The spectroscopic parameters of sodium cyanide, NaCN (X 1A'), revisited

The study of the rotational spectrum of NaCN (X $^1$A') has recently been extended in frequency and in quantum numbers. Difficulties have been encountered in fitting the transition frequencies within experimental uncertainties. Various trial fits traced the difficulties to the incomplete diagonalization of the Hamiltonian. Employing fewer spectroscopic parameters than before, the transition frequencies could be reproduced within experimental uncertainties on average. Predictions of $a$-type $R$-branch transitions with $K_a \le 7$ up to 570 GHz should be reliable to better than 1 MHz. In addition, modified spectroscopic parameters have been derived for the 13C isotopic species of NaCN.Comment: 5 pages, no figure, J. Mol. Spectrosc., appeared; CDMS links update

Functional linear regression via canonical analysis

We study regression models for the situation where both dependent and independent variables are square-integrable stochastic processes. Questions concerning the definition and existence of the corresponding functional linear regression models and some basic properties are explored for this situation. We derive a representation of the regression parameter function in terms of the canonical components of the processes involved. This representation establishes a connection between functional regression and functional canonical analysis and suggests alternative approaches for the implementation of functional linear regression analysis. A specific procedure for the estimation of the regression parameter function using canonical expansions is proposed and compared with an established functional principal component regression approach. As an example of an application, we present an analysis of mortality data for cohorts of medflies, obtained in experimental studies of aging and longevity.Comment: Published in at http://dx.doi.org/10.3150/09-BEJ228 the Bernoulli (http://isi.cbs.nl/bernoulli/) by the International Statistical Institute/Bernoulli Society (http://isi.cbs.nl/BS/bshome.htm

Robust Pilot Decontamination Based on Joint Angle and Power Domain Discrimination

We address the problem of noise and interference corrupted channel estimation in massive MIMO systems. Interference, which originates from pilot reuse (or contamination), can in principle be discriminated on the basis of the distributions of path angles and amplitudes. In this paper we propose novel robust channel estimation algorithms exploiting path diversity in both angle and power domains, relying on a suitable combination of the spatial filtering and amplitude based projection. The proposed approaches are able to cope with a wide range of system and topology scenarios, including those where, unlike in previous works, interference channel may overlap with desired channels in terms of multipath angles of arrival or exceed them in terms of received power. In particular we establish analytically the conditions under which the proposed channel estimator is fully decontaminated. Simulation results confirm the overall system gains when using the new methods.Comment: 14 pages, 5 figures, accepted for publication in IEEE Transactions on Signal Processin

Cycles in Mallows random permutations

We study cycle counts in permutations of (Formula presented.) drawn at random according to the Mallows distribution. Under this distribution, each permutation (Formula presented.) is selected with probability proportional to (Formula presented.), where (Formula presented.) is a parameter and (Formula presented.) denotes the number of inversions of (Formula presented.). For (Formula presented.) fixed, we study the vector (Formula presented.) where (Formula presented.) denotes the number of cycles of length (Formula presented.) in (Formula presented.) and (Formula presented.) is sampled according to the Mallows distribution. When (Formula presented.) the Mallows distribution simply samples a permutation of (Formula presented.) uniformly at random. A classical result going back to Kolchin and Goncharoff states that in this case, the vector of cycle counts tends in distribution to a vector of independent Poisson random variables, with means (Formula presented.). Here we show that if (Formula presented.) is fixed and (Formula presented.) then there are positive constants (Formula presented.) such that each (Formula presented.) has mean (Formula presented.) and the vector of cycle counts can be suitably rescaled to tend to a joint Gaussian distribution. Our results also show that when (Formula presented.) there is a striking difference between the behavior of the even and the odd cycles. The even cycle counts still have linear means, and when properly rescaled tend to a multivariate Gaussian distribution. For the odd cycle counts on the other hand, the limiting behavior depends on the parity of (Formula presented.) when (Formula presented.). Both (Formula presented.) and (Formula presented.) have discrete limiting distributions—they do not need to be renormalized—but the two limiting distributions are distinct for all (Formula presented.). We describe these limiting distributions in terms of Gnedin and Olshanski's bi-infinite extension of the Mallows model. We investigate these limiting distributions further, and study the behavior of the constants involved in the Gaussian limit laws. We for example show that as (Formula presented.) the expected number of 1-cycles tends to (Formula presented.) —which, curiously, differs from the value corresponding to (Formula presented.). In addition we exhibit an interesting “oscillating” behavior in the limiting probability measures for (Formula presented.) and (Formula presented.) odd versus (Formula presented.) even.</p

Steady State Convergence Acceleration of the Generalized Lattice Boltzmann Equation with Forcing Term through Preconditioning

Several applications exist in which lattice Boltzmann methods (LBM) are used to compute stationary states of fluid motions, particularly those driven or modulated by external forces. Standard LBM, being explicit time-marching in nature, requires a long time to attain steady state convergence, particularly at low Mach numbers due to the disparity in characteristic speeds of propagation of different quantities. In this paper, we present a preconditioned generalized lattice Boltzmann equation (GLBE) with forcing term to accelerate steady state convergence to flows driven by external forces. The use of multiple relaxation times in the GLBE allows enhancement of the numerical stability. Particular focus is given in preconditioning external forces, which can be spatially and temporally dependent. In particular, correct forms of moment-projections of source/forcing terms are derived such that they recover preconditioned Navier-Stokes equations with non-uniform external forces. As an illustration, we solve an extended system with a preconditioned lattice kinetic equation for magnetic induction field at low magnetic Prandtl numbers, which imposes Lorentz forces on the flow of conducting fluids. Computational studies, particularly in three-dimensions, for canonical problems show that the number of time steps needed to reach steady state is reduced by orders of magnitude with preconditioning. In addition, the preconditioning approach resulted in significantly improved stability characteristics when compared with the corresponding single relaxation time formulation.Comment: 47 pages, 21 figures, for publication in Journal of Computational Physic

Spectroscopic parameters for silacyclopropynylidene, SiC2_2, from extensive astronomical observations toward CW Leo (IRC +10216) with the Herschel satellite

A molecular line survey has been carried out toward the carbon-rich asymptotic giant branch star CW Leo employing the HIFI instrument on board of the Herschel satellite. Numerous features from 480 GHz to beyond 1100 GHz could be assigned unambiguously to the fairly floppy SiC$_2$ molecule. However, predictions from laboratory data exhibited large deviations from the observed frequencies even after some lower frequency data from this survey were incorporated into a fit. Therefore, we present a combined fit of all available laboratory data together with data from radio-astronomical observations.Comment: 7 pages, 1 figure, J. Mol. Spectrosc., appeared; CDMS links corrected (version 2; current version: 3; may be updated later this year

Toy amphiphiles on the computer: What can we learn from generic models?

Generic coarse-grained models are designed such that they are (i) simple and (ii) computationally efficient. They do not aim at representing particular materials, but classes of materials, hence they can offer insight into universal properties of these classes. Here we review generic models for amphiphilic molecules and discuss applications in studies of self-assembling nanostructures and the local structure of bilayer membranes, i.e. their phases and their interactions with nanosized inclusions. Special attention is given to the comparison of simulations with elastic continuum models, which are, in some sense, generic models on a higher coarse-graining level. In many cases, it is possible to bridge quantitatively between generic particle models and continuum models, hence multiscale modeling works on principle. On the other side, generic simulations can help to interpret experiments by providing information that is not accessible otherwise.Comment: Invited feature article, to appear in Macromolecular Rapid Communication

Inactivation of the tumor suppressor gene Apc synergizes with H. pylori to induce DNA damage in murine gastric stem and progenitor cells

Helicobacter pylori infection is a major risk factor for the development of gastric cancer. The bacteria reside in close proximity to gastric surface mucous as well as stem and progenitor cells. Here, we take advantage of wild-type and genetically engineered murine gastric organoids and organoid-derived monolayers to study the cellular targets of H. pylori-induced DNA damage and replication stress and to explore possible interactions with preexisting gastric cancer driver mutations. We find using alkaline comet assay, single-molecule DNA fiber assays, and immunofluorescence microscopy of DNA repair foci that H. pylori induces transcription-dependent DNA damage in actively replicating, Leucine-rich-repeat containing G-Protein-Coupled Receptor 5 (Lgr5)-positive antral stem and progenitor cells and their Troy-positive corpus counterparts, but not in other gastric epithelial lineages. Infection-dependent DNA damage is aggravated by Apc inactivation, but not by Trp53 or Smad4 loss, or Erbb2 overexpression. Our data suggest that H. pylori induces DNA damage in stem and progenitor cells, especially in settings of hyperproliferation due to constitutively active Wnt signaling

Generic two-phase coexistence in nonequilibrium systems

Gibbs' phase rule states that two-phase coexistence of a single-component system, characterized by an n-dimensional parameter-space, may occur in an n-1-dimensional region. For example, the two equilibrium phases of the Ising model coexist on a line in the temperature-magnetic-field phase diagram. Nonequilibrium systems may violate this rule and several models, where phase coexistence occurs over a finite (n-dimensional) region of the parameter space, have been reported. The first example of this behaviour was found in Toom's model [Toom,Geoff,GG], that exhibits generic bistability, i.e. two-phase coexistence over a finite region of its two-dimensional parameter space (see Section 1). In addition to its interest as a genuine nonequilibrium property, generic multistability, defined as a generalization of bistability, is both of practical and theoretical relevance. In particular, it has been used recently to argue that some complex structures appearing in nature could be truly stable rather than metastable (with important applications in theoretical biology), and as the theoretical basis for an error-correction method in computer science (see [GG,Gacs] for an illuminating and pedagogical discussion of these ideas).Comment: 7 pages, 6 figures, to appear in Eur. Phys. J. B, svjour.cls and svepj.clo neede

Dependence of the superconducting effective mass on doping in cuprates

Using a doping-determined multiband model spectrum of a "typical'' cuprate the effective mass of the paired carriers is calculated on the whole doping scale. Large $m_{ab}$ values quench rapidly with leaving the very underdoped region. Further slower diminishing of $m_{ab}$ reproduces the trend towards restoring the Fermi-liquid behaviour in cuprates with progressive doping. The interband superconducting condensate density ($n_s$) shows similar behaviour to the transition temperature and superconducting gaps. The $n_s(0)/m_{ab}$ ratio has an expressed maximum close to optimal doping as also the thermodynamic critical field. All the overlapping band components are intersected by the chemical potential at this. The pairing strength and the phase coherence develop simultaneously. In spite of its simplicity, the model describes the behaviour of various cuprate characteristics on the doping scale.Comment: 9 pages, 5 figure