Spontaneous Symmetry Breaking via Inhomogeneities and the Differential Surface Tension.

We discuss spontaneously broken quantum field theories with a continuous global symmetry group via the constraint effective potential. Employing lattice simulations with constrained values of the order parameter, we demonstrate explicitly that the path integral is dominated by inhomogeneous field configurations and that these are unambiguously related to the flatness of the effective potential in the broken phase. We determine characteristic features of these inhomogeneities, including their topology and the scaling of the associated excess energy with their size. Concerning the latter we introduce the differential surface tension-the generalization of the concept of a surface tension pertaining to discrete symmetries. Within our approach, spontaneous symmetry breaking is captured merely via the existence of inhomogeneities, i.e., without the inclusion of an explicit breaking parameter and a careful double limiting procedure to define the order parameter. While here we consider the three-dimensional O(2) model, we also elaborate on possible implications of our findings for the chiral limit of QCD.

Calculation of the axion mass based on high-temperature lattice quantum chromodynamics.

Unlike the electroweak sector of the standard model of particle physics, quantum chromodynamics (QCD) is surprisingly symmetric under time reversal. As there is no obvious reason for QCD being so symmetric, this phenomenon poses a theoretical problem, often referred to as the strong CP problem. The most attractive solution for this requires the existence of a new particle, the axion-a promising dark-matter candidate. Here we determine the axion mass using lattice QCD, assuming that these particles are the dominant component of dark matter. The key quantities of the calculation are the equation of state of the Universe and the temperature dependence of the topological susceptibility of QCD, a quantity that is notoriously difficult to calculate, especially in the most relevant high-temperature region (up to several gigaelectronvolts). But by splitting the vacuum into different sectors and re-defining the fermionic determinants, its controlled calculation becomes feasible. Thus, our twofold prediction helps most cosmological calculations to describe the evolution of the early Universe by using the equation of state, and may be decisive for guiding experiments looking for dark-matter axions. In the next couple of years, it should be possible to confirm or rule out post-inflation axions experimentally, depending on whether the axion mass is found to be as predicted here. Alternatively, in a pre-inflation scenario, our calculation determines the universal axionic angle that corresponds to the initial condition of our Universe.

Androgenic effects of a Canadian bleached kraft pulp and paper effluent as assessed using threespine stickleback (Gasterosteus aculeatus).

The presence of unidentified estrogens and androgens in effluents from pulp and paper mills is well documented. However, their role in effluent effects on fish reproduction remains unclear. The objective of this study was to investigate the hypothesis that reproductive impacts of a modern pulp mill effluent are mediated by androgens and/or estrogens in the effluent. Male and female threespine stickleback were exposed to biologically treated Canadian bleached kraft mill effluent under flow-through conditions in the laboratory at 0, 1, 10 and 100% (v/v) dilutions. After 7 and 21 d of exposure, steroidogenesis was assessed using in vitro incubations of gonadal tissue in both males and females. mRNA expression of the estrogen-regulated gene vitellogenin, and the androgen-responsive gene spiggin were assessed using quantitative RT-PCR in the livers of male and posterior kidneys of female stickleback, respectively. Hepatic 7-ethoxyresorufin-O-deethylase (EROD) activity was assessed in both sexes. Effluent extracts were examined for estrogenic and androgenic bioactivity using receptor binding bioassays, and were screened for pulp and paper related extractives and steroidal androgens using GC-MS. This effluent up-regulated spiggin mRNA in the kidney of female stickleback at 10% and 100% (v/v) effluent at 21 d, but not at 7 d of exposure. This change at the mRNA expression of the gene was associated with an increase in cell height in kidney proximal tubule epithelial cells at 100% effluent after both 7 and 21 d. Liver vitellogenin mRNA in male stickleback was not induced at either 7 or 21 d. EROD was induced at 10 and 100% after 21 d of exposure in both sexes, but not after 7 d of exposure. Despite evidence of exposure to androgens, there was no reduction in steroidogenic capacity at any effluent dilution. Effluent extracts were capable of eliciting the displacement of androgens and estrogens from receptors, but androgenic potency was 4-fold greater. A screen of more than 30 androgenic androstane steroids showed no detections. Hence, the androgenic constituents in this particular effluent remain unknown.

Assessing the biological status of fish in a river receiving pulp and paper mill effluents.

This study compared the use of sentinel species- and community-based field approaches for assessing the biological status of fish living in a river receiving pulp and paper mill effluents. Three approaches were compared. Two approaches used sentinel species. One of these involved an internal/external examination of the fish that leads to the calculation of a fish health assessment index (HAI) and the other involved biochemical measurements of hepatic mixed function oxidase (MFO) activity and plasma steroid levels. The third approach characterized the fish community structure according to an index of biotic integrity (IBI). The comparison focused on how the methods respond to the hypothesis that recent process modifications/effluent treatment changes, resulting in demonstrable improvements in effluent quality, have beneficial effects on fish. Neither of the approaches using sentinel fish indicated clear mill-related influences either before or after the process modifications/effluent treatment changes. There was no evidence of depressed plasma steroids and increased MFO activity in fish frequently associated with mill effluent exposure in previous studies. While the HAI was higher at stations downstream from two mills, this could not be linked to effluent exposure alone. In contrast, the study of community structure showed a substantial improvement in fish assemblages at all the mill sites.

Perspectives on Canadian field studies examining the potential of pulp and paper mill effluent to affect fish reproduction.

The results and interpretations of published Canadian field studies on the reproductive status of fish in waters receiving pulp and paper mill effluent discharges were reviewed. Most of the information was obtained from indicator measurements such as gonad size, fecundity, and serum steroid levels in wild fish sampled at reference and effluent-exposed sites. Difficulties in selecting appropriate sampling sites, natural variability, and the ecological relevance of the indicator measurements were identified as major complicating factors for the interpretation of the field data. Consequently, it was not possible to conclude to what extent, if any, widespread effects on fish reproduction are being caused by pulp and paper mill effluents or that specific manufacturing processes are causing such effects. Further research on the normal variability and predictive capability of reproductive indicators, for example, using an integrated approach (i.e., laboratory testing, mesocosm studies, and field work), is recommended.

Improved effluent quality at a bleached kraft mill as determined by laboratory biotests.

A life-cycle experiment with fathead minnows and Ceriodaphnia survival/reproduction tests were used to evaluate the quality of the effluent from a bleached kraft mill after the implementation of various process modifications and effluent treatment changes. In the life-cycle experiment, the fish were exposed in the laboratory to well water (control) and five concentrations (1.25%, 2.5%, 5%, 10%, or 20%) of effluent from the egg stage to sexual maturity and reproduction (approximately 190 d). None of the effluent concentrations significantly affected the hatching of the eggs, the mortality, weight, length, gender balance, reproduction, and prevalence of visible morphological or histopathological abnormalities of the hatched fish, and the hatchability of the first generation eggs. In Ceriodaphnia tests, the IC25 of the effluent affecting reproduction was approximately 80%. This threshold concentration is well above the 0.7% average yearly concentration of the effluent that exists in the recipient near the point of discharge. The results of these biotests were compared to the results of the same biotests conducted earlier with the effluent from the mill prior to process and treatment modifications. The comparison indicated that since the earlier work, the quality of the mill's effluent improved substantially. Threshold concentrations affecting fathead minnows in the life-cycle experiment and the Ceriodaphnia tests increased by more than eightfold and approximately twofold, respectively. While the most important change in the mill operating conditions responsible for the improvement could not be identified, these results indicate that mills can undertake process and treatment modifications that result in the discharge of effluents seemingly compatible with the aquatic environment.

The effects of a secondary-treated bleached kraft mill effluent on aquatic organisms as assessed by short-term and long-term laboratory tests.

The chronic effects of secondary-treated effluent from a bleached kraft mill were assessed by means of long-term and short-term laboratory tests. In the long-term test, the effects of the effluent on the life cycle of fathead minnows (Pimephales promelas) were studied. In this experiment, which began with the egg stage and continued through to sexual maturity and reproduction, the fish were exposed in the laboratory to well water (control) and five concentrations (viz., 1.25, 2.5, 5, 10, or 20%) of effluent for 275 days. The effluent concentrations did not significantly affect the hatching of the eggs, the mortality of the hatched fish, the incidence of visible morphological abnormalities, the mortality and the hatchability of the first generation eggs and larvae, and the weights of minnows at various stages of development. Based on a conservative evaluation of the data, a significant finding of this work was that effluent concentrations > or = 2.5% caused lower egg production as well as changes in the gender balance (i.e., increased numbers of individuals with male secondary sexual characteristics) of the fish. Further work is required to understand the causes and ecological significance of these findings. Two short-term tests, each lasting 7 days, were also run. In one, even 100% effluent did not reduce the survival or growth of minnow larvae, correctly predicting the lack of effluent effects on similar endpoints in the long-term test. In the other short-term test, while the survival of Ceriodaphnia was also unaffected by 100% effluent, their reproductive capacity was reduced, but only at effluent concentrations an order of magnitude greater than those affecting the reproduction of minnows in the long-term test.

Effects of a secondary-treated thermomechanical pulp mill effluent on aquatic organisms as assessed by short- and long-term laboratory tests.

The chronic effects of secondary-treated effluent from a thermomechanical pulp (TMP) mill were assessed by means of long-term and short-term laboratory toxicity tests. The effluent used for the tests was sampled at a western Canadian mill using mostly softwoods and < 10% recycled fiber as furnish. In the long-term test, the effects of the effluent on the life cycle of fathead minnows (Pimephales promelas) were studied. In this experiment, which began with the egg stage and continued through to sexual maturity and reproduction, the fish were exposed in the laboratory to well water (control) and five concentrations (1.25%, 2.5%, 5%, 10%, or 20%) of effluent for 202 d. None of the effluent concentrations significantly affected the hatching of the eggs, the mortality, weight, length, gonad size, gender balance, and reproduction of the hatched fish, the prevalence of gross morphological and histopathological changes, and the hatchability of the first generation eggs. Two short-term tests, each lasting 7 d, were also performed. In these tests, 100% effluent caused no change in the survival/growth of minnow larvae or in the survival/reproduction of Ceriodaphnia.

A laboratory exposure procedure for screening pulp and paper mill effluents for the potential of causing increased mixed function oxidase activity in fish.

To better understand the relationships between pulp manufacturing processes and mixed function oxidase (MFO) enzyme induction in fish, a practical and standardized exposure procedure is required. This study was undertaken to develop a laboratory-based exposure procedure to quantify the relative MFO induction potencies of different types of pulp and paper mill effluents. One major consideration in developing the procedure was to ensure that the protocol was practical so that tests could be performed in a short time, with small volumes of effluents and using simple experimental conditions. A series of concentration-response and time-course experiments were conducted to find the minimum time and effluent concentration which could distinguish the ability of different effluents to cause significant MFO induction in rainbow trout in the laboratory. Experiments were also conducted to determine the effects of biotic and abiotic factors such as loading density, fish size and feeding regime. This study showed that the exposure of rainbow trout in the laboratory to 10% concentration of secondary-treated effluent for 96 h caused significant increases in hepatic MFO activity. The magnitude of MFO induction was comparable to other field and laboratory observations. While fish size, loading density and feeding regime were found to affect the test results, consistent responses within a laboratory using this protocol are possible, provided that these factors are standardized. Therefore, the short-term exposure approach described in this paper could be a relevant tool for assessing the ability of different types of pulp and paper mill effluents to cause MFO induction in fish.