Ionizing radiation from hydrogen recombination strongly suppresses the lithium scattering signature in the CMB

It has been suggested that secondary CMB anisotropies generated by neutral lithium could open a new observational window into the universe around the redshift z~400, and permit a determination of the primordial lithium abundance. The effect is due to resonant scattering in the allowed Li i doublet (2s2S1/2-2p2P1/2,3/2), so its observability depends on the formation history of neutral lithium. Here we show that the ultraviolet photons produced during hydrogen recombination are sufficient to keep lithium in the Li ii ionization stage in the relevant redshift range and suppress the neutral fraction by ~3 orders of magnitude from previous calculations, making the lithium signature unobservable

Primordial helium recombination III: Thomson scattering, isotope shifts, and cumulative results

Upcoming precision measurements of the temperature anisotropy of the cosmic microwave background (CMB) at high multipoles will need to be complemented by a more complete understanding of recombination, which determines the damping of anisotropies on these scales. This is the third in a series of papers describing an accurate theory of HeI and HeII recombination. Here we describe the effect of Thomson scattering, the $^3$He isotope shift, the contribution of rare decays, collisional processes, and peculiar motion. These effects are found to be negligible: Thomson and $^3$He scattering modify the free electron fraction $x_e$ at the level of several $\times 10^{-4}$. The uncertainty in the $2^3P^o-1^1S$ rate is significant, and for conservative estimates gives uncertainties in $x_e$ of order $10^{-3}$. We describe several convergence tests for the atomic level code and its inputs, derive an overall $C_\ell$ error budget, and relate shifts in $x_e(z)$ to the changes in $C_\ell$, which are at the level of 0.5% at $\ell =3000$. Finally, we summarize the main corrections developed thus far. The remaining uncertainty from known effects is $\sim 0.3$ in $x_e$.Comment: 19 pages, 15 figures, to be submitted to PR

DNA bending by a phantom protein

Background: Despite its stiffness, duplex DNA is extensively bent and folded during packiging and gene expression in biological systems. Modulation of the electrostatic repulsion between phosphate in the DNA backbone may be important in the bending of DNA by proteins. Here we analyze the shape of DNA molecules that have been modified chemically to mimic the electrostatic consequences of a bund proteinResults: We have simulated salt bridges between DNA phosphates and cationic amino acid sidechains of a phantom protein by tethering ammonium cations to one face of the DNA helix. Thethered ammonium cations, but not neutral acetylated controls, induced DNA to bend toward its neutralized surface.Conclusions: The shape of DNA molecules bearing a laterally-asymmetric distribution of tethered cations agrees qualitatively with theoretical predictions and with results previously obtained using neutral phosphate analogs. These data suggest principles that might be applied to the design of artificial DNA-bending proteins

Primordial helium recombination II: two-photon processes

Interpretation of precision measurements of the cosmic microwave background (CMB) will require a detailed understanding of the recombination era, which determines such quantities as the acoustic oscillation scale and the Silk damping scale. This paper is the second in a series devoted to the subject of helium recombination, with a focus on two-photon processes in He I. The standard treatment of these processes includes only the spontaneous two-photon decay from the 2^1S level. We extend this treatment by including five additional effects, some of which have been suggested in recent papers but whose impact on He I recombination has not been fully quantified. These are: (i) stimulated two-photon decays; (ii) two-photon absorption of redshifted HeI line radiation; (iii) two-photon decays from highly excited levels in HeI (n^1S and n^1D, with n>=3); (iv) Raman scattering; and (v) the finite width of the 2^1P^o resonance. We find that effect (iii) is highly suppressed when one takes into account destructive interference between different intermediate states contributing to the two-photon decay amplitude. Overall, these effects are found to be insignificant: they modify the recombination history at the level of several parts in 10^4.Comment: 19 pages, 11 figures, to be submitted to PR

A Systematic Review and Meta-Analysis of Outcomes for Type 1 Diabetes after Bariatric Surgery

Background. The utility of bariatric surgery in type 1 diabetes remains controversial. The aim of the present study is to evaluate glycemic control outcomes in obese patients with type 1 diabetes after bariatric surgery. Methods. A comprehensive search of electronic databases was completed. Inclusion criteria included human adult subjects with BMI ≥35 kg/m2 and a confirmed diagnosis of type 1 diabetes who underwent a bariatric surgical procedure. Results. Thirteen primary studies (86 patients) were included. Subjects had a mean age of 41.16±6.76 years with a mean BMI of 42.50±2.65 kg/m2. There was a marked reduction in BMI postoperatively at 12 months and at study endpoint to 29.55±1.76 kg/m2 (P<0.00001) and 30.63±2.09 kg/m2 (P<0.00001), respectively. Preoperative weighted mean total daily insulin requirement was 98±26 IU/d, which decreased significantly to 36±15 IU/d (P<0.00001) and 42±11 IU/d (P<0.00001) at 12 months and at study endpoint, respectively. An improvement in HbA1c was also seen from 8.46±0.78% preoperatively to 7.95±0.55% (P=0.01) and 8.13±0.86% (P=0.03) at 12 months and at study endpoint, respectively. Conclusion. Bariatric surgery in patients with type 1 diabetes leads to significant reductions in BMI and improvements in glycemic control

A framework to assess the impact of flooding on the release of microplastics from waste management facilities

The impact of flood on waste management facilities can induce the release of micro pollutants to freshwater systems with concerning impacts on the marine environment, agricultural ecosystems, and human health. Almost 30% of the total waste managed in the UK in 2019 was characterised by Microplastic Releasers (MPRs): plastic waste, synthetic textile, rubber waste, and mix/undifferentiated materials that are able to or contain items that can deteriorate and fragment into micro components. In recent years, the management of solid waste and its contribution to flood-driven microplastic pollution has been limited with a focus on plastic waste mismanagement specifically, and the assessment of the risk is long overdue. We present a new methodology combining publicly available data on waste with pluvial and fluvial flood extent maps. The methodology was applied to the UK where the impact of pluvial flood on waste management facilities shows a 3-fold increment between 20 and 50-year return period in waste at risk of releasing microplastics during inundation resulting in almost 5 million tonnes per day. The methodology was applied to the UK where the impact of pluvial flood on waste management facilities shows a 3-fold increment between 20 and 50-year return period resulting in almost 5 million tonnes of waste per day at risk of releasing microplastics during inundation. We conclude that further studies at the local scale are necessary to establish site-specific mitigation measures and containment systems able to decrease the flood-induced microplastic mobilisation from waste management facilities

Effects of preservation methods of muscle tissue from upper-trophic level reef fishes on stable isotope values (δ13C and δ15N)

© The Author(s), 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in PeerJ 3 (2015): e874, doi:10.7717/peerj.874.Research that uses stable isotope analysis often involves a delay between sample collection in the field and laboratory processing, therefore requiring preservation to prevent or reduce tissue degradation and associated isotopic compositions. Although there is a growing literature describing the effects of various preservation techniques, the results are often contextual, unpredictable and vary among taxa, suggesting the need to treat each species individually. We conducted a controlled experiment to test the effects of four preservation methods of muscle tissue from four species of upper trophic-level reef fish collected from the eastern Gulf of Mexico (Red Grouper Epinephelus morio, Gag Mycteroperca microlepis, Scamp Mycteroperca phenax, and Red Snapper Lutjanus campechanus). We used a paired design to measure the effects on isotopic values for carbon and nitrogen after storage using ice, 95% ethanol, and sodium chloride (table salt), against that in a liquid nitrogen control. Mean offsets for both δ13C and δ15N values from controls were lowest for samples preserved on ice, intermediate for those preserved with salt, and highest with ethanol. Within species, both salt and ethanol significantly enriched the δ15N values in nearly all comparisons. Ethanol also had strong effects on the δ13C values in all three groupers. Conversely, for samples preserved on ice, we did not detect a significant offset in either isotopic ratio for any of the focal species. Previous studies have addressed preservation-induced offsets in isotope values using a mass balance correction that accounts for changes in the isotope value to that in the C/N ratio. We tested the application of standard mass balance corrections for isotope values that were significantly affected by the preservation methods and found generally poor agreement between corrected and control values. The poor performance by the correction may have been due to preferential loss of lighter isotopes and corresponding low levels of mass loss with a substantial change in the isotope value of the sample. Regardless of mechanism, it was evident that accounting for offsets caused by different preservation methods was not possible using the standard correction. Caution is warranted when interpreting the results from specimens stored in either ethanol or salt, especially when using those from multiple preservation techniques. We suggest the use of ice as the preferred preservation technique for muscle tissue when conducting stable isotope analysis as it is widely available, inexpensive, easy to transport and did not impart a significant offset in measured isotopic values. Our results provide additional evidence that preservation effects on stable isotope analysis can be highly contextual, thus requiring their effects to be measured and understood for each species and isotopic ratio of interest before addressing research questions.Funding was provided by a grant to CD Stallings and TS Switzer from the National Oceanic and Atmospheric Administration, Cooperative Research Program (NA12NMF4540081)

Primordial helium recombination. I. Feedback, line transfer, and continuum opacity

Precision measurements of the cosmic microwave background temperature anisotropy on scales ℓ>500 will be available in the near future. Successful interpretation of these data is dependent on a detailed understanding of the damping tail and cosmological recombination of both hydrogen and helium. This paper and two companion papers are devoted to a precise calculation of helium recombination. We discuss several aspects of the standard recombination picture, and then include feedback, radiative transfer in He i lines with partial redistribution, and continuum opacity from H i photoionization. In agreement with past calculations, we find that He ii recombination proceeds in Saha equilibrium, whereas He i recombination is delayed relative to Saha due to the low rates connecting excited states of He i to the ground state. However, we find that at z<2200 the continuum absorption by the rapidly increasing H i population becomes effective at destroying photons in the He i 21Po-11S line, causing He i recombination to finish around z≃1800, much earlier than previously estimated