Mechanical Action Research Articles

Numerical study of the mechanical behavior of the hip joint under therapeutic acoustic impact

Degenerative diseases are one of the main causes of disability in the middle-aged and older population. One of the most common diseases is osteoporosis and osteonecrosis of the femoral head. For the prevention and treatment of osteoporosis, osteopenia, and osteonecrosis, external mechanical stimulation based on ultrasound and shock wave exposure is used, based on local ultrasonic or shock wave exposure in the area of pathology. The effect of external mechanical action is based on mechanobiological principles, the essence of which is that a certain level of pressure (mechanical stress) and deformation leads to the growth and differentiation of various types of biological tissue. To obtain a therapeutic effect, it is necessary to correctly choose the parameters of exposure and the place of its application. Usually, these problems are solved empirically. In this work, the possibility of creating conditions for bone tissue regeneration under external acoustic impact on a healthy hip joint and a joint affected by osteonecrosis was studied numerically. The study was carried out using the method of mobile cellular automata. The results obtained showed the effectiveness of the use of medium- and high-intensity ultrasound exposure for the prevention of osteopenia and osteoporosis. When exposed to ultrasound on a joint with osteonecrosis of the head, the creation of conditions for osteogenesis and chondrogenesis in the affected area is observed only with high-intensity loading. Thus, the hypothesis that low-intensity ultrasound therapy is effective only in combination with other methods of treatment was con-firmed. It was found that shock-wave action of low intensity promotes the division of biological cells and their transfer, thereby creating conditions for the regeneration of bone tissues. This conclusion is consistent with the results of most experimental studies.

Improving Handling Systems of Tomato (Solanum lycopersicum) in Cameroon

In Cameroon, tomato (Solanum lycopersicum) is among the most important fruits with a consumption of about 35%. A 5-months study was conducted in two tomato production basins, namely Tsinfou and Litieu. This study aims to reduce postharvest losses of tomato for contribute to increase income and standard of living of producers in the Menoua division. The postharvest technics adopted by producers, transporters and traders were identified through investigations and direct observations. The rate loss of tomato and its deterioration over a certain period of time were evaluated. Also, the type, nature and causes of these postharvest losses were determined. The results from this study show that, inappropriate post-harvest technics are practiced in all links of the supply chain. The average rate loss during harvest, transport, conservation is 7.50%, 6.50% and 35.50% respectively. They are caused by mechanical, biological and microbial actions, environmental and socio-economic factors. These losses reduce actor's incomes and the availability of tomatoes on the market, hence the inaccessibility for poor citizens. Avoiding overloading and mixed transport of tomato crates with other products and using planks in lorry to overlap crates to minimize compression are two technics implemented by this study for reduce tomatoes postharvest losses. Establishment of affordable processing and conservation units, qualified workforce and maintaining a good state of roads should be adopted.

Integrated training sessions by a neuropsychologist and a speech therapist in the rehabilitation of persons in chronic critical condition by the example of FRCC ICMR

BACKGROUND: The study relevance is associated with the significant complexity of the treatment of patients with chronic impairment of consciousness. A successful treatment of chronic impairment of consciousness is formed from a comprehensive medical and multidisciplinary rehabilitation efforts aimed at restoring the consciousness, including a combination of various pharmacological and non-pharmacological methods. Modern rehabilitation techniques, with a competent approach to their development and application, not only are characterized by a significant potential in the context of improving the quality of life, but are also capable of providing a significant progress in alleviating the severity of the disease. At the same time, there are still no reliable methods in this area, which is a significant medical and social problem.
 AIM: Approbation and evaluation of the effectiveness of integrative sessions by a neuropsychologist and a speech therapist in the rehabilitation of persons in chronic critical condition, by the example of the Federal Research and Clinical Center of Intensive Care Medicine and Rehabilitology (FRCC ICMR).
 MATERIALS AND METHODS: 40 patients with diagnosed chronic impairment of consciousness were examined 20 patients in the main group and 20 patients in the control group. The rehabilitation work was carried out with the main group patients for 12 months, based on a developed system of integrated sessions of a neuropsychologist and a speech therapist. The evaluation of the rehabilitation work effectiveness was carried out at the time points of 6 and 12 months by monitoring the dynamics of improvement at the level of consciousness according to the CRS-R scale.
 RESULTS: We describe in detail the methodology and practical experience of integrated sessions of a neuropsychologist and a speech therapist in the rehabilitation of persons in chronic critical condition provided at the FRCC ICMR. A stable improvement in the level of consciousness, according to the CRS-R scale, was shown in patients with chronic impairment of consciousness, who underwent the integrated sessions of a neuropsychologist and a speech therapist.
 CONCLUSIONS: We have proven the effectiveness of an integrative approach to the rehabilitation of patients with chronically impaired consciousness, based on combined sessions of a neuropsychologist and a speech therapist. It has been confirmed that the simultaneous use of complex neuropsychological and speech therapy effects (exercises given by a neuropsychologist with a focus on the tactile gnosis in combination with the methods of active speech therapy mechanical action, known as an activating speech therapy massage) can ensure the progress in the rehabilitation of patients with chronic impairment of consciousness in comparison with the same techniques applied in a sequential manner.

IMPROVEMENT OF VIBRATING EQUIPMENT FOR CLEANING CONTAMINATION OF PARTS AND UNITS IN AUTO REPAIR INDUSTRY

The paper considers the task of increasing the durability and safe operation of the device by eliminating the resonant beat of the vibration equipment during the starting torque. During the operation of automobiles, contaminants form on the surface of individual parts and assemblies, their high-quality cleaning is achieved by chemical and mechanical action on these contaminants. The use of more active chemicals is more costly and pollutes the environment. Therefore, it is desirable to achieve an increase in the efficiency of washing and cleaning by increasing the mechanical effect on pollution. It is proposed to improve the equipment for the vibrational cleaning of contamination of parts, which allows to ensure the elimination of resonant beating of the vibrating equipment during the application of the starting torque. The disadvantage of existing technologies is that during the washing and cleaning of parts with the help of vibrating machines, a phenomenon of resonance occurs, that is, a momentary beating occurs, which destroys bearing assemblies and seals, and there is a possibility of chemical liquid spilling out. To ensure the durability and safe operation of vibration devices, it is necessary to eliminate the resonant beating of the vibration equipment during the application of the starting moment. The technical result, which can be obtained when using a device for resonance-free vibration cleaning of contamination of parts, allows to ensure the elimination of resonant beating of vibrating equipment during the starting moment. The proposed technology for non-resonant vibration cleaning of contamination of parts, which contains a frame bath, flexible flange and membrane, metal washers, rubber gaskets and a vibration unit with a rotary hydraulic imbalance, in the process of operation, allows to increase the durability and safety of the device by eliminating the resonant beating of the vibrating equipment during starting moment.

The Study of the Relationship of Individual Psychological Characteristics and Self-Expression Strategies in Interpersonal Relationships

Introduction. Competent self-expression determines success in planning and promoting the goals of a communicator focused on achieving results in different spheres of life. At the same time, preferred behavioural strategies and personality features are not always apprehended by a person and, consequently, not always used effectively. The urgency to study the problem is due to the insufficient representation of studies of behavioural strategies and individual psychological characteristics of subjects.Purpose. Study of the interrelationships of individual psychological characteristics and behavioural strategies of selfexpression of personality at different stages of professional formation and development.Materials and Methods. The following methodological tools were selected: the methodology for diagnosing the level of reflexivity, the questionnaire Style of Self-Regulation of the Behaviour ― SSB–98, the Test of Affiliation Motives, the Personality Orientation in Communication Test, the Self-Confidence Test, the questionnaire Volitional Qualities in person, the questionnaire Strategies of Self-Expression.Results. Girls prefer the strategy of ‘anxiety to please’ and ‘tracking the impression made’, boys prefer the ‘variability of behaviour’. Women are less likely to track the impression made on the interlocutor and, if necessary, they can dominate and manipulate. Men, in contrast, more closely monitor their behaviour peculiarities and do not tend to show dependence and weakness. Self-confident subjects are characterized by social courage and initiative and apply the ‘self-promotion’ strategy. Dialogical ― strive to be accepted by the target audience, take the initiative. They are not characterized by the strategy of ‘variability of behaviour’. Reflexive subjects are characterized by the use of dialogue and the use of the strategies ‘variability of behaviour’ and ‘self-promotion’.Discussion and Conclusion. It is assumed that the unoften use of the ʻimpression trackingʼ strategy by women is related to the action of the gender education mechanism. It is confirmed that at different stages of age and professional development, behavioural strategies are conditioned by individual psychological characteristics of the personality, which are in demand in the process of self-expression. The data obtained contribute to the theoretical substantiation of the problem and allow us to develop a model of the self-expression of a personality depending on its psychological characteristics.

Mesoscale modelling of SFRC based on 3D RBSM considering the effects of fiber shape and orientation

In this study, a mesoscale model of steel fiber reinforced concrete (SFRC) based on 3D RBSM (rigid body spring model), was proposed to take the fiber shapes (straight and hook end) and orientation into account in concrete. The steel fibers were distributed into the Voronoi mesh system of RBSM, and a zero-size spring was assigned at the interface of Voronoi mesh crossed by discrete fiber, to transfer the fiber pullout load to the nearest nodes of RBSM. The straight steel fiber was modeled based on proposed local bond-slip relationship and the mechanical hook action was proposed additionally to model the hook end fiber. The model can predict the macroscopic response and cracking of SFRC made with straight and hook end fibers under direct tensile and bending loads. The analysis results found the mechanical hook action as the governing parameter for hook end fiber then the bond-slip properties for straight fiber. The fiber orientation and matrix spalling due to friction induced pullout load component, were found prominent for steel fiber. The anisotropy induced by fiber shapes and orientations was headed by hook end fiber with superior macroscopic load capacity by delaying the crack propagation and transformation.

Uptake Routes and Biodistribution of Polystyrene Nanoplastics on Zebrafish Larvae and Toxic Effects on Development

Polystyrene (PS) is the most widely used plastic polymer. It is mainly used to produce disposable products. Due to its resistance to degradation, PS can remain in the environment for a long time. Its mechanical, physical and biological actions determine the release of smaller fragments, which are able to penetrate organisms and accumulate in target organs. Fertilized Danio rerio eggs were exposed to concentrations of 10 and 20 mg/L of fluorescent, amino-modified polystyrene nanoplastics (nPS-NH2) with diameters of 100 and 50 nm for 96h, according to OECD guidelines (2013). Uptake, biodistribution, toxicity, oxidative stress and apoptosis were evaluated; moreover, we carried out a simulation to study the interactions between nPS-NH2 and defined regions of three receptors: STRA6, Adgrg6 and CNTN4/APLP2. We demonstrated that after being internalized, nPS-NH2 could reach the head and bioaccumulate, especially in the eyes. Moreover, they could lead to oxidative stress and apoptosis in the several regions where they bioaccumulated due to their interaction with receptors. This study confirmed the danger of nanoplastic wastes released in the environment.

Trace elements as potential modulators of puberty-induced amelioration of oxidative stress and inflammation in childhood obesity.

Although puberty is known to influence obesity progression, the molecular mechanisms underlying the role of sexual maturation in obesity-related complications remains largely unexplored. Here, we delve into the impact of puberty on the most relevant pathogenic hallmarks of obesity, namely oxidative stress and inflammation, and their association with trace element blood status. To this end, we studied a well-characterized observational cohort comprising prepubertal (N = 46) and pubertal (N = 48) children with obesity. From all participants, plasma and erythrocyte samples were collected and subjected to metallomics analysis and determination of classical biomarkers of oxidative stress and inflammation. Besides the expected raise of sexual hormones, pubertal children displayed better inflammatory and oxidative control, as reflected by lower levels of C-reactive protein and oxidative damage markers, as well as improved antioxidant defense. This was in turn accompanied by a healthier multielemental profile, with increased levels of essential elements involved in the antioxidant system and metabolic control (metalloproteins containing zinc, molybdenum, selenium, and manganese) and decreased content of potentially deleterious species (total copper, labile free iron). Therefore, our findings suggest that children with obesity have an exacerbated inflammatory and oxidative damage at early ages, which could be ameliorated during pubertal development by the action of trace element-mediated buffering mechanisms.

Study on material removal mechanism of sapphire wafer with CeO2 coated diamond composite abrasives via green polishing

Toxic and polluted ingredients are normally employed in the chemical mechanical polishing of sapphire wafers, which results in widespread environmental pollution. Thus, developing a novel green polishing technology is a significant challenge to achieve ultra-smooth and efficient polishing. In this study, novel CeO2 coated diamond composite abrasives were used in the semi-fixed abrasive polishing of sapphire wafers, which were successfully synthesized by a modified precipitation approach without using explosive hazardous chemicals. During the whole polishing process, the polishing slurry only contains deionized water, without any other chemical reagents, to avoid environmental pollution. Polishing results showed that the surface roughness of sapphire polished by the composite abrasives was reduced to 6.1 nm, which was 26.5 % lower than that of pure diamond. Meanwhile, the material removal rate was 1.46 nm/min, with an improvement of 10.6 %, as well as a reduction in residual stress by approximately 29.8 %. Combined with the theory of micro-contact mechanics, the polishing mechanism and interfacial contact behavior of composite abrasives were investigated in depth through the analysis of polished sapphire surface and wear debris. The improvement of polishing performance may be attributed to the enhancement of solid-state reaction and its mutual balance with the mechanical removal action of composite abrasives.

Inhibition of Fe4Ge3O12 formation in the leaching process of zinc oxide dust containing germanium by ultrasonic and iron powder

Low leaching efficiency of germanium has always been a difficult point hindering the efficient utilization of zinc oxide dust containing germanium. Based on the previous research results that the formation of insoluble Fe4Ge3O12 leads to germanium loss in the leaching process, a new process of reduction leaching of zinc oxide dust containing germanium enhanced by ultrasonic and iron powder is proposed. Under optimized conditions, the germanium leaching efficiency can be increased by 9.17%, reaching 93.43%. When leaching, the addition of iron powder can reduce the Fe3+ formed in the leaching process and hinder the formation of insoluble Fe4Ge3O12, which can increase the leaching efficiency of germanium by 5.30%. At the same time, strong mechanical action of ultrasonic can fully disperse the iron powder in the leaching system, avoiding the phenomenon of insufficient local reduction. More importantly, the addition of ultrasonic can reduce the dissolved oxygen in the solution system and produce strong reducing hydrogen free radicals (H), strengthening the reduction leaching effect, thus the germanium leaching efficiency is further increased by 3.87%. The research results provide a new method and theoretical guidance for the efficient utilization of zinc oxide dust containing germanium, which is of great significance.

Dietary zearalenone alters gill epithelial morphology and subsequent risk of infection: Insights from a freshwater grass carp (Ctenopharyngodon idella) model

The mechanical action of zearalenone (ZEA) on different species has been the focus of attention. However, current knowledge of the mode of action and detailed mechanism of ZEA in aquatic species remains limited. According to the maximum detectable dose of commercial fish feed (511 μg kg−1), 1440 freshwater edible grass carp (Ctenopharyngodon idella) with an initial weight of 15.34 ± 0.06 g that were fed six graded levels of dietary ZEA (0, 535, 1041, 1548, 2002 and 2507 μg kg−1 diet). After 70 d, impaired gill epithelial barrier function was confirmed in ZEA-exposed grass carp in terms of the differential expression of tight junctions (TJs), increased oxidative stress levels, and excessive apoptosis promoted cell death. Subsequently, the health status of the fish was determined by immersion (3 h) of Flavobacterium columnare. ZEA-exposed fish displayed the highest incidence of gill rot at 3 d postinfection. Concordantly, at higher doses, ZEA could significantly decrease immune component [(e.g., acid phosphatase (ACP), lysozyme (LZ) and Complement 3 (C3)] activities and antimicrobial peptides (AMPs) transcription abundance and increase substantially inflammatory cytokines. Furthermore, we found that the nuclear factor-erythroid 2-related factor 2 (Nrf2), the nuclear factor κB (NF-κB), and the target of rapamycin (TOR) may be partially involved in associated regulation, thus indicating a potential regulatory network affected by ZEA. In summary, our findings suggest that ZEA disrupts the barrier function of fish gills and increases the risks of pathogen infection. The current recommended guidance values for ZEA in aquaculture (2000 μg kg−1) are insufficient to preclude toxic potential, and increased public concern about ZEA in feed and feedstuff is essential.

Epigenetic Changes Occurring in Plant Inbreeding

Inbreeding is the crossing of closely related individuals in nature or a plantation or self-pollinating plants, which produces plants with high homozygosity. This process can reduce genetic diversity in the offspring and decrease heterozygosity, whereas inbred depression (ID) can often reduce viability. Inbred depression is common in plants and animals and has played a significant role in evolution. In the review, we aim to show that inbreeding can, through the action of epigenetic mechanisms, affect gene expression, resulting in changes in the metabolism and phenotype of organisms. This is particularly important in plant breeding because epigenetic profiles can be linked to the deterioration or improvement of agriculturally important characteristics.

Abnormally high work hardening ability and excellent comprehensive properties of copper alloys due to multiple twins and precipitates

In the present work, the Cu-1.35Ni-1Co-0.55Si alloy with multiple twins and ultra-low interfacial mismatch precipitates was obtained by liquid nitrogen dynamic plastic deformation (DPD) and aging treatment. It has abnormally high work hardening ability, which is more than twice that of the previous DPD treatment without aging. In addition, it has excellent comprehensive properties, and its strength, electrical conductivity, and elongation are 816.4 MPa, 40.2% IACS and 11.3% respectively. The fine multiple twins do not coarsen significantly during peak aging, and the dispersed nano precipitates (∼3 nm) further enhance the strength of the Cu-Ni-Co-Si alloy. In addition, the low interfacial mismatch strain between the precipitates and the matrix also ensures adequate elongation. The Cu-Ni-Co-Si alloy has high strength, electrical conductivity, and ductility under the simultaneous action of various mechanisms (grain boundary strengthening, precipitation strengthening, dislocation strengthening and stacking faults). This strategy paves a new avenue for developing precipitation-strengthened alloys with excellent comprehensive properties.

An Apparent Permeability Model in Organic Shales: Coupling Multiple Flow Mechanisms and Factors.

It is of great significance to study shale apparent permeability under the action of multiple flow mechanisms and factors because shale reservoirs possess complex pore structures and flow mechanisms. In this study, the confinement effect was considered, with the thermodynamic properties of gas being modified, and the law relating to the conservation of energy adopted to characterize bulk gas transport velocity. On this basis, the dynamic change of pore size was assessed, from which shale apparent permeability model was derived. The new model was verified by three steps: experimental and molecular simulation results of rarefied gas transport, shale laboratory data, and comparison with different models. The results revealed that, under the conditions of low pressure and small pore size, the microscale effects became obvious, which significantly improved gas permeability. Through comparisons, the effects of surface diffusion and matrix shrinkage, including the real gas effect, were obvious in the smaller pore sizes; nevertheless, the stress sensitivity effect was stronger in larger pore sizes. In addition, shale apparent permeability and pore size decreased with an increase in permeability material constant and increased with increasing porosity material constant, including internal swelling coefficient. The permeability material constant had the greatest effect on gas transport behavior in nanopores, followed by the porosity material constant; however, the internal swelling coefficient had the least effect. The results of this paper will be important for the prediction and numerical simulation of apparent permeability relating to shale reservoirs.

Changes of the cardiac baroreflex bandwidth during postural challenges.

Baroreflex is commonly typified from heart period (HP) and systolic arterial pressure (SAP) spontaneous variations in the frequency domain mainly by estimating its sensitivity. However, an informative parameter linked to the rapidity of the HP response to SAP changes, such as the baroreflex bandwidth, remains unquantified. We propose a model-based parametric approach for estimating the baroreflex bandwidth from the impulse response function (IRF) of the HP-SAP transfer function (TF). The approach accounts explicitly for the action of mechanisms modifying HP regardless of SAP changes. The method was tested during graded baroreceptor unloading induced by head-up tilt (HUT) at 15°, 30°, 45°, 60°, and 75° (T15, T30, T45, T60, and T75) in 17 healthy individuals (age: 21-36 yr; 9 females and 8 males) and during baroreceptor loading obtained via head-down tilt (HDT) at -25° in 13 healthy men (age: 41-71 yr). The bandwidth was estimated as the decay constant of the monoexponential IRF fitting. The method was robust because the monoexponential fitting described adequately the HP dynamics following an impulse of SAP. We observed that 1) baroreflex bandwidth is reduced during graded HUT and this narrowing is accompanied by the reduction of the bandwidth of mechanisms that modify HP regardless of SAP changes and 2) baroreflex bandwidth is not affected by HDT but that of SAP-unrelated mechanisms becomes wider. This study provides a method for estimating a baroreflex feature that provides different information compared with the more usual baroreflex sensitivity while accounting explicitly for the action of mechanisms changing HP irrespective of SAP.

The anti-inflammatory effect of lutein in broilers is mediated by regulating Toll-like receptor 4/myeloid-differentiation-factor 88 signaling pathway

The anti-inflammatory role of lutein has been widely recognized, however, the underlying mechanism is still not fully elucidated. Hence, the effects of lutein on the intestinal health and growth performance of broilers and the action of mechanism were investigated. 288 male yellow-feathered broilers (1-day old) were randomly allocated to 3 treatment groups with 8 replicates of 12 birds each, and the control group was fed a broken rice-soybean basal diet, while the test groups were fed a basal diet added with 20 mg/kg and 40 mg/kg of lutein (LU20, LU40), respectively. The feeding trial lasted for 21 d. The results showed that 40 mg/kg lutein supplementation tended to increase ADFI (P=0.10) and ADG (P=0.08) of broilers. Moreover, the addition of lutein caused a decreasing trend of gene expression and concentration of proinflammatory cytokines IL-1β (P=0.08, P=0.10, respectively) and IL-6 (P=0.06, P=0.06, respectively) and also tended to decrease the gene expression of TLR4 (P=0.09) and MyD88 (P=0.07) while increasing gene expression and concentration of anti-inflammatory cytokines IL-4 and IL-10 (P < 0.05) in the jejunum mucosa of broilers. Additionally, lutein supplementation increased the jejunal villi height of broilers (P < 0.05) and reduced villi damage. The experiment in vitro showed that lutein treatment reduced the gene expression of IL-1β, IL-6, and IFN-γ in chicken intestinal epithelial cells (P < 0.05). However, this effect was diminished after knock-down of TLR4 or MyD88 genes using RNAi technology. In conclusion, lutein can inhibit the expression and secretion of proinflammatory cytokines in the jejunum mucosa and promote intestinal development of broilers, and the anti-inflammatory effect may be achieved by regulating TLR4/MyD88 signaling pathway.

Somatically evoked cough responses help to identify patients with difficult-to-treat chronic cough: a six-month observational cohort study.

Recently we identified in patients with chronic cough a sensory dysregulation via which the urge-to-cough (UTC) or coughing are evoked mechanically from "somatic points for cough" (SPCs) in the neck and upper trunk. We investigated the prevalence and the clinical relevance of SPCs in an unselected population of patients with chronic cough. From 2018 to 2021, symptoms of 317 consecutive patients with chronic cough (233 females) were collected on four visits (V1-V4) 2 months apart at the Cough Clinic of the University Hospital in Florence (I). Participants rated the disturbance caused by the cough (0-9 modified Borg Scale). We attempted to evoke coughing and/or UTC using mechanical actions in all participants who were subsequently categorised as responsive (somatic point for cough positive, SPC+) or unresponsive (SPC-) to these actions. An association was established between chronic cough and its commonest causes; treatments were administered accordingly. 169 patients were SPC+ and had a higher baseline cough score (p<0.01). In most of the patients, the treatments reduced (p<0.01) cough-associated symptoms. All patients reported a decrease (p<0.01) in cough score at V2 (from 5.70±1.4 to 3.43±1.9 and from 5.01±1.5 to 2.74±1.7 for SPC+ and SPC- patients respectively). However, whilst in SPC- patients the cough score continued to decrease indicating virtually complete cough disappearance at V4 (0.97±0.8), in SPC+patients this variable remained close to V2 values during the entire follow-up. Our study suggests that the assessment of SPCs may identify patients whose cough is unresponsive and are eligible for specific treatments. This work was funded by an unrestricted grant from Merck (Italy).

Coupled Chemical and Mechanical Damage Model for Acid-Corroded Sandstone

Taking the sandstone subjected to pH = 1 and 3 HCl solutions as the research object, a dynamic chemical damage model was established based on mineral dissolution theory and chemical kinetics principles. A mechanical damage model of sandstone was also established by continuous damage mechanics theory. Moreover, a coupled chemical and mechanical damage model was deduced through microstress analysis, and a damage constitutive model for acid-corroded sandstone was constructed based on the Weibull distribution and the D–P criterion. The results showed that the acid–rock reaction showed evident time dependence, and the reaction rate decreased with the prolongation of corrosion time. The chemical damage variables of corroded sandstone subjected to pH = 1 and 3 HCl solutions reached 0.34 and 0.12 after 180 days, respectively. The damages caused by chemical and mechanical actions are nonlinear with the generalized damage. The chemical action can slow down the deterioration rate of sandstone under load, which was more obvious as the immersion time extended and the pH values of the solution declined. The stress state could change the deterioration process of sandstone, and the damage rate declined as the confining pressure increased. Finally, the uniaxial and triaxial compression test results verified the theoretical model, and the two agreed well, which verified that the coupled damage model is reasonable and applicable.

Contribution of bubble activity to the efficacy of histotripsy and catheter-directed recombinant tissue plasminogen activator for treatment of porcine thrombi in vitro

Histotripsy has been shown to be a promising adjuvant treatment for deep vein thrombosis (DVT), using the mechanical action of bubble clouds to enhance thrombolytic activity and reduce the risk of complications. The objective of this study was to compare the effects of histotripsy with and without recombinant tissue-plasminogen activator, rt-PA in a physiologic, in vitro model mimicking porcine DVT. Highly retracted porcine whole blood clots were treated for 1 h with catheter-directed infusions of either saline or rt-PA [0.04 mg/ml] at 25 ml/h, either with or without histotripsy exposure. Five-cycle, 1.5 MHz histotripsy pulses with a peak negative pressure of 32 MPa and pulse repetition frequency of 40 Hz were applied along the catheter at 0.3 mm/s and repeated 1 mm on either side. This application pattern was repeated 6 times, totaling approximately 120 to 144 K pulses per clot. B-mode and passive cavitation images were acquired every 10pulses. The combination of rt-PA and histotripsy was more efficacious for recanalization than saline with histotripsy, saline, or rt-PA alone. Histotripsy exposure, but not rt-PA, improved mass loss (p &amp;lt; 0.01). These in vitro data support our hypothesis that the mechanical action of histotripsy-induced bubble clouds enhances catheter-directed thrombolytic.

Instrumentation for histotripsy ultrasound therapy: Evolution toward the clinic

Histotripsy is a method of ultrasound therapy using very intense, focused sound fields to fragment tissue causing controlled and localized necrosis principally through mechanical actions of cavitation. Highly specialized instrumentation (transducers and electrical drivers) is required to produce these extreme sound fields for research into cavitation physics and therapeutic applications of histotripsy. This paper will describe the evolution of histotripsy instrumentation from the first devices up to the latest phased-array systems with hundreds of channels and transmit-receive capability. While early histotripsy systems used tone bursts generators with limited bandwidth (called “class-D” circuits) for transducer excitation, more recent ones are based on a switched inductor principle to produce shorter duration acoustic emissions. This method has been tested for peak excitation voltages up to 5 kV and 40 A in compact modular systems suitable for phased-arrays. Receive of acoustic signals by the therapeutic array for aberration correction and cavitation mapping is achieved by sensing current generated by the transducer greatly simplifying transmit-receive circuitry while maintaining very large dynamic range. A novel distributed architecture was developed for data handling and signal processing using off-the-shelf FPGA evaluation modules interfaced by ethernet. These latest features will be key to successful clinical translation and widespread adoption of histotripsy.