A neuronal network model of interictal and recurrent ictal activity

We propose a neuronal network model which undergoes a saddle-node bifurcation on an invariant circle as the mechanism of the transition from the interictal to the ictal (seizure) state. In the vicinity of this transition, the model captures important dynamical features of both interictal and ictal states. We study the nature of interictal spikes and early warnings of the transition predicted by this model. We further demonstrate that recurrent seizures emerge due to the interaction between two networks.Comment: 9 pages, 7 figure

Hormonal contraceptive methods and risk of HIV acquisition in women : a systematic review of epidemiological evidence

Peer reviewedPublisher PD

The performance of RAMS in representing the convective boundary layer structure in a very steep valley

Data from a comprehensive field study in the Riviera Valley of Southern Switzerland are used to investigate convective boundary layer structure in a steep valley and to evaluate wind and temperature fields, convective boundary layer height, and surface sensible heat fluxes as predicted by the mesoscale model RAMS. Current parameterizations of surface and boundary layer processes in RAMS, as well as in other mesoscale models, are based on scaling laws strictly valid only for flat topography and uniform land cover. Model evaluation is required to investigate whether this limits the applicability of RAMS in steep, inhomogeneous terrain. One clear-sky day with light synoptic winds is selected from the field study. Observed temperature structure across and along the valley is nearly homogeneous while wind structure is complex with a wind speed maximum on one side of the valley. Upvalley flows are not purely thermally driven and mechanical effects near the valley entrance also affect the wind structure. RAMS captured many of the observed boundary layer characteristics within the steep valley. The wind field, temperature structure, and convective boundary layer height in the valley are qualitatively simulated by RAMS, but the horizontal temperature structure across and along the valley is less homogeneous in the model than in the observations. The model reproduced the observed net radiation, except around sunset and sunrise when RAMS does not take into account the shadows cast by the surrounding topography. The observed sensible heat fluxes fall within the range of simulated values at grid points surrounding the measurement sites. Some of the scatter between observed and simulated turbulent sensible heat fluxes are due to sub-grid scale effects related to local topograph

The epidemic of obesity in South Africa: a study in a disadvantaged community.

Objective: The objective of this study was: 1) to determine the anthropometric profile of adults In Mamre, a small town In South Africa, which has a population of mixed ancestry ("colored" people of Afro-Euro-Malay-Khoisan ancestry); and 2) to determine the change In this profile between 1989 and 1996. Design: Cross-sectional surveys conducted In random samples of adults In 1989 and 1996. Participants: The subjects were 684 women and 529 men In 1989, and 546 women and 430 men In 1996, aged 15 and older. Main Outcome Measures; The following measurements were recorded: height, weight, and circumference of waist, hips, and mid-upper arm. Results: Based on data from the 1996 survey, 32% of women are obese (body mass index [BMI] ;;: 30) at ages 25-44 years, rising to 49% at ages 45-64 years. A much lower prevalence of obesity is seen in men: 14"10 at ages 35-64 years. Obesity levels significantly increased in women between the two surveys (P=.015): up from 44% in 1989 to 49% in 1996 at ages 45-64 years. There was an Increase In the prevalence of overweight (BMI 25-29.9) in men, though not in obesity. Mean 8MI increased by about 3% In women and 2% in men between 1989 and 1996. Conclusions; This study conducted among people of mixed ancestry living In a disadvantaged community In South Africa shows that half of middle-aged women are obese. A rising trend In 8MI was seen in adults of both sexes between 1989 and 1996. This trend may be explained by factors associated with rural-urban transition, Including electrification, reduced physical activity, and Increasing availability of energy-dense food

No evidence of an 11.16 MeV 2+ state in 12C

An experiment using the 11B(3He,d)12C reaction was performed at iThemba LABS at an incident energy of 44 MeV and analyzed with a high energy-resolution magnetic spectrometer, to re-investigate states in 12C published in 1971. The original investigation reported the existence of an 11.16 MeV state in 12C that displays a 2+ nature. In the present experiment data were acquired at laboratory angles of 25-, 30- and 35- degrees, to be as close to the c.m. angles of the original measurements where the clearest signature of such a state was observed. These new low background measurements revealed no evidence of the previously reported state at 11.16 MeV in 12C

Dicarbon­yl[4-(2,6-dimethyl­phenyl­amino)­pent-3-en-2-onato-κ2 N,O]rhodium(I)

In the title compound, [Rh(C13H16NO)(CO)2], a square-planar coordination geometry is observed around the RhI atom, formed by the N and O atoms of the bidentate ligand and two C atoms from two carbonyl ligands. The RhI atom is displaced from the plane through these surrounding atoms by 0.0085 (2) Å. The dihedral angle between the benzene ring and the N—C—C—C—O plane is 89.82 (6)°, and the N—Rh—O bite angle for the bidentate ligand is 90.53 (6)°. An inter­molecular C—H⋯O inter­action is observed between a methyl group of the benzene ring and a carbonyl O atom

Improving cost-effectiveness of hypertension management at a community health centre

Objectives. To describe the pattern of prescribing for hypertension at a community health centre (CHC) and to evaluate the impact of introducing treatment guidelines and restricting availability of less cost-effective antihypertensive drugs on prescribing patterns, costs of drug treatment and blood pressure (BP) control.Design. Before/after intervention study.Setting. Medium-sized CHC in the Cape Flats area of Cape Town.Subjects. 1 084 hypertensive patients attending the CHC, who had at least two prescriptions for antihypertensive drugs during a 1-year period starting on 1 January 1992. Interventions. 1. Implementation of stepped-care guidelines for hypertension, specifying treatment with more cost-effective drugs and minimising drug treatment. 2. Reducing availability for routine prescribing by CHC doctors of 10 less cost-effective antihypertensive drugs or drug combinations.Outcome measures. 1. Mean number of drugs prescribed per patient. 2. Proportion of prescriptions for: each major class of antihypertensive drug; restricted availability and freely prescribable drugs; and more and less cost-effective drugs. 3. Mean monthly cost of drugs prescribed per patient. 4. Mean blood pressure and proportion of BP readings controlled (<160/95 mmHg) or uncontrolled (≥160/95 mmHg).Results. A mean of 1.7 active drugs was prescribed per patient per visit. The most frequently prescribed drugs were thiazide-like diuretics (44.8%), centrally acting agents (28.4%) and b-blockers (13.2%). Mean monthly drug costs per patient decreased significantly by R1.99 (24.2%) from R8.24 to R6.25 between the first and last prescription for each patient (exclusive of any reduction due to withdrawal of treatment). This was attributable to reduced prescribing of more expensive drugs withdrawn from routine use and a 51.1% increase in prescribing of the most cost-effective drugs. The overall annual cost-saving of the changes in prescribing for this CHC are estimated at R75 150. Blood pressure control did not change significantly.Conclusion. The pattern of changes in prescribing and drug costs was consistent with a causal effect of the interventions. The study demonstrates the potential forimproving cost-effectiveness of hypertension care in primary care in South Africa and the potential for research in this setting

Hypertension care at a Cape Town community health centre

Objectives. To describe the demographic profile of hypertensive patients and the quality of care for hypertension at a Cape Town community health centre (CHC).Design. Prospective, descriptive study.Setting and subjects. Medium-sized CHC, attended by 1098 hypertensive patients during a 1-year period from 1 January 1992.Outcome measures. Default rate - proportion of due visits not attended. Loss to follow-up - proportion of patients persistently defaulting or not responding to recall. Frequency of blood pressure measurement - per 12 due visits. Compliance - proportion of patients collecting ≥ 75% of antihypertensive drugs. Blood pressure control - mean blood pressure of aggregated readings; and proportion controlled (<160/95 mmHg) on the basis of all blood pressure readings and mean blood pressures of individual patients with two or more readings during the study period.Results. More than half (51.6%) of the hypertensive patients were aged ≥ 65 years; 81.7% were female. The default rate was between 11.9% and 19.4%. Compliance was high (76.9%). Loss to follow-up was 8.1 %. Blood pressure was recorded a mean of 4.0 times per 12 due visits. There were no significant gender differences with regard to these measures. Mean blood pressure was 158.3/89.6 mmHg. Over half (56.7%) of all individual readings over the year were uncontrolled and 51.4% of patients were found to be uncontrolled when categorised by their mean blood pressure. Control was significantly poorer among women ≥ 65 years.Conclusion. We found better compliance, more frequent blood pressure measurement, and lower defaulting and loss to follow-up compared with previous South African studies in similar settings. Despite this, blood pressure control was mediocre. Possible explanations for this are discussed. The low proportion of male hypertensives attending the CHC suggests that the accessibility or acceptability of care is poor for this group. The study illustrates the potential for research in this setting and for the use of computers to monitor the quality of primary care.