Radiocommunication in tunnels

Two processes for the improvement of a bifilar line used as a support for propagation in an underground gallery are described. They consist in introducing networks on the line to bring about energy exchanges between the two propagation modes which characterise it.     

Dynamic polymorphic phase transitions in a model binary triglyceride system measured by position-sensitive X-ray diffraction methods

X-ray diffraction measurements have been made on a binary mixture of pure tripalmitin and tristearin which undergoes particular polymorphic phase transitions on heating from the solid. The results were obtained using a position-sensitive detector which can record the whole diffraction pattern in time periods less than a minute. This allows many patterns to be recorded during the transformations where heating rates can be up to several^oC/min. As such the transitory existence of the intermediate β' phase has been unambiguously identified. The results serve to exhibit the usefulness of the X-ray apparatus and indicate its potential for future studies in dynamic crystallization and melting. On behalf of Loders-Croklaan     

The Scope of High-Speed Photography

Picture exposure time and frame repetition rate are the two fundamental parameters which define most high-speed systems. The various light sources, continuous and those of short duration are reviewed. Air sparks and xenon filled gas tubes have the advantage of short durations of a few microseconds and can be used as either single flashes or in multiple form.

Considerable diversity of cameras exist. They fall into the two categories of those that form normal and separate Images or those in which the photographic image is “dissected” by the taking mechanism and then re-constructed afterwards by optical means. Examples of both types are given.

Film drum cameras provide a simple and cheaper technique when the event lasts for a reasonably short time. Electro optical shutters are beginning to be widely employed. In aero-dynamic flow research, many of these methods are combined with Schlieren systems.

Applications of the methods have been made to zoological animal motion studies and to the biological sciences for living material under the microscope. The field of application has been widest in the physical and engineering sciences. Military applications in connection with projectile trajectories, impact studies and explosions in air and underwater have been the spur to much research and development of quipment.     

The politics of plants

Food security is not a new concern, but has taken on new dimensions in recent years. Here we position food security in a broader context relating to the use and management of global biomass resources, and specifically the push to develop a ‘bio-based economy’. We note a growing focus on plants as a source of innovative solutions to complex problems including food security, energy security, climate change and global environmental health. However, we also note that plants are a renewable but finite resource, and propose that renewed enthusiasm for plants is resulting in an increasingly complicated ‘politics of plants,’ as competition for limited land and biomass resources intensifies—the clash between food security and energy security over biofuels being an obvious example. Plants are a common thread across many policy domains including agriculture, energy, environment, health, and industry, and as such we suggest that they might provide a focal point for joined-up thinking and governance. We identify this broader picture as an important backdrop for discussions regarding food security, and from our proposed framework develop a number of recommendations for further investigation.

Fractionally spaced linear and decision-feedback detectors fortransmultiplexers

We investigate improved detectors for transmultiplexer-based high bit rate transmission over dispersive channels like telephone wires. The transmitter is based on a synthesis stage. For the receiver, we design fractionally spaced single-input/multiple-output linear detectors, possibly upgraded with a multiple-input/multiple-output decision-feedback section, for an MMSE criterion. The performance of the system is investigated for filter banks, classical DMT, and different channels. The potential of these detectors is demonstrated,     

Differential scanning calorimetry of confectionery fats: Part II—Effects of blends and minor components

Differential scanning calorimetry (DSC) measurements of the crystallization and melting phenomena of typical confectionery fats are presented. The results show the sensitivity and reproducibility with which DSC data can be used to classify the types of confectionery fat. Calculations of the reproducibility of crystallization and melting parameters obtained from DSC are presented. In addition, the effects are shown on the thermograms of progressive changes in formulation to a typical cocoa butter equivalent. Further, the effects brought on by the presence of minor components, such as trisaturated triglycerides and other polar materials, which are common in confectionery fats, are described and quantified. On behalf of Loders-Croklaan, Wormerveer, Netherlands.     

Underground use of a coaxial cable with leaky sections

The optimum efficiency of a leaky cable as a support for radio communications in tunnels involves a compromise between high leakage fields and a low increase of the coaxial mode attenuation. The latter is an important disadvantage of continuous leaky feeders. To obviate this, short leaky sections can be inserted in an otherwise well-shielded coaxial cable. These sections act as mode converters or radiators. A theoretical analysis based on coupled line theory enables us to determine the optimum characteristics of the leaky sections. Numerous experiments were carried out in a tunnel at various frequencies, using different lengths and characteristics of the leaky sections.     

Differential scanning calorimetry of confectionery fats. Pure triglycerides: Effects of cooling and heating rate variation

Differential scanning calorimetry (DSC) measurements of the crystallization and melting phenomena of pure forms of the three principal triglycerides present in cocoa butter and related confectionery fats are presented. The results are used to exhibit the usefulness of the DSC technique for potential application in quality control of these types of material, but also as a warning of the difficulties in interpretation of data. The results also serve as a reference for future use in DSC studies of similar materials. On behalf of Loders-Croklaan.     

The effect of lauric-based molecules on trilaurin crystallization

The crystal growth of trilaurin and the effect of partial laurates upon it have been investigated by using temperature gradient microscopy with differential scanning calorimetry and X-ray diffraction. The complex nature of trilaurin crystallization was demonstrated. It was found that the addition of monolaurin and lauric acid increased the crystal growth rate of trilaurin but decreased the facet and crystal size. Conversely, there was a significant reduction in growth rate upon the addition of dilaurin isomers. Crystal morphology was also altered, and the relative stability of the metastable phases was increased. The growth rate was lower for a sample containing 1–3 dilaurin than for one containing 1–2 dilaurin. It is postulated that the varying effects are caused by the varying sizes and shapes of the additive molecules.     

Neutron diffraction studies of liquid and crystalline trilaurin

Neutron diffraction has been employed to investigate the structure of trilaurin in both liquid and crystalline states. The combination of long-wavelength (4.5 Å) neutrons and wide angular ranges of detection (～6<2θ[^o]<～100) per mitted a large range of momentum transfer to be acceessed (～0.15?1]<～2) in a single scan of the detector. The chemical technique of selective deuteration of chosen parts of the triglyceride molecules was used to enhance specific aspects of the diffraction pattern and elucidate structures formed. The well established layer structure in the solid phases was confirmed in the diffraction patterns. It was also established that long-range ordering in the solid resulting from chain-chain registry disappeared when the solid melts. However, we found no evidence for long-range ordering in the form of persistence of a layer-layer spacing correlation in the liquid state. We postulate from the diffraction patterns a molecular arrangement resembling the arrangement found in the nematic phase of liquid crystals, where the layer structure is relaxed from that smectic-like arrangement for the crystalline phase. The data also reveal that this lack of order is not dependent on temperature in the liquid phase and persists into the super-cooled region below the normal β melting point.