The history and effects of alien plant control in the Cape of Good Hope Nature Reserve, 1941–1987

Concern about the invasion of this reserve by alien trees and shrubs, principally Acacia cyclops, A. saligna, A. longifolia, Eucalyptus lehmannii and Pinus pinaster, was first expressed in 1941, 2years after its proclamation. Control operations were started by 1943 and were almost totally ineffective for at least the first 35years; no systematic control strategy was implemented, follow-up control work was inadequate to prevent reestablishment of felled thickets and the supervision of control teams was deficient. Linkage of control operations to firewood production was a significant factor in this failure. In 1974 a 10-year control strategy was drawn up and in the late 1970’s began to be effectively implemented. Surveys of 40 plots in the centre of the reserve in 1966, 1976–80 and 1986 showed increasing densities of species other than the easily controlled P. pinaster up to 1976–80. Since then almost all individuals>1,8m in height have been eliminated and indications from smaller height classes are that seed banks are being depleted. Explanations are advanced for the successes and failures experienced during the 47years of control. Some of the side-effects of these invasions and their control are discussed. One conclusion is that this reserve requires a qualified ecologist on its staff

The alien flora of the Cape of Good Hope Nature Reserve

An annotated species list of the alien vascular plant flora of the Cape of Good Hope Nature Reserve is presented. The flora comprises five gymnosperm and 68 angiosperm species that are definitely alien to the reserve and four angiosperm species that are possibly alien. The life-form distribution of the alien flora is shown to be significantly different from that of the indigenous flora; trees, shrubs and annual herbs are more important in the alien flora, and dwarf shrubs and perennial herbs are much less important. Biotic factors are suggested as being important in determining the success of alien invasions, in particular grazing by ungulates. The invasion rate is currently about one new species per year. By ceasing to introduce tree species and by restricting human disturbance, the rate of invasion of new species could be reduced

Formal knowledge networks : a study of Canadian experiences

French version available in IDRC Digital Library: Réseaux formels du savoir : une étude des expériences canadienne

Réseaux formels du savoir : une étude des expériences canadiennes

Version anglaise disponible dans la Bibliothèque numérique du CRDI: Formal knowledge networks : a study of Canadian experience

Integrating Communication Skills and Planning Techniques

Practitioners have long stressed the need to teach professional commumcations skills to planning students. This paper describes ten years of experience in teaching a course in which communications skills and techniques of gathering and analyzing information are taught concurrently while investigating a problem of importance in the community. The course involves an ongoing collaboration, a "marriage of convenience," between an academic and a planner, casting city/county planning staff as clients for students This has proven useful for pedagogy and has had some positive impact on the community.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69149/2/10.1177_0739456X9201100206.pd

Pulsed Magnetic Field Measurements of the Composite Fermion Effective Mass

Magnetotransport measurements of Composite Fermions (CF) are reported in 50 T pulsed magnetic fields. The CF effective mass is found to increase approximately linearly with the effective field $B^*$, in agreement with our earlier work at lower fields. For a $B^*$ of 14 T it reaches $1.6m_e$, over 20 times the band edge electron mass. Data from all fractions are unified by the single parameter $B^*$ for all the samples studied over a wide range of electron densities. The energy gap is found to increase like $\sqrt{B^*}$ at high fields.Comment: Has final table, will LaTeX without error

A microflow cytometer for microsphere-based immunoassays using integrated optics and inertial particle focussing

We present work towards a microflow cytometer for performing multiplex immunoassays using commercially available fluorescently-labelled microspheres. The device consists of a silica chip with integrated GeO2:SiO2 channel waveguides which deliver excitation light orthogonally to an etched flow channel [1], [2]. The rectangular cross section, 2:1 aspect ratio flow channel and flow rate create an inertial focussing effect on the microspheres [3] which ensures they flow through the plane of maximum optical excitation, halfway up the height of the channel, with minimal positional variation. The optical waveguide core is fabricated by magnetron sputtering of GeO2:SiO2 films which are then etched to form channel waveguides by ICP etching. The silica cladding, up to 13.5 µm thick, is deposited by either flame hydrolysis deposition or a combination of magnetron sputtering followed by PECVD. Fluidic channels are etched with ICP etching. Channels with the dimensions of 14.1 µm x 27.5 µm and near vertical sidewalls (91°±4°) have been produced in silica as shown in the cross section in Figure 1A. Figure 1B shows a device with the fluidic channel etched through waveguides clad with PECVD silica. Design parameters were established with PDMS test channels 25.5 µm deep by 12.2 µm wide. Figures 2A and 2B show transmission fluorescence imaging of streaks from multiple 5.6µm diameter microspheres flowing at 0.49 m/s down the fluidic channel. The microspheres are shown to be focused into a tight stream at 15 mm from the channel entrance in Figure 2C, indicating the minimum channel length required for the final devices. Future work will include dual channel quantification of microsphere fluorescence and development of an assay for TNFalpha and later multiplex measurements. Collection of fluorescence with channel waveguides and also characterisation of transmission measurements from flowing microspheres will also be studied

Observed photodetachment in parallel electric and magnetic fields

We investigate photodetachment from negative ions in a homogeneous 1.0-T magnetic field and a parallel electric field of approximately 10 V/cm. A theoretical model for detachment in combined fields is presented. Calculations show that a field of 10 V/cm or more should considerably diminish the Landau structure in the detachment cross section. The ions are produced and stored in a Penning ion trap and illuminated by a single-mode dye laser. We present preliminary results for detachment from S- showing qualitative agreement with the model. Future directions of the work are also discussed.Comment: Nine pages, five figures, minor revisions showing final publicatio

SPIDER: Probing the Early Universe with a Suborbital Polarimeter

We evaluate the ability of SPIDER, a balloon-borne polarimeter, to detect a divergence-free polarization pattern ("B-modes") in the Cosmic Microwave Background (CMB). In the inflationary scenario, the amplitude of this signal is proportional to that of the primordial scalar perturbations through the tensor-to-scalar ratio r. We show that the expected level of systematic error in the SPIDER instrument is significantly below the amplitude of an interesting cosmological signal with r=0.03. We present a scanning strategy that enables us to minimize uncertainty in the reconstruction of the Stokes parameters used to characterize the CMB, while accessing a relatively wide range of angular scales. Evaluating the amplitude of the polarized Galactic emission in the SPIDER field, we conclude that the polarized emission from interstellar dust is as bright or brighter than the cosmological signal at all SPIDER frequencies (90 GHz, 150 GHz, and 280 GHz), a situation similar to that found in the "Southern Hole." We show that two ~20-day flights of the SPIDER instrument can constrain the amplitude of the B-mode signal to r<0.03 (99% CL) even when foreground contamination is taken into account. In the absence of foregrounds, the same limit can be reached after one 20-day flight.Comment: 29 pages, 8 figures, 4 tables; v2: matches published version, flight schedule updated, two typos fixed in Table 2, references and minor clarifications added, results unchange