Measurement of the In0.52Al0.48As valence-band hydrostatic deformation potential and the hydrostatic-pressure dependence of the In0.52Al0.48As/InP valence-band offset

We have measured the In0.52Al0.48As valence-band hydrostatic deformation potential from the hydrostatic-pressure dependence of the In0.52Al0.48As/InP valence-band offset which was measured from 0 to 35 kbar at room temperature. Due to the type-II band lineup, the radiative recombinations across the InP band gap and between the InP conduction band and the In0.52Al0.48As valence band were both observed in the photoluminescence spectra. This enables us to measure directly the changes of the valence-band offset under pressure. The hydrostatic-pressure derivative of the valence-band offset was measured to be 0.00.4 meV/kbar. The predictions of the pressure dependence from band-offset models (dielectric midgap and model-solid theories) agree with the measurement to within 1 meV/kbar. The In0.52Al0.48As valence-band hydrostatic deformation potential is found to be -0.8 eV which compares well with the dielectric midgap theory. Using the reported pressure dependence of the GaAs/AlAs valence-band offset, the valence-band hydrostatic deformation potentials of InxAl1-xAs (0x0.52) are linearly interpolated as -1.9x+0.2 eV

Measurement of the GaAs/AlAs valence-band offset from a single quantum well near the Γ-X crossover

An iterative procedure which utilizes the type-I and type-II transitions of a GaAs/AlAs single quantum well is used to determine the GaAs/AlAs valence-band offset. The iteration is based on the fact that the confinement energy is not sensitive to the change of the barrier potential. It has the advantage that knowledge of the thickness of the quantum well is not necessary to determine the valence-band offset. Both the type-I and type-II transitions can be observed in the low-temperature photoluminescence spectrum if the GaAs is thin enough so that the lowest-energy level of the electron in the GaAs well is higher than the X-conduction-band minimum of the adjacent AlAs. We illustrate this procedure with a 35 Å GaAs/AlAs single quantum well, and the valence-band offset is found to be 36% of the Γ-gap difference

Photoluminescence measurements of tensile-strained GaAs/In0.07Al0.93As quantum wells

GaAs/In0.07Al0.93As tensile-strained quantum wells were grown on [001] GaAs substrates using molecular-beam epitaxy. The incorporation of tensile strain is made possible by preparing a 1-μm-thick In0.07Al0.93As relaxed buffer which is followed by the growth of quantum wells. The strain of the GaAs was measured using Raman spectroscopy and photoluminescence. The photoluminescence measurements from wells ranging in thickness from 25 to 100 Å reveal that the observed optical transition originates from the electron-light hole recombination for a 100 Å well and from the electron-heavy hole recombination if the well thickness is less than 40 Å. Therefore, a thick Al-rich InxAl1-x As relaxed buffer on the GaAs substrate can be used to engineer the relative energy position of the light and heavy holes for GaAs-based quantum wells

In vitro micropropagation and ex vitro acclimation of Bupleurum kaoi - An endangered medicinal plant native to Taiwan

This study reports an improved protocol for in vitro-shoot multiplication and ex vitro acclimation of Bupleurum kaoi, an endangered medicinal herb. Nodal segments were cultured in half-strength Murashige and Skoog (MS) basal medium supplemented with different concentrations of benzyladenine (BA) and kinetin. The presence of 0.25 mg l(-1) BA induced the highest number of shoots per explant after 8 wk of culture. Although BA was more effective than kinetin on shoot multiplication, it induced hyperhydric shoots at all concentrations tested. The use of dispense paper (DP) instead of aluminum foil (AF) for container closure was found to reduce hyperhydricity and improve ex vitro acclimation. The best survival rate (61%) was obtained when plantlets were grown in MS basal medium containing 0.5 mg l(-1) indole-3-butyric acid and 0.1-0.2 mg l(-1) alpha-naphthaleneacetic acid using DP as container closure. Leaves of the plant treated with AF6 (two layers of AF as container closure and 6 wk of incubation) lacked epicuticular wax and possessed larger stomata, higher stomata density, and fewer functional stomata compared to those of plants treated with AF2+DP4 (two layers of AF for 2 wk, then replaced AF by three layers of DP for 4 wk) and ex vitro-acclimated plantlets

The transition from the adiabatic to the sudden limit in core level photoemission: A model study of a localized system

We consider core electron photoemission in a localized system, where there is a charge transfer excitation. The system is modelled by three electron levels, one core level and two outer levels. The model has a Coulomb interaction between these levels and the continuum states into which the core electron is emitted. The model is simple enough to allow an exact numerical solution, and with a separable potential an analytic solution. We calculate the ratio r(omega) between the weights of the satellite and the main peak as a function of the photon energy omega. The transition from the adiabatic to the sudden limit takes place for quite small photoelectron kinetic energies. For such small energies, the variation of the dipole matrix element is substantial and described by the energy scale Ed. Without the coupling to the photoelectron, the corresponding ratio r0(omega) is determined by Ed and the satellite excitation energy dE. When the interaction potential with the continuum states is introduced, a new energy scale Es=1/(2Rs^2) enters, where Rs is a length scale of the interaction potential. At threshold there is typically a (weak) constructive interference between intrinsic and extrinsic contributions, and the ratio r(omega)/r0(omega) is larger than its limiting value for large omega. The interference becomes small or weakly destructive for photoelectron energies of the order Es. For larger energies r(omega)/r0(omega) therefore typically has a weak undershoot. If this undershoot is neglected, r(omega)/r0(omega) reaches its limiting value on the energy scale Es.Comment: 18 pages, latex2e, 13 eps figure

Perturbative Approach to Higher Derivative Theories with Fermions

We extend the perturbative approach developed in an earlier work to deal with Lagrangians which have arbitrary higher order time derivative terms for both bosons and fermions. This approach enables us to find an effective Lagrangian with only first time derivatives order by order in the coupling constant. As in the pure bosonic case, to the first order, the quantized Hamiltonian is bounded from below whenever the potential is. We show in the example of a single complex fermion that higher derivative interactions result in an effective mass and change of vacuum for the low energy modes. The supersymmetric noncommutative Wess-Zumino model is considered as another example. We also comment on the higher derivative terms in Witten's string field theory and the effectiveness of level truncation.Comment: Latex, 21 pages, minor modification, ref. adde

Guidelines for the management of biliary tract and ampullary carcinomas: surgical treatment

The only curative treatment in biliary tract cancer is surgical treatment. Therefore, the suitability of curative resection should be investigated in the first place. In the presence of metastasis to the liver, lung, peritoneum, or distant lymph nodes, curative resection is not suitable. No definite consensus has been reached on local extension factors and curability. Measures of hepatic functional reserve in the jaundiced liver include future liver remnant volume and the indocyanine green (ICG) clearance test. Preoperative portal vein embolization may be considered in patients in whom right hepatectomy or more, or hepatectomy with a resection rate exceeding 50%–60% is planned. Postoperative complications and surgery-related mortality may be reduced with the use of portal vein embolization. Although hepatectomy and/or pancreaticoduodenectomy are preferable for the curative resection of bile duct cancer, extrahepatic bile duct resection alone is also considered in patients for whom it is judged that curative resection would be achieved after a strict diagnosis of its local extension. Also, combined caudate lobe resection is recommended for hilar cholangiocarcinoma. Because the prognosis of patients treated with combined portal vein resection is significantly better than that of unresected patients, combined portal vein resection may be carried out. Prognostic factors after resection for bile duct cancer include positive surgical margins, especially in the ductal stump; lymph node metastasis; perineural invasion; and combined vascular resection due to portal vein and/or hepatic artery invasion. For patients with suspected gallbladder cancer, laparoscopic cholecystectomy is not recommended, and open cholecystectomy should be performed as a rule. When gallbladder cancer invading the subserosal layer or deeper has been detected after simple cholecystectomy, additional resection should be considered. Prognostic factors after resection for gallbladder cancer include the depth of mural invasion; lymph node metastasis; extramural extension, especially into the hepatoduodenal ligament; perineural invasion; and the degree of curability. Pancreaticoduodenectomy is indicated for ampullary carcinoma, and limited operation is also indicated for carcinoma in adenoma. The prognostic factors after resection for ampullary carcinoma include lymph node metastasis, pancreatic invasion, and perineural invasion