Evaluation of coated QCM for the detection of atmospheric ozone

A coated acoustic wave sensor has been developed to selectively detect atmospheric ozone. The selective detection has been assessed using a variety of coatings: beeswax, gallic acid, indigo carmine, polybutadiene, potassium iodide and sodium nitrite. Polybutadiene was the most sensitive with a limit of detection of 55 ppb. The sensitivity was improved by operating at higher harmonics and was shown to increase linearly with harmonic up to the 11th harmonic. This novel work shows that ozone detection can be improved by operating at the crystals' harmonic frequencies and in conjunction with a suitable flow rate, a potentially highly sensitive and fast response sensor can be created based on acoustic wave technolog

Forecasting Cosmological Constraints from Redshift Surveys

Observations of redshift-space distortions in spectroscopic galaxy surveys offer an attractive method for observing the build-up of cosmological structure, which depends both on the expansion rate of the Universe and our theory of gravity. In this paper we present a formalism for forecasting the constraints on the growth of structure which would arise in an idealized survey. This Fisher matrix based formalism can be used to study the power and aid in the design of future surveys.Comment: 7 pages, 5 figures, minor revisions to match version accepted by MNRA

Increased abundance of frost mRNA during recovery from cold stress is not essential for cold tolerance in adult Drosophila melanogaster.

Frost (Fst) is a candidate gene associated with the response to cold in Drosophila melanogaster because Fst mRNA accumulation increases during recovery from low temperature exposure. We investigated the contribution of Fst expression to chill-coma recovery time, acute cold tolerance and rapid cold hardening (RCH) in adult D. melanogaster by knocking down Fst mRNA expression using GAL4/UAS-mediated RNA interference. In this experiment, four UAS-Fst and one tubulin-GAL4 lines were used. We predicted that if Fst is essential for cold tolerance phenotypes, flies with low Fst mRNA levels should be less cold tolerant than flies with normal levels of cold-induced Fst mRNA. Cold-induced Fst abundance and recovery time from chill-coma were not negatively correlated in male or female flies. Survival of 2 h exposures to sub-zero temperatures in Fst knockdown lines was not lower than that in a control line. Moreover, a low temperature pretreatment increased survival of severe cold exposure in flies regardless of Fst abundance level during recovery from cold stress, suggesting that Fst expression is not essential for RCH. Thus, cold-induced Fst accumulation is not essential for cold tolerance measured as chill-coma recovery time, survival to acute cold stress and RCH response in adult D. melanogaster

Covariance of cross-correlations: towards efficient measures for large-scale structure

We study the covariance of the cross-power spectrum of different tracers for the large-scale structure. We develop the counts-in-cells framework for the multi-tracer approach, and use this to derive expressions for the full non-Gaussian covariance matrix. We show, that for the usual auto-power statistic, besides the off-diagonal covariance generated through gravitational mode-coupling, the discreteness of the tracers and their associated sampling distribution can generate strong off-diagonal covariance, and that this becomes the dominant source of covariance as k>>k_f=2 pi/L. On comparison with the derived expressions for the cross-power covariance, we show that the off-diagonal terms can be suppressed, if one cross-correlates a high tracer-density sample with a low one. Taking the effective estimator efficiency to be proportional to the signal-to-noise ratio (SN), we show that, to probe clustering as a function of physical properties of the sample, i.e. cluster mass or galaxy luminosity, then the cross-power approach can out perform the auto-power one by factors of a few. We confront the theory with measurements of the mass-mass, halo-mass, and halo-halo power spectra from a large ensemble of N-body simulations. We show that there is a significant SN advantage to be gained from using the cross-power approach when studying the bias of rare haloes. The analysis is repeated in configuration space and again SN improvement is found. We estimate the covariance matrix for these samples, and find strong off-diagonal contributions. The covariance depends on halo mass, with higher mass samples having stronger covariance. In agreement with theory, we show that the covariance is suppressed for the cross-power. This work points the way towards improved estimators for clustering studies.Comment: Several significant improvements to the earlier version: for instance it is shown more clearly how shot noise corrections may generate off-diagonal covariance in the power spectrum. Original version submitted to MNRAS on 18th September 2008. This version 18 pages, 7 figure

Baryon oscillations in galaxy and matter power-spectrum covariance matrices

We investigate large-amplitude baryon acoustic oscillations (BAO's) in off-diagonal entries of cosmological power-spectrum covariance matrices. These covariance-matrix BAO's describe the increased attenuation of power-spectrum BAO's caused by upward fluctuations in large-scale power. We derive an analytic approximation to covariance-matrix entries in the BAO regime, and check the analytical predictions using N-body simulations. These BAO's look much stronger than the BAO's in the power spectrum, but seem detectable only at about a one-sigma level in gigaparsec-scale galaxy surveys. In estimating cosmological parameters using matter or galaxy power spectra, including the covariance-matrix BAO's can have a several-percent effect on error-bar widths for some parameters directly related to the BAO's, such as the baryon fraction. Also, we find that including the numerous galaxies in small haloes in a survey can reduce error bars in these cosmological parameters more than the simple reduction in shot noise might suggest.Comment: 11 pages, 11 figures, accepted to MNRAS. Minor changes to match accepted version. CosmoPy (Cosmological Python) code available at http://ifa.hawaii.edu/cosmopy

A novel screen for genes associated with pheromone-induced sterility

For honey bee and other social insect colonies the 'queen substance' regulates colony reproduction rendering workers functionally sterile. The evolution of worker reproductive altruism is explained by inclusive fitness theory, but little is known of the genes involved or how they regulate the phenotypic expression of altruism. We previously showed that application of honeybee queen pheromone to virgin fruit flies suppresses fecundity. Here we exploit this finding to identify genes associated with the perception of an ovary-inhibiting social pheromone. Mutational and RNAi approaches in Drosophila reveal that the olfactory co-factor Orco together with receptors Or49b, Or56a and Or98a are potentially involved in the perception of queen pheromone and the suppression of fecundity. One of these, Or98a, is known to mediate female fly mating behaviour, and its predicted ligand is structurally similar to a methyl component of the queen pheromone. Our novel approach to finding genes associated with pheromone-induced sterility implies conserved reproductive regulation between social and pre-social orders, and further helps to identify candidate orthologues from the pheromone-responsive pathway that may regulate honeybee worker sterility

Markov-chain reconstruction of the 2dF Galaxy Redshift Survey real-space power spectrum

The real-space power spectrum of L* galaxies measured from the 2dF Galaxy Redshift Survey (2dFGRS) is presented. Markov-Chain Monte-Carlo (MCMC) sampling was used to fit radial and angular modes resulting from a Spherical Harmonics decomposition of the 2dFGRS overdensity field (described in Percival et al. 2004) with 16 real-space power spectrum values and linear redshift-space distortion parameter \beta(L*,0). The recovered marginalised band-powers are compared to previous estimates of galaxy power spectra. Additionally, we provide a simple model for the 17 dimensional likelihood hyper-surface in order to allow the likelihood to be quickly estimated given a set of model band-powers and \beta(L*,0). The likelihood surface is not well approximated by a multi-variate Gaussian distribution with model-independent covariances. Instead, a model is presented in which the distribution of each band-power has a Gaussian distribution in a combination of the band-power and its logarithm. The relative contribution of each component was determined by fitting the MCMC output. Using these distributions, we demonstrate how the likelihood of a given cosmological model can be quickly and accurately estimated, and use a simple set of models to compare estimated likelihoods with likelihoods calculated using the full Spherical Harmonics procedure. All of the data are made publically available (from http://www.roe.ac.uk/~wjp/, enabling the Spherical Harmonics decomposition of the 2dFGRS of Percival et al. (2004) to be easily used as a cosmological constraint.Comment: 9 pages, 5 figures, MNRAS accepte

Neutrino masses from clustering of red and blue galaxies: a test of astrophysical uncertainties

Combining measurements of the galaxy power spectrum and the cosmic microwave background (CMB) is a powerful means of constraining the summed mass of neutrino species sum(m_nu), but is subject to systematic uncertainties due to non-linear structure formation, redshift-space distortions and galaxy bias. We empirically test the robustness of neutrino mass results to these effects by separately analyzing power spectra of red and blue galaxies from the Sloan Digital Sky Survey (SDSS-II) Data Release 7 (DR7), combined with the CMB five-year Wilkinson Microwave Anisotropy Probe (WMAP5) data. We consider fitting for a range of maximum wavenumber k using twelve different galaxy bias models. For example, using a new model based on perturbation theory and including redshift space distortions (Saito et al. 2009), the all-galaxy power spectrum combined with WMAP5 for a wavenumber range of k<0.2 Mpc/h yields 95% CL sum(m_nu)<0.46 eV. The red and blue galaxy power spectra give 0.41 and 0.63 eV respectively for this model. Using mock catalogues, we find the expected difference in these limits assuming a true neutrino mass of zero is 0.10 + or - 0.14 eV. Thus the difference of 0.22 eV between upper limits on neutrino mass for red and blue galaxies is approximately 1 sigma from the expected value. We find similar results for the other models and k ranges tested. This indicates good agreement for current data but hints at possible issues for next-generation surveys. Being able to perform such systematic tests is advantageous, and future surveys would benefit by including broad galaxy populations and luminosities that enable such a decomposition.Comment: 15 pages, 6 figures, matches version published in MNRA

In vitro studies of the adhesive interactions of neutrophil granlocytes

The adhesion of rabbit neutrophil granulocytes to cultured pig atortic endothelial cells, to serum coated glass and to each other has been studied under a variety of conditions using adhesion-to-substratum and aggregation assays. Under standard conditions, in the presence of balanced salt solution (BSS) and serum alone a number of variables were found to alter the level of adhesion to serum coated glass and endothelium. Changes in time of incubation, cell number, serum concentration and assay volume all altered the observed level of adhesion. Adhesion to serum coated glass was higher than to endothelial cells. The inflammatory mediators histamine and 5-hydroxytryptamine (5-HT) had slight inhibitory effects while bradykinin had no significant effect on adhesion. Anti-inflammatory drugs were examined. Aspirin, hydrocortisone and colchicine all reduced adhesion. Prednisolone, indamethacin and amino-n-caproic acid had no significant effect on adhesion. A range of miscellaneous agents were tested for effects on adhesion. These were aminophylline, formalin, heparin and several sugars and had slight, if any, inhibitory effects on adhesion. A range of chemotactic factors were shown to have diverse effects on adhesion. At chemotactically optimal concentrations, s-casein casein, alkali-denatured human serum albumin (HSA) and several synthetic n-formyl-di-and tri-peptides reduced neutrophil adhesion after short (≤30 min.) periods of incubation. Detailed study of one such peptide, n-formyl methionyl-leucyl-phenylalanine revealed that at higher than chemotactic optimum concentrations, neutrophil adhesion was less reduced and that after longer times of incubation, was increased. An inverse relationship was observed between neutrophil adhesiveness and locomotion. This was shown at various concentrations and times. In parallel with increased neutrophil adhesion, an increase in lysosomal enzyme secretion was demonstrated. This, and the adhesive increase were inhibited by the presence of hydrocortisone sodium succinate. No increases in endothelial adhesiveness induced by chemotactic factors were ever observed. It was concluded that the adhesive changes observed were not related to the process of margination in vivo but that they may be related to the pattern of neutrophil movement in vivo

A Robust Distance Measurement and Dark Energy Constraints from the Spherically-Averaged Correlation Function of Sloan Digital Sky Survey Luminous Red Galaxies

We measure the effective distance to z=0.35, D_V(0.35), from the overall shape of the spherically-averaged two-point correlation function of the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) luminous red galaxy (LRG) sample. We find D_V(0.35)=1428_{-73}^{+74} without assuming a dark energy model or a flat Universe. We find that the derived measurement of r_s(z_d)/D_V(0.35)=0.1143 \pm 0.0030 (the ratio of the sound horizon at the drag epoch to the effective distance to z=0.35) is more tightly constrained and more robust with respect to possible systematic effects. It is also nearly uncorrelated with \Omega_m h^2. Combining our results with the cosmic microwave background and supernova data, we obtain \Omega_k=-0.0032^{+0.0074}_{-0.0072} and w=-1.010^{+0.046}_{-0.045} (assuming a constant dark energy equation of state). By scaling the spherically-averaged correlation function, we find the Hubble parameter H(0.35)=83^{+13}_{-15} km s^{-1}Mpc^{-1} and the angular diameter distance D_A(0.35)=1089^{+93}_{-87} Mpc. We use LasDamas SDSS mock catalogs to compute the covariance matrix of the correlation function, and investigate the use of lognormal catalogs as an alternative. We find that the input correlation function can be accurately recovered from lognormal catalogs, although they give larger errors on all scales (especially on small scales) compared to the mock catalogs derived from cosmological N-body simulations.Comment: revised, 12 pages, 12 figure