X-ray quantum optics with M\"ossbauer nuclei embedded in thin film cavities

A promising platform for the emerging field of x-ray quantum optics are M\"ossbauer nuclei embedded in thin film cavities probed by near-resonant x-ray light, as used in a number of recent experiments. Here, we develop a quantum optical framework for the description of experimentally relevant settings involving nuclei embedded in x-ray waveguides. We apply our formalism to two settings of current experimental interest based on the archetype M\"ossbauer isotope 57Fe. For present experimental conditions, we derive compact analytical expressions and show that the alignment of medium magnetization as well as incident and detection polarization enable the engineering advanced quantum optical level schemes. The model encompasses non-linear and quantum effects which could become accessible in future experiments.Comment: 13 pages, 6 figure

Collective effects between multiple nuclear ensembles in an x-ray cavity-QED setup

The setting of Moessbauer nuclei embedded in thin-film cavities has facilitated an aspiring platform for x-ray quantum optics as shown in several recent experiments. Here, we generalize the theoretical model of this platform that we developed earlier [Phys. Rev. A 88, 043828 (2013)]. The theory description is extended to cover multiple nuclear ensembles and multiple modes in the cavity. While the extensions separately do not lead to qualitatively new features, their combination gives rise to cooperative effects between the different nuclear ensembles and distinct spectral signatures in the observables. A related experiment by Roehlsberger et al. [Nature 482, 199 (2012)] is successfully modeled, the scalings derived with semiclassical methods are reproduced, and a microscopic understanding of the setting is obtained with our quantum mechanical description.Comment: 18 pages, 6 figure

STUDIES ON THYSANURA. II. ORIENTATION REACTIONS OF MACHILOIDES DELANYI WYGODZINSKY AND CTENOLEPISMA LONGICAUDATA ESCHERICH TO TEMPERATURE, LIGHT AND ATMOSPHERIC HUMIDITY

Zoologica Africana 3(1): 43-5

Studies on Thysanura I the water economy of Machiloides Delanyi Wygodzinsky and Ctenolepisma Longicaudata Escherich

Zoologica Africana 3(1): 21-4

Dynamic formation of Rydberg aggregates at off-resonant excitation

The dynamics of a cloud of ultra-cold two-level atoms is studied at off-resonant laser driving to a Rydberg state. We find that resonant excitation channels lead to strongly peaked spatial correlations associated with the buildup of asymmetric excitation structures. These aggregates can extend over the entire ensemble volume, but are in general not localized relative to the system boundaries. The characteristic distances between neighboring excitations depend on the laser detuning and on the interaction potential. These properties lead to characteristic features in the spatial excitation density, the Mandel $Q$ parameter, and the total number of excitations. As an application an implementation of the three-atom CSWAP or Fredkin gate with Rydberg atoms is discussed. The gate not only exploits the Rydberg blockade, but also utilizes the special features of an asymmetric geometric arrangement of the three atoms. We show that continuous-wave off-resonant laser driving is sufficient to create the required spatial arrangement of atoms out of a homogeneous cloud.Comment: 8 pages, 7 figure

Aspects of the biology of aestivation in Bulinus (Physopsis) africanus (Krauss) (Gastropoda, Pulmonata)

Aestivation, a period of dormancy during hot, dry conditions, is known to occur in both the Prosobranchia and the Pulmonata among freshwater Gastropoda. While there have been numerous accounts, mainly by field ecologists concerned with bilharziasis control, of the survival value of aestivation in the Gastropoda, little is known of its underlying physiological mechanisms. Results of investigations into the physiological basis of aestivation in the freshwater Prosobranchia, confined to the family Ampulariidae, have been conflicting, fundamental differences having been shown to exist between different species of the genus Pila . Only a single comprehensive study, that by von Brand and his coworkers on the planorbid snail Australorbis glabratus*, forms the basis of our knowledge of the aestivation process in the aquatic Pulmonata. In view of the conflicting results obtained in investigations on freshwater Prosobranchia, the general applicability of the findings for Australorbis glabratus to other freshwater Pulmonata was open to question. The present investigation on the planorbid snail Bulinus (Physopsis) afriaanus, a species known to be a successful aestivator, was prompted by the obvious need for a further comprehensive study on an aquatic pulmonate species . The results presented here show that aestivation in this species is a definite physiological state, characterised by a depression of the metabolic rate, which not only aids in husbanding the snails I metabolic resources. during the enforced starvation which must necessarily accompany aestivation, but also constitutes a form of resistance adaptation to the transient high temperatures which aestivating snails are bound to encounter. Loss of body water is shown to be important in initiating aestivation, but it is also the factor most likely to prove lethal during the course of aestivation. The results confirm and extend the earlier findings for Australorbis glabratus. The results are discussed in the context of our present knowledge of aestivation in other Gastropoda, both aquatic and terrestrial, and also in relation to other forms of resistance adaptation. As expected, the investigation raises more questions than it answers, thus directions for further research, arising out of the present findings, are suggested

Food resource sharing and partitioning among some fishes of the Pongolo River floodplain

The diets of 12 fish species which coexist in the Pongolo floodplain lakes were determined from an analysis of the contents of 3 691 stomachs collected over a period of 12 months. Although almost all species were found to feed on a variety of foods, with consequent dietary overlaps, quantitative analysis of the results showed that distinct preferences for specific food types considerably ameliorated the effects of such overlaps. Partitioning within the major food categories, differences in relative population sizes, spatial and temporal differences in feeding and shifts in diet following inputs of seasonally occurring foods, all tended further to reduce effective competition between species. The results are discussed in the broader context of colonization of the Pongolo system by a tropical fish community in circumstances where the principles of island biogeography may be expected to apply

Osmoregulation by means of a Hitherto unsuspected osmoregulatory organ in two grapsid crabs

Zoologica Africana 2 (1): 127-12

Experimental Data from the Benchmark SuperCritical Wing Wind Tunnel Test on an Oscillating Turntable

The Benchmark SuperCritical Wing (BSCW) wind tunnel model served as a semi-blind testcase for the 2012 AIAA Aeroelastic Prediction Workshop (AePW). The BSCW was chosen as a testcase due to its geometric simplicity and flow physics complexity. The data sets examined include unforced system information and forced pitching oscillations. The aerodynamic challenges presented by this AePW testcase include a strong shock that was observed to be unsteady for even the unforced system cases, shock-induced separation and trailing edge separation. The current paper quantifies these characteristics at the AePW test condition and at a suggested benchmarking test condition. General characteristics of the model's behavior are examined for the entire available data set