Powder processing methodology for fabrication of Copper/Graphite composite materials with enhanced thermal properties

International audienceThis study focuses on the powder processing methodology (PPM) for the fabrication of metal matrix composite using Graphite flakes (Grf) reinforced Copper (Cu). The manufacturing route involved (1) a reductive treatment of Grf powder to purify and increase its quality, (2) the mixing of the Cu and the Grf (0–40 vol%) powders with a fast and efficient Resonant Acoustic (RA) mixer, and finally (3) the cold and hot-pressing of composite powders. Comparison of PPM is made with literature and a usual method used in our laboratory. The quality of Grf after different steps was analyzed by Raman spectroscopy and XRD. Microstructure of the composite materials were analyzed by SEM. It was shown that this new PPM demonstrated better composite structural and thermal properties even at low volume fraction of Grf with a maximum of 630 W·m−1·K−1 obtained with 40 vol% of Grf at 70 °C

Neonatal screening for congenital hypothyroidism: Results and perspectives

Systematic screening for congenital hypothyroidism in the neonate constitutes a major progress in the prevention of mental retardation, as the condition occurs in 1/4,000 newborns and necessarily results in brain damage if not properly detected and treated during the first days of life. Screening and diagnostic and therapeutic procedures are discussed, as well as outcome and prognosis of the affected infants. Primary thyroid-stimulating hormone screening is almost universally recommended. Early therapy (within 14 days) with appropriate doses of thyroxine (about 10 μg/kg/day) will prevent any brain damage even in case of evidence of fetal hypothyroidism, as thyroxine of maternal origin will reach the fetus and largely protect him. Neonatal thyroid screening is also a particularly sensitive monitoring tool in the evaluation of the effects and of the correction of iodine deficiency at the population level.SCOPUS: re.jinfo:eu-repo/semantics/publishe

L'adaptation de l'enfant à une carence iodée grave: Pathogénie du goitre endémique

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Control of iodine deficiency in Western and Central Europe

The paper summarizes the updated information published in peer review journals on the status of iodine deficiency in Western and Central Europe. Nationwide evaluations of the prevalence of goiter and of the concentrations of urinary iodine were conducted dunng recent years in 17 of the 31 countries of Western and Central Europe, mostly in school-aged children. Fourteen of the 31 countries had reached a normal status of iodine nutrition, three countries were close to iodine sufficiency, iodine deficiency persisted in 13 other countries and data are missing for Albania. The most important alterations of thyroid function due to iodine deficiency in Europe occur in neonates and very young infants. The major measure for the prevention of iodine deficiency is the fortification of all salt for human and animal consumption and for the food industry. The recommended daily intake of iodine for all ages in all inhabitants in Europe are as follows: 90 μg/day from 0 to 59 month, 120 μg/day between 6 and 12 years, 100 μg/day in adolescents and adults and 200 μg/day in pregnant and lactating women. The main guidelines for the correction of iodine deficiency in Europe are included.SCOPUS: re.jinfo:eu-repo/semantics/publishe

The disorders induced by iodine deficiency

This paper reviews present knowledge on the etiology, pathophysiology, complications, prevention, and therapy of the disorders induced by iodine deficiency. The recommended dietary allowances of iodine are 100 μg/day for adults and adolescents, 60-100 μg/day for children aged 1 to 10 years, and 35-40 μg/day in infants aged less than 1 year. When the physiological requirements of iodine are not met in a given population, a series of functional and developmental abnormalities occur including thyroid function abnormalities and, when iodine deficiency is severe, endemic goiter and cretinism, endemic mental retardation, decreased fertility rate, increased perinatal death, and infant mortality. These complications, which constitute a hindrance to the development of the affected populations, are grouped under the general heading of iodine deficiency disorders (IDD). At least one billion people are at risk of IDD. Iodine deficiency, therefore, constitutes one of the most common preventable causes of mental deficiency in the world today. Most of the affected populations live in montainous areas in preindustrialized countries, but 50 to 100 million people are still at risk in Europe. The most important target groups to the effects of iodine deficiency from a public health point of view are pregnant mothers, fetuses, neonates, and young infants because the main complication of IDD, i.e. brain damage resulting in irreversible mental retardation, is the consequence of thyroid failure occurring during pregnancy, fetal, and early postnatal life. The main cause of endemic goiter and cretinism is an insufficient dietary supply of iodine. The additional role of naturally occurring goitrogens has been documented in the case of certain foods (milk, cassava, millet, nuts) and bacterial and chemical water pollutants. The mechanism by which the thyroid gland adapts to an insufficient iodine supply is to increase the trapping of iodide as well as the subsequent steps of the intrathyroidal metabolism of iodine leading to preferential synthesis and secretion of triiodotyronine (T3). They are triggered and maintained by increased secretion of TSH, which is ultimately responsible for the development of goiter. The acceleration of the main steps of iodine kinetics and the degree of hyperstimulation by TSH are much more marked in the pediatric age groups, including neonates, than in adults, and the development of goiter appears as an unfavorable side effect in the process of adaptation to iodine deficiency during growth. The most serious complication of iodine deficiency is endemic cretinism, a syndrome characterized by irreversible mental retardation together with either a predominant neurological syndrome or predominant hypothyroidism, or a combination of both syndromes. The prophylactic action of iodine on the incidence of both types of cretinism demonstrates the fundamental etiological role of iodine deficiency. The possible additional roles of thyroid growth-blocking immunoglobulins and of selenium deficiency have been suggested. The pathogenic roles of maternal and fetal hypothyroidism or a combination of both as well as of hypothyroidism present during the postnatal period are clearly established, but the relative importance of the three mechanisms in the pathogenesis of the various clinical manifestations of endemic cretinism is not entirely clearly established. A particularly important issue established both in severe and moderate conditions of iodine deficiency is that obvious neurointellectual deficits due to the deficiency are also frequently observed in individuals who do not present any of the other signs of endemic cretinism. The status of iodine nutrition was recently reevaluated in all European countries, including those in the Eastern part of the continent. Iodine deficiency is presently under control in only 5 countries (Austria, Finland, Norway, Sweden, and Switzerland). All other countries are still affected to varying degrees, especially in the southern and central parts of the continent. The public health consequences of iodine deficiency in Europe are an elevated thyroidal uptake of radioiodine that aggravates the risk of thyroid cancer in case of a nuclear accident, the occasional presence of neurointellectual deficits in schoolchildren, elevated frequencies of transient primary hypothyroidism and of transient hyperthyrotropinemia in young infants. Neonatal screening for congenital hypothyroidism using serum TSH as primary screening test appears as a particularly sensitive index of the effects of iodine deficiency at a population level and as a monitoring tool in the evaluation of the effects of iodine prophylaxis. Although theoretically entirely preventable, IDD still prevail in the world because of various socioeconomical, cultural, and political limitations to adequate programs of iodine supplementation, especially in Europe.SCOPUS: re.jinfo:eu-repo/semantics/publishe

Etude d'une endémie goitreuse en Afrique centrale: influence de la croissance et des facteurs d'environnement sur la fonction thyroïdienne

Doctorat en sciences médicalesinfo:eu-repo/semantics/nonPublishe

Nutrition iodée et hypothyroïdie néonatale.

This paper summarizes the research activities and the actions conducted and implemented by the author during the past 30 years in the field of the disorders induced by iodine deficiency and by neonatal hypothyroidism. This work was conducted within the framework of the activities of the author in the Department of Pediatrics in Saint-Pierre Hospital. The work resulted in original contributions to epidemiology, etiopathogenesis, clinical manifestations, diagnostic procedures, complications, prevention and therapy of the disorders resulting from iodine deficiency or neonatal hypothyroidism. Special attention was devoted to the prevention of impairment of brain and intellectual development resulting from both conditions in the infant.SCOPUS: re.jinfo:eu-repo/semantics/publishe

Rôle de facteurs goitrigènes distincts de la carence iodée dans l'étiologie du goitre.

The main cause of endemic and sporadic goiter is a deficiency in the dietary supply of iodine. However, iodine deficiency is not the only cause of goiter. This paper reviews present knowledge on the role of naturally occurring goitrogens in the etiology of goiter. Vegetables from the Cruciferae family, chronic consumption of poorly detoxified cassava containing large amounts of cyanogenic glucosides, flavonoids, humic substances originating from the organic residues in the soil are clearly involved in the etiology of endemic goiter. Iodine excess, especially in the newborn infants, lithium and thiocyanate overload resulting from smoking habits can be responsible for the development of goiter in non endemic areas.SCOPUS: re.jinfo:eu-repo/semantics/publishe

Les troubles dus à la déficience iodée.

1. An insufficient dietary supply of iodine results in the development of a variety of disorders of thyroid function and development of the fetus and young infants, grouped under the general heading of Iodine Deficiency Disorders, IDD. Endemic goiter constitutes the most spectacular disorder from the clinical and epidemiological point of view. However, the most serious consequence of iodine deficiency is the impact on neuro-intellectual development at a population level, varying from endemic mental retardation to the complete picture of endemic cretinism. 2. Considering that mental retardation due to iodine deficiency represents the longterm consequence of hypothyroidism occurring during the perinatal period, it is presently recognized that the target groups to the effects of iodine deficiency at a population level are, by order of priority, the fetus, the newborn, the pregnant woman, the child and, finally, the adult. 3. The newborn is more susceptible than the adult to the effects of iodine deficiency. Consequently, systematic screening for congenital hypothyroidism in endemic areas is a particularly sensitive index for detecting the presence and action of goitrogens in the environment and for monitoring the effects of programs of iodine prophylaxis. 4. IDD are particularly prevalent in developing countries. However, large areas or even countries in Europe are still obviously iodine deficient. For example, the iodine intake in adults in Belgium is 50 to 70 micrograms/day which is lower than the recommended dietary allowance for iodine (at least 100 micrograms/day). 5. IDD should be corrected on a world scale, including in Europe. Special attention should be devoted to the protection of mother and child. Within this framework, the iodine content of formula milk should be increased in Europe. 6. Finally, correction of iodine deficiency in Europe would decrease the avidity of the thyroid for iodide and, consequently, would constitute the most efficient preventive measure in case of nuclear fallout.SCOPUS: re.jinfo:eu-repo/semantics/publishe

L'hypothyroïdie congénitale et son dépistage systématique

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