Dynamics of levitated objects in acoustic vortex fields

Acoustic levitation in gaseous media provides a tool to process solid and liquid materials without the presence of surfaces such as container walls and hence has been used widely in chemical analysis, high-temperature processing, drop dynamics and bioreactors. To date high-density objects can only be acoustically levitated in simple standing-wave fields. Here we demonstrate the ability of a small number of peripherally placed sources to generate acoustic vortex fields and stably levitate a wide range of liquid and solid objects. The forces exerted by these acoustic vortex fields on a levitated water droplet are observed to cause a controllable deformation of the droplet and/or oscillation along the vortex axis. Orbital angular momentum transfer is also shown to rotate a levitated object rapidly and the rate of rotation can be controlled by the source amplitude. We expect this research can increase the diversity of acoustic levitation and expand the application of acoustic vortices.

A numerical simulation of acoustic field within liquids subject to three orthogonal ultrasounds

When one beam of ultrasound propagates along a single direction in liquids, the cavitation effect is always confined to a limited volume close to the ultrasonic source. This greatly limits the application of power ultrasound in liquid processing and materials fabrication. In this study, a methodology for applying three orthogonal ultrasounds within liquids has been proposed. By solving the Helmholtz equation, the sound field distribution characteristics are investigated in 1D (one dimensional), 2D (two dimensional) and 3D (three dimensional) ultrasounds at their resonant frequencies, which show that the coherent interaction of three beams of ultrasounds is able to strikingly promote the sound pressure level and reinforce the mean acoustic energy density as compared with that in 1D case. Hence, the potential cavitation volume is enlarged remarkably. This opens new possibilities for the design and optimization of ultrasonic technology in fabricating materials.

Note: Attenuation motion of acoustically levitated spherical rotor

Here we observe the attenuation motion of spherical rotors levitated by near-field acoustic radiation force and analyze the factors that affect the duration time of free rotation. It is found that the rotating speed of freely rotating rotor decreases exponentially with respect to time. The time constant of exponential attenuation motion depends mainly on the levitation height, the mass of rotor, and the depth of concave ultrasound emitter. Large levitation height, large mass of rotor, and small depth of concave emitter are beneficial to increase the time constant and hence extend the duration time of free rotation.

The near-field acoustic levitation of high-mass rotors

Here we demonstrate that spherical rotors with 40 mm diameter and 0-1 kg mass can be suspended more than tens of micrometers away from an ultrasonically vibrating concave surface by near-field acoustic radiation force. Their rotating speeds exceed 3000 rpm. An acoustic model has been developed to evaluate the near-field acoustic radiation force and the resonant frequencies of levitation system. This technique has potential application in developing acoustic gyroscope.

Measurement and simulation of acoustic radiation force on a planar reflector

The accurate calculation of the acoustic radiation force is important for ultrasonic application techniques. Usually, the acoustic radiation force can be divided into the near-field and the far-field force according to the ratio of the emitter-reflector distance to the wavelength. In this study, appropriate theories and methods are explored to simulate the far-field and the near-field acoustic radiation force exerted on a planar reflector. The comparison between simulation and experiment indicates that the far-field force is not sensitive to the boundary shape and size while the near-field force is highly sensitive to the boundary size. Only the acoustic model with the minimized boundary size could yield the near-field force consistent with the experiment. Further calculations reveal that the far-field force first increases and then decreases with the rise of the reflector radius, and that the near-field force fluctuates with the acoustic frequency, especially when the emitter-reflector distance is very small. The near-field repulsive force can be changed into the attractive force when the acoustic frequency is lowered.

Acoustic levitation with self-adaptive flexible reflectors

Two kinds of flexible reflectors are proposed and examined in this paper to improve the stability of single-axis acoustic levitator, especially in the case of levitating high-density and high-temperature samples. One kind is those with a deformable reflecting surface, and the other kind is those with an elastic support, both of which are self-adaptive to the change of acoustic radiation pressure. High-density materials such as iridium (density 22.6 gcm(-3)) are stably levitated at room temperature with a soft reflector made of colloid as well as a rigid reflector supported by a spring. In addition, the containerless melting and solidification of binary In-Bi eutectic alloy (melting point 345.8 K) and ternary Ag-Cu-Ge eutectic alloy (melting point 812 K) are successfully achieved by applying the elastically supported reflector with the assistance of a laser beam.

High performance liquid chromatographic determination of a new antifungal compound, ADKZ in rat plasma

A high performance liquid chromatography (HPLC) method was developed and validated for the determination of ADKZ (1-(1H-1,2,4-triazole)-2-(2,4-diflurophenyl) -3-[N-methyl-N-(4-iodo-benzyl)amino]-2-propanol) in rat plasma. The compound was extracted from plasma samples by liquid-liquid extraction, and an isomeric compound of ADKZ (1-(1H-1,2,4-triazole)-2-(2,4-diflurophenyl)-3-[N-methyl-N -(3-iodo-benzyl)amino]-2-propanol) was used as the internal standard (IS), which were analyzed on a reversed-phase C18 column (5 microm, 200 mm x 4.6 mm i.d.). The extracted plasma samples were eluted with acetonitrile-0.018 M triethylamine solution adjusted to pH 3.2 with phosphoric acid (35:65, v/v). The effluent was monitored by a UV detector at 230 nm. The retention time of ADKZ was 7.1 min and IS 8.2 min. The calibration curves were linear in the concentration range of 0.02-2.00 microg/ml with the correlation coefficients greater than 0.999. The quantification limit of ADKZ in rat plasma was 0.02 microg/ml. Intra- and inter-day precision ranged from 2.6 to 7.9% and 3.1 to 9.6%, respectively. The extraction recovery from plasma was no less than 80%. No endogenous interferences were observed with either ADKZ or IS. The method has been successfully used to support the pre-clinical pharmacokinetic studies of ADKZ in rats.

Chiral liquid chromatography resolution and stereoselective pharmacokinetic study of tetrahydropalmatine enantiomers in dogs

A selective chiral high performance liquid chromatographic (HPLC) method coupled with achiral column was developed and validated to separate and quantify tetrahydropalmatine (THP) enantiomers in dog plasma. Chromatography was accomplished by two steps: (1) racemic THP was separated from biological matrix and collected on a Kromasil C18 column (150 mmx4.6 mm, 5 microm) with the mobile phase acetonitrile-0.1% phosphoric acid solution, adjusted with triethylamine to pH 6.15 (47:53); (2) enantiomeric separation was performed on a Chiralcel OJ-H column (250 mmx4.6 mm, 5 microm) with the mobile phase anhydrous ethanol. The detection wavelength was set at 230 nm. (+)-THP and (-)-THP were separated with a resolution factor (Rs) of at least 1.6 and a separation factor (alpha) greater than 1.29. Linear calibration curves were obtained over the range of 0.025-4 microg/ml in plasma for each of (+)-THP and (-)-THP (R2>0.999) with a limit of detection (LOD) of 0.005 microg/ml and the recovery was greater than 88% for each enantiomer. The relative standard deviation (R.S.D.) and relative error values were less than 10% at upper and lower concentrations. The method was used to determine the pharmacokinetics of THP enantiomers after oral administration of racemic THP. The results presented herein showed the stereoselective disposition kinetics of THP in dogs and were a further contribution to the understanding of the kinetic behavior of THP analogues.

Study of stereoselective pharmacokinetics of anisodamine enantiomers in rabbits by capillary electrophoresis

The purpose of this study was to determine the pharmacokinetics of anisodamine enantiomers in plasma after oral and intravenous administration of racemic anisodamine in rabbits. A capillary electrophoresis method for the simultaneous separation of two pairs of enantiomers in plasma has been firstly developed and validated. Using a 75 mM phosphate buffer containing 25 mM carboxymethylated-gamma-cyclodextrin at pH 2.5, good resolution was achieved on a 45-cm uncoated fused-silica capillary at the voltage of 20 kV and 25 degrees C. The pharmacokinetics of individual anisodamine enantiomers were characterized using the CE assay, the sole method of enantiomeric separation for anisodamine. Pharmacokinetic analysis of results indicated that anisodamine enantiomers showed non-stereoselective disposition or stereoselective disposition in different rabbits. For the rabbits with non-stereoselective disposition, similar pharmacokinetic characteristics were observed between (6S, 2'S)- and (6R, 2'R)-, or (6S, 2'R)- and (6R, 2'S)-anisodamine. For the rabbits with stereoselective disposition, (6S, 2'S)- and (6R, 2'S)-anisodamine were below the established LOD, while the two remaining enantiomers also had similar pharmacokinetic profiles. Further investigations remain necessary to find out the underlying mechanism about the stereoselective disposition of (6S, 2'S)- and (6R, 2'S)-anisodamine.

Low-level prenatal lead exposure and neurobehavioral development of children in the first year of life: a prospective study in Shanghai

We used a prospective study design to assess the effects of prenatal low-level lead exposure on the development of urban, inner-city children in Shanghai. Umbilical cord blood samples wee consecutively collected from 605 live newborns. Two hundred and fifty-seven samples were excluded from the study due to clotting. Lead levels were determined on 348 cord blood samples. The geometric mean was 9.2 micrograms/dl. Based on their cord blood lead levels, infants were classified into two exposure groups: 104 in a relatively low lead group (lead levels < or = 30 percentile), and 104 in a relatively high lead group (lead levels > or = 70 percentile). Seventy-five subjects failed to complete the study, and 133 babies were included in the final cohort: 69 babies in the high lead group and 64 in the low lead group. At 3, 6, and 12 months, the Bayley Scales of Infant Development were administered and capillary blood lead levels were measured. Detailed information was obtained on a wide range of variables relevant to infant development. At all three ages, the Mental Development index (MDI) scores, adjusted for confounders, were inversely related to the infants' cord blood lead levels. The difference of the mean adjusted MDI scores between low and high lead groups was 3.4 at 3 months, 6.3 at 6 months, and 5.2 at 12 months of age. These differences were statistically significant at all time points. No significant association between cord blood lead levels and the Psychomotor Development Index (PDI) scores was detected at all three visits after adjustment for confounders. Postnatal lead levels were unrelated to concurrent developmental status. We conclude that prenatal low-level lead exposure, which is relatively common in Shanghai, is associated with an adverse developmental impact on children through the first year of life.

Umbilical cord blood lead levels in Shanghai, China

This study was designed to determine the cord blood lead (BPb) levels of babies born in one urban area of Shanghai, and to preliminarily identify the demographic, social environment and prenatal factors which have an effect on the cord BPb concentrations. From August to November 1993, umbilical cord blood samples were obtained from 605 live newborns in the Yangpu Maternal and Child Hospital. 257 samples were excluded from measurement because of clotting. In 348 cord samples, the geometric mean of cord BPb levels was 9.2 micrograms/dl, with a 95% confidence interval of the mean 8.86-9.54 (micrograms/dl). 142 babies (40.8%) had cord BPb levels of 10 micrograms/dl or greater. As a result of this high percentage of newborns with BPb levels equal to or greater than 10 micrograms/dl, we estimate that each year in the Shanghai City about 60,000 newborns are at risk for developing neuropsychological deficiencies caused by maternal lead exposure during pregnancy. To investigate the factors affecting cord blood levels, the subjects with levels greater than the 70th percentile (10.7 micrograms/dl) (n = 104) and less than the 30th percentile (7.4 micrograms/dl) (n = 104) were selected to compare the demographic, environment and prenatal medical history. Increased BPb levels at birth were associated with maternal passive smoking, a family member being occupationally exposed to lead, proximity to major traffic way, household coal combustion, neighborhood coal combustion, low level of maternal occupations, and the increasing occurrence of having the high lead foodstuff pidan (preserved duck egg) during pregnancy. We conclude that prenatal lead exposure has become an important health issue for young children in Shanghai.

Growth promoting effect of zinc supplementation in infants of high-risk pregnancies

This study was made to determine whether zinc deficiency is one of the factors involved in growth retardation of infants of high-risk pregnancies. The high risk factors were hypertension of pregnancy, diabetes mellitus, congenital heart disease, chronic nephritis, rheumatic heart disease and hyperthyroidism. 102 neonatal infants were divided into 3 groups: breast fed group, 37 cases; test group, 32 cases formula-fed with supplementary zinc 1.14-2.28 mg/kg/d; and control group, 33 cases formula-fed and supplemented with Vitamin B complex as placebo. The groups were divided by double-blind and randomized method. There were no differences in the 3 groups in sex ratio, growth status and serum zinc concentration at the beginning of the study. Anthropometric data were obtained at 0, 3 and 6 months.