A Simplified Cellular Automaton Model for City Traffic

We systematically investigate the effect of blockage sites in a cellular automaton model for traffic flow. Different scheduling schemes for the blockage sites are considered. None of them returns a linear relationship between the fraction of ``green'' time and the throughput. We use this information for a fast implementation of traffic in Dallas.Comment: 12 pages, 18 figures. submitted to Phys Rev

Photoassociative spectroscopy at long range in ultracold strontium

We report photoassociative spectroscopy of $^{88}$Sr$_2$ in a magneto-optical trap operating on the ${^1S_0}\to{^3P_1}$ intercombination line at 689 nm. Photoassociative transitions are driven with a laser red-detuned by 600-2400 MHz from the ${^1S_0}\to{^1P_1}$ atomic resonance at 461 nm. Photoassociation takes place at extremely large internuclear separation, and the photoassociative spectrum is strongly affected by relativistic retardation. A fit of the transition frequencies determines the ${^1P_1}$ atomic lifetime ($\tau=5.22 \pm 0.03$ ns) and resolves a discrepancy between experiment and recent theoretical calculations.Comment: 4 pages, 4 figures, submitte

Nischendifferenzierung zweier nah verwandter Neophyten im urbanen Raum

The alien Galinsoga ciliata and G. parviflora are widely distributed in Switzerlandin rural as well as urban areas. They are both regarded as weeds, are oftensympatric and grow in similar ecological settings. In urban environments, the otherwiseslight ecological differences between species appear to be more expressed,but quantitative studies analyzing the distribution pattern, habitat and substratepreferences of both species were missing. In the city of Basel (Switzerland) Galinsogaciliata (Raf.) Blake and G. parviflora Cav. were mapped onto a 500 m3500 mgrid. At each locality population density, habitat and substrate type were recorded.G. ciliata was more wide-spread and seven times more frequent than G. parviflora.These differences existed despite G. ciliata being introduced to Europe and to Baselmuch later than G. parviflora.In contrast to G. parviflora, which was absent in the peripheral areas of thetown, the stands of G. ciliata were spread over the whole town area. Despite thefact that both species prefer nutrient- and humus-rich soil and coexisted in nutrientrichhabitats in the city of Basel, G. parviflora grows more often in pavement gapsand crevices of stones, concrete or asphalt than G. ciliata. The lower frequency ofG. parviflora, its smaller aggregations, and the exploitation of the most extremehabitats demonstrate the weak competitiveness compared with G. ciliata.Hence, in urban areas, where the growth conditions for the two weed speciesare not optimal, G. parviflora could maintain its presence by showing a clear nichedifferentiation compared to G. ciliata. Betr. die Ausbreitung von zwei Galinsoga-Arten in Base

A model for an inland port in Australia

This paper examines the role of an inland port particular to the outer regions of Melbourne, Australia. In this study, it has been experienced that the broad use of terminology, in the Melbourne context, has been a stumbling block. In its particular context, this has provided the impetus for the development of a model for an inland port that is unambiguous. It is clear from international examples that such a development acts as a significant potential nucleus for regional economic growth, but the lack of a facilitated discussion is an impediment. This model is offered as a facilitator and a useful tool in the construction of a common understanding

Using Absorption Imaging to Study Ion Dynamics in an Ultracold Neutral Plasma

We report optical absorption imaging of ultracold neutral plasmas.Images are used to measure the ion absorption spectrum, which is Doppler-broadened. Through the spectral width, we monitor ion equilibration in the first 250ns after plasma formation. The equilibration leaves ions on the border between the weakly coupled gaseous and strongly coupled liquid states. On a longer timescale of microseconds, we observe radial acceleration of ions resulting from pressure exerted by the trapped electron gas.Comment: 4 pages, 4 figure

Spectroscopic determination of the s-wave scattering lengths of 86Sr and 88Sr

We report the use of photoassociative spectroscopy to determine the ground state s-wave scattering lengths for the main bosonic isotopes of strontium, 86Sr and 88Sr. Photoassociative transitions are driven with a laser red-detuned by up to 1400 GHz from the 1S0-1P1 atomic resonance at 461 nm. A minimum in the transition amplitude for 86Sr at -494+/-5 GHz allows us to determine the scattering lengths 610a0 < a86 < 2300a0 for 86Sr and a much smaller value of -1a0 < a88 < 13a0 for 88Sr.Comment: 4 pages, 3 figures, submitted to Physical Review Letter

Verbreitung und Standorte des schmalblättrigen Kreuzkrauts (Senecio inaequidens) und anderer Neophyten in der Stadt Basel (Schweiz)

In the city of Basel (Switzerland) Senecio inaequidens and five other neophytes(Ambrosia artemisiifolia, Berteroa incana, Cynodon dactylon, Helianthustuberosus s.l. and Juncus tenuis) were mapped onto 61 500 m 500 m quadrats. Ateach locality frequency, biotope and soil quality were recorded. In Basel S. inaequidens is moderately spread and sparse. Since its first occurrence on railway areas in the early eighties of the last century S. inaequidens has started to colonise the city, many individuals or low density stands were observed in this study occuring across the city. In Basel S. inaequidens grows mainly on open soils with humus rich soil or coarse gravel. A. artemisiifolia, B. incana, C. dactylon, H. tuberosus s.l. and J. tenuis are in Basel sparsely spread and sparse in number. For each species information on the history of its colonisation, their current distribution, frequency, and its ecology in Basel are shown and discussed

Do wildflower strips enhance pest control in organic cabbage?

Within this project we assess whether wildflower strips and companion plants increase the control of cabbage pests Plutella xylostella L. (Lepidoptera: Plutellidae), Mamestra brassicae L. (Lepidoptera: Noctuidae) and Pieris rapae L. (Lepidoptera: Pieridae) by (1) naturally occurring parasitoids and predators and (2) mass‐releasedn Trichogramma brassciae (Bezdenko) (Hymenoptera: Trichogrammatidae) parasitoids. Two organic cabbage fields were used for this study: adjacent to each field a wildflower strip was sown and companion plants (Centaurea cyanus L. (Asteraceae)) intermixed within the crop. Within each field ~15,000 M. brassicae eggs were placed out to determine the parasitism rates by mass‐released T. brassicae and to assess the levels of egg predation. Over 1,000 lepidopteran larvae were collected and screened for hymenopteran and tachinid parasitoid DNA using a multiplex PCR assay. Invertebrate generalist predators (n=1,063) were collected for DNA‐based gut content analysis. The wildflower strip had a significant positive effect on M. brassicae egg parasitism rates as rates increased 5‐fold in the vicinity to the strip. Moreover, companion plants enhanced invertebrate predation on M. brassicae eggs. Both, the release of T. brassicae and the use of companion plants, however, did not significantly increase egg parasitism rates. The infestation of plants by caterpillars increased with distance to the wildflower strip and there was a trend of decreasing larval parasitism rates with distance to the strip. Currently the invertebrate predators are being molecularly analysed to assess predation on unparasitized and parasitized lepidopteran pests