First-order structure

Zhou HH, Ma RL, Sheng LS, Xiang BR, An DK. 2003. Determination of first-order structure of somatostatin by electrospray ionization mass spectrometry. Yao Xue Xue Bao 38 617 (article in Chinese). 

Horie, Y., Fukami, T. and Mase, S., First Order Structural Phase Transition in BaPbj B Og and the Scaling Law. Solid State Comm. 62(7) 471 (1987). 

Fig. 9. Illustration of the first order structural change in [TTF]+[Cu(tfd)2] associated with the ordering at 240 °K of the rotationally disordered -CF3 groups. Only the TTF units are shown for clarity (Ref. 52)...

First-order structure (Chain length, tacticity, sequence)... 

In such a way, an ordered supermolecular structure could be spontaneously formed from polymers exhibiting a random coil structure. The fundamental cause of this transformation is naturally the first-order structure of the polymer, i.e. its chemical structure. If a polymer with the proper structural units was prepared, then fiber formation would be accelerated and would especially account for the formation of a highly ordered structure. 

Lacorre and his group developed the LAMOX family of oxide iou couductors. Theses materials are based ou the La2Mo209 pareut compouud and are competitive with existing electrolytes at temperatures above the a- o-fi first-order structural phase transition, at 580°C. Associated with this transition is a dramatic improvement in the ionic conductivity to 10 Scm" at 720°C. The structure of... 

The quantity m is a scaled volume fraction of the NPs. For rod-like NPs of diameter D and length L it is roughly given by u L D. This term enforces a first-order structural transition from the isotropic Snp=0) to an orientationally liquid-crystal-like ordered phase (5 Afp>0) at the critical scaled concentration u=u =2.1. For the LC free-energy density f b f e simplified... 

Silver iodide undergoes a first order structural phase transition at 420 K from the / -phase (hexagonal Wurtzite structure), which is metastable with respect to the / -phase (cubic sphalerite structure), to the a-phase where the I - ions occupy a bcc lattice within which the Ag+ ions jump rapidly between a number of possible sites. The ionic conductivity is very high upon melting it actually decreases. Agl is probably the most widely studied fast ion conductor, with much of the work concentrating on determination of the exact distribution of Ag+ sites and conduction pathways. 

Fig. 42. Structural and magnetic phase diagram tor the Co Ni MnGe system. Tu is the temperature of the first-order structural transition, the Neel temperature, Tc the Curie temperature. Structures SS, simple spiral CS, cycloidal spiral FS ferromagnetic spiral (Zach et al. 1984, Niziol et al. 1982).

The UV2OS formed in this way is dark blue and is stable in air for moderate lengths of time. Long-term storage in a desiccator is satisfactory. The compound is orthorhombic with a = 11.272 k, b = 4.971 A, and c = 3.389 A. A reversible first-order structural transformation occurs at 125° to e-LiV O, which is also orthorhombic with a = 11.335 k, b = 4.683 A, and c = 3.589 A. Above 300° the structure changes irreversibly to that of the thermally stable y-UV2O5. 

The structure of (5,5) carbon nanotube has been calculated for its quasistatic expansion up to the elongation of 20 %. Two first order structural phase transitions with the change of the atomic structure symmetry were revealed as the result of the nanotube expansion. For the elongation greater than 13 % the structure of nanotube corresponds to the metallic phase without the Peierls gap. The considered phenomena can be observed experimentally at ultra low temperatures. 

However, the first-order structural transition temperatures Tq are too high for this mechanism to be operative. A remarkable sensitivity on the stoichiometry of Tq has been noted (Bucher et al. 1976). Since the Th3P4 structure is rather complicated, so are the phonon spectra and the band structure a quantitative analysis is therefore very difficult. 

The conformational entropy defined by Eq. 1 is directly related to the flexibility or rigidity of given polymer chains. Thermodynamic properties of the bulk state are known to be largely affected by the flexibility of the polymer chain. The RIS information is fundamentally important in predicting bulk properties of polymers from a given first-order structure. A great deal of effort has been made to elucidate the role of conformational entropy in determining the phase transition behavior of chain molecules. 

This iterative construction may be envisaged from a physical standpoint. This produces mathematical relationships that will be useful later on. If the initiator is a cube of side length /o, made of some material of uniform mass density po, the first-order structure (obtained after one iteration) would have a porosity void volume divided by total volume) equal to 7/27 and a mass density pi equal to 20pol21. After the second iteration, theporosity 02 would increase to 329/729 ( 0.45) and the density P2 would decrease to 400/Oo/729 ( 0.55po). At the nth iteration, porosity and density would be given by... 

Nucleosome The first-order structural unit for the packing of DNA in chromatin, consisting of 146 bp of DNA wrapped 1.75 times around a core octamer of histone proteins. Successive nucleosomes are connected by stretches of linker DNA. 

The appearance of a tweed microstructure near the transition temperature may suggest a martensitic transformation, which in most cases is a first-order structural transition. Such transitions are very common in low-temperature (LT) superconductor materials (Krumhansl 1992) like VsSi and NbaSn or in ceramics and alloys undergoing chemical phase separation. 

The first ordered structures for SERS were reported during the early 1980s by Liao et al. [95,96], who obtained regularly ordered SERS substrates by depositing Ag particles over periodic arrays of silica posts that were fabricated by photolithography. Since the 1990s, with the rapid development in the field of nanofabrication, many ordered periodic arrays of nanoparticles for SERS have been made. 

The Fourier transform of the derivatives of the first order structure factor is slightly more involved. The sum over the JV/y Bravais cell positions Xp only... 

The situation is even more complicated when the thiol group content is determined in proteins. All the methods given above were used for such a determination and the complications given were complex-formation with other functional groupings, adsorption of proteins, denaturation and other changes of structure of the second or even first order structure of proteins. Proteins in aqueous solutions, when extremely carefully treated, contain almost no free titratable groups. It is, for instance, questionable, whether or not, after denaturation with ethanol on the one hand and with an aqueous ammoniacal medium on the other, the same thiol groups are liberated for the reaction with heavy metals. Thus the above deduction can also be applied here the results should be treated as relative values, and only those obtained under identical conditions should be compared. 

Kq = a constant that is independent of shear rate but is related to the first order structural decay process and is expressed in the minutes... 

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