Dopamine and the regulation of cell proliferation in gerbil (Meriones unguiculatus) pyloric mucosa

The epithelium of the digestive system mucosa consists of a highly dynamic cell population. The conditions under which mitotic activity in the gastrointestinal epithelium is regulated is as yet poorly understood. Nevertheless, it is assumed that some biogenic amines might be involved. Having demonstrated that dopaminergic cells occur in the stomach of gerbils (Meriones unguiculatus), in the present study we examined the influence of dopamine antagonist haloperidol on the proliferation of epithelial cells in the mucosa of the stomach. Proliferating cells were detected immunocytochemically and quantified after in-vivo labeling with 5-bromo-2'-desoxyuridine in both haloperidol- and saline-treated animals. The results show that acute doses of haloperidol significantly increases the proliferation rate in the pyloric mucosa, suggesting that dopamine plays a probable modulatory role in the regulation of mitotic activity. These findings are discussed with regard to the role of paraneurons in regulating epithelial mitosis.     

Fanconi anemia complementation group E: clinical and cytogenetic data of the first patient

The clinical and cytogenetic data of the first patient proven to belong to the fifth Fanconi anemia complementation group are described. The Turkish boy presented with psychomotoric retardation, growth retardation, retarded bone age, brachycephaly, hypotelorism, epicanthus, syndactyly, brachydactyly, renal dystopia, and cryptorchism. In addition, an asymmetrical skeletal anomaly was seen with a double distal phalanx of the left thumb and hypoplasia of the right thumb. Typical hematological features of the disorder developed, at the age of 2.5 years, about 1 year after diagnosis. Cytogenetic studies confirmed the clinical diagnosis and revealed a spontaneous chromosomal instability and hypersensitivity to the cross-linking agents diepoxybutane and Trenimon. The findings in the patient, who is considered to be the standard for the fifth Fanconi anemia complementation group, are compared with data reported for other patients affected with Fanconi anemia.     

Design and testing of the Minotaur advanced grid-stiffened fairing

A composite grid-stiffened structure concept was selected for the payload fairing of the Minotaur launch vehicle. Compared to sandwich structures, this concept has an advantage of smaller manufacturing costs and lighter weight. To reduce weight the skin pockets are allowed to buckle visibly up to about 0.5 cm peak displacement.

Various failure modes were examined for the composite grid-stiffened structure. The controlling criterion for this design was a joint failure in tension between the ribs and skin of the structure. The identification of this failure mechanism and the assessment of bounding strains required to control it required extensive test and analysis effort. Increasing skin thickness to control skin buckling resulted in reduced strains between the skin and ribs.

Following the identification of the relevant failure criteria, a final design for the fairing was generated. The resulting 6 m tall fairing was constructed of a tow-placed carbon fiber composite grid structure that was over-wrapped to create a laminated skin. Upon completion of curing and machining, the fairing was cut in half to create the classic “clam-shell” fairing. Static qualification testing demonstrated the structural integrity of the fairing, thereby proving the design and manufacturing process. Loads were applied incrementally in a static loading scenario. The applied load envelope exceeded worst-case dynamic flight conditions with an added safety factor of 25%. At peak load the fairing maintained structural integrity while remaining within the required displacement envelope for payload safety.

Data were collected during the test from a variety of sensors including traditional displacement transducers and strain gages. In addition, full field displacement was monitored at critically loaded fairing sections by means of digital photogrammetry. This paper summarizes the test results, presents the overall performance of the fairing under the test loads, correlates test response and analysis, and identifies lessons learned.

Work continues at the Air Force Research Laboratory (AFRL) and Boeing to identify means of further controlling tensile failure of the un-reinforced polymer bonded joint between the ribs and skin. Stiffening of skin adjacent to the joints and introduction of lightweight foam jackets at the interior of the fairing both show promise of delaying joint failure to higher loads.     

Surface Actuation of Lightweight Mirrors with Shape Memory Alloy

The ability to create lightweight mirrors that can maintain surface accuracy is a major technical challenge for future space telescopes. Processing-induced errors and surface errors due to temperature excursions and gravity sag (zero gravity in space) make it impossible to correct the surface of thin mirror face-sheets by conventional point actuators. The challenges are compounded by the requirements for mirrors to have adequate stiffness for pointing accuracy. An experimental and analytical study was conducted to explore the feasibility of correcting the shape of lightweight (≈1 kg/m2) mirrors using a “Nitinol” (nickel-titanium) shape memory alloy (SMA). Shape memory alloys are increasingly used as smart devices in aerospace applications. Their primary advantage over other smart materials (i.e., piezo-ceramics and piezo-polymers) is in their ability to undergo large strains and displacements and thus enable the development of smart mechanisms. Active shape correction is the only means of mitigating heat and zero-gravity-induced distortions in space-based optical imaging systems. The repeatability and reliability of a possible actuation system based on properties of the SMA wires were studied by testing the stress-strain and stress recovery behavior under controlled conditions. Embedded SMA wires were then used to actuate a composite beam, and the movement induced by actuation was monitored with the Moiré interferometry method.     

Wind Velocity Sensorless Maximum Power Point Tracking Algorithm in Grid-connected Wind Energy Conversion System

This article proposes a wind velocity sensorless hill-climb searching algorithm in the grid-connected field-oriented controlled permanent magnet synchronous generator based wind energy conversion system. The proposed method improves the speed and accuracy of initial tracking. Pseudo-optimum points are used to track the exact optimum points using the power versus speed characteristics of a wind turbine for various wind velocities. This research emphasizes that the pseudo-optimum points using the power versus speed characteristics are always less than and much nearer to the exact optimum points. The small-step forward tracking after pseudo-optimum points improves the accuracy of this algorithm. Moreover, this method improves the tracking speed for various wind velocities. The system used for this research consists of a back-to-back sinusoidal pulse-width modulation converter between the generator and the grid. The performance of the proposed method is analyzed mathematically and verified by simulation using MATLAB/Simulink software (The Mathworks, Natick; Massachusetts, USA).     

Towards carbon-free flame spray synthesis of homogeneous oxide nanoparticles from aqueous solutions

Flame-assisted spray pyrolysis (FASP) is a versatile process for synthesis of nanoparticles from a broad choice of precursors and solvents. Water is an attractive solvent particularly for inexpensive inorganic precursors (e.g. metal nitrates) as it can effectively reduce the process cost. Furthermore when water usage is combined with a carbon-free fuel (e.g. H₂), nanoparticles can be made without forming CO₂. Here such a FASP process is explored for synthesis of Bi₂O₃ and other oxide nanoparticles from aqueous precursor solutions. The flame temperature was measured by FTIR emission–transmission spectroscopy while powders were characterized by X-ray diffraction and N₂ adsorption. At low FASP fuel gas (H₂ or C₂H₂) flow rates or process temperatures, product powders had a bimodal crystal size distribution. Its large and small modes were made by droplet- and gas-to-particle conversion, respectively. Homogeneous Bi₂O₃ and CeO₂ powders were obtained for sufficiently high flow rates of either C₂H₂ or H₂. Prolonged high temperature residence times promoted precursor evaporation from the spray droplets and yielded homogeneous nanostructured powders by gas-to-particle conversion. In contrast, FASP of aqueous solutions of aluminum nitrate yielded rather large particles by droplet-to-particle conversion at all fuel flows investigated.