Spatial temperature distribution in human hairy and glabrous skin after infrared CO2 laser radiation

<p>Abstract</p> <p>Background</p> <p>CO₂lasers have been used for several decades as an experimental non-touching pain stimulator. The laser energy is absorbed by the water content in the most superficial layers of the skin. The deeper located nociceptors are activated by passive conduction of heat from superficial to deeper skin layers.</p> <p>Methods</p> <p>In the current study, a 2D axial finite element model was developed and validated to describe the spatial temperature distribution in the skin after infrared CO₂laser stimulation. The geometry of the model was based on high resolution ultrasound scans. The simulations were compared to the subjective pain intensity ratings from 16 subjects and to the surface skin temperature distributions measured by an infrared camera.</p> <p>Results</p> <p>The stimulations were sensed significantly slower and less intense in glabrous skin than they were in hairy skin (MANOVA, p < 0.001). The model simulations of superficial temperature correlated with the measured skin surface temperature (r > 0.90, <it>p </it>< 0.001). Of the 16 subjects tested; eight subjects reported pricking pain in the hairy skin following a stimulus of 0.6 J/cm²(5 W, 0.12 s, d1/e²= 11.4 mm) only two reported pain to glabrous skin stimulation using the same stimulus intensity. The temperature at the epidermal-dermal junction (depth 50 μm in hairy and depth 133 μm in glabrous skin) was estimated to 46°C for hairy skin stimulation and 39°C for glabrous skin stimulation.</p> <p>Conclusions</p> <p>As compared to previous one dimensional heat distribution models, the current two dimensional model provides new possibilities for detailed studies regarding CO₂laser stimulation intensity, temperature levels and nociceptor activation.</p

Gamma Oscillations in the Mouse Primary Visual Cortex as an Endophenotype of Schizophrenia

Gamma oscillations (20-50 Hz) are a robust component of brain activity associated with information processing, but are also part of the background spontaneous activity during various brain states including sleep and anesthesia. Our goal was to examine the changes in gamma oscillations that result from pharmacological and genetic manipulations of glutamatergic transmission which produce endophenotypes of schizophrenia. We recorded local field potentials (LFP) and single units through the depth of the mouse primary visual cortex in vivo and examined the alterations in gamma frequency activity under both normal and pathological conditions. Our results indicate that both in awake and anesthetized animals, baseline gamma frequency power in the LFP is increased throughout the cortical lamina, and the signal-to-noise ratio of gamma oscillations produced by a visual stimulus is diminished, most notably in the superficial layers. In addition, the entrainment of single units to the local oscillations in the LFP is reduced in the supragranular (L2/3) and infragranular (L5/6) layers. This work supports the hypothesis that alterations in glutamatergic transmission result in changes to gamma oscillations in primary sensory areas and is consistent with the hypothesis that these changes are associated with disrupted sensory perception

Social foundations of the mathematics curriculum: a rationale for change

The nature of educational aims as criteria for worthwhile curriculum practice is explored and a cross-section of aims for mathematics education is discussed. An aim for mathematics education which emphasises the social aspect of the subject in its being, its conduct and its applications is identified and epistemological foundations for such a view of the nature of the subject are explored. It is argued that such an epistemological perspective of mathematics would be reflected in the social context of the mathematics classroom, arising from a methodology in which the subject would become more problematic and open to change, investigation and hypothesis. The aims of two major mathematics curriculum development projects (the Nuffield Mathematics Project and the School Mathematics Project) are examined to determine the extent to which their aims may take the 'social' nature of mathematics into account. The probable social context of mathematics classrooms using their materials is postulated in an attempt to characterise the nature of the subject as it is reflected in these materials. A view of the nature of mathematics held by practising teachers and by pupils is then established by drawing upon, and extrapolating from, evidence relating to the social context of mathematics classrooms at primary and secondary level. Conclusions follow, which suggest that fundamental change in mathematics education requires, as a first step, the adoption of a new epistemological perspective of the subject in order that the pursuit of the aim which emphasises the social nature of mathematics is achieved. It is suggested that this, in turn, ultimately could lead to the desired balance in the mathematics curriculum which hitherto has been lacking

Severity of Giardia infection associated with post-infectious fatigue and abdominal symptoms two years after

<p>Abstract</p> <p>Background</p> <p>A high rate of post-infectious fatigue and abdominal symptoms two years after a waterborne outbreak of giardiasis in Bergen, Norway in 2004 has previously been reported. The aim of this report was to identify risk factors associated with such manifestations.</p> <p>Methods</p> <p>All laboratory confirmed cases of giardiasis (n = 1262) during the outbreak in Bergen in 2004 received a postal questionnaire two years after. Degree of post-infectious abdominal symptoms and fatigue, as well as previous abdominal problems, was recorded. In the statistical analyses number of treatment courses, treatment refractory infection, delayed education and sick leave were used as indices of protracted and severe <it>Giardia </it>infection. Age, gender, previous abdominal problems and symptoms during infection were also analysed as possible risk factors. Simple and multiple ordinal logistic regression models were used for the analyses.</p> <p>Results</p> <p>The response rate was 81% (1017/1262), 64% were women and median age was 31 years (range 3-93), compared to 61% women and 30 years (range 2-93) among all 1262 cases. Factors in multiple regression analysis significantly associated with abdominal symptoms two years after infection were: More than one treatment course, treatment refractory infection, delayed education, bloating and female gender. Abdominal problems prior to <it>Giardia </it>infection were not associated with post-infectious abdominal symptoms. More than one treatment course, delayed education, sick leave more than 2 weeks, and malaise at the time of infection, were significantly associated with fatigue in the multiple regression analysis, as were increasing age and previous abdominal problems.</p> <p>Conclusion</p> <p>Protracted and severe <it>giardiasis </it>seemed to be a risk factor for post-infectious fatigue and abdominal symptoms two years after clearing the <it>Giardia </it>infection.</p