A Vehicular Traffic Flow Model Based on a Stochastic Acceleration Process

A new vehicular traffic flow model based on a stochastic jump process in vehicle acceleration and braking is introduced. It is based on a master equation for the single car probability density in space, velocity and acceleration with an additional vehicular chaos assumption and is derived via a Markovian ansatz for car pairs. This equation is analyzed using simple driver interaction models in the spatial homogeneous case. Velocity distributions in stochastic equilibrium, together with the car density dependence of their moments, i.e. mean velocity and scattering and the fundamental diagram are presented.Comment: 27 pages, 6 figure

Complex coastlines responding to climate change: do shoreline shapes reflect present forcing or “remember” the distant past?

A range of planform morphologies emerge along sandy coastlines as a function of offshore wave climate. It has been implicitly assumed that the morphological response time is rapid compared to the timescales of wave climate change, meaning that coastal morphologies simply reflect the extant wave climate. This assumption has been explored by focussing on the response of two distinctive morphological coastlines – flying spits and cuspate capes – to changing wave climates, using a coastline evolution model. Results indicate that antecedent conditions are important in determining the evolution of morphologies, and that sandy coastlines can demonstrate hysteresis behaviour. In particular, antecedent morphology is particularly important in the evolution of flying spits, with characteristic timescales of morphological adjustment on the order of centuries for large spits. Characteristic timescales vary with the square of aspect ratios of capes and spits; for spits, these timescales are an order of magnitude longer than for capes (centuries vs. decades). When wave climates change more slowly than the relevant characteristic timescales, coastlines are able to adjust in a quasi-equilibrium manner. Our results have important implications for the management of sandy coastlines where decisions may be implicitly and incorrectly based on the assumption that present-day coastlines are in equilibrium with current conditions

Clinical and diagnostic features of Bartter and Gitelman syndromes

Background: Bartter and Gitelman syndromes are autosomal recessive disorders of renal tubular salt handling. Due to their rarity, limited long-term data are available to inform prognosis and management. / Methods: Long-term longitudinal data were analysed for 45 children with pathogenic variants in SLC12A1 (n = 8), KCNJ1 (n = 8), CLCNKB (n = 17), BSND (n = 2) and SLC12A3 (n = 10) seen at a single centre between 1984 and 2014. Median follow-up was 8.9 [interquartile range (IQR) 0.7–18.1] years. / Results: Polyhydramnios and prematurity were seen in children with SLC12A1 and KCNJ1 mutations. Patients with CLCNKB mutations had the lowest serum potassium and serum magnesium and the highest serum bicarbonate levels. Fractional excretion of chloride was >0.5% in all patients prior to supplementation. Nephrocalcinosis at presentation was present in the majority of patients with SLC12A1 and KCNJ1 mutations, while it was only present in one patient with CLCNKB and not in SLC12A3 or BSND mutations. Growth was impaired, but within the normal range (median height standard deviation score −1.2 at the last follow-up). Impaired estimated glomerular filtration rate (eGFR <90 mL/min/1.73 m2) at the last follow-up was seen predominantly with SLC12A1 [71 mL/min/1.73 m2 (IQR 46–74)] and KCNJ1 [62 mL/min/1.73 m2 (IQR 48–72)] mutations. Pathological albuminuria was detected in 31/45 children. / Conclusions: Patients with Bartter and Gitelman syndromes had a satisfactory prognosis during childhood. However, decreased eGFR and pathologic proteinuria was evident in a large number of these patients, highlighting the need to monitor glomerular as well as tubular function. Electrolyte abnormalities were most severe in CLCNKB mutations both at presentation and during follow-up. Fractional excretion of chloride prior to supplementation is a useful screening investigation in children with hypokalaemic alkalosis to establish renal salt wasting

Heat shock proteins and regulatory T cells

Heat shock proteins (HSPs) are important molecules required for ideal protein function. Extensive research on the functional properties of HSPs indicates that HSPs may be implicated in a wide range of physiological functions including immune function. In the immune system, HSPs are involved in cell proliferation, differentiation, cytokine release, and apoptosis. Therefore, the ability of the immune system, in particular immune cells, to function optimally and in unison with other physiological systems is in part dependent on signaling transduction processes, including bidirectional communication with HSPs. Regulatory T cells (Tregs) are important T cells with suppressive functions and impairments in their function have been associated with a number of autoimmune disorders. The purpose of this paper is to examine the relationship between HSPs and Tregs. The interrelationship between cells and proteins may be important in cellular functions necessary for cell survival and expansion during diseased state

South African research in the hydrological sciences: 1999-2002

The principal activities of South African researchers in hydrology and water resources during the reporting period have been concerned with ground- and surface-water interactions, rainfall-runoff modelling, the establishment of improved regional water resource databases, the management of transboundary water resource systems, the ecological reserve, and quantifying the impacts of streamflow reduction activities. Most of these studies have focused on supporting the radically new provisions of the National Water Act of 1998

FBG-based optical interface to support a multisector antenna in a spectrally efficient fiber radio system

We propose and demonstrate a fiber Bragg grating (FBG)-based optical interface for use in a spectrally efficient fiber-radio network with multisector antennas. The system has the novel feature of being specifically developed for use in existing wavelength-division-multiplexed network infrastructures. The proposed scheme supports transport of a remote local oscillator (LO) and three subcarrier multiplexed data channels, destined for different antenna sectors, using a single wavelength. The composite signal was contained within a 25-GHz band, selected via a 25-GHz dispersion-flattened FBG. Recovery of the LO and data channels is performed via optical filtering, using either a novel single grating incorporating multiple phase shifts or multiple narrow bandwidth gratings. Our measurements show that all channels within the 25-GHz band are successfully recovered with less than 2-dB optical power penalty between channels. The use of the 25-GHz grating exhibits an improvement in sensitivity of 3 dB for all data channels

The impact of constructive operating lease capitalisation on key accounting ratios

Current UK lease accounting regulation does not require operating leases to be capitalised in the accounts of lessees, although this is likely to change with the publication of FRS 5. This study conducts a prospective analysis of the effects of such a change. The potential magnitude of the impact of lease capitalisation upon individual users' decisions, market valuations, company cash flows, and managers' behaviour can be indicated by the effect on key accounting ratios, which are employed in decision-making and in financial contracts. The capitalised value of operating leases is estimated using a method similar to that suggested by Imhoff, Lipe and Wright (1991), adapted for the UK accounting and tax environment, and developed to incorporate company-specific assumptions. Results for 1994 for a random sample of 300 listed UK companies show that, on average, the unrecorded long-term liability represented 39% of reported long-term debt, while the unrecorded asset represented 6% of total assets. Capitalisation had a significant impact (at the 1% level) on six of the nine selected ratios (profit margin, return on assets, asset turnover, and three measures of gearing). Moreover, the Spearman rank correlation between each ratio before and after capitalisation revealed that the ranking of companies changed markedly for gearing measures in particular. There were significant inter-industry variations, with the services sector experiencing the greatest impact. An analysis of the impact of capitalisation over the five-year period from 1990 to 1994 showed that capitalisation had the greatest impact during the trough of the recession. Results were shown to be robust with respect to key assumptions of the capitalisation method. These findings contribute to the assessment of the economic consequences of a policy change requiring operating lease capitalisation. Significant changes in the magnitude of key accounting ratios and a major shift in company performance rankings suggest that interested parties' decisions and company cash flows are likely to be affected

Accounting for heterogeneity in θ-σ relationship:application to wheat phenotyping using ΕMI

Geophysical methods, such as electromagnetic induction (EMI), can be effective for monitoring changes in soil moisture at the field scale, particularly in agricultural applications. The electrical conductivity (σ) inferred from EMI needs to be converted to soil moisture content (θ) using an appropriate relationship. Typically, a single global relationship is applied to an entire agricultural field, however, soil heterogeneity at the field scale may limit the effectiveness of such an approach. One application area that may suffer from such an effect is crop phenotyping. Selecting crop varieties based on their root traits is important for crop breeding and maximizing yield. Hence, high throughput tools for phenotyping the root system architecture and activity at the field-scale are needed. Water uptake is a major root activity and, under appropriate conditions, can be approximated by measuring changes in soil moisture from time-lapse geophysical surveys. We examine here the effect of heterogeneity in the θ-σ relationship using a crop phenotyping study for illustration. In this study, the θ-σ relationship was found to vary substantially across a field site. To account for this, we propose a range of local (plot specific) θ-σ models. We show that the large number of parameters required for these models can be estimated from baseline σ and θ measurements. Finally, we compare the use of global (field scale) and local (plot scale) models with respect to ranking varieties based on the estimated soil moisture content change