Stanly

British thermal unit (Btu) The most commonly used industrial heal unit the amount of heat required to raise 1 lb of water through UF under specified conditions. Since the specific heat of water varies, particularly with temperature, the actual value of Btu is dependent on the conditions chosen as stan-... 

Boyd D.P., Gould R.G., Quinu J.R, Sparks R., Stanly J.H., Herrmansfedt W.B. A proposed dynamic cardiac 3-D densitometer for early detection and evaluation of heart disease., IEEE Trans. Nucl. Sci., V. NS-26, 1979, p.2724-2727. 

Spin den sitieshelp to predict the observed coupling con slants in electron spin rcsonan ce (HSR) spectroscopy. From spin density plots you can predict a direct relalitin sh ip between the spin density on a carbon atom an d th c couplin g con stan t assti-ciated with ati adjacent hydrogen. 

Th is discussion focuses on th e individual compon en ts of a typical molecular mechanics force field. It illustrates the mathematical functions used, wdi y those functions are chosen, and the circiim -Stan ces u n der wh ich the fun ction s become poor approxirn atiori s. Part 2 of th is book, Theory and Melhadx, includes details on the implementation of the MM+,. AM BHR, RlO-g and OPl.S force fields in HyperChem. 

The relative sizes ofthe poten tial barriers in dicate that the AF force con Stan t is larger th an the V con stan t. fh e ph ase sh ift is 180 degrees for th e Fourier compoiien t with a two-fold barrier. Minima occur at 180, 0, and I 80 degrees and maxima at 90 and 90... 

Once HyperChem calciilates potential energy, it can obtain all of th c forces on the n uclei at negligible addition a I expen se, I h is allows for rapid optimi/ation of equilibrium and tran sitiori-state geometries and th e possibility of com put in g force con stan ts, vibra-tiorial modes, and molecular dynamics trajectories. 

For a stable irajocutry, use a I3ath relaxation con slant greater than 0.1 ps. A con Stan t of 0.01 ps Is too small and causes dlsinrbances in a sitn ulaiiori ... 

Restrain ts add poten lial term s to a force field calcu lalion. ravoriu g ih c value ih at you sped fy in a restrain i. Th e larger th e value of the harm on ic force con stan t. th c m ore tigh tly th e calculation restrain s th c value. 

Before run ti in g a molecu lar dyn am ics sim ulatioti with solvent and a m olccular median ics meth od, choose the appropriate dielectric con Stan i. You specify th e type an d value of th c dielectric con slari t in thehorce hield Option s dialog box. ITi e dielectric con star t defines the screen irig effect of solvent molecules on nonbonded (electrostalic) in teraction s. 

A til Stan cc-dcpM don 1 diolacLric con sLtiii L is com in on ly used to mimic ihe effect of solvent in moleciiltir mechanics ctilciikilioiis, in the absence ol explicit water molecules. 

I o sorn c ex ten t you can rn on itor eon stan t tern peratii re sim ula-tion s by th e tern perature (I KMP) an cl its deviation (D TKM P) or by kinetic en ergy (KKIN) an d its deviation (D HKIN). Plot th ese values using the HyperChem Molecular Averages dialog box. 

You can use two types of dielectric fun ction s a con stan t an d a dis-tan ce-depen den t dielectric. Use con stan t dielectric for in i- floio systems and for molecular systems wfith explicit solvent molecules. 

The above poten tial describes the m onopole-m on opole interactions of atomic charges c. and q. a distance R.. apart. Normally th CSC eh arge in teractiori s arc corn pti ted on ly for non bon ded atom s and once again the I 4 in tcraetioti s m igti t be treated differen ily from the more normal nonborided interactions (I 5 relationship or rn ore). Th c dielectric con Stan t t used in th c calculation is sometimes scaled or made distance-dependent, as described in the next section. ... 

Th c fun ction al form for bon d stretch in g in HlOa, as in CHARMM, is quadratic only and is identical to that shown in equation (1 1) on page I 75. Th e bond stretch in g force con stan ts are in units of... 

I lic 3-alorn and 4-atoni rcstrairiis behave just like those for two atoms, except tliat the dialog hox requests an angle rather than a distance and the accompanying request for a force constant requires either a bending force constant (3-atorn case) or a torsional force con Stan t (4-atorn case). 

So only the two-electron integrals wilh p. > v. and I>aand [p.v > 7.a need to he computed and stored. Dp.v.la on ly appears m Gpv, and Gvp, w hereas ih e original two-electron integrals con tribute to other matrix elemen is as well. So it is m iich easier to form ih e Fock matrix by using the siipermairix D and modified density matrix P th an the regular format of the tw O-electron in tegrals and stan dard den sity m atrix. 

ZINDO/I is based on a modified version of the intermediate neglect of differential overlap (INOOh which was developed by Michael /ern cr of the Quan turn Th cory Project at th e Lin iversity oIFIorida. Zerner s original IXDO/1 used the Slater orbital exponents with a distance dependence for the first rorv transition metals only. (See Thvorel. Chirn. Ada (Bed.) 53, 21-54 (1979).) However, in HyperChem con stan I orbital expon en ts are used for all the available elements, as recommended by. Anderson, Kdwards, and /.erner, /norg. Chern. 25, 2728-2732,1986,... 

The Restart check box can be used in ctiii junction with the explicit editing of a IIIX file to assign completely user-specified initial velocities. This may be useful in classical trajectory analysis of chemical reactions where the initial velocities and directions of the reactants are varied to statistically determine the probability of reaction occurring, or n ot, in the process of calculating a rate con -Stan t. 

If th e Con Stan t tern peraLu re option h as n ot been selected, HyperCh cm s m oiccu lar dyn am ics uses con stan t volum e an d con -slant total energy corresponding to a rn icrocanon ical enscmhle. 

In addition to bein g able to plot sim pie in stan tan eous values of a quantity x along a trajectory and reporting the average, , HyperChem can also report information about the deviation of x from its average value. Ihese RMS deviations may have particular sign ifican ce in statistical tn ech an ics or just represen t lh e process of convergence of the trajectory values. 

If Lh c con Stan t Ictn pcratti re a Igori Lli rn is used in a trajectory analysis, then the initial conditions arc constantly being modified according to the sirn ulation of th c con stan t tern perattirc bath an d th e relaxation of th e m olecu lar system to that bath temperature, fhe effect of such a bath on a trajectory analysis is less studied than for th c sirn 11 lation of cqu i libriii m behavior. 

The key dimension m NMR is the frequency axis All of the spectra we have seen so far are ID spectra because they have only one frequency axis In 2D NMR a stan dard pulse sequence adds a second frequency axis Only pulsed FT NMR spectrometers are capable of carrying out 2D experiments... 

Mass spectra are reproduced with permis Sion from EPA/NIH Mass Spectral Data Base Supplement I S R Heller and G W A l lne National Bureau of Stan dards 1980... 

CD ROM set includes 8 important and stan dard mechanisms that can be used directly from the CD or im ported into your own lec ture presentation Digital Content Manager—... 

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