Platelet shape

The plasticity of clay-water mixtures is due principally to two factors the flat platelet shape of the clay particles and their small size. When clay is wet, the water, which under such conditions is known as water of plasticity, envelops each particle, acts as a lubricant between the particles, and allows them, when an external force is applied to the mixture, to readily slide along each other, as shown in Figure 51. 

Clays are usually cation-exchangeable aluminosilicates, and exfoliated clay particles have a platelet shape with nanoscopic size. Cast protein-clay films on electrodes have been used to immobilize proteins. The Clay/Mb electrode has good electrocatalytic properties for the reduction of oxygen and hydrogen peroxide [236] and the biosensors can also be made based on these properties. 

It seems more important to focus on problems that may arise in the course of a quantitative evaluation of electron photomicrographs of an organic pigment. Automatic image analyzers cannot extract information from images which indicate more or less agglomerated, nonisometric, or even platelet-shaped particles. 

A primarily platelet-shaped -modification may also be obtained by the phtha-lonitrile process if particularly pure phthalonitrile is employed [18]. 

Microdiffraction patterns are taken from individual particles after the reduction treatment and are shown in Figs. 3a-d. Most particles with platelet shape and straight edges produce similar microdiffraction patterns, one of which is shown in Fig. 3a. It is indexed as PtsSi with CusAu structure on [100] zone axis. Figs. 3b and 3c show the diffraction patterns from the not reacted Pt on [100] and [310] zone axes, respectively. Particles with irregular forms show various diffractions and a considerable amount of them can be attributed to Pt Sis. One such pattern is shown in Fig. 3d, exhibiting Pt Sis on [152] zone axis. 

Platelets can be activated by a variety of agents including the physiologic agonists ADP, thromboxane A2, epinephrine, collagen, and thrombin. Platelet activation is generally associated with a change in platelet shape (except for epinephrine-induced platelet activation) from discs to spiny spheres with pseudopodia. Platelet pseudopod formation is dependent on actin polymerization in the activated platelets. The interaction of actin filaments with myosin, mediated by calcium (9), facilitates platelet contractile activity (e.g., clot retraction). 

Spreading and defective pseudopod formation seen in this condition can be explained by the fact that the platelet microtubules play a critical role in maintaining the discoid form of platelets and controlling platelet shape and pseudopod formation (21,49). 

Mechanism of Action A hematologic agent that reduces platelet production and prevents platelet shape changes caused by platelet aggregating agents. Therapeutic Effect Inhibits platelet aggregation. 

For anisometric particles (e.g., needle- or platelet-shaped particles) mathematical statistics may likewise be applied [1.10]. The two-dimensional logarithmic normal distribution of the length L and breadth B of the particles also allows the representation and calculation of the characteristic parameters and mean values. The eccentricity of the calculated standard deviation ellipse (Fig. 2) is a measure of the correlation between the length and breadth of the particle. By using more than two... 

The pigments are formed in the fish scales as platelet-shaped crystals (0.05 pm x 1-10 pm x 20-50 pm). A commercial synthetic process for producing purines with this crystal shape has not been found. An aqueous suspension of fish scales is, therefore, extracted with organic solvents to dissolve and remove the proteins. The remaining dispersion contains purine crystals and scale which are separated from one another by a complicated washing and phase-transfer process [5.216]. 

The theonezolides A-C (431-433) were isolated from the sponge Theonella sp. They are 37-membered macrocyclic compounds consisting of two principal fatty acid chains with various functionalities such as a sulfate ester, an oxazole, and a thiazole [336, 337]. Compounds 431-433 displayed cytotoxic activity against L1210 and KB cells and were found to have a unique bioactivity in terms of induction of rabbit platelet shape change and aggregation [338]. 

McClue, S.J., Brazell, C., and Stahl, S.M. (1989) Hallucinogenic drugs are partial agonists of the human platelet shape change response a physiological model of the 5-HT2 receptor. Biological Psychiatry 26, 297—302. 

Many platelet agonists, such as ADF) TXA2, epinephrine, serotonin, and thrombin, interact with specific transmembrane receptors that are coupled to G-proteins, initiating several signaling pathways that lead to PLC activation ending in platelets shape change and granule secretion (Fig. 4). 

The P2YI and P2YI2 receptors are 2 G protein-coupled, which selectively contributes to platelet aggregation. The P2YI receptor is responsible for ADP-induced platelet shape changes and transient aggregation, whereas the... 

The key of the mechanical and physico-chemical properties of bone lies in its micro- and nanostructure. The apatite crystals of the mineral phase are nanocrystalline and irregular platelet shaped with dimensions in the range of... 

Adair JH, Li T, Kido T, et al. Recent developments in the preparation and properties of nanometer-size spherical and platelet-shaped particles and composite particles. Mater Sci Eng 1998 R23 139-242. 

For anisomeric particles (e.g., needle- or platelet-shaped particles) mathematical statistics may likewise be appUed [1.14]. The two-dimensional logarithmic normal... 

Bismuth-containing special effect pigments based on platelet-shaped crystals of bismuth oxide chloride (bismuth oxychloride, BiOCl) have been known for a long time (see Section 5.3.1.3). 

Natural pearl essence is isolated as a silky lustrous suspension from fish scales. The organic pigment particles in the suspension are platelet-shaped with a very high aspect ratio (0.05 pm x 1-10 pm x 20-50 pm), and consist of 75-97% guanine and 3-25% hypoxanthine (natural fish silver) [5.122, 5.123, 5.128, 5.130]. 

Special care has to be taken to ensure parallel alignment of the platelet-shaped pigment particles during their application. In most cases the pigments can be dispersed homogeneously by simply and carefully stirring them into a suitable liquid system. 

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