Cycling amongst Māori: Patterns,influences and opportunities

This paper outlines the results of mixed-methods research on Māori and cycling. Our findings suggest that Māori cycle at similar rates to Pākehā (NZ European); however conditions may differ, possibly indicating higher levels of “necessity cycling” amongst Māori. Māori experience similar barriers to cycling, including a lack of suitable cycling infrastructure, but these occur against a backdrop of stark social, economic and transport-related inequities. Particular barriers for Māori may include inflexible work conditions, concerns about neighbourhood safety, inadequate provision for social cycling, and lack of access to places of importance to Māori. We identify potential solutions, including more whānau-friendly and culturally safe cycling infrastructure, and cycling programmes designed around Māori commitments to whanaungatanga and kaitiakitanga.     

Application of an advanced multi-surface kinematic constitutive soil model

The implementation of the non-linear elastic multi-surface plastic kinematic constitutive soil model ALTERNAT into a general uncoupled finite element program called ALTICA is described. The principal features of the model are discussed and its implementation into an initial stress type excess plastic stress redistribution algorithm. To show the abilities of the model and validate the algorithm, several examples are presented including the calibration of the model to a real sand with measured monotonic and cyclic properties. In the monotonic examples, the ability of ALTICA to accurately reproduce the predicted collapse load of geotechnical structures is demonstrated using the results of finite element simulations of two typical boundary value problems (with known analytical or numerical solutions). In the cyclic examples, results of cyclic liquefaction simulation using both a non-inertial ‘static’ and inertial ‘dynamic’ algorithm are presented. Copyright © 1999 John Wiley & Sons, Ltd.     

Conservative behaviour of riverine dissolved organic carbon in the Severn Estuary: chemical and geochemical implications

The distribution, variability and chemical behaviour of dissolved organic carbon (DOC) was investigated over 2$\text{1}\text{2}$ years in the Severn Estuary and Bristol Channel, UK. The concentrations of riverine DOC (3.1–7.8 mg C l^?1) covaried with river flow and were invariably conservative in this turbid slowly flushing (~200 days) estuary, indicating that any microbial degradation, chemical flocculation or adsorption processes do not affect the flux of riverine DOC through the estuary. The DOC inputs from the Severn (1.7–2.7 × 10¹⁰ g Cyr^?1) and other rivers (2.6–3.4 × 10¹⁰ g Cyr^?1) are the principal sources of DOC in the estuary and correspond to an export of 0.7–1.1% of the terrestrial productivity from the river catchment to the ocean. This export rate is in accord with recent predictions derived from global compilations of organic inputs from rivers and would imply that the global flux of riverine DOC could be as high as 7.8 × 10¹⁴ g Cyr^?1 which is 5 times greater than some previous estimates.The geochemical significance of a conservative delivery of riverine DOC to the ocean is that irrespective of which flux estimate is considered, such river inputs would make a significant contribution (~SO%) to oceanic DOC, and that the steady-state oceanic DOC flux would have to be significantly greater than present estimates (2.9 × 10¹⁴ g Cyr^?1) which are based on a mean radio carbon age of 3400 yr.An alternative, more realistic DOC flux model, which assumes a polydisperse age distribution about the mean age, is shown to yield the higher oceanic DOC fluxes required. Flocculation and adsorption processes would remove less than 10% and 0.2% respectively of riverine DOC in estuaries.     

Off-shelf fluxes of labile materials by an upwelling filament in the NW Iberian Upwelling System

Daily changes in the concentrations of carbon and nitrogen species were monitored during the course of a Lagrangian drifter experiment in a recurrent upwelling filament south of Cape Finisterre (NW Iberian Upwelling System). A drifting buoy released at the southern edge of the upwelling centre generated by the Cape moved 60km southwestwards from 3 to 7 August 1998. Organic matter in the 50m deep study water mass (average 77±2 μM C) consisted of: 57μM C of dissolved organic matter (DOM) with a C/N molar ratio of 19±2; 6μM C of DOM with a C/N ratio of 9±2, and 14μM C of 50% DOM and 50% suspended organic matter (POM_susp) with a C/N ratio of 6.0±0.4.Net conversion of consumed inorganic salts into accumulated TOM=POM_susp+DOM was 40% for nitrogen and 30% for carbon. Since the parcel of water crossed the shelf-edge, these conversion efficiencies are equivalent to net horizontal export-ratio of 0.4 and 0.3 respectively. A second drifter was deployed in the offshore-end of the filament, and was displaced 20km west between 14 and 17 August 1998. Nitrate was exhausted in the surface water and no significant changes were observed in the variables measured during the course of the second experiment. Low C/N ratios (6.5±0.4) and rapid POM_susp/DOM inter-conversion in the 20 μM C excess observed in the study volume points to the persistence of the labile materials formed on the shelf during transport to the ocean. Our data demonstrate

a) the key role of upwelling filaments in off-shelf export of organic materials and

b) the major contribution of DOM to this horizontal export, a previously unaccounted amount.

The high nitrogen content of the materials exported make them attractive organic substrates for use by microbial populations in the adjacent oligotrophic ocean.     

Primary production and nutrient assimilation in the Iberian upwelling in August 1998

Primary production was measured during two Lagrangian experiments in the Iberian upwelling. The first experiment, in a body of upwelled water, measured day-to-day changes in phytoplankton activity as the water mass moved south along the shelf break. Nutrient concentrations decreased over a five day period, with concomitant increases in phytoplankton biomass. Initially the maximum phytoplankton biomass was in the upper 10m but after four days, a sub-surface chlorophyll maximum was present at 30m. Depth-integrated primary production at the beginning of the experiment was 70mmolC.m⁻².d⁻¹ (838mgC.m⁻².d⁻¹) and reached a maximum of 88mmolC.m⁻².d⁻¹ (1053mgC.m⁻².d⁻¹) on day 3. On day 1, the picoplankton fraction (<2μm) was slightly more productive than larger (>5μm) phytoplankton, but the increase in overall production during the drift experiment was by these larger cells. Nitrate was the dominant nitrogen source. As nutrient concentrations declined, ammonium became increasingly more important as a nitrogen source and the f-ratio decreased from 0.7 to 0.5. Picoplankton cells (<2μm) were responsible for most (65–80%) of the ammonium uptake. The C:N:P uptake ratios were very close to the Redfield ratio for the first four days but as nutrients became depleted high C:N uptake ratios (11 to 43) were measured. Over the period of the experiment, nitrate concentration within the upper 40m decreased by 47.91mmolN.m⁻². In vitro estimates, based on ¹⁵N nitrate uptake, accounted for 56% of the decrease in nitrate concentration observed in the drifting water mass. Ammonium uptake over the same four day period was 16.28mmolN.m⁻², giving a total nitrogen uptake of 43.18mmolN.m⁻².In the second experiment, an offshore filament was the focus and a water mass was sampled as it moved offshore. Nutrient concentrations were very low (nitrate was <10nmol l⁻¹ and ammonium was 20–40nmol l⁻¹). Primary production rate varied between 36mmolC.m⁻².d⁻¹ (436mgC.m⁻².d⁻¹) and 21mmolC.m⁻².d⁻¹ (249mgC.m⁻².d⁻¹). Picophytoplankton was the most productive fraction and was responsible for a constant proportion (ca 0.65) of the total carbon fixation. Uptake rates of both nitrate and ammonium were between 10 and 20% of those measured in the upwelling region. Urea could be a very significant nitrogen source in these waters with much higher uptake rates than nitrate or ammonium; urea turnover times were ca. one day but the source of the urea remains unknown. Urea uptake had a profound effect on calculated f ratios. If only nitrate and ammonium uptake was considered, f ratios were calculated to be 0.42–0.46 but inclusion of urea uptake reduced the f ratio to <0.1. The primary production of this oligotrophic off-shore filament was driven by regenerated nitrogen.     

AK Herculis — An atypical W UMa-type system

AK Herculis is a contact binary of spectral class F with a number of obvious peculiarities such as a displacement of secondary eclipse from phase 0 _. ^P 500, unequal heights of the maxima, and a possibly sinusoidal (60 yr) period variation. The light curve is variable and shows erratic short-term behavior, although the latter effects are not unusual for a short period contact binary. Here we present new photoelectric light curves in theB andV passbands and derive several new times of minima. The new observations are compared graphically with seven earlier light curves. We analyzed the new observations and those by Bookmyer (1972) by the method of differential corrections. We find that the temperature difference between components is too large (1000 K) for AK Her to be considered a normal W UMa-system, but too small to allow a detached configuration obeying the mass-luminosity law. The solutions of both series of observations clearly indicate a contact configuration. Other unusual findings include a bolometric albedo greater than 2, and rather low values for the limb-darkening coefficients. We offer some possible reasons for these peculiarities. The mass ratio seems well determined from the photometry and is about 0.26, which is much lower than assumed in most earlier papers. The brightness and color of the known visual companion, ADS 10408B, were found by the differential corrections program. They agree, within observational error, with values found directly at the 200-in. telescope by Eggen, despite the fact that the B component contributes only a few percent of the light of the multiple system. The suggestion by Schmidt and Herczeg (1959) that a fourth body is responsible for the sinusoidal period variation seems stronger now than when first proposed. To encourage a search for this hypothetical component, we have tabulated expected values for its angular separation and relative mass with respect to the eclipsing pair, as well as the amplitude of the expected variable proper motion of the eclipsing pair. Discovery as a visual component seems impossible with present means, but the variable proper motion should be detectable. Thus we suggest that ADS 10408A (AK Her) be observed astrometrically. If a search for the predicted variable proper motion proves negative, mass transfer would remain the only plausible mechanism to explain the period change. We advance a different reason than did Schmidt and Herczeg to explain the phase lag of secondary eclipse.