Regions R2 Research Articles

Investigation of varicella-zoster virus variation by heteroduplex mobility assay.

Heteroduplex mobility assays of 37 regions were performed on ten UK isolates of varicella zoster virus, four from cases of zoster, and six from cases of chickenpox. The variation between isolates was found to be 0.061%, which is at least five times lower than any other member of the human herpesvirus family. Fifteen of the 37 regions tested had 29 single nucleotide polymorphisms, and over half the polymorphisms were located in four gene fragments. Of the 29 SNPs, eleven were non-synonymous and these were clustered in six genes. Isolates from a child and her mother to whom she had transmitted the virus, were identical at every locus tested. All other viruses could be distinguished by a combination of SNPs and length polymorphisms of the repeat regions R1, R2 and R5.

Energetics of the lower tropospheric eddies in wave number domain during northern summer monsoon

Lower tropospheric energetics and energy processes of zonal waves for three consecutive northern summer monsoon seasons of 1994, 1995 and 1996 are presented. Fourier technique is used. The features of the tropical and extra-tropical regions are very well reflected by the data set used for this study. The results do not show marked year to year variations in the pattern of energy processes. The character of energy processes differs significantly from one latitudinal region to other. Wave to zonal mean flow interactions and wave to wave interactions are almost opposite in character over R1 (10° S -10° N) and R2 (10° N -30° N). L (n) interaction indicates that R1 acts as source of kinetic energy to the waves over R2. Particularly, standing waves I and 2 over RI are the major source of kinetic energy to the waves over R2. Extra-tropical region R3 (30° N -50° N) is dominated by transient waves while tropical regions R1 and R2 are dominated by standing waves. Medium and short waves have significant contributions over extra-tropical region whereas tropical regions are dominated by long waves. The pattern of energy processes over R3 is somewhat similar to the energy processes over R1. This is because both the regions have anti-cyclonic lateral shear.

INITIAL FRACTURE MECHANISMS IN NICKEL ALLOYED PM STEEL

Abstract— Initial fatigue crack propagation mechanisms at near threshold conditions were studied for four nickel‐alloyed, powder‐metallurgy (PM) steels. Fatigue fracture surfaces were obtained by testing smooth rectangular specimens at 30 Hz and under constant amplitude and zero mean stress conditions. Materials based on Distaloy AE were used in two densities, namely 7.15 and 7.45 g/cm3.All the fracture surfaces were composed of three morphological regions (i) a macrocrack initiation region Rl where cracks propagated preferentially through particles (ii) a macrocrack growth region R2 and (iii) an unstable crack growth region R3 where cracks propagated preferentially between particles. Initial fatigue crack growth, in region R1, was controlled by the propagation of short cracks whose dimensions were comparable to the material microstructure. The subsequent fatigue crack growth in regions R2 and R3 was controlled by ductile rupture between microvoids. Transparticle fracture in region R1 was independent of pore distribution, while interparticle fracture in regions R2 and R3 was dependent on pore distribution.

Influence of Speed on the Tribochemical Reaction Products and the Associated Transitions for the Dry Sliding of Silicon Nitride against Steel

Dry sliding of Si3N4 against steel has been studied using a pin‐on‐disk machine as a function of speed at a pressure of 15.5 MPa. Four types of friction and wear behaviors can be observed with associated transition in their values, called regions R1, R2, R3, and R4. R1 (0.1 to 1.25 ms‐1) is associated with high friction as well as the wear rate of the pin and the negligible wear rate of the disk. In R2 (1.25 to 3.5 ms‐1) friction is low and the wear rate of the pin is negligible but the wear rate of the disk is high. The friction and the wear rate of the pin as well as that of the disk are high in R3 (3.5 to 6.5 ms‐1). In R4 (6.5 to 12.0 ms‐1) the friction is low. The wear rate of the pin is similar to that in R3, while that of the disk is very low. SEM, EDXA, XRD, and IR reveal that each of these changes is associated with certain tribochemical interaction. R1 is associated with reaction between Si3N4 and water vapor to form hydrated silica (SiO2·nH2O), R2 is controlled by softening of SiO2·nH2O, R3 is characterized by microfracture and limited formation of Y2SiO5, and R4 is associated with increased formation of Y2SiO5 and SiO2.

Recognizing Voronoi Diagrams with Linear Programming

Let P = {P1, …, Pn} be a finite set of distinct points in ℝd and let Ri be the set of points whose distance from Pi is less than or equal to the distance from every other point in P. The collection of regions R1, …, Rn is called the Voronoi diagram generated by P. Our main result is a polynomial time algorithm for recognizing whether or not a given tessellation of ℝd into polyhedra is a Voronoi diagram. This is accomplished by describing a linear program that has a solution if and only if the given tessellation is a Voronoi diagram. As a consequence, for each Ri of a Voronoi diagram, the set of points in Ri contained in some generating set P is either a singleton or the interior of a polyhedron. We also give a polynomial time algorithm for describing this set for each Ri. Finally, this leads to a second algorithm for recognizing Voronoi diagrams; this algorithm also relies on linear programming but, for fixed dimension d, it is strongly polynomial and has linear time complexity. INFORMS Journal on Computing, ISSN 1091-9856, was published as ORSA Journal on Computing from 1989 to 1995 under ISSN 0899-1499.

Analysis of the influence of proteolytic cleavage on the structural organization of the surface of the west nile flavivirus leads to the isolation of a protease-resistant E protein oligomer from the viral surface

In order to analyze the organization of the membrane proteins pre M, M, and E of the West Nile (WN) flavivirus we have studied the influence of proteolytic cleavage of intact virus on the structure of these proteins. The amino acid sequence of all proteins is known, all six disulfides present in the viral E protein have been identified, and it has been suggested that the E protein contains regions R1, L1, R2, L2, and R3, which together form the E protein ectodomain followed by a car☐yterminal membrane anchor region (Th. Nowak and G. Wengler (1987) Virology 156, 127–137) . The results of our analyses can be summarized as follows: (1) The surface of the WN virus contains E protein oligomers; the E protein molecules present in these structures contain two segments which are exposed to proteolytic attack; the segments are located in parts L1 and R3 of the E protein. (2) Proteolytic cleavage of these oligomers in these regions neither destroys nor releases the oligomers from the viral surface. (3) The WN virus surface contains a layer of 7-nm ring-shaped subunits identifiable by electron microscopy which are neither destroyed nor released by proteolytic cleavage. (4) An E protein trimer can be isolated from the surface of protease-treated WN virus. This trimer is morphologically similar to the 7-nm ring-shaped element which can be identified on the surface of native and protease-treated WN virus by electron microscopy.

Approximation theorem for establishing root-locus topology

An algebraic approximation theorem is formulated which enables topologies of root-locus plots to be established by grouping poles and zeros into regions R1 and R2 so that, for points s1 in R1 and s2 in R2, |s1| ≪ |s2|.

Certain problems related to the cutting of a simply connected plane region by a continuum

1. If R is a simply connected plane region whose frontier F is bounded and C is a simple arc lying in R save for its end points, it is well known that C enjoys the following properties: (a) R R C consists of two simply connected regions R1 and R2; (b) C is a part of the frontiers of both R1 and R2; (c) F+C is the union of the frontiers of R1 and R2. Nothing could be simpler than this theorem, but when one desires to use it, certain questions arise. For instance, what precisely are the frontiers of R1 and R2? If F is the union of two continua H and K, can C be so drawn that its ends lie on two components of H. K? If so, will the frontiers of the two regions be C+H and C+K? These questions are readily answered in the case that F is a simple closed curve, but the answers in this case do not always remain correct when F is more complicated. In particular, a negative answer to the second question suggests the substitution of a more general continuum for C and this in turn leads to a re-examination of the truth of the resulting extension of the theorem. Such an extension has been made elsewheret and it is intended in the present article to examine further these questions and certain related topics. The first and third of the questions suggested above are discussed in ??3-6. The remainder of the paper deals with the situation arising when the arc C is replaced by a special kind of irreducible continuum and with related questions of accessibility. In particular, it is shown that under certain broad conditions the second and third of the above questions can be answered in the affirmative if the arc C is replaced by a slightly more general continuum. 2. Notation. In addition to the common notation of the aggregate theory, the following will be used. The whole plane is denoted throughout by Z. If F is a continuum, a component of Z F whose frontier is F is called a principal component; a component of Z F whose frontier is a proper part of F is called secondary. A