7,783 research outputs found
Entrepreneurship as nexus of change: the syncretistic production of the future
This paper deals with the issue of how the future is created and the mechanisms through which it is produced and conceived. Key to this process appears to be social interaction and how it is used to bring about change. Examining the entrepreneurial context by qualitative longitudinal research techniques, the study considers the situations of three entrepreneurs. It demonstrates that the web of relationships in which individuals are engaged provide the opportunity to enact the environment in new ways, thus producing organizations for the future. It further provides empirical evidence for a Heideggerian reading of strategy-as-practice, extending this conceptualization to account for the temporal dimension
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
A genotyping protocol for multiple tissue types from the polyploid tree species Sequoia sempervirens (Cupressaceae).
Premise of the studyIdentifying clonal lineages in asexually reproducing plants using microsatellite markers is complicated by the possibility of nonidentical genotypes from the same clonal lineage due to somatic mutations, null alleles, and scoring errors. We developed and tested a clonal identification protocol that is robust to these issues for the asexually reproducing hexaploid tree species coast redwood (Sequoia sempervirens).MethodsMicrosatellite data from four previously published and two newly developed primers were scored using a modified protocol, and clones were identified using Bruvo genetic distances. The effectiveness of this clonal identification protocol was assessed using simulations and by genotyping a test set of paired samples of different tissue types from the same trees.ResultsData from simulations showed that our protocol allowed us to accurately identify clonal lineages. Multiple test samples from the same trees were identified correctly, although certain tissue type pairs had larger genetic distances on average.DiscussionThe methods described in this paper will allow for the accurate identification of coast redwood clones, facilitating future studies of the reproductive ecology of this species. The techniques used in this paper can be applied to studies of other clonal organisms as well
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 âflatâ dielectric response in the frequency range considered. The influence of possible interfacial features on the measured results is discussed
Influence of absorbed moisture on the dielectric properties of epoxy resins
The dielectric response of two bisphenol-A epoxy resin systems Araldite CY1301 (Tg ~ 50°C) and Araldite CY1311 (Tg ~0°C) was studied at different levels of absorbed moisture. The dielectric measurements were carried out over the frequency range 1 mHz to 100 kHz and the results were characterised in terms of dc bulk electrical conduction and dielectric processes. The characteristic parameters (frequency and magnitude) of all processes have been found to be moisture dependent. In both resins above the glass transition temperature, absorbed moisture was found to be implicated in the formation of a bulk quasi-dc dielectric response consistent with cluster formation of the absorbed water molecules
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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
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Dielectric spectroscopy study of thermally-aged extruded model power cables
âModelâ extruded power cables, having a much reduced geometry but using the same extrusion techniques and materials as full-sized cables, have been examined using dielectric spectroscopy techniques to study their thermal ageing effects. Cables insulated with homo-polymer XLPE and co-polymer of XLPE with micron-sized ethylene-butyl-acrylate (EBA) islands were studied by both frequency-domain and time-domain dielectric spectroscopy techniques after accelerated thermal ageing under 135°C for 60 days. In the frequency domain, a frequency response analyzer (FRA) was used to measure the frequency range from 10-4Hz to 1Hz at temperatures from 20°C to 80°C. In the time domain, a special charging/discharging current measurement system was developed to measure the frequencies from 10-1Hz to 102Hz. These techniques were chosen to cope with the extremely low dielectric losses of the model cables. The results are compared with those from new model power cables that were degassed at 80°C for 5 days. Thermal ageing was found to increase the low-frequency conductivity, permittivity and the discharging current. Both homo- and co-polymer cables have substantial increase of dielectric loss after ageing
How Does a Dipolar Bose-Einstein Condensate Collapse?
We emphasize that the macroscopic collapse of a dipolar Bose-Einstein
condensate in a pancake-shaped trap occurs through local density fluctuations,
rather than through a global collapse to the trap center. This hypothesis is
supported by a recent experiment in a chromium condensate.Comment: Proceedings of 17th International Laser Physics Worksho
The Effects of Tree Density on Pasture Production Under Acacia Melanoxylon
Silvi-pastoral systems could contribute to greater total productivity and more sustainable land management of grazed pastures in New Zealand. Despite this potential, little is known of the interactions of tree species and environment on pasture growth. In this paper we report the effects of tree density on pasture yield in an Acacia melanoxylon silvi-pastoral system. The results show decreasing pasture yield with increasing tree density, although the extent of the reduction is less than would be expected under Pinus radiata. Results suggest that shade is the dominant factor causing yield decline in this study, while reduced N availability is clearly implicated in previous studies with pine trees. This study will provide more data on which a mechanistic model of tree-pasture interactions can be based
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