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PubMed2000

An in vitro investigation of diamond-like carbon as a femoral head coating.

Wear of polyethylene acetabular components of hip implants is a significant clinical problem. In prosthetic hip surgery, polyethylene wear is identified as a factor that limits the life of the implant; it is known that the production of debris can cause adverse tissue reactions that may lead to extensive bone loss around the implant, and consequently loosening of the fixation. A new class of so-called Diamond-Like Carbon coatings, applied to titanium femoral heads was compared to ceramic and metallic heads in terms of wear behavior against UHMWPE using a hip joint simulator with a bovine calf serum lubricant. A thin film of Diamond-Like Carbon was deposited directly onto titanium (Ti6Al4V) head using chemical vapor deposition. The wear of polyethylene coupled with Diamond-Like Carbon coated femoral heads was comparable to that obtained with the polyethylene coupled with commercial alumina femoral heads.

Alloys↗
PubMed1987

The drawing of squares and diamonds: a perceptual-motor task analysis.

The aim of the present study was to establish the role of perceptual-motor factors in copying an equilateral four-sided figure. Children, 5 to 12 years, and adults, were asked to copy the figure presented in either "square" or "diamond" orientation under five conditions: control; large model presentation; neutral picture frame surround; partial visual information reduction; and total visual information loss. The model was present at all times. Scores were orientation and angular variability. Developmental trends were found for both figures; the diamond was less well performed than the square at all ages tested. Three perceptual-motor factors were found to be important: formulation of the movement plan; movement programming, and sensory feedback. The difficulty of the diamond is thought to be due to the high programming and hence planning demands in drawing oblique lines. Both kinaesthesis and sequential vision are important factors in drawing; and only from 12 years of age are environmental cues used efficiently to orient the figure.

Adolescent↗
PubMed1994

Diamond flap anoplasty in infants and children with an intractable anal stricture.

After posterior sagittal anorectoplasty for imperforate anus a prolonged course of anal dilatations is necessary until the scar softens. Although rare, severe stricture after this procedure is difficult to resolve. Y-V plasty is not entirely satisfactory because the pedicle advanced into the anus has some tension, which tends to retract producing recurrent stricture. The authors performed a diamond-shaped island anoplasty in eight children with postoperative and strictures (one after an unsuccessful Y-V plasty), with prompt resolution of the stricture in five. The island flap anoplasty consists of a diamond-shaped flap of skin formed laterally, with complete separation of skin and subcutaneous attachments around the periphery of the flap. The skin island is supplied with blood from the deep tissue. An incision is made through the scarred anal ring and into the mucosa, a distance of half the length of the diamond, which is then advanced into the mucosal defect. The defect lateral to the advanced flap is sutured closed. The island of skin descends naturally into the anus, under no tension. The procedure can be performed simultaneously in the 3 o'clock and 9 o'clock positions, and can later be repeated anteriorly and posteriorly, although this has not been necessary. Two of the eight children have required no dilatation postoperatively, a distinct advantage in the 4-year-old patient. One segment in one child sloughed, resulting in repeat stricture that is responding to dilatation. The other seven children are doing well with their colostomies closed.

Anus, Imperforate↗
PubMed1991

Biocompatibility of diamond-like carbon coating.

Diamond-like carbon coating is an inert, impervious hydrocarbon coating with properties suitable for use in the biomedical field, particularly in orthopaedic implants. Mouse peritoneal macrophages and mouse fibroblasts were grown on tissue culture plates treated with diamond-like carbon and the biocompatibility assessed both biochemically and morphologically. This investigation showed that diamond-like carbon coating caused no adverse effects on cells in culture and therefore merits further investigation as a coating for biomedical use.

Animals↗
PubMed2006

Improving dispersion of nanometer-size diamond particles by acoustic cavitation.

A novel acoustic-dispersion method for fine diamond particles was developed. Two samples of nanometer-sized diamond particles were used. They had primary particle sizes of 5 nm (ND5) and 150 nm (ND150). Disaggregation of agglomerated particles using ultrasound and surface modification of ND5 and ND150 were investigated. The ND5 and ND150 particles aggregated to secondary particles, having sizes on the order of micrometers. The surfaces of ND5 and ND150 particle were modified due to chemical reactions and the particles were disaggregated by acoustic cavitation. The ND5 particles were disaggregated to give an average particle size of about 100 nm by ultrasound exposure with average acoustic intensities higher than 800 W/m(2). The agglomerated ND150 particles with size of 15 microm were disaggregated to reach an average particle size of about 300 nm by ultrasound exposure with an average acoustic intensity higher than 2000 W/m(2). The surfaces of ND5 and ND150 particles were found to be modified with hydroxyl groups resulting from acoustic cavitation. This could lead to a well dispersed solution of nanometer-sized diamond particles in water.

Journal Article↗
PubMed1995

High-dose intravenous methylprednisolone therapy for patients with Diamond-Blackfan anemia refractory to conventional doses of prednisone.

OBJECTIVES: To assess the efficacy and toxicity of very high doses of glucocorticoids in patients with congenital pure red cell aplasia (Diamond-Blackfan anemia) who did not respond to standard doses of prednisone. STUDY DESIGNS: We prospectively treated eight patients with transfusion-dependent Diamond-Blackfan anemia with high intravenous doses of methylprednisolone. All patients had previously not responded to one or more oral courses of prednisone in standard doses and were dependent on erythrocyte transfusions. Every patient initially received methylprednisolone at a dose of 30 mg/kg per day, followed by slow tapering for 4 weeks, but none responded. All patients then received a second treatment course starting at 100 mg of methylprednisolone per kilogram per day, again followed by slow tapering of the dosage. RESULTS: Three patients had a complete response that has been sustained for 21+, 31+, and 41+ months, respectively. One patient had a partial response. Toxic effects included a rise in serum alanine aminotransferase activity in all patients, transient diabetes mellitus in one child, and three episodes of bacteremia in two patients with intravenous access devices. CONCLUSIONS: We conclude that very high doses of methylprednisolone may induce sustained remission in some patients with transfusion-dependent Diamond-Blackfan anemia refractory to standard-dose prednisone therapy.

Adolescent↗
PubMed2002

Phototherapeutic keratectomy versus diamond burr polishing of Bowman's membrane in the treatment of recurrent corneal erosions associated with anterior basement membrane dystrophy.

PURPOSE: To compare the efficacy of phototherapeutic keratectomy (PTK) to epithelial debridement and polishing of Bowman's membrane using a diamond burr (DB) in the treatment of recurrent corneal erosions associated with anterior basement membrane (ABM) dystrophy. DESIGN: Retrospective nonrandomized comparative trial. METHODS: Medical records of 39 patients (42 eyes) who underwent a PTK or DB procedure for recurrent corneal erosions associated with ABM dystrophy between March 1992 and June 2000 were reviewed. History of injury, prior treatment received, and the corneal slit-lamp findings were noted in all patients. In both procedures, all loose epithelium was completely removed. In PTK patients, 5 microm of Bowman's membrane was ablated with the excimer laser. In patients who underwent DB treatment, a hand-held battery-driven diamond dusted burr was used to gently and uniformly polish Bowman's membrane in the area of the epithelial defect. MAIN OUTCOME MEASURES: Symptomatic improvement, recurrence of painful erosions, development of haze, and change in the visual acuity. Statistical analysis was performed for comparison of data between the two groups. RESULTS: Fifteen eyes of 14 patients underwent PTK, and 27 eyes of 25 patients underwent epithelial debridement and DB treatment. In the PTK group, mild haze was seen in five (35.7%) eyes. Recurrence of painful erosions was seen in four eyes (26.7%). The mean follow-up was 17.6 +/- 5.7 months (range, 0.7-81.9 months). Best-corrected visual acuity was better in five eyes (35.7%) after the procedure and the same in nine eyes (64.3%). In the DB group, mild haze was seen in seven eyes (25.9%). Recurrence of painful erosions was seen in three eyes (11.1%). The mean duration of follow-up was 6.7 months (range, 1-24.2 months). Best-corrected visual acuity was better in 3 eyes (14.3%), the same in 17 eyes (81%), and worse in 1 eye (4.8%) after the procedure. Final visual acuity was not available for one eye in the PTK group and 6 eyes in the DB group. There was no statistically significant difference in haze (Fisher's exact test, P = 0.38), recurrence of erosions (Kaplan-Meier analysis with log rank, P = 0.73), and vision being better or the same (Fisher's exact test, P = 0.6) between the PTK and DB groups. CONCLUSIONS: Both PTK and DB treatment are effective methods of treating recurrent corneal erosions associated with ABM dystrophy. Diamond burr treatment, being a simpler, less expensive office procedure with a tendency toward lesser incidence of haze and recurrence in this study, seems to have advantages over PTK in the treatment of recurrent corneal erosions. Further prospective studies are required to confirm the long-term efficacy of DB treatment in the management of recurrent corneal erosions associated with ABM dystrophy.

Basement Membrane↗
PubMed2000

Investigation of atomic structures of diamond-like amorphous carbon by electron energy loss spectroscopy

Research into amorphous carbon films has been developed to such an extent that the film property can be fine tuned to mimic that of the crystalline counterparts, be it diamond, graphite, or even fullerene-like. This flexibility makes such films ideal for a wide range of applications from anti-abrasive window coating to lubricating layers on the surface of magnetic hard-disk. Not only are their mechanical properties interesting, electrically the diamond-like amorphous carbon films are also easier to dope than crystalline diamond, making them potentially a better alternative to amorphous silicon for photovoltaic devices. We will show that electron energy loss spectroscopy, in particular the carbon 1s core absorption spectroscopy, has been instrumental in revealing the nature of the bonding between carbon atoms. Such information allows microstructure models to be developed for proper understanding of the observed properties and providing scientific basis for future improvement.

Journal Article↗
PubMed2003

Gradient liquid chromatography of leucine-enkephalin peptide and its metabolites with electrochemical detection using highly boron-doped diamond electrode.

Boron-doped diamond thin film (BDD) electrodes have been used to study the oxidation reactions and to detect leucine-enkephalinamide (LEA) and its metabolites, tyrosine (T), tyrosyl-alanine (TA), tyrosyl-alanine-glycine (TAG) and leucine-enkephalin (LE) using cyclic voltammetry (CV), flow-injection analysis (FIA), and gradient liquid chromatography (LC) with amperometric detection. At diamond electrodes, well-defined and highly reproducible cyclic voltammograms were obtained with signal-to-background (S/B) ratios 5-10 times higher than those observed for glassy carbon (GC) electrodes. The analytical peaks of LC for LEA and its metabolites were well resolved. No deactivation of BDD electrodes was found after several experiments with standard as well as plasma samples, indicating high stability of the electrode. Calibration curves were linear over a wide range from 0.06 to 30 microM with regression coefficients of 0.999 for all compounds. The limits of detection obtained based on a signal-to-noise ratio of 3:1 were 3, 2.2, 2.7, 20 and 11 nM for T, TA, TAG, LE and LEA, respectively. These values were at least one order lower than those obtained at GC electrodes, which has given limits of detection of 22.88, 20.64, 89.57, 116.04 and 75.67 for T, TA, TAG, LE and LEA, respectively. Application of this method to real samples was demonstrated and validated using rabbit serum samples. This work shows the promising use of conducting diamond as an amperometric detector in gradient LC, especially for the analysis of enkephalinamide and its metabolites.

Boron↗
PubMed2000

Extended and Point Defects in Diamond Studied with the Aid of Various Forms of Microscopy.

It is shown that star disclinations can be a significant source of stress in chemical vapor deposited (CVD) diamond. This purely geometrical origin contrasts with other sources of stress that have been proposed previously. The effectiveness is demonstrated of the use of electron irradiation using a transmission electron microscope (TEM) to displace atoms from their equilibrium sites to investigate intrinsic defects and impurities in CVD diamond. After irradiation, the samples are studied by low temperature photoluminescence microscopy using UV or blue laser illumination. Results are given that are interpreted as arising from isolated <100> split self-interstitials and positively charged single vacancies. Negatively charged single vacancies can also be revealed by this technique. Nitrogen and boron impurities may also be studied similarly. In addition, a newly developed liquid gallium source scanned ion beam mass spectrometry (SIMS) instrument has been used to map out the B distribution in B doped CVD diamond specimens. The results are supported by micro-Raman spectroscopy.

Journal Article↗
PubMed2005

All-diamond microelectrode array device.

We report the development of all-diamond microelectrochemical devices, namely, a microelectrode array (MEA), in which a periodic array structure with well-defined diameters, distance, and hexagonal unit cell pattern is micromachined using a combination of state-of-the-art microwave-induced plasma growth and laser ablation shaping techniques to prepare and coat a patterned boron-doped diamond (BDD) substrate with an intrinsic diamond insulating layer. The active BDD element can be tuned to between 10 and 50 microm in diameter with a 10 times diameter center-to-center distance between two adjacent conducting elements, which are exactly coplanar to the dielectric surroundings. This type of device should enable applications in harsh conditions such as high temperature, high pressure, and resistive media under dynamic flow regimes.

Journal Article↗
PubMed2006

In vitro continuous amperometry with a diamond microelectrode coupled with video microscopy for simultaneously monitoring endogenous norepinephrine and its effect on the contractile response of a rat mesenteric artery.

Continuous amperometry with a diamond microelectrode and video microscopy were used to record (in vitro) endogenous norepinephrine release simultaneously with the evoked contractile response of a mesenteric artery from a healthy Sprague Dawley rat. Norepinephrine (NE) is a vasoconstricting neurotransmitter released from sympathetic nerves that innervate the smooth muscle cell layers surrounding arteries and veins. Using these two techniques along with several drugs, the NE released at sympathetic neuroeffector junctions nearby the microelectrode was measured as an oxidation current. Key to the amperometric measurement was the use of a diamond microelectrode because of the response sensitivity, reproducibility, and stability it provided. NE release was elicited by electrical stimulation at frequencies between 1 and 60 Hz, with a maximum response seen at 20 Hz. Confirmation that the oxidation current was, in fact, associated with endogenous NE came from the results of several drugs. Tetrodotoxin (TTX, 0.3 microM), a voltage-dependent sodium channel antagonist that blocks nerve conduction, abolished both the oxidation current and the arterial constriction. The alpha(2)-adrenergic autoreceptor antagonist, yohimbine (1.0 microM), caused an increase in the oxidation current and the corresponding constriction. The addition of cocaine (10 microM), an antagonist that inhibits neuronal NE reuptake, caused both the oxidation current and the contractile response to increase. These results, combined with the fact that the hydrodynamic voltammetric E(1/2) for endogenous NE was identical to that for a standard solution, confirmed that the oxidation current was due to NE and that this compound caused, at least in part, the contractile response. The results demonstrate that continuous amperometric monitoring of NE with a diamond microelectrode and video imaging of vascular tone allow real time local measurement of the temporal relationship between nerve-stimulated NE release and arterial constriction.

Animals↗
PubMed2003

Diamond-type lipid cubic phase with large water channels.

This paper describes a diamond cubic phase with large water channels and determines the temperature dependence of the bilayer thickness in the cubic monoolein/octylglucoside/water system based on time-resolved synchrotron X-ray diffraction data. The X-ray diffraction study established a diamond-type lipid cubic phase with large water channels (Dlarge), which has not been previously reported. It is a distinct phase, different from the diamond cubic phase with normal water channels (Dnormal). The larger channels might allow an enhanced entrapment efficiency of biomolecules in lipid cubic phases. The X-ray diffraction patterns recorded during a thermal scan showed a cubic-cubic structural transition from Dlarge to Dnormal. The obtained cubic phases displayed much larger lattice spacings as compared to those of pure monoolein at full hydration.

Glucosides↗
PubMed2005

Insulator-metal transition of intrinsic diamond.

Insulator-metal transitions are translations characterized by a sudden change in electron transport properties from localized to itinerant behavior of electrons. In most cases, it is detected in strongly disordered semiconductors as a function of temperature with statistically distributed donors and/or acceptors. Here, we show that reversible insulator-metal transitions take place in H-terminated intrinsic (undoped) single crystalline diamond, if immersed into redox-electrolyte solutions at room temperature. The change is generated by valence-band electrons of diamond, which tunnel into the redox-electrolyte, where they occupy empty electronic sites. We applied cyclic voltammetry experiments to characterize the insulator-metal transition in combination with different redox couples. The experiments show that transfer doping accounts for the experimentally detected phenomena, and that intrinsic diamond is a promising candidate for chemical sensing in a variety of applications.

Journal Article↗
PubMed2006

Raman imaging and Kelvin probe microscopy for the examination of the heterogeneity of doping in polycrystalline boron-doped diamond electrodes.

The issue of the heterogeneity of boron doping in microcrystalline diamond films was addressed by four different methods: micro-Raman spectroscopy and Raman imaging, Kelvin probe force microscopy, conducting atomic force microscopy, and scanning electrochemical microscopy. The samples were commercially available films from Windsor Scientific, with an average boron concentration of about 5 x 10(20) cm(-3). In agreement with previous works, all of the methods showed that the boron uptake was nonuniform across the surface of the electrode. Two different types of regions were evidenced, with metallic or semiconducting properties that were characterized with different types of Raman spectra. The line shape of these spectra was strongly dependent on the excitation wavelength. Local variations in electroactivity were evidenced by the SECM curves, which are related to the electronic properties of the individual grains, which, in turn, are governed by the boron content of the individual crystallites. In this study, two different micro-Raman imaging techniques were used that reveal the grain structure of the films: the images constructed from the diamond line intensity perfectly reproduced the optical image obtained by illuminating the sample in reflection. The method also allows detection of the presence of nondiamond carbon, especially in the metallic parts of the samples. Other spectral features (intensity of the boron-related broad lines, as well as the frequency and width of the diamond line) were used to construct images. In every case, the grain structure of the film was revealed, as well as twinning within individual crystallites. All approaches revealed that no enhanced doping or boron depletion occurred at the grain boundaries.

Journal Article↗
PubMed1998

Malignant myeloid transformation with isochromosome 7q in Shwachman-Diamond syndrome.

Shwachman-Diamond syndrome is an autosomal recessive disorder characterized by exocrine pancreatic dysfunction, bony metaphyseal dysostosis, various degrees of cytopenia, and a striking tendency to develop myelodysplastic syndrome and acute myeloblastic leukemia. Isochromosome 7 [i(7q)] is a rare non-random cytogenetic abnormality of myeloid cells in hematological malignancy. We report two cases of Shwachman-Diamond syndrome in which patients developed myelodysplastic syndrome and i(7q), detected by G-banding karyotype analysis and fluorescence in situ hybridization. Three other children have been previously reported to have myelodysplastic syndrome in association with i(7q); two of them had Shwachman-Diamond syndrome. Isochromosome 7q may be a fairly specific marker of myeloid malignant transformation in this syndrome and play a role in its pathogenesis.

Bone Marrow Cells↗
PubMed2000

Minimal compression of ultrathin sections with use of an oscillating diamond knife.

With the aim to minimize compression artefacts in ultrathin sections, coincident with the stroke direction, we have invented an oscillating diamond knife. Results and theoretical considerations explaining its function are discussed. During conventional ultrathin sectioning the resultant compression is in the order of 20-35% of section height. This holds true for sections of samples embedded into Lowicryl HM20 and of the polymer polystyrene, cut with a 45 degrees diamond knife and floated on water. The oscillating knife reduces this compression almost completely. It consists of a diamond knife on which a low voltage piezoelectric translator (piezo) is mounted, which oscillates when the piezo is driven by an alternating voltage source. No additional cutting artefacts were observed in the micrographs when they were compared with sections produced without oscillating the knife.

Acrylic Resins↗