Velocity half-sphere model for multiple light scattering in turbid media

We extend the traditional diffusion theory by distinguishing between the energy radiance in the forward and backward directions at each point in space. This approach leads to a new effective source for the diffusion equation that is nonzero for an anisotropic light source. It differs significantly from the diffusion theory for short source-detector spacings. We derive an analytical solution for the two lowest-order velocity moments of the radiance.

Generalized diffusion solution for light scattering from anisotropic sources

The traditional diffusion theory, often used for isotropic sources, becomes inaccurate at short source-detector spacings and cannot be applied to media with large absorption or with small scattering strengths. We show that for any type of source anisotropy, a Green's-function-based procedure can remove these limitations. The accuracy of the new approach is examined through a comparison with the numerical solution to the radiative transfer equation.

Determination of g and mu using multiply scattered light in turbid media

We propose an inversion scheme to reconstruct the scattering coefficient mu and the anisotropy factor g that characterize the optical properties of a turbid medium. It is based on a theory for the scattering of light inside the medium from an angularly collimated light source. We demonstrate the feasibility of this method using light scattering data obtained from a Monte Carlo simulation.

Bridging the microscopic and macroscopic theories for light reflected from disordered plane-parallel dielectric slabs

For a system of randomly arranged plane-parallel dielectric layers with randomly varying index of refraction and width, we compare the reflection coefficient derived from the Maxwell equations with that of the Boltzmann theory. For a strictly monochromatic field this coefficient is an oscillatory function of the laser frequency. We show how suitable frequency or ensemble averaging permits a comparison of the two theories. The calculation of the usual Boltzmann scattering coefficient from microscopic parameters can be improved to permit a better agreement with the exact Maxwell data.

Iterative approach to Maxwell equations for dielectric media of spatially varying refractive index

We propose an iterative method to solve the Maxwell equations for a one-dimensional model system with spatially varying permittivity. We construct solutions that are iterative in the scattering order, equivalent to the number of scattering events along the forward and backward directions. A numerical implementation of this approach is also presented.

Comparison of the Maxwell and Boltzmann theory for multilayered dielectric random media

Based on the transfer matrix theory for electromagnetic fields, we develop a corresponding theory for intensity transport in a one-dimensional random medium. We show the conditions for which the Maxwell equations, the intensity transport theory, and the Boltzmann equation can lead to similar predictions. We generalize the transfer matrix theory to study intensity modulated waves and compare its predictions with those obtained from the Maxwell and Boltzmann equations.

A stakeholder approach towards hospital accreditation in India

Accreditation has been recommended as a mechanism for assuring the quality of private sector health services in low-income countries, especially where regulatory systems are weak. A survey was conducted in Mumbai, India, in 1997-98 to elicit the views of the principal stakeholders on the introduction of accreditation and what form it should take. There was a high level of support for the classical features: voluntary participation, a standards-based approach to assessing hospital performance, periodic external assessment by health professionals, and the introduction of quality assurance measures to assist hospitals in meeting these standards. Hospital owners, professional bodies and government officials all saw potential - though different - advantages in accreditation: for owners and professionals it could give them a competitive edge in a crowded market, while government officials reckoned it could increase their influence over an unregulated private market. Areas of disagreement emerged; for example, hospital owners were opposed to government or third party payment bodies having a dominant role in running an accreditation system. The growing strength of a health service user representative lobby in Mumbai is an additional reason why this would be a suitable place for piloting such a system. The biggest obstacle to introducing accreditation in poorly resourced settings, such as India, is in how to finance it. The provisional support of the principal stakeholders for such a development, demonstrated in this study, will require a commitment from government and policymakers if the potential benefits of accreditation to the health of the population are to be realised.

IL-25 induces IL-4, IL-5, and IL-13 and Th2-associated pathologies in vivo

We have characterized a cytokine produced by Th2 cells, designated as IL-25. Infusion of mice with IL-25 induced IL-4, IL-5, and IL-13 gene expression. The induction of these cytokines resulted in Th2-like responses marked by increased serum IgE, IgG(1), and IgA levels, blood eosinophilia, and pathological changes in the lungs and digestive tract that included eosinophilic infiltrates, increased mucus production, and epithelial cell hyperplasia/hypertrophy. In addition, our studies show that IL-25 induces Th2-type cytokine production by accessory cells that are MHC class II(high), CD11c(dull), and lineage(-). These results suggest that IL-25, derived from Th2 T cells, is capable of amplifying allergic type inflammatory responses by its actions on other cell types.

West syndrome and other infantile epileptic encephalopathies--Indian hospital experience

Children with infantile epileptic encephalopathies comprising 3.5% of the Pediatric Neurology Clinic registrations in a tertiary care hospital were retrospectively analyzed. Data were retrieved from case records and analyzed for seizure semiology, prenatal and perinatal insults, developmental status and relevant investigations. The various therapeutic modalities and their influence on spasm frequency, long-term development and final seizure status were compared. The two primary outcome variables analyzed included final seizure status and developmental outcome. Of the 94 infantile epileptic encephalopathies, West syndrome was the commonest (55.3%), of which two thirds were symptomatic. Etiological factors were prenatal in 66.6% and perinatal in 33.3%. The initial response to ACTH was good in 54.5% with subsequent relapse in 27.8% and for prednisolone was 52.9 and 44.4%, respectively, compared to 25.3% spasms control with conventional antiepileptic drugs. Disease category of infantile epileptic encephalopathies evolved in 4, i.e. early myoclonic encephalopathy to West syndrome 1, early infantile epileptic encephalopathy to West syndrome 1, West syndrome to Lennox-Gastaut syndrome 2. Psychomotor retardation was seen in 88.2%, with 16.1% having normal development at onset of spasms. Microcephaly was associated with delayed development but did not influence final seizure outcome. Final seizure outcome was poor in children with delayed development at onset (adjusted odds ratio [OR]=4), delay in diagnosis >12 months (OR=2.27) and in children with Lennox-Gastaut syndrome (OR=4.75). ACTH/prednisolone and antiepileptic treatment versus antiepileptics alone showed a good final seizure response in 36.6% versus 20%. Development on follow up was delayed in children with initial psychomotor retardation (OR=23.4) and abnormal electroencephalogram (OR=7.46). Perinatal factors constituted one third of symptomatic West syndrome. The use of ACTH/corticosteroids resulted in good initial spasm control though final seizure outcome and development were unaffected. Prednisolone had similar response to ACTH in spasm control but higher subsequent relapse rate. Vigabatrin was useful though often unaffordable. The identification of a neurometabolic etiology, though uncommon, has significant therapy implications. Delay in diagnosis was common and negatively influenced final seizure outcome.

Functional importance and caffeine sensitivity of ryanodine receptors in primary lymphocytes

Calcium signaling patterns are important for the specific regulation of activation and effector function in lymphocytes. Studies of [Ca2+]i regulation in lymphocytes, including the involvement of ryanodine receptors (RyR) and the importance of caffeine-sensitive pools, have been carried out mainly in lymphocyte cell lines and the presence and functional importance of these pools in primary lymphocytes has not been addressed. Here we show by confocal microscopy that caffeine caused a prompt but transitory increase of [Ca2+]i in primary lymphocytes, an effect that was inhibited by pre-treatment with ryanodine. Furthermore, the increase of [Ca2+]i in CD4+ and CD8+ MLR T lymphocytes stimulated by 5 microg/ml concanavalin A was significantly inhibited by pretreatment with caffeine. In functional studies, caffeine decreased cytotoxicity against myocyte target cells which is probably related to an altered calcium signaling in CD8+ MLR lymphocytes. Caffeine also terminated spontaneous Ca2+ oscillations and induced a rise in [Ca2+]i in CD4- and CD8- MLR lymphocytes probably of B cell origin. These results demonstrate that caffeine alters Ca2+ signaling in primary lymphocytes, and suggest that RyR, probably the skeletal muscle receptor (RyR-1) and brain receptor (RyR-3), are involved in mediating this effect. It is also possible that blocking of inositol-1,4,5-triphosphate (IP3) receptors is involved in the effects of caffeine on lymphocyte activation.

Knowledge and attitudes in multicultural health care

Health professionals' knowledge of ethnic minority cultures and lifestyles was assessed to determine whether the respondents' cultural background and experience of working with ethnic minorities affected the health care delivered by them and to assess the need for training. Improving access to health services for ethnic minorities requires continuing education and training of all health professionals.