Acoustic signatures of submicron contrast agents

Previous studies have revealed that hard-shelled submicron contrast agents exhibit large relative expansions and strong acoustical echoes that can be observed experimentally, and predicted by theoretical simulations. In this paper, we study harmonic imaging and pulse-pair imaging techniques designed to assist in the differentiation of these contrast agents from tissue. For harmonic imaging, we apply a high-sensitivity, narrowband strategy that differentiates the microbubble from tissue based on the generation of strong harmonic echoes. For pulse-pair imaging, we apply high spatial resolution, wideband strategies using phase inversion, which relies on the frequency differences observed in response to phase-inverted pulses, and signal subtraction, which takes advantage of the amplitude differences in response to identical pulses. The bubble-to-phantom signal amplitude ratio in the absence of motion approaches 20 dB using phase inversion and 30 dB using signal subtraction; both techniques are robust for up to 50 microm of simulated motion. With the experience gained in these studies, we hope to advance the development of multi-pulse or shaped-pulse techniques that are optimized for specific clinical applications.     

Advancing human nutrition without degrading land resources through modeling cropping systems in the Ethiopian highlands

Food shortage in sub-Saharan Africa is generally considered a function of limited access to food, with little thought to nutritional quality. Analyzing household production of nutrients across farming systems could be valuable in guiding the improvement of those systems. An optimization model was employed to analyze the scenario of human nutrition and cropland allocation in enset (Enset ventricosum)/root crop-based and cereal-based systems of the Ethiopian Highlands. The type and amount of nutrients produced in each system were analyzed, and an optimization model was used to analyze which cropping strategies might improve the nutritional quality of the household using existing resources. Both production systems were in food deficit, in terms of quantity and quality of nutrients, except for iron. The energy supply of resource-poor households in the enset/root crop-based system was only 75% of the recommended daily dietary allowance (RDA) of the World Health Organization (WHO), whereas resource-rich farmers were able to meet their energy, protein, zinc, and thiamine demands. Extremely high deficiency was found in zinc, calcium, vitamin A, and vitamin C, which provided only 26.5%, 34%, 1.78%, and 12%, of the RDA, respectively. The RDA could be satisfied if the land area occupied by enset, kale, and beans were expanded by about 20%, 10%, and 40%, respectively, at the expense of maize and sweet potato. The cereal-based system also had critical nutrient deficits in calcium, vitamin A, and vitamin C, which provided 30%, 2.5%, and 2% of the RDA, respectively. In the cereal system, the RDA could be fully satisfied by reducing cropland allocated to barley by about 50% and expanding the land area occupied by faba beans, kale, and enset. A shift from the cereal/root crop-dominated system to a perennial-enset dominated system would decrease soil erosion by improving the crop factor by about 45%. This shift would also have a very strong positive impact on soil fertility management. However, any policy suggestions for change in cropland allocation should be done through negotiations with households, communities, and district stakeholders.     

Mechanisms of contrast agent destruction

Various applications of contrast-assisted ultrasound, including blood vessel detection, perfusion estimation, and drug delivery, require controlled destruction of contrast agent microbubbles. The lifetime of a bubble depends on properties of the bubble shell, the gas core, and the acoustic waveform impinging on the bubble. Three mechanisms of microbubble destruction are considered: fragmentation, acoustically driven diffusion, and static diffusion. Fragmentation is responsible for rapid destruction of contrast agents on a time scale of microseconds. The primary characteristics of fragmentation are a very large expansion and subsequent contraction, resulting in instability of the bubble. Optical studies using a novel pulsed-laser optical system show the expansion and contraction of ultrasound contrast agent microbubbles with the ratio of maximum diameter to minimum diameter greater than 10. Fragmentation is dependent on the transmission pressure, occurring in over 55% of bubbles insonified with a peak negative transmission pressure of 2.4 MPa and in less than 10% of bubbles insonified with a peak negative transmission pressure of 0.8 MPa. The echo received from a bubble decorrelates significantly within two pulses when the bubble is fragmented, creating an opportunity for rapid detection of bubbles via a decorrelation-based analysis. Preliminary findings with a mouse tumor model verify the occurrence of fragmentation in vivo. A much slower mechanism of bubble destruction is diffusion, which is driven by both a concentration gradient between the concentration of gas in the bubble compared with the concentration of gas in the liquid, as well as convective effects of motion of the gas-liquid interface. The rate of diffusion increases during insonation, because of acoustically driven diffusion, producing changes in diameter on the time scale of the acoustic pulse length, thus, on the order of microseconds. Gas bubbles diffuse while they are not being insonified, termed static diffusion. An air bubble with initial diameter of 2 microns in water at 37 degrees C is predicted to fully dissolve within 25 ms. Clinical ultrasound contrast agents are often designed with a high molecular weight core in an attempt to decrease the diffusion rate. C3F8 and C4F10 gas bubbles of the same size are predicted to fully dissolve within 400 ms and 4000 ms, respectively. Optical experiments involving gas diffusion of a contrast agent support the theoretical predictions; however, shelled agents diffuse at a much slower rate without insonation, on the order of minutes to hours. Shell properties play a significant role in the rate of static diffusion by blocking the gas-liquid interface and decreasing the transport of gas into the surrounding liquid. Static diffusion decreases the diameter of albumin-shelled agents to a greater extent than lipid-shelled agents after insonation.     

Integrated psychological services in the Greeley-Evans public schools.

Integrated school psychological services were implemented 12 years ago in the Greeley-Evans Public Schools by combining the positions of school psychologist and school social worker and placing each professional in an elementary school full-time. After 5 years, services were expanded to secondary schools such that all schools had a full-time school psychologist. Using Bennett's (1988) model for the evaluation of alternative services to determine success in meeting stated goals, a number of positive outcomes were achieved. A time-use survey indicated increased involvement with a variety of interventions for school psychologists. The results of a consumer satisfaction questionnaire given to teachers, administrators, and support personnel also suggested positive perceptions of the new role. Additionally, placement of students with significant emotional disturbance decreased over this time period relative to a 34% student enrollment increase. It is hoped that the long-term implementation of an alternative school psychological services model such as this one will encourage others to enact ecologically responsive services relative to their unique systems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The influence of linguistic experience on the cognitive processing of pitch in speech and nonspeech sounds.

In the present experiment, the authors tested Mandarin and English listeners on a range of auditory tasks to investigate whether long-term linguistic experience influences the cognitive processing of nonspeech sounds. As expected, Mandarin listeners identified Mandarin tones significantly more accurately than English listeners; however, performance did not differ across the listener groups on a pitch discrimination task requiring fine-grained discrimination of simple nonspeech sounds. The crucial finding was that cross-language differences emerged on a nonspeech pitch contour identification task: The Mandarin listeners more often misidentified flat and falling pitch contours than the English listeners in a manner that could be related to specific features of the sound structure of Mandarin, which suggests that the effect of linguistic experience extends to nonspeech processing under certain stimulus and task conditions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Wear behaviour of some low alloyed steels under combined impact/abrasion contact conditions

The wear behaviour of some low alloyed steels has been investigated using a laboratory impeller–tumbler wear test equipment in which the steel samples are worn by angular granite particles under combined impact/abrasion wear contact conditions. The wear of the steels was evaluated by weight loss of the steel samples while the wear mechanisms of the steels were investigated by post-test light optical microscopy (LOM), scanning electron microscopy and energy dispersive X-ray analysis. The worn steel surfaces display a very rough surface topography with pronounced craters and distinct grooves caused by high and low angle impacts, i.e. abrasive wear, respectively. Besides, fragments of embedded granite particles are frequently observed in the worn surface of the steels. The wear of the steels tends to decrease with increasing steel hardness. However, instead of using the bulk hardness value the hardness of the worn/plastically deformed surface layer should be used when modelling the wear resistance. Further, the wear resistance of the steels was found to be dependent on the microstructure and chemical composition. Steels with similar type of microstructure show a linear decrease in weight loss with decreasing grain size and increasing carbon content.     

Atmospheric water vapor retrieval by means of both a GPS networkand a microwave radiometer during an experimental campaign in Cagliari,Italy, in 1999

Considers the remote sensing of atmospheric integrated precipitable water vapor (IPWV) using a Global Positioning System (GPS) network in the Mediterranean area during the whole year 1999. The assessment of IPWV retrieval has been carried out by means of an experimental campaign conducted in the proximity of the city of Cagliari, Italy, located on the southern coast of Sardinia in the Mediterranean Sea. The authors have compared GPS estimates with co-located measurements from a microwave dual-channel water vapor radiometer (WVR) collected in nonprecipitating conditions and with observations from radiosondes released four times a day from the Cagliari-Elmas Airport, approximately 15 km away from the GPS and WVR site. The long-term comparison has shown a fairly good agreement among the two remote sensors and the radiosonde observations, with a higher correlation between GPS and WVR     

Shyness and symptoms of illness in young children.

Investigated the association between shyness and symptoms of illness in young children and the types of symptoms differentiating shy and nonshy children. 16 shy children and 16 nonshy children (mean age 7 yrs 3 mo) were matched on sex, parental education, familial stress, and height-weight ratio. For 4 wks, parents recorded their children's health complaints and their own observations and conclusions of their children's health. There were more days on which shy children complained of unwellness and parents observed symptoms of unwellness than for nonshy children. Shy children made more affective complaints and were observed to experience more gastrointestinal upset. Several interpretations of the results are presented including the possibilities that lower thresholds for arousal in the hypothalamic-pituitary-adrenal axes of shy children affected their immunocompetence, that parents of shy children and the children themselves were more sensitive to symptoms of illness, and that feeling unwell may contribute to shy behaviour. Results suggest that the health of shy children merits further study. (PsycINFO Database Record (c) 2010 APA, all rights reserved)