Transitional studies

Okamoto Y and U H E Hansmann 1995. Thermodynamics of Helix-coil Transitions Studied 1 Multicanonical Algorithms. Journal of Physical Chemistry 99 11276-11287. 

The ability of XPD and AED to measure the short-range order of materials on a very short time scale opens the door for surface order—disorder transition studies, such as the surface solid-to- liquid transition temperature, as has already been done for Pb and Ge. In the caseofbulkGe, a melting temperature of 1210 K was found. While monitoring core-level XPD photoelectron azimuthal scans as a function of increasing temperature, the surface was found to show an order—disorder temperature 160° below that of the bulk. 

NiS Vibrational, magnetic, and electronic properties in semimetalhc antiferromagnetic and in metallic phase phase transition study... 

Table 7.8 Summary of results obtained for the four Os Mossbauer transitions studied. The absorber thickness d refers to the amount of the resonant isotope per unit area. The estimates of the effective absorber thickness t are based on Debye-Waller factors / for an assumed Debye temperature of 0 = 400 K. For comparison with the full experimental line widths at half maximum, Texp, we give the minimum observable width = 2 S/t as calculated from lifetime data.

The Xenopus system has proven instrumental in determining the mechanism controlling exit from mitosis at the metaphase/anaphase transition. Studies in this area have relied heavily on extracts prepared from fully mature oocytes/ unfertilized eggs that are arrested at metaphase of the second meiotic division. Upon Ca2+ addition, anaphase is initiated and the extract enters the first embryonic cell cycle to replicate DNA. The activity responsible for metaphase arrest was discovered by Masui at the same time as MPF (Masui Markert 1971), and given the name cytostatic factor (CSF). CSF has never been purified... 

A small bowel transit study can be used to evaluate intestinal propulsion and clearance, and the presence of Enterobacteriacea (Gram-negative bacilli) in the small bowel indicates delayed transit [111]. The wide normal variability, however, makes transit tests rather insensitive, and thus less useful clinically [126, 127], It is also a problem that accelerated and delayed transit may coexist in neuropathies and confuse the interpretation. Finally, as nutrients are mostly absorbed in the proximal small bowel, and the rate and pattern of transit vary along the intestine, segmental failure of transit is easily missed by global... 

In vivo methods, which are few, measure the residence time of bioadhesives at the application site [47]. Techniques like y-scintigraphy, the perfused intestinal loop and radiolabeled transit studies using Cr-labeled bioadhesive polymer [48] and Tc-labeled polycarbophil [49] have been employed for this purpose. 

The ionic models discussed in section 1.12 involve some sort of empiricism in the evaluation of repulsive and dispersive potentials. They thus need accurate parameterization based on experimental values. They are useful in predicting interaction energies within a family of isostructural compounds, but cannot safely be adopted for predictive purposes outside the parameterized chemical system or in cases involving structural changes (i.e., phase transition studies). 

Equation 2.47 describes the interdependence of thermal expansion, compressibility, and heat capacity of a first-order transition and furnishes a precise tool for the evaluation of the internal consistency of experimental data in solid state transition studies (see Helgeson et al., 1978 for a careful application of eq. 2.47). 

The oscillator strengths obtained for the different transitions studied in the present work with the RQDO methodology, and the use of the two forms of the transition operator, the standard one, and that corrected for core-valence polarization, are collected in Tables 1 to 8, where other data, from several theoretical and experimental sources, have been included for comparative purposes. The former comprise the large-scale configuration interaction performed with the use of the CIVS computer package [19] by Hibbert and Hansen [20] The configuration interaction (Cl) procedure of... 

The materials and methods used in this work have been described in detail in the original publications (1 3). Briefly, the DNA used in the gelation work was prepared by extensive sonication of calf thymus DNA it had a degree of polymerization of 200 30 base pairs (bp). The DNA used in the ordinary-extraordinary transition studies was prepared by nuclease digestion of chromatin from chicken erythrocytes it was an equimolar mixture of two sizes, 140 bp and 160 bp, averaged to 150 bp. 

Specifying a coupling scheme between shells we arrive at a number of concrete formulas for the transitions studied. As in the case of (25.7), let us present the submatrix element in the right side of (25.28) as follows ... 

The a transition is not included in the considered temperature range. For CMI contents equal to or higher than 10%, two transitions are observed. At low temperatures a shoulder is present, whose extent increases with increasing CMI (y transition). Studies performed on copolymers with maleimide unit N-substituted by isopropyl or phenyl groups [79] do not show this low-temperature transition, which appears to be specific for cyclohexylmaleimide. Such a situation is analogous to the one encountered with poly(cyclohexyl methacrylate) described in Sect. 3. Consequently, this low-temperature transition is assigned to the internal motion of the cyclohexyl ring, i.e. the chair-chair inversion represented in Fig. 7. 

Ab initio calculations by Durandurdu and Drabold [273] also support the existence of amorphous-amorphous transition in Ge. They found that LDA Ge was abruptly transformed to an HDA form at 12.75 GPa by using the same computational protocol as that used in their LDA-VHDA transition study of Si [266]. The density of the resultant HDA form is about 20% higher than that of LDA Ge, and its Nc is calculated as 8. This HDA form therefore strongly resembles the VHDA form of Si, rather than the HDA form of Si. This simulation in passing shows that the transition is irreversible, which is consistent with the experiment by Principi et al. [272],... 

Metabolic Transit. Free Amadori Compounds. It is well known that the synthetic Amadori compounds of the free amino acids are absorbed by the intestine and excreted unchanged in the urine (9,28,30). The transport is not active as observed with deoxyfructosyltryptophan (30) and c-deoxyfructosyllysine (40), and the level of absorption depends on the nature of the amino acid and on the conditions of ingestion. Nutritional assays and metabolic transit studies performed with radioactive Amadori compounds of tryptophan (12,30), leucine (12), and lysine (9,28,41) given orally or intravenously on normal or anti-biotics-treated animals have shown that the intestinal microflora can regenerate part of the amino acid. This can be absorbed subsequently at a very low level by the caecum or the large intestine and incorporated into the tissue proteins or utilized by the intestinal microflora. Barbiroli (13) showed also that some intestinal enzymes were able to liberate some amino acids from their Amadori compounds but to a very small... 

The chemical modifications of the tryptophan residues lead to a decrease in the nutritive value of proteins as observed in autoclaved soja meals (124), heated meats (125), heated casein (126), and heated skim milk (122) this last reference is probably the most reliable work published in this field. The nutritional effects and the metabolic transit of heat-treated and oxidized tripeptide (gly-try—gly) have been investigated (123,132,137) recently only the metabolic transit study is related here. 

The metabolic transit studies of the molecules formed provide information complementary to those obtained by the conventional nutritional approaches. This information can be used to control the analytical methods, to explain the nutritional responses, and also to foresee the possible physiological effects. The extrapolation to humans of the results... 

We come now to the second study, described ten years later [23]. The main development was the employment of a tunable dye laser to pump the A <— X + transition. Rotational levels in the ground state with J = 1 to 29, in the v = 0 vibrational level, were pumped by the laser and radioffequency hyperfine transitions studied. The range of J levels studied meant that the effective Hamiltonian required the addition of terms describing the dipolar and scalar interactions between the 23Na nuclear spins. These terms were given earlier in our discussion of the D2 molecule, and the complete effective Hamiltonian is ... 

The origin of the electric dipole intensity for the AMj = 1 transitions studied merits further consideration. If the static magnetic field is 5 kG, the motional electric field has a magnitude of approximately 3 V cm-1 and is perpendicular to the applied magnetic field. This electric field mixes a state [./, Mj) with the states. J 1, Mj 1) and in order to obtain non-zero electric dipole transition moments for the transitions. /. Mj) o IJ, Mj 1), the oscillating electric field must be applied parallel to the static magnetic field. 

The magnetic resonance spectrum of HF was studied some nine years earlier than the electric resonance spectrum by Baker, Nelson, Leavitt and Ramsey [93] in this case the transitions studied were magnetic dipole, corresponding to reorientation of the proton and fluorine nuclear spins. Values of the nuclear spin rotation and dipolar constants were essentially confirmed by the later electric resonance measurements. We now describe measurements of the electric resonance spectrum in the additional presence of a strong magnetic field, carried out by de Leeuw and Dymanus [89]. 

Figure 8.43. A-doubling and 14N hyperfine splitting for the 2n3/2, J = 13/2 rotational level of NO, and the transitions studied by Meerts and Dymanus [124],...

The spectrum follows rules similar to those described in chapter 8 for the molecular beam magnetic resonance study of 7Li79Br, which also has a + ground state and two nuclear spins of 3/2. In that case the transitions studied were nuclear spin transitions within the J = 1 level, but the effective Hamiltonian is similar in the two cases. The Hamiltonian used by Low, Varberg, Connelly, Auty, Howard and Brown [89] contained rotational, quadrupolar and nuclear spin-rotation terms,... 

The NCI radical conforms well to Hund s case (b), as may be seen from figure 10.49 which shows the rotational levels up to N = 4, with their associated triplet spin splitting. The figure also shows the eleven rotational transitions studied [138], Each of these transitions exhibited a complex nuclear hyperfrne splitting, and an example is shown in... 

Figure 11.13 shows the energy levels involved and the transitions studied for H2 in the N = 1 rotational level of the G 1 + state. The experiments were performed using a fixed microwave frequency, typically 9204 MHz, and the resonances detected by scanning the magnetic field amplitude modulation of the microwave power at 100 kHz and lock-in amplifier detection were employed. Polarising filters were used to detect the fluorescence, so that changes in polarisation could be observed. 

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