Search

Background & aims Irritable bowel syndrome (IBS) manifests as chronic abdominal pain. One pathophysiological theory states that the brain–gut axis is responsible for pain control in the intestine. Although several studies have discussed the structural changes in the brain of IBS patients, most of these studies have been conducted in Western populations. Different cultures and sexes experience different pain sensations and have different pain responses. Accordingly, we aimed to identify the specific changes in the cortical thickness of Asian women with IBS and to compare these data to those of non-Asian women with IBS. Methods Thirty Asian female IBS patients (IBS group) and 39 healthy individuals (control group) were included in this study. Brain structural magnetic resonance imaging was performed. We used FreeSurfer to analyze the differences in the cortical thickness and their correlations with patient characteristics. Results The left cuneus, left rostral middle frontal cortex, left supramarginal cortex, right caudal anterior cingulate cortex, and bilateral insula exhibited cortical thinning in the IBS group compared with those in the controls. Furthermore, the brain cortical thickness correlated negatively the severity as well as duration of abdominal pain. Conclusions Some of our findings differ from those of Western studies. In our study, all of the significant brain regions in the IBS group exhibited cortical thinning compared with those in the controls. The differences in cortical thickness between the IBS patients and controls may provide useful information to facilitate regulating abdominal pain in IBS patients. These findings offer insights into the association of different cultures and sexes with differences in cortical thinning in patients with IBS.

As the building sector accounts for about 30% of Taiwan’s carbon footprint, improving the Green Building Literacy (GBL) of building owners or users through general education is important to the carbon reduction commitment. This study aimed to use Delphi method and action research to innovate undergraduate curriculum of Green Building Introduction in general education to foster GBL. According to the suggestions by the Delphi panel and guidance of GBL model which was constructed from paper review and countrywide survey data by using structural equation modeling, the GBL curriculum not only conveys the knowledge of fact but more emphasizes on the knowledge for action and basic design skill through the involvement in the specific activities, which are also used to improve students’ attitudes and responsibility to promote their behavioral performance. The evaluation of the curriculum showed that there are significant improvements in the cognitive domain and the attitude-behavior domain of students’ GBL.

The progress of light-emitting-diode (LED) development based on nitride nanocolumn (NC) growth, including InGaN/GaN quantum-well (QW) growth on NCs and regularly arranged GaN NC growth, is first reviewed. Then, the coalescence-overgrowth results based on patterned GaN NC growth are introduced. The overgrowth quality dependence on NC cross-sectional size and NC spacing size is discussed. Generally, a smaller NC dimension and spacing size lead to higher overgrowth quality, including lower threading dislocation (TD) density and larger lateral domain size. Next, the emission enhancement results of blue- and green-emitting InGaN/GaN QW and LED structures based on NC growth and coalescence overgrowth are presented. Significant enhancements (up to ~100% output intensity increase in a blue LED) are demonstrated. For LED applications, the TD density reduction in an overgrown GaN template can more effectively enhance the emission efficiency of a blue LED, when compared with a green LED.

Phosphor-free monolithic InGaN-based white-light LED has the advantages of simpler device process and potentially higher efficiency. Several techniques have been developed for implementing such white-light LEDs. Among them, the key issue is the growth of a high-quality high-indium InGaN/GaN quantum well (QW). An underlying InGaN layer growth technique is introduced for enhancing the crystal quality of a high-indium QW. To demonstrate the superior properties of a QW grown with this technique, a green LED is fabricated based on the underlying growth technique to compare with another LED of the same emission wavelength based on the conventional growth method. Then, the underlying growth technique is used to grow three yellow-emitting QWs of high efficiency. The yellow photons mix with blue light from an overgrown blue-emitting QW to produce white light. The improved properties of the phosphor-free monolithic white-light LED are discussed in detail.

The crystal quality, as determined by X-ray diffraction, of GaN epitaxial films synthesized by MOCVD overgrowth of oriented GaN nanocolumns on Si(1 1 1) is studied as a function of film thickness and compared with control films grown on sapphire substrate. Samples were characterized using a three-beam X-ray diffraction technique from which depth-dependent rocking-curve widths (for the (0 1 1¯ 3)/(0 1¯ 12¯) crystal plane) are obtained as functions of depth. Through the examination of four samples prepared under conditions spanning key growth parameters it is found that optimizing for overgrowth at higher substrate temperatures can lead to coalesced films with significantly narrower rocking-curve widths. The results indicate that initially disconnected crystal domains stemming from individual columns do merge under the right conditions and that the coalesced crystal improves with increasing thickness. Overgrowth with the substrate temperature at 1000 °C (the highest of the study) resulted in a GaN overgrowth with properties superior to those of the control sample, a standard high-quality 2 μm MOCVD GaN thin-film grown on sapphire substrate.

We use the techniques of high-resolution transmission electron microscopy and strain state analysis (SSA) to show the material nanostructures of two InGaN/GaN quantum-well (QW) samples. In one of the samples, a low-indium InGaN/GaN QW is grown before five high-indium ones, which are grown under the same conditions as those for growing the five QWs in another sample (the control sample). From the calibrations of the average indium contents of those QWs based on the SSA images, it is found that the QWs close to the low-indium one have higher indium contents than those in the control sample. Such an increase of indium incorporation is attributed to the pre-strain effect of the low-indium QW on the barrier layer right above it. The pre-strain effect diminishes along the growth of more QWs. This effect represents an effective approach for increasing indium contents for implementing yellow-red light-emitting diodes based on InGaN/GaN QW structures.

We grew and processed a blue/green two-wavelength light-emitting diode (LED) based on the mixture of two kinds of quantum wells (QW) in epitaxial growth. The X-ray diffraction and photoluminescence measurements indicated that the crystalline structure and the basic optical property of individual kinds of QW are not significantly changed in the mixed growth. The relative electroluminescence (EL) intensity of the two colors depends on the injection current level, which controls the hole concentration distribution among the QWs. At low injection levels, the top green-emitting QW dominates in EL. As the injection current increases, the blue-emitting QWs beneath become dominating. We also coated CdSe-ZnS nanocrystals on the top of the two-wavelength LED for converting blue photons into red light. With the coating of such nanocrystals, the device emits blue, green, and red lights for white light generation

Coalescence overgrowth of GaN nanocolumns on Si and sapphire substrates with metalorganic chemical vapor deposition is implemented to show high crystal and optical qualities. Depth-dependent X-ray diffraction is realized to understand the coalescence growth process.

Nitride nanostructures and nano-photonics, including an MOCVD prestrained InGaN/GaN quantum well growth technique for orange and white LED fabrication and surface plasmon coupling with an InGaN/GaN quantum well for light emission enhancement, are reported.

A prestrained MOCVD growth technique is introduced to enhance the indium incorporation of InGaN/GaN quantum wells for effectively emitting yellow-red light such that white-light light-emitting diodes can be fabricated without using phosphors.

We report some recent developments in all-semiconductor multi-color and white-light light-emitting diodes. The potential of the development of phosphor-free all-InGaN/GaN quantum-well white-light light-emitting diode will be evaluated.

Two approaches for fabricating white-light light-emitting diodes are discussed, including the stacking of various InGaN/GaN quantum wells for mixing into white light and the use of ll-VI nano-crystals for converting short-wavelength photons into long-wavelength light.

High-quality coalescence overgrowth of patterned-grown GaN nanocolumns on c-plane sapphire substrate with metal organic chemical vapor deposition is demonstrated. Although domain structures of a tens of micron scale in the overgrown layer can be identified with cathodoluminescence measurement, from atomic force microscopy (AFM) measurement, the surface roughness of the overgrown layer in an area of 5×5 μm2 is as small as 0.411 nm, which is only one-half that of the high-quality GaN thin-film template directly grown on sapphire substrate (the control sample). Based on the AFM and depth-dependent x-ray diffraction measurements near the surface of the overgrown layer, the dislocation density is reduced to the order of 107 cm−2, which is one order of magnitude lower than that of the control sample and two to three orders of magnitude lower than those of ordinary GaN templates for fabricating light-emitting diodes. Also, the lateral domain size, reaching a level of ∼2.7 μm, becomes three times larger than the ...

The enhanced emission efficiency and reduced spectral shifts of a green InGaN/GaN quantum-well (QW) light-emitting-diode epitaxial structure by using the prestrained growth technique when compared with a control sample of the same emission spectrum with conventional growth are demonstrated. By adding an ∼7%-indium InGaN/GaN QW to the structure before the growth of designated emitting high-indium QWs, the growth temperature of the emitting QWs can be raised by 30 °C while keeping about the same emission wavelength around 544 nm in photoluminescence (PL) and 525 nm in electroluminescence (EL). The internal quantum efficiency, room-temperature PL intensity, and EL intensity at the injection current of 20 mA are increased by ∼167%, ∼140%, and ∼182%, respectively. Also, the spectral blueshift range in increasing injection current in the range of 50 mA is decreased by 46%. Based on the pump-power dependent PL measurement, it is found that the quantum-confined Stark effect (QCSE) becomes weaker in the prestraine...

The authors demonstrate superior crystal quality of a-plane GaN grown on r-plane sapphire substrate based on the flow modulation epitaxy (FME) technique, in which the Ga atom supply is alternatively switched on and off with continuous nitrogen supply. With the FME technique, a high growth rate of 2.3μm∕h can still be achieved. With or without epitaxial lateral overgrowth (ELOG), either c- or m-mosaic condition is significantly improved in the samples of using FME. With ELOG, the surface roughness can be reduced from 1.58to0.647nm in an area of 10×10μm2 microns by using the FME technique. Based on the results of photoluminescence measurement, one can also conclude the better optical property of the FME-grown a-plane GaN thin films. Besides, it is shown that tensile strain is more relaxed in the FME samples.

The authors demonstrate the coalescence overgrowth of GaN nano-columns on a (111) Si substrate with metalorganic chemical vapor deposition to show high-quality optical properties in the overgrown film. Plan-view scanning electron microscopy (SEM) shows coalesced surface morphology, although hexagonal structures are still visible in the images. The cross-section cathodoluminescence (CL) image shows more efficient emission in the overgrowth layer than from the nano-column layer. The plan-view CL image demonstrates that the emitted light is mainly from the hexagonal structures. The photoluminescence measurement result indicates that the emission efficiency of the overgrown layer is even higher than that of an undoped GaN thin film of high quality. The presence of hexagonal structures correlates to surface roughness values in the range of several nanometres.

We compare the x-ray diffraction (XRD) results of two InGaN∕GaN quantum-well (QW) structures to observe the effects of prestrained growth by depositing a low-indium QW before the growth of five high-indium QWs. From the results of reciprocal space mapping, we observe the fully strained condition in the QWs of the control sample. However, in the sample of prestrained growth, the average strain is partially relaxed. By using an XRD fitting algorithm for calibrating QW parameters, we obtain reasonable values for the compositions and thicknesses of the QWs in both samples. In particular, by assuming a nonuniform strain relaxation distribution among the five high-indium QWs in the prestrained sample, we obtain reasonable composition variations among the QWs. The high-indium QW closest to the low-indium one is most strain-relaxed and has the highest indium incorporation, leading to the longest-wavelength emission. The observed red shift with increasing electron penetration depth in the cathodo-luminescence spectra of the prestrained sample is consistent with the distributions of calibrated strain relaxation and indium composition. The results of high-resolution transmission electron microscopy and effective band gap calculation also agree with the above conclusions.

The authors demonstrate the spectral redshift of the quantum wells (QWs) designated for green emission into the orange range in a light-emitting diode by adding a violet-emitting QW at the bottom in metal-organic chemical vapor deposition. An electroluminescence redshift of 53nm was obtained. The cathodoluminescence spectra indicated that the long-wavelength QWs close to the violet one were strongly influenced by this added QW and mainly emitted the orange photons. Those near the top were less affected. This influence is supposed to originate from the prestrained effect in the barrier layer right above the violet QW. Such a prestrained effect is expected to be more effective when the underlying QW is well shaped and the heterojunction strain is strong, like the case of the violet QW. This effect is weak between the high-indium QWs, in which the formation of indium-rich clusters releases the strain.

The immature developments of p-type ZnO and ZnO-related ternary or quaternary compound and the small lattice mismatch between ZnO and GaN stimulate interest in the hybrid growth of ZnO and GaN. In this research, we compared the nanostructures and optical properties of two ZnO thin-film samples grown under the same conditions but on different underlying materials (sapphire and GaN). With the high growth temperature of 450°C, both samples show domain structures. However, in contrast to the sample of ZnO on sapphire, the sample of ZnO on GaN starts with smaller domains (a few tens of nanometers in width) of almost vertical boundaries at the interface and evolves into larger domains (around 100nm in width). The 30° twist of the basal plane in ZnO with respect to its underlying sapphire does not occur in the sample of ZnO on GaN. Within a domain of ZnO on sapphire, misfit and threading dislocations can be periodically observed along the interface with the separation of about 8nm. The transition of the lattice ...

The 60's drought (1961-1966) which hit the Northeastern United States, had its center over the Delaware River Basin and caused water supply shortages to New York City, Philadelphia, and many other towns and industries in the Basin. Until this event occurred, the existing water supply sources and those planned for the future had been considered adequate, as they were designed for the worst drought of record (usually thc 1930-31 drought). In view of this "change in hydrol- ogy,'' the Delaware River Basin Commission authorized a study (DRBC Resolution 67-4) to re-evalu- ate the adequacy of existing and planned water supply sources of the Delaware River Basin and its Service Area (New York City and northern New Jersey). Synthetic hydrology is a tool which can be used to overcome many of the limitations of the traditional approach. By analyzing generated streamflow traces in this study, it has been determined that there is a definite relationship between the accumulated rainfall deficiency during the drought and the return pcriods associated with various durations of runoff in the drought. This indicated that generated traces can be used to standardize the hydrology over an area where the intensity of drought varicd. This represented an important facet in the study, because it provided a means to equalize the effects of this drought over the study area, and gave the Delaware kver Basin Commis- sion more information so that it could better plan and manage its water resources equitably, not only for the peoplc within the Basin, but for the New York City and northern New Jersey areas as well. Synthetic hydrology was used to determine yield-probability relationships for 50-year periods, and storage-yield-frequency relationships for existing and planned water-supply reservoirs. It was also used to determine yield-probability relationships for reservoir systems within the Basin. In the study, it was determined that monthly streamflow traces and uniform draft rates could be used in yield analysis because of the magnitude of the reservoirs and because seasonal variations of draft rate are small in the study area. Although it was found that with the streamflow generating models (first order Markov) in com- mon use today, it is not possible to definitely determine the actual frequency of a very scverc historic drought, it is possible to place a drought in perspective by using synthetic hydrology. The study showed that it is a useful tool in determining water availability over a basin and is useful in studying water management problems such as interbasin transfers, and reservoir systems operations. (KEY WORDS: drought; water supply; planning; synthetic hydrology; yield-probability ; storage- yield frequency; reservoir operations; water management; Delaware River Basin)