Moscow State University

About: Moscow State University is a education organization based out in Moscow, Russia. It is known for research contribution in the topics: Laser & Population. The organization has 66747 authors who have published 123358 publications receiving 1753995 citations. The organization is also known as: MSU & Lomonosov Moscow State University.

Isolation of exosomes by differential centrifugation: Theoretical analysis of a commonly used protocol.

Abstract: Exosomes, small (40–100 nm) extracellular membranous vesicles, attract enormous research interest because they are carriers of disease markers and a prospective delivery system for therapeutic agents. Differential centrifugation, the prevalent method of exosome isolation, frequently produces dissimilar and improper results because of the faulty practice of using a common centrifugation protocol with different rotors. Moreover, as recommended by suppliers, adjusting the centrifugation duration according to rotor K-factors does not work for “fixed-angle” rotors. For both types of rotors – “swinging bucket” and “fixed-angle” – we express the theoretically expected proportion of pelleted vesicles of a given size and the “cut-off” size of completely sedimented vesicles as dependent on the centrifugation force and duration and the sedimentation path-lengths. The proper centrifugation conditions can be selected using relatively simple theoretical estimates of the “cut-off” sizes of vesicles. Experimental verification on exosomes isolated from HT29 cell culture supernatant confirmed the main theoretical statements. Measured by the nanoparticle tracking analysis (NTA) technique, the concentration and size distribution of the vesicles after centrifugation agree with those theoretically expected. To simplify this “cut-off”-size-based adjustment of centrifugation protocol for any rotor, we developed a web-calculator.

Facile Synthesis of Hematite Quantum-Dot/Functionalized Graphene-Sheet Composites as Advanced Anode Materials for Asymmetric Supercapacitors

Abstract: For building high-energy density asymmetric supercapacitors, developing anode materials with large specific capacitance remains a great challenge. Although Fe2O3 has been considered as a promising anode material for asymmetric supercapacitors, the specific capacitance of the Fe2O3-based anodes is still low and cannot match that of cathodes in the full cells. In this work, a composite material with well dispersed Fe2O3 quantum dots (QDs, ≈2 nm) decorated on functionalized graphene-sheets (FGS) is prepared by a facile and scalable method. The Fe2O3 QDs/FGS composites exhibit a large specific capacitance up to 347 F g−1 in 1 m Na2SO4 between –1 and 0 V versus Ag/AgCl. An asymmetric supercapacitor operating at 2 V is fabricated using Fe2O3/FGS as anode and MnO2/FGS as cathode in 1 m Na2SO4 aqueous electrolyte. The Fe2O3/FGS//MnO2/FGS asymmetric supercapacitor shows a high energy density of 50.7 Wh kg−1 at a power density of 100 W kg−1 as well as excellent cycling stability and power capability. The facile synthesis method and superior supercapacitive performance of the Fe2O3 QDs/FGS composites make them promising as anode materials for high-performance asymmetric supercapacitors.

Observation of a Narrow Pentaquark State, Pc (4312)+, and of the Two-Peak Structure of the Pc (4450)+

Abstract: A narrow pentaquark state, P_{c}(4312)^{+}, decaying to J/ψp, is discovered with a statistical significance of 7.3σ in a data sample of Λ_{b}^{0}→J/ψpK^{-} decays, which is an order of magnitude larger than that previously analyzed by the LHCb Collaboration. The P_{c}(4450)^{+} pentaquark structure formerly reported by LHCb is confirmed and observed to consist of two narrow overlapping peaks, P_{c}(4440)^{+} and P_{c}(4457)^{+}, where the statistical significance of this two-peak interpretation is 5.4σ. The proximity of the Σ_{c}^{+}D[over ¯]^{0} and Σ_{c}^{+}D[over ¯]^{*0} thresholds to the observed narrow peaks suggests that they play an important role in the dynamics of these states.

Moving contact lines in liquid/liquid/solid systems

Abstract: A general mathematical model which describes the motion of an interface between immiscible viscous fluids along a smooth homogeneous solid surface is examined in the case of small capillary and Reynolds numbers. The model stems from a conclusion that the Young equation, σ1 cos θ = σ2 − σ3, which expresses the balance of tangential projection of the forces acting on the three-phase contact line in terms of the surface tensions σi and the contact angle θ, together with the well-established experimental fact that the dynamic contact angle deviates from the static one, imply that the surface tensions of contacting interfaces in the immediate vicinity of the contact line deviate from their equilibrium values when the contact line is moving. The same conclusion also follows from the experimentally observed kinematics of the flow, which indicates that liquid particles belonging to interfaces traverse the three-phase interaction zone (i.e. the ‘contact line’) in a finite time and become elements of another interface – hence their surface properties have to relax to new equilibrium values giving rise to the surface tension gradients in the neighbourhood of the moving contact line. The kinematic picture of the flow also suggests that the contact-line motion is only a particular case of a more general phenomenon – the process of interface formation or disappearance – and the corresponding mathematical model should be derived from first principles for this general process and then applied to wetting as well as to other relevant flows. In the present paper, the simplest theory which uses this approach is formulated and applied to the moving contact-line problem. The model describes the true kinematics of the flow so that it allows for the ‘splitting’ of the free surface at the contact line, the appearance of the surface tension gradients near the contact line and their influence upon the contact angle and the flow field. An analytical expression for the dependence of the dynamic contact angle on the contact-line speed and parameters characterizing properties of contacting media is derived and examined. The role of a ‘thin’ microscopic residual film formed by adsorbed molecules of the receding fluid is considered. The flow field in the vicinity of the contact line is analysed. The results are compared with experimental data obtained for different fluid/liquid/solid systems.