Toughening of Dental Porcelain by Tetragonal ZrO2 Additions

The effect on mechanical behavior of ZrO₂ additions to a dental porcelain was investigated. The ZrO₂ was introduced into the glassy matrix phase of the porcelain by refritting the all-glass porcelain constituent. X-ray diffraction indicated that a sizeable fraction of the ZrO₂ was retained in the tetragonal form after the porcelain was fired. Zirconia additions to the porcelain produced substantial improvements in fracture toughness, strength, and thermal shock resistance.     

Matrix unit cell scheduler (MUCS) for input-buffered ATM switches

This paper presents a novel matrix unit cell scheduler (MUCS) for input-buffered asynchronous transfer mode (ATM) switches. The MUCS concept originates from a heuristic strategy that leads to an optimal solution for cell scheduling. Numerical analysis indicates that input-buffered ATM switches scheduled by MUCS can utilize nearly 100% of the available link bandwidth. A transistor-level MUCS circuit has been designed and verified using HSPICE. The circuit features a regular structure, minimal interconnects, and a low transistor count. HSPICE simulation indicates that using 2-μm CMOS technology, the MUCS circuit can operate at clock frequency of 100 MHz     

An outbreak of malignant catarrhal fever in young rusa deer (Cervus timorensis)

On the basis of clinical signs and histological findings eight 9-month-old male rusa deer (Cervus timorensis) were diagnosed with sheep associated-malignant catarrhal fever. Following a variable course involving rectal temperatures around 40.5 degrees C, depression, inappetence, diarrhoea, corneal opacity and hypopyon all animals died or were euthanased over a 5-week period. Severe multifocal vasculitis, mainly periglomerular and in the arcuate vessels were consistent histological findings which in the past have been adequate to confirm clinical diagnosis of sheep associated-malignant catarrhal fever. A nested polymerase chain reaction test has been used to detect a sheep associated-malignant catarrhal fever PRC product, 238 base-pairs in size, in DNA extracted from lymphocyte preparations. The result supported the diagnosis of sheep associated-malignant catarrhal fever in these deer.     

The significance of traumatic intraventricular haemorrhage in severe head injury

Since the advent of computed tomography (CT) traumatic intraventricular haemorrhage (IVH) has been diagnosed more often. It has reportedly been associated with a poor prognosis, but pure or solitary IVH is rare, suggesting that other lesions occurring concurrently with it may contribute to the poor outcome. In a series of 65 patients with severe head injury (GCS < or = 8), 14 (22%) had IVH on initial CT. Death rate in these 14 was 21%, not significantly different from that in patients without IVH (14%), although a significantly higher proportion of patients without IVH had a good outcome. These results suggest that mortality is related to other lesions associated with IVH rather than to IVH alone and that the presence of IVH does not necessarily lead to a poor outcome.     

Management of nasopharyngeal and oropharyngeal stenosis in children

Nasopharyngeal stenosis and oropharyngeal stenosis are rare and challenging problems in the pediatric population. The most common etiology is currently the surgical trauma associated with adenotonsillectomy. Stenosis can vary from a thin band to a complete obstructing cicatrix. Presenting symptoms range from mild hyponasal speech to severe airway obstruction. We present a series of eight children with varying degrees of stenosis and associated symptoms. Choice of treatment varied with the severity of disease. In our series, successful interventions included triamcinolone acetonide injection, lysis of adhesions, rotational and advancement mucosal flaps, and jejunal free flap. Preoperative evaluation and individualized surgical repair are essential for successful treatment.     

Neurotransmitter receptor plasticity in aging

Neurotransmitter receptor plasticity is an important part of the compensatory processes by which the central nervous system adapts to pathological insult, long-term exposure to drugs or neuronal loss with advanced age. Receptor plasticity can be manifest as changes in the number of receptors (i.e., up- or down-regulation), changes in expression of mRNA for discrete receptor proteins, or alterations in receptor coupling to signal transduction systems. Evidence exists for impaired plasticity of neurons in the aged brain, which results in decreased ability to adjust to changes in their environment. However, such data are highly dependent on the neurotransmitter examined, the stimulus for receptor regulation and the animal model chosen for study. For example, senescent rats show an age-related impairment of muscarinic receptor up- or down-regulation after long-term exposure to cholinergic drugs. Thus, young rats exposed to chronic (three weeks) intracerebroventricular infusions of methylatropine or oxotremorine exhibit compensatory changes in the density of muscarinic receptors in frontal cortex and hypothalamus. In contrast, 3H-QNB binding is unaltered in the same brain regions of identically treated senescent rats. Similar observations of impaired muscarinic receptor plasticity in senescent animals have been confirmed by other investigators. Age-related differences in coupling of brain muscarinic receptors to G-proteins and in muscarinic receptor-stimulated phosphoinositide hydrolysis have also been reported. Interestingly, neuropeptides such as neurotensin, cholecystokinin and VIP can potentiate carbachol-stimulated phosphoinositide hydrolysis in frontal cortex of both young and aged rats. This adds another level at which cholinergic neurotransmission may be modulated in senescent animals. Potential age-related differences in the effects of chronic drug treatments or experimental brain lesions on muscarinic receptor coupling to second messenger systems or on expression of mRNA for particular muscarinic receptors are currently unknown. Hence, it is possible that senescent animals may show additional deficiencies in plasticity of muscarinic receptor mediated signal transduction or expression of muscarinic receptors subtypes.     

Virtual reality in Africa – for Africa

The paper describes a number of virtual reality projects taking place in Africa. The availability of VR on PCs, it is argued, has made access possible for a large number of users. Applications for education and training and applications that preserve and promote African culture are particularly highlighted.     

Radiopharmacology of inhaled 133Xe in skeletal sites containing deposits of Gaucher cells

Gaucher's disease is a lysosomal storage disease in which cells of the reticuloendothelial system accumulate the lipid glucocerebroside. It is characterized by slowly progressive visceral and osseous involvement. One of the latter manifestations includes lipid infiltration of bone marrow. We monitored the rate of inhaled 133Xe uptake and wash-out over diseased and normal metaphyseal and epiphyseal areas of the knee. Twenty-two patients (15 adults, 7 children) with various degrees of previously diagnosed Gaucher's disease were positioned supine under a gamma-camera interfaced to a computer system. All patients rebreathed 133Xe gas from a closed system for 10 min followed by 14 min of wash-out. Digitized images of the lung, liver, spleen, bony sites and soft tissue were obtained at 1 min intervals during the wash-in and wash-out phases. Counts for each ROI were normalized per 100 pixels and plotted as a function (time). Maximum uptake was also calculated by relating the counts/ROI/100 pixels to the 10 min integrated lung count during equilibrium (the administered "dose"). There was essentially no 133Xe uptake in liver and spleen involved with Gaucher's disease. Monophasic uptake and biphasic wash-out curves were observed in the limited investigative population. Skeletal Gaucher deposits released the 133Xe at a greater rate relative to soft tissue.