Small nuclear particles

Principles and Characteristics Particle-induced X-ray emission spectrometry (PIXE) is a high-energy ion beam analysis technique, which is often considered as a complement to XRF. PIXE analysis is typically carried out with a proton beam (proton-induced X-ray emission) and requires nuclear physics facilities such as a Van der Graaff accelerator, or otherwise a small electrostatic particle accelerator. As the highest sensitivity is obtained at rather low proton energies (2-4 MeV), recently, small and relatively inexpensive tandem accelerators have been developed for PIXE applications, which are commercially available. Compact cyclotrons are also often used. 

In a sample of bulk Pt metal, all of the nuclei have the same interaction with the conduction electrons and thus see the same local field. The resulting NMR line is quite narrow. However, in our samples of small Pt particles, many of the nuclei are near a surface where the state of the conduction electron is disturbed. This tends to reduce the Knight shift for these nuclei. Since the Pt particles in our samples are of many different sizes and shapes, this reduction in the Knight shift is not the same for every nuclear spin near a surface. Thus, we obtain a broad "smear" of Knight shifts resulting in the lineshapes of Figure 5. 

In preliminary evaluations a Nuclear Data ND-PSA Particle Sizing Amplifier (PSA) was interfaced between the Royco and the MCA. The PSA, which could serve as either a linear or logarithmic amplifier, was operated in the log mode to develop an output signal which would be more nearly proportional to the log of the particle diameter and spread the small-diameter particle count over a larger number of chemnels. The distribution displayed on... 

Decompose in a mild way the cluster after its adsorption on the surface of a metal oxide, to remove the ligands, and try to keep the size and possibly the structure of its metallic core as if the support by itself could stabilize a small metal particle with the same nuclearity of the metallic core of the original molecular cluster. 

Removal of introns. snRNP = small nuclear ribonucleoprotein particle. 

Birnstiel, M. L., ed. (1988) Small Nuclear Ribonucleoprotein Particles, Springer, Vienna/ New York... 

To assist in the modification and processing of mRNAs, eukaryotic cells contain in their nuclei small nuclear RNAs (snRNAs), which are complexed with specific proteins to form small nuclear ribonucleoprotein particles (snRNPs). These RNAs have been named U1, U2, U3,.. . , U13 and range in size from 100 to 220 bases. One, U3, is... 

B1. Bachmann, M., Falke, D., Schroder, H. C., and Muller, W. E., Intracellular distribution of the La antigen in CV-1 cells after herpes simplex virus type 1 infection compared with the localization of U small nuclear ribonucleoprotein particles. J. Gen. Virol. 70, 881-891 (1989). 

The principle of small nuclear changes was given a theoretical basis by George Gamow. In 1928 he derived a successful theory of alpha decay, in which the nucleus is quantized and only small particles, such as protons or alpha particles, have a finite probability of tunneling through the nuclear barrier and escaping the nucleus. That... 

The small nuclear ribonucleoprotein particles (snRNPs or snurps ) that carry out the splicing reaction use RNA-RNA basepairing to select the splice sites. Almost all intron-exon junctions contain the sequence AG-GU with the GU beginning the intron sequence. Furthermore, the consensus sequence for the beginning of the intron has a longer sequence complementary to the U1 RNA. Thus, assembly of the splicing complex, called the spliceosome, starts when the RNA component of the U1 snRNP base pairs with the junction between the 3 end of the exon and the 5 end of the intron. See Figure 12-13. 

Table 11.4 Small Nuclear Ribonucleoprotein Particles (snRNP) in Splicing of mRNA Precursors...

Maniatis, T. and Reed, R. 1987. The role of small nuclear ribonucleo-protein particles in pre-mRNA splicing. Nature, 325, 673-678. 

The endoplasmic reticulum (ER) is composed of flattened sacs and tubes of membranous bilayers that extend throughout the cytoplasm enclosing a large intracellular space. The luminal space (Fig. 1-5) is continuous with the outer membrane of the nuclear envelope (Fig. 1-10). It is involved in the synthesis of proteins and their transport to the cytoplasmic membrane (via vesicles, small spherical particles with an outer bilayer membrane). The rough ER (RER) has flattened stacks of membrane that are studded on the outer (cytoplasmic) face with ribosomes (discussed later in this section) that... 

Small nuclear ribonucleoprotein particle Soil organic carbon store-operated channel Suppressors of cytokine signaling Superoxide dismutase CuZn-SOD enzyme (intracellular)... 

Small Nuclear Ribonucleoprotein (RNA Plus Protein) Particle... 

The tropospheric air always contains a considerable amount of small submicron particles, the so-called Aitken particles (AP), which are widely spread. Experimental data show that, on the average, not less than 50-75% of the total mass concentration of AP fall on sulfates [43]. The average percentage of the mass concentration of organic and nitrate components in the aerosol of the sub-micron range is estimated at 20-25% [2, 22]. Undoubtedly, nuclear explosions (with a yield of about 10 NO molecules per 1 Mt of trinitrotoluene equivalent [12] should generate great amounts of nitrate and sulfate aerosols, but there are no estimates so far. 

D, Keller W. Functions of the abundant U-snRNPs. In Small Nuclear Ribonucleoprotein Particles. Birnstiel ML, ed. 1988. Springer-Verlag, Berlin. 53. 

Pikielny CW, Rosbash M. Specific small nuclear RNAs are associated with yeast spliceosomes. Cell 1986 45 869-877. Frendewey D, Kramer A, Keller W. Different small nuclear ribonucleoprotein particles are involved in different steps of splicing complex formation. Cold Spring Harb. Symp. Quant. Biol. 1987 52 287-298. 

Konarska, M, Sharp PA. Interactions between small nuclear 81. ribonucleoprotein particles in formation of spliceosomes. Cell 1987 49 763-774. 

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