Effective Rheology of Bubbles Moving in a Capillary Tube

We calculate the average volumetric flux versus pressure drop of bubbles moving in a single capillary tube with varying diameter, finding a square-root relation from mapping the flow equations onto that of a driven overdamped pendulum. The calculation is based on a derivation of the equation of motion of a bubble train from considering the capillary forces and the entropy production associated with the viscous flow. We also calculate the configurational probability of the positions of the bubbles.Comment: 4 pages, 1 figur

Alignment of the ALICE Inner Tracking System with cosmic-ray tracks

37 pages, 15 figures, revised version, accepted by JINSTALICE (A Large Ion Collider Experiment) is the LHC (Large Hadron Collider) experiment devoted to investigating the strongly interacting matter created in nucleus-nucleus collisions at the LHC energies. The ALICE ITS, Inner Tracking System, consists of six cylindrical layers of silicon detectors with three different technologies; in the outward direction: two layers of pixel detectors, two layers each of drift, and strip detectors. The number of parameters to be determined in the spatial alignment of the 2198 sensor modules of the ITS is about 13,000. The target alignment precision is well below 10 micron in some cases (pixels). The sources of alignment information include survey measurements, and the reconstructed tracks from cosmic rays and from proton-proton collisions. The main track-based alignment method uses the Millepede global approach. An iterative local method was developed and used as well. We present the results obtained for the ITS alignment using about 10^5 charged tracks from cosmic rays that have been collected during summer 2008, with the ALICE solenoidal magnet switched off.Peer reviewe

Compensatory Intracranial Arterial Dilatation in Extracranial Carotid Atherosclerosis: The Northern Manhattan Study

BACKGROUND: There is a scarcity of data supporting the association between atherosclerosis and dolichoectasia (DE) in unbiased samples. AIMS: To test the hypothesis that the association between DE and extracranial carotid atherosclerosis depends on the degree of collateral circulation. METHODS: The Northern Manhattan Study MRI substudy consists of 1290 participants who remained stroke-free at the time of MRI. Arterial diameters were collected in all participants with available MRA. Dolichoectasia was defined as a head-size adjusted diameter > 2 SD for each artery. Carotid Doppler was used to evaluate for carotid atherosclerosis (carotid plaque, maximum plaque thickness [MCPT] and intima media thickness [cIMT]). RESULTS: We included 994 participants with available Doppler and MRA data (mean age 63 years, 60% female). Any DE was reported in 16% of participants, 54% had at least one carotid plaque and the mean cIMT was 0.92 ± 0.09 mm. After adjusting for demographic and clinical characteristics, there was no association between markers of carotid atherosclerosis and DE. However, stratifying by collaterals, it was observed that DE was more likely in the anterior and posterior circulations when collaterals were available among participants with carotid atherosclerosis. These associations were confirmed by noting an increment in arterial diameters in the corresponding arteries ipsilateral and contralateral to each carotid as well as in the posterior circulation. CONCLUSIONS: We did not find an association of extracranial carotid atherosclerosis with DE. However, we found that DE is more frequent when intracranial collaterals are available suggesting a compensatory process that needs further investigation