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Biomedical subjects

M Roubin

Publications and source records attributed to M Roubin.

At least 19 recordsLinked to original sources
PubMed2000

Octahedral deformations and cationic displacements in the ferroelectric PbHf(0.8)Ti(0.2)O(3): a neutron powder diffraction study from 10 to 770 K

Neutron powder diffraction data, collected over the temperature range 10-770 K, have been analysed in order to make a detailed characterization of the sequence of phase transitions occurring in the Hf-rich ferroelectric PbHf(0.8)Ti(0.2)O3, titanium hafnium lead oxide. Over the whole temperature range this compound undergoes two phase transitions, which involve cationic displacements and octahedral deformations (tilt and/or distortion) leading to strongly distorted perovskite-type structures. The first transition appears around 415 K between two ferroelectric rhombohedral phases: a low-temperature nonzero-tilt phase F(RL) (space group R3c) and an intermediate zero-tilt phase FRH (space group R3m). The second one, detected around 520 K, is associated with a ferroelectric to-paraelectric transition between the FRH phase and the Pc cubic phase (space group Pm3m). From high-resolution neutron powder diffraction data (diffractometer 3T2-LLB, Saclay, France, lambda = 1.2251 A), the crystallographic structure of the three successive phases has been accurately determined at the following temperatures: T = 10 K (FRL): space group R3c, Z = 6, a(hex) = 5.7827 (1), c(hex) = 14.2702 (4) A, V(hex) = 413.26 (2) A3; T = 150 K (F(RL)): space group R3c, Z = 6, a(hex) = 5.7871 (1), C(hex) = 14.2735 (4) A, V(hex) = 413.98 (3) A3; T = 290 K (FRL): space group R3c, Z = 6, a(hex) = 5.7943 (1), C(hex) = 14.2742 (5) A, V(hex) = 415.04 (3) A3; T = 440 K (F(RH)): space group R3c, Z = 6, a(hex) = 5.8025 (1), c(hex) = 14.2648 (4) A, V(hex) = 415.94 (3) A3; T = 520 K (Pc): space group Pm3m, Z = 1, a(cub) = 4.1072 (2) A, V(cub) = 69.29 (1) A3. In addition, a neutron powder thermodiffractometry experiment, performed between 290 and 770 K (diffractometer D1B-ILL, Grenoble, France, lambda = 2.533 A), has been used to study in situ the temperature-induced phase transitions. From sequential Rietveld refinements, the temperature dependence of the cation displacements and the rotation and/or distortion of oxygen octahedra was derived.

Journal Article↗
PubMed1999

Temperature-dependent neutron powder diffraction evidence for splitting of the cationic sites in ferroelectric PbHf0.4Ti0.6O3.

Temperature-dependent neutron powder diffraction experiments (diffractometer 3T2-LLB, Saclay, France, lambda = 1.227 Å) have been performed on the perovskite-like lead hafnate titanate PbHf(0.4)Ti(0.6)O(3). This compound belongs to the solid solution denoted PHT, which derives from the well known ferroelectric PZT series. It exhibits a ferroelectric-to-paraelectric phase transition around 620 K, between the low-temperature tetragonal phase and the high-temperature cubic phase. The tetragonal structure of the ferroelectric phase has been refined at 10 and 300 K using a Rietveld-type method: space group P4mm with Z = 1; a(t) = 3.999 (1), c(t) = 4.120 (1) Å, c/a = 1.030, V = 65.89 Å(3) at 10 K; a(t) = 4.012 (1) and c(t) = 4.100 (1) Å, c/a = 1.022, V = 65.99 Å(3) at 300 K. The cubic structure of the paraelectric phase has also been refined at 720 K: space group Pm3;m, Z = 1, a(c) = 4.046 (1) Å, V = 66.23 Å(3). Cation displacements and oxygen-octahedra elongations have been observed as a function of temperature. Evidence for peculiar behaviour associated with the relative shifts of the Hf and Ti atoms (thought until now to be on the same crystallographic site) was found through an anomaly of the mean-square atomic displacements of the Hf/Ti pseudo-nucleus. The PDF Nos for PbHf(0.4)Ti(0.6)O(3) are 48-49-9 and 48-49-10.

Journal Article↗
PubMed1985

Embryonic testicular regression syndrome and severe mental retardation in sibs.

The embryonic testicular regression syndrome associated with severe mental retardation is reported in three 46,XY sibs each of whom has a 46,XY chromosome complement. A fourth sib, a sister, also is severely retarded mentally; her chromosome complement is 46,XX. The 46,XY individuals, who were raised as females, presented varying degrees of genital ambiguity, indicating that their gonadal activities had been arrested at different times during embryogenesis. No trace of gonadal tissue could be found in either patient. The coincidence of the embryonic testicular regression syndrome and severe mental retardation in the same sibship is discussed.

Adult↗
PubMed1977

[Dicentric Y chromosome in a male pseudohermaphrodite 45,X/46,X, dic (Y)/47, XYY].

The mosaicism 45,X/46,XY,terrea(Y,Y)(pterpter)/47,XYY was observed in an 8-month-old child with male pseudohermaphroditism. The presence of a 47,XYY population points to a post-zygotic origin of the rearrangement. The loss of Yp material is in favor of localization of masculinization factor(s) to the proximal segment of Yq. Twenty-two relevant observations reported in the literature previously are discussed.

Chromosomes↗
PubMed1977

[Distal trisomy 15q].

A patient with distal 15q trisomy resulting from malsegregation of a maternal t(13;15)(q33;q21.2) showed the following symptoms: micro-dolichocephaly, palpebral fissures slightly oriented downwards and outwards, a large nose, pronounced micrognathia, prominent authelices, ligamental abnormalities, osseous malformations evocative of diastrophic dwarfism, severe congenital heart defect, and profound encephalopathy. He died at five months of age. This observation is compared with two others from the literature.

Abnormalities, Multiple↗
PubMed1976

[Partial 7 q trisomy. One or 2 syndromes? Apropos of a new case].

Partial trisomy 7qter due to malsegregation of a familial balanced translocation t(7;8)(q33;p113) is reported in a 2-year-old boy with the following features: psychomotor retardation (IQ = 46); hypotonia; normal; facial asymetry with palpebral fissures slanted downwards and outwards, deeply set eyes, and divergent strabismus.

Child↗
PubMed1976

[Trisomy 10 p. A previously reported case explained by binding].

A previously reported male infant having died at 4 months, was considered trisomic Cp, his mother being carrier of balanced translocation t(Cp-;Bq +). Reexamination of the chromosome complement after R-banding showed the translocation to be t(4;10)(q35;p11). The propositus was therefore trisomic 10p. The essential clinical features were: a small birth weight and a short birth length; hypotonia; psychomotor retardation; dolichocephalia; a high and bulky forehead; narrow lips; large, lowset ears with a posterior rotation; a small chin; bone and joint anomalies; dextrocardia.

Abnormalities, Multiple↗
PubMed1975

Partial trisomy 9q: a new syndrome.

Two unrelated patients with a strikingly similar phenotype (low birth weight and poor thriving; mental retardation; dolichocephaly; beaked nose; deeply set eyes; prominent maxilla and receding small chin; long fingers with a peculiar clench) were partially trisomic for two different segments of 9q. The segment found to be trisomic in both patients is small and corresponds to the q31q32 region. This new syndrome is compared to observations of trisomy 9 reported in the literature.

Blood Group Antigens↗
PubMed1975

[Partial trisomy 14q II.--Partial trisomy 14q due to a maternal t(12; 14) (q24.4; q21)].

The phenotype of an 18-month-old male infant trisomic for the proximal portion of the long arm of chromosome 14 was reported and compared with that of previously reported cases. For the identification of the resulting syndrome, the most consistent features are psychomotor and growth retardation, and an oval, dysmorphic facies which includes a distinctive form of the mouth and a prominent nose. The trisomy in the child reported here is due to a familial translocation transmitted by the mother and present in at least three generations: t(12;14)(q24.4;q21). The 12q duplication in the child's genome is minimal and does not seem to have contributed to his phenotype.

Abnormalities, Multiple↗
PubMed1975

[Pure trisomy 9p 47,XX,+ del(9) (q11). Discovery of one cell 46,XX, del(9) (q11) in the father].

A case is reported of "pure" trisomy 9p: 47,XX,+del(9) (q11). The affected 6-year-old girl has moderate psychomotor retardation (IQ near 70), with speech retardation. She is mildly dysmorphic, with the characteristic features of trisomy 9p: a "worried look", a unilateral grin, slant of the palpebral fissures, a globulous nose, brachymesophalangia and the characteristic dermatoglyphic features. The parents karyotypes are normal, except for one cell from the father which had the karyotype 46,XY,del(9)(q11), the implications of which are discussed.

Child↗
PubMed1975

[Partial 11q monosomy and trigonocephaly. A new syndrome].

Partial monosomy 11q occurring de novo and concerning the 11q231 leads to qter region, is reported in a 2-month-old boy. This observation together with three others from the literature allows the individualization of a syndrome characterized by: severe growth retardation: more or less pronounced mental retardation; trigonocephaly; facial dysmorphia.

Chromosome Deletion↗