14,787 research outputs found
Cosmic Attractors and Gauge Hierarchy
We suggest a new cosmological scenario which naturally guarantees the
smallness of scalar masses and VEVs, without invoking supersymmetry or any
other (non-gravitationaly coupled) new physics at low energies. In our
framework, the scalar masses undergo discrete jumps due to nucleation of closed
branes during (eternal) inflation. The crucial point is that the step size of
variation decreases in the direction of decreasing scalar mass. This scenario
yields exponentially large domains with a distribution of scalar masses, which
is sharply peaked around a hierarchically small value of the mass. This value
is the "attractor point" of the cosmological evolution
Rethinking the GDR opposition: reform, resistance and revolution in the other Germany
This thesis looks at communist-oriented opposition in the GDR. Specifically, it considers reconstructions of this phenomenon within state-mandated memory since German unification in 1990. It presents three case studies of particular representative value. The first is dedicated to Paul Merker and how his entanglement in questions surrounding antifascism and antisemitism has become a significant trope in narratives of national (de-)legitimisation since 1990. The second delves into the phenomenon of the dissident through the aperture of prominent singer-songwriter, Wolf Biermann. Viewed as a proponent of ‘true’ communism who confronted the SED with uncomfortable truths, this study interrogates the Biermann legend. The third looks at the canonised opposition of the 1980s and how memory thereof tends to omit the left-wing views of these groups in order to portray them as striving for liberal democracy and national unification.
The dissertation concludes that communist-oriented opposition presents a rich seam with which the FRG’s public guardians of memory are able to communicate narratives significant to contemporary national legitimation and identity. It argues that awareness of the ideological conditioning of representations of the past and the significance of this for contemporary political debates should be taken into account more than is frequently the case
Nitrogen superfractionation in dense cloud cores
We report new calculations of interstellar 15N fractionation. Previously, we
have shown that large enhancements of 15N/14N can occur in cold, dense gas
where CO is frozen out, but that the existence of an NH + N channel in the
dissociative recombination of N2H+ severely curtails the fractionation. In the
light of recent experimental evidence that this channel is in fact negligible,
we have reassessed the 15N chemistry in dense cloud cores. We consider the
effects of temperatures below 10 K, and of the presence of large amounts of
atomic nitrogen. We also show how the temporal evolution of gas-phase isotope
ratios is preserved as spatial heterogeneity in ammonia ice mantles, as
monolayers deposited at different times have different isotopic compositions.
We demonstrate that the upper layers of this ice may have 15N/14N ratios an
order of magnitude larger than the underlying elemental value. Converting our
ratios to delta-values, we obtain delta(15N) > 3,000 per mil in the uppermost
layer, with values as high as 10,000 per mil in some models. We suggest that
this material is the precursor to the 15N `hotspots' recently discovered in
meteorites and IDPsComment: accepted by MNRA
Investigating the noise residuals around the gravitational wave event GW150914
We use the Pearson cross-correlation statistic proposed by Liu and Jackson,
and employed by Creswell et al., to look for statistically significant
correlations between the LIGO Hanford and Livingston detectors at the time of
the binary black hole merger GW150914. We compute this statistic for the
calibrated strain data released by LIGO, using both the residuals provided by
LIGO and using our own subtraction of a maximum-likelihood waveform that is
constructed to model binary black hole mergers in general relativity. To assign
a significance to the values obtained, we calculate the cross-correlation of
both simulated Gaussian noise and data from the LIGO detectors at times during
which no detection of gravitational waves has been claimed. We find that after
subtracting the maximum likelihood waveform there are no statistically
significant correlations between the residuals of the two detectors at the time
of GW150914.Comment: 14 pages, 7 figures. Minor text and figure changes in final v3.
Notebooks for generating the results are available at
https://github.com/gwastro/gw150914_investigatio
Intragenic meiotic recombination in Schizosaccharomyces pombe is sensitive to environmental temperature changes
Open Access via the Springer Compact Agreement Acknowledgments We are grateful to Miguel G. Ferreira, Jürg Kohli, Josef Loidl, Fekret Osman, Gerald R. Smith, Walter W. Steiner, and Matthew Whitby for providing strains. We thank Josef Loidl for critically reading an earlier version of this manuscript. This work was supported by the Biotechnology and Biological Sciences Research Council UK (BBSRC) [grant number BB/F016964/1], and the University of Aberdeen (College of Life Sciences and Medicine Start-up grant to AL).Peer reviewedPublisher PD
Flow Dynamics And Plasma Heating Of Spheromaks In SSX
We report several new experimental results related to flow dynamics and heating from single dipole-trapped spheromaks and spheromak merging studies at SSX. Single spheromaks (stabilized with a pair of external coils, see Brown, Phys. Plasmas 13 102503 (2006)) and merged FRC-like configurations (see Brown, Phys. Plasmas 13, 056503 (2006)) are trapped in our prolate (R = 0.2 m, L = 0.6 m) copper flux conserver. Local spheromak flow is studied with two Mach probes (r(1) = rho(i) ) calibrated by time-of-flight with a fast set of magnetic probes at the edge of the device. Both Mach probes feature six ion collectors housed in a boron nitride sheath. The larger Mach probe will ultimately be used in the MST reversed field pinch. Line averaged flow is measured by ion Doppler spectroscopy (IDS) at the midplane. The SSX IDS instrument measures with 1 mu s or better time resolution the width and Doppler shift of the C-III impurity (H plasma) 229.7 nm line to determine the temperature and line-averaged flow velocity (see Cothran, RSI 77, 063504 (2006)). We find axial flows up to 100 km/s during formation of the dipole trapped spheromak. Flow returns at the wall to form a large vortex. Recent high-resolution IDS velocity measurements during spheromak merging show bi-directional outflow jets at +/- 40 km/s (nearly the Alfven speed). We also measure T-i \u3e= 80 eV and T-e \u3e= 20 eV during spheromak merging events after all plasma facing surfaces are cleaned with helium glow discharge conditioning. Transient electron heating is inferred from bursts on a four-channel soft x-ray array. The spheromaks are also characterized by a suite of magnetic probe arrays for magnetic structure B(r,t), and interferometry for n(e) . Finally, we are designing a new oblate, trapezoidal flux conserver for FRC studies. Equilibrium and dynamical simulations suggest that a tilt-stable, oblate FRC can be formed by spheromak merging in the new flux conserver
Synthesis and characterization of biodegradable lignin nanoparticles with tunable surface properties
Lignin nanoparticles can serve as biodegradable carriers of biocidal actives with minimal environmental footprint. Here we describe the colloidal synthesis and interfacial design of nanoparticles with tunable surface properties using two different lignin precursors, Kraft (Indulin AT) lignin and Organosolv (high-purity lignin). The green synthesis process is based on flash precipitation of dissolved lignin polymer, which enabled the formation of nanoparticles in the size range of 45–250 nm. The size evolution of the two types of lignin particles is fitted on the basis of modified diffusive growth kinetics and mass balance dependencies. The surface properties of the nanoparticles are fine-tuned by coating them with a cationic polyelectrolyte, poly(diallyldimethylammonium chloride). We analyze how the colloidal stability and dispersion properties of these two types of nanoparticles vary as a function of pH and salinities. The data show that the properties of the nanoparticles are governed by the type of lignin used and the presence of polyelectrolyte surface coating. The coating allows the control of the nanoparticles’ surface charge and the extension of their stability into strongly basic regimes, facilitating their potential application at extreme pH conditions
Electric field control of the magnetic chiralities in ferroaxial multiferroic RbFe(MoO4)2
The coupling of magnetic chiralities to the ferroelectric polarisation in
multiferroic RbFe(MoO) is investigated by neutron spherical
polarimetry. Because of the axiality of the crystal structure below
= 190 K, helicity and triangular chirality are
symmetric-exchange coupled, explaining the onset of the ferroelectricity in
this proper-screw magnetic structure - a mechanism that can be generalised to
other systems with "ferroaxial" distortions in the crystal structure. With an
applied electric field we demonstrate control of the chiralities in both
structural domains simultaneously.Comment: 5 pages, 4 figure
Horticultural protocols for experimental studies of eyebrights (Euphrasia, Orobanchaceae):Student Project
Parasitic plants are particularly challenging to cultivate as the growth conditions must be suitable for the parasite, the host, and their interaction. Here, we review our progress growing British native eyebrights (Euphrasia), a group of hemiparasitic plants found in diverse habitats in Britain and Ireland. We consider the protocols required to grow them under a range of conditions, including the laboratory, in pot trials, in cultivated fields, and in the wild. We highlight the need to use seed stratification to break seed dormancy, to replicate planting to overcome low seed viability, and to manage host plants to avoid competition. While Euphrasia can be successfully grown in different environments more work is required to develop reliable horticultural protocols for growing plants under natural conditions
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