Comment on ``Constraints on the strength of primordial B-fields from big bang nucleosynthesis reexamined''

Recently Cheng, Olinto, Schramm and Truran (COST) reexamined the constraints from big bang nucleosynthesis (BBN) on the strength of primordial magnetic fields. Their bottom line agreed with that of an earlier recent paper on the subject (Kernan, Starkman and Vachaspati (KSV)), both in its final limit on the magnetic field during BBN, and in its conclusion that for allowed values of the magnetic field the dominant factor for BBN is the increased expansion rate at a given temperature caused by the energy density of the magnetic field, $B^2/8\pi$. However, their conclusion that weak interaction rates increased with increasing B-field at these low field values contradicted the earlier results of KSV. In this comment we point out that the Taylor series expansion of the weak interaction rate about B=0 used in COST is not well-defined, while the Euler-McLaurin expansion of KSV is well-behaved and reliable. Using the Euler-McLaurin expansion we find that the weak interaction rates decrease rather than increase with increasing B-field at small values of the B-field.Comment: 4 pages, Latex, submitted to Phys. Rev.

When research setting is important: the influence of subordinate self-esteem on reactions to abusive supervision

In this paper, we argue that the conflicting theoretical views regarding the role that self-esteem plays in the decision to become aggressive can be explained by the particular research methodology used. Specifically, we examine how individuals respond to a perceived abusive supervisor in two settings: (1) using scenarios and (2) in a field study. Results indicate that individuals with high selfesteem are more likely to become aggressive in response to an abusive supervisor in settings where they are asked what they would do (using scenarios). However, in field research settings, where they are asked what they did do, individuals with low self-esteem were more likely to become aggressive in response to an abusive supervisor

DNA Mismatch Repair-Dependent Suppression of Genotoxicity of Benzo[a]pyrene Diol Epoxide

DNA mismatch repair (MMR) plays an important role in preserving genomic stability and reducing cancer risk. Environmental exposures to polycyclic aromatic hydrocarbons (PAHs) are believed to contribute significantly to carcinogenesis. PAHs are found in food, air, water and soil and upon bioactivation can form diol epoxides which are electrophilic in nature and can adduct to DNA, creating bulky PAH-DNA lesions. Preliminary data in the Buermeyer laboratory demonstrated that mutations induced by benzo[a]pyrene diol epoxide (BPDE) occur at higher rates in MLH1-deficient HCT 116+Ch2 cell line (30±7 mutations per 100 nM BPDE) versus a genetically matched MLH1-proficient line HCT 116+Ch3 cell line (10±4 mutations per 100 nM BPDE). I hypothesized that the role for MMR in suppressing mutation is a phenomenon generalizable to other cell lines. I measured BPDE-induced mutation rates in the parent cell line HCT 116, and in another genetically matched MSH6-proficient and -deficient set. I found an induced mutation rate of 30±5 mutations per 100 nM BPDE using HCT 116 cells, not significantly different from the induced mutation rate with HCT 116+Ch2 cells. In addition, we characterized mutants from HCT 116+Ch2 clones and identified 25 individual mutations with the predominance of G→T transversions

DNA Mismatch Repair-Dependent Suppression of Genotoxicity of Benzo[a]pyrene Diol Epoxide

DNA mismatch repair (MMR) plays an important role in preserving genomic stability and reducing cancer risk. Environmental exposures to polycyclic aromatic hydrocarbons (PAHs) are believed to contribute significantly to carcinogenesis. PAHs are found in food, air, water and soil and upon bioactivation can form diol epoxides which are electrophilic in nature and can adduct to DNA, creating bulky PAH-DNA lesions. Preliminary data in the Buermeyer laboratory demonstrated that mutations induced by benzo[a]pyrene diol epoxide (BPDE) occur at higher rates in MLH1-deficient HCT 116+Ch2 cell line (30±7 mutations per 100 nM BPDE) versus a genetically matched MLH1-proficient line HCT 116+Ch3 cell line (10±4 mutations per 100 nM BPDE). I hypothesized that the role for MMR in suppressing mutation is a phenomenon generalizable to other cell lines. I measured BPDE-induced mutation rates in the parent cell line HCT 116, and in another genetically matched MSH6-proficient and -deficient set. I found an induced mutation rate of 30±5 mutations per 100 nM BPDE using HCT 116 cells, not significantly different from the induced mutation rate with HCT 116+Ch2 cells. In addition, we characterized mutants from HCT 116+Ch2 clones and identified 25 individual mutations with the predominance of G→T transversions.

Magnetic fields in the early universe in the string approach to MHD

There is a reformulation of magnetohydrodynamics in which the fundamental dynamical quantities are the positions and velocities of the lines of magnetic flux in the plasma, which turn out to obey equations of motion very much like ideal strings. We use this approach to study the evolution of a primordial magnetic field generated during the radiation-dominated era in the early Universe. Causality dictates that the field lines form a tangled random network, and the string-like equations of motion, plus the assumption of perfect reconnection, inevitably lead to a self-similar solution for the magnetic field power spectrum. We present the predicted form of the power spectrum, and discuss insights gained from the string approximation, in particular the implications for the existence or not of an inverse cascade.Comment: 12 pages, 2 figure

Modelling phosphorus fluxes in Loweswater

1. This is the final report to the Loweswater Care Project (in support of the Catchment Restoration Fund for England) ECRC-ENSIS Project 298, 'Loweswater 12-13'. The study was concerned with the spatial and temporal concentrations of sediment phosphorus (P) in the lake and the use of P measurements from the water column and inflow and outflow samples to derive a simple mass balance model for P in the lake. 2. A review of published and unpublished literature on Loweswater highlighted trends in water chemistry since the mid-eighteenth century. Land use and farming practises have changed over the past 200 years which have led to increased nutrient loading to the lake with significant increases occurring in the mid part of the last century. Agricultural intensification is likely to be a significant cause of the problem as well as inadequate septic tank management. Local management efforts, led by the Loweswater Care Project, has sought to reduce the primary sources of nutrients reaching the lake, but total phosphorus (TP) concentrations in the lake remain higher than desired. 3. Temperature and dissolved oxygen (DO) profiling confirmed that the site stratified in summer with major changes in DO occurring below a depth of 8 m. The deeper waters were almost entirely anoxic. During stratification the maximum TP value was recorded at the lake bottom. This is a clear indication that P is being released from the lake bed during summer stratification. 4. Analysis of the stream water from the Dub Beck inflow (data for 2013), shows that P influx remains high enough to explain the elevated lake water P concentrations, despite considerable efforts to reduce catchment P sources. 5. Analysis of the water column P profiles shows that P release from the sediment is only a minor contribution to the P load. While the sediment core data reveals a substantial pool of P in the sediment very little of this should be released each year to the water column. In 2013 it is estimated that more than 90% of the P came from the catchment and only ~10% from the sediment. 6. As with all modelling exercises there are uncertainties inherent in the approach. In this case the model output is based on a single year of input data for the inflow P flux calculations and it would be preferable to have a longer data series to inform the modelling. Inflow fluxes are highly dependent on flow conditions and here, in the absence of flow data from Dub Beck, we used data from a nearby stream. Further, the monthly sampling has resulted in most samples being taken in low flow conditions, thus missing potential storm flow conditions. Finally, stream input information is restricted to Dub Beck, and contributions from the other stream is unknown. 7. Nevertheless, the results from the modelling are clear and on that basis we conclude that the priority is for P loading to the lake to be reduced by better catchment management and that lake manipulation is not warranted. Integrated catchment management supported by modelling together with local stakeholder engagement should provide the most effective means of improving the condition of the lake