Chemical abundances of planetary nebulae from optical recombination lines - II. The neon abundance of NGC 7009

We present high-quality observations of Ne II optical recombination lines (ORLs) for the bright Saturn Nebula NGC 7009. The measured line fluxes are used to determine Ne2+/H+ abundance ratios. The results derived from individual multiplets of the 3s–3p and 3p–3d configurations agree reasonably well, although values derived from the 3d–4f transitions, for which only preliminary effective recombination coefficients are available, tend to be higher by a factor of 2 than those derived from the 3–3 transitions – a pattern also seen in other nebulae analysed by us previously. The ORL Ne2+/H+ abundance ratios of NGC 7009 are found to be higher by a factor of 4 than those derived from the optical collisionally excited lines [Ne III] λλ3868, 3967 and from the infrared fine-structure lines [Ne III] 15.5 and 36 μm, similar to the patterns found for C, N and O, analysed previously by Liu et al. The result is in line with the general conclusion that while the ratios of heavy-element abundances, derived from ORLs on the one hand and from CELs on the other hand, vary from target to target and cover a wide range from unity to more than an order of magnitude, the discrepancy factor for the individual elements, C, N, O and Ne, is found to be approximately the same magnitude for a given nebula, a result which may have a fundamental implication for understanding the underlying physical cause(s) of the large discrepancies between heavy-element abundances derived from these two types of emission line. The result also indicates that while the absolute abundances of heavy elements relative to hydrogen remain uncertain, the abundance ratios of heavy elements, such as C/O, N/O and Ne/O, are probably secure, provided that the same type of emission line, i.e. ORLs or CELs, is used to determine the abundances of both heavy elements involved in the ratio. For NGC 7009, the total neon abundances derived from the CELs and ORLs, on a logarithmic scale where H=12.0, are 8.24±0.08 and 8.84±0.25, respectively. The latter is about a factor of 5.5 higher than the solar neon abundance

Chemical abundances of planetary nebulae from optical recombination lines - III. The Galactic bulge PN M 1-42 and M 2-36

We present deep, high-resolution optical spectra of two Galactic bulge planetary nebulae (PN), M 1-42 and M 2-36. The spectra show very prominent and rich optical recombination lines (ORLs) from C, N, O and Ne ions. Infrared spectra from graphic were also obtained using the Short and Long Wavelength Spectrometer (SWS and LWS) on board ISO. The optical and infrared spectra, together with archival IUE spectra, are used to study their density and thermal characteristics and to determine elemental abundances. We determine the optical and UV extinction curve towards these two bulge PN using observed H I and He II recombination line fluxes and the radio free–free continuum flux density. In the optical, the reddening curve is found to be consistent with the standard Galactic extinction law, with a total to selective extinction ratio graphic. However, the extinction in the UV is found to be much steeper, consistent with the earlier finding of Walton, Barlow & Clegg. The rich ORL spectra from C, N, O and Ne ions detected from the two nebulae have been used to determine the abundances of these elements relative to hydrogen. In all cases, the resultant ORL abundances are found to be significantly higher than the corresponding values deduced from collisionally excited lines (CELs). In M 2-36, the discrepancies are about a factor of 5 for all four elements studied. In M 1-42, the discrepancies reach a factor of about 20, the largest ever observed in a PN. M 1-42 also has the lowest Balmer jump temperature ever determined for a PN, graphic, 5660 K lower than its [O III] forbidden line temperature. We compare the observed intensities of the strongest O II ORLs from different electronic configurations, including λ4649 from graphic, λ4072 from graphic, λ4089 from graphic, and λ4590 and λ4190 from the doubly excited graphic and graphic configurations, respectively. In all cases, in spite of the fact that the ratios of the ORL to CEL ionic abundances span a wide range from ∼graphic, the intensity ratios of λ4649, λ4072, λ4590 and λ4190 relative to λ4089 are found to be nearly constant, apart from some small monotonic increase of these ratios as a function of electron temperature. Over a range of Balmer jump temperature from graphic, the variations amount to about 20 per cent for the graphic and graphic transitions and a factor of 2 for the primed transitions, and are consistent with the predictions of the current recombination theory. Our results do not support the claim by Dinerstein, Lafon & Garnett that the relative intensities of O II ORLs vary from nebula to nebula and that the scatter is largest in objects where the discrepancies between ORL and CEL abundances are also the largest. We find that the ORL to CEL abundance ratio is highly correlated with the difference between the temperatures yielded by the [O III] forbidden line ratio and by the H I Balmer jump, providing the strongest evidence so far that the two phenomena, i.e. the disparity between ORL and CEL temperature and abundance determinations, are closely related. However, temperature fluctuations of the type envisaged by Peimbert are unable to explain the low ionic abundances yielded by IR fine-structure lines. The very low Balmer jump temperature of M 1-42, coupled with its very low Balmer decrement density, may also be difficult to explain with a chemically inhomogeneous composite model of the type proposed by Liu et al. for NGC 6153

ERα inhibits epithelial-mesenchymal transition by suppressing Bmi1 in breast cancer

published_or_final_versio

ERα inhibits epithelial-mesenchymal transition by suppressing Bmi1 in breast cancer

published_or_final_versio

ISO LWS observations of planetary nebula fine-structure lines

We have obtained 43–198 μm far-infrared (IR) spectra for a sample of 51 Galactic planetary nebulae (PN) and protoplanetary nebulae (PPN), using the Long Wavelength Spectrometer (LWS) on board the Infrared Space Observatory (ISO). Spectra were also obtained of the former PN candidate Lo 14. The spectra yield fluxes for the fine-structure lines [N II] 122 μm, [N III] 57 μm and [O III] 52 and 88 μm emitted in the ionized regions and the [O I] 63- and 146-μm and [C II] 158-μm lines from the photodissociation regions (PDRs), which have been used to determine electron densities and ionic abundances for the ionized regions and densities, temperatures and gas masses for the PDRs. The strong [N III] and [O III] emission lines detected in the LWS spectrum taken centred on Lo 14 could be associated with the nearby strong radio and infrared source G 331.5–0.1. We find that the electron densities yielded by the [O III] 88 μm/52 μm doublet ratio are systematically lower than those derived from the optical [Ar IV] λ4740/λ4711 and [Cl III] λ5537/λ5517 doublet ratios, which have much higher critical densities than the 52- and 88-μm lines, suggesting the presence of density inhomogeneities in the nebulae. Ionic abundances, N+/H+,N2+/H+ and O2+/H+, as well as the N2+/O2+ abundance ratio, which provides a good approximation to the N/O elemental abundance ratio, are derived. Although ionic abundances relative to H+ deduced from the far-IR fine-structure lines are sensitive to the adopted electron density and the presence of density inhomogeneities, the strong dependence on the nebular physical conditions is largely cancelled out when N2+/O2+ is calculated from the 57 μm/(52 μm+88 μm) flux ratio, owing to the similarity of the critical densities of the lines involved. The temperatures and densities of the PDRs around 24 PN have been determined from the observed [O I] and [C II] line intensity ratios. Except for a few objects, the deduced temperatures fall between 200 and 500 K, peaking around 250 K. The densities of the PDRs vary from 104–105 cm−3, reaching 3×105 cm−3 in some young compact PN. With a derived temperature of 1600 K and a density of 105 cm−3, the PDR of NGC 7027 is one of the warmest and at the same time one of the densest amongst the nebulae studied. For most of the PN studied, the [C II]-emitting regions contain only modest amounts of material, with gas masses ≲0.1 M⊙. Exceptional large PDR masses are found for a few nebulae, including NGC 7027, the bipolar nebulae M2-9 and NGC 6302, the young dense planetary nebulae BD+30°3639, IC 418 and NGC 5315, and the old, probably recombining, nebulae IC 4406 and NGC 6072

Transcriptional and Post-Transcriptional Mechanisms for Oncogenic Overexpression of Ether À Go-Go K+ Channel

The human ether-à-go-go-1 (h-eag1) K+ channel is expressed in a variety of cell lines derived from human malignant tumors and in clinical samples of several different cancers, but is otherwise absent in normal tissues. It was found to be necessary for cell cycle progression and tumorigenesis. Specific inhibition of h-eag1 expression leads to inhibition of tumor cell proliferation. We report here that h-eag1 expression is controlled by the p53−miR-34−E2F1 pathway through a negative feed-forward mechanism. We first established E2F1 as a transactivator of h-eag1 gene through characterizing its promoter region. We then revealed that miR-34, a known transcriptional target of p53, is an important negative regulator of h-eag1 through dual mechanisms by directly repressing h-eag1 at the post-transcriptional level and indirectly silencing h-eag1 at the transcriptional level via repressing E2F1. There is a strong inverse relationship between the expression levels of miR-34 and h-eag1 protein. H-eag1antisense antagonized the growth-stimulating effects and the upregulation of h-eag1 expression in SHSY5Y cells, induced by knockdown of miR-34, E2F1 overexpression, or inhibition of p53 activity. Therefore, p53 negatively regulates h-eag1 expression by a negative feed-forward mechanism through the p53−miR-34−E2F1 pathway. Inactivation of p53 activity, as is the case in many cancers, can thus cause oncogenic overexpression of h-eag1 by relieving the negative feed-forward regulation. These findings not only help us understand the molecular mechanisms for oncogenic overexpression of h-eag1 in tumorigenesis but also uncover the cell-cycle regulation through the p53−miR-34−E2F1−h-eag1 pathway. Moreover, these findings place h-eag1 in the p53−miR-34−E2F1−h-eag1 pathway with h-eag as a terminal effecter component and with miR-34 (and E2F1) as a linker between p53 and h-eag1. Our study therefore fills the gap between p53 pathway and its cellular function mediated by h-eag1

Retinal ganglion cell repopulation for vision restoration in optic neuropathy: a roadmap from the RReSTORe Consortium

Retinal ganglion cell (RGC) death in glaucoma and other optic neuropathies results in irreversible vision loss due to the mammalian central nervous system's limited regenerative capacity. RGC repopulation is a promising therapeutic approach to reverse vision loss from optic neuropathies if the newly introduced neurons can reestablish functional retinal and thalamic circuits. In theory, RGCs might be repopulated through the transplantation of stem cell-derived neurons or via the induction of endogenous transdifferentiation. The RGC Repopulation, Stem Cell Transplantation, and Optic Nerve Regeneration (RReSTORe) Consortium was established to address the challenges associated with the therapeutic repair of the visual pathway in optic neuropathy. In 2022, the RReSTORe Consortium initiated ongoing international collaborative discussions to advance the RGC repopulation field and has identified five critical areas of focus: (1) RGC development and differentiation, (2) Transplantation methods and models, (3) RGC survival, maturation, and host interactions, (4) Inner retinal wiring, and (5) Eye-to-brain connectivity. Here, we discuss the most pertinent questions and challenges that exist on the path to clinical translation and suggest experimental directions to propel this work going forward. Using these five subtopic discussion groups (SDGs) as a framework, we suggest multidisciplinary approaches to restore the diseased visual pathway by leveraging groundbreaking insights from developmental neuroscience, stem cell biology, molecular biology, optical imaging, animal models of optic neuropathy, immunology & immunotolerance, neuropathology & neuroprotection, materials science & biomedical engineering, and regenerative neuroscience. While significant hurdles remain, the RReSTORe Consortium's efforts provide a comprehensive roadmap for advancing the RGC repopulation field and hold potential for transformative progress in restoring vision in patients suffering from optic neuropathies

Spatially Resolved Distribution Function and the Medium-Range Order in Metallic Liquid and Glass

The structural description of disordered systems has been a longstanding challenge in physical science. We propose an atomic cluster alignment method to reveal the development of three-dimensional topological ordering in a metallic liquid as it undercools to form a glass. By analyzing molecular dynamic (MD) simulation trajectories of a Cu64.5Zr35.5 alloy, we show that medium-range order (MRO) develops in the liquid as it approaches the glass transition. Specifically, around Cu sites, we observe “Bergman triacontahedron” packing (icosahedron, dodecahedron and icosahedron) that extends out to the fourth shell, forming an interpenetrating backbone network in the glass. The discovery of Bergman-type MRO from our order-mining technique provides unique insights into the topological ordering near the glass transition and the relationship between metallic glasses and quasicrystals

Observation of a ppb mass threshoud enhancement in \psi^\prime\to\pi^+\pi^-J/\psi(J/\psi\to\gamma p\bar{p}) decay

The decay channel $\psi^\prime\to\pi^+\pi^-J/\psi(J/\psi\to\gamma p\bar{p})$ is studied using a sample of $1.06\times 10^8$ $\psi^\prime$ events collected by the BESIII experiment at BEPCII. A strong enhancement at threshold is observed in the $p\bar{p}$ invariant mass spectrum. The enhancement can be fit with an $S$-wave Breit-Wigner resonance function with a resulting peak mass of $M=1861^{+6}_{-13} {\rm (stat)}^{+7}_{-26} {\rm (syst)} {\rm MeV/}c^2$ and a narrow width that is $\Gamma<38 {\rm MeV/}c^2$ at the 90% confidence level. These results are consistent with published BESII results. These mass and width values do not match with those of any known meson resonance.Comment: 5 pages, 3 figures, submitted to Chinese Physics