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

Business in Nebraska #294 - March 1969

Extent of Corporation Farming in Nebraska (Dorothy Switzer) Concern has been expressed in many quarters over the apparent increase in the number of nonfarm corporations that are buying land and initiating new farming enterprises in Nebraska. It has become important, therefore, to know the facts about the number of these corporations and the amount of farm land they are operating in the state. This information has recently been made available because Nebraska is one of 22 states included in a preliminary report summarizing a survey of corporate farming. Reprints State and Local Taxes in Nebraska (E. S. Wallace) According to figures recently released Nebrdska ranked 32nd among the 50 states in state and local taxes per resident in 1907. Of the 18 states below Nebraska, 11 were in the Southeast Region. In the Plains Region only Missouri and North Dakota were lower. Review Business Summary (R. L. Busboom) Both Physical Volume and Dollar Volume indexes indicate Nebraska\u27s general level of business activity in December, 1968, was that above that of the same month last year. Both indexes also indicate that the November, 1968, general level of business appears to have been maintained through December. Both the Nebraska indexes were, however, at levels approximately 4% lower than those of the U.S. On a month-to-month bases, however, Nebraska\u27s changes were nearly equal to those of the U.S

Business in Nebraska #297 - June 1969

Nebraska\u27s Export of Agricultural Products (Dorothy Switzer) Nebraska moved up from fourth to third place among the seven states in the West North Central region in dollar volume of agricultural exports in fiscal 1968 and retained its position as ninth ranking state in the nation, according to recent data from the U.S. Department of Agriculture. Sales amounting to $229.5 million of Nebraska farm products constituted 14.5$1,578.9 billion in volume of sales. Business Summary (R. L. Busboom) Generally, the State\u27s business activity in March was well above that of last year. A 13 percent rise in physical volume combined with the well - known rise in level of prices to effect an overall dollar volume increase of 30 percent. A large increase in construction activity was the major factor in the overall, year -to -year gain. Employment levels were notably higher in 1969 than in 1968. Manufacturing employment was nearly 5 percent higher and other employment showed a gain of 4 percent. Revised Population Estimates (E. S. Wallace) In making 1968 county and city population estimates it was necessary to change slightly the methodology used, since the head tax has been repealed and is no longer available as one of the indicators. In connection with publication of 1968 estimates in our April issue it was stated that some previous estimates would be recalculated using the new method and that if substantial differences were indicated previous estimates would be revised. Review

A Method for Individual Source Brightness Estimation in Single- and Multi-band Data

We present a method of reliably extracting the flux of individual sources from sky maps in the presence of noise and a source population in which number counts are a steeply falling function of flux. The method is an extension of a standard Bayesian procedure in the millimeter/submillimeter literature. As in the standard method, the prior applied to source flux measurements is derived from an estimate of the source counts as a function of flux, dN/dS. The key feature of the new method is that it enables reliable extraction of properties of individual sources, which previous methods in the literature do not. We first present the method for extracting individual source fluxes from data in a single observing band, then we extend the method to multiple bands, including prior information about the spectral behavior of the source population(s). The multi-band estimation technique is particularly relevant for classifying individual sources into populations according to their spectral behavior. We find that proper treatment of the correlated prior information between observing bands is key to avoiding significant biases in estimations of multi-band fluxes and spectral behavior, biases which lead to significant numbers of misclassified sources. We test the single- and multi-band versions of the method using simulated observations with observing parameters similar to that of the South Pole Telescope data used in Vieira, et al. (2010).Comment: 11 emulateapj pages, 3 figures, revised to match published versio

Fiber Optic Cables for Transmission of High-Power Laser Pulses in Spaceflight Applications

Lasers with high peak power pulses are commonly used in spaceflight missions for a wide range of applications, from LIDAR systems to optical communications. Due to the high optical power needed, the laser has to be located on the exterior of the satellite or coupled through a series of free space optics. This presents challenges for thermal management, radiation resistance, and mechanical design. Future applications will require multiple lasers located close together, which further complicates the design. Coupling the laser energy into a fiber optic cable allows the laser to be relocated to a more favorable position on the spacecraft. Typical fiber optic termination procedures are not sufficient for injection of these high-power laser pulses without catastrophic damage to the fiber endface. In the current study, we will review the causes of fiber damage during high-power injection and discuss our new manufacturing procedures that overcome these issues to permit fiber use with high reliability in these applications. We will also discuss the proper methods for launching the laser pulses into the fiber to avoid damage and how this is being implemented for current spaceflight missions

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

Amplification of simian retroviral sequences from human recipients of baboon liver transplants

Investigations into the use of baboons as organ donors for human transplant recipients, a procedure called xenotransplantation, have raised the specter of transmitting baboon viruses to humans and possibly establishing new human infectious diseases. Retrospective analysis of tissues from two human transplant recipients with end-stage hepatic disease who died 70 and 27 days after the transplantation of baboon livers revealed the presence of two simian retroviruses of baboon origin, simian foamy virus (SFV) and baboon endogenous virus (BaEV), in multiple tissue compartments. The presence of baboon mitochondrial DNA was also detected in these same tissues, suggesting that xenogeneic 'passenger leukocytes' harboring latent or active viral infections had migrated from the xenografts to distant sites within the human recipients. The persistence of SFV and BaEV in human recipients throughout the posttransplant period underscores the potential infectious risks associated with xenotransplantation