1,853 research outputs found
The challenge to democracy IV. The test of citizenship
When democracy is challenged there comes to its people a test of their worthiness of the citizenship enjoyed. That the test is too little publicized and that it is too often ignored by those failing to measure up to it makes it no less rigorous, no less demanding and no less indicative of possible service to democracy. An understanding of the test entails a knowledge of the privileges extended to those people, the obligations incurred, the obstacles in the way of the fullest enjoyment of that citizenship and the opportunities offered.
Not only are American citizens guaranteed certain often-mentioned rights, but most may enjoy many privileges in which they take pride. Not only is one guaranteed certain rights upon which his life and liberty are believed to depend, but certain privileges are extended to him for the benefit of the community. Not only is his life and liberty protected from others, but he and his fellows may have an appropriate part in determining the conditions under which they live and have liberty
Star Formation Rate from Dust Infrared Emission
We examine what types of galaxies the conversion formula from dust infrared
(IR) luminosity into the star formation rate (SFR) derived by
Kennicutt (1998) is applicable to. The ratio of the observed IR luminosity,
, to the intrinsic bolometric luminosity of the newly (\la 10
Myr) formed stars,
, of a galaxy can be determined by a mean dust opacity in the
interstellar medium and the activity of the current star formation. We find
that these parameters area being is very large, and many nearby normal and active star-forming
galaxies really fall in this area. It results from offsetting two effects of a
small dust opacity and a large cirrus contribution of normal galaxies relative
to starburst galaxies on the conversion of the stellar emission into the dust
IR emission. In conclusion, the SFR determined from the IR luminosity under the
assumption of like Kennicutt (1998) is reliable within
a factor of 2 for all galaxies except for dust rich but quiescent galaxies and
extremely dust poor galaxies.Comment: Accepted by ApJL: 6 pages (emulateapj5), 2 figures (one is an extra
figure not appeared in ApJL
Laparoscopy in the Treatment of Early Cervical Carcinoma
Recent investigators have used several indications to incorporate laparoscopy in the management of patients with cervical cancer. This manuscript reviews the current literature on the role of modern
operative laparoscopy in early cervical cancer and recommends a simple approach for its use in these
patients
Probing lepton flavour violation in scattering and conversion on nucleons
We study lepton flavour-violating interactions which could result in the
-lepton production in the scattering or in
conversion on nucleons at high energies. Phenomenological bounds on the
strength of interactions are extracted from
the combined result of the NOMAD and CHORUS experiments on searching for
oscillations. Some of these bounds supersede limits
from rare decays. We also propose a ``missing energy'' type experiment
searching for conversion on nucleons. The experiment can be
performed at a present accelerator or at a future neutrino factory.Comment: 13 pages, 4 figure
Cold and warm dust along a merging galaxy sequence
We investigate the cold and warm dust properties during galaxy interactions
using a merging galaxy sample ordered into a chronological sequence from pre-
to post-mergers. Our sample comprises a total of 29 merging systems selected to
have far-infrared and sub-millimeter observations. The sub-millimeter data are
mainly culled from the literature while for 5 galaxies (NGC 3597, NGC 3690, NGC
6090, NGC 6670 and NGC 7252) the sub-millimeter observations are presented here
for the first time. We use the 100-to-850 micron flux density ratio,
f_{100}/f_{850}, as a proxy to the mass fraction of the warm and the cold dust
in these systems. We find evidence for an increase in f_{100}/f_{850} along the
merging sequence from early to advanced mergers and interpret this trend as an
increase of the warm relative to the cold dust mass. We argue that the two key
parameters affecting the f_{100}/f_{850} flux ratio is the star-formation rate
and the dust content of individual systems relative to the stars. Using a
sophisticated model for the absorption and re-emission of the stellar UV
radiation by dust we show that these parameters can indeed explain both the
increase and the observed scatter in the f_{100}/f_{850} along the merging
galaxy sequence. We also discuss our results under the hypothesis that
elliptical galaxies are formed via disc galaxy mergers.Comment: Accepted for publication in MNRA
The Energetics of Molecular Gas in NGC 891 from H2 and FIR Spectroscopy
We have studied the molecular hydrogen energetics of the edge-on spiral
galaxy NGC\,891, using a 34-position map in the lowest three pure rotational
H lines observed with the Spitzer Infrared Spectrograph. The S(0), S(1),
and S(2) lines are bright with an extinction corrected total luminosity of
L, or 0.09\% of the total-infrared luminosity
of NGC\,891. The H line ratios are nearly constant along the plane of the
galaxy -- we do not observe the previously reported strong drop-off in the
S(1)/S(0) line intensity ratio in the outer regions of the galaxy, so we find
no evidence for the very massive cold CO-free molecular clouds invoked to
explain the past observations. The H level excitation temperatures increase
monotonically indicating more than one component to the emitting gas. More than
99\% of the mass is in the lowest excitation (T 125 K) ``warm''
component. In the inner galaxy, the warm H emitting gas is 15\% of
the CO(1-0)-traced cool molecular gas, while in the outer regions the fraction
is twice as high. This large mass of warm gas is heated by a combination of the
far-UV photons from stars in photo-dissociation regions (PDRs) and the
dissipation of turbulent kinetic energy. Including the observed far-infrared
[OI] and [CII] fine-structure line emission and far-infrared continuum emission
in a self-consistent manner to constrain the PDR models, we find essentially
all of the S(0) and most (70\%) of the S(1) line arises from low excitation
PDRs, while most (80\%) of the S(2) and the remainder of the S(1) line emission
arises from low velocity microturbulent dissipation.Comment: Accepted for publication in The Astrophysical Journal. Figure 10
available at http://www.physics.uoc.gr/~vassilis/papers/ngc891.pd
Absorption-Line Probes of Gas and Dust in Galactic Superwinds
We discuss moderate resolution spectra of the NaD absorption-line in a sample
of 32 far-IR-bright starburst galaxies. In 18 cases, the line is produced
primarily by interstellar gas, and in 12 of these it is blueshifted by over 100
km/s relative to the galaxy systemic velocity. The absorption-line profiles in
these outflow sources span the range from near the galaxy systemic velocity to
a maximum blueshift of 400 to 600 km/s. The outflows occur in galaxies
systematically viewed more nearly face-on than the others. We therefore argue
that the absorbing material consists of ambient interstellar gas accelerated
along the minor axis of the galaxy by a hot starburst-driven superwind. The NaD
lines are optically-thick, but indirect arguments imply total Hydrogen column
densities of N_H = few X 10^{21} cm^{-2}. This implies that the superwind is
expelling matter at a rate comparable to the star-formation rate. This
outflowing material is very dusty: we find a strong correlation between the
depth of the NaD profile and the line-of-sight reddening (E(B-V) = 0.3 to 1
over regions several-to-ten kpc in size). The estimated terminal velocities of
superwinds inferred from these data and extant X-ray data are typically 400 to
800 km/s, are independent of the galaxy rotation speed, and are comparable to
(substantially exceed) the escape velocities for (dwarf) galaxies. The
resulting loss of metals can establish the mass-metallicity relation in
spheroids, produce the observed metallicity in the ICM, and enrich a general
IGM to 10 solar metallicity. If the outflowing dust grains survive their
journey into the IGM, their effect on observations of cosmologically-distant
objects is significant.Comment: 65 pages, including 16 figures. ApJ, in pres
Use of Organic Fertilizers to Enhance Soil Fertility, Plant Growth, and Yield in a Tropical Environment
Soils rarely have sufficient nutrient for crops to reach their potential yield. Applying organic fertilizers without prior knowledge of their properties may cause yield decline under low application or pollute the environment with excessive application. Understanding the nutrient variability and release pattern of organic fertilizers is crucial to supply plants with sufficient nutrients to achieve optimum productivity, while also rebuilding soil fertility and ensuring protection of environmental and natural resources. This chapter presents the authors’ experiences with different organic amendments under Hawaii\u27s tropical conditions, rather than an intensive literature review. For meat and bone meal by‐products (tankage), batch‐to‐batch variability, nutrient content/release pattern and quality, and plant growth response to the liquid fertilizer produced from tankage were evaluated. For animal livestock, dairy manure (DM) and chicken manure (CM) quality, changes in soil properties, and crop biomass production and root distributions were evaluated. For seaweed, an established bio‐security protocol, nutrient, especially potassium (K) variability, and plant growth and yield response were evaluated in different tropical soils
Spatially Resolved Spitzer-IRS Spectroscopy of the Central Region of M82
We present high spatial resolution (~ 35 parsec) 5-38 um spectra of the
central region of M82, taken with the Spitzer Infrared Spectrograph. From these
spectra we determined the fluxes and equivalent widths of key diagnostic
features, such as the [NeII]12.8um, [NeIII]15.5um, and H_2 S(1)17.03um lines,
and the broad mid-IR polycyclic aromatic hydrocarbon (PAH) emission features in
six representative regions and analysed the spatial distribution of these lines
and their ratios across the central region. We find a good correlation of the
dust extinction with the CO 1-0 emission. The PAH emission follows closely the
ionization structure along the galactic disk. The observed variations of the
diagnostic PAH ratios across M82 can be explained by extinction effects, within
systematic uncertainties. The 16-18um PAH complex is very prominent, and its
equivalent width is enhanced outwards from the galactic plane. We interpret
this as a consequence of the variation of the UV radiation field. The EWs of
the 11.3um PAH feature and the H_2 S(1) line correlate closely, and we conclude
that shocks in the outflow regions have no measurable influence on the H_2
emission. The [NeIII]/[NeII] ratio is on average low at ~0.18, and shows little
variations across the plane, indicating that the dominant stellar population is
evolved (5 - 6 Myr) and well distributed. There is a slight increase of the
ratio with distance from the galactic plane of M82 which we attribute to a
decrease in gas density. Our observations indicate that the star formation rate
has decreased significantly in the last 5 Myr. The quantities of dust and
molecular gas in the central area of the galaxy argue against starvation and
for negative feedback processes, observable through the strong extra-planar
outflows.Comment: 15 pages, 12 figures, 3 tables, ApJ, emulateap
The structure of protostellar envelopes derived from submillimeter continuum images
High dynamic range imaging of submillimeter dust emission from the envelopes
of eight young protostars in the Taurus and Perseus star-forming regions has
been carried out using the SCUBA submillimeter camera on the James Clerk
Maxwell Telescope. Good correspondence between the spectral classifications of
the protostars and the spatial distributions of their dust emission is
observed, in the sense that those with cooler spectral energy distributions
also have a larger fraction of the submillimeter flux originating in an
extended envelope compared with a disk. This results from the cool sources
having more massive envelopes rather than warm sources having larger disks.
Azimuthally-averaged radial profiles of the dust emission are used to derive
the power-law index of the envelope density distributions, p (defined by rho
proportional to r^-p), and most of the sources are found to have values of p
consistent with those predicted by models of cloud collapse. However, the
youngest protostars in our sample, L1527 and HH211-mm, deviate significantly
from the theoretical predictions, exhibiting values of p somewhat lower than
can be accounted for by existing models. For L1527 heating of the envelope by
shocks where the outflow impinges on the surrounding medium may explain our
result. For HH211-mm another explanation is needed, and one possibility is that
a shallow density profile is being maintained in the outer envelope by magnetic
fields and/or turbulence. If this is the case star formation must be determined
by the rate at which the support is lost from the cloud, rather than the
hydrodynamical properties of the envelope, such as the sound speed.Comment: Accepted for publication in the Astrophysical Journa
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