Biomedical subjects

Luis López

Publications and source records attributed to Luis López.

10 recordsLinked to original sources

PubMed2006

Evaluation of channel coding and decoding algorithms using discrete chaotic maps.

In this paper we address the design of channel encoding algorithms using one-dimensional nonlinear chaotic maps starting from the desired invariant probability density function (pdf) of the data sent to the channel. We show that, with some simple changes, it is straightforward to make use of a known encoding framework based upon the Bernoulli shift map and adapt it readily to carry the information bit sequence produced by a binary source in a practical way. On the decoder side, we introduce four already known decoding algorithms and compare the resulting performance of the corresponding transmitters. The performance in terms of the bit error rate shows that the most important design clue is related not only to the pdf of the data produced by the chosen discrete map: the own dynamics of the maps is also of the highest importance and has to be taken into account when designing the whole transmitting and receiving system. We also show that a good performance in such systems needs the extensive use of all the evidence stored in the whole chaotic sequence.

Journal Article↗

PubMed2005

Self-adapting network topologies in congested scenarios.

Most studies in complex networks assume that once a link is created between two nodes it is never deleted. However, there is a recent interest towards systems where links can be rapidly rewired. An important issue in that type of networks is to discover the topology that, given a search algorithm, optimizes the search process. In this paper, we present a system model that, depending on the current network congestion, makes nodes to establish link connections so that the resulting topologies tend to a starlike topology when congestion is small and to randomlike topologies when congestion becomes relevant. Those topologies have been shown to be optimal in the above-mentioned conditions. Such a model can be easily implemented in practice and therefore, may be relevant in areas as the topology management of peer-to-peer networks.

Journal Article↗

PubMed2005

[A transcultural study on stirred strawberry yogurt: consumer acceptability versus sensory quality with trained panel].

The present work was designed in order to obtain the cut off point, to be used in a shelf life study on whole stirred strawberry yogurt. The study was simultaneously carried out in Argentina, Chile and Costa Rica, assaying the same kind of product, elaborated in each one of the countries. The sensory quality parameters obtained from trained panelists and the consumers acceptability, were correlated by using the cut off point methodology through a quality evaluation by the Karlsruhe scale. According to preliminary studies, the storage at 42 degrees C produced considerable damage on parameters such as pH, acidity (volumetric assay), viscosity and sensory quality. For each sample, the cut off point was determined. This value corresponds to the threshold score for the sensory quality, where the consumer starts to perceive negative changes in the product, when comparing with the fresh product. The rejection percentage was also calculated according to the cut off point. The cut off points and the percentage of rejection obtained by the three participating countries were similar. Data obtained from Costa Rica showed changes in color, acidity and rancidity. Argentinean yogurts developed acidity that had a negative effect on texture, appearance and residual flavors. Chilean samples presented a sensory quality that remains almost without change through the studied time. The differences of the deterioration pattern amongst the three countries, demonstrates that the products are different in formulation and elaboration process, in spite of been the same kind of yogurt. This could be explained by differences specified in the regulation of each country.

Adult↗

PubMed2004

Angiotensin-converting enzyme and alpha-2-macroglobulin gene polymorphisms are not associated with Alzheimer's disease in Colombian patients.

Polymorphisms in alpha-2-macroglobulin (A2M) and angiotensin-converting enzyme (ACE) genes have been considered as risk factors for Alzheimer's disease (AD) independently of the risk conferred by the apolipoprotein E sigma4 allele (APOEsigma4) in diverse populations. In the present study, we have analysed the distribution of genotypes and alleles of the insertion/deletion (I/D) polymorphisms of ACE and A2M in 83 AD patients and 69 normal controls in Colombia. Our results showed that there is no association between the I/D polymorphisms of ACE and A2M with AD (P = 0.788 and P = 0.538, respectively). Using logistic regression and multiple correlation analysis (MCA), we confirmed that the main risk factor associated and consistently grouped with AD patients in this population is APOE4, but this association was not observed with alleles and genotypes of ACE and A2M.

Aged↗

PubMed2004

The treatment of subtrochanteric nonunions with the long gamma nail: twenty-six patients with a minimum 2-year follow-up.

OBJECTIVE: To assess the efficacy of the long Gamma nail in the treatment of subtrochanteric nonunions. DESIGN: Retrospective. SETTING: Multicenter (university teaching hospital, private centers). PATIENTS: Twenty-nine consecutive patients with noninfected sub-trochanteric nonunions following fractures previously treated with different methods of internal fixation. INTERVENTION: Implant removal, corrective osteotomy as needed (3 cases), fixation with a long Gamma nail, and cancellous bone grafting where bone loss (5 cases), all done in a 1-stage procedure. MAIN OUTCOME MEASUREMENTS: Analysis of clinic and radiologic results. Outcome assessment comparing the preinjury status with the status at a minimum follow-up of 24 months. RESULTS: At 2 years, 2 patients had died and another patient was lost to follow-up. Thus, 26 patients completed a median follow-up of 27 months (range 24-41 months). Twenty-three of these patients achieved union after 1 procedure (88% effective initial treatment), and 2 patients achieved union after 1 additional procedure each (exchange of a broken nail and bone grafting, respectively), rising the rate of union to 25 of the 26 patients (96%) in a mean of 7 months (range 4-11 months). The other patient remained ununited at the time of her final follow-up. In addition to the broken nail, breakage of the distal bolts occurred in 2 patients with less than 10 mm shortening. Twenty-one of the 26 patients (80.7%) were restored to their preinjury status. CONCLUSION: Subtrochanteric nonunion can be treated effectively using the long Gamma nail for skeletal stabilization, following removal of previously implanted devices.

Adult↗

PubMed2003

[Microbiological quality and effect of washing and disinfection of pre-cut Chilean vegetables].

Actually it is possible to find a great offer of pre-cut vegetables in the Chilean market. These products present certain advantages, such as saving time in their preparation at home. The microbiological quality of some of these vegetables, pre-cut celery and pre-cut cabbage was assayed. Two different types of the products were studied. The traditional pre-cut vegetable and another one, which is also pre-cut but it is labeled as "ready-to-eat" (minimally processed). The last one could be consumed without previous washing or disinfecting. The assayed microbiological parameters were: total plate count, Enterobacteriaceae count, total coliforms and fecal coliforms most probable number, investigation of Escherichia coli and absence or presence of Salmonella. The effect of washing and washing and disinfecting on the natural microflora was also carried out. A disinfectant product for home use was obtained from the market. When comparing the obtained results for the two vegetables from both types, a high level of total plate count, Enterobacteriaceae count and total coliforms most probable number was observed. Fecal coliforms were detected only in samples of the traditional type in both vegetables. In each case E. coli was identified. No samples showed presence of Salmonella. Washing and washing and disinfecting effect was low. The maximum reduction of the present microflora of both vegetables was only up to 2 logarithm cycles.

Apium↗

PubMed2002

Information transfer in chaos-based communication.

This paper presents fundamentals of a theory to characterize chaos-based communication. We describe the amount of information a dynamical system is able to transmit, the dynamical channel capacity, which takes into account the information that a dynamical system generates.

Journal Article↗

PubMed2002

Relation between structure and size in social networks.

In the context of complex network systems, we model social networks with the property that there is certain degradation of the information flowing through the network. We analyze different kinds of networks, from regular lattices to random graphs. We define an average coordination degree for the network, which can be associated with a certain notion of efficiency. Assuming that there is a limit to the information a person may handle, we show that there exists a close relationship between the structure of the network and its maximum size.

Journal Article↗

PubMed2002

[In vitro germicide action of disinfectant products used in the food industry].

There is a wide offer of disinfectant products, for the food industry, available in the market, such as chlorine, iodine and quaternary ammonium compounds and their respective derivatives. However, new alternative products have emerged, for instance grapefruit seed extract, and peracetic and lactic acids. The present study was carried out in order to analyze in vitro the germicide effect, from the grapefruit seed extract (400 ppm), peracetic acid (2000 ppm) and lactic acid (20,000 ppm) at the manufacturer recommended action time, and other additional times. The germicide effect was tested against microorganisms such as Escherichia coli, Staphylococcus aureus, Streptococcus faecalis and Pseudomonas aeruginosa. In each case, the death kinetic was determined through the evaluation of the germicide effect (%), specific death rate (t-1) and the decimal reduction time (min). From the evaluated products, the best germicidal effect at the manufacturer conditions was reached by peracetic acid (2000 ppm) at 1 min, which presented the lower decimal reduction times compared with the other tested microorganisms. Generally speaking, Gram positive microorganisms showed a greater sensibility to the disinfectant action.

Disinfectants↗

PubMed2002

[Optimization of a spaghetti formula enriched with dietary fiber and micronutrients for elderly people].

Several studies have demonstrated low dietary fiber intake in elderly people, which increases the risk of diseases such as constipation, colon cancer and diverticulosis. A spaghetti formula enriched with lupin fibre was developed to increase the dietary fibre intake in elderly people, as spaghetti are frequently consumed in this age group. Sweet lupin bran (Vitafiber) was used as fibre source and gluten was used as improving additive. Response surface methodology with a two variable composite rotatable design was applied to optimize the formulations. The independent variables were lupin bran (7.14-14.29%) and gluten Vital (0.1-2.0%). The dependent variables were the responses of a trained 10-member sensory panel who evaluated the sensory quality parameters color, shape, aroma, flavor and texture by the Karlsruhe 9-point test. The optimized formula was prepared with 66.7% semoline, 7.14% lupin bran, 1.05% gluten and 24.7% water, enriched with 0.019% of a vitamin premix (A. E, D, B2, B12 and folic acid) and with 0.41% of a mineral premix (Ca, Fe, Zn), in order to meet 30% of the RDA for the elderly per 100 g dry spaghetti. The dietary fibre content of the optimized product was 11.05 g/100 g. The study showed that fibre-enriched spaghetti formula is a good way to increase dietary fibre intake in elderly people, as it is a common food, simple to prepare and easy to eat.

Aged↗