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The prevalence of kidney failure continues to rise globally. Dialysis is a treatment option for individuals with kidney failure; after the decision to initiate dialysis has been made, it is critical to involve individuals in the decision on which dialysis modality to choose. This review, based on evidence arising from the literature, examines the role of shared decision-making (SDM) in helping those with kidney failure to select a dialysis modality. SDM was found to lead to more people with kidney failure feeling satisfied with their choice of dialysis modality. Individuals with kidney failure must be cognizant that SDM is an active and iterative process, and their participation is essential for success in empowering them to make decisions on dialysis modality. The educational components of SDM must be easy to understand, high quality, unbiased, up to date, and targeted to the linguistic, educational, and cultural needs of the individual. All individuals with kidney failure should be encouraged to participate in SDM and should be involved in the design and implementation of SDM approaches.

Anemia is an important complication in patients with chronic kidney disease. Peritoneal dialysis (PD) is one of the most common modalities of kidney replacement therapy for patients with end-stage kidney disease. PD is particularly prevalent in the Asian Pacific region. Among the different countries and regions, including mainland China, Hong Kong, Japan, Malaysia, Singapore, South Korea, and Thailand, PD accounts for 2.8% to 74.6% of the dialysis population. In addition, 82% to 96% of the PD populations from these countries and regions are receiving erythropoiesis-stimulating agents (ESAs). Asian Pacific countries and regions follow the latest KDIGO (Kidney Disease: Improving Global Outcomes) guidelines for the initiation of treatment of anemia in PD patients. The types of ESAs commonly used include shorter-acting (epoetin alfa and beta) and longer-acting agents, including darbepoetin alfa or methoxy polyethylene glycol-epoetin beta. The most commonly used ESAs in Mainland China, Malaysia, Singapore, and Thailand are the shorter-acting agents, whereas in Hong Kong, Japan, and South Korea, longer-acting ESAs are most common. Oral iron therapy is still the most commonly used iron supplement. The route and dosage of iron administration in PD patients requires more research studies. With the introduction of oral hypoxia-inducible factor prolyl hydroxylase inhibitors into clinical use, the landscape of treatment of anemia in the PD population in the Asia Pacific region may change in the coming years.

We have analyzed a photoluminescence (PL) spectrum in a GaAs/AlAs type-II superlattice and have statistically confirmed stable existence of an electron-hole droplet (EHD) state. Although the PL spectrum consists of spectral components of the EHD, exciton and biexciton states, we have succeeded in decomposing the admixed spectrum into the respective components. In addition, posterior probability distributions of spectral parameters have been obtained in all spectral components from 30,000 times samplings through a replica exchange Monte Carlo method. By using mean values of their posterior probabilities, the PL spectrum can be completely reproduced by the sum of these spectral components. The stability energy of the EHD state has a sharp distribution in its posterior probability and has been confirmed to be enough larger than the ambient thermal energy. This fact is a strong evidence for the stable formation of the EHD state in the GaAs/AlAs type-II superlattice.

Temporal profiles of photoluminescence (PL) from the cavity polariton at the ground state in a CuBr microcavity at 10 K have been investigated from the viewpoint of the cavity-polariton condensation. We measured angle-resolved reflectance spectra to characterize the cavity-polariton dispersions, cavity-photon dispersion, and quality factor from which the intrinsic cavity-polariton lifetime was estimated. The threshold-like changes of the PL intensity, band width, and energy of the lower polariton as a function of excitation power are consistent with previously reported experimental results for the cavity-polariton condensation. It was found that the PL rise and decay times are markedly decreased by the cavity-polariton condensation, which can be attributed to the appearance of the bosonic final state stimulation and intrinsic lifetime of polaritons in the relaxation and decay processes, respectively.

Background Porphyromonas gingivalis is s major oral bacterium closely associated with periodontal diseases including periodontitis and directly affects host cellular signaling. The phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway plays multiple roles in various cell functions including cell survival and glucose metabolism. In this review, we describe the effect of gingipains on the PI3K/Akt signaling pathway in P. gingivalis infection. Highlight Gingipains inactivate PI3K and Akt in gingival epithelial cells infected with P. gingivalis . These events occur independently of invasion of this organism into the cells and are required for the enzymatic activity of gingipains. Furthermore, 3-Phosphoinositide-dependent protein kinase-1 (PDK1) failed to translocate to the plasma membrane from the cytosol following PI3K inactivation. Additionally, dephosphorylation of Akt downstream proteins, including glycogen synthase kinase 3 (GSK3), mammalian target of rapamycin (mTOR), and Bad, occurs in parallel with the dysregulation of PI3K/PDK1/Akt cascades. Conclusion This review describes the biological characterization of gingipains, which inactivate PI3K and Akt, and disorder the PI3K/Akt signaling pathway. Hence, gingipains may decrease cellular physiological functions, eventually disrupting the gingival epithelium and causing development of periodontal diseases.

Pathophysiological bone resorption is commonly associated with periodontal disease and involves the excessive resorption of bone matrix by activated osteoclasts. Receptor activator of nuclear factor (NF)-κB ligand (RANKL) signaling pathways have been proposed as targets for inhibiting osteoclast differentiation and bone resorption. The fungal secondary metabolite (+)-terrein is a natural compound derived from Aspergillus terreus that has previously shown anti-interleukin-6 properties related to inflammatory bone resorption. However, its effects and molecular mechanism of action on osteoclastogenesis and bone resorption remain unclear. In the present study, we showed that 10 µM synthetic (+)-terrein inhibited RANKL-induced osteoclast formation and bone resorption in a dose-dependent manner and without cytotoxicity. RANKL-induced messenger RNA expression of osteoclast-specific markers including nuclear factor of activated T-cells cytoplasmic 1 (NFATc1), the master regulator of osteoclastogenesis, cathepsin K, tartrate-resistant acid phosphatase (Trap) was completely inhibited by synthetic (+)-terrein treatment. Furthermore, synthetic (+)-terrein decreased RANKL-induced NFATc1 protein expression. This study revealed that synthetic (+)-terrein attenuated osteoclast formation and bone resorption by mediating RANKL signaling pathways, especially NFATc1, and indicated the potential effect of (+)-terrein on inflammatory bone resorption including periodontal disease.

Porphyromonas gingivalis is a major pathogen of periodontal diseases, including periodontitis. We have investigated the effect of P. gingivalis infection on the PI3K/Akt (protein kinase B) signaling pathway in gingival epithelial cells. Here, we found that live P. gingivalis, but not heat-killed P. gingivalis, reduced Akt phosphorylation at both Thr-308 and Ser-473, which implies a decrease in Akt activity. Actually, PI3K, which is upstream of Akt, was also inactivated by P. gingivalis. Furthermore, glycogen synthase kinase 3α/β, mammalian target of rapamycin, and Bad, which are downstream proteins in the PI3K/Akt cascade, were also dephosphorylated, a phenomenon consistent with Akt inactivation by P. gingivalis. However, these events did not require direct interaction between bacteria and host cells and were independent of P. gingivalis invasion into the cells. The use of gingipain-specific inhibitors and a gingipain-deficient P. gingivalis mutant KDP136 revealed that the gingipains and their protease activities were essential for the inactivation of PI3K and Akt. The associations between the PI3K regulatory subunit p85α and membrane proteins were disrupted by wild-type P. gingivalis. Moreover, PDK1 translocation to the plasma membrane was reduced by wild-type P. gingivalis, but not KDP136, indicating little production of phosphatidylinositol 3,4,5-triphosphate by PI3K. Therefore, it is likely that PI3K failed to transmit homeostatic extracellular stimuli to intracellular signaling pathways by gingipains. Taken together, our findings indicate that P. gingivalis attenuates the PI3K/Akt signaling pathway via the proteolytic effects of gingipains, resulting in the dysregulation of PI3K/Akt-dependent cellular functions and the destruction of epithelial barriers.

Cognitive impairment (CI) associated with chronic kidney disease (CKD) has received attention as an important problem in recent years. Causes of CI with CKD are multifactorial, and include cerebrovascular disease, renal anemia, secondary hyperparathyroidism, dialysis disequilibrium, and uremic toxins (UTs). Among these causes, little is known about the role of UTs. We therefore selected 21 uremic compounds, and summarized reports of cerebro-renal interactions associated with UTs. Among the compounds, uric acid, indoxyl sulfate, p-cresyl sulfate, interleukin 1-β, interleukin 6, TNF-α, and PTH were most likely to affect the cerebro-renal interaction dysfunction; however, sufficient data have not been obtained for other UTs. Notably, most of the data were not obtained under uremic conditions; therefore, the impact and mechanism of each UT on cognition and central nervous system in uremic state remains unknown. At present, impacts and mechanisms of UT effects on cognition are poorly understood. Clarifying the mechanisms and establishing novel therapeutic strategies for cerebro-renal interaction dysfunction is expected to be subject of future research.

We have investigated the photon-field-shape effect on the Rabi splitting energies in ZnO microcavities with HfO2/SiO2 distributed Bragg reflectors (DBRs). The thickness of the ZnO active layer was fixed to λ/2 corresponding to a half of an effective resonant wavelength of the lowest-lying exciton. The photon-field shape was tuned to a node type or an antinode type by changing the order of the refractive indices in the DBRs. We obtained the cavity-polariton dispersions from angle-resolved reflectance spectra measured at 10 K. The Rabi splitting energies were evaluated from the analysis of the cavity-polariton dispersions with a phenomenological Hamiltonian for the strong coupling between the three kinds of excitons peculiar to ZnO labeled A, B, and C and the cavity photon. It was found that the Rabi splitting energies in the antinode-type microcavity are almost a half of those in the node-type microcavity. We semi-quantitatively analyzed the photon-field-shape effect, taking account of the overlap between the exciton and photon-field envelope functions.

We have performed time-resolved photoluminescence (PL) spectroscopy for ZnO thin films with thicknesses of 90, 460, and 2800 nm under intense excitation condition. We clearly observed the P emission due to inelastic exciton–exciton scattering. It was found that, in the 460- and 2800-nm thick samples, the decay time of the P emission considerably depends on the detection energy inversely proportional to the group velocity of the polariton in a bulk crystal with each factor of proportionality. In contrast, the energy dependence is less remarkable in the 90-nm thick sample. The decay times are basically shortened with a decrease in the film thickness. The thickness dependence of the P-emission-decay profiles is explained by considering the crossover from the polariton modes in the 2800-nm thick sample (bulk-like film) to the exciton-/photon-like modes in the 90-nm thick sample (nanofilm).

Objective JTT-751 is a novel phosphate binder containing ferric citrate as the active ingredient. This study investigated long-term safety and efficacy of JTT-751 for hyperphosphatemia in patients receiving hemodialysis. Design and Methods This was 52-week, phase 3, multicenter, open-label, dose titration, long-term study. All patients were receiving thrice-weekly hemodialysis for ≥3 months before the initiation of the study. JTT-751 was given at titrated doses between 1.5 and 6.0 g/day. Main Outcome Measures Safety endpoints were adverse events and adverse drug reactions. Efficacy outcomes were the change in serum phosphate, corrected serum calcium, and intact parathyroid hormone. Changes in ferritin, transferrin saturation, and doses of erythropoiesis-stimulating agents (ESAs) and intravenous iron formulations were additional outcomes. Results One hundred and eighty patients were included in the trial. Dose-titrated JTT-751 decreased mean serum phosphate after administration and satisfactorily maintained serum phosphate concentrations throughout the entire duration of the 52-week trial. Mean serum phosphate concentrations were kept lower than 5.5 mg/dL from weeks 5 to 52. The most common adverse events were gastrointestinal disorders, which were mild to moderate in intensity. Serum ferritin concentrations rose to a peak around week 28 and stabilized thereafter. The mean intravenous iron dose decreased from 57.3 mg/4 weeks (weeks 0-12) to 3.6 mg/4 weeks (weeks 28-52); weekly ESA dose declined by 25% over the same time frame, while mean hemoglobin concentrations remained stable. Conclusion JTT-751 1.5-6.0 g/day controls serum phosphorus concentrations and reduces the need for ESAs and intravenous iron in patients receiving hemodialysis.

We have investigated sub-picosecond-range carrier-transport processes in undoped GaAs/n-type GaAs (i-GaAs/n-GaAs) epitaxial layer structures with various i-GaAs-layer thicknesses d ranging from 200 to 2000 nm, focusing on the relation between carrier-transport processes and terahertz electromagnetic wave frequency. Initially, using numerical simulation and photoreflectance measurement, we confirm that a decrease in d enhances the built-in electric field in the i-GaAs layer. In the time-domain terahertz waveform, it is observed that the intense monocycle oscillation induced by the surge current of photogenerated carriers, the so-called first burst, is followed by the oscillation patterns originating from the coherent GaAs longitudinal optical (LO) phonon. From the Fourier power spectra of the terahertz waveforms, it is clarified that the decrease in d causes a high frequency shift of the band of the first burst. Consequently, we conclude that, in the sub-picosecond time range, the photogenerated carriers are monotonously accelerated by the built-in electric field without being affected by intervalley scattering. The present conclusion signifies that the frequency-tunable terahertz emitters are realized by controlling i-GaAs-layer thickness. We also find the intensity of the coherent LO phonon band is enhanced by a decrease in d.

Control of bacterial infection-induced inflammatory responses is one of the effective therapeutic approaches of periodontal diseases. Natural products such as lipid mediators and metabolites from microorganisms have been used for decreasing inflammation. We previously reported that (+)-terrein inhibited activation of STAT3 and ERK1/2 in interleukin-6 (IL-6) signaling cascade, leading to prevent vascular endothelial growth factor (VEGF) secretion in human gingival fibroblasts (HGFs). However, little is still known about the role of (+)-terrein on inflammatory responses. In this study, we provided the possibility of novel action that (+)-terrein inhibits activation of Janus-activated kinase 1 (JAK1), which has a central function in IL-6 signaling cascade, and alters expression of mRNAs and proteins induced by IL-6/soluble IL-6 receptor (sIL-6R) stimulation in HGFs. First, we performed PCR array to examine IL-6/sIL-6R-induced mRNA expression, and then expression of mRNA and protein of colony stimulating factor-1 (CSF1) and VEGF were clearly determined by quantitative RT-PCR and ELISA, respectively. Treatment with (+)-terrein suppressed expression of mRNA and protein of CSF1 and VEGF by IL-6/sIL-6R stimulation. Next, to test the effect of (+)-terrein on IL-6/sIL-6R signaling cascade, we demonstrated whether (+)-terrein affects phosphorylation of JAK1 and its downstream proteins, Akt and SHP-2. Western blotting revealed that (+)-terrein inhibited IL-6/sIL-6R-induced phosphorylation of JAK1, Akt, and SHP-2. Therefore, (+)-terrein suppresses IL-6/sIL-6R-induced expression of CSF1 and VEGF via inhibition of JAK1, Akt, and SHP-2. Based on our results, we suggest that (+)-terrein is a candidate compound for anti-inflammatory effect associated with IL-6 signaling.

We have investigated the upconversion of photoluminescence (PL) due to subband resonances in a simple GaAs(15.3 nm)/AlAs(4.5 nm) multiple quantum well embedded in a p-i-n diode structure. The systematic measurements of the PL spectra and the calculated results of the interband transition energies as a function of electric field strength reveal that the PL bands from the electron subbands with n=3 (E3) and n=4 (E4) sharply appear under the first-nearest-neighbor resonance conditions between the E1 and E3 subbands and the E1 and E4 subbands, respectively, owing to the carrier injection to the E3 and E4 subbands from the E1 subband. This result indicates that the resonant tunneling due to the subband resonance is a dominant mechanism for the carrier population in the higher lying subbands. Utilizing these subband resonances, we have demonstrated the upconversion of PL from the E3 and E4 subbands under the excitation condition of the fundamental interband transition between the E1 and the n=1 heavy-hole subbands.

We report on the photoluminescence (PL) properties of a GaAs (20 nm)/AlAs (20 nm) multiple quantum well under high-density-excitation conditions at excitation energies near the fundamental exciton energies. The biexciton-PL band is dominant in a relatively low-excitation-power region. The PL originating from exciton–exciton scattering, the so-called P emission, suddenly appears with an increase in excitation power. The excitation-energy dependence of the intensity of the P-PL band indicates that the excitation energy higher than the fundamental heavy-hole exciton by the energy of the longitudinal optical (LO) phonon is the most efficient for the P PL. This suggests that the LO-phonon scattering plays an important role in the relaxation process of excitons leading to the P PL. The appearance of the P-PL band remarkably suppresses the intensity of the biexciton-PL band; namely, the exciton–exciton scattering process prevents the formation of biexcitons. Furthermore, we have confirmed the existence of optical gain due to the exciton–exciton scattering process with use of a variable-stripe-length method.

We have investigated the characteristics of exciton polaritons in a ZnO microcavity with HfO 2 /SiO 2 distributed Bragg reflectors. The results of the angle-resolved reflectance spectra were analyzed by calculating the cavity polariton dispersions with a phenomenological Hamiltonian for the coupling between the cavity photon and three kinds of excitons labeled A , B , and C peculiar to ZnO. The vacuum-Rabi-splitting energy is estimated to be ∼80 meV. The reflectance dips originating from the cavity polaritons shift to lower energy side with an increase in temperature. We discuss the temperature dependence of the cavity-polariton energies of the ZnO microcavity on the basis of the phenomenological Hamiltonian taking account of the temperature dependence of the exciton energies with Varshni’s law.

SummaryBackgroundHeart failure (HF) often accompanies chronic kidney disease (CKD) in the elderly. This clinical condition is a critical socio-medical issue, because high-dose diuretic therapy stimulates the renin–angiotensin–aldosterone axis and sympathetic nervous system outflow, and may thus result in vicious cycles of cardio-renal deterioration, leading to excess hospitalization and death. Peritoneal dialysis (PD) is a renal replacement therapy used for maintenance dialysis, and is characterized by the continuous removal of fluid. The present study examined the clinical feasibility and effects of a novel style of PD for elderly CKD patients with refractory HF.MethodsTwelve elderly CKD patients (stages 3–5) with refractory HF [New York Heart Association (NYHA) class III, n=9; IV, n=3; mean age, 81±6 years] received PD treatment. Patients had episodes of >3 hospitalizations in the previous year, and were initially treated with ≤19 sessions of sequential hemofiltration, followed by incremental PD, with 3 PD sessions/week (8h each) at the start, increasing in frequency and dwelling time as clinically indicated.ResultsDuring follow-up (median, 26.5 months), PD was well tolerated by all patients, and no patients required hospitalization for HF. Three patients died due to non-HF-related events. All patients showed improvements in NYHA functional class (class I, n=9; class II, n=3) and significant decreases in the dose of diuretics prescribed (P

We have investigated annealing ambient effects on optical properties of GaInNAs/GaAs single quantum wells with the use of photoluminescence (PL) spectroscopy sensitive to localization of carriers and photoreflectance (PR) spectroscopy sensitive to the intrinsic band-edge transition. We examined two annealing ambient sequences: tertiarybutylarsine and H 2 in the annealing process and H 2 in the cooling process. The PL efficiency at room temperature is markedly improved in the H 2 ambient annealing process. We found from systematic results of PL and PR spectra that the PL efficiency at room temperature is in connection with the Stokes shift at 10 K, which is a measure of carrier localization, and the broadening factor of the band-edge transition.

We investigated the influence of methylviologen (MV 2+ ), which accelerates the photoetching process used for controlling size distribution, on the photoluminescence (PL) properties of colloidal CdS quantum dots (QDs). A combination of the photoetching process and surface modification with a Cd(OH) 2 layer enabled us to prepare size- and surface-controlled CdS QDs. The efficiency of the photoetching process is extremely enhanced by the addition of MV 2+ . The temperature dependence of PL decay profiles indicates that MV 2+ does not affect the PL properties of QDs. Consequently, the addition of MV 2+ results in a highly efficient preparation of size-controlled CdS QDs without degradation of the PL efficiency.

We have investigated the optical properties of GaInNAs/GaAs single quantum wells grown by metalorganic vapor-phase epitaxy on misoriented GaAs substrates with the use of photoluminescence (PL) spectroscopy sensitive to localization of carriers and photoreflectance (PR) spectroscopy sensitive to the intrinsic band-edge transition. We have found from systematic results of PL spectra, PL-decay profiles and PR spectra that the band-edge energy of the quantum well is lowered with increasing offset angle from 2° to 15° toward (1 1 1)A and that the localization of carriers due to disorders of the band-edge state is enhanced.

We have investigated effects of a trimethylantimony (TMSb) flow to the interface between GaAs buffer layer and InGaAsN quantum-well layer on localization of carriers in InGaAsN/GaAs single quantum wells (SQWs) grown by metal organic vapor phase epitaxy from the viewpoint of photoluminescence (PL) properties. We also measured photoreflectance spectroscopy in order to determine the energy of the band-edge transition. The Stokes shift of the PL-peak energy under a weak excitation condition decreases from 20meV in no TMSb flow to 15meV in the TMSb flow of 5 × 10 -7 mol/min. The PL-decay time in the low-energy PL tail related to localized states is obviously shortened by the TMSb flow. The decay profiles detected at various energies can be explained by a stretched exponential form peculiar to disordered systems. The overall results of the PL characterization demonstrate that the carrier localization is reduced by the TMSb flow to the interface.

We have investigated the time-resolved photoluminescence spectra of the P emission due to exciton–exciton scattering in CuI thin films at various temperatures by using an optical-Kerr-gating method with a time resolution of 0.4 ps. It is found that the rise time of the P emission hardly changes with temperature. Since the rise time reflects collision processes of excitons in the lowest ( n = 1 ) exciton state, the temperature dependence demonstrates that the exciton–collision rate is hardly influenced by temperature. On the other hand, the decay time of the P emission becomes faster from 8 to 5 ps with increasing temperature from 10 to 150 K. This is due to the enhancement of the contribution of the photon state away from the polariton-bottleneck region to the photon-like polariton state leading to the P emission owing to thermal broadening in momentum space; namely the photon nature of the photon-like polariton becomes considerable.

We have investigated photoluminescence (PL) properties of PbS quantum dots (QDs) prepared by a colloidal method. The QDs were dispersed into polyvinyl alcohol films in order to investigate the temperature dependence of optical properties. In the visible region, both absorption and PL peaks are clearly observed. The temperature dependence of the absorption energy in QDs is quite different from that in a bulk crystal; the dependence is quantitatively analyzed by considering a thermal-expansion effect on the quantum confinement in QDs. The PL spectra are composed of three PL bands which are classified into two types. Two PL bands among them with the Stokes shifts of 0.25 and 0.47 eV at 10 K are attributed to the defect-related PL bands, and another with the relatively small Stokes shift of 0.17 eV exhibits characteristics of shallow trapped states in the temperature dependence of PL.

We have investigated photoluminescence (PL) properties of high-quality ZnO thin films prepared by an RF-magnetron sputtering method. The X-ray-diffraction patterns indicate that the crystalline thin film is preferentially oriented along the [0 0 0 1] crystal axis. By introducing a low-temperature buffer layer and by growing thin films at a high temperature of 600 °C, the crystal quality of ZnO thin films is markedly improved. In addition, we have found that ambience during a cooling process to room temperature after the deposition is another important factor to improve the PL properties; namely, the defect-related PL disappears and the free exciton PL with a sharp width is observed by cooling thin films in the presence of oxygen. Furthermore, under high-density excitation conditions, a PL band due to an exciton–exciton scattering process, the so-called P emission, is observed.

We have investigated the dynamical properties of the coherent longitudinal optical (LO) phonon in CuI thin films grown on a NaCl substrate by vacuum deposition. The intense coherent LO phonon in the CuI thin film is observed under the exciton–excitation conditions. Moreover, the pump-energy dependence of the amplitude of the coherent LO phonon shows peaks at the heavy-hole and light-hole exciton energies. The enhancement of the coherent LO phonon under the exciton-resonance condition is much larger than that in an ordinary semiconductor quantum well system such as a GaAs/AlAs one. These facts demonstrate that the intense coherent LO phonon is generated under the exciton–excitation condition in a material with a strong exciton–phonon interaction such as CuI.

We have investigated the coupled mode of excitonic quantum beats and coherent GaAs-like longitudinal optical (LO) phonons in GaAs/AlAs multiple quantum wells with the splitting energy of heavy- and light-hole excitons close to the LO phonon energy. The time-domain signals show the coherent oscillation of the coupled mode between the quantum beat and the LO phonon with a fast dephasing time and the long-lived coherent GaAs-like LO phonon oscillation. The dependence of the coupled-mode frequency on splitting energy exhibits an anticrossing behavior. We demonstrate that the amplitude of the long-lived coherent LO phonon is manipulated by controlling the coupled mode with a double-pulse excitation technique.

We have investigated optical properties of high-quality ZnO thin films grown by a sputtering method. By introducing a low-temperature buffer layer of ZnO, the lattice-mismatched strain is relaxed and the crystallinity is improved remarkably. In the absorption spectrum at 10 K, the absorption peaks of the A and B excitons are observed. In the photoluminescence (PL) spectrum, the free-exciton PL is observed and the defect-related PL is negligibly weak. These results clearly indicate high crystallinity of the film. Furthermore, under high-density excitation conditions, a PL band originating from an inelastic scattering process of excitons, the so-called P emission, is observed in the ZnO thin film.

We have investigated scintillation properties of Na-doped CsI (CsI:Na) thin films grown by vacuum deposition. The Na-related luminescence, which is the dominant scintillation of CsI:Na, is activated by heat treatment and associated with formation of NaI nanoparticles. It is found that the Na-related luminescence, which is remarkably degraded in atmosphere, the so-called hygroscopic property, is reversibly recovered in vacuum, while the luminescence due to the self-trapped exciton of CsI hardly decreases in ambient conditions. This finding indicates that the hygroscopic property of CsI:Na results from degradation of NaI nanoparticles embedded in the CsI:Na thin film and that the recovery in vacuum is due to recrystallization. This is a novel proposal to explain the high hygroscopicity of CsI:Na. Furthermore, it is demonstrated from the temperature dependence of the luminescence properties that the energy transfer from the host material of CsI to the NaI nanoparticles is mediated through thermally activated hopping of the self-trapped exciton of CsI.

We have investigated photoluminescence (PL) properties of localized states induced by nitrogen alloying in a Ga 1− x In x N y As 1− y /GaAs single quantum well (SQW) with x =0.33 and y =0.008, comparing with those in a Ga 1− x In x As/GaAs SQW without nitrogen. In order to determine the intrinsic band edge, we also used photoreflectance (PR) spectroscopy that is sensitive to the optical transitions at critical points. The PR line width of the band-edge transition in the GaInNAs/GaAs SQW is much broader than that in the GaInAs/GaAs SQW, which indicates that considerable disorders are introduced by nitrogen alloying. The PL-peak energy of the GaInNAs/GaAs SQW, which has a Stokes shift of ∼20 meV at 10 K, continuously shifts to the band edge with an increase in excitation power, reflecting the localization nature of carriers. The PL-decay profile related to the localized states clearly exhibits a stretched exponential feature peculiar to a disordered system. It is concluded that the PL properties at low temperature are dominated by random potentials caused by nitrogen alloying.

Helicobacter pylori produces a potent exotoxin, VacA, which causes progressive vacuolation as well as gastric injury. Although VacA was able to interact with two receptor-like protein tyrosine phosphatases, RPTPbeta and RPTPalpha, RPTPbeta was found to be responsible for gastric damage caused by VacA. To define the region of RPTPbeta involved in VacA binding, we made mutants of human cDNA RPTPbeta-B, a short receptor form of RPTPbeta. Immunoprecipitation experiments to assess VacA binding to RPTPbeta-B mutants indicated that five residues (QTTQP) at positions 747-751 of the extracellular domain of RPTPbeta-B (which is commonly retained in RPTPbeta-A, a long form of RPTPbeta) play a crucial role in its interaction with VacA, resulting in vacuolation as well as Git-1 phosphorylation. Transfected cells expressing deletion mutant Delta752, which lacks QTTQP, or the double point mutant Delta747 (T748A,T749A) had diminished vacuolation in response to VacA. Treatment of RPTPbeta-B and Delta747 (which have QTTQP at 747-751) with neuraminidase and O-glycosidase diminished their VacA binding, whereas chondroitinase ABC did not have an effect. No inhibitory effect of pleiotrophin, a natural RPTPbeta ligand, on VacA binding to RPTPbeta-B or Delta747 was observed, supporting the conclusion that the extracellular region of RPTPbeta-B responsible for VacA binding is different from that involved in binding pleiotrophin. These data define the region in the RPTPbeta extracellular domain critical for VacA binding, in particular the sequence QTTQP at positions 747-751 with crucial threonines at positions 748 and 749 and are consistent with a role for terminal sialic acids possibly because of threonine glycosylation.

We have investigated the dynamical properties of the coherent GaAs-like longitudinal optical (LO) phonon and the quantum beat of excitons in GaAs/AlAs multiple quantum wells with different splitting energies of the heavy-hole and light-hole excitons by using a reflection-type pump–probe technique. It has been found that the coherent GaAs-like LO phonon in the multiple quantum well is remarkably enhanced as the splitting energy approaches to the LO phonon energy of GaAs. The pump-energy dependence of the intensity of the coherent GaAs-like LO phonon is similar to that of the excitonic quantum beat in the multiple quantum wells with the splitting energy nearly equal to the LO phonon energy of GaAs. We conclude that the enhancement of the coherent LO phonon is induced by the coupling of the excitonic quantum beat with the coherent GaAs-like LO phonon through the longitudinal polarization.

The scintillation mechanism in Na-doped CsI (CsI:Na) crystalline thin films grown by vacuum deposition has been investigated from the aspects of optical and structural properties. It is found that a heat treatment of the thin film activates the Na-related luminescence corresponding to the dominant scintillation in a CsI:Na crystal. The surface morphology of the thin films measured by atomic force microscope demonstrates that the heat treatment causes the formation of nanoparticles. From the excitation spectrum of the Na-related luminescence and the temperature dependence of the luminescence properties, it is concluded that the scintillation of CsI:Na is caused by the energy transfer from the host material of CsI to NaI nanoparticles.

We have investigated the Bose-Einstein (BE) statistics behavior of the exciton-biexciton (EX-BEX) system during the photoluminescence decay processes at 5 K in a (GaAs) 1 2 /(AlAs) 1 2 type-II superlattice. Owing to the long lifetime of the type-II exciton, which is of the order of microseconds due to the indirect transition nature, we have precisely evaluated the density relation between the EX and BEX from the line-shape analysis of time-resolved photoluminescence spectra. At an EX density around 1 × 10 1 0 /cm 2 , the BEX density suddenly increases with a threshold-like profile. This behavior is quantitatively explained by the framework of BE statistics of the EX-BEX system. It is demonstrated that the threshold-like increase of the BEX density is recurred by the incidence of a second-excitation pulse with a time delay, which leads to the dynamical control of the BE statistics behavior.

We have investigated exciton dynamics in surface-modified CdS quantum dots (QDs) prepared by a colloidal method. The size- and surface-controlled CdS QDs have been successfully prepared by using a size-selective photoetching and surface modification technique. The decay profiles exhibit an unusual temperature dependence: increase of the decay time with increase in temperature. The temperature dependence of the decay profiles can be explained in terms of a three-level model including the exciton state with a triplet origin, the so-called dark-exciton state.

We have investigated Franz–Keldysh oscillations (FKOs) from a base-emitter junction in an InGaP/GaAs heterojunction bipolar transistor structure using photoreflectance spectroscopy. The profiles of the FKOs originating from the InGaP emitter are compared with the line shapes calculated with the use of electro-optic functions. It is found that the line shape of the FKOs is remarkably affected by interference of probe light due to the multiple layer structure. Taking account of the interference effect, we have derived a novel analysis method for a convenient linear plot of the extremum positions of FKOs. The band-gap energy estimated with the present method well agrees with the band-gap energy obtained from the photoluminescence measurement of an InGaP/GaAs heterostructure for a reference.

Persistent Helicobacter pylori colonization in the stomach induces gastritis and peptic ulcer and interferes with ulcer healing. Most strains of H. pylori produce a cytotoxin, VacA, that induces cytoplasmic vacuolation in epithelial cells with structural and functional changes, leading to gastric injury. VacA is known to cause cell death by mitochondrial damage. We hypothesized that VacA might disrupt other signaling pathways; to that end, we examined the effects of VacA on MAPKs to elucidate their role in the abnormalities seen in VacA-treated cells. VacA stimulated phosphorylation of p38 and Erk1/2, but not JNK, in AZ-521 cells. Both phosphorylation and kinase activation of p38 were maximal 10-30 min after addition of VacA and declined thereafter. Treatment with anti-VacA antibody or the p38 inhibitor SB203580 blocked p38 phosphorylation caused by VacA and inhibited VacA-induced phosphorylation of activating transcription factor 2 (ATF-2), which is implicated in transcriptional control of stress-responsive genes. These data indicate that VacA stimulates a p38/ATF-2-mediated signal pathway. However, 10 μm SB203580, which is sufficient to decrease p38 phosphorylation, did not inhibit VacA-induced cellular vacuolation, decrease in mitochondrial membrane potential, or cytochrome c release from mitochondria. These results suggest that VacA-induced activation of p38/ATF-2-mediated signal pathway is independent of cellular vacuolation, decrease in mitochondrial membrane potential, or cytochrome c release from mitochondria caused by VacA. The cytotoxin may thus act independently on several cellular targets, leading to disruption of signaling, regulatory, and metabolic pathways.

Helicobacter pylori vacuolating cytotoxin, VacA, induces vacuolation, mitochondrial damage, cytochrome c release, and apoptosis of gastric epithelial cells. To detect gastric proteins that serve as VacA receptors, we used VacA co-immunoprecipitation techniques following biotinylation of the cell surface and identified p250, a receptor-like protein-tyrosine phosphatase β (RPTPβ) as a VacA-binding protein (Yahiro, K., Niidome, T., Kimura, M., Hatakeyama, T., Aoyagi, H., Kurazono, H., Imagawa, K., Wada, A., Moss, J., and Hirayama, T. (1999) J. Biol. Chem. 274, 36693–36699). VacA causes vacuolation of G401 cells, a human kidney tumor cell line, although they do not express RPTPβ. By co-immunoprecipitation with VacA, we identified p140 as a potential receptor in those cells. p140 purified by chromatography on a peanut agglutinin affinity matrix contained internal amino acid sequences of RGEENTDYVNASFIDGYRQK and AEGILDVFQTVK, which are identical to those in RPTPα. The peptide mass fingerprinting of p140 by time of flight-MS analysis also supported this identification. Treatment of G401 cells with RPTPα-morpholino antisense oligonucleotide before exposure to toxin inhibited vacuolation. These data suggest that RPTPα acts as a receptor for VacA in G401 cells. Thus, two receptor tyrosine phosphatases, RPTPα and RPTPβ, serve as VacA receptors.

We have investigated coherent LO phonon–plasmon coupled (LOPC) modes in an (InAs) 1 /(GaAs) 30 strained-layer superlattice (SL) with a miniband structure. By generating carriers in the miniband, the GaAs-like LOPC modes are observed. In spectrally resolved pump–probe measurements, it is found that the intensity of the lower branch (L − ) of the LOPC mode is enhanced around the transition energies at the miniband critical points, the mini-Brillouin-zone center and edge. In addition, the decay time of the L − mode in the SL hardly depends on the detection energy. These properties of the LOPC mode will be discussed from the viewpoint of the effect of the miniband structure.

We report on the appearance of Bose–Einstein statistics of the exciton–biexciton system in a (GaAs) 12 /(AlAs) 12 type-II superlattice. The density relation of the exciton and biexciton is estimated from time-resolved photoluminescence spectra at various excitation powers and bath temperatures. The long lifetime of the type-II exciton, e.g., 2 μs at 5 K, enables us to obtain the precise information of the density relation. In a relatively low exciton-density region, the biexciton density obeys a well-known square law. At an exciton density around 1×10 10 cm −2 , the biexciton density suddenly increases with a threshold-like nature. This behavior, which is realized at temperatures up to 8 K, can be understood from Bose–Einstein statistics.

We have investigated the dynamical properties of coherent exciton states in CuI thin films grown by vacuum deposition using a transmission-type pump–probe technique at 10 K. The absorption spectrum exhibits the energy splitting of the heavy-hole (HH) and light-hole (LH) excitons caused by thermal strains, where the splitting energy is 14.0 meV. In the case of the simultaneous excitation of the HH and LH excitons, the time-domain signal clearly shows the damped oscillation with a frequency of 3.3 THz corresponding to the splitting energy, while such an oscillation signal is not observed for the excitation of the HH or LH exciton only. These results conclusively demonstrate that the observed oscillation signal is due to the quantum beat between the HH and LH excitons. We discuss the pump energy and pump-power dependence of the quantum beat signal from the aspect of the relaxation dynamics of excitons.

Photoluminescence (PL) spectra and scanning near-field optical microscope (SNOM) images have been measured at low temperature to investigate the compositional fluctuations in GaN x As 1− x epilayers grown on GaAs by metalorganic vapor-phase epitaxy. Time-resolved PL has been employed to study the optical transitions and their dynamic processes. Our results suggest that the PL emission from GaN x As 1− x epilayer at low temperature is dominated by localized exciton recombination induced by compositional fluctuations. Furthermore, we directly observed the distribution of the compositional inhomogeneity in the GaN x As 1− x samples even with a small N-content of 0.5% by measuring SNOM images. The emission spot size of less than 1 μm is estimated for the GaN x As 1− x (N=0.5%) epilayer, and its size tends to decrease with increasing nitrogen concentration.

In GaAs/AlAs type-II superlattices, the lowest-energy exciton consists of the X electron and Γ heavy hole that are confined in the AlAs and GaAs layers, respectively. The separation of the electron and hole both in real space and in momentum space leads to rich stages of the excitonic processes. Those are reviewed from the following aspects: the fundamental properties connecting with controllability, biexcitons, and condensation phases as bosons (excitonic superfluidity) and fermions (electron–hole droplet).

We report on the photoluminescence and carrier-transport properties of a GaAs(6.2 nm)/AlAs(1.7 nm) superlattice embedded in a p–i–n diode structure from the viewpoint of the intersubband scattering under an applied bias voltage (electric field). We have found the enhancement of the photoluminescence intensity in the reverse-bias region from 4 to 16 V, accompanying a dip structure. The transient photocurrent simultaneously exhibits delayed-transport profiles in the above bias region. The calculated results of the energies of the Γ1, Γ2 and X1 subbands indicate that the electron scattering between the Γ and the X subbands causes the above experimental results.

We have investigated the excitonic properties of In0.15Ga0.85As/GaAs strained single quantum wells by using photoreflectance spectroscopy and a variational calculation method. We clearly detected the photoreflectance signal of the type-II light-hole exciton, which consists of an electron confined in the InGaAs layer and a light hole located in the thick GaAs layer, in addition to the type-I heavy-hole exciton confined in the InGaAs layer. The calculated results of the overlap integral of the envelope function in the type-II light-hole exciton predict that the oscillator strength is remarkably enhanced with decreasing the InGaAs-layer thickness. This is demonstrated by the layer-thickness dependence of the photoreflectance intensity of the type-II light-hole exciton.

We have investigated the electric-field effects on the cw and time-resolved photoluminescence (PL) properties in a marginal type-I GaAs/AlAs superlattice (SL) whose lowest X state (X1) is situated in the lowest Γ(Γ1) miniband. In the low bias voltage regime, the PL spectra reveal the transition between type-I and type-II radiative recombination processes caused by Wannier–Stark localization. In contrast, in the high bias voltage regime, the decay time of the time-resolved PL is prolonged. This is because of delayed carrier transport caused by Γ–X transfer. From these results, it was found that marginal type-I SLs present various interesting phenomena that originate from the competitive carrier transport among the Γ miniband, the localized Γ Stark–ladder states, and the X1 state.

We have studied the photoluminescence properties of a GaAs/InAlAs strained superlattice as a function of an applied electric field. We have detected the appearance of light-hole Stark-ladder photoluminescence resulting from heavy-hole–light-hole resonance induced by the applied electric field. From calculated overlap integrals between electron and hole wave functions, it is demonstrated that the light-hole Stark-ladder photoluminescence is observable in a GaAs/InAlAs superlattice.

We have investigated the influence of strain effects on hole-subband resonances in GaAs/InAlAs strained superlattices. The samples consist of the same superlattice structure with different buffer layers. We have found that the photocurrent–voltage characteristics exhibit peaky structures due to the hole-subband resonance and that the resonant conditions are modified by the difference in the lattice constant of the buffer layers. The resonant conditions have been discussed from the subband-energy calculation based on an effective-mass approximation taking into account the strain effects.

We report on the observation of the Franz–Keldysh oscillations associated with the second-electron and heavy-hole minibands, in which the second-electron miniband lies above the barrier potential, in a GaAs(7.0 nm)/Al0.1Ga0.9As (3.5 nm) superlattice by using electroreflectance spectroscopy. The reduced mass estimated from the Franz–Keldysh oscillations is consistent with that estimated from the miniband–dispersion relation based on the effective mass approximation around a zero-electric field, and becomes heavier with an increase in the electric field. The electric-field dependence of the reduced mass correlates with the localization of the electron envelope function. We discuss these results from an envelope-function forms calculated by a transfer-matrix method.

We have investigated the terahertz (THz) radiation from the coherent GaAs-like longitudinal optical (LO) phonons at room temperature in GaAs/AlAs multiple quantum wells utilizing an optical gating method with an ultrashort pulse laser. It has been found that the intensity of the THz radiation with a long dephasing time is markedly enhanced under the condition that the energy spacing between the fundamental heavy-hole and light-hole excitons is almost equal to the LO-phonon energy. This fact demonstrates that the impulsive excitonic interference, which produces no beating oscillation at room temperature owing to a very fast dephasing time, acts as a driving force for the coherent LO phonon emitting the intense THz radiation.