Density layers

To yield high storage densities, layer thicknesses in the order of the focused laser beam are necessary in the storage medium, measuring about 1 )Tm. In commercial WORM disks based on pure dye layers, layer thicknesses are even lower at about 0.1 )Tm. With thicknesses as low as these, it becomes... 

We attributed the sudden increase in entropy at x 0.5 where stage 1 should begin to form to combined contributions from configurational and vibrational entropy [22], Configurational entropy goes with in-plane or the out-of-plane lithium vacancy disorder . This translates into either the formation of lower Li density layers or the presence of Li stacking faults. Indeed a possible mechanism of the stage 1 phase formation may involve a... 

Density layering through a longitudinal cross section of an idealized ocean basin. Source From Chester, R. (2003). Marine Geochemistry, 2nd ed. Blackwell Publishing, p. 143. 

A prominent component of cytoplasm consists of microtubules which appear under the electron microscope to have a diameter of 24 2 nm and a 13 - to 15-nm hollow core.307-310 However, the true diameter of a hydrated microtubule is about 30 nm and the microtubule may be further surrounded by a 5-20 nm low density layer of associated proteins. Microtubules are present in the most striking form in the flagella and cilia of eukaryotic cells (Fig. 1-8). The stable microtubules of cilia are integral components of the machinery causing their motion (Chapter 19). Labile microtubules, which form and then disappear, are often found in cytoplasm in which motion is taking place, for example, in the pseudopodia of the ameba. The mitotic spindle... 

Isolated microtubules always contain small amounts of larger 300-kDa microtubule-associated proteins (MAPS).330 These elongated molecules may in part lie in the grooves between the tubulin subunits and in part be extended outward to form a low-density layer around the tubule.283 309 Nerve cells that contain stable microtubules have associated stabilizing proteins.331 A family of proteins formed by differential splicing of mRNA are known as tau. The tau proteins are prominent components of the cytoskeleton of neurons. They not only interact with microtubules but also undergo reversible phosphorylation. Hyperphosphorylated tau is the primary component of the paired helical filaments found in the brains of persons with Alzheimer disease.330... 

Because of increased interest in the position of the hydrogen sulfide boundary in recent years, the depth of this feature was studied carefully. It was found that the hydrogen sulfide with formal boundary of 0.3 iM appears in density layer ao = 16.10-16.20 kgm 3 [17,19,26,33,39,40]. According to [40] the concentration of hydrogen sulfide increases from its first appearance defined as 0.3 (jlM quasi-linearly to 300-400 m with a vertical gradient of 0.6-0.7 iM nr1. The more frequent sampling performed during the past few years has allowed us... 

The decrease in the sum of nitrate, nitrite, and ammonium that is observed in the 0 = 15.90-16.00kgm-3 density layer is usually explained by denitrification [26,46], consumption by chemosynthesis [23], or/and anammox, the reaction between nitrite and ammonia [47,48]. From the comparison of the vertical gradients (Fig. 3) the role of nitrate becomes comparable with that of oxygen only in the lower part of the redox layer. Nitrate can be consumed for denitrification and reduction by thiosulfate, elemental sulfur, and sulfide [49,50]. The role of nitrate as a potential oxidizer of reduced manganese and iron is actively being discussed now [51], but the presence of these reactions has not been proved or widely accepted. If they exist, these reactions... 

We used these data for calculation of carbonate system parameters. The calculations were made with a standard set of equations [32], For these calculations we corrected the alkalinity changes for phosphate, ammonia, and sulfide as is recommended for the Black Sea [74]. The results of these calculations revealed the formation of two minima of CO2. A well-pronounced shallower minimum with relative decrease of concentrations by 0.015 mM and a total inorganic carbon (TIC) decrease by 0.040 mM was observed at the density layer = 15.85-15.95 kgm-3, and a smoothed deeper minimum was observed below the sulfide boundary. In the anoxic water the pH slightly decreases down to 75-7.6, and alkalinity increases to 4.50-4.55 mM (Fig. 4). 

Density layer oq = 15.50-15.70 kg nr3. In the upper part of the redox zone, concentrations of dissolved oxygen decrease to 15-20 iM, and its vertical gradient abruptly decreases and becomes equal to that of nitrate. In this layer, nitrate, instead of oxygen, becomes the main oxidizer. Nitrate is rapidly consumed and its concentrations decrease rapidly. The reason for the decrease in the vertical gradient of oxygen is because there is a decrease in the rate of reactions that consume oxygen, probably the mineralization of OM [37]. 

Density layer = 15.85-15.95 kgm-3. In the middle of the redox zone, oxidizers diffusing from the upper layer (oxygen and nitrate) decrease to zero. This occurs simultaneously with the disappearance of reductants (ammonia, Mn(II), methane) diffusing up from the anoxic zone. A minimum of phosphate is also found here. This layer may be very thin, probably only 3-5 m, and its position may vary over the density range specified. 

Density layer oq = 16.10-16.15 kgm 3. This layer constitutes the lower part of the redox zone. The onset of hydrogen sulfide occurs just below the depths of maximum particulate manganese and iron. The reduction of Mn(III) and Mn(IV) by sulfide is very intensive [63,75] and model estimates [88] suggest these reactions can balance the hydrogen sulfide flux from below. A deeper phosphate maximum occurs about 5-10 m below the appearance of hydrogen sulfide. The vertical gradient of hydrogen sulfide increases at this depth (Fig. 2). 

Analysis of the Z8 peptide engineered virus demonstrated preferential growth of ZnS particles oriented in the [001] direction perpendicular to the viral surface. Alternatively, the shorter A7 peptide sequence resulted in high density layers of ZnS (8-16 quantum dots per 10 nm of virus) particles due to... 

In contrast to the dark cloud chemistry, the molecules in circumstellar envelopes (IRC -f 10216) seem to be created continuously in a small, high temperature high density layer- which allow fast thermodynamic equilibrium- and subsequently expelled into the lower density cool envelope. There they are observed with an... 

Figure 8 illustrates the nature of the chemically stratified lake. The upper (low density) layer, called the mixolimnion, is separated at a level called the chemocline from the high density lower layer called the monimolimnion. The chemocline forms a real barrier. The two layers circulate independently mixing very little. Smith and Lee demonstrated the definite stability of such stratification in ancient Lake Uinta (4). 

The work of Bell, Block, and others motivated J. R. A. Pearson (P2) to propose in 1958 a radically different theoretical model for the thermal convection problem a constant density layer with temperature-dependent surface tension. 

This foam-like material holds promise for a wide range of applications where the low density and environmental friendliness are of great importance the ultra-low-density layered architectures result in favorable mechanical and thermal insulation properties [Pojanavaraphan et al, 2010). 

Fig. 11.3 The amount of dissolved gas determines the nature and extent of the surface structuration. 300 nm thick 250 kDa PS films were immersed during 10 min in water at pH 1.5 and then studied by AFM in air. Before treating the surfaces, the aqueous soiutirai was in contact with air during different periods of time after degassing as indicated, to change the amount of gas dissolved, (a) Shortly after degassing the preferential adsorption of ions at the water/polymer interface is likely to be responsible for the observed self-assembled nanostructure. Increasing amounts of gas in the solution move the ions away from the polymer surface limiting the structuration below the bubbles (b), or the low-density layer (c). Adapted with permission from [21]. Copyright (2011) American Chemical Society...

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