.. _before_getting_started:
.. |check| raw:: html
.. |uncheck| raw:: html
Before getting started
======================
The following is a list of some requirements and recommendations to help prepare
the 2D dataset for inversion.
Common recommendations/requirements
'''''''''''''''''''''''''''''''''''
.. list-table::
:widths: 2 98
* - |uncheck|
- **Dataset shear**
The inversion method assumes that the 2D dataset is sheared, such that one of the
dimensions corresponds to a pure anisotropic spectrum. The anisotropic
cross-sections are centered at 0 Hz.
**Required**: Apply a shear transformation before proceeding.
* - |uncheck|
- **Calculate the noise standard deviation**
Use the noise region of your spectrum to calculate the standard deviation of the
noise. You will require this value when implementing cross-validation.
Spinning Sideband correlation dataset specific recommendations
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
.. list-table::
:widths: 2 98
* - |uncheck|
- **Data-repeat operation**
A data-repeat operation on the time-domain signal corresponding to the sideband
dimension makes the spinning sidebands look like a stick spectrum after a
Fourier transformation, a visual, which most NMR spectroscopists are familiar
from the 1D magic-angle spinning spectrum. Like a zero-fill operation, a spinning
sideband data-repeat operation is purely cosmetic and adds no information.
In terms of computation, however, a data-repeated spinning-sideband spectrum will
take longer to solve.
**Strongly recommended**: Avoid data-repeat operation.
Magic angle flipping dataset specific recommendations
'''''''''''''''''''''''''''''''''''''''''''''''''''''
.. list-table::
:widths: 2 98
* - |uncheck|
- **Isotropic shift correction along the anisotropic dimension**
Ordinarily, after shear, a MAF spectrum is a 2D isotropic *v.s.* pure anisotropic
frequency correlation spectrum. In certain conditions, this is not true. In a MAF
experiment, the sample holder (rotor) physically swaps between two angles
(:math:`90^\circ \leftrightarrow 54.735^\circ`). It is possible to have a
slightly different external magnetic fields at the two angles, in which case,
there is an isotropic component along the anisotropic dimension, which is not
removed by the shear transformation.
**Required**: Correct for the isotropic offset along the
anisotropic dimension by adding an appropriate coordinates-offset.
* - |uncheck|
- **Zero-fill operation**
Zero filling the time domain dataset is purely cosmetic. It makes the spectrum
look visually appealing, but adds no information, that is, a zero-filled dataset
contains the same information as a non-zero filled dataset. In terms of
computation, however, a zero-filled spectrum will take longer to solve.
**Recommendation**: If zero-filled, try to keep the total number of points along
the anisotropic dimension in the range of 120 - 150 points.