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At least 289 records · Page 16Linked to original sources
PubMed2002

Laser blepharoplasty: diamond laser scalpel compared to the free beam CO2 laser.

BACKGROUND: Blepharoplasty has long been employed for functional and cosmetic purposes. Different modalities have been utilized to incise and remove excess eyelid tissue in an attempt to improve surgical technique. OBJECTIVE: This study compares a free beam CO2 laser to a diamond surgical scalpel combined with a CO2 laser for performance of blepharoplasty. METHODS: Ten patients underwent bilateral upper lid blepharoplasty. One side was randomly assigned to the free beam CO2 laser technique, while the other side was performed with the diamond laser scalpel. Intraoperative surgical times and hemostasis were measured. Masked observers assessed postoperative parameters at day 1, week 1, week 2, week 4, and month 4. These assessments were analyzed clinically and statistically. RESULTS: The two modalities produced similar results for the intraoperative and postoperative parameters studied. CONCLUSION: The diamond laser scalpel has the advantage of tactile feedback and the option of use without coagulation.

Blepharoplasty↗
PubMed2001

[Excimer laser versus diamond fraise: equal short-term outcome of corneal smoothing in pterygium operations].

BACKGROUND: The treatment of pterygia often results in irregular astigmatism. Corneal smoothing at the end of surgery plays a major role in the development of astigmatism. The aim of our study was to compare the efficiency of corneal smoothing performed by phototherapeutic keratectomy compared with the conventional method performed by a diamond fraise. The effect of postoperative excimer laser smoothing on refraction, visual acuity and irregular astigmatism was investigated. PATIENTS AND METHODS: 32 eyes underwent pterygium excision using a standardized surgical procedure. In addition 9 eyes underwent postoperative phototherapeutic keratectomy of the wound region with an excimer laser, 23 eyes were treated with a diamond fraise for corneal smoothing. The postoperative examination was performed 7, 14 and 30 days after surgery. Corneal topography was performed by a computer-assisted videokeratoscope (TMS-1). The results were evaluated by the Fourier transform analysis. RESULTS: Both methods showed similar results concerning refraction and visual acuity postoperatively. Preoperatively all patients had an irregular flattening of the corneal topography in the area of the pterygium. Postoperatively a small irregular flattening was left in eyes treated with a diamond fraise. In the excimer laser treated group a steepening in the corneal topography could be observed. CONCLUSIONS: The phototherapeutic keratectomy with excimer laser in the treatment of pterygia suggests to be a gentle alternative creating a smooth wound surface. Despite of this advantage the treatment with the excimer laser effects a remarkable increase in administration and expense.

Adult↗
PubMed2004

Phase stability of nanocarbon in one dimension: nanotubes versus diamond nanowires.

Since their discovery in 1990, the study of sp2 bonded carbon nanotubes has grown into a field of research in it's own right; however the development of the sp3 analog, diamond nanowires, has been slow. A number of theoretical models have been proposed to compare the relative stability of diamond and graphite at the nanoscale; and more recently, to compare nanodiamonds and fullerenes. Presented here is a study of the phase stability of nanocarbon in one-dimension. The structural energies of carbon nanotubes and diamond nanowires have been calculated using density functional theory within the generalized gradient approximation, and used to determine the atomic heat of formation as a function of size.

Journal Article↗
PubMed1980

Evluation of diamond radiation dosemeters.

The effect of beam energy, dose rate and temperature on seven commercial diamond electrical conductivity detectors was studied. The diamond dimensions were approximately 1 mm X 1 mm X 3 mm. Clinical photon nd electron beams were used for irradiation. The photon energy response normalised to 60Co was observed to have a maximum of 1.37 +/- 0.06 at 122 keV and the dose rate response was slightly non-linear, in agreement with the theory for insulators. Temperature effects were small and different for each detector. Two of the seven detectors gave repeatable results (+/- 5%) over five years, two others were much less satisfactory and three were rejected after preliminary tests. It is concluded that natural diamond can be used for the manufacture of reliable, small and near soft-tissue-equivalent dosemeters but that until the crystal selection and final product testing have been adequately standardised, the user needs to select the reliable dosemeters from a batch.

Carbon↗
PubMed1981

Dosimetry with a diamond operating as a resistor.

A very pure diamond with contacts of graphite has a linear current-voltage characteristic when subjected to irradiation. The resistivity is inversely proportional to the dose rate and the sensitivity is extremely high for gamma- and X-rays and electron beams. It is concluded that diamond resistors are suitable for clinical radiation dosimetry. This conclusion is also based on earlier work in which diamonds were used as pinpoint counters.

Carbon↗
PubMed2005

The Diamond STING server.

Diamond STING is a new version of the STING suite of programs for a comprehensive analysis of a relationship between protein sequence, structure, function and stability. We have added a number of new functionalities by both providing more structure parameters to the STING Database and by improving/expanding the interface for enhanced data handling. The integration among the STING components has also been improved. A new key feature is the ability of the STING server to handle local files containing protein structures (either modeled or not yet deposited to the Protein Data Bank) so that they can be used by the principal STING components: (Java)Protein Dossier ((J)PD) and STING Report. The current capabilities of the new STING version and a couple of biologically relevant applications are described here. We have provided an example where Diamond STING identifies the active site amino acids and folding essential amino acids (both previously determined by experiments) by filtering out all but those residues by selecting the numerical values/ranges for a set of corresponding parameters. This is the fundamental step toward a more interesting endeavor-the prediction of such residues. Diamond STING is freely accessible at http://sms.cbi.cnptia.embrapa.br and http://trantor.bioc.columbia.edu/SMS.

Acid Anhydride Hydrolases↗
PubMed2000

Direct local epitaxy of diamond on Si(100) and surface-roughening-induced crystal misorientation

A direct diamond epitaxy on the silicon substrate is demonstrated not only at the interface formed during the growth process but also at the nucleation sites. The small (001) terraces with dimensions of several atomic distances at the site of nucleation are formed due to the roughening of silicon surface and lead to the grain misorientation. A model is presented which attempts to explain the initial stages of diamond growth. Predictions are made for methods of improving the nucleation of epitaxial diamond crystallites.

Journal Article↗
PubMed2001

Scanning tunneling microscopy studies of temperature-dependent etching of diamond (100) by atomic hydrogen.

We present a technique for obtaining atomic resolution ultrahigh vacuum scanning tunneling microscopy images of diamond (100) films, and use this technique to study the temperature dependence of the etching of epitaxial diamond (100) films by atomic hydrogen. We find that etching by atomic hydrogen is highly temperature dependent, resulting in a rough and pitted surface at T approximately 200 and 500 degrees C, respectively. At T approximately 1000 degrees C etching results in a smooth surface and is highly anisotropic, occurring predominantly in the direction of dimer rows. This observation supports recent theoretical models that propose anisotropic etching as the mechanism for the growth of smooth diamond (100) films.

Journal Article↗
PubMed2006

Quantization of 2D hole gas in conductive hydrogenated diamond surfaces observed by electron field emission.

Discrete jumps are observed in the emitted current density (J) versus extraction electric field (E) curves in electron field emission measurements from a conductive, hydrogen-terminated air-exposed diamond surface. These jumps are well reproduced by computations based on the assumption that a 2D nanoscale quantum system with discrete energy levels exists in the diamond near-surface layer. The present results confirm the formation of well-defined quantum states of holes in the 2D surface layer present on hydrogenated air-exposed diamond surfaces.

Journal Article↗
PubMed1998

Synthetic diamond-based position-sensitive photoconductive detector development for the Advanced Photon Source.

A novel X-ray beam-position detection device that we call a position-sensitive photoconductive detector (PSPCD) is designed to have synthetic diamond as its substrate material. We proved that it is feasible to use synthetic diamond to make a hard X-ray position-sensitive detector based on the photoconductivity principle and that it acts as a solid-state ion chamber. Experiments on different PSPCD samples using synthetic diamond with a high-heat-flux white undulator beam, as well as with monochromatic hard X-ray beams, have been performed at the Advanced Photon Source. Recent test results with the PSPCD in the quadrant configuration as an X-ray beam-position monitor and in a multipixel array as an X-ray beam profiler are presented in this paper.

Journal Article↗
PubMed1989

The effectiveness of root debridement in open flap procedures by means of a comparison between hand instruments and diamond burs. A SEM study.

The goal of the present in vivo study was to evaluate human roots by means of scanning electron microscopy (SEM), after treating the root surfaces either with conventional hand instruments or with newly developed diamond burs. Peculiar root anatomy often makes perfect instrumentation with hand instruments difficult or impossible. On 20 teeth destined for extraction because of severe periodontitis, the root surfaces were exposed by mucoperiosteal flap procedures. Ten roots were then planed using fine curettes, and 10 were instrumented using diamond burs. Following extraction, the root surfaces were stained and photographed. Stained areas were examined by SEM. On the 20 test teeth, 79 surfaces were evaluated. From these, 381 stained zones were checked by SEM for the presence of bacteria. A total of 216 stained areas from teeth treated by hand instruments was evaluated; 15 of these (6.9%) contained bacteria. Of roots treated by diamond burs, 165 stained areas were evaluated; 9 (5.5%) exhibited bacteria. Thus, both methods resulted in root surfaces that were essentially bacteria-free.

Adult↗
PubMed1995

Dosimetric characterization of radiosurgical beams with a diamond detector.

Dosimetric characteristics of small diameter 6 MV photon beams for a commercial radiosurgery system have been measured in a solid water phantom with a new diamond detector and compared with measurements using a p-type Si photon diode, small volume cylindrical and parallel plate ionization chambers, and radiographic films. Tissue maximum ratios (TMR) and total scatter factors (S c.p) were measured with the three ionometric (diamond, diode, ion chamber) detectors for 12 circular beams ranging in diameter from 12.5 to 40 mm. The TMR values obtained with the three ionometric detectors agreed well (+/- 1%) for all cone sizes and depths investigated when the displacement of the sensitive volume of the detector from its front surface is taken into account. The S c.p factors obtained with the ionometric detectors also agreed well (+/- 1.2%) for field sizes greater than 20 mm in diameter. For smaller field sizes, the cylindrical and parallel plate chambers measure a smaller S c.p factor, as a result of the steep dose gradients across their sensitive volumes. Cross-beam profiles acquired with the diamond detector agree well with the measurements with the diode detector and radiographic film. A distortion in the measured profiles in terms of broadened penumbra is observed with a small volume cylindrical ionization chamber.

Biophysical Phenomena↗
PubMed2004

Three-dimensional hydrogen microscopy in diamond.

A microprobe of protons with an energy of 17 million electron volts is used to quantitatively image three-dimensional hydrogen distributions at a lateral resolution better than 1 micrometer with high sensitivity. Hydrogen images of a <110>-textured undoped polycrystalline diamond film show that most of the hydrogen is located at grain boundaries. The average amount of hydrogen atoms along the grain boundaries is (8.1 +/- 1.5) x 10(14) per square centimeter, corresponding to about a third of a monolayer. The hydrogen content within the grain is below the experimental sensitivity of 1.4 x 10(16) atoms per cubic centimeter (0.08 atomic parts per million). The data prove a low hydrogen content within chemical vapor deposition-grown diamond and the importance of hydrogen at grain boundaries, for example, with respect to electronic properties of polycrystalline diamond.

Journal Article↗
PubMed1998

Low-field electron emission from undoped nanostructured diamond

Strong and sustained electron emission at low electric fields was observed in undoped, nanostructured diamond. Electron emission of 10 milliamperes per square centimeter was observed at applied fields of 3 to 5 volts per micrometer. These are the lowest fields ever reported for any field-emitting material at technologically useful current densities. The emitter consists of a layer of nanometer-size diamond particulates, which is heat-treated in a hydrogen plasma. These emission characteristics are attributed to the particles' high defect density and the low electron affinity of the diamond surface. Such emitters are technologically useful, because they can be easily and economically fabricated on large substrates.

Journal Article↗
PubMed2000

Remobilization in the cratonic lithosphere recorded in polycrystalline diamond

Polycrystalline diamonds (framesites) from the Venetia kimberlite in South Africa contain silicate minerals whose isotopic and trace element characteristics document remobilization of older carbon and silicate components to form the framesites shortly before kimberlite eruption. Chemical variations within the garnets correlate with carbon isotopes in the diamonds, indicating contemporaneous formation. Trace element, radiogenic, and stable isotope variations can be explained by the interaction of eclogites with a carbonatitic melt, derived by remobilization of material that had been stored for a considerable time in the lithosphere. These results indicate more recent formation of diamonds from older materials within the cratonic lithosphere.

Journal Article↗
PubMed1997

Comparison of the InPouch TV culture system and Diamond's modified medium for detection of Trichomonas vaginalis.

This study compared the use of Diamond's modified medium to InPouch for the culture of Trichomonas vaginalis from pooled vaginal secretions. The sensitivity for InPouch was 82.4% (61/74) versus 87.8% (65/74) for Diamond's modified medium. There were no significant differences in the sensitivity and negative predictive value of InPouch compared to Diamond's modified medium.

Adult↗
PubMed1999

Effects of temperature on the survival of Tritrichomonas foetus in transport, Diamond's and InPouch TF media.

The abilities of two isolates of Tritrichomonas foetus to survive and replicate in transport and Diamond's medium or in the InPouch TF system (Bio-Med Diagnostics) when exposed to different temperatures for different periods were determined in a series of experiments. Tubes containing thioglycollate transport medium or pouches were inoculated with 4000 to 5000 organisms and kept for up to seven days at 37 degrees C, 22 degrees C, 4 degrees C, or -20 degrees C. When the holding time had elapsed, the numbers of motile T foetus were counted. Samples in transport medium were transferred to Diamond's medium, and both the pouches and tubes containing Diamond's medium were incubated at 37 degrees C. The cultures were examined and counted four or five times during the 10 to 14 day culture period. The sensitivity of the test under the different conditions, expressed as the number of positive cultures/the total number of samples x 100, varied from zero to 100 per cent depending upon the combination of variables considered. In each medium, with both isolates of T foetus, all samples kept for up to four days at 22 degrees C or 37 degrees C were positive. All cultures of samples kept more than five days at 4 degrees C were negative. No positive cultures were detected when samples were kept more than three hours at -20 degrees C. The day on which the cultures reached mean peak concentration varied with the temperature at which the samples had been kept before they were cultured.

Animals↗