Lysophosphatic acid modulates prostaglandin secretion in the bovine uterus

Lysophosphatidic acid (LPA) modulates prostaglandin (PG) synthesis via LPA receptor 3 (LPAR3) in the murine endometrium. The lack of functional LPAR3 in mice may lead to embryo mortality. In the present study, we examined the role of LPA in the bovine uterus. We confirmed that LPA is locally produced and released from the bovine endometrium. Moreover, there are enzymes involved in LPA synthesis (phospholipase (PL) D(2) and PLA2G1B) in the bovine endometrium during estrous cycle and early pregnancy. Expression of the receptor for LPA (LPAR1) was positively correlated with the expression of PGE(2) synthase (PGES) and negatively correlated with the expression of PGF(2alpha) synthase (aldose reductase with 20 alpha-hydroxysteroid dehydrogenase activity - PGFS) during early pregnancy. In vivo LPA induced P4 and PGE(2) secretion was inhibited by LPAR1 antagonist (Ki16425). The overall results indicate that LPA is locally produced and released from the bovine endometrium. Moreover, LPAR1 gene expression in the endometrium during the estrous cycle and early pregnancy indicates that LPA may play autocrine and/or paracrine roles in the bovine uterus. LPAR1 gene expression is positively correlated with the expression of the enzyme responsible for luteotropic PGE(2) production (PGES) in endometrium. In cow, LPA stimulates P4 and PGE(2) secretion. Thus, LPA in the bovine reproductive tract may indirectly (via endometrium) or directly support corpus luteum action via the increase of P4 synthesis and the increase of PGE(2)/PGF(2)(alpha) ratio. It suggests that LPA may serve as an important factor in the maintenance of early pregnancy in cow.     

Highly efficient electron field emission from graphene oxide sheets supported by nickel nanotip arrays

Electron field emission is a quantum tunneling phenomenon whereby electrons are emitted from a solid surface due to a strong electric field. Graphene and its derivatives are expected to be efficient field emitters due to their unique geometry and electrical properties. So far, electron field emission has only been achieved from the edges of graphene and graphene oxide sheets. We have supported graphene oxide sheets on nickel nanotip arrays to produce a high density of sharp protrusions within the sheets and then applied electric fields perpendicular to the sheets. Highly efficient and stable field emission with low turn-on fields was observed for these graphene oxide sheets, because the protrusions appear to locally enhance the electric field and dramatically increase field emission. Our simple and robust approach provides prospects for the development of practical electron sources and advanced devices based on graphene and graphene oxide field emitters.     

Reconstructing the flight kinematics of swarming and mating in wild mosquitoes

We describe a novel tracking system for reconstructing three-dimensional tracks of individual mosquitoes in wild swarms and present the results of validating the system by filming swarms and mating events of the malaria mosquito Anopheles gambiae in Mali. The tracking system is designed to address noisy, low frame-rate (25 frames per second) video streams from a stereo camera system. Because flying A. gambiae move at 1–4 m s⁻¹, they appear as faded streaks in the images or sometimes do not appear at all. We provide an adaptive algorithm to search for missing streaks and a likelihood function that uses streak endpoints to extract velocity information. A modified multi-hypothesis tracker probabilistically addresses occlusions and a particle filter estimates the trajectories. The output of the tracking algorithm is a set of track segments with an average length of 0.6–1 s. The segments are verified and combined under human supervision to create individual tracks up to the duration of the video (90 s). We evaluate tracking performance using an established metric for multi-target tracking and validate the accuracy using independent stereo measurements of a single swarm. Three-dimensional reconstructions of A. gambiae swarming and mating events are presented.     

Properties of InAs grown on misoriented GaAs substrates by atmospheric pressure metal–organic vapor phase epitaxy

InAs epilayers were grown by atmospheric pressure metal–organic vapor phase epitaxy on GaAs (1 0 0) exactly oriented substrates and misoriented by 2° and 10° toward [1 1 1]A. The layers had varying thicknesses and were deposited under the same growth conditions. Atomic force microscopy analysis show that surface morphology depends on surface misorientation and presents a low root mean square. High resolution X-ray diffraction analysis and Hall effect measurements were preformed to check the substrate misorientation effect on the crystalline quality and electrical properties respectively.     

An Investigation on the Reduced Ability of IF-MoS2 Nanoparticles to Reduce Friction and Wear in the Presence of Dispersants

Inorganic fullerene-like molybdenum disulfide (IF-MoS₂) nanoparticles are known to exhibit great friction and wear-reducing abilities in severe boundary lubrication regimes, when added to a base oil alone. Their use in fully formulated lubricants was investigated in this study, and the tribological benefits attributed to the IF-MoS₂ nanoparticles were found to be lost in the presence of dispersants. Various experimental techniques were used on three reference oils (base oil containing only IF-MoS_2, only dispersants and both IF-MoS₂ and dispersants) in order to understand the effect of succinimide-based dispersants on the three phases needed for effective nanoparticle-based lubrication, namely (1) the passing of the nanoparticles through the contact (2) the exfoliation of the IF-MoS₂ inside the contact and (3) the adhesion of the released MoS₂ platelets on the friction surfaces. The dispersants were shown to improve the dispersion of the nanoparticles in the oil by reducing their agglomeration, but prevented the adhesion of a low-friction MoS₂ tribofilm on the steel surfaces. In-situ contact visualization revealed that the well-dispersed nanoparticles passed through the contact and exfoliated nanoparticles were observed after tribological testing. These results imply that nanoparticle dispersion itself does not seem to be an issue concerning nanoparticle effectiveness, even though the reduced agglomerate size and inertia may have affected nanoparticle flow near the contact, as well as entrapment and exfoliation conditions inside the contact. The use of succinimide-based dispersants may, however, have affected the tribochemistry of the contact, by an excessive adsorption on the steel surfaces and/or by encapsulating the released MoS₂ platelets, preventing tribofilm adhesion. A balance was finally found between nanoparticle dispersion and friction reduction, but for very low dispersant concentrations and after a running-in period. The role of succinimide-based dispersants and their effect on nanoparticle lubrication were discussed in the light of these results.     

Experimental methods of actuation, characterization and prototyping of hydrogels for bioMEMS/NEMS applications

As a member of the smart polymer material group, stimuli responsive hydrogels have achieved a wide range of applications in microfluidic devices, micro/nano bio and environmental sensors, biomechanics and drug delivery systems. To optimize the utilization of a hydrogel in various micro and nano applications it is essential to have a better understanding of its mechanical and electrical properties. This paper presents a review of the different techniques used to determine a hydrogel's mechanical properties, including tensile strength, compressive strength and shear modulus and the electrical properties including electrical conductivity and dielectric permittivity. Also explored the effect of various prototyping factors and the mechanisms by which these factors are used to alter the mechanical and electrical properties of a hydrogel. Finally, this review discusses a wide range of hydrogel fabrication techniques and methods used, to date, to actuate this family of smart polymer material.     

Synthesis, characterization, and analyses of mechanical, adhesion, and thermal properties of polysiloxane resin modified with segmented polyurethane

Novel heat-resistant coating materials with excellent adhesion properties were prepared by modification of polysiloxane resin (PSil) with a pre-synthesized tailored polyurethane/polyurea copolymer end-capped with siloxane (PU). The modification was achieved by crosslinking the hydroxyl group of PSil and ethoxy group of PU in the presence of di-n-butyltin dilaurate. The chemical structure of PU was analyzed by Fourier Transform Infrared and Hydrogen-1 Nuclear Magnetic Resonance spectroscopic methods. A series of modified silicone resins (MSRs) have been synthesized and investigated. The molecular weights of the resins were determined by means of gel permeation chromatography. The morphology of the MSR studied by scanning electron microscopy has shown that the resin containing 30% of PU has a small particle size and a good particle size distribution. The adhesion and the mechanical properties of the resins containing 20, 30, and 40% of PU have shown a good performance. Using thermogravimetric analysis, the thermal properties and the thermal degradation of the MSR were investigated.     

Effects of Surfactants on the Properties of Styrene/Methacrylate–Type Superplasticizer in Cement Paste

Copolymer emulsion lattices based on styrene (St) with methacrylate monomers, were synthesized with composition ratio (5/5) in the presence of a co-surfactants that consists of dodecyl benzene sodium sulfonate with polyvinyl alcohol (DBSS/PVA) and DBBS with polyoxyethylene glycol monomethyl ether (DBBS/POE). The obtained latices were characterized by ¹H NMR, rheological and morphological techniques. The effect of latices on the physicomechanical properties of ordinary Portland cement (OPC) pastes was investigated. The results showed that the addition of water mixed to the cement with copolymer improves most of the specific characteristics of OPC.     

Long term effects of salt on activity, population structure and floc characteristics in enriched bacterial cultures of nitrifiers

The effect of salinity on the activity, the composition of nitrifiers and floc characteristics of nitrifying sludge was studied. Non-adapted and adapted (to 10 g NaCl-Cl⁻/L for one year) enriched cultures of nitrifiers were tested in three sequencing batch reactors. Salt was increased gradually with 5 up to 40 g Cl⁻/L.No difference in steady state activity was observed between the adapted and non-adapted sludge. The activities of ammonia and nitrite oxidizers dropped 36% and 11%, respectively, at salt concentrations of 10 g Cl⁻/L. At 40 g Cl⁻/L inhibition reached 95% of salt free activity for ammonia and nitrite oxidizers in both adapted and non-adapted reactors. Nitrosomonas europaea and Nitrobacter sp. (fluorescent in situ hybridization) were the only nitrifiers present at high salt levels. Increased salt concentrations resulted in better settling characteristics of the nitrifying sludge. After 118 days the sludge was brought back to the initial conditions (0 g Cl⁻/L for non-adapted and 10 g Cl⁻/L for adapted). Despite the change in population composition similar kinetics as before the salt stress were observed.