4,684 research outputs found
Mattia Damiani (1705â1776), poet and scientist in eighteenth century Tuscany
Mattia Damiani da Volterra (1705â1776), ârenowned Doctor,â was the author
in 1754 of a collection of scientifi c poems, Le Muse Fisiche (The Physical Muses) on
two subjects: Newtonian physics and the plurality of the worlds. Damianiâs interest
in science was precocious, but even at that, it was superimposed on his studies in
jurisprudence completed in Pisa in 1726. In 2003, Damianiâs lost text, De Hygrometris
et eorum defectibus disputatio (Disputation about hygrometers and their defects),
which was printed in 1726 in Pisa, was brought to light. It characterizes him as a
young scientist who refl ected upon the properties and limits of laboratory instruments
and on nascent aspects of climatology. In this Disputation, a delightful amalgamation
of scientifi c and humanistic literature is pursued. A discussion of the properties
and limits of contemporary hygrometers and a comparison of the Cartesian and
Newtonian hypotheses about cloud formations are interspersed with quotations of
verses on natural phenomena, mostly from poems of the classic ageâa prelude to
the authorâs future involvement in writing scientifi c verses. The poetry of Damiani,
which often shows a musicality comparable to that of the poet Giacomo Leopardi
(1798â1837), deserves to be recognized and saved from oblivion. Especially remarkable
is the implicit âmultimediaâ project of a union among science, poetry, theater,
and music. The rediscovered Disputation about hygrometers opens a new window on
the personages involved and on the evolution of meteorological concepts in Europe in
the context of the then-new Galilean and Newtonian physics
An Extreme Case of a Misaligned Highly Flattened Wind in the Wolf-Rayet Binary CX Cephei
CX Cep (WR 151) is the WR+O binary (WN5+O5V) with the second shortest period
known in our Galaxy. To examine the circumstellar matter distribution and to
better constraint the orbital parameters and mass-loss rate of the WR star, we
obtained broadband and multi-band (i.e. UBVRI) linear polarization observations
of the system. Our analysis of the phase-locked polarimetric modulation
confirms the high orbital inclination of the system (i.e. ). Using the
orbital solution of Lewis et al. (1993) we obtain masses of
and for the O and WR stars respectively, which agree with
their spectral types. A simple polarimetric model accounting for finite stellar
size effects allowed us to derive a mass-loss rate for the WR star of
. This result was remarkably independent of
the model's input parameters and favors an earlier spectral type for the WR
component (i.e. WN4). Finally, using our multi-band observations, we fitted and
subtracted from our data the interstellar polarization. The resulting constant
intrinsic polarization of is misaligned in relation to the orbital plane
(i.e. vs. ) and is the highest intrinsic
polarization ever observed for a WR star. This misalignment points towards a
rotational (or magnetic) origin for the asymmetry and contradicts the most
recent evolutionary models for massive stars (Meynet & Maeder 2003) which
predict spherically symmetric winds during the WR phase (i.e. ).Comment: 26 pages, 4 figures. Astrophysical Journal (submited
Systemic inflammatory response syndrome, quick sequential organ function assessment, and organ dysfunction: insights from a prospective database of ED patients with infection
Background A proposed revision of sepsis definitions has abandoned the systemic inflammatory response syndrome (SIRS), defined organ dysfunction as an increase in total Sequential Organ Function Assessment (SOFA) score of\ua0â„ 2, and conceived âqSOFAâ (quick SOFA) as a bedside indicator of organ dysfunction. We aimed to (1) determine the prognostic impact of SIRS, (2) compare the diagnostic accuracy of SIRS and qSOFA for organ dysfunction, and (3) compare standard (Sepsis-2) and revised (Sepsis-3) definitions for organ dysfunction in ED patients with infection. Methods Consecutive ED patients admitted with presumed infection were prospectively enrolled over 3 years. Sufficient observational data were collected to calculate SIRS, qSOFA, SOFA, comorbidity, and mortality. Results We enrolled 8,871 patients, with SIRS present in 4,176 (47.1%). SIRS was associated with increased risk of organ dysfunction (relative risk [RR] 3.5) and mortality in patients without organ dysfunction (OR 3.2). SIRS and qSOFA showed similar discrimination for organ dysfunction (area under the receiver operating characteristic curve, 0.72 vs\ua00.73). qSOFA was specific but poorly sensitive for organ dysfunction (96.1%\ua0and 29.7%, respectively). Mortality for patients with organ dysfunction was similar for Sepsis-2 and Sepsis-3 (12.5%\ua0and 11.4%, respectively), although 29%\ua0of patients with Sepsis-3 organ dysfunction did not meet Sepsis-2 criteria. Increasing numbers of Sepsis-2 organ system dysfunctions were associated with greater mortality. Conclusions SIRS was associated with organ dysfunction and mortality, and abandoning the concept appears premature. A qSOFA score\ua0â„ 2 showed high specificity, but poor sensitivity may limit utility as a bedside screening method. Although mortality for organ dysfunction was comparable between Sepsis-2 and Sepsis-3, more prognostic and clinical information is conveyed using Sepsis-2 regarding number and type of organ dysfunctions. The SOFA score may require recalibration
Asymptotic Scaling and Infrared Behavior of the Gluon Propagator
The Landau gauge gluon propagator for the pure gauge theory is evaluated on a
32^3x64 lattice with a physical volume of (3.35^3x6.7)fm^4. Comparison with two
smaller lattices at different lattice spacings allows an assessment of finite
volume and finite lattice spacing errors. Cuts on the data are imposed to
minimize these errors. Scaling of the gluon propagator is verified between
beta=6.0 and beta=6.2. The tensor structure is evaluated and found to be in
good agreement with the Landau gauge form, except at very small momentum
values, where some small finite volume errors persist. A number of functional
forms for the momentum dependence of the propagator are investigated. The form
D(q^2)=D_ir+D_uv, where D_ir(q^2) ~ (q^2+M^2)^-\eta and D_uv is an infrared
regulated one-loop asymptotic form, is found to provide an adequate description
of the data over the entire momentum region studied - thereby bridging the gap
between the infrared confinement region and the ultraviolet asymptotic region.
The best estimate for the exponent \eta is 3.2(+0.1/-0.2)(+0.2/-0.3), where the
first set of errors represents the uncertainty associated with varying the
fitting range, while the second set of errors reflects the variation arising
from different choices of infrared regulator in D_uv. Fixing the form of D_uv,
we find that the mass parameter M is (1020+/-100)MeV.Comment: 37 pages, RevTeX, 16 postscript figures, 7 gif figures. Revised
version accepted for publication in Phys. Rev. D. Model functions and
discussion of asymptotic behaviour modified; all model fits have been redone.
This paper, including postscript version of all figures, can be found at
http://www.physics.adelaide.edu.au/~jskuller/papers
An Architecture for Multi-User Software Development Environments
We present an architecture for multi-user software development environments, covering general, process-centered and rule-based MUSDEs. Our architecture is founded on componentization, with particular concern for the capability to replace the synchronization component - to allow experimentation with novel concurrency control mechanisms - with minimal effects on other components while still supporting integration. The architecture has been implemented in the MARVEL SD
Dynamical chiral symmetry breaking and confinement with an infrared-vanishing gluon propagator?
We study a model Dyson-Schwinger equation for the quark propagator closed
using an {\it Ansatz} for the gluon propagator of the form \mbox{} and two {\it Ans\"{a}tze} for the quark-gluon vertex: the
minimal Ball-Chiu and the modified form suggested by Curtis and Pennington.
Using the quark condensate as an order parameter, we find that there is a
critical value of such that the model does not support dynamical chiral
symmetry breaking for . We discuss and apply a confinement test which
suggests that, for all values of , the quark propagator in the model {\bf is
not} confining. Together these results suggest that this Ansatz for the gluon
propagator is inadequate as a model since it does not yield the expected
behaviour of QCD.Comment: 21 Pages including 4 PostScript figures uuencoded at the end of the
file. Replacement: slight changes of wording and emphasis. ADP-93-215/T133,
ANL-PHY-7599-TH-93, FSU-SCRI-93-108, REVTEX 3.
Annual variation in the levels of transcripts of sex-specific genes in the mantle of the common mussel, Mytilus edulis
Mytilus species are used as sentinels for the assessment of environmental health but sex or stage in the reproduction cycle is rarely considered even though both parameters are likely to influence responses to pollution. We have validated the use of a qPCR assay for sex identification and related the levels of transcripts to the reproductive cycle. A temporal study of mantle of Mytilus edulis found transcripts of male-specific vitelline coat lysin (VCL) and female-specific vitelline envelope receptor for lysin (VERL) could identify sex over a complete year. The levels of VCL/VERL were proportional to the numbers of sperm/ova and are indicative of the stage of the reproductive cycle. Maximal levels of VCL and VERL were found in February 2009 declining to minima between July - August before increasing and re-attaining a peak in February 2010. Water temperature may influence these transitions since they coincide with minimal water temperature in February and maximal temperature in August. An identical pattern of variation was found for a cryptic female-specific transcript (H5) but a very different pattern was observed for oestrogen receptor 2 (ER2). ER2 varied in a sex-specific way with male > female for most of the cycle, with a female maxima in July and a male maxima in December. Using artificially spawned animals, the transcripts for VCL, VERL and H5 were shown to be present in gametes and thus their disappearance from mantle is indicative of spawning. VCL and VERL are present at equivalent levels in February and July-August but during gametogenesis (August to January) and spawning (March to June) VCL is present at lower relative amounts than VERL. This may indicate sex-specific control mechanisms for these processes and highlight a potential pressure point leading to reduced reproductive output if environmental factors cause asynchrony to gamete maturation or release
MOST Spacebased Photometry of the Transiting Exoplanet System HD 189733: Precise Timing Measurements for Transits Across an Active Star
We have measured transit times for HD 189733b passing in front of its bright
(V = 7.67) chromospherically active and spotted parent star. Nearly continuous
broadband optical photometry of this system was obtained with the MOST
(Microvariability & Oscillations of STars) space telescope during 21 days in
August 2006, monitoring 10 consecutive transits. We have used these data to
search for deviations from a constant orbital period which can indicate the
presence of additional planets in the system that are as yet undetected by
Doppler searches. There are no transit timing variations above the level of
s, ruling out super-Earths (of masses 1 - 4 M_{\earth}) in the 1:2
and 2:3 inner resonances and planets of 20 M_{\earth} in the 2:1 outer
resonance of the known planet. We also discuss complications in measuring
transit times for a planet that transits an active star with large star spots,
and how the transits can help constrain and test spot models. This has
implications for the large number of such systems expected to be discovered by
the CoRoT and Kepler missions.Comment: 26 pages, 7 figures, accepted to Ap
The Discovery of Three New z>5 Quasars in the AGN and Galaxy Evolution Survey
We present the discovery of three z>5 quasars in the AGN and Galaxy Evolution
Survey (AGES) spectroscopic observations of the NOAO Deep Wide-Field Survey
(NDWFS) Bootes Field. These quasars were selected as part of a larger Spitzer
mid-infrared quasar sample with no selection based on optical colors. The
highest redshift object, NDWFS J142516.3+325409, z=5.85, is the
lowest-luminosity z>5.8 quasar currently known. We compare mid-infrared
techniques for identifying z>5 quasars to more traditional optical techniques
and show that mid-infrared colors allow for selection of high-redshift quasars
even at redshifts where quasars lie near the optical stellar locus and at z>7
where optical selection is impossible. Using the superb multi-wavelength
coverage available in the NDWFS Bootes field, we construct the spectral energy
distributions (SEDs) of high-redshift quasars from observed Bw-band to 24
microns (rest-frame 600 Angstroms - 3.7 microns). We show that the three
high-redshift quasars have quite similar SEDs, and the rest-frame composite SED
of low-redshift quasars from the literature shows little evolution compared to
our high-redshift objects. We compare the number of z>5 quasars we have
discovered to the expected number from published quasar luminosity functions.
While analyses of the quasar luminosity function are tenuous based on only
three objects, we find that a relatively steep luminosity function with Psi
L^(-3.2) provides the best agreement with the number of high-redshift quasars
discovered in our survey.Comment: 9 page, 7 figures. Accepted for publication in A
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