A Search for Exozodiacal Dust and Faint Companions Near Sirius, Procyon, and Altair with the NICMOS Coronagraph

We observed Sirius, Altair, and Procyon with the NICMOS Coronagraph on the Hubble Space Telescope to look for scattered light from exozodiacal dust and faint companions within 10 AU from these stars. We did not achieve enough dynamic range to surpass the upper limits set by IRAS on the amount of exo-zodiacal dust in these systems, but we did set strong upper limits on the presence of nearby late-type and sub-stellar companions.Comment: 10 pages, 4 figure

A Candidate Protoplanet in the Taurus Star Forming Region

HST/NICMOS images of the class I protostar TMR-1 (IRAS04361+2547) reveal a faint companion with 10.0" = 1400 AU projected separation. The central protostar is itself resolved as a close binary with 0.31" = 42 AU separation, surrounded by circumstellar reflection nebulosity. A long narrow filament seems to connect the protobinary to the faint companion TMR-1C, suggesting a physical association. If the sources are physically related then we hypothesize that TMR-1C has been ejected by the protobinary. If TMR-1C has the same age and distance as the protobinary then current models indicate its flux is consistent with a young giant planet of several Jovian masses.Comment: 16 pages, 1 figure, Accepted by Astrophysical Journal Letters, Related information is available at http://www.extrasolar.co

Planetary Dynamics and Habitable Planet Formation In Binary Star Systems

Whether binaries can harbor potentially habitable planets depends on several factors including the physical properties and the orbital characteristics of the binary system. While the former determines the location of the habitable zone (HZ), the latter affects the dynamics of the material from which terrestrial planets are formed (i.e., planetesimals and planetary embryos), and drives the final architecture of the planets assembly. In order for a habitable planet to form in a binary star system, these two factors have to work in harmony. That is, the orbital dynamics of the two stars and their interactions with the planet-forming material have to allow terrestrial planet formation in the habitable zone, and ensure that the orbit of a potentially habitable planet will be stable for long times. We have organized this chapter with the same order in mind. We begin by presenting a general discussion on the motion of planets in binary stars and their stability. We then discuss the stability of terrestrial planets, and the formation of potentially habitable planets in a binary-planetary system.Comment: 56 pages, 29 figures, chapter to appear in the book: Planets in Binary Star Systems (Ed. N. Haghighipour, Springer publishing company

Licensed human natural killer cells aid dendritic cell maturation via TNFSF14/LIGHT

Interactions between natural killer (NK) cells and dendritic cells (DC) aid DC maturation and promote T cell responses. Here, we have analysed the response of human NK cells to tumor cells and we identify a pathway by which NK-DC interactions occur. Gene expression profiling of tumor-responsive NK cells identified the very rapid induction of TNFSF14 (also known as LIGHT), a cytokine implicated in the enhancement of anti-tumor responses. TNFSF14 protein expression was induced by three primary mechanisms of NK cell activation, namely via the engagement of CD16, by the synergistic activity of multiple target cell-sensing NK cell activation receptors and by the cytokines IL-2 and IL-15. For anti-tumor responses, TNFSF14 was preferentially produced by the licensed NK cell population, defined by the expression of inhibitory receptors specific for self-MHC class I molecules. In contrast, IL-2 and IL-15 treatment induced TNFSF14 production by both licensed and unlicensed NK cells, reflecting the ability of pro-inflammatory conditions to override the licensing mechanism. Importantly, both tumor and cytokine activated NK cells induced DC maturation in a TNFSF14-dependent manner. The coupling of TNFSF14 production to tumor-sensing NK cell activation receptors links the tumor immune surveillance function of NK cells to DC maturation and adaptive immunity. Furthermore, regulation by NK cell licensing helps to safeguard against TNFSF14 production in response to healthy tissues

X-Ray, FUV, and UV Observations of alpha Centauri B: Determination of Long-term Magnetic Activity Cycle and Rotation Period

We have been carrying out a study of stellar magnetic activity, dynamos, atmospheric physics, and spectral irradiances from a sample of solar-type G0-5 V stars with different ages. One of the major goals of this program is to study the evolution of the Sun's X-ray through NUV spectral irradiances with age. Of particular interest is the determination of the young Sun's elevated levels of high-energy fluxes because of the critical roles that X-ray through FUV emissions play on the photochemical and photoionization evolution of early, young planetary atmospheres and ionospheres. Motivated by the current exoplanetary search missions that are hunting for earth-size planets in the habitable zones of nearby main-sequence G-M stars, we are expanding our program to cooler, less luminous, but much more numerous main-sequence K-type stars, such as alpha Centauri B. The long life (2-3x longer than our Sun) and slow evolution of K stars provide nearly constant energy sources for possible hosted planets. Presented here are X-ray, UV, and recently acquired FUV observations of the K1 V star alpha Cen B. These combined high-energy measures provide a more complete look into the nature of alpha Cen B's magnetic activity and X-UV radiances. We find that alpha Cen B has exhibited significant long-term variability in X-ray through NUV emission fluxes, indicating a solar-like long-term activity cycle of P_cycle = 8.84 years. In addition, analysis of the short-term rotational modulation of mean light due to the effects of magnetically active regions has yielded a well-determined rotation period of P_rotation = 36.2 days. alpha Cen B is the only old main-sequence K star with a reliably determined age and rotation period, and for early K-stars, is an important calibrator for stellar age/rotation/activity relations

Hydrogen Sulfide Is a Novel Protector of the Retinal Glycocalyx and Endothelial Permeability Barrier

This is the final version. Available on open access from Frontiers Media via the DOI in this recordData Availability Statement: The original contributions presented in the study are included in the article/supplementary material. The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.Significantly reduced levels of the anti-inflammatory gaseous transmitter hydrogen sulfide (H2S) are observed in diabetic patients and correlate with microvascular dysfunction. H2S may protect the microvasculature by preventing loss of the endothelial glycocalyx. We tested the hypothesis that H2S could prevent or treat retinal microvascular endothelial dysfunction in diabetes. Bovine retinal endothelial cells (BRECs) were exposed to normal (NG, 5.5 mmol/L) or high glucose (HG, 25 mmol/L) ± the slow-release H2S donor NaGYY4137 in vitro. Glycocalyx coverage (stained with WGA-FITC) and calcein-labeled monocyte adherence were measured. In vivo, fundus fluorescein angiography (FFA) was performed in normal and streptozotocin-induced (STZ) diabetic rats. Animals received intraocular injection of NaGYY4137 (1 μM) or the mitochondrial-targeted H2S donor AP39 (100 nM) simultaneously with STZ (prevention) or on day 6 after STZ (treatment), and the ratio of interstitial to vascular fluorescence was used to estimate apparent permeability. NaGYY4137 prevented HG-induced loss of BREC glycocalyx, increased monocyte binding to BRECs (p ≤ 0.001), and increased overall glycocalyx coverage (p ≤ 0.001). In rats, the STZ-induced increase in apparent retinal vascular permeability (p ≤ 0.01) was significantly prevented by pre-treatment with NaGYY4137 and AP39 (p < 0.05) and stabilized by their post-STZ administration. NaGYY4137 also reduced the number of acellular capillaries (collagen IV + /IB4-) in the diabetic retina in both groups (p ≤ 0.05). We conclude that NaGYY4137 and AP39 protected the retinal glycocalyx and endothelial permeability barrier from diabetes-associated loss of integrity and reduced the progression of diabetic retinopathy (DR). Hydrogen sulfide donors that target the glycocalyx may therefore be a therapeutic candidate for DR.Medical Research Council (MRC)British Heart FoundationRoyal SocietyBrian Ridge ScholarshipNational Eye Research CentreMasonic Charitable Foundatio

Spatio-temporal Models of Lymphangiogenesis in Wound Healing

Several studies suggest that one possible cause of impaired wound healing is failed or insufficient lymphangiogenesis, that is the formation of new lymphatic capillaries. Although many mathematical models have been developed to describe the formation of blood capillaries (angiogenesis), very few have been proposed for the regeneration of the lymphatic network. Lymphangiogenesis is a markedly different process from angiogenesis, occurring at different times and in response to different chemical stimuli. Two main hypotheses have been proposed: 1) lymphatic capillaries sprout from existing interrupted ones at the edge of the wound in analogy to the blood angiogenesis case; 2) lymphatic endothelial cells first pool in the wound region following the lymph flow and then, once sufficiently populated, start to form a network. Here we present two PDE models describing lymphangiogenesis according to these two different hypotheses. Further, we include the effect of advection due to interstitial flow and lymph flow coming from open capillaries. The variables represent different cell densities and growth factor concentrations, and where possible the parameters are estimated from biological data. The models are then solved numerically and the results are compared with the available biological literature.Comment: 29 pages, 9 Figures, 6 Tables (39 figure files in total