Study of the surface electromigration of In on Si(111) surfaces by the use of micro-electron-beams

The surface electromigration (SE) of ultrathin In films on Si(111)4 × 1-In surfaces has been investigated using experimental techniques based on μ-electron beams. On the basis of the finding that the SE velocity enhances as the strength of the electrostatic field (EF) fed through the substrate enhances, it is strongly suggested that the driving force of SE is an EF rather than a DC current fed through the substrate. It is found that a patch of ultrathin In film changes to an In patch of 1 × 1 periodicity during SE which is accompanied by spotty parts (named fine-polygons) at both the cathode and anode sides of the In patch. It is found that the fine-polygons are created at the cathode side and are stationary but grow in size to be eventually incorporated into the In-patch. A few In-islands are found on the cathode side of the In-patch and they show no translation but cycles of appearance, growth, decay, and disappearance during SE, by which mass-transportation is achieved. A plausible microscopic model for the SE is presented based on these findings.     

On the evaluation of the energies of hybridized valence states

The method of evaluation of the valence-state energy from the observed term values, as proposed originally by Moffitt [1] for unhybridized valence state and extended by Öpik [3] to the hybridized one, is critically reviewed. It is shown for the hybridized valence states that off-diagonal terms, corresponding to interactions among multiplets of the same symmetry arising from different configurations participating in the hybridized valence state, must also be considered in addition to the diagonal terms considered in Öpik's method. Actual procedure of doing this is given. A numerical example given shows that the improvement of Öpik's method proposed here may be ignored in a crude theory but is worth considering in order that the accurate value of the valence-state energy be obtained.

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Zusammenfassung Das Verfahren zur Berechnung der Energie von Valenzzuständen, wie es von Öpik für den Fall hybridizierter Orbitale erweitert wurde, wird bezüglich der Behandlung von Nichtdiagonalelementen kritisiert. Es wird gezeigt, daß solche Terme, die der Wechselwirkung von Multipletts gleicher Symmetrie, aber verschiedener Konfiguration entsprechen, nur bei verhältnismäßig groben Rechnungen vernachlässigt werden dürfen. Anhand eines Beispiels wird gezeigt, daß sie bei größeren Ansprüchen an die Genauigkeit eingeschlossen werden sollten.

     

Synthesis of nonionic reduced-sugar based bola amphiphiles and gemini surfactants with an α,ω-diamino-(oxa)alkyl spacer

Reduced-sugar based gemini surfactants with an α,ω-diamino-(oxa)alkyl spacer exhibit a rich pH-dependent aggregation behavior and are efficient DNA carriers in gene transfection. Herein, we describe an improved synthetic procedure for these amphiphiles. First, a series of novel nonionic bolaform amphiphiles with identical headgroups and α,ω-diamino-(oxa)alkyl spacers were synthesized by reductive aminations involving α,ω-diaminoalkanes and the appropriate sugars or aldehydes. The bolaform compounds were used as starting materials for the synthesis of the corresponding reduced-sugar based gemini surfactants in a reductive alkylation reaction employing a polymer-bound cyanoborohydride. A series of new gemini surfactants have been synthesized and characterized.     

N-Arylation of 4-fluoro-5-trimethylsilyl-1H-pyrazole

The 1,3-dipolar cycloaddition reaction of fluoro(trimethylsilyl)acetylene prepared in situ with an excess of diazomethane smoothly proceeded to give the corresponding 4-fluoro-5-trimethylsilyl-1H-pyrazole in 84% yield. The copper iodide-catalyzed N-arylation of the fluorinated pyrazole with a variety of aryl iodides afforded N-aryl-4-fluoropyrazoles as desilylation products in good to excellent yields.     

Byzantine wall paintings from Mani (Greece): microanalytical investigation of pigments and plasters

The present case study concerns the technology of Byzantine wall paintings from the Mani Peninsula, Greece. An assemblage of 12 Byzantine churches, constructed in the tenth to fifteenth century, was included in an initial analytical survey. Two random samples of wall paintings were taken in each monument in order to study their micro stratigraphy and the composition of pigment and plaster layers. Polished sections were fabricated for examination with optical microscopy and scanning electron microscopy (SEM). Furthermore, selected samples were powdered and analysed with Fourier-transformed infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The analytical results achieved in this case study provided general conclusions concerning painting techniques for wall paintings in a rather provincial area of the Byzantine Empire. The palette comprised mainly earthen pigments like ochres and carbon black but occasionally also other pigments like cinnabar, minium and ultramarine. In view of future studies, a portable X-ray fluorescence analysis (XRF) set-up was tested.     

d-band broadening of noble-metal particles

For Cu particles embedded in a SiO₂ matrix, the size-dependent change in the width of the d-band has been investigated in the size region from about 35 to 160 Å in diameter by measuring the energy position of the interband-transition absorption of Cu island films in the photon-energy region from 1.5 to 6.5 eV. This position gives the energy spacing which reflects the width of the d-band. Below about 100 Å in diameter, the energy spacing increased with decreasing particle size. This increase supports the d-band broadening due to lattice contractions.     

Large stabilization of a DNA duplex by the deoxyadenosine derivatives tethering an aromatic hydrocarbon group

Novel deoxyadenosine derivatives tethering a phenyl or naphthyl group by means of an amido linker have been synthesized, and these derivatives, stacking on the 5' end of a DNA duplex, provide free energy contributions equal to or greater than that of the Watson-Crick A/T base pair.     

Systematic determination of the Slater-Condon parameters of atoms and ions with 1s 2 2s m 2p n configurations

Semiempirical values of the Slater parameters F ²(2p,2p) and G ¹(2s, 2p) have been determined for the atoms and ions with the electron configurations 1s ²2s ^m2p ⁿ from the experimental atomic energy levels. Particular attention has been paid to get the values of the parameters to be used for semiempirical calculations on molecular electronic structure. The calculation has also yielded E _av's, the average energies of configurations of these atoms. Evaluation of the semiempirical or effective value of F ⁰ from E of an appropriate electron-transfer reaction, based on the idea presented by Anno [15], is also referred to in the present paper. The semiempirical values of the Slater parameters as well as those of E's and E _av's show almost linear dependence upon atomic number Z through isoelectronic series. From the overall tendency of the correlation lines, it is pointed out that the assignment of atomic energy levels of Na⁵⁺ (1s ²2p ⁴) must be wrong.

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Zusammenfassung Semiempirische Werte der Slater-Parameter F ²(2p,2p) und G ¹(2s, 2p) wurden für die Atome und Ionen mit der Elektronenkonfiguration 1s ²2s ^m2p ⁿ aus den experimentellen atomaren Energietermen bestimmt. Insbesondere wurden die Parameter bestimmt, die für semiempirische Berechnungen der Elektronenstruktur von Molekülen benötigt werden. Die Berechnung ergibt weiterhin Werte von E _av, der Durchschnittsenergie der Konfigurationen der genannten Atome. Die vorliegende Arbeit geht auch auf die Bestimmung des semiempirischen bzw. effektiven Wertes von F ⁰ aus E einer geeigneten Elektronenübertragungsreaktion ein, die auf die Arbeit von Anno [15] zurückgeht. Die semiempirischen Werte der Slater-Parameter sowie der E und E _av zeigen annähernd lineare Abhängigkeit von der Atomnummer Z innerhalb isoelektronischer Reihen. Aus dem Gesamtverhalten der genannten Kurven wird geschlossen, da die Zuordnung der atomaren Energieterme von Na⁵⁺(1s ²2p ⁴) falsch sein dürfte.

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Résumé Détermination à partir des niveaux d'énergie atomiques expérimentaux des valeurs semi-empiriques des paramètres de Slater F ²(2p, 2p) et G ¹(2s, 2p) pour les atomes et les ions ayant les configurations 1s ²2s ^m2p ⁿ. On a fait particulièrement attention d'obtenir les valeurs des paramètres à utiliser pour des calculs moléculaires semi-empiriques. Le calcul a aussi fourni les énergies moyennes des configurations de ces atomes. On évoque aussi le calcul de la valeur semi-empirique ou effective de F ⁰ à partir du E d'une réaction appropriée de transfert électronique, selon une idée de Anno [15]. Les valeurs semiempiriques des paramètres de Slater, ainsi que celles des E et E _moy, montrent une dépendance presque linéaire au nombre atomique Z à travers les séries isoélectroniques. A partir des tendances générales des lignes de corrélation, on remarque que l'attribution des niveaux d'énergie atomiques de Na⁵⁺(1s ²2p ⁴) doit être fausse.

     

Quantification of cerebral metabolites in glioma patients with proton MR spectroscopy using T2 relaxation time correction

This study was aimed to investigate the significance of absolute concentration of metabolites in glioma patients using proton MR spectroscopy (MRS) with T2 relaxation time correction using three different echo times. The absolute concentrations of metabolites in 7 normal subjects and in 23 gliomas (10 low-grade, 13 high-grade) were obtained by proton MRS using a tissue water signal as an internal standard. The signal intensities of metabolites and tissue water were corrected by T2 relaxation time. In low-grade glioma, the T2 relaxation time of NAA was shorter, and T2 relaxation time of water was prolonged as compared to normal subjects (p < 0.001). In high-grade glioma, the T2 relaxation time of NAA (p < 0.001) and T2 relaxation time of Cr (p < 0.01) were shorter, and T2 relaxation time of water (p < 0.001) was prolonged as compared to normal subjects. Moreover, high-grade gliomas revealed a shorter T2 relaxation time of Cr than low-grade gliomas (p < 0.05). In glioma, NAA and Cr concentration were decreased, and Cho were increased as compared to normal subjects. Moreover, high-grade glioma revealed a significant lower Cr (p < 0.001) and Cho (p < 0.01) concentration compared to low-grade gliomas. Low Cr concentration is the most reliable indicator of malignancy in glioma. Cho concentration did not correlate with malignancy in gliomas.