Context.
Isolated stellar-mass black holes accrete gas from their surroundings, often at supersonic speeds, and can form outflows that may influence the accreted gas. The latter process, known as ...mechanical feedback, can significantly affect the accretion rate.
Aims.
We use hydrodynamical simulations to assess the impact of mechanical feedback on the accretion rate when the black hole moves supersonically through a uniform medium.
Methods.
We carried out three-dimensional (3D) hydrodynamical simulations of outflows fueled by accretion that interact with a uniform medium, probing scales equivalent to and larger than the accretor gravitational sphere of influence. In the simulations, the accretor is at rest and the medium moves at supersonic speeds. The outflow power is assumed to be proportional to the accretion rate. The simulations were run for different outflow-medium motion angles and velocity ratios. We also investigated the impact of different degrees of outflow collimation, accretor size, and resolution.
Results.
In general, the accretion rate is significantly affected by mechanical feedback. There is a minor reduction in accretion for outflows perpendicular to the medium motion, but the reduction quickly becomes more significant for smaller angles. Moreover, the decrease in accretion becomes greater for smaller medium-to-outflow velocity ratios. On the other hand, the impact of outflow collimation seems moderate. Mechanical feedback is enhanced when the accretor size is reduced. For a population of black holes with random outflow orientations, the average accretion rate drops by (low–high resolution) ∼0.2 − 0.4 and ∼0.1 − 0.2 for medium-to-outflow velocity ratios of 1/20 and 1/100, respectively, when compared to the corresponding cases without outflow.
Conclusions.
Our results strongly indicate that on the considered scales, mechanical feedback can easily reduce the energy available from supersonic accretion by at least a factor of a few. This aspect should be taken into account when studying the mechanical, thermal, and non-thermal output of isolated black holes.
Adipose tissue modulates energy homeostasis by secreting leptin, but little is known about the factors governing leptin production. We show that succinate, long perceived as a mediator of immune ...response and lipolysis, controls leptin expression via its receptor SUCNR1. Adipocyte-specific deletion of Sucnr1 influences metabolic health according to nutritional status. Adipocyte Sucnr1 deficiency impairs leptin response to feeding, whereas oral succinate mimics nutrient-related leptin dynamics via SUCNR1. SUCNR1 activation controls leptin expression via the circadian clock in an AMPK/JNK-C/EBPα-dependent manner. Although the anti-lipolytic role of SUCNR1 prevails in obesity, its function as a regulator of leptin signaling contributes to the metabolically favorable phenotype in adipocyte-specific Sucnr1 knockout mice under standard dietary conditions. Obesity-associated hyperleptinemia in humans is linked to SUCNR1 overexpression in adipocytes, which emerges as the major predictor of adipose tissue leptin expression. Our study establishes the succinate/SUCNR1 axis as a metabolite-sensing pathway mediating nutrient-related leptin dynamics to control whole-body homeostasis.
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•Extracellular succinate in adipocytes controls circadian clock and leptin via SUCNR1•SUCNR1 modulates leptin via AMPK/JNK-BMAL1-C/EBPα-dependent signaling•The metabolic impact of SUCNR1 deficiency in adipocytes is dependent on nutritional status•Hyperleptinemia in human obesity is related to overactive succinate/SUCNR1 signaling
Villanueva-Carmona et al. describe a new function for the succinate/SUCNR1 axis in controlling leptin expression in adipocytes via a mechanism involving the circadian clock. This system is overactivated in obesity, which might contribute to obesity-related hyperleptinemia.
Recent molecular data have suggested that non-neoplastic cells are powerful modulators that may confer a selective advantage or disadvantage on the outcome of follicular lymphoma (FL) patients.
The ...prevalence of the principal inflammatory and immune-infiltrated cells was measured immunohistochemically in the tissue of 211 FL patients, and associations were sought with their traditional clinicobiologic characteristics.
Our results confirmed the presence of a large number of T lymphocytes (CD4+ and CD8+) and CD57+ cells and, at a moderate level, the presence of TIA-1+ cytotoxic cells, CD68+ macrophages, CD123+ plasmacytoid cells, and FOXP3+ regulatory T cells among the pool of non-neoplastic cells. In addition to the conventional clinical variables, univariate analysis identified a low level of infiltrated CD8+ T lymphocytes as a significantly negative prognostic factor of overall survival. The following significant differences in the abundance of cells of specific and nonspecific immunity were observed in relation to the clinicobiologic features of FL: (1) a reactive microenvironment mainly made up of T lymphocytes and macrophages was significantly associated with a favorable clinical behavior of FL patients; and (2) a reactive microenvironment infiltrated predominantly by CD57+ T cells was associated with a significantly higher frequency of adverse clinicobiologic manifestations such as "B" symptoms and bone marrow involvement.
Our results demonstrate the existence of two specific patterns in the reactive microenvironment of FL, an immunosurveillance pattern (T lymphocytes and macrophages) and an immune-escape pattern (CD57+ T cells), that were directly associated with the clinicobiologic features of these patients.
Breast cancer (BC) comprises four immunohistochemical surrogate subtypes of which triple-negative breast cancer (TNBC) has the highest risk of mortality. Axillary lymph nodes (ALNs) are the regions ...where BC cells first establish before distant metastasis, and the presence of tumor cells in the ALN causes an immune tolerance profile that contrasts with that of the nonmetastatic ALN (ALN−). However, few studies have compared the immune components of the ALNs− in BC subtypes. The present study aimed to determine whether differences between immune populations in the primary tumor and ALNs− were associated with the luminal A or TNBC subtype. We evaluated a retrospective cohort of 144 patients using paraffin-embedded biopsies. The TNBC samples tended to have a higher histologic grade and proliferation index and had higher levels of immune markers compared with luminal A in primary tumors and ALNs−. Two methods for validating the multivariate analysis found that histologic grade, intratumoral S100 dendritic cells, and CD8 T lymphocytes and CD57 natural killer cells in the ALNs− were factors associated with TNBC, whereas CD83 dendritic cells in the ALNs− were associated with the luminal A subtype. In conclusion, we found that intratumoral regions and ALNs− of TNBC contained higher concentrations of markers related to immune tolerance than luminal A. This finding partially explains the worse prognosis of patients with TNBC.
Fetal programming has been proposed as a key mechanism underlying the association between intrauterine exposure to maternal diabetes and negative health outcomes in offspring. To determine whether ...gestational diabetes mellitus (GDM) might leave an imprint in fetal precursors of the amniotic membrane and whether it might be related to adverse outcomes in offspring, a prospective case‐control study was conducted, in which amniotic mesenchymal stem cells (AMSCs) and resident macrophages were isolated from pregnant patients, with either GDM or normal glucose tolerance, scheduled for cesarean section. After characterization, functional characteristics of AMSCs were analyzed and correlated with anthropometrical and clinical variables from both mother and offspring. GDM‐derived AMSCs displayed an impaired proliferation and osteogenic potential when compared with control cells, accompanied by superior invasive and chemotactic capacity. The expression of genes involved in the inflammatory response (TNFα, MCP‐1, CD40, and CTSS) was upregulated in GDM‐derived AMSCs, whereas anti‐inflammatory IL‐33 was downregulated. Macrophages isolated from the amniotic membrane of GDM mothers consistently showed higher expression of MCP‐1 as well. In vitro studies in which AMSCs from healthy control women were exposed to hyperglycemia, hyperinsulinemia, and palmitic acid confirmed these results. Finally, genes involved in the inflammatory response were associated with maternal insulin sensitivity and prepregnancy body mass index, as well as with fetal metabolic parameters. These results suggest that the GDM environment could program stem cells and subsequently favor metabolic dysfunction later in life. Fetal adaptive programming in the setting of GDM might have a direct negative impact on insulin resistance of offspring.
Context.
LS 5039 is a powerful high-mass gamma-ray binary that probably hosts a young non-accreting pulsar. However, despite the wealth of data available, the means by which the non-thermal emitter ...is powered are still unknown.
Aims.
We use a dynamical-radiative numerical model, and multiwavelength data, to constrain the properties of a hypothetical pulsar wind that would power the non-thermal emitter in LS 5039.
Methods.
We ran simulations of an ultrarelativistic (weakly magnetized) cold
e
±
-wind that Compton scatters stellar photons and that dynamically interacts with the stellar wind. The effects of energy losses on the unshocked
e
±
-wind dynamics, and the geometry of the two-wind contact discontinuity, are computed for different wind models. The predicted unshocked
e
±
-wind radiation at periastron, when expected to be the highest, is compared to LS 5039 data.
Results.
The minimum possible radiation from an isotropic cold
e
±
-wind overpredicts the X-ray to gamma-ray fluxes at periastron by a factor of ∼3. In the anisotropic (axisymmetric) wind case X-ray and ≳100 MeV data are not violated by wind radiation if the wind axis is at ≲20−40° from the line of sight (chance probability of ≲6−24%), depending on the anisotropic wind model, or if the wind Lorentz factor ∈10
2
− 10
3
, in which case the wind power can be higher, but it requires
e
±
-multiplicities of ∼10
6
and 10
9
for a 10
−2
s and 10 s pulsar period, respectively.
Conclusions.
The studied model predicts that a weakly magnetized cold pulsar
e
±
-wind in LS 5039 should be strongly anisotropic, with either a wind Lorentz factor ∈10
2
− 10
3
and very high multiplicities or with a fine-tuned wind orientation. A weakly magnetized, cold baryon-dominated wind would be a possible alternative, but then the multiplicities should be rather low, while the baryon-to-
e
±
energy transfer should be very efficient at wind termination. A strongly magnetized cold wind seems to be the most favorable option as it is consistent with recent research on pulsar winds and does not require fine-tuning of the pulsar wind orientation, and the wind multiplicity and Lorentz factor are less constrained.
Context.
Dark matter may consist, at least partially, of primordial black holes formed during the radiation-dominated era. The radiation produced by accretion onto primordial black holes leaves ...characteristic signatures on the properties of the medium at high redshift, before and after hydrogen recombination. Therefore, reliable modeling of accretion onto these objects is required to obtain robust constraints on their abundance.
Aims.
We investigate the effect of mechanical feedback, that is, the impact of outflows (winds and– or –jets) on the medium, on primordial black hole accretion, and thereby on the associated radiation.
Methods.
Using analytical and numerical calculations, we studied for the first time the possibility that outflows can reduce the accretion rate of primordial black holes with masses similar to those detected by the LIGO-Virgo collaboration.
Results.
Despite the complexity of the accretion rate evolution, mechanical feedback is useful in to significantly reducing the primordial black hole accretion rate, at least by one order of magnitude, when outflows are aligned with the motion of the compact object. If the outflow is perpendicular to the direction of motion, the effect is less important, but it is still non-negligible.
Conclusions.
Outflows from primordial black holes, even rather weak ones, can significantly decrease the accretion rate, effectively weakening abundance constraints on these objects. Our results motivate further numerical simulations with a more realistic setup, which would yield more precise quantitative predictions.
ABSTRACT
High-mass microquasar jets, produced in an accreting compact object in orbit around a massive star, must cross a region filled with stellar wind. The combined effects of the wind and orbital ...motion can strongly affect the jet properties on binary scales and beyond. The study of such effects can shed light on how high-mass microquasar jets propagate and terminate in the interstellar medium. We study for the first time, using relativistic hydrodynamical simulations, the combined impact of the stellar wind and orbital motion on the properties of high-mass microquasar jets on binary scales and beyond. We have performed 3-dimensional relativistic hydrodynamic simulations, using the PLUTO code, of a microquasar scenario in which a strong weakly relativistic wind from a star interacts with a relativistic jet under the effect of the binary orbital motion. The parameters of the orbit are chosen such that the results can provide insight on the jet-wind interaction in compact systems like for instance Cyg X-1 or Cyg X-3. The wind and jet momentum rates are set to values that may be realistic for these sources and lead to moderate jet bending, which together with the close orbit and jet instabilities could trigger significant jet precession and disruption. For high-mass microquasars with orbit size a ∼ 0.1 AU, and (relativistic) jet power $L_j\sim 10^{37}(\dot{M}_w/10^{-6}\, {\rm M}_\odot \, {\rm yr}^{-1})$ erg s−1, where $\dot{M}_w$ is the stellar wind mass rate, the combined effects of the stellar wind and orbital motion can induce relativistic jet disruption on scales ∼1 AU.
Context.
High-mass gamma-ray binaries are powerful nonthermal galactic sources, some of them hosting a pulsar whose relativistic wind interacts with a likely inhomogeneous stellar wind. So far, ...modeling these sources including stellar wind inhomogeneities has been done using either simple analytical approaches or heavy numerical simulations, none of which allow for an exploration of the parameter space that is both reasonably realistic and general.
Aims.
Applying different semi-analytical tools together, we study the dynamics and high-energy radiation of a pulsar wind colliding with a stellar wind with different degrees of inhomogeneity to assess the related observable effects.
Methods.
We computed the arrival of clumps to the pulsar wind-stellar wind interaction structure using a Monte Carlo method and a phenomenological clumpy-wind model. The dynamics of the clumps that reach deep into the pulsar wind zone was computed using a semi-analytical approach. This approach allows for the characterization of the evolution of the shocked pulsar wind region in times much shorter than the orbital period. With this three-dimensional information about the emitter, we applied analytical adiabatic and radiative models to compute the variable high-energy emission produced on binary scales.
Results.
An inhomogeneous stellar wind induces stochastic hour-timescale variations in the geometry of the two-wind interaction structure on binary scales. Depending on the degree of stellar wind inhomogeneity, 10–100% level hour-scale variability in the X-rays and gamma rays is predicted, with the largest variations occurring roughly once per orbit.
Conclusions.
Our results, based on a comprehensive approach, show that present X-ray and future very-high-energy instrumentation can allow us to trace the impact of a clumpy stellar wind on the shocked pulsar wind emission in a gamma-ray binary.
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