Aminotetryls: Synthesis,spectral characterization,thermal decomposition and explosive properties

This paper describes the synthesis and spectral investigations of two amino derivatives of N-methyl-N-(2,4,6-trinitrophenyl)nitramine (tetryl). Also discussed are the results from thermal decomposition studies on the three explosives, viz. tetryl, 3-aminotetryl (3 AT) and 3,5-diaminotetryl (3,5 DAT) and preliminary work on the explosive properties of the last two compounds. The aminotetryls have been prepared by the amination of the corresponding chlorotetryls. The yield was 87% for 3 AT, but was only 33% for 3,5 DAT, probably due to steric crowding around the benzene nucleus. The mass spectra show interesting differences in the electron impact fragmentation patterns of the three tetryls with the M⁺ ion relative intensities following the order 3,5 DAT > 3 AT > tetryl, which could be due to (a) resonance stabilization and (b) hydrogen bonding effects. Evidence for the latter is also found in the infrared spectra of these compounds. Arrhenius kinetic parameters derived from thermal decomposition studies of the three compounds are presented and show that 3,5 DAT is thermally less stable than 3 AT. Explosive sensitiveness tests indicate that the diamino compound is the most sensitive, the trend being 3,5 DAT > 3 AT > tetryl. This is contrary to the generally found desensitizing influence of NH₂ groups on the thermal stability and explosive sensitiveness of trinitroaromatic energetic molecules. Mechanisms to account for the observed thermal decomposition behaviour and explosive sensitiveness patterns are discussed.     

Optimized centre-feed clarifier design for the Tai Po Sewage Treatment Works,Hong Kong

Stability of sludge blanket is a critical factor controlling the performance of clarifiers. A three-dimensional computational fluid dynamics (CFD) model was applied to optimize the clarifier design at the Tai Po Sewage Treatment Works, Hong Kong. Validated by field data, the CFD model evaluated the key clarifier design elements including side-water depth, centre-feed inlet, flocculation well and returned activated sludge (RAS) flow. Based on field observations and modelling results, the new design aims at eliminating the strong turbulence typical of centre-feed inlets in the clarifier, thus creating a better flocculation environment, and reducing disturbance to the sludge blanket. The modelling results also demonstrated a marked improvement in clarifier performance after the increase in clarifier depth and hence sludge storage capacity. The increased storage capacity reduces the risk of high sludge blanket levels upsetting the clarified effluent quality under high flow or solids loading conditions.     

Multiphoton Physics

Abstract

We discuss recent developments in the generation of ultra-intense laser pulses and show how these can be used to study matter in the presence of electric fields that compete with that due to the nucleus. This has led to a very rapid growth in a wide range of multiphoton studies, many of which are represented in this volume.     

The Development of a Spacer Layer Imaging Method (SLIM) for Mapping Elastohydrodynamic Contacts

Optical interferometry has proved to be a valuable experimental tool in the study of elastohydrodynamic lubrication (EHD). It is a technique that gives detailed information on the lubricant film distribution within the contact; however, the sensitivity is limited and it is only recently, with the development of the spacer layer optical technique, that the study of the thin film lubrication regime has been possible. The limitation of the spacer layer technique is that generally only one measurement is taken from the center of the contact. The next logical step in the development of this technique is, therefore, a system that combines the mapping capabilities of the original optical method with the thin film capabilities of the spacer layer approach.

This paper describes the development of a contact mapping technique that uses the spacer layer approach to visualize, and measure, thin lubricant films in concentrated contacts. The development of the technique is described and its application to both static and moving contacts reported. Thin EHD films (down to 10 nm) have been measured and mapped.     

Visual servo control. I. Basic approaches

This paper is the first of a two-part series on the topic of visual servo control using computer vision data in the servo loop to control the motion of a robot. In this paper, we describe the basic techniques that are by now well established in the field. We first give a general overview of the formulation of the visual servo control problem. We then describe the two archetypal visual servo control schemes: image-based and position-based visual servo control. Finally, we discuss performance and stability issues that pertain to these two schemes, motivating the second article in the series, in which we consider advanced techniques     

Graphing the death of Escherichia coli

The graphical presentation of measurements of the progress over time of bacterial death or inactivation is discussed. Specifically, the Weibull distribution may be a useful generalisation of the exponential distribution. Data from experiments on the non-thermal death of Escherichia coli reported by Shadbolt et al. [Int. J. Food Microbiol. 49 (1999) 129] are reexamined to support this claim.     

Views of hospital staff on the management of hypertension

A questionnaire concerning the detection and management of hypertension was presented to 265 hospital doctors, 114 medical students and 59 student nurses. Of these 75% were completed. Although only 76% thought that routine measurement was necessary in outpatients, 92% of respondents thought that blood pressure (BP) should be measured routinely in all in-patients. A total of 17% of all doctors and 11% of physicians indicated that they would not use drug treatment until the diastolic BP exceeded 105 mmHg. Thirty-four per cent of respondents still use diastolic phase IV and 84% felt that BP should be measured 2-4 times before deciding on treatment but the posture of the patient (lying, sitting or standing) during recording was inconsistent. Seventy-seven per cent of respondents indicated that they recorded BP to the nearest 5 mmHg and 4% to the nearest 10 mmHg. Despite the literature on the subject, there are still widely differing opinions amongst medical staff on how to record BP and at what level it should be treated.     

Crazing and fracture of polystyrene

The effects of the concentration of internal lubricants on the deformation and fracture of commercial polystyrenes produced by bulk and suspension polymerization routes are described. The addition of internal lubricant in the range 0 to 6% was shown to cause a decrease in the extent of craze-yielding and in the incidence of secondary fracture features, and over-all the changes in behaviour were similar to those observed when the test temperature is increased.     

Non-conventional injection molding of poly(lactide) and poly(ε-caprolactone) intended for orthopedic applications

Biodegradable polymers such as poly(lactide) (PLA) and poly(epsilon-caprolactone) (PCL) are increasingly used in biomedical applications as temporary implants. However, melt processing of these materials in particular of PLA is difficult due to the temperature sensitivity. Within this study, PLA and PCL were injection molded conventionally and by using the process shear controled orientation in injection molding (SCORIM) in order to investigate the effect of processing parameters on the physical properties of the moldings. Therefore, flexural testing, differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), molecular weight (MW) and orientation measurements were performed. PLA showed high sensitivity to melt temperature. In the case of amorphous poly(DL-lactide), the molecular weight and subsequently the ductility is substantially reduced by processing at higher melt temperatures. In the case of crystallizable poly(L-lactide), higher melt temperatures and shear induced by the SCORIM process resulted in enhanced crystallinity, which compromised the mechanical properties. Generally, SCORIM processing improved the mechanical properties, in particular the ductility, by orientating the molecular structure. PCL was shown to be less sensitive to shear and temperature than PLA. Stress at yield and stiffness are more improved by SCORIM processing. However, the processing temperature in combination with the grade used proved to be influential for the mechanical properties of resulting moldings.     

The microstructure and deformation of model ABS compounds

Model ABS compounds have been used to investigate the effect of graft frequency and rubber particle size on microstructure and mechanical properties. Graft frequency was found to have a marked effect on the microstructure of ABS polymers and increasing the graft frequency resulted in an improvement in the dispersion of the rubber phase.