4,916 research outputs found
Legumes as a Biological Tool to Address the Sustainability of Ruminant Production Systems
Growing public concern regarding accelerated rates of climate change, the depletion and degradation of natural resources such as biodiversity water and soils, coupled with policy commitments to address these challenges, are placing increasing pressures to enhance sustainability metrics associated with agriculture in general, and ruminant production systems in particular. At EU and indeed global scale, there has probably never before been so many potentially conflicting challenges for agriculture. On one hand, agricultural systems need to produce more, to feed the increasing global human population, while at the same time being much less reliant on economically and environmentally costly chemical inputs and protecting natural resources. Within this paper we provide an overview of recent research that demonstrates the potential contributions that legume inclusion within grass swards can make to developing more sustainable and resilient ruminant productions systems
Security Proof for Quantum Key Distribution Using Qudit Systems
We provide security bounds against coherent attacks for two families of
quantum key distribution protocols that use -dimensional quantum systems. In
the asymptotic regime, both the secret key rate for fixed noise and the
robustness to noise increase with . The finite-key corrections are found to
be almost insensitive to .Comment: 5 pages, 1 figure, version 3 corrects equations (9) and (11), and
slightly modifies the figure to reflect the change to equation (11
Lack of involvement of known DNA methyltransferases in familial hydatidiform mole implies the involvement of other factors in establishment of imprinting in the human female germline
BACKGROUND:
Differential methylation of the two alleles is a hallmark of imprinted genes. Correspondingly, loss of DNA methyltransferase function results in aberrant imprinting and abnormal post-fertilization development. In the mouse, mutations of the oocyte-specific isoform of the DNA methyltransferase Dnmt1 (Dnmt1o) and of the methyltransferase-like Dnmt3L gene result in specific failures of imprint establishment or maintenance, at multiple loci. We have previously shown in humans that an analogous inherited failure to establish imprinting at multiple loci in the female germline underlies a rare phenotype of recurrent hydatidiform mole.
RESULTS:
We have identified a human homologue of the murine Dnmt1o and assessed its pattern of expression. Human DNMT1o mRNA is detectable in mature oocytes and early fertilized embryos but not in any somatic tissues analysed. The somatic isoform of DNMT1 mRNA, in contrast, is not detectable in human oocytes. In the previously-described family with multi-locus imprinting failure, mutation of DNMT1o and of the other known members of this gene family has been excluded.
CONCLUSIONS:
Mutation of the known DNMT genes does not underlie familial hydatidiform mole, at least in the family under study. This suggests that trans-acting factors other than the known methyltransferases are required for imprint establishment in humans, a concept that has indirect support from recent biochemical studies of DNMT3L
Do ultrafast exciton-polaron decoherence dynamics govern photocarrier generation efficiencies in polymer solar cells?
All-organic-based photovoltaic solar cells have attracted considerable
attention because of their low-cost processing and short energy payback time.
In such systems the primary dissociation of an optical excitation into a pair
of photocarriers has been recently shown to be extremely rapid and efficient,
but the physical reason for this remains unclear. Here, two-dimensional
photocurrent excitation spectroscopy, a novel non-linear optical spectroscopy,
is used to probe the ultrafast coherent decay of photoexcitations into
charge-producing states in a polymer:fullerene based solar cell. The
two-dimensional photocurrent spectra are interpreted by introducing a
theoretical model for the description of the coupling of the electronic states
of the system to an external environment and to the applied laser fields. The
experimental data show no cross-peaks in the two-dimensional photocurrent
spectra, as predicted by the model for coherence times between the exciton and
the photocurrent producing states of 20\,fs or less
Finite-key security against coherent attacks in quantum key distribution
The work by Christandl, K\"onig and Renner [Phys. Rev. Lett. 102, 020504
(2009)] provides in particular the possibility of studying unconditional
security in the finite-key regime for all discrete-variable protocols. We spell
out this bound from their general formalism. Then we apply it to the study of a
recently proposed protocol [Laing et al., Phys. Rev. A 82, 012304 (2010)]. This
protocol is meaningful when the alignment of Alice's and Bob's reference frames
is not monitored and may vary with time. In this scenario, the notion of
asymptotic key rate has hardly any operational meaning, because if one waits
too long time, the average correlations are smeared out and no security can be
inferred. Therefore, finite-key analysis is necessary to find the maximal
achievable secret key rate and the corresponding optimal number of signals.Comment: 9 pages, 4 figure
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A quantitative evolved gas analysis for extra-terrestrial samples
Evolved gas analysis (EGA) has been successfully applied to the studies of meteorites and Apollo lunar samples. It consists of linear heating of a material with registration of the released volatile compounds, typically using a spectrometric technique. However, so far no quantitative comparison was possible of the amount of gases released during heating of a sample. To address this limitation, we have developed a Quantitative EGA (QEGA) technique using our custom-built Finesse mass spectrometry system. It is based on calibration of the quadrupole mass spectrometer with reference gases (e.g. CO2, CO, H2, O2, N2 or their mixtures with known relative abundances) with known flow rate. The method was tested using simple chemical compounds such as CaCO3, which give well-known amounts of pure gases during their thermal decomposition. We present initial QEGA data on two reference meteorites, Allende and Murchison. Our QEGA work is also informing the design and operation of ProSPA spaceflight instruments being developed to perform analogous experiments in situ on the lunar surface through the European Space Agency's PROSPECT payload on Luna 27
EVALUATING THE EFFECTIVENESS OF THE COURSEWARE DEVELOPMENT PROJECT: PILOT STUDIES
This project involves a comprehensive generalizable and transferable evaluation of the Courseware Development Project (CDP) at Dalhousie University\u27s School of Business Administration. This C$3 million, three-year project is divided into four levels over three time phases. The results of the study of the impact of this unique project are expected to be both relevant and applicable to other universities in Canada and throughout the world. This on-going evaluation of the CDP centers around a systems model where: inputs are divided into drivers and materials; throughputs are the conversion processes on a matrix composed of six parties (faculty, students, staff, administrators, organizational structure and processes, and contributing/participating corporations) as the rows and the four levels of the CDP as the columns; and outputs are divided into manifest and latent variables. Demographic, attitudinal, behavioral, and organizational variables will be used in a time series analysis. Using an action research model over the proposed three-year full study, the researchers will assess which elements Of the project are effective at the end of each year of the evaluation. Based on this information the researchers will keep the effective elements in place for the next year and modify any ineffective elements based on the first year\u27s results and competing theory. This cycle will be repeated after year two. Thus the proposed study will contribute to evaluation methodology as described in this paper by treating simultaneously both a case study and a quasiexperiment of the impact of computers on (business) education. A preliminary description of the effects arising from Level 0, the integration of computers in the business school, and Level 1, courseware development. is given here. The general impact of the project upon faculty, staff, and students is described and preliminary findings are presented
All-Optical Broadband Excitation of the Motional State of Trapped Ions
We have developed a novel all-optical broadband scheme for exciting,
amplifying and measuring the secular motion of ions in a radio frequency trap.
Oscillation induced by optical excitation has been coherently amplified to
precisely control and measure the ion's secular motion. Requiring only laser
line-of-sight, we have shown that the ion's oscillation amplitude can be
precisely controlled. Our excitation scheme can generate coherent motion which
is robust against variations in the secular frequency. Therefore, our scheme is
ideal to excite the desired level of oscillatory motion under conditions where
the secular frequency is evolving in time. Measuring the oscillation amplitude
through Doppler velocimetry, we have characterized the experimental parameters
and compared them with a molecular dynamics simulation which provides a
complete description of the system.Comment: 8 pages, 10 figure
Polysaccharide utilization loci and nutritional specialization in a dominant group of butyrate-producing human colonic Firmicutes
Acknowledgements The Rowett Institute of Nutrition and Health (University of Aberdeen) receives financial support from the Scottish Government Rural and Environmental Sciences and Analytical Services (RESAS). POS is a PhD student supported by the Scottish Government (RESAS) and the Science Foundation Ireland, through a centre award to the APC Microbiome Institute, Cork, Ireland. Data Summary The high-quality draft genomes generated in this work were deposited at the European Nucleotide Archive under the following accession numbers: 1. Eubacterium rectale T1-815; CVRQ01000001–CVRQ0100 0090: http://www.ebi.ac.uk/ena/data/view/PRJEB9320 2. Roseburia faecis M72/1; CVRR01000001–CVRR010001 01: http://www.ebi.ac.uk/ena/data/view/PRJEB9321 3. Roseburia inulinivorans L1-83; CVRS01000001–CVRS0 100 0151: http://www.ebi.ac.uk/ena/data/view/PRJEB9322Peer reviewedPublisher PD
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Beagle 2: Mission to Mars — current status
Beagle 2, developed in the UK, was launched on June 2, 2003. It landed on Mars on December 25th, 2003 in Isidis Planitia, a large sedimentary basin. To date, the team is awaiting signals from the Beagle 2 lander. Current status of the mission will be reported
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