[Late diagnosis of rhinocerebral mucormycosis in patients with COVID-19 (case studies)]. / Pozdnyaya diagnostika rinotserebral'nogo mukormikoza u bol'nykh COVID-19 (klinicheskie nablyudeniya).

From the beginning of the COVID-19 pandemic, the incidence of secondary infections (both bacterial and fungal) has increased due to immune suppression associated with the use of corticosteroids or broad-spectrum antibiotics as a part of COVID-19 treatment protocol, which may exacerbate a pre-existing fungal disease or cause a new infection. Ophthalmologists are often involved in taking medical and surgical decisions in these complex cases. In this regard, a strong clinical suspicion should be applied to possible secondary fungal infections in COVID-19. Their early diagnosis and treatment may reduce mortality due to COVID-19 associated rhinocerebral mucormycosis (ROCM). This article describes two clinical cases of late detection of ROCM with two different scenarios, and compare the features of these cases with the literature data.

[Primary amyloidoma of the brain]. / Pervichnaya amiloidoma golovnogo mozga.

Primary brain amyloidoma is rare tumor-like lesion characterized by focal accumulation of insoluble fibrillar aggregates of amyloid in brain tissue without systemic amyloidosis. Literature review and a case report of primary brain amyloidoma in 61 years old female are given with a special attention on the complexity of preoperative diagnosis.

[Protocol for histological examination of liver transplant dysfunction]. / Protokol gistologicheskogo issledovaniia disfunktsii transplantata pecheni.

The protocol for histological examination of liver transplant dysfunction, which is used at the A.I. Burnazyan, Federal Medical and Biophysical Center and has been developed on the basis of the liver transplant rejection protocol designed at the University of Pittsburgh, is proposed for routine use.

[Morphological features of IgG4-related lesions at various sites]. / Morfologicheskie osobennosti IgG4-sviazannykh porazhenii razlichnykh lokalizatsii.

OBJECTIVE: To determine the morphological features of IgG4-related lesions and to improve pathomorphological criteria for diagnosing various clinical variants of IgG4-related disease. MATERIAL AND METHODS: Biopsy and surgical materials from 100 patients with tumor-like lesions at various sites (63 cases of IgG4-related lesion and 37 cases of non-IgG4-related inflammatory processes) were studied. Histological and immunohistochemical studies were conducted to determine the absolute counts of CD138+ cells, IgG+ and IgG4+ in the inflammatory infiltrates, as well as IgG4/IgG and IgG4/CD138 cell ratios. RESULTS: When IgG4-related disease manifested, pancreatic, lacrimal, and salivary gland lesions prevailed. Brisk lymphoplasmacytic infiltration is characteristic for tissue damage in the eye, salivary glands, thyroid, pancreas, and skin. The formation of moiré fibrosis was specific to damages to the pancreas, liver and bile ducts, and eye tissues. Obliterative phlebitis is most often observed in pancreatic and salivary gland lesions. According to international criteria, the frequency of achieving the required level of IgG4+ plasma cells in each organ was high in lesions of the pancreas, bile ducts, and lymph nodes and that was low in lesions of the salivary and lacrimal glands and skin. The IgG4+/CD138+ and IgG4+/IgG+ cell ratios exceeded 40% in all cases. CONCLUSION: The morphologic diagnosis of IgG4-related disease is based on the detection of lymphoplasmacytic infiltration, moiré fibrosis, and obliterative phlebitis, as well as on the calculation of the absolute number of IgG4+ plasma cells in the inflammatory infiltrate and on the determination of IgG4+/IgG+ and IgG4+/CD138+ cell ratios. The number of IgG4+ plasma cells depends on the location of the lesion and on the phase of the process.

[Primary splenic angiosarcoma]. / Pervichnaia angiosarkoma selezenki.

Primary splenic angiosarcoma is a rare and high-grade vascular tumor having a significant metastatic potential. The authors give the data available in the literature and describe their own case of primary splenic angiosarcoma in a 42-year-old male patient with multiple distant metastases in the lymph nodes and skin. The paper shows some difficulties in the morphologic diagnosis of this tumor.

[Gastric cancer concurrent with IgG4-related disease: A clinical case and a review of literature]. / Sochetanie raka zheludka s IgG4-svyazannoi bolezn'yu (klinicheskoe nablyudenie i obzor literatury).

The paper presents the data available in the literature on IgG4-related disease (IgG4-RD) concurrent with malignancies at different sites, as well as possible common pathogenetic mechanisms of their development and morphological diagnostic criteria for IgG4-RD. The authors give their own observation of gastric signet ring cell carcinoma concurrent with morphologically verified IgG4-RD.

Role of three-body interactions in formation of bulk viscosity in liquid argon.

With the aim of locating the origin of discrepancy between experimental and computer simulation results on bulk viscosity of liquid argon, a molecular dynamic simulation of argon interacting via ab initio pair potential and triple-dipole three-body potential has been undertaken. Bulk viscosity, obtained using Green-Kubo formula, is different from the values obtained from modeling argon using Lennard-Jones potential, the former being closer to the experimental data. The conclusion is made that many-body inter-atomic interaction plays a significant role in formation of bulk viscosity.

[A case of IgG4-related sclerosing disease with lymphadenopathy and thymus involvement].

The paper describes a case of generalized lymphadenopathy clinically recognized as malignant lymphoma in a 59-year-old woman. Her death occurred from bilateral pneumonia. Autopsy also showed a tumor-like mass in the thymus. On histological examination, the lymph nodes, thymus, and spleen exhibited an intensive polyclonal IgG4+ plasma cell infiltration. Lymphoid plasma cell infiltration with increased count of IgG+ plasma cells, progressive sclerosis, and phlebitis obliterans were found in the pancreas and peripancreatic adipose tissue, liver, kidney, epicardium, thyroid, pituitary, skin, and other organs. The case was regarded as IgG4-related sclerosing disease manifesting itself as lymphadenopathy and thymus enlargement.

[IgG4-related sclerosing disease].

IgG4-related sclerosing disease (IgG4-RSD) is a systemic one in which IgG4-positive plasma cells and T lymphocytes extensively infiltrate various organs. The clinical manifestations of the disease include autoimmune pancreatitis, sclerosing cholangitis, cholecystitis, sialodenitis, retroperitoneal fibrosis, tubulointestitial nephritis, interstitial pneumonia, prostatitis, inflammatory pseudotumors and lymphadenopathy, all related with significantly elevated serum IgG4 levels. Tissue fibrosis with obliterative phlebitis of the affected organs is pathologically induced. The disease occurs predominantly in elderly men and responds well to steroid therapy. Since malignant tumors are frequently suspected on initial presentation, IgG4-RSD should be considered in the differential diagnosis to avoid unnecessary surgery.

Effective surface viscosities of a particle-laden fluid interface.

The Einstein formula for the effective shear viscosity of low Reynolds number suspension flows is generalized to the case of flat, low-concentration, particle-laden interfaces separating two immiscible fluids. The effective surface shear and dilational viscosities of this system is found to be eta{s}=5/3(eta{1}+eta{2})R phi and zeta{s}=5(eta_{1}+eta_{2})R phi , correspondingly, where eta{1} and eta{2} are the shear viscosities of two bulk fluids and phi is the surface concentration of spherical particles of radius R . The formula is found to be in excellent agreement with data obtained using multicomponent lattice Boltzmann equation simulation.

Multicomponent lattice Boltzmann method for fluids with a density contrast.

We present and verify a multicomponent lattice Boltzmann simulation scheme for two immiscible and incompressible fluids with a large density contrast. Our method is constructed from a continuum approximation description of a single inhomogeneous, and essentially incompressible, fluid. The equations that arise from this analysis are mapped onto an established multicomponent lattice Boltzmann method. The approach avoids the computational expense of a numerical solution of the fluid pressure field in a separate step. We present results obtained with our model which validate the initial assumptions and verify correct static and dynamic operation of the model up to a fluid density contrast ratio of more than 500. The paper concludes with an example that illustrates the potential utility of the approach by modeling a gas bubble rising under gravity and breaking through a free surface.

Waves at surfactant-laden liquid-liquid crystal interface.

A theoretical study is presented of surface waves at a monomolecular surfactant film between an isotropic liquid and a nematic liquid crystal for the case when the surfactant film is in the isotropic two-dimensional fluid phase and induces homeotropic (normal to the interface) orientation of the nematic director. The dispersion relation for the surface waves is obtained, and different surface modes are analyzed with account being taken of the anchoring induced by the surfactant layer, the curvature energy of the interface, and the anisotropy of the viscoelastic coefficients. The dispersion laws for capillary and dilatational surface modes retain structure similar to that in isotropic systems, but involve anisotropic viscosity coefficients. Additional modes are related to relaxation of the nematic director field due to anchoring at the interface. The results can be used to determine different properties of nematic-surfactant-isotropic interfaces from experimental data on surface light scattering.

Shear viscosity of bulk suspensions at low Reynolds number with the three-dimensional lattice Boltzmann method.

We report three-dimensional parallel Lagrangian particle simulations using the lattice Boltzmann method, conducted at a low Reynolds number. Using modified Lees-Edwards boundary conditions and directly calculated viscous dissipation, we show that it is possible to recover excellent agreement with the Einstein viscosity formula in the low concentration limit and to predict viscosity corrections for larger concentrations.

Local membrane length conservation in two-dimensional vesicle simulation using a multicomponent lattice Boltzmann equation method.

We present a method for applying a class of velocity-dependent forces within a multicomponent lattice Boltzmann equation simulation that is designed to recover continuum regime incompressible hydrodynamics. This method is applied to the problem, in two dimensions, of constraining to uniformity the tangential velocity of a vesicle membrane implemented within a recent multicomponent lattice Boltzmann simulation method, which avoids the use of Lagrangian boundary tracers. The constraint of uniform tangential velocity is carried by an additional contribution to an immersed boundary force, which we derive here from physical arguments. The result of this enhanced immersed boundary force is to apply a physically appropriate boundary condition at the interface between separated lattice fluids, defined as that region over which the phase-field varies most rapidly. Data from this enhanced vesicle boundary method are in agreement with other data obtained using related methods [e.g., T. Krüger, S. Frijters, F. Günther, B. Kaoui, and J. Harting, Eur. Phys. J. 222, 177 (2013)10.1140/epjst/e2013-01834-y] and underscore the importance of a correct vesicle membrane condition.

Comment on "Fluctuations of elastic interfaces in fluids: theory, lattice-Boltzmann model, and simulation".

The formulas for the force exerted by the interface upon the fluids, given by Stelitano and Rothman [Phys. Rev. E 62, 6667 (2000)] are corrected.

Shape of an isotropic droplet in a nematic liquid crystal: the role of surfactant.

We investigate theoretically, and numerically, the shape of a droplet of an isotropic fluid immersed in a nematic liquid crystal in the presence of an interfacial layer of surfactant; the droplet size is assumed to be small compared to the extrapolation length of the nematic and homeotropic alignment is favored by the anchoring energy at the nematic-isotropic interface. In a certain range of droplet sizes, the droplets are found to be lens shaped with the rotation axis aligned along the imposed director field and the aspect ratio dependent upon the ratio of anchoring strength and surface tension coefficients. For anchoring strengths large compared to the surface tension, the curvature of the edge of lens is controlled by the bending rigidity of surfactant.

Lattice Boltzmann algorithm for surface tension with greatly reduced microcurrents.

We present an algorithm for inserting an interface between the immiscible phases of a multicomponent lattice Boltzmann fluid which is based solely upon the appropriate continuum physics: stress boundary conditions and continuity of velocity. Results are presented for the algorithm when applied to static, neutrally buoyant drops. It is shown that the present algorithm gives a significant reduction in the spurious velocities which are reported for previous schemes and a concomitant improvement in the isotropy of the interface.

Generalized lattice Boltzmann algorithm for the flow of a nematic liquid crystal with variable order parameter.

A lattice Boltzmann (LB) scheme is described, which recovers the equations developed by Qian-Sheng for the hydrodynamics of a nematic liquid crystal with a tensor order parameter. The standard mesoscopic LB scalar density is generalized to a tensor quantity and the macroscopic momentum, density, and tensor order parameter are recovered from appropriate moments of this mesoscopic density. A single lattice Boltzmann equation is used with a direction dependent Bhatnagar, Gross, and Krook (BGK) collision term, with additional forcing terms to recover the antisymmetric terms in the stress tensor. A Chapman-Enskog analysis is presented, which demonstrates that the Qian-Sheng scheme is recovered, provided a lattice with sixth-order isotropy is used. The method is validated against analytical results for a number of cases including flow alignment of the order tensor and the Miesowicz viscosities in the presence of an aligning magnetic field. The algorithm accurately recovers the predicted changes in the order parameter in the presence of aligning flow, and magnetic, fields. Preliminary results are given for an extension of the method to model the interface between isotropic and nematic fluids.

Effective surface-shear viscosity of an incompressible particle-laden fluid interface.

The presence of even a small amount of surfactant at the particle-laden fluid interface subjected to shear makes surface flow incompressible if the shear rate is small enough [T. M. Fischer et al., J. Fluid Mech. 558, 451 (2006)]. In the present paper the effective surface shear viscosity of a flat, low-concentration, particle-laden incompressible interface separating two immiscible fluids is calculated. The resulting value is found to be 7.6% larger than the value obtained without account for surface incompressibility.

Effective surface dilatational viscosity of highly concentrated particle-laden interfaces.

The effective surface dilatational viscosity is calculated of a flat interface separating two immiscible fluids laden with half-immersed monodisperse rigid spherical non-Brownian particles in the limit of high particle concentration. The derivation is based upon the facts that (i) highly concentrated particle arrays in a plane form a hexagonal structure and (ii) the dominant contribution to the viscous dissipation rate arises in the thin gaps between neighboring particles.