Non-spherical collapse of an air bubble subjected to a lithotripter pulse

In order to better understand the contribution of bubble collapse to stone comminution in shockwave lithotripsy, the shockinduced and Rayleigh collapse of a spherical air bubble is investigated using numerical simulations, and the free-field collapse of a cavitation bubble is studied experimentally. In shock-induced collapse near a wall, it is found that the presence of the bubble greatly amplifies the pressure recorded at the stone surface; the functional dependence of the wall pressure on the initial standoff distance and the amplitude are presented. In Rayleigh collapse near a solid surface, the proximity of the wall retards the flow and leads to a more prominent jet. Experiments show that re-entrant jets form in the collapse of cavitation bubbles excited by lithotripter shockwaves in a fashion comparable to previous studies of collapse near a solid surface

Oligonucleotide sequences forming short self-complimentary hairpins can expedite the down-regulation of Coprinopsis cinerea genes

Gene silencing in fungi is often induced by dsRNA hairpin forming constructs the preparation of which can require multiple cloning steps. To simplify gene silencing in the filamentous fungi we have evaluated a high throughput cloning method for target sequences using the homobasidiomycete Coprinopsis cinerea, the GFP reporter and a commercially available vector system. The pSUPER RNAi System™, which was developed for mammalian experiments, exploits the human H1 Polymerase III (Pol III) RNA gene promoter and expedites cloning/expression of specific user-defined oligonucleotide sequences to form short self-complimentary hairpins. Transformation of C. cinerea with pSUPER constructs harboring specific oligonucleotides (19 nt stem length) enabled recovery of transformants with reduced transcripts of the GFP transgene, that were less fluorescent in protein assays and microscopic phenotypes. This technological advance should expedite functional genomic studies in C. cinerea and has wider potential for utility in other homobasidiomycete and filamentous fungi

Method and system to synchronize acoustic therapy with ultrasound imaging

Interference in ultrasound imaging when used in connection with high intensity focused ultrasound (HIFU) is avoided by employing a synchronization signal to control the HIFU signal. Unless the timing of the HIFU transducer is controlled, its output will substantially overwhelm the signal produced by ultrasound imaging system and obscure the image it produces. The synchronization signal employed to control the HIFU transducer is obtained without requiring modification of the ultrasound imaging system. Signals corresponding to scattered ultrasound imaging waves are collected using either the HIFU transducer or a dedicated receiver. A synchronization processor manipulates the scattered ultrasound imaging signals to achieve the synchronization signal, which is then used to control the HIFU bursts so as to substantially reduce or eliminate HIFU interference in the ultrasound image. The synchronization processor can alternatively be implemented using a computing device or an application-specific circuit

Design and characterization of a research electrohydraulic lithotripter patterned after the Dornier HM3

An electrohydraulic lithotripter has been designed that mimics the behavior of the Dornier HM3 extracorporeal shock wave lithotripter. The key mechanical and electrical properties of a clinical HM3 were measured and a design implemented to replicate these parameters. Three research lithotripters have been constructed on this design and are being used in a multi-institutional, multidisciplinary research program to determine the physical mechanisms of stone fragmentation and tissue damage in shock wave lithotripsy. The acoustic fields of the three research lithotripters and of two clinical Dornier HM3 lithotripters were measured with a PVDF membrane hydrophone. The peak positive pressure, peak negative pressure, pulse duration, and shock rise time of the focal waveforms were compared. Peak positive pressures varied from 25 MPa at a voltage setting of 12 kV to 40 MPa at 24 kV. The magnitude of the peak negative pressure varied from -7 to -12 MPa over the same voltage range. The spatial variations of the peak positive pressure and peak negative pressure were also compared. The focal region, as defined by the full width half maximum of the peak positive pressure, was 60 mm long in the axial direction and 10 mm wide in the lateral direction. The performance of the research lithotripters was found to be consistent at clinical firing rates (up to 3 Hz). The results indicated that pressure fields in the research lithotripters are equivalent to those generated by a clinical HM3 lithotripter

An Empirical Bayes Approach to Estimating Ordinal Treatment Effects

Ordinal variables — categorical variables with a defined order to the categories, but without equal spacing between them — are frequently used in social science applications. Although a good deal of research exists on the proper modeling of ordinal response variables, there is not a clear directive as to how to model ordinal treatment variables. The usual approaches found in the literature for using ordinal treatment variables are either to use fully unconstrained, though additive, ordinal group indicators or to use a numeric predictor constrained to be continuous. Generalized additive models are a useful exception to these assumptions (Beck and Jackman 1998). In contrast to the generalized additive modeling approach, we propose the use of a Bayesian shrinkage estimator to model ordinal treatment variables. The estimator we discuss in this paper allows the model to contain both individual group level indicators and a continuous predictor. In contrast to traditionally used shrinkage models that pull the data toward a common mean, we use a linear model as the basis. Thus, each individual effect can be arbitrary, but the model “shrinks” the estimates toward a linear ordinal framework according to the data. We demonstrate the estimator on two political science examples: the impact of voter identification requirements on turnout (Alvarez, Bailey, and Katz 2007), and the impact of the frequency of religious service attendance on the liberality of abortion attitudes (e.g., Singh and Leahy 1978, Tedrow and Mahoney 1979, Combs and Welch 1982)

The Effect of Voter Identification Laws on Turnout

Since the passage of the “Help America Vote Act” in 2002, nearly half of the states have adopted a variety of new identification requirements for voter registration and participation by the 2006 general election. There has been little analysis of whether these requirements reduce voter participation, especially among certain classes of voters. In this paper we document the effect of voter identification requirements on registered voters as they were imposed in states in the 2000 and 2004 presidential elections, and in the 2002 and 2006 midterm elections. Looking first at trends in the aggregate data, we find no evidence that voter identification requirements reduce participation. Using individual-level data from the Current Population Survey across these elections, however, we find that the strictest forms of voter identification requirements — combination requirements of presenting an identification card and positively matching one’s signature with a signature either on file or on the identification card, as well as requirements to show picture identification — have a negative impact on the participation of registered voters relative to the weakest requirement, stating one’s name. We also find evidence that the stricter voter identification requirements depress turnout to a greater extent for less educated and lower income populations, but no racial differences.Carnegie Corporation of New York; John S. and James L. Knight Foundatio

Erupting Dwarf Novae in the Large Magellanic Cloud

We report the first likely detections of erupting Dwarf Novae (DN) in an external galaxy: the Large Magellanic Cloud. Six candidates were isolated from approximately a million stars observed every second night over 11 nights with the CTIO 8K x 8K Mosaic2 CCD imager. Artificial dwarf nova and completeness tests suggest that we are seeing only the brightest of the LMC DN, probably SS Cygni-like CVs, but possibly SU UMa-type cataclysmics undergoing superoutbursts. We derive crude but useful limits on the LMC DN surface density, and on the number of DN in the LMC. Many thousands of cataclysmic variables in the Magellanic Clouds can be discovered and characterized with 8 meter class telescopes.Comment: Accepted for publication in AJ, 28 pages, 9 figures total, Figures 1 and 8 are supplied separately in jpeg forma

The Value of Student Right-to-Know Data in Assessing Community College Performance

Traditionally, community colleges were judged on their number of enrollments and their ability to provide postsecondary education to a wide variety of students. Recently, however, state and federal policymakers have become increasingly concerned with student outcomes, and some states have even begun to consider linking the funding of community colleges to their performance on student outcome measures. In 1990, Congress passed the Student Right-to- Know (SRK) and Campus Security Act. It requires that all colleges report graduation rates to the National Center for Education Statistics (NCES) in order for their students to receive federal financial aid. These Student Right-to-Know graduation rates are part of the Integrated Postsecondary Education Data System (IPEDS). The SRK rates are the only performance measures available for virtually every undergraduate institution in the nation, including community colleges, but critics assert that the rates understate the success of community colleges in several important ways