Common envelope

The conformation that a furanoid compound will adopt in the crystal is not readily predicted. A furanoid compound can adopt one of four envelope conformations in which C-2 or C-3 is endo or exo, namely, 2E, E2, 3E, and E3 less commonly, it may adopt a twist conformation. The energy difference between the four common envelope conformations may be so slight that other effects predominate in determining the conformation that the compound will adopt, both in the crystal and in solution. Such effects include those caused by hydrogen bonding, solvation, and close contacts with an aglycon. 

W Ursae Majoris stars can be understood as contact binary stars with a common envelope (Lucy 1968). They subdivide into two types The A-type are earlier in spectral class than about F5, are believed to have radiative envelopes, and associate primary (deeper) eclipse minimum with transit eclipse. The W-type have spectral classes later than F5, are believed to have convective envelopes, and associate primary minimum with occultation eclipse. Controversy has surrounded the explanation of W-type light curves. 

Figure 19. Escape time Tc as a function of noise strength D for various a. Above roughly lg 1/D = 1.5, a power-law behavior is observed that corresponds to Eq. (114). The curve [Eq. (113)] for a — 2.0 appears to represent a common envelope.

Comparing the stress distributions in the coarse and the fine TBC microstructures generated with the higher-order analysis, we observe virtually no difference in the pure ceramic region. In the functionally graded regions, differences are expected due to differences in the microstructural scales. However, one common feature exhibited by the stress distributions in the two mierostructures is the common envelope within which the stress oscillations in the... 

With two stars orbiting one another inside this common envelope, friction between the stars and envelope, which will not be rotating at the same rate, will cause the two stars to spiral towards each other. Orbital energy will be converted to heat until sufficient has been lost to eject the envelope [52]. The result is a much closer binary (orbital period typically between 0.1 and 10 d)... 

If the secondary is a white dwarf, then the sdB star must originally have been the less massive star in the binary system. A previous phase of stable mass transfer must have transferred the envelope of the original primary to the secondary, allowing the core to become a helium white dwarf and reversing the mass ratio in the binary system. The common envelope phase occurs when the new primary evolves to become a red giant, and the resulting system contains an sdB star and a white dwarf. 

An alternative channel for the formation of sdB stars considers the ultimate fate of binary systems which are so evolved as to comprise two white dwarfs in a close binary orbit. This predicates a binary system which has passed through several stages of mass transfer (whether common-envelope or stable Roche-lobe overflow) to leave these remnants. 

Another merger model suggests that some post-common-envelope sdB binaries could share the white dwarf merger fate [64]. The idea is that the post-sdB star, which is a hybrid white dwarf containing a partially-burnt CO... 

Five-member furanose rings are also not planar. The furanose ring can have a common envelope conformation (E), with four atoms coplanar and the fifth out of the plane (any of the four carbons or the oxygen). For the envelop, the conformation is defined by the one atom that is above or below the plane, such as E and E3 for C3 above and below the plane (Cl—C2—C4—04) respectively. It can also have a less common twist... 

For the furanose ring, which is adopted by some hexoses and pentoses, the five-member ring is only slightly puckered and exists in three forms, the more common envelope (E) and the less common twist (T). For the more stable envelope forms, and E3, the conformation is defined by the C3 atom that is above or below, the plane (described by C1,C2, C4 and 04). 

A sine-shape has side lobes which impair the excitation of a distinct slice. Other pulse envelopes are therefore more commonly used. Ideally, one would like a rectangular excitation profile which results from a sine-shaped pulse with an infinite number of side lobes. In practice, a finite pulse duration is required and therefore the pulse has to be truncated, which causes oscillations in the excitation profile. Another frequently used pulse envelope is a Gaussian frmction ... 

Sources of radiation are all of lower than ideal intensity. One of the most commonly used is a mercury discharge in a quartz envelope, most of the higher-wavenumber radiation coming from the quartz rather than from the discharge plasma. 

Spira.1- Wound Modules. Spiral-wound modules were used originally for artificial kidneys, but were fuUy developed for reverse osmosis systems. This work, carried out by UOP under sponsorship of the Office of Saline Water (later the Office of Water Research and Technology) resulted in a number of spiral-wound designs (63—65). The design shown in Figure 21 is the simplest and most common, and consists of a membrane envelope wound around a perforated central coUection tube. The wound module is placed inside a tubular pressure vessel, and feed gas is circulated axiaUy down the module across the membrane envelope. A portion of the feed permeates into the membrane envelope, where it spirals toward the center and exits through the coUection tube. 

Standard Chemical Pump. In 1961, the American National Standards Institute (ANSI) iatroduced a chemical pump standard (29), known as ANSI B73.1, that defined common pump envelope dimensions, connections for the auxiUary piping and gauges, seal chamber dimensions, parts mnout limits, and baseplate dimensions. This definition was to ensure the user of the availabiUty of iaterchangeable pumps produced by different manufacturers, as well as to provide plant designers with standard equipment. A typical ANSI chemical pump, known as of the mid-1990s as ASME B73.1M-1991, is shown ia Figure 6. 

For a building with sharp corners, Cp is almost independent of the wind speed (i.e., Reynolds number) because the flow separation points normally occur at the sharp edges. This may not be the case for round buildings, w here the position of the separation point can be affected by the wind speed. For the most common case of the building with a rectangular shape, Cp values are normally between 0.6 and 0.8 for the upwind wall, and for the leeward wall 0,6 < C, < —0.4. Figure 7.99 and Table 7.32 show an example of the distribution of surface pressure coefficient values on the typical industrial building envelope. 

Another difficulty with the infrared method is that of determining the band center with sufficient accuracy in the presence of the fine structure or band envelopes due to the overall rotation. Even when high resolution equipment is used so that the separate rotation lines are resolved, it is by no means always a simple problem to identify these lines with certainty so that the band center can be unambiguously determined. The final difficulty is one common to almost all methods and that is the effect of the shape of the potential barrier. The infrared method has the advantage that it is applicable to many molecules for which some of the other methods are not suitable. However, in some of these cases especially, barrier shapes are likely to be more complicated than the simple cosine form usually assumed, and, when this complication occurs, there is a corresponding uncertainty in the height of the potential barrier as determined from the infrared torsional frequencies. In especially favorable cases, it may be possible to observe so-called hot bands i.e., v = 1 to v = 2, 2 to 3, etc. This would add information about the shape of the barrier. 

Many enveloped viruses share a common mechanism of fusion, mediated by a virus-encoded glycoprotein that contains heptad repeats in its extraceUnlar domain. Dnring the fnsion process, these domains rearrange to form highly structured and thermodynamically stable coiled-coils. Viruses encoding fusion proteins that have these domains inclnde members of the paramyxovirus family (e.g., respiratory syncytial virus, metapneumovirus, and measles virus), ebola virus, influenza, and members of the retroviridae (e.g., human T cell lenkemia virus type-1 and human immunodeficiency virus type-1, HlV-1). Peptide inhibitors of fusion that disrupt the... 

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