Engineering gold alloys for plasmonics

We demonstrate the formation of metal alloys in Au–Ag, Au–Cu and Au–Pd systems and the experimental determination of their optical properties using optical transmission and reflection spectroscopy. The optical constants define the plasmon resonance wavelength and electromagnetic field local intensity. However, the optical constants behavior cannot be precisely modeled based on the data of pure metals due to unknown morphology and composition of the alloy. It has to be determined experimentally. We demonstrate the surface-enhanced Raman scattering using alloy metals. Depending on the metal to which molecules are adsorbed, we observe enhancement of different Raman modes. It is mainly due to the chemical enhancement effect between metal and molecules.     

Self-diffusion of aluminium in the intermetallic compound Fe-48 at.% Al

The self-diffusion coefficient of Al in the B2-type intermetallic compound Fe-48 at.% Al has been determined using the intrinsic diffusion coefficients of Fe and Al and the self-diffusion coefficient of Fe with the help of the Darken-Manning relation. The self-diffusion coefficient of Al in Fe-48 at.% Al is estimated to be a factor of about 0.6 smaller than that of Fe, and the activation energy for the self-diffusion of Al is obtained to be 280 kJ mol^?1 which is a little larger than the value of 262 kJ mol^?1 for the self-diffusion of Fe, indicating that the diffusion mechanisms for both components are nearly equal.     

Diffusion of chromium and manganese in γ-TiAl

The γ-TiAl intermetallic compound with suitable alloying additions has shown considerable promise as a material for high-temperature applications. Diffusion studies in this alloy system are useful in assessment of their creep behaviour and structural stability in service conditions. Tracer diffusion coefficients of ⁵¹Cr and ⁵⁴Mn in a γ-TiAl intermetallic compound containing 54.1 at. % aluminium were determined in the temperature range from 1095 to 1470?K. The temperature dependence of both the diffusing species follows a linear Arrhenius behaviour and can be expressed as D _Cr?=?4.4?×?10^?3exp(?350?kJ?mol^?1/RT)?m^2?s^?1 and D _Mn?=?1.2?×?10^?3?×exp(?326?kJ?mol^?1/RT)?m^2?s^?1. The data are analysed on the basis of empirical correlations between the diffusion and melting parameters applicable for conventional mono-vacancy diffusion mechanism in metals. It is concluded that impurity diffusion in γ-TiAl occurs through the migration of thermal vacancies via nearest-neighbour or next-nearest neighbour jumps.     

Momentum dependence of spin polarization for beta emitting nuclei produced through charge exchange reaction at intermediate energy

Hyperfine interactions were studied in the intermetallic compound GdRh₂Si₂ by perturbed angular correlation (PAC) technique using ¹⁸¹Hf(¹⁸¹Ta) probe nuclei. The measurements were performed in the temperature range 15–285 K. The PAC spectra above the antiferromagnetic ordering temperature of the GdRh₂Si₂ compound (T _N ～ 106 K), were analyzed using a model that included only electric quadrupole interactions. The observed major fraction was assigned to the ¹⁸¹Hf(¹⁸¹Ta) probe substituting the Gd atoms. The PAC spectra below Néel temperature were analyzed using combined electric quadrupole and magnetic dipole interactions. The B_hf value at Gd, measured at 15 K was found to be 1.4(1) T which, is smaller, when compared with the values obtained in this compound using other nuclear probes, ¹⁵⁵Gd (B_hf ～ 30 T) and ¹⁴⁰Ce (B_hf ～ 26 T). The present result using ¹⁸¹Hf(¹⁸¹Ta) probe is quite interesting since it shows that the contribution to B_hf at Gd due the host is smaller than other components which contribute to the hyperfine field. The temperature dependence of B_hf shows an anomalous behavior.     

Design,Synthesis and Physical Properties of New Liquid Crystal Materials for Active Matrix LCD (1)

Abstract

Liquid crystal materials having a decahydronaphthalene ring structure were designed for active matrix LCD and were prepared by hydrogenation of the ocatahydronaphthalenes obtained through the reaction of a fluorinated phenyl magnesium bromide with the 6-alkyl-decahydronaphthalen-2-ones and followed by dehydration. These compounds exhibit wide nematic temperature ranges with low melting points and very low birefringences. These results are useful for design of new liquid crystal mixtures for TFT-displays.     

Addendum to “On the Sectional Geometric Genus of Quasi-Polarized Varieties,I” by Yoshiaki Fukuma

Let (X, L) be a polarized manifold defined over the complex number field with dim X = n such that L is very ample. In this article, we will improve the classification of (X, L) with g ₂(X, L) = h ²(𝒪 _X ) + 1 which was obtained in Fukuma (Fukuma 2004 Fukuma , Y. ( 2004 ). On the sectional geometric genus of quasi-polarized varieties, I . Comm. Alg. 32 : 1069 – 1100 .[Taylor &; Francis Online], [Web of Science ®] , [Google Scholar], Theorem 3.6), where g ₂(X, L) denotes the second sectional geometric genus of (X, L).     

Catalytic Condensation of Primary Amines, Dehydrogenation of Secondary Amines, and Dealkylation of Tertiary Amines over Solid-State Rhenium Sulfide Clusters with an Octahedral Metal Framework

When solid-state rhenium sulfide clusters with an octahedral metal framework are treated in a hydrogen stream above 300 °C, a catalytic activity for condensation of butylamine to yield N-butylidenebutylamine develops. Primary amines such as ethylamine, pentylamine, and hexylamine are also converted to the corresponding N-alkylidenealkylamines. Secondary amines such as diethylamine, dipropylamine, and dibutylamine are dehydrogenated to the corresponding N-alkylidenealkylamines. When triethylamine is allowed to react, dealkylation proceeds to yield diethylamine and its dehydrogenated product N-ethylideneethylamine. Trimethylamine is also dealkylated to dimethylamine. This series of catalytic behavior is the same as that of palladium and platinum metals. The similarity in selectivity is attributable to the rhenium atom that accepts electrons from the sulfur ligands leading to isoelectronic with the platinum group metals.     

Catalytic Cycloisomerization of 1,5‐Enynes to 1,3‐Cyclohexadienes via Ruthenium Vinylidene Intermediates

Another way to dienes : The ruthenium‐catalyzed 6‐endo‐cycloisomerization of 1,5‐enynes gives the corresponding 1,3‐cyclohexadienes in high to excellent yields. This novel synthetic and catalytic method constitutes another way to selectively prepare 1,3‐cyclohexadienes, this cyclic diene skeleton being a core subunit in many natural products and a useful building block for a variety of organic transformations.

     

Solvation of xyloglucan in water/alcohol systems by molecular dynamics simulation

Xyloglucan in water solution turns into a gel with addition of alcohol such as methanol and ethanol. In regard to this phenomenon, we investigated the adhesive property of alcohol to xyloglucan and proposed the mechanism of the gelation by molecular dynamics (MD) simulation of a xyloglucan in water, water/methanol, and water/ethanol solution for 10 ns. The alcohol molecules showed its adhesive property to the xyloglucan and made the swelling-shrinking motion of the xyloglucan slow. Alcohol molecules solvated to the xyloglucan mainly in hydrophobic way so as to fill the void of water hydration shell, resulting in reformation of the hydrogen-bond network of water molecules around the solute. We also found that alcohol molecules have strong tendency to hydrogen-bond on xylose O3 in xyloglucan. According to these results, we proposed the gelation mechanism of xyloglucan in water/alcohol solution.     

Pattern Formations in Heat Convection Problems

After Bénard＇s experiment in 1900, Rayleigh formulated heat convection problems by the Oberbeck-Boussinesq approximation in the horizontal strip domain in 1916. The pattern formations have been investigated by the bifurcation theory, weakly nonlinear theories and computational approaches. The boundary conditions for the velocity on the upper and lower boundaries are usually assumed as stress-free or no-slip. In the first part of this paper, some bifurcation pictures for the case of the stress-free on the upper boundary and the no-slip on the lower boundary are obtained. In the second part of this paper, the bifurcation pictures for the case of the stress-free on both boundaries by a computer assisted proof are verified. At last., Bénard-Marangoni heat convections for the ease of the free surface of the upper boundary are considered.