Noise from spatial heterogeneity changes signal amplification magnitude and increases the variability in dose responses

In most molecular level simulations, spatial heterogeneity is neglected by the well-mixed condition assumption. However, the signals of biomolecular networks are affected from both time and space, which are responsible for diverse physiological responses. To account the spatial heterogeneity in the kinetic model, we consider multiple subvolumes of a reaction, introduce parameters representing transfer of ligands between the volumes, and reduce this to an error-term representing the difference between the well-mixed condition and the actual spatial factors. The error-term approach allows modelling of varying spatial heterogeneity without increasing computational burden exponentially. The effect of varying this term, d, between 0 (well-mixed) and 1 (no mixing) and of adding noise to the kinetic constants was then investigated and correlated with knowledge of the behaviour of real systems and situations where network models are inadequate. The spatial distribution effects on the epidermal growth factor receptor (EGFR) in human mammary epithelial tissue, which is involved in proliferation and tumorigenesis, are studied by introducing noisy kinetic constants. The steady-state of the dose response in the EGFR is strongly affected by spatial fluctuations. The ligand-bound receptor is reduced up to 50% from the response without spatial fluctuations and the variance of the steady-state is increased at least 2-fold from the one for no spatial fluctuations. On the other hand, dynamic properties such as the rising time and overshoot are less sensitive to spatial noise

Magnetization-controlled spin transport in DyAs/GaAs layers

Electrical transport properties of DyAs epitaxial layers grown on GaAs have been investigated at various temperatures and magnetic fields up to 12T. The measured longitudinal resistances show two distinct peaks at fields around 0.2 and 2.5T which are believed to be related to the strong spin-disorder scattering occurring at the phase transition boundaries induced by external magnetic field. An empirical magnetic phase diagram is deduced from the temperature dependent experiment, and the anisotropic transport properties are also presented for various magnetic field directions with respect to the current flow.Comment: 3 pages with 3 figure

Imprinted Networks as Chiral Pumps

We investigate the interaction between a chirally imprinted network and a solvent of chiral molecules. We find, a liquid crystalline polymer network is preferentially swollen by one component of a racemic solvent. This ability to separate is linked to the chiral order parameter of the network, and can be reversibly controlled via temperature or a mechanical deformation. It is maximal near the point at which the network loses its imprinted structure. One possible practical application of this effect would be a mechanical device for sorting mixed chiral molecules.Comment: 4 pages, 5 figure

Quantum Reciprocity Conjecture for the Non-Equilibrium Steady State

By considering the lack of history dependence in the non-equilibrium steady state of a quantum system we are led to conjecture that in such a system, there is a set of quantum mechanical observables whose retarded response functions are insensitive to the arrow of time, and which consequently satisfy a quantum analog of the Onsager reciprocity relations. Systems which satisfy this conjecture can be described by an effective Free energy functional. We demonstrate that the conjecture holds in a resonant level model of a multi-lead quantum dot.Comment: References revised to take account of related work on Onsager reciprocity in mesoscopics by Christen, and in hydrodynamics by Mclennan, Dufty and Rub

Deriving global structure of the Galactic Magnetic Field from Faraday Rotation Measures of extragalactic sources

We made use of the two latest sets of Rotational Measures (RMs) of extra-galactic radio sources, namely the NRAO VLA Sky Survey otation Measures Catalogue, and a compilation by Kronberg&Newton-McGee(2011), to infer the global structure of the Galactic Magnetic Field (GMF). We have checked that these two data sets are consistent with each other. Motivated by clear patterns in the observed distribution of RMs over the sky, we considered GMF models consisting of the two components: disk (spiral or ring) and halo. The parameters of these components were determined by fitting different model field geometries to the observed RMs. We found that the model consisting of a symmetric (with respect to the Galactic plane) spiral disk and anti-symmetric halo fits the data best, and reproduces the observed distribution of RMs over the sky very well. We confirm that ring disk models are disfavored. Our results favor small pitch angles around -5 degrees and an increased vertical scale of electron distribution, in agreement with some previous studies. Based on our fits, we identify two benchmark models suitable for studies of cosmic ray propagation, including the ultra-high energies.Comment: 15 pages, 14 figures, 4 tables misprints corrected, presentation improved generally matches the published versio

The Luminosity Function of high-redshift QSOs - A combined analysis of GOODS and SDSS

Aims: In this work the luminosity function of QSOs is measured in the redshift range 3.5<z<5.2 for the absolute magnitude interval -21<M_{145}<-28. The determination of the faint end of the luminosity function at these redshifts provides important constraints on models of joint evolution of galaxies and AGNs. Methods: We have defined suitable criteria to select faint QSOs in the GOODS fields, checking in detail their effectiveness and completeness. Spectroscopic follow-up of the resulting QSO candidates has been carried out. The confirmed sample of faint QSOs is compared with a brighter one derived from the SDSS. We have used a Monte-Carlo technique to estimate the properties of the luminosity function, checking various parameterizations for its shape and evolution. Results: Models based on Pure Density Evolution show better agreement with observation than models based on Pure Luminosity Evolution. However a different break magnitude with respect to z~2.1 is required at 3.5<z<5.2. Models with a steeper faint end score a higher probability. We do not find any evidence for a flattening of the bright end at redshift z>3.5. Conclusions: The estimated space density evolution of QSOs indicates a suppression of the formation and/or feeding of Supermassive Black Holes at these redshifts. The QSO contribution to the UV background is insufficient to ionize the IGM at 3.5<z<5.2.Comment: 17 pages, 13 ps figures, A&A accepted. Updated to journal versio

The influence of baryons on the mass distribution of dark matter halos

Using a set of high-resolution N-body/SPH cosmological simulations with identical initial conditions but run with different numerical setups, we investigate the influence of baryonic matter on the mass distribution of dark halos when radiative cooling is NOT included. We compare the concentration parameters of about 400 massive halos with virial mass from $10^{13}$ \Msun to $7.1 \times 10^{14}$ \Msun. We find that the concentration parameters for the total mass and dark matter distributions in non radiative simulations are on average larger by ~3% and 10% than those in a pure dark matter simulation. Our results indicate that the total mass density profile is little affected by a hot gas component in the simulations. After carefully excluding the effects of resolutions and spurious two-body heating between dark matter and gas particles, we conclude that the increase of the dark matter concentration parameters is due to interactions between baryons and dark matter. We demonstrate this with the aid of idealized simulations of two-body mergers. The results of individual halos simulated with different mass resolutions show that the gas profiles of densities, temperature and entropy are subjects of mass resolution of SPH particles. In particular, we find that in the inner parts of halos, as the SPH resolution increases the gas density becomes higher but both the entropy and temperature decrease.Comment: 8 pages, 6 figures, 1 table, ApJ in press (v652n1); updated to match with the being published versio

Origin of central abundances in the hot intra-cluster medium - I. Individual and average abundance ratios from XMM-Newton EPIC

The hot intra-cluster medium (ICM) is rich in metals, which are synthesized by supernovae (SNe) explosions and accumulate over time into the deep gravitational potential well of clusters of galaxies. Since most of the elements visible in X-rays are formed by type Ia (SNIa) and/or core-collapse (SNcc) supernovae, measuring their abundances gives us direct information on the nucleosynthesis products of billions of SNe since the epoch of the star formation peak (z ~ 2-3). In this study, we use the EPIC and RGS instruments onboard XMM-Newton to measure the abundances of 9 elements (O, Ne, Mg, Si, S, Ar, Ca, Fe and Ni) from a sample of 44 nearby cool-core galaxy clusters, groups, and elliptical galaxies. We find that the Fe abundance shows a large scatter (~20-40%) over the sample, within 0.2$r_{500}$ and, especially, 0.05$r_{500}$. Unlike the absolute Fe abundance, the abundance ratios (X/Fe) are quite uniform over the considered temperature range (~0.6-8 keV), and with a limited scatter. In addition to a unprecedented treatment of systematic uncertainties, we provide the most accurate abundance ratios measured so far in the ICM, including Cr/Fe and Mn/Fe that we firmly detect (>4{\sigma} with MOS and pn independently). We find that Cr/Fe, Mn/Fe and Ni/Fe, differ significantly from the proto-solar values. However, the large uncertainties in the proto-solar abundances prevent us from making a robust comparison between the local and the intra-cluster chemical enrichments. We also note that, interestingly, and despite the large net exposure time (~4.5 Ms) of our dataset, no line emission feature is seen around ~3.5 keV.Comment: 17 pages, 9 figures, accepted for publication in A&