A Mott-like State of Molecules

We prepare a quantum state where each site of an optical lattice is occupied by exactly one molecule. This is the same quantum state as in a Mott insulator of molecules in the limit of negligible tunneling. Unlike previous Mott insulators, our system consists of molecules which can collide inelastically. In the absence of the optical lattice these collisions would lead to fast loss of the molecules from the sample. To prepare the state, we start from a Mott insulator of atomic 87Rb with a central region, where each lattice site is occupied by exactly two atoms. We then associate molecules using a Feshbach resonance. Remaining atoms can be removed using blast light. Our method does not rely on the molecule-molecule interaction properties and is therefore applicable to many systems.Comment: Proceedings of the 20th International Conference on Atomic Physics (ICAP 2006), edited by C. Roos, H. Haffner, and R. Blatt, AIP Conference Proceedings, Melville, 2006, Vol. 869, pp. 278-28

Simple pressure-tuned Fabry–Pérot interferometer

A simple, compact and inexpensive pressure-tuned Fabry–Pérot interferometer is presented. It is used as a laser locking reference for optical frequencies where the use of an atomic reference is impractical. The scanning range is several GHz. Absolute positioning of the interferometer with an accuracy of 7 MHz7MHz rms over a range of 2 GHz2GHz is possible. The instrument is temperature stabilized and shows long-term drift of 16 MHz16MHz rms over 48 h48h.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87892/2/033105_1.pd

Time evolution of Matrix Product States

In this work we develop several new simulation algorithms for 1D many-body quantum mechanical systems combining the Matrix Product State variational ansatz with Taylor, Pade and Arnoldi approximations to the evolution operator. By comparing all methods with previous techniques based on Trotter decompositions we demonstrate that the Arnoldi method is the best one, reaching extremely good accuracy with moderate resources. Finally we apply this algorithm to studying the formation of molecules in an optical lattices when crossing a Feschbach resonance with a cloud of two-species hard-core bosons.Comment: More extensive comparison with all nearest-neighbor spin s=1/2 models. The results in this manuscript have been superseded by a more complete work in cond-mat/061021

Social acceptability of a marine protected area: The case of Reunion Island

This paper examines variations in social acceptability of a Marine Protected Area (MPA) prior to implementation. The influence of a number of factors, including socio-economic characteristics, perception of coral resources state of health and attitudes towards non-compliance with regulations are analysed. During May 2006, 640 questionnaires were distributed to school children around Reunion Island, Western Indian Ocean, for completion by their parents, following an informal educational activity made in school. From a 73% (n = 469) response rate, results showed that 78% of participants were in favour of the MPA. Analysis further identified that those supportive of the MPA were generally from higher socio-professional categories, had a negative perception of the coral reef ecosystem's health and were not originally from Reunion. In contrast, locals (born in Reunion) from lower socio-professional categories or with no employment activity and having a positive perception of the health status of coral reefs offered no opinion on the MPA. Attitudes towards enforcement and compliance highlighted that SCUBA divers, fishers and jet skiers attributed a higher value to the protection of the coral reef environment through enforcement of MPA regulations than to their own use of the coral reef resource. When asked about the use of penalties to deter non-compliance, swimmers were awarded the lowest fines, followed by SCUBA divers, fishers then jet skiers being awarded the highest fines. Thus, the more severe the act of non-compliance by a resource user group was perceived to be, the more these users themselves disapproved of non-compliant behaviour and supported use of high penalties. The survey design through focusing on school children's parents, demonstrated a simple and cost-effective method for data collection while providing environmental education, which could be employed in similar case studies elsewhere

Who to Host: Competition Interactions between Parasitoid Wasp Species

The availability of resources plays an important role in the survival and fitness of all organisms, one\u27s ability to find and utilize resources can impact interactions between them and their environments. The interaction between organisms for resources can lead to interspecific competition, amongst two different species, or intraspecific competition, amongst the same species. In an experiment to test for competitive interactions between the parasitoid wasp species of N. vitripennis and M. digitata that utilize a fresh fly papua as their host to aid in the reproduction of their offspring. Over a period of time testing for conditions of interspecific and intraspecific competition by measuring their mean offspring produced we set up five vials to isolate each respective competition interaction. In vials one and two used as a control for the experiment, one wasp from one wasp species was placed inside one vial with its own host. For vials two and three, two wasps from one wasp species were placed inside one vial with a host to test for intraspecific competition interactions. To test for interspecific competition interactions one wasp from each species\u27 was placed inside vial five with a host. From the analysis of our results through the excel software we determined that the two species while in competition have a predicted outcome of unstable coexistence. Further, both wasp species mean offspring produced were significantly impacted by interspecific competition. Overall the impact of competition interactions among both species impacts their overall fitness which sets up a model to further test how competition influences an organism\u27s availability and success with utilizing resources in their environments

Relation between plaque type, plaque thickness, blood shear stress, and plaque stress in coronary arteries assessed by X-ray Angiography and Intravascular Ultrasound

Purpose: Atheromatic plaque progression is affected, among others phenomena, by biomechanical, biochemical, and physiological factors. In this paper, the authors introduce a novel framework able to provide both morphological (vessel radius, plaque thickness, and type) and biomechanical (wall shear stress and Von Mises stress) indices of coronary arteries. Methods: First, the approach reconstructs the three-dimensional morphology of the vessel from intravascular ultrasound(IVUS) and Angiographic sequences, requiring minimal user interaction. Then, a computational pipeline allows to automatically assess fluid-dynamic and mechanical indices. Ten coronary arteries are analyzed illustrating the capabilities of the tool and confirming previous technical and clinical observations. Results: The relations between the arterial indices obtained by IVUS measurement and simulations have been quantitatively analyzed along the whole surface of the artery, extending the analysis of the coronary arteries shown in previous state of the art studies. Additionally, for the first time in the literature, the framework allows the computation of the membrane stresses using a simplified mechanical model of the arterial wall. Conclusions: Circumferentially (within a given frame), statistical analysis shows an inverse relation between the wall shear stress and the plaque thickness. At the global level (comparing a frame within the entire vessel), it is observed that heavy plaque accumulations are in general calcified and are located in the areas of the vessel having high wall shear stress. Finally, in their experiments the inverse proportionality between fluid and structural stresses is observed

Investigating the Nectar Preferences of Bumblebees while Foraging: are Total Responses a Good Metric?

The declining population of bumblebees worldwide poses an unmistakable threat to ecological systems and biodiversity. Therefore, a deep understanding of the factors at play when bees are foraging is crucial to conservation efforts. This research aims to explore the energy that foraging bumblebees are willing to expend at a known food source after the food has stopped, and if these responses reveal sugar concentration preferences. In this experiment a novel approach was used, adapted from psychology research on addiction, to measure bee’s preferences for different concentration of sugar-water (nectar). First, how many rewards the bees earned if they were given 1 reward each time they visited an artificial flower (fixed ratio) was measured. Next, the bee was ran again but the cost of each reward was increased by 1 visit each time the bee consumed the reward (progressive ratio). This functionally made the reward progressively more expensive. This was repeated until the bee returned to the colony or stopped responding. These messages were alternated between until the bee had completed a fixed and progressive ratio for each reward type. (30%, 45%, and 60% sucrose). This research found that the preferences bees demonstrated no preference in sugar concentration. Progressive ratio sessions likely mimic wild conditions better because flowers are drained of nectar throughout the day by competing pollinators and they produce less nectar as they age. Researchers should consider using progressive ratio a measure of preference because it better matched wild conditions. Preferences measured using free-access to food are likely overstated

Herpetofauna and Tarantula Avoidance: a Missouri Glades Location Survey

Missouri glades are home to a variety of herpetofauna and one species of tarantula: Aphonopelma hentzi (Texas brown tarantula). These animals traverse through their environment very differently. Herpetofauna tend to travel in search of food, while tarantulas are usually restricted to foraging in areas very close to their burrows. Due to this contrast, and because of potential predator-prey relationships, I wanted to see if there was a pattern in the distances between these two groupings. To do this I conducted a location survey to determine how far each individual was from the nearest spider. After analyzing the data, it was discovered that the further someone was from a tarantula, the more likely they were to find herpetofauna. This indicates that there is a potential avoidance between herpetofauna and tarantulas

Does a bumblebee’s size influence foraging behavior?

Current studies of Bumblebees (Bombus impatiens) have shown that they prefer plants that have a higher concentration of sugar over those that are of a lower concentration. However, there is little research analyzing the impact of the size difference amongst bumblebee foragers. During our experiment, we tested if larger bumblebees demonstrate a propensity to pursue nectar rewards more frequently compared to smaller bees. We hypothesized that the smaller bumblebees would forage less than the larger ones under a fixed ratio and three different sugar concentrations. We found that our hypothesis was partly correct: smaller bees initially earned fewer rewards, but they began to consume the same amount as large bees as sugar concentration increased. This discovery will be a crucial starting point for further research into factors contributing to small & large bees performing the same amount of foraging activities