2,249 research outputs found
Overview of nucleon structure studies
A brief overview of the recent activity in the measurement of the elastic
electromagnetic proton and neutron form factors is presented. It is discussed
how the quality of the data has been greatly improved by performing double
polarization experiments, and the role of two-photon exchange processes will be
highlighted. The spatial information on the quark charge distribibutions in the
nucleon resulting from the form factors measurements will be discussed, as well
as the steady rate of improvements made in the lattice QCD calculations. It is
discussed how generalized parton distributions have emerged as a unifying theme
in hadron physics linking the spatial densities extracted from form factors
with the quark momentum distribution information residing in quark structure
functions. The recent progress in the electromagnetic excitation of the
resonance will also briefly be discussed.Comment: prepared for Proceedings of International Nuclear Physics Conference
(INPC07), typos corrected + references adde
Following Black Hole Scaling Relations Through Gas-Rich Mergers
We present black hole mass measurements from kinematic modeling of
high-spatial resolution integral field spectroscopy of the inner regions of 9
nearby (ultra-)luminous infrared galaxies in a variety of merger stages. These
observations were taken with OSIRIS and laser guide star adaptive optics on the
Keck I and Keck II telescopes, and reveal gas and stellar kinematics inside the
spheres of influence of these supermassive black holes. We find that this
sample of black holes are overmassive ( M) compared to
the expected values based on black hole scaling relations, and suggest that the
major epoch of black hole growth occurs in early stages of a merger, as opposed
to during a final episode of quasar-mode feedback. The black hole masses
presented are the dynamical masses enclosed in 25pc, and could include
gas which is gravitationally bound to the black hole but has not yet lost
sufficient angular momentum to be accreted. If present, this gas could in
principle eventually fuel AGN feedback or be itself blown out from the system.Comment: accepted to Ap
Parents, children and the porous boundaries of the sexual family in law and popular culture
This article focuses on a perceived ideological overlap between popular cultural and judicial treatments of sex and conjugality that contributes to a discursive construction of parenthood and parenting. The author perceives that in both legal and popular cultural texts, there is a sense in which notions of ‘natural’ childhood are discursively constituted as being put at risk by those who reproduce outside of dominant sexual norms, and that signs of normative sexuality (typically in the form of heterosexual coupling) may be treated as a sign of safety. These ideas are rooted in ancient associations between fertility, sexuality and femininity that can also be traced in the historical development of the English language. With the help of commentators such as Martha Fineman, the article situates parents and children within a discourse of family which prioritises conjugality, with consequences for the ways in which the internal and external boundaries of families are delineated
Report on the State of Available Data for the Study of International Trade and Foreign Direct Investment
This report, prepared for the Committee on Economic Statistics of the American Economic Association, examines the state of available data for the study of international trade and foreign direct investment. Data on values of imports and exports of goods are of high quality and coverage, but price data suffer from insufficient detail. It would be desirable to have more data measuring value-added in trade as well as prices of comparable domestic and imported inputs. Value data for imports and exports of services are too aggregated and valuations are questionable, while price data for service exports and imports are almost non-existent. Foreign direct investment data are of high quality but quality has suffered from budget cuts. Data on trade in intellectual property are fragmentary. The intangibility of the trade makes measurement difficult, but budget cuts have added to the difficulties. Modest funding increases would result in data more useful for research and policy analysis.
The Spectral Energy Distribution of CO lines in M82
We present an analysis of the excitation conditions of the molecular gas in
the streamers and the outflow of M82 based on observations obtained at the IRAM
30m telescope. Our analysis of J=1-0 and J=2-1 transitions of CO and 13CO and
the CO(3-2) line in 13 regions outside the central starburst disk shows that
the gas density within the streamer/outflow system is about an orderof
magnitude lower (n(H2) ~ 10^3 cm^-3) than in the central molecular disk. We
have used an LVG model and data from the literature to constrain the flux
density in each CO transition (the `CO line SED') arising from the
streamer/outflow system and the central starburst disk itself. Globally, we
find that the CO flux density up to the J=3-2 line is dominated by the diffuse
outer regions while lines above the J=5-4 transition are almost exclusively
emitted by the central starburst disk. We compare the CO line SED of M82 to CO
observations of galaxies at high redshift and suggest that small high-J/low-J
CO flux density ratios (observed in some of these sources) are not necessarily
caused by a different excitation of the central molecular gas concentration,
but may result from an additional, more extended and diffuse gas reservoir
around these systems, reminiscent of the situation in M82.Comment: 12 pages, 7 figures, accepted by A&
We must become gatekeepers : editing indigenous writing
With the proliferation of Indigenous texts currently published by specialist and mainstream publishers, non-Indigenous editors increasingly find themselves negotiating the uncomfortable territories of race, politics and power for which current training (in an Australian context) leaves them poorly prepared. Indigenous writer Anita Heiss advocates the employment of Indigenous editors as an \u27ideal\u27 solution, though few are currently working in the Australian industry. Margaret McDonell, an experienced non-Indigenous editor of Indigenous texts, suggests non-Indigenous editors need to \u27undertake a journey of learning\u27 during which \u27assumptions, biases, tastes and preconceptions\u27 are examined. Yet this presents a difficult task within a postcolonial society, when, as identified by Clare Bradford, even the classification of texts into genres such as fiction and the short story represents an entirely Eurocentric construct, \u27not readily correspond[ing] with Aboriginal schemata\u27. The Australian Society of Authors\u27 discussion paper \u27Writing about Indigenous Australia: Some Issues to Consider and Protocols to Follow\u27 provides practical guidelines that may be adapted for editorial use. This article canvasses these and other ideas with a focus on establishing an ethical and appropriately sensitive cross-cultural approach to editing Indigenous writing.<br /
Warm Molecular Gas Traced with CO J=7->6 in the Galaxy's Central 2 Parsecs: Dynamical Heating of the Circumnuclear Disk
We present an 11 arcsec resolution map of the central two parsecs of the
Galaxy in the CO J =7->6 rotational transition. The CO emission shows rotation
about Sgr A*, but also evidence for non-circular turbulent motion and a clumpy
morphology. We combine our dataset with available CO measurements to model the
physical conditions in the disk. We find that the molecular gas in the region
is both warm and dense, with T~200-300 K, n_H2~50,000-70,000 cm^-3. The mass of
warm molecular gas we measure in the central two parsecs is at least 2000
M_solar, about 20 times the UV-excited atomic gas mass, ruling out an UV
heating scenario for the molecular material. We compare the available spectral
tracers with theoretical models and conclude that molecular gas is heated with
magneto-hydrodynamic shocks with v~10-20 kms and B~0.3-0.5 mG. Using the
conditions derived with the CO analysis, we include the other important
coolants--neutral oxygen and molecular hydrogen--to estimate the total cooling
budget of the molecular material. We derive a mass to luminosity ratio of 2-3
M_solar/ L_solar, which is consistent with the total power dissipated via
turbulent decay in 0.1 pc cells with v_rms~15 kms. These size and velocity
scales are comparable to the observed clumping scale and the velocity
dispersion. At this rate, the material near Sgr A* its dissipating its orbital
energy on an orbital timescale, and cannot last for more than a few orbits. Our
conclusions support a scenario in which the features near Sgr A* such as the
CND and northern arm are generated by infalling clouds with low specific
angular momentum.Comment: 31 pages, including 5 figures, accepted for publication in Ap
The promoter from SlREO, a highly-expressed, root-specific Solanum lycopersicum gene, directs expression to cortex of mature roots
Root-specific promoters are valuable tools for targeting transgene expression, but many of those already described have limitations to their general applicability. We present the expression characteristics of SlREO, a novel gene isolated from tomato (Solanum lycopersicum L.). This gene was highly expressed in roots but had a very low level of expression in aerial plant organs. A 2.4-kb region representing the SlREO promoter sequence was cloned upstream of the uidA GUS reporter gene and shown to direct expression in the root cortex. In mature, glasshouse-grown plants this strict root specificity was maintained. Furthermore, promoter activity was unaffected by dehydration or wounding stress but was somewhat suppressed by exposure to NaCl, salicylic acid and jasmonic acid. The predicted protein sequence of SlREO contains a domain found in enzymes of the 2-oxoglutarate and Fe(II)-dependent dioxygenase superfamily. The novel SlREO promoter has properties ideal for applications requiring strong and specific gene expression in the bulk of tomato root tissue growing in soil, and is also likely to be useful in other Solanaceous crop
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