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Cavitation in soft matter
Cavitation is the sudden, unstable expansion of a void or bubble within a liquid or solid subjected to a negative hydrostatic stress. Cavitation rheology is a field emerging from the development of a suite of materials characterization, damage quantification, and therapeutic techniques that exploit the physical principles of cavitation. Cavitation rheology is inherently complex and broad in scope with wide-ranging applications in the biology, chemistry, materials, and mechanics communities. This perspective aims to drive collaboration among these communities and guide discussion by defining a common core of high-priority goals while highlighting emerging opportunities in the field of cavitation rheology. A brief overview of the mechanics and dynamics of cavitation in soft matter is presented. This overview is followed by a discussion of the overarching goals of cavitation rheology and an overview of common experimental techniques. The larger unmet needs and challenges of cavitation in soft matter are then presented alongside specific opportunities for researchers from different disciplines to contribute to the field
An International Urogynecological Association (IUGA)/International Continence Society (ICS) joint report on the terminology for the conservative and nonpharmacological management of female pelvic floor dysfunction
There has been an increasing need for the terminology on the conservative management of female pelvic floor dysfunction to be collated in a clinically based consensus report.This Report combines the input of members and elected nominees of the Standardization and Terminology Committees of two International Organizations, the International Urogynecological Association (IUGA) and the International Continence Society (ICS), assisted at intervals by many external referees. An extensive process of nine rounds of internal and external review was developed to exhaustively examine each definition, with decision-making by collective opinion (consensus). Before opening up for comments on the webpages of ICS and IUGA, five experts from physiotherapy, neurology, urology, urogynecology, and nursing were invited to comment on the paper.A Terminology Report on the conservative management of female pelvic floor dysfunction, encompassing over 200 separate definitions, has been developed. It is clinically based, with the most common symptoms, signs, assessments, diagnoses, and treatments defined. Clarity and ease of use have been key aims to make it interpretable by practitioners and trainees in all the different specialty groups involved in female pelvic floor dysfunction. Ongoing review is not only anticipated, but will be required to keep the document updated and as widely acceptable as possible.A consensus-based terminology report for the conservative management of female pelvic floor dysfunction has been produced, aimed at being a significant aid to clinical practice and a stimulus for research
Single-breath-hold photoacoustic computed tomography of the breast
We have developed a single-breath-hold photoacoustic computed tomography (SBH-PACT) system to reveal detailed angiographic structures in human breasts. SBH-PACT features a deep penetration depth (4 cm in vivo) with high spatial and temporal resolutions (255 µm in-plane resolution and a 10 Hz 2D frame rate). By scanning the entire breast within a single breath hold (~15 s), a volumetric image can be acquired and subsequently reconstructed utilizing 3D back-projection with negligible breathing-induced motion artifacts. SBH-PACT clearly reveals tumors by observing higher blood vessel densities associated with tumors at high spatial resolution, showing early promise for high sensitivity in radiographically dense breasts. In addition to blood vessel imaging, the high imaging speed enables dynamic studies, such as photoacoustic elastography, which identifies tumors by showing less compliance. We imaged breast cancer patients with breast sizes ranging from B cup to DD cup, and skin pigmentations ranging from light to dark. SBH-PACT identified all the tumors without resorting to ionizing radiation or exogenous contrast, posing no health risks
Photoacoustic microscopy of cerebral blood-oxygenation dynamics in mice
In this work, we exploit the high depth and temporal resolutions of PAM to noninvasively image the blood-oxygenation dynamics of multiple cortex vessels in the mouse brain simultaneously in response to controlled hypoxic and hyperoxic challenges. The dark-field photoacoustic microscopy (PAM) technique was enhanced to image the cortex vasculature of the mouse brain in vivo using endogenous hemoglobin contrast with one second temporal resolution. The maximum values of about 20% with standard deviation ± 1.2% were found to vary significantly among the cortex vessels studied. The hypoxic response time to rise from 10 % to 90 % of maximum was 63 ± 6 sec. The reverse response time for this event was 16 ± 2 sec
Recursive Least Squares Filtering Algorithms for On-Line Viscoelastic Characterization of Biosamples
The mechanical characterization of biological samples is a fundamental issue in biology
and related fields, such as tissue and cell mechanics, regenerative medicine and diagnosis of diseases.
In this paper, a novel approach for the identification of the stiffness and damping coefficients
of biosamples is introduced. According to the proposed method, a MEMS-based microgripper
in operational condition is used as a measurement tool. The mechanical model describing the
dynamics of the gripper-sample system considers the pseudo-rigid body model for the microgripper,
and the Kelvin–Voigt constitutive law of viscoelasticity for the sample. Then, two algorithms based
on recursive least square (RLS) methods are implemented for the estimation of the mechanical
coefficients, that are the forgetting factor based RLS and the normalised gradient based RLS
algorithms. Numerical simulations are performed to verify the effectiveness of the proposed approach.
Results confirm the feasibility of the method that enables the ability to perform simultaneously two
tasks: sample manipulation and parameters identification
Breast Cancer: Modelling and Detection
This paper reviews a number of the mathematical models used in cancer modelling and then chooses a specific cancer, breast carcinoma, to illustrate how the modelling can be used in aiding detection. We then discuss mathematical models that underpin mammographic image analysis, which complements models of tumour growth and facilitates diagnosis and treatment of cancer. Mammographic images are notoriously difficult to interpret, and we give an overview of the primary image enhancement technologies that have been introduced, before focusing on a more detailed description of some of our own recent work on the use of physics-based modelling in mammography. This theoretical approach to image analysis yields a wealth of information that could be incorporated into the mathematical models, and we conclude by describing how current mathematical models might be enhanced by use of this information, and how these models in turn will help to meet some of the major challenges in cancer detection
Wall influence on dynamics of a microbubble
The nonlinear dynamic behaviour of microscopic bubbles near a wall is
investigated. The Keller-Miksis-Parlitz equation is adopted, but modified to
account for the presence of the wall. This base model describes the time
evolution of the bubble surface, which is assumed to remain spherical, and
accounts for the effect of acoustic radiation losses owing to liquid
compressibility in the momentum conservation. Two situations are considered:
the base case of an isolated bubble in an unbounded medium; and a bubble near a
solid wall. In the latter case, the wall influence is modeled by including a
symmetrically oscillating image bubble. The bubble dynamics is traced using a
numerical solution of the model equation. Subsequently, Floquet theory is used
to accurately detect the bifurcation point where bubble oscillations stop
following the driving ultrasound frequency and undergo period-changing
bifurcations. Of particular interest is the detection of the subcritical period
tripling and quadrupling transition. The parametric bifurcation maps are
obtained as functions of non-dimensional parameters representing the bubble
radius, the frequency and pressure amplitude of the driving ultrasound field
and the distance from the wall. It is shown that the presence of the wall
generally stabilises the bubble dynamics, so that much larger values of the
pressure amplitude are needed to generate nonlinear responses.Comment: 25 pages, 14 figure
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