The derivation of the formyl-group oxygen of chlorophyll b in higher plants from molecular oxygen.

The mechanism of formation of the formyl group of chlorophyll b has long been obscure but, in this paper, the origin of the 7-formyl-group oxygen of chlorophyll b in higher plants was determined by greening etiolated maize leaves, excised from dark-grown plants, by illumination under white light in the presence of either H218O or 18O2 and examining the newly synthesized chlorophylls by mass spectroscopy. To minimize the possible loss of 18O label from the 7-formyl substituent by reversible formation of chlorophyll b-71-gem-diol (hydrate) with unlabelled water in the cell, the formyl group was reduced to a hydroxymethyl group during extraction with methanol containing NaBH4: chlorophyll a remained unchanged during this rapid reductive extraction process. Mass spectra of chlorophyll a and [7-hydroxymethyl]-chlorophyll b extracted from leaves greened in the presence of either H218O or 18O2 revealed that 18O was incorporated only from molecular oxygen but into both chlorophylls: the mass spectra were consistent with molecular oxygen providing an oxygen atom not only for incorporation into the 7-formyl group of chlorophyll b but also for the well-documented incorporation into the 131-oxo group of both chlorophylls a and b [see Walker, C. J., Mansfield, K. E., Smith, K. M. & Castelfranco, P. A. (1989) Biochem. J. 257, 599–602]. The incorporation of isotope led to as much as 77% enrichment of the 131-oxo group of chlorophyll a: assuming identical incorporation into the 131 oxygen of chlorophyll b, then enrichment of the 7-formyl oxygen was as much as 93%. Isotope dilution by re-incorporation of photosynthetically produced oxygen from unlabelled water was negligible as shown by a greening experiment in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea. The high enrichment using 18O2, and the absence of labelling by H218O, unequivocally demonstrates that molecular oxygen is the sole precursor of the 7-formyl oxygen of chlorophyll b in higher plants and strongly suggests a single pathway for the formation of the chlorophyll b formyl group involving the participation of an oxygenase-type enzyme

What do people do with porn? qualitative research into the consumption, use and experience of pornography and other sexually explicit media

This article reviews qualitative research into the consumption of pornography and other sexually explicit media emerging from a range of subject areas. Taking a critique of quantitative methods and a focus on measuring sexual effects and attitudes as a starting point, it considers the proposition that qualitative work is more suited to an examination of the complex social, cultural and political constructions of sexuality. Examining studies into the way men, women and young people see, experience, and use explicit media texts, the article identifies the key findings that have emerged. Qualitative work shows that sexuality explicit media texts are experienced and understood in a variety of ways and evoke strong and often contradictory reactions, not all of which are represented in public debates about pornography. These texts function in a range of different ways, depending on context; as a source of knowledge, a resource for intimate practices, a site for identity construction, and an occasion for performing gender and sexuality. The article reviews these studies and their findings, identifying what they suggest about directions for future research, both in terms of developing methodology and refining approaches to sexuality and media consumption.</p

A Monte Carlo simulation of the Sudbury Neutrino Observatory proportional counters

The third phase of the Sudbury Neutrino Observatory (SNO) experiment added an array of 3He proportional counters to the detector. The purpose of this Neutral Current Detection (NCD) array was to observe neutrons resulting from neutral-current solar neutrino-deuteron interactions. We have developed a detailed simulation of the current pulses from the NCD array proportional counters, from the primary neutron capture on 3He through the NCD array signal-processing electronics. This NCD array Monte Carlo simulation was used to model the alpha-decay background in SNO's third-phase 8B solar-neutrino measurement.Comment: 38 pages; submitted to the New Journal of Physic

Low-Multiplicity Burst Search At The Sudbury Neutrino Observatory

Results are reported from a search for low-multiplicity neutrino bursts in the Sudbury Neutrino Observatory. Such bursts could indicate the detection of a nearby core-collapse supernova explosion. The data were taken from Phase I (1999 November-2001 May), when the detector was filled with heavy water, and Phase II (2001 July-2003 August), when NaCl was added to the target. The search was a blind analysis in which the potential backgrounds were estimated and analysis cuts were developed to eliminate such backgrounds with 90% confidence before the data were examined. The search maintained a greater than 50% detection probability for standard supernovae occurring at a distance of up to 60 kpc for Phase I and up to 70 kpc for Phase II. No low-multiplicity bursts were observed during the data-taking period.Natural Sciences and Engineering Research Council, CanadaIndustry Canada, CanadaNational Research Council, CanadaNorthern Ontario Heritage Fund, CanadaAtomic Energy of Canada, Ltd., CanadaOntario Power Generation, CanadaHigh Performance Computing Virtual Laboratory, CanadaCanada Foundation for Innovation, CanadaCanada Research Chairs, CanadaDepartment of Energy, USNational Energy Research Scientific Computing Center, USAlfred P. Sloan Foundation, USScience and Technology Facilities Council, UKFundacao para a Ciencia e a Technologia, PortugalAstronom

Searches For High-Frequency Variations In The B-8 Solar Neutrino Flux At The Sudbury Neutrino Observatory

We have performed three searches for high-frequency signals in the solar neutrino flux measured by the Sudbury Neutrino Observatory, motivated by the possibility that solar g-mode oscillations could affect the production or propagation of solar B-8 neutrinos. The first search looked for any significant peak in the frequency range 1-144 day(-1), with a sensitivity to sinusoidal signals with amplitudes of 12% or greater. The second search focused on regions in which g-mode signals have been claimed by experiments aboard the Solar and Heliospheric Observatory satellite, and was sensitive to signals with amplitudes of 10% or greater. The third search looked for extra power across the entire frequency band. No statistically significant signal was detected in any of the three searches.Natural Sciences and Engineering Research Council, CanadaIndustry Canada, CanadaNational Research Council, CanadaNorthern Ontario Heritage Fund, CanadaAtomic Energy of Canada, Ltd., CanadaOntario Power Generation, CanadaHigh Performance Computing Virtual Laboratory, CanadaCanada Foundation for InnovationDept. of Energy, USNational Energy Research Scientific Computing Center, USScience and Technologies Facilities Council, UKAstronom

Low Multiplicity Burst Search at the Sudbury Neutrino Observatory

Results are reported from a search for low-multiplicity neutrino bursts in the Sudbury Neutrino Observatory (SNO). Such bursts could indicate detection of a nearby core-collapse supernova explosion. The data were taken from Phase I (November 1999 - May 2001), when the detector was filled with heavy water, and Phase II (July 2001 - August 2003), when NaCl was added to the target. The search was a blind analysis in which the potential backgrounds were estimated and analysis cuts were developed to eliminate such backgrounds with 90% confidence before the data were examined. The search maintained a greater than 50% detection probability for standard supernovae occurring at a distance of up to 60 kpc for Phase I and up to 70 kpc for Phase II. No low-multiplicity bursts were observed during the data-taking period.Comment: 11 pages, 4 figures, submitted to Ap

Combined Analysis of all Three Phases of Solar Neutrino Data from the Sudbury Neutrino Observatory

We report results from a combined analysis of solar neutrino data from all phases of the Sudbury Neutrino Observatory. By exploiting particle identification information obtained from the proportional counters installed during the third phase, this analysis improved background rejection in that phase of the experiment. The combined analysis resulted in a total flux of active neutrino flavors from 8B decays in the Sun of (5.25 \pm 0.16(stat.)+0.11-0.13(syst.))\times10^6 cm^{-2}s^{-1}. A two-flavor neutrino oscillation analysis yielded \Deltam^2_{21} = (5.6^{+1.9}_{-1.4})\times10^{-5} eV^2 and tan^2{\theta}_{12}= 0.427^{+0.033}_{-0.029}. A three-flavor neutrino oscillation analysis combining this result with results of all other solar neutrino experiments and the KamLAND experiment yielded \Deltam^2_{21} = (7.41^{+0.21}_{-0.19})\times10^{-5} eV^2, tan^2{\theta}_{12} = 0.446^{+0.030}_{-0.029}, and sin^2{\theta}_{13} = (2.5^{+1.8}_{-1.5})\times10^{-2}. This implied an upper bound of sin^2{\theta}_{13} < 0.053 at the 95% confidence level (C.L.)

A Search for Neutrinos from the Solar hep Reaction and the Diffuse Supernova Neutrino Background with the Sudbury Neutrino Observatory

A search has been made for neutrinos from the hep reaction in the Sun and from the diffus

Independent measurement of the total active B8 solar neutrino flux using an array of He3 proportional counters at the Sudbury Neutrino Observatory

The Sudbury Neutrino Observatory (SNO) used an array of 3He proportional counters to measure the rate of neutral-current interactions in heavy water and precisely determined the total active (νx) 8B solar neutrino flux. This technique is independent of previous methods employed by SNO. The total flux is found to be 5.54-0.31+0.33(stat)-0.34+0.36(syst)×106  cm-2 s-1, in agreement with previous measurements and standard solar models. A global analysis of solar and reactor neutrino results yields Δm2=7.59-0.21+0.19×10-5  eV2 and θ=34.4-1.2+1.3 degrees. The uncertainty on the mixing angle has been reduced from SNO’s previous results

The MAJORANA DEMONSTRATOR: A Search for Neutrinoless Double-beta Decay of Germanium-76

The {\sc Majorana} collaboration is searching for neutrinoless double beta decay using $^{76}$Ge, which has been shown to have a number of advantages in terms of sensitivities and backgrounds. The observation of neutrinoless double-beta decay would show that lepton number is violated and that neutrinos are Majorana particles and would simultaneously provide information on neutrino mass. Attaining sensitivities for neutrino masses in the inverted hierarchy region, $15 - 50$ meV, will require large, tonne-scale detectors with extremely low backgrounds, at the level of $\sim$1 count/t-y or lower in the region of the signal. The {\sc Majorana} collaboration, with funding support from DOE Office of Nuclear Physics and NSF Particle Astrophysics, is constructing the {\sc Demonstrator}, an array consisting of 40 kg of p-type point-contact high-purity germanium (HPGe) detectors, of which $\sim$30 kg will be enriched to 87% in $^{76}$Ge. The {\sc Demonstrator} is being constructed in a clean room laboratory facility at the 4850' level (4300 m.w.e.) of the Sanford Underground Research Facility (SURF) in Lead, SD. It utilizes a compact graded shield approach with the inner portion consisting of ultra-clean Cu that is being electroformed and machined underground. The primary aim of the {\sc Demonstrator} is to show the feasibility of a future tonne-scale measurement in terms of backgrounds and scalability.Comment: Proceedings for the MEDEX 2013 Conferenc