Mlig-SKP1 Gene Is Required for Spermatogenesis in the Flatworm Macrostomum lignano

In a free-living flatworm, Macrostomum lignano, an S-phase kinase-associated protein 1 (SKP1) homologous gene was identified as enriched in proliferating cells, suggesting that it can function in the regulation of stem cells or germline cells since these are the only two types of proliferating cells in flatworms. SKP1 is a conserved protein that plays a role in ubiquitination processes as a part of the Skp1-Cullin 1-F-box (SCF) ubiquitin ligase complex. However, the exact role of Mlig-SKP1 in M. lignano was not established. Here, we demonstrate that Mlig-SKP1 is neither involved in stem cell regulation during homeostasis, nor in regeneration, but is required for spermatogenesis. Mlig-SKP1(RNAi) animals have increased testes size and decreased fertility as a result of the aberrant maturation of sperm cells. Our findings reinforce the role of ubiquitination pathways in germ cell regulation and demonstrate the conserved role of SKP1 in spermatogenesis.     

Synthesis and surface properties of amphiphilic fluorine-containing diblock copolymers

Amphiphilic diblock copolymers (DCs) of 2,3,4,5,6-pentafluorostyrene (PFS) and 2-hydroxyethyl methacrylate (HEMA) of different composition and molecular weights were prepared by two-step reversible addition–fragmentation chain transfer (RAFT) polymerization and first used for preparation of superhydrophobic coatings for cotton/polyester fabrics. The transition from hydrophobic to superhydrophobic coatings is controlled by the ratio between poly(2,3,4,5,6-pentafluorostyrene) (PPFS) block and poly(2-hydroxyethyl methacrylate) (PHEMA) block lengths (P_n^PFS/P_n^HEMA). The increase in P_n^PFS/P_n^HEMA is accompanied by a significant increase in water (θ^Н₂^О) and diiodomethane (θ^CH₂^I₂) contact angles, which reach the plateau at P_n^PFS/P_n^HEMA = 3.5 and remains almost constant up to P_n^PFS/P_n^HEMA = 6.2. Surface modification of the cotton/polyester fabric with the DC having P_n^PFS/P_n^HEMA = 6.2 produced superhydrophobic surface with θ^Н₂^О = 158 ± 4° and contact angle hysteresis CAH = 5 ± 2°, and θ^CH₂^I₂ = 107 ± 3°.     

Reconstruction of large-scale flow structures in a stirred tank from limited sensor data

We combine reduced order modeling and system identification to reconstruct the temporal evolution of large-scale vortical structures behind the blades of a Rushton impeller. We performed direct numerical simulations at Reynolds number 600 and employed proper orthogonal decomposition (POD) to extract the dominant modes and their temporal coefficients. We then applied the identification algorithm, N4SID, to construct an estimator that captures the relation between the velocity signals at sensor points (input) and the POD coefficients (output). We show that the first pair of modes can be very well reconstructed using the velocity time signal from even a single sensor point. A larger number of points improves accuracy and robustness and also leads to better reconstruction for the second pair of POD modes. Application of the estimator derived at Re = 600 to the flows at Re = 500 and 700 shows that it is robust with respect to changes in operating conditions.     

Dynamic measurements and their metrological support in the photometry of subnano- and picosecond ranges

Questions that arise in measurements of the peak power and time parameters of optical pulses in the subnano- and picosecond range are discussed. Methods of development and problems that arise in this area of photometry are considered. Translated from Izmeritel'naya Tekhnika, No. 11, pp. 24–27, November, 1998.