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At least 811 records · Page 45Linked to original sources
PubMed2001

A proposal for a transition mechanism from the diamond to the lonsdaleite type.

A phase transition between the diamond (Fd3;m) and the lonsdaleite types (P6(3)/mmc) may be described as a deformation of a homogeneous sphere packing with three contacts per sphere (type 3/10/o1) in the common subgroup Pnna of Fd3;m and P6(3)/mmc. The frequently observed transition between the zinc-blende (F4;3m) and the wurtzite types (P6(3)mc) may be described in an analogous way as a deformation of a heterogeneous sphere packing in the subgroup Pna2(1). The proposed model guarantees the three-dimensional connection during the whole transformation process. By this property it is distinguished from other models.

Journal Article↗
PubMed2002

X-ray four-quadrant diamond phase-retarder system to compensate for off-axis and chromatic aberrations.

An X-ray transmission-type double phase-retarder system that can compensate for off-axis aberration (phase-shift inhomogeneity due to angular divergence of incident X-rays) has been developed and its advantage over a conventional single transmission-type X-ray phase retarder was demonstrated. However, it was noticed that the transmission-type X-ray phase retarder suffers from not only off-axis aberration but also chromatic aberration (phase-shift inhomogeneity due to energy spread of incident X-rays). In this paper, a transmission-type X-ray four-quadrant phase-retarder system is proposed that can compensate for both off-axis and chromatic aberrations. The X-ray four-quadrant phase-retarder system is composed of four transmission-type X-ray phase retarders. The scattering planes of four phase-retarder diamond crystals are set to be inclined by 45 degree, 135 degree (= 45 degree + 90 degree), 225 degree (= 45 degree + 180 degree) and 315 degree (= 45 degree + 270 degree), respectively, with respect to the plane of incident polarization. Under the conditions of 7709 eV photon energy, 1.5 eV energy spread and 45" angular divergence (FWHM) of incident X-rays, the X-ray four-quadrant phase-retarder system created 0.98 degree of vertical-linear polarization from horizontal-linear polarization. This value was favorably compared to 0.89 and 0.96, which were obtained by the single and double phase-retarder systems, respectively. The principle of the X-ray four-quadrant phase-retarder system will be described together with its advantage over the single and double phase-retarder systems.

Journal Article↗
PubMed2002

The structure of orange HgI2. II. Diamond-type structure and twinning.

The metastable orange crystals of HgI(2) comprise three different crystal structures all of which are built from corner-linked Hg(4)I(10) supertetrahedra. Two of the structures are end members with the maximum degree of order (MDO) of a polytypic layer structure. In this paper, the third structure (D) determined from X-ray diffraction, a crystal chemical discussion of the four known tetrahedral HgI(2) structures, and a twinning model are presented. All the various diffraction results published during the past 70 years are now explained. The Hg(4)I(10) supertetrahedra of the tetragonal structure D are corner-linked into two interpenetrating diamond-type networks. The stable red form and the three orange structures show the same cubic densest packing of I atoms and differ only in the distribution of Hg atoms in the tetrahedral voids. Transformations between the structures may involve only movements of Hg atoms, as implied by larger thermal displacement parameters of Hg than of I. A multiply twinned conglomerate of MDO1, MDO2 and D, each structure occurring in three orientations, results in metrically cubic crystals whose Bragg reflections are very close to reciprocal lattice points.

Journal Article↗
PubMed2005

Facilities for high-pressure research with the diamond anvil cell at GSECARS.

An overview of facilities for high-pressure research with the diamond anvil cell (DAC) at the GeoSoilEnviroCARS (GSECARS) sector at the Advanced Photon Source (Argonne, Illinois) is presented. There are three operational experimental stations (13-ID-C, 13-ID-D and 13-BM-D) where DAC instrumentation is installed for various types of experiments at high pressure and extreme temperature conditions. A fourth station (13-BM-C) is under construction and will be operational in 2006. While most X-ray diffraction experiments have been undertaken with powder samples so far, there is a growing demand for single-crystal diffraction (SCD) at high pressure. As one of the principal components at GSECARS, SCD is currently under rapid development. Other relevant techniques have also been developed for obtaining complementary information from powder or single-crystal samples at high pressure. For example, an on-line Brillouin system is installed and operational at 13-BM-D for acoustic velocity and single-crystal elasticity determinations. In addition, various X-ray spectroscopy techniques (e.g. X-ray emission and X-ray Raman) are employed for measuring electronic and magnetic properties. Future developments are discussed with the DAC program at GSECARS.

Journal Article↗
PubMed1998

High-pressure solution X-ray scattering of protein using a hydrostatic cell with diamond windows.

A hydrostatic high-pressure cell (maximum pressure 700 MPa) with synthetic diamond windows is applied to measure small-angle X-ray scattering of a protein at high pressure. Use of the present cell allows an accurate solvent background correction, providing quantitative analyses. The performance of the present cell for X-ray scattering is shown by using lysozyme as a sample solution. From the Guinier plot, values of the radius of gyration of lysozyme are evaluated to be 15.31 +/- 0.09 A at 1 atm (0.10 MPa) and 14.80 +/- 0.15 A at 400 MPa.

Journal Article↗
PubMed2001

Surface acoustic wave reflection from diamond-like carbon thin film reflecting arrays on LiNbO3 substrates.

Surface acoustic wave (SAW) reflection from diamond-like carbon (DLC) strip reflecting arrays on Y-Z LiNbO3 is investigated. The reflection from DLC strips with triangular cross section has been observed. Reflection increases in alternating DLC and Al strips in 90 degrees reflecting arrays in comparison with pure Al structures. The values of reflection coefficient per period in the slanted reflecting arrays are estimated to be about 1.0% for pure DLC strips (height to wavelength ratio equal to 0.02), 2% for uniform Al coating on DLC reflecting arrays, and 3.5% for alternating DLC and Al strips. This value is higher than that for pure Al strips by about 0.7%. Reflection properties are briefly discussed, and preparation technique is presented.

Journal Article↗
PubMed2003

High velocity SAW using aluminum nitride film on unpolished nucleation side of free-standing CVD diamond.

High performances surface acoustic wave (SAW) filters based on aluminium nitride (AlN)/diamond layered structure have been fabricated. The C-axis oriented aluminum nitride films with various thicknesses were sputtered on unpolished nucleation side of free-standing polycrystalline chemical vapor deposition (CVD) diamond obtained by silicon substrate etching. Experimental results show that high order modes as well as Rayleigh waves are excited. Experimental results are in good agreement with the theoretical dispersion curves determined by software simulation with Green's function formalism. We demonstrate that high phase velocity first mode wave (so-called Sezawa wave) with high electromechanical coupling coefficient are obtained on AlN/diamond structure. This structure also has a low temperature coefficient of frequency (TCF), and preliminary results suggest that a zero TCF could be expected.

Journal Article↗
PubMed2004

Skeletal phenotype in patients with Shwachman-Diamond syndrome and mutations in SBDS.

Pancreatic exocrine and bone marrow dysfunctions are considered to be universal features of Shwachman-Diamond syndrome (SDS) whereas the associated skeletal dysplasia is variable and not consistently observed. The genetic defect in SDS has recently been identified; causative mutations have been shown in the SBDS gene. The aims of this study were to characterize the nature, frequency, and age-related changes of radiographic skeletal abnormalities in patients with SBDS mutations and to assess genotype-phenotype correlation. Fifteen patients (mean age 9.7 years) with a clinical diagnosis of SDS and documented SBDS gene mutations were included. Review of their skeletal radiographs showed abnormalities in all patients. The skeletal changes were variable, even in patients with identical genotypes. The typical features were (1) delayed appearance of secondary ossification centers, (2) variable widening and irregularity of the metaphyses in early childhood, followed by progressive thickening and irregularity of the growth plates, and (3) generalized osteopenia. There was a tendency towards normalization of the epiphyseal maturation defect and progression of the metaphyseal changes with age. The results suggest that the characteristic skeletal changes are present in all patients with SDS and SBDS mutations, but their severity and localization varies with age. No phenotype-genotype correlation was observed.

Adolescent↗
PubMed1975

Haem synthesis in the Diamond-Blackfan syndrome.

The response of bone marrow to erythropoietin (EPO) from five children with the Diamond-Blackfan syndrome, also known as congenital hypoplastic anaemia (CHA), was tested in tissue culture by measurement of haem synthesis. Studies of 13 control marrows indicated that the maximum EPO effect occurred at approximately 70 h incubation using an EPO concentration of 0.2-0.3 units/ml and a nucleated cell concentration of 5 x 10(6) per culture. Under these conditions, haem synthesis was 121% greater in EPO-stimulated than in unstimulated cultures. Patients with CHA with anaemia and diminished marrow erythroids had reduced or absent haem synthesis. In one patient, haem production became normal after a spontaneous remission, and was not inhibited by autologous plasma drawn at the time of diagnosis. Plasma from three patients did not show inhibitory activity when cultured with control marrow. In contrast, plasma from an adult with acquired pure red cell aplasia produced striking inhibition of haem synthesis when cultured with control marrow. We conclude that, in comparison to some cases of the adult acquired condition, CHA is not due to inhibitors or antibodies. When present, erythroid precursors in children with CHA are capable of responding normally to EPO with increased haem synthesis.

Anemia, Aplastic↗
PubMed1989

An intrinsic progenitor defect in Diamond-Blackfan anaemia.

To determine whether the erythropoietin (epo) insensitivity of erythroid progenitor differentiation in congenital pure red cell aplasia or Diamond-Blackfan anaemia is intrinsic to the progenitor itself or is due to defective accessory cell function or active suppression, progenitors from normals and two patients (one steroid resistant and one spontaneously remitting), separated from all known accessory cells using sequential negative selection techniques (adherence, E-rosetting, and direct and indirect immune-panning), were studied. Initially, we evaluated three patients with DBA using unfractionated bone marrow mononuclear cells. Progenitors from two steroid non-responsive patients showed insensitivity to crude epo (c-epo) while one steroid responsive patient demonstrated normal in vitro sensitivity to c-epo. When recombinant epo (r-epo) was used in place of c-epo, the two steroid non-responders continued to demonstrate in vitro progenitor epo insensitivity. However, sensitivity of progenitors from the steroid responder, which was normal in the presence of c-epo, became abnormal when recombinant epo (r-epo) was substituted. Thus, using unfractionated bone marrow, the abnormal response to epo of progenitors from some patients with DBA appears to be obscured by stimulating factors termed erythroid burst-promoting activity (BPA) which are present in c-epo. Using fractionated highly enriched progenitors, from normals and a steroid responsive patient a final 3-10-fold enrichment of progenitors was achieved, but no such enrichment was seen when marrow from a steroid resistant patient was cultured. The epo sensitivities of normal and of patient erythroid progenitors were similar. However, at sub-optimal epo concentrations in both patients CFU-E responsiveness to crude BPA was abnormal compared to the three controls. We conclude from these studies that in DBA: (a) the failure of erythropoiesis is due to an intrinsic progenitor defect; (b) this defect involves progenitor insensitivity to factors in addition to erythropoietin: and (c) there exists a spectrum of disease reflected in the degree of the in vitro abnormality observed.

Adolescent↗
PubMed1991

Treatment of Diamond-Blackfan anaemia with haematopoietic growth factors, granulocyte-macrophage colony stimulating factor and interleukin 3: sustained remissions following IL-3.

We have treated six transfusion-dependent, steroid-unresponsive, Diamond-Blackfan anaemia (DBA) patients with the recombinant human growth factors granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-3 (IL-3), administered sequentially with an interim rest period. GM-CSF was given at a dose of 500 micrograms/m2/d subcutaneously for 6 weeks. Three patients increased their absolute reticulocyte counts 1.5-35-fold (mean 20.8-fold) and into the normal range, but only one showed a reduction in transfusion requirements. Between 4 and 25 weeks after discontinuation of GM-CSF, these six patients were treated with recombinant human IL-3, at doses of 60 or 125 micrograms/m2/d subcutaneously for 4-6 weeks. Three increased their absolute reticulocyte counts from 2- to 28-fold (mean 10.6-fold) and two required fewer transfusions. One of these two patients has remained transfusion independent for over a year since completion of IL-3 therapy, and the second patient required infrequent transfusions for 9 months and then became transfusion independent for the subsequent 5 months. The sustained clinical remissions seen in two of the six patients after IL-3 therapy is very encouraging and further studies in a larger cohort of DBA patients with IL-3 alone or in combination with GM-CSF or other growth factors should be carried out.

Adolescent↗
PubMed1992

The production of steel factor mRNA in Diamond-Blackfan anaemia long-term cultures and interactions of steel factor with erythropoietin and interleukin-3.

Diamond-Blackfan anaemia (DBA) is a congenital macrocytic anaemia. To investigate whether DBA is due to hyporesponsiveness to or hypoproduction of Steel factor (SF), we compared the in vitro responsiveness of the BFU-E contained in the Ficoll-Hypaque non-adherent cell fraction of six DBA marrows with that of four normal marrows and one transient erythroblastopenia of childhood (TEC) marrow. In addition, we studied the effect of soluble SF on long-term marrow cultures (LTMC) and analysed the stromal cells from these cultures for SF mRNA transcripts. All the patients showed an erythropoietin dose-related increase of small BFU-E. The number and size of BFU-E was increased with the addition to the epo of IL-3 or SF; IL-3+SF was not synergistic. The addition of soluble SF to LTMC of DBA patients was associated with a small but consistent increase in non-adherent cell production and an increase in the number of progenitors. Messenger RNA from immortalized stromal cell lines of three patients and from primary bone marrow stromal cells of one patient showed the presence of expected SF transcripts by PCR analysis. These results demonstrate that this group of DBA patients responds to SF and produces SF mRNA normally, indicating that SF itself is not involved in DBA pathophysiology. The effects observed suggest that, despite the lack of evidence for a causative role, SF may prove to be effective treatment for such patients.

Adult↗
PubMed1993

Long-term survival and cure after marrow transplantation for congenital hypoplastic anaemia (Diamond-Blackfan syndrome).

Four patients with Diamond-Blackfan syndrome (congenital hypoplastic anaemia) whose disease was resistant to corticosteroid treatment and who were red blood cell transfusion-dependent, were given marrow grafts from allogeneic human-leucocyte-antigen (HLA)-identical siblings. The patients were conditioned with regimens including cyclophosphamide and busulfan. Three of four patients had sustained and complete marrow engraftment. One patient showed early signs of haematopoietic recovery but died on day 35 of pulmonary toxicity. The three surviving patients are well with normal haematopoiesis and Karnofsky performance scores of 100%, 3.0, 7.4 and 10.6 years after transplantation. Congenital hypoplastic anaemia can be treated successfully by allogeneic marrow grafts.

Acute Disease↗
PubMed1994

Age-related alterations in erythroid and granulopoietic progenitors in Diamond-Blackfan anaemia.

Mechanisms involved in the erythroid failure characterizing Diamond-Blackfan anaemia (DBA) remain unidentified. The general consensus is that the defect is intrinsic to the marrow erythroid progenitor, but the target progenitor cell has not been precisely identified, and in vitro studies have revealed considerable heterogeneity between patients. In order to understand better the meaning of such a biological heterogeneity, we examined the in vitro response of erythroid progenitors CFU-E (colony-forming unit-erythroid) and BFU-E (burst-forming unit-erythroid) to erythropoietin (Epo), interleukin-3 (IL-3) and stem cell factor (SCF) in a large series of 24 patients from 1 month to over 20 years of age. Results of colony assays revealed a striking correlation between the age of the patient and the extent of the abnormalities detected in vitro. Therefore, despite profound anaemia, 80% (7/10) of the patients studied within 1 year of diagnosis had normal numbers of both CFU-E and BFU-E which exhibited a normal response to cytokines. In contrast, 12/14 patients followed up for more than 3 years had decreased numbers of erythroid progenitors, in seven cases associated with decreased colony-forming unit granulocyte-macrophage (CFU-GM). The number of CFU-E and BFU-E was not normalized even by the addition of high concentrations of combined Epo, IL-3 and SCF.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1995

Is there a role for interleukin-3 in Diamond-Blackfan anaemia? Results of a European multicentre study.

Forty patients (nine adults aged 20-54; 31 children aged 1-17) with Diamond-Blackfan anaemia (DBA) were treated with recombinant human interleukin-3 (IL-3) in a European multicentre compassionate-need study. IL-3 was given as a daily subcutaneous injection at a starting dose of 2.5 micrograms/kg, escalating at day 21 to 5 micrograms/kg, and then to 10 micrograms/kg if there was no response, for a total duration of 12 weeks. Three children achieved a significant response, achieving sustained remissions off all therapy. At the time of entry, one was steroid-responsive and transfusion-independent, and two were transfusion-dependent. Two adults had a transient reduction in transfusion requirements, but could not tolerate the complete course of therapy. Eosinophilia was common; neutrophil and platelet counts were unaffected except in three patients in whom previously noted mild thrombocytopenia was transiently exacerbated. Clinical response to IL-3 did not correlate with in vitro culture results. A comparison of individual patient characteristics of our study with previously reported series confirms earlier impressions that patients who have never achieved significant in vivo erythropoiesis in response to steroids or during a spontaneous remission are highly unlikely to respond to IL-3. In contrast, there may be a 50% chance of a sustained remission, off steroids, in children who are steroid-dependent and transfusion-independent at the time of IL-3 therapy, suggesting a possible role for a short course of IL-3 earlier in the treatment of children with steroid-responsive DBA.

Adolescent↗
PubMed1995

The effect of human flt-3 ligand on committed progenitor cell production from normal, aplastic anaemia and Diamond-Blackfan anaemia bone marrow.

We investigated the effect of the human ligand for flt-3 (FL) on the committed progenitor colony formation of normal bone marrow (BM) (n = 9) and BM from four aplastic anaemia (AA) and three Diamond-Blackfan anaemia (DBA) patients. Methylcellulose committed progenitor cell assays were carried out using FL alone and in combinations with granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-3 (IL-3) and c-kit ligand (KL). FL alone had a limited, though significant, effect on the production of granulocyte-macrophage colony-forming unit (CFU-GM) colonies from normal BM and showed an additive effect with IL-3 and GM-CSF separately, but not in combination. FL did not increase the stimulation of KL and did not have an effect on the production of erythroid progenitor colonies. FL had no effect on the AA and DBA BMs studied.

Adult↗
PubMed1995

Diamond-Blackfan anaemia: three patterns of in vitro response to haemopoietic growth factors.

Culture of bone marrow from patients with Diamond-Blackfan anaemia (DBA) has previously shown a variable progenitor response to growth factor stimulation. An extensive standardized study has now been undertaken to investigate the presence of distinct sub-groups in this disorder. In vitro response of bone marrow progenitors to recombinant human growth factors, including stem cell factor, was examined in 18 DBA patients and five normal donors, assessing BFU-E, CFU-GM and CFU-GEMM development. In 16 of the DBA patients a synergistic response to combinations of growth factors was observed with optimal growth in cultures containing erythropoietin, interleukin-3 and stem cell factor. Growth factor induced erythroid response formed three distinct groups, based on BFU-E numbers: type I (mean age 4.87 years) showed > 70% normal erythroid response; type II (mean age 13.87 years) showed < 70% normal; and type III (mean age 15.29 years) < 5% normal. CFU-GM response also followed the trigrouping. The results suggest more than one pathogenic mechanism for the erythroid failure in DBA, indicating DBA may be composed of more than one distinct disorder, and further suggest the defect in DBA may not be confined to the erythroid series.

Adolescent↗
PubMed2005

Haematopoietic stem cell transplantation for Shwachman-Diamond disease: a study from the European Group for blood and marrow transplantation.

This report assessed the results of allogeneic stem cell transplantation (allo-SCT) in 26 patients with Shwachman-Diamond disease (SDS) and severe bone marrow abnormalities. The conditioning regimen was based on busulphan (54%), total body irradiation (23%), fludarabine (15%) or other chemotherapy combinations (8%). Standard prevention of graft versus host disease (GVHD) with cyclosporin +/- methotrexate was adopted in 54% of the patients whilst in vivo or in vitro T-cell depletion was used in 17 and four patients respectively. Neutrophil and platelet engraftment were achieved in 21 (81%) and 17 (65%) of 26 patients after a median time of 18 days and 29 days respectively. The incidence of grade III and IV acute GVHD was 24% and of chronic GVHD 29%. Nine patients died after a median time of 70 d, post-SCT. After a median follow-up of 1.1 years, the transplant-related mortality was 35.5% (95% CI 17-54) whilst the overall survival was 64.5% (95% CI 45.7-83.2). Allo-SCT was found to be successful in more than half of SDS patients with severe bone marrow dysfunction. Further improvements would be anticipated by a better definition of the optimum time in the course of disease to transplant and by the adoption of less toxic conditioning regimens.

Adolescent↗