7,697 research outputs found
CII* Absorption in Damped Lyman Alpha Systems: (II) A New Window on the Star Formation History of the Universe
Starting from the SFR per unit physical area, determined for DLAs using the C
II* method, we obtain the SFR per unit comoving volume at 3, and
find that it agrees with that for the Lyman Break Galaxies (LBGs). Though the
mass of produced stars indicated by the SFRs is consistent with the current
densities of known stellar populations, the mass of metals produced by =2.5
is 30 times larger than detected in absorption in DLAs. The most likely
solutions to this ``missing metals'' problem is that star formation occurs in
compact bulge regions. We search for evidence of feedback and find no
correlations between the SFR per unit area and N(H I), but possible
correlations between SFR per unit area and low-ion velocity width and SFR per
unit area and metal abundance. We show that (a) the correlation between cooling
rate and dust-to-gas ratio is positive evidence for grain photoelectric
heating, (b) the CMB does not significantly populate the C II excited
fine-structure states, and (c) the ratio of CII* to resonance-line optical
depths is a sensitive probe of the multi-phase structure of the DLA gas. We
address recent arguments that DLAs are comprised only of WNM gas, and show them
to be inconclusive. Despite the rough agreement between SFR per unit comoving
volume for DLAs and LBGs, current evidence indicates these are distinct
populations
Search for cold gas in z>2 damped Lyman-alpha systems: 21-cm and H_2 absorption
(Abridged) We present the results of a systematic GBT and GMRT survey for
21-cm absorption in a sample of 10 DLAs at 2<z_abs<3.4. Analysis of L-band VLBA
images of the background QSOs are also presented. We detect 21-cm absorption in
only one DLA (at z_abs = 3.1745 towards J1337+3152). Combining our data with
the data from the literature (a sample of 28 DLAs) and assuming the measured
core fraction at milliarcsecond scale to represent the gas covering factor, we
find that the HI gas in DLAs at z> 2 is predominantly constituted by WNM. The
detection rate of 21-cm absorption seems to be higher for systems with higher
N(HI) or metallicity. However, no clear correlation is found between the
integrated 21-cm optical depth (or spin temperature) and either N(HI),
metallicity or velocity spread of the low ionization species. There are 13 DLAs
in our sample for which high resolution optical spectra covering the expected
wavelength range of H_2 absorption are available. We report the detection of
H_2 molecules in the z_abs = 3.3871 21-cm absorber towards J0203+1134 (PKS
0201+113). In 8 cases, neither H_2 nor 21-cm absorption are detected. The lack
of 21-cm and H_2 absorption in these systems can be explained if most of the HI
in these DLAs originate from low density high temperature gas. In one case we
have a DLA with 21-cm absorption not showing H_2 absorption. In two cases, both
species are detected but do not originate from the same velocity component. In
the remaining 2 cases 21-cm absorption is not detected despite the presence of
H_2 with evidence for the presence of cold gas. All this is consistent with the
idea that the H_2 components seen in DLAs are compact (with sizes of < 15 pc)
and contain only a small fraction (i.e typically <10%) of the total N(HI)
measured in the DLAs.Comment: Accepted for publication in MNRA
Velocity-Metallicity Correlation for high-z DLA Galaxies: Evidence for a Mass-Metallicity Relation?
We used our database of VLT-UVES quasar spectra to build up a sample of 70
Damped Lyman-alpha (DLA) or strong sub-DLA systems with total neutral hydrogen
column densities of log N(HI)>20 and redshifts in the range 1.7<z_abs<4.3. For
each of the systems, we measured in an homogeneous manner the metallicities
relative to Solar, [X/H] (with X=Zn, or S or Si), and the velocity widths of
low-ionization line profiles, Delta V. We provide for the first time evidence
for a correlation between DLA metallicity and line profile velocity width,
which is detected at the 6.1sigma significance level. This confirms the trend
previously observed in a much smaller sample by Wolfe & Prochaska (1998). The
best-fit linear relation is [X/H]=1.55(\pm 0.12) log Delta V -4.33(\pm 0.23)
with Delta V expressed in km/s. The slope of the DLA velocity-metallicity
relation is the same within uncertainties between the higher (z_abs>2.43) and
the lower (z_abs<2.43) redshift halves of our sample. However, the two
populations of systems are statistically different. There is a strong redshift
evolution in the sense that the mean metallicity and mean velocity width
increase with decreasing redshift. We argue that the existence of a DLA
velocity-metallicity correlation, over more than a factor of 100 spread in
metallicity, is probably the consequence of an underlying mass-metallicity
relation for the galaxies responsible for DLA absorption lines. Assuming a
simple linear scaling of the galaxy luminosity with the mass of the dark-matter
halo, we find that the slope of the DLA velocity-metallicity relation is
consistent with that of the luminosity-metallicity relation derived for local
galaxies. [...] abridged.Comment: 10 pages, 4 figures, A&A in pres
Dynamics of the spontaneous breakdown of superhydrophobicity
Drops deposited on rough and hydrophobic surfaces can stay suspended with gas
pockets underneath the liquid, then showing very low hydrodynamic resistance.
When this superhydrophobic state breaks down, the subsequent wetting process
can show different dynamical properties. A suitable choice of the geometry can
make the wetting front propagate in a stepwise manner leading to {\it
square-shaped} wetted area: the front propagation is slow and the patterned
surface fills by rows through a {\it zipping} mechanism. The multiple time
scale scenario of this wetting process is experimentally characterized and
compared to numerical simulations.Comment: 7 pages, 5 figure
Herd-level risk factors of bovine tuberculosis in England and Wales after the 2001 foot-and-mouth disease epidemic
We present the results of a 2005 case–control study of bovine tuberculosis (bTB) breakdowns in English and Welsh herds. The herd management, farming practices, and environmental factors of 401matched pairs of case and control herds were investigated to provide a picture of herd-level risk factors in areas of varying bTB incidence. A global conditional logistic regression model, with region-specific variants, was used to compare case herds that had experienced a confirmed bTB breakdown to contemporaneous control herds matched on region, herd type, herd size, and parish testing interval. Contacts with cattle from contiguous herds and sourcing cattle from herds with a recent history of bTB were associated with an increased risk in both the global and regional analyses. Operating a farm over several premises, providing cattle feed inside the housing, and the presence of badgers were also identified as significantly associated with an increased bTB risk. Steps taken to minimize cattle contacts with neighboring herds and altering trading practices could have the potential to reduce the size of the bTB epidemic. In principle, limiting the interactions between cattle and wildlife may also be useful; however this study did not highlight any specific measures to implement
A convergent spectroscopy-based approach for Vcmax across leaf age and growth environments.
Abstract OOS 2-2
Detection of molecular hydrogen at z=1.15 toward HE 0515-4414
A new molecular hydrogen cloud is found in the sub-damped Ly-alpha absorber
[log N(HI)=19.88+/-0.05] at the redshift z=1.15 toward the bright quasar
HE0515-4414 (zem = 1.71). More than 30 absorption features in the Lyman band
system of H2 are identified in the UV spectrum of this quasar obtained with the
Space Telescope Imaging Spectrograph (STIS) aboard the Hubble Space Telescope.
The H2-bearing cloud shows a total H2 column density N(H2)=(8.7^{+8.7}_-{4.0})
10^16 cm^-2, and a fractional molecular abundance f(H2)=(2.3^{+2.3}_{-1.1})
10^-3 derived from the H2 lines arising from the J=0-5 rotational levels of the
ground electronic vibrational state. The estimated rate of photodissociation at
the cloud edge I_0<=1.8 10^{-8} s^-1 is much higher than the mean Galactic disk
value, I_MW~=5.5 10^{-11} s^-1. This may indicate an enhanced star-formation
activity in the z=1.15 system as compared with molecular clouds at z~=3 where
I~=I_MW. We also find a tentative evidence that the formation rate coefficient
of H2 upon grain surfaces at z=1.15 is a factor of 10 larger than a canonical
Milky Way value, R_MW~=3 10^-17 cm^3 s^-1. The relative dust-to-gas ratio
estimated from the [Cr/Zn] ratio is equal to k=0.89+/-0.19 (in units of the
mean Galactic disk value), which is in good agreement with a high molecular
fraction in this system. The estimated line-of-sight size of L~=0.25 pc may
imply that the H2 is confined within small and dense filaments embedded in a
more rarefied gas giving rise to the z=1.15 sub-damped Ly-alpha absorber.Comment: 10 pages, 7 figures, accepted for publication in A&
Tres medici, duo athei? The Physician as Atheist and the Medicalization of the Soul
Until recently, examinations of the ‘mind-body problem’ in historical context paid only cursory attention to its specifically medical dimension, if at all. At best, some ‘folk physiology’ was entertained, usually to laugh at it (the pineal gland, animal spirits). Conversely, historians of neuroscience or of artificial intelligence (Jeannerod 1985, Dupuy 2000) often present figures like La Mettrie as heroic early cases of ‘naturalization’, giving an experimental basis to materialism: their symmetrically inverse mistake is to take professions of medical authority too literally (although there are genuine cases where all of the above does coalesce – where ‘actors’ categories mysteriously transcend historiographic projections –, such as Hieronymus Gaub’s reflections on the ‘regimen of the mind’ in the mid-eighteenth century, or, more theoretically, Guillaume Lamy’s Epicurean-inflected Anatomical Discourses on the Soul, eighty years earlier). Contrary to the denial of the relevance of medicine in early modern philosophy, as regards issues such as the body-soul (then body-mind) relation among others, it seems patently difficult to separate medical theory, medically nourished philosophical speculation, and metaphysics. This is the case, whether in Descartes, Gaub, the ‘animist’ Georg-Ernest Stahl, or materialists such as Guillaume Lamy and La Mettrie: medicine, or rather ‘a certain idea of medicine’, is everywhere.
Here I focus on the motif of a radical medicine – a medical precursor of the Radical Enlightenment (Israel 2001, 2006, 2007), symbolized negatively by the slogan, tres medici, duo athei, or ‘where there are three doctors, there are two atheists’, i.e. medicine as a basis for atheism. This theme runs through various works of medical or medico-theological propaganda: Thomas Browne’s 1643 De religio medici begins with Browne regretting rumors of doctors being atheists as the “general scandal of my Profession”; Germain de Bezançon’s 1677 Les médecins à la censure works hard at rebutting the saying, “Bon Physicien, mauvais chrétien.” But these are examples of the fear of a radical medicine – a medicine that denies the existence of an immortal soul, or even defends materialism and atheism. Are there positive statements of this doctrine? Indeed, attacks on it are much more common than statements identifying with it, like medical versions of natural theology in general.
In fact, just as there were theologically motivated medical works, there were also medically motivated works of radical or heretical theology, like William Coward’s Second Thoughts on the Human Soul (Coward 1702, building on Overton 1644), which engaged in polemics concerning the nature of the soul – mortal or immortal? (Thomson 2008). Parallel to the mortalist trend, but flowing into a common genre of radical, medico-materialist texts (sometimes anonymous, such as L’Âme Matérielle, from the 1720s) are at least two other strands of radical medicine: a post-Cartesian focus on medicina mentis and the nature of the mind (Henricus Regius, Hieronymus Gaub, Antoine Le Camus), and an Epicurean medicine, in which mind and body are organismically united, with an additional hedonistic component, notably in Lamy, Mandeville and La Mettrie (Wright 1991, Wolfe and van Esveld 2014). The focus on a medicine of the mind (Corneanu, ms. 2013) is obviously connected to a ‘medicalization of the soul’: there was a body-soul problem in and for medicine, a sort of medicalized ‘pneumatology’. Radical medicine is located somewhere in between the early forms of ‘naturalization’ or ‘medicalization’ of the soul and the pose of scientific neutrality that is characteristic of early nineteenth-century medicine (as in Cabanis, Bichat or Bernard): it is a short-lived episode. I seek to reconstruct this intellectual figure, in which mortalist, post-Cartesian and Epicurean strands intersect and sometimes come together. I suggest that medically influenced materialism in the Radical Enlightenment (e.g. in the later French cases, La Mettrie, Ménuret and Diderot), is different from later, more experimentally focused and more quantitatively oriented forms of medical materialism, precisely because of its radical dimension. This radical medicine often insists on vitality, as opposed to “anatomie cadavérique”: it is vital and hedonistic, a medicine concerned with maintaining bodily pleasure.Until recently, examinations of the 'mind-body problem' in historical context paid only cursory attention to its specifically medical dimension, if at all. At best, some 'folk physiology' was entertained, usually to laugh at it (the pineal gland, animal spirits). Conversely, historians of neuroscience or of artificial intelligence (Jeannerod M, The brain machine. The development of neurophysiological thought, trans. D. Urion, Harvard University Press, Cambridge, 1985; Dupuy J-P, The mechanization of the mind: on the origins of cognitive science, trans. M.B. DeBevoise, Princeton University Press, Princeton, 2000) often present figures like La Mettrie as heroic early cases of 'naturalization', giving an experimental basis to materialism: their symmetrically inverse mistake is to take professions of medical authority too literally (although there are genuine cases where all of the above does coalesce where 'actors' categories mysteriously transcend historiographic projections -, such as Hieronymus Gaub's reflections on the 'regimen of the mind' in the mid-eighteenth century, or, more theoretically, Guillaume Lamy's Epicurean-inflected Anatomical Discourses on the Soul, eighty years earlier). Contrary to the denial of the relevance of medicine in early modern philosophy, as regards issues such as the body-soul (then body-mind) relation among others, it seems patently difficult to separate medical theory, medically nourished philosophical speculation, and metaphysics. This is the case, whether in Descartes, Gaub, the 'animist' Georg-Ernest Stahl, or materialists such as Guillaume Lamy and La Mettrie: medicine, or rather 'a certain idea of medicine', is everywhere.Here I focus on the motif of a radical medicine - a medical precursor of the Radical Enlightenment (Israel J, Radical enlightenment. Philosophy and the making of modernity, 1650-1750, Oxford University Press, Oxford, 2001; Israel J, Enlightenment contested. Oxford University Press, Oxford, 2006, Israel J, Enlightenment, radical enlightenment and the "medical revolution" of the late seventeenth and eighteenth centuries. In: Grell OP, Cunningham A (ed) Medicine and religion in enlightenment Europe. Ashgate, Aldershot, pp 5-28, 2007), symbolized negatively by the slogan, tres medici, duo athei, or 'where there are three doctors, there are two atheists', i.e. medicine as a basis for atheism. This theme runs through various works of medical or medico-theological propaganda: Thomas Browne's 1643 De religio medici begins with Browne regretting rumors of doctors being atheists as the "general scandal of my Profession"; Germain de Bezancon's 1677 Les medecins a la censure works hard at rebutting the saying, "Bon Physicien, mauvais chretien." But these are examples of the fear of a radical medicine - a medicine that denies the existence of an immortal soul, or even defends materialism and atheism. Are there positive statements of this doctrine? Indeed, attacks on it are much more common than statements identifying with it, like medical versions of natural theology in general.In fact, just as there were theologically motivated medical works, there were also medically motivated works of radical or heretical theology, like William Coward's Second Thoughts on the Human Soul (Coward W, Second thoughts on the human soul. R. Basset, London, 1702, building on Overton 1644), which engaged in polemics concerning the nature of the soul - mortal or immortal? (Thomson A, Bodies of thought: science, religion, and the soul in the early enlightenment. Oxford University Press, Oxford, 2008). Parallel to the mortalist trend, but flowing into a common genre of radical, medico-materialist texts (sometimes anonymous, such as L'Ame Materielle, from the 1720s) are at least two other strands of radical medicine: a post-Cartesian focus on medicina mentis and the nature of the mind (Henricus Regius, Hieronymus Gaub, Antoine Le Camus), and an Epicurean medicine, in which mind and body are organismically united, with an additional hedonistic component, notably in Lamy, Mandeville and La Mettrie (Wright JP, Locke, Willis, and the seventeenth-century epicurean soul. In: Osler MJ (ed) Atoms, Pneuma, and Tranquillity: Epicurean and stoic themes in European thought. Cambridge University Press, Cambridge, pp 239-258, 1991; Wolfe CT, van Esveld M, The material soul: strategies for naturalising the soul in an early modern epicurean context. In: Kambaskovic D (ed) Conjunctions: body, soul and mind from Plato to the enlightenment. Springer, Dordrecht, pp 371-421, 2014). The focus on a medicine of the mind (Corneanu, (ms. 2013), The care of the whole man: medicine and theology in the late renaissance, 2013) is obviously connected to a 'medicalization of the soul': there was a body-soul problem in and for medicine, a sort of medicalized 'pneumatology'. Radical medicine is located somewhere in between the early forms of 'naturalization' or 'medicalization' of the soul and the pose of scientific neutrality that is characteristic of early nineteenth-century medicine (as in Cabanis, Bichat or Bernard): it is a short-lived episode. I seek to reconstruct this intellectual figure, in which mortalist, post-Cartesian and Epicurean strands intersect and sometimes come together. I suggest that medically influenced materialism in the Radical Enlightenment (e.g. in the later French cases, La Mettrie, Menuret and Diderot), is different from later, more experimentally focused and more quantitatively oriented forms of medical materialism, precisely because of its radical dimension. This radical medicine often insists on vitality, as opposed to "anatomie cadaverique": it is vital and hedonistic, a medicine concerned with maintaining bodily pleasure
Cold Gas Kinematics in an L* Spiral Galaxy at z=0.437: The Nature of Damped Lyman-alpha Absorbers
Westerbork Radio Synthesis Telescope observations of the redshifted 21cm line
absorber against the z_em = 0.871 double lobed quasar 3C196 show that the
intervening absorber is an L approximately equal L* spiral galaxy (3C196-G1)
and that the absorbing layer of cold gas extends to radii of at least 30
h_50^-1 kpc. The new data solve several long standing puzzles about this system
by (1) discovering a second 21cm absorption feature, corresponding to
absorption against the NE lobe of the background radio source and (2) spatially
``resolving'' the two absorption features to isolate the absorption along the
two lines of sight to the opposing radio lobes. These findings resolve the
disagreement in redshift between the UV metal and 21cm lines, and as well as
demonstrating that the neutral layer does absorb both lobes of the background
radio source. Simple kinematic models with an inclined, rotating gas disk match
the observed 21cm profile and are also compatible with both the redshift and
velocity spread of the absorption measured in UV resonance lines along a third,
independent line of sight to the quasar nucleus and with the lack of 21cm
absorption in as earlier VLBI experiment that was sensitive to opacity against
the hot spot in the northern lobe. The inferred rotation speed and luminosity
for the galaxy are compatible with the z approximately 0 Tully-Fisher Relation.
This system illustrates well how 21cm absorption against extended background
radio sources is a powerful tool in determining the nature of the damped
Lyman-alpha class of QSO absorption line system.Comment: 9 pages, accepted at A&
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