The core of the nearby S0 galaxy NGC 7457 imaged with the HST planetary camera

We have observed the nearby S0 galaxy NGC 7457 with the Planetary Camera of the Hubble Space Telescope. Spatial structure is observable at the diffraction-limited resolution of the 2.4 m HST primary despite the effects of spherical aberration. The central distribution of starlight appears consistent with a y ~ -1.0 power law for r 3 x 10^4 L_☉ pc^(-3) (V band). This is now the second densest core known after M32. From the ground, NGC 7457 resembles any number of unresolved elliptical galaxies, which suggests that compact dense cores may be common. The images of NGC 7457 demonstrate that HST can still provide unique and astrophysically interesting information on the central structure of galaxies

The Postcollapse core of M15 imaged with the HST planetary camera

We have obtained U-band images of the M15 core with the Planetary Camera of the Hubble Space Telescope. We are able to resolve stars down to the main-sequence turnoff (m_v≈ 19.4) into the cluster center. We use crowded field photometry techniques to decompose M15 into bright resolved stars and a residual component consisting of stars at turnoff brightness or fainter. The residual component comprises 59% of the cluster light and follows a y = -0.71 power-law distribution for r > 1". The residual component flattens off interior to this radius and has a large core with r_c = 2".2 = 0.13 pc. The core size may reflect postcollapse core expansion. The resolved stars have a slightly shallower distribution (y = - 0.53) but have an abrupt overdensity for r < 1".5, which accounts for the unresolved surface brightness cusp at ground resolution. The bright stars do not become more highly concentrated at still smaller radii, however; neither the bright stars nor the residual component form a cusp at subarcsecond resolution. The total central density of light in all components is 8 x 10^5 L_☉ pc^(-3) (U-band). The Peterson, Seitzer, and Cudworth central velocity dispersion implies a high core M/L ≈ 8 (U-band). The existence of a core rather than a cusp at the 0.1 pc scale may imply that the centrally deduced dark matter is in a diffuse form rather than a massive black hole

Matrix metalloproteinases in human melanoma cell lines and xenografts: increased expression of activated matrix metalloproteinase-2 (MMP-2) correlates with melanoma progression

Matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) are involved in tumour progression and metastasis. In this study, we investigated the in vitro and in vivo expression patterns of MMP-1, MMP-2, MMP-3, MMP-9, TIMP-1 and TIMP-2 mRNA and protein in a previously described human melanoma xenograft model. This model consists of eight human melanoma cell lines with different metastatic behaviour after subcutaneous (s.c.) injection into nude mice. MMP-1 mRNA was detectable in all cell lines by reverse transcription polymerase chain reaction (RT-PCR), but the expression was too low to be detected by Northern blot analysis. No MMP-1 protein could be found using Western blotting. MMP-2 mRNA and protein were present in all cell lines, with the highest expression of both latent and active MMP-2 in the highest metastatic cell lines MV3 and BLM. MMP-3 mRNA was expressed in MV3 and BLM, and in the non-metastatic cell line 530, whereas MMP-3 protein was detectable only in MV3 and BLM. None of the melanoma cell lines expressed MMP-9. TIMP-1 and TIMP-2 mRNA and protein, finally, were present in all cell lines. A correlation between TIMP expression level and metastatic capacity of cell lines, however, was lacking. MMP and TIMP mRNA and protein expression levels were also studied in s.c. xenograft lesions derived from a selection of these cell lines. RT-PCR analysis revealed that MMP-1 mRNA was present in MV3 and BLM xenografts, and to a lesser extent in 530. Positive staining for MMP-1 protein was found in xenograft lesions derived from both low and high metastatic cell lines, indicating an in vivo up-regulation of MMP-1. MMP-2 mRNA was detectable only in xenografts derived from the highly metastatic cell lines 1F6m, MV3 and BLM. In agreement with the in vitro results, the highest levels of both latent and activated MMP-2 protein were observed in MV3 and BLM xenografts. With the exception of MMP-9 mRNA expression in 530 xenografts, MMP-3, MMP-9, and TIMP-1 mRNA and protein were not detectable in any xenograft, indicating a down-regulated expression of MMP-3 and TIMP-1 in vivo. TIMP-2 mRNA and protein were present in all xenografts; interestingly, the strongest immunoreactivity of tumour cells was found at the border of necrotic areas. Our study demonstrates that of all tested components of the matrix metalloproteinase system, only expression of activated MMP-2 correlates with increased malignancy in our melanoma xenograft model, corroborating an important role of MMP-2 in human melanoma invasion and metastasis. © 1999 Cancer Research Campaig

Ionization fronts and shocked flows - The structure of the Orion Nebula at 0".1

We present HST Wide-Field Camera images of a field in the Orion Nebula obtained in emission from [S II], Hβ, and [O II]. The morphology of the [S II] emission is markedly different from the other lines. While Hβ and [O II] are distributed fairly smoothly, [S II] is dominated by filamentary features with widths between 0".1 and 1" which sharply highlight ionization fronts moving into dense neutral material. These photoionization fronts act as probes of the structure of the cavity walls of this blister H II region. Their morphology indicates that while the surfaces into which they are moving are textured, subarcsecond clumps with high density contrast are uncommon. An exception is a bow shock-shaped ionization front seen along the face of a solar system-sized (0".6 = 270 AU) clump which is itself seen in extinction. The field contains a number of HH objects and related structures, many of which were previously recognized as such, but whose complex structure is revealed here by the resolution of HST. These include M42 HH 1, which is seen to be an intricate structure of knots and filaments with a head-tail morphology. M42 HH 2 shows structure from both the shocked cavity walls and the shocked atomic outflow. M42 HH 5-7 break into numerous condensations with an appearance reminiscent of HH 7-11. All objects with a bow shockshaped structure (i.e., M42 HH 1, 5, 7, and 10) show enhanced Hβ emission at the apex of the structure where the shock should be strongest. M42 HH 8 and 9 may be HH objects viewed face-on, or alternatively condensations photoionized by a nearby A or B star. Emission from [S II] traces shocks at the walls of an ionized jet apparently emanating from a star in a dark cloud. This cloud seen in extinction is coincident with H_2 Peak 1, which we propose is on the near side of the nebula

WFPC2 Studies of the Crab Nebula. I. HST and ROSAT Imaging of the Synchrotron Nebula

We present images of the Crab synchrotron nebula obtained with the Wide Field and Planetary Camera 2 (WFPC2) on board the Hubble Space Telescope. These data are compared with ROSAT HRI images, and with 0':5 resolution Canada-France-Hawaii Telescope (CFHT) images previously published by van den Bergh & Pritchet (1989). These data strengthen the emerging picture of the Crab as a cylindrically symmetrical object with an axis running southeast to northwest, and inclined by ~20°-30° with respect to the plane of the sky. Identification of structure very near to the pulsar which shares this symmetry helps to better establish the link between the symmetry axis of the nebula and the spin axis of the pulsar. We report the discovery of a bright knot of visible emission located 0º.65 to the southeast of the pulsar, along the axis of the system. This knot and a second knot 3".8 from the pulsar appear to be present but not well resolved in the 1988 CFHT image, indicating that they are persistent structures. The inner knot is interpreted as a shock in the pulsar wind ~ 1500 AU above the pole of the pulsar. No corresponding knots are seen to the northwest of the pulsar, which may indicate that the characteristics of the wind from the two poles are not symmetrical. The closest of the "wisps" to the northwest of the pulsar appear to close into a ringlike "halo" encircling the axis of the nebula. The wisps are resolved, with widths of ~ 0".2. This allows· calculation of their volumes and volume emissivities, and in turn their equipartition fields and pressures. Equipartition pressures calculated for the knots and wisps are typically 10 to as much as 80 times the equipartition pressure calculated for the nebula as a whole. The wisps show significant substructure which changed considerably between 1988 and 1994. Previous reports of relativistic motions of the wisps were probably due to changes in the unresolved substructure of these features. Comparison of the CFHT and WFPC2 images show remarkable changes in the inner nebula, but inferences about physical conditions based on this comparison are limited by the resolution of the CFHT data and the long 5 year baseline between the images. The structure of the nebula in 1994 may be inconsistent with the recent model by Gallant & Arons (1994). Very fine fibrous texture visible in the WFPC2 image follows the structure of the X-ray torus. A puzzling anticorrelation is seen between the X-ray and visible surface brightness through part of the torus. Long contiguous low contrast features with widths of ~ 1"-2" are seen to run throughout the volume of the nebula. These features are seen to move outward through the nebula at velocities in excess of homologous expansion. These features trace the magnetic structure of the nebula; they are probably due to differences in emissivity accompanying varying degrees of departure from equipartition at roughly constant total pressure. Visible fibers "drape over" and appear to expand away from an X-ray counterjet to the northwest of the pulsar, supporting the interpretation of the counterjet as a directed flow of energy along the symmetry axis of the nebula. Other associations are also seen between X-ray and visible structures, including X-ray emission surrounding the east and west bays. An association is proposed between the observed structure of the nebula and different latitude zones found in models of winds from partially oblique rotators. We concur with previous suggestions that the X-ray torus and the sharp visible fibers associated with it mark a shock at r_s ~ 1.2 x 10^(18) cm in an equatorial striped magnetic wind. The halo and anvil arise at a distance of ~ 1.4 x 10^(17) cm from the pulsar in a helically polarized wind at latitudes greater than about 35°. Well collimated polar jets may be responsible for the knots to the southeast of the pulsar and for the jet and counterjet seen at X-ray and visible wavelengths

Angiostatin generating capacity and anti-tumour effects of D-penicillamine and plasminogen activators

BACKGROUND: Upregulation of endogenous angiostatin levels may constitute a novel anti-angiogenic, and therefore anti-tumor therapy. In vitro, angiostatin generation is a two-step process, starting with the conversion of plasminogen to plasmin by plasminogen activators (PAs). Next, plasmin excises angiostatin from other plasmin molecules, a process requiring a donor of a free sulfhydryl group. In previous studies, it has been demonstrated that administration of PA in combination with the free sulfhydryl donor (FSD) agents captopril or N-acetyl cysteine, resulted in angiostatin generation, and anti-angiogenic and anti-tumour activity in murine models. METHODS: In this study we have investigated the angiostatin generating capacities of several FSDs. D-penicillamine proved to be most efficient in supporting the conversion of plasminogen to angiostatin in vitro. Next, from the optimal concentrations of tPA and D-penicillamine in vitro, equivalent dosages were administered to healthy Balb/c mice to explore upregulation of circulating angiostatin levels. Finally, anti-tumor effects of treatment with tPA and D-penicillamine were determined in a human melanoma xenograft model. RESULTS: Surprisingly, we found that despite the superior angiostatin generating capacity of D-penicillamine in vitro, both in vivo angiostatin generation and anti-tumour effects of tPA/D-penicillamine treatment were impaired compared to our previous studies with tPA and captopril. CONCLUSION: Our results indicate that selecting the most appropriate free sulfhydryl donor for anti-angiogenic therapy in a (pre)clinical setting should be performed by in vivo rather than by in vitro studies. We conclude that D-penicillamine is not suitable for this type of therapy

Stellar photometry with the Hubble Space Telescope Wide-field/Planetary camera - A progress report

We describe the prospects for the use of the Wide-Field/Planetary Camera (WFPC) for stellar photometry. The large halos of the point-spread function (PSF) resulting from spherical aberration and from spatial, temporal, and color variations of the PSF are the main limitations to accurate photometry. Degradations caused by crowding are exacerbated by the halos of the PSF. Here we attempt to quantify these effects and determine the current accuracy of stellar photometry with the WFPC. In realistic cases, the brighter stars in crowded fields have 0.09 mag errors; fainter stars have larger errors depending on the degree of crowding. We find that measuring Cepheids in Virgo Cluster galaxies is not currently possible without inordinate increases in exposure times

Moduli backreaction and supersymmetry breaking in string-inspired inflation models

We emphasize the importance of effects from heavy fields on supergravity models of inflation. We study, in particular, the backreaction of stabilizer fields and geometric moduli in the presence of supersymmetry breaking. Many effects do not decouple even if those fields are much heavier than the inflaton field. We apply our results to successful models of Starobinsky-like inflation and natural inflation. In most scenarios producing a plateau potential it proves difficult to retain the flatness of the potential after backreactions are taken into account. Some of them are incompatible with non-perturbative moduli stabilization. In natural inflation there exist a number of models which are not constrained by backreactions at all. In those cases the correction terms from heavy fields have the same inflaton-dependence as the uncorrected potential, so that inflation may be possible even for very large gravitino masses.Comment: 29 pages, 1 figure, comments added, subsection 2.3 added, published versio

Revisiting Some Developments of Boundary Elements for Thick Plates in Brazil

This work reviews the developments of Boundary Element Method formulations to solve several types of plate bending problems, including non-linear bending. The formulation is developed and solved using the standard BEM procedure, and different integration approaches were discussed and tested. Object oriented implementation issues are commented. Results were obtained for linear and non-linear elastic bending as well as buckling of selected cases of thick plates, including cases of step variation in thickness under large displacements regime