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K C Hsieh

Publications and source records attributed to K C Hsieh.

13 recordsLinked to original sources
PubMed2006

Plasma acceleration above martian magnetic anomalies.

Auroras are caused by accelerated charged particles precipitating along magnetic field lines into a planetary atmosphere, the auroral brightness being roughly proportional to the precipitating particle energy flux. The Analyzer of Space Plasma and Energetic Atoms experiment on the Mars Express spacecraft has made a detailed study of acceleration processes on the nightside of Mars. We observed accelerated electrons and ions in the deep nightside high-altitude region of Mars that map geographically to interface/cleft regions associated with martian crustal magnetization regions. By integrating electron and ion acceleration energy down to the upper atmosphere, we saw energy fluxes in the range of 1 to 50 milliwatts per square meter per second. These conditions are similar to those producing bright discrete auroras above Earth. Discrete auroras at Mars are therefore expected to be associated with plasma acceleration in diverging magnetic flux tubes above crustal magnetization regions, the auroras being distributed geographically in a complex pattern by the many multipole magnetic field lines extending into space.

Journal Article↗
PubMed2005

Dynamics of Saturn's magnetosphere from MIMI during Cassini's orbital insertion.

The Magnetospheric Imaging Instrument (MIMI) onboard the Cassini spacecraft observed the saturnian magnetosphere from January 2004 until Saturn orbit insertion (SOI) on 1 July 2004. The MIMI sensors observed frequent energetic particle activity in interplanetary space for several months before SOI. When the imaging sensor was switched to its energetic neutral atom (ENA) operating mode on 20 February 2004, at approximately 10(3) times Saturn's radius RS (0.43 astronomical units), a weak but persistent signal was observed from the magnetosphere. About 10 days before SOI, the magnetosphere exhibited a day-night asymmetry that varied with an approximately 11-hour periodicity. Once Cassini entered the magnetosphere, in situ measurements showed high concentrations of H+, H2+, O+, OH+, and H2O+ and low concentrations of N+. The radial dependence of ion intensity profiles implies neutral gas densities sufficient to produce high loss rates of trapped ions from the middle and inner magnetosphere. ENA imaging has revealed a radiation belt that resides inward of the D ring and is probably the result of double charge exchange between the main radiation belt and the upper layers of Saturn's exosphere.

Atmosphere↗
PubMed2004

Solar wind-induced atmospheric erosion at Mars: first results from ASPERA-3 on Mars Express.

The Analyzer of Space Plasma and Energetic Atoms (ASPERA) on board the Mars Express spacecraft found that solar wind plasma and accelerated ionospheric ions may be observed all the way down to the Mars Express pericenter of 270 kilometers above the dayside planetary surface. This is very deep in the ionosphere, implying direct exposure of the martian topside atmosphere to solar wind plasma forcing. The low-altitude penetration of solar wind plasma and the energization of ionospheric plasma may be due to solar wind irregularities or perturbations, to magnetic anomalies at Mars, or both.

Journal Article↗
PubMed2002

A nebula of gases from Io surrounding Jupiter.

Several planetary missions have reported the presence of substantial numbers of energetic ions and electrons surrounding Jupiter; relativistic electrons are observable up to several astronomical units (au) from the planet. A population of energetic (>30[?]keV) neutral particles also has been reported, but the instrumentation was not able to determine the mass or charge state of the particles, which were subsequently labelled energetic neutral atoms. Although images showing the presence of the trace element sodium were obtained, the source and identity of the neutral atoms---and their overall significance relative to the loss of charged particles from Jupiter's magnetosphere---were unknown. Here we report the discovery by the Cassini spacecraft of a fast (>103[?]km[?]s-1) and hot magnetospheric neutral wind extending more than 0.5[?]au from Jupiter, and the presence of energetic neutral atoms (both hot and cold) that have been accelerated by the electric field in the solar wind. We suggest that these atoms originate in volcanic gases from Io, undergo significant evolution through various electromagnetic interactions, escape Jupiter's magnetosphere and then populate the environment around the planet. Thus a 'nebula' is created that extends outwards over hundreds of jovian radii.

Journal Article↗
PubMed2001

Performance evaluation of single-sludge reactor system treating high-strength nitrogen wastewater.

In the single-sludge reactor system treating high-strength nitrogen wastewater (similar to anaerobically pretreated piggery wastewater), the NH4(+)-N removal efficiencies (98-82%) are higher than total nitrogen removal efficiencies (71-43%). The mixed liquor recycle ratio only imposes a slight effect on total nitrogen removal efficiency. The alkalinity change data could be used for monitoring and control of the reactor system. To evaluate the performance of the single-sludge reactor system, a simplified nitrification-denitrification model (with nitrification capacity, denitrification capacity, and denitrification potential concepts) and a graphically analytical technique are proposed. It turns out that ammonia nitrification and total nitrogen removal efficiencies are strongly dependent on the process load and reactor configuration, and an optimal operating condition requires a proper match between nitrification and denitrification.

Aerobiosis↗
PubMed2001

Differentiation of benign and malignant gastric stromal tumors using endoscopic ultrasonography.

BACKGROUND: Endoscopic ultrasonography (EUS) is a useful modality to show the sonographic features of gastric stromal tumors (GST) which originate from the gastric wall, but it is difficult to distinguish benign from malignant tumors. This study tried to discriminate between them by their EUS patterns. METHODS: EUS patterns were obtained from 52 histologically proved GST. The tumor size, echo patterns and irregular margin were analyzed. RESULTS: Of 52 GST, 11 were leiomyosarcoma and 41 were leiomyoma. The mean sizes of the leiomyoma and leiomyosarcoma were 3.3 +/- 1.1 cm and 7.1 +/- 2.2 cm (p < 0.01). Using a tumor size > or = 5 cm as a criterion for malignancy resulted in a sensitivity of 72.7% and a specificity of 85.4%. A sonolucent area inside the tumor, resulted in a sensitivity and specificity of 81.8% and 80.5%. With an irregular tumor margin, the sensitivity and specificity were 90.9% and 90.2%. A combination of all 3 criteria, resulted in a sensitivity and specificity of 72.7% and 90.2%. For benign tumors, the criteria of tumor < 5 cm, no sonolucent areas and no irregular margin had a sensitivity of 80.5% and a specificity of 100%. CONCLUSION: Tumor size is not a sensitive criterion of malignancy. An irregular margin and sonolucent areas in the tumor have better sensitivity and specificity for the diagnosis of malignant GST. On the contrary, a GST smaller than 5 cm in size with neither a sonolucent area nor an irregular tumor margin strongly suggests a benign lesion.

Endosonography↗
PubMed1999

Surgical treatment of morbid obesity with vertical banded gastroplasty: a comparison between TA90-4.8 and TA90-B.

BACKGROUND: In this study, we wanted to determine the results of vertical banded gastroplasty for morbid obesity and compare the results of using the TA90-4.8 with using the TA90-B instrument. METHODS: Patients with body weight over 100% of or 45 kg above their ideal body weight, body mass index (BMI) over 40 kg/m2, or BMI over 35 kg/m2 with osteoarthritis, venous stasis, sleep apnoea, or frequent abortion were selected for surgical intervention. They were purposely divided into two groups. Vertical banded gastroplasty was performed in group A with two applications of TA90-4.8 (N = 26) and in group B with one application of TA90-B (N = 24). The outlet of the gastric pouch was 10 to 12 mm and reinforced with a 1.5 cm strip of Marlex to give a circumference of 5.5 cm. The follow-up body weight, BMI, and percentage of weight in excess of the ideal weight were compared between the two groups. The results were classified as excellent (0 to 25% excess weight), fair (26 to 50% excess weight), good (51 to 75% excess weight), poor (76 to 100% excess weight), and worse (> 100% excess weight). A failure was defined as a body weight of greater than 76% excess weight and a repeated operation being needed regardless of the ultimate outcome. RESULTS: There were no differences between the two groups regarding age, gender, preoperative body weight, BMI, and excess weight. The operative time was longer for group A (175 +/- 39 min) than for of group B (140 +/- 23 min) (p < 0.0001). In the follow-up period, the postoperative body weight, BMI, and excess weight showed no differences between the two groups. Four patients in group A had poor results, three due to staple disruption and one due to sweet-eating. One patient in group B had stenosis of the stomach pouch and needed another operation to release the stenosis. Thus, five failures (10%) were found in this study. CONCLUSION: Vertical banded gastroplasty is an effective modality for treating morbid obesity. Two applications of TA90-4.8 are not recommended because they result in frequent staple disruption.

Adult↗
PubMed1994

Follicular fluid levels of insulin-like growth factor I, insulin-like growth factor binding protein I, and ovarian steroids collected during ovum pick-up.

OBJECTIVE: To evaluate interrelationships between levels of insulin-like growth factor I (IGF-I), insulin-like growth factor binding protein (IGFBP-I), and ovarian steroids in late preovulatory follicular fluid (FF) after pituitary desensitization with GnRH agonist and controlled ovarian hyperstimulation. DESIGN: Follicular fluid and matched serum were collected during the ovum pick-up. Insulin-like growth factor binding protein I, E2, P, and androstenedione (A) were measured by means of RIA, whereas T was measured by means of fluoroimmunoassay and IGF-I by means of immunoradiometric assay. SETTING: University teaching hospital. PARTICIPANTS: Fifty-nine patients underwent 62 ovum pick-ups for IVF. MAIN OUTCOME MEASURES: Levels of IGF-I, IGFBP-I, E2, P4 (representative of follicular maturity), T, and A in FF and the volume of this fluid were determined. Levels of E2 to A (representative of aromatase activity) in FF were examined in relation to the volume of FF. RESULTS: Levels of FF-IGF-I decreased with increasing volume of FF. This observation is unprecedented. In contrast, FF-P increased with increasing volume of FF. The reverse relationships with FF volume between FF-IGF-I and FF-P may not be causal because no correlation was found between concentrations of FF-IGF-I and FF-P. Our findings are consistent with and complementary to those in previous reports. The follicular fluid E2:A ratio, FF-E2, FF-A, FF-T, and FF-IGFBP-I were not found to be correlated with volume of FF. CONCLUSION: Decreased levels of FF-IGF-I with unaltered levels of FF-IGFBP-I in larger follicles may favor a shift toward diminished action of IGF-I at the time of immediate preovulation. The physiological significance of this shift remains uncertain as it is not reflected in the levels of steroids in FF.

Adult↗