2,634 research outputs found
Recapping the History of the Antipodes: Reappraising Absolute and Relative Connotations
Article originally published by Research in Geographic EducationDuring the first half of the 20th century teaching and learning about the antipodes were considered a fundamental element within the undergraduate geography curricula. However, in the 1970s the antipodes were absent from Bacon’s surveys of domain, core, and sphere concepts in human and physical geography. In fast forwarding to the 21st century, the term has virtually disappeared from introductory-level geography curricula. This exploration confirms that rather than being an obscure concept, the antipodes percolate across a diverse range of illustrations in mathematics, cartography, geology, astronomy, to cultural geography, literature and social theory. Our discourse supports reclaiming the antipodes for their geodetic value within the undergraduate introductory geography curriculum, but stresses sensitivities when using relative connotations in social, cultural, and political arenas
SANDALWOOD AS A COMPONENT OF AGROFORESTRY: EXPLORATION OF PARASITISM AND COMPETITION WITH THE WANULCAS MODEL
Sandalwood is an important component of agroforestry systems in the drier Eastern parts of Indonesia, although its value to farmers is still limited by existing policies and regulation of marketing. As a relatively slow growing root parasite, sandalwood will interact with other components in a complex pattern of competition and host-parasite relationships, depending on root distribution and rooting depth of potential hosts. We describe a number of modifications to the generic tree-soil-crop simulation model WaNuLCAS, that allow exploration of the transition between parasitism and competition. The key variable in this transition is the effectiveness of formation of the parasitic link for all situations where roots of the host and parasite occur in the same volume of soil. At low values of this effectiveness competition dominates, at higher values sandalwood will weaken the host, until it effectively kills it, leading to an optimum response of sandalwood to the effectiveness parameter. Unresolved questions in the formulation of the model are the lifespan of parasitized roots and the question whether or not sandalwood will allocate energy resources for maintenance respiration of host roots after the formation of haustoria. The'desk study' reported here was intended to focus subsequent field studies on these unresolved issues
Hyaluronan concentration and size distribution in human knee synovial fluid: variations with age and cartilage degeneration.
BackgroundOne potential mechanism for early superficial cartilage wear in normal joints is alteration of the lubricant content and quality of synovial fluid. The purpose of this study was to determine if the concentration and quality of the lubricant, hyaluronan, in synovial fluid: (1) was similar in left and right knees; (2) exhibited similar age-associated trends, whether collected postmortem or antemortem; and (3) varied with age and grade of joint degeneration.MethodsHuman synovial fluid of donors (23-91 years) without osteoarthritis was analyzed for the concentrations of protein, hyaluronan, and hyaluronan in the molecular weight ranges of 2.5-7 MDa, 1-2.5 MDa, 0.5-1 MDa, and 0.03-0.5 MDa. Similarity of data between left and right knees was assessed by reduced major axis regression, paired t-test, and Bland-Altman analysis. The effect of antemortem versus postmortem collection on biochemical properties was assessed for age-matched samples by unpaired t-test. The relationships between age, joint grade, and each biochemical component were assessed by regression analysis.ResultsJoint grade and the concentrations of protein, hyaluronan, and hyaluronan in the molecular weight ranges of 2.5-7 MDa, 1-2.5 MDa, and 0.5-1 MDa in human synovial fluid showed good agreement between left and right knees and were similar between age-matched patient and cadaver knee joints. There was an age-associated decrease in overall joint grade (-15Â %/decade) and concentrations of hyaluronan (-10.5Â %/decade), and hyaluronan in the molecular weight ranges of 2.5-7 MDa (-9.4Â %/decade), 1-2.5 MDa (-11.3Â %/decade), 0.5-1 MDa (-12.5Â %/decade), and 0.03-0.5 MDa (-13.0Â %/decade). Hyaluronan concentration and quality was more strongly associated with age than with joint grade.ConclusionsThe age-related increase in cartilage wear in non-osteoarthritic joints may be related to the altered hyaluronan content and quality of synovial fluid
Sandalwood as a Component of Agroforestry: Exploration of Parasitism and Competition with the Wanulcas Model
Sandalwood is an important component of agroforestry systems in the drier Eastern parts of Indonesia, although its value to farmers is still limited by existing policies and regulation of marketing. As a relatively slow growing root parasite, sandalwood will interact with other components in a complex pattern of competition and host-parasite relationships, depending on root distribution and rooting depth of potential hosts. We describe a number of modifications to the generic tree-soil-crop simulation model WaNuLCAS, that allow exploration of the transition between parasitism and competition. The key variable in this transition is the effectiveness of formation of the parasitic link for all situations where roots of the host and parasite occur in the same volume of soil. At low values of this effectiveness competition dominates, at higher values sandalwood will weaken the host, until it effectively kills it, leading to an optimum response of sandalwood to the effectiveness parameter. Unresolved questions in the formulation of the model are the lifespan of parasitized roots and the question whether or not sandalwood will allocate energy resources for maintenance respiration of host roots after the formation of haustoria. The'desk study' reported here was intended to focus subsequent field studies on these unresolved issues
Time-Dependent Point Source Search Methods in High Energy Neutrino Astronomy
We present maximum-likelihood search methods for time-dependent fluxes from
point sources, such as flares or periodic emissions. We describe a method for
the case when the time dependence of the flux can be assumed a priori from
other observations, and we additionally describe a method to search for bursts
with an unknown time dependence. In the context of high energy neutrino
astronomy, we simulate one year of data from a cubic-kilometer scale neutrino
detector and characterize these methods and equivalent binned methods with
respect to the duration of neutrino emission. Compared to standard
time-integrated searches, we find that up to an order of magnitude fewer events
are needed to discover bursts with short durations, even when the burst time
and duration are not known a priori.Comment: LaTeX; 17 Pages, 4 figures; submitted to Astroparticle Physic
Study of the Spectral and Temporal Characteristics of X-Ray Emission of the Gamma-Ray Binary LS 5039 with Suzaku
We report on the results from Suzaku broadband X-ray observations of the
galactic binary source LS5039. The Suzaku data, which have continuous coverage
of more than one orbital period, show strong modulation of the X-ray emission
at the orbital period of this TeV gamma-ray emitting system.The X-ray emission
shows a minimum at orbital phase ~ 0.1, close to the so-called superior
conjunction of the compact object, and a maximum at phase ~0.7, very close to
the inferior conjunction of the compact object. The X-ray spectral data up to
70 keV are described by a hard power-law with a phase-dependent photon index
which varies within Gamma ~1.45 - 1.61. The amplitude of the flux variation is
a factor of 2.5, but is significantly less than that of the factor ~8 variation
in the TeV flux. Otherwise the two light curves are similar, but not identical.
Although periodic X-ray emission has been found from many galactic binary
systems, the Suzaku result implies a phenomenon different from the "standard"
origin of X-rays related to the emission of the hot accretion plasma formed
around the compact companion object. The X-ray radiation of LS5039is likely to
be linked to very-high-energy electrons which are also responsible for the TeV
gamma-ray emission. While the gamma-rays are the result of inverse Compton
scattering by electrons on optical stellar photons, X-rays are produced via
synchrotron radiation. Yet, while the modulation of the TeV gamma-ray signal
can be naturally explained by the photon-photon pair production and anisotropic
inverse Compton scattering, the observed modulation of synchrotron X-rays
requires an additional process, the most natural one being adiabatic expansion
in the radiation production region.Comment: 9 pages, 7 figures, Accepted for publication in ApJ, references
fixed, a few typos correcte
A Letter of Intent to Install a milli-charged Particle Detector at LHC P5
In this LOI we propose a dedicated experiment that would detect
"milli-charged" particles produced by pp collisions at LHC Point 5. The
experiment would be installed during LS2 in the vestigial drainage gallery
above UXC and would not interfere with CMS operations. With 300 fb of
integrated luminosity, sensitivity to a particle with charge
can be achieved for masses of GeV,
and charge for masses of GeV,
greatly extending the parameter space explored for particles with small charge
and masses above 100 MeV.Comment: 19 pages, 7 figure
- …