The growth and properties of the GaN cap layers crystallized by metalorganic vapor phase epitaxy were studied concerning the composition of the underlying AlGaN layer, type of induced strains and the ...desorption of the GaN during the initial cooling step after the epitaxy process. The composition of the underlying AlGaN layers was controlled by the growth conditions, while the type of the stresses (tensile or compressive) was induced by applying GaN or AlN buffer layer respectively. Structures with different thicknesses of the GaN cap layer have been grown and analyzed. Three series of samples containing AlGaN underlayers with different aluminium content (20%, 40% and 60%) were grown. The influence of those underlayers composition and type of induced surface strains on the growth of the GaN cap was discussed. High resolution X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy and atomic force microscopy, as well as in-situ reflectometry, were used for sample analysis. It has been shown, that the type of surface strains on top of the AlGaN layer and GaN-AlGaN lattice mismatch strongly influence the final cap layer thickness. It was also confirmed, that a significant reduction of the cap thickness causes its discontinuity, leads to the removal of gallium from the top part of the AlGaN layer by evaporation and thus leads to the formation of a thin aluminium-rich layer at the AlGaN/GaN interface.
•Controlling the desorption of GaN to adjust the thickness of the layer.•Surface strains have a strong impact on the GaN cap layer.•Highly concentrated AlGaN influenced the structural properties of GaN cap layers.
Palladium was deposited gradually under ultrahigh vacuum onto a well-defined surface of (0001)-oriented n-type GaN, at room temperature. Each deposition step was followed by annealing. ...Physicochemical properties of the Pd adlayers were in situ investigated prior to and after annealing by the X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, low-energy electron diffraction, scanning tunneling microscopy and atomic force microscopy techniques. Annealing resulted in the formation of GaPd
2
and GaPd intermetallic compounds at 550 °C and at 800 °C. Even for thicker layers, the compounds were strongly dispersed, forming 3D nanostructures. The substrate uncovered by the compounds revealed Ga-rich GaN(0001)-(1 × 1) surface. Formation of Ga-Pd-N bonds or Pd nitrides was not detected at the surface. The Ga-Pd intermetallic compound surface engineered on the GaN(0001) substrate can be used as the strongly dispersed catalyst or a model catalyst.
The electronic and magnetic structure of the octahydrophosphate vivianite, Fe3(PO4)2·8H2O, has been investigated by cluster molecular orbital calculations in local spin density approximation. Optical ...and Mössbauer spectra are well reproduced by the calculations, and the differences between the two iron sites can be correlated with differences in the geometrical structure of the first coordination sphere. The spin structure within the crystallographic ac plane is derived and explained on the basis of different superexchange pathways via edges of the phosphate tetrahedra. The calculations demonstrate that quite large clusters (up to 118 atoms) are necessary to arrive at reliable results.
The electronic structures of Alq
3
/Si(100), Alq
3
/LiBr/Si(100), and Alq
3
/KCl/Si(100) systems are presented in this report. Their energy level diagrams were prepared and discussed. The formation ...of the LiBr and KCl interfacial layers between an Alq
3
film and a Si(100) substrate results in a decrease of the energy barrier at the interface. The studies were carried out in situ in ultrahigh vacuum by ultraviolet photoelectron spectroscopy. Alq
3
as well as LiBr and KCl layers were vapour evaporated onto n‐type Si(100) crystal. The electron affinity of clean Si(100) surface was 4.0 eV, and the position of the valence band maximum was 0.7 eV below
E
F
. The energetic distance between the valence band maximum of Si(100) and the highest occupied molecular orbital level were 1.5, 2.6, and 2.2 eV, for the Alq
3
/Si(100), Alq
3
/LiBr/Si(100), and Alq
3
/KCl/Si(100) systems, respectively.
Vascular complications following liver transplantation is reviewed based upon literature data and our own results. Our study conclusions are mostly based on literature data, because our center does ...not have the liver transplantation experience of other centers worldwide. Thus, we may conclude, that the number and character of complications does not differ from those reported by other centers. The enbloc technique used in liver harvesting minimizes the risk of arterial damage in case of vascular anomalies. Recipient retransplantation is the most effective treatment method in cases of hepatic arterial occlusion. Doppler ultrasound examinations are effective to monitor vascular blood flow in the transplanted liver.
Palladium was deposited gradually under ultrahigh vacuum onto a well-defined surface of (0001)-oriented n-type GaN, at room temperature. Each deposition step was followed by annealing. ...Physicochemical properties of the Pd adlayers were in situ investigated prior to and after annealing by the X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, low-energy electron diffraction, scanning tunneling microscopy and atomic force microscopy techniques. Annealing resulted in the formation of GaPd sub(2) and GaPd intermetallic compounds at 550 degree C and at 800 degree C. Even for thicker layers, the compounds were strongly dispersed, forming 3D nanostructures. The substrate uncovered by the compounds revealed Ga-rich GaN(0001)-(1 1) surface. Formation of Ga-Pd-N bonds or Pd nitrides was not detected at the surface. The Ga-Pd intermetallic compound surface engineered on the GaN(0001) substrate can be used as the strongly dispersed catalyst or a model catalyst.
The electronic structure of iron-rich epidote has been investigated by cluster molecular orbital calculations in local spin density approximation. Calculated quadrupole splittings for Fe(III) at both ...the M1 and M3 sites are in quantitative agreement with the experimental values obtained by Mössbauer spectroscopy. A detailed analysis of the theoretical results shows that a strong tetragonal compression of the M3 octahedron is responsible for the unusually large value of the quadrupole splitting of FeM3(III). The corresponding electric field gradient (efg) is dominated by the anisotropy of the valence shell of iron, whereas the ligands contribute only about 15% to the efg. The calculations emphasize that rather large clusters, extending beyond the second coordination sphere of iron, are necessary for a reliable description. Small clusters including only the first coordination sphere of iron generally yield misleading results due to unsaturated oxygen bonds and relatively large cluster charges.
Geriatric assessment for oncologists Korc-Grodzicki, Beatriz; Holmes, Holly M; Shahrokni, Armin
Cancer biology & medicine,
12/2015, Letnik:
12, Številka:
4
Journal Article
Recenzirano
Odprti dostop
The world is experiencing aging of its population. Age-specific incidence rates of cancer are higher and cancer is now recognized as a part of aging. Treating older patients can be challenging. The ...clinical behavior of some tumors changes with age and the aging process itself brings physiological changes leading to decline in the function of organs. It is essential to identify those patients with longer life expectancy, potentially more likely to benefit from aggressive treatment vs. those that are more vulnerable to adverse outcomes. A primary determination when considering therapy for an older cancer patient is a patient＇s physiologic, rather than chronologic age. In order to differentiate amongst patients of the same age, it is useful to determine if a patient is fit or frail. Frail older adults have multiple chronic conditions and difficulties maintaining independence. They may be more vulnerable to therapy toxicities, and may not have substantial lasting benefits from therapy. Geriatric assessment（GA） may be used as a tool to determine reversible deficits and devise treatment strategies to mitigate such deficits. GA is also used in treatment decision making by clinicians, helping to risk stratify patients prior to potentially high-risk therapy. An important practical aspect of GA is the feasibility of incorporating it into a busy oncology practice. Key considerations in performing the GA include： available resources, patient population, GA tools to use, and who will be responsible for using the GA results and develop care plans. Challenges in implementing GA in clinical practice will be discussed.
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