Interaction of soil, water and TNT during degradation of TNT on contaminated soil using subcritical water

Subcritical water was used at laboratory scale to reveal information with respect to the degradation mechanism of TNT on contaminated soil. Highly contaminated soil (12% TNT) was heated with water at four different temperatures, 150, 175, 200 and 225 degrees C and samples were obtained at appropriate time intervals. At the same time, similar experiments were performed with TNT spiked on to clean soil, sand and pure water in order to compare and eliminate various factors that may be present in the more complex contaminated soil system. Subcritical water was successful at remediating TNT-contaminated soil. TNT destruction percentages ranged between 98 and 100%. The aim of this work was to study the soil-water-contaminant interaction and determine the main physical parameters that affect TNT degradation. It was shown that the rate-limiting step of the process is the extraction/diffusion of TNT molecules from the soil core to the soil surface, where they degrade. Additionally, it was determined that the soil matrix also catalyses degradation to a lesser extent. Autocatalytic effects were not clearly observed.     

Extending the continuous tuning range of an external-cavity diode laser

The continuous tuning range of an external-cavity diode laser can be extended by making small corrections to the external-cavity length through an electronic feedback loop so that the cavity resonance condition is maintained as the laser wavelength is tuned. By maintaining the cavity resonance condition as the laser is tuned, the mode hops that typically limit the continuous tuning range of the external-cavity diode laser are eliminated. We present the design of a simple external-cavity diode laser based on the Littman-Metcalf external-cavity configuration that has a measured continuous tuning range of 1 GHz without an electronic feedback loop. To include the electronic feedback loop, a small sinusoidal signal is added to the drive current of the laser diode creating a small oscillation of the laser power. By comparing the phase of the modulated optical power with the phase of the sinusoidal drive signal using a lock-in amplifier, an error signal is created and used in an electronic feedback loop to control the external-cavity length. With electronic feedback, we find that the continuous tuning range can be extended to over 65 GHz. This occurs because the electronic feedback maintains the cavity resonance condition as the laser is tuned. An experimental demonstration of this extended tuning range is presented in which the external-cavity diode laser is tuned through an absorption feature of diatomic oxygen near 760 nm.     

Significance of warm prestress to crack initiation during thermal shock

During a loss of coolant accident (LOCA) followed by operation of the emergency core cooling system, the inside wall of a nuclear pressure vessel is subjected to high thermal stresses that can cause extension of a pre-existing flaw. During this event the crack-tip stress intensity factor, K_I, may achieve its maximum value early in the transient, but the critical level for crack initiation, K_Ic, may not be reached until minutes later at which time the loading has decreased from its peak. It is shown that this phenomenon, termed warm prestress (WPS), can preclude crack extension when K_I equals or exceeds K_Ic.NRL has conducted an experimental study, employing three-point bend specimens, to investigate the potential for elevation in K_Ic by WPS, and to translate the significance of this behavior into structural terms in the sense of minimizing crack extension in a nuclear vessel during a LOCA. From the experiments it is concluded that the mechanisms associated with WPS act to elevate the K_Ic of the material at the crack tip and that this fact can greatly minimize crack extension that would have been predicted theoretically without consideration of WPS. The experiments demonstrated that failure never occurs during the unloading portion of the simulated LOCA path. This finding is of major significance to the integrity of a vessel. For example, with relatively deep cracks there is a combination of conditions wherein initiation ordinarily would be predicted as K_Ic is reached along a decreasing K_I path. For this set of conditions the present research studies have shown that the WPS phenomenon will preclude all such crack initiation.In terms of margin of safety against fracture it is shown that the elevation in K_Ic caused by WPS is not uniform but depends upon the WPS level, the degree of unloading, and the increment between the temperature of WPS and the failure temperature. For LOCA conditions, however, it is concluded that WPS can result in an effective elevation in K_Ic up to the WPS level assuming, of course, that metallurgically the material is capable of exhibiting this level of toughness.In terms of structural significance it is clear that WPS by itself cannot prevent the initiation of shallow cracks. Specifically, for a reference calculational vessel under the worst combination of conditions including a long, axial flaw and severe radiation embrittlement it is shown that a shallow crack can extend to a relative depth of 0.34 of the wall thickness; further crack extension is prevented by WPS. However, cracks having initial depths greater than 0.2 of the wall are prevented, by WPS, from extending any amount. Finally, it was observed that an elastic analysis of crack extension during a LOCA has predicted nearly complete penetration of the wall without consideration of WPS. Factoring WPS into the same analysis results in predicted crack extension of greatly reduced proportions such that complete penetration of the wall does not occur. Thus, WPS may form a key element upon which to base the assurance of vessel integrity during a LOCA.     

Risk factors for cardiorespiratory and all cause mortality in men and women in urban Scotland: 15 year follow up

STUDY OBJECTIVE: To describe the relationship between risk factors, risk behaviours, symptoms and mortality from cardiorespiratory diseases in an urban area with high levels of socioeconomic deprivation. A cohort study of 15,411 men and women aged 45-64, comprising 80% of the general population of Paisley and Renfrew, Scotland. OUTCOMES: Mortality after 15 years from coronary heart disease(ICD 410-4), stroke(ICD 430-8), respiratory disease(ICD 460-519) and all causes. MAIN RESULTS: Mortality rates from all causes were 19% in men aged 45-49, 31% in men aged 50-54, 42% in men aged 55-59 and 57% in men aged 60-64. The rates are considerably higher than those reported in previous UK prospective studies. For women the rates were 12%, 18%, 25% and 38% respectively. In general men and women showed similar relationships between risk factor levels and mortality rates. People in manual occupations had higher mortality rates. Raised levels of systolic and diastolic blood pressure were associated with increased coronary, stroke and all cause mortality rates. Plasma cholesterol had no such association with all cause mortality rates. High and low levels of body mass index were associated with higher mortality rates than intermediate levels. A relationship between short stature and increased mortality rates was observed in men and women. FEV1 expressed as a percentage of the expected value showed the strongest relationship with mortality rates, particularly for respiratory disease, but also for deaths from coronary heart disease, stroke and all causes. CONCLUSIONS: A similar pattern of relationship between risk factor levels and mortality rates exists in men and women in Renfrew and Paisley. Respiratory impairment as measured by FEV1% predicted appears to be the most likely explanation of the observed high all cause mortality rates in this population.     

Canine fucosidosis: a model for retroviral gene transfer into haematopoietic stem cells

To investigate the role of endovascular treatment we performed a retrospective study of our patients with multiple intracranial aneurysms seen in our institution between October 1992 and March 1995. This period was chosen to study a homogeneous group of patients since the appearance of controlled detachable coils, and to obtain the largest number of patients with angiographic follow-up of the aneurysms treated. We studied 53 patients with a total of 128 aneurysms, in 46 of whom we treated 67 aneurysms by the endovascular approach. Of these, 5 aneurysms in 3 patients were treated by occlusion of the parent vessel and 62 aneurysms in 43 patients with coils, 52 with Guglielmi detachable coils and 10 with mechanically detachable spirals. Complete occlusion was obtained in 58 aneurysms, and partial occlusion in 9. The therapy caused permanent neurological deficit in 3 cases (6.5%), and there was 1 case of rebleeding (incomplete occlusion of the aneurysm). No deaths occurred. All aneurysms were treated in 29 of the 53 patients. Endovascular procedures were used for 16 patients (30%), surgery was performed in 1 patient (2%) and the two were combined in 12 (23%). In 23 of 53 cases (43%), unruptured aneurysms were left untreated, usually because of their small size. In 1 patient with unruptured aneurysms, the endovascular approach failed and the patient refused surgery.     

On non-Hookean behaviour of carbon fibres in bending

The deformation characteristics of a range of single, large diameter pitch-based carbon fibres, and some PAN- and rayon-based fibres, were studied in elastica loop bending experiments. In pitch-based fibres, non-Hookean behaviour was found to occur at lower strains the greater the fibre anisotropy. Only elastic deformation to failure, at strains of 3%, was found for low-modulus, nearly isotropic pitch- and rayon-based fibres. The non-linear elastic behaviour in pitch-based fibres resulted in pronounced hysteresis and discontinuities in the stress-strain plots on both unloading and reloading the loops. These effects are due to the initiation, propagation and possible healing of transverse microcracks on the compression side of the fibres.     

Appropriateness of the Wechsler Preschool and Primary Scale of Intelligence for gifted children.

The extent to which the WPPSI provides items of sufficient difficulty for gifted children was investigated using a sample of 306 4–6 yr olds with IQs of 120 and above. All subtests investigated were found to have an inadequate level of difficulty, and 6 of the subtests were inadequate for half or more of the Ss. Results question the viability of scatter analysis and validity of subtest scores when using the WPPSI with gifted children. (4 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Correlations between microstructural parameters, micromechanical properties and wear resistance of plasma sprayed ceramic coatings

The micromechanical integrity of a ceramic plasma sprayed (PS) coating is determined by the size and distribution of the defects found in the coating, such as porosity, the inter-lamellar microcrack density, the intra-lamellar microcrack density as well as the lamellar, or splat, dimensions. In this work, several micromechanical tests were used to advance our understanding of the relationships between the different microstructural parameters found in PS ceramic coatings. The tests included depth sensing indentation, micro and macrohardness testing, and controlled scratch testing. Abrasive and erosive wear tests were performed on the same set of coatings, including plasma sprayed alumina and chromia, as well as sintered alumina as a reference material. The best correlations were found between the material hardness (H), the level of porosity (P) and the abrasive wear volume (W). Knoop hardness measurements provided the best correlation with wear data, followed by scratch hardness and Vickers hardness. An exponential function of the type W=k/Hⁿ was found, where k and n are constants. A similar function describes the correlation of wear volume with the elastic modulus of the coating. Fracture toughness could only be correlated with wear volume when combined with hardness in a function of the type W=k/H^0.5K_c^0.5. The incorporation into this function of a “microstructural factor” M=Pⁿ improves the correlation.