4,684 research outputs found

    Mattia Damiani (1705–1776), poet and scientist in eighteenth century Tuscany

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    Mattia Damiani da Volterra (1705–1776), “renowned Doctor,” 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. Damiani’s interest in science was precocious, but even at that, it was superimposed on his studies in jurisprudence completed in Pisa in 1726. In 2003, Damiani’s 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 age—a prelude to the author’s future involvement in writing scientifi c verses. The poetry of Damiani, which often shows a musicality comparable to that of the poet Giacomo Leopardi (1798–1837), deserves to be recognized and saved from oblivion. Especially remarkable is the implicit “multimedia” 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

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    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. i=65oi=65^o). Using the orbital solution of Lewis et al. (1993) we obtain masses of 33.9M⊙33.9 M_{\odot} and 23.9M⊙23.9 M_{\odot} 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 0.3−0.5×10−5M⊙/yr0.3-0.5\times10^{-5} M_{\odot}/yr. 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 3−43-4% is misaligned in relation to the orbital plane (i.e. ΞCIP=26o\theta_{CIP}=26^o vs. Ω=75o\Omega=75^o) 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. CIP=0CIP=0%).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

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    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\ua0≄ 2, and conceived “qSOFA” (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\ua0≄ 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

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    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

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    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?

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    We study a model Dyson-Schwinger equation for the quark propagator closed using an {\it Ansatz} for the gluon propagator of the form \mbox{D(q)∌q2/[(q2)2+b4]D(q) \sim q^2/[(q^2)^2 + b^4]} 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 b=bcb=b_c such that the model does not support dynamical chiral symmetry breaking for b>bcb>b_c. We discuss and apply a confinement test which suggests that, for all values of bb, 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

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    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

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    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 ±45{\pm}45 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

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    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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