Time-resolved spectroscopy of the primary photosynthetic processes of membrane-bound reaction centers from an antenna-deficient mutant of Rhodobacter capsulatus

The primary photosynthetic reactions in whole membranes of the antenna-deficient mutant strain U43 (pTXA6–10) of Rhodobacter capsulatus are studied by transient absorption and emission spectroscopy with subpicosecond time resolution. Extensive similarities between the transient absorption data on whole membranes and on isolated reaction centers support the idea that the primary processes in isolated reaction centers are not modified by the isolation procedure

Cultivar considerations and pod sealants for straight-combining canola in Saskatchewan

Non-Peer ReviewedWhile the recommended and preferred harvest practice in western Canada is to swath canola (Brassica napus L.), there is appreciable interest in straight-combining this crop. In a recent study, five cultivars were harvested according to one of four harvest treatments and evaluated for seed yield, yield loss due to shattering, percent green seed and seed size. The cultivars included four B. napus hybrids and an open-pollinated canola quality B. juncea variety. Harvest strategies were swathed, straight-combined without a pod sealant, straight-combined with Pod Ceal DC® and straight-combined with Pod-Stik®. While average yields ranged from 894-3066 kg ha-1, cultivar rankings for yield were generally consistent across sites. Seed yields were equal when averaged across harvest treatments and sites, but swathed yields differed from straight-combined yields 50% of the time for individual sites. At two sites, straight-combining produced 142-370 kg ha-1 higher yields than swathing while, when harvest was delayed due to unfavourable weather, swathed yields were 276-413 kg ha-1 higher. A 217 kg ha-1 yield increase occurred with pod sealants at one site, but there were no differences amongst the two products and pod sealants did not affect yields of straight-combined canola at the remaining seven sites. Pod sealants did not have a measurable effect on shattering losses, even under high shattering conditions. In contrast, cultivar effects on seed loss were generally significant with losses from one of the napus cultivars being particular and consistently low, especially when overall shattering losses were high. On average, losses for all cultivars were 4% of the total yield when harvest was completed reasonably close to the optimal stage. Straight-combining resulted in a small but significant increase in percent green seed and seed size but pod sealants did not affect seed quality in any cases. In conclusion, straight-combining can be a viable alternative to swathing, but substantial yield losses may occur if harvest is delayed too long. Important varietal differences in shattering losses were detected and cultivar selection appears to be a factor of greater importance than pod sealants for growers planning to straight-combine canola

Cosmological Parameter Extraction from the First Season of Observations with DASI

The Degree Angular Scale Interferometer (\dasi) has measured the power spectrum of the Cosmic Microwave Background anisotropy over the range of spherical harmonic multipoles 100<l<900. We compare this data, in combination with the COBE-DMR results, to a seven dimensional grid of adiabatic CDM models. Adopting the priors h>0.45 and 0.0<=tau_c<=0.4, we find that the total density of the Universe Omega_tot=1.04+/-0.06, and the spectral index of the initial scalar fluctuations n_s=1.01+0.08-0.06, in accordance with the predictions of inflationary theory. In addition we find that the physical density of baryons Omega_b.h^2=0.022+0.004-0.003, and the physical density of cold dark matter Omega_cdm.h^2=0.14+/-0.04. This value of Omega_b.h^2 is consistent with that derived from measurements of the primordial abundance ratios of the light elements combined with big bang nucleosynthesis theory. Using the result of the HST Key Project h=0.72+/-0.08 we find that Omega_t=1.00+/-0.04, the matter density Omega_m=0.40+/-0.15, and the vacuum energy density Omega_lambda=0.60+/-0.15. (All 68% confidence limits.)Comment: 7 pages, 4 figures, minor changes in response to referee comment

Role of tyrosine M210 in the initial charge separation of reaction centers of Rhodobacter sphaeroides

Femtosecond spectroscopy was used in combination with site-directed mutagenesis to study the influence of tyrosine M210 (YM210) on the primary electron transfer in the reaction center of Rhodobacter sphaeroides. The exchange of YM210 to phenylalanine caused the time constant of primary electron transfer to increase from 3.5 f 0.4 ps to 16 f 6 ps while the exchange to leucine increased the time constant even more to 22 f 8 ps. The results suggest that tyrosine M210 is important for the fast rate of the primary electron transfer

Spin excitations in the antiferromagnet NaNiO2

In NaNiO2, Ni3+ ions form a quasi two dimensional triangular lattice of S = 1=2 spins. The magnetic order observed below 20K has been described as an A type antiferromagnet with ferro- magnetic layers weakly coupled antiferromagnetically. We studied the magnetic excitations with the electron spin resonance for frequencies 1-20 cm-1, in magnetic fields up to 14 T. The bulk of the results are interpreted in terms of a phenomenological model involving bi-axial anisotropy for the spins: a strong easy-plane term, and a weaker anisotropy within the plane. The direction of the easy plane is constrained by the collective Jahn-Teller distortion occurring in this material at 480 K

Highly effective and isotropic pinning in epitaxial Fe(Se,Te) thin films grown on CaF2 substrates

We report on the isotropic pinning obtained in epitaxial Fe(Se,Te) thin films grown on CaF2 (001) substrate. High critical current density values larger than 1 MA/cm2 in self field in liquid helium are reached together with a very weak dependence on the magnetic field and a complete isotropy. Analysis through Transmission Electron Microscopy evidences the presence of defects looking like lattice disorder at a very small scale, between 5 and 20 nm, which are thought to be responsible for such isotropic behavior in contrast to what observed on SrTiO3, where defects parallel to the c-axis enhance pinning in that directio

The impact of DCD and NBPT concentration on nitrification and volatilization

Non-Peer ReviewedNitrification inhibitors are used in agriculture to slow the conversion of ammonium to nitrate by inhibiting ammonia monoxygenace (AMO), which is found within the Nitrosomonas bacteria. There are two ways to inhibit nitrification of the AMO enzyme, namely, (a) competitive inhibition: The inhibitor will compete to occupy AMO's active site; by blocking the active site, it slows the conversion of ammonium to nitrate preventing loss of nitrates, and, (b) non-competitive inhibition: The inhibitor can temporarily inactivate the AMO enzyme by altering the active site. Dicyandiamide (DCD) is a competitive inhibitor. The amount of DCD delivered by a product has a direct impact on how well a product will inhibit loss of nitrogen through nitrification. Research shows the concentration of DCD in the soil has a direct influence on the percent of nitrification. Higher concentrations of DCD equate to higher percentage of nitrification inhibition. The results of a two-year program that compares two products, one containing 8500 ppm and one 870ppm of DCD and approximately equal concentration of a volatilization inhibitor will be presented

Pressure-Induced Superconductivity in Sc to 74 GPa

Using a diamond anvil cell with nearly hydrostatic helium pressure medium we have significantly extended the superconducting phase diagram Tc(P) of Sc, the lightest of all transition metals. We find that superconductivity is induced in Sc under pressure, Tc increasing monotonically to 8.2 K at 74.2 GPa. The Tc(P) dependences of the trivalent d-electron metals Sc, Y, La, and Lu are compared and discussed within a simple s-d charge transfer framework.Comment: to be published in Phys. Rev. B (Brief Reports