Computer simulations of two-dimensional melting with dipole-dipole interactions

We perform molecular dynamics and Monte Carlo simulations of two-dimensional melting with dipole-dipole interactions. Both static and dynamic behaviors are examined. In the isotropic liquid phase, the bond orientational correlation length 6 and susceptibility 6 are measured, and the data are fitted to the theoretical ansatz. An algebraic decay is detected for both spatial and temporal bond orientational correlation functions in an intermediate temperature regime, and it provides an explicit evidence for the existence of the hexatic phase. From the finite-size scaling analysis of the global bond orientational order parameter, the disclination unbinding temperature Ti is estimated. In addition, from dynamic Monte Carlo simulations of the positional order parameter, we extract the critical exponents at the dislocation unbinding temperature Tm. All the results are in agreement with those from experiments and support the Kosterlitz-Thouless-Halperin-Nelson-Young (KTHNY) theory.Comment: 23 pages, 12figure

Compressible flow structures interaction with a two-dimensional ejector: a cold-flow study

An experimental study has been conducted to examine the interaction of compressible flow structures such as shocks and vortices with a two-dimensional ejector geometry using a shock-tube facility. Three diaphragm pressure ratios ofP4 =P1 = 4, 8, and 12 have been employed, whereP4 is the driver gas pressure andP1 is the pressure within the driven compartment of the shock tube. These lead to incident shock Mach numbers of Ms = 1:34, 1.54, and 1.66, respectively. The length of the driver section of the shock tube was 700 mm. Air was used for both the driver and driven gases. High-speed shadowgraphy was employed to visualize the induced flowfield. Pressure measurements were taken at different locations along the test section to study theflow quantitatively. The induced flow is unsteady and dependent on the degree of compressibility of the initial shock wave generated by the rupture of the diaphragm

Cartoon controversies: law student views about free speech and Zapiro’s satirisation of South Africa’s president

Although the Constitutional Court has been a protector of freedom of expression, major controversies about speech illustrate deep divisions among South Africans. This article explores attitudes of law students at the University of the Witwatersrand to freedom of expression. The authors take the realist view that these students are future legal interpreters of the Constitution and their attitudes may well have an impact on future jurisprudence. They follow-up previous research which measured attitudes to political freedom of expression by asking students about their responses to a sample of Zapiro cartoons depicting President Zuma. After exploring the role of cartoons in a democracy, the article looks at new data obtained by questioning final year students about the same cartoons four years after the initial study. The new data substantially confirms earlier results which indicate that Wits students would not robustly support Zapiro’s right to create his more controversial caricatures. This result reinforces the view that supporters of freedom of expression in South Africa may not be able to call upon consistent or robust elite and popular support in resisting banning or criminalisation of speech.MM2017http://www.tandfonline.com/doi/full/10.1080/02587203.2017.133884

Performance Gap Between Men and Women in Ironman Triathlons

PURPOSE: The increased participation and performance improvement of women in Ironman triathlons (IM) have been showing that the performance gap with men is shorter than ever. Thus, this study aimed to explore this performance gap by discipline (swimming, cycling, and running) and age-groups. METHODS: Publicly available data from all IM events from 2002 to 2022 were used for this analysis. Each performance variable (swimming, cycling, running, and overall) were included as dependent variables in general linear model with gender and category (elite, age-groups) as independent factors. The effect size (Cohen’s d and delta percentage) was calculated for every “male vs. female” comparison. RESULTS: A total of 741,973 entries were analyzed (women=145,008; men=596,965) and 12,670 of those were categorized as elite. For elite athletes, the running portion presented the smallest performance gap (7.3%, d = 0.432), whereas cycling and swimming showed a similar gap (swim: 10.7%, d=0.676; cycle: 10.0%, d = 1.132). For age-groupers, the largest gap was cycling (7.87%, d =0.633). In addition, age-groupers between 30 and 49 years showed the largest performance gap (7.9% - 8.0%), when compared to younger (old) or older (\u3e49 years old) athletes (5.0 – 6.9%). CONCLUSION: Overall, men consistently outperform women in all three disciplines of IM. However, the performance gap varies based on age group, level, and discipline. While elite athletes have small performance gaps in running, age-groupers have their largest performance gap in cycling. Additionally, age-groupers within 30-49 years of age have the largest performance gap amongst amateur athletes in IM

Patterns of ‘balancing between hope and despair’ in the diagnostic phase: a grounded theory study of patients on a gastroenterology ward

Aim: The aim of the study was to learn how patients going through the diagnostic phase experienced and handled their situation. Background: Many studies report about the stressful diagnostic phase; however, none has presented a conceptual theory where the concepts are sufficiently related to each other. The Theory of Preparative Waiting has previously been published as a descriptive grounded theory and describes the experience of a group of gastroenterology patients going through the diagnostic phase. Method: A classical grounded theory design was used, with data derived from 18 in-depth interviews with 15 patients in a gastroenterology ward at a Norwegian University Hospital. Interviews were conducted during 2002–2003. Findings: Participants’ main concern was found to be how they could prepare themselves for the concluding interview and life after diagnosis. The theoretical code of ‘balancing’ had four patterns; controlling pain, rational awaiting, denial, and accepting. These patterns of ‘balancing’ guided how participants used the categories of ‘Preparative Waiting Theory’ ‘seeking and giving information’, ‘interpreting clues’, ‘handling existential threats’ and ‘seeking respite’. Patterns were strategies, so one person could use more than one pattern. Conclusion: The diagnostic phase was a difficult time for the participants and the ‘Preparative Waiting Theory’ can assist nurses in assessing how patients prepare themselves differently for getting a diagnosis. All patients would find it helpful to be followed up by a designated contact person at the ward; however, patients using mostly the patterns of controlling pain and denial would benefit most from such support

Error-resistant Single Qubit Gates with Trapped Ions

Coherent operations constitutive for the implementation of single and multi-qubit quantum gates with trapped ions are demonstrated that are robust against variations in experimental parameters and intrinsically indeterministic system parameters. In particular, pulses developed using optimal control theory are demonstrated for the first time with trapped ions. Their performance as a function of error parameters is systematically investigated and compared to composite pulses.Comment: 5 pages 5 figure

States prepared by decay

We consider the time evolution of a discrete state embedded in a continuum. Results from scattering theory can be utilized to solve the initial value problem and discuss the system as a model of wave packet preparation. Extensive use is made of the analytic properties of the propagators, and simple model systems are evaluated to illustrate the argument. We verify the exponential appearence of the continuum state and its propagation as a localized wave packet.Comment: 22 pages, Latex2.09, 6 Postscript figures embedded using psfig, see also http://www.physics.helsinki.fi/~kasuomin/ To appear in a Special Issue of Journal of Modern Optics (1997