Search

This study explores the rigidity of Pickering-stabilised microbubbles subjected to low-amplitude ultrasound. Such microbubbles might be suitable ultrasound contrast agents. Using an adapted Rayleigh–Plesset equation, we modelled the dynamics of microbubbles with a 7.6-N m−1 shell stiffness under 1-MHz, 0.2-MPa sonication. Such dynamics were observed experimentally, too, using high-speed photography. The maximum expansions were agreeing with those predicted for Pickering-stabilised microbubbles. Subjecting microbubbles to multiple time-delayed pulses yielded the same result. We conclude that Pickering-stabilised microbubbles remain very stable at low acoustic amplitudes.

Magnesium (Mg) alloy has attracted significant attention as a bioresorbable scaffold for use as a next-generation stent because of its mechanical properties and biocompatibility. However, Mg alloy quickly degrades in the physiological environment. In this study, we investigated whether applying a parylene C coating can improve the corrosion resistance of a Mg alloy stent, which is made of ‘Original ZM10’, free of aluminum and rare earth elements. The coating exhibited a smooth surface with no large cracks, even after balloon expansion of the stent, and improved the corrosion resistance of the stent in cell culture medium. In particular, the parylene C coating of a hydrofluoric acid-treated Mg alloy stent led to excellent corrosion resistance. In addition, the parylene C coating did not affect a polymer layer consisting of poly(ε-caprolactone) and poly(D,L-lactic acid) applied as an additional coating for the drug release to suppress restenosis. Parylene C is a promising surface coating for bioresorbable Mg alloy stents for clinical applications.

Prophylactic doses of droperidol are effective in preventing postoperative nausea and vomiting (PONV). However, due to concerns of QT interval prolongation and ventricular arrhythmias, the safety of droperidol for PONV prophylaxis has been debated. A 70-year-old woman was scheduled for total knee arthroplasty. She had a history of aortic valve replacement. Oral aprindine (40 mg/day) was prescribed. Preoperative electrocardiogram showed mild QT interval prolongation (QTc = 475 ms). Anesthesia was induced using propofol, remifentanil, and rocuronium, and maintained using desflurane, remifentanil, and a bolus dose of rocuronium. The surgery was uneventful. At the time of skin closure, droperidol (1.25 mg) was administered intravenously for PONV prophylaxis. Twenty-three minutes after administration of droperidol, a sudden onset of premature cardiac contraction was observed, which progressed directly to ventricular tachycardia and atrioventricular block. Arrhythmia due to droperidol-induced QT interval prolongation was strongly suspected. Intravenous magnesium sulfate (2 g) and atropine (0.5 mg) were administered immediately. The ventricular tachycardia resolved quickly after the magnesium injection. Following the resolution of the arrhythmia, the patient was extubated. The patient experienced ventricular tachycardia after a prophylactic dose of droperidol that resulted from QT interval prolongation due to the preoperative medication. It may be prudent to avoid even low-dose droperidol in the background of already present QT prolongation, especially when multiple putative QT-prolonging drugs are used.

Mechanisms of BBB opening were investigated using a capillary model created by a three-dimensional cell culture technique. The model was made using human umbilical vein endothelial cells (HUVECs) suspended in collagen gel. Incubation with endothelial growth factor for one week resulted in the creation of capillary lumens, and a suspension of microbubbles supplemented with FITC-dextran, SYTOX Blue, and Calcein-AM was introduced inside the lumens. Bubble-cell interaction under exposure to short pulsed ultrasound of 1.0 MHz in center frequency and 0.4 MPa in peak negative pressure was captured using a high-speed camera, and lumen and endothelial cell damage was visualized using fluorescence microscopy. High-speed observation showed that non-uniform contraction of a bubble caused significant local deformation of the lumen beside the bubble, and strong extravasation from the lumen (FITC-dextran) and significant membrane damage of the endothelial cells (SYTOX Blue) were confirmed at this location. Lethal damage was also observed frequently (Calcein). On the other hand, cells on the opposite side of the lumen received stretching force during bubble expansion, and smaller extravasation and cell damage maintained the integrity of endothelial cells. These suggested the presence of different mechanisms of BBB opening.

Background Carbon dioxide embolism is a life-threatening complication of laparoscopic hepatectomy. Case presentation A 59-year-old man was admitted for laparoscopic hepatectomy. Approximately 5 h after commencing the operation, we observed a gradual decline in the SpO2 from 100 to 94%, reduction in the ETCO2 from 44 to 19 mmHg, reduction in the systolic blood pressure from 100 to 82 mmHg, and elevation of the heart rate from 82 to 120 beats/min. Intraoperatively, the image displayed on the laparoscopic monitor revealed a small tear in the vein. The inspired O2 fraction was raised to 1.0, intravenous phenylephrine (0.1 mg bolus) was administered, and the respiratory rate was increased. After the patient was stabilized, the injured vein was cut and sealed. After the embolic event, the entire operation was completed without complications. Conclusions Careful observation of the laparoscopic monitor is important, particularly during establishment of pneumoperitoneum in patients undergoing laparoscopic hepatectomy.

Background Decreased perfusion in the lower extremities is one of the several adverse effects of placing patients in a lithotomy or Trendelenburg position during surgery. This study aimed to evaluate the effects of patient positioning in lower limb perfusion patients undergoing robotic-assisted laparoscopic radical prostatectomy (RARP) using near-infrared spectroscopy (NIRS). Methods This observation study comprised 30 consenting males with American Society of Anaesthesiologists physical status classes I and II (age range, ≥20 to

Hydrophobic particles inherently resist being suspended. Hydrophobic particles might be regarded as tiny solid particles surrounded by a thin gaseous shell. It has been hypothesised that hydrophobic particles act as cavitation nuclei. This cavitation behaviour would explain the translation speeds observed when hydrophobic polystyrene microspheres were driven through a liquid medium by means of ultrasound. These translation speeds corresponded to those observed with gas microbubbles of similar sizes. If hydrophobic particles do have a thin gaseous layer surrounding the solid cores, a sound field of sufficient pressure amplitude might force the gas layer to form and inertial cavity and subsequently fragment during the collapse phase. In this study, we investigated whether hydrophobic particles can be forced to suspend by using ultrasound. Hydrophobic particles of the materials C65 and ZnO can be forced to be suspended in water using ultrasound. The high-speed observations confirm that hydrophobic particles can act as cavitation nuclei. The lack of cavitation after the first pulse indicates that the gas layer surrounding the hydrophobic particle dissolves after inertial cavitation., Comment: 6 pages, 3 figures (7 frames), Submitted to the 40th Symposium on UltraSonic Electronics (USE2019)

An antibubble is a gas bubble with a liquid droplet inside. Antibubbles have a potential role in ultrasonic imaging, ultrasound-guided drug delivery, and hydrocarbon leakage detection. The liquid core droplets inside antibubbles can be stabilised with a process called Pickering stability. Other systems proposed include spoke crystals to suspend the droplet or endoskeletal structures. In this study, the oscillatory response of microscopic endoskeletal antibubbles to ultrasound has been investigated, primarily to determine whether the presence of an endoskeleton attenuates the oscillation amplitude of the antibubble. Three emulsions containing (anti)bubbles were prepared for evaluation. Each emulsion was pipetted into the observation chamber of a high-speed microscopic observation system. A high-speed camera, operating at 10 million frames per second, was couples to the microscope. During camera recording, the materials were subjected to ultrasound pulses from a laboratory-assembled single-element transducer. The presence of an endoskeleton with droplets hampers the oscillation of antibubbles as compared to identical bubbles without endoskeleton and droplet content., Comment: 6 papers, 4 figures, submitted to the 40th Symposium on UltraSonic Electronics (USE2019)

International audience; In this study, we investigated if hydrophobic particles of the materials carbon black and zinc oxide act as cavitation nuclei, using high-speed photography during 1-MHz, low-amplitude sonication. Carbon black particles were observed to lose their gaseous shells and become acoustically inactive, whilst zinc oxide particles were observed to generate bubbles without becoming acoustically inactive. Zinc oxide might be a suitable candidate for an ultrasound contrast agent. Carbon black might be a suitable candidate for ultrasound-guided drug delivery.

International audience; Antibubbles have been under investigation as potential vehicles in ultrasound-guided drug delivery. It is assumed that antibubbles can expand unhampered, but cannot contract beyond the size of their inner core. In this study, this hypothesis was tested on endoskeletal antibubbles and reference bubbles. These were subjected to 3-cycle pulses of 1-MHz ultrasound, whilst being recorded with a high-speed camera operating at 10 million frames per second. At low acoustic amplitudes (200 kPa), antibubbles and bubbles oscillated symmetrically. At high acoustic amplitudes (1.00 MPa), antibubbles and bubbles oscillated asymmetrically, but antibubbles significantly more so than bubbles. Furthermore, fragmentation and core release were observed at these amplitudes. This finding may have implications for ultrasound-guided drug delivery using antibubbles.

Recently, the demand for a bio-absorbable coronary stent to promote recovery after an operation has increased. An option for such a stent is one made of a magnesium alloy, which has biodegradable properties. However, magnesium alloys have lower rigidity and lower ductility than other metals; as such, an appropriate stent structure is required to ensure radial rigidity. In this study, design parameters for an AZ31 magnesium alloy stent with sufficient radial rigidity were investigated. The necessary radial rigidity was determined by comparison tests against commercially available stents. The design parameters of the cell struts were selected and the optimum values to achieve high radial rigidity were investigated by means of elastic–plastic finite element analysis. Finally, a trial model stent based on the optimized design parameters was produced. It was confirmed that the model had sufficient radial rigidity, with no fracturing evident during crimping and expansion processes.

Cracking and delamination behavior of small rounded-rectangular gold thin films called “strips” with a thickness less than one micrometer was observed under cyclic and stepwisely-increased trapezoidal tensions. Three strips in different directions were deposited on a polycarbonate plate specimen which was subjected to tensile loading. Straight slit and Vickers indentation were introduced as initial defects on each strip and cracking and delamination which were initiated around the defects were observed. In strips with slit, delamination was observed when introducing the slit. It was suggested that the delamination was caused by the residual stress accumulated during deposition. The growth of delamination was also observed during cyclic tension. In strips with indentation, complex cracking and delamination behavior was observed depending on the strip direction, which seemed to be attributed to the interactive effect of residual stress by deposition and external mechanical loading.

BACKGROUND Subcritical water treatment is considered an environment-friendly method to liquefy biomass to prepare valuable chemicals. Several researchers have studied the solid obtained after autohydrolysis treatment for use as reinforcement in biocomposities and was the base pulp and paper technologies. The novelty of this present research is the use of solid in the manufacture of starch foams. RESULTS Subcritical water was used to extract hemicellulosic carbohydrate from walnut shells at temperatures from 160 to 260 °C for 15 min and at 200 °C for various treatment times. The maximum yield was obtained at 200 °C for 15 min. The residue of the walnut shells obtained at the maximum carbohydrates extraction yield was used to prepare a biodegradable foam by compounding with corn starch using a technique similar to compression molding. It was found that replacing 20% of the corn starch by the residue had no deleterious effects on the density and morphology, as indicated by scanning electron microscopy. The prepared foams had a dense outer skin and a less dense interior with large, mostly open cells. The flexural strains were similar to that of foamed polystyrene and the flexural modulus and flexural stresses were larger. CONCLUSION It was considered that the prepared biodegradable foam was a promising material to take the place of plastic products in the future. © 2014 Society of Chemical Industry

Minor salivary gland sialolithiasis occurs in ~1 % of all sialolithiasis cases. We report a case of sialolithiasis considered to have occurred in the minor salivary gland in two areas of the upper lip, with special emphasis on the findings from image examinations. A 33-year-old male complained of a painless mass on the left upper lip. At the first examination, there was a nodular, hard swelling that involved the left cuspid area of the upper lip. Although a panoramic radiograph revealed no abnormality, an intraoral radiograph showed a small radiopaque body with a laminar pattern. Computed tomography images indicated that a calcified body was present in two areas of the upper lip. On magnetic resonance imaging, the lesion was observed as a lower-signal area than the surrounding soft tissue. The mass had a high signal in the central area in the T2 and short T1 inversion recovery images. The sonogram showed a hypoechoic mass with an echogenic structure in the central area. An excisional biopsy of the left upper lip was performed under local anesthesia. A well-demarcated mass with a calcified body was enucleated. The histopathologic diagnosis was sialoadenitis with sialolithiasis. Most cases of minor salivary gland sialolithiasis are solitary, with multiple sialolithiasis being extremely rare. Sonograms are useful in the diagnosis of minor salivary gland sialolithiasis. Careful imaging examination is necessary to identify multiple lesions and select appropriate treatments.

The magnesium alloys, that have high specific strength, are often applied to the industrial products. However, the magnesium alloys exhibit low ductility at the room temperature on account of its hexagonal close-packed structure. It is difficult to give large deformation to the magnesium alloys at room temperature. Therefore, the plastic forming of a magnesium alloy sheet needs the process at warm temperature. In the present work, the procedure of thermal-mechanical coupled analyses are employed. The numerical simulations of warm deep drawings have been performed in order to evaluate the dependence of the temperature on the plastic forming of a magnesium alloy AZ31 sheet. The mechanical properties of the magnesium alloy AZ31 shall be described as the functions depending on temperature. The shapes of punches and die holes are rectangle whose aspect ratios are 1.5 or 2.0. The corners of punches and dies are heated locally at 473K. The influence of local heating on the formability have been investigated. The relation between the blank size and the formability has been also estimated. As the results of numerical simulations, it was shown that the formability of deep drawing was improved by local heating to the punch and the die. When the blanks of various sizes were tried, the distributions of the plastic strain rate around the die corner were changed. Therefore, the deviation of the plastic flow and the temperature distribution arose in a sheet. Consequently, it is necessary to optimize the blank sizes according to the shape of die holes in addition to the forming temperature.

New rotary to linear conversion mechanism named "reverse-type differential rotary to linear conversion mechanism (RDRLCM)" was invented for simultaneous achievement of large load capacity and precise displacement control, for compression test devices and press forming machines. The new mechanism was developed and incorporated as loading systems into an original biaxial compression test device, and thus, its fundamental performance was investigated. The results revealed that the loading system by the new rotary to linear conversion mechanism were able to generate compression force of about three times larger than that by a conventional feed-screw mechanism for the same input torque. In addition, the generated compressive force was maintained while the compressive motion was interrupted. These facts confirm the advantage to use RDRLCM for compression test devices as well as for press forming machines.

This paper reports the evaluation method of the waterproofing system for underground structure applied on earth retaining walls prior to concrete casting. We examined two tests, the first test is water leak test by using semi-full sized specimen with actual components, and the second test is water leak test by using small sized specimen with the weakness points of this waterproofing system. As a result of the first test, separators and damaged parts are the weakness points of watertightness of this waterproofing system. For the second test, there is deference of watertightness of the specimen between vertical casting concrete and horizontal casting. When the concrete is casted vertically, there will be made air space under separators or rough composition of concrete near waterproofing layer and the water from outside will infiltrate easily if it penetrate through waterproofing layer. So it is necessary for the evaluation method of this waterproofing system to make specimen made of vertical casting concrete.

Asymmetric conventional metal spinning was performed in this study to break through the limitation of ordinary axisymmetric spinning. A synchronous spinning machine was developed for this purpose; in this case, the mandrel motion, mandrel feed, and roller feed were synchronized by pulse control. Trial spinning experiments were carried out on a 1-mm-thick aluminum sheet to obtain an asymmetric truncated-elliptical-cone-shaped product. The roller path was traced using a control software by taking into account the errors caused by the step pulse control. Asymmetric sheet metal forming was successfully carried out by using the developed synchronous spinning method. The characteristics of asymmetric spinning were discussed by comparing the shape of the product, strain distributions, and force components with those obtained in the case of axisymmetric spinning.