Metallic Series Research Articles

Rare earth size dependence of Nernst thermopower in ferromagnetic perovskites: R0.6Sr0.4CoO3 (R = La, Pr, and Nd)

Here, we report the Nernst thermopower (Sxy)- generation of a dc electrical voltage transverse to the applied temperature gradient and magnetic field- in the ferromagnetic metallic oxide series: R0.6Sr0.4CoO3 for rare earth cations (R = La, Pr and Nd) of different ionic radii. Besides Sxy, longitudinal thermopower (Sxx) and resistivity in absence of an external magnetic field were also measured. In each of these samples, Sxy increases rapidly around the ferromagnetic Curie temperature (TC), goes through a maximum value at a certain temperature, and decreases towards zero in low temperatures. The field dependence of Sxy measured at a fixed temperature exhibits hysteresis similar to magnetization, which indicates magnetic contribution (anomalous) to the measured Sxy. The sample possessing the largest ionic radius (R = La) shows the maximum Sxy value (~0.264 μV/K for H = 2 kOe) in this series. Our work guides that future studies need to be focused on the La-based cobaltites to enhance Sxy value through optimizing compositions.

Study of Relative Metallic Character of Noble Metals Cu, Ag and Au at Normal Temperatures

The relative metallic character of noble metals, Cu, Ag & Au has been suggested by their physical and chemical properties. Their position in the metallic series is in the neighborhood of that of Li, Mg and Zn. These Metals are inferior of Li, Mg, Zn, Fe, Co and Ni in metallic character. Li, Mg, Zn, Fe, Co and Ni are inferior to Na, K, Rb, Cs, Ca, Ba and Sr. The noble metals have simple metallic character in physical properties at normal temperatures.

Structural, Elastic, Electronic Properties and Interatomic Interactions in Metallic Tetraboride Series MB4 (M = Ru, Rh, Pd, Os, Ir, and Pt) Obtained from FLAPW–GGA Calculations

The report presents the results of systematic first-principle FLAPW–GGA calculations of a series of metallic tetraborides MB4 (where M = Ru, Rh, Pd, Os, Ir, and Pt) with space groups Pmmn, Immm, R-3m, and Pnnm. Their equilibrium structural parameters, cohesion and formation energies, elastic constants, anisotropies, Vickers microhardnesses, Debye temperatures, sound velocities, as well as electronic properties and interatomic interactions are estimated and analyzed as compared to each other and the available theoretical data.

Electrofluid hydrolysis enhances the production of fermentable sugars from corncob via in/reverse-phase induced voltage

To improve the economic value of lignocellulosic biomasses, an innovative electrofluidic technology has been applied to the efficient hydrolysis of corncob. The system combines fluidic reactors and induced voltages via magnetoelectric coupling effect. The excitation voltage had a positive impact on reducing sugar content (RSC). But, the increase of voltage frequency at 400–700Hz caused a slight decline of the RSC. Higher temperature limits the electrical effect on the hydrolysis at 70–80°C. The energy efficiency increased under the addition of metallic ions and series of in-phase induced voltage to promote hydrolysis. In addition, the 4-series system with in-phase and reverse-phase induced voltages under the synchronous magnetic flux, exhibited a significant influence on the RSC with a maximum increase of 56%. High throughput could be achieved by increasing series in a compact system. Electrofluid hydrolysis avoids electrochemical reaction, electrode corrosion, and sample contamination.

Benign Tracheal Stenosis Should Never be Stented With Metallic Devices

In this issue of Archivos de Bronconeumologia Serrano et al.1 report the results of an elegant experimental study on the rabbit trachea. The authors hypothesise that drug-eluting stents attenuate granuloma formation leading to inflammatory stenosis, which is a well-known adverse effect of metallic stents on the tracheal epithelium. As commented by the authors in the text, in 2005 the US Food and Drug Administration alerted healthcare professionals “to serious complications associated with the use of metallic tracheal stents in patients with benign airway disorders. . .including all covered and uncovered metallic tracheal stents”.2 In that safety alert for medical products, potential complications were described as “obstructive granulation tissue, stenosis at the ends of the stent, migration of the stent, mucous plugging, infection, and stent fracture”. Moreover, the notification alerted against the use of metallic stents as a bridge for definitive therapies due to the risks associated with removal. FDA recommendations are supported by the authors’ data. In their series, 40% of the cases (14 out of 30 animals) died as a result of the procedure. In the metallic stent series, mortality due to tracheal obstruction occurred in 80% of cases (8/10 rabbits). Therefore, we totally agree with the authors’ main conclusion: steel stents should never be indicated for the treatment of inflammatory tracheal stenosis. The second conclusion of the investigation (nitinol tracheal stents are the least reactive) is arguable, and should be reported in a different manner, since in the authors’ series, 20% of the nitinol stent-treated cases (2 out of 10) died due to airway obstruction. This would be a non-acceptable rate of adverse events in clinical series. Thus, it should be clearly stated that nitinol stents used inside a healthy trachea, in the authors’ experimental setting, were associated with mortality in 20% of cases. The use of drug-eluting stents in the airways has been rarely reported. Chao et al.3 implanted biodegradable cis-platinum

Enhanced effect of local fields in subwavelength metallic series nanocavities from surface plasmon polaritons

The enhancement and confinement characteristics of the local field in the two-dimensional (2D) subwavelength-size series cavities structure are investigated numerically by using the boundary integral method. The series cavities are built of two pieces of finite silver thin slabs with subwavelength corrugations on their inner boundaries, set in a face-to-face arrangement with a separating space, and the central part is a narrow channel (NC). We calculate the average amplitude of the local field in the NC as a function of the wavelength for exploring the influence of the structural parameters and demonstrate the amplitude distribution of the magnetic field in the structure and the cross-section distributions of the local field in the NC region along both the longitudinal axis direction and the transverse directions. The simulations show that the local field in the NC has significant enhancement, up to 2 orders of magnitude, of the incident light field, and the local light field is confined to a small region less than one fifth of the resonant wavelength in the longitudinal direction and one twentieth of the resonant wavelength in the lateral direction. Replacing the metallic material of the cavity walls with the semiconductor germanium leads to the complete disappearance of the enhancement of the local field. It is clearly shown that surface plasmon polaritons on the metal play a critical role for this enhancement phenomenon. The influences of various geometric parameters on the resonant wavelength and the peak value of the average amplitude of the local field are extensively investigated.

Nonuniversality of the non-Fermi-liquid state inCeRhSb1−xSnxcompounds on the Sn-rich side

We examine the electronic properties of the $\mathrm{Ce}\mathrm{Rh}{\mathrm{Sb}}_{1\ensuremath{-}x}{\mathrm{Sn}}_{x}$ metallic series with $0.78\ensuremath{\leqslant}x\ensuremath{\leqslant}1$ by treating the non-Fermi liquid (NFL) state of CeRhSn as a reference state. A nonuniversal behavior of the NFL phase is observed as a function of $x$, which is attributed to enhanced magnetic disorder effects introduced by alloying, from one side and to the role of spin fluctuations due to Rh $4d$ electrons from the other. The NFL behavior at the lowest temperatures is attributed to quantum critical fluctuations among $4f$ electrons due to Ce, whereas the spin fluctuations become pronounced at higher temperatures $Tg6\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. Thus, in Sn-rich samples those two types of fluctuations coexist. An itinerant-electron type of spin-glass-like state with a small magnetic moment appears at temperatures $T\ensuremath{\leqslant}5\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. These studies complement our previous work on the same system in the Sb-rich region, i.e., with $0\ensuremath{\leqslant}xl0.2$, where the Kondo semiconducting state evolves into NFL state via a quantum critical point located at $x\ensuremath{\cong}0.12$.

Strong correlation effects of the Re5delectrons on the metal-insulator transition inCa2FeReO6

We have investigated the electronic structure of polycrystalline ${\mathrm{Ca}}_{2}\mathrm{Fe}\mathrm{Re}{\mathrm{O}}_{6}$ using photoemission spectroscopy and band-structure calculations within the local-density $\text{approximation}+U$ $(\mathrm{LDA}+U)$ scheme. In valence-band photoemission spectra, a double-peak structure which is characteristic of the metallic double-perovskite series has been observed near the Fermi level $({E}_{\mathrm{F}})$, although it is less distinct compared to the ${\mathrm{Sr}}_{2}\mathrm{Fe}\mathrm{Mo}{\mathrm{O}}_{6}$ case. The leading near-${E}_{\mathrm{F}}$ structure has a very weak spectral weight at ${E}_{\mathrm{F}}$ above the metal-insulator transition (MIT) temperature ${T}_{\mathrm{MI}}$ of $\ensuremath{\sim}140\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, and it loses the ${E}_{\mathrm{F}}$ weight below ${T}_{\mathrm{MI}}$, forming a small energy gap. To reproduce this small energy gap in the calculation, we require a very large effective $U$ $({U}_{\mathrm{eff}})$ for Re $(4\phantom{\rule{0.3em}{0ex}}\mathrm{eV})$ in addition to a relatively large ${U}_{\mathrm{eff}}$ for Fe $(4\phantom{\rule{0.3em}{0ex}}\mathrm{eV})$. Although the most of the experimental features can be interpreted with the help of the band theory, the overall agreement between the theory and experiment was not satisfactory. We demonstrate that the effective transfer integral between Fe and Re is actually smaller than that between Fe and Mo in ${\mathrm{Ca}}_{2}\mathrm{Fe}\mathrm{Mo}{\mathrm{O}}_{6}$, which can explain both the MIT and very high ferrimagnetic transition temperature.

A thermophysical study of the melting process in alkyl chain metal n-alkanoates: The thallium (I) series

The peculiar thermal behavior of the thallium(I) n-alkanoates series (consisting in several transitions between polymorphic and mesomorphic phases) in comparison with other metallic n-alkanoates series is stated. The allowance of highly accurate adiabatic heat capacity data permits a study of the CH2 contributions to the lattice heat capacity curve at low temperature. Moreover, in this series an anomalous gradual enhancement of the lattice heat capacity has been interpreted from vibrational spectroscopy results as a noncooperative effect due to the internal hindered rotation of the alkyl chain (formation of gauche defects, even in the solid state). The thermodynamics of the “stepwise melting process” from the totally ordered solid at low temperature to the isotropic liquid is based on a revised lattice heat-capacity curve. This was used to evaluate the energy and entropy not only of the clear first order transitions present in the series but also of the described noncooperative effect. The CH2 enthalpy and entropy contribution for this series is estimated and a comparison with the published values for other series is carried out. Moreover, the texture of the mesophases is revealed by polarized light microscopy.

Fe-57 Mössbauer study of the (FeCo)75SiB metallic alloy series

Liquid-quenched metallic amorphous alloys (FeCo)75(SiB) have been studied by 57Fe Mössbauer spectroscopy at room temperature. Direct insight in the short-range order (SRO) and the bonding properties involving Fe atoms in these alloys is presented, taking apart clearly the metal and metalloid influence over such properties. A large increase of the SRO is found in the Co-rich alloys which is also affected by variations in the relative concentration of metalloids Si and B. Such SRO changes influence the bonding of Si and B with Fe. The substitution of B for Si decreases the Fe 3d polarization in the Co-rich alloys with large SRO.

Onset of itinerant ferromagnetism from Pauli paramagnet or semiconducting state in some Heusler phases

The study of different series of Heusler phases shows the influence of filling the 3d band on the formation of a local moment on Co sites, and on the intersite interactions. The cases of a metallic series, and a metal to semiconducting transition are compared.

The magnetostriction of CoFeNiMo metallic glasses measured with a tunneling transducer

The longitudinal magnetostriction as a function of the Co/Fe content of the metallic glass series Co 72− x Fe x Ni 3 Mo 1Si 12B 12, for 0 ≤ x ≤ 10, is reported. The measurement is performed using a novel technique, based on electron tunneling, which provides a highly sensitive, noncontact, quasi-dc and direct measurement of magnetostrictive strains. The minimum value of the longitudinal magnetostriction measured is (−1.65±0.24) ppm for 0% Fe, and the maximum (in this composition range) is (2.51±0.15) ppm for 10% Fe, with a zero-magnetostriction composition of 5.25% Fe. These data are compared to those previously reported for a similar metallic glass series, but with higher Mo content. Increasing the Mo content in these glasses is shown to decrease the Fe content at the zero-magnetostriction composition point.

Final-state screening contributions to the L3M4,5M4,5 and M5N4,5N4,5 Auger transitions in the 4d metals.

We report measurements of the effective Coulomb interaction of the final-state holes, or Auger parameter, of the ${\mathit{L}}_{3}$${\mathit{M}}_{4,5}$${\mathit{M}}_{4,5}$ transition in the 4d metallic series. By applying the excited-atom version of the quasiatomic model of hole screening, we show that it is possible to extract experimentally a purely valence-electron contribution to the Auger parameter. The systematic dependence on atomic number clearly manifests the effect of the type of screening charge. Comparison with 4d ${\mathit{M}}_{5}$${\mathit{N}}_{4,5}$${\mathit{N}}_{4,5}$ results indicates independence of the final-state nature within experimental error (\ensuremath{\simeq}\ifmmode\pm\else\textpm\fi{}0.5 eV), lending support to interpretations of d-band holes as corelike. The similarity with model results for the 5d series is striking and there is general agreement with calculations of metallic renormalization of the Auger parameter in the 4d series.

σ and π-interactions of the pyrrolic ligand of sandwich-like lanthanide phthalocyanines determined from magnetic susceptibility and ligand-field theory

The magnetic susceptibility data of praseodymium, neodymium, gadolinium, holmium and erbium phthalocyanines taken in the 80–300 K or 4.2–300 K ranges are reported. The σ- and π-interactions of the pyrrolic nitrogen ligand with the praseodymium, neodymium, holmium and erbium f-orbitals are obtained from angular overlap model ligand-field calculations including the full ground-state manifold. The position of the pyrrolic nitrogen ligand in the metallic two-dimensional spectrochemical series is reported. The results show that the pyrrolic nitrogen is a weak σ-donor and a moderate π-donor ligand. The cross-term AOM parameter e πσ is necessary in order to get good fits.

Deuterium/hydrogen fractionation in sulfate hydrate-water systems

The D/H fractionation factors (..cap alpha..) of some of the sulfate hydrate-water systems were measured. A dependence of ..cap alpha.. on cationic parameters and M-H/sub 2/O distance was found. The D/H fractionation factors of various hydrate-water systems were divided into two groups with respect to their ..cap alpha.. values: one having ..cap alpha.. 1. There is almost no change in ..cap alpha.. for crystal-water systems having SO/sub 4//sup 2 -/ as the anion of the first transition metallic ion series from Fe/sup 2 +/ to Zn/sup 2 +/ except for Cu/sup 2 +/. The result is related to the common structure of the hydration sphere of cations and the common distance of M-H/sub 2/O. The exceptional case for Cu/sup 2 +/ is attributed to the distorted structure of octahedra surrounding Cu/sup 2 +/. A similar type of behavior of protons leading to the residual entropy has been found in some of the crystal-water systems having ..cap alpha.. > 1. 45 references, 3 figures, 3 tables.

金属資源シリーズ

金属資源シリーズ

金属資源シリーズ-クロム-

金属資源シリーズ-クロム-

金属資源シリーズ-バナジウム-

金属資源シリーズ-バナジウム-

Inhibition of glutathione- S- aryltransferase from rat liver by organogermanium, lead and tin compounds

Compounds having three carbon—germanium, carbon—tin or carbon—lead bonds were found to be effective inhibitors of rat liver glutathione- S-aryltransferase activity with K i, values in the μM range. Classical competitive inhibition was observed with l,2-dichloro-4-nitrobenzene as the limiting substrate. However, when the second substrate, glutathione, was limiting, inhibition of the mixed type occurred. Within the metallic series IVb, triethylsilane chloride was not active, while the effectiveness as inhibitors increased through triethylgermanium chloride, triethyltin bromide and triethyllead chloride. Except in the case of sulfur, the fourth group or atom bonded to tin in a series of triphenyltin compounds had little effect on inhibitory activity. Sodium sulfide or 2,3-dimercapto-1-propanol (BAL) was capable of protecting glutathione- S-aryltransferase from inhibition by triphenyltin chloride. Glutathione conjugations at aromatic carbon atoms were much more sensitive to inhibition by organotins than were conjugations at alkyl carbons or epoxides.

2. 分散強化形合金の機械的諸性質について : 金属系複合材料について

2. 分散強化形合金の機械的諸性質について : 金属系複合材料について