Many superconducting materials are composed of weakly coupled conducting layers. Such a layered structure has a very strong influence on the properties of vortex matter in a magnetic field. This ...review focuses on the properties of the Josephson vortex lattice generated by the magnetic field applied in the direction of the layers. The theoretical description is based on the Lawrence-Doniach model in the London limit, which takes only the phase degree of freedom of the superconducting order parameter into account. In spite of its simplicity, this model leads to an amazingly rich set of phenomena. We review in detail the structure of an isolated vortex line and various properties of the vortex lattice, in both dilute and dense limits. In particular, we extensively discuss the influence of the layered structure and thermal fluctuations on the selection of lattice configurations at different magnetic fields.
Background: Electrical nerve stimulation is commonly used to perform peripheral nerve blocks. The purpose of this study was to investigate the relation between stimulating currents and the distance ...between the needle‐tip and stimulated nerves.
Methods: In 18 volunteers the radial and ulnar nerves were stimulated in the elbow region from opposite directions. Needle‐to‐nerve distances were measured by high‐frequency ultrasound when motor responses to electrical stimulation were elicited with currents of 5, 2, 1 and 0.5 mA and impulse widths of 0.1 ms. Additionally, current thresholds for nerve stimulation were identified when the needle‐tip was in contact with the nerve.
Results: The ulnar nerves responded to electrical stimulation from a significantly greater distance than the radial nerves. Threshold levels at needle‐to‐nerve contact ranged from 0.4 to 4.5 mA for the radial nerve and from 0.32 to 2.0 mA for the ulnar nerve. They were significantly lower for the ulnar nerve than for the radial nerve. Currents required to obtain neuromuscular responses often exceeded the recommended current levels for nerve stimulation.
Conclusions: Our results show significant differences in the ease of stimulation between the radial and ulnar nerves. High current thresholds and short nerve‐to‐needle distances were often needed to obtain neuromuscular responses in two nerves in the elbow region.
Innovation and entrepreneurship are based on new combinations, constructed within social networks. The literature on social networks refers to Schumpeter's analysis of new combinations, but is ...limited in its use of his understanding of the range of innovations and long-term aspects of entrepreneurship. Using the case of Josiah Wedgwood, a quintessential Schumpeterian entrepreneur, this article analyses how social networks contribute to a broad range of innovations over an extended period, involving both strong and weak ties. It shows how social network research in innovation and entrepreneurship benefits from Schumpeterian insights on the wide forms of innovation and longer term influences on network structures.
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•Case study of innovation strategy in Crossrail, a major transportation project.•Crossrail is Europe’s largest infrastructure project.•Large transportation projects in the past have ...not managed to innovate strategically.•Crossrail has strategic systems and practices to encourage innovation.
This article examines how innovation can be strategically incorporated into transportation systems. Large transportation systems generally have a poor record in systematically integrating innovation in their development, construction and operation. Our research setting is Crossrail, a major new railway traversing London, where the creation and implementation of an innovation strategy formalized and systemized its approach to innovation. Based on in-depth, semi-structured interviews with project leaders and participant observation, the paper critically analyses the formulation, implementation and performance of Crossrail’s innovation strategy. Crossrail’s management explicitly uses an ‘open innovation’ strategy that incentivizes partners, contractors, and clients to innovate in the project. Its strategy guides decisions and priorities on innovation and the types and levels of innovation that best match project aims. The paper holds lessons for those developing, operating and studying large transportation systems both now and into the future.
Precision measurements of the vortex phase diagram in single crystals of the layered superconductor Bi2Sr2CaCu2O8+delta in oblique magnetic fields confirm the existence of a second phase transition, ...in addition to the usual first-order vortex-lattice melting line Hm(T). The transition has a strong first-order character, is accompanied by strong hysteresis, and intersects the melting line in a tricritical point (Hm perpendicular, Hcr parallel). Its field dependence and the changing character of the melting line at the tricritical point strongly suggest that the ground state for magnetic fields closely aligned with the superconducting layers is a lattice of uniformly tilted vortex lines.
We calculate the melting line of the pancake-vortex system in a layered superconductor, interpolating between two-dimensional (2D) melting at high fields and the zero-field limit of single-stack ...evaporation. Long-range interactions between pancake vortices in different layers permit a mean-field approach, the "substrate model, " where each 2D crystal fluctuates in a substrate potential due to the vortices in other layers. We find the thermal stability limit of the 3D solid, and compare the free energy to a 2D liquid to determine the first-order melting transition and its jump in entropy.
Deceleration without dark matter Jackson, J. C.; Dodgson, Marina
Monthly Notices of the Royal Astronomical Society,
03/1997, Letnik:
285, Številka:
4
Journal Article
Recenzirano
Odprti dostop
In homogeneous isotropic cosmological models the angular size θ of a standard measuring rod changes with redshift z in a manner that depends upon the parameters of the model. It has been argued that ...as a population ultracompact (milliarcsecond) radio sources measured by very long-baseline interferometry (VLBI) do not evolve with cosmic epoch, and thus comprise a set of standard objects, at least in a statistical sense. Here we examine the angular-size/redshift relation for 256 ultracompact sources with z in the range 0.5 to 3.8 for cosmological models with two degrees of freedom (Ω0 and Λ0,). The canonical inflationary cold dark matter model (Ω0 = 1, Λ0 = 0) appears to be ruled out by the observed relationship, whereas low-density models with a cosmological constant of either sign are favoured.
The dynamics of national innovation systems (NISs) are a source of considerable academic and policy interest, especially when to address new competitive challenges they involve changing institutions ...and relationships within successful systems. This paper examines the case of Taiwan which is embarking on a new phase in its approach to building its national innovative capacity through creating the infrastructure for a biotechnology industry. By examining the process and mechanisms by which new biotechnology innovation networks are being created, and contrasting their development with existing networks, we analyse the dynamics of Taiwan's NIS. The paper reviews the prospects for this new phase in Taiwan's transition from ‘imitation’ to ‘innovation’. The paper aims to add to the understanding of how innovation systems evolve. It is concerned with the contributors, processes and challenges of NIS evolution and the form and meaning of its dynamic changes.
Significant new university initiatives are usually analysed from the perspectives of government policy, university strategy or the entrepreneurship of particular individuals, but rarely from the view ...of their interdependencies. This paper reports on the creation of four Smart State Institutes at the University of Queensland in Australia and the concatenation of circumstances, decisions and actions that led to their formation. In the course of just over a decade, these Institutes, addressing biotechnology, nanotechnology, neuroscience and the molecular and cellular basis of disease, have developed into a cluster of scientific research of global significance, raising over $1 billion in investment and employing 1300 staff. A case study approach was employed in the analysis, involving 59 semi-structured interviews with key individuals involved at the organisational, regional and national levels. A range of archival data were collected and analysed to help construct a rigorous chronology of the key events, reports and actions that led to the development of the Institutes. Our research identifies the importance of the policy context, at both the Federal and State levels, conducive to the investment in the new Institutes. It shows how the University's leadership and strategy took advantage of policy conditions, with a number of individual academic entrepreneurs providing the actions necessary to shape and guide the creation of the Institutes. Private philanthropy played a crucial role as animateur amongst the contributors. We argue the importance of the mutually reinforcing and concurrent contribution of all these actors and draw lessons for future government and university policy.
A randomized, double-blind, placebo-controlled single oral dose study was done in order to examine whether codeine has an additive analgesic effect to that of paracetamol for moderate and strong ...postoperative pain after abdominal surgery. The maximum recommended single dose of paracetamol 1000 mg (Paracet) was compared with a combination of a submaximal dose of paracetamol 800 mg plus codeine 60 mg (Paralgin forte) and placebo for pain relief after Caesarean section in 125 patients.
Visual analogue pain intensity score (VAS 0-100 mm) and categorical pain relief score were recorded for 6 hours after the study drug intake. The main efficacy variables analyzed were: pain intensity difference and summed pain intensity differences during the first 3 and 6 h after study drug intake, total pain relief during the first 3 and 6 h, global evaluation score at the end of the observation period, and time to rescue analgesic.
Because of protocol violations, 17 patients were excluded from the analysis of effects. Among the 108 patients included in the analysis of analgesic effect, 49 patients had moderate baseline pain (VAS between 40 and 60 mm on a 100 mm scale), and 59 patients had strong baseline pain (VAS more than 60 mm). In patients with strong baseline pain, statistically highly significant differences were documented in efficacy variables between the active drugs and placebo and between the two active drugs. However, in patients with moderate baseline pain, no differences were found between the study drugs in any of the analgesic efficacy variables.
This study thus confirms that codeine has additive analgesic effect to paracetamol in pain after surgery. Our results show the importance of initial pain intensity in postoperative assessment of analgesic drugs. Assay-sensitivity and test power are increased by selecting patients with sufficiently high initial pain intensity and by comparing groups of patients with identical surgery and similar demographic variables.
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