Mismatch tuning

Golan Y, Hutchison JL, Rubinstein I, Hodes G (1996) Epitaxial size control by mismatch tuning in electrodeposited Cd(Se, Te) quantum dots on 111 gold. Adv Mater 8 631-633... 

Chen WT, Shen HS, Liu RS, Attfield JP (2012) Cation-size-mismatch tuning of photoluminescence in oxynitride phosphors. J Am Chem Soc 134 8022... 

The first example, also being the example introducing optimal control to solid-state NMR [40] and further elaborated on later [161], is optimal control versions of the DCP experiment. This experiment was a natural choice for numerical improvements as it is widely used and it is well known that this experiment is sensitive to offsets, rf mismatch relative to the MAS-modified Hartmann-Hahn condition, and rf inhomogeneity. In particular the two latter effects may reduce significantly the performance of 15N to 13C transfers, severely complicate setup of such experiments, and render these critically sensitive to altered tuning/rf conditions in the course of potentially long experiments for biological samples. 

A mismatch in the lattice parameters of materials on both sides of an interface results in strain that is released by lattice distortions and dislocations next to the interface. Understanding the release mechanisms of the strain is crucial in order to tune the properties of the interface. 

Another class of toroidal NMR probes is formed by toroid cavity detectors (TCD) [31]. These TCD have been mounted into cylindrical metallic autoclaves to study spin relaxation effects of gases under pressure [31]. If the toroid cavity detector is the metallic pressure vessel itself it is called a toroid cavity autoclave (TCA) probe [32, 33]. These probes can be tuned to higher resonance frequencies than TCDs and also show better spectral resolution [29]. Figure 2.12 shows the design of a TCA where the autoclave body is built from phosphorus bronze [33] keeping the field distortions of the magnetic field Bq, induced by susceptibility mismatches... 

Diastereomeric tuning The coexistence of two types of chiralities in the structure (one central and one axial) makes it possible to exploit the interplay of different stereogenic moieties. Interestingly, the matched and mismatched combination is strongly dependent on the type of reaction to which the diastereomers are applied. 

Since the design and the tuning of the observer can be achieved independently from the adopted controller, the latter can be adopted in conjunction with observers different from those presented in this chapter. The model-based observer (5.23) needs a good knowledge of the reaction kinetics this may be regarded as a limitation for its practical application, where a certain degree of mismatch between... 

While solid matrices have been employed successfully, they may be less than ideal for controlled mechanistic studies. A more appropriate technique for controlled doublet photochemistry appears to be two-photon excitation in solution. In this experiment, the first photon is used to initiate radical ion formation, whereas the second photon, appropriately delayed to coincide with the maximum concentration of the radical cation so generated and tuned to its absorption maximum, serves to excite these intermediates. However, we hasten to add that the benefits of this technique have yet to be demonstrated. The photoinduced rearrangement of radical cations very likely will benefit substantially from a mismatch between (quartet vs. doublet) potential surfaces, much as triplet sensitized isomer-izations can be ascribed to mismatches between triplet and ground state surfaces. 

A way to stretch or compress metal surface atoms in a controlled way is to deposit them on top of a substrate with similar crystal symmetry, yet with different atomic diameter and lattice constant. Such a single monolayer of a metal supported on another is called an overlayer. Metal overlayers strive to approach the lattice constant of their substrate without fully attaining it hence, they are strained compared to their own bulk state [24, 25]. The choice of suitable metal substrates enables tuning of the strain in the overlayer and of the chemisorption energy of adsorbates. A Pt monolayer on a Cu substrate, for instance, was shown to bind adsorbates much weaker than bulk platinum due to compressive strain induced by the lattice mismatch between Pt and Cu, with Cu being smaller [26]. 

In a magnetic resonance experiment designed to record the rotational spectrum, the fixed radiation frequency would be close to the resonant zero-field frequency, with the mismatch being tuned with a swept magnetic field. Equation (9.95) enables us to calculate the behaviour of the levels as a function of magnetic field strength we show the results for both the TV = 1 and 2 rotational levels in figure 9.25, appropriate for the CN radical where yv=0 has the value 217.5 MHz [55]. 

These, then, are the reasons why magnetic resonance methods, microwave or far-infrared laser, have had limited success with 2A diatomic radicals. Similar considerations apply to nonlinear polyatomic radicals in doublet states success in far-infrared laser magnetic resonance depends upon the magnitude of the spin-rotation coupling, and the size of the energy mismatch between the transition frequency and the laser frequency, since the mismatch has to be magnetically tuned. This becomes less of a limitation as more laser frequencies become available, except that one then needs to know in advance which laser frequency to choose. It becomes part of the search problem ... 

Typically the source is tuned with the sample in place and then locked to match the cavity resonance frequency so as to achieve maximum energy storage and minimum reflected power. This reflected power is directed through a one-way coupler called a circulator to a crystal diode detector to convey information about sample absorption in the cavity. An iris opening to the cavity is adjusted to match the impedance of the cavity to that of the source so as to produce minimum reflection of radiation from the cavity. This condition gives maximum sensitivity for the impedance mismatch produced when sample absorption occurs in the cavity. 

Petitjean A, Barton JK. Tuning the DNA reactivity of cis-platinum conjugation to a mismatch-specific metallointercalator. J. Am. Chem. Soc. 2004 126 14728-14729. 

Figure Ila shows how an ideal cosine amplitude modulation of the RF carrier wave could be approximated by a rectangular RF pulse scheme, which is much easier to implement. Such a scheme comprises of pulses with alternating phases of 0° and 180° and is referred to as FAM. As was already mentioned, the modulation frequency should be tuned such that Vm matches tq, at least during part of the excitation. Due to the sample spinning, the quadrupolar splitting of many crystallites will pass through the v n value. It was shown that mismatches between and the powder i/qS do not create large phase distortions and simultaneous adiabatic and direct coherence transfer processes result in relatively pure MQ SQ transfers. By pure we mean that no significant phase dispersions are observed when looking at the transfer of each crystallite separately.

By analyzing the dynamic mismatch, adjust 0. The direction of the deviation should indicate whether the feedforward correction is applied too soon or too late, causing dynamic mismatch. Figure 15.55b shows the feedforward control performance after 0 is tuned. 

Song et al (2006) proposed a multivariable purity control scheme using the m-parameters as manipulated variables and a model predictive control scheme based on linear models that are identified from nonlinear simulations. The approach proposed by Schramm, Griiner, and Kienle (2003) for purity control has been modified by several authors (Kleinert and Lunze, 2008 Fiitterer, 2008). It gives rise to relatively simple, decentralized controllers for the front positions, but an additional purity control layer is needed to cope with plant-model mismatch and sensor errors. Vilas and Van de Wouwer (2011) augmented it by an MPG controller based on a POD (proper orthogonal collocation) model of the plant for parameter tuning of the local PI controllers to cope with the process nonlinearity. 

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