Systems thinking: critical thinking skills for the 1990s and beyond

This pdf article discusses the need for teaching systems thinking and critical thinking skills. Systems thinking and systems dynamics are important for developing effective strategies to close the gap between the interdependent nature of our problems and our ability to understand them. This article calls for a clearer view of the nature of systems thinking and the education system into which it must be transferred. Educational levels: Graduate or professional

Thin film process forms effective electrical contacts on semiconductor crystals

Process makes microscopic, low-resistance electrical contacts on hexagonal n-type silicon carbide crystals used for microelectronic devices. A vacuum deposition of aluminum is etched to expose the bare silicon carbide where the electrical contacts are made. Sputtering alternating layers of tantalum and gold forms the alloy film

Helical motion of magnetic flux tubes in the solar atmosphere

Photospheric granulation may excite transverse kink pulses in anchored vertical magnetic flux tubes. The pulses propagate upwards along the tubes with the kink speed, while oscillating wakes are formed behind the wave front in a stratified atmosphere. The wakes oscillate at the kink cut-off frequency of stratified medium and gradually decay in time. When two or more consecutive kink pulses with different polarizations propagate in the same thin tube, then the wakes corresponding to different pulses may superimpose. The superposition sets up helical motions of magnetic flux tubes in the photosphere/chromosphere as seen by recent Hinode movies. The energy carried by the pulses is enough to heat the solar chrmosphere/corona and accelerate the solar wind.Comment: Accepted in ApJ

Experimental results of the control of a vortical flow by tangential blowing

The results of a wind tunnel test to investigate the controlling effects of tangential, leading edge blowing on the vortical flow over a delta wing are given. Blowing is used to directly control the crossflow separation points at the rounded leading edge and hence, the trajectory of the feeding sheet and the location of the vortex. Experiments were conducted for both co-flowing and counter-flowing configurations over a range of angles of attack from 0 to 90 degrees. Results in the form of pressure distributions, overall force coefficients and flow mappings were obtained. The emphasis is on data presentation rather than detailed analysis. The initial results indicate that the co-flowing configuration was capable of extending the regime of stable, controlled vortical flow over the upper surface by approximately 30 degrees angle of attack for modest blowing requirements. Increases in maximum normal force coefficient of approximately 30% were achieved and significant rolling moments produced at angles of attack from 30 to 60 degrees. The counter-flowing configuration indicated only minor lift augmentation with the exception of an isolated occurrence at 20 degrees angle of attack. At that condition, with very weak blowing, a lift augmentation of approximately 20 was measured

Force on a moving point impurity due to quantum fluctuations in a Bose-Einstein condensate

An analytic expression is derived for a force on a weak point impurity arising from the scattering of quantum fluctuations in a slow-moving, weakly interacting, three-dimensional Bose-Einstein condensate at zero temperature. In an infinitely extended geometry, this force is shown to exist at any arbitrarily small flow velocity below Landau's critical velocity. Furthermore, this force is shown to be directly proportional to the flow speed.Comment: v2: corrected notation and other minor change

A Multi-Dimensional Trust Model for Heterogeneous Contract Observations

In this paper we develop a novel probabilistic model of computational trust that allows agents to exchange and combine reputation reports over heterogeneous, correlated multi-dimensional contracts. We consider the specific case of an agent attempting to procure a bundle of services that are subject to correlated quality of service failures (e.g. due to use of shared resources or infrastructure), and where the direct experience of other agents within the system consists of contracts over different combinations of these services. To this end, we present a formalism based on the Kalman filter that represents trust as a vector estimate of the probability that each service will be successfully delivered, and a covariance matrix that describes the uncertainty and correlations between these probabilities. We describe how the agents’ direct experiences of contract outcomes can be represented and combined within this formalism, and we empirically demonstrate that our formalism provides significantly better trustworthiness estimates than the alternative of using separate single-dimensional trust models for each separate service (where information regarding the correlations between each estimate is lost)

Aiming for the quiet eye in biathlon

The duration of the so-called "Quiet Eye" (QE) - the final fixation before the initiation of a critical movement - seems to be linked to better perceptual-motor performances in various domains. For instance, experts show longer QE durations when compared to their less skilled counterparts. The aim of this paper was to replicate and extend previous work on the QE [Vickers and Williams 2007] in elite biathletes in an ecologically valid environment. Specifically, we tested whether longer QE durations result in higher shooting accuracy. To this end, we developed a gun-mounted eye tracker as a means to obtain reliable gaze data without interfering with the athletes' performance routines. During regular training protocols we collected gaze and performance data of 9 members (age 19.8 ± 0.45) of the German national junior team. The results did not show a significant effect of QE duration on shooting performance. Based on our findings, we critically discuss various conceptual as well as methodological issues with the QE literature that need to be aligned in future research to resolve current inconsistencies.The duration of the so-called "Quiet Eye" (QE) - the final fixation before the initiation of a critical movement - seems to be linked to better perceptual-motor performances in various domains. For instance, experts show longer QE durations when compared to their less skilled counterparts. The aim of this paper was to replicate and extend previous work on the QE [Vickers and Williams 2007] in elite biathletes in an ecologically valid environment. Specifically, we tested whether longer QE durations result in higher shooting accuracy. To this end, we developed a gun-mounted eye tracker as a means to obtain reliable gaze data without interfering with the athletes' performance routines. During regular training protocols we collected gaze and performance data of 9 members (age 19.8 ± 0.45) of the German national junior team. The results did not show a significant effect of QE duration on shooting performance. Based on our findings, we critically discuss various conceptual as well as methodological issues with the QE literature that need to be aligned in future research to resolve current inconsistencies

Slow solitary waves in multi-layered magnetic structures

The propagation of slow sausage surface waves in a multi-layered magnetic configuration is considered. The magnetic configuration consists of a central magnetic slab sandwiched between two identical magnetic slabs (with equilibrium quantities different from those in the central slab) which in turn are embedded between two identical semi-infinite regions. The dispersion equation is obtained in the linear approximation. The nonlinear governing equation describing waves with a characteristic wavelength along the central slab much larger than the slab thickness is derived. Solitary wave solutions to this equation are obtained in the case where these solutions deviate only slightly from the algebraic soliton of the Benjamin-Ono equation

Risk Factors for Anaemia Among HIV Infected Children Attending Care and Treatment Clinic at Muhimbili National Hospital in Dar es Salaam, Tanzania

There is paucity of data describing the risk factors for anaemia among HIV infected children in Tanzania. This cross sectional study was carried out to determine the contributing factors for anaemia among HIV-infected children attending Muhimbili National Hospital in Dar es Salaam. Both univariate and multivariate logistic regression analyses were performed to identify possible factors associated with anaemia in HIV-infected children. A total of 75 (44%) patients among 167 recruited HIV-infected children aged 6 months to 59 months of were found to be anaemic (Hg<11g/dl). Multivariate logistic regression demonstrated that not being on HAART (OR 3.40, 95%CI (1.20-9.60), having CD4% <25% (OR 2.30, 95%CI (1.20-34.60), having a history of tuberculosis (TB) (OR 3.23, 95%CI (1.10-9.70) and having hookworm infestation (OR 5.97, 95%CI (1.92-18.4) were independent risk factors for anaemia among HIV infected children. The analyses also showed that being HIV positive for ≥ 2.5 years resulted into a low risk of severe anaemia compared to being HIV positive for < 2.5 years. Taking multivitamins (OR 0.07, 95%, CI (0.020-0.30) and antihelminthics (OR 0.27, 95%CI (0.10-0.74) were also protective against anaemia in children. Similar factors (with exception of using antihelmintics) were associated with severe anaemia. In conclusion the factors associated with anaemia in HIV infected children were multifactorial in nature. Efforts to correct anaemia in HIV infected children should include use of HAART and treatment of infections such as TB and hookworms

Mock Catalogs for UHECR Studies

We provide realistic mock-catalogs of cosmic rays above 40 EeV, for a pure proton composition, assuming their sources are a random subset of ordinary galaxies in a simulated, volume-limited survey, for various choices of source density: 10^-3.5 Mpc^-3, 10^-4.0 Mpc^-3 and 10^-4.5 Mpc^-3. The spectrum at the source is taken to be E^-2.3 and the effects of cosmological redshifting as well as photo-pion and e^+ e^- energy losses are included.Comment: 7 pages, 4 figure