A covariant and gauge invariant formulation of the cosmological "backreaction"

Using our recent proposal for defining gauge invariant averages we give a general-covariant formulation of the so-called cosmological "backreaction". Our effective covariant equations allow us to describe in explicitly gauge invariant form the way classical or quantum inhomogeneities affect the average evolution of our Universe.Comment: 12 pages, no figures. Typos corrected, matches version to appear in JCA

New Superembeddings for Type II Superstrings

Possible ways of generalization of the superembedding approach for the supersurfaces with the number of Grassmann directions being less than the half of that for the target superspace are considered on example of Type II superstrings. Focus is on n=(1,1) superworldsheet embedded into D=10 Type II superspace that is of the interest for establishing a relation with the NSR string.Comment: 26 pages, LaTeX, JHEP.cls and JHEP.bst style files are used; v2: misprints corrected, comments, acknowledgments, references adde

Accelerating the Universe with Gravitational Waves

Inflation generically produces primordial gravitational waves with a red spectral tilt. In this paper we calculate the backreaction produced by these gravitational waves on the expansion of the universe. We find that in radiation domination the backreaction acts as a relativistic fluid, while in matter domination a small dark energy emerges with an equation of state w=-8/9.Comment: 18 pages, 4 figures. Replaced with version published by JCAP - some discussion and references added concerning second-order gravitational waves, typeset in JHEP styl

To boldly go: the next generation of the Digital Mineral Library at Curtin University

After its success with the Australian National Data Service (ANDS)-funded Major Open Data Collection (MODC) project, Curtin University is working on the next phase of the Digital Mineral Library to integrate data from the SHRIMP ion microprobe, encourage greater data sharing among geoscientists and expand the coverage of the collection

Factors Related to Shell Deaths During Artificial Incubation of Ostrich Eggs.

The ostrich industry experiences a high rate of embryonic mortalities during artificial incubation of eggs. Embryonic deaths were studied from data recorded on 37 740 fertile eggs incubated artificially during the 1998–2005 breeding seasons. Roughly 10 000 eggs that sustained embryonic mortalities were classified according to the stage and nature of death, i.e. before 21 days of incubation, after 21 days of incubation, deaths after pipping and rotten eggs. Although infection may have played a role in ~1300 rotten eggs, no detailed knowledge of the pathogens involved was available. The remainder of deaths could not be related to pathogens and the deaths were thus generally referred to as non-infectious. The overall level of embryonic mortality in all the eggs studied was 28.5 %. Overall embryonic mortality was affected by incubator, with higher levels (57.0 %) found in eggs incubated in an African Incubator® and also in eggs that were transferred between incubators during incubation (38.1 %). Overall embryonic mortality also increased in eggs produced by older females. Eggs produced in the autumn had the highest level of embryonic mortality at 53.6 %, whereas eggs produced in the winter had a marginally higher level of embryonic mortalities of 29.2 % compared with eggs produced during summer (27.4 %). Eggs produced by South African (SA) Black males crossed to Zimbabwean Blue females had high levels of embryonic losses of 45.7 %. The embryonic mortality of eggs produced by SA Blacks or Zimbabwean Blue breeding birds subjected to pure breeding was similar at ~33–34 %, but embryonic mortality was improved in eggs produced by Zimbabwean Blue males crossed to SA Black females (27 %). Embryonic mortality was increased in eggs that were set directly (32.0 %) or subjected to longer than 6 days of storage (43.5 %). Embryonic mortality was affected by year. The results that were obtained will assist in determining non-infectious factors that have a negative effect on hatching success. Steps can thus be taken to eliminate such factors that may compromise hatching success

Genetic Parameters for Ostrich Incubation Traits in South Africa.

Data obtained from a pair-mated ostrich flock located at Oudtshoorn, South Africa, were used to estimate genetic parameters for egg weight (EWT), weight of day-old chicks (CWT), water loss to 21 (WL21) and 35 (WL35) days of incubation, and pipping time (PT) for between 13 806 and 19 913 artificially incubated ostrich eggs during the 2003 – 2006 production years. Data were initially analysed as single traits using ASREML. Covariance components and ratios were subsequently derived from two-trait analyses. Single-trait estimates of heritability (h2) were 0.46 ± 0.08 for EWT, 0.34 ± 0.07 for CWT, 0.34 ± 0.07 for WL21, 0.27 ± 0.06 for WL35 and 0.16 ± 0.04 for pipping time. Estimates of maternal genetic effects (m2) were 0.23 ± 0.12 for EWT and 0.29 ± 0.10 for CWT. A maternal permanent environmental effect amounted to 0.25 ± 0.10 for EWT, 0.12 ± 0.09 for CWT, 0.25 ± 0.04 for WL21 and 0.30 ± 0.04 for WL35. Genetic correlations with EWT amounted to -0.21 ± 0.13 for WL21 and to -0.12 ± 0.14 for WL35. Corresponding correlations with CWT were -0.43 ± 0.07 and -0.54 ± 0.11. Parameters indicate that it should be possible to alter evaporative water loss of ostrich eggs by genetic selection. A feasible selection strategy, however, needs to be devised as it is challenging to effect genetic change in a trait with an intermediate optimum

Changes in the Air Cell Volume of Artificially Incubated Ostrich Eggs.

A total of 2160 images of candled, incubated ostrich eggs were digitized to determine the percentage of egg volume occupied by the air cell at different stages of incubation. The air cell on average occupied 2.5% of the volume of fresh eggs. For eggs that hatched successfully, this volume increased to an average of 24.4% at 41 days of incubation, just prior to hatching. Air cell volume at 29 days of incubation for infertile eggs (19.3%) was significantly higher when compared to dead-in-shell (DIS) eggs (14.3%) and eggs that hatched (13.8%). There was a significantly larger air cell volume in eggs that hatched normally compared with DIS eggs at 41 days of incubation (28.3% vs. 21.7%, respectively). No differences in air cell volume were observed up to day 17 of incubation for eggs that hatched normally between eggs that exhibited high, average or low rates of water loss, but from 20 days of incubation the air cell volume was significantly larger for high weight loss eggs. However, for the DIS eggs, air cell volume was consistently larger in eggs that exhibited high rates of water loss. Air cell volume was largely independent of adult strain (SA Black or Zimbabwean Blue) or whether chicks were assisted to hatch. Although some subtle differences in air cell size were detected between hatched and DIS chicks during this study, it is unlikely to find useful application in the broader industry

CMB temperature anisotropy at large scales induced by a causal primordial magnetic field

We present an analytical derivation of the Sachs Wolfe effect sourced by a primordial magnetic field. In order to consistently specify the initial conditions, we assume that the magnetic field is generated by a causal process, namely a first order phase transition in the early universe. As for the topological defects case, we apply the general relativistic junction conditions to match the perturbation variables before and after the phase transition which generates the magnetic field, in such a way that the total energy momentum tensor is conserved across the transition and Einstein's equations are satisfied. We further solve the evolution equations for the metric and fluid perturbations at large scales analytically including neutrinos, and derive the magnetic Sachs Wolfe effect. We find that the relevant contribution to the magnetic Sachs Wolfe effect comes from the metric perturbations at next-to-leading order in the large scale limit. The leading order term is in fact strongly suppressed due to the presence of free-streaming neutrinos. We derive the neutrino compensation effect dynamically and confirm that the magnetic Sachs Wolfe spectrum from a causal magnetic field behaves as l(l+1)C_l^B \propto l^2 as found in the latest numerical analyses.Comment: 31 pages, 2 figures, minor changes, matches published versio

The Hubble rate in averaged cosmology

The calculation of the averaged Hubble expansion rate in an averaged perturbed Friedmann-Lemaitre-Robertson-Walker cosmology leads to small corrections to the background value of the expansion rate, which could be important for measuring the Hubble constant from local observations. It also predicts an intrinsic variance associated with the finite scale of any measurement of H_0, the Hubble rate today. Both the mean Hubble rate and its variance depend on both the definition of the Hubble rate and the spatial surface on which the average is performed. We quantitatively study different definitions of the averaged Hubble rate encountered in the literature by consistently calculating the backreaction effect at second order in perturbation theory, and compare the results. We employ for the first time a recently developed gauge-invariant definition of an averaged scalar. We also discuss the variance of the Hubble rate for the different definitions.Comment: 12 pages, 25 figures, references added, clarity improved, frame switching subtlety fixed, results unchanged, v3 minor typos fixe

Preeclampsia is associated with compromized maternal synthesis of long chain polyunsaturated fatty acids leading to offspring deficiency

Obesity and excessive lipolysis are implicated in preeclampsia (PE). Intrauterine growth restriction is associated with low maternal body mass index and decreased lipolysis. Our aim was to assess how maternal and offspring fatty acid metabolism is altered in mothers in the third trimester of pregnancy with PE (n=62) or intrauterine growth restriction (n=23) compared with healthy pregnancies (n=164). Markers of lipid metabolism and erythrocyte fatty acid concentrations were measured. Maternal adipose tissue fatty acid composition and mRNA expression of adipose tissue fatty acid–metabolizing enzymes and placental fatty acid transporters were compared. Mothers with PE had higher plasma triglyceride (21%, P<0.001) and nonesterified fatty acid (50%, P<0.001) concentrations than controls. Concentrations of major n−6 and n−3 long-chain polyunsaturated fatty acids in erythrocytes were 23% to 60% lower (all P<0.005) in PE and intrauterine growth restriction mothers and offspring compared with controls. Subcutaneous adipose tissue Δ−5 and Δ−6 desaturase and very long-chain fatty acid elongase mRNA expression was lower in PE than controls (respectively, mean [SD] control 3.38 [2.96] versus PE 1.83 [1.91], P=0.030; 3.33 [2.25] versus 1.03 [0.96], P<0.001; 0.40 [0.81] versus 0.00 [0.00], P=0.038 expression relative to control gene [square root]). Low maternal and fetal long-chain polyunsaturated fatty acid concentrations in PE may be the result of decreased maternal synthesis