Biomedical subjects
Publications and source records attributed to H Zhu.
A case of Ebstein anomaly in a 2-day-old newborn is presented. The complementary roles of two-dimensional Doppler echocardiography and magnetic resonance imaging in managing this cardiac malformation are emphasized.
PURPOSE: The purpose of this report is to describe the design and construction of an 8 T/80 cm whole-body MRI system operating at 340 MHz. METHOD: The 8 T/80 cm magnet was constructed from 414 km of niobium titanium superconducting wire. The winding of this wire on four aluminum formers resulted in a total inductance of 4,155 H. Gradient subsystems included either a body gradient or a head gradient along with a removable shim insert. The magnet and gradient subsystems were interfaced to two spectrometers. These provided the control of the gradient amplifiers and the two sets of four RF power amplifiers. The latter provide in excess of 8 kW of RF power from 10 to 140 MHz and 10 kW of RF power from 245 to 345 MHz. A dedicated computer-controlled patient table was designed and assembled. The entire system is located in a clinical setting, facilitating patient-based studies. RESULTS: The 8 T/80 cm magnet was energized without complication and achieved persistent operation using 198.9 A of current, thereby storing 81.5 MJ of magnetic energy. Exceptional performance was observed for nearly all components both in isolation and when combined within the complete system. CONCLUSION: An 8 T/80 cm MRI system has been assembled. The magnet subsystem is extremely stable and is characterized by good homogeneity and acceptable boil-off rates.
Reducing surface and subsurface losses of herbicides in the soil and thus their potential contamination of water resources is a national concern. This study evaluated the effectiveness of sugarcane (Saccharum spp.) residue (mulch cover) in reducing nonpoint-source contamination of applied herbicides from sugarcane fields. Specifically, the effect of mulch residue on herbicide retention was quantified. Two main treatments were investigated: a no-till treatment and a no-mulch treatment. The amounts of extractable atrazine [2-chloro-4-(isopropylamino)-6-ethylamino-s-triazine], metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one], and pendimethalin [N-(ethylpropyl)-3,4-dimethyl-2,6-dinitroaniline] from the mulch residue and the surface soil layer were quantified during the 1999 and 2000 growing seasons. Significant amounts of applied herbicides were intercepted by the mulch residue. Extractable concentrations were at least one order of magnitude higher for the mulch residue compared with that retained by the soil. Moreover, the presence of mulch residue on the sugarcane rows was highly beneficial in minimizing runoff losses of the herbicides applied. When the residue was not removed, a reduction in runoff-effluent concentrations, as much as 50%, for atrazine and pendimethalin was realized. Moreover, the presence of mulch residue resulted in consistently lower estimates for rates of decay or disappearance of atrazine and pendimethalin in the surface soil.
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Sorption and desorption kinetics are essential components for modeling the movement and retention of applied agricultural chemicals in soils and the fraction of chemicals susceptible to runoff. In this study, we investigated the retention characteristics of sugarcane (Saccharum spp. hybrid) mulch residue for atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine) based on studies of sorption-desorption kinetics. A sorption kinetic batch method was used to quantify retention of the mulch residue for a wide range of atrazine concentrations and reaction times. Desorption was performed following 504 h of sorption using successive dilutions, followed by methanol extraction. Atrazine retention by the mulch residue was well described using a linear model where the partitioning coefficient (K(d)) increased with reaction time from 10.40 to 23.4 cm3 g(-1) after 2 and 504 h, respectively. Values for mulch residue K(d) were an order of magnitude higher than those found for Commerce silt loam (fine-silty, mixed, superactive, nonacid, thermic Fluvaquentic Endoaquepts) where the sugarcane crop was grown. A kinetic multireaction model was successful in describing sorption behavior with reaction time. The model was equally successful in describing observed hysteretic atrazine behavior during desorption for all input concentrations. The model was concentration independent where one set of model parameters, which was derived from all batch results, was valid for the entire atrazine concentration range. Average atrazine recovery following six successive desorption steps were 63.67 +/- 4.38% of the amount adsorbed. Moreover, a hysteresis coefficient based on the difference in the area between sorption and desorption isotherms was capable of quantifying hysteresis of desorption isotherms.
OBJECTIVE: To determine subsets and functional characteristics of peripheral blood lymphocytes in men with infertility associated with anti-sperm antibodies. SUBJECTS AND METHODS: Blood from 28 infertile men with anti-sperm antibodies and 34 fertile control males were tested for the lymphocyte subsets by indirect immunofluorescence and also for lymphocyte transformation responses to phytohemagglutinin (PHA), ConA, and pokeweed mitogen (PWM). Also studied were effects of seminal plasma on the lymphocyte transformation responses. RESULTS: Percentages of CD3, -4, and -8 cells and lymphocyte blastogenic responses to PHA and ConA were significantly lowered in patients. Percentage of B-cells, CD4/CD8 ratio, and blastogenic response to PWM were increased. All seminal plasmas suppressed lymphocyte blastogenesis induced by PHA, PWM, and ConA, but the suppressive effect on PHA and PWM by patients' plasma was less than that of controls. CONCLUSIONS: The results suggest that number and function of T-lymphocytes, especially CD8 cells, are lessened and those of CD4 and B-cells enhanced in the infertile patients. These factors would be conducive to development of an immunologic response to sperm.