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Biomedical subjects

H Popescu

Publications and source records attributed to H Popescu.

14 recordsLinked to original sources
PubMed2005

Comparison of laser ion acceleration from the front and rear surfaces of thin foils.

The comparative efficiency and beam characteristics of high-energy ions generated by high-intensity short-pulse lasers (approximately 1-6 x 10(19) W/cm2) from both the front and rear surfaces of thin metal foils have been measured under identical conditions. Using direct beam measurements and nuclear activation techniques, we find that rear-surface acceleration produces higher energy particles with smaller divergence and a higher efficiency than front-surface acceleration. Our observations are well reproduced by realistic particle-in-cell simulations, and we predict optimal criteria for future applications.

Journal Article↗
PubMed2003

Evidence of ultrashort electron bunches in laser-plasma interactions at relativistic intensities.

The second harmonic of the laser light (2omega(0)) is observed on the rear side of thick solid targets irradiated by a laser beam at relativistic intensities. This emission is explained by the acceleration by the laser pulse in front of the target of short bunches of electrons separated by the period (or half the period) of the laser light. When reaching the rear side of the target, these electron bunches emit coherent transition radiation at 2omega(0). The observations indicate that, in our conditions, the minimum fraction of the laser energy transferred to these electron bunches is of the order of 1%.

Journal Article↗
PubMedDate not supplied

Morphotypic aspects in the cryptorchidic child.

The morphotype of 40 children with cryptorchidism (18 bilateral, 22 unilateral), selected by complex endocrine examination, was assessed in relation to age and clinical form of cryptorchidism. The morphotype was established on the basis of 9 anthropometric parameters (weight, stature, pube-ground distance, a-a, thr-thr, thoracic, abdominal, hips and cephalic circumferences). The malformed lot consists of 28 children with common and 12 with symptome cryptorchidism (5 adiposogenital, 3 male Turner's syndrome and 3 with gonadal dysgenesis). In the child with symptom cryptorchidism, the morphogram reveals, irrespective of age, a morphotype which corresponds in point of absolute dimensions and proportions, to the somatotype in which cryptorchidism as a symptome is included. The child with common cryptorchidism has irrespective of age, a normal or short stature and is underweight. Compared to the stature, the head is small, the lower limbs are short, the trunk is long and the hips are well developed. In our series of common cryptorchid child, the most marked statural deficit was found between 11 and 15 years as well as under the age of 6.

Body Constitution↗
PubMedDate not supplied

Somatotype of children with gonadal dysgenesis and structural anomalies of genitalia.

The somatotype of 92 children with sexual structural anomalies of whom 28 with female Turner's syndrome, 22 with Klinefelter's syndrome, 20 with adreno-genital syndrome, 14 with hypospadias, 2 with Reinfenstein's syndrome and 6 with feminizing testis was established on the basis of biometric and genetically determined morphologic characteristics (dermatoglyphics, pigment complex). A morphogram utilizing 12 anthropometric and 5 dermatoglyphic parameters was constructed; it can be used in phenotypical differentiation of the anatomo-clinical variants of structural anomalies of the genitalia and gonads. The 12 anthropometric parameters were: weight, stature, height of the head + neck segment, the sternum-symphysis distance, length of arms and legs, the biacromial and bitrochanterian diameters, the circumference of the thorax, abdomen, hips and head. The dermatoglyphic parameters were: the digital delta index, TFRC, a-b ridge count, the ATD angle and the A line obliquity. For longitudinal assessment of the phenotype of children with structural anomalies of genitalia and gonads, the authors propose utilization of the percentile diagrams regarding weight, stature, pubes to floor distance, and the biacromial and bitrochanterian diameters.

Adolescent↗
PubMedDate not supplied

Receptivity disorders in gonadal dysgeneses. i. Klinefelter's syndrome.

Long-term variation (21-30 days) in the gonadotropic hormones level and testosterone was followed up in Klinefelter's syndrome (chromatine positive). Clinically, the authors followed up the development of the androgen-dependent target tissues before and after administration of 400 mg testosterone/month for 6 months. It was also found a fluctuation in the gonadotropic hormones secretion on a 21-30-day trial which differs from that of the normal adult male. We noticed a great variability of the androgen-dependent structures development in one and the same subject or in different subjects, and a low response to the action of big and prolonged doses of testosterone. The authors interpret these findings as a decrease in the sensitivity of the androgen-dependent target structures (hypothalamus and peripheral tissues) induced genetically and fundamenting the concept of the existence of a receptivity pathology.

Adolescent↗
PubMedDate not supplied

Somatotyping in the obese children and adolescents.

Age-related somatic variability studied by 15 anthropometric parameters was assessed in 278 subjects (138 boys and 140 girls) aged between 5 and 20 years. Of these, 30% had simple obesity, 10.0% obesity associated with hypothyroidism, 10.0% obesity with diabetes, 25% obesity with adrenocortical reaction, 23.5% functional adiposo-genital syndrome and 1.5% Cushing's syndrome. The peculiarities related to the somatic development as a whole, the degree of bone development, and adiposity are interpreted in the main clinical forms of obesity, on the basis of the morphogram.

Adolescent↗