33 research outputs found
Densitometry and Thermometry of Starburst Galaxies
With a goal toward deriving the physical conditions in external galaxies, we
present a survey of formaldehyde (H2CO) and ammonia (NH3) emission and
absorption in a sample of starburst galaxies using the Green Bank Telescope. By
extending well-established techniques used to derive the spatial density in
star formation regions in our own Galaxy, we show how the relative intensity of
the 1(10)-1(11) and 2(11)-2(12) K-doublet transitions of H2CO can provide an
accurate densitometer for the active star formation environments found in
starburst galaxies (c.f. Mangum et al. 2008). Similarly, we employ the
well-established technique of using the relative intensities of the (1,1),
(2,2), and (4,4) transitions of NH3 to derive the kinetic temperature in
starburst galaxies. Our measurements of the kinetic temperature constrained
spatial density in our starburst galaxy sample represent the first mean density
measurements made toward starburst galaxies. We note a disparity between
kinetic temperature measurements derived assuming direct coupling to dust and
those derived from our NH3 measurements which points to the absolute need for
direct gas kinetic temperature measurements using an appropriate molecular
probe. Finally, our spatial density measurements point to a rough constancy to
the spatial density (10^{4.5} to 10^{5.5} cm^{-3}) in our starburst galaxy
sample. This implies that the Schmidt-Kennicutt relation between L_{IR} and
M_{dense}: (1) Is a measure of the dense gas mass reservoir available to form
stars, and (2) Is not directly dependent upon a higher average density driving
the star formation process in the most luminous starburst galaxies.Comment: 4 pages, to appear in proceedings of The 5th Zermatt ISM Symposiu
A simple point of care test can indicate the need for periodontal therapy to reduce the risk for adverse pregnancy outcomes in mothers attending antenatal clinics
INTRODUCTION: Although the association between periodontal disease (PD) and adverse pregnancy
outcomes has gained recognition amongst antenatal healthcare workers, not much has changed in
practice to address it. This prospective study tested the hypothesis that BANA (N-benzoyl-DL-arginine-
2-naphthylamide), a diagnostic test for PD, may inform obstetricians and other antenatal healthcare
practitioners, of the risk of adverse pregnancy outcomes in mothers attending antenatal clinics.
METHODS: At first visit, the presence of suspected periodontopathogens was assessed by BANA testing
of dental plaque from 443 mothers attending antenatal clinics in KwaZulu-Natal, South Africa and an
association later sought with pregnancy outcomes. The accuracy of BANA to predict adverse pregnancy
outcomes was evaluated by the calculation of likelihood ratios. The study complied with the
Declaration of Helsinki.
RESULTS: Significant differences were found between pregnancy outcomes of BANA-negative and
BANA-positive mothers (p<0.0001). BANA showed sensitivity and negative predictive values of 87%
and 91%; 75% and 78%; 87% and 94% in detecting low birth weight, preterm delivery, and preterm
low birth weight delivery respectively.
CONCLUSION: This study confirms that BANA may indicate the need for periodontal therapy to reduce
the risk of adverse pregnancy outcomes and could form part of the routine antenatal examination.National Research Foundation (NRF
ATLASGAL: 3 mm class I methanol masers in high-mass star formation regions
Interstellar matter and star formatio
Spanning forests and the q-state Potts model in the limit q \to 0
We study the q-state Potts model with nearest-neighbor coupling v=e^{\beta
J}-1 in the limit q,v \to 0 with the ratio w = v/q held fixed. Combinatorially,
this limit gives rise to the generating polynomial of spanning forests;
physically, it provides information about the Potts-model phase diagram in the
neighborhood of (q,v) = (0,0). We have studied this model on the square and
triangular lattices, using a transfer-matrix approach at both real and complex
values of w. For both lattices, we have computed the symbolic transfer matrices
for cylindrical strips of widths 2 \le L \le 10, as well as the limiting curves
of partition-function zeros in the complex w-plane. For real w, we find two
distinct phases separated by a transition point w=w_0, where w_0 = -1/4 (resp.
w_0 = -0.1753 \pm 0.0002) for the square (resp. triangular) lattice. For w >
w_0 we find a non-critical disordered phase, while for w < w_0 our results are
compatible with a massless Berker-Kadanoff phase with conformal charge c = -2
and leading thermal scaling dimension x_{T,1} = 2 (marginal operator). At w =
w_0 we find a "first-order critical point": the first derivative of the free
energy is discontinuous at w_0, while the correlation length diverges as w
\downarrow w_0 (and is infinite at w = w_0). The critical behavior at w = w_0
seems to be the same for both lattices and it differs from that of the
Berker-Kadanoff phase: our results suggest that the conformal charge is c = -1,
the leading thermal scaling dimension is x_{T,1} = 0, and the critical
exponents are \nu = 1/d = 1/2 and \alpha = 1.Comment: 131 pages (LaTeX2e). Includes tex file, three sty files, and 65
Postscript figures. Also included are Mathematica files forests_sq_2-9P.m and
forests_tri_2-9P.m. Final journal versio
Microarcsecond astrometry in the Local Group
Contains fulltext :
72660.pdf (publisher's version ) (Open Access)IAU Symposium No. 248, 15 oktober 200
Systematische Erweiterung der mikrostrukturellen Charakterisierung ferritischer Schweißgüter
This paper deals with the analytic gap during the microstructural examination of ferritic weld metals and points out which methods can be used to perform a meaningful evaluation of the weld metal microstructure. The designers of filler materials and the respective metallographs are provided with a tool to specifically search for weaknesses in the microstructural composition and invalidate them by alloying on the basis of their metallurgical context
Erhöhung der Tragfähigkeit von GV-Verbindungen durch den Einsatz von Klebstoff
Wenn schubbeanspruchte Anschlüsse im Stahlbau Belastungen aus Schwingungen und/oder Lastumkehr ausgesetzt sind, kein Schlupf auftreten darf und auf der Baustelle gefügt werden muss, sind gleitfest vorgespannte Schraubverbindungen vorzusehen. Diese so genannten GV-Verbindungen müssen mit hohem Herstellungsaufwand gefertigt werden, was auf die Reibflächenvorbehandlung zurückzuführen ist. Wird der Korrosionsschutz für die Stahlkonstruktion durch eine Feuerverzinkung gewährleistet, sind für die Reiboberflächen ohne aufwendige Nachbehandlung geringe Haftreibungszahlen festzustellen, die zudem stark in Abhängigkeit von der sich ausbildenden Zinkschicht schwanken. Vor diesem Hintergrund wurden in einem kürzlich abgeschlossenen Forschungsvorhaben Untersuchungen angestellt, die eine Erhöhung der Tragfähigkeit in GV-Verbindungen durch den Einsatz von Klebstoff aufzeigen. Für die erhebliche Traglaststeigerung gegenüber den elementaren Fügeverfahren – Klebung oder GV-Verbindung – ist bei der Verfahrenskombination, die im Weiteren als vorgespannte Hybridverbindung verstanden wird, die eingebrachte Vorspannkraft verantwortlich. Bei sorgfältiger Kombination beider Verfahren können die Einzeltragfähigkeiten in etwa addiert werden
Observations of the new transient radio source in the central region of M82
Item does not contain fulltex