Rotating solenoidal perfect fluids of Petrov type D

We prove that aligned Petrov type D perfect fluids for which the vorticity vector is not orthogonal to the plane of repeated principal null directions and for which the magnetic part of the Weyl tensor with respect to the fluid velocity has vanishing divergence, are necessarily purely electric or locally rotationally symmetric. The LRS metrics are presented explicitly.Comment: 6 pages, no figure

Shear-free perfect fluids with a solenoidal electric curvature

We prove that the vorticity or the expansion vanishes for any shear-free perfect fluid solution of the Einstein field equations where the pressure satisfies a barotropic equation of state and the spatial divergence of the electric part of the Weyl tensor is zero.Comment: 9 page

Purely radiative perfect fluids

We study `purely radiative' (div E = div H = 0) and geodesic perfect fluids with non-constant pressure and show that the Bianchi class A perfect fluids can be uniquely characterized --modulo the class of purely electric and (pseudo-)spherically symmetric universes-- as those models for which the magnetic and electric part of the Weyl tensor and the shear are simultaneously diagonalizable. For the case of constant pressure the same conclusion holds provided one also assumes that the fluid is irrotational.Comment: 12 pages, minor grammatical change

Shearfree perfect fluids with solenoidal magnetic curvature and a gamma-law equation of state

We show that shearfree perfect fluids obeying an equation of state p=(gamma -1) mu are non-rotating or non-expanding under the assumption that the spatial divergence of the magnetic part of the Weyl tensor is zero.Comment: 11 page

Silent universes with a cosmological constant

We study non-degenerate (Petrov type I) silent universes in the presence of a non-vanishing cosmological constant L. In contrast to the L=0 case, for which the orthogonally spatially homogeneous Bianchi type I metrics most likely are the only admissible metrics, solutions are shown to exist when L is positive. The general solution is presented for the case where one of the eigenvalues of the expansion tensor is 0.Comment: 11 pages; several typos corrected which were still present in CGQ version; minor change

Near-Infrared Adaptive Optics Imaging of the Central Regions of Nearby Sc Galaxies: I. M33

Near-infrared images obtained with the Canada-France-Hawaii Telescope (CFHT) Adaptive Optics Bonnette (AOB) are used to investigate the stellar content within 18 arcsec of the center of the Local Group spiral galaxy M33. AGB stars with near-infrared spectral-energy distributions similar to those of giants in the solar neighborhood and Baade's Window are detected over most of the field. The bolometric luminosity function (LF) of these stars has a discontinuity near M_{bol} = -5.25, and comparisons with evolutionary tracks suggest that most of the AGB stars formed in a burst of star formation 1 - 3 Gyr in the past. The images are also used to investigate the integrated near-infrared photometric properties of the nucleus and the central light concentration. The nucleus is bluer than the central light concentration, in agreement with previous studies at visible wavelengths. The CO index of the central light concentration 0.5 arcsec from the galaxy center is 0.05, which corresponds to [Fe/H] = -1.2 for simple stellar systems. Hence, the central light concentration could not have formed from the chemically-enriched material that dominates the present-day inner disk of M33.Comment: 23 pages of text + 11 figures; to appear in A

Local cosmic string in generalised scalar tensor theory

A recent investigation shows that a local gauge string with a phenomenological energy momentum tensor, as prescribed by Vilenkin, is inconsistent in Brans-Dicke theory. In this work it has been shown that such a string is consistent in a more general scalar tensor theory where $\omega$ is function of the scalar field.A set of solutions of full nonlinear Einstein's equations for interior region of such a string are presented.Comment: 7 pages, latex format, minor changes according to referee's suggestions, revised version submitted in Phys.Rev.

Dynamical Mass Estimates for Five Young Massive Stellar Clusters

We have obtained high-dispersion spectra for four massive star clusters in the dwarf irregular galaxies NGC 4214 and NGC 4449, using the HIRES spectrograph on the Keck I telescope. Combining the velocity dispersions of the clusters with structural parameters and photometry from images taken with HST, we estimate mass-to-light ratios and compare these with simple stellar population (SSP) models in order to constrain the stellar mass functions (MFs). For all clusters we find mass-to-light ratios which are similar to or slightly higher than for a Kroupa MF, and thereby rule out any MF which is deficient in low-mass stars compared to a Kroupa-type MF. The four clusters have virial masses ranging between 2.1E5 Msun and 1.5E6 Msun, half-light radii between 3.0 and 5.2 pc, estimated core densities in the range 2E3 Msun pc^-3 to 2E5 Msun pc^-3 and ages between 200 Myr and 800 Myr. We also present new high-dispersion near-infrared spectroscopy for a luminous young (about 15 Myr) cluster in the nearby spiral galaxy NGC 6946, which we have previously observed with HIRES. The new measurements in the infrared agree well with previous estimates of the velocity dispersion, yielding a mass of about 1.7E6 Msun. The properties of the clusters studied here are all consistent with the clusters being young versions of the old globular clusters found around all major galaxies.Comment: 30 pages, including 7 figures and 9 tables. Corrected an error in Table 2: The colors listed for N6946-1447 were not reddening corrected. This also affected Table 9 and Fig 2, 6 and

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An aggressive poorly differentiated plurihormonal Pit-1-positive adenoma

In July 2017, a 35-year-old woman was referred to our care for treatment of a large pituitary mass with an unusually high growth rate. She presented with right-sided ptosis and diplopia (n. III palsy), increasing retrobulbar pain and vertigo. Although laboratory investigations were consistent with acromegaly, she exhibited no clear phenotypic traits. During transsphenoidal surgery aimed at biopsy, typical adenomatous tissue was encountered, upon which it was decided to proceed to debulking. Histopathological analysis demonstrated a poorly differentiated plurihormonal Pit-1-positive adenoma with focal growth hormone (GH) and prolactin positivity, positive SSTR2 staining and a Ki-67 of 20–30%. Postoperative magnetic resonance imaging (MRI) examination revealed a large tumour remnant within the sella invading the right cavernous sinus with total encasement of the internal carotid artery and displacement of the right temporal lobe. As a consequence, she was treated additionally with radiotherapy, and a long-acting first-generation somatostatin analogue was prescribed. Subsequently, the patient developed secondary hypocortisolism and diabetes mellitus despite adequate suppression of GH levels. In September 2019, her symptoms recurred. Laboratory evaluations indicated a notable loss of biochemical control, and MRI revealed tumour progression. Lanreotide was switched to pasireotide, and successful removal of the tumour remnant and decompression of the right optic nerve was performed. She received adjuvant treatment with temozolomide resulting in excellent biochemical and radiological response after three and six courses. Symptoms of right-sided ptosis and diplopia remained. Evidence for systemic therapy in case of tumour progression after temozolomide is currently limited, although various potential targets can be identified in tumour tissue