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P Lavalle

Publications and source records attributed to P Lavalle.

10 recordsLinked to original sources

Adhesion Probability of Colloidal Particles with Repulsive Soft Interaction.

Computer simulations of the irreversible adhesion of charged colloidal particles at a solid/liquid interface are performed to determine whether the distribution of particles in the vicinity of a preadsorbed (also charged) one follows the Boltzmann law applied to an a priori uniform adhesion probability, as first assumed by Adamczyk et al. (J. Colloid Interface Sci. 140, 123 (1990)). If true, this would indicate that the whole information on the deposition process is contained in the potential energy distribution on the adsorbing surface. In general, diffusion in a field of force and the irreversibility of the process induce significant deviations from the Boltzmann-weighted uniform adhesion density. Nevertheless, it is shown that for particles characterized by a small gravitational energy this procedure leads to a reasonable first approximation of the distribution of the particles over the adsorbing surface. This observation thus demonstrates the validity of Adamczyk's assumption and extends its range of applicability to the case of a weak gravitational field. Copyright 1999 Academic Press.

Journal Article

Red blood cell adhesion on a solid/liquid interface.

Red blood cells (RBCs), previously fixed with glutaraldehyde, adhere to glass slides coated with fibrinogen. The RBC deposition process on the horizontal glass surface is investigated by analyzing the relative surface covered by the RBCs, as well as the variance of this surface coverage, as a function of the concentration of particles. This study is performed by optical microscopy and image analysis. A model, derived from the classical random sequential adsorption model, has been developed to account for the experimental results. This model highlights the strong influence of the hydrodynamic interactions during the deposition process.

Adsorption

[Epidemiologic study of mycetomas in Mexico. Apropos of 502 cases].

The epidemiological data of 502 mycetomas studied in the Department of Mycology, "Centro Dermatológico Pascua", Mexico City, were analysed. Mycetomas prevail in males (79.7%), they are more frequent between 16 and 45 years of age (75%) and among rural workers (62.5%); they preferentially affect lower limbs (62.5%); these data are generally similar to the known publications on the matter. Actinomycetomas are the most frequent with 97.2% of the cases, distributed as follows: Nocardia: 85.6% among which 71.9% are N. brasiliensis, Actinomadura madurae: 9.6%, Streptomyces somaliensis: 1.6%, Actinomadura pelletieri: only one case: 0.2%. Eumycetomas, a total of 9, are due to Madurella mycetomi (2), Madurella grisea (2), an undetermined black grain (1), Acremonium sp. and Fusarium sp. (1), Fusarium, sp. (1), Pseudallescheria boydii (1), and an undetermined white grain (1).

Actinomyces

[Cephalic mycetoma, caused by Streptomyces somaliensis, involving the cranial cavity].

A case of cephalic mycetoma caused by Streptomyces somaliensis which has involved the orbit and craneal cavity with exoftalmus and symptoms of irritation and brain compression is reported. The patient has improved with a medical treatment (sulfomethoxazol-trimetoprim) associated with a descompressive craniectomy. The authors comment the geographic distribution of the agents of mycetoma especially of S. somaliensis very rare specie in America. Only 10 proved cases of Mycetoma caused by this Actinomycete have been found in Mexico. Our patient came from the state of Chihuahua, in the north of Mexico and is the second case from this state and the most septentrional (parallel 32 degrees) in the American continent.

Adult

Itraconazole for deep mycoses: preliminary experience in Mexico.

Itraconazole has been used as oral therapy for deep mycoses since July 1984 in our institution. So far, therapy has been evaluated for eight patients: one with cutaneous coccidioidomycosis; two with chromomycosis (Fonsecaea pedrosoi); and five with sporotrichosis (three fixed, one lymphangitic, and one disseminated). Clinical and mycologic evaluations were done at the beginning of treatment, 15 days after the initiation of treatment, and monthly thereafter. Dosage was 100-200 mg per day, and duration of treatment was based on response. The cases of coccidioidomycosis and lymphangitic sporotrichosis were mycologically cured after two and seven months of treatment with 100 mg per day, respectively. The six other patients required higher doses. Two patients with sporotrichosis and one with chromomycosis were cured, and one patient with sporotrichosis and one with chromomycosis were markedly improved. In one patient with sporotrichosis, treatment was discontinued because of the slow response. No adverse reactions to treatment were reported.

Adult

[Epidemiology of mycetoma in Mexico: study of 2105 cases].

A survey was carried out in Mexico to determine the incidence and epidemiological characteristics of mycetoma. Data was collected from a total of 2105 cases of mycetoma throughout a 30 year period (1956-1985), with an average incidence of 70 cases per year. Results showed a sex distribution of 76.1% male and 23.9% females. Age distribution indicated a 35% between 16 to 30 and 23% between 31 to 40 year old population. Most cases occurred in land-workers (60.2%) and in housewives with rural residence (21.3%). Lesions occurred most frequently in lower limbs (64.1%), trunk (17.4%) and upper limbs (13.6%). The geographic distribution within Mexico revealed that the States with the highest incidence were: Jalisco, Nuevo León, San Luis Potosi, Morelos and Guerrero The predominant etiologic agents found 97.8% corresponded to actinomycetes, from which Nocardia brasiliensis (86.6%) and Actinomadura madurae (10.2%) showed the higher frequency. Eumycetoma (2.2%) was due to Madurella grisea and M. mycetomatis in most cases.

Adolescent

Red blood cell adhesion on a solid/liquid interface: comparison of two models.

Discoid red blood cells (RBCs) deposited irreversibly on a horizontal glass surface are studied by means of optical microscopy and image analysis. The relative surface covered by the RBCs, as well as the variance of this surface coverage as a function of the cell concentration, are analyzed and compared to the results derived from the ballistic deposition (BD) model. This model describes the irreversible deposition of spherical particles under the influence of an infinitely large gravitation force and does not allow for overlaps between adsorbed particles. In spite of these characteristics, the BD model permits, surprisingly, to reproduce our experimental observations on the deposition of RBCs on a flat surface. This finding is discussed, in particular in respect to a former study where a model was developed for colloidal particles of this particular geometric shape.

Cell Adhesion