Emerging Massive Star Clusters Revealed: High Resolution Imaging of NGC 4449 from the Radio to the Ultraviolet

We present a multi-wavelength study of embedded massive clusters in the nearby (3.9 Mpc) starburst galaxy NGC 4449 in an effort to uncover the earliest phases of massive cluster evolution. By combining high resolution imaging from the radio to the ultraviolet, we reveal these clusters in the process of emerging from their gaseous and dusty birth cocoons. We use Very Large Array (VLA) observations at centimeter wavelengths to identify young clusters surrounded by ultra-dense HII regions, detectable via their production of thermal free-free radio continuum. Ultraviolet, optical and infrared observations are obtained from the Hubble and Spitzer Space Telescope archives for comparison. We detect 39 compact radio sources towards NGC 4449 at 3.6 cm using the highest resolution (1.3") and sensitivity (RMS ~ 12 uJy) VLA image of the galaxy to date. We reliably identify 13 thermal radio sources and their physical properties are derived using both nebular emission from the HII regions and SED fitting to the stellar continuum. These radio detected clusters have ages < 5 Myr and stellar masses of order 10^4 Msun. The measured extinctions are quite low: 12 of the 13 thermal radio sources have Av < 1.5, while the most obscured source has Av ~ 4.3. By combining results from the nebular and stellar emission, we find an I-band excess that is anti-correlated with cluster age and an apparent mass-age correlation. Additionally, we find evidence that local processes such as supernovae and stellar winds are likely playing an important role in triggering the current bursts of star formation within NGC 4449.Comment: Accepted for publication in the Astronomical Journal. 20 pages, 14 figure

Weyl-Conformally-Invariant Lightlike p-Brane Theories: New Aspects in Black Hole Physics and Kaluza-Klein Dynamics

We introduce and study in some detail the properties of a novel class of Weyl-conformally invariant p-brane theories which describe intrinsically lightlike branes for any odd world-volume dimension. Their dynamics significantly differs from that of the ordinary (conformally non-invariant) Nambu-Goto p-branes. We present explicit solutions of the Weyl-invariant lightlike brane- (WILL-brane) equations of motion in various gravitational models of physical relevance exhibiting various new phenomena. In D=4 the WILL-membrane serves as a material and charged source for gravity and electromagnetism in the coupled Einstein-Maxwell-WILL-membrane system; it automatically positions itself on (``straddles'') the common event horizon of the corresponding matching black hole solutions, thus providing an explicit dynamical realization of the membrane paradigm in black hole physics. In product spaces of interest in Kaluza-Klein theories the WILL-brane wraps non-trivially around the compact (internal)dimensions and still describes massless mode dynamics in the non-compact (space-time) dimensions. Due to nontrivial variable size of the internal compact dimensions we find new types of physically interesting solutions describing massless brane modes trapped on bounded planar circular orbits with non-trivial angular momentum, and with linear dependence between energy and angular momentum.Comment: 28 pages, published versio

A new wrinkle on the enhancon

We generalize the basic enhancon solution of Johnson, Peet and Polchinski by constructing solutions without spherical symmetry. A careful consideration of boundary conditions at the enhancon surface indicates that the interior of the supergravity solution is still flat space in the general case. We provide some explicit analytic solutions where the enhancon locus is a prolate or oblate sphere.Comment: 19 pages, no figure

Morphological and anatomical studies on Tacca leontopetaloides (L.) Kuntze (Taccaceae) in Nigeria

Tacca leontopetaloides is the only species in the genus Tacca naturally distributed in the Guinea savannah and dry rainforest regions in Nigeria. The study was conducted to contribute to scientific knowledge on the macro-morphological and anatomical features of the plant collected from 4 locations (Akoko, Eruwa, Bazza and Ile-Ife) across the Nigeria and to determine the effect of environmental factors on its anatomy. Leaf epidermal peel of the 4 samples, leaf and stem Transverse Sections (T.S) and stem Tangential Longitudinal Section (T.L.S) and Radial Longitudinal Section (R.L.S) as well as stem fibres were prepared and studied. A wide range of similarities and differences were noted in the anatomical features of the 4 samples studied. The similarities include, but not limited to stomata being anomocytic, epidermis hypostomatic, cuticle single-layered and striated, vascular bundles conjointed collateral, epidermis undulating, stem rays uniserrate and procumbent, stem fibres non-septate and non-storeyed. Wide range of variations are noted in stomata density and measurements, epidermal cell density, guard cell measurements, cuticle thickness, vascular bundle arrangement, shapes of parenchyma and sclerenchyma cells and many other anatomical features. The variations observed among the samples studies were attributed to the prevailing environmental factors in each collection site.Morphological and anatomical studies on Tacca leontopetaloides (L.) Kuntze (Taccaceae) in Nigeri

Centaurus A at Hard X-rays and Soft Gamma-rays

Centaurus A, at a distance of less than 4 Mpc, is the nearest radio-loud AGN. Its emission is detected from radio to very-high energy gamma-rays. Despite the fact that Cen A is one of the best studied extragalactic objects the origin of its hard X-ray and soft gamma-ray emission (100 keV < E < 50 MeV) is still uncertain. Observations with high spatial resolution in the adjacent soft X-ray and hard gamma-ray regimes suggest that several distinct components such as a Seyfert-like nucleus, relativistic jets, and even luminous X-ray binaries within Cen A may contribute to the total emission in the MeV regime that has been detected with low spatial resolution. As the Spectral Energy Distribution of Cen A has its second maximum around 1 MeV, this energy range plays an important role in modeling the emission of (this) AGN. As there will be no satellite mission in the near future that will cover this energies with higher spatial resolution and better sensitivity, an overview of all existing hard X-ray and soft gamma-ray measurements of Cen A is presented here defining the present knowledge on Centaurus A in the MeV energy range.Comment: 8 pages, 5 figures, article for conference proceedings "The Many Faces of Centaurus A"; accepted for publication in PAS

Double-Scaling Limit of Heterotic Bundles and Dynamical Deformation in CFT

We consider heterotic string theory on Eguchi-Hanson space, as a local model of a resolved A_1 singularity in a six-dimensional flux compactification, with an Abelian gauge bundle turned on and non-zero torsion. We show that in a suitable double scaling limit, that isolates the physics near the non-vanishing two-cycle, a worldsheet conformal field theory description can be found. It contains a heterotic coset whose target space is conformal to Eguchi-Hanson. Starting from the blow-down limit of the singularity, it can be viewed as a dynamical deformation of the near-horizon fivebrane background. We analyze in detail the spectrum of the theory in particular examples, as well as the important role of worldsheet non-perturbative effects.Comment: 45 pages, no figures; ver2: typos corrected, references added, an extra tadpole-free model covere

Can a Tool That Automates Insulin Titration Be a Key to Diabetes Management?

Abstract Background: Most patients who use insulin do not achieve optimal glycemic control and become susceptible to complications. Numerous clinical trials have shown that frequent insulin dosage titration is imperative to achieve glycemic control. Unfortunately, implementation of such a paradigm is often impractical. We hypothesized that the Diabetes Insulin Guidance System (DIGS?) (Hygieia, Inc., Ann Arbor, MI) software, which automatically advises patients on adjustment of insulin dosage, would provide safe and effective weekly insulin dosage adjustments. Subjects and Methods: In a feasibility study we enrolled patients with type 1 and type 2 diabetes, treated with a variety of insulin regimens and having suboptimal glycemic control. The 12-week intervention period followed a 4-week baseline run-in period. During the intervention, DIGS processed patients' glucose readings and provided insulin dosage adjustments on a weekly basis. If approved by the study team, the adjusted insulin dosage was communicated to the patients. Insulin formulations were not changed during the study. The primary outcome was the fraction of DIGS dosage adjustments approved by the study team, and the secondary outcome was improved glycemic control. Results: Forty-six patients were recruited, and eight withdrew. The DIGS software recommended 1,734 insulin dosage adjustments, of which 1,731 (99.83%) were approved. During the run-in period the weekly average glucose was stable at 174.2±36.7?mg/dL (9.7±2.0?mmol/L). During the following 12 weeks, DIGS dosage adjustments resulted in progressive improvement in average glucose to 163.3±35.1?mg/dL (9.1±1.9?mmol/L) (P<0.03). Mean glycosylated hemoglobin decreased from 8.4±0.8% to 7.9±0.9% (P<0.05). Concomitantly, the frequency of hypoglycemia decreased by 25.2%. Conclusions: The DIGS software provided patients with safe and effective weekly insulin dosage adjustments. Widespread implementation of DIGS may improve the outcome and reduce the cost of implementing effective insulin therapy.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98442/1/dia%2E2011%2E0303.pd

An Enhanced eBook Facilitates Parent-Child Talk During Shared Reading by Families of Low Socioeconomic Status

Language input plays a key role in children’s language development, but children from families of low socioeconomic status often get much less input compared to more advantaged peers. In “dialogic reading” (Whitehurst et al., 1988), parents are trained to ask children open-ended questions while reading, which effectively builds expressive vocabulary in at-risk children. In the research reported here, a dialogic questioning character in a narrated eBook provided effortless support for parents to ask questions while reading. Parents of lower socioeconomic status talked more than three times as much with their children using significantly more utterances and unique words when using the eBook with questioner, compared to parents using the unmodified eBook. Children also talked much more, with more varied language, in this condition. By the end of the session, parents took over asking their own unprompted questions and engaged in more conversational turns with their children. This intervention has promise to increase parent-child conversation to help bridge the word gap

High resolution radio continuum survey of M33: I. The radio maps

We study the exponential scale length of total radio emission, the spectral index distribution, and the linear radio polarization in the Scd galaxy M33. Observations were carried out using the 3.6 cm dual channel and the 6.2 cm four channel receivers of the 100--m Effelsberg telescope along with the L-band VLA D--array at 20 cm. High spatial resolution and sensitivity in both total and linearly polarized radio continuum emission from M33 were achieved. We found considerable extended emission, not only from the main arms I S and I N, but also from the weaker arms. The large--scale magnetic field exhibits well--ordered spiral structure with almost the same orientation as that of the optical spiral arms, however, it does not show a clear structural correlation or anti--correlation with the optical arms. There is a north-south asymmetry in polarization that is frequency-dependent. We found that the ring mean spectral index versus radius increases faster beyond $R$ = 4 kpc. At each wavelength, the exponential scale length is larger inside than outside $R$ = 4 kpc. From the larger scales lengths at $R$ $<$ 4 kpc, we conclude that star forming regions are mainly spread over the region $R$ $<$ 4 kpc without a dominant nuclear concentration. Furthermore, at $R$ $<$ 4 kpc, a spatial correlation between cosmic rays and star forming regions may exist. From the behaviour of the mean spectral indices obtained from different pairs of the radio continuum data at 3.6, 6.2, and 20 cm, we confirm that a decrease in the thermal fraction causes an increase in the spectral index. The frequency-dependent asymmetry in the polarization hints to an asymmetry in Faraday depolarization.Comment: 16 pages, 13 figures, accepted for publication in the Astronomy and Astrophysics Journa