ABSTRACT X-ray bursts are thermonuclear flashes on the surface of accreting neutron stars, and reliable burst models are needed to interpret observations in terms of properties of the neutron star ...and the binary system. We investigate the dependence of X-ray burst models on uncertainties in (p, γ), ( , γ), and ( , p) nuclear reaction rates using fully self-consistent burst models that account for the feedbacks between changes in nuclear energy generation and changes in astrophysical conditions. A two-step approach first identified sensitive nuclear reaction rates in a single-zone model with ignition conditions chosen to match calculations with a state-of-the-art 1D multi-zone model based on the Kepler stellar evolution code. All relevant reaction rates on neutron-deficient isotopes up to mass 106 were individually varied by a factor of 100 up and down. Calculations of the 84 changes in reaction rate with the highest impact were then repeated in the 1D multi-zone model. We find a number of uncertain reaction rates that affect predictions of light curves and burst ashes significantly. The results provide insights into the nuclear processes that shape observables from X-ray bursts, and guidance for future nuclear physics work to reduce nuclear uncertainties in X-ray burst models.
X-ray burst model predictions of light curves and the final composition of the nuclear ashes are affected by uncertain nuclear masses. However, not all of these masses are determined experimentally ...with sufficient accuracy. Here we identify the remaining nuclear mass uncertainties in X-ray burst models using a one-zone model that takes into account the changes in temperature and density evolution caused by changes in the nuclear physics. Two types of bursts are investigated-a typical mixed H/He burst with a limited rapid proton capture process (rp-process) and an extreme mixed H/He burst with an extended rp-process. When allowing for a 3 variation, only three remaining nuclear mass uncertainties affect the light-curve predictions of a typical H/He burst (27P, 61Ga, and 65As), and only three additional masses affect the composition strongly (80Zr, 81Zr, and 82Nb). A larger number of mass uncertainties remain to be addressed for the extreme H/He burst, with the most important being 58Zn, 61Ga, 62Ge, 65As, 66Se, 78Y, 79Y, 79Zr, 80Zr, 81Zr, 82Zr, 82Nb, 83Nb, 86Tc, 91Rh, 95Ag, 98Cd, 99In, 100In, and 101In. The smallest mass uncertainty that still impacts composition significantly when varied by 3 is 85Mo with 16 keV uncertainty. For one of the identified masses, 27P, we use the isobaric mass multiplet equation to improve the mass uncertainty, obtaining an atomic mass excess of −716(7) keV. The results provide a roadmap for future experiments at advanced rare isotope beam facilities, where all the identified nuclides are expected to be within reach for precision mass measurements.
Abstract The elemental abundances between strontium and silver ( Z = 38–47) observed in the atmospheres of very metal-poor stars in the Galaxy may contain the fingerprint of the weak r -process and ν ...p -process occurring in early core-collapse supernovae explosions. In this work, we combine various astrophysical conditions based on a steady-state model to cover the richness of the supernova ejecta in terms of entropy, expansion timescale, and electron fraction. The calculated abundances based on different combinations of conditions are compared with stellar observations, with the aim of constraining supernova ejecta conditions. We find that some conditions of the neutrino-driven outflows consistently reproduce the observed abundances of our sample. In addition, from the successful combinations, the neutron-rich trajectories better reproduce the observed abundances of Sr–Zr ( Z = 38–40), while the proton-rich ones, Mo–Pd ( Z = 42–47).
Insights into cancer genetics can lead to therapeutic opportunities. By cross-referencing chromosomal changes with an unbiased genetic screen we identify the ephrin receptor A7 (
EPHA7) as a tumor ...suppressor in follicular lymphoma (FL).
EPHA7 is a target of 6q deletions and inactivated in 72% of FLs. Knockdown of EPHA7 drives lymphoma development in a murine FL model. In analogy to its physiological function in brain development, a soluble splice variant of
EPHA7 (EPHA7
TR)
interferes with another Eph-receptor and blocks oncogenic signals in lymphoma cells. Consistent with this drug-like activity, administration of the purified EPHA7
TR protein produces antitumor effects against xenografted human lymphomas. Further, by fusing EPHA7
TR to the anti-CD20 antibody (rituximab) we can directly target this tumor suppressor to lymphomas in vivo. Our study attests to the power of combining descriptive tumor genomics with functional screens and reveals EPHA7
TR as tumor suppressor with immediate therapeutic potential.
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► Cancer genomics and genetic screens are complementary tools in cancer gene discovery ► EPHA7
TR is a soluble tumor suppressor that is lost in ∼70% of follicular lymphomas ► EPHA7
TR blocks EPHA-receptor activation and ERK and SRC signals in lymphoma ► An anti-CD20-EPHA7
TR fusion antibody is a new therapeutic reagent against lymphoma
A soluble splice variant of EPHA7 blocks oncogenic signals in lymphoma cells and exerts antitumor effects in vivo. Treatment with this soluble receptor, as well as an EPHA7-antibody fusion amelioriates disease in mouse models of lymphoma, presenting a therapeutic approach for this chemotherapy-refractive disease.
X-ray observations of transiently accreting neutron stars during quiescence provide information about the structure of neutron star crusts and the properties of dense matter. Interpretation of the ...observational data requires an understanding of the nuclear reactions that heat and cool the crust during accretion and define its nonequilibrium composition. We identify here in detail the typical nuclear reaction sequences down to a depth in the inner crust where the mass density is using a full nuclear reaction network for a range of initial compositions. The reaction sequences differ substantially from previous work. We find a robust reduction of crust impurity at the transition to the inner crust regardless of initial composition, though shell effects can delay the formation of a pure crust somewhat to densities beyond . This naturally explains the small inner crust impurity inferred from observations of a broad range of systems. The exception are initial compositions with A ≥ 102 nuclei, where the inner crust remains impure with an impurity parameter of Qimp 20 owing to the N = 82 shell closure. In agreement with previous work, we find that nuclear heating is relatively robust and independent of initial composition, while cooling via nuclear Urca cycles in the outer crust depends strongly on initial composition. This work forms a basis for future studies of the sensitivity of crust models to nuclear physics and provides profiles of composition for realistic crust models.
The importance of mass measurements for astrophysical capture processes in general, and for the rp-process in X-ray bursts in particular is discussed. A review of the current uncertainties in the ...effective lifetimes of the major waiting points
Ge
64
,
Se
68
, and
Kr
72
demonstrates that despite of recent measurements uncertainties are still significant. It is found that mass measurements with an accuracy of the order of 10 keV or better are desirable, and that reaction rate uncertainties play a critical role as well.
Context. Moderately r-process-enriched stars (r-I; +0.3 ≤ Eu/Fe ≤ +1.0) are at least four times as common as those that are greatly enriched in r-process elements (r-II; Eu/Fe > +1.0), and the ...abundances in their atmospheres are important tools for obtaining a better understanding of the nucleosynthesis processes responsible for the origin of the elements beyond the iron peak. Aims. The main aim of this work is to derive abundances for a sample of seven metal-poor stars with −3.4 ≤ Fe/H ≤ −2.4 classified as r-I stars, to understand the role of these stars for constraining the astrophysical nucleosynthesis event(s) that is (are) responsible for the production of the r-process, and to investigate whether they differ, in any significant way, from the r-II stars. Methods. We carried out a detailed abundance analysis based on high-resolution spectra obtained with the VLT/UVES spectrograph, using spectra in the wavelength ranges 3400–4500 Å, 6800–8200 Å, and 8700–10 000 Å, with resolving power R ~ 40 000 (blue arm) and R ~ 55 000 (red arm). The OSMARCS LTE 1D model atmosphere grid was employed, along with the spectrum synthesis code Turbospectrum. Results. We have derived abundances of the light elements Li, C, and N, the α-elements Mg, Si, S, Ca, and Ti, the odd-Z elements Al, K, and Sc, the iron-peak elements V, Cr, Mn, Fe, Co, and Ni, and the trans-iron elements from the first peak (Sr, Y, Zr, Mo, Ru, and Pd), the second peak (Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb), the third peak (Os and Ir, as upper limits), and the actinides (Th) regions. The results are compared with values for these elements for r-II and “normal” very and extremely metal-poor stars reported in the literature, ages based on radioactive chronometry are explored using different models, and a number of conclusions about the r-process and the r-I stars are presented. Hydrodynamical models were used for some elements, and general behaviors for the 3D corrections were presented. Although the abundance ratios of the second r-process peak elements (usually associated with the main r-process) are nearly identical for r-I and r-II stars, the first r-process peak abundance ratios (probably associated with the weak r-process) are more enhanced in r-I stars than in r-II stars, suggesting that differing nucleosynthesis pathways were followed by stars belonging to these two different classifications.
Despite recent advances in frontline therapy for diffuse large B-cell lymphoma (DLBCL), at least a third of those diagnosed still will require second or further lines for relapsed or refractory ...(rel/ref) disease. A small minority of these can be cured with standard chemoimmunotherapy/stem-cell transplant salvage approaches. CD19-directed chimeric antigen receptor T-cell (CAR-19) therapies are increasingly altering the prognostic landscape for rel/ref patients with DLBCL and related aggressive B-cell non-Hodgkin lymphomas. Long-term follow up data show ongoing disease-free outcomes consistent with cure in 30-40% after CAR-19, including high-risk patients primary refractory to or relapsing within 1 year of frontline treatment. This has made CAR-19 a preferred option for these difficult-to-treat populations. Widespread adoption, however, remains challenged by logistical and patient-related hurdles, including a requirement for certified tertiary care centers concentrated in urban centers, production times of at least 3-4 weeks, and high per-patients costs similar to allogeneic bone-marrow transplantation. Bispecific antibodies (BsAbs) are molecular biotherapies designed to bind and activate effector T-cells and drive them to B-cell antigens, leading to a similar cellular-dependent cytotoxicity as CAR-19. May and June of 2023 saw initial approvals of next-generation BsAbs glofitamab and epcoritamab in DLBCL as third or higher-line therapy, or for patients ineligible for CAR-19. BsAbs have similar spectrum but generally reduced severity of immune related side effects as CAR-19 and can be administered in community settings without need to manufacture patient-specific cellular products. To date and in contrast to CAR-19, however, there is no convincing evidence of cure after BsAbs monotherapy, though follow up is limited. The role of BsAbs in DLBCL treatment is rapidly evolving with trials investigating use in both relapsed and frontline curative-intent combinations. The future of DLBCL treatment is bound increasingly to include effector cell mediated immunotherapies, but further optimization of both cellular and BsAb approaches is needed.
Protein expression evolves under greater evolutionary constraint than mRNA levels, and translation efficiency represents a primary determinant of protein levels during stimuli adaptation. This raises ...the question as to the translatome remodelers that titrate protein output from mRNA populations. Here, we uncover a network of RNA-binding proteins (RBPs) that enhances the translation efficiency of glycolytic proteins in cells responding to oxygen deprivation. A system-wide proteomic survey of translational engagement identifies a family of oxygen-regulated RBPs that functions as a switch of glycolytic intensity. Tandem mass tag-pulse SILAC (TMT-pSILAC) and RNA sequencing reveals that each RBP controls a unique but overlapping portfolio of hypoxic responsive proteins. These RBPs collaborate with the hypoxic protein synthesis apparatus, operating as a translation efficiency checkpoint that integrates upstream mRNA signals to activate anaerobic metabolism. This system allows anoxia-resistant animals and mammalian cells to initiate anaerobic glycolysis and survive hypoxia. We suggest that an oxygen-sensitive RBP cluster controls anaerobic metabolism to confer hypoxia tolerance.
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