Mechanism Controlling Permeability Change in Clays due to Changes in Pore Fluid

When a water-saturated clayey soil is leached with an organic fluid such as heptane, it has been found that under some conditions the hydraulic conductivity (or the permeability) increases manyfold. While it is generally agreed that physicochemical changes (e.g., compression of double-layer thickness) and the consequent alterations to the internal fabric (e.g., shrinkage of clusters) are responsible in most cases for such an increase, the underlying mechanism is not clearly understood. Two possible mechanisms are (1) formation of a few macrocracks due to shrinkage of clusters and (2) uniform increase in intercluster porosity throughout the volume of the soil due to shrinkage of clusters. The objective of the study presented here is to examine the most plausible mechanism of permeability increase caused by leaching. With the aid of Olsen’s permeability equation based on the cluster model, Poiseuille’s law for laminar fluid flow between two parallel plates, physicochemical theories, and experimental permeability data, it is shown that the formation of macrocracks is the most plausible mechanism of permeability increase.     

Nutritional value of mixtures of baladi bread and broad beans

Several supplementation mixtures to the local Egyptian bread were designed and tested for their p.e.r. and n.p.u. values using weanling rats. In the first experiment, broad beans (var. baladi) were subjected to five different methods of preparation and each of the products was added to bread-based diets at 50 : 50 nitrogen ratio. When the p.e.r. (1.78) and n.p.u. (53) values of the raw beans were set as 100 and 100, the respective following values are obtained: 94, 98 for soaked; 94, 87 for germinated followed by boiling and 59, 79 for autoclaved beans (1 h). In the second experiment 11 different protein mixtures were tested for their p.e.r. values. The tested protein mixture with the lowest p.e.r. value is that from bread + 0.5% DL-Met (p.e.r. = 1.3). The most favourable mixture found is bread + Met + Lys + Thr (p.e.r. = 3.3) to bring it to level furnished by whole egg, followed by the mixtures bread N and raw broad bean N 40:60 (p.e.r. = 3.0); bread N and stewed broad bean N 70:30 (p.e.r. = 2.8). Upon supplementation with 0.5% DL-Met mean p.e.r. values of 3.0 and 2.7 were obtained for raw and stewed broad beans diets, respectively. The amino acid analyses showed losses of 10 and 35% in the lysine and S-containing amino acids, respectively, after autoclaving the beans for 1 h.     

Decarbonising road transport with hydrogen and electricity: Long term global technology learning scenarios

Both fuel cell and electric vehicles have the potential to play a major role in a transformation towards a low carbon transport system that meets travel demands in a cleaner and more efficient way if hydrogen and electricity was produced in a sustainable manner. Cost reductions are central to this challenge, since these technologies are currently too expensive to compete with conventional vehicles based on fossil fuels. One important mechanism through which technology costs fall is learning-by-doing, the process by which cumulative global deployment leads to cost reduction. This paper develops long-term scenarios by implementing global technology learning endogenously in the TIAM-UCL global energy system model to analyse the role of hydrogen and electricity to decarbonise the transport sector. The analysis uses a multi-cluster global technology learning approach where key components (fuel cell, electric battery and electric drive train), to which learning is applied, are shared across different vehicle technologies such as hybrid, plug-in hybrid, fuel cell and battery operated vehicles in cars, light goods vehicles and buses. The analysis shows that hydrogen and electricity can play a critical role to decarbonise the transport sector. They emerge as complementary transport fuels, rather than as strict competitors, in the short and medium term, with both deployed as fuels in all scenarios. However, in the very long-term when the transport sector has been almost completely decarbonised, technology competition between hydrogen and electricity does arise, in the sense that scenarios using more hydrogen in the transport sector use less electricity and vice versa.     

Critical State of Granular Materials Based on the Sliding-Rolling Theory

By representing the assembly by a simplified column model, a constitutive theory was recently developed for a two-dimensional assembly of rods. This theory, referred to as the sliding-rolling theory, is extended in this paper to represent the triaxial stress-strain behavior of granular materials. The sliding-rolling theory provides a dilatancy rule and an expression for the slope of the line of zero dilatancy in the stress space. These rules are then combined with triaxial observations to provide a microstructural interpretation of the critical state of granular materials. According to the theory, the slope of the critical state line in the stress space depends on the interparticle friction angle and the degree of contact normal anisotropy. To verify the basic ideas of the sliding-rolling theory, numerical experiments are conducted using the discrete-element method on three-dimensional assemblies of spheres.     

Triaxial Behavior of Kaolinite in Different Pore Fluids

Due to the existence of physicochemical effects, the pore fluid type generally has a significant influence on the geotechnical behavior of clays. The present paper focuses on the stress-strain and shear-strength behavior of kaolinite in various pore fluids. Kaolinite specimens, initially prepared by 1D consolidation of kaolinite∕water slurries, were isotropically consolidated in a triaxial cell to the desired consolidation pressure. The specimens were then leached with the desired fluid and sheared under undrained condition to failure. Six different fluids including water, formamide, ethanol, acetic acid, triethylamine, and heptane were used. It was observed that leaching with certain fluids converts the otherwise normally consolidated specimens into overconsolidated specimens with respect to the stress-strain behavior of the soil. As a result of the apparent overconsolidation, the shear strength of the triaxial specimens increases. The results are discussed in relation to the change in physicochemical factors. A possible cause of apparent overconsolidation is presented, with some supporting physicochemical analyses.     

Investigation of pulse pedestal and dynamic chirp formation on picosecond pulses after propagation through an SOA

The authors investigate the propagation of picosecond pulses through semiconductor optical amplifiers using the measurement technique of frequency resolved optical gating. The work shows the generation of significant pulse pedestals and frequency chirp across the optical pulses, which initially have a duration of 2 ps. As the input peak power of the optical pulses is increased from 2.4 to 80 mW, the pulse pedestals increased by 20 dB and the chirp became significantly more nonlinear. The generated pedestals and the nonlinear output chirp may cause serious degradation in high-speed communications systems employing wavelength-division-multiplexing and optical time-division-multiplexing techniques.     

Two-Photon-Absorption-Based OSNR Monitor for NRZ-PSK Transmission Systems

A two-photon absorption microcavity-based technique for monitoring in-band optical signal-to-noise ratio (OSNR) in nonreturn-to-zero phase-shift-keying systems is presented. Experiments using a 10-Gb/s differential phase-shift-keying system showed that accurate measurements ($pm$1 dB) were possible for OSNRs in excess of 20 dB.      

Cavity Length Independent Continuous Repetition Rate Tuning of a Self-Seeded Gain-Switched Fabry–PÉrot Laser

We propose a novel method that allows continuous repetition rate tuning of a self-seeded gain-switched Fabry-Perot laser without the need for change in cavity length. This is achieved by employing a linearly chirped fiber Bragg grating with a large dispersion parameter. The dispersed pulses overlap to produce a continuous-wave-like feedback into the gain-switched laser cavity. By using the proposed experimental setup, we demonstrate pulses portraying sidemode suppression ratios of at least 30 dB and widths of about 30 ps over the entire repetition rate tuning range of 2.5-10 GHz.     

Interactions and implications of renewable and climate change policy on UK energy scenarios

As a response to the twin challenges of climate change mitigation and energy security, the UK government has set a groundbreaking target of reducing the UK’s economy-wide carbon emissions by 80% from 1990 levels by 2050. A second key UK energy policy is to increase the share of final energy consumption from renewables sources to 15% by 2020, as part of the wider EU Renewable Directive. The UK’s principle mechanisms to meet this renewable target are the Renewable Obligation (RO) in the electricity sector, the Renewable Transport Fuel Obligation (RTFO), and most recently the Renewable Heat Programme (RHP) for buildings. This study quantifies a range of policies, energy pathways, and sectoral trade-offs when combining mid- and long-term UK renewables and CO₂ reduction policies. Stringent renewable policies are the binding constraints through 2020. Furthermore, the interactions between RO, RTFO, and RHP policies drive trade-offs between low carbon electricity, bio-fuels, high efficiency natural gas, and demand reductions as well as resulting 2020 welfare costs. In the longer term, CO₂ reduction constraints drive the costs and characteristics of the UK energy system through 2050.     

Supplementary and weaning foods for the Egyptian child

Attempts were made to prepare 5 protein rich food mixtures to be used as supplementary and weaning foods for children from 6 months of age onwards. They contain vegetable and animal protein sources. They were prepared in a way to simplify their use. Potatoes, carrots and peas were the basal ingredient in each mixture. The protein content of the mixtures ranges from 16-20% with a chemical score not less than 50%. The mixtures contained most of the essential amino acids in optimal concentrations, except methionine and cystine which are slightly lower than the amounts recommended by FAO. The nutritive value of each mixture estimated by the slope ratio bioassay procedure was high. They are nutritionally superior to casein, used as a reference protein. They differ slightly when compared with each other.