Entanglement between a qubit and the environment in the spin-boson model

The quantitative description of the quantum entanglement between a qubit and its environment is considered. Specifically, for the ground state of the spin-boson model, the entropy of entanglement of the spin is calculated as a function of α, the strength of the ohmic coupling to the environment, and ɛ, the level asymmetry. This is done by a numerical renormalization group treatment of the related anisotropic Kondo model. For ɛ=0, the entanglement increases monotonically with α, until it becomes maximal for α→1-. For fixed ɛ>0, the entanglement is a maximum as a function of α for a value, α=αM

On the relationship between the critical temperature and the London penetration depth in layered organic superconductors

We present an analysis of previously published measurements of the London penetration depth of layered organic superconductors. The predictions of the BCS theory of superconductivity are shown to disagree with the measured zero temperature, in plane, London penetration depth by up to two orders of magnitude. We find that fluctuations in the phase of the superconducting order parameter do not determine the superconducting critical temperature as the critical temperature predicted for a Kosterlitz–Thouless transition is more than an order of magnitude greater than is found experimentally for some materials. This places constraints on theories of superconductivity in these materials.

The Genus Wolbachia

Numerous invertebrate species form long lasting symbioses with bacteria (Buchner, 1949; Buchner, 1965). One of the most common of these bacterial symbionts is Wolbachia pipientis, which has been estimated to infect anywhere from 15–75% of all insect species (Werren et al., 1995a; West et al., 1998; Jeyaprakash and Hoy, 2000; Werren and Windsor, 2000) as well as many species of arachnids, terrestrial crustaceans and filarial nematodes (O’Neill et al., 1997a; Bandi et al., 1998). In most arthropod associations, Wolbachia act as reproductive parasites manipulating the reproduction of their hosts to enhance their own vertical transmission. There appears to be little direct fitness cost to the infected host besides the costs arising from the reproductive manipulations. However instances have been reported where Wolbachia can be either deleterious (Min and Benzer, 1997; Bouchon et al., 1998) or beneficial (Girin and Boultreau, 1995; Stolk and Stouthamer, 1995; Wade and Chang, 1995; Vavre et al., 1999b; Dedeine et al., 2001) to their hosts. Wolbachia were first described as intracellular Rickettsia-like organisms (RLOs), infecting the gonad cells of the mosquito, Culex pipiens (Hertig and Wolbach, 1924), and were later named 'Wolbachia pipientis' (Hertig, 1936). It was not until the work of Yen and Barr (Yen and Barr, 1971; Yen and Barr, 1973) that Wolbachia were implicated in causing crossing incompatibilities between different mosquito populations (Laven, 1951; Ghelelovitch, 1952). When polymerase chain reaction (PCR) diagnostics for Wolbachia became available, it became clear that this agent was both extremely widespread and also responsible for a range of different reproductive phenotypes in the different hosts it infected (O’Neill et al., 1992; Rousset et al., 1992; Stouthamer et al., 1993). The most common of these are cytoplasmic incompatibility, inducing parthenogenesis, overriding host sex-determination, and male-killing (O’Neill et al., 1997a). As of the time of this writing, more than 450 different Wolbachia strains with unique gene sequences, different phenotypes, and infecting different hosts have been deposited in GenBank and the Wolbachia host database (http://www.wolbachia.sols. uq.edu.au).

The potential of virulent Wolbachia to modulate disease transmission by insects

A virulent strain of Wolbachia has recently been identified in Drosophila that drastically reduces adult lifespan. It has been proposed that this phenotype might be introduced into insect disease vector populations to reduce pathogen transmission. Here we model the requirements for spread of such an agent and the associated reduction in disease transmission. First, a simulation of mosquito population age structure was used to describe the age distribution of mosquitoes transmitting dengue virus. Second, given varying levels of cytoplasmic incompatibility and fecundity effect, the maximum possible longevity reduction that would allow Wolbachia to invade was obtained. Finally, the two models were combined to estimate the reduction in disease transmission according to different introduction frequencies. With strong CI and limited effect of fecundity, an introduction of Wolbachia with an initial frequency of 0.4 could result in a 60–80% reduction of transmitting mosquitoes. Greater reductions are possible at higher initial release rates.

Maternal transmission efficiency of Wolbachia superinfections in Aedes albopictus populations in Thailand

We examined the transmission efficiency of 2 strains of Wolbachia bacteria that cause cytoplasmic incompatibility in field populations of Aedes albopictus by polymerase chain reaction assay. We found mainland and island populations throughout Thailand to be superinfected with group A and B bacteria. Of 320 Wolbachia-positive adult mosquitoes, 97.5% were infected with both groups. Single infected individuals of each Wolbachia group were encountered in nearly equal numbers. We screened 550 offspring from 80 field-collected mothers and found the transmission efficiency of group A Wolbachia to be 96.7% and that of group B Wolbachia to be 99.6%. Mothers that did not transmit both Wolbachia infections to all of their offspring were significantly larger in size than those with perfect transmission fidelity. We discuss our findings in relation to the prospects of the use of Wolbachia as a gene-driving mechanism.

Evolution of Wolbachia pipientis transmission dynamics in insects

Wolbachia pipientis is an intracellular bacterial parasite of arthropods that enhances its transmission by manipulating host reproduction, most commonly by inducing cytoplasmic incompatibility. The discovery of isolates with modified cytoplasmic incompatibility phenotypes and others with novel virulence properties is an indication of the potential breadth of evolutionary strategies employed by Wolbachia.

Wolbachia pipientis: bacterial density and unidirectional cytoplasmic incompatibility between infected populations of Aedes albopictus

Unidirectional cytoplasmic incompatibility is seen when certain Wolbachia-infected insect populations are crossed. Two hypotheses might explain this phenomenon: superinfections with mutually incompatible strains of Wolbachia producing incompatibility when crossed to individuals infected with only a single bacterial strain or, alternatively, a bacterial dosage model, with differences in Wolbachia densities responsible for the incompatibility. A quantitative PCR assay was set up as a general method to compare Wolbachia densities between populations. Using this assay in unidirectionally incompatible stocks of the mosquito Aedes albopictus, we have determined that densities are significantly higher in Houston than in the Mauritius and Koh Samui stocks. This is consistent with a dosage model for the observed crossing patterns, but does not rule out the possibility that superinfection is the primary cause of the incompatibility.

Bidirectional incompatibility between conspecific populations of Drosophila simulans

Cytoplasmic incompatibility (CI) describes the phenomenon whereby eggs fertilized by sperm from insects infected with a rickettsial endosymbiont fail to hatch. Unidirectional CI between conspecific populations of insects is a well documented phenomenon. Bidirectional CI has, however, only been described in mosquito populations, and recently between closely related species of parasitic wasps, where it is of interest as both an unusual form of reproductive isolation and as a potential means of insect population suppression. Here we report on the first known example of bidirectional CI between conspecific populations of Drosophila simulans. Further, we show that defects as early as the first cleavage division are associated with CI. This observation suggests that the cellular basis of CI involves disruption of processes before or during zygote formation and that CI arises from defects in the structure and/or function of the sperm during fertilization.

The effect of organisational culture perceptions on the relationship between budgetary participation and managerial job-related outcomes

The impact of managers' perceptions of their organizational culture (OC) on the relationship between budgetary participation (BP) and managerial job-related outcomes, operationalized as managerial performance and job-related tension (JRT) is examined. Data supported predictions that increasing BP would lower JRT for managers perceiving a high emphasis on innovation within their OC, regardless of their perceptions of an emphasis on attention to detail. When managers perceived low innovation, however, their perception of level of attention to detail had a significant effect on the relationship between BP and JRT.

A hybrid planning method for transmission networks in a deregulated environment

The reconstruction of power industries has brought fundamental changes to both power system operation and planning. This paper presents a new planning method using multi-objective optimization (MOOP) technique, as well as human knowledge, to expand the transmission network in open access schemes. The method starts with a candidate pool of feasible expansion plans. Consequent selection of the best candidates is carried out through a MOOP approach, of which multiple objectives are tackled simultaneously, aiming at integrating the market operation and planning as one unified process in context of deregulated system. Human knowledge has been applied in both stages to ensure the selection with practical engineering and management concerns. The expansion plan from MOOP is assessed by reliability criteria before it is finalized. The proposed method has been tested with the IEEE 14-bus system and relevant analyses and discussions have been presented.