Disentanglement and Decoherence by Open System Dynamics

The destruction of quantum interference, decoherence, and the destruction of entanglement both appear to occur under the same circumstances. To address the connection between these two phenomena, we consider the evolution of arbitrary initial states of a two-particle system under open system dynamics described by a class of master equations which produce decoherence of each particle. We show that all initial states become separable after a finite time, and we produce the explicit form of the separated state. The result extends and amplifies an earlier result of Di\'osi. We illustrate the general result by considering the case in which the initial state is an EPR state (in which both the positions and momenta of a particle pair are perfectly correlated). This example clearly illustrates how the spreading out in phase space produced by the environment leads to certain disentanglement conditions becoming satisfied.Comment: 15 Page

Disentanglement by Dissipative Open System Dynamics

This paper investigates disentanglement as a result of evolution according to a class of master equations which include dissipation and interparticle interactions. Generalizing an earlier result of Di\'{o}si, the time taken for complete disentanglement is calculated (i.e. for disentanglement from any other system). The dynamics of two harmonically coupled oscillators is solved in order to study the competing effects of environmental noise and interparticle coupling on disentanglement. An argument based on separability conditions for gaussian states is used to arrive at a set of conditions on the couplings sufficient for all initial states to disentangle for good after a finite time.Comment: Paper in conjunction with and following on from P.J. Dodd and J.J. Halliwell: quant-ph/031206

Influence of the temperature on the dielectric properties of epoxy resins

Electrical degradation processes in epoxy resins, such as electrical treeing, were found to be dependent on the temperature at which the experiments were carried out. Therefore, it is of considerable research interest to study the influence of temperature on the dielectric properties of the polymers and to relate the effect of temperature on these properties to the possible electrical degradation mechanisms. In this work, the dielectric properties of two different epoxy resin systems have been characterized via dielectric spectroscopy. The epoxy resins used were bisphenol-A epoxy resins Araldite CY1301 and Araldite CY1311, the later being a modified version of the former with added plasticizer. The CY1301 samples were tested below and above their glass transition temperature, while the CY1311 were tested well above it. Both epoxy systems possess similar behaviour above the glass transition temperature, e.g. in a flexible state, which can be characterized as a low frequency dispersion (LFD). On the other hand, it was found that below the glass transition temperature CY1301 samples have almost “flat” dielectric response in the frequency range considered. The influence of possible interfacial features on the measured results is discussed

An Audit of export services in England: developing business focused support

One of the key thresholds in the development of small and medium sized enterprises is exporting and trading internationally. A brief review of the academic and practitioner literature highlights a number of benefits associated with exporting that include exposure to differing ways of ‘how to do’ business and opportunities for the development of joint ventures and strategic alliances. However, several regions within the United Kingdom perceive that they have too few SMEs who trade internationally. Recent estimates suggest that approximately three per cent of the SMEs in the United Kingdom are actively exporting (Bank of England, 1999). Government policy makers have responded to such concerns by providing a range of support programmes to increase the number of SMEs who trade internationally and enhance the skills and capabilities of those SMEs who export, so that they can efficiently and effectively manage the exporting and market development process. Therefore, in the majority of the English regions, there are a range of publicly funded organisations providing advice, consultancy, information and training to SMEs wishing to trade internationally and those businesses already exporting. In addition, SMEs can access a number of export services from private sector organisations such as banks, accountants, freight forwarders and export agents. There has been no overall national ‘stocktake’ or audit of such provision. However, the need for such a stocktake is becoming increasingly important due to the introduction of a number of new support organisations into the institutional landscape and the re-organisation and re-branding of British Trade International as Trade Partners UK and the appointment of a series of Regional International Trade Directors. The introduction of the Small Business Service will have a major impact on the coverage and nature of provision for exporting SMEs within each of the English regions. The introduction of the Small Business Service, however, provides an opportunity to explore and examine alternative configurations of small business support and the types of organisation that are best placed to satisfy the needs of exporting SMEs. This paper presents the key findings to emerge from an audit of export services within each of the English regions. Based on a research and development project undertaken in conjunction with Trade Partners UK, the paper offers insights into: • The coverage of export services available to SMEs within England; • The effectiveness and appropriateness of current configuration of export services; • The ways in which the effectiveness of the current configuration of export services could be enhanced. The audit was based on a series of face-to-face and telephone interviews with local, regional and national providers of export provision. A key argument within the paper is that effective configurations of export and trade development support arise from insights into, and appropriate responses to, the exporting and trade development process as experienced by SMEs. The paper concludes with a number of implications in terms of how business-driven forms of support can be developed.</p

The measurement of very low conductivity and dielectric loss in XLPE cables: A possible method to detect degradation due to thermal aging

The dielectric response of crosslinked polyethylene (XLPE) insulated, miniature power cables, extruded with inner and outer semicons, was measured over the frequency range 10-4 to 104 Hz at temperatures from 20 to 100 °C. A dielectric spectrometer was used for the frequency range 10-4 to 10-2 Hz. A bespoke noise-free power supply was constructed and used to measure the dc conductivity and, using a Fourier transform technique, it was also used to measure the very low dielectric tanδ losses encountered at frequencies of 1 to 100 Hz. Tanδ measurements of <;10-5 were found in this frequency range and attributed to a β-mode dielectric relaxation lying above 100 Hz due to motion of chain segments in the amorphous region and an β-mode relaxation lying below 1 Hz window due to twists of chains in the crystal lamellae. The dc conductivity measurements were consistent with those of the dielectric spectrometer and indicate lower dc conductivities in vacuum degassed cables than have been previously reported for XLPE (less than 10-17 S.m-1). The conduction process is thermally activated with an activation energy of approximately 1.1 eV. Higher conductivities were found for non-degassed cables. A transformer ratio bridge was used for measurements in the range 1 to 10 kHz; loss in this region was shown to be due to the series resistance of the semicon layers. Thermal ageing of the cables at 135 °C for 60 days caused significant increases in the conductivity and tanδ and it is considered that such measurements may be a sensitive way of measuring electrical degradation due to thermal aging

Variation in Lepidopteran Occurrence in Hemlock-Dominated and Deciduous-Dominated Forests of Central Appalachia

Eastern hemlock, (Tsuga canadensis Carrière, Pinaceae), is threatened with extirpation by an exotic invasive herbivore, the hemlock woolly adelgid, (Adelges tsugae Annand, Homoptera: Adelgidae). Given this threat, a broader and more detailed knowledge of the community associated with eastern hem- lock is merited. As Lepidoptera are important members of forest communities, this study was initiated to determine the relative occurrence of Lepidoptera in hemlock-dominated and deciduous-dominated habitats by evaluating abundance, species richness, temporal variation, and composition overlap. Lepidoptera were surveyed using blacklight traps from May – August 2010 at two collection sites in the Appalachian region of eastern Kentucky. The first collection site was within a forest stand dominated by mixed deciduous species, the second site possessed an overstory of eastern hemlock. Lepidoptera ≥ 20 mm in wingspan were identified and enumerated, yielding a total of 1,020 individuals of ≥ 137 species and 18 families. The total number of Lepidoptera captured in May and June was fewer than in July and August (P ≤ 0.05). The composition of the assemblage varied between collection sites as well as seasonally; 85 species were identified at the deciduous site and 107 species were identified at the hemlock site. While 27 species were recorded only at the deciduous site, 49 species were unique to the hemlock site. Of those unique to the hemlock site, five species were either detritivores or conifer specialists. These data demonstrate the importance of both deciduous and hemlock-dominated forest habitats for many species of Lepidoptera in Appalachia. Our study forms a foundation for understanding species richness patterns of Lepidoptera in hemlock forests in North America and is a useful baseline for comparisons of richness and diversity post invasion by the hemlock woolly adelgid

A simple operational interpretation of the fidelity

This note presents a corollary to Uhlmann's theorem which provides a simple operational interpretation for the fidelity of mixed states.Comment: 1 pag