Evidence Of Cavitation Research Articles

Ultrasonographic characteristics of splenic stromal sarcoma in 13 dogs.

The identification of a solitary splenic mass on abdominal ultrasound is a common occurrence; however, diagnosis based on imaging alone remains a challenge. Multiple studies have tried to identify key characteristics that denote a benign or malignant lesion before splenectomy. Differential diagnoses commonly include hemangiosarcoma, hematoma, extramedullary hematopoiesis, and lymphoid hyperplasia. While comprehensive, this list fails to consider the less frequent neoplasms such as splenic stromal sarcoma. This retrospective study aimed to evaluate 13 dogs diagnosed with canine splenic stromal sarcoma and determine common characteristics noted on abdominal ultrasound. Masses were solid, without evidence of cavitation, and arising from the mid-body of the spleen. While abdominal ultrasound does not provide a definitive diagnosis for splenic stromal sarcoma, it should be considered when identifying a solitary, solid, noncavitary splenic mass.

Eco-Friendly Blends of Recycled PET Copolymers with PLLA and Their Composites with Chopped Flax Fibres.

The structure and properties of blends of a novel polyethylene terephthalate copolymer (COPET) obtained by chemical recycling of commercial PET with high-molar-mass poly-L-lactide (PLLA) are investigated and compared to corresponding composites with chopped flax fibres. The focus is on the morphology at nano- and micro-scales, on the thermal characteristics and on the mechanical behaviour. The blends are immiscible, as evidenced by virtually unchanged glass transition temperatures of the blend components compared to the neat polymers (49 °C for COPET and 63 °C for PLLA by DSC). At low PLLA content, the blends display a sea-island morphology with sub-micron to micron droplet sizes. As the composition approaches 50/50, the morphology transitions to a coarser co-continuous elongated structure. The blends and composites show strongly improved stiffness compared to COPET above its glass transition temperature, e.g., from melt behaviour at 60 °C for COPET alone to almost 600 MPa for the 50/50 blend and 500 MPa for the 20% flax composite of the 80/20 COPET/PLLA blend. The flax fibres increase the crystallisation rate of PLLA in blends with dispersed PLLA morphology. The evidence of cavitation on the fracture surfaces of blends shows that despite the immiscibility of the components, the interfacial adhesion between the phases is excellent. This is attributed to the presence of aliphatic ester spacers in COPET. The tensile strength of the 80/20 blend is around 50 MPa with a Young's modulus of 2250 MPa. The corresponding 20% flax composite has similar tensile strength but a high Young's modulus equal to 6400 MPa, which results from the individual dispersion and strong adhesion of the flax fibres and leads close to the maximum possible reinforcement of the composite, as demonstrated by tensile tests and nano-indentation. The Ashby approach to eco-selection relying on the embodied energy (EE) further clarifies the eco-friendliness of the blends and their composites, which are even better positioned than PLLA in a stiffness versus EE chart.

Progress in the development of a contactless ultrasonic processing route for alloy grain refinement

A high frequency tuned electromagnetic (EM) induction coil can be used to induce ultrasonic pressure waves leading to gas cavitation in alloy melts. This is a useful ‘contactless’ approach compared to the usual immersed sonotrode technique. One then expects the same benefits obtained in the traditional ultrasonic treatment (UST) of melts, such as degassing, microstructure refinement and dispersion of particles. However, such an approach avoids melt contamination due to probe erosion prevalent in immersed sonotrodes and it has the potential to be used on higher temperature and reactive alloys. Induction stirring due to the Lorentz force produced by the coil is an added benefit, allowing for the treatment of large melt volumes, a current limitation of UST systems. At ultrasonic frequencies (> 20 kHz), due to the ‘skin effect’ electromagnetic forces vibrate just a thin volume by the surface of the metal facing the induction source. These vibrations are transmitted as acoustic pressure waves into the bulk and to achieve sufficient fluctuation amplitudes for cavitation, acoustic resonance is sought by carefully adjusting the generator frequency. This is akin to the tuning of a musical instrument, where the geometry and sound properties of the metal, crucible and surrounding structure play an important part. In terms of modelling, this is a multi-physics system, since fluid flow with heat transfer and phase change are coupled to electromagnetic and acoustic fields. The various models used and their coupling are explained in this paper, together with the various complications arising by the physics of cavitation. Experimental validation is obtained on a prototype rig featuring a conical induction coil inserted into the melting crucible containing the various alloys being examined. When resonance is reached, measurements demonstrate strong stirring, evidence of cavitation and finally grain refinement.

275. Delayed Diagnosis of Histoplasmosis in Pediatric Patients due to Atypical Clinical Presentations

BackgroundHistoplasmosis is a systemic mycosis with a wide range of clinical manifestations which represents a diagnostic challenge. It affects immunocompromised patients but also, previously healthy individuals that are exposed to a large inoculum of Histoplasma. The aim of our study was to describe the clinical presentation, epidemiologic features, laboratory/imaging findings and outcome of pediatric patients with histoplasmosis.Methodsa retrospective study including patients diagnosed as Histoplasmosis according to ICD-10 at a tertiary care center in Mexico City during 2009 to 2019. Clinical, epidemiological and laboratory/imaging data were gathered from each patient’s clinical file.Results5 patients with diagnosis of histoplasmosis were included; 2 patients were classified as proven with histopathologic confirmation, 2 patients as probable and 1 patient as possible according to the EORTC/MSG. The mean age of presentation was 7 years, 3/5 patients were male and 3/5 reported exposure to bats. Diagnosis was delayed by an average time of 6 months due to the variability of clinical presentations (progressive disseminated histoplasmosis, spinal histoplasmosis, cerebral histoplasmosis, intestinal histoplasmosis and mild acute pulmonary histoplasmosis). For the diagnosis, 1/5 had positive ELISA, 1/5 positive immunodiffusion (M band), 1/5 positive EIA in cerebrospinal fluid and 2/5 with histopathology findings that matched histoplasmosis. Pulmonary imaging with interstitial infiltrates in 4/5 and evidence of cavitation in one patient. Hemophagocytic syndrome was a complication in 1/5 and medullary syndrome was developed in the patient with spinal histoplasmosis which resolved with treatment. Liposomal amphotericin B was the treatment in 4/5, followed by itraconazole as the maintenance therapy.ConclusionThis study shows variable clinical presentations of Histoplasmosis which resulted in an important delay in diagnosis. This study highlights the importance of diagnostic suspicion in both healthy children and immunocompromised patients, always taking into account epidemiological risks such as exposure to bats.Disclosures All authors: No reported disclosures.

Laser-induced fluorescence measurements in a single-ring test rig: Evidence of cavitation and the effect of different operating conditions and lubricants in cavitation patterns and initiation

The laser-induced fluorescence technique is based on the excitation of molecules of a fluorescent material by a light source. The main advantage of this technique is that it has the potential to quantify the lubricant film thickness throughout the cycle. Similar to all the other optical techniques, it has this major advantage compared to the electrical techniques where the oil film can be measured only under the piston rings. In this work, experimental data from a simulating single-ring test rig are presented and further parametric analysis is given regarding cavitation in lubricants that was, at first, in the case of the single-ring test rig, evident in laser-induced fluorescence measurements. Different lubricants are used for the laser-induced fluorescence experiments and the different laser-induced fluorescence signals are analysed and interpreted compared to their physical and chemical properties and, furthermore, with the aid of imaging through a glass liner, a clearer picture is given regarding the cavitation shapes together with the respective laser-induced fluorescence measurements and cavitation initiation.

The Negative Clinical Impact of Diabetes on Tuberculosis: A Cross-Sectional Study in New Jersey.

ContextNumerous studies have investigated a link between tuberculosis (TB) and type 2 diabetes mellitus (DM) in high-incidence countries. There is a need to characterize the relationship of TB and DM in the United States.ObjectiveTo characterize the clinical and demographic differences in patients with TB with and without DM.DesignCross-sectional.SettingThis study was performed at an institutional center providing TB care for New Jersey.Patients or Other ParticipantsA total of 353 cases of TB were seen at the Lattimore Clinic between 2009 and 2014. After excluding those with HIV infection and those under 19 years of age, 73 cases of TB were reviewed.Intervention(s)No interventions performed.Main Outcome Measure(s)Sputum culture positivity, time to culture conversion, extent of disease on chest x-ray, and degree of cavitation on chest x-ray. Outcome measures were determined prior to data collection.ResultsExtent of disease on chest x-ray was higher for DM+ cases compared with DM− cases (P = 0.007). A total of 24% of DM+ cases had evidence of cavitation on chest x-ray compared with 5% of DM− cases (P = 0.03). DM+ cases were slightly more likely to have positive sputum cultures than were DM− cases (P = 0.07). The median time to sputum culture conversion was 27.5 days in the DM+ group vs 18.0 days in the DM− group (P = 0.26).ConclusionsExtent of disease on chest x-ray was significantly more severe in the DM+ group than in the DM− group.

Core-shell rubber nanoparticle reinforcement and processing of high toughness fast-curing epoxy composites

To simultaneously address the lower toughness and the build-up of internal heat for fast-curing epoxy matrices, the influence of nominal 100 nm and 300 nm core-shell rubber (CSR) particles on the properties and rheo-kinetics were studied. The fracture energy was enhanced by a factor of 14.5, up to 2572 ± 84 J m−2 with 14.5 wt% of the nominal 300 nm diameter CSR particles, with evidence of cavitation and plastic void growth of the rubber core combined with shear band yielding of the epoxy matrix. These toughening mechanisms were modelled with an approximately linear increase up to 10 wt% for both particle types. At higher concentrations, deviation between the measured and modelled data was observed due to insufficient epoxy to dissipate additional energy. The CSR particles were not filtered out or damaged during the manufacturing of composites and reduced the total heat of reaction with a linear correlation, demonstrating a multi-functionality of simultaneous toughening and reduction of the exothermic peak.

The embryogenesis of the equine femorotibial joint: The equine interzone.

Articular cartilage regeneration is the focus and goal of considerable research effort. Since articular chondrocytes descend from a distinct cohort of progenitor cells located in embryonic nascent joints (interzones), establishing the timing of equine interzone formation is an essential first step towards understanding equine joint and articular cartilage development. To establish the time frame during which the equine femorotibial interzone forms. Descriptive anatomical study. Equine embryos were harvested at 37 (E37), 40, 42, 45, 50 and 65 days' gestation. The femorotibial interzone was examined using high-resolution episcopic microscopy of E37, E42, E45, E50 and E65. Additional histology and collagen-II-immunohistochemistry were performed on E42. At E37, the femorotibial interzone is first visible as a uniform layer, while at E42 the interzone is fully formed and consists of 3 morphologically distinct layers. The first evidence of cavitation was seen at E45. At E50, the cruciate ligaments were well formed and by E65, joint formation appeared complete. The embryogenesis of the equine femorotibial joint is similar to the developmental timeline of stage-matched human and murine embryos. Further studies looking at interzone formation on a cellular and molecular level may further our understanding of the intricate developmental patterns and pathways of articular cartilage development.

Development of heartwood in response to water stress for radiata pine in Southern New South Wales, Australia

Heartwood development and other functional changes in stem conductance in response to water stress in radiata pine were investigated using two contrasting climatic areas (high-altitude sub-alpine vs. warm–dry inland) of the Hume region of New South Wales, Australia. The study included mature (34.5–36.5 years old) and young stands (10–11 years old) measured under normal climate and during an extreme drought. The effect of water stress on heartwood development was examined using sapwood percentage, sapwood saturation, development of dry sapwood and evidence of cavitation in sapwood. Trees at the warm–dry site developed heartwood at faster rates than on the high-altitude site. At breast height, the mature stands of the warm–dry site had 8–14 % less sapwood. Extensive cavitation towards the sapwood/heartwood boundary occurred in some of the mature and young stands on the warm–dry site. We postulated that in water-limiting environments, cavitation of the inner sapwood precedes heartwood formation and is an adaptation mechanism that regulates stem conductance capacity and thus water use in the tree. The drought of 2006 led to decreases in moisture associated with cavitation not previously reported for radiata pine and demonstrated the drought hardiness of the species. In the warm–dry site, breast-height sapwood saturation dropped to 58 and 82 % for suppressed and average-sized trees in a mature unthinned stand; and 75–78 % for two young stands. These saturation levels, however, only imply average values as some cells cavitated whilst others were fully saturated. Cavitation occurred in a localized fashion affecting small to large groups of cells.

Preliminary In Vivo Testing of a Novel Pump for Short-Term Extracorporeal Life Support

Blood pumps used for temporary circulatory support have limitations. We propose a novel device designed for short-term extracorporeal support that is intrinsically volume responsive, afterload insensitive, and incapable of cavitation or excessive hemolysis. After in vitro testing, we performed the initial in vivo implantations and assessments. The BioVAD prototype (MC3, Inc, Ann Arbor, MI) was implanted in 6 adult male sheep (60.2±2.8 kg) through the left ventricular apex and descending thoracic aorta. Arterial, left and right atrial, and pump inlet and outlet pressures and BioVAD flow were measured and recorded. The animals were volume loaded to assess volume responsiveness, and the inlet lines were abruptly clamped during maximum support to observe for cavitation. An acute heart failure model was created with rapid ventricular pacing, and the animals were supported for 4 hours. Peak flow was 3.19±0.56 L/min and increased to 3.71±0.53 L/min with 20 mm Hg vacuum-assisted drainage. Without manual changes in pump settings, pump flow increased 17.5% with volume loading. During acute venous line occlusion, there was no evidence of cavitation, and inlet suction was minimal. Hemodynamics were maintained for 4 hours during acute heart failure. The BioVAD provided adequate flow in an acute in vivo model. Its design may be superior for short-term extracorporeal support.

Early-age acoustic emission measurements in hydrating cement paste: Evidence for cavitation during solidification due to self-desiccation

In this study, the acoustic emission activity of cement pastes was investigated during the first day of hydration. Deaired, fresh cement pastes were cast in sealed sample holders designed to minimize friction and restraint. The majority of acoustic emission events occurred in lower water to cement ratio pastes, while cement pastes with higher water to cement ratios showed significantly less acoustic activity. These acoustic events occurred around the time of setting. A layer of water on the surface of the cement pastes substantially reduced acoustic emission activity at the time of setting. According to these experimental results, the acoustic emission measured around setting time was attributed to cavitation events occurring in the pores of the cement paste due to self-desiccation. This paper shows how acoustic emission might be used to indicate the time when the fluid–solid transition occurs in a cement paste, often referred to as time-zero. Knowledge of time-zero is fundamental for determining when mechanical properties develop and in calculations of residual stresses.

In Vitro Evaluation of a Micro-Doppler Catheter for Detection and Aspiration of Venous Air Emboli

Venous air embolism (VAE) is a potentially fatal complication of surgery when open veins at a surgical site are exposed to ambient air pressure which exceeds the pressure in the venous system. Common techniques of detecting VAE are precordial Doppler monitoring and transesophogeal echocardiography. Precordial Doppler monitoring has poor accuracy and transesophogeal echocardiography is expensive and user-intensive. In both methods, a separate catheter must be inserted into the vena cava so that an embolus may be aspirated if it is detected. We created a micro-Doppler assembly using two ceramic transducers fitted over a 5.8F multiorifice central venous catheter. This micro-Doppler catheter (MDC) was tested in vitro using a static tank and an artificial vena cava (AVC). The MDC was also tested for acoustic pressure and current leakage in the static tank and for heat generation and cavitation in the AVC. The MDC was able to detect bubbles more than 2 mm in diameter with 100% accuracy. A blinded observer was able to identify the onset of vapor lock in 10 of 10 trials. The same observer was able to terminate vapor lock in 10 of 10 trials. The acoustic pressures measured were <1.8 MPa. There was no increase in temperature in the AVC over 24 h and there was no evidence of cavitation in the AVC over 4 h. We have created a MDC that can detect air emboli and relieve vapor lock in a simulated vena cava and atrium. This catheter could be placed percutaneously in the vena cava. Based on the measurements of acoustic pressure, temperature in the AVC and lack of cavitation in the AVC, the device appears to be safe for use in humans. More studies are required to determine if the catheter could be used to detect and aspirate VAE during surgeries where VAE is likely, such as sitting craniotomy.

Observations of cavitation and boiling in a tissue-mimicking phantom due to high intensity focused ultrasound

Bubbles generated by acoustic cavitation or boiling are often observed during high intensity focused ultrasound (HIFU) medical treatments. In this work, high-speed video imaging, a 20-MHz focused acoustic transducer, and the driving voltage to our 2-MHz HIFU source are used to distinguish between cavitation and boiling in a tissue-mimicking gel phantom at peak focal intensities up to 30,000 W/cm2. Bubble dynamics are modeled using a reduced order model that accounts for evaporation and condensation, heat and gas transfer across the interface, and temperature changes in the surrounding liquid. The model includes vapor trapping, whereby the noncondensable gas slows diffusion of vapor to the interface, thereby limiting condensation. At the transducer focus, evidence of cavitation is observed in the first millisecond before disappearing. Boiling is observed several milliseconds later, after sufficient heating of the focal volume to 100&amp;lt;th&amp;gt;°C. The disappearance of cavitation can be explained in part by the observed motion of bubbles away from the focal region due to radiation-pressure forces and in part by the softening of bubble collapses by vapor trapping. Thus, at clinical HIFU amplitudes, bubble dynamics and their impact on image-feedback and/or therapy change dramatically in only milliseconds. [Work supported by NIH DK43881 and NSBRI SMS00402.]

Phase I and biomarker study of ABT869, a multiple receptor tyrosine kinase inhibitor, in patients with refractory solid malignancies

3519 Background: ABT869 is an orally administered, potent and specific inhibitor of all VEGF and PDGF family tyrosine kinases, including FLT-3, and c-kit receptors. Methods: A phase I study of ABT869 in patients with refractory solid malignancies was initiated to determine the maximum tolerable dose (MTD) of ABT869 given by continuous once-daily oral dosing; evaluate ABT869 pharmacokinetics; assess pharmacodynamic effects on plasma VEGF and circulating endothelial cells (CECs); evaluate tumor response, including an assessment of microcirculatory parameters DCE-MRI. Dose escalation was planned in dose cohorts of 3 patients each. Treatment periods (TP) were defined as 21 days and tumor assessments were performed using CT scans every 6 weeks. DCE-MRI was done at baseline, day 3 and 14 of the first cycle. Cohort expansion to 6 patients was planned if dose limiting toxicity (DLT) occurred in the first cycle of treatment, and MTD was defined as the dose at which ≥ 2/6 patients experienced DLT. Results: 21 evaluable patients (11 male, 10 female patients median age 58 range 29–76) were treated; 6 at 10mg per day, 12 at 0.25mg/kg/day and 3 at 0.3mg/kg/day. Cycle 1 DLTs included fatigue (grade(G) 3 DLT in 1 patient at 10mg), G3 foot rash, proteinuria and hypertension in 1 patient each at 0.25mg/kg/day (RPTD) and 2 patients with G3 hypertension, including G3 proteinuria in one of these patients, at 0.3mg/kg/day (MTD). Other common treatment-related adverse events at RPTD included asthenia, myalgia, mouth irritation, pneumothorax related to cavitating lung nodule in 2 patients. Pharmacokinetics of ABT869 demonstrated oral clearance of 2.8 ± 1.2 L/h, (mean ± SD, N=16) and half-life of 16.9 ± 5.0 h, with minimal drug accumulation at day 15. 2 PRs were seen in NSCLC patients and stable disease &gt; 4 TPs was observed in 12 patients, with CT scan evidence of cavitation of pulmonary disease and reduced DCE-MRI derived parameters. Mean peak plasma VEGF levels were increased significantly from baseline (p=0.031). CEPs and CECs were reduced in most patients by day 15. Conclusions: 0.25mg/kg/day is the RPTD of ABT869. Modulation of plasma VEGF, CECs and DCE MRI show drug activity consistent with antiangiogenic activity. Promising clinical activity is seen, particularly in NSCLC. No significant financial relationships to disclose.

Surfaces formed by subcritical crack growth in silicate glasses

The topography of surfaces formed in glass by subcritical crack growth was investigated by a method of mapping using atomic force microscopy. The objective of the study was to determine how well upper and lower surfaces matched after having been formed by a crack moving at slow velocity. The question arose, were features left in the fracture surfaces of silicate glasses that would indicate the formation of cavities during the fracture process? Studies were performed on silica glass and soda-lime-silicate glass. Fracture surfaces were formed either in water or in moist environments at velocities that ranged from 10 -2 m/s down to 10 -10 m/s. This procedure covered almost the entire range of velocities used for subcritical crack growth experiments in glass. Opposing fracture surfaces formed during our studies were found to over the entire range of velocities and for all environments studied. For silica glass, the surfaces were found to match to an accuracy of better than 0.3nm normal to the fracture surface and 5nm within the fracture surface. For soda-lime-silicate glass, surfaces were found to match to an accuracy of 0.5 nm to 0.8nm normal to the fracture surface and 5 nm within the fracture surface. Within these limits, no evidence for cavitation was found in either glass.

Crack growth of natural rubber using a modified double cantilever beam

The objective of this work is to investigate the crack growth properties of a natural rubber vulcanizate. This work utilizes a modified double cantilever beam (DCB) for measuring the crack propagation in natural rubber. Results of the crack growth in the plane strain dominated DCB are presented and compared to results from plane stress single edge notch test specimens. It is found that the crack growth rate in natural rubber under plane strain conditions is one hundred times faster than under plane stress. The failure surface of the DCB is examined for cavitation occurring within the rubber due to high hydrostatic pressure. No evidence of cavitation was found.

Detection of cavitation in rubber phase of rubber toughened poly (methyl methacrylate) using thermal contraction measurements

Measurements of mechanical properties and thermal expansion–contraction behaviour have been carried out on plain PMMA and on a transparent grade of rubber toughened (RT) PMMA. Uniaxial tensile tests at 23°C show that the stress–strain (σ–ε) curve for the RTPMMA begins to deviate from linearity at ε ≈ 1·5%, and reaches a load maximum at ε ≈ 6·7%. Visible whitening begins at ε ≈ 1·5%, and intensifies with increasing strain, but annealing for 3 h at 115°C restores the material to its initial transparent condition. Thermal expansion and contraction tests show that pre-straining to ε ≥ 2% produces a marked decrease in the coefficient of thermal expansion (CTE) of RTPMMA over the temperature range -20 to +50°C, where the rubber is above its Tg. Lower pre-strains have little effect on expansion–contraction behaviour. Annealing after pre-straining leaves the CTE unchanged at its reduced value if the pre-strain is above 3%. However, it causes an increase in CTE towards its initial value in specimens pre-strained to ε= 2%. This work provides clear evidence for cavitation in the rubber particles. It also shows that annealing after pre-straining does not completely restore the rubber's resistance to cavitation. Creep tests at 23°C on pre-strained specimens, both before and after annealing, demonstrate that rubber particle cavitation promotes a substantial acceleration in strain rates.

Role of the grain-boundary phase on the elevated-temperature strength, toughness, fatigue and creep resistance of silicon carbide sintered with Al, B and C

The high-temperature mechanical properties, specifically strength, fracture toughness, cyclic fatigue-crack growth and creep behavior, of an in situ toughened silicon carbide, with Al, B and C sintering additives (ABC-SiC), have been examined at temperatures from ambient to 1500°C with the objective of characterizing the role of the grain-boundary film/phase. It was found that the high strength, cyclic fatigue resistance and particularly the fracture toughness displayed by ABC-SiC at ambient temperatures was not severely compromised at elevated temperatures; indeed, the fatigue-crack growth properties up to 1300°C were essentially identical to those at 25°C, whereas resistance to creep deformation was superior to published results on silicon nitride ceramics. Mechanistically, the damage and shielding mechanisms governing cyclic fatigue-crack advance were essentially unchanged between ∼25°C and 1300°C, involving a mutual competition between intergranular cracking ahead of the crack tip and interlocking grain bridging in the crack wake. Moreover, creep deformation was not apparent below ∼1400°C, and involved grain-boundary sliding accommodated by diffusion along the interfaces between the grain-boundary film and SiC grains, with little evidence of cavitation. Such unusually good high-temperature properties in ABC-SiC are attributed to crystallization of the grain-boundary amorphous phase, which can occur either in situ, due to the prolonged thermal exposure associated with high-temperature fatigue and creep tests, or by prior heat treatment. Moreover, the presence of the crystallized grain-boundary phase did not degrade subsequent ambient-temperature mechanical properties; in fact, the strength, toughness and fatigue properties at 25°C were increased slightly.

Comments on the mechanism of microbial cell disruption in high-pressure and high-speed devices

The dominant mechanism for microbial cell disruption in a high-pressure homogenizer and a high-speed homogenizer used in this study has been identified. It was found that the cavity collapse and the pressure pulse resulting from such a collapse have a significant influence on the rates of cell disruption. The similarities among the operating conditions for the decomposition of the aqueous KI solution to liberate iodine, the reaction occurring only under cavitating conditions, and that required for the substantial disruption of microbial cells have been pointed out. The liberation of iodine by the aqueous KI decomposition is treated as evidence of cavitation, and hence microbial cell disruption occurring at an identical discharge pressure confirms the mechanism of cell disruption as cavitation, in the high-pressure homogenizer valve. In the case of the high-speed homogenizer, shear and cavitation both play a significant role in cell disruption.

Physics of ultrasonic surgery using tissue fragmentation

The ultrasonic surgical aspirator employs a vibrating metal tip to fragment tissue and then aspirates the debris through the hollow center of the tip. The mechanism of interaction has been stated to be poorly understood, most likely related to cavitation, possibly acting in concert with other mechanical actions. The role of stroke, suction, frequency, tissue type, and tip area have been examined with regard to tissue fragmentation rate. Suction is shown to make a significant contribution to the interaction. Photographic and acoustic data from experiments in water and on a range of fresh pig tissues are used to investigate the fragmentation effect. A model for the primary mechanism for tissue fragmentation is presented. This involves the horn-tip impact and other mechanical forces, operating in combination with hydrodynamic forces applied to the tissue on the forward stroke in each cycle. No evidence of cavitation in tissue was observed.