Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Functionality built

Let us consider lithium as an example. In the usual treatment of this metal a set of molecular orbitals is formulated, each of which is a Bloch function built from the 2s orbitals of the atoms, or, in the more refined cell treatment, from 2s orbitals that are slightly perturbed to satisfy the boundary conditions for the cells. These molecular orbitals correspond to electron energies that constitute a Brillouin zone, and the normal state of the metal is that in which half of the orbitals, the more stable ones, are occupied by two electrons apiece, with opposed spins. [Pg.374]

The most common calibration model or function in use in analytical laboratories assumes that the analytical response is a linear function of the analyte concentration. Most chromatographic and spectrophotometric methods use this approach. Indeed, many instruments and software packages have linear calibration (regression) functions built into them. The main type of calculation adopted is the method of least squares whereby the sums of the squares of the deviations from the predicted line are minimised. It is assumed that all the errors are contained in the response variable, T, and the concentration variable, X, is error free. Commonly the models available are Y = bX and Y = bX + a, where b is the slope of the calibration line and a is the intercept. These values are the least squares estimates of the true values. The following discussions are only... [Pg.48]

The most important aspect of the study of Co(II) metalloenzymes is the possibility of using the metal ion as a functional, built-in reporter of the dynamics of the active site. The spectral and magnetic properties of Co (II) carbonic anhydrase have given valuable clues to the catalytic function of this enzyme. The recent studies of Co(II) alkaline phosphatase and Co (II) carboxypeptidase A indicate the general applicability of this approach to enzymes where the probe properties of the constitutive metal ion are poor. The comparison of the absorption spectra of these enzymes and low-molecular weight models have shown that the proteins provide irregular, and in some cases nearly tetrahedral environments. It is obvious, however, that a knowledge of the crystal structures of the enzymes is necessary before the full potential of this method can be exploited. [Pg.191]

However, to obtain results with good accuracy, it is also necessary to include a pseudostate (or localized) channel, which accounts for those closed channels that have not been included, as well as for the multiple ionization channels, since the set of single-ionization PWCs alone would be incomplete. The localized channel may comprise a large number of normalized many-electron functions /, built from localized orbitals... [Pg.287]

ICP-MS can provide semiquantitative analysis for about 70 elements by using element response functions built into the instrument software and calibration of only a few elements [205,206]. Most elements are more than 90% ionized in the ICP (with the exception of elements with ionization potentials greater than about 8 eV). Ion transmission efficiency is a smooth function of mass. The natural isotopic abundances of the elements are well known. Therefore, it is possible to predict the relative sensitivities of the elements and any isobaric overlaps. [Pg.122]

An interesting recent study of the perturbations of the 3II and. 4 11 states of CO due to spin-orbit and rotational-orbit interactions has appeared.320 By including Cl functions built from HF orbitals optimized for each state, good agreement was obtained between theory and experiment in most cases, but the single-configuration approximation is seriously in error. [Pg.120]

Another design question relates directly to the issue of function. The question is whether first to establish reliable networks and synthesize crystals based upon such networks, and then to modify the building blocks to introduce a desired function while maintaining the reliability of the network. Alternatively, one can take molecules with functionality built-in and then try to develop them, perhaps by minor synthetic modification into building blocks for a suitable network that will permit a functional crystalline material to be prepared. These issues have been examined in Section 7. [Pg.65]

The generality and importance of the above results cannot be overemphasized. The wavefunction for the valence electrons may be optimized by variation of y alone, using the effective Hamiltonian in (47) with appropriate orthonormality constraints. In practice this means that, for a function built up from orbitals r of the valence space, it is only necessary to replace matrix elements < r h a > by... [Pg.386]

If we develop the torsional solutions of equation (113) on the basis of double products of trigonometric functions (built up with 16 cosine and 15 sine ones), the Hamiltonian matrix to be diagonalized would be of order 31 x 31 = 961. [Pg.61]

E n if one starts from SCF estimates of a complex nature, only real SCF Wave functions have been obtained as a result of the calculations, and this means that both the occupied and virtual SCF orbitals form a real orthonoimalized set, spanning the whole subspace of the LCAO basis orbitals, as noted previously. This implies also that all the matrix elements of ttie Hamiltonian between determlnantal wave functions built up from these SCF orbitals are necessarily real. UtllMng this fact, and following the derivation given in [20], the Hessian can be given as... [Pg.104]

Here Y is the determinant wave function built up from N spln-orbltals of type (4.3), and the derivatives are taken in the point V = t.e. forall tipk O. [Pg.105]

SP synthetic strategy to 3.107 The designed SP synthetic scheme (Fig. 3.43) supported the intermediate 3.112 via its free hydroxyl function, built the precursor of the... [Pg.127]

COTS software functionality disabled by configuration is not redimdant code in the truest sense, on the basis that the disabled software is intended to be enabled according to the need of a particular implementation. Examples of where functionality may be disabled without creating redundant code include hbrary software (e.g., printer driver routines or statistical functions), built-in testing software, and embedded diagnostic instructions. [Pg.220]

Each of these methods is based on the AFDF approach. Within the framework of the conventional Hartree-Fock-Roothaan-Hall self-consistent field linear combination of atomic orbitals (LCAO) ab initio representation of molecular wave functions built from molecular orbitals (MOs), the AFDF principle can be formulated using fragment density matrices. For a complete molecule M of some nuclear configuration K, using an atomic orbital (AO) basis of a set of n AOs density matrix P can be determined using the coefficients of AOs in the occupied MOs. The electronic density p(r) of the molecule M, a function of the three-dimensional position variable r, can be written as... [Pg.202]

If H denotes the total Hamiltonian of the H2 molecule, CF found A as a function of the internuclear distance R by minimizing < H > with respect to the wave function (24). Their findings were (a) for R <. 6Requiiibrium, A = 1 (b) for R > 1.6 Requilibriums A falls quite rapidly to zero as the H2 molecule is stretched further. For A = 1, Eq. (24) is the molecular orbital wave function built as a linear combination of atomic orbitals, whereas for R > 1.6 ReqUiiibrium one sees that electrons quickly go back on to their own atoms . [Pg.210]

Equation 6-4 applies to small sets of data. It says, Find the deviations from the mean d square them, sum them, divide the sum by A/ - 1, and take the square root. The quantity A/ - 1 is called the number of degrees of freedom. Scientific cal culators usually have the standard deviation function built in. Many can find the population standard deviation o- as well as the sample standard deviation, s. For any small data set, you should use the sample standard deviation, s. [Pg.115]

With specific functionality built-in, each building block qualified as only one type of fitting. Vast combinatorial diversity, however, was made possible by an extensive range of building blocks that could satisfy each type. For example, any aryl, fused aryl or heteroaryl monoaldehyde could be utilized as a female terminal and any cyclic ketone with active a,a -methylene groups could constitute a rigid male-male union. [Pg.225]

The pheromone 151 possesses an anti-relationship between the two hydroxyl functions built in its structure (Scheme 43). The estabUshment of such an antistereochemistry requires the AD of a (Z)-olefin, a process which usually proceeds with moderate enantiocontrol. To overcome this difficulty, Lohray [120] performed the asymmetric dihydroxylation of the isomeric ( )-alkene 149 and inverted selectively one of the chiral center via an intramolecular lactonization reaction on the derived cyclic sulfate 150. [Pg.736]

It is well known, of course, that the n and cr orbitals that are used in these calculations are built from atomic orbitals which are rough approximations to the accurate wave functions. Thus the electronic density calculated from the James and Coolidge function for the hydrogen molecule is very different from that obtained from the usual functions built from atomic orbitals.63 It is thus at least possible that a very accurate wave function for an aromatic hydrocarbon would give an electronic density which could resemble Fig. 4a. If this should prove not to be the case, then scheme 4b could be used where the delocalized bond of naphthalene now contains 32 electrons. [Pg.176]


See other pages where Functionality built is mentioned: [Pg.205]    [Pg.280]    [Pg.386]    [Pg.316]    [Pg.357]    [Pg.467]    [Pg.341]    [Pg.488]    [Pg.20]    [Pg.298]    [Pg.1047]    [Pg.159]    [Pg.205]    [Pg.517]    [Pg.23]    [Pg.38]    [Pg.79]    [Pg.227]    [Pg.99]    [Pg.277]    [Pg.2476]    [Pg.296]    [Pg.205]    [Pg.15]    [Pg.133]    [Pg.65]    [Pg.151]    [Pg.781]    [Pg.75]    [Pg.772]    [Pg.158]    [Pg.164]   
See also in sourсe #XX -- [ Pg.124 ]




SEARCH



Built-In Functions of VBA

Built-in functions

Built-in sensor functions

Electronically Conducting Polymers with Built-In or Pendant Redox Functionalities

Library functions, built

MATLAB functions built

Products with Built in Sensor Functions

Syntheses Which Involve the Reaction of Selenols on a Pre-built Functionalized Cyclopropane Ring

Using Built-In Functions

Using MATLAB Built-In Functions

© 2024 chempedia.info