Maneuvering Aspects and 3D Effects of Active Airfoil Flow Control

An active flow control experiment was conducted on a cropped NACA 0018 airfoil to study 3D effects and maneuverability aspects made possible by a segmented actuation system installed in the airfoil. The 14 piezo-fluidic actuators were installed at the corner of the cropped region, inclined at 30° to the local surface, facing downstream. Operating all actuators at unison significantly increased lift and generated a pitch-down moment. Operating all actuators at the same magnitude but varying the phase along the span generated larger lift-increment, with respect to the uniform phase excitation. Significant rolling moment can be generated when only half-span of the wing is actuated. The latter effect, as indicated by the 3D pressure distribution, persists to the leading edge even though the excitation was introduced close to the trailing edge. When a pair, out of the possible fourteen actuators is not operating, very little of the control authority is lost. This is an important finding when issues like fault tolerance and robustness of fluidic-piezo actuators are considered.     

Disrupting the MAD2L2-Rev1 Complex Enhances Cell Death upon DNA Damage

DNA-damaging chemotherapy agents such as cisplatin have been the first line of treatment for cancer for decades. While chemotherapy can be very effective, its long-term success is often reduced by intrinsic and acquired drug resistance, accompanied by chemotherapy-resistant secondary malignancies. Although the mechanisms causing drug resistance are quite distinct, they are directly connected to mutagenic translesion synthesis (TLS). The TLS pathway promotes DNA damage tolerance by supporting both replication opposite to a lesion and inaccurate single-strand gap filling. Interestingly, inhibiting TLS reduces both cisplatin resistance and secondary tumor formation. Therefore, TLS targeting is a promising strategy for improving chemotherapy. MAD2L2 (i.e., Rev7) is a central protein in TLS. It is an essential component of the TLS polymerase zeta (ζ), and it forms a regulatory complex with Rev1 polymerase. Here we present the discovery of two small molecules, c#2 and c#3, that directly bind both in vitro and in vivo to MAD2L2 and influence its activity. Both molecules sensitize lung cancer cell lines to cisplatin, disrupt the formation of the MAD2L2-Rev1 complex and increase DNA damage, hence underlining their potential as lead compounds for developing novel TLS inhibitors for improving chemotherapy treatments.     

Rapid Formation of Non-canonical Phospholipid Membranes by Chemoselective Amide-Forming Ligations with Hydroxylamines**

There has been increasing interest in methods to generate synthetic lipid membranes as key constituents of artificial cells or to develop new tools for remodeling membranes in living cells. However, the biosynthesis of phospholipids involves elaborate enzymatic pathways that are challenging to reconstitute in vitro. An alternative approach is to use chemical reactions to non-enzymatically generate natural or non-canonical phospholipids de novo. Previous reports have shown that synthetic lipid membranes can be formed in situ using various ligation chemistries, but these methods lack biocompatibility and/or suffer from slow kinetics at physiological pH. Thus, it would be valuable to develop chemoselective strategies for synthesizing phospholipids from water-soluble precursors that are compatible with synthetic or living cells Here, we demonstrate that amide-forming ligations between lipid precursors bearing hydroxylamines and α-ketoacids (KAs) or potassium acyltrifluoroborates (KATs) can be used to prepare non-canonical phospholipids at physiological pH conditions. The generated amide-linked phospholipids spontaneously self-assemble into cell-like micron-sized vesicles similar to natural phospholipid membranes. We show that lipid synthesis using KAT ligation proceeds extremely rapidly, and the high selectivity and biocompatibility of the approach facilitates the in situ synthesis of phospholipids and associated membranes in living cells.     

Influence of hydrodynamic coupling on pair diffusion in a quasi-one-dimensional colloid system

The effect of hydrodynamic interaction on the separation dependence of the center of mass and relative pair diffusion coefficients of colloid particles in a quasi-one-dimensional system, including the influence of proximate walls, is calculated using the method of reflections. There is excellent agreement between the theoretical predictions and the experimental data. We show that the separation dependence of the relative pair diffusion coefficient has an oscillatory structure on the scale length of the correlation length in the system, and we directly relate that oscillatory structure to the pair correlation function of the system.     

Evolution from threshold of a hollow Atom's X-Ray emission spectrum: the Cu k(h)alpha(1,2) hypersatellites

The first pure high-resolution photoexcited K(h)alpha(1,2) hypersatellite spectrum from a hollow Cu atom is measured. Its K(h)alpha(2)- Kalpha(1) shift and the K(h)alpha(1,2) lines' splitting, widths, and intensity ratio are accurately determined. Such spectra are uniquely suited to study relativistic correlation effects, transition from LS to intermediate coupling, and the Breit-Wigner interaction. The threshold energy and the spectrum's evolution with excitation energy are also measured. The roles of relativity and Breit interaction are explored by comparison with ab initio Dirac-Fock calculations.     

Effect of hydrostatic pressure on characteristics of GaAs-Ge1−x(GaAs)x heterojunctions

The conditions of obtention of nGaAs-pGe_1–x(GaAs)_x alloy heterojunctions and the behavior of the electrical and photoelectric characteristics of these structures under hydrostatic compression were investigated. It is shown that the mechanism of current transport in this structure is of the tunneling-recombination type. The pressure coefficients of the forbidden gap width in the solid solution, the effective electron mass in gallium arsenide, and the height of the potential barrier were experimentally determined.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 90–93, February, 1979.     

In-plane dynamics of membranes with immobile inclusions

Cell membranes are anchored to the cytoskeleton via immobile inclusions. We investigate the effect of such anchors on the in-plane dynamics of a fluid membrane and mobile inclusions (proteins) embedded in it. The immobile particles lead to a decreased diffusion coefficient of mobile ones and suppress the correlated diffusion of particle pairs. Because of the long-range, quasi-two-dimensional nature of membrane flows, these effects become significant at a low area fraction (below 1%) of immobile inclusions.