Strategies to enhance the excitation energy-transfer efficiency in a light-harvesting system using the intra-molecular charge transfer character of carotenoids

Fucoxanthin is a carotenoid that is mainly found in light-harvesting complexes from brown algae and diatoms. Due to the presence of a carbonyl group attached to polyene chains in polar environments, excitation produces an excited intra-molecular charge transfer. This intra-molecular charge transfer state plays a key role in the highly efficient (∼95%) energy-transfer from fucoxanthin to chlorophyll a in the light-harvesting complexes from brown algae. In purple bacterial light-harvesting systems the efficiency of excitation energy-transfer from carotenoids to bacteriochlorophylls depends on the extent of conjugation of the carotenoids. In this study we were successful, for the first time, in incorporating fucoxanthin into a light-harvesting complex 1 from the purple photosynthetic bacterium, Rhodospirillum rubrum G9+ (a carotenoidless strain). Femtosecond pump-probe spectroscopy was applied to this reconstituted light-harvesting complex in order to determine the efficiency of excitation energy-transfer from fucoxanthin to bacteriochlorophyll a when they are bound to the light-harvesting 1 apo-proteins

Shadow of a Colossus: A z=2.45 Galaxy Protocluster Detected in 3D Ly-a Forest Tomographic Mapping of the COSMOS Field

Using moderate-resolution optical spectra from 58 background Lyman-break galaxies and quasars at $z\sim 2.3-3$ within a $11.5'\times13.5'$ area of the COSMOS field ($\sim 1200\,\mathrm{deg}^2$ projected area density or $\sim 2.4\,h^{-1}\,\mathrm{Mpc}$ mean transverse separation), we reconstruct a 3D tomographic map of the foreground Ly$\alpha$ forest absorption at $2.2<z<2.5$ with an effective smoothing scale of $\sigma_{3d}\approx3.5\,h^{-1}\,\mathrm{Mpc}$ comoving. Comparing with 61 coeval galaxies with spectroscopic redshifts in the same volume, we find that the galaxy positions are clearly biased towards regions with enhanced IGM absorption in the tomographic map. We find an extended IGM overdensity with deep absorption troughs at $z=2.45$ associated with a recently-discovered galaxy protocluster at the same redshift. Based on simulations matched to our data, we estimate the enclosed dark matter mass within this IGM overdensity to be $M_{\rm dm} (z=2.45) = (9\pm4)\times 10^{13}\,h^{-1}\,\mathrm{M_\odot}$, and argue based on this mass and absorption strength that it will form at least one $z\sim0$ galaxy cluster with $M(z=0) = (3\pm 2) \times 10^{14}\,h^{-1}\mathrm{M_\odot}$, although its elongated nature suggests that it will likely collapse into two separate clusters. We also point out a compact overdensity of six MOSDEF galaxies at $z=2.30$ within a $r\sim 1\,h^{-1}\,\mathrm{Mpc}$ radius and $\Delta z\sim 0.006$, which does not appear to have a large associated IGM overdensity. These results demonstrate the potential of Ly$\alpha$ forest tomography on larger volumes to study galaxy properties as a function of environment, as well as revealing the large-scale IGM overdensities associated with protoclusters and other features of large-scale structure.Comment: To be submitted to ApJ. Figure 3 can be viewed on Youtube: https://youtu.be/KeW1UJOPMY

C IV and other Metal Absorption Line Systems in 18 z = 4 Quasars

We present a modest survey of quasar metal line absorption systems at redshifts 2.3–4.5. Relatively high signal-to-noise ratio (~25 pixel^(-1)) spectra of 18 quasars at 2 Å FWHM resolution show many absorption systems with strong metal lines in the region redward of the Lyα emission lines. We conducted a systematic search and found 55 C IV doublets, 19 Si IV doublets, three Mg II doublets, and seven N V doublets. The present data alone hint that the number of C IV absorption doublets per unit redshift, N(z), decreases with increasing redshift for 2.3 0.3 Å are approximately 55% of all C IV systems with W > 0.15 Å, but by z ≃ 4 that percentage is less than 37%. Similar conclusions were reached by Sargent, Boksenberg, & Steidel and by Steidel, primarily at lower redshifts. However, we measure approximately twice the density of C IV systems at 2.3 0.15 Å that was reported by Steidel. The probability that our sample and previous samples come from the same distribution is only ~2%. But this could be a statistical accident because it is an a posteriori comparison. We believe that the systems that we report are real, and we have no other explanation for this difference. For Si IV absorption lines, there is a 1 σ hint of evolution with the same sense. In contrast, Lyα and Mg II systems are known to show evolution of the opposite sense with more absorbers at larger redshifts. The physical cause of this difference may be a mixture of ionization and chemical evolution effects

Cosmological parameters sigma_8, the baryon density, and the UV background intensity from a calibrated measurement of H I Lyman-alpha absorption at z = 1.9

We identify a concordant model for the intergalactic medium (IGM) at redshift z=1.9 that uses popular values for cosmological and astrophysical parameters and accounts for all baryons with an uncertainty of 6%. We have measured the amount of absorption, DA, in the Ly-alpha forest at redshift 1.9 in spectra of 77 QSO from the Kast spectrograph. We calibrated the continuum fits with realistic artificial spectra, and we found that averaged over all 77 QSOs the mean continuum level is within 1-2% of the correct value. Absorption from all lines in the Ly-alpha forest at z=1.9 removes DA=15.1 +/- 0.7% of the flux between 1070 and 1170 (rest) Angstroms. This is the first measurement using many QSOs at this z, and the first calibrated measurement at any redshift. Metal lines absorb 2.3 +/- 0.5%, and LLS absorb 1.0 +/- 0.4% leaving 11.8 +/- 1.0% from the lower density bulk of the IGM. Averaging over Delta z=0.1 or 154 Mpc, the dispersion is 6.1 +/- 0.3% including LLS and metal lines, or 3.9 (+0.5, -0.7)% for the lower density IGM alone, consistent with the usual description of large scale structure. LLS and metal lines are major contributors to the variation in the mean flux, and they make the flux field significantly non-Gaussian. We find that a hydrodynamic simulation on a 1024 cubed grid in a 75.7 Mpc box reproduces the observed DA from the low density IGM with parameters values H_o=71 km/s/Mpc, Omega_Lambda=0.73, Omega_m=0.27, Omega_b=0.044, sigma_8=0.9 and a UV background that has an ionization rate that is 1.08 +/- 0.08 times the prediction by Madau, Haardt & Rees (1999).Comment: Submitted to Ap

Understanding/unravelling carotenoid excited singlet states.

Carotenoids are essential light-harvesting pigments in natural photosynthesis. They absorb in the blue–green region of the solar spectrum and transfer the absorbed energy to (bacterio-)chlorophylls, and thus expand the wavelength range of light that is able to drive photosynthesis. This process is an example of singlet–singlet excitation energy transfer, and carotenoids serve to enhance the overall efficiency of photosynthetic light reactions. The photochemistry and photophysics of carotenoids have often been interpreted by referring to those of simple polyene molecules that do not possess any functional groups. However, this may not always be wise because carotenoids usually have a number of functional groups that induce the variety of photochemical behaviours in them. These differences can also make the interpretation of the singlet excited states of carotenoids very complicated. In this article, we review the properties of the singlet excited states of carotenoids with the aim of producing as coherent a picture as possible of what is currently known and what needs to be learned

Spectroscopic Analysis of H I Absorption Line Systems in 40 HIRES Quasars

We list and analyze H I absorption lines at redshifts 2 < z < 4 with column density (12 < log(N_HI) < 19) in 40 high-resolutional (FWHM = 8.0 km/s) quasar spectra obtained with the Keck+HIRES. We de-blend and fit all H I lines within 1,000 km/s of 86 strong H I lines whose column densities are log(N_HI/[cm^-2]) > 15. Unlike most prior studies, we use not only Lya but also all visible higher Lyman series lines to improve the fitting accuracy. This reveals components near to higher column density systems that can not be seen in Lya. We list the Voigt profile fits to the 1339 H I components that we found. We examined physical properties of H I lines after separating them into several sub-samples according to their velocity separation from the quasars, their redshift, column density and the S/N ratio of the spectrum. We found two interesting trends for lines with 12 < log(N_HI) < 15 which are within 200-1000 km/s of systems with log(N_HI) > 15. First, their column density distribution becomes steeper, meaning relatively fewer high column density lines, at z < 2.9. Second, their column density distribution also becomes steeper and their line width becomes broader by about 2-3 km/s when they are within 5,000 km/s of their quasar.Comment: 32 pages, 14 figures, accepted for publication in the Astronomical Journal. A complete version with all tables and figures is available at http://www.astro.psu.edu/users/misawa/pub/Paper/40hires.ps.g

Exploring Entrepreneurial Skills and Competencies in Farm Tourism

Diversification to farm tourism is increasingly seen as a viable development strategy to promote a more diverse and sustainable rural economy and to counter declining farm incomes. However, our understanding of the dynamics of the modern farm tourism business and the entrepreneurial and competitive skills farmers require in making the transition from agriculture to a diversified - and service based - enterprise remains limited. Hence, the aim of this paper is to explore the range of skills and competencies that farmers in the North West of England identify as important when adopting a diversification strategy to farm tourism. With the findings indicating that that whilst a range of managerial skills are valued by farmers, they lack many of the additional business and entrepreneurial competencies required for success. Moreover, this paper acknowledges the need to generate consensus on the requisite skill-set that farm tourism operators require, along with a need for a currently fragmented rural tourism literature to acknowledge the significance of rural entrepreneurship and the characteristics of successful farmers and farm tourism ventures

The Deuterium to Hydrogen Abundance Ratio Towards a Fourth QSO: HS0105+1619

We report the measurement of the primordial D/H abundance ratio towards QSO \object. The column density of the hydrogen in the $z \simeq 2.536$ Lyman limit system is high, \lnhi $= 19.422 \pm 0.009$ \cmm, allowing for the deuterium to be seen in 5 Lyman series transitions. The measured value of the D/H ratio towards QSO \object is found to be D/H$= 2.54 \pm 0.23 \times 10^{-5}$. The metallicity of the system showing D/H is found to be $\simeq 0.01$ solar, indicating that the measured D/H is the primordial D/H within the measurement errors. The gas which shows D/H is neutral, unlike previous D/H systems which were more highly ionized. Thus, the determination of the D/H ratio becomes more secure since we are measuring it in different astrophysical environments, but the error is larger because we now see more dispersion between measurements. Combined with prior measurements of D/H, the best D/H ratio is now D/H$= 3.0 \pm 0.4 \times 10^{-5}$, which is 10% lower than the previous value. The new values for the baryon to photon ratio, and baryonic matter density derived from D/H are $\eta = 5.6 \pm 0.5 \times 10^{-10}$ and \ob $=0.0205 \pm 0.0018$ respectively.Comment: Minor text and reference changes. To appear in the May 10, 2001 issue of the Astrophysical Journa