Microwave Characteristics of an Independently Biased 3-stack InGaP/GaAs HBT Configuration

This paper investigates various important microwave characteristics of an independently biased 3-stack InGaP/GaAs heterojunction bipolar transistor (HBT) monolithic microwave integrated circuit (MMIC) chip at both small-signal and large-signal operation. By taking the advantage of the independently biased functionality, bias condition for individual transistor can be adjusted flexibly, resulting in the ability of independent control for both small-signal and large-signal performances. It was found that at small-signal operation stability and isolation characteristics of the proposed configuration can be significantly improved by controlling bias condition of the second-stage and the third-stage transistors while at large-signal operation its linearity and power gain can be improved through controlling the bias condition of the first-stage and the third-stage transistors. To demonstrate the benefits of using such an independently biased configuration, a measured optimum large-signal performance at an operation frequency of 1.6 GHz under an optimum bias condition for the high gain, low distortion were obtained as: PAE = 23.5 %, Pout = 12 dBm; Gain = 32.6 dB at IMD3 = -35 dBc. Moreover, to demonstrate the superior advantage of the proposed configuration, its small-signal and large-signal performance were also compared to that of a single stage common-emitter, a conventional 2-stack, an independently biased 2-stack and a conventional 3-stack configuration. The compared results showed that the independently biased 3-stack is the best candidate among the configurations for various wireless communications applications

量子効果デバイスならびにトランジスタにおける電力利得発生メカニズムの解明および改善

電気通信大学201

A Novel Wideband Bandpass Filter using H-shaped DGS

This paper presents a novel compact wide-band bandpass filter (BPF) having good selectivity. It is designed using a dual-plane structure which consists of a parallel-coupled microstrip line on the upper surface and three H-shape defected ground structures (DGS) on the ground plane. By adding three H-shape DGS units on the ground plane, then properly adjusting their dimensions and position, the bandwidth and selectivity of the designed filter can be significantly improved. A compact prototype of wide-band microstrip bandpass filter has been designed, fabricated and measured for the wireless systems applications. The filter exhibits a center frequency at 4.8 GHz, passband from 2.8 GHz to 6.8 GHz with best insertion loss and return loss of 0.8 dB and 40 dB, respectively. The measured results agrees well with the theoretical expectations validating the proposed design

Criteria of “persistent vomiting” in the WHO 2009 warning signs for dengue case classification

Introduction: Dengue is a viral disease that spreads rapidly in the tropic and subtropic regions of the world and causes 22,000 deaths annually. In 2009, the World Health Organization (WHO) released a new classification of dengue infections, which divided them into three categories: dengue without warning sign (D), dengue with warning sign (DWS), and severe dengue (SD). However, researchers have been using different criteria to define persistent vomiting; therefore, we aimed to evaluate the ability of the number of vomiting times in early prediction of SD development among D/DWS patients. Method: A hospital-based cohort study was conducted in Ben Tre-south of Vietnam. We enrolled confirmed dengue patients with D and DWS at admission. The final classification was determined on the discharged day for every patient based on the classification of WHO 2009 without using vomiting symptom, using the receiver operating characteristic (ROC) curve to evaluate the ability of the number of vomiting times in early prediction of SD development among D/DWS patients. Result: The prevalence of vomiting symptom was higher in SD group than D/DWS group (92 versus 46 %, p = 0.006), and the median of the number of vomiting times was higher in SD group than D/DWS group (2.5 versus 0, p = 0.001). To distinguish SD from D/DWS, the ROC curve of the number of vomiting episodes showed that the area under the curve was 0.77; with the cut point of two, the sensitivity and specificity were 92 and 52 %, respectively. Conclusion: The number of vomiting times could be a good clinical sign which can early predict SD from the group of D/DWS. We suggest the definition of persistent vomiting should be vomiting two times or more per day

A Novel Independently Biased 3-Stack GaN HEMT Configuration for Efficient Design of Microwave Amplifiers

The power amplifier (PA) and low-noise amplifier (LNA) are the most critical components of transceiver systems including radar, mobile communications, satellite communications, etc. While the PA is the key component of the transmitter (TX), the LNA is the key component of the receiver (RX) of the transceiver system. It is pointed out that traditional design approaches for both the LNA and PA face challenging drawbacks. When designing an LNA, the power gain and noise figure of the LNA are difficult to improve simultaneously. For PA design, it indicates that efficiency and linearity of the PA are also hard to improve simultaneously. This study aims to surmount this by proposing a novel independently biased 3-stack GaN high-electron-mobility transistor (HEMT) configuration for efficient design of both PA and LNA for next generation wireless communication systems. By employing an independently biased technique, the proposed configuration can offer superior performance at both small-signal (SS) for LNA design and large-signal (LS) for PA design compared with other typical circuit configurations. Simulation results show that by utilizing an adaptive bias control of each transistor of the proposed configuration, both power gain and noise figure can be improved simultaneously for the LNA design. Moreover, efficiency and linearity can be also improved at the same time for the PA design. Compared results with other typical configurations including a single-stage, conventional cascode, independently biased cascode, and conventional 3-stack reveals that the proposed configuration exhibits superior advantages at both SS and LS operation

Realization of Desired Plasmonic Structures via a Direct Laser Writing Technique

International audienc

Effects of Dietary Inclusion of Canthaxanthin- and α-Tocopherol-Loaded Liposomes on Growth and Muscle Pigmentation of Rainbow Trout (Oncorhynchus mykiss)

Dietary inclusion of canthaxanthin, a common carotenoid pigment, has been long practiced in aquaculture to give the favorable flesh color in farmed salmonids. However, carotenoids are associated with limited solubility and poor physicochemical stability, and their dose in fish feed is widely regulated. In this study, we included canthaxanthin- and α-tocopherol-loaded liposomes into fish diets and evaluated the effects of supplemented fish feed on fish growth, color, nutrition, and canthaxanthin deposition in fillets of cultured rainbow trout (Oncorhynchus mykiss). The liposomes were fabricated using lecithin as phospholipids with the initial concentrations (IC = mcanthaxanthin/mlipids, % wt/wt) of canthaxanthin at 0.1%, 0.5%, and 1.0%. Particle size characterization showed that liposome mean sizes were 109.70 ± 6.36, 105.10 ± 8.41, and 109.20 ± 5.66 nm (mean ± SD; n = 3), respectively, corresponding with liposomes synthesized at canthaxanthin IC = 0.1%, IC = 0.5%, and IC = 1%. The polydispersity index (PDI) of all samples remained lower than 0.2. There were no significant differences in the mean size and PDI between blank lecithin liposome and canthaxanthin- and α-tocopherol-loaded liposomes. The encapsulation efficiency of canthaxanthin- and α-tocopherol-loaded liposomes decreased when increasing the concentration of canthaxanthin in lecithin liposomes, with EE% values of IC = 0.1%, IC = 0.5%, and IC = 1% being 85.3 ± 2.1, 72.9 ± 1.8, and 55.3 ± 2.6, respectively. For fish growth, at the end of the experiment, final weight was significantly higher in fish fed with diet supplemented with 1 g/kg canthaxanthin- and α-tocopherol-loaded liposomes (IC = 0.5%) in comparison to other experimental control groups. The difference in color of the salmon muscle was most apparent after two months of feeding. However, after three months, there was no noticeable change in the color score of the fish muscle, indicating saturation of color of the fish muscle. The above results suggest the potential of canthaxanthin- and a-tocopherol-loaded liposomes as the red pigment in fish aquaculture

Serological and Molecular Epidemiology of Chikungunya Virus Infection in Vietnam, 2017–2019

Chikungunya fever is an acute febrile illness caused by the chikungunya virus (CHIKV), which is transmitted by Aedes mosquitoes. Since 1965, only a few studies with limited scope have been conducted on CHIKV in Vietnam. Thus, this study aimed to determine the seroprevalence and molecular epidemiology of CHIKV infection among febrile patients in Vietnam from 2017 to 2019. A total of 1063 serum samples from 31 provinces were collected and tested for anti-CHIKV IgM and IgG ELISA. The 50% focus reduction neutralization test (FRNT50) was used to confirm CHIKVneutralizing antibodies. Quantitative real-time RT–PCR (RT–qPCR) was performed to confirm the presence of the CHIKV genome. The results showed that 15.9% (169/1063) of the patients had anti-CHIKV IgM antibodies, 20.1% (214/1063) had anti-CHIKV IgG antibodies, 10.4% (111/1063) had CHIKV-neutralizing antibodies, and 27.7% (130/469) of the samples were positive in RT–qPCR analysis. The E1 CHIKV genome sequences were detected among the positive RT–qPCR samples. Our identified sequences belonged to the East/Central/South/African (ECSA) genotype, which has been prevalent in Vietnam previously, suggesting CHIKV has been maintained and is endemic in Vietnam. This study demonstrates a high prevalence of CHIKV infection in Vietnam and calls for an annual surveillance program to understand its impact.Viruses, 15(10), art. no. 2065; 202

Validation of the accuracy of the modified World Federation of Neurosurgical Societies subarachnoid hemorrhage grading scale for predicting the outcomes of patients with aneurysmal subarachnoid hemorrhage.

BackgroundEvaluating the prognosis of patients with aneurysmal subarachnoid hemorrhage (aSAH) who may be at risk of poor outcomes using grading systems is one way to make a better decision on treatment for these patients. This study aimed to compare the accuracy of the modified World Federation of Neurosurgical Societies (WFNS), WFNS, and Hunt and Hess (H&H) Grading Scales in predicting the outcomes of patients with aSAH.MethodsFrom August 2019 to June 2021, we conducted a multicenter prospective cohort study on adult patients with aSAH in three central hospitals in Hanoi, Vietnam. The primary outcome was the 90-day poor outcome, measured by a score of 4 (moderately severe disability) to 6 (death) on the modified Rankin Scale (mRS). We calculated the areas under the receiver operator characteristic (ROC) curve (AUROCs) to determine how well the grading scales could predict patient prognosis upon admission. We also used ROC curve analysis to find the best cut-off value for each scale. We compared AUROCs using Z-statistics and compared 90-day mean mRS scores among intergrades using the pairwise multiple-comparison test. Finally, we used logistic regression to identify factors associated with the 90-day poor outcome.ResultsOf 415 patients, 32% had a 90-day poor outcome. The modified WFNS (AUROC: 0.839 [95% confidence interval, CI: 0.795-0.883]; cut-off value≥2.50; PAUROCConclusionsIn this study, the modified WFNS, WFNS, and H&H scales all had good discriminatory abilities for the prognosis of patients with aSAH. Because of the better effect size in predicting poor outcomes, the modified WFNS scale seems preferable to the WFNS and H&H scales