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Contrast mechanisms in photothermal scanning tunneling microscopy (1994)

Probst, O. ; Grafström, S. ; Fritz, J. ; [et al.]

Springer

Applied physics 59 (1994), S. 109-113

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ISSN: 1432-0630

Keywords: 42.60.Fc ; 61.30 ; 68.15

Source: Springer Online Journal Archives 1860-2000

Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics

Notes: Abstract By irradiation of the tunneling junction of a scanning tunneling microscope with intensity-modulated laser light a gap-width modulation due to thermal expansion of tip and sample was produced. Photothermal images were obtained by spatial mapping of the resulting modulation of the tunneling current or its logarithm. The various mechanisms responsible for the observed contrast are discussed quantitatively. In case of a highly corrugated gold film on mica the contrast arises mainly from either the current variations caused by the non-zero reaction time of the current control loop or from a geometry factor. In both cases the images reflect certain properties of the sample topography. On the other hand, for a liquid-crystal film adsorbed on graphite a contrast on a molecular scale was found which is attributed to variations of the effective barrier height.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00332202

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Structure evolution in the PbO-ZrO2-TiO2 sol-gel system: Part I — Characterization of prehydrolyzed precursors (1994)

Coffman, P. R. ; Dey, S. K.

Springer

Journal of sol gel science and technology 1 (1994), S. 251-265

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ISSN: 1573-4846

Keywords: precursor synthesis ; complexation reactions ; spectroscopy and analytical chemistry ; ferroelectric films

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology

Notes: Abstract In this investigation, several spectroscopic and analytical techniques were used to determine the chemical compositions and structures of the lead, zirconium, titanium, and Pb-(Zr, Ti) alkoxides involved in the sol-gel synthesis of PZT thin films. These techniques included 1H, 13C, and 207Pb NMR; FT-IR; gas chromatography; Karl Fischer titration; and number-average molecular weights (M n ) determined by cryoscopy. It was found that the titanium precursor had a M n of 548 and a formula of [Ti(OCH2CH2OCH3)4]1.6; the zirconium precursor had a M n of 1015 and a formula of [Zr(OCH2CH2OCH3)4]2.6; and the lead precursor had a formula Pb6(OOCCH3)5(OCH2CH2OCH3)7. 4 H2O and a molecular weight of 2131 (M n =2113). It was observed that residual water from the incomplete dehydration of lead acetate trihydrate coupled with released water due to the esterification of acetic acid caused M-O-M (M=Pb, Zr, Ti) bonds in the Pb-(Zr, Ti) alkoxide. Two possible isomeric structures of the Pb-(Zr, Ti) alkoxide have been proposed. They are both cyclic and have a formula of Pb2M′M″O2(OR)8(ROH)2, (M′M″=Zr and/or Ti) and a molecular weight of 1336 (M n =1386).

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00486168

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Resistance to Ascochyta blight in chickpea - Genetic basis (1993)

Dey, S. K. ; Singh, Gurdip

Springer

Euphytica 68 (1993), S. 147-153

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ISSN: 1573-5060

Keywords: chickpea ; Cicer arietinum ; resistance ; Ascochyta blight ; Ascochyta rabiei ; genetics

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Summary Genetic regulation of host resistance in chickpea-Ascochyta rabiei interaction system is governed by two dominant complementary genes each in the genotypes GLG 84038 and GL 84099, whereas the resistance in a black seeded genotype ICC 1468 was controlled by one dominant and one recessive independent gene. In all the genotypes, resistance is operated by inter-allelic interactions. The genes conferring resistance in GLG 84038 were found to be different to those operating in GL 84099 and ICC 1468. Among the five dominant genes dispersed in 3 genotypes under study, at least one has been reported for the first time, as to date, only three dominant genes have been reported in the literature. The four identified dominant genes in GLG 84038 and GL 84099 have been named as Arc1, Arc2 (in GLG 84038) and Arc3, Arc4 (in GL 84099). The undistinguished dominant gene in ICC 1468 has been named as Arc5(3,4) as it could not be equated or differentiated from Arc3 or Arc4. The recessive gene in ICC 1468 has been named as Arc1. Generation mean analysis of the 6 resistant × susceptible crosses involving the same genotypes, revealed that the genes conferring resistance in any of the 3 genotypes did not follow simple Mendelian inheritance but were influenced by inter allelic interactions. Additive gene effect along with dominance were operative in all the 3 genotypes under study in conferring resistance. However, the mechanism of resistance in GLG 84038 and GL 84099 were primarily additive in nature while that in ICC 1468, dominance as well as dominance × dominance interactions were more important than additive gene action.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00024163

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