An exo-poly-alpha-D-galacturonosidase, PehB, is required for wild-type virulence of Ralstonia solanacearum

Ralstonia solanacearum, which causes bacterial wilt disease of many plant species, produces several extracellular plant cell wall-degrading enzymes that are suspected virulence factors. These include a previously described endopolygalacturonase (PG), PehA, and two exo-PGs. A gene encoding one of the exo-PGs, pehB, was cloned from R. solanacearum K60. The DNA fragment specifying PehB contained a 2,103-bp open reading frame that encodes a protein of 74.2 kDa with a typical N-terminal signal sequence. The cloned pehB gene product cleaves polygalacturonic acid into digalacturonic acid units. The amino acid sequence of pehB resembles that of pehX, an exo-PG gene from Erwinia chrysanthemi, with 47.2% identity at the amino acid level. PehB also has limited similarity to plant exo-PGs from Zea mays and Arabidopsis thaliana. The chromosomal pehB genes in R. solanacearum wild-type strain K60 and in an endo-PG PehA- strain were replaced with an insertionally inactivated copy of pehB. The resulting mutants were deficient in the production of PehB and of both PehA and PehB, respectively. The pehB mutant was significantly less virulent than the wild-type strain in eggplant virulence assays using a soil inoculation method. However, the pehA mutant was even less virulent, and the pehA pehB double mutant was the least virulent of all. These results suggest that PehB is required for a wild-type level of virulence in R. solanacearum although its individual role in wilt disease development may be minor. Together with endo-PG PehA, however, PehB contributes substantially to the virulence of R. solanacearum.     

The incidence of diapause in seventeen populations of the flour moth, Ephestia kuehniella Zeller (Lepidoptera: Pyralidae)

Samples of Ephestia kuehniella were examined for diapause at 20 and 25°C in continuous darkness, continuous light and three other photoperiods. The samples came from five flour mills and five unheated stores in England, and from Scotland, Egypt, Finland and Japan, together with three laboratory reared stocks. Some larvae entered diapause in all but three of the English stocks, in all stocks from other countries, and in a 10-yr old laboratory stock from Japan but not in two other stocks reared in the laboratory for over 30 yr. In continuous darkness at 25°C, the incidence of diapause exceeded 10% in eleven stocks, 25% in eight, and 50% in three stocks, while in darkness at 20°C the proportions were usually much smaller. In other light regimes there was a much lower incidence of diapause, 10% being reached in only six experiments out of more than eighty. Markedly more larvae entered diapause when reared on the maize or wheat flour available in mills than on a nutritious laboratory diet of wheatfeed, glycerol and yeast.     

Structure and process in semantic memory: New evidence based on speed–accuracy decomposition.

Reaction-time and accuracy data obtained from studies of sentence verification have not been rich enough to answer certain important theoretical questions about structures and processes in human semantic memory. However, a new technique called speed-accuracy decomposition (Meyer, Irwin, Osman, & Kounios, 1986) may help solve this problem. The technique allows intermediate products of sentence verification to be analyzed more precisely. Three experiments with speed-accuracy decomposition indicate that verification processes produce useful partial information before they are completed. Such information appears to accumulate continuously at a rate whose magnitude depends on the degree of relatedness between semantic categories. This outcome is consistent with continuous computational (e.g., semantic-feature comparison) models of semantic memory. An analysis of reaction-time minima suggests that a discrete all-or-none search process may also contribute at least occasionally to sentence verification. Further details regarding the nature of these processes and the memory structures on which they operate can be inferred from additional results obtained through speed-accuracy decomposition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A continuum thermodynamic analysis of cohesive zone models

A global thermodynamic analysis of the running crack problem is presented. The crack is modeled as an evolving partially cohesive interface endowed with a thermodynamic structure distinct from that of the surrounding body. Constitutive relationships for the cohesive part of the crack surface are formulated in a general way that allows one to account for various dissipative mechanisms and to recover most of the cohesive zone models available from the literature. Particular attention is focused on some of the fundamental and necessary requirements for formulating cohesive zone models. The relationship between such requirements and the interface evolution is discussed and analysed.     

Defect structures and nonbasal slip of C36 laves phase MgNi2 in a two-phase alloy

The microstructure of the C36 Laves phase MgNi₂ in a two-phase Ni-15 at. pct Mg alloy was studied using electron microscopy. Both intrinsic and extrinsic stacking faults were found on the basal plane. The displacement vectors of the faults and Burgers vectors of partial dislocations either lying on the basal faults or bounding each side of the faults were analyzed using high-resolution transmission electron microscopy (TEM). Nonbasal faults were found on the pyramidal planes {1011} and {1012} and the prismatic plane {1010}, all connected to basal faults. The displacement vector of the pyramidal faults was determined to be 1/12 〈4043〉. The microstructure was also studied after room-temperature compression, and nonbasal slip was found to be the major deformation mode.     

Age-specific incidence of cancer in Kingston and St. Andrew, Jamaica, 1988-1992

During the period 1988-1992, a total of 4,030 malignant neoplasms were recorded in Kingston and St. Andrew, Jamaica. These comprised 1,829 in males and 2,201 in females. Histological confirmation was obtained in 83.4%. The crude incidence rate for males was 128.5, and 136.2 for females. The age-standardized rates (ASR) were 179.9 for males and 166.1 for females. Age-specific rates by site, sex and age are tabulated. Attention is drawn to increased incidence for cancers of prostate, larynx, bronchus and non-Hodgkin's lymphoma in males. There was also an increase in female breast cancer (crude rate 36.0; ASR 47.1). Invasive cervix cancer has shown no significant change in incidence. Neoplasms of the body of the uterus have increased (crude rate 7.6; ASR 9.5). The rise in cancer of breast and body of uterus suggests that the influence of exogenous oestrogens should be considered.     

Successfully Managing the Multivendor Environment

The coordination of services from multiple sources—management of the multivendor environment—is a many-faceted responsibility for the MIS manager. There are inherent problems in such an environment, but the MIS manager can take steps to ensure that the benefits and opportunities presented by the multivendor environment are realized.     

Extracting Straight Lines

This paper presents a new approach to the extraction of straight lines in intensity images. Pixels are grouped into line-support regions of similar gradient orientation, and then the structure of the associated intensity surface is used to determine the location and properties of the edge. The resulting regions and extracted edge parameters form a low-level representation of the intensity variations in the image that can be used for a variety of purposes. The algorithm appears to be more effective than previous techniques for two key reasons: 1) the gradient orientation (rather than gradient magnitude) is used as the initial organizing criterion prior to the extraction of straight lines, and 2) the global context of the intensity variations associated with a straight line is determined prior to any local decisions about participating edge elements.