No Crisis for Big Bang Nucleosynthesis

Contrary to a recent claim, the inferred primordial abundances of the light elements are quite consistent with the expectations from standard big bang nucleosynthesis when attention is restricted to direct observations rather than results from chemical evolution models. The number of light neutrino (or equivalent particle) species ($N_\nu$) can be as high as 4.53 if the nucleon-to-photon ratio ($\eta$) is at its lower limit of $1.65 \times 10^{-10}$, as constrained by the upper bound on the deuterium abundance in high redshift quasar absorption systems. Alternatively, with $N_\nu = 3$, $\eta$ can be as high as $8.90 \times 10^{-10}$ if the deuterium abundance is bounded from below by its interstellar value.Comment: 10 pages LaTeX (uses ReVTeX), including 3 PostScript figures (uses epsf); Full paper available from ftp://ftp.physics.ox.ac.uk/pub/local/users/sarkar/BBNcrisisnot.ps.gz ; Revised to include discussion of new deuterium observations in quasar absorption systems and helium-3 measurement in local interstellar gas, updated Fig 1, no change in conclusions, resubmitted to Phys. Rev. Let

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.

"Just So" Neutrino Oscillations Are Back

Recent evidence for oscillations of atmospheric neutrinos at Super-Kamiokande suggest, in the simplest see-saw interpretation, neutrino masses such that `just so' vacuum oscillations can explain the solar neutrino deficit. Super-K solar neutrino data provide preliminary support for this interpretation. We describe how the just-so signal---an energy dependent seasonal variation of the event rate, might be detected within the coming years and provide general arguments constraining the sign of the variation. The expected variation at radiochemical detectors may be below present sensitivity, but a significant modulation in the $^7$Be signal could shed light on the physics of the solar core---including a direct measure of the solar core temperature.Comment: 4 pages, revtex, 4 ps figs: new refs added, and Super-K energy resolution function incorporate

Evaluation of kochia as a high yielding forage crop for saline soils

Non-Peer ReviewedForage dry matter yields of up to 11,670 kg/ha, at a soil conductivity of 12 ms/cm, were measured in three years of trials at several saline sites in Saskatchewan. Feed values were comparable to common hays, based on in vitro analyses and a digestibility and intake trial done with sheep. Salt accumulation in kochia forage was higher than other forages but was calculated to be not significant in saline soil reclamation. Potassium was the major cation accumulated by kochia forage even though the saline soils were high in soluble sodium and magnesium cations. A Texas accession gave a much higher forage yield in a greenhouse trial than a Saskatchewan selection, and did not set seed in greenhouse and field trials. Further work is needed to turn this wild plant into a crop is discussed

Reciprocating, buoyancy-driven radial pumping on centrifugal microfluidic platforms

Centrifugal microfluidic systems bear great potential for applications where ruggedness, portability, ease-of-use, and cost efficiency are critical. However, due to the unidirectional nature of the centrifugal pumping force, the number of sequential process steps which can be integrated on these “Lab-on-a-Disc” (LoaD) devices is limited by their finite radial extension. To significantly widen this bottleneck and thus expand the scope of applications that can be ported on these LoaD platforms, various groups have developed a range of centripetal pumping mechanisms. Here, we present two advancements over our previous efforts in this area by combining buoyancy-based pumping with dissolvable film (DF) valves. First, we present a buoyancy-driven, reciprocating flow of a dense liquid initially located an upper reservoir and a sample in a peripheral reservoir. Secondly, we combine buoyancy-driven centripetal pumping with sample discretization and metering to fully integrate and automate a liquid handling protocol towards implementing a multi-parameter bioassay on a disc