Capacitation-associated protein tyrosine phosphorylation and membrane fluidity changes are impaired in the spermatozoa of asthenozoospermic patients

Sperm protein tyrosine phosphorylation has been associated with capacitation, motility changes, zona binding, and fertilizing ability. We previously demonstrated that gradient-isolated human sperm subpopulations differ in their plasma membrane composition, their ability to phosphorylate proteins in tyrosine residues, and their capacity to undergo hyperactivation. In this study, we have characterized capacitation-associated changes in protein tyrosine phosphorylation and membrane fluidity in spermatozoa of asthenozoospermic and normozoospermic patients consulting for infertility. Semen samples were studied at baseline and after a capacitating incubation with or without the addition of a permeable cAMP analog and a phosphodiesterase inhibitor. Basic sperm and computer-assisted motion parameters, hyperactivation, protein tyrosine phosphorylation (immunofluorescence and Western blot), and membrane fluidity (fluorescent Laurdan probe) were the main study parameters. In comparison with normozoospermic and proven-fertile donor semen, asthenozoospermic samples showed lower motility, velocity, and amplitude of lateral head displacement, both originally and after a 6-h capacitating incubation. Unlike those in normal samples, asthenozoospermic spermatozoa were unable to increase protein tyrosine phosphorylation during capacitation. Such impairment, however, was overcome when they were incubated with a membrane-permeable cAMP analog and a phosphodiesterase inhibitor, indicating a possible membrane defect. Confirming this hypothesis, plasma membranes of asthenozoospermic sperm showed decreased fluidity (increased Laurdan polarization), even after a capacitating incubation. In conclusion, spermatozoa from functional asthenozoospermic samples may owe their poor motility, and their inability to properly capacitate and develop hyperactivation, to an impairment in the tyrosine phosphorylation of critical proteins caused by decreased membrane fluidity. These findings suggest a molecular pathogenetic mechanism for a common seminal pathology associated with male infertility.     

Influence of intrachain double bonds on the properties of solution grown single crystals of polyethylene

The influence of intrachain trans double bonds, statistically distributed along a polyethylene chain, on the structure and behaviour of chain-folded single crystals has been studied. The dependence upon the percentage of double bonds of dissolution and thermal properties, external crystal habit, X-ray diffraction in the wide- and low-angle regions, of solution grown single crystals of ethylene-butadiene copolymers may be interpreted by assuming that a certain amount of CH₂CHCHCH₂ units are incorporated in the lattice as defects. The results of the bromination of single crystals of a sample of ethylene-butadiene copolymers show that about the 56% of double bonds, not accessible to bromine, are situated not on the fold surface but in the inner part of the crystals.     

Top-down design methodology of a multi-bit continuous-time delta–sigma modulator

Transistor-level simulation of complex systems involving analog and digital parts is a time-consuming task. The growing interaction of analog and digital devices calls for the use of top-down design methodologies, resulting in behavioral modeling at different levels of abstraction. In this article, an advanced design methodology using a combination of behavioral models and transistor-level models is presented. This methodology is very interesting for complex mixed-signal IC design, improving the design flexibility and reducing the simulation time. To validate the proposed methodology, a continuous-time delta–sigma modulator based on a high-speed low-resolution quantizer is modeled, taking into account their nonidealities such as excess loop delay, clock jitter and feedback DAC element mismatch. The main features of the multi-bit quantizer are 3-bit resolution with 4 GHz sampling rate and FOM of about 7 pJ/conv. This modulator samples signals at high-IF, performing directly the analog-to-digital conversion in the modern RF front-end receivers.     

Arsenical grafted membranes for immobilization of thioredoxin-like proteins

In this work, we describe the cografting of glycidyl methacrylate and dimethyl acrylamide onto a macroporous polysulfone polymer. Aminophenyl arsenical compounds were covalently attached to the copolymer through epoxy ring add-on reactions followed by a 2-mercaptoethanol activation. Thioredoxin and thioredoxin-fusion proteins were immobilized onto this surface and detected by specific antibody recognition. Preservation of native protein folding was confirmed by the detection of the enzymatic activity of an unstable fusion protein. Immobilized fusion protein onto the modified material maintains the enzymatic activity for a longer time, up to two weeks, against the free protein under the same storage conditions that remains active for 2 days.     

Short-term maternal psychological stress in the post-conception period in ewes affects fetal growth and gestation length

Fetal development can be influenced by maternal environment in the peri-conceptional period. This study investigated the effect of maternal feed intake and psychological stress within the first 6 days after conception on embryo development and fetal growth. Superovulated ewes (n=40) were artificially inseminated with semen from one ram. Ewes were then divided into four groups (n=10): group 1 (control) was fed at maintenance level, group 2 (high) at 2x maintenance, and group 3 (low) at 0.5x maintenance on days 2-6 after conception. Group 4 (stress) was fed at maintenance level and then an intense physical and psychological stress challenge was applied for 1 h only on days 2 and 3 after conception. Embryos were recovered at day 6. A total of 113 transferable grade embryos were transferred singly into synchronized untreated recipients, while the remaining embryos (n=165) were fixed and stained for cell counts. Post-conception maternal stress or feed intake did not alter the cell count or grade of day 6 embryos. Fetuses from the stress group had longer crown-rump lengths at day 30 and longer femur length at day 58. Fetuses from the stressed and high feed groups had greater abdominal circumferences at day 85. Subsequent birth weights were not significantly different. Ewes carrying lambs from the stress treatment had shorter gestation lengths. These results show that short-term perturbations of the post-conception maternal environment have measurable effects on fetal development and gestation length.     

Analysis of degradation mechanisms of crystalline silicon PV modules after 12 years of operation in Southern Europe

The long‐term reliability of photovoltaic modules is crucial to ensure the technical and economic viability of PV as a successful energy source. The analysis of degradation mechanisms of PV modules is key to ensure current lifetimes exceeding 25 years. This paper presents the results of the investigations carried out on the degradation mechanisms of a crystalline silicon PV installation of 2 kWp after 12 years of exposure in Málaga, Spain. The analysis was conducted by visual inspection, infrared thermography and electrical performance evaluation. By visual inspection, the most relevant defects in the modules were identified and ranked according to their frequency. The electrical performance was assessed by comparing the characteristic parameters of the individual modules, obtained by outdoor measurements at the start and end of the exposure period. The correlation of the visual defects and the shifts in the electrical parameters was analysed. The results presented show that glass weathering, delamination at the cell‐EVA interface and oxidation of the antireflective coating and the cell metallization grid were the most frequently occurring defects found. The total peak power loss, including the initial light induced degradation, was 11.5%, which corresponded almost totally to a loss in short‐circuit current. Copyright © 2011 John Wiley & Sons, Ltd.     

A multimode CMOS PA with a single propagation path

Analog Integrated Circuits and Signal Processing - In this paper a four mode 130 nm RF CMOS power amplifier (PA) in a single propagation path topology is presented and evaluated with IEEE...     

Ablative Properties of Polyurethanes Reinforced with Organoclay

Ablation resistance and mechanical properties of polyurethane-based composites containing different amounts (up to 5 wt%) of organoclay were correlated with the morphological characterization. The crosslinking density of the polyurethane increased with the amount of organoclay. At low concentration (up to 1 wt%), the organoclay was well exfoliated, while at higher concentration, both exfoliated and intercalated platelets were found. A linear correlation was observed between the tensile test and the concentration of organoclay. Erosion velocity decreased 40% with the incorporation of 5% of organoclay. POLYM. ENG. SCI., 60:630–635, 2020. © 2020 Society of Plastics Engineers     

A volume element model (VEM) for energy systems engineering

This work presents a simplified modeling and simulation approach for energy systems engineering that is capable of providing quick and accurate responses during system design. For that, the laws of conservation are combined with available empirical and theoretical correlations to quantify the diverse types of flows that cross the system and produce a simplified tridimensional mathematical model, namely a volume element model (VEM). The physical domain of interest is discretized in space, thus producing a system of algebraic and ODEs with respect to time, whose solution delivers the project variables spatial distribution and dynamic response. In order to illustrate the application of the VEM in energy systems engineering, three example problems are considered: (i) a regenerative heat exchanger; (ii) a power electronic building block (PEBB); and (iii) a notional all‐electric ship. The same mathematical model was used to analyze problems (ii) and (iii), that is, the thermal management of heat‐generating equipment packaging. In the examples, the converged mesh had a total of 20, 2000, and 7725 volume elements. The third problem led to the largest simulation, which for steady‐state cases took between 5 and 10 min of computational time to reach convergence and for the ship dynamic response 50 min (i.e., 80,000 s of real time). The regenerative heat exchanger model demonstrated how VEM allowed for the coexistence of different phases (subsystems) within the same volume element. The thermal management model was adjusted and experimentally validated for the PEBB system, and it was possible to perform a parametric and dynamic analysis of the PEBB and of the notional all‐electric ship. Therefore, because of the observed combination of accuracy and low computational time, it is expected that the model could be used as an efficient tool for design, control, and optimization in energy systems engineering. Copyright © 2014 John Wiley & Sons, Ltd.