Matthew O’Donnell

High-frequency ultrasound array element using thermoelastic expansion in an elastomeric film

The thermoelastic effect was used to produce high-frequency, broadband ultrasound in water. A pulsed diode laser, followed by an erbium-doped fiber amplifier, was focused onto a light-absorbing film deposited on a glass substrate. Conversion efficiency was improved by over 20 dB using an elastomeric film instead of a more commonly used metallic one. Radiation pattern measurements show that considerable energy is radiated at +/−45° for frequencies beyond 50 MHz. These results show that the thermoelastic effect can be used to produce phased arrays for high-frequency ultrasound imaging.

Triplex ultrasound: elasticity imaging to age deep venous thrombosis.

Deep venous thrombosis (DVT), and its sequela, pulmonary embolism (PE), is the leading cause of preventable in-hospital mortality in the USA and other developed countries. After it is detected, acute clots must be differentiated from chronic DVT for appropriate treatment. However, there are no reliable thrombus staging methods presently available in clinical practice. In this study, we tested the hypothesis that blood clots can be detected and staged using a triplex ultrasound (US) test. Triplex US is based on a gold standard duplex US technique augmented by US-based reconstructive elasticity imaging. Fibrin-composed blood clots harden with development and organization. By imaging clot elasticity, it may be possible to both detect and differentiate clots and, therefore, provide an urgently needed noninvasive means of DVT staging.

Optoacoustic imaging using thin polymer étalon

Optical detection of ultrasound is a promising technique for high frequency imaging arrays. Detection resolution approaches the optical resolution, which can be on the order of the optical wavelength. We describe here an optical technique for ultrasound detection based on a thin (10μm) Fabry–Perot etalon optimized for high resolution imaging. The signal to noise ratio (SNR) approaches that of an ideal piezoelectric transducer over a 100MHz bandwidth. Array functionality is demonstrated by scanning a probe beam along a line. Thermoelastic excitation was applied to generate acoustic waves in a test phantom containing a single “pointlike” source. An image of the source was reconstructed using signals acquired from the etalon detector array.

Ultrasound detection using polymer microring optical resonator

Application of polymer waveguide microring resonators for high-frequency ultrasound detection is presented. The device consists of a microring optical resonator coupled to a straight optical waveguide which serves as input and output ports. Acoustic waves irradiating the ring waveguide induce strain modifying the waveguide cross section. As a consequence, the effective refractive index of optical waves propagating along the ring is modified. The sharp wavelength dependence of the high Q-factor resonator enhances the optical response to acoustic strain. High sensitivity is demonstrated experimentally in detecting broadband ultrasound pulses from a 10MHz transducer. Methods of extending the technique to form multi-element ultrasonic arrays for imaging applications are proposed.

Reconstructive Elasticity Imaging

Changes in soft tissue elasticity are usually related to some abnormal, pathological process. Because the Young’s modulus can differ by orders of magnitude between soft tissues,l there has been consistent interest in tissue elasticity. Unfortunately, no imaging modality, including ultrasound, nuclear magnetic resonance (MRI) and computed tomography (CT), can directly provide information about elasticity. Recently, several investigators2-6 have used internal motion induced by external forces to monitor tissue mechanical properties. Although mechanical properties are ultimately linked to patterns of internal deformation, deformational geometry can greatly affect the pattern as well. Consequently, to uniquely image tissue elasticity, the Young’s modulus must be reconstructed from estimates of internal displacement and strain.

Photolithographic micromolding of ceramics using plasma etched polyimide patterns

Features as fine as 4 μm with high aspect ratio were produced from ceria‐zirconia ceramic using a thick plasma‐etched polyimide layer as a micromold.

Statistical construction learning: Does a Zipfian problem space ensure robust language learning?

One of the key mysteries of language development is that each of us as learners has had different language experiences and yet somehow we have converged on broadly the same language system. From diverse, noisy samples, we end up with similar competence. How so? Some views hold that there are constraints in the learner’s estimation of how language works, as expectations of linguistic universals preprogrammed in some innate language acquisition device. Others hold that the constraints are in the dynamics of language itself – that language form, language meaning, and language usage come together to promote robust induction by means of statistical learning over limited samples. The research described here explores this question with regard English verbs,!their grammatical form, semantics, and patterns of usage.

P1E-1 Left Ventricular Phantom with Pulsatile Circulation for Ultrasound Strain Rate Imaging

Strain rate imaging has been proposed to quantitatively evaluate myocardial deformation and potentially quantify injury of ischemic heart disease (IHD) and remodeling of myocardial infarction (MI). However, because deformation of the cardiac wall is complex and three-dimensional, its hard to evaluate imaging algorithms (e.g., 2D/3D speckle tracking for strain rate estimation) without a well-controlled experimental system producing LV wall heart deformation patterns similar to those encountered clinically. Tissue-mimicking Polyvinyl Alcohol (PVA) cryogel LV phantoms of the left ventricle were constructed and connected to a pulsatile circulatory system for quantitative analysis of regional LV deformation using ultrasound and MR imaging. Two types were constructed: one mimicking a normal LV, and the other an otherwise normal LV but with a single hard inclusion representing a transmural infarct with higher stiffness. The hard inclusion exhibited an elastic modulus above 6 times greater than the surrounding heart wall. Both phantoms were deformed using the pulsatile pump at a stroke volume of 15ml, 20 beats per minute, and systole/diastole ratio 50:50. A specially designed commercial ultrasound scanner (iU22, Philips, Bothell, MA) was used at high frame rate. A strain estimation algorithm based on adaptive 2D speckle tracking was validated

Modest XPath and XQuery for corpora: Exploiting deep XML annotation

Abstract This paper outlines a modest approach to XPath and XQuery, tools allowing the navigation and exploitation of XML-encoded texts. The paper starts off from where Andrew Hardie’s paper “Modest XML for corpora: Not a standard, but a suggestion” (Hardie 2014) left the reader, namely wondering how one’s corpus can be usefully analyzed once its XML-encoding is finished, a question the paper did not address. Hardie argued persuasively that “there is a clear benefit to be had from a set of recommendations (not a standard) that outlines general best practices in the use of XML in corpora without going into any of the more technical aspects of XML or the full weight of TEI encoding” (Hardie 2014: 73). In a similar vein this paper argues that even a basic understanding of XPath and XQuery can bring great benefits to corpus linguists. To make this point, we present not only a modest introduction to basic structures underlying the XPath and XQuery syntax but demonstrate their analytical potential using Obama’s 2009 Inaugural Address as a test bed. The speech was encoded in XML, automatically PoS-tagged and manually annotated on additional layers that target two rhetorical figures, anaphora and isocola. We refer to this resource as the Inaugural Rhetorical Corpus (IRC). Further, we created a companion website hosting not only the Inaugural Rhetorical Corpus, but also the Inaugural Training Corpus) (a training corpus in the form of an abbreviated version of the IRC to allow manual checks of query results) as well as an extensive list of tried and tested queries for use with either corpus. All of the queries presented in this paper are at beginners to lower-intermediate levels of XPath/XQuery expertise. Nonetheless, they yield fruitful results: they show how Obama uses the inclusive pronouns we and our as a discursive strategy to advance his political strategy to re-focus American politics on economic and domestic matters. Further, they demonstrate how sentence length contributes to the build-up of climactic tension. Finally, they suggest that Obama’s signature rhetorical figure is the isocolon and that the overwhelming majority of isocola in the speech instantiate the crescens type, where the cola gradually increase in length over the sequence.

Linking learner corpus and experimental data in studying second language learners' knowledge of verb-argument constructions*

Abstract This paper combines data from learner corpora and psycholinguistic experiments in an attempt to find out what advanced learners of English (first language backgrounds German and Spanish) know about a range of common verbargument constructions (VACs), such as the ‘V about n’ construction (e.g. she thinks about chocolate a lot). Learners’ dominant verb-VAC associations are examined based on evidence retrieved from the German and Spanish subcomponents of ICLE and LINDSEI and collected in lexical production tasks in which participants complete VAC frames (e.g. ‘he ___ about the...’) with verbs that may fill the blank (e.g. talked, thought, wondered). The paper compares findings from the different data sets and highlights the value of linking corpus and experimental evidence in studying linguistic phenomena