High speed imaging of bubble clouds generated in pulsed ultrasound cavitational therapy--histotripsy

Our recent studies have demonstrated that mechanical fractionation of tissue structure with sharply demarcated boundaries can be achieved using short (< 20 micros), high intensity ultrasound pulses delivered at low duty cycles. We have called this technique histotripsy. Histotripsy has potential clinical applications where noninvasive tissue fractionation and/or tissue removal are desired. The primary mechanism of histotripsy is thought to be acoustic cavitation, which is supported by a temporally changing acoustic backscatter observed during the histotripsy process. In this paper, a fast-gated digital camera was used to image the hypothesized cavitating bubble cloud generated by histotripsy pulses. The bubble cloud was produced at a tissue-water interface and inside an optically transparent gelatin phantom which mimics bulk tissue. The imaging shows the following: (1) Initiation of a temporally changing acoustic backscatter was due to the formation of a bubble cloud; (2) The pressure threshold to generate a bubble cloud was lower at a tissue-fluid interface than inside bulk tissue; and (3) at higher pulse pressure, the bubble cloud lasted longer and grew larger. The results add further support to the hypothesis that the histotripsy process is due to a cavitating bubble cloud and may provide insight into the sharp boundaries of histotripsy lesions.     

MIP model for efficient dimensioning of real-world FTTH trees

We propose a mixed-integer programming (MIP) formulation for a problem of optimal dimensioning of equipment of the fiber-to-the-home optical access network (FTTH-OAN). The optimization aims at minimizing capital expenditures (CAPEX) related to deployment of the FTTH-OAN, i.e., the cost of active equipment (OLTs and OLT cards), cost of passive equipment (optical splitters, cables, fibers, fibers terminations, splices, closures), cost of site preparations (building, cabinets), and cost of necessary labor (duct preparation and rollout of cables). The formulation has been implemented and validated. General results based on selected real-world scale numerical experiments are presented.     

On optimal trajectory for the multi-period evolution of FTTx networks

Telecommunication Systems - We propose a business/cost model for long-period changes of customer demands in FTTx networks. We show how to exploit this model in the formulation of a MIP optimization...     

Evolution of bubble clouds induced by pulsed cavitational ultrasound therapy - histotripsy

Mechanical tissue fractionation can be achieved using successive, high-intensity ultrasound pulses in a process termed histotripsy. Histotripsy has many potential clinical applications where noninvasive tissue removal is desired. The primary mechanism for histotripsy is believed to be cavitation. Using fast-gated imaging, this paper studies the evolution of a cavitating bubble cloud induced by a histotripsy pulse (10 and 14 cycles) at peak negative pressures exceeding 21MPa. Bubble clouds are generated inside a gelatin phantom and at a tissue-water interface, representing two situations encountered clinically. In both environments, the imaging results show that the bubble clouds share the same evolutionary trend. The bubble cloud and individual bubbles in the cloud were generated by the first cycle of the pulse, grew with each cycle during the pulse, and continued to grow and collapsed several hundred microseconds after the pulse. For example, the bubbles started under 10 microm, grew to 50 microm during the pulse, and continued to grow 100 microm after the pulse. The results also suggest that the bubble clouds generated in the two environments differ in growth and collapse duration, void fraction, shape, and size. This study furthers our understanding of the dynamics of bubble clouds induced by histotripsy.     

Negative social evaluation, but not mere social presence, elicits cortisol responses to a laboratory stressor task.

Background: Recent research has supported the premise that performance conditions characterized by social-evaluative threat, in which an aspect of the self could be judged by others, are associated with cortisol responses. However, it remains unclear whether this effect is due to negative social evaluation per se or simply the presence of another during a performance situation. Method: In the present study, 89 undergraduates delivered a speech in 1 of 3 conditions: in front of an evaluative audience panel (social-evaluative threat [SET]), in the presence of an inattentive confederate (PRES), or alone in a room (non-SET). Results: Consistent with hypotheses, participants in the SET condition demonstrated a significant cortisol response, while those in the non-SET and PRES conditions did not show increases in this hormone. Further, participants in the SET condition who reported greater posttask levels of self-conscious cognitions and emotions demonstrated the greatest increases in cortisol. Conclusion: These findings suggest that the mere social presence of others is not driving the changes in cortisol observed under social-evaluative threat; instead, explicit negative social evaluation may be responsible for increases in this health-relevant physiological parameter. (PsycINFO Database Record (c) 2010 APA, all rights reserved)