On the equivalence of Eulerian and Lagrangian variables for the two-component Camassa-Holm system

The Camassa-Holm equation and its two-component Camassa-Holm system generalization both experience wave breaking in finite time. To analyze this, and to obtain solutions past wave breaking, it is common to reformulate the original equation given in Eulerian coordinates, into a system of ordinary differential equations in Lagrangian coordinates. It is of considerable interest to study the stability of solutions and how this is manifested in Eulerian and Lagrangian variables. We identify criteria of convergence, such that convergence in Eulerian coordinates is equivalent to convergence in Lagrangian coordinates. In addition, we show how one can approximate global conservative solutions of the scalar Camassa-Holm equation by smooth solutions of the two-component Camassa-Holm system that do not experience wave breaking

Temperature-dependent preferences for advertisement-call frequency in females of Hyla versicolor

Abstract only availableMale treefrogs produce loud and persistent acoustic signals called advertisement calls to attract mates. Ectothermic animals like frogs face an interesting challenge, in that temperature can significantly impact characteristics of the species-specific advertisement call. The mate-choice preferences of female gray treefrogs (H. versicolor) have been extensively studied (reviewed by Gerhardt & Huber 2002). It has been found that females prefer calls with standard frequency peaks of 1.1 kHz + 2.2 kHz over calls with higher and lower frequencies at 20º C. However, it is not known how this preference is affected by temperature. To determine whether acoustic preferences based on frequency are temperature-dependent, I collected female frogs during their breeding season and tested them in a temperature-controlled anechoic testing chamber. I generated ten different computer-synthesized advertisement calls that ranged in frequency between 0.55 + 1.1 kHz to 1.5 + 3.0 kHz. In two-speaker choice tests conducted at three different temperatures (15º C, 20º C and 25º C), females "chose" (moved within 10 cm of a speaker) between a call with standard frequency peaks of 1.1 + 2.2 kHz and one of the nine alternative calls. Preliminary results indicate the preferred frequencies appeared to remain 1.1 + 2.2 kHz at lower temperatures. However, at higher temperatures, female frogs were more likely to approach high-frequency calls. These results will be discussed in the context of known temperature-dependent physiological processes in the inner ear of frogs.NIH grant to H.C. Gerhard

Two-Photon Doppler cooling of alkaline-earth-metal and ytterbium atoms

A new possibility of laser cooling of alkaline-earth-metal and Ytterbium atoms using a two-photon transition is analyzed. We consider a $^{1}S_{0}$ - $^{1}S_{0}$ transition, with excitation in near resonance with the $^{1}P_{1}$ level. This greatly increases the two-photon transition rate, allowing an effective transfer of momentum. The experimental implementation of this technique is discussed and we show that for Calcium, for example, two-photon cooling can be used to achieve a Doppler limit of 123 microKelvin. The efficiency of this cooling scheme and the main loss mechanisms are analyzed.Comment: 7 pages, 5 figure

Jugendforschung

Dieser Beitrag liefert einen Überblick über die historische Entwicklung der Jugendforschung in Deutschland vom 18. Jahrhundert bis zur Gegenwart. Dabei werden zunächst historische Entwicklungslinien ausgehend von den Anfängen der Jugendforschung bis in die 1990er Jahre grob nachgezeichnet. Anschließend werden aktuelle Forschungstendenzen und Theoriediskurse der Jugendforschung vorgestellt und in diesem Kontext zukünftige Herausforderungen etwa im Hinblick auf den Bereich der Forschung zu sozialer Ungleichheit, auf das Themenfeld der Weltgesellschaft oder auf die Problematik der demografischen Entwicklung skizziert.info:eu-repo/semantics/acceptedVersio

Pufendorf, Samuel

During the last two decades, Samuel von Pufendorf’s (1632–1694) natural law philosophy has become the subject of renewed and growing attentiveness among intellectual historians and philosophers (Seidler 2015). In the late-seventeenth century and early eighteenth century, Pufendorf was the most widely-read moral and political philosopher in Europe, whose reputation is most clearly exemplified in the impressive number of translations and editions of his works. Pufendorfian natural law theory offered a shared vocabulary and conceptual possibilities for the discussion of morality, politics and interstate relations for numerous eighteenth-century thinkers, such as Christian Thomasius, the authors of the Scottish Enlightenment and Jean-Jacques Rousseau. Pufendorf spent large parts of his career in princely courts and portrayed the history of states and their natural law foundations in his widely circulated historical works (Seidler 1997). Moreover, he also wrote on the issues of theology and church-state relations (Döring 1992, Zurbuchen 1998).Peer reviewe

Interventions to improve work outcomes in work-related PTSD: a systematic review

<p>Abstract</p> <p>Background</p> <p>Posttraumatic stress disorder acquired at work can be debilitating both for workers and their employers. The disorder can result in increased sick leave, reduced productivity, and even unemployment. Furthermore, workers are especially unlikely to return to their previous place of employment after a traumatic incident at work because of the traumatic memories and symptoms of avoidance that typically accompany the disorder. Therefore, intervening in work-related PTSD becomes especially important in order to get workers back to the workplace.</p> <p>Methods</p> <p>A systematic literature search was conducted using Medline, PsycINFO, Embase, and Web of Science. The articles were independently screened based on inclusion and exclusion criteria, followed by a quality assessment of all included articles.</p> <p>Results</p> <p>The systematic search identified seven articles for inclusion in the review. These consisted of six research articles and one systematic review. The review focused specifically on interventions using real exposure techniques for anxiety disorders in the workplace. In the research articles addressed in the current review, study populations included police officers, public transportation workers, and employees injured at work. The studies examined the effectiveness of EMDR, cognitive-behavioural techniques, and an integrative therapy approach called brief eclectic psychotherapy. Interestingly, 2 of the 6 research articles addressed add-on treatments for workplace PTSD, which were designed to treat workers with PTSD who failed to respond to traditional evidence-based psychotherapy.</p> <p>Conclusions</p> <p>Results of the current review suggest that work-related interventions show promise as effective strategies for promoting return to work in employees who acquired PTSD in the workplace. Further research is needed in this area to determine how different occupational groups with specific types of traumatic exposure might respond differently to work-tailored treatments.</p

Magnetic trapping of metastable 3P2^3P_2 atomic strontium

We report the magnetic trapping of metastable $^3P_2$ atomic strontium. Atoms are cooled in a magneto-optical trap (MOT) operating on the dipole allowed $^1S_0-^1P_1$ transition at 461 nm. Decay via $^1P_1\to {^1D_2}\to {^3P_2}$ continuously loads a magnetic trap formed by the quadrupole magnetic field of the MOT. Over $10^8$ atoms at a density of $8 \times 10^9$ cm$^{-3}$ and temperature of 1 mK are trapped. The atom temperature is significantly lower than what would be expected from the kinetic and potential energy of atoms as they are transferred from the MOT. This suggests that thermalization and evaporative cooling are occurring in the magnetic trap.Comment: This paper has been accepted by PR