility, we still have a limited understanding of the genes responsible for proper GnRH neuron development and function in adulthood. GnRH neurons originate in the olfactory placode then migrate into the brain. Homeodomain transcription factors expressed within GnRH neurons or along their migratory path are candidate genes for inherited infertility. Using a combined in vitro and in vivo approach, we have identified Ventral Anterior Homeobox 1 (Vax1) as a novel homeodomain transcription factor responsible for GnRH neuron maturation and fertility. GnRH neuron counts in Vax1 knock-out embryos revealed Vax1 to be required for the presence of GnRH-expressing cells at embryonic day 17.5 (E17.5), but not at E13.5. To localize the effects of Vax1 on fertility, we generated Vax1flox mice and crossed them with Gnrhcre mice to specifically delete Vax1 within GnRH neurons. GnRH staining in Vax1flox/flox:GnRHcre mice show a total absence of GnRH expression in the adult. We performed lineage tracing in Vax1flox/flox:GnRHcre:RosaLacZ mice which proved GnRH neurons to be alive, but incapable of expressing GnRH. The absence of GnRH leads to delayed puberty, hypogonadism and complete infertility in both sexes. Finally, using the immortalized model GnRH neuron cell lines, GN11 and GT1-7, we show that VAX1 is a direct regulator of Gnrh1 transcription by binding key ATTA sites within the Gnrh1 promoter. This study identifies VAX1 as a key transcription factor regulating GnRH expression and establishes VAX1 as a novel candidate gene implicated in heritable infertility
Inelastic relaxation and noise temperature in S/N/S junctions
We studied electronic relaxation in long diffusive superconductor / normal
metal / superconductor (S/N/S) junctions by means of current noise and
transport measurements down to very low temperature (100mK). Samples with
normal metal lengths of 4, 10 and 60 micrometer have been investigated. In all
samples the shot noise increases very rapidly with the voltage. This is
interpreted in terms of enhanced heating of the electron gas confined between
the two S/N interfaces. Experimental results are analyzed quantitatively taking
into account electron-phonon interaction and heat transfer through the S/N
interfaces. Transport measurements reveal that in all samples the two S/N
interfaces are connected incoherently, as shown by the reentrance of the
resistance at low temperature. The complementarity of noise and transport
measurements allows us to show that the energy dependence of the reentrance at
low voltage is essentially due to the increasing effective temperature of the
quasiparticles in the normal metal.Comment: 5 pages, 4 figures, to be published in EPJ
Cepheid Variables in the Maser-Host Galaxy NGC 4258
We present results of a ground-based survey for Cepheid variables in NGC
4258. This galaxy plays a key role in the Extragalactic Distance Scale due to
its very precise and accurate distance determination via VLBI observations of
water masers. We imaged two fields within this galaxy using the Gemini North
telescope and GMOS, obtaining 16 epochs of data in the SDSS gri bands over 4
years. We carried out PSF photometry and detected 94 Cepheids with periods
between 7 and 127 days, as well as an additional 215 variables which may be
Cepheids or Population II pulsators. We used the Cepheid sample to test the
absolute calibration of theoretical gri Period-Luminosity relations and found
good agreement with the maser distance to this galaxy. The expected data
products from the Large Synoptic Survey Telescope (LSST) should enable Cepheid
searches out to at least 10 Mpc.Comment: Accepted for publication in the Astronomical Journa
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