Combined Diffusion-Relaxometry MRI to Identify Dysfunction in the Human Placenta

Purpose: A combined diffusion-relaxometry MR acquisition and analysis pipeline for in-vivo human placenta, which allows for exploration of coupling between T2* and apparent diffusion coefficient (ADC) measurements in a sub 10 minute scan time. Methods: We present a novel acquisition combining a diffusion prepared spin-echo with subsequent gradient echoes. The placentas of 17 pregnant women were scanned in-vivo, including both healthy controls and participants with various pregnancy complications. We estimate the joint T2*-ADC spectra using an inverse Laplace transform. Results: T2*-ADC spectra demonstrate clear quantitative separation between normal and dysfunctional placentas. Conclusions: Combined T2*-diffusivity MRI is promising for assessing fetal and maternal health during pregnancy. The T2*-ADC spectrum potentially provides additional information on tissue microstructure, compared to measuring these two contrasts separately. The presented method is immediately applicable to the study of other organs

Evidence for a Black Hole and Accretion Disk in the LINER NGC 4203

We present spectroscopic observations from the Hubble Space Telescope that reveal for the first time the presence of a broad pedestal of Balmer-line emission in the LINER galaxy NGC 4203. The emission-line profile is suggestive of a relativistic accretion disk, and is reminiscent of double-peaked transient Balmer emission observed in a handful of other LINERs. The very broad line emission thus constitutes clear qualitative evidence for a black hole, and spatially resolved narrow-line emission in NGC 4203 can be used to constrain its mass, with M_BH less than 6 x 10^6 solar masses at 99.7% confidence. This value implies a ratio of black-hole mass to bulge mass of less than approximately 7 x 10^-4 in NGC 4203, which is less by a factor of ~3 - 9 than the mean ratio obtained for other galaxies. The availability of an independent constraint on central black-hole mass makes NGC4203 an important testbed for probing the physics of weak active galactic nuclei. Assuming M_BH near the detection limit, the ratio of observed luminosity to the Eddington luminosity is approximately 10^-4. This value is consistent with advection-dominated accretion, and hence with scenarios in which an ion torus irradiates an outer accretion disk that produces the observed double-peaked line emission. Follow-up observations will make it possible to improve the black-hole mass estimate and study variability in the nuclear emission.Comment: 10 pages (LaTeX, AASTeX v4.0), 2 postscript figures, accepted for publication in The Astrophysical Journal Letter

Telomerase prevents accelerated senescence in glucose-6-phosphate dehydrogenase (G6PD)-deficient human fibroblasts

Fibroblasts derived from glucose-6-phosphate dehydrogenase (G6PD)-deficient patients display retarded growth and accelerated cellular senescence that is attributable to increased accumulation of oxidative DNA damage and increased sensitivity to oxidant-induced senescence, but not to accelerated telomere attrition. Here, we show that ectopic expression of hTERT stimulates telomerase activity and prevents accelerated senescence in G6PD-deficient cells. Stable clones derived from hTERT-expressing normal and G6PD-deficient fibroblasts have normal karyotypes, and display no sign of senescence beyond 145 and 105 passages, respectively. Activation of telomerase, however, does not prevent telomere attrition in earlier-passage cells, but does stabilize telomere lengths at later passages. In addition, we provide evidence that ectopic expression of hTERT attenuates the increased sensitivity of G6PD-deficient fibroblasts to oxidant-induced senescence. These results suggest that ectopic expression of hTERT, in addition to acting in telomere length maintenance by activating telomerase, also functions in regulating senescence induction

SuperMassive Black Holes in Bulges

We present spatially extended gas kinematics at parsec-scale resolution for the nuclear regions of four nearby disk galaxies, and model them as rotation of a gas disk in the joint potential of the stellar bulge and a putative central black hole. The targets were selected from a larger set of long-slit spectra obtained with the Hubble Space Telescope as part of the Survey of Nearby Nuclei with STIS (SUNNS). They represents the 4 galaxies (of 24) that display symmetric gas velocity curves consistent with a rotating disk. We derive the stellar mass distribution from the STIS acquisition images adopting the stellar mass-to-light ratio normalized so as to match ground-based velocity dispersion measurements over a large aperture. Subsequently, we constrain the mass of a putative black hole by matching the gas rotation curve, following two distinct approaches. In the most general case we explore all the possible disk orientations, alternatively we constrain the gas disk orientation from the dust-lane morphology at similar radii. In the latter case the kinematic data indicate the presence of a central black hole for three of the four objects, with masses of 10^7 - 10^8 solar masses, representing up to 0.025 % of the host bulge mass. For one object (NGC2787) the kinematic data alone provide clear evidence for the presence of a central black hole even without external constraints on the disk orientation. These results illustrate directly the need to determine black-hole masses by differing methods for a large number of objects, demonstrate that the variance in black hole/bulge mass is much larger than previously claimed, and reinforce the recent finding that the black-hole mass is tightly correlated with the bulge stellar velocity dispersion.Comment: 26 pages, 11 Postscript figures, accepted for publication on Ap

Potential for allocative harm in an environmental justice data tool

Neighborhood-level screening algorithms are increasingly being deployed to inform policy decisions. We evaluate one such algorithm, CalEnviroScreen - designed to promote environmental justice and used to guide hundreds of millions of dollars in public funding annually - assessing its potential for allocative harm. We observe the model to be sensitive to subjective model decisions, with 16% of tracts potentially changing designation, as well as financially consequential, estimating the effect of its positive designations as a 104% (62-145%) increase in funding, equivalent to \$2.08 billion (\$1.56-2.41 billion) over four years. We also observe allocative tradeoffs and susceptibility to manipulation, raising ethical concerns. We recommend incorporating sensitivity analyses to mitigate allocative harm and accountability mechanisms to prevent misuse

Double-Peaked Broad Emission Lines in NGC 4450 and Other LINERs

Spectra taken with HST reveal that NGC 4450 emits Balmer emission lines with displaced double peaks and extremely high-velocity wings. This characteristic line profile, previously seen in a few nearby LINERs and in a small fraction of broad-line radio galaxies, can be interpreted as a kinematic signature of a relativistic accretion disk. We can reproduce the observed profile with a model for a disk with a radial range of 1000-2000 gravitational radii and inclined by 27 degrees along the line of sight. The small-aperture HST data also allow us to detect, for the first time, the featureless continuum at optical wavelengths in NGC 4450; the nonstellar nucleus is intrinsically very faint, with M_B = -11.2 mag for D = 16.8 Mpc. We have examined the multiwavelength properties of NGC 4450 collectively with those of other low-luminosity active nuclei which possess double-peaked broad lines and find a number of common features. These objects are all classified spectroscopically as "type 1" LINERs or closely related objects. The nuclear luminosities are low, both in absolute terms and relative to the Eddington rates. All of them have compact radio cores, whose strength relative to the optical nuclear emission places them in the league of radio-loud active nuclei. The broad-band spectral energy distributions of these sources are most notable for their deficit of ultraviolet emission compared to those observed in luminous Seyfert 1 nuclei and quasars. The double-peaked broad-line radio galaxies Arp 102B and Pictor A have very similar attributes. We discuss how these characteristics can be understood in the context of advection-dominated accretion onto massive black holes.Comment: To appear in The Astrophysical Journal. Latex, 15 pages, embedded figures and tabl

The Survey of Nearby Nuclei with the Space Telescope Imaging Spectrograph: Emission-Line Nuclei at Hubble Space Telescope Resolution

We present results from a program of optical spectroscopy for 23 nearby galaxies with emission-line nuclei. This investigation takes advantage of the spatial resolution of the Hubble Space Telescope to study the structure and energetics of the central ~10-20 pc, and the resulting data have value for quantifying central black hole masses, star formation histories, and nebular properties. This paper provides a description of the experimental design, and new findings from the study of emission lines. The sample targets span a range of nebular spectroscopic class, from H II to Seyfert nuclei. This data set and the resulting measurements are unique in terms of the sample size, the range of nebular class, and the investigation of physical scales extending down to parsecs. The line ratios indicative of nebular ionization show only modest variations over order-of-magnitude differences in radius, and demonstrate in a systematic way that geometrical dilution of the radiation field from a central source cannot be assumed as a primary driver of ionization structure. Comparisons between large- and small-aperture measurements for the H II/LINER transition objects provide a new test that challenges conventional wisdom concerning the composite nature of these systems. We also list a number of other quantitative results that are of interest for understanding galaxy nuclei, including (1) the spatial distribution/degree of concentration of Hα emission as a function of nebular type; (2) the radial variation in electron density as a function of nebular type; and (3) quantitative broad Hα estimates obtained at a second epoch for these low-luminosity nuclei. The resulting measurements provide a new basis for comparing the nuclei of other galaxies with that of the Milky Way. We find that the Galactic center is representative across a wide span of properties as a low-luminosity emission-line nucleus

Quantization of Superflow Circulation and Magnetic Flux with a Tunable Offset

Quantization of superflow-circulation and of magnetic-flux are considered for systems, such as superfluid $^3$He-A and unconventional superconductors, having nonscalar order parameters. The circulation is shown to be the anholonomy in the parallel transport of the order parameter. For multiply-connected samples free of distributed vorticity, circulation and flux are predicted to be quantized, but generically to nonintegral values that are tunably offset from integers. This amounts to a version of Aharonov-Bohm physics. Experimental settings for testing these issues are discussed.Comment: 5 two-column pages, ReVTeX, figure available upon request (to [email protected]