Aberrant function

In addition to cooperating with B cells in the production of antibodies, CD4 T cells help in the production of a second population of T cells bearing the CD8 marker. These T cells recognize their corresponding, or cognate, antigen presented by MHC class I products. MHC class I is expressed by all nucleated cells, and 

In addition to their direct effects, CD8 T cells, as well as CD4 T cells, produce a number of cytokines when they are activated. Some of them are important in amplifying the immune response itself — for example, by influencing the class of antibody produced. Other cytokines engender inflammatory reactions. Although useful in limiting infection, inflammation may have adverse effects. To protect itself, the body also produces anti-inflammatory cytokines. 

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Scheepers A, Joost HG, Schurmann A (2004) The glucose transporter families SGLT and GLUT molecular basis of normal and aberrant function. JPEN J Parenter Enteral Nub 28 364-371... 

H(u) is the Fourier Transform of h(r) and is called the contrast transfer function (CTF). u is a reciprocal-lattice vector that can be expressed by image Fourier coefficients. The CTF is the product of an aperture function A(u), a wave attenuation function E(u) and a lens aberration function B(u) = exp(ix(u)). Typically, a mathematical description of the lens aberration function to lowest orders builds on the Weak Phase Approximation and yields the expression ... 

The phase shift induced by the aberration function, can be understood geometrically in terms of the path length difference between a diffracted beam in an ideal lens and in a lens affected by aberrations. This path length difference is a function of the diffraction angle 0 Ag, which is the reason why it is more convenient to describe the imaging process in Fourier space. 

Only considering aberrations due to spherical aberration, Cs, and defocus, z, it can be shown that the aberration function, x, can be expressed as... 

Figure 4.7 gives some basic information on the best known neurotransmitters, their precursors, the enzymes involved in their synthesis, their principal receptors and their metabolites. Drugs that modulate any of the steps involved will affect the availability of the respective neurotransmitter and thus might be used as a potential therapeutic principle to affect the aberrant functioning of one or several neurotransmitter systems... 

Figure 8a and b illustrate Eqs. 9 and 10, respectively. The normahzed aberration function

It has been suggested that BMAA in protein may function as an endogenous neurotoxic reservoir in humans, and may slowly release the neurotoxin directly into the brain during protein metabolism. Incorporation of a nonproternaceous amino acid into a protein may have other serious impacts, such as creating proteins of aberrant function or occurrence [76]. 

There is no reason for an experimental Bragg peak to be exactly described by a simple analytical function. Bragg peaks are generally very complicated objects. In the early usual simplified formalism, still in use, the experimental function h x) describing a broadened Bragg peak profile observed on a powder diffraction pattern is due to the convolution of the instrumental aberration function g(x) with the sample function fix) ... 

Figure 6.11 Equatorial aberration coupled with the receiving slit width calculated by the proposed method (solid line) and as a convolution (open circles) of JFS with the rectangle function (dashed line) representing the receiving slit. The vertical line at 20° represents the Bragg angle to which the aberration function is related. (Reprinted from Ref. 53. Permission of the International Union of Crystallography.)...

Figure 6.18 shows the convolution of the aberration function / (e) with the receiving-slit instrumental function. Here the profile calculated according to the proposed method is also represented. The calculation was carried out with a fixed point A at the center of the source points A2 lie on the y-axis from the... 

Electrons change the phase on passing through an electron lens due to the spherical aberration and defocus. The aberration function x(u), proportional to the change in phase of the electron wave, is described by... 

The aberration function is decomposed into sums of mathematical functions, making possible the classification of the aberrations. For this decomposition, it has proven convenient to use particular sets of orthogonal polynomials, the most common of which are the Zernike polynomials. With the Zernike polynomials, each polynomial represents a particular type of aberration, having its own characteristic effect on imaging and optical lithography. ... 

For pure phase objects, the observed contrast results from the aberration function. For uncorrected HRTEM imaging, if the value of defocus Af equals to the Scherzer defocus, the aberration function x(u) jr/2 over as large a range Au of u. In this case, if the sample is sufficiently thin to be a weak phase object and if the phase is proportional to the projected potential, a imiform phase shift for all u (except u = 0) results in an image wave function in which the contrast is linearly proportional to the projected potential. 

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