Coupling of dry matter and nitrogen accumulation in ryegrass

The logistic model has proven very useful in relating dry matter production of warm season perennial forage grasses to applied nitrogen. A recent extension of the model coupled dry matter and plant N accumulation through a common response coefficient c. The objective of this analysis was to apply the extended logistic model to cool season Gulf annual ryegrass (Lolium multiflorum Lam.) and to establish a common response coefficient c between accumulation of dry matter and plant N. Analysis of variance established the validity of this hypothesis. The model accurately described response of dry matter, plant N removal, and plant N concentration to applied N, with an overall correlation coefficient of 0.9954. Furthermore, the model closely described the relationship between yield and plant N removal, as well as between plant N concentration and plant N removal. The logistic equation is well-behaved and simple to use on a pocket calculator. It can be used to estimate yields and plant N removal in evaluation of agricultural production and environmental quality.     

Thermoplastic Sizing of Carbon Fibres in High Temperature Polyimide Composites

Thermoplastic sizing of various carbon fibres has been evaluated as a means of controlling the microcracking resistance, transflexural strength (TFS), and thermo-oxidative stability (TOS) of PMR-15 matrix composites. Four different fibre/thermoplastic size combinations were selected for this study, based on their higher TOS than appropriate controls. Data are presented for the transverse microcrack (TVM) density/inch, and the subsequent delamination of [0,90]_4s laminates induced by thermal cycling (-196 to 350°C for 20 cycles). Results for composite TFS, conditioned TFS (after heating in air at 350°C), and TOS (350°C and 316°C) are also reported. One fibre/thermoplastic size combination gave both good microcracking resistance, and significantly improved TOS, in composite when compared with current commercially-available material.     

Parallel Plates Compared with Conventional Rods as TDR Waveguides for Sensing Soil Moisture

Dielectric methods of estimating the water content of soils, especially TDR, have become accepted as routine measurement techniques. Basic to the TDR technique is the waveguide, which is inserted into the soil for obtaining measurements of the effective soil permittivity, from which water content is estimated. In this study we compare the use of flat stainless steel plates with cylindrical stainless steel rods. We suggest that the use of plates gives a more even distribution of electromagnetic energy within the soil volume sampled and reduces the so called ``skin effect' where the electromagnetic energy is concentrated close to the surface of the electrodes. Plates will not be suitable for all measurement purposes but wherever they can be applied they should result in more representative measurements from the medium under investigation. Calculations of electrical field intensity are presented to compare the relative energy density between the electrodes. Field and laboratory studies were alsoconducted considering some of the practicalities of using the alternative waveguides.     

Quantification and visualization of anisotropy in trabecular bone

A number of methods for measuring anisotropy in trabecular bone using high‐resolution X‐ray computed tomography exist, which give different answers but have not been compared in detail. In this study, we examine the mean‐intercept length (MIL), star volume distribution (SVD) and star length distribution (SLD) methods, their algorithmic implementation for three‐dimensional (3D) data, and how their results relate to each other. A uniform ordered sampling scheme for determining which orientations to sample during analysis enhances the reproducibility of anisotropy and principal component direction determinations, with no evident introduction of biasing. This scheme also facilitates the creation of a 3D rose diagram that can be used to gain additional insights from the data. The directed secant algorithm that is frequently used for traversing pixel and voxel grids for these calculations is prone to bias unless a previously unreported normalization is used. This normalization ameliorates the bias present when using cubic voxels, and also permits calculations on data sets in which the slice spacing is not equal to the pixel spacing. Overall, the three methods for quantification of anisotropy give broadly similar results, but there are systematic divergences that can be traced to their differences in data and processing, and which may impact on their relative utility in estimating mechanical properties. Although discussed in the context of computed tomography of trabecular bone, the methods described here may be applied to any 3D data set from which fabric information is desired.     

Aggregate effects and measuring regional dynamics

Empirical models of regional adjustment often control for aggregate effects when estimating the impact of region-specific shocks on local economies. It is, however, difficult to filter out the effects of aggregate shocks—such as oil shocks, uncertainty shocks, or national recessions—because the incidence of these shocks varies across space and time. We propose an improved econometric method to control for this form of spatiotemporal heterogeneity, thereby yielding more accurate estimation of the effects of local shocks on regional economies. Applying the method to US states, we find that labour demand shocks are mostly absorbed through changes in participation; the migration response to these shocks is limited; and recoveries are highly protracted     

风景园林与绿色基础设施在城市流域水资源规划中的重要作用

通过绿色基础设施途径,处理美国波士顿北部的马萨诸塞州城市流域的水资源规划问题。从多个尺度为风景园林师提供水资源规划的经验与启发,探究公众对新型绿色基础设施解决方案的态度与偏好,以及公众偏好对于整体规划设计的重要作用。     

Associations between evaporative cooling and dust‐mite allergens,endotoxins, and β‐(1 → 3)‐d‐glucans in house dust: A study of low‐income homes

Recent work suggests that evaporative coolers increase the level and diversity of bioaerosols, but this association remains understudied in low‐income homes. We conducted a cross‐sectional study of metropolitan, low‐income homes in Utah with evaporative coolers (n = 20) and central air conditioners (n = 28). Dust samples (N = 147) were collected from four locations in each home and analyzed for dust‐mite allergens Der p1 and Der f1, endotoxins, and β‐(1 → 3)‐d ‐glucans. In all sample locations combined, Der p1 or Der f1 was significantly higher in evaporative cooler versus central air conditioning homes (OR = 2.29, 95% CI = 1.05‐4.98). Endotoxin concentration was significantly higher in evaporative cooler versus central air conditioning homes in furniture (geometric mean (GM) = 8.05 vs 2.85 EU/mg, P < .01) and all samples combined (GM = 3.60 vs 1.29 EU/mg, P = .03). β‐(1 → 3)‐d ‐glucan concentration and surface loads were significantly higher in evaporative cooler versus central air conditioning homes in all four sample locations and all samples combined (P < .01). Our study suggests that low‐income, evaporative cooled homes have higher levels of immunologically important bioaerosols than central air‐conditioned homes in dry climates, warranting studies on health implications and other exposed populations.     

Book reviews

Landscape and Power in Vienna

Robert Rotenberg

Baltimore and London, The John Hopkins University Press, 1995, ISBN 0-8018-4961-6, 416 pp, £33.00, ($39.95), hb

The Avebury Cycle

Michael Dames

London, Thames & Hudson Ltd, 2nd edition (revised), ISBN 0-500-27886-5, 240 pp, 201 illus., £10.95 ($16.95), pb

Landscapes of Settlement: prehistory to the present

Brian K. Roberts

London and New York, Routledge, 1996, ISBN 0-415-11968-5, x +181 pp, £47.50 hb, £16.99 pb

The Body Language of Trees: a handbook of failure analysis

Claus Mattheck & Helge Breloer (translator: Robert Strouts)

London, HMSO, 1996, ISBN 0 11 753067 0, 239 pp, £17.50     

Pentachlorophenol adsorption and desorption characteristics of granular activated carbon-I. Isotherms

The adsorption/desorption of pentachlorophenol (PCP) with Calgon F300 granular activated carbon (GAC) was studied and modelled. A modified Radke-Prausnitz (1972) isotherm model, incorporating a temperature- and pH-dependent proportionality constant, was found to best describe the observed PCP adsorption and desorption. The modified isotherm is valid in the ranges 4 ≤ pH ≤ 11 and 10 ≤ T ≤ 60°C. The activation energy of PCP adsorption was calculated to be 5.2 kJ/mol. At 30°C, PCP adsorbed strongly, and the rate of subsequent desorption was very low. However, the amount of PCP desorbed could be increased significantly by increasing the temperature to 60°C.     

Taking the High Line: elevated parks,transforming neighbourhoods,and the ever-changing relationship between the urban and nature

The popularity and impact of the High Line in New York mirrors the complex reality of contemporary provision of public space. The development of the project, its relationship to its surroundings and the evolving trend of elevated parks are analyzed in relation to the role of urban green space and impacts of Landscape Urbanism.

The High Line shows the way to a new role for urban green space by utilizing abandoned infrastructure. In analysing the narrative of the High Line, this article stresses the importance of understanding localities and connectivity. Based on observations as well as a review of the literature and media, the article concludes that great landscaping does not create great places without careful consideration of the surrounding community and residents.