Platelet defects in natural diamond. II. Determination of structure

1985 ◽  
Vol 52 (5) ◽  
pp. 623-641 ◽  
Author(s):  
P. Humble ◽  
D. F. Lynch ◽  
A. Olsen
Keyword(s):  
Natural Diamond ◽  
Platelet Defects

The value of Electron Microscope studies of imperfect natural diamonds

1990 ◽  
Vol 48 (4) ◽  
pp. 194-195
Author(s):  
J C Walmsley ◽  
A R Lang
Keyword(s):  
Electron Microscope ◽  
Classification Scheme ◽  
Natural Diamond ◽  
Sudden Change ◽  
Growth Conditions ◽  
Diamond Growth ◽  
Major Constituent ◽  
Natural Diamonds ◽  
Type Ia ◽  
Platelet Defects

Interest in the defects and impurities in natural diamond, which are found in even the most perfect stone, is driven by the fact that diamond growth occurs at a depth of over 120Km. They display characteristics associated with their origin and their journey through the mantle to the surface of the Earth. An optical classification scheme for diamond exists based largely on the presence and segregation of nitrogen. For example type Ia, which includes 98% of all natural diamonds, contain nitrogen aggregated into small non-paramagnetic clusters and usually contain sub-micrometre platelet defects on {100} planes. Numerous transmission electron microscope (TEM) studies of these platelets and associated features have been made e.g. . Some diamonds, however, contain imperfections and impurities that place them outside this main classification scheme. Two such types are described.First, coated-diamonds which possess gem quality cores enclosed by a rind that is rich in submicrometre sized mineral inclusions. The transition from core to coat is quite sharp indicating a sudden change in growth conditions, Figure 1. As part of a TEM study of the inclusions apatite has been identified as a major constituent of the impurity present in many inclusion cavities, Figure 2.

Current perspectives in antithrombotic therapy

2001 ◽  
Vol 21 (03) ◽  
pp. 82-96 ◽  
Author(s):  
D. Hoppensteadt ◽  
O. Iqbal ◽  
R. L. Bick ◽  
J. Fareed
Keyword(s):  
Blood Coagulation ◽  
Antithrombotic Therapy ◽  
Thrombotic Event ◽  
The United States ◽  
Vascular Thrombosis ◽  
Common Cause ◽  
Coagulation Protein ◽  
Coronary Events ◽  
Platelet Defects

SummaryThrombotic disorders are the most common cause of death in the United States. About two million individuals die each year from an arterial or venous thrombosis or related disorders. About 80% to 90% of all cases of thrombosis can now be defined with respect to cause. Of these, over 50% occur in patients who harbor a congenital or acquired blood coagulation protein or platelet defect which caused the thrombotic event. It is obviously of major importance to define those individuals harboring such a defect as this allows: 1) appropriate antithrombotic therapy to decrease risks of recurrence; 2) determination of the length of time the patient must remain on therapy for secondary prevention; and 3) allow for testing of family members of those harboring a blood coagulation protein or platelet defect which is hereditary (about 50% of all coagulation and platelet defects mentioned above). Aside from mortality, significant additional morbidity occurs from both arterial or venous thrombotic events, including, but not limited to paralysis (non-fatal thrombotic stroke), cardiac disability (repeated coronary events), loss of vision (retinal vascular thrombosis), fetal waste syndrome (placental vascular thrombosis), stasis ulcers and other manifestations of post-phlebitic syndrome, etc.

scholarly journals PLSR-based surface damaged layer depth determination of sawed natural diamond

2020 ◽  
Vol 6 (12) ◽  
pp. 125630
Author(s):  
Guangfeng Shi ◽  
Wang Fu ◽  
Shukun Wang ◽  
Dongdong Han ◽  
Min Chen ◽  
...  
Keyword(s):  
Natural Diamond ◽  
Layer Depth ◽  
Depth Determination

Platelet defects in natural diamond. I. Measurement of displacement

1985 ◽  
Vol 52 (5) ◽  
pp. 605-621 ◽  
Author(s):  
P. Humble ◽  
J. K. Mackenzie ◽  
A. Olsen
Keyword(s):  
Natural Diamond ◽  
Platelet Defects

scholarly journals Determination of the platelet structure in natural diamond by ADF-STEM

2016 ◽  
pp. 331-332 ◽  
Author(s):  
Svetlana Korneychuk ◽  
Stuart Turner ◽  
Artem Abakumov ◽  
Johan Verbeeck
Keyword(s):  
Natural Diamond ◽  
Platelet Structure

Indentation at the Nanometer Scale on Ultra Thin Films of Diamond-Like Carbon

1994 ◽  
Vol 356 ◽  
Author(s):  
Sandrine Bec ◽  
André Tonck ◽  
Jean-Luc Loubet
Keyword(s):  
Thin Films ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Elastic Recovery ◽  
Contact Stiffness ◽  
Natural Diamond ◽  
Tangential Displacement ◽  
Diamond Like Carbon ◽  
New Instrument

AbstractUltra thin films (50 nm and 180 nm) of amorphous diamond-like carbon on a silicon substrate produced by laser ablation are tested by nanoindentation with a new instrument deriving from a Surface Force Apparatus. Quasi-static measurements of the load and dynamic measurements of the contact stiffness are continuously and simultaneously recorded versus the penetration depth. Scanning lines on the tested surface before and after indentation are made by means of tangential displacement of the diamond indenter on the surface.The tests are conducted with maximum loads from 50 μN to 2500 μN, which correspond to maximum indentation depths between 7 nm and 70 nm. The indentation curves show near elastic recovery but scanning lines and/or topographic images on the surfaces show detectable plastic prints. Despite the extremely small residual indentation depths for these ultra thin films, we show how the hardness value we calculate from the indentation curves with an elastoplastic theory is in good agreement with the hardness value we calculate from the indentation print profile. The determination of the Young's modulus, even at the smallest indentation depths, must take into account the mechanical properties of the substrate. The determination of both values, hardness and elastic modulus, also requires a calibration procedure for the geometry of the tip and knowledge of the piling-up effect.We find that the apparent hardness and the apparent Young's modulus of the tested diamondlike films are high. They are underestimated in comparison with the real values. A rough correction which overestimates the Young’s modulus gives higher values than those of natural diamond.

scholarly journals Typical Changes of Platelet Volume During and After Extracorporeal Circulation

1977 ◽  
Author(s):  
E. Wenzel ◽  
E. Saavedra ◽  
I. Volkmar ◽  
H. Monadjemi ◽  
E. Pöhler ◽  
...  
Keyword(s):  
Extracorporeal Circulation ◽  
Heart Surgery ◽  
Open Heart Surgery ◽  
Volume Distribution ◽  
Platelet Volume ◽  
Essential Information ◽  
Particle Size Analyzer ◽  
The Mean ◽  
Platelet Defects

In 32 patients undergoing open-heart-surgery with extracorporeal circulation (ECC), platelet volume distribution curves (PVD) during and immediately and 24 and 48 hours after cardiopulmonary bypass were examined by an electronic particle size analyzer based on the Coulter-Counter-System. The PVD changes, i.e., the reduction of the mean platelet volume (MPV) and the platelet fall correlates significantly with the bypass time (r = 0.78). Two hours after the end of ECC, these changes remained completely irreversible or only partially reversible in patients with perfusion times longer than 60 minutes. In most of the patients with shorter perfusion times, we observed a normalisation of PVD curves and return of platelets to counts approaching normal levels.Some plasma coagulation parameters (i.e., concentration of clottable fibrinogen, FDP) were estimated in parallel and were found to be in good correlation with the platelet defects.In patients with marked changes of MPV up to 48 hours after the end of surgery, a pathologic volume distribution curve of thrombocytes was observed, but platelet counts returned in most of them to normal values. This indicates that the determination of PVD, as a simple reliable diagnostic parameter, gives more essential information about platelet damage than does the platelet count alone.

Galactic orbits of stars

1966 ◽  
Vol 25 ◽  
pp. 93-97
Author(s):  
Richard Woolley
Keyword(s):  
Globular Cluster ◽  
Potential Field ◽  
High Velocity ◽  
Velocity Vector ◽  
Variable Stars ◽  
The Sun ◽  
Proper Motions ◽  
Rr Lyrae ◽  
The Galaxy

It is now possible to determine proper motions of high-velocity objects in such a way as to obtain with some accuracy the velocity vector relevant to the Sun. If a potential field of the Galaxy is assumed, one can compute an actual orbit. A determination of the velocity of the globular clusterωCentauri has recently been completed at Greenwich, and it is found that the orbit is strongly retrograde in the Galaxy. Similar calculations may be made, though with less certainty, in the case of RR Lyrae variable stars.

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