Enhancement-Mode Ambipolar Thin-Film Transistors and CMOS Logic Circuits using Bilayer Ga2O3/NiO Semiconductors

Recent advancements in power electronics have been driven by Ga2O3-based ultrawide bandgap (UWBG) semiconductor devices, enabling efficient high-current switching. However, integrating Ga2O3 power devices with essential silicon CMOS logic circuits for advanced control poses fabrication challenges. Researchers have introduced Ga2O3-based NMOS and pseudo-CMOS circuits for integration, but these circuits may either consume more power or increase the design complexity. Hence, this article proposes Ga2O3-based CMOS realized using heterogeneous 3D-stacked bilayer ambipolar transistors. These ambipolar transistors consist of HfO2/NiO/Ga2O3/NiO/HfO2 heterostructures that are wrapped around by the Ti/Au gate electrode, resulting in record high electron and hole current on/off ratios of 109 and 107. The threshold voltage, subthreshold swing, and current density measured from 100 ambipolar devices (across 5 batches) are around -7.99 ± 0.92 V (p-channel) and 7.81 ± 0.81 V (n-channel), 0.59 ± 0.07 V/dec (p-channel) and 0.61 ± 0.06 V/dec (n-channel), and 0.99 ± 0.26 mA/mm (p-channel) and 58.23 ± 12.99 mA/mm (n-channel), respectively. All the 100 ambipolar devices showed decent long-term stability over a period of 200 days, exhibiting reliable electrical performance. The threshold voltage shift (ΔVTH) after negative bias stressing for a period of 3500 s is around 11.52 V (p-channel) and 10.21 V (n-channel), respectively. Notably, the n-channels exhibit ∼2 orders higher on/off ratio than the best Ga2O3 unipolar transistors at 300 °C. Moreover, the polarities of ambipolar transistors are reconfigurable into p- or n-MOS, which are integrated to demonstrate CMOS inverter, NOR, and NAND logic gates. The switching periods from "0" to "1" and from "1" to "0" of NOR are 0.12 and 0.17 μs, and those of NAND are 0.16 and 0.13 μs. This work lays the foundation of oxide-semiconductor-based CMOS for future integrated electronics.

[Study on the fit testing for the workers wearing hearing protection device in machinery manufacturing enterprises]

Objective: To investigate the occupational noise hazards in five machinery manufacturing enterprises, and to evaluate the individual noise reduction values and influencing factors of workers wearing hearing protection device (HPD) by individual fit testing. Methods: From November 2021 to January 2022, 5 machinery manufacturing enterprises in Bao'an District of Shenzhen were selected to conduct an occupational health survey to understand the noise exposure level of workers. The 3MTM E-A-RfitTM fitness test system was used to test the baseline individual sound attenuation value level (PAR) of the daily wear of the ear protecters for 485 workers in typical noise working positions. Workers whose PAR values could not meet the requirements of noise reduction at work were instructed to wear and repeated tests were conducted. PAR results of the workers before and after the intervention were collected and analyzed. Results: The noise workers who received the suitability test were mainly distributed in 24 types of work, the job noise exposure level was 80.2 dB (A) ~ 95.0 dB (A), and the job noise excess rate was 52.5% (138/263). The median baseline PAR [M (Q(1), Q(3)) ] for 485 workers was 6.0 (0.0, 14.0) dB. The baseline PAR of male workers, those with more than 15 years of working experience, those with more than 15 years of using ear guards, those who considered ear guards comfortable to wear, those with college degree or above, and those exposed to noise level 90 dB (A) were higher, and the difference was statistically significant (P<0.05). A total of 275 workers (56.7%) did not pass the baseline PAR test, and there was no statistically significant difference in the intervention rate of workers in different noise groups (P>0.05). PAR in subjects who did not pass baseline after intervention increased from 0.0 (0.0, 3.0) dB to 15.0 (12.0, 18.2) dB. Conclusion: The workplace noise hazard of machinery manufacturing enterprises is serious, and there is a great difference between the baseline PAR and the nominal value of the hearing guard worn by the noise exposed workers. The intervention measures can effectively improve the protective effect of wearing ear protectors.

Transferable Ga2O3 Membrane for Vertical and Flexible Electronics via One-Step Exfoliation

Transferable Ga₂O₃ thin film membrane is desirable for vertical and flexible solar-blind photonics and high-power electronics applications. However, Ga₂O₃ epitaxially grown on rigid substrates such as sapphire, Si, and SiC hinders its exfoliation due to the strong covalent bond between Ga₂O₃ and substrates, determining its lateral device configuration and also hardly reaching the ever-increasing demand for wearable and foldable applications. Mica substrate, which has an atomic-level flat surface and high-temperature tolerance, could be a good candidate for the van der Waals (vdW) epitaxy of crystalline Ga₂O₃ membrane. Beyond that, benefiting from the weak vdW bond between Ga₂O₃ and mica substrate, in this work, the Ga₂O₃ membrane is exfoliated and transferred to arbitrary flexible and adhesive tape, allowing for the vertical and flexible electronic configuration. This straightforward exfoliation method is verified to be consistent and reproducible by the transfer and characterization of thick (∼380 nm)/thin (∼95 nm) κ-phase Ga₂O₃ and conductive n-type β-Ga₂O₃. Vertical photodetectors are fabricated based on the exfoliated Ga₂O₃ membrane, denoting the peak response at ∼250 nm. Through the integration of Ti/Au Ohmic contact and Ni/Ag Schottky contact electrode, the vertical photodetector exhibits self-powered photodetection behavior with a responsivity of 17 mA/W under zero bias. The vdW-bond-assisted exfoliation of the Ga₂O₃ membrane demonstrated here could provide enormous opportunities in the pursuit of vertical and flexible Ga₂O₃ electronics.

Reflective metalens with an enhanced off-axis focusing performance

Metalenses are one of the most promising metasurface applications. However, all-dielectric reflective metalenses are rarely studied, especially regarding their off-axis focusing performance. After experimentally studying the material optical properties in this work, we propose reflective metalens based on titanium dioxide (TiO₂) and silicon dioxide (SiO₂), which operate at a visible wavelength of 0.633 µm. Unlike conventional reflective metalenses based on metallic mirrors, the proposed device was designed based on a modified parabolic phase profile and was integrated onto a dielectric distributed Bragg reflector periodic structure to achieve high reflectivity with five dielectric pairs. The focusing efficiency characteristics of the metalens were experimentally studied for beam angles of incidence between 0^∘ and 30^∘. The results reveal that the focusing efficiency for the modified metalens design remains higher than 54%, which is higher than 50%, making it promising for photonic miniaturization and integration.

Ultrasensitive Flexible κ-Phase Ga2O3 Solar-Blind Photodetector

Flexible Ga₂O₃ photodetectors have attracted considerable interest owing to their potential use in the development of implantable, foldable, and wearable optoelectronics. In particular, β-phase Ga₂O₃ has been most widely investigated due to the highest thermodynamic stability. However, high-quality β-phase Ga₂O₃ relies on the ultrahigh crystallization temperature (usually ≥750 °C), beyond the thermal tolerance of most flexible substrates. In this work, we epitaxially grow a high-quality metastable κ-phase Ga₂O₃ (002) thin film on a flexible mica (001) substrate under 680 °C and develop a flexible κ-Ga₂O₃ thin film photodetector with ultrahigh performance. Epitaxial κ-Ga₂O₃ and the mica substrate are maintained to be thermally stable up to 750 °C, suggesting their potential for harsh environment applications. The responsivity, on/off ratio, detectivity, and external quantum efficiency of the fabricated photodetector are 703 A/W, 1.66 × 10⁷, 4.08 × 10¹⁴ Jones, and 3.49 × 10⁵ %, respectively, for 250 nm incident light and a 20 V bias voltage. These values are record-high values reported to date for flexible Ga₂O₃ photodetectors. Furthermore, the flexible photodetector shows robust flexibility for bending radii of 1, 2, and 3 cm. More importantly, it shows strong mechanical stability against 10,000 bending test cycles. These results reveal the significance of high-quality κ-phase Ga₂O₃ grown heteroepitaxially on a flexible mica substrate, especially its potential for use in future flexible solar-blind detection systems.

Quasi-Epitaxial Growth of β-Ga2O3-Coated Wide Band Gap Semiconductor Tape for Flexible UV Photodetectors

The epitaxial growth of technically important β-Ga₂O₃ semiconductor thin films has not been realized on flexible substrates due to the limitations of high-temperature crystallization conditions and lattice-matching requirements. We demonstrate the epitaxial growth of β-Ga₂O₃(-201) thin films on flexible CeO₂(001)-buffered Hastelloy tape. The results indicate that CeO₂(001) has a small bi-axial lattice mismatch with β-Ga₂O₃(-201), inducing simultaneous double-domain epitaxial growth. Flexible photodetectors are fabricated on the epitaxial β-Ga₂O₃-coated tape. Measurements reveal that the photodetectors have a responsivity of 4 × 10⁴ mA/W, with an on/off ratio reaching 1000 under 254 nm incident light and 5 V bias voltage. Such a photoelectrical performance is within the mainstream level of β-Ga₂O₃-based photodetectors using conventional rigid single-crystal substrates. More importantly, it remained robust against more than 20,000 bending test cycles. Moreover, the technique paves the way for the direct in situ epitaxial growth of other flexible oxide semiconductor devices in the future.

Localized surface plasmon resonance-enhanced solar-blind Al0.4Ga0.6N MSM photodetectors exhibiting high-temperature robustness

The appealing properties of tunable direct wide bandgap, high-temperature robustness and chemical hardness, make Al_xGa_1-xN a promising candidate for fabricating robust solar-blind photodetectors (PDs). In this work, we have utilized the optical phenomenon of localized surface plasmon resonance (LSPR) in metal nanoparticles (NPs) to significantly enhance the performance of solar-blind Al_0.4Ga_0.6N metal-semiconductor-metal PDs that exhibit high-temperature robustness. We demonstrate that the presence of palladium (Pd) NPs leads to a remarkable enhancement by nearly 600, 300, and 462%, respectively, in the photo-to-dark current ratio (PDCR), responsivity, and specific detectivity of the Al_0.4Ga_0.6N PD at the wavelength of 280 nm. Using the optical power density of only 32μW cm^-2at -10 V, maximum values of ∼3 × 10³, 2.7 AW^-1, and 2.4 × 10¹³Jones are found for the PDCR, responsivity and specific detectivity, respectively. The experimental observations are supported by finite difference time domain simulations, which clearly indicate the presence of LSPR in Pd NPs decorated on the surface of Al_0.4Ga_0.6N. The mechanism behind the enhancement is investigated in detail, and is ascribed to the LSPR induced effects, namely, improved optical absorption, enhanced local electric field and LSPR sensitization effect. Moreover, the PD exhibits a stable operation up to 400 K, thereby exhibiting the high-temperature robustness desirable for commercial applications.

[Application of Chen's pancreaticojejunostomy technique in laparoscopic pancreaticoduodenectomy (116 cases report)]

Objective: To investigate the safety and feasibility of longitudinal transpancreatic U-sutures invaginated pancreatojejunostomy (Chen's pancreaticojejunostomy technique) in laparoscopic pancreaticoduodenectomy (LPD). Methods: Clinical data of 116 consecutive patients who underwent LPD using Chen's pancreaticojejunostomy technique in Hunan Provincial People's Hospital from May 2017 to December 2018 were retrospectively analyzed. Among these patients, 66 were males and 50 were females. The median age was 58 years old (32-84 yeas old). All 116 patients underwent pure laparoscopic whipple procedure with Child reconstruction method, using Chen's pancreaticojejunostomy technique. The intraoperative and postoperative data of patients were analyzed. Results: All 116 patients underwent LPD successfully. The mean operative time was (260.3±33.5) minutes (200-620 minutes). The mean time of pancreaticojejunostomy was (18.2±7.6) minutes (14-35 minutes). The mean time of hepaticojejunostomy was (14.6±6.3) minutes (10-25 minutes). The mean time of gastrojejunostomy was (12.0±5.5) minutes (8-20 minutes). The mean estimated blood loss was (106.0±87.6) ml (20-800 ml). Postoperative complications were: 11.2%(13/116) of cases had postoperative pancreatic fistula (POPF), including 10.3% (12/116) of biochemical fistula and 0.9%(1/116) of grade B POPF, no grade C POPF occurred; 10.3%(12/116) had gastrojejunal anastomotic bleeding; 3.4%(4/116) had hepaticojejunal anastomotic fistula; 3.4%(4/116) had delayed gastric emptying; 4.3% (5/116) had localized abdominal infection; 12.1%(14/116) had pulmonary infection; postoperative mortality were 0(0/116) and 1.7%(2/116) within 30 days and 90 days, respectively. One patient died of massive abdominal bleeding secondary to Gastroduodenal artery pseudoaneurysm rupture, the other patient died of extensive tumor recurrence and metastasis after surgery. Conclusions: Chen's pancreaticojejunostomy technique is safe and feasible for LPD.It is an option especially for surgeons who have not completed the learning curve of LPD.

[Exploration on laparoscopic hepatectomy on central liver tumor: a report of 40 cases]

Objective: To assess the safety and feasibility of the application of the laparoscopic modality in the perioperative treatment of central liver tumors. Methods: Collecting all the clinical information of a total of 40 patients with central liver tumors who received laparoscopic resection treatment carried out at Department of Hepatological Surgery of People's Hospital of Hunan Provincial from January 2016 to December 2018 to take a retrospective review. There were 19 males and 21 females.The age was (59.5±14.5) years (range: 15 to 71 years) . There were 26 cases of primary hepatic carcinoma (24 cases of hepatocellular carcinoma, 2 cases of cholangiocellular carcinoma) , 8 cases of hepatic cavernous hemangioma, 1 case of metastatic hepatic carcinoma, 5 cases of hepatocellular adenoma. The maximum diameter of tumors were (6.2±2.9) cm (range: 2 to 13 cm) . The patient's information about hepatectomy methods, blocking mode and time of blood flow, operation time, intraoperative blood loss, intraoperative blood transfusion rate, post-operative hospitalization time, perioperative reoperation and postoperative complications were collected. Results: A total of 40 patients all were treated with laparoscopic surgery. The surgical procedure was as follows: 2 patients received the right hepatic lobectomy (Ⅴ, Ⅵ, Ⅶ and Ⅷ segments) , 2 patients received the left hepatic lobectomy (Ⅱ, III and Ⅳ segments) , 13 patients received mesohepatectomy (Ⅳ, Ⅰ and Ⅷ segments) , 2 patients received left hepatic trisegmentectomy (Ⅱ, Ⅲ, Ⅳ and Ⅷ segments) , 2 patients received right hepatic trisegmentectomy (Ⅳ, Ⅴ, Ⅵ, Ⅶ and Ⅷ segments) , 7 patients received Ⅷ segmentectomy, 1 patient received Ⅳ segmentectomy, 3 patients received Ⅴ and Ⅷ segmentectomy, 5 patients received hepatic caudate lobe resection (Ⅰ, Ⅸ segments) , and 3 patients received local tumors resection.Pathological results: there were 26 cases of primary hepatic carcinoma (24 cases of hepatocellular carcinoma, 2 cases of cholangiocellular carcinoma) , 8 cases of hepatic cavernous hemangioma, 1 case of metastatic hepatic carcinoma, 5 cases of hepatocellular adenoma; the pathological reports of all malignant tumor cases all showed negative incisal edge. The operative time was (333±30) minutes (range: 280 to 380 minutes) ; the intraoperative hepatic portal occlusion period was (58±13) minutes (range: 30 to 90 minutes) ; the intraoperative hemorrhage was (173±129) ml (range: 20 to 600 ml) ; the intraoperative blood transfusion rate was 2.5% (1/40) ; the postoperative incidence of bile leakage was 2.5% (1/40) , the hospital discharge of 1 patient with bile leakage was approved after conservative treatments like T pipe decompression and adequate drainage; there was 1 case of abdominal infection and 1 case of pulmonary infection, both of which were discharged from the hospital with conservative treatments; there were no other serious postoperative complications. The postoperative hospital stay was (10.7±2.7) days (range: 6 to 16 days) ; there were no perioperative mortality and reoperation cases. Conclusion: In the centers with abundant laparoscopic hepatectomy experiences, the laparoscopic resection is proved to be safe and feasible in the perioperative treatments of central liver tumors by the highly selective cases, the adequate preoperative assessment and reasonable surgical techniques and approach.

Restoration of erectile function with intracavernous injections of endothelial progenitor cells after bilateral cavernous nerve injury in rats

Endothelial progenitor cells (EPCs) are bone marrow-derived endothelial cells capable of circulating, proliferating, and differentiating into mature endothelial cells. Circulating EPCs can be directly recruited to some extent at sites of injury, and their administration could accelerate repair or endothelialization of the damaged tissue. We investigated the effects of intracavernous injections of EPCs into the corpora cavernosa of rats with erectile dysfunction (ED) caused by bilateral cavernous nerve (CN) injury. Overall, 24 male Sprague-Dawley rats were randomized into three groups: sham surgery, vehicle-only, or EPC treatment. Rats in the EPC treatment and vehicle-only groups were subjected to bilateral CN injury before injection of EPCs or vehicle, respectively, into the corpora cavernosa. Four weeks after surgery, erectile function was assessed by measuring maximum intracavernosal pressure (ICP), change in ICP, area under the ICP curve, and ratio of change in ICP and mean arterial pressure (MAP; ΔICP/MAP). Penile tissue was histomorphometrically analyzed for the expression of neural nitric oxide synthase (nNOS), neurofilament-1 (NF-1), von Willebrand factor (vWF), endothelial NOS (eNOS), and smooth muscle cell content. Maximum ICP and all other functional parameters of erectile function were significantly reduced in the vehicle-only group vs. the sham and EPC treatment groups (all p < 0.001). Smooth muscle cell content was decreased in the vehicle-only vs. the sham and EPC treatment groups (both p < 0.01). Expressions of vWF and eNOS in the dorsal artery were significantly higher in the EPC treatment than the vehicle-only group (p < 0.05). In conclusion, EPC treatment restored erectile function in a rat model of bilateral CN injury through recruitment of EPCs toward the dorsal artery and preservation of smooth muscle cells in the corpus cavernosum. These findings elucidate the therapeutic potential of EPCs for treating ED in humans.

Regularly patterned multi-section GaN nanorod arrays grown with a pulsed growth technique

The growth of regularly patterned multi-section GaN nanorod (NR) arrays based on a pulsed growth technique with metalorganic chemical vapor deposition is demonstrated. Such an NR with multiple sections of different cross-sectional sizes is formed by tapering a uniform cross section to another through stepwise decreasing of the Ga supply duration to reduce the size of the catalytic Ga droplet. Contrast line structures are observed in either a scanning electron microscopy or transmission electron microscopy image of an NR. Such a contrast line-marker corresponds to a thin Ga-rich layer formed at the beginning of GaN precipitation of a pulsed growth cycle and illustrates the boundary between two successive growth cycles in pulsed growth. By analyzing the geometry variation of the contrast line-markers, the morphology evolution in the growth of a multi-section NR, including a tapering process, can be traced. Such a morphology variation is controlled by the size of the catalytic Ga droplet and its coverage range on the slant facets at the top of an NR. The comparison of emission spectra between single-, two-, and three-section GaN NRs with sidewall InGaN/GaN quantum wells indicates that a multi-section NR can lead to a significantly broader sidewall emission spectrum.

Multi-section core-shell InGaN/GaN quantum-well nanorod light-emitting diode array

The growth of a two-section, core-shell, InGaN/GaN quantum-well (QW) nanorod- (NR-) array light-emitting diode device based on a pulsed growth technique with metalorganic chemical vapor deposition is demonstrated. A two-section n-GaN NR is grown through a tapering process for forming two uniform NR sections of different cross-sectional sizes. The cathodoluminescence (CL), photoluminescence (PL), and electrolumines-cence (EL) characterization results of the two-section NR structure are compared with those of a single-section NR sample, which is prepared under the similar condition to that for the first uniform NR section of the two-section sample. All the CL, PL, and EL spectra of the two-section sample (peaked between 520 and 525 nm) are red-shifted from those of the single-section sample (peaked around 490 nm) by >30 nm in wavelength. Also, the emitted spectral widths of the two-section sample become significantly larger than their counterparts of the single-section sample. The PL spectral full-width at half-maximum increases from ~37 to ~61 nm. Such variations are attributed to the higher indium incorporation in the sidewall QWs of the two-section sample due to the stronger strain relaxation in an NR section of a smaller cross-sectional size and the more constituent atom supply from the larger gap volume between neighboring NRs.

Thermally induced variations of strain condition and emission behavior in flat and bendable light-emitting diodes on different substrates

The emission behaviors of four light-emitting diodes (LEDs) of different substrate structures, including a lateral LED grown on sapphire, a vertical LED wafer-bonded onto Si (111), a bendable LED Ag-epoxied onto a flat metal, and another bendable LED Ag-epoxied onto a metal of a curved surface, under different duty cycles of current injection are compared. Their different variation trends of emission behavior with injection duty cycle are attributed to the different thermally-induced strain conditions in the epitaxial layers, which are controlled by their substrate structures, in increasing injection duty cycle or current level. The results of Raman scattering measurements during LED operation show that a stronger tensile strain is generated under heating for reducing the quantum-confined Stark effect and hence increasing emission efficiency when the epitaxial layer is not tightly bonded onto a hard substrate. Such a behavior is particularly stronger when the epitaxial layer is bent.

Growth of Highly Conductive Ga-Doped ZnO Nanoneedles

The molecular beam epitaxy growth of highly degenerate Ga-doped ZnO (GaZnO) nanoneedles (NNs) based on the vapor-liquid-solid (VLS) growth mode using Ag nanoparticles (NPs) as the growth catalyst is demonstrated. It is shown that when the growth substrate temperature is sufficiently high, a portion of a Ag NP can be melted for serving as the catalyst to precipitate GaZnO on the residual Ag NP and form a GaZnO NN. Record-low turn-on and threshold electric fields in the field emission test of the grown GaZnO NNs are observed. Also, a record-high field enhancement factor in field emission is calibrated. Such superior field emission performances are attributed to a few factors, including (1) the low work function and high conductivity of the grown GaZnO NNs due to highly degenerate Ga doping, (2) the sharp-pointed geometry of the vertically aligned GaZnO NNs, (3) the Ag doping in VLS precipitation of GaZnO for further reducing NN resistivity, and (4) the residual small Ag NP at the NN tip for making the tip even sharper and tip conductivity even higher.

Regularly patterned non-polar InGaN/GaN quantum-well nanorod light-emitting diode array

The growth and process of a regularly patterned nanorod (NR)- light-emitting diode (LED) array with its emission from sidewall non-polar quantum wells (QWs) are demonstrated. A pyramidal un-doped GaN structure is intentionally formed at the NR top for minimizing the current flow through this portion of the NR such that the injection current can be effectively guided to the sidewall m-plane InGaN/GaN QWs for emission excitation by a conformal transparent conductor (GaZnO). The injected current density at a given applied voltage of the NR LED device is similar to that of a planar c-plane or m-plane LED. The blue-shift trend of NR LED output spectrum with increasing injection current is caused by the non-uniform distributions of QW width and indium content along the height on a sidewall. The photoluminescence spectral shift under reversed bias confirms that the emission of the fabricated NR LED comes from non-polar QWs.

Extraordinary N atom tunneling in formation of InN shell layer on GaN nanorod m-plane sidewall

We report the extraordinary tunneling process that finds the lower cohesive energy route for stablizing InN shell layer on m-plane sidewall of GaN nanorod. The [0001] orientated GaN nanorod array is grown on sapphire substrate patterned with Ga nanoparticle by metal-organic vapor deposition method, based on which the simulation structures of c-plane top surface and m-plane sidewall surface is constructed for the first-principles calculations. The results show that the introduction of In wetting monolayer could effectively lower the cohesive energy of adalayers on non-polar GaN surfaces. Most importantly, it is revealed that there exists an extraordinary tunneling process in which the N atoms will drag out the In wetting atoms and tunnel through to form stable InN shell layer on the nanorod sidewall.

Dependencies of the emission behavior and quantum well structure of a regularly-patterned, InGaN/GaN quantum-well nanorod array on growth condition

To achieve green emission from the sidewall non-polar quantum wells (QWs) of a GaN nanorod (NR) light-emitting diode, regularly patterned InGaN/GaN QW NR arrays are grown under various growth conditions of indium supply rate, QW growth temperature, and QW growth time for comparing their emission wavelength variations of the top-face c-plane and sidewall m-plane QWs based on photoluminescence and cathodoluminescence (CL) measurements. Although the variation trends of QW emission wavelength by changing those growth conditions in the NR structure are similar to those in the planar structure, the emission wavelength range of the QWs on an NR is significantly shorter than that in a planar structure under the same growth conditions. Under the growth conditions for a longer NR QW emission wavelength, the difference of emission wavelength between the top-face and sidewall QWs is smaller. Also, the variation range of the emission wavelength from the sidewall QWs over different heights on the sidewall becomes larger. On the other hand, strain state analysis based on transmission electron microscopy is undertaken to calibrate the average QW widths and average indium contents in the two groups of QW of an NR. The variation trends of the calibrated QW widths and indium contents are consistent with those of the CL emission wavelengths from various portions of NR QWs.

Indium droplet formation in InGaN thin films with single and double heterojunctions prepared by MOCVD

Indium gallium nitride (InGaN) samples with single heterojunction (SH) and double heterojunction (DH) were prepared using metal-organic chemical vapor deposition. SH has a layer of InGaN thin film (thicknesses, 25, 50, 100, and 200 nm) grown on an uGaN film (thickness, 2 μm). The DH samples are distinguished by DH uGaN film (thickness, 120 nm) grown on the InGaN layer. Reciprocal space mapping measurements reveal that the DH samples are fully strained with different thicknesses, whereas the strain in the SH samples are significantly relaxed with the increasing thickness of the InGaN film. Scanning electron microscopy results show that the surface roughness of the sample increases when the sample is relaxed. High-resolution transmission electron microscopy images of the structure of indium droplets in the DH sample indicate that the thickness of the InGaN layer decreases with the density of indium droplets. The formation of these droplets is attributed to the insufficient kinetic energy of indium atom to react with the elements of group V, resulting to aggregation. The gallium atoms in the GaN thin film will not be uniformly replaced by indium atoms; the InGaN thin film has an uneven distribution of indium atoms and the quality of the epitaxial layer is degraded.

Efficiency improvement of a vertical light-emitting diode through surface plasmon coupling and grating scattering

The enhancement of output intensity, the generation of polarized output, and the reduction of the efficiency droop effect in a surface plasmon (SP) coupled vertical light-emitting diode (LED) with an Ag nano-grating structure located between the p-GaN layer and the wafer bonding metal for inducing SP coupling with the InGaN/GaN quantum wells (QWs) are demonstrated. In fabricating the vertical LED, the patterned sapphire substrate is removed with a photoelectrochemical liftoff technique. Based on the reflection measurement from the metal grating structure and the numerical simulation result, it is found that the localized surface plasmon (LSP) resonance induced around the metal grating crest plays the major role in the SP-QW coupling process although a hybrid mode of LSP and surface plasmon polariton can be generated in the coupling process. By adding a surface grating structure to the SP-coupled vertical LED on the n-GaN side, the output intensity is further enhanced, the output polarization ratio is further increased, and the efficiency droop effect is further suppressed.

Light-emitting device with regularly patterned growth of an InGaN/GaN quantum-well nanorod light-emitting diode array

A light-emitting device consisting of a two-dimensional regularly patterned InGaN/GaN quantum well (QW) nanorod (NR) light-emitting diode (LED) array is implemented and characterized. The NR p-i-n structure includes n-GaN NR core and essentially conformal p-GaN shell. The active regions include nonpolar sidewall QWs and polar top-face QWs. A conformal layer of transparent GaZnO of low resistivity is deposited onto the NR LED structure for spreading the injection current over the sidewalls. It is found that the blue-shift range of the output spectral peak in increasing injection current is smaller than that of a planar LED of about the same operation wavelength in a similar variation range of injection current density although it is nonzero. The small blue-shift range is attributed to the mixed emission contributions from the nonpolar sidewall QWs and polar top-face QWs.

Vertical light-emitting diodes with surface gratings and rough surfaces for effective light extraction

For enhancing the light extraction of a light-emitting diode, surface grating fabrication based on a simple method of combining photoelectrochemical (PEC) etching with phase mask interferometry has been demonstrated. To understand the optimum grating period in forming a surface grating on a vertical light-emitting diode (VLED), we construct a Llyod's interferometer within PEC electrolyte (KOH) to fabricate surface gratings of various periods on VLEDs for comparing their light extraction efficiencies. Also, to compare the effectiveness of light extraction enhancement between surface grating and rough surface, VLEDs with the rough surfaces fabricated with two different KOH wet etching methods are fabricated. The comparisons of VLED characterizations show that among those grating VLEDs, the light extraction is more effective in a VLED of a smaller grating period. Also, compared with VLEDs of rough surfaces, the grating VLEDs of short grating periods (<2 μm) have the higher light extraction efficiencies, even though the root-mean-square roughness of the rough surface is significantly larger than the grating groove depth.

Comparison of emission characteristics between the CdZnO/ZnO quantum wells on ZnO and GaN templates

CdZnO/ZnO quantum well (QW) samples are grown on GaN and ZnO templates with plasma-assisted molecular beam epitaxy under different conditions of substrate temperature, Cd effusion cell temperature, and O(2) flow rate for emission characteristics comparison. It is found that the Cd incorporation on the ZnO template is generally lower, when compared with that on the GaN template, such that the O(2) flow rate needs to be reduced for stoichiometric CdZnO/ZnO QW growth on the ZnO template. Besides the wurtzite (wt) CdZnO structure, the rock-salt (rs) CdZnO structure exists in the CdZnO well layers when the total Cd content is high. The rs structure may dominate over the wt structure in photoluminescence intensity when the total Cd content is high. In either group of samples on the GaN and ZnO templates, the emission efficiency first increases and then decreases with increasing total Cd content. The low emission efficiency at low (high) Cd content is attributed to the weaker quantum confinement (the poorer crystal quality) of the QWs. The emission efficiencies of the QW samples on the GaN template are generally higher than those on the ZnO template. The carrier localization behavior in a CdZnO/ZnO QW, grown on either GaN or ZnO template, is significantly weaker than that in an InGaN/GaN QW. The strength of the quantum-confined Stark effect generally increases with increasing Cd content in either group of samples on the GaN and ZnO templates.

Geometry and composition comparisons between c-plane disc-like and m-plane core-shell InGaN/GaN quantum wells in a nitride nanorod

With the nano-imprint lithography and the pulsed growth mode of metalorganic chemical vapor deposition, a regularly-patterned, c-axis nitride nanorod (NR) array of quite uniform geometry with simultaneous depositions of top-face, c-plane disc-like and sidewall, m-plane core-shell InGaN/GaN quantum well (QW) structures is formed. The differences of geometry and composition between these two groups of QW are studied with scanning electron microscopy, cathodoluminescence, and transmission electron microscopy (TEM). In particular, the strain state analysis results in TEM observations provide us with the information about the QW width and composition. It is found that the QW widths are narrower and the indium contents are higher in the sidewall m-plane QWs, when compared with the top-face c-plane QWs. Also, in the sidewall m-plane QWs, the QW width (indium content) decreases (increases) with the height on the sidewall. The observed results can be interpreted with the migration behaviors of the constituent atoms along the NR sidewall from the bottom.

Effects of overgrown p-layer on the emission characteristics of the InGaN/GaN quantum wells in a high-indium light-emitting diode

The counteraction between the increased carrier localization effect due to the change of composition nanostructure in the quantum wells (QWs), which is caused by the thermal annealing process, and the enhanced quantum-confined Stark effect in the QWs due to the increased piezoelectric field, which is caused by the increased p-type layer thickness, when the p-type layer is grown at a high temperature on the InGaN/GaN QWs of a high-indium light-emitting diode (LED) is demonstrated. Temperature- and excitation power-dependent photoluminescence (PL) measurements are performed on three groups of sample, including 1) the samples with both effects of thermal annealing and increased p-type thickness, 2) those only with the similar thermal annealing process, and 3) those with increased overgrowth thickness and minimized thermal annealing effect. From the comparisons of emission wavelength, internal quantum efficiency (IQE), spectral shift with increasing PL excitation level, and calibrated activation energy of carrier localization between various samples in the three groups, one can clearly see the individual effects of thermal annealing and increased p-type layer thickness. The counteraction leads to increased IQE and blue-shifted emission spectrum with increasing p-type thickness when the thickness is below a certain value (20-nm p-AlGaN plus 60-nm p-GaN under our growth conditions). Beyond this thickness, the IQE value decreases and the emission spectrum red shifts with increasing p-type thickness.

Fabrication of surface metal nanoparticles and their induced surface plasmon coupling with subsurface InGaN/GaN quantum wells

Based on the fabrication of Ag nanoparticles (NPs) with controlled geometry and surface density on an InGaN/GaN quantum well (QW) epitaxial structure, which contains indium-rich nano-clusters for producing localized states and free-carrier (delocalized) states in the QWs, and the characterization of their localized surface plasmon (LSP) coupling behavior with the carriers in the QWs, the interplay behavior of LSP coupling with carrier delocalization in the QWs is demonstrated. By using the polystyrene nanosphere lithography technique with an appropriate nanosphere size and adjusting the post-fabrication thermal annealing condition, the induced LSP resonance wavelength of the fabricated Ag NPs on the QW sample can match the QW emission wavelength for generating the coherent coupling between the carriers in the QWs and the induced LSP. The coupling leads to the enhancement of radiative recombination rate in the QWs and results in increased photoluminescence (PL) intensity, red-shifted PL spectrum, reduced PL decay time, and enhanced internal quantum efficiency. It is found that the observed effects are mainly due to the LSP coupling with the delocalized carriers in the QWs.

Ultrafast ablation dynamics in fused silica with a white light beam probe

This study demonstrates a non-degenerate pump-probe spectroscopy with a white light beam probe based on a regenerative, amplified, mode-locked, Ti:sapphire laser. This white light beam probe is produced by supercontinuum generation of sapphire crystal after ultra-short pulse excitation. To implement the pump-probe experimental operation, the ablation dynamics with and without fresh spot measurements in fused silica samples are demonstrated. Combining the time-resolved differential reflection profiles in the white light range and X-ray photoelectron spectroscopy spectra of fused silica, the following ablation dynamics processes can be observed: Without fresh spot measurements, once carriers are excited, first, the three absorption bands of the intrinsic defect sites are observed within 750 fs. Then, a fast recovery is observed. This recovery comes from defect-trapped carriers excited to conduction bands through hot-carrier-phonon interactions. In the final step, a rapidly rising signal is observed after 800 fs. This signal rise comes from the creation of free-electron plasma, the density of which increases with increasing excitation energy accumulation. With fresh spot measurements, time delay of carrier dynamics among the three bands can be identified clearly within 750 fs. The intrinsic defect sites of fused silica play the key role during the ultrafast laser ablation process.

Surface plasmon coupling with radiating dipole for enhancing the emission efficiency of a light-emitting diode

The experimental demonstrations of light-emitting diode (LED) fabrication with surface plasmon (SP) coupling with the radiating dipoles in its quantum wells are first reviewed. The SP coupling with a radiating dipole can create an alternative emission channel through SP radiation for enhancing the effective internal quantum efficiency when the intrinsic non-radiative recombination rate is high, reducing the external quantum efficiency droop effect at high current injection levels, and producing partially polarized LED output by inducing polarization-sensitive SP for coupling. Then, we report the theoretical and numerical study results of SP-dipole coupling based on a simple coupling model between a radiating dipole and the SP induced on a nearby Ag nanoparticle (NP). To include the dipole strength variation effect caused by the field distribution built in the coupling system (the feedback effect), the radiating dipole is represented by a saturable two-level system. The spectral and dipole-NP distance dependencies of dipole strength variation and total radiated power enhancement of the coupling system are demonstrated and interpreted. The results show that the dipole-SP coupling can enhance the total radiated power. The enhancement is particularly effective when the feedback effect is included and hence the dipole strength is increased.

Infections caused by Gordonia species at a medical centre in Taiwan, 1997 to 2008

The inability of conventional identification systems to accurately identify Gordonia spp. often results in the misdiagnosis of infections by these rare pathogens, which require genomic sequencing for precise identification. In the present study, we describe nine cases of the various types of infection caused by Gordonia spp. From 1997 to 2008, 66 isolates (from 30 patients) initially identified as Rhodoccus spp. by conventional biochemical methods, by the Bacteriology Laboratory of National Taiwan University Hospital, were retrospectively analysed to assess the accuracy of species identification. Fifteen of these isolates (from nine patients) were later found to be Gordonia spp. by two molecular methods: PCR-restriction fragment length polymorphism for heat shock protein gene (hsp65) and the 16S rRNA gene sequencing analysis. Gordonia sputi (n = 8) was the most common species, followed by Gordonia terrae (n = 7). Most of the isolates were isolated from blood (n = 11), followed by soft tissue (n = 2) and eye (n = 2). Five patients presented with bacteraemia and two of these had catheter-related bloodstream infection. Two patients had soft tissue infections and another two patients had infective keratitis and conjunctivitis. The random amplified polymorphic DNA patterns for isolates from different patients were different, indicating that they were genetically unrelated. Accurate identification with molecular methods is required if the role of Gordonia spp. in causing infection is to be recognized.

Clinical significance of nontuberculous mycobacteria isolates in elderly Taiwanese patients

The aim of this study was to investigate the clinical significance of nontuberculous mycobacteria (NTM) isolates in elderly Taiwanese patients. From 2004 through 2008, patients >65 years old with NTM isolation were identified. The definitions of NTM disease followed the American Thoracic Society and Infectious Disease Society of America (ATS/IDSA) criteria. Among the 3,175 NTM isolates, Mycobacterium avium complex (MAC; n = 1,118, 35.2%) was the most prevalent species, followed by M. abscessus (n = 545, 17.2%). Among the 1,633 elderly patients with NTM isolates, the most prevalent NTM species were MAC (n = 592, 36.3%) and M. fortuitum complex (n = 311, 19.0%). NTM colonization was found in 1,339 (80.4%) patients and only 326 (19.6%) patients had NTM diseases. During the study period, the annual incidence rates (per 100,000 inpatients and outpatients) of NTM colonization and disease both increased significantly (p < 0.0001) from 10.5 to 15.8 and from 2.1 to 4.3, respectively. Isolated pulmonary NTM infections compromised 294 (90.2%) of the 326 elderly cases of NTM disease. In conclusion, this study found an increasing trend in the incidence of both NTM isolates and NTM diseases among elderly Taiwanese patients. MAC and M. abscessus were the most frequent species causing various types of NTM disease.

Corn stunt spiroplasma: isolation, cultivation, and proof of pathogenicity

A spiroplasma isolated from corn infected with corn stunt disease has been successfully cultivated in vitro. Acid formation was associated with its growth in liquid medium, and fried egg-shaped or granulated colonies developed on solid agar medium. Healthy leafhopper vectors injected with or allowed to feed on isolates from various serial passages through liquid medium were able to transmit the corn stunt agent to healthy corn plants, inducing typical corn stunt disease in the plants. The spiroplasma was reisolated and cultivated from such diseased plants and was indistinguishable morphologically from the original isolates. These results provide the first definite proof that the corn stunt disease is caused by the corn stunt spiroplasma.

Diagnostic performance of an enzyme-linked immunospot assay for interferon-gamma in extrapulmonary tuberculosis varies between different sites of disease

OBJECTIVES

To evaluate diagnostic performance of an enzyme-linked immunospot assay for interferon-gamma (T SPOT-TB) in patients with suspected extrapulmonary tuberculosis (TB).

METHODS

From January 2007 to December 2008, patients with suspected extrapulmonary TB were prospectively enrolled from 2 tertiary care hospitals.

RESULTS

A total of 138 patients with suspected extrapulmonary TB were enrolled; 50 patients had positive culture for Mycobacterium tuberculosis and 39 patients had probable TB. The sites of infection were lymph node (n = 20), pleura (n = 19), bone/joint (n = 15), urinary tract (n = 7), peritoneum (n = 7), meninges (n = 6), disseminated (n = 5), intestine (n = 3), pericardium (n = 2), skin (n = 2), throat (n = 1), neck (n = 1), and genitalia (n = 1). The overall sensitivity and specificity were 79.8% (71/89) and 81.6% (40/49). The sensitivity ranged from 100% for tuberculous meningitis, tuberculous pericarditis, and intestinal TB, 95% for lymphadenitis, to 42.9% for tuberculous peritonitis. The sensitivity of the T SPOT-TB assay was 70.6% in immunocompromised patients and 85.5% in immunocompetent patients (p = 0.09).

CONCLUSIONS

The T SPOT-TB assay can be a useful tool for diagnosing extra-pulmonary TB in immunocompetent and immunocompromised patients, particularly for tuberculous meningitis, pericarditis, lymphadenitis, and intestinal TB.

YC-1 induces apoptosis of human renal carcinoma A498 cells in vitro and in vivo through activation of the JNK pathway

BACKGROUND AND PURPOSE

The aim of this study was to elucidate the mechanism of YC-1{3-(5'-hydroxy methyl-2'-furyl)-1-benzylindazole}-induced human renal carcinoma cells apoptosis and to evaluate the potency of YC-1 in models of tumour growth in mice.

EXPERIMENTAL APPROACH

YC-1-mediated apoptosis was assessed by analysis of MTT, SRB, DAPI staining and flow cytometry analysis. Knockdown of JNK protein was achieved by transient transfection using siRNA. The mechanisms of action of YC-1 on different signalling pathways involved were studied using western blot. Fas clustering was analysed by confocal microscopy and in vivo efficacy was examined in a A498 xenograft model.

KEY RESULTS

YC-1 displayed cytotoxicity in renal carcinoma cells at 10(-7)-10(-8) M. Increased condensation of chromatin was observed and an increase in the cell population in subG1 phase. Moreover, YC-1 triggered mitochondria-mediated and caspase-dependent pathways. YC-1 significantly induced Fas ligand expression, but did not modify either the protein levels of death receptors or ligands. In addition, Fas clustering in cells responsive to YC-1 was observed, suggesting involvement of a Fas-mediated pathway. Furthermore, YC-1 markedly induced phosphorylation of JNK and a JNK inhibitor, SP600125, and siRNA JNK1/2 significantly reversed YC-1-induced cytotoxicity and protein expression. We suggest that YC-1 induced JNK phosphorylation, the upregulation of FasL and Fas receptor clustering to promote the activation of caspases 8 and 3, resulting in apoptosis. Finally, we demonstrated the antitumour effect of YC-1 in vivo.

CONCLUSIONS AND IMPLICATIONS

These data suggest that YC-1 is a good candidate for development as an anticancer drug.

Transdermal testosterone gel increases serum testosterone levels in hypogonadal men in Taiwan with improvements in sexual function

A randomized, double-blind, placebo-controlled trial was conducted to (1) evaluate efficacy and safety of transdermal testosterone gel (AndroGel) for hypogonadal men in Taiwan, and (2) observe improvements in sexual function through international index of erectile function (IIEF) scores. Eligible hypogonadal men were randomized to receive 50 mg/day transdermal testosterone gel (TTG) or placebo for 3 months. Primary end point was change from baseline in total testosterone (TT) and free testosterone (FT). Secondary end points were change from baseline in serum hormone levels (such as dihydrotestosterone (DHT), estradiol (E2), luteinizing hormone (LH), follicle-stimulating hormone (FSH) and sex-hormone-binding globulin (SHBG)) and changes in IIEF scores. Safety evaluations included adverse events (AEs) and skin irritation assessment. Compared with baseline, the TTG group (n=20) had statistically significant increases in mean TT levels at month 1 (P=0.024) and month 2 (P=0.025), but no significant changes at month 3. TT levels in the placebo group (n=18) showed no statistically significant change at any visit. Changes in FT levels paralleled changes in TT levels in both groups. TTG group IIEF scores were significantly increased at month 3 (P=0.01), compared with a decline in placebo scores. No drug-related AEs occurred in the TTG group; the placebo group had 2 AEs (mild skin rash). In conclusion, TTG effectively restores serum TT and FT levels to a normal physiological range for hypogonadal men in Taiwan and improves sexual function.

Skin and soft tissue infection caused by non-tuberculous mycobacteria

SETTING

A medical centre in Taipei, Taiwan.

OBJECTIVE

To investigate the trend and characteristics of patients with non-tuberculous mycobacteria (NTM) related skin and soft tissue infection.

DESIGN

A total of 63 patients with culture-proven diseases were identified from January 1997 to December 2004. The medical records of all patients were reviewed.

RESULTS

Twenty-seven patients were infected with rapidly growing mycobacteria (RGM), 19 with Mycobacterium marinum, six with M. avium complex (MAC), five with M. kansasii and six with other species. Most patients presented with a protracted cutaneous lesion without systemic symptoms, and two thirds of the patients had a history of exposure. Seventy-three per cent of the lesions involved the extremities. Underlying illness with suppressed immunity was documented in 30.2% of the patients, and was most prevalent in patients with MAC (100%) and M. kansasii (60%). Of the patients, 62% underwent at least one surgical intervention, and 77.8% received treatment with different antimicrobial combinations. Most patients (86%) recovered completely. Granulomatous inflammation was found in 88.9% of biopsied tissue associated with M. marinum infection, 31.8% with RGM and 25.0% with MAC.

CONCLUSION

A combination of surgery and antimicrobials cured most patients with microbiologically proven localised NTM skin and soft tissue infection.

Characteristics of natural organic matter degradation in water by UV/H2O2 treatment

This study evaluated the UV/H2O2 system for degradation of natural organic matter in water. The photolysis experiments were conducted in a 10-l batch reactor using a 450-watt high-pressure mercury vapor lamp as the light source. The addition of H2O2 in water greatly improved the rate of humic acid degradation by UV light and 90% of the humic acid was removed within 30 min of photolysis. Kinetic data showed that the first-order reaction could be used to describe the kinetics of both humic acid oxidation and H2O2 decomposition, and the optimum H2O2 dose was 0.01%-0.05% for humic acid oxidation. It was also observed that the absorption of UVC (UV with wavelength between 200 and 280 nm) is responsible for the dissociation of H2O2 to generate the reactive hydroxyl radicals. Depending on the initial dosages, the H2O2 added to the system can be completely decomposed by UV within 50 to 90 minutes. Upon UV irradiation, the humic intermediates with smaller molecular sizes increase as a result of the degradation of larger humic substances. Photolysis of surface water also shows that the UV/H2O2 was effective in reducing trihalomethanes (THMs) formation in treating surface water with high contents of organic precursors. The distribution of THMs shifted from chlorine-THMs to bromine-THMs after UV/H2O2 treatments when bromide was present in water. However, higher H2O2 dosages would be necessary for the photolysis of surface water containing high concentrations of organic THM precursors. As observed from the Fourier transform infrared (FTIR) spectra, the functional groups of treated humic acids were destructed significantly, including -OH (from -COOH and -COH), aromatic -C=C, and -C=O conjugated with aromatic rings.

Estimating the delay of the fMRI response

We propose a fast, efficient, general, simple, valid, and robust method of estimating and making inference about the delay of the fMRI response modeled as a temporal shift of the hemodynamic response function (HRF). We estimate the shift unbiasedly using two optimally chosen basis functions for a spectrum of time shifted HRFs. This is done at every voxel, to create an image of estimated delays and their standard deviations. This can be used to compare delays for the same stimulus at different voxels, or for different stimuli at the same voxel. Our method is compared to other alternatives and validated on an fMRI data set from an experiment in pain perception.

A general statistical analysis for fMRI data

We propose a method for the statistical analysis of fMRI data that seeks a compromise between efficiency, generality, validity, simplicity, and execution speed. The main differences between this analysis and previous ones are: a simple bias reduction and regularization for voxel-wise autoregressive model parameters; the combination of effects and their estimated standard deviations across different runs/sessions/subjects via a hierarchical random effects analysis using the EM algorithm; overcoming the problem of a small number of runs/session/subjects using a regularized variance ratio to increase the degrees of freedom.

Lactate dehydrogenase genes of caiman and Chinese soft-shelled turtle, with emphasis on the molecular phylogenetics and evolution of reptiles

L-Lactate dehydrogenase (LDH) cDNAs encoding for LDH-A(4) (muscle) and LDH-B(4) (heart) isozymes from caiman (Caiman crocodilus apaporiensis) belonging to the order Crocodilia and Chinese soft-shelled turtle (Pelodiscus sinensis) belonging to the order Chelonia were sequenced. The phylogenetic relationships of the newly determined cDNA and their deduced protein sequences, as well as the previously published sequences of vertebrate LDH isozymes, were analyzed by various phylogenetic tree construction methods. These results indicated that Chelonia is indeed more closely related to Crocodilia. The divergent times between caiman and alligator, turtle and soft-shelled turtle, and Chelonia and Crocodilia were estimated to be approximately 36, 100 and 177 million years, respectively.

Role of cupric ions in the H2O2/UV oxidation of humic acids

The purpose of this study is to reveal the role of cupric ions as a natural water contaminant in the H2O2/UV oxidation of humic acids. Humic acids are naturally occurring organic matter and exhibit a strong tendency of complexation with some transition metal ions. Chlorination of humic acids causes potential health hazards due to formation of trihalomethane (THM). The removal of THM precursors has become an issue of public concern. The H2O2/UV process is capable of mineralizing humic acids due to formation of a strong oxidant, hydroxyl radicals, in reaction solution. Experiments were conducted in a re-circulated photoreactor. Different cupric concentrations (0-3.8 mg/l) and different pH values (4-9) were controlled to determine their effects on the degradation of humic acids, UV light absorbance at 254 nm, and H2O2. The presence of cupric ions inhibits humic mineralization and decreases the rate of destruction of humic acids which absorb UV light at 254 nm. On the other hand, the higher the cupric concentration, the lower the H2O2 decomposition rate. In the studied pH range, the minimum of total organic carbon (TOC) removal occurs at pH = 6 in the presence of 2.6 mg/l of cupric ions; both acidification (pH = 4) and alkaline condition (pH = 9) lead to a better removal of TOC. It is inferred from this study that the cupric-complexed form of humic acids is more refractory than the non-complexed one.

Analysis of native microflora and selection of strains antagonistic to human pathogens on fresh produce

The native microflora of three types of produce (green bell peppers, Romaine lettuce, and prepeeled baby carrots) and two types of sprouting seeds (alfalfa and clover) were investigated. Aerobic plate count (APC) for each produce or seed type as determined on Pseudomonas agar F (PAF) with incubation at 28 degrees C was in the range of 4 to 7 log CFU per g of tissue or seed. There was no significant difference (P > or = 0.05) in APC when the determinations were made with three agar media including PAF, brain heart infusion agar, and plate count agar. However, the APC as determined from plates that were incubated at 28 degrees C was significantly (P < or = 0.05) higher than with incubation at 37 degrees C. Fluorescent pseudomonads accounted for 23 to 73% of APC and 6 to 18% of APC recovered from carrots, pepper, and lettuce were pectolytic. Forty-eight strains of pectolytic bacteria were randomly isolated and identified, respectively, as members of the genera of Pseudomonas, Erwinia, Bacillus, Xanthomonas, or Flavobacterium. Lactic acid bacteria and/or yeast were consistently isolated from baby carrots, lettuce, and sprouting seeds (alfalfa or clover) but not from green bell peppers. Approximately 120 strains of indigenous microflora were tested for their ability to inhibit the growth of Salmonella Chester, Listeria monocytogenes, Escherichia coli, or Erwinia carotovora subsp. carotovora on PAF. Six isolates capable of inhibiting the growth of at least one pathogen were isolated and identified, respectively, as Bacillus spp. (three strains), Pseudomonas aeruginosa (one strain), Pseudomonas fluorescens (strain A3), and yeast (strain D1). When green pepper disks were inoculated with strains A3 and D1, the growth of Salmonella Chester and L. monocytogenes on the disks was reduced by 1 and 2 logs, respectively, over a period of 3 days. Application of strains A3 and D1 as potential biopreservatives for enhancing the quality and safety of fresh produce is discussed.

Hydroxyl radical scavenging role of chloride and bicarbonate ions in the H2O2/UV process

Simultaneous effect of inorganic anions, such as chloride and bicarbonate ions, on the scavenging of hydroxyl radicals (HO*) in the H2O2/UV process is the focus of this paper. The model compound of n-chlorobutane (BuCl) was used as the probe of HO*. By changing the pH conditions (2-9) and the concentrations of NaCl (0.25-2500 mM) and NaHCO3 (25 mM), the variation of HO* concentrations and the rate of H2O2 decomposition were compared. In general, the BuCl and H2O2 follow closely the first-order reaction within the first 10 and 40 min, respectively. In the presence of chloride alone at the pH range of 2-6, the HO* concentration in the reaction mixture increases with the increase of pH, and the HO* concentration at pH = 6 is 100 times of that at pH = 2. Including bicarbonate species in the solution, the peak HO* concentration was found at a certain pH, which shifts from 4, 5, to 5-7, as the molar ratios of chloride/bicarbonate species increase from 1 to 100. In addition, without bicarbonate species HO* concentration decreases significantly with increasing chloride concentration but remained rather unchanged beyond 1250 mM. In contrast, the HO* scavenging in the presence of bicarbonate species became relatively significant only when the chloride concentration reached beyond 250 mM. Throughout all experiments of different water quality conditions, the H2O2 decomposition rate remains rather unchanged.

Inhibition of the expression of inducible nitric oxide synthase and cyclooxygenase-2 in macrophages by 7HQ derivatives: involvement of IkappaB-alpha stabilization

Nitric oxide is an important biological mediator associated with multiple pathophysiological phenomena, such as platelet aggregation, vasodilation, septic shock, and autoimmune diseases. Prostaglandins, derived from cyclooxygenases, play prominent roles in homeostasis and inflammation. In this study, we characterized the effects of 7HQ derivatives (7-[(4-methylene-5-oxo-2-R-2-tetrahydrofuranyl) methoxy]-3,4-dihydrocarbostyril, where R is methyl, phenyl, p-fluorophenyl and p-phenylphenyl; 7HQ-1,-2,-3 and-4, respectively) in murine RAW 264.7 cells, a macrophage-like cell line. Lipopolysaccharide, the active component of endotoxin, significantly induced the expression of inducible nitric oxide synthase and cyclooxygenase-2, leading to the accumulation of nitrite and prostaglandin E(2), respectively. These actions of lipopolysaccharide were inhibited by 7HQ derivatives; additionally, the inhibition of the expression, rather than the activity, of inducible nitric oxide synthase correlated well with that of nitric oxide formation. Western blotting and electrophoretic mobility shift assay results demonstrated that the 7HQ derivatives could effectively inhibit IkappaB-alpha degradation and nuclear factor kappaB (NF-kappaB) translocation. At higher concentrations, 7HQ derivatives also inhibited cyclooxygenase-2 enzyme activity. These results suggest that 7HQ derivatives exhibit inhibitory effects on lipopolysaccharide-induced nitric oxide production and expression of inducible nitric oxide synthase and cyclooxygenase-2 through inhibition of IkappaB-alpha degradation and NF-kappaB activation.

Effectiveness of transperitoneal and trans-retroperitoneal laparoscopic adrenalectomy versus open adrenalectomy

PURPOSE

This study compared the effectiveness of laparoscopic adrenalectomy, using either a transperitoneal or trans-retroperitoneal approach, with that of open adrenalectomy in patients with benign adrenal tumors.

METHODS

From February 1995 to April 2000, laparoscopic adrenalectomy was performed on 31 patients with adrenal tumors, including 16 aldosteronomas, 10 Cushing's adenomas, three nonfunctioning tumors, and two pheochromocytomas. A lateral trans-retroperitoneal approach was used for the first 16 patients and a lateral transperitoneal approach was used for the last 15 patients. Twenty-one patients who received open adrenalectomy during the same period served as a control group. Comparisons were made between laparoscopy and open groups, and between transperitoneal and trans-retroperitoneal groups.

RESULTS

Conversion to open adrenalectomy was necessary in two cases--both in the trans-retroperitoneal group during the first 2 years of the study period. No other intraoperative complications occurred and blood transfusion was not used. Compared with the open group, the laparoscopic group had less blood loss (71 vs 124 mL), resumed oral feeding earlier (28 vs 60 hr), required less postoperative narcotics (45 vs 120 mg meperidine), and had shorter postoperative hospital stays (4.9 vs 7.6 days) (all p < 0.05). The mean operative time was longer in the laparoscopic group (203 vs 123 min, p < 0.001). There were no significant differences between the transperitoneal and trans-retroperitoneal laparoscopy groups in any of the studied parameters, except that the operative time was longer in the trans-retroperitoneal laparoscopy group (244 vs 166 minutes, p < 0.01).

CONCLUSIONS

Decreased blood loss, less postoperative pain, earlier resumption of oral feeding, and shorter hospital stays were achieved in patients undergoing laparoscopic adrenalectomy. These findings indicate that laparoscopic adrenalectomy is the treatment of choice for benign adrenal tumors. The transperitoneal approach yielded shorter operative time than the trans-retroperitoneal approach, because it offered a clearer view and familiar landmarks.

Photodegradation of humic acids in the presence of hydrogen peroxide

A batch photoreactor was used to evaluate the UV/H2O2 oxidation process for the removal of humic acids in water. A 450-W UV lamp with high-pressure mercury vapor was employed as the light source. The residues of humic acids and hydrogen peroxide were measured for assessment of process performance and understanding of process reaction behavior. The UV photolysis alone can play an important role in the degradation of humic acids. The presence of hydrogen peroxide was found to promote the degradation efficiency. However, excessive dosage of H2O2 does not further improve the degradation of humic acids. On the contrary, the lower the H2O2 dosage the higher the amount of humic acids which can be removed. Aeration with air does not favor the removal efficiency of humic acids as the oxidation lasts for a sufficiently long time. The presence of carbonate species deteriorates the humic acids' removal, whereas it results in a larger amount of H2O2 decomposition.

Effect of percent free prostate-specific antigen measurement on improving the specificity of serum prostate-specific antigen testing in Taiwanese patients

BACKGROUND AND PURPOSE

Measurement of percent free prostate-specific antigen (fPSA) has been shown to enhance the diagnostic performance of traditional serum PSA determination. We sought to determine whether measurement of percent fPSA could improve the specificity of serum total PSA testing in the detection of prostate cancer in Taiwanese patients with intermediate serum PSA concentrations.

METHODS

The medical records of 211 patients examined from March 1998 through March 2000 were analyzed retrospectively; all had a serum total PSA concentration of between 4.1 and 20.0 ng/mL and negative digital rectal examination (DRE) findings, and had undergone a prostate biopsy. Biopsy results were correlated with the serum total PSA concentration and percent fPSA, which were determined using a microparticle enzyme immunoassay. Percent fPSA was calculated as the ratio of fPSA to total PSA multiple by 100. The sensitivity and specificity were calculated and the receiver operating characteristic (ROC) curves were generated from different cutoff values of percent fPSA and total PSA.

RESULTS

Thirty-four patients (16.1%) had positive biopsy results (prostate cancer). Patients with positive biopsy results had significantly lower percent fPSA values than those with negative results (11.7% vs 16.0%, p < 0.001). Patients with a lower percent fPSA (< 10%) had a higher probability of a positive biopsy result than those with a high percent fPSA (> 20%) (positive biopsy rate, 29% vs 10%, p < 0.05). Using a cutoff value of 25% fPSA or below, the sensitivity, specificity, and positive predictive value in differentiating patients with positive biopsy results from those with negative results were 97%, 13%, and 18%, respectively. Consequently, 27 unnecessary biopsies could have been avoided at the cost of missing one cancer. The area under the ROC curve was 0.68 for percent fPSA and 0.63 for total PSA (p > 0.05).

CONCLUSIONS

For Taiwanese patients with a serum PSA concentration of between 4.1 and 20.0 ng/mL, the incidence of prostate cancer is relatively low; measurement of percent fPSA only weakly enhances the specificity of serum PSA testing in detecting prostate cancer.

Influence of pH on the dewatering of activated sludge by Fenton's reagent

The specific filtration resistance, moisture, and SVI were used to evaluate the influence of pH on the filtration and dewatering efficiencies when applying Fenton's reagent to treat the excess sludge. The excess sludge used in this study was obtained from the wastewater treatment plant of An-Ping Industrial Park in Tainan, Taiwan. Results show that initial pH has no significant effect on the filtration efficiency of sludge by using the Fenton (Fe2+/H2O2) system as the treatment process. However, the reduction of specific resistance by Fenton-like (Fe3+/H2O2) process decreased suddenly to a level similar to that obtained from the control experiment at initial pH > 4.5. For the moisture of cake sludge, both Fenton and Fenton-like systems have the same tendency; the moisture of cake sludge increased slightly with increasing the initial pH. The SVI values for Fenton process decreased with increasing the initial pH, but the opposite result was obtained from the Fenton-like and control system; higher pH was not favorable for the sludge settling.