Simulation and experimental study of a K-band extended interaction oscillator for microwave processing systems

High-power microwave sources have been widely applied for material processing in scientific research and manufacturing. The development of stable, high-frequency, high-power microwave sources is essential for achieving efficient microwave processing. This study proposes using a square doubly reentrant coupled-cavity as the slow-wave resonant structure in a K-band extended interaction oscillator (EIO). This design allows for ease of fabrication and high-power capability. The EIO is designed to operate in single 0-mode. The simulation results show that the competing π/5-mode can be effectively suppressed by properly choosing the width and location of the output coupler. The simulation and experiments successfully demonstrate stable, single-mode, tunable, high-performance operation of the EIO. The experimental measurements show a maximum output power of 1.776 kW (18.56% electronic efficiency), and a wave frequency of 24.324 GHz at a beam voltage of 17.4 kV and beam current of 550 mA. The EIO microwave source is suitable for interdisciplinary applications that require higher heating rates and greater uniformity.

High performance and high power circularly polarized horn antenna for K-band microwave processing systems

A single-ridged K-band circularly polarized horn antenna offering excellent performance has been developed by improving the polarization conversion and manufacturing complexity. The numerical and experimental results are consistent showing the return loss of this antenna to be less than -20 dB and the axial ratio at the boresight direction to be less than 0.7 dB in the frequency range from 23.5 GHz to 24.5 GHz. In addition, the gain of this antenna is higher than 20 dB. The newly designed circularly polarized horn antenna has a simple structure and outperforms many existing circular polarization devices in high-power operations.

Recurrent intussusception among infants less than 2 years of age in Vietnam

In some settings, rotavirus vaccines have been associated with a low-level risk of intussusception, the most common cause of bowel obstruction in infants. As Vietnam prepares to introduce rotavirus vaccine into the national immunization program, we sought to better characterize the epidemiology of recurrent intussusception. We enrolled children <2 years of age who were hospitalized for intussusception retrospectively from January 2013 through December 2014 and prospectively from January 2015 through December 2016 at 2 hospitals in Vietnam. We enrolled 2477 children. Nearly all children were successfully treated by enema with low surgery rate (1%). We found 10% of children (n = 254) experienced at least once recurrence (range: 1-6) and 57% of first recurrences happened within the first 12 weeks after treatment of the first episode. The median age at first intussusception was 13 months for children without a recurrent episode and 10 months for children with a recurrence. The symptoms of the recurrent cases were milder with less vomiting (67%), bloody stool (7%) and fever (10%) compared to the initial cases (p < 0.01). We found the rate of recurrences following enema reduction of intussusception to be similar to that reported from other countries. Due to the high rate of intussusception and recurrent episodes in Vietnam, a better understanding of the cause of recurrent intussusception will be critical in assessing intussusception cases after rotavirus introduction.

Significance of wild vegetables in micronutrient intakes of women in Vietnam: an analysis of food variety

The association between food variety and nutrient intake/health status among rural women was tested in two agro-ecological settings in Vietnam. Special emphasis was placed on the significance of wild vegetables 'Rau Dai' in micronutrient supply and on the usefulness of food variety analysis in determining their current role. Data from 7-day food frequency interviews and a nutrition/health survey with 93 and 103 rural women in the Mekong Delta and the Central Highlands, respectively, were used in the analysis. Energy and nutrient intakes in the groups with the highest food variety score (FVS) (high = > or = 21) in the two regions were compared to those with the lowest food variety score (low = < or = 15). The high FVS groups in both regions also had a more diversified diet in terms of food categories. With the exception of low iron and riboflavin intakes in all groups, the high FVS groups had relatively adequate diets. A large variety of vegetables was used and only approximately half of the vegetable species were cultivated. In both regions the high FVS groups used a significantly greater variety of vegetables than the low FVS groups. Wild vegetables contributed significantly to the overall micronutrient intakes, mostly carotene, vitamin C and calcium intakes, but only the contribution to carotene intake was significantly higher in the high FVS group. Overall, we conclude that a food variety analysis is a useful tool in capturing the dietary role of wild vegetables.

Inhibitory effect of evodiamine on aldosterone release by Zona glomerulosa cells in male rats

Evodiamine is a bioactive alkaloid extracted from a Chinese herb named Wu-Chu-Yu, which possesses thermoregulatory, analgesic, and cardiovascular effects. Some studies have demonstrated that evodiamine reduces blood pressure through acting on endothelium and smooth muscle cells to produce a vasodilatory effect, but whether it affects aldosterone secretion is unclear. The purpose of this study was to examine the effect of evodiamine on aldosterone release in adrenal zona glomerulosa (ZG) cells. ZG cells were isolated from the adrenal glands of adult male rats and incubated with angiotensin II (Ang II, 1x10(-7) M) and 3H-pregnenolone in the presence or absence of evodiamine (1x10(-6)-1x10(-3) M) at 37 degrees C for one hour. The concentration of aldosterone in the media was measured by a radioimmunoassay. The level of radioactivity incorporated into aldosterone and its precursors after incubation of ZG cells with 3H-pregnenolone was analyzed by thin-layer chromatography. The results demonstrated that evodiamine decreased the basal level of and Ang II-induced release level of aldosterone in rat ZG cells. Administration of evodiamine also decreased the level of radioactivity incorporated into 3H-corticosterone and 3H-aldosterone following incubation of ZG cells with 3H-pregnenolone. This suggest that evodiamine affects aldosterone release in rat adrenal glomerulosa cells by acting on Ang II-associated pathway and reducing the activity of 11 beta-hydroxylase (an enzyme which coverts deoxycorticosterone to corticosterone) during the steroidogenesis of aldosterone.

Effects of fasting on aldosterone secretion in ovariectomized rats

The present study was designed to assess the effect of fasting on aldosterone secretion in ovariectomized (Ovx) rats. Ovx rats were divided into fed (allowed access to food ad libitum) and fasted (deprived of food for 24 hours) groups. The trunk blood of fed and fasted rats was collected after decapitation. In the in vitro study, adrenal zona glomerulosa (ZG) cells from fed or fasted rats were incubated with angiotensin II (Ang II, 10(-6) M), adrenocorticotropic hormone (ACTH, 10(-9) M), or forskolin (an activator of adenylyl cyclase, 10(-6) M) at 37 degrees C for 30 min. The levels of aldosterone in medium and plasma extracts were measured by radioimmunoassay. Results showed that the levels of plasma aldosterone in fasted rats were lower than those in fed rats. There were no significant differences in basal and Ang II-stimulated aldosterone secretion between fed and fasted groups. The increment of aldosterone induced by ACTH in fasted group was significantly less than that in fed group. Administration of forskolin led to a significant increase in aldosterone secretion in both fed and fasted groups. Fasted group had a decreased aldosterone secretion in response to forskolin as compared with fed group. In summary, these results suggest that fasting decreases aldosterone secretion in Ovx rats through a mechanism in part involving a reduction of aldosterone production in response to ACTH, a decreased activity of adenylyl cyclase, and/or an inhibition of post-cAMP pathway in ZG cells.

Minocycline-induced hyperpigmentation

A 70-year-old man developed hyperpigmentation of his forearms, hands, fingernails, sclerae, ears, and teeth after 9 years of therapy with minocycline for acne rosacea. Minocycline is widely used in the treatment of acne vulgaris and uncommonly produces the side effect of hyperpigmentation. This effect does not appear to be dose-dependent and usually resolves within months to years after discontinuation of therapy. Discoloration of adult teeth, however, is generally permanent.