On block updating in Markov random field models for disease mapping. (REVISED, May 2001)

Gaussian Markov random field (GMRF) models are commonly used to model spatial correlation in disease mapping applications. For Bayesian inference by MCMC, so far mainly single-site updating algorithms have been considered. However, convergence and mixing properties of such algorithms can be extremely bad due to strong dependencies of parameters in the posterior distribution. In this paper, we propose various block sampling algorithms in order to improve the MCMC performance. The methodology is rather general, allows for non-standard full conditionals, and can be applied in a modular fashion in a large number of different scenarios. For illustration we consider three different models: two formulations for spatial modelling of a single disease (with and without additional unstructured parameters respectively), and one formulation for the joint analysis of two diseases. We apply the proposed algorithms to two datasets known from the literature. The results indicate that the largest benefits are obtained if parameters and the corresponding hyperparameter are updated jointly in one large block. In certain situations, even updating of all or nearly all parameters in one block may be necessary. Implementation of such block algorithms is surprisingly easy using methods for fast sampling of Gaussian Markov random fields (Rue, 2000). By comparison, estimates of the relative risk and related quantities, such as the posterior probability of an exceedence relative risk, based on single-site updating, can be rather misleading, even for very long runs. Our results may have wider relevance for efficient MCMC simulation in hierarchical models with Markov random field components

Basic Metals. XIV. Synthesis and Crystal Structure of C5_5H5_5(PMe3_3)CoS5_5 : A New Metallapentathia Heterocycle

Der Zweikernkomplex C$_5$H$_5$(PMe$_3$)Co($\mu$-CO)$_2$Mn(CO)C$_5$H$_4$Me (8) reagiert mit stöchiometrischen Mengen S$_8$ in praktisch quantitativer Ausbeute zu C$_5$H$_5$(PMe$_3$)CoS$_5$ (4). Der Koba.ltapentathia-Heterocyclus 4 ist ebenfalls aus C$_5$H$_5$(PMe$_3$)Co(h$^2$-CS$_2$) (5) und S$_8$ zugänglich. 4 kristallisiert monoklin mit den Gitterkonstanten a = 8,467(3) A, b = 12,128(4) A, c = 14,210(4) A und $\beta$ = 102,20(2)°_ Die Sesselform des sechsgliedrigen CoS$_5$-Rings entspricht derjenigen in den bekannten Verbindungen (C$_5$H$_5$)$_2$TiS$_5$ und (C$_5$H$_5$)$_2$VS$_5$ , wobei in 4 der Cyclopentadienylligand die axiale und die Trimethylphosphingruppe die ä.quatoriale Position einnehmen.The dinuclear complex C$_5$H$_5$(PMe$_3$)Co($\mu$-CO)$_2$Mn(CO)C$_5$H$_4$Me (8) reaots with stoichiometric amounts of S$_8$ to form C$_5$H$_5$(PMe$_3$)CoS$_5$ (4) in practica.lly quantitative yields. The cobalt. apentathia heterocycle 4 is a.lso obtained by the reaction of C$_5$H$_5$(PMe$_3$)Co(h$^2$-CS$_2$) (5) with S$_8$, Cry. stals of 4 are monoclinic with a = 8.467(3) A, b = 12.128(4) A, c = 14.210(4) A and $\beta$ = 102.20(2)°. The chair form of the six·membered CoS$_5$ ringcorresponds to that of the compounds (C$_5$H$_5$)$_2$TiS$_5$ and (C$_5$H$_5$)$_2$VS$_5$ In 4, the cyclopentadienyl ligand occupies the axial and the trimethylphosphine group the equatorial position

Supernova explosions and the birth of neutron stars

We report here on recent progress in understanding the birth conditions of neutron stars and the way how supernovae explode. More sophisticated numerical models have led to the discovery of new phenomena in the supernova core, for example a generic hydrodynamic instability of the stagnant supernova shock against low-mode nonradial deformation and the excitation of gravity-wave activity in the surface and core of the nascent neutron star. Both can have supportive or decisive influence on the inauguration of the explosion, the former by improving the conditions for energy deposition by neutrino heating in the postshock gas, the latter by supplying the developing blast with a flux of acoustic power that adds to the energy transfer by neutrinos. While recent two-dimensional models suggest that the neutrino-driven mechanism may be viable for stars from about 8 solar masses to at least 15 solar masses, acoustic energy input has been advocated as an alternative if neutrino heating fails. Magnetohydrodynamic effects constitute another way to trigger explosions in connection with the collapse of sufficiently rapidly rotating stellar cores, perhaps linked to the birth of magnetars. The global explosion asymmetries seen in the recent simulations offer an explanation of even the highest measured kick velocities of young neutron stars.Comment: 10 pages, 8 figures, 19 ps files; to be published in Proc. of Conf. "40 Years of Pulsars: Millisecond Pulsars, Magnetars, and More", August 12-17, 2007, McGill Univ., Montreal, Canada; high-resolution images can be obtained upon request; incorrect panel in fig.8 replace

A beta-herpesvirus with fluorescent capsids to study transport in living cells.

Fluorescent tagging of viral particles by genetic means enables the study of virus dynamics in living cells. However, the study of beta-herpesvirus entry and morphogenesis by this method is currently limited. This is due to the lack of replication competent, capsid-tagged fluorescent viruses. Here, we report on viable recombinant MCMVs carrying ectopic insertions of the small capsid protein (SCP) fused to fluorescent proteins (FPs). The FPs were inserted into an internal position which allowed the production of viable, fluorescently labeled cytomegaloviruses, which replicated with wild type kinetics in cell culture. Fluorescent particles were readily detectable by several methods. Moreover, in a spread assay, labeled capsids accumulated around the nucleus of the newly infected cells without any detectable viral gene expression suggesting normal entry and particle trafficking. These recombinants were used to record particle dynamics by live-cell microscopy during MCMV egress with high spatial as well as temporal resolution. From the resulting tracks we obtained not only mean track velocities but also their mean square displacements and diffusion coefficients. With this key information, we were able to describe particle behavior at high detail and discriminate between particle tracks exhibiting directed movement and tracks in which particles exhibited free or anomalous diffusion

Cloaking and imaging at the same time

In this letter, we propose a conceptual device to perform subwavelength imaging with positive refraction. The key to this proposal is that a drain is no longer a must for some cases. What's more, this device is an isotropic omnidirectional cloak with a perfect electric conductor hiding region and shows versatile illusion optical effects. Numerical simulations are performed to verify the functionalities.Comment: 15 pages, 4 figure

2-Amino-4-aryl-5-oxo-4,5-dihydropyrano[3,2-c]chromene-3-carbonitriles with Microtubule-Disruptive, Centrosome-Declustering, and Antiangiogenic Effects in vitro and in vivo

A series of fifteen 2‐amino‐4‐aryl‐5‐oxo‐4,5‐dihydropyrano[3,2‐c]chromene‐3‐carbonitriles (1 a–o) were synthesized via a three‐component reaction of 4‐hydroxycoumarin, malononitrile, and diversely substituted benzaldehydes or pyridine carbaldehydes. The compounds were tested for anticancer activities against a panel of eight human tumor cell lines. A few derivatives with high antiproliferative activities and different cancer cell specificity were identified and investigated for their modes of action. They led to microtubule disruption, centrosome de‐clustering and G2/M cell cycle arrest in 518 A2 melanoma cells. They also showed anti‐angiogenic effects in vitro and in vivo