Easy targets and the timing of conflict

Contestants have to choose whether to initiate a contest or war, or whether to remain peaceful for another period. We find that agents wait and initiate the contest once their rival is sufficiently weak to be an easy target. -- Die Gegner in einem potentiellen Konflikt müssen sich in jeder Periode entscheiden, ob sie den Konflikt eröffnen oder ob sie weiterhin friedlich bleiben. Wir zeigen, dass die Gegner warten und erst dann den Konflikt initiieren, wenn der Gegner hinreichend schwach und damit leicht zu besiegen ist.Timing of conflict,war,easy targets

Delay in contests

Why is there delay in contests? In this paper we follow and extend the line of reasoning of Carl von Clausewitz to explain delay. For a given contest technology, delay may occur if there is an asymmetry between defense and attack, if the expected change in relative strengths is moderate, and if the additional cost of investment in future strength is low. -- In Konfliktsituationen findet der ’showdown’ häufig mit einer Verzögerung statt. Das ist überraschend, weil sich mit der Verzögerung die Konfliktsituation bestenfalls für einen der beiden Kontrahenten verbessern kann. Derjenige, dessen Position im Konflikt sich verschlechtert, sollte eigentlich auf eine schnelle Konfliktlösung drängen. Carl von Clausewitz erklärte die mögliche Verzögerung aus der Vorteilhaftigkeit der Defensive: wer eine schnelle Konfliktlösung erzwingen will, muss in die Offensive. Wir bestätigen diese Einsicht von Clausewitz in einer formalen Analyse. Die Analyse ergibt ferner, dass auch ein schwacher Gegner zum Angreifer werden kann, wenn sich seine Position im Zeitablauf erheblich verschlechtert, und zeigt, dass zukünftige Kosten der Konfliktvorbereitung eher eine frühe Konfliktlösung begünstigen.Delay,contest,conflict

Dependence of the electronic structure of self-assembled InGaAs/GaAs quantum dots on height and composition

While electronic and spectroscopic properties of self-assembled In_{1-x}Ga_{x}As/GaAs dots depend on their shape, height and alloy compositions, these characteristics are often not known accurately from experiment. This creates a difficulty in comparing measured electronic and spectroscopic properties with calculated ones. Since simplified theoretical models (effective mass, k.p, parabolic models) do not fully convey the effects of shape, size and composition on the electronic and spectroscopic properties, we offer to bridge the gap by providing accurately calculated results as a function of the dot height and composition. Prominent results are the following. (i) Regardless of height and composition, the electron levels form shells of nearly degenerate states. In contrast, the hole levels form shells only in flat dots and near the highest hole level (HOMO). (ii) In alloy dots, the electrons' ``s-p'' splitting depends weakly on height, while the ``p-p'' splitting depends non-monotonically. In non-alloyed InAs/GaAs dots, both these splittings depend weakly on height. For holes in alloy dots, the ``s-p'' splitting decreases with increasing height, whereas the ``p-p'' splitting remains nearly unchaged. Shallow, non-alloyed dots have a ``s-p'' splitting of nearly the same magnitude, whereas the ``p-p'' splitting is larger. (iii) As height increases, the ``s'' and ``p'' character of the wavefunction of the HOMO becomes mixed, and so does the heavy- and light-hole character. (iv) In alloy dots, low-lying hole states are localized inside the dot. Remarkably, in non-alloyed InAs/GaAs dots these states become localized at the interface as height increases. This localization is driven by the biaxial strain present in the nanostructure.Comment: 14 pages, 12 figure

Singlet-triplet splitting, correlation and entanglement of two electrons in quantum dot molecules

Starting with an accurate pseudopotential description of the single-particle states, and following by configuration-interaction treatment of correlated electrons in vertically coupled, self-assembled InAs/GaAs quantum dot-molecules, we show how simpler, popularly-practiced approximations, depict the basic physical characteristics including the singlet-triplet splitting, degree of entanglement (DOE) and correlation. The mean-field-like single-configuration approaches such as Hartree-Fock and local spin density, lacking correlation, incorrectly identify the ground state symmetry and give inaccurate values for the singlet-triplet splitting and the DOE. The Hubbard model gives qualitatively correct results for the ground state symmetry and singlet-triplet splitting, but produces significant errors in the DOE because it ignores the fact that the strain is asymmetric even if the dots within a molecule are identical. Finally, the Heisenberg model gives qualitatively correct ground state symmetry and singlet-triplet splitting only for rather large inter-dot separations, but it greatly overestimates the DOE as a consequence of ignoring the electron double occupancy effect.Comment: 13 pages, 9 figures. To appear in Phys. Rev.

Undergraduate mechanical engineering design courses at the University of Johannesburg from an accreditation perspective

Abstract: The undergraduate Mechanical Engineering Design curriculum in the Department of Mechanical Engineering Science at the University of Johannesburg is discussed in this paper. The emphasis is on accreditation by the Engineering Council of South Africa (ECSA) and accompanying international accreditation through the Washington accord. The course content in the four undergraduate years of study is given in short. Measures to meet accreditation targets, including required exit level outcomes, set by ECSA are spelt out. The CDIO principle is also considered and the level of compliance with the CDIO requirements is indicated

Impact of Plant-Based Meat Alternatives on the Gut Microbiota of Consumers: A Real-World Study

Eating less meat is increasingly seen as a healthier, more ethical option. This is leading to growing numbers of flexitarian consumers looking for plant-based meat alternatives (PBMAs) to replace at least some of the animal meat they consume. Popular PBMA products amongst flexitarians, including plant-based mince, burgers, sausages and meatballs, are often perceived as low-quality, ultra-processed foods. However, we argue that the mere industrial processing of ingredients of plant origin does not make a PBMA product ultra-processed by default. To test our hypothesis, we conducted a randomised controlled trial to assess the changes to the gut microbiota of a group of 20 participants who replaced several meat-containing meals per week with meals cooked with PBMA products and compared these changes to those experienced by a size-matched control. Stool samples were subjected to 16S rRNA sequencing. The resulting raw data was analysed in a compositionality-aware manner, using a range of innovative bioinformatic methods. Noteworthy changes included an increase in butyrate metabolising potential—chiefly in the 4-aminobutyrate/succinate and glutarate pathways—and in the joint abundance of butyrate-producing taxa in the intervention group compared to control. We also observed a decrease in the Tenericutes phylum in the intervention group and an increase in the control group. Based on our findings, we concluded that the occasional replacement of animal meat with PBMA products seen in flexitarian dietary patterns can promote positive changes in the gut microbiome of consumers

Electric field control and optical signature of entanglement in quantum dot molecules

The degree of entanglement of an electron with a hole in a vertically coupled self-assembled dot molecule is shown to be tunable by an external electric field. Using atomistic pseudopotential calculations followed by a configuration interaction many-body treatment of correlations, we calculate the electronic states, degree of entanglement and optical absorption. We offer a novel way to spectroscopically detect the magnitude of electric field needed to maximize the entanglement.Comment: 4 pages, 6 figure