Role of Oxygen in Rare Earth Chalcogenide Semiconductors

1987 ◽  
Vol 97 ◽  
Author(s):  
Cheryl M. Vaughan ◽  
William B. White
Keyword(s):  
Rare Earth ◽  
Unit Cell Volume ◽  
Oxygen Impurity ◽  
Ordered Structure ◽  
Impurity Bands ◽  
Beta Structure ◽  
Effect Of Oxygen ◽  
High Degree ◽  
Degree Of Order

ABSTRACTOxygen uptake by the rare earth chalcogenides takes place through a series of ordered compounds. At high oxygen concentrations the distinct and nearly stoichiometric oxychalcogenides, Ln202X (X = S, Se, Te) appear. For the chalcogenides of the larger rare earths there appears an ordered oxygen-containing beta structure, Ln10X14OxX1-x (X = S, Se). The vibrational spectrum of the trigonal oxysulfide structure contains four infrared and four Raman bands (2 A2u + 2 Eu + 2 Alg + 2 Eg). Band wavenumbers across the La to Lu series vary linearly with unit cell volume. The Raman bands are sharp indicating a high degree of order in the intermediate compounds. The Raman bands of the beta structure are remarkably sharp indicating that this compound also has a highly ordered structure. Known data plus synthesis data are combined to form not-impossible phase diagrams for the larger rare earth sulfide systems. The effect of oxygen in both series of compounds is to produce small wavenumber shifts rather than high wavenumber oxygen impurity bands.

How do Impurities Affect the Growth of μc-Si:H?

1998 ◽  
Vol 507 ◽  
Author(s):  
Toshihiro Kamei ◽  
Makoto Fukawa ◽  
Tatsuyuki Nishimiya ◽  
Masao Isomura ◽  
Michio Kondo ◽  
...  
Keyword(s):  
Small Volume ◽  
Volume Fraction ◽  
Defect Density ◽  
Hydrogen Desorption ◽  
Oxygen Impurity ◽  
Surface Hydrogen ◽  
Small Volume Fraction ◽  
Higher Temperature ◽  
Effect Of Oxygen

ABSTRACTUltra clean plasma CVD process opens the doorway to clarify the role of impurities in the growth process of μc-Si:H. A reduction of impurity levels during the growth extends the temperature range for crystalline formation to lower side, i.e., high-crystallinity μc-Si:H formation even at room temperature, substantially reduces midgap defect density at 200°C, and enlarges crystalline grain size at 350°C. These results imply that impurities disrupt crystalline formation even on hydrogen covered surface. The crystalline-to-amorphous transition is induced by a loss of surface hydrogen coverage due to thermal hydrogen desorption at higher temperature of ∼450°C irrespective of the effect of oxygen impurity. Light-soaking experiments for the series of the films from a-Si:H to μc-Si:H films with different crystalline volume fraction indicate that the presence of small volume fraction of crystallite significantly suppresses light induced defect creation under the present light soaking condition of 3SUN 60°C 6hr. These results are explained in terms of preferential recombination of photo-excited carriers in the crystallite.

Feasibility of Molecular Structure Determination With a High Resolution Electron Microscope

1968 ◽  
Vol 26 ◽  
pp. 338-339
Author(s):  
T. A. Welton
Keyword(s):  
Electron Microscope ◽  
Substrate Surface ◽  
Helical Axis ◽  
Base Plane ◽  
Resolution Electron ◽  
High Resolution Electron Microscope ◽  
High Degree ◽  
Degree Of Order ◽  
Purine Pyrimidine

An ultimate design goal for an improved electron microscope, aimed at biological applications, is the determination of the structure of complex bio-molecules. As a prototype of this class of problems, we propose to examine the possibility of reading DNA sequence by an imaginable instrument design. This problem ideally combines absolute importance and relative simplicity, in as much as the problem of enzyme structure seems to be a much more difficult one.The proposed technique involves the deposition on a thin graphite lamina of intact double helical DNA rods. If the structure can be maintained under vacuum conditions, we can then make use of the high degree of order to greatly reduce the work involved in discriminating between the four possible purine-pyrimidine arrangements in each base plane. The phosphorus atoms of the back bone form in projection (the helical axis being necessarily parallel to the substrate surface) two intertwined sinusoids. If these phosphorus atoms have been located up to a certain point on the molecule, we have available excellent information on the orientation of the base plane at that point, and can then locate in projection the key atoms for discrimination of the four alternatives.

Comparison of TEM and STM observations of small silver clusters on different carbon supports

1990 ◽  
Vol 48 (4) ◽  
pp. 264-265
Author(s):  
Bernd Tesche ◽  
Tobias Schilling
Keyword(s):  
Vibration Isolation ◽  
Pyrolytic Graphite ◽  
Carbon Film ◽  
Silver Clusters ◽  
Carbon Supports ◽  
Stacking Order ◽  
System P ◽  
High Resolution Tem ◽  
High Degree ◽  
Degree Of Order

The objective of our work is to determine:a) whether both of the imaging methods (TEM, STM) yield comparable data andb) which method is better suited for a reliable structure analysis of microclusters smaller than 1.5 nm, where a deviation of the bulk structure is expected.The silver was evaporated in a bell-jar system (p 10−5 pa) and deposited onto a 6 nm thick amorphous carbon film and a freshly cleaved highly oriented pyrolytic graphite (HOPG).The average deposited Ag thickness is 0.1 nm, controlled by a quartz crystal microbalance at a deposition rate of 0.02 nm/sec. The high resolution TEM investigations (100 kV) were executed by a hollow-cone illumination (HCI). For the STM investigations a commercial STM was used. With special vibration isolation we achieved a resolution of 0.06 nm (inserted diffraction image in Fig. 1c). The carbon film shows the remarkable reduction in noise by using HCI (Fig. 1a). The HOPG substrate (Fig. 1b), cleaved in sheets thinner than 30 nm for the TEM investigations, shows the typical arrangement of a nearly perfect stacking order and varying degrees of rotational disorder (i.e. artificial single crystals). The STM image (Fig. 1c) demonstrates the high degree of order in HOPG with atomic resolution.

The Organization of Actin Filaments in the Stereocilia of the Bird Cochlea

1980 ◽  
Vol 38 ◽  
pp. 554-555
Author(s):  
E.J. Battles ◽  
D. DeRosier ◽  
J.C. Saunders ◽  
L.G. Tilney
Keyword(s):  
Hair Cell ◽  
Diffraction Pattern ◽  
Sea Urchin ◽  
Actin Filaments ◽  
Optical Diffraction ◽  
Dense Material ◽  
Apical Surface ◽  
Structural Rigidity ◽  
High Degree ◽  
Degree Of Order

Extending from the apical surface of each hair cell of the chick cochlea are from 75 to 200 microvilli or stereocllia and one true cllium, the kinocilium. The stereocllia are arranged in rows of progressively increasing length (Fig. 1). Within each tapering sterocilium is a bundle of actin filaments with over 900 filaments near the tip yet only approximately 25 at the base where filaments are enmeshed in a dense material (Fig. 1); from here some of the filaments enter the apical surface of the cell (cuticular plate) as a rootlet. Examination of longitudinal sections of the stereocilia (Fig. 2) show that the filaments are aligned parallel to each other and show considerable order. Examination of an optical diffraction pattern of this bundle (Fig. 4) reveal that the actin filaments are packed such that the crossover points of adjacent actin filaments are inregister. A prominent reflection at 125Å−1 demonstrates that the filaments are cjossbridged by a macromolecular bridge situated at an average of 125Å−1 intervals (Fig. 4) in transverse sections the filaments appear hexagonally packed although there are regions where the filaments are less ordered (Fig. 3). In images processed in the computer to remove, noise and enhance detail periodic nature of the bridge can be clearly seen (see arrows Fig. 5). This image resembles that of an actin paracrystal formed from sea urchin extract composed of bundles of actin filaments crossbridged by a second protein. Thus the actin filaments in the bird stereocilia by being cross-bridged and packed with a high degree of order and produces a structure with considerable structural rigidity. Embryos were studied at various stages in development in an attempt to determine how the stereocilia form and how does the actin packing develops. These stages will be discussed.

THE PROVENANCE OF WINE: THE ROLE OF BEDROCK AND SOIL IN TRANSFERRING TRACE AND RARE EARTH ELEMENTS INTO WINE GRAPES, SONOMA COUNTY, CA

2019 ◽  
Author(s):  
Kylie E. Dupuis ◽  
◽  
Owen A. Anfinson ◽  
Laura Waters ◽  
Holli M. Frey ◽  
...  
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Wine Grapes ◽  
Sonoma County

Effect of oxygen impurity on thermal conduction rate of poly‐crystalline Si 3 N 4

2021 ◽  
Author(s):  
Hwan Soo Dow ◽  
Moonkyong Na ◽  
Yeon Wook Jung ◽  
Seung Geun Jo ◽  
Jung Woo Lee
Keyword(s):  
Thermal Conduction ◽  
Oxygen Impurity ◽  
Effect Of Oxygen

scholarly journals Roles of ncRNAs as ceRNAs in Gastric Cancer

Genes ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 1036
Author(s):  
Junhong Ye ◽  
Jifu Li ◽  
Ping Zhao
Keyword(s):  
Gastric Cancer ◽  
Research Strategy ◽  
Circular Rnas ◽  
Messenger Rnas ◽  
Cerna Network ◽  
Degree Of Malignancy ◽  
High Degree ◽  
Competitive Endogenous Rna ◽  
Made In

Although ignored in the past, with the recent deepening of research, significant progress has been made in the field of non-coding RNAs (ncRNAs). Accumulating evidence has revealed that microRNA (miRNA) response elements regulate RNA. Long ncRNAs, circular RNAs, pseudogenes, miRNAs, and messenger RNAs (mRNAs) form a competitive endogenous RNA (ceRNA) network that plays an essential role in cancer and cardiovascular, neurodegenerative, and autoimmune diseases. Gastric cancer (GC) is one of the most common cancers, with a high degree of malignancy. Considerable progress has been made in understanding the molecular mechanism and treatment of GC, but GC’s mortality rate is still high. Studies have shown a complex ceRNA crosstalk mechanism in GC. lncRNAs, circRNAs, and pseudogenes can interact with miRNAs to affect mRNA transcription. The study of the involvement of ceRNA in GC could improve our understanding of GC and lead to the identification of potential effective therapeutic targets. The research strategy for ceRNA is mainly to screen the different miRNAs, lncRNAs, circRNAs, pseudogenes, and mRNAs in each sample through microarray or sequencing technology, predict the ceRNA regulatory network, and, finally, conduct functional research on ceRNA. In this review, we briefly discuss the proposal and development of the ceRNA hypothesis and the biological function and principle of ceRNAs in GC, and briefly introduce the role of ncRNAs in the GC’s ceRNA network.

Surgeon-performed Ultrasound for Primary Hyperparathyroidism

2013 ◽  
Vol 79 (7) ◽  
pp. 681-685 ◽  
Author(s):  
Worthington G. Schenk ◽  
John B. Hanks ◽  
Philip W. Smith
Keyword(s):  
Primary Hyperparathyroidism ◽  
Class 1 ◽  
Additional Imaging ◽  
Surgical Cure ◽  
Operative Findings ◽  
Enhanced Computed Tomography ◽  
High Degree ◽  
Tomography Scan ◽  
Parathyroid Imaging

The role of preoperative parathyroid imaging continues to evolve. This study evaluated whether surgeon-performed ultrasound (U/S) obviates the need for other imaging studies and leads to a focused exploration with a high degree of surgical success. From July 2010 to February 2012, 200 patients presenting with nonfamilial primary hyperparathyroidism underwent neck U/S in the surgeon's office. The U/S interpretation was classified as Class 1 if an adenoma was identified with high confidence, Class 2 if a possible but not definite enlarged gland was imaged, and Class 0 (zero) if no adenoma was identified. The findings were correlated with subsequent intra-operative findings. There were 144 Class 1 U/Ss (72%); of 132 patients coming to surgery, 96.2 per cent had surgical findings concordant with preoperative U/S and all had apparent surgical cure. Twenty-nine patients (14.5%) had Class 2 U/S; the 31 per cent confirmed false-positives in this group were usually colloid nodules. Fourteen of 27 with Class 0 U/S underwent surgery after being offered dynamically enhanced computed tomography scan. All 200 patients were apparent surgical cures. Surgeon-performed U/S is expedient, convenient, inexpensive, and accurate. A clearly identified adenoma can safely lead to a focused limited exploration and avoid additional imaging 93 per cent of the time.

The academic profession in Russia’s two capitals: The impact of 20 years of transition

2017 ◽  
Vol 16 (5) ◽  
pp. 626-644 ◽  
Author(s):  
Elizaveta Sivak ◽  
Maria Yudkevich
Keyword(s):  
Large Scale ◽  
Academic Career ◽  
Academic Profession ◽  
University Faculty ◽  
Key Characteristics ◽  
Personal Strain ◽  
High Degree ◽  
The Impact ◽  
Russian Universities

This paper studies the dynamics of key characteristics of the academic profession in Russia based on the analysis of university faculty in the two largest cities in Russia – Moscow and St Petersburg. We use data on Russian university faculty from two large-scale comparative studies of the academic profession (‘The Carnegie Study’ carried out in 1992 in 14 countries, including Russia, and ‘The Changing Academic Profession Study’, 2007–2012, with 19 participating countries and which Russia joined in 2012) to look at how faculty’s characteristics and attitudes toward different aspects of their academic life changed over 20 years (1992–2011) such as faculty’s views on reasons to leave or to stay at a university, on university’s management and the role of faculty in decision making. Using the example of universities in the two largest Russian cities, we demonstrate that the high degree of overall centralization of governance in Russian universities barely changed in 20 years. Our paper provides comparisons of teaching/research preferences and views on statements concerning personal strain associated with work, academic career perspectives, etc., not only in Russian universities between the years 1992 and 2012, but also in Russia and other ‘Changing Academic Profession’ countries.

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