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Biomedical subjects

F Brauer

Publications and source records attributed to F Brauer.

17 recordsLinked to original sources
PubMed2006

Modelling the transmission dynamics of acute haemorrhagic conjunctivitis: application to the 2003 outbreak in Mexico.

We model an outbreak of acute haemorrhagic conjunctivitis (AHC) using a simple epidemic model that includes susceptible, infectious, reported, and recovered classes. The model's framework considers the impact of underreporting and behaviour changes on the transmission rate and is applied to a recent epidemic of AHC in Mexico, using a fit to the cumulative number of cases to estimate model parameters, which agree with those derived from clinical studies. The model predicts a 'mean time from symptomatic onset to diagnosis' of 1.43 days (95 per cent CI: 1-2.5) and that the final size of the Mexican epidemic was underreported by 39 per cent. We estimate that a primary infectious case generates approximately 3 secondary cases (R0* = 2.64, SD 0.65). We explore the impact of interventions on the final epidemic size, and estimate a 36 per cent reduction in the transmission rate due to behaviour changes. The effectiveness of the behaviour changes in slowing the epidemic is evident at 21.90 (SD 0.19) days after the first reported case. Results therefore support current public health policy including expeditious announcement of the outbreak and public health information press releases that instruct individuals on avoiding contagion and encourage them to seek diagnosis in hospital clinics.

Adenoviridae↗
PubMed2001

Models for transmission of disease with immigration of infectives.

Simple models for disease transmission that include immigration of infective individuals and variable population size are constructed and analyzed. A model with a general contact rate for a disease that confers no immunity admits a unique endemic equilibrium that is globally stable. A model with mass action incidence for a disease in which infectives either die or recover with permanent immunity has the same qualitative behavior. This latter result is proved by reducing the system to an integro-differential equation. If mass action incidence is replaced by a general contact rate, then the same result is proved locally for a disease that causes fatalities. Threshold-like results are given, but in the presence of immigration of infectives there is no disease-free equilibrium. A considerable reduction of infectives is suggested by the incorporation of screening and quarantining of infectives in a model for HIV transmission in a prison system.

Communicable Diseases↗
PubMed1998

Surgical techniques for arteriovenous malformations in functional areas: focus on the superior temporal gyrus.

Direct surgical intervention of arteriorvenous malformations (AVMs) in functional areas has been accepted as a standard mode of treatment. However, safe and successful intervention requires that such factors as exact location, size, vascular supply, and drainage be considered. Importantly, surgical techniques must be individualized to each patient, based on hemodynamic anatomy of the AVM. This paper discusses AVMs in the superior temporal lobe, which have a complex neuronal anatomy and circulatory system; the authors present 22 patients with AVMs of various sizes and describe the surgical techniques specific for the indicated location. Surgical procedures adhered to the following principles: 1) avoid brain tissue removal; 2) preserve microcirculation; 3) maintain circulation of the isolated major draining vein to access the AVM core; 4) compartmental isolation; and 5) preservation of functional area cortex covering the AVM. All patients underwent total resection except one, who had a subtotal resection. Neurological and occupational recovery was remarkable except for partial hemianesthesia in one patient; two patients are still in rehabilitation. This is the first description of a direct surgical approach to AVMs in the superior temporal gyrus, where management is challenging because the lesions may extend elsewhere, such as to Broca's and Wernicke's areas. The results suggest that the procedure is promising.

Adolescent↗
PubMed1996

Effects of treatment and prevalence-dependent recruitment on the dynamics of a fatal disease.

This paper studies models for the sexual transmission of HIV/AIDS that incorporate changes in behaviour and the effects associated with HIV treatment. The recruitment rate into the core is assumed to be a function of the prevalence of the disease within the core, and it may trigger the existence of periodic solutions through Hopf bifurcations, provided that there is at least a weak demographic interaction with the noncore. The recruitment function is set up for two cases: dependence on the total proportion of infectious individuals and dependence on the proportion of treated infectious individuals only. In the general model, numerical evidence suggests that both cases may produce periodic solutions when the perception of the risk of joining the core group is sufficiently high. Two limiting cases are also studied: when the growth rate of the core and noncore groups are essentially the same, and when treatment has no effect on the transmission rate of infected individuals.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Can somatosensory evoked potential monitoring predict energy dynamics during controlled hypotension?

Somatosensory evoked potentials and redox (reduction/oxidation ratio) of cytochrome a,a3 were studied simultaneously before, during, and after controlled hypotension used for arteriovenous malformation resection. These studies were also conducted before and after ED-IC (external-internal carotid) bypass procedures for treatment of patients with transient ischaemic attacks. The former served as an acute model and the latter as a chronic model of low blood flow (ischaemia). The use of non-invasive reflection spectrophotometry (for redox studies) in conjunction with somatosensory evoked potentials (SSEP) has demonstrated that metabolic and electrophysiological changes parallel each other during "controlled" hypotension. The authors conclude that an analysis of SSEP changes are valuable in the study of metabolic and functional states of the brain during controlled hypotension.

Animals↗
PubMed1992

The effect of measurement conditions on MCG inverse solutions.

A magnetic inverse solution that uses a single current dipole in a homogeneous volume conductor with realistic torso shape was tested numerically to establish the effect of magnetic noise, number of measurement points, and torso size on the localization accuracy. Seven different sites of cardiological interest were selected as locations for the source dipole. The three components of the magnetic field were calculated as if measured by second order gradiometers, Gaussian noise was added, and Monte Carlo tests performed for inverse solutions using a single field component, or all three combined. It was found that for any of the single component solutions, and a signal-to-noise ratio of 100, 25 measuring points are sufficient for good accuracy; just 12 points are needed if all three components are used together. If, however, the torso size of the inverse solution is different from that of the field data by 10 or 20%, a larger error occurs, even for 56 measurement points and no noise. In this case, the field component orthogonal to the measurement grid, Bz, yields better results than the other two components, or even all three combined. We conclude that a multichannel system measuring the z component of the magnetic field in about 30 locations would be the best choice to locate a dipolar source, provided the torso of the field data is closely matched by the model used in the inverse solution. To this effect, scaling of the torso model can easily be included in the computation. Imaging techniques could be used to accommodate different torso shapes.

Bias↗
PubMed1991

Investigations of phagocytosis concerning the immunological defence mechanism of Mytilus edulis using a sublethal luminescent bacterial assay (Photobacterium phosphoreum).

1. A simple method for the determination of phagocytosis activity using mussel hemocytes by measuring the bioluminescence is presented. 2. The immunological defence activity based on phagocytosis is measured and quantified by a luminescent bacterial assay with Photobacterium phosphoreum. 3. The measuring system allows us to establish the stress of the immunological defence mechanism of organisms exposed to chemicals and polluted rivers or sewage. Results with reference substances and the phagocytosis indices of exposed mussels from Norwegian aquaculture plants compared to those of mussels from the German Wadden Sea are given as examples.

Animals↗
PubMed1990

Models for the spread of universally fatal diseases.

In the formulation of models of S-I-R type for the spread of communicable diseases it is necessary to distinguish between diseases with recovery with full immunity and diseases with permanent removal by death. We consider models which include nonlinear population dynamics with permanent removal. The principal result is that the stability of endemic equilibrium may depend on the population dynamics and on the distribution of infective periods; sustained oscillations are possible in some cases.

Communicable Diseases↗
PubMed1988

Safety limits of controlled hypotension in humans.

Controlled hypotension is a safe and convenient means of allowing a surgeon to perform intracranial aneurysm, arteriovenous malformation and vascular tumor surgery. The mean arterial pressure between 40 and 60 mmHg induces diminished pulsatile arterial pressure, thus preventing rupture of these abnormal vasculatures. It is still possible to maintain cerebral metabolism in the functional level within this 40-60 mmHg blood pressure range. This statement is based on our experience of the physical and neurological outcome of patients after surgery, and on analyses of somatosensory evoked potential and redox of cytochrome a, a3 in the mitochondria of the cerebral cortical cells.

Adolescent↗
PubMed1980

[Post-traumatic alpha-and mu-wave-foci (author's transl)].

28 patients with an activated focus (8-12 c/s focus) in the central region were examined for mu-wave-activity utilizing visual and calculation of the coherence function. Over 60% (18 patients) of these foci were mu-wave-foci. This type of mu-waves was decidedly less sensitive to change in vigilance than physiological mu-waves. Seven foci were alpha-foci and three foci could be classified as neither alpha- nor mu-wave-foci since they did not react to sensory and sensomotoric stimuli. Furthermore, it was demonstrated that the pathological mu-waves and the pathological alpha-waves were very similar in their characteristics.

Adolescent↗
PubMed1978

Heparin activity monitoring during vascular surgery.

Twelve patients undergoing vascular surgery were administered heparin according to preexisting protocols. The response to heparin and the rate of decay were measured by use of the activated coagulation time (ACT). The results showed a significant patient variability to response to and decay of heparin. In addition, a dose-response curve for heparin administration was established in sixteen patients undergoing vascular surgery. The ACT proved to be a simple and accurate monitor of heparin activity. It also made possible a steady state of anticoagulation throughout the duration of the vascular procedure. The reversal of the heparin effect could also be precisely determined by this test.

Aged↗
PubMedDate not supplied

Models for diseases with vertical transmission and nonlinear population dynamics.

Vertical transmission, the direct transfer of a disease from an infective parent to a new born offspring, is an important aspect of many diseases. Most of what is known for vertical transmission models assumes birth rates proportional to population size. We consider models with nonlinear population dynamics and finite carrying capacity and analyze the stability of equilibria in the special case in which the overall birth rate does not depend on infective population size.

Female↗