Electrical and physical characteristics of the Al2O3/InGaAs interfaces with (1 1 1)A and (1 0 0) orientations were investigated in an attempt to understand the origin of electron mobility enhancement in the (1 1 1)A-channel metal-insulator-semiconductor field-effect-transistor. The (1 1 1)A interface has less As atoms of high oxidation states as probed by X-ray photoelectron spectroscopy. The electrical measurements showed that energy distribution of the interface traps for the (1 1 1)A interface is shifted toward the conduction band as compared to that for the (1 0 0) interface. Laterally-compressed cross-section transmission electron microscopy images showed that the characteristic lengths of the interface roughness are different between the (1 1 1)A and (1 0 0) interfaces. The contributions of the Coulomb and roughness scattering mechanisms are discussed based on the experimental results. 相似文献
Polysulfones bearing a derivative of alanyl residue employed as chiral selectors were prepared by polymer modification. The specific rotation ([α]D) of the polysulfone with a derivative of D ‐alanyl residue (PSf‐Ac‐D ‐Ala) was determined to be 2.87 deg · cm2 · g?1 (c = 1.00 g · dL?1 in DMF) and that with L ‐alanyl residue (PSf‐Ac‐L ‐Ala) to be ‐2.36 deg · cm2 · g?1 (c = 1.00 g · dL?1 in DMF). The membrane from PSf‐Ac‐D ‐Ala preferentially adsorbed the D ‐isomer of Glu from racemic mixture of Glu and vice versa. Chiral separation ability was studied by applying a potential difference as a driving force for membrane transport. The permselectivity of PSf‐Ac‐D ‐Ala toward D ‐Glu (αD/L) was determined to be 1.40, and that of PSf‐Ac‐L ‐Ala toward the L ‐isomer (αL/D) to be 1.48 at 18.0 V, reflecting their adsorption selectivity.
Dihydroxyacetone phosphate (DHAP)‐dependent aldolases have been widely used for the organic synthesis of unnatural sugars or derivatives. The practicality of using DHAP‐dependent aldolases is limited by their strict substrate specificity and the high cost and instability of DHAP. Here we report that the DHAP‐dependent aldolase L ‐rhamnulose 1‐phosphate aldolase (RhaD) accepts dihydroxyacetone (DHA) as a donor substrate in the presence of borate buffer, presumably by reversible in situ formation of DHA borate ester. The reaction appears to be irreversible, with the products thermodynamically trapped as borate complexes. We have applied this discovery to develop a practical one‐step synthesis of the non‐caloric sweetener L ‐fructose. L ‐Fructose was synthesized from racemic glyceraldehyde and DHA in the presence of RhaD and borate in 92 % yield on a gram scale. We also synthesized a series of L ‐iminocyclitols, which are potential glycosidase inhibitors, in only two steps. 相似文献
The photocatalytic oxidation of CO into CO2 with oxidants such as NO, N2O and O2 proceeded efficiently on a Mo/SiO2 with high Mo dispersion under UV light irradiation. It was found that the reaction rate greatly depended on the kind and concentration of the oxidant. Photoluminescence investigations reveal the close relationship between the reaction rate and the relative concentration of the photo-excited Mo6+-oxide species, i.e. charge transfer–excited–triplet state (Mo5+–O−)*, under steady-state reaction conditions. Moreover, the photocatalytic oxidation of CO with O2 in excess H2 was carried out to test suitability for applications to supplying pure H2. This reaction was seen to proceed efficiently on Mo/SiO2 with a high CO conversion of 100% and CO selectivity of 99% after 180 min under UV light irradiation, showing higher photocatalytic performance than TiO2 (P-25) photocatalyst. UV–vis, XAFS, photoluminescence and FT-IR investigations revealed that the high reactivity of the charge transfer–excited–triplet state (Mo5+–O−)*, with CO as well as the high reactivity of the photoreduced Mo-oxide species (Mo4+-species) with O2 to produce the original Mo-oxide species (Mo6+O2−), played a crucial role in the reactions. 相似文献
The individual and combined effects of changes in water quality (i.e. pH, initial concentrations of arsenate (As(V)) and competing ions) and empty bed contact time (EBCT) on As(V) removal performance of a fixed-bed adsorber (FBA) packed with a nanostructured goethite-based granular porous adsorbent were systematically studied under environmentally relevant conditions. Rapid small scale column tests (RSSCTs) were extensively conducted at different EBCTs with synthetic waters in which pH and the concentrations of competing ions (phosphate, silicate, and vanadate) were controlled. In the absence of the competing ions, the effects of initial As(V) concentration, pH, and EBCT on As(V) breakthrough curves were successfully predicted by the homogeneous surface diffusion model (HSDM) with adsorption isotherms predicted by the extended triple layer model (ETLM). The interference effects of silicate and phosphate on As(V) removal were strongly influenced by pH, their concentrations, and EBCT. In the presence of silicate (≤21 mg/L as Si), a longer EBCT surprisingly resulted in worse As(V) removal performance. We suggest this is because silicate, which normally exists at much higher concentration and moves more quickly through the bed than As(V), occupies or blocks adsorption sites on the media and interferes with later As(V) adsorption. Here, an alternative operating scheme of a FBA for As(V) removal is proposed to mitigate the silicate preloading. Silicate showed a strong competing effect to As(V) under the tested conditions. However, as the phosphate concentration increased, its interference effect dominated that of silicate. High phosphate concentration (>100 μg/L as P), as experienced in some regions, resulted in immediate As(V) breakthrough. In contrast to the observation in the presence of silicate, longer EBCT resulted in improved As(V) removal performance in the presence of phosphate. Vanadate was found to compete with As(V) as strongly as phosphate. This study reveals the competitive interactions of As(V) with the competing ions in actual adsorptive treatment systems and the dependence of optimal operation scheme and EBCT on water quality in seeking improved As(V) removal in a FBA. 相似文献
To clarify the relationship between earthquakes and electrical phenomena, signals of three parameters were observed continuously at Sennan in Akita Prefecture, Japan: ground acceleration (GAC), earth potential difference (EPD), and electrostatic field in the atmosphere (EFA). A large metal plate was used as an electrostatic antenna to observe EFA variation. For this paper, we used the digital natural observation (D-NOB) method as a signal processing technique and found clear EPD and EFA waveforms during seismic wave propagation. Our observation and examination results show that GAC causes EPD variation. Subsequently, the EPD variation induces EFA variation 相似文献
