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Biomedical subjects

A Delgado

Publications and source records attributed to A Delgado.

At least 37 records · Page 2Linked to original sources
PubMed2003

Functional nodes in dynamic neural networks for bioprocess modelling.

This contribution presents a novel method for the direct integration of a-priori knowledge in a neural network and its application for the online determination of a secondary metabolite during industrial yeast fermentation. Hereby, existing system knowledge is integrated in an artificial neural network (ANN) by means of 'functional nodes'. A generalized backpropagation algorithm is presented. For illustration, a set of ordinary differential equations describing the diacetyl formation and degradation during the cultivation is incorporated in a functional node and integrated in a dynamic feedforward neural network in a hybrid manner. The results show that a hybrid modelling approach exploiting available a-priori knowledge and experimental data can considerably outperform a pure data-based modelling approach with respect to robustness, generalization and necessary amount of training data. The number of training sets were decreased by 50%, obtaining the same accuracy as in a conventional approach. All incorrect decisions, according to defined cost criteria obtained with the conventional ANN, were avoided.

Journal Article↗
PubMed2002

In vitro-in vivo characterization of gentamicin bone implants.

A gentamicin carrier system composed of calcium phosphates, poly(DL-lactide) (PLA) and gentamicin was developed and characterized in vitro and in vivo for use in the prevention and treatment of bone infection. Four formulations were prepared according to an experimental design based on the Hadamard matrix. The technological variables included in the design were: gentamicin loading with respect to the implant weight, weight average molecular weight (M(w)) of the PLA as a compound of the matrix and the presence or absence of a PLA coating of 200 kDa. The variable to be optimized in vitro was the gentamicin release level during the first week. According to this goal, the selected formulation was F-D which was composed of 80% phosphates (25% hydroxyapatite, HAP and 75% tricalcium phosphate, TCP), 20% PLA (M(w), 30 kDa) and 3.5% gentamicin sulfate (GS) and was coated with PLA (M(w), 200 kDa). To elucidate the in vitro release mechanism of this implant, another implant lot (F-X) uncoated, but with identical matrix composition, was prepared. Results showed that the PLA coating delay the gentamicin release, indicating that part of the antibiotic released from the matrix diffuses through the polymer coating film. The selected formulation was tested in the femur of rabbits and showed a faster release rate in vivo than in vitro. This is due to a greater degree of PLA degradation, changes in the phosphate blend, and bone tissue invading the implant. Gentamicin concentration in the areas of the bone closest to the implant was higher than the minimum inhibitory concentration (MIC) against Staphylococcus aureus.

Animals↗
PubMed2002

Optimizing high strength acetic acid bioprocess by cognitive methods in an unsteady state cultivation.

Methods of adapting micro-organisms to an inhibiting factor in an active industrial bioprocess were examined with an acetic acid fermentation as model. With the aim of automatic control, a fuzzy-logic system was developed on the basis of the collected knowledge of skilled vinegar brewers. In a first step, this fuzzy system was to assess the actual adaptation degree of the bacteria on the basis of data from robust and reasonably priced sensors. From this information an appropriate setpoint value for the inhibiting factor 'final acid concentration' was derived for each batch cycle. As a result a further acid tolerance was found after several batch cycles. This adaptation effect should be used to increase the product concentration to more than 20 g per 100 ml acetic acid with a high productivity. The stepwise adapted culture was productive over the aimed acetic acid concentration, a 10% improvement of the product formation rate could be found compared with the status before conditioning. High product concentration and increased productivity finally result in shorter cycle times, less transport and storage volumes, an improved utilization of energy and material resources, and, last but not least, they are an essential steps towards the fulfillment of economical and ecological demands.

Acetic Acid↗
PubMed2002

Kinetic parameters of lithium and aluminium doped quartz from thermoluminescence glow curves.

The thermoluminescence (TL) glow curves of irradiated annealed and non-annealed synthetic beta-quartz (Li0.73Al0.73Si1.27O4) synthesised using the ceramic method have been studied. Annealed samples (1200 degrees C for 12 h) exhibit some changes of shape and intensity in the TL glow curves when compared to non-annealed samples in the range of 0.1-5 Gy. These changes can be attributed mainly to thermal alkali self-diffusion through the lattice interfaces involving modifications in the components of the luminescent traps. In non-annealed samples six groups of components at about 100 degrees C, 130 degrees C, 160 degrees C, 210 degrees C, 330 degrees C and 450 degrees C can be found, whereas annealed samples only display one very intense peak at a lower temperature (deconvoluted into three peaks at 90 degrees C, 105 degrees C and 130 degrees C) and a lower intensity second wide broad emission at approximately 240 degrees C. In this paper, a computerised curve-fitting based on general order kinetics has been used to characterise the glow curve structure resolving trapping parameters for each glow peak: trap depth (E), frequency factor (s) and the order of the kinetics (b). The dose dependence of the individual components of the glow curve has been also studied. These data allow us to select the most stable component for use in dosimetric purposes.

Aluminum↗
PubMed2002

Study of real heating profiles in routine TLD readout: influences of temperature lags and non-linearities in the heating profiles on the glow curve shape.

This paper reports on the results of a heating profile analysis using a commercial routine read-out system with non-contact hot nitrogen heating, using linear heating gas profiles. Glow curves of TLD-100 were analysed for different linear heating gas rates from 1 degree C x s(-1) to 30 degrees C x s(-1). The analysis of the individual peak maxima (Peak 2-5) leads to an approximation of the real heating profile in the TL detector. It was found that the real heating profile deviates strongly from linearity, and that the temperature lag between the heating gas and the detector reaches values up to some tens of degrees C. The consequences of this non-linearity, with respect to the resulting glow curves, are discussed in this paper. These results lead to a better understanding of the shape of routine TL glow curves and help to improve the use of glow curves analysis in routine services. In addition, a simple procedure is described which allows calculation of the real heating profile based on the heating gas temperature profile. This model shows a very good match between experimental data and calculated values.

Hot Temperature↗
PubMed2002

Pilot study on the application of computerised glow curve analysis in TL based personal dosimetry services.

Preliminary results of an inter-laboratory collaborative work on the application of computerised glow curve analysis to TL personal dosimetry are presented. Very simple analysis methods have proved to be useful for the evaluation of glow curves similar to those encountered in the dosimetric control of radiation workers. A first result obtained in the study has been the possibility of simplifying the TL working procedures by eliminating pre-annealing or pre-heating steps employed in conventional systems to avoid low temperature peaks. The presence of these unwanted peaks can be detected by the computerised evaluation methods, discriminating their contribution to the dosimetric TL data.

Computer Systems↗
PubMed2002

Luminescence characteristics of dental ceramics for retrospective dosimetry: a preliminary study.

Ceramic materials that are widely employed in dental prosthetics and repairs exhibit luminescent properties. Because of their use in the body, these materials are potentially of interest in situations where retrospective dosimetry for individuals is required but where monitoring was not planned. The luminescent properties of dental ceramics obtained from Germany, Spain and the UK were examined. Linear dose-response characteristics were obtained in the range < 100 mGy to 10 Gy using thermoluminescence (TL), optically stimulated luminescence (OSL) and infrared-stimulated luminescence (IRSL) measurement techniques. Measurements of time-resolved luminescence were also performed to examine the nature of the luminescence recombination under visible (470 nm) and IR (855 nm) stimulation. The results obtained by TL and optically stimulated techniques suggest that there may be deeper traps than previously observed in certain types of dental ceramic. Such traps may be less susceptible to optical and athermal fading than was reported in earlier studies.

Ceramics↗
PubMed2001

[Being a male or female doctor is different in medical practice].

OBJECTIVES: To identify the differences between the clinical practice (conduct) of male and female doctors and its determining factors; and to find the variability in the various conducts studied which is explained by a set of variables, gender among them. DESIGN: Cross-sectional, multi-centre descriptive study. SETTING: Andalusian health centres with populations of over 100000 inhabitants. PARTICIPANTS: Selection of 159 primary care doctors with postgraduate training by means of simple randomised sampling. 56% were men, 44% women, with power of comparisons at 68%. MEASUREMENTS AND MAIN RESULTS: Self-administered questionnaire to measure the dependent variable, overall conduct (clinical practice) and 11 dimensions of this conduct. Independent variables were: determinants of conduct identified by the theory of reasoned action (attitudes and subjective norm) and by the theory of social learning (self-efficacy and control locus), gender and other social and demographic variables and work conditions variables. Multiple linear regression models were constructed to explain each conduct analysed. Being a female doctor affects positively overall conduct and conduct in information, psycho-social guidance, prevention of obesity, active recruitment for family planning and collaboration with nurses. CONCLUSIONS: In Andalusia women general practitioners have a more marked orientation towards the psycho-social sides of care than their male colleagues. They give more information to their patients and more frequently perform preventive activities linked to their gender. They also rely on the work of their nurses more than male doctors.

Adult↗
PubMed2001

Stabilizing distinguishable qubits against spontaneous decay by detected-jump correcting quantum codes.

A new class of error-correcting quantum codes is introduced capable of stabilizing qubits against spontaneous decay arising from couplings to statistically independent reservoirs. These quantum codes are based on the idea of using an embedded quantum code and exploiting the classical information available about which qubit has been affected by the environment. They are immediately relevant for quantum computation and information processing using arrays of trapped ions or nuclear spins. Interesting relations between these quantum codes and basic notions of design theory are established.

Journal Article↗
PubMed2001

Intrapallidal D2 dopamine receptors control globus pallidus neuron activity in the rat.

Because activation of D2 dopamine receptors inhibits gamma-aminobutyric acid (GABA) release from intrapallidal nerve terminals, we measured the effects of modifiers of dopamine D2 receptors on the firing rate of single neurons in the globus pallidus (GP) of the anesthetized rat. The predominant effect of intrapallidal administration of the selective D2 agonist quinpirole was an increase in the rate of spontaneous firing while the D2 blocker sulpiride caused a decrease. The spontaneous firing of GP neurons is inhibited by stimulation of the GABAergic striatopallidal projection. We therefore measured the effects of modifiers of D2 receptors on striatal inhibition of GP neurons and found that intrapallidal quinpirole blocked the inhibitory effects of striatal stimulation while sulpiride enhanced them. These experiments show that both the spontaneous rate of firing of pallidal neurons and its modification by striatopallidal inputs is controlled by intrapallidal dopamine D2 receptors. In addition, taken together with other findings in the literature, our results suggest that activation of dopamine D2 receptors within the globus pallidus leads to inhibition of GABA release from presynaptic terminals.

Action Potentials↗
PubMed2001

In vivo-in vitro study of biodegradable methadone delivery systems.

Three one-week controlled-release methadone formulations: polylactic acid microspheres (F-PLA) and poly(lactide-co-glycolide) microspheres (F-PLGA) with 24 and 30% methadone content, respectively, and an implant of 50:50 poly(lactide-co-glycolide): methadone, were evaluated in vitro and in vivo. The implant released the total amount of methadone in vitro while microsphere formulations released the methadone incompletely, 63% from F-PLA and 85% from F-PLGA in a week. Methadone release in vivo was estimated by deconvolution, F-PLGA giving a bioavailability >99% (methadone was totally released in 48h), while the estimated bioavailability of F-PLA was lower than expected. The bioavailability of the implant by deconvolution was around 60%, but absence of methadone in the implant indicated its complete release. These differences are due to an increase in methadone clearance after 72 h of the in vivo experimental period had passed, disturbing a good in vivo-in vitro correlation. A linear correlation between in vitro methadone release and in vivo release calculated from the amount of drug remaining within the implant, was found until the drug was completely released.

Animals↗
PubMed2001

[Women's attitudes to menopause and predictive variables].

OBJECTIVE: To find what women's attitudes to the menopause are and how these attitudes relate to certain personal variables. DESIGN: Multi-centre, transversal study. SETTING: 5 clinics at three urban and teaching health centres in Granada. PARTICIPANTS: A systematic randomised sample of women = 18 who attended on demand in June 1998: alpha = 0.05, accuracy = 3 and standard deviation from the scale of attitudes (SA), found through prior sampling, was 15.4. N = 101 women. INTERVENTIONS: Questionnaire through interview after consultation. MEASUREMENTS AND MAIN RESULTS: Dependent variable: scale of attitudes to the menopause with 29 items. INDEPENDENT VARIABLES: age, marital status, educational qualifications, work situation, cultural group, religion, continuity with her doctor, utilisation, menopausal status, perception of autonomy, opinion of the menopause, feelings towards the menopause, perceived health. ANALYSIS: homogeneity and validity of SA. Descriptive, univariate analysis of SA with independent variables. Multiple linear regression: we found 7 factors that explained 66.5% of variance. Age 43.4 +/- 17.5. 50.5% had not reached the menopause; 10.9% were in the peri-menopause; and 37.6% in the menopause. 70.3% had feelings of relief or were neutral; 54.5% had a positive view; and 21.8% expressed no opinion. The variables explaining attitudes were feeling, continuity, opinion, utility, autonomy and perceived health. CONCLUSIONS: Women had positive or neutral feelings and opinions about the menopause. Their attitudes to it were related to these variables and not to other social or demographic variables or to their menopausal status.

Adult↗
PubMed2001

Computerised glow curve analysis: a tool for routine thermoluminescence dosimetry.

The basic features of computerised glow curve analysis methods are presented, together with the advantages derived from their use for dosimetry. The rapid development of personal computers with progressively greater computation capability has permitted the application of different analysis methods for practical dosimetry. A very simple glow curve analysis method, specifically developed for the measurement of low or very low doses usually measured in personal and environmental dosimetry, is also discussed.

Electronic Data Processing↗
PubMed2001

Harmonisation and dosimetric quality assurance in individual monitoring for external radiation.

The current situation amongst Member States is that there are widely differing national requirements for dosimetric services and for dosemeter performance. It is clear that with the free movement of workers within the European Union (EU) and the requirements for individual dosimetry given in Council Directive 96/29 EURATOM, a degree of harmonisation of requirements and procedures of EU Member States would be desirable. A EURADOS action group, made up of members from each of the EU Member States plus Switzerland, was set up with the overall objectives of consolidating within the EU the quality of individual monitoring using personal dosemeters and assisting movement towards harmonised procedures. An outline of the work of the action group is given and the term 'harmonisation' is discussed.

Europe↗
PubMed2001

Present status of approval procedures in the EU member states and Switzerland.

The European Union Council Directive 96/29/EURATOM requires that 'individual monitoring shall be ... based on individual measurements which are established by an approved dosimetric service' and that 'Each Member State shall make arrangements to recognise, as appropriate, the capacity of ... approved dosimetric services'. At present, approval of dosimetric services does not have the same meaning within EU Member States and Switzerland. In some countries, service and dosemeter approval is clearly separated, in some others only one of the two is supposed to be tested, and in others no approval is required. Dosimetric requirements and criteria are based on different international documents (e.g. IEC, ISO, ANSI, CEC report) or national specific rules. Approval frequency can be once, every 2 or more years. Approval can be based on either evaluation of technical and management reports, irradiation tests, inspection on-site or the three steps together. In most cases, approval involves photon dosimetry while beta and neutron dosimetry test procedures are not as well established. However, comparisons may lead to some convergent evolution of procedures and to a greater degree of harmonisation and quality consolidation.

European Union↗