Roller-Screw Inerter:a Novel Strut-Mounted Device for Vibration Isolation

The struts that connect the main rotor and gearbox assembly to the fuselage carry the weight of airframe and payload during flight, and guarantee smooth operation to the drive system. While performing the functions they are designed for, these struts transmit the vibratory loads originating from the main rotor periodic aerodynamic loading to the airframe with essentially negligible alleviation. One technique to cure this problem is to implement strut-mounted vibration alleviation devices, to improve ride comfort by isolating the airframe from the main rotor excitation. This work presents a novel strutmounted vibration attenuation device and demonstrates the concept through experiments and numerical analysis. The design is based on a roller screw inerter, which is mounted in parallel to the strut, sharing its attachment points. The inerter transforms the relative displacement between the two ends of the strut into a corresponding rotation of a body about an axis parallel to that of the strut. As a result, the inerter applies to its two terminals a counter-force proportional to their relative acceleration. In the ideal, frictionless case, a global isolation of the fuselage can be achieve

Peroxidase catalysed formation of prostaglandins from arachidonic acid.

Horseradish peroxidase and bovine lactoperoxidase (EC 1.11.1.7), when incubated aerobically with arachidonate, gave rise to the formation of substances identified by bioassay as prostaglandin F2 alpha (PGF2 alpha)- and prostaglandin E2 (PGE2)-like compounds. Boiling of enzymes, which suppressed their capacity to peroxidize guaiacol, also destroyed their capacity to convert arachidonate into PG-like compounds. The rates of formation of PG-like compounds rapidly declined with time, approaching zero after 10 and 20 min for PGE2 alpha- and PGE2-like compounds, respectively. Addition of more enzyme further promoted the reaction. Horseradish and lacto-peroxidases showed optimum pH values of 9.0 and 10.0, respectively. Both enzymes exhibited apparent Km values of about 5 x 10(-5) M for arachidonate. Some reducing agents such as ascorbic acid, NADH and adrenaline dose-dependently inhibited this reaction. The haem poison, phenylhydrazine, also inhibited, with an IC50 of 1 x 10(-7) M. Indomethacin inhibited only the formation of PGE2-like compounds with an IC50 of about 3 x 10(-6) M. As compared to a standard commercial preparation of horseradish peroxidase, the purified horseradish basic and acidic isoenzymes exhibited a higher activity, towards arachidonate whereas other haemoproteins, possessing peroxidase activity, were less active. TLC and GC-MS analyses performed on the reaction products led to the identification of PGF2 alpha, PGE2 and PG6K1 alpha and other unidentified arachidonate derivatives. At 25 degrees, pH 9.5, horseradish peroxidase, acting on saturating concentration of arachidonate, catalysed the formation of 60 mumol/min/mmole enzyme of PGE2 + PGF2 alpha. This appears to be the first report of the synthesis of prostaglandins catalysed by peroxidases