Semi-Analytic Stellar Structure in Scalar-Tensor Gravity

Precision tests of gravity can be used to constrain the properties of hypothetical very light scalar fields, but these tests depend crucially on how macroscopic astrophysical objects couple to the new scalar field. We develop quasi-analytic methods for solving the equations of stellar structure using scalar-tensor gravity, with the goal of seeing how stellar properties depend on assumptions made about the scalar coupling at a microscopic level. We illustrate these methods by applying them to Brans-Dicke scalars, and their generalization in which the scalar-matter coupling is a weak function of the scalar field. The four observable parameters that characterize the fields external to a spherically symmetric star (the stellar radius, R, mass, M, scalar `charge', Q, and the scalar's asymptotic value, phi_infty) are subject to two relations because of the matching to the interior solution, generalizing the usual mass-radius, M(R), relation of General Relativity. We identify how these relations depend on the microscopic scalar couplings, agreeing with earlier workers when comparisons are possible. Explicit analytical solutions are obtained for the instructive toy model of constant-density stars, whose properties we compare to more realistic equations of state for neutron star models.Comment: 39 pages, 9 figure

Biological and physical mechanisms of cerebral aneurysms formation, growth and rupture

According to various researchers, the prevalence of unruptured cerebral aneurysms (CAs) in the general population varies from 2 to 5 %. In the vast majority of cases, CAs do not have clinical and neurological manifestations and are discovered incidentally during routine neuroimaging studies. CAs can cause intracranial hemorrhage. As a rule, hemorrhages of this type occur in patients aged 40–60 years. It has been established that about 10–15 % of patients die from an aneurysmal hemorrhage before they receive specialized medical care. Recurrent aneurysmal intracranial hemorrhage is the main cause of high mortality and disability in this group of patients. The search for literature sources in the scientific databases PubMed/Medline, EMBASE, Cochrane Library and eLibrary demonstrated the existence of numerous studies devoted to the study of molecular biology and biophysical mechanisms of formation, growth and rupture of CAs. Combining the results of these studies was the motivation for writing this literature review. The paper reflects in detail the role of inflammation and molecular genetic factors in the growth and rupture of the CAs, and presents the biophysical factors of the rupture of the CAs. The authors pay special attention to the shape, size and coefficient of the CAs as the most important geometric risk factors for the formation and rupture of the CAs. This review presents current data on mathematical modeling of various types of CAs with an assessment of the risk of rupture of the latter, which has found its application in wide clinical practice. The authors also attempted to describe the hemodynamic features in various types of CAs. In turn, the type of blood flow in the CAs cavity largely depends on the size and shape of the latter and the geometry of the carrier artery, which is the basis for preoperative planning and the choice of tactics for surgical treatment of patients with unruptured CAs

RADIOSURGICAL TREATMENT OF BENIGN SMALL EYELID TUMORS

Aim of the study – to evaluate the long-term results of the radiosurgical method using microsurgical techniques for the treatment of small benign eyelid tumors. Material and methods. In Ocular Oncology Centre of Helmholtz Moscow Research Institute of Eye Diseases for the period from 2012 to 2018 year 248 patients were examined and treated (108 children aged 12 ± 1.2 years and 140 adults aged 46 ± 8.1 years) with benign eyelid tumors: pigmented (nevus), vascular (capillary hemangiomas), epithelial (follicular keratosis, keratopapilloma). The Surgitron EMC radiosurgery device was used as surgical aids. All patients used microsurgical technique. The longitudinal size of the tumors was 3.4 ± 0.5 mm, transverse – 6 ± 0.8 mm. All patients after surgical treatment underwent histopathological study. The observation period is on average 6 ± 1.4 years. Results. In 133 (53.6 %) of 248 patients, nevi were detected, in 76 (30.7 %) – keratopapilloma and inverted follicular keratosis, in 39 (15.7 %) – capillary hemangioma. Various modifications of radiosurgical treatment were used depending on the location of the tumor, its size, the degree of activity using different modes and powers from 1 to 4 Wt. Intraoperative complications were not noted. The early postoperative period was accompanied by the presence of signs of mild inflammation, which was stopped by local therapy. The formation of a tender scar was observed on average after 7 ± 2 days. Two cases (0.8 %) of recurrence of keratopapilloma were noted 2 years after the first operation. Tumors were removed by radio excision. Conclusion. Benign eyelid tumors, especially of melanocytic origin, are subject to obligatory dynamic observation, and if minimal signs of their progression are detected, their surgical removal is indicated. Radiosurgical treatment using microsurgical techniques is the method of choice in the treatment of small benign eyelid tumors and depends on the size of the tumor, its localization and the nature of the tumor process. The use of the radiosurgical method with obligatory microsurgical technique for treating benign tumors of small sizes with the observance of the rules of radicalness and antiblasticity allows maintaining visual functions with simultaneous surgical treatment, providing normal anatomical and topographic correlations of the anterior segment of the eye and high quality of life of the patient

Competition between glassiness and order in a multi-spin glass

A mean-field multi-spin interaction spin glass model is analyzed in the presence of a ferromagnetic coupling. The static and dynamical phase diagrams contain four phases (paramagnet, spin glass, ordinary ferromagnet and glassy ferromagnet) and exhibit reentrant behavior. The glassy ferromagnet phase has anomalous dynamical properties. The results are consistent with a nonequilibrium thermodynamics that has been proposed for glasses.Comment: revised version, 4 pages Revtex, 2 eps-figures. Phys. Rev. E, Rapid Communication, to appea

Predictive model of small choroidal melanoma progression after eye-saving treatment based on clinical, morphometric and immunological parameters

Choroidal melanoma is a malignant tumor characterized by early metastasis and poor vital prognosis. Prognostic indexes for the tumor development are of importance, depending on various factors and making it possible to optimize therapeutic measures. Usage of present models for prediction of the uveal melanoma course enables optimal management of the patients with a malignant tumor upon primary admission, and to perform maximally efficient counseling. So far, however, a complex of clinical, morphometric and immunological indexes predictive for unfavorable course of initial choroidal melanoma following the eye-saving treatment remains not fully determined. Our purpose was to create a prognostic model for initial choroidal melanoma after eye-saving treatment, basing on clinical, morphometric and immunological parameters.We have performed examination and treatment of 31 patients with small choroidal melanoma (53.7 to 12.2 years old). To perform the analysis, we used clinical data (age, decreased vision, tumor localization, degree of pigmentation, presence of hemorrhages, orange pigmentation), morphometric indexes (intra- and subretinal exudate and disorganization of pigment of the retinal epithelium) and immunological parameters (serum levels of pro-inflammatory, pro-angiogenic, proliferative, metastasis-causing cytokines). Selection of variables for this model was based on assessment of significant differences between the groups with chorio-retinal scar (n = 14) and residual tumor and/or continued tumor growth (n = 17).Multivariate analysis with conditional exclusion of variables revealed prognostic significance with four markers: morphometric, i.e., disorganization of the pigment in retinal pigment epithelium – Z1 (rs = 0.455); immunological, increased blood serum concentration of hepatocyte growth factor (HGF) – Z2 (rs = 0.377); level of pro-inflammatory chemokine RANTES – Z3 (rs = 0.362), content of transforming growth factor (TGF-2â) – Z4 (rs = 0.431). A formula was calculated where P (z) is the value of the logistic function; Z, linear combination of symptoms; bo , intercept (free term), bi – regression coefficients for parameters Zi.P (z) = 1 : 1 + e – b0– b1z1– b2z2– b3z3– b4z4The logistic function increases monotonically and takes the values from 0 to 1 for any b and Z values [P∈ (0;1)]. If P (Z) is under the cutoff value, chorioretinal scar prognosis is predicted, at the higher values, a residual tumor or continued growth is expected. In ROC analysis, the area under the curve with this model was 0.891±0.11, thus providing good predictive quality.Usage of the predictive model is a possible solution for planning and correcting treatment strategy in the patients with small choroidal melanoma, in order to minimize complications and errors, and to ensure control of treatment

Study of 2b-decay of Mo-100 and Se-82 using the NEMO3 detector

After analysis of 5797 h of data from the detector NEMO3, new limits on neutrinoless double beta decay of Mo-100 (T_{1/2} > 3.1 10^{23} y, 90% CL) and Se-82 (T_{1/2} > 1.4 10^{23} y, 90% CL) have been obtained. The corresponding limits on the effective majorana neutrino mass are: m < (0.8-1.2) eV and m < (1.5-3.1) eV, respectively. Also the limits on double-beta decay with Majoron emission are: T_{1/2} > 1.4 10^{22} y (90% CL) for Mo-100 and T_{1/2}> 1.2 10^{22} y (90%CL) for Se-82. Corresponding bounds on the Majoron-neutrino coupling constant are g < (0.5-0.9) 10^{-4} and < (0.7-1.6) 10^{-4}. Two-neutrino 2b-decay half-lives have been measured with a high accuracy, T_{1/2} Mo-100 = [7.68 +- 0.02(stat) +- 0.54(syst) ] 10^{18} y and T_{1/2} Se-82 = [10.3 +- 0.3(stat) +- 0.7(syst) ] 10^{19} y.Comment: 5 pages, 4 figure