Phase separation of InxGa1−xN into Ga-rich and In-rich regions has been studied by electron energy-loss spectroscopy (EELS) in a monochromated, aberration corrected scanning transmission electron microscope (STEM). We analyze the full spectral information contained in EELS of InGaN, combining for the first time studies of high-energy and low-energy ionization edges, plasmon, and valence losses. Elemental maps of the N K, In M4,5 and Ga L2,3 edges recorded by spectrum imaging at 100 kV reveal sub-nm fluctuations of the local indium content. The low energetic edges of Ga M4,5 and In N4,5 partially overlap with the plasmon peaks. Both have been fitted iteratively to a linear superimposition of reference spectra for GaN, InN, and InGaN, providing a direct measurement of phase separation at the nm-scale. Bandgap measurements are limited in real space by scattering delocalization rather than the electron beam size to ∼10 nm for small bandgaps, and their energetic accuracy by the method of fitting the onset of the joint density of states rather than energy resolution. For an In0.62Ga0.38N thin film we show that phase separation occurs on several length scales.

Phase separation of InxGa1-xN alloys into Ga-rich and In-rich regions was observed by a number of research groups for samples grown with high indium content, x. Due to the radiation sensitivity of InGaN to beam damage by fast electrons, high-resolution imaging in transmission electron microscopy (TEM) or core-loss electron energy-loss spectroscopy (EELS) may lead to erroneous results. Low-loss EELS can yield spectra of the plasmon loss regions at much lower electron fluxes. Unfortunately, due to their delayed edge onset, the low energetic core losses of Ga and In partially overlap with the plasmon peaks, all of which shift with indium content.

Here we demonstrate a method to quantify phase separation in InGaN thin films from the low-loss region in EELS by simultaneously fitting both plasmon and core losses over the energy range of 13-30eV. Phase separation is shown to lead to a broadening of the plasmon peak and the overlapping core losses, resulting in an unreliable determination of the indium concentration from analyzing the plasmon peak position alone if phase separation is present. For x=0.3 and x=0.59, the relative contributions of the binary compounds are negligibly small and indicate random alloys. For x nom.=0.62 we observed strong broadening, indicating phase separation.

In a young infant with divided left atrium, unroofed coronary sinus syndrome, and persistent left superior caval vein, the pulmonary venous blood was successfully routed, after atrial septectomy, to the mitral valve by constructing a baffle using the partially detached diaphragm which had initially separated the pulmonary venous and vestibular components of the left atrium. The baffle was augmented with a patch of untreated autologous pericardium.

Experimental results from the first monochromated and aberration-corrected scanning transmission electron microscope operated at 200 kV are described. The formation of an electron probe with a diameter of less than 0.2 nm at an energy width significantly under 0.3 eV and its planned application to the chemical analysis of nanometer-scale structures in materials science are described. Both energy and spatial resolution will benefit from this: The monochromator improves the energy resolution for studies of energy loss near edge structures. The Cs corrector allows formation of either a smaller probe for a given beam current or yields, at fixed probe size, an enhanced beam current density using a larger condenser aperture. We also point out another advantage of the combination of both components: Increasing the convergence angle by using larger condenser apertures in an aberration-corrected instrument will enlarge the undesirable chromatic focus spread. This in turn influences spatial resolution. The effect of polychromatic probe tails is proportional to the product of convergence angle, chromatic aberration constant, and energy spread. It can thus be compensated for in our new instrument by decreasing the energy width by the same factor as the beam convergence is increased to form a more intense probe. An alternative in future developments might be hardware correction of the chromatic aberration, which could eliminate the chromatic probe spread completely.

Histone RNA 3′ processing in vitro produces one or more 5′ cleavage products corresponding to the mature histone mRNA 3′ end, and a group of 3′ cleavage products whose 5′ ends are mostly located several nucleotides downstream of the mRNA 3′ end. The formation of these 3′ products is coupled to the formation of 5′ products and dependent on the U7 snRNP and a heat-labile processing factor. These short 3′ products therefore are a true and general feature of the processing reaction. Identical 3′ products are also formed from a model RNA containing all spacer nucleotides downstream of the mature mRNA 3′ end, but no sequences from the mature mRNA. Again, this reaction is dependent on both the U7 snRNP and a heat-labile factor. Unlike the processing with a full-length histone pre-mRNA, this reaction produces only 3′ but no 5′ fragments. In addition, product formation is inhibited by addition of cap structures at the model RNA 5′ end, indicating that product formation occurs by 5′-3′ exonucleolytic degradation. This degradation of a model 3′ product by a 5′-3′ exonuclease suggests a mechanism for the release of the U7 snRNP after processing by shortening the cut-off histone spacer sequences base paired to U7 RNA.

In order to understand the value of any theory, one has to know its origins and background. This is especially true of the various dependency theories, which have always been more than just ‘theories of theorists for theorists’. Dependency theories can only be understood against the background of Latin American politics in the 1960s. Taking this into account, there was an obvious connection between the Cuban Revolution on the one hand, and the unfulfilled expectations of development caused by the failure of modernisation efforts, on the other. The basic idea behind dependency theories is the explanation of the historically unequal relations between Latin America and the North Atlantic economies (Europe and the United States). Dependency theories are essentially attempts to justify government policies to acquire control of national development.