Search

We have developed a systematic communication training program for preclinical training using a dialog simulator,as a new teaching approach for pharmacy students.The communication training consisted of 3 processes for the clinical case scenarios that were devised (e.g.anamnesis at pharmacy,instructing patients in compliance,prescription questions,instruction in self-injection).In the first,students checked interview items using a dialog simulator as the introductory phase of the training (process 1).In the second,students used this to prepare role-plays consisting of interviews with simulated patients (SP) in small groups (process 2).Students took turns at being the patient,pharmacist and observer in small groups and then students received feedback from SPs on their performance as pharmacists in the role-plays (process 3).Faculty participated in the communication training with regard to its scheduling and in the role-playing as patients.Afterwards,we conducted a questionnaire survey of the students’impressions of such training using a dialog simulator and subjected the results to CS analysis in order to evaluate the areas for improvement in the communication-training program.Students’evaluations with regard to the effectiveness of self-learning were both significant and interesting.While there was a little dissatisfaction with the speech recognition function of the simulator and it was considered to require the most improvement (rating of 18.78),our findings indicate that our original program using such a device in systematic communication training is useful in helping students to acquire communication skills.

The electrical interface properties of GaN metal–oxide–semiconductor (MOS) capacitors with an Al2O3 gate insulator formed by atomic layer deposition method using three kinds of oxidants were investigated by the capacitance–voltage technique, Terman method, and conductance method. We found that O3 and the alternate supply of H2O and O3 (AS-HO) are effective for reducing the interface trap density (D it) at the energy range of 0.15 to 0.30 eV taking from the conduction band minimum. On the other hand, we found that surface potential fluctuation (σs) induced by interface charges for the AS-HO oxidant is much larger than that for a Si MOS capacitor with a SiO2 layer formed by chemical vapor deposition despite the small D it values for the AS-HO oxidant compared with the Si MOS capacitor. This means that the total charged center density including the fixed charge density, charged slow trap density, and charged interface trap density for the GaN MOS capacitor is higher than that for the Si MOS capacitor. Therefore, σs has to be reduced to improve the performances and reliability of GaN devices with the Al2O3/GaN interfaces.

We have introduced a communication training program using problem-based learning (PBL) and simulated patients (SP) as a new teaching approach for pharmacy students.The communication training consisted of 5 processes involving 3 clinical scenarios that we designed (patient #1 : smoking cessation instruction,patient #2 ; taking anamnesis in pharmacy,patient #3 ; explanation of over-the-counter drug including health consultation).For smoking cessation instruction,first,the students were given the scenario and discussed how to solve the problems in small groups (process 1,2 and 3).They then shared the information collected by each group and prepared an instruction sheet for role-playing (process 4 and 5).In the roleplaying,students played the part of the pharmacist and received feedback from SP.Afterwards,we conducted a questionnaire survey of the students’impressions of the training using the Learning Management System and subjected the results to CS analysis in order to determine the areas of the communication program needing improvement.The evaluation of the program with regard to the role-playing with the SP and the feedback from them after it produced some interesting and significant results,with students feeling that the procedure for providing the feedback and teacher engagement in the small group discussion (SGD) required the most improvement (ratings of 10.22 and 5.10,respectively).These results indicate that our communication training program utilizing PBL and SP is a useful way for students to acquire communication skills and of increasing their motivation towards such training.

The net doping characteristics of Si-doped n-GaN grown on Si(1 1 1) substrate and on c-sapphire substrate by MOVPE were investigated. In case the carrier concentration is less than 1×10 17 cm −3 , the n-GaN on Si has a strong compensation behavior. But it seems that it does not depend on carbon concentration as p-type dopant, but on other acceptors associated with crystal defects. AlGaN/GaN HEMTs were fabricated on both substrates. DC performance of the devices fabricated on Si substrate is in no way inferior to that of devices grown on sapphire substrate.

In this paper, we demonstrate a novel method to integrate photonic crystals (PhCs) on GaN-based blue light-emitting diodes (LEDs) using a silicon substrate as a mold for forming the PhCs. This method starts with fabricating a 2D grooved Si substrate as that mold. Subsequently, GaN-based epitaxial layers are grown on the Si mold-substrate, which effectively reduces the dislocation density in GaN by enhanced lateral epitaxial growth. After the epitaxial layers are bonded onto a highly reflective substrate, the Si mold-substrate is removed. This substrate-transfer technique replicates PhC from the mold-substrate on the LED surface free from processing damages. The resultant LEDs with PhC have outperformed the LEDs without PhC in the optical output power by 80%, taking advantage of the enhanced light extraction by PhC.

The AlGaN/GaN heterostructures (HSs) with reduced dislocation density were grown on 4-in. a-plane sapphire substrate. The two-dimensional electron gas (2DEG) was observed for AlGaN/GaN HSs on a-plane sapphire. A complete pinch off AlGaN/GaN high electron mobility transistors (HEMTs) were demonstrated with a maximum drain current density (IDSmax) of 551 mA/mm and transconductance maximum (gmmax) of 134 mS/mm. Compared to c-plane grown HEMTs, two orders of magnitude low gate leakage current was observed on a-plane grown HEMTs with enhanced barrier height. The low gate leakage is due to enhanced Schottky barrier height and reduced dislocation density of GaN grown on a-plane sapphire.

The circadian clock system is necessary to adapt endogenous physiological functions to daily variations in environmental conditions. Abnormality in circadian rhythms, such as the sleep-wake cycle and the timing of hormonal secretions, is implicated in various physiological and psychiatrical disorders. Recent molecular studies have revealed that oscillation in the transcription of specific clock genes plays a central role in the generation of 24h cycles of physiology and behavior. It has been noticed that patients receiving chemotherapeutic agents experience disturbances in their behavioral and physical performances, including circadian rhythms. To explore the underlying mechanism of chemotherapeutic agent-induced disturbance of these rhythms, we investigated the influence of 5-fluorouracil (5-FU), one of the most widely used chemotherapeutic agents for the treatment of cancers, on the expression of clock genes. Treatment of cultured NIH3T3 cells with 5-FU for 48 h resulted in a significant reduction of mRNA levels of Period1 (Per1) and Period2 (Per2) without affecting cell viability; however, treatment with the same amount of uracil, a structural analog of 5-FU, had little effect on the expression of clock genes. Consistent with its inhibitory actions, continuous administration of 5-FU (2 mg/kg/h) to mice attenuated the oscillation in the expressions of Per1 and Per2 in the liver and suprachiasmatic nuclei, the center of the mammalian circadian clock. These results reveal a possible pharmacological action by the chemotherapeutic agent 5-FU on the circadian clock mechanism, which is the underlying cause of its adverse effects on 24-h rhythms of physiology and behavior.

AlGaN films and deep ultraviolet light-emitting diode (UV-LED) structures with AlGaN multi-quantum wells (MQWs) were grown directly on 2-in.-diameter epitaxial AlN/sapphire template (AlN template) by metalorganic chemical vapor deposition (MOCVD). It was confirmed that crack-free and good-crystal-quality AlGaN films and UV-LED structures can be grown on AlN template without the use of any buffer layer technique such as superlattice structures or pulsed atomic layer deposition. This seemed to be mainly due to the in-plane compressive stress caused by using AlN template as underlying substrates. Deep UV-LED devices were successfully fabricated using MOCVD-grown wafers. Electroluminescence spectra for those LEDs exhibited sharp near-band emissions ranging from 265 to 277 nm, depending on their Al compositions in MQWs. It was also confirmed that the insertion of a thin AlN layer between the active region and the p-type cladding layer can drastically suppress a parasitic sub-band emission around 320 nm.

Cannabidiol, a non-psychoactive component of cannabis, has been reported to have interactions with Delta(9)-tetrahydrocannabinol (Delta(9)-THC). However, such interactions have not sufficiently been clear and may have important implications for understanding the pharmacological effects of marijuana. In the present study, we investigated whether cannabidiol modulates the pharmacological effects of Delta(9)-THC on locomotor activity, catalepsy-like immobilisation, rectal temperature and spatial memory in the eight-arm radial maze task in mice. In addition, we measured expression level of cannabinoid CB(1) receptor at striatum, cortex, hippocampus and hypothalamus. Delta(9)-THC (1, 3, 6 and 10 mg/kg) induced hypoactivity, catalepsy-like immobilisation and hypothermia in a dose-dependent manner. In addition, Delta(9)-THC (1, 3 and 6 mg/kg) dose-dependently impaired spatial memory in eight-arm radial maze. On the other hand, cannabidiol (1, 3, 10, 25 and 50 mg/kg) did not affect locomotor activity, catalepsy-like immobilisation, rectal temperature and spatial memory on its own. However, higher dose of cannabidiol (10 or 50 mg/kg) exacerbated pharmacological effects of lower dose of Delta(9)-THC, such as hypoactivity, hypothermia and impairment of spatial memory. Moreover, cannabidiol (50 mg/kg) with Delta(9)-THC (1 mg/kg) enhanced the expression level of CB(1) receptor expression in hippocampus and hypothalamus. Cannabidiol potentiated pharmacological effects of Delta(9)-THC via CB(1) receptor-dependent mechanism. These findings may contribute in setting the basis for interaction of cannabinoids and to find a cannabinoid mechanism in central nervous system.

Metalorganic chemical vapor deposition (MOCVD) of a crack-free, mirror surface of GaN on 150-mm-diameter (1 1 1) Si substrate was performed using a horizontal MOCVD system. We used the combination of an AlGaN/AlN nucleation layer with an AlN/GaN strained superlattice structure (SLS) for strain control. A good mirror surface morphology was obtained over the entire GaN surface. Transmission electron microscopy (TEM) showed that screw dislocations were terminated at the interface of the GaN top layer and SLS. A pit density of 4×10 9 cm −2 was determined by atomic force microscopy, the mean thickness of the GaN top layer was approximately 0.4 μm, and the uniformity (1 sigma) was 4.37%. Asymmetrical reciprocal-lattice space mapping (RSM) measurement and TEM observation showed that the GaN film was fully relaxed. Relaxation occurs at both the interface of the SLS and AlN buffer layer and the interface of the GaN top layer and SLS.

In this paper, we reveal an activation energy of a frequency-dependent drain conductance in AlGaN/GaN HEMT. Firstly, using two-port vector network characteristics at a low frequency less than MHz, it is confirmed that frequency dependence of a drain conductance (Gd) results in peculiar behavior in S22 of the AlGaN/GaN HEMT. In order to obtain the activation energy of the process of the frequency response of the Gd, we evaluate temperature dependence of a time constant (τ) of the frequency-dependent Gd, which can be obtained by exponential fitting of the Gd. With an Arrhenius plot for the Gd, the activation energy of the process can be estimated to be 0.13 eV. This activation energy is as exactly same as that we obtained from pulsed I-V measurements with which an electron capture process can be evaluated. Therefore, peculiar behavior in S22 we observed in very low frequency two-port network measurements is concluded to result from the electron capture process in the epitaxial layer.

InAlN/GaN based high-electron-mobility transistors (HEMTs) are of immense interest due to its high power, high speed and high temperature capabilities. Lattice matched In 0.18 Al 0.82 N/GaN HEMTs with its high polarization induced two-dimensional electron gas (2-DEG) can outperform AlGaN/GaN HEMTs and mitigate strain related issues [1–3]. Also, In 0.18 Al 0.82 N/GaN heterostructures can be used for power switching and converter applications, which require enhancement-mode (E-mode) devices with high drain current density (I DS,max ) and positive threshold voltage (V th ). Nevertheless, InAlN/GaN Schottky barrier (SB-HEMT) is prone to high gate leakage, which degrades On/Off current ratio (I on/Ioff ) and subthreshold slope (SS). In past, several oxides such as SiO 2 , SiN, HfO 2 and ZrO 2 were used for InAlN/GaN metal-oxide-semiconductor (MOS-HEMTs) to reduce gate leakage [4–8]. However till date, there is no report available for the transport properties of In 0.18 Al 0.82 N/GaN/Si MOS-HEMTs using atomic layer deposited (ALD) Al 2 O 3 . In this paper, enhanced transport properties of Al 2 O 3 /In 0.18 Al 0.82 N/GaN MOS-HEMT and its potential as E-mode device is presented.

In this paper, we discuss an ohmic contact resistance (R c ) in a recessed-gate normally-off AlGaN/GaN MIS-HEMT with a δ-doped GaN Cap Layer. This structure ensures high uniformity of a threshold voltage (V th ) by a selective dry-etching of GaN over AlGaN at a gate region. At the δ-doped region of the GaN cap layer, diffusion of electrons toward the surface leaves excess ionized donors, resulting in compensation of negative polarization charges between the GaN cap and the AlGaN barrier. Thanks to this effect, we successfully obtained an low R c of less than 0.1 Ωmm by reduction of band-barrier at the interface between the GaN cap and the AlGaN barrier.

Background Unintended exposure to antitumor agents from an oral medicine may place healthcare workers and patients taking medicine at risk. In this study, the exposure to blister pack by CP (cyclophosphamide) and appropriate preventive procedures were examined. Findings CP detected inside the blister pack of the tested seven lots by LC-MS/MS ranged from 8.2 to 199.6 ng. Raman imaging clearly showed that CP ingredient was completely covered by the tablet coating layer and had not leached out of the tablet. In addition, the amount of CP detected inside the vials was suppressed under the lower detection limit until day 28, and only 6.0 ng was detected only at day 56. Conclusions Various amounts of CP were contaminated to not only the inside of the blister pack but also the outside. This contamination may be caused not only by the manufacturing environment but also by the CP oral tablets themselves through volatilization of CP. Refrigerated storage of CP oral tablets may protect healthcare workers and patients from contact with CP. Electronic supplementary material The online version of this article (doi:10.1186/s40780-015-0020-9) contains supplementary material, which is available to authorized users.

Al0.26Ga0.74N/AlN/GaN high-electron-mobility transistor (HEMT) structures with AlN interfacial layers of various thicknesses were grown on 100-mm-diameter sapphire substrates by metalorganic vapor phase epitaxy, and their structural and electrical properties were characterized. A sample with an optimum AlN layer thickness of 1.0 nm showed a highly enhanced Hall mobility (μHall) of 1770 cm2/Vs with a low sheet resistance (ρs) of 365 Ω/sq. (2DEG density ns = 1.0 × 1013/cm2) at room temperature compared with those of a sample without the AlN interfacial layer (μHall = 1287 cm2/Vs, ρs = 539 Ω/sq., and ns = 0.9 × 1013/cm2). Electron transport properties in AlGaN/AlN/GaN structures were theoretically studied, and the calculated results indicated that the insertion of an AlN layer into the AlGaN/GaN heterointerface can significantly enhance the 2DEG mobility due to the reduction of alloy disorder scattering. HEMTs were successfully fabricated and characterized. It was confirmed that AlGaN/AlN/GaN HEMTs with the optimum AlN layer thickness show superior DC properties compared with conventional AlGaN/GaN HEMTs.

We present results of some novel AlGaN/GaN heterojunction field-effect transistors (HFETs) specifically developed for RF front-end and power applications. To reduce the parasitic resistance, two unique techniques: selective Si doping into contact area and a superlattice (SL) cap structure, are developed. With the selective Si doping method, a transistor with an on-state resistance as low as 1.86 Ω·mm and a Tx/Rx switch IC with very low insertion loss (0.26 dB) and very high power handling capability (P1dB over 40 dBm) were obtained. With the SL cap HFETs, an ultra low source resistance of 0.4 Ω·mm was achieved and excellent DC and RF performances were demonstrated. The typical characteristics of these HFETs are: maximum transconductance of over 400 mS/mm, maximum drain current of 1.2 A/mm, cut-off frequency of 60 GHz, maximum oscillation frequency of 140 GHz, and a very low noise figure of 0.7 dB with 15 dB gain at 12 GHz. For power applications, in order to significantly reduce fabrication cost, we fabricated the AlGaN/GaN HFET on a conductive Si substrate with a source-via grounding (SVG) structure. The device has a very low on-state sheet resistance of 1.9 mΩ·cm2, a high off-state breakdown voltage of 350 V, and a current handling capability of 150 A. In addition, a sub-nano second switching response with t r of 98 ps and t f of 96 ps with a current density as high as 2.0 kA/cm2 is demonstrated for the first time.

Influences of gate-recess etching with BCl3 plasma in drain current (ID) collapse were performed on different cap layers (i-GaN, n-GaN, and p-GaN) grown AlGaN/GaN high-electron-mobility transistors (HEMTs). Due to the decrease of dynamic-source-resistance by gate-recess, the increase of maximum drain current density and maximum extrinsic transconductance were observed in all cap layers grown AlGaN/GaN HEMTs. After gate-recess etching, about 14 and 17% of decrease in ID collapse were observed on n-GaN and p-GaN cap layers HEMTs, respectively when compared to non-recessed HEMTs. However, increase (~47%) of ID collapse was observed in i-GaN cap layer HEMTs. The decrease of ID collapse in doped GaN cap layer HEMTs is possibly due to the compensation of dopant related traps with plasma induced traps. The increase of ID collapse in i-GaN cap layer HEMTs may be due to the incorporation of damage related traps by gate-recess etching. The decrease and increase of trapping effects were qualitatively confirmed by white-light illuminated IDS–VDS characteristics. An increase of gate leakage current in all recessed gate AlGaN/GaN HEMTs are due to the BCl3 plasma induced damage.

Transverse-optical (TO) and longitudinal-optical (LO) phonons in Si-doped and undoped n-GaN films have been studied by infrared reflection spectroscopy. The former film has been grown by metalorganic chemical vapor deposition (MOCVD) to a thickness of 2.3 µm, while the latter by hydride vapor phase epitaxy (HVPE) to a thickness of 35 µm. Both films are deposited on the c-surface of sapphire substrates with the surface of the c-plane of the wurtzite structure. Oblique-incidence infrared reflection spectroscopy has permitted us to observe the A1 mode, as well as the E1 mode, of polar optical phonons. The reflection spectra observed for s- and p-polarizations can be described well in terms of Gervais and Piriou's four-parameter semi-quantum oscillator model taking account of the LO-phonon–plasmon coupling. It is found that in the MOCVD-grown film, the damping energies of the phonons are markedly graded along the growth direction of the film. It is suggested that the lattice strain is quite large in the interface zone but is reduced rapidly upon going beyond about 1 µm from the interface. Accordingly, the HVPE film has a good lattice quality throughout the film.

It has been reported recently that the sapphire substrate can be etched inside a metalorganic chemical vapor deposition reactor through GaN decomposition-induced reaction, and that device-quality GaN films can be grown on thus etched substrates with residual gallium droplets acting as nucleation sites [Hao et al., Appl. Phys. Lett 84 (2004) 4041]. In the present study, a maskless lateral epitaxial over growth (LEO) method is proposed to produce GaN films with reduced dislocation density through the use of in situ etched sapphire substrates. The microstructure of such GaN films was investigated by transmission electron microscopy and scanning electron microscopy, and the effect of lateral over growth has been confirmed. Dislocations in such GaN films were further analyzed through etch-pits density experiment and it has been found that this maskless LEO method is very effective to reduce pure edge dislocation density in the GaN films.

1. To test whether an ischemic insult increases the susceptibility to cyclosporine A (CsA)-induced neurotoxicity, we examined the effect of CsA on the minimal electroshock-induced convulsions in mice treated with a transient middle cerebral artery occlusion (MCAO) for a short period (2 h). 2. This MCAO produced small to mid-sized infarcted regions in the cerebral hemisphere with increasing post-operative days. In MCAO mice, CsA (30 mg/kg, i.p.) elevated the incidence of minimal electroshock-induced convulsions to 90–100% over that in sham mice (20–30%) at 1–7 days but not 14 days post-surgery. 3. In light of these findings, the possibility that CsA increases the risk of convulsions in patients with cerebral infarction and/or at an early stage following focal cerebral ischemia would have to be considered.

Hot flushes are the most common complaint of menopausal women. In the present study, a new animal model of hot flushes was established. Tail skin temperature was measured with a thermo tracer after mice were subjected to a forced exercise task using a motor driven treadmill. In ovariectomized mice, forced exercise for 10 min was most effective in increasing tail skin temperature over that of sham-operated mice. This elevation was blocked by estradiol replacement (1 mg/kg per week for 3 weeks), suggesting that our model simulates menopausal hot flushes. Keywords:: ovariectomy, forced exercise, menopausal flushing

Different-Al-content AlxGa1-xN/GaN (0.26≤x≤0.52) high-electron-mobility transistor (HEMT) structures were grown on large-area 100-mm-diameter sapphire substrates by metalorganic vapor phase epitaxy (MOVPE). A low sheet resistance of approximately 380 Ω/sq. and an in-wafer total variation of 7.6% with a standard deviation of 1.6% were obtained for the sample with the highest Al content of 0.52. The two-dimensional electron gas (2DEG) density and room-temperature Hall mobility of the Al0.52Ga0.48N/GaN HEMT structures were 1.76×1013/cm2 and 971 cm2/Vs with in-wafer total variations of 7.8% and 8.1%, respectively. HEMTs were successfully fabricated and they exhibited good dc characteristics. The dependence of maximum source–drain current density on Al content was consistent with the Al content dependence of sheet carrier concentration. The highest source–drain current density of 1033 mA/mm with a maximum extrinsic transconductance of 228 mS/mm was obtained for 2-µm-gate-length Al0.52Ga0.48N/GaN HEMTs.

We have systematically studied the effect of various interlayers on epiwafer bowing in AlGaN/GaN high-electron-mobility transistor (HEMT) structures on sapphire substrates by using an interlayer insertion method. The interlayers including aluminum increase the epiwafer bowing independently of growth temperature. However, both InGaN-based interlayers and low-temperature-deposited GaN interlayers suppress the epiwafer bowing. When multilayers are used as interlayers, the effect on epiwafer bowing is enhanced compared with that in the case of using single interlayers. The minimum bowing values were lower than 10 µm, which were accomplished by using multilayers. The crystalline qualities of AlGaN/GaN HEMTs with interlayers were satisfactory and the performance of these HEMTs was better than that of conventional AlGaN/GaN HEMTs without interlayers. Epiwafers with reduced bowing exhibited a reduced strain in GaN layers compared with that of GaN layers with larger bowing, which indicates that strain control in the epitaxial layers is important for reducing the epiwafer bowing.

We report the improved characteristics of GaInN multiple-quantum-well (MQW) light-emitting diodes (LEDs) on Si substrate by an insertion of distributed Bragg reflector (DBR). The DBR-based GaInN MQW LED structures were grown on 2-in-diameter n-Si (1 1 1) substrates using a metalorganic chemical vapor deposition method. The number of Al 0.3 Ga 0.7 N/AlN pairs in DBR was changed from 1 to 5. No cracks were observed over the entire area of the DBR-based LED structure with less than 3-pair DBR. The light output power of the 3-pair DBR-based LED is approximately two times larger than that of the non-DBR-based LED.

The concentration of F center in high-surface-area anatase titania nanoparticles prepared by MOCVD are studied with electron paramagnetic resonance measurements at different time and different temperatures. The results show that the kinetics of F center is dominated by surface process rather than bulk process. With increasing temperature, two temperature dependent regions for the concentration of F center can be clearly identified. The starting temperature and activation energy of the surface process are determined to be 357.4 K and 0.085 eV, respectively. The reaction of F center with oxygen is of zero order and the concentration of F center can be well described by C ( T , t ) = 1.7 × 10 18 exp ( − 986.87 T ) ( 1 − t 386.1 ) ( g − 1 ) .

The present study was designed to clarify the involvement of nitric oxide (NO) signaling in the adverse effect of cyclosporine on the blood–brain barrier. Cyclosporine increased the permeability of sodium-fluorescein and the cellular accumulation of rhodamine 123, a substrate of P-glycoprotein, in mouse brain endothelial (MBEC4) cells. This effect was markedly enhanced two- to threefold when MBEC4 cells were cocultured with rat astrocytes or C6 glioma cells. Direct and continuous electrochemical measurement of NO demonstrated that cyclosporine dose-dependently increased histamine- and phenylephrine-evoked NO production in MBEC4 cells and astrocytes, respectively. A NO synthase inhibitor (NG-monomethyl- l -arginine) blocked slightly and markedly cyclosporine-induced impairment of the endothelial barrier in the monolayer and coculture system, respectively. These findings suggest that cyclosporine impairs the brain endothelial barrier function by accelerating NO production in the brain endothelial and astroglial cells. This event may be interpreted as triggering the occurrence of cyclosporine neurotoxicity.

The effects of rapid thermal annealing (RTA) on the optical properties of GaNAs∕GaAs triple quantum wells grown by chemical beam epitaxy are studied in detail by photoluminescence (PL) spectroscopy at 77K. Special emphasis is put on the RTA-induced PL peak blueshift. It is found that the blueshift is neither due to nitrogen diffusion from well layer to barrier layer nor due to homogenization of nitrogen composition fluctuations. The blueshift is due to the coupling between the radiative recombination of PL emission and the nonradiative recombination of nonradiative centers. A quantitative model is proposed in which the blueshift is proportional to the relative change of the concentration of nonradiative centers. This model quantitatively explains not only our present results but also previous observations.

Effects of rapid-thermal-annealing (RTA) cover material on the properties of GaNAs/GaAs triple quantum wells (QWs) grown by chemical beam epitaxy (CBE) are studied in detail. Si wafer, GaAs wafer, and GaAs layer grown on GaAs substrate at low temperature are used as RTA cover materials. The results show that RTA cover material exerts significant influence on the properties of the QWs. The QWs using GaAs layer show not only the lower root mean square (RMS) roughness of sample surface but also the lower photoluminescence linewidth compared with those using GaAs wafer and Si wafer. The best RTA cover material is neither GaAs wafer nor Si wafer. The best RTA cover material is GaAs layer grown at low temperature from the viewpoints of both surface morphology and optical properties. The results obtained in this work are helpful for quality improvement of (In)GaNAs using RTA.

Most traditional security for capsule-type active networks focused on node-level security mechanism that tries to restrict resource consumption of a packet at a node. Network level security mechanism, which restricts resource consumption in the whole network like ttl in ipv4, is also necessary for capsule. We propose high-performance per-packet authentication mechanism for this purpose. The proposed authentication mechanism uses packet-loss-resistant one-time password algorithm to avoid multiple packet exchanges between user terminals and routers. Since the address in a node where a packet’s authentication data is stored can be easily calculated from the information contained in the packet, we can authenticate the packet without searching a database. The overhead in the packet for authentication information is 46 bytes, and a Linuxpc with a 2.8 GHz Intel Pentium 4 processor can authenticate and process a packet in 22 µs, which corresponds to 45,000 authentications per second.

InGaN multiple-quantum-well light-emitting diodes (LEDs) were grown on an AlN/sapphire template by metalorganic chemical vapor deposition. The crystalline quality was investigated by x-ray diffraction and electron-beam-induced current. The thermal stability of the LED was demonstrated by measurements of current-voltage, light output power-current, and electroluminescence (EL) spectra at different temperatures. The output power at 200 mA decreased by 7.3% for the LED on the template upon increasing temperature from 25 to 95°C, while that for the LED on sapphire decreased by 23.9%. The peak external quantum efficiency decreased from 0.23% to 0.22% and from 0.15% to 0.10% for the LEDs on the template and on sapphire, respectively. The EL spectrum peak at 20 mA shifted to lower energy by 17.2 meV for the LED on the template upon increasing temperature, while that for the LED on sapphire shifted by 32.7 meV. The LED on the template exhibited a higher output power and a better thermal stability with respect to the conventional LED on sapphire using a low-temperature GaN buffer layer, which is due to the low threading dislocation density in the active layer and the high thermal conductivity of AlN layer.

Photoluminescence (PL) studies were carried out on AlInGaN epilayers grown at different temperatures. An abnormal broad peak, which enhanced with the increase of Al incorporation, was observed below the band gap energy of AlInGaN in the 77 K PL measurement. We assigned it to the non-optimum growth temperature for aluminum containing alloys since such emission can be suppressed at higher growth temperature. Thus, high temperature (HT) was proposed for AlInGaN growth. The quality of HT-grown quaternary AlInGaN alloys was superior to that of low-temperature-grown ones, their structural and optical properties are comparable to that of GaN. In addition, incorporating indium is also helpful to suppress this abnormal emission, which maybe due to the indium localization effect. Finally, high performance AlInGaN MQWs structure had also been demonstrated at a higher growth temperature.

In most hospital wards, nurses make the parenteral nutrition (TPN) preparations for patients. In April 1997, pharmacists at Yame General Hospital, started making aseptic TPN preparations in internal medicine wards to further improve pharmaceutical care. In August 2002, this service was expanded to include all wards and the average monthly number of aseptic TPN preparations increased to 818. When we conducted a cost-benefit analysis on the aseptic TPN preparations made by pharmacists, it was found that the return on investment [ROI= (benefit-cost) /cost] was initially-18%. Through the analysis, we pinpointed variable factors affecting materials costs and other expenses arising in the making of aseptic TPN preparations and by managing such costs were able to increase ROI markedly to 39%. Our detailed analysis of costs thus enabled the making of aseptic TPN preparations by pharmacists to make a significant contribution to our hospital, and they also improved the quality of life of patients. It may also be useful to apply cost-benefit analysis to the evaluation of other clinical pharmaceutical services such as TDM and pain management.

Zn ion implantation along the c axis was investigated in order to fabricate a highly resistive GaN layer. It was calculated that Zn ions effectively transfer their energy to the crystal atoms due to the heavy mass. This energy transfer was able to create implanted damage, which induced the highly resistive layer. Secondary ion mass spectroscopy (SIMS) profile of Zn atoms revealed that Zn ions penetrated over 1μm into GaN layer at the ion energy of 350 keV. In the electrical characterization of the Zn implanted layer, it was found that thermal annealing at 500°C removed the Poole-Frenkel current and high sheet resistance of 2×1013Ω/sq was obtained. AlGaN/GaN HEMT (high electron mobility transistor) with Zn implanted isolation had good electrical characteristics.

In this paper, the growth and characterizations of AlInGaN quaternary alloys on sapphire substrate are presented. The room temperature PL peaks of the quaternary layers were in the range of 335–375 nm with full-width at half-maximum (FWHM) values ranged between 50 and 69 meV. The X-ray rocking curves of quaternary layers for (0 0 0 4) diffraction exhibited narrow FWHM values ranged from 250 to 320 arcsec. To the best of our knowledge, these are the best results among those published in the literature. In additoin, anomalous blue-shift behavior was observed in PL measurement when temperature changed from 300 to 77 K, which was due to the band tail states in quaternary AlInGaN caused by alloy compositional fluctuation.

For the purpose of the practical use of GaN-based electronic devices, we demonstrated the growth of 100-mm-diameter AlGaN/GaN heterostructures on c-face sapphire substrates by metalorganic vapor phase epitaxy (MOVPE). The obtained films have specular surface, good crystal quality and good uniformity of the Al composition across the entire epitaxial wafer. These epitaxial wafers showed a relatively high electron mobility, 1320 ± 80 cm2/Vs with the sheet carrier concentration of 8.4 ± 0.5 × 1012/cm3 at room temperature, across the entire epitaxial wafer. High-electron-mobility transistors (HEMTs) fabricated on the 100-mm-diameter epitaxial wafer also exhibited good dc characteristics. Typical values of the peak extrinsic transconductance and the maximum drain current density were 200 mS/mm and 534 mA/mm, respectively, for the device with the gate length of 2.0 μm and the gate width of 15.0 μm. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Quaternary AlInGaN epilayers were grown on sapphire substrates by atmospheric pressure metalorganic chemical vapour deposition (MOCVD). The characterization data indicate that the grown quaternary AlInGaN epilayers are of high-quality. The influence of indium incorporation on the properties of quaternary epilayers were studied. The PL spectra of the quaternary layers showed narrow full-width at half-maximum (FWHM) values (52 meV) at room temperature, which are comparable to that of GaN. The X-ray rocking curves of quaternary layers for (0004) diffraction exhibited narrow FWHM values ranged from 250 to 280 arcsec. To the best of our knowledge, these are the best results among those published in the literature. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Recessed gate AlGaN/GaN high electron mobility transistors (HEMTs) grown on sapphire substrate have been fabricated. In order to improve FET performances, we optimized the layer structure and the electrode arrangement of the HEMT, and hence 0.15 μm gate-length AlGaN/GaN-HEMTs with recessed gate were successfully fabricated and the obtained transconductance was as high as 450 mS/mm. In this paper we describe the improvement of HEMT layer structures on sapphire substrate, the optimisation of an offset arrangement of gate electrodes, and the results of DC/RF measurements of our HEMTs. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Highly resistive layers are formed by the implantation of Zn ion along the c axis of GaN and AlGaN/GaN epitaxial layers. Heavy ions such as Zn have been desirable for the formation of highly resistive layers, because ions effectively transferred their energy to the crystal atoms rather than the electrons in GaN. A sheet resistance Rs as high as 3.8×1011 Ω/sq was obtained on GaN layers after the ion implantation. Rs increased up to 2.2×1013 Ω/sq after the annealing at 500 °C for 300 s in an N2 atmosphere. The thermal activation energy Er for this sample was 0.67 eV. It was found that the experimental data in current–voltage characteristics were fitted to the equation included the Poole–Frenkel current and resistive (ohmic) current. The difference of Rs between the as-implanted and 500 °C annealed samples was due to the Poole–Frenkel current. The Poole–Frenkel current overcame the resistive one, and dominated the current mechanism in the case of the samples annealed at 200 °C or less. On the other hand, for...

Lightly doped n-GaN epilayers were grown by metal-organic chemical vapor deposition (MOCVD) on sapphire substrates. The grown n-GaN epilayers were characterized using atomic force microscopy (AFM), X-ray diffraction (XRD), photoluminescence and Hall effect measurements. Enhanced PL intensity and low dark spot density (DSD) were observed on the aligned step structure n-GaN. The samples with these aligned step structure showed high electron mobilities with good structural and optical properties, while the samples with the anisotropic step structure showed broadened XRD FWHM values, low mobilities, and poor structural and optical properties. The low Hall mobility of n-GaN is due to the scattering of charged threading dislocations. A clear correlation was observed between Hall mobility and DSD by AFM. The AFM surface observation is also a better method for the evaluation of the electron mobility of lightly doped MOCVD grown n-GaN.

An excellent on/off current ratio of 1010 and a nearly ideal subthreshold slope of 65 mV/dec was confirmed in a p-InGaN/AlGaN/GaN high-electron-mobility transistor. Favorable I-V characteristics were achieved with the p-InGaN cap layer under the gate electrode. A dry etching technique with a low-damage p-InGaN cap layer resulted in a significantly low leakage current of 10-11 A/mm.

Anatase titania nanoparticles are prepared at 700°C by metalorganic chemical vapor deposition (MOCVD) and the nanoparticles are collected by thermophoretic collection method. The effect of collection distance on the lattice structure of the nanoparticles is investigated, followed by discussion. The results show that the collection distance exerts a significant influence on the lattice structure of the nanoparticles. With decreasing collection distance, the lattice constant a increases while c decreases simultaneously, resulting in more significant lattice distortion. X-ray photoelectron spectroscopy and electron paramagnetic resonance results show that both oxygen and titanium vacancies exist in the nanoparticles. Vacancies in the nanoparticles are responsible for the lattice distortion.

High-quality GaN films were grown on epitaxial AlN/sapphire templates by metal-organic vapor phase epitaxy. The Hall mobility as high as 790 cm2/V s with the carrier concentration of 7.6×1016 cm−3 at 300 K along with low dislocation density of 5×107 cm−2 have been achieved. The X-ray rocking curve full-width at half-maximum were 61 and 232 arcsec for the (0 0 0 4) and (2024) reflections, respectively. Atomic force microscopy images showed smooth surface morphology and clear step formation. Additionally, pit terminations could be hardly found. Photoluminescence measurement revealed a higher intensity near the band edge.

Anatase titania nanoparticles with a particle size of about 10 nm are prepared by metalorganic chemical vapor deposition (MOCVD) and the anatase-rutile tranformation of the nanoparticles is investigated and discussed. The results show that anatase-rutile transformation takes place in a wide range of temperature. When annealing time is 1 h, the anatase-rutile transformation temperature of the nanoparticles is as high as 900 to 1200°C, which is comparable to that of micrometer-sized titania. Based upon X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA) results, a possible transformation mechanism is proposed. The high transformation temperature of the nanoparticles is primarily attributed to the retardation of the initial particle growth of the anatase phase due to the lattice strains in the nanoparticles before transformation proceeds.

Atmospheric pressure-metal organic chemical vapour deposition (AP-MOCVD) was used to grow InAs and InGaAs quantum dots (QDs) on GaAs/Si substrate. The influence of growth temperature on the QD density and distribution was investigated. Scanning probe microscopy (AFM and DFM) was used to investigate the growth behaviour of the QD structure. The growth properties of InAs/InGaAs QDs on the highly stressed GaAs/Si substrate under S–K growth mode at different deposition temperatures have been analysed. It was identified that the growth temperature plays major role in determining the growth and distribution of both InAs and InGaAs QDs due to the temperature-dependent dislocation propagation from the GaAs/Si substrate. The growth of InGaAs QDs was found “In” composition dependent. A high QD density of ∼5×10 10 –6×10 10 cm −2 was obtained on GaAs/Si at a growth temperature of 500 °C.