22,514 research outputs found
Initial stages of cavitation damage and erosion on copper and brass tested in a rotating disk device
In view of the differences in flow and experimental conditions, there has been a continuing debate as to whether or not the ultrasonic method of producing cavitation damage is similar to the damage occurring in cavitating flow systems, namely, venturi and rotating disk devices. In this paper, the progress of cavitation damage during incubation periods on polycrystalline copper and brass tested in a rotating disk device is presented. The results indicate several similarities and differences in the damage mechanism encountered in a rotating disk device (which simulates field rotary devices) and a magnetostriction apparatus. The macroscopic erosion appears similar to that in the vibratory device except for nonuniform erosion and apparent plastic flow during the initial damage phase
On autonomous terrain model acquistion by a mobile robot
The following problem is considered: A point robot is placed in a terrain populated by an unknown number of polyhedral obstacles of varied sizes and locations in two/three dimensions. The robot is equipped with a sensor capable of detecting all the obstacle vertices and edges that are visible from the present location of the robot. The robot is required to autonomously navigate and build the complete terrain model using the sensor information. It is established that the necessary number of scanning operations needed for complete terrain model acquisition by any algorithm that is based on scan from vertices strategy is given by the summation of i = 1 (sup n) N(O sub i)-n and summation of i = 1 (sup n) N(O sub i)-2n in two- and three-dimensional terrains respectively, where O = (O sub 1, O sub 2,....O sub n) set of the obstacles in the terrain, and N(O sub i) is the number of vertices of the obstacle O sub i
Nature of heterochromatin
This article does not have an abstract
Floral anatomy of Rivina humilis L., and the theory of carpel polymorphism
This article does not have an abstract
Hydrology of the Korapuzha estuary, Malabar, Kerala State
A preliminary enquiry on the hydrological and planktological conditions in the
river mouth region was conducted during the period 1950-52 and the results published
in an abstract form (George, 1953a). This study was later extended to
cover the 25 Ian seaward region of the estuary in 1954. As is well known, the
Malabar coast is highly productive from the fisheries point of view and it was
also observed that the sea waters of the inshore region off Calicut are rich in plankton
and nutrient salts (George, 1953b). Results of the present investigation would
therefore serve to assess the influence of land drainage in the enrichment and replenishment
of the coastal waters and allied factors
Crafts and gear used for marine fishing along the Andhra Pradesh coast
Until the middle of nineteen sixties fishing
for marine finfishes and shellfishes along the
Andhra Pradesh coast used to be carried out
employing indigenous non-mechanised crafts.
Subsequently trawlers and later mechanised
vessels operating gillnets came into use which
resulted in the increased fish production. Use
of outboard engine on indigenous crafts for
reaching fishing grounds is a recent feature of
near the coast fishing. The different kinds of
non-mechanised and mechanised crafts and
gear employed in the region are dealt with in
this article
Reentrant Peak Effect in an anisotropic superconductor 2H-NbSe_2 : Role of disorder
The reentrant nature of Peak Effect is established in a single crystal of
2H-NbSe_2 via electrical transport and dc magnetisation studies. The role of
disorder on the reentrant branch of PE has been examined in three single
crystals with varying levels of quenched random disorder. Increasing disorder
presumably shrinks the (H,T) parameter space over which vortex array retains
spatial order. Although, the upper branch of the PE curve is somewhat robust,
the lower reentrant branch of the same curve is strongly affected by disorder.Comment: 5 Pages of text, 4 figure
Studies on nucleotidases in plants: isolation and properties of the monomeric form of the crystalline and homogeneous mung bean nucleotide pyrophosphatase
Mung bean nucleotide pyrophosphatase isolated in a crystalline and homogeneous form as a dimer with a molecular weight of 65000 was converted by AMP into a tetramer. The tetramer was enzymatically active with altered kinetic properties. This conversion of the dimeric form by AMP to a tetrameric one was prevented by treating the dimer with p-hydroxymercuribenzoate. The molecular weight of the p-hydroxymercuribenzoate-treated enzyme was determined to be 32700 by a combination of Stokes' radius (2.4 nm) and sedimentation velocity (S20,w = 1.9 S), by thin-layer gel chromatography on superfine Sephadex G-200 and by sodium dodecylsulfate/polyacrylamide gel electrophoresis. The monomer obtained by treatment of the native enzyme with p-hydroxymercuribenzoate was isolated by passage of the dissociated enzyme through a column of Biogel P-200. The monomer was optimally active at 37°C, whereas the dimer and tetramer were active at 49°C. All the three enzyme forms were maximally active at pH 9.4. The Km and V (measured as rate of FAD hydrolysis per mg protein) for FAD of the three enzyme forms were for the monomer, 0.5mM and 7.0 μmolmin-1, for the dimer, 0.25mM and 3.3 μmolmin-1 and for the tetramer, 0.58mM and 2.5 μmolmin-1, respectively. The time course of the reaction of the monomer was linear and comparable to the initial fast rate of the dimer. The monomer was not converted to a tetramer or a dimer on the addition of AMP; and it was irreversibly inhibited by urea and EDTA. ATP and ADP were noncompetitive inhibitors of the monomer
- …