Reconstructing cosmological density and velocity fields

I present a new quasi-linear method for reconstructing cosmological density and velocity fields from all-sky redshift surveys. The method is used to reconstruct the velocity field, dipole, bulk flows and distortion parameter (ß = Ω⁰.⁶/b from the PSCz survey.Analytic expressions for the cosmic variance and shot noise uncertainties on the reconstructed velocity field are presented. It is found that the uncertainties are reduced if reconstruction is carried out in the Local Group frame. The uncertainty on the dipole is also found.A generalized version of the Path Interchange Zel'dovich Approximation (PIZA ) is presented. PIZA is a simple Lagrangian reconstruction method based on the Zel’dovich Approximation and the Least Action Principle, which reconstructs cosmological fields given the present day real space positions of galaxies. The generalizations take account of redshift space distortions, incomplete sky coverage, and the selection function. The method can be used to estimate ß from radial velocities, bulk flows and the dipole.Generalized PIZA has been tested using a set of PSCz-like simulations. The reconstructed radial peculiar velocity field is com pared with that o f the simulation and that reconstructed by linear theory.The generalized PIZA is applied to the IRAS PSCz Survey. The dipole, bulk velocities and peculiar velocity field, and the derived value of ß are presented. The Local Group is found to have an average displacement of 1225kms⁻¹ in the direction of (l,b) = (264°,42°). From this it is found that (ß = 0.512 ± 0.141

Assessing The Use Of Sedation Prior To Carbon Dioxide Euthanasia Of Mice

Carbon dioxide (CO2) administration is the most commonly used method of euthanasia of mice in research, yet questions remain regarding whether CO2 euthanasia is associated with pain and stress. This study aims to characterize the level of pain and stress induced in mice during CO2 euthanasia, and to determine if premedication with acepromazine or midazolam, or anesthetic induction with isoflurane, alters these levels during CO2 euthanasia. Mice were assigned to one of six euthanasia groups: (control) CO2 only at a flow rate that displaces 20% of the cage volume per minute (V/min); premedication with acepromazine (5 mg/kg), midazolam (5 mg/kg), or saline followed by 20% V/min CO2; induction with 5% isoflurane followed by > 100% V/min CO2; or 100% V/min CO2 only. Behavioral measures of stress included ultrasonic sound recordings and analysis of video recordings, by an observer blinded to group identity, to assess increased respiratory effort, increased activity, and pain. Physiological parameters of stress were assessed by measuring plasma adrenocorticotropic hormone (ACTH) and corticosterone levels immediately post-euthanasia. Finally, we assessed the acute neuromolecular marker of pain and stress, c-fos, by quantitative PCR. The use of premedication with acepromazine or midazolam did not significantly alter behavioral indicators of stress but did significantly induce a higher level of c-fos expression in the brain compared to 20% V/min CO2 alone. Furthermore, the use of isoflurane induction prior to CO2 euthanasia significantly increased stress in the mice based on both behavioral and neuromolecular indicators. These data strongly indicate that in comparison to the other modalities analyzed in this study, 20% V/min CO2 is a humane, rapid euthanasia method that is not associated with significant pain or stress in mice

What works? A comparative evaluation of the roles of student adviser and personal tutor in relation to undergraduate student retention

Anglia Ruskin University (ARU) is a large HEI with (at the start of our study) about 24,000 students and two main campuses in Cambridge and Chelmsford, as well as a smaller campus in Peterborough and Fulbourn. It has a student population characterised by large numbers of mature, part-time students, many with non-traditional backgrounds. Over recent years, we have adjusted our regional focus away from having many small FE partners to fewer but larger joint venture (JV) relationships. Consistency of higher education (HE) experience across all of Anglia Ruskin, including the JV partners, is a key aspiration for us

Transparent soil for imaging the rhizosphere

Understanding of soil processes is essential for addressing the global issues of food security, disease transmission and climate change. However, techniques for observing soil biology are lacking. We present a heterogeneous, porous, transparent substrate for in situ 3D imaging of living plants and root-associated microorganisms using particles of the transparent polymer, Nafion, and a solution with matching optical properties. Minerals and fluorescent dyes were adsorbed onto the Nafion particles for nutrient supply and imaging of pore size and geometry. Plant growth in transparent soil was similar to that in soil. We imaged colonization of lettuce roots by the human bacterial pathogen Escherichia coli O157:H7 showing micro-colony development. Micro-colonies may contribute to bacterial survival in soil. Transparent soil has applications in root biology, crop genetics and soil microbiology

Implicit attitudes towards smoking predict long-term relapse in abstinent smokers

It has previously been argued that implicit attitudes toward substance-related cues drive addictive behavior. Nevertheless, it remains an open question whether behavioral markers of implicit attitude activation can be used to predict long-term relapse. The main objective of this study was to examine the relationship between implicit attitudes toward smoking-related cues and long-term relapse in abstaining smokers. Implicit attitudes toward smoking-related cues were assessed by means of the Implicit Association Test (IAT) and the evaluative priming task (EPT). Both measures were completed by a group of smokers who volunteered to quit smoking (patient group) and a group of nonsmokers (control group). Participants in the patient group completed these measures twice: once prior to smoking cessation and once after smoking cessation. Relapse was assessed by means of short telephone survey, 6 months after completion of the second test session. EPT scores obtained prior to smoking cessation were related to long-term relapse and correlated with self-reported nicotine dependence as well as daily cigarette consumption. In contrast, none of the behavioral outcome measures were found to correlate with the IAT scores. These findings corroborate the idea that implicit attitudes toward substance-related cues are critically involved in long-term relapse. A potential explanation for the divergent findings obtained with the IAT and EPT is provided

The Inverse Redshift-Space Operator: Reconstructing Cosmological Density and Velocity Fields

We present the linear inverse redshift space operator which maps the galaxy density field derived from redshift surveys from redshift space to real space. Expressions are presented for observers in both the CMBR and Local Group rest frames. We show how these results can be generalised to flux--limited galaxy redshift surveys. These results allow the straightforward reconstruction of real space density and velocity fields without resort to iterative or numerically intensive inverse methods. As a corollary to the inversion of the density in the Local Group rest frame we present an expression for estimating the real space velocity dipole from redshift space, allowing one to estimate the Local Group dipole without full reconstruction of the redshift survey. We test these results on some simple models and find the reconstruction is very accurate. A new spherical harmonic representation of the redshift distortion and its inverse is developed, which simplifies the reconstruction and allows analytic calculation of the properties of the reconstructed redshift survey. We use this representation to analyse the uncertainties in the reconstruction of the density and velocity fields from redshift space, due to only a finite volume being available. Both sampling and shot-noise variance terms are derived and we discuss the limits of reconstruction analysis. We compare the reconstructed velocity field with the true velocity field and show that reconstruction in the Local Group rest frame is preferable, since this eliminates the major source of uncertainty from the dipole mode. These results can be used to transform redshift surveys to real space and may be used as part of a full likelihood analysis to extract cosmological parameters.Comment: 13 pages (Latex), 6 postscript figures included, accepted for publication in MNRA