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At least 19 recordsLinked to original sources
PubMed2004

Raman spectroscopy of diamond and doped diamond.

The optimization of diamond films as valuable engineering materials for a wide variety of applications has required the development of robust methods for their characterization. Of the many methods used, Raman microscopy is perhaps the most valuable because it provides readily distinguishable signatures of each of the different forms of carbon (e.g. diamond, graphite, buckyballs). In addition it is non-destructive, requires little or no specimen preparation, is performed in air and can produce spatially resolved maps of the different forms of carbon within a specimen. This article begins by reviewing the strengths (and some of the pitfalls) of the Raman technique for the analysis of diamond and diamond films and surveys some of the latest developments (for example, surface-enhanced Raman and ultraviolet Raman spectroscopy) which hold the promise of providing a more profound understanding of the outstanding properties of these materials. The remainder of the article is devoted to the uses of Raman spectroscopy in diamond science and technology. Topics covered include using Raman spectroscopy to assess stress, crystalline perfection, phase purity, crystallite size, point defects and doping in diamond and diamond films.

Carbon↗
PubMed1999

A Monte Carlo comparison of the response of the PTW-diamond and the TL-diamond detectors in megavoltage photon beams.

A detailed Monte Carlo study of the PTW-diamond solid state detector response in megavoltage photon beams (60Co gamma rays to 25 MV x rays) has been performed with the EGS4 Monte Carlo Code. The sensitive volume of the diamond detector is a disk of diameter 4.4 mm and thickness 0.40 mm. The phantom material was water and the irradiation depth was usually 3 cm but additional simulations were performed at six other depths for the 10 and 25 MV x rays. Results show that the PTW-diamond detector response per unit of absorbed dose is constant within 1% for photon beam energies ranging from 60Co gamma rays to 25 MV x rays. Accurate depth dose curves for 10 and 25 MV x-ray beams may be measured with the diamond detector since the response per unit of absorbed dose at different depths in a water phantom is also constant to within 1% for depths ranging from 3 to 25 cm and field sizes ranging from 2.5 cm by 2.5 cm to 10 cm by 10 cm. An examination of the difference between the PTW-diamond detector and the wall-less form of the detector (e.g., TLDs) revealed that there is no significant difference in their response in megavoltage photon beams. This implies that the encapsulation of the diamond dosimeter causes less than a 1.3% change in its response for these megavoltage photon beams. Analysis of the total dose deposited in the sensitive volume of the detector shows that the PTW-diamond detector behaves as an intermediate-sized cavity, not a simple Bragg-Gray cavity, since the dose contribution from photon interactions within the cavity (alpha(c)) to the total cavity dose is 8% for 25 MV x rays and increases to 42% for 60Co gamma rays.

Calibration↗
PubMed1990

Effects of the diamond grit sizes of the commercial dental diamond points on the weight-load cutting of bovine enamel and glass-ceramic Typodont teeth.

To evaluate the effect of the diamond grit size of commercial dental diamond points on the dental cutting, we conducted weight-load cutting tests on bovine enamel and glass-ceramic typodont teeth using 3 different diamond grit sizes and air-bearing and ball-bearing air-turbine driven handpieces. With the transverse load applied on the diamond point varied between 20 and 80 g, we measured rotational cutting speed and cutting volume. Generally, increases in applied load caused decreases in rotational cutting speed and increases in cutting volume. The intensity of this trend, however, differed between grit sizes. Regular grit diamond points most strongly showed this tendency, while super-fine grit diamond points were least affected. Fine grit diamond points behaved in a manner similar to regular grit points.

Animals↗
PubMedDate not supplied

Oral megadose methylprednisolone therapy for refractory Diamond-Blackfan anemia. International Diamond-Blackfan Anemia Study Group.

PURPOSE: Several reports describe children with refractory transfusion-dependent Diamond-Blackfan anemia who responded to extremely large doses of methylprednisolone. Limitations in available data prompted further exploration of this treatment approach. PATIENTS AND METHODS: This prospective treatment protocol was designed to test the efficacy and toxicity of oral megadose methylprednisolone in children with Diamond-Blackfan anemia who had previously failed to respond to standard doses of prednisone and who were dependent on regular packed red blood cell transfusions. Patients were treated with oral methylprednisolone, starting at a dose of 100 mg/kg per day, tapering slowly to 5 mg/kg per day at the end of 4 weeks and to 2 mg/kg per day after 7 weeks of induction therapy. Therapy was continued for a total of 23 weeks. Efficacy was assessed by increase in peripheral blood reticulocytes and increase or stabilization in hemoglobin concentration, which was maintained during and after steroid tapering. RESULTS: Nine children with Diamond-Blackfan anemia were registered on the study, and all were evaluable. Disease in four of the children failed to respond to megadose methylprednisolone therapy. The other five patients demonstrated a partial or complete response during the initial 4 to 8 weeks of therapy, but all subsequently experienced relapse during the ensuing 2 months as the corticosteroid dose was tapered. All patients required resumption of transfusions, although one later remitted spontaneously. Toxicity of megadose methylprednisolone was modest. CONCLUSION: None of nine children with refractory Diamond-Blackfan anemia treated with oral megadose methylprednisolone exhibited a clinically significant response. Alternative therapeutic strategies are required.

Administration, Oral↗
PubMed2006

Iron oxide modified diamond blends containing ultradispersed diamond.

Iron oxide modified diamond blends containing different amounts of ultradispersed diamond were prepared and characterized by nitrogen physisorption, X-ray diffraction, temperature programmed reduction, Mössbauer and IR spectroscopy. The catalytic behavior of these composite materials in methanol decomposition to hydrogen, carbon monoxide, and methane has been also studied. The initial state and phase transformations of the supported highly dispersed iron oxide particles in various pretreatment media, as well as their reductive and catalytic properties, strongly depend on the ultradispersed diamond content in the diamond blends.

Journal Article↗
PubMedDate not supplied

A study of the optical micrometer, the coin gauge, and the diamond knife micrometer in diamond knife calibration.

Reproducible results in refractive keratectomy are greatly influenced by an accurate setting of the diamond knife blade length. In this study, we evaluated the accuracy and reproducibility of three existing techniques of blade calibration: the KOI coin gauge, the KOI diamond knife handle micrometer, and the Magnum optical micrometer. Serial blade length measurements of three similarly designed KOI diamond knives were made using each of the above calibration methods. The three knife handle micrometers had the largest measurement error (3.55%, 2.83%, 1.82%), and therefore the sole reliance of the handle micrometer for blade calibration was not recommended. The measurements made by the coin gauge on the three knives had measurement errors of 1.03%, 1.64%, and 1.46%. The optical micrometer achieved an accuracy of 0.005 mm and an interobserver precision of 0.009 mm. We prefer using the optical micrometer because the potential for parallax error is eliminated; it has a lower risk of blade damage; it is easier to use; and it also allows detection of defects in the footplates, the diamond knife, and of the wobbling blade, which may contribute to calibration error.

Calibration↗
PubMed2001

Osteogenic sarcoma associated with Diamond-Blackfan anemia: a report from the Diamond-Blackfan Anemia Registry.

PURPOSE: Diamond-Blackfan anemia (DBA) is a congenital pure red cell aplasia, usually presenting in infancy or early childhood. A review of the literature strongly supports a predisposition to hematopoietic malignancy. Recently, solid tumors have been reported, some attributable to hemosiderosis and/or androgen therapy. Two cases of osteogenic sarcoma have also been documented. An analysis from the Diamond-Blackfan Anemia Registry was performed to evaluate the cancer risk in patients with DBA. METHODS: The Diamond-Blackfan Anemia Registry of North America (DBAR) is a comprehensive database of patients with DBA enrolled, after informed consent, through outreach to pediatric hematologists and family groups. The patients and/or their families complete a detailed questionnaire, and a review of medical records and telephone interviews are performed to complete and clarify the information provided. RESULTS: Of the 354 patients registered in the DBAR, there were six patients meeting the accepted diagnostic criteria for DBA who were found to have malignancies. Three patients had osteogenic sarcoma diagnosed, one with myelodysplastic syndrome, one with colon carcinoma, and one with a soft tissue sarcoma. CONCLUSION: There appears to be an association of osteogenic sarcoma with DBA. A young age at presentation may be a feature of DBA-associated osteogenic sarcoma. Because of the immaturity of the database, the actuarial risk for osteogenic sarcoma and other cancers in individuals with DBA cannot be ascertained. Speculation is made regarding the nature of the molecular defect leading to the association of DBA and osteogenic sarcoma.

Adolescent↗
PubMed2006

Substitutional boron in nanodiamond, bucky-diamond, and nanocrystalline diamond grain boundaries.

Although boron has been known for many years to be a successful dopant in bulk diamond, efficient doping of nanocrystalline diamond with boron is still being developed. In general, the location, configuration, and bonding structure of boron in nanodiamond is still unknown, including the fundamental question of whether it is located within grains or grain boundaries of thin films and whether it is within the core or at the surface of nanoparticles. Presented here are density functional tight-binding simulations examining the configuration, potential energy surface, and electronic charge of substitutional boron in various types of nanocrystalline diamond. The results predict that boron is likely to be positioned at the surface of isolated particles and at the grain boundary of thin-film samples.

Journal Article↗
PubMedDate not supplied

The Diamond Blackfan Anemia Registry: tool for investigating the epidemiology and biology of Diamond-Blackfan anemia.

Diamond-Blackfan anemia (DBA) is a heterogeneous genetic disorder characterized by red cell aplasia and congenital anomalies. One of what appears to be multiple DBA genes has been cloned. Affected individuals in the same family may vary dramatically as to the degree of anemia, response to corticosteroids, and the presence of congenital anomalies. The epidemiology of DBA has been gleaned largely from literature reviews. This approach is limited because of the two-fold disadvantage of the reporting bias inherent in the literature and the lack of an active patient database. The Diamond Blackfan Anemia Registry of North America (DBAR) is designed to overcome these disadvantages to study the epidemiology and biology of DBA. The DBAR is a comprehensive database of patients with DBA who are enrolled after informed consent is obtained. Identification of patients is made through outreach to pediatric and adult hematologists and the Diamond Blackfan Anemia Foundation. The patients and/or their families complete a detailed questionnaire. A review of medical records and telephone interviews are performed to complete and clarify the information provided. To date, 354 patients have been enrolled in the DBAR. Using this database, important epidemiologic, clinical, and laboratory observations have been made with regard to the clinical presentation, the inheritance of DBA, the genetics of congenital malformations, the therapeutic outcome, including the efficacy of hematopoietic stem cell transplantation, and the recognition of DBA as a cancer predisposition syndrome. In particular, the database is an essential substrate for DBA gene discovery.

Child↗
PubMed2006

Improving clinical care and elucidating the pathophysiology of Diamond Blackfan anemia: an update from the Diamond Blackfan Anemia Registry.

Diamond Blackfan anemia (DBA) is a heterogeneous genetic disorder characterized by red cell aplasia, congenital anomalies, and a predisposition to cancer. Although incompletely understood, the erythroid failure in DBA appears to result from the accelerated apoptosis of affected erythroid progenitors/precursors. One of what appears to be multiple DBA genes, coding for a ribosomal protein RPS 19, has been cloned. Even within multiplex families individuals may vary dramatically as to the degree of anemia, response to treatment and the presence of congenital anomalies. The Diamond Blackfan Anemia Registry (DBAR), a comprehensive database of pediatric and adult patients with DBA who are enrolled after informed consent, was designed to overcome two significant obstacles encountered in the study of a rare disease; the reporting bias inherent in the literature and the lack of an active patient database. To enroll, patients, their families and their physicians complete a detailed questionnaire. A review of medical records and telephone interviews are performed to complete and clarify the information provided. As of May 1, 2005, 420 patients have been enrolled in the DBAR. Epidemiological, clinical, and laboratory data have been collected and analyzed. The DBAR has provided new information on the clinical presentation, outcome and genetics of DBA as well as a better description of congenital malformations and cancer predisposition. This has resulted both in improved clinical care of patients with DBA as well as providing new insights into the pathophysiology of this complex disorder.

Adolescent↗
PubMed2004

Diamond and diamond-like carbon from a preceramic polymer.

The synthesis of poly(hydridocarbyne), one of a class of carbon-based random network polymers and a structural isomer of polyacetlyene, is reported. The network backbone of this polymer is primarily composed of tetrahedrally hybridized carbon atoms, each bearing one hydride substituent and linked via three carbon-carbon single bonds into a three-dimensional random network of fused rings. This atomic-level carbon network backbone confers unusual properties on the polymer, including facile thermal decomposition to form diamond or diamond-like carbon high-quality films at atmospheric pressure, by direct deposition or by chemical vapor deposition (CVD), without the use of hydrogen or any other reagent.

Journal Article↗
PubMed1999

Pregnancy in bone marrow failure syndromes: Diamond-Blackfan anaemia and Shwachman-Diamond syndrome.

Pregnancy in bone marrow failure syndromes has risk to mother and fetus. There are fewer than 30 reports of cases with Diamond-Blackfan anaemia (DBA), and none with Shwachman-Diamond syndrome (SD). We report two DBA and one SD cases. One DBA mother received transfusions intra-partum, and the other only post-partum. Both required caesarean sections (C-sections) for failure of labour to progress and severe pre-eclampsia respectively. Both subsequently resumed pre-pregnancy steroid-induced control of anaemia. approximately 40% of DBA pregnancies required maternal transfusions; 25% delivered by C-section. The SD patient also had Ehlers-Danlos (ED) syndrome and urticaria pigmentosa (UP). Her blood counts were adequate until week 38, when the platelet count dropped and a C-section was performed. Pregnancy management in marrow failure disorders requires obstetricians with expertise in high-risk pregnancies, and haematologists with experience with marrow failure syndromes.

Adult↗
PubMed1986

The diamond knife "semi": a substitute for glass or conventional diamond knives in the ultramicrotomy of thin and semi-thin sections.

The diamond knife "semi" for ultramicrotomes was originally designed by its manufacturer (DIATOME S.A.), for cutting semi-thin sections from 0.2 micron to 2.0 micron. Cutting tests of Epon-embedded material (nervous system, myelin sheat) with this knife have shown that the quality of semi-thin sections is equivalent or better than that obtained with a glass knife, and much time could be saved during the microtomy of serial sections. The quality of thin sections (0.07 micron to 0.12 micron) is excellent and comparable to that obtained with a conventional diamond knife. Furthermore, when adjacent sections are cut thin and semi-thin (for immunochemistry or high voltage microscopy), both are excellent in that they are of uniform thickness. In conclusion, this tool has advantages for both light microscopy and transmission electron microscopy.

Animals↗
PubMed1997

Molecular epidemiology of insulin-dependent diabetes mellitus: WHO DiaMond Project. WHO DiaMond Molecular Epidemiology Sub-Project Group.

The WHO DiaMond Molecular IDDM Epidemiology Sub-Project is testing the hypothesis that population variation in the frequency of high-risk HLA-DQ alleles is a primary determinant of the global patterns of IDDM incidence. Data are currently available for 16 populations, and reveal significant variations in the frequencies of HLA-DQA1 and DQB1 alleles among the case and the control groups. However, DQA1 x Arg-(52) and DQB1 x non-Asp-57 (ND) were consistent and independent markers of IDDM susceptibility in all populations, except Japan. Individuals who carried only DQA1 x R and DQB1 x ND alleles had an IDDM risk similar to that observed for first degree relatives of affected individuals (3%-5%). Such information is essential for the development of clinical strategies or disease prevention approaches for the general population or individuals at high-risk. Thus, the DiaMond Molecular Epidemiology Sub-Project provides an excellent model that can be followed to assess the impact of new genetic discoveries on medicine and public health practice for diabetes and other chronic diseases.

Adolescent↗
PubMed2001

Hematopoietic stem cell transplantation for Diamond Blackfan anemia: a report from the Diamond Blackfan Anemia Registry.

The Diamond Blackfan Anemia (DBA) Registry of North America is a detailed database of patients with DBA from the United States and Canada. To date, 354 patients have been registered. From this database an analysis of the outcome of hematopoietic stem cell transplantation for DBA was undertaken. Of the 20 transplanted patients who met criteria for the diagnosis of DBA, eight underwent an allogeneic HLA-matched sibling hematopoietic stem cell transplant (SCT) and 12 an alternative donor SCT. The median age at transplant for all patients was 6 years 2 months; 3 years 10 months vs 9 years 1 month for HLA-matched sibling and alternative donor SCT, respectively. All of the HLA-matched sibling transplants were done using a non-irradiation-containing regimen, whereas the majority of alternative donor transplants were performed using total body irradiation. The survival for HLA-matched sibling vsalternative donor transplant was 87.5% +/- 11.7% vs 14.1% +/- 12.1% at greater than 5 years from SCT (P = 0.015). The use of HLA-matched sibling SCT should be considered for all patients with suitable donors. However, alternative donor SCT in DBA must be approached cautiously, the potential for severe aplastic anemia (SAA) or hematopoietic malignancy not withstanding.

Adolescent↗
PubMed2004

Low-frequency Raman and Brillouin spectroscopy from graphite, diamond and diamond-like carbons, fullerenes and nanotubes.

Inelastic light scattering by acoustic phonons (Brillouin scattering) is a useful tool for probing material properties at the submicrometre scale. In media which are statistically homogeneous at this scale, it gives access to the acoustic properties and the elastic moduli. In nanostructures it probes the vibrational properties at the mesoscopic scale. Applications to carbonaceous materials are reviewed.

Acoustics↗