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PubMed2006

Evaluation of CVD diamond coating layer using leaky Rayleigh wave.

In the present study, the possibility of using leaky Rayleigh waves as a nondestructive tool for the evaluation of CVD diamond coating layer is explored experimentally. For this purpose, a set of CVD diamond coated specimens are prepared and the leaky Rayleigh waves are measured in an immersion, pulse-echo setup. For the proper analysis of the acquired signals we propose a novel signal analysis approach, namely the "time trace angular scan (TTAS)" image. Then, the proposed approach together with the backward radiation profiles are applied for the analysis of signals acquired in the initial experiments. The TTAS image shows the entire information on both time-of-arrival and angle of incidence of the signals for the proper "time-angle windowing." Then, the backward radiation profile of the windowed signals provides adequate parameters from which nondestructive evaluation of the coated specimens is carried out.

Journal Article↗
PubMed1999

Disinfection of dental diamond burs contaminated with hepatitis B virus.

STATEMENT OF PROBLEM: Hepatitis B infection (HBV) is a significant hazard in the dental environment because the virus may be transmitted through contaminated dental instruments. PURPOSE: This study determined whether cold disinfectants can inactivate HBV DNA and HBV surface antigens on diamond burs contaminated with HBV and whether ultrasonication can increase the antiviral properties of these agents. MATERIAL AND METHODS: Sterile dental diamond burs were contaminated with serum from a patient who tested positive for HBV surface antigen and hepatitis B viral DNA. The burs were air dried and placed in solutions containing either Cidex, Asepsys, TBS, Rotagerm, Virkon disinfectants, or a control phosphate buffered saline. Burs were divided into 2 groups and disinfected for 15 minutes. The first group was ultrasonicated; the second group was not ultrasonicated during disinfection. All the burs were transferred to phosphate buffered saline and ultrasonicated to remove any remaining viral particles. The ultrasonicate was tested for the presence of HBV surface antigen with a microparticle enzyme immunoassay and for hepatitis B viral DNA with a chemiluminescent molecular hybridization assay. RESULTS: TBS did not require ultrasonication to inactivate viral DNA and surface antigen. Rotagerm and Virkon inactivated surface antigen and viral DNA only with ultrasonication. Cidex and Asepsys inactivated viral DNA but not surface antigen with ultrasonication. CONCLUSION: The chlorine containing compound TBS was the most active disinfectant tested and did not require ultrasonication to destroy HBV. The remaining disinfectants should be used with ultrasonication to inactivate HBV.

Analysis of Variance↗
PubMed2000

In vitro analyses of diamond-like carbon coated stents. Reduction of metal ion release, platelet activation, and thrombogenicity.

Coronary artery stents can induce platelet activation by shear forces, contact to the biomaterial, and release of metal ions. This activation is one important trigger for thrombosis. Coating of stents is a possible approach to prevent this side effect. The purpose of this study was to evaluate in vitro the biocompatibility of stents coated with diamond-like carbon (DLC). Semiquantitative energy-dispersive X-ray microanalyses showed a complete coverage of the DLC stents. Flow cytometric analyses revealed a significantly higher increase of mean channel fluorescence intensity for the activation-dependent antigens CD62p and CD63 in non-coated compared to DLC-coated stents (p<0.05). Atomic adsorption spectrophotometry analyses revealed a significant release of nickel and chromium metal ions by non-coated stents over a storage period of 96 hours in human plasma (p<0.05). In contrast, only minimal concentrations of released ions could be detected in the case of DLC-coated stents. Similar observations were made with inductively coupled plasma mass spectrometry analyses. Here, high concentrations of molybdenum and manganese ions were released from non-coated stents (p<0.05), while release of these ions from DLC-coated stents was virtually undetectable (p=0.1 for molybdenum and p=0.4 for manganese). Coating of intracoronary stents with diamond-like carbon significantly improves biocompatibility. This biocompatible coating may therefore contribute to a reduction in thrombogenicity.

Alloys↗
PubMed1999

Discordant detection of monosomy 7 by GTG-banding and FISH in a patient with Shwachman-Diamond syndrome without evidence of myelodysplastic syndrome or acute myelogenous leukemia.

The myelodysplastic syndromes (MDS) are a group of hematologic disorders commonly affecting elderly persons and often leading to acute myelogenous leukemia (AML). Although rare in children, when MDS does occur, it is frequently part of a congenital disorder such as Shwachman-Diamond syndrome (SDS). Monosomy 7 and/or deletion of part or all of 7q are poor prognostic signs in MDS and AML, although the pathophysiologic relationship between this finding and MDS or AML is unclear. Shwachman-Diamond syndrome is an inherited illness characterized by exocrine pancreatic insufficiency and by congenital neutropenia. Patients with SDS are at increased risk of developing myelodysplastic syndrome (MDS) and acute myelogenous leukemia (AML). Because monosomy 7 is a poor prognostic sign in MDS and AML, establishing its presence is important. However, different methods of detection of monosomy 7 may lead to different results in some patients. We present the case of a 10-year-old girl known to have SDS, who had a bone marrow aspiration and biopsy done to rule out MDS and AML. By light microscopy, the patient's bone marrow was unremarkable. GTG-banding showed the following karyotype: 45,XX,-C[3]/47,XX,+C[1]/46,XX[45]. Fluorescence in situ hybridization (FISH) was performed with a chromosome 7-specific alpha-satellite probe (D7Z1). Almost all (373 of 376) cells exhibited only one chromosome 7 signal. A second marrow aspiration done 6 months later showed an essentially normal karyotype by GTG-banding. Fluorescence in situ hybridization with the same chromosome 7 probe showed 230 of 250 cells to be monosomic for chromosome 7. A whole chromosome 7 painting probe demonstrated disomy for chromosome 7 in 90 of 90 cells; however, subtle heteromorphism in the centromeric regions of the 2 copies of chromosome 7 was noted in some cells. This case demonstrates that FISH and GTG-banding can give discordant results, that the two should be viewed as complementary technologies, and that both have a place in a full karyotypic analysis. Furthermore, this case demonstrates for the first time that heteromorphism and/or subtle structural abnormalities of chromosome 7, previously associated with MDS and AML, can exist without clinical or morphologic signs of these illnesses. It will be of interest to further study the relationship, if any, between SDS and various structural abnormalities of chromosome 7 in MDS and AML, and to elucidate the molecular mechanisms of pathogenesis, physiology, and treatment of these disorders.

Bone Marrow↗
PubMed1999

Diamond detector measurements near simulated air channels for narrow photon beams.

BACKGROUND AND PURPOSE: To evaluate the combined effect of increased photon transmission, reduced photon scatter, increased secondary electron range and loss of electronic equilibrium for narrow 6-MV beams in and around a simulated air channel. MATERIALS AND METHODS: A measuring method was developed in-house for relative dose measurements near simulated air-like/soft-tissue interfaces in an automated water phantom. A Styrofoam cylinder (density 0.03 g/cm3) of 2-cm diameter was submersed in the water phantom and irradiated with small rectangular radiation fields. The field length was fixed at 10 cm and the field widths ranged from 1 to 4 cm. The axis of the foam cylinder and the long side of the field were parallel. A water layer of 2 cm was realised upstream of the cylinder. Relative depth dose and profiles behind the foam cavity were assessed using a diamond detector with a sensitive crystal thickness of 0.21 mm located at 1 mm from the top of the encapsulation. RESULTS: The dose at central axis 1.1 mm behind the cavity was found to be 92 and 74% for a field size of 10 x 2 and 10 x 1 cm2, respectively. The highly convex dose profile of the 10 x 1-cm2 field, characterising the homogeneous case, is flattened. CONCLUSIONS: The diamond detector is an excellent choice as a detector in small photon fields with high-dose gradients as they occur near air channels, provided the orientation of the detector is appropriate. Doses near air channels are subject to significant local variations as a function of small changes of field width, and local underdosing may occur in particular cases.

Models, Structural↗
PubMed2003

The 5-V window of polarizability of fluorinated diamond electrodes in aqueous solutions.

Heavily doped diamond films are quite actively studied for their promising applications in industrial as well as in fundamental electrochemistry (both for physicochemical studies and in the field of electroanalysis), because of their very high stability toward chemical and electrochemical oxidative attacks. Fluorinated diamond electrodes exhibit an exceptionally lower electrocatalytic activity toward reactions involving adsorbed intermediates, as a result of the F-termination of the surface dangling bonds. This feature allows the investigation of the widest range of potentials for an electrode material in aqueous solution, being limited only by the formation of free hydrogen [E degrees (H*/H2) = -2.3 V(SHE)] and hydroxyl [E degrees (*OH,H+/H2O) = 2.74 V(SHE)] radicals, at the two boundaries of the approximately 5-V polarization window.

Letter↗
PubMed2005

Chlorinated phenol analysis using off-line solid-phase extraction and capillary electrophoresis coupled with amperometric detection and a boron-doped diamond microelectrode.

The analysis of chlorinated phenols (2-chlorophenol, 3-chlorophenol, 4-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, pentachlorophenol) in river water was accomplished using off-line solid-phase extraction (SPE) and capillary electrophoresis coupled with electrochemical detection. A key to the sensitive, reproducible, and stable detection of these pollutants was the use of a boron-doped diamond microelectrode in the amperometric detection mode. An off-line SPE procedure was utilized to extract and preconcentrate the pollutants prior to separation and detection, with ENVI-Chrom P, a highly cross-linked styrene-divinylbenzene copolymer, being employed as the sorbent. Pollutant recoveries in the 95-100% range with relative standard deviations of 1-4% were achieved. The diamond microelectrode provided a low and stable background current with low peak-to-peak noise. The oxidative detection of the pollutants was accomplished at +1.05 V vs Ag/AgCl without the need for electrode pretreatment. The method was evaluated in terms of the linear dynamic range, sensitivity, limit of quantitation, response precision, and response stability. A reproducible electrode response was observed during multiple injections of the chlorinated phenol solutions with a relative standard deviation of < or =5.4%. Good electrode response stability was observed over many days of continuous use with no significant electrode deactivation or fouling. The separation efficiencies for all six pollutants were greater than 170,000 plates/m. The minimum concentration detectable for all six ranged from 0.02 to 0.2 ppb (S/N > or = 3) using a 250:1 preconcentration factor.

Boron↗
PubMed2004

Reactivity of a (mu-oxo)(mu-hydroxo)diiron(III) diamond core with water, urea, substituted ureas, and acetamide.

A series of iron(III) complexes of the tetradentate ligand BPMEN (N,N'-dimethyl-N,N'-bis(2-pyridylmethyl)ethane-1,2-diamine) were prepared and structurally characterized. Complex [Fe(2)(mu-O)(mu-OH)(BPMEN)(2)](ClO(4))(3) (1) contains a (mu-oxo)(mu-hydroxo)diiron(III) diamond core. Complex [Fe(BPMEN)(urea)(OEt)](ClO(4))(2) (2) is a rare example of a mononuclear non-heme iron(III) alkoxide complex. Complexes [Fe(2)(mu-O)(mu-OC(NH(2))NH)(BPMEN)(2)](ClO(4))(3) (3) and [Fe(2)(mu-O)(mu-OC(NHMe)NH)(BPMEN)(2)](ClO(4))(3) (4) feature N,O-bridging deprotonated urea ligands. The kinetics and equilibrium of the reactions of 1 with ligands L (L = water, urea, 1-methylurea, 1,1-dimethylurea, 1,3-dimethylurea, 1,1,3,3-tetramethylurea, and acetamide) in acetonitrile solutions were studied by stopped-flow UV-vis spectrophotometry, NMR, and mass spectrometry. All these ligands react with 1 in a rapid equilibrium, opening the four-membered Fe(III)(mu-O)(mu-OH)Fe(III) core and forming intermediates with a (HO)Fe(III)(mu-O)Fe(III)(L) core. The entropy and enthalpy for urea binding through oxygen are DeltaH degrees = -25 kJ mol(-1) and DeltaS degrees = -53.4 J mol(-1) K(-1) with an equilibrium constant of K(1) = 37 L mol(-1) at 25 degrees C. Addition of methyl groups on one of the urea nitrogen did not affect this reaction, but the addition of methyl groups on both nitrogens considerably decreased the value of K(1). An opening of the hydroxo bridge in the diamond core complex [Fe(2)(mu-O)(mu-OH)(BPMEN)(2)] is a rapid associative process, with activation enthalpy of about 60 kJ mol(-1) and activation entropies ranging from -25 to -43 J mol(-1) K(-1). For the incoming ligands with the -CONH(2) functionality (urea, 1-methylurea, 1,1-dimethylurea, and acetamide), a second, slow step occurs, leading to the formation of stable N,O-coordinated amidate diiron(III) species such as 3 and 4. The rate of this ring-closure reaction is controlled by the steric bulk of the incoming ligand and by the acidity of the amide group.

Acetamides↗
PubMed2001

Molecular dynamics simulation of a lipid diamond cubic phase.

This paper presents the first atomistic simulation of a cubic membrane phase. Using the molecular dynamics simulation technique both the global and the local organization of glycerolmonoolein molecules inside the diamond cubic phase are studied. Multinanosecond simulations reveal that the center of the cubic bilayer remains close to the infinite periodic minimal surface that describes the diamond geometry. We further show that the equilibrium structure of the surfactant molecules inside the cubic phase is very similar to their structure inside a simulated lamellar bilayer. The small differences arise from the packing constraints of the surfactants within the cubic phase which has an area per surfactant that increases toward the bilayer center.

Computer Simulation↗
PubMed2002

Direct electrochemistry of cytochrome C at nanocrystalline boron-doped diamond.

Direct electron transfer of horse heart cytochrome c is measured at a nanocrystalline boron-doped diamond thin-film electrode. A quasi-reversible, diffusion-controlled cyclic voltammetric response is observed for untreated diamond. The peak currents change linearly with the concentration, and importantly, there is no electrode fouling. The results, observed for a hydrogen-terminated and uncharged surface, (i.e., no ionizable carbon-oxygen functional groups), raise interesting questions about the necessary surface interactions of cytochrome c for relatively rapid electrode kinetics.

Boron↗
PubMed2003

The oxidation of diamond: the geometry and stretching frequency of carbonyl on the (100) surface.

Microwave plasma deposited (100) diamond films have been thermally oxidized in dry O2 between 500 and 723 degrees C. The roughness of a single crystalline grain following oxidation is consistent with a layer-by-layer mechanism for the removal of carbon monoxide. The resulting surface exhibits infrared absorption bands at 1731 and 905 cm-1, attributed to the stretching and bending modes of a surface bonded carbonyl group. The former is within 1 cm-1 of the structurally analogous molecule 2-adamantanone. These data are consistent with the carbonyl groups being present on diamond (100) terraces.

Journal Article↗
PubMed2006

Detailed structure of diamond-type lipid cubic nanoparticles.

Supramolecular three-dimensional self-assembly of nonlamellar lipids with fragments of the protein immunoglobulin results in a bicontinuous cubic phase fragmented into nanoparticles with open water channels (cubosomes). The structure of the diamond-type cubic nanoparticles is characterized experimentally by freeze-fracture electron microscopy, and it is mathematically modeled with nodal surfaces emphasizing the fluid-like undulations of the cubosomic interfaces. Based on scaling-up and scaling-down approaches, we present stable and intermediate-kind nanoparticles resulting from the cubosomic growth. Our results reveal the smallest stable diamond-type cubosomic entity that can serve as a building block of more complex nanostructured fluid drug delivery vehicles of therapeutic proteins. The evidence presented for lipid-bilayer undulations in the surface region of the protein/lipid cubosomes could have important consequences for possible applications of these hierarchically organized porous nanoparticles.

Lipids↗
PubMed2006

Dynamics and kinetics of heat transfer at the interface of model diamond [111] nanosurfaces.

A molecular dynamics simulation was performed to study the effect of an applied force on heat transfer at the interface of model diamond [111] nanosurfaces. The force was applied to a small, hot nanosurface at 800, 1000, or 1200 K brought into contact with a larger, colder nanosurface at 300 K. The relaxation of the initial nonequilibrium interfacial force occurs on a subpicosecond time scale, much shorter than that required for heat transfer. Heat transfer occurs with exponential kinetics and a rate constant that increases linearly with the interfacial force according to 7 x 10(-4) ps(-1)/nN. This rate constant only increases by at most 10% as the temperature of the hot surface is increased from 800 to 1200 K. Replacing the interfacial H-atoms on both surfaces by D atoms also has a very small effect on the heat transfer. However, if one nanosurface has H atoms on its interface and the other nanosurface's interface has D atoms, then there is a marked 25% decrease in the rate constant for heat transfer. Increasing the size of the hot surface, and, thus, the interfacial contact area, increases the rate of heat transfer but not the rate constant. For the same interfacial force, different anharmonic models for the nanosurfaces' potential energy function give the same heat transfer rate constant. The possibility of quantum effects for heat transfer across the diamond interface is considered.

Journal Article↗
PubMed1998

Wear of ultra-high molecular weight polyethylene against damaged and undamaged stainless steel and diamond-like carbon-coated counterfaces.

The wear of ultra-high molecular weight polyethylene (UHMWPE) in artificial joints and the resulting wear debris-induced osteolysis remains a major clinical concern in the orthopaedic sector. Third-body damage of metallic femoral heads is often cited as a cause of accelerated polyethylene wear, and the use of ceramic femoral heads in the hip is gaining increasing favour. In the knee prostheses and for smaller diameter femoral heads, the application of hard surface coatings, such as diamond-like carbon, is receiving considerable attention. However, to date, there has been little or no investigation of the tribology of these coatings in simulated biological environments. In this study, diamond-like carbon (DLC) has been compared to stainless steel in its undamaged form and following simulated third-body damage. The wear of UHMWPE was found to be similar when sliding against undamaged DLC and stainless steel counterfaces. DLC was found to be much more damage resistant than DLC. Under test conditions that simulate third-body damage to the femoral head, the wear of UHMWPE was seven times lower against DLC than against stainless steel (P < 0.05). The study shows DLC has considerable potential as a femoral bearing surface in artificial joints.

Journal Article↗
PubMed2000

Schwachman-Diamond syndrome. A case report.

Schwachman-Diamond syndrome is an autosomal recessive disorder consisting of exocrine pancreatic insufficiency and neutropenia. The typical pathological finding with this syndrome is fatty infiltration in the pancreas of patients. We report a case of Scwachman-Diamond syndrome examined with abdominal ultrasonography, CT and radiography.

Abdomen↗
PubMed2000

Autoerythrocyte sensitization (Gardner-Diamond) syndrome.

We describe the clinical presentation and course of a patient with autoerythrocyte sensitization (Gardner-Diamond) syndrome, and review the literature for similar cases. A 37-yr-old female presented with recurrent episodes of painful ecchymotic bruising over the anterior aspect of both thighs. These episodes were precipitated by emotional stress. The diagnosis was confirmed by induction of similar lesions by intradermal injection of the patient's own washed red blood cells and hemoglobin. The lesions did not recur for 6 months after the cause of her emotional stress was relieved. Autoerythrocyte sensitization (Gardner-Diamond) syndrome should be considered in the differential diagnosis of purpura, especially in patients with psychiatric problems.

Adult↗
PubMed1997

Successful hematopoietic reconstitution by transplantation of umbilical cord blood cells in a transfusion-dependent child with Diamond-Blackfan anemia.

A 4-year-old boy with Diamond-Blackfan anemia and a history of multiple transfusions underwent umbilical cord blood transplantation from his HLA-identical female sibling born by vaginal delivery at 38 weeks. The patient was prepared with busulfan, cyclophosphamide and antilymphocyte globulin. Methotrexate and cyclosporin A were given for the prophylaxis of GVHD. Regimen-related toxicity was not observed and successful engraftment occurred, including the erythroid series. No evidence of acute or chronic GVHD has been observed for 14 months after transplantation. This is the first case of successful umbilical cord blood transplantation to a patient with Diamond-Blackfan anemia.

Blood Transfusion↗
PubMed2001

Successful unrelated bone marrow transplantation for Shwachman-Diamond syndrome.

A 5-year-old boy with Shwachman-Diamond syndrome underwent unrelated HLA-identical bone marrow transplantation for severe pancytopenia. Conditioning was with busulfan, thiotepa and cyclophosphamide plus rabbit anti-lymphocyte serum. Engraftment for neutrophils and platelets was observed on days +18 and +41, respectively. Transplant-related side-effects were mild and transient. After a follow-up of 32 months, the patient is alive and enjoys a normal life, off any immunosuppressives. Immunological and hematological reconstitution is complete while other phenotypic characteristics (pancreatic insufficiency, short stature, femur dysostosis) are stable. Although experience in this field is scarce, we speculate that bone marrow failure in Shwachman-Diamond syndrome (even if not linked to the appearance of clonal disorders or leukemic transformation) is an indication for bone marrow transplantation and may be associated with a better outcome.

Bone Marrow Diseases↗