Network Position and Throughput Performance of Seaports

ISBN 978 90 5487 858 2The determinants of throughput volume at a given set of ports have rarely been approached from a network perspective. This paper proposes a set of novel indicators describing the relative situation of seaports in the worldwide maritime network of container shipping in 2006, which are distinguished among five categories: circulation (calls, vessels, and operators), foreland (distance to other ports and distribution of connections), connectivity itself (number of connections to other ports), centrality (betweenness and eccentricity), and neighbourhood (strength and clustering indices). Main results help to classify ports according to their location and function in the network, while they stress which parameters most influence throughput volumes. Although centrality indicators highly correlate with throughput, the latter seems to be influenced mostly by the geographic parameter of the maximum distance link to another port

Information erasure and the generalized second law of black hole thermodynamics

We consider the generalized second law of black hole thermodynamics in the light of quantum information theory, in particular information erasure and Landauer’s principle (namely, that erasure of information produces at least the equivalent amount of entropy). A small quantum system outside a black hole in the Hartle-Hawking state is studied, and the quantum system comes into thermal equilibrium with the radiation surrounding the black hole. For this scenario, we present a simple proof of the generalized second law based on quantum relative entropy. We then analyze the corresponding information erasure process, and confirm our proof of the generalized second law by applying Landauer’s principle

The Quantum Interest Conjecture

Although quantum field theory allows local negative energy densities and fluxes, it also places severe restrictions upon the magnitude and extent of the negative energy. The restrictions take the form of quantum inequalities. These inequalities imply that a pulse of negative energy must not only be followed by a compensating pulse of positive energy, but that the temporal separation between the pulses is inversely proportional to their amplitude. In an earlier paper we conjectured that there is a further constraint upon a negative and positive energy delta-function pulse pair. This conjecture (the quantum interest conjecture) states that a positive energy pulse must overcompensate the negative energy pulse by an amount which is a monotonically increasing function of the pulse separation. In the present paper we prove the conjecture for massless quantized scalar fields in two and four-dimensional flat spacetime, and show that it is implied by the quantum inequalities.Comment: 17 pages, Latex, 3 figures, uses eps

Osteoarthritis prevalence in retired national football league players with a history of ankle injuries and surgery

Context: Ankle injuries are common at all levels of American football, and retired National Football League (NFL) players have a high prevalence of osteoarthritis (OA), but little is known about how ankle injuries influence OA prevalence and daily activities in this population or how surgical interventions for such injuries alter the risk of OA. Objective: To examine (1) the association of ankle-injury history with OA prevalence, (2) the association of surgical intervention after ankle injury with OA prevalence, and (3) the relationships among ankle injuries, reported OA, and daily activities in retired NFL players. Design: Case-control study. Setting: Survey. Patients or Other Participants: Data from the Retired NFL Players General Health Survey. Main Outcome Measure(s): We created a 7-category main exposure variable that differentiated respondents by football-related ankle injury and surgical intervention. Multivariable binomial regression models were used to estimate prevalence ratios and 95% confidence intervals. Among those reporting OA, we examined the distribution of responses regarding whether OA affected daily activities. Results: Among the 2446 respondents, 920 participants experienced OA in any joint during their lifetime. Compared with those reporting no ankle injuries, the prevalence of OA was higher among those with a history of ankle injury. Also, the prevalence of OA was higher among those who had undergone surgery versus those who had not. The number of retired NFL players who reported that OA often affected their daily activities increased with the number of ankle injuries. Conclusions: Among former NFL players, a history of ankle injury increased the prevalence of OA. More ankle injuries increased the probability that OA negatively affected daily activities. Future prospective research is needed to better determine the influence of surgical intervention at the ankle or foot on OA

A Statistical Study on the Morphology of Rays and Dynamics of Blobs in the Wake of Coronal Mass Ejections

In this paper, with a survey through the Large Angle and Spectrometric Coronagraph (LASCO) data from 1996 to 2009, we present 11 events with plasma blobs flowing outwards sequentially along a bright coronal ray in the wake of a coronal mass ejection. The ray is believed to be associated with the current sheet structure that formed as a result of solar eruption, and the blobs are products of magnetic reconnection occurring along the current sheet. The ray morphology and blob dynamics are investigated statistically. It is found that the apparent angular widths of the rays at a fixed time vary in a range of 2.1-6.6 (2.0-4.4) degrees with an average of 3.5 (2.9) degrees at 3 (4) Rs, respectively, and the observed durations of the events vary from 12 h to a few days with an average of 27 h. It is also found, based on the analysis of blob motions, that 58% (26) of the blobs were accelerated, 20% (9) were decelerated, and 22% (10) moved with a nearly-constant speed. Comparing the dynamics of our blobs and those that are observed above the tip of a helmet streamer, we find that the speeds and accelerations of the blobs in these two cases differ significantly. It is suggested that these differences of the blob dynamics stem from the associated magnetic reconnection involving different magnetic field configurations and triggering processes.Comment: 12 pages, 6 figures, accepted by Solar Physic

Geomagnetic storm dependence on the solar flare class

Content. Solar flares are often used as precursors of geomagnetic storms. In particular, Howard and Tappin (2005) recently published in A&A a dependence between X-ray class of solar flares and Ap and Dst indexes of geomagnetic storms which contradicts to early published results. Aims. We compare published results on flare-storm dependences and discuss possible sources of the discrepancy. Methods. We analyze following sources of difference: (1) different intervals of observations, (2) different statistics and (3) different methods of event identification and comparison. Results. Our analysis shows that magnitude of geomagnetic storms is likely to be independent on X-ray class of solar flares.Comment: 3 pages, 1 tabl

Observed Effect of Magnetic Fields on the Propagation of Magnetoacoustic Waves in the Lower Solar Atmosphere

We study Hinode/SOT-FG observations of intensity fluctuations in Ca II H-line and G-band image sequences and their relation to simultaneous and co-spatial magnetic field measurements. We explore the G-band and H-line intensity oscillation spectra both separately and comparatively via their relative phase differences, time delays and cross-coherences. In the non-magnetic situations, both sets of fluctuations show strong oscillatory power in the 3 - 7 mHz band centered at 4.5 mHz, but this is suppressed as magnetic field increases. A relative phase analysis gives a time delay of H-line after G-band of 20\pm1 s in non-magnetic situations implying a mean effective height difference of 140 km. The maximum coherence is at 4 - 7 mHz. Under strong magnetic influence the measured delay time shrinks to 11 s with the peak coherence near 4 mHz. A second coherence maximum appears between 7.5 - 10 mHz. Investigation of the locations of this doubled-frequency coherence locates it in diffuse rings outside photospheric magnetic structures. Some possible interpretations of these results are offered.Comment: 19 pages, 6 figure