Radio Remnants of Compact Binary Mergers - the Electromagnetic Signal that will follow the Gravitational Waves

The question "what is the observable electromagnetic (EM) signature of a compact binary merger?" is an intriguing one with crucial consequences to the quest for gravitational waves (GW). Compact binary mergers are prime sources of GW, targeted by current and next generation detectors. Numerical simulations have demonstrated that these mergers eject energetic sub-relativistic (or even relativistic) outflows. This is certainly the case if the mergers produce short GRBs, but even if not, significant outflows are expected. The interaction of such outflows with the surround matter inevitably leads to a long lasting radio signal. We calculate the expected signal from these outflows (our calculations are also applicable to short GRB orphan afterglows) and we discuss their detectability. We show that the optimal search for such signal should, conveniently, take place around 1.4 GHz. Realistic estimates of the outflow parameters yield signals of a few hundred $\mu$Jy, lasting a few weeks, from sources at the detection horizon of advanced GW detectors. Followup radio observations, triggered by GW detection, could reveal the radio remnant even under unfavorable conditions. Upcoming all sky surveys can detect a few dozen, and possibly even thousands, merger remnants at any give time, thereby providing robust merger rate estimates even before the advanced GW detectors become operational. In fact, the radio transient RT 19870422 fits well the overall properties predicted by our model and we suggest that its most probable origin is a compact binary merger radio remnant

The Chemotherapeutic Drug 5-Fluorouracil Promotes PKR-Mediated Apoptosis in a p53- Independent Manner in Colon and Breast Cancer Cells

The chemotherapeutic drug 5-FU is widely used in the treatment of a range of cancers, but resistance to the drug remains a major clinical problem. Since defects in the mediators of apoptosis may account for chemo-resistance, the identification of new targets involved in 5-FU-induced apoptosis is of main clinical interest. We have identified the ds-RNA-dependent protein kinase (PKR) as a key molecular target of 5-FU involved in apoptosis induction in human colon and breast cancer cell lines. PKR distribution and activation, apoptosis induction and cytotoxic effects were analyzed during 5-FU and 5-FU/IFNα treatment in several colon and breast cancer cell lines with different p53 status. PKR protein was activated by 5-FU treatment in a p53-independent manner, inducing phosphorylation of the protein synthesis translation initiation factor eIF-2α and cell death by apoptosis. Furthermore, PKR interference promoted a decreased response to 5-FU treatment and those cells were not affected by the synergistic antitumor activity of 5-FU/IFNα combination. These results, taken together, provide evidence that PKR is a key molecular target of 5-FU with potential relevance in the clinical use of this drug

Observations of Lyα\alpha Emitters at High Redshift

In this series of lectures, I review our observational understanding of high-$z$ Ly$\alpha$ emitters (LAEs) and relevant scientific topics. Since the discovery of LAEs in the late 1990s, more than ten (one) thousand(s) of LAEs have been identified photometrically (spectroscopically) at $z\sim 0$ to $z\sim 10$. These large samples of LAEs are useful to address two major astrophysical issues, galaxy formation and cosmic reionization. Statistical studies have revealed the general picture of LAEs' physical properties: young stellar populations, remarkable luminosity function evolutions, compact morphologies, highly ionized inter-stellar media (ISM) with low metal/dust contents, low masses of dark-matter halos. Typical LAEs represent low-mass high-$z$ galaxies, high-$z$ analogs of dwarf galaxies, some of which are thought to be candidates of population III galaxies. These observational studies have also pinpointed rare bright Ly$\alpha$ sources extended over $\sim 10-100$ kpc, dubbed Ly$\alpha$ blobs, whose physical origins are under debate. LAEs are used as probes of cosmic reionization history through the Ly$\alpha$ damping wing absorption given by the neutral hydrogen of the inter-galactic medium (IGM), which complement the cosmic microwave background radiation and 21cm observations. The low-mass and highly-ionized population of LAEs can be major sources of cosmic reionization. The budget of ionizing photons for cosmic reionization has been constrained, although there remain large observational uncertainties in the parameters. Beyond galaxy formation and cosmic reionization, several new usages of LAEs for science frontiers have been suggested such as the distribution of {\sc Hi} gas in the circum-galactic medium and filaments of large-scale structures. On-going programs and future telescope projects, such as JWST, ELTs, and SKA, will push the horizons of the science frontiers.Comment: Lecture notes for `Lyman-alpha as an Astrophysical and Cosmological Tool', Saas-Fee Advanced Course 46. Verhamme, A., North, P., Cantalupo, S., & Atek, H. (eds.) --- 147 pages, 103 figures. Abstract abridged. Link to the lecture program including the video recording and ppt files : https://obswww.unige.ch/Courses/saas-fee-2016/program.cg

A tectonically driven Ediacaran oxygenation event.

The diversification of complex animal life during the Cambrian Period (541-485.4 Ma) is thought to have been contingent on an oxygenation event sometime during ~850 to 541 Ma in the Neoproterozoic Era. Whilst abundant geochemical evidence indicates repeated intervals of ocean oxygenation during this time, the timing and magnitude of any changes in atmospheric pO₂ remain uncertain. Recent work indicates a large increase in the tectonic CO₂ degassing rate between the Neoproterozoic and Paleozoic Eras. We use a biogeochemical model to show that this increase in the total carbon and sulphur throughput of the Earth system increased the rate of organic carbon and pyrite sulphur burial and hence atmospheric pO₂. Modelled atmospheric pO₂ increases by ~50% during the Ediacaran Period (635-541 Ma), reaching ~0.25 of the present atmospheric level (PAL), broadly consistent with the estimated pO₂ > 0.1-0.25 PAL requirement of large, mobile and predatory animals during the Cambrian explosion

Effects of ovariectomy and anabolic steroid implantation on the somatotrophic axis in feedlot heifers

A 2 x 2 factorial experimental design was used to evaluate effects of ovariectomy and implantation (200 mg trenbolone acetate and 28 mg estradiol benzoate; Synovex-Plus) on the performance, serum urea nitrogen, serum insulin like growth factor -1 (IGF-1), and mRNA expression of hepatic IGF-1, growth hormone (GH) receptor and estrogen receptor-α as well as pituitary GH, estrogen receptor-α and GH releasing hormone receptor in feedlot heifers. Thirty-two British x Continental heifers were randomly assigned to either an ovariectomized (OVX) or intact group and then to either a control group or a Synovex-Plus implant group. Heifers were fed a 900 g/kg concentrate steam-flaked maize based diet for 42 d. Liver biopsies were taken before OVX for baseline expression of IGF-1, GH receptor and hepatic estrogen receptor-α, which did not differ between treatment groups. Blood and body weight (BW) were taken on d 0, 28, and 42 and one heifer/pen was slaughtered on d 42 for liver and pituitary tissue samples. Initial and final BW did not differ due to OVX or implant. No gender x treatment interaction was observed for average daily gain (ADG) or final BW. Neither OVX nor implant affected ADG for the final 14 d of the feeding period, but 28 and 42 d ADG were greater in implanted than in control heifers. No 2- or 3-way interactions with day were observed for serum urea nitrogen. Serum urea nitrogen was greater in control heifers than in implanted heifers, but gender had no effect. Both implant and OVX increased serum IGF-1 and a gender x treatment interaction was observed. Neither gender nor implant treatment affected hepatic estrogen receptor-α, hepatic IGF-1, hepatic GH receptor, GH releasing hormone receptor, GH, or pituitary estrogen receptor-α. Data indicate that implanting heifers with Synovex-plus increases serum IGF-1, but the reason for this increase cannot be explained by mRNA expression of key somatotropic genes in the present study.A 2 x 2 factorial experimental design was used to evaluate effects of ovariectomy and implantation (200 mg trenbolone acetate and 28 mg estradiol benzoate; Synovex-Plus) on the performance, serum urea nitrogen, serum insulin like growth factor -1 (IGF-1), and mRNA expression of hepatic IGF-1, growth hormone (GH) receptor and estrogen receptor-α as well as pituitary GH, estrogen receptor-α and GH releasing hormone receptor in feedlot heifers. Thirty-two British x Continental heifers were randomly assigned to either an ovariectomized (OVX) or intact group and then to either a control group or a Synovex-Plus implant group. Heifers were fed a 900 g/kg concentrate steam-flaked maize based diet for 42 d. Liver biopsies were taken before OVX for baseline expression of IGF-1, GH receptor and hepatic estrogen receptor-α, which did not differ between treatment groups. Blood and body weight (BW) were taken on d 0, 28, and 42 and one heifer/pen was slaughtered on d 42 for liver and pituitary tissue samples. Initial and final BW did not differ due to OVX or implant. No gender x treatment interaction was observed for average daily gain (ADG) or final BW. Neither OVX nor implant affected ADG for the final 14 d of the feeding period, but 28 and 42 d ADG were greater in implanted than in control heifers. No 2- or 3-way interactions with day were observed for serum urea nitrogen. Serum urea nitrogen was greater in control heifers than in implanted heifers, but gender had no effect. Both implant and OVX increased serum IGF-1 and a gender x treatment interaction was observed. Neither gender nor implant treatment affected hepatic estrogen receptor-α, hepatic IGF-1, hepatic GH receptor, GH releasing hormone receptor, GH, or pituitary estrogen receptor-α. Data indicate that implanting heifers with Synovex-plus increases serum IGF-1, but the reason for this increase cannot be explained by mRNA expression of key somatotropic genes in the present study. Keywords: Synovex-plus, mRNA, genderSouth African Journal of Animal Science Vol. 38 (3) 2008: pp. 207-21