12,411 research outputs found
The use of LANDSAT digital data and computer implemented techniques for an erosion hazard-reforestation needs assessment
There are no author-identified significant results in this report
DBI Realizations of the Pseudo-Conformal Universe and Galilean Genesis Scenarios
The pseudo-conformal universe is an alternative to inflation in which the
early universe is described by a conformal field theory on approximately flat
space-time. The fields develop time-dependent expectation values, spontaneously
breaking the conformal symmetries to a de Sitter subalgebra, and fields of
conformal weight zero acquire a scale invariant spectrum of perturbations. In
this paper, we show that the pseudo-conformal scenario can be naturally
realized within theories that would ordinarily be of interest for DBI
inflation, such as the world-volume theory of a probe brane in an AdS bulk
space-time. In this approach, the weight zero spectator field can be associated
with a geometric flat direction in the bulk, and its scale invariance is
protected by a shift symmetry.Comment: 34 page
Permeability evolution across carbonate hosted normal fault zones
Acknowledgements: The authors would like to thank Total E&P and BG Group for project funding and support, and the Industry Technology Facilitator for facilitating the collaborative development (grant number 3322PSD). The authors would also like to express their gratitude to the Aberdeen Formation Evaluation Society and the College of Physical Sciences at the University of Aberdeen for partial financial support. Raymi Castilla (Total E&P), Fabrizio Agosta and Cathy Hollis are also thanked for their constructive comments and suggestions to improve the standard of this manuscript as are John Still and Colin Taylor (University of Aberdeen) for technical assistance in the laboratory. Piero Gianolla is thanked for his editorial handling of the manuscript.Peer reviewedPostprin
Do Gender Differences in Perceived Prototypical Computer Scientists and Engineers Contribute to Gender Gaps in Computer Science and Engineering?
Women are vastly underrepresented in the fields of computer science and engineering (CS&E). We examined whether women might view the intellectual characteristics of prototypical individuals in CS&E in more stereotype-consistent ways than men might and, consequently, show less interest in CS&E. We asked 269 U.S. college students (187, 69.5% women) to describe the prototypical computer scientist (Study 1) or engineer (Study 2) through open-ended descriptions as well as through a set of trait ratings. Participants also rated themselves on the same set of traits and rated their similarity to the prototype. Finally, participants in both studies were asked to describe their likelihood of pursuing future college courses and careers in computer science (Study 1) or engineering (Study 2). Across both studies, we found that women offered more stereotype-consistent ratings than did men of the intellectual characteristics of prototypes in CS (Study 1) and engineering (Study 2). Women also perceived themselves as less similar to the prototype than men did. Further, the observed gender differences in prototype perceptions mediated the tendency for women to report lower interest in CS&E fields relative to men. Our work highlights the importance of prototype perceptions for understanding the gender gap in CS&E and suggests avenues for interventions that may increase womenâs representation in these vital fields
Deep dielectric charging of regolith within the Moon\u27s permanently shadowed regions
Abstract Energetic charged particles, such as galactic cosmic rays (GCRs) and solar energetic particles (SEPs), can penetrate deep within the lunar surface, resulting in deep dielectric charging. This charging process depends on the GCR and SEP currents, as well as on the regolith\u27s electrical conductivity and permittivity. In permanently shadowed regions (PSRs) near the lunar poles, the discharging timescales are on the order of a lunation (âŒ20 days). We present the first predictions for deep dielectric charging of lunar regolith. To estimate the resulting subsurface electric fields, we develop a data-driven, one-dimensional, time-dependent model. For model inputs, we use GCR data from the Cosmic Ray Telescope for the Effects of Radiation on board the Lunar Reconnaissance Orbiter and SEP data from the Electron, Proton, and Alpha Monitor on the Advanced Composition Explorer. We find that during the recent solar minimum, GCRs create persistent electric fields up to âŒ700 V/m. We also find that large SEP events create transient but strong electric fields (â„106 V/m) that may induce dielectric breakdown. Such breakdown would likely result in significant modifications to the physical and chemical properties of the lunar regolith within PSRs. Key Points Energetic charged particles deep dielectrically charge the lunar regolithWe model the resulting subsurface electric fieldsThe electric fields may be great enough to induce dielectric breakdown
Assessing the potential of remotely-sensed drone spectroscopy to determine live coral cover on Heron Reef
Coral reefs, as biologically diverse ecosystems, hold significant ecological and economic value. With increased threats imposed on them, it is increasingly important to monitor reef health by developing accessible methods to quantify coral cover. Discriminating between substrate types has previously been achieved with in situ spectroscopy but has not been tested using drones. In this study, we test the ability of using point-based drone spectroscopy to determine substrate cover through spectral unmixing on a portion of Heron Reef, Australia. A spectral mixture analysis was conducted to separate the components contributing to spectral signatures obtained across the reef. The pure spectra used to unmix measured data include live coral, algae, sand, and rock, obtained from a public spectral library. These were able to account for over 82% of the spectral mixing captured in each spectroscopy measurement, highlighting the benefits of using a public database. The unmixing results were then compared to a categorical classification on an overlapping mosaicked drone image but yielded inconclusive results due to challenges in co-registration. This study uniquely showcases the potential of using commercial-grade drones and point spectroscopy in mapping complex environments. This can pave the way for future research, by increasing access to repeatable, effective, and affordable technology
Moduli spaces of G2 manifolds
This paper is a review of current developments in the study of moduli spaces
of G2 manifolds. G2 manifolds are 7-dimensional manifolds with the exceptional
holonomy group G2. Although they are odd-dimensional, in many ways they can be
considered as an analogue of Calabi-Yau manifolds in 7 dimensions. They play an
important role in physics as natural candidates for supersymmetric vacuum
solutions of M-theory compactifications. Despite the physical motivation, many
of the results are of purely mathematical interest. Here we cover the basics of
G2 manifolds, local deformation theory of G2 structures and the local geometry
of the moduli spaces of G2 structures.Comment: 31 pages, 2 figure
Primordial Magnetic Fields, Right Electrons, and the Abelian Anomaly
In the standard model there are charges with abelian anomaly only (e.g.
right-handed electron number) which are effectively conserved in the early
universe until some time shortly before the electroweak scale. A state at
finite chemical potential of such a charge, possibly arising due to asymmetries
produced at the GUT scale, is unstable to the generation of hypercharge
magnetic field. Quite large magnetic fields ( gauss at GeV with typical inhomogeneity scale ) can be
generated. These fields may be of cosmological interest, potentially acting as
seeds for amplification to larger scale magnetic fields through non-linear
mechanisms. Previously derived bounds on exotic violating operators may
also be evaded.Comment: Revised version, to appear in Phys. Rev. Lett.. Analysis has been
extended to larger chemical potentials, for which large magnetic fields
survive at the electroweak scale. Previous bounds on violating
operators are also evaded in this cas
Organic Food and Agriculture - Ethics
Organic food is produced without the use of synthetic fertilizers and pesticides. Four further exclusions in organic production are: genetically modified organisms (GMOs), irradiation, prophylactic antibiotics, and engineered nanoparticles. These six exclusions differentiate organic agriculture from chemical agriculture. Agriculture and food harvesting and production date back millennia, and until about a century ago that history is de facto organic. The Industrial Revolution ushered in an era of novel production strategies. Agriculture was not immune to new views of industrialization and reductionism. Advances in chemistry enabled some implementation of such views. Early in the diffusion of chemical farming practices, the Austrian mystic Rudolf Steiner (1865â1924) called for a differentiated agriculture free of these new synthetic chemical inputs. The terminology, theory, and practices of biodynamic agriculture evolved (in the 1920s and 1930s) from Steinerâs Agriculture Course of 1924. It was a guided evolution, coordinated by Ehrenfried Pfeiffer (1899â1961) in Switzerland. The UK agriculturist, Lord Northbourne (1896â1982), invited Pfeiffer to lead a conference on biodynamics at his farm in Kent (in 1939). The following year Northbourne published his manifesto of organic farming, âLook to the Land.â In that book, he coined the term âorganic farmingâ and wrote of a contest of âorganic versus chemical farmingâ.The ideas and ideals of organic farming quickly proliferated internationally off the back of Northbourneâs 1940 book. Organic farming is now practiced in at least 179 countries, accounts for 50.9 million agricultural hectares, and a market value of US$ 81.6 billion (âŹ75 billion)
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