Etch rate and spectroscopic ablation studies of Er:YAG laser-irradiated dentine

The interaction of a 200-mus Er:YAG laser at 2.94 mum with human molar dentine has been studied by ablation depth rate measurements as well as time-resolved and optical multichannel analyzer emission spectroscopy. Ablation rates indicate a threshold fluence of ~5.2 J cm(-2) for significant material removal with a low-fluence (<20 J cm(-2)) effective optical absorption coefficient of ~700 cm(-1). Deviation from a Beer's law dependence is significant in the range ~20 to ~60 J cm(-2) and indicates a maximum effective plume absorption of ~1200 cm(-1) at ~40 J cm(-2), coinciding with the appearance of strong line and broadband optical emission in the visible region. Time-of-flight emission measurements yield maximum species-resolved ablation velocities of up to ~1.2 x 10(6) cm s(-1), enabling calculation of plasma temperatures. The results suggest that etch-rate characteristics are driven by changes in plume absorption dynamics, which have a strong dependency on incident laser fluence.     

Socioeconomic determinants of health. The contribution of nutrition to inequalities in health

Social class differences in health are seen at all ages, with lower socioeconomic groups having greater incidence of premature and low birthweight babies, heart disease, stroke, and some cancers in adults. Risk factors including lack of breast feeding, smoking, physical inactivity, obesity, hypertension, and poor diet are clustered in the lower socioeconomic groups. The diet of the lower socioeconomic groups provides cheap energy from foods such as meat products, full cream milk, fats, sugars, preserves, potatoes, and cereals but has little intake of vegetables, fruit, and wholewheat bread. This type of diet is lower in essential nutrients such as calcium, iron, magnesium, folate, and vitamin C than that of the higher socioeconomic groups. New nutritional knowledge on the protective role of antioxidants and other dietary factors suggests that there is scope for enormous health gain if a diet rich in vegetables, fruit, unrefined cereal, fish, and small quantities of quality vegetable oils could be more accessible to poor people.     

Pathophysiologic theories in the etiology of Meniere's disease

The etiology of the attacks of vertigo that occur in Meniere's disease is discussed in this article. None of the current theories remain tenable in view of recent findings concerning the physiology and pathophysiology of the cochlea and endolymphatic sac. A new theory suggests that a narrowed duct becomes obstructed by debris that is cleared by a combination of the secretion of hydrophillic proteins within the sac and a hormone, saccin, that increases the volume of endolymph within the cochlea. It is proposed that the sudden restoration of longitudinal flow initiates the attacks of vertigo.     

Is diurnal variation of mood associated with parasympathetic activity?

70 patients older than 50 years (mean age: 60.2 years) underwent a CD-spondylodesis from 1987 to 1991 for degenerative changes of the lumbar spine, and were followed for 2 years. 88.2% improved, but only 47.1% showed a good-to-excellent result. Patients with fair and poor outcomes had had significantly more operations on the lumbar spine (p < 0.001), had a greater extent of preoperative lumbar kyphosis (p < 0.05), motor weakness (p < 0.05), had less vertebral slips (p < 0.01), had less posterior distraction postoperatively (p < 0.001), and had a greater extent of postoperative motor weakness compared to patients with good-to-excellent outcomes. Age, sex, duration of back/leg pain, taking of analgetic drugs, preoperative pain status, profession, range of walking, time of operation, number of fused segments, blood loss, blood transfusion, postoperative profile of the spine did not show any significant influence upon clinical results. Already at 6-months-follow-up there was significant difference of the clinical outcome (p < 0.001), making improvement of a then fair or poor result unlikely.