Credibility in the Regression case Revisited (A Late Tribute to Charles A. Hachemeister)

Many authors have observed that Hachemeisters Regression Model for Credibility - if applied to simple linear regression - leads to unsatisfactory credibility matrices: they typically ‘mix up' the regression parameters and in particular lead to regression lines that seem ‘out of range' compared with both individual and collective regression lines. We propose to amend these shortcomings by an appropriate definition of the regression parameters: -intercept -slope Contrary to standard practice the intercept should however not be defined as the value at time zero but as the value of the regression line at the barycenter of time. With these definitions regression parameters which are uncorrected in the collective can be estimated separately by standard one dimensional credibility techniques. A similar convenient reparametrization can also be achieved in the general regression case. The good choice for the regression parameters is such as to turn the design matrix into an array with orthogonal column

Signatures of Interstellar-Intracluster Medium Interactions: Spiral Galaxy Rotation Curves in Abell 2029

We investigate the rich cluster Abell 2029 (z~0.08) using optical imaging and long-slit spectral observations of 52 disk galaxies distributed throughout the cluster field. No strong emission-line galaxies are present within ~400 kpc of the cluster center, a region largely dominated by the similarly-shaped X-ray and low surface brightness optical envelopes centered on the giant cD galaxy. However, two-thirds of the galaxies observed outside the cluster core exhibit line emission. H-alpha rotation curves of 14 cluster members are used in conjunction with a deep I band image to study the environmental dependence of the Tully-Fisher relation. The Tully-Fisher zero-point of Abell 2029 matches that of clusters at lower redshifts, although we do observe a relatively larger scatter about the Tully-Fisher relation. We do not observe any systematic variation in the data with projected distance to the cluster center: we see no environmental dependence of Tully-Fisher residuals, R-I color, H-alpha equivalent width, and the shape and extent of the rotation curves.Comment: 22 pages, 6 figures, 3 tables; to appear in the August 2000 Astronomical Journa

One-Bead Microrheology with Rotating Particles

We lay the theoretical basis for one-bead microrheology with rotating particles, i.e, a method where colloids are used to probe the mechanical properties of viscoelastic media. Based on a two-fluid model, we calculate the compliance and discuss it for two cases. We first assume that the elastic and fluid component exhibit both stick boundary conditions at the particle surface. Then, the compliance fulfills a generalized Stokes law with a complex shear modulus whose validity is only limited by inertial effects, in contrast to translational motion. Secondly, we find that the validity of the Stokes regime is reduced when the elastic network is not coupled to the particleComment: 7 pages, 5 figures, submitted to Europhys. Let

Public Participation Organizations and Open Policy:A Constitutional Moment for British Democracy?

This article builds on work in Science and Technology Studies and cognate disciplines concerning the institutionalization of public engagement and participation practices. It describes and analyses ethnographic qualitative research into one “organization of participation,” the UK government–funded Sciencewise program. Sciencewise’s interactions with broader political developments are explored, including the emergence of “open policy” as a key policy object in the UK context. The article considers what the new imaginary of openness means for institutionalized forms of public participation in science policymaking, asking whether this is illustrative of a “constitutional moment” in relations between society and science policymaking

The Influence of Environment on the Star Formation Rates of Galaxies

We have used a sample of 15749 galaxies taken from the Las Campanas Redshift Survey to investigate the effects of environment on the rate of star formation (SFR) in galaxies. The size and homogeneity of this data set allows us to sample, for the first time, the entire range of galactic environment, from the voids to the clusters, in a uniform manner, thus, we could decouple the local galaxy density from the membership in associations. This decoupling is very crucial for constraining the physical processes responsible for the environmental dependencies of SFR. On the other hand, the use of an automatically-measured concentration index (C), rather than Hubble type, allows us to cleanly separate the morphological component from the SFR vs. environment relationship. We find that cluster galaxies exhibit lower SFR for the same C than field galaxies, while a further division of clusters by `richness' reveals a new possible excitation of `starbursts' in poor clusters. Meanwhile, a more general environmental investigation reveals that the SFR of a given C shows a continuous correlation with the local density. Interestingly, this trend is also observed both inside and outside of clusters, implying that physical processes responsible for this correlation might not be intrinsic to the cluster environment. On the other hand, galaxies with differing levels of SFR appear to respond differently to the local density. Low levels of SFR are more sensitive to environment inside than outside of clusters. In contrast, high levels of SFR, identified as ``starbursts'', are as sensitive to local density in the field as in clusters. We conclude that at least two separate processes are responsible for the environmental sensitivity of the SFR.Comment: 25 pages, 10 figures, submitted to Ap

An Untriggered Search for Optical Bursts

We present an untriggered search for optical bursts with the ROTSE-I telephoto array. Observations were taken which monitor an effective 256 square degree field continuously over 125 hours to m_{ROTSE}=15.7. The uniquely large field, moderate limiting magnitude and fast cadence of $\sim$10 minutes permits transient searches in a new region of sensitivity. Our search reveals no candidate events. To quantify this result, we simulate potential optical bursts with peak magnitude, m_{p}, at t=10 s, which fade as f=(\frac{t}{t_{0}}) ^{\alpha_{t}}, where \alpha_t < 0. Simple estimates based on observational evidence indicate that a search of this sensitivity begins to probe the possible region occupied by GRB orphan afterglows. Our observing protocol and image sensitivity result in a broad region of high detection efficiency for light curves to the bright and slowly varying side of a boundary running from [\alpha_{t},m_{p}]=[-2.0,6.0] to [-0.3,13.2]. Within this region, the integrated rate of brief optical bursts is less than 1.1\times 10^{-8} {\rm s}^{-1} {\rm deg}^{-2}. At $\sim$22 times the observed GRB rate from BATSE, this suggests a limit on \frac{\theta_{opt}}{\theta_{\gamma}}\lesssim 5 where \theta_{opt} and \theta_{\gamma} are the optical and gamma-ray collimation angles, respectively. Several effects might explain the absence of optical bursts, and a search of the kind described here but more sensitive by about 4 magnitudes should offer a more definitive probe.Comment: 8 pages, 6 figures, 1 tabl

Structure of Polyelectrolytes in Poor Solvent

We present simulations on charged polymers in poor solvent. First we investigate in detail the dilute concentration range with and without imposed extension constraints. The resulting necklace polymer conformations are analyzed in detail. We find strong fluctuations in the number of pearls and their sizes leading only to small signatures in the form factor and the force-extension relation. The scaling of the peak in the structure factor with the monomer density shows a pertinent different behavior from good solvent chains.Comment: 7 pages, 5 figures. submitted to EP

Credibility in the regression case revisited (A late tribute to Charles A

ABSTRACT Many authors have observed that Hachemelsters Regression Model for Credlbdlty -ff apphed to simple linear regresston-leads to unstmsfactory credibility matrices they typically &apos;max up&quot; the regressmn parameters and m particular lead to regression hnes that seem &apos;out of range&apos; compared with both mdwldual and collectwe regression hnes We propose to anaend these shortcomings by an appropriate deflnmon of the regression parameters: -intercept -slope Contrary to standard pracnce the intercept should however not be defined as the value at time zero but as the value of the regressmn hne at the barycenter of tmle. With these definmons regression parameters which are uncorrelated m the collective can be estimated separately by standard one d~menmonal credibility techmques A slmdar convement reparalnetnzat~on can also be achieved in the general regresstun case The good choice for the regression parameters Is such as to turn the design mamx into an array with orthogonal column,