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At least 523 records · Page 29Linked to original sources
PubMed2001

Wear simulation of total hip prostheses with polyethylene against CoCr, alumina and diamond-like carbon.

The wear of ultra-high molecular weight polyethylene acetabular cups was studied with a new biaxial hip wear simulator using diluted calf serum as a lubricant. The cups had been packed and gamma-irradiated in argon. The cups were articulated against two established types of femoral head, alumina and CoCr, and one experimental type, CoCr coated with diamond-like carbon (DLC). The diameter of the heads was 28 mm. Polyethylene against alumina and against CoCr were studied because their clinical wear behaviour is relatively well known. The new simulator was validated with these established materials. The wear mechanisms, including the size and shape of the wear particles, agreed well with those seen in clinical studies. The average wear rates of the cups against alumina and CoCr heads were 48 and 56 mg per 1 million cycles, respectively. The order is in agreement with clinical observations. The average wear rate against DLC was 58 mg per 1 million cycles. As a counterface for polyethylene, DLC did not markedly differ from alumina and CoCr.

Aluminum Oxide↗
PubMedDate not supplied

Morphological behaviour of osteoblasts on diamond-like carbon coating and amorphous C-N film in organ culture.

Similar to diamond-like carbon (DLC) coating, amorphous carbon nitride (C-N) films can be extremely hard and wear-resistant. They may serve as candidates for the solution to the problem of aseptic loosening of total hip replacements. Morphological behaviour of osteoblasts on silicon, DLC-coated silicon and amorphous C-N film-deposited silicon in organ culture was investigated by scanning electron microscopy. Cells on the silicon wafers were able to attach, but were unable to follow this attachment with spreading. In contrast, the cells attached, spread and proliferated on the DLC coatings and amorphous C-N films without apparent impairment of cell physiology. The morphological development of cells on the coatings and films was similar to that of cells in the control. The preliminary results support the biocompatibility of DLC coating and are encouraging for the potential biomedical applications of amorphous C-N film.

Animals↗
PubMed1996

A comparison of wire brush and diamond fraise superficial dermabrasion for photoaged skin. A clinical, immunohistologic, and biochemical study.

BACKGROUND: Superficial dermabrasion has a proven beneficial effect on photoaged skin, but little is known about the differences between the two major modalities used in dermabrasion, the diamond fraise (DF) and the wire brush (WB). OBJECTIVE: We compared the clinical, immunohistologic, and biochemical changes after superficial dermabrasion with DF and WB. METHODS: Eight photoaged patients (mean age, 68 years; range, 49 to 80 years) underwent facial dermabrasion to the level of the papillary dermis. Clinical assessments were performed at baseline and at 3 and 12 weeks after dermabrasion. Biopsy specimens were taken from both dermabraded halves at the same time points and assessed by routine histologic and immunohistologic examinations, western blot analysis, and radioimmunoassay. Scoring of intracellular and extracellular transforming growth factor-beta 1 was based on a semiquantitative ordinal scale (0 = no staining to 4 = maximum staining) in half-unit increments. The score for each specimen represents the average of values obtained from four high-power fields. RESULTS: Both methods of dermabrasion resulted in significant resolution of actinic keratoses, lentigines, and wrinkling. No statistical significance was noted between the two methods in regard to clinical efficacy. Significantly fewer milia occurred after DF than after WB. Solar elastosis decreased with both the WB and DF. Immunohistologic examination demonstrated a highly significant increase in papillary dermal fibroblast staining for amino terminal procollagen I (type I pN-collagen) at 3 weeks for both DF and WB compared to baseline. Staining at 12 weeks had decreased from the peak noted at week 3, but was still significantly increased from baseline. Western blotting of type I pN-collagen demonstrated a 5.4-fold (p = 0.01) increase from baseline at 3 weeks and a 4.9-fold (p = 0.002) increase at 12 weeks after dermabrasion with the WB. Similarly, the DF produced a 4.9-fold (p = 0.006) increase at 3 weeks and a 5.1-fold (p = 0.008) increase at 12 weeks after dermabrasion. Western blotting of amino terminal procollagen III (type III pN-collagen) showed a 6.1-fold (p = 0.07) increase from baseline at 3 weeks and a 3.9-fold (p = 0.04) increase at 12 weeks after dermabrasion with the DF. The WB showed a 3.8-fold (p = 0.07) increase from baseline at 3 weeks and a 5.1-fold (p = 0.05) increase at 12 weeks. Transforming growth factor-beta 1 demonstrated a significant increase in extracellular staining with DF (3.3 +/- 0.2) and WB (3.7 +/- 0.2) from baseline (1.2 +/- 0.2, p < 0.001) at 3 weeks. CONCLUSION: Superficial dermabrasion with DF and WP appears to be similarly efficacious in the treatment of photoaged skin. Significant increases in type I pN-collagen, type III pN-collagen, and TGF-beta 1 occurred in the papillary dermis after both types of dermabrasion. These results suggest that increased fibroblast activity and consequent collagen I and III synthesis underlie the clinical improvement.

Aged↗
PubMed1999

Root-end cavity preparation after apicoectomy using a new type of sonic and diamond-surfaced retrotip: a 1-year follow-up study.

PURPOSE: This study evaluated the outcome of periradicular surgery using a new set of retrotips for root-end cavity preparation. PATIENTS AND METHODS: Forty-three patients who had 50 consecutively treated teeth with periradicular pathology were enrolled in this prospective study. After apicoectomy, root-end cavity preparation was performed, using diamond-surfaced retrotips driven by a sonic handpiece; EBA-cement was used as the root-end filling material. Healing assessment was based on clinical and radiographic criteria. RESULTS: At the 1-year follow-up, 82% of the reexamined surgical cases presented with successful healing. Fourteen percent of the treated teeth were deemed as improved (partial healing), and 4% were classified as failures. CONCLUSION: The new retrotips were found to be ideal for root-end cavity preparation. They simplify the surgical approach to root ends where the working space is limited by restricted access. Root-ends prepared with this new sonoabrasive technique yielded excellent results at the 1-year follow-up examination.

Adolescent↗
PubMed2003

Indoor light on thermoluminescence of CVD diamond film used as a high-energy photon dosimeter.

The effect of light on polycrystalline diamond film that was produced by chemical vapor deposition and is used as a thermoluminescent dosimeter should be considered, although some researchers have indicated that such an effect was theoretically unlikely to happen. A 15 min exposure to a normal desk light bulb induces significant thermoluminescence (TL) comparable to a 0.5 Gy exposure to high-energy photons. This light-induced TL will be saturated within 2 h. The saturated TL intensity depends on the frequency of the light and the blue light dominates. The TL peak area at a temperature of 605 K is insensitive to light but is sensitive to high-energy photons. Another peak at about 410 K is caused by light only, because the TL from the ionization radiation at the same location is bleached. The effect of light could be easily distinguished by a numerical or an experimental method. Lamps with a green lampshade or pure red lights are suggested for use as indoor light sources. To reduce the effect of light, pre-heating treatment before readout is also suggested.

Diamond↗
PubMedDate not supplied

Diamond blackfan anemia stem cells fail to repopulate erythropoiesis in NOD/SCID mice.

Diamond Blackfan Anemia (DBA) is a congenital disorder characterized by decreased red blood cell production and developmental abnormalities. We herein show that DBA progenitors produced lower numbers of phenotypically normal erythroid colonies in vitro, whereas nonerythroid colonies were normally abundant and developed. To determine whether DBA stem cells are capable of producing early erythroid, monocyto-granulocytic, and lymphoid progenitors in vivo we used a mouse xenotransplantation model. We demonstrate that DBA stem cells poorly repopulated erythroid progeny in NOD/SCID mice, whereas the monocyto-granulocytic and lymphoid progenies were repopulated normally. Therefore, we conclude that disordered DBA erythropoiesis may be a result of defective erythroid-lineage commitment and maintenance of early erythroid progenitors.

Anemia, Diamond-Blackfan↗
PubMed2001

Aromatic hydrocarbons, diamonds, and fullerenes in interstellar space: puzzles to be solved by laboratory and theoretical astrochemistry.

New research is presented, and previous research is reviewed, on the emission and absorption of interstellar aromatic hydrocarbons. Emission from aromatic hydrocarbons dominates the mid-infrared emission of many galaxies, including our own Milky Way galaxy. Only recently have aromatic hydrocarbons been observed in absorption in the interstellar medium, along lines of sight with high column densities of interstellar gas and dust. Much work on interstellar aromatics has been carried out, with astronomical observations and laboratory and theoretical astrochemistry. In many cases, the predictions of laboratory and theoretical work are confirmed by astronomical observations but, in other cases, clear discrepancies exist that provide problems to be solved by a combination of astronomical observations, laboratory studies, and theoretical studies. The emphasis of this paper will be on current outstanding puzzles concerning aromatic hydrocarbons that require further laboratory and theoretical astrochemistry to resolve. This paper will also touch on related topics where laboratory and theoretical astrochemistry studies are needed to explain astrophysical observations, such as a possible absorption feature due to interstellar 'diamonds' and the search for fullerenes in space.

Absorption↗
PubMed2002

Long term tissue response to titanium coated with diamond like carbon.

Diamond like carbon (DLC) coatings were deposited on to Ti substrates by plasma enhanced chemical vapor deposition technique. Ti and DLC/Ti samples were implanted in skeletal muscle of rabbits. The samples were explanted after 1, 3, 6 and 12 months and the tissue-cell interaction was studied. Our data indicate both DLC/Ti and bare Ti to be compatible with skeletal muscle.

Animals↗
PubMed2003

Proliferation deficiency of multipotent hematopoietic progenitors in ribosomal protein S19 (RPS19)-deficient diamond-Blackfan anemia improves following RPS19 gene transfer.

Diamond-Blackfan anemia (DBA) is a congenital bone marrow failure syndrome characterized by a specific deficiency in erythroid progenitors. Since some patients with DBA develop a reduction in thrombocytes and granulocytes with age, we asked whether multipotent hematopoietic progenitors from DBA patients had normal proliferative capacity in liquid expansion cultures. CD34(+) cells derived from DBA patients showed deficient proliferation in liquid culture containing IL-3, IL-6, and SCF. Single CD34(+) CD38(-) cells from DBA patients exhibited deficient proliferation recruitment in a limiting dilution assay containing IL-3, IL-6, SCF, Tpo, FL, and G-CSF or containing IL-3, IL-6, and SCF. Our findings suggest that the underlying hematopoietic defect in DBA may not be limited to the erythroid lineage. Since a fraction of DBA patients have a deficiency in ribosomal protein S19 (RPS19), we constructed lentiviral vectors containing the RPS19 gene for overexpression in hematopoietic progenitors from RPS19-deficient DBA patients. Enforced expression of the RPS19 transgene improved the proliferation of CD34(+) cells from DBA patients with RPS19 mutation. Similarly, enforced expression of RPS19 improved erythroid development of RPS19-deficient hematopoietic progenitors as determined by colony assays and erythroid differentiation cultures. These findings suggest that gene therapy for RPS19-deficient DBA is feasible.

Anemia, Diamond-Blackfan↗
PubMed2001

Voltammetric determination of L-cysteine at conductive diamond electrodes.

Boron-doped diamond (BDD) electrodes were used to examine L-cysteine (CySH) oxidation in alkaline media. The results of the voltammetric and polarization measurements showed that at BDD electrodes the overall CySH oxidation reaction is controlled by the initial electrochemical step, i.e., the oxidation of the CyS- electroactive species. The same conclusion was supported by the results of a study of pH effects. Conversely, at glassy carbon (GC) electrodes, the same reaction is controlled by the desorption of the reaction products. These results account for the poor response for CySH determination at GC compared to BDD. It was found that BDD exhibits excellent behavior for CySH determination, clearly outperforming GC. The results demonstrate that measurement of the peak current for CySH oxidation can be used as a basis for simple method for determining CySH in the micromolar concentration range by the use of BDD electrodes.

Cysteine↗
PubMed2002

Single-particle mass spectrometry of polystyrene microspheres and diamond nanocrystals.

High-resolution mass spectra of single submicrometer-sized particles are obtained using an electrospray ionization source in combination with an audio frequency quadrupole ion-trap mass spectrometer. Distinct from conventional methods, light scattering from a continuous Ar-ion laser is detected for particles ejected out of the ion trap. Typically, 10 particles are being trapped and interrogated in each measurement. With the audio frequency ion trap operated in a mass-selective instability mode, analysis of the particles reveals that they all differ in mass-to-charge ratio (m/z), and the individual peak in the observed mass spectrum is essentially derived from one single particle. A histogram of the spectra acquired in 10(2) repetitions of the experiment is equivalent to the single spectrum that would be observed when an ion ensemble of 10(3) particles is analyzed simultaneously using the single-particle mass spectrometer (SPMS). To calibrate such single-particle mass spectra, secular frequencies of the oscillatory motions of the individual particle within the trap are measured, and the trap parameter qz at the point of ejection is determined. A mass resolution exceeding 10(4) can readily be achieved in the absence of ion ensemble effect. We demonstrate in this work that the SPMS not only allows investigations of monodisperse polystyrene microspheres, but also is capable of detecting diamond nanoparticles with a nominal diameter of 100 nm, as well.

Diamond↗
PubMed2006

Solid-phase extraction and elution on diamond (SPEED): a fast and general platform for proteome analysis with mass spectrometry.

This paper presents a new solid-phase extraction and elution platform based on surface-functionalized diamond nanocrystallites. Compared with conventional methods, the platform facilitates purification and concentration of intact proteins and their enzymatic digests for ensuing sodium dodecyl sulfate-polyacrylamide gel electrophoresis or matrix-assisted laser desorption/ionization mass spectrometry analysis without prior removal of the adsorbent. One-pot work flow involving reduction of disulfide bonds, protection of free cysteine residues, washing off residual chemicals, and proteolytic digestion of adsorbed proteins can be performed directly on the particles. The utility and versatility of this protein workup platform were demonstrated with liquid chromatography-electrospray ionization tandem mass spectrometry in proteome analysis of human urine. The proteome analysis of each urine sample can be completed in 8 h.

Amino Acid Sequence↗
PubMed2006

Selective detection method derived from a controlled diffusion process at metal-modified diamond electrodes.

A novel, selective methodology is derived based on the difference between the diffusion processes at microelectrodes (i.e., hemispherical diffusion) and the macroelectrode (i.e., linear diffusion) in a metal-implanted boron-doped diamond electrode (metal-BDDs). As an example, the selective detection of glucose in a solution containing interference species such as ascorbic acid and uric acid is demonstrated. The electrochemical properties of BDD, which are low background current, extremely high stability, and (especially) inactivity toward glucose, play an important role in realizing these differences in the diffusion characteristics. The present methodology can be applied not only to selective glucose detection by the metal-BDD system but also to other selective detection systems.

Ascorbic Acid↗
PubMed2007

Reusable platinum nanoparticle modified boron doped diamond microelectrodes for oxidative determination of arsenite.

Boron doped diamond (BDD) macro- and microelectrodes were modified by electrodeposition of platinum nanoparticles using a multipotential step electrodeposition technique and used for the oxidative determination of arsenite, As(III). The formation of Pt nanoparticles was evident from cyclic voltammetry measurement, whereas AFM and SEM revealed the size and size distribution of deposited Pt nanoparticles. Raman spectroscopy illustrated a correlation between the typical BDD signature and the number of platinum deposition cycles. Linear sweep voltammetry performed with the modified BDD microelectrode outperformed its macrocounterpart and resulted in very low detecting currents with enhanced signal-to-noise ratios. With linearity up to 100 ppb and a detection limit of 0.5 ppb, the electrochemical system was applicable for processing tap and river water samples. Over 150 repetitive runs could be performed, and electrochemical etching of platinum allowed the reuse of the BDD microelectrode. The presence of copper and chloride ions, the two most severe interferents at levels commonly found in groundwater, did not interfere with the assay.

Arsenites↗
PubMed2004

Electrochemical inactivation of triclosan with boron doped diamond film electrodes.

This research investigated an electrochemical method for inactivating contaminated stockpiles of the biocidal agent, triclosan. The goal of the electrolysis was to produce products that were amenable to treatment in conventional activated sludge treatment systems. Triclosan oxidation in electrochemical cells with boron doped diamond (BDD) film anodes was investigated in aqueous solutions at a pH value of 12. Chronoamperometry experiments showed that direct oxidation of triclosan occurred at potentials below those for H2O, Cl-, or OH- oxidation. Measurable rates of triclosan oxidation began at potentials above 0.4 V with respect to the standard hydrogen electrode (SHE), while potentials of 0.5, 1.3, and 1.8 V were required to obtain measurable oxidation rates of H2O, Cl-, and OH-, respectively. At anode potentials below 2 V, the dominant electrode reaction involved direct triclosan oxidation, while indirect oxidation was the dominant pathway at higher potentials. However, cyclic voltammetry experiments showed that direct oxidation of triclosan resulted in the formation of a passivating film on the electrode that could only be removed by oxidation at potentials above 3 V. Direct triclosan oxidation showed a very weak potential dependence, suggesting that its oxidation was limited by chemical dependent factors rather than by an outer-sphere electron transfer reaction. Organic triclosan oxidation products consisted primarily of chlorinated acetic acids and chlorinated phenolic compounds. Although the byproducts of triclosan oxidation became increasingly less reactive with increasing electrolysis time, triclosan could be completely oxidized to CO2 at current densities above 2 mA/cm2. Microtox testing indicated that residual triclosan accounted for nearly all the toxicity in the treated water, despite the fact that chlorinated byproduct concentrations were significantly higher than those of triclosan itself.

Anti-Infective Agents, Local↗
PubMed2005

Electrochemical oxidation of hydroquinone, resorcinol, and catechol on boron-doped diamond anodes.

The electrochemical oxidation of aqueous wastes polluted with hydroquinone, resorcinol, or catechol on boron-doped diamond electrodes has been studied. The complete mineralization of the organic waste has been obtained independently of the nature of each isomer. No aromatic intermediates were found during the treatment, and solely aliphatic intermediates (carboxylic acids C4 and C2, mainly) were detected in the three cases. Although as from the bulk electrolyses study no differences in the electrochemical oxidation of dihydroxybenzenes seem to exist, different voltammetric behavior between resorcinol and the other two isomers was obtained in the voltammetric study. Catechol and hydroquinone have a reversible quinonic form, and a cathodic reduction peak appears in their voltammograms. The characterization of the first steps in the electrochemical oxidation of the three dihydroxybenzenes showed the formation of a larger number of intermediates in the oxidation of catechol, although no carbon dioxide was detected in its oxidation. Conversely, the oxidation of resorcinol and hydroquinone lead to the formation of important concentrations of carbon dioxide. The nondetection of aromatic intermediates, even if small quantities of charge are passed, confirms that the oxidation must be carried out directly on the electrode surface or by hydroxyl radicals generated by decomposition of water.

Boron↗
PubMed2005

Adsorption of acrylonitrile on diamond and silicon (001)-(2 x 1) surfaces: effects of dimer structure on reaction pathways and product distributions.

Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) are used to compare the reaction of acrylonitrile with Si(001) and C(001) (diamond) surfaces. Our results show that reaction with Si(001) and C(001) yield very different product distributions that result from fundamental differences in the ionic character of these surfaces. While acrylonitrile reacts with the C(001) surface via a [2 + 2] cycloaddition reaction in a manner similar to nonpolar molecules such as alkenes and disilenes, reaction with the Si(001) surface occurs largely through the nitrile group. This work represents the first experimental example of how differences in dimer structure lead to very different chemistry for C(001) compared to that for Si(001). The fact that Si(001) reacts with the strongly polar nitrile group of acrylonitrile indicates that the zwitterionic character of this surface controls its reactivity. C(001) dimers, on the other hand, behave more like a true molecular double bond, albeit a highly strained one. Consequently, while alternative strategies will be necessary for chemical modification of Si(001), traditional schemes from organic chemistry for functionalization of alkenes and disilenes may be available for building molecular layers on C(001).

Acrylonitrile↗
PubMed2005

Diamond cubic phase of monoolein and water as an amphiphilic matrix for electrophoresis of oligonucleotides.

We used a cubic liquid crystal formed by the nonionic monoglyceride monoolein and water as a porous matrix for the electrophoresis of oligonucleotides. The diamond cubic phase is thermodynamically stable when in contact with a water-rich phase, which we exploit to run the electrophoresis in the useful submarine mode. Oligonucleotides are separated according to size and secondary structure by migration through the space-filling aqueous nanometer pores of the regular liquid crystal, but the comparatively slow migration means the cubic phase will not be a replacement for the conventional DNA gels. However, our demonstration that the cubic phase can be used in submarine electrophoresis opens up the possibility for a new matrix for electrophoresis of amphiphilic molecules. From this perspective, the results on the oligonucleotides show that water-soluble particles of nanometer size, typical for the hydrophilic parts of membrane-bound proteins, may be a useful separation motif. A charged contamination in the commercial sample of monoolein, most likely oleic acid that arises from its hydrolysis, restricts useful buffer conditions to a pH below 5.6.

Diamond↗