Room-temperature synthesis, hydrothermal recrystallization, and properties of metastable stoichiometric FeSe.

Room-temperature precipitation from aqueous solutions yields the hitherto unknown metastable stoichiometric iron selenide (ms-FeSe) with tetragonal anti-PbO type structure. Samples with improved crystallinity are obtained by diffusion-controlled precipitation or hydrothermal recrystallization. The relations of ms-FeSe to superconducting ß-FeSe(1-x) and other neighbor phases of the iron-selenium system are established by high-temperature X-ray diffraction, DSC/TG/MS (differential scanning calorimetry/thermogravimetry/mass spectroscopy), (57)Fe Mössbauer spectroscopy, magnetization measurements, and transmission electron microscopy. Above 300 °C, ms-FeSe decomposes irreversibly to ß-FeSe(1-x) and Fe(7)Se(8). The structural parameters of ms-FeSe (P4/nmm, a = 377.90(1) pm, c = 551.11(3) pm, Z = 2), obtained by Rietveld refinement, differ significantly from literature data for ß-FeSe(1-x). The Mössbauer spectrum rules out interstitial iron atoms or additional phases. Magnetization data suggest canted antiferromagnetism below T(N) = 50 K. Stoichiometric non-superconducting ms-FeSe can be regarded as the true "parent" compound for the "11" iron-chalcogenide superconductors and may serve as starting point for new chemical modifications.

European-American Children's and Adolescents' Evaluations of Interracial Exclusion.

No research, to date, has investigated the role of ethnic school composition (and intergroup contact) on European-American youth's use of stereotypes to explain interracial discomfort in the context of peer exclusion. In this study European-American 4th, 7th and 10th grade students (N = 414), attending low and high ethnically diverse public schools (with low and high self-reports of cross-race/ethnic friendships, respectively) evaluated three contexts of interracial exclusion (at lunch time, at a school dance, and at a sleepover). In addition to age and context effects, participants enrolled in high diversity schools were less likely to use stereotypes to explain racial discomfort, more likely to view racial exclusion as wrong, and more likely to estimate that racial exclusion occurs, than were participants enrolled in low diversity schools. These findings have implications for the role of social experience on racial attitudes and judgments about exclusion.

Incommensurately modulated lanthanide coinage-metal diarsenides. I. CeAu(1-delta)As2 [delta = 0.015 (2)]--a new distortion variant of the HfCuSi2 type with irregularly stacked cis-trans chains of arsenic atoms.

Rare-earth metal coinage-metal diarsenides LnTAs2 (Ln = Y, La, Ce-Lu; T = Cu, Ag, Au) are known to crystallize in structures closely related to the HfCuSi2 type, which comprises a stacking sequence of puckered TAs layers and planar square As nets, separated by the Ln atoms. CeAu(1-delta)As2, with delta = 0.015 (2), shows an incommensurate positional modulation of the arsenic atoms in the planar As nets. Based on X-ray diffraction data on a twinned crystal, a structure model in the monoclinic superspace group P12(1)/m1(alpha0gamma)00 (No. 11.1) with basic unit-cell parameters of a = 5.804 (1), b = 5.814 (1), c = 10.179 (1) A and beta = 90.09 (8) degrees is presented. The components of the modulation wavevector q = alphaa* + 0b* + gammac* are alpha = 0.08 (1) and gamma = 0.39 (1). The structure comprises cis-trans chains and rectangles of As atoms and displays an intricate stacking sequence of the modulated arsenic nets. Rod groups and layer groups of the respective arrangements are identified and the arrangement of different motifs of the modulated As net is discussed.

Incommensurately modulated lanthanide coinage-metal diarsenides. II. GdCuAs2, GdAu(1-delta)As2 and TbAu(1-delta)As2--new distortion variants of the HfCuSi2 type with irregularly stacked zigzag chains of arsenic atoms.

GdCuAs2, GdAu(1-delta)As2 and TbAu(1-delta)As2 crystallize as incommensurately modulated variants of the HfCuSi2 type. Structure models have been developed in the monoclinic superspace group P12(1)/m1(alpha0gamma)00 (No. 11.1). The components of the modulation wavevectors q = alphaa* + 0b* + gammac* are alpha = 0.04 (1) and gamma = 0.48 (1) for GdCuAs2, alpha = 0.03 (1) and gamma = 0.48 (1) for GdAu(1-delta)As2 and alpha = 0.02 (1) and gamma = 0.46 (1) for TbAu(1-delta)As2. The predominant effect of the positional modulation is the distortion of a square net of arsenic atoms, which results in planar zigzag chains. Rod groups and layer groups of the respective structure motifs are identified and discussed.

Superspace description of the modulated structure of the metal-salt-hybrid Bi(7-delta)Ni2Br(5-2delta) (delta = 1/9).

The compound Bi(7-delta)Ni2Br(5-2delta) = (Bi3Ni)2[Bi(1-delta)Br4]Br(1-2delta) (delta = 1/9) is a sub-bromide of the intermetallic phase Bi3Ni. Its crystal structure contains metallic rods, 1infinity[Bi3Ni], which are embedded in a salt-like matrix of bromido-bismuthate(III) and bromide anions. The non-stoichiometry originates from the variation of the number n of trans edge-sharing octahedra in the [Bi(n)Br(4n + 2)]((n + 2)-) oligomers (3 < or = n < or = 5), as well as from vacancies on the sites of the isolated Br atoms. The simplified structure is described in the orthorhombic space group Cmcm with a = 4.0660 (4), b = 23.305 (3), c = 17.130 (2) A. It shows a statistical distribution of vacancies and orientational disorder of the concatenated octahedra. By choosing the modulation vector q = a*/9 + b*/2, the additional weak reflections of the diffraction pattern can be indexed. In the [3 + 1]-dimensional superspace group Pmnm(alpha(1/2)0)000, an ordered structure model is achieved. The modulated crystal structure bears a strong resemblance to the somewhat higher oxidized sub-bromide Bi(7-delta)Ni2Br5 (delta = 1/9).

Magnetic and electrical transport anomalies of RMAs(2) (R = Pr and Sm, M = Ag and Au).

The results of magnetization, heat capacity and electrical resistivity (ρ) studies of the compounds RMAs(2) (R = Pr and Sm; M = Ag, Au), crystallizing in an HfCuSi(2)-derived structure, are reported. PrAgAs(2) orders antiferromagnetically at T(N) = 5 K. The Au analog, however, does not exhibit long range magnetic order down to 1.8 K. We infer that this is due to subtle differences in their crystallographic features, particularly noting that both the Sm compounds with identical crystal structures as that of the former order magnetically nearly at the same temperature (about 17 K). It appears that, in PrAgAs(2), SmAgAs(2) and SmAuAs(2), there is an additional magnetic transition at a lower temperature, as though the similarity in the crystal structure results in similarities in magnetism as well. The ρ for PrAgAs(2) and PrAuAs(2) exhibits a negative temperature coefficient in some temperature range in the paramagnetic state. SmAuAs(2) exhibits a magnetic Brillouin-zone gap effect in ρ at T(N), while SmAgAs(2) shows a well-defined broad minimum well above T(N) around 45 K. Thus, these compounds reveal interesting magnetic and transport properties.

A Novel Coordination Mode of 7-Methyl-7-sila-nido-undecaborate(1-).

B-N-M bridges, resulting from the activation of two B,H units, are present in the anion [Nb(MeSiB(10)H(8))(µ-NMe(2))(2)Br(3)](-) (see structure depicted). Thus, this is an example for a hitherto unknown coordination mode in the chemistry of heteroborane clusters.

Young people's experience of the Canadian youth justice system: interacting with police and legal counsel.

Young people's knowledge and experience of the youth justice system was examined to explore self-reported factors that influenced their decisions regarding assertion versus waiver of rights to silence and legal counsel. Participants were 50 adolescents from Toronto, Canada ranging in age from 12 to 18 (mean age=15.6 years). Results of semi-structured interviews indicated that while over 60% of participants recalled being told of their rights to silence and counsel, three-quarters did not contact a lawyer at the police station and half of those asked by police answered their questions. Findings suggest that the awareness of due process rights is not sufficient to mitigate the atmosphere of coercion that characterizes the police station. Implications and limitations of the study are discussed.

Adolescents' and children's knowledge about rights: some evidence for how young people view rights in their own lives.

The present study examined the development of knowledge about rights from childhood to adolescence. One hundred and sixty-nine 8-16-year-olds participated in individual semi-structured interviews assessing knowledge and importance of rights both generally and in children's and adolescents' lives. Detailed content analyses indicated that a global stage account may not capture key features of the development of young people's knowledge about rights. Even the oldest adolescents consistently "defined" rights in concrete rather than abstract terms. In contrast, by 10 years of age the majority of subjects were aware of the universal nature of rights. These results suggest that what adolescents and children think about rights appears to be influenced by how they view rights in their own lives. The findings are discussed in terms of developmental theory and in relation to practical implications for children's rights.

Children's and adolescents' understanding of rights: balancing nurturance and self-determination.

This study examined the development of young people's understanding of nurturance and self-determination rights. One hundred and sixty-nine participants from 5 age groups (8, 10, 12, 14, and 16 years of age) participated in a semistructured interview containing hypothetical vignettes, in which a story character wished to exercise a self-determination right or nurturance right that conflicted with the wishes or practices of those in authority. Participants were asked to decide if they would support the story character's request for rights and to justify their decisions. Younger children (8- to 12-year-olds) were significantly less likely to identify both nurturance and self-determination rights as salient than were older participants (14- to 16-year-olds). The types of reasoning participants exhibited for the two types of rights differed at all ages. Reasoning about nurturance rights did not show an age-related progression from concrete to abstract, whereas reasoning about self-determination rights was more likely to exhibit such a progression. Results suggest that previous attempts to explain the development of understanding of rights in terms of global stages does not fully capture children's and adolescents' reasoning, and, in particular, such a framework may not account for the differences in young people's thinking about the 2 types of rights.

Comparative analysis of the immunophenotypes of decidual and peripheral blood large granular lymphocytes and T cells during early human pregnancy.

PROBLEM: The functional role of the leukocytes in the decidual is not clear. They may regulate the maternal immune response to the fetal allograft. However, the factors controlling maternal and fetal communication have not yet been identified. METHOD: A comparative analysis of the phenotypes of decidual and peripheral blood large granular lymphocytes (LGLs) and T lymphocytes in early human pregnancy was performed on decidual tissue and blood samples obtained from ten patients at therapeutic abortion. RESULTS: Whereas most of the decidual LGLs were found to have a CD56bright++ phenotype, most of the peripheral blood NK cells (90%) showed the classical CD56dim+ phenotype, and only a small proportion were CD56bright+ cells. Another striking difference was found in the expression of very late antigen 1 (VLA-1, CD49a): Almost all the decidual CD56bright++ LGLs, but virtually none of the peripheral blood CD56+ NK cells expressed this antigen. Further differences were found in the expression of CD16, CD44, CD45RA, CD54, and CD57. There were also differences in phenotype between T cells derived from decidual tissue and those derived from peripheral blood. Approximately 31% of the CD3+ decidual T cells expressed VLA-1, but this antigen was virtually absent on peripheral blood T cells. A further difference was seen in the expression of HLA-DR. This activation antigen was found on 32 +/- 13% of the decidual T cells but only 8 +/- 5% of the peripheral blood T cells. Additionally, the proportion of cells expressing CD38 was higher among decidual than peripheral blood T cells. CONCLUSION: The findings suggest that both decidual LGLs and a subset of decidual T cells are activated and possibly play a role in the control of trophoblast growth and placental development.

Spleen findings in generalized mastocytosis. A clinicopathologic study.

BACKGROUND: Little information regarding the morphologic findings of the spleen in generalized mastocytosis (GM) is available and no comprehensive review of the literature on this subject has been published. METHODS: The authors reviewed their records to study the macroscopic and microscopic features of the spleen in 53 patients; the authors also studied these features in 135 patients reported in the literature. Thus, a total of 188 patients with GM were studied. RESULTS: Splenomegaly was noted in 72% of the patients, including 71% of the patients from the authors' files and 73% of the patients reported in the literature. The spleen weight, recorded in 39 of the patients, ranged from 160 g to 2300 g; in 29 (80%) patients the spleen weighed more than 500 g and in 4 (10%) patients, more than 2000 g. However, mast cell (MC) infiltration of the spleen was recorded in only 65 (34%) patients (patients from authors' records, 39%; patients reported in literature, 32%). The following combinations were extremely rare: splenomegaly without evidence of MC infiltration (n = 1); and histologic evidence of MC infiltration in the absence of splenomegaly (n = 2). The histologic findings of the spleen could be assessed in nine of the patients from the authors' files, eight of whom had MC infiltration. In four patients, infiltration was diffuse and confined mainly to the red pulp; in the other four patients, it was more focal and involved mainly the white pulp. Spleen plasmacytosis was found in eight patients, eosinophilia in five, hemosiderosis in seven, and fibrosis in six. Concurrent acute nonlymphoblastic leukemia was diagnosed in four patients, none of whom had the skin lesions of urticaria pigmentosa. CONCLUSIONS: The authors' findings show that (1) splenomegaly is a common finding in GM and often is pronounced; (2) MC infiltration probably is the most important factor in the pathogenesis of splenomegaly in this disease; and (3) two different patterns of MC infiltration (diffuse and focal) can be identified in GM.

The decidua of early human pregnancy: immunohistochemistry and function of immunocompetent cells.

Like the endometrial stroma, the decidua contains lymphoreticular cells, and these are probably involved in immunological interactions between the conceptus and the mother. Lymphoreticular cells in decidual tissue obtained from 12 patients undergoing therapeutic abortion of an intact pregnancy at 6-10 weeks' gestation were investigated in this study. Immunophenotyping with a broad panel of monoclonal antibodies revealed various subpopulations of lymphoreticular cells. Macrophages (Ki-M6+, Ki-M7+, Ki-M8+, KP1+, MAC 387+ and Ki-M1P+) represented the largest fraction of intradecidual lymphoreticular cells. CD3+ and CD8+ lymphocytes were found in moderate numbers and CD4+ cells in small numbers. The majority of the intradecidual lymphoid cells exhibited an unusual phenotype [CD7+, CD2+, CD56+, triple negative (CD3-, CD4-, CD8)]. The distribution of these unusual lymphocytes mirrored that of the so-called endometrial stromal granulocytes. A few of these stromal granulocytes reacted with the macrophage-associated antibody KP1, but not with Ki-M1P, another macrophage marker. This was confirmed by immuno-electron microscopy. The finding that intradecidual CD3+ lymphocytes express neither the alpha/beta nor the gamma/delta heterodimer of the T cell antigen receptor was unexpected. However, these cells did express the alpha/beta heterodimer after in vitro culture with PHA-P and recombinant exogenous interleukin-2. No stimulated T lymphocytes expressing activation antigens could be detected. B lymphocytes, T and B immune accessory cells and CD15+ granulocytes were found only in small numbers or were absent. Amongst cells expressing NK cell markers, CD57+ and CD16+ cells were found in small to moderate numbers, while CD56+ cells were detected in large numbers.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunohistology of the human spleen after bone marrow transplantation for leukemia with special reference to the early post-transplantation period.

Immunohistochemical investigations were undertaken on paraffin-embedded tissue from the spleens of seven patients who had died after bone marrow transplantation (BMT) for leukemia. Parallel investigations were undertaken on three surgically resected traumatically ruptured (but otherwise normal) spleens and three spleens removed at autopsy from accident victims. 1) Up to ten weeks after BMT, the splenic lymphoid tissue was extremely atrophic. Lymphoid follicles (LFs) and periarteriolar lymphatic sheaths (PALS) were completely absent. A considerable increase in lymphoid cells in the red pulp and formation of small LFs and PALS occurred only in the longest surviving patient, who had died 50 weeks after BMT. 2) B cells (L26+, 4KB5+, Ki-B3+) were almost completely absent in the early post-transplantation period and thus T cells (UCHL1+) represented the major constituent of the hypoplastic splenic lymphoid tissue. Considerable numbers of T cells were already found two weeks after BMT. T-immune-accessory reticulum cells (S-100 protein+) were found in the PALS of the controls, but were absent in three of the BMT recipients. The findings clearly reflect the marked immunodeficiency in the early post-transplantation period, during which many patients (4/7 in this study) die of opportunistic infections, and are in line with the fact that the earliest signs of reconstitution of the immune system have been found to occur at three months post-transplantation. Since six of our BMT recipients had suffered from graft-versus-host disease our findings probably do not fully correspond to those when the immune system undergoes undisturbed reconstitution.

Blood findings in generalized mastocytosis: evidence of frequent simultaneous occurrence of myeloproliferative disorders.

Blood findings in 61 cases of generalized mastocytosis (GM) were evaluated. The cases were divided into two major variants: Systemic mastocytosis (SM; n = 34) with urticaria pigmentosa-like skin lesions, and malignant mastocytosis (MM; n = 27), without skin involvement. The following results were obtained: (1) Significant differences between MM and SM were found in the main haematological parameters (erythrocyte, platelet and leucocyte counts and haemoglobin level); normal values were found in 16 of the SM cases, but never in MM. (2) The main pathological findings were: in SM, anaemia (9/34) and leucocytosis (5/34); and in MM, leucocytosis (19/27), monocytosis (14/27), eosinophilia (12/27), bicytopenia (12/27, mostly anaemia with thrombocytopenia), basophilia (10/27) and isolated anaemia (7/27). (3) The major finding was a significant difference between MM and SM in the incidence of myeloproliferative disorders (MPD), myelodysplasia and mast cell leukaemia (MCL): these disorders occurred in 23 (92%) MM patients, but only in two (6%) SM patients (P less than 0.001). The four instances of MCL and two of myelodysplasia all occurred with MM. Of the 19 cases of MPD, six (SM, 1; MM, 5) were acute variants (acute myeloid and myelomonocytic leukaemias) and 13 (SM, 1; MM, 12) were chronic variants. No case of malignant lymphoma was noted. (4) The blood picture in 10 of 13 chronic MPD cases represented an atypical chronic myeloid leukaemia for which the preliminary descriptive term 'mastocytosis-associated MPD' is proposed. (5) A survey of 103 published cases (SM, 77; MM, 26) yielded similar findings, including a high incidence of MPD and MCL in MM. These findings add further weight to the argument for recognizing SM and MM as two separate entities.

Immediate and long-term effects on visual acuity of surgically induced strabismus in kittens.

In order to isolate some of the factors responsible for strabismic amblyopia as well as to ascertain the time course of its development, frequent measurements were made of the visual acuity of the two eyes of kittens following imposition of surgically induced strabismus. Following behavioural training on a jumping stand, strabismus was induced in all but one animal by simple section of either the lateral (esotropia) or medial (exotropia) rectus muscle of one eye. The one exception was a kitten on which esotropia was induced by another common but more radical surgical procedure that involved removal of the body of both the lateral rectus and superior oblique muscles of one eye. There was a surprising difference between the immediate consequences for vision of section of the lateral and medial rectus muscles that were reflected by equally large differences in the magnitude of the amblyopia that developed eventually in the two situations. Following section of the lateral rectus muscle, there was an immediate reduction in the visual acuity of the operated eye of as much as 2 octaves after which vision returned to normal levels over 4 to 8 days. The acuity of the two eyes remained comparable for a few days after which the vision of the operated eye began to decline once more, signalling the onset of amblyopia some 10 to 12 days following imposition of strabismus. In contrast to the severity of these effects, the effects observed following section of the medial rectus were both mild and transitory. Furthermore, whereas all kittens that were rendered esotropic early developed amblyopia, none of the kittens that were made exotropic at the same age did so. Together, these results suggest that factors associated with the immediate consequences of the surgical procedure employed to produce a misalignment of the visual axes may contribute to the severity of the effects of surgically induced strabismus.