Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Diamond”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2Linked to original sources
PubMed2006

A multinational assessment of complications in type 1 diabetes: the DiaMond substudy of complications (DiaComp) level 1.

The objectives of this study were to describe the global geographic variation of microvascular and macrovascular complications in childhood onset type 1 diabetes (T1D) and to relate any such variation to diabetes care activities such as self blood glucose monitoring and intensive insulin therapy. The DiaComp study is a multinational (17 countries) cross-sectional study of complications in T1D (n=2,657). All participants were diagnosed at < 15 years of age and had a diabetes duration of 5-24 years when surveyed. Complications were assessed by self-report of physician diagnosis. Twenty-two centres in 17 countries achieved at least a 67% response rate and are included in the analyses. Central European centres exhibited high rates of retinopathy (Lithuania=31.6%, Romania=24.2%), laser treatment (Lithuania=25.4%) and neuropathy (Lithuania=29.9%, Romania=12.4%) in those with short duration of diabetes (5-15 years), as did Cuba for neuropathy (15.4%). For retinopathy the geographic variation in the short-duration group was also pronounced, ranging from 1.6% in Italy to 41.6% in Lithuania, and from 0% in Brazil, Italy and Australia, to 29.9% in Lithuania for laser treatment. Variation was less dramatic for the prevalence of complications in the long-duration group (15-25 years). Hypertension and duration were strong consistent predictors of all complications, while women had higher prevalence for half the complications (retinopathy, laser treatment and renal disease). Intensive insulin therapy and self-monitoring of blood glucose showed little association with prevalence of complications. In conclusion, this first population-based account of the geographic variation of T1D complications has demonstrated substantial variation. However, the healthcare practice variables that were measured contributed little toward explaining this variation.

Adolescent↗
PubMed2000

Cutting efficiency of three diamond bur grit sizes.

BACKGROUND: Tooth preparation requires safe, efficient and rapid cutting, and diamond burs routinely are used for extracoronal preparation and gross tooth reduction. Coarser-grit diamond burs often are used for gross tooth reduction, with tooth surface finishes being sacrificed for the presumed greater cutting rates, or CRs, of the coarser diamond burs. The authors compared the CRs of medium-, coarse- and super-coarse-grit diamond burs. METHODS: The authors used a self-contained dental treatment system with digitally controlled handpiece speed, torque and water flow rate to cut a machinable glass ceramic cutting substrate with medium-, coarse- and super-coarse-grit diamond burs from the same manufacturer under a load of 147.5 grams (0.9 kilonewton at the bur tip) and a coolant flow rate of 22 milliliters per minute. They made three cuts through 13-millimeter bars of the cutting substrate with six diamond burs of each grit size. They determined CRs as the transection time per millimeter and analyzed CR data by one-way analysis of variance and post hoc Scheffé tests. RESULTS: The authors found no statistically significant difference in CR (P > .05) between the three diamond bur grit sizes for the first (13 mm) cuts. When they compared the three cuts (39 mm total cut length), they found no difference (P > .05) between CRs for coarse- and super-coarse-grit diamond burs, but they did find that the super-coarse-grit diamond burs cut faster than the medium-grit diamond burs (P < .01). CONCLUSION: Differences in CR for the three diamond bur grit sizes are due to the greater decrease in CR for the medium-grit diamond burs (50 percent) compared with the CRs of the coarse- and super-coarse-grit diamond burs (35 percent and 25 percent, respectively) over the total cutting period. CLINICAL IMPLICATIONS: Coarser-grit diamond burs may be useful for extensive gross tooth preparations, but dental professionals should be aware of the associated effects of the coarser grit on surface finish, heat generation and enamel damage.

Analysis of Variance↗
PubMed2005

[Studies on nano-diamond prepared by explosive detonation by Raman and infrared spectroscopy].

Nano-diamond was synthesized by TNT/RDX explosives detonation in a steel chamber and characterized by X-ray diffraction (XRD), laser Raman spectroscopy, and infrared spectroscopy. XRD results indicate that nano-diamond has cubic diamond structure. The parameter of unit cell of nano-diamond is 0.359 23 nm and is 0.72% larger than that of the bulk diamond. The high-density defects and other impurity atoms in the nano-diamond structure may lead to the large lattice constant. The examination results of Raman spectra show that the Raman band is broader and shifts to l ow frequency by 3 cm(-1), because the size of nano-diamond reaches nanometer order. There is little graphite in the nano-diamond. There are two peaks in FTIR of the nano-diamond, which are characteristic peaks of diamond at 1 262 and 1 134 cm(-1). Besides these two peaks, there are six peaks at 3 422, 1 643, 2 971, 2 930, 2 857 and 1 788 cm(-1) respectively. The FTIR bands at 2 930 and 2 857 cm(-1) are the antisymmetrical and symmetrical stretch vibration absorption spectra of CH2 respectively. The 3 422 cm(-1) is the stretch vibration absorption peak of O-H. The 1 634 cm(-1) confirms that there are H2O in the nano-diamond. The 2 971 cm(-1) is the antisymmetrical stretch vibration absorption peak of CH3. The 1 788 cm(-1) is the stretch vibration absorption peak of C=O. These indicate that there are H and O elements in the nano-diamond. From the mechanism of the nano-diamond, the authors discuss the reason for the vibration absorption peaks of O-H, CH2, CH3, and C=O, existing in the FTIR of the nano-diamond.

Algorithms↗
PubMed2003

Properties of diamond under hydrostatic pressures up to 140 GPa.

Diamond is the archetypal covalent material. Each atom in an sp(3) configuration is bonded to four nearest neighbours. Because of its remarkable properties, diamond has been extensively studied. And yet our knowledge of the properties of diamond under very high pressure is still incomplete. Although diamond is known to be the preferred allotrope of carbon at high pressure, the possibility of producing under pressure high-density polymorphs of diamond, including metallic forms, has been discussed. Structural changes have already been reported in diamond under non-hydrostatic pressures around 150 GPa and large deformation. However, measurements of the properties of diamond under hydrostatic pressure have been limited to below 40 GPa. Here, we report accurate measurements of the volume and of the optical phonon frequency of diamond under hydrostatic pressure up to 140 GPa. We show that diamond is more compressible than currently expected. By combining the volume and the frequency pressure shifts, we deduce that diamond remains very stable under pressure: it is a Gruneisen solid up to at least 140 GPa, and the covalent bond is even slightly strengthened under pressure. Finally, the optical phonon frequency versus pressure is calibrated here to be used as a pressure gauge for diamond anvil cell studies in the multi-megabar range.

Crystallography, X-Ray↗
PubMed2003

[Manufacture of diamond blades via microsystem technology].

PURPOSE: The application of diamond knives has steadily increased in ophthalmic surgery. However, the geometry of the blade, its thickness and the sharpness of the cutting edge are limited by the abrasive diamond polishing process, e. g. the crystalline morphology of the bulk material and the grinding powder used. A new generation of diamond blades is presented herewith allowing free choice of blade shape and thickness and possessing excellent sharpness due to a new polishing process. METHODS: The new production method is based on a high-quality CVD (chemical vapour deposition) diamond film of some tenths of microns thickness, deposited on a silicon wafer as microchip technology. The mechanical properties of this synthetic diamond film are almost equal to those of a natural diamond and the surface of this film is mirror-like after deposition without requiring post-polishing. The shape of the blade can be freely defined and is transferred into the diamond film by a plasma polishing process adopted from microsystem technology. RESULTS: The new production method results in highly reproducible diamond blades. Concave blades and round shapes can now be realised without the restrictions of the conventional production process. The force-free fabrication method even allows realisation of miniaturized blades (e. g. width < 0.125 mm, thickness < 50 microm) far beyond the possibilities of conventional diamond blade production. Plasma polishing by means of gas atoms results in extreme sharpness with the cutting edge radius in the range of approx. 3 nm. CONCLUSIONS: Utilising microsystem technology we were able to manufacture reproducible artificial diamond blades. The new process offers for the first time surgeons a possibility of designing blades with a geometry close to their personal needs. Furthermore, the potential of facet-free ergonomically shaped diamond blades may stimulate further improvements towards novel surgical techniques.

Cataract Extraction↗
PubMed2004

Thermodynamics of diamond nucleation on the nanoscale.

To have a clear insight into the diamond nucleation upon the hydrothermal synthesis and the reduction of carbide (HSRC), we performed the thermodynamic approach on the nanoscale to elucidate the diamond nucleation taking place in HSRC supercritical-fluid systems taking into account the capillary effect of the nanosized curvature of the diamond critical nuclei, based on the carbon thermodynamic equilibrium phase diagram. These theoretical analyses showed that the nanosize-induced interior pressure of diamond nuclei could drive the metastable phase region of the diamond nucleation in HSRC into the new stable phase region of diamond in the carbon phase diagram. Accordingly, the diamond nucleation is preferable to the graphite phase formation in the competing growth between diamond and graphite upon HSRC. Meanwhile, we predicted that 400 MPa should be the threshold pressure for the diamond synthesis by HSRC in the metastable phase region of diamond, based on the proposed thermodynamic nucleation on the nanoscale.

Journal Article↗
PubMed2004

Surface transfer doping of diamond.

The electronic properties of many materials can be controlled by introducing appropriate impurities into the bulk crystal lattice in a process known as doping. In this way, diamond (a well-known insulator) can be transformed into a semiconductor, and recent progress in thin-film diamond synthesis has sparked interest in the potential applications of semiconducting diamond. However, the high dopant activation energies (in excess of 0.36 eV) and the limitation of donor incorporation to (111) growth facets only have hampered the development of diamond-based devices. Here we report a doping mechanism for diamond, using a method that does not require the introduction of foreign atoms into the diamond lattice. Instead, C60 molecules are evaporated onto the hydrogen-terminated diamond surface, where they induce a subsurface hole accumulation and a significant rise in two-dimensional conductivity. Our observations bear a resemblance to the so-called surface conductivity of diamond seen when hydrogenated diamond surfaces are exposed to air, and support an electrochemical model in which the reduction of hydrated protons in an aqueous surface layer gives rise to a hole accumulation layer. We expect that transfer doping by C60 will open a broad vista of possible semiconductor applications for diamond.

Journal Article↗