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The centre of the Milky Way Galaxy hosts a black hole with a solar mass of about 4 million (Sagittarius A * (Sgr A)) that is very quiescent at present with a luminosity many orders of magnitude below those of active galactic nuclei 1 . Reflection of X-rays from Sgr A * by dense gas in the Galactic Centre region offers a means to study its past flaring activity on timescales of hundreds and thousands of years 2 . The shape of the X-ray continuum and the strong fluorescent iron line observed from giant molecular clouds in the vicinity of Sgr A * are consistent with the reflection scenario 3-5 . If this interpretation is correct, the reflected continuum emission should be polarized 6 . Here we report observations of polarized X-ray emission in the direction of the molecular clouds in the Galactic Centre using the Imaging X-ray Polarimetry Explorer. We measure a polarization degree of 31% ± 11%, and a polarization angle of -48° ± 11°. The polarization angle is consistent with Sgr A * being the primary source of the emission, and the polarization degree implies that some 200 years ago, the X-ray luminosity of Sgr A * was briefly comparable to that of a Seyfert galaxy., (© 2023. The Author(s), under exclusive licence to Springer Nature Limited.)

Pulsar wind nebulae are formed when outflows of relativistic electrons and positrons hit the surrounding supernova remnant or interstellar medium at a shock front. The Vela pulsar wind nebula is powered by a young pulsar (B0833-45, aged 11,000 years) 1 and located inside an extended structure called Vela X, which is itself inside the supernova remnant 2 . Previous X-ray observations revealed two prominent arcs that are bisected by a jet and counter jet 3,4 . Radio maps have shown high linear polarization of 60% in the outer regions of the nebula 5 . Here we report an X-ray observation of the inner part of the nebula, where polarization can exceed 60% at the leading edge-approaching the theoretical limit of what can be produced by synchrotron emission. We infer that, in contrast with the case of the supernova remnant, the electrons in the pulsar wind nebula are accelerated with little or no turbulence in a highly uniform magnetic field., (© 2022. The Author(s), under exclusive licence to Springer Nature Limited.)

A black hole x-ray binary (XRB) system forms when gas is stripped from a normal star and accretes onto a black hole, which heats the gas sufficiently to emit x-rays. We report a polarimetric observation of the XRB Cygnus X-1 using the Imaging X-ray Polarimetry Explorer. The electric field position angle aligns with the outflowing jet, indicating that the jet is launched from the inner x-ray-emitting region. The polarization degree is 4.01 ± 0.20% at 2 to 8 kiloelectronvolts, implying that the accretion disk is viewed closer to edge-on than the binary orbit. These observations reveal that hot x-ray-emitting plasma is spatially extended in a plane perpendicular to, not parallel to, the jet axis.

Magnetars are neutron stars with ultrastrong magnetic fields, which can be observed in x-rays. Polarization measurements could provide information on their magnetic fields and surface properties. We observed polarized x-rays from the magnetar 4U 0142+61 using the Imaging X-ray Polarimetry Explorer and found a linear polarization degree of 13.5 ± 0.8% averaged over the 2- to 8-kilo-electron volt band. The polarization changes with energy: The degree is 15.0 ± 1.0% at 2 to 4 kilo-electron volts, drops below the instrumental sensitivity ~4 to 5 kilo-electron volts, and rises to 35.2 ± 7.1% at 5.5 to 8 kilo-electron volts. The polarization angle also changes by 90° at ~4 to 5 kilo-electron volts. These results are consistent with a model in which thermal radiation from the magnetar surface is reprocessed by scattering off charged particles in the magnetosphere.

Most of the light from blazars, active galactic nuclei with jets of magnetized plasma that point nearly along the line of sight, is produced by high-energy particles, up to around 1 TeV. Although the jets are known to be ultimately powered by a supermassive black hole, how the particles are accelerated to such high energies has been an unanswered question. The process must be related to the magnetic field, which can be probed by observations of the polarization of light from the jets. Measurements of the radio to optical polarization-the only range available until now-probe extended regions of the jet containing particles that left the acceleration site days to years earlier 1-3 , and hence do not directly explore the acceleration mechanism, as could X-ray measurements. Here we report the detection of X-ray polarization from the blazar Markarian 501 (Mrk 501). We measure an X-ray linear polarization degree Π X of around 10%, which is a factor of around 2 higher than the value at optical wavelengths, with a polarization angle parallel to the radio jet. This points to a shock front as the source of particle acceleration and also implies that the plasma becomes increasingly turbulent with distance from the shock., (© 2022. The Author(s).)

The vast majority of known nonaccreting neutron stars (NSs) are rotation-powered radio and/or γ-ray pulsars. So far, their multiwavelength spectra have all been described satisfactorily by thermal and nonthermal continuum models, with no spectral lines. Spectral features have, however, been found in a handful of exotic NSs and were thought to be a manifestation of their unique traits. Here, we report the detection of absorption features in the x-ray spectrum of an ordinary rotation-powered radio pulsar, J1740+1000. Our findings bridge the gap between the spectra of pulsars and other, more exotic, NSs, suggesting that the features are more common in the NS spectra than they have been thought so far.

The central pointlike X-ray source of the Cassiopeia A supernova remnant was discovered in the Chandra first light observation and found later in the archival ROSAT and Einstein images. The analysis of these data does not show statistically significant variability of the source. Because of the small number of photons detected, different spectral models can fit the observed spectrum. The power-law fit yields the photon index gamma=2.6-4.1, and luminosity L(0.1-5.0 keV&parr0;=&parl0;2-60&parr0;x1034 ergs s-1 for d=3.4 kpc. The power-law index is higher, and the luminosity lower, than those observed from very young pulsars. One can fit the spectrum equally well with a blackbody model with T=6-8 MK, R=0.2-0.5 km, and Lbol=&parl0;1.4-1.9&parr0;x1033 ergs s-1. The inferred radii are too small, and the temperatures too high, for the radiation to be interpreted as emitted from the whole surface of a uniformly heated neutron star. Fits with the neutron star atmosphere models increase the radius and reduce the temperature, but these parameters are still substantially different from those expected for a young neutron star. One cannot exclude, however, the possibility that the observed emission originates from hot spots on a cooler neutron star surface. An upper limit on the (gravitationally redshifted) surface temperature is Tinfinitys<1.9-2.3 MK, depending on the chemical composition of the surface and the star's radius. Among several possible interpretations, we favor a model of a strongly magnetized neutron star with magnetically confined hydrogen or helium polar caps (Tinfinitypc approximately 2.8 MK, Rpc approximately 1 km) on a cooler iron surface (Tinfinitys approximately 1.7 MK). Such temperatures are consistent with the standard models of neutron star cooling. Alternatively, the observed radiation may be interpreted as emitted by a compact object (more likely, a black hole) accreting from a residual disk or from a late-type dwarf in a close binary.

The mechanism responsible for the formation of cardiac connective tissue and vascular components in early ontogenesis from various embryonal layings and the subsequent coexistance and interaction of two myocardial blood supply system in the formed heart at all stages of postnatal life form the basis for morphological and functional characteristics of organ specificity. The findings are of direct interest to practical cardiologists and cardiosurgeons who analyze some conditions which are likely to involve compensatory mechanisms in inadequate coronary blood supply of the heart.

Concepts of the structure, function and development of stromal components of the heart based on the author's studies and the literature data are discussed. The presence in the heart of stromal components of two generations (provisory and definitive) developing from different embryonic rudiments in suggested. Histogenetic processes of the stromal development at early stages of heart organogenesis are described. A detailed description of chondroid provisory tissue and sinusoidal vessels ensuring stromal and trophic functions with respect to muscular elements of myocardium is provided. A comparative characteristic of chondroid tissue and cartilage is given. Attention is given to stromal components which, being derivatives of the provisory stroma, are present in the heart of humans and vertebrates, constituting an obligatory part of the united connective tissue stroma and blood supply system of the heart. An original scheme is proposed reflecting general pattern of the development and interaction of stromal heart components of two generations, having different sources of origin. Observations supported by an original scheme are made regarding the place of stromal heart components in the system of supportive structures of the organism. Organ specificity of heart stroma is supposed to be a basis for using aortal-valval complex of pigs as bioprostheses in modern cardiac surgery.

The chondroid tissue of the heart is an obligate provisional+ formation of the organ in question. It is formed during early stages of ontogenesis, develops maximally during the antenatal period and is preserved in the postnatal one. In a number of vertebrates it is the base for formation of cartilage and even bone in stroma of the heart. The ++chondroid tissue in embryos and fetuses performs, as regards the myocardium, stromal and trophic functions, further they are performed by the definitive connective-tissue stroma, in it vessels of the coronary system are situated. There are some reasons to suppose that the elements of the chondroid stroma are preserved during the postnatal ontogenesis in the myocardial intestinum, taking part in its metabolism.

Biopsy specimens of the skin of the back of the forearm and hand in 20 patients with systemic scleroderma were studied using histological and electron microscopy methods. There were revealed evidences of intensified neofibrillogenesis, changes in collagen structures of the derma (destruction and defects of packing of collagenous fibrills, variability of their thickness in a fibre) and in the microcirculatory bed. In 18 out of 20 cases the nuclei of the connective-tissue cells and cells of the basal layer of the epidermis contained the so-called nuclear bodies, which are considered by a number of authors as an indirect evidence of a viral infection. The process of an intensified neoformation of collagen fibrils considerably predominated over destructive processes in collagen structures.

A radiological examination associated with fibergastroscopy was performed in 145 gastric cancer patients. All these patients were radically operated upon--extremely subtotal resection of the stomach was accomplished. The preoperative diagnosis of gastric cancer with both technics used simultaneously proved to be correct in 96.55%. However, the anatomical and ulcerous-infiltrative growth, especially in their cardiac and subcardiac localization are found to present the greatest diagnostic difficulties. The data obtained made it possible to believe that the detailed diagnosis of gastric cancer should comprise two steps--a radiological examination and fibergastroscopy.

The complex diagnosis of early forms of cancer of the large intestine should comprise the knowledge of the clinical picture, analysis of the disease, the results of rectoromanoscopy, irrogoscopy, colonofibroscopy, and cytological diagnosis. The use of the mentioned technics would help to improve the diagnosis of early forms of colonic cancer.

Morphological studies of 14 chorionallantoic membranes and organs of chick embryos which had been infected on the 7--8th day of incubation with leucocytic mass from patients with systemic lupus erythematosus were carried out. Corresponding virological and morphological control studies were performed. The changes observed were repeatedly reproduced in multiple inoculations (from the 2nd to the 16th passage). Apart from morphological changes, which may be listed among general pathological processes (impairment of the circulation, dystrophy, proliferation), changes testifying to a possible cytopathic effect disintegration of nuclei, formation of gigantic cells and multinuclear symplasts were also noted. The most pronounced changes, both in the chorionallantoic membrane and in internal organs, were observed on the 3rd--5th passage and on the 3rd--5th day of incubation following inoculation. They correlated with the clinical activity of the process in patients from whom the blood for inoculation had been taken. The data obtained justify the assumption concerning the existence in the blood of the patients with systemic lupus erythematosus a transplantable agent producing a cytopathic action, and may be considered as a new indirect corroborative evidence in favour of the concept of the viral nature of systemic lupus erythematosus.

The results of isotope gastroscintigraphy, performed in 160 patients with tumor and pretumor diseases of the stomach, are reported. Based on a clinico-morphological estimation of gastroscintigraphic findings, it was found that in 115 (72%) patients the data of scanning coincided with the ultimate diagnosis. In 25 (16%) patients pseudopositive and in 20 (12%)--pseudonegative scannograms were obtained. The greatest number of pseudonegative results was noted in patients with gastric cancer (in 19 of 20), in 10 of them tumor being located in the cardiac portion of the stomach. The precision of diagnosing tumors in other anatomical portion of the stomach was 90%. In patients with pretumor lesions the character of scannographic alterations was dependent on the rate of impairment of gastric mucosa function and structure.